GB1297942A - - Google Patents

Abstract

1297942 Leather tanning processes NATIONAL RESEARCH DEVELOPMENT CORP 4 March 1970 [4 March 1969] 11545/69 Heading C6C A process for improving the resistance to water penetration of a leather which results from tanning a hide or skin with a basic salt of a multivalent metal, e.g. chrome tanned leather, comprises treating the leather with an aqueous solution of a salt of a substituted alkylene dicarboxylic acid in which the alkyline chain contains up to six carbon atoms and is substituted with from 1 to 3 hydrophobic organic groups each containing from 6 to 22 carbon atoms, and further treating the leather with a salt of a multivalent metal. Preferably, both treatments with a salt of a multivalent metal use chromium sulphate, although aluminium, zirconium or cerium salts may also be used. The hydrophobic organic substituent groups in the substituted alkyline dicarboxylic acid preferably contain from 12 to 22 carbon atoms. In a preferred example, chromium sulphate tanned leather prepared from pickled stock is neutralized to a pH of 8 to 8À3 with sodium bicarbonate or ammonia and then treated with an aqueous solution of an ammonium salt o- C14 alkenyl succinic acid, the acid being sold under the Registered Trade Mark "Bavon", after which further tanning with chromium sulphate is carried out, the leather is rinsed, neutralized and dried. Benzyl alcohol or white spirit may be added to the solution containing the salt of C14 alkenyl succinic acid. Where a soft leather is desired, the leather may be treated with a mixture of sodium phthalate and sodium formate prior to neutralizing with sodium bicarbonate or ammonia. This mixture may alternatively be added to the cromium sulphate during the further chrome tanning step. Smooth grained leather may be obtained by lightly acidifying the leather on the outer surface to pH 3À0 to 4À0 after treatment with the alkenyl succinic acid salt.