JPS62212225A - Production of zirconia-containing fine powder - Google Patents

Abstract

PURPOSE:To produce zirconia-containing fine powder having improved dispersibility, by adding a basic substance to an aqueous solution of a Zr salt or it and a specific metallic salt to give a hydroxide, dehydrating, drying and calcining. CONSTITUTION:A basic substance such as NaOH, NH3, etc., is added to an aqueous solution containing a Zr salt (e.g. ZrCl4) or it and at least one salt of metal selected from Y, Ca and Mg to give hydroxide precipitate, which is sufficiently washed with water, filtered and separated from the mother liquor. Then, the precipitate is dispersed into an organic solvent such as benzene, propanol, etc., distilled under heating, dewatered, dehydrated, put in an autoclave, pressurized under heating until pressure reaches >=0.5kg/cm<2>G, pressure in the autoclave is rapidly reduced, the precipitate is dried and calcined at 300-1,200 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing fine zirconia powder with excellent dispersibility.

Zirconia has three types of crystal structures: monoclinic, tetragonal, and cubic, and has a corrosion resistance of 9 toughness.

Because it has properties not found in other materials, such as oxygen ion conductivity, it is used in a variety of applications such as oxygen sensors, electronic components, various structural materials, and biological materials, and is expected to become increasingly important as a material in the future. is expected. Further, the fine powder with excellent dispersibility provided by the present invention has the following uses. That is, it is used for reinforced ceramics or dispersion-strengthened alloys by being dispersed in ceramics or metals, and it is also dispersed in base materials such as glass, plastic molded products, sheets, films, etc., or coating films are formed on the above base materials. It is used to impart or improve functions such as heat resistance, antireflection, conductivity, ultraviolet absorption, enhanced hardness, chemical resistance, and durability to the base material.

In particular, when applied to a transparent substrate, the above functions can be imparted and improved without impairing the transparency of the substrate.

[Conventional technology]

As a method for producing zirconia fine powder, a hydroxide precipitate is removed by completely mixing an aqueous solution containing a zirconium salt or a salt of at least one metal of yttrium, calcium, or magnesium as a stabilizer with an alkali. A method is known in which a fine powder containing zirconia is produced by washing the precipitate with water, drying, and calcining it.

However, the powder obtained by this method is only one in which the particles are aggregated and have poor dispersibility.

In Japanese Patent Publication No. 59-39367, for the purpose of improving dispersibility, the precipitated particles of hydroxide containing zirconium that have been washed with water are not dried and calcined immediately after being separated from the mother liquor.
A method is disclosed in which precipitated particles are dispersed in an organic solvent and subjected to heating distillation to remove water, and the primary particles are dispersed in the organic solvent, followed by drying and firing under reduced pressure and atmospheric pressure.

Although the described method has shown some improvement in dispersibility, it is still insufficient. Further improvement is required especially when the particle size is small and tends to aggregate.

The reason why precipitated particles of hydroxide containing zirconium aggregate during the drying process is due to the moisture in the precipitate.

Therefore, in order to remove water from the hydroxide precipitate prior to the drying process, methods such as washing the hydroxide with an all-organic solvent, or dispersing the hydroxide in an organic solvent and removing water by azeotropic distillation are applied. Ru. However, these methods alone were not able to completely remove the moisture in the hydroxide precipitate, and during the drying process, the residual moisture acted to cause the precipitate particles to coagulate, causing the hydroxide precipitate to shrink. It becomes a dry body. In the subsequent firing process, agglomeration and shrinkage further progress, resulting in a powder with poor dispersibility.

The present inventors have discovered that by drying under pressure a hydroxide precipitate from which water has been removed using an organic solvent, a zirconia-based fine powder with greatly improved dispersibility can be obtained. This led to the present invention.

〔means〕

That is, the present invention is specified as follows.

Zirconium salt or zirconium salt and yttrium,
A hydroxide precipitate is obtained by mixing a basic substance with an aqueous solution containing a salt of at least one metal such as calcium or magnesium, and the precipitate is washed with water, filtered, and then dispersed in an organic solvent, followed by heating distillation. A method for producing a zirconia-containing fine powder, which comprises dehydrating, drying under pressure, and then firing.

The present invention will be explained in more detail below.

An aqueous solution of water-soluble zirconium salts such as zirconium chloride, zirconium nitrate, zirconium sulfate, and organic acid zirconium salts, or one or more compounds soluble in the aqueous solution of water-soluble salts of yttrium, calcium, and magnesium or water-soluble zirconium salts. Prepare an aqueous solution.

