JP3313771B2 - Method for producing inorganic oxide particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously producing inorganic oxide particles having an extremely narrow particle size distribution, that is, monodisperse inorganic oxide particles. The monodisperse inorganic oxide particles obtained by the production method according to the present invention have a coefficient of variation (a value obtained by expressing the standard deviation of the particle diameter in percentage based on the average particle diameter) of 15%.
The following is a characteristic of the particle structure that the particles have a small particle size distribution and substantially no pores. Therefore, it can be used as a material requiring high added value, for example, a filler material, a medical / dental material, a cosmetic material, a light diffusing material, a precision polishing material, and the like.

[0002]

2. Description of the Related Art Conventionally, an organic metal compound is hydrolyzed,
Various methods for producing inorganic oxide particles by a condensation reaction are known. For example, a method for producing spherical silica is an example. Taking this example as an example, if ammonia water is added to a solution obtained by diluting ethoxysilane in which silicon and ethanol are combined with ethanol while adjusting the pH,
The ethoxysilane undergoes a hydrolysis reaction with water, and silicon hydroxide and ethanol are formed in the reaction solution, which increase and reduce water. On the other hand, this silicon hydroxide
In parallel, a dehydration-condensation reaction occurs one after another, generating oxides, that is, fine silica particles, and growing in a spherical shape. The following is a generalized view of the overall reaction process using alkoxides, which are typical examples of organometallic compounds. Hydrolysis reaction; M (OR) _x + XH ₂ O → M (OH) _x + XROH Condensation reaction; M (OH) _X → MO _{X / 2} + (X / 2) H ₂ O (where M is a metal element, R Represents an alkyl group.)

[0003] In producing the above silica particles,
A method of synthesizing monodispersed spherical particles by hydrolytic condensation of alkoxysilane, which is an organosilicon compound, in an aqueous alcohol solution using ammonia as a catalyst in a batch method is disclosed in W. K. Sto
ber et al. (J. Colloid)
& Interface Sci. , 26, 62-6
9 (1968)). In this method, the reaction is carried out in a single vessel. When the reaction is carried out on a small scale, particles having excellent monodispersity can be synthesized. In the mixing operation described above, it takes a long time to homogenize the mixture due to a large amount of the solution, its viscosity, the limit of the stirring efficiency of the apparatus, and the like, and the monodispersity of the obtained particles tends to be deteriorated. In particular, when obtaining large silica particles having an average particle size of submicron or more,
No excellent monodispersity could be obtained.

Japanese Patent Application Laid-Open No. 62-91418 discloses a technique for producing titania particles by subjecting titania particles to hydrolysis and condensation of alkoxytitanium in a batch system. However, the mixing and homogenization of the reaction solution similarly requires time, and the alkoxy titanium is
Since it is extremely reactive and rapidly undergoes a hydrolysis reaction with moisture in the atmosphere, an unspecified reaction easily intervenes at the gas-liquid interface. For this reason, the reaction process became more uneven over each part of the solution, generating complicated fine particles, and it was not possible to obtain titania particles having excellent monodispersibility. Further, in order to prevent the above reaction at the gas-liquid interface, it is necessary to provide an anhydrous gas atmosphere, which complicates the operation. As described above, in the conventional method, when the production scale is increased, the batch system as described above has been adopted.

On the other hand, a continuous synthesis method of monodispersed spherical particles of TiO ₂ is disclosed in Ogihara et al. (J. Am. Cer. Soc., 72 (9) 1598).
1601 (1989)). In this method, each raw material solution of an organic solution of a hydrolyzable organic metal and an organic solution of pH-adjusted water is mixed by a static mixer, and then transported through a long pipe to synthesize particles. In this method, a flow velocity distribution is generated at the center and the wall of the tube during transportation of the mixed reaction solution, and the distribution of the solution in the tube can be distributed. For this reason,
There is a drawback that the state of the chemical reaction changes depending on the transport location in the tube, causing a difference in the size of the grown particles, and the particle size distribution of the synthesized particles is deteriorated.

