METHOD FOR PRODUCTION OF IRON OXIDE PIGMENTS Russian patent published in 1996 - IPC

FIELD: production of dyes. SUBSTANCE: initially suspension is prepared by interaction of solution of ferrum sulfate with aqueous solution of ammonia and by oxidation with oxygen of air. Thus obtained suspension is mixed with solution of ferrum sulfate and oxidized at elevated temperature. Said oxidation is carried out simultaneously with neutralization. The latter process takes place with the help of carbamide as its dry salt or with the help of aqueous solution having concentration 200-500 g/dm³. Rate of supply of said carbamide is 0.3-3.0 g/h per 1 dm³ of reaction volume. EFFECT: improves efficiency of method, simplifies technology. 2 cl, 1 tbl