TWI910741B - Hollow silica sol containing monovalent alkali metal ions, its manufacturing method, stabilization method, and coating-forming components and films containing it. - Google Patents

Abstract

　　The present invention relates to a method and a manufacturing method for improving the stability of aqueous sols and organic solvent sols containing highly stable hollow silica particles, thereby improving the stability of the aforementioned sols whose shelf life has been reduced. The solution of this invention is the aforementioned hollow silica sol, which comprises hollow silica particles and monovalent alkali metal ions with space within an outer shell. The monovalent alkali metal ions are contained in a sol at a ratio of 7.12 × ^10⁻⁶ to 285 × ^10⁻⁶ moles of _SiO₂ in the hollow silica particles, converted to _M₂O (where M represents monovalent alkali atoms). The average particle size of this sol after being stored at 50°C for 48 hours, as measured by dynamic light scattering, is within 2.0 times smaller than the average particle size measured by dynamic light scattering before storage. The average particle size measured by dynamic light scattering is 20~150 nm. A stabilization method for reducing the increased dynamic light scattering particle size involves adding monovalent alkali metal ions to a hollow silica sol containing an increased dynamic light scattering particle size compared to the manufacturing dynamic light scattering particle size, in a ratio relative to the _SiO2 of the hollow silica particles in the hollow silica sol.

Description

Hollow silica sol containing monovalent alkali metal ions, its manufacturing method, stabilization method, and coating-forming components and films containing the same.

The present invention relates to a sol containing monovalent alkali metal ions such as sodium ions dispersed in water or an organic solvent, a method for manufacturing the sol, and a coating forming composition thereof.

Hollow silica particles, which have a silica shell and a space inside the shell, possess characteristics such as low refractive index, low thermal conductivity (thermal insulation), and electrical insulation. Hollow silica particles consist of a core, which is equivalent to a cavity, and an outer shell forming the core. By forming a silica layer on the outer side of the core in an aqueous medium, and then removing the core, an aqueous dispersion of hollow silica particles can be obtained. A type of silicon oxide microparticle with a cavity inside its shell has been disclosed. It is characterized by an average particle size in the range of 5 to 500 nm, a refractive index in the range of 1.15 to _1.38 , a molar ratio of _MoX / _{SiO2 (} where silicon oxide is represented by _SiO2 and inorganic oxides other than silicon oxide are represented by MOX) in the range of 0.0001 to 0.2, and an alkali oxide content of less than 5 ppm ( _A2O , where A is the alkali metal element) (see Patent Document 1).

A type of silica microparticle has been disclosed, characterized by having porous material and/or cavities in the interior of its outer shell. The ratio of the specific surface area (SB) to the specific surface area (SC) (SB/SC) of the microparticle, as determined by the BET method, is in the range of 1.1 to 5. The refractive index is in the range of 1.15 to 1.38. The content of alkali metal oxides, expressed as _M₂O (M: alkali metal element) per silica microparticle, is less than 5 ppm. The content of ammonia and/or ammonium ions per silica microparticle, expressed as _NH₃, is less than 1500 ppm (see Patent Document 2). (But Dp: average particle size (nm) of silicon oxide microparticles, ρ: density (g/ml)). [Previous Art Documents] [Patent Documents]

[Patent Document 1] Japanese Patent Application Publication No. 2011-046606 [Patent Document 2] Japanese Patent Application Publication No. 2013-121911

[Problem to be Solved by the Invention] This invention relates to aqueous sols and organic solvent sols containing highly stable hollow silica particles, and further to methods for improving the stability of the aforementioned sols whose shelf life has been reduced, as well as their manufacturing methods. [Means for Solving the Problem]

The first point of view in this invention is a hollow silica sol, which comprises hollow silica particles with internal space within a shell and monovalent alkali metal ions. The monovalent alkali metal ions are contained in a sol with a mole number of _M₂O (where M represents monovalent alkali metal atoms) relative to the mole number of _SiO₂ in the hollow silica particles ranging from ^7.12 × 10⁻⁶ to 285 × ^10⁻⁶. The average particle size of this sol, measured by dynamic light scattering after being stored at 50°C for 48 hours, is within 2.0 times smaller than the average particle size measured by dynamic light scattering before storage. Alternatively, it could be a hollow silica sol containing hollow silica particles with internal space within a shell, and _SiO₂ relative to the hollow silica particles, converted to _M₂O (where M represents a monovalent alkali metal), in a molar ratio of 7.12 × ^10⁻⁶ to 285 × ^10⁻⁶ containing monovalent alkali metal ions. Furthermore, the particle size obtained by dynamic light scattering after storage at 50°C for 48 hours is within 2.0 times that before storage. A second viewpoint is the hollow silica sol of the first viewpoint, wherein the aforementioned monovalent alkali metal ions are sodium ions. The third viewpoint refers to the hollow silica sol of the first or second viewpoint, wherein the average particle size, determined by dynamic light scattering, is 20-150 nm. The fourth viewpoint refers to the hollow silica sol of any one of the first to third viewpoints, further comprising an amine, wherein the amine content relative to the _SiO₂ of the hollow silica particles is 0.001-10% by mass. The fifth viewpoint refers to the hollow silica sol of the fourth viewpoint, wherein the aforementioned amine is at least one amine selected from the group consisting of primary, secondary, and tertiary amines having 1-10 carbon atoms. The sixth viewpoint refers to the hollow silica sol of the fourth or fifth viewpoint, wherein the aforementioned amine is a water-soluble amine with a water solubility of 80 g/L or higher. The seventh viewpoint refers to any of the hollow silica sols described in viewpoints 1 through 6, wherein the hollow silica particles contain aluminum atoms forming aluminate silicate sites. These aluminum atoms are bonded to the surface of the hollow silica particles, and the mass of these aluminum atoms, relative to the mass of _SiO₂ in the hollow silica particles, is in the range of 100-20000 ppm ( _A ) when converted to _Al₂O₃ . The mass of these aluminum atoms is determined by leaching. Alternatively, the seventh viewpoint refers to any of the hollow silica sols described in viewpoints 1 through 6, wherein the hollow silica particles contain aluminum atoms forming aluminate silicate sites. The mass of these aluminum atoms is determined by leaching and is bonded to the surface of the hollow silica particles by Al₂O₃. The ratio of _2O3 to _1g of _SiO2 in hollow silicon oxide particles is 100~20000ppm/ _SiO2 ratio (A) bond. The eighth viewpoint is the hollow silica sol of the seventh viewpoint, wherein the above-mentioned leaching method for determining the leaching of aluminum atoms from compounds containing aluminum atoms bonded to the surface of hollow silica particles is performed using an aqueous solution of at least one inorganic acid selected from the group consisting of sulfuric acid, nitric acid, and hydrochloric acid. Alternatively, the hollow silica sol of the seventh viewpoint is used, wherein the leaching method for determining the leaching of hollow silica particles in an aqueous solution of at least one inorganic acid selected from the group consisting of sulfuric acid, nitric acid, and hydrochloric acid, wherein the ratio of compounds containing aluminum atoms bonded to the surface of hollow silica particles leached from the hollow silica particles to 1 _g of _SiO2 of the hollow silica particles is calculated as _Al2O3 (A). The ninth viewpoint refers to the hollow silica sol of viewpoints 7 and 8, wherein the mass of aluminum atoms present in the entire hollow silica particles, expressed as _Al₂O₃ relative to the mass of _SiO₂ in the hollow silica particles _, is 120~50000 ppm (B). This mass of aluminum atoms is determined by a dissolution method using hydrofluoric acid aqueous solution to dissolve the hollow silica particles. The ratio (A)/(B) is 0.002~1.0. Alternatively, the ninth viewpoint refers to the hollow silica sol of viewpoints 7 and 8, wherein the mass of aluminum atoms present in the entire hollow silica particles, expressed as _Al₂O₃ relative to the mass of _SiO₂ in the hollow silica particles, is determined by a dissolution method using hydrofluoric acid aqueous solution to dissolve the hollow silica particles. _{The 2} :1g ratio is bonded at a ratio of 120~50000ppm/ _SiO2 (B), where (A)/(B) is 0.001~1.0. The 10th point is any of the hollow silica sols in points 1 to 9, which contains the hollow silica particles described above with a ratio of [specific surface area of silica particles measured by BET method (nitrogen adsorption method) (C)]/[specific surface area of silica particles converted by self-transmitting electron microscopy (D)] of 1.40~5.00.

The 11th viewpoint is a hollow silica sol from any of the 1st to the 10th viewpoints, comprising hollow silica particles with a surface charge of ₅ to 250 μeq/g of SiO2 per 1g, or a hollow silica sol from any of the 1st to the 10th viewpoints, comprising hollow silica particles with a surface charge of 5 to 250 μeq/g of SiO2 per _1g . The 12th viewpoint is a hollow silica sol from any of the 1st to the 11th viewpoints, wherein the hollow silica particles further comprise hollow silica particles coated with at least one silane compound selected from the group represented by formulas (1) and (2) below. In formula (1), ^R1 is a group bonded to a silicon atom, and independently represents an alkyl, halogenated alkyl, alkenyl, aryl, or an organic group having an epoxy, (meth)acryl, teryl, amino, urea, polyether, carboxyl, protected carboxyl, carboxyl-derived group, amide, or cyano group and bonded to a silicon atom by a Si-C bond, or a combination of such groups; ^R2 is a group or atom bonded to a silicon atom, and independently represents an alkoxy, acetoxy, hydroxyl, or halogen atom having 1 or more carbon atoms, or a combination of such groups; a represents an integer from 1 to 3; in formula (2), R ³ represents a group bonded to a silicon atom and independently represents an alkyl, halogenated alkyl, alkenyl, aryl, or an organic group having an epoxy, (meth)acryl, teryl, amino, urea, polyether, carboxyl, protected carboxyl, carboxyl-derived, amide, or cyano group and bonded to a silicon atom by a Si-C bond, or a combination of such groups. ^R4 represents a group or atom bonded to a silicon atom and independently represents an alkoxy, acetoxy, hydroxyl, or halogen atom having one or more carbon atoms, or a combination of such groups. Y represents a group or atom bonded to a silicon atom and represents an alkyl, NH, or oxygen atom. b represents an integer from 1 to 3, and c represents an integer of 0 or 1. Point 13 refers to a hollow silica sol from any of points 1 to 12, wherein the dispersion medium is water, an alcohol, ketone, ether, amide, urea, or ester having 1 to 10 carbon atoms. Point 14 refers to a coating-forming composition comprising hollow silica particles derived from any of the hollow silica sols from points 1 to 13, and an organic resin or polysiloxane. Point 15 refers to a membrane having a visible light transmittance of 80% or more, obtained from the coating-forming composition of point 14. The 16th viewpoint is a method for manufacturing hollow silica sol as described in any of the 1st to 13th views, comprising the following steps (I) to (II): (I) step: preparing a hollow silica sol containing a dispersion medium; (II) step: adding and adjusting monovalent metal ions to the hollow silica sol of step ( _I ) in a molar ratio of 7.12 × ^10⁻⁶ to 285 × ^10⁻⁶ relative to the _SiO₂ of the hollow silica particles. The 17th viewpoint is the same as the 16th viewpoint in the method for manufacturing hollow silica sol, wherein in step (II) above, the monovalent alkali metal ion is sodium ion. The 18th viewpoint is the same as the 17th viewpoint in the method for manufacturing hollow silica sol, wherein in step (II) above, the adjustment of the sodium ion content is to bring the hollow silica sol obtained in step (I) into contact with a cation exchange resin, or to add a sodium source. The 19th viewpoint is the same as the 17th viewpoint in the method for manufacturing hollow silica sol, wherein in step (II) above, the addition of the sodium source is the addition of sodium hydroxide. The 20th point is the manufacturing method of hollow silica sol as described in any of the 16th to 19th points, wherein the dispersion medium in steps (I) and (II) above is water, alcohol, ketone, ether, amide, urea or ester having 1 to 10 carbon atoms. The 21st point is a method for manufacturing hollow silica sol as described in any of the 16th to 20th points, wherein in step (I), step (II), or both steps above, at least one of the following steps (i) to (iv) is added: (i) adding an amine to the hollow silica sol; (ii) adding sodium aluminate as an aluminum source and heating to form aluminosilicate sites on the hollow silica particles; (iii) replacing the dispersion medium with another dispersion medium; and (iv) coating the hollow silica particles with at least one silane compound selected from the group consisting of formulas (1) and (2). The 22nd viewpoint is a stabilization method for hollow silica sol similar to the 1st viewpoint. This method stabilizes hollow silica sol containing hollow silica particles within a shell. Its characteristic feature is that for hollow silica sol where the average particle size, as measured by dynamic light scattering, has increased compared to the manufacturing stage, the method adds monovalent metal ions, using a mole ratio of the moles of _M₂O (where M represents monovalent metal atoms) to the moles of _SiO₂ in the hollow silica sol particles, which is 7.12 × ^10⁻⁶ ~ 285 × ^10⁻⁶ . This reduces the increased average particle size measured by dynamic light scattering. Alternatively, a stabilization method for hollow silica sol as described in the first viewpoint could be used. This method involves stabilizing hollow silica sol containing hollow silica particles within a shell. The method is characterized by adding monovalent metal ions to the hollow silica sol, which has an increased particle size compared to the particle size measured by dynamic light scattering at the time of manufacturing. The molar ratio of monovalent metal ions to _{SiO₂ (converted to M₂O ,} where M represents a monovalent metal) of the hollow silica particles in the hollow silica sol is 7.12 × ^10⁻⁶ to 285 × ^10⁻⁶ , thereby reducing the increased particle size measured by dynamic light scattering. The 23rd viewpoint is the stabilization method for hollow silica sol as described in viewpoint 22, wherein the aforementioned monovalent alkali metal ions are sodium ions. [Invention Effect]

Hollow silica sol, a dispersion containing hollow silica particles, is stable, thus allowing for the production of hollow silica sols with minimal particle size variation and no aggregation of the particles. When using highly stable hollow silica sols as coatings, the small particle size variation reduces surface roughness and improves transparency. The amount of alkali metal ions (e.g., sodium ions) in the hollow silica sol is preferably within a certain range; excessive amounts can lead to alkali metal ion leaching from the coating and problems with the coating's electrical insulation. Furthermore, when the amount is too small, the hollow silica particles have a lower specific gravity than solid silica particles because the outer shell is hollow. Therefore, the repulsive force of the particles is low, and the particles tend to aggregate and condense easily. In this case, a certain amount of alkali metal ions (such as sodium ions) are needed to increase the particle repulsive force.

