CS243747B1 - Process for preparing pink-purple zirconium pigment from zirconium mineral. - Google Patents

Abstract

The solution concerns the preparation of a pink-violet ceramic pigment of the zircon type from the zircon mineral. Zircon is first decomposed with a mixture of potassium and sodium hydroxide at a temperature of 650 to 1,000 °C in an amount of 3 to 6 parts by weight of the mixture per 10 parts of zircon. Alkali are not removed from the decomposition products for the actual preparation of the pigment, they remain in the mixture and are used as an alkaline component of the mineralizer. The halide component of the mineralizer is introduced by sprinkling the decomposition products with hydrofluoric and hydrochloric acid. Another source of halides is the chromophore used in an amount of 0.5 to 5 parts by weight - ferrous chloride. The loose mixture is fired at a temperature of 650 to 1,000 °C to a pink-violet pigment. The amount of chromophore used in the mixture can be used to regulate the color shade of the pigment. The solution can be used in the ceramic industry. It allows the preparation of high-quality ceramic pigment from cheap starting materials and β possible use of some waste (mixture of hydroxides, ferrous chloride tetrahydrate).

Description

The invention relates to a process for the preparation of a pink-violet zirconium-type ceramic pigment from a zirconium mineral.

Zirconium-type pigments are usually prepared from a mixture of zirconia and silica of mineral origin. The mixture further comprises mineralizers, most often in the form of alkali halides, and chromophores, which in the case of the preparation of pink zirconium pigments are iron compounds, which are converted to iron oxide when the mixture is fired. However, the preparation of zircon pigments also uses cheaper starting material - zirconium mineral. It is uncoloured and must first be decomposed into the zirconium and silica component in the first stage and only from its decomposition products after their possible further treatment zircon pigments are prepared. However, the starting material is a thermally and chemically very stable substance. The decomposition methods used are based on the use of high temperatures or plasma, others on chlorination in a reducing environment at high temperatures or on alkaline melting. In the first case, the decomposition of mineral by high temperatures or plasma, while the processing of the decomposition products into zircon pigments is very simple, it is a disproportionately demanding operation in terms of energy and construction. Similarly, when using chlorination in a reducing environment, in addition, the decomposition products need to be further processed to pigmentary zirconium dioxide, while the silica component of the starting mineral is separated and can no longer be used in the actual synthesis of the pigment. products usable for the synthesis of zirconium pigments - alkaline melting - are almost exclusively used as flux of soda · This process already works with temperatures more accessible to pigmentary plants and the cost of soda is also favorable, but

- 2 243 747 also has some disadvantages · It requires, for example, a disproportionately large consumption of soda with respect to the amount of zirconium to be decomposed. It also requires, as a rule, the subsequent demanding treatment of the decomposition products so that they can be used for the actual preparation of zircon pigments. In most cases, it is difficult to leach the hot decomposition products with water or sulfuric acid to remove large amounts of alkali used for decomposition. The zirconium and siliceous components must then be recovered from the extracts, which further complicates the pigment preparation process. Also in this operation, the silica component is lost, so that the pigment mixture needs to be supplemented with mineral silica. While some processes do not require a leaching operation, the decomposition products are only treated by the addition of sulfuric acid after melting the zirconium with soda; after the mixture is supplemented with mineralizers and chromophore from n, they then directly prepare the pigment. This process is used, for example, to prepare a blue zirconia pigment from a zirconium mineral. However, the quality of the pigment is poor, in particular the degree of conversion to the zirconium silicate which is the basis of the pigment is low and the color shade of the pigment is also not significant.

Said drawbacks have no process for the preparation of a pink-violet zirconium pigment from zirconium mineral (10% by weight). parts zircon decomposes at 650 to 1000 ° C 8 preferably at a temperature of 750 to 900 ° C, _i.e. by treatment with 3-6, preferably 4-5 wt. parts of a mixture of hydroxides containing potassium hydroxide and sodium hydroxide in a mass ratio of 3 to 1: 1, β preferably 1.8 to 1.3: 1 95%) · Waste hardening baths from the mechanical engineering industry, which are essentially a mixture of potassium hydroxide and sodium in mass, can be used as fluxes. According to the invention, the alkali is only used in relatively small masses. · Decomposition products are a mixture of zirconium-potassium-zirconate silicate and zirconium-disodium silicate and

The potassium and sodium ions contained therein then act according to the invention as the alkaline components of the mineralizer in the actual pigment synthesis. The halide components of the mineralizer are added in the form of hydrofluoric acid and hydrochloric acid. Therefore, further according to the invention, the cooled decomposition products are sprinkled with hydrofluoric acid in an amount corresponding to at least 1.5, preferably 2 to

