JPH06321541A - Production of zirconia singly dispersed spherical ultrafine particle powder - Google Patents

Abstract

PURPOSE:To provide a method for economically, efficiently and massively producing a zirconia singly dispersed spherical ultrafine particle powder having excellent perfectly isolated dispersibility in an ultrafine particle region of 0.1-0.8mum at the lowest cost. CONSTITUTION:A method for producing the zirconia singly dispersed spherical ultrafine particle powder comprises mixing a zirconia compound such as zirconyl chloride, zirconium hydroxide, zirconia hydrate or basic zirconium carbonate with hydrochloric acid or water to give a homogeneous mixture or solution comprising ZrO2, HCl, H2O and a compound such as a metal salt in a chemical composition molar ratio of 1:0.8-2.0:6-10:0-0.2, respectively, subjecting the mixture or solution to a hydrothermic treatment at 100-220 deg.C for a necessary optimal time in a hydrothermic treatment container, while the contents in the container are moved, cooling the container at a temperature of <=50 deg.C in the closed state, lyophilizing the cooled contents at a temperature of <=50 deg.C, and subsequently thermally treating the dried product at a temperature of >=100 deg.C, thus providing the zirconia singly dispersed spherical ultrafine particle powder having a particle diameter of 0.1-0.8mum.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention has excellent properties useful as a raw material powder for fine ceramics, that is, as a raw material powder for ceramics containing zirconia as a main component or a ceramic containing a zirconium compound, and for special cosmetics or The present invention relates to a method for inexpensively producing a large amount of submicron zirconia monodisperse spherical ultrafine powder which is also useful as a pigment.

[0002]

BACKGROUND ART As a raw material fine powder for fine ceramics, especially for a sintered body, the molding packing density can be increased,
Sintering progresses uniformly to obtain a homogeneous microstructure of a sintered body with good dimensional accuracy. In the solid-phase reaction with other components, the mixing is uniform and a homogeneous reaction product is obtained. In view of the above advantages, fine particles having high purity, uniformity, spherical shape, and excellent isolation are generally required.

Conventionally, a known method for producing such monodisperse zirconia fine particles is by hydrolysis of an alcohol solution of alkoxide (J. Am. Cer.
a. Soc. 72 [3] 421-26 (1989)), and isolated monodisperse spherical amorphous zirconia fine particles of about 1 μm are obtained, but the ZrO ₂ concentration is 0.1.
Since it is necessary to use an extremely dilute solution of about mol / l or less, the amount produced in a given apparatus volume is extremely small, and the raw material alkoxide and alcohol are expensive.
In general, it is inferior in economic efficiency and has a drawback that it is not suitable for industrial mass production. Therefore, in zirconia, the monodisperse spherical fine particles can be used only for a special purpose, and have not been used as a ceramic raw material.

At present, zirconia fine powder used as a raw material for sintering zirconia-based fine ceramics is generally composed of ultrafine particles having a particle size of 0.2 to 0.4 μm. Mostly, crystalline calcined zirconium hydroxide or a calcined product such as a colloidal product having a particle size of 0.1 μm or less is finely pulverized by a pole mill or the like to produce, and the industrially used one is not spherical, Currently, it is not monodisperse.

The present inventor has already used, as a method for producing spherical particles that can be economically processed in large quantities, crystalline hydrous zirconyl chloride alone or a metal oxide containing this as a main component and capable of forming a solid solution in ZrO _2. A patent application was filed for a method for producing a spherical zirconia fine particle of about 0.5 to 1 μm by heating and reacting a solid mixture containing a small amount of a compound in a closed container at 150 ° C. to 300 ° C., and heating and dehydrating the mixture. 62-107
578), or the crystalline hydrous zirconyl chloride as it is,
Alternatively, a slight amount of water may be added to hydrothermally treat at 150 ° C. to 200 ° C., and this may be heated and dehydrated to obtain spherical zirconia fine particles of about 0.5 to 1 μm (Journal of Ceramic Society of Japan, 98 [3] 300-04 (199
0)) announced.

