GB401137A - Manufacture of easily soluble ester-salts of leuco-vat-dyestuffs - Google Patents

Abstract

The acid disulphuric ester salts of leuco-vat dyes are converted into their lithium salts which are characterized by an excellent solubility in water. In general such salts are prepared by treating the acid disulphuric ester of leuco-vat dyes in the form of their salts with a volatile base such as pyridine, piperidine, ammonia, dimethylaniline or aniline, with lithium carbonate or hydroxide and then expelling the volatile base by distillation; thus in preparing an acid disulphuric ester of a leuco-vat dye by treating a suspension of a leuco-vat dye in a tertiary base with an addition product of sulphur trioxide and a tertiary base, lithium carbonate is added and the solution distilled. Or the preparation may involve double decomposition with formation of an insoluble salt; thus a barium salt of a disulphuric acid ester of a leuco-vat dye may be treated with lithium carbonate or sulphate. Reference is made to the production of the lithium salts of the disulphuric acid esters of dichloro- and dibromoanthanthrone (cf. Specification 260,998, [Class 2 (iii), Dyes &c.]), dibromodibenzpyrenequinone, pyranthrone and dibromopyranthrone (cf. Specification 320,368, [Class 2 (iii), Dyes &c.]), indanthrene and dichlorindanthrene (cf. Specification 322,277, [Class 2 (iii), Dyes &c.]), dibenzanthrone and isodibenzanthrone and substitution products thereof. The products are useful for printing purposes. Specifications 186,057, [Class 2 (iii), Dyes &c.], and 363,669 also are referred to. The Specification as open to inspection under Sect. 91 comprises the production of lithium salts of leuco sulphuric esters of vat dyes generally, but this subject-matter does not appear in the Specification as accepted.