UNITED STATES PATENT OFFICE

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP81-00120R000100010056-5
• Release Decision: RIFPUB
• Original Classification: K
• Document Page Count: 37
• Document Creation Date: December 22, 2016
• Document Release Date: December 8, 2003
• Sequence Number: 56
• Content Type: CONT

Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010056-5 Re. 27,444
V intcu otites .patent jmce Reissued July 18, 1972
1 2
features thereof will become apparent as the description
27444 proceeds.
FOR THE PRODUCTION OF POROUS In principle the objects of the present invention are
PLASTICS AND PRODUCTS achieved by providing a stable water-in-oil emulsion of
Guenther Will, Zimrnerstrasse 11, Darmstadt, Germany 5 the following composition:
No Drawing. Original No. 3,256,219, dated June 14,
1966, Ser. No. 301,920, Aug. 13, 1963, which is a (1) Water or an aqueous solution containing at least
continuation-in-part of Ser. No. 45,786, July 28, 1960. about [403 25% water forming the dispersed phase; anal
Application for reissue Sept. 11, 1970, Ser. No. 71,347 (2) A polymerizable organic liquid or a liquid the sub-
Claims priority, application Germany, July 28, 1959, stantial portions of which consist of a polymerizable or-
W 26,093 10 ganic liquid which contains the following components:
Int. Cl. C08f 45/24, 47/08 (a) A polymerizable organic liquid consisting of a po-
U.S. Cl. 260-2.5 R 46 Claims lymerizable organic compound having a low molecular
Matter enclosed in heavy brackets [ ] appears In the weight or of several organic compounds of a low molecu-
original patent but forms no part of this reissue specifl- lar wegiht which are copolymerizable with each other, said
cation; matter printed in italics indicates the additions 15 liquid being designated as constituent (a); and
made by reissue. (b) At least one organic compound of low molecular
weight which is not copolymerizable with the constituent
ABSTRACT OT THE DISCLOSURE (a) and/or at least one organic compound of high mo-
lecular weight which is not copolymerizable with the con-
Production of useful shaped articles, formed of porous 20 stituent (a) and/or at least one organic compound of high
plastic, by emulsifying droplets of an aqueous medium in molecular weight which is copolymerizable with the con-
an organic liquid containing polymerizable organic com- stituent (a), said organic compound being soluble and
pounds(s) and emulsifying agent(s) and, without break- contained in solution in the constituent (a) from which
ing the dispersed nature of the emulsion, polymerizing it solution it is at least partly separated and precipitated at
until the organic liquid has been converted to solid form. 25 least in the phase boundary by the dispersed phase (1),
whereby it acts as an emulsifier, said compound being
designated as constituent (b).
The present application is a continuation-in-part of ap- (c) If required, at least one organic compound of low
plication Ser. No. 45,786, filed July 28, 1960, and en- molecular weight which is not copolymerizable with the
titled, "Production of Cellular Materials From Vinyl- 30 constituent (a) and/or at least one organic compound of
type Resins," now abandoned. high molecular weight which is not copolymerizable with
This invention relates to a process for the production the constituent (a) and/or at least one organic compound
of porous plastics and the products produced thereby. of high molecular weight which is copolymerizable with
Several methods have been disclosed for the manufac- the constituent (a) and which is soluble and contained in
ture of porous plastic materials of sponge or foam-like 35 solution in the constituent (a), from which solution it is
structure. One known method, which is analogous to not separated and precipitated at the phase boundary by
that used in powder metallurgy sintering, is merely to com- the dispersed phase (1), may be added. This compound,
pact a powdered or granular polymer at a temperature or compounds, is designated as constituent (c), all of
slightly below its melting point. In this way the par- said compounds (a), (b), and (c) forming the continuous
ticles are not fused intimately together but hollow spaces 40 phase. The thus composed emulsion is then polymerized
are left in the interstices of the mass. in the presence of the usual polymerization initiators and
According to another method, the powdered polymer is activators to the porous polymer composition the pores of
mixed with a granular soluble salt, for instance, a water- which, depending on the polymerization conditions, may
soluble salt and is heated until it is softened or molten to still contain the aqueous liquid initially forming the dis-
a compact mass. The soluble salt is then leached from 45 persed phase (1) which [is finally] may be completely or
the mass by a solvent, for instance, by water. The re- partly eliminated from the thus obtained porous plastics.
maining product is porous. Its density is dependent on In the porous plastics obtained in the afore-mentioned
the amount of soluble salt mixed with the polymer prior way, the pores are produced by the dispersed phase (1)
to heating the same. and the structure of the plastic is produced by the con-
It is also known to produce porous plastics by polymer- 50 tinuous phase (2).
izing a polymerizable compound and subjecting it either The fundamental discovery of the present invention is
during or after its polymerization to the action of gases that it is possible to form water-in-oil emulsions in which
or of gas-producing compounds. This method suffers, the aqueous phase remains in its dispersed state even
among others, from the drawback that it can be applied during and after the monomer is polymerized. These
but to a relatively small number of plastics, and that it 5,5 emulsions can be prepared by making use of microgels
does not allow one to regulate in a simple way the volume acting as the emulsifiers.
ratio of solid substance to pores, as well as the diameter These microgels are believed to be peculiar to poly-
of the individual pores. meric systems. When a polymer is dissolved in a sol-
It is the object of the present invention to provide a vent, and a non-solvent for said polymer is introduced
process for the production of porous plastics which proc- 60 into said solution, a turbid phase appears to precipitate
ess is an improvement over said prior art process. out of solution. This turbid phase consists of finely di-
Another object of the present invention consists in pro- vided droplets containing polymer, solvent, and non-sol-
viding a substantially stable composition containing a po- vent, and on further examination these droplets generally
lymerizable monomer which composition, on subsequent prove to be gelatinous. This formation of microgels is
polymerization, yields a porous plastic of improved prop- 65 fundamentally different from a system which does not
erties. contain polymers. For instance, when sugar is in aque-
A further object of the present invention consists in ous solution and a non-solvent for sugar is added, the
providing a porous polymer composition the pores of sugar is precipitated in pure form, there being no turbid
which are filled with a liquid material. phase containing sugar, solvent, and non-solvent. For
Still another object of the present invention is to provide 70 a more detailed explanation of the theory underlying the
an improved porous plastic of high strength properties. formation of microgels, reference is made to the text-
Other objects of the present invention and advantaeenus hnnk_ "Prinninlac of PM,,,,,o.. r,' "-:stry" by P. J. Flory,
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Cornell University Press, Ithaca, New York, 1953, Chap-
ers VIII-3 and XIII.
In the present invention the relationship between the
solvent, non-solvent, and polymer or component (b) are
extremely important. By varying these relationships, it 5
is possible to produce either sponge-like materials hav-
ing intercommunicating pores or, on the other hand,
foam-like material having isolated non-intercommunicat-
ing pores. Before proceeding with a discussion of these
different possibilties, attention is directed to the follow- 10
ing definitions of solvent, non-solvent, and polymer, as
used in the present invention.
A solvent, or component (a) as defined hereinabove,
is a liquid in which the polymer, or component (b) as de-
fined hereinabove, is soluble at least to the extent of 15
about 0.5 part, by weight, of the polymer in 100 parts,
by weight, of solvent, preferably 2 parts of polymer in
100 parts of solvent.
A non-solvent, or dispersed phase (1) as defined here-
inabove, is a liquid in which the polymer has a solubility
of less than about 10.0 parts by weight, of polymer, pref-
erably less than 1.0 part in 100 parts of non-solvent.
Furthermore, the non-solvent should be soluble in the
solvent in a range of about 0.001 part to 20 parts of
non-solvent, preferably about 0.005-0.1 part to 100 parts
of solvent. (All of the solubilities as described above
are those determined at room temperature or, if the mon-
omer is a solid at room temperature, at 100? C.)
According to the process of the present invention
porous plastics can be produced in which the volume ratio
of solid matter to pores is approximately from 1:0.25 to
1:20 and in which the individual pores have a diameter
approximately from 0.1? to 600?. The volume ratio of
solid matter to pores can be regulated in a simple man-
ner by a corresponding selection of the ratio between
the compounds forming the continuous phase (2) and
the liquid forming the dispersed phase (1), while the
diameter of the individual pores can be determined by
producing a finer or coarser dispersion of the dispersed
phase (1) in the continuous phase (2).
The process according to the present invention for the
production of porous plastics must not be confused with
the conventional emulsion polymerization processes.
The latter processes are characterized in that an oil-in-
water emulsion containing
(a) water or an aqueous
phase (2),
4
less than 25] at least about 40% by weight, and prefer-
ably not less than 70%, by weight, of water.
In case the dispersed phase (I) does not exclusively
consist of water, it contains, besides water, other additives.
which are soluble in water. Examples of such added
compounds are alcohols, in particular lower monohydric
aliphatic alcohols like methanol, ethanol, n- and iso-pro-
panol, 'and n-, iso- and tertiary butanol: furthermore
lower organic acids like actic acid and propionic acid.
moreover lower ethers and lowerketones like methyl ethyl
ether and dimethylkctone as well as inorganic salts like
sodium chloride, potassium sulfate, sodium sulfate, mag-
nesium sulfate, and magnesium chloride.
Organic liquids with a high dielectric constant like
formamide and dimethylformamide, or saccharose, glu-
cose, fructose, or other carbohydrates in aqueous solution
may also be used as the dispersed phase (1).
As stated above, the water-in-oil emulsion forming the
starting material for producing the porous plastic ac-
cording to the present invention contains, as principal
member of the continuous phase (2) described herein-
above, a polymerizable organic liquid or solvent desig-
nated hereinabove as component (a) which is a polymer-
izable organic liquid consisting of a polymerizable organic
compound of low molecular weight or of several organic
compounds of low molecular weight that are copolymer-
izable with each other. The continuous phase should in
general contain not less than 10%, by weight, and pref-
erably not less than 45%, by weight, of said constituent
(a). It is also possible to use a solution of one or sev-
eral non-liquid, copolymerizable organic compounds of
low molecular weight in one or several liquid copolymer-
izable organic compounds of low molecular weight. Com-
pounds containing at least one group of the formula
C112=C< or CFI=CC
-IC-CH=CH-ICI''-
0
are particularly suitable as liquid polymerizable com-
pounds of low molecular weight. Examples thereof are
compounds which contain, attached to an aromatic nu-
cleus, vinyl or a-alkyl vinyl groups such as styrene, divinyl
benzene, o-, m-, p- and a-methyl styrene, furthermore,
esters and ethers of vinyl alcohol such as vinyl acetate,
divinyl phthalate, divinyl maleate, vinyl butyl ether, di-
vinyl ethanediol ether; additionally, acrylic and meth-
acrylic acid esters such as ethyl acrylate, 1,2-propanediol
diacrylate, methyl methacrylate, ethanediol dimethacry-
late, butene-2-diol-1,4-dimethacrylate, maleic acid diethyl
ester; furthermore unsaturated hydrocarbon halides and
cyanides such as vinylidene chloride, allyl chloride,
chloroprene acrylonitriles, furthermore unsaturated ali-
phatic hydrocarbons such as isoprene; as well as the esters
and ethers of allyl and methallyl alcohols such as diallyl
phthalate, methallyl methyl fumarate, 1,2,3-tri(allyloxy)
propane, di-alkyl diglycol carbonate, di-allylmalleate.
Suitable for being used as non-liquid polymerizable
monomers of low molecular weight are gaseous and solid
compounds, for instance, butadiene, vinylchloride, vinyl
naphthalene, vinyl carbazole.
The other essential constituent of the continuous phase
(2) is the compound (b) which is, as stated above, at
least one organic compound of low molecular weight that
is not copolymerizable with the constituent (a) and/or
at least one organic compound of high molecular weight
which is or, respectively, is not copolymerizable with the
constituent (a), whereby said constituent (b) must be
soluble in the constituent (a) and must, at least partly,
be separated and precipitated from said solution at the
phase boundary by the constituent of the dispersed phase
(l ), whereby it acts as an emulsifier.
To find out whether a polymer can be used as constitu-
(t3) a polymerizable organic liquid or a liquid consisting
substantially of a polymerizable organic liquid as the
dispersed phase (1), and 50
(y) an emulsifier or a mixture of emulsifiers, respectively,
and/or a protective colloid or a mixture of protective
colloids, respectively,
is polymerized in the presence of polymerization initia- 55
tors, and, if desired, in the presence of polymerization
activators.
In said processes the plastic is obtained in the form of
small, noncohesive, compact beads.
The emulsifiers which were used heretofore were solu- (30
ble in at least one or both of the liquid phases and due
to their chemical properties are able to reduce the inter-
facial surface tension between the water and oil phases.
Although some of these emulsifiers can be satisfactorily
utilized to form an emulsion of water-in-vinyl-type mon- 0)
omers, it is well known that such emulsions will break
on polymerization of the monomer. In other words,
prior to the present invention, it was found that the dis-
persed water phase in a water-in-vinyl-type monomer will
coalesce before a solid polymerized structure is formed. 70
The water-in-oil-emulsions, which are useful in carry-
ing out the process according to the present invention
contain, as mentioned under (1), water or substantially
water as agent forming the dispersed phase (I).
In general, the dispersed phase (I) is to contain [not 7,5
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ent (b), the following simple small-scale test is carried
out in the following manner. Either the prospective con-
stituent (b), i.e., the polymer is added to water or the spe-
cific aqueous solution of the dispersed phase (1), i.e., the
non-solvent whereafter the constituent (a), i.e., the po-
lymerizable monomeric solvent is admixed. Or the pros-
pective constituent (b), i.e., the polymer is first dissolved
in the constituent (a), i.e., the polymerizable monomeric
solvent, whereafter water or the specific aqueous solu-
tion of the dispersed phase (1), i.e., the non-solvent is
added. For instance, 1% to 2%, by weight, of the con-
stituent (b) are dissolved in constituent (a) and a few
drops of water or of the specific aqueous solution, are
added to '?10 cc. of said solution of constituent (b) to be
tested in constituent (a). The mixture is shaken thor-
oughly and centrifuged at 2000 revolutions to 3000 revo-
lutions per minute until phase separation takes place.
Any compound is suitable for use of constituent (b) in
combination with constituent (a) and the aqueous solu-
tion (1) which produces in this test a turbid mixture of
separation into separate phases. As a rule the more
stable water-in-oil emulsions are obtained, the more pro-
nounced is the separation or precipitation of the constitu-
ent (b) by the aqueous phase (1).
Suitable compounds (b) are in particular those which
contain a major portion of hydrophobic groups and only
a minor portion of hydrophilic groups. Such compounds
are especially adapted to form the above mentioned
microgel. The particular type of microgel which is formed
on addition of water or the above mentioned aqueous
solution, i.e., the non-solvent (1) to the solution of sol-
vent constituent (a) and polymer constituent (b) is not
especially affected by the amount of non-solvent (1).
Larger amounts of non-solvent (1) merely result in larger
amounts of water-in-oil emulsion. However, the polymer-
ization is very considerably affected by the type of con-
stituent (b) employed.
Suitable representatives of low molecular weight con-
sttiuents (b) which are not copolymerizable with con-
stituent (a) but are soluble therein and are precipitated
from their solutions in constituent (a) by the addition
of the aqueous solution (1) are emulsifiers as they are
ordinarily employed for preparing water-in-oil emulsions,
for instance, esters of higher fatty acids with relatively low
molecular polyhydric aliphatic alcohols, esters of higher
fatty alcohols with lower and higher fatty acids, amides
of higher fatty acids as well as salts of higher alkyl sul-
fonie acids.
However, the preferred and particularly suitable com-
pounds for use as constituent (b) are polymerization prod-
ucts and polycondensation products which are not at all
or only slightly soluble in water and which contain, as
hydrophilic groups, carboxyl groups, carboxylate groups,
carboxamide groups, hydroxyl groups, ester groups, ether
groups, amino groups, ammonium groups, sulfonic acid
groups, sulfonate groups, and/or sulfoxide groups.
Such non-copolymerizable compounds of high molec-
ular weight are, for instance, copolymerization products
having an acid number of about 8 to 12, of polymerizable
Particularly suitable interpolymerizable compounds of
high molecular weight are, for instance, polycondensa-
tion products of the unsaturated polyester type containing
carboxyl groups and/or hydroxyl groups and/or ether
5 groups. Such unsaturated polyesters are composed of
25 constituent (b). Other unsaturated or saturated dicar-
boxylic acids, like endomethylene tetrahydrophthalic
acid, tetrahydrophthalic acid, o-, m- and p-phthalic acid,
succinic acid, and adipic acid, may also be employed as
condensation components of the unsaturated polyesters.
30 Furthermore, mono-, tri-, or polybasic carboxylic acids,
such as propionic acid, 1,2,4-benzene, tricarboxylic acid,
and 1,2,4,5-benzene tetracarboxylic acid and mono-, tri-,
or polyhydric alcohols, such as benzyl alcohol, 1,2-di-(al-
lyloxy)-3-prop anol. Glycerol, and pentaerythritol as well
35 as hydroxy carboxylic acids, such as 4-hydroxy methyl
carboxylic acids, such as acrylic acid, and hydrophobic
polymerizable organic compounds, such as styrene, as well
as copolymerization products of said type in which the
carboxyl groups are partly or completely neutralized with
organic or inorganic bases or are converted into carbox-
amide group by means of ammonia or amines. Polym-
erization products and copolymerization products of sty-
rene, of methyl methacrylate, and of vinyl acetate which
are prepared by emulsion polymerization in the presence
of persulfates and which, therefore, contain sulfonic acid
or. sulfonate groups, respectively; may be used. Further-
more, for instance, saturated polymerization products and
saturated polycondensation products which contain as
hydrophilic groups, exclusively or practically exclusively
ester and/or ether groups like polymethyl methacrylate
and cellulose acetobutyrate may also be used.
polyesters of polybasic, in particular dibasic, carboxylic
acids and of polyhydric, in particular dihydric, alcohols.
These unsaturated polyesters may also contain the radi-
cals of monovalent carboxylic acids and/or the radicals
of monovalent alcohols and/or the radicals of hydroxy
carboxylic acids provided such unsaturated polyesters
contain polymerizable ethylenically unsaturated groups.
Such polyesters are described, for instance, in the book on
"Polyesters and Their Applications" by J. Bjorksten, H.
Tovey, B. Harker and J. Henning, Reinhold Publishing
Corporation, New York.
The polyesters can be prepared, for instance, from their
components by a fusion-type condensation or a condensa-
tion under azeotropic conditions. Dihydric alcohols, for
instance, ethanediol, 1,2-propanediol, 1,3-propanediol, di-
ethylene glycol and 1-allyl-2,3-hydroxypropanediol, in ap-
proximately stoichiometric quantities can be converted
with e-ethylenically unsaturated dicarboxylic acids such
as maleic and fumaric acid, into polyesters suitable as
cyclohexane carboxylic acid can be used as additional
components of the unsaturate polyesters.
Particularly stable emulsions are obtained with un-
saturated polyesters in which the residual carboxylic
groups are partly or completely neutralized with com-
pounds having a basic reaction. Suitable compounds of
basic reaction are, for instance, sodium hydroxide, potas-
sium hydroxide, magnesium hydroxide, calcium hydrox-
ide, ammonia, amines such as ethylamine, tri(p-hydroxy
ethyl) amine, and a-methyl-p-hydroxy ethylamine, fur-
thermore water-soluble precondensation products of
aminoplasts, such as precondensation products of formal-
dehyde and melamine, formaldehyde and urea, of form-
aldehyde and dicyandiamide. Thus, to a water-in-oil emul-
sion containing a polymerizable organic liquid (a) and
an unsaturated polyester obtained from unsaturated di-
carboxylic acid and polyhydric alcohol as emulsifying
agent (b), one may add between about 0.01% and about
15% of the water-soluble preliminary condensation prod-
uct of melamine and formaldehyde, calculated on the
polymerizable organic liquid (a).
There may also be mentioned as copolymerizable com-
pounds of high molecular weight polymerization products
containing hydrophilic groups and, in addition, gr(':ns
which can be further polymerized. Examples of ; , h
polymeriztion products are prepolymerization products
from compounds containing hydrophilic groups as well
as at least two polymerizable vinylidene groups, such as
diallyl phthalate and ethylene glycol dimethacrylate, fur-
65 thermore precopolymerization products from compounds
containing hydrophilic groups as well as at least two
polymerizable vinylidene groups and compounds contain-
ing one polymerizable vinylidene group such as preco-
polymerization products from diallyl phthalate and allyl
acetate or from ethylene glycol dimethacrylate and methyl
methacrylate.
The efficiency of the component (b) as an emulsifier is
often increased by adding water-soluble organic com-
pounds of low molecular weight containing a hydrophilic
as well as a hydrophobic group additionally to the water
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forming the dispersed phase (1) of the water-in-oil emul-
sion. Compounds which are suitable for this purpose are,
in particular, alcohols, organic acids, ethers, and ketones
as they are mentioned hereinabove as agents forming the
dispersed phase (1). It is possible to readily find by
means of the above-mentioned small-scale test which
agent forming the dispersed phase (1) is particularly suit-
able for being employed together with given agent (a)
and (b) forming the continuous phase (2).
Suitable polymer constituents (b) of the continuous
phase (2) have a minimum molecular weight of about
1,000. The preferred molecular weight range is between
20,000 and 200,000.
It has been found that the pH-value of the solvent-
polymer-non-solvent system is also of importance. For
instance, to form a structure having non-intercommuni-
cating pores, it is necessary that the pH of the non-solvent
aqueous solutions be higher than 5.0. An example of
this system is: Polymethacrylate as the polymer, styrene
as the solvent monomer, and a mixture of ethanol and
water as the non-solvent. The microgel which consists
of polymethacrylate, styrene, ethanol, and water has an
affinity for the ethanol-water non-solvent mixture. This
is due to the high concentration of polymethacrylate in
the microgel and because said polymer contains ester
linkages which are comparatively polar, thereby attract-
ing the polar non-solvent. Similar systems are formed
when the non-solvent contains water-soluble vinyl mono-
mers such as acrylic acid, vinyl alcohol and acrylonitrile.
These latter systems work especially well in the presence
of water-soluble polymerization initiators.
In contrast to porous structures containing non-inter-
communicating cells, it is also possible to obtain what
may be called a coherent system containing contiguous
intercommunicating pores. This structure is obtained
when the microgel has a poor affinity for the non-solvent.
For instance, when polystyrene prepared by emulsion po-
lymerization and having a molecular weight of at least
10,000 is dissolved in methyl methacrylate, it is pre-
cipitated by small amounts of water. The microgel in
this case contains a high proportion of polystyrene and
therefore, it has a rather low affinity for the non-solvent
water. When this system is polymerized with the aid
of heat and a soluble peroxide, the water-in-ester emul-
sion undergoes a phase change at a certain stage of polym-
erization thereby resulting in a solid polymerization
product having a three-dimensional framework, similar
to a sponge, containing the non-solvent water throughout.
In these systems wherein water is utilized as the non-
solvent, the formation of a coherent mass is favored by
pH values lower than 5.
Due to the complexities of the relationship between
microgel and non-solvent, it is rather difficult to predict
in many cases whether the pores of the polymerization
product will be communicating or non-communicating.
In general, both types of pores are produced in the polym-
erization products obtained from water-in-oil emulsions
according to the present invention, since a wide range
of polarities can be imparted to all the materials used,
i.e., the solvent or constituent (a), the polymer or con-
stituent (b), and non-solvent or agent forming the dis-
persed phase (1). In general, a foam-like, predominantly
non-intercommunicating cell structure is obtained by tak-
ing care that the interfacial surface tension between the
polymer solution in the solvent monomer and the non-
solvent is higher than the interfacial surface tension be-
tween the solvent monomer and the non-solvent alone.
Likewise, if a predominantly coherent plastic is desired,
the interfacial surface tension between the polymer solu-
tion in the solvent monomer and the non-solvent is pref-
erably lower than the interfacial tension between the sol-
vent monomer and the non-solvent alone.
As stated hereinabove, there may be added, if re-
quired, to the monomer constituent (a) and the emulsify-
which may be an organic compound of low molecular
weight that is not copolymerizable with the constituent
(a) and/or an organic compound of high molecular
weight that is not copolymerizable with the constituent
(a) and/or an organic compound of high molecular
weight that is copolymerizable with the constituent (a)
provided said compounds are soluble in constituent (a)
and are not separated or precipitated from said solution
at the phase boundary by the agent forming the inner
phase (1).
Suitable compounds of low molecular weight of the
above mentioned type are, for instance, esters of lower
alcohols with lower carboxylic acids or dicarboxylic
acids, such as dibutyl phthalate and dimethyl adipate.
These compounds can serve as plasticizers for the final
porous plastics.
Suitable non-copolymerizable compounds of high mo-
lecular weight as mentioned above are in particular homo-
polymers and copolymers which are free of hydrophilic
groups as, for instance, bulk or precipitation polymers of
styrene or vinylchloride, which has been prepared by
using organic peroxides as polymerization initiators.
