Hollow silica sol dispersed in highly hydrophobic solvent

Abstract

[Problem] To provide: a hollow silica organosol obtained by dispersing hollow silica particles in a highly hydrophobic organic solvent, in which aggregation of the hollow silica particles is suppressed and stable dispersion is maintained; a method for producing the hollow silica organosol; and a resin composition which contains the organosol. [Solution] A hollow silica organosol containing components (A) to (E) described below, wherein the component (A) is contained in an amount of 1% by mass to 70% by mass relative to the total amount (100% by mass) of the organosol, and a method for producing the hollow silica organosol. Component (A): aluminum atom-containing hollow silica particles having an average secondary particle diameter of 20-200 nm as determined by a dynamic light scattering method; component (B): an alcohol having a boiling point of 80°C to 200°C and having no ether bond; component (C): an organic solvent having a relative dielectric constant of 1-20 at 20°C and being other than component (B); and component (D): a silane compound

Description

Hollow silica sol dispersed in a highly hydrophobic solvent

[0001] The present invention relates to an organosol in which hollow silica particles containing aluminum atoms are dispersed, and more particularly to an organosol in which the hollow silica particles are stably dispersed in a hydrophobic solvent without agglomerating, a method for producing the same, and a resin composition containing the organosol.

[0002] Silica sols are used in various fields as abrasives and functional inorganic fillers. Although silica sols are stable and do not gel in alkaline environments, when alkaline silica sols are incorporated into compositions using organosilicon compounds or resins as binders, they tend to become cloudy or thicken due to their alkalinity. Furthermore, when preparing organo-silica sols by solvent substitution, mixing with alcohols or other substances can lead to gelation, posing a challenge. On the other hand, in acidic environments, the low zeta potential of silica particles results in low electrical repulsion, making silica sols unstable and prone to gelation. Nevertheless, silica sols are often required in acidic environments, such as in acidic abrasives, raw materials for ceramic fibers, and chromium-based surface treatment agents.

[0003] Furthermore, in an attempt to improve compatibility with resin solutions and acquire usefulness as a microfiller to impart scratch resistance and other properties when added to coating agents and paint binders, a method for producing an organic solvent-dispersed inorganic oxide sol has been proposed (Patent Document 1), in which inorganic oxide fine particles, in which primary alkoxy groups are bonded to silicon atoms on the surface of the inorganic oxide fine particles, are stably dispersed in an organic solvent. The examples in the same document disclose that the aforementioned organic solvent-dispersed oxide sol is produced by adding trialkoxysilane to a silica sol dispersed in a hydrophilic solvent such as methanol to surface-treat the silica particles in the sol, and then replacing the dispersion medium of the sol with a hydrophobic solvent such as toluene in the presence of a primary alcohol having 3 to 12 carbon atoms.

[0004] On the other hand, hollow silica particles, which have a silica outer shell and a space inside the outer shell, possess characteristics such as low refractive index, low thermal conductivity (thermal insulation), and electrical insulation. Hollow silica particles consist of a core corresponding to a cavity and an outer shell forming the outside of the core. An aqueous dispersion of hollow silica particles can be obtained by forming a silica layer on the outside of template particles in an aqueous medium, and then removing the template particles. For example, a method has been disclosed in which core-shell particles are produced by reacting a silane compound and an aluminum precursor with an organic polymer in a micelle or inverse micelle form in a Si / Al molar ratio of 7 to 15 to form an aluminosilicate shell. This is then reacted with a basic aqueous solution or an acidic aqueous solution to simultaneously form pores in the shell (outer shell) and remove the core, and then a hydrothermal reaction is performed by heating at 160 to 200°C to produce a hollow silica sol with a high density of shell (see Patent Document 2).

[0005] Japanese Patent Publication No. 2005-200294, Korean Patent No. 10-1659709

[0006] When applying silica sols to a wide variety of fields, for example, when mixing them with resin materials to form composite materials, using silica sols stably dispersed not only in hydrophilic solvents but especially in hydrophobic organic solvents can be advantageous in manufacturing, considering factors such as handling properties and reduced curing and drying times. However, in the case of hollow silica particles, the dispersibility of the particles themselves is expected to decrease due to the cavity structure. In particular, hydrophobic solvent-dispersed organosols obtained by solvent substitution from hydrophilic solvents are susceptible to the influence of ionic components (cations and anions) around the particles, and aggregation is also likely to occur due to surface treatment or the addition of certain alcohols.

[0007] The present invention provides a hollow silica organosol in which hollow silica particles are dispersed in a highly hydrophobic organic solvent such as methyl isobutyl ketone or ethyl acetate, and provides a hollow silica organosol in which aggregation of the hollow silica particles is suppressed and stable dispersion is maintained.

[0008] The present invention relates, in first aspect, to a hollow silica organosol containing the following components (A), (B), (C), and (D), wherein component (A) is present in a proportion of 1% to 70% by mass based on the total amount (100% by mass) of the organosol: (A) component: hollow silica particles containing aluminum atoms having an average secondary particle diameter of 20 to 200 nm as measured by dynamic light scattering; (B) component: an alcohol having a boiling point of 80°C to 200°C and not having an ether bond; (C) component: an organic solvent other than component (B) having a relative permittivity of 1 to 20 at 20°C; (D) component: a silane compound. The present invention relates, in second aspect, to the hollow silica organosol described in first aspect, further comprising an anion as component (E) in a mass unit of 0.1 to 500 ppm relative to the total mass of the organosol. The third aspect relates to the hollow silica organosol described in the first aspect, further comprising a polymerization inhibitor in mass units of 10 to 10,000 ppm as component (F). The fourth aspect relates to the hollow silica organosol described in the first aspect, wherein the (average secondary particle diameter by dynamic light scattering method) / (average primary particle diameter by transmission electron microscopy observation) of the (A) hollow silica particles is 0.70 or more and 2.40 or less. The fifth aspect relates to the hollow silica organosol described in the first aspect, wherein the (A) hollow silica particles satisfy the following (i) to (iii): (i) the thickness of the outer shell of the hollow silica particles is 3 to 15 nm, (ii) the surface charge amount per gram of the hollow silica particles is 10 μeq / g to 200 μeq / g, and (iii) the amount of aluminum atoms present in the entire hollow silica particle is Al ２ O ３ Converted to 120 to 50,000 ppm / SiO2 relative to the mass of the hollow silica particles. ２ The sixth aspect relates to the hollow silica organosol described in the first aspect, wherein component (D) is at least one silane compound selected from the group consisting of compounds represented by the following formulas (1) and (2). (In formula (1), R １is a group bonded to a silicon atom, independently representing an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having an epoxy group, a (meth)acryloyl group, a mercapto group, an amino group, a ureido group, a polyether group, a carboxy group, a protected carboxy group, a carboxy group generating group, an imide group, or a cyano group and bonded to the silicon atom by a Si—C bond, or representing a combination of these groups, R ２ is a group or atom bonded to a silicon atom, independently representing an alkoxy group, an acyloxy group, a hydroxy group, or a halogen atom, or representing a combination of these groups or atoms, a represents an integer of 1 to 3, in formula (2), R ３ is a group bonded to a silicon atom, independently representing an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having an epoxy group, a (meth)acryloyl group, a mercapto group, an amino group, a ureido group, a polyether group, a carboxy group, a protected carboxy group, a carboxy group generating group, an imide group, or a cyano group and bonded to the silicon atom by a Si—C bond, or representing a combination of these groups, R ４ is a group or atom bonded to a silicon atom, independently representing an alkoxy group, an acyloxy group, a hydroxy group, or a halogen atom, or representing a combination of these groups or atoms, Y is a group or atom bonded to a silicon atom, representing an alkylene group, an NH group, or an oxygen atom, b represents an integer of 1 to 3, c represents an integer of 0 or 1.) As a seventh aspect, the (A) hollow silica particles have a surface area of 1 nm ２ per 0.1 to 10 of which the surface is coated with the silane compound of the (D) component, or the particles formed by bonding the silane compound of the (D) component to the surface, relating to the hollow silica organosol according to the sixth aspect. As an eighth aspect, the alcohol of the (B) component is at least one selected from the group consisting of alcohols having 3 to 8 carbon atoms, relating to the hollow silica organosol according to the first aspect. As a ninth aspect, the (A) hollow silica particles have a surface area of 1 nm ２The present invention relates to a hollow silica organosol according to the first aspect, wherein the particles are formed by the bonding of the alcohol of component (B) to the surface at a rate of 0.01 to 1.0 particles per particle. The present invention relates to a hollow silica organosol according to the first aspect, wherein the organic solvent of component (C), having a relative permittivity of 1 to 20 at 20°C, is selected from the group consisting of ketones, esters, ethers, and hydrocarbons. The present invention relates to a hollow silica organosol according to the second aspect, wherein the anion of component (E) is one or more inorganic anions selected from the group consisting of sulfate ions, nitrate ions, carbonate ions, chloride ions, bromide ions, and phosphate ions. The present invention relates to a hollow silica organosol according to the first aspect, further comprising a sulfate ester as component (G). The thirteenth aspect relates to the hollow silica organosol described in the third aspect, wherein the polymerization inhibitor of component (F) is selected from the group consisting of 2,6-diisobutylphenol, 3,5-di-tert-butylphenol, 2,6-di-tert-butyl-p-cresol, 3,5-di-tert-butyl-p-cresol, 4-methoxyphenol (p-methoxyphenol), hydroquinone, hydroquinone monomethyl ether, pyrogallol, naphthylamine, benzoquinone, tert-butylcatechol, cuprous chloride, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 4,4'-thiobis(3-methyl-6-tert-butylphenol), N-nitrosophenylhydroxyamine salts (ammonium salts, cerium salts, etc.), nitrosophenylhydroxyamine aluminum salts, and diphenylnitrosamines. The fourteenth aspect relates to a resin composition comprising the hollow silica organosol described in the first aspect and an organic resin material or a polysiloxane resin.The 15th aspect relates to the resin composition according to the 14th aspect, wherein the organic resin material is at least one selected from the group consisting of styrene resins, epoxy resins, thioepoxy resins, novolac resins, cyanate resins, phenolic resins, acrylic resins, maleimide resins, polyester resins, urethane resins, polyurea resins, polyimide resins, polyamide resins, polyamic acid resins, polyhydroxyimide resins, polybenzoxazole resins, polybenzimidazole resins, polybenzothiazole resins, polyhydroxyamide resins, polyhydroxyazomethine resins, polyether resins, polybenzoxazine resins, polytetrafluoroethylene resins, cycloolefin polymer resins, unsaturated polyester resins, vinyl triazine resins, polyphenylene sulfide resins, crosslinkable polyphenylene oxide resins, curable polyphenylene ether resins, and condensation resins. The sixteenth aspect relates to the resin composition described in the fourteenth aspect, wherein the content of hollow silica particles of component (A) is 50 to 200 phr relative to the total mass of the resin composition, and further comprises a polymerization initiator and a leveling agent. The 17th aspect relates to a resin composition described in any one of the 14th to 16th aspects, which has applications in semiconductor device materials, semiconductor element materials, semiconductor resist materials, nanoimprint materials, insulating film materials, copper-clad laminate materials, printed circuit board materials, printed board materials, printing ink materials, pigments, paints, encapsulant materials, hard coat materials, 3D printing materials, anti-reflective film materials, automotive parts materials, electronic parts materials, mechanical components, adhesive materials, battery materials, power generation materials, charge-impregnating materials, conductivity-impregnating materials, powder flowability-impregnating materials, cosmetic materials, flexible wiring materials, liquid crystal display materials, organic EL display materials, micro-LED display materials, QD-EL display materials, flexible display materials, antenna materials, optical wiring materials, sensing materials, or thermal insulation materials.The 18th aspect relates to a coating containing the following components (A), (B), and (D) and an organic resin material, wherein the film refractive index is 1.1 to 1.45 and the haze is 0.01% to 0.08% when the film thickness is 100 nm: (A) component: hollow silica particles containing aluminum atoms, with an average secondary particle diameter of 20 to 200 nm as determined by dynamic light scattering; (B) component: an alcohol with a boiling point of 80°C to 200°C and without ether bonds; (D) component: a silane compound. Organic resin materials: At least one selected from the group consisting of styrene resins, epoxy resins, thioepoxy resins, novolac resins, cyanate resins, phenolic resins, acrylic resins, maleimide resins, polyester resins, urethane resins, polyurea resins, polyimide resins, polyamide resins, polyamic acid resins, polyhydroxyimide resins, polybenzoxazole resins, polybenzimidazole resins, polybenzothiazole resins, polyhydroxyamide resins, polyhydroxyazomethine resins, polyether resins, polybenzoxazine resins, polytetrafluoroethylene resins, cycloolefin polymer resins, unsaturated polyester resins, vinyl triazine resins, polyphenylene sulfide resins, crosslinkable polyphenylene oxide resins, curable polyphenylene ether resins, and condensation resins. The 19th aspect relates to a method for producing a hollow silica organosol according to the first aspect, comprising the step of replacing a mixture obtained by adding an alcohol having a boiling point of 80°C to 200°C to a methanol-dispersed silica sol containing aluminum atom-containing hollow silica particles with the aforementioned (C) organic solvent by ultrafiltration, heating under reduced pressure, or heating under normal pressure. The 20th aspect relates to a method for producing a hollow silica organosol according to the 19th aspect, comprising the step of contacting the methanol-dispersed silica sol containing aluminum atom-containing hollow silica particles with a cation exchange resin before adding the alcohol having a boiling point of 80°C to 200°C.The 21st aspect relates to a method for producing a hollow silica organosol according to the 19th or 20th aspect, comprising the step of adding at least one silane compound selected from the group consisting of compounds represented by the following formulas (1) and (2) to a sol containing aluminum atom-containing silica particles, after the (C) substitution step with an organic solvent, and heating and stirring at 10°C to 95°C for 0.1 hours to 20 hours. (In formula (1), R １ R represents a group that is bonded to a silicon atom and independently represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having an epoxy group, (meth)acryloyl group, mercapto group, amino group, ureido group, polyether group, carboxyl group, protected carboxyl group, carboxyl group generating group, imide group, or cyano group, and is bonded to a silicon atom by a Si-C bond, or represents a combination of these groups. ２ R is a group or atom bonded to a silicon atom, independently representing an alkoxy group, an acyloxy group, a hydroxyl group, or a halogen atom, or a combination thereof, where a represents an integer from 1 to 3, and in formula (2), R ３ R represents a group that is bonded to a silicon atom and independently represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having an epoxy group, (meth)acryloyl group, mercapto group, amino group, ureido group, polyether group, carboxyl group, protected carboxyl group, carboxyl group generating group, imide group, or cyano group, and is bonded to a silicon atom by a Si-C bond, or represents a combination of these groups. ４(b represents a group or atom bonded to a silicon atom, independently representing an alkoxy group, an acyloxy group, a hydroxyl group, or a halogen atom, or a combination thereof; Y represents a group or atom bonded to a silicon atom, representing an alkylene group, an NH group, or an oxygen atom; b represents an integer from 1 to 3; and c represents an integer of 0 or 1.) The 22nd aspect relates to a method for producing a hollow silica organosol according to the 21st aspect, further comprising the step of substitution with the (C) organic solvent after the step of adding and heating and stirring the silane compound. The 23rd aspect relates to a method for producing a hollow silica organosol according to the 12th aspect, further comprising the step of substitution with an organic resin material or a polysiloxane resin after the step of substitution with the (C) organic solvent. The 24th aspect is a method for producing a composite material, comprising the steps of: (A) a methanol-dispersed silica sol containing aluminum atom-containing hollow silica particles, (B) an alcohol having a boiling point of 80°C to 200°C and not having an ether bond, and then replacing the mixture with (C) an organic solvent by ultrafiltration, heating under reduced pressure, or heating under normal pressure; after the step of replacing with the (C) organic solvent, adding at least one (D) silane compound selected from the group consisting of compounds represented by the following formulas (1) and (2) to the sol containing aluminum atom-containing silica particles, and heating and stirring at 10°C to 95°C for 0.1 hours to 20 hours; after the step of adding the silane compound and heating and stirring, further replacing with the (C) organic solvent, and after the step of replacing with the (C) organic solvent, replacing the dispersion medium with an organic resin material or a polysiloxane resin, wherein the (A) aluminum atom-containing hollow silica particles have an average secondary particle diameter of 20 to 200 nm as measured by dynamic light scattering. The present invention relates to a manufacturing method wherein the (C) organic solvent has a relative permittivity of 1 to 20 at 20°C and is an organic solvent other than component (B). (In formula (1), R １R represents a group that is bonded to a silicon atom and independently represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having an epoxy group, (meth)acryloyl group, mercapto group, amino group, ureido group, polyether group, carboxyl group, protected carboxyl group, carboxyl group generating group, imide group, or cyano group, and is bonded to a silicon atom by a Si-C bond, or represents a combination of these groups. ２ R is a group or atom bonded to a silicon atom, independently representing an alkoxy group, an acyloxy group, a hydroxyl group, or a halogen atom, or a combination thereof, where a represents an integer from 1 to 3, and in formula (2), R ３ R represents a group that is bonded to a silicon atom and independently represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having an epoxy group, (meth)acryloyl group, mercapto group, amino group, ureido group, polyether group, carboxyl group, protected carboxyl group, carboxyl group generating group, imide group, or cyano group, and is bonded to a silicon atom by a Si-C bond, or represents a combination of these groups. ４ (b represents a group or atom bonded to a silicon atom, independently representing an alkoxy group, an acyloxy group, a hydroxyl group, or a halogen atom, or a combination thereof; Y represents a group or atom bonded to a silicon atom, representing an alkylene group, an NH group, or an oxygen atom; b represents an integer from 1 to 3; and c represents an integer of 0 or 1.) The 25th aspect relates to a composite material comprising (A) hollow silica particles containing aluminum atoms having an average secondary particle diameter of 20 to 200 nm as determined by dynamic light scattering, (B) an alcohol having a boiling point of 80°C to 200°C and not having an ether bond, (D) a silane compound, and an organic resin material or a polysiloxane resin.

