JP2017226567A - Silica-based hollow particle, core-shell particle, and polystyrene particle, as well as production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: silica-based hollow particles which are uniformly filled with ease when various articles are filled therewith, because coagulation thereof is suppressed, particles with small aspect ratio amount to a rate of a predetermined range, and a coefficient of variation of the particle diameter thereof is within a predetermined range; core-shell particles from which the silica-based hollow particles can be produced; and polystyrene particles which can be suitably used for production of them, and to provide production methods with which the silica-based hollow particles, the core-shell particles, and the polystyrene particles can be produced.SOLUTION: In silica-based hollow particles, particles with aspect ratios of 1.5 or less amount to 95% or more of the total particles, and coefficient of variation of the particle diameter thereof is 20-60%.SELECTED DRAWING: None

Description

  The present invention relates to silica-based hollow particles, core-shell particles and polystyrene particles, and methods 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 characteristics such as electrical, optical, and thermal properties change greatly. Therefore, there is a possibility of application as a new highly functional material.

  As the structure of the inorganic oxide fine particles, there are a dense type, a porous type, and a hollow type. Among these, hollow-type hollow particles are attracting attention as new high-functional materials because of their characteristics 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 a hollow polystyrene particle produced by the production method have been proposed (for example, see Non-Patent Document 1). .

  However, in the hollow silica particles and the production method thereof described in Non-Patent Document 1, the particle size distribution of the hollow silica particles has not been sufficiently studied. If the particle size distribution of the produced hollow silica particles is small, such as the hollow silica particles described in Non-Patent Document 1, the filling rate is reduced when various articles are filled as a highly functional material, and the high function. There is a problem that the characteristics expected as a conductive material cannot be fully exhibited.

  Further, the hollow silica particles described in Non-Patent Document 1 have not been sufficiently studied for dispersibility, and have a problem that they aggregate. When the hollow silica particles are aggregated, when various articles are filled as a highly functional material, there is a problem that uniform filling is difficult.

  Further, as a result of intensive studies, the inventor has paid attention to the fact that silica-filled hollow particles having a large aspect ratio have a low filling rate when filled into various articles as a highly functional material. Such silica-based hollow particles have a problem that they cannot sufficiently exhibit the characteristics expected as a highly functional material.

  Accordingly, there is a demand for the development of silica-based hollow particles in which aggregation is suppressed, the particle size distribution is large, and the aspect ratio is small, and the core-shell particles and polystyrene particles that can produce the silica-diameter hollow particles. Development of the manufacturing method which can manufacture a silica diameter hollow particle, a core-shell particle, and a polystyrene particle is calculated | 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. Aggregation is suppressed, particles having a small aspect ratio occupy a specific range, and the particle diameter variation coefficient is within a specific range. To provide a silica-based hollow particle that can be easily uniformly filled when filled in an article, a core-shell particle that can produce the silica-based hollow particle, and a polystyrene particle that can be suitably used for the production thereof. Objective. Moreover, an object of this invention is to provide the manufacturing method which can manufacture the said silica type hollow particle, core-shell particle, and a polystyrene particle.

  As a result of intensive studies to achieve the above object, the present inventor has found that particles having an aspect ratio of 1.5 or less occupy 95% or more of the entire particle, and that the particle diameter variation coefficient is 20 to 60%. According to the hollow particles, the inventors have found that the above object can be achieved, and have completed the present invention.

