METHOD OF PRODUCING IRON OXIDE PIGMENTS Russian patent published in 2019 - IPC C09C1/24 C09C1/00 

FIELD: technological processes.

SUBSTANCE: invention relates to production of inorganic pigments. Method of producing iron oxide pigments involves thermal treatment of the starting material. Raw material is prepared by mixing of high-iron red mud of alumina production, carbonate soda Na₂CO₃, calcium oxide CaO and caustic soda NaOH. Heat treatment of initial material is carried out in a rotating tubular furnace to produce clinker, which is milled and divided into three parts. One portion of the clinker is mixed with CaO, the mixture is ground in a stream of a medium-module alkali-aluminate solution with Na₂O_ku concentration, equal to 300–310 g/dm³, and caustic module α_ku, equal to 14–15 units. Obtained crude suspension is directed for leaching and a red pigment suspension is obtained in the mother solution. Cake obtained after filtering the cake is washed with water, dried, passed through a sieve and a commercial red pigment is obtained. Second portion of the clinker is mixed with CaO, the mixture is ground in a stream of a high-modulus alkali-aluminate solution with Na₂O_ku concentration, equal to 330–360 g/dm³, and caustic module α_ku, equal to 34–35 units. Crude suspension is directed for leaching and a suspension of red-brown pigment is obtained in the mother solution. Cake obtained after filtration of the suspension is washed with water, dried, passed through a sieve and a commercial red-brown pigment is obtained. Third part of the clinker is mixed with CaO and NaOH; the obtained mixture is ground in a stream of NaOH solution. Crude suspension is directed for leaching, which is carried out in a tubular pipe-like apparatus, as a result of which a brown pigment suspension in a mother solution is obtained. Cake obtained after filtering the cake is washed with water and dried, passed through a sieve and a commercial brown pigment is obtained.

EFFECT: invention widens the range of methods for producing iron oxide pigments with production of pigments of different color characteristics in a single process stream.

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