JP2003267727A - Method for producing fine particle of hydrated zirconia and method for producing zirconia powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a zirconia powder having little adsorption of water molecules or hydroxy groups and little aggregation, wherein the method is also capable of safely and easily producing the powder having a high specific surface area suited as a raw material for injection molding that is required to have high accuracy. <P>SOLUTION: The method for producing fine particles of hydrated zirconia is characterized by hydrolyzing an aqueous solution containing a zirconium salt in the presence of a nonionic surface active agent having a number-average molecular weight of 1,000-100,000, and the method for producing the zirconia powder is characterized by drying and calcining aggregate of the fine particles of the hydrated zirconia obtained by adding an alkali to the fine particles obtained by the above method or to a suspension containing those fine particles. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing hydrated zirconia fine particles and a method for producing zirconia powder.

[0002]

2. Description of the Related Art Sintered zirconia is widely used in various applications such as structural materials, mechanical parts, optical communication parts, electronic materials and battery members. It is also used for applications that require dimensional accuracy.

The ceramics injection molding method is widely used industrially as a method for accurately mass-producing products having a three-dimensional complex shape, and is also used for molding connector parts of optical fibers.

Various methods such as a neutralization coprecipitation method, a hydrolysis method, an alkoxide method and a hydrothermal method are known as a wet method for producing a zirconia powder as a raw material for producing a zirconia sintered body. Among these methods, the alkoxide method and the hydrothermal method are high in cost and inferior in production efficiency.
The neutralization coprecipitation method and the hydrolysis method are widely used industrially.

In the neutralization coprecipitation method, Y ³⁺ and Ca, which are stabilizers, are used.
This is a method for obtaining a zirconia powder by adding an alkali to an aqueous solution containing a metal salt such as ²⁺ , Mg ²⁺ , Ce ⁴⁺ and a zirconium salt, and drying and calcination the precipitates formed as respective hydroxides. . In this method, the generated hydroxide has a low bulk density, and the hydroxide decomposes and dehydrates during calcination to generate pores, resulting in a low density when made into a sintered body and sufficient mechanical strength. There is a drawback that the surface accuracy cannot be obtained.

Further, in the neutralization precipitation method, when calcination is made into zirconia powder, zirconium hydroxide is decomposed to generate hydroxide ions and water molecules, which are adsorbed on the powder surface and hydrated. Due to reaction or hydrogen bonding, the primary particles are likely to be bonded to form hard secondary particles. When injection molding is performed using such a zirconia powder, it is difficult to disperse it as primary particles when kneading with a resin binder, and
Since hydroxyl groups and water molecules adsorbed on the surface tend to repel the resin binder, it is difficult for the zirconia powder and the resin binder to form a uniform kneaded product, and defects in the sintered body are likely to occur.

In particular, in applications requiring high surface accuracy and dimensional accuracy such as connector parts for optical fibers, it is necessary to reduce the crystal grain size of the sintered body.
Zirconia powder having a high specific surface area of about m ² / g or more is often used. However, if the calcination temperature is set lower than that of the prior art in order to obtain a high specific surface area, the adsorption amount of hydroxyl groups and water molecules further increases. Moreover, the number of primary particles contained in one secondary particle increases, and the aggregation of primary particles becomes more problematic. In the case of injection-molding a highly accurate molded product using such a powder having a high specific surface area, a large amount of resin bander is required and more uniform kneading is required.

For these reasons, the zirconia powder produced by the neutralization coprecipitation method is unsuitable as a raw material for the injection molding method.

The hydrolysis method uses Y ³⁺ , Ca as a stabilizer.
^{A method} of hydrolyzing an aqueous solution containing a metal salt such as ²⁺ , Mg ²⁺ and Ce ⁴⁺ and a zirconium salt at high temperature to form hydrated zirconia fine particles, which are dried and calcined to obtain a zirconia powder. .