[0009] According to the present invention, a hollow silica organosol can be provided in which aluminum atom-containing hollow silica particles are dispersed in a highly hydrophobic organic solvent such as methyl isobutyl ketone or ethyl acetate. In particular, according to the present invention, a hollow silica organosol can be provided in which the ratio of the average secondary particle diameter to the average primary particle diameter of the hollow silica particles in the organosol is small, and the change in the average secondary particle diameter is small before and after storage at 50°C for 4 weeks, that is, a hollow silica organosol can be provided in which aggregation of hollow silica particles is suppressed and good dispersion stability is maintained. Furthermore, according to the manufacturing method of the present invention, even if the dispersion medium is a highly hydrophobic organic solvent, aggregation of hollow silica particles is suppressed and a hollow silica organosol with stable dispersion can be produced. The silica sol dispersed in a highly hydrophobic organic solvent according to the present invention is expected to be developed into new applications and fields, such as compounding with resins, which was difficult to apply with conventional aqueous silica sols. In particular, the organosol according to the present invention, in which hollow silica particles are dispersed in a hydrophobic solvent, is expected to enable compounding with various polymers, which was previously considered difficult, and the various properties such as electrical insulation mentioned above can be applied in a wide variety of fields.

[0010] The present invention relates to a hollow silica organosol comprising (A) hollow silica particles containing aluminum atoms, (B) an alcohol having a boiling point of 80°C to 200°C and not having ether bonds, (C) an organic solvent other than component (B) having a relative permittivity of 1 to 20 at 20°C, and (D) a silane compound.

[0011] The hollow silica organosol according to the present invention is a dispersion system in which (A) aluminum atom-containing hollow silica particles (hereinafter also simply referred to as "hollow silica particles," "hollow silica," or "silica particles") are dispersed in (C) an organic solvent, which is the main dispersion medium. The hollow silica particles are silica (SiO ２ It is a particle that has an outer shell containing ) and has a space inside the outer shell.

[0012] [(A) Aluminum atom-containing hollow silica particles] The aluminum atom-containing hollow silica particles of component (A) according to the present invention are silica (SiO ２ It is a particle that has an outer shell containing ) and has a space inside the outer shell.

[0013] In the above-mentioned hollow silica particles containing aluminum atoms, the amount of aluminum atoms present in the entire hollow silica particle (i.e., the entire particle including the surface and interior) (in short, the aluminum atom content in the hollow silica particle) is Al ２ O ３ Converted to 120 to 50,000 ppm / SiO2 relative to the mass of the hollow silica particles. ２ (Silica particles) can be used. For example, the amount of aluminum atoms is 300 to 20,000 ppm / SiO ２ , or 500 to 20,000 ppm / SiO ２ , or 500 to 10,000 ppm / SiO ２ , or 500-5,000 ppm / SiO ２ , or 500-1,000 ppm / SiO ２ This can be done. In this specification, the amount of aluminum atoms present in the entire hollow silica particle is expressed in units of ppm / SiO2, relative to the mass (g) of the hollow silica particle. ２ The amount of aluminum atoms present in the entire hollow silica particle can be determined by a dissolution method using hydrofluoric acid aqueous solution (also called hydrofluoric acid aqueous solution). Specifically, the amount of aluminum atoms present in the entire hollow silica particle can be determined by dissolving the hollow silica particle in hydrofluoric acid aqueous solution and measuring and analyzing the resulting solution using an ICP emission spectrometer. ２ O ３ It can be expressed in terms of . A more specific procedure is as follows: First, the silica sol in question is dried to remove the dispersion medium and obtain hollow silica particles. 250 mg of these particles are dissolved in an aqueous hydrofluoric acid solution (for example, a mixture of 2.5 ml of 60% nitric acid and 2.5 ml of 38% hydrofluoric acid) to obtain an aqueous solution. The amount of aluminum atoms in the aqueous solution is measured using an ICP emission spectrometer, and Al ２ O ３ The aluminum atom content (ppm) is obtained by converting this to ppm. By dividing this by the mass of the silica particles, the total amount of aluminum atoms present in the hollow silica particles (Al ２ O ３ (ppm) / SiO ２) can be calculated.

[0014] In the (A) aluminum atom-containing hollow silica particles according to the present invention, the aluminum atoms may exist as aluminosilicate. In a preferred embodiment, the hollow silica particles have aluminosilicate formed on at least the surface of the particles, and aluminosilicate may be formed not only on the surface of the particles but also inside the hollow silica particles.

[0015] Furthermore, in the hollow silica organosol according to the present invention, the hollow silica particles have an average secondary particle diameter (DLS average particle diameter: Z average particle diameter, harmonic mean particle diameter) of 20 to 200 nm as determined by dynamic light scattering (DLS) method, preferably in the range of 20 to 150 nm, 30 to 150 nm, 40 to 150 nm, 50 to 150 nm, 50 to 120 nm, or 50 to 100 nm. The DLS average particle diameter represents the average value of the secondary particle diameter (dispersed particle diameter), and the larger the DLS average particle diameter, the more aggregated the silica particles in the medium are considered to be. The above DLS average particle diameter values ​​are (initial) values ​​before the thermal stability test described below, but since the hollow silica particles in the hollow silica organosol according to the present invention are particles with excellent dispersion stability, the DLS average particle diameter values ​​can be considered to be approximately within the above numerical range even after the above test.

[0016] <Thermal Stability Test> The thermal stability test involves storing the hollow silica organosol in question at 50°C for four weeks. The average secondary particle diameter (DLS average particle diameter) obtained by dynamic light scattering before the thermal stability test is (X ０ ), the average secondary particle diameter (DLS average particle diameter) obtained by dynamic light scattering after the thermal stability test is (X ４ｗ When this is the case, the ratio of particle size before and after the test (DLS ratio) = (X ４ｗ ) / (X ０ The stability of the sol can be evaluated by (X). In the hollow silica organosol of the present invention, (X ４ｗ ) / (X ０The value of ) is preferably 0.70 or more and 1.10 or less, and the ratio is preferably, for example, 1.00 or more and 1.05 or less.

[0017] The average primary particle diameter of the aluminum atom-containing hollow silica particles according to the present invention can be 20 to 100 nm as observed by a transmission electron microscope (TEM), and can be in the range of, for example, 30 to 100 nm, 30 to 80 nm, or 30 to 70 nm.

[0018] <Dispersibility Evaluation> The aggregation state of hollow silica particles in the medium can be evaluated from the ratio of the average secondary particle diameter of the hollow silica particles measured by dynamic light scattering to the average primary particle diameter observed by transmission electron microscopy (TEM). That is, as an indicator of the dispersibility of the hollow silica organosol of the present invention, the ratio [average secondary particle diameter / average primary particle diameter] of the average secondary particle diameter (DLS average particle diameter) of the hollow silica particles measured by dynamic light scattering to the average primary particle diameter of the hollow silica particles observed by transmission electron microscopy (TEM) can be used. In the hollow silica particles of the present invention, the [average secondary particle diameter (DLS) / average primary particle diameter (TEM)] is preferably 0.70 or more and 2.40 or less, more preferably 0.70 or more and 2.00 or less, for example, 1.00 or more and 2.00 or less.

[0019] Furthermore, in the hollow silica particles according to the present invention, the specific surface area determined by the BET method (nitrogen gas adsorption method) is, for example, 18 to 200 m². ２ / g, or 50-160m ２ / g, or 60-160m ２ / g, or 70-160m ２ / g, or 80-150m ２ It can be expressed as / g.

[0020] Furthermore, the outer shell of the aluminum atom-containing hollow silica particles according to the present invention can be observed with a transmission electron microscope (TEM). In the case of the hollow silica particles according to the present invention, the thickness of the outer shell observed with a transmission electron microscope can be, for example, in the range of 3.0 to 15.0 nm, or 3.0 to 12.0 nm, preferably 3.0 to 8.0 nm.

[0021] The aluminum atom-containing hollow silica particles according to the present invention preferably have a surface charge amount (negative charge amount) per gram of hollow silica particles of, for example, 10 to 250 μeq / g, or it can be in the range of 20 to 100 μeq / g, 25 to 150 μeq / g, 25 to 100 μeq / g, 25 to 50 μeq / g, or 25 to 45 μeq / g.

[0022] Furthermore, in the acidic region, the high absolute value of the zeta potential of hollow silica particles causes electrical repulsion, which is desirable from the viewpoint of dispersibility. The surface charge of hollow silica particles changes, as one factor, depending on the amount of aluminum atoms (aluminosilicate) present in the hollow silica particles, as described above. For example, the amount of aluminum atoms (Al) present throughout the silica particles... ２ O ３ Conversion, SiO ２ The amount is 120 ppm / SiO ２ If the value is less than the limit, the stability of the hollow silica particles tends to decrease. On the other hand, the aluminum atoms (Al) present throughout the silica particles tend to decrease. ２ O ３ Conversion, SiO ２ The amount is 50,000 ppm / SiO ２ In the above cases, at the aqueous sol stage, the particle size after doping tends to increase compared to the particle size measured by dynamic light scattering (DLS average particle size) before doping with aluminum atoms.

[0023] Furthermore, the refractive index of the aluminum atom-containing hollow silica particles according to the present invention can be in the range of, for example, 1.20 to 1.45, 1.20 to 1.40, or 1.20 to 1.30.

[0024] The hollow silica organosol of the present invention contains hollow silica particles, which are component (A), in a proportion of 1% to 70% by mass based on the total amount (100% by mass) of the organosol, and can also contain them in proportions of, for example, 5% to 60% by mass, 10% to 50% by mass, 10% to 40% by mass, or 10% to 35% by mass. In this specification, the silica particle concentration in the silica sol is a value obtained by a calcination method, specifically, by calcining the target silica sol at, for example, 1000°C for 30 minutes or more, and dividing the mass of the calcined residue by the mass of the target silica sol. The mass of the calcined residue is also sometimes referred to as "silica solids".

[0025] [Component (B): Alcohol with a boiling point of 80°C to 200°C and without ether bonds] The hollow silica organosol according to the present invention contains an alcohol with a boiling point of 80°C to 200°C as component (B). The alcohol may be one which does not have ether bonds. In the present invention, the boiling point of the alcohol refers to the value at a pressure of 101,325 Pa (standard atmospheric pressure) and can be measured by a standard method under a pressure environment of 101,325 Pa. The alcohol with a boiling point of 80°C to 200°C can be selected by referring to the values ​​in the Solvent Handbook (Kodansha, 1976). The boiling point of the alcohol as component (B) can be 80°C to 200°C, 80 to 180°C, 80 to 160°C, 90 to 200°C, 95 to 200°C, or 90 to 160°C. By using an alcohol with a boiling point of 80°C to 200°C, the dispersion stability of hollow silica particles is improved, resulting in good storage stability as a hollow silica organosol. When mixed with a resin composition to form a coating, the alcohol can be efficiently removed by heating, resulting in a coating with high drying properties and smoothness.

[0026] The alcohol component (B) can exist in the hollow silica organosol according to the present invention in a manner in which it is bonded to at least a portion of the surface of the aluminum atom-containing hollow silica particles (A). That is, the hydroxyl group of the alcohol (B) and the silanol group present on the surface of the aluminum atom-containing hollow silica particles (A) undergo transesterification, thereby allowing the alcohol (B) to be bonded to the surface of the hollow silica particles (A). The transesterification of the hydroxyl group and the silanol group introduces an ester group derived from the alcohol (B) to the surface of the hollow silica particles (A), which is expected to improve the dispersion stability of the hollow silica particles (A) in the organic solvent (C) described later. The alcohol (B) can also be transesterified with the silane compound (D) described later, such as an alkoxy group that may be contained in the silane compound. Therefore, when the (D) silane compound is in a state in which it coats or binds to the surface of the (A) aluminum atom-containing hollow silica particles as described later, the (B) alcohol can transesterify with alkoxys and the like that may be present in the (D) silane compound near the surface of the hollow silica particles, and the introduction of ester groups derived from the (B) alcohol to the (A) particle surface (of the silane compound) is expected to further improve the dispersion stability in the (C) organic solvent.

[0027] In one embodiment, the hollow silica particles (A) according to the present invention described above have a surface area of ​​1 nm ２ The particles can be formed with 0.01 to 1 alcohol of component (B) bonded to the surface. That is, the amount of alcohol of component (B) bonded to the hollow silica particles of (A) (amount of surface treatment) is such that the surface of the hollow silica particles is 1 nm ２The amount of alcohol can be such that, for example, the number of alcohol particles is about 0.01 to 1, or about 0.1 to 1, or about 0.1 to 0.5. The production of (A) hollow silica particles in which the alcohol of component (B) is bonded to the surface, that is, the transesterification reaction between the hydroxyl group of the alcohol of (B) and the silanol group present on the surface of the (A) hollow silica particles, can be obtained, for example, by adding the alcohol to a sol containing hollow silica particles and then heating and stirring it at 10 to 95°C for about 0.1 to 20 hours. At this time, the amount of alcohol of (B) added to the hollow silica particles in the sol containing hollow silica particles can be such that, for example, the mass ratio of silica particles / alcohol = 0.01 to 1. This reaction can be carried out simultaneously with the production of hollow silica particles in which at least a portion is coated with a silane compound (reaction of (A) hollow silica particles and (D) silane compound), which will be described later.

[0028] (B) As the alcohol of component (B), alcohols having 3 to 8 carbon atoms are preferred. For example, monohydric alcohols such as n-propanol, n-butanol, n-heptanol, n-pentanol, n-hexanol, n-heptanol, n-octanol and their isomers (e.g., linear, branched, or cyclic alcohols, or primary, secondary, or tertiary alcohols, such as 2-propanol, i-butanol, and 2-ethylhexanol) having the above boiling point can be used. Note that polyhydric alcohols may impart excessive hydrophilicity, which may reduce their dispersibility in hydrophobic solvents. (A) Considering the ease of transesterification with silanol groups on the surface of hollow silica particles, linear alcohols or primary or secondary alcohols are preferred, and considering the dispersion stability in organic solvents (C) described later, monohydric alcohols are preferred. Among the specific examples above, n-propanol, n-butanol, and n-hexanol can be preferably used as the alcohol of component (B).

[0029] In the hollow silica organosol according to the present invention, the amount of alcohol of component (B) can be, for example, 0.1 to 15% by mass relative to the mass of the sol. This amount is the total amount of alcohol that is bound to the hollow silica particles and alcohol that is contained in the sol (free from the particles).

[0030] [Component (C): Organic solvent other than component (B) with a relative permittivity of 1 to 20 at 20°C] The hollow silica organosol according to the present invention contains an organic solvent as component (C) with a relative permittivity of 1 to 20 at 20°C. In the present invention, the organic solvent of component (C) can function as a dispersion medium for (A) aluminum atom-containing hollow silica particles and is distinct from the alcohol of component (B) described above. Component (C) can generally be treated as an organic solvent with higher hydrophobicity compared to component (B), and may also include amphiphilic organic solvents. The relative permittivity of the organic solvent of component (C) at 20°C can be 1 to 20, 3 to 20, 5 to 20, 1 to 17, 1 to 15, 3 to 17, or 5 to 15. By setting the relative permittivity of the organic solvent of component (C) at 20°C to 1 to 20, a highly hydrophobic hollow silica organosol can be obtained, and when mixed with a resin material to form a composite material, improved handling and reduced curing and drying time can be expected.

[0031] The dielectric constant can be measured, for example, by using 50 mL of the organic solvent with a water content of 5 ppm or less as a measurement sample, and applying an AC voltage of 1 MHz using a Keycom (now Keysight) E4980A precision LCR meter and a Keycom DPT-013-050 electrode. An organic solvent with a dielectric constant of 1 to 20 at 20°C can be selected by referring to the values ​​in the Solvent Handbook (Kodansha, 1976).

[0032] The organic solvent for component (C) can be selected from the group consisting of ketones, esters, ethers, and hydrocarbons, and has the above-mentioned predetermined dielectric constant. When two or more solvents are used as component (C), it is preferable that the dielectric constant of the mixed solvent as a whole is within the above range.

