JPS5879866A - Manufacture of fine powder for ceramics - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Concerning powder manufacturing method.

Ceramics, which are metal oxides such as alumina and silica, are widely used due to their excellent heat resistance, corrosion resistance, and insulation properties. A wide variety of special functions have been discovered in aluminum, and it is becoming an increasingly important material.

Because the sintering temperature is extremely high when applied to It can be distributed. However, in order to stably produce metal oxide fine particles using this method, it is necessary to concentrate and dry the aqueous dispersion at a low concentration during the process, which requires a large amount of energy and is not efficient. The development of a method for concentrating is desired.

The present invention provides a novel manufacturing method for concentrating the above-mentioned fine powder for ceramics that can be sintered at low temperatures with low energy and high efficiency.

At the same time, the present invention provides a method for producing a fine powder for ceramics that can be kneaded and molded without kneading a molding binder by interposing a water-soluble polymer.

That is, the present invention is characterized in that conductive fine particles are concentrated in an aqueous dispersion of metal oxide fine particles with a particle size of 05μ or less obtained by hydrolyzing one or more metal alcoholades, and then dried. This is a method for producing fine powder for ceramics, which involves adding a water-soluble polymer deeply into an aqueous dispersion, depositing the water-soluble polymer on the electrode surface at the same time as metal oxide fine particles, and then concentrating the water-soluble polymer. This is a method for producing fine powder for ceramics containing a binder component, which is characterized by drying.

As the metal oxide of the present invention, any oxide obtained as described above from a metal alcolade that can form a metal alcolade can be used, and in particular, monovalent to tetravalent oxides can be used.
Oxides of valent metals are common, such as alumina, phosphoric acid,
Magnesium oxide, barium oxide, strontium oxide, lead oxide, zirconium oxide, nitrogen oxide, tin oxide, yttrium oxide, thorium oxide, etc., or a mixture of one or more alcoholates of the above metals, By hydrolyzing with water, it is possible to obtain a dispersion (so-called sol) of an oxide or a double oxide consisting of two or more metal oxides, which has a particle size of 0.5 μm or less and is stable in an aqueous phase.

If the particle size of the metal oxide of the present invention exceeds 0.5 μm, the sol in the aqueous phase becomes unstable and the sintering temperature during film formation increases, which is inappropriate, and the particle size is preferably 0.1 μm or less.
It is particularly preferred to have a particle size of 0.002 to 0.005 microns.

The aqueous dispersion of a metal oxide of the present invention is obtained by hydrolysis of a metal alcoholide, so it contains alcohol as well as water, but the alcohol is separated and removed unless alcohol is compatible with water. There's no need. From this point of view, methanol, ethanol, and isopropanol are the most common alcohols used in metal alcoholades.

Metal oxide fine particles usually have a positive or negative surface potential in the aqueous phase depending on their type, so if a conductive substance is used as an electrode and electricity is applied, the metal oxide fine particles with a positive charge will become a negative electrode or a negative electrode. The charged metal oxide fine particles are electrophoresed to the cathode, deposited on the surface of the conductive material, lose their surface charge, and are deposited.

The conductive non-electrolyte material used as the electrode of the present invention may be any material as long as it has conductivity and does not elute ions into the aqueous phase and contaminate the electrophoresis bath when electricity is applied. It is possible to use many materials that are less corrosive, such as lead, titanium alloy, gold, sea bream, platinum, and carbon.

