JP2003002973A - Method for producing fine spherical silicone particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain fine spherical particles having a small average particle diameter without reducing a yield and also without diluting a reaction solution. SOLUTION: In the method for producing the fine spherical silicone particles, comprising hydrolyzing an organotrialkoxysilane in an acidic solvent to obtain the silanol solution, adding and mixing an aqueous alkaline solution with the solution, and subjecting the mixture to a polycondensation reaction in a stationary state to form the fine spherical silicone particles, an organic solvent easily mischble in water is added to the reaction system, when or before the aqueous alkaline solution is added and mixed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing spherical silicone fine particles, and more particularly to a method for producing spherical polyorganosilsesquioxane fine particles having a small average particle diameter with good working efficiency.

[0002]

2. Description of the Related Art Conventionally, as a method for obtaining spherical polyorganosilsesquioxane fine particles, for example, Japanese Patent Laid-Open No.
The method disclosed in 0-186148 is known.

This method involves the addition of organotrialkoxysilanes such as methyltrialkoxysilane from 2 to 600
It is hydrolyzed in acidic water adjusted to an electric conductivity of μS / cm to give an organosilanetriol or its partial condensate solution, and an alkaline aqueous solution is added to this solution and mixed to cause a polycondensation reaction in a stationary state to give a spherical shape. This is a method of obtaining silicone fine particles.

According to this method, spherical silicone fine particles having a uniform particle size can be obtained, and the particle size can be controlled by controlling the amount of water during hydrolysis.

However, in order to obtain spherical silicone fine particles having a small particle diameter by this method, dilution or
Since it is necessary to increase the amount of water relative to the water of the organotrialkoxysilane, there is a problem in that when producing spherical silicone fine particles having a small particle size, the production efficiency with respect to time and apparatus volume becomes low.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned conventional problems, and has a small diameter of spherical silicone fine particles having an average particle diameter of 0.1 to 5 μm.
Alternatively, a spherical silicone fine particle having a small average particle diameter in the range of 0.1 to 5 μm and a small standard deviation with respect to the average particle diameter, preferably a standard deviation precisely controlled to 10% or less of the average particle diameter, can be efficiently used. It is an object to provide a method that can be manufactured.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to achieve the above object, and as a result, have found that the organosilanetriol obtained by hydrolysis before the hydrolysis of the organotrialkoxysilane is alkaline. By adding an easily soluble organic solvent to water until the aqueous solution is added or simultaneously with the addition of the alkaline aqueous solution,
It was found that the average particle size of the obtained spherical silicone fine particles, that is, polymethylsilsesquioxane fine particles, can be reduced without lowering the concentration of the organotrialkoxysilane in water.

The present invention has been made on the basis of such findings, and the method for producing spherical silicone fine particles of the present invention according to claim 1 is that (A) an organotrialkoxysilane is hydrolyzed in acidic water. , A solution of organosilanetriol and / or a partial condensate thereof (hereinafter, simply,
A silanol solution), and (B) adding and mixing an alkaline aqueous solution to the silanol solution, and subjecting the mixed solution to a polycondensation reaction with the organosilanetriol and / or its partial condensate in a stationary state. In the method for producing spherical silicone fine particles, which comprises the step of forming spherical silicone fine particles, at the time of adding the alkaline aqueous solution in the step (B) or before adding the alkaline aqueous solution in the step (B), The reaction system is characterized in that an easily soluble organic solvent is added to 5 to 80 parts by weight of water per 100 parts by weight of organotrialkoxysilane used for the reaction.

According to this manufacturing method, the average particle size is 0.
Spherical silicone fine particles having a small diameter in the range of 1 to 5 μm can be obtained.

In the method for producing spherical silicone fine particles according to the present invention, the organotrialkoxysilane (A) is hydrolyzed in acidic water adjusted to have an electric conductivity of 2 to 600 μS / cm. A step of obtaining a silanol solution, and (B) adding and mixing an alkaline aqueous solution to the silanol solution, and allowing the mixed solution to stand.
In the method for producing spherical silicone fine particles, which comprises a step of subjecting the silanol solution to a polycondensation reaction to form spherical silicone fine particles, a reaction system at the time of adding the alkaline aqueous solution in the step (B) or before the addition. And organotrialkoxysilane 10 used in the reaction
The feature is that an easily soluble organic solvent is added to 5 to 80 parts by weight of water per 0 parts by weight.

