JPH06142491A - Composite particle, hollow particle and their production - Google Patents

Abstract

PURPOSE:To provide a spherical polymer-metal compd. composite particle having excellent heat resistance, toughness, light resistance, wear resistance, etc., and bioadaptability and affinity to an antigen and antibody of particle surfaces by consisting core of a polymer and shell of a titanium compd. and/or silicon compd. CONSTITUTION:The core of the spherical polymer-metal compd. composite particle consists of a polymer and the shell of that consists of a titanium compd. and/or silicon compd. The composite particle constituted in such a manner has the high strength and the high heat resistance and is able to develop a high function. These particles are adequately used for cosmetics, electronic materials, semiconductor materials, paints. polishing agents, spacers, coating materials, optical materials, catalysts, fillers, drugs, diagnostic drugs, toners, resin modifiers, ink, adsorbents, UV resistant materials, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to composite particles, hollow particles and a method for producing them, and more specifically, it has high strength and high heat resistance and is capable of exhibiting high functions. Semiconductor materials, polishing agents, coating agents,
Paint particles, spacers, optical materials, catalysts, fillers, medicines, diagnostic agents, toners, resin modifiers, inks, adsorbents, composite particles preferably used for UV resistant materials and the like, and a method for producing the same, and a hiding rate, Large adsorption rate, specific surface area, etc.
The present invention relates to hollow particles suitably used for microcapsule materials, concealing materials, column fillers, catalysts, cosmetics, UV-resistant materials and the like, and a method for producing the same.

[0002]

Polymer particles having a narrow particle size distribution are used as standard particles, carrier particles for diagnostic agents, lubricants and the like.
However, since the polymer particles are poor in strength, when used as standard particles and lubricants, for example, the particles are often deformed or disintegrated under the condition of high shear or high temperature. As a result, the inherent properties of the polymer particles are not utilized and the range of use thereof is extremely limited. In order to improve these drawbacks, a method of polymer particles, for example, a method of copolymerizing a crosslinkable monomer or the like into a highly crosslinked product has been proposed, but the polymer particles obtained by the method are still satisfactory. It has not yet reached the desired performance.

Further, the polymer particles have been applied to diagnostic agents, pharmaceutical agents, etc., but their application range is limited due to their limited affinity with antigens and antibodies, biocompatibility, etc. There is.

On the other hand, many kinds of metal compound particles are used for ceramics such as electronic materials, magnetic materials, optical materials, heat resistant materials, etc., and in response to diversification of applications and diversification of performance. Therefore, various composite particles have been proposed. For example, iron oxide particles coated with a silicon compound are subjected to heat treatment to prevent the shape of the needle-shaped magnetic material from being deformed or sintering between magnetic materials, and iron powder coated with copper. It has been reported that the composite particles are used to increase the strength as a powder metallurgy material, or the composite particles in which iron oxide particles are coated with antimony and aluminum oxide are used to increase the heat resistance. . However, since most of these are composite particles of metal compounds, it is not possible to sufficiently cope with the diversification of applications. Therefore, the development of composite particles capable of expressing various functions is required especially in the fields of electronic materials, optical materials, etc. Has been done.

In recent years, among the ceramic particles, hollow metal compound particles have attracted attention as being particularly useful. As a method for producing the same, for example, a method of producing basic particles by an aerosol method, heating and drying, a metal compound is used. Method of spraying, drying and firing an aqueous sol, w / o type or o / w
A method of preparing an / o type emulsion and heating it to remove water and oil has been proposed. However, the hollow particles obtained by these production methods are all significantly inferior in strength,
Also, the particle size distribution tends to widen.

[0006]

As described above, the polymer particles having a narrow particle size distribution have excellent performance when used in high value-added fields such as standard particles, pharmaceuticals and diagnostic agents. Since it is a polymer, it is inferior in heat resistance, toughness, light resistance, abrasion resistance, and the like, and also has biocompatibility and affinity for particle surface antigens and antibodies. Therefore, there is a demand for the development of composite particles in which these defects are corrected, for example, the surface of the particles is coated with a metal compound. Further, also in applications of other polymer particles, for example, in the fields of hiding materials, lubricants, column fillers, etc., development of metal compound particles having performance different from that of conventional polymer particles is desired.

