JPH06171944A - Production of zirconium oxide powder - Google Patents

Abstract

(57) [Summary] [Structure] An aqueous zirconium salt solution is heated in the presence of amorphous hydrated zirconia to hydrolyze, and then neutralized, and hydrated zirconia particles are separated from the obtained hydrated zirconia slurry. Comprising calcining the hydrated zirconia particles,
Method for producing zirconium oxide powder. [Effect] The anions in hydrated zirconia obtained by the hydrolysis reaction, which was difficult in the prior art, are reduced, so that high-purity zirconium oxide is obtained, and strong agglomeration occurs during calcination of the hydrated zirconia. The obtained zirconium oxide has good formability, and the sintered body obtained by sintering the formed body has high strength.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to structural materials, machine parts,
The present invention relates to a method for producing zirconium oxide powder which is a raw material of zirconia porcelain widely used for tools, electronic materials and the like.

[0002]

As a method for producing zirconia powder, there are various methods such as a neutralization coprecipitation method, a hydrolysis method, an alkoxide method and a hydrothermal method.

In the neutralization coprecipitation method, it is difficult to obtain a coprecipitate having a uniform composition, the neutralization coprecipitate is in the form of a gel, the workability such as washing with water is poor, and a lump is formed after calcination and crushed. However, there is a problem in that impurities are mixed in the crushing process.

In the hydrolysis method, it takes a long time to obtain a high reaction rate, and it is difficult to completely deposit a metal compound as a stabilizer, and the hydrolysis product is separated when it is separated by furnace and washed. However, it is difficult to control the composition; and further, there is a problem that a fine and uniform precursor obtained by hydrolysis is strongly aggregated by drying. A method of azeotropic dehydration with an organic solvent in order to suppress this aggregation is also known, but the use of a large amount of organic solvent is industrially problematic.

The alkoxide method and hydrothermal method are not suitable for industrial production because the raw materials and manufacturing equipment are special and expensive.

As described above, the conventional manufacturing method has a problem, but in recent years, a manufacturing method which takes advantage of both the neutralization method and the hydrolysis method has been disclosed.

The method is (1) JP-B-4-31359. A solution containing a sol of monoclinic zirconia secondary agglomerated particles produced by heating and hydrolysis of an aqueous zirconium salt solution and a divalent or trivalent metal ion is added with ammonia. A method for producing a zirconia-based fine powder, characterized in that a solid-phase portion produced by adding a zirconia is separated, dried, and calcined (2) JP-A-4-31359. Yttria-stabilized zirconia-based ceramic raw material powder by hydrolysis The method for producing a yttria-stabilized zirconia-based raw material powder, which comprises hydrolyzing and subsequently performing a neutralization reaction.

In both the methods (1) and (2), particles which are easily reactive and easily sinterable are obtained by a hydrolysis method, and other metal atoms are neutralized and precipitated to obtain a uniform composition ratio. This is a method of obtaining particles.

[0009]

However, the hydrated zirconia particles separated from the slurry obtained by hydrolysis and neutralization in these methods are difficult to remove anions, and therefore the hydrated zirconia is calcined. When the zirconium oxide powder is obtained, the anion is C
It is released in the form of l ₂ , SOx, NOx and the like. These are harmful to the human body and not only corrode the calcination apparatus and its peripheral equipment, but also have a problem in the characteristics of the obtained zirconium oxide powder itself. That is, in the calcining step, the particles are likely to undergo strong agglomeration after the release of the anions, and the powder composed of the particles thus strongly agglomerated is difficult to pulverize and the energy loss becomes large. Moreover, problems such as mixing of impurities are likely to occur in the crushing process. Further, even if pulverized, the obtained zirconium oxide powder is likely to be a powder having poor moldability, and therefore, the zirconium oxide sintered body obtained by molding and sintering the powder has strength, density, etc. Is low.

It is an object of the present invention to provide a method for producing zirconium oxide powder which does not leave anionic impurities in the hydrated zirconia and thereby does not cause the above-mentioned problems due to anions. .

[0011]

[Means for Solving the Problems] The present inventors have found out that the cause of the anion remaining in the hydrated zirconia particles separated as described above is due to hydrolysis, and are keenly aware of a method for eliminating the cause. As a result of research, the present invention has been reached.