[0033] Examples of the above ketones include aliphatic ketones having 1 to 10 carbon atoms. Specifically, examples include, but are not limited to, methyl ethyl ketone (MEK), diethyl ketone, methyl propyl ketone, methyl isobutyl ketone (MIBK), methyl amyl ketone, cyclopentanone, cyclohexanone, and methylcyclopentanone. Examples of the above esters include aliphatic esters having 1 to 10 carbon atoms. Specifically, examples include methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate (EAC), propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl acrylate, ethyl acrylate, propyl acrylate, dimethyl maleate, diethyl maleate, dipropyl maleate, dimethyl adipate, diethyl adipate, dipropyl adipate, propylene glycol monomethyl ether acetate, and others. Examples of the above ethers include aliphatic ethers having 1 to 10 carbon atoms. Specifically, examples include, but are not limited to, dimethyl ether, ethyl methyl ether, diethyl ether, tetrahydrofuran, 1,4-dioxane, propylene glycol monomethyl ether, and 3-methyl-3-methoxy-1-butanol. Examples of the above hydrocarbons include n-hexane, cyclohexane, toluene, xylene, and halogenated hydrocarbons such as carbon tetrachloride, dichloroethane, and chlorobenzene.

[0034] In the present invention, the organic solvent, which is component (C), can be included in proportions of, for example, 0.001% to 90% by mass, 0.01% to 90% by mass, 0.1% to 90% by mass, 1% to 90% by mass, or 10% to 90% by mass, based on the total amount (100% by mass) of the hollow silica organosol.

[0035] [(D) Silane Compound] The hollow silica organosol of the present invention further comprises a silane compound which is component (D) below. The silane compound of component (D) above can be at least one silane compound selected from the group consisting of compounds represented by the following formulas (1) and (2).

[0036] In the above formula (1), R １ R represents a group that is bonded to a silicon atom and independently represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having an epoxy group, (meth)acryloyl group, mercapto group, amino group, ureido group, polyether group, carboxyl group, protected carboxyl group, carboxyl group generating group, imide group, or cyano group, and is bonded to a silicon atom by a Si-C bond, or represents a combination of these groups. ２ R is a group or atom bonded to a silicon atom, which independently represents an alkoxy group, an acyloxy group, a hydroxyl group, or a halogen atom, or a combination thereof, where a is an integer from 1 to 3. In the definition of a group in a silane compound as used herein, "independently" means that multiple groups can each independently represent a group defined as an option. That is, for example, in formula (1), R １ If there are two or more (a is 2 to 3), then there are multiple R １ These may be the same group (for example, all methyl groups) or a combination of different groups (for example, a methyl group and a phenyl group, or a methyl group and a (meth)acryloylpropyl group when a is 2).

[0037] In the above formula (2), R ３R represents a group that is bonded to a silicon atom and independently represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having an epoxy group, (meth)acryloyl group, mercapto group, amino group, ureido group, polyether group, carboxyl group, protected carboxyl group, carboxyl group generating group, imide group, or cyano group, and is bonded to a silicon atom by a Si-C bond, or a combination of these groups. ４ b represents a group or atom bonded to a silicon atom, independently representing an alkoxy group, an acyloxy group, a hydroxyl group, or a halogen atom, or a combination thereof; Y represents a group or atom bonded to a silicon atom, representing an alkylene group, an NH group, or an oxygen atom; b represents an integer from 1 to 3; and c represents an integer of 0 or 1.

[0038] In the above formula, examples of alkyl groups include linear or branched alkyl groups having 1 to 18 carbon atoms, and cyclic alkyl groups having 3 to 10 carbon atoms. Examples include, but are not limited to, methyl groups, ethyl groups, linear, branched, or cyclic propyl groups, butyl groups, pentyl groups, hexyl groups, heptyl groups, octyl groups, nonyl groups, and decyl groups.

[0039] The above-mentioned halogenated alkyl group is an alkyl group substituted with one or more halogen atoms. Specific examples of such alkyl groups include those described above, namely linear or branched alkyl groups having 1 to 18 carbon atoms, and cyclic alkyl groups having 3 to 10 carbon atoms. Examples of the halogen atoms include fluorine atoms (for example, as a trifluoropropyl group), chlorine atoms, bromine atoms, iodine atoms, and the like.

[0040] Examples of the above-mentioned alkenyl groups include alkenyl groups having 2 to 10 carbon atoms, which may be linear, branched, or cyclic, and the position of the double bond in the alkenyl group is not particularly limited. Examples include, but are not limited to, ethenyl groups (vinyl groups), linear, branched, or cyclic propenyl groups, butenyl groups, pentenyl groups, and hexenyl groups.

[0041] The above-mentioned aryl group may include, for example, an aryl group having 6 to 30 carbon atoms, such as a phenyl group, a 1-naphthyl group, a 2-naphthyl group, a 1-anthryl group, a 2-anthryl group, a 9-anthryl group, a 1-pyrenyl group, a 2-pyrenyl group, and so on.

[0042] Examples of organic groups having the epoxy group mentioned above include glycidoxymethyl group, glycidoxyethyl group, glycidoxypropyl group, glycidoxybutyl group, and 2-(3,4-epoxycyclohexyl)ethyl group. The (meth)acryloyl group mentioned above refers to both the acryloyl group and the methacryloyl group. Examples of organic groups having the (meth)acryloyl group include methacryloyloxymethyl group, acryloyloxymethyl group, methacryloyloxyethyl group, acryloyloxyethyl group, 3-methacryloyloxypropyl group, and 3-acryloyloxypropyl group. Note that methacryloyloxy group and acryloyloxy group are also called methacryloxy group and acryloxy group. Examples of organic groups having the mercapto group mentioned above include ethyl mercapto group, 3-mercaptopropyl group, butyl mercapto group, hexyl mercapto group, octyl mercapto group, and mercaptophenyl group. Examples of organic groups having the above-mentioned amino group include aminomethyl group, 2-aminoethyl group, 3-aminopropyl group, N-2-(aminoethyl)-3-aminopropyl group, N-(1,3-dimethyl-butylidene)aminopropyl group, N-phenyl-3-aminopropyl group, N-(vinylbenzyl)-2-aminoethyl-3-aminopropyl group, dimethylaminoethyl group, and dimethylaminopropyl group. Examples of organic groups having the above-mentioned carboxyl group include carboxymethyl group, carboxyethyl group, carboxypropyl group, and carboxybutyl group. Furthermore, the above-mentioned protected carboxyl group refers to a carboxyl group protected by a protecting group used in ordinary organic synthesis reactions. Furthermore, the above-mentioned carboxyl group generating group refers to a group in which the carboxyl group is esterified or amidated by alcohols, amines, etc.Specific examples of silane compounds containing organic groups having a protected carboxyl group and a carboxyl group generating group include silane coupling agents having a carboxylic acid ester structure. In the silane coupling agent described above, the carboxylic acid ester portion and the alkoxysilyl group may be linked by an alkylene group, or by an alkylene group containing a heteroatom (nitrogen atom, oxygen atom).The silane coupling agent can be used as an amino acid generator because, if the carboxylic acid ester portion undergoes hydrolysis to become a carboxylic acid and contains a nitrogen atom (heteroatom), hydrolysis will result in the formation of an amino acid due to the presence of a carboxyl group and an amino group. For example, the product shown in formula (1-1), manufactured by Shin-Etsu Chemical Co., Ltd., trade name X-88-475, can be used. Examples of organic groups having the above imide group include the N-succinimidyl group. Examples of organic groups having the above cyano group include the cyanoethyl group and the 3-cyanopropyl group.

[0043] The alkoxy group mentioned above may include, but is not limited to, alkoxy groups having 1 to 10 carbon atoms, such as methoxy, ethoxy, propoxy, and isopropoxy groups.

[0044] The above-mentioned acyloxy group is a group derived by removing a hydrogen atom from the carboxyl group (-COOH) of a carboxylic acid compound, and specific examples include acyloxy groups having 2 to 10 carbon atoms.

[0045] Examples of the halogen atoms mentioned above include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

[0046] Furthermore, examples of the alkylene group mentioned above include alkylene groups derived from the alkyl groups described above. Specific examples include, but are not limited to, linear, branched, or cyclic alkylene groups having 1 to 10 carbon atoms, such as methylene, ethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, heptamethylene, octamethylene, nonamethylene, and decamethylene groups.

[0047] As a specific example of a silane compound represented by formula (1), for example, a silane compound represented by the following formula (3) can be given.

[0048] In the above formula (3), R ５R represents a group that bonds to a silicon atom and independently represents an alkyl group having 1 to 3 carbon atoms, an aryl group having 6 to 30 carbon atoms, or an organic group having a (meth)acryloyl group, an alkenyl group, or a carboxyl group generating group and is bonded to a silicon atom by a Si-C bond, or a combination of these groups. ６ is a group or atom bonded to a silicon atom, representing either an independent alkoxy group having 1 to 3 carbon atoms, or a combination thereof, where d represents an integer from 1 to 3. Specific examples of these groups are those listed above, and examples of alkyl groups having 1 to 3 carbon atoms include the alkyl groups with 1 to 3 carbon atoms mentioned above.

[0049] Furthermore, as a specific example of a silane compound represented by formula (1), for example, a silane compound represented by the following formula (4) can be given.

[0050] In the above formula (4), R ７ and R ８ R represents a group that is bonded to a silicon atom, each independently representing an alkyl group having 1 to 3 carbon atoms, an aryl group having 6 to 10 carbon atoms, or an organic group having a (meth)acryloyl group and bonded to a silicon atom by a Si-C bond. ９ This refers to a group or atom bonded to a silicon atom, which independently represents an alkoxy group having 1 to 3 carbon atoms, or a combination thereof. Specific examples of these groups are those listed above. As for alkyl groups having 1 to 3 carbon atoms and aryl groups having 6 to 10 carbon atoms, examples of alkyl groups having 1 to 3 carbon atoms and aryl groups having 6 to 10 carbon atoms can be given in the aforementioned examples of alkyl groups and aryl groups.

[0051] Furthermore, specific examples of silane compounds represented by formulas (1) and (2) above include compounds that can form a trimethylsilyl group on the surface of silica particles. Examples of such compounds include those represented by the following formulas (1-2), (2-1), and (2-2). In the above formula (1-2), R １２ The group is an alkoxy group, such as a methoxy group or an ethoxy group. The silane compounds represented by formulas (1-2), (2-1), and (2-2) above can be silane compounds manufactured by Shin-Etsu Chemical Co., Ltd.

[0052] The (A) aluminum atom-containing hollow silica particles according to the present invention may be particles in which at least a portion of their surface is coated with the silane compound of component (D). In the present invention, "coated with a silane compound" refers to a state in which the surface of the silica particle is coated with a silane compound, and also includes a state in which the silane compound is bonded to the surface of the silica particle. "A state in which the surface of the silica particle is coated with a silane compound" means that the silane compound coats at least a portion of the surface of the silica particle, that is, it includes a state in which the silane compound covers a portion of the surface of the silica particle, and a state in which the silane compound covers the entire surface of the silica particle. This state does not depend on whether or not the silane compound is bonded to the surface of the silica particle. Furthermore, "a state in which the silane compound is bonded to the surface of the silica particle" means that the silane compound is bonded to at least a portion of the surface of the silica particle, that is, it includes a state in which the silane compound is bonded to a portion of the surface of the silica particle, a state in which the silane compound is bonded to a portion of the surface of the silica particle and covers at least a portion of the surface, and a state in which the silane compound is bonded to the entire surface of the silica particle and covers the entire surface. In other words, the silane compound of component (D) can function as a surface modifier for the aluminum atom-containing hollow silica particles (A).

[0053] As mentioned above, the alcohol of component (B) can be transesterified with alkoxy groups and the like that may be present in the silane compound (D). Therefore, when (A) aluminum atom-containing hollow silica particles are coated with the silane compound of component (D), the hydroxyl group of the alcohol of (B) described above can be transesterified with alkoxy groups and the like that may be present in the silane compound (D) near the surface of the hollow silica particles, thereby introducing ester groups derived from the alcohol of (B) to the silane compound near the surface of (A) particles, which can contribute to improving the dispersion stability in the organic solvent (C).

[0054] Hollow silica particles, in which at least a portion is coated with a silane compound, can be obtained, for example, by adding a silane compound to a sol containing hollow silica particles, and then heating and stirring at 10 to 95°C for about 0.1 to 20 hours. At this time, the amount of silane compound added to the hollow silica particles in the sol containing hollow silica particles can be, for example, a ratio of silane compound / hollow silica particles = 0.1 to 10.0 by mass ratio. In one embodiment, the hollow silica particles (A) according to the present invention have a surface area of ​​1 nm ２ The particles can be composed of 0.1 to 10 particles per unit, with their surfaces coated with the silane compound of component (D), or particles in which the silane compound of component (D) is bonded to the surface. That is, the amount of coating (surface treatment) of the (A) hollow silica particles with the silane compound of component (D) is the amount of the surface of the hollow silica particles up to 1 nm. ２ The amount can be such that the number of silicon atoms in the silane compound is, for example, about 0.1 to 10 or about 0.1 to 6.

[0055] The treatment (reaction) of silica particles with the above-mentioned silane compound proceeds through the reaction between the silanol groups generated by the hydrolysis of the silane compound and the hydroxyl groups (silanol groups) on the surface of the silica particles. The presence of water is necessary for this hydrolysis, but if the silica sol is a sol in an aqueous solvent, the aqueous solvent can play this role, and if it is an organic solvent sol obtained by solvent substitution of the aqueous medium with an organic solvent, the water remaining in the organic solvent can play this role. For example, water present in the organic solvent at a concentration of 0.01 to 1% by mass can be used for hydrolysis.

[0056] Furthermore, hydrolysis can be carried out with or without a catalyst. If the silica particle surface is on the acidic side (pH less than 7), hydrolysis can be carried out without a catalyst. When a catalyst is used, examples include metal chelate compounds, organic acids (acetic acid, oxalic acid, lactic acid, etc.), inorganic acids (hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, etc.), organic bases (heterocyclic amines, quaternary ammonium salts, sodium methoxide, sodium ethoxide, potassium methoxide, potassium ethoxide, etc.), and inorganic bases (ammonia, sodium hydroxide, potassium hydroxide, etc.).

[0057] [Component (E): Anion] The hollow silica organosol according to the present invention may further contain an anion as component (E).

[0058] The anion of component (E) can be included in an amount of, for example, 0.1 to 500 ppm relative to the total mass of the hollow silica organosol, thereby improving the dispersion stability of the (A) aluminum atom-containing hollow silica particles in the sol. The content of the anion of component (E) can be 6 to 500 ppm, 6 to 300 ppm, 10 to 400 ppm, or 30 to 300 ppm. By setting the content of the anion of component (E) to 0.1 to 500 ppm, stable dispersion can be maintained while reducing the viscosity of the hollow silica organosol.

[0059] The above-mentioned anion is specifically one or more anions selected from inorganic anions, for example, inorganic anions selected from the group consisting of sulfate ions, nitrate ions, carbonate ions, chloride ions, and phosphate ions. In particular, it is preferable that the (E) component contains a sulfate ion. These anions can be added to the sol in the form of acids such as sulfuric acid, nitric acid, or acetic acid, or in the form of salts such as sodium chloride.

[0060] [Component (F): Polymerization inhibitor] The hollow silica organosol according to the present invention may further contain a polymerization inhibitor as component (F) if necessary. Examples of polymerization inhibitors include 2,6-diisobutylphenol, 3,5-di-tert-butylphenol, 2,6-di-tert-butyl-p-cresol, 3,5-di-tert-butyl-p-cresol, 4-methoxyphenol (p-methoxyphenol), hydroquinone, hydroquinone monomethyl ether, pyrogallol, naphthylamine, benzoquinone, tert-butylcatechol, cuprous chloride, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 4,4'-thiobis(3-methyl-6-tert-butylphenol), N-nitrosophenylhydroxyamine salts (ammonium salts, cerium salts, etc.), nitrosophenylhydroxyamine aluminum salts, and diphenylnitrosamines. The content (amount added) of polymerization inhibitor in the hollow silica organosol can be, for example, 10 to 10,000 ppm, 10 to 1,000 ppm, 10 to 500 ppm, 10 to 300 ppm, 10 to 1,000 ppm, 10 to 500 ppm, or 50 to 1,000 ppm by mass. There may be only one type of polymerization inhibitor, or two or more types. If there are two or more types, it is preferable that the total amount is within the above range. By setting the content of polymerization inhibitor to 10 ppm or more, the storage stability of the hollow silica organosol having polymerizable functional groups can be improved. Furthermore, by setting the content of polymerization inhibitor to 10,000 ppm or less, the reactivity of the resin composition containing the hollow silica organosol having polymerizable functional groups and an organic resin material or a polysiloxane resin can be improved.

[0061] [Component (G): Sulfate Ester] The hollow silica organosol according to the present invention may also contain a sulfate ester as component (G). Examples of the sulfate ester include butyl sulfate, propyl sulfate, and hexyl sulfate. The content of the sulfate ester in the hollow silica organosol can be, for example, about 1 to 100 ppm by mass. There may be only one type of sulfate ester, or there may be two or more types. If there are two or more types, it is preferable that the total amount is within the above range. By setting the content of the sulfate ester to 1 to 100 ppm, the sulfate ester can be adsorbed onto the cation sites (sites where Al atoms exist) on the surface of the hollow silica particles contained in the hollow silica organosol, thereby increasing the stability of the hollow silica particle surface and improving the dispersion stability of the hollow silica particles in the hollow silica organosol.

