FREMGANGSMAADE TIL FREMSTILLING AF AZOPIGMENTER VED DIAZOTERING OG KOBLING

In a process for preparing azo pigments by the azo coupling reaction of a diazo component with the equivalent amount of a coupling component which is sparingly soluble under acid and neutral pH conditions below 65 DEG C, an acid solution of the diazo component is continuously mixed with the alkaline solution of the coupling component at below 65 DEG C for less than 1 minute, and the mass flows of the diazo component and the coupling component are control-set to a certain pH between 2 and 9, as a result of which a portion of the coupling component is immediately converted into the desired azo pigment while at the same time the remainder of the coupling component precipitates in a finely crystalline reactive form and is not converted into the desired azo pigment with still unconverted diazo component until a post reaction phase.