JP2009203115A - Hollow silica particle and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hollow silica particle having a small average particle diameter and a small specific surface area and its manufacturing method. <P>SOLUTION: (1) The hollow silica particle has an average particle diameter of 0.1-1 μm, at least 80% of its total particles have a particle diameter not more than the average particle diameter ±30%, and its BET specific surface area is less than 30 m<SP>2</SP>/g. (2) The manufacturing method of a hollow silica particle having a BET specific surface area less than 30 m<SP>2</SP>/g comprises firing a hollow silica particle (A) that exhibits a peak at a diffraction angle (2θ) corresponding to a plane distance (d) of between a range of 1-12 nm in a powder X-ray diffractometry and that contains air inside of the grains or a core shell type silica particle (B) enclosing a material that forms hollow sites by disappearing by fire at a temperature higher than 950°C. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to hollow silica particles and a method for producing the same.

The hollow silica particles having a small average particle diameter and a small specific surface area can contain air and various compounds and materials therein, and thus can be used for various applications as various materials.
As a method for producing the hollow silica particles, a method using an O / W type or W / O type emulsification system is common, and porous hollow silica particles are usually obtained by vacuum drying at a low temperature. The obtained hollow silica particles have a particle diameter of several μm or more, and particles having a smaller particle diameter and a small specific surface area have not been obtained.
For example, Patent Document 1 discloses a method for producing hollow silica particles by foaming and vitrifying silica gel powder obtained from a silicic acid solution containing a surfactant at a high temperature (about 1200 ° C.). However, the average particle diameter of the hollow silica particles obtained by this method is as large as about 20 to 70 μm.
Patent Document 2 discloses a method for producing hollow porous particles by forming an O / W type emulsion into an O / W / O type emulsion and then forming a water-soluble precipitate. The average particle size of is about 1 to 20 μm.
Patent Document 3 discloses a method for producing spherical hollow porous silica particles by polycondensation reaction using an O / W emulsification system. The average particle diameter of the obtained particles is about 3 μm, and the specific surface area is It is about 320 m ² / g.
Patent Document 4 discloses a method for producing hollow porous silica particles using a W / O emulsification system, but the average particle diameter of the obtained particles is about 3.5 μm.

Japanese Patent Publication No. 1-51455 Japanese Patent Publication No. 5-9133 Japanese Patent No. 2590428 Japanese Patent Laid-Open No. 11-29318

  This invention makes it a subject to provide the hollow silica particle with a small average particle diameter and a specific surface area, and its manufacturing method.

The present inventors have found that the above-described problems can be solved by subjecting hollow mesoporous silica to a high-temperature baking treatment.
That is, the present invention provides the following (1) and (2).
(1) Hollow silica particles having an average particle size of 0.05 to 1 μm, 80% or more of the particles having a particle size within an average particle size of ± 30%, and a BET specific surface area of less than 30 m ² / g .
(2) In powder X-ray diffractometry, hollow silica particles (A) containing air inside the particles that show a peak at a diffraction angle (2θ) corresponding to a surface spacing (d) in the range of 1 to 12 nm, or firing A method for producing hollow silica particles having a BET specific surface area of less than 30 m ² / g, wherein the core-shell type silica particles (B) encapsulating a material that disappears and forms a hollow part are fired at a temperature exceeding 950 ° C.

  ADVANTAGE OF THE INVENTION According to this invention, the hollow silica particle with a small average particle diameter and specific surface area, and its efficient manufacturing method can be provided.

[Hollow silica particles]
The hollow silica particles of the present invention (hereinafter also simply referred to as “hollow silica particles”) have an average particle diameter of 0.05 to 1 μm, and 80% or more of the total particles have an average particle diameter within ± 30%. And the BET specific surface area is less than 30 m ² / g.
The average particle diameter of the hollow silica particles is a number average particle diameter, and can be appropriately adjusted in consideration of the use etc., but is preferably 0.1 to 0.9 μm, more preferably 0.15 to 0.8 μm, and further Preferably it is 0.2-0.7 micrometer. The hollow silica particles preferably have a particle size of 80% or more, more preferably 85% or more, still more preferably 90% or more, and particularly preferably 95% or more of the whole particles within an average particle size of ± 30%. It is desirable that the particles are composed of a group of particles having a very uniform particle diameter.
In addition, the BET specific surface area of the hollow silica particles is preferably 20 m ² / g or less, more preferably 15 m ² / g or less, and most preferably 10 m ² / g or less from the viewpoint of stable retention of inclusions. preferable.

