JPS6158220B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides ultrafine particles of metal compounds and metalloid compounds such as metal or metalloid hydroxides, carbonates, sulfides, formates, acetates, etc., which are raw materials for metal or metalloid oxides or metal or metalloid compounds. Regarding manufacturing methods. Unless otherwise specified, "metal" is used below.
The term is used to mean "metal or metalloid." Metal oxide fine particles are used in large quantities in catalysts, ceramic materials, electronic materials, magnetic materials, adsorbents, jewelry, powder metallurgy materials, and the like. The characteristics of metal oxide fine particles required for these uses include particle size, uniformity of particle size distribution, purity, uniform and easy mixing of multicomponent metal oxides, economic efficiency, and the like. The smaller the metal oxide particles, the more active they are.
Furthermore, since the specific surface area is large, ultrafine metal oxide particles are useful as the above-mentioned material. Particle uniformity is important in producing a homogeneous product because it improves particle packing during molding. Impurities adversely affect catalyst activity and sintering. The reaction of ceramics, that is, the sintering of multicomponent systems, is generally a high-temperature solid-phase reaction, so the reaction rate is slow, and the reaction proceeds by repeating the following steps: baking, cooling, crushing, mixing again, and baking again. Therefore,
By homogeneously mixing the ingredients before baking and further increasing the reaction rate, multiple baking operations can be omitted or shortened. Various methods have been developed to produce fine metal oxide powders. For example, a method is known in which a metal salt solution is supplied into a fluid energy mill operated at 500°C or higher, and oxidation, decomposition, and pulverization are performed simultaneously to obtain a fine powder (Japanese Patent Publication No. 8637/1983).
Japanese Patent Publication No. 47-6207 discloses that a combustible liquid is explosively combusted and the heat generated is used to instantaneously oxidize a metal salt to obtain a fine powder. Although the particle size of the metal oxide obtained in this way is from several tens of angstroms to several hundreds of angstroms, these devices are unsatisfactory in terms of economy and particle size distribution. Furthermore, a method is known in which aluminum hydroxide is obtained by blowing carbon dioxide gas into a sodium hydroxide solution containing aluminum ions, such as the carbon dioxide gas blowing method used in the production of aluminum hydroxide.
The size of particles obtained by this method is approximately several micrometers, and the particle size distribution is not uniform. In the method of producing metal hydroxide by adding aqueous ammonia to an aluminum chloride solution, particles grow during precipitation and become particles of about 70 Å to 1000 Å, making it impossible to obtain a product with a wide and uniform particle size distribution. In this case, even if the reaction solution is diluted or stirred, no significant effect can be obtained. We have solved the above problems at once and found a method to inexpensively produce uniform fine particles of several tens of angstroms of metal compounds. Therefore, the present invention provides a method for supplying a reactive gas mixed with an inert gas or air to a solution of a metal compound or a metalloid compound other than an alkali metal compound,
The mixed gas is absorbed from the gas-liquid interface, and ultrafine particles of the reaction product insoluble in the solvent are created by a precipitation reaction between the metal compound or metalloid compound and the reactive gas within the liquid film, and the product superfine particles are produced. The present invention relates to a method for producing ultrafine particles of a metal compound or metalloid compound, which includes vigorous stirring so that the particles quickly escape from a liquid film. When the reactive gas is supplied, when the reactive gas is supplied alone or when the ratio of the reactive gas to the mixed gas is large, the product particles include ultrafine particles and relatively large particles. In such cases, ultrafine particles and relatively large particles can be separated by filtration. Therefore, the present invention also provides a method for supplying a reactive gas alone or in a mixture with an inert gas or air to a solution of a metal compound or a metalloid compound other than an alkali metal compound, and discharging the reactive gas from the gas-liquid interface. Alternatively, by absorbing a mixed gas, ultrafine particles of a reaction product insoluble in the solvent are created through a precipitation reaction between the metal compound or metalloid compound and the reactive gas within a liquid film, and the ultrafine particles of the product are immediately produced. The present invention relates to a process for producing ultrafine metal or metalloid compound particles comprising vigorous stirring to break up the liquid film and then separating the ultrafine particles of the product from larger particles of the product. According to the present invention, a solution of a soluble metal compound other than an alkali metal compound, such as a soluble metal salt, a soluble base, a soluble acid, is placed in a reaction vessel and reacted with an acidic or basic gas alone or diluted with an inert gas or air. to produce fine particles of reaction products such as solvent-insoluble compounds such as hydroxides, carbonates, sulfides, and organic acid salts. The above reaction takes place within the liquid film, and the product quickly escapes from the liquid film due to vigorous stirring and is carried into the interior of the liquid. The end point of the reaction can be determined by reading the PH change with a PH meter inserted into the reaction solution. The product thus obtained can be obtained as a fine metal compound powder by washing and drying after separation. When the product is composed of ultrafine particles and relatively large particles, the relatively large particles are removed by filtration, and then the ultrafine particles are washed, separated, and dried using a centrifuge, and the primary particles are separated from metal compounds. Obtain ultrafine powder. The present invention has the above-mentioned configuration, and the generated metal compound can be obtained as an extremely fine and uniform fine powder as primary particles, and such a fine powder can be converted into metal oxide fine powder by heating in air after drying. It becomes a powder, or a fine metal powder when heated in a reducing atmosphere.
The particle size of the obtained ultrafine metal oxide particles is 20 Å to 200 Å.
It is about Å. The metal compound that can be used in the present invention is one that is soluble in the solvent used and that can quickly undergo a precipitation reaction with the reactive gas used. That is, compounds of all metals and metalloids other than those belonging to Group Ia of the Periodic Table of Elements may be used as long as they meet the above conditions. Solvents that can be used in the present invention can be water or organic solvents such as acetone, ethanol, ether, benzene, and the like. Reactive gases that can be used in the present invention can be basic gases such as ammonia, amines, etc. or acidic gases such as carbon dioxide, hydrogen sulfide, hydrochloric acid, acetic acid, formic acid, etc. Various concentrations of the solution and gas used in the present invention can be used, but in order to make the particle size more uniform, it is preferably about 0.1 to 0.5 mole/concentration. Also, the gas concentration is generally 1/10 to 1/10
00 can be diluted with inert gas or air, but this will vary depending on the type of metal compound used. According to the present invention, when two or more component metal compounds are used as raw materials to obtain the product ultrafine particles of the present invention as mixture ultrafine particles of two or more components, products of each component should be produced.
If the PH ranges are the same, co-products may occur and a homogeneous mixture of two or more compounds can be obtained, whereas if the products of each component are produced in different PH ranges, the products of each component may be formed. By suspending or floating each type of ultrafine particle in a solvent as a colloid, and mixing two or more types of suspensions or colloid solutions, it is possible to mix to the same degree as mixing liquids together. Furthermore, if the ultrafine particles of the product of the present invention are produced by appropriately selecting the metal compound and reactive gas so that by-products are volatilized during heating and sintering, it is also possible to obtain highly pure metal oxides. As described above, the ultrafine particles obtainable according to the present invention are extremely advantageous for magnetic materials, electronic materials, ceramic materials, adsorbents, and the like. According to the method of the present invention, uniform ultrafine particles can be obtained as follows. The reactive gas present in the gas phase dissolves into the solution containing the metal compound through the gas-liquid interface, resulting in an increase in the acid or alkali concentration based on the reactive gas in the liquid film. This acid or alkali reacts with the metal compound to form a product that is insoluble in the solvent. The concentration of this product is high within the liquid boundary film and is low inside the liquid outside the liquid boundary membrane. The high concentration of reaction products within the liquid film causes nucleation and subsequent rapid particle growth. At this time, since the growth is rapid, a region depleted of reaction products is created around the particles, and the growth of the particles is suppressed. Along with this depleted region, the particles escape from the liquid film by riding the violent movement of the liquid due to stirring and are carried away into a solution with a low concentration of reaction products. The particles dissolve again inside the liquid, but when the concentration of the reaction product in the solution increases to a level where it does not dissolve again, the product starts to be produced again. This concentration can be determined by the change in pH. Therefore, ultrafine reaction product particles can be produced without causing the particles to grow more than necessary. The invention is illustrated by the following examples in conjunction with the drawings. Example 1 Using the apparatus shown in Fig. 1, reaction vessel 1 (300
ml) with ice, then add 0.2 ml to the container.
200 ml of mol/l aqueous AlCl ₃ solution was added to this solution 3 to absorb 100% ammonia gas and raise the pH to 4.1. The solution is stirred with stirring blade 2 (motor rotation speed
850 RPM) until the mixture is bubbly. When this state is reached, a mixed gas of ammonia and nitrogen (NH ₃ :
N ₂ =3:1000) was supplied through the supply pipe 4. The mixed gas was mixed and supplied from an ammonia gas cylinder 6 and a nitrogen gas cylinder 7 through a flow rate regulator 13, a capillary 8, and a mixing tube 9 filled with glass wool. The unreacted mixed gas was discharged from the discharge pipe 5. PH meter 1 measures the change in PH of the liquid in the reaction vessel.
1, and when the pH reached the end point of the reaction, the supply of the mixed gas was stopped. The resulting product was washed by centrifugation and then calcined to various temperatures. The particle size of the obtained alumina was measured by small-angle X-ray scattering. The results were as follows.