On the other hand, for ceramics applicable to many fields such as optical materials and electronic materials, the development of composite particles composed of a composition having an ultraviolet shielding property, an adsorptive property, a thickening property and the like, and a composition not having these properties has been developed. Was wanted. Further, it has been desired to impart ultraviolet ray shielding property, adsorptivity, etc. to the hollow metal compound particles which have been used in the fields of catalysts, microcapsules, cosmetics, etc. in recent years.

[0008]

The present invention is, first of all, to
The present invention provides a spherical polymer-metal compound composite particle, wherein (a) the core is a polymer and (b) the shell is a titanium compound and / or a silicon compound.

Secondly, according to the present invention, spherical polymer particles are uniformly dispersed in an alcohol solution of titanium alkoxide and / or a silicon alkoxide or an alcohol / water mixed solution, and the spherical polymer particles are hydrolyzed to give a solution. A spherical polymer-metal compound composite particle is obtained by providing a uniform titanium compound and / or silicon compound coating layer on the surface and further heat-treating, if necessary, to provide a method for producing the composite particle. It is a thing.

Thirdly, the present invention provides a spherical hollow particle comprising a titanium compound and / or a silicon compound and having pores inside.

Fourthly, the present invention is characterized in that the polymer of the core is decomposed by heating the above-mentioned composite particles, pores are provided inside the particles, and further reduction treatment is carried out if necessary. A method for producing particles is provided.

[Spherical Polymer-Metal Compound Composite Particles] The spherical polymer-metal compound composite particles will be described below.

As the spherical polymer particles serving as the core of the composite particles, in order to have particularly excellent heat resistance, a crosslinkable monomer is used, if necessary, during the polymerization of the spherical polymer particles of the core. However, it is preferable to crosslink. Specific examples of the polymer forming the spherical polymer particles include styrene and α-
Unsaturated aromatics such as methylstyrene, halogenated styrene and divinylbenzene; unsaturated esters such as vinyl acetate and vinyl propionate; unsaturated nitriles such as acrylonitrile; methyl acrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, 2-
Unsaturated carboxylic acid alkyl esters such as ethylhexyl acrylate, 2-ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, ethylene glycol diacrylate, and ethylene glycol dimethacrylate; other than these, butadiene, isoprene, acrylic acid, methacrylic acid, acrylamide, methacrylamide, Examples thereof include glycidyl acrylate, glycidyl methacrylate, N-methylol acrylamide, N-methylol methacrylamide, 2-hydroxyethyl acrylate, acrylic acrylate, and allyl methacrylate. You may use these individually or in mixture of 2 or more types.

The spherical polymer particles can be produced by, for example, emulsion polymerization, suspension polymerization, dispersion polymerization or the like of the above monomers. It can also be obtained by crushing a preformed polymer bulk. The particle size of the spherical polymer particles obtained as described above is usually 0.05 to 50 μm,
It is preferably 0.05 to 20 μm, more preferably 0.
It is 1 to 10 μm.

On the other hand, it is the titanium compound and / or the silicon compound that form the shell of the composite particles. The titanium compound is preferably an oxide such as TiO or TiO ₂ when it is desired to have an excellent ultraviolet shielding property. As the silicon compound, SiO ₂ is preferable in order to make the compound particularly excellent in adsorptivity and thickening property.

[Method for Producing Spherical Polymer-Metal Compound Composite Particles] The method for producing the polymer-metal compound composite particles of the present invention will be described below. The production of the composite particles is carried out in a alcohol solution or an alcohol / water mixed solution by hydrolyzing a metal alkoxide selected from titanium alkoxide and / or silicon alkoxide to obtain a spherical polymer particle having a core of a metal compound. The surface is uniformly coated and, if necessary, subjected to heat treatment.

Examples of the metal alkoxide include T
i (OCH₃)_Four, Ti (OC₂H_Five) _Four, Ti (iso-
OC₃H₇)_Four, Ti (OC_FourH₉)_FourTitanium Arco etc.
Xide, Si (OCH₃)_Four, Si (OC₂H_Five), Si
(Iso-OC₃H₇)_Four, Si (t-OC_FourH₉)_FourEtc.
Examples include recon alkoxide. These metal arco
The oxidants may be used alone or in combination of two or more.
You can

The amount of the above metal alkoxide used is 0.01.
Mmol / reaction mixture 1 liter or more, more preferably 0.1.
1 mmol / l or more of reaction mixture, particularly preferably 1
Mmol / reaction mixture 1 liter or more, and the upper limit is generally 1,000 mmol / reaction mixture 1 liter or less. The reaction mixture means a mixture of a metal alkoxide and an alcohol solution or an alcohol / water mixed solution.

