JPH03218915A - Production of silica powder - Google Patents

Abstract

PURPOSE:To obtain isolated silica particles of large particle size having a sharp distribution of the particle size by allowing specified methoxysilanes to coexist in the method of hydrolysis of tetraethoxysilane in a water-org. solvent dispersion liquid in which seed particles are dispersed. CONSTITUTION:Tetraethoxysilane is added to a water-org. solvent dispersion liquid (heel sol) in which seed particles are dispersed to effect hydrolysis of this tetraethoxysilane, so that the particles grow by deposition of silica on the seed particles. In this process, the hydrolysis reaction is effected in the coexistence of methoxysilanes expressed by (CH3O)n.(C2H5O)4-n.Si(n=1 to 4). These methoxysilanes may be priorly mixed with the tetraethyoxysilane and then added to the heel sol, or may be added to the heel sol with the tetraethoxysilane.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a method for producing silica particles, and more particularly to a method for producing silica particles that have a sharp particle size distribution and are monodispersed.

TECHNICAL BACKGROUND OF THE INVENTION Conventionally, a method has been known in which silica particles are obtained by hydrolyzing an alkoxysilane such as tetraethoxysilane in a water-alcohol mixed solvent.

In addition, as a method for obtaining large-sized silica particles, silica particles obtained by hydrolysis of alkoxysilane or inorganic oxides obtained by other methods are used as seed particles, and the seed particles are added to the reaction liquid in which they are dispersed. A known method is to obtain large-sized silica particles with a sharp particle size distribution by adding alkoxysilane to perform hydrolysis, depositing silica particles on seed particles, and growing the particles.

In order to obtain particles with a sharp particle size distribution using the above particle growth method, in addition to ensuring that the particle size distribution of the core seed particles is sharp, it is necessary to add alkoxysilane to the dispersion liquid in which the seed particles are dispersed. It is preferable to ensure that the hydrolyzate is deposited on the surface of the seed particles during hydrolysis. If new nuclei are generated from the hydrolyzate, it will be difficult to obtain silica particles with a sharp particle size distribution.

As a method to prevent the formation of new nuclei due to the hydrolyzate of alkoxysilane, the addition rate when tetraethoxysilane is continuously added to the seed particle dispersion is controlled to prevent the formation of new nuclei. A method for preventing excess tetraethoxysilane from being present in the dispersion (Japanese Unexamined Patent Publication No. 62-72514), in which tetraethoxysilane is not added continuously but in small amounts divided into several portions. A method (Japanese Unexamined Patent Publication No. 63-265806) has been proposed.

However, the silica particles obtained by these methods do not necessarily have sufficient uniformity, and it has been particularly difficult to suppress the formation of small-sized silica particles. Furthermore, it takes a long time to obtain monodisperse silica particles having a desired particle size, which poses a problem in productivity.

Purpose of the Invention The present invention has been made in view of the above-mentioned prior art, and provides a method for efficiently producing large-sized silica particles having a sharp particle size distribution and being monodispersed. The present invention aims to provide a method for producing silica particles.

Summary of the Invention The method for producing monodisperse silica particles according to the present invention includes adding tetraethoxysilane to a water-organic solvent dispersion in which seed particles are dispersed, hydrolyzing the tetraethoxysilane, and dispersing the seed particles onto the seed particles. When manufacturing monodispersed silica particles by attaching silica to particles and growing them, the hydrolysis reaction of tetraethoxysilane is performed using the formula [1] (CHO) ・(CHO) ・Si
...[I]3 n 2 5 4-n (n is 1 to 4 in the formula) It is characterized in that it is carried out in the coexistence of methoxysilanes represented by the following formula.

DETAILED DESCRIPTION OF THE INVENTION The method for producing monodispersed silica particles according to the present invention will be specifically described below.

First, in the present invention, a water-organic solvent dispersion in which metal oxides or metal hydroxides such as silica are dispersed as seed particles is prepared. At this time, if the particle sizes of the seed particles are not uniform, the final silica particles obtained will not be uniform in particle size. The seed particles dispersed in the water-organic solvent dispersion are metal oxide particles or metal hydroxide particles, but other particles with uniform particle sizes can also be used depending on the case. Note that the seed particles do not necessarily have to be silica particles.

