JP2000178357A - Production of fine silicone particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce fine silicone particles while enabling the average particle size to be controlled accurately and efficiently in a specified range by hydrolyzing a methyltrialkoxysilane in acidic water preadjusted to a specified electric conductivity by the addition of an acid catalyst and dropping the resultant hydrolyzate into an aqueous alkali solution to polycondense the hydrolyzate. SOLUTION: A methyltrialkoxysilane: CH3Si(OR)3 [wherein R is a (substituted) alkyl] is hydrolyzed in acidic water preadjusted to an electric conductivity of 0.5-200 mS/m, and the resultant water-alcohol solution of CH3 Si(OH)3 and/or a partial condensate thereof is dropped into an aqueous alkali solution and thus is polycondensed, giving fine silicone particles having an average particle size controlled in the range of 0.1-1 μm. An aqueous inorganic acid solution prepared by dissolving an inorganic acid, which acts as a catalyst, in an excess amount of water is used as the acid catalyst. Water added to the acid catalyst is preferably ion-exchange water having an electric conductivity of 0.1 mS/m or lower. The amount of water is preferably 2-10 mol per mol of the methyltrialkoxysilane.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing silicone microparticles, and more particularly, to a method for producing silicone microparticles, which has a spherical shape, a uniform particle size, and a particle size of 0.1 μm to 1
The present invention relates to a method for producing silicone fine particles capable of precisely controlling the average particle diameter in the range of μm.

[0002]

2. Description of the Related Art Conventionally, the following methods have been known as methods for producing silicone fine particles.

JP-A-60-13813 discloses that methyltrialkoxysilane and / or a partially hydrolyzed condensate thereof is converted to a chlorine atom present in the methyltrialkoxysilane and / or a partially hydrolyzed condensate thereof. Hydrolysis / condensation in an aqueous solution of ammonia or amine to which an amount sufficient for neutralization is further added with a necessary amount as a catalyst, whereby a polymethylsilsesquioxane powder having excellent free-flow properties is obtained. It is disclosed.

Japanese Unexamined Patent Publication (Kokai) No. 63-77940 discloses a method for producing spherical silicone fine particles, which includes methyltrialkoxysilane and / or a partially hydrolyzed condensate thereof or methyltrialkoxysilane and / or a part thereof. The mixed solution of the hydrolysis condensate and the organic solvent is placed in the upper layer, and the mixed solution of ammonia and / or the amine and the organic solvent is placed in the lower layer, and methyltrialkoxysilane and / or its partial hydrolysis condensate Are hydrolyzed and condensed to produce polymethylsilsesquioxane powders having a true spherical shape in which the shape of each particle is independent and a particle size distribution in the range of ± 30% of the average particle size.

Further, Japanese Patent Application Laid-Open No. Sho 63-295637 discloses that the amount of methyltrialkoxysilane and / or its partially hydrolyzed condensate is reduced to 1/10 or less of the weight of water, A method for producing a spherical silicone powder having an average particle diameter of 0.05 to 0.8 μm by adjusting the concentration of an amine to 0.01 to 5% by weight is disclosed.

[0006] The silicone powder obtained by such a method is used for the purpose of imparting water repellency, imparting lubricity and the like.
Used as a modifying additive in paints, plastics, rubber, cosmetics, paper, etc.

However, spherical silicone fine particles cannot be obtained by the production method disclosed in Japanese Patent Application Laid-Open No. 60-13813. Further, according to the method described in JP-A-63-77940, spherical silicone fine particles having a particle size range of 0.1 to 1.0 μm cannot be obtained. By the way, the average particle diameter of the silicone fine particles used for the purpose of imparting the slipperiness of the plastic film for video tapes is 0.1 to 1.0 μm.
m, control is required within a very narrow range of variation of the average particle diameter (standard deviation) of ± 0.05 μm for each production unit.

However, Japanese Patent Application Laid-Open No. 63-295637
However, the manufacturing method described in Japanese Patent Application Laid-Open No. H10-209400 has a problem in that control cannot be performed within such a narrow range of variation, and the efficiency of the apparatus is insufficient, such as using a large amount of water.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve such a conventional problem.
An object of the present invention is to provide a method for producing silicone fine particles capable of precisely and efficiently controlling the average particle diameter within the range of μm.

