Disperses of surface-treated silicon oxide-containing inorganic oxide particles and methods of their production.

Abstract

The invention proposes a dispersion of inorganic oxide particles exhibiting high dispersion stability even at high temperatures or high salt concentrations. This dispersion consists, as a dispersion, of inorganic oxide particles bound to silanes with hydrolyzable silane-modified surfaces, and a liquid medium as a dispersion medium, in which the dispersion medium contains hydrolyzable silane hydrolysis products; the ratio (number of moles of silicon atoms of hydrolyzable silane hydrolysis products in the dispersion medium) / (number of moles of silicon atoms of silane bound to the surfaces of the inorganic oxide particles) is between 0.2 and 30; and Q4 is greater than the value before silane surface modification, where Q4 corresponds to the case where the number of bridging oxygen atoms between silicon atoms of the silicon oxide particles is 4 / 2 per silicon atom as determined by Si-NMR observation.The inorganic oxide particles have an average particle diameter ranging from 5 nm to 100 nm and are particles containing silicon oxide and at least one inorganic oxide selected from the group of aluminum oxide, tin oxide, zircon oxide, titanium oxide, and antimony oxide. The invention relates to particles of a single metal oxide, a mixed metal oxide, or a mixed oxide with a nucleus-shell structure.

Description

Surface-treated silica-containing inorganic oxide particle dispersion and method for producing the same

[0001] The present invention relates to a dispersion of silica-containing inorganic oxide particles whose surfaces have been silane-treated, and a method for producing the same.

[0002] Dispersions of silica-containing inorganic oxide particles, particularly silica sols, are liquids in which silica particles are dispersed in a dispersion medium. One method for highly dispersing silica particles is to increase the absolute value of the zeta potential between silica particles to enhance the repulsive force between silica particles. One such method involves modifying the surface of silica particles with a silane coupling agent having a cationic or anionic functional group when the dispersion medium is an aqueous solution, or with a silane coupling agent having a hydrophobic organic group when the dispersion medium is an organic solvent. For example, a method for producing an organic solvent-dispersed silica sol has been disclosed, which includes a step of surface-treating a hydrophilic inorganic oxide sol by adding a silicon alkoxide having two or more alkoxide groups bonded to the silicon atom, or a silicon alkoxide having one or more hydroxyl groups bonded to the silicon atom and one or more alkoxide groups bonded to the silicon atom, and a step of replacing the dispersion medium with a non-alcoholic organic solvent in the presence of a primary alcohol having 3 to 12 carbon atoms (see Patent Document 1). Disclosed is a dispersion of surface-treated particles, which comprises metal oxide particles having a refractive index of 1.65 or more and a first organosilicon compound bonded to the surface thereof, a second organosilicon compound that is not bonded to the metal oxide particles, and an organic solvent, wherein the (first organosilicon compound) / (second organosilicon compound) ratio is 0.1 to 9.0 (see Patent Document 2).

[0003] JP 2005-200294 JP 2020-164374

[0004] The present invention provides a dispersion of silica-containing inorganic oxide particles, particularly a dispersion of silica particles, which has high dispersion stability even under high temperature and high salt conditions.

[0005] In a first aspect, the present invention provides a dispersion containing, as a dispersoid, silane-bonded silica-containing inorganic oxide particles surface-modified with a hydrolyzable silane, and a liquid medium as a dispersion medium, wherein the dispersion medium contains a hydrolyzate of the hydrolyzable silane, the ratio of (the number of moles of silicon atoms in the hydrolyzate of the hydrolyzable silane in the dispersion medium) / (the number of moles of silicon atoms of the silane bonded to the surface of the inorganic oxide particles) is 0.2 to 30, and the dispersion contains silica-containing inorganic oxide particles in which, as determined by Si-NMR observation, Q4, in which the number of bridging oxygen atoms between silicon atoms of the silica particles per silicon atom is 4 / 2, has increased compared to before surface modification with the silane. As a second aspect, the dispersion according to the first aspect, wherein the silica-containing inorganic oxide particles are silica particles having an average particle size of 5 nm to 100 nm, or at least one inorganic oxide particle selected from the group consisting of silica and alumina, tin oxide, zirconium oxide, titanium oxide, and antimony oxide, and the silica-containing inorganic oxide particles are silica particles, composite metal oxide particles of silica and another metal oxide, or composite oxide particles of silica and another metal oxide having a core-shell structure; as a third aspect, the dispersion according to the first aspect, wherein the hydrolyzable silane is a compound represented by any one of formulas (1) to (3): (In formula (1), R ３ is an alkyl group, a halogenated alkyl group, an alkenyl 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 is bonded to a silicon atom by a Si—C bond, and R ４ represents an alkoxy group, an acyloxy group, or a halogen group, a represents an integer of 1 to 3, and in formulas (2) and (3), R ５ and R ７ is an alkyl group having 1 to 3 carbon atoms and bonded to a silicon atom by a Si—C bond, and R ６ and R ７ represents an alkoxy group, an acyloxy group, or a halogen group; Y represents an alkylene group, an NH group, or an oxygen atom; ５ and R ７wherein at least one of the groups represented by the formula (1) is an alkyl group having 1 to 3 carbon atoms and bonded to the silicon atom by a Si—C bond, b is an integer of 1 to 3, c is an integer of 0 or 1, d is an integer of 1 to 3, and e is an integer of 1 to 3. As a fourth aspect, the dispersion according to the third aspect, wherein a hydrolyzed compound of a hydrolyzable silane in the dispersion medium contains a silane compound in which a in formula (1) is an integer of 1, and the hydrolyzed compound has T0, T1, T2, and T3 structures in which the ratios of bridging oxygen atoms between silicon atoms per silicon atom are 0 / 2, 1 / 2, 2 / 2, and 3 / 2, respectively, as measured by Si-NMR, and the (T2+T3) / (T0+T1) is a specific value (2 to 15), or the (T1+T2+T3) / (T0) ratio is a specific value (5 to 100). As a fifth aspect, the dispersion according to the third aspect, wherein the hydrolyzate of the hydrolyzable silane in the dispersion medium contains a silane compound in which the hydrolyzed compound of the silane compound in formula (1) where a is an integer of 2 has a D0, D1, and D2 structure in which the ratios of bridging oxygen atoms between silicon atoms are 0 / 2, 1 / 2, or 2 / 2 per silicon atom as measured by Si-NMR, and the (D1+D2) / (D0) ratio is 0.1 to 10, or the (D2) / (D0+D1) ratio is 0.01 to 10; as a sixth aspect, the dispersion according to any one of the first to fifth aspects, wherein the value obtained by dividing the amount of water vapor adsorption on the silica-containing inorganic oxide particles by the amount of nitrogen gas adsorption, (specific surface area calculated from the amount of water vapor adsorption) / (specific surface area calculated from the amount of nitrogen gas adsorption), is 0.15 to 0.95 compared to the silica particles before addition of the silane compound; as a seventh aspect, the dispersion according to any one of the first to fifth aspects, wherein the dispersion comprises the following steps (A) and (B): Step (A): obtaining an aqueous dispersion of the silica-containing inorganic oxide particles; Step (B): adding a hydrolyzable silane to the aqueous dispersion of the silica-containing inorganic oxide particles at a pH of 2.0 to 6.5 to a particle surface area of ​​0.3 to 100 particles / nm ２and, as an eighth aspect, the method for producing a dispersion using an organic solvent as a dispersion medium according to the seventh aspect, which includes, after step (B), a step (C) of replacing the aqueous medium of the dispersion obtained in step (B) with an organic solvent.

[0006] Dispersions of silica-containing inorganic oxide particles, particularly inorganic particles such as silica, ensure dispersion stability through interparticle repulsion. Taking silica particles as an example, silanol groups are present on the surface of the silica particles, and the negative charge of the silanol groups causes interparticle repulsion. The absolute value of the charge varies depending on the pH and salts in the dispersion. Surface-treated particles exist that are less susceptible to the effects of pH and salts. For example, in the case of silica particles, methods of surface treatment include using a hydrolyzable silane compound having a positively charged cationic functional group on the silica particle surface, and using a hydrolyzable silane compound having a negatively charged anionic functional group. These methods involve the electrical repulsion between the cationic and anionic functional groups, respectively, resulting in interparticle repulsion.

[0007] Although it depends on the density of the functional group bonded to the surface of silica particles, it is difficult to modify the entire particle surface with the functional group, and the repulsive force between particles is not necessarily sufficient under pH conditions or salt concentration conditions.However, the silane compound having functional groups added to the dispersion of silica particles includes silanes having functional groups bonded to the surface of silica particles (bonded silanes), and silanes having functional groups that are not bonded to silica particles and are dissolved in the dispersion medium (hereinafter referred to as free silanes).The silanes having functional groups in the dispersion medium exist between silica particles, and because they have the same functional group, repulsive force occurs between bonded silanes and free silanes, and the silica particles not only generate repulsive force between particles but also between these silane monomers, resulting in a dispersion with high dispersion stability.