Such polymers not only affect the properties of the final
plastic such as its elasticity, hardness, and inflammability,
but also the stability and other properties of the emul-
sion during its polymerization.
Other suitable copolymerizable substances of high
molecular weight useful as constituents (c) are in particu-
lar homopolymers and copolymers which are free of hy-
drophilic groups but still contain vinylidene groups.
Examples of such substances are copolymerization prod-
ucts of styrene and butadiene. Such compounds are ad-
vantageously used to produce final products with particu-
larly good electrical properties. The water-in-oil emul-
sions to be used in the process according to the present
invention are preferably prepared in the following man-
ner: The constituents (a), (b), and, if required, (c)
forming the continuous phase (2) are mixed to form a
solution whereupon the aqueous agent forming the dis-
persed phase (1) is slowly added to said solution while
stirring and/or shaking so as to form an emulsion.
Thereby, care must be taken that the resulting water-in-
oil emulsion is not converted into an oil-in-water emul-
sion. In some cases it may be necessary to prepare the
water-in-oil emulsion in another sequence of steps from
its constituents. Thus it is possible first to mix the con-
stituent (a) or the solvent of the continuous phase (2)
with the aqueous agent or the non-solvent forming the
dispersed phase (1) and thereafter to add the constituent
(b) or the polymer or, if required, the constituents (b)
and (c) of the continuous phase (2). Usually the emul-
sions according to the present invention are prepared
under atmospheric pressure and at room temperature.
However, if desired, it is also possible to operate at higher
or lower pressure and/or at higher or lower temperature.
The water-in-oil emulsions according to the present in-
vention contain the constituents forming the continuous
phase (2) and the aqueous agent forming the dispersed
phase (1) at a volume ratio of from about 1:0.25 to
about 1:20, preferably at a volume ratio of from 1:1 to
1:10. The weight ratio of the constituent (a) or solvent
of the continuous phase (2) to the constituent (b) or
the polymer of the continuous phase (2) is an general be-
tween about 1:0.0002 and about 1:0.2, preferably be-
tween 1:0.0001 and 1:0.1. However, it may also be in-
creased up to 1:4 if the constituent (b) is an organic
substance of a high molecular weight. The weight ratio
of the constituent (a) of the continuous phase (2) to the
constituent (c) of the continuous phase (2) may range
from 1:0 to 1:3.8 provided the weight ratio of the con-
stituent (a) to the sum of the constituents (b) and (c)
does not become smaller than 1:4.
In order to prepare porous plastics according to the
present invention the resulting water-in-oil emulsions are
ing polymer constituent (h) a further constituent (c) 75, nolymerized. Pnlvmerizatinn may hr initiated by admix-
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ing water-soluble as well as oil-soluble initiators, or ini-
tiators and activators, respectively, preferably at tem-
peratures between about 0? C. and about 100? C. If
initiators and activators are jointly used, it may be of
advantage that one of these compounds be water-soluble, 5
whereas the other one be soluble in oil. Suitable water-
soluble initiators or activators, respectively, are those
which are usually employed in emulsion polymeriza-
tion such as alkali formaldehyde sulfoxylate, persul-
fates and hydrogen peroxide or, respectively, sodium 10
hydrogen sulfite and cobalt chloride. Suitable oil-
soluble initiators or activators, respectively, are also
the conventional ones, such as benzoylperoxide, lauroyl
peroxide, ethyl methyl ketone peroxide, cyclohexanone
peroxide, and azo di-isobutyric acid nitrile, or, re- 15
spectively, N,N-di-isopropyt-p-toluidine or other tertiary
amines and cobalt naphthenate. The initiators and acti-
vators are employed in quantities of from 0.1% to 10%,
by weight, or, respectively, from 0.01% to 5%, by weight,
preferably from 0.5% to 4%, by weight, or, respectively, 20
0.1% to 4%, by weight, calculated for the total weight of
the emulsion. It may be of advantage for increasing the
"pot life" of the emulsion by dividing the same in two
portions and adding the initiator to the one of said por-
tions and the activator to the other one. Shortly before 25
use the two portions are combined to yield the porous
plastic.
The emulsions to which initiators or, respectively,
initiators and activators have been added polymerize and
harden depending upon their composition, the type and 30
quantity of initiator or, respectively, of initiator and
activator added, and the polymerization temperature,
within a period of time ranging from a few minutes to
several hours and yield porous plastics, the pores of which
are filled with water, i.e., the aqueous dispersed phase 35
(1). The water diffuses in the course of time from the
resulting porous structures or it is eliminated therefrom
by a heat and/or pressure treatment. Although it could
be expected that, on polymerization of the above-de-
scribed water-in-oil emulsion, polymerization products 40
are obtained which contain the aqueous medium or non-
solvent forming the dispersed phase (1) in the plastic
structure in the form of fine droplets that are not inter-
connected with each other, the resulting porous plastics
have also numerous pores which are interconnected with 45
each other and are open at the surface of the plastic.
This phenomenon is probably due to the fact that the
water-in-oil emulsion becomes somewhat unstable during
the course of the polymerization, so that the individual
droplets of the dispersed phase cohere. This is in agree- 50
ment with the fact that relatively unstable water-in-oil
emulsions or emulsions which have been rendered un-
stable by the admixture of certain additives such as com-
pounds of acid reaction or compounds forming com-
pounds of acid reaction, respectively, for instance, am- 55
monium chloride, sulfuryl chloride, and p-toluene sul-
fonyl chloride yield in the course of their polymerization,
polymerization products with a pronounced coherence be-
tween the individual droplets of the aqueous agent form-
ing the dispersed phase (1).
As has been found, the amount of water added is of 60
considerable importance in the production of a finely
porous body on block polymerization of a water-in-oil
emulsion according to the present invention. The amount
of water required in order to produce a well-drying 65
product can readily be determined by simple preliminary
tests. In general said amount should not be less than
25%, by volume, of the total water-in-oil emulsion.
Preferably amounts of water ranging from 45% to 95%,
e.g. at least 50%, and more advantageously from 60% 70
to 90%, e.g. more than 66%, by volume, calculated for
the water-in-oil emulsion are used for carrying out the
process according to the present invention.
Drying of the resulting porous polymerized body is
considerably improved by employing, as emulsifiers, 75
polymers of high molecular weight which are in'oluble
or hardly soluble in water, as this has been mentioned
hereinabove in connection with the constituent (b).
Such polymers are used in amounts between about 0.1%
and about 2.5%, and preferably between about 0.3% and
about 1.2%, of the polymerizable portion of the mixture,
with the water-in-oil emulsion containing at least 50% of
said polymerizable organic liquid (a).
The preparation of stable water-in-oil emulsions con-
taining such large amounts of water results in the water
being dispersed in the form of spherical droplets having
a diameter between less than 1u, to approximately 50k.
The spherical shape of the droplets yields cells of highly
spherical form which impart to the final porous body an
extremely high resistance to compression and which show
when compared with foams of the same density obtained
by blowing with gases or vapors, a compressive strength
that is increased by more than 200%.
According to another embodiment of the present inven-
tion compounds capable of generating gases under the
polymerization and/or drying conditions, for instance, at
increased temperature or decreased pressure may be added
to the aqueous phase (1) or the continuous phase (2).
Such gas generation may be caused by decomposition of
said compound or by the transition of said compound
from the dissolved or liquid state into the gaseous state.
For instance, the aqueous phase (1) may contain com-
pounds which readily split off carbon dioxide, or relatively
readily volatile, water-soluble lipophobic compounds such
as carbon dioxide. The constituents of the continuous
phase (2) may contain, as blowing agent, relatively
readily volatile, hydrophobic substances, for instance,
halogenated hydrocarbons, such as 1,1-dichloro-2,2-di-
fluoro ethane. The blowing agent can be added to the
emulsion in a coventional manner in the course of its
preparation. The amount of blowing agent should not
exceed about 20%, by weight, and should preferably be
about 10%, by weight, of the total emulsion.
The water-in-oil emulsions as they are employed in the
process according to the present invention may contain
conventional additives as they are employed in the plastic
art, for instance, plasticizers, dyes and pigments, organic
and inorganic fillers, agents rendering the plastic thixo-
tropic, fireproofling agents as well as inorganic or organic
fibers, fabrics and woven textile materials. The process
and products according to the invention can be applied
for many products because, on the one hand, most of
the known polymerizable monomeric organic compounds
can be converted into plastics of known chemical com-
position and because, on the other hand, the properties
of the porous plastics, due to the starting monomers and
polymers used, are essentially the same as those of the
corresponding non-porous plastics. Therefore, it is pos-
sible for a person skilled in the art to predict approxi-
mately which properties the individual porous plastics of
known chemical composition will have. Hence, it is not
difficult for a person skilled in the art to select suitable
starting materials for the production of porous plastics
of predetermined properties.
In order to produce porous plastic articles according
to the process of the present invention, the water-in-oil
emulsion can be applied in the required thickness, for
instance, to workpieces, materials, and tools of various
types made from wood, metal, plastic, rubber, concrete,
brickwork, Qr the like. Coatings may be produced there-
from or sheets, plates, webs or foils, if care is taken, for
instance, by employing a mold release compound so that
the coating does not firmly adhere to the mold material.
The coatings and plates and the like bodies are heat in-
sulating and soundproof and, therefore, of particular im-
portance, for instance, in the building art as flooring, wall
and ceiling covering or facing or as supporting building
material of light weight. The sheets and foils with inter-
communicating cells are useful, for instance, as "brea-
thing" artificial leather, i.e., leather permeable to air
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or as "breathing" packing material, i.e., packing material
which is permeable to air, in particular, if fibers, fabrics
or woven textile material or organic materials are em-
ployed in the production of such articles. The properties
of the resulting artificial leather can be adjusted to those
of natural leather by adding hydrophilic fillers thereto.
Products obtained according to the process of the present
invention are also useful as cork substitute.
Furthermore, it is possible to use the water-in-oil
emulsions according to the present invention as adhesives
or to produce laminated bodies therefrom in which layers,
for instance, from the above-mentioned materials, alter-
nate with layers of porous plastic made from water-in-oil
emulsions. Shaped bodies of almost any shape, for in-
stance, flat and corrugated plates, sheets, buttons, struc-
tural sections, door frames, pipes, casings, containers,
shoe lasts can also be manufactured from such water-in-
oil emulsions according to techniques known per se in the
manufacture of synthetic resins. Thereby, it is often
advantageous to admix fibers and/or organic or inorganic,
if desired, expanded filler materials such as mica, lava,
pumice, and perlite. Thus, there can be obtained, de-
pending upon the proportion of fibrous materials to emul-
sion, fibrous articles impregnated with plastics or articles
reinforced with fibers, for instance, glass fibers. If filler
materials are employed, their amounts added may be not
only quite small, but also so large that they are the pre-
dominant component of the finished shaped article, for
instance, light building plates and that therein the plastic
material, it may be provided with a protective coating
scaling the cells.
Removal of the aqueous dispersed phase (1) after
polymerization from the resulting porous plastic is
achieved, for instance, by drying at elevated temperature,
in a vacuum, by compressing the plastic, or by allowing
it to stand in an air current whereby the water evaporates.
The resulting plastic articles may be rendered substan-
tially fireproof by adding fireproofing agents such as
chlorinated paraffins or water soluble salts such as am-
monium carbonate thereto.
The hardened plastic articles may be coated, for in-
stance, sprayed with lacquers or coated with metal or the
like foils applied thereto by an adhesive.
As stated above, the resulting plastic material can be
used for many purposes, for instance, for manufacturing
advertising and packing material, toys and household
goods, for interior decoration, shop windows, decoration
for fair stalls, lamps, furniture, signboards or billboards,
orthopedic devices, material for splinting bone fractures
and others.
The following examples serve to illustrate the present
invention without, however, limiting the same thereto.
Example I
Two parts, by volume, of styrene containing 2% lauroyl
peroxide as polymerization initiator, about 3% of poly-
styrene of a low intrinsic viscosity, and 0.3% of poly-
methacrylate are emulsified by stirring with one part, by
volume, of a mixture of 20% of ethanol and 80% of
water containing 0.0 1% of acetic acid.
The resulting viscous water-in-oil emulsion is poured
in a mold wherein it is polymerized and hardened at a
temperature of about 50? C. A solid porous mass, the
pores of which are filled with water-ethanol is obtained.
The liquid is subsequently evaporated from the pores
by standing in air.
Finely, porous filters for gases and liquids as well as sepa-
rators for storage batteries may also be produced by the
process according to the present invention. The electrical
resistance to the present invention. The inner electrical
resistance of such separators is particularly low, if they
are manufactured from emulsions containing inorganic
salts dissolved in the aqueous agent forming the dispersed
phase (1).
In place of fibrous materials such as glass fibers, or, re-
spectively, in addition thereto, there may be embedded
in the emulsion according to the present invention re-
inforcing elements such as metal. screens, perforated rub-
ber and plastic plates or sheets, and others.
The emulsions according to the present invention may
be polymerized in suitable molds, for instance, by casting.
In order to increase the rate of production of such cast
articles, a solid polymer either in the form of a powder
or in the form of a highly viscous solution, may be ob-
tained prior to the polymerization of the emulsion, thereby
increasing the rate of polymerization. Such polymer
powders or solutions can be added prior to or subsequent
to the emulsifying step. Preferred polymers are the
polymerization product of the used monomers, for in-
stance, polymethacrylate when using methacrylate as
constituent (a), polystyrene when using styrene as con-
stituent (a), etc.
Thus, an emulsion according to the present invention
which will polymerize very rapidly includes a solution
of an activator such as a tertiary amine,.an emulsifying
polymer in a polymerizable monomer, a non-solvent which
emulsifies with the latter two ingredients, and a solid
polymer mixed with a suitable amount of an initiator
such as lauroyl peroxide. Products made from a com-
position such as the one just mentioned will harden in a
relatively short time when heated to a sufficiently high
temperature. Furthermore, upon hardening, the mass
will be readily separable from the mold due to the fact
that water will act as a lubricant and mold release agent
on the surface of the cast mass.
When producing cellular plastic with predominantly
non-intercommunicating cells, it is possible to produce
structural building materials wherein the cells are filled
with dyestuffs or with agents protecting against ionizing
radiation, and the like. To prevent subsequent escaping
Example 2
One part, by volume, of methyl methacrylate contain-
ing 0.2% of polystyrene and 2.5% of methyl polymeth-
acrylate is stirred with two parts of an aqueous solution
of 0.55% of potassium persulfate, 0.1% of sodium sul-
fite, and 0.2% of acrylic acid which is adjusted to a pH
between 8.0 and 9.0 by the addition of ammonia. The
resulting water-in-oil emulsion is heated to a temperature
between 70? C. and 80? C. for about half an hour and
poured on a plate or in a mold which is also maintained
at a temperature between 70? C. and 80? C. After half
an hour to two hours, polymerization and hardening is
completed and an opaque plastic sheet or molded article
is obtained which contains water in finely dispersed most-
ly non-intercommunicating droplets.
Example 3
One part, by volume, of styrene containing 3% of poly-
vinyl acetate, 5% of dioctyl phthalate, and 1.5% of
cumen peroxide is vigorously shaken with one part of
a mixture of ethanol and water (2:1, by volume) which
contains 0.05% of disodium saccharate and 0.01% of fer-
rous sulfate FeSO4 and has a pH of about 9.0. The
resulting water-in-oil emulsion is then heated to a tem-
perature of 60-70? C. while stirring. After the emulsion
becomes thick and creamy, it is poured on a plate which
is also held at,a temperature of about 70? C. A plastic
sheet is obtained containing mostly non-comr?,.:nit ing
droplets of the methanol-water mixture. It is own up
to a foam-like material by heating to a temperature above
130? C.
Example 4
70 One part, by volume, of a mixture containing 2 parts
of acrylonitrile and 1 part of vinylidene chloride, which
mixture contains 1% of polystyrene and 1.5% of poly-
methacrylate is emulsified by stirring with one part of
and diffusion of the cell contents from the cellular elastic 7a of glucose. 0.05% of ferrous sulfate. and 0_t % of sodium
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13
ethylene diamine tetra-acetate, said aqueous solution be-
ing of neutral reaction. After heating the mixture to
40? C. while stirring continuously for about ten minutes,
the resulting water-in-oil emulsion is poured on a plate
and set in a warm place. A milky plastic sheet is ob-
tained, which can be transformed into a foam-like ma-
terial by slowly heating the same at a temperature above
170? C. for some time. When the volume of the plastic
sheet does not increase any more, the resulting copolymer
is cooled rapidly to form a stable foam-like sheet.
Example 5
0.6 part, by weight, of styrene containing, in solution
2% of lauroyl peroxide and 2% of polystyrene and one
part, by weight, of a water-ethanol mixture (3:1) are
filled in an autoclave provided with a stirring device.
Gaseous butadiene is then introduced until 0.4 part, by
weight, thereof are absorbed. This mixture is then heat-
ed to 35? C. until the pressure decreases to about atmos-
pheric pressure. The autoclave is then opened, and the
resulting water-in-oil emulsion is filled in warm molds.
After about half an hour, polymerization and hardening
is completed. The molds are opened and the resulting
porous copolymers are dried in a warm air-stream.
Example 6
In 92.5 g. of methacrylic acid methyl ester as constit-
uent (a) of the compounds of the continuous phase (2)
there are dissolved 5 g. of polystyrene produced by emul-
sion polymerization in the presence of persulfate as con-
stituent (b) of the components of the continuous phase
(2) and 3.5 g. of a 50% benzoylperoxide paste. 1.7
g. of dimethyl-p-toluidine and 500 g. of water which
forms the dispersed phase (1) are added to said solution
while stirring vigorously. The resulting water-in-oil
emulsion is stirred at a temperature of 50? C. until a
homogeneous [cast] casting mass is formed which is
14
Example 9
In a mixture consisting of 80 g. of methyl methacry-
late and 20 g. of ethylene glycol di-methacrylate as con-
stituent (a) of the components forming the continuous
phase (2) there are dissolved 1.8 g. of dimethyl-p-tolui-
dine and 2.5 g. of a copolymerization product of 25% of
vinyl acetate and 75% of methyl methacrylate produced
by emulsion polymerization in the presence of persulfate
as a first portion of the constituent (b) of the components
forming the continuous phase (2). The solution is vig-
orously stirred for 15-20 minutes together with 80 g.
of poly-methyl methacrylate as a second portion of said
constituent (b) with the addition of 150 cc. of water
as the component of the dispersed phase (1). After ad-
dition of 2 g. of benzoylperoxide dissolved in 15 cc, of
ethyl methacrylate, the resulting water-in-oil emulsion
is then applied to a glass fiber fleece which is impregnated
therewith by enclosing it between two foils and press-
ing. Hardening is effected by heating at a temperature
of 50? C. for 10 minutes to 15 minutes. A porous plastic
plate reinforced by glass fibers is obtained thereby. The
water contained therein is evaporated by heating at a tem-
perature between 25? C. and 30? C. within about 24
hours.
Example 10
In a mixture consisting of 90 cc. of styrene and 10 cc.
of acrylonitrile as constituent (a) of the components
forming the continuous phase (2) there are dissolved
5 cc. of a 60% solution of methyl isobutyl ketone per-
oxide, 2 g. of polystyrene obtained by emulsion polym-
erization in the presence of persulfate as a first por-
tion of the constituent (b) of the components forming
the continuous phase (2) and 1 cc. of a 10% solution
of cobalt naphthenate. 100 cc. of the resulting solution
are mixed with 100 cc. of water as the component of
the dispersed phase (1) while stirring, until a water-in-
oil emulsion is formed. 100 g. of polymethyl meth-
acrylate as a second portion of said constituent (b) are
added to said emulsion. The mixture is poured into a
mold and polymerized at a temperature between 60? C.
and 70? C. A molded body of a porous polymerization
product is obtained from which the pore-forming water
is evaporated by heating at a temperature of 20-25? C.
for several hours.
poured into molds and polymerized at a temperature of
50? C. Porous plastic articles are obtained containing
water in finely dispersed form. The water can be elim- 40
inated on heating at a temperature of 60? C.
Example 7
In 100 cc. of styrene as constituent (a) of the compo-
nents of the continuous phase (2) there are dissolved 2 g.
of polystyrene produced by emulsion polymerization in
the presence of persulfate as constituent (b) of the com-
ponents of the continuous phase (2), 5 cc, of a 60% solu-
tion of methyl isobutyl ketone peroxide and 0.3 cc. of a
10% solution of cobalt naphthenate. 60 cc. of said solu-
tion are added to 40 cc. of a mixture composed of 93 cc.
the dispersed phase (1). The mixture is stirred until a
water-in-oil emulsion is formed. The emulsion is polym-
erized in a mold at a temperature between 70? C. and
90? C. A porous plastic article is obtained from which
the components of the dispersed phase (1) can be elim-
inated by heating at a temperature between 60? C. and
70? C.
Example 8
100 cc. of methyl methacrylate as constituent (a) of
the components of the continuous phase (2) are added
to 1.6 g. of dimethyl-p-toluidine and then mixed with 100
g. of polymethyl methacrylate as constituent (b) of the
components of the continuous phase (2) in which 2 g.
of benzoylperoxide are finely dispersed. The mixture is
stirred together with 200 cc. of a mixture of 89 cc. of
water and i l cc. of isopropanol which mixture forms the
dispersed phase (1) until a water-in-oil emulsion is
formed. The emulsion is then polymerized in a mold
,at a temperature between 40? C. and 50? C. for 10 min-
utes to 15 minutes. A porous shaped body is obtained
from which the aqueous dispersed phase can be expelled
Example 11
To a mixture consisting of 65 g. of an unsaturated poly-
ester of the acid number 40 prepared from maleic acid,
phthalic acid, and propylene glycol at a molar ratio
of 2:1:3.3 as constituent (b) of the components forming
the continuous phase (2) and 35 g. of styrene as con-
stituent (a) of the components forming the continuous
phase (2) there are added 2 g. of benzoylperoxide and,
thereafter, slowly 100 cc. of water as component forming
the dispersed phase (1). The mixture is vigorously stirred
at a temperature of 10? C. until a water-in-oil emulsion
is formed. The emulsion is mixed with 0.18 -g. of di-
methyl-p-toluidine, poured on a glass plate to form a
layer of the desired uniform thickness, for instance, be-
tween 1 mm. and 15 mm. and polymerized and hardened
by heating at a temperature of 30? C. for 10 minutes.
The water can be evaporated from the resulting porous
plates by heating at a temperature between 80? C. and
100? C.
Example 12
65 g. of the unsaturated polyester described in Exam-
ple 11 as a first portion of the constituent (b) of the
components forming the continuous phase (2) as well as
1.5 g. of a copolymerization product of the acid number
10 prepared from styrene and acrylic acid as a second
portion of said constituent (b) are dissolved in 65 g. of
(a) A mixture of diallyl phthalate and styrene at a
ratio of 1:3, by weight, or
(b) In 65 g. of allylchloride, or
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15
(c) In 65 g. of vinylacetate.
The compounds mentioned under
hereinabove are the constituents (a)
of the continuous phase (2).
(a), (b), and (c)
of the components
To each of these solutions there are added 100 cc.
of water as component of the dispersed phase (1) after
the addition of 2 g. of benzoylperoxide. The mixtures
are then emulsified by stirring vigorously. Each of the
resulting emulsions is mixed with 0.18 g. of dimethyl-p-
toluidine, poured on a glass plate to form layers of uni-
form thickness, and polymerized and hardened at tem-
peratures of 60-70? C. Porous plastic sheets and plates
are obtained thereby.
Example 13
A prepolymerization product of sirupy consistency as
constituent (b) of the components forming the continu-
ous phase (2) as it is obtained from 70 g. of methyl meth-
acrylate, which still contains monomeric methyl methac-
rylate as constituent (a) of the components forming the
continuous phase (2) is thoroughly mixed with 16.5 g.
of ethylene glycol di-methylacrylate, 4.0 g. of a paste
containing 50% of benzoylperoxide, and 10.0 g. of poly-
yinylchloride powder as constituent (c) of the compo-
nents forming the continuous phase (2). The mixture
is stirred with 100 g. of water as component forming the
dispersed phase (1) until a water-in-oil emulsion is
formed. The emulsion is allowed to stand for some time
for the purpose of de-aeration, whereafter 1.5 g. of di-
methyl-p-toluidine are added. It is spread in the desired
thickness, for instance, of 5 mm. to 10 mm. onto a fiat
surface. The resulting coating is polymerized at a tern-
perture of 60? C. for 10 minutes to 15 minutes. The
water is allowed to evaporate by standing at a tempera-
ture of 20? C.
Example 14
To a mixture consisting of 65.0 g. of the unsaturated
polyester described in Example 11 as constituent (b) of
the components forming the continuous phase (2) and
35.0 g. of styrene as constituent (a) of the components
forming the continuous phase (2) there are added 4.0 g.
of a paste containing 50% of benzoylperoxide as well
as 5.0 g. of polyvinylchloride powder as constituent (c)
of the components forming the continuous phase (2).