In this invention, stability is improved by combining amine molecules and sodium ions as alkali components. This is believed to be due to the presence of large amine molecules and sodium ions on the particle surface, which further enhances the repulsive force between silicon oxide particles. Furthermore, in this invention, aluminate silicate sites can be formed by doping aluminum atoms onto the surface of silicon oxide particles. The presence of alkali metals that counteract the negatively charged aluminum atoms further improves the stability of the aluminate silicate sites.

This invention relates to a hollow silica sol, which comprises hollow silica particles with internal space within an outer shell and monovalent alkali metal ions. The molar ratio of monovalent alkali metal ions (converted to _M₂O , where M represents a monovalent alkali metal atom) to _SiO₂ in the hollow silica particles is between 7.12 × ^10⁻⁶ and 285 × ^10⁻⁶. The average particle size obtained by dynamic light scattering after storage at 50°C for 48 hours is within 2.0 times that of the particle size obtained before storage. The hollow silica particles have a silica outer shell with internal space within the shell. Hollow silica is obtained by forming a shell with silica as the main component on the surface of a portion of the surface that is equivalent to a core in a dispersion medium, and then removing the portion that is equivalent to the core.

Hollow silica particles need to be stably dispersed in a dispersion medium. However, the surface of hollow silica particles contains silanol groups, organic functional groups, and aluminate silicate sites doped with aluminum atoms. Stability can be achieved by adding monovalent alkali metal ions to the surface of the hollow silica particles. Regarding silanol groups, organic functional groups, and aluminate silicate sites, hydroxyl groups and other polymerizable functional groups exist. The interaction between these polymerizable functional groups leads to weak condensation (entanglement) between particles and particle instability or particle size increase due to crosslinking caused by hydrogen bonds. However, by adding monovalent alkali metal ions to these polymerizable functional groups, it is believed that the morphology of the hydroxyl groups can be changed, and the factors causing instability can be suppressed. These polymerizable functional groups can sometimes become unstable upon heating, and the stability of the hollow silica sol can be evaluated by confirming its stability after 48 hours at 50°C. Examples of monovalent alkali metal ions include lithium ions, sodium ions, potassium ions, malon ions, and cesium ions, but lithium ions, sodium ions, and potassium ions are preferred, especially sodium ions.

The content of monovalent alkali metal ions in the dispersion (sol) can be expressed as follows: the molar ratio of monovalent alkali metal ions per mass of _SiO2 in hollow silicon oxide particles, converted to _M2O (where M represents monovalent alkali metal atoms), can be 7.12× ^10⁻⁶ ~ 285× ^10⁻⁶ , or 7.12× ^10⁻⁶ ~ 237× ^10⁻⁶ , or 7.12× ^10⁻⁶ ~ 190× ^10⁻⁶ , or 20× ^10⁻⁶ ~ 285× ^10⁻⁶ , or 50× ^10⁻⁶ ~ 285× ^10⁻⁶ . Furthermore, the content of the aforementioned monovalent alkali metal ions can be set in the dispersion (sol) to a molar ratio of 15ppm to 600ppm, or 15ppm to 500ppm, or 15ppm to 400ppm per mass of _SiO2 of hollow silicon oxide particles, converted to _M2O (where M represents monovalent alkali metal atoms).

In this invention, the average particle size of the hollow silica sol, determined by dynamic light scattering, can be set to a range of 20-150 nm. Furthermore, the dynamic light scattering particle size of the aforementioned hollow silica sol after being stored at 50°C for 48 hours is within 2.0 times, 1.5 times, or 1.1 times that before storage. A smaller dynamic light scattering particle size after storage at 50°C for 48 hours compared to before storage is also included in this invention. Therefore, the lower limit value can be set to 0.8 times or more, 0.9 times or more, or 1.0 times or more. In this invention, by containing sodium ions within the aforementioned range, the stability of the hollow silica sol can be ensured. This means that the sol containing hollow silica particles can contain sodium ions within the aforementioned range before it becomes unstable. Furthermore, by adding the aforementioned sodium ions to the sol containing unstable hollow silica particles, the agglomerated state of the hollow silica particles can be disintegrated, and the particle size range of the hollow silica particles can be returned to that of the pre-agglomerated state.

In this invention, aluminum atoms are represented by measuring the aluminum present on the surface of silicon oxide particles using an aqueous solution of at least one inorganic acid selected from the group consisting of sulfuric acid, nitric acid, and _hydrochloric acid, and converting it to _Al₂O₃ . That is, the aluminum atoms are bonded to the hollow silica particle surface in a ratio _{( A)} of 100~20000 ppm/SiO2, or 100~15000 ppm/ _SiO2 , or 100~10000 ppm/ _SiO2 , or 200~5000 ppm/ _SiO2 , or 500~5000 ppm/ _SiO2 , or 800~3000 ppm/ _{SiO2 ,} based on _the mass of aluminum atoms determined by the leaching method. The presence and formation of aluminate silicate sites on the silica particle surface are important for dispersion in solvents and resins. Aluminum atoms present as aluminate silicates on the surface of silica particles are leached (dissolved) by leaching (leaching) the silica particles with an aqueous solution of at least one inorganic acid selected from the group consisting of sulfuric acid, nitric acid, and hydrochloric acid, causing the aluminum atoms to form a structure similar to aluminum salts, aluminum oxides, or aluminum hydroxides. The aluminum atoms in this solution can be determined using an ICP-based spectrophotometer and converted to _Al₂O₃ . In particular _, an aqueous solution of nitric acid can be used for leaching (dissolving). The aqueous solution of nitric acid used in the leaching method can have a pH range of 0.5–4.0, 0.5–3.0, 0.5–2.0, or 1.0–1.5; typically, an aqueous solution of nitric acid with a pH of 1.0 can be used. For example, 100 mL of the above-mentioned nitric acid aqueous solution is added to 1 g of silicon oxide and kept at a temperature of 20~70°C or 40~60°C for 10~24 hours to leach aluminum compounds from the surface of silicon oxide particles, which are then used as analytical samples.

In this invention, the so-called silica particle surface can be defined as the region from which aluminum compounds can be dissolved by the above-mentioned leaching method. This can be achieved by evaporating the solvent from silica sol, drying the silica sol at 250°C, grinding it into silica powder, adding 20 mL of pH 1.0 nitric acid aqueous solution to 0.2 g of the silica powder and shaking it thoroughly, maintaining it in a constant temperature bath at 50°C for 17 hours, and then centrifuging and filtering _. The aluminum content in the resulting filtrate is determined by ICP emission spectrophotometry. By dividing the aluminum content converted to _{Al₂O₃ by} the mass of the silica powder, the amount of aluminum bonded to the silica particle surface ( _Al₂O₃ / _SiO₂ ) (ppm) can be calculated. Furthermore, even when aluminate silicates are formed on the surface of silica particles, depending on the manufacturing method, there are cases where aluminate silicates can be selectively formed not only on the surface but also inside the silica particles. The mass of aluminum atoms present in the entire hollow silica particles, including the surface and the interior _, is converted _{to Al₂O₃} and is bonded to the silica particles in a ratio (B) of 120~50000ppm _{/ SiO₂} , or 500~20000ppm/ _SiO₂ , or 500~10000ppm/SiO₂, or 1000~5000ppm/ _SiO₂ , or 1000~4000ppm/ _SiO₂ .

The ratio (A)/ratio (B) of the aluminum content on the surface of the silicon oxide particles to that in the entire silicon oxide particles can be set within the range of 0.001~1.0, 0.01~1.0, 0.1~1.0, 0.3~1.0, or 0.4~1.0. The aluminum atoms present in the entire silicon oxide particles can be determined by dissolving the silicon oxide particles in an aqueous solution of hydrofluoric acid using a dissolution method, and then converted to _Al₂O₃ . That is, the aluminum atoms present in the entire silicon oxide particles as aluminate silicates can be dissolved in _an aqueous solution of hydrofluoric acid, and the determination can _be performed using an ICP-based spectrophotometer, and then converted to _Al₂O₃ to represent the aluminum atoms present in the entire silicon oxide particles. The hydrofluoric acid aqueous solution only needs to be concentrated enough to dissolve the silicon oxide particles; for example, a 48% by mass hydrofluoric acid aqueous solution can be used. Furthermore, in order to completely dissolve the silicon oxide particles, the amount of hydrofluoric acid aqueous solution used must be at least equivalent to the silicon oxide particles, preferably 1.1 to 1000 equivalents in molar ratio.

Thus, by forming aluminosilicate sites on the surface of silica particles, the negative charge (surface charge) of the hollow silica particles present on the surface _of the silica particles is measured in the range of 5~250 μeq/g, or 5~150 μeq/g, or 5~100 μeq/g, or 25~150 μeq/g, or 25~100 μeq/g per 1g of SiO2. The aforementioned hollow silica particles can be obtained by dispersing them in a hollow silica sol. A hollow silica sol with an average particle size of 20~150 nm, determined by dynamic light scattering, can be obtained by dispersing hollow silica particles in a sol in a dispersion medium. Hollow silica is obtained by forming a shell mainly composed of silica on the surface of a core portion in a dispersion medium, and then removing the core portion. In this state, it is a hollow silica aqueous sol. The resulting hollow silica aqueous sol can be solvent-replaced with an alcohol solvent, which is an organic solvent. The alcohol solvent preferably has ether bonds and is preferably an alcohol with 1 to 5 carbon atoms, such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, etc. Subsequently, after coating with a silane compound as needed, solvent replacement can be performed with other organic solvents.

In this invention, examples of organic solvents include alcohols, ketones, ethers, amides, ureas, and esters having 1 to 10 carbon atoms. Alcohols having 1 to 10 carbon atoms are aliphatic alcohols, such as primary, secondary, and tertiary alcohols. Furthermore, polyols can also be used, such as diols and triols.

Examples of monohydric first-order alcohols include methanol, ethanol, 1-propanol, 1-butanol, and 1-hexanol. Examples of monohydric second-order alcohols include 2-propanol, 2-butanol, cyclohexanol, propylene glycol monomethyl ether, and propylene glycol monoethyl ether. Examples of monohydric third-order alcohols include tributanol. Examples of dihydric alcohols include methanediol, ethylene glycol, and propylene glycol. Examples of trihydric alcohols include glycerol.

Aliphatic ketones are preferred as ketones with 1 to 10 carbon atoms. Examples include acetone, methyl ethyl ketone, diethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl pentyle ketone, cyclohexanone, and methyl cyclopentanone. Aliphatic ethers are preferred as ethers with 1 to 10 carbon atoms. Examples include dimethyl ether, ethyl methyl ether, diethyl ether, tetrahydrofuran, and 1,4-dioxane.

Examples of amides with 5 to 20 carbon atoms include N-methylpyrrolidone, dimethylacetamide, and diethylacetamide. Examples of ureas with 5 to 20 carbon atoms include tetramethylurea and 1,3-dimethyl-2-imidazolium ketone. Aliphatic esters with 1 to 10 carbon atoms are preferred. Examples include methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl acrylate, ethyl acrylate, propyl acrylate, dimethyl maleate, diethyl maleate, dipropyl maleate, dimethyl adipate, diethyl adipate, and dipropyl adipate.

In the hollow silica aqueous sol and hollow silica organic solvent sol of the above-mentioned raw materials, the average particle size of the hollow silica particles, as determined by dynamic light scattering (DLS method), is 20~150 nm, 30~150 nm, 40~150 nm, 50~150 nm, 50~120 nm, or 50~100 nm. Furthermore, the average primary particle size observed by transmission electron microscopy can be in the range of 20~150 nm, 30~150 nm, 40~150 nm, 50~150 nm, 50~120 nm, or 50~100 nm.

Furthermore, the specific surface area (C) determined by the BET method (nitrogen adsorption method) can be set to 18~200 ^m² /g, or 50~160 ^m² /g, or 60~160 ^m² /g, or 70~160 ^m² /g, or 80~150 ^m² /g. Also, the specific surface area (D) converted from a transmission electron microscope is 18~136 ^m² /g, or 18~90 ^m² /g, or 18~68 ^m² /g, or 18~54 ^m² /g, or 18~27 ^m² /g, or 18~23 ^m² /g.

Therefore, the ratio of [specific surface area (C) measured by the BET method (nitrogen adsorption method)] to [specific surface area (D) converted by transmission electron microscopy] can be set to a range of 1.40~5.00, or 1.40~3.50, or 1.50~3.00, or 1.50~2.80. When the value of (C)/(D) is close to 1.0, it indicates that there is no space inside the outer shell of the silicon oxide particle; when the value of (C)/(D) exceeds 1.0, it indicates that there is a hollow silicon oxide particle with space inside the outer shell of the silicon oxide particle. Furthermore, the outer shell thickness of hollow silicon oxide particles, observable by a transmission electron microscope, can be in the range of 3.0~15.0 nm, or 4.0~12.0 nm, or 5.0~10.0 nm. Moreover, the refractive index of the aforementioned hollow silicon oxide particles can be obtained in the range of 1.20~1.45, or 1.20~1.40, or 1.25~1.40.

Furthermore, the hollow silica sol is used with a _SiO2 particle concentration of 1-50% by mass or 5-40% by mass, typically 10-30% by mass. The pH of the above sol can be adjusted to acidic to alkaline. Adjustment to acidic is done by adding inorganic or organic acids. Adjustment to alkaline is done by adding inorganic or organic bases. As an organic base, amines can be added for the purpose of adjusting pH and surface charge. The pH on the acidic side can be set from pH 1 to less than 7, and the pH on the alkaline side can be set from pH 7 to 13.

The aqueous sol of hollow silica can be set to a pH range of 2.0~6.0 or 2.0~4.5 before the addition of amine. By adding amine, it can be adjusted to a range of, for example, 3.0~10.0 or 3.0~9.0. In the case of organic solvent sol, the above pH refers to the pH when the organic solvent sol is mixed with an equal mass of pure water at a 1:1 ratio. Although the pH can be measured when using organic solvents that are miscible with water, it is preferable to measure the pH in advance during the methanol solvent sol stage when the solvent is replaced with the hydrophobic organic solvent described later. For example, in the case of hydrophilic organic solvents such as methanol sol and propylene glycol monomethyl ether sol, the determination can be performed using a solution of pure water and sol mixed in a 1:1 mass ratio. In the case of hydrophobic organic solvents such as methyl ethyl ketone sol, the determination can be performed using a solution of pure water, methanol, and methyl ethyl ketone mixed in a 1:1:1 mass ratio.

Hollow silica organic solvent sol involves replacing an aqueous solvent with an alcohol solvent containing 1 to 5 carbon atoms, thereby replacing the solvent with an organic solvent. However, water may remain in this process. In the alcohol solvent stage of hollow silica, the residual water content in the sol may be 0.1 to 3.0% by mass or 0.1 to 1.0% by mass. Furthermore, in the organic solvent stage of hollow silica (where the dispersion medium is an organic solvent other than alcohol), the content may be 0.01 to 0.5% by mass. The viscosity of the hollow silica organic solvent sol can be set in the range of 1.0 to 10.0 mPa·s.

