KR100279766B1 - Method for preparing silica slurry for particle growth of pyrolytic silica nucleus and silica particles produced by this method - Google Patents

Abstract

The present invention relates to a method for preparing silica slurry for particle growth of pyrolytic silica nuclei by improving the irregularity of shape and size limitation by using tetraethylorthosilicate (hereinafter referred to as 'TEOS'), hydrolysis and condensation polymerization of water. will be. The manufacturing method is for growing the particles of pyrolysis silica nuclei, dispersing the silica particles in distilled water for a predetermined time, filtering only the dispersed of the silica particles, and the dispersion solution in a vacuum evaporator Maintaining a base component with ammonia water for concentrating, dissolving the growth nuclei of silica particles in the base component in alcohol, and performing sonication to separately separate the silica particles of the mixed solution; And dividing the amount of TEOS into a plurality of portions after the sonication process and repeating the reaction with the dispersion aqueous solution a plurality of times. Accordingly, by using pyrolytic silica, which is relatively inexpensive and widely commercialized, as a nucleus, TEOS is grown by hydrolysis and condensation polymerization with water, thereby increasing the weight fraction (5-10 wt%) and producing particles. It is possible to reduce the amount of TEOS used in the production of highly uniform, high purity spherical silica particles can be economically produced.

Description

Method for preparing silica slurry for grain growth of pyrolytic silica nuclei

The present invention relates to a method for producing a silica slurry, and more particularly, to improve irregularity of shape and size limitation by using tetrae-thylorthosilicate (hereinafter referred to as 'TEOS'), water hydrolysis, and polycondensation reaction. The present invention relates to a method for producing a silica slurry for particle growth of pyrolytic silica nuclei.

In general, spherical monodisperse silica particles were formed by hydrolysis and condensation polymerization of TEOS with water in an alcohol solvent under a basic atmosphere, which was initially studied by Stober. . Such monodisperse silica particles are particles having a uniform size and shape, and are used in a wide range of fields such as fine ceramics, paints, pharmaceuticals, and photographic photosensitizers, and their industrial added value is very high.

The Stover uses the Sol-gel-method, which has been studied a lot for inorganic materials, and has excellent chemical uniformity in multicomponent systems, and has a high specific surface area even at a relatively low sintering temperature. A breakthrough was made in obtaining dispersed silica (SiO ₂ ) particles.

The polymerization reaction of TEOS (Si (OC ₂ H ₅ ) ₄ ) by the sol-gel method is changed depending on the catalyst of the acid or base used. Generally, when an acid catalyst is used, three-dimensional network structure rather than growth into particles is used. Gels are formed, and when using a base catalyst (generally ammonia or ammonia water), spherical particles are formed. At this time, the reaction is typically performed at high pH for the purpose of producing spherical silica of micrometer or less. Both processes go through the steps of hydrolysis and polycondensation of TEOS. The conventional reaction scheme is as follows.

Si (OC ₂ H ₅ ) ₄ + 4H ₂ O → Si (OH) ₄ + 4C ₂ H ₅ OH

Si (OH) ₄ → SiO ₂ + 2H ₂ O

In the production of monodisperse spherical particles through the sol-gel method, the spherical particles are grown by hydrolysis and condensation reaction of TEOS under an ammonia catalyst, and the various variables such as TEOS concentration, water concentration, ammonia concentration and reaction temperature The exact reactor mechanism is still being studied since it is influenced by it.

In recent years, proposals have been made to overcome the shortcomings of the Stower method by growing TEOS by hydrolysis and condensation polymerization with water using relatively inexpensive and widely commercialized pyrolytic silica as a nucleus. .

That is, Bogush (GH Bogush, M. ATracy, C. F. Zukoski IV, J. Non-Cryst. Solid. 104, 95, 1998) and the like are used to determine the silica particles prepared by the conventional stover and the like. ) To grow silica particles and increase the weight fraction through the hydrolysis and polymerization reaction of TEOS. The correlation between the concentration of each reactant and the particle size is presented through particle growth reaction using TEOS, ammonia and water of various concentrations. In addition, S. Coenen et al prepared colloidal silica (Ludox AS-40) as a nucleus to produce a silica particle dispersion system of higher concentration and uniform size.

