GB398150A - An improved process for stripping goods dyed with vatdyestuffs - Google Patents

Abstract

Fibres dyed with vat-dyes are stripped by treating with hot alkali hydrosulphite in presence of a quaternary ammonium compound having an alkylating action. The fibres should be dyed with vat-dyes of which the leuco-compounds have little or no affinity for the fibre when treated with alkylating agents. Such vat-dyes include indigoid vat-dyes, anthraquinone vat-dyes, such as the benzoylated aminoanthraquinones, and the products of Specifications 205,525, 231,688, 234,086, and 237,872, [all in Class 2 (iii), Dyes &c.]. Particularly suitable quaternary ammonium compounds are those of the general formula <FORM:0398150/IV/1> and of these, those sulphonated in the benzyl residue. In examples (1) cotton dyed with Cibanone Brown GR is stripped in a bath of hydrosulphite containing the sulphonic acid of dimethylphenylbenzylammonium chloride; cotton dyed with Ciba Blue 2B, Cibanone Red 4B and Cibanone Orange 2R and wool dyed with indigo are similarly stripped; (2) cotton dyed with Ciba Brilliant Rose R is stripped in a bath of hydrosulphite containing dimethylphenylbenzylammonium chloride; similarly a material dyed with Ciba Red 3B or Ciba Rose BG may be stripped, and in the latter case there may alternatively be used the methyl sulphate of trimethyl-a -naphthylammonium or the benzyldimethyl - b - oxyethylammonium chloride, or o -oxyethylpyridinium chloride or its stearic ester: (3) cotton dyed with Ciba Brown G is stripped in a bath of hydrosulphite containing oleylaminoethyldiethylmethyl-ammonium sulphomethylate. Specification 216,622, [Class 2 (iii), Dyes &c.], also is referred to.