GB414218A - Manufacture of chromiferous dyestuffs - Google Patents

Abstract

Chromiferous azo dyes are made by treating isolated chromium compounds of azo dyes an o-aminonaphthol sulphonic acid --> a naphthol which contain less than 1 atom of chromium for each group capable of being chromed, with an agent whose aqueous solution has an alkaline reaction, which term includes an alkaline agent that yields chromium. They dye marine blue tints and may be applied according to the processes of Specifications 364,148 and 408,497. The starting chromium azo dyes may be obtained according to Specifications 269,522 and 316,231, [both in Class 2 (iii)]. In examples: (1) the dyestuff 1-amino-2-naphthol-4-sulphonic acid --> b -naphthol is dissolved in caustic soda and sugar, treated with Cr2O3, formic and oxalic acids and the isolated dyestuff boiled with caustic soda, filtered, neutralized with hydrochloric acid and salted out; the alkaline mixture may also be worked up by adding oxalic acid and hydrochloric acid to neutralize, boiling, filtering and evaporating to dryness; (2) and (3) the same dyestuff is chromed with chromium formate and the chromium compound heated with caustic soda with or without sugar; the dyestuff is isolated as in (1) and in the alternative method tartaric acid is used instead of oxalic acid. An example of the dyeing process is given. Other alkaline agents specified are caustic potash, ammonia, sodium carbonate, and alkali chromite. Specification 283,979, [Class 2 (iii)], also is referred to. The Specification as open to inspection under Sect. 91 comprises also the following components: 2-amino-1-naphthol-4-sulphonic acid, 1-amino-2-naphthol-6-sulphonic acid, 1-amino-2-naphthol-4 : 8- or 4 : 6-disulphonic acid and 1-amino-2-naphthol-6-chlor- or 6-brom-4-sulphonic: a -naphthol, 8-chlor- or 5 : 8-dichlor-a -naphthol, and tertiary alkali phosphate and borax as alkaline agents. In an example, the dyestuff 1-amino-2-naphthol-4-sulphonic acid --> a -naphthol is treated with chromium formate and the partially chromed dyestuff refluxed with caustic soda. Further examples of the dyeing process are also given in which benzene sulphonic acid is added to a sulphuric acid dye-bath. This subject-matter does not appear in the Specification as accepted.