The resulting mixture is stirred together with 150 g. of
water as component forming the dispersed phase (1) until
a water-in-oil emulsion is formed. After its de-aeration
it is mixed with 30.0 g. of styrene and 0.8 g. of dimethyl-
p-toluidine, poured into molds, and polymerized and
hardened at a temperature of 20? C. A porous shaped
body is obtained from which the water is eliminated by
Example 15
A mixture is prepared from 35.0 g. of styrene, 25.0 g.
of isoprene, both being the constituents (a) of the com-
ponents forming the continuous phase (2), 60 g. of the
unsaturated polyester described in Example [6] 11 to
which Z.0 g. of benzoyl peroxide and 3.0 g. of triethanola-
mine are added to cause salt formation, said polyester salt
being the constituent (b) of the components forming the
continuous phase (2). The mixture is stirred together with
0.5 g. of dimethyl-p-toluidine and 80.0 g. of water as
component forming the dispersed phase (1) until a water-
in-oil emulsion is formed. Said emulsion is poured into
molds and is polymerized and hardened at 25 ? C. The
water is eliminated from the resulting porous shaped
article by heating at a temperature of 100? C.
Example 16
product from diallyl phthalate as constituent (b) of the
components forming the continuous phase (2). The mix-
ture is stirred together with 75.0 g. of water as component
forming the dispersed phase (1) until a water-in-oil emul-
sion is formed. The resulting emulsion is poured into
molds at a temperature of 50? C. and is polymerized.
Thereafter, the water is eliminated from the resulting
porous shaped bodies by heating at 100? C.
Example 17
To 93.0 g. of methyl methacrylate as constituent (a)
of the components forming the continuous phase (2)
there are added 5.0 g. of polystyrene produced by emul-
sion polymerization in the presence of persulfate, said
polystyrene being the constituent (b) of the components
forming the continuous phase (2), 2.0 g. of benzoyl
peroxide, 1.5 g. of dimethyl-p-toluidine and 100.0 g. of
a copolymerization product powder as filler as it is ob-
tained from 40 parts of styrene and 60 parts of the un-
saturated polyester described in Example 11. The mix-
ture is stirred with 150 g. of water as component form-
ing the dispersed phase (1), until a water-in-oil emul-
sion is formed. The emulsion is poured into molds and
polymerized and hardened at a temperature of 50? C.
The water is eliminated from the obtained porous shaped
bodies by heating to 100? C.
Example 18
10 g. of benzoylperoxide are dissolved in 500 g. of an
unsaturated polyester as described in Example 11 and
167 g. of styrene. 600 g. of water are slowly and grad-
ually added to said solution at 5-10? C. while stirring
until a white, creamy water-in-oil emulsion is formed.
A solution of 0.8 g. of dimethyl-p-toluidine in 100 g. of
styrene is stirred into said emulsion. The resulting fluid
emulsion is cast into plate molds in a thickness of about
5 mm. The mold is exposed in a water bath to a tem-
perature of 50? C. The cast resin polymerizes and
hardens within about 10 minutes to 15 minutes. The
water is removed from the porous plastic plates by heat-
ing to 100? C. The resulting plates have a density of 0.6.
Example 19
In place of styrene as used in Example 18, there is em-
ployed the same amount of methyl methacrylate while
the other components, catalysts, emulsifying procedure,
polymerization conditions, and removal of the water
proceed in the same manner as described in said Example
18. A finely porous molded article of a density of 0.6
is obtained.
It may be mentioned that water-soluble protective
colloids and surface-active agents must not be present
in the emulsions because such protective colloids and sur-
55 face-active agents would prevent formation of water-in-
oil emulsions as they are required in accordance with
the present invention.
The amount of non-solvent or component forming the
dispersed phase, i.e., of water or an aqueous liquid, is
60 chosen so that it corresponds to the desired total pore
volume and thus permits exact adjustment of said pore
volume. Although the resulting porous plastic bodies
are of considerable porosity, they still show smooth or
bright surfaces depending upon the mold walls.
65 The use of water as pore-forming component has con-
siderable advantages. It prevents excessive overheating,
even when the polymerization proceeds strongly exo-
thermically, especially when using rapid activators. The
polymerization heat can be dissipated more readily. Thus
70 it is possible to produce molded bodies of large size with-
A mixture consisting of 75.0 g. of diallyl phthalate and out any excessive expansion of the polymerization prod-
25.0 g. of methyl methacrylate, both being the constituent uct. The volume of the resulting plastic body varies
(a) of the components forming the continuous phase only slightly with respect to the starting volume of the
(2) is mixed with 2.0 g. of benzoylperoxide, 1.5 g. of water-in-oil emulsion. Shrinkage is insignificant. The
dimeth __.!a__, 1__ 1 -- _-- _1...1:1., Ie .. ,1 f .., the molds or
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from surfaces on which they were cast due to the forma-
tion of a water film or of water vapors.
As stated above, the breathing activity of plates, sheets,
coatings, foils made according to the present invention
is excellent. The same is tnie with respect to their sound- 5
absorbing and heat-insulating properties. The new plas-
tics have very good elasticity properties and exhibit all the
other working and processing advantages of plastics over
other materials such as wood. Due to their fine porosity
they can readily be drilled or nailed. They are especially 10
valuable as leather substitute. The preferred leather sub?
stitute material is composed of the porous polymeriza-
tion product of styrene or methyl methacrylate with an
unsaturated polyester as constituent (b) of the continuous
phase (2).
Of course, many changes and variations may be made
in the composition of the various components of the
water-in-oil emulsions, in their polymerization, the re-
moval of the dispersed phase (1) therefrom and the like
18
sisting of water and aqueous solutions of water-
soluble alcohols, lower organic acids, lower alka-
nones, alkali metal salts, and magnesium salts, said
aqueous medium forming the aqueous dispersed
phase, said aqueous solutions containing at least about
25% by weight, of water,
(2) as dispersion medium, an organic liquid contain-
ing
(a) a polymerizable organic liquid selected from
the group consisting of a polymerizable com-
pound having at least one ethylenically unsah.-
rated group [,a polymerizable compound having
at least one group of the formula
-C-c1I=uIl-c--1
in accordance with the principles set forth herein and in 20
the claims annexed hereto.
I claim:
1. A method of producing solid materials having a
plurality of droplets dispersed therein, which method
comprises forming a stable water-in-oil emulsion com- 25
posed of water, methyl-methacrylate, as the oil phase,
and polystyrene having a molecular weight of at least
10,000 as the emulsifier, and polymerizing the methyl-
acrylate to form polymethylmethacrylate without break-
ing the dispersed nature of the emulsion, thereby forming 30
solid polymethylmethacrylate having a plurality of water
droplets dispersed therein.
2. A method of producing solid materials having a
plurality of droplets dispersed therein, which method
comprises forming a stable water-in-oil emulsion com- 35
posed of water, styrene, as the oil phase, and polystyrene,
as the emulsifier; and polymerizing the styrene to form
polystyrene without breaking the dispersed nature of the
emulsion, thereby forming a solid plastic material having
a plurality of water droplets dispersed therein.
3. A method of producing solid materials having a
plurality of droplets dispersed therein, which method
comprises forming a stable water-in-oil emulsion com-
posed of water, a mixture of styrene and acrylonitrile, as
the oil phase, and polystyrene, as the emulsifier; and
polymerizing the mixture of styrene and acrylonitrile to
form a copolymerization product therefrom without
breaking the dispersed nature of the emulsion, thereby
forming a solid plastic material having a plurality of
water droplets dispersed therein.
4. A method of producing solid materials having a plu-
rality of droplets dispersed therein, which method com-
prises forming a stable water-in-oil emulsion composed
of water, styrene, as the oil phase, and an unsaturated
and copolymerizable mixtures thereof, said
polymerizable organic liquid forming the oil
phase; and
(b) a substantially water-insoluble polymeric
compound being soluble in said polymerizable
organic liquid, said compound being selected
from the group consisting of substantially water-
insoluble polymerization products, [substan-
tially water-insoluble polycondensation prod-
ucts, substantially water-insoluble unsaturated
polyesters obtained from unsaturated polycar-
boxylic acids and polyhydric alcohols] and mix-
tures thereof, said polymeric compounds con-
taining hydrophilic groups in an amount insuffi-
cient to essentially increase their solubility in
water, said polymeric compound forming the
emulsifying agent on contact with said aqueous
medium;
and polymerizing the polymerizable organic liquid in said
water-in-oil emulsion to form the respective polymeriza-
tion product without breaking the dispersed nature of the
emulsion, thereby forming a solid plastic material having
a plurality of water droplets dispersed therein.
7. A process for the production of porous plastics,
which process comprises forming a stable water-in-oil
emulsion containing
,(1) an aqueous medium selected from the group con-
sisting of water and an aqueous solution, said aque-
ous medium being the agent forming the dispersed
phase, said aqueous solution containing at least
about 25%, by weight, of water, and
(2) as dispersion medium, an organic liquid contain-
ing
(a) a polymerizable organic liquid selected from
the group consisting of a polymerizable organic
compound and at least two such organic
compounds being co-polymerizable with each
other;
(b) at least one organic compound being co-
polymerizable with said polymerizable organic
liquid (a), said organic compound being soluble
in and being contained in solution by said po-
lymerizable organic liquid (a) and being at
least partly separated from said solution at the
phase boundary by addition thereto of said
aqueous medium (1), thereby acting as an
emulsifier; and
(c) at least another organic compound-being sol-
uble in and contained in solution by said po-
lymerizable organic liquid (a) and not being
separated from said solution at the phase
boundary by the addition of said aqueous medi-
um (1), said organic liquid (2) forming the
continuous phase,
polymerizing said water-in-oil emulsion in the presence
propylene glycol, as the emulsifier; and polymerizing the
styrene to form polystyrene without breaking the dis-
persed nature of the emulsion, thereby forming a solid
plastic material having a plurality of water droplets dis-
persed therein.
5. A method of producing solid materials having a
plurality of droplets dispersed therein, which method
comprises forming a stable water-in-oil emulsion com-
posed of water, styrene, as the oil phase, an unsaturated
propylene glycol, as the emulsifier, and polyvinylchloride
powder; and polymerizing the styrene to form polystyrene
without breaking the dispersed nature of the emulsion,
thereby forming a solid plastic material having a plurality
of water droplets dispersed therein.
6. A method of producing solid materials having a
plurality of droplets dispersed therein, which method com-
prises forming a stable water-in-oil emulsion composed
of
(1) an aqueous medium selected from the group con-
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19
of conventional polymerization initiators as well as con-
ventional polymerization activators without breaking the
water-in-oil emulsion, and, at least partly, removing the
aqueous medium (1) from the resulting porous plastic.
8. The process according to claim 7, wherein the re-
sulting water-in-oil emulsion contains at least 50%, by
volume, of water.
9. The process according to claim 7, wherein the re-
sulting water-in-oil emulsion contains more than 66%,
by volume, of water.
10. The process according to claim 7, wherein the
aqueous medium is an aqueous solution of an inorganic
salt.
11. The process according to claim 7, wherein the
spherical droplets of water contained in the resulting
water-in-oil emulsion have a diameter not exceeding 50g.
12. The process according to claim 7, wherein the
polymerizable organic liquid (a) is a compound selected
from the group consisting of styrene, an acrylic acid ester,
a methacrylic acid ester, and a mixture thereof.
13. The process according to claim 7, wherein the
organic compound (b) is an unsaturated polyester, the
free carboxyl groups of which are at least partly neutral-
ized by a compound of basic reaction.
14. The process according to claim 7, wherein fillers,
fibrous materials, and reinforcing agents are added to
the water-in-oil emulsion.
15. The process according to claim 7, wherein between
0.01% and about 15%, calculated for the polymerizable
organic liquid (a), of the water soluble preliminary con-
densation product of melamine and formaldehyde are
added to the water-in-oil emulsion containing a polym-
erizable vinyl compound as polymerizable organic liquid
(a) and an unsaturated polyester obtained from an un-
saturated dicarboxylic acid and a polyhydric alcohol as
emulsifying agent (b), said unsaturated polyester being
soluble in and dissolved by said polymerizable vinyl
compound.
16. The process according to claim 7, wherein between
about [0.05%] 0.1% and about 2.5%, calculated for
the polymerizable portion of the water-in-oil emulsion
of the emulsifying agent (b) consisting of a polymeriza-
tion product of high molecular weight being soluble in
the water-insoluble polymerizable ethylenically unsatu-
rated organic liquid (a), and at least 50% of said po-
lymerizable organic liquid (a) are present in said water-
in-oil emulsion.
17. The process according to claim 16, wherein be-
tween about 0.3% and about 1.2%, calculated for the
polymerizable portion of the water-in-oil emulsion of
the emulsifying agent (b) consisting of a polymerization
product of high molecular weight being soluble in the
water-insoluble polymerizable ethylenically unsaturated
organic liquid (a), and at least 50% of said polymerizable
organic liquid (a) are present in said water-in-oil
emulsion.
18. The porous plastic produced by the process of
claim 7.
19. A method of producing porous plastic shaped prod-
ucts, which method comprises forming a stable water-in-
oil emulsion composed of water, methylmethacrylate, as
the oil phase, and polystyrene having a molecular weight
of at least 10,000 as the emulsifier, shaping the emulsion
to the desired product, polymerizing the methylmeth-
acrylate to form poly methyl methacrylate without breaking
the dispersed nature of the emulsion, thereby forming the
solid shaped polymethylmethacrylate product having a
plurality of water droplets dispersed therein, and at least
partly removing the water from the resulting product.
. 20. A method of producing porous plastic shaped prod-
ucts which method comprises forming a stable water-in-
oil emulsion composed of water, styrene as the oil phase
and polystyrene as the emulsifier, shaping the emulsion
to the desired product, polymerizing the styrene to form
polystyrene without breaking the dispersed nature of the
emulsion, thereby forming the solid shaped plastic prod-
uct having a plurality of water droplets dispersed there-
in, and at least partly removing the water from the result-
ing product.
21. A method of producing porous plastic shaped prod-
ucts, which method comprises forming a stable water-in-
oil emulsion composed of water, a mixture of styrene and
acrylonitrile as the oil phase, and polystyrene as the emul-
sifier, shaping the emulsion to the desired product, polym-
erizing the mixture of styrene and acrylonitrile to form
a copolymerization product therefrom without breaking
the dispersed nature of the emulsion, thereby forming the
solid shaped plastic product having a plurality of water
droplets dispersed therein, and at least partly removing
the water from the resulting product.
22. A method of producing porous plastic shaped prod-
ucts, which method comprises forming a stable water-in-
oil emulsion composed of water, styrene as the oil phase,
and an unsaturated polyester obtained from maleic acid,
phthalic acid, and propylene glycol as the emulsifier, shap-
ing the emulsion to the desired product polymerizing the
styrene to form polystyrene without breaking the dis-
persed nature of the emulsion, thereby forming the solid
shaped plastic product having a plurality of water drop-
lets dispersed therein, and at least partly removing the
water from the resulting product.
23. A method of producing porous plastic shaped prod-
ucts, which method comprises forming a stable water-in-
30 oil emulsion composed of water, styrene as the oil phase,
an unsaturated polyester obtained from maleic acid,
phthalic acid, and propylene glycol as the emulsifier, and
polyvinylchloride powder, shaping the emulsion to the
desired product, polymerizing the styrene to form poly-
33 styrene without breaking the dispersed nature of the
emulsion, thereby forming the solid shaped plastic prod-
uct having a plurality of water droplets dispersed therein,
and at least partly removing the water from the resulting
product.
24. A method of producing porous plastic shaped pro-
ducts, which method comprises forming a stable water-
in-oil emulsion composed of
(1) an aqueous medium forming the aqueous dispersed
phase and
(2) as dispersion medium, an organic liquid containing
(a) a polymerizable organic liquid forming the
oil phase and
(b) an emulsifying agent,
shaping the emulsion to the desired product, polymeriz-
ing the polymerizable organic liquid in said water-in-oil
emulsion to form the respective polymerization product
without breaking the dispersed nature of the emulsion,
thereby forming the solid shaped plastic product having
a plurality of water droplets dispersed therein, and at least
partly removing the water from the resulting product.
25. A method of producing porous plastic shaped prod-
ucts, which method comprises forming a stable water-in-
oil emulsion composed of
(1) an aqueous medium forming the aqueous dispersed
phase and
(2) as dispersion medium, an organic liquid containing
(a) a polymerizable organic liquid forming the oil
phase and
(b) an emulsifying agent,
the water content of said water-in-oil emulsion being be-
70 tween about 25% and about 95%, shaping the emulsion
to the desired product, polymerizing the polymerizable
organic liquid in said water-in-oil emulsion to form the
respective polymerization product without breaking the
dispersed nature of the emulsion, thereby forming the
75 solid shaped plastic product having a plurality of water
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droplets dispersed therein, and at least partly removing
the water from the resulting product.
26. The porous plastic shaped product produced by the
[process, method of claim 24.
27. A method in accordance with claim 24 wherein
said emulsifying agent (b) includes an unsaturated poly-
ester, the free carboxyl groups of which have at least
partly been converted to salts.
28. A method in accordance with claim 24 wherein said
emulsion contains reinforcing fibers.
29. A method in accordance with claim 24 wherein said
emulsion is shaped in a mold having the shape of a useful
object and polymerized therein.
30. A method in accordance with claim 24 wherein said
aqueous medium is present in said emulsion in the form
of droplets having a diameter not exceeding 50?.
31. A method in accordance with claim 24 wherein said
dispersion medium includes a water-insoluble organic
compound having more than one polymerizable ethyl-
enically unsaturated group.
32. A method in accordance with claim 24 wherein
said emulsifying agent includes a polymeric compound
which has hydrophilic groups and will form a turbid
phase or precipitate when a solution of said compound in
said dispersion medium is contacted with said aqueous
medium, the amount of said hydrophilic group being in-
sufficient to. increase the solubility of said polymeric
compounds to the extent that they become essentially
soluble in water.
33. A method in accordance with claim 24 wherein said
aqueous phase is a solution of ethanol in water, said
emulsifying agent (b) is polystyrene, said polymerization
is continued until the water-in-oil emulsion is hardened
to a solid shaped plastic product having a plurality of
droplets of said solution dispersed therein in contiguous
intercommunicating pores, and at least part of the solu-
tion is removed by exposing said product to air at room
temperature.
34. A method of producing solid materials having a
plurality of droplets dispersed therein, which method
comprises forming a stable water-in-oil emulsion corn-
posed of
(1) an aqueous medium selected from the group eon-
sisting of water and aqueous solutions of water-
soluble alcohols, lower organic acids, lower
alkanones, alkali metal salts, and magnesium salts
said aqueous medium forming the aqueous dispersed
phase, said aqueous solutions containing at least about
40% by weight, of water,
(2) as dispersion medium, an organic liquid contain-
ing
(a) a polymerizable organic liquid selected from
the group consisting of a polymerizable corn-
pound having at least one ethylenically tun-
saturated group and copolymerizable mixtures
thereof, said polymerizable organic liquid form-
ing the oil phase; and
(b) a substantially water-insoluble polymeric
compound' being soluble in said polymerizable
organic liquid, said compound being selected
from the group consisting of substantially water-
insoluble polymerization products, and mixtures
thereof, said polymeric compounds containing
hydrophilic groups in an amount insufficient to
essentially increase their solubility in water, said
polymeric compound forming the emulsifying
agent on contact with said aqueous medium;
and polymerizing the polymerizable organic liquid in said
water-in-oil emulsion to form the respective polymeriza-
tion product without breaking the dispersed nature of the
emulsion, thereby forming a solid plastic material having
a plurality of water droplets dispersed therein.
35. A method in accordance with claim 34 wherein
said emulsifying agent (b) includes an unsaturated poly-
22
ester, the free carboxyl groups of which have at least
partly been converted to salts.
36. A method in accordance with claim 34 wherein
said emulsion contains reinforcing fibers.
37. A method in accordance with claim 34 wherein
said emulsion is shaped in a mold having the shape of a
useful object and polymerized therein.
38. A method in accordance with claim 34 wherein
said aqueous medium is present in said emulsion in the
form of droplets having a diameter not exceeding S0?.
39. A method in accordance with claim 34 wherein
said dispersion medium includes a water-insoluble organic
compound having more than one polymerizable ethyleni-
cally unsaturated group.
40. A method of producing solid materials having a
plurality of droplets dispersed therein, which method
comprises forming a stable water-in-oil emulsion coni-
posed of
(1) an aqueous solution of water-soluble magnesium
salt forming the aqueous dispersed phase, said aque-
ous solution containing at least about 40% by weight,
of water,
(2) as dispersion medium, an organic liquid contain-
ing
(a) polymerizable organic liquid selected from
the group consisting of a polymerizable com-
pound having at least one ethylenically unsatu-
rated group and copolymerizable mixtures
thereof, said polymerizable organic liquid form-
ing the oil phase; and
(b) substantially water-insoluble polymeric com-
pound being soluble in said polymerizable or-
ganic liquid, said compound being selected from
the group consisting of substantially water-in-
soluble polymerization products, and mixtures
thereof, said polymeric compounds containing
hydrophilic groups in an amount insufficient to
essentially increase their solubility in water,
said polymeric compound forming an ernulsi-
and polymerizing the polymerizable organic liquid in
said water-in-oil emulsion to form the respective polym-
erization product without breaking the dispersed nature
of the emulsion, thereby forming a solid plastic material
having plurality of water droplets dispersed therein.
41. A method of producing solid materials having a
plurality of droplets dispersed therein, which method
comprises forming a stable water-in-oil emulsion com-
posed of
(1) an aqueous solution of water-soluble alkali metal
salt forming the aqueous dispersed phase, said aque-
ous solution containing at least about 40% by weight,
of water,
(2) as dispersion medium, an organic liquid contain-
(a) polymerizable organic liquid selected from
the group consisting of a polymerizable com-
pound having at least one ethylenically unsatu-
rated group and copolymerize mixtures thereof,
said polymerizable organic liquid forming the
oil phase; and
(b) substantially water-insoluble polymeric com-
pound being soluble in said polymerizable or-
ganic liquid, said compound being selected from
the group consisting of substantially water-in-
soluble polymerization products, and mixtures
thereof, said polymeric compounds containing
hydrophilic groups in an amount insufficient to
essentially increase their solubility in water, said
polymeric compound forming an emulsifying
agent on contact with said solution;
and polymerizing the polymerizable organic liquid in said
water-in-oil emulsion to form the respective polynreriza-
75 tion product without hreakine the dispersed nature of the
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emulsion, thereby forming a solid plastic material having
a plurality of water droplets dispersed therein.
42. A method of producing solid materials having a
plurality of droplets dispersed therein, which method
comprises forming a stable water-in-oil emulsion com-
posed of
(1) an aqueous solution of water-soluble lower al-
kanone forming the aqueous dispersed phase, said
aqueous solution containing at least about 40% by
weight, of water,
(2) as dispersion medium, an organic liquid contain-
ing
(a) polymerizable organic liquid selected from the
group consisting of a polymerizable compound
having at least one ethylenically unsaturated
group and copolyrnerizable mixtures thereof,
said polymerizable organic liquid forming the
oil phase; and
(b) substantially water-insoluble polymeric com-.
pound being soluble in said polynrerizable or-
ganic liquid, said compound being selected from
the group consisting of substantially water-in-
soluble polymerization products, and mixtures
thereof, said polymeric compounds containing
hydrophilic groups in an amount insufficient to
essentially increase their solubility in water, said
polymeric compound forming an emulsifying
agent on contact with said solution;
and polymerizing the polymerizable organic liquid in said
water-in-oil emulsion to form the respective polymeriza-
tion product without breaking the dispersed nature of the
emulsion, thereby forming a solid plastic material having
a plurality of water droplets dispersed therein.
43. A method of producing solid materials having a
plurality of droplets dispersed therein, which method
comprises forming a stable water-in-oil emulsion com-
posed of
(1) an aqueous solution of water-soluble lower or-
ganic acid forming the aqueous dispersed phase, said
aqueous solution containing at least about 40% by
weight, of water,
(2) as dispersion medium, an organic liquid contain-
ing
(a) polymerizable organic liquid selected from the
group consisting of a polymerizable compound
having at least one ethylenically unsaturated
group and copolymerizable mixtures thereof,
said polymerizable organic liquid forming the
oil phase; and
(b) substantially water-insoluble polymeric com-
pound being soluble in said polymerizable or-
ganic liquid, said compound being selected from
the group consisting of substantially water-in-
soluble polymerization products, and mixtures
thereof, said polymeric compounds containing
hydrophilic groups in an amount insufficient to
essentially increase their solubility in water, said
polymeric compound forming an emulsifying
agent on contact with said solution;
and polymerizing the polymerizeable organic liquid in
said water-in-oil emulsion to form the respective polym-
erization product without breaking the dispersed nature
of the emulsion, thereby forming a solid plastic material
having a plurality of water droplets dispersed therein.
