Hydrophobic organic solvent-dispersed silica sol and method for producing the same

Abstract

[Problem] To provide a silica sol dispersed in a nonaqueous solvent, especially a hydrophobic solvent, to improve the compatibility with organic materials, and a method for producing the same. [Solution] A silica sol containing an alkali, where at least two alkoxy groups are present as Si-OCH3 and Si-OR1 (where R1 represents a C2-10 organic group optionally having an oxygen atom) on or near the surface of silane-coated silica particles, having said silica particles having a molar ratio of (Si-OR1 / (Si-OCH3) of 0.17-10 as the dispersoid and having at least one hydrophobic organic solvent selected from the group consisting of ketones, ethers, esters, amides, and hydrocarbons as the dispersion medium. The average particle size of the silica particles by dynamic light scattering is 5-200 nm. The silica sol contains at least one alkali comprising an amine, a quaternary ammonium hydroxide, an alkali metal hydroxide, an alkali metal alkoxide, an aliphatic carboxylic acid alkali metal salt, and an aromatic carboxylic acid alkali metal salt.

Description

[Technical Field] 【0001】 This invention relates to a silica sol dispersed in a hydrophobic solvent and a method for producing the same. [Background technology] 【0002】 Attempts have been made to improve the properties of coatings by incorporating silica particles into resin and film coating compositions, and to improve the properties of cured products by incorporating silica particles into resin matrices. These attempts utilize a dispersion of colloidal silica (silica sol), but silica sol dispersed in a non-aqueous solvent (organosilica sol) is used to improve compatibility with organic materials. For example, steps (A) and (B) below: (A) A step of surface-treating inorganic oxide particles in a hydrophilic inorganic oxide sol containing 25 to 100% by mass of a hydrophilic solvent having a boiling point of 100°C or lower in the dispersion medium, by adding a silicon alkoxide having two or more alkoxy groups bonded to a silicon atom, or a silicon alkoxide having one or more hydroxyl groups bonded to a silicon atom and one or more alkoxy groups bonded to a silicon atom, and A method for producing an organic solvent-dispersed inorganic oxide sol is disclosed, which includes the step of replacing the dispersion medium of the surface-treated inorganic oxide sol obtained in step (A) with a non-alcoholic organic solvent in the presence of a primary alcohol having 3 to 12 carbon atoms (see Patent Document 1). 【0003】 This method discloses a process in which the hydroxyl groups on the surface of inorganic oxide particles such as silica react with an alcohol, introducing alkoxy groups and organicating them to obtain an inorganic oxide sol dispersed in an organic solvent such as toluene. For example, a silica sol obtained by reacting methanol-dispersed silica sol with phenyltrimethoxysilane and dispersing it in toluene solvent is disclosed. A silica sol (silica sol) in which silica particles with an average particle size of 5 to 100 nm, on which organic groups containing unsaturated bonds between carbon atoms and alkoxy groups are bonded to the surface, are dispersed in a ketone-based solvent, wherein the number of organic groups containing unsaturated bonds between carbon atoms is 0.5 to 2.0 per nm. 2, alkoxy groups: 0.1-2.0 per nm 2 A silica sol is disclosed in which (organic group containing unsaturated bonds between carbon atoms) / (alkoxy group) is bonded in a ratio of 0.5 to 5.0 molars (see Patent Document 2). A method for producing a hydrophobic silica sol in which the pH is increased by treating a hydrophobic silica sol with an acidic pH with an alkali has been disclosed (see Patent Document 3). [Prior art documents] [Patent Documents] 【0004】 [Patent Document 1] Japanese Patent Publication No. 2005-200294 [Patent Document 2] International Publication No. 230823 [Patent Document 3] Japanese Patent Publication No. 4-092808 [Overview of the Initiative] [Problems that the invention aims to solve] 【0005】 This invention provides a silica sol dispersed in a non-aqueous solvent, particularly a hydrophobic solvent, to improve compatibility with organic substances, and a method for producing the same. The organosilica sol can undergo silane treatment of the silica particle surface, and the addition of amines provides a silica sol with improved stability. [Means for solving the problem] 【0006】 From a first perspective, the present invention provides Si-OR on or near the surface of silane-coated silica particles. 0 and Si-OR 1 (However, R 0 R is an alkyl group having 1 to 4 carbon atoms. 1 R represents an organic group having 2 to 10 carbon atoms, which may have an oxygen atom. 0 and R 1 These are not the same chemical group. There are at least two types of alkoxy groups represented by ). (Si-OR1 ) / (Si-OR 0 ) having a molar ratio of 0.17 to 10 as a dispersoid, At least one hydrophobic organic solvent selected from the group consisting of ketones, ethers, esters, amides, and hydrocarbons is used as a dispersion medium, and a silica sol containing an alkali, As a second aspect, the above Si-OR 0 The silica sol according to the first aspect, wherein is Si-OCH3, As a third aspect, the silica particles have an average particle diameter of 5 to 200 nm by the dynamic light scattering method, and the silica sol according to the first or second aspect, As a fourth aspect, the above R 1 The silica sol according to the first aspect, wherein is an ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, 1-methoxy-2-propyl group, 1-ethoxy-2-propyl group, or phenyl group, As a fifth aspect, the silane coating of the silica particles is represented by formulas (1) to (3): 【Chemical formula】 (In formula (1), R 3 Each is an organic group having an alkyl group, halogenated alkyl group, alkenyl group, aryl group, or epoxy group, (meth)acryloyl group, mercapto group, amino group, ureido group, or cyano group and bonded to a silicon atom by a Si-C bond, and R 4 Each represents an alkoxy group, acyloxy group, or halogen group, a represents an integer of 1 to 3, In formulas (2) and (3), R 5 And R 7 Each is an alkyl group having 1 to 3 carbon atoms or an aryl group having 6 to 30 carbon atoms and bonded to a silicon atom by a Si-C bond, and R 6 And R 8 Each represents an alkoxy group, acyloxy group, or halogen group, Y represents an alkylene group, NH group, or oxygen atom, b is an integer of 1 to 3, c is an integer of 0 or 1, and d is an integer of 1 to 3.) A silica sol according to any one of the first to fourth views, which is a hydrolysis product of at least one silane compound selected from the group consisting of the following: As a sixth point of view, the silica sol according to any one of the first to fifth points of view contains at least one of the alkalis, which consists of an amine, a quaternary ammonium hydroxide, an alkali metal hydroxide, an alkali metal alkoxide, an aliphatic alkali metal carboxylic acid salt, and an aromatic alkali metal carboxylic acid salt. As a seventh point, the silica sol described in the sixth point, wherein the pH of the liquid measured by mixing the above alkali-containing silica sol, methanol, and pure water in a mass ratio of 1:1:1 to 1:2:1 is 4.0 to 9.5, and The eighth aspect is a method for producing silica sol according to any one of the first to seventh aspects, which includes the following steps (A) to (C), the following step (A-1) after the completion of step (A) and before step (C), and the following step (A-2) after the completion of step (A-1) and before the completion of all steps. (A) Process: The above silica particles have an average particle size of 5-200 nm as determined by dynamic light scattering, and contain alcohol R with 1-4 carbon atoms. 