Process for making azo pigments

Azo Pigments are made by subjecting a diazo component to an azo coupling reaction with the equivalent quantity of a coupling component difficultly soluble at less than 65 DEG C. in the aqueous/acid and aqueous/neutral pH-ranges. More specifically, an aqueous/acid-solution of the diazo component is continuously mixed at a temperature of less than 65 DEG C. within a period of less than 1 minute with the aqueous/alkaline solution of the coupling component and a predetermined pH between 2 and 9 is established by controlling the flow of the mass streams of diazo component and coupling component; in this way a portion of the coupling component is caused to undergo immediate reaction to the azo pigment to be made whereas the balance portion of the coupling component simultaneously commences precipitating as finely crystalline reactive matter, which is reacted in a post-reaction phase with unreacted diazo component to give the azo pigment to be made.