JP2882040B2 - Method for producing hydrated zirconia sol - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a hydrated zirconia sol which is an intermediate for producing a zirconia-based ceramic raw material powder,
The present invention relates to a method for producing a hydrated zirconia sol which can make the above-mentioned raw material powder excellent in formability and solid solubility with a stabilizer.

[Related Art] Conventionally, as a method for producing a hydrated zirconia sol by hydrolysis of an aqueous solution of a zirconium salt, a method of performing a hydrothermal treatment at 120 to 300 ° C. containing an aqueous solution containing a water-soluble zirconium salt (US Pat. No. 2,984,628) Method of boiling and hydrolyzing an aqueous solution containing a water-soluble zirconium salt (Inorg. Chem. 3,146 (1964)) Add hydrogen peroxide or a compound that generates hydrogen peroxide to an aqueous solution containing a water-soluble zirconium salt, and heat at 80 to 300 ° C. Heat treatment method (JP-B-61-43286) After the zirconium salt aqueous solution is hydrolyzed, 0.1
A method of separating particles having a diameter of about 0.3 μm by a sedimentation method or the like (Japanese Unexamined Patent Publication No.
No. 8-217430).

[Problems to be Solved by the Invention] According to the studies made by the present inventors, the smaller the crystallite of the hydrated zirconia sol, the more the yttria, calicia, and yttria commonly used in the production of sol and zirconia ceramics.
It is presumed that when a zirconia powder is obtained by mixing with a stabilizer such as magnesia or ceria and calcining, the solid solution reaction is accelerated. In particular, the concentration of zirconyl chloride is 0.4 m
ol /, and the chloride ion concentration is 0.8 or more and 2.0 mol
/ The crystallites of the hydrated zirconia sol obtained by hydrolysis treatment under the following conditions are obtained with a crystallite of 40 A or less, and when the crystallite of the hydrated zirconia sol becomes 40 A or less, the effect is remarkably exhibited. There is expected. The particle size of the hydrated zirconia sol is 0.1 μm or more in average particle size, and in the particle size range.
When the average particle diameter is smaller than 0.1 μm, when the sol is calcined to obtain zirconia powder, a strong agglomerate is formed, and the moldability and the properties of the sintered body are poor. A zirconia powder is obtained.

By the way, the hydrated zirconia sol obtained by the methods of and has a particle diameter of less than 500A,
As described above, during calcination, strong agglomeration occurs, and the resulting zirconia powder is difficult to mold, making the ceramic raw material powder unsuitable. Further, since the method is a hydrothermal synthesis method, it is not suitable for industrial mass production and is not practical.
The hydrated zirconia sol obtained by the methods described in (1) and (2) has a crystallite larger than 40A, and is considered to be hardly dissolved in the stabilizer as described above. Further, the method requires centrifugal separation of particles having a particle size of 0.1 to 0.3 μm, which makes industrialization difficult and impractical.

The present invention has solved such disadvantages in the conventional method, that is, a zirconia powder having a large particle size and a small crystallite, and thus having a good molded shape, and further having a solid solution with a stabilizer such as yttria. It is an object of the present invention to provide a method capable of producing a hydrated zirconia sol suitable for the production of zirconia by a simple process.

[Means for Solving the Problems] The present invention relates to a method for producing a hydrated zirconia sol by hydrolysis of an aqueous solution of zirconyl chloride, comprising 0.4 mol / mol
A zirconyl chloride aqueous solution adjusted so that the zirconyl chloride concentration is less than 0.8 and 2.0 mol / mol or less in chloride ion concentration, and the pH of the reaction solution at the end of the hydrolysis reaction is in the range of 0.4 or more and 1 or less. A method for producing a hydrated zirconia sol by performing a hydrolysis treatment at a temperature not lower than 80 ° C. and not higher than the boiling temperature. Hereinafter, the present invention will be described in more detail.

The particle size of the hydrated zirconia sol obtained in the present invention can be obtained by particle size observation using an electron microscope or particle size measurement using a particle size distribution analyzer, for example, a photon correlation method or the like.

