INORGANIC OXIDE SOL DISPERSED IN HYDROCARBON AND PRODUCTION METHOD THEREFOR

Abstract

A sol of inorganic oxide particles is stably dispersed in a hydrophilic organic solvent containing a hydrocarbon such as a paraffinic hydrocarbon or a naphthenic hydrocarbon. The sol contains a dispersion medium containing an organic solvent containing a C.sub.6-18 paraffinic hydrocarbon, a C.sub.6-18 naphthenic hydrocarbon, or a mixture of these, a C.sub.4-8 alcohol having a carbon chain with a carbon-carbon bond in the molecule in an amount of 0.1 to 5% by mass in the entire dispersion medium, and inorganic oxide particles having an average particle diameter of 5 to 200 nm as measured by dynamic light scattering as a dispersoid, wherein the inorganic oxide particles contain a C.sub.1-3 alkyl group bonded to a silicon atom and a C.sub.4-18 alkyl group. The paraffinic hydrocarbon is a normal paraffinic hydrocarbon or an isoparaffinic hydrocarbon. The naphthenic hydrocarbon is a saturated aliphatic cyclic hydrocarbon substitutable with a C.sub.1-10 alkyl group.

Claims

1. A sol comprising inorganic oxide particles as a dispersoid; and a dispersion medium containing an organic solvent containing a C.sub.6-18 paraffinic hydrocarbon, a C.sub.6-18 naphthenic hydrocarbon, or a mixture of these, and a C.sub.4-8 alcohol having a carbon-carbon bond in the molecule, wherein: the alcohol is contained in an amount of 0.1 to 5% by mass in the entire dispersion medium, the inorganic oxide particles have an average particle diameter of 5 to 200 nm as measured by dynamic light scattering, and the inorganic oxide particles contain a silicon atom bonded to a C.sub.1-3 alkyl group and a silicon atom bonded to a C.sub.4-18 alkyl group.

2. The sol according to claim 1, wherein the inorganic oxide particles contain a silane compound in which a C.sub.4-18 alkyl group is bonded to a silicon atom and a silane compound in which a C.sub.1-3 alkyl group is bonded to a silicon atom in proportions by mole of 1:0.1 to 30 in terms of silicon atom.

3. The sol according to claim 1, wherein the paraffinic hydrocarbon is a normal paraffinic hydrocarbon or an isoparaffinic hydrocarbon.

4. The sol according to claim 1, wherein the naphthenic hydrocarbon is a saturated aliphatic cyclic hydrocarbon substitutable with a C.sub.1-10 alkyl group.

5. The sol according to claim 1, wherein the alcohol is n-butanol, n-pentanol, or n-hexanol.

6. The sol according to claim 1, wherein the inorganic oxide particles are particles of an oxide of at least one metal selected from the group consisting of Si, Ti, Fe, Cu, Zn, Y, Zr, Nb, Mo, In, Sn, Sb, Ta, W, Pb, Bi, and Ce.

7. The sol according to claim 6, wherein the inorganic oxide particles are silica particles, zirconia particles, or titania particles.

8. The sol according to claim 6, wherein the inorganic oxide particles are metal oxide particles having a core-shell structure in which the surface of a core particle formed of at least one metal oxide selected from the group consisting of tin oxide, zirconium oxide, and titanium oxide is coated with at least one selected from among silica, tin oxide, antimony oxide, and tungsten oxide.

9. The sol according to claim 1, wherein the inorganic oxide particles are coated with a silane compound of the following
R.sup.1.sub.aSi(R.sup.2).sub.4-a  Formula (1) (wherein R.sup.1 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 via an Si—C bond; at least one R.sup.1 is a C.sub.4-18 alkyl group and is bonded to a silicon atom via an Si—C bond; R.sup.2 is an alkoxy group, an acyloxy group, or a halogen group; and a is an integer of 1 to 3).

