WO2014098163A1 - Core-shell-particle production method, and hollow-particle production method - Google Patents

Core-shell-particle production method, and hollow-particle production method Download PDF

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WO2014098163A1
WO2014098163A1 PCT/JP2013/083995 JP2013083995W WO2014098163A1 WO 2014098163 A1 WO2014098163 A1 WO 2014098163A1 JP 2013083995 W JP2013083995 W JP 2013083995W WO 2014098163 A1 WO2014098163 A1 WO 2014098163A1
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core
particles
shell
metal oxide
producing
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PCT/JP2013/083995
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French (fr)
Japanese (ja)
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雄一 ▲桑▼原
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旭硝子株式会社
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G23/00—Compounds of titanium
    • C01G23/04—Oxides; Hydroxides
    • C01G23/047—Titanium dioxide
    • C01G23/053—Producing by wet processes, e.g. hydrolysing titanium salts
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/30—Particle morphology extending in three dimensions
    • C01P2004/32—Spheres
    • C01P2004/34—Spheres hollow
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer

Definitions

  • the present invention relates to a method for producing core-shell particles and a method for producing hollow particles using the same.
  • Patent Document 1 discloses that a spherical polymer particle is uniformly dispersed in an alcohol solution or an alcohol / water mixed solution of titanium alkoxide and / or silicon alkoxide, and a titanium compound is formed on the surface of the spherical polymer particle by a hydrolysis reaction.
  • a method for producing core-shell type composite particles by providing a coating layer or a silicon compound coating layer is described.
  • a method is described in which the composite particles are heated to decompose the polymer as a core, thereby forming voids in the particles to produce hollow particles.
  • Patent Document 1 describes an example in which a hydrolysis reaction was performed with a core particle content of 1.5 to 20 g and a metal alkoxide content of 1 to 40 g per liter of the reaction mixture. Yes. From the viewpoint of production efficiency, it is preferable to increase the content of the core particles in the reaction solution.
  • the present invention has been made in view of the above circumstances, and is capable of stably producing a core-shell particle or hollow particle having a good shape even when the concentration of the reaction solution is high. It aims to provide a method.
  • the gist of the present invention is the following [1] to [13].
  • a method for producing core-shell particles comprising a step of subjecting the precursor to hydrolysis and dehydration condensation to form a coating layer made of the metal oxide on the surface of the core particles.
  • [11] A step of producing core-shell particles in which a coating layer made of a metal oxide is formed on the surface of the core particles by the production method according to any one of [1] to [10], Heating the core-shell particles to decompose and remove the core particles.
  • core-shell particles or hollow particles having a good shape can be stably produced even when the concentration of the reaction solution is high.
  • Example 1B It is an electron micrograph of the hollow particles obtained in Example 1B.
  • 2 is an electron micrograph of Example 2.
  • 4 is an electron micrograph of Example 3.
  • 6 is an electron micrograph of Example 4.
  • 6 is an electron micrograph of Example 5.
  • 6 is an electron micrograph of Example 6.
  • the core particles in the present invention are particles made of a polymer (polymer particles).
  • the polymer that forms the core particles is not particularly limited.
  • a known organic polymer can be suitably used in the core-shell particles used for the production of hollow particles.
  • the organic polymer is not particularly limited as long as core particles having a desired particle diameter can be obtained.
  • the organic polymer is preferably a homopolymer or copolymer of a monomer selected from the group consisting of (meth) acrylic monomers, styrene monomers, diene monomers, imide monomers, and amide monomers.
  • Acrylic monomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, (meth ) Pentyl acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, lauryl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, ( (Meth) acrylic acid dodecyl, (meth) acrylic acid phenyl, (meth) acrylic acid methoxyethyl, (meth) acrylic acid ethoxyethyl, (meth) acrylic acid propoxyethyl, (meth) acrylic acid butoxyethyl, (meth) acrylic acid Ethoxy
  • Styrene monomers include styrene, methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, diethyl styrene, triethyl styrene, propyl styrene, butyl styrene, hexyl styrene, heptyl styrene, octyl styrene, fluorostyrene, chlorostyrene, bromostyrene, Examples thereof include dibromostyrene, chloromethylstyrene, nitrostyrene, acetylstyrene, methoxystyrene, ⁇ -methylstyrene, vinyltoluene, sodium p-styrenesulfonate, and the like.
  • diene monomer examples include butadiene, isoprene, cyclopentadiene, 1,3-pentadiene, dicyclopentadiene, and the like.
  • imide monomers include maleimide, N-methylmaleimide, N-phenylmaleimide, N-cyclohexylmaleimide, 6-aminohexyl succinimide, 2-aminoethyl succinimide, and the like.
  • amide monomers examples include acrylamide derivatives such as acrylamide and N-methylacrylamide; allylamine derivatives such as N, N-dimethylacrylamide and N, N-dimethylaminopropylacrylamide; acrylamide derivatives such as acrylamide and N-methylacrylamide Aminostyrenes such as N-aminostyrene;
  • polystyrene or polymethyl methacrylate as the polymer for forming the core particles from the viewpoint of availability.
  • Polymer core particles can be produced by a known method. For example, it can be produced by a method in which a monomer is polymerized by a known polymerization method such as emulsion polymerization, suspension polymerization, or dispersion polymerization to form a particulate polymer. Alternatively, the core particles can also be produced by a method in which a bulk polymer is produced by a known polymerization method and then pulverized to form particles.
  • a known polymerization method such as emulsion polymerization, suspension polymerization, or dispersion polymerization to form a particulate polymer.
  • the core particles can also be produced by a method in which a bulk polymer is produced by a known polymerization method and then pulverized to form particles.
  • the average particle diameter of the core particles is preferably 0.01 to 100 ⁇ m, more preferably 0.03 to 50 ⁇ m, and particularly preferably 0.1 to 5 ⁇ m.
  • the average particle diameter is not less than the lower limit of the above range, core-shell particles having good uniform dispersibility in the liquid can be easily obtained, and when the average particle diameter is not more than the upper limit, precipitation of particles in the liquid is difficult to occur. Easy dispersibility.
  • the particle diameter of the core particles affects the size of the pores of the hollow particles.
  • the average particle size of the core particles in the core-shell particles used for producing the hollow particles is preferably 0.01 to 100 ⁇ m, more preferably 0.03 to 50 ⁇ m, and particularly preferably 0.1 to 5 ⁇ m.
  • the average particle diameter of the core particle in this specification is a volume-based 50% median diameter of the particle diameter measured by the dynamic light scattering method.
  • the average particle diameter of the core-shell particles in this specification is an average value of the particle diameters of 10 particles randomly selected in an image obtained by observation with a microscope. As the microscope, a scanning electron microscope or a transmission electron microscope can be used.
  • the metal oxide precursor means a compound from which the target metal oxide is obtained by hydrolysis and dehydration condensation reaction.
  • the metal oxide in this invention should just be a thing which can be produced
  • One type of metal oxide may be used to form the coating layer, or two or more types of metal oxide may be used in combination to form the coating layer.
  • the reaction rate of hydrolysis is relatively fast, formation of a coating layer is likely to be poor when the concentration in the reaction solution is high, and titanium oxide is effective in applying the production method of the present invention. Is more preferable.
  • a known metal oxide precursor can be used. It is preferable to use a metal alkoxide in that it is easy to form a metal oxide from the precursor.
  • the number of carbon atoms of the alkoxy group in the metal alkoxide is preferably 1 to 6, and more preferably 1 to 4.
  • the titanium oxide precursor includes alkoxy titanium (titanium alkoxide), titanium chloride and the like, and alkoxy titanium is preferable.
  • the alkoxytitanium include tetraalkoxytitanium (tetramethoxytitanium, tetraethoxytitanium, tetrapropoxytitanium, tetrabutoxytitanium, titanium dichloride diisopropoxide, and the like).
  • titanium chloride include titanium tetrachloride. Of these, tetraalkoxytitanium is preferred in that the metal oxide can be easily formed from the precursor.
  • the complexing agent in the present invention means a compound capable of coordinating with a metal oxide precursor.
  • Specific examples of the complexing agent include ⁇ -diketones such as acetylacetone, ethylenediamine, bipyridine, ethylenediaminetetraacetic acid, phenanthroline, porphyrin, crown ether and the like.
  • An organic solvent is used as a dispersion medium in the reaction solution.
  • the organic solvent include alcohols and glycol solvents. Of these, alcohol is preferred because it is inexpensive.
  • An organic solvent may be used individually by 1 type, and may mix and use 2 or more types. Specific examples of the alcohol include saturated alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and tert-butanol.
  • the dispersion medium may contain water in addition to the organic solvent, but it is preferable that the content of water is small in that the reaction rate of hydrolysis and dehydration condensation reaction can be easily controlled. For example, the content of water is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably no water with respect to the total amount of the organic solvent and water.
  • the manufacturing method of the present embodiment includes a hydrolysis and dehydration condensation reaction of a metal oxide precursor in a reaction solution containing a dispersion medium, core particles, a metal oxide precursor, and a complexing agent. And forming a coating layer made of a metal oxide on the surface of the core particle. That is, the method for producing core-shell particles of the present embodiment includes a dispersion medium, core particles, a metal oxide precursor, and 0.01 to 0.25 mol of complexing agent with respect to 1 mol of the metal of the precursor.
  • the liquid temperature (reaction temperature) of the reaction solution is not particularly limited, and the reaction solution may be heated or cooled, or may be room temperature. For example, it can be in the range of 0 to 80 ° C. As the reaction temperature is higher, the reaction rate of hydrolysis and dehydration condensation reaction tends to increase. A temperature of 40 ° C. or lower is preferable because the reaction rate can be easily controlled, and a temperature of 0 ° C. or higher is preferable because the reaction solution is hardly frozen. 5 to 30 ° C. is more preferable. Room temperature is preferable in that heating or cooling equipment is unnecessary, and for example, 15 to 25 ° C is preferable.
  • the following method is mentioned as an example of the manufacturing method of a specific core-shell particle.
  • core particles are dispersed in a dispersion medium.
  • the complexing agent is mixed and dissolved.
  • a metal oxide precursor is added and mixed to prepare a reaction solution.
  • a metal chelate compound such as titanium acetylacetonate is obtained by mixing a metal oxide precursor and a complexing agent. Separately mix the dispersion medium and the core particles.
  • a liquid containing the metal chelate compound is added to and mixed with the mixed liquid of the dispersion medium and the core particles to prepare a reaction liquid.
  • the method (i) is preferable because the core-shell particles can be easily produced stably.
  • the order of adding the core particles, the complexing agent, and the optional components to the dispersion medium is arbitrary. Since the hydrolysis and dehydration condensation reaction may occur when the metal oxide precursor and the dispersion medium come into contact with each other, it is preferable to add the metal oxide precursor last.
  • the liquid temperature immediately before the addition of the metal oxide precursor is preferably a predetermined reaction temperature.
  • the core particles may be added in powder form, or may be added in the state of a dispersion (sol) in which the core particles are dispersed in an organic solvent.
  • the core particle content in the reaction solution is preferably 0.01 to 15.0 mass%, more preferably 0.05 to 5.0 mass%.
  • it is at least the lower limit of the above range, it is easy to synthesize core-shell particles with good productivity, and when it is at most the upper limit, aggregation of the particles can be easily suppressed and a core-shell particle dispersion with good uniform dispersibility can be easily obtained.
  • the content of the metal oxide precursor in the reaction solution is expressed as a value converted into the solid content mass of the metal oxide, it is 0.01 to 6.0 mass with respect to the total weight of the reaction solution (total solution weight). % Is preferable, and 0.03 to 2.0 mass% is more preferable.
  • the amount of the metal oxide precursor used is preferably set according to the thickness of the coating layer (shell) to be obtained.
  • the content of the metal oxide precursor in the reaction solution is preferably 0.03% by mass or more, more preferably 0.1% by mass or more in that the effect of applying the production method of the present invention is large. More preferred.
  • the addition amount of the complexing agent is too small, the effect of addition cannot be obtained, and if it is too large, formation failure of the coating layer tends to occur.
  • the content of the complexing agent in the reaction solution is 0.01 to 0.25 mol, preferably 0.03 to 0.20 mol, per mol of the precursor metal.
  • the reaction solution prepared in this manner is stirred while maintaining a predetermined reaction temperature, and the precursor of the metal oxide is subjected to hydrolysis and dehydration condensation reaction, thereby forming the metal oxide on the surface of the core particle.
  • Core-shell particles with a coating layer formed are obtained.