[0010]

Means for Solving the Problems The process for producing silicone microparticles of the present invention comprises: (A) a general formula: CH ₃ Si (OR) ₃ (I) wherein R is a substituted or unsubstituted alkyl group; Is hydrolyzed in acidic water adjusted to an electric conductivity of 0.5 to 200 mS / m by adding an acid catalyst to obtain a general formula: CH ₃ Si (OH) ( ₃ ) obtaining a water / alcohol solution of methylsilanetriol and / or a partial condensate thereof represented by (II);
A step of dropping a water / alcohol solution of the methylsilanetriol and / or a partial condensate thereof into an aqueous alkali solution and performing a polycondensation reaction to obtain a suspension containing silicone fine particles.

The silicone fine particles obtained by the production method of the present invention are spherical and have extremely uniform particle diameters in the range of 0.1 μm to 1 μm in average particle diameter, and furthermore, variation (standard deviation) of average particle diameter in each production unit. Is ± 0.0
The variation is controlled to an extremely narrow range of 5 μm.

The manufacturing method of the present invention comprises the following two steps.

In the first step (step (A)) of the production method of the present invention, the methyltrialkoxysilane represented by the general formula (I) is hydrolyzed in the presence of an acid catalyst, and Methylsilanetriol represented by the formula (II) and / or
Or a step of obtaining a partial condensate thereof.

As the methyltrialkoxysilane in the first step, for example, a compound obtained by alkoxylating methyltrichlorosilane with a suitable alcohol by a known method can be used. That is, R in the general formula (I) represents an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a 2-methoxyethyl group, a 2-ethoxyethyl group, a 2-propoxyethyl group, a 2-butoxy group. A substituted alkyl group such as an ethyl group is exemplified.

Of these, a methyl group, an ethyl group and a 2-methoxyethyl group are preferred from the viewpoint of the reaction rate.
Particularly, a methyl group is preferable.

In the hydrolysis reaction in the first step, an aqueous solution of an inorganic acid in which an inorganic acid serving as a catalyst is dissolved in excess water is used. The purpose of using an inorganic acid as an acid catalyst in this way is to control the hydrolysis reaction to control the molecular weight of the obtained methylsilanetriol and / or its partial condensate.

When an organic acid is used as the acid catalyst, it becomes difficult to efficiently control the hydrolysis reaction.

The inorganic acid used as an acid catalyst in the present invention may be exemplified by a hydrogen acid such as hydrochloric acid and hydrofluoric acid, and an oxo acid such as sulfuric acid and nitric acid. Is preferred.

The amount of the acid catalyst used is such that the electric conductivity of the aqueous solution used for hydrolyzing the methyltrialkoxysilane is 0.1 to 200 mS / m, preferably 0.5 to 100 mS / m.
The amount is in the range of mS / m.

The electric conductivity of the water to which the acid catalyst is added is 0.1
When it is less than mS / m, hydrolysis does not proceed sufficiently, and when it exceeds 200 mS / m, it becomes difficult to control the variation in particle diameter to an extremely narrow range.

The water to which the acid catalyst is added in the first step (water before the addition of the acid catalyst) is 0.1 m in electric conductivity.
S / m or less of ion-exchanged water is preferable,
It is more preferable that the ion-exchanged water is at most mS / m.

The amount of water used in the hydrolysis in the first step is preferably 2 to 10 mol per 1 mol of methyltrialkoxysilane. When the amount of water is less than 2 mol, hydrolysis does not proceed sufficiently, and when it exceeds 10 mol, methylsilanetriol and / or its partial condensate becomes unstable and tends to precipitate.

The temperature at the time of the hydrolysis is preferably in the range of 10 to 60 ° C. in order to precisely control the final average particle size of the silicone fine particles and its standard deviation, and the reaction is preferably performed in this range. The hydrolysis reaction of the first step is 1 to
This is done by continuing to stir the mixture for 10 hours.

In the second step (step (B)) of the production method of the present invention, methylsilanetriol and / or a partial condensate thereof obtained in the first step or obtained by further diluting with water Is added to an aqueous alkali solution to obtain a suspension containing silicone fine particles by a polycondensation reaction.