That is, the present invention relates to the following silica-based hollow particles, core-shell particles, and production methods thereof.
1. Silica-based hollow particles characterized in that particles having an aspect ratio of 1.5 or less occupy 95% or more of the entire particles, and the coefficient of variation in particle diameter is 20 to 60%.
2. Item 2. The silica-based hollow particles according to Item 1, wherein the average particle size is 30 to 150 nm.
3. Item 3. The silica-based hollow particles according to Item 1 or 2, wherein the silica-based hollow particles include silica, or silica and a metal oxide.
4). Item 4. The silica-based hollow particle according to any one of Items 1 to 3, which is an antireflection film material, an insulating film material, or a heat insulating material.
5. A core-shell particle having a silica-based shell covering the polystyrene particle with the polystyrene particle containing a dispersant as a core,
A core-shell particle characterized in that particles having an aspect ratio of 1.5 or less occupy 95% or more of the entire particle, and the coefficient of variation in particle diameter is 20 to 60%.
6). Item 6. The core-shell particle according to Item 5, wherein the silica-based shell contains silica or silica and a metal oxide.
7). A polystyrene particle characterized in that particles having an aspect ratio of 1.5 or less occupy 95% or more of the whole particle, the coefficient of variation in particle diameter is 20 to 60%, and a dispersant is contained.
8). A method for producing silica-based hollow particles,
(1) A step of carrying out a polymerization reaction of the styrene monomer in a solution containing a styrene monomer, a dispersant, and a mixed solvent to prepare polystyrene particles, wherein the mixed solvent is a mixture of water and acetone. Step 1, which is a solvent
(2) The solution is prepared by adding and stirring (i) the polystyrene particles, (ii) alkoxysilane, or alkoxysilane and metal alkoxide, and (iii) a basic catalyst to the solvent. In the step 2 of forming the core-shell particle having the silica particle as a core and having a silica-based shell covering the polystyrene particle, and (3) by thermally decomposing the polystyrene particle which is the core of the core-shell particle Step 3 for removing the polystyrene particles
Manufacturing method.
9. Item 9. The production method according to Item 8, wherein the mixed solvent used in Step 1 has a mass ratio of 90:10 to 20:80 of water and acetone.
10. Item 10. The production method according to Item 8 or 9, wherein the dispersant is at least one selected from polyvinylpyrrolidone and hydroxypropylcellulose.
11. Item 11. The production method according to any one of Items 8 to 10, wherein the alkoxysilane includes tetraalkoxysilane.
12 Item 12. The manufacturing method according to any one of Items 8 to 11, wherein the silica-based hollow particles comprise 95% or more of particles having an aspect ratio of 1.5 or less, and a particle diameter variation coefficient of 20 to 60%.
13. The manufacturing method in any one of claim | item 8 -12 whose average particle diameters of the said silica type hollow particle are 30-150 nm.
14 A method for producing core-shell particles, comprising:
(1) A step of carrying out a polymerization reaction of the styrene monomer in a solution containing a styrene monomer, a dispersant, and a mixed solvent to prepare polystyrene particles, wherein the mixed solvent is a mixture of water and acetone. Step 1, which is a solvent
(2) The solution is prepared by adding and stirring (i) the polystyrene particles, (ii) alkoxysilane, or alkoxysilane and metal alkoxide, and (iii) a basic catalyst to the solvent. Step 2 of forming a core-shell particle having the silica particle as a core and having a silica-based shell covering the polystyrene particle
Manufacturing method.
15. A method for producing polystyrene particles,
(1) A step of carrying out a polymerization reaction of the styrene monomer in a solution containing a styrene monomer, a dispersant, and a mixed solvent to prepare polystyrene particles, wherein the mixed solvent is a mixture of water and acetone. The manufacturing method including the process 1 which is a solvent.

In the silica-based hollow particles of the present invention, agglomeration is suppressed, particles having a small aspect ratio occupy a specific range, and the particle diameter variation coefficient is in a specific range, so that various articles can be filled. In this case, it is easy to fill uniformly. Further, the core-shell particles of the present invention are also suppressed from agglomerating, and particles having a small aspect ratio occupy a specific range and the coefficient of variation in particle diameter is within a specific range. It can be manufactured easily. Moreover, the polystyrene particle of this invention can be used suitably for manufacture of the said silica type hollow particle and core-shell particle.
Moreover, 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.

2 is a diagram showing a TEM image of the silica-based hollow particles of Example 1 at a magnification of 200,000 times. FIG. 4 is a diagram showing a TEM image of the silica-based hollow particles of Example 2 at a magnification of 200,000 times. FIG. 4 is a diagram showing a TEM image of the silica-based hollow particles of Example 3 at a magnification of 200,000 times. FIG. 4 is a diagram showing a TEM image of the silica-based hollow particles of Comparative Example 1 at a magnification of 200,000 times. FIG. It is a figure which shows the TEM image of 200,000-times multiplication factor of the silica-type hollow particle of the comparative example 3.

  Hereinafter, the manufacturing method of the hollow silica particle of this invention is demonstrated 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 entire particles, and the coefficient of variation in particle diameter is 20 to 60%. Silica-based hollow particles having the above characteristics have a particle diameter variation coefficient in a specific range, and particles having an aspect ratio of 1.5 or less occupy a specific range. Is suppressed. In addition, since the coefficient of variation of the particle diameter is in a specific range, and particles having an aspect ratio of 1.5 or less occupy a specific range, it is easy to uniformly fill various articles. The core-shell particles of the present invention also have a particle diameter variation coefficient in a specific range, and particles having an aspect ratio of 1.5 or less occupy a specific range, so the particle diameter is not uniform and agglomeration occurs. It is suppressed. Further, according to the production method of the present invention, by adjusting polystyrene particles using a specific solvent in Step 1, the coefficient of variation of the particle diameter of the core-shell particles formed in Step 2 becomes a specific range, and the aspect ratio Particles of 1.5 or less come to occupy a specific range, and aggregation of the core-shell particles is suppressed. For this reason, aggregation is suppressed by the step 3 of thermally decomposing and removing the polystyrene particles as the core of the core-shell particles, the coefficient of variation of the particle diameter is in a specific range, and the aspect ratio is 1. Since particles of 5 or less occupy a specific range, silica-based hollow particles that can be uniformly filled can be easily produced when various articles are filled.

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 whole, and the coefficient of variation is 20 to 60%.