[0008] In the present invention, it has been found that a specific ratio (0.2 to 30) of (the number of moles of silicon atoms in the hydrolyzate of hydrolyzable silane in the dispersion medium) to (the number of moles of silicon atoms in the silane bonded to the surface of inorganic oxide particles) provides a dispersion of silica particles with high dispersion stability. Furthermore, when the dispersion medium is an organic solvent, silica particles have hydrophilic properties based on silanol groups, which differ from the liquid properties of the organic solvent. Therefore, the silanol groups of the silica particles are surface-treated with a silane having a hydrophobic functional group to achieve high compatibility with organic solvents. It is difficult to modify the entire particle with a silane having a hydrophobic functional group. However, by ensuring compatibility with a silane monomer having a hydrophobic functional group in the portions of the silica particles not modified with the hydrophobic functional group, a dispersion with high dispersibility in organic solvents can be obtained.

[0009] In the present invention, it is preferable that the hydrolyzed product of the hydrolyzable silane in the dispersion medium exists in such a way that the repulsive force between the silica particles and the silane monomer is delocalized throughout the dispersion medium, and therefore it is preferable that the polymerization of the free silane does not proceed excessively. For example, when using a silane having three hydrolyzable groups, the hydrolyzed product of the silane compound has T0, T1, T2, and T3 structures in which the ratio of bridging oxygen between silicon atoms per silicon atom is 0 / 2, 1 / 2, 2 / 2, and 3 / 2 as measured by Si-NMR, and it is preferable that (T2 + T3) / (T0 + T1) is a specific value (2 to 15, preferably 2 to 10), or the (T1 + T2 + T3) / (T0) ratio is a specific value (5 to 100, preferably 5 to 50). While either of these may be satisfied, it is more preferable to satisfy both. Furthermore, when using a hydrolyzable silane having two hydrolyzable groups, it is preferable that the (D1+D2) / (D0) ratio be a specific value (0.1 to 10) or the (D2) / (D0+D1) ratio be a specific value (0.01 to 10) for the D0, D1, and D2 structures in which the ratio of bridging oxygen between silicon atoms is 0 / 2, 1 / 2, or 2 / 2 per silicon atom in Si-NMR observation of the hydrolyzed compound of the silane compound. Either one of these may be satisfied, but it is more preferable that both be satisfied.

[0010] For silica-containing inorganic oxide particles, particularly silica particles, the ratio (specific surface area calculated from water vapor adsorption) / (specific surface area calculated from nitrogen gas adsorption), calculated by dividing the amount of water vapor adsorption by the amount of nitrogen gas adsorption, is set to 0.15 to 0.95 compared to silica particles before the addition of the silane compound, thereby making the inorganic oxide particles highly compatible with a wide range of media, from aqueous to organic solvents. Silica particles satisfying these bonded silanes and free silanes have an increased Q4, where the number of bridging oxygen atoms between silicon atoms of the silica particles is 4 / 2 per silicon atom, as determined by Si-NMR observation, compared to before surface modification with the silane. For example, the increase ratio can be set to a range of 1.01 to 1.5 or 1.01 to 1.15.

[0011] The present invention provides a dispersion containing, as a dispersoid, silane-bonded silica-containing inorganic oxide particles surface-modified with a hydrolyzable silane and a liquid medium as a dispersion medium, wherein the dispersion medium contains a hydrolyzate of the hydrolyzable silane, the ratio of (the number of moles of silicon atoms in the hydrolyzate of the hydrolyzable silane in the dispersion medium) / (the number of moles of silicon atoms of the silane bonded to the surface of the inorganic oxide particles) is 0.2 to 30, preferably 0.2 to 15, and wherein Si-NMR observation reveals that the number of bridging oxygen atoms between silicon atoms of the silica particles is 4 / 2 per silicon atom, Q4, has increased compared to before surface modification with the silane.

[0012] In the present invention, the average particle diameter of an inorganic substance, for example, an aqueous silica sol (colloidal silica particles), refers to the specific surface area diameter measured by the nitrogen adsorption method (BET method) unless otherwise specified. The specific surface area diameter (average particle diameter (specific surface area diameter) D (nm)) measured by the nitrogen adsorption method (BET method) is calculated based on the specific surface area S (m ２ / g), the silica-containing inorganic oxide particle diameter is given by the formula D(nm) = 2720 / S. The silica-containing inorganic oxide particles are silica particles having an average particle diameter of 5 nm to 100 nm, preferably 5 to 60 nm, as measured by the BET method, or at least one inorganic oxide particle selected from the group consisting of silica and alumina, tin oxide, zirconium oxide, titanium oxide, and antimony oxide. The silica-containing inorganic oxide particles include silica particles, composite metal oxides of silica and other metal oxides, and composite oxide particles having a core-shell structure of silica and other metal oxides. For example, silica particles are preferably used as the single metal oxide, and examples of composite metal oxides include composite metal oxide particles of silica and alumina, and composite metal oxide particles of tin oxide and silica. Examples of composite oxide particles having a core-shell structure include titanium oxide or titanium oxide and zirconium oxide as the core and tin oxide and silica as the shell.

[0013] In the present invention, the silica-containing inorganic oxide particles are obtained as a dispersion in a dispersion medium at a concentration of, for example, 1 to 50% by mass. The dispersion of the present invention comprises the following steps (A) and (B): step (A): obtaining an aqueous dispersion of the silica-containing inorganic oxide particles; step (B): adding a hydrolyzable silane to the aqueous dispersion of the silica-containing inorganic oxide particles at a pH of 2.0 to 6.5 to a concentration of 0.3 to 100 particles / nm2 in terms of the number of silanes per particle surface area; ２The method includes a step of adding an aqueous dispersion of silica-containing inorganic oxide particles in a range of 1 to 7 times the stirring time at room temperature, followed by stirring at room temperature and then heating to a temperature within a range of 50 to 99°C. The stirring time after heating is 1 to 7 times the stirring time at room temperature. The aqueous dispersion of silica-containing inorganic oxide particles obtained in step (A) is obtained as a dispersion of silica-containing inorganic oxide particles in an aqueous medium at a concentration of, for example, 1 to 50% by mass. For example, aqueous silica sol is produced using water glass as a starting material, and includes the steps of a) cation-exchanging the water glass to obtain activated silicic acid, and b) heating the activated silicic acid to obtain silica particles. In step a), a mineral acid (e.g., hydrochloric acid, nitric acid, or sulfuric acid) is added to the activated silicic acid to highly purify it, and metal impurities other than silica are eluted by cation exchange and anion exchange, whereby activated silicic acid from which metal impurities and unnecessary anions have been removed can be used. In step b), an alkali component (e.g., NaOH or KOH) is added to the activated silicic acid to grow silica particles. In order to promote the growth of silica particles, a seed solution and a feed solution are prepared by adding an alkali to the activated silicic acid obtained in step a), and the seed solution is heated while the feed solution is supplied to increase the silica particle diameter, thereby obtaining an aqueous silica sol with a desired particle diameter. In step (B), the pH of the aqueous dispersion of silica-containing inorganic oxide particles obtained in step (A) can be adjusted to 2.0 to 6.5, and a hydrolyzable silane can be added. An acid or alkali can be used to adjust the pH.

