Process for making azo pigments

US4920205A · kind A · utility

Assignee

• Hoechst GmbH · DE

Inventors

• Heinrich Rehberg · Kornwestheim, DE
• Hartmut Behringer · Nidderau, DE

Key dates

• Filing date: Mar 28, 1989
• Grant date: Apr 24, 1990
• Expiry date: Mar 28, 2009

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C09B41/006
• WIPO field: Basic materials chemistry
• WIPO sector: Chemistry

Abstract

Azo pigments are made by subjecting a diazo component to an azo coupling reaction with the equivalent quantity of a coupling component difficultly soluble at less than 65.degree. C. in the aqueous/acid and aqueous/netural pH-ranges. More specifically, an aqueous/alkaline solution of the coupling component is continuously mixed in a first reaction step with an aqueous solution of acetic acid, boric acid, phosphoric acid, hydrochloric acid or sulfuric acid at a temperature lower than 65.degree. C. within a period of less than 1 minute, during which the coupling component commenences precipitating at least partially as reactive matter; next, the suspension obtained is continuously mixed, in a second reaction step immediately following the first reaction step, with an aqueous/acid solution of the diazo component at a temperature of less than 65.degree. C. within a period of less than 1 minute, and a predetermined pH between 2 and 9 is established by controlling the flow of the mass streams of diazo component and coupling component whereby a portion of the coupling component is caused to undergo immediate reaction to the azo pigment to be made; the balance portion of the coupling compon…