44. A method of producing solid materials having a
plurality of droplets dispersed therein, which method
comprises forming a stable water-in-oil emulsion com-
posed of
(1) an aqueous solution of water-soluble alcohols
forming the aqueous dispersed phase, said aqueous
solution containing at least about 40% by weight,
of water,
,(2) as dispersion medium, an organic liquid contain-
ing
24
the group consisting of a polymerizable com-
pound having at least one ethylenically un-
saturated group and copolymerizable mixtures
thereof, said polynrerizable organic liquid form-
ing the oil phase; and
(b) substantially water-insoluble polymeric com-
pound being soluble in said polynrerizable or-
ganic liquid, said compound being selected
from the group consisting of substantially water-
insoluble polymerization products, and mixtures
thereof, said polymeric compounds containing
hydrophilic groups in an amount insufficient to
essentially increase their solubility in water, said
polymeric compound forming an emulsifying
agent on contact with said solution;
and polymerizing the polymerizable organic liquid in said
water-in-oil emulsion to form the respective polymeriza-
tion product without breaking the dispersed nature of the
emulsion, thereby forming a solid plastic material having
a plurality of water droplets dispersed therein.
45. A method of producing solid materials having a
plurality of droplets dispersed therein, which method com-
prises forming a stable water-in-oil emulsion composed
of
(1) water forming the aqueous dispersed phase;
(2) as dispersion medium, an organic liquid contain-
ing
(a) polymerizable organic liquid selected from
the group consisting of a polymerizable com-
pound having at least one ethylenically unsat-
urated group and copolyrnerizable mixtures
thereof, said polymerizable organic liquid form-
ing the oil phase; and
(b) substantially water-insoluble polymeric com-
pound being soluble in said polymerizable or-
ganic liquid, said compound being selected
from. the group consisting of substantially water-
insoluble polymerization products, and mixtures
thereof, said polymeric compounds containing
hydrophilic groups in an amount insufficient to
essentially increase their solubility in water, said
polymeric compound forming an emulsifying
agent on contact with said water;
and polymerizing the polymerizable organic liquid in said
water-in-oil emulsion to form the respective polymeriza-
tion product without breaking the dispersed nature of the
emulsion, thereby forming a solid plastic material having
a plurality of water droplets dispersed therein.
46. The process according to claim 7 wherein said
aqueous solution contains at least about 40% by weight,
of water.
References Cited
The following references, cited by the Examiner, are
of record in the patented file of this patent or the original
patent.
UNITED STATES PATENTS
2,473,801
6/1949
Kropa.
2,505,353
4/1950
Fisk.
2,726,177
12/1955
Lew.
2,739,909
3/1956
Rosenthal.
2,843,556
7/1958
Moorman.
1,967,220
7/1934
Barret et al,
2,016,199
10/1935
Howard.
2,112,529
3/1938
Hazell.
2,120,935
6/1938
Groff.
2,220,685
11/1940
Myers.
2,327,968
8/1943
Ripper.
2,443,735
6/1948
Kropa.
2,533,270
1271950
Linkletter.
2,655,496
10/1953
Adams..
2,864,777
12/1958
Greenhoe.
2,912,399
11/1959
Bartl.
(Additional references on following page)
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 Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010056-5
27,444
25
UNITED STATES PATENTS
2,947,7.35 8/1960 Bartl.
3,206,441 9/1965 Von Bonin.
3,284,393 11/1966 Vanderhoff et al.
2,700,026 1/1955 Dibert ------------- 260-29.6
2,872,423 2/1959 Goldstein --------- 260-29.6
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558,970 1/1957 Belgium.
565,530 1/1958 Belgium.
763,396 12/ 1956 Great Britain.
26
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Wenning: Makromolekular-Chemie, 1956, pp. 196-
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U.S. C1. X.R.
117-126 GB, 132 C, 135.5, 138.8 UA, 161 K, 161 UZ;
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 Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010056-5
United States Patent Office
3,055,966
Patented Sept. 25, 1962
1 2
3,055,966
MICROPOROUS MATERIAL. SEPARATOR AND
METHOD OF MAKING SEPARATOR
Erik Gustav Sundberg, Nol, Sweden, assignor to Aktic-
bolaget Tudor, Stockholm, Sweden, a corporation of
Sweden
No Drawing. Filed Dec. 17, 1959, Ser. No. 860,111
Claims priority, application Sweden Dec. 20, 1958
10 Claims. (Cl. 136-146)
This invention relates to microporous plates and more
particularly to such plates which may be adventageously
used as separators or diaphragms between the electrodes
of electric batteries or accumulators.
One. requisite of a separator for an electric accumula-
tor is a high degree of microporosity to allow diffusion
of the electrolyte and free movement of ions. The pore
size of the separator must be small enough to prevent
conductive particles from the electrode plates from pene-
trating the separators and in that way causing shortcir-
cuiting between said electrode plates.
Other requisites are low, uniform and unchangeable
electrical resistance, good chemical resistance against the
powerful oxidizing attacks to which separators in electric
accumulators are exposed during excessive rates of charge
passes in one direction and in the opposite direction dur-
ing discharging, in consequence of which the above said
change in electric resistance arises. Suitable separators
should not only have a low, but also a constant or uni-
form resistance in both directions.
It is therefore an object of the present invention to pro-
vide a separator and a method for production thereof,
which will be of high microporosity, low -and unchange-
able internal resistance and yet contains pores of such a
smallness as to mechanically screen metallic particles
from the active material of the plate of one polarity from
another of opposite polarity.
Another object of the invention is to provide a separa-
tor that will have sufficient mechanical strength to main-
and discharge, and sufficient strength and toughness to
withstand handling and to maintain the shape of the
separator when wet.
The surface of a microporous sheet suitable as a separa-
tor.between electrode plates in an electric accumulator
should have a low friction coefficient and a good wearing
resistance and solidity in order not to become destroyed
through movement of the electrodes relative the separa-
tors. Such a movement, though with small amplitude,
occurs especially in batteries for traction type vehicles.
Additionally, increasing mechanical pressure is applied
to separators when tightly assembled in an accumulator
cell together with electrodes in consequence of the grow-
ing thickness of the latter during service.
The provision of satisfactory separators for electric
accumulators presents increasing problems primarily due
to recent advancements in the battery art. Wood sepa-
rators, which earlier have been successfully employed, are
in many cases unsuitable today because this type of sepa-
rator cannot be stored in dry condition and consequently
cannot be used in so-called dry charged batteries. More-
over, some ingredients in present day batteries, which are
found either in the electrolyte or in the active material,
have been found to cause disintegration of cellulose ma-
terial previously used as separators.
Microporous rubber separators have also been used
to some extent in the battery art. Such separators, how-
ever, have been found to be relatively fragile and in-
flexible and, additionally, show only poor wearing re-
sistance.
Separators consisting of cellulose fibers and impregnated
with different resins have also been used, but they have
poor porosity in consequence of which the internal elec-
tric resistance of a battery cell equipped with that type of
separator is undersirably high.
In recent years, separators made from different suitable
resinous materials have been tried. Also, many attempts
have been made to use polyvinylchloride as a material
for separators; however, the risk of chloride poisoning
from the batteries has prevented its wide acceptance for
general use. This previously used synthetic material
has, however, been of a polar type material which is less
desirable because of the fact that the condition of polar
substances is influenced by the ion flow, which causes a
tain shape during handling and when in a wet condition.
It is a further object of the invention to provide a
separator of the type described above that is highly re-
sistant to the oxidizing condition in a storage battery.
It is a still further object of the invention to provide
an improved method for the production of separators and
diaphragms for electric storage batteries and also for the
production of microporous sheet like material suitable
for making these separators.
Further objects will be apparent to those skilled in the
art from the following description and from the ap-
pended claims.
The microporous sheet material of this invention is
made of a non-polar polyolefine which is treated with an
inorganic salt, a swellable material, and a leaching liquid
30 to provide the microporosity.
The non-polar compounds have straight molecule chains
and are known as straight linked materials. Due to its
molecular construction such material is smooth and
separators made from such material have a low friction
35 coefficient, which in turn reduces the friction between elec-
trodes and separators. Polyethylene, polypropylene,
polybutylene and other polyolefines are examples of the
different kinds of non-polar materials that may be used.
The inorganic salt used may be sodium sulphate, potas-
40 sium sulphate, aluminum sulphate, or magnesium sulphate.
The swellable material may be starch, for example, and
the leaching liquid may be water or a suitable acid or lye
depending on what salts and what swellable material are
added to the polyolefine.
45 In a preferred embodiment of the present invention, a
microporous sheet material is made of 5 to 35% micro-
porous polyethylene, 45 to 85% inorganic material, and
1 to 20% starch. It is important that the amount of in-
organic salt be considerably larger than the amount of
50 organic expandable material. A specific example of the
composition is as follows:
Percent
Polyethylene ---------------------------------- 12
55 Sodium sulphate---------.---------------------- 78
Starch --------------------------------------- 10
In the first step of the process the polyethylene is pul-
verized and mixed with a levigated inorganic salt such as
80 sodium sulphate. Next a small amount of starch which
swells in a liquid is mixed in. In the mixture of fine
particles, the amount of leachable material is smaller
than the amount of the inorganic salt. Said inorganic
material constitutes mainly the pore former while the
65 advantage of said organic expandable material is that the
leaching of said inorganic salt is facilitated when the ma-
terial is brought into the form of a sheet and in this form
has been stabilized. Consequently, the main purpose of
said organic material is not to serve as a pore former in
70 itself, but to facilitate leaching of the inorganic salt.
change in the conductive resistance of said material In Aftpr 0- ni.lvprvprt ; -;.*..+~ 4....,o been mixed to
a Approved For Release 2009/04/10: CIA-RDP81-00120R000100010056-5 o a flattened out
 Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010056-5
3 4
slsarw in a so called calendar roller mill to the desired and a swellable material, subjecting said mixture to
conditions sufficient to cause said inorganic salt to form
the mix in powder form is first passed pores in said polymer material, and leaching the remnants
Irclct t'tp
,
ttw+.qb prating rollers at which time the polyethylene of said inorganic salt from said mixture, said salt rem-
it at ksst partially melted and sinters together, where- 5 nants being made readily accessible to the leaching liquid
s,l+s ttse resulting mat passes through cold rollers and by the swelling of said swellable material.
tlxte "km tin its definitive thickness and stabilizes in the 2. A method of manufacturing a microporous parti-
drured d.mcnvon. Lion wall for use between electrodes in an electric storage
hest. the material is exposed to a leaching process in battery comprising the steps of mixing resinous poly-
s-h..h the organic material, starch, swells and thereby to olefine polymer material together with an inorganic salt
faca::atcs the solution of the inorganic salt in water, for and a swellable material, treating said mixture until the
csa:*sp!c. Thereafter, the material may be dried and resinous particles are sintered together, bringing the sin.
tut into the desired shape. If desired, the material may tered mass into sheet form, and leaching the remnants of
tv trcatcd with sulphuric acid or the like to decompose ? said inorganic salt from said mixture, the swellable ma-
anJ teach the starch out before drying. 15 terial enlarging during said leaching to facilitate removal
the nneroporous polyethylene sheet thus formed is of said inorganic salt.
suitable as a separator material owing to its resistance 3. A method of manufacturing a microporous parti-
aga,axt osidizing attacks. Further, since the material has tion wall for use between electrodes in an electric storage
a Low frtclion coefficient, a thorough wearing is not to battery comprising the steps of mixing resinous poly-
be apprehended, due to the friction between electrode 20 olefine polymer material together with an inorganic salt
plates and separators. Moreover, a separator in accord- and a swellable material, forming said mixture into
ancc s?ith the present invention is flexible, has a high sheet form, and treating the sheet-like body in a liquid
sohd+ty, and its raw material costs and cost of production until the swellable material swells and the inorganic salt
site low. Alw characteristic of the separator is the fact is dissolved.
th.+t active particles that may come from the electrode 25 4. A method of making a microporous non-polar poly-
plates will not stick to its surface. In that way, the olefine storage battery electrode partition wall comprising
porosity of said separator is not reduced, and therefore the steps of mixing an inorganic salt and a swellable
an ad-.antageous result is obtained with respect to the material with polyolefine to form a substantially ho-
internal resistance and capacity of a storage battery cell. mogeneous mixture, forming said mixture into a sheet-
l'utthcr, through the treatment of calendering, an orienta- 30 like body, and treating said body with a leaching liquid,
lion of the molecule chains in the plane of the produced said inorganic salt forming pores in said polyolefine ma-
sheet is obtained, thereby improving the mechanical terial and said swellable material swelling sufficiently
stability and friction coefficient. Sometimes it may be to enable said salt to be removed from said mixture after
advantageous to undertake a pre-orientation of the mole- said pore formation.
cule chains in the material by extrusion, and to use said 35 5. A method as defined in claim 4 wherein said swell-
pre-oriented materials as initial material when calender- able material is starch.
ing to sheet shape. 6. In a method of manufacturing a microporous ma-
1 he leaching procedures may also be varied as appears terial from a resinous thermoplastic polymeric material
suitable with respect to the composition of the material containing a dispersion of particles of an inorganic salt,
mixture and the salts in said mixture. Sometimes it may 40 the step of adding a swellable material to said plastic to
be advantageous to undertake the leaching procedure or enhance leaching of said inorganic salt by swelling suffi-
a part of it during the electrolysis, at which time the sheet ciently to render said inorganic salt readily accessible to
material passes between electrodes in a suitable electro- a leaching liquid.
lyre, in order to hasten the redeeming of said inorganic 7. A composition of matter for use in making a micro-
salt. 45 porous material causing about 5 to 35% a resinous thermo-
According to another method of production, the mix- plastic polymeric material, 45 to 85% inorganic salt,
lure of material of powdered or pulverized material is and about 1 to 20% starch, said starch being added in
distributed in a layer of even thickness to a belt or the sufficient amount to facilitate leaching of said inorganic
like and is brought to sinter together so that a relatively salt from said composition of matter by swelling when
thick and a loosely joined mat is formed, which by roll- 5o exposed to a leaching liquid and thereby rendering said
ing. preferably during influence of heat, is reduced to the inorganic salt readily accessible to a leaching liquid.
desired thickness and is stabilized, as by cold rolling. 8. A composition of matter for use in making a micro-
Instead of rolling, one or more pressure procedures, as porous sheet-like material comprising a non-polar resin-
by plane plates, may be used. ous polyolefine polymer, an inorganic salt, and a swell-
7he invention may be embodied in other specific forms 55 able material capable of swelling upon contact with a
without departing from the spirit or essential character- solvent liquid when applied to said mixture to leach said
isti4s thereof. The present embodiments are therefore inorganic salt from said composition of matter.
to be considered in all respects as illustrative and not 9. The composition as defined in claim 8, wherein said
restrictise, the scope 'of the invention being indicated by polyolefine is selected from the group consisting of poly-
the appended claims rather than by the foregoing descrip- 60 ethylene, polypropylene, and polybutylene.
tion, and all changes which come within the meaning 10. The composition as defined in claim 8, in which the
and range of equivalency of the claims are therefore in- inorganic salt is selected from the group consisting of
tended to be embraced therein. aluminum sulphate, sodium sulphate, potassium sulphate,
What is claimed and desired to be secured by United and magnesium sulphate.
States Letters Patent is: 65 veoe.e.,..o. !`sod :...r,a
lion wall for use between electrodes in an electric storage UNITED STATES PATENTS
battery comprising the steps of mixing a resinous poly- 2,138,712 Saffert ----------------- Nov. 29, 1938
oletinc polymer material together with an inorganic salt 2,676,929 Duddy ----------------- Apr. 27, 1954
Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010056-5
 ? +
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Aug. 24, 1965
H. J. STRAUSS 3,202,733
METHOD OF MAKING MICROPOROUS ?LLS?IC
Filed Varch 6. 1962
F%g. /
Fig2
2
13 . F/g. .
1
Approved For Release 2009/04/10: CIA-RDP81-00120R000100010056-5
 Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010056-5
3.282.733
METHOD OF MAKING MICROPOROI$
PLASTIC
Howard 3. Strauss, Elkins Park, Pa., asslenor to ESS-
Reeves Corporation. a corporation of Delve
Filed Afar. 6, 1562, Ser. No. 177,795
13 Claims (CL. 264-49)
This invention relates to a method of making micro-
porous. plastics and has for an object the preparation of
micropcwous plastics having softening points significantly
higher than 300' F., such as fluorocarbon resins.
The preparation of plastics having softening points sig-
nificantly higher than 300' F. has not been prepared in
microporous form by an extractive process due. to the dif-
ficulty of dispersing a pore-.forming agent in a plastic hav-
ing such an extremely high melting point.. The plastics in
the group generically known as fluorocarbon resins have
such high melting points. Fluorocarbon resins, as well
known in the art, include such plastic materials as poly-
tetrafluoroethylene (sold commercially under the trade-
mark Teflon) and a polychlorotrifluoroethylene (sold
commercially under the trademark Kcl-F) and equiva-
lents, such as described in Modern Plastics Encyclopedia
3,202,733
Patented Aug. 24, I9(t5
metal impregnated with a fine dispersion of plastic Ia
water
FIG. 4 is a view similar to FIGS. 2 and 3 showing the
FIG. 5 is a view similar to FIG. 4 showing the fused
microporous plastic after the removal of the metal by
dissolution; and
FIG. 6 is a diagrammatic view showing a layer of
microporous plastic having a layer of non-porous plastic
laminated or otherwise secured to one side thereof.
In making a microporous plastic in accordance with
the present invention, it is first necessary to prepare a
microporous form of the desired shape and of a material
which is capable of being heated to the fusion tempera=
ture of the plastic. For convenience the present inven-
tion will be described in connection with the method of
producing microporous Teflon although it is to be under-
stood that this method is applicable to other microporous
plastic materials and particularly other microporous plas-
tic materials having softening points significantly higher
than 300' F. such as fluorocarbon resins.
In regard to Teflon, the fusion temperature is in the
order of 750' F. and thus the microporous form 10 of
FIG. I must be made of a material capable of being
heated to at least 750' F. Several materials for the
microporous form may be used, but a preferred material
and one which has been used by thee applicant to make
microporous Teflon is a sintered plaque of carbonyl
nickel. Other suitable materials for the microporous form
diagrammatically illustrated as sheet 10 in FIG. I are a
plaque of carbonyl iron and also plaques of various sin-
tered powdered metals. Carbonyl is used because is pro-
duces plaques of very low density. Other porous metal
forms may be used, such for example as porous steel, al-
though the density of the latter is substantially higher than
the density of carbonyl.
While the porous metal form 10 of FIG. I has been
shown in the form of a sheet, it is to be understood that
the porous metal form may be made in any desired shape
including tubular shape. After the porous metal form 10
has been made into the desired shape, it is impregnated
with an aqueous dispersion of the plastic. Such a dis-
persion of Teflon is available commercially under the
name Teflon 30, see pages 90-96 of "Fluorocarbons" by
Rudner. This is a fine dispersion of Teflon in water, i.e.,
very small particles of tetrafluoroethylene resin suspended
in water. The dispersion is a hydrophobic, negatively
charged colloid averaging about 0.5 micron in diameter.
It usually contains about 59-61 ?o by weight Teflon as
solids, and is stabilized with a non-ionic wetting agent.
The particle size of the Teflon is considerably smaller
than the pore ooenicg in the porous nickel plaque or
form 10. It is important that this relationship of pore
size be maintained when using other plastics or other
porous metal forms, i.e., the particle size of the plastic
must be smaller than the pore openings in the porous
metal forms. To provide this relationship, the ratio of
the average particle size of the metal powder to the aver-
age particle size of the p1 'stic should be about 10 to I or
greater. IR other words, with a Teflon dispersion the
particle size of the metal powder should have an average
diameter of five microns or more. If a smaller ratio were
used the impregnation would not be sufficiently uniform.
The n icroporous structure of the porous metal form
10 is shown on enlarged scale in FIG. 2. The metal
particles 11 of the form have been sectioned for metal
and the un-sectioned portions of FIG. 2 represent the
void areas.
In FIG. 3 it will be seen that the porous metal form 10
has been impregnated with a fine dispersion of the plas-
tic in water i.e. Teflon 30. The plastic has been indicated
Issue for 1961 and in the book entitled "Fluorocarbons," 25
by Rudner, published by Reinhold Publishing Corp., New
York (11.958).
The principal manner in which such plastic materials as
Teflon TFE (polytetrafluoroethylene) or Teflon FEE' (co-
polymer of tetrafluoroethylene and hexafluoropropylene) 30
have heretofore been made porous is by the sintering of
the particulate plastic after it has been laid down in the
form of a sheet. This prior process is difficult to carry
out properly, produces poor strength, non-uniform pore
structure and rather large pores which are unsuitable for
many purposes.
The present invention is directed to the method of pro-
ducing a truly microporous form of plastic by an extrac-
tive method which enables the size of the pore structure
to be accurately controlled an:; at the same time per-
mits the microporous plastic to be produced in substan-
tially any physical shape desired.
In accordance with the present invention, there is pro-
visaed a method of making microporous plastic including
the steps of impregnating a porous metal form with a fine
dispersion of the plastic in water and drying the form to
remove the water while leaving a residue of the plastic in
the pores of the metal form. The plastic impregnated
form is heated to a temperature and for a period of time
sufficient to fuse the plastic in the pores of the metal form
and the metal is thereafter removed from the plastic im-
pregnated form by dissolution thereby producing a micro-
porous plastic having a geometric shape corresponding to
the original porous metal form and having a pore struc-
ture corresponding in volume to the metal in the original
form plus the volume of the water which was removed by
drying.
The method is particularly adapted for making micro-
porous fluorocarbon resin which is particularly suited for
use as electrolytic diaphragms and corrosion-resistant
linings.
For a more detailed understanding of the invention and
for further objects and advantages thereof, reference is to
be had to the following description taken in conjunction
with the. accompanying drawings in which:
FIG. I is a diagrammatic view of a porous metal form
useful in practicing the method of the present invention;
FIG. 2 is a fractional view of a portion of FIG. I en-
larged many tines to show the porous metal structure of
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the form in FIG. 1;
FIG. 3 is a view similar to FIG. 2 with the porous
 Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010056-5
3,^,302,733
by the small dots 13 and combination with the water
fills the void areas between the nictal partkies 11. In
order to more thoroughly impregnate the metal form 19
with the Teflon 30 dispersion, the impregnation is assisted
by subjecting the impregnation operation to a high
vacuum, for example in & be order of 28" of mercury.
4
The present invention is partictdarly suited for making
electrolytic c a'hragms which are corrosion resistant and
have the des a-,-3 ,nicroporous characteristics. The pore
size of the re"u_ains microporous plastic may be controlled
in various w-aws. In the first place, the pore size may be
controlled by the pore structure of the porous metal form
10. Seccndiy. the pore size may be controlled by the
concentration of the Teflon dispersion. For example,
to provide &T-zw voids in the end product more water is
used in the d----r-ion. To provide smaller voids in the
end product. ic-ss water is used in. the dispersion. The
pore size man also be controlled by the number of im-
pregnations cf use porous metal form 10: the higher the
number of impregnations. the smaller the resulting pore
size in the end product. Lastly, the pore size in the end
product may be controlled by impregnating the form after
it has been simuercd so as to fill up some of the voids with
inert material Thus, the unsintered plastic or Teflon
will be preser.:' as a filler when the form is impregnated
after the sintraag operation.
While the present invention is applicable to various
uses where &,r entire Teflon structure is microporous,
it is also appi cable to uses where only one side of the
strucure is mice oporous, such as for example as in cor-
rosion resisters linings. In this latter application, it is
desirabla that one side of the corrosion resistant lining
be microporoszs so that it may be readily adhesively se-
cured to the ode of a metal container but the opposite
side or surface. of the Teflon lining should be solid or non-
30 rorous so as to prevent passage of the corrosive material
through the hthng. A product of this type is illustrated
in FIG. 6 where the porous Teflon surface is indicated
at 16 whereas the non-porous Teflon surface is indi-
cated at 17. To prepare a sheet such as illustrated in
35 FIG. 6 the microporous portion indicated as layer X
is produced is the foregoing manner described in con-
nection wit!. FIGS. 1-5. If a thin non-porous layer
of Teflon is desired on one side of the porous layer
X such thin rata-porous layer may be produced by coat-
40 ing the one sir3e with Teflon 30, drying the coating, and
then applying a second coating, followed by subsequent
drying and repeating the coating and drying opera-
tion until the desired thickness is obtained.
Where a re'atively thick non-porous coating of Teflon
43 is desired. at 17, this may be obtained by laminating a
solid Teflon sheet to the porous sheet X by pressing the
two sheets tote her and heating them to the fusion tem-
perature of Tzi'oa. In this cmbbodiment, the laminat-
ing step shoakl be performed when the microporous plastic
50 is in the form illustrated in FIG. 4, i.e., before the metal
has been rem sed. After the sintering or fusion of the
non-porous Tefan layer to the layer of Teflon and metal
og FIG. 4, the iarninated or fused sheet is then subjected
to the step of dissolution to remove the metal either
55 electrolytically or chemically in the manner described
above.
It is to be undestood that the invention is not limited
to the specific arrangements shown that changes and
modificattiores may be made within the scope of the
60 appended claims.