[0006]

SUMMARY OF THE INVENTION The present invention is directed to a method for stably and continuously producing monodisperse particles having a better particle size distribution by improving the drawbacks of the conventional inorganic oxide particle production technology. The purpose is to provide.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies and studies to achieve the above object, and as a result, in a method for continuously producing an inorganic oxide using a reaction tube, a reaction solution in a tube after mixing a raw material solution. A new means for equalizing the transport speed of the particles has been found, and it has been found that particles having a sharper particle size distribution can be easily synthesized. The present invention has been made based on the above findings.

[0008] That is, the method of the present invention for producing inorganic oxide particles is characterized in that, as described in the claims, a solution in which a hydrolyzable organometallic compound is dissolved in an organic solvent is used.
In a method for producing inorganic oxide particles by mixing a solution in which H-adjusted water is dissolved in an organic solvent, causing a hydrolysis reaction with the water of the adjusted water, and performing a subsequent condensation reaction, The above-mentioned reactions are carried out while continuously injecting and mixing the solution at a predetermined ratio into the reaction tube and mixing and transporting the mixed solution into individual small volumes by intermittently sending bubbles into the reaction tube. Where to make it.

In the method for producing inorganic oxide particles of the present invention, the hydrolyzable organometallic compound to be used undergoes hydrolysis and condensation reaction in the reaction solution to synthesize a desired metal oxide. If it does, at least one known metal compound of Group I, Group II, Group III, Group IV and Group V of the periodic table may be employed without any limitation. The metal alkoxide compound (M (OR) _x ) is a preferred example. In addition, a metal alkoxide group (OR) substituted with a carbonyl group (CO) or β-dicarbonyl group, or a metal soap (M (RCOO) _n ) And those in which an organic group is bonded to a metal via oxygen, such as a chelate compound, can also be used. A typical example of the synthesis of silica particles is represented by the general formula Si (OR) ₄ or SiR ′.
_An organosilicon compound such as an alkoxysilane represented by _n (OR) _{4 -n} or a low condensate obtained by partially hydrolyzing the organosilicon compound is easily available industrially, and one or two or more thereof are obtained. Is preferably used in order to obtain silica particles having excellent monodispersibility. 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.

The organic solvent for dissolving the above-mentioned organometallic compound and pH-adjusted water is a substance which dissolves the above-mentioned organometallic compound and water, such as alcohols such as methanol, ethanol and propanol, and ketones such as acetone. Any substance may be used as long as it does not decompose the metal compound. In particular, methanol, ethanol, and propanol are generally easily available materials and are suitable.

The pH-adjusted water mixed with the organic solution
The H value is appropriately selected depending on the type of the organometallic compound.
Ammonia, alkali metal hydroxides, mixtures thereof, and the like can be used as appropriate as the alkali raw material in the case of making it alkaline. In the case of acidic water, a known inorganic acid or organic acid can be appropriately used. In the method of the present invention, the two organic solutions are always continuously injected into the reaction tube at a predetermined ratio and mixed, but immediately after the injection, bubbles are intermittently fed into the tube to separate the injected solution. Is preferred. As the gas intermittently fed into the reaction tube, any substance can be used as long as it does not make the reaction state of the solution nonuniform, such as dry air, argon, nitrogen, oxygen, and helium. can do. Since the partitioned reaction solution is diffused and mixed in the tube, a special stirring operation is not usually required. However, if necessary, the solution may be stirred before the gas is introduced.

