Patent GB-1188404-A (GB)
Title: Process for Dressing Leather
Inventor: SCHROER WALTER
IPC: C08F263/04
Filed: 1967-05-31
Abstract: 1,188,404. Coated leather. FARBENFABRIKEN BAYER A.G. 31 May, 1967 [2 June, 1966], No 25087/67. Heading B2E. [Also in Division C3] Natural or imitation leather is dressed with a composition comprising a solution in an organic solvent of a high molecular weight polyurethane and/or polyurea prepared by reacting at least one compound containing hydroxyl and/or amino groups and having a molecular weight of 500 to 20,000 with 0.03-0.60 equivalent per cent of at least one polyisocyanate, (b) 5-100% of vinylchloride graft co-polymer composed of 60-95% vinyl chloride, 1 to 25% of a co-polymer of ethylene and vinyl acetate having a vinyl acetate content of 50 to 80% and 1 to 15% of an ester or semi-ester of an alpha, beta-unsaturated mono-or di-carboxylic acid of structure: (in which R 1  represents an hydroxyalkyl group, R 2  is a hydrogen atom or a methyl group, R 3  is an alkyl, aryl, alkaryl, cycloalkyl or hydroxy alkyl groups and R 4  is a hydrogen atom or a hydroxyalkyl group), if desired with the use of catalysts. The composition may also comprise chain lengthening agents having reactive hydrogen atoms and molecular weight <500 catalyst, and a solution of a further polyisocyanate. The leather may be primed. Examples of suitable compounds containing hydroxyl and/or amino groups and polyisocyanates and chain lengthening agents are described. The further polyisocyanates which may be added to the solution can be the same as those used for the preparation of reaction product (a). Suitable compounds co-polymerisable with vinyl chloride for use in the preparation of the graft polymers are hydroxy ethyl acrylate, hydroxy propylmethacrylate, and esters of maleic or fumaric acid. Additional cross-linking of the graft co-polymers may be carried out with formaldehyde in the form of a gas, solution or in the form of a compound which gives off formaldehyde e.g. C-, N-, P-, O- or S- methylol compounds or their methyl ethers, cyclic acetals of formaldehyde, methylol-N-acetals, formals, urea formaldehyde or melamine formaldehyde adducts. Other compounds reactive with isocyanate may be added to the solution e.g. compounds carrying hydroxyl groups and/or amino groups, polyoxymethaylene glycols and hydroxy alkylation products of polyhydric alcohols, amines or phosphoric acids, hydroxylic or amino functional organo siloxanes. Organo functional polysiloxanes may be incorporated during the preparation of reaction product (a) to increase its hydrophobic character. Polymers may also be combined with the polyurethane-polyisocyanate solution to modify the handle, elasticity and hardness of the product e.g. poly(styrene-acrylonitrile), poly(butadiene-acrylonitrile), polymethacrylates polychlorobutadiene, polycarbonates and polyoxymethylene. These polymers may also contain groups that are reactive with isocyanate. The coating may be carried out in one or more applications. The coating may be used as dressing layer for dressings containing collodium dyes, as a protective layer on aniline leathers which are coloured but not pigmented and which are primed with polymer dispersions. Polyurethanes dissolved in organic solvents without graft polymers (b) may be used as primer coating and middle layer. Organic and/or inorganic pigments or dyes, fillers such as silicic acid, aluminium silicates, talcum, kieselguhr or metal salts of fatty acids, natural or semi-synthetic or synthetic compounds such as natural resins, cellulose esters, silicone oils, polymers soluble in organic solvents may be incorporated into the dressing. The dressings may be applied by brushing, spraying. The coated surface may be ironed between individual applications, or .the surface may be ground or polished after application of the primer coating. In the Examples 1) a top dressing for chrome calf leather comprised 220 parts of a 35% solution of a polyurethane prepared from a mixture of a polyester of adipic acid and ethylene glycol, 2, 4- and 2, 6-toluylene diisocyanate isomeric mixture, and trimethylolpropane, 300 parts of a 15% solution of an ethylene-vinyl acetate copolymer grafted with vinyl chloride and maleic acid cyclohexyl semiester, 70 parts of a polyisocyanate of toluylene diisocyanate and trimethylol propane, 900 parts toluene, 900 parts ethyl acetate and 710 parts p-ethoxyethyl acetate; 2) a chrome calf leather fat dyed with aniline dye, primed with a composition comprising an aqueous dispersion of a butadiene-acrylonitrile copolymer, casein gloss agent, water, was treated with a dressing composition comprising 100 parts of a 10% solution in methyl ethyl ketone of a polyurethane prepared by reacting a mixed polyester of adipic acid and hexane-1, 6-diol/2, 2-dimethylpropane-1, 3- diol, glycol, an organo siloxane of formula: diphenyl methane-4, 4'-diisocyanate and 1, 4- butanediol, 35 parts of a 10% solution, in methyl ethyl ketone of an ethylene-vinyl acetate copolymer grafted with vinyl chloride and maleic acid cyclohexyl semiester, 5 parts of a 20% solution of collodion wool, 10 parts of the polyisocyanate of example 1, 90 parts toluene, 90 parts ethyl acetate, 35 parts betaethoxyethyl acetate, and 35 parts of a mixture of aliphatic and aromatic hydrocarbons; 3) chrome kid leather was dressed with two applications, the first application comprising a 10% solution of a polyurethane prepared from a polyester of adipic acid and 1, 6-hexane diol, and 2, 4- and 2, 6- toluene diisocyanate, a 10% solution of a co-polymer of ethylene and vinyl acetate grafted with vinyl chloride and 2-hydroxy propyl methacrylate, a triturated mixture of carbon black in the said polyurethane with beta-ethoxy ethyl acetate, the polyisocyanate of Example 1), toluene, ethyl acetate and beta-ethoxy ethyl acetate, and the second application comprising a 10% solution of the polyurethane of the first application, a 10% solution of the graft co-polymer of the first application, dispersed silicic acid, the carbon black trituration described in the first application, the polyisocyanate of example 1, toluene ethyl acetate and beta-ethoxy ethyl acetate.