Preparation of a coupling product of bisiazotized 2,2',5,5'- tetrachloro-4, 4'-diaminobiphenyl with two equivalents of n-acetoacetyl-2, 4- dimethylanilide

摘要

The industrial preparation of C.I. Pigment Yellow 81 by conventional coupling methods has the disadvantage that traces of polychlorinated biphenyls are formed in the course of the reaction of the two components. PPThe invention now provides that the addition of quaternary dialkyldiallylammonium compounds during the azo coupling will decisively suppress the PCB-forming secondary reactions during the pigment synthesis.