[0062] The hollow silica organosol according to the present invention can have its pH adjusted from acidic to alkaline. The pH can be set to less than 7 on the acidic side and 7 or more and 13 or less on the alkaline side. Adjustment to acidity is performed by adding an inorganic acid or organic acid, and adjustment to alkalinity is performed by adding an inorganic base or organic base. The pH of the hollow silica organosol according to the present invention can be measured using a solution obtained by mixing pure water, methanol, and the organosol in a mass ratio of 1:1:1. Generally, the pH of silica sols is measured in the form of an organic solvent sol that can be mixed with water. In the case of aqueous sols, it can be measured as is, and in the case of hydrophilic organic solvent sols such as methanol, it can be measured using a solution obtained by mixing pure water and the sol in a mass ratio of 1:1. Furthermore, when a hydrophobic organic solvent such as methyl ethyl ketone sol is used as the dispersion medium, the pH can be measured using a solution obtained by mixing pure water, methanol, and the hydrophobic organic solvent sol such as methyl ethyl ketone in a mass ratio of 1:1:1.

[0063] Also, the viscosity (20 °C) of the hollow silica organosol according to the present invention can be set, for example, in the range of 1.0 to 100,000.0 mPa·s. The viscosity of the hollow silica organosol can be appropriately adjusted with the above-described (C) organic solvent. For example, when the (C) organic solvent is an organic solvent having a viscosity (20 °C) of 1.0 to 2.0 mPa·s, the viscosity (20 °C) of the hollow silica organosol having a silica particle concentration of 20% by mass can be set in the range of 1.0 to 10.0 mPa·s.

[0064] The hollow silica organosol according to the present invention may contain other particles other than the hollow silica particles, for example, solid silica particles or inorganic oxide particles other than Si, as long as the effects of the present invention are not impaired. Examples of the inorganic oxide particles other than Si include colloidal oxides of one or more atoms selected from the group consisting of Al, Ti, Zr, Fe, Cu, Zn, Li, Na, K, Mg, Ca, Cs, Sr, Ba, B, Ga, Y, Nb, Mo, In, Sn, Sb, Ta, W, Ge, Pb, P, As, Rb, Bi, and Ce, colloidal composite oxides of two or more of these atoms, or colloidal mixed oxides. As the form of the oxide of the atom, for example, Al ２ O ３ , TiO ２ , Fe ２ O ３ , CuO, ZnO, Y ２ O ３ , ZrO ２ , Nb ２ O ５ , MoO ３ , In ２ O ３ , SnO ２ , Sb ２ O ５ , Ta​​​​​​​​​​​Examples thereof include the following. These inorganic oxide particles can take any of the forms of a solid structure, a hollow structure, and a porous structure. The particle diameters of the above solid silica particles and inorganic oxide particles are not particularly limited. For example, the average primary particle diameter by TEM observation can be 3 nm to 200 nm, or 3 nm to 100 nm, or 3 nm to 50 nm, or 3 nm to 30 nm, or 3 nm to 20 nm, or more than 3 nm and less than 20 nm, and can be, for example, in the range of 4 to 15 nm, or 5 to 10 nm. Also, the specific surface area value of the solid silica particles and inorganic oxide particles used in combination is not particularly limited. For example, it can be 18 m ２ / g to 1,000 m ２ / g, or 50 to 1,000 m ２ / g, or 80 m ２ / g to 1,000 m ２ / g, or 100 m ２ / g to 1,000 m ２ / g, or 200 m ２ / g to l,000 m ２ / g, or 250 m ２ / g to 1,000 m ２ / g, or 300 m ２ / g to 800 m ２ / g. When solid silica particles and inorganic oxide particles are used in combination, the addition amount can be 100 to 0.01% by mass, or 80 to 0.01% by mass, or 60 to 0.01% by mass, or 40 to 0.01% by mass, or 30 to 0.01% by mass, or 20 to 0.01% by mass, or 10 to 0.01% by mass, or 5 to 0.01% by mass with respect to the addition amount of the hollow silica particles.

[0065] [Method for Producing Hollow Silica Organosol] The hollow silica organosol of the present invention is produced by adding the alcohol of component (B) to a methanol-dispersed silica sol containing aluminum atom-containing hollow silica particles, and then replacing the dispersion medium of the methanol-dispersed silica sol with the organic solvent of component (C) by ultrafiltration, heating under reduced pressure, or heating under normal pressure. The methanol-dispersed silica sol containing aluminum atom-containing hollow silica particles can be obtained, for example, by replacing the dispersion medium of an aqueous-dispersed silica sol containing aluminum atom-containing hollow silica particles, which is produced by the following steps.

[0066] <Aqueous Dispersible Silica Sol> The aqueous dispersion silica sol containing the aluminum atom-containing hollow silica particles can be manufactured by the following steps: (i) Step: Prepare an aqueous sol containing hollow silica particles; (ii) Add an aluminum compound to the aqueous sol prepared in step (i) per gram of hollow silica particles, Al ２ O ３ The process involves adding an aluminum atom-containing hollow silica aqueous dispersion silica sol in a proportion of 0.0001 to 0.5 g, holding it at 40 to 260°C for 0.1 to 24 hours.

[0067] (i) The hollow silica particles that make up the aqueous sol containing hollow silica particles prepared in step (i) (also referred to as hollow silica aqueous sol) have an outer shell composed of silica and a space inside the outer shell. The "hollow silica particles" prepared in step (i) are, so to speak, raw material hollow silica particles and are distinguished from the aluminum atom-containing hollow silica particles mentioned above, that is, they are hollow silica particles that do not contain aluminum atoms (however, the presence of aluminum atoms at the impurity level is permissible). The raw material hollow silica particles are obtained by forming an outer shell mainly composed of silica on the surface of a part corresponding to a core called a so-called template in an aqueous dispersion medium, and then removing the part corresponding to the core (template). The template can be made using an organic material (e.g., hydrophilic organic resin particles such as polyethylene glycol, polystyrene, or polyester) or an inorganic material (e.g., hydrophilic inorganic compound particles such as calcium carbonate or sodium aluminate). The aqueous sol containing the raw material hollow silica particles prepared in step (i) can be a non-hydrothermally treated hollow silica aqueous sol, a hydrothermally treated hollow silica aqueous sol, or a mixture thereof. The non-hydrothermally treated hollow silica aqueous sol is an aqueous sol of silica particles treated in an aqueous medium via a heating temperature of less than 100°C, for example, 20°C to less than 100°C, 40°C to less than 100°C, or 50°C to less than 100°C. The hydrothermally treated silica aqueous sol is an aqueous sol of silica particles treated in an aqueous medium via a heating temperature of 100°C to 240°C, or 110°C to 240°C. The above raw material hollow silica aqueous sol (non-hydrothermally treated hollow silica aqueous sol, hydrothermally treated hollow silica aqueous sol, or a mixture thereof) may, in step (ii) described below, be configured such that the raw material hollow silica particles in the aqueous sol contain aluminum atoms, specifically, an aluminosilicate site is formed on the outer shell of the hollow silica particles. Since the aluminosilicate site may hold alkali metals, the measurement by the dissolution method using the hydrofluoric acid aqueous solution described above indicates that aluminum atoms are present throughout the hollow silica particles that are the raw material. ２ O ３ Converted (relative to the mass of hollow silica particles): 120–50,000 ppm / SiO ２The raw material, a hollow silica aqueous sol, can be selected so that it exists in a certain proportion.

[0068] Step (ii) is a step in which an aluminum compound is added to the hollow silica aqueous sol (raw material) prepared in step (i) above, and heated and held to obtain an aluminum atom-containing hollow silica aqueous dispersion silica sol. Through this step, the aluminum compound is applied to the outside of the hollow silica particles of the raw material (so to speak, impregnation), causing aluminum atoms to be present on the surface of the hollow silica particles, that is, aluminosilicate sites are formed on at least the surface of the particles.

[0069] (Raw material) When an aluminum compound is applied (impregnated) from the outside after the formation of hollow silica particles, there are two methods: one in which the hollow silica particles are pre-treated with hydrothermal energy to improve the density of the outer shell, and then the aluminum compound is impregnated into the hollow silica particles by heat treatment; and another in which the aluminum compound is impregnated into hollow silica particles that have not been pre-treated with hydrothermal energy by heat treatment. In both the former and latter methods, the aluminum atoms (Al) present throughout the hollow silica particles are measured by the dissolution method using the hydrofluoric acid aqueous solution as described above. ２ O ３ It is preferable to impregnate the aluminum compound such that the amount of (converted) present is in the specific proportion mentioned above.

[0070] (ii) The aluminum compound used in the process is Al per gram of hollow silica particles in the hollow silica aqueous sol. ２ O ３The amount that can be added is in the range of 0.0001 to 0.5 g, 0.001 to 0.1 g, or 0.001 to 0.05 g in conversion. The heating temperature in step (ii) is 40 to 260°C, 50 to 260°C, or 60 to 240°C. The heating temperature can be 40 to less than 100°C, 50 to less than 100°C, or 60 to less than 100°C in the case of non-hydrothermal treatment, and 100 to 260°C, or 150 to 240°C in the case of hydrothermal treatment. The heating time in step (ii) can be in the range of 0.1 to 48 hours, 0.1 to 24 hours, 0.1 to 10 hours, or 1 to 10 hours. Furthermore, the impregnation of the aluminum compound into the hollow silica particles and the formation of aluminosilicate to achieve the desired amount of aluminum atoms depends on the processing temperature in step (ii), and it is essential to perform the heat treatment within the above temperature range.

[0071] Specific examples of the above-mentioned aluminum compounds include at least one aluminum compound selected from the group consisting of aluminates, aluminum alkoxides, and their hydrolysates. Examples of aluminates include sodium aluminate, potassium aluminate, calcium aluminate, magnesium aluminate, ammonium aluminate, and aluminate amine salts. Examples of aluminum alkoxides include aluminum isopropoxide and aluminum butoxide. Among these, aluminates such as sodium aluminate can be preferably used.

[0072] The above aluminum compound can be added to the hollow silica aqueous sol in solid or aqueous form, and it is preferable to add it in aqueous form. When the above aluminum compound is added to the hollow silica aqueous sol in aqueous form, the concentration of the aluminum compound in the aqueous solution can be in the range of 0.01 to 20% by mass, 0.1 to 10% by mass, or 0.5 to 5% by mass. The addition of the above aluminum compound can be carried out under stirring of the hollow silica aqueous sol. This addition can be completed before heating, added before heating and completed during heating, or added throughout the entire heating time.

[0073] The aqueous silica sol containing the above-mentioned aluminum atom-containing hollow silica particles may undergo a step of adding sulfuric acid to the aqueous sol and holding it at a predetermined temperature (a so-called leaching step) in order to dissolve aluminum atom-containing components that were not doped onto the surface or inside of the hollow silica particles, as well as metal impurities contained in the particles, into the liquid. This step may be carried out, for example, by adding sulfuric acid at a ratio of about 0.1 ppm to 500 ppm relative to the mass of particles in the sol, and then holding it at 5 to 100°C for 0.1 to 48 hours. This step allows sulfate ions (anions) derived from the added sulfuric acid to be present in the system (sol). If necessary, the aqueous sol containing the aluminum atom-containing hollow silica particles may also include a step of contacting it with a cation exchange resin before or after the sulfuric acid addition and holding at the predetermined temperature in order to remove impurity base components such as metal-containing components remaining in the system, metal-containing components dissolved into the liquid by the addition of sulfuric acid, and counterionic components that are dissolved by the added sulfuric acid and affect the stability of the sol. The step of contacting this aqueous sol with the cation exchange resin may be repeated multiple times.

[0074] <Methanol-Dispersed Silica Sol> The aqueous-dispersed silica sol containing aluminum atom-containing hollow silica particles obtained in this way can be further processed by replacing the dispersion medium with methanol through ultrafiltration, heating under reduced pressure, or heating under normal pressure, as described above, to obtain a methanol-dispersed silica sol containing aluminum atom-containing hollow silica particles. The reduced pressure conditions can be around 10 to 600 Torr, and the heating conditions can be around 30 to 200°C. It is possible that some water may remain in the solvent conversion process from aqueous sol to methanol sol. For example, the residual water content in the methanol-dispersed silica sol of aluminum atom-containing hollow silica particles can be around 0.1 to 3.0% by mass, or 0.1 to 1.0% by mass.

[0075] Furthermore, the obtained methanol-dispersed silica sol may include a step of contacting it with a cation exchange resin, and this step of contacting it with the cation exchange resin may be repeated multiple times. By contacting the methanol-dispersed silica sol with a cation exchange resin, the amount of metal-containing components remaining in the system is reduced, thereby suppressing the aggregation of aluminum atom-containing hollow silica particles in the sol in which the dispersion medium is replaced with (C) organic solvent, as described later, and improving dispersibility.

[0076] <Hollow Silica Organosol (Organic Organic Dispersed Silica Sol)> As described above, the hollow silica organosol of the present invention is manufactured by adding the alcohol of component (B) to a methanol-dispersed silica sol containing aluminum atom-containing hollow silica particles, and then replacing the dispersion medium of the methanol-dispersed silica sol with the organic solvent of component (C) by ultrafiltration, heating under reduced pressure, or heating under normal pressure. The reduced pressure conditions can be approximately 10 to 600 Torr, and the heating conditions can be approximately 30 to 200°C. If the hollow silica organosol of the present invention contains a polymerization inhibitor (F), it can be added to the system before, during, or after the step of replacing with the organic solvent.

[0077] Furthermore, the silane compound (D) contained in the hollow silica organosol according to the present invention may be added to the system after the step of substituting the methanol-dispersed silica sol with the organic solvent of component (C), and preferably the surface of the hollow silica particles may be treated with the silane compound. In one embodiment, after the step of substituting component (C) with the organic solvent, the process may include adding at least one silane compound selected from the group consisting of compounds represented by formulas (1) and (2) to the sol containing aluminum atom-containing hollow silica particles, and heating and stirring at 10°C to 95°C for 0.1 hours to 20 hours. This step of adding the silane compound and heating and stirring may be performed multiple times. The silane compound (D) may also be added at the earlier stage of the water-dispersed silica sol or methanol-dispersed silica sol, as long as the effects of the present invention are not impaired. In other words, the (D) surface treatment step of hollow silica particles with a silane compound can also be carried out at the stage of water-dispersed silica sol or methanol-dispersed silica sol. In this case as well, the aforementioned silane compound is added to the sol, and then heating and stirring is performed at 10°C to 95°C for about 0.1 to 20 hours.

[0078] The method for producing hollow silica organosols of the present invention is not particularly limited except that it includes the essential step of replacing the dispersion medium of methanol-dispersed silica sol with (C) organic solvent by ultrafiltration, heating under reduced pressure, or heating under normal pressure as described above. For example, the heating and stirring step after adding the (D) silane compound (a step of treating the surface of aluminum atom-containing hollow silica particles with the silane compound) is optional, and the replacement step with (C) organic solvent and the addition of the silane compound and heating and stirring step can be performed in any order and in multiple combinations. For example, after the addition of the (D) silane compound and heating and stirring step, the replacement step with (C) organic solvent by ultrafiltration / heating under reduced pressure / heating under normal pressure as described above may be performed, and the combination / order / number of times these steps are not limited. Furthermore, when other particles besides the hollow silica particles mentioned above, such as solid silica particles or inorganic oxide particles other than Si, are used in combination, the timing of their addition is not particularly limited. However, as an example, the particles can be added before or after the (D) silane compound addition and heating / stirring step, or simultaneously with the addition of the silane compound. Additionally, heating and stirring can be optionally carried out at 10°C to 95°C for approximately 0.1 to 20 hours.

[0079] Furthermore, the hollow silica organosol of the present invention may contain an anion which is component (E). In this case, in order to adjust the content of component (E), the organosol may be brought into contact with an anion exchange resin, and then an anion component (for example, sulfuric acid, etc.) may be added again so that the anion content in the sol becomes a predetermined amount. This step of contacting with the anion exchange resin can be carried out in any order before or after the (C) organic solvent substitution step or the silane compound addition and heating stirring step.

[0080] Furthermore, after the step of replacing the dispersion medium of the methanol-dispersed silica sol with the organic solvent of component (C), a step of replacing the organic solvent, which is the dispersion medium, with an organic resin material or polysiloxane resin described later may be performed. In the above step, for example, after obtaining the hollow silica organosol according to the present invention, the organic resin material or polysiloxane resin described later may be added and mixed to the sol, and the organic solvent may be removed or reduced by distillation by heating under reduced pressure as necessary, and the organic solvent may remain after this operation. Alternatively, the organic resin material or polysiloxane resin described later may be dissolved in the organic solvent of component (C) in advance, and this may be added and mixed to the hollow silica organosol, and the organic solvent may be removed or reduced by distillation by heating under reduced pressure as necessary (the organic solvent may remain after this operation). Also, when adding the organic resin material or polysiloxane resin described later, the polymerization inhibitor (such as 4-methoxyphenol) described above may be incorporated into the sol.