That is, according to the present invention, an aqueous zirconium salt solution is heated in the presence of non-crystalline hydrated zirconia to hydrolyze it and then neutralized, and hydrated zirconia particles are separated from the obtained hydrated zirconia slurry. A method for producing a zirconium oxide powder, which comprises calcination of the hydrated zirconia particles.

The details will be described below.

The zirconium salt used in the present invention may be any water-soluble one, and examples thereof include zirconium chloride, zirconium nitrate, zirconium sulfate, zirconium oxychloride and the like.

In the present invention, the concentration of the zirconium salt aqueous solution is preferably 2 mol / liter or less for Zr. This is because the lower the concentration, the lower the productivity, but if it is too high, the hydrolysis may take time or the hydrolysis may become difficult. About Zr 0.05-1mo
1 / l is more preferred.

In the present invention, amorphous hydrated zirconia is allowed to coexist in the aqueous zirconium salt solution. As a means for this, non-hydrated hydrated zirconia may be added to the zirconium salt aqueous solution, or a method of neutralizing a part of the zirconium salt aqueous solution with an alkali before hydrolyzing it can be used.

The content of non-crystalline hydrated zirconia in the liquid to be hydrolyzed is preferably 50% or less in terms of Zr with respect to the total of the zirconium salt. The hydrated zirconia, which is considered to have a content of more than 50%, becomes a gel like the one obtained by the neutralization method, the workability in washing with water and the like is deteriorated, and it becomes a lump after calcination, which makes crushing difficult. There are problems such as. If the amount is too small, it becomes difficult to reduce the amount of anions remaining in the hydrated zirconia particles separated from the liquid through hydrolysis-neutralization. Zr is more preferably 1 to 40%, most preferably 1
It is 0 to 30%.

Subsequently, the zirconium salt aqueous solution in which the non-crystalline hydrated zirconia is made to coexist is heated and hydrolyzed to obtain a hydrated zirconia particle slurry. In particular, according to the method of boiling under reflux, it is not necessary to use a heat and pressure resistant device.

The hydrolysis is preferably carried out until the hydrolysis rate reaches 50 to 95%. The hydrolysis rate is 50%
If it is less than 100%, the uniform fine particle properties obtained by hydrolysis will be impaired by the subsequent neutralization. On the other hand, if it is higher than 95%, hydrolysis will take a long time, which is not economical, or a raw material solution. This is because such a high hydrolysis rate cannot be achieved when the concentration of H is high. It is considered that during the hydrolysis, the non-crystalline hydrated zirconia coexisting in the aqueous zirconium salt solution also dissolves as the hydrolysis progresses to form a zirconium salt, which is further hydrolyzed. In the present specification, the term “hydrolysis rate” means that non-crystalline hydrated zirconia is also supplied to the hydrolysis step as a zirconium salt, and the reaction solution has a molecular weight cutoff of 300.
It is obtained by filtering with a 10,000 ultrafiltration membrane and measuring the residual Zr amount in the obtained filtrate by ICP (inductively coupled plasma) emission spectroscopic analysis.

In the present invention, since the non-crystalline hydrated zirconia coexists in the water-soluble aqueous zirconium salt solution before the hydrolysis, the hydrolysis time can be shortened and the hydrolysis can be advantageously carried out.

In the case of producing a zirconium oxide powder containing a stabilizer, a salt of Y, Mg, Ca, Ce or the like, an aqueous solution thereof or an oxide of these metals may be added to the raw material liquid, and a solid salt or an oxide may be added. The product can be added after the hydrated zirconia particles are collected, dried, and calcined.

After the hydrolysis, the solution is neutralized with an aqueous alkali solution such as sodium hydroxide, potassium hydroxide, aqueous ammonia and urea. Neutralization is preferably carried out until the pH reaches 8-10. When the pH is less than 8, it is difficult to completely precipitate the hydrated zirconia particles, and when the pH is more than 10, the washing load in the fractionation of the hydrated zirconia particles after the neutralization becomes large. If the concentration of the alkaline aqueous solution is too high, stirring may be difficult during precipitation formation, and the homogeneity of the system may deteriorate. If it is too low, the amount of the system becomes enormous and it is not economical. It is preferable to select from among them in a timely manner. The neutralization can be performed by either a batch method or a flow method. The neutralization is preferably performed at 50 ° C or higher, more preferably 80 ° C or higher. This is because the higher the temperature, the smaller the amount of residual anions in the separated hydrated zirconia particles.