10. The sol according to claim 9, wherein the inorganic oxide particles are coated with at least one silane compound selected from the group consisting of silane compounds of Formula (1) and the following Formulae (2) and (3):
[R.sup.3.sub.bSi(R.sup.4).sub.3-b].sub.2Y.sub.c  Formula (2)
R.sup.5.sub.dSi(R.sup.6).sub.4-d  Formula (3) (wherein R.sup.3 and R.sup.5 are each a C.sub.1-3 alkyl group and bonded to a silicon atom via an Si—C bond; R.sup.4 and R.sup.6 are each an alkoxy group, an acyloxy group, or a halogen group; Y is an alkylene group, an NH group, or an oxygen atom; at least one R.sup.3 and at least one R.sup.5 are a C.sub.1-3 alkyl group and bonded to a silicon atom via an Si—C bond; 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).

11. The sol according to claim 1, wherein, when the concentration of the inorganic oxide particles is 50% by mass or less, the viscosity at 20° C. of the sol is 1.0 to 10.0 times the viscosity at 20° C. of the organic solvent containing the C.sub.6-18 paraffinic hydrocarbon, the C.sub.6-18 naphthenic hydrocarbon, or a mixture of these, which serves as the dispersion medium.

12. The sol according to claim 11, wherein, when the concentration of the inorganic oxide particles is 5 to 50% by mass, the viscosity at 20° C. of the sol is 1.0 to 10.0 times the viscosity at 20° C. of the organic solvent containing the C.sub.6-18 paraffinic hydrocarbon, the C.sub.6-18 naphthenic hydrocarbon, or a mixture of these, which serves as the dispersion medium.

13. A production method for the sol according to claim 9, the method comprising the following steps (A) to (D): step (A): a step of preparing a sol containing a C.sub.4-8 alcohol having a carbon-carbon bond in the molecule in an amount of 15% by mass or more in the entire dispersion medium, from a sol containing, as a dispersoid, inorganic oxide particles having an average particle diameter of 5 to 200 nm as measured by dynamic light scattering, and an aqueous solvent or a C.sub.1-3 alcohol as a dispersion medium; step (B): a step of adding a silane compound of the following Formula (1) to the sol prepared in the step (A), and allowing reaction to proceed at a temperature of 20° C. to the boiling point of the dispersion medium for 0.1 to 6 hours. step (C): a step of adding a C.sub.6-18 paraffinic hydrocarbon, a C.sub.6-18 naphthenic hydrocarbon, or a mixture of these to the sol prepared in the step (B), and removing water and/or the alcohol to the outside of the system; and step (D): a step of adding at least one silane compound selected from the group consisting of silane compounds of the following Formulae (2) and (3) to the sol prepared in the step (C) if necessary, and allowing reaction to proceed at a temperature of 20° C. to the boiling point of the dispersion medium for 0.1 to 6 hours:
R.sup.1.sub.aSi(R.sup.2).sub.4-a  Formula (1)
[R.sup.3.sub.bSi(R.sup.4).sub.3-b].sub.2Y.sub.c  Formula (2)
R.sup.5.sub.dSi(R.sup.6).sub.4-d  Formula (3) (in Formula (1), R.sup.1 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 via an Si—C bond; at least one R.sup.1 is a C.sub.4-18 alkyl group and is bonded to a silicon atom via an Si—C bond; R.sup.2 is an alkoxy group, an acyloxy group, or a halogen group; and a is an integer of 1 to 3; and, in Formulae (2) and (3), R.sup.3 and R.sup.5 are each a C.sub.1-3 alkyl group and bonded to a silicon atom via an Si—C bond; R.sup.4 and R.sup.6 are each an alkoxy group, an acyloxy group, or a halogen group; Y is an alkylene group, an NH group, or an oxygen atom; at least one R.sup.3 and at least one R.sup.5 are a C.sub.1-3 alkyl group and bonded to a silicon atom via an Si—C bond; 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).

