JP6953114B2 - Silica-based hollow particles, core-shell particles and polystyrene particles, and methods for producing them. - Google Patents

Description

The present invention relates to silica-based hollow particles, core-shell particles and polystyrene particles, and a method for producing them.

In recent years, research on inorganic oxide fine particles has been conducted. When the inorganic oxide becomes nano-sized, the properties of the substance change, and the properties such as electrical, optical, and thermal properties also change significantly. Therefore, it has the potential to be applied as a new high-performance material.

The structure of the inorganic oxide fine particles includes a dense type, a porous type, and a hollow type. Among them, hollow type hollow particles are attracting attention as a new highly functional material because they have features such as low density and large specific surface area.

As a method for producing hollow inorganic oxide fine particles, a method for producing hollow silica particles using polystyrene particles as a core and hollow polystyrene particles produced by the production method have been proposed (see, for example, Non-Patent Document 1). ..

However, in the hollow silica particles described in Non-Patent Document 1 and the method for producing the hollow silica particles, the particle size distribution of the hollow silica particles has not been sufficiently studied. If the particle size distribution of the hollow silica particles to be produced is small, such as the hollow silica particles described in Non-Patent Document 1, the filling rate becomes low when the hollow silica particles are filled into various articles as a highly functional material, resulting in high functionality. There is a problem that the properties expected as a sex material cannot be fully exhibited.

Further, the hollow silica particles described in Non-Patent Document 1 have not been sufficiently studied for their dispersibility and have a problem of agglutination. When the hollow silica particles are aggregated and filled in various articles as a highly functional material, there is a problem that it is difficult to uniformly fill them.

As a result of diligent studies, the present inventor has further focused on the fact that silica-diameter hollow particles having a large aspect ratio have a low filling rate when filled in various articles as a highly functional material. Such silica-based hollow particles have a problem that they cannot sufficiently exhibit the properties expected as a highly functional material.

Therefore, it is required to develop silica-based hollow particles having suppressed aggregation, a large particle size distribution, and a small aspect ratio, core-shell particles and polystyrene particles capable of producing the silica-diameter hollow particles. Development of a production method capable of producing silica-diameter hollow particles, core-shell particles, and polystyrene particles is required.

Bull.Korean Chem.Soc.2011, Vol.32, No5 Fabrication of Uniform Hollow Silica Nanospheres using a Cationic Polystyrene Core

The present invention has been made in view of the above, and is various because agglomeration is suppressed, particles having a small aspect ratio occupy a ratio in a specific range, and the coefficient of variation of the particle size is in a specific range. To provide silica-based hollow particles that are easily filled uniformly when filled in an article, core-shell particles that can produce the silica-based hollow particles, and polystyrene particles that can be suitably used for producing these. The purpose. Another object of the present invention is to provide a production method capable of producing the silica-based hollow particles, core-shell particles and polystyrene particles.

As a result of diligent research to achieve the above object, the present inventor is a silica-based particle having an aspect ratio of 1.5 or less accounting for 95% or more of the total particles and a coefficient of variation of the particle size of 20 to 60%. According to the hollow particles, it was found that the above object can be achieved, and the present invention has been completed.

That is, the present invention relates to the following silica-based hollow particles, core-shell particles, and a method for producing them.
1. 1. Silica-based hollow particles characterized in that particles having an aspect ratio of 1.5 or less occupy 95% or more of the total particles, and the coefficient of variation of the particle size is 20 to 60%.
2. Item 2. The silica-based hollow particles according to Item 1, which have an average particle size of 30 to 150 nm.
3. 3. Item 2. The silica-based hollow particles according to Item 1 or 2, wherein the silica-based hollow particles contain silica or silica and a metal oxide.
4. Item 2. The silica-based hollow particles according to any one of Items 1 to 3, which are an antireflection film material, an insulating film material, or a heat insulating material.
5. Core-shell particles having polystyrene particles containing a dispersant as a core and having a silica-based shell covering the polystyrene particles.
A core-shell particle characterized in that particles having an aspect ratio of 1.5 or less occupy 95% or more of the total particles, and the coefficient of variation of the particle size is 20 to 60%.
6. Item 2. The core-shell particles according to Item 5, wherein the silica-based shell contains silica or silica and a metal oxide.
7. Polystyrene particles characterized in that particles having an aspect ratio of 1.5 or less occupy 95% or more of the total particles, the coefficient of variation of the particle size is 20 to 60%, and a dispersant is contained.
8. A method for producing silica-based hollow particles.
(1) A step of preparing polystyrene particles by polymerizing the styrene monomer in a solution containing a styrene monomer, a dispersant, and a mixed solvent. The mixed solvent is a mixture of water and acetone. Step 1, which is a solvent,
(2) The solution is prepared by adding (i) the polystyrene particles, (ii) alkoxysilane, or alkoxysilane and a metal alkoxide, and (iii) a basic catalyst to a solvent and stirring to prepare the solution. In the steps 2 and (3) of forming core-shell particles having a silica-based shell covering the polystyrene particles with the polystyrene particles as the core, and (3) thermally decomposing the polystyrene particles which are the cores of the core-shell particles. , Step 3 to remove the polystyrene particles
Manufacturing method, including.
9. Item 8. The production method according to Item 8, wherein the mixed solvent used in the step 1 has a mixing ratio of water and acetone in a mass ratio of 90: 10 to 20:80.
10. Item 8. The production method according to Item 8 or 9, wherein the dispersant is at least one selected from polyvinylpyrrolidone and hydroxypropyl cellulose.
11. Item 8. The production method according to any one of Items 8 to 10, wherein the alkoxysilane contains a tetraalkoxysilane.
12. Item 8. The production method according to any one of Items 8 to 11, wherein the silica-based hollow particles have an aspect ratio of 1.5 or less, accounting for 95% or more of the total, and a particle size variation coefficient of 20 to 60%.
13. Item 8. The production method according to any one of Items 8 to 12, wherein the silica-based hollow particles have an average particle size of 30 to 150 nm.
14. A method for producing core-shell particles.
(1) A step of preparing polystyrene particles by polymerizing the styrene monomer in a solution containing a styrene monomer, a dispersant, and a mixed solvent. The mixed solvent is a mixture of water and acetone. Step 1, which is a solvent,
(2) The solution is prepared by adding (i) the polystyrene particles, (ii) alkoxysilane, or alkoxysilane and a metal alkoxide, and (iii) a basic catalyst to a solvent and stirring to prepare the solution. In the step 2, the polystyrene particles are used as a core, and core-shell particles having a silica-based shell covering the polystyrene particles are formed.
Manufacturing method, including.
15. It is a method for producing polystyrene particles.
(1) A step of preparing polystyrene particles by polymerizing the styrene monomer in a solution containing a styrene monomer, a dispersant, and a mixed solvent. The mixed solvent is a mixture of water and acetone. A production method comprising step 1 which is a solvent.

