CS263138B1 - A method for preparing a blue-violet ceramic pigment from a zirconium mineral - Google Patents

Abstract

The starting zirconium oxide decomposes in 3 ml of potassium and sodium hydroxide at a temperature above 600 °C. The mixture of hydroxides is used only in the most necessary amount -2.5 to 0 parts by weight per 10 parts of zirconium. Alkali ions are not removed from the ammonium oxide after decomposition and, on the contrary, are used as the alkaline component of the mineralizer in the actual synthesis of the pigment. The halide component of the mineralizer is added in the form of hydrofluoric and hydrochloric acids in an amount of at least 0.5 parts by weight of hydrogen halides. After adding a chromophore in the form of at least 0.5 parts by weight of cobalt dihydrogen phosphate dihydrate, the oxide is fired at temperatures above 100 °C to a blue-violet pigment.

Description

The invention relates to a process for the preparation of a zirconium-type blue-violet ceramic pigment containing condensed cobalt phosphates. The starting zirconium raw material for pigment preparation is zirconium mineral.

Ceramic pigments of the zirconium type are microcrystals of synthetic zirconium silicate having a structure corresponding to the zirconium mineral, which are colored by admixtures of either transition metal ions or inclusions of colored particles of some inorganic compounds. The use of certain cobalt compounds, most commonly cobalt oxide, or compounds which provide this calcination as coloring agents for the preparation of zircon pigments is known. However, these pigments have a blue-gray coloration, with only the gray shade being caused by the cobalt component incorporated in the zirconium structure, while the blue shade is due to the cobalt fractions that are not retained in the pigment microcrystals. For some ceramic glazes, this pigment, which is actually a blend, is useful for dyeing to a blue-gray hue. However, in other glazes, especially high temperature glazing, the free cobalt blue dyeing is ineffective. It is not protected against the aggressive environment of the molten glaze and discoloures. The resulting color shade is gray, since it is caused only by the cobalt component trapped in the zirconium 2 263 13θ new microcrystals where it is exposed to the glaze environment. The preparation of a zirconium pigment with a blue-violet coloration, stable even after application in ceramic glazes, is described in Czech author's certificate no.243,657. low-grade zirconia · The pigment synthesis mineralizer used is a combination of several components from not very common chemicals ·

The above-mentioned drawbacks are eliminated by a process for preparing a blue-violet zirconium zirconium ceramic pigment pigment as a starting material. to 95 ° C _from 2.5 to 8 wt. parts _of preferably 4 to 5.5% by weight / part of a mixture of hydroxides comprising potassium and sodium hydroxide in a weight ratio of 0.5: 1 _{to each} other, preferably in a weight ratio of 2 to 1.3: 1. The decomposition temperatures used correspond to those commonly used in the ceramics industry, or are even lower, and the zirconium decomposition takes place to a high degree (above 90%). As the fluxes (hydroxide mixtures), waste quenching baths from the engineering industry, which are essentially % mixture of potassium hydroxide and sodium in wt. ratio of about 3: 2. According to the invention, these alkali are only used in relatively small masses, so that zirconium pigment can be prepared directly from the decomposition products directly without the otherwise mostly used treatment (difficult leaching). sodium-potassium, which is advantageous for the synthesis of the pigment according to the invention. The potassium and sodium ions contained therein are capable of acting as an effective alkaline component of the pigment synthesis mineralizer. The halide components of the mineralizer are then easily added in the form of hydrohalic acids. Therefore, the decomposition products according to the invention are sprayed with acid after cooling

% Of the hydrofluoric / 3-fluoride (3), preferably at a concentration of 15 to 25% by weight and in an amount corresponding to at least 0.5 part by weight, preferably 1.6 to 2 parts by weight of hydrogen fluoride, and further sprinkled with hydrochloric acid, a concentration of 12 to 22% by weight and in an amount corresponding to at least 0.5 parts by weight, preferably 1 to 1.5 parts by weight of hydrogen chloride. As the acids of lower concentrations, i.e. diluted, are preferably used, various hydrohalic acids can also be used According to the invention, the chromophore is admixed in an amount of 0.5 to 6 parts by weight, preferably 2.5 to 3.5 parts by weight, of a portion of dlhydrogenphosphonate dihydrate after the acidic spraying. cobalt · Instead of pure dihydrogen phosphate, a paste prepared in advance from phosphoric acid of at least 60% concentration and an oxide or hydroxide, carbonate or cobalt (II) hydroxide and a P / Co mole ratio of 1.8 to 2.2 are also formed in the paste by microcrystals of cobalt dihydrogen phosphate, which are chromophore · The mixture is then fired at temperatures above 600 ° C / preferably at 750 to 900 ° C · During firing, chromophore dehydration and condensation reactions of phosphate anion occur as the cobalt pyrophosphate progresses to the majority of the final dicobaltate cyclotetaphosphate (when firing temperatures above 1060 ° C are used, also higher linear cobalt phosphates). Alkaline zirconium silicates, with the help of halides, produce microcrystals of zirconium silicate, into which intensely colored dicobaltate cyclopentaphosphate particles grow in the course of synthesis as coloring inclusions. The product is a blue-violet pigment which, after firing, may eventually be leached with water or mineral acid, preferably at temperatures above 60 ° C. However, since the alkali content of the stillage is adequate, no washing is required and the stillage can be directly applied to the ceramic glaze as a pigment.

