HEAT-STABLE IRON OXIDE BLACK PIGMENTS, PROCESSES FOR THEIR PRODUCTION AND THEIR USE

摘要

A heat-stable iron oxide black pigment resistant to hydrothermal treatment in air at temperatures above 180 DEG C. and which has a specific BET surface of 0.5 to 5 m2/g is useful as a coloring agent for building materials, paints, cements, bricks and so forth and is prepared by reacting an aqueous solution of FeOOH, iron (II) salts and alkalis at elevated temperature and precipitating iron oxide from the solution with Na2CO3 at temperatures in the range from 80 DEG C. to the boiling point of the solution.