According to this method, the average particle size is 0.1 to 0.1.
It is possible to obtain spherical silicone fine particles having a smaller diameter in the range of 5 μm and a smaller standard deviation with respect to the average particle diameter.

In the present invention, the electric conductivity is used as the concentration unit of acid or alkali because the amount of acid or alkali used is very small and the error becomes large in weight unit.

In the step (A) in the method for producing spherical silicone fine particles of the present invention, the organotrialkoxysilane is hydrolyzed in acidic water obtained by adding an acidic catalyst to water,
This is a step of obtaining a silanol solution.

Examples of the organotrialkoxysilane used in the present invention include the organotrialkoxysilanes represented by the following general formula (I). R ¹ Si (OR ² ) ₃ ... (I) (In the formula, R ¹ represents a monovalent group selected from the group consisting of a substituted or unsubstituted alkyl group, an alkenyl group and a phenyl group, R ² represents the same or different substituted or unsubstituted alkyl group)

This organotrialkoxysilane is hydrolyzed in acidic water to form an organosilanetriol represented by the following general formula (II) and / or a partial condensate thereof. R ¹ Si (OH) ₃ …………… (II)

R ¹ in the above general formula (I) is
A methyl group is suitable, and as R ² , an alkyl group such as methyl, ethyl and butyl; and 2-methoxyethyl, 2-ethoxyethyl, 2-propoxyethyl, 2
An alkoxy-substituted hydrocarbon group such as -butoxyethyl is exemplified, and a methyl group, an ethyl group, and a 2-methoxyethyl group are preferable because of a high hydrolysis rate, and a methyl group is particularly preferable. Preferred methyltrialkoxysilanes include methyltrimethoxysilane, methyltriethoxysilane, methyltri-n-propoxysilane, methyltriisopropoxysilane and methyltris (2
-Methoxyethoxy) silane is exemplified, and one or two
A mixture of two or more species is used.

As the organotrialkoxysilane represented by the general formula (I), for example, organotrichlorosilane alkoxylated with a suitable alcohol by a known method is preferably used.

Hydrolysis of the organotrialkoxysilane is carried out in a reaction system in which water is acidified by adding an acidic catalyst. As the acid used for the acidic catalyst, either an organic acid or an inorganic acid can be used.

Examples of the organic acid include formic acid, acetic acid, propionic acid, oxalic acid, citric acid, etc., but it is easy to control the electric conductivity and control the partial condensation reaction of the produced polymethylsilanetriol. Acetic acid is particularly preferred due to its ease of use.

As the inorganic acid, any inorganic acid can be used as long as it does not leave impurities such as ionic substances that limit the use of the finally obtained polymethylsilsesquioxane fine particles. However, hydrochloric acid is particularly preferable because it is easily available.

The presence of a small amount of hydrogen chloride or organochlorosilanes such as methyltrichlorosilane contained as impurities in the organotrialkoxysilane changes the electric conductivity of water used for hydrolysis and affects the hydrolysis reaction. Should be avoided as much as possible because it will hinder the achievement of the object of the present invention of precisely controlling the average particle size of the polyorganosilsesquioxane fine particles finally obtained and its standard deviation.

As water used for hydrolysis, ion-exchanged water having an electric conductivity of less than 2 μS / cm is suitable.

Since the amount of acid used varies depending on the amount of water used, it is desirable to control it by the electrical conductivity of the acid aqueous solution in which the acid is dissolved.

The electrical conductivity of the aqueous acid solution used for hydrolysis in the present invention is preferably in the range of 2 to 600 μS / cm. When the electric conductivity is less than 2 μS / cm,
Sufficient hydrolysis cannot be obtained, and the standard deviation of the particle size distribution is more than 10% of the average particle size, that is, polymethylsilsesquioxane fine particles having a large particle size variation are likely to be formed.

When the electric conductivity exceeds 600 μS / cm, the hydrolysis reaction is difficult to control, and it becomes difficult to arbitrarily control the average particle diameter of the finally obtained polyalkylsilsesquioxane fine particles.

The amount of water used for the hydrolysis reaction is preferably in the range of 1 to 50 mol per 1 mol of organotrialkoxysilane. If the amount of water is less than 1 mol,
When the hydrolysis does not proceed sufficiently and exceeds 50 mol, the yield of the finally obtained polymethylsilsesquioxane fine particles is reduced and the production efficiency is reduced.