[0081] [Resin Composition] The present invention also covers resin compositions comprising the above-mentioned hollow silica organosol and an organic resin material or polysiloxane resin. In the resin composition, the aluminum atom-containing hollow silica particles, which are component (A), can be, for example, 1% to 90% by mass of the total solid content (100% by mass), and the organic resin material or polysiloxane resin can be, for example, 10% to 99% by mass. The solid content in the resin composition refers to all components other than the solvent, and can be calculated from the residue obtained by heating the resin composition at a temperature of about 200 to 300°C to remove the solvent. The resin composition according to the present invention may also contain the above-mentioned (F) polymerization inhibitor. In addition, the present invention also covers resin compositions comprising aluminum atom-containing silica particles obtained by removing the (C) organic solvent, which is the dispersion medium, from the organosol and the above-mentioned organic resin material or polysiloxane resin.

[0082] As the organic resin material, for example, thermosetting or photocurable resin materials (curable resins) can be selected, and examples include reactive monomers and polymers. Examples include, but are not limited to, styrene resins, epoxy resins, thioepoxy resins, novolac resins, cyanate resins, phenolic resins, acrylic resins, maleimide resins, polyester resins, urethane resins, polyurea resins, polyimide resins, polyamide resins, polyamic acid resins, polyhydroxyimide resins, polybenzoxazole resins, polybenzimidazole resins, polybenzothiazole resins, polyhydroxyamide resins, polyhydroxyazomethine resins, polyether resins, polybenzoxazine resins, polytetrafluoroethylene resins, cycloolefin polymer resins, unsaturated polyester resins, vinyl triazine resins, polyphenylene sulfide resins, crosslinkable polyphenylene oxide resins, curable polyphenylene ether resins, and condensation resins.

[0083] Examples of the above acrylic resins include polymethyl methacrylate, polyacrylic acid esters obtained by copolymerizing methyl methacrylate and styrene, sodium polyacrylate obtained by copolymerizing sodium acrylate, methyl acrylate and vinyl acetate, polyacrylonitrile obtained by copolymerizing acrylonitrile, methyl acrylate and methyl methacrylate, and polyacrylamide obtained by hydrolyzing acrylonitrile. In addition, polyfunctional (meth)acrylates and polyfunctional urethane (meth)acrylates having two, three, four, or more functional groups in the molecule can also be mentioned as the above acrylic resins. Examples include neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and dipentaerythritol hexa(meth)acrylate.

[0084] Furthermore, the resin composition of the present invention may optionally contain various curing agents, such as amine-based curing agents, acid anhydride-based curing agents, radical-generating curing agents (thermal radical generators, photoradical generators), acid-generating curing agents (thermal acid generators or photoacid generators), and base generators (thermal base generators, photobase generators). In addition, the resin composition of the present invention may optionally contain conventional additives. Examples of such additives include surfactants (leveling agents), pigments, colorants, thickeners, adhesion promoters, sensitizers, defoamers, coatability improvers, lubricants, stabilizers (antioxidants, heat stabilizers, light-resistant stabilizers, etc.), plasticizers, dissolution accelerators, fillers, antistatic agents, and development inhibitors (diazonaphthoquinone, etc.). These additives may be used individually or in combination of two or more. The resin composition can be cured, for example, by coating it onto a substrate or filling it into a predetermined mold and then heating, irradiating with light, or a combination thereof. Furthermore, the aforementioned resin composition and cured products containing hollow silica organosols are also subject to the present invention.

[0085] For example, one embodiment of the resin composition is one in which the content of hollow silica particles of component (A) is 50 to 200 phr relative to the total mass of the resin composition, and further comprises a polymerization initiator and a leveling agent. As the polymerization initiator, the component listed as component (F) above may be used, and as the leveling agent (surfactant), anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, and silicone-based surfactants may be used. The amount of polymerization initiator can be in the range of 1 to 20 parts (1 to 20 phr) per 100 parts by mass of resin in the resin composition. The amount of leveling agent (surfactant) can be in the range of 10 to 2000 ppm relative to the total mass of the resin composition.

[0086] In one embodiment, a hollow silica organosol can be provided in which an alcohol having a boiling point of 80°C to 200°C and containing an ether bond is used instead of component (B). Specifically, for example, a hollow silica organosol is disclosed that contains (A) component: aluminum atom-containing hollow silica particles having an average secondary particle diameter of 20 to 200 nm or 20 to 150 nm as measured by dynamic light scattering, (B2) an alcohol having a boiling point of 80°C to 200°C and containing an ether bond, (C2) an organic solvent other than component (B2) having a relative permittivity of 1 to 20 at 20°C, and (D) component: a silane compound, wherein component (A) is contained in a proportion of 1% to 70% by mass based on the total amount (100% by mass) of the organosol. In this embodiment, components (A) and (D) can be the components described above. Furthermore, (B2) alcohols having a boiling point of 80°C to 200°C and containing an ether linkage include aliphatic alcohols with 1 to 10 carbon atoms containing an ether linkage, such as propylene glycol monomethyl ether and 3-methyl-3-methoxy-1-butanol. Also, amphiphilic alcohols can be given as component (B2). Furthermore, (C2) organic solvents other than component (B2) that have a relative permittivity of 1 to 20 at 20°C include, for example, those selected from the group consisting of ketones, esters, ethers, and hydrocarbons, which have the above-mentioned predetermined relative permittivity and are other than component (B2). Examples of these ketones, esters, ethers, and hydrocarbons are those given in component (C) above.

[0087] [Applicable to] The hollow silica organosol and resin composition containing the organosol according to the present invention are preferably used for semiconductor device materials, semiconductor element materials, semiconductor resist materials, nanoimprint materials, insulating film materials, copper-clad laminate materials, printed circuit board materials, printed board materials, printing ink materials, pigments, paints, encapsulant materials, hard coat materials, 3D printing materials, anti-reflective film materials, automotive parts materials, electronic parts materials, mechanical components, adhesive materials, battery materials, power generation materials, charge-impregnating materials, conductivity-impregnating materials, powder flowability-impregnating materials, cosmetic materials, flexible wiring materials, liquid crystal display materials, organic EL display materials, micro-LED display materials, QD-EL display materials, flexible display materials, antenna materials, optical wiring materials, sensing materials, or thermal insulation materials.

[0088] For example, thermosetting materials and photocuring materials using the resin composition containing the hollow silica organosol of the present invention have characteristics such as transparency and low curing shrinkage, and can be used for coating and bonding electronic components, optical components (anti-reflective coatings), and precision mechanical components. For example, they can be used for bonding optical elements such as lenses in mobile phones and cameras, light-emitting diodes (LEDs), and semiconductor lasers (LDs), liquid crystal panels, biochips, camera lenses and prisms, magnetic components in hard disks of personal computers, pickups in CD and DVD players (the part that captures light information reflected from the disc), speaker cones and coils, motor magnets, circuit boards, electronic components, and internal engine components of automobiles. They can also be used as hard coat materials (coating materials) for surface protection of automobile bodies, lamps and electrical appliances, building materials, plastics, etc. For example, they can be applied to automobile and motorcycle bodies, headlight lenses and mirrors, plastic lenses in eyeglasses, mobile phones, game consoles, optical films, ID cards, etc. For ink materials used to print on metals such as aluminum and plastics, applications include inks for printing on cards such as credit cards and membership cards, switches and keyboards in electrical appliances and office automation equipment, and inkjet printer inks for CDs and DVDs. Furthermore, applications include complex three-dimensional cured products combined with 3D CAD, stereolithography for industrial product model making, and coatings, adhesives, optical waveguides, and thick-film resists for optical fibers. It can also be suitably used as insulating resins for electronic materials such as anti-reflective films, semiconductor encapsulating materials, adhesives for electronic materials, printed circuit board materials, interlayer insulating film materials, and encapsulating materials for power modules, as well as insulating resins used in high-voltage equipment such as generator coils, transformer coils, and gas-insulated switchgear.

[0089] In one embodiment, a coating comprising hollow silica particles of component (A), an alcohol of component (B), a silane compound of component (D), and the organic resin material can be described, wherein the coating has a refractive index of 1.1 to 1.45 and a haze of 0.01% to 0.08% when the film thickness is 100 nm. A film with a refractive index of 1.5 or less can be evaluated as a low refractive index film, and the above coating can have the characteristics of a low refractive index and a low haze value (high transparency). In the above coating, the alcohol of component (B) is present on the surface of the hollow silica particles of component (A), for example, on a surface area of ​​1 nm of the particles. ２ The particles can exist in a configuration where they are bonded at a ratio of approximately 0.01 to 1.0 particles per unit. The coating may also contain the organic solvent of component (C). The coating can be formed by applying the aforementioned resin composition to a substrate and then heating (firing) the resulting coating film. During coating formation (i.e., the step of removing the organic solvent of component (C) from the coating film by firing while promoting the polymerization of the resin contained in the resin composition), including the alcohol of component (B) in the film improves the dispersibility of the hollow silica particles of component (A) in the resulting coating, and consequently, it is expected that a coating with excellent transparency (for example, a haze value of 0.01 to 0.08%) can be obtained.

[0090] [Composite materials and methods for manufacturing the same] This specification also discloses methods for manufacturing composite materials. This manufacturing method comprises the steps of: (A) a methanol-dispersed silica sol containing aluminum atom-containing hollow silica particles, (B) an alcohol having a boiling point of 80°C to 200°C and not having ether bonds, and then replacing the mixture with (C) an organic solvent by ultrafiltration, heating under reduced pressure, or heating under normal pressure; after the (C) organic solvent replacement step, adding at least one (D) silane compound selected from the group consisting of compounds represented by formulas (1) and (2) to the sol containing aluminum atom-containing silica particles, and heating and stirring at 10°C to 95°C for 0.1 to 20 hours; after the silane compound addition and heating and stirring step, further replacing with the (C) organic solvent; and after the (C) organic solvent replacement step, replacing the dispersion medium with an organic resin material or a polysiloxane resin, wherein the (A) aluminum atom-containing hollow silica particles have an average secondary particle diameter of 20 to 200 nm or 20 to 150 nm as measured by dynamic light scattering. The present invention relates to a manufacturing method wherein the (C) organic solvent has a relative permittivity of 1 to 20 at 20°C and is an organic solvent other than component (B). The steps of substituting components (A) to (D), organic resin materials or polysiloxane resins, and (C) organic solvent, as well as the step of adding and stirring the (D) silane compound, in the above steps can be carried out using the same components as those used in the hollow silica organosol described above, and in the same steps as those used in its manufacturing method. Furthermore, the composite material obtained by this manufacturing method may contain the (C) organic solvent.

[0091] The present invention also discloses a composite material comprising (A) hollow silica particles containing aluminum atoms having an average secondary particle diameter of 20 to 200 nm or 20 to 150 nm as determined by dynamic light scattering, (B) an alcohol having a boiling point of 80°C to 200°C and not having ether bonds, (D) a silane compound, and an organic resin material or a polysiloxane resin. The composite material may also be configured to include the organic solvent of component (C) above.

[0092] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0093] The silica aqueous sol, silane compound, polymerization inhibitor, and organic solvent used as raw materials in the examples, comparative examples, and reference examples are as follows.

[0094] (Raw material: hollow silica aqueous sol) ・Water-dispersed silica sol A: Product name HKT-A20-40D-3 (manufactured by Ningbo Dilato), water-dispersed silica sol of hollow silica particles. Physical properties as determined by the physical property evaluation described later: Average primary particle diameter 38 nm by TEM, outer shell thickness 5 nm, specific surface area 118 m² by BET method ２ / g, refractive index 1.3, average particle diameter by DLS method: 50 nm, amount of aluminum atoms present in the entire hollow silica particle: Al ２ O ３ Converted to 1 ppm / SiO ２ Water-dispersible silica sol B: Product name HKT-A20-70D (manufactured by Ningbo Dilato), water-dispersible silica sol of hollow silica particles. Physical properties as determined by the physical property evaluation described below: Average primary particle diameter 65 nm, outer shell thickness 8 nm, specific surface area 89 m² by BET method. ２ / g, refractive index 1.2, average particle diameter by DLS method: 87 nm, amount of aluminum atoms present in the entire hollow silica particle: Al ２ O ３ Converted to 1 ppm / SiO ２ Water-dispersible silica sol C: Product name HKT-A20-50D (manufactured by Ningbo Dilato), water-dispersible silica sol of hollow silica particles. Physical properties as determined by the physical property evaluation described below: Average primary particle diameter 55 nm, outer shell thickness 7 nm, specific surface area 104 m² by BET method. ２ / g, refractive index 1.2, average particle diameter by DLS method: 69 nm, amount of aluminum atoms present in the entire hollow silica particle: Al ２ O ３ Converted to 1 ppm / SiO ２Water-dispersible silica sol D: Product name HKT-A20-95D (manufactured by Ningbo Dilato), water-dispersible silica sol of hollow silica particles. Physical properties as determined by the physical property evaluation described below: Average primary particle diameter 94 nm by TEM, outer shell thickness 8 nm, specific surface area 79 m² by BET method. ２ / g, refractive index 1.2, average particle diameter by DLS method: 120 nm, amount of aluminum atoms present throughout hollow silica particles: Al ２ O ３ Converted to 1 ppm / SiO ２ Less than (raw material: solid silica aqueous sol) ・Water-dispersed silica sol E: Product name ST-OXS (manufactured by Nissan Chemical Corporation), water-dispersed silica sol of solid silica particles. Values ​​based on the physical property evaluation described below: Average primary particle diameter 5 nm by TEM, specific surface area 496 m² by BET method ２ / g, refractive index 1.4, silica particle concentration 10.4 mass%, pH 2.8, amount of aluminum atoms present in the entire solid silica particle is Al ２ O ３ Converted to 1700 ppm / SiO ２

[0095] (Silane compounds (surface modifiers, silanes manufactured by Shin-Etsu Chemical Co., Ltd.)) ・MPS: 3-methacryloxypropyltrimethoxysilane (trade name KBM-503) ・AcPS: 3-acryloxypropyltrimethoxysilane (trade name KBM-5103) ・PTMS: phenyltrimethoxysilane (trade name KBM-103) (Polymerization inhibitors) ・MEHQ: p-methoxyphenol (manufactured by Kawaguchi Chemical Industry Co., Ltd., trade name: MQ)

[0096] (Organic solvents) ・MeOH: Methanol (manufactured by Kanto Chemical Co., Ltd., Kagoshima Grade 1) ・n-BtOH: n-Butanol (boiling point 117.7°C, manufactured by Kanto Chemical Co., Ltd., special grade) ・n-ProOH: n-Propanol (boiling point 97.2°C, manufactured by Kanto Chemical Co., Ltd., Kagoshima Grade 1) ・n-HxOH: n-Hexanol (boiling point 157.1°C, manufactured by Kanto Chemical Co., Ltd., Kagoshima Special Grade) ・1-DdcOH: 1-Dodecanol (boiling point 259°C, manufactured by Kanto Chemical Co., Ltd., Kagoshima Grade 1) ・MIBK: Methyl isobutyl ketone (dielectric constant at 20°C 13.11, manufactured by Kanto Chemical Co., Ltd., Kagoshima Grade 1) ・EAC: Ethyl acetate (dielectric constant at 20°C 6.02, manufactured by Kanto Chemical Co., Ltd., special grade) - MMB: 3-methyl-3-methoxy-1-butanol (dielectric constant at 20°C 13.3, manufactured by Junsei Chemical Co., Ltd., special grade) - PGMEA: propylene glycol 1-monomethyl ether 2-acetate (dielectric constant at 20°C 8.3, manufactured by Kanto Chemical Co., Ltd., special grade) The boiling point and dielectric constant of the above organic solvents were referenced from the Solvent Handbook (Kodansha, 1976). Note that the boiling point is the value at a pressure of 101,325 Pa (standard atmospheric pressure) and can be measured by a standard method under a pressure environment of 101,325 Pa. Furthermore, the dielectric constant at 20°C can also be measured by using 50 mL of an organic solvent with a water content of 5 ppm or less as a measurement sample, and applying an AC voltage of 1 MHz using a Keycom (now Keysight) E4980A precision LCR meter and a Keycom DPT-013-050 electrode.

[0097] The physical properties of the water-dispersed silica sol (the raw material), the hollow silica organosols prepared in the examples, comparative examples, and reference examples (hereinafter sometimes simply referred to as silica sol, organosol, organic solvent-dispersed silica sol, etc.), and the silica sols and silica particles during the manufacturing process of the hollow silica organosols were evaluated according to the following method.

[0098] (Silica particles in silicasol (SiO ２(Measurement of Concentration) The silica particle concentration of water-dispersed silica sol and organic solvent-dispersed silica sol was calculated by placing the silica sol in a crucible, removing the solvent by heating on a hot plate, and then calcining at 1000°C. The resulting calcined residue was weighed, and the silica particle concentration (mass%) was calculated. As will be described later, the sols prepared in each example contain sulfuric acid, etc., but after the calcination, trace amounts of organic components are almost completely eliminated by volatilization / thermal decomposition, and the amount of added sulfuric acid and other organic components is very small, so the concentration calculated by the above method can be treated as the concentration of silica particles in the silica sol.