Thus, highly stable monodisperse particles, which have been widely studied for the production of particles with uniform distribution sizes ranging from several nm to several tens of nm, have optical, magnetic, and electrodynamic colloidal physical properties. It has the advantage of being uniform.

However, as described above, in the case of the currently commercialized and widely used precipitation method (Ludox) is composed of very small silica particles of about 20nm, compared to the particles produced by the sol-gel method Wide size distribution In addition, in the case of pyrolytic silica prepared by the gas phase method, most of them also have a size of 40 nm or less and a wide size distribution, and have disadvantages of irregular particle shapes. In addition, the spherical silica particles prepared by the above method has the disadvantage that the size of the uniformity and high purity, while the weight fraction is too low, the price of the reactant TEOS is very expensive. There is a problem that the industrial application is almost impossible, and it is used only as an extremely limited use for research or experiment as a model particle.

In order to solve the above problems, Japan has invented a method for preparing silica particles, such as Japanese Patent Application Laid-Open No. Hei 6-48720, which is a mixed solvent of alcohol and ammonia water in order to form silica seeds into particles of a desired size. The sonication is performed for a predetermined time by dispersing the particles into pieces and separating the particles individually using ultrasonic waves. At this time, the aqueous dispersion solution is maintained at a pH of about 10 using the ammonia water. Into such an aqueous solution, the TEOS reactant is injected to grow to a constant size by properly calculating the ratio of the conventional particle volume and the reactant. Here, the reaction time of the TEOS is one hour to allow the particles to grow sufficiently.

By the way, in the method of producing the silica particles as described above, the silica particles are sufficiently grown, but the size of the particles is not constant, and because of the non-uniformity, it is inconvenient to use a special filtering process to filter only the particles having a second constant size. There is a problem, and because the process is performed, the process is increased, the productivity is reduced, the cost of building the equipment is increased, there is a problem that the production cost is increased.

The present invention has been invented to solve the above problems, to improve the economics of the disadvantages of the Sol-gel method, and to produce silica particles of several tens of nm size, which is conventionally commercialized pyrolytic silica, in order to produce monodisperse silica particles of a desired size. The pyrolysis silica nucleus is used for the particle growth reaction through the sol-gel method used as the nucleus, and variably controls the size and shape of the final particles produced by the injection of TEOS having a time difference and a change in operating parameter conditions (nucleus concentration and amount of TEOS). It is an object of the present invention to provide a method for producing a silica slurry for grain growth.

1 and 2 are transmission micrographs of silica particles prepared by a method for preparing silica slurry for particle growth of pyrolytic silica nuclei according to the present invention.

3 is a transmission micrograph of silica particles prepared by the method for preparing silica slurry grown only with TEOS without growth nuclei.

The object is, according to the present invention, for the particle growth of the pyrolytic silica nucleus, dispersing the silica particles in distilled water for a predetermined time, and filtering only the dispersed of the silica particles, and Maintaining a base atmosphere with ammonia water to concentrate the dispersion solution with a vacuum evaporator, dissolving the growth nuclei of the silica particles in the base atmosphere in alcohol, and separately separating the silica particles in the mixture solution. It is achieved by a method of producing a silica slurry for particle growth of the pyrolytic silica nucleus, comprising the step of performing, and the step of dividing the amount of TEOS after the sonication step into a plurality of portions and repeating the reaction with the dispersion solution a plurality of times.

In addition, it is preferable to further include the step of filtering the dispersed silica particles only a plurality of times.

Here, the concentration of the pyrolytic silica particles used as the growth nucleus is preferably at least 0.002 g / ml.

Then, the molar ratio with the pyrolytic silica to the TEOS is adjusted to be at least about 0.5 mol, and the pH is preferably adjusted to be at least about 9 ~ 11.5.