A method for preparing such a water-organic solvent dispersion in which seed particles are dispersed includes a method of adding powdered seed particles or a seed particle dispersion, such as silica sol, to a water-organic solvent mixed solution. Alternatively, there is a method in which an alkoxysilane or metal alkoxide is hydrolyzed in a mixed solution of water and an organic solvent according to a known method to obtain a seed particle dispersion having a uniform particle size.

In this way, a water-organic solvent dispersion (hereinafter sometimes referred to as "heel sol") in which seed particles are dispersed is obtained. In order to stabilize the liquid, an alkali such as ammonia can also be added.

The concentration of the organic solvent in the water-organic solvent dispersion in which the seed particles are dispersed is preferably 35 to 97% by weight. As such an organic solvent, alcohol is particularly preferably used, and specifically, methanol, ethanol,
Lower alcohols such as n-propanol, isopropanol, n-butanol, and isobutanol are used.

Moreover, a mixed solvent of these lower alcohols can also be used.

Furthermore, a mixture of water, alcohol, and an organic solvent other than alcohol can be used as a water-organic solvent dispersion. In such a case, an organic solvent is used that has good compatibility with water and alcohol, and also with alkoxysilane.

Examples of such organic solvents include glycols such as ethylene glycol, esters such as ethyl acetate, and ketones such as methyl ethyl ketone.

The concentration of the seed particles in the water-organic solvent dispersion is preferably 0.05 to 20.0% by weight in terms of oxide concentration. The oxide concentration of seed particles is 0.05% by weight
If it is less than that, new seed particles may be generated in the subsequent step of attaching the tetraethoxysilane hydrolysis product to the seed particles, and the resulting particles tend to have a broad particle size distribution. On the other hand, if the oxide concentration of the seed particles exceeds 20.0% by weight, the particles tend to aggregate during the step of adhering the tetraethoxysilane hydrolysis product to the seed particles.

Next, while keeping the heel sol alkaline, tetraethoxysilane is added to the heel sol obtained as described above to hydrolyze it, and the tetraethoxysilane hydrolysis product is deposited on the sheet particles to form seed particles. grow.

In the present invention, one or more methoxysilanes represented by the following formula [I] are allowed to coexist during hydrolysis of tetraethoxysilane.

(CO O) ・(CIIO) 3 n 2 5 4-n'S1
゜"[1 (in the formula, 1 is 1 to 4) The methoxysilanes used in the present invention refer to the above formula [1
] Specifically, there are monomethoxytriethoxysilane, dimethoxydiethoxysilane, trimethoxymonoethoxysilane, and tetramethoxysilane.

The above methoxysilanes may be mixed with tetraethoxysilane in advance and added to the heel sol, or may be added to the heel sol simultaneously with the tetraethoxysilane. These methoxysilanes have a total amount of 0.0 Jl per mole of tetraethoxysilane added to Heel Sol to obtain particles of a predetermined particle size. 0 5 x 1 0
-2 to 6. O x 10-2 mol (both S
+ 0 2 conversion) Preferably 0.1 x - 2 10 to 5. Preferably, it is used in an amount of OX10'.

If the amount of methoxysilanes is less than 0.05 x 10' mol per 1 mol of tetraethoxysilane, the effect of adding methoxysilanes will not be noticeable and new seed particles will be generated during hydrolysis. There is. On the other hand, if the amount of methoxysilane exceeds 6.0 x 10-2 mol per 1 mol of tetraethoxysilane, the rate of hydrolysis of tetraethoxysilane becomes too fast and a hydrolyzate is deposited on the surface of the seed particles. In some cases, the hydrolysis products may generate new seed particles.

Methoxysilanes added to the reaction system are also hydrolyzed at the same time as tetraethoxysilane and deposited on the seed particles.

In the present invention, tetraethoxysilane is usually added continuously to the heel sol at a constant rate, but it may also be added in a fixed amount at a time and repeated.

When tetraethoxysilane is added to the heel sol, the pH of the heel sol changes due to hydrolysis.

