Preparation of transparent pigmentary forms of 4,4',7,7'-tetrachlorothioindigo

US4332955A · kind A · utility

Assignee

• BASF SE

Inventors

• Helmut Hoch
• Erwin Hahn · Heidelberg, DE
• Heinrich Hiller · Monsheim, DE

Key dates

• Filing date: Apr 7, 1980
• Grant date: Jun 1, 1982
• Expiry date: Apr 7, 2000

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C09B67/0077
• WIPO field: Basic materials chemistry
• WIPO sector: Chemistry

Abstract

A transparent pigmentary form of 4,4',7,7'-tetrachlorothioindigo is prepared by oxidizing the leuco compound of tetrachlorothioindigo in aqueous alkaline suspension, in the presence of a dithionite, at from 20.degree. to 100.degree. C., with simultaneous exposure to shearing forces. Preferably, the oxidation is carried out in the presence of a surfactant. The pigment obtained gives brilliant, transparent full-shade colorations, while white reductions have a deep pure reddish hue.