Patent GB-1301174-A (GB)
Title: Artificial leather
IPC: C09K23/52
Filed: 1970-03-17
Abstract: 1301174 Laminates DAINIPPON INK & CHEMICALS Inc 17 March 1970 [17 March 1969 7 April 1969] 12874/70 Heading B5N [Also in Divisions B2 and C3] An artificial leather comprises a layer (d) of cloth laminated with a foamed sheet (c) of thickness 0À2 to 1 mm. and having a tensile strength of at least 100 kg./cm.<SP>2</SP>, an elongation of at least 200% and a tenacity at 100% elongation of 5 to 50 kg./cm.<SP>2</SP>, the sheet having been obtained by drying an aqueous dispersion of polyurethane resin in concentration of at least 25% by weight and of particle size up to 5 microns, the dispersion having a specific gravity of up to 0À7 and containing minute gas bubbles and 10 to 100% (based on the weight of the resin) of a hygroscopic porous material of particle size not greater than 30 mesh. There may be laminated with (c) a surface film (a) selected from polyurethane, polyamide and polyacrylic resins and having a thickness of 0À002 to 2 mm., or a skin layer (b) of thickness up to 0À5 mm. of an unfoamed polyurethane resin, a film of which has a tensile strength, elongation and tenacity as defined above for (c), obtained by drying an aqueous dispersion of a polyurethane resin of particle size up to 5 microns in a concentration of at least 25% by weight. The layer (b) may contain up to 200% of a filler. The leather may comprise both (a) and between it and (c) the skin layer (b). The leather may be produced by: applying to a layer (e) of release material a solution of a surface treating agent and drying the solution to give the film (a), applying to the film (a) an aqueous dispersion containing gas bubbles obtained by mixing the hygroscopic porous material into the dispersion of polyurethane resin and drying the dispersion to give sheet (c); or applying to the film (a) an aqueous dispersion of polyurethane resin containing no gas bubbles and drying the dispersion to give film (b), applying to film (b) the aqueous dispersion containing minute gas bubbles and drying the dispersion to give sheet (c); and then laminating the base cloth (d) with sheet (c) and stripping off layer (e). In other methods: the aqueous dispersion containing gas bubbles is applied to layer (e) and dried to give sheet (c), or the aqueous dispersion containing no gas bubbles is applied to layer (e) and dried to give film (b) and the aqueous dispersion containing minute gas bubbles is applied to film (b) and dried to give sheet (c); and then the base cloth (d) is adhered to the sheet (c), layer (e) is removed and a solution of a surface treating agent is applied to sheet (c) or film (b) respectively and dried to give film (a). Wrinkles may be imparted to the leather, e.g. by hand, by employing a release material which is embossed, by pressing the leather with embossing rolls. The hygroscopic porous material may be silica gel, alumina gel, zeolite, homopolymers or copolymers of vinyl chloride, vinyl acetate and acrylic esters. Examples of suitable polyurethane resins for the aqeuous dispersions are given as well as of stabilizers, colourants, fillers and thickeners therefor. The release material may be films of polyethylene, polypropylene, polyester, silicone paper. The base cloth may be knit or woven fabrics of natural fibres, e.g. cotton wool and artificial fibres, e.g. cellulose acetate, polyamide, polyester, acrylonitrile and polypropylene; non-woven fabrics bonded, e.g. by acrylic esters, natural or synthetic rubber, or polyurethanes. The base cloth may be adhered by pressure and heat, or by means of an adhesive, e.g. an aqueous starch solution, aqueous polyvinyl alcohol solution and aqueous solutions of water-soluble rubber, and organic solvent polyacrylic ester resin, polyurethane resin, natural and synthetic rubber solutions. The surface treating agent for film (a) may be polyurethane resin, polyamino acid resins, e.g. homopolymers and copolymers of glycine, alanine, phenylalanine, leucine, isoleucine, valine, glutamic acid, ornithine, lysine, arginine, cystine, methionine, preferably poly(gamma.methyl glutamate), polyacrylic resins, e.g. polymethyl methacrylate, methylmethacrylate methacrylic alkyl esters and/or acrylic alkyl esters, copolymers and mixtures thereof with vinyl chloride polymers and copolymers with ethylene and vinyl acetate, polyamides obtained from diamines and dibasic acids, and by ring-opening polymerization of caprolactam, preferably N- methoxy methylated polycaprolactam. The surface treating agent solution and the polyurethane dispersions may be applied by knife, roll coater.