Patent GB-384800-A (GB)
Title: Process for the production of azo dyestuffs
IPC: C09B29/00
Filed: 1931-12-10
Abstract: Azo dyes are obtained by coupling monodiazotized 4-nitro-1 : 3-diaminobenzene with a component; the latter may, in some cases; be a monoazo dyestuff.  The products may be further diazotized and coupled with components in substance or on the fibre.  The monoazo products containing sulphonic, carboxylic or other groups rendering them soluble in water, dye wool, leather and other animal fibres from acid baths, while those carrying further azo groups dye cotton.  Some of the unsulphonated monoazo dyes are suitable for use as pigments and for dyeing cellulose acetate. The preparation of the following dyestuffs is described in examples: (1) 4-nitro-1 : 3-diaminobenzene --> sodium N-methylaniline-o -sulphonate (saponified), which dyes cellulose acetate fast orange shades changing to violet-black on diazotization and development with 2 : 3-oxynaphthoic acid; if the coupling component is replaced by cresidine the product dyes cellulose acetate fast red; (2) 4 - nitro-1 : 3 - diaminobenzene --> diethylaniline, which dyes cellulose acetate fast red shades changing to orange-brown on diazotization and development with 2 : 3-oxynaphthoic acid; (3) 4 - nitro - 1 : 3 - diaminobenzene --> p-cresol, which dyes cellulose acetate yellow-brown; (4) 4-nitro-1 : 3-diaminobenzene --> 1-naphthylamine, which dyes cellulose acetate fast red shades changing to violet-black on diazotization and development with 2 : 3-oxynaphthoic acid; if the coupling component is replaced by 1-ethylaminonaphthalene and by 2-naphthylamine the products dye cellulose acetate a rich deep brown and a reddish brown respectively; (5) 4-nitro-1 : 3-diaminobenzene --> 2-naphthol-3 : 6-disulphonic acid, which dyes wool orange from an acid bath; (6) 4-nitro-1 : 3-diaminobenzene --> (alkaline) 2 : 8 : 3 : 6-aminonaphtholdisulphonic acid, which dyes wool bordeaux from an acid bath; (7) 4-nitro-1 : 3-diaminobenzene --> (alkaline) H-acid --> resorcinol \sM 4 - nitro - 1 : 3 - diaminobenzene, which gives full brown dyeings on leather; a similar product is obtained when the H-acid is replaced by 1 : 8 : 4 : 6-aminonaphtholdisulphonic acid; (8) 3- or 4-nitraniline --> resorcinol \sM H-acid or 1 : 8 : 4 : 6-acid (alkaline) \sM 4 - nitro - 1 : 3 - diaminobenzene, which gives similar but redder dyeings on leather; (9) 4-nitro-1 : 3-diaminobenzene --> 3 : 5-dioxybenzoic acid, which gives yellow-brown dyeings on leather; (10) 4-nitro-1 : 3-diaminobenzene --> 1- (4<1>-sulpho) phenyl-3-methyl-5-pyrazolone, which gives reddish-yellow dyeings, fast to light, on wool; (11) 4-nitro-1 : 3-diaminobenzene --> 4-nitro-1 : 3-diaminobenzene, which dyes acetate silk yellow; (12) 4-nitranilinesulphonic acid --> 2 : 4-dioxybenzoic acid \sM 4-nitro-1 : 3-diaminobenzene, which gives havana brown dyeings on chrometanned or vegetable-tanned leather; a similar product is obtained when the coupling component is replaced by 3 : 5-dioxybenzoic acid; (13) 2 - aminophenol - 6 - sulphonic acid --> resorcinol \sM 4 - nitro - 1 : 3 - diaminobenzene, which gives yellowish brown dyeings on chrometanned or vegetable-tanned leather; the chromium compound, obtained by boiling the dyestuff solution with chromous formate, dyes leather red-brown.