Also, by combining these methods, an alkali is added to a suspension containing metal salts such as Y ³⁺ , Ca ²⁺ , Mg ²⁺ , Ce ⁴⁺ , which serve as a stabilizer, and hydrated zirconia fine particles. Then, a method of obtaining a zirconia powder by drying and calcining the generated precipitate has also been proposed.

In the method utilizing the hydrolysis reaction of these zirconium salts, since hydrated zirconia fine particles have many water molecules on the surface, hydration agglomeration upon drying or hydrogen bonds between adsorbed water molecules may occur. Agglomeration is generated to form coarse particles, and when the dry powder containing such coarse particles is calcined, the powder becomes hard and contains large agglomerates.

When a sintered body is formed by using a powder containing such large agglomerates, the sintering becomes non-uniform, which causes a decrease in accuracy. For this reason, in order to produce a zirconia sintered body for optical fiber connector parts, it is necessary to grind it into a fine and uniform powder, but when vigorous grinding is carried out, the tetragonal crystals of the zirconia powder are stressed. Induced phase transition occurs to form monoclinic crystals, and the ratio of tetragonal crystals decreases. When a sintered body is manufactured using such a low tetragonal zirconia powder, the monoclinic system becomes a tetragonal system at the sintering temperature, which causes a volume change due to the phase transition and causes a decrease in density and accuracy. Become.

In addition to the hard secondary particles, the zirconia powder has low lipophilicity due to the influence of the hydroxyl groups and water molecules adsorbed on the surface, and is not suitable for uniform kneading with the resin binder. Long kneading time and large kneading torque are required.

As a means for solving these problems, a method has been disclosed in which an organic solvent is added to a suspension of hydrated zirconia fine particles or azeotropic distillation is carried out by heating, followed by drying and calcination to obtain a zirconia powder ( Patent 1320727, Japanese Patent Publication No. 6
-24981).

However, in such a method, since drying is performed in the presence of an organic solvent, there is a risk of fire or explosion, and there is a safety problem. Furthermore, a fluidized bed slurry dryer or a spray dryer is used for usual industrial drying, but in the above method, the suspension of hydrated zirconia fine powder may contain an organic solvent and may be strongly acidic. Yes, it requires explosion-proof, acid-resistant, specially-designed and very expensive equipment.

On an industrial scale, the amount of organic solvent used becomes enormous, and in addition to the problem as a dangerous substance, the adverse effect on the environment becomes a very serious problem.

[0017]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and its main purpose is to reduce adsorption of water molecules and hydroxyl groups and to knead with a resin binder. An object of the present invention is to provide a method for producing a zirconia powder which is easy and has little aggregation, and which can safely and easily produce a powder having a high specific surface area suitable as a raw material for injection molding which requires high accuracy.

[0018]

The inventor of the present invention has conducted extensive studies in order to achieve the above object. As a result, when producing a hydrated zirconia suspension by hydrolyzing an aqueous solution containing a zirconium salt, by performing hydrolysis in the presence of a specific nonionic surfactant, a hydroxyl group for hydrated zirconia fine particles is obtained. It was found that the adsorbed amount of water molecules can be greatly reduced, and as a result, it is possible to obtain hydrated zirconia fine particles with less aggregation. When the hydrated zirconia fine particles thus obtained are calcined to produce a zirconia powder, even if the calcination temperature is low, the adsorption amount of water molecules and hydroxyl groups is small,
It was found that a zirconia powder having good lipophilicity and less aggregation can be produced, and the present invention has been completed here.

That is, the present invention provides the following method for producing hydrated zirconia fine particles and method for producing zirconia powder. 1. A method for producing hydrated zirconia fine particles, which comprises hydrolyzing an aqueous solution containing a zirconium salt in the presence of a nonionic surfactant having a number average molecular weight of 1,000 to 100,000. 2. The amount of the nonionic surfactant used is 1 when the zirconium atom contained in the aqueous solution is converted to zirconia.
The method for producing hydrated zirconia fine particles according to item 1, wherein the amount is 100 parts by weight, which is 0.1 to 2 parts by weight. 3. The hydrated zirconia fine particles obtained by the method of the above item 1 or 2, or an aggregate of hydrated zirconia fine particles obtained by adding an alkali to a suspension containing the hydrated zirconia fine particles is dried and calcined. A method for producing a zirconia powder, which comprises forming a zirconia powder by means of the method. 4. The method for producing a zirconia powder according to item 3, wherein the calcination temperature is 600 to 1000 ° C., and the BET specific surface area of the obtained zirconia powder is 13 m ² / g or more.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION In the method for producing zirconia powder of the present invention, first, an aqueous solution containing a zirconium salt as a raw material is prepared.