The hollow silica sol of this invention may contain amines. The amines used in this invention may be water-soluble amines with a water solubility of 80 g/L or more, or 100 g/L or more. The aqueous hollow silica sol of the raw material may contain amines, or amines and ammonia, in the hollow silica organic solvent sol obtained by solvent substitution. The amines may be added in the range of 0.001~10% by mass, 0.01~10% by mass, or 0.1~10% by mass relative to the _SiO2 of the hollow silica particles. Furthermore, the amine or amine and ammonia can be expressed as total nitrogen content in the hollow silica particle organic solvent sol, for example, in the range of 10~100000 ppm, or 100~10000 ppm, or 100~3000 ppm, or 100~2000 ppm, typically in the range of 200~2000 ppm.

Examples of the amines mentioned above include aliphatic amines and aromatic amines, but aliphatic amines are preferred. The amine may be at least one amine selected from the group consisting of primary, secondary, and tertiary amines having 1 to 10 carbon atoms. These amines are water-soluble and are at least one amine selected from the group consisting of primary, secondary, and tertiary amines having 1 to 10 carbon atoms. Examples of primary amines include monomethylamine, monoethylamine, monopropylamine, monoisopropylamine, monobutylamine, monoisobutylamine, monodibutylamine, monotertbutylamine, monomethanolamine, monoethanolamine, monopropanolamine, monoisopropanolamine, monobutanolamine, monoisobutanolamine, monodibutanolamine, monotertbutylamine, etc.

Examples of secondary amines include dimethylamine, diethylamine, dipropylamine, diisopropylamine, N-methylethylamine, N-ethylisobutylamine, diethanolamine, diethanolamine, dipropanolamine, diisopropanolamine, N-methanolethylamine, N-methylethanolamine, N-ethanolisobutylamine, and N-ethylisobutylamine. Examples of tertiary amines include trimethylamine, triethylamine, tripropylamine, triisopropylamine, tributylamine, triisobutylamine, tridibutylamine, tritertbutylamine, trimethanolamine, triethanolamine, tripropanolamine, triisopropanolamine, tributanolamine, triisobutylamine, tridibutylamine, tritertbutylamine, tripentylamine, ethyl 3-(dimethylamino)acrylate, ethyl 2-(dimethylamino)acrylate, ethyl 2-(dimethylamino)methacrylate, ethyl 2-(diethylamino)acrylate, and ethyl 2-(diethylamino)methacrylate.

The water solubility of the aforementioned amines is preferably 80 g/L or higher, or 100 g/L or higher. These amines are preferably primary or secondary amines; secondary amines are preferred due to their low volatility and high solubility, and examples include diisopropylamine and diethanolamine. In this invention, by including the aforementioned amines, the surface charge of the hollow silicon oxide particles can be set to 5 μeq/g or higher, or 25 μeq/g or higher per _1g of SiO₂. Typically, it can be set to a range of 5~250 μeq/g, 25~250 μeq/g, 25~100 μeq/g, or 25~80 μeq/g. In this invention, by adjusting the type and amount of the aforementioned amines, the surface charge of the hollow silicon oxide particles can be adjusted to any desired surface charge.

In this invention, the surface of hollow silicon oxide particles may be coated with a silane compound. As the silane compound, a hydrolysate of at least one silane compound from the group consisting of formula (1) and formula (2) may be selected for coating. In formula (1), ^R1 is alkyl, halogenated alkyl, alkenyl, aryl, or an organic group having polyether, epoxy, (meth)acrylyl, teryl, amino, urea, or cyano groups, and is bonded to silicon atoms by Si-C bonds; ^R2 represents alkoxy, acetoxy, or halogen groups; a represents an integer from 1 to 3; In formula (2), ^R3 is alkyl with 1 to 3 carbon atoms or aryl with 6 to 30 carbon atoms and is bonded to silicon atoms by Si-C bonds; ^R4 represents alkoxy, acetoxy, or halogen groups; Y represents alkyl, NH, or oxygen atoms; b is an integer from 1 to 3; c is an integer of 0 or 1; and d is an integer from 1 to 3.

The alkyl groups mentioned above are alkyl groups having 1 to 18 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, dibutyl, tributyl, cyclobutyl, 1-methylcyclopropyl, 2-methylcyclopropyl, n-pentyl, 1-methyln-butyl, 2-methyln-butyl, 3-methyln-butyl, 1,1-dimethyln-propyl, 1,2-dimethyln-propyl, 2,2-dimethyln-propyl, 1-ethyln-propyl, cyclopentyl, 1-methylcyclobutyl, 2-methylcyclobutyl, 3-methylcyclopropyl Butyl, 1,2-dimethylcyclopropyl, 2,3-dimethylcyclopropyl, 1-ethylcyclopropyl, 2-ethylcyclopropyl, n-hexyl, 1-methyl-n-pentyl, 2-methyl-n-pentyl, 3-methyl-n-pentyl, 4-methyl-n-pentyl, 1,1-dimethyl-n-butyl, 1,2-dimethyl-n-butyl, 1,3-dimethyl-n-butyl, 2,2-dimethyl-n-butyl, 2,3-dimethyl-n-butyl, 3,3-dimethyl-n-butyl, 1-ethyl-n-butyl, 2-ethyl-n-butyl, 1,1,2-trimethyl-n-propyl, 1 2,2-Trimethyl-n-propyl, 1-Ethyl-1-methyl-n-propyl, 1-Ethyl-2-methyl-n-propyl, Cyclohexyl, 1-Methylcyclopentyl, 2-Methylcyclopentyl, 3-Methylcyclopentyl, 1-Ethylcyclobutyl, 2-Ethylcyclobutyl, 3-Ethylcyclobutyl, 1,2-Dimethylcyclobutyl, 1,3-Dimethylcyclobutyl, 2,2-Dimethylcyclobutyl, 2,3-Dimethylcyclobutyl, 2,4-Dimethylcyclobutyl, 3,3-Dimethylcyclobutyl, 1-n-propylcyclopropyl, 2-n-propylcyclopropyl 1-Isopropylcyclopropyl, 2-Isopropylcyclopropyl, 1,2,2-Trimethylcyclopropyl, 1,2,3-Trimethylcyclopropyl, 2,2,3-Trimethylcyclopropyl, 1-Ethyl-2-methylcyclopropyl, 2-Ethyl-1-methylcyclopropyl, 2-Ethyl-2-methylcyclopropyl and 2-Ethyl-3-methylcyclopropyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecanyl, octadecyl, etc., but not limited to these. Furthermore, the alkyl group may be an alkyl group derived from the above-mentioned alkyl groups.

The aryl groups mentioned above are aryl groups with 6 to 30 carbon atoms, such as phenyl, naphthyl, anthracene, and pyrene. The alkenyl groups are alkenyl groups with 2 to 10 carbon atoms, such as vinyl, 1-propenyl, 2-propenyl, 1-methyl-1-vinyl, 1-butenyl, 2-butenyl, 3-butenyl, 2-methyl-1-propenyl, 2-methyl-2-propenyl, 1-ethylvinyl, 1-methyl-1-propenyl, 1-methyl-2-propenyl. 1-Pentenyl, 2-Pentenyl, 3-Pentenyl, 4-Pentenyl, 1-n-Propylvinyl, 1-Methyl-1-Butenyl, 1-Methyl-2-Butenyl, 1-Methyl-3-Butenyl, 2-Ethyl-2-Propylene, 2-Methyl-1-Butenyl, 2-Methyl-2-Butenyl, 2-Methyl-3-Butenyl, 3-Methyl-1-Butenyl, 3-Methyl-2-Butenyl, 3-Methyl-3-Butenyl, 1,1-Dimethyl-2-Propylene, 1-Isopropylethylene The group includes, but is not limited to, 1,2-dimethyl-1-propenyl, 1,2-dimethyl-2-propenyl, 1-cyclopentenyl, 2-cyclopentenyl, 3-cyclopentenyl, 1-hexenyl, 2-hexenyl, 3-hexenyl, 4-hexenyl, 5-hexenyl, 1-methyl-1-pentenyl, 1-methyl-2-pentenyl, 1-methyl-3-pentenyl, 1-methyl-4-pentenyl, 1-n-butylvinyl, 2-methyl-1-pentenyl, 2-methyl-2-pentenyl, etc.

Examples of the aforementioned alkoxy groups are alkoxy groups having 1 to 10 carbon atoms, such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, dibutoxy, tributoxy, n-pentoxy, 1-methyl n-butoxy, 2-methyl n-butoxy, 3-methyl n-butoxy, 1,1-dimethyl n-propoxy, 1,2-dimethyl n-propoxy, 2,2-dimethyl n-propoxy, 1-ethyl n-propoxy, n-hexyloxy, etc., but not limited to these. The aforementioned acetylation groups are acetylation groups with 2 to 10 carbon atoms, examples of which include methyl carbonyloxy, ethyl carbonyloxy, n-propyl carbonyloxy, isopropyl carbonyloxy, n-butyl carbonyloxy, isobutyl carbonyloxy, dibutyl carbonyloxy, tributyl carbonyloxy, n-pentyl carbonyloxy, 1-methyl n-butyl carbonyloxy, 2-methyl n-butyl carbonyloxy, 3-methyl n-butyl carbonyloxy, 1,1-dimethyl n-propyl carbonyloxy, 1,2-dimethyl n-propyl carbonyloxy, 2,2-dimethyl n-propyl carbonyloxy, 1-ethyl n-propyl carbonyloxy, n-hexyl carbonyloxy, 1-methyl n-pentyl carbonyloxy, 2-methyl n-pentyl carbonyloxy, etc., but are not limited to these. Examples of halogen groups include fluorine, chlorine, bromine, iodine, etc. Examples of organic groups having a polyether group include polyetherpropyl having an alkoxy group. For example, (CH ₃ O) ₃ SiC ₃ H ₆ (OC ₂ H ₄ )nOCH _3. n can be used in the range of 1~100 or 1~10.

Examples of organic groups containing an epoxy group include 2-(3,4-epoxycyclohexyl)ethyl and 3-glycidoxypropyl. The term (meth)acrylic acid refers to both acrylonitrile and methacrylic acid. Examples of organic groups containing a (meth)acrylic acid include, for example, 3-methacrylic acidoxypropyl and 3-acrylic acidoxypropyl.

Examples of organic groups containing a guanidine group include, for example, 3-guanidine propyl. Examples of organic groups containing an amino group include, for example, 2-aminoethyl, 3-aminopropyl, N-2-(aminoethyl)-3-aminopropyl, N-(1,3-dimethylbutylene)aminopropyl, N-phenyl-3-aminopropyl, N-(vinylbenzyl)-2-aminoethyl-3-aminopropyl, etc. Examples of organic groups containing a urea group include, for example, 3-ureopropyl. Examples of organic groups containing a cyano group include, for example, 3-cyanopropyl. Preferably, the compound of formula (2) is formed on the surface of silicon oxide particles.

Examples of such compounds are as follows. In the above formula, ^R12 is an alkoxy group, such as methoxy or ethoxy. The silane compound described above can be a silane compound manufactured by Shin-Etsu Chemical Industry Co., Ltd. The process involves applying a hydroxyl group, or, in the case of silicon oxide particles, a silanol group, to the surface of the silicon oxide particles, thereby coating the surface of the silicon oxide particles with the silane compound through siloxane bonds. The reaction can be carried out at temperatures ranging from 20°C to the boiling point of the dispersion medium, but for example, within the range of 20°C to 100°C. The reaction time can be approximately 0.1 to 6 hours.

The aforementioned silane compound, based on the coating amount on the surface of silicon oxide particles, is added to the silicon oxide sol at a coating amount equivalent to ^0.1 to 6.0 silicon atoms ^per nm². Water is necessary for the hydrolysis of the aforementioned silane compound; however, if the sol is made with an aqueous solvent, that aqueous solvent is used. Water remaining in the solvent after replacing the aqueous solvent with an organic solvent can be used. For example, water present at 0.01 to 1% by mass can be used. Furthermore, hydrolysis can be carried out using a catalyst or without one.

In the case of hydrolysis without a catalyst, acidic sites exist on the surface of the silicon oxide particles. When using a catalyst, examples of hydrolysis catalysts include metal chelates, organic acids, inorganic acids, organic bases, and inorganic bases. Examples of metal chelates as hydrolysis catalysts include triethoxymono(acetylacetonate)titanium and triethoxymono(acetylacetonate)zirconia. Examples of organic acids as hydrolysis catalysts include acetic acid and oxalic acid. Examples of inorganic acids as hydrolysis catalysts include hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid, and phosphoric acid. Examples of organic bases as hydrolysis catalysts include pyridine, pyrrole, piperazine, and grade IV ammonium salts. Examples of inorganic alkalis that act as hydrolysis catalysts include, for example, ammonia, sodium hydroxide, and potassium hydroxide. Organic acids are at least one organic acid selected from the group consisting of dialiphatic carboxylic acids, aliphatic oxycarboxylic acids, amino acids, and chelating agents. Examples of dialiphatic carboxylic acids include oxalic acid, malonic acid, and succinic acid; examples of aliphatic oxycarboxylic acids include glycolic acid, lactic acid, malic acid, tartaric acid, and citric acid; examples of amino acids include glycine, alanine, cellulose, leucine, serine, and threonine; and examples of chelating agents include ethylenediaminetetraacetic acid, L-aspartic-N,N-diacetic acid, and diethylenetriaminepentaacetic acid. Examples of organic acid salts include alkali metal salts, ammonium salts, and amine salts of the above-mentioned organic acids. Examples of alkali metals include sodium and potassium.

In this invention, a film-forming composition comprising the aforementioned hollow silica organic solvent sol and organic resin or polysiloxane can be obtained. The film-forming composition is obtained by selectively mixing the organic resin or polysiloxane with a thermosetting or photosetting resin. It can also be a cured product containing curing agents such as amine-based curing agents, anhydride-based curing agents, free radical generating curing agents (thermal free radical generating agents, photofree radical generating agents), or acid generating curing agents (thermal acid generating agents or photoacid generating agents). This composition can be applied to or filled onto a substrate and cured by heating, light irradiation, or a combination thereof. Organic resins and polysiloxanes (curing resins) include, for example, resins with functional groups such as epoxy or (meth)acrylic groups, or isocyanate resins. For example, light-curing polyfunctional acrylates are preferred.

Examples of polyfunctional acrylates include those with 2, 3, 4 or more functional groups in their molecules, such as neopentyl glycol di(meth)acrylate, trihydroxymethylpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and dipentaerythritol hexa(meth)acrylate. These polyfunctional acrylates may also be described below.

