JPH038703A - Production process for platelet particles of metal oxide - Google Patents

Abstract

PURPOSE:To enable high-efficiency production of platelet particles of metal oxide by hydrolyzing an organometallic compound and dehydrating the hydrolyzate in an electric field so that the thermal diffusion motion of the metal oxide particles are regulated in a two-dimensional direction to make the particles into platelets. CONSTITUTION:The reactor is equipped with the anode and cathode inside. A solution of an organometallic compound such as tetramethoxysilane in an organic solvent such as ethanol, a small amount of water and a catalyst such as aqueous ammonia are charged in the reactor. Then, direct current is applied between the electrodes to effect hydrolysis and dehydration in an electric field. Thus, the formed fine particles of metal oxide such as silicon oxide are regulated in their thermal diffusion motion into a two-dimensional direction whereby platelet particles of metal oxide suitable for fine ceramics or paper-coating pigment are obtained. The application of electric field may be limited only to the dehydration reaction stage.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for producing metal oxide plate-like particles, and more particularly to a method for efficiently producing non-spherical plate-like metal oxide particles.

<Prior art> A method for producing metal oxide particles is a method in which silica particles of 0.05 to 2 μm are produced by contacting an alkyl silicate with ammonia and water in an alcohol solvent (J
, Co11oid & InterfaceSc
i,,26.62. (1968)), a method for producing silica particles by mixing and contacting alkyl silicate, ammonia, and water in a solvent containing alcohol and a hydrocarbon (Japanese Patent Application Laid-open No. 153110/1983), hydration of an organometallic compound in an alcoholic solvent Decomposes to an average particle size of 0.0
Method for producing 5-2 μm oxide spherical particles (Japanese Unexamined Patent Publication No. 1983
2-207356), Method for producing monodispersed hydrated silica from hydrolysis of ethyl orthosilicate (Journal of the Chemical Society of Japan 1981. (91, 1503-1505), Monodisperse/spherical sol of metal oxides and hydroxides) (Japan Chemical Industry Center, New Experimental Chemistry Course (2) Interfaces and Colloids p323) etc. are known. These methods can yield monodisperse fine particles. However, the resulting particles are spherical. and is not plate-like.

On the other hand, fine ceramics and paper coating pigments.

Internal fillers for paper, fillers for plastics, pigments for paints.

Non-spherical inorganic oxide particles such as root-like, JI-fibrous or lump-like particles are required in the fields of cosmetic vehicles, chemical industries such as ceramics, and building materials. As a method for producing such non-spherical inorganic oxide particles, there is a method for producing plate-shaped kaolinite (Clays and Clay Mineral
s 33(3), 200-206. (1985
)), method for producing hexagonal plate-shaped ferrite particles (Japanese Patent Publication No. 6015574), method for producing β-iron oxyhydroxide particles (Japanese Patent Publication No. 61-288), flaky α-ferric oxide particles (Japanese Unexamined Patent Publication No. 61-122127), a method for manufacturing synthetic mica powder (Unexamined Japanese Patent Publication No. 63-18396)
Publication No. 2), etc. are known. However, neither of these uses organic metal compounds as raw materials. Therefore, when producing inorganic oxide particles using these methods, high temperature and high pressure are required for the reaction, and an oxidation reaction using molecular oxygen is required, so the resulting particles tend to aggregate and become monolithic. Difficult to obtain dispersions.

<Purpose of the Invention> As a result of intensive research into a method for producing monodisperse plate particles by eliminating the drawbacks of the above-mentioned method for producing plate particles, the present inventor has developed a method for producing monodisperse plate particles using an organometallic compound as a raw material. The inventors have discovered that 1q of monodisperse metal oxide plate particles can be obtained by carrying out at least the dehydration reaction under an electric field during hydrolysis and dehydration reactions, and have thus arrived at the present invention.

An object of the present invention is to provide a method for efficiently producing metal oxide plate particles using a metal compound.

<Advantageous Effects of the Invention> According to the present invention, an object of the present invention is to provide a method for producing metal oxide particles by avoiding a hydrolysis reaction of an organometallic compound and then subjecting it to a dehydration reaction. Metal oxide plate-like particles, characterized in that the thermal diffusion movement of the generated metal oxide fine particles is regulated in two-dimensional directions by at least carrying out a dehydration reaction under an electric field to form plate-like particles. This is achieved by the manufacturing method.

The organometallic compound used in the present invention is
Metal compounds containing hydrolyzable modified groups, such as silicon and titanium, as exemplified in Japanese Patent No. 7356.

Any metal compound such as zirconium that can be hydrolyzed to form a metal oxide (inorganic oxide) may be used.
)4 (However, M is Si, Ti or Zr, and R
is an alkyl group) are particularly preferred. Specifically, tetramethoxysilane, tetraethoxysilane, and tetraisopropoxysilane.