As the zirconium salt used as a raw material, any water-soluble zirconia salt can be used without particular limitation. it can. Furthermore, zirconium hydroxide may be contained in the raw material.

The concentration of the zirconium salt in the aqueous solution is not particularly limited, but considering productivity, reaction time and the like, the total amount of zirconium atoms contained in the aqueous solution is about 0.5 to 1 mol / l. It is preferable.

Next, the aqueous solution containing the zirconium salt is heated to hydrolyze the zirconium salt to obtain a suspension of hydrated zirconia fine particles. The heating temperature is usually 90 to 1
The temperature may be about 00 ° C, preferably about 96 to 100 ° C. The heating time is not particularly limited,
Depending on the heating temperature, the time may be such that the zirconium salt can be sufficiently hydrolyzed, and usually about 50 to 200 hours.

In the method of the present invention, a nonionic surfactant having a number average molecular weight in the range of about 1,000 to 100,000 may be added to an aqueous solution containing a zirconium salt before carrying out the above-mentioned hydrolysis reaction. is necessary.

By carrying out the hydrolysis reaction in the presence of such a specific nonionic surfactant, the hydrophilic group of the nonionic surfactant is adsorbed on the surface of the hydrated zirconia fine particles produced by the hydrolysis. , Hydrophobic lipophilic groups in the same molecule inhibit the adsorption of water on the surface of hydrated zirconia, and when dried, agglomeration is reduced, and hydrated zirconia fine particles with a small amount of adsorption of hydroxyl groups and water molecules are obtained. be able to.

On the other hand, when an anionic surfactant is used, the surfactant and the zirconium ion are ion-bonded to each other before the hydrolysis reaction to inhibit the formation of hydrated zirconia fine particles. In addition, when a cationic surfactant is used, it repels electrically with zirconium ions and cannot sufficiently adsorb the surfactant on the hydrated zirconium fine particles.

The nonionic surfactant needs to be added before hydrolysis. When added after the start of the hydrolysis reaction, water molecules are immediately adsorbed on the surface of the hydrated zirconia that is formed, and the nonionic surfactant is adsorbed on the outside, so the adsorption of water molecules cannot be inhibited. .

The nonionic surfactant used in the present invention is required to have a number average molecular weight within the range of about 1,000 to 100,000. When the molecular weight is below this range, the lipophilic group is short and a sufficient hydrophobic effect cannot be obtained, which is not preferable. On the other hand, when the molecular weight exceeds this range, the lipophilic group is too long, resulting in insufficient water solubility,
In the aqueous solution, the surface active agent alone forms micelles and cannot be sufficiently adsorbed on the hydrated zirconia fine particles.

The amount of the nonionic surfactant added is preferably about 0.1 part by weight or more, where the amount of zirconium atom contained in the aqueous solution converted to the amount of zirconia is 100 parts by weight. If the amount added is less than this, the effect of adding the nonionic surfactant cannot be sufficiently obtained.
The upper limit of the amount of the nonionic surfactant added is not particularly limited, but the effect cannot be further improved because the surface adsorption amount of the hydrated zirconia fine particles is saturated even if added in excess. Usually, it is preferable that the amount of zirconium atom contained in the aqueous solution converted to the amount of zirconia is 100 parts by weight and about 2 parts by weight or less.