The above-mentioned method by the present inventor is a method in which monoclinic zirconia ultrafine crystals of 0.01 μm or less are temporarily soft-aggregated into spherical particles of about 0.5 to 1 μm by hydrothermal reaction of a concentrated starting composition. If the product is obtained, and this agglomeration is left as it is, it will disintegrate immediately into the original monoclinic zirconia ultrafine crystals of 0.01 μm or less and become a semi-transparent sol. It has been found that spherical particles which are stable to water can be formed by dry fixing. Therefore, it is a completely new and innovative method for producing spherical zirconia fine particles, and since a particularly thick mixture is processed, a characteristic feature is that a large amount of product can be obtained for a given apparatus volume. Ta °

However, the above paper (Journal of the Ceramic Society of Japan, 98 [3] 300-04 (199
As can be clearly seen in the electron micrograph of the resulting spherical microparticles shown in 0)), the agglomerated particles are relatively uniform spheres, but they are partially fused to each other There was a defect that the particles were aggregated in the third order and the isolation and dispersibility of the constituent particles in the powder state were extremely insufficient. At this point in the study, it is still unknown at which stage in the manufacturing process the phenomenon of fusion and agglomeration of spherical fine particles occurs, and there is an optimum time for spherical agglomeration. It was also completely unknown that the aggregated fine particles gradually fused. Therefore, the produced powder obtained by this method is poor in practicality as it is.

[0008]

The object of the present invention is to completely eliminate the fusion and agglomeration of spherical fine particles, which is the drawback of the above method, and to complete the production of fine particles by the concentrated raw material treatment method. As a result of the hydrothermal treatment of the starting material with a very high concentration of about 5 mol / l, it was completely isolated and dispersible in the submicron ultrafine particle region of 0.1 to 0.8 μm, which has never been obtained before. It is intended to provide a method for economically producing the excellent monodisperse spherical ultrafine particle powder of zirconia in a large amount at the lowest cost and efficiently.

[0009]

In order to solve such a problem, the present inventor has repeated a number of experiments and studies, especially on the ZrOCl ₂ -Zr (OH) ₄ -H ₂ O system,
By conducting extensive research by varying the composition, it was found that the particle size of the spherical agglomerated particles produced could be adjusted to 0.1 to 0.8 μm, and the uniform monodispersity of these particles was increased to completely It was found that the following method is indispensable to obtain a zirconia monodisperse spherical ultrafine particle powder which is isolated and has excellent dispersibility.

That is, in the present invention, first, zirconyl chloride, zirconium hydroxide or hydrated zirconia, hydrochloric acid, water or the like is used as a main starting material, and the chemical composition ratio is 0.8 mol of HCl to 1 mol of ZrO _2. ˜2.0 mol, H ₂ O 6 to 10 mol, and a compound such as a metal salt in a range of 0 to 0.2 mol. Mixing to form a uniform mixture, and this mixture in an acid-resistant closed hydrothermal container while moving the mixture by rotating the container, etc.
Hydrothermal treatment at a temperature of 0 ° C for the required optimum time
It was found that it is necessary for the hydrothermal reaction to proceed uniformly and uniformly, and the uniformity of the spherical agglomerated ultrafine particles to be formed is ensured only by these treatments.

The reaction product is a thick mud-like substance which is composed mainly of spherical agglomerated ultrafine particles of monoclinic zirconia and has almost no fluidity, but they are fused to each other when heated and dried at about 50 ° C. or higher. It was discovered that coarse aggregates tended to be formed. Therefore, the product of the hydrothermal reaction is cooled to 50 ° C or lower in a hydrothermal container while being hermetically sealed, and then dried under reduced pressure at a temperature of 50 ° C or lower before heating and drying to remove most of water and hydrochloric acid. It is indispensable to remove them, and after that, the first heat treatment at a temperature of 100 ° C. or higher makes spherical aggregates isolated without partial fusion, and spherical aggregated ultrafine particles excellent in monodispersity are obtained. It was found that a stable ultrafine particle powder can be obtained.

[0012]

SPECIFIC STRUCTURE In the present invention, zirconyl chloride, zirconium hydroxide or hydrated zirconia, hydrochloric acid, water or the like is used as a main starting material, and a chemical composition ratio of ZrO ₂ is 1 mol of ZrO _2. 0.0 mol, H ₂ O 6-10
It is necessary to mix the moles and compounds such as metal salts so as to be in the range of 0 to 0.2 moles, and pulverize and mix them in advance to form a uniform mud-like mixture. The required amount of HCl and H ₂ O is 0.8 to 0.1 mol of HCl based on 1 mol of ZrO _2.
2.0 mol, H ₂ O was limited to a very narrow range of 6 to 10 mol because the diameter of the agglomerated spherical particles of the product was HCl and H.
_It decreases with a decrease in the ratio of ₂ O, the particle size becomes about 0.1 μm or less when HCl is 0.8 mol or less, the spherical shape and the isolation are deteriorated, and the hydrothermal reaction of HCl is 2.0 mol or more. It requires a high temperature and a long time to finish, and the pressure in the hydrothermal container under strong acidity is too high to be practical. On the other hand, when H ₂ O is 6 mol or less, the fluidity of the raw material is poor and the product is uniform. Not
This is because when H ₂ O is 10 mol or more, the fluidity of the product becomes too high and the isolation of the spherical agglomerated particles is impaired due to water.