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

  When the said silica type compound contains compounds other than a silica, it is preferable that the silica type hollow particle contains a silica and a metal oxide. Examples of the metal oxide include metal oxides capable of forming a metal alkoxide, and specific examples include oxides such as aluminum, titanium, and zirconium. When an aluminum oxide is used, the surface charge (eg, zeta potential) of the silica-based shell can be adjusted. Further, when a titanium or zirconium oxide is used, the refractive index of the silica-based shell can be adjusted.

  The variation coefficient of the particle diameter 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 variation coefficient of the particle diameter of the silica-based hollow particles is within the above range, aggregation of the silica-based hollow particles can be suppressed, and when various articles are filled, it is easy to uniformly fill them.

In the present specification, the coefficient of variation of the silica-based hollow particles and the core-shell particles described below is a photograph of particles under the condition of an acceleration voltage of 200 kV using a TEM (transmission electron microscope: JEM-2010, manufactured by JEOL Ltd.). This is a value calculated based on the following formula by measuring 100 short diameters arbitrarily selected and obtaining an average value.
(Coefficient of variation) = [(Standard deviation of particle short diameter) ÷ (Average value of particle short diameter)] × 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 whole particles. When particles having an aspect ratio of 1.5 or less are less than 95% of the entire particles, aggregation of the silica-based hollow particles cannot be suppressed, and when various articles are filled, it is difficult to uniformly fill them. The particles having an aspect ratio of 1.5 or less are preferably 97% or more, and more preferably 99%.

In the present specification, of the silica-based hollow particles, the ratio of the particles having an aspect ratio of 1.5 or less to the whole particles, and the core-shell particles to be described later occupy the particles of 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 JEOL Ltd.), a photograph of particles was taken under the conditions of a magnification of 200,000 times and an acceleration voltage of 200 kV. The particle major axis and the minor particle diameter of the particles are measured, and the aspect ratio of each particle is determined based on the following formula. Next, the number of particles having an aspect ratio of 1.5 or less in 100 particles is counted, and the number is defined as a ratio (%) of the particles having an aspect ratio of 1.5 or less to the entire particles.
(Aspect ratio) = (Particle major axis) / (Particle minor axis)

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

  In the present specification, the average particle diameter 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 thickness of the membrane (shell) forming the silica-based hollow particles is preferably 2 to 40 nm, and more preferably 2 to 20 nm. When the thickness of the membrane is within the above range, the shell strength can be maintained while increasing the porosity of the silica-based hollow particles. In addition, in this specification, the thickness of the above-mentioned film is measured with a TEM (Transmission Electron Microscope: JEM-2010, manufactured by JEOL Ltd.) under a condition of 200 kV. It is an 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 in association with each other, when they are filled in various articles, they can be more uniformly filled. In the present specification, the state where the silica-based hollow particles are associated with each other indicates a state where the hollow portions of the plurality of silica-based hollow particles are joined together to form one hollow portion, The fact that the silica-based hollow particles are not substantially associated means a state where the hollow portions of the silica-based hollow particles are not joined. Moreover, it can confirm that the silica type hollow particle of this invention has not associated by observing the photograph of the silica type hollow particle image | photographed using the said TEM.

  As described above, the silica-based hollow particles of the present invention are suppressed from agglomeration, have a large particle size distribution, and have a small aspect ratio. Therefore, when filled in various articles, the silica-based hollow particles are easily filled uniformly. For this reason, it is suitable as a highly functional material, and 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 a silica-based shell covering the polystyrene particles with polystyrene particles containing a dispersant as the core, and particles having an aspect ratio of 1.5 or less are 95% or more of the entire particles. The coefficient of variation of the particle diameter is 20 to 60%. Aggregation is suppressed in the core-shell particles, the particle size distribution is large, and the aspect ratio is small, and the hollow silica particles of the present invention can be easily produced by thermally decomposing polystyrene particles.

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

  The average particle diameter 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 diameter of the polystyrene particles in the above range, the average particle diameter 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 aggregation of the polystyrene particles can be further suppressed. As a dispersing agent, if a polystyrene particle can be manufactured, it will not specifically limit, A well-known dispersing agent can be used. Examples of the dispersant include polyvinyl pyrrolidone, hydroxypropyl cellulose, polyvinyl alcohol (PVA), polyethylene oxide, polypropylene oxide, collagen, polysaccharide (gum arabic), and the like. Polyvinyl pyrrolidone and hydroxypropyl cellulose are preferable in that aggregation of core-shell particles formed in Step 2 described later can be suppressed. The said dispersing agent can be used individually by 1 type or in mixture of 2 or more types.

  Although content of the dispersing agent in a polystyrene particle is not specifically limited, 0.01-100 mass% is preferable with respect to 100 mass% of said polystyrene particles, and 0.05-100 mass% is more preferable. When the content of the dispersant is within the above range, aggregation of polystyrene particles can be further suppressed.