Further, after the pH adjustment, it is preferable to stir and hold for 1 hour or longer, preferably 6 hours or longer, and more preferably 12 hours or longer in order to reduce the amount of residual anions. The processing temperature is also preferably 50 ° C or higher, more preferably 80 ° C or higher.

The hydrated zirconia particles are separated from the hydrated zirconia slurry obtained as described above by filtration, washing and the like. The hydrated zirconia particles obtained by hydrolysis were difficult to filter by a usual method because they were too fine, but those of the present invention had a large particle size and were easily filtered. Further, impurities such as anions can be easily removed by washing. The washing is preferably performed with pure water until the pH of the filtrate becomes 9 or less, more preferably with warm water.

The hydrated zirconia particles thus separated are dried. The drying is preferably carried out by spraying and drying the hydrated zirconia particles into a slurry after the washing. Drying methods other than spray drying, for example, in static drying,
The dried powder becomes a block shape and it is difficult to uniformly perform heat treatment by calcination, and a crushing step is required after drying in order to make it uniform, resulting in an increase in the number of steps and a large energy loss. The temperature of the spray drying may be a temperature usually used, preferably 50 to 250 ° C, 100 to 200 ° C.
Is more preferable.

The hydrated zirconia particle powder is calcined.
The calcination is performed under normal conditions, that is, 600 to 13 in the atmosphere.
It may be performed at about 00 ° C.

After the calcination, if necessary, pulverize,
Obtain zirconium oxide powder.

[0028]

The reason why the high-performance zirconium oxide can be produced by the production method of the present invention is not always clear, but it is presumed that the reason is as follows.

In the hydrolysis reaction, zirconium ions exchange anions with hydroxide ions in the raw material zirconium salt aqueous solution to form crystalline hydrated zirconia.
In this hydrolysis reaction, it is difficult to exchange all the anions, and the resulting crystalline hydrated zirconia contains
Anions tend to remain.

In the present invention, by coexisting the non-crystalline hydrated zirconia during the hydrolysis, the decrease in the pH of the system due to the hydrolysis becomes small, and the anion is incorporated into the resulting crystalline hydrated zirconia. Is suppressed and further neutralized after hydrolysis,
While maintaining the uniform fine particle characteristics of the hydrated zirconia obtained by hydrolysis, to produce a hydrated zirconia particle slurry, the hydrated zirconia particles separated from such a slurry are dried and calcined. It is estimated that the zirconium oxide powder thus obtained has good moldability, and the sintered body obtained by sintering it has high strength and high density.

[0031]

According to the production method of the present invention, the anions in the hydrated zirconia obtained by the hydrolysis reaction, which was difficult in the prior art, are reduced, so that high-purity zirconium oxide is obtained, and the hydrated zirconia is obtained. The zirconium oxide obtained does not form strong agglomerates during calcination, and the zirconium oxide obtained has good formability, and the sintered body obtained by sintering the formed body has high strength.

[0032]

【Example】

Example 1 An amorphous hydrated zirconia was added to an aqueous zirconium oxychloride solution having a ZrO ₂ conversion concentration of 50 g / liter so as to be 10% of the total Zr content.

The aqueous solution was hydrolyzed by boiling under reflux until the hydrolysis rate reached 90%.

The obtained hydrated zirconia sol had an average primary particle diameter of 100 nm (the same applies hereinafter with a particle size distribution measuring device by the photon correlation method).

The solution after the hydrolysis was neutralized by adding an aqueous solution of sodium hydroxide having a normal concentration of 1N. PH after neutralization
Was 9.

[0036] After the neutralization, filtration, washing until the pH of the filtrate is 8 with pure water at 80 ° C., ZrO ₂ concentration in terms of 200
A g / liter slurry was prepared.

The slurry was spray-dried with a spray dryer. The obtained hydrated zirconia powder was spherical, and its lightly loaded bulk density was 1.15 g / cm ³ .

The powder was held at 900 ° C. for 2 hours and calcined to obtain a zirconium oxide powder. EXAMPLE ₂ YCl Y 2 O ₃ in terms of 3mol% (Y ₂ O ₃ in terms of value and ZrO
_{2 For} the total with the converted value. Hereinafter, the same), a hydrated zirconia slurry was obtained under the same conditions as in Example 1 except that an aqueous zirconium oxychloride solution having a ZrO ₂ conversion concentration of 50 g / liter was used.