The silica-based hollow particles of the present invention are filled in various articles because aggregation is suppressed, particles having a small aspect ratio occupy a ratio in a specific range, and the coefficient of variation of the particle size is in a specific range. If so, it is easy to fill evenly. Further, the core-shell particles of the present invention are also suppressed from agglomeration, particles having a small aspect ratio occupy a ratio in a specific range, and the coefficient of variation of the particle size is in a specific range. It can be easily manufactured. In addition, the polystyrene particles of the present invention can be suitably used for producing the silica-based hollow particles and core-shell particles.
In addition, the production method of the present invention can easily produce silica-based hollow particles, core-shell particles, and polystyrene particles in which aggregation is suppressed.

It is a figure which shows the TEM image of the silica-based hollow particle of Example 1 with a magnification of 200,000 times. It is a figure which shows the TEM image of the silica-based hollow particle of Example 2 with a magnification of 200,000 times. It is a figure which shows the TEM image of the silica-based hollow particle of Example 3 with a magnification of 200,000 times. It is a figure which shows the TEM image of the silica-based hollow particle of the comparative example 1 with a magnification of 200,000 times. It is a figure which shows the TEM image of the silica-based hollow particle of the comparative example 3 with a magnification of 200,000 times.

Hereinafter, the method for producing hollow silica particles of the present invention will be described in detail.

In the silica-based hollow particles of the present invention, particles having an aspect ratio of 1.5 or less occupy 95% or more of the total particles, and the coefficient of variation of the particle size is 20 to 60%. In the silica-based hollow particles having the above characteristics, the coefficient of variation of the particle size is in a specific range, and particles having an aspect ratio of 1.5 or less occupy a ratio in the specific range, so that the particle size is not uniform and aggregates. Is suppressed. Further, since the coefficient of variation of the particle size is in a specific range and particles having an aspect ratio of 1.5 or less occupy a ratio in the specific range, it is easy to be uniformly filled when various articles are filled. Further, also in the core-shell particles of the present invention, the coefficient of variation of the particle size is in a specific range, and particles having an aspect ratio of 1.5 or less occupy a ratio in the specific range, so that the particle size is not uniform and aggregation occurs. It is suppressed. Further, according to the production method of the present invention, by adjusting the polystyrene particles using a specific solvent in step 1, the coefficient of variation of the particle size of the core-shell particles formed in step 2 becomes a specific range, and the aspect ratio becomes. Particles with a value of 1.5 or less occupy a specific range, and agglomeration of core-shell particles is suppressed. Therefore, by the step 3 of thermally decomposing and removing the polystyrene particles which are the cores of the core-shell particles, aggregation is suppressed, the coefficient of variation of the particle size is in a specific range, and the aspect ratio is 1. Since particles of 5 or less occupy a ratio in a specific range, silica-based hollow particles that are easily uniformly filled when filled in various articles can be easily produced.

1. 1. Silica-based hollow particles In the silica-based hollow particles of the present invention, particles having an aspect ratio of 1.5 or less occupy 95% or more of the total, and the coefficient of variation is 20 to 60%.

The silica-based compound forming the silica-based hollow particles is not particularly limited as long as it contains silica, and may be formed only of silica.

When the silica-based compound contains a compound other than silica, the silica-based hollow particles preferably contain silica and a metal oxide. Examples of the metal oxide include oxides of metals capable of forming metal alkoxides, and specific examples thereof include oxides of aluminum, titanium, zirconium and the like. By using an oxide of aluminum, the surface charge (zeta potential, etc.) of the silica-based shell can be adjusted. Further, the refractive index of the silica-based shell can be adjusted by using oxides of titanium and zirconium.

The coefficient of variation of the particle size of the silica-based hollow particles of the present invention is 20 to 60%. 20 to 50% is preferable, and 20 to 40% is more preferable. When the coefficient of variation of the particle size of the silica-based hollow particles is within the above range, the aggregation of the silica-based hollow particles can be suppressed, and when the silica-based hollow particles are filled in various articles, the silica-based hollow particles can be easily filled uniformly.

In the present specification, the coefficient of variation of the silica-based hollow particles and the core-shell particles described later is photographed of the particles using a TEM (transmission electron microscope: JEM-2010, manufactured by JEOL Ltd.) under the condition of an acceleration voltage of 200 kV. Is taken, the minor axis of 100 arbitrarily selected particles is measured, the average value is obtained, and the value is calculated based on the following formula.
(Coefficient of variation) = [(standard deviation of particle minor axis) ÷ (average value of particle minor axis)] × 100

In the silica-based hollow particles of the present invention, particles having an aspect ratio of 1.5 or less occupy 95% of the total particles. If the amount of particles having an aspect ratio of 1.5 or less is less than 95% of the total number of particles, the aggregation of silica-based hollow particles cannot be suppressed, and when the particles are packed in various articles, it is difficult to uniformly fill them. The particles having an aspect ratio of 1.5 or less are preferably 97% or more, more preferably 99%.

In the present specification, the ratio of the silica-based hollow particles to the total particles having an aspect ratio of 1.5 or less, and the ratio of the core-shell particles to be described later to the total particles having an aspect ratio of 1.5 or less. The ratio is measured by the following method. That is, using a TEM (transmission electron microscope: JEM-2010, manufactured by Nippon Denshi Co., Ltd.), photographs of particles were taken under the conditions of a magnification of 200,000 times and an acceleration voltage of 200 kV, and each of the 100 arbitrarily selected particles was taken. The particle major axis and the particle minor axis of the particles are measured, and the aspect ratio of each particle is obtained based on the following formula. Next, the number of particles having an aspect ratio of 1.5 or less out of 100 particles is counted, and the number is defined as the ratio (%) of the particles having an aspect ratio of 1.5 or less to the total number of particles.
(Aspect ratio) = (Particle major axis) ÷ (Particle minor axis)

The average particle size of the silica-based hollow particles is preferably 30 to 150 nm, more preferably 35 to 120 nm, and even more preferably 35 to 100 nm. When the average particle size is in the above range, the aggregation of silica-based hollow particles can be further suppressed, and when the silica-based hollow particles are filled in various articles, the silica-based hollow particles can be easily filled more uniformly.

In the present specification, the average particle size is a value measured under the condition of an acceleration voltage of 200 kV using a TEM (transmission electron microscope: JEM-2010, manufactured by JEOL Ltd.).

The film thickness of the film (shell) forming the silica-based hollow particles is preferably 2 to 40 nm, more preferably 2 to 20 nm. When the thickness of the film is in the above range, the shell strength can be maintained while increasing the porosity of the silica-based hollow particles. In the present specification, the thickness of the film is determined by taking a photograph of the particles with a TEM (transmission electron microscope: JEM-2010, manufactured by JEOL Ltd.) under the condition of 200 kV, and of 100 particles arbitrarily selected. This is the average value obtained by measuring the shell thickness.