14. The production method according to claim 13, wherein the method further comprises the following step (E) after the step (D): step (E): a step of adding a C.sub.8-18 paraffinic hydrocarbon, a C.sub.8-18 naphthenic hydrocarbon, or a mixture of these, and removing the alcohol.

Description

EXAMPLES

Example 1

[0091] Step (A): A 1 L three-necked round-bottom flask was charged with 500 g of a silica sol dispersed in methanol (product name: MA-ST-ZL-IP, average primary particle diameter: 85 nm as measured by observation with a transmission electron microscope, silica concentration: 40% by mass, available from Nissan Chemical Corporation), and the solvent was replaced by n-butanol (special grade, available from Kanto Chemical Co., Inc.) with a rotary evaporator, to thereby prepare a silica sol (average primary particle diameter: 85 nm, silica concentration: 40% by mass) dispersed in a mixed solvent of methanol and n-butanol (mixing proportions=4:6).

[0092] Step (B): To the silica sol was added 2.52 g of decyltrimethoxysilane (i.e., the aforementioned silane coupling agent) (product name: KBM-3103C, available from Shin-Etsu Chemical Co., Ltd.). The resultant mixture was maintained at 65° C. for three hours with stirring.

[0093] Step (C): Subsequently, the solvent was replaced by Exxsol DSP145/160 with a rotary evaporator, to thereby prepare a silica sol (average primary particle diameter: 85 nm, silica concentration: 40% by mass) dispersed in a mixed solvent of methanol, n-butanol, and Exxsol DSP145/160 (mixing proportions=2:13:15).

[0094] Step (D): Thereafter, 10.3 g of hexamethyldisilazane as a trimethylsilyl group (product name: SZ-31, available from Shin-Etsu Chemical Co., Ltd.) was added to the silica sol, and the resultant mixture was heated at 65° C. for five hours. The silica sol was found to contain silica particles containing a silicon atom containing a decyl group and a silicon atom containing a methyl group in proportions by mole of 1:13.3 in terms of silicon atom.

[0095] Step (E): After completion of the reaction, the silica sol was transferred to a 1 L eggplant-shaped flask, and the solvent was replaced by Exxsol DSP145/160, to thereby produce a silica sol dispersed in Exxsol DSP145/160 (solid content (in terms of SiO.sub.2): 50% by mass, average particle diameter as measured by dynamic light scattering: 102 nm, Ostwald viscosity at 20° C. (specific gravity: 0.880, solid content: 20% by mass): 1.06 mPa.Math.s, Ostwald viscosity at 20° C. (specific gravity: 0.958, solid content: 30% by mass): 1.35 mPa.Math.s, Ostwald viscosity at 20° C. (specific gravity: 1.144, solid content: 50% by mass): 2.97 mPa.Math.s, n-butanol content of the dispersion medium: 1.0% by mass, balance: Exxsol DSP145/160).

[0096] The Exxsol DSP145/160 solvent was found to have an Ostwald viscosity at 20° C. (specific gravity: 0.760) of 0.81 mPa.Math.s.

[0097] The viscosity of the resultant sol was 1.31 times (solid content: 20% by mass), 1.67 times (solid content: 30% by mass), and 3.67 times (solid content: 50% by mass) the viscosity of Exxsol DSP145/160 at 20° C.

Example 2

[0098] A silica sol dispersed in Exxsol DSP145/160 was produced in the same manner as in Example 1, except that 2.52 g of decyltrimethoxysilane (silane coupling agent) was replaced by 1.98 g of hexyltrimethoxysilane (product name: KBM-3063, available from Shin-Etsu Chemical Co., Ltd.) in the step (B). The silica sol was found to contain silica particles containing a silicon atom containing a hexyl group and a silicon atom containing a methyl group in proportions by mole of 1:13.3 in terms of silicon atom.

