GB898991A - Process for dyeing or printing textile materials - Google Patents

Abstract

In the dyeing or printing of textile materials such as those of cellulose or aromatic polyester fibres with vat dyestuffs, the materials are impregnated or printed with a leuco-vat dyestuff in which the hydroxyl groups formed by reducing the keto groups are esterified with a carboxylic or sulphonic acid of which the acyl residue contains at least one group imparting solubility in water, such as quaternary ammonium or preferably a sulphonic acid group, and at any stage of the process prior to the oxidation to reform the vat dyestuff, the leuco ester is treated with an alkali and a strong reducing agent consisting of sodium hydrosulphite or thiourea dioxide. The aqueous dyebath, padding liquor or printing paste may contain the leuco ester, the alkali, e.g. sodium hydroxide, and the reducing agent, or, alternatively, the materials may first be padded with an aqueous solution of the leuco ester, then, if desired, dried and, subsequently treated with an aqueous solution of the alkali and the reducing agent, and in either case the materials are finally heated or streamed and oxidised, if desired, in the presence of an oxidising agent such as hydrogen peroxide or sodium perborate. The vat dyestuffs from which the leuco esters are derived may be of the anthraquinone, perylene or indigoid series and the esterifying acyl residue may be that of an aliphatic, heterocyclic or, more especially, an aromatic acid. Examples are given. Specifications 337,846, 497,327, 720,790, 741,053 and 769,688 are referred to.