Patent ID: 6028178
Filing Date: 2000-02-22
Classification: C08K,C09B,C09D,G03G

Abstract:
A process for the preparation of an azo pigment of the formula (1) ##STR27## which has a specific surface area of the pigment powder of more than 45 m.sup.2 /g, by azo coupling of 1,2-bis(2-aminophenoxy)ethane bis-diazonium salt (diazo component) with 5-acetoacetyl-aminobenzimidazol-2-one (coupling component), which comprises carrying out the azo coupling at a temperature of between 5 and 35.degree. C. and adding the diazo component to the initially charged coupling component over the course of not over 30 minutes with or without the addition prior to, during or after the azo coupling of an ionic or nonionic surfactant, and then subjecting the agglomerated prepigment which has been formed to a solvent finish in an organic or aqueous organic medium.