It is preferable that the silica-based hollow particles of the present invention are not substantially associated. When the silica-based hollow particles are not associated with each other, it becomes easier to fill various articles more uniformly. In the present specification, the state in which the silica-based hollow particles are associated means a state in which the hollow portions of the plurality of silica-based hollow particles are joined to form one hollow portion. The fact that the silica-based hollow particles are not substantially associated means a state in which the hollow portions of the silica-based hollow particles are not bonded. Further, the fact that the silica-based hollow particles of the present invention are not associated can be confirmed by observing a photograph of the silica-based hollow particles taken by using the above TEM.

As described above, the silica-based hollow particles of the present invention suppress agglomeration, have a large particle size distribution, and have a small aspect ratio, so that when they are packed in various articles, they are easily filled uniformly. Therefore, it is suitable as a high-performance material, and in particular, it can be suitably used as an antireflection film material, an insulating film material, or a heat insulating material.

2. Core-shell particles The core-shell particles of the present invention have polystyrene particles containing a dispersant as a core and have a silica-based shell that coats the polystyrene particles, and 95% or more of the particles have an aspect ratio of 1.5 or less. The coefficient of variation of the particle size is 20 to 60%. The core-shell particles have suppressed aggregation, a large particle size distribution, and a small aspect ratio, and the hollow silica particles of the present invention can be easily produced by thermally decomposing the polystyrene particles.

The silica-based shell that coats the polystyrene particles is the same as the silica-based compound that forms the silica-based hollow particles described above. Further, the thickness of the silica-based shell is the same as the film thickness of the film (shell) forming the above-mentioned silica-based hollow particles.

The average particle size of the polystyrene particles is preferably 20 to 150 nm, more preferably 25 to 120 nm, still more preferably 25 to 100 nm. By setting the average particle size of the polystyrene particles in the above range, the average particle size of the silica-based hollow particles can be set in an appropriate range.

The polystyrene particles contain a dispersant. When the polystyrene particles contain the dispersant, the dispersant is present on the surface of the polystyrene particles, and the aggregation of the polystyrene particles can be further suppressed. The dispersant is not particularly limited as long as polystyrene particles can be produced, and a known dispersant can be used. Examples of the dispersant include polyvinylpyrrolidone, hydroxypropyl cellulose, polyvinyl alcohol (PVA), polyethylene oxide, polypropylene oxide, collagen, polysaccharide (Arabic gum), and the like. Among them, the aggregation of polystyrene particles is suppressed. Polyvinylpyrrolidone and hydroxypropyl cellulose are preferable because they can suppress the aggregation of core-shell particles formed in step 2 described later. The above-mentioned dispersant can be used alone or in combination of two or more.

The content of the dispersant in the polystyrene particles is not particularly limited, but is preferably 0.01 to 100% by mass, more preferably 0.05 to 100% by mass, based on 100% by mass of the polystyrene particles. When the content of the dispersant is in the above range, the aggregation of polystyrene particles can be further suppressed.

The coefficient of variation of the particle size of the core-shell particles of the present invention is 20 to 60%. 20 to 50% is preferable, and 20 to 40% is more preferable. Since the coefficient of variation of the particle size of the core-shell particles is within the above range, the coefficient of variation of the particle size of the silica-based hollow particles obtained by thermally decomposing the polystyrene particles which are the cores of the core-shell particles should be within the above range. When the silica-based hollow particles are suppressed from agglomeration and the silica-based hollow particles are filled in various articles, they can be easily filled uniformly.

In the core-shell particles of the present invention, particles having an aspect ratio of 1.5 or less occupy 95% of the total particles. When the amount of particles having an aspect ratio of 1.5 or less is less than 95% of the total particles, the aggregation of silica-based hollow particles obtained by thermally decomposing the polystyrene particles which are the cores of the core-shell particles cannot be suppressed, and various articles. When filled in, it is difficult to fill evenly. The particles having an aspect ratio of 1.5 or less are preferably 97% or more, more preferably 99%.

The average particle size of the core-shell particles is preferably 30 to 150 nm, more preferably 35 to 120 nm, and even more preferably 35 to 100 nm. When the average particle size is in the above range, the aggregation of silica-based hollow particles can be further suppressed, and when the silica-based hollow particles are filled in various articles, the silica-based hollow particles can be easily filled more uniformly.

The film thickness of the film (shell) forming the core-shell particles is preferably 2 to 40 nm, more preferably 2 to 20 nm. When the thickness of the film is in the above range, the shell strength can be maintained while increasing the porosity of the silica-based hollow particles.

It is preferable that the core-shell particles of the present invention are not substantially associated. When the core-shell particles are not associated with each other, when the silica-based hollow particles obtained by thermally decomposing the polystyrene particles which are the cores of the core-shell particles are filled in various articles, they are easily filled more uniformly. In the present specification, the state in which the core-shell particles are associated means a state in which the polystyrene particles, which are the cores of the plurality of core-shell particles, are joined to form one secondary particle, and the core-shell. The fact that the particles are not substantially associated means that the polystyrene particles, which are the cores of the core-shell particles, are not bonded. Further, the fact that the core-shell particles of the present invention are not associated can be confirmed by observing a photograph of the core-shell particles taken by using the above TEM.

3. 3. Polystyrene particles The polystyrene particles of the present invention are polystyrene particles having an aspect ratio of 1.5 or less, accounting for 95% or more of the total, having a coefficient of variation of particle size of 20 to 60%, and containing a dispersant. Since the polystyrene particles have a particle size variation coefficient and an aspect ratio within the above ranges and contain a dispersant, they are used in step 1 of the method for producing core-shell particles of the present invention and the method for producing silica-based hollow particles, which will be described later. By being adjusted and used in step 2, agglomeration is suppressed, core-shell particles having a large particle size distribution and a small aspect ratio can be produced, and by using the core-shell particles in step 3, various articles can be produced. The hollow silica particles of the present invention, which are easily filled uniformly, can be easily produced.

The polystyrene particles are the same as the polystyrene particles forming the core-shell particles described above. The average particle size and zeta potential of the polystyrene particles are the same as those of the polystyrene particles forming the core-shell particles described above.

The coefficient of variation of the particle size of the polystyrene particles of the present invention is 20 to 60%. It is preferably 25 to 55%, more preferably 30 to 50%. When the average particle size of the polystyrene particles is in the above range, the fluctuation coefficient of the particle size of the core-shell particles can be in the above-mentioned range, and it can be obtained by thermally decomposing the polystyrene particles which are the cores of the core-shell particles. The fluctuation coefficient of the particle size of the silica-based hollow particles can be set in the above range, and when the aggregation of the silica-based hollow particles is suppressed and the silica-based hollow particles are filled in various articles, they are uniformly filled. It becomes easy to be filled.

