JPS59111922A - Production of fine powder of zirconium oxide - Google Patents

Abstract

PURPOSE:An aqueous solution of zirconium salt is controlled in its pH, Zr concentration and sulfate ion concentration to effect the preipitation of an insoluble Zr salt and the precipitate is converted into the hydroxide with an alkaline substance, then dried and roasted to produce fine particles of ZrO2 with uniform particle size. CONSTITUTION:An aqueous solution of a Zr salt containing ZrO2 is controlled so that its pH becomes 0-2.5, its concentration becomes 0.1-2.0mol/l and the SO4<-->/Zr molar ratio ranges from 0.1-1.0. The resultant aqueous solution is heated, when necessary, and the reaction is effected under stirring to form an insoluble Zr salt containing sulfate ion. The precipitate is washed and converted into its hydroxide by reaction with an alkaline substance such as aqueous ammonia, then the hydroxide is dried, crushed and roasted. The process gives fine particles of ZrO2 of almost spherical form, thus showing good dispersibility.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the production of fine zirconium oxide powder whose particle size is uniformly controlled.

Zirconium oxide fine powder is used as a raw material for electromagnetic ceramics, wear-resistant tool ceramics, etc., and is desired to have high purity, particle size distribution within the range according to the purpose, and low manufacturing cost. 1 has been written.

The above objectives cannot be fully satisfied because there is a risk of contamination with impurities in the mechanical pulverization method, which is one of the current methods for producing fine zirconium oxide powder. When hydroxide particles with a particle size of 1 μm or less are synthesized in a liquid using a chemical treatment method using crushed inorganic salts or organic substances, solid-liquid separation is extremely difficult, and the dry product is difficult to separate. Are there problems such as extreme cases where the product becomes a gel-like substance that is difficult to crush? However, it does not fully satisfy the requirements that the manufacturing method is simple and that it can be produced industrially in large quantities.

In the present invention a, in order to overcome these drawbacks, l:su, for example, 2ZrO804.
O2-8H20 or Zr50g (804)2 ・14H
We make fine particles of insoluble zirconium salt with a uniform particle size and a composition such as 20. alkaline substance vc
After converting into a processed hydroxide, it is possible to produce fine zirconium oxide powder with a uniform particle size by drying and roasting.

According to Kenpo, by adjusting the pH 1 temperature, zirconium concentration, and sulfate radical concentration of the solution, it is possible to obtain well-formed, almost spherical particles with a certain average particle size in the particle size range of 0.01 to 2 μm. A powder can be obtained. In addition, solid-liquid separation is easy due to its filtration properties, and it does not become a gel-like substance even when dried, making it easy to crush.

To explain the present invention in more detail, any water-soluble zirconium salt can be used as the raw material. If an insoluble salt is used as the starting material, it may be changed to a water-soluble salt. A range of 0.1 to 2.0 mol/l is appropriate for the zirconium concentration, but the optimum range is 0.2 to 1.0 mol/l.
The concentration is While setting the hydrogen ion concentration of this zirconium aqueous solution at an appropriate point within the range of 1 pHo to 2.5, the sulfate radical concentration (so neemolar concentration/Zr molar concentration) was adjusted.
= Adjust to a desired ratio from 0.1 to 1.0. FIG. 1 is a relationship diagram of the molar ratio of sulfate to zirconium, the pH of the solution, n, and the particle size of the zirconium oxide powder to be obtained. Sulfate radical concentration a: Refer to this diagram to select the concentration corresponding to the desired particle size. pH
Once the sulfate concentration is adjusted, a precipitate of insoluble zirconium salts is formed. Although the precipitation reaction proceeds even if left at room temperature, it is accelerated by heating (from room temperature to the boiling point), and the reaction rate is close to 100%, although it varies depending on the pH and the concentration of sulfate groups.

After precipitation and solid-liquid separation of the soluble zirconium salt thus obtained, zirconium hydroxide is produced by directly adding an alkaline substance such as aqueous ammonia to the reaction Q. The hydroxide particles thus obtained are separated, thoroughly washed with water, and then dried. Observation of this dried product using a transmission electron microscope shows that it is well dispersed in primary particles. After completing this simple pulverization process, it is roasted at 700 to 800C to form an oxide.

Zirconium is generally dissolved in Zirconium salt aqueous solution.
It is dissolved in the rO state. The solubility of ZrO at 25C is 1 mol/l around pH 0.6, 1 Onnol/l around pH 1.5, and 10-3 m around pH 2.0.
ol/l is 1 o mol/l near pH 2.5, but 4 is actually stabilized in a supersaturated state at rrpHl of 5 to 2.0, and has considerable solubility. Methods for generating hydroxide precipitation from this supersaturated state include: 1) Increase the rate of hydroxide precipitation generation by heating.

