Dyeing cellulose textile with vat or sulphur dyestuff - using alpha=hydroxy carbonyl cpd. as sole reducing agent by heating side stream to dissolve ppte.

摘要

Dyeing textile materials of cellulose fibres, opt. mixed with synthetic fibres, with vat or S. dyestuffs (I) is carried out in aq. dyebaths (II) in the presence of alpha-hydroxycarbonyl cpds. (III) as reducing agent for (I) and alkali, followed by fixing of the reduced (I) to the textile by oxidn. and after-treatment. The novel features are that (a) a fraction (IV) comprising up to 10 (wt.)% of the aq. liquor is taken from (II) contg. (I) in the reduced form and pptd. (I); (b) (IV) is heated to a temp. at least 15 deg. C above that of the (II) and kept at this temp. unitl the pptd. (I) present has re-dissolved; and (c) (IV) is cooled to the temp. of (II) and returned to (II). Only (III) is needed as reducing agent, instead of the usual mixt. The depth of colour, fastness to rubbing and brilliance correspond to those obtd. with caustic alkali and hydrosulphite. The process is useful for dyeing natural and regenerated cellulose fibres, e.g. staple rayon or polynosic fibres, and mixts. e.g. with polyesters, polyamides or polyacrylonitrile, pref. in the form of yarn, fabric or ne