  The variation coefficient of the particle diameter of the core-shell particle 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 diameter of the core-shell particles is in the above range, the coefficient of variation of the particle diameter of the silica-based hollow particles obtained by pyrolyzing the polystyrene particles that are the core of the core-shell particles is set in the above-described range. In the case where the aggregation of the silica-based hollow particles is suppressed, and when the silica-based hollow particles are filled in various articles, it is easy to uniformly fill the particles.

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

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

  2-40 nm is preferable and, as for the film thickness of the film | membrane (shell) which forms a core-shell particle, 2-20 nm is more preferable. When the thickness of the membrane is within 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, the silica-based hollow particles obtained by pyrolyzing the polystyrene particles that are the core of the core-shell particles are more easily filled uniformly. In the present specification, the state in which the core-shell particles are associated indicates a state in which polystyrene particles, which are the cores of a plurality of core-shell particles, are joined to form one secondary particle. “Particles are not substantially associated” means a state in which polystyrene particles that are cores of core-shell particles are not joined. Moreover, it can confirm that the core-shell particle | grains of this invention have not associated by observing the photograph of the core-shell particle image | photographed using the said TEM.

3. Polystyrene particles The polystyrene particles according to the present invention are polystyrene particles having an aspect ratio of 1.5 or less occupying 95% or more of the whole, a particle diameter variation coefficient of 20 to 60%, and a dispersant. The polystyrene particles have a particle diameter variation coefficient and an aspect ratio in the above range and contain a dispersant. Therefore, in step 1 of the method for producing core-shell particles of the present invention and the method for producing silica-based hollow particles 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. By using the core-shell particles in Step 3, various articles can be produced. When filled, the hollow silica particles of the present invention that are easily filled uniformly can be easily produced.

  The polystyrene particles are the same as the polystyrene particles that form the core-shell particles described above. Moreover, the average particle diameter and zeta potential of the polystyrene particles are the same as those of the polystyrene particles forming the above-described core-shell particles.

  The variation coefficient of the particle diameter of the polystyrene particles of the present invention is 20 to 60%. 25 to 55% is preferable, and 30 to 50% is more preferable. When the average particle diameter of the polystyrene particles is in the above range, the coefficient of variation of the particle diameter of the core-shell particles can be set in the above-mentioned range, and the polystyrene particles that are the core of the core-shell particles are obtained by pyrolysis. The variation coefficient of the particle diameter of the silica-based hollow particles can be within the above-described range, and when the silica-based hollow particles are agglomerated and the silica-based hollow particles are filled in various articles, they are uniform. It becomes easy to be filled.

In this specification, the coefficient of variation 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 a SEM (scanning electron microscope: JSM-6700F, manufactured by JEOL Ltd.). It is a value calculated based on the following formula by measuring the average particle diameter of 100 short diameters.
(Coefficient of variation) = [(Standard deviation of particle short diameter) ÷ (Average value of particle short diameter)] × 100

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

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

In this specification, the average value of the aspect ratio of the polystyrene particles is determined by using a SEM (scanning electron microscope: JSM-6700F, manufactured by JEOL Ltd.) under the conditions of a magnification of 100,000 times and an acceleration voltage of 5 kV. This is a value calculated based on the following equation by taking a photograph, measuring the particle long diameter and particle short diameter of 100 arbitrarily selected particles, and determining the average value of each.
(Average value of aspect ratio) = (Average value of particle major axis) ÷ (Average value of particle minor axis)

  The polystyrene particles of the present invention are preferably not substantially associated. When the polystyrene particles are not associated, the association of the core-shell particles and silica-based hollow particles formed using the polystyrene particles is suppressed, and when the obtained silica-based hollow particles are filled into various articles, It becomes easy to fill more uniformly. In this specification, the state in which polystyrene particles are associated indicates a state in which a plurality of polystyrene particles are joined to form one secondary particle, and the polystyrene particles are substantially associated. Not doing means a state where polystyrene particles are not joined. In addition, it can confirm that the polystyrene particle of this invention has not associated by observing the photograph of the polystyrene particle image | photographed using said SEM.

4). Method for producing silica-based hollow particles The method for producing silica-based hollow particles of the present invention comprises:
(1) A step of carrying out a polymerization reaction of the styrene monomer in a solution containing a styrene monomer, a dispersant, and a mixed solvent to prepare polystyrene particles, wherein the mixed solvent is a mixture of water and acetone. Step 1, which is a solvent
(2) The solution is prepared by adding and stirring (i) the polystyrene particles, (ii) alkoxysilane, or alkoxysilane and metal alkoxide, and (iii) a basic catalyst to the solvent. In the step 2 of forming the core-shell particle having the silica particle as a core and having a silica-based shell covering the polystyrene particle, and (3) by thermally decomposing the polystyrene particle which is the core of the core-shell particle Step 3 of removing the polystyrene particles.

<Step 1>
Step 1 is a step of preparing polystyrene particles by performing a polymerization reaction of the styrene monomer in a solution containing (1) a styrene monomer, a dispersant, and a mixed solvent, and the mixed solvent includes water and It is a process which is a mixed solvent with acetone.