The hollow silica particles of the present invention preferably do not show a peak at a diffraction angle (2θ) corresponding to a range of crystal lattice spacing (d) of less than 1 nm in powder X-ray diffraction (XRD) measurement.
It is preferable that the hollow silica particles of the present invention show substantially no pore distribution at 1 nm or more in the pore size distribution. The average thickness of the outer shell portion is preferably thin as long as the hollow silica particles can maintain the strength as a carrier, and the average diameter (average volume) of the hollow portion is preferably larger from the viewpoint of holding a large amount of inclusions. From these viewpoints, the average thickness of the outer shell is usually 0.5 to 500 nm, preferably 2 to 400 nm, more preferably 3 to 300 nm.
The ratio of [average thickness of outer shell portion / average particle diameter of hollow silica particles] is usually 0.01 to 0.9, preferably 0.05 to 0.8, more preferably 0.1 to 0. 7.
The average particle diameter of the hollow silica particles and the average thickness of the outer portion can be appropriately adjusted depending on the production conditions of the hollow silica particles (A) as a raw material, the particle diameter of the hollow part forming material, the firing conditions, and the like.

[Method for producing hollow silica particles]
Although there is no restriction | limiting in particular in the manufacturing method of the hollow silica particle of this invention, According to the method containing following process (I) and (II), it can manufacture efficiently.
Step (I): a hollow silica particle (A) containing air inside the particle (hereinafter also simply referred to as “hollow silica particle (A)”), or a core shell containing a material that disappears by firing to form a hollow part Step of preparing type silica particles (B) (hereinafter also simply referred to as “silica particles (B)”).
Step (II): A step of firing the hollow silica particles (A) or the silica particles (B) obtained in the step (I) at a temperature exceeding 950 ° C.
Hereinafter, details of the steps (I) and (II) and each component used therein will be described.

Process (I)
Step (I) is a step of preparing hollow silica particles (A) or silica particles (B). The method is not particularly limited as long as it is a method capable of producing hollow silica particles (A) or silica particles (B), but a method including the following steps AD is more preferable.
Step A: 0.1 to 50 g / L of the polymer particles (a-1) or 0.1 to 100 mmol / L of the hydrophobic organic compound (a-2), and the following general formulas (1) and (2) And 0.1 to 100 mmol / L of one or more (b) selected from quaternary ammonium salts represented by the formula (1)) and 0.1 to 100 mmol of silica source (c) that produces a silanol compound by hydrolysis. Step of preparing an aqueous solution containing / L.
[R ¹ (CH ₃ ) ₃ N] ⁺ X ⁻ (1)
[R ¹ R ² (CH ₃ ) ₂ N] ⁺ X ⁻ (2)
(In the formula, R ¹ and R ² each independently represents a linear or branched alkyl group having 4 to 22 carbon atoms, and X represents a monovalent anion.)
Step B: The aqueous solution obtained in Step A is stirred at a temperature of 10 to 100 ° C., has an outer shell composed of silica, and has polymer particles (a-1) or a hydrophobic organic compound (a -2) Step of preparing an aqueous dispersion of proto-core-shell type silica particles Step C: Step of separating core-shell type silica particles (B) from the aqueous dispersion obtained in Step B Step D: Obtained in Step C Step of firing the core-shell type silica particles (B) to obtain hollow silica particles (A)

Hereinafter, steps A to D will be described.
[Step A]
[Polymer particles (a-1)]
As the polymer particles (a-1) used in the step A, particles of one or more polymers selected from a cationic polymer, a nonionic polymer and an amphoteric polymer are preferable, and a substantially water-insoluble polymer is preferable.
The average particle size of the polymer particles used in Steps A to D is preferably 0 for the purpose of obtaining a compound having a fine particle size and a uniform particle size distribution, which is a feature of the hollow silica particles of the present invention. It is desirable that the thickness is 0.02 μm to 1 μm, more preferably 0.05 μm to 0.9 μm, still more preferably 0.1 μm to 0.8 μm, and particularly preferably 0.12 μm to 0.7 μm. Further, the polymer particles preferably have a particle size of 80% or more, more preferably 85% or more, further preferably 90% or more, particularly preferably 95% or more of the whole particles within an average particle size of ± 30%. It is desirable that the particles are composed of a group of particles having a very uniform particle diameter.

[Cationic polymer]
The cationic polymer is preferably a polymer that can be dispersed as a polymer emulsion in a medium containing a continuous phase in an aqueous system in the presence of a cationic surfactant, and is cationic in the presence of a cationic surfactant. Those obtained by emulsion polymerization of a monomer mixture, particularly a monomer mixture containing an ethylenically unsaturated monomer having a cationic group, by a known method are preferred.
Examples of the cationic monomer include an acid neutralized product of a monomer having an amino group, or a quaternary ammonium salt obtained by quaternizing the monomer with a quaternizing agent.
As a specific example of the cationic monomer, a (meth) acrylate having a dialkylamino group or a trialkylammonium group is more preferable, and a (meth) acrylate having a dialkylamino group or a trialkylammonium group is most preferable.
In the present specification, (meth) acrylate means acrylate, methacrylate, or both.