Tetrabutoxysilane, tetramethoxytitaniumtetraethoxytitanium, tetraisopropoxytitanium, tetrabutoxytitanium, tetramethoxyzircon, tetraethoxyzircon, tetraisopropoxyzircon, tetrabutoxyzircon, tetra(2-ethylhexyl)titanate, zirconium acetate, zirconium oxa rate.

Zirconium lactate, titanium lactate, titanium acetylacetonate, zircon acetylacetonate-1~
, titanium octylene glycolate, titanium triethanolaminate, and the like.

The organometallic compound is preferably purified silicon.

The main raw materials are organic metal compounds such as titanium and zirconium, but they also contain sodium.

Potassium, rubidium, cesium, magnesium.

Composite particles of oxides of silica, titanium, zirconium and oxides of the above metals are obtained by coexisting organometallic compounds or inorganic salts such as calcium, strontium, barium, boron, aluminum, gallium, and indium and hydrolyzing them. You can also do that. At that time, silicon in the oxide particles.

70% atomic ratio of titanium and zirconium oxides
It is preferable to set it as above.

As a solvent for carrying out the hydrolysis reaction and dehydration reaction of the above-mentioned organometallic compound, alcoholic solvents or solvents containing alcohol and hydrocarbons are exemplified in JP-A-62153110M and JP-A-62-207356. is preferred. Alcohols in alcoholic solvents include methanol, ethanol, isopropanol,
Butanol, isoamyl alcohol, ethylene glycol, propylene glycol, etc. can be used singly or in combination. A portion of an organic solvent such as dioxane, diethyl ether, or ethyl acetate may also be mixed into these solvents. Furthermore, the hydrocarbon is not particularly limited as long as it is compatible with alcohol.

From 5 to 5 carbon atoms due to the ease of solvent recovery and the price of hydrocarbons.
12 aliphatic and alicyclic groups.

Aromatic hydrocarbons are preferred, and hydrocarbons having 6 to 9 carbon atoms are particularly preferred. Such hydrocarbons include n-hexane, n-hebutane, cyclohexane, methylcyclohexane, benzene, toluene.

Examples include xylene and the like.

The use of the above-mentioned solvent m for organometallic compounds has the effect of suppressing particle aggregation and making the particle size uniform, but on the other hand, the rate of dehydration reaction tends to slow down and production efficiency tends to decrease. . On the other hand, if the amount of solvent is too small, the generated fine particles tend to aggregate. Therefore, the ratio of the solvent to the organometallic compound is preferably 2 to 70 times (8, more preferably 4 to 50 times).

Regarding the method of adding the organometallic compound to the solvent, the organometallic compound may be added at once or may be added in several parts. Alternatively, after adding the organometallic compound to the solvent, this solution may be added to a different solvent.

In order to hydrolyze the organometallic compound, the amount of filtered water added needs to be at least twice the molar ratio of the organometallic compound. Although the amount is preferably 4 times or more, there is no adverse effect on the hydrolysis reaction due to a large amount of water. However, if the amount is too large, the speed of the dehydration reaction will slow down and the production efficiency will decrease, so it is preferably 200 times or less.

As a catalyst for hydrolysis reaction and/or dehydration reaction, N
1*, cations such as Na+ and S'042- H2
An anionic catalyst component such as PO4- can be added, but its presence or absence and duration vary depending on the type of organometallic compound used.

The hydrolysis reaction and/or dehydration reaction can be carried out at any temperature and pressure, but from the viewpoint of operability, it is preferable to carry out the reaction at a temperature below the boiling point and above the freezing point of the solvent used under normal pressure.

The electric field in the present invention is the application of a direct current electric field or an alternating direct current electric field between a pair or more of cathode/anode elements installed in a reactor in which a hydrolysis and/or dehydration reaction is carried out. The strength of this electric field is greater than or equal to 50 V/cm per unit spacing between the negative/anode elements.

If the electric field strength is less than 50 v/cIn, the thermal diffusion motion of the fine particles (core particles) cannot be sufficiently restricted substantially in two-dimensional directions, which is not preferable. The strength of the electric field may be changed continuously or stepwise depending on the progress of the reaction, but only once.

One or more pairs of cathode/eleven pole elements installed in the reactor must be kept wholly or partially immersed in the reaction solution at all times. Due to the reaction under such an electric field, the thermal diffusion motion of the generated fine particles (core particles) is regulated in a substantially two-dimensional direction, and therefore the growth of the fine particles is regulated in the two-dimensional direction to become plate-like particles.

According to the present invention, metal oxide plate-like particles are formed in a monodisperse state t'c
It can be manufactured efficiently. The plate-like particles obtained by the method of the present invention have excellent particle size uniformity, for example, 0.01 to 2
0um, even 0.01-10μT11, especially 0.05
It has an average particle size of ~4 μm, and 2.5 or more, and even 3
．． Those having an average plate ratio (plate diameter/plate thickness) of 5 or more, such as Reramix, paper coating pigment 1, internal filler for paper, filler for plastics.

It is useful in fields such as pigments for paints, vehicles for cosmetics, ceramics, and as a lubricant for base films for magnetic recording media, such as polyester films.