The film-forming composition of this invention may include a surfactant (leveling agent). Anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, and silicone surfactants may be used as the surfactant (leveling agent). The surfactant (leveling agent) may be added in the range of 0.01~5 phr or 0.01~1 phr relative to organic resins or polysiloxanes. Examples of anionic surfactants used in this invention include sodium and potassium salts of fatty acids, alkylbenzene sulfonates, higher alcohol sulfates, polyoxyethylene alkyl ether sulfates, α-sulfonated fatty acid esters, α-olefinic acids, monoalkyl phosphates, and alkyl sulfonates. Examples of alkylbenzene sulfonates include sodium salts, potassium salts, and lithium salts, including C10-C16 alkylbenzene sulfonates, C10-C16 alkylbenzene sulfonic acids, and alkylnaphthalene sulfonates.

Higher alcohol sulfates include sodium dodecyl sulfate (sodium lauryl sulfate), triethanolamine lauryl sulfate, and ammonium lauryl sulfate, all with 12 carbon atoms. Polyoxyethylene alkyl ether sulfates include sodium polyoxyethylene styrene ether sulfate, ammonium polyoxyethylene styrene ether sulfate, sodium polyoxyethylene decyl ether sulfate, ammonium polyoxyethylene decyl ether sulfate, sodium polyoxyethylene lauryl ether sulfate, ammonium polyoxyethylene lauryl ether sulfate, sodium polyoxyethylene tridecyl ether sulfate, and sodium polyoxyethylene oleyl cetyl ether sulfate. α-Alkenyl sulfonates include sodium α-alkenyl sulfonate.

Examples of alkyl sulfonates include sodium 2-ethylhexyl sulfate. Examples of cationic surfactants used in this invention include, for example, alkyl trimethyl ammonium salts, dialkyl dimethyl ammonium salts, alkyl dimethyl benzyl ammonium salts, and amine salts. Alkyl trimethyl ammonium salts are fourth-order ammonium salts, possessing chloride or bromide ions as counterions. Examples include, for example, dodecyl trimethyl ammonium chloride, cetyl trimethyl ammonium chloride, cocoalkyl trimethyl ammonium chloride, and alkyl (C16-18) trimethyl ammonium chloride. Dialkyl dimethyl ammonium salts have two lipophilic backbones and two methyl groups. An example is bis(hydrogenated tallow) dimethyl ammonium chloride. Examples include dialcyl dimethyl ammonium chloride, dicosyl dimethyl ammonium chloride, di-hardened tallow alkyl dimethyl ammonium chloride, and dialkyl(C14-18) dimethyl ammonium chloride.

Alkyl dimethyl benzyl ammonium salts are quaternary ammonium chlorides containing one lipophilic backbone, two methyl groups, and benzyl groups. Examples include alkyl (C8-18) dimethyl benzyl ammonium chloride. Ammonium salts in which the hydrogen atom is substituted with one or more hydrocarbon groups include, for example, N-methyl dihydroxyethylamine fatty acid ester hydrochloride. Examples of amphoteric surfactants used in this invention include N-alkyl-β-alanine type alkylamine fatty acid salts, alkyl carboxyl alkyl betaine type alkyl betaine, and N,N-dimethyl dodecylamine oxide type alkylamine oxide. Examples of such alkaloids include lauryl betaine, stearyl betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazoline betaine, and lauryl dimethylamine oxide.

The nonionic surfactants used in this invention are selected from polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, alkyl glucosides, polyoxyethylene fatty acid esters, sucrose fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and fatty acid alkyl alcohol amides. Examples of polyoxyethylene alkyl ethers include polyoxyethylene dodecyl ether (polyoxyethylene lauryl ether), polyoxyethylene alkyl lauryl ether, polyoxyethylene tridecyl ether, polyoxyethylene alkyl tridecyl ether, polyoxyethylene myristate ether, polyoxyethylene cetyl ether, polyoxyethylene oil ether, polyoxyethylene stearate ether, oxyethylene sorbitan ether, polyoxyethylene-2-ethylhexyl ether, and polyoxyethylene isodecyl ether. Examples of polyoxyethylene alkylphenol ethers include polyoxyethylene styrene ether, polyoxyethylene nonylphenyl ether, polyoxyethylene styrene ether, and polyoxyethylene tribenzylphenyl ether.

Alkyl glucosides include decyl glucoside and lauryl glucoside. Polyoxyethylene fatty acid esters include polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene monooleate, polyethylene glycol distearate, polyethylene glycol dioleate, and polypropylene glycol dioleate. Sorbitan fatty acid esters include sorbitan monocaprylate, sorbitan monolaurate, sorbitan monomyristate, sorbitan monopalmitate, sorbitan monostearate, sorbitan distearate, sorbitan tristearate, sorbitan monooleate, sorbitan trioleate, sorbitan monosesquioleate, and their ethylene oxide adducts.

Polyoxyethylene sorbitan fatty acid esters include polyoxyethylene dehydrated sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, and polyoxyethylene sorbitan triisostearate. As for fatty acid alkylamines, there are coconut oil fatty acid diethanolamine, tallow fatty acid diethanolamine, laurate diethanolamine, and oleic acid diethanolamine.

In addition, examples include polyoxyalkyl ethers or polyoxyalkyl glycols such as polyoxyethylene polyoxypropylene glycol and polyoxyethylene fatty acid esters, polyoxyalkylene oil ethers cured with polyoxyethylene castor oil, alkyl ethers of sorbitan fatty acid esters, alkyl polyglycosides, sorbitan monooleate, and sucrose fatty acid esters. Silicone-based surfactants can be used. Silicone-based surfactants are compounds whose main chain has repeating units containing siloxane bonds. The weight-average molecular weight of silicone-based surfactants can be used in the range of 500 to 50,000. These can be modified silicone-based surfactants, for example, those with organic groups introduced into the side chains and/or ends of polysiloxane. Examples of organic groups include amine, epoxy, alicyclic epoxy, carbitol, teryl, carboxyl, aliphatic ester, aliphatic amide, and polyether. Examples of silicone-based surfactants include Toray Silicone DC3PA, Toray Silicone SH7PA, Toray Silicone DC11PA, Toray Silicone SH21PA, Toray Silicone SH28PA, Toray Silicone SH29PA, Toray Silicone SH30PA, Toray Silicone SH8400 (manufactured by Toray Dow Corning), Silwet L-77, L-7280, L-7001, L-7002, L-7200, L-7210, L-7220, L-7230, L7500, L-7600, L-7602, L-7604, L-7605, L-7622, L-7657, L-8500, and L-8610 (all under the Momentive Performance Injection brand). Products manufactured by Materials Co., Ltd. include KP-341, KF-6001, and KF-6002 (all manufactured by Shin-Etsu Silicon Oxide Co., Ltd.), BYK307, BYK323, and BYK330 (all manufactured by BYK Chemie Co., Ltd.). For example, the trade name L-7001 (manufactured by DOWSIL Co., Ltd.) is a better choice for polyether-modified silicone.

In this invention, a coating forming composition comprising the aforementioned organic solvent sol and organic resin or polysiloxane can be obtained. The coating forming composition can remove the organic solvent from the organic solvent sol, becoming a coating forming composition comprising hollow silica particles and organic resin. In the case of the thermosetting coating forming composition described above, relative to resins containing functional groups such as epoxy or (meth)acrylic groups, the thermosetting agent can be added in the range of 0.01~50 phr or 0.01~10 phr. For example, relative to functional groups such as epoxy or (meth)acrylic groups, the thermosetting agent can be contained in a ratio of 0.5~1.5 equivalents, preferably 0.8~1.2 equivalents. The equivalent of thermosetting agent to curing resin is expressed as the equivalent ratio of thermosetting agent to functional group.

Examples of thermosetting agents include phenolic resins, amine-based curing agents, polyamide resins, imidazoles, polythiols, acid anhydrides, thermal free radical generators, and thermal acid generators. Free radical generator-based curing agents, acid anhydride-based curing agents, and amine-based curing agents are particularly preferred. These thermosetting agents can be used even in solid form by dissolving them in a solvent. However, because the evaporation of the solvent reduces the density of the cured material and causes a decrease in strength and water resistance due to the formation of pores, it is preferable that the curing agent itself is liquid at room temperature and pressure. Examples of phenolic resins include phenolic varnish resins and cresol phenolic varnish resins.

Examples of amine-based hardeners include piperidine, N,N-dimethylpiperazine, triethyldiamine, 2,4,6-tris(dimethylaminomethyl)phenol, benzyldimethylamine, 2-(dimethylaminomethyl)phenol, diethyltriamine, triethyltetraamine, tetraethylpentamine, diethylaminopropylamine, N-aminoethylpiperazine, di(1-methyl-2-aminocyclohexyl)methane, menthyldiamine, isophorone diamine, diaminodicyclohexylmethane, 1,3-diaminomethylcyclohexane, xylenediamine, m-phenylenediamine, diaminodiphenylmethane, diaminodiphenyl sulfone, 3,3'-diethyl-4,4'-diaminodiphenylmethane, and diethyltoluenediamine. Among these, liquid diethyltriamine, triethyltetraamine, tetraethylpentamine, diethylaminopropylamine, N-aminoethylpiperazine, di(1-methyl-2-aminocyclohexyl)methane, menthene diamine, isophorone diamine, diaminodicyclohexylmethane, 3,3'-diethyl-4,4'-diaminodiphenylmethane, and diethyltoluene diamine are preferred. Polyamide resins are formed by the condensation of dimer acids and polyamines, and are polyamides containing both primary and secondary amines in their molecules.

Examples of imidazole derivatives include 2-methylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole trimellitate, and epoxyimidazole adducts. Polythiols are those containing thiols at the ends of polypropylene glycol chains or polyethylene glycol chains, preferably in liquid form.

As an anhydride-based curing agent, it is preferably an anhydrous form of a compound having a plurality of carboxyl groups in one molecule. Examples of such anhydride-based curing agents include phthalic anhydride, trimellitic anhydride, pyromellitic tetracarboxylic anhydride, benzophenone tetracarboxylic anhydride, ethylene glycol dipremetyl phthalate, glycerol trimellitic tricarboxylic phthalate, maleic anhydride, tetrahydrophthalic anhydride, methyl tetrahydrophthalic anhydride, n-methylene tetrahydrophthalic anhydride, methyl n-methylene tetrahydrophthalic anhydride, methylbutenyl tetrahydrophthalic anhydride, dodecenyl succinic anhydride, hexahydrophthalic anhydride, methyl hexahydrophthalic anhydride, succinic anhydride, methylcyclohexene dicarboxylic anhydride, chlorobenzyl anhydride, etc. Examples of thermal acid generators include strontium salts and phosphonium salts, but strontium salts are preferred. Examples of such compounds include the following. R can be an alkyl group having 1 to 12 carbon atoms or an aryl group having 6 to 20 carbon atoms, with a preference for an alkyl group having 1 to 12 carbon atoms.

Among these, the preferred formulations are methyltetrahydrophthalic anhydride, methyl-5-norbornene-2,3-dicarboxylic anhydride (methyl methacrylate anhydride, methyl hemicyanate anhydride), hydrogenated methyl methacrylate anhydride, methylbutenyltetrahydrophthalic anhydride, dodecenylsuccinic anhydride, methyl hexahydrophthalic anhydride, and mixtures of methyl hexahydrophthalic anhydride and hexahydrophthalic anhydride, which are liquid at room temperature and pressure. These liquid anhydrides have a viscosity of approximately 10 mPa·s to 1000 mPa·s as measured at 25°C. Examples of thermal free radical generators include 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylpentanitrile), 4,4'-azobis(4-cyanopentanoic acid), dimethyl 2,2'-azobis(2-methylpropionic acid) ester, 2,2'-azobis(2-methylpropamidinium) dihydrogen phosphate, 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrogen phosphate, tert-butyl hydrogen peroxide, cumene hydrogen peroxide, di-tert-butyl peroxide, dicumene peroxide, benzoyl peroxide, etc. These are available from Tokyo Chemical Industry Co., Ltd.

Furthermore, when obtaining the aforementioned hardened material, a hardening aid may also be used appropriately. Examples of hardening aids include organophosphorus compounds such as triphenylphosphine and tributylphosphine, fourth-order phosphonium salts such as ethyltriphenylphosphine bromide and diethyl methyltriphenylphosphine phosphate, and fourth-order ammonium salts such as 1,8-diazabicyclo(5,4,0)undec-7-ene, 1,8-diazabicyclo(5,4,0)undec-7-ene with octanoic acid, zinc octanoate, and tetrabutylammonium bromide. These hardening aids may be contained in a ratio of 0.001 to 0.1 parts by weight relative to 1 part by weight of the hardener. The composition is a thermosetting varnish obtained by mixing resin, hardener, and hardening aids as needed. These mixtures can be carried out in a reaction vessel using stirring blades or a kneader.

The mixing is carried out by heating at a temperature of 60°C to 100°C for 0.5 to 1 hour. The resulting curable film-forming composition is a thermosetting coating composition with a suitable viscosity, for example, for use as a liquid sealant. The liquid thermosetting film-forming composition can be adjusted to any viscosity. Since it is used as a transparent sealant for LEDs and the like using casting, potting, printing, or other methods, it can be partially sealed at any location. After directly applying the liquid thermosetting composition to LEDs or the like in liquid form using the above method, and then drying and curing it, an epoxy resin cured body can be obtained. A thermosetting coating composition (thermosetting coating composition) is applied to a substrate and heated at a temperature of 80~200°C to obtain a cured product. In the case of the photocurable resin composition in the above-mentioned coating composition, a photocuring agent (photoradical generator, photoacid generator) may be added in the range of 0.01~50 phr or 0.01~10 phr, relative to resins containing functional groups such as epoxy or (meth)acrylic groups. For example, the photocuring agent (photoradical generator, photoacid generator) may be contained in a proportion of 0.5~1.5 equivalents, preferably 0.8~1.2 equivalents, relative to functional groups such as epoxy or (meth)acrylic groups. The equivalent of photocuring agent to curing resin is expressed as the equivalent ratio of photocuring agent to functional group. Photoradical generators that can generate free radicals directly or indirectly through light irradiation are not particularly restricted.