It is not necessary to add an organic solvent to control the particle size.

The alkali used in the second step may be any one as long as its aqueous solution shows basicity. This alkali is used as a neutralizing agent for the inorganic acid used in the first step, and is used as a neutralizer in the second step. Acts as a catalyst for the condensation reaction.

Examples of the alkali include metal hydroxides such as lithium hydroxide, sodium hydroxide and potassium hydroxide, ammonia and monomethylamine,
Amines such as dimethylamine can be exemplified. Among these, ammonia or amines such as monomethylamine and dimethylamine are preferable because they do not leave trace amounts of impurities that limit the use of silicone fine particles, and ammonia is particularly preferable because it is easily removed. The amount of the alkali used is an amount that neutralizes the inorganic acid and effectively acts as a catalyst for the polycondensation reaction.For example, in the case of using ammonia as the alkali, all the amounts used in the first step and the second step are used. 0.05 parts by weight or more (as NH ₃ ) is used per 100 parts by weight of water.

The required amount of alkali to be added can be easily determined experimentally, although the degree of dissociation differs for each alkali.

In the polycondensation reaction of the second step, an aqueous alkali solution is charged into a reaction vessel, and the methylsilanetriol obtained in the first step and / or a partial condensate thereof (hereinafter, referred to as the first step) are stirred while sufficiently stirring the inside of the reaction vessel. , "Silanol solution"
) Is dropped and brought into contact with the alkaline solution.

The dropping rate of the silanol solution is preferably such that the whole amount is dropped over 5 minutes or more, and particularly preferably 10 to 240.
It is more preferable to drop the solution over a period of minutes. In addition, basically, if the amount of the hydrolyzate adjusted in the first step increases, the scale in the second step also increases, so that the dropping time varies greatly depending on the reaction scale if the dropping rate per unit time is the same. Never. The stirring in the second step is
It is desirable to continue for about 2 to 10 hours after the addition of the silanol solution, as well as during the addition.

By performing the polycondensation reaction in this manner, a suspension containing silicone fine particles can be obtained.
Further, if necessary, dehydration, drying, and crushing can be performed to obtain silicone fine particles.

[0032]

According to the production method of the present invention, the average particle diameter is 0.1 μm to 1 μm, which has been difficult with the conventional production method.
Within the range of m, silicone fine particles whose average particle diameter is precisely controlled can be obtained with high yield and high device efficiency.

The silicone fine particles obtained by the production method of the present invention are useful as a surface modifier for paints, plastics, rubbers, papers and the like.

[0034] Particularly, a plastic film slipperiness imparting agent used for video tapes and video printer tapes,
It is suitable as a heat resistance imparting agent.

[0035]

The present invention will now be described by way of Examples and Comparative Examples.
This will be described in more detail. In these examples, parts represent parts by weight. The present invention is not limited by these examples.

Example 1 First Step In a reaction vessel equipped with a thermometer, a reflux condenser and a stirrer, an electric conductivity measured by using an electric conductivity meter (CM-11P manufactured by Toa Denpa Kogyo KK). Was charged with 1242 parts of distilled water having a concentration of 0.136 mS / m, and an aqueous solution of hydrochloric acid was added to adjust the electric conductivity of the mixed solution to 9.96 mS / m.

While stirring this solution at 23 ° C., 1360 parts of methyltrimethoxysilane was added. Hydrolysis proceeded, and the temperature rose to 50 ° C. in about 5 minutes to obtain a transparent reaction solution. . Then, after stirring was continued for 3 hours, filtration was performed to obtain a silanol solution.

The average molecular weight of methylsilanetriol and / or its partial condensate in the silanol solution obtained by this hydrolysis reaction was determined by using GPC (gel permeation chromatography) using THF (tetrahydrofuran) as a developing solvent. Was measured by GPC was measured using GPC system-11 manufactured by Showa Denko. The measured average molecular weight was 430.

Second Step Water 3 was placed in a reaction vessel equipped with a thermometer, a reflux condenser and a stirrer.
875 parts and 23 parts of a 25% aqueous ammonia solution were charged.

While stirring the mixture at 24 ° C., 1000 parts of the silanol solution obtained in the first step was added dropwise over about 10 minutes.