0 OH (however R 0 The process of obtaining a silica sol using ) as a dispersion medium, (B) Step: R of the silica sol obtained in step (A) 0 Removal of some or all of OH, and R 1 OH structure (however, R 1 R represents an organic group having 2 to 10 carbon atoms, which may have an oxygen atom. 0 and R 1 The process involves adding an alcohol having the following chemical groups: (C) Step: R of the silica sol obtained in step (B) 0 OH and R 1 A step of removing some or all of the alcohol in the OH structure and adding at least one hydrophobic organic solvent selected from the group consisting of ketones, ethers, esters, amides, and hydrocarbons. (A-1) Step: A step of coating the silica sol obtained in step (A) with at least one silane compound represented by formulas (1) to (3) above. (A-2) Step: Adding at least one alkali, consisting of an amine, a quaternary ammonium hydroxide, an alkali metal hydroxide, an alkali metal alkoxide, an aliphatic carboxylic acid alkali metal salt, and an aromatic carboxylic acid alkali metal salt, to the silica sol obtained in step (A-1). [Effects of the Invention] 【0007】 Hydrophobic organic solvents such as ketones, ethers, esters, amides, and hydrocarbons are highly valuable as solvents used in a wide range of applications, including dilution of paints, inks, and adhesives, reaction solvents in pharmaceuticals and agricultural chemicals, basic raw materials for derivative products, and cleaning agents. On the other hand, attempts have been made to improve the properties of coatings by incorporating silica particles into coating compositions for resins and films, and to improve the properties of cured products by incorporating silica particles into resin matrices. When incorporating silica particles into various applications to improve performance, silica particles are used as colloidal particles. Since silica powder inevitably aggregates, silica is added to resins and other materials in the form of a colloidal silica dispersion (silica sol). In this case, silica sol dispersed in an organic solvent with high compatibility with the resin is used. 【0008】 The present invention provides silica sols dispersed in hydrophobic organic solvents such as ketones, ethers, esters, amides, and hydrocarbons, which have high utility as solvents. Organo-silica sols are typically prepared by first producing a silica sol dispersed in water (aqueous silica sol), then replacing the dispersion medium from water to a lower alcohol (e.g., methanol), and further replacing it with a hydrophobic organic solvent such as a ketone, ether, ester, amide, or hydrocarbon of the choice, thereby obtaining a silica sol with a hydrophobic organic solvent such as a ketone, ether, ester, amide, or hydrocarbon as the dispersion medium. 【0009】 Silica particles have silanol groups on or near their surface, and by replacing the dispersion medium from water to methanol, the hydroxyl groups of the silanols are converted to methoxy groups. Alternatively, by performing solvent replacement with a high-boiling point alcohol before replacing the dispersion medium from methanol to a hydrophobic organic solvent such as a ketone, ether, ester, amide, or hydrocarbon, a silica sol of the hydrophobic organic solvent such as a ketone, ether, ester, amide, or hydrocarbon can be obtained. As a result, the silanol groups on or near the surface of the silica particles have at least two types of alkoxy groups. For example, at least two types of alkoxy groups are present, such as a methoxy group and an alkoxy group of the high-boiling point alcohol. The relative proportions of at least two of these alkoxy groups significantly affect the stability of silica sols dispersed in hydrophobic organic solvents such as ketones, ethers, esters, amides, and hydrocarbons. Silica sols dispersed in hydrophobic organic solvents such as ketones, ethers, esters, amides, and hydrocarbons are stabilized by coating the surface of the silica particles with silane compounds, thereby covalently bonding functional groups that do not change into silanols. [Modes for carrying out the invention] 【0010】 This invention relates to the surface or vicinity of silane-coated silica particles with Si-OR 0 and Si-OR 1 (However, R 0 R is an alkyl group having 1 to 4 carbon atoms. 1 R represents an organic group having 2 to 10 carbon atoms, which may have an oxygen atom. 0 and R 1 These are not the same chemical group.) There are at least two types of alkoxy groups represented as (Si-OR 1 ) / (Si-OR 0 The silica sol contains an alkali, with silica particles having a molar ratio of 0.17 to 10 as the dispersed phase, and at least one hydrophobic organic solvent selected from the group consisting of ketones, ethers, esters, amides, and hydrocarbons as the dispersion medium. The above Si-OR 0 and Si-OR 1 In R 0 and R 1 These are not the same chemical group. That is, Si-OR 0 If it is Si-OCH3, then Si-OR 1 is R 1 This refers to an organic group having 2 to 10 carbon atoms, which is not a methyl group and may also contain an oxygen atom. Also, the number of carbon atoms is R 0 <R 1 It can also have the following relationship. The number of carbon atoms is R 0 <R 1 Having a relationship means having an Si-OR relationship. 0 and Si-OR 1 In the relationship, Si-OR 0 If it is Si-OCH3, then Si-OR 1 is R 1 This indicates that the organic group has two or more carbon atoms, and may also have an oxygen atom, representing organic groups with 2 to 10 carbon atoms. 【0011】 The above Si-OR 0 The hydroxyl groups of silanol groups on or near the surface of silica particles disperse the aqueous medium, which is the dispersion medium for aqueous silica sol, into an alcohol R with 1 to 4 carbon atoms. 0 OH (however R 0 ) represents an alkyl group having 1 to 4 carbon atoms. ) When substituted, R 0 The polyfunctional silane has an alkoxy group formed by a reversible reaction with OH, and the alkoxy or hydroxyl group not bonded to the particle is bonded to the particle, and the medium is an alcohol R with 1 to 4 carbon atoms. 0 It contains substances produced by a reversible reaction with OH. The above Si-OR 0 For example, this could represent Si-OCH3, Si-OC2H5, or Si-OC3H7. Si-OCH3 is a particularly preferred example. 【0012】 Also, the above Si-OR 1 Base (however, R 1R represents an organic group having 2 to 10 carbon atoms, which may have an oxygen atom. 0 and R 1 These are not the same chemical group. ) is the R of the dispersion medium. 