Examples of photoradical generators and photoradical polymerization initiators include imidazole compounds, diazo compounds, bisimidazole compounds, N-arylglycine compounds, organic azido compounds, titanium diacene compounds, aluminum oxide compounds, organic peroxides, N-alkoxypyridinium salts, and thiotonone compounds. Examples of azido compounds include p-azidobenzaldehyde, p-azidoacetophenone, p-azidobenzoic acid, p-azidobenzylidene acetophenone, 4,4'-diaazidochalcone, 4,4'-diaazidodiphenyl sulfide, and 2,6-bis(4'-azidobenzylidene)-4-methylcyclohexanone, etc. Examples of diazo compounds include 1-diazo-4-N,N-dimethylaminophenyl chloride and 1-diazo-4-N,N-diethylaminophenylboronide. Examples of diimidazole compounds include 2,2'-bis(ortho-chlorophenyl)-4,5,4',5'-tetra(3,4,5-trimethoxyphenyl)1,2'-diimidazole and 2,2'-bis(ortho-chlorophenyl)4,5,4',5'-tetraphenyl-1,2'-diimidazole, etc. Examples of titanium-ceramethylene compounds include dicyclopentadienyl-titanium-dichloride, dicyclopentadienyl-tere-diphenyl, dicyclopentadienyl-titanium-bis(2,3,4,5,6-pentafluorophenyl), dicyclopentadienyl-titanium-bis(2,3,5,6-tetrafluorophenyl), dicyclopentadienyl-titanium-bis(2,4,6-trifluorophenyl), dicyclopentadienyl-titanium-bis(2,6-difluorophenyl), and dicyclopentadienyl-titanium-bis(2,6-difluorophenyl). Alkenyl-titanium-bis(2,4-difluorophenyl), bis(methylcyclopentadienyl)-titanium-bis(2,3,4,5,6-pentafluorophenyl), bis(methylcyclopentadienyl)-titanium-bis(2,3,5,6-tetrafluorophenyl), bis(methylcyclopentadienyl)-titanium-bis(2,6-difluorophenyl), and dicyclopentadienyl-titanium-bis(2,6-difluoro-3-(1H-pyrrole-1-yl)-phenyl), etc.

Examples of photoradical generators include 1,3-bis(tert-butyldioxycarbonyl)benzophenone, 3,3',4,4'-tetracyclo(tert-butyldioxycarbonyl)benzophenone, 3-phenyl-5-isooxazolone, 2-piperylbenzimidazole, 2,2-dimethoxy-1,2-diphenylethyl-1-one, 1-hydroxycyclohexylphenyl ketone, and 2-benzyl-2-dimethylamino-1-(4-morpholinylphenyl)-butanone. Examples of such photoradical polymerizers include, for instance, those manufactured by BASF under the trade name Irgacure TPO (containing 2,4,6-trimethylbenzoyldiphenylphosphine oxide) (formula (c1-1-1)), manufactured by IGM RESINS under the trade name Omnirad 819 (containing bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide) (formula (c1-1-2)), and manufactured by IGM RESINS under the trade name Irgacure 184 (containing 1-hydroxycyclohexylphenyl ketone) (formula (c1-1-3)).

There are no particular restrictions on photoacid generators, as long as they can generate acid directly or indirectly through light irradiation. Specific examples of photoacid generators include triazine compounds, acetophenone derivatives, diazonium compounds, diazomethane compounds, sulfonic acid derivatives, iodonium salts, strontium salts, phosphonium salts, selenium salts, thallium salts, metallocene complexes, and iron-aromatic hydrocarbon complexes.

Examples of onium salts used as photoacid generators include diphenylmethylene chloride, diphenylmethylene trifluoromethanesulfonate, diphenylmethylene methanesulfonate, diphenylmethylene toluenesulfonate, diphenylmethylene bromide, diphenylmethylene tetrafluoroborate, diphenylmethylene hexafluoroantimonate, diphenylmethylene hexafluoroarsenate, bis(p-tert-butylphenyl)methylene hexafluorophosphate, bis(p-tert-butylphenyl)methylene methanesulfonate, bis(p-tert-butylphenyl)methylene trifluoromethanesulfonate, and bis(p-tert-butylphenyl)methylene tetrafluoroborate. Salts, bis(p-tert-butylphenyl) monazine chloride, bis(p-chlorophenyl) monazine chloride, bis(p-chlorophenyl) monazine tetrafluoroborate, and further, bis(alkylphenyl) monazine salts such as bis(4-tert-butylphenyl) monazine hexafluorophosphate, alkoxycarbonylalkoxyalkoxytrialkylaryl monazine salts (e.g., 4-[(1-ethoxycarbonyl-ethoxy)phenyl]-(2,4,6-trimethylphenyl)-monazine hexafluorophosphate), and bis(alkoxyaryl) monazine salts (e.g., bis(alkoxyphenyl) monazine salts such as (4-methoxyphenyl)phenyl monazine hexafluoroantimonate).

Examples of strontium salts include triphenylstrontium chloride, triphenylstrontium bromide, tri(p-methoxyphenyl)strontium tetrafluoroborate, tri(p-methoxyphenyl)strontium hexafluorophosphonate, tri(p-ethoxyphenyl)strontium tetrafluoroborate, triphenylstrontium trifluoromethanesulfonate, triphenylstrontium hexafluoroantimonate, and triphenylstrontium hexafluorophosphate. (4-Phenylacetylthiophenyl)diphenyl strontium hexafluoroantimonate, (4-Phenylacetylthiophenyl)diphenyl strontium hexafluorophosphate, bis[4-(diphenylsulfonyl)phenyl]sulfide-bis-hexafluoroantimonate, bis[4-(diphenylsulfonyl)phenyl]sulfide-bis-hexafluorophosphate, (4-methoxyphenyl)diphenyl strontium hexafluoroantimonate, etc.

Examples of phosphonium salts include triphenylphosphonium chloride, triphenylphosphonium bromide, tris(p-methoxyphenyl)tetrafluoroborate, tris(p-methoxyphenyl)phosphonium hexafluorophosphonate, tris(p-ethoxyphenyl)phosphonium tetrafluoroborate, 4-chlorobenzyldiazoium hexafluorophosphate, and benzyltriphenylphosphonium hexafluoroantimonate. Examples of phosphonium salts include selenodium salts such as triphenylselenodium hexafluorophosphate, and metallocene complexes such as (n5 or n6-isopropylbenzene)(n5-cyclopentadienyl)fer(II) hexafluorophosphate.

Alternatively, the following compounds can also be used as photoacid generators.

As photoacid generators, strontium salt compounds and _monazine salt compounds are preferred. Examples of such anions include _CF3SO3- ^, _C4F9SO3- ^, _C8F17SO3- , _{camphorsulfonic} acid _anions ^, toluenesulfonic acid anions, _{BF4- , PF6-} ^{, AsF6-} _, and ^SbF6- . Particularly preferred are anions such as phosphorus hexafluoride and antimony _hexafluoride ^, which exhibit strong acidity. The film-forming composition of this invention may _include conventional additives as needed. Examples of such additives include pigments, colorants, thickeners, sensitizers, defoamers, paint modifiers, lubricants, stabilizers (antioxidants, heat stabilizers, light stabilizers, etc.), plasticizers, solubilizers, fillers, and antistatic agents. These additives can be used alone or in combination of two or more. Examples of coating methods for the film-forming components of this invention include flow coating, spin coating, spray coating, screen printing, casting, rod coating, curtain coating, roller coating, gravure coating, dipping, and narrow-slit coating.

In this invention, the photocoating composition (film-forming composition) can be applied to a substrate and cured by light irradiation. It can also be heated before and after light irradiation. The coating thickness can be selected from approximately 0.01 μm to 10 mm depending on the intended use of the cured material. For example, it can be approximately 0.05 to 10 μm (especially 0.1 to 5 μm) for photoresist, approximately 5 μm to 5 mm (especially 100 μm to 1 mm) for printed circuit boards, and approximately 0.1 to 100 μm (especially 0.3 to 50 μm) for optical thin films. When a transparent coating is obtained, the visible light transmittance of the coating can be 80% or more, or 90% or more, typically 90% to 96%.

The light irradiated or exposed when using photoacid generators can be, for example, gamma rays, X-rays, ultraviolet rays, or visible light, and is usually visible light or ultraviolet light, especially ultraviolet light. The wavelength of the light is, for example, 150~800 nm, preferably 150~600 nm, and more preferably around 150~400 nm. The amount of irradiated light varies depending on the coating thickness, but can be, for example, 2~20000 mJ/ ^cm² , preferably around 5~5000 mJ/ ^cm² . The light source can be selected according to the type of light being exposed. For example, in the case of ultraviolet light, low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, deuterium lamps, halogen lamps, laser light (helium-cadmium lasers, excimer lasers, etc.) can be used. The aforementioned components undergo a hardening reaction under such light irradiation. When using a hot acid generator or a photoacid generator, the heating of the coating after light irradiation is performed as needed at, for example, 60~350°C, preferably around 100~300°C. The heating time can be selected from more than 3 seconds (e.g., 3 seconds to about 5 hours), for example, 5 seconds to 2 hours, preferably around 20 seconds to 30 minutes, and usually around 1 minute to 3 hours (e.g., 5 minutes to 2.5 hours).

Furthermore, when forming patterns or images (e.g., in the manufacture of printed wiring boards), the coating formed on the substrate can be exposed to the pattern. This pattern exposure can be performed by laser scanning or by irradiating the substrate with light through a photomask. The unexposed areas (unexposed portions) generated by such pattern exposure can be developed (or dissolved) with a developer to form patterns or images. As a developer, an alkaline aqueous solution or an organic solvent can be used. Examples of alkaline aqueous solutions include aqueous solutions of alkaline metal hydroxides such as potassium hydroxide, sodium hydroxide, potassium carbonate, and sodium carbonate; aqueous solutions of tetramethylammonium hydroxide, tetraethylammonium hydroxide, and choline; and aqueous solutions of amines such as ethanolamine, propylamine, and ethylenediamine.

The aforementioned alkaline developing solution is generally an aqueous solution of less than 10% by mass, preferably 0.1% to 3.0% by mass. Furthermore, alcohols and surfactants can be added to the above developing solution, preferably 0.05% to 10 parts by mass of each relative to 100 parts by mass of the developing solution. Among these, a 0.1% to 2.38% by mass aqueous solution of tetramethylammonium hydroxide can be used. Furthermore, common organic solvents can be used as developing solutions, such as acetone, acetonitrile, toluene, dimethylformamide, methanol, ethanol, isopropanol, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol propyl ether, propylene glycol butyl ether, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, propylene glycol propyl ether acetate, propylene glycol butyl ether acetate, ethyl lactate, cyclohexanone, etc., and one or a mixture of two or more of these solvents can be used. Propylene glycol methyl ether, propylene glycol methyl ether acetate, and ethyl lactate are particularly preferred.

In this invention, adhesion promoters can be added to improve adhesion to the substrate after development. Examples of such adhesion promoters include chlorosilanes such as trimethylchlorosilane, dimethylvinylchlorosilane, methyldiphenylchlorosilane, and chloromethyldimethylchlorosilane; alkoxysilanes such as trimethylmethoxysilane, dimethyldiethoxysilane, methyldimethoxysilane, dimethylvinylethoxysilane, diphenyldimethoxysilane, and phenyltriethoxysilane; silazanes such as hexamethyldisilazane, N,N'-bis(trimethylsilyl)urea, dimethyltrimethylsilaneamine, and trimethylsilylimidazolium; and vinyltrichlorosilane, 3- Silanes such as chloropropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-(N-piperidinyl)propyltrimethoxysilane; heterocyclic compounds such as benzotriazole, benzimidazole, indazole, imidazole, 2-piperylbenzimidazole, 2-piperylbenzothiazole, 2-piperylbenzoxazole, urea, thiouracil, piperimidazole, and piperylpyrimidine; ureas such as 1,1-dimethylurea and 1,3-dimethylurea; or thiourea compounds. One or more of the aforementioned adhesion promoters may be used. The amount of these adhesion promoters added in the solid fraction is usually less than 18% by weight, preferably 0.0008 to 9% by weight, and more preferably 0.04 to 9% by weight.

This invention may also include sensitizers. Examples of usable sensitizers include anthracene, phenothiazine, perylene, thiotonone, benzophenone-thiotonone, etc. Furthermore, examples of sensitizing pigments include thiopyranium salt pigments, anthocyanin pigments, quinoline pigments, styrene-quinoline pigments, ketocumarin pigments, thiotonone pigments, xanthine pigments, oxonol pigments, cyanine pigments, rhodamine pigments, pyranium salt pigments, etc. This is a particularly effective anthracene-based sensitizer. By combining it with a cationic curing catalyst (a radiosensitive cationic polymerization initiator), it can rapidly increase sensitivity while also possessing free radical polymerization initiation capabilities. The use of this invention's hybrid cationic curing system and free radical curing system simplifies the catalyst selection. Specific anthracene compounds include dibutoxyanthracene and dipropoxyanthraquinone. The sensitizer is added at a ratio of 0.01 to 20% by weight, preferably 0.01 to 10% by weight, in the solids fraction. The components of this invention can be photocured or thermocured using photoradioactive agents, thermal radical generators, photoacid generators, or thermal acid generators. For example, when using photoacid generators or thermal acid generators, the composition can maintain good storage stability because commonly used epoxy curing agents (such as amines or acid anhydrides) are not used, or even if they are used, their content is extremely low.

The above composition was found to be suitable for photoionic polymerization. It exhibits a higher curing speed than previous liquid epoxy compounds (e.g., alicyclic epoxy compounds with an epoxy cyclohexyl ring). Due to the rapid curing speed, the amount of acid generator required can be reduced, and weak acid generators can also be used. Reducing the amount of acid generator is important for preventing metal corrosion even when acidic active species remain after UV irradiation. The rapid curing speed allows for thick film curing. UV irradiation curing makes it suitable for heat-sensitive materials (mechanical materials). The thermosetting and photocuring materials using the coating composition of this invention can be used for coating and bonding electronic components, optical components (anti-reflective films), and precision mechanical components with characteristics such as low dielectric constant, low dielectric loss factor, fast curing, high transparency, and low curing shrinkage. For example, they can be used for bonding components such as lenses in mobile phones and cameras, optical elements in light-emitting diodes (LEDs) and semiconductor lasers (LDs), liquid crystal panels, biochips, lenses and prisms in cameras, magnetic components in hard drives of personal computers, pickups (the part that captures light information reflected from the disc) in CD and DVD players, speakers and coils in loudspeakers, magnets in motors, circuit boards, electronic components, and internal components of automobile engines.

As a hard coating material for surface protection of automobile bodies, lights, electronic products, building materials, and plastics, it can be applied to, for example, automobile and motorcycle bodies, headlight lenses and mirrors, plastic lenses for glasses, mobile phones, game consoles, optical films, ID cards, etc. As an ink material for printing on metals such as aluminum and plastics, it can be used for printing on cards such as credit cards and membership cards, switches and keyboards in electronic products and OA machines, and inkjet printer inks for CDs and DVDs. Examples include the technology of combining with 3D CAD to harden resin into complex three-dimensional objects, the application of light modeling in the creation of industrial product models, the coating of optical fibers, and subsequent applications in optical waveguides and thick film resists.

