GB435477A - Improvements in or relating to the dyeing of leather - Google Patents

Abstract

Disazo dyes; acid wool and mordant dyes, dyeing with.--Chrome or vegetable tanned leather is dyed by applying thereto a disazo dye obtained by coupling with resorcinol either diazotized aminosalicylic acid or diazotized picramic acid and coupling the monoazo product with either diazotized aminosalicylic acid or diazotized picramic acid. In an example, chrome calf leather is tumbled in a dyeing drum with an aqueous solution of sodium bicarbonate at about 55 DEG C. until neutral to litmus, an aqueous solution of the dyestuff, aminosalicylic acid (2 mols.) \sQ resorcinol, is added, the tumbling is continued for 20 minutes, an aqueous solution of commercial formic acid is added and tumbling is continued for a further 30 minutes; the leather, thus dyed a full level yellowish brown, is fat-liquored and dried. The dyestuff may be replaced by aminosalicylic acid --> resorcinol \sM picramic acid or by picramic acid (2 mols) \sQ resorcinol. The Specification as open to inspection under Sect. 91 comprises also the use of the above diazo components substituted, e.g. by halogen or by one or more alkyl, alkoxy, hydroxy, nitro, carboxylic or sulphonic groups and the use of resorcinol substituted, e.g. by halogen or by one or more alkyl, alkoxy, hydroxy, nitro or sulphonic groups. This subject-matter does not appear in the Specification as accepted.