Process for the preparation of azo pigments by diazotizing in a dipolar aprotic organic solvent and azo pigments obtained therefrom

摘要

Azo pigments are obtained by diazotizing a diazotizable aromatic amine without solubilizing groups in anhydrous dipolar aprotic water-miscible solvents with the stoichiometric amount or a small excess of nitrosylsulfuric acid or nitrosyl chloride, coupling the diazonium compound so obtained with a coupling component and isolating the pigment obtained in usual manner. This process is carried out in homogeneous solution and yields azo pigments the advantageous properties of which cannot be achieved by other methods, for example, the excellent purity, grain softness, narrow range of particle size distribution, excellent dispersibility in plastic materials and color lacquers, high gloss and excellent opacity in color lacquers.