<Example> The present invention will be further explained below with reference to Examples.

Note that parts in the examples indicate heavy products. Further, the characteristic values and characteristics of the ladder in the present invention are determined and defined as follows.

(1) Average particle size of particles Centrifugal automatic particle size measuring device CAPA-50 manufactured by Horiba, Ltd.
0).

(2) Particle shape The obtained particles are observed using a scanning electron microscope.

Example-1 A pair of cathode element and anode element were provided in a reactor, the distance between them was maintained at 50 mm, and 27 parts of ethyl orthosilicate and 33 parts of methanol were added at the same time.

Rough, 100 parts of ethanol and 17 parts of 28% ammonia water
Immediately after simultaneously adding 1 part and 3 parts of distilled water, a 450 V DC electric field alternating at 30 second intervals was applied to the cathode/anode element. After reacting for 30 minutes at room temperature, the application of the electric field was stopped, 200 parts of ethanol was added to the reactor, and the reaction product was taken out. The average particle size of the generated silicon oxide particles is 0.5
2 μm, and the average plate ratio (plate diameter/plate thickness) was 7. The particles were monodisperse particles.

Example-2 The spacing between each pair of cathode elements and anode elements was maintained at 8M, and ter from one end of a reactor in which three pairs of negative/positive elements were installed
A volume of 50 parts of t-butyl alcohol, 2 parts of tetraisopropyl titanate, and 0.2 parts of distilled water were continuously supplied. At this time, the applied electric field is applied from the upstream side at an alternating interval of 10
The voltage was 150V DC electric field for 10 seconds, a 250V DC electric field for 10 seconds, and 500V DC electric field for 30 seconds. The total amount of feed was adjusted so as to keep the reactor at 1 and the average residence time of the reactor at 60 minutes, and the reaction product was taken out from the other end. The produced titanium oxide particles were monodisperse particles, the average particle size was 0.23 μm, and the shape of each particle was plate-like (average plate-like ratio=7).

Example 3 A pair of cathode elements and anode elements were provided in a reactor, the distance between them was maintained at 20 m, and 30 parts of tert-butyl alcohol, 70 parts of isopropanol, 8 parts of zirconium tetra-n-butoxide, and 2 parts of distilled water were prepared. parts were added at the same time. Immediately thereafter, a DC electric field of 300 V was applied at alternating intervals of 15 seconds to carry out the reaction at room temperature. After reacting for 50 minutes, a DC electric field of 5 oov <alternating interval 15 seconds> was applied for 40 minutes. Thereafter, the application of the electric field was stopped, 200 parts of distilled water was added to the reactor, and the reaction product was taken out. The generated zirconium oxide particles are monodisperse particles, and the average particle size is 0.1
The particle size was 8 μm, and the shape of each particle was plate-like.

Comparative Example-1 100% ethanol in a complete mixing tank reactor equipped with a stirrer
17 parts of 28% ammonia water and 2 parts of distilled water were added and mixed well. Thereafter, 33 parts of methanol and 9 parts of ethyl orthosilicate were added simultaneously, and the mixture was allowed to react at room temperature for 60 minutes while stirring at a slow speed. Thereafter, the reaction product was taken out. The average particle size of the silicon oxide particles produced by the reaction was 0.72 μm. The shape of the particles was perfectly spherical.

Comparison Control 2: Add 3 parts of tetraethyl titanate, 100 parts of ethanol, and 0.2 parts of distilled water to a complete mixing tank reactor equipped with a stirrer, and add 4 parts of tetraethyl titanate at room temperature while rotating the stirrer at 20 rpm.
The reaction was allowed to proceed for 0 minutes. After the reaction was completed, the product was taken out and spherical titanium oxide particles with an average particle size of 0.21 μm were obtained.

Comparative Example-3 100 parts of isopropanol, 5 parts of zirconium tetra-n-butoxide, and 1 part of distilled water were added to a complete mixing tank reactor equipped with a stirrer, and lj! The reaction was allowed to proceed at room temperature for 30 minutes while rotating the stirrer at 100 rpm.

After the reaction was completed, the product was taken out and the average particle size was 0.1.
Spherical zirconium oxide particles with a diameter of 8 μm were obtained.

Claims (1)

[Scope of Claims] 1. A method for producing metal oxide particles by subjecting an organometallic compound to a hydrolysis reaction and then subjecting it to a dehydration reaction, in which at least the dehydration reaction of the above two reactions is carried out under an electric field. A method for producing metal oxide plate-like particles, characterized in that the thermal diffusion movement of the generated metal oxide fine particles is restricted in two-dimensional directions to form plate-like particles. 2.Claim 1, wherein the organometallic compound is a metal alkoxide.
Manufacturing method described. 3. The manufacturing method according to claim 1 or 2, wherein the main metal component of the organometallic compound is silicon, titanium, or zirconium. 4. The manufacturing method according to claim 1, wherein the electric field is a DC electric field or an alternating DC electric field with a potential gradient of 50 V/cm or more.