What is claimed is:
1. A methai of making microporous plastic having a
functional tcrr ;perature in excess of 500' F. comprising
the steps of ,impregnating a porous metal form with a
65 fine dispersion of the plastic in water, drying the form to
remove the wv'er while leaving a residue of the plastic
in the pores e the metal form, heating the plastic im-
pregnated forte to a temperature and for a period of
i0 time sufliciect to fuse the plastic in the pores of the
metal form, z nd removing the metal from the plastic
impregnated rc?r-,n by dissolution thereby producing a
mieroporot s a `:-Stic having a geometric shape correspond-
ing to the on final porous metal form and having pore
,.truc'tiire c?.~rr_~r,nnndin,. in' votnme to the metal in the
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Teflon 30 dispersion, it is carefully dried so as to elimi-
nate the water associated with the Teflon 30 dispersion
thereby leavng a residue of Teflon TFE in the pores of
the metal form 10. Thin residue is indicated at 13 in
FIG. 4. The drying operation is accomplished by heating
the impregnated metal form to a temperature within the
range of about 100' F. to 160' F. and substantially be-
low the boiling point of water to assure proper urstribu-
tion of residues.
As will be seen in FIG.- 4. the plain areas 14 represent
the voids resulting frorm the drying operation and these
voids 14 are of substantially less area than the on?inal
void areas in the porous; metal form 10 illustrated in
FIG. 2. After the metal -form 10 has been dried leaving
a porous structure inching metal particles 11 and a
residue of Teflon TFE as indicated in FIG. 4. the metal
form 10 is then subjected to temperatures and for a ocriod
of time which will fuse the Teflon. For exampi.:, the
Teflon will fuse when stsi;jected to a temperature in the
order of 750' F. for a riariod of about one hour. After
the Teflon has been fused, the pore structure of the im-
pregnated form 10 will continue to be similar to that
shown in FIG. 4, the essential difference being that the
Teflon is now in a fused smte.
After the fusion step the metal form 10 will include
continuous phases of metal. Teflon and air. In order to
be sure to expose the metal at the surfaces, the surface of
the impregnated form is prepared by light sanding such
as with a fine emery paper. The next step is to remove
the metal from the plastic impregnated form. This may
be accomplished either chemical or electrolytic dis-
solution. For example, with a nickel form, the nickel
may be removed by making the form an anode in a bath
of dilute sulphuric acid. A suitable electrolyte may have
a strength in the order of 10% sulphuric acid. A suitable
voltage across the electrodes may be in the order of two
volts D.C. The electrolyte may be changed when the
dissolution action slows ttup. Such electrolytic dissolu-
tion is.preferred since ere gas is produced. The nickel
may also he dissolved chemically, such as in a solution
of hydrochloric acid or a solution of hydrochloric acid
and nitric acid, the latter being known generally by the
term "aqua regia." This will dissolve the nickel in the
form 10 but hydrogen is produced and remains in the
pores of the form and slss down the action. Since the
metal or nickel phase is continuous, it can be completely
removed in the foregoing manner. leaving voids 15 and 14
which together represent The volume of the metal form
plus the volume of the water which was removed by the
drying operation. The voids 15 produced by dissolution
of the metal particles are !illustrated in FIG. 5 where it
will be noted that the metal particles 11 have been elimi-
nated from the microporonas form 10 and all that remains
is the Teflon structure 13. In this way a "negative" image
of the original pore structure of the metal plaque, FIG. 2,
modified by the voids 1414, produced by the evaporation
of water after the original impregnation, is obtained.
The variations that are inherent in this process will
permit the preparation of microporous plastic having
functional temperatures in excess of 500' F. As pointed
out above, the m croporsn s plastic need not be prepared
in sheet form, but rather can be prepared in any form
in which porous metals can be made. The technology of
making carbonyl iron plaques is such that practically any
physical shape can be ma .1e and the physical form of the
resultant microporous plastic will of course reflect the
geometrical properties of the metal plaque or form from
wh;.?h it war rn.cte
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5 6
original metal form plus the volume of the water which one side thereof non-porous a.mpnsing the steps of im-
was removed by drying. , pregnating a porous metal form with a fine dispersion of
2. The method according to claim 1 wherein the step the plastic in water, drying the form to remove the water
or impregnating is performed under a high vacuum. while leaving a re kiuc of the plastic in the pores of the
3. The method according to claim 1 wherein the metal metal form. heating the plastic impregnated form to a
is removed from the plastic impregnated form by chemi- temperature and for a period of time sufficient to fuse
cal dissolution. the plastic in the pores of the metal form, removing the
4. The method according to claim I wherein the metal from the plastic impregnated form by dissolution
metal is removed from the plastic impregnated form by thereby producing a microporous plastic having a geo-
electrolytic dissolution. I;t metric shape corresponding to the original porous form
5. The method according to claim I wherein the plastic and having pore structure corresponding in volume to the
impregnated form is heated to substantially above room metal in the original metal form plus the volume of water
temperature before removing the metaL which was removed by drying. and thereafter coating one
6. A method of making microporous fluorocarbon side of the microporous plastic with a fine dispersion of
resin having a functional temperature in excess of 500' the plastic in water, drying the coated side of the micro-
F. comprising the steps of impregnating a porous metal porous plastic to remove the water while leaving a residue
form with a fine dispersion of the fluorocarbon resin of the plastic in the pores of the side of the microporous
in water, drying the form to remove the water while plastic, and repeating the last two steps of the foregoing
leaving a residue of the fluorocarbon resin in the pores method until the desired thickness of non-microporous
of the metal form, heating the fluorocarbon resin im- 30 plastic is obtained on the selected side of the microporous
pregnated form to the fusion temperature of the fluoro- plastic.
carbon resin and for a period of time sufliiient to fuse 12. A method of making a microporous plastic having
the fluorocarbon resin in the porous and metal form, a functional temperature in excess of 500' F. and having
and removing the metal from the fluorocarbon resin a non-porous side thereof comprising the steps of impreg-
impregnated form by dissolution thereby producing a 25 nating a porous metal form with a fine dispersion of the
microporous fluorocarbon resin having a geometric shape r plastic in water, drying the form to remove the water
corresponding to the original porous metal form and while leaving a residue of the plastic in the pores of the
having pore structure correspon'ing in volume to the metal form, laminating a solid sheet of plastic to one
metal in the original metal forn_ plus the volume of side of the plastic impregnated form by placing the solid
water which was removed by drying. 00 sheet against the side of the plastic impregnated form
7. The method according to claim 6 wherein the step under pressure, beating the plastic impregnated form and
of impregnating is performed undo a high vacuum, the laminated solid sheet of porous plastic to a tempera-
11. The method according to claim 6 wherein the porous ture and for a period of time sufficient to fuse the plastic
metal form comprises a plague of carbonyl nickel hav- in the pores of the metal form, and removing the metal
ing a predetermined geometic shape. 35 from the plastic impregnated form by dissolution thereby
9. The method according o claim 6 wherein the porous producing a microporous plastic having a geometric shape
metal form comprises a plaque of carbonyl iron having a corresponding to the original porous form and having
predetermined geometric shape. pore structure corresponding in volume to the metal in
10. A method of making a predetermined geometric the original metal form plus the volume of the water
shape of microprous F iiytetrafluoroethylene having a 40 which was removed by drying and one side of the micro-.
functional temperature in excess of 500? F. comprising porous plastic having laminated thereto a solid non-porous
the steps of impregnating a porous metal form having the sheet of the plastic material.
desired geometric shape with a fine dispersion of the 13. The method according to claim 1 wherein the ratio
polytetrafluoroethylene in water while subjecting the im- of the average particle size of the metal to that of the
pregnation step to vacuum, drying the form to remove 4,, average particle size of the plastic is in the order of 10:1
the water while leaving a residue of the polytetrafluoro- or greater.
ethylene in the pores of the metal form, heating the poly- References Cited by the Examiner
tetrafloroethylene impregnated form to a temperature
r a time sufliicent to fuse polytetrafluoroethylene UNITED STATES PATENTS
d f
o
an
r'0
in the pores of the metal form, and removing the metal
from the polytetrafluoroethylene impregnated form by
dissolution thereby producing a microporous polyietra-
to
d'
eometric shape correspon mg
h
h
l
aving g
ene
y
fluoroet
the porous metal form and having pore structure cor- 66
responding in volume to the metal in the original metal
form plus the volume of the water which was removed by
241
623
2
12/52
Met al. _______ 156-155 X
et
MacKay
5
,
,
2,62,249
6/58
5 X
156-1
Goss
a l
3,009,207
11/61
RomesburgetaL
FOREIGN PATENTS
552,914
2/58 Canada.
drying. ROBERT F. WHITE, Primary Examiner.
11. A method of making a microporous plastic having
a functional temperature in excess of 500? F. and having 60 MORRIS LIEBMAN, Examiner.
Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010056-5
 Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010056-5
United States Patent Office 3,235,409
Patented Feb. 15, 1966
2
The preferred pH range during irradiation is from about
3 to about 6.
3,235,409
IRRADIATED BATTERY SEPARATOR
MEMBRANES
George K. Greminger, Jr., and Garth H. Beaver, both of
Midland, Mich., assignors to The Dow Chemical Com-
pany, Midland, Mich., a corporation of Delaware
No Drawing. Filed July 14, 1961, Ser. No. 123,995
2 Claims. (Cl. 136-146)
The present invention concerns ion-permeable mem-
branes that are advantageously adaptable for a variety
of uses wherein the passage of ions through a water-insolu-
ble but bibulous barrier is of interest. Particularly,
the invention relates to membranes of certain water-solu-
ble mixed cellulose ether derivatives insolubilized with
high energy ionizing radiation.
In the prior art, A. A. Miller, in United States Letters
Patent No. 2,895,891, teaches how water-soluble cellulose
ethers can be cross-linked with high energy radiation
in the presence of water to provide materials useful for
fibers, tapes, fabrics, electrical insulation and the like.
It has now been discovered that certain mixed by-
droxyalkyl methyl cellulose ethers in the form of an
aqueous sot are cross-linked with controlled amounts of
high energy ionizing radiation to provide water-insoluble,
yet bibulous, membranes that are exceptionally useful in
ermeability is of particular in-
in ion
r
h
li
i
p
e
e
ons w
cat
app
terest. One such application involves the use of such The layers of the aqueous sot are formed by any con-
membranes in the construction of primary galvanic dry venient means. The actual forming operation that may
cells. The problems encountered in this art and the 30 be employed most effectively with any particular sot is,
objects to be attained with improved separators for use to some extent, dependent upon the amount of cellulose
in battery construction are set forth by N. C. Cahoon in ether solids present in the sot. With lower amounts,
United States Letters Patent No. 2,534,336. say from about 1 up to 20 percent by weight of the cellu-
In this reference, it is proposed to prepare separators lose ether, the forming of the layers to be irradiated is
from membranes of water-soluble alkyl cellulose ethers 33 effectively accomplished by casting a film on an inert sup-
which have been either insolubilized with a polybasic porting surface of any desired shape. Sols that contain
acid or coated on an inert, water-insoluble but ion-perme- larger amounts of the cellulose ether solids are sufficiently
able, supporting substrate to provide a composite sepa- viscous or thick that they can be extruded to provide a
rator stock. layer in any continuous shape. When employed as
Later teachings in the art are directed to improve sepa- 40 battery separators, the membranes should have, for effec-
rators prepared from specific alkyl cellulose ethers, e.g., tive operation, a uniform thickness in the dry state within
methyl cellulose ethers (United States Letters Patent No. the range from about 1 up to 4 mils.
2,551,799) and alkali-soluble methyl cellulose ethers con- While the irradiated membranes of the invention are
taining from 10 to 20 percent methoxyl content (United usually employed as the sole component of the battery
States Letters Patent No. 2,900,433). As will be demon- 45 separator, it is possible to prepare such membranes on
strated in the following, the membranes of the present an ion-permeable, water-insoluble support backing. For
invention achieve a highly surprising improvement over example, a two component separator is prepared by cat-
other irradiated cellulose ethers and separators heretofore endering or coating a thin paper support with the aqueous
taught or suggested by the prior art. sol as described above and thereafter subjecting the coated
In accordance with the invention, a superior ion- 50 support to high energy radiation in the manner that the
permeable, bibulous membrane is prepared by subjecting sot alone would be irradiated.
a layer of an aqueous sot or dispersion containing from In a representative operation illustrative of the inven-
about 1 up to about 50 percent by weight of certain by- tion, a water dispersion containing 7 percent by weight
droxyalkyl methyl cellulose ethers to a dose of high energy 65 of a hydroxypropyl methyl cellulose ether having a
radiation of from about 0.25 up to 5 megarads. The methoxyl degree of substitution within the range from
wet bibulous layer thus treated can be utilized for an 1.68 to 1.82 and a hydroxypropyl degree of substitution
ion-permeable but water-insoluble membrane as produced wiithin the range from 0.17 to 0.3 was prepared with the
or it can be subsequently dried at moderate temperatures conventional hot and cold water technique. The dry
.for more convenient handling and manipulation. Upon cellulose ether powder was first mixed with about 0.2
rewetting, the dried hydrophilic layer can absorb several 60 of the required amount of water at a temperature of
times its weight of water to provide an ion-permeable about 85? C. and after thus wetting the powder, the re-
membrane comparable to that initially obtained upon mainder of the required water was added as cold water.
irradiation of the sot. The pH of the sot was adjusted to 5.0 with a small amount
then ccntri-
Operable cellulose ethers have a'hydroxyalkyl degree of 86 of hydrochloric acid.
order to remove The aqueous sot was as the result-
substitution (D.S.) for each glucose residue moiety of
about 0.05 and about 0.5 and a methyl degree of sub- ing clear sot was cast into a 35 mil layer on a flat stain-
stitution for each glucose residue moiety of about 0.9 less steel plate. This layer was irradiated with a 2 mev.
to about 2. The hydroxyalkyl groups contain from 2 (million electron-volt) electron beam supplied from a
to 4 carbons: Van de Graaff accelerator having a total power capacity
If necessary, the pH of the sot is adjusted to within 70 of 0.5 kilowatt. The beam current employed was 225
tb? ^^^?- - ?'- - ' ^? ^1-t a nrinr to lv-in,r irr;,dtated_ microamperes and the total dose applied was 1.5 megarads.
Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010056-5
Ionizing radiation that can be employed in the practice
of the present invention may range from about 50,000
up to 20,000,000 electron volts or more depending upon
the thickness of the sot layer and the concentration of
the cellulose ether therein. The dosage employed is
specified in millions of rads. A rad is defined as 100
ergs of radiation energy absorbed per gram of material
exposed. Examples of sources for such radiation are
neutrons or mixed neutron and gamma radiation such
as can be obtained in atomic reactors. Preferably, from
the standpoint of convenience of operation, the high
energy ionizing radiation source is an electron accelerat-
ing device. Ordinarily when employing high energy elec-
trons, the dosage rate is expressed as beam current amper-
age. In the practice of the invention, beam currents in
the range from 25 to 5,000 microamperes can be
employed.
20 Membranes of any practicable shape or thickness up
to several inches can be prepared in accordance with the
invention. The particular needs of the application for
such membranes under consideration will determine the
effective and optimum thicknesses. The actual thick-
25 ness of the membrane, dry or wet, will be determined
in part by the concentration of the cellulose ether in the
 Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010056-5
3,235,409
4
l
bl
u
se ethers such as water-so
Subsequently, the irradiated layer was dried under hydroxyalkyl methyl celluloe
ambient room conditions and removed from the stainless hydroxybutyl methyl cellulose ethers and hydroxyethyl
steel plate. The dry membrane thus prepared was 1.5 methyl cellulose ethers can be employed in place of the
mils thick. above hydroxypropyl methyl cellulose ethers to achieve
A second membrane was prepared in an identical man- 5 comparable results. Likewise, similarly improved re-
ner except that the radiation dose utilized was 3.0 sults are achieved when magnesium can anodes are sub-
rucgarads stituted for the zinc cans employed above.
The above-prepared bibulous membranes were cut What is claimed is:
into suitable shapes and incorporated into newly fabri- 1. A primary galvanic dry cell comprising a soluble
cated galvanic cells as separators between the electrolytic 10 metallic anode, an insoluble cathods, a depolarizer mix, an
paste and soluble metallic anode. Standard zinc cans electrolyte and a separator between said soluble metallic
and carbon rods were employed for the anode and anode and said deploarizer mix, said separator being com-
cathode, respectively. The electrolytic paste contained posed of a water-insoluble, bibulous membrane having
2 parts by weight of an electrolyte and 5 parts by weight a thickness from about 1 up to about 4 mils prepared by
of a depolarizer mix. The electrolyte consisted of an 15 subjecting a layer of an aqueous sol having a pH within the
aqueous solution containing 150 grams per liter of am- range from about 2 to about 8 and containing from about
monium chloride, 90 grams per liter of zinc chloride and 1 up to 50 percent by weight of a hydroxyalkyl methyl eel-
0.5 grarn per liter of mercuric chloride. The depolarizer lulose ether wherein the hydroxyalkyl group contains from
mix consisted of 86 percent by weight manganese oxide, 2 to 4 carbon atoms and the ether is characterized by a
4.2 percent by weight ammonium chloride and 9.8 per- 20 hydroxyalkyl degree of substitution for each glucose resi-
cent by weight carbon black. due moiety from about 0.05 to about 0.5 and methyl de-
The assembled batteries were tested by discharging gree of substitution for each glucose residue moiety from
them 5 minutes per day in a circuit having an impedance about 0.9 to about 2 to a dose of high energy ionizing
of 4 ohms. Assuming a 0.75 volt cut-off point as deter- radiation of from about 0.25 up to 5 megarads.
mining the useful life of a cell, the lives of the batteries 25 2. A primary galvanic dry cell comprising a soluble
were thus ascertained. The battery that contained the metallic anode, an insoluble cathode, a depolarizer mix,
separator that had been treated with 1.5 megarads had an electrolyte and a separator between said soluble metal-
a useful life of 372 minutes. The battery having a sepa- lie anode and said depolarizer mix, said separator being
rator of the second prepared membrane had a useful life composed of a water-insoluble, bibulous, composite mem-
of 325 minutes. 30 brane prepared by coating an ion-permeable water-in-
In other operations similar to those of the foregoing, soluble support with an aqueous sol having a pH from
additional batteries were prepared wherein the separators about 2 up to about 8 and containing from about 1 up
were of kraft paper and commercial battery separator to about 50 percent by weight of hydroxyalkyl methyl
paper. The useful lives of otherwise identical, batteries cellulose ether wherein the hydroxyalkyl groups contain
prepared with each of the above separator membranes 35 from 2 to 4 carbon atoms and the ether is characterized
were ascertained in accordance with the above test pro- by a hydroxyalkyl degree of substitution for each glucose
cedures. Batteries prepared with the kraft and com- residue moiety of about 0.05 to about 0.5 and a methyl
mercial battery papers had lives of 17 and 195 minutes, degree of substitution for each glucose residue moiety
respectively. of about 0.9 to about 2, and thereafter subjecting the com-
Additional batteries were prepared in identical manner 40 posite to a dose of high energy ionizing radiation of from
to that above except that the battery separator employed about 0.25 up to about 5 megarads.
was a membrane obtained by irradiating a 7 percent
aqueous sol of a methyl cellulose ether. A 2 percent References Cited by the Examiner
ueous solution of the methyl cellulose ether exhibited UNITED STATES PATENTS
a
q
a viscosity of 25 centipoises at 20? C. Different radia- 45
megarads with the thickness of the dried irradiated film
varying from 1 to 2 mils. The maximum battery life
achieved with the separators thus prepared was 272
minutes.
2,882,331
4/1959
Zenczak 136-146
2,895,891
7/1959
Miller ------------- 204-154
2,942,057
6/1960
Huber et al. _-____-__ 136-146
WINSTON A. DOUGLAS, Primary Examiner.
JOHN R. SPECK, JOHN H. MACK, Examiners.
Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010056-5
 ti
Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010056-5
United States Patent Chace
3,427,206
Patented Feb. 11, 1969
i . 2
3.427,206
SEPARATOR FOR ALKALINE CELLS
Paul Scardaville. East Northport, Thomas Wetherell, New
York, and Lawrence Sears, Woodside, N.Y., assignors
to RAI Research Corporation, Long Island City, N.Y.,
a corporation of New York
No Drawing. Filed Feb. 26, 1965, Ser. No. 435.690
US. Cl. 136-146 15 Claims
Int. CL HOIm 3/02
For many years. the only suitable separator mem-
branes available were ccllulosics such as cellophane and
supported and unsupported sausage casings, which are a
purer form of regenerated cellulose.
The cellulosics absorb sufficient electrolyte so as to
have low electrical resistances. Furthermore, they slow
the advance of silver oxides toward the negative plate
by virtue of their reactivity towards silver oxides. That
is, they are oxidized by the silver oxides, which in turn
are reduced to silver metal which is deposited within
and on the cellulosic separator. Furthermore, their swol-
len. gel-like state. which they possess when immersed in
alkaline electrolytes, tends to retard the growth of zinc
dendrites in silver-zinc cells.
The eellulosics have several inherent disadvantages.
They are. first of all, subject to hydrolytic attack by the
electrolyte and undergo Oxidative degradation in alkaline
media. This attack most likely, takes place by a mecha-
nism whereby cleavage occurs at the gem-diol po,itions
of tic rings. Thus they are not notably long-lived, espe-
cially at elevated temperatures such as occur on high rate
ABSTRACT OF THE DISCLOSURE
A separator for secondary alkaline cells comprising a
thin sheet of a graft copolymer of a polyethylene base
and a graft of a polymer of an ethylenically unsaturated
carboxylic acid, such as an acrylic acid. The polyethylene
may first be crosslinked by irradiation and then immersed
in a solution of an acrylic acid and subjected to further
irradiation to form the graft copolymer.
This invention rto secondary alkaline cells and charge and discharge.
more Particularly invention relates l e to s for the same. Secondly, the mechanism whereby cellulosic membranes
slow the
mpor-
The secondary alkaline battery systems, nickel-cadmi- advance o e silver oxides, not
but, only hat
more somew
ea available silver ca, but, mimpoT
um, silver-cadmium. and silver-zinc offer several advan- flat
25 reduces so heavily
oe
tages over lead acid cells. One advantage is the abilit , lw ith metellle e
y theft it t becomes electrically e the conductive. membrane Since the electrode
to deliver a greater amount of energy for a given weight. vsstmblies are tightly packed. these electrically conductive
This advantage is particularly characteristic of the silver- silver-loaded. membranes offer a path to short circuit
cadmium and silver-zinc eel. The --n-
ability to deliver to compensate for their instability and for their tendency
a high discharge current. Thus alkaline secondary battery to "load" with silver to the point.of becoming electrically
systems are extremely attractive for various :ommzrcial, conductive. The loading of the cellulose membranes with
military, ,and aerospace a^rlications in portable, powered silver in effect advances the silver electrode towards the
appliances of nit tvn.?
ff
su
er from inc of the cell in spite of the multiple layers of separator
disadvantage of limited cycle life. This disadvantage has material.
limited their usefulness in spite of their advantages of The penalty paid for the use of thick. rnultilayer sys-
high energy content compared to lead acid cells as above (ems having a thickness of 15 to 25 mils (.015 to .025
noted. One reason for the limited cycle life of silver- 40 inch) or more, is a considerab+.e reduction in the avail-
cu dmium and silver-zinc cells is the slight
but by no
,
able energy and currt ditf th
enensy oe system as com-
means insignificant, solubility of silver oxides in the alka- pared to that which is theoretically possible.
line electrolyte, which customarily is 30 to 45% KOH. A major improvement in separators has been made by
e tlse oxidestion. Tr eat inai othntrue`ssolutioncand?tin the use of conductive membranes prepared by introducing
ou
i
and
g
,-
is- fil Flh i
,ms.or exampe, tentroduction of carboxyl groups
charge of the negative plate. a into a polyethylene base polymer yields an ionically con-
Cycle life in the silver-zinc system is further impaired ductive membrane inert to both hydrolysis and oxidation
by the high solubility of zinc oxide as potassium zincate. attack in the electrolyte. It has been found that in order
Zinc dendrites are deposited on the negative plate during 50 to obtain low electrical resistance, high concentrations of
charge, as a result of the reduction of zincate ir. solution carboxyl groups are needed.
to metallic zinc. These dendrites rapidly span the narrow Radiation produced graft copolymers in thin sheet form,
gap between the positive and negative plates and short containing an ethylenically unsaturated carboxylic acid
circuit the cell. _
_ ,_ , " r?
rafted to
line cells and nimenais nccorang tot his invention. Polyethylene is a
part;--ularly those having silver electrodes. preferred polyolefin, and acrylic and methacrylic acids
Battery engineers hay, sought suitable new separator ma- are preferred ethylenically unsaturated acids. These co-
terials.
