JPH0442324B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing spherical silica particles of uniform particle size.

[Conventional technology]

A method for producing 0.05 μm to 2 μm silica fine particles by contacting an alkyl silicate with ammonia and water in an alcohol solvent has been disclosed by W. Stober et al. [J. Colloid & Interface
Sci., 26 , 62 (1968)].

Furthermore, a method is known in which a solution obtained by dissolving a metal alkoxide in an organic solvent is mixed with a solution consisting of water and a dispersant, and the metal alkoxide is hydrolyzed to produce fine ceramic powder (Unexamined Japanese Patent Publication No. Publication No. 166203 (Sho 60-166203). There has also been a report on the addition of ethanol, aqueous ammonia, and ethyl silicate to observe the reaction conditions and the progress of silica sphere growth as well as the particle size distribution (``Powders and Powder Metallurgy'' Vol. 23).
Volume 4, No. 137-142).

[Problems to be solved by the invention] Conventional alcohol solvent - alkyl silicate -
In the ammonia-water silica particle manufacturing method, it is not easy to control the particle size and particle size distribution, and secondary agglomeration of particles is likely to occur, so it is important to industrially produce particles with uniform particle sizes. It was difficult.

Furthermore, in the method disclosed in JP-A-60-166203, a dispersant is used to suppress agglomeration of particles produced by hydrolysis. However, this method is aimed at synthesizing extremely fine silica particles;
It is unsuitable for the synthesis of silica particles of relatively large particle size and uniform particle size.

In addition, with the conventional one-step production method of silica particles, it takes a long time to obtain the desired particle size, especially relatively large silica particles, and the particle size lacks uniformity. It was hot.

The present inventors have discovered that by first generating silica particles as a nucleus by a conventional method and then slowly growing these particles, silica particles of uniform particle size can be obtained in a short time, and have arrived at the present invention.

That is, an object of the present invention is to obtain spherical silica particles having a uniform particle size.

Another object of the present invention is to obtain highly purified spherical silica particles with high reaction efficiency.

[Means for solving problems]

The present invention provides a method for producing silica particles, comprising:
Silica characterized by hydrolyzing an alkyl silicate with water and ammonia in an alcohol solvent to generate silica particle nuclei, then adding an alkyl silicate and a hydrocarbon to grow and size the silica particle nuclei. This is a method for producing particles.

The alkyl silicate used in the present invention is an alkyl ester of orketic acid (H ₄ SiO ₄ ) and is represented by the general formula Si(OR) ₄ (R: alkyl group), and the alkyl group R usually has 1 to 1 carbon atoms. Although it is about 5,
Particularly preferred are alkyl silicates having 2 to 3 carbon atoms, such as ethyl silicate and propyl silicate, in view of their reactivity and ease of availability on an industrial scale.

The alcohol used in the present invention may be one that dissolves the alkyl silicate, and various liquid alcohols can be used, but if the number of carbon atoms is too large, the particle size distribution will become broad, which is not preferable.
Generally, alkyl alcohols having 1 to 6 carbon atoms can be used, but particularly preferred are alkyl alcohols having 1 to 3 carbon atoms, such as methanol, ethanol, and propanol.

Generation of silica particle nuclei, which is the first step of the present invention, can be carried out by hydrolyzing an alkyl silicate using water and ammonia in an alcohol solvent. Hydrolysis conditions can vary depending on the target particle size, but the amount of alcohol solvent to be used is 1 to 1 by weight relative to the alkyl silicate.
50 times, particularly preferably 2 to 20 times.

The amount of water added to hydrolyze the alkyl silicate needs to be at least 4 times the molar ratio of the alkyl silicate, but is usually about 5 to 100 times. The amount of ammonia may vary depending on the type of alkyl silicate used, the intended particle size, etc., but is approximately 1 to 20 times the amount of alkyl silicate in molar ratio.

The silica particle core of the present invention is prepared by stirring and mixing alkyl silicate, ammonia, and water in an alcohol solvent at 10 to 100°C for 5 minutes to several hours as described above.

The step can be carried out by adding and mixing an alkyl silicate and a hydrocarbon to a solution containing silica particle nuclei obtained in the first step. For example, the first
Alcohol, hydrocarbon and ammonia are added and mixed to the solution containing the silica particle nuclei obtained in the process,
An alkyl silicate can then be added to allow the growth of silica particle nuclei.

The amounts of ammonia and alkyl silicate used in the second step may vary depending on the target particle size, but are each 1 to 30 times, particularly preferably 2 to 20 times, the amounts used in the first step. When the target particle size is relatively large, it is necessary to increase the amount of ammonia and alkyl silicate added, but in such a case, it is desirable to dilute these reagents with an alcohol solvent before adding.

