GB456844A - Process for dyeing leather - Google Patents

Abstract

Acid wool, substantive and mordant dyes, dyeing with; azo dyes.--Leather, especially chrome leather, is dyed by applying thereto an azo dyestuff, free from heavy metal in complex form, obtainable by coupling with a b -amino-naphtholsulphonic acid or an N-derivative thereof either (a) a diazo compound, other than one of the benzene series substituted by a b : g -dioxypropyl ether residue, having no hydroxy group in o-position to the diazo group, no alkylated amino group in p-position to the diazo group and no free amino group as substituent, or (b) a diazoazo compound, having no hydroxy group in o-position to the diazo group and no free amino group as substituent, the components, in any case, being so selected that the dyestuff contains at least two sulphonic acid groups or one sulphonic acid and one carboxylic acid group. Other acid or substantive dyestuffs may be added to the dyebath. The following examples are specified: (1) neutralized chrome calf leather is treated in a drum in an aqueous solution at 60 DEG C. of the dyestuff, p-sulphanilic acid --> (alkaline) phenyl-g -acid, and is then stuffed to obtain a brown dyeing on the grain and flesh sides; the flesh side can be ground off without exposing undyed fibres; (2) dry and ground off chrome calf velours leather, after an egging in hot water, is dyed at 60 DEG C. with the dyestuff obtained by coupling diazotized p-sulphanilic acid in alkaline medium with a mixture of phenyl-g -acid (60 per cent) and phenyl-J-acid (40 per cent), the dyebath being exhausted by addition of formic acid, and is then stuffed; the reddish brown dyeing obtained is fast to water and to grinding off; (3) neutralized chrome horse leather is dyed in a bath at 60 DEG C. containing the dyestuffs 4-nitraniline-2-sulphonic acid --> (acid) phenyl-g -acid and Direct deep black E extra; the black dyeing obtained is deep in the grain and, therefore, fast to grinding off the grain side. A table is also given showing the shades obtained with the following dyestuffs, o-sulphanilic acid --> (alkaline) phenyl-g -acid or phenyl-J-acid, 2-naphthylamine - 4 : 8 - disulphonic acid --> (alkaline) phenyl-g -acid, aniline --> (alkaline) m-carboxyphenyl-g -acid, aminoazobenzene --> (alkaline) 2 : 8 : 3 : 6-aminonaphtholdisulphonic acid, 4-nitraniline-2-sulphonic acid --> (acid) phenyl-g -acid, 5-nitro-2-anisidine-4-sulphonic acid --> (acid) phenyl-g -acid or phenyl-J-acid, 2-nitraniline-4-sulphonic acid or metanilic acid --> (acid) 2 : 3 : 6-aminonaphtholsulphonic acid, p-sulphanilic acid --> (alkaline) 2-(o -hydroxyethyl) amino-8-naphthol-6-sulphonic acid and aminoazobenzenedisulphonic acid --> (acid) g -acid or (alkaline) phenyl-g -acid.