[0099] This procedure produced a silica sol dispersed in Exxsol DSP145/160 (solid content (in terms of SiO2): 50% by mass, average particle diameter as measured by dynamic light scattering: 117 nm, Ostwald viscosity at 20° C. (specific gravity: 1.143, solid content: 50% by mass): 6.00 mPa.Math.s, n-butanol content of the dispersion medium: 1.0% by mass, balance: Exxsol DSP145/160). The Exxsol DSP145/160 solvent was found to have an Ostwald viscosity at 20° C. (specific gravity: 0.760) of 0.81 mPa.Math.s.

[0100] The viscosity of the resultant sol was 7.40 times (solid content: 50% by mass) the viscosity of Exxsol DSP145/160 at 20° C.

Example 3

[0101] A silica sol dispersed in Exxsol DSP145/160 was produced in the same manner as in Example 1, except that 2.52 g of decyltrimethoxysilane (silane coupling agent) was replaced by 3.60 g of octadecyltrimethoxysilane (available from Tokyo Chemical Industry Co., Ltd.) in the step (B). The silica sol was found to contain silica particles containing a silicon atom containing an octadecyl group and a silicon atom containing a methyl group in proportions by mole of 1:13.3 in terms of silicon atom.

[0102] This procedure produced a silica sol dispersed in Exxsol DSP145/160 (solid content (in terms of SiO.sub.2): 50% by mass, average particle diameter as measured by dynamic light scattering: 99 nm, Ostwald viscosity at 20° C. (specific gravity: 1.148, solid content: 50% by mass): 3.04 mPa.Math.s, n-butanol content of the dispersion medium: 1.0% by mass, balance: Exxsol DSP145/160).

[0103] The Exxsol DSP145/160 solvent was found to have an Ostwald viscosity at 20° C. (specific gravity: 0.760) of 0.81 mPa.Math.s.

[0104] The viscosity of the resultant sol was 3.75 times (solid content: 50% by mass) the viscosity of Exxsol DSP145/160 at 20° C.

Example 4

[0105] A silica sol dispersed in Exxsol DSP145/160 was produced in the same manner as in Example 1, except that 17.3 g of hexamethyldisilazane (i.e., trimethylsilyl group-containing compound) was replaced by 10.4 g of hexamethyldisiloxane (product name: KF-96L, available from Shin-Etsu Chemical Co., Ltd.) in the step (D). The silica sol was found to contain silica particles containing a silicon atom containing a decyl group and a silicon atom containing a methyl group in proportions by mole of 1:13.3 in terms of silicon atom.

[0106] This procedure produced a silica sol dispersed in Exxsol DSP145/160 (solid content (in terms of SiO.sub.2): 50% by mass, average particle diameter as measured by dynamic light scattering: 110 nm, Ostwald viscosity at 20° C. (specific gravity: 1.142, solid content: 50% by mass): 2.86 mPa.Math.s, n-butanol content of the dispersion medium: 1.0% by mass, balance: Exxsol DSP145/160).

[0107] The Exxsol DSP145/160 solvent was found to have an Ostwald viscosity at 20° C. (specific gravity: 0.760) of 0.81 mPa.Math.s.

[0108] The viscosity of the resultant sol was 3.53 times (solid content: 50% by mass) the viscosity of Exxsol DSP145/160 at 20° C.

Example 5

[0109] A silica sol dispersed in Exxsol DSP145/160 was produced in the same manner as in Example 1, except that 17.3 g of hexamethyldisilazane (i.e., trimethylsilyl group-containing compound) was replaced by 13.4 g of trimethylmethoxysilane (product name: Z-6013, available from Dow Corning Toray) in the step (D). The silica sol was found to contain silica particles containing a silicon atom containing a decyl group and a silicon atom containing a methyl group in proportions by mole of 1:13.3 in terms of silicon atom.

[0110] This procedure produced a silica sol dispersed in Exxsol DSP145/160 (solid content (in terms of SiO.sub.2): 50% by mass, average particle diameter as measured by dynamic light scattering: 107 nm, Ostwald viscosity at 20° C. (specific gravity: 1.143, solid content: 50% by mass): 2.86 mPa.Math.s, n-butanol content of the dispersion medium: 1.0% by mass, balance: Exxsol DSP145/160).

