GB821229A - Method of manufacturing electrically conductive membranes - Google Patents

Abstract

A solid electrolytically-conductive, selectively permeable, unfractured ion-exchange membrane of an insoluble, infusible, solid polymer in which the ion-exchange groups have a dissociation constant of at least 10-5 and an ion-exchange capacity of at least 0.3 milliequivalents per gram of solid material corrected for the solvent and reinforcing material content, in a gel form with an organic solvent is prepared (1) by dispersing the polymer forming material in at least 25% by weight on the total weight of organic solvent, (2) casting the dispersion as a membrane, (3) polymerizing and curing to the insoluble, infusible state in the presence of the solvent and under conditions preventive of the escape of the solvent, and (4) maintaining the solvent content of the structure. The polymers may be the addition type, e.g. copolymers of divinyl benzene, di-isopropenyl benzene and diallyl ether, and dimethacrylate esters of ethylene or tetraethylene glycols with acrylic or methacrylic acids and esters, maleic anhydride, styrene, styrene p-sulphonic acids or esters, p-chloromethyl styrene, p-dialkylamino styrene, dialkyl p-vinyl benzylamine, trialkyl p-vinyl benzyl ammonium salts, N-alkyl vinyl pyridinium salts, acrylonitrile, vinyl acetate and chloride, vinylidene chloride, and allyl alcohol; or the condensation type, e.g. condensates of aldehydes with phenol and substituted phenols, dihydroyybenzenes, phloroglucinol, aniline and substituted anilines, metaphenylene diamine, melamine, urea, guanidine and guanidine derivatives, polyhydic phenols and polyalkylene polyamines and of ketones with amines. The ion-exchange groups may be cation-permeable carboxylic or sulphonic ions with hydrogen or sodium associated therewith or anion permeable with mobile hydroxyl or chloride ions associated therewith, p, s- and t-amino or quaternary ammonium groups and not more than 4 milliequivalents or ion-exchange groups are incorporated for each mol. of cross-linking agent and not less than 1 equivalent of ion-exchange groups for each 10 mols. of monomer and may be present in the polymerizable components or incorporated after the gel is formed. Solvents mentioned are the lower aliphatic alcohols, saturated ethers, such as dioxane, saturated halogenated aliphatic liquids, such as ethylene chloride, ketones, or aromatic hydrocarbons such as toluene, and the dispersion of polymerizable components or partially polymerized components may be cast alone or with reinforcing material such as glass cloth, paper, polyvinylidene chloride screen, cellulose and polyvinyl chloride, battery paper, and polystyrene-coated glass fibre mat either admixed in the unpolymerized solution or present in the moulds or castings. The polymerizable components may be partially pre-polymerized before casting, and after polymerization the polymeric gel may be converted to an hydrous gel form by leaching repeatedly with water, or if the solvent is water-immiscible by an intermediate solvation with a mutually miscible liquid. Examples describe (1) the copolymerization of maleic anhydride and divinyl benzene with a 2-azo-bis (isobutyronitrile) catalyst in dioxane, by heating at 6.5 DEG C. when cast between two glass plates on glass cloth; (2) copolymerization of ethyl styrene and divinyl benzene with benzoyl peroxide in toluene cast as above, followed by sulphonation to ion-exchange resin; (3) condensation of a sulphonated mixture of resorcinol and phenol in methanol solution with paraformaldehyde; (4) condensation of diethylene triamine with resorcinol and paraformaldehyde and methanol; (5) copolymerization of a 2-vinyl pyridine quaternized with dimethyl sulphate, with divinyl benzene; (6) copolymerization of 2-vinyl pyridine and divinyl benzene in toluene with 2-azo-bis (isobutyronitrile) cast as above and quaternized with dimethyl sulphate in ethanol. The cast membranes are leached with water and equilibrated with sodium hydroxide, hydrochloric acid or sodium chloride. Specification 720,002 is referred to.