  • the average particle diameter of the core-shell particles is preferably 0.01 to 200 ⁇ m, more preferably 0.03 to 100 ⁇ m, and particularly preferably 0.1 to 10 ⁇ m. When the average particle diameter is not less than the lower limit of the above range, uniformly dispersed core-shell particles can be obtained, and when the average particle diameter is not more than the upper limit, precipitation of particles can be prevented and a slurry having good dispersibility can be obtained.
  • the ratio of the average particle size of the core particles to the average particle size of the core-shell particles is preferably 0.50 to 0.99, and more preferably 0.77 to 0.97.
  • the ratio of the average particle diameter is not less than the lower limit of the above range, the effect of stabilizing the production of the core-shell particles due to the formation of the coating layer by electroadsorption to the core particles can be sufficiently obtained.
  • the function as the core-shell particle is sufficiently exhibited.
  • the mechanism by which the coating layer is formed on the surface of the core particle is considered as follows. That is, hydrolysis and dehydration condensation reaction of the metal oxide precursor occurs in the stirred reaction liquid. By this reaction, it is considered that the metal oxide precipitates in the form of fine particles, and the metal oxide particles move to the surface of the core particles and are adsorbed and deposited, whereby the coating layer grows. Normally, the core particles and the metal oxide particles each have a surface charge, and the metal oxide particles move to the surface of the core particles by electrophoresis (movement based on electrical interaction) and are adsorbed. It is thought. When the content of the metal oxide precursor in the reaction solution increases, the amount of metal oxide particles deposited per unit time in the reaction solution increases.
  • the complexing agent is coordinated to the metal of the precursor of the metal oxide, so that the hydrolysis and dehydration condensation reaction of the precursor is moderated.
  • the hydrolysis and dehydration condensation reaction of the precursor of the metal oxide becomes slow, and the precipitation rate of the metal oxide particles becomes slow, so that the aggregation of the metal oxide particles can be suppressed.
  • the complexing agent is contained in the reaction solution so that the molar ratio of the metal oxide precursor metal to the complexing agent is within a predetermined range.
  • the method for producing hollow particles of the present embodiment includes the steps of producing core-shell particles in which a coating layer made of a metal oxide is formed on the surface of the core particles, heating the core-shell particles, and And a step of decomposing and removing the particles. That is, the hollow particle production method of the present embodiment includes a dispersion medium, a core particle, a metal oxide precursor, and a predetermined amount of a complexing agent; the dispersion medium, the core particle, a metal oxide precursor; And a complexing agent is mixed; a coating layer made of a metal oxide is formed on the surface of the core particles; and the core particles are decomposed and removed.
  • the core-shell particles obtained by the above production method are heated in an atmosphere containing oxygen, such as air, so that the core particles made of the polymer are decomposed and gasified to be removed. Since the gasified polymer is scattered through the shell of the core-shell particles, hollow particles having pores inside are obtained.
  • the method for heating the core-shell particles is not particularly limited. For example, a method in which dried particles obtained by drying core-shell particles are heated in a heating furnace, and a coating solution in which core-shell particles are dispersed in an organic solvent such as alcohol is applied on a heat-resistant substrate, and then heated in a heating furnace. Methods and the like.
  • the heating temperature for heating the core-shell particles may be higher than the decomposition temperature of the polymer forming the core particles.
  • the heating temperature (the highest temperature in the heating step) is preferably 100 ° C. or higher, more preferably 300 ° C. or higher, and further preferably 400 ° C. or higher.
  • the upper limit of the heating temperature is not particularly limited, but is preferably less than the melting point of the metal oxide to be formed (for example, the melting point of titanium oxide is 1870 ° C.) in that the phenomenon that the shell melts and the internal vacancies disappear hardly occurs. More preferably, the melting point is 200 ° C. or more lower than the melting point. That is, the upper limit of the heating temperature is preferably 1870 ° C.
  • the heating time is not particularly limited as long as the polymer forming the core particles is sufficiently decomposed and removed.
  • the time from the start of temperature increase to the start of temperature decrease is preferably 1 minute to 100 hours, and more preferably 3 minutes to 50 hours.
  • the heating rate when heating the core-shell particles is preferably 30 to 3,000 ° C./hour, more preferably 100 to 1,000 ° C./hour.
  • the average particle size of the hollow particles is preferably 0.01 to 200 ⁇ m, more preferably 0.03 to 100 ⁇ m, and particularly preferably 0.1 to 10 ⁇ m. If the average particle diameter is not less than the lower limit of the above range, hollow particles having good uniform dispersibility in the liquid can be easily obtained, and if it is not more than the upper limit, precipitation of particles in the liquid is difficult to occur and good. Easy dispersibility.
  • the ratio of the average pore diameter (inner diameter) when the average particle diameter (outer diameter) of hollow particles is 1 (hereinafter also referred to as the ratio of inner diameter average / outer diameter average) is 0.50 to 0.99 is preferable, and 0.77 to 0.97 is more preferable.
  • the average particle diameter of the hollow particles in the present specification is an average value of the particle diameters (outer diameters) of 10 particles randomly selected in an image obtained by observation with a microscope.
  • the average value of the pore diameter (inner diameter) of the hollow particles in the present specification is the average value of the diameter (inner diameter) of ten randomly selected holes in the image obtained by observation with a transmission microscope. is there.
  • core-shell particles having a good shape can be stably obtained, hollow particles having a good shape can be stably produced by using this. be able to.
  • the hollow particles obtained by the production method of the present invention can be suitably used for, for example, a low reflection material, a heat insulating material, a light scattering material, a drug delivery and the like.
  • hollow particles made of titanium oxide are suitable for light scattering materials and the like because they have a large refractive index difference between the internal pores and the shell.
  • the core-shell particles obtained by the production method of the present invention produce hollow particles. In addition to the use as an intermediate for the purpose, for example, it can be suitably used for a matte material or the like.
  • the room temperature is 15 ° C.
  • the following method was used for the measurement.
  • [Measurement method of average particle diameter of core particles] The particle size distribution was measured using a dynamic light scattering nanotrack particle size analyzer (manufactured by Nikkiso Co., Ltd., product name: UPA-EX150 type), and the volume-based 50% median diameter was determined to obtain the average particle size.
  • [Measurement method of average particle diameter of hollow particles] The average particle size of the hollow particles is measured randomly by observing the hollow particles obtained by removing the core particles of the core-shell particles by the method of each example with a scanning electron microscope on the glass substrate.
  • the average value of the 10 particles selected in the above was determined and used as the average particle size.
  • the inner diameter of the hollow particles was measured randomly by observing the hollow particles obtained by removing the core particles of the core-shell particles by the method of each example with a transmission electron microscope on the glass substrate, and measuring the diameter (inner diameter) of the pores.
  • the average value of 10 selected particles was obtained and used as the inner diameter of the hollow particles (the diameter of the pores).
  • Preparation Example 1 Preparation of core particles
  • a solution obtained by adding 0.75 g of styrene (manufactured by Tokyo Chemical Industry Co., Ltd.) to 49.24 ml of distilled water was heated to 70 ° C. in a thermostatic bath, and then 2,2′-azobis (2- 0.012 g of methylpropionamidine) dihydrochloride (AIBA) was added. While maintaining this at 70 ° C., the mixture was stirred for 8 hours to cause a polymerization reaction, thereby obtaining a dispersion in which core particles (polystyrene particles) made of polystyrene were dispersed in water.
  • AIBA 2,2′-azobis (2- 0.012 g of methylpropionamidine) dihydrochloride
  • the dispersion was centrifuged at a rotational speed of 10,000 rpm for 30 minutes using a centrifuge (manufactured by KOKUSAN, product name: H-2000B, the same applies hereinafter) to obtain a precipitate of polystyrene particles.
  • the precipitate was diluted with ethanol (manufactured by Kanto Chemical Co., Ltd., the same shall apply hereinafter) so that the solid content concentration was 1.5% by mass.
  • This was repeated three times to obtain a polystyrene particle sol dispersed in an ethanol solvent.
  • the content of polystyrene particles in the obtained polystyrene particle sol was 1.5% by mass, and the average particle diameter of the polystyrene particles in the polystyrene particle sol was 0.24 ⁇ m.
  • Example 1A Production of core-shell particles
  • tetraisopropoxy titanium manufactured by Kanto Chemical Co., Inc., the same applies hereinafter
  • acetylacetone is used as the complexing agent.
  • 0.0075 g of acetylacetone manufactured by Junsei Co., Ltd. was added to 7.78 g of ethanol at room temperature.
  • reaction solution (total amount: 10 g), which was stirred at room temperature (15 ° C.) for 30 minutes.
  • the content of polystyrene particles in the reaction solution is 0.3% by mass
  • the content of tetraisopropoxytitanium is a value converted to the solid content mass of titanium oxide and is 0.59% by mass with respect to the total weight of the reaction solution. It is.
  • the content of acetylacetone is 0.1 mol with respect to 1 mol of titanium of tetraisopropoxytitanium.
  • a core-shell particle sol in which core-shell particles in which a coating layer made of titanium oxide was formed on the surface of polystyrene particles (core particles) was dispersed in ethanol was obtained.
  • the content of the core-shell particles in the obtained core-shell particle sol was 0.89% by mass.
  • the average particle diameter of the obtained core-shell particles was 0.25 ⁇ m, and the ratio of the average particle diameter of the core particles to the average particle diameter of the core-shell particles (core particle diameter / core-shell particle diameter) was 0.97.
  • the main production conditions of this example and the physical property values of the product are shown in the “Example 1B” column of Table 1 below.
  • Example 1B Production of hollow particles
  • Example 2 2.71 g of the core-shell particle sol obtained in Example 1A was added to 17.29 g of ethanol and stirred at room temperature for 10 minutes to prepare a coating solution. About 3 g of the coating solution was dropped onto soda lime glass (Asahi Glass Co., Ltd., the same applies hereinafter) having a length of 100 mm, a width of 100 mm, and a thickness of 2 mm, and a spin coater (Mikasa 1H-360S, the same applies hereinafter). A coating film was formed by spin coating under the conditions of 500 rpm and 20 seconds. The coating film was heated from 60 ° C. to 600 ° C.
  • FIG. 1 is an electron micrograph of the obtained hollow particles observed with a scanning electron microscope.
  • Example 1C Production of core-shell particles, production of hollow particles
  • Core shell particles were prepared as in Example 1A. However, 7.79 g of ethanol and 0.0038 g of acetylacetone were used.
  • Example 1D Production of core-shell particles, production of hollow particles
  • Example Core shell particles were prepared as in Example 1A. However, 0.0150 g of acetylacetone was used. The content of acetylacetone in the reaction solution is 0.2 mol with respect to 1 mol of titanium of tetraisopropoxytitanium. In this way, a core-shell particle sol was obtained.
  • the production conditions and physical property values of the products are shown in Table 1 below. Further, hollow particles were produced in the same manner as in Example 1B.
  • Example 2 This example is a comparative example in which core-shell particles were produced in Example 1A without containing a complexing agent in the reaction solution.
  • 2.0 g of the polystyrene particle sol obtained in Preparation Example 1 was added to 7.79 g of ethanol at room temperature, 0.21 g of tetraisopropoxy titanium was further added, and the mixture was stirred at room temperature (15 ° C.) for 30 minutes.
  • the main production conditions of this example and the physical properties of the product are shown in Table 1 below.
  • an observation sample fired on glass was prepared in the same manner as in Example 1B.
  • FIG. 2 is an electron micrograph obtained by observing the observation sample thus obtained with a scanning electron microscope.
  • Examples 3 to 6 A core-shell particle sol was obtained in the same manner as in Example 1A except that the composition of the reaction solution was changed as shown in Table 1. Table 1 below shows main production conditions and physical properties of the products in each example. Using the sol obtained after stirring for 30 minutes, an observation sample fired on glass was prepared in the same manner as in Example 1B. 3 to 6 are electron micrographs obtained by observing the observation sample thus obtained with a scanning electron microscope. [Example 7: Production of core-shell particles, production of hollow particles] (Example) Core shell particles were prepared as in Example 1A. However, 0.0115 g of 2,2′-bipyridine (manufactured by Nacalai Tesque) was used as a complexing agent.
  • 2,2′-bipyridine manufactured by Nacalai Tesque
  • the content of 2,2′-bipyridine in the reaction solution is 0.1 mol with respect to 1 mol of titanium of tetraisopropoxytitanium.
  • a core-shell particle sol was obtained.
  • the average particle diameter of the obtained core-shell particles was 0.25 ⁇ m, and the ratio of the average particle diameter of the core particles to the average particle diameter of the core-shell particles (core particle diameter / core-shell particle diameter) was 0.97.
  • hollow particles were produced in the same manner as in Example 1B.
