GB1168872A - Vapour-Permeable Coatings - Google Patents

Abstract

1,168,872. Leather substitutes. SANYO CHEMICAL INDUSTRIES Ltd. 8 May, 1967 [7 May, 1966], No. 21361/67. Heading B2E. Leather substitutes are prepared by coating a fibrous substrate with a solution of a substantially linear urethane polymer in a solvent which is inert with respect to the substrate, removing the solvent from the polymer by treating the coated substrate with a solvent which is a solvent of the polymer solvent yet inert with respect to the urethane polymer and the substrate and cross-linking the urethane polymer with at least one aldehyde containing 1 to 4 carbon atoms for at least one derivative of formaldehyde with which there are at least two groups of the general formula N(OH 2 OR) n in which R is a hydrogen atom or a methyl group and n is 1 or 2, at any stage in the production of the leather substitute. The fibrous substrates may be woven, non-woven or knitted fabrics and felts made from polyamides, polyesters, viscose rayon, wool, cotton, glass or mixtures of these. Inert liquids used for extraction of the polymer solvent may be water, ethylene, glycol, monoethyl, ether, hydroxyethyl acetate, ethylene glycol, glycerine or mixtures of these. The aldehyde may be formaldehyde, acetaldehyde, glyoxal or mixtures thereof. Suitable formaldehyde derivatives are methylol urea, methylol melamine, dimethylol adipic acid diamide, dimethylol butane diol urethane, dimethylol ethylene urea, dimethylol hydroxy ethylene urea, tetramethylol acetylene urea, dimethylol triazone, hexamethylol melamine and the methyl ethers thereof. A catalyst may be used to accelerate the action of the cross-linking unit with the urethane groups or urea groups of the polymer. Such catalysts may be inorganic acids such as hydrochloric acid, phosphoric acid, organic acids such as acetic acid, oxalic acid, amine salts such as the hydrochloride salts of mono- and di-alkyl amines, inorganic salts such as magnesium chloride, zinc nitrate, sodium hydrogen sulphate, sodium ethyl sulphate, barium ethyl sulphate, ammonium salts such as ammonium chloride and mixtures thereof. The cross-linking agent may be added to urethane polymer at any stage, e.g. added the agent to the solution of the urethane polymer before it is applied to the substrate, applied to the substrate before it is coated with a solution of urethane polymer, added to the inert liquid used for extraction step or sprayed as a solution onto the substrate coating of the polymer. The coated substrate may be dipped into a separately prepared bath containing the cross-linking agent. The cross-linking reaction is generally carried out after the extraction step by heating a coated substrate to a temperature of from 80 to 250‹C. and the preferred amount of crosslinking agent to be added to the polymer is 0.5-5% by weight based on the weight of the urethane polymer. The coating may be applied by spraying, knife coating, roller coating, casting, pressing or dipping. The product may be buffed and top-dressed.