In the present specification, the fluctuation coefficient of the polystyrene particles is arbitrarily selected by taking a photograph of the particles under the condition of an acceleration voltage of 5 kV using an SEM (scanning electron microscope: JSM-6700F, manufactured by JEOL Ltd.). It is a value calculated based on the following formula by measuring the minor axis of only 100 particles to obtain an average value.
(Coefficient of variation) = [(standard deviation of particle minor axis) ÷ (average value of particle minor axis)] × 100

In the polystyrene particles of the present invention, particles having an aspect ratio of 1.5 or less occupy 95% of the total particles. When the amount of particles having an aspect ratio of 1.5 or less is less than 95% of the total particles, the aggregation of silica-based hollow particles obtained by thermally decomposing the polystyrene particles which are the cores of the core-shell particles cannot be suppressed, and various articles. When filled in, it is difficult to fill evenly. The particles having an aspect ratio of 1.5 or less are preferably 97% or more, more preferably 99%.

In the present specification, the ratio of the polystyrene particles having an aspect ratio of 1.5 or less to the total particles is measured by the following method. That is, using an SEM (scanning electron microscope: JSM-6700F, manufactured by Nippon Denshi Co., Ltd.), photographs of particles were taken under the conditions of a magnification of 100,000 times and an acceleration voltage of 5 kV, and each of the 100 arbitrarily selected particles was taken. The particle major axis and the particle minor axis of the particles are measured, and the aspect ratio of each particle is obtained based on the following formula. Next, the number of particles having an aspect ratio of 1.5 or less out of 100 particles is counted, and the number is defined as the ratio (%) of the particles having an aspect ratio of 1.5 or less to the total number of particles.
(Aspect ratio) = (Particle major axis) ÷ (Particle minor axis)

In the present specification, the average value of the aspect ratio of the polystyrene particles is determined by using an SEM (scanning electron microscope: JSM-6700F, manufactured by Nippon Denshi Co., Ltd.) under the conditions of a magnification of 100,000 times and an acceleration voltage of 5 kV. A photograph is taken, the particle major axis and the particle minor axis of 100 arbitrarily selected particles are measured, and the average value of each is obtained, and the value is calculated based on the following formula.
(Average value of aspect ratio) = (Average value of particle major axis) ÷ (Average value of particle minor axis)

It is preferable that the polystyrene particles of the present invention are not substantially associated. When the polystyrene particles are not associated, the association of the core-shell particles and the silica-based hollow particles formed by using the polystyrene particles is suppressed, and the obtained silica-based hollow particles are filled in various articles. It becomes easier to fill more uniformly. In the present specification, the state in which the polystyrene particles are associated means a state in which a plurality of polystyrene particles are joined to form one secondary particle, and the polystyrene particles are substantially associated with each other. "Not" means that the polystyrene particles are not bonded. The fact that the polystyrene particles of the present invention are not associated can be confirmed by observing a photograph of the polystyrene particles taken using the above SEM.

4. Method for Producing Silica-based Hollow Particles The method for producing silica-based hollow particles of the present invention is as follows.
(1) A step of preparing polystyrene particles by polymerizing the styrene monomer in a solution containing a styrene monomer, a dispersant, and a mixed solvent. The mixed solvent is a mixture of water and acetone. Step 1, which is a solvent,
(2) The solution is prepared by adding (i) the polystyrene particles, (ii) alkoxysilane, or alkoxysilane and a metal alkoxide, and (iii) a basic catalyst to a solvent and stirring to prepare the solution. In the steps 2 and (3) of forming core-shell particles having a silica-based shell covering the polystyrene particles with the polystyrene particles as the core, and (3) thermally decomposing the polystyrene particles which are the cores of the core-shell particles. The step 3 for removing the polystyrene particles is included.

<Step 1>
Step 1 is a step of preparing polystyrene particles by polymerizing the styrene monomer in a solution containing (1) a styrene monomer, a dispersant, and a mixed solvent. The mixed solvent is water. This is a step in which the solvent is a mixture with acetone.

(Styrene monomer)
The styrene monomer is not particularly limited as long as polystyrene particles can be produced, but those containing a structural unit derived from a hydrophobic monomer such as alkyl (meth) acrylate and other copolymerizable monomer structural units. preferable. Preferable examples thereof include alkyl (meth) acrylate styrene having an alkyl group having 3 to 22 carbon atoms, 2-methyl styrene and the like.

The concentration of the styrene monomer used in step 1 in the solution is not particularly limited, but is preferably 0.1 to 20% by mass, preferably 0.2 to 10% by mass, based on 100% by mass of the above solution. More preferred. By setting the above concentration, the average particle size of the obtained polystyrene particles and the average particle size of the hollow silica particles as the final product can be controlled to about 30 to 150 nm.

(Dispersant)
The dispersant is not particularly limited as long as polystyrene particles can be produced, and a known dispersant can be used. Examples of the dispersant include polyvinylpyrrolidone, hydroxypropyl cellulose, polyvinyl alcohol (PVA), polyethylene oxide, polypropylene oxide, and the like. Among them, a core shell formed in step 2 described later by suppressing aggregation of polystyrene particles. Polyvinylpyrrolidone and hydroxypropyl cellulose are preferable because they can suppress the aggregation of particles. The above-mentioned dispersant can be used alone or in combination of two or more.

The concentration of the dispersant used in step 1 in the solution is not particularly limited, but is preferably 0.01 to 10% by mass, more preferably 0.05 to 5% by mass, based on 100% by mass of the solution. By setting the above concentration, the aggregation of polystyrene particles can be further suppressed, and the aggregation of core-shell particles formed in step 2 described later can be further suppressed.

(Mixed solvent)
The mixed solvent used in step 1 is a mixed solvent of water and acetone. By using such a mixed solvent, the coefficient of variation of the particle size of the core polystyrene particles does not become too small and the aspect ratio does not become too large, and the particle size of the core-shell particles formed in step 2 described later. The coefficient of variation and aspect ratio of can be adjusted to a specific range.

The mass ratio of water and acetone in the mixed solvent is not particularly limited, and is preferably 90:10 to 20:80, more preferably 80:20 to 40:60. By setting the mass ratio of water and acetone in the above range, it becomes easy to adjust the coefficient of variation and the aspect ratio of the particle size of the core-shell particles formed in step 2 described later to the above-mentioned specific range.

