JP3364261B2 - Method for producing metal oxide fine particles - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of producing metal oxide particles having a very uniform particle size, that is, so-called good monodispersibility in a high slurry state. [0002] Conventionally, hydrolyzable organic metal compounds such as tetraethoxysilane are hydrolyzed in a reaction solution such as water, ammonia and alcohol to form metal oxide particles such as silica. How to get is known. Although the metal oxide particles produced by such a method have good monodispersibility, they are very useful as various fillers, spacers, raw materials for ceramics, etc., but are practically used on an industrial scale. At present, few examples are found. [0003] The reason for the delay in commercialization is that the metal alkoxide such as tetraethoxysilane as a raw material is relatively expensive, and the slurry concentration of the metal oxide particles to be produced in the liquid phase cannot be increased. This is probably due to low productivity. In general, when attempting to increase the slurry concentration, it was not possible to obtain inorganic oxide particles having good monodispersity due to aggregation of particles, or generation of new small particles. . However, recently, there have been known attempts to increase the slurry concentration to improve the productivity. For example, in JP-A-3-22839, methyl silicate is reacted with aqueous ammonia to obtain colloidal silica having a slurry concentration (silica concentration) of 25%.
However, the colloidal silica synthesized here had a particle size of 5 to 40 μm, which was hardly a monodisperse particle. Japanese Patent Application Laid-Open No. 4-77309 discloses a method for producing silica particles by hydrolyzing an alkoxysilane in the presence of an anionic or nonionic surfactant. This method describes that silica particles were synthesized at a high slurry concentration of 26.2% by weight using tetramethoxysilane as a raw material and a slurry concentration (solid concentration). However, as described in Examples, the particle size that can be synthesized is in a narrow range of 0.14 to 0.30 μm, and the standard deviation when the average particle size is 0.23 μm is 0.16 μm. And it was hard to say monodisperse particles. In addition, it is described that the particle size of silica produced by adding a surfactant is reduced, and it is difficult to synthesize particles having a large particle size of 0.4 μm or more. On the other hand, Japanese Patent Application Laid-Open No. 62-52119 discloses that a hydrolyzable organic silicon compound is hydrolyzed without substantially changing the concentrations of water and ammonia in a reaction solution, whereby the particle size is reduced to 0.1. 05 to 50 μm
In this range, highly monodisperse silica particles having a particle diameter variation coefficient of 10% or less are obtained. However, the slurry concentration was as low as several percent. SUMMARY OF THE INVENTION The present invention relates to a metal oxide particle having an extremely high monodispersity as known in the art.
The present invention provides a method for producing a slurry at a high slurry concentration of 0% or more. Means for Solving the Problems The present inventors have made intensive studies to solve the above problems. As a result, when simultaneously dropping the hydrolyzable organometallic compound and the alkaline aqueous solution into the alkaline aqueous solution, use an alkaline aqueous solution containing 1 to 6 moles of water relative to the number of moles of the metal element in the organometallic compound. Due to the main production conditions, the variation coefficient of the particle size of the synthesized particles is 10% or less,
Moreover, they have found that the reaction solution after the completion of the synthesis can be synthesized at a high slurry concentration of 10% or more, thereby completing the present invention. That is, the present invention provides a method for producing metal oxide fine particles at a high slurry concentration of 10% by weight or more by hydrolyzing an organic metal compound which can be hydrolyzed in an alkaline aqueous solution. At the latest, before the water in the alkaline aqueous solution is consumed and disappears, the hydrolyzable organic metal compound and the alkaline aqueous solution (II) are mixed with the metal element 1 in the organic metal compound.