Next, the aqueous solution is mixed with a basic substance such as sodium hydroxide, sodium carbonate, or ammonia, particularly preferably aqueous ammonia, to obtain a hydroxide precipitate. The precipitate is thoroughly washed with water and separated from the mother liquor by filtration.

The precipitate thus obtained is dispersed in an organic solvent and water is removed by heated distillation. The organic solvents to be used include aromatic compounds such as benzene, toluene, xylene, and phenol, aliphatic alcohols such as glopanol, butanol, (butanol, octatool, isoamyl alcohol, hexanol, and cyclohexanol), and esters such as methyl benzoate. can be used, but hydrophilic alcohols having 3 to 10 carbon atoms, such as pronoJ?nol, butanol, pentanol, and octatool, are particularly preferred. It is desirable that the total amount of water in the precipitate is within the water solubility of the alcohol used.The precipitate that has been dehydrated by distillation is then placed in an autoclave and heated and pressurized.After reaching the set pressure, the pressure is increased. Drying is carried out while discharging the organic solvent so that the organic solvent remains constant, and when the organic solvent is no longer discharged, the pulp of the autoclave is opened and the pressure inside the autoclave is rapidly reduced, so that the organic solvent remains in the precipitate layer inside the autoclave. Drain the organic solvent and water all at once and dry it. If the organic solvent and water are not completely drained, air or nitrogen gas is further introduced into the autoclave to pressurize it, and then the pressure inside the autoclave is rapidly reduced. By repeating this operation several times, the precipitate in the autoclave is dried.

The thus obtained dried precipitate is taken out of the autoclave and calcined in a calcining furnace at a temperature of 300 to 1200°C to obtain fine zirconia powder with good dispersibility.

[Effect]

By drying the precipitate from which all water has been removed using an organic solvent under pressure, the precipitate can be dried without shrinking.
Therefore, agglomeration of the primary particles can be prevented even in the next firing step, and a fine powder with good dispersibility can be obtained. The effect of the present invention is recognized as long as the pressurization condition is 0.5 atm (r-dipressure) or more, but it is preferably applied from 3 atm to its critical pressure.

Furthermore, drying under pressure allows for uniform drying in a comparatively shorter time than under reduced pressure or normal pressure, and is therefore an advantageous method for streamlining the drying process.

In addition to the methods described above, as a method for obtaining a hydroxide precipitate by mixing an aqueous solution containing a zirconium salt and a basic substance, the basic substance may be added directly to the aqueous solution containing all the zirconium salts, or Although an aqueous solution containing a zirconium salt may be added to an aqueous solution of a basic substance, it is necessary to uniformly disperse stabilizers such as yttrium oxide, calcium oxide, magnesium oxide, etc. in zirconia and use fine powder with a uniform particle size. In order to obtain zirconium salt, an aqueous solution containing a zirconium salt and an aqueous solution of a basic substance are each quantitatively fed into a stirring reactor using a metering pump or the like so that the - inside the reactor remains constant, and the reaction is carried out. A flow reaction system is desirable, in which the reaction is carried out continuously while the reaction liquid is flowing out so that the amount of liquid in the reactor remains constant.

Example 1 3 mol% as ittria (Y2O,)? A mixed aqueous solution of yttrium chloride and zirconium oxychloride was prepared so as to contain yttrium chloride and zirconium oxychloride. The liquid concentration is zirconia (ZrO2)
As 0.15 mol/! And so. Internal volume 2 with overflow tube and stirrer! Water was placed in a seed reactor and aqueous ammonia was added thereto to adjust the pH to 1s.s. Add the above mixed aqueous solution to this at 1 minute per minute! At the same time, aqueous ammonia (28% by weight aqueous solution) II: - in the tank is about 8.
5, respectively, using a metering pump. The hydroxide was discharged through an overflow pipe and received in a separate tank. During the reaction, the volume of the reaction solution was kept at about 2J, and the - of the reaction solution was kept at about 8.5.
The neutralization coprecipitation reaction was carried out continuously while finely adjusting the amount of ammonia water so that it was ±0.2. The obtained hydroxide was washed by sonic decantation until the chlorine ion concentration in the mother liquor became 2 PPM or less, and then the hydroxide was separated from the mother liquor by filtration. The hydroxide thus obtained 5 Kg 'k n-butanol 40! dispersed in
Dehydration is carried out by performing atmospheric distillation until the solution temperature reaches 105°C, and then the sludge containing this dehydrated hydroxide is obtained. J-t-5! was placed in an autoclave. Next, the pressure in the autoclave was increased by heating, and n-butanol and water were discharged while the control pulp was operated so that the pressure inside the autoclave became 5 to 9/c1rI2. After about 30 minutes, no discharge of n-butanol or water was observed, so the control pulp was fully opened, the remaining n-butanol was discharged all at once, and the hydroxide was dried. After cooling, the dried product was taken out of the autoclave and further fired at 700°C for 1 hour in a firing furnace to obtain fine zirconia powder 503? containing Y2O33 mole and having good dispersibility. was gotten. The fine powder observed has a specific surface area of 77 m''/? and an average particle size of 0.
．． It was 0.013 μm.