[0014] Examples of acids include mineral acids such as hydrochloric acid, sulfuric acid, and nitric acid, and organic acids such as formic acid, oxalic acid, citric acid, acetic acid, lactic acid, malic acid, succinic acid, tartaric acid, butyric acid, fumaric acid, propionic acid, and ascorbic acid. Examples of alkalis include ammonia, amines, quaternary ammonium hydroxides, alkali metal hydroxides, alkali metal alkoxides, and alkali metal salts of aliphatic carboxylic acids. Examples of amines include primary amines, secondary amines, and tertiary amines. Examples of primary amines include methylamine, ethylamine, n-propylamine, and i-propylamine. Examples of secondary amines include ethyl-n-propylamine, ethyl-i-propylamine, dipropylamine, di-i-propylamine, ethylbutylamine, n-propylbutylamine, dibutylamine, ethylpentylamine, n-propylpentylamine, i-propylpentylamine, dipentylamine, ethyloctylamine, i-propyloctylamine, butyloctylamine, and dioctylamine. Examples of the tertiary amine include triethylamine, ethyl di-n-propylamine, diethyl n-propylamine, tri-n-propylamine, tri-i-propylamine, ethyl dibutylamine, diethyl butylamine, i-propyl dibutylamine, di-i-propyl butylamine, tributylamine, ethyl dipentylamine, diethyl pentylamine, tripentylamine, methyl dioctylamine, dimethyl octylamine, ethyl dioctylamine, diethyl octylamine, and trioctylamine. The quaternary ammonium hydroxide is preferably a tetraalkylammonium hydroxide having a total of 4 to 40 carbon atoms. Examples include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetra-n-propylammonium hydroxide, tetra-i-propylammonium hydroxide, tetrabutylammonium hydroxide, and ethyl trimethylammonium hydroxide. 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 alkali metal salts of saturated aliphatic carboxylic acids and alkali metal salts of unsaturated aliphatic carboxylic acids having 10 to 30 carbon atoms. Examples of alkali metal salts include sodium and potassium. Examples of alkali metal salts of saturated aliphatic carboxylic acids include alkali metal salts of lauric acid, alkali metal salts of myristate, alkali metal salts of palmitic acid, and alkali metal salts of stearic acid. Examples of alkali metal salts of unsaturated aliphatic carboxylic acids include alkali metal salts of oleic acid, alkali metal salts of linoleic acid, and alkali metal salts of linolenic acid.

[0015] The hydrolyzable silane used in step (B) can be at least one silane compound selected from the group consisting of the above formulas (1) to (3). ３ is an alkyl group, a halogenated alkyl group, an alkenyl 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 is bonded to a silicon atom by a Si—C bond, and R ４ represents an alkoxy group, an acyloxy group, or a halogen group, a represents an integer of 1 to 3, and in formulas (2) and (3), R ５ and R ７ is an alkyl group having 1 to 3 carbon atoms and bonded to a silicon atom by a Si—C bond, and R ６ and R ７ represents an alkoxy group, an acyloxy group, or a halogen group; Y represents an alkylene group, an NH group, or an oxygen atom; ５ and R ７ at least one of which is an alkyl group having 1 to 3 carbon atoms and is bonded to a silicon atom via a Si-C bond; b is an integer of 1 to 3; c is an integer of 0 or 1; d is an integer of 1 to 3; and e is an integer of 1 to 3.

[0016] The alkyl group is an alkyl group having 1 to 18 carbon atoms, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, a cyclopropyl group, an n-butyl group, an i-butyl group, an s-butyl group, a t-butyl group, a cyclobutyl group, a 1-methyl-cyclopropyl group, a 2-methyl-cyclopropyl group, an n-pentyl group, a 1-methyl-n-butyl group, a 2-methyl-n-butyl group, a 3-methyl-n-butyl group, a 1,1-dimethyl-n-propyl group, a 1,2-dimethyl-n-propyl group, a 2,2-dimethyl-n-propyl group, a 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 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 the alkylene group include, but are not limited to, 3-trimethylcyclopropyl, 1-ethyl-2-methylcyclopropyl, 2-ethyl-1-methylcyclopropyl, 2-ethyl-2-methylcyclopropyl, and 2-ethyl-3-methylcyclopropyl groups, as well as hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl groups. Examples of the alkylene group include alkylene groups derived from the alkyl groups described above.

[0017] The alkenyl group is an alkenyl group having 2 to 10 carbon atoms, and examples thereof include ethenyl, 1-propenyl, 2-propenyl, 1-methyl-1-ethenyl, 1-butenyl, 2-butenyl, 3-butenyl, 2-methyl-1-propenyl, 2-methyl-2-propenyl, 1-ethylethenyl, 1-methyl-1-propenyl, 1-methyl-2-propenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl, 1-n-propylethenyl, 1-methyl-1-butenyl, 1-methyl-2-butenyl, 1-methyl-3-butenyl, 2-ethyl-2-propenyl, 2-methyl-1-butenyl, 2-methyl-2-butenyl, 2-methyl-3-butenyl, 3 ...2-butenyl, 1-methyl-3-butenyl, 2-methyl-2-propenyl, 2-methyl-3-butenyl, 3-n-propylethenyl, 1-methyl-1-butenyl, 1-methyl-2-butenyl, 1-methyl-3-butenyl, 2-methyl-2-propenyl, 2-methyl-3-butenyl, 3-n-propylethenyl, 1-methyl-2-butenyl, 1-methyl-3-butenyl, 2-methyl-2-butenyl, 2-methyl-3-butenyl, 3-n-propylethenyl Examples of alkyl groups include, but are not limited to, 1-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, and 2-methyl-2-pentenyl group.

[0018] The alkoxy group includes alkoxy groups having 1 to 10 carbon atoms, such as methoxy, ethoxy, n-propoxy, i-propoxy, n-butoxy, i-butoxy, s-butoxy, t-butoxy, n-pentyloxy, 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, and n-hexyloxy, but is not limited to these.

[0019] Examples of the acyloxy group having 2 to 10 carbon atoms include, but are not limited to, a methylcarbonyloxy group, an ethylcarbonyloxy group, an n-propylcarbonyloxy group, an i-propylcarbonyloxy group, an n-butylcarbonyloxy group, an i-butylcarbonyloxy group, an s-butylcarbonyloxy group, a t-butylcarbonyloxy group, an n-pentylcarbonyloxy group, a 1-methyl-n-butylcarbonyloxy group, a 2-methyl-n-butylcarbonyloxy group, a 3-methyl-n-butylcarbonyloxy group, a 1,1-dimethyl-n-propylcarbonyloxy group, a 1,2-dimethyl-n-propylcarbonyloxy group, a 2,2-dimethyl-n-propylcarbonyloxy group, a 1-ethyl-n-propylcarbonyloxy group, an n-hexylcarbonyloxy group, a 1-methyl-n-pentylcarbonyloxy group, and a 2-methyl-n-pentylcarbonyloxy group. Examples of the halogen group include fluorine, chlorine, bromine, and iodine. The (meth)acryloyl group refers to both an acryloyl group and a methacryloyl group. The compounds represented by formulas (2) and (3) are preferably compounds capable of forming trimethylsilyl groups on the surface of silica particles. Examples of such compounds include the following: In the above formula, R １２ is an alkoxy group, such as a methoxy group or an ethoxy group. This is a process in which the hydroxyl groups on the surface of the silica particles, for example, silanol groups in the case of silica particles, react with the silane compound to coat the surfaces of the silica particles with the silane compound through siloxane bonds.

[0020] The reaction temperature can be from 20° C. to the boiling point of the dispersion medium, for example, in the range of 20° C. to 100° C. The reaction time can be about 0.1 to 6 hours.

[0021] Preferred functional groups include amino groups, epoxy groups, alkyl groups, and phenyl groups, such as aminopropyl groups, aminoethylaminopropyl groups, methyl groups, phenyl groups, glycidoxypropyl groups, epoxycyclohexylethyl groups, and trifluoropropyl groups. Corresponding silane compounds include aminopropyltrimethoxysilane, aminopropyltriethoxysilane, aminoethylaminopropyltrimethoxysilane, aminoethylaminopropyltriethoxysilane, aminoethylaminopropylmethyldimethoxysilane, aminoethylaminopropylmethyldiethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, glycidoxypropyltrimethoxysilane, glycidoxypropyltriethoxysilane, epoxycyclohexylethyltrimethoxysilane, epoxycyclohexylethyltriethoxysilane, trifluoropropyltrimethoxysilane, and trifluoropropyltriethoxysilane.

[0022] The silane compound is applied to the surface of the silica particles in such an amount that the number of silicon atoms in the silane compound is 0.1 / nm ２ ~4.0 pieces / nm ２ The silica particle surfaces can be coated by adding a silane compound equivalent to the coating amount to the silica sol. Water is required for the hydrolysis of the silane compound, but if the sol is an aqueous solvent, then that aqueous solvent can be used. The hydrolysis can be carried out with or without a catalyst. When the hydrolysis is carried out without a catalyst, the silica particle surface acts as a catalyst, and a silica sol with a pH of 2.0 to 6.5 can be used.

[0023] When a catalyst is used, examples of the hydrolysis catalyst 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(acetylacetonato)titanium and triethoxy mono(acetylacetonato)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.

[0024] In step (B) above, a hydrolyzable silane is added to the aqueous dispersion of inorganic oxide particles obtained in step (A). After stirring for 0.01 to 2 hours at room temperature (e.g., approximately 15 to 25°C), the mixture is heated to a temperature of 50 to 99°C and stirred for 0.01 to 14 hours. The stirring time after heating to 50 to 99°C is preferably 1 to 100 times, or 1 to 7 times, the stirring time at room temperature. If the ratio is less than 1, the hydrolyzate of the hydrolyzable silane will not be sufficiently coated on the inorganic oxide particles (e.g., silica particles), and the silane compound present in the dispersion medium will be locally coated later, preventing uniform coating. Furthermore, if the ratio is 7 times or more, the proportions of T1, T2, T3, D1, and D2 structures will decrease, which is undesirable in terms of particle repulsion.

