Process for the preparation of chlorozincate salts of benzo thiazolium azo dyestuffs by alkylating with dialkylsulfate in aqueous medium in the presence of Zn-containing acid acceptor at pH.ltoreq.7

Abstract

Chlorozincate salts of benzothiazonium azo compounds are prepared by reacting benzothiazolium azo compounds with an dialkylsulfate having from 1 to 4 carbon atoms in the alkyl radicals, which process comprises carrying out the reaction in an aqueous medium at a temperature of from 10.degree. to 80.degree. C. in the presence of an acid acceptor and the alkylation with the use of from 1.8 to 2.5 mols of the dialkylsulfate, calculated on the starting azo dyestuff, at a pH not exceeding 7. The prepared benzothiazolium azo compound is precipitated as chlorozincate salt, especially with the use of an alkali metal chloride. According to this process, the chlorozincate salts are obtained in higher purity. A perceptible decomposition of the benzothiazolium azo compound does not occur. Chemicals, for example the alkylation agent and acid-binding agents need be used in a small quantity. In addition to this economy and to the less pollution of the waste water, the process has the advantage that it can be carried out with the use of a small reaction volume.

Dependencies are inferred from the claim text.