In the composition having a very high concentration of Zr component as described above, the liquid portion in the mixture is small, and the product after the reaction becomes a thick mud having almost no fluidity. It is necessary to make the raw material uniform by rotating it. When the reaction product is fixed in place, the isolation of the agglomerated particles at the bottom becomes somewhat worse, and the upper surface layer becomes somewhat coarser than at the bottom, impairing the monodispersity.

To carry out the process of the invention, the starting composition:
The three variables of temperature and time must be in proper relationship. Naturally, the higher the temperature, the shorter the required treatment time, but in general, the higher the ratio of HCl / H ₂ O in the raw material composition, the larger the agglomerated particle size generated, and the longer the required hydrothermal treatment time. The temperature of the hydrothermal reaction at this time is 100 to 220 ° C.
The reason for limiting the above is that the reaction hardly progresses at 100 ° C. or lower, and at 220 ° C. or higher, the pressure of hydrochloric acid vapor is high and it becomes difficult to work with an ordinary apparatus. The most practical hydrothermal treatment temperature is 130 ° C to 180 ° C. Further, even if this hydrothermal treatment time was too long, sufficient results were not obtained, and it was found that there is an optimum hydrothermal treatment time for each combination of the raw material composition and the treatment temperature. When the hydrothermal treatment time exceeds this optimum time, the produced spherical agglomerated particles gradually collapse and the isolation becomes worse. The optimum hydrothermal treatment time becomes longer as the amount of HCl in the raw material composition increases, and becomes shorter as the hydrothermal treatment temperature becomes higher. The specific optimum temperature is experimentally determined for each raw material composition and treatment temperature. There must be.

The reaction product of the hydrothermal treatment in the present invention is
It is a thick mud that has almost no fluidity and consists mainly of spherical agglomerated ultrafine particles of monoclinic zirconia.
When heated and dried at 0 ° C. or higher, they are easily partially fused to each other to form secondary or tertiary aggregated particles, and do not become isolated monodispersed spherical aggregated particles. The reaction product is cooled to 50 ° C. or lower in a hydrothermal container while being hermetically sealed, and before heating and drying,
First, it is essential to dry under reduced pressure at a temperature of 50 ° C. or lower to remove most of water and hydrochloric acid. The temperature of this reduced-pressure drying has an upper limit of about 50 ° C., and the lower the temperature, the better the isolated dispersibility of the spherical aggregated particles.

The zirconia monodisperse spherical ultrafine particles thus obtained are easily disintegrated and dispersed when they are still put in water to form a sol in which ultrafine crystals of 0.01 μm or less of ultrafine crystals are dispersed. As it will change, 100 ℃
The above heat treatment is required. By this heat treatment, the soluble zirconium salt etc. slightly remaining as an unreacted substance is converted into Z.
It is considered that the particle size changes to rO ₂ , the spherical ultrafine particles are immobilized, and it becomes stable to water.

[0017]

EXAMPLES Some examples of the present invention will be shown below to more specifically describe the present invention.

[0018] Example 1 Reagent zirconyl chloride _{(ZrOCl 2 · 8H 2 O)} , semi-dried hydrous zirconium hydroxide _(ZrOH 4 · 0.9H
₂ O) and distilled water were mixed in the proportions shown in Table 1 and mixed well by grinding in a mortar.
And a mixture of 4 samples of D were prepared. As shown in Table 1, the chemical compositions of these compounds are 1.0 mol to 1.9 mol of HCl and 7.0 mol to 8.2 mol of H ₂ O per mol of ZrO _2. Corresponding and all are within the scope of the claims. Each of these mixtures was filled in a hard Teflon container (internal volume: 25 ml) in a pressure resistant container made of stainless steel. The volume of each mixture was about 20 ml, and the filling rate was about 80% of the inner volume of the container. Each pressure-resistant container filled with the raw material mixture was hermetically sealed, set on a rotating shaft in a hot air circulation type dry oven, and heat-treated at 200 ° C. for a predetermined time while rotating the pressure-resistant container so that the inside would roll. . The optimum time required for hydrothermal treatment is as shown in Table 1, and it becomes longer as the molar ratio of HCl and H ₂ O increases.

