The United States of America As Represented by the Administrator of the

The United States of America As Represented by the Administrator

Li-Chen Hsu

Dean W Sheibley

Warren H Philipp

Charles E May

Lorra L Rieker

Michelle A Manzo

Olga D Gonzalez-Sanabria

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.

Alkaline battery containing a separator of a cross-linked copolymer of

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.

Polyvinyl alcohol cross-linked with two aldehydes

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. The cross-linking reaction is then carried out to produce the final product.

Cross-linked polyvinyl alcohol and method of making same

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.

In-situ cross linking of polyvinyl alcohol

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. Low electrical resistivity, desirable in those applications, can be achieved by incorporating a highly conductive water soluble resin, such as polyacrylic acid, with the polyvinyl alcohol.

Method of cross-linking polyvinyl alcohol and other water soluble resins

Triazine compounds and cross-linked polymer compositions are made by heating aromatic nitriles to a temperature in the range of from about 100.degree. C. to about 700.degree. C., and preferably in the range of from about 200.degree. C. to about 350.degree. C. in the presence of a catalyst or mixture of catalysts selected from one or more of the following groups: (A) organic sulfonic and sulfinic acids, (B) organic phosphonic and phosphinic acids, and (C) metallic acetylacetonates, at a pressure in the range of from about atmospheric pressure to about 10,000 p.s.i., and preferably in the range of from about 200 p.s.i. to about 750 p.s.i. Aromatic nitrile-modified (terminated and/or appended) imide, benzimidazole, imidazopyrrolone, quinoxaline, and other condensation type prepolymers or their precopolymers are made which are trimerized with or without a filler by the aforementioned catalytic trimerization process into triaryl-s-triazine ring containing or cross-linked polymeric or copolymeric products useful in applications requiring high thermal-oxidative stability and high performance structural properties at elevated temperatures.

Catalytic trimerization of aromatic nitriles and triaryl-s-triazine ring

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.

In situ self cross-linking of polyvinyl alcohol battery separators

Triazine compounds and cross-linked polymer compositions are made by heating aromatic nitriles to a temperature in the range of from about 100.degree.0 C. to about 700.degree. C., and preferably in the range of from about 200.degree. C. to about 350.degree. C. in the presence of a catalyst or mixture of catalysts selected from one or more of the following groups: (A) organic sulfonic and sulfinic acids, (B) organic phosphonic and phosphinic acids, and (C) metallic acetylacetonates, at a pressure in the range of from about atmospheric pressure to about 10,000 p.s.i., and preferably in the range of from about 200 p.s.i. to about 750 p.s.i. Aromatic nitrile-modified (terminated and/or appended) imide, benzimidazole, imidazopyrrolone, quinoxaline, and other condensation type prepolymers or their precopolymers are made which are trimerized with or without a filler by the aforementioned catalytic trimerization process into triaryl-s-triazine ring containing or cross-linked polymeric or copolymeric products useful in applications requiring high thermal-oxidative stability and high performance structural properties at elevated temperatures.

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Westlake, OH, United States of America

Li-Chen Hsu