[0099] (pH Measurement of Silica Sol) The pH of water-dispersed silica sol was measured at 20°C using a pH meter (manufactured by Toa DKK Co., Ltd., product name: MM-43X). The pH of organic solvent-dispersed silica sol was measured at 20°C using the above pH meter. When the organic solvent used as the dispersion medium was methanol (MeOH), the pH of the solution was obtained by mixing the organic solvent-dispersed silica sol with pure water in a mass ratio of 1:1. When the organic solvent was MIBK, EAC, etc., the pH of the solution was obtained by mixing the organic solvent-dispersed silica sol, MeOH, and pure water in a mass ratio of 1:1:1. When the solution was obtained by mixing the organic solvent-dispersed silica sol with pure water in a mass ratio of 1:1, it was also expressed as pH(1+1). When the solution was obtained by mixing the organic solvent-dispersed silica sol, MeOH, and pure water in a mass ratio of 1:1:1, it was also expressed as pH(1+1+1).

[0100] (Specific surface area value (S) by nitrogen gas adsorption method Ｎ２ (Measurement of specific surface area by BET method) Specific surface area value of silica particles by nitrogen gas adsorption method in water-dispersed silica sol (S Ｎ２ ) After removing water-soluble cations from the aqueous dispersion silica sol with an H-type cation exchange resin (manufactured by Dow Chemical, trade name: Amberlite IR-120B), the silica sol is dried at 290°C to obtain a measurement sample, which is then measured using a nitrogen gas adsorption specific surface area analyzer, trade name Monosorb (manufactured by Quantachrome Instruments Japan LLC), with N ２ A mixed gas of 30% nitrogen and 70% helium (He) was used as the carrier gas, and measurements were taken using the B.E.T. single-point method.

[0101] (Measurement of average particle diameter by DLS method (average secondary particle diameter by dynamic light scattering method)) The average particle diameter by DLS method (average secondary particle diameter by dynamic light scattering method: also called Z-average particle diameter or DLS average particle diameter) was measured using a dynamic light scattering particle diameter analyzer (Malvern Panalogical, trade name: Zetasizer Nano). 0.1 g of the target silica sol was placed in a glass cell with an optical path length of 10 mm, and the same solvent as the dispersion medium of the silica sol was added to obtain a silica sol with a silica particle concentration adjusted so that the count rate when the attenuator was set to 7 was 200 to 400 kcps. Specifically, water was added to the water-dispersed silica sol described later, MeOH to the MeOH-dispersed silica sol, MIBK to the MIBK-dispersed sol, and EAC to the EAC-dispersed sol, respectively, to obtain silica sols in which the silica particle concentration was adjusted so that the count rate when the attenuator was set to 7 was 200 to 400 kcps. The prepared silica sol was placed in the cell, and the height of the liquid surface from the bottom of the cell was adjusted to about 1 cm, and the average particle diameter of the silica sol was measured by the DLS method using the attenuator 7.

[0102] (Measurement of average primary particle diameter by TEM (transmission electron microscope)) Particles in the target silica sol were photographed using a transmission electron microscope (product name JEM-F200, manufactured by JEOL Ltd.), and 300 arbitrarily selected particles were binarized using an automated image processing and analysis system (product name LUZEX' AP, manufactured by Nireco Corporation). The diameter obtained by converting the projected area to a circular size was measured as the average primary particle diameter (HEYWOOD diameter).

[0103] (Measurement / Dissolution Method of Aluminum Amount Present in the Entire Silica Particle) The precisely weighed silica sol was dried, and 250 mg of the resulting particles were dissolved in 2.5 ml of nitric acid (manufactured by Kanto Chemical Co., Ltd., trade name: Nitric Acid 1.38, purity 60.0%) and 2.5 ml of 38% hydrofluoric acid (manufactured by Tama Chemical Industry Co., Ltd., trade name: hydrofluoric acid) to obtain an aqueous solution. The amount of aluminum in the obtained aqueous solution was measured using an ICP-OES analyzer (manufactured by Rigaku Corporation, trade name: CIROS120 EOP), and the amount of aluminum present in the entire silica particle was determined as Al ２ O ３The amount relative to the mass of silica particles (Al ２ O ３ (ppm) / SiO ２ ) was requested.

[0104] (Measurement of Surface Charge of Silica Particles) The target silica sol was added to 10 mL of methanol to obtain a silica particle concentration of 0.5% by mass, and this was prepared as the measurement sample. Using a particle charge meter (Voyt Turbo Co., Ltd., product name PCD-06), a 0.001 mol / liter (N / 1000) DADMAC solution (Voyt Turbo Co., Ltd.) was used as the cation standard titrator, and the titration value was measured until the flow potential of the measurement sample became zero. The obtained titration value was divided by the amount of silica particles contained in the measurement sample to obtain the surface charge amount (μeq / g) per gram of silica particles. Note that DADMAC refers to poly(diallyldimethylammonium chloride).

[0105] (Measurement of the amount of alcohol or organosilane compound bonded to the surface of silica particles) 4 ml of silica sol obtained in the examples, comparative examples, or reference examples was placed in a 42 ml pear-shaped sedimentation tube (manufactured by Thermo Fisher Scientifics, trade name: Nalgene Oak Ridge), 4 ml of methyl ethyl ketone and 20 ml of hexane were added, and the mixture was allowed to stand for 5 minutes to induce turbidity, separation, or precipitation due to aggregation. Then, the mixture was centrifuged using a centrifuge (manufactured by Tommy Seikou Co., Ltd., trade name: High-speed refrigerated centrifuge Suprema 21) (temperature: 5°C, rotation speed: 20000 rpm, time: 30 minutes), and the supernatant was removed. Then, 4 ml of acetone was added, and the precipitate obtained by centrifugation was redissolved in a test tube mixer (AS ONE Corporation, trade name: MVM-10), and then 20 ml of hexane was added. Then, the mixture was centrifuged, and the supernatant was removed. Subsequently, 4 ml of acetone was added, and the precipitate obtained by centrifugation was redissolved in a test tube mixer, after which 20 ml of hexane was added. After centrifugation, the supernatant was removed. The obtained precipitate (mixture) was vacuum dried (temperature: 60°C, pressure: -0.1 MPa), and the resulting powder was ground in a mortar for 10 minutes to obtain silica particles (powder). The obtained silica particles were heated at 150°C to remove adsorbed water and used as the measurement sample. The carbon content (Cp: mass%) of the silica particles (measurement sample) was measured using an elemental analyzer (PerkinElmer, model name: Elemental Analyzer 2400II). 0.2 g of the powder obtained above was mixed with 10 mL of 0.05 N sodium hydroxide aqueous solution and left at room temperature for 1 day. If there were any undissolved substances, they were removed by filtration or centrifugation, and the solution portion was measured by gas chromatography to determine the amount of alcohol bound to the surface (amount of alcohol bound with a boiling point of 80°C to 200°C: particles / nm). ２ The specific surface area (S) obtained by nitrogen gas adsorption was measured. Furthermore, the specific surface area value (S) obtained by nitrogen gas adsorption was used to calculate the amount of alcohol bonded per unit area. Ｎ２ ) was used. In addition, the amount of carbon content corresponding to the amount of alkoxy groups obtained from GC (gas chromatography) was subtracted from the carbon content of the powder obtained from the elemental analysis above to determine the amount of silane compounds bound to the surface (organosilane compound binding amount: particles / nm). ２The amount of organic silane compound bonded per unit area was quantified using the specific surface area value (S) obtained by the nitrogen gas adsorption method described above. Ｎ２ ) was used.

[0106] (Measurement of refractive index of silica particles) The following procedures 1) to 3) were used for measurement. 1) Preparation of aqueous sol varnish containing silica particles 20.00 g of 3-glycidoxypropyltrimethoxysilane (Momentive Co., Ltd., trade name SILQUEST A-187T) was weighed into a poly container, and 18.57 g of methanol and 4.57 g of 0.01 N hydrochloric acid aqueous solution were added thereto, and the mixture was stirred at room temperature for 5 hours. 6.00 g of a methanol solution of 2,4-aluminum pentanedione (Al(acac)3) (10% by mass Al(acac)3) prepared in advance was added as a curing agent, and the mixture was stirred for 10 minutes to prepare a partial hydrolysate of 3-glycidoxypropyltrimethoxysilane (GPS) (concentration: 43% by mass). A silica particle aqueous sol-containing varnish (silica particle concentration: 4% by mass, silica particle content: 50 phr, 100 phr, or 150 phr) was prepared by weighing 0.25 g of a methanol solution (10% by mass L-7604) of the prepared GPS partial hydrolysate, water, methanol, and leveling agent (DOWSIL trade name L-7604) into a brown bottle and stirring at room temperature for 30 minutes. 2) Preparation of silica particle-containing film Approximately 1 mL of the silica particle aqueous sol-containing varnish obtained in 1) (containing amount (silica particles): 50 phr, 100 phr, or 150 phr) was dropped onto a UV-O3 treated Si substrate. Using a spin coater (Mikasa Corporation, product name Opticoat MS-B100), the varnish was uniformly spread on the Si substrate under the following conditions: increasing to 200 rpm in 2 seconds, 200 rpm × 10 seconds, further increasing to 800 rpm in 2 seconds, 800 rpm × 5 seconds, and then decreasing to 0 rpm in 5 seconds. Subsequently, the film was baked on a hot plate at 80°C for 5 minutes and then heat-treated in an oven at 120°C for 1 hour to prepare a silica particle-containing film (containing amount of silica particles: 50 phr, 100 phr, or 150 phr).3) Measurement of refractive index of silica particle-containing film and calculation of refractive index of silica particles The refractive index of the silica particle-containing film obtained in 2) (silica particle content: 50 phr, 100 phr, or 150 phr) was measured using an ellipsometer (product name: Multi-incidence angle spectroscopic ellipsometer VASE, manufactured by J.A. Woolam Japan Co., Ltd.). Separately, the refractive index of a film without silica particles, similarly prepared using only the partial hydrolysate of GPS, was also measured. The refractive index of the measured-down-to-one-silica-containing film was plotted against the silica particle content and extrapolated so that the silica particle content was 100% by mass to determine the refractive index of the silica particles.

[0107] (Measurement of sulfuric acid content in aqueous dispersion silica sol (hereinafter, sulfuric acid content in the system)) The target aqueous dispersion silica sol was diluted 10 times with pure water, and the amount of sulfate ions in the diluted solution was measured by ion chromatography using an anion analyzer (product name Dionex ICS-2100, manufactured by Thermo Scientific). The amount of sulfuric acid in the system (ppm) was calculated from the obtained amount of sulfate ions.

[0108] (Amount of anions in the organic solvent-dispersed silica sol (SO ４ ２－ (Measurement) 50 mg of the target organosilica sol was mixed with 1.5 mL of methanol, then mixed with 1.5 mL of 10 mM NaOH aqueous solution. The resulting solution was centrifuged using an ultracentrifuge (himac CS100FNX) at 55,000 rpm for 60 minutes. The sulfate ion, nitrate ion, and chloride ion amounts of the supernatant were measured by ion chromatography using an anion analyzer (product name Dionex ICS-2100, Thermo Scientific). The total amount of these ions was used to calculate the amount of anions in the system (ppm). In all of the measured examples, comparative examples, and reference examples, nitrate ions and chloride ions were not detected (below the detection limit), so the "anion amount (SO ４ ２－ It was displayed as )

[0109] (Method for measuring sulfate esters) The presence or absence of sulfate esters in the supernatant obtained above was measured using a mass spectrometer LC-MS / MS (SCIEX Corporation, product name TT5600) (evaluated as detected / not detected).

[0110] (Method for measuring polymerization inhibitor content) The target organosilica sol was centrifuged (55,000 rpm, 60 minutes) using an ultracentrifuge (Eppendorf Hi-Mac Technologies, Ltd., product name CS100FNX), and the content of polymerization inhibitors in the obtained supernatant was measured using a GC-MS (Shimadzu Corporation, product name TQ0830), and the content of polymerization inhibitors in the organosilica sol was calculated.

[0111] (Measurement of moisture content (mass%)) The moisture content of the target sol was measured by Karl Fischer titration using a Karl Fischer moisture meter (manufactured by Kyoto Electronics Manufacturing Co., Ltd., product name: MKA-610).

[0112] (Measurement of alcohol content (mass%) with boiling points of 80°C to 200°C) The amount of alcohol contained in the target sol was measured using gas chromatography (Shimadzu Corporation, product name: GC-2014s) under the conditions described below. Column: 3 mm x 1 m glass column Packing material: Polar Pack Q Column temperature: 130 to 230°C (heating increase of 8°C / min) Carrier: N ２ 40 mL / min, Detector: FID, Injection volume: 1 μL, Internal standard: Acetonitrile.

[0113] (Measurement of silica sol viscosity) The viscosity of the silica sol in question was measured at 20°C using an Ostwald viscometer (manufactured by Shibata Scientific Co., Ltd.).

[0114] (Measurement of outer shell thickness) Particles in hollow silica sol were photographed using a transmission electron microscope (product name JEM-F200, manufactured by JEOL Ltd.), and 300 arbitrarily selected particles were binarized using an automated image processing and analysis system (product name LUZEX' AP, manufactured by Nireco Corporation). The inner diameter, obtained by converting the projected area to a circular shape, was averaged, the difference from the primary particle diameter of the TEM was measured, and the obtained results were averaged.

[0115] (Thermal Stability Evaluation) 15 g of silica sol obtained in the Examples, Comparative Examples, or Reference Examples was sealed in a 20 ml glass bottle and stored at 50°C for 4 weeks. Subsequently, the DLS ratio was calculated using the following formula (1) as an indicator of the change over time after 4 weeks of storage at 50°C, based on the DLS average particle size (measurement method: see above) of the silica sol to be evaluated before and after storage at 50°C, and the thermal stability of the silica sol was evaluated. However, (X) in the following formula (1) ０ ) indicates the DLS average particle size before the thermal stability test (immediately after sol preparation), (X 4ｗ ) indicates the average DLS particle size after thermal stability test 1 (after storage at 50°C for 4 weeks). DLS ratio: (X ４ｗ ) / (X ０ ) ... (Equation (1)) Thermal stability was evaluated in four stages, A to D, as shown below. The results obtained are shown in Table 1 (Table 1-1, Table 1-2) and Table 2. <Thermal Stability Test Evaluation Criteria> A: DLS ratio is 1.00 or more and 1.05 or less B: DLS ratio is 0.70 or more and less than 1.00, or greater than 1.05 and 1.10 or less C: DLS ratio is greater than 1.10 and 2.00 or less D: DLS ratio is greater than 2.00 and less than 0.70, or silica sol becomes cloudy, phase separation occurs, or precipitates form

[0116] (Dispersibility evaluation) DLS average particle size of silica sol obtained in the examples, comparative examples, or reference examples (X of the above (thermal stability evaluation)) ０ The particle size ratio was calculated using the following formula (2) as an indicator of dispersibility, based on the average primary particle size measured by TEM (measurement method: see above), and the thermal stability of the silica sol was evaluated. Particle size ratio: (X ０ ) / (Average primary particle diameter by TEM) ... (Equation (2)) Dispersibility was evaluated in four stages, A to D, as shown below. The results obtained are shown in Table 1 (Table 1-1, Table 1-2) and Table 2. <Dispersibility Test Evaluation Criteria> A: Particle size ratio is 1.00 or more and 2.00 or less B: Particle size ratio is 0.70 or more and less than 1.00, or greater than 2.00 and 2.40 or less C: Particle size ratio is greater than 2.40 and 8.00 or less D: Particle size ratio is greater than 8.00 and less than 0.70, or silica sol becomes cloudy, phase separation occurs, or sedimentation occurs

[0117] (Example 1) Step 1-1: Preparation of MeOH-dispersed silica sol of aluminum atom-containing hollow silica particles. 1856 g of aqueous-dispersed silica sol A was placed in a 3 L poly container and stirred at a rotational speed of 650 rpm with a mechanical stirrer equipped with a glass stirring blade. Under this stirring, Al ２ O ３ 32.2 g of an aqueous sodium aluminate solution diluted to a concentration of 1.0% by mass was added dropwise over 1 minute, and the mixture was stirred at the same rotational speed for 30 minutes. 763 g of pure water was then added, and the mixture was stirred for an additional 10 minutes to obtain the mixture. Next, 2500 g of this mixture was placed in a 3 L stainless steel autoclave container and heat-treated at 150°C for 5 hours under stirring at 80 rpm, and then cooled to below 50°C. 1.51 g of an 8.2% aqueous sulfuric acid solution was added dropwise to 1700 g of the resulting heat-treated aqueous silica sol, and the mixture was stirred at room temperature at a stirring speed of 800 rpm for 1 hour to obtain a sulfuric acid-added heat-treated aqueous silica sol. Next, the obtained sulfuric acid-added heat-treated aqueous silica sol was passed through 200 mL of cation exchange resin (H-type Amberlite (product name) IR-120B, harmonic mean diameter 0.6-0.8 mm, Organo Co., Ltd.) packed into a column at a space velocity (SV) of 5 / hour to obtain aqueous silica sol 1 of aluminum atom-containing hollow silica particles. Subsequently, this obtained aqueous silica sol 1 of aluminum atom-containing hollow silica particles was heat-treated at 80°C for 10 hours, then cooled to below 30°C, and then passed through cation exchange resin (H-type Amberlite (product name) IR-120B) packed into a column again at a space velocity (SV) of 5 / hour to obtain aqueous silica sol 2 of aluminum atom-containing hollow silica particles. The pH of the obtained aqueous silica sol 2 of aluminum atom-containing hollow silica particles was 2.8, and the amount of sulfuric acid in the system was 73 ppm. Furthermore, the specific surface area (S) by the BET method was calculated. Ｎ２ ) 117m ２ / g, TEM average primary particle diameter 38 nm, silica particle concentration 13.4 mass%, viscosity 1.6 mPa·s, DLS average particle diameter 51 nm, amount of aluminum atoms present throughout hollow silica particles: Al ２ O ３ Converted to 590 ppm / SiO ２ The surface charge per gram of hollow silica particles was 25 μeq / g, and the outer shell thickness was 5 nm.