After each sample was heat-treated, it was left at room temperature for 10 hours together with a pressure resistant container, and then unsealed. As a result, a white thick mud-like substance having almost no fluidity was formed. Each of these was scraped out on an evaporation dish and placed in a vacuum desiccator as it was, and dried under reduced pressure by a vacuum pump. In the dried state under reduced pressure, all of these products are white soft powder aggregates, but if they are put into water as they are, they are easily dispersed in primary ultrafine particles of 0.01 μm or less to form a translucent sol. give. However, by heating at about 250 ° C. for several hours, it was not redispersed in water. This product is
It was a soft lump and was easily loosened to a powder just by holding it lightly. Scanning electron micrographs of this powder show well isolated 0.63-0.
It can be seen that it is composed of spherical monodisperse ultrafine particles of 7 μm. The samples of B, C, and D are almost the same, but the particle size thereof becomes smaller as the molar ratio of HCl and H ₂ O becomes smaller, as shown in Table 1.

[0020]

[Table 1]

[0021] Example 2 Reagent zirconyl chloride _{(ZrOCl 2 · 8H 2 O)} , semi-dried hydrous zirconium hydroxide _(ZrOH 4 · 3.9H
₂ O) and distilled water were mixed in the proportions shown in Table 2, respectively, and ground and mixed in a mortar in the same manner as in Example 1 to prepare three types of E, F, and G samples in a muddy state. A mixture was made. The chemical compositions of these are also shown in Table 2. These mud-like mixtures were hydrothermally treated in the same manner as in Example 1 at 150 ° C. or 130 ° C., respectively. Since the treatment temperature was low, the optimum hydrothermal treatment time was somewhat long as shown in Table 2 although the amount of HCl was small.

After heat treatment, each sample was cooled to room temperature and left open in the same manner as in Example 1 while keeping the vessel sealed, the concentrated mud-like product was placed in a vacuum desiccator, and dried under reduced pressure by a vacuum pump.
In this state, all of these products were white soft powder aggregates, and the spherical aggregated ultrafine particles could be stabilized against water by applying heat treatment at about 250 ° C. for several hours. This product was also a very soft lump, and was easily loosened by just holding it lightly to give a powder. According to an electron micrograph of the powder, all were well-isolated spherical fine particles, and the particle diameters obtained from the photograph are shown in Table 2. It was as shown in.

[0023]

[Table 2]

[0024] EXAMPLE 3 Reagents zirconyl chloride _{(ZrOCl 2 · 8H 2 O)} , semi-dried hydrous zirconium hydroxide _(ZrOH 4 · 3.9H
₂ O), and distilled water, sample H to which yttrium hydroxide was added so as to form tetragonal zirconia as a solid solution in zirconia was mixed in the proportions shown in Table 2, and the same as in Example 1. The mixture was ground and mixed in a mortar to prepare a mud-like mixture.
The chemical composition is also shown in Table 2. This mud-like mixture was hydrothermally treated at 200 ° C. in the same manner as in Example 1.

After heat treatment, this sample was cooled to room temperature while being hermetically sealed as in Example 1, placed in a vacuum desiccator, dried under reduced pressure by a vacuum pump, and then heated to about 1000 ° C.
It was calcined for 2 hours. Although this product was in the form of a lump that was somewhat harder than that of only the constant temperature heat treatment of Examples 1 and 2, it was easily disintegrated into a powder by lightly grinding it in a mortar or the like, and powder X-ray diffraction showed a tetragonal zirconia crystal. , And the scanning electron micrograph of this powder consisted of well-isolated monodisperse spherical ultrafine particles of 0.35 to 0.4 μm as shown in FIG.

[0026]

As is apparent from the above description, according to the present invention, it is possible to obtain 0.2 to 0.2 which has never been obtained conventionally.
It becomes possible to produce zirconia monodisperse spherical ultrafine particles that are completely isolated and have excellent dispersibility in the ultrafine particle region of 0.7 μm. Therefore, it is expected that the performance of zirconia-based fine ceramics will be greatly improved. In addition, the raw materials are relatively inexpensive, the manufacturing process is relatively simple, and hydrothermal treatment can be performed at an extremely high concentration of about 5 mol / l at a ZrO ₂ concentration, resulting in extremely high efficiency and economically most advantageous. It is possible to manufacture zirconia powder inexpensively and in large quantities. Therefore, it is considered that there is a possibility that the zirconia powder production system in the world may be renewed.

[Brief description of drawings]

FIG. 1 is a scanning electron micrograph of a representative sample A.

FIG. 2 is a scanning electron micrograph of a representative sample H in which yttrium is solid-dissolved.

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[Procedure amendment]

[Submission date] September 9, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be amended] Detailed explanation of the invention

[Correction method] Change

[Correction content]

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention has excellent properties useful as a raw material powder for fine ceramics, that is, as a raw material powder for ceramics containing zirconia as a main component or a ceramic containing a zirconium compound, and for special cosmetics or The present invention relates to a method for inexpensively producing a large amount of submicron zirconia monodisperse spherical ultrafine powder which is also useful as a pigment.