Water in the aqueous alkaline solution (II) is 1 to 6
A method for producing metal oxide fine particles, characterized in that both are independently and simultaneously dropped at a supply ratio of twice the molar ratio, and that the hydrolyzable organometallic compound is dropped in a liquid to be hydrolyzed. It is. The alkaline aqueous solution (I) used in the present invention refers to an aqueous solution having a pH of greater than 7, or an aqueous solution of an alcohol such as methanol, ethanol, propanol, isopropanol, butanol, ethylene glycol, propylene glycol, acetone, methyl alcohol or the like. A liquid in which ketones such as ruethyl ketone, ethers such as dioxane and diethyl ether, ethers such as ethyl acetate, and other organic solvents that are compatible with water are used alone or in combination. As the base for making it alkaline, ammonia, LiOH, NaOH, KOH and the like are used without any limitation. The proportion of water in the alkaline aqueous solution varies depending on the type of the organometallic compound used, and cannot be unconditionally determined, but is preferably in the range of 3 to 95%, more preferably 5 to 40%. Next, as the hydrolyzable organometallic compound which is a raw material of the present invention, any known compounds can be used without any limitation as long as they are hydrolyzed to a metal oxide in the above-mentioned alkaline aqueous solution. Is done. Representative examples of hydrolyzable organometallic compounds include, for example, those represented by the general formula S
Alkoxysilanes represented by i (OR) ₄ or SiR ^′ _n (OR) _4-n or low-condensates obtained by partially hydrolyzing alkoxysilanes are industrially easily available, and one or two of them are The above mixture is preferably used. In the above general formula, R and R ^′ are alkyl groups, for example, a lower alkyl group such as a methyl group, an ethyl group, an isopropyl group, and a butyl group is preferable. n is an integer of 1 to 3. As other hydrolyzable organometallic compounds, hydrolyzable organometallic compounds of Groups I, II, III and IV of the periodic table are used without any particular limitation. . For example, the general formula M ¹ (OR), M
² (OR) ₂ , M ³ (OR) ₃ , M ⁴ (OR) ₄ (where R is an alkyl group), or one or two alkoxide groups (O
Compounds in which R) is substituted by a carboxyl group or a β-dicarbonyl group are preferred. Where M ¹ is a Group I metal, M ² is a Group II metal, M ³ is a Group III metal, M
⁴ is a Group IV metal, specifically, for example, lithium, sodium, potassium, magnesium, calcium, strontium, barium, aluminum, titanium, zirconium, germanium, hafnium, tin or lead. The above compounds generally preferably used in the present invention are more specifically exemplified by Si (OM
e) alkoxysilanes such as ₄ , Si (OEt) ₄ , and their low condensates; NaOCH ₃ , NaOC ₂ H ₅ , Na
An organic sodium compound such as OC ₃ H ₇ and a Group I compound substituted with Li, K or the like in place of the above Na; Mg (O
CH ₃ ) ₂ , Mg (OC ₂ H ₅ ) ₂ , Mg (OC ₃ H ₇ ) ₂ , M
g (OC ₄ H ₉ ) ₂ , an organomagnesium compound such as Mg (OC ₅ H ₁₁ ) ₂ and the above Mg, Ca, Sr,
Group II compound substituted by Ba or the like; Al (OC
_{2 H 5) 3, Al (} OC 3 H 7) in place of _{3, Al (OC 4 H 9} ) compounds such as ₃ and the Al, Part I was replaced by B, etc.
II _{compound; Ti (O-isoC 3 H} 7) 4, Ti (O
-NC ₄ H ₉ ) ₄ , and the like, and the above-described Ti-substituted IV-substituted Zr, Ge, Hf, Sn, Pb, etc.
Group compounds and the like. In addition, CaCl ₂ , Ca
Compounds such as (HOC ₆ H ₄ COO) ₂ .H ₂ O can also be suitably used. In order to carry out the present invention, the above-mentioned organometallic compounds may be used alone or in combination of two or more. In order to produce composite oxide particles composed of silicon and other metals, a partially hydrolyzed alkoxysilane or a low-condensate obtained by partially hydrolyzing other It is also preferable to simply mix with the hydrolyzable organometallic compound of the above or to use a composite alkoxide generated by a reflux operation or the like after the mixing in carrying out the present invention. The above-mentioned hydrolyzable organometallic compound may be used after being diluted with an organic solvent such as alcohol. However, in order to increase the slurry concentration, it may be used without any dilution or at all. 50% dilution rate
It is desirable to keep it to the extent. In the present invention, the number of moles of water is 1 to 6 times the number of moles of the metal element in the organometallic compound separately prepared at the same time when the hydrolyzable organometallic compound is dropped in the liquid. It is necessary to drop the alkaline aqueous solution (II) at a supply ratio such that If the simultaneous dropping of the alkaline aqueous solution is not performed, it is difficult to obtain a highly monodisperse slurry of the metal oxide fine particles having a high concentration of 10% or more. Further, when the slurry is manufactured at a high slurry concentration of 10% or more, if the supply molar ratio of the water is smaller than 1 mole, the water required for hydrolysis is insufficient.