2.5 wt. % of hydrogen fluoride and hydrochloric acid in an amount corresponding to at least 0.8, preferably 1 to 1.5 parts by weight of hydrogen chloride. The potash is added to the mixture, which is still free-flowing, in an amount of 0.5 to 5 wt. and the mixture ee is fired at a temperature of 650 to 1000 ° C, preferably at a temperature of 700 to 850 ° C, to a pink-violet pigment. Thus, other chloride ions are introduced into the mixture by the chromophore, which also contribute to the formation of pigment by their mineralization effects and iron (III) ions, which gradually convert to iron (III) to form hematite particles when the mixture is fired. Intensely colored hematite particles immediately grow into the resulting zirconium pigment micro-crystals. The large amount of alkali metal halide ions present in the mixture causes iron ions to be trapped directly into the pigment structure in small quantities as well as alkaline ions, especially potassium ions, and also to a greater extent halide ions. As a result, the basic pink shade of the pigment achieved by the ingrown hematite particles changes markedly into violet. By using the amount of chromophore in the range according to the invention, it is possible to control the resulting pigment shade from pink or beige pink (5 parts by weight of ferrous chloride) through pink violet (1 to 3.5 parts by weight) to brick violet (0.5 to 1 part by weight). weight part of chromophore). If the chromophore - ferrous chloride - is used in the form of tetrahydrate, which is a waste product in the steel industry, then the crystalline water that is released when the mixture is fired also has a positive effect on the pigment formation reaction and its color. The resulting sludge is then somewhat more baked, but can be relatively easily broken up into individual primary particles. According to the invention, the pigment leach is optionally leached with water or a dilute mineral acid, preferably hydrochloric acid, before being applied to the ceramic glaze. Mineralizer and chromophore residues

4,243,747 in the stillage is relatively low, especially when using a decomposition mixture of hydroxides and chromophore in the lower half of the ranges of the invention *, and thus the operation of the final pigment leaching is not necessary.

Advantages of the method according to the invention:

- the method uses cheaper starting materials - mineral zircon

the temperatures used to decompose the mineral are favorable and commonly available in the ceramic industry

- the consumption of alkaline flux for decomposition is low; in addition, a waste hardening bath of mechanical engineering containing potassium and sodium hydroxide can be used successfully

- achieved degree of mineral decomposition is high - around 95%

- the process does not require a demanding leaching operation of mineral decomposition products with difficult processing of the extracts into a zirconium and siliceous component to prepare the pigment

- alkali ions in decomposition products are used as an alkaline component of the mineralizer in the actual preparation of the pigment, so it is no longer necessary to add to the mixture

- the ferrous chloride chromophore can be used in the form of tetrahydrate, a waste product of the steel industry

- the chloride component of the chromophore contributes to pigment formation by its mineralizing effects; the crystalline water released during calcination from the chromophore also favorably affects pigment formation

- the color of the pigment can be regulated by the amount of chromophore added in the range according to the invention, from pink, pink-violet to brick violet

- Pigment firing temperatures are favorable and correspond to those of pink pigments when prepared from mineral zirconium and silicon oxides

- the pigment quality is high both in terms of the degree of conversion to zirconium silicate (93 to 98%) and in terms of color

the yield of the process according to the invention is high and makes it possible to prepare the pigment in amounts corresponding to 83 to 95% by weight

- 5 zirconium starting mineral used ²⁴³ 747

- all intermediates are in solid phase and in loose form, so manipulation with them and pigment burning are simple operations in this respect

Example 1 g of zirconium mineral (containing 96% zirconium silicate) was decomposed with a hydroxide mixture containing 20 g of potassium hydroxide and 10 g of sodium hydroxide at 850 ° C for 2 h. Decomposition proceeded to 95% · After decomposition products were decomposed 70 g of hydrofluoric acid 20% wt. concentration. The mixture was further admixed with 28 g of iron (II) chloride (anhydrous) and the mixture was fired at 750 ° C for 2 h. The lime was washed with dilute hydrochloric acid while hot and the remaining solid phase was 59 g of a lightly violet pink pigment containing 95% zirconium silicate. The pigment was applied in an amount of 10% by weight to a high-temperature ceramic glaze with a glazing temperature of 1280 ° C, which it dyed to the same color shade.

Example 2

100 g of zirconium mineral (containing 94% zirconium silicate) were decomposed with 40 g of spent quenching baths containing potassium hydroxide and sodium hydroxide in wt. ratio 3: 2 at a temperature of 900 ° C for 1 h. Decomposition proceeded to 93%. After cooling, the decomposition products were carefully poured over with 65 g of 20% by weight hydrofluoric acid. concentration and 50 g of hydrochloric acid 18 wt. concentration. The mixture was further admixed with 25 g of ferrous chloride tetrahydrate and the mixture was fired at 700 ° C for 2 h. The leach was leached with hot water and the remaining solid phase was 88 g of a pink-violet pigment containing 96% zirconium silicate. The pigment was applied in an amount of 7% to a borosilicate titanium glaze with a glazing temperature of 1050 ° C, which was dyed to the same pink-violet hue.

Claims (1)

SUBJECT OF THE INVENTION 243 747 Process for preparing a pink-violet zirconium pigment from a zirconium mineral, characterized in that ae 10 wt. parts of zirconium decomposes at a temperature of 650 to 1000 ° C, preferably at a temperature of 750 to 900 ° C, by treatment with 3 to 6, preferably 4 to 5 wt. parts by weight of a mixture of hydroxides containing potassium and sodium hydroxide in mutual mass. a ratio of 3 to 1: 1, preferably 1.8 to 1.3: 1, and the cooled decomposition products are sprinkled with hydrofluoric acid in an amount corresponding to at least 1.5> 9, preferably 2 to 2.5 wt. % of hydrogen fluoride, and hydrochloric acid in an amount corresponding to at least 0.8, and preferably 1 to 1.5 wt. 0.5 to 5 wt. The mixture is baked at a temperature of 650 to 1000 ° C, and preferably at a temperature of 700 to 850 ° C, to a pink-violet pigment which is optionally precipitated with water or a dilute mineral acid, preferably hydrochloric acid, before being applied to the ceramic glaze.