[0025] In the present invention, a state in which the hydrolyzable silane hydrolysate is bonded to silica particles and a state in which the hydrolyzable silane hydrolysate is present in the dispersion medium coexist. Both states contribute to the stability of the inorganic oxide sol (silica sol) when the ratio of (the number of moles of silicon atoms in the hydrolyzable silane hydrolysate in the dispersion medium) / (the number of moles of silicon atoms in the silane bonded to the surface of the inorganic oxide particles) is 0.2 to 30.

[0026] When the hydrolysate of the hydrolyzable silane of the present invention is bonded to silica particles, the amount of silanol in the silica particles decreases, and this is characterized by the fact that, as observed by Si-NMR, Q4, in which the number of bridging oxygen atoms between silicon atoms of the silica particles is 4 / 2 per silicon atom, increases compared to before surface modification with the silane.

[0027] When the hydrolyzate of the hydrolyzable silane is bonded to the silica particles, the ratio of the specific surface area calculated from the amount of water vapor adsorbed to the silica particles divided by the specific surface area calculated from the amount of nitrogen gas adsorbed is (specific surface area calculated from the amount of water vapor adsorbed) / (specific surface area calculated from the amount of nitrogen gas adsorbed), which is 0.15 to 0.95 compared to the silica particles before the addition of the silane compound.

[0028] This is a numerical value indicating that silanol groups on the surface of silica particles have been replaced with silane compounds having functional groups. Furthermore, the hydrolyzate of hydrolyzable silane in the dispersion medium is characterized by containing a silane compound in which the hydrolyzed compound of the silane compound in formula (1), where a is an integer of 1, has T0, T1, T2, and T3 structures in which the ratio of bridging oxygen between silicon atoms per silicon atom is 0 / 2, 1 / 2, 2 / 2, and 3 / 2, respectively, as measured by Si-NMR, and the (T2 + T3) / (T0 + T1) ratio is 2 to 10, or the (T1 + T2 + T3) / (T0) ratio is 5 to 100. While either one of these conditions may be satisfied, it is more preferable to satisfy both. The hydrolyzate of the hydrolyzable silane in the dispersion medium is characterized by containing a silane compound in which the hydrolyzed compound of the silane compound in formula (1) where a is an integer of 2 has, in terms of D0, D1, and D2 structures in which the ratio of bridging oxygen atoms between silicon atoms is 0 / 2, 1 / 2, or 2 / 2 per silicon atom as measured by Si-NMR, a (D1+D2) / (D0) ratio of 0.1 to 10, or a (D2) / (D0+D1) ratio of 0.01 to 10. Either one of these may be satisfied, but it is more preferable to satisfy both.

[0029] The dispersion of the present invention thus obtained can be further subjected to step (C) after step (B): step (C): a step of replacing the aqueous medium of the dispersion obtained in step (B) with an organic solvent, thereby obtaining a dispersion in which the organic solvent is the dispersion medium.

[0030] Examples of organic solvents include alcohols, ketones, ethers, esters, amides, and hydrocarbons. Alcohols are alcohols having 1 to 10 carbon atoms, such as methanol, ethanol, i-propanol, n-propanol, and butanol. Ketones are linear or cyclic aliphatic ketones having 3 to 30 carbon atoms, such as methyl ethyl ketone, diethyl ketone, methyl propyl ketone, methyl isobutyl ketone, diisobutyl ketone, methyl amyl ketone, and cyclohexanone. Ethers are linear or cyclic aliphatic ethers 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, butyl acetate, sec-butyl acetate, methoxybutyl acetate, amyl acetate, n-propyl acetate, i-propyl 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. The amide is an aliphatic amide having 3 to 30 carbon atoms, such as dimethylacetamide, dimethylformamide, N-methylpyrrolidone, and N-ethylpyrrolidone. The hydrocarbon is a linear or cyclic aliphatic or aromatic hydrocarbon having 6 to 30 carbon atoms, such as hexane, heptane, octane, nonane, decane, benzene, toluene, and xylene.

[0031] The silica-containing inorganic oxide sol (e.g., silica sol) of the present invention can be used for high-salt dispersion medium sols, adhesives, release agents, semiconductor encapsulants, LED encapsulants, paints, film internal additives, hard coating agents, photoresist materials, printing inks, detergents, cleaners, various resin additives, insulating compositions, rust inhibitors, lubricants, metal processing oils, film coating agents, stripping agents, well treatment agents, etc.

[0032] (Measuring Instruments) Analysis of aqueous silica sol (pH value, electrical conductivity, viscosity, DLS average particle size, silane bond amount), and analysis of samples prepared using the aqueous silica sol after room temperature salt resistance tests or high temperature salt resistance tests were performed using the following instruments. DLS average particle size (average particle size by dynamic light scattering): A dynamic light scattering particle size measuring instrument, Zetasizer Nano (manufactured by the Malvern Division of Spectris K.K.). pH: A pH meter (manufactured by DKK Toa Corporation). Electrical conductivity: An electrical conductivity meter (manufactured by DKK Toa Corporation). Viscosity: A BMII viscometer (manufactured by Tokyo Keiki Co., Ltd.). Silane bond amount: An organic trace element analyzer CHNS / O analyzer (PerkinElmer Japan Co., Ltd.) or a TN measuring device TN-2100V Total Nitrogen Analyzer (Mitsubishi Chemical Analytech Co., Ltd.) was used. Si-NMR: ADVANCED NEO (manufactured by Bruker Corporation) was used. Nitrogen gas adsorption amount: MONOSORB (manufactured by Quantachrome Instruments) was used. Water vapor adsorption amount: A Q5000SA adsorption analyzer (manufactured by TA Instruments Japan Co., Ltd.) was used.

[0033] [Evaluation of Silica Sol] (Removal of Silane (Free Silane) Not Bonded to Silica Particles) 2 g of aqueous silica sol and 4 g of pure water were placed in a 15 ml centrifugal filter unit (trade name: Amicon Ultra 15, manufactured by Merck Ltd.), and centrifuged for 20 minutes at a centrifugal force of 2770 G. After centrifugation, the liquid discharged to the bottom of the unit was discarded, and the same mass of pure water as the discarded liquid was added to the aqueous silica sol concentrated on the filter to redisperse it, and then centrifuged again for 20 minutes at a centrifugal force of 2770 G. The above procedure was repeated a total of four times to obtain an aqueous silica sol from which free silane had been removed.

[0034] (Measurement of Carbon Amount) The aqueous silica sol from which the free silane had been removed was heated and dried at 100°C, and pulverized in a mortar to obtain a silica sol powder. The carbon amount of the obtained silica sol powder was measured using an organic trace element metal analyzer, and the silane bond amount was calculated from the obtained carbon amount using the following formula: Surface treatment amount = (Cm ÷ Cn ÷ Sc × A) / (Ct × Cs) where Cm is the carbon content, Cn is the carbon molecular weight, Sc is the number of carbon atoms in the silane, A is Avogadro's number, Ct is the mass of the silica particles, and Cs is the silica specific surface area. The silane bond amount obtained by measuring the carbon amount is expressed in units of (particles / nm ２ )

[0035] (Measurement of Nitrogen Amount) The nitrogen amount of the aqueous silica sol from which the free silane had been removed was measured using a TN measuring device, and the silane bond amount was calculated from the obtained nitrogen amount using the following formula: Surface treatment amount = (Nm ÷ Nn ÷ Sn × A) / (Ct × Cs) where Nm is the nitrogen content, Nn is the nitrogen molecular weight, Sn is the number of nitrogen atoms in the silane, A is Avogadro's number, Ct is the mass of silica particles, and Cs is the silica specific surface area. The silane bond amount obtained by measuring the nitrogen amount is expressed in units of (particles / nm ２ )

[0036] (Measurement of water vapor adsorption amount) The aqueous silica sol obtained by removing the free silane was dried on a hot plate at 80°C to obtain silica gel, which was then crushed in a mortar and further dried at 150°C for 3 hours to obtain a dry silica powder. Based on the BET theory, the specific surface area (m ２ / g) was measured (water vapor BET method).

[0037] (Measurement of nitrogen gas adsorption amount) The aqueous silica sol obtained by removing the free silane was dried on a hot plate at 80°C to obtain silica gel, which was then crushed in a mortar and further dried at 150°C for 3 hours to obtain a dry silica powder. Based on the BET theory, the specific surface area (m ２ / g) was measured (BET method, i.e., nitrogen gas BET method).