0 OH, R 1 OH structure (however, R 1 This represents an organic group with 2 to 10 carbon atoms, which may contain an oxygen atom. When substituted for an alcohol containing ), it forms Si-OH or Si-OR 0 And, R 1 It has an alkoxy group that can be reversibly formed with an alcohol in an OH structure. In this invention, (Si-OR 1 ) / (Si-OR 0 The molar ratio of ) is present in proportions of 0.17 to 10, and in particular (Si-OR 1 It is preferable that the molar ratio of ) / (Si-OCH3) is between 0.17 and 10. In at least one hydrophobic organic solvent selected from the group consisting of ketones, ethers, esters, amides, and hydrocarbons, the ketone is a linear or cyclic aliphatic ketone having 3 to 30 carbon atoms, such as methyl ethyl ketone, diethyl ketone, methyl propyl ketone, methyl isobutyl ketone, diisopropyl ketone, diisobutyl ketone, methyl amyl ketone, and cyclohexanone. The ether is a linear or cyclic aliphatic ether having 3 to 30 carbon atoms, such as diethyl ether and tetrahydrofuran. The ester is a linear or cyclic ester having 2 to 30 carbon atoms, such as ethyl acetate, n-butyl acetate, sec-butyl acetate, methoxybutyl acetate, amyl acetate, n-propyl acetate, isopropyl acetate, ethyl lactate, butyl lactate, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, phenyl acetate, phenyl lactate, and phenyl propionate. Amides are aliphatic amides with 3 to 30 carbon atoms, such as dimethylacetamide, dimethylformamide, N-methylpyrrolidone, and N-ethylpyrrolidone. Hydrocarbons are linear or cyclic aliphatic or aromatic hydrocarbons with 6 to 30 carbon atoms, such as hexane, heptane, octane, nonane, decane, benzene, toluene, and xylene. 【0013】 R 1 OH structure alcohols are R 1 This represents an organic group having 2 to 10 carbon atoms, which may contain an oxygen atom, and the oxygen atom can exist in the form of an ether bond or a hydroxyl group. The above R 1 Examples of these groups include ethyl group, n-propyl group, i-propyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, n-pentyl group, i-pentyl group, 1-methoxy-2-propyl group, 1-ethoxy-2-propyl group, 1-propoxy-2-propyl group, 2-ethoxyethyl group, 2-hydroxyethyl group, 1-hydroxy-2-ethyl group, 3-methoxybutyl group, phenyl group, etc. 1The following groups can be preferably used: ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, 1-methoxy-2-propyl group, 1-ethoxy-2-propyl group, and phenyl group. R 1 Examples of OH structure alcohols include ethanol, n-propanol, i-propanol, n-butanol, isobutanol, s-butanol, t-butanol, n-pentanol, ethylene glycol, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and propylene glycol monopropyl ether. 【0014】 The sol of the present invention has a solid content of 0.1 to 60% by mass, or 1 to 55% by mass, or 10 to 55% by mass. Here, the solid content is the total components of the sol excluding the solvent component. The sol of the present invention is obtained with an average particle diameter in the range of 5 to 200 nm or 5 to 150 nm by dynamic light scattering (DLS) of silica particles, and with an average primary particle diameter in the range of 5 to 200 nm, 5 to 150 nm, or 5 to 100 nm by transmission electron microscopy observation of silica particles. The silica sol of the present invention is produced by the following steps (A) to (C): (A) Process: Silica particles have an average particle size of 5-200 nm as determined by dynamic light scattering, and contain alcohol R with 1-4 carbon atoms. 0 OH (however R 0 The process of obtaining a silica sol using ) as a dispersion medium, (B) Step: R of the silica sol obtained in step (A) 0 Removal of some or all of OH, and R 1 OH structure (however, R 1 R represents an organic group having 2 to 10 carbon atoms, which may have an oxygen atom. 0 and R 1 The process involves adding an alcohol having the following chemical groups: (C) Step: R of the silica sol obtained in step (B) 0 OH and R 1A step of removing part or all of the alcohol having an OH structure and adding at least one hydrophobic organic solvent selected from the group consisting of ketones, ethers, esters, amides, and hydrocarbons is included. 【0015】 The silica sol using methanol as a dispersion medium is obtained starting from an aqueous silica sol. The aqueous silica sol is obtained starting from water glass, and consists of: a) a step of cation-exchanging water glass to obtain active silicic acid; b) a step of heating the active silicic acid to obtain silica particles. In step a), in order to purify the active silicic acid, a mineral acid (for example, hydrochloric acid, nitric acid, or sulfuric acid) is added, and active silicic acid obtained by removing metal impurities and unnecessary anions by cation exchange and anion exchange in which metal impurities other than silica are eluted can be used. In step b), an alkaline component (for example, NaOH, KOH) is added to the active silicic acid to grow the silica particles. In order to promote the particle growth of the silica particles, a seed liquid and a feed liquid in which an alkali is added to the active silicic acid obtained in step a) are prepared, and the feed liquid is supplied while heating the seed liquid to increase the silica particle diameter, whereby an aqueous silica sol having an arbitrary particle diameter can be obtained. More preferably, among the alkaline components added in step b), an acidic silica sol from which alkali ions present outside the particles have been removed is suitable as the starting material of the present invention. 【0016】 In step (A) of the present invention, the silica particles have an average particle diameter of 5 to 200 nm by the dynamic light scattering method, and a silica sol having an alcohol R 0 OH (where R 0 represents an alkyl group having 1 to 4 carbon atoms.) as a dispersion medium can be obtained. (B) Step: A step of removing part or all of the R 0 OH of the silica sol obtained in step (A) and adding an alcohol having an R 1 OH structure (however, R 1 represents an organic group having 2 to 10 carbon atoms which may have an oxygen atom, and R 0 and R 1 are not the same chemical group). Also, the number of carbon atoms is R0 <R 1 can also have the following relationship. For the above R 0 partial or complete removal of OH and addition of an alcohol having an R 1 OH structure, although it is a so-called solvent replacement, it is not necessary to completely remove R 0 OH, and it is also possible to remove R 0 OH in a subsequent process or for some R 0 OH to remain. R 0 Removal of OH and addition of an alcohol having an R 1 OH structure can be performed either simultaneously or one of them can be performed first. 