The hydrolysis conditions for the second step are 10-100℃, 1-10
It takes about an hour.

Note that in the second step of the present invention, hydrocarbons are added for the purpose of preventing particle agglomeration. Since this hydrocarbon is compatible with alcohol, it is not particularly limited as long as it is compatible with alcohol. From the viewpoint of ease of solvent recovery and price of hydrocarbons, aliphatic with 5 to 12 carbon atoms, Alicyclic and aromatic hydrocarbons are preferred, and those having 6 to 9 carbon atoms are particularly preferred. Examples of particularly preferred hydrocarbons include n-hexane, n-heptane, cyclohexane, methyl-cyclohexane, benzene, toluene, xylene, and the like.

〔Example〕

Hereinafter, the present invention will be explained using examples.

Example 1 120 g of ethanol and 5 g of ethyl silicate
cc flask, and 40 ml of concentrated ammonia water was added at 50°C and 300 rpm to generate silica particle nuclei. (Average particle total 0.5μm).

Next, 30 g of ethanol, 20 g of n-hexane,
A mixed solution of 15g of ethyl silicate was prepared under the same conditions.
It was slowly added dropwise over 15 minutes, and stirring was continued for an additional 30 minutes to prepare silica particles (average particle size
0.8μm).

FIG. 1 is a scanning electron micrograph of the particle structure of the obtained silica fine particles.

Furthermore, the particle size and particle size distribution of the generated particle nuclei and particles were measured using a centrifugal automatic particle size analyzer (Horiba, Ltd.,
CAPA-500).

The particle size distributions of particle nuclei and silica particles are shown in FIGS. 4 and 5, respectively.

From Figures 4 and 5, it can be seen that although the particle size of the silica particle nuclei was non-uniform during the silica particle nucleus generation in the first step, the particle size of the silica particles was was found to be extremely uniform.

Example 2 120g of ethanol and 10g of ethyl silicate
20 g of concentrated ammonia water was added at 0° C. and 300 rpm to generate silica particle nuclei (average particle size: 0.8 μm).

Next, 240 g of ethanol, 40 g of n-hexane,
Add 150g of ammonia water to the flask, and add a mixed solution of 100g of ethanol and 100g of ethyl silicate.
Add slowly over 60 minutes, stir for another 60 minutes,
Silica fine particles were prepared (average particle size 2.1 μm).
FIG. 4 is a scanning electron micrograph of the particle structure of the obtained silica fine particles. Furthermore, the particle size distribution of particle nuclei and silica particles was measured in the same manner as in Example 1, and the results are shown in FIGS. 6 and 7.

As is clear from FIGS. 6 and 7, the first
Although the particle size of the silica particle nuclei was non-uniform during the silica particle nucleus generation step, the particle size of the silica particles became extremely uniform after the second step, particle preparation step.

Comparative example 1 500ml of 160g of ethanol and 40g of concentrated ammonia water
Pour into a flask and slowly drip 20g of ethyl silicate at 30℃ and 300rpm over 20 minutes.
Stirring was continued for a minute to prepare silica particles. Third
The figure is a scanning electron micrograph of the obtained silica particle structure. The particle size distribution of the obtained silica particles is shown in FIG.

〔Effect of the invention〕

Although spherical silica particles can be obtained by the conventionally known alkyl silicate hydrolysis of alcohol-ammonia-hydrogen, the particles have a poor shape and lack uniformity in particle size, as shown in FIG.

However, in the method of the present invention, FIGS.
As is clear from the figure, silica particles with excellent uniformity in shape and particle size can be easily obtained.

The silica particles obtained in the present invention can be used for ceramics, catalyst materials, pigments, paints, synthetic resins,
Used as a filler in synthetic fibers.

[Brief explanation of drawings]

1 and 2 are scanning electron micrographs of the particle structure of silica particles obtained by the method of the present invention, and FIG. 3 is a scanning electron micrograph of the particle structure of silica particles obtained by the conventional method. , 4th
6 and 6 show the particle size distribution of silica particle nuclei, and FIGS. 5, 7, and 8 show the particle size distribution of silica particles.

Claims (1)

[Claims] 1. In a method for producing silica particles, an alkyl silicate is hydrolyzed with water and ammonia in an alcohol solvent to generate silica particle nuclei,
A method for producing silica particles, characterized in that an alkyl silicate and a hydrocarbon are then added to grow and size the silica particle nuclei.