  • the average particle diameter of the obtained hollow particles was 0.25 ⁇ m, and the ratio of inner diameter average / outer diameter average of the hollow particles was 0.97.
  • Example 8 Production of core-shell particles, production of hollow particles
  • Core shell particles were prepared as in Example 1A.
  • polystyrene particles having an average particle diameter of 1 ⁇ m were used as core particles (the content of polystyrene particles in the polystyrene particle sol was 1.5% by mass, and the polystyrene particle sol used was 2.0 g).
  • the content of acetylacetone in the reaction solution is 0.1 mol with respect to 1 mol of titanium of tetraisopropoxytitanium. In this way, a core-shell particle sol was obtained.
  • the average particle diameter of the obtained core-shell particles was 1.03 ⁇ m, and the ratio of the average particle diameter of the core particles to the average particle diameter of the core-shell particles (core particle diameter / core-shell particle diameter) was 0.97. Further, hollow particles were produced in the same manner as in Example 1B. The average particle diameter of the obtained hollow particles was 1.03 ⁇ m, and the ratio of the inner diameter average / outer diameter average of the hollow particles was 0.97.
  • the hollow particles obtained by the production method of the present invention can be suitably used for, for example, a low reflection material, a heat insulating material, a light scattering material, a drug delivery and the like.
  • the core-shell particle obtained by the manufacturing method of this invention can be used suitably for a mat

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Abstract

Provided are methods with which satisfactorily shaped core-shell particles and hollow particles can be stably produced even in cases when reaction-solution concentration is high. A core-shell-particle production method is provided with a step in which, in a reaction solution including a dispersion medium, core particles, a metal-oxide precursor, and 0.01-0.25 mol of a complexing agent per 1 mol of metal in the precursor, the precursor is subjected to a hydrolysis and dehydration condensation reaction to form, on surfaces of the core particles, a coating layer comprising the metal oxide. A hollow-particle production method is provided with a step in which the obtained core-shell particles are heated to breakdown and remove the core particles.

Description

コアシェル粒子の製造方法および中空粒子の製造方法Method for producing core-shell particles and method for producing hollow particles
　本発明はコアシェル粒子の製造方法、およびそれを用いた中空粒子の製造方法に関する。 The present invention relates to a method for producing core-shell particles and a method for producing hollow particles using the same.
　中空粒子の製造方法として、まず粒子状のコア（内核）の表面上にシェル（外殻）が形成されたコアシェル粒子を製造し、次いでコアを熱処理や化学的処理によって除去することにより、残ったシェルからなる中空粒子を得る方法がある。
　特許文献１には、チタニウムアルコキシドおよび／またはシリコンアルコキシドのアルコール溶液中またはアルコール／水混合溶液中に、球状重合体粒子を均一に分散せしめ、加水分解反応により該球状重合体粒子の表面にチタニウム化合物被覆層またはシリコン化合物被覆層を設けることによってコアシェル型の複合粒子を製造する方法が記載されている。また該複合粒子を加熱してコアである重合体を分解することによって、粒子内部に空孔を形成して中空粒子を製造する方法が記載されている。 As a method for producing hollow particles, first, core-shell particles in which a shell (outer shell) is formed on the surface of a particulate core (inner core) are produced, and then the core is removed by heat treatment or chemical treatment. There is a method for obtaining hollow particles made of a shell.
Patent Document 1 discloses that a spherical polymer particle is uniformly dispersed in an alcohol solution or an alcohol / water mixed solution of titanium alkoxide and / or silicon alkoxide, and a titanium compound is formed on the surface of the spherical polymer particle by a hydrolysis reaction. A method for producing core-shell type composite particles by providing a coating layer or a silicon compound coating layer is described. In addition, a method is described in which the composite particles are heated to decompose the polymer as a core, thereby forming voids in the particles to produce hollow particles.
日本特開平６－１４２４９１号公報Japanese Unexamined Patent Publication No. 6-142491
　特許文献１に記載されているように、金属アルコキシドを加水分解反応させてコア粒子の表面に金属酸化物の被覆層を設ける方法でコアシェル粒子を製造しようとしても、条件によっては良好な形状のコアシェル粒子が得られない場合がある。
　例えば特許文献１の実施例には、反応混合液１リットル当たりのコア粒子の含有量を１．５～２０ｇ、金属アルコキシドの含有量を１～４０ｇとして加水分解反応を行った例が記載されている。
　製造効率の点からは反応液中のコア粒子の含有量を多くする方が好ましいが、本発明者等の知見によれば、反応液中のコア粒子の含有量を多くすると、それに応じて被覆層を形成するために必要な金属アルコキシドの添加量が多くなり、その結果、コア粒子の表面に均一な金属酸化物の被覆層（シェル）が形成されない場合がある。被覆層（シェル）が良好に形成されていないと、形状が良好な中空粒子は得られない。 As described in Patent Document 1, even if an attempt is made to produce a core-shell particle by a method in which a metal alkoxide is hydrolyzed to provide a coating layer of a metal oxide on the surface of the core particle, a core-shell having a good shape depending on conditions Particles may not be obtained.
For example, the example of Patent Document 1 describes an example in which a hydrolysis reaction was performed with a core particle content of 1.5 to 20 g and a metal alkoxide content of 1 to 40 g per liter of the reaction mixture. Yes.
From the viewpoint of production efficiency, it is preferable to increase the content of the core particles in the reaction solution. However, according to the knowledge of the present inventors, if the content of the core particles in the reaction solution is increased, coating is performed accordingly. The amount of metal alkoxide added to form the layer increases, and as a result, a uniform metal oxide coating layer (shell) may not be formed on the surface of the core particle. If the coating layer (shell) is not formed well, hollow particles having a good shape cannot be obtained.
　本発明は前記事情に鑑みてなされたもので、反応液の濃度が高い場合でも良好な形状のコアシェル粒子または中空粒子を安定して製造できるようにした、コアシェル粒子の製造方法および中空粒子の製造方法を提供することを目的とする。 The present invention has been made in view of the above circumstances, and is capable of stably producing a core-shell particle or hollow particle having a good shape even when the concentration of the reaction solution is high. It aims to provide a method.
　本発明は以下の［１］～［１３］の構成を要旨とするものである。
［１］　分散媒と、コア粒子と、金属酸化物の前駆体と、前記前駆体の金属１モルに対して０．０１～０．２５モルの錯化剤と、を含む反応液中で、前記前駆体を加水分解および脱水縮合反応させて、前記コア粒子の表面に前記金属酸化物からなる被覆層を形成する工程を有することを特徴とするコアシェル粒子の製造方法。
［２］　前記金属酸化物が酸化チタンである、上記［１］に記載のコアシェル粒子の製造方法。
［３］　前記前駆体がテトラアルコキシチタンである上記［１］または［２］に記載のコアシェル粒子の製造方法。 The gist of the present invention is the following [1] to [13].
[1] In a reaction liquid containing a dispersion medium, core particles, a metal oxide precursor, and 0.01 to 0.25 mol of a complexing agent with respect to 1 mol of the metal of the precursor, A method for producing core-shell particles, comprising a step of subjecting the precursor to hydrolysis and dehydration condensation to form a coating layer made of the metal oxide on the surface of the core particles.
[2] The method for producing core-shell particles according to [1], wherein the metal oxide is titanium oxide.
[3] The method for producing core-shell particles according to [1] or [2], wherein the precursor is tetraalkoxytitanium.
［４］　前記反応液における前記前駆体の含有量が、反応液全量に対して、反応後酸化物換算で０．０１～６．０質量％である、上記［１］～［３］のいずれか一項に記載のコアシェル粒子の製造方法。
［５］　前記コア粒子の平均粒子径が０．０１～１００μｍである上記［１］～［４］のいずれか一項に記載のコアシェル粒子の製造方法。
［６］　前記錯化剤がアセチルアセトン、エチレンジアミン、ビピリジン、エチレンジアミン四酢酸、フェナントロリン、ポルフィリン、およびクラウンエーテルからなる群から選ばれる一種以上である上記［１］～［５］のいずれか一項に記載のコアシェル粒子の製造方法。 [4] Any of the above [1] to [3], wherein the content of the precursor in the reaction solution is 0.01 to 6.0% by mass in terms of oxide after reaction with respect to the total amount of the reaction solution. The method for producing core-shell particles according to claim 1.
[5] The method for producing core-shell particles according to any one of [1] to [4], wherein the core particles have an average particle diameter of 0.01 to 100 μm.
[6] The method according to any one of [1] to [5], wherein the complexing agent is one or more selected from the group consisting of acetylacetone, ethylenediamine, bipyridine, ethylenediaminetetraacetic acid, phenanthroline, porphyrin, and crown ether. A method for producing core-shell particles.
［７］　前記コア粒子がポリスチレン粒子またはポリメチルメタクリレート粒子である上記［１］～［６］のいずれか一項に記載のコアシェル粒子の製造方法。
［８］　前記反応液における前記コア粒子の含有量が、０．０１～１５．０質量％である上記［１］～［７］のいずれか一項に記載のコアシェル粒子の製造方法。 [7] The method for producing core-shell particles according to any one of [1] to [6], wherein the core particles are polystyrene particles or polymethyl methacrylate particles.
[8] The method for producing core-shell particles according to any one of [1] to [7] above, wherein the content of the core particles in the reaction solution is 0.01 to 15.0% by mass.
［９］　前記コアシェル粒子の平均粒子径に対する前記コア粒子の平均粒子径の比（コア粒子／コアシェル粒子）が０．５０～０．９９である上記［１］～［８］のいずれか一項に記載のコアシェル粒子の製造方法。
［１０］　前記加水分解および脱水縮合反応させる温度が０～８０℃の範囲である上記［１］～［９］のいずれか一項に記載のコアシェル粒子の製造方法。 [9] The above [1] to [8], wherein the ratio of the average particle diameter of the core particles to the average particle diameter of the core-shell particles (core particle / core-shell particles) is 0.50 to 0.99. The manufacturing method of core-shell particle | grains as described in any one of.
[10] The method for producing core-shell particles according to any one of [1] to [9] above, wherein the temperature for the hydrolysis and dehydration condensation reaction is in the range of 0 to 80 ° C.
［１１］　上記［１］～［１０］のいずれか一項に記載の製造方法によってコア粒子の表面に金属酸化物からなる被覆層が形成されたコアシェル粒子を製造する工程と、
　前記コアシェル粒子を加熱して、前記コア粒子を分解除去する工程と、を有することを特徴とする中空粒子の製造方法。
［１２］　前記加熱温度が１００～１８７０℃である、上記［１１］に記載の中空粒子の製造方法。
［１３］　前記中空粒子の平均粒子径が０．０１～２００μｍである、上記［１１］または［１２］に記載の中空粒子の製造方法。 [11] A step of producing core-shell particles in which a coating layer made of a metal oxide is formed on the surface of the core particles by the production method according to any one of [1] to [10],
Heating the core-shell particles to decompose and remove the core particles.
[12] The method for producing hollow particles according to [11], wherein the heating temperature is 100 to 1870 ° C.
[13] The method for producing hollow particles according to [11] or [12] above, wherein the average particle diameter of the hollow particles is 0.01 to 200 μm.
　本発明によれば、反応液の濃度が高い場合でも良好な形状のコアシェル粒子または中空粒子を安定して製造できる。 According to the present invention, core-shell particles or hollow particles having a good shape can be stably produced even when the concentration of the reaction solution is high.
例１Ｂで得られた中空粒子の電子顕微鏡写真である。It is an electron micrograph of the hollow particles obtained in Example 1B. 例２の電子顕微鏡写真である。2 is an electron micrograph of Example 2. 例３の電子顕微鏡写真である。4 is an electron micrograph of Example 3. 例４の電子顕微鏡写真である。6 is an electron micrograph of Example 4. 例５の電子顕微鏡写真である。6 is an electron micrograph of Example 5. 例６の電子顕微鏡写真である。6 is an electron micrograph of Example 6.
［コア粒子］
　本発明におけるコア粒子は、重合体からなる粒子（重合体粒子）である。コア粒子を形成する重合体は特に限定されない。この重合体としては例えば、中空粒子の製造に用いられるコアシェル粒子において公知の有機ポリマーを好適に用いることができる。
　前記有機ポリマーとしては、所望の粒子径のコア粒子が得られればよく特に限定されるものではない。該有機ポリマーとしては、（メタ）アクリル系モノマー、スチレン系モノマー、ジエン系モノマー、イミド系モノマー、およびアミド系モノマーからなる群から選ばれるモノマーの単独重合体または共重合体が好ましい。 [Core particles]
The core particles in the present invention are particles made of a polymer (polymer particles). The polymer that forms the core particles is not particularly limited. As this polymer, for example, a known organic polymer can be suitably used in the core-shell particles used for the production of hollow particles.