Ideally., battery separators for cells having silver elec. arpolymers have low e ionically conductive tandlinresistance. These ert to hydrolysis and ox9da-
.trodes should be absorptive. readily allow passage of 80 Live attack in the electrolyte. Moreover, they can be made
electrolyte ions so as to possess a low electrical resist- very thin, I to 1.5 mils wet thickness, as compared to 4
rnee, trot be adverselq affected by concentrated potassium to 6 mils wet thickness for the better cellulosic mem-
hydroxide solutions. be stable over the temperature range . branes. They slow the advance of dissolved silver oxides
of -40? F. to 200? F., be impermeable to dissolved toward- the negative electrode without being oxidized and
silver oxides and zincate ion and be inert to oxidation 65 without reducing the silver oxides to metallic silver. Far-
b, silver oxide, silver peroxide and nascent oxygen. thermore, they are capable o, being aeated at 125? C.
The usual porous mats and so-called micro-porous ma- (about 250? F.) in 4055 potassium hydroxide for 16
aerials, such as are used in tie lead ac'd system, do not hours without deteriorating.
significantly prolong the lives of these cells, as these The rate of diffusion of dissolved silver oxides and
separators have too open a structure. They do not im- 70 zincate ions and the penetrability by zinc dendrites varies
pede the passage of zincate ions or colloidal particles, in graft co 1 mer s f
c
para ors as a unc.uon Of the degree
nor slow the growth of zinc dendrif.? - Po Y
Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010056-5 -nee the crystallinity, of
 Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010056-5
3
3,427,206
the polyolefin starting material. Since grafting occurs only
in the amorphous regions, the more crystalline po ye:hyl-
ene starting materials yic;d membranes w;:a fewer and
smaller pores. This has been demonstrated ;a permeability
studies and cell testing.
5
Prior to this invention it was throught that membranes'
with low graft levels would have higher resistance but
would have a greater cycle life than high graft level mem-
branes, due to the decreased permeability to silver oxides
and zinc ions in the low graft membranes.
It has been found unexpectedly according to the pres-
ent invention that high graft membranes prepared from
radiation cross linked polyethylene are vastly superior to
other graft copolymer membranes. This unexpected sir
pcriority has been demonstrated in comparative tests of
high and low graft level membranes under identical test
conditions.
Cells according to the present invention are of the sec-
ondary alkaline t%pe, containing a positive electrode, a
negative electrode, an alkaline electrolyte, and a sepa-
rator between the adjacent electrodes of opposite polarity.
The positive electrode may be of a known electrode ma-
terial such as silver or nickel and the negative electrode
likewise of a known electrode material such as Line or
cadmium. Thus. silver-zinc, silver-cadmium, nickel-cad-
mium and nickel-zinc alkaline cells are within the pur-
view of this imrntion. Each electrode may contain a
single plate or a plurality of plates as is known in the art.
Conventional alkaline electrolytes, such as 30 to 45%
aqueous potassium hydroxide. may be used.
The novel separator materials according to the present
invention are graft copolymers in which the base is a film
of a polyolefin and the graft is a polymer of an ethyleni-
cally unsaturated carboxylic acid. Polyethylene is a pre-
ferred base material; blends of polyethylene with other
olefinic polymer,, as for example a polyethylene-polyiso-
butylene blend are also suitable. For best results the poly-
ethylene should he cross linked. Cross linking is most
readily achieved by exposure to a radiation source such as
the beam of an electron accelerator until the total dose
is at least 10 megarads. The total dose is generally in the
range of 10 to 70 megarads. It is seldom necessary or de-
sirable to irradiate to doses higher than 70 megarads.
Other means for cross linking which will give an equiva-
lent amount of cross linking are also suitable. For ex-
ample, polyethylene may be cross linked with known
cross linking agents such as divinyl benzene if desired.
Cross linking of the polyethylene base is preferably car-
ried out prior to grafting.
The graft polymer is preferably polyacrylic acid, poly-
methacrylic acid, or a copolymer of acrylic acid and
methacrylic acid. Polymers of other ethylenically unsatu-
rated carboxylic acids are also suitable however. The graft
may be prepared by immersing the base film of polyethyl-
ene or other pulyolefin in a solution of monomer, e.g.
acrylic acid, methac^ilic acid, or mixtures thereof. The
solvent is preferably a liquid aliphatic or aromatic hydra
carbon, such as hexane, heptane, benzene, toluene or
xylene. A small amount of a chlorinated hydrocarbon
polymerization promoter such as carbon tetrachloride is
also present in the monomer solution. The monomer solu-
tion with base film immersed is then exposed to polym-
erization conditions. Polymerization is preferably carried
out by exposure of the monomer solution to a radiation
4
to about 1.5 mils. A preferred polyethylene base film
will have a thickness of about 1.0 mil.
The total separator thickness in cells of this invention
is preferably about 0.25 to about 9.0 mils. One or more
layers of membrane may be used in order to achieve
this thickness. Excellent results have been obtained for
example with two la.?ers of membrane according to this
invention having a total separator thickness of 3 mils
when compressed, i.e., a thickness of 1.5 mils per layer.
This invention will now be described with reference
to specific embodiments thereof as illustrated in the ex-
amples which follow: -
Example 1
A battery separator membrane is prepared from 1.0
mil, 0.914 density polyethylene film as follows: The po'.y-
ethylere film is cross linked by irradiation under the beam
of an electron accelerator to a total dose of 10 megarads.
The cross linked film is rolled up with a cheesecloth
spacer and immersed in. a solution consisting of 25%
glacial acrylic acid. 7.5% CC14 and 67.55benzene (all
solution percentages by volume). The film-solution com-
bination is then irradiated to a total dose of 1.012 mega-
rads at a dose rate of 50.600 rads/hour using a cobalt-
60 radiation source. The film is then washed free of
homopolymer. Y his gives a graft copolymer of a poly-
ethylene base and a poly acrylic acid graft, the graft con-
stituting 5.0 mole percent of the total.
Example 2
A battery separator is prepared from 1.0 mil, 0.922
density polyethylene film as follows: The film is cross
linked by irradiation under the beam of an electron ac-
celerator to a total dose of 30 megarads. The film is then
rolled up with an absorbent interlayer and the roll im-
mersed in a monomer solution consisting of. 30% by
volume gla^'.tl acrylic acid. 67% by volume benzene,
toluene or xylene and 3% by volume carbon tetrachlo-
ride. The film-solution combination is then irradiated to
a-dose of 2.23 megarads at a dose rate of 17,200 rads/
hour using a cobalt-60 radiation source. The membrane
is washed free of homopolymer. This gives a graft copoly-
mer in ' which the polyacrylie acid graft constitutes 5.4
mole percent of the total.
A battery separator is prepared from 0.9 mil, 0.960
density polyethylene film as follows: The film is cross
linked by irradiation under the beam of an electron ac-
celerator to a total dose of 30 megarads. The cross iinked
film is then rolled up in absorbent paper and immersed
in a solution consisting of 30% by volume glacial meth-
acrylic acid and 705% benzene. The film-solution com-
bination is then irradiated to a total dose of 2.7 negarads
at a dose rate of 17,800 rads/hour using a cobalt-60
radiation source. The membrane is washed free of homo-
polymer. This gives a graft copolymer of a polyethylene
base and polyacrylic acid graft, the graft constituting 7.1
mole percent of the total.
Example 4
A battery separator is prepared from 0.9 mil, 0.960
density polyethylene film having a melt index of 5.0 as
follows: The film is cross linked by irradiation under the
beam of an electron accelerator to a total dose of 30
megarads. The film is then rolled up in absorbent paper
and immersed in a solution consisting of 25% by volume
glacial acrylic acid, 70% by volume benzene and 5% by
volume carbon tetrachloride. The film-solution combina-
t' tt
source, such as cobalt-60. The total radiation dose is suf. 65
ficient to effect polymerization and ordinarily is at least
I megarad. The amount of graft is generally 5 to IS mole
percent, in which the molecular weight of the graft ma-
terial is based on the molecular weight of the monomer
and the .ei h
__- - 70
f
h
t o
t
e
i
I is en ,rradiated at, a dose rate of 22,300 rads/hour
the calculation is the formula weight of a methylene unit. to a total dose of 3.35 megarads. The membrane is
Battery separators according to this invention are pre- washed free of h 1
o
mopo "A Thts^g.-.. a graft graft, th-
ymer. pared gin thicknesses ranging from about 0.25 to about mer of nnlveihvl
2. Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010056-5 he acid graft, the
the total.
 Approved
For Release 2009/04/10: CIA-RDP81-00120R000100010056-5
'-Q A07 OM
5
Example S
A battery separator is prepared from 1.0 mill, 0.917
density polyethylene film as follows: The film is cross
linked by irradiation under the beam of an electron
accelerator to a total dose of 70 megarads. The film is
rolled up with an i_,terlayer of absorbent paper and ;m-
mersed in a solution consisting of 25% glacial acrylic
acid, 70% benzene, and 5% carbon tetrachloride (all per-
centages by volume). The film-solution combination is
irradiated at a dose rate of 1.4,500 rads/hour to a total
dose of 1.044 megarads using a cobal*.-60 radiation source.
The film is washed free of homopolymer. The graft co-
polymer "is then subjected to a second grafting under the
same conditions as described in this example. This gives
a graft copolymer in which the graft constitutes 10.1 mole
percent of the total
Example 6,
A battery separator is prepared from 1.0 mil, 0.960
density, 0.2 melt index polyethylene film as follows: The
film is cross linked by irradiation under the beam of an
el-.tron accelerator to a total dose of 50 megarads. The
film is then rolled tip with a cheesecloth spacer and im-
mersed in a solution consisting of 25%b by volume glacial
acrylic acid and 75% by volume benzene. The film-solu-
tion combination is irradiated to a total dose of 1.73
megarads at a dose rate of 14,500 rads/hour using a co-
ba!t-60 radiation source. The film is washed free of homo-
polymer and the --rafting step as described above is re-
peated. This gives a graft copolymer containing 5.8 mole
percent of a polyacrylic acid graft.
Example 7
A battery separator. is prepared from 1.0 mil, 0.922
density polyethylene film as follows: The film is rolled
up with an absorbent spacer. The roll is immersed in a
solution containing 25% glacial acrylic acid; 70% toluene,
and 5% carbon tetrachloride (all percentages by volume).
The film-solution combination is irradiated to a total
dose of 1.6 megarads at a dose rate of 16,000 rads/hour
using a cobalt-60 radiation source. The membrane is
washed free of homopolymer. The polyethylene is then
cross linked by irradiation of the membrane under the
beam of an electron accelerator to a dose of 30 megarads.
This gives a graft copolymer containing 7.3 mole per-
cent of graft.
Example B
A battery separator is prepared from 1.0 mil, 0.917
6'
corporated in test cells and tested as described in Ex-
Example 10
Test cells having three plates and a capacity of two
ampere hours each were constructed using the various
separators indicated below. Three cells of each of the
indicated separator materials were constructed. All cells
were silver oxide-zinc cells having an alkaline electrolyte.
Each cell had two layers of separator membrane having
a total. separator thickness of 3.0 mils. All cells were put
on a cycle life test using a cycle of 35 minutes discharge
and 85 minutes charge. Separator materials and the num-
ber of cycles to failure are indicated in Table I below.
TABLE I
Separator: Cycles to failure
(average values for 3 cells)
Low density, uncrosslinked .
7.8 mole percent graft (high graft) -------- 174
Low density, uncrosslinked
5.4 mole percent graft (low graft) -------- 279
High density, uncrosslinked
11.9 mole percent graft (high graft level) -__- 532
High density crosslinked,
30 mrads high graft level ---------------- 249
Low density, crosslinked,
30 meads high graft level ---------------- 508
Example 11
A number of 25 ampere hour silver-zinc cells having
an alkaline electrolyte and various separator materials as
indicated in Table lI below were built. All were tested on
the same test cycle of 35 minutes discharge and 85 minutes
charge, discharging to a 25% depth of discharge. Each
cell had four layers of separator membrane, with a total
separator thickness of 6.0 mils. Results showing the num-
be, f cycles to failure are indicated in Table IL
TABLE U
Separator:
High density, uncross-
linked 12.2 mole
percent graft ------- 414 average.
Low density, cross-
linked (30mrad) 10
mole percent graft __ 580 average.
Low density, cross-
linked 13 mole
percent graft ------ 2130 average (still cycling).
density polyethylene as follows: The polyethylene film 50
is cross linked with divinyl benzene. This is accomplished'
by immersing a film in a Seib solution of divinyl benzene
in benzene and Irradiating the combination of film and
solution at a dose rate of 13,100 cads/hour to a total
dose of 0.223 megarad. After rinsing in benzene, the
cross linked film is rolled up with an absorbent interlayer
and immersed in a solution consisting of 1 part glacial
acrylic acid and 3 parts benzene by volume. The film-
We claim:
1. A secondary alkaline cell comprising a positive elec-
trode, a negative electrode, an aqueous alkaline electro-
lyte, and a separator between said electrodes, said separa.
tor comprising a thin. sheet of graft copolymer of a poly-
ethylene base and a graft of a polymer of an ethylenically
unsaturated carboxylic acid wherein said graft is 5-15
mole percent of said polyethylene.
2. A secondary alkaline cell comprising a positive elec-
trode, a negative electrode, an aqueous alkaline electro-
lyte, and a separator between said eiec codes, said separa-
tor comprising a thin sheet of a graft copolymer of a poly-
solution combination is irradiated at a dose rate of 13,100
rads/bour to' a total dose of 1.71 megarads. This gives a 60
graft copolymer containing 14.8 mole percent of poly-
acrylic acid graft.
Example 9
A battery separator is prepared from a 1.0 mil firm
extruded from a 0.938 density polyolefin resin consisting
of a blend of polyisobtttylene polyethylene as follows:
The polyolefin film is rolled up with c:n absorbent spacer.
The roll is immersed in a solution consisting of I part
glacial acrylic acid, 2.8 parts of benzene and 0.2 part of a
'50% divinyl benzene solution. The film-solution combina-
tion is irradiated to a dose of 2.256 megarads at a dose
rate of 18,800 rads/hour using a cobalt-60 source. The
copolymer contains 6.2 mole. percent grafted acrylic acid.
11 Battery separators according to this invention were ia-
ethylene base and a graft selected from the group con-
sisting of polyacrylic acid, polymethacrylic acid, and
g5 acrylic acid-methactylic acid copolymers wherein said
graft is 5-15 mole percent of said polyethylene.
3. A secondary alkaline cell comprising a positive elec-
trode, a negative electrode, an aqueous alkaline electro-
lyte, and a separator between said electrodes, said separa-
70 tor comprising a thin sheet of a graft copolymer of a
base of crosslinked polyethylene and a graft selected from
the group consisting of polyacrylic acid, polymethacrylic
acid, and acrylic acid-me Lb acrylic acid copolymers.
4. A secondary alkaline celi comprising a positive elec-
trode, a negative electrode, an aqueous alkaline electro-
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 Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010056-5
3,427,206
7
lyte, and a separator between said electrodes, said separa-
tor comprising a thin sheet of a graft copolymer of a base
of radiation cross linked polyethylene and a graft selected
from the group consisting of polvacrylic acid, polymetha-
crylic acid, and acrylic acid-methacrylic acid copolymers.
S. A secondary alk. lice cell comprising a positive elec-
trode, a negative electrode, an aqueous alkaline electro-
lyte, and a separator between said electrodes, said separa-
tot comprising a thin sheet of a gi aft copolymer of a base
of polyethylene cross linked by exposure to a radiation
dose of at least 10 megarads and a graft selected from the
group consisting of polyacrylic acid, polymethacr3lie acid,
and acrylic acid?methactylic acid copolymers.
6. A secondary alkaline cell comprising a positive elec-
trode, a negative electrode, an aqueous alkaline electro-
lyte, and a separator between said electrodes, said separa-
tor comprising a thin sheet of a graft copolymer of a base
of a polyethylene-poyisobutylene blend and' a g: aft select-
ed from the.. group consisting of polyacrylic acid, poly-
methacrylic acid, and acrylic acid-methacrylic acid
copolymers.
7. A secondary alkaline cell comprising a positive elec-
trode, a negative electrode, ar aqueous alkaline electro-
lyte, and a separator between said electrodes, said separa-
tor having a total thickness of 0.25 to 9.0 mils and com-
prising at least one thin sheet of a graft copolymer of a
polyolefin base and a graft selected from the group con-
sisting of polyacrylic acid, polymethacrylic acid, and ac-
rylic acid-methacrylic acid copolymers.
8. A secondary alkaline cell comprising a positive elec-
trode, a negative electrode, an aqueous alkaline electro-
lyte, and a separator between said electrodes, said separa-
tor comprising a plurality of thin sheets of a graft
copolymer of a polyolefin base and a graft selected from
the group consisting of polyacrylic acid, polymethacrylic
acid, and acrylic acid-methacrylic acid copolymers, each
sheet having a thickness of 0.25 to 2.0 mils.
9, The cell of claim S wherein said graft is formed by
8
irradiation of said polyethylene in an organic solution
of monomers of said acids, and said graft is 5-1S mole
percent of said polyethylene.
10. The cc!] of claim S wherein said separator has a
thickness of about 0.25 to about 2 mils.
11. The cell of clai..t S wherein said polyethylene is
crosslinked by exposure to a radiation dose of at least 30
megarads.
12. The secondary alkaline cell of claim 5 wherein
said graft copolymer is a radiation graft of said poly-
ethylcn_ in a solution of monomers of said acids.
13. The secondary alkaline cell of claim 12 w:terein
said radiation graft is of a dose rate of from about 13,100
to about 50,500 rads per hour to provide a total dose of
at least about 1 megarad.
14. The secondary alkaline cell of claim S wherein
said graft copolymer is polyethylene irradiated in an or-
ganic solution of monomers 3f said acids and wherein said
base is polyethylene subsequently cross linked by said
exposure to said radiation dose.
15. The secondary alkaline cell of claim 14 wherein
said base is polyethylene cross linked by said exposure to
a radiation dose of at least 10 megarads and said irradia-
tion of said graft is of a lower dose than 10 megarads.
References Cited
UNITED STATES PATENTS
2,965,697
12/1960
Duddy ------------- 136-146
3,101,276
8/1963
Hendricks -___---___-- 117-56
3,111,424
11/1963
Le Clair -------- 117-93.31 X
3,188,165
6/1965
Magat et al. ----- 117-93.31 X
3,240,723
3/1966
Friedlander ------- 136-146 X
WINSTON A. DOUGLAS, Primary Examiner.
35 DONALD L.WALTON, Assistant Examiner.
U.S. Cl. X.R.
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 Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010056-5
Jan. 13, 1970 C. BERGER ET AL 3,489,610
BATTERY HAVING A POROUS INSOLUBLE HYDROUS
INORGANIC OXIDE SEPARATOR
Filed June 30, 1964
9-.3
CA~2.L .$.E.QGER
A.Z. L~vV-F qsc, L
I~ONlaLO t3? ~7VICCLELL.gN1~
INVENTORS
BY q.. n
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 Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010056-5 3,489,610
JLJi I.v,..L " L."L .10 R dL L I11. t.FJ J dA.. Patented Jan. 13, 1970
3,489,610
BATTERY HAVING A POROUS INSOLUBLE
HYDROUS INORGANIC OXIDE SEPARATOR
Carl Berger, Corona Del Mar, Arie E. Levy-Pascal, Palo
Alto, and Donald It. McClelland, Newbury Park, Calif.,
assignors, by mesne assignments, to McDonnell Doug-
las Corporation, Santa Monica, Calif., a corporation
of Maryland
Filed June 30, 1964, Ser. No. 379,093
Int. Cl. HOIm 3/02
2
A further object of the invention is the design of a
battery particularly suited for air-borne applications, of
small weight, capable of being charged and discharged
over a large number of cycles, and operating particularly
at elevated temperatures, said batteries being capable
of withstanding temperatures of the order of 100? C.
and higher, and which can take advantage of increased
electrochemical activity and decreased electrolyte re-
sistance at such elevated temperatures.
A still further object is the design of batteries and
inorganic battery separators which are chemically inert
particularly at elevated temperatures, are geometrically
stable, readily wetted by electrolyte, are not attacked
by silver oxide, can be made with controlled porosity,
and which resist puncture by dendritic growth.
A still further object is the provision of improved high
energy density batteries, particularly 'silver-zinc cells,
incorporating inorganic separators which are strong,
rigid and capable of supporting electrodes of opposite
polarity, yet having a porosity sufficient to permit transfer
of hydroxyl ions through the separator but preventing
penetration of the electrode ions into and through the
separator.
Other objects and advantages will appear herinafter.
The present invention is based on the discovery that
inorganic separators, particularly porous separators or
membranes, and preferably composed of insoluble hy-
drous inorganic or metal axides such as hydrous zircon-
ium oxides, have many advantages over the use of organic
separators, in high energy density batteries. Thus, the
inorganic separators of the invention are chemically
inert at all operating temperatures and particularly at
elevated temperatures, e.g., above 100? C. The porosity
of such inorganic separators is easily controlled and can
be varied to control resistance and diffusion of ions
through the separator. Such separators have geometric
stability, are readily wetted by alkaline electrolytes, and
are not chemically attacked by silver oxide. Further, the
rigid microporous structure of such inorganic separators
does not allow dendrite growth through the separator.
It is a particular feature of the inorganic separators ac-
cording to the invention that although such separators
can be formed into thin, strong, rigid membranes, satis-
factory porosity can be provided in such hydrous metal
oxide separators by various procedures of formation de-
scribed below, such that the separators permit and facili-
tate transfer of electrolyte ions through the separator, but
prevent transfer of electrode ions such as silver and zinc
ions through the separator so that no treeing of, for ex-
ample, zinc dendrites can occur in the separator. Thus,
maximum porosity should be about 40%, and minimum
porosity about 5%, and hence the separators of the inven-
tion have a porosity in the range from about 5% to about
40%. Generally, porosity of the hydrous metal oxide sep-
arator of the invention can range from about 8% to about
40%, preferably from about 10% to about 25%, as meas-
ured by water absorption according to the expression:
Weight after water saturation-dry weight 100
dry weight
The inorganic separators according to the invention are
quite thin, and can have a thickness, e.g., in the range of
about.005 to about 0.050 inch.
If the porosity of the separators is greater than about
40%, the strength of the separators is reduced danger-
ously to a point where the separator is easily broken or
shattered, especially during assembly of the battery, and
is incapable of properly supporting the electrodes, and
too porous to prevent electrode ion passage, and if the
porsity is below about 5%, the effectiveness of the battery
is materially and undesirably reduced due to the sub-
stantially reduced amount of electrolyte which can be re-
This invention relates to batteries, particularly high
energy density batteries, and is especially concerned
with the provision of improved inorganic membranes or
separators for use in batteries, and to improved battery
construction embodying efficient inorganic separators
having a porous internal structure and pore size charac-
teristics preventing transfer of electrode ions such as
zinc and silver ions through the separator.
Batteries are an important source of energy storage 20
for power generation in air-borne systems. An important
type of battery particularly suited for such applications
are the high energy density alkaline electrolyte cells
using such electrode combinations as silver-zinc, silver-
cadmium and nickel-cadmium. High energy density bat- 25
teries are generally battery systems which have a sub-
stantially higher energy per unit of weight than conven-.
tional, e.g., lead, storage batteries. Thus, high energy
density batteries can develop, e.g., 100 to 140 watt hours
of energy per pound. In addition to important air-borne
applications, such high energy density batteries have
many other applications such as in portable tools and
appliances, television, radio and record players, engine
starting, portable X-ray units and the like. However,
batteries in use at the present time have not given suf-
ficiently long life, nor have they been able to operate
at the extremes of high and low temperatures.
In high energy density batteries such as silver-zinc,
nickel-cadmium, silver-cadmium, the separator performs
the function of retaining electrolyte, e.g., potassium hy-
droxide, separating the electrodes, and preventing mi-
gration of electrode ions or growth of dendritic crystals
of electrode ions which short circuit the battery. It has
been known to employ organic separators in such bat-
teries but. these have several disadvantages. Thus, such
organic separators are not chemically stable especially
at temperatures above 50' C., they tend to swell exces-
sively at elevated temperatures and most organics are not
readily wetted by cautic solutions. Further, organics are
not inert to silver oxide in caustic solutions and organic
materials are generally soft and pliable and are subject
to puncture by dendrite growth.
Some of the prinicipal objectives in battery develop-
ment and also objects of the present invention, are to
obtain a higher energy per unit weight, permit operation
in a higher thermal environment, and increase the life
of a battery both in stand-by and discharge-recharge
cycling.
proved high energy density batteries having extended
periods of life and which are capable of operation at high
temperatures of the order of about 100' C. and above,
and to provide improved inorganic battery separators
especially designed for use in such batteries.
Another object of the invention is the development of
inorganic battery separators and improved battery con-
structions, particularly for silver-zinc, silver-cadmium,
nickel-cadmium, and other high energy density battery
systems, for operation at temperatures from ambient up
to 100' to 2000 C.
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tamed by the 'separator, thereby preventing required dif-
fusion of electrolyte ions.
