JPH0891821A - Production of spherical hollow porous silica particles - Google Patents

Abstract

PURPOSE: To produce high purity silica particles by a sol-gel method. CONSTITUTION: Alcohol, water and an acid catalyst are added to tetra-ethyl orthosilicate, partial hydrolysis is carried out and dibutyl phthalate is added. The resultant soln. is brought into emulsification and polycondensation by mixing and stirring in an aq. ammonia soln. contg. a surfactant to produce the objective high purity spherical hollow porous silica particles having low specific gravity, e.g. spherical hollow porous silica particles having 2-8μm average particle diameter, about 300m<2> /g specific surface area and 0.16g/ml bulk density.

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 spherical hollow silica used as an inorganic filler for sustained release particles, cosmetics, etc., and particularly to a method for producing spherical hollow porous silica particles by the sol-gel method. The present invention relates to a manufacturing method.

[0002]

2. Description of the Related Art A method for producing hollow porous particles is as follows. A w / o emulsion consisting of water glass and a benzene solution of a surfactant and a w / o / w emulsion from an alkaline earth metal aqueous solution are prepared, and then a silicate is prepared. Due to the reaction of. However, it was difficult to remove impurities by this method, and it was difficult to produce high-purity hollow porous particles.

[0003]

The conventional spherical hollow silica particles and a method for producing the same are w / o / w using water glass.
It is a method of preparing an emulsion and has problems in stability, production time, and purity of produced particles. The present invention is intended to solve these technical problems by a method of emulsifying after partial hydrolysis using the sol-gel method.

[0004]

According to the present invention, tetraethyl orthosilicate is subjected to partial hydrolysis by adding alcohol, water and an acid catalyst, and then dibutyl phthalate is added, and this solution is treated with a surfactant. This is a method for producing spherical hollow porous silica particles by a polycondensation reaction by mixing and stirring and emulsifying in an aqueous ammonia solution containing.

The present invention will be described in more detail. When tetraethyl orthosilicate (TEOS) is hydrolyzed with an acid catalyst such as hydrochloric acid, the reaction proceeds by an electrophilic reaction, so if one of the alcohol groups of the alkoxide is replaced with a hydroxyl group, the subsequent hydrolysis will occur due to the reduction of the negatively charged portion of the alcohol group. It is slow and does not completely hydrolyze. Due to this action, the silica alkoxide has a hydrophobic alcohol group and a hydrophilic hydroxyl group. In order to surely proceed such a partial hydrolysis reaction, it is necessary to use an acid catalyst and carry out the reaction with 6 mol of alcohol and 4 mol or less of water per 1 mol of TEOS. Also,
Without about 1 mole of alcohol, a solid is produced during partial hydrolysis and is required as an inhibitor. The optimum reaction conditions are as follows: 1 mol of TEOS to 1 to 1 alcohol
About 5 mol and 1-2 mol of water were suitable.

When dibutyl phthalate was added to this partially hydrolyzed alkoxide solution, and the mixture was added to an aqueous ammonia solution and stirred strongly using an emulsifier or the like, the hydrophobic groups of the alkoxide faced to the organic solvent side and the hydrophilic groups to the aqueous solution side. o
/ W form an emulsion. The hydrolysis / polycondensation reaction of the alkoxide partially hydrolyzed by the base catalyst of ammonia proceeds mainly from the interface of the o / w emulsion. Since the reaction-inactive dibutyl phthalate added is present in the oil droplets of the emulsion, the central portion of the oil droplets is unlikely to be silica particles. After the completion of the reaction, these organic solvents can be easily washed and removed by the hollow porous wall, and thus spherical hollow porous silica particles can be produced. Further, the average particle diameter of the produced particles can be adjusted by changing the stirring speed of the aqueous solution, and thus the spherical hollow porous silica particles having the average particle diameter of 2 to 8 μm can be produced.

[0007]

Examples Tetraethyl orthosilicate (TEOS) 20
ml is used, and the partial hydrolysis reaction is TEOS: ethanol:
Add water: hydrochloric acid in a molar ratio of 1: 2: 1: 0.03, and
What was performed with a reaction time of 0 minutes was prepared. Add 5 ml of dibutyl phthalate and add 0.003% surfactant (Twe
300 ml of 1.75% aqueous ammonia solution containing en-80)
Particles are generated while stirring (4000 rpm) with an emulsifier. Then, the mixture was left standing for about 1 day, filtered under pressure with a membrane filter, and washed with alcohol to obtain silica particles.
The characteristics of the particles dried under vacuum at 50 ° C. are shown in Table 1. For comparison, the bulk specific gravity of silica particles (average particle size of about 0.5 μm) prepared by the usual sol-gel method is 0.77 g / m 2.
1, the specific surface area is 20 m ² / g, and it can be seen that the silica particles of this method are porous particles. As a result of observing the cross section of the polished particles with an electron microscope, it was confirmed that these were spherical hollow silica particles.

[0008]

[Table 1]

[0009]

Industrial Applicability According to the present invention, highly pure spherical hollow porous silica particles can be industrially advantageously obtained.

Claims (1)

[Claims] 1. Tetraethyl orthosilicate is subjected to partial hydrolysis by adding alcohol, water and an acid catalyst, and then dibutyl phthalate is added, and this solution is mixed and stirred in an aqueous ammonia solution containing a surfactant. A method of producing spherical hollow porous silica particles by emulsification, polycondensation reaction.