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

  Although the density | concentration in the solution of the styrene monomer used in the process 1 is not specifically limited, It is preferable that it is 0.1-20 mass% with respect to 100 mass% of said solutions, and it is 0.2-10 mass%. More preferred. By setting to the said density | concentration, the average particle diameter of the polystyrene particle obtained and the average particle diameter of the hollow silica particle which is a final product can be controlled to about 30-150 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 dispersing agent include polyvinyl pyrrolidone, hydroxypropyl cellulose, polyvinyl alcohol (PVA), polyethylene oxide, polypropylene oxide, and the like. Among these, the core shell formed in step 2 described below, which suppresses aggregation of polystyrene particles. Polyvinyl pyrrolidone and hydroxypropyl cellulose are preferable in that aggregation of particles can be suppressed. The said dispersing agent can be used individually by 1 type or in mixture of 2 or more types.

  Although the density | concentration in the solution of the dispersing agent used in the process 1 is not specifically limited, 0.01-10 mass% is preferable with respect to 100 mass% of said solutions, and 0.05-5 mass% is more preferable. By setting to the said density | concentration, aggregation of a polystyrene particle can be suppressed more and aggregation of the core-shell particle formed at the process 2 mentioned later can be suppressed more.

(Mixed solvent)
The mixed solvent used in step 1 is a mixed solvent of water and acetone. By using such a mixed solvent, the particle diameter variation coefficient of the particle diameter of the polystyrene particles as the core does not become too small, and the aspect ratio does not become too large, and the particle diameter of the core-shell particles formed in Step 2 described later. The coefficient of variation and the aspect ratio 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, and more preferably 80:20 to 40:60. By setting the mass ratio of water and acetone within the above range, it becomes easy to adjust the coefficient of variation and the aspect ratio of the particle diameter of the core-shell particles formed in Step 2 described later to the above 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. Among these, it is more preferable to use radical polymerization initiators such as organic oxides and azo compounds. The organic oxide is represented by a general formula RO-OR, and the azo compound is represented by a general formula A-CN = CN-A. Specifically, benzoyl peroxide, 2,2′-azobis (isobutylamidine) dihydrochloride (AIBA), 4,4′-azobis-4-cyanovaleric acid, azobisisobutyronitronyl (AIBN), 2 , 2′-azobis (2-methylpropioamido) dihydrochloride (AAPH), preferably 2,2′-azobis (isobutylamidine) dihydrochloride (AIBA), 2,2′-azobis (2-methylpro) Pioamido) dihydrochloride (AAPH). Among 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.

  Although the density | concentration in the solution of the cationic polymerization initiator used in the said process 1 is not specifically limited, When a solution is 100 mass%, it is preferable that it is 0.01-1 mass%. By setting to the said density | concentration, the average particle diameter of the polystyrene particle obtained and the average particle diameter of the hollow silica particle which is a final product can be controlled to about 30-150 nm.

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

  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 be slow, and if it is too high, the solvent may evaporate and the polymerization reaction may not be continued.

  Although the reaction time of the said polymerization reaction is not specifically limited, It is preferable that it is 1 to 720 minutes, and it is more preferable that it is 10 to 600 minutes. When the said reaction time is too short, there exists a possibility that reaction may become inadequate.

  Polystyrene particles are prepared by the polymerization reaction. The average particle diameter 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 diameter of the polystyrene particles in the above range, the average particle diameter of the core-shell particles formed in Step 2 and the average particle diameter of the silica-based hollow particles manufactured in Step 3 can be set in an appropriate range. it can.

  Polystyrene particles are prepared by the step 1 described above.

<Process 2>
In step 2, (2) a solvent is prepared by adding (i) the polystyrene particles, (ii) alkoxysilane, or alkoxysilane and metal alkoxide, and (iii) a basic catalyst to the solvent. To form core-shell particles having the polystyrene particles as a core and having a silica-based shell covering the polystyrene particles in the solution.

(solvent)
As the solvent used in step 2, it is preferable to use water. 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 preferably used. As the solvent, it is more preferable to use an alcohol of the same type as that generated by hydrolysis of a silicon compound. By using an alcohol of the same type as that generated by hydrolysis of the silicon compound, the solvent can be easily recovered and reused.

  The said solvent can also be used individually by 1 type, and 2 or more types of solvents can also be mixed and used for it.

  As the solvent, water and a hydrophilic solvent may be mixed and used. The mass ratio of the hydrophilic solvent: water is not limited, but 90:10 to 10:90 is preferable, and 50:50 to 10:90 is more preferable. By making the said mass ratio into the above-mentioned range, it is easy to control the average particle diameter of the hollow silica particle obtained to about 30-150 nm.

  A hydrophobic solvent can also be used as the solvent. 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, branched or cyclic alkane having 6 to 10 carbon atoms such as hexane, cyclohexane, heptane, octane, and isooctane can be used. Of these, octane is more preferable.