It is also possible to perform electrophoresis using an aqueous dispersion of the metal oxide fine particles mentioned above, or by adding a water-soluble polymer to the bath. It is also possible to control. The above-mentioned water-soluble polymers include metal water-soluble polymers such as polyvinyl alcohol, polyacrylamide, polyvinylpyrrolidone, hydroquine ethylcellulose, #hull, polyethylene glycol, ethyl heptylulose, methoxycellulose,
Nonionic water-soluble polymers such as gum arabic, fir gum, and locust pea gum; for example, carboxyl methyl cellulose, unsaturated carboxylic acid salts alone or copolymers; anionic water-soluble polymers such as xanthan gum and carrageenan;
For example, various water-soluble polymers can be used, such as cationic water-soluble polymers such as polyamide amine, unsaturated quaternary ammonium salt copolymer, polyethyleneimine, cationized polyacrylamide, and cationized starch. A type having good entrainment with gold is appropriately selected and used depending on the type of metal oxide fine particles.

These water-soluble polymers are uniformly mixed with the obtained ceramic particles, and in processes such as pressure molding of ceramic particles, they act as binders between the particles and help maintain the shape of the molded product. , decomposes and disappears during sintering.

The content of the above-mentioned water-soluble polymer in the bone is usually 20% by weight or less, preferably 10% by weight or less, and particularly preferably 2 to 8% by weight, based on the metal oxide.

If the amount of water-soluble polymer is too large, the shrinkage rate after sintering will increase, the density of the sintered ceramic will decrease, or it will become porous, which is often undesirable. 10-250 volts DC, power supply 4-
The electrodes are immersed for a desired period of time.

The metal oxide or the mixture of metal oxide and water-soluble polymer deposited on the electrode is scraped off and dried at a temperature suitable for sintering to remove residual moisture or alcohol, thereby producing the fine powder for ceramics of the present invention. get it.

The electrode is shaped into a roll or a belt, a part of which is immersed in a lightning electrophoresis bath, and a device is connected to scrape off the metal oxide deposited on the exposed part to drive the roll or belt to continuously deposit the metal oxide. A method of continuously removing the precipitated metal oxide from the electrophoresis bath, such as a method of scraping off the deposited metal oxide, is usually preferred.

The fine powder for ceramics obtained by the method of the present invention described above can be sintered at low temperatures, and excellent ceramic products can be obtained.

Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to the Examples.

In addition, unless otherwise specified below, parts are based on weight.

Example 1 2.00% of 204y triisopropoxyaluminum
Pour into 80°C ion-exchange water at 0f with stirring and stir for 1 hour.Add 200f of 1N hydrochloric acid,
The mixture was stirred at 8° C. for 48 hours to perform hydrolysis and obtain an aqueous alumina dispersion. The average particle size of alumina measured by a scanning electron microscope was 0.02 μm, the alumina concentration in the aqueous dispersion was about 2 μm, and the isopropanol contained in the parent system was about 8% by weight.

The above alumina aqueous dispersion was placed in a porcelain container, a cylindrical drum-shaped lead electrode was half immersed in the liquid as a cathode, a plate-shaped lead electrode was used as an anode, and the electrode was connected to a 100-port DC power source to energize it. did. The cylindrical drum was rotated at a speed of 2 revolutions per minute, and a blade-type oyster remover was applied to the part not immersed in the liquid to scrape off the paste-like alumina deposited on the cylindrical drum.

The volatile components (water and impropatul) of the scraped alumina paste were approximately 40% by weight. When this paste-like alumina was heated in a hot air dryer at 110°C for 30 minutes, fine alumina powder with a volatile component of 0.02μ was obtained, and the particle size of the -order particles was 0.02μ. No change was observed.

This alumina fine powder 20? After adding 5% polyvinyl alcohol aqueous solution 209 and kneading it, it was dried at 110°C for 1 hour, then molded into a sheet with a thickness of 2 mm using a press at 100 kg/c, and heated at 900°C in an electric and air furnace. When sintering was performed for 1 hour, the alumina particles were sufficiently sintered to obtain a high quality ceramic sheet.

Example 2 To 1000 f of the aqueous dispersion of Example 1, 209 aqueous polyvinyl alcohol solutions were added, and electrophoresis was carried out in exactly the same manner as in Example 1 to obtain a paste-like alumina deposited on a cylindrical drum-shaped electrode.

