Dispersion of Organic Pigments with Modern Dispersion Equipment

A previous paper had shown that milling organic pigments at elevated temperatures often improves colour development through better wetting. The present investigation shows that heat can, nevertheless, have an overall adverse effect on colour strength and hue of pigments which partially dissolve (and subsequently recrystallise) in a vehicle system under the combined action of heat and impact. Likewise, metastable polymorphic pigments should be dispersed at the lowest possible temperature to minimise hue shifts and/or loss of colour strength.