RU2346018C1 - Method of obtaining black iron oxide pigment - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: present invention pertains to production of black iron oxide pigments and can be used in paint and coating industry. The black iron oxide pigment is obtained from burning red mud - aluminous production waste. Before burning, the red mud is sorted according to size, with selection of the 0.02 mm fraction and further selection of the 0.02-0.045 mm fraction. These fractions are burnt in a controlled atmosphere with oxygen deficiency at 500-1000°C temperature.

EFFECT: obtaining iron oxide pigment of a pure black colour with 8-10 g/m² coverage using aluminous production wastes - red mud, without more raw materials and additives and pollution of the environment.

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Description

The invention relates to the production of inorganic pigments, namely iron oxide pigments of black color, and can be used in the paint and varnish industry, the production of building and other pigmented materials.

A known method of producing iron oxide pigments with a structure of γ-Fe ₂ O ₃ containing 0.1-12.0% SiO ₂ and 0.02-5.0% Al ₂ O ₃ by burning a mixture of Fe ₃ O ₄ , SiO ₂ , Al ₂ O ₃ at 200-700 ° C with the supply of air and oxygen. The method is intended to produce brown pigments. The disadvantage of this method is the instability of the chemical composition, which does not exclude the appearance of various shades.

There is also known a method for producing red iron oxide pigment from red mud, waste from alumina production, by calcining it in a mixture with phosphomel.

Closest to the technical nature of the claimed invention is a "Method for producing iron oxide pigments." [Patent No. 2047631. Declared August 17, 1992. Published on November 10th, 1995. Authors - Kalinichenko II, Sokolov VI, Nikonenko EA, Kolesnikova MP, Purtov AI]. In this method, separation is preliminarily performed according to size classes with the selection of a fraction of particles no larger than 0.02 mm, and calcination of this fraction at 290-850 ° C. The pigments are pure red due to α-Fe ₂ O ₃ .

The disadvantage of this method is the inability to obtain black pigment due to the small amount in the selected fraction of sulfide sulfur, which is necessary for the reduction of Fe (III) to Fe (II).

The objective of the invention is to obtain a black pigment due to the additional selection of a fraction from 0.02 to 0.045 mm containing a higher amount of sulfide sulfur while maintaining uniformity of the dispersed composition and a spreading rate of 8-10 g / m ² . [Kalinichenko I.I., Kolesnikova M.P., Nikonenko E.A., Sokolov V.I., Purtov A.I. Granulometric composition of red mud. Depot. VINITI, September 27, 1996, No. 2892 - B96, Moscow, 1996. - 5 p.].

This problem is solved in that the red mud before calcination is divided into size classes with a selection of fractions up to 0.02 mm and an additional 0.02 to 0.045 mm, moreover, these fractions are calcined in a controlled atmosphere (reducing atmosphere, inert gases, vacuum) at temperature 500-1000 ° С.

An increase in the content of sulfide sulfur due to an additional selection of the fraction from 0.02 to 0.045 mm and a decrease in the oxygen content in the gas phase leads to the formation of mixed iron oxides in the pigment, which leads to the black color of the resulting pigment, and the presence of fineness of not more than 0.045 mm ensures sufficient uniformity of composition and hiding power of the obtained pigment.

The lower limit of the temperature range of calcination is due to the fact that at 500 ° С the reduction of Fe ₂ O ₃ to FeO and Fe ₃ O ₄ begins. The upper limit is 1000 ° C, since pigment sintering begins at a higher temperature.

The claimed method was obtained black iron oxide pigment from red mud, taken from the dumps of the Bogoslovsky aluminum plant, the following chemical composition in terms of oxides, wt.%: Fe ₂ O ₃ - 35.4; Al ₂ O ₃ - 14.6; CaO - 11.5; S is 1.36; TiO ₂ - 3.9; SiO ₂ - 7.5; Na ₂ O - 3.4; CO ₂ - 3.5 (without IFR).

A sample of red sludge weighing 35 kg with a moisture content of 39% was divided into size classes. A fraction no larger than 0.045 mm was selected, which had the following chemical composition in terms of oxides, wt.%: Fe ₂ O ₃ - 43.0; Al ₂ O ₃ - 13.5; CaO - 7.0; S is 1.2; TiO ₂ - 3.8; SiO ₂ - 6.5 (without IFR). The yield of the fraction is 89.9%.

After separation by size classes, the selected fraction was filtered off, washed to a pH of washings of 8.5, and dried, after which the sample was divided into parts and calcined in various modes. The table shows the technological parameters and characteristics of the target product obtained by the claimed method. The chemical composition of the product is determined by the composition of the fraction - 0.045 mm The difference from the prototype is the color of the pigment, a larger percentage of the yield of the useful fraction, the temperature range, the use of sulfide sulfur as a reducing agent.

The determination of color and hiding power of the obtained pigment was carried out on the basis of standard methods. [Dobrovolsky I., Bolshakov A. et al. Methods of technical analysis of pigment production. Chelyabinsk, South Ural Book Publishing House, 1973. P.212-213].

Using the proposed method provides the following technical results:

- obtaining iron oxide pigment of a pure black color with a hiding power of 8-10 g / m ² ;

- use of waste from the production of alumina - red mud (up to 90%) without additional raw materials and additives;

- complete absence of harmful emissions into the environment;

- use for the reduction of Fe (III) in Fe (II) sulfide sulfur, which is present in the composition of the initial slurry.

Table 1 Characterization of the obtained pigments Fineness class, mm. Sample weight, kg Calcination temperature, ° С Wednesday Color The residue after wet sieving on a sieve 0063,% Spreading rate, g / m ² Dispersibility, microns According to the claimed method Finer 0.045 mm weight 31 kg 290 Restorative atmosphere Brown 0.05 9 28 Argon Brown 0.05 9 28 Vacuum P ~ 1.10 ^-3 atm Brown 0.05 9 28 500 Restorative atmosphere Gray black 0.04 9 27 Argon Gray black 0.04 8 27 Vacuum P ~ 1.10 ^-3 atm Gray black 0.04 8 27 850 Restorative atmosphere Pure black 0,03 10 thirty Argon Pure black 0,03 10 thirty Vacuum P ~ 1.10 ^-3 atm Pure black 0,03 10 thirty 1000 Restorative atmosphere Pure black 0.05 10 thirty Argon Pure black 0.05 10 thirty Vacuum P ~ 1.10 ^-3 atm Pure black 0.05 10 thirty According to the method of the prototype Smaller than 0.02 mm. Weight 24 kg 290 Air Dark red 0.05 9 32 500 Air Pure red 0,03 7 27 850 Air Pure red 0.05 eleven thirty

Claims (1)

A method of obtaining a black iron oxide pigment from red mud - waste from alumina production, including calcining it, characterized in that the red mud before calcination is divided into size classes with a fraction of up to 0.02 mm and optionally from 0.02 to 0.045 mm, and calcining these fractions are carried out in a controlled atmosphere with a lack of oxygen at a temperature of 500-1000 ° C.