【0017】 These can be carried out by an evaporation method or an ultrafiltration method. For example, a silica sol having R 0 OH as a dispersion medium obtained in step (A) is placed in a flask, and the liquid temperature in the flask is 40 - 90 °C and the above R 1 OH structure (however, R 1 represents an organic group having 2 - 10 carbon atoms which may have an oxygen atom, and R 0 and R 1 are not the same chemical group.) can be added to perform solvent replacement. The solvent replacement can be carried out under normal pressure or reduced pressure. Under reduced pressure, it can be carried out at a pressure of, for example, 50 - 600 Torr. The time required for solvent replacement can be carried out in about 0.1 - 10 hours. (C) Step: A step of removing a part or all of R 0 OH and an alcohol having an R 1 OH structure from the silica sol obtained in step (B) and adding at least one hydrophobic organic solvent selected from the group consisting of ketones, ethers, esters, amides, and hydrocarbons. For the above R 0 OH (especially methanol) and a part or all of an alcohol having an R 1 OH structure, and adding at least one hydrophobic organic solvent selected from the group consisting of ketones, ethers, esters, amides, and hydrocarbons, although it is a so-called solvent replacement, it is not necessary to completely remove methanol and R 1- There is no need to remove alcohols with an OH structure, and some methanol and R 1 It is also possible for alcohols with an OH structure to remain. This can be done by evaporation. 0 OH (especially methanol) and R 1 The removal of the OH-structured alcohol and the addition of at least one hydrophobic organic solvent selected from the group consisting of ketones, ethers, esters, amides, and hydrocarbons can be performed simultaneously, or one of them can be performed first. 【0018】 After the completion of step (A) above and before step (C), the following step (A-1) is performed: Step (A-1): The silica sol obtained in step (A) is coated with a hydrolysate of at least one silane compound selected from the group consisting of formulas (1) to (3). Step (A-1) can also be performed again after step (A-2). In formula (1), R 3 Each of these is an organic group having an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an epoxy group, a (meth)acryloyl group, a mercapto group, an amino group, a ureido group, or a cyano group, and is bonded to a silicon atom by a Si-C bond, R 4 Each of the following represents an alkoxy group, an acyloxy group, or a halogen group, and a represents an integer from 1 to 3. In equations (2) and (3), R 5 and R 7 Each of these is an alkyl group having 1 to 3 carbon atoms, or an aryl group having 6 to 30 carbon atoms, and is bonded to a silicon atom by a Si-C bond, R 6 and R 8 Each of the following groups represents an alkoxy group, an acyloxy group, or a halogen group; Y represents an alkylene group, an NH group, or an oxygen atom; 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. 【0019】 The alkyl groups mentioned above are alkyl groups having 1 to 18 carbon atoms, for example, methyl group, ethyl group, n-propyl group, i-propyl group, cyclopropyl group, n-butyl group, i-butyl group, s-butyl group, t-butyl group, cyclobutyl group, 1-methyl-cyclopropyl group, 2-methyl-cyclopropyl group, n-pentyl group, 1-methyl-n-butyl group, 2-methyl-n-butyl group, 3-methyl-n-butyl group, 1,1-dimethyl-n-propyl group, 1,2-dimethyl-n-propyl group, 2,2-dimethyl-n-propyl group, 1-ethyl- n-propyl group, cyclopentyl group, 1-methyl-cyclobutyl group, 2-methyl-cyclobutyl group, 3-methyl-cyclobutyl group, 1,2-dimethyl-cyclopropyl group, 2,3-dimethyl-cyclopropyl group, 1-ethyl-cyclopropyl group, 2-ethyl-cyclopropyl group, n-hexyl group, 1-methyl-n-pentyl group, 2-methyl-n-pentyl group, 3-methyl-n-pentyl group, 4-methyl-n-pentyl group, 1,1-dimethyl-n-butyl group, 1,2-dimethyl-n-butyl group, 1,3-dimethyl-n-butyl group , 2,2-dimethyl-n-butyl group, 2,3-dimethyl-n-butyl group, 3,3-dimethyl-n-butyl group, 1-ethyl-n-butyl group, 2-ethyl-n-butyl group, 1,1,2-trimethyl-n-propyl group, 1,2,2-trimethyl-n-propyl group, 1-ethyl-1-methyl-n-propyl group, 1-ethyl-2-methyl-n-propyl group, cyclohexyl group, 1-methyl-cyclopentyl group, 2-methyl-cyclopentyl group, 3-methyl-cyclopentyl group, 1-ethyl-cyclobutyl group, 2-ethyl-cyclobutyl Group, 3-ethyl-cyclobutyl group, 1,2-dimethyl-cyclobutyl group, 1,3-dimethyl-cyclobutyl group, 2,2-dimethyl-cyclobutyl group, 2,3-dimethyl-cyclobutyl group, 2,4-dimethyl-cyclobutyl group, 3,3-dimethyl-cyclobutyl group, 1-n-propyl-cyclopropyl group, 2-n-propyl-cyclopropyl group, 1-i-propyl-cyclopropyl group, 2-i-propyl-cyclopropyl group, 1,2,2-trimethyl-cyclopropyl group, 1,2,3-trimethyl-cyclopropyl group, 2,2,Examples of such groups include, but are not limited to, 3-trimethylcyclopropyl group, 1-ethyl-2-methylcyclopropyl group, 2-ethyl-1-methylcyclopropyl group, 2-ethyl-2-methylcyclopropyl group and 2-ethyl-3-methylcyclopropyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, etc. Furthermore, alkylene groups can be derived from the alkyl groups mentioned above. 【0020】 Examples of the above-mentioned halogenated alkyl groups include groups in which the hydrogen atoms of the alkyl group are substituted with halogen atoms such as fluorine, chlorine, bromine, and iodine. The aryl group mentioned above is an aryl group having 6 to 30 carbon atoms, and examples include the phenyl group, naphthyl group, anthracene group, and pyrene group. Alkenyl groups are alkenyl groups having 2 to 10 carbon atoms, including ethenyl group, 1-propenyl group, 2-propenyl group, 1-methyl-1-ethenyl group, 1-butenyl group, 2-butenyl group, 3-butenyl group, 2-methyl-1-propenyl group, 2-methyl-2-propenyl group, 1-ethylethenyl group, 1-methyl-1-propenyl group, 1-methyl-2-propenyl group, 1-pentenyl group, 2-pentenyl group, 3-pentenyl group, 4-pentenyl group, 1-n-propylethenyl group, 1-methyl-1-butenyl group, 1-methyl-2-butenyl group, 1-methyl-3-butenyl group, 2-ethyl-2-propenyl group, 2-methyl-1-butenyl group, 2-methyl-2-butenyl group, 2-methyl-3-butenyl group, and 3 Examples of but not limited to the following are methyl-1-butenyl group, 3-methyl-2-butenyl group, 3-methyl-3-butenyl group, 1,1-dimethyl-2-propenyl group, 1-i-propylethenyl group, 1,2-dimethyl-1-propenyl group, 1,2-dimethyl-2-propenyl group, 1-cyclopentenyl group, 2-cyclopentenyl group, 3-cyclopentenyl group, 1-hexenyl group, 2-hexenyl group, 3-hexenyl group, 4-hexenyl group, 5-hexenyl group, 1-methyl-1-pentenyl group, 1-methyl-2-pentenyl group, 1-methyl-3-pentenyl group, 1-methyl-4-pentenyl group, 1-n-butylethenyl group, 2-methyl-1-pentenyl group, 2-methyl-2-pentenyl group, etc. 【0021】 The alkoxy groups mentioned above include, but are not limited to, alkoxy groups having 1 to 10 carbon atoms, such as methoxy group, ethoxy group, n-propoxy group, i-propoxy group, n-butoxy group, i-butoxy group, s-butoxy group, t-butoxy group, n-pentyloxy group, 1-methyl-n-butoxy group, 2-methyl-n-butoxy group, 3-methyl-n-butoxy group, 1,1-dimethyl-n-propoxy group, 1,2-dimethyl-n-propoxy group, 2,2-dimethyl-n-propoxy group, 1-ethyl-n-propoxy group, and n-hexyloxy group. The above-mentioned acyloxy groups, which have 2 to 10 carbon atoms, include, but are not limited to, methyl carbonyloxy group, ethyl carbonyloxy group, n-propyl carbonyloxy group, i-propyl carbonyloxy group, n-butyl carbonyloxy group, i-butyl carbonyloxy group, s-butyl carbonyloxy group, t-butyl carbonyloxy group, n-pentyl carbonyloxy group, 1-methyl-n-butyl carbonyloxy group, 2-methyl-n-butyl carbonyloxy group, 3-methyl-n-butyl carbonyloxy group, 1,1-dimethyl-n-propyl carbonyloxy group, 1,2-dimethyl-n-propyl carbonyloxy group, 2,2-dimethyl-n-propyl carbonyloxy group, 1-ethyl-n-propyl carbonyloxy group, n-hexyl carbonyloxy group, 1-methyl-n-pentyl carbonyloxy group, and 2-methyl-n-pentyl carbonyloxy group. 