(Cationic polymerization initiator)
In step 1, the solution preferably contains a cationic polymerization initiator. The cationic polymerization initiator is not particularly limited as long as polystyrene particles can be obtained, and known inorganic peroxides, organic initiators, redox agents and the like can be used. Above all, it is more preferable to use a radical polymerization initiator such as an organic oxide or an azo compound. Organic oxides are represented by the general formula RO-OR, and azo compounds are represented by the general formula A-CN = CN-A. Specifically, benzoyl peroxide, 2,2'-azobis (isobutylamidine) dihydrochloride (AIBA), 4,4'-azobis-4-cyanovaleric acid, azobisisobutyronitonicyl (AIBN), 2 , 2'-azobis (2-methylpropioamide) dihydrochloride (AAPH), preferably 2,2'-azobis (isobutylamidin) dihydrochloride (AIBA), 2,2'-azobis (2-methylpro) Pioamide) dihydrochloride (AAPH). Of these, 2,2'-azobis (isobutylamidine) dihydrochloride (AIBA) and 4,4'-azobis-4-cyanovaleric acid are more preferable, and 2,2'-azobis (isobutylamidine) dihydrochloride (AIBA). Is more preferable.

The concentration of the cationic polymerization initiator used in the above step 1 in the solution is not particularly limited, but is preferably 0.01 to 1% by mass with the solution as 100% by mass. By setting the above concentration, the average particle size of the obtained polystyrene particles and the average particle size of the hollow silica particles as the final product can be controlled to about 30 to 150 nm.

(Polymerization reaction)
In step 1, the polymerization reaction of the styrene monomer is carried out in a solution containing the styrene monomer, the dispersant, and the mixed solvent. The polymerization reaction can be carried out by mixing and stirring the above solutions.

The temperature during the polymerization reaction of the solution in step 1 is not particularly limited, but is preferably 40 ° C. or higher and lower than the boiling point of the solvent, and more preferably 50 to 90 ° C. If the reaction temperature is too low, the reaction rate may slow down, and if it is too high, the solvent may evaporate and the polymerization reaction may not be able to continue.

The reaction time of the polymerization reaction is not particularly limited, but is preferably 1 to 720 minutes, more preferably 10 to 600 minutes. If the reaction time is too short, the reaction may be insufficient.

Polystyrene particles are prepared by the above polymerization reaction. The average particle size of the polystyrene particles is preferably 20 to 150 nm, more preferably 25 to 120 nm, still more preferably 25 to 100 nm. By setting the average particle size of the polystyrene particles in the above range, the average particle size of the core-shell particles formed in step 2 and the average particle size of the silica-based hollow particles produced in step 3 can be set in an appropriate range. can.

Polystyrene particles are prepared by the step 1 described above.

<Process 2>
In step 2, (2) the polystyrene particles, (ii) alkoxysilane, or alkoxysilane and metal alkoxide, and (iii) basic catalyst are added to and stirred in a solvent to prepare a solution. This is a step of forming core-shell particles having the polystyrene particles as a core and having a silica-based shell covering the polystyrene particles in the solution.

(solvent)
Water is preferably used as the solvent used in step 2. By using water, core-shell particles can be formed inexpensively and safely.

As the solvent, a hydrophilic solvent can also be used. Examples of the hydrophilic solvent include alcohols such as methanol, ethanol, n-propanol, isopropanol, ethylene glycol, propylene glycol and 1,4-butanediol, ketones such as acetone and methyl ethyl ketone, and esters such as ethyl acetate. be able to. Among these, alcohols are preferably used, and methanol, ethanol, and isopropanol are more preferable. As the solvent, it is more preferable to use an alcohol of the same type as the alcohol produced by hydrolysis of the silicon compound. By using an alcohol of the same type as the alcohol produced by hydrolysis of the silicon compound, the solvent can be easily recovered and reused.

One of the above solvents may be used alone, or two or more kinds of solvents may be mixed and used.

As the solvent, water and a hydrophilic solvent may be mixed and used. The mass ratio of hydrophilic solvent: water is not limited, but 90:10 to 10:90 is preferable, and 50:50 to 10:90 is more preferable. By setting the mass ratio in the above range, the average particle size of the obtained hollow silica particles can be easily controlled to about 30 to 150 nm.

As the solvent, a hydrophobic solvent can also be used. Examples of the hydrophobic solvent include organic hydrocarbon solvents having a water solubility of less than about 1 g per 100 g at 100 ° C. As such a hydrophobic solvent, a linear or branched or cyclic alkane having 6 to 10 carbon atoms, for example, hexane, cyclohexane, heptane, octane, or isooctane can be used. Among them, octane is more preferable.

(Polystyrene particles)
As the polystyrene particles used in the step 2, the polystyrene particles prepared in the above step 1 may be used.

The concentration of polystyrene particles in the solution is preferably 0.01 to 50% by mass, more preferably 0.01 to 20% by mass.

(Alkoxysilane)
The alkoxysilane used in step 2 is not particularly limited, and for example, the general formula (1)
Si (OR ¹ ) ₄ (1)
Examples thereof include tetraalkoxysilanes and derivatives thereof. In the above general formula (1), R ¹ is the same or different and is an alkyl group, preferably a lower alkyl group having 1 to 8 carbon atoms, and more preferably a lower alkyl group having 1 to 4 carbon atoms. More preferably, it is a lower alkyl group having 1 to 3 carbon atoms. A methyl group, an ethyl group, a propyl group, an isobutyl group, butyl group, pentyl group, can be exemplified a hexyl group or the like, in that it is possible to obtain a dense silica shell, tetra R ¹ is a methyl group Methylsilane (TMS) is more preferred. Further, if the number of carbon atoms is too large, silica may be difficult to be produced. The dense silica-based shell is a silica-based shell in which siloxane bonds are more completely formed and there are few remaining silanol groups.

As the alkoxysilane used in step 2, the general formula (2) is also used.
Si (OR ¹ ) ₃ R ² (2)
Examples thereof include trialkoxysilanes represented by and derivatives thereof. In the general formula (2), R ^{1 is the same as R 1 in the} general formula (1), and R ² is hydrogen or the same alkyl group as the alkyl group described as ^{R 1.}

Examples of the derivative of the alkoxysilane include a low condensate obtained by partially hydrolyzing the alkoxysilane.

The above-mentioned alkoxysilane may be used alone or in combination of two or more. Above all, it is preferable to contain trialkoxysilane and tetraalkoxysilane in that aggregation can be prevented at the stage of core-shell particles and surface modification with a silane coupling agent or the like is facilitated.

The concentration of alkoxysilane in the above solution is preferably 0.01 to 50% by mass, more preferably 0.01 to 20% by mass.

(Metal alkoxide)
In step 2, the arcosisisilane and the metal alkoxide may be mixed and used. The metal alkoxide is not particularly limited, and known metal alkoxides can be used. Examples of such metal alkoxides include aluminum alkoxides, titanium alkoxides, zirconium alkoxides and the like. When aluminum alkoxide is used, the surface charge (zeta potential, etc.) of the silica-based shell can be adjusted. Further, when titanium alkoxide or zirconium alkoxide is used, the refractive index of the silica-based shell can be adjusted.