The organic polymer is not particularly limited as long as core particles having a desired particle diameter can be obtained. The organic polymer is preferably a homopolymer or copolymer of a monomer selected from the group consisting of (meth) acrylic monomers, styrene monomers, diene monomers, imide monomers, and amide monomers.
　アクリル系モノマーとしては、（メタ）アクリル酸メチル、（メタ）アクリル酸エチル、（メタ）アクリル酸プロピル、（メタ）アクリル酸イソプロピル、（メタ）アクリル酸ブチル、（メタ）アクリル酸イソブチル、（メタ）アクリル酸ペンチル、（メタ）アクリル酸ヘキシル、（メタ）アクリル酸２－エチルヘキシル、（メタ）アクリル酸オクチル、（メタ）アクリル酸ラウリル、（メタ）アクリル酸ノニル、（メタ）アクリル酸デシル、（メタ）アクリル酸ドデシル、（メタ）アクリル酸フェニル、（メタ）アクリル酸メトキシエチル、（メタ）アクリル酸エトキシエチル、（メタ）アクリル酸プロポキシエチル、（メタ）アクリル酸ブトキシエチル、（メタ）アクリル酸エトキシプロピル、ジエチルアミノエチル（メタ）アクリレート、ジアルキルアミノアルキル（メタ）アクリレート、（メタ）アクリルアミド、Ｎ－メチロール（メタ）アクリルアミド、ジアセトンアクリルアミド、グリシジル（メタ）アクリレート、エチレングリコールのジアクリル酸エステル、ジエチルグリコールのジアクリル酸エステル、トリエチレングリコールのジアクリル酸エステル、ポリエチレングリコールのジアクリル酸エステル、ジプロピレングリコールのジアクリル酸エステル、トリプロピレングリコールのジアクリル酸エステル、エチレングリコールのジメタクリル酸エステル、ジエチレングリコールのジメタクリル酸エステル、トリエチレングリコールのジメタクリル酸エステル、ポリエチレングリコールのジアクリル酸エステル、プロピレングリコールのジメタクリル酸エステル、ジプロピレングリコールのジメタクリル酸エステル、トリプロピレングリコールのジメタクリル酸エステル等が挙げられる。 Acrylic monomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, (meth ) Pentyl acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, lauryl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, ( (Meth) acrylic acid dodecyl, (meth) acrylic acid phenyl, (meth) acrylic acid methoxyethyl, (meth) acrylic acid ethoxyethyl, (meth) acrylic acid propoxyethyl, (meth) acrylic acid butoxyethyl, (meth) acrylic acid Ethoxypropyl, diethylaminoethyl (meth) acrylate , Dialkylaminoalkyl (meth) acrylate, (meth) acrylamide, N-methylol (meth) acrylamide, diacetone acrylamide, glycidyl (meth) acrylate, ethylene glycol diacrylate, diethyl glycol diacrylate, triethylene glycol Diacrylate, polyethylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate Esters, polyethylene glycol diacrylate, propylene glycol dimethacrylate Le, dimethacrylates of dipropylene glycol, dimethacrylate ester of tripropylene glycol.
　スチレン系モノマーとしては、スチレン、メチルスチレン、ジメチルスチレン、トリメチルスチレン、エチルスチレン、ジエチルスチレン、トリエチルスチレン、プロピルスチレン、ブチルスチレン、ヘキシルスチレン、ヘプチルスチレン、オクチルスチレン、フロロスチレン、クロルスチレン、ブロモスチレン、ジブロモスチレン、クロルメチルスチレン、ニトロスチレン、アセチルスチレン、メトキシスチレン、α－メチルスチレン、ビニルトルエン、ｐ－スチレンスルホン酸ナトリウム等が挙げられる。
　ジエン系モノマーとしては、ブタジエン、イソプレン、シクロペンタジエン、１，３－ペンタジエン、ジシクロペンタジエン等が挙げられる。
　イミド系モノマーとしては、マレイミド、Ｎ－メチルマレイミド、Ｎ－フェニルマレイミド、Ｎ－シクロヘキシルマレイミド、６－アミノヘキシルコハク酸イミド、２－アミノエチルコハク酸イミド等が挙げられる。
　アミド系モノマーとしては、アクリルアミド、Ｎ－メチルアクリルアミドなどのアクリルアミド系誘導体；Ｎ、Ｎ－ジメチルアクリルアミド、Ｎ、Ｎ－ジメチルアミノプロピルアクリルアミド等のアリルアミン系誘導体；アクリルアミド、Ｎ－メチルアクリルアミド等のアクリルアミド系誘導体；Ｎ－アミノスチレン等のアミノスチレン類等が挙げられる。 Styrene monomers include styrene, methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, diethyl styrene, triethyl styrene, propyl styrene, butyl styrene, hexyl styrene, heptyl styrene, octyl styrene, fluorostyrene, chlorostyrene, bromostyrene, Examples thereof include dibromostyrene, chloromethylstyrene, nitrostyrene, acetylstyrene, methoxystyrene, α-methylstyrene, vinyltoluene, sodium p-styrenesulfonate, and the like.
Examples of the diene monomer include butadiene, isoprene, cyclopentadiene, 1,3-pentadiene, dicyclopentadiene, and the like.
Examples of imide monomers include maleimide, N-methylmaleimide, N-phenylmaleimide, N-cyclohexylmaleimide, 6-aminohexyl succinimide, 2-aminoethyl succinimide, and the like.
Examples of amide monomers include acrylamide derivatives such as acrylamide and N-methylacrylamide; allylamine derivatives such as N, N-dimethylacrylamide and N, N-dimethylaminopropylacrylamide; acrylamide derivatives such as acrylamide and N-methylacrylamide Aminostyrenes such as N-aminostyrene;
　特に、入手容易性の点で、コア粒子を形成する重合体として、ポリスチレンまたはポリメチルメタクリレートを用いることが好ましい。 In particular, it is preferable to use polystyrene or polymethyl methacrylate as the polymer for forming the core particles from the viewpoint of availability.
　重合体からなるコア粒子は公知の方法により製造できる。例えば、単量体を乳化重合、懸濁重合、または分散重合等の公知の重合法により重合させて、粒子状の重合体を生成させる方法によって製造することができる。または公知の重合法によりバルク状の重合体を生成した後、これを粉砕して粒子状とする方法によってもコア粒子を製造することができる。 Polymer core particles can be produced by a known method. For example, it can be produced by a method in which a monomer is polymerized by a known polymerization method such as emulsion polymerization, suspension polymerization, or dispersion polymerization to form a particulate polymer. Alternatively, the core particles can also be produced by a method in which a bulk polymer is produced by a known polymerization method and then pulverized to form particles.
　コア粒子の平均粒子径は、０．０１～１００μｍが好ましく、０．０３～５０μｍがより好ましく、０．１～５μｍが特に好ましい。該平均粒子径が上記範囲の下限値以上であると、液中での均一分散性が良好なコアシェル粒子が得られやすく、上限値以下であると液中での粒子の沈殿が生じにくく、良好な分散性が得られやすい。
　特に中空粒子の製造に用いるコアシェル粒子の場合、コア粒子の粒子径は中空粒子の空孔の大きさに影響する。中空粒子の製造に用いるコアシェル粒子におけるコア粒子の平均粒子径は、０．０１～１００μｍが好ましく、０．０３～５０μｍがより好ましく、０．１～５μｍが特に好ましい。該平均粒子径が上記範囲の下限値以上であると、液中での中空粒子の良好な均一分散性が得られやすく、上限値以下であるとコア粒子の除去を容易に行いやすい。
　本明細書におけるコア粒子の平均粒子径は、動的光散乱法で測定される粒子径の、体積基準の５０％メジアン径である。
　本明細書におけるコアシェル粒子の平均粒子径は、顕微鏡で観察して得られる像において無作為に選ばれた１０個の粒子の粒子径の平均値である。顕微鏡としては走査型電子顕微鏡、又は透過型電子顕微鏡を用いることができる。 The average particle diameter of the core particles is preferably 0.01 to 100 μm, more preferably 0.03 to 50 μm, and particularly preferably 0.1 to 5 μm. When the average particle diameter is not less than the lower limit of the above range, core-shell particles having good uniform dispersibility in the liquid can be easily obtained, and when the average particle diameter is not more than the upper limit, precipitation of particles in the liquid is difficult to occur. Easy dispersibility.
In particular, in the case of core-shell particles used for the production of hollow particles, the particle diameter of the core particles affects the size of the pores of the hollow particles. The average particle size of the core particles in the core-shell particles used for producing the hollow particles is preferably 0.01 to 100 μm, more preferably 0.03 to 50 μm, and particularly preferably 0.1 to 5 μm. When the average particle diameter is not less than the lower limit of the above range, good uniform dispersibility of the hollow particles in the liquid can be easily obtained, and when it is not more than the upper limit, the core particles can be easily removed.
The average particle diameter of the core particle in this specification is a volume-based 50% median diameter of the particle diameter measured by the dynamic light scattering method.
The average particle diameter of the core-shell particles in this specification is an average value of the particle diameters of 10 particles randomly selected in an image obtained by observation with a microscope. As the microscope, a scanning electron microscope or a transmission electron microscope can be used.
［金属酸化物・金属酸化物の前駆体］
　本発明において、金属酸化物の前駆体とは、これを加水分解および脱水縮合反応させることにより目的の金属酸化物が得られる化合物を意味する。
　本発明における金属酸化物は、前駆体を加水分解および脱水縮合反応させる方法で生成できるものであればよい。１種の金属酸化物を用いて被覆層を形成してもよく、２種以上の金属酸化物を併用して被覆層を形成してもよい。特に、加水分解の反応速度が比較的速いために、反応液中の濃度が高い場合に被覆層の形成不良が生じやすく、本発明の製造方法を適用することによる効果が大きい点で、酸化チタンがより好ましい。 [Metal oxide and metal oxide precursors]
In the present invention, the metal oxide precursor means a compound from which the target metal oxide is obtained by hydrolysis and dehydration condensation reaction.
The metal oxide in this invention should just be a thing which can be produced | generated by the method of hydrolyzing and dehydrating condensation reaction of a precursor. One type of metal oxide may be used to form the coating layer, or two or more types of metal oxide may be used in combination to form the coating layer. In particular, since the reaction rate of hydrolysis is relatively fast, formation of a coating layer is likely to be poor when the concentration in the reaction solution is high, and titanium oxide is effective in applying the production method of the present invention. Is more preferable.
　金属酸化物の前駆体は公知のものを用いることができる。前駆体から金属酸化物の形成が容易である点で金属アルコキシドを用いることが好ましい。金属アルコキシドにおけるアルコキシ基の炭素数は１～６が好ましく、１～４がより好ましい。
　例えば酸化チタンの前駆体としては、アルコキシチタン（チタニウムアルコキシド）、チタニウムクロライド等が挙げられ、アルコキシチタンが好ましい。
　アルコキシチタンの例としては、テトラアルコキシチタン（テトラメトキシチタン、テトラエトキシチタン、テトラプロポキシチタン、テトラブトキシチタン、チタニウムジクロライドジイソプロポキシド等）等が挙げられる。チタニウムクロライドの例としては、チタニウムテトラクロライド等が挙げられる。これらのうち、前駆体から金属酸化物の形成が容易である点でテトラアルコキシチタンが好ましい。 A known metal oxide precursor can be used. It is preferable to use a metal alkoxide in that it is easy to form a metal oxide from the precursor. The number of carbon atoms of the alkoxy group in the metal alkoxide is preferably 1 to 6, and more preferably 1 to 4.
For example, the titanium oxide precursor includes alkoxy titanium (titanium alkoxide), titanium chloride and the like, and alkoxy titanium is preferable.
Examples of the alkoxytitanium include tetraalkoxytitanium (tetramethoxytitanium, tetraethoxytitanium, tetrapropoxytitanium, tetrabutoxytitanium, titanium dichloride diisopropoxide, and the like). Examples of titanium chloride include titanium tetrachloride. Of these, tetraalkoxytitanium is preferred in that the metal oxide can be easily formed from the precursor.
［錯化剤］
　本発明における錯化剤は、金属酸化物の前駆体に配位結合可能な化合物を意味する。
　錯化剤の具体例としては、アセチルアセトン等のβ－ジケトン、エチレンジアミン、ビピリジン、エチレンジアミン四酢酸、フェナントロリン、ポルフィリン、クラウンエーテル等が挙げられる。 [Complexing agent]
The complexing agent in the present invention means a compound capable of coordinating with a metal oxide precursor.
