Preparation of improved heat stable yellow iron oxide pigments

摘要

Yellow iron oxide pigments having improved heat stability are prepared by subjecting an alkaline slurry of conventional yellow iron oxide, a soluble ferric salt, and sodium aluminate to a hydrothermal (autoclave) treatment at 100 DEG -240 DEG C., separating and slurrying the resultant solid product, and subjecting that product to a second hydrothermal treatment of 250 DEG -350 DEG C. The original iron oxide has a heat stability (based on color change from yellow to red) temperature of about 203 DEG C., while the final product shows a change at 270 DEG C.