【0022】 Examples of the halogen groups mentioned above include fluorine, chlorine, bromine, and iodine. Examples of organic groups having an epoxy group include the 2-(3,4-epoxycyclohexyl)ethyl group and the 3-glycidoxypropyl group. The above term "(meth)acryloyl group" refers to both an acryloyl group and a methacryloyl group. Examples of organic groups having a (meth)acryloyl group include 3-methacryloxypropyl group and 3-acryloxypropyl group. An example of an organic group containing a mercapto group is the 3-mercaptopropyl group. 【0023】 Examples of organic groups having an amino group include 2-aminoethyl group, 3-aminopropyl group, N-2-(aminoethyl)-3-aminopropyl group, N-(1,3-dimethylbutylidene)aminopropyl group, N-phenyl-3-aminopropyl group, and N-(vinylbenzyl)-2-aminoethyl-3-aminopropyl group. An example of an organic group having a ureido group is the 3-ureidopropyl group. An example of an organic group having a cyano group is the 3-cyanopropyl group. 【0024】 Formulas (2) and (3) above are preferably compounds that can form a trimethylsilyl group on the surface of silica particles. Examples of such compounds are listed below. [ka] In the above formula, R 12 These are alkoxy groups, such as methoxy and ethoxy groups. 【0025】 This process involves the reaction of hydroxyl groups, such as silanol groups in the case of silica particles, with the silane compound on the surface of silica particles, thereby coating the surface of the silica particles with the silane compound through siloxane bonding. The reaction temperature can be from 20°C to the boiling point of the dispersion medium, but can be carried out in the range of 20°C to 100°C, for example. The reaction time can be approximately 0.1 to 6 hours. In addition to the trimethylsilyl group, formulas (2) and (3) above may have preferred functional groups such as monomethylsilyl group, dimethylsilyl group, methacryloxypropylsilyl group, and phenyl group. Corresponding silane compounds include trimethylmethoxysilane, trimethylethoxysilane, hexamethyldisilazane, hexamethyldisiloxane, methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropyltriethoxysilane, acryloxypropyltrimethoxysilane, acryloxypropyltriethoxysilane, phenyltrimethoxysilane, and phenyltriethoxysilane. 【0026】 The above silane compound is defined as having a coating amount on the silica particle surface, with a silicon atom count of 0.1 atoms / nm in the silane compound. 2 ~6.0 pieces / nm 2 The silica particle surface can be coated by adding a silane compound equivalent to the coating amount to the silica sol. The hydrolysis of the above silane compounds requires water; however, if an aqueous solvent sol is used, those aqueous solvents are used, and if an alcohol solvent sol with 1 to 3 carbon atoms is used, an aqueous medium is used. 0 The water remaining in the alcohol solvent after solvent substitution with an OH alcohol can be used. This remaining water is the water that remains when a sol of an aqueous medium is substituted with a sol of an alcohol solvent having 1 to 3 carbon atoms. For example, water present in the alcohol at a concentration of 1% by mass or less, for example, 0.01 to 1% by mass, can be used. Furthermore, hydrolysis can be carried out with or without a catalyst. When the process is carried out without a catalyst, the silica particle surface is on the acidic side, and a methanol silica sol with a pH of 2-6 (measured with methanol and water in a 1:1 ratio) can be used. When a catalyst is used, examples of hydrolysis catalysts include metal chelate compounds, organic acids, inorganic acids, organic bases, and inorganic bases. Examples of metal chelate compounds used as hydrolysis catalysts include triethoxy mono(acetylacetonate) titanium and triethoxy mono(acetylacetonate) zirconium. Examples of organic acids used as hydrolysis catalysts include acetic acid and oxalic acid. Examples of inorganic acids used as hydrolysis catalysts include hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid, and phosphoric acid. Examples of organic bases used as hydrolysis catalysts include pyridine, pyrrole, piperazine, and quaternary ammonium salts. Examples of inorganic bases used as hydrolysis catalysts include ammonia, sodium hydroxide, and potassium hydroxide. 【0027】 In this invention, the following (A-2) step is performed between the end of step (A-1) and the end of all steps: Step (A-2): This step may include adding at least one alkali, consisting of an amine, a quaternary ammonium hydroxide, an alkali metal hydroxide, an alkali metal alkoxide, an aliphatic carboxylic acid alkali metal salt, and an aromatic carboxylic acid alkali metal salt, to the silica sol obtained in step (A-1). The amount of alkali added is preferably such that the pH of the silica sol is between 4.0 and 9.5. The amount of alkali added is present as a content in the silica sol. The pH of the hydrophobic organic solvent silica sol of the present invention is measured by mixing the silica sol, methanol, and pure water in a mass ratio of 1:1:1 or 1:2:1. 【0028】 Examples of amines include secondary and tertiary amines with a total number of carbon atoms ranging from 5 to 35. Examples of the above secondary amines include ethyl-n-propylamine, ethylisopropylamine, dipropylamine, diisopropylamine, ethylbutylamine, n-propylbutylamine, dibutylamine, ethylpentylamine, n-propylpentylamine, isopropylpentylamine, dipentylamine, ethyloctylamine, i-propyloctylamine, butyloctylamine, and dioctylamine. Examples of the above-mentioned tertiary amines include triethylamine, ethyldi-n-propylamine, diethyl-n-propylamine, tri-n-propylamine, triisopropylamine, ethyldibutylamine, diethylbutylamine, isopropyldibutylamine, diisopropylethylamine, diisopropylbutylamine, tributylamine, ethyldipentylamine, diethylpentylamine, tripentylamine, methyldioctylamine, dimethyloctylamine, ethyldioctylamine, diethyloctylamine, trioctylamine, benzyldibutylamine, and diazabicycloundecene. Among the above amines, secondary and tertiary amines having an alkyl group with a total number of carbon atoms of 6 to 35 are preferred, such as diisopropylamine, tripentylamine, triisopropylamine, dimethyloctylamine, and trioctylamine. As the quaternary ammonium hydroxide, tetraalkylammonium hydroxide with a total number of carbon atoms of 4 to 40 is preferred. Examples include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetra-n-propylammonium hydroxide, tetra-i-propylammonium hydroxide, tetrabutylammonium hydroxide, and ethyltrimethylammonium hydroxide. 【0029】 Examples of alkali metal hydroxides include sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate. Examples of alkali metal alkoxides include sodium methoxide, sodium ethoxide, potassium methoxide, and potassium ethoxide. Examples of alkali metal salts of aliphatic carboxylic acids include saturated alkali metal salts and unsaturated alkali metal salts of aliphatic carboxylic acids having 2 to 30 carbon atoms. Examples of alkali metals include sodium and potassium. Examples of saturated alkali metal salts of aliphatic carboxylic acids include alkali metal salts of laurate, alkali metal salts of myristate, alkali metal salts of palmitate, and alkali metal salts of stearate. 