[0002]

BACKGROUND ART As a raw material fine powder for fine ceramics, especially for a sintered body, the molding packing density can be increased,
Sintering progresses uniformly to obtain a homogeneous microstructure of a sintered body with good dimensional accuracy. In the solid-phase reaction with other components, the mixing is uniform and a homogeneous reaction product is obtained. In view of the above advantages, fine particles having high purity, uniformity, spherical shape, and excellent isolation are generally required.

Conventionally, a known method for producing such monodisperse zirconia fine particles is by hydrolysis of an alcohol solution of alkoxide (J. Am. Cer.
a. Soc. 72 [3] 421-26 (1989)).
Thus, isolated monodisperse spherical amorphous zirconia fine particles having a size of about 1 μm can be obtained, but the ZrO ₂ concentration is 0.
Since it is necessary to use an extremely dilute solution of about 1 mol / 1 or less, the production amount for a given apparatus volume is extremely small,
In addition, since the raw material alkoxide and alcohol are expensive, they are generally inferior in economic efficiency and have a drawback that they are not suitable for industrial mass production. Therefore, in zirconia, the monodisperse spherical fine particles can be used only for a special purpose, and have not been used as a ceramic raw material.

At present, zirconia fine powder used as a raw material for sintering zirconia-based fine ceramics is generally composed of ultrafine particles having a particle size of 0.2 to 0.4 μm. Crystalline zirconium hydroxide, or 0. Most of them are produced by finely pulverizing a calcined product such as a colloidal product having a size of μm or less with a ball mill or the like.
At present, it is neither spherical nor monodisperse.

The present inventor has already used, as a method for producing spherical particles that can be economically processed in large quantities, crystalline hydrous zirconyl chloride alone or a metal oxide containing this as a main component and capable of forming a solid solution in ZrO _2. A patent application was filed for a method of producing a spherical zirconia fine particle of about 0.5 to 1 μm by heating and reacting a solid mixture containing a small amount of a compound in a closed container at 150 ° C. to 300 ° C. -107
578), or the crystalline hydrous zirconyl chloride as it is,
Alternatively, a slight amount of water may be added to hydrothermally treat at 150 ° C. to 200 ° C., and this may be heated and dehydrated to obtain spherical zirconia fine particles of about 0.5 to 1 μm (Journal of Ceramic Society of Japan, 98 [3] 300-04 (199
0)) announced.

The above method by the present inventor is a product obtained by temporarily soft agglomerating monoclinic zirconia ultrafine particles of 0.01 μm or less into a spherical shape of about 0.5 to 1 μm by hydrothermal reaction of a concentrated starting composition. If this agglomeration is left as it is, it will disintegrate immediately when poured into water and disperse into the original monoclinic zirconia ultrafine crystals of 0.01 μm or less to form a translucent sol. It has been found that by drying and immobilizing it on, it becomes stable spherical particles in water. Therefore, it is a completely new and innovative method for producing spherical zirconia fine particles, and since a particularly thick mixture is processed, a characteristic feature is that a large amount of product can be obtained for a given apparatus volume. It was

However, the above paper (Journal of the Ceramic Society of Japan, 98 [3] 300-04 (199
As can be clearly seen in the electron micrograph of the resulting spherical microparticles shown in 0)), the agglomerated particles are relatively uniform spheres, but they are partially fused to each other There was a defect that the particles were aggregated in the third order and the isolation and dispersibility of the constituent particles in the powder state were extremely insufficient. At this point in the study, it is still unknown at which stage in the manufacturing process the phenomenon of fusion and agglomeration of spherical fine particles occurs, and there is an optimum time for spherical agglomeration. It was also completely unknown that the aggregated fine particles gradually fused. Therefore, the produced powder obtained by this method is poor in practicality as it is.

[0008]

The object of the present invention is to completely eliminate the fusion and agglomeration of spherical fine particles, which is a drawback of the above method, and complete a fine powder manufacturing method by a concentrated raw material treatment method. By hydrothermal treatment of an extremely concentrated starting material with a Zr concentration of about 5 mol / l, completely isolated and dispersed in a submicron ultrafine particle region of 0.1 to 0.8 μm, which has never been obtained before. The present invention provides a method for producing a large amount of zirconia monodisperse spherical ultrafine particle powder, which is excellent in terms of cost, economically, at the lowest cost, and efficiently.