A high energy density battery is accordingly provided
according to the invention emhodying an insoluble?hy-
dious meal oxide separator generally having the porosity
characteristics ahove indicated, in combination with elec-
trodes of opposite polarity, e.g., zinc and silver electrodes,
preferably in supported relation adjacent opposite sides
of the separator. Such relatively rigid inorganic separator
provides support for the electrodes even though the sep-
arator is very thin and has porous characteristics, as de-
scribed above. These batteries, in addition to having long
cycle life at elevated temperatures, have exhibited excel-
lent charging of iiciency under severe operating conditions.
By the terms "porous membrane" and "porous sep-
arator" employed herein, is intended to denote a mem-
brane-thin plate, latticework, network or matrix having
an inner structure of interconnecting micropores between
its opposing surfaces.
The insoluble porous hydrous metal oxide membranes
have properties and are particularly adapted to use in
fuel cells and batteries where extremely strong membranes
are required to maintain electrode ion separation be-
tween the electrodes of the battery or fuel cell, and
wherein operating temperatures may approach and exceed
150' C. Moreover, the present invention has the distinct
advantage of allowing membranes to be stored in an inert
form for indefinite periods of time without change and
to be .employed as high strength porous membranes or
separators for batteries as needed.
For the purposes of this invention, the term "insoluble
hydrous metal oxides" includes those water insoluble ma-
terials containing one or more metal atoms, oxygen atoms,
and an indeterminate quantity of water. The hydrous
metal oxides do not necessarily have a definite stoichio-
metric combination or definite crystal structure and may
contain ionic impurities. The water insoluble hydrous
metal oxides which can be employed to form the sep-
arators of the invention are the water insoluble hydrous
oxides of metals selected from the following groups of
metals in the Periodic Table: III-A, III-B, IV-A, IV-B,
V-A, V-B, VI-B, VII-B, VIII, the Lanthanide Series and
the Actinide Series. The elements or metals forming in-
soluble hydrous oxides which are of greatest practical im-
portance at the present time are: Al (III), Ga (III), In
(III), Sc (III), Y (III), Zr (IV), Ti (IV), Hf (IV), Pb
(II), Si (IV), Ge (IV), Sri (IV), Sb (III, V), Bi (III),
As (V), V (V), Nb (V), Ta (V), Cr (III), Mo (IV, VI),
W. (IV, VI), M.n (IV), Re (IV), Tc (IV). Fe (11I), Co
(II), Ni (II), Ac (III), Th (11I), U (IV, VI), Pu (IV),
La (111), Ce (IV), and Yb (111). Other valence states of
some of these elements may also he useful.
Materials which are particularly useful for producing
inorganic separators according to the invention are the
hydrous oxides of zirconium, titanium, antimony, tung-
sten, silicon, scandium, bismuth, vanadium, aluminum and
cerium. Hydrous zirconium oxide separators are especially
desirable.
Battery separators according to the invention can be
prepared by various techniques. Thus, for example a sep-
arator can be prepared by (1) conversion of acid salts
to the corresponding hydrous oxides, as described in the
copending application Ser. No. 326,985, now Patent No.
3,346,422, filed Nov. 29, 1963, of Carl Berger, (2) flame
spraying insoluble metal oxides accompanied by hydro-
lytic activation, as described in the copending applications
Serial No. 327,114, now abandoned of Norman Michael
and Ser. No. 327,038, now Patent No. 3.392,103, of Carl
Berger, both filed Nov. 29, 1963, and (3) impregnating
porous ceramics such as alumina or zirconia with a gel
of an insoluble hydrous metal oxide such as hydrous zir-
conium oxide, as described in copending application Ser.
No. 326,740, filed Nov. 29, 1963, of Carl Berger.
In method (I) noted above, an acid salt such as zir-
conium phosphate, can be treated with alkali, e.g., potas-
sium hydroxide, to form hydrous zirconium oxide. "
According to method (2) described above, metal oxide
such as zirconia is flame-sprayed and the resulting an-
hydrous ceramic membrane is then treated with high tem-
perature steam or with alkali, e.g., KOH, to partially re-
hydrate the base ceramic material to its hydrous state.
In procedure (3) noted above, a gel-filled membrane
is formed by filling the pores of a strong porous thin plate,
such as a ceramic plate, e.g., a flame-sprayed zirconia
membrane, with insoluble hydrous metal oxide gel, e.g.,
a hydrous gel of zirconium oxide.
The descriptions of the above processes as described in
the above copending applications are all incorporated
herein by reference.
By the above-noted techniques, inorganic materials
having excellent chemical resistance, good electrical re-
sistivity and high strength can be formed into battery
separators according to the invention. However, it is
20 noteworthy that the hydrous metal oxides of which the
invention separators are formed, provide less internal
resistance than do sintered metal oxides, and such re-
duced internal resistance is a distinct advantage in pro-
ducing efficient battery separators which have long cycle
25 life, particularly for high energy density batteries. Fur-
ther, the hydrous metal oxides hereof have ion exchange
properties rendering such materials useful as ion exchange
membranes in fuel cells.
By employing the procedures noted above, inorganic
:t4 separators comprising hydrous metal oxides, particularly
hydrous zirconium oxide, are readily produced and which
have a controlled porosity within the ranges noted above.
However, it will be understood that insoluble hydrous
metal oxide membranes or separators produced by other
35 procedures are also within the purview of the invention.
After formation of the hydrous oxide separator or
membrane, electrodes are positioned on opposite surfaces
or opposite sides of the separator. For this purpose the
electrodes, e.g., zinc and silver electrodes, can be flame-
40 sprayed onto opposite surfaces of the separator or the
respective electrodes can be pressed against opposite sur-
faces of the separator. The hydrous metal oxide mem-
brane can be impregnated with electrolyte, e.g., KOH,
either before or after the electrodes are assembled on
45 opposite sides of the separator. The entire assembly in-
cluding the separator and the electrodes are then assembled
or clamped together to form a battery. If desired, the
entire assembly then can be encapsulated in an encap-
sulating resin. A variety of resins can be employed for
50 this purpose, including epoxies, polyesters, phenolics,
melamines, and silicones, epoxies being preferred. The
resins are usually mixed with catalysts or hardeners, or
both.
The invention will be further described in relation to
55 sembly according to the invention;
FIG. I is a schematic representation of a battery as-
sembly according to the invention;
FIG. 2 is a schematic illustration of a modification of
the battery unit of FIG. 1;
00 FIG. 3 shows the manner of assembly of a separator
and electrodes to form a battery according to the in-
vention; and
FIG. 4 shows a modification of the assembly of FIG. 3.
Referring to FIG. 1, an insoluble hydrous metal oxide
65 membrane, e.g., hydrous zirconium oxide, represented by
numeral 10, formed, for example, by any of the proce-
dures noted above, is flame-sprayed as described above
on opposite surfaces or sides with a zinc electrode indi-
70 cated at 12, and with a silver electrode indicated at 14.
Wires 16 and 18 connect the electrodes 12 and 14 re-
spectively to a load 20.
In the modification of FIG. 2, a hydrous oxide sepa-
rator 22 is provided and has pressed against opposite sides
75 thereof a zinc electrode 24 and a silver electrode 26.
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5
Wires 28 and 30 connect the respective electrodes 24
and 26 of opposite polarity, in series to a load 32.
In the modification of FIG. 2, the zinc and silver
electrodes are prepared in any suitable manner, e.g., by
forming a paste of these electrode materials as described
below and pressing the paste against, and causing it to
adhere to and to impregnate, the opposite surfaces of
the inorganic separator of the invention.
During discharge of the batteries illustrated in FIGS.
1 and 2, as is well known, the zinc is converted to zinc
oxide and the silver oxide to silver, and during charging
of such batteries the silver is oxidized to silver oxide
and the zinc oxide is reduced to zinc. Because of these re-
versible reactions, the terms "silver" and "zinc," the terms
"silver" and "cadmium" and the terms "nickel" and
"cadmium," referring to the metals forming the respective
electrodes of such battery systems, are intended to denote
either the respective metals themselves or the correspond-
ing oxides thereof.
The pores of the separator 10 or 22 are filled with
an alkaline electrolyte. It will be noted in the schematic
illustrations of FIGS. I and 2 that the separator aids in
supporting the sprayed on metal electrodes 12 and 14,
or the electrodes 24 and 26 pressed against opposite
surfaces of the separator. However, certain electrodes,
particularly the zinc electrode, even when so supported,
slump and deteriorate, causing failure of the battery
after a number of charge-discharge cycles.
By further supporting the electrodes, particularly the
zinc electrode to minimize or substantially eliminate the
slumping or collapse of the electrode, according to the
invention described in the copending application Ser. No.
378,859, filed June 29, 1964 of Carl Berger and Frank C.
Arrance, cycle life of the battery is substantially increased
at temperatures of the order of 100? C., and efficiency of
the battery is improved.
The following are examples of practice of the in-
vention:
A hydrous zirconium oxide membrane having a po-
rosity of about 15% is prepared as described in Example
XXVII of the above copending application Ser. No.
326,985, by ball milling 450 grains of hydrous Zr02 with
450 grams concentrated phosphoric acid for 18 hours.
This material is dried for 15 hours at 160? C., granulated
to -32 and +80 mesh particles, and pressed into a 2"
disc 0-20" thick, at 15 tons pressure and sintered at 300? C.
for 24 hours. The homogeneous zirconium phosphate
membrane thus formed is treated with a 30% solution of
potassium hydroxide under conditions to draw the solu-
tion into the pores of the membrane by suction, convert-
ing the membrane to a hydrous zirconium oxide mem-
brane.
Silver electrode material is prepared using equal parts
of silver oxide and silver. These materials are mixed with
a high speed vibrating mixer and pressed at 5 tons to
about 15 tons total load into 2 inch diameter discs about
0.100 inch thick. The pressed discs are placed between
flat smooth vitreous ceramic plates and sintered for one
to four hours at temperatures ranging from 250? to
600' C. After cooling to room temperature, the sintered
discs are cut to size and spot welded to a fine nickel
screen.
The silver electrodes are prepared for use by electro-
lytic oxidation or charging at room temperature in 20%
to 40% KOH. After forming, the electrode is removed
from the charging stand and assembled in a battery as
described below.
Zinc electrodes are prepared by mixing about 90 parts
zinc oxide, 7 parts li O, and 3 parts polyvinyl alcohol
in a high speed vibratory mixer. After mixing, a weighed
amount of this material is placed in an electrode com-
partment in contact with a fine nickel screen, mixed with
a small amount of 30% K011 and electrolyzed.
The separator and electrodes described above are as-
sembled to form a battery as shown in FIG. 3, employ-
ing a plastic case 34 formed of two symmetrical, e.g.,
Teflon, half portions 36 and 38 which are bolted together
as indicated at 40. Compartments 36 and 38 of the case
have recesses 42 formed therein to receive the zinc and
silver electrodes 44 and 46 respectively, prepared as de-
scribed above. The inorganic separator 48 is disposed cen-
trally between the case portions 36 and 38 so that the
electrodes 44 and 46 are pressed against opposite sur-
faces of such separator. Teflon spacers 50 and 52 are pro-
vided about the periphery of separator 48, to form a leak-
proof seal. Nickel screens 53 and 55 are embedded in
electrodes 44 and 46 adjacent to the bottom of the com-
partment recesses 42, and silver terminal wires 54 and
56 are connected respectively to the screens 53 and 55,
and are brought through the plastic electrode sections at
the top of the assembly as shown. Small electrolyte reser-
voirs 58 and 59 are provided in the upper portion of the
20 respective electrode compartments 36 and 38.
In the modification shown in FIG. 4, it will be noted
that the zinc and silver electrodes 44' and 46' are spaced
from and are not in direct contact with, the inorganic
separator 48, forming captive electrolyte compartments
25 60 and 62 between such electrodes and separator 48, in-
suring a full supply of electrolyte filling the pores of the
separator at all times.
Batteries of the types described above and illustrated
in FIGS. 3 and 4, can be cycled for about 300 to about
500 half hour discharge and half hour charge cycles
at 100 ? C.
However, where the electrodes are not in direct con-
tact with the separator, as in the embodiment of FIG. 4,
the battery often fails due to the slumping of the un-
supported zinc electrode 44'.
If the electrodes are supported with respect to the
separator, for example, if the electrodes are in direct con-
tact with the separator, as illustrated in FIG. 3, so that
the zinc electrode has less tendency to slump and break
through the separator, a substantially larger number of
charge and discharge cycles can be obtained. Furnishing
support for the zinc electrode according to the above-
noted Berger-Arrance application Ser. No. 378,859, pro-
vides improved results.
Discharge of such batteries over a period of days has
resulted in current densities of 27 amperes per square
foot at 1.2 volts and at ambient temperatures. Higher
temperatures will improve the performance of the bat-
tery without deteriorating the hydrous zirconium oxide
separator.
A hydrous titanium oxide membrane is prepared as
described in Example XXVIII of the above copending
application Ser. No. 326,985, by first dissolving 200 grams
of titanium chloride in 500 cc. of water and precipitating
titanium phosphate with a 1.0 M solution of phosphoric
acid at a pH of 3. The precipitate is washed, dried for
24 hours at 110? C., granulated and pressed into a mem-
brane 0.02 inch thick at 15 tons total load. The mem-
brane is then sintered at 1,000? C. for 15 hours to form
the pyrophosphate. The membrane thus formed is sup-
ported in a 10 liter autoclave containing 1 liter of water
and subjected to steam at 2,300 p.s.i. and about 350? C.
for 96 hours. The membrane is then treated with a 30%
solution' of potassium hydroxide drawn through the pores
of the membrane by suction, forming a hydrous titanium
oxide membrane. Such membrane has a porosity of
about 12%.
This membrane is employed as a separator in the
battery of Example 1 in place of the hydrous zirconium
oxide separator thereof. Results similar to Example 1
are obtained.
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EXAMPLE 3
A hydrous zirconium oxide membrane having a thick-
ness of about 0.020 inch and a porosity of about 15%
is obtained, as described in Example V of the above co-
pending application, Ser. No. 327.1 14, by treating a flame-
sprayed zirconia membrane in an autoclave containing
I liter of water. The membrane is exposed therein to
steam at 1,500 p.s.i. and approximately 315? C. for
650 hours.
The resulting hydrous zirconium oxide membrane is
employed as a separator in the battery unit of Example 1
herein. Results similar to Example 1 are obtained.
EXAMPLE 4
A hydrous antimony oxide membrane having a thick-
ness of about 0.02 inch is prepared, as described in Ex-
ample VI of above copending application Ser. No.
327,114, by compacting and sintering antimony oxide at
500? C. and exposing the sintered membrane in an auto-
clave containing water, to steam at 2.1)00 p.s.i. and about
340? C. for 750 hours. The nicmbrane so formed is em-
ployed as separator in the battery unit of Example I
above, in place of the hydrous zirconium; oxide separator,
obtaining results similar to those in Example 1.
EXAMPLE 5
A hydrous tungstic oxide membrane about 0.02 inch
thick is prepared according to Example IX of above co-
pending application, Ser. No. 327,038. by compacting
tungstic oxide and sintering at 1,000? C. The membrane
is then treated in an autoclave with 30% sodium hy-
droxide solution and exposed therein to steam at 2,300
p.s.i.and about 350? C. for 350 hours.
The resulting membrane is employed as separator in
the battery unit of Example 1 above in place of the an-
hydrous zirconium oxide membrane. A battery capable
of operating over a large number of discharge-charge
cycles at 100? C. is obtained.
EXAMPLE 6
A battery substantially the same as that of Example I
is fabricated except that a separator is used which is
formed as described in Example XIII of above copend-
ing application, Ser. No. 326,740. Such separator is pro-
duced by treating a flame-sprayed zirconia membrane that
is flooded with water in a diffusion apparatus in which
the flooded membrane is a divider between the two com-
partments thereof, one filled with a waterglass solution
and the other with it 6.0 N solution of nitric acid and
diffusion of 'the reagents into the membrane allowed to
continue for 24 hours. After removal from the diffusion
apparatus the pores of the membrane are filled with a
hydrous gel of silicon dioxide.
A battery as in Example 1, employing such a separator
in place of the hydrous zirconium oxide separator thereof
is capable of operating for over 100 discharge-charge
cycles of 30 minutes each at elevated temperatures.
EXAMPLE 7
A battery substantially the same as Example I is-fabri-
cated except that the separator employed therein is ob-
tained as described in Example XIV of the above copend-
ing application, Ser.. No. 326,740, by flooding a flame-
sprayed zirconia membrane having a porosity of about
27% with water, and employing the flooded membrane
as the divider between two compartments of a diffusion
apparatus, one filled with a 2.0 M zireonyl nitrate solu-
tion and the other with a 6.0 M ammonium hydroxide
solution. Diffusion of the reagents into the membrane is
allowed to continue for 24 hours. After removal front
the ditusion app:uatus, the pores of the men rune are
tilled with a hydrous gel of zirconium oxide.
The battery containing such flame-sprayed r.ircomia
membrane impregnated with a hydiuus gel of zirconium
oxide can operate for about 300 to about 500 discharge-
8
charge cycles each of 30 minutes duration at tempera-
ture of 125? C.
EXAMPLE 8
A battery substantially similar to that of Example I is
assembled, except that the electrodes are silver and
cadmium.
Such battery can be cycled for about 1,000 to about
3,000 discharge-charge cycles at 100? C. without loss-of
effective capacity.
EXAMPLE 9
A battery substantially similar to that of Example I
is assembled, except that the electrodes are nickel and
cadmium.
Such a battery can be cycled for about 1,000 to about
3.000 discharge-charge cycles at 100? C. without loss of
effective capacity.
EXAMPLE 10
The hydrous zirconium oxide membrane described in
Example I above can function as an anion exchanger in
a hydrazine-oxygen fuel cell.
EXAMPLE 11
A porous ceramic membrane 2" in diameter and 0.02
inch thick is prepared from scandium oxide, as described
in Example II of above copending application Ser. No.
327,114, by compacting and sintering at 1,800? C. and 20
tons total load. The membrane is treated in an autoclave
with water and superheated steam at 2,000 p.s.i. and about
340? C. for 750 hours, forming a hydrous scandium oxide
membrane having a porosity of about 12%.
Such membrane is employed in the battery of Example
1 in place of the hydrous zirconium oxide separator there-
of. Results similar to Example 1 are obtained.
EXAMPLE 12
A hydrous cerium oxide membrane having a thickness
of about 0.02 inch and a porosity of about 15% is ob-
tained as described in Example XII of the above copend-
ing application, Ser. No. 327,114 by compacting and sin-
tering cerium oxide at ?300? C. and treating the resulting
membrane in an autoclave with water and steam at 2,300
p.s.i. and about 350? C. for 450 hours.
The resulting hydrous cerium oxide membrane is em-
ployed as a separator in the battery unit of Example 1
herein. Results similar to Example I are obtained.
EXAMPLE 13
A battery substantially the same as that of Example 1
is fabricated except that a separator is used which is
formed as described in Example XVIII of above copend-
ing application Ser. No. 326,740. Such a separator is pro-
duced by flooding a flame-sprayed zirconia membrane
with an aqueous solution of 1.0 M bismuth chloride con-
taining 10% urea, and filling the pores of the membrane-
with the hydrous gel of bismuth oxide.
Such a battery can operate on the order of about 100
discharge-charge cycles of 30 minutes each at 100? C.
EXAMPLE 14
A battery substantially the same as that of Example I is
fabricated except that a separator is used which is pro-
duced by impregnating the pores of a flame-sprayed zir-
conia membrane with a hydrous gel of vanadium oxide
according to the procedure of above copending applica-
tion Ser. No. 326,740.
The resulting battery can operate for a period of the
order of about 100 discharge-charge cycles of 30 minutes
each at 100? C.
EXAMPLE 15
A ballery sa,hstanli,tlly similar to that of Example 1 is
fabricated, except that in place of the separator of Ex-
ample I, a 'IcIlnn tie r itor of substantially the same
thickness is employed.
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The Teflon is not readily wetted by the KOH electrolyte,
causing the separator to have high resistance, and as a
result the efficiency and capacity of the battery are sub-
stantially reduced. Such a battery runs for only about
25 discharge-charge cycles at 100? C. before battery
EXAMPLE 16
A hydrous zirconium oxided membrane prepared as in
Example I above, but having a porosity of about 3%, is
employed in a battery unit as described in Example 1.
This battery has a capacity of only about 5 amperes per
square foot as compared to the 27 amperes per square
foot of the battery of Example 1.
10
junction with any. desired electrode system, including
silver-zinc, silver-cadtnium, nickel-cadmium, and the like.
While we have described particular embodiments of
our invention for purposes of illustration, it will be under-
stood that the invention is not to be taken as limited ex-
cept by the scope of the appended claims.
We claim:
1. A battery comprising a pair of electrodes of op-
posite polarity and a porous separator between said elec-
trodes for retaining electrolyte and permitting transfer of
electrolyte ions, said separator consisting essentially of a
porous insoluble hydrous inorganic oxide and said
separator having a porosity permitting transfer of elec-
trolyte ions through such separator, but preventing trans-
fer of electrode ions therethrough.
A hydrous zirconium oxide membrane is prepared as drous inorganic oxide being a porous insoluble hydrous
in Examp4e 1 above, but having a porosity of about 75%. metal oxide wherein said metallic element is selected
This battery runs for only about 50 to about 75 dis- from the group consisting of Al, Ga, In, Sc, Y, Zr, Ti, Hf,
charge-charge cycles before failing, as compared to the 20 Pb, Si, Ge, Sri, Sb, Bi, As, V, Nb, Ta, Cr, Mo, W, Mn, Re,
substantially larger number of such cycles for the battery Tc, Fe, Co, Ni, Ac, Th, U, Pu, La, Ce and Yb, and said
of Exampile i. separator having a porosity in the range from about 5%
From the foregoing, it is seen that the invention pro- to about 40%.
vides a high energy density battery embodying hydrous 3. A battery comprising a pair of electrodes of opposite
metal oxide membranes or separators having porous 25 polarity and a porous rigid separator between said elec-
characteristics which prevent migration of electrode ions, trodes for retaining electrolyte and permitting transfer
such as silver and zinc ions through the separator to op- of electrolyte ions, said separator consisting essentially of
posite electrodes, while permitting free transfer of hy- a porous insoluble hydrous metal oxide and said separator
droxyl ions through the separator. Such inorganic mem- having a porosity in the range from about 5% to about
branes permit substantially higher temperatures of op- 30 40%.
eration of the order of 100? C. and above, without de- 4. A battery comprising a pair of electrodes of opposite
terioration of these membranes as compared to prior art, polarity and a porous rigid separator between said elec-
e.g., organic separators, are resistant to oxidation by elec- trodes for retaining electrolyte and permitting transfer of
trodes, e.g., silver oxide, and are radiation resistant. Bat- electrolyte ions, and an electrolyte in the pores of said
teries incorporating the separators of the, invention are 33 separator, said electrodes being disposed in supported re-
capable of being cycled through many discharge-charge lation against opposite surfaces of said separator, said
cycles without any substantial loss of capacity. Such separator consisting essentially of a porous insoluble hy-
separators are of rigid, relatively inflexible structure, and drous metal oxide and said separator having a porosity in
are capable of supporting to some degree electrodes placed the range from about 5% to about 40%.
on opposite sides of the separator in contact therewith. 40 5. A battery comprising a pair of electrodes of opposite
We are aware of U.S. Patent 1,863,070. The patent polarity and a porous rigid separator between said elec-
describes filters or diaphragms which can be employed trodes for retaining electrolyte and permitting transfer of
for electrolytic purposes, by heating or sintering. of chro- electrolyte ions, said separator consisting essentially of
mium oxide together with other compounds which, on a porous insoluble hydrous metal oxide of a metal selected
being heated, decompose, leaving pores, to thereby control 45 from the group consisting of zirconium, titanium, anti-
or increase pore size of the chromium oxide body to mony, tungsten, silicon, scandium, bismuth, vanadium,
obtain a high porosity membrane. It is stated in the aluminum and cerium, said hydrous oxide separator hav-
patent that other heavy metal oxides such as zirconium ing a porosity in the range from about 5% to about 40%.
oxide can also be used. 6. A battery comprising a pair of electrodes of opposite
The hydrous metal oxide separators of the invention 50 polarity and a porous separator between said electrodes
have advantages for use in batteries not possessed by the for retaining electrolyte and permitting transfer of elect
sintered oxides of the patent. Thus, for example, although trolyte ions, and an electrolyte in the pores of said sepa-
the insoluble hydrous oxide separators of the invention rator, said separator being a rigid membrane consisting
are dielectric materials and have substantial internal re- essentially of a porous insoluble hydrous metal oxide of a
sistance. their resistance in this respect is not nearly as high 55 metal selected from the group consisting of zirconium,
as that of the sintered inorganic oxides such as the sin- titanium, antimony, tungsten, silicon, scandium, bismuth,
tered cbromium oxide and the sintered zirconium oxide vanadium, aluminum and cerium, said hydrous oxide
diaphragms of the patent, and thus, batteries embodying separator having a porosity in the range of about 10% to
the hydrous oxide separators of the invention have sub- about 25%.
ktantially less internal resistance and are therefore more 60 7. A battery comprising a pair of electrodes of op-
efficient than batteries employing the sintered chromium posite polarity and a porous separator between said elec-
oxide and sintered zirconium oxide diaphragms of the trodes for retaining electrolyte and permitting transfer of
patent. Further, the sintered metal oxide diaphragms of electrolyte ions, and an electrolyte in the pores of said
the above patent have a substantially greater porosity separator, said separator b - . a rigid membrane consist-
than the hydrous oxide separators of the invention and 65 ing essentially of hydrous z. ? }nium oxide and said sepa-
would result in batteries of -substantially reduced cycle rator having a porosity in the range from about 5% to
life and of low strength. , about 40%.