The nonionic surfactant can be used without particular limitation as long as it satisfies the above-mentioned conditions. In particular, a surfactant containing no metal component is included in order to prevent metal impurities from remaining in the zirconia powder. Is preferred. Specific examples of such nonionic surfactants include water-soluble polymers such as polyethylene glycol, polyvinyl alcohol and polyvinylpyrrolidone, and cellulose derivatives such as carboxymethyl cellulose and methyl cellulose.

In the method of the present invention, the types of additives other than the nonionic surfactant, the crystallites of the hydrated zirconia fine particles and the size of the primary particles due to the hydrolysis conditions are not particularly limited.

The suspension of hydrated zirconia fine particles obtained by hydrolysis contains unreacted zirconium ions, oxyzirconium ions and the like in addition to hydrated zirconia fine particles having a nonionic surfactant adsorbed on the surface. Anions associated with raw materials such as ions, excess nonionic surfactant not adsorbed on hydrated zirconia fine particles, and the like are included. Among these, particularly unreacted zirconium ion and oxyzirconium ion are purified by an ultrafiltration method using a hollow fiber filter or the like, a solid-liquid separation is performed by a centrifugal separator, and a solid content is redispersed in pure water. It is preferable to remove it by such means. This step also has an effect of removing metal impurity ions contained in the raw material.

A stabilizer is further added to the suspension of hydrated zirconia fine particles obtained by hydrolysis. The stabilizer can be added at any time before or after performing the above-mentioned hydrolysis reaction. However, when unreacted zirconium ions, oxyzirconium ions and the like are removed, stabilizer ions are also removed. Therefore, it is preferable to add the stabilizer after performing the removal treatment.

Stabilizers include Y ³⁺ , Ca ²⁺ , M
Metal salts such as g ²⁺ and Ce ⁴⁺ can be used. The stabilizer is usually added as an aqueous solution, but a metal salt may be directly added and dissolved.

The kind and amount of the metal salt used as the stabilizer may be the same as those in the conventional method for producing partially stabilized zirconia powder or stabilized zirconia powder.
For example, when a metal salt of Y ³⁺ is used as a stabilizer, in order to produce partially stabilized zirconia, the Y ₂ O ₃ concentration in the obtained zirconia powder is _{2 to 4} mol.
%, And in order to produce a stabilized zirconia, Y ₂ in the obtained zirconia powder should be added.
It may be added so that the O ₃ concentration is about 4 to 10 mol%.

Next, the suspension containing hydrated zirconia is dried to obtain hydrated zirconia powder. There are no particular restrictions on the drying method, drying conditions, etc., and the drying temperature may be about 100 to 150 ° C., which is the same level as the normal drying temperature. If the drying temperature is too high, the adsorbed nonionic surfactant may be decomposed.
It is necessary to avoid drying at a high temperature that exceeds 10 ° C. In addition, if drying is performed for a long time by a method such as static drying, fine particles of hydrated zirconia and ions of the stabilizer may be separated. Therefore, dry in a short time by a spray drying method or the like. Is preferred.

Instead of directly drying the suspension containing hydrated zirconia, an alkali is added to the suspension containing hydrated zirconia and a stabilizer to coagulate and stabilize the hydrated zirconia. Precipitating the agent as hydroxide,
After that, the precipitate may be dried. In this case, since the hydrated zirconia and the stabilizer are not separated during drying, a static drying method or a fluidized bed dryer such as a slurry dryer can be used.

The alkali may be usually added as an aqueous solution, but in the case of a component which is easily dissolved in the suspension, it may be added directly. The amount of alkali added is preferably such that the pH of the suspension containing hydrated zirconium is about 10 or more.

As the alkali, it is preferable to use a water-soluble alkali containing no metal ions such as ammonia and water-soluble amines. As the water-soluble amines, for example,
Although an alkylamine such as methylamine can be used, an alkylamine having about 6 or less carbon atoms is particularly preferable in terms of good solubility. On the other hand, the use of an alkali containing a metal ion such as sodium hydroxide is unsuitable because the metal remains as an impurity in the final zirconia powder and affects the sintering characteristics.