The reaction tube used in the method of the present invention comprises:
Any structure may be used as long as the individual liquids separated by the intermittently supplied gas can be transported stably without being mixed with each other during a predetermined reaction period. For example, it is preferable that a tube having a required length and a cross-sectional area of approximately 0.05 to ² cm ² in a tube has a helical vertical structure and the reaction solution is transported from a lower portion to an upper portion. At this time, the bubble section and the solution section are arranged alternately in the tube and exhibit a regular matrix pattern,
The length of each of these parts is preferably several mm to several cm. Further, the reaction tube is preferably made of a material that does not wet the reaction solution badly and is not eroded by the reaction solution.
For example, a thermoplastic resin (fluororesin, nylon) can be suitably used. After completion of the reaction, the solution is in the form of a slurry and flows out from the outlet of the reaction tube. After solid-liquid separation or centrifugation, the solution is subjected to a treatment such as drying to obtain product particles.

The method for producing oxide particles according to the present invention can continuously produce inorganic oxide particles having more excellent monodispersity as compared with the conventional method. When using a silicon compound and continuously synthesizing silica particles in the presence of alkaline water, an average particle size of about 0.0
It is preferable because spherical particles having excellent monodispersity of 5 to 2 μm can be obtained particularly stably. Similarly, when silica particles are continuously synthesized in the presence of acidic water, polyhedral or spherical particles having an average particle diameter of about 0.001 to 0.5 μm and excellent in monodispersity can be stably obtained. This is preferable. The average particle size of these silica particles can be controlled by the concentration of alkoxysilane or ammonia, reaction temperature, time, and the like.

[0014]

Examples Examples of the method for producing inorganic oxide particles of the present invention will be described with reference to comparative examples in which silica particles are produced. Example 1 630 g of tetraethoxysilane, which is a hydrolyzable organometallic compound, was added to 9500 ml of an ethanol solvent.
The organic solution dissolved and mixed in the solution and 4800 ml of ammonia water adjusted to pH 12.5 were mixed with ethanol solvent 5000 m
Each of the organic solutions dissolved and mixed in the solution was prepared in a tank equipped with a temperature controller for maintaining the temperature of the solution at 23 ° C., and the solution in the tank was constantly transferred to each of the tanks using a liquid quantitative transport pump.
Injection is performed at a flow rate of 0 ml / min through a T-tube connected to the lower part of a polyethylene reaction pipe having an inner diameter of 4 mm and a length of 300 m wound around a spiral vertical type (diameter 1 m, height about 65 cm). The two liquids are merged and mixed by a T-shaped tube, and the dry air supplied from the air compressor via the dehydration tower immediately into the pipe near the merge point using a solenoid on-off valve is used for about 0.5 second every about 0.5 second. Blow 3 ml and divide the solution into approximately 0.3 ml volumes. The length of the bubble section and the solution section in the pipe is about 2.4 cm, respectively, and they alternately form a regular array pattern, and are sequentially transported to the top of the pipe by the pressure of the supplied gas. During this time, the solution is also kept at 23 ° C.

After the two liquids are combined and mixed, the solution immediately undergoes a hydrolysis reaction and a condensation reaction, becomes cloudy, and silica particles are formed and gradually grow. The slurry flowing out from the upper outlet of the pipe was subjected to solid-liquid separation and then dried to obtain silica particles. During this time, the slurry was sampled every hour, and the silica particles obtained in the same manner were observed using a scanning electron microscope (JXA-840A manufactured by JEOL Ltd.), and the particle size distribution was determined from the obtained photographs. . As a result, the average value of the silica particles was 0.43 per hour.
μm, the coefficient of variation was in the range of 9 to 11%, and it was found that spherical silica particles having excellent monodispersity could be easily and stably obtained. The comparison between the measurement results of the specific gravity and the specific surface area and the data of the non-porous silica confirms that the silica particles have substantially no pores, and is suitable for use as a filler material or the like due to its shape and dimensional characteristics.