[0111] The Exxsol DSP145/160 solvent was found to have an Ostwald viscosity at 20° C. (specific gravity: 0.760) of 0.81 mPa.Math.s.

[0112] The viscosity of the resultant sol was 3.53 times (solid content: 50% by mass) the viscosity of Exxsol DSP145/160 at 20° C.

Example 6

[0113] A silica sol dispersed in Exxsol DSP145/160 was produced in the same manner as in Example 1, except that n-butanol (i.e., compatibilizing agent) was replaced by 1-hexanol (available from Tokyo Chemical Industry Co., Ltd.) in the step (A). The silica sol was found to contain silica particles containing a silicon atom containing a decyl group and a silicon atom containing a methyl group in proportions by mole of 1:13.3 in terms of silicon atom.

[0114] This procedure produced a silica sol dispersed in Exxsol DSP145/160 (solid content (in terms of SiO.sub.2): 50% by mass, average particle diameter as measured by dynamic light scattering: 101 nm, Ostwald viscosity at 20° C. (specific gravity: 1.141, solid content: 50% by mass): 2.94 mPa.Math.s, 1-hexanol content of the dispersion medium: 1.0% by mass, balance: Exxsol DSP145/160).

[0115] The Exxsol DSP145/160 solvent was found to have an Ostwald viscosity at 20° C. (specific gravity: 0.760) of 0.81 mPa.Math.s.

[0116] The viscosity of the resultant sol was 3.63 times (solid content: 50% by mass) the viscosity of Exxsol DSP145/160 at 20° C.

Example 7

[0117] Step (A): A 500 mL three-necked round-bottom flask was charged with 300 g of a silica sol dispersed in methanol (product name: MT-ST, average primary particle diameter: 12 nm as measured by observation with a transmission electron microscope, silica concentration: 30% by mass, available from Nissan Chemical Corporation), and the solvent was replaced by n-butanol solvent with a rotary evaporator, to thereby prepare a silica sol (average primary particle diameter: 12 nm, silica concentration: 30% by mass) dispersed in a mixed solvent of methanol and n-butanol (mixing proportions=4:6).

[0118] Step (B): To the silica sol was added 13.8 g of decyltrimethoxysilane (i.e., the aforementioned silane coupling agent) (product name: KBM-3103C, available from Shin-Etsu Chemical Co., Ltd.). The resultant mixture was maintained at 65° C. for three hours with stirring.

[0119] Step (C): Subsequently, the solvent was replaced by Exxsol DSP145/160 with a rotary evaporator, to thereby prepare a silica sol (average primary particle diameter: 12 nm, silica concentration: 30% by mass) dispersed in a mixed solvent of methanol, n-butanol, and Exxsol DSP145/160 (mixing proportions=2:13:15).

[0120] Step (D): Thereafter, 56.7 g of hexamethyldisilazane (i.e., trimethylsilyl group-containing compound) (product name: SZ-31, available from Shin-Etsu Chemical Co., Ltd.) was added to the silica sol, and the resultant mixture was heated at 65° C. for five hours. The silica sol was found to contain silica particles containing a silicon atom containing a decyl group and a silicon atom containing a methyl group in proportions by mole of 1:13.3 in terms of silicon atom.

[0121] Step (E): After completion of the reaction, the silica sol was transferred to a 500 mL eggplant-shaped flask, and the solvent was replaced by Exxsol DSP145/160, to thereby produce a silica sol dispersed in Exxsol DSP145/160 (solid content (in terms of SiO.sub.2): 50% by mass, average particle diameter as measured by dynamic light scattering: 18 nm, Ostwald viscosity at 20° C. (specific gravity: 0.876, solid content: 20% by mass): 1.57 mPa.Math.s, Ostwald viscosity at 20° C. (specific gravity: 0.950, solid content: 30% by mass): 1.69 mPa.Math.s, Ostwald viscosity at 20° C. (specific gravity: 1.131, solid content: 50% by mass): 6.29 mPa.Math.s, n-butanol content of the dispersion medium: 1.0% by mass, balance: Exxsol DSP145/160).