In the above method for forming the hydrated zirconia aggregate precipitate and the hydroxide of the stabilizer, it is preferable to wash the mixture with water to remove anions and metal impurity ions before drying. In this case, for example, by washing with an alkaline aqueous solution, chlorine ions contained in the mixture can be efficiently removed. As the alkali, the same compound as that used for aggregating the hydrated zirconia aggregate precipitate can be used. In this case, when washing the aggregate of hydrated zirconia with an alkaline aqueous solution, the pH of the slurry to which the alkaline aqueous solution was added was adjusted.
It is preferable to maintain a high hydroxide ion concentration of 10 or more.

A zirconia powder can be obtained by calcining after obtaining a dry powder containing hydrated zirconia by the above method. The calcination conditions are not particularly limited, and may be the same as in the normal zirconia powder manufacturing method. For example, the desired zirconia powder can be obtained by heating at about 600 to 1200 ° C. for about 5 to 10 hours in an oxygen-containing atmosphere such as air. By calcination, the hydrated zirconia solid-dissolves a stabilizer to form a partially stabilized zirconia or a stabilized zirconia powder. At this time, since the nonionic surfactant adsorbed on the surface of the hydrated zirconia fine particles decomposes and becomes mainly carbon dioxide and water vapor, which evaporates, it remains as an impurity in the finally obtained zirconia powder. There is nothing to do. Further, since the amount of the nonionic surface active agent added is small and, in general, it is not an explosive or a dangerous substance, it can be fired in an ordinary calcining furnace.

The zirconia powder thus obtained is
After calcination, there is little agglomeration and the average particle size is small, so a fine powder that can be used as a raw material for a sintered body can be obtained by slight pulverization. At this time, since it is not necessary to perform vigorous stirring, a phase transition to a monoclinic crystal hardly occurs, and a zirconia powder having a high tetragonal crystal ratio can be obtained. Further, since there are few hydroxyl groups and water molecules adsorbed on the surface, the zirconia powder has high lipophilicity and excellent kneadability with the resin binder.

In particular, when the calcination temperature is in the range of about 600 to 1000 ° C., the BET specific surface area is 13 m ² /
It is possible to obtain a zirconia powder having a very high specific surface area of about g or more. Also for the zirconia powder having a high specific surface area obtained in this manner, there is little aggregation after calcination, and since there are few hydroxyl groups and water molecules adsorbed on the surface, excellent kneadability with the resin binder, in particular, It becomes a highly lipophilic zirconia powder suitable for injection molding.

The zirconia powder obtained by the method of the present invention can be effectively used in various molding methods such as extrusion molding, tape molding and doctor blade molding, and particularly when it has a high specific surface area of about 13 m ² / g or more. Is
It is suitable for injection molding.

[0045]

According to the method of the present invention, a zirconia powder with less aggregation can be obtained. Since the obtained zirconia powder can be made into a fine powder that can be used as a sintered body raw material by slight pulverization, stress-induced phase displacement is unlikely to occur, and a zirconia powder having a high tetragonal crystal ratio can be obtained. Further, since the zirconia powder has few hydroxyl groups and water molecules adsorbed on the surface and has high lipophilicity, it has good kneadability with a resin binder.

By adjusting the calcination temperature,
It is possible to obtain a zirconia powder with a high specific surface area,
Also in this case, a zirconia powder with less aggregation and less adsorption of water molecules can be obtained. Therefore, the obtained zirconia powder having a high specific surface area also has good lipophilicity, good kneadability with a resin binder, and a zirconia powder suitable for injection molding. By using such high specific surface area zirconia powder, dimensional accuracy by injection molding method,
It is possible to manufacture a large number of zirconia sintered bodies having a complicated shape with excellent surface accuracy and the like.

Further, since the method for producing zirconia powder of the present invention does not use an organic solvent, it is a method having high safety and very little adverse effect on the environment.

[0048]

EXAMPLES The present invention will be described in more detail with reference to examples.