Furthermore, the coating composition of this invention can be preferably used as an insulating resin for electronic materials such as anti-reflective films, semiconductor sealing materials, adhesives for electronic materials, printed wiring substrate materials, interlayer insulating film materials, buffer coatings for semiconductors, enamel insulating materials, and sealing materials for power modules, or as an insulating resin used in high-voltage machines such as generator coils, transformer coils, and gas-insulated switching devices. The hollow silica sol of this invention can be manufactured by including the following steps (I) to (II). (I) Step: The step of manufacturing hollow silica sol. (II) Step: For the hollow silica sol in step (I), the molar ratio of monovalent alkali metal ions (converted to _M₂O , where M represents monovalent alkali metal atoms) to _SiO₂ of hollow silica particles is adjusted to a ratio of 7.12 × ^10⁻⁶ ~ 285 × ^10⁻⁶. Through this step, hollow silica sol can be obtained. In step (II) above, sodium ions are preferred as the monovalent alkali metal ions. In step (II) above, the sodium ion content can be adjusted by contacting the hollow silica sol obtained in step (I) with a cation exchange resin or by adding a sodium source. In step (II) above, sodium hydroxide is preferably added as the sodium source, and preferably an aqueous solution of sodium hydroxide. The dispersion medium for steps (I) and (II) can be water, alcohols, ketones, ethers, amides, ureas, or esters with 1 to 10 carbon atoms. Examples of such dispersion media include the solvents mentioned above.

In this invention, at least one of the following steps (i) to (iv) may be added to steps (I), (II), or both: (i) adding an amine to the hollow silica sol; (ii) adding sodium aluminate as an aluminum source and heating to form aluminosilicate sites on the hollow silica particles; (iii) replacing the dispersion medium with another dispersion medium; and (iv) coating the hollow silica particles with at least one silane compound selected from the group consisting of formulas (1) and (2). Therefore, this invention provides a stabilization method for hollow silica sol containing hollow silica particles with space within an outer shell. In this method, monovalent alkali metal ions (converted to _M₂O , where M represents a monovalent alkali atom) are added to the hollow silica sol at a molar ratio of 7.12 × 10⁻⁶ to 285 ^{× 10⁻⁶} of the _SiO₂ in the hollow silica sol, relative to the SiO₂ of the hollow silica particles in the hollow silica sol, thereby reducing the increased dynamic light scattering ^particle size. In the above stabilization method, sodium ions can be used as the monovalent alkali metal ions.

In step (ii), the hollow silica sol is prepared in an aqueous sol, with 0.0001~0.5g of aluminum compound added per 1g of hollow silica particles, and the process is carried out at 40~260°C for 0.1~24 hours. The amount of aluminum compound added per 1g of hollow silica particles in step (ii) can be in the range of 0.0001~0.5g, 0.001~0.1g, or 0.001~0.05g. Furthermore, the heating temperature in step (ii) is 40~260℃, or 50~260℃, or 60~240℃. However, in cases of non-hydrothermal treatment, it is used at 40~below 100℃, or 50~below 100℃, or 60~below 100℃. In cases of hydrothermal treatment, it can be carried out at 100~260℃, or 150~240℃. The heating time in step (ii) can be in the range of 0.1~48 hours, or 0.1~24 hours, or 0.1~10 hours, or 1~10 hours.

(I) The hollow silica particles used in step (I) have a silica shell with a space inside the shell. Hollow silica is obtained by forming a shell with silica as the main component on the surface of a portion equivalent to a core in an aqueous dispersion medium, and then removing the portion equivalent to the core. The template can be made using organic materials (e.g., hydrophilic organic resin particles such as polyethylene glycol, polystyrene, and polyester) or inorganic materials (e.g., hydrophilic inorganic compound particles such as calcium carbonate and sodium aluminate). The hollow silica aqueous sol used as a raw material in step (I) can be used in an aqueous medium and subjected to non-hydrothermal treatment at heating temperatures of, for example, 20 to 100°C, 40 to 100°C, or 50 to 100°C. Alternatively, the hollow silica aqueous sol used in step (I) can be used in an aqueous medium and subjected to hydrothermal treatment at heating temperatures of 100°C to 240°C, or 110 to 240°C.

The hollow silica sol used in this invention can be a non-hydrothermal treated hollow silica aqueous sol, a hydrothermal treated hollow silica aqueous sol, or a mixture thereof. This involves forming aluminate silicate sites on the outer shell of the hollow silica particles. However, since the aluminate silicate sites may remain alkaline, the hollow silica sol is selected based on the aluminum atoms measured by leaching method and converted _{to Al₂O₃ ,} with a _SiO₂ mass relative to the hollow silica particles being 100~20000ppm/ _SiO₂ bonded to the surface of the hollow silica particles. (ii) In step (ii), an aluminum compound is added to the hollow silica aqueous sol. Aluminum compounds can be added to hollow silica aqueous sol in solid or aqueous solution form. (ii) The aluminum compound used in step (ii) is at least one aluminum compound selected from the group consisting of aluminates, aluminum alkoxides, and their hydrolysates, and can be used in aqueous solutions containing these compounds. Examples of aluminates include sodium aluminate, potassium aluminate, calcium aluminate, magnesium aluminate, ammonium aluminate, and aluminum aluminate amines. Examples of alkoxides include isopropyl aluminate and butyrate. Aluminates are particularly preferred.

The aluminum compound is added in aqueous solution to the hollow silica aqueous sol obtained in step (I), but the concentration of the aqueous aluminum compound solution is in the range of 0.01~20% by mass, or 0.1~10% by mass, or 0.5~5% by mass. The addition can be carried out under stirring of the hollow silica aqueous sol obtained in step (I). The addition can be completed before heating, or it can be added during the entire heating time. The desired amount of aluminum compound impregnated in the hollow silica particles depends on the processing temperature of step (ii), and the heating treatment must be carried out within the above temperature range. Step (i) may further include a step of adding an amine. The amine can be added as described above and can be contained in the hollow silica sol within the above range.

Step (ii) above, after heating the addition of the aforementioned aluminum compound, or at least one additive consisting of the aforementioned aluminum compound, an amine, and a neutral salt, may include a step of contacting a cation exchange resin, a step of adding an acid, or a combination thereof. The cation exchange resin is an H-type strongly acidic cation exchange resin, and may subsequently contact an anion exchange resin. The acid may be an inorganic acid such as sulfuric acid, nitric acid, hydrochloric acid, or phosphoric acid, or an organic acid such as citric acid, acetic acid, malic acid, lactic acid, succinic acid, tartaric acid, butyric acid, fumaric acid, propionic acid, or formic acid. In this invention, step (ii) above can be performed by adding an aluminum compound (e.g., sodium aluminate) and heating it at 100-240°C for 0.1-48 hours, followed by adding an acid (e.g., sulfuric acid, nitric acid, hydrochloric acid) and contacting it with a cation exchange resin. The addition of the acid is achieved through a leaching process in which the aluminum-containing components not doped into the particles and the metallic impurities contained in the particles are dissolved into the liquid by heating. These metallic components are then removed with a cation exchange resin. After heating and curing at 40-100°C for 0.1-48 hours, the contact with the cation exchange resin is performed again.

As in step (iii), the aqueous medium of the hollow silica aqueous sol is further replaced with an alcohol, ketone, ether, or ester having 1 to 10 carbon atoms. Further, it may include step (iv) of adding at least one silane compound selected from the group consisting of formulas (1) and (2) above and heating. Steps (iii) and (iv) are performed after step (ii) is completed. In step (iii), the solvent is replaced with an alcohol having 1 to 10 carbon atoms. In step (iv), at least one silane compound selected from the group consisting of formulas (1) and (2) above is added and heated, and then the solvent is replaced with a ketone, ether, amide, urea, or ester having 1 to 10 carbon atoms. By using the above-described method for manufacturing hollow silica sol, the surface charge of the hollow silica particles contained in the sol can be adjusted. [Example]

The present invention is illustrated in more detail by the following embodiments and comparative examples, but the present invention is not limited to the following embodiments. The hollow silica sol used in the embodiments and comparative examples is as follows.

[Hollow Silica Sol] Water-dispersed hollow silica sol (manufactured by Ningbo Dilato, trade name: HKT-A20-40D, hollow silica aqueous sol heated in an aqueous medium at a temperature of 100℃~240℃, pH 9.3, dynamic light scattering particle size 55nm, TEM average primary particle size: 43nm, TEM converted specific surface area (D) ^63m² /g, specific surface area ratio (C/D ratio) 2.4, silica concentration 20% by mass, Na content: ^14ppm /SiO₂, i.e., _Na₂O content expressed as a molar ratio of _Na₂O to _SiO₂ is 6.64× ^10⁻⁶ moles/ _SiO₂ ).

[Alkaline Compounds] Sodium hydroxide aqueous solution (Kanto Chemical Co., Ltd., trade name: 4 mol/L sodium hydroxide solution) Diethanolamine (Tokyo Chemical Industry Co., Ltd., trade name: diethanolamine) The physical properties of aqueous dispersed hollow silica sol, dispersions of silica particles prepared in the examples and comparative examples, and the hollow silica sol and dispersions in the dispersion preparation steps were determined and evaluated according to the following methods.

[Determination of _SiO₂ Concentration] The concentration of silicon oxide in water-dispersed hollow silica sol, methanol-dispersed hollow silica sol, and the dispersion of surface-modified silicon oxide particles in the manufacturing process of the methanol-dispersed hollow silica sol is calculated by taking the hollow silica sol or dispersion into a crucible, removing the solvent by heating, calcining at 1000°C, and measuring the calcination residue.

[pH Measurement] A pH meter (manufactured by Toa DKK Corporation, trade name: MM-43X) was used at 25°C. For organic solvents such as methanol sol and propylene glycol monomethyl ether sol, which are miscible with water, a solution of pure water and the sol in a 1:1 mass ratio was used for measurement. For organic solvent sols such as methyl ethyl ketone, which have low water solubility, a solution of pure water, methanol, and the organic solvent sol in a 1:1:1 mass ratio was used for measurement.

[Determination of Moisture Content] The moisture content of organic solvent-dispersed sols was determined by the Carl Fischer titration method.

[Analysis Method for Na Content] 0.2 g of the dried hollow silica sol powder was treated with 20 mL of 48% hydrofluoric acid solution to remove silica components. The residue was dissolved in 20 mL of 0.1 mole/L (N/10) nitric acid aqueous solution. The Na content in the resulting aqueous solution was determined using an ICP-OES analyzer (trade name CIROS120 EOP, manufactured by RIGAKU Co., Ltd.). The Na content was then divided by the Si content to determine the total Na content in all silica particles.

[Determination of Particle Size by Dynamic Light Scattering (DLS)] The particle size of the dynamic light scattering method is determined using a dynamic light scattering particle size measuring device (manufactured by Spectris, trade name: Zettersizer Nano). The Z-mean particle size is used for dynamic light scattering particle size determination.

[Determination of Specific Surface Area (C)( _SN2 ) by Nitrogen Adsorption Method (BET Method)] The specific surface area ( _SN2 ) of silica particles in water-dispersed hollow silica sol by nitrogen adsorption method is determined by removing water-soluble cations in the water-dispersed hollow silica sol with a cation exchange resin (manufactured by Dow Chemical Co., Ltd., trade name: Amberlite IR-120B), drying the hollow silica sol at 290°C to prepare a test sample, and measuring it using a Monosorb (manufactured by Quantachrome Instruments Co., Ltd., Japan) specific surface area measuring device for nitrogen adsorption method.

[Determination of average first-order particle size using TEM (Transmission Electron Microscope)] A transmission electron microscope (JEOL Ltd., trade name: JEM-F200) was used to photograph silica particles in hollow silica sol. An automatic image processing and analysis device (Nireco Ltd., trade name: LUZEX’AP) was used to binarize approximately 300 randomly selected particles. The diameter of the projected area after circular conversion was determined as the average first-order particle size (HEYWOOD diameter).

[TEM-converted specific surface area (D)] Assuming true spherical particles with a true density of 2.2 g/ ^cm³ , the average first-order particle size obtained by [measurement of the average first-order particle size by TEM (transmission electron microscope)] is used to calculate (TEM-converted specific surface area (D) = 2720 / average first-order particle size).

[Determination of Aluminum Content (A) Bonded to the Surface of Hollow Silica Particles / Leaching Method] Cationic components in hollow silica sol were removed using H-type cationic exchange resin. The dried material, after solvent removal by heat treatment, was pulverized in a mortar and then treated at 250°C for 2 hours. 0.2 g of the resulting powder was added to a 50 mL PP sample bottle containing 20 mL of 0.1 molar/L (N/10) nitric acid aqueous solution and vigorously shaken by hand. Next, it was ultrasonically treated for 10 minutes using an AS ONE ASU CLEANER ASU-10M ultrasonic cleaner to ensure thorough mixing of the powder and the nitric acid aqueous solution. The mixture was then placed in a 50°C constant temperature bath and maintained for 17 hours. Subsequently, the internal solution was cooled to room temperature and fed into a centrifugal ultrafilter (Amicon Ultra-15, molecular weight cutoff 10,000) for centrifugation. The aluminum content in the filtrate was determined using an ICP luminescence analyzer. The amount of aluminum bonded to the surface of the hollow silica particles was converted _{to Al₂O₃} to calculate the ratio of the _SiO₂ mass of the hollow _silica ( _Al₂O₃ (ppm)/ _SiO₂ ).

[Determination/Dissolution Method of Aluminum Content (B) in All Hollow Silica Particles] 0.2 g of powder obtained by drying a precisely weighed hollow silica sol was treated with 20 mL of 48% (w/w) hydrofluoric acid solution to remove the silica component. The residue was dissolved in 20 mL of 0.1 mol/L (N/10) nitric acid aqueous solution. The aluminum content in the aqueous solution was determined using an ICP-based luminescence analyzer _{. The ratio of aluminum content in all hollow silica particles to SiO2 in} the hollow silica was calculated using _Al2O3 conversion ( _Al2O3 ( _ppm )/ _SiO2 ).

[Determination of Surface Charge of Hollow Silica Particles] Hollow silica sol was added to 10 mL of methanol and diluted to a silica concentration of 0.5% by mass to prepare the test sample. Using a particle charge meter (Voith Turbo, trade name PCD-06), a 0.001 mole/L (N/1000) diallyl dimethyl ammonium chloride solution (Voith Turbo) was used as the cation standard titrant. The titration was measured until the flow potential of the test sample reached zero. The surface charge (μeq/g- _SiO₂ ) was calculated by dividing the titration value by the mass of silica in the test sample.

