Patent GB-856327-A (GB)
Title: Membrane materials and process for producing the same
IPC: H01M50/489
Filed: 1957-09-30
Abstract: A membranaceous composition is characterized by a microporous film-like polymeric matrix formed of a material selected from the group consisting of polyvinyl chloride, polyvinyl butyral and copolymers of vinyl chloride with monomers selected from the group consisting of vinyl acetate, vinylidene chloride and acrylonitrile, said matrix having a finely divided solid hydrophilic polymeric material, which is characterized by the ability to swell in water and aqueous solutions uniformly dispersed therethrough and firmly held therein, the polymeric matrix material and hydrophilic polymeric material being present in proportions within the range of from 1 to 4 parts by weight hydrophilic material to each part by weight of matrix material. An inert synthetic fibrous material is also preferably present in the matrix material.  Specified hydrophilic polymeric materials are non-ion-selective substances selected from polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide and water soluble natural gums, and ion-selective crosslinked polymeric substances, such as a copolymer of methacrylic acid and divinyl benzene, a polyamine type ion-exchange resin, a polystyrene sulphonic acid resin, a polystyrene phosphonic acid resin or a strong base type ion exchange resin High molecular weight aromatic hydrocarbons may be added as plasticizers.  The microporous material is produced by incorporating finely divided particles of the hydrophilic polymeric material in a mixture of matrix material and a solvent therefor, sheeting the mixture, and then leaching out the solvent. Suitable solvents are methyl ethyl ketone, methyl isobutyl ketone, acetone, cyclopentanone, dimethyl formamide, glycol monoethyl ether and diethylene glycol monoethyl ether.  In an Example (1) finely ground polyvinyl alcohol is mixed with a dimethyl formamide solution of a polyvinyl chlorideacrylonitrile copolymer, the mixture is coated on to a flat surface, solvent is removed by immersion in running water and the film remaining is dried.  The products are useful as battery separators.ALSO:A membranceous composition is characterised by a microporous film-like polymeric matrix formed of a material selected from polyvinyl chloride, polyvinyl butyral and copolymers of vinyl chloride with monomers selected from vinyl acetate, vinylidene chloride and acrylonitrile, said matrix having a finely-divided solid hydrophilic material, which is characterised by its ability to swell in water and aqueous solutions uniformly dispersed therethrough and firmly held therein, the polymeric matrix material and hydrophilic polymeric material being present in proportions with the range of from 1 to 4 parts by weight of hydrophilic material to each part by weight of matrix material. An inert synthetic fibrous material is also preferably present in the matrix material.  Specified hydrophilic polymeric materials are polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide and water-soluble natural gums and ion-selective cross-linked polymeric substances such as a copolymer of methacrylic acid and divinyl benzene, a polyamine type ion-exchange resin, a polystyrene sulphonic acid resin, a polystyrene phosphonic acid resin or a strong base type ion-exchange resin.  The microporous material is produced by incorporating the finely divided particles of the hydrophilic polymeric material in a mixture of matrix material and a solvent therefor, sheeting the mixture, and then leaching out the solvent.  Suitable solvents are methyl ethyl ketone, methyl isobutyl ketone, acetone, cyclopentanone, dimethyl formamide, glycol monoethyl ether and diethylene glycol monoethyl ether.