RU2270176C2 - Method for production of ammonium alum-based pigments - Google Patents

Abstract

FIELD: ceramic industry, in particular production of heat resistant pigments for decoration of faience and porcelain ware.

SUBSTANCE: claimed method includes application of ammonium alum Al₂(SO₄)₃(NH₄)₂SO₄.24H₂O and transition metal Ti, V, Cr, Mn, Fe, Co, Ni salts or salts of metals with chromophore properties (e.g., lanthanides) as starting components. Mixture containing dehydrated ammonium alum and one dissoluble chromophore metal salt is placed in corundum crucible, heated to 200°C and hold at the said temperature for 120 min to release crystalline water from alum. Then solution is heated and boiled, metals is decomposed to pure oxides and conditioned at 800°C for 60 min. After that product is heated up to final synthesis temperature, namely o 1250-1500°C and hold at this temperature for 60-90 min.

EFFECT: pigments of improved purity; simplified and economical method with increased yield.

1 cl, 1 ex, 2 dwg

Description

The invention relates to the ceramic industry, in particular to the production of heat-resistant pigments for decorating porcelain and earthenware.

A number of traditional methods for producing ceramic pigments are known, in which alumina Al ₂ O ₃ is the main component. Alumina, kaolin, pegmatite, feldspars and other aluminosilicates can serve as a source of Al ₂ O ₃ . The main requirement for the starting materials for obtaining pigments is a high degree of purity [1, 2, 3].

A known method [4] of obtaining pigments by traditional technology, including operations:

- preparation of the mixture by joint grinding of components in ball mills;

- drying the mixture to a certain moisture content;

- wiping the mixture through sieves;

- firing pigments;

- wet grinding of pigments in ball mills;

- drying of pigments.

The disadvantage of this method is that during the processing of components in ball mills and other technological equipment, impurities are introduced that pollute the main product, as well as the use of substances that, as a rule, do not meet the purity requirements. The disadvantages also include the duration of the process, a large number of redistributions, high energy and metal consumption.

Closest to the proposed invention is the production of pigments by coprecipitation, [5], including operations:

- the preparation of solutions of metal salts of a certain concentration, serving as components of the pigment;

- precipitation of hydroxides from solution with alkalis;

- vacuum filtration;

- drying the resulting mixture;

- firing pigments;

- grinding the pigment to a specific particle size distribution.

The disadvantage of this method is the low economic efficiency as a result of large irreversible loss of pigment mass (up to 42%) [5].

The claimed invention is aimed at eliminating these disadvantages.

The background of the invention is the problem of creating persistent inorganic pigments for reflecting reference measures of color coordinate units of non-self-luminous objects.

The present invention is based on the solution of the problem of obtaining pure pigments, i.e. without impurities, with a sharp increase in the yield of suitable product, as well as a significant simplification of the process with a corresponding increase in economic efficiency.

The objective of the invention is achieved by the fact that in the method according to the invention used as a source of Al ₂ O ₃ , aluminum ammonium alum Al ₂ (SO ₄ ) ₃ · (NH ₄ ) ₂ SO ₄ · 24H ₂ O, are mixed with one of the water-soluble salts metal from a series of Ti, V, Cr, Mn, Fe, Co, Ni, Pr, the mixture is placed in an oven in a corundum crucible and heated to the temperature of the synthesis of the pigment, depending on the selected metal and kept at this temperature for the time required to obtain the pigment . The heating is carried out in steps: first, to a temperature of 200 ° C until the crystallization water is removed from the alum-aluminum alum and the metal salt is dissolved in it, then it is kept at this temperature for 120 minutes, after which the heating is continued until the solution is evaporated and the metal salts (aluminum and one of chromophores - Ti, V, Cr, Mn, Fe, Co, Ni, Pr) to pure oxides and incubated at a temperature of 800 ° C for 60 minutes; then in the same corundum crucible the mixture is heated to temperatures of 1250-1500 ° C, the furnace is cooled and the finished product is unloaded.

