Process for preparing a highly concentrated aqueous press cakes of an azo disperse dye from dilute aqueous suspension thereof wherein surfactant is added before the dye is isolated

US4785082A · kind A · utility

Assignee

• Hoechst GmbH · DE

Inventors

• Joachim Weide · Kelkheim, DE
• Erwin Dietz · Kelkheim, DE
• Reinhold Deubel · Bad Soden am Taunus, DE

Key dates

• Filing date: Nov 5, 1985
• Grant date: Nov 15, 1988
• Expiry date: Nov 5, 2005

Classification

• Technology area (CPC B): Performing Operations; Transporting
• CPC primary: B01D37/03
• WIPO field: Chemical engineering
• WIPO sector: Chemistry

Abstract

According to the invention, addition of one or more surfactants having a cloud point in aqueous solution to an aqueous suspension of an azo disperse dye gives after the isolation of the dye at a temperature above the cloud point aqueous press cakes containing a large amount of this dye. The direct processing of press cakes as obtained for example after the synthesis and isolation of azo disperse dyes to practical dispersions for use requires a minimum dye content in the press cakes. The minimum content is frequently not obtained when conventional methods of isolation are used, so that it is necessary to proceed via the indirect route of drying to obtain powders and redispersing the powders. By using the process according to the invention it is possible to cut out the costly indirect route or, if desired, to reduce the expense of drying to obtain powders by an appreciable margin.