Metal alkoxides are easily hydrolyzed at room temperature or by heating, for example Ti (OH) ₄ , Ti.
A hydroxide or oxide such as O ₂ , Si (OH) ₄ and SiO ₂ is formed, and these are uniformly coated on the surface of the spherical polymer particle serving as the core.

Examples of the alcohol used as a solvent in the production of the above composite particles include saturated alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol and t-butanol. These alcohols alone
Alternatively, two or more kinds can be mixed and used. Regarding the usage ratio of alcohol and water, it is preferable that the amount of water is 1 liter or less per liter of alcohol.

The amount of spherical polymer particles used is 0.001 g.
/ Reaction mixture 1 l or more, more preferably 0.01 g /
The reaction mixture is 1 liter or more, particularly preferably 0.05 g / reaction mixture 1 liter or more, and the upper limit is generally 1000 g / reaction mixture 1 liter or less.

What is important in the method for producing the composite particles is to uniformly disperse the spherical polymer particles as the core in the alcohol solution. For example, if the dispersion state is poor and the spherical polymer particles that become the core particles aggregate and form a few to several hundreds of agglomerates, the metal compound will be coated from above and uniform composite particles will not be generated. . Also,
In some cases, the produced composite particles are associated with each other and aggregated in the solution, and cannot be redispersed.

In order to improve these drawbacks, it is preferable to add an alcohol-soluble polymer and / or a surfactant as a dispersibility improving agent to the alcohol solution. The amount of these dispersibility improvers used is preferably 1 part by weight or more, more preferably 3 to 300 parts by weight, and particularly preferably 5 to 100 parts by weight of the spherical polymer particles to be the core.
It is 250 parts by weight.

Preferred as the alcohol-soluble polymer or surfactant are polyvinylpyrrolidone, polyvinyl alcohol, sodium polycarboxylate, sodium hexametaphosphate, sodium naphthalenesulfonate, sodium dodecylbenzenesulfonate, sodium dodecylsulfate and the like. More preferred are polyvinylpyrrolidone and sodium dodecyl sulfate. You may use these individually or in mixture of 2 or more types.

In principle, there are two types of mechanisms for forming spherical polymer-metal compound composite particles. One is a mechanism in which a hydrolyzed metal ion or a complex formed by hydrolysis is adsorbed on the surface of the core spherical polymer particles to form a coating layer. The other is that very small metal compound fine particles are initially formed, and by heteroaggregation, the metal compound fine particles are adsorbed on the surface of the spherical polymer particle as the core, and the metal compound layer grows on the particle surface. It is a mechanism to go. With this latter mechanism, the thickness of the coating layer can be controlled by the number and particle size of the metal compound fine particles adsorbed on the surface of the spherical polymer particles as the core.

In order to cause the above-mentioned heteroaggregation, it is not always necessary to give the spherical polymer particles as the core a charge, but it is preferable to give a positive or negative charge.

For example, when the hydrolysis reaction of the metal salt occurs at a pH higher than the isoelectric point of the metal compound fine particles, spherical polymer particles having a positive charge can be used as the core for efficient adsorption. Further, when the hydrolysis reaction of the metal salt occurs at a pH lower than the isoelectric point of the metal compound fine particles, the spherical polymer particles having a negative charge can be used for the efficient adsorption.

When the shell composition is a hydroxide of titanium and / or silicon, it can be converted into an oxide by heat treatment. For example, the shell is Ti (OH)
_{In the case of 4} and / or Si (OH) ₄ , heating is performed in an inert gas atmosphere or in the presence of an enzyme, preferably at 50 ° C. or higher, more preferably at 100 ° C. or higher, and below the decomposition temperature of the core polymer particles. By doing so, it can be converted into TiO ₂ and / or SiO ₂ .

Further, the above TiO ₂ and / or Si
In the case of O ₂ , it can be converted to TiO and / or SiO by partial reduction in a hydrogen gas atmosphere, preferably at 100 ° C. or higher, more preferably at 200 ° C. or higher, and below the decomposition temperature of the core polymer particles. .

The spherical polymer-metal compound composite particles obtained as described above have a particle diameter of 0.07 to 50 μm, more preferably 0.1 to 50 μm, and particularly preferably 0.1 to 10.
μm, and the ratio of the particle size of the core spherical polymer particles to the particle size of the composite particles is preferably 0.4 to 0.9.
9, more preferably 0.5 to 0.99, and particularly preferably 0.6 to 0.99.

