Fine particles preparation of Red Lake C Pigment by supercritical fluid

Fine material preparation for several kinds of pigments (Red Lake C, C.I. Pigment Blue and C.I. Pigment Yellow) was investigated under supercritical conditions. In the experiments, acetone was used as solvent and carbon dioxide as anti-solvent were applied in the recrystallization processes. To obtain the ultrafine particle products, a series of 5-500 mu m nozzles were used to disperse the solution out from the crystallizer. Experimental results showed that operations under supercritical conditions were able to provide very small particles, e.g. less than 1 mu m in diameter, very narrow size distribution and spherical morphology. Further study also showed that the particle size could be controlled by temperature, pressure and nozzle size. (C) 1998 Elsevier Science B.V.