【0030】 Examples of alkali metal salts of unsaturated aliphatic carboxylic acids include alkali metal salts of oleate, alkali metal salts of linoleate, and alkali metal salts of linolenate. Alkali metal salts of unsaturated aliphatic carboxylates, particularly potassium oleate, can be preferably used. Examples of alkali metal salts of aromatic carboxylic acids include benzoates, salicylates, and phthalates. 【0031】 In the present invention, since the silica sol is dispersed in at least one hydrophobic organic solvent selected from the group consisting of ketones, ethers, esters, amides, and hydrocarbons, it is preferable that the silica particles have irreversible hydrophobic groups on their surface. Therefore, it is preferable that they be coated with a hydrolysate of at least one silane compound represented by formulas (1) to (3). These silane coatings are preferably carried out on the acidic side. Furthermore, the silanol groups on or near the surface of the silica particles are R 0 In the OH solvent, a portion is Si-OR 0 It changes to the base, R 0 R in OH solvent 1 By adding the OH solvent, R 0 O-groups and remaining silanol groups are R 1 It changes to an O-group. Also, when substituting with at least one hydrophobic organic solvent selected from the group consisting of ketones, ethers, esters, amides, and hydrocarbons, the R in the sol 1 OH / R 0 As the ratio of OH increases, 0 O-groups and remaining silanol groups are alkoxy R 1 It changes to an O-group. This reaction is promoted on the acidic side, but is inhibited by the addition of the above amine, (Si-OR 1 ) / (Si-OR 0 The molar ratio of ) is in the range of 0.17 to 10, and in particular (Si-OR 1 This results in silica particles with a molar ratio of ) / (Si-OCH3) ranging from 0.17 to 10. 【0032】 The present invention is a silica sol dispersed in at least one hydrophobic organic solvent selected from the group consisting of ketones, ethers, esters, amides, and hydrocarbons, and can be used, for example, as an adhesive, mold release agent, semiconductor encapsulant, LED encapsulant, paint, film additive, hard coat agent, photoresist material, printing ink, cleaning agent, cleaner, additive for various resins, insulating composition, rust inhibitor, lubricant, metalworking oil, film coating agent, release agent, etc. [Examples] 【0033】 (Analysis method for particulate alcohols) 4 mL of sample was mixed with 20 mL of n-hexane, centrifuged at 2770 G, the supernatant was discarded, and the precipitate was separated. The precipitate was then redissolved with 2-4 mL of acetone, and n-hexane was added again until it condensed. This process of separating the precipitate by centrifugation at 2770 G was repeated twice. The resulting precipitate was vacuum-dried at 150°C to obtain a dry powder. 0.2 g of the powder obtained above was mixed with 10 mL of 0.05 N sodium hydroxide aqueous solution and left at room temperature for 1 day. Any undissolved material was removed by filtration or centrifugation, and the amount of alcohol bound to the surface was measured by gas chromatography of the solution portion. 【0034】 Example 1 A methanol silica sol (average primary particle size 22 nm, silica concentration 40.6% by mass, moisture content 2.4%, manufactured by Nissan Chemical Corporation) was prepared. 1200g of the above methanol sol was placed in a 2L round-bottom flask. While stirring the sol with a magnetic stirrer, 120g of n-butyl alcohol and 32.3g of methacryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name KBM-503) were added, and the solution temperature was maintained at 60°C for 2 hours. Then, 1.95g of diisopropylamine was added, and the solution temperature was raised to 67°C and maintained for 1 hour. Furthermore, 12.3g of methacryloxypropyltrimethoxysilane was added, and the solution temperature was maintained at 67°C for 1 hour. Subsequently, MIBK (methyl isobutyl ketone) is supplied while the solvent is evaporated using a rotary evaporator at a reduced pressure of 480-125 Torr and a bath temperature of 80°C, replacing the dispersion medium of the sol with MIBK. The mixture is then filtered through a filter paper with an average aperture of 1 μm, resulting in a transparent colloidal-colored MIBK-dispersed silica sol (SiO2 40.5% by mass, viscosity (20°C) 2.8 mPa·s, water content 0.03% by mass, methanol 0.1% by mass, n-butyl alcohol 5% by mass, average particle size of silica particles 23 nm by dynamic light scattering method, methacrylate group binding to silica particles 1.4 groups / nm). 2 The amount of methoxy groups bonded to silica particles is 0.5 / nm. 2 , butoxy group bonding amount: 0.36 / nm 2 The result obtained was obtained. The molar ratio of (Si-OC4H9) / (Si-OCH3) was 0.72. When this sol, methanol, and pure water were mixed in a 1:1:1 ratio by weight, the pH of the resulting liquid was measured with a pH meter and found to be 9.0. This sol showed no increase in viscosity even after being stored in a sealed glass container at 50°C for four weeks. 【0035】 Example 2 A water-dispersible silica sol (average primary particle size 12 nm, pH 3, silica concentration 33% by mass, manufactured by Nissan Chemical Corporation) was prepared. 1000g of the above silica sol was placed in a 2L glass reactor equipped with a stirrer, condenser, thermometer, and two inlets. While the sol in the reactor was kept boiling, methanol vapor generated in a separate boiler was continuously blown into the silica sol in the reactor, gradually raising the liquid level and replacing the water with methanol. The replacement was stopped when the volume of the distillate reached 9L, yielding 1100g of methanol-dispersed silica sol. The obtained methanol-dispersed silica sol had an SiO2 concentration of 30.5% by mass, a water content of 1.6% by mass, and a viscosity of 2 mPa·s. 1000g of the above methanol sol was placed in a 1L round-bottom flask, and while stirring the sol with a magnetic stirrer, 150g of n-butyl alcohol and 77.5g of methyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name KBM-13) were added, and the liquid temperature was maintained at 60°C for 5 hours. Subsequently, n-butyl acetate was supplied while evaporating the solvent using a rotary evaporator at a reduced pressure of 500-80 Torr and a bath temperature of 80°C, replacing the dispersion medium of the sol with n-butyl acetate. Then, 0.6 g of tri-n-pentylamine (0.9 mmol per 100 g of SiO2 in the silica particles) was added to form a transparent colloidal silica sol dispersed by n-butyl acetate (SiO2 40.5% by mass, viscosity (20°C) 3.2 mPa·s, water 0.02% by mass, methanol 0.02% by mass, n-butyl alcohol 4% by mass). The average particle size of the silica particles measured by dynamic light scattering after dilution with n-butyl acetate was 19 nm, and the number of methyl groups attached to the silica particles was 1.4 / nm. 2 The amount of methoxy groups attached to silica particles is 0.44 / nm. 2 , butoxy group bonding amount 0.71 / nm 2 The result obtained was obtained. The molar ratio of (Si-OC4H9) / (Si-OCH3) was 1.61. When the pH of a liquid obtained by mixing silica sol, methanol, and pure water in a 1:2:1 ratio by weight was measured with a pH meter, it was found to be 5.3. This sol showed no increase in viscosity even after being stored in a sealed glass container at 50°C for four weeks. 