[Method for Producing Hollow Particles] A method for producing spherical hollow particles made of a titanium compound and / or a silicon compound and having pores inside will be described below.
In the production of hollow particles, the spherical polymer-metal compound composite particles obtained above are heated to 100 ° C or higher, more preferably 450 ° C or higher, depending on the type of the core polymer in the presence of air or oxygen. Then, the polymer of the core is decomposed and gasified to be scattered from the inside of the particles to form pores inside the particles. Further, if necessary, reduction treatment can be performed to obtain hollow particles having various compositions.

That is, the shell composition of the spherical hollow particles is T
In the case of iO ₂ , SiO ₂ or the like, for example, the hollow particles are partially reduced in a hydrogen gas atmosphere at preferably 100 ° C. or higher, more preferably 200 ° C. or higher to obtain Ti.
It can be converted to O, SiO, or the like.

In the above method for producing hollow particles, the spherical polymer particles of the core are not particularly limited, but they are completely decomposed,
In order to facilitate gasification, it is preferably not crosslinked. As a result, it is possible to form pores at a low temperature in a short time. For example, when the spherical polymer particles of the core are crosslinked, the temperature is 800 ° C or higher, more preferably 110 ° C or higher.
It is necessary to heat above 0 ° C. Therefore, as the monomer component of the polymer of the core, it is preferable to use a monomer such as styrene, acrylonitrile or vinyl acetate as a main component and not be crosslinked, from the viewpoint of being decomposed by heating.

When the heating temperature is 1200 ° C. or higher, cracks are easily formed on the surface of the hollow particles, and when the heating rate and the cooling rate are rapid, the shell tends to collapse. Therefore, the rate of temperature rise is preferably 30 ° C./min or less, and the rate of cooling is preferably 20 ° C./min or less.

By the above production method, hollow particles having a monodisperse and uniform shell layer can be obtained, and the particle diameter and the pore diameter can be freely controlled.

The particle size of the hollow particles obtained as described above is usually 0.04 to 50 μm, preferably 0.04 to 40 μm.
m, more preferably 0.1 to 10 μm, and particularly preferably 0.2 to 1 μm. The ratio of the inner diameter to the outer diameter of the particles is usually 0.3 to 0.99, and preferably 0.5 to 0.99.
0.99, particularly preferably 0.6 to 0.99.

[0037]

The present invention is described in detail below with reference to examples, but the present invention is not limited to these.

Synthesis Example (Production of Spherical Polymer Particles Used as Core) Example-1 574 g of distilled water, 1.0 g of potassium persulfate and 0.30 sodium dodecyl sulfate were placed in a 4-neck flask for 1 l polymerization.
g was added and stirred for 10 minutes to completely dissolve them.
Next, 100 g of styrene was added, and the mixture was stirred for 5 minutes while purging with N ₂ gas. After that, the flask was put in a water bath and reacted at 80 ° C. for 4 hours, and then cooled to room temperature. After cooling, filter paper was used to remove agglomerates. The total solid content of the obtained spherical polymer particle dispersion liquid comprising the styrene polymer was 14.7% by weight. The average particle size of the spherical polymer particles was 0.42 μm. Distilled water was added so that the concentration of the spherical polymer particle dispersion liquid would be 5 g / l.

Example-2 576 g of distilled water and Trit in a four-necked flask for 1 l polymerization.
on X-100 (Rohm and Haas Company, nonionic surfactant) 0.5 g and 2,2'-azobis (2
-Methylpropionitrile) (AIBN. Aldrich) 1.0 g was added and stirred for 10 minutes to completely complete Trit.
on X-100, AIBN was dissolved. Next, 100 g of styrene was added, and while purging with N ₂ gas, 5
Stir for minutes. Then, this flask was put in a water bath and reacted at 70 ° C. for 12 hours, and then cooled to room temperature. After cooling, filter paper was used to remove agglomerates. The total solid content of the obtained spherical polymer particle dispersion liquid comprising styrene polymer particles was 14.2% by weight. The average particle size of the spherical polymer particles was 0.17 μm. Distilled water was added so that the concentration of the spherical polymer particle dispersion liquid would be 5 g / l.