  The cationic polymer contains a structural unit derived from the cationic monomer, but in addition to the cationic monomer structural unit, the cationic polymer is derived from a hydrophobic monomer such as an alkyl (meth) acrylate or an aromatic ring-containing monomer. It is more preferable to contain a structural unit. Preferable examples thereof include styrenic monomers such as alkyl (meth) acrylate, styrene or 2-methylstyrene having an alkyl group having 1 to 30 carbon atoms, preferably 3 to 22 carbon atoms, more preferably 3 to 18 carbon atoms. , Aryl esters of (meth) acrylic acid such as benzyl (meth) acrylate, aromatic group-containing vinyl monomers having 6 to 22 carbon atoms, or vinyl acetate. Of these, alkyl (meth) acrylate and styrene are most preferred.

The hydrophobic monomer means a polymerizable organic compound that has low solubility in water and forms a phase separation with water. Examples of the hydrophobic monomer include compounds having a LogP value of 0 or more, preferably 0.5 or more, and 25 or less. Here, LogP means a logarithmic value of a 1-octanol / water partition coefficient of a chemical substance, and is a numerical value calculated by a fragment approach by SRC's LOGKOW / KOWWIN Program. Specifically, the chemical structure of a chemical substance is decomposed into its constituent components, and the hydrophobic fragment constants of each fragment are integrated (Meylan, WM and PH Howard. 1995. Atom / fragment contribution method for octanol-water partition coefficients. See J. Pharm. Sci. 84: 83-92).
The cationic monomer constituting unit constituting the cationic polymer may be a small amount, and most constituting the cationic polymer may be constituted by a constituent unit derived from the hydrophobic monomer. The total amount of the cationic monomer constituent unit and the constituent unit derived from the hydrophobic monomer in the cationic polymer is 70 to 100% by mass, more preferably 80 to 100% by mass, and particularly preferably 95 to 100% by mass. In particular, the weight ratio of [(constituent unit derived from cationic monomer) / (constituent unit derived from hydrophobic monomer)] is preferably 0.001 to 0.5, more preferably 0.002 from the viewpoint of particle formation. It is -0.3, Most preferably, it is 0.003-0.1.

[Nonionic polymer]
Nonionic polymer means a polymer that has no charge in aqueous solution. The nonionic polymer is a polymer derived from a monomer having no charge, that is, a nonionic monomer, and can be obtained by polymerizing a nonionic monomer by a known emulsion polymerization method, non-emulsifier polymerization method or the like.
Nonionic monomers include the hydrophobic monomers (paragraph [0017]) mentioned in the description of the cationic polymer. Preferable examples thereof include one or more selected from alkyl (meth) acrylates having an alkyl group having 1 to 30 carbon atoms, preferably 3 to 22 carbon atoms, more preferably 3 to 18 carbon atoms, vinyl acetate, and styrene. Can be mentioned.
Specific examples of nonionic polymers include polystyrene, ethyl acrylate / ethyl methacrylate copolymer, ethyl acrylate / methyl methacrylate copolymer, octyl acrylate / styrene copolymer, butyl acrylate / vinyl acetate copolymer, methyl methacrylate / butyl. Examples thereof include acrylate / octyl acrylate copolymers, vinyl acetate / styrene copolymers, vinyl pyrrolidone / styrene copolymers, butyl acrylate, and polystyrene acrylate resins.

Among the cationic polymer, the nonionic polymer and the amphoteric polymer, the cationic polymer and the nonionic polymer are preferable, and the cationic polymer is more preferable from the viewpoint of easy formation of the hollow silica particles (A).
For the production of the hollow silica particles (A), a polymer that does not substantially dissolve in water is used. For this purpose, a method for increasing the polymerization ratio of a hydrophobic monomer, a method for crosslinking, and the like can be employed.
Preferred examples of such a polymer include a copolymer of a hydrophobic monomer selected from alkyl (meth) acrylate and styrene and a (meth) acrylate having a cationic group, and one or more hydrophobic properties selected from alkyl (meth) acrylate and styrene. Mention may be made of nonionic polymers composed of monomers.
Said polymer can be used individually or in mixture of 2 or more types.
The shape and form of the polymer particles are not particularly limited, and the size of the particles can be changed or the particles can be formed into a true spherical shape, an egg shape, or the like according to the purpose of use of the composite silica particles. By changing the size and particle size distribution of the polymer particles, the particle size of the hollow silica particles (A) and the size of the hollow part can be appropriately adjusted.