Specific examples of the complexing agent include β-diketones such as acetylacetone, ethylenediamine, bipyridine, ethylenediaminetetraacetic acid, phenanthroline, porphyrin, crown ether and the like.
［分散媒］
　反応液中の分散媒として有機溶媒を用いる。該有機溶媒としては、アルコール、グリコール系溶媒等が挙げられる。これらのうち安価である点でアルコールが好ましい。有機溶媒は１種を単独で用いてもよく、２種以上を混合して用いてもよい。
　アルコールの具体例としては、メタノール、エタノール、１－プロパノール、２－プロパノール、１－ブタノール、２－ブタノール、ｔｅｒｔ－ブタノール等の飽和アルコールが挙げられる。
　分散媒は有機溶媒の他に水を含んでもよいが、加水分解および脱水縮合反応の反応速度を制御しやすい点で、水の含有量は少ない方が好ましい。例えば有機溶媒と水の合計量に対して、水の含有量は２０質量％以下が好ましく、１０質量％以下がより好ましく、水を含まないことがさらに好ましい。 [Dispersion medium]
An organic solvent is used as a dispersion medium in the reaction solution. Examples of the organic solvent include alcohols and glycol solvents. Of these, alcohol is preferred because it is inexpensive. An organic solvent may be used individually by 1 type, and may mix and use 2 or more types.
Specific examples of the alcohol include saturated alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and tert-butanol.
The dispersion medium may contain water in addition to the organic solvent, but it is preferable that the content of water is small in that the reaction rate of hydrolysis and dehydration condensation reaction can be easily controlled. For example, the content of water is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably no water with respect to the total amount of the organic solvent and water.
＜コアシェル粒子の製造方法＞
　本発明のコアシェル粒子の製造方法の好ましい実施形態を説明する。
　本実施形態の製造方法は、分散媒と、コア粒子と、金属酸化物の前駆体と、錯化剤とを含有する反応液中で、金属酸化物の前駆体を加水分解および脱水縮合反応させて、コア粒子の表面に金属酸化物からなる被覆層を形成する工程を有する。
　すなわち本実施形態のコアシェル粒子の製造方法は、分散媒、コア粒子、金属酸化物の前駆体、および、前記前駆体の金属１モルに対して０．０１～０．２５モルの錯化剤を用意し；分散媒、コア粒子、金属酸化物の前駆体、および錯化剤を混合し；コア粒子の表面に金属酸化物からなる被覆層を形成させることを特徴とする。
　反応液の液温（反応温度）は特に限定されず、反応液の加熱または冷却を行ってもよく、室温とすることもできる。例えば０～８０℃の範囲とすることができる。反応温度が高いほど加水分解および脱水縮合反応の反応速度が速くなる傾向がある。該反応速度を制御しやすい点で４０℃以下が好ましく、反応液の凍結が生じにくい点で０℃以上が好ましい。５～３０℃がより好ましい。加熱または冷却の設備が不要である点で室温が好ましく、例えば１５～２５℃が好ましい。 <Method for producing core-shell particles>
A preferred embodiment of the method for producing core-shell particles of the present invention will be described.
The manufacturing method of the present embodiment includes a hydrolysis and dehydration condensation reaction of a metal oxide precursor in a reaction solution containing a dispersion medium, core particles, a metal oxide precursor, and a complexing agent. And forming a coating layer made of a metal oxide on the surface of the core particle.
That is, the method for producing core-shell particles of the present embodiment includes a dispersion medium, core particles, a metal oxide precursor, and 0.01 to 0.25 mol of complexing agent with respect to 1 mol of the metal of the precursor. Prepared; mixing dispersion medium, core particles, metal oxide precursor, and complexing agent; and forming a coating layer made of metal oxide on the surface of the core particles.
The liquid temperature (reaction temperature) of the reaction solution is not particularly limited, and the reaction solution may be heated or cooled, or may be room temperature. For example, it can be in the range of 0 to 80 ° C. As the reaction temperature is higher, the reaction rate of hydrolysis and dehydration condensation reaction tends to increase. A temperature of 40 ° C. or lower is preferable because the reaction rate can be easily controlled, and a temperature of 0 ° C. or higher is preferable because the reaction solution is hardly frozen. 5 to 30 ° C. is more preferable. Room temperature is preferable in that heating or cooling equipment is unnecessary, and for example, 15 to 25 ° C is preferable.
　具体的なコアシェル粒子の製造方法の例としては、以下の方法が挙げられる。（ｉ）まず分散媒にコア粒子を分散させる。次に錯化剤を混合し溶解させる。さらに金属酸化物の前駆体を添加混合して反応液を調製する。（ｉｉ）金属酸化物の前駆体と錯化剤とを混合しチタニウムアセチルアセトナートといった金属キレート化合物を得る。分散媒とコア粒子を別途混合する。分散媒とコア粒子との混合液に金属キレート化合物が含まれる液を添加混合して反応液を調製する。安定にコアシェル粒子が製造しやすいことから（ｉ）の方法が好ましい。
　分散媒への、コア粒子、錯化剤、および任意成分の添加順序は任意である。金属酸化物の前駆体と分散媒とが接触すると加水分解および脱水縮合反応が生じ得るため、金属酸化物の前駆体は最後に添加することが好ましい。また金属酸化物の前駆体を添加する直前の液温が、所定の反応温度となっていることが好ましい。
　コア粒子は粉末状で添加してもよく、コア粒子を有機溶媒に分散させた分散液（ゾル）の状態で添加してもよい。 The following method is mentioned as an example of the manufacturing method of a specific core-shell particle. (I) First, core particles are dispersed in a dispersion medium. Next, the complexing agent is mixed and dissolved. Further, a metal oxide precursor is added and mixed to prepare a reaction solution. (Ii) A metal chelate compound such as titanium acetylacetonate is obtained by mixing a metal oxide precursor and a complexing agent. Separately mix the dispersion medium and the core particles. A liquid containing the metal chelate compound is added to and mixed with the mixed liquid of the dispersion medium and the core particles to prepare a reaction liquid. The method (i) is preferable because the core-shell particles can be easily produced stably.
The order of adding the core particles, the complexing agent, and the optional components to the dispersion medium is arbitrary. Since the hydrolysis and dehydration condensation reaction may occur when the metal oxide precursor and the dispersion medium come into contact with each other, it is preferable to add the metal oxide precursor last. The liquid temperature immediately before the addition of the metal oxide precursor is preferably a predetermined reaction temperature.
The core particles may be added in powder form, or may be added in the state of a dispersion (sol) in which the core particles are dispersed in an organic solvent.
　反応液におけるコア粒子の含有量は、０．０１～１５．０質量％が好ましく、０．０５～５．０質量％がより好ましい。上記範囲の下限値以上であると生産性良くコアシェル粒子を合成しやすく、上限値以下であると粒子の凝集が抑えられやすく、均一分散性が良好なコアシェル粒子分散体が得られやすい。
　反応液における金属酸化物の前駆体の含有量は、金属酸化物の固形分質量に換算した値で表すと、反応液の総重量（溶液総重量）に対して０．０１～６．０質量％が好ましく、０．０３～２．０質量％がより好ましい。上記範囲の下限値以上であると充分な反応速度が得られやすく、良好な生産性が得られやすい。上限値以下であると金属酸化物前駆体同士の反応が充分に抑制されやすく、コアシェル粒子の良好な製造効率が得られやすい。
　反応液中における金属酸化物の前駆体の含有量が、少ないほどコア粒子の表面に形成される被覆層の厚さ、すなわちコアシェル粒子のシェル（外殻）の厚さが薄くなる。したがって、金属酸化物の前駆体の使用量は、得ようとする被覆層（シェル）の厚さに応じて設定することが好ましい。
　特に、本発明の製造方法を適用することによる効果が大きい点で、反応液における金属酸化物の前駆体の含有量が０．０３質量％以上であることが好ましく、０．１質量％以上がより好ましい。 The core particle content in the reaction solution is preferably 0.01 to 15.0 mass%, more preferably 0.05 to 5.0 mass%. When it is at least the lower limit of the above range, it is easy to synthesize core-shell particles with good productivity, and when it is at most the upper limit, aggregation of the particles can be easily suppressed and a core-shell particle dispersion with good uniform dispersibility can be easily obtained.
When the content of the metal oxide precursor in the reaction solution is expressed as a value converted into the solid content mass of the metal oxide, it is 0.01 to 6.0 mass with respect to the total weight of the reaction solution (total solution weight). % Is preferable, and 0.03 to 2.0 mass% is more preferable. When it is at least the lower limit of the above range, a sufficient reaction rate is easily obtained, and good productivity is easily obtained. When the amount is not more than the upper limit, the reaction between the metal oxide precursors can be sufficiently suppressed, and good production efficiency of the core-shell particles can be easily obtained.
The smaller the content of the metal oxide precursor in the reaction solution, the thinner the coating layer formed on the surface of the core particle, that is, the thickness of the shell (outer shell) of the core-shell particle. Therefore, the amount of the metal oxide precursor used is preferably set according to the thickness of the coating layer (shell) to be obtained.
In particular, the content of the metal oxide precursor in the reaction solution is preferably 0.03% by mass or more, more preferably 0.1% by mass or more in that the effect of applying the production method of the present invention is large. More preferred.
　本発明において錯化剤の添加量は、少なすぎると添加効果が得られず、多すぎると被覆層の形成不良が生じやすくなる。反応液における錯化剤の含有量は、前記前駆体の金属１モルに対して０．０１～０．２５モルであり、０．０３～０．２０モルが好ましい。 In the present invention, if the addition amount of the complexing agent is too small, the effect of addition cannot be obtained, and if it is too large, formation failure of the coating layer tends to occur. The content of the complexing agent in the reaction solution is 0.01 to 0.25 mol, preferably 0.03 to 0.20 mol, per mol of the precursor metal.
　このようにして調製した反応液を、所定の反応温度に維持しつつ撹拌して、金属酸化物の前駆体を加水分解および脱水縮合反応させることにより、コア粒子の表面上に金属酸化物からなる被覆層が形成されたコアシェル粒子が得られる。
　コアシェル粒子の平均粒子径は、０．０１～２００μｍが好ましく、０．０３～１００μｍがより好ましく、０．１～１０μｍが特に好ましい。該平均粒子径が上記範囲の下限値以上であると均一に分散されたコアシェル粒子を得ることができ、上限値以下であると粒子の沈殿を防ぎ、分散性の良いスラリーを得ることができる。
　コアシェル粒子の平均粒子径に対するコア粒子の平均粒子径の比（コア粒子／コアシェル粒子）は、０．５０～０．９９が好ましく、０．７７～０．９７がより好ましい。該平均粒子径の比が上記範囲の下限値以上であるとコア粒子への電気的吸着によって被覆層が形成されることによる、コアシェル粒子の製造安定化の効果が充分に得られやすく、上限値以下であるとコアシェル粒子としての機能が充分に発揮されやすい。 The reaction solution prepared in this manner is stirred while maintaining a predetermined reaction temperature, and the precursor of the metal oxide is subjected to hydrolysis and dehydration condensation reaction, thereby forming the metal oxide on the surface of the core particle. Core-shell particles with a coating layer formed are obtained.
The average particle diameter of the core-shell particles is preferably 0.01 to 200 μm, more preferably 0.03 to 100 μm, and particularly preferably 0.1 to 10 μm. When the average particle diameter is not less than the lower limit of the above range, uniformly dispersed core-shell particles can be obtained, and when the average particle diameter is not more than the upper limit, precipitation of particles can be prevented and a slurry having good dispersibility can be obtained.
The ratio of the average particle size of the core particles to the average particle size of the core-shell particles (core particle / core-shell particle) is preferably 0.50 to 0.99, and more preferably 0.77 to 0.97. When the ratio of the average particle diameter is not less than the lower limit of the above range, the effect of stabilizing the production of the core-shell particles due to the formation of the coating layer by electroadsorption to the core particles can be sufficiently obtained. When it is below, the function as the core-shell particle is sufficiently exhibited.