If the heel sol is no longer alkaline, the seed particles may aggregate or new seed particles may be generated, which is undesirable because the particle size distribution of the final particles becomes broad. Therefore, when adding tetraethoxysilane, the heel sol is kept alkaline.

The pH of the heal sol is preferably 10-13. In order to keep the heel sol alkaline, it is sufficient to add an alkali to the heel sol, and examples of such alkalis include ammonia gas, aqueous ammonia, amines, alkali metal hydroxides, and quaternary ammonium salts. may be used alone or in combination.

The hydrolysis temperature of tetraethoxysilane is not particularly limited, but when a temperature higher than the boiling point of water or alcohol is employed, it is preferable to pressurize the solution so that it maintains a liquid phase. However, performing the hydrolysis reaction of tetraethoxysilane above the critical temperature of alcohol present in the reaction system may change the composition ratio in the liquid phase, so it is not recommended to perform the hydrolysis reaction below the critical temperature. preferable.

In depositing the hydrolysis product on the seed particles,
It is preferable that the alcohol concentration in the reaction system is 35 to 97% by weight. If the alcohol concentration is less than 35% by weight, the compatibility with the added tetraethoxysilane will be poor and emulsion will occur, and the seed particles will tend to aggregate or amorphous products that are not spherical will be obtained. If it exceeds 97% by weight, the hydrolysis rate of tetraethoxysilane tends to become too slow. The alcohol concentration in the reaction system can be adjusted by adding water and alcohol together with tetraethoxysilane to the reaction system, alcohol in an amount of 10 mol or less per 1 mol of tetraethoxysilane, and water in an amount of 10 mol or less per 1 mol of tetraethoxysilane. It is preferably added in an amount of 2.0 to 24.0 mol per mol of tetraethoxysilane.

Effects of the Invention The silica particles obtained by the method of the present invention have almost no agglomerated particles because tetraethoxysilane is hydrolyzed and deposited on seed particles in the coexistence of a specific amount of methoxysilares to cause particle growth. They are monodispersed, spherical particles with an extremely sharp particle size distribution. Furthermore, there are very few small particles, for example, particles with a particle size of less than 172 mm, which is the average particle size. In addition, in the past, if particle growth was performed for a long time to obtain particles with a large particle size, the particle size distribution became broad and the number of agglomerated particles increased, but in the present invention, the large particle size of about 10 μm or more It is possible to obtain particles with a sharp particle size distribution.

Furthermore, the time required to obtain particles of a desired particle size, which conventionally required several days, can be significantly shortened. Furthermore, since the concentration of silica particles in the dispersion medium can be increased to about 20% by weight, manufacturing efficiency can be increased and costs can be reduced.

Example 1 Ethanol 3.930g, 28wt% ammonia water 7
A mixed solution of 10 g and 5,190 g of pure water was maintained at 35° C., and 180 g of tetraethoxysilane-A to which methoxysilanes as shown in Table 1 were added was added to this mixed solution while stirring. After adding tetraethoxysilane, it was stirred for 2 hours, and then 28% by weight aqueous ammonia was added at 50% by weight.
Add 0g, adjust the pH to 12.5, and adjust the average particle size to 0.1.
A heel sol with a solid content concentration of 0.48% by weight (as SiO2) in which seed particles with a 1 μm C■ value of 21% were dispersed was obtained.

Production of monodispersed silica particles Tetraethoxysilane-A21,20 in which the methoxysilanes shown in Table 1 were added to the heel sol obtained above.
0 g and 18,700 g of 3% by weight aqueous ammonia were simultaneously added over 15 hours while maintaining the heel sol at 35° C. and pH 12.5.

Table 2 shows the properties of the monodispersed silica particles in the obtained water-alcohol dispersion medium.

Further, a micrograph (X7500) of the obtained silica particles is shown in FIG.

Example 2 Production of monodispersed particles Heel Sol 6.400 obtained by the same method as Example 1
g, 43.600 g of tetraethoxysilane-B to which the methoxysilanes shown in Table 1 were added, and 65.800 g of a water-ethanol mixed solution (56% by weight of water, 60% by weight of ethanol, 4% by weight of ammonia), Added at the same time at 20 hours. During the addition, Healsol was kept at 35℃, ptt11.
．． It was held at 3.

