METHOD FOR PREPARING BROWN PHOSPHATE IRON OXIDE PIGMENT Russian patent published in 1997 - IPC

FIELD: chemical industry. SUBSTANCE: claimed process comprises depositing product with ammonia solution from iron (III) nitrate solution containing phosphoric acid additive at Fe₂O₃:P₂O₅ molar ratio of 1.00:(0.12-0.18) in the presence of urea at Fe₂O₃:CO(NH₂)₂ molar ratio of 1.0:(3.0-4.0) at 90-100 C at which temperature residue is aged for 2-5 hours to adjust pH of medium to 5-7, and the residue is subsequently filtered, washed, dried and heat treated at 500-700 C. The resulting product has dyeing power of 130-150 %, covering power of 80-100 g/sq.m and heat resistance of 60-700 C. EFFECT: more efficient preparation process. 1 tbl