Process for preparing liquid low-salt aqueous reactive dyestuff compositions

US4585459A · kind A · utility

Assignee

• Hoechst GmbH · DE

Inventors

• Konrad Opitz · Liederbach, DE
• Gunther Schwaiger · Frankfurt, DE

Key dates

• Filing date: Apr 4, 1985
• Grant date: Apr 29, 1986
• Expiry date: Apr 4, 2005

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C09B67/0096
• WIPO field: Basic materials chemistry
• WIPO sector: Chemistry

Abstract

A process is described for separating sodium sulfate from aqueous solutions, containing less than 2% by weight of chloride, of certain fiber-reactive copper-formazan dyestuffs wherein this dyestuff solution is cooled down to a temperature between +5.degree. C. and -15.degree. C. In the course of the cooling the sodium sulfate precipitates in the form of the decahydrate and can be separated off in conventional manner, for example by filtration. The products obtained in this way are liquid low-salt aqueous copper-formazan dyestuff preparations which contain less than 4% by weight of sodium sulfate.