[0038] (Salt Tolerance Evaluation) (Preparation of Salt Tolerance Test Sample) A stirring bar was placed in a 200 ml polystyrene bottle, and 3.6 g of each silica sol produced in the Examples or Comparative Examples was added and stirred with a magnetic stirrer. While stirring with the magnetic stirrer, 46.4 g of pure water and 100 g of a brine solution with a salt concentration of 6% by mass were added and stirred for 1 hour. This was used as a salt tolerance test sample for evaluating the heat resistance and salt tolerance when the silica sol was adjusted to a silica concentration of 0.5% by mass under a salt concentration of 4% by mass. The pH, electrical conductivity, and DLS average particle size of the aqueous silica sol (silica particles) in the sample were evaluated for the obtained salt tolerance test sample.

[0039] (Evaluation of room temperature salt tolerance) 150 g of the salt tolerance test sample was placed in a 200 ml sealable polystyrene container, and after sealing, the polystyrene container was left standing at 20 ° C. for a predetermined time, and then the appearance, pH, electrical conductivity, and DLS average particle size of the aqueous silica sol (silica particles) in the salt tolerance test sample were evaluated. The salt tolerance was evaluated by judging the salt tolerance (see the following salt tolerance judgment) based on the measurement results of the DLS average particle size of the aqueous silica sol (silica particles) in the sample after a predetermined time (10 hours) at 20 ° C., and by evaluating the appearance.

[0040] (Judgment of salt tolerance) A: The ratio of the DLS average particle size after the salt tolerance test to the DLS average particle size before the test is 1.1 or less. B: The ratio of the DLS average particle size after the salt tolerance test to the DLS average particle size before the test is 1.2 to 1.5. C: The ratio of the DLS average particle size after the salt tolerance test to the DLS average particle size before the test is 1.6 to 2.4. D: The ratio of the DLS average particle size after the salt tolerance test to the DLS average particle size before the test is 2.5 to 20.0. E: The ratio of the DLS average particle size after the salt tolerance test to the DLS average particle size before the test is 20.1 or more, or the product is cloudy and exhibits solid-liquid separation. The salt tolerance test result A is the most favorable, followed by B, C, D, and E in that order.

[0041] (High-temperature salt resistance evaluation-1) 65 g of the salt resistance test sample was placed in a 120 ml sealable Teflon (registered trademark) container and sealed. The Teflon (registered trademark) container was then placed in a dryer at 100°C and held at 100°C for a predetermined time (10 hours). The appearance, pH, electrical conductivity, and DLS average particle size of the aqueous silica sol (silica particles) in the sample were then evaluated. High-temperature salt resistance was evaluated according to the same criteria as those used to evaluate salt resistance in the room-temperature salt resistance evaluation.

[0042] (High-temperature salt resistance evaluation-2) High-temperature salt resistance was evaluated in the same manner as in (High-temperature salt resistance evaluation-1) above, except that the dryer temperature was set to 120°C and the holding time was set to 10 hours.

[0043] (Preparation of Aqueous Silica Sol) (Example 1) 1000 g of aqueous silica sol (Snowtex (trade name) ST-O, manufactured by Nissan Chemical Industries, Ltd., silica concentration 20.5 mass %, average particle size by BET method 11.7 nm, average particle size by DLS method 18.6 nm) and a magnetic stirrer were placed in a 2000 ml glass recovery flask, and the silane compound was mixed with the silica in the aqueous silica sol at a concentration of 0.5 particles / nm with respect to the surface area of ​​the silica. ２ 9.4 g of 3-glycidoxypropyltrimethoxysilane (Dynasylan GLYMO manufactured by Evonik) was added so that the temperature reached 60°C. A cooling tube containing tap water was then placed on top of the recovery flask, and the aqueous sol was heated to 60°C while refluxing. The temperature was maintained at 60°C for 4 hours, including the time required for heating, and then cooled. The stirring time after heating to 60°C was within 1 to 7 times the stirring time at room temperature. After cooling to room temperature, the aqueous sol was removed, yielding 1,009.4 g of aqueous sol containing an aqueous silica sol surface-treated with a silane compound. The pH, electrical conductivity, viscosity, and average particle size of the aqueous silica sol of Example 1 were evaluated using DLS. The silane bond amount of the aqueous silica sol of Example 1 was evaluated according to (Evaluation of Silane Bond Amount). A salt tolerance test sample was prepared according to <Preparation of Salt Tolerance Test Sample>, and after maintaining it at 20°C for 10 hours according to <Evaluation of Room Temperature Salt Tolerance>, the sample was removed and its room temperature salt tolerance was evaluated.

[0044] Example 2 The silica in the aqueous silica sol (Snowtex (trade name) ST-O, manufactured by Nissan Chemical Industries, Ltd., average particle size by BET method: 11.7 nm, average particle size by DLS method: 18.6 nm) was mixed with the silane compound at a density of 8.0 particles / nm 2 relative to the surface area of ​​the silica in the aqueous silica sol. ２ The same procedure as in Example 1 was performed, except that 149.7 g of 3-glycidoxypropyltrimethoxysilane (Dynasylan GLYMO manufactured by Evonik) was added so that the pH became 1,149.7 g. The aqueous silica sol of Example 2 was evaluated for pH, electrical conductivity, viscosity, and average particle size by DLS. The silane bond amount of the aqueous silica sol of Example 2 was evaluated according to (Evaluation of silane bond amount). A salt resistance test sample was prepared according to (Preparation of salt resistance test sample), and after holding at 100°C for 10 hours according to (Evaluation of high-temperature salt resistance-1), the sample was removed and the high-temperature salt resistance was evaluated.

[0045] (Example 3) For silica in an aqueous silica sol (Snowtex (trade name) ST-O manufactured by Nissan Chemical Industries, Ltd., average particle size by BET method: 11.7 nm, average particle size by DLS method: 18.6 nm), the silane compound was distributed at a density of 30.8 particles / nm with respect to the surface area of ​​the silica in the aqueous silica sol. ２ The same procedure as in Example 1 was performed, except that 576.2 g of 3-glycidoxypropyltrimethoxysilane (Dynasylan GLYMO manufactured by Evonik) was added so that the pH value became 1,576.2 g. The aqueous silica sol of Example 3 was evaluated for pH, electrical conductivity, viscosity, and average particle size by DLS. The silane bond amount of the aqueous silica sol of Example 3 was evaluated according to (Evaluation of silane bond amount). A salt resistance test sample was prepared according to (Preparation of salt resistance test sample), and after holding at 100°C for 10 hours according to (Evaluation of high-temperature salt resistance-1), the sample was removed and the high-temperature salt resistance was evaluated.

[0046] Example 4 For silica in an aqueous silica sol (Snowtex (trade name) ST-O manufactured by Nissan Chemical Industries, Ltd., average particle size by BET method: 11.7 nm, average particle size by DLS method: 18.6 nm), the silane compound was distributed at a density of 46.2 particles / nm with respect to the surface area of ​​the silica in the aqueous silica sol. ２The same procedure as in Example 1 was performed, except that 864.3 g of 3-glycidoxypropyltrimethoxysilane (Dynasylan GLYMO manufactured by Evonik) was added so that the pH became 1,864.3 g. The aqueous silica sol of Example 4 was evaluated for pH, electrical conductivity, viscosity, and average particle size by DLS. The silane bond amount of the aqueous silica sol of Example 4 was evaluated according to (Evaluation of silane bond amount). A salt resistance test sample was prepared according to (Preparation of salt resistance test sample), and after holding at 100°C for 10 hours according to (Evaluation of high-temperature salt resistance-1), the sample was removed and the high-temperature salt resistance was evaluated.

[0047] (Example 5) For silica in an aqueous silica sol (Snowtex (trade name) ST-O manufactured by Nissan Chemical Industries, Ltd., average particle size by BET method: 11.7 nm, average particle size by DLS method: 18.6 nm), the silane compound was dispersed at a density of 0.5 particles / nm with respect to the surface area of ​​the silica in the aqueous silica sol. ２ The same procedure as in Example 1 was repeated, except that 5.4 g of methyltrimethoxysilane (KBM-13, manufactured by Shin-Etsu Chemical Co., Ltd.) was added so that the pH became 5.4 g, and 1005.4 g of aqueous sol was obtained. The pH, electrical conductivity, viscosity, and average particle size by DLS method of the aqueous silica sol of Example 5 were evaluated. The silane bond amount of the aqueous silica sol of Example 5 was evaluated according to (Evaluation of silane bond amount). A salt tolerance test sample was prepared according to (Preparation of salt tolerance test sample), and after holding at 20°C for 10 hours according to (Evaluation of room temperature salt tolerance), the sample was removed and the room temperature salt tolerance was evaluated.