[Table] Example 2 The same procedure as in Example 1 was carried out except that 0.5 mol/aqueous AlCl ₃ solution and 100% ammonia gas were used instead of the mixed gas. After washing the resulting product several times, it became a colloid.
Scoop this colloidal liquid through an electron microscope mesh covered with a collodion membrane, dry it on paper, and then place it in a vacuum.
The sample was heated to 500°C and cooled, and then observed using an electron microscope. The observation diagram is shown in Fig. 2. The size and shape of each primary particle of aluminum hydroxide can be clearly observed. Large particles are about 200 Å and small particles are about 30 Å. Because the liquid concentration was high and 100% ammonia gas was used, relatively large particles that had grown were quite visible. Example 3 Except for using a 0.1 mol/AlCl ₃ aqueous solution and a mixed gas concentration of 3/1000 (N ₂ :NH ₃ =1000:3),
It was carried out in the same manner as in Example 1. Electron microscopy was performed under the same conditions as described in Example 2. As can be seen from Figure 3, there are no large particles, and uniform particles of about 30 Å are formed. Example 4 0.1 mol/Ba(OH) ₂ aqueous solution and 100%
Perform the same operation as in Example 1 using CO ₂ gas.
A product of _BaCO3 was obtained. As can be seen from Figure 4, when observed with an electron microscope, particles of about 100 Å and particles of several μm were formed. There were no intermediate-sized particles, and the large particles probably grew due to the high CO ₂ concentration. Example 5 The same procedure as in Example 1 was carried out except that a mixed gas of a 0.1 mol/molar AlCl ₃ aqueous solution and N ₂ gas bubbled into dimethylamine at room temperature was used. Electron microscopic observation was carried out under the same conditions as described in Example 2. As can be seen from Figure 5, particles of less than 100 Å were formed.