The concentration of the metal alkoxide in the solution is preferably 0.01 to 50% by mass, more preferably 0.01 to 20% by mass.

In step 2, the alkoxysilane and the metal alkoxide may be added separately to prepare a solution, or the alkoxysilane and the metal alkoxide may be mixed, hydrolyzed, and then added to the solution. By mixing alkoxysilane and metal alkoxide, hydrolyzing them, and then adding them to the solution, the following formula (3)
Si-OM (3)
It is possible to form a silica-based shell having a bond represented by and uniformly containing the metal represented by M in the formula (3).

In the above formula (3), M represents a metal, preferably aluminum, titanium, or zirconium.

Examples of the method of mixing the above-mentioned alkoxysilane and the metal alkoxide, hydrolyzing the mixture, and then adding the metal alkoxide to the solution include the methods described in Japanese Patent Application Laid-Open No. 2005-41722.

(Basic catalyst)
The basic catalyst used in step 2 is not particularly limited, and a known basic catalyst can be used, but in particular, an organic base catalyst containing no metal component and a metal in terms of avoiding mixing of metal impurities. Inorganic catalysts containing no components are suitable. Examples of the organic base catalyst include nitrogen-containing organic base catalysts such as ethylenediamine, diethylenetriamine, triethylenetetraamine, urea, ethanolamine, tetramethylammonium hydroxide (TMAH), tetramethylguanidine, and basic amino acids. .. Moreover, the ammonia water is mentioned as the said inorganic base catalyst. An organic base catalyst having low volatility is preferable because it does not volatilize in the temperature range when the step 2 is performed. In the case of volatilizing base, it may be added continuously to maintain the pH of the solution. In addition, ammonia water is preferable because it is inexpensive and economically superior.

The basic catalyst may be used alone or in combination of two or more.

The concentration of the basic catalyst in the above solution is preferably 0.1 to 5% by mass, more preferably 0.5 to 3% by mass.

In step 2, a solution is prepared by adding (i) polystyrene particles, (ii) alkoxysilane, or alkoxysilane and metal alkoxide, and (iii) basic catalyst to the above solvent and stirring to prepare a solution. Among them, core-shell particles having polystyrene particles as a core and having a silica-based shell covering the polystyrene particles can be formed.

The temperature of the solution in the above step 2 is not particularly limited, but is preferably 5 to 200 ° C, more preferably 5 to 150 ° C. If the temperature is too low, the reaction rate may slow down, and if it is too high, the solvent may evaporate.

The stirring time in the above step 2 is not particularly limited, but is preferably 1 to 1200 minutes, and more preferably 1 to 600 minutes. If the stirring time is too short, the reaction may be insufficient.

By the step 2 described above, it is possible to form core-shell particles having the polystyrene particles as the core and having a silica-based shell covering the polystyrene particles.

<Step 3>
Step 3 is a step of removing the polystyrene particles by thermally decomposing the polystyrene particles, which are the cores of the core-shell particles. Since the inside of the core-shell particles is filled with polystyrene particles as a core, it is possible to make the inside of the shell hollow by removing the polystyrene particles to produce silica-based hollow particles that can be used as a highly functional material. can.

In step 3, the polystyrene particles are removed by thermal decomposition. The thermal decomposition is not particularly limited, and examples thereof include firing. In the case of firing, if the firing temperature is too low, polystyrene particles and other organic components may remain in the silica-based hollow particles, and if the firing temperature is too high, the shell may be destroyed. Therefore, as a method for removing polystyrene particles by firing, for example, using an ultrasonic atomizer, a two-fluid nozzle, or the like, the solution prepared in step 2 is sprayed into an electric furnace, and the solution is preferably 350 in the electric furnace. Examples thereof include a method of firing in a high temperature region of ~ 1500 ° C., more preferably 400 to 1200 ° C., still more preferably 600 to 1000 ° C. By firing for a sufficient time to remove the polystyrene particles by this method, the polystyrene particles can be removed from the core shell particles with almost no destruction of the shell.

When removing polystyrene particles by spraying the solution prepared in step 2 into an electric furnace and firing it, a low temperature in a temperature range of about 150 to 250 ° C. is in front of the high temperature region of the electric furnace. It is preferable to provide a region so that the sprayed solution passes through the low temperature region and then is sprayed into the high temperature region. As the sprayed solution passes through the low temperature region, the solvent in the solution gradually evaporates, which promotes the formation of silica-based hollow particles in the droplets of the spray liquid. If the low temperature region is not provided, the formation of silica-based hollow particles is insufficient, and the shape of the silica-based hollow particles may be distorted.

The average particle size of the silica-based hollow particles obtained through the above steps is preferably 30 to 150 nm, more preferably 35 to 120 nm, and even more preferably 35 to 100 nm. When the average particle size of the obtained silica-based hollow particles is in the above range, the aggregation of the silica-based hollow particles can be further suppressed, and when the silica-based hollow particles are filled in various articles, they are easily filled more uniformly. Become.

In the silica-based hollow particles obtained through the above steps, particles having an aspect ratio of 1.5 or less preferably occupy 95% of the total particles, more preferably 97% or more, still more preferably 99%. By having the above ratio of particles having an aspect ratio of 1.5 or less of the obtained silica-based hollow particles, aggregation of the silica-based hollow particles can be suppressed, and when the silica-based hollow particles are filled in various articles, they are uniform. It becomes easy to be filled in.

The aspect ratio of the silica-based hollow particles obtained through the above steps is preferably 1.0 to 1.6, more preferably 1.0 to 1.4, and even more preferably 1.0 to 1.2. When the aspect ratio of the obtained silica-based hollow particles is in the above range, the aggregation of the silica-based hollow particles can be further suppressed, and when the silica-based hollow particles are filled in various articles, the silica-based hollow particles can be easily filled more uniformly. ..

The coefficient of variation of the particle size of the silica-based hollow particles obtained through the above steps is preferably 20 to 60%, more preferably 20 to 50%, still more preferably 20 to 40%. When the coefficient of variation of the particle size of the obtained silica-based hollow particles is within the above range, aggregation of the silica-based hollow particles can be suppressed, and when the silica-based hollow particles are filled in various articles, they are easily filled uniformly. Become.

By the step 3 described above, the polystyrene particles, which are the cores of the core-shell particles, are thermally decomposed and the polystyrene particles can be removed.

