Characteristics and Dispersion Stability of Copper-Phthalocyanine Pigments

Copper-phthalocyanine (CP) pigment surface was modified by its derivatives containing acid or base functional groups. The surface-modified CP pigments were characterized with three viewpoints : (1) ζ-potential in aqueous system, (2) acid and base amounts in methyl isobutyl ketone and (3) heat of adsorption of acid and base. The relationship between these characteristics and dispersion stability of the pigments in acrylic paints was also investigated. The dispersion stability was determined by TI value (ratio of viscosity at 6 rpm/ at 60 rpm). Isoelectric point (IEP) in ζ-potential, acid and base amounts, and heat of adsorption of the surface-modified CP pigments changed as it had been predicted from the structure of functional group of CP pigment derivatives used for the modification. When pigments were classified with their IEP value, the dispersion stability of acidic pigments was good in basic polymer, and vice versa, following Sörensen's acid-base concept. Heat of adsorption of acetic acid and triethyamline was correlated with the dispersion stability in acidic polymer and in basic polymer, respectively. Base amounts of pigments also effected dispersion stability in acidic polymer