[Brief explanation of the drawing]

FIG. 1 shows a schematic diagram of the apparatus used in the invention. 2, 3, 4 and 5 are electron microscope images of product particles of the present invention obtained according to Example 2, Example 3, Example 4 and Example 5, respectively. . 1... Reaction container, 2... Stirring blade, 3... Solution, 4... Supply pipe, 5... Discharge pipe, 6... Ammonia gas cylinder, 7... Nitrogen gas cylinder, 8...
Capillary, 9... Mixing tube, 10... PH meter electrode, 11... PH meter, 12... Motor, 13... Flow rate adjustment device, 14... Recorder.

Claims (1)

[Claims] 1. A reactive gas mixed with an inert gas or air is supplied to a solution of a metal compound or metalloid compound other than an alkali metal compound, and the mixed gas is absorbed from the gas-liquid interface to form a liquid boundary. Ultrafine particles of the reaction product insoluble in the solvent are created by a precipitation reaction between the metal compound or metalloid compound and the reactive gas within the membrane, and the product is vigorously stirred so that the ultrafine particles quickly escape from the liquid film. A method for producing ultrafine particles of a metal compound or a metalloid compound, comprising: 2. A reactive gas is supplied alone or mixed with an inert gas or air to a solution of a metal compound or metalloid compound other than an alkali metal compound, and the reactive gas or mixed gas is absorbed from the gas-liquid interface. The precipitation reaction between the metal compound or metalloid compound and the reactive gas within the liquid film produces ultrafine particles of the reaction product insoluble in the solvent, and the reaction product is vigorously heated so that the product particles quickly escape from the liquid film. A method for producing fine particles of a metal compound or metalloid compound comprising stirring and then separating ultrafine particles of the product from larger particles of the product.