［作用・効果］
　コア粒子の表面に被覆層が形成されるメカニズムについては、以下のように考えられる。すなわち、撹拌されている反応液中で金属酸化物の前駆体の加水分解および脱水縮合反応が生じる。該反応により、金属酸化物が微細な粒子状で析出し、該金属酸化物の粒子がコア粒子の表面に移動して吸着され、堆積することにより被覆層が成長すると考えられる。通常、コア粒子および該金属酸化物の粒子はそれぞれ表面電荷を有しており、金属酸化物の粒子は電気泳動（電気的な相互作用に基づく移動）によりコア粒子の表面に移動して吸着されると考えられる。
　そして、反応液における金属酸化物の前駆体の含有量が多くなると、反応液中での単位時間当たりの金属酸化物粒子の析出量が多くなる。このため、該金属酸化物粒子がコア粒子の表面に吸着する前に、該金属酸化物粒子どうしが凝集しやすくなる。その結果被覆層の形成不良が生じやすくなると考えられる。
　本実施形態では反応液に錯化剤を含有させることにより、該錯化剤が金属酸化物の前駆体の金属に配位結合して、該前駆体の加水分解および脱水縮合反応を緩やかにすると考えられる。例えば下式（１）に示されるように、１分子のアセチルアセトンがテトラアルコキシチタンにキレートとして配位結合すると、テトラアルコキシチタンのアルコキシ基が１個減るため、反応性が低下すると考えられる。
　このようにして金属酸化物の前駆体の加水分解および脱水縮合反応が緩やかになり、金属酸化物粒子の析出速度が遅くなることにより、金属酸化物粒子どうしの凝集が抑えられると考えられる。 [Action / Effect]
The mechanism by which the coating layer is formed on the surface of the core particle is considered as follows. That is, hydrolysis and dehydration condensation reaction of the metal oxide precursor occurs in the stirred reaction liquid. By this reaction, it is considered that the metal oxide precipitates in the form of fine particles, and the metal oxide particles move to the surface of the core particles and are adsorbed and deposited, whereby the coating layer grows. Normally, the core particles and the metal oxide particles each have a surface charge, and the metal oxide particles move to the surface of the core particles by electrophoresis (movement based on electrical interaction) and are adsorbed. It is thought.
When the content of the metal oxide precursor in the reaction solution increases, the amount of metal oxide particles deposited per unit time in the reaction solution increases. For this reason, before the metal oxide particles are adsorbed on the surface of the core particles, the metal oxide particles are easily aggregated. As a result, it is considered that poor formation of the coating layer is likely to occur.
In this embodiment, by adding a complexing agent to the reaction solution, the complexing agent is coordinated to the metal of the precursor of the metal oxide, so that the hydrolysis and dehydration condensation reaction of the precursor is moderated. Conceivable. For example, as shown in the following formula (1), when one molecule of acetylacetone is coordinated to tetraalkoxytitanium as a chelate, the alkoxy group of tetraalkoxytitanium is reduced by one, so that the reactivity is considered to be lowered.
In this way, the hydrolysis and dehydration condensation reaction of the precursor of the metal oxide becomes slow, and the precipitation rate of the metal oxide particles becomes slow, so that the aggregation of the metal oxide particles can be suppressed.
Figure JPOXMLDOC01-appb-C000001
Figure JPOXMLDOC01-appb-C000001
　一方、後述の比較例に示されるように、反応液中における錯化剤の含有量が多すぎると被覆層の形成不良が生じやすくなる。これは、金属酸化物の前駆体に配位結合する錯化剤の分子数が増大することによって、析出した金属酸化物粒子の電荷が減少して電気泳動し難くなり、コア粒子表面への吸着、堆積が生じ難くなるためと考えられる。
　したがって本実施形態では、反応液に錯化剤を、金属酸化物の前駆体の金属と錯化剤とのモル比が所定の範囲内となるように含有させる。これにより、金属酸化物粒子が生成する速度と、該金属酸化物粒子のコア粒子への吸着が生じる速度とのバランスを良好に制御することができる。このため金属酸化物の前駆体の含有量が多い場合でもコア粒子の表面に被覆層が均一に形成され、良好な形状のコアシェル粒子が安定して得られる。 On the other hand, as shown in a comparative example to be described later, when the content of the complexing agent in the reaction solution is too large, poor formation of the coating layer tends to occur. This is because the number of molecules of the complexing agent coordinated to the precursor of the metal oxide increases, so that the charge of the deposited metal oxide particles decreases, making electrophoresis difficult and adsorption to the core particle surface. This is thought to be because deposition is less likely to occur.
Accordingly, in this embodiment, the complexing agent is contained in the reaction solution so that the molar ratio of the metal oxide precursor metal to the complexing agent is within a predetermined range. Thereby, it is possible to satisfactorily control the balance between the speed at which the metal oxide particles are generated and the speed at which the metal oxide particles are adsorbed on the core particles. For this reason, even when the content of the metal oxide precursor is large, the coating layer is uniformly formed on the surface of the core particle, and the core-shell particle having a good shape can be stably obtained.
＜中空粒子の製造方法＞
　本実施形態の中空粒子の製造方法は、前記製造方法で、コア粒子の表面に金属酸化物からなる被覆層が形成されたコアシェル粒子を製造する工程と、前記コアシェル粒子を加熱して、前記コア粒子を分解除去する工程とを有することを特徴とする。
　すなわち本実施形態の中空粒子の製造方法は、分散媒、コア粒子、金属酸化物の前駆体、および、所定量の錯化剤を用意し；分散媒、コア粒子、金属酸化物の前駆体、および錯化剤を混合し；コア粒子の表面に金属酸化物からなる被覆層を形成させ；および、コア粒子を分解除去することを特徴とする。
　本実施形態では、上記の製造方法で得られたコアシェル粒子を、空気中など、酸素を含有する雰囲気中で加熱することにより、重合体からなるコア粒子を分解しガス化させて除去する。ガス化された重合体はコアシェル粒子のシェルを通過して飛散するため、内部に空孔を有する中空粒子が得られる。
　コアシェル粒子を加熱する方法は特に限定されない。例えばコアシェル粒子を乾燥させた乾燥粒子を加熱炉で加熱する方法、コアシェル粒子をアルコール等の有機溶媒中に分散させた塗布液を、耐熱性を有する基板上に塗布したものを加熱炉で加熱する方法等が挙げられる。 <Method for producing hollow particles>
The method for producing hollow particles of the present embodiment includes the steps of producing core-shell particles in which a coating layer made of a metal oxide is formed on the surface of the core particles, heating the core-shell particles, and And a step of decomposing and removing the particles.
That is, the hollow particle production method of the present embodiment includes a dispersion medium, a core particle, a metal oxide precursor, and a predetermined amount of a complexing agent; the dispersion medium, the core particle, a metal oxide precursor; And a complexing agent is mixed; a coating layer made of a metal oxide is formed on the surface of the core particles; and the core particles are decomposed and removed.
In the present embodiment, the core-shell particles obtained by the above production method are heated in an atmosphere containing oxygen, such as air, so that the core particles made of the polymer are decomposed and gasified to be removed. Since the gasified polymer is scattered through the shell of the core-shell particles, hollow particles having pores inside are obtained.
The method for heating the core-shell particles is not particularly limited. For example, a method in which dried particles obtained by drying core-shell particles are heated in a heating furnace, and a coating solution in which core-shell particles are dispersed in an organic solvent such as alcohol is applied on a heat-resistant substrate, and then heated in a heating furnace. Methods and the like.
　コアシェル粒子を加熱する際の加熱温度は、コア粒子をなす重合体の分解温度以上であればよい。例えば加熱温度（加熱工程中で最も高い温度）が１００℃以上であることが好ましく、３００℃以上がより好ましく、４００℃以上がさらに好ましい。該加熱温度の上限は特に限定されないが、シェルが融解して内部空孔が消失する現象が生じにくい点では、形成させる金属酸化物の融点以下（例えば酸化チタンの融点は１８７０℃）が好ましく、該融点から２００℃以上低いことがより好ましい。すなわち加熱温度の上限としては、１８７０℃以下が好ましく、１６７０℃以下がより好ましく、１５００℃以下がさらに好ましい。
　加熱時間はコア粒子をなす重合体が充分に分解除去される時間であればよく、特に限定されない。例えば昇温を開始してから降温を開始するまでの時間が１分～１００時間が好ましく、３分～５０時間がより好ましい。
　コアシェル粒子を加熱する際の昇温速度は３０～３，０００℃／時間が好ましく、１００～１，０００℃／時間がより好ましい。該昇温速度が上記範囲の下限値以上であると良好な製造効率が得られやすく、上記範囲の上限値以下であると均一形状の中空粒子が得られやすい。 The heating temperature for heating the core-shell particles may be higher than the decomposition temperature of the polymer forming the core particles. For example, the heating temperature (the highest temperature in the heating step) is preferably 100 ° C. or higher, more preferably 300 ° C. or higher, and further preferably 400 ° C. or higher. The upper limit of the heating temperature is not particularly limited, but is preferably less than the melting point of the metal oxide to be formed (for example, the melting point of titanium oxide is 1870 ° C.) in that the phenomenon that the shell melts and the internal vacancies disappear hardly occurs. More preferably, the melting point is 200 ° C. or more lower than the melting point. That is, the upper limit of the heating temperature is preferably 1870 ° C. or less, more preferably 1670 ° C. or less, and further preferably 1500 ° C. or less.
The heating time is not particularly limited as long as the polymer forming the core particles is sufficiently decomposed and removed. For example, the time from the start of temperature increase to the start of temperature decrease is preferably 1 minute to 100 hours, and more preferably 3 minutes to 50 hours.
The heating rate when heating the core-shell particles is preferably 30 to 3,000 ° C./hour, more preferably 100 to 1,000 ° C./hour. When the temperature increase rate is not less than the lower limit of the above range, good production efficiency can be easily obtained, and when it is not more than the upper limit of the above range, uniform shaped hollow particles can be easily obtained.
　中空粒子の平均粒子径は、０．０１～２００μｍが好ましく、０．０３～１００μｍがより好ましく、０．１～１０μｍが特に好ましい。該平均粒子径が上記範囲の下限値以上であると液中での均一分散性が良好な中空粒子が得られやすく、上限値以下であると、液中での粒子の沈殿が生じにくく、良好な分散性が得られやすい。
　中空粒子の平均粒子径（外径）を１とするときの空孔の径（内径）の平均値の比（以下、内径平均／外径平均の比ということもある。）は０．５０～０．９９が好ましく、０．７７～０．９７がより好ましい。該内径平均／外径平均の比が上記範囲の下限値以上であると、コア粒子への電気的吸着によって被覆層が形成されることによる、コアシェル粒子の製造安定化の効果が充分に得られやすく、上限値以下であるとシェルに充分な機械的強度が付与されやすい。
　本明細書における中空粒子の平均粒子径は、顕微鏡で観察して得られる像において無作為に選ばれた１０個の粒子の粒子径（外径）の平均値である。顕微鏡としては走査型電子顕微鏡、又は透過型電子顕微鏡を用いることができる。
　本明細書における中空粒子の空孔の径（内径）の平均値は、透過型顕微鏡で観察して得られる像において無作為に選ばれた１０個の空孔の径（内径）の平均値である。 The average particle size of the hollow particles is preferably 0.01 to 200 μm, more preferably 0.03 to 100 μm, and particularly preferably 0.1 to 10 μm. If the average particle diameter is not less than the lower limit of the above range, hollow particles having good uniform dispersibility in the liquid can be easily obtained, and if it is not more than the upper limit, precipitation of particles in the liquid is difficult to occur and good. Easy dispersibility.
The ratio of the average pore diameter (inner diameter) when the average particle diameter (outer diameter) of hollow particles is 1 (hereinafter also referred to as the ratio of inner diameter average / outer diameter average) is 0.50 to 0.99 is preferable, and 0.77 to 0.97 is more preferable. When the ratio of the inside diameter average / outside diameter average is equal to or more than the lower limit of the above range, the effect of stabilizing the production of the core-shell particles can be sufficiently obtained by forming the coating layer by electrical adsorption onto the core particles. It is easy and sufficient mechanical strength is easily given to a shell as it is below an upper limit.
The average particle diameter of the hollow particles in the present specification is an average value of the particle diameters (outer diameters) of 10 particles randomly selected in an image obtained by observation with a microscope. As the microscope, a scanning electron microscope or a transmission electron microscope can be used.
The average value of the pore diameter (inner diameter) of the hollow particles in the present specification is the average value of the diameter (inner diameter) of ten randomly selected holes in the image obtained by observation with a transmission microscope. is there.
　本実施形態によれば、上述したように、良好な形状のコアシェル粒子が安定して得られるため、これを用いて中空粒子を製造することにより、良好な形状の中空粒子を安定して製造することができる。 According to the present embodiment, as described above, since core-shell particles having a good shape can be stably obtained, hollow particles having a good shape can be stably produced by using this. be able to.