Example 1 2 mol of a 1 mol / l aqueous solution of zirconium oxychloride, 3 mol of zirconium hydroxide and a number average molecular weight of 75
A solution prepared by dissolving 6 g of polyethylene glycol of 00 in 100 ml of pure water was added, and pure water was added to bring the total amount to 5
It was liter. In this case, the amount of zirconium atoms contained in the aqueous solution converted to zirconia powder was 100 parts by weight, and the amount of polyethylene glycol added was 0.7.
Parts by weight.

This aqueous solution was heated to 100 ° C. and hydrolyzed for 72 hours to obtain a hydrated zirconia suspension.

The obtained suspension was filtered and washed through a ultrafiltration filter while adding pure water until no zirconium ions were detected in the filtrate.

The amount of hydrated zirconia in the hydrated zirconia suspension after washing was measured, and a 2 mol / l yttrium chloride aqueous solution corresponding to the amount where the Y / Zr molar ratio was 3/97 was added, and the whole was added. The total solution volume was 5 liters.

The suspension was sufficiently stirred and 15N aqueous ammonia was added to obtain a precipitate of a hydrated zirconia aggregate.

The precipitate of the obtained hydrated zirconia aggregate was washed with ammonia water having a pH of 10 or more to remove chlorine ions, then recovered, dried in an oven at 150 ° C., crushed, and then at 997 ° C. It was calcined for 10 hours.

The average secondary particle size of the calcined powder measured by a laser diffraction / scattering particle size distribution meter was 10.2 μm.

Then, pure water was added to the calcined powder to obtain an average of 2
Wet ball milling was performed for 5 hours to obtain a zirconia powder having a secondary particle size of 0.5 to 1 μm. The tetragonal crystal ratio of the obtained zirconia powder measured by X-ray diffractometry was 68%.

The BET specific surface area of the obtained zirconia powder was 15 m ² / g. About this powder, J
The lipophilicity was evaluated by the same method except that liquid paraffin was used instead of linseed oil as the oil to be dropped in the oil absorption test method of the pigment test evaluation method of IS-K5101-1978. The results are shown in Table 1 below.

Further, with respect to 230 g of the obtained powder, 20 g of polybutyl methacrylate as a resin binder,
Add 9 g of ethylene vinyl acetate copolymer, 7 g of stearic acid, and 3 g of n-butyl phthalate to give a volume of 100.
Kneading was performed with a cc lab blast mill at a temperature of 140 ° C. at a rotor rotation speed of 30 rpm, the average torque of kneading was measured, and the time until the torque value became constant and constant was determined. The results are shown in Table 1 below.

Example 2 2 mol of a 1 mol / l aqueous solution of zirconium oxychloride was added with 3 mol of zirconium hydroxide and a number average molecular weight of 75.
A solution prepared by dissolving 3 g of polyethylene glycol of 00 in 100 ml of pure water was added, and then pure water was added to bring the total amount to 5
It was liter. In this case, the amount of zirconium atoms contained in the aqueous solution converted to zirconia powder was 100 parts by weight, and the amount of polyethylene glycol added was 0.4.
8 parts by weight.

This aqueous solution was heated to 100 ° C. and hydrolyzed for 72 hours to obtain a hydrated zirconia suspension.

The obtained suspension was filtered and washed through a ultrafiltration filter while adding pure water until no zirconium ions were detected in the filtrate.

The amount of hydrated zirconia in the hydrated zirconia suspension after washing was measured, and a 2 mol / l yttrium chloride aqueous solution corresponding to the Y / Zr molar ratio of 3/97 was added, and the whole was added. The total solution volume was 5 liters.

This suspension was thoroughly stirred and 15N aqueous ammonia was added to obtain a precipitate of hydrated zirconia aggregates.

The obtained precipitate of the hydrated zirconia aggregate was washed with ammonia water having a pH of 10 or more to remove chloride ions, recovered, dried in an oven at 150 ° C., crushed, and then at 997 ° C. It was calcined for 10 hours.

The average secondary particle diameter of the calcined powder measured by a laser diffraction / scattering particle size distribution analyzer was 7.4 μm.

