Process for the preparation of dyestuffs

US5541299A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Roderich Raue · Dover, US
• Alfred Brack · Odenthal, DE
• Karl-Heinrich Lange · Burscheid, DE

Key dates

• Filing date: Sep 23, 1994
• Grant date: Jul 30, 1996
• Expiry date: Sep 23, 2014

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C09B41/009
• WIPO field: Basic materials chemistry
• WIPO sector: Chemistry

Abstract

Dyestuffs of the formula ##STR1## in which D is the radical of an aromatic or heterocyclic diazo component and K is the radical of an aromatic or heterocyclic coupling component, or is the radical of an active methylene compound, are obtained in an ecologically advantageous manner by reacting an aromatic or heterocyclic diazo components of the formula EQU D--NH.sub.2 and a coupling component of the formula EQU H--K with a nitrite, for example NaNO.sub.2, in the presence of CO.sub.2 at a pressure of 5-100 at. The process is suitable in particular for the preparation of concentrated dye-stuff solutions, because expensive operations, such as, for example, pressure permeation and reverse osmosis, can be omitted.