2) Add alkali IJ' (+-) in excess to generate a precipitate. 3) Suspend fine particles as seed crystals. There are six possible methods.

Method 1) Specifically shown in Comparative Example (a) below, a flask with a reflux condenser was prepared with a ZrO2 equivalent concentration of 50 f/l and a pH of 1.2.
When you pour the liquid into it and heat it with a heater until it boils, hydrolysis will occur gradually and zirconium hydroxide will precipitate. The hydrolysis rate at this time was extremely slow, and boiling was continued for 4 days in a row, resulting in only about 0% of zirconium being precipitated. There are few particles that become the core when precipitation occurs, and is there an acid when precipitation occurs? This is thought to be because the OH- concentration in the solution decreases due to release, making it difficult for hydroxide to be generated. In this case, the particle size of the hydroxide particles is generally very fine, 20 to 50^,
Has sedimentation properties. When this precipitate is separated and dried, it becomes a white lumpy dried product that is somewhat hard and requires time to grind.

Method 2) Specifically, as shown in Comparative Example (kl) below, when aqueous ammonia is added to a solution with a ZrO2 equivalent concentration of 50 f/l and neutralized to pH 71, a precipitate of zirconium hydroxide is formed. It is a gel-like precipitate with very poor r-permeability.When this precipitate dries, it becomes a semi-transparent blocky dry product, which is very hard and cannot be turned into a fine powder unless a special pulverization method is used.

Method 6) Noting that the hydrolysis time was very slow in the experimental example of method 1), in order to speed up the hydrolysis time, as shown in Comparative Example (C) below, zirconium hydroxide, which is the core of precipitation, was of fine particles are added. As a result, zirconium hydroxide can be precipitated in about 2 days with a yield of 60 to 70%, whereas it takes 4 days for hydrolysis in method 1). The properties of the hydroxide particles in this case are the same as in the current method.

However, each of these methods has advantages and disadvantages as described below, and there are problems in actual operation.

Method 1) Hydrolysis takes time.

Yield is low.

The particles are dispersed and the particle size is small.

Solid-liquid separation possible.

Method 2) Good yield.

Difficult to crush dry products.

Particles are agglomerated.

Solid-liquid separation is not possible.

Method 3) The hydrolysis rate is faster than method 1).

Yield is low.

The particles are dispersed and the particle size is small.

Solid-liquid separation possible.

On the other hand, what are the advantages of the three methods mentioned above? A method that includes everything and avoids all disadvantages? This is what we provide.

That is, when a sulfate group is added to the zrO2+ solution, 2Z
rO8O4-ZrO2-8H20 Arage Zr50g
An insoluble basic sulfate with a composition such as (SO4)2-1'4H20 precipitates. When synthesizing these, pH1
By appropriately regulating the sulfate concentration and temperature, insoluble salts of zirconium can be obtained quickly and quantitatively.

These precipitates are fine white precipitates, have good settling and filtration properties, and are powder-like when dried. These compounds can be easily converted into hydroxides by adding an alkaline substance. The hydroxide obtained in this way has all the engineering properties of basic sulfate precipitation, and when it is dried and roasted at 700 - soo c, the -order particle size becomes 10.
Zirconium oxide fine powder with a size close to a spherical shape of 0 to 200 A and good dispersibility can be obtained.

In the present invention, as described above, once the insoluble zirconium salt is precipitated, then the insoluble zirconium salt is precipitated. A fine powder with a controlled average particle size through the simple operation of converting it into hydroxide with alkali? It is easy to filter and grind. Therefore, a generally used reaction tank with a stirrer is sufficient for the reaction equipment, and a normal centrifuge for solid-liquid separation is sufficient. It is very easy to mass-produce. It also has the advantage of safety since it does not involve flammable substances such as organic solvents or high temperature and high pressure conditions such as in an autoclave.

Next, Examples and Comparative Examples [, 1] will be explained in more detail.

Example 1 Zirconium carbonate (ZrO2 content 40-45% 12
．． Dissolve 5kg in 1.5t of hydrochloric acid (section 56) and 1.5t of water to create a zirconium hydrochloric acid solution. After obtaining it, it was diluted with water to give a ZrO2 equivalent concentration of 50! il/l and adjust the pH to 1.00. Ammonium sulfate? Add 0.55 mol to 1 mol of zirconium and bring to 80C with stirring.
After a period of reaction, an insoluble zirconium salt is precipitated.

After thoroughly washing the precipitate with decant washing, aqueous ammonia is added to adjust the pH to 8 to 9, and the precipitate is suction filtered and washed with water.