［用途］
　本発明の製造方法で得られる中空粒子は、例えば低反射材料、断熱材、光散乱材、ドラックデリバリー等に好適に用いることができる。
　特に酸化チタンからなる中空粒子は内部空孔とシェルとの間で大きな屈折率差を有するため、光散乱材等に好適である
　また本発明の製造方法で得られるコアシェル粒子は、中空粒子を製造するための中間体としての用途の他に、例えば艶消し材等に好適に用いることができる。 [Usage]
The hollow particles obtained by the production method of the present invention can be suitably used for, for example, a low reflection material, a heat insulating material, a light scattering material, a drug delivery and the like.
In particular, hollow particles made of titanium oxide are suitable for light scattering materials and the like because they have a large refractive index difference between the internal pores and the shell. Also, the core-shell particles obtained by the production method of the present invention produce hollow particles. In addition to the use as an intermediate for the purpose, for example, it can be suitably used for a matte material or the like.
　以下に実施例を用いて本発明をさらに詳しく説明するが、本発明はこれら実施例に限定されるものではない。
　以下の例において、室温は１５℃である。測定方法は以下の方法を用いた。
［コア粒子の平均粒子径の測定方法］
　動的光散乱式ナノトラック粒度分析計（日機装社製、製品名：ＵＰＡ－ＥＸ１５０型）を用いて粒度分布を測定し、体積基準の５０％メジアン径を求めて平均粒子径とした。
［中空粒子の平均粒子径の測定方法］
　中空粒子の平均粒子径は、ガラス基板上で、コアシェル粒子のコア粒子を各例の方法で除去した中空粒子を、走査型電子顕微鏡で観察して粒子径（外径）を計測し、無作為に選んだ粒子１０個の平均値を求めて平均粒子径とした。
［中空粒子の内径（空孔の径）の測定方法］
　中空粒子の内径は、ガラス基板上で、コアシェル粒子のコア粒子を各例の方法で除去した中空粒子を、透過型電子顕微鏡で観察して空孔の径（内径）を計測し、無作為に選んだ粒子１０個の平均値を求めて中空粒子の内径（空孔の径）とした。 Hereinafter, the present invention will be described in more detail using examples, but the present invention is not limited to these examples.
In the following example, the room temperature is 15 ° C. The following method was used for the measurement.
[Measurement method of average particle diameter of core particles]
The particle size distribution was measured using a dynamic light scattering nanotrack particle size analyzer (manufactured by Nikkiso Co., Ltd., product name: UPA-EX150 type), and the volume-based 50% median diameter was determined to obtain the average particle size.
[Measurement method of average particle diameter of hollow particles]
The average particle size of the hollow particles is measured randomly by observing the hollow particles obtained by removing the core particles of the core-shell particles by the method of each example with a scanning electron microscope on the glass substrate. The average value of the 10 particles selected in the above was determined and used as the average particle size.
[Measurement method of inner diameter of hollow particles (hole diameter)]
The inner diameter of the hollow particles was measured randomly by observing the hollow particles obtained by removing the core particles of the core-shell particles by the method of each example with a transmission electron microscope on the glass substrate, and measuring the diameter (inner diameter) of the pores. The average value of 10 selected particles was obtained and used as the inner diameter of the hollow particles (the diameter of the pores).
［調製例１：コア粒子の調製］
　蒸留水４９．２４ｍｌ中にスチレン（東京化成工業社製）０．７５ｇを加えた溶液を、恒温槽内で７０℃まで昇温させた後、重合開始剤として２，２’－アゾビス（２－メチルプロピオンアミジン）ジヒドロクロライド（ＡＩＢＡ）を０．０１２ｇ加えた。これを７０℃に保持しつつ８時間攪拌して重合反応させ、ポリスチレンからなるコア粒子（ポリスチレン粒子）が水中に分散した分散液を得た。
　該分散液を、遠心分離器（ＫＯＫＵＳＡＮ社製、製品名：Ｈ－２０００Ｂ、以下同様。）を用い、回転数１００００ｒｐｍで３０分間遠心分離処理し、ポリスチレン粒子の沈殿物を得た。続いてこの沈殿物を、固形分濃度が１．５質量％となるようにエタノール（関東化学社製、以下同様。）で希釈した。これを３回繰り返し、エタノール溶媒に分散されたポリスチレン粒子ゾルを得た。
　得られたポリスチレン粒子ゾル中のポリスチレン粒子の含有量は１．５質量％であり、該ポリスチレン粒子ゾル中のポリスチレン粒子の平均粒子径は０．２４μｍであった。 [Preparation Example 1: Preparation of core particles]
A solution obtained by adding 0.75 g of styrene (manufactured by Tokyo Chemical Industry Co., Ltd.) to 49.24 ml of distilled water was heated to 70 ° C. in a thermostatic bath, and then 2,2′-azobis (2- 0.012 g of methylpropionamidine) dihydrochloride (AIBA) was added. While maintaining this at 70 ° C., the mixture was stirred for 8 hours to cause a polymerization reaction, thereby obtaining a dispersion in which core particles (polystyrene particles) made of polystyrene were dispersed in water.
The dispersion was centrifuged at a rotational speed of 10,000 rpm for 30 minutes using a centrifuge (manufactured by KOKUSAN, product name: H-2000B, the same applies hereinafter) to obtain a precipitate of polystyrene particles. Subsequently, the precipitate was diluted with ethanol (manufactured by Kanto Chemical Co., Ltd., the same shall apply hereinafter) so that the solid content concentration was 1.5% by mass. This was repeated three times to obtain a polystyrene particle sol dispersed in an ethanol solvent.
The content of polystyrene particles in the obtained polystyrene particle sol was 1.5% by mass, and the average particle diameter of the polystyrene particles in the polystyrene particle sol was 0.24 μm.
［例１Ａ：コアシェル粒子の製造］（実施例）
　本例では金属酸化物の前駆体として酸化チタンの前駆体であるテトライソプロポキシチタン（関東化学社製、以下同様。）を用い、錯化剤としてアセチルアセトンを用いる。
　まず、室温のエタノール７．７８ｇに、アセチルアセトン（純正化学社製）を０．００７５ｇ加えた。これに調製例１で得たポリスチレン粒子ゾルを２．０ｇ加え、さらにテトライソプロポキシチタンを０．２１ｇ加えて反応液（全量１０ｇ）とし、これを室温（１５℃）で３０分間攪拌した。
　反応液中におけるポリスチレン粒子の含有量は０．３質量％であり、テトライソプロポキシチタンの含有量は酸化チタンの固形分質量に換算した値で、反応液総重量に対して０．５９質量％である。アセチルアセトンの含有量は、テトライソプロポキシチタンのチタン１モルに対して０．１モルである。
　こうしてポリスチレン粒子（コア粒子）の表面に酸化チタンからなる被覆層が形成されたコアシェル粒子が、エタノール中に分散されているコアシェル粒子ゾルを得た。
　得られたコアシェル粒子ゾル中のコアシェル粒子の含有量は０．８９質量％であった。
　得られたコアシェル粒子の平均粒子径は０．２５μｍであり、該コアシェル粒子の平均粒子径に対するコア粒子の平均粒子径の比（コア粒子径／コアシェル粒子径）は０．９７であった。
　本例の主な製造条件と生成物の物性値を下記表１の「例１Ｂ」欄に示す。 [Example 1A: Production of core-shell particles] (Example)
In this example, tetraisopropoxy titanium (manufactured by Kanto Chemical Co., Inc., the same applies hereinafter), which is a precursor of titanium oxide, is used as the precursor of the metal oxide, and acetylacetone is used as the complexing agent.
First, 0.0075 g of acetylacetone (manufactured by Junsei Co., Ltd.) was added to 7.78 g of ethanol at room temperature. To this, 2.0 g of the polystyrene particle sol obtained in Preparation Example 1 was added, and 0.21 g of tetraisopropoxy titanium was further added to obtain a reaction solution (total amount: 10 g), which was stirred at room temperature (15 ° C.) for 30 minutes.
The content of polystyrene particles in the reaction solution is 0.3% by mass, and the content of tetraisopropoxytitanium is a value converted to the solid content mass of titanium oxide and is 0.59% by mass with respect to the total weight of the reaction solution. It is. The content of acetylacetone is 0.1 mol with respect to 1 mol of titanium of tetraisopropoxytitanium.
In this way, a core-shell particle sol in which core-shell particles in which a coating layer made of titanium oxide was formed on the surface of polystyrene particles (core particles) was dispersed in ethanol was obtained.
The content of the core-shell particles in the obtained core-shell particle sol was 0.89% by mass.
The average particle diameter of the obtained core-shell particles was 0.25 μm, and the ratio of the average particle diameter of the core particles to the average particle diameter of the core-shell particles (core particle diameter / core-shell particle diameter) was 0.97.
The main production conditions of this example and the physical property values of the product are shown in the “Example 1B” column of Table 1 below.
［例１Ｂ：中空粒子の製造］（実施例）
　例１Ａで得られたコアシェル粒子ゾル２．７１ｇを、エタノール１７．２９ｇ中に添加し、室温で１０分攪拌して塗布液を調製した。縦１００ｍｍ×横１００ｍｍ×厚さ２ｍｍのソーダライムガラス（旭硝子社製、以下同様。）上に該塗布液を３ｇ程度滴下し、スピンコーター（ＭＩＫＡＳＡ社製、１Ｈ－３６０Ｓ、以下同様。）により、回転数５００ｒｐｍ、２０秒の条件でスピンコートして塗膜を形成した。該塗膜を、電気炉にて３００℃／時間の昇温速度で６０℃から６００℃まで昇温し、６００℃で３０分保持して焼成したのち降温を開始し、２００℃まで炉内で除冷した後、室温まで空冷した。こうしてガラス上に中空粒子を得た。
　得られた中空粒子の平均粒子径は０．２５μｍであり、中空粒子の内径平均／外径平均の比は０．９７であった。
　図１は、得られた中空粒子を走査型電子顕微鏡にて観察した電子顕微鏡写真である。
［例１Ｃ：コアシェル粒子の製造、中空粒子の製造］（実施例）
　例１Ａと同様にコアシェル粒子を製造した。ただしエタノールを７．７９ｇ用い、アセチルアセトンを０．００３８ｇ用いた。反応液におけるアセチルアセトンの含有量は、テトライソプロポキシチタンのチタン１モルに対して０．０５モルである。このようにしてコアシェル粒子ゾルを得た。製造条件と生成物の物性値を下記表１に示す。
　さらに例１Ｂと同様に中空粒子を製造した。
［例１Ｄ：コアシェル粒子の製造、中空粒子の製造］（実施例）
　例１Ａと同様にコアシェル粒子を製造した。ただしアセチルアセトンを０．０１５０ｇ用いた。反応液におけるアセチルアセトンの含有量は、テトライソプロポキシチタンのチタン１モルに対して０．２モルである。このようにしてコアシェル粒子ゾルを得た。製造条件と生成物の物性値を下記表１に示す。
　さらに例１Ｂと同様に中空粒子を製造した。 [Example 1B: Production of hollow particles] (Example)
2.71 g of the core-shell particle sol obtained in Example 1A was added to 17.29 g of ethanol and stirred at room temperature for 10 minutes to prepare a coating solution. About 3 g of the coating solution was dropped onto soda lime glass (Asahi Glass Co., Ltd., the same applies hereinafter) having a length of 100 mm, a width of 100 mm, and a thickness of 2 mm, and a spin coater (Mikasa 1H-360S, the same applies hereinafter). A coating film was formed by spin coating under the conditions of 500 rpm and 20 seconds. The coating film was heated from 60 ° C. to 600 ° C. at a temperature rising rate of 300 ° C./hour in an electric furnace, held at 600 ° C. for 30 minutes, fired, and then started to cool down to 200 ° C. in the furnace. After cooling, it was air cooled to room temperature. Thus, hollow particles were obtained on the glass.
The average particle diameter of the obtained hollow particles was 0.25 μm, and the ratio of inner diameter average / outer diameter average of the hollow particles was 0.97.
FIG. 1 is an electron micrograph of the obtained hollow particles observed with a scanning electron microscope.
[Example 1C: Production of core-shell particles, production of hollow particles] (Example)
Core shell particles were prepared as in Example 1A. However, 7.79 g of ethanol and 0.0038 g of acetylacetone were used. The content of acetylacetone in the reaction solution is 0.05 mol with respect to 1 mol of titanium of tetraisopropoxytitanium. In this way, a core-shell particle sol was obtained. The production conditions and physical property values of the products are shown in Table 1 below.
Further, hollow particles were produced in the same manner as in Example 1B.
[Example 1D: Production of core-shell particles, production of hollow particles] (Example)
Core shell particles were prepared as in Example 1A. However, 0.0150 g of acetylacetone was used. The content of acetylacetone in the reaction solution is 0.2 mol with respect to 1 mol of titanium of tetraisopropoxytitanium. In this way, a core-shell particle sol was obtained. The production conditions and physical property values of the products are shown in Table 1 below.