[0048] (Example 6) For silica in an aqueous silica sol (Nissan Chemical Industries, Ltd., Snowtex (trade name) ST-O, average particle size by BET method: 11.7 nm, average particle size by DLS method: 18.6 nm), the silane compound was dispersed at a concentration of 0.5 particles / nm with respect to the surface area of ​​the silica in the aqueous silica sol. ２The same procedure as in Example 1 was repeated, except that 4.8 g of dimethyldimethoxysilane (KBM-22, manufactured by Shin-Etsu Chemical Co., Ltd.) was added so that the pH became 4.8 g. The aqueous silica sol of Example 6 was evaluated for pH, electrical conductivity, viscosity, and average particle size by DLS. The silane bond amount of the aqueous silica sol of Example 6 was evaluated according to (Evaluation of silane bond amount). A salt tolerance test sample was prepared according to (Preparation of salt tolerance test sample), and after holding at 20°C for 10 hours according to (Evaluation of room temperature salt tolerance), the sample was removed and the room temperature salt tolerance was evaluated.

[0049] (Example 7) For silica in an aqueous silica sol (Snowtex (trade name) ST-O manufactured by Nissan Chemical Industries, Ltd., average particle size by BET method: 11.7 nm, average particle size by DLS method: 18.6 nm), the silane compound was dispersed at a density of 0.5 particles / nm with respect to the surface area of ​​the silica in the aqueous silica sol. ２ The same procedure as in Example 1 was repeated, except that 9.8 g of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (KBM-303, manufactured by Shin-Etsu Chemical Co., Ltd.) was added so that the pH became 9.8 g, and 1,009.8 g of an aqueous sol was obtained. The aqueous silica sol of Example 7 was evaluated for pH, electrical conductivity, viscosity, and average particle size by DLS. The silane bond amount of the aqueous silica sol of Example 7 was evaluated according to (Evaluation of silane bond amount). A salt tolerance test sample was prepared according to (Preparation of salt tolerance test sample), and after holding at 20°C for 10 hours according to (Evaluation of room temperature salt tolerance), the sample was removed and the room temperature salt tolerance was evaluated.

[0050] (Example 8) For silica in an aqueous silica sol (Snowtex (trade name) ST-O manufactured by Nissan Chemical Industries, Ltd., average particle size by BET method: 11.7 nm, average particle size by DLS method: 18.6 nm), the silane compound was dispersed at a density of 0.5 particles / nm with respect to the surface area of ​​the silica in the aqueous silica sol. ２The same procedure as in Example 1 was repeated, except that 8.6 g of trifluoropropyltrimethoxysilane (KBM-7103, manufactured by Shin-Etsu Chemical Co., Ltd.) was added so that the pH became 8.6 g, and 1,008.6 g of an aqueous sol was obtained. The pH, electrical conductivity, viscosity, and average particle size by DLS method of the aqueous silica sol of Example 8 were evaluated. The silane bond amount of the aqueous silica sol of Example 8 was evaluated according to (Evaluation of silane bond amount). A salt tolerance test sample was prepared according to (Preparation of salt tolerance test sample), and after holding at 20°C for 10 hours according to (Evaluation of room temperature salt tolerance), the sample was removed and the room temperature salt tolerance was evaluated.

[0051] (Example 9) For silica in an aqueous silica sol (Snowtex (trade name) ST-O manufactured by Nissan Chemical Industries, Ltd., average particle size by BET method: 11.7 nm, average particle size by DLS method: 18.6 nm), the silane compound was distributed at a density of 8.0 particles / nm with respect to the surface area of ​​the silica in the aqueous silica sol. ２ The same procedure as in Example 1 was repeated, except that a liquid prepared by previously mixing 114.1 g of lactic acid and 140.2 g of aminopropyltriethoxysilane (KBE-903, manufactured by Shin-Etsu Chemical Co., Ltd.) and stirring for 30 minutes so that the pH value became 1,254.3 g was added. The pH, electrical conductivity, viscosity, and average particle size of the aqueous silica sol of Example 9 were evaluated using a DLS method. The silane bond amount of the aqueous silica sol of Example 9 was evaluated according to (Evaluation of silane bond amount). A salt tolerance test sample was prepared according to (Preparation of salt tolerance test sample), and after holding at 20°C for 10 hours according to (Evaluation of room temperature salt tolerance), the sample was removed and the room temperature salt tolerance was evaluated.

[0052] Example 10 114.1 g of lactic acid was added to silica in an aqueous silica sol (Snowtex (trade name) ST-O, manufactured by Nissan Chemical Industries, Ltd., average particle size by BET method: 11.7 nm, average particle size by DLS method: 18.6 nm) and stirred with a magnetic stirrer, and the silane compound was distributed at a density of 8.0 particles / nm with respect to the surface area of ​​the silica in the aqueous silica sol. ２The same procedure as in Example 1 was repeated, except that 113.6 g of aminopropyltrimethoxysilane (KBM-903, manufactured by Shin-Etsu Chemical Co., Ltd.) was added so that the pH value became 1,227.7 g of an aqueous sol. The pH, electrical conductivity, viscosity, and average particle size by DLS were evaluated for the aqueous silica sol of Example 10. The silane bond amount of the aqueous silica sol of Example 10 was evaluated according to (Evaluation of silane bond amount). A salt tolerance test sample was prepared according to (Preparation of salt tolerance test sample), and after holding at 20°C for 10 hours according to (Evaluation of room temperature salt tolerance), the sample was removed and the room temperature salt tolerance was evaluated.

[0053] Example 11 228.2 g of lactic acid was added to silica in an aqueous silica sol (Snowtex (trade name) ST-O, manufactured by Nissan Chemical Industries, Ltd., average particle size by BET method: 11.7 nm, average particle size by DLS method: 18.6 nm) and stirred with a magnetic stirrer, and the silane compound was distributed at a density of 8.0 particles / nm with respect to the surface area of ​​the silica in the aqueous silica sol. ２ The same procedure as in Example 1 was repeated, except that 140.9 g of aminoethylaminopropyltrimethoxysilane (KBM-603, manufactured by Shin-Etsu Chemical Co., Ltd.) was added so that the pH value became 1,369.1 g of an aqueous sol was obtained. The pH, electrical conductivity, viscosity, and average particle size of the aqueous silica sol of Example 11 were evaluated by DLS. The silane bond amount of the aqueous silica sol of Example 11 was evaluated according to (Evaluation of silane bond amount). A salt resistance test sample was prepared according to (Preparation of salt resistance test sample), and after holding at 120°C for 10 hours according to (Evaluation of high-temperature salt resistance-2), the sample was removed and the room-temperature salt resistance was evaluated.

[0054] Example 12 228.2 g of lactic acid was added to silica in an aqueous silica sol (Snowtex (trade name) ST-O, manufactured by Nissan Chemical Industries, Ltd., average particle size by BET method: 11.7 nm, average particle size by DLS method: 18.6 nm) and stirred with a magnetic stirrer, resulting in a silane compound concentration of 8.0 particles / nm with respect to the surface area of ​​the silica in the aqueous silica sol. ２The same procedure as in Example 1 was repeated, except that 130.7 g of aminoethylaminopropylmethyldimethoxysilane (KBM-602, manufactured by Shin-Etsu Chemical Co., Ltd.) was added so that the pH value became 1,358.9 g of an aqueous sol. The pH, electrical conductivity, viscosity, and average particle size of the aqueous silica sol of Example 12 were evaluated using a DLS method. The silane bond amount of the aqueous silica sol of Example 12 was evaluated according to (Evaluation of silane bond amount). A salt resistance test sample was prepared according to (Preparation of salt resistance test sample), and after holding at 120°C for 10 hours according to (Evaluation of high-temperature salt resistance - 2), the sample was removed and the room-temperature salt resistance was evaluated.

[0055] (Example 13) The silica in the aqueous silica sol (Snowtex (trade name) ST-OXS manufactured by Nissan Chemical Industries, Ltd., silica concentration 10.5 mass %, average particle size by BET method 5.0 nm, average particle size by DLS method 8.1 nm) was measured at a concentration of 8.0 silane compounds / nm2 relative to the surface area of ​​the silica in the aqueous silica sol. ２ The same procedure as in Example 1 was repeated, except that 179.4 g of 3-glycidoxypropyltrimethoxysilane (Dynasylan GLYMO manufactured by Evonik) was added so that the pH value became 1,179.4 g. The aqueous silica sol of Example 13 was evaluated for pH, electrical conductivity, viscosity, and average particle size by DLS. The silane bond amount of the aqueous silica sol of Example 13 was evaluated according to (Evaluation of silane bond amount). A salt resistance test sample was prepared according to (Preparation of salt resistance test sample), and after holding at 100°C for 10 hours according to (Evaluation of high-temperature salt resistance-1), the sample was removed and the high-temperature salt resistance was evaluated.