[0118] Subsequently, 1000 g of the resulting aqueous dispersion silica sol 2 of aluminum atom-containing hollow silica particles was placed in a 2 L round-bottom flask. Using a rotary evaporator, the pressure was reduced to 580 Torr and heated to 120°C, at which point the water, which was the solvent (dispersion medium), was replaced with methanol (MeOH). Then, methanol was added to adjust the concentration, and a 20% by mass MeOH-dispersed silica sol of aluminum atom-containing hollow silica particles (pH (1+1) 3.8) was obtained. 500 g of the obtained MeOH-dispersed silica sol was passed through a 100 cc glass column packed with 50 ml of cation exchange resin (product name Amberlite IR-120B) at a space velocity (sv) of 7 / hour to obtain a cation exchange-treated MeOH-dispersed silica sol. The physical properties of the obtained cation-exchange treated MeOH-dispersed silica sol were as follows: pH (1+1) 3.0, average primary particle diameter 38 nm by TEM, average DLS particle diameter 61 nm, viscosity 1.1 mPa·s, moisture content 1.1 mass%, and silica particle concentration 19.7 mass%.

[0119] Step 1-2: Preparation of hollow silica particle MIBK-dispersed silica sol. 40.1 g of the cation exchange-treated MeOH-dispersed silica sol obtained in Step 1-1 was placed in a 300 mL round-bottom flask, and 8.1 g of n-butanol (n-BtOH) and 17.6 g of MIBK were added. Then, the solvent methanol (MeOH) was removed by distillation under reduced pressure of 450 Torr and heated at a bath temperature of 80°C using a rotary evaporator, and 45.5 g of sol was obtained, with the silica particle concentration concentrated to 17.6% by mass. 0.009 g of MEHQ and 0.402 g of MPS, which are polymerization inhibitors, were added to the obtained sol, and then a reflux condenser was attached to the 300 mL round-bottom flask, and the sol was heated and aged at a liquid temperature of 60°C for 3 hours. Subsequently, using a rotary evaporator, the sol was solvent-replaced while supplying 120 g of MIBK at a pressure of 450 to 115 Torr and a bath temperature of 80°C, yielding 40.0 g of the MIBK-dispersed silica sol of Example 1. The composition, physical properties, and evaluation results of the obtained MIBK-dispersed silica sol are shown in Table 1. The obtained hollow silica organosol showed no sedimentation and exhibited good dispersibility (dispersed in the dispersion medium without turbidity or aggregation; the same applies hereafter).

[0120] (Example 2) In step 1-2, the amount of n-butanol added was changed from 8.1 g to 4.1 g, and the amount of solvent supplied during MIBK substitution was changed to 60 g. Except for these changes, the MIBK-dispersed silica sol of Example 2 was obtained by the same procedure as in Example 1. The composition and physical properties of the obtained MIBK-dispersed silica sol are shown in Table 1. The obtained hollow silica organosol showed good dispersibility with no precipitates.

[0121] (Example 3) In step 1-2, the amount of MPS 0.402 g was changed to AcPS 0.394 g, and the final silica particle concentration was changed from 20% by mass to 15% by mass. Except for these changes, the MIBK-dispersed silica sol of Example 3 was obtained by the same procedure as in Example 1. The composition, physical properties, and evaluation results of the obtained MIBK-dispersed silica sol are shown in Table 1. The obtained hollow silica organosol showed good dispersibility with no precipitates.

[0122] (Example 4) In step 1-2, n-butanol was replaced with 12.0 g of n-ProOH, and the amount of MIBK supplied during MIBK substitution was changed to 43 g. The MIBK-dispersed silica sol of Example 3 was obtained by the same procedure as in Example 1. The composition, physical properties, and evaluation results of the obtained MIBK-dispersed silica sol are shown in Table 1. The obtained hollow silica organosol showed good dispersibility with no precipitates.

[0123] (Example 5) In step 1-2, n-butanol was replaced with 4.1 g of n-HxOH to obtain the MIBK-dispersed silica sol of Example 5 by the same procedure as in Example 1. The composition, physical properties, and evaluation results of the obtained MIBK-dispersed silica sol are shown in Table 1. The obtained hollow silica organosol showed good dispersibility with no precipitates.

[0124] (Example 6) In step 1-2, the MIBK 17.6 g was replaced with EAC 17.6 g, the supply of MIBK 120 g in the rotary evaporator was changed to EAC 124 g, and the pressure during substitution was changed from 450-115 Torr to 300 Torr. Except for these changes, the EAC-dispersed silica sol of Example 6 was obtained by the same procedure as in Example 4. The composition, physical properties, and evaluation results of the obtained EAC-dispersed silica sol are shown in Table 1. The obtained hollow silica organosol showed good dispersibility with no precipitates.

[0125] (Example 7) 2000 g of aqueous dispersion silica sol A was placed in a 3 L plastic container and stirred at a rotation speed of 650 rpm with a mechanical stirrer equipped with a glass stirring blade. Under this stirring, Al ２ O ３ 35.0 g of an aqueous sodium aluminate solution diluted to a concentration of 1.0% by mass was added dropwise over 1 minute, and the mixture was stirred at the same rotational speed for 30 minutes. 716 g of pure water was then added, and the mixture was stirred for an additional 10 minutes to obtain the mixture. Next, 2443 g of this mixture was placed in a 3 L stainless steel autoclave container and heated at 150°C for 5 hours under stirring at 80 rpm, after which it was cooled to below 50°C. 1000 g of the resulting aqueous dispersion silica sol of aluminum atom-containing hollow silica particles was placed in a 2 L round-bottom flask. Using a rotary evaporator, the pressure was reduced to 580 Torr, and the solvent (dispersion medium), water, was replaced with methanol (MeOH) while heated to 120°C. Methanol was then added to adjust the concentration, and a 20% by mass MeOH-dispersed silica sol of aluminum atom-containing hollow silica particles (pH (1+1) 6.1) was obtained. 500 g of the obtained MeOH-dispersed silica sol was passed through a 100 cc glass column packed with 50 ml of cation exchange resin (product name Amberlite IR-120B) at a space velocity (sv) of 7 / hour to obtain cation exchange treated MeOH-dispersed silica sol 1. The physical properties of the obtained cation exchange treated MeOH-dispersed silica sol 1 were pH (1+1) 3.4, DLS average particle size 66 nm, moisture content 1.0 mass%, silica particle concentration 20.0 mass%, and the amount of aluminum atoms present in the entire hollow silica particle was Al ２ O ３ Converted to 742 ppm / SiO ２ In step 1-2 of Example 1, where the surface charge was 25 μeq / g, the MIBK-dispersed silica sol of Example 7 was obtained by the same procedure as in Example 1, except that cation-exchange treated MeOH-dispersed silica sol 1 was used instead of cation-exchange treated MeOH-dispersed silica sol 1. The composition, physical properties, and evaluation results of the obtained MIBK-dispersed silica sol are shown in Table 1. The obtained hollow silica organosol showed good dispersibility with no precipitates.

[0126] (Example 8) Step 8-1: Preparation of MeOH-dispersed silica sol of aluminum atom-containing hollow silica particles In step 1-1 of Example 1, water-dispersed silica sol B was used instead of water-dispersed silica sol A, Al ２ O ３ Except for changing the amount of sodium aluminate aqueous solution diluted to a 1.0% by mass concentration added from 32.2 g to 64.4 g, the same procedure as in Step 1-1 of Example 1 was performed to obtain Cation Exchange Treated MeOH-Dispersed Silica Sol 2. The physical properties of the obtained Cation Exchange Treated MeOH-Dispersed Silica Sol 2 were: pH (1+1) 3.2, average primary particle diameter by TEM 65 nm, DLS average particle diameter 98 nm, viscosity 1.7 mPa·s, moisture content 0.7% by mass, silica particle concentration 21.1% by mass, and the amount of aluminum atoms present in the entire hollow silica particles was Al ２ O ３ Converted to 1534 ppm / SiO ２ The surface charge was 27 μeq / g.

[0127] Step 8-2: Preparation of hollow silica particle MMB-dispersed silica sol. The procedure was the same as in Step 1-2 of Example 1, except that cation exchange treated MeOH-dispersed silica sol 2 was used instead of cation exchange treated MeOH-dispersed silica sol, and MMB was used instead of MIBK. 40.0 g of MMB-dispersed silica sol for Example 8 was obtained. The composition, physical properties, and evaluation results of the obtained MMB-dispersed silica sol are shown in Table 1. The obtained hollow silica organosol showed good dispersibility with no precipitates.

[0128] (Example 9) The same procedure as in Example 8 was followed, except that PGMEA was used instead of MMB in step 8-2 of Example 8, to obtain 40.0 g of PGMEA-dispersed silica sol of Example 9. The composition, physical properties, and evaluation results of the obtained PGMEA-dispersed silica sol are shown in Table 1. The obtained hollow silica organosol showed good dispersibility with no precipitates.

[0129] (Example 10) 196 g of the cation exchange treated MeOH-dispersed silica sol 1 obtained in the process of Example 7 was placed in a 500 mL round-bottom flask, and 19.6 g of n-butanol and 86.4 g of PGMEA were added. Then, the solvent methanol (MeOH) was removed by distillation in a rotary evaporator under reduced pressure of 450 Torr and heated at a bath temperature of 80°C, obtaining 202.9 g of sol concentrated to a silica particle concentration of 20.0% by mass. 0.039 g of MEHQ and 3.21 g of PTMS, which are polymerization inhibitors, were added to the obtained sol, and then a reflux condenser was attached to the 500 mL round-bottom flask, and heating and aging was carried out at a liquid temperature of 60°C for 3 hours. Subsequently, using a rotary evaporator, the sol was solvent-replaced while supplying 116 g of PGMEA at a pressure of 450-70 Torr and a bath temperature of 80°C, yielding 226.1 g of the PGMEA-dispersed silica sol of Example 10. The composition, physical properties, and evaluation results of the obtained PGMEA-dispersed silica sol are shown in Table 1. The obtained hollow silica organosol showed good dispersibility with no precipitates.

[0130] (Example 11) 2000 g of aqueous-dispersed silica sol C was placed in a 3 L plastic container and stirred at a rotation speed of 650 rpm with a mechanical stirrer equipped with a glass stirring blade. Under this stirring, Al ２ O ３37.0 g of an aqueous sodium aluminate solution diluted to a concentration of 1.0% by mass was added dropwise over 1 minute, and the mixture was stirred at the same rotational speed for 30 minutes. 716 g of pure water was then added, and the mixture was stirred for an additional 10 minutes to obtain the mixture. Next, 2443 g of this mixture was placed in a 3 L stainless steel autoclave container and heated at 150°C for 5 hours under stirring at 80 rpm, and then cooled to below 50°C. 1000 g of the resulting aqueous dispersion silica sol of aluminum atom-containing hollow silica particles was placed in a 2 L round-bottom flask. Using a rotary evaporator, the pressure was reduced to 580 Torr, and the solvent (dispersion medium), water, was replaced with methanol (MeOH) while heated to 120°C. Methanol was then added to adjust the concentration, and a 20% by mass MeOH-dispersed silica sol of aluminum atom-containing hollow silica particles (pH (1+1) 6.1) was obtained. 500 g of the obtained MeOH-dispersed silica sol was passed through a 100 cc glass column packed with 50 ml of cation exchange resin (product name Amberlite IR-120B) at a space velocity (sv) of 7 / hour to obtain cation exchange treated MeOH-dispersed silica sol 2. The physical properties of the obtained cation exchange treated MeOH-dispersed silica sol 2 were: pH (1+1) 3.1, DLS average particle size 78 nm, moisture content 0.8 mass%, silica particle concentration 18.1 mass%, and the amount of aluminum atoms present in the entire hollow silica particle was Al ２ O ３ Converted to 918 ppm / SiO ２750 g of the obtained cation exchange treated MeOH-dispersed silica sol 2, which had a surface charge of 23 μeq / g, was placed in a 2 L round-bottom flask, and 250 g of MeOH, 71.3 g of n-butanol, and 418 g of MIBK were added. Then, the solvent methanol (MeOH) was removed by distillation under reduced pressure of 450 Torr and heated at a bath temperature of 80°C using a rotary evaporator, and 1000 g of sol was obtained in which the silica particle concentration was concentrated to 15.0 mass%. After adding 0.14 g of MEHQ and 6.16 g of MPS, which are polymerization inhibitors, to the obtained sol, a reflux condenser was attached to a 500 mL round-bottom flask, and heating and aging was carried out at a liquid temperature of 60°C for 3 hours. Subsequently, using a rotary evaporator, the sol was solvent-replaced while supplying 2000 g of MIBK at a pressure of 450-70 Torr and a bath temperature of 80°C, yielding 750 g of the MIBK-dispersed silica sol of Example 11. The composition, physical properties, and evaluation results of the obtained MIBK-dispersed silica sol are shown in Table 1. The obtained hollow silica organosol showed good dispersibility with no precipitates.

[0131] (Example 12) 2000 g of aqueous-dispersed silica sol D was placed in a 3 L plastic container and stirred at a rotational speed of 650 rpm with a mechanical stirrer equipped with a glass stirring blade. Under this stirring, Al ２ O ３74.0 g of an aqueous sodium aluminate solution diluted to a concentration of 1.0% by mass was added dropwise over 1 minute, and the mixture was stirred at the same rotational speed for 30 minutes. 716 g of pure water was then added, and the mixture was stirred for an additional 10 minutes to obtain the mixture. Next, 2443 g of this mixture was placed in a 3 L stainless steel autoclave container and heated at 150°C for 5 hours under stirring at 80 rpm, after which it was cooled to below 50°C. 1500 g of the resulting aqueous dispersion silica sol of aluminum atom-containing hollow silica particles was placed in a 3 L round-bottom flask. Using a rotary evaporator, the pressure was reduced to 580 Torr, and the solvent (dispersion medium), water, was replaced with methanol (MeOH) while heated to 120°C. Methanol was then added to adjust the concentration, and a 20% by mass MeOH-dispersed silica sol of aluminum atom-containing hollow silica particles (pH (1+1) 6.3) was obtained. 1000 g of the obtained MeOH-dispersed silica sol was passed through a 200 cc glass column packed with 100 ml of cation exchange resin (product name Amberlite IR-120B) at a space velocity (sv) of 7 / hour to obtain cation exchange treated MeOH-dispersed silica sol 3. The physical properties of the obtained cation exchange treated MeOH-dispersed silica sol 3 were: pH (1+1) 3.2, DLS average particle size 140 nm, moisture content 1.3 mass%, silica particle concentration 16.6 mass%, and the amount of aluminum atoms present in the entire hollow silica particle was Al ２ O ３ Converted to 1650 ppm / SiO ２110.9 g of the obtained cation exchange treated MeOH-dispersed silica sol 3, which had a surface charge of 26 μeq / g, was placed in a 300 mL round-bottom flask, and 9.2 g of n-butanol and 20.3 g of PGMEA were added. Then, the solvent methanol (MeOH) was removed by distillation under reduced pressure of 450 Torr and heated at a bath temperature of 80°C using a rotary evaporator, and 110 g of sol was obtained in which the silica particle concentration was concentrated to 16.6 mass%. After adding 0.02 g of MEHQ and 0.60 g of MPS, which are polymerization inhibitors, to the obtained sol, a reflux condenser was attached to the 300 mL round-bottom flask, and heating and aging was carried out at a liquid temperature of 60°C for 3 hours. Subsequently, using a rotary evaporator, the sol was solvent-replaced while supplying 63.7 g of PGMEA at a pressure of 450-70 Torr and a bath temperature of 80°C, yielding 103 g of the PGMEA-dispersed silica sol of Example 11. The composition, physical properties, and evaluation results of the obtained PGMEA-dispersed silica sol are shown in Table 1. The obtained hollow silica organosol showed good dispersibility with no precipitates.

[0132] (Reference Example 1) 200 g of the cation exchange treated MeOH-dispersed silica sol 2 obtained in Example 11 was placed in a 1000 mL round-bottom flask, 0.04 g of MEHQ and 3.4 g of MPS were added, and a reflux condenser was attached to the 1000 mL round-bottom flask. The mixture was then heated and aged at a liquid temperature of 60°C for 3 hours. After that, 32.2 g of water-dispersed silica sol E was added, and the mixture was heated and aged again at a liquid temperature of 60°C for 3 hours. Next, distillation was carried out while supplying MeOH until the water content in the sol was 1.5% by mass or less. The silica particle concentration was then diluted to 15% by mass with 20 g of n-butanol and MIBK. Using a rotary evaporator, the solvent of the sol was replaced while supplying MIBK at a pressure of 450 to 115 Torr and a bath temperature of 80°C, and the mixture was concentrated to a silica particle concentration of 20% by mass to obtain MIBK-dispersed silica sol. Table 1 shows the composition, physical properties, and evaluation results of the obtained MIBK-dispersed silica sol. The obtained hollow silica organosol showed good dispersibility, with no precipitates.