Hydrolysis of an aqueous solution of zirconyl chloride produces a hydrated zirconia sol and an acid.
Decreases. When these aqueous solutions of zirconyl chloride having a zirconia equivalent concentration of less than 0.1 mol / are heated without any treatment to complete the hydrolysis, the pH of the reaction diameter becomes larger than 1, and the chloride ion concentration is further increased. 0.
Less than 8 mol /. Therefore, in carrying out the present invention, an acid is added to the aqueous solution of zirconyl chloride in advance.
The pH is lowered, and a chlorine compound that does not significantly affect the pH is added to increase the chloride ion concentration, so that the pH of the system at the end of the hydrolysis reaction is 0.4 to 1 and the chloride ion concentration is 0.8.
It must be more than 2 mol / or less. Examples of the acid to be added include inorganic acids such as hydrochloric acid, nitric acid and sulfuric acid, and other organic acids such as acetic acid and citric acid may also be used. Preferably it is hydrochloric acid. Examples of the chlorine compound include ammonium chloride, metal chlorides, for example, an alkali metal or an alkaline earth metal such as sodium chloride and calcium chloride, and aluminum chloride. Ammonium chloride and sodium chloride are preferred.

The zirconia equivalent concentration of zirconyl chloride is 0.1 or more
When the hydrolysis is completed by heating an aqueous solution of less than 0.4 mol /, the pH of the reaction system falls within the range of 0.4 or more and 1 or less, but the chloride ion concentration is less than 0.8 mol /. In this case, pH
It is necessary to increase the chloride ion concentration by adding only a chlorine compound that does not significantly affect the water content, so that the chloride ion concentration of the system at the end of the hydrolysis reaction is 0.8 to 2 mol / l. As the chlorine compound to be added, those described above may be used.

If the pH at the end of the hydrolysis reaction is greater than 1, 0.1
A hydrated zirconia sol having an average particle size of μm or more and a crystallite of 40 A or less cannot be produced, and when the pH is less than 0.4, the average particle size of the hydrated zirconia sol becomes smaller than 0.1 μm and the reaction rate decreases. And the reaction time becomes longer. Furthermore, when the chloride ion concentration is less than 0.8 mol /, hydrated zirconia having a crystallite of 40 A or less cannot be obtained,
Also, when the chloride ion concentration is greater than 2 mol /, the crystallinity of the hydrated zirconia decreases and the reaction rate decreases,
The reaction time becomes longer.

The hydrolysis conditions of the raw material liquid prepared above, that is, the reaction temperature, must be set to 80 ° C. or higher and the boiling temperature or lower. When the reaction temperature is higher than the boiling temperature, the crystallite of hydrated zirconia becomes larger than 40A and the average particle size becomes smaller than 0.1 μm, so that the desired hydrated zirconia sol cannot be produced, and further hydrothermal synthesis is performed. Therefore, industrial mass production becomes difficult, so that it is not practical. When the reaction temperature is lower than 80 ° C., it takes a long time to complete the hydrolysis reaction, so that the production efficiency decreases.

The reaction time is about 50 to 150 hours, depending on the reaction temperature.

[Action] It is not clear why the crystallites and particle size of the hydrated zirconia sol depend on the chloride ion concentration and pH of the reaction system, particularly the chloride ion concentration and pH at the end of the reaction. Is known to be composed of secondary particles in which primary particles having good crystallinity are aggregated (Japanese Patent Publication No. Sho 61).
Chloride ion is considered to be a factor that adsorbs on crystal nuclei of hydrated zirconia generated during the hydrolysis reaction, inhibits crystal growth, and reduces primary particles (crystallites). The pH is considered to be a factor acting on the secondary particles, and the interaction between the primary particles formed by the hydrolysis reaction and the synergistic effect with the pH of the reaction system causes the aggregation between the primary particles. This is presumed to be due to the promotion of bonding, which affects the particle size of the formed secondary particles.

