GB493770A - A process of dying leather - Google Patents

Abstract

Leather is dyed brown shades with water-soluble monoazo dyestuffs obtainable by coupling a diazo compound of an amine of the benzene series, containing at least once the group -CH2.SO3H attached directly to the nucleus, with 2-amino-8-naphthol-6-sulphonic acid or an N-alkyl or N-aryl derivative thereof. In examples: (1) chrome - tanned calf is neutralized, rinsed and dyed with the dyestuff 4-aminobenzylsulphonic acid --> (alkaline) 2 : 8 : 6-acid (sodium salt), after which formic acid is added and the leather is greased and finished; (2) chrome-tanned goat skin is deacidified and dyed with the dyestuff 4-amino-benzylsulphonic acid --> (alkaline) N-methyl-2 : 8 : 6-acid (sodium salt); (3) East India kips are drummed with the dyestuff sodium 3-amino-4-methoxybenzylsulphonate --> (alkaline) N-phenyl-2 : 8 : 6-acid (sodium salt), with addition of formic acid; (4) leather is dyed as in (1) with the dyestuff 3 - amino - 1 : 4 - di - (sulphomethyl) - benzene --> (alkaline) N - phenyl-2 : 8 : 6-acid (sodium salt). A sample has been furnished under Sect. 2 (5) of chrome-tanned calf dyed by the process of (1) above with the dyestuff sodium 3-amino-4-methoxybenzylsulphonate --> (acid) 2 : 8 : 6-acid. 3-Amino-4-methoxybenzylsulphonic acid is obtainable by heating 3-nitro-4-methoxybenzyl chloride with aqueous sodium sulphite and reducing the nitro group. 3 - Amino - 1 : 4 - di - (sulphomethyl) - benzene is obtainable similarly from 3-nitro-1 : 4-di-(chloromethyl)- benzene. The Specification as open to inspection under Sect. 91 comprises also the manufacture of the monoazo dyestuffs. The following alternative components are specified for use in the manufacture of the dyestuffs of certain of the examples given above: (2) N-ethyl-2 : 8 : 6-acid (sodium salt); 2- and 3-aminobenzylsulphonic acids; (3) 3-amino-4-ethoxybenzylsulphonic acid; (4) N-p-methoxyphenyl-2 : 8 : 6-acid. In additional examples: (5) 3 - amino - 4 - methylbenzylsulphonic acid or 3 - amino - 6 - acetylaminobenzylsulphonic acid is diazotized and coupled alkaline with 2 : 8 : 6-acid (sodium salt); the products dye chrometanned goatskin by the process of (2) above; (7) 3-chloro- or bromo-4-aminobenzylsulphonic acid is diazotized and coupled alkaline with 2 : 8 : 6-acid (sodium salt); the products dye chrome-tanned calf as in (1) above; (8) 4-amino-3-sulphobenzylsulphonic acid is diazotized and coupled alkaline with N-phenyl-2 : 8 : 6-acid (sodium salt); the product dyes leather as in (3) above. This subject-matter does not appear in the Specification as accepted.