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

  It is preferable that the density | concentration of the polystyrene particle in the said solution is 0.01-50 mass%, and it is more preferable that it is 0.01-20 mass%.

(Alkoxysilane)
It does not specifically limit as alkoxysilane used at the process 2, For example, General formula (1)
Si (OR ¹ ) ₄ (1)
The tetraalkoxysilane shown by these, or its derivative (s) is mentioned. In the 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, more preferably a lower alkyl group having 1 to 4 carbon atoms, More preferably, it is a C1-C3 lower alkyl group. 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 Methoxysilane (TMOS) is more preferred. On the other hand, if the carbon number is too large, silica may not be easily generated. 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.

Examples of the alkoxysilane used in step 2 include the general formula (2).
Si (OR ¹ ) ₃ R ² (2)
Or a derivative 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 alkoxysilane derivative include low-condensates obtained by partially hydrolyzing the alkoxysilane.

  The said alkoxysilane may be used independently and may be used in mixture of 2 or more types. Among them, it is preferable to contain trialkoxysilane and tetraalkoxysilane from the viewpoint that aggregation can be prevented at the stage of core-shell particles and surface modification with a silane coupling agent or the like becomes easy.

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

(Metal alkoxide)
In step 2, an alkoxysilane and a metal alkoxide may be mixed and used. It does not specifically limit as a metal alkoxide, A well-known thing can be used. Examples of such metal alkoxide include aluminum alkoxide, titanium alkoxide, zirconium alkoxide and the like. When aluminum alkoxide is used, the surface charge (such as zeta potential) of the silica-based shell can be adjusted. Moreover, when a titanium alkoxide and a zirconium alkoxide are used, the refractive index of a silica-type shell can be adjusted.

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

In step 2, the solution may be prepared by separately adding alkoxysilane and metal alkoxide, or the alkoxysilane and metal alkoxide may be mixed and hydrolyzed before being added to the solution. An alkoxysilane and a metal alkoxide are mixed, hydrolyzed, and then added to the solution, whereby the following formula (3)
Si-OM (3)
And a silica-based shell containing a metal represented by M in the formula (3) uniformly.

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

  As a method of mixing the alkoxysilane and the metal alkoxide and adding them to the solution after hydrolysis, for example, a method described in JP-A-2005-41722 can be mentioned.

(Basic catalyst)
The basic catalyst used in step 2 is not particularly limited, and a known basic catalyst can be used. In particular, an organic base catalyst that does not contain a metal component in terms of avoiding the incorporation of metal impurities, and metal An inorganic catalyst containing no components is preferred. 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, ammonia water is mentioned as said inorganic type base catalyst. An organic base catalyst having low volatility is preferred in that it does not evaporate in the temperature range when performing step 2. In the case of a volatilizing base, it may be added continuously to maintain the pH of the solution. Aqueous ammonia is preferred because it is inexpensive and economically superior.

  The said basic catalyst may be used individually by 1 type, and may mix and use 2 or more types.

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

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

  Although the temperature of the solution in the said process 2 is not specifically limited, 5-200 degreeC is preferable and 5-150 degreeC is more preferable. When the said temperature is too low, there exists a possibility that reaction rate may become slow, and when too high, there exists a possibility that a solvent may evaporate.

  Although the stirring time in the said process 2 is not specifically limited, It is preferable that it is 1-120 minutes, and it is more preferable that it is 1-600 minutes. When the stirring time is too short, the reaction may be insufficient.

  By the process 2 demonstrated above, the core-shell particle which has the said silica particle as a core and has a silica-type shell which coat | covers the said polystyrene particle can be formed.

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

  In step 3, the polystyrene particles are removed by thermal decomposition. Although it does not specifically limit as said pyrolysis, For example, baking is mentioned. 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. For this reason, as a method for removing polystyrene particles by firing, for example, an ultrasonic atomizer, a two-fluid nozzle or the like is used to spray the solution prepared in step 2 into an electric furnace, and preferably 350 in the electric furnace. A method of firing in a high temperature region of ˜1500 ° C., more preferably 400-1200 ° C., and still more preferably 600-1000 ° C. is mentioned. By baking for a time sufficient 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 and firing the solution prepared in step 2 in an electric furnace, a low temperature in a temperature range of about 150 to 250 ° C. is provided before 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 is then sprayed to 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 solution. When the low temperature region is not provided, the formation of silica-based hollow particles becomes insufficient, and the shape of the silica-based hollow particles may be distorted.

  30-150 nm is preferable, as for the average particle diameter of the silica type hollow particle obtained through the said process, 35-120 nm is more preferable, and 35-100 nm is still more preferable. When the average particle diameter 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 various articles are filled, it is easier to pack 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, and even more preferably 99%. When the silica hollow particles to be obtained have an aspect ratio of 1.5 or less, the proportion of silica hollow particles can be suppressed, and when the hollow silica particles are filled in various articles, they are uniform. It becomes easy to be filled.