The average particle size of the polyalkylsilsesquioxane fine particles can be controlled by the amount of water used during hydrolysis, and the standard deviation of the average particle size can be controlled by the electric conductivity during hydrolysis. You can

The hydrolysis reaction is not particularly limited, but in order to control the organosilanetriol and / or its partial condensate with a high yield and to control the average particle size and its standard deviation with high accuracy, the hydrolysis temperature is in the range of 10 to 60 ° C. 1 to temperature
It is preferable to carry out the reaction while maintaining it for 6 hours.

Thus, the hydrolysis of the organotrialkoxysilane used in the first step causes the organosilanetriol and / or its partial condensate to react with excess water other than that consumed for hydrolysis. It is obtained in the form of a solution dissolved in a mixture with the alcohol formed. As will be described later, when an easily soluble organic solvent is added to water in the reaction system in the step (A), the added organic solvent also exists in the solution.

In the step (B) of the present invention, an alkaline aqueous solution is rapidly added to and mixed with the organosilanol solution after the step (A), and the homogeneously mixed reaction system is allowed to stand still more rapidly. It is done by putting it in.

The addition of the organic solvent in the present invention is (A)
It is possible to carry out at any stage from the state of water before the addition of the organotrialkoxysilane to the water used in the step of to the time of the addition of the alkaline aqueous solution in the step of (B). The closer to the timing of the addition of the alkaline aqueous solution in the step (a), the greater the effect of reducing the average particle size is, and it is most preferable to carry out it simultaneously with the addition of the alkaline aqueous solution.

The organic solvent used in the present invention may be of any type as long as it is easily soluble in water, but when the solvent to be added is the same as the alcohol derived from alkoxysilane,
The effect does not appear unless it is added immediately before or at the same time as the addition of the alkaline aqueous solution. As such an organic solvent, alcohols such as methanol, ethanol, isopropyl alcohol (IPA) and t-butyl alcohol, and ketones such as acetone are suitable.

From the viewpoint of resource reuse, it is preferable that the solvent to be added be the same as the alcohol derived from alkoxysilane. That is, in this case, since the added organic solvent and the by-product of hydrolysis are the same type of alcohol, both can be simultaneously recovered by the same distillation operation, and without fractionation operation after recovery. , Can be reused as it is. From this point of view, methanol, ethanol, isopropyl alcohol (IPA)
Is preferably used.

On the other hand, the effect of reducing the particle size increases as the number of carbon atoms in the alcohol increases and the amount of addition increases. From this viewpoint, it is preferable to use t-butyl alcohol.

The amount of the water-soluble organic solvent added to the silanol solution is 5 to 80 parts by weight, preferably 10 parts by weight per 100 parts by weight of the organotrialkoxysilane used.
˜70 parts by weight. The amount of this organic solvent does not include the amount of alcohols by-produced by hydrolysis of the organotrialkoxysilane.

The step (B) of the production method of the present invention comprises
This is a step of obtaining spherical polyorganosilsesquioxane fine particles by a polycondensation reaction from the silanol solution obtained in the step (A).

The alkaline aqueous solution used in the step (B) may be a basic aqueous solution. This alkaline aqueous solution acts not only as a neutralizing agent for the acid used in the step (A) but also as a catalyst for the polycondensation reaction of the organosilanetriol and / or its partial condensate.

Examples of the alkaline substance used in such an alkaline aqueous solution include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide and potassium hydroxide; ammonia; and organic amines such as monomethylamine and dimethylamine. It can be illustrated. Among these, ammonia and organic amines are preferable because they do not leave a trace amount of impurities that limit the use of the obtained spherical polyorganosilsesquioxane fine particles,
Ammonia is particularly preferred because it is easily removed.

The amount of the alkaline aqueous solution used is such that it neutralizes the acid and effectively acts as a catalyst for the polycondensation reaction. Also, the reaction system that is rapidly added and mixed and uniformly mixed is used as a polyorgano This is an amount that can maintain the time during which the silsesquioxane fine particles can be promptly placed in a static state before being produced and deposited.

That is, assuming that the amount required for neutralization is exceeded, for example, an aqueous ammonia solution having a concentration of 0.1 to 0.5% is added to 100 parts by weight of the silanol solution obtained in the step (A). 0.5 to 5 parts by weight is added.