Aggregation is likely to occur, and when the molar ratio is larger than 6 times, new core particles are more likely to be generated and the monodispersity is lowered, which is unsuitable as a synthesis condition. The optimum supply ratio of the alkaline aqueous solution (II) must be appropriately selected from the above range depending on the type of the hydrolyzable organometallic compound used. For example, when a low condensate obtained by partially hydrolyzing alkoxysilane is used as the organometallic compound, the supply ratio is preferably relatively small, and a composite alkoxide composed of silicon and another metal is used. In such cases, it is often better that the supply ratio is relatively large. The composition of the alkaline aqueous solution (II) is not particularly limited except that the supply ratio of water in the solution is important as described above, and is the same as that of the alkaline aqueous solution (I) described above. It may be prepared. However, in order to synthesize at a high slurry concentration of 10% or more, the water concentration should be 50 to 50%.
It is preferably as high as 99.9%. When the simultaneous dripping of the alkaline aqueous solution (II) is started, the alkaline aqueous solution (I) initially charged is used.
It is necessary to start before the water in the reaction solution is consumed by the hydrolysis and disappears, and there is no particular limitation as long as it is before this. It is the simplest method in the production process to start at the same time as the dropping of the hydrolyzable organometallic compound. When simultaneous dropping is started after the water in the reaction solution of the initially charged alkaline aqueous solution (I) is consumed by the hydrolysis and disappears, only aggregates containing the spherical particles that have been grown up to that point are obtained. On the other hand, if the simultaneous dripping of the alkaline aqueous solution (I) is started after the hydrolyzable organometallic compound is dripped to some extent, particles having more excellent monodispersity may be obtained. When dripping of the hydrolyzable organometallic compound is started, the water in the reaction solution is consumed by the hydrolysis reaction, and the concentration of water in the reaction solution decreases. Combining in such a state may improve the monodispersibility. The drop of the hydrolyzable organometallic compound is
It is essential to drip in the liquid. The term “drop in liquid” means that the tip of the dropping port is immersed in the reaction solution when the solution is dropped into the reaction solution of the alkaline aqueous solution. The position of the tip of the dropping port is not particularly limited as long as it is in the liquid, but a position where sufficient stirring is performed, such as near the stirring blade, is desirable. If, for example, the liquid is dropped from above the reaction solution without being dropped in the liquid, the particles tend to aggregate. On the other hand, the alkaline aqueous solution (I) to be simultaneously dropped is not particularly required to be dropped in the liquid, but is preferably dropped in the liquid near the stirring blade because the stirring is sufficiently performed. In order to increase the monodispersity, the dropping rate can also be a production factor. The lower the dropping rate is, the better the monodispersity tends to be. However, when the dropping rate is low, it takes a long time until the synthesis is completed, which is not practical. Therefore, it is also a preferable embodiment for carrying out the present invention to reduce the dropping speed in the early stage of the synthesis and increase the dropping speed in the latter half. It is necessary that the hydrolyzable organometallic compound and the alkaline aqueous solution be continuously dropped from the start of the dropping to the end thereof. The term “continuous” as used herein means that an interval of usually 10 minutes or more, preferably 3 minutes or more is not provided. The dropping speed is not necessarily required to be constant, but when changing the dropping speed, it is desirable to change it continuously. Japanese Patent Application Laid-Open No. 4-77309 describes that water is added several times.
Such a method is not a preferable method because the atmosphere in the reaction solution is disturbed by abrupt addition of water, and aggregation of particles and generation of new core particles occur. Incidentally, the high slurry concentration referred to in the present invention depends on the type of the organometallic compound used, and cannot be unconditionally determined. However, it is explained as follows. For example, tetraethoxysilane (Si (O (O
When Et) ₄ ) is used, a hydrolysis reaction occurs as shown in the following formula, so that the molecular weight of silica (about 60) is calculated by dividing Si (OEt) ₄ + 2H ₂ O-> SiO ₂ + 4E on the right side.
