GB444169A - Improvements in or relating to the stripping of dyes from textile materials - Google Patents

Abstract

Textile materials dyed with basic, azoic, alizarine and vat dyestuffs are stripped by treatment with an aqueous solution of a quaternary phosphonium or sulphonium salt containing a straight or branched chain of not less than 10 carbon atoms. The bath may also contain an alkali, or an acid, or a reducing agent such as sodium hydrosulphite or sodium sulphoxylate formaldehyde, or a soluble soap or other detergent, or two or more of these. Suitable stripping agents are: cetyl-trimethylphosphonium bromide; dodecyl-trimethylphosphonium bromide; hexadecyl-triethylphosphonium bromide; cetyldimethyl - sulphonium methyl sulphate; benzylcetyl methylsulphonium methyl sulphate; dodecyl-dimethylsulphonium bromide. When stripping basic dyes it is usually sufficient to heat in an aqueous liquor containing the phosphonium or sulphonium salt; with azoic, alizarine and vat dyestuffs, a reducing agent and an acid or alkali are necessary, and in the case of vat dyestuffs a soluble soap or other detergent must be used. There are a number of examples; in some of these, to obtain a white, a final hypochlorite or hydrogen peroxide bath or a soap boil or both of these is employed. Specifications 398,818, 400,239, 422,466, 422,556, 434,810, and 436,076 are referred to. Benzyl cetyl methyl sulphonium methyl sulphate is prepared by treating cetyl mercaptan with sodium in methanol and then heating with benzyl chloride. The resulting cetyl mercaptan is then heated with dimethyl sulphate. Dodecyl dimethyl sulphonium bromide is made by heating dodecylmethyl sulphide with methyl bromide. Dodecylmethyl sulphide is prepared by reacting dodecyl mercaptan and dimethyl sulphate in aqueous alkali. Reference has been directed by the Comptroller to Specification 434,810.