Patent GB-981642-A (GB)
Title: Method of making vapor permeable sheet materials
IPC: D06N3/14
Filed: 1962-11-21
Abstract: Microporous films and sheets are made by (a) applying to a non-adherent surface (e.g. of glass, metal, plastic or a fibrous substrate coated with a release coating) a layer of a solution of a polymer in an organic solvent; (b) bathing the layer with a mixture of an organic solvent for the polymer and a non-solvent for the polymer which is at least partially miscible with the said solvent until the layer is coagulated into a cellular structure of interconnected micropores, the solvent; non-solvent weight ratio in the mixture being from 10:90 to 95:5; (c) removing substantially all solvent from the layer, e.g. by evaporation if the solvent is the more volatile or by bathing the layer with a polymer non-solvent at least partially miscible with the solvent, and, (d) removing substantially all non-solvent from the layer; the polymer used being selected so that it will have a maximum elastic deformation strength of at least 100 p.s.i. from the end of step (c) until the end of step (d). Specified polymers are polyurethane elastomers made by reacting an organic diisocyanate with an active hydrogen containing polyalkylene ether glycol or a hydroxyl terminated polyester and reacting the resulting isocyanate terminated prepolymer with a chain extender having two active hydrogen atoms bonded to amino nitrogen atoms; polyesters made by reacting dicarboxylic acids, esters or acid halides with glycols; P.V.C., copolymers of vinyl chloride with ethylenically unsaturated monomers, e.g. vinyl acetate, vinylidene chloride or diethyl maleate; polyamides; polyvinyl butyral; poly-a -methyl styrene; polyvinylidene chloride; alkyl esters of acrylic acid and methacrylic acids; chlorosulphonated polyethylene; polystyrene; butadiene-acrylonitrile copolymers; cellulose esters and ethers. Examples describe the production of microporous material from compositions containing polyurethanes and polyvinyl chloride. Specification 919,500 is referred to.ALSO:Vapour-permeable sheet materials are produced by (a) applying to a substrate a layer of a solution of a polymer in an organic solvent; (b) bathing the layer with a mixture of an organic solvent for the polymer and a non-solvent for the polymer which is at least partially miscible with the said solvent until the layer is coagulated into a cellular structure of interconnected micropores, the solvent:non-solvent weight ratio in the mixture being from 10 : 90 to 95 : 5; (c) removing substantially all of the solvent from the layer, e.g. by evaporation if the solvent is the more volatile or by bathing the layer with a polymer non-solvent at least partially miscible with the solvent; and (d) removing substantially all of the non-solvent from the layer; the polymer used being selected so that it will have a maximum elastic deformation strength of at least 100 p.s.i. from the end of step (c) until the end of step (d).  Specified polymers are polyurethane elastomers made by reacting an organic diisocyanate with an active-hydrogen-containing polyalkyleneether glycol or a hydroxyl-terminated polyester and reacting the resulting isocyanate-terminated prepolymer with a chain extender having two active hydrogen atoms bonded to amino nitrogen atoms; polyesters made by reacting dicarboxylic acids, esters or acid halides with glycols; polyvinyl chloride; copolymers of vinyl chloride with minor amounts of ethylenically unsaturated monomers, e.g. vinyl acetate, vinylidene chloride or diethyl maleate; polyamides; polyvinyl butyral; polyalphamethylstyrene; polyvinylidene chloride; alkyl esters of acrylic and methacrylic acids; chlorosulphonated polyethylene, polystyrene; butadiene/acrylonitrile copolymers; cellulose esters and ethers. The substrate may be a woven, knitted or non-woven fabric, a waterleaf or a natural or synthetic leather or suede, the examples relating to the coating of a non-woven fibrous sheet of poly(ethyleneterephthalate) impregnated with a hydrazine-extended polyurethane elastomer.  The microporous films of the invention may also be applied to non-adherent surfaces, e.g. of glass or metal, from which they may subsequently be stripped (see Division C3). Specification 919,500 is referred to.