JP2590428B2 - Method for producing spherical hollow porous silica particles - Google Patents

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

[0002]

2. Description of the Related Art A method for producing hollow porous particles involves forming a w / o / w emulsion comprising a water glass and a benzene solution of a surfactant and an aqueous alkaline earth metal solution and then forming a silicate. There is a reaction. However, it is difficult to remove impurities by this method, and it is difficult to produce high-purity hollow porous particles.

[0003]

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

[0004]

According to the present invention, a partial hydrolysis is carried out by adding alcohol, water and an acid catalyst to tetraethyl orthosilicate, and then dibutyl phthalate is added. In this method, spherical hollow porous silica particles are produced by mixing, stirring and emulsifying in a contained ammonia aqueous solution, and performing a polycondensation reaction.

The present invention will be described in further detail. When tetraethyl orthosilicate (TEOS) is hydrolyzed with an acid catalyst such as hydrochloric acid, the reaction proceeds by an electrophilic reaction. When one of the alcohol groups of the alkoxide is replaced with a hydroxyl group, the subsequent hydrolysis is performed due to a decrease in the negatively charged portion of the alcohol group. The rate is slow and there is no complete hydrolysis. Due to this effect, the silica alkoxide has a hydrophobic alcohol group and a hydrophilic hydroxyl group. In order to ensure that such a partial hydrolysis reaction proceeds, it is necessary to use an acid catalyst and to 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 formed during the partial hydrolysis and is required as an inhibitor. Optimum reaction conditions are as follows: 1 mole of TEOS and 1 mole of alcohol.
About 5 moles and about 1 to 2 moles of water were appropriate.

When dibutyl phthalate is added to the partially hydrolyzed alkoxide solution, added to an aqueous ammonia solution and vigorously stirred using an emulsifier or the like, the hydrophobic group of the alkoxide is directed toward the organic solvent and the hydrophilic group toward the aqueous solution. o
/ W form an emulsion. The hydrolysis / polycondensation reaction of the alkoxide partially hydrolyzed by the base catalyst of ammonia mainly proceeds 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 in the oil droplets is unlikely to become silica particles. After completion of the reaction, these organic solvents can be easily washed and removed by the hollow porous walls, so that spherical hollow porous silica particles can be produced. Further, by changing the stirring speed of the aqueous solution, the average particle size of the produced particles can be adjusted, and thus spherical hollow porous silica particles having an average particle size of 2 to 8 μm can be produced.

[0007]

EXAMPLE Tetraethyl orthosilicate (TEOS) 20
ml, using TEOS: ethanol:
Water: hydrochloric acid was added at a molar ratio of 1: 2: 1: 0.03, and 9
A sample that had a reaction time of 0 minutes was prepared. To this was added 5 ml of dibutyl phthalate, and a 0.003% surfactant (Twe
300 ml of 1.75% aqueous ammonia solution containing en-80)
Particles are formed therein while stirring with an emulsifier (4000 revolutions / minute). Thereafter, the mixture was allowed to stand for about 1 day, filtered under pressure through a membrane filter, and washed with alcohol to obtain silica particles.
The properties of the particles vacuum dried at 50 ° C. are shown in Table 1. As a comparison, the bulk specific gravity of silica particles (average particle size of about 0.5 μm) prepared by a usual sol-gel method is 0.77 g / m 2.
1, the specific surface area is 20 m ² / g, which indicates that the silica particles of the present method are porous particles. Further, as a result of observing the polished particle cross section with an electron microscope, it was confirmed that this was a spherical hollow particle of silica.

[0008]

[Table 1]

[0009]

According to the present invention, high-purity spherical hollow porous silica particles can be industrially advantageously obtained.

Claims (1)

(57) [Claims] 1. An alcohol, water and an acid catalyst are added to tetraethyl orthosilicate to cause partial hydrolysis, and then dibutyl phthalate is added. This solution is mixed and stirred in an aqueous ammonia solution containing a surfactant. , Emulsification and polycondensation reaction to produce spherical hollow porous silica particles.