[0056] (Example 14) The silica in the aqueous silica sol (Snowtex (trade name) ST-OL manufactured by Nissan Chemical Industries, Ltd., silica concentration 20.5 mass %, average particle size by BET method 45.0 nm, average particle size by DLS method 78.0 nm) was dispersed at a density of 32.7 silane compounds / nm with respect to the surface area of ​​the silica in the aqueous silica sol. ２The same procedure as in Example 1 was repeated, except that 159.0 g of 3-glycidoxypropyltrimethoxysilane (Dynasylan GLYMO manufactured by Evonik) was added so that the pH value became 1,159.0 g. The aqueous silica sol of Example 14 was evaluated for pH, electrical conductivity, viscosity, and average particle size by DLS. The silane bond amount of the aqueous silica sol of Example 14 was evaluated according to (Evaluation of silane bond amount). A salt resistance test sample was prepared according to (Preparation of salt resistance test sample), and after holding at 100°C for 10 hours according to (Evaluation of high-temperature salt resistance-1), the sample was removed and the high-temperature salt resistance was evaluated.

[0057] (Comparative Example 1) An aqueous silica sol (Snowtex (trade name) ST-O, manufactured by Nissan Chemical Industries, Ltd.) was used as the aqueous silica sol of Comparative Example 1. The pH, electrical conductivity, viscosity, and DLS average particle size of the aqueous silica sol (silica particles) of Comparative Example 1 were evaluated. The silane bond amount of the aqueous silica sol of Comparative Example 1 was evaluated according to (Evaluation of silane bond amount). A salt resistance test sample was prepared according to (Preparation of salt resistance test sample), and after holding at 20°C for 10 hours according to (Evaluation of room temperature salt resistance), the sample was removed and the room temperature salt resistance was evaluated.

[0058] (Comparative Example 2) 1,149.7 g of aqueous silica sol was obtained by the same procedure as in Example 2. 800 g of pure water was added to 200 g of the aqueous silica sol of Example 2, and the mixture was filtered by ultrafiltration until 200 g was removed. 800 g of pure water was added again, and the same procedure was repeated four times to obtain 200 g of aqueous silica sol from which free silane had been removed. The aqueous silica sol of Comparative Example 2 was evaluated for pH, electrical conductivity, viscosity, and average particle size by DLS method. The silane bond amount of the aqueous silica sol of Comparative Example 2 was evaluated according to (Evaluation of Silane Bond Amount). A salt resistance test sample was prepared according to (Preparation of Salt Resistance Test Sample), and after holding at 100°C for 10 hours according to (High-Temperature Salt Resistance Evaluation-1), the sample was removed and its high-temperature salt resistance was evaluated.

[0059] (Comparative Example 3) The silica in the aqueous silica sol (Snowtex (trade name) ST-O manufactured by Nissan Chemical Industries, Ltd., average particle size by BET method: 11.7 nm, average particle size by DLS method: 18.6 nm) was measured, and the silane compound was distributed at a density of 2.0 particles / nm with respect to the surface area of ​​the silica in the aqueous silica sol. ２ The same procedure as in Example 1 was performed, except that 35.1 g of methyltrimethoxysilane (KBM-13, manufactured by Shin-Etsu Chemical Co., Ltd.) was added so that the pH became 1,035.1 g. The aqueous silica sol of Comparative Example 3 was evaluated for pH, electrical conductivity, viscosity, and average particle size by DLS. The silane bond amount of the aqueous silica sol of Comparative Example 3 was evaluated according to (Evaluation of silane bond amount). A salt tolerance test sample was prepared according to (Preparation of salt tolerance test sample), and after holding at 20°C for 10 hours according to (Evaluation of room temperature salt tolerance), the sample was removed and the room temperature salt tolerance was evaluated.

[0060] (Comparative Example 4) 1000 g of aqueous silica sol (Snowtex (trade name) ST-O, manufactured by Nissan Chemical Industries, Ltd., silica concentration = 20.5 mass %, BET method average particle size 11.7 nm, DLS average particle size 18.6 nm) and a magnetic stirrer were placed in a 2000 ml glass recovery flask, and the silane compound was mixed with the silica in the aqueous silica sol at a concentration of 8.0 particles / nm with respect to the surface area of ​​the silica. ２ 149.7 g of 3-glycidoxypropyltrimethoxysilane (Dynasylan GLYMO manufactured by Evonik) was added so that the pH became 1,149.7 g, thereby obtaining 1,149.7 g of an aqueous sol. The aqueous silica sol of Comparative Example 4 was evaluated for pH, electrical conductivity, viscosity, and average particle size by DLS. The silane bond amount of the aqueous silica sol of Comparative Example 4 was evaluated according to (Evaluation of silane bond amount). A salt tolerance test sample was prepared according to (Preparation of salt tolerance test sample), and after holding at 20°C for 10 hours according to (Evaluation of room temperature salt tolerance), the sample was removed and the room temperature salt tolerance was evaluated.

[0061] Comparative Example 5: 1,254.3 g of aqueous silica sol was obtained by the same procedure as in Example 9. 800 g of pure water was added to 200 g of the aqueous silica sol of Example 9, and the mixture was filtered by ultrafiltration until 200 g was removed. 800 g of pure water was added again, and the same procedure was repeated four times to obtain 200 g of aqueous silica sol from which free silane had been removed. The pH, electrical conductivity, viscosity, and average particle size of the aqueous silica sol of Comparative Example 5 were evaluated by DLS. The silane bond amount of the aqueous silica sol of Comparative Example 5 was evaluated according to (Evaluation of silane bond amount). A salt tolerance test sample was prepared according to (Preparation of salt tolerance test sample), and after holding at 20°C for 10 hours according to (Evaluation of room temperature salt tolerance), the sample was removed and the room temperature salt tolerance was evaluated.

[0062] (Comparative Example 6) 1227.7 g of aqueous silica sol was obtained by the same procedure as in Example 10. 800 g of pure water was added to 200 g of the aqueous silica sol of Example 10, and the mixture was filtered by ultrafiltration until 200 g was removed. 800 g of pure water was added again, and the same procedure was repeated four times to obtain 200 g of aqueous silica sol from which free silane had been removed. The pH, electrical conductivity, viscosity, and average particle size of the aqueous silica sol of Comparative Example 6 were evaluated by DLS method. The silane bond amount of the aqueous silica sol of Comparative Example 6 was evaluated according to (Evaluation of silane bond amount).

[0063] (Comparative Example 7) An aqueous silica sol (Snowtex (trade name) ST-OXS, manufactured by Nissan Chemical Industries, Ltd.) was used as the aqueous silica sol of Comparative Example 7. The pH, electrical conductivity, viscosity, and DLS average particle size of the aqueous silica sol (silica particles) of Comparative Example 7 were evaluated. The silane bond amount of the aqueous silica sol of Comparative Example 7 was evaluated according to (Evaluation of silane bond amount). A salt resistance test sample was prepared according to (Preparation of salt resistance test sample), and after holding at 20°C for 10 hours according to (Evaluation of room temperature salt resistance), the sample was removed and the room temperature salt resistance was evaluated.

[0064] Comparative Example 8 An aqueous silica sol (Snowtex (trade name) ST-OL, manufactured by Nissan Chemical Industries, Ltd.) was used as the aqueous silica sol of Comparative Example 8. The pH, electrical conductivity, viscosity, and DLS average particle size of the aqueous silica sol (silica particles) of Comparative Example 8 were evaluated. The silane bond amount of the aqueous silica sol of Comparative Example 8 was evaluated according to (Evaluation of Silane Bond Amount). A salt tolerance test sample was prepared according to (Preparation of Salt Tolerance Test Sample), and after holding at 20°C for 10 hours according to (Evaluation of Room Temperature Salt Tolerance), the sample was removed and the room temperature salt tolerance was evaluated. A brine test sample was prepared according to (Preparation of Salt Tolerance Test Sample), and after holding at 20°C for 10 hours according to (Evaluation of Room Temperature Salt Tolerance), the sample was removed and the room temperature salt tolerance was evaluated. Tables 1 to 6 show the compositions (component concentrations) and salt tolerance test results of the aqueous silica sols of the Examples, and Tables 7 and 8 show the compositions (component concentrations) and salt tolerance test results of the aqueous silica sols of Comparative Examples.

