Dialysis monitored preparation of metal salts of azo pigments

摘要

Azo dyestuff coupling process in which the amount of excess diazo or coupling component is continuously monitored and the addition of diazo component or coupling component to the reaction is automatically controlled by means of an automatic chemical analyzer which incorporates a dialyzer module, which process is characterized in that azo metal salt pigments derived from sulphonated intermediates can be obtained by precipitating the pigment by adding a water-soluble metal salt to the water-soluble sulphonated azo dyestuff at some stage prior to the passage of the sample stream through the dialyzer.