[0133] (Comparative Example 1) A MIBK-dispersed silica sol of Comparative Example 1 was obtained by the same procedure as in Example 1, except that n-butanol was not added in step 1-2. The composition, physical properties, and evaluation results of the obtained MIBK-dispersed silica sol are shown in Table 2. The obtained MIBK-dispersed silica sol was cloudy, the DLS average particle size was 111 nm, and some aggregation was observed.

[0134] (Comparative Example 2) An attempt was made to prepare MIBK-dispersed silica sol using the same procedure as in Example 1, except that the MeOH-dispersed silica sol was not subjected to cation exchange in step 1-1, and the MeOH-dispersed silica sol before cation exchange treatment was used in step 1-2. However, the desired sol could not be obtained because it gelled during the solvent exchange.

[0135] (Comparative Example 3) The EAC-dispersed silica sol of Comparative Example 3 was obtained by the same procedure as in Example 6, except that n-propanol was not added in step 1-2. The composition, physical properties, and evaluation results of the obtained EAC-dispersed silica sol are shown in Table 2. The obtained EAC-dispersed silica sol was cloudy, the DLS average particle size was 92 nm, and some aggregation was observed.

[0136] (Comparative Example 4) An attempt was made to prepare an MIBK-dispersed silica sol using the same procedure as in Example 2, except that n-butanol was replaced with 1-dodecanol in step 1-2. However, the desired sol could not be obtained because it gelled during the solvent exchange.

[0137]

[0138]

[0139]

[0140] Based on the above results, the hollow silica organosols of Examples 1 to 12, as well as the organosol of Reference Example 1 which used solid silica particles in combination, exhibited good thermal stability and good dispersibility in highly hydrophobic organic solvents. On the other hand, the sols of Comparative Examples 1 and 3, which did not contain alcohols with boiling points of 80°C to 200°C and no ether bonds, exhibited poor thermal stability and poor dispersibility in hydrophobic organic solvents.

[0141] (Coating Evaluation) A 10% by mass PGME (propylene glycol monomethyl ether) solution of product name: UA-306H (urethane acrylate prepolymer, Kyoeisha Chemical Co., Ltd.) as a binder was mixed in the following order: a 1% by mass PGME solution of product name: Omnirad 907 (α-aminoalkylphenone compound, IGM Resins) as a polymerization initiator, a 1% by mass PGME solution of product name: KP-412 (methacrylic base-type surface modifier, Shin-Etsu Silicone Co., Ltd.) as a leveling agent, PGME as a solvent, and the hollow silica organosol of the example or comparative example described in Table 3. The mixture was stirred for 15 minutes, and the resulting mixture was filtered (PTFE, pore size 1 μm) to obtain the coating solution (compared to the binder: SiO ２ A coating solution containing 100 phr of a polymerization inhibitor, 3 phr of a polymerization inhibitor, 500 ppm of a leveling agent, and 3% by mass of solids (total amount of binder and hollow silica particles) was prepared. A reference example coating solution was also prepared using the same procedure, except that hollow silica organosol was not added.

[0142] Using the above coating solution, a cured film was prepared on a substrate under the following conditions: LR (Low reflective index) thin film sample (LR single layer) - Substrate: Alkali-free glass (Eagle glass) - Coating: Spin coating - Solvent removal: 80°C - 5 minutes - UV curing: 200 mJ / cm ２ @365nm (N ２ (Purge included) ・Illuminance: 104 mW / cm ２ ・Cured film thickness: 100nm

[0143] (Evaluation method for the cured film) ・Refractive index: Measured using a rotational compensator type high-speed spectroscopic ellipsometer, product name M-2000 (J.A. Woolam Japan Co., Ltd.). ・HAZE: Measured using a spectroscopic haze meter, product name SH 7000 (manufactured by Nippon Denshoku Industries Co., Ltd.).

[0144]

[0145] As shown in Table 3, the cured films using hollow silica sols in Examples 1, 3-7 showed lower haze values ​​and superior transparency compared to the cured films using hollow silica sols in Comparative Examples 1 and 3, which did not contain alcohols with boiling points between 80°C and 200°C that do not have ether bonds. Furthermore, while the refractive index of the cured film in the reference example (without silica sol) was 1.5, which falls within the category of low refractive index films, the refractive index of the cured films in the examples was even lower, at 1.4 or less.

Claims

1. A hollow silica organosol containing the following components (A), (B), (C), and (D), wherein component (A) is present in a proportion of 1% to 70% by mass based on the total amount (100% by mass) of the organosol: (A) component: hollow silica particles containing aluminum atoms, having an average secondary particle diameter of 20 to 200 nm as determined by dynamic light scattering; (B) component: an alcohol having a boiling point of 80°C to 200°C and not having an ether bond; (C) component: an organic solvent other than component (B), having a relative permittivity of 1 to 20 at 20°C; (D) component: a silane compound.

2. The hollow silica organosol according to claim 1, further comprising an anion as component (E) in an amount of 0.1 to 500 ppm by mass relative to the total mass of the organosol.

3. The hollow silica organosol according to claim 1, further comprising a polymerization inhibitor in an amount of 10 to 10,000 ppm by mass as component (F).

4. The hollow silica organosol according to claim 1, wherein the ratio of (average secondary particle diameter by dynamic light scattering method) / (average primary particle diameter by transmission electron microscopy observation) of the hollow silica particles (A) is 0.70 or more and 2.40 or less.

5. The hollow silica organosol according to claim 1, wherein the (A) hollow silica particles satisfy the following (i) to (iii): (i) the outer shell thickness of the hollow silica particles is 3 to 15 nm, (ii) the surface charge amount per gram of the hollow silica particles is 10 μeq / g to 200 μeq / g, (iii) the amount of aluminum atoms present in the entire hollow silica particle is Al ２ O ３ Converted to 120 to 50,000 ppm / SiO2 relative to the mass of the hollow silica particles. ２ That is the case.

6. The hollow silica organosol according to claim 1, wherein component (D) is at least one silane compound selected from the group consisting of compounds represented by the following formulas (1) and (2). (In formula (1), R １ R represents a group that is bonded to a silicon atom and independently represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having an epoxy group, (meth)acryloyl group, mercapto group, amino group, ureido group, polyether group, carboxyl group, protected carboxyl group, carboxyl group generating group, imide group, or cyano group, and is bonded to a silicon atom by a Si-C bond, or represents a combination of these groups. ２ R is a group or atom bonded to a silicon atom, independently representing an alkoxy group, an acyloxy group, a hydroxyl group, or a halogen atom, or a combination thereof, where a represents an integer from 1 to 3, and in formula (2), R ３ R represents a group that is bonded to a silicon atom and independently represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having an epoxy group, (meth)acryloyl group, mercapto group, amino group, ureido group, polyether group, carboxyl group, protected carboxyl group, carboxyl group generating group, imide group, or cyano group, and is bonded to a silicon atom by a Si-C bond, or represents a combination of these groups. ４ (where b represents a group or atom bonded to a silicon atom, independently representing an alkoxy group, acyloxy group, hydroxyl group, or halogen atom, or a combination thereof; Y represents a group or atom bonded to a silicon atom, representing an alkylene group, NH group, or oxygen atom; b represents an integer from 1 to 3; and c represents an integer of 0 or 1.) 7. The hollow silica particles (A) have a surface area of ​​1 nm ２ The hollow silica organosol according to claim 6, wherein the particles are coated on the surface with the silane compound of component (D) at a rate of 0.1 to 10 particles per particle, or the silane compound of component (D) is bonded to the surface of the particles.

8. The hollow silica organosol according to claim 1, wherein the alcohol of component (B) is at least one selected from the group consisting of alcohols having 3 to 8 carbon atoms.

9. The (A) hollow silica particles are particles in which the alcohol of the (B) component is bonded to the surface at a ratio of 0.01 to 1.0 per 1 nm² of the surface area. The hollow silica organosol according to claim 1. ２ ​ 10. The hollow silica organosol according to claim 1, wherein the organic solvent having a dielectric constant of 1 to 20 at 20°C for component (C) is selected from the group consisting of ketones, esters, ethers, and hydrocarbons.

11. The hollow silica organosol according to claim 2, wherein the anion of component (E) is one or more inorganic anions selected from the group consisting of sulfate ions, nitrate ions, carbonate ions, chloride ions, bromide ions, and phosphate ions.

12. The hollow silica organosol according to claim 1, further comprising a sulfate ester as component (G).

13. The hollow silica organosol according to claim 3, wherein the polymerization inhibitor of component (F) is selected from the group consisting of 2,6-diisobutylphenol, 3,5-di-tert-butylphenol, 2,6-di-tert-butyl-p-cresol, 3,5-di-tert-butyl-p-cresol, 4-methoxyphenol (p-methoxyphenol), hydroquinone, hydroquinone monomethyl ether, pyrogallol, naphthylamine, benzoquinone, tert-butylcatechol, cuprous chloride, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 4,4'-thiobis(3-methyl-6-tert-butylphenol), N-nitrosophenylhydroxyamine salt (ammonium salt, cerium salt, etc.), nitrosophenylhydroxyamine aluminum salt, and diphenylnitrosamine.

14. A resin composition comprising the hollow silica organosol described in claim 1 and an organic resin material or a polysiloxane resin.

15. The resin composition according to claim 14, wherein the organic resin material is at least one selected from the group consisting of styrene resins, epoxy resins, thioepoxy resins, novolac resins, cyanate resins, phenolic resins, acrylic resins, maleimide resins, polyester resins, urethane resins, polyurea resins, polyimide resins, polyamide resins, polyamic acid resins, polyhydroxyimide resins, polybenzoxazole resins, polybenzimidazole resins, polybenzothiazole resins, polyhydroxyamide resins, polyhydroxyazomethine resins, polyether resins, polybenzoxazine resins, polytetrafluoroethylene resins, cycloolefin polymer resins, unsaturated polyester resins, vinyl triazine resins, polyphenylene sulfide resins, crosslinkable polyphenylene oxide resins, curable polyphenylene ether resins, and condensation resins.

16. The resin composition according to claim 14, wherein the content of hollow silica particles of component (A) is 50 to 200 phr relative to the total mass of the resin composition, and further comprises a polymerization initiator and a leveling agent.

17. A resin composition according to any one of claims 14 to 16, which has applications in semiconductor device materials, semiconductor element materials, semiconductor resist materials, nanoimprint materials, insulating film materials, copper-clad laminate materials, printed circuit board materials, printed board materials, printing ink materials, pigments, paints, encapsulant materials, hard coat materials, 3D printing materials, anti-reflective film materials, automotive parts materials, electronic parts materials, mechanical components, adhesive materials, battery materials, power generation materials, charge-impregnating materials, conductivity-impregnating materials, powder fluidity-impregnating materials, cosmetic materials, flexible wiring materials, liquid crystal display materials, organic EL display materials, micro-LED display materials, QD-EL display materials, flexible display materials, antenna materials, optical wiring materials, sensing materials, or thermal insulation materials.

18. A coating comprising the following components (A), (B), and (D) and an organic resin material, wherein the film refractive index is 1.1 to 1.45 and the haze is 0.01% to 0.08% when the film thickness is 100 nm: (A) component: hollow silica particles containing aluminum atoms, with an average secondary particle diameter of 20 to 200 nm as determined by dynamic light scattering; (B) component: an alcohol having a boiling point of 80°C to 200°C and not having an ether bond; (D) component: a silane compound. Organic resin materials: At least one selected from the group consisting of styrene resins, epoxy resins, thioepoxy resins, novolac resins, cyanate resins, phenolic resins, acrylic resins, maleimide resins, polyester resins, urethane resins, polyurea resins, polyimide resins, polyamide resins, polyamic acid resins, polyhydroxyimide resins, polybenzoxazole resins, polybenzimidazole resins, polybenzothiazole resins, polyhydroxyamide resins, polyhydroxyazomethine resins, polyether resins, polybenzoxazine resins, polytetrafluoroethylene resins, cycloolefin polymer resins, unsaturated polyester resins, vinyl triazine resins, polyphenylene sulfide resins, crosslinkable polyphenylene oxide resins, curable polyphenylene ether resins, and condensation resins.

19. A method for producing a hollow silica organosol according to claim 1, comprising the step of replacing a mixture obtained by adding an alcohol having a boiling point of 80°C to 200°C to a methanol-dispersed silica sol containing aluminum atom-containing hollow silica particles with the (C) organic solvent by ultrafiltration, heating under reduced pressure, or heating under normal pressure.

20. A method for producing a hollow silica organosol according to claim 19, comprising the step of contacting a methanol-dispersed silica sol containing aluminum atom-containing hollow silica particles with a cation exchange resin before adding an alcohol having a boiling point of 80°C to 200°C.

21. A method for producing a hollow silica organosol according to claim 19 or 20, comprising the step of adding at least one silane compound selected from the group consisting of compounds represented by the following formulas (1) and (2) to a sol containing aluminum atom-containing silica particles, after the substitution step of (C) with an organic solvent, and heating and stirring at 10°C to 95°C for 0.1 hours to 20 hours. (In formula (1), R １ R represents a group that is bonded to a silicon atom and independently represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having an epoxy group, (meth)acryloyl group, mercapto group, amino group, ureido group, polyether group, carboxyl group, protected carboxyl group, carboxyl group generating group, imide group, or cyano group, and is bonded to a silicon atom by a Si-C bond, or represents a combination of these groups. ２ R is a group or atom bonded to a silicon atom, independently representing an alkoxy group, an acyloxy group, a hydroxyl group, or a halogen atom, or a combination thereof, where a represents an integer from 1 to 3, and in formula (2), R ３ R represents a group that is bonded to a silicon atom and independently represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having an epoxy group, (meth)acryloyl group, mercapto group, amino group, ureido group, polyether group, carboxyl group, protected carboxyl group, carboxyl group generating group, imide group, or cyano group, and is bonded to a silicon atom by a Si-C bond, or represents a combination of these groups. ４ (where b represents a group or atom bonded to a silicon atom, independently representing an alkoxy group, acyloxy group, hydroxyl group, or halogen atom, or a combination thereof; Y represents a group or atom bonded to a silicon atom, representing an alkylene group, NH group, or oxygen atom; b represents an integer from 1 to 3; and c represents an integer of 0 or 1.) 22. A method for producing a hollow silica organosol according to claim 21, further comprising the step of substitution with the organic solvent (C) after the step of adding the silane compound and heating and stirring.

23. A method for producing a hollow silica organosol according to claim 22, comprising the step of replacing the dispersion medium with an organic resin material or a polysiloxane resin after the step of replacing with an organic solvent (C).

24. A method for producing a composite material, comprising the steps of: (A) a methanol-dispersed silica sol containing aluminum atom-containing hollow silica particles, (B) an alcohol having a boiling point of 80°C to 200°C and not having ether bonds, and then replacing the mixture with (C) an organic solvent by ultrafiltration, heating under reduced pressure, or heating under normal pressure; after the step of replacing with the (C) organic solvent, adding at least one (D) silane compound selected from the group consisting of compounds represented by the following formulas (1) and (2) to the sol containing aluminum atom-containing silica particles, and heating and stirring at 10°C to 95°C for 0.1 hours to 20 hours; after the step of adding the silane compound and heating and stirring, further replacing with the (C) organic solvent, and after the step of replacing with the (C) organic solvent, replacing the dispersion medium with an organic resin material or a polysiloxane resin, wherein the (A) aluminum atom-containing hollow silica particles have an average secondary particle diameter of 20 to 200 nm as determined by dynamic light scattering. A method for producing organic solvent (C) wherein the organic solvent has a relative permittivity of 1 to 20 at 20°C and is an organic solvent other than component (B). (In formula (1), R １ R represents a group that is bonded to a silicon atom and independently represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having an epoxy group, (meth)acryloyl group, mercapto group, amino group, ureido group, polyether group, carboxyl group, protected carboxyl group, carboxyl group generating group, imide group, or cyano group, and is bonded to a silicon atom by a Si-C bond, or represents a combination of these groups. ２ R is a group or atom bonded to a silicon atom, independently representing an alkoxy group, an acyloxy group, a hydroxyl group, or a halogen atom, or a combination thereof, where a represents an integer from 1 to 3, and in formula (2), R ３ R represents a group that is bonded to a silicon atom and independently represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having an epoxy group, (meth)acryloyl group, mercapto group, amino group, ureido group, polyether group, carboxyl group, protected carboxyl group, carboxyl group generating group, imide group, or cyano group, and is bonded to a silicon atom by a Si-C bond, or represents a combination of these groups. ４ (where b represents a group or atom bonded to a silicon atom, independently representing an alkoxy group, acyloxy group, hydroxyl group, or halogen atom, or a combination thereof; Y represents a group or atom bonded to a silicon atom, representing an alkylene group, NH group, or oxygen atom; b represents an integer from 1 to 3; and c represents an integer of 0 or 1.) 25. A composite material comprising (A) hollow silica particles containing aluminum atoms, having an average secondary particle diameter of 20 to 200 nm as determined by dynamic light scattering, (B) an alcohol having a boiling point of 80°C to 200°C and not having ether bonds, (D) a silane compound, and an organic resin material or a polysiloxane resin.

Images