[Hydrophobic organic compound (a-2)]
In the present invention, the hydrophobic organic compound (a-2) means a compound that has low solubility in water and forms a phase separation with water. Preferably, the compound is dispersible in the presence of the quaternary ammonium salt. Examples of such hydrophobic organic compounds include compounds having a LogP value of 1 or more, preferably 2 to 25.
(C) Examples of the hydrophobic organic compound include oils such as hydrocarbon compounds, ester compounds, fatty acids having 6 to 22 carbon atoms, alcohols having 6 to 22 carbon atoms, and silicone oils, and various kinds such as fragrances, agricultural chemicals, and pharmaceuticals. A base material etc. can be mentioned.
When a hydrophobic organic compound is used, the particle size of the hollow silica particles (A) and the size of the hollow part are affected by the size of the droplets of the hydrophobic organic compound, so the melting point and reaction temperature of the hydrophobic organic compound , And can be appropriately adjusted depending on the stirring speed, the surfactant used, and the like.

[Quaternary ammonium salt (b)]
The quaternary ammonium salt (b) is used for forming mesopores and dispersing the polymer particles (a-1) or the hydrophobic organic compound (a-2).
R ¹ and R ² in the general formulas (1) and (2) are linear or branched alkyl groups having 4 to 22 carbon atoms, preferably 6 to 18 carbon atoms, and more preferably 8 to 16 carbon atoms. It is. Examples of the alkyl group having 4 to 22 carbon atoms include various butyl groups, various pentyl groups, various hexyl groups, various heptyl groups, various octyl groups, various nonyl groups, various decyl groups, various dodecyl groups, various tetradecyl groups, and various hexadecyl groups. , Various octadecyl groups, various eicosyl groups, and the like.
X in the general formulas (1) and (2) is preferably one selected from monovalent anions such as halogen ions, hydroxide ions, nitrate ions, and sulfate ions from the viewpoint of obtaining high crystallinity. That's it. X is more preferably a halogen ion, still more preferably a chlorine ion or a bromine ion, and particularly preferably a bromine ion.

Examples of the alkyltrimethylammonium salt represented by the general formula (1) include butyltrimethylammonium chloride, hexyltrimethylammonium chloride, octyltrimethylammonium chloride, decyltrimethylammonium chloride, dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, hexadecyltrimethyl Ammonium chloride, stearyltrimethylammonium chloride, butyltrimethylammonium bromide, hexyltrimethylammonium bromide, octyltrimethylammonium bromide, decyltrimethylammonium bromide, dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide Bromide, stearyl trimethyl ammonium bromide, and the like.
Examples of the dialkyldimethylammonium salt represented by the general formula (2) include dibutyldimethylammonium chloride, dihexyldimethylammonium chloride, dioctyldimethylammonium chloride, dihexyldimethylammonium bromide, dioctyldimethylammonium bromide, didodecyldimethylammonium bromide, ditetradecyl. Examples thereof include dimethylammonium bromide.
Among these quaternary ammonium salts (b), from the viewpoint of forming regular mesopores, alkyltrimethylammonium salts represented by the general formula (1) are particularly preferred, and alkyltrimethylammonium bromide or alkyltrimethyl Ammonium chloride is more preferred, and dodecyltrimethylammonium bromide or dodecyltrimethylammonium chloride is particularly preferred.

[Silica source (c)]
A silica source (c) produces | generates a silanol compound by hydrolysis of alkoxysilane etc., and can mention the compound shown by following General formula (3)-(7).
SiY ₄ (3)
R ³ SiY ₃ (4)
R ³ ₂ SiY ₂ (5)
R ³ ₃ SiY (6)
Y ₃ Si—R ⁴ —SiY ₃ (7)
(In the formula, each R ³ independently represents an organic group in which a carbon atom is directly bonded to a silicon atom, R ⁴ represents a hydrocarbon group or a phenylene group having 1 to 4 carbon atoms, and Y represents A monovalent hydrolyzable group that becomes a hydroxy group by hydrolysis.)
More preferably, in the general formulas (3) to (7), each R ³ is independently a hydrocarbon group having 1 to 22 carbon atoms in which a part of hydrogen atoms may be substituted with fluorine atoms, Specifically, it is an alkyl group, a phenyl group, or a benzyl group having 1 to 22 carbon atoms, preferably 4 to 18 carbon atoms, more preferably 6 to 18 carbon atoms, and particularly preferably 8 to 16 carbon atoms, and R ⁴ Is an alkanediyl group having 1 to 4 carbon atoms (methylene group, ethylene group, trimethylene group, propane-1,2-diyl group, tetramethylene group, etc.) or phenylene group, and Y is more preferably 1 to 22 carbon atoms. Is a C1-C8, particularly preferably C1-C4 alkoxy group or a halogen group excluding fluorine.