Table 2 shows the properties of the monodispersed silica particles in the obtained water-alcohol dispersion medium.

Example 3 Preparation of Heal Sol After dissolving 0.5 g of NaOH in 8,500 g of pure water, silica sol (CATALOID S manufactured by Catalysts Kasei Kogyo Co., Ltd.) was dissolved in 8,500 g of pure water.
+-80P. Add 410g of (average particle size 0.08μm, CV value 15%), and further add 10g of isopropyl alcohol.
．． Added 300g.

Ammonia gas was then bubbled through the mixture until the pH was 11.3.

Production of monodispersed silica particles 37,300 g of tetraethoxysilane-C to which the methoxysilanes shown in Table 1 were added to the heel sol prepared as described above, and a water-monoethylene glycol mixed solution (73% by weight of water, At the same time, 42.100 g of monoethylene glycol (20% by weight, 7% by weight of ammonia) was added over 5 hours while maintaining the heel sol at 60° C. and pH 11.3.

Table 2 shows the properties of the obtained monodispersed silica particles.

Example 4 Preparation of Heal Sol Monodispersed silica particle dispersion obtained in Example 25.
000g and 5.000g of ethanol were mixed, and further 600g of 28% by weight ammonia water was added to adjust the pH to 12.
It was set as 4.

Production of monodisperse silica particles 42.300 g of tetraethoxysilane-D to which the methoxysilanes shown in Table 1 were added to the heel sol prepared as described above, and 34.10 g of 8% by weight ammonia water
0 g were added simultaneously over 23 hours. The Healsol was maintained at 25° C. and pH 12.0 during the addition.

Table 2 shows the properties of the obtained monodispersed silica particles.

Example 5 Preparation of Heal Sol Monodispersed silica particle dispersion obtained in Example 46.
000g, and 3.000g of monoethylene glycol was mixed with it. Blow ammonia gas into it. H12.7
It was prepared as follows.

Preparation of monodispersed silica particles 22,800 g of the above-described tetraethoxysilane D shown in Table 1 was added to the heel sol prepared as above.
and a water-monoethylene glycol mixed solution (68% by weight of water, 30% by weight of monoethylene glycol, 2% by weight of ammonia)
At the same time, 40.800 g of Healsol (% by weight) was added over 18 hours while maintaining the temperature at 25° C. and pH 12.0.

Table 2 shows the properties of the obtained monodispersed silica particles.

Example 6 Preparation of Heal Sol After dissolving 0.5 g of NaOH in 8,500 g of pure water, silica sol (CATALQIDSt-35 manufactured by Catalysts & Chemical Industry Co., Ltd.) was dissolved in 8,500 g of pure water.
0, average particle size 0.008, um, CV value 13%) 850
Then, 12,000 g of methanol was added.

Ammonia gas was blown into this to adjust p}111.5.

Production of monodisperse silica particles 6.200 g of tetraethoxysilane-E to which the methoxysilanes shown in Table 1 were added to the heel sol prepared as described above and a mixed solution of water and methanol (59% by weight of water, 40% by weight of methanol) were added to the heel sol prepared as described above. %, ammonia 1% by weight) 18
．． 700 g were added simultaneously over 12 hours. The Healsol was maintained at 60° C. and pH 11.0 during the addition.

Table 2 shows the properties of the obtained monodispersed silica particles.

Examples 7 to 8 Heel sol obtained in Example 1 and tetraethoxysilane-F to which methoxysilanes shown in Table 1 were added (Example 7) or tetraethoxysilane-G to which methoxysilanes were added (Example 7) Monodisperse silica particles were obtained under the same conditions as in Example 1 except that Example 8) was used.

The results are shown in Table 2.

Example 9 Preparation of Heal Sol 350.2 g of ethanol and 16.4 g of purified tetraethoxysilane-K without adding methoxysilanes shown in Table 1
A mixed solution of 350.2 g of ethanol, 78.0 g of 28% aqueous ammonia and 5.4 g of pure water was added to the mixed solution, and the mixture was stirred for 2 hours to obtain a heal sol. During the operation, the temperature of the reaction solution was maintained at 15°C. The average particle size of the seed particles in the obtained heel sol was 0.19 μm, the CV value was 0.5%, and the solid content concentration was 0.59 wt% (S iO
2).

