Patent GB-1278941-A (GB)
Title: A method of producing sheet materials similar to leather
IPC: D06N3/00
Filed: 1969-09-18
Abstract: 1278941 Leather-like materials KURARAY KK 18 Sept 1969 [20 Sept 1968 31 Oct 1968 15 Nov 1968] 45981/69 Heading B5N A leather-like sheet material is produced by applying a layer of a solution of a polymer capable of being coagulated by a wet process on to a smooth surfaced impervious support, immersing the polymer solution applied to the support into a coagulation bath to coagulate the polymer solution layer into a porous structure and bonding a flexible substrate to the surface of the resulting porous film which has not been in contact with the support, the porous film being stripped from the support after coagulation and before or after bonding to the substrate. The support may be a metallic belt, films or sheets of polymeric material, e.g. polyethylene, polypropylene, polyamides, polyester or polyvinyl alcohol, sheets obtained by laminating these films or sheets to woven or non-woven fabrics or paper or smooth-surfaced sheets obtained by impregnating and coating woven or non-woven fabrics with solutions of these polymers and then effecting coagulation. The support may have an embossed surface. The polymer coagulated by a wet process may be a solution of a polyester, polyesteramide, polyamide, poly. vinylchloride, polyvinyl butyral, poly-alphamethylstyrene, polyvinylidene chloride, polyurethane, polymer or copolymer of an alkyl ester of acrylic or methaorylic acid, chlorinated polyethylene, chlorosulphonated polyethylene, copolymer of butadiene and acrylonitrile or synthetic rubber or mixture thereof, in N,N-dimethyl-formamide or acetamide, N,N-diethylformamide, dioxane, gamma-butyrolactone, N- methyl-2-pyrrolidone, ethyl acetate, phenol, chloroform, dimethylsulphoxide, tetrahydrofuran or tetramethyl alone or in a mixture with water, ketones or alcohols. The polymer solution may also contain pigments, e.g. carbon black or titanium oxide, surface-active agents, coagulation regulators, carriers, fillers, softening agents, water-proofing agents, light stabilizers and heat stabilizers. The coagulation bath may comprise a non-solvent for the polymer, e.g. methanol, ethylene glycol, glycerine, toluene or benzene, alone or in admixture with up to 20% by weight of a solvent. Prior to the application of the polymer layer, the support may be coated with a solution or dispersion of a coagulation regulator, e.g. a hydrocarbon, carboxylic acid, carboxylate, amide, nitrile, sulphonate, ureide or urethane having an alkyl group having 4-50 carbon atoms, in acetone, methyl ethyl ketone, methyl or ethyl acetate or alcohol, benzene, toluene or tetrahydrofuran. Alternatively the support may be coated with a high molecular weight substance, e.g. a polyamide, polycarbonate, polyacrylonitrile, polyacrylate, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer or polyurethane elastomer, alone or in the form of a solution or dispersion optionally in admixture with a phenol or urea resin. The coagulated polymer layer may be bonded to the substrate by means of a two-part or one-part polyurethane adhesive, a mixture of polyvinyl acetate and an acrylate or a self-cross-linkable nitrile-butadiene rubber which may be applied by spraying, brushing, roller coating or blade coating. In the examples the substrate is produced by melt extruding a mixture of nylon-6 and polystyrene, crimping the drawn filaments and cutting them into staple fibres which are made into a non- woven fibrous mat and needle-punched, im-. pregnating the mat with a solution of a polyurethane in dimethyl formamide coagulating the polyurethane by immersing the mat into an aqueous solution of dimethyl formamide, removing the polystyrene from the fibres by treatment with hot toluene and slicing the surface of the mat thus treated to obtain a flexible substrate having a smooth surface.