GB186057A - Manufacture of products for dyeing or printing textile fibres and other materials - Google Patents

Abstract

Reduction products of vat-dyes (indigo, thioindigo, anthraquinone hydroazines &c.) are converted into enolic ethereal salts which are stable in air, by the reaction of acids with the hydroxyl groups of the said reduction products. The conversion may be effected by general methods, for example, by action of an acid chloride on the leuco dyestuff in the presence of a tertiary base; the ethereal salts of sulphuric acid are obtained by the use of chlorsulphonic acid in the presence of a tertiary base, the product being then converted into a stable salt. In an example, dihydro-indigo is added to a pyridine solution of chlorsulphonic acid in an atmosphere of carbon dioxide and the mass diluted with water and crystallized; the pyridine salt so obtained is converted into an alkali or other salt. Specification 23396/99 is referred to.ALSO:Animal or vegetable fibres are dyed or printed with the stable enolic ethereal salts obtained by the reaction of acids with the hydroxyl groups of reduction products of vat-dyes (indigo, thioindigo, anthraquinone hydroazines &c.); these products are converted on the fibre into the dyestuffs by hydrolysis and oxidation, or by treatment with an oxidizing agent only; the latter method is available particularly in the case of sulphuric acid derivatives of dihydro-indigo and dihydro-thioindigo which are hydrolized and oxidized simultaneously by ferric chloride, bromine, chloride of lime or the like, even in neutral solution.