Preferable examples of the silica source (c) include the following compounds.
-The silane compound in which Y is a C1-C3 alkoxy group or a halogen group except a fluorine in General formula (3).
In general formula (4) or (5), Y is an alkoxy group having 1 to 3 carbon atoms or a halogen group excluding fluorine, and R ³ is a phenyl group, a benzyl group, or a part of a hydrogen atom Is a trialkoxysilane or dialkoxysilane, which is a hydrocarbon group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms, substituted with a fluorine atom.
In General Formula (6), Y is an alkoxy group having 1 to 3 carbon atoms or a halogen group excluding fluorine, and R ³ is a phenyl group, a benzyl group, or a hydrogen atom partially substituted with a fluorine atom. Monoalkoxysilane which is a hydrocarbon group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms.
A compound in which Y is a methoxy group and R ⁴ is a methylene group, an ethylene group or a phenylene group in the general formula (7).
Among these, tetramethoxysilane, tetraethoxysilane, phenyltriethoxysilane, and 1,1,1-trifluoropropyltriethoxysilane are particularly preferable.

Polymer particles (a-1) or hydrophobic organic compound (a-2) in the aqueous solution in step A (hereinafter, both are also collectively referred to as “component (a)”), quaternary ammonium salt (b), And the content of the silica source (c) is as follows.
The content of the component (a-1) is preferably 0.1 to 50 g / L, more preferably 0.3 to 40 g / L, and particularly preferably 0.5 to 30 g / L.
The content of the component (a-2) is 0.1 to 100 mmol / L, more preferably 1 to 100 mmol / L, and particularly preferably 5 to 80 mmol / L.
The content of component (b) is preferably 0.1 to 100 mmol / L, more preferably 1 to 100 mmol / L, particularly preferably 5 to 80 mmol / L, and the content of component (c) is And preferably 0.1 to 100 mmol / L, more preferably 1 to 100 mmol / L, and particularly preferably 5 to 80 mmol / L.
There is no restriction | limiting in particular in the order which contains (a)-(c) component. For example, (i) the suspension of the component (a), the component (b) and the component (c) are added in this order while stirring the aqueous solution, (ii) the suspension of the component (a) while stirring the aqueous solution, (B) Component and (c) component can be added simultaneously, (iii) Suspension of (a) component, (b) Component, (c) Stirring after addition of component, etc. can be employed. However, among these, the method (i) is preferable.
The aqueous solution containing the components (a) to (c) may contain other components such as an organic compound such as methanol and an inorganic compound as long as the formation of protocore-shell particles is not inhibited. As described above, when it is desired to carry other elements other than silica and organic groups, metal raw materials such as alkoxy salts and halide salts containing these metals can be added during or after production.

[Step B]
Step B is a step of preparing an aqueous dispersion of protocore-shell type silica particles. The aqueous solution obtained in Step A is stirred for a predetermined time at a temperature of 10 to 100 ° C., preferably 10 to 80 ° C., and then allowed to stand to leave the polymer particles (a-1) or the hydrophobic organic compound (a-2). A protocore shell in which mesopores are formed on the surface of quaternary ammonium salt (b) and silica source (c), and polymer particles (a-1) or hydrophobic organic compound (a-2) are included inside Type silica particles can be deposited. Although the stirring treatment time varies depending on the temperature, protocore-shell type silica particles are usually formed at 10 to 80 ° C. for 0.1 to 24 hours. The mesopores of the protocore-shell type silica particles obtained at this time are in a state where the surfactant used in the production is clogged.
The obtained protocore-shell type silica particles are obtained in a state suspended in water. Depending on the application, it can be used as it is, but preferably the protocore-shell type silica particles are used separately. As a separation method, a filtration method, a centrifugal separation method, or the like can be employed.
When the protocore-shell type silica particles obtained in step B contain a cationic surfactant or the like, the cationic surfactant or the like can be removed by contacting the acidic solution once or a plurality of times. Examples of the acidic solution to be used include inorganic acids such as hydrochloric acid, nitric acid and sulfuric acid; organic acids such as acetic acid and citric acid; liquids obtained by adding a cation exchange resin or the like to water or ethanol. Hydrochloric acid is particularly preferable. The pH is usually adjusted to 1.5 to 5.0.
The particles from which the surfactant has been removed from the pores by the above method have a mesopore structure on the surface, and have a high BET specific surface area. Polymer particles (a-1) or hydrophobic organic compounds (a-2) Is a proto-core-shell type silica particle.