5. Method for producing core-shell particles The method for producing core-shell particles of the present invention is as follows.
(1) A step of preparing polystyrene particles by polymerizing the styrene monomer in a solution containing a styrene monomer, a dispersant, and a mixed solvent. The mixed solvent is a mixture of water and acetone. Step 1, which is a solvent,
(2) The solution is prepared by adding (i) the polystyrene particles, (ii) alkoxysilane, or alkoxysilane and a metal alkoxide, and (iii) a basic catalyst to a solvent and stirring to prepare the solution. Among them, the production method includes a step 2 of forming core-shell particles having the polystyrene particles as a core and having a silica-based shell covering the polystyrene particles.

The steps 1 and 2 are the same as the steps 1 and 2 described in the method for producing silica-based hollow particles. Since the polystyrene particles produced by the method for producing core-shell particles of the present invention can be removed by thermally decomposing the polystyrene particles which are the cores of the core-shell particles, the above-mentioned method for producing silica-based hollow particles It is suitable as the core-shell particles used in step 3 of the above.

6. Method for producing polystyrene particles The method for producing polystyrene particles of the present invention is as follows.
(1) A step of preparing polystyrene particles by polymerizing the styrene monomer in a solution containing a styrene monomer, a dispersant, and a mixed solvent. The mixed solvent is a mixture of water and acetone. It is a production method including step 1 which is a solvent.

The step 1 is the same as the step 1 described in the method for producing silica-based hollow particles and the method for producing core-shell particles. The polystyrene particles produced by the method for producing polystyrene particles of the present invention have a particle size variation coefficient and an aspect ratio of 1.5 or less in the above range, and contain a dispersant. By adjusting in step 1 of the above-mentioned manufacturing method of silica-based hollow particles and using in step 2, agglomeration is suppressed, a large particle size distribution, and a small aspect ratio are produced. By using the core-shell particles in step 3, the hollow silica particles of the present invention, which are easily uniformly filled when filled in various articles, can be easily produced.

Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the examples.

Example 1
Polystyrene particles and core-shell particles were prepared according to the production conditions shown in Table 1 according to the formulation shown in Table 2, and silica-based hollow particles were produced. Specifically, it is as follows.

(Step 1: Production of polystyrene particles)
Polystyrene particles were produced under the formulations and conditions shown in Table 2. Styrene monomer (manufactured by Aldrich), mixed solvent of ultrapure water and acetone, 2,2'-azobis (isobutylamidine) dihydrochloride (AIBA) (manufactured by Sigma-Aldrich) as a cationic polymerization initiator, dispersant It was synthesized by a batch-type reaction system using PVP (polyvinylpyrrolidone) as a solvent.

Specifically, first, a reaction device including a 1 L four-necked flask, a stirring blade, a mantle heater, and a cooling device was prepared.

Next, 382.5 g of ultrapure water, 467.5 g of acetone, and PVP (K90 molecular weight 630,000 manufactured by Tokyo Kasei Kogyo Co., Ltd.) were injected into a four-necked flask, and the stirring conditions were 250 rpm in a nitrogen atmosphere. The mixture was recirculated with stirring and heated for 10 minutes until the temperature did not change. The temperature at this time was 63 ° C. Then, the styrene monomer was added and heated for 5 minutes until the temperature did not change to uniformly disperse the styrene monomer to prepare a solution. The temperature of the solution was 63 ° C. The styrene monomer used was previously washed with 0.1 M-NaOH to remove the stabilizer.

Next, a 5% by mass AIBA aqueous solution previously dissolved in ultrapure water was added to the solution as a polymerization initiator to initiate the polymerization reaction. After a polymerization reaction was carried out at 63 ° C. for 10 hours in a nitrogen atmosphere, the mixture was cooled to room temperature to produce polystyrene particles in the solution.

(Step 2: Manufacture of core-shell particles)
Core-shell particles were produced according to the formulations and conditions shown in Table 2. Specifically, first, a reaction device equipped with a 1 L four-necked flask, a stirring blade, and a water bath was prepared. A solution in which the polystyrene particles produced in the above step 1 were dispersed was placed in a flask, methanol was added as a solvent, and a 25% aqueous ammonia solution was added to prepare solution B. Solution A was prepared by mixing TMOS and methanol. While keeping the solution B at 30 ° C., the solution A was added in 3 portions at intervals of 30 minutes. Stirring at 250 rpm for 1 hour, the polystyrene particles were used as the core in the solution to form core-shell particles having a silica-based shell covering the polystyrene particles.

The solution in which the core-shell particles were dispersed obtained in step 2 was dried on a hot plate at a temperature of 150 ° C. to obtain a powder of core-shell particles.

(Step 3: Manufacture of silica-based hollow particles)
The core-shell particles obtained in step 2 were heat-treated at a temperature of 700 ° C. to remove polystyrene particles to produce silica-based hollow particles.

Examples 2 and 3, Comparative Examples 1 to 4
The production conditions were set to the production conditions of Tables 1 and 2, and silica-based hollow particles were produced in the same manner as in Example 1 except that polystyrene particles and core-shell particles were prepared according to the formulation shown in Table 2.

In Examples and Comparative Examples, the characteristics of the polystyrene particles, core-shell particles and silica-based hollow particles obtained in steps 1 to 3 were measured by the following methods.

(Average particle size)
Using silica-based hollow particles and core-shell particle TEM (transmission electron microscope: JEM-2010, manufactured by JEOL Ltd.), photographs of the particles were taken under the condition of an acceleration voltage of 200 kV, and 100 particle minor diameters arbitrarily selected were selected. The length was measured and the average value was calculated, which was used as the average particle size.
Using a polystyrene particle SEM (scanning electron microscope: JSM-6700F, manufactured by Nippon Denshi Co., Ltd.), take a picture of the particles under the condition of an acceleration voltage of 5 kV, and measure the minor axis of 100 arbitrarily selected particles. The average value was calculated and used as the average particle size.

(Coefficient of variation of particle size)
Using silica-based hollow particles and core-shell particle TEM (transmission electron microscope: JEM-2010, manufactured by JEOL Ltd.), photographs of the particles were taken under the condition of an acceleration voltage of 200 kV, and 100 particle minor diameters arbitrarily selected were selected. The length was measured to obtain the average value, which was calculated based on the following formula.
(Coefficient of variation) = [(standard deviation of particle minor axis) ÷ (average value of particle minor axis)] × 100
Using a polystyrene particle SEM (scanning electron microscope: JSM-6700F, manufactured by JEOL Ltd.), a photograph of the particles was taken under the condition of an acceleration voltage of 5 kV, and the minor axis of 100 arbitrarily selected particles was measured. The average value was calculated and calculated based on the following formula.
(Coefficient of variation) = [(standard deviation of particle minor axis) ÷ (average value of particle minor axis)] × 100