[0122] The Exxsol DSP145/160 solvent was found to have an Ostwald viscosity at 20° C. (specific gravity: 0.760) of 0.81 mPa.Math.s.

[0123] The viscosity of the resultant sol was 1.94 times (solid content: 20% by mass), 2.09 times (solid content: 30% by mass), and 7.77 times (solid content: 50% by mass) the viscosity of Exxsol DSP145/160 at 20° C.

Example 8

[0124] Step (A): A 1 L three-necked round-bottom flask was charged with 500 g of a zirconia sol dispersed in methanol (product name: HZ-400M7, specific surface area: 190 to 200 m.sup.2/g, average primary particle diameter: 15 nm as measured by observation with a transmission electron microscope, solid content: 40% by mass, available from Nissan Chemical Corporation), and the solvent was replaced by n-butanol (special grade, available from Kanto Chemical Co., Inc.) with a rotary evaporator, to thereby prepare a zirconia sol (specific surface area: 190 to 200 m.sup.2/g, solid content concentration: 40% by mass) dispersed in a mixed solvent of methanol and n-butanol (mixing proportions=4:6).

[0125] Step (B): To the zirconia sol was added 26.2 g of decyltrimethoxysilane (i.e., the aforementioned silane coupling agent) (product name: KBM-3103C, available from Shin-Etsu Chemical Co., Ltd.). The resultant mixture was maintained at 65° C. for three hours with stirring.

[0126] Step (C): Subsequently, the solvent was replaced by Exxsol DSP145/160 with a rotary evaporator, to thereby prepare a zirconia sol (specific surface area: 190 to 200 m.sup.2/g, solid content concentration: 40% by mass) dispersed in a mixed solvent of methanol, n-butanol, and Exxsol DSP145/160 (mixing proportions=1:9:5).

[0127] Step (D): Thereafter, 107.3 g of hexamethyldisilazane as a trimethylsilyl group (product name: SZ-31, available from Shin-Etsu Chemical Co., Ltd.) was added to the zirconia sol, and the resultant mixture was heated at 65° C. for five hours. The zirconia sol was found to contain silica particles containing a silicon atom containing a decyl group and a silicon atom containing a methyl group in proportions by mole of 1:13.3 in terms of silicon atom.

[0128] Step (E): After completion of the reaction, the zirconia sol was transferred to a 1 L eggplant-shaped flask, and the solvent was replaced by Exxsol DSP145/160, to thereby produce a zirconia sol dispersed in Exxsol DSP145/160.

[0129] This procedure produced a zirconia sol dispersed in Exxsol DSP145/160 (solid content (in terms of ZrO.sub.2): 30% by mass, average particle diameter as measured by dynamic light scattering: 44 nm, Ostwald viscosity at 20° C. (specific gravity: 1.024, solid content: 30% by mass): 3.06 mPa.Math.s, n-butanol content of the dispersion medium: 1.0% by mass, balance: Exxsol DSP145/160).

[0130] The Exxsol DSP145/160 solvent was found to have an Ostwald viscosity at 20° C. (specific gravity: 0.760) of 0.81 mPa.Math.s.

[0131] The viscosity of the resultant sol was 3.78 times (solid content: 30% by mass) the viscosity of Exxsol DSP145/160 at 20° C.

Example 9

[0132] Step (A): A 1 L three-necked round-bottom flask was charged with 500 g of a silica sol dispersed in methanol (product name: MA-ST-L, average primary particle diameter: 45 nm as measured by observation with a transmission electron microscope, silica concentration: 40% by mass, available from Nissan Chemical Corporation), and the solvent was replaced by n-butanol (special grade, available from Kanto Chemical Co., Inc.) with a rotary evaporator, to thereby prepare a silica sol (average primary particle diameter: 45 nm