Hereinafter, a method for preparing a silica slurry for particle growth of pyrolytic silica cores according to the present invention will be described in detail with reference to the accompanying drawings. 1 and 2 are transmission micrographs of silica particles prepared by a method for preparing silica slurry for particle growth of pyrolytic silica nuclei according to the present invention, and FIG. 3 is a method for preparing silica slurry grown only with TEOS without growth nuclei. Transmission micrograph of the silica particles produced by the.

First, a method of producing spherical uniform size silica particles is proposed through a sol-gel method using pyrolytic silica particles prepared by gas phase as a growth nucleus and TEOS as a precursor.

In other words, when pyrolytic silica is used as a growth nucleus, the shape, size, size distribution, and weight of the silica particles finally obtained by the concentration of pyrolysis silica, the amount of TEOS participating in the particle growth reaction, and the dispersibility of the pyrolysis silica used as the growth nucleus. It will have an important effect on the fraction. At this time, aerosil (Aerosil; Degussa Co) OX-50 is used as the pyrolytic silica particles produced by the gas phase method.

First, the solid pyrolytic silica particles are dispersed in distilled water. At this time, since the pyrolytic silica particles are not sufficiently dispersed and the particles are easily aggregated, the reaction must be preceded by sufficient pretreatment.

In the pretreatment process, the pyrolytic silica particles are dispersed in water and settled for a long time from one week to ten days to precipitate very large aggregated particles, and then only those dispersed in single particles are taken into account. Perform filtration several times using. Since the treated Aerosil OX-50 dispersion is very low in weight, it is maintained at pH 10 using ammonia water for concentration in a vacuum evaporator and at least for sonication that separates the particles individually using ultrasonic waves. Run for about 10 minutes. At this time, it is preferable to perform the sonication for about 25 to 30 minutes.

It is preferable to maintain the concentration of pyrolytic silica particles evenly dispersed in distilled water to about 0.002 ~ 0.2g / ml through the pre-treatment of the growth nucleus, and to use at least 4 times the ethyl alcohol as a solvent compared to the volume of the aqueous solution of pyrolytic silica. Do. Ethyl alcohol as a solvent is put in the reactor in advance, and the temperature is fixed at 25 ° C. using a thermostat, and then ammonia water is added so that the pH is in the range of 11 to 11.5. Next, an aqueous solution containing pyrolytic silica, which is a growth nucleus prepared in advance, is added in advance, and finally, the molar ratio with pyrolytic silica to TEOS is added in an amount of about 1 to 2 mol, and the silica particles are grown by reacting at least 10 hours for 30 hours. At this time, TEOS injects a predetermined amount at least once, and preferably, two to three injections are divided at predetermined time intervals to obtain more uniform silica particles. Since the injection is divided, the gelation phenomenon can be prevented so as not to increase the concentration of silicic acid during the reaction. In particular, the size of the silica particles can be adjusted to a desired size according to the number of times of the reaction by dividing the reference amount of the TEOS 10 times or more. For example, in the case of reacting by dividing the reference amount by 10 times, if the size of the particles can be grown to 10 scale, the size of the particles to be reacted 2 or 3 times or 6 or 7 times of the 10 times is determined. It can grow to 2 to 3 scales or 6 to 7 scales to control the growth of particles freely to the desired size.

Therefore, the final weight fraction can be improved to about 5 to 10% through the particle growth method using pyrolytic silica as a growth nucleus.

The silica slurry produced by the method for producing a silica slurry for particle growth of the pyrolytic silica nucleus of the present invention as described above will be described in more detail with reference to Examples.

Example 1

Pyrolytic silica, Aerosil OX-50, is used as a growth nucleus.

1) Reaction condition

2) Reaction Procedure

In Table 1 and Table 2, the reaction conditions and procedures, that is, in the case of A, is compared with the case of using the alcohol used as the solvent methyl alcohol (methylalcohol) and ethyl alcohol (ethylalcohol), in the case of B the final pH This is a comparison between the case where the control was performed with ammonia water and the case where tetramethylammoniumhydroxide (hereinafter referred to as 'TMAH') was used.