Then, pure water was added to the calcined powder to give an average of 2
Wet ball milling was performed for 5 hours to obtain a zirconia powder having a secondary particle size of 0.5 to 1 μm. The tetragonal crystal ratio of the obtained zirconia powder measured by the X-ray diffraction method was 66%.

The BET specific surface area of the obtained zirconia powder was 15.5 m ² / g. The lipophilicity of this powder was evaluated in the same manner as in Example 1, and the time until the kneading torque value became constant was determined. The results are shown in Table 1 below.

Example 3 2 mol of a 1 mol / l aqueous solution of zirconium oxychloride was added with 3 mol of zirconium hydroxide and a number average molecular weight of 4
100g of 5,000 polyvinyl alcohol 1.5g
The solution dissolved in pure water was added, and then pure water was added to bring the total amount to 5 liters. In this case, the amount of zirconium atoms contained in the aqueous solution converted to zirconia powder is 1
The amount of polyvinyl alcohol added is 0.004 parts by weight.

This aqueous solution was heated to 100 ° C. and hydrolyzed for 72 hours to obtain a hydrated zirconia suspension.

The obtained suspension was filtered and washed through a ultrafiltration filter while adding pure water until zirconium ions were not detected in the filtrate.

The amount of hydrated zirconia in the hydrated zirconia suspension after washing was measured, and a 2 mol / l yttrium chloride aqueous solution corresponding to the Y / Zr molar ratio of 3/97 was added, and the whole was added. The total solution volume was 5 liters.

This suspension was sufficiently stirred and 15N aqueous ammonia was added to obtain a precipitate of aggregates of hydrated zirconia.

The obtained precipitate of the hydrated zirconia aggregate was washed with ammonia water having a pH of 10 or more to remove chloride ions, and then recovered, dried in an oven at 150 ° C., crushed, and then at 997 ° C. It was calcined for 10 hours.

The average secondary particle size of the calcined powder measured by a laser diffraction / scattering type particle size distribution analyzer was 9.2 μm.

Next, pure water was added to the calcined powder to make an average of 2
Wet ball milling was performed for 5 hours to obtain a zirconia powder having a secondary particle size of 0.5 to 1 μm. The tetragonal crystal ratio of the obtained zirconia powder measured by the X-ray diffraction method was 70%.

The BET specific surface area of the obtained zirconia powder was 14.8 m ² / g. The lipophilicity of this powder was evaluated in the same manner as in Example 1, and the time until the kneading torque value became constant was determined. The results are shown in Table 1 below.

Comparative Example 1 3 mol of zirconium hydroxide was added to 2 liter of a 1 mol / l aqueous solution of zirconium oxychloride, and pure water was added to make the total amount 5 liter.

This aqueous solution was heated to 100 ° C. and hydrolyzed for 72 hours to obtain a hydrated zirconia suspension.

The obtained suspension was filtered and washed through a ultrafiltration filter while adding pure water until zirconium ions were not detected in the filtrate.

The amount of hydrated zirconia in the hydrated zirconia suspension after washing was measured, and a 2 mol / l yttrium chloride aqueous solution corresponding to the Y / Zr molar ratio of 3/97 was added, and the whole was added. The total solution volume was 5 liters.

The suspension was thoroughly stirred and 15N aqueous ammonia was added to obtain a precipitate of aggregates of hydrated zirconia.

The precipitate of the obtained hydrated zirconia aggregate was washed with ammonia water having a pH of 10 or more to remove chloride ions, then recovered, dried in an oven at 150 ° C., crushed, and then at 997 ° C. It was calcined for 10 hours.

The average secondary particle size of the calcined powder measured by a laser diffraction / scattering particle size distribution analyzer was 46.4 μm.

Then, pure water was added to the calcined powder to give an average of 2
Wet ball mill pulverization was performed for 24 hours to obtain a secondary particle size of 0.5 to 1 μm to obtain zirconia powder. The tetragonal crystal ratio of the obtained zirconia powder measured by an X-ray diffraction method was 46%.