The paste-like alumina had alumina content of 55 parts, 6 parts of tivolivinyl alcohol, 36 parts of water, and 3% isopropanol. Next, drying was carried out in the same manner as in Example 1, and fine alumina powder with a volatile content of 0.3 was obtained. This fine alumina powder was formed into a 21-it thick sheet using a press at 100 V4/cd, and sintered in an electric furnace at 900°C for 1 hour. The alumina particles were sufficiently sintered together and a high-quality ceramic sheet was obtained. It was done.

Example 6 152f of tetramethoxysilane was added to 1.0001 of 90
Pour into a 50.2% poly(acrylamide ammonium acrylate) ion exchange aqueous solution at ℃ with stirring,
Continue stirring for 1 hour and add 100f of 14 thiammonia water.
was added to perform hydrolysis at 90°C for 24 hours to obtain an aqueous silica dispersion. The average particle size of silica was 0.04μ, the silica concentration in the aqueous dispersion was about 5T, and the methyl alcohol contained in the parent was about 11T. [90% of the silica acrylamide unit, 10% of the ammonium acrylate unit] The above silica aqueous dispersion was placed in a magnetic container, a cylindrical drum-shaped lead electrode was half immersed in the solution as an anode, and a plate-shaped electrode was half immersed in the solution as a cathode. Electricity was applied by connecting to an 80 volt DC power source using lead electrodes.

In the same manner as in Example 1, the paste-like silica deposited on the cylindrical drum serving as the anode was scraped off.

The volatile components (water and methyl alcohol) of the scraped silica paste were about 40%.

This paste-like silica was dried in the same manner as in Example 1,
A fine silica powder with a volatile content of 0.2% was obtained.

This fine silica powder was pressed in the same manner as in Example 2,
When a sheet with a thickness of 2 mm was molded and sintered in an electric furnace at 1000° C. for 1 hour, the silica particles were sufficiently sintered together and a good ceramic sheet was obtained.

Example 4 2842 tetraisopropoxy titanium and 2551 diisopropoxy barium were poured into 98°C 5000f ion-exchanged water with stirring, and while stirring was continued for 1 hour, 1N-HCl 2009 was added, and the mixture was heated at 98°C for 48 hours. Hydrolysis was performed to obtain an aqueous dispersion of barium titanate.

The average particle size of barium titanate was 0.02 μ, the concentration of barium titanate in the aqueous dispersion was about 4%, and the isopropanol contained in the parent system was about 6 μ.

The above barium titanate aqueous dispersion was placed in a porcelain container, a cylindrical drum-shaped lead electrode was half immersed in the liquid as a cathode, and a plate-shaped lead electrode was used as an anode, connected to a 150 volt DC power source. The power was turned on. Electrophoresis was carried out in the same manner as in Example 1 to obtain barium titanate paste deposited on a cylindrical drum-shaped electrode. When drying was carried out in the same manner as in Example 1, fine barium titanate powder containing 45% O and volatile content was obtained. This notrium titanate fine powder 20
When sintering was carried out in an electric furnace prepared by adding 1 liter of hydroxyethyl cellulose aqueous solution 201 to f, the norium titanate was sufficiently sintered and a high quality ceramic sheet was obtained.

Patent applicant: Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Claims] An electrode made of a conductive non-electrolyte is immersed in an aqueous dispersion of metal oxide fine particles with a particle size of 0.5μ or less obtained by hydrolyzing 11 or more metal alcoholades and energized. A method for producing fine powder for ceramics, which comprises electrophoretically depositing metal oxide fine particles, concentrating the metal oxide fine particles on the surface of an electrode, and then drying. 2. A water-soluble polymer is added to an aqueous dispersion, and the water-bathable polymer is precipitated on the electrode surface at the same time as the metal oxide fine particles, concentrated, and then dried.It is characterized by containing a binder component. A method for producing a fine powder for ceramics according to claim 1.