[Steps C and D]
Step C is a step of separating the core-shell type silica particles (B) from the aqueous dispersion obtained in Step B. Step D is a step of firing the core-shell type silica particles (B) obtained in Step C. This is a step of obtaining hollow silica particles (A).
In step C, the core-shell type silica particles (B) can be separated from the aqueous dispersion, and contacted with an acidic aqueous solution, washed with water, and dried as necessary. Moreover, after processing at high temperature, in process D, it is preferably fired in an electric furnace or the like at 350 to 800 ° C., more preferably at 450 to 700 ° C. for 1 to 10 hours, and the inner polymer (a-1) or hydrophobic The organic compound (a-2) is removed. Although the basic structure of the outer shell part of the obtained hollow silica particles (A) is not changed, the inner polymer (a-1) or the hydrophobic organic compound (a-2) is removed by calcination.
In the present invention, since the core-shell type silica particles containing the polymer (a-1) or the hydrophobic organic compound (a-2) are fired, the shape and form of the polymer particles (a-1) to be included are particularly desired. By controlling in advance to the state, hollow silica particles (A) having a desired shape and form can be easily produced. For example, by firing core-shell type silica particles having a true spherical polymer inside, hollow silica particles (A) having an internal hollow shape and a true spherical shape can be produced.

Of the hollow silica particles (A) and the core-shell type silica particles (B) obtained as described above, in the powder X-ray diffraction measurement, the diffraction angle (2θ corresponding to the range of the surface spacing (d) of 1 nm to 12 nm. ) Is preferred.
The average pore diameter of the mesopore structure of the hollow silica particles (A) obtained in the step (I) is preferably 1 to 8 nm, more preferably 1 to 5 nm, and the mesopore diameter is determined by the hollow silica particles (A 70 mass% or more, preferably 75 mass% or more, more preferably 80 mass% or more of the average pore diameter is within ± 30 mass%.
The BET specific surface area of the hollow silica particles (A) is preferably 100 to 1500 m ² / g, more preferably 200 to 1500 m ² / g, and still more preferably 300 to 1500 m ² / g.
The average particle diameter of the hollow silica particles (A) is preferably 0.05 to 2 μm, more preferably 0.05 to 1.5 μm, still more preferably 0.1 to 1.2 μm. The hollow silica particles preferably have a primary particle size of 80% or more of the total primary particles, more preferably 85% or more, still more preferably 90% or more, and particularly preferably 95% or more within an average particle size of ± 30%. It is desirable that it is composed of a group of particles having a very uniform particle size.
The average thickness of the outer shell part (mesoporous silica part) is preferably as thin as the hollow silica particles can maintain the strength as a carrier, and the average diameter (average volume) of the hollow part is from the viewpoint of retaining a large amount of inclusions. Larger is preferable. From these viewpoints, the average thickness of the outer shell is usually 0.5 to 500 nm, preferably 2 to 400 nm, more preferably 3 to 300 nm.
The ratio of [average thickness of outer shell portion / average particle diameter of hollow silica particles] is usually 0.01 to 0.9, preferably 0.05 to 0.8, more preferably 0.1 to 0. 7.
The average particle diameter, average outer shell thickness, BET specific surface area, average pore diameter, and powder X-ray diffraction (XRD) pattern of the hollow silica particles (A) can be measured by the methods described in the examples.

Process (II)
Step (II) is a step of firing the hollow silica particles (A) or silica particles (B) obtained in step (I) at a temperature exceeding 950 ° C.
The firing temperature is such that the pores are appropriately baked, the average particle size is 0.05 to 1 μm, 80% by mass or more of the whole particles is within the average particle size ± 30%, and the BET specific surface area is less than 30 m ² / g. From this viewpoint, the temperature is preferably 960 ° C to 1500 ° C, more preferably 970 to 1300 ° C, and still more preferably 980 to 1200 ° C.
Firing can be performed using an electric furnace or the like, and the firing time varies depending on the firing temperature and the like, but is usually 0.5 to 10 hours, preferably 1 to 6 hours.
In the present invention, the hollow silica particles (A) are produced once in the step (I), and then fired at a temperature exceeding 950 ° C. in the step (II) to obtain the hollow silica particles obtained in the step (I). Without changing the basic structure of (A), hollow silica particles having a reduced average particle diameter and BET specific surface area can be obtained. Alternatively, the silica particles (B) obtained in the step (I) may be directly fired at a temperature exceeding 950 ° C. to obtain the hollow silica particles of the present invention. In the present invention, it is more preferable to obtain hollow silica particles having a small BET specific surface area by once producing the hollow silica particles (A) and then further firing.