[0065]

[0066]

[0067]

[0068]

[0069]

[0070]

[0071]

[0072] The types (symbols) of silane compounds in the table represent the following: LTAC: lauryltrimethylammonium chloride (trade name: Cathiogen TML), active ingredient 30.0%, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. GPS: 3-glycidoxypropyltrimethoxysilane (trade name: Dynasylan GLYMO), manufactured by Evonik Corporation MTMS: methyltrimethoxysilane (trade name: KBM-13), manufactured by Shin-Etsu Chemical Co., Ltd. DMS: dimethyldimethoxysilane (trade name: KBM-22), manufactured by Shin-Etsu Chemical Co., Ltd. EPCHS: (3,4-epoxycyclohexyl)ethyltrimethoxysilane (trade name: KBM-303), manufactured by Shin-Etsu Chemical Co., Ltd. TFPS: trifluoropropyltrimethoxysilane (trade name: KBM-7103), manufactured by Shin-Etsu Chemical Co., Ltd. APTES: 3-aminopropyltriethoxysilane "trade name KBE-903", manufactured by Shin-Etsu Chemical Co., Ltd. APTMS: 3-aminopropyltrimethoxysilane "trade name KBM-903", manufactured by Shin-Etsu Chemical Co., Ltd. AEAPTMS: N-2-(aminoethyl)-3-aminopropyltrimethoxysilane "trade name KBM-603", manufactured by Shin-Etsu Chemical Co., Ltd. AEAPMDMS: N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane "trade name KBM-602", manufactured by Shin-Etsu Chemical Co., Ltd.

[0073] (Measurement of free silane bonding state) The aqueous silica sol of the present invention is expected to have a greater effect in improving the stability of silica particles depending on the form of the free silane contained therein. The form of the free silane was determined by adding 6 g of aqueous silica sol to a 15 ml centrifugal filter unit (trade name: Amicon Ultra 15 (Merck Co., Ltd.)) and centrifuging it for 20 minutes at a centrifugal force of 2770 G. The liquid containing the free silane discharged to the bottom of the unit was analyzed by Si-NMR to calculate the content ratio of the T structure or D structure. The T structure was measured for Examples 2, 9, 10, 13, and 15, and the measurement results are shown in Table 9. The D structure was measured for Example 12, and the measurement results are shown in Table 10.

[0074]

[0075] (Measurement of the bonding state of bonded silane) The aqueous silica sol of the present invention is expected to have a greater effect of improving the stability of silica particles by bonding a portion of the silane compound to the surface of the silica particles. The form of the bonded silane was analyzed by analyzing the liquid obtained in (removal of free silane) by Si-NMR and calculating the proportion of Q structure. The Q structure was measured for Examples 2, 5, 6, 7, 8, 9, 10, 11, 12, 13, and 14 and Comparative Examples 1, 7, and 8, and the measurement results are shown in Table 11.

[0076]

[0077] (Specific surface area calculated from water vapor adsorption amount / specific surface area calculated from nitrogen gas adsorption amount) The aqueous silica sol of the present invention is expected to have a greater effect in improving the stability of silica particles because the silanol groups on the silica particle surface are replaced by silane compounds having functional groups. The value obtained by dividing the specific surface area calculated from the water vapor adsorption amount on silica particles by the specific surface area calculated from the nitrogen gas adsorption amount, i.e., (specific surface area calculated from water vapor adsorption amount) / (specific surface area calculated from nitrogen gas adsorption amount), indicates that the silanol groups on the silica particle surface have been replaced by silane compounds having functional groups. The water vapor adsorption amount and nitrogen gas adsorption amount were analyzed according to the procedures (measurement of water vapor adsorption amount) and (measurement of nitrogen gas adsorption amount). The water vapor adsorption amount and nitrogen gas adsorption amount were measured for Examples 1, 2, 5, 7, 8, 13, and 14 and Comparative Examples 1, 3, 7, and 8. The values ​​after the silane compound treatment were divided by the values ​​before the silane compound treatment using the formula (specific surface area calculated from the water vapor adsorption amount) / (specific surface area calculated from the nitrogen gas adsorption amount). The measurement results are shown in Table 12.

[0078]

[0079] The present invention can provide a dispersion of inorganic oxide particles, particularly a dispersion of silica particles, which has high dispersion stability even under high temperature or high salt conditions.

Claims

1. A dispersion comprising hydrolyzable-silane surface-modified silane-bonded silica-containing inorganic oxide particles as a disperse phase and a liquid medium as a dispersion medium, wherein the dispersion medium contains a hydrolyzate of the hydrolyzable silane, and the ratio of (the number of moles of silicon atoms in the hydrolyzate of the hydrolyzable silane in the dispersion medium) / (the number of moles of silicon atoms of the silane bonded to the surface of the inorganic oxide particles) is 0.2 to 30, and Q4 in which the crosslinking oxygen between the silicon atoms of the silica particles is 4 / 2 per silicon atom as observed by Si-NMR is increased compared to before the surface modification of the silane, and the dispersion contains the silica-containing inorganic oxide particles.

2. The silica-containing inorganic oxide particles are silica particles having an average particle diameter of 5 nm to 100 nm, or at least one inorganic oxide particle selected from the group consisting of silica and alumina, tin oxide, zirconium oxide, titanium oxide, and antimony oxide, and the silica-containing inorganic oxide particles are silica particles, a composite metal oxide of silica and another metal oxide, or composite oxide particles having a core-shell structure of silica and another metal oxide. The dispersion according to claim 1.

3. The hydrolyzable silane is represented by the formula (1) to formula (3): (In formula (1), R ３ is an alkyl group, a halogenated alkyl group, an alkenyl 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 is bonded to a silicon atom by an Si—C bond, and R ４ represents an alkoxy group, an acyloxy group, or a halogen group, a represents an integer of 1 to 3. In formula (2) and formula (3), R ５ and R ７ are alkyl groups having 1 to 3 carbon atoms and are bonded to a silicon atom by an Si—C bond, R ６ and R ７ represent an alkoxy group, an acyloxy group, or a halogen group, Y represents an alkylene group, an NH group, or an oxygen atom, and at least one of the R ５ and R ７ is an alkyl group having 1 to 3 carbon atoms and is bonded to a silicon atom by an Si—C bond, b is an integer of 1 to 3, c is an integer of 0 or 1, d is an integer of 1 to 3, and e is an integer of 1 to 3.) The dispersion according to claim 1 or claim 2, which is at least one silane compound selected from the group consisting of.) 4. In the hydrolyzate of the hydrolyzable silane in the dispersion medium, for the hydrolyzate of the silane compound in which a in the formula (1) is an integer of 1, the ratio of the crosslinking oxygen between silicon atoms shows 0 / 2, 1 / 2, 2 / 2, and 3 / 2 per silicon atom for the T0, T1, T2, and T3 structures observed by Si-NMR, and (T2 + T3) / (T0 + T1) is a specific value (2 to 15), or the (T1 + T2 + T3) / (T0) ratio is a specific value (5 to 100). The dispersion according to claim 3, which contains a silane compound.

5. In the hydrolyzate of the hydrolyzable silane in the dispersion medium, for the hydrolyzate of the silane compound in which a in the formula (1) is an integer of 2, the ratio of the crosslinking oxygen between silicon atoms shows 0 / 2, 1 / 2, 2 / 2 per silicon atom for the D0, D1, and D2 structures observed by Si-NMR, and the (D1 + D2) / (D0) ratio is 0.1 to 10, or the (D2) / (D0 + D1) ratio is 0.01 to 10. The dispersion according to claim 3, which contains a silane compound.

6. The value obtained by dividing the amount of water vapor adsorbed by the silica-containing inorganic oxide particles by the amount of nitrogen gas adsorbed ((specific surface area calculated from the amount of water vapor adsorbed) / (specific surface area calculated from the amount of nitrogen gas adsorbed)) is 0.15 to 0.95 as compared with the silica particles before the addition of the silane compound. The dispersion according to any one of claims 1 to 5.

7. The following step (A) to step (B): (A) step: a step of obtaining an aqueous dispersion of the silica-containing inorganic oxide particles; (B) step: a hydrolyzable silane is added to the aqueous dispersion of the silica-containing inorganic oxide particles at a pH of 2.0 to 6.5 in a ratio of the number of the silanes per nm of the particle surface area in the range of 0.3 to 100 pieces / nm ２ and after stirring at room temperature, the temperature is raised to a temperature within 50 to 99 °C, and the stirring time after the temperature rise is within 1 to 100 times the stirring time at room temperature. The method for producing a dispersion according to any one of claims 1 to 6, which includes this step.

8. After the step (B), further step (C): Step (C): A step of replacing the aqueous medium of the dispersion obtained in the step (B) with an organic solvent. The method for producing a dispersion using an organic solvent as a dispersion medium according to claim 7, which includes this step.