(Ratio of particles with an aspect ratio of 1.5 or less to the total particles)
Using silica-based hollow particles and core-shell particle TEM (transmission electron microscope: JEM-2010, manufactured by Nippon Denshi Co., Ltd.), photographs of the particles were taken under the conditions of a magnification of 200,000 times and an acceleration voltage of 200 kV, and arbitrarily selected. The particle major axis and the particle minor axis of each of the 100 particles were measured, and the aspect ratio of each particle was determined based on the following formula. Next, the number of particles having an aspect ratio of 1.5 or less out of 100 particles was counted, and the number was taken as the ratio of the particles having an aspect ratio of 1.5 or less to the total number of particles.
(Aspect ratio) = (Particle major axis) ÷ (Particle minor axis)
Using a polystyrene particle SEM (scanning electron microscope: JSM-6700F, manufactured by Nippon Denshi Co., Ltd.), photographs of the particles were taken under the conditions of a magnification of 100,000 times and an acceleration voltage of 5 kV, and each of the 100 arbitrarily selected particles was taken. The particle major axis and the particle minor axis of the particles are measured, and the aspect ratio of each particle is obtained based on the following formula. Next, the number of particles having an aspect ratio of 1.5 or less out of 100 particles is counted, and the number is defined as the ratio of the particles having an aspect ratio of 1.5 or less to the total number of particles.
(Aspect ratio) = (Particle major axis) ÷ (Particle minor axis)

In Comparative Examples 1 to 3, the coefficient of variation of the particle size, the proportion of particles having an aspect ratio of 1.5 or less, and the average particle size could not be measured because the number of particles whose shape can be clearly determined in the TEM photograph was small.

(result)
The silica-based hollow particles obtained in Examples 1 to 3 and Comparative Examples 1 to 4 were analyzed using a TEM. FIGS. 1 to 3 show TEM images of the silica-based hollow particles obtained in Examples 1 to 3. It was found that agglomeration of these silica-based hollow particles was suppressed. Further, in Examples 1 to 3, particles having an aspect ratio of 1.5 or less occupy 95% or more of the total particles, and the coefficient of variation of the particle size is 20 to 60%, so that various articles were filled. In the case, it was found that it was easy to be filled uniformly.

FIG. 4 is a diagram showing a TEM image of the silica-based hollow particles of Comparative Example 1. From FIG. 4, it was found that in Comparative Example 1, the silica-based hollow particles were agglomerated because the dispersant was not added in the step 1.

In Comparative Examples 2 to 4, the mixed solvent of water and methanol was used in step 1, and the coefficient of variation of the polystyrene particles was small, so that the coefficient of variation of the core-shell particles and the silica-based hollow particles was also small. , It was found that it is difficult to uniformly fill various articles.

Claims (9)

Silica-based hollow particles in which particles having an aspect ratio of 1.5 or less occupy 95% or more of the total particles and have a coefficient of variation of 20 to 60%.
The average particle size is 30-150 nm,
Silica-based hollow particles in which the silica-based compound forming the silica-based hollow particles is formed only of silica. The silica-based hollow particles according to claim 1, which are an antireflection film material, an insulating film material, or a heat insulating material. A core-shell particle having a cationic polystyrene particle containing a dispersant as a core and a silica-based shell covering the cationic polystyrene particle.
Particles with an aspect ratio of 1.5 or less occupy 95% or more of the total particles, and the coefficient of variation of the particle size is 20 to 60%.
The average particle size is 30-150 nm,
The dispersant is at least one selected from polyvinylpyrrolidone, hydroxypropyl cellulose, polyvinyl alcohol, polyethylene oxide, polypropylene oxide, collagen, and polysaccharides.
Core-shell particles in which the silica-based compound forming the silica-based shell is formed only of silica. The silica-based hollow particles according to claim 1 or 2, or the cationic polystyrene particles for producing the core-shell particles according to claim 3.
Particles with an aspect ratio of 1.5 or less occupy 95% or more of the total particles, and the coefficient of variation of the particle size is 20 to 60%.
Cationic polystyrene particles containing at least one dispersant selected from polyvinylpyrrolidone, hydroxypropyl cellulose, polyvinyl alcohol, polyethylene oxide, polypropylene oxide, collagen, and polysaccharides. The method for producing silica-based hollow particles according to claim 1 or 2.
(1) A step of preparing cationic polystyrene particles by carrying out a polymerization reaction of the styrene monomer in a solution containing a styrene monomer, a dispersant, a cationic polymerization initiator, and a mixed solvent, wherein the mixing is performed. solvents, Ri mixed solvent der of water and acetone, the dispersing agent, Ru least 1 Tanedea selected polyvinylpyrrolidone, hydroxypropylcellulose, polyvinyl alcohol, polyethylene oxide, polypropylene oxide, collagen, and polysaccharides Step 1,
(2) To a solvent, (i) the cationic polystyrene particles, at least one selected from (ii) trialkoxysilane and tetraalkoxysilane, and (iii) a basic catalyst are added and stirred to prepare a solution. By doing so, the steps 2 and (3) of forming core-shell particles having the cationic polystyrene particles as the core and having a silica-based shell covering the cationic polystyrene particles in the solution, and (3) the core of the core-shell particles. , by pyrolysis of the cationic polystyrene particles, step 3 of removing the cationic polystyrene particles
Manufacturing method, including. The production method according to claim 5, wherein the mixed solvent used in the step 1 has a mixing ratio of water and acetone in a mass ratio of 90: 10 to 20:80. The production method according to claim 5 or 6, wherein the dispersant is at least one selected from polyvinylpyrrolidone and hydroxypropyl cellulose. The method for producing core-shell particles according to claim 3.
(1) A step of preparing cationic polystyrene particles by carrying out a polymerization reaction of the styrene monomer in a solution containing a styrene monomer, a dispersant, a cationic polymerization initiator, and a mixed solvent. solvents, Ri mixed solvent der of water and acetone, the dispersing agent, Ru least 1 Tanedea selected polyvinylpyrrolidone, hydroxypropylcellulose, polyvinyl alcohol, polyethylene oxide, polypropylene oxide, collagen, and polysaccharides To steps 1 and (2), (i) the cationic polystyrene particles, at least one selected from (ii) trialkoxysilane and tetraalkoxysilane, and (iii) a basic catalyst are added and stirred. In the solution, the cationic polystyrene particles are used as the core, and the core-shell particles having the silica-based shell covering the cationic polystyrene particles are formed in the solution.
Manufacturing method, including. The method for producing cationic polystyrene particles according to claim 4, wherein (1) a polymerization reaction of the styrene monomer in a solution containing a styrene monomer, a dispersant, a cationic polymerization initiator, and a mixed solvent. was carried out, a step of preparing a cationic polystyrene particles, the mixed solvent, Ri mixed solvent der of water and acetone, the dispersing agent is polyvinylpyrrolidone, hydroxypropylcellulose, polyvinyl alcohol, polyethylene oxide, polypropylene oxides, collagen, and steps 1 Ru least Tanedea selected from polysaccharides, manufacturing method.

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