VERFAHREN ZUR HERSTELLUNG VON AZOPIGMENTEN.

摘要

A process for prodn. of azo pigments by an azo coupling reaction between a diazo component (I) and an equiv. amt. of a coupling component (II) which is difficultly soluble in the aq. acid and aq. neutral pH range at temps. below 65 deg.C, comprises continuously mixing an aq. acid soln. of the (I) with an aq. alkaline soln. of the (II) at a temp. below 65 deg.C, in a time period of less than 1 min., and controlling the pH to a predetermined value between 2 and 9 by suitable adjustment of the amt. of the streams of (I) and (II) so that part of the (II) is immediately converted to the required azo pigment whilst the remainder of the (II) is simultaneously precipitated in fine crystalline reactive form and is only reacted with still uncovered (I) to form the desired azo pigment in a post reaction phase. Pref. the continuous mixing of the components is accomplished in less than 6 sec. Control of the pH may be assisted by adding a buffer. Pref. the temp. during the azo coupling reaction, including the post-reaction phase, is 10-55 deg.C and 60-98% of the (II) is converted immediately to azo pigment. Pref. the pptd. reactive form of the coupling component (II) has enolate, phenolate or naphtholate gps. on the particle surface, depending on its chemical constitution.