Process for the preparation of chlorozincate salts of thiazolium azo dyestuffs

US4269768A · kind A · utility

Assignee

• Hoechst GmbH · DE

Inventors

• Rudolf Neeb · Offenbach am Main, DE
• Kurt Hohmann · Ybbs an der Donau, AT
• Reinhard Mohr · Offenbach am Main, DE

Key dates

• Filing date: Jul 6, 1979
• Grant date: May 26, 1981
• Expiry date: Jul 6, 1999

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C09B44/20
• WIPO field: Basic materials chemistry
• WIPO sector: Chemistry

Abstract

Chlorozincate salts of thiazolium azo compounds are prepared by reacting thiazolium 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 about 10.degree. to 50.degree. C. in the presence of a zinc compound capable of binding acid, and 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 8, preferably at 3-7. The prepared thiazolium azo compound is precipitated as chlorozincate salt, especially by means of an alkali metal chloride. According to this process, the chlorozincate salts are obtained in higher purity. A perceptible decomposition of the thiazolium 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.