Pigment composition and preparation process thereof

摘要

A pigment composition is composed of an intimate mixture of an organic pigment and a polymer. The content of the organic pigment is 75-95 wt. % based on the whole pigment composition. Monomers which form the polymer include 0-40 wt. % of styrene, 20-70 wt. % of a methacrylic ester and 20-50 wt. % of methacrylic acid. The total proportion of styrene, the methacrylic ester and methacrylic acid is at least 85 wt. % of the entire monomers. The pigment composition is prepared by mixing the organic pigment with an aqueous alkaline solution, which contains the polymer and an alkali metal salt, alkali metal hydroxide, lower amine or ammonium, to form an aqueous dispersion. The organic pigment and polymer are then subjected to coprecipitation, preferably, by lowering the pH of the aqueous dispersion beyond 7.0.