Various measurements of the hollow silica particles obtained in Production Examples, Examples and Comparative Examples were performed by the following methods.
(1) Measurement of powder X-ray diffraction (XRD) Using a powder X-ray diffraction apparatus (manufactured by Rigaku Denki Kogyo Co., Ltd., trade name: RINT2500VPC), X-ray source: Cu-kα, tube voltage: 40 mA, tube current: Powder X-ray diffraction measurement was performed under the conditions of 40 kV, sampling width: 0.02 °, divergence slit: 1/2 °, divergence slit length: 1.2 mm, scattering slit: 1/2 °, and light receiving slit: 0.15 mm. went. A continuous scanning method was used in which the scanning range was a diffraction angle (2θ) of 1 to 70 ° and the scanning speed was 4.0 ° / min. The measurement was performed by packing the pulverized sample in an aluminum plate.
(2) Observation of particle shape The particle shape was observed using an electrolytic emission type high resolution scanning electron microscope (manufactured by Hitachi, Ltd., trade name: FE-SEM S-4000).
(3) Measurement of average primary particle diameter, average hollow part diameter, and average outer shell part thickness Particles at an acceleration voltage of 160 kV using a transmission electron microscope (TEM) (trade name: JEM-2100, manufactured by JEOL Ltd.) Was observed. The diameter, hollow diameter, and outer shell thickness of all particles in five fields of view containing 20-30 particles were measured on a photograph, and the average primary particle diameter, average hollow diameter, and average outer shell thickness were measured. Asked. In addition, observation was performed using what attached to Cu mesh (200-A mesh by Oken Shoji Co., Ltd.) with the carbon support film for high resolution, and removed the excess sample by the blow.
(4) Measurement of BET specific surface area and average pore diameter Using a specific surface area / pore distribution measuring device (manufactured by Shimadzu Corporation, trade name: ASAP2020), the BET specific surface area is determined by a multipoint method using liquid nitrogen. Measurements were made and values were derived in the range where parameter C was positive. The BJH method was adopted to derive the average pore diameter, and the pore diameter at the peak value was defined as the average pore diameter. The sample was pretreated at 250 ° C. for 5 hours.

Production Example 1 (Production of hollow silica particles (A) and silica particles (B))
In a 2 L-separafull flask, 600 parts of ion-exchanged water, 99.5 parts of methyl methacrylate and 0.5 part of methacryloyloxyethyltrimethylammonium chloride were added, and the temperature was raised to an internal temperature of 70 ° C. Next, 0.5 part of 2,2′-azobis (2-aminodipropane) dihydrochloride (manufactured by Wako Pure Chemical Industries, Ltd., trade name: V-50) is added to the ion-exchanged water 5 as a water-soluble initiator. The solution dissolved in the part was added and heated and stirred (300 rpm) for 3 hours.
Thereafter, the mixture is further cooled by heating and stirring (300 rpm) at 75 ° C. for 3 hours, and then the aggregate is filtered through a 200 mesh (aperture approximately 75 μm) from the obtained mixed solution to obtain a suspension of cationic polymer particles ( A solid (effective content) content of 14% by mass, an average primary particle size of 280 nm, and a proportion of ± 30% of the average particle size was 100% by mass).
Next, 6 kg of water, 2 kg of methanol, 45 g of 1M aqueous sodium hydroxide, 35 g of dodecyltrimethylammonium bromide, and 33 g of the cationic polymer particle suspension obtained above were stirred in a 10 L flask, and the aqueous solution was stirred. Then, 34 g of tetramethoxysilane was slowly added, stirred for 5 hours, and then aged for 12 hours.
Next, the obtained white precipitate was filtered through a membrane filter having a pore size of 0.2 μm, washed with 10 L of water, dried at 100 ° C. for 5 hours, and silica particles (protocore-shell type silica particles) B1) was obtained.
The obtained dry powder was heated to 600 ° C. at a rate of 1 ° C./min with an air flow (3 L / min) using a baking furnace (manufactured by Motoyama Co., Ltd., trade name: SK-2535E). The organic component was removed by baking at 2 ° C. for 2 hours to obtain hollow silica particles (A1).
As a result of performing powder X-ray diffraction (XRD) measurement on the powder of the hollow silica particles (A1) and the silica particles (B1), both of the hollow silica particles (A1) and the silica particles (B1) have a crystal lattice spacing (d ) = Very strong peak at 2.9 nm, weak peaks at d = 1.7 nm and d = 1.5 nm, the mesopores of the hollow silica particles (A1) and silica particles (B1) have a hexagonal arrangement It was confirmed. No XRD peak was observed in the region of d = 1.0 nm or less. Further, it was confirmed by SEM observation that the hollow silica particles (A1) and the silica particles (B1) had a spherical particle shape.
Further, from TEM observation, the hollow silica particles (A1) have a hollow structure, the average primary particle diameter is 560 nm, the average hollow part diameter is 280 nm, the average outer shell part thickness is 140 nm, and the outer shell part is a hexagonal array. It was confirmed that the mesopores showed a radial direction from the center of the particle toward the outside of the outer shell. All primary particles had a primary particle size within an average primary particle size of ± 30%.
Further, this hollow silica particle (A1) powder had a BET specific surface area of 1230 m ² / g and an average pore diameter of 1.48 nm.
The silica particles (B1) have a core-shell structure, an average primary particle diameter of 560 nm, an average core part diameter of 280 nm, an average outer shell part thickness of 140 nm, and the outer shell part having uniform mesopores exhibiting a hexagonal arrangement. It was confirmed that the mesopores penetrated radially from the center of the particle toward the outside of the outer shell. All primary particles had a primary particle size within an average primary particle size of ± 30%.