Example-3 70 g of the spherical polymer particle dispersion obtained in Example-2, 929 g of distilled water and 1.0 g of sodium persulfate were placed in a 1-liter four-necked flask for polymerization and stirred for 10 minutes to remove sodium persulfate. Dissolved. Next, 90 g of styrene and 10 g of divinylbenzene were added, and while purging with N ₂ gas, 5
Stir for minutes. After that, the flask was put in a water bath and reacted at 70 ° C. for 12 hours, and then cooled to room temperature.
After cooling, filter paper was used to remove agglomerates. The total solid content of the obtained spherical polymer particle dispersion liquid comprising the styrene / divinylbenzene copolymer was 9.6% by weight, and the average particle diameter of the spherical polymer particles was 0.35 μm. Distilled water was added so that the concentration of the spherical polymer particle dispersion liquid would be 5 g / l.

Example-4 STADEX SC-310 manufactured by Nippon Synthetic Rubber Co., Ltd.
-S (spherical styrene polymer particles) was used. The average particle size was 3.1 μm. It was prepared by adding distilled water so that the concentration of the spherical polymer particle dispersion was 5 g / l.

Example 5 Divinylbenzene, an azo polymerization initiator [V-59, manufactured by Wako Pure Chemical Industries, Ltd.], t-butylhydroquinone, sodium lauryl sulfate and water in a weight ratio of 100: 10: 0.
The mixture was mixed and stirred at a ratio of 5: 0.5: 2 to emulsify to obtain an aqueous dispersion of a polymerizable monomer having a particle size of 0.3 to 20 μm. Polystyrene monodisperse liquid with an average particle size of 3 μm (solid content 1
8.1% by weight) was added to 113.3 parts of water to disperse the mixture, and 60 parts of a 5% by weight aqueous solution of polyvinyl alcohol was added to the aqueous dispersion of the seed particles, and the temperature was raised to 83 ° C. . An aqueous dispersion of the polymerizable monomer and a 1% by weight aqueous solution of polyvinyl alcohol were added dropwise to the aqueous dispersion of the seed particles over 6 hours to obtain monodisperse polymer particles having an average particle diameter of 20 μm. The concentration of this spherical polymer particle dispersion is 5
It was prepared by adding distilled water so as to be g / l.

Example 1 Spherical polymer particle dispersion liquid obtained in Example 1 (concentration 5 g /
l) 60 ml, polyvinylpyrrolidone (Mw, 360,000)
0.6 g, tetra-n-butyl titanate (monomer) 1
0 g and 2 l of water / ethanol were placed in a separable flask. The reaction mixture was stirred well with a homogenizer and then heated at 80 ° C. for 4 hours for hydrolysis. Then, the mixture is cooled to room temperature, the composite particles are settled by centrifugation, the supernatant solution is separated, distilled water is added, the particles are completely dispersed by a homogenizer, and then the washing step of separating the composite particles is performed five times. I repeated. Then, the obtained composite particles were dried at room temperature. When the obtained composite particles were observed with an electron microscope, the average particle size was 0.46 μm, and the particle size ratio of the core to the particle size was 0.91. It was a composite particle. Infrared absorption spectrum, X-ray diffraction, thermogravimetric analysis,
When analyzed by elemental analysis and an electrophoresis apparatus, it was confirmed that the core was a polystyrene polymer and the shell was a composite particle composed of TiO ₂ . An electron micrograph of this composite particle is shown in FIG.

The reaction system of Example 1 has the following component ratios. Styrene polymer of Example-1 1.5 g / reaction mixture 1 l, tetra-n-butyl titanate (monomer) 5 g / reaction mixture 1 l, polyvinylpyrrolidone (Mw, 360,000) 0.3 g / reaction mixture 1 l, Water / ethanol 3 (% by volume).

Examples 2 to 15 Basically the same method as in Example 1, except that the components used during hydrolysis and the production conditions were changed as shown in Tables 1 to 3. It was set to 15. The shapes and compositions of the resulting composite particles are shown in Tables 1 to 3 together with Example 1.

[0046]

[Table 1]

[0047]

[Table 2]

[0048]

[Table 3]

Example 16 5 g of composite particles having a core of styrene / divinylbenzene copolymer and a shell of TiO 2 obtained in Example 4 were heated from room temperature to 300 ° C. under the condition of 10 ° C./min in a hydrogen gas atmosphere. Then, it was held at 300 ° C. for 3 hours. Then, it was cooled to room temperature at a rate of 10 ° C./min. The average particle size of the obtained composite particles was 0.42 μm, and the ratio of the core particle size to the particle outer diameter was 0.86. When the composite particles were analyzed in the same manner as in Example 1, the core was a styrene / divinylbenzene copolymer and the shell was TiO 2.