[Example 1] (a) Step: 150g of water-dispersed hollow silica sol (manufactured by Ningbo Dilato, trade name: HKT-A20-40D) was fed into a 500cc pear-shaped flask. While stirring with a magnetic stirrer, sodium hydroxide aqueous solution was added dropwise to make the sodium content in the water-dispersed hollow silica sol 384 ppm/SiO ₂ (i.e., the Na ₂ O content is 182.16×10 ^-6 mol/SiO ₂ as the mole ratio of Na ₂ O to SiO ₂ ). The resulting silica sol had a pH of 10.1, a particle size of 55 nm measured by dynamic light scattering, an average primary particle size of 43 nm observed by TEM, a silica concentration of 20% by mass, a specific surface area (C) of 150 ^m² /g measured by BET, a specific surface area (D) of 63 ^m² /g measured by TEM, and a specific surface area ratio (C/D ratio) of _2.4 . The amount of aluminum bonded to the particle surface (A), converted to _Al₂O₃ relative to the mass of _SiO₂ in the hollow silica particles, was 0.1 ppm. The amount of aluminum present in all particles (B), converted to _Al₂O₃ relative to the mass of _SiO₂ in the hollow silica particles, was... The mass ratio of ₂ is 0.5 ppm, the (A/B) ratio is 0.20, and the sodium content in the water-dispersed hollow silica sol is 384 ppm/SiO ₂ , that is, the Na ₂ O content, expressed as the molar ratio of Na ₂ O to SiO ₂ , is 182 × 10 ^{- 6} moles/SiO _2. (b) Step: Subsequently, 56 g of methanol was added to 150 g of the obtained water-dispersed hollow silica sol. Using a rotary evaporator, under heating and depressurization (bath temperature: 120°C, depressurization degree: 580 Torr), methanol was fed in while water was distilled off to obtain a methanol dispersion of hollow silica (methanol-dispersed hollow silica sol). When the moisture content of the methanol-dispersed hollow silica sol reaches 2.0% by mass or less, methanol replacement is stopped, and 150g of methanol-dispersed hollow silica sol is obtained. The obtained methanol-dispersed hollow silica sol had a silica concentration of 21% by mass, a water content of 1.3% by mass, a particle size of 66 nm by dynamic light scattering, a pH of 9.0, a specific surface area (C) of 150 _m² /g by BET method, a specific surface area (D) of 63 ^m² /g by TEM, and a specific surface area ratio (C/D ratio) of 2.4. The amount of aluminum bonded to the particle surface (A ₎ , converted to _Al₂O₃ relative to the mass of _SiO₂ in the hollow silica particles, was 0.1 ppm. The amount of aluminum present in all particles (B), converted to _Al₂O₃ relative to the mass of _SiO₂ in the hollow silica particles _, was 0.5 ppm, and the (A/B) ratio was 0.20. The sodium content in the methanol-dispersed hollow silica sol was 384 ppm/SiO₂. ₂ , meaning the _Na₂O content, expressed as the molar ratio of _Na₂O to _SiO₂, is 182 × ^10⁻⁶ moles/ _SiO₂ . The obtained methanol-dispersed hollow silica sol was sealed in a 30cc glass bottle and then stored for 48 hours in an explosion-proof constant-temperature bath (manufactured by ESPEC, trade name: constant-temperature bath with safety door) at 50°C. The stability of the methanol-dispersed hollow silica sol was confirmed by comparing the light scattering particle size before and after storage at 50°C. For dynamic light scattering particles before 50°C, a value within 2.0 times the value after 48 hours of storage at 50°C was rated as "stable"; a value exceeding 2.0 times was rated as "unstable". The stability of the methanol-dispersed hollow silica sol obtained in Example 1 is shown in Table 1.

[Example 2] (a) Step: 150g of water-dispersed hollow silica sol (manufactured by Ningbo Dilato, trade name: HKT-A20-40D) was fed into a 500cc pear-shaped flask. While stirring with a magnetic stirrer, sodium hydroxide aqueous solution was added dropwise to make the sodium content in the water-dispersed hollow silica sol 384 ppm/SiO ₂ (i.e., the Na ₂ O content, expressed as the molar ratio of Na ₂ O to SiO ₂ , is 182.16×10 ^-6 moles/SiO ₂ ). Then, while stirring with a magnetic stirrer, 0.16g of diethanolamine was added dropwise. The obtained silica sol had a pH of 10.2, a particle size of 55 nm by dynamic light scattering, an average primary particle size of 43 nm observed by TEM, a silica concentration of 20% by mass, a specific surface area (C) of 150 ^m² /g by BET method, a specific surface area (D) of 63 ^m² /g converted by TEM, and a specific surface area ratio (C/D ratio) of 2.4. The amount of aluminum bonded to the particle surface (A ₎ , converted to _Al₂O₃ relative to the mass of _SiO₂ in the hollow silica particles, was 0.1 ppm. The amount of aluminum present in all particles (B), converted _{to Al₂O₃} relative to the mass of SiO₂ in the hollow silica particles, was... The mass ratio of ₂ is 0.5 ppm, the (A/B ratio) is 0.20, and the sodium content in the water-dispersed hollow silica sol is 384 ppm/SiO ₂ , that is, the Na ₂ O content, expressed as the molar ratio of Na ₂ O to SiO ₂ , is 182 × 10 ^{- 6} moles/SiO _2. (b) Step: Subsequently, 56 g of methanol was added to 150 g of the obtained water-dispersed hollow silica sol. Using a rotary evaporator, under heating and depressurization (bath temperature: 120°C, depressurization degree: 580 Torr), methanol was fed in while water was distilled off to obtain a methanol dispersion of hollow silica (methanol-dispersed hollow silica sol). When the moisture content of the methanol-dispersed hollow silica sol reaches 2.0% by mass or less, methanol replacement is stopped, and 150g of methanol-dispersed hollow silica sol is obtained. The obtained methanol-dispersed hollow silica sol had a silica concentration of 21% by mass, a water content of 0.4% by mass, a particle size of 66 nm by dynamic light scattering, a specific surface area (C) of 150 _m² /g by _BET method, and a specific surface area (D) of 63 ^m² /g by TEM conversion, with a specific surface area ratio (C/ _D ratio) of 2.4. The amount of aluminum bonded to the particle surface (A), converted from Al₂O₃ to the mass of _SiO₂ in the hollow silica particles, was 0.1 _ppm . The amount of aluminum present in all particles (B), converted from _Al₂O₃ to the mass of _SiO₂ in the hollow silica particles, was 0.5 ppm, with an (A/B ratio) of 0.20. The sodium content in the methanol-dispersed hollow silica sol was 384 ppm/ _SiO₂ , i.e., Na₂O₃. The _Na₂O content, expressed as a mole ratio of _Na₂O to _SiO₂ , was 182 × ^10⁻⁶ moles/ _SiO₂ . The same stability tests as in Example 1 were performed and are shown in Table 1.

[Example 3] (a) Step: 150g of aqueous dispersion of hollow silica sol (manufactured by Ningbo Dilato, trade name: HKT-A20-40D) was fed into a 500cc pear-shaped flask. While stirring with a magnetic stirrer, sodium hydroxide aqueous solution was added dropwise to make the sodium content in the aqueous dispersion of hollow silica sol 384 ppm/SiO ₂ (i.e., the Na ₂ O content, expressed as the molar ratio of Na ₂ O to SiO ₂ , is 182.16×10 ^-6 moles/SiO ₂ ). Then, while stirring with a magnetic stirrer, 0.16g of diethanolamine was added dropwise. The obtained silica sol had a pH of 10.2, a particle size of 55 nm by dynamic light scattering, an average primary particle size of 43 nm observed by TEM, a silica concentration of 20% by mass, a specific surface area (C) of 150 ^m² /g by BET method, a specific surface area (D) of 63 ^m² /g converted by TEM, and a specific surface area ratio (C/D ratio) of 2.4. The amount of aluminum bonded to the particle surface (A ₎ , converted to _Al₂O₃ relative to the mass of _SiO₂ in the hollow silica particles, was 0.1 ppm. The amount of aluminum present in all particles (B), converted _{to Al₂O₃} relative to the mass of SiO₂ in the hollow silica particles, was... The mass ratio of ₂ is 0.5 ppm, the (A/B ratio) is 0.20, and the sodium content in the water-dispersed hollow silica sol is 384 ppm/SiO ₂ , that is, the Na ₂ O content, expressed as the molar ratio of Na ₂ O to SiO ₂ , is 182 × 10 ^{- 6} moles/SiO _2. (b) Step: Subsequently, 56 g of methanol was added to 150 g of the obtained water-dispersed hollow silica sol. Using a rotary evaporator, under heating and depressurization (bath temperature: 120°C, depressurization degree: 580 Torr), methanol was fed in while water was distilled off to obtain a methanol dispersion of hollow silica (methanol-dispersed hollow silica sol). When the water content of the methanol-dispersed hollow silica sol reaches below 2.0% by mass, methanol replacement is stopped, yielding 150g of methanol-dispersed hollow silica sol. 30g of the methanol-dispersed hollow silica sol is fed into a 50cc pear-shaped flask, and 0.33g of pure water is added while stirring with a stirrer. The obtained methanol-dispersed hollow silica sol had a silica concentration of 21% by mass, a water content of 1.5% by mass, a particle size of 66 nm by dynamic light scattering, a specific surface area (C) of 150 ^m² /g by _BET method, and a specific surface area (D) of 63 ^m² /g by TEM conversion, with a specific surface area ratio (C/D ratio) of _2.4 . The amount of aluminum bonded to the particle surface (A), converted from _Al₂O₃ to the mass of _SiO₂ in the hollow silica particles, was 0.1 ppm. The amount of aluminum present in all particles (B), converted from _Al₂O₃ to the mass of _SiO₂ in the hollow silica particles, was 0.5 ppm, with an (A/B ratio) of 0.20. The sodium content in the methanol-dispersed hollow silica sol was 384 ppm/ _SiO₂ , i.e., Na₂O₂ _. The O content, expressed as the mole ratio of _Na₂O to _SiO₂ , was 182 × ^10⁻⁶ moles/ _SiO₂ . The same stability tests as in Example 1 were performed and are shown in Table 1.

[Example 4] (a) Step: 150g of aqueous dispersion of hollow silica sol (manufactured by Ningbo Dilato, trade name: HKT-A20-40D) was fed into a 500cc pear-shaped flask. While stirring with a magnetic stirrer, sodium hydroxide aqueous solution was added dropwise to make the sodium content in the aqueous dispersion of hollow silica sol 192 ppm/SiO ₂ (i.e., the Na ₂ O content, expressed as the molar ratio of Na ₂ O to SiO ₂ , is 91.08×10 ^-6 moles/SiO ₂ ). Then, while stirring with a magnetic stirrer, 0.16g of diethanolamine was added dropwise. The resulting silica sol had a pH of 9.8, a particle size of 55 nm measured by dynamic light scattering, an average primary particle size of 43 nm as observed by TEM, a silica concentration of 20% by mass, a specific surface area (C) of 150 ^m² /g measured by BET, a specific surface area (D) of 63 ^m² /g measured by TEM, and a specific surface area ratio (C/D ratio) of _2.4 . The amount of aluminum bonded to the particle surface (A), converted to _Al₂O₃ relative to the mass of _SiO₂ in the hollow silica particles, was 0.1 ppm. The amount of aluminum present in all particles (B), converted to _Al₂O₃ relative to the mass of _SiO₂ in the hollow silica particles, was... The mass ratio of ₂ is 0.5 ppm, the (A/B ratio) is 0.20, and the sodium content in the water-dispersed hollow silica sol is 192 ppm/SiO ₂ , that is, the Na ₂ O content, expressed as the molar ratio of Na ₂ O to SiO ₂ , is 91 × 10 ^{- 6} moles/SiO _2. (b) Step: Subsequently, 56 g of methanol was added to 150 g of the obtained water-dispersed hollow silica sol. Using a rotary evaporator, under heating and depressurization (bath temperature: 120°C, depressurization degree: 580 Torr), methanol was fed in while water was distilled off to obtain a methanol dispersion of hollow silica (methanol-dispersed hollow silica sol). When the moisture content of the methanol-dispersed hollow silica sol reaches 2.0% by mass or less, methanol replacement is stopped, and 150g of methanol-dispersed hollow silica sol is obtained. The obtained methanol-dispersed hollow silica sol had a silica concentration of 21% by mass, a water content of 0.6% by mass, a particle size of 66 nm by dynamic light scattering, a specific surface area (C) of 150 ^m² /g by _BET method, and a specific surface area (D) of 63 ^m² /g by TEM conversion, with a specific surface area ratio (C/D ratio) of _2.4 . The amount of aluminum bonded to the particle surface (A), converted from _Al₂O₃ to the mass of _SiO₂ in the hollow silica particles, was 0.1 ppm. The amount of aluminum present in all particles (B), converted from _Al₂O₃ to the mass of _SiO₂ in the hollow silica particles, was 0.5 ppm, with an (A/B ratio) of 0.20. The sodium content in the methanol-dispersed hollow silica sol was 192 ppm/ _SiO₂ , i.e., Na₂O₂ _. The O content, expressed as the mole ratio of _Na₂O to _SiO₂ , was 182 × ^10⁻⁶ moles/ _SiO₂ . The same stability tests as in Example 1 were performed and are shown in Table 1.

