Preparation of vat dyes and pigments of the perinone series

US5074919A · kind A · utility

Assignee

• Hoechst GmbH · DE

Inventors

• Erwin Dietz · Kelkheim, DE
• Gustav Kapaun · Bad Soden, DE
• Siegfried Schiessler · Frankfurt am Main, DE

Key dates

• Filing date: Oct 26, 1989
• Grant date: Dec 24, 1991
• Expiry date: Oct 26, 2009

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C09B57/12
• WIPO field: Basic materials chemistry
• WIPO sector: Chemistry

Abstract

The conventional condensation of naphthalene-1,4,5,8-tetracarboxylic acid with 1,2-diaminobenzene gives the resulting naphthoylenebisbenzimidazole isomers together in the cis and trans form. It is desirable to shift the isomer ratio of the mixture obtained toward the desirable trans product and to reduce the amount of cis product obtained. It is also desirable to develop a process of preparation which optimizes the yield and improves the waste water situation. This object is achieved according to the invention by subjecting virtually stoichiometric amounts of the starting compounds to a precondensation at 60.degree. to 110.degree. C. in an aqueous medium and then completing the condensation in the aqueous medium in a second stage at 130.degree. to 180.degree. C.