Advantages of the method of preparation of the blue-violet ceramic pigment according to the invention:

- 4,263,138

- cheaper basic raw material - zirconium mineral - is used for pigment preparation,

- the consumption of alkaline flux for decomposition is low and a waste hardening bath from machinery containing potassium and sodium hydroxide can be successfully used; alkali ions in decomposition products are also used as an alkaline component of the mineralizer in the actual pigment synthesis,

- the preparation of the pigment in pigs does not require difficult intermediate operations for the treatment of decomposition products,

- use dilute waste acids as the halide component of the synthesis mineralallizer

- if the ee operates under the conditions mentioned preferably, all the intermediates and products are in solid phase and in free-flowing form, so that handling and firing of the pigment are simple operations in this respect,

- the digestion temperatures of the mineral and of the actual pigment synthesis are favorable and correspond to (or lower) temperatures used in the ceramic industry,

- the degree of mineral degradation achieved is high (about 90%) and the yield of the whole pigment preparation according to the invention is also high (representing 80 to 90% by weight of the starting zirconium),

- pigment quality is high both in terms of stability, high degree of conversion to zirconium silicate (up to 80%), and also in terms of color intensity, which in addition can be controlled by the amount of chromophore used in the mixture ·

Example 1 g of zirconium mineral (containing 96% zirconium silicate) was decomposed with a mixture of hydroxides containing 21 g of potassium hydroxide and 14 g of sodium hydroxide at 850 ° C for 2 h. The decomposition proceeded to 92%. After cooling, the decomposition products were sprayed with 56 g of 20% by weight hydrofluoric acid. concentration and 47 g of hydrochloric acid 17 wt. konoentrace. The mixture was further admixed with 18 g of di263 138 cobalt dibasic dihydrate and the roe deer was fired at 850 ° C for 1.5 h. The flask was washed with dilute hydrochloric acid and boiled and the remaining solid phase was 63.4 g of blue-violet pigment containing 84% Zirconium Silicate * The pigment was applied in an amount of 6 to a high temperature silicate glaze which, after glazing at 1300 ° C, gave a blue-violet color.

Example 2

100 g of zirconium mineral (containing 94% zirconium silicate) was decomposed with 45 g of spent potassium baths containing 3: 2 potassium hydroxide and sodium hydroxide ₍ at a temperature of 900 ° C for 1 h). of 94% · After decomposition, decomposition products were sprinkled with 42 g of hydrofluoric acid 38% by weight of conoentraoe and 33 g of hydrochloric acid of 35% by weight of concentration * 30 g of the mixture prepared the day before 85% wt.% (H 2 PO 4) in a ratio corresponding to a P / Co molar of 2%. The resulting mixture was fired at 800 ° C for 2 hours, the slurry was hot washed with water and the remaining solid phase was 92 g of blue-violet pigment with a content of 80% zirconium silicate · The pigment was applied in an amount of 10% by weight into the borosilicate glaze, which after glazing at 1040 ° C gave a blue-violet color.

Claims (1)

SUBJECT OF THE INVENTION 263 138 Process for preparing a blue-white ceramic pigment from zirconium mineral, characterized in that decomposition products of zirconium mineral obtained from 10 parts by weight of mineral are used by decomposition at a temperature of more than 600 ° C, preferably at a temperature of 750 to 950 ° C. , 5 No * 8 weight parts, preferably 4 to 5.5 part by weight · hydroxide mixture comprising potassium hydroxide and sodium carbonate in a weight ratio of 4 to 0.5: 1 _from preferably in a weight ratio of 2 · to 1.3: 1, wherein after decomposition, the cooled products are sprinkled with hydrofluoric acid preferably at a concentration of 15 to 25 in an amount corresponding to at least 0.5 parts by weight, preferably 1.6 to 2 parts by weight of hydrogen fluoride, further sprinkled with hydrochloric acid, preferably a concentration of 12 to 22% by weight in an amount corresponding to at least 0.5 parts by weight, preferably 1.1 and 21.5 wt. díl _; chlorovodíbgnaícž kesweá is added 0.5 to 6 weight · parts, preferably 2.5 to 3.5 weight part ·, cobalt dihydrogen phosphate dihydrate and the mixture is fired at temperatures above 600 ° C _/ s, preferably at a temperature of 750 to 900 ° C _s and, after firing, optionally even leached with water or mineral acid, preferably at temperatures above 60 ° C ·