GB566585A - Production of improved skins - Google Patents

Abstract

566,585. Treating and tanning skins. DU PONT DE NEMOURS & CO., E. I., and COOLIDGE, C. June 2, 1943, No. 8824. [Class 76] Skins are treated with a solution of a polyvinyl alcohol before, simultaneously with, or after tanning. The term polyvinyl alcohol is defined to mean a water-soluble material consisting predominantly of hydrolysed or partially hydrolysed vinyl organic ester polymers. Completely or partially hydrolysed vinyl acetate polymers and copolymers from a mixture of vinyl organic esters or from vinyl organic esters and olefinic hydrocarbons, such as ethylene, propylene and isobutylene, or from vinyl organic esters and chlorinated olefines such as vinyl chloride, unsymmetrical dichlorethylene and trichlorethylene may be used. Preferably, 5-10 per cent of the polyvinyl alcohol based on the weight of the drained pickled skin is employed and impregnation is effected at room temperature until penetration is complete. In examples, pickled calf skins are depickled with sodium chloride and sodium acetate, treated with the polyvinyl alcohol, and then tanned with formaldehyde, or formaldehyde followed by aluminium sulphate ; and in a further example treatment is effected simultaneously with the polyvinyl alcohol and the half sodium salt of the hydrolysed styrene. maleic anhydride interpolymer described in Specification 642,222, tanning being completed with aluminium sulphate. Vegetable tanning agents such as quebracho extract may, however, used, or synthetic tanning agents such as hydrolysed styrene - maleic anhydride copolymers or those containing sulphonic acid and carboxyl groups, or solutions of aluminium iron or chromium salts. The pH of the skins to be treated should lie between 3 and 8 and the treated skins may be made more pliable by impregnation with glycerin.