  1.0-1.6 are preferable, as for the aspect ratio of the silica type hollow particle obtained through the said process, 1.0-1.4 are more preferable, and 1.0-1.2 are still more preferable. When the aspect ratio of the obtained silica-based hollow particles is within the above range, the aggregation of the silica-based hollow particles can be further suppressed, and when various articles are filled, it becomes easier to pack more uniformly. .

  The variation coefficient of the particle diameter 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 variation coefficient of the particle diameter of the obtained silica-based hollow particles is in the above range, the aggregation of the silica-based hollow particles can be suppressed, and when filled in various articles, it is easy to be filled uniformly. Become.

  By the process 3 demonstrated above, the said polystyrene particle which is the core of the said core-shell particle is thermally decomposed, and the said polystyrene particle can be removed.

5. Method for producing core-shell particles The method for producing core-shell particles of the present invention comprises:
(1) A step of carrying out a polymerization reaction of the styrene monomer in a solution containing a styrene monomer, a dispersant, and a mixed solvent to prepare polystyrene particles, wherein the mixed solvent is a mixture of water and acetone. Step 1, which is a solvent
(2) The solution is prepared by adding and stirring (i) the polystyrene particles, (ii) alkoxysilane, or alkoxysilane and metal alkoxide, and (iii) a basic catalyst to the solvent. In the manufacturing method, the 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 said process 1 and the process 2 are the same as the process 1 and 2 demonstrated in the manufacturing method of the said silica type hollow particle. Since the core-shell particles produced by the method for producing core-shell particles of the present invention can be removed by thermally decomposing polystyrene particles that are the core of the core-shell particles, the method for producing silica-based hollow particles described above It is suitable as a core-shell particle used in the step 3.

6). Production method of polystyrene particles The production method of polystyrene particles of the present invention is:
(1) A step of carrying out a polymerization reaction of the styrene monomer in a solution containing a styrene monomer, a dispersant, and a mixed solvent to prepare polystyrene particles, wherein the mixed solvent is a mixture of water and acetone. It is a manufacturing method including the process 1 which is a solvent.

  Step 1 is the same as 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 according to the present invention have a particle diameter variation coefficient and a ratio of particles having an aspect ratio of 1.5 or less in the above range and contain a dispersant. The core-shell particles that are adjusted in step 1 of the production method and the silica-based hollow particle production method and are used in step 2 to suppress aggregation, have a large particle size distribution, and have a small aspect ratio. When the core-shell particles are used in step 3, the hollow silica particles of the present invention that can be uniformly filled can be easily produced when various articles are filled.

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

Example 1
Under the production conditions in Table 1, polystyrene particles and core-shell particles were prepared with the formulation in Table 2 to produce silica-based hollow particles. Specifically, it is as follows.

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

  Specifically, first, a reactor equipped with a 1 L four-necked flask, stirring blades, a mantle heater, and a cooling device was prepared.

  Subsequently, 382.5 g of ultrapure water, 467.5 g of acetone, and PVP (K90 molecular weight 630,000, manufactured by Tokyo Chemical Industry Co., Ltd.) as a dispersant were poured into a four-necked flask and stirred at 250 rpm in a nitrogen atmosphere. The mixture was refluxed with stirring and heated for 10 minutes until the temperature did not change. The temperature at this time was 63 ° C. Next, a styrene monomer was added, and the solution was heated by heating for 5 minutes until the temperature did not change to uniformly disperse the styrene monomer. The temperature of the solution was 63 ° C. In addition, the styrene monomer used what previously wash | cleaned by 0.1M-NaOH and removed the stabilizer.

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

(Process 2: Production of core-shell particles)
Core-shell particles were produced with the formulation and conditions shown in Table 2. Specifically, first, a reactor equipped with a 1 L four-necked flask, stirring blades, and a water bath was prepared. The solution in which the polystyrene particles produced in Step 1 were dispersed was placed in the flask, methanol was added as a solvent, and a 25% aqueous ammonia solution was added to prepare Liquid B. A solution A was prepared by mixing TMOS and methanol. While keeping the B liquid at 30 ° C., the A liquid was added in three portions at 30 minute intervals. The mixture was stirred at 250 rpm for 1 hour to form core-shell particles having silica particles as a core in the solution and having a silica-based shell covering the polystyrene particles.

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

(Step 3: Production of silica-based hollow particles)
The core-shell particles obtained in step 2 were heat-treated at a temperature of 700 ° C., thereby removing the polystyrene particles and producing silica-based hollow particles.

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

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

(Average particle size)
Using silica-based hollow particles and core-shell particles TEM (transmission electron microscope: JEM-2010, manufactured by JEOL Ltd.), a photograph of the particles was taken under the condition of an acceleration voltage of 200 kV, and 100 arbitrarily selected short particle diameters were obtained. The average value was calculated by measuring the length to obtain the average particle size.
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 arbitrarily selected 100 particle short diameters were measured. The average value was calculated and used as the average particle size.