[Effects of the Invention] As described above, according to the present invention, a zirconia powder having a large particle diameter and a small crystallite, and thus having good moldability, and further having a solid solution with a stabilizer such as yttria is well formed. A hydrated zirconia sol suitable for production can be produced.

The hydrated zirconia sol having an average particle size of 0.1 μm or more and a crystallite of 40 A or less obtained in the present invention depends on the zirconium salt concentration, the anion concentration, the amount of acid or alkali added, and the like. The sol particle size and the crystallite can be controlled by appropriately setting the conditions so that the pH of the suspension at the end of the hydrolysis reaction can be controlled within the range limited by the present invention.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples.

Example 1 To 100 ml of 2 mol / zirconium oxychloride, 30 g of ammonium chloride was added, and distilled water was added.
mol / aqueous solution. The chlorine ion concentration at this time is
0.96 mol /. The prepared raw material liquid was boiled for 100 hours with stirring to perform a hydrolysis reaction. After the completion of the reaction, the pH of the suspension was 0.7.

The average particle size of the obtained hydrated zirconia by photon correlation method is 0.24 μm, and the crystallite size by powder X-ray diffraction is about 36.
A.

Example 2 Example 2 was carried out under the same conditions as in Example 1 except that sodium chloride was used instead of ammonium chloride. Of the suspension after the end of the reaction
pH was 0.65 and chloride ion concentration was 1.0 mol /.

The average particle size of the obtained hydrated zirconia by photon correlation method is 0.26 μm, and the crystallite size by powder X-ray diffraction is about 34
A.

Example 3 To 25 ml of 2 mol / zirconium oxychloride, 300 ml of 1 mol / hydrochloric acid and 30 g of sodium chloride were added, and distilled water was added to obtain an aqueous solution of 0.05 mol / in terms of zirconia. At this time, the chloride ion concentration was 0.9 mol /. The prepared raw material liquid was boiled for 80 hours with stirring to perform a hydrolysis reaction. After the completion of the reaction, the pH of the suspension was 0.68.

The average particle size of the obtained hydrated zirconia by photon correlation method is 0.25 μm, and the crystallite size by powder X-ray diffraction is about 38
A.

Example 4 The procedure was carried out in the same manner as in Example 3 except that sodium chloride was used instead of ammonium chloride. Of the suspension after the end of the reaction
pH was 0.71 and chloride ion concentration was 1 mol /.

The average particle size of the obtained hydrated zirconia by photon correlation method is 0.28 μm, and the crystallite size by powder X-ray diffraction is about 32.
A.

Comparative Example 1 Distilled water was added to 100 ml of 2 mol / zirconium oxychloride to prepare a 0.2 mol / conversion aqueous solution of zirconia, and the mixture was boiled for 100 hours to perform a hydrolysis reaction. PH of suspension after completion of reaction
Was 0.69.

The average particle size of the obtained hydrated zirconia by photon correlation method was 0.25 μm, and the crystallite size by powder X-ray diffraction was 53A.

Comparative Example 2 Distilled water was added to 25 ml of 2 mol / zirconium oxychloride to make an aqueous solution of 0.05 mol / in terms of zirconia, and the mixture was boiled for 80 hours to carry out a hydrolysis reaction. PH of suspension after completion of reaction
Was 1.2.

The average particle size of the obtained hydrated zirconia by photon correlation method is 0.07 μm, and the crystallite size by powder X-ray diffraction is 75A.
Met.

Claims (1)

(57) [Claims] 1. A method for producing a hydrated zirconia sol by hydrolysis of an aqueous solution of zirconyl chloride, comprising:
An aqueous solution of zirconyl chloride adjusted so that the zirconyl chloride concentration is less than 0.8, the chloride ion concentration is 0.8 to 2.0 mol / or less, and the pH of the reaction solution at the end of the hydrolysis reaction is in the range of 0.4 to 1 is 80 or less. A method for producing a hydrated zirconia sol, wherein the hydration zirconia sol is subjected to a hydrolysis treatment at a temperature of not lower than a boiling point and a boiling point.