Example 1
5 g of the hollow silica particles (A1) obtained in Production Example 1 were transferred to a baking dish, and baked at 1000 ° C. for 2 hours in air using a high-speed heating electric furnace manufactured by Motoyama Co., Ltd., product name: SK-2535E. .
Table 1 shows the physical properties of the resulting hollow silica particles before and after firing. In the measurement of the average pore diameter of the hollow silica particles after firing, it was confirmed that there was no peak at 1 nm or more. Further, in the powder X-ray diffraction measurement, it was confirmed that there was no peak in the diffraction angle (2θ) corresponding to the range where the crystal lattice spacing (d) was less than 1 nm.
Example 2
Using the core-shell type silica particles (B1) obtained by the production method 1, firing was performed under the same conditions as in Example 1.
Table 1 shows the physical properties of the resulting hollow silica particles before and after firing. In the measurement of the average pore diameter of the hollow silica particles after firing, it was confirmed that there was no peak at 1 nm or more. Further, in the powder X-ray diffraction measurement, it was confirmed that there was no peak in the diffraction angle (2θ) corresponding to the range where the crystal lattice spacing (d) was less than 1 nm.

  Since the hollow silica particles of the present invention can enclose air and various compounds and materials therein, they can be suitably used for applications such as lightweight materials, reinforcing fillers, paint fillers, and functional material-containing capsules. Moreover, according to the method of the present invention, hollow silica particles having a small average particle size and specific surface area can be efficiently produced.

Claims (6)

Hollow silica particles having an average particle size of 0.05 to 1 μm, 80% or more of the particles having a particle size within an average particle size of ± 30%, and a BET specific surface area of less than 30 m ² / g.   The hollow silica particles according to claim 1, wherein, in powder X-ray diffraction measurement, the silica lattice spacing (d) does not show a peak at a diffraction angle (2θ) corresponding to a range of less than 1 nm. In powder X-ray diffractometry, the hollow silica particles (A) containing air inside the particles exhibiting a peak at a diffraction angle (2θ) corresponding to a surface spacing (d) in the range of 1 to 12 nm, or disappeared by firing. A method for producing hollow silica particles having a BET specific surface area of less than 30 m ² / g, wherein the core-shell type silica particles (B) enclosing the material forming the hollow part are fired at a temperature exceeding 950 ° C.   The manufacturing method of the hollow silica particle of Claim 3 whose calcination temperature is 960-1500 degreeC. The manufacturing method of the hollow silica particle of Claim 3 or 4 with which a core-shell type silica particle (B) is obtained from the process containing following process AC.
Step A: 0.1 to 50 g / L of the polymer particles (a-1) or 0.1 to 100 mmol / L of the hydrophobic organic compound (a-2), and the following general formulas (1) and (2) And 0.1 to 100 mmol / L of one or more (b) selected from quaternary ammonium salts represented by the formula (1)) and 0.1 to 100 mmol of silica source (c) that produces a silanol compound by hydrolysis. Of preparing an aqueous solution containing / L [R ¹ (CH ₃ ) ₃ N] ⁺ X ⁻ (1)
[R ¹ R ² (CH ₃ ) ₂ N] ⁺ X ⁻ (2)
(In the formula, R ¹ and R ² each independently represents a linear or branched alkyl group having 4 to 22 carbon atoms, and X represents a monovalent anion.)
Step B: The aqueous solution obtained in Step A is stirred at a temperature of 10 to 100 ° C., has an outer shell composed of silica, and has polymer particles (a-1) or a hydrophobic organic compound (a Step 2 for preparing an aqueous dispersion of proto-core-shell type silica particles having -2) Step C: Step for separating the core-shell type silica particles (B) from the aqueous dispersion obtained in Step B   The method for producing hollow silica particles according to any one of claims 3 to 5, wherein the hollow silica particles (A) containing air inside the particles are obtained by firing the core-shell type silica particles (B).