Example 2 The production conditions in Example 1 were partially changed, 458 g of tetramethoxysilane was used as the organometallic compound, the pH value of aqueous ammonia was adjusted to 11.8, and the reaction was performed with an inner diameter of 6 mm and a total length of 135 m. Using a pipe, the amount of liquid split in the pipe is about 0.6 ml (the length of the liquid in the pipe is about 2.1 cm).
1 (bubble length in the pipe is about 3.5 cm), and silica particles were produced and observed in the same manner. As a result, the average diameter of the particles was 0.15 μm every hour, and the variation coefficient was 1
It was 2 to 14%, and it was found that spherical silica particles having excellent monodispersibility could be easily and stably obtained. These silica particles have substantially no pores and are suitable for use as precision abrasives or the like because of their shape and dimensional characteristics.

Example 3 The production conditions in Example 1 were partially changed, and 1600 g of tetrapropoxysilane was used as the organometallic compound, and the pH value of aqueous ammonia was 13.0.
The temperature of each solution before and after the reaction was all kept at 50 ° C., and silica particles were produced and observed in the same manner. As a result, the average particle diameter of the obtained silica particles is 0.68 μm per hour, the coefficient of variation is 10 to 11%, and spherical silica particles excellent in monodispersity can be easily and stably obtained. I understood that. The silica particles have substantially no pores and are suitable for use as a filler material or the like because of their shape and dimensional characteristics.

Comparative Example: Silica particles were produced under the same conditions as in Example 1 except that dry air was not introduced.
Obtained particles were similarly observed. As a result, the average particle size of the particles is 0.41 μm per hour, the coefficient of variation is 25 to 40%, and the monodispersity is very poor. Was about the same.

The average particle diameter of the particles obtained in each of the above embodiments can be increased or decreased by changing the transport speed of the reaction solution to the pipe, the length of the pipe, and the like. In addition, the particles obtained in each of the above examples are grown as seed particles by a seed particle method so that the particle diameter of the silica seed particles is increased to several μm to several tens of μm, and used as a spacer material for a liquid crystal display panel. Can be used.

The method for producing the inorganic oxide particles of the present invention is not limited to the silica particles of the above examples, but may be any of the groups I to I of the periodic table.
Group V metal oxide particles, for example, Fe, Ga, Cr,
Oxide particles composed of one or more of Al, Zr, Ti, Nb and Ta can be similarly produced.

[0021]

As described above, according to the method for producing inorganic oxide particles of the present invention, the above-mentioned two organic solutions are mixed, and a hydrolysis reaction and a condensation reaction are caused to produce the inorganic oxide particles. In doing so, the mixed solution is divided into small volumes of individual solutions by the feed gas in the reaction tube and sequentially transported, and the reaction is performed, so that the generation of particles due to the difference in the flow velocity distribution of the reaction solution in the tube, It is possible to continuously and stably produce initial oxide particles having no sharpness in growth, a sharper particle size distribution than conventional production methods, and excellent monodispersity.

Claims (3)

(57) [Claims] 1. A method in which a solution in which a hydrolyzable organometallic compound is dissolved in an organic solvent and a solution in which pH-adjusted water is dissolved in an organic solvent are mixed, and a hydrolysis reaction and a condensation reaction are performed to form inorganic oxide particles. In the production method, the above two solutions are continuously and continuously injected at a predetermined ratio into a reaction tube, mixed, and the mixed solution is divided into individual small volumes by intermittently sending gas into the reaction tube. A method for continuously producing inorganic oxide particles, wherein the above-mentioned reactions are carried out while transporting. 2. The method according to claim 1, wherein the organometallic compound is an organosilicon compound, the pH-adjusted water is alkaline, and the average particle size is 0.1 to 0.2 . 0
The method for continuously producing inorganic oxide particles according to claim 1, wherein monodisperse spherical silica particles of 5 to 2 µm are produced. 3. The method according to claim 1, wherein the organometallic compound is an organosilicon compound, the pH-adjusted water is acidic, and the average particle size is 0.1 to 0.3 . 001-001
The method for continuously producing inorganic oxide particles according to claim 1, wherein monodisperse silica particles of 0.5 µm are produced.