[0009]

In order to solve such a problem, the present inventor has repeated a number of experiments and studies, especially on the ZrOCl ₂ -Zr (OH) ₄ -H ₂ O system,
By conducting extensive research by varying the composition, it was found that the particle size of the spherical agglomerated particles produced could be adjusted to 0.1 to 0.8 μm, and the uniform monodispersity of these particles was increased to completely It was found that the following method is indispensable to obtain a zirconia monodisperse spherical ultrafine particle powder which is isolated and has excellent dispersibility.

That is, the present invention is as follows. First, zirconyl chloride, zirconium hydroxide, hydrated zirconia, basic zirconium carbonate.
Zirconium compounds such as Ni and hydrochloric acid or water
When mixed, the chemical composition ratio is 1 mol of ZrO ₂ , and HCl is added.
But 0.8 to 2.0 mol, _{H 2} O is 6 to 10 mol, and compounds such as metal salts becomes 0 to 0.2 mol, homogeneous mixture
Or it is necessary to a solution, the other, previously the material due pulverized and mixed to a homogeneous mixture or solution, and the composition in acid resistance of the sealed hydrothermal vessel, due the rotation of the container 10 while moving contents
It is necessary to carry out hydrothermal treatment at a temperature of 0 to 220 ° C. for a necessary optimum time in order for the hydrothermal reaction to proceed uniformly and uniformly, and for the first time by these treatments, the uniformity of the spherical agglomerated ultrafine particles produced is ensured. I was found to be done.

The reaction product is a thick mud-like substance which is composed mainly of spherical agglomerated ultrafine particles of monoclinic zirconia and has almost no fluidity, but they are fused to each other when heated and dried at about 50 ° C. or higher. It was discovered that coarse aggregates tended to be formed. Therefore, the product of the hydrothermal reaction is cooled to 50 ° C or lower in a hydrothermal container while being hermetically sealed, and then dried under reduced pressure at a temperature of 50 ° C or lower before heating and drying to remove most of water and hydrochloric acid. It is absolutely necessary to remove it, and after that, by first performing heat treatment at a temperature of 100 ° C. or higher, spherical aggregates are isolated without partial fusion and spherical aggregated ultrafine particles excellent in monodispersity are obtained, They have found that it becomes ultrafine powder powder that is stable against water.

[0012]

[Specific Structure] In the present invention, zirconyl chloride, zirconium hydroxide, hydrated zirconia, basic zirconium carbonate
Mixing zirconium compounds such as hydrochloric acid or water
Then, with respect to the chemical composition ratio of 1 mole of ZrO ₂ , HCl is 0.8 to 2.0 moles, H ₂ O is 6 to 10 moles, and compounds such as metal salts are 0 to 0.2 moles . Even mixture
Or a solution is required. Required HCl and H
As the amount of ₂ O, relative to 1 mole of ZrO _2, the HCl is 0.8 to 2.0 mol, _{H 2} O is limited to a very narrow range of 6 to 10 moles, of the product of aggregated spherical particles Diameter is H
Decreases with decreasing ratio of Cl to H ₂ O, HCl is 0.8
If it is less than molar, the particle size will be about 0.1 μm or less,
The isolation becomes worse, and when HCl is 2.0 mol or more,
The end of the hydrothermal reaction requires high temperature and a long time, and the pressure of the hydrothermal device under strong acidity becomes too high to be practical, while H ₂
When O is 6 mol or more, the fluidity of the raw material is poor and the product is not uniform, and when H ₂ O is 10 mol or more, the fluidity of the product becomes too high, and the isolation of the spherical aggregated particles is impaired due to water. Because it is done.

In the composition having a very high concentration of Zr component as described above, the liquid portion in the mixture is small, and the product after the reaction becomes a thick mud having almost no fluidity. It is necessary to make the raw material uniform by rotating it. When the reaction product is statically fixed, the isolation of the aggregated particles at the bottom becomes somewhat worse, and the upper surface layer becomes somewhat coarser than at the bottom, impairing the monodispersity.

To carry out the process of the invention, the starting composition:
The three variables of temperature and time must be in proper relationship. Naturally, the higher the temperature, the shorter the required treatment time, but in general, the higher the ratio of HCl / H ₂ O in the raw material composition, the larger the agglomerated particle size generated, and the longer the required hydrothermal treatment time. The temperature of the hydrothermal reaction at this time is 100 to 220 ° C.
The reason for limiting the above is that the reaction hardly progresses at 100 ° C. or lower, and at 220 ° C. or higher, the pressure of hydrochloric acid vapor is high and it becomes difficult to work with an ordinary apparatus. The most practical hydrothermal treatment temperature is 130 ° C to 180 ° C. Further, even if this hydrothermal treatment time was too long, sufficient results were not obtained, and it was found that there is an optimum hydrothermal treatment time for each combination of the raw material composition and the treatment temperature. When the hydrothermal treatment time exceeds this optimum time, the produced spherical agglomerated particles gradually collapse and the isolation becomes worse. The optimum hydrothermal treatment time becomes longer as the amount of HCl in the raw material composition increases, and becomes shorter as the hydrothermal treatment temperature becomes higher, but the specific optimum temperature must be experimentally determined for the raw material composition and the treatment temperature, respectively. I have to.