According to the invention, the mixture is placed and the final product is obtained in the same crucible.

In addition, the crucible material in which the synthesis takes place is selected on the basis of the identity of the chemical composition with the main component of the pigment, which eliminates the possibility of contamination with extraneous impurities of the main product.

The analysis of the prior art by the applicant, including a search by patent and scientific and technical sources of information and identification of sources containing information about the analogue, allowed to establish that the applicant did not find analogues characterized by signs that are identical to all the essential features of the proposed method, therefore, the claimed method meets the criteria "novelty" and "inventive step".

The essence of the invention lies in the fact that the property of aluminum-alum alum is used during heating to isolate crystallization water, in which salts of chromophore metals are dissolved. The process of water evolution and decomposition of salts proceeds with active stirring of the reaction mixture as a result of gas evolution, and due to this there is a uniform distribution of components throughout the volume.

The essence of the method is illustrated by a specific example of the invention with reference to the accompanying drawings, which depict the following:

figure 1 - temperature treatment of the pigment;

figure 2 - spectral absorption curve.

Example

Alumina alum Al ₂ (SO ₄ ) ₃ · (NH ₄ ) ₂ SO ₄ · 24H ₂ O and nitric acid cobalt Co (NO ₃ ) ₂ · 6Н ₂ O in a ratio of 10: 1 based on aluminum oxides are poured into the corundum crucible and cobalt. Weighed components do not mix. The crucible is placed in a chamber furnace and heated according to a predetermined program: the rate of temperature rise is 10 degrees per minute, at a temperature of 200 ° C, hold for 120 minutes, then bring the temperature to 800 ° C at the same speed and hold for 60 minutes. Final firing is carried out at a temperature of 1250 ° C for 60 minutes. After cooling the furnace, the finished pigment is discharged from the crucible. The process time without taking into account the cooling of the furnace is 8 hours (Fig. 1).

The technical result of the invention was to obtain finely divided pigment powders without the use of traditional methods of pre-mixing the components and grinding the final product. In addition, the pigments have a clean, bright color, which is confirmed by the nature of the spectral absorption curves having a pronounced maximum and steeply falling slopes (figure 2).

The method has a very simple technology.

According to the applicant, the invention meets the criterion of "industrial applicability". The criterion of "industrial applicability" is confirmed by the relevance of the method and its practical binding to production technologies.

In the above description of the present invention, a specific example of its implementation has been disclosed. However, it is obvious that its various options and modifications can be implemented without departing from the essence and scope of patent claims of the invention.

Information sources

1. Vizir V.A., Martynov M.A. Ceramic paints - Kiev: Technique. 1964 .-- 256 s.

2. Belenky E.F., Riskin I.V. Chemistry and technology of pigments. - L .: Chemistry. 1974.

3. Tumanov S.G. Synthesis of ceramic paints. Physico-chemical foundations of ceramics. - M .: Promstroyizdat. 1956. - From 273-292.

4. Ceramic production processes, ed. W.D. Kingery. - M .: Publishing house of foreign literature. -1969. - Part 1U. 22 sec

5. Food I.V., Zalevskaya T.L., Putilina E.N. Synthesis of pigments by coprecipitation. Glass and ceramics. Number 3.

Claims (1)

A method of producing pigments based on aluminum-ammonium alum, including mixing dry alum and a metal-chromophore compound, stepwise heating with intermediate exposure and subsequent heating to the temperature of the final pigment synthesis, depending on the selected metal with aging and subsequent cooling, characterized in that it is used as a chromophore a water-soluble metal salt from the series Ti, V, Cr, Mn, Co, Ni, Pr, alum and the chromophore are placed in an oven in a corundum crucible, exposure is carried out at a temperature of 200 ° C for 120 mi to release water of crystallization of alum, and then continue heating to evaporation of the solution and decomposition of the metal salts to pure oxides and kept at a temperature of 800 ° C for 60 minutes, then heated to a final temperature of synthesis pigment 1250-1500 ° C.

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