Patent GB-446820-A (GB)
Title: Process for the manufacture of dyestuffs containing chromium
IPC: C09B45/48
Filed: 1934-10-31
Abstract: Chromium compounds of azo dyes are made by treating in an acid medium and in the absence of substantial amounts of chroming agents, the primary chromed compounds resulting from the action of chroming agents on o-oxyazo dyes in a neutral or very slightly acid medium, or a mixture of dyestuffs containing chromium of which one at least is such a primary chromed o-oxyazo dyestuff, the acidity of the treating medium being obtained by the addition of mineral, organic or sulphoaromatic acids, acid salts, substances capable of giving rise to acid bodies or mixtures comprising several of these compounds (the treatment of chromed complexes of the o-oxyazo dyes: o-aminophenols or o-aminonaphthols --> pyrazolones being excluded).  The products obtained are called secondary chromed compounds.  The acid treatment may be applied to the o-oxyazo dyes without separation from their chroming media or after isolation therefrom and may be stopped before the complete transformation of the primary into the secondary chromed compound.  The secondary compounds yield brighter and more even shades and are generally faster to light. In examples: (1) the dyestuff 1-amino-2-naphthol-4-sulpho acid --> b -naphthol is autoclaved with common salt, chromium formate and sodium acetate in aqueous solution and the primary chromed compound obtained is heated with hydrochloric acid (pure fast blue on animal fibres); (2) the dyestuff from the nitro-diazo compound of 1 - amino - 2 - naphthol - 4 - sulphonic acid and b  - naphthol is heated with a solution of chromium naphthalene-1:5-disulphonate and caustic soda to form the primary compound and the mixture is heated with formic acid to obtain the secondary compound or a mixture of the primary and secondary compounds (black shades on wool); (3) the chromed complex obtained in the absence of mineral acid from the dyestuff 1-amino-2-naphthol-4- sulphonic acid --> 1-phenyl-3-methyl-5-pyrazolone is mixed with sulphuric acid (cf. Specification 358,146) and the primary chromed compound of the azo dye 2-aminophenol-5-sulphonic acid --> b -naphthol and autoclaved for 20 hours (bordeaux); (4) the isolated primary compound of (2) is heated with hydrochloric acid; the ammonium salt of the product gives fast grey shades on animal fibres. Specification 365,113 also is referred to.  The Specification as open to inspection under Sect. 91 comprises also the treatment of chromium compounds of o-oxyazo dyes in acid medium in general and the following examples: (1) the dyestuff 2-aminophenol-4-sulphonic acid --> 1-phenyl-3-methyl-5-pyrazolone is refluxed with chrome alum and sodium acetate to form the primary chromium compound and the heating is then continued for 24 hours to form the secondary compound; the free acid of the latter may be used as a pigment dye and the salts for dyeing natural or artificial fibres; (2) the primary compound of the preceding example is mixed with dilute sulphuric acid and the paste obtained is dried in a vacuum; a mixture of primary and secondary compounds is obtained (orange on animal fibres); (3) the primary chromed compound of 1-amino-2-naphthol - 4 - sulphonic acid --> 1 - phenyl - 3-methyl-5-pyrazolone is autoclaved with aqueous benzenesulphonic acid.  This subject-matter does not appear in the Specification as accepted.