Moreover, hydrous metal oxides employed in the =ma- 8. A battery comprising a pair of electrodes of op-
rators of the invention have ion exchange character - s, posite polarity and .a porous separator between said elec-
which render such separators particularly suited t .rse 71) trodes for retaining electrolyte and permitting transfer of
in fuel cells as well as in batteries, whereas the sintered electrolyte ions, said electrodes being disposed in supported
oxide diaphragms of the patent have no ion exchange relation against opposite surfaces of said separator, said
properties. separator being a rigid membrane consisting essentially of
It will be understood that the hydrous metal oxide hydrous zirconium oxide and said separator having a
separators of the invention can be employed in con- 75 porosity in the range from about 5110 to about 40%.
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11 12
9. A battery comprising zinc and silver electrodes and
a porous rigid separator between said electrodes for re-
taining electrolyte and permitting transfer of electrolyte
ions, said separator consisting essentially of a porous in-
soluble hydrous metal oxide of a metal selected from the
group consisting of zirconium, titanium, antimony, tung-
sten, silicon, scandium, bismuth, vanadium, aluminum
and cerium, said hydrous oxide separator having a Porosity
in the range from about 5% to about 40%.
10. A battery comprising zinc and silver electrodes and
a porous separator between said electrodes for retaining
electrolyte and permitting transfer of electrolyte ions, and
an electrolyte in the pores of said separator, said separator
being a strong rigid membrane consisting essentially of
hydrous zirconium oxide and said separator having a
porosity in the range from about 5% to about 40%.
11. A battery as defined in claim 10, wherein the po-
rosity of said membrane ranges from about 10% to about
25%.
12. A battery comprising a pair of electrodes of op-
posite polarity and a porous separator between said elec-
trodes for retaining electrolyte and permitting transfer of
electrolyte ions, said separator being composed of a porous
thin rigid inert plate, a gel of a porous insoluble hydrous
inorganic oxide filling the pores of said plate, and said
separator having a porosity permitting transfer of elec-
trolyte ions through such separator, but preventing trans-
fer of electrode ions therethrough.
13. A battery comprising a pair of electrodes of op-
posite polarity and a porous separator between said elec-
trodes for retaining electrolyte and permitting transfer of
electrolyte ions, said separator being composed of a porous
thin rigid inert ceramic plate, a gel of hydrous zirconium
oxide. filling the pores of said plate, and said separator
having a porosity in the range from about 5% to about
40%.
14. A battery comprising a pair of electrodes of op-
posi.e polarity and a porous separator between said elec-
trodes for retaining electrolyte and permitting transfer of
.electrolyte ions, said separator being composed of a por-
ous flame-sprayed rigid inert zirconia membrane, a gel of
hydrous zirconium oxide filling the pores of said mem-
brane and said separator having a porosity in the range
from about 5% to about 40%.
References Cited
UNITED STATES PATENTS
483,692
10/1892
Lehman ------------
136-142
2,422,045
6/1947
Ruben -------------
136-1.54
2,698,305
12/ 1954
Plank et al. --------
252-317
3,056,647
10/1962
Amphlett ----------
136-153
3,147,149
9/1964
Postal --------------
136-163
3,276,910
10/1966
Grasselli et al. ---__-__ 136-86
3,257,239
6/1966
Shultz et al. _______-__ 136-86
3,266,940
8/1966
Caesar -------------- 136-86
WINSTON A. DOUGLAS, Primary Examiner
DONALD L. WALTON, Assistant Examiner
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 Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010056-5 3,498,840
United "es ate t ce Patented Mar. 3, 1970
3,495,840
SEPARATOR FOR ALKALINE BATTERIES AND
METHOD OF MAKING SAME
Howard Eugene Hoyt and Helmuth Louis Pftuger, Hun-
tingdon Valley, Pa., assign?rs to Borden, Inc., a corpo-
ration of New Jersey
No Drawing. Filed Nov. 2, 1967, Ser. No. 679,980
Int. Cl. H01m 3102; C08f 15/18
U.S. Cl. 136-6 10 Claims
2
The invention also comprises the resultant membranes and
to electrochemical cells utilizing said membranes.
DETAILED DESCRIPTION
In carrying out the method of this invention, the co-
polymer is prepared by copolymerizing a methacrylate
ester and a more easily-hydrolyzable monomer copolym-
erizable therewith selected from the group consisting of
esters of CI-C8 alkyl alcohols with an alpha-beta unsatu-
rated acid. The proportion of copolymerizable easily hy-
drolyzable monomer may be 10 to 60 mole-percent of the
total ester monomers, and preferably 15 to 50 mole-per-
cent, in the copolymer.
As to materials, the methacrylate ester used may be
the reaction product of any C, to Cs alkyl alcohol, pref-
erably C, to C4, with methacrylic acid. Example of suit-
able alcohols are methanol, ethanol, propanol, and buta-
nol.
The copolymerizable monomer is preferably again the
reaction product of a Cr to C4 alkyl alcohol with acrylic
acid although other alpha-beta unsaturated acids such as
itaconic, maleic, or fumaric can be used.
The copolymer prepared is then subjected to saponifica-
tion conditions, i.e., treated with an excess of alkali (such
as ammonium hydroxide, sodium hydroxide, and the like)
at 100 C. or less. Under such conditions only the easily
hydrolyzable ester is substantially saponified and the hy-
drolyzed polymer thus contains the following units ran-
domly distributed throughout the copolymer within the
molar ratios noted:
ABSTRACT OF THE DISCLOSURE
This invention relates to the preparation of membranes
suitable for use as separators in concentrated alkaline bat-
tery cells by selective solvolysis of copolymers of meth-
acrylate esters with acrylate esters followed by addition
of a base and to the resultant, products.
ORIGIN OF THE INVENTION
The invention described herein was made in the per-
formance of work under a NASA contract and is subject
to the provision of Section 305 of the National Aeronau-
tics and Space Act of 1958, Public Law 85-568 (72 STAT.
435; 42 USC 2457).
BACKGROUND OF THE INVENTION
The cycle life of rechargeable battery cells is limited by
the tendency of the electrodes to short circuit and it is
known that this tendency can be slowed down by the
use of a separator membrane between the electrodes.
Such a separator must have low resistance to the passage
of an electrolytic current and in many applications it must
also be stable against oxidation. This is particularly the
case with alkaline silver-zinc or silver-cadmium cells, the
silver oxide in such cells being a powerful oxidizing agent.
For this reason, separators heretofore used have not
proven satisfactory since cells of only a very limited cy-
cling life can be obtained.
Attempts to use membranes of polyacrylic acid which is
known to be extremely resistant to oxidation and whose
inherent polarity makes it compatible with concentrated
alkali and which is receptive, in association with said alk-
ali, to the passage of an electrolytic current have not been
successful since polyacrylic acid as a membrane is solu-
ble in alkali. One effective way of exploiting the advanta- acrylic or substituted acrylic acids with acrylate or meth-
geous inherent properties of polyacrylic acid is to incor- acrylate esters.
porate it into a film with an insolubilizing polymer such
as methyl cellulose. While such formulations do possess
a high degree of resistance to oxidation, the methyl cel-
lulose combination is not as oxidation-resistant as poly-
acrylic acid by itself.
SUMMARY OF THE INVENTION
It- has now been found that certain copolymers of meth-
acrylate esters. with acrylic acid form membranes that
possess the required combination of properties, namely,
extreme oxidation resistance, insolubility in concentrated
aqueous alkali, and high conductivity of an electrolytic
current when in equilibrium with battery alkali.
The instant invention comprises the method of making
these copolymers by first copolymerizing a methacrylate
ester (or esters) with a more readily hydrolyzable ester,
followed by a selective saponification whereby the meth-
acrylate ester moieties remain essentially intact and the
readily hydrolyzable ester moiety is saponified and to the
partial or complete neutralization of the relatively brittle
copolymer acid with a base to make membranes which are
sufflicently flexible in the dry state so that they may he
wrapped around electrodes without damage by handling.
B: CHI
L.uOORJ
IRI' R'
and iCH_
35 wherein R is C1-C, alkyl group, R' is hydrogen or car-
boxylate ion, and R" is hydrogen, carboxylate, or car-
boxylate, or carboxylate methyl ion. It is understood that
the cation portion of the saponifying alkali is a counter
40 ion to the negative carboxylate or carboxylate methyl ion.
By this means it has been found possible to produce
polymers containing a much higher proportionality of
carboxyl groups than it is possible to obtain by direct
copolymerization of methacrylate ester with acrylic acid,
45 it being well known in the art of copolymerization of
olefinic monomers that great difficulty is encountered in
50 One advantage of this procedure is that a controllable
range of polarity can be accomplished by synthetic means
as opposed to the use of materials of the prior art which
have a fixed polarity range. Thus, it appears possible to
control the ratio of the acid moiety in the copolymer to
65 correspond to optimum electrolytic conduction of any
concentration of alkali, from 20% to 50%, potassium hy-
droxide for example.
Following saponification of the methacrylate-acrylate
copolymers the hydrolyzed product may be recovered in
60 acid form. For this purpose the saponification product is
added to aqueous mineral acid with stirring. We have
found that the acid form of the hydrolyzed copolymers is
much less soluble in water than the alkaline form. Pre-
cipitation occurs and the acid form of copolymer can be
65 readily recovered by filtration and washing.
For purposes of laying down the films of this inven-
tion it is preferred to neutralize or partially neutralize
the acid form by the addition of a suitable base. It has
been surprisingly found that the relatively brittle co-
70 polymer acid is converted by this neutralization to a ma-
terial sufficiently flexible in the dry state that it may
be wrapped with ease around electrodes without damage
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by handling. The base used for the said neutralization may
include potassium hydroxide, sodium hydroxide, tetra-
methylammonium hydroxide, ammonia, substituted
amines such as methylamine, ethylamine, dimethyl amine,
propylamine, ethanolamine, triethanolamine, propyla-
mine, aniline, pyridine and quinoline. Preferred bases
are hydroxy propylamine and triethanolamine.
The aqueous solution may be cast in sheet form and
evaporated to dryness. Other forms may be made as
for example plates, slabs, "buttons," films and the like.
Solutions should not be so concentrated as to precipitate
the components before drying.
Good flexibility in the film is of particular importance
in the construction of the individual battery cells during
the operation of wrapping the separators around the elec-
trodes. In one common technique a so-called U wrap is
made whereby two positive electrodes are placed butt end
to butt end on a sheet of separator and after, for ex-
ample, six wraps of the pair the wrapped assembly is
aqueous methanol and titrated with 5 N NaOH. This
gave a value of 4.8 ml. N/I per gram of polymer and
corresponded to 42.3 mol percent hydrolysis of the
copolymer ester to free acid groups.
Analysis of the product for carbon and
Equiv. to combined
acrylic acid, mol
Wt. percent percent
55.6 44.0
7.25 30. R
37.16 42.3
EXAMPLE 3
One gram of the acidic polymer of Example 2 was
dissolved in 9 ml. water by solubilizing with 1 ml. of
reagent ammonia. A film was cast from this solution
using a doctor blade on a levelled glass plate. Upon
drying a thin film formed on the glass which was too
brittle to remove, shattering into small pieces when
scraped. It is believed that the dried film was of sub-
stantially the same composition as the original acid
polymer of Example 2, having reverted by evaporation
of ammonia to the precursor acid polymer.
EXAMPLE 4
One gram of the acidic polymer of Example 2 was
dissolved in 4 ml. water by solubilizing with 0.45 gram
3-hydroxypropylamine, an amount stoichiometrically
equivalent to the acid groups present. The solution was
cast at 22 mils clearance as in Example 3. The dried
film measured 1.5 mils in thickness. It was very flexible
and slightly tacky, showing a tendency to stick to itself
when pressure was applied. It was insoluble in 45% KOH
and in this medium showed a specific resistance of 7.2
ohms-cm. of swollen thickness. This low electrolytic
resistance was somewhat below that of an unplasticized
cellophane film (PUDO 119) such as is currently used
for batteries, the comparison value for the latter being
9.8 ohms-cm. of swollen thickness.
EXAMPLE 5
Ten grams of the acid polymer of Example 2 was dis-
solved in 130 ml. water solubilized with 2.25 grams 3-
hydroxypropylamine, an amount stoichiometrically equiv-
alent to half the acid groups of the polymer, plus 10
ml. reagent ammonia, an excess over the total acid groups
present. The solution was cast at 30 mils clearance on
the doctor blade to give a dried film of 1.6 mils thick-
ness. This film was of a flexibility and softness inter-
mediate between that of Examples 3 and 4, being neither
sticky nor brittle. It gave a flex test of 2368 cycles be-
fore breaking (MIT Flex Test ASTM D643-43). The
tensile strength of the film was 2390 p.s.i. and the per-
cent elongation at break 189%. The specific resistance
of the film was 26 ohms-cm. in 45% KOH.
EXAMPLE 6
Two grams of the acid polymer of Example 2 were
folded at the junction in the form of the letter U. When 20
separators of poorer flexibility are used cracks tend to
occur in the separator at the base of the U, particularly
in the outer wraps, thus destroying the utility of the
separator at these points. We have found experimentally
that this is particularly likely to occur below a certain 25
critical threshold of flexibility, corresponding to with-
standing at least about 800 flex cycles as measured by the
ASTM Folding Endurance Test D643-43 with 200 grams
tension on the specimen.
The invention will be further described in connection
with the following examples which are set forth for
the purpose of illustration only and wherein proportions
are in parts by weight unless specifically stated to the
contrary.
EXAMPLE 1
To a one liter resin flask equipped with stirrer, reflux
condenser, heater, addition appurtenances and nitrogen
purge the following were charged:
Benzene (distilled over sodium) ------------ ml-- 500
Methyl methacrylate ---------- grams-- 100 (1 mol)
Ethyl acrylate _________________do____ 100 (1 mol)
Azobisisobutyronitrile __________________gram__ 0.2
After purging with nitrogen the benzene was brought
to reflux. After 2 hours 25 ml. benzene containing 0.2
grams azobisisobutylronitrile was added and the reaction
held 'at 75? C. for a total of 19 hours. At the end of this
time a solids determination showed 29.6% of nonvolatiles
which corresponded to a conversion to polymer of
about 94%.
The reaction mixture was cast as a thin film on a
large foil tray in the fume hood.-This was removed from
the foil and vacuum dried to constant weight at 50? C.
for 6 hours.
By saponification a sample consumed standard alkali
corresponding to 4.22 ml. N/1 per gram of polymer.
This corresponded to 42.2 mol percent of the ester groups
present.
EXAMPLE 2
64 grams of the coploymer ester of Example 1 were
saponified by heating on a steam bath with 2500 ml.
isopropanel, 925 ml. water and 52 grams of 30% KOH
for 18 hours. The isopropanol was then distilled off and
the resulting aqueous solution was added slowly to 200
ml. of water containing 10 ml. concentrated sulfuric acid.
A white fibrous solid precipitated out. This was filtered
off and washed repeatedly with cold water.
The white solid was first air-dried, then vacuum dried
for several hours at 154? F. to constant weight. The yield
of. dry product was 47.2 grams. This represented a con-
version, of copolymer ester to partially hydrolyzed ester, of
83.7% based on the prognosticated degree of hydrolysis
of the analytical saponification of Example 1.
A sample of the acidic polymer was dissolved in
60 dissolved in 27 ml. water by solubilizing with 1.45 ml.
30% KOH. This amount of KOH corresponded to a
stoichiometric equivalent of the acid function. The 1.4
mil film cast from this solution was hard and flexible,
giving an average of 12,566 cycles in the ASTM fold
65 test. Tensile strength was 2340 p.s.i. Resistance in 45%
KOH was 35.7 ohms-cm.
EXAMPLE 7
Two grams of the acid polymer of Example 2 were
dissolved in 27 ml. water by solubilizing with .74 gram
triethanolamine (0.5 equivalent) and 1.7 ml. reagent am-
monia. The 1.7 mil film prepared by casting this solu-
tion was hard and flexible (5741 cycles in the ASTM
fold test). Resistance in 45% KOH was 35.7 ohms-cm.
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3,498,840
5
the silver-zinc, silver-cadmium, or other like alkaline
cells,
It will be understood that it is intended to cover all
changes and modifications of the examples of the in-
vention herein chosen for the purpose of illustration
which do not constitute departures from the spirit and
scope of the invention.
What is claimed is:
1. The method of making an oxidation resistant, highly
conductive battery separator membrane comprising the
steps of copolymerizing (a) a CI-C8 alkyl ester of meth-
acrylic acid and (b) a readily hydrolyzable CI-C8 alkyl
ester of an alpha-beta unsaturated acid which ester is
more readily hydrolyzable than said methacrylic ester, se-
lectively saponifying said copolymer so as to substantially
saponify all of said readily hydrolyzable moity in the co-
polymer without any substantial saponification of said
methacrylic acid moiety, and forming the thus saponified
polymer into a membrane.
2. The method of claim 1 wherein ester (a) is methyl
methacrylate, ester (b) is ethyl acrylate and the copolymer
contains from about 10 to about 60 mol-percent of ethyl
acrylate.
3. The method of claim 1 wherein the saponified co-
polymer is converted to the acid form by contact with an
acid prior to formation of the membrane.
4. The method of claim 3 wherein the acid form of the
6
6. A battery separator for alkaline electrochemical cells
comprising the membrane made according to the process
of claim 3.
7. A battery separator for alkaline electrochemical
cells comprising the membrane made according to the
process of claim 4.
8. An alkaline electrochemical cell comprising elec-
trodes, a concentrated aqueous alkali fluid, and the battery
separator of claim 5 interposed between the electrodes.
9. An alkaline silver cell comprising electrodes, a con-
centrated aqueous alkali fluid, and the battery separator
of claim 6 interposed between the electrodes.
10. An alkaline silver-zinc cell comprising a silver elec-
trode, a zinc electrode, a concentrated aqueous alkali fluid,
15 and the battery separator of claim 7 interposed between
the electrodes.
References Cited
UNITED STATES PATENTS
3,284,382
11/1966
Rosser et al. --___ 136-146 XR
3,330,702
7/1967
Horowitz ----------- 136-146
3,376,168
4/1968
Horowitz ----------- 136-146
WINSTON A. DOUGLAS, Primary Examiner
L. L. WALTON, Assistant Examiner
U.S. Cl. X.R.
136-146, 148; 260-86.1E
copolymer is at least partially neutralized by a base prior
to formation of the membrane.
5. A battery separator for alkaline electrochemical cells 30
comprising the membrane made according to the process
of claim 1.
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 Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010056-5
United States Patent
[721 Inventor Thomas J. Wetherell
New York, N.Y.
[211 Appl. No. 793,894
[221 Filed Jan.24, 1969
[45] Patented Oct. 26, 1971
[73] Assignee High Energy ProcessIng Corporation
New Bedford, Mass.
[54] BATTERY SEPARATOR
4 Claims, No Drawhtgs
1521 U.S. CI ........................................................ 136/146,
117/93.31
1511 int. CL ................................... .... 1101m 3/00
(501 Field of Search ................. ....................... 136/146,
References Cited
UNITED STATES PATENTS
2,482,062 9/1949 Hanson ........................
fill
2,965,697 12/1960 Duddy .......................... 136/140
3,092,519 6/1963 Olson ........................... 136/146
3,101,276 8/1963 Hendricks .................... 117156
3,111,424 11/1963 LeClair ........................ 117/93.31 X
3,186,876 6/1965 Piechon ........................ 13C,1143
3,188,165 6/1965 Magat et at ................... 117/93.31 X
3,216,864 11/1965 Bushrod et al. ............... 136/148
3,240,723 3/1966 Friedlander .................. 260/2.1
3,330,702 7/1967 Horowitz ...................... 136/146
3,427,206 2/1969 Scardaville et al............ 136/146
Primary Examiner-Winston A. Douglas
Assistant Examiner-A. Skapars
Attorney-Irving Seidman
ABSTRACT: A battery separator for alkaline storage batteries
of the nonwoven fiber mat type; the fiber mat being im-
pregnated with a polymeric binder and a monomeric wetting
agent, the thus impregnated mat being subjected to irradiation
to form a cross-linked unitary structure.
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 Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010056-5
1
BATTERY SEPARATOR
BACKGROUND OF THE INVENTION
2
weight is about 2 ounces per square yard.
The calendared web is then sprayed with an aqueous solu-
tion of acrylic acid, in an amount such that the residual acid i
n
Storage (batteries of the alkaline type, such as those utilizing the finished product amounts to about 5 percent by weight
a potassium hydroxide electrolyte, have their operational effi- 5 thereof
ciency severely circumscribed by the nature of the separator The impregnated and coated web is then subjected to a 7
elements used in the battery. Mev linear accelerator to produce an irradition of about 2
Various separator elements have been proposed including megarads. The resultant product is then converted to battery
the fiber mat-type having various binder impregnants, It has separator e!aments in a manner known in the art.
been found that with known separator elements, high rate 10 It has been found that the use of battery separators of the in-
charging may be adversely affected; migratory phenomena stant invention, the efficiency of alkaline-type storage batte-
within the cell may become excessive to thereby reduce the ef- ries using potassium hydroxide electrolyte, as in a nickel-cad-
fciency of the device, and other battery characteristics such mium battery, is substantially improved and such battery is re-
as holding a charge, the discharge curve, etc., may be relative- markably free of adverse migration phenomena and the like.
ly poor. is It is understood that in lieu of polypropylene fibers,
Accordingly, an object of this invention is to provide an im- polyethylene or polyamid fibers may be used. Also, the denier
proved fiber mat battery separator which increases the effi- of the fibers may range from about 1.5 to about 15.
ciency of battery charge and discharge. The web impregnant may be constituted of polymeric un-
Another object of this invention is to provide an improved saturated organic acids such as polymethacrylic acid and
battery separator of the character described, wherein the 20 polyitaconic acid in lieu of polyacrylic acid. The binder con-
fibers of the mat and impregnating agents for the mat are centration may range from about 2 percent to about 15 per-
selected so that upon suitable irradiation of the impregnated cent based on the total weight of the finished product.
mat, across-finking action takes place as between the several gIn aplace of the acrylic acid-wetting agent, other unsaturated . such constituents of the mat, to produce a unitary structure having 25 andthea like. m monomer can be comb in dtw thya trace
c acid
improved properties as they relate to usage in alkaline storage amount (I to 5 percent by weight) of a monofunctional
batteries. monomer'such as divinylbenzene to reduce the radiation
Other objects of this invention will in part be obvious and in dosage for the cross-linking action.
part hereinaEleer pointed out.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In accordance with the instant invention, a nonwoven fiber
mat is formed from selected polymeric fibers of suitable deni-
er and staple length; the mat then being impregnated with an
aqueous solution of a polymeric unsaturated organic acid; the
impregnated web being then hot calendared to a desired
thickness and sprayed with a solution of a monomeric unsatu-
rated organic acid-wetting agent. The thus impregnated web is
subjected to selected conditions of irradiation to produce
cross-linking effects and unitizing the web.
Thus, by way of illustration, a battery separator web of the
instant invention was made as follows:
A nonwoven fiber web was formed on a Curlator Rando-
Webber or other web forming equipment, utilizing
polypropylene fibers of 3 denier, 1 9/16 inches staple length.
The web is then saturated with an aqueous solution of
polyacrylic acid, which is used in amounts to constitute 5 per-
cent by weight of the completed article.
The saturated web is then calendared by a stand of heated
calendar rolls to a thickness of about 8 mils. The material
3,615,865
While the irradiation is preferably of the order of I to 2
30 megarads; the range may be from about 0.5 to 25 megarads.
I claim:
1. A battery separator for alkaline storage batteries com-
prising a nonwoven, matted web of polymeric fibers selected
from the group consisting of polypropylene, polyethylene and
35 polyamide, a polymeric saturant distributed through said web,
said saturant being selected from the group consisting of
polyacrylic acid, polymethacrylic acid and polyitaconic acid.
and a coating on said saturated web, said coating being
selected from the group consisting of acrylic acid and
40 methacrylic acid, said saturant and coating being irradiated in
situ to provide a cross-linking of the fibers, saturant and coat-
ing.
2. A battery separator as in claim 1 wherein said fibers are
of polypropylene having a 3 denier and a stable length of
about 1.5 to about 2.0 inches.
3. A battery separator as in claim 1 wherein said fibers have
a denier of from about 1.5 to about 10.0.
4. A battery separator as in claim 1. wherein said saturant
amounts to about 5 percent by weight of the irradiated web.
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