PROCESS FOR PREPARING YELLOW IRON-CALCIUM PIGMENT Russian patent published in 1994 - IPC

FIELD: preparation of paint-and-varnish materials. SUBSTANCE: the FeSO₄ solution is heated to 25-40 C, lime milk is added in an amount that affords the degree of precipitation of FeSO₄ to 15-20 wt % . Air is fed. The mixture is oxidized for 4-6 hr till the pH is reduced from 6 to 4 and heated to 75-100 C, lime milk is fed in portions and the pH is maintained constant at 3.5-5.4. The mixture is filtered and dried at 110 C. The pigment is yellow of various hues. The covering power 22-35 22-35 п/m² and the oil number 35-40 g/100 pigment. EFFECT: improved properties of the pigment. 2 cl, 1 tbl