Abstract: A battery separator for an alkaline battery. The separator comprises a cross-linked copolymer of vinyl alcohol units and unsaturated carboxylic acid units. The cross-linked copolymer is insoluble in water, has excellent zincate diffusion and oxygen gas barrier properties and a low electrical resistivity. Cross-linking with a polyaldehyde cross-linking agent is preferred.

Abstract: An improved zinc electrode for alkaline cells includes up to about ten percent by weight of Ba(OH).sub.2.8H.sub.2 O with about five percent being preferred. The zinc electrode may or may not be amalgamated with mercury.

Abstract: A flexible, porous battery separator comprising a coating applied to a porous, flexible substrate. The coating comprises:(a) a thermoplastic rubber-based resin which is insoluble and unreactive in the alkaline electrolyte,(b) a polar organic plasticizer which is reactive with the alkaline electrolyte to produce a reaction product which contains a hydroxyl group and/or a carboxylic acid group, and(c) a mixture of polar particulate filler materials which are unreactive with the electrolyte, the mixture comprising at least one first filler material having a surface area of greater than 25 meters.sup.2 /gram, at least one second filler material having a surface area of 10 to 25 meters.sup.2 /gram, wherein the volume of the mixture of filler materials is less than 45% of the total volume of the fillers and the binder, the filler surface area per gram of binder is about 20 to 60 meters.sup.2 /gram, and the amount of plasticizer is sufficient to coat each filler particle.A method of forming the battery separator.

Abstract: A film-forming polyvinyl alcohol resin is admixed, in aqueous solution, with a dialdehyde cross-linking agent which is capable of cross-linking the polyvinyl alcohol resin and a water soluble acid aldehyde containing a reactive aldehyde group capable of reacting with hydroxyl groups in the polyvinyl alcohol resin and an ionizable acid hydrogen atom. The dialdehyde is present in an amount sufficient to react with from 1 to 20% by weight of the theoretical amount required to react with all of the hydroxyl groups of the polyvinyl alcohol. The amount of acid aldehyde is from 1 to 50% by weight, same basis, and is sufficient to reduce the pH of the aqueous admixture to 5 or less. The admixture is then formed into a desired physical shape, such as by casting a sheet or film, and the shaped material is then heated to simultaneously dry and cross-link the article.

Abstract: A flexible, porous battery separator comprising a coating applied to a porous, flexible substrate. The coating comprises:(a) a thermoplastic rubber-based resin which is insoluble and unreactive in the alkaline electrolyte,(b) a polar organic plasticizer which is reactive with the alkaline electrolyte to produce a reaction product which contains a hydroxyl group and/or a carboxylic acid group, and(c) a mixture of polar particulate filler materials which are unreactive with the electrolyte, the mixture comprising at least one first filler material having a surface area of greater than 25 meters.sup.2 /gram, at least one second filler material having a surface area of 10 to 25 meters.sup.2 /gram, wherein the volume of the mixture of filler materials is less than 45% of the total volume of the fillers and the binder, the filler surface area per gram of binder is about 20 to 60 meters.sup.2 /gram, and the amount of plasticizer is sufficient to coat each filler particle.A method of forming the battery separator.

Abstract: A method of making a membrane comprised of a hydrochloric acid-insoluble sheet of a mixture of a rubber and a powdered ion transport material is disclosed. The sheet can be present as a coating upon a flexible and porous substrate. These membranes can be used in oxidation-reduction electrical accumulator cells wherein the reduction of one member of a couple is accompained by the oxidation of the other member of the couple on the other side of the cell and this must be accompained by a change in chloride ion concentration in both sides. The method comprises preparing a mixture of fine rubber particles, a solvent for the rubber and a powdered ion transport material. The mixture is formed into a sheet and dried to produce a microporous sheet. The ion transport material includes particles ranging from about 0.01 to 10 microns in size and comprises from 20 to 50 volume percent of the microporous sheet.