The slurry was spray dried with a spray dryer. The obtained hydrated zirconia powder was spherical, and its lightly loaded bulk density was 1.25 g / cm ₃ .

The powder was held at 900 ° C. for 2 hours and calcined to obtain a partially stabilized zirconium oxide powder.

Example 3 YCl-containing ₃ mol% Y ₂ O ₃ conversion ZrO ₂ conversion concentration 5
Total Z in 0 g / liter zirconium oxychloride aqueous solution
An aqueous solution of sodium hydroxide having a normal concentration of 1 was added so that 10% of the r content was precipitated as non-crystalline hydrated zirconia, to obtain a non-crystalline hydrated zirconia-containing zirconium salt aqueous solution.

The aqueous solution was hydrolyzed by boiling under reflux until the hydrolysis rate reached 90%.

The obtained hydrated zirconia sol had an average primary particle diameter of 110 nm.

The solution after hydrolysis was neutralized by adding an aqueous solution of sodium hydroxide having a concentration of 1N. P after neutralization
H was 10.

While being stirred, the neutralized aqueous solution was kept under reflux at the boiling temperature for 24 hours.

After the above holding, the mixture was filtered and washed with pure water at 80 ° C. until the pH of the filtrate became 9, and the concentration was reduced to 200 in terms of ZrO _2.
A g / liter slurry was prepared.

The slurry was spray dried with a spray dryer. The obtained hydrated zirconia powder was spherical, and its lightly loaded bulk density was 1.25 g / cm ³ .

The powder was held at 900 ° C. for 2 hours for calcination to obtain a partially stabilized zirconium oxide powder.

Comparative Example 1 YCl content of ₃ mol% as Y ₂ O _{3 and} ZrO ₂ conversion concentration of 5
A 0 g / liter zirconium oxychloride aqueous solution was subjected to boiling hydrolysis under reflux until the hydrolysis rate reached 90%.

The obtained hydrated zirconia sol had an average primary particle diameter of 90 nm.

The above sol was spray-dried with a spray dryer, and the obtained dry powder was held at 850 ° C. for 2 hours for calcination to obtain a zirconium oxide powder.

Comparative Example 2 YCl-containing ₃ mol% as Y ₂ O _{3 and} ZrO ₂ -converting concentration 5
A 0 g / liter aqueous solution of zirconium oxychloride was hydrolyzed by boiling under reflux until the hydrolysis rate reached 90%.

The obtained hydrated zirconia sol had an average primary particle diameter of 100 nm.

The hydrolyzed aqueous solution was neutralized by adding a 1 N aqueous sodium hydroxide solution. Final pH
Was pH 9.

After the neutralization, the mixture was filtered and washed with pure water at 80 ° C. until the pH of the filtrate became 8, and then a hydrated zirconia slurry having a ZrO ₂ conversion concentration of 200 g / liter was obtained.

The slurry was spray dried with a spray dryer. The obtained hydrated zirconia powder was spherical, and its lightly loaded bulk density was 1.20 g / cm ³ .

The powder was held at 900 ° C. for 2 hours for calcination to obtain a zirconium oxide powder.

Table 1 shows the composition of each powder of Examples and Comparative Examples.
Summarized in.

The powder obtained in the examples was a high-purity powder containing a small amount of chlorine ions.

With respect to the zirconium oxide powders obtained in Examples and Comparative Examples, 57 mm × at a pressure of 700 kg / cm.
It was molded into 34 mm × about 5 mm. 2 at 1500 ℃ after molding
By firing for a time, a sintered body was obtained. The sintered body density was measured by the Archimedes method. Furthermore, a test piece of 3 mm × 4 mm × about 40 mm was cut out from the obtained sintered body, and the room temperature three-point bending strength was measured by the method specified in JIS R 1601.

The average results of 30 samples are shown in Table 2.

[0062]

[Table 1]

[0063]

[Table 2]

Claims (1)

[Claims] 1. An aqueous zirconium salt solution is heated in the presence of non-crystalline hydrated zirconia to hydrolyze, and then neutralized, and hydrated zirconia particles are separated from the obtained hydrated zirconia slurry, and the hydrated zirconia is hydrated. A method for producing zirconium oxide powder, which comprises calcining zirconia particles.