Production of monodisperse silica particles Tetraethoxysilane 10 was prepared by adding the methoxysilanes shown in Table 1 to 800 g of the heel sol obtained above.
A mixed solution of 842.5 g of ethanol, 397 g of ethanol, 318 g of 28% aqueous ammonia, and 767 g of pure water was added over 19 hours while the reaction solution was maintained at 35°C.

Subsequently, 1403 g of ethanol, 28% was added to this reaction solution.
After adding a mixed solution of 477 g of ammonia water and 17 g of pure water, while maintaining the temperature at 35°C, add a mixed solution of 1047 g of tetraethoxysilane-8, 494 g of ethanol, 395 g of 28% ammonia water and 954 g of pure water to 19 g of pure water.
Added over time.

Furthermore, a mixed solution of 976 g of ethanol, 527 g of 28% aqueous ammonia and 19 g of pure water was added to 4110 g of the silica particle dispersion obtained above, and then, while maintaining the temperature at 35°C, 853 g of tetraethoxysilane-H, 403 g of ethanol, A mixed solution of 322 g of 28% aqueous ammonia and 777 g of pure water was added over 15 hours.

Table 2 shows the properties of the monodispersed silica particles in the water-alcohol dispersion medium thus obtained.

Example 10 Production of monodispersed silica particles The same conditions as in Example 9 were used except that the heel sol obtained in Example 9 and the tetraethoxysilane to which the methoxysilanes shown in Table 1 were added were used. Monodisperse silica particles shown in Figure 1 were obtained.

A heel sol was obtained under the same conditions as in Example 9, except that tetraethoxysilane-H (Example 11) and tetraethoxysilane-1 (Example 12) were used.

Production of monodisperse silica particles Monodisperse silica particles shown in Table 2 were obtained under the same conditions as in Example 9, except that the above Healsol and tetraethoxysilane were used.

Comparative Example 1 Using the heel sol of Example 1, purified tetraethoxysilane>'-7,t without adding methoxysilanes was used instead of tetraethoxysilane-A of Example 1, and the addition time was 78 hours. The other conditions were the same as in Example 1.

The results are shown in Table 2.

A second micrograph (X3500) of the obtained silica particles
As shown in the figure.

Note that tetraethoxysilane-A-K is S r C l
4 and ethanol in a conventional manner to prepare crude tetraethoxysilane, which was then purified by distillation (purity 100% by gas chromatography). Next, a predetermined amount of methoxysilane was added to each purified tetraethoxysilane.

In addition, the particle size of the monodispersed silica particles was measured using a light transmission particle size analyzer (Horiba CAPA700) except for Example 6, and in Example 6, a laser Dobler particle size analyzer (HIAC/ NiCOMP370 made by ROYCO
HPL). The CV value (uniformity coefficient) is
Calculated using the following formula.

2 D p D = Particle size when the cumulative weight is 16% 1 D 84% 2 D,・Average particle size In addition, 1/2・D, in Table 1 is the average particle size (D,). The percentage of particles with a particle size of less than 172 mm.

[Brief explanation of drawings]

FIG. 1 is a micrograph (X7500) of the silica particles obtained in Example 1, and FIG. 2 is a micrograph (13500) of the silica particles obtained in Comparative Example 1.

Claims (2)

[Claims] (1) Tetraethoxysilane is added to a water-organic solvent dispersion in which seed particles are dispersed, the tetraethoxysilane is hydrolyzed, and silica is attached onto the seed particles to cause particle growth. When producing dispersed silica particles, the hydrolysis reaction of tetraethoxysilane is
Formula [I] (CH_3O)_n・(C_2H_5O)_4_-_n
-Si (n=1-4)...[I] A method for producing monodisperse silica particles, characterized by carrying out in the coexistence of methoxysilanes represented by: (2) Above (CH_3O)_n・(C_2H_5O)_
4_-_n・Si is used in an amount of 0.05×10^-^2 to 6.0×10^-^2 mol (each molar ratio converted to SiO_2) per 1 mol of tetraethoxysilane The manufacturing method according to item 1.