The value (about 28%) obtained by dividing the total amount of tOH particles (about 244) becomes the theoretical upper limit of the slurry concentration. Actually, the concentration of the slurry is about 40 to 80% of the above upper limit value due to the presence of the solvent and the like. When an oligomer of tetramethoxysilane (for example, Colcoat Co., Ltd., product name: methyl silicate 51) is used as the organometallic compound, the theoretical upper limit of the slurry concentration is as high as about 50%. The concentration can be as high as 30% or more. As described above, the upper limit of the slurry concentration varies depending on the type of the organometallic compound used. The high slurry concentration referred to in the present invention generally means 10% to 10%.
It is in the range of 40% and at least at the end of synthesis. Therefore, the slurry concentration during the synthesis may be lower than this range. The temperature of the reaction tank at the time of performing the hydrolysis may be in the range of 0 to 50 ° C., and is appropriately selected depending on the type of the hydrolyzable organometallic compound to be used. In addition, the reaction vessel used for the hydrolysis, other reaction conditions, and the like may be any known one without any limitation. According to the method of the present invention, metal oxide particles having extremely high monodispersity can be produced at a high slurry concentration of 10% or more. Such an improvement in productivity greatly reduces the price of the particles, thus allowing them to be used in applications where conventional applications were impossible. For example, it can be used as general industrial materials such as fillers and additives for plastics and films, and raw materials for ceramics. EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited by these examples. The molar ratio of the metal element in the hydrolyzable organometallic compound at the time of producing the particles and the water in the alkaline aqueous solution which is simultaneously dropped into the liquid is simply referred to as the molar ratio. The average particle size and the standard deviation value were obtained by measuring the particle size of 100 arbitrary particles in an image taken by an electron microscope and using the following formula. ## EQU1 ## (Where Xi represents the i-th particle diameter, and n
= 100. Example 1 400 g and 100 g of methanol and aqueous ammonia (25% by weight) were charged into a 4 liter glass reactor equipped with stirring blades, respectively, and mixed well to prepare a reaction solution. Next, while maintaining the temperature of the reaction solution at 30 ° C., 5 g of tetraethoxysilane (Kanto Chemical Co., Ltd., product name: tetraethoxysilane, purity: 3N) was added, and the mixture was stirred for 30 minutes to generate core particles. Then, tetraethoxysilane (Si (OEt) 4, Colcoat Co., Ltd., product name; ethyl silicate 28) at a rate of 8.3 g / min, and aqueous ammonia (25% by weight) at a rate of 2.7 g / min.
Each of them was simultaneously dropped separately into the reaction solution. In this case, the supply molar ratio of water to metal was 2.8. Four hours after the start of the dropwise addition, the dropwise addition was completed, and 2,000 g of tetraethoxysilane and 640 g of aqueous ammonia were added dropwise. After the stirring was further continued for 1 hour, the solution in the system was taken out. The weight of the solution taken out was 3145 g. This solution was filtered and dried at 200 ° C.
When calcined at 900 ° C., 575 g of silica particles were obtained. Therefore, the slurry concentration at this time was 18%. The obtained silica particles had a true spherical shape, an average particle diameter of 0.77 μm, and a standard deviation of 1.067. Example 2 Silica particles were synthesized in the same manner as in Example 1 except that ethanol was used instead of methanol, and the temperature of the reaction solution was changed to 40 ° C. The supply molar ratio of water at this time was 2.8. The solution weighed 3140 g and the silica particles 575
g were obtained. Therefore, the slurry concentration at this time is 1
8%. The silica particles thus obtained were spherical and had an average particle diameter of 2.12 μm and a standard deviation of 1.04.
It was 4. Example 3 While maintaining the temperature of the reaction solution at 10 ° C., a tetramethoxysilane oligomer (Si (OMe) 4 dimer to hexamer, average tetramer, Colcoat Co., Ltd., product name: methyl silicate 51) at a rate of 6.3 g / min with aqueous ammonia (2
5 wt%) at a rate of 2.0 g / min, and silica particles were synthesized in the same manner as in Example 1, except that 1500 g of tetramethoxysilane oligomer and 480 g of aqueous ammonia were dropped. At this time, the supply molar ratio of water was 1.6.