The theoretical resin concentration in the step (B) is 2
It is preferably 0% or less, more preferably 10% or less.

In the step (B), a silanol solution is charged into a reaction vessel, and the silanol solution is added with the above-mentioned alkaline solution, or an alkaline solvent and a water-soluble organic solvent, and optionally stirred. Promptly and uniformly mix by the means of. The addition method is not particularly limited as long as it can be effectively added within the minimum mixing time, and it may be added from above the silanol solution or may be fed into the silanol solution through a nozzle or the like. The mixing time is a suitable minimum time required to dissolve the alkali catalyst in the reaction system, and for example, 5 to 30 ° C., preferably 10 minutes.
0.5 to 1 including the addition time at a temperature of -20 ° C
It takes 0 minutes, preferably 0.5 to 3 minutes.

After uniformly mixing the reaction system, the system is allowed to stand to complete polycondensation. Standing allows a preferred average particle size and standard deviation of 10% or less of the average particle size,
Since the efficiency with respect to time and apparatus volume is excellent, for example, 2 to 24 hours, preferably 2 to 24 hours at the above mixing temperature.
Do it for 10 hours.

In order to obtain a fine powder having a small standard deviation, it is preferable that the time interval from the completion of establishment of the stationary state to the production / precipitation of fine particles is large.

By the polycondensation reaction in the step (B), spherical polyorganosilsesquioxane fine particles can be obtained as a disversion or sol in a water / alcohol mixture.

The spherical silicone microparticles obtained by the present invention are spherical polyorganosilsesquioxane microparticles, and these spherical silicone microparticles can be used in the form of a disversion or sol, and if necessary, further Appropriate treatments such as filtration, drying and crushing may be performed to collect the fine powder.

[0047]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail with reference to Examples and Comparative Examples. In these examples, parts represent parts by weight. The invention is not limited by these examples.

Example 1 [Step (A)] A reaction vessel equipped with a thermometer, a reflux condenser and a stirrer was charged with an electric conductivity meter (CM manufactured by Toa Denpa Kogyo KK).
-11P) has an electrical conductivity of 1.02μS
Was charged with 360 parts of water, and acetic acid was added to make the electric conductivity of the mixed solution 5.19 μS / cm.

While stirring this solution at 25 ° C., 60 parts of methyltrimethoxysilane was added thereto,
Hydrolysis proceeded and the temperature rose to 35 ° C in about 15 minutes. After further stirring for 2 hours, the mixture was cooled to 18 ° C. to obtain a silanol solution.

[Step (B)] The electrical conductivity of the silanol solution obtained in the step (A) was 3.76 μS / cm. Then, while stirring this silanol solution at 18 ° C., 10 parts of isopropyl alcohol (IPA) and 0.4 parts of
% Aqueous ammonia solution (3 parts) were added at the same time, and the mixture was stirred for 3 minutes, then stopped and left to stand for 4 hours.

In this step, about 20 minutes after the addition of the aqueous ammonia solution, particles were drawn out and the whole reaction vessel became cloudy. The reaction solution was allowed to stand for 4 hours, passed through a 200-mesh wire net, and suction-filtered to obtain a wet cake. This was dried at 200 ° C. for 12 hours to obtain a white powder.

When the powder was observed with an electron microscope, the particle shape was a true sphere. The powder was measured with a particle size distribution analyzer (LS100Q manufactured by COULTER Co., Ltd.) with a refractive index set to 1.425. The average particle diameter was 2.53 μm and the standard deviation was 0.24 μm. It was

This powder was placed in a magnetic crucible and placed in air for 9
When it was heated to 00 ° C and pyrolyzed, the remaining amount was 89.0.
%Met. This is a value close to 89.6% of the theoretical amount of polymethylsilsesquioxane that undergoes oxidative pyrolysis to give silicon dioxide. As a result of X-ray analysis of this thermal decomposition product, it was confirmed to be amorphous silica.

Example 2 Spherical silicone fine particles were obtained in the same manner as in Example 1 except that the addition amount of isopropyl alcohol was changed to 35 parts.

Example 3 Spherical silicone fine particles were obtained in the same manner as in Example 1 except that isopropyl alcohol was added 30 minutes before the addition of a 0.4% aqueous ammonia solution.

Example 4 Spherical silicone fine particles were obtained in the same manner as in Example 1 except that isopropyl alcohol was added immediately before the addition of organotrialkoxysilane.