(Particle diameter variation coefficient)
Using silica-based hollow particles and core-shell particles TEM (transmission electron microscope: JEM-2010, manufactured by JEOL Ltd.), a photograph of the particles was taken under the condition of an acceleration voltage of 200 kV, and 100 arbitrarily selected short particle diameters were obtained. The average value was obtained by measuring the length and calculated based on the following formula.
(Coefficient of variation) = [(Standard deviation of particle short diameter) ÷ (Average value of particle short diameter)] × 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 100 arbitrarily selected short particle diameters were measured. The average value was determined and calculated based on the following formula.
(Coefficient of variation) = [(Standard deviation of particle short diameter) ÷ (Average value of particle short diameter)] × 100

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

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

(result)
The silica-based hollow particles obtained in Examples 1 to 3 and Comparative Examples 1 to 4 were analyzed using TEM. 1-3 show TEM images of the silica-based hollow particles obtained in Examples 1-3. These silica-based hollow particles were found to be inhibited from agglomerating. In Examples 1 to 3, particles having an aspect ratio of 1.5 or less accounted for 95% or more of the entire particles, and the coefficient of variation in particle diameter was 20 to 60%. In this case, it was found that uniform filling was easy.

  4 is a view showing a TEM image of the silica-based hollow particles of Comparative Example 1. FIG. From FIG. 4, it was found that silica-based hollow particles were aggregated in Comparative Example 1 because no dispersant was added in Step 1.

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

Claims (15)

  Silica-based hollow particles characterized in that particles having an aspect ratio of 1.5 or less occupy 95% or more of the entire particles, and the coefficient of variation in particle diameter is 20 to 60%.   The silica-based hollow particles according to claim 1, having an average particle diameter of 30 to 150 nm.   The silica-based hollow particles according to claim 1 or 2, wherein the silica-based hollow particles include silica or silica and a metal oxide.   The silica-based hollow particle according to any one of claims 1 to 3, which is an antireflection film material, an insulating film material, or a heat insulating material. A core-shell particle having a silica-based shell covering the polystyrene particle with the polystyrene particle containing a dispersant as a core,
A core-shell particle characterized in that particles having an aspect ratio of 1.5 or less occupy 95% or more of the entire particle, and the coefficient of variation in particle diameter is 20 to 60%.   The core-shell particle according to claim 5, wherein the silica-based shell includes silica or silica and a metal oxide.   Polystyrene particles characterized in that particles having an aspect ratio of 1.5 or less occupy 95% or more of the whole particles, the coefficient of variation in particle diameter is 20 to 60%, and contain a dispersant. A method for producing silica-based hollow particles,
(1) A step of carrying out a polymerization reaction of the styrene monomer in a solution containing a styrene monomer, a dispersant, and a mixed solvent to prepare polystyrene particles, wherein the mixed solvent is a mixture of water and acetone. Step 1, which is a solvent
(2) The solution is prepared by adding and stirring (i) the polystyrene particles, (ii) alkoxysilane, or alkoxysilane and metal alkoxide, and (iii) a basic catalyst to the solvent. In the step 2 of forming the core-shell particle having the silica particle as a core and having a silica-based shell covering the polystyrene particle, and (3) by thermally decomposing the polystyrene particle which is the core of the core-shell particle Step 3 for removing the polystyrene particles
Manufacturing method.   The mixed solvent used in the step 1 is a production method according to claim 8, wherein a mixing ratio of water and acetone is 90:10 to 20:80 by mass ratio.   The manufacturing method according to claim 8 or 9, wherein the dispersant is at least one selected from polyvinylpyrrolidone and hydroxypropylcellulose.   The said alkoxysilane is a manufacturing method in any one of Claims 8-10 containing tetraalkoxysilane.   The silica-based hollow particles according to any one of claims 8 to 11, wherein particles having an aspect ratio of 1.5 or less occupy 95% or more of the whole particles, and a coefficient of variation in particle diameter is 20 to 60%. Method.   The manufacturing method in any one of Claims 8-12 whose average particle diameter of the said silica type hollow particle is 30-150 nm. A method for producing core-shell particles, comprising:
(1) A step of carrying out a polymerization reaction of the styrene monomer in a solution containing a styrene monomer, a dispersant, and a mixed solvent to prepare polystyrene particles, wherein the mixed solvent is a mixture of water and acetone. Step 1, which is a solvent
(2) The solution is prepared by adding and stirring (i) the polystyrene particles, (ii) alkoxysilane, or alkoxysilane and metal alkoxide, and (iii) a basic catalyst to the solvent. Step 2 of forming a core-shell particle having the silica particle as a core and having a silica-based shell covering the polystyrene particle
Manufacturing method. A method for producing polystyrene particles,
(1) A step of carrying out a polymerization reaction of the styrene monomer in a solution containing a styrene monomer, a dispersant, and a mixed solvent to prepare polystyrene particles, wherein the mixed solvent is a mixture of water and acetone. The manufacturing method including the process 1 which is a solvent.