As shown in FIG. 1, the silica grown by the reaction conditions and the reaction procedure as described above, when ethanol is used as the alcoholol, relatively large particles can be obtained, and the size is closer to the monodispersed system. It can be seen that the distribution, and when the ammonia water is used for the final pH control, the particle shape is close to the spherical shape, it can be seen that it has a uniform size distribution.

Example 2

In order to improve the dispersibility of pyrolytic silica particles used as early growth nuclei, aerosil OX-50 particles were dispersed in water and precipitated for a long time from one week to ten days to precipitate very large aggregated particles. Filter several times. Since the pre-treated Aerosil OX-50 dispersion solution is very low in weight, the pH is maintained at about 10 using ammonia water, followed by concentration and growth reaction using a vacuum evaporator.

Particle growth experiments using pyrolytic silica dispersions prepared for several steps of pretreatment were carried out under the reaction conditions shown in Table 3 below.

In this case, the reaction is carried out by sequentially adding TEOS at sufficient intervals for 24 hours. At this time, the pre-processed samples are 5-1, 6-1, and the sample of TEOS input is 5-2, 6-3. To obtain a more uniform particle size distribution, the amount of TEOS involved in the reaction is slightly reduced to change the composition of water and alcohol.

As the reaction proceeds as described above, the pH tends to be lowered. In order to compensate for this, the pH lowered by using ammonia water is adjusted to be maintained in the range of 11.0 to 11.5. As shown in FIG. 2, the thus-produced silita particles are found to have a very improved dispersibility of the particles in both cases, and are grown to have a shape almost close to a perfect sphere. At this time, the size of the silica particles is small, about tens of nm.

On the other hand, the reaction composition of the production of the growth nucleus, that is, the particle without a seed (Seed) is shown in Table 4 below.

As shown in FIG. 3, the shape and size of the silica particles prepared in Table 4 may be proportional to the amount of TEOS participating in the reaction.

In other words, the size distribution of the particles increases as the size of TEOS increases and the size of the particles increases.The size of particles prepared by using the Sobel method without using crystal nuclei is about 40-50 nm and about 90-100 nm. It can be seen that the distribution size of has a fairly uniform spherical particle. However, the silica suspension prepared through this pure sol-gel reaction has a very low weight fraction of 2 to 3 wt%, and the price of TEOS, a precursor of the sol-gel reaction, is too high, which may cause difficulties in actual commercialization. .

The present invention is relatively inexpensive and widely commercialized using pyrolytic silica as a nucleus to grow TEOS by hydrolysis and condensation polymerization with water, thereby increasing the weight fraction (5 ~ 10wt%), producing particles It is possible to reduce the amount of TEOS used in the very uniform, high-purity spherical silica particles can be economically produced.

Claims (4)

A method for producing a silica slurry for grain growth of pyrolytic silica nuclei; Dispersing the silica particles in distilled water for a predetermined time; Filtering only the dispersed ones of the silica particles; Maintaining a base component with ammonia water to concentrate the dispersion solution with a vacuum evaporator; Dissolving the growth nuclei of the silica particles in the base component crisis in alcohol; Performing sonication to separately separate the silica particles of the mixed solution; And diluting the amount of TEOS into a plurality of portions after the sonication process, and repeatedly reacting the dispersion solution with the dispersion solution a plurality of times. The method of claim 1, wherein the concentration of the pyrolytic silica particles used as the growth nucleus is at least 0.002 g / ml. According to claim 1, wherein the molar ratio of the pyrolytic silica to the TEOS is adjusted to at least about 0.5 mol, pH is adjusted to at least about 9 ~ 11.5 of the silica slurry for the growth of the particles of the pyrolytic silica nucleus Manufacturing method. The method of claim 1, further comprising the step of filtering the dispersed silica particles only a plurality of times.