After completion of the dropwise addition, stirring was continued for 6 hours. During the stirring, fine particles of polymethylsilsesquioxane were precipitated, and the reaction solution turned into a milky white dispersion.

This was set in a centrifugal separator to settle the fine particles, taken out, and dried in a drier at 200 ° C. for 24 hours to obtain white fine particles.

Observation of these fine particles with an electron microscope revealed that the particles had a true spherical shape and an average particle size of 0.68 μm.
m, and the standard deviation was 0.09 μm.

The fine particles are placed in a magnetic crucible and placed in air for 9 hours.
When heated to 00 ° C. for pyrolysis, the remaining amount was 89.1.
%Met. This is a value close to the theoretical amount of 89.6%, in which polymethylsilsesquioxane is oxidized and thermally decomposed into silicon dioxide. Also, as a result of R-ray analysis of this pyrolyzate,
It was confirmed to be amorphous silica. This confirmed that the obtained white fine particles were polymethylsilsesquioxane. Examples 2 to 6 In the same manner as in Example 1, polymethylsilsesquioxane fine particles were obtained under the conditions shown in Table 1. Table 2 shows the results.

[0045]

[Table 1] [Examples 7 to 9] Polymethylsilsesquioxane fine particles were obtained in the same manner as in Examples 1 to 6, except that a reaction vessel having better heat retention than the reaction vessel used in the first step was used. Table 3 shows the average particle size and standard deviation of the obtained fine particles.
As shown in FIG.

FIGS. 1 to 3 show images of the fine particles obtained in Examples 7 to 9 taken by a scanning electron microscope.

[0047]

[Table 2]

[Table 3] Comparative Example 1 Distilled water 124 having an electrical conductivity of 0.168 mS / m was placed in a reaction vessel equipped with a thermometer, a reflux condenser, and a stirrer.
Two parts were charged, and an aqueous solution of hydrochloric acid was added to adjust the electric conductivity of the mixed solution to 2030 mS / m. While stirring at 25 ° C., 1360 parts of methyltrimethoxysilane was added. Hydrolysis proceeded, and the temperature rose to 61 ° C. in 3 minutes to obtain a transparent reaction solution. Then, when stirring was continued for several hours, the solution became cloudy, and when the stirring was stopped, the reaction solution was separated into two layers. When the lower layer was separated and analyzed, it was found that methylsilanetriol precipitated due to an increase in molecular weight and / or a partial condensate thereof was the main component.

[Brief description of the drawings]

FIG. 1 is a photograph showing the particle structure of polymethylsilsesquioxane fine particles of Example 7.

FIG. 2 is a photograph showing the particle structure of polymethylsilsesquioxane fine particles of Example 8.

FIG. 3 is a photograph showing the particle structure of polymethylsilsesquioxane fine particles of Example 9.

Claims (5)

[Claims] (A) a methyltrialkoxysilane represented by the general formula: CH ₃ Si (OR) ₃ (I) wherein R represents a substituted or unsubstituted alkyl group; Hydrolysis in acidic water adjusted to an electric conductivity of 0.5 to 200 mS / m by addition of a catalyst yields methylsilanetriol represented by the general formula: CH ₃ Si (OH) ₃ (II) and And / or a step of obtaining a water / alcohol solution of the partial condensate thereof; and (B) dropping the water / alcohol solution of the methylsilanetriol and / or the partial condensate thereof into an aqueous alkali solution to carry out a polycondensation reaction to carry out polycondensation. Obtaining a suspension containing: a method for producing silicone fine particles. 2. The method according to claim 1, wherein the acid catalyst used in the step (A) is an inorganic acid. 3. The silicone fine particles according to claim 1, wherein the average molecular weight of methylsilanetriol and / or a partial condensate thereof produced in the step (A) is in the range of 100 to 1,000. Manufacturing method. 4. The production of silicone fine particles according to claim 1, wherein the water to which the acid catalyst is added in the step (A) is ion-exchanged water having an electric conductivity of 0.5 mS / m or less. Method. 5. The silicone fine particles according to claim 1, wherein the amount of water used in the step (A) is in the range of 2 to 10 mol per 1 mol of methyltrialkoxysilane. Production method.