METHOD OF CHEMICAL PROCESSING OF NEPHELINE CONCENTRATE FOR OBTAINING LIGHT-RESISTANT CHROMATIC AND ANTI-CORROSIVE PIGMENTS Russian patent published in 2005 - IPC

FIELD: chemical and paint-and-varnish industries.

SUBSTANCE: proposed method includes introduction of nepheline concentrate into 20-25-% phosphoric acid in portions. Amount of H₃PO₄ is 130% of stoichiometric magnitude. Decomposition of nepheline concentrate is performed for 3-4 times. Each time, after complete decomposition of subsequent portion of nepheline concentrate, silicon acid solution is separated from non-decomposed minerals. Silicon acid is partially dehydrated at 95-100°C. Gel thus obtained is filtered and washed with 10-% H₃PO₄. Mixture of filtrate and flushing phosphoric acid is directed for decomposition stage of next portion of nepheline concentrate. Washed gel is mixed with gel obtained during decomposition of subsequent portions of nepheline concentrate, pulped in water, boiled, washed, filtered, dried and subjected to heat treatment at 500°C for obtaining SiO₂. Last portion of filtrate and flushing H₃PO₄ is diluted with water by 150%, neutralized with nepheline concentrate to pH=3.0-4.0 and dried at temperature of 60-80°C. As a result, hydrated anti-corrosive pigment is obtained. After calcination of this pigment at temperature of 500°C, condensed anti-corrosive pigment is obtained. 20-40-% of iron oxide or chromatic organic pigment may be added to pigments obtained or to their mixture. Powder-like day fluorescent organic pigment (belophore) in the amount of 1-3 mass-% may be added to silicon dioxide for obtaining bleaching agent for pigments.

EFFECT: enhanced efficiency.

7 cl, 4 tbl, 12 ex