Example 5 Spherical silicone fine particles were obtained in the same manner as in Example 1 except that the organic solvent added was 10 parts of methyl alcohol.

Example 6 The organic solvent added was 10 parts of t-butyl alcohol,
Spherical silicone fine particles were obtained in the same manner as in Example 1 except that the addition amount of 0.4% aqueous ammonia solution was changed to 20 parts.

Comparative Example 1 Spherical silicone fine particles were obtained in the same manner as in Example 1 except that the organic solvent was not added.

Comparative Example 2 Spherical silicone fine particles were obtained in the same manner as in Comparative Example 1 except that the addition amount of 0.4% aqueous ammonia solution was changed to 20 parts.

Table 1 shows the average particle size and standard deviation of the spherical silicone particles obtained in each of the examples and comparative examples, together with the timing of addition of the starting material and the organic solvent.

[0062]

[Table 1] From these Examples and Comparative Examples, it can be seen that the average particle diameter of the obtained spherical silicone fine particles becomes small depending on the presence or absence of the addition of the organic solvent, the type of the organic solvent to be added and the timing of the addition. Moreover, according to the examples, spherical silicone fine particles having a standard deviation of 10% or less of the average particle diameter and a small variation in particle diameter can be obtained.

[0063]

According to the production method of the present invention, spherical silicone fine particles having a smaller average particle diameter can be produced without reducing the production efficiency of the spherical silicone fine particles with respect to time and apparatus volume.

The spherical polymethylsilsesquioxane fine particles obtained by the production method of the present invention are insoluble in an organic solvent and non-meltable, and the surface thereof is excellent in water repellency and lubricity, and is superior to the inorganic powder. While having a low specific gravity, it has characteristics that it is superior to organic powders in heat resistance, and also has less cohesiveness and superior dispersibility. Further, the most significant feature is that the standard deviation of the average particle diameter is controlled to be extremely small, so that the particle diameter is made uniform, which is excellent in imparting slipperiness and rolling property, and has a uniform light reflection or light diffusing action.

Therefore, taking advantage of such characteristics,
It is useful as a filler and a slipperiness improver in paints, plastics, rubber, paper, cosmetics, etc., or as an additive for modifying plastics for the purpose of adding a light diffusion function to an optical liquid crystal display device.

Claims (5)

[Claims] 1. A step of hydrolyzing (A) an organotrialkoxysilane in acidic water to obtain a solution of organosilanetriol and / or a partial condensate thereof,
(B) An alkaline aqueous solution is added to and mixed with the solution of the organosilanetriol and / or its partial condensate, and the mixed solution is allowed to stand, and the organosilanetriol and / or its partial condensate is subjected to a polycondensation reaction. And a step of forming spherical silicone particles, the method comprising the steps of: (B) adding the alkaline aqueous solution, or (B) adding the alkaline aqueous solution. A method for producing spherical silicone fine particles, characterized in that 5-80 parts by weight of water per 100 parts by weight of organotrialkoxysilane used in the reaction is added to the reaction system with an easily soluble organic solvent. 2. A step of hydrolyzing (A) an organotrialkoxysilane in acidic water adjusted to an electric conductivity of 2 to 600 μS / cm to obtain a solution of an organosilanetriol and / or a partial condensate thereof. , (B) an alkaline aqueous solution is added to and mixed with the solution of the organosilanetriol and / or the partial condensate thereof, and the mixed solution is allowed to stand to polycondense the organosilanetriol and / or its partial condensate. In the method for producing spherical silicone fine particles, the method comprises the steps of reacting to form spherical silicone fine particles, which are used in the reaction system during or before the addition of the alkaline aqueous solution in the step (B). 5 to 80 per 100 parts by weight of organotrialkoxysilane
A method for producing spherical silicone fine particles, which comprises adding an easily soluble organic solvent to parts by weight of water. 3. The method for producing spherical silicone fine particles according to claim 1, wherein the water-soluble organic solvent is a monohydric alcohol having 2 or more carbon atoms. 4. The organotrialkoxysilane comprises:
The method for producing spherical silicone fine particles according to any one of claims 1 to 3, which is methyltrimethoxysilane. 5. The water used for hydrolysis is ion-exchanged water having an electric conductivity of less than 2 μS / cm before being acidified, according to any one of claims 1 to 4. 1. A method for producing spherical silicone fine particles.