GB925768A - An improved dyeing process - Google Patents

Abstract

Cellulose materials are dyed by applying an onium compound of a vat dyestuff containing at most 8 fused carbocyclic rings, at least one stage of the process being performed in the presence of a reducing agent. The dyeing is fixed by splitting-off the onium group. The onium groups may be ammonium, sulphonium or isothiouronium groups bound to the nucleus through a methylene bridge. They may be obtained by quaternating amino groups or by converting mercapto-methyl compounds by rearrangement into ternary sulphonium salts by known methods or by treating mono- or bischloromethyl compounds of vattable dyestuffs with (a) tertiary amines such as pyridine, picoline, isoquinoline, quinoline, trimethylamine, triethylamine, benzyl-dimethylamine, diethylaminoethyl alcohol or dimethyl-cyclohexylamine, or (b) an alkali metal compound of a mercaptan such as methyl mercaptan, n-butyl mercaptan, cyclohexyl mercaptan, benzyl mercaptan, thiophenol or para-thiocresol and converting the sulphide formed into a ternary sulphonium salt by means of dimethyl sulphate, or methyl paratoluene sulphonate, or (c) thiourea, N-methylthiourea, N:N-dimethylthiourea or tri- or tetramethylthiourea. Suitable vat dyestuffs are anthraquinones either containing an unmodified 9:10-dioxoanthracene ring or containing fused carbocyclic or heterocyclic rings or from the perylene tetracarboxylic acid, naphthalene tetracarboxylic acid or indigoid vat dye series. They may contain usual substituents such as halogen atoms, alkyl, alkoxy, acylamino, sulphone or sulphonamide groups. The dyestuffs may also contain a water-solubilizing group capable of being split off, e.g. a sulphate group. The dyes may be applied to regenerated cellulose, linen or especially cotton by padding or from a dyebath. Fixation may be achieved by maintaining the impregnated material in the vat state in the presence of an acid-binding agent and a reducing agent at 10 DEG -40 DEG C. for 2-48 hours, particularly by the pad-roll process. Dyeing from a dyebath may be achieved below 50 DEG C. in which case the dyebath may contain neutral electrolyte such as sodium chloride or sulphate. Specified reducing agents are sodium sulphide, hydrosulphide, hydrosulphite and thiourea dioxide and the specified acid-binding agents are sodium hydroxide and carbonate. The reducing agent and alkali may be applied together with the dye, during or after the dyeing process. Printing may be effected with a thickened printing paste. A reoxidative aftertreatment may be included as well as soaping and washing prior to drying. Examples are given in which are used dyes of the following formulae: <FORM:0925768/IV(a)/1> Specifications 613,980, 613,982, 613,983 and 850,159 are referred to.