The BET specific surface area of the obtained zirconia powder was 14.8 m ² / g. The lipophilicity of this powder was evaluated in the same manner as in Example 1, and the time until the kneading torque value became constant was determined. The results are shown in Table 1 below.

Comparative Example 2 2 mol of a 1 mol / l aqueous solution of zirconium oxychloride was added with 3 mol of zirconium hydroxide and a number average molecular weight of 20.
A solution prepared by dissolving 6 g of polyethylene glycol of 0 in 100 ml of pure water was added, and then pure water was added to make the total amount 5 liters. In this case, the amount of zirconium atoms contained in the aqueous solution converted to zirconia powder was 100 parts by weight, and the amount of polyethylene glycol added was 0.97.
Parts by weight.

This aqueous solution was heated to 100 ° C. and hydrolyzed for 72 hours to obtain a hydrated zirconia suspension.

The obtained suspension was filtered and washed through a ultrafiltration filter while adding pure water until zirconium ions were not detected in the filtrate.

The amount of hydrated zirconia in the hydrated zirconia suspension after washing was measured, and a 2 mol / l yttrium chloride aqueous solution corresponding to the amount where the molar ratio of Y / Zr was 3/97 was added, and the whole was added. The total solution volume was 5 liters.

The suspension was sufficiently stirred and 15N aqueous ammonia was added to obtain a precipitate of aggregates of hydrated zirconia.

The obtained precipitate of the hydrated zirconia aggregate was washed with ammonia water having a pH of 10 or more to remove chloride ions, and then recovered, dried in an oven at 150 ° C., crushed, and then at 997 ° C. It was calcined for 10 hours.

The average secondary particle size of the calcined powder measured by a laser diffraction / scattering particle size distribution analyzer was 49.7 μm.

Next, pure water was added to the calcined powder to give an average of 2
Wet ball mill pulverization was performed for 24 hours to obtain a secondary particle size of 0.5 to 1 μm to obtain zirconia powder. The tetragonal crystal ratio of the obtained zirconia powder was 43% as measured by the X-ray diffraction method.

The BET specific surface area of the obtained zirconia powder was 14.8 m ² / g. The lipophilicity of this powder was evaluated in the same manner as in Example 1, and the time until the kneading torque value became constant was determined. The results are shown in Table 1 below.

[0095]

[Table 1] As is clear from the above results, when a zirconia powder was produced without adding a nonionic surfactant (Comparative Example 1), and when a zirconia powder was produced using a nonionic surfactant having a low molecular weight. In this case (Comparative Example 2), a large amount of agglomerates were generated during calcination, and it took a long time to pulverize, so that the tetragonal crystal ratio of the obtained zirconia powder was significantly reduced. Further, in these cases, the obtained zirconia powder had a large oil absorption amount, required a large kneading torque, and required a long time for uniform kneading.

Comparative Example 3 2 mol of a 1 mol / l aqueous solution of zirconium oxychloride was added with 3 mol of zirconium hydroxide and a number average molecular weight of 50.
6 g of 0000 polyethylene glycol was added, and pure water was further added to make the total amount 5 liters.

In this case, polyethylene glycol became a gelatinous mass and was not dissolved or dispersed in the liquid, so that the operation thereafter was stopped.

Claims (4)

[Claims] 1. A method for producing hydrated zirconia fine particles, which comprises hydrolyzing an aqueous solution containing a zirconium salt in the presence of a nonionic surfactant having a number average molecular weight of 1,000 to 100,000. 2. The use amount of the nonionic surfactant is 0.1 to 2 parts by weight based on 100 parts by weight of the zirconium atom contained in the aqueous solution converted to zirconia. Method for producing hydrated zirconia fine particles. 3. A hydrated zirconia fine particle obtained by the method according to claim 1 or an aggregate of hydrated zirconia fine particles obtained by adding an alkali to a suspension containing the hydrated zirconia fine particles is dried. And calcination to form zirconia powder. 4. The calcination temperature is 600 to 1000 ° C., and the BET specific surface area of the obtained zirconia powder is 13 m ² / g.
It is above, The manufacturing method of the zirconia powder of Claim 3.