GB418381A - Azo dyes - Google Patents

Abstract

Azo dyes giving yellow or brown shades on leather are obtained by coupling catechin with one or more diazotized amines containing one or more sulphonic, carboxylic or other groups sufficient to render the dyes soluble in water. Catechin may be coupled with three equivalents of a diazo component, but the preferred dyes are obtained by using two equivalents of a diazo component or one equivalent of each of two different diazo components, preferably selected so that the dyes contain two sulphonic or carboxylic groups or one of each. When o-oxydiazo or o-carboxydiazo compounds are used, the dyes may be converted into complex metallic derivatives by standard methods. In the examples: (1) catechin is coupled with between two and three equivalents of diazotized metanilic acid, sulphanilic acid, naphthionic acid or picramic acid; (2) diazotized aniline is coupled with catechin and the product is coupled with diazotized 3-amino-5-sulpho-2-hydroxybenzoic acid; diazotized sulphanilic acid may also be used as first component; (3) a disazo dye obtained as in example 2 is boiled with aqueous copper sulphate to yield a copper derivative; (4) the mononitrated diazo oxide from 1-amino-2-naphthol-4-sulphonic acid is coupled with catechin, and the product is coupled with diazotized 2-aminophenol-4-sulphonic acid; the dye yields a copper derivative when boiled with aqueous copper sulphate; (5) diazotized 2-aminophenol-4-sulphonic acid is coupled with catechin and the product is coupled with diazotized 3-amino-5-sulpho-2-hydroxybenzoic acid; the dye yields a chromium derivative when boiled with aqueous chromium fluoride; (6) two equivalents of the diazo oxide from 1-amino-2-naphthol-4-sulphonic acid are coupled with catechin; the dye yields a chromium derivative when boiled with aqueous chromium fluoride; (7) the mononitrated diazo oxide from 1-amino-2-naphthol-4-sulphonic acid is coupled with an equimolecular proportion of catechin; the dye yields a chromium derivative when boiled with aqueous chromium fluoride; (8) the disazo dye of example 4 is coupled with diazotized 3-amino-5-sulpho-2-hydroxybenzoic acid; the product yields a chromium derivative when boiled with aqueous chromium fluoride. Specifications 14836/88 and 11902/93, [both in Class 2], are referred to.