Further, hollow particles were produced in the same manner as in Example 1B.
［例２］（比較例）
　本例は、例１Ａにおいて、反応液に錯化剤を含有させずにコアシェル粒子を製造した比較例である。
　まず、室温のエタノール７．７９ｇに、調製例１で得たポリスチレン粒子ゾルを２．０ｇ加え、さらにテトライソプロポキシチタンを０．２１ｇ加えて、室温（１５℃）で３０分間攪拌した。
　本例の主な製造条件と生成物の物性値を下記表１に示す。
　３０分間攪拌後に得られたゾルを用い、例１Ｂと同様にしてガラス上で焼成された観察用試料を調製した。図２はこのようにして得られた観察用試料を走査型電子顕微鏡にて観察した電子顕微鏡写真である。 [Example 2] (Comparative example)
This example is a comparative example in which core-shell particles were produced in Example 1A without containing a complexing agent in the reaction solution.
First, 2.0 g of the polystyrene particle sol obtained in Preparation Example 1 was added to 7.79 g of ethanol at room temperature, 0.21 g of tetraisopropoxy titanium was further added, and the mixture was stirred at room temperature (15 ° C.) for 30 minutes.
The main production conditions of this example and the physical properties of the product are shown in Table 1 below.
Using the sol obtained after stirring for 30 minutes, an observation sample fired on glass was prepared in the same manner as in Example 1B. FIG. 2 is an electron micrograph obtained by observing the observation sample thus obtained with a scanning electron microscope.
［例３～６］（比較例）
　反応液の配合を表１に示す通りに変更したほかは例１Ａと同様にしてコアシェル粒子ゾルを得た。各例の主な製造条件と生成物の物性値を下記表１に示す。
　３０分間攪拌後に得られたゾルを用い、例１Ｂと同様にしてガラス上で焼成された観察用試料を調製した。図３～６はこのようにして得られた観察用試料を走査型電子顕微鏡にて観察した電子顕微鏡写真である。
［例７：コアシェル粒子の製造、中空粒子の製造］（実施例）
　例１Ａと同様にコアシェル粒子を製造した。ただし錯化剤として２，２’－ビピリジン（ナカライテスク社製）の０．０１１５ｇを用いた。反応液における２，２’－ビピリジンの含有量は、テトライソプロポキシチタンのチタン１モルに対して０．１モルである。このようにしてコアシェル粒子ゾルを得た。得られたコアシェル粒子の平均粒子径は０．２５μｍであり、該コアシェル粒子の平均粒子径に対するコア粒子の平均粒子径の比（コア粒子径／コアシェル粒子径）は０．９７であった。
　さらに例１Ｂと同様に中空粒子を製造した。得られた中空粒子の平均粒子径は０．２５μｍであり、中空粒子の内径平均／外径平均の比は０．９７であった。
［例８：コアシェル粒子の製造、中空粒子の製造］（実施例）
　例１Ａと同様にコアシェル粒子を製造した。ただしコア粒子として平均粒径が１μｍのポリスチレン粒子（ポリスチレン粒子ゾル中のポリスチレン粒子の含有量は１．５質量％、用いたポリスチレン粒子ゾルは２．０ｇであった。）を用いた。反応液におけるアセチルアセトンの含有量は、テトライソプロポキシチタンのチタン１モルに対して０．１モルである。このようにしてコアシェル粒子ゾルを得た。得られたコアシェル粒子の平均粒子径は１．０３μｍであり、該コアシェル粒子の平均粒子径に対するコア粒子の平均粒子径の比（コア粒子径／コアシェル粒子径）は０．９７であった。
　さらに例１Ｂと同様に中空粒子を製造した。得られた中空粒子の平均粒子径は１．０３μｍであり、中空粒子の内径平均／外径平均の比は０．９７であった。 [Examples 3 to 6] (Comparative example)
A core-shell particle sol was obtained in the same manner as in Example 1A except that the composition of the reaction solution was changed as shown in Table 1. Table 1 below shows main production conditions and physical properties of the products in each example.
Using the sol obtained after stirring for 30 minutes, an observation sample fired on glass was prepared in the same manner as in Example 1B. 3 to 6 are electron micrographs obtained by observing the observation sample thus obtained with a scanning electron microscope.
[Example 7: Production of core-shell particles, production of hollow particles] (Example)
Core shell particles were prepared as in Example 1A. However, 0.0115 g of 2,2′-bipyridine (manufactured by Nacalai Tesque) was used as a complexing agent. The content of 2,2′-bipyridine in the reaction solution is 0.1 mol with respect to 1 mol of titanium of tetraisopropoxytitanium. In this way, a core-shell particle sol was obtained. The average particle diameter of the obtained core-shell particles was 0.25 μm, and the ratio of the average particle diameter of the core particles to the average particle diameter of the core-shell particles (core particle diameter / core-shell particle diameter) was 0.97.
Further, hollow particles were produced in the same manner as in Example 1B. The average particle diameter of the obtained hollow particles was 0.25 μm, and the ratio of inner diameter average / outer diameter average of the hollow particles was 0.97.
[Example 8: Production of core-shell particles, production of hollow particles] (Example)
Core shell particles were prepared as in Example 1A. However, polystyrene particles having an average particle diameter of 1 μm were used as core particles (the content of polystyrene particles in the polystyrene particle sol was 1.5% by mass, and the polystyrene particle sol used was 2.0 g). The content of acetylacetone in the reaction solution is 0.1 mol with respect to 1 mol of titanium of tetraisopropoxytitanium. In this way, a core-shell particle sol was obtained. The average particle diameter of the obtained core-shell particles was 1.03 μm, and the ratio of the average particle diameter of the core particles to the average particle diameter of the core-shell particles (core particle diameter / core-shell particle diameter) was 0.97.
Further, hollow particles were produced in the same manner as in Example 1B. The average particle diameter of the obtained hollow particles was 1.03 μm, and the ratio of the inner diameter average / outer diameter average of the hollow particles was 0.97.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　表１の結果、および図１～６の写真に示されるように、図１の例では良好な中空粒子が得られたが、図２の例では、コア粒子の一部で表面被覆は起きているものの、被覆性は悪く、またテトライソプロポキシチタン単体で粒子化したものも散見された。
　また、錯体の添加量を多くした図３の例ではコア粒子への被覆性が低下し、さらに錯体の添加量を多くした図４～６の例では中空粒子は得られず、代わりに開口した膜が形成された。 As shown in the results of Table 1 and the photographs of FIGS. 1 to 6, good hollow particles were obtained in the example of FIG. 1, but in the example of FIG. However, the coatability was poor, and some particles of tetraisopropoxytitanium were made into particles.
Further, in the example of FIG. 3 in which the addition amount of the complex was increased, the covering property to the core particles was lowered, and in the examples of FIGS. 4 to 6 in which the addition amount of the complex was further increased, hollow particles were not obtained, but instead opened. A film was formed.
　本発明の製造方法で得られる中空粒子は、例えば低反射材料、断熱材、光散乱材、ドラックデリバリー等に好適に用いることができる。また本発明の製造方法で得られるコアシェル粒子は、中空粒子を製造するための中間体としての用途の他に、例えば艶消し材等に好適に用いることができる。
　なお、２０１２年１２月２１日に出願された日本特許出願２０１２－２８０２１７号の明細書、特許請求の範囲、図面及び要約書の全内容をここに引用し、本発明の明細書の開示として、取り入れるものである。 The hollow particles obtained by the production method of the present invention can be suitably used for, for example, a low reflection material, a heat insulating material, a light scattering material, a drug delivery and the like. Moreover, the core-shell particle obtained by the manufacturing method of this invention can be used suitably for a mat | matte material etc. other than the use as an intermediate body for manufacturing a hollow particle, for example.
The entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2012-280217 filed on December 21, 2012 are cited here as disclosure of the specification of the present invention. Incorporated.

Claims (13)

  1. 　分散媒と、コア粒子と、金属酸化物の前駆体と、前記前駆体の金属１モルに対して０．０１～０．２５モルの錯化剤と、を含む反応液中で、前記前駆体を加水分解および脱水縮合反応させて、前記コア粒子の表面に前記金属酸化物からなる被覆層を形成する工程を有することを特徴とするコアシェル粒子の製造方法。 In a reaction liquid containing a dispersion medium, core particles, a metal oxide precursor, and 0.01 to 0.25 mol of a complexing agent with respect to 1 mol of the metal of the precursor, the precursor And a process of forming a coating layer made of the metal oxide on the surface of the core particle by hydrolyzing and dehydrating condensation.
  2. 　前記金属酸化物が酸化チタンである、請求項１に記載のコアシェル粒子の製造方法。 The method for producing core-shell particles according to claim 1, wherein the metal oxide is titanium oxide.
  3. 　前記前駆体がテトラアルコキシチタンである請求項１または２に記載のコアシェル粒子の製造方法。 The method for producing core-shell particles according to claim 1 or 2, wherein the precursor is tetraalkoxytitanium.
  4. 　前記反応液における前記前駆体の含有量が、反応液全量に対して０．０１～６．０質量％である、請求項１～３のいずれか一項に記載のコアシェル粒子の製造方法。 The method for producing core-shell particles according to any one of claims 1 to 3, wherein a content of the precursor in the reaction solution is 0.01 to 6.0 mass% with respect to a total amount of the reaction solution.
  5. 　前記コア粒子の平均粒子径が０．０１～１００μｍである請求項１～４のいずれか一項に記載のコアシェル粒子の製造方法。 The method for producing core-shell particles according to any one of claims 1 to 4, wherein the average particle diameter of the core particles is 0.01 to 100 µm.
  6. 　前記錯化剤がアセチルアセトン、エチレンジアミン、ビピリジン、エチレンジアミン四酢酸、フェナントロリン、ポルフィリン、およびクラウンエーテルからなる群から選ばれる一種以上である請求項１～５のいずれか一項に記載のコアシェル粒子の製造方法。 The method for producing core-shell particles according to any one of claims 1 to 5, wherein the complexing agent is one or more selected from the group consisting of acetylacetone, ethylenediamine, bipyridine, ethylenediaminetetraacetic acid, phenanthroline, porphyrin, and crown ether. .
  7. 　前記コア粒子がポリスチレン粒子またはポリメチルメタクリレート粒子である請求項１～６のいずれか一項に記載のコアシェル粒子の製造方法。 The method for producing core-shell particles according to any one of claims 1 to 6, wherein the core particles are polystyrene particles or polymethyl methacrylate particles.
  8. 　前記反応液における前記コア粒子の含有量が、０．０１～１５．０質量％である請求項１～７のいずれか一項に記載のコアシェル粒子の製造方法。 The method for producing core-shell particles according to any one of claims 1 to 7, wherein the content of the core particles in the reaction solution is 0.01 to 15.0 mass%.
  9. 　前記コアシェル粒子の平均粒子径に対する前記コア粒子の平均粒子径の比（コア粒子／コアシェル粒子）が０．５０～０．９９である請求項１～８のいずれか一項に記載のコアシェル粒子の製造方法。 The ratio of the average particle diameter of the core particle to the average particle diameter of the core-shell particle (core particle / core-shell particle) is 0.50 to 0.99. Production method.
  10. 　前記加水分解および脱水縮合反応させる温度が０～８０℃の範囲である請求項１～９のいずれか一項に記載のコアシェル粒子の製造方法。 The method for producing core-shell particles according to any one of claims 1 to 9, wherein a temperature for the hydrolysis and dehydration condensation reaction is in a range of 0 to 80 ° C.
  11. 　請求項１～１０のいずれか一項に記載の製造方法によってコア粒子の表面に金属酸化物からなる被覆層が形成されたコアシェル粒子を製造する工程と、
    　前記コアシェル粒子を加熱して、前記コア粒子を分解除去する工程と、を有することを特徴とする中空粒子の製造方法。     A step of producing core-shell particles in which a coating layer made of a metal oxide is formed on the surface of the core particles by the production method according to any one of claims 1 to 10;
    Heating the core-shell particles to decompose and remove the core particles.
  12. 　前記加熱温度が１００～１８７０℃である、請求項１１に記載の中空粒子の製造方法。 The method for producing hollow particles according to claim 11, wherein the heating temperature is 100 to 1870 ° C.
  13. 　前記中空粒子の平均粒子径が０．０１～２００μｍである、請求項１１または１２に記載の中空粒子の製造方法。 The method for producing hollow particles according to claim 11 or 12, wherein the hollow particles have an average particle diameter of 0.01 to 200 µm.
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