Fti, washed at 80C so that no sulfate groups were detected.
Dry with. After simple pulverization into a dry product, it is roasted at 700C for 5 hours. In this case, the yield was 97.5cm, the specific surface area was 40.87y+j/f, and the bulk density was 1.43f//ffl.
, tap density 2.46 ff1crl, average particle size 1.7
0ttm.

The crystal shape was monoclinic.

Example 2 Zirconium oxychloride crystal (Zr0O12.8H,O
Dissolve J in water and make ZrO2a degree to 220-250 Y
/l solution, diluted with water, and converted to ZrO2 in SO
y7t solution? Adjust the pH to 1.30. This solution was added at a ratio of 45 moles of ammonium sulfate '1Zr021 to 45 moles of skin, and reacted at 80C for 1 hour to obtain a precipitate of an insoluble zirconium salt. Ammonia water in this precipitation? The mixture was added to adjust the pH to 8 to 9, converting the precipitate into hydroxide, filtering and washing, drying at 80C, and roasting at 700C for 5 hours. In this case, the yield is 99.5%, the specific surface area is 55.0 m2/7, the bulk density is 0.53 t/d, and the tap density is 1.15 f/d.
The average grain size was 0.23 μm, and the crystal structure was monoclinic.

Example 3 Zirconium carbonate (ZrO2 content 4j] to 45) 10
kg of hydrochloric acid (36%), dissolved in 3 tons of water, and then this? ZrO2 content 50 when diluted with water? /l liquid 80t
K Tsuguru. At this time, the pH was 1.5 to 1.7. In this solution, ammonium sulfate f is added to 0.4 moles per 21 moles of Zr0.
The mixture was added in a proportion of 5 moles and reacted at 80C for 1 hour.

Next, ammonia water was added to this reaction solution to pH 8~? Solid-liquid separation is performed using a centrifuge.

After thorough washing with water, the hydroxide was dried and roasted at 700C for 10 hours. In this case, the yield i is 99.9%, the specific surface area is 66.3.17y, the bulk density is 0.39 f/7, the tap density is 0.73 V/d, the average grain size is 0.1 μm or less, and the crystal type is monolithic. Orthoclic 'T: Yes.

The above example is a typical example, but as a result of many more tests, we found that the molar ratio of sulfate and zirconium, the pH of the solution at 7Z, and the average particle size of the final ZrO2 were determined. The relationship a is as shown in Figure 1. In this way, the particle size of the Zr02 product can be adjusted from the conditions used to produce the insoluble sulfate compound.

Comparative Example (a) As in Example 1, the concentration in terms of ZrO2 was so? /
L, pT (1 ton was added to a solution of 1 and 2) and heated and boiled in a flask equipped with a reflux condenser. Hydrolysis occurred and a precipitate of zirconium hydroxide was obtained, but the rate was extremely slow and the reaction rate was 60% in 4 days. This precipitate was separated and dried to obtain a white lump, but it was difficult to grind and a fine powder could not be obtained.

(b) KZr'02 equivalent concentration T50 as in Example 1
A solution i1t of f//l and pH 1 and 2 was taken, and ammonia water was added thereto to pH 7 and neutralized with Oi to form a precipitate of zirconium hydroxide. This precipitate had low settling properties and was extremely difficult to filter. The dried precipitate is semi-transparent and lumpy.
It was also very hard and could not be crushed into a desired fine powder.

(C) Same as Example 1, ZrO2 equivalent concentration is 50
A solution 2iz of f/l, pH 1,2 was taken, and all fine powder of zirconium hydroxide was added thereto for the purpose of removing hydrolyzed Venus. As a result, zirconium hydroxide was precipitated in 2 days with a yield of 65%. The dry product of this precipitate contained white lumps that were difficult to grind, and the desired fine powder could not be obtained.

[Brief explanation of drawings]

Fig. 1 is a relationship diagram showing the relationship between the molar ratio of acid radicals and zirconium, the pH of the solution at that time, and the average particle size of the finally obtained zirconium oxide powder. Applicant: Dowa Chemical Co., Ltd. Company diagram 1

Claims (1)

[Claims] An aqueous solution of zirconium salt has a hydrogen ion concentration of 0.
~2.5 range, zirconium concentration 75J0.1~2.
In the range of 0 mol/l, the molar ratio of sulfate radicals/zirconium is 0
．． A precipitate of an insoluble zirconium salt containing a sulfate group is generated from this solution by adjusting the ratio to be in the range of 1 to 1.0, and the resulting precipitate is reacted with an alkaline substance to form a hydroxide. thing? A method for producing fine zirconium oxide powder, which comprises drying and roasting.