Examples 17 to 21 Basically the same method as in Example 16, except that the composite particles used and the firing conditions were changed as shown in Table 4 were Examples 17 to 21. The shape, composition, etc. of the resulting composite particles are shown in Table 4 together with Example 16.

[0051]

[Table 4]

Example 22 The core obtained in Example 1 was a styrene polymer, and the shell was T.
5 g of composite particles of iO ₂ was heated from room temperature to 600 in an air atmosphere.
The temperature was raised to 10 ° C./min and held at 600 ° C. for 3 hours. Then, it was cooled to room temperature at a rate of 10 ° C./min. When the obtained hollow particles were observed with an electron microscope, the average particle diameter was 0.42 μm, and the ratio of the inner pore diameter to the particle outer diameter was 0.86. When the hollow particles were analyzed by infrared absorption spectrum, X-ray diffraction, elemental analysis, electrophoresis, etc., it was confirmed that the hollow particles were hollow particles having a core of TiO ₂ and a shell of TiO ₂ . An electron micrograph of this composite particle is shown in FIG.

Examples 23 to 31 Basically, the same method as in Example 22 was used, except that the composite particles used and the production conditions were changed as shown in Tables 5 and 6 to obtain Examples 23 to 31. did. The shape, composition, etc. of the resulting hollow particles are shown in Tables 5 and 6 together with Example 22.

[0054]

[Table 5]

[0055]

[Table 6]

Example 32 ₂ g of the TiO ₂ particles obtained in Example 22 was heated from room temperature to 300 ° C. under the conditions of 10 ° C./min in a hydrogen gas atmosphere and held at 300 ° C. for 1 hour. Then, it was cooled to room temperature at a rate of 10 ° C./min. The obtained hollow particles had an average particle size of 0.40 μm and a ratio of internal pore size to particle size of 0.88. When the hollow particles were analyzed by infrared absorption spectrum, X-ray diffraction, elemental analysis and the like, the core was void and the shell was TiO 2.

Examples 33 to 35 Basically, the same method as in Example 32 was used, except that the hollow particles used and the production conditions were changed as shown in Table 7 to obtain Examples 33 to 35. The shape, composition, etc. of the resulting hollow particles are shown in Table 7 together with that of Example 32.

[0058]

[Table 7]

[0059]

INDUSTRIAL APPLICABILITY The present invention relates to composite particles and hollow particles which are widely used in various applications, and a method for producing them, which has high strength, high heat resistance, can exhibit high functions, and can be used in cosmetics and electronic products. Materials, semiconductor materials, paints, abrasives, spacers, coating agents, optical materials, catalysts, fillers, pharmaceuticals,
Composite particles suitably used for diagnostic agents, toners, resin modifiers, inks, adsorbents, UV resistant materials, etc., and a method for producing the same,
The present invention also relates to hollow particles having a large hiding rate, adsorption rate, specific surface area and the like, which are suitably used for optical materials, microcapsule materials, hiding materials, cosmetics, column fillers, catalysts and the like, and a method for producing the same.

[Brief description of drawings]

FIG. 1 is an electron micrograph showing the structure of a spherical styrene polymer (core) / TiO ₂ composite particle obtained in Example 1. The scale in the figure indicates 0.5 μm.

2 is an electron micrograph showing the structure of hollow TiO ₂ particles obtained in Example 22. FIG. The scale in the figure is 0.5 μm
Indicates.

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Claims (4)

[Claims] 1. Spherical polymer-metal compound composite particles, wherein (a) the core is a polymer and (b) the shell is a titanium compound and / or a silicon compound. 2. Spherical polymer particles are uniformly dispersed in an alcohol solution of a titanium alkoxide and / or a silicon alkoxide or in an alcohol / water mixed solution, and a titanium compound is uniformly formed on the surface of the spherical polymer particles by a hydrolysis reaction. Alternatively, the method for producing composite particles according to claim 1, wherein a silicon compound coating layer is provided, and if necessary, heat treatment is performed. 3. A spherical hollow particle comprising a titanium compound and / or a silicon compound and having pores inside. 4. The polymer of the core is decomposed by heating the composite particle according to claim 1, to give pores inside the particle, and further, if necessary, reduction treatment is performed. A method for producing the hollow particles described above.