【0036】 Example 3 A water-dispersible silica sol (average primary particle size 12 nm, pH 3, silica concentration 33% by mass, manufactured by Nissan Chemical Corporation) was prepared. 1000g of the above silica sol was placed in a 2L glass reactor equipped with a stirrer, condenser, thermometer, and two inlets. While the sol in the reactor was kept boiling, methanol vapor generated in a separate boiler was continuously blown into the silica sol in the reactor, gradually raising the liquid level and replacing the water with methanol. The replacement was stopped when the volume of the distillate reached 9L, yielding 1100g of methanol-dispersed silica sol. The obtained methanol-dispersed silica sol had an SiO2 concentration of 30.5% by mass, a water content of 1.6% by mass, and a viscosity of 2 mPa·s. 800g of the above methanol sol was placed in a 1L round-bottom flask, and while stirring the sol with a magnetic stirrer, 57g of n-butyl alcohol and 52.8g of methyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name KBM-13) were added, and the liquid temperature was maintained at 60°C for 5 hours. Then, 15.2g of dimethyldimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name KBM-22) was added, and the liquid temperature was maintained at 60°C for 3 hours. After cooling, 0.48 g of tripentylamine (0.9 mmol per 100 g of SiO2 in the silica particles) was added, and cyclohexanone was supplied while evaporating the solvent using a rotary evaporator at a reduced pressure of 500-70 Torr and a bath temperature of 80-90°C, thereby replacing the dispersion medium of the sol with cyclohexanone. This resulted in a colorless, transparent cyclohexanone-dispersed silica sol (38% by mass of SiO2, viscosity (20°C) 12 mPa·s, water content 0.04% by mass, methanol 0.2% by mass, n-butyl alcohol 2% by mass). The average particle size of the silica particles measured by dynamic light scattering after dilution with MEK (methyl ethyl ketone) was 22 nm, and the number of methyl groups attached to the silica particles was 1.4 / nm. 2 The amount of methoxy groups attached to silica particles is 0.49 / nm. 2 , butoxy group bonding amount 0.15 / nm 2The result obtained was obtained. The molar ratio of (Si-OC4H9) / (Si-OCH3) was 0.31. When the pH of a liquid obtained by mixing silica sol, methanol, and pure water in a 1:1:1 weight ratio was measured with a pH meter, it was found to be 4.8. Even after being placed in a sealed glass container and kept at 50°C for four weeks, there was no increase in viscosity or particle size as measured by dynamic light scattering. 【0037】 Example 4 A water-dispersible silica sol (average primary particle size 12 nm, pH 3, silica concentration 33% by mass, manufactured by Nissan Chemical Corporation) was prepared. 1000g of the above silica sol was placed in a 2L glass reactor equipped with a stirrer, condenser, thermometer, and two inlets. While the sol in the reactor was kept boiling, methanol vapor generated in a separate boiler was continuously blown into the silica sol in the reactor, gradually raising the liquid level and replacing the water with methanol. The replacement was stopped when the volume of the distillate reached 12L, yielding 1100g of methanol-dispersed silica sol. The obtained methanol-dispersed silica sol had an SiO2 concentration of 30.5% by mass, a water content of 0.5% by mass, and a viscosity of 2 mPa·s. 1000 g of the above methanol-dispersed silica sol was placed in a 1 L round-bottom flask. While stirring the sol with a magnetic stirrer, 100 g of n-butyl alcohol and 34.2 g of phenyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name KBM-103) were added, and the liquid temperature was maintained at 60°C for 2 hours. Next, 46.3 g of hexamethyldisiloxane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name KF-96L) was added, and the liquid temperature was maintained at 60°C for 2 hours. After cooling, 0.92 g of trioctylamine (0.8 mmol per 100 g of SiO2 in the silica particles) was added, and the solvent was evaporated using a rotary evaporator at a reduced pressure of 450-120 Torr and a bath temperature of 80°C while supplying diisopropyl ketone. By replacing the dispersion medium of the sol with diisopropyl ketone, a colorless and transparent diisopropyl ketone-dispersed silica sol was obtained (SiO2 50.5% by mass, viscosity (20°C) 7.5 mPa·s, water 0.02% by mass, methanol 0.1% by mass, n-butyl alcohol 3% by mass). The average particle size of the silica particles measured by dynamic light scattering of the silica particles after dilution with diisobutyl ketone was 16 nm, and the number of phenyl groups attached to the silica particles was 0.8 / nm. 2 The amount of methoxy groups attached to silica particles is 0.45 / nm. 2 , butoxy group bonding amount 0.47 / nm 2 The result obtained was obtained. The molar ratio of (Si-OC4H9) / (Si-OCH3) was 1.04. When the pH of a liquid obtained by mixing silica sol, methanol, and pure water in a 1:1:1 weight ratio was measured with a pH meter, it was found to be 7.2. After placing this sol in a sealed glass container and storing it at 50°C for 4 weeks, its viscosity (at 20°C) was 7.5 mPa·s, and the particle size of the silica particles, determined by dynamic light scattering, was 16 nm, indicating good storage stability. 【0038】 Comparative Example 1 The procedure was the same as in Example 1, except that n-butyl alcohol was not added. A transparent colloidal MIBK-dispersed silica sol was obtained (SiO2 40.5% by mass, viscosity (20°C) 2.0 mPa·s, water 0.05% by mass, methanol 0.1% by mass, average particle size of silica particles 21 nm by dynamic light scattering method, methacrylate group binding to silica particles 1.4 groups / nm). 2 The amount of methoxy groups bonded to silica particles is 0.5 / nm. 2 ) was obtained. When the pH of a liquid obtained by mixing silica sol, methanol, and pure water in a 1:1:1 weight ratio was measured with a pH meter, it was found to be 9.0. This silica sol was placed in a sealed glass container. Initially, its viscosity was 2.0 mPa·s and the average particle size of silica particles measured by dynamic light scattering was 21 nm. After being kept at 50°C for 4 weeks, the viscosity became 2.2 mPa·s and the average particle size of silica particles measured by dynamic light scattering became 27 nm. The stability of this silica sol was insufficient. 