GB563288A - Improvements in or relating to the production of leather and of compositions for usetherein - Google Patents

Abstract

Skins are tanned by treating them with compositions obtained by reaction of maleic anhydride and an unsaturated cycloaliphatic hydrocarbon having a six-membered cycloaliphatic ring with at least one open chain substituent on the ring and containing at least one carbon to carbon double bond which may be either in the ring or in the open chain, e.g. a cyclic terpene. A polymerisable vinyl, vinylene, or vinylidene compound may also be present in the reaction. The compositions may contain a foam-depressant such as octanol. The tanned skins may be treated with an aldehyde or with a salt of aluminium, iron, titanium, copper, zirconium or chromium along with acetic, tartaric or citric acids or soluble salts thereof. The products may be used alone or in conjunction with the tanning agents described in Specifications 530,643, 542,222, [Group VIII], and 552,122, or with vegetable tanning agents, chrome tans or tanning agents containing sulphonic acid groups. Cyclic terpenes which may be used include dipentene, a -and b -pinene, camphene, a -terpinene, phelandrene, and terpinolene and other suitable compounds include vinyl cyclohexene, vinyl cyclohexane and methylene cyclohexane. The higher molecular weight portions of the reaction products are more suitable and are obtained by extracting the lower molecular weight portions with ether. The reaction mixture may contain 20-60 per cent of a cyclic terpene, 35-60 per cent maleic anhydride and 50-30 per cent of vinyl compound by weight. The pH of the tanning solution is best maintained at about 4. Examples are given of tanning agents obtained by polymerizing (1) commercial dipentene, maleic anhydride, and styrene or vinyl acetate in presence of benzoyl peroxide; (2) maleic anhydride and a -terpinene, extracting low molecular weight products with ether and mixing with a styrene-maleic anhydride polymer of Specification 542,222; (3) maleic anhydride, a -pinene and styrene in xylene; (4) vinyl cyclohexene, maleic anhydride and styrene; (5) maleic anhydride, methylene cyclohexane; (6) b -pinene and maleic anhydride with or without styrene. Other unsaturated compounds which may be used in the reaction are vinyl phenyl ethers, methyl vinyl ketone, indene acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, methacrylamide, acrylonitrile and methacrylonitrile.