Abstract: A film-forming polyvinyl alcohol polymer is mixed with a polyaldehyde-polysaccharide cross-linking agent having at least two monosaccharide units and a plurality of aldehyde groups per molecule, preferably an average of at least one aldehyde group per monosaccharide units. The cross-linking agent, such as a polydialdehyde starch, is used in an amount of about 2.5 to 20% of the theoretical amount required to cross-link all of the available hydroxyl groups of the polyvinyl alcohol polymer. Reaction between the polymer and cross-linking agent is effected in aqueous acidic solution to produce the cross-linked polymer. The polymer product has low electrical resistivity and other properties rendering it suitable for making separators for alkaline batteries. In that event, the mixture of polymer and cross-linking agent is formed into a sheet or film or the like and the film is cut to size and otherwise fabricated into a configuration suitable for a particular end use.

Abstract: A method of producing a cross-linked polyvinyl alcohol structure, such as a battery separator membrane or electrode envelope. An aqueous solution of a film-forming polyvinyl alcohol is admixed with an aldehyde cross-linking agent at basic pH to inhibit cross-linking. The cross-linking agent, preferably a dialdehyde such as glutaraldehyde, is used in an amount of from about 1/2 to about 20% of the theoretical amount required to cross-link all of the hydroxyl groups of the polymer. The aqueous admixture is formed into a desired physical shape, such as by casting a sheet of the solution. The sheet is then dried to form a self-supporting film. Cross-linking is then effected by immersing the film in aqueous acid solution. The resultant product has excellent properties for use as a battery separator, including a low electrical resistivity, the value of which is principally determined by the amount of cross-linking which is easily and closely controlled by the amount of cross-linking agent added to the polymer.

Abstract: A self-supporting sheet structure comprising a water soluble, non-cross-linked polymer such as polyvinyl alcohol which is capable of being cross-linked by reaction with hydrogen atom radicals and hydroxyl molecule radicals is contacted with an aqueous solution having a pH of less than 8 and containing a dissolved salt in an amount sufficient to prevent substantial dissolution of the non-cross-linked polymer in the aqueous solution. The aqueous solution is then irradiated with ionizing radiation to form hydrogen atom radicals and hydroxyl molecule radicals and the irradiation is continued for a time sufficient to effect cross-linking of the water soluble polymer to produce a water-insoluble polymer sheet structure. The method has particular application in the production of battery separators and electrode envelopes for alkaline batteries.

Abstract: A battery separator is produced from a polyvinyl alcohol sheet structure which is subjected to an in situ, self cross-linking process by selective oxidation of the 1,2 diol units present in the polyvinyl alcohol sheet structure. The 1,2 diol units are cleaved to form aldehyde end groups which subsequently cross-link through acetalization of the 1,3 diol units of the polyvinyl alcohol. Selective oxidation is achieved using a solution of a suitable oxidizing agent such as periodic acid or lead tetraacetate.

Abstract: Membranes comprising a hydrochloric acid-insoluble sheet of a mixture of a rubber and a powdered ion transport material. The sheet can be present as a coating upon a flexible and porous substrate. These membranes can be used in oxidation-reduction electrical accumulator cells wherein the reduction of one member of a couple is accompanied by the oxidation of the other member of the couple on the other side of the cell and this must be accompanied by a change in chloride ion concentration in both sides.

Abstract: There is disclosed a flexible separator for use between the electrodes of Ni-Cd and Ni-Zn batteries using alkaline electrolytes. The separator is made by coating a porous substrate such as sheets or mats of asbestos or other materials with a battery separator composition. The coating material includes a rubber-based resin copolymer, a plasticizer and inorganic and organic fillers which comprise 55% by volume or less of the coating as finally dried. One or more of the filler materials, whether organic or inorganic, is preferably active with the alkaline electrolyte to produce pores in the separator coating. The plasticizer is an organic additive such as a material which is hydrolyzed by the alkaline electrolyte to improve conductivity of the separator coating.

Abstract: Gels are formed from silica powders and hydrochloric acid. The gels can then be impregnated into a polymeric foam and the resultant sheet material can then be used in applications where the transport of chloride ions is desired. Specifically disclosed is the utilization of the sheet in electrically rechargable redox flow cells which find application in bulk power storage systems.