【0039】 Comparative Example 2 The procedure was the same as in Example 2, except that the amine was not added after the n-butyl acetate substitution. Transparent colloidal-colored n-butyl acetate dispersed silica sol (SiO2 40.5% by mass, viscosity (20°C) 3.2 mPa·s, water content 0.02% by mass, methanol 0.02% by mass, n-butyl alcohol 4% by mass). Average particle size of silica particles measured by dynamic light scattering after dilution with n-butyl acetate: 20 nm, Methoxy group binding density to silica particles: 0.42 / nm. 2 , butoxy group bonding amount 0.70 / nm 2 The result obtained was (Si-OC4H9) / (Si-OCH3) with a molar ratio of 1.67. When the pH of a liquid obtained by mixing silica sol, methanol, and pure water in a 1:2:1 ratio by weight was measured with a pH meter, it was found to be 3.5. This sol, placed in a sealed glass container, initially had a viscosity of 3.2 mPa·s and an average particle size of 20 nm determined by dynamic light scattering of silica particles. However, after being kept at 50°C for 4 weeks, the viscosity increased to 6.0 mPa·s and the average particle size of silica particles, determined by dynamic light scattering, increased to 37 nm, indicating that the stability of this silica sol was insufficient. 【0040】 Comparative Example 3 Except for not adding an amine after diisopropyl ketone substitution, the process was the same as in Example 4. Diisopropyl ketone-dispersed silica sol (50.5% by mass of SiO2, viscosity (20°C) 8.6 mPa·s, moisture 0.02% by mass, methanol 0.1% by mass, n-butyl alcohol 3% by mass, and diisobutyl ketone) was diluted and measured by dynamic light scattering, yielding an average particle size of 22 nm and a phenyl group bond count of 0.8 groups / nm. 2 The amount of methoxy groups attached to silica particles is 0.44 / nm. 2, butoxy group bonding amount 0.49 / nm 2 The result obtained was (Si-OC4H9) / (Si-OCH3), which had a molar ratio of 1.11. When the pH of a liquid obtained by mixing silica sol, methanol, and pure water in a 1:1:1 weight ratio was measured with a pH meter, it was found to be 4.6. This silica sol was placed in a sealed glass container. Initially, its viscosity was 8.6 mPa·s and the average particle size of silica particles measured by dynamic light scattering was 22 nm. After being kept at 50°C for two weeks, the viscosity decreased to 19 mPa·s and the average particle size of silica particles measured by dynamic light scattering was 54 nm. The stability of this silica sol was insufficient. [Industrial applicability] 【0041】 To improve compatibility with organic substances, we provide silica sol dispersed in a non-aqueous solvent, particularly a hydrophobic solvent, and a method for producing the same.

Claims

[Claim 1] Si-OR on or near the surface of silane-coated silica particles ０ and Si-OR １ (However, R ０ R is an alkyl group having 1 to 4 carbon atoms. １ R represents an organic group having 2 to 10 carbon atoms, which may have an oxygen atom. ０ and R １ There are at least two types of alkoxy groups represented by (where R0 and R1 are not the same chemical group, and the number of carbon atoms in R0 and R1 are in the relationship R0 < R1). (Si-OR １ ) / (Si-OR ０ The silica particles having a molar ratio of ) in proportion to 0.17 to 10 are used as the dispersed phase. A silica sol containing an alkali, wherein the dispersion medium is at least one hydrophobic organic solvent selected from the group consisting of ketones, ethers, esters, amides, and hydrocarbons. The alkali is a secondary or tertiary amine having 5 to 35 carbon atoms. The pH of the liquid obtained when the above alkali-containing silica sol, methanol, and pure water are mixed in a mass ratio of 1:1:1 is greater than 4.0 and less than or equal to 9.

5. The silica sol containing the alkali is a silica sol containing 10 to 55% by mass of solids. [Claim 2] The above Si-OR ０ is Si-OCH ３ The silica sol according to claim 1, wherein it is [Claim 3] The silica sol according to claim 1, wherein the silica particles have an average particle diameter of 5 to 200 nm as determined by dynamic light scattering. [Claim 4] The above R １ The silica sol according to claim 1, wherein is an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, a 1-methoxy-2-propyl group, a 1-ethoxy-2-propyl group, or a phenyl group. [Claim 5] The silane coating of the above silica particles is given by formulas (1) to (3): 【Chemistry 1】 (In formula (1), R ３ Each of these is an organic group having an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an epoxy group, a (meth)acryloyl group, a mercapto group, an amino group, a ureido group, or a cyano group, and is bonded to a silicon atom by a Si-C bond, R ４ Each of the following represents an alkoxy group, an acyloxy group, or a halogen group, and a represents an integer from 1 to 3. In equations (2) and (3), R ５ and R ７ Each of these is an alkyl group having 1 to 3 carbon atoms, or an aryl group having 6 to 30 carbon atoms, and is bonded to a silicon atom by a Si-C bond, R ６ and R ８ (wherein 'b' represents an alkoxy group, an acyloxy group, or a halogen group, Y represents an alkylene group, an NH group, or an oxygen atom, 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 silica sol according to claim 1, which is a hydrolysis product of at least one silane compound selected from the group consisting of the following. [Claim 6] A method for producing silica sol according to any one of claims 1 to 5, comprising the following steps (A), (B), and (C), comprising the following step (A-1) after the completion of step (A) and before step (C), and comprising the following step (A-2) after the completion of step (A-1) and before the completion of all steps. (A) Step: The above silica particles have an average particle size of 5 to 200 nm as determined by dynamic light scattering, and contain an alcohol R with 1 to 4 carbon atoms. ０ OH (however R ０ The process of obtaining a silica sol using an alkyl group having 1 to 4 carbon atoms as a dispersion medium, (B) Step: R of the silica sol obtained in step (A) ０ Removal of part or all of OH, and R １ OH structure (however, R １ R represents an organic group having 2 to 10 carbon atoms, which may have an oxygen atom. ０ and R １ The process involves adding an alcohol having the following chemical groups: (C) Step: R of the silica sol obtained in step (B) ０ OH and R １ A step of removing some or all of the alcohol in the OH structure and adding at least one hydrophobic organic solvent selected from the group consisting of ketones, ethers, esters, amides, and hydrocarbons. (A-1) Step: A step of coating the silica sol obtained in step (A) with at least one silane compound represented by the following formulas (1) to (3). (A-2) Step: A step of adding an alkali of a secondary or tertiary amine having 5 to 35 carbon atoms to the silica sol obtained in step (A-1). 【Chemistry 2】 (In formula (1), R3 is an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having an epoxy group, a (meth)acryloyl group, a mercapto group, an amino group, a ureido group, or a cyano group and bonded to a silicon atom by a Si-C bond, R4 is an alkoxy group, an acyloxy group, or a halogen group, and a is an integer from 1 to 3.) In formulas (2) and (3), R5 and R7 are each alkyl groups having 1 to 3 carbon atoms, or aryl groups having 6 to 30 carbon atoms, bonded to a silicon atom by a Si-C bond; R6 and R8 each represent an alkoxy group, an acyloxy group, or a halogen group; Y represents an alkylene group, an NH group, or an oxygen atom; 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.

Images