The reaction product of the hydrothermal treatment in the present invention is
It is a thick mud that has almost no fluidity and consists mainly of spherical agglomerated ultrafine particles of monoclinic zirconia.
When heated and dried at 0 ° C. or higher, they are easily partially fused to each other to form secondary or tertiary aggregated particles, and do not become isolated monodispersed spherical aggregated particles. The reaction product is cooled to 50 ° C. or lower in a hydrothermal container while being hermetically sealed, and before heating and drying,
First, it is essential to dry under reduced pressure at a temperature of 50 ° C. or lower to remove most of water and hydrochloric acid. The temperature of this reduced-pressure drying has an upper limit of about 50 ° C., and the lower the temperature, the better the isolated dispersibility of the spherical aggregated particles.

The zirconia monodisperse spherical ultrafine particles thus obtained are easily disintegrated and dispersed when they are still put into water, and the ultrafine sol in which ultrafine crystals of 0.01 μm or less are dispersed. Therefore, in order to obtain ultra-fine powder that is stable against water, after drying under reduced pressure at 100 ° C
The above heat treatment is required. By this heat treatment, the soluble zirconium salt etc. slightly remaining as an unreacted substance is converted into Z.
It is considered that the particle size changes to rO ₂ , the spherical ultrafine particles are immobilized, and it becomes stable to water.

[0017]

EXAMPLES Some examples of the present invention will be shown below to more specifically describe the present invention.

[0018] Example 1 Reagent zirconyl chloride _{(ZrOCl 2 · 8H 2 O)} , semi-dried hydrous zirconium hydroxide _(ZrOH 4 · 0.9H
₂ O), and distilled water were mixed in the proportions shown in Table 1 and mixed well in a mortar to mix A, B, and
A mixture of four kinds of samples C and D was prepared. These chemical compositions are as shown in Table 1, with respect to 1 mole of ZrO _2, HCl 1.0 mol to 1.9 mol, also _{H 2}
O corresponds to 7.0 mol-8.2 mol, all within the scope of the claims. Each of these mixtures was filled in a hard Teflon container (internal volume: 25 ml) in a pressure resistant container made of stainless steel. The volume of each mixture was about 20 ml, and the filling rate was about 80% of the inner volume of the container. Each pressure-resistant container filled with the raw material mixture was hermetically sealed, set on a rotating shaft in a hot air circulation type dry oven, and heat-treated at 200 ° C. for a predetermined time while rotating the pressure-resistant container so that the inside would roll. . The minimum time required for hydrothermal treatment is as shown in Table 1, and the longer the molar ratio of HCl to H ₂ O, the longer it becomes.

After each sample was heat-treated, it was left at room temperature for 10 hours together with a pressure resistant container, and then unsealed. As a result, a white, almost mud-like substance having almost no fluidity was formed. Each of these was scraped out on an evaporation dish and placed in a vacuum desiccator as it was, and dried under reduced pressure by a vacuum pump. In the dried state under reduced pressure, all of these products are white soft powder aggregates, but if they are put into water as they are, they are easily dispersed in primary ultrafine particles of 0.01 μm or less to form a translucent sol. give. However, by heating at about 250 ° C. for several hours, it was not redispersed in water. This product is
It was a soft lump and was easily loosened to a powder just by holding it lightly. Scanning electron micrographs of this powder show well isolated 0.63-0.
It can be seen that it is composed of spherical monodisperse ultrafine particles of 7 μm. The samples of B, C, and D are almost the same, but the particle size thereof becomes smaller as the molar ratio of HCl and H ₂ O becomes smaller, as shown in Table 1.

[0020]

[Table 1]

[0021] Example 2 Reagent zirconyl chloride _{(ZrOCl 2 · 8H 2 O)} , semi-dried hydrous zirconium hydroxide _(Zr (OH) 4 · 3.9H
₂ O) and distilled water were mixed in the proportions shown in Table 2 and ground and mixed in a mortar in the same manner as in Example 1 to prepare three types of E, F, and G samples in the form of mud. A mixture was made. The chemical compositions of these are also shown in Table 2. These mud-like mixtures were hydrothermally treated at 150 ° C. or 130 ° C. in the same manner as in Example 1. Since the treatment temperature was low, the optimum hydrothermal treatment time was somewhat long as shown in Table 2 although the amount of HCl was small.