Met. The weight of the solution is 2500 g and the silica particles are 7
63 g were obtained. Therefore, the slurry concentration at this time was 31%. The silica particles thus obtained were spherical and had an average particle diameter of 0.79 μm and a standard deviation of 1.
089. Example 4 245 g and 105 g of isopropanol and ammonia water (25% by weight) were charged into a 4 liter glass reactor equipped with stirring blades, respectively, and stirred while maintaining the temperature of the reaction solution at 40 ° C. Next, 943 g of tetramethoxysilane (Si (OMe) 4, Colcoat Co., trade name; methyl silicate 39) was charged into a 3-liter Erlenmeyer flask, and 350 g of methanol and 0.1 wt. % Hydrochloric acid aqueous solution (35% hydrochloric acid, Wako Pure Chemical Industries, Ltd.
49 g (diluted with water to 1000) was added and stirred for about 10 minutes. Subsequently, tetrabutoxy titanium (Ti (OBu)
4, Nippon Soda Co., Ltd., product name; B-1 (TBT)) 308
g was diluted with 544 g of isopropanol, and a yellow transparent homogeneous solution (composite alkoxide of Si and Ti) was added.
Got. 3192 g of the above-mentioned composite alkoxide was added.
At a rate of 6 g / min, ammonia water (25% by weight) 7
10 g was simultaneously dropped into the reaction solution at a rate of 1.5 g / min over 8 hours. The supply molar ratio of water at this time was 4.2. The solution weighed 3250 g and contained 440 particles.
g was obtained. Therefore, the slurry concentration at this time is 14
%Met. The resulting particles are spherical and have an average particle size of 0.1.
60 μm, and the standard deviation was 1.092. Example 5 A composite alkoxide obtained in the same manner as in Example 4 was dropped alone at an average speed of 1.1 g / min for 3 hours. Subsequently, the dropping speed of the composite alkoxide was 4.5 g / mi.
m, and at the same time, ammonia water (25% by weight).
It was simultaneously dropped into the reaction solution at a rate of 4 g / min. In addition,
The supply molar ratio of water at this time was 4.0. After about 10 hours, the dropping was completed. The solution weighed 3250 g and contained 440 particles.
g was obtained. Therefore, the slurry concentration at this time is 14
%Met. The resulting particles are spherical and have an average particle size of 0.1.
60 μm, and the standard deviation was 1.073. Comparative Example 1 0.88 g of ammonia water (25% by weight) dropped simultaneously
Silica particles were synthesized in the same manner as in Example 1, except for using / min. The supply molar ratio of water at this time was 0.9.
It was one. Under these conditions, the reaction solution began to agglomerate during the synthesis, and it became difficult to stir, so the experiment was interrupted. COMPARATIVE EXAMPLE 2 2.7 g / aqueous ammonia water (25% by weight) was added simultaneously.
Particles were synthesized in the same manner as in Example 4 except that the amount was changed to min. In this case, the supply molar ratio of water was 7.6. The weight of the solution taken out was 3840 g, and 440 g of particles were obtained. Therefore, the slurry concentration at this time was 12%. However, the obtained particles contained many agglomerated particles having a size of several tens of μm to several hundreds of μm, and independent spherical particles had a wide distribution of 0.1 to 0.7 μm.

Claims (1)

(1) A method for producing metal oxide fine particles at a high slurry concentration of 10% by weight or more by hydrolyzing an organic metal compound which can be hydrolyzed in an alkaline aqueous solution. In the aqueous solution (I), the hydrolyzable organometallic compound and the alkaline aqueous solution (II) are used at the latest before the water in the alkaline aqueous solution is consumed and disappears.
Are independently and simultaneously and continuously dropped at a supply ratio in which the water in the alkaline aqueous solution (II) is 1 to 6 moles per mole of the metal element in the organometallic compound,
In addition, a method for producing metal oxide fine particles, wherein a hydrolyzable organic metal compound is dropped in a liquid and hydrolyzed.