[Example 5] (a) Step: 150g of aqueous dispersion of hollow silica sol (manufactured by Ningbo Dilato, trade name: HKT-A20-40D) was fed into a 500cc pear-shaped flask. While stirring with a magnetic stirrer, sodium hydroxide aqueous solution was added dropwise to make the sodium content in the aqueous dispersion of hollow silica sol 192 ppm/SiO ₂ (i.e., the Na ₂ O content, expressed as the molar ratio of Na ₂ O to SiO ₂ , is 91.08×10 ^-6 moles/SiO ₂ ). Then, while stirring with a magnetic stirrer, 0.16g of diethanolamine was added dropwise. The resulting silica sol had a pH of 9.8, a particle size of 55 nm measured by dynamic light scattering, an average primary particle size of 43 nm as observed by TEM, a silica concentration of 20% by mass, a specific surface area (C) of 150 ^m² /g measured by BET, a specific surface area (D) of 63 ^m² /g measured by TEM, and a specific surface area ratio (C/D ratio) of _2.4 . The amount of aluminum bonded to the particle surface (A), converted to _Al₂O₃ relative to the mass of _SiO₂ in the hollow silica particles, was 0.1 ppm. The amount of aluminum present in all particles (B), converted to _Al₂O₃ relative to the mass of _SiO₂ in the hollow silica particles, was... The mass ratio of ₂ is 0.5 ppm, the (A/B ratio) is 0.20, and the sodium content in the water-dispersed hollow silica sol is 192 ppm/SiO ₂ , that is, the Na ₂ O content, expressed as the molar ratio of Na ₂ O to SiO ₂ , is 91 × 10 ^{- 6} moles/SiO _2. (b) Step: Subsequently, 56 g of methanol was added to 150 g of the obtained water-dispersed hollow silica sol. Using a rotary evaporator, under heating and depressurization (bath temperature: 120°C, depressurization degree: 580 Torr), methanol was fed in while water was distilled off to obtain a methanol dispersion of hollow silica (methanol-dispersed hollow silica sol). When the water content of the methanol-dispersed hollow silica sol reaches below 2.0% by mass, methanol replacement is stopped, yielding 150g of methanol-dispersed hollow silica sol. 30g of the obtained methanol-dispersed hollow silica sol is fed into a 50cc pear-shaped flask, and 0.27g of pure water is added while stirring with a stirrer. The obtained methanol-dispersed hollow silica sol has a silica concentration of 21% by mass, a water content of 1.5% by mass, a particle size of 66 nm by dynamic light scattering, a specific surface area (C) of 150 ^m² /g by _BET method, and a specific surface area (D) of 63 ^m² /g by TEM conversion, with a specific surface area ratio (C/D ratio) of _2.4 . The amount of aluminum bonded to the particle surface (A), converted from _Al₂O₃ to the mass of _SiO₂ in the hollow silica particles, is 0.1 ppm. The amount of aluminum present in all particles (B), converted from _Al₂O₃ to the mass of _SiO₂ in the hollow silica particles, is 0.5 ppm, with an (A/B ratio) of 0.20. The sodium content in the methanol-dispersed hollow silica sol is 192 ppm/ _SiO₂ , i.e., Na The _Na₂O content, expressed as a mole ratio of _Na₂O to _SiO₂ , was 182 × ^10⁻⁶ moles/ _SiO₂ . The same stability tests as in Example 1 were performed and are shown in Table 1.

[Example 6] (a) Step: 150g of water-dispersible hollow silica sol (manufactured by Ningbo Dilato, trade name: HKT-A20-40D) was fed into a 500cc pear-shaped flask, and 0.16g of diethanolamine was added dropwise while stirring with a magnetic stirrer. The obtained silica sol was at pH 9.5, with a particle size of 55 nm measured by dynamic light scattering and an average primary particle size of 43 nm observed by TEM. The silica concentration was 20% by mass. The specific surface area (C) by BET method was 150 ^m² /g, and the TEM-converted specific surface area (D) was 63 ^m² /g, resulting in a specific surface area ratio (C/D ratio) of _2.4 . The amount of aluminum bonded to the particle surface (A), expressed as _Al₂O₃ relative to the mass of _SiO₂ in the hollow silica particles, was 0.1 ppm. The amount of aluminum present in all particles (B), expressed as _Al₂O₃ relative to the mass of SiO₂ in the hollow silica particles _, was... The mass ratio of ₂ is 0.5 ppm, the (A/B ratio) is 0.20, and the sodium content in the water-dispersed hollow silica sol is 14 ppm/SiO ₂ , that is, the Na ₂ O content, expressed as the molar ratio of Na ₂ O to SiO ₂ , is 6.64 × 10 ^{- 6} moles/SiO _2. (b) Step: Subsequently, 56 g of methanol was added to 150 g of the obtained water-dispersed hollow silica sol. Using a rotary evaporator, under heating and depressurization (bath temperature: 120°C, depressurization degree: 580 Torr), methanol was fed in while water was distilled off to obtain a methanol dispersion of hollow silica (methanol-dispersed hollow silica sol). When the water content of the methanol-dispersed hollow silica sol reaches below 2.0% by mass, methanol replacement is stopped, and 150g of methanol-dispersed hollow silica sol is obtained. (c) Step: Subsequently, while stirring with a magnetic stirrer, a methanol-diluted sodium hydroxide aqueous solution is added dropwise to 100g of the obtained methanol-dispersed hollow silica sol to make the sodium content in the water-dispersed hollow silica sol 384ppm/ _SiO2 , that is, the _Na2O content, expressed as the molar ratio of _Na2O to _SiO2 , is 182.16× ^10-6 moles/ _SiO2 ). The obtained methanol-dispersed hollow silica sol had a silica concentration of 20% by mass, a water content of 1.8% by mass, a particle size of 78 nm by dynamic light scattering, a specific surface area (C) of 150 _m² /g by _BET method, and a specific surface area (D) of 63 ^m² /g by TEM conversion, with a specific surface area ratio (C/D ratio) of _2.4 . The amount of aluminum bonded to the particle surface (A), converted from _Al₂O₃ to the mass of _SiO₂ in the hollow silica particles, was 0.1 ppm. The amount of aluminum present in all particles (B), converted from _Al₂O₃ to the mass of _SiO₂ in the hollow silica particles, was 0.5 ppm, with an (A/B ratio) of 0.20. The sodium content in the methanol-dispersed hollow silica sol was 384 ppm/ _SiO₂ , i.e., Na₂O₂ _. The O content, expressed as the mole ratio of _Na₂O to _SiO₂ , was 182 × ^10⁻⁶ moles/ _SiO₂ . The same stability tests as in Example 1 were performed and are shown in Table 1.

[Comparative Example 1] (a) Step: 150g of aqueous dispersion of hollow silica sol (manufactured by Ningbo Dilato, trade name: HKT-A20-40D) was fed into a 500cc pear-shaped flask, and 0.16g of diethanolamine was added dropwise while stirring with a magnetic stirrer. (b) Step: Subsequently, 56g of methanol was added to 150g of the obtained aqueous dispersion of hollow silica sol. Using a rotary evaporator, under heating and reduced pressure (bath temperature: 120℃, reduced pressure: 580 Torr), methanol was added while distilling off water to obtain a methanol dispersion of hollow silica (methanol dispersion of hollow silica sol). When the moisture content of the methanol-dispersed hollow silica sol reached below 2.0% by mass, methanol replacement was stopped, yielding 150g of methanol-dispersed hollow silica sol. The obtained methanol-dispersed hollow silica sol had a silica concentration of 20% by mass, a moisture content of 0.8% by mass, and a dynamic light scattering particle size of 123nm. The _Na₂O content, expressed as a mole ratio of _Na₂O to _SiO₂ , was 6.64 × ^10⁻⁶ moles/ _SiO₂ . The same stability tests as in Example 1 were performed and are shown in Table 1.

Examples 1 to 6, which use dynamic light scattering to measure an average particle size of 20-150 nm and contain sols with a molar ratio of _7.12 × ^10⁻⁶ to 285× ^10⁻⁶ for monovalent alkali metal ions converted to _M₂O (where M represents monovalent alkali metal atoms) relative to SiO₂ of hollow silicon oxide particles, showed that after storage at 50°C for 48 hours, the dynamic light scattering particle size was within 2.0 times that before storage, confirming high stability. On the other hand, even though the average particle size of the dynamic light scattering method is 20~150nm, the sol containing monovalent alkali metal ions converted to _M2O (but M represents monovalent alkali metal atoms) relative to the molar ratio of _SiO2 in hollow silicon oxide particles does not reach 7.12× ^10-6. After being stored at 50°C for 48 hours, the particle size value of the dynamic light scattering method is more than 2.0 times that before storage, confirming low stability.

Furthermore, as shown in Table 1, even for sols containing sols with an average particle size of 20~150nm using the dynamic light scattering method, and where the molar ratio of monovalent alkali metal ions (converted to _M₂O , but M represents monovalent alkali metal atoms) to _SiO₂ in hollow silica particles does not reach 7.12× ^10⁻⁶ , the resulting monovalent alkali metal ion molar ratio (converted to _M₂O , but M represents monovalent alkali metal atoms) to _SiO₂ in hollow silica particles, after methanol replacement and adjustment with added monovalent alkali metal ions, is 7.12× ^10⁻⁶ to 285×10⁻⁶. Example 6, containing a sol at a ratio of ^-6 , showed that the particle size measured by dynamic light scattering after storage at 50°C for 48 hours was within 2.0 times that before storage, confirming high stability. [Industrial Applicability]

This invention relates to aqueous sols and organic solvent sols containing highly stable hollow silica particles, and further to methods for improving the stability of the aforementioned sols whose shelf life has been reduced, and methods for their manufacture.

Claims (23)

A hollow silica sol comprises hollow silica particles with spaces within an outer shell and monovalent alkali metal ions. The monovalent alkali metal ions are contained in a sol at a ratio of 7.12 × ^10⁻⁶ to 285 × ^10⁻⁶ moles of _SiO₂ in the hollow silica particles, converted to _M₂O (where M represents monovalent alkali metal atoms). The average particle size of the sol after storage at 50°C for 48 hours, measured by dynamic light scattering, is within 2.0 times that of the average particle size measured by dynamic light scattering before storage. For example, in request item 1, hollow silica sol, the aforementioned monovalent alkali metal ions are sodium ions. For example, in Request 1, the hollow silica sol has an average particle size of 20-150 nm as determined by dynamic light scattering. The hollow silica sol in claim 1 further contains an amine, and the amine has a mass of 0.001 to 10 _SiO2 relative to the hollow silica particles. For example, in the hollow silica sol of claim 4, the amine is selected from at least one amine selected from the group of primary, secondary and tertiary amines having 1 to 10 carbon atoms. For example, in the hollow silica sol of claim 4, the amine mentioned above is a water-soluble amine with a water solubility of 80 g/L or more. As in claim 1, the hollow silica sol contains aluminum atoms forming aluminate silicate sites. These aluminum atoms are bonded to the surface of the hollow silica particles. The mass of these aluminum atoms, relative to the mass of _SiO2 in the hollow silica particles, is in the range of 100 to 20,000 ppm (A) when converted to _{Al2O3 .} The mass of these aluminum atoms is determined by leaching. As in claim 7, the leaching method for determining the leaching of aluminum atoms from a compound containing aluminum atoms bonded to the surface of hollow silica particles is performed using an aqueous solution of at least one inorganic acid selected from the group consisting of sulfuric acid, nitric acid, and hydrochloric acid. For example, in the hollow silica sol of claim 7, the mass of aluminum atoms present in the hollow silica particles is expressed as a ratio (B) of 120 to 50,000 ppm of _SiO2 in the hollow silica particles when converted from _{Al2O3 .} The mass of aluminum atoms is determined by a dissolution method in which the hollow silica particles are dissolved in an aqueous solution of hydrofluoric acid. The ratio (A)/ratio (B) is 0.002 to 1.0. The hollow silica sol in Request 1 contains the aforementioned hollow silica particles in a ratio of [specific surface area (C) of silica particles as determined by the BET method (nitrogen adsorption method)] / [specific surface area (D) of silica particles as calculated by a self-transmitting electron microscope] of 1.40 to 5.00. The hollow silica sol in Request 1 contains hollow silica particles with a surface charge of 5~250 μeq/g per _1g of SiO2. As in claim 1, the hollow silica sol further comprises hollow silica particles coated with at least one silane compound selected from the group represented by formulas (1) and (2) below. In formula (1), ^R1 is a group bonded to a silicon atom and independently represents an alkyl, halogenated alkyl, alkenyl, aryl, or an organic group having an epoxy, (meth)acryl, teryl, amino, urea, polyether, carboxyl, protected carboxyl, carboxyl-derived group, amide, or cyano group and bonded to a silicon atom by a Si-C bond, or a combination of such groups; ^R2 is a group or atom bonded to a silicon atom and independently represents an alkoxy, acetoxy, hydroxyl, or halogen atom having 1 or more carbon atoms, or a combination of such groups; a represents an integer from 1 to 3; in formula (2), R ³ represents a group bonded to a silicon atom and independently represents an alkyl, halogenated alkyl, alkenyl, aryl, or an organic group having an epoxy, (meth)acryl, teryl, amino, urea, polyether, carboxyl, protected carboxyl, carboxyl-derived, amide, or cyano group and bonded to a silicon atom by a Si-C bond, or a combination of such groups. ^R4 represents a group or atom bonded to a silicon atom and independently represents an alkoxy, acetoxy, hydroxyl, or halogen atom having one or more carbon atoms, or a combination of such groups. Y represents a group or atom bonded to a silicon atom and represents an alkyl, NH, or oxygen atom. b represents an integer from 1 to 3, and c represents an integer of 0 or 1. For example, in the hollow silica sol of Request 1, the dispersion medium of the aforementioned hollow silica sol is water, alcohol, ketone, ether, amide, urea or ester with 1 to 10 carbon atoms. A film-forming composition comprising hollow silica particles derived from hollow silica sol as described in any of claims 1 to 13 and an organic resin or polysiloxane. A membrane having a visible light transmittance of 80% or more, obtained from a coating composition as claimed in claim 14. A method for manufacturing a hollow silica sol as described in any of claims 1 to 13, comprising the following steps (I) to (II): (I) preparing a hollow silica sol containing a dispersion medium; (II) adding and adjusting monovalent metal ions to the hollow silica sol of step ( _I ) in a molar ratio of 7.12 × ^10⁻⁶ to 285 × ^10⁻⁶ relative to the _SiO₂ of the hollow silica particles. For example, in the method for manufacturing hollow silica sol in claim 16, in step (II) above, the monovalent alkali metal ion is sodium ion. For example, in the method of manufacturing hollow silica sol in claim 17, in step (II) above, the adjustment of sodium ion content is to bring the hollow silica sol obtained in step (I) into contact with the cationic exchange resin, or to add a sodium source. For example, in the method for manufacturing hollow silica sol in claim 17, in step (II) above, the sodium source is added as sodium hydroxide. For example, in the method for manufacturing hollow silica sol in claim 16, the dispersion medium in steps (I) and (II) above is water, alcohol, ketone, ether, amide, urea or ester with 1 to 10 carbon atoms. The method for manufacturing hollow silica sol as claimed in claim 16, wherein in step (I), step (II), or both steps above, at least one step selected from (i) to (iv) below is added: (i) adding an amine to the hollow silica sol; (ii) adding sodium aluminate as an aluminum source and heating to form aluminosilicate sites on the hollow silica particles; (iii) replacing the dispersion medium with another dispersion medium; and (iv) coating the hollow silica particles with at least one silane compound selected from the group consisting of formulas (1) and (2). A stabilization method for hollow silica sol as described in claim 1, comprising hollow silica sol containing hollow silica particles within a shell, characterized in that for hollow silica sol whose average particle size, as measured by dynamic light scattering, has increased compared to the manufacturing stage, the method involves adding monovalent alkali ions in a mole ratio of the moles of the aforementioned monovalent alkali ions converted to _M₂O (where M represents a monovalent alkali atom) to the moles of _SiO₂ in the hollow silica sol particles, which is 7.12 × ^10⁻⁶ ~ 285 × ^10⁻⁶ , thereby reducing the increased average particle size measured by dynamic light scattering. For example, in claim 22, the stabilization method for hollow silica sol, wherein the aforementioned monovalent alkali metal ions are sodium ions.