Using this fine powder to make 500 yen using the rubber press method? /
A cylindrical body with a diameter of 10 fiφ and a length of 12 pieces was molded at a pressure of -, and the pore size distribution was measured using a porosimeter. As a result, only pores with an average size of 0.015 μm caused by secondary particles were found, and no pores caused by agglomerated particles were observed, resulting in a fine powder with good dispersibility.

The results of this porosimeter are shown in FIG.

Comparative Example 1 Hydroxide 5 prepared in the same manner as in Example 1 and washed with water was dehydrated by distillation at atmospheric pressure in n-butanol in the same manner as in Example 1 using 9e. The slurry containing the dehydrated hydroxide was then dried at 70° C. for 8 hours under reduced pressure. By firing the obtained dried product in a firing furnace at 700°C for 1 hour, Y2O3-containing zirconia fine powder 507
%'i got. The obtained fine powder has a specific surface area of 60 m2
/9-.

Using this fine powder, the rubber press method
At a pressure of Kg/crIr2, the diameter is 10 mm and the length is 12 mm.
A cylindrical body was formed and the pore size distribution was measured using a porosimeter. As a result, an average of 0.0
An average of 0.5 mm due to the 23 μm pores as well as the agglomerated particles.
Pores of 0.055 μm were also observed, indicating that the fine powder had insufficient dispersibility.

The results of this porosimeter are shown in FIG.

Example 2 Pure water 3! Zirconium oxychloride 290P,! : Calcium chloride (CaCt2'6H20) 6.09% was dissolved in an aqueous solution by adding ammonia water under stirring until -10 to obtain a hydroxide precipitate, washed with water by decantation, and filtered. The hydroxide was separated from the mother liquor. The obtained hydroxide was dispersed in 1-pentanol and dehydrated by distillation under atmospheric pressure until the solution temperature reached 110°C, and then the slurry containing all of the dehydrated hydroxide was poured into an automatic slurry. I put it in a crepe. Increase the pressure by heating the autoclave, and control pulp' so that the pressure inside the autoclave becomes 20K9/cm2.
e While operating, ethanol and water were discharged from 1-. After about 15 minutes, no discharge of 1-pentanol and water was observed, and then the control pulp was fully opened to discharge the remaining 1--2 pentanol and water all at once. After this, nitrogen gas was further introduced into the autoclave and the inside of the autoclave (D pressure? 10 K4/cm2
By raising the pressure to 100%, then fully opening the control valve, and repeating the operation twice to rapidly reduce the pressure inside the autoclave, the trace amount of 1 remaining in the autoclave was removed.
- Pentanol and moisture were completely drained and drying was performed. The dried material was calcined at 900°C for 3 hours.
A fine zirconia powder containing 0.03 molti and having good dispersibility was obtained. The specific surface area of this fine powder was 30 m2/9-.

Using this fine powder, a cylindrical body with a diameter of 10 mm and a length of 12 was formed using a rubber press method at a pressure of 1000 to 9/cm'', and the pore size distribution was measured using a porosimeter.The results were as follows. - average 0.035 due to secondary particles
It was a fine powder with good dispersibility, with only μm pores and no pores due to aggregated particles.

[Brief explanation of drawings]

FIG. 1 is a graph showing the pore distribution of the zirconia powder obtained in Example 1, and FIG. 2 is a graph showing the pore distribution of the zirconia powder obtained in Comparative Example 1.

Claims (1)

[Claims] (1) A hydroxide precipitate is obtained by mixing a basic substance with an aqueous solution containing a zirconium salt or a zirconium salt and a salt of at least one metal of yttrium, calcium, and magnesium, and the precipitate is washed and filtered with water. A method for producing a zirconia-containing fine powder, which comprises dispersing it in an organic solvent, dehydrating it by heating and distilling it, drying it under pressure, and then firing it.