After heat treatment, each sample was cooled to room temperature and left open in the same manner as in Example 1 while keeping the vessel sealed, the concentrated mud-like product was placed in a vacuum desiccator, and dried under reduced pressure by a vacuum pump.
In this state, all of these products were white soft powder aggregates, and the spherical aggregated ultrafine particles could be stabilized against water by applying a heat treatment at about 250 ° C. for several hours. This product is also a very soft lump, and is easily loosened to a powder by just holding it lightly, and according to the electron micrograph of this powder, all are well isolated spherical fine particles,
The particle size obtained from the photograph is shown in Table 2.

[0023]

[Table 2]

[0024] EXAMPLE 3 Reagents chloride Hijirukoniru _{(ZrOCl 2 · 8H 2 O)} , semi-dried hydrous zirconium hydroxide (Zr _(OH) 4 · 3.9
H ₂ O), distilled water, and yttrium hydroxide were added so as to form tetragonal zirconia as a solid solution in zirconia, and sample H was blended in the proportions shown in Table 2 and the same as in Example 1. Then, the mixture was ground and mixed in a mortar to prepare a mud-like mixture. The chemical composition is also shown in Table 2. This mud-like mixture was hydrothermally treated at 200 ° C. in the same manner as in Example 1.

After heat treatment, this sample was cooled to room temperature while being hermetically sealed in the same manner as in Example 1, placed in a vacuum desiccator, dried under reduced pressure by a vacuum pump, and then heated to about 1000 ° C.
It was calcined for 2 hours. This product was in the form of a lump that was somewhat harder than that of the low temperature heat treatments of Examples 1 and 2, but it was easily disintegrated into a powder by lightly grinding it with a mortar or the like, and powder X-ray diffraction showed tetragonal zirconia. The peak of the crystal was shown, and the scanning electron micrograph of this powder was composed of well-isolated monodisperse spherical ultrafine particles of 0.35 to 0.4 μm as shown in FIG.

Example 4 Basic Zirconium Carbonate (Zr ₂ O ₂ (OH) ₂ CO ₃
206.0 g of (6.06H ₂ O) was weighed and
When mixed with 83.3 ml of 2N concentrated hydrochloric acid, carbon dioxide gas
It evolved into a clear solution. Chemical composition ratio of this solution
Is calculated by adding 1 mol of ZrO ₂ to HCl of 1.0.
Moles, 7.0 moles of H ₂ O,
Hit A portion of this solution was taken and processed as in Example 2.
Then, hydrothermal treatment was performed at 150 ° C. for 24 hours. Next
Sample was then treated exactly as in Example 1,
The products were all well isolated according to electron micrographs
Spherical particles

[0027]

As is apparent from the above description, according to the present invention, it is possible to obtain 0.2 to 0.2 which has never been obtained conventionally.
It becomes possible to produce zirconia monodisperse spherical ultrafine particles that are completely isolated and have excellent dispersibility in the ultrafine particle region of 0.7 μm. Therefore, it is expected that the performance of zirconia-based fine ceramics will be greatly improved. In addition, the raw material is relatively inexpensive, the manufacturing process is relatively simple, and the hydrothermal treatment can be performed at a ZrO ₂ concentration of 5 mol / 1, which is an extremely high concentration. It is possible to manufacture zirconia powder inexpensively and in large quantities. Therefore, it is considered that there is a possibility that the zirconia powder production system in the world may be renewed.

Claims (1)

[Reference number] 0010 [Claims] 1. A main starting material is zirconyl chloride, zirconium hydroxide or hydrated zirconia, hydrochloric acid, water or the like, and the chemical composition ratio is 1 mol of ZrO ₂ to HC.
1 to 0.8 to 2.0 moles, H ₂ O to 6 to 10 moles, and compounds such as metal salts in the range of 0 to 0.2 mole, and pulverized and mixed in advance to obtain a uniform mixture. In an acid-resistant closed hydrothermal container, hydrothermal treatment was performed at a temperature of 100 to 220 ° C for the optimum time while moving the mixture by rotating the container, etc., and the container was cooled to 50 ° C or less while being sealed. After that, the concentrated mud-like substance which is the reaction product is first dried under reduced pressure at a temperature of 50 ° C or lower to remove most of water and hydrochloric acid to form a solidified product, which is then heat-treated at a temperature of 100 ° C or higher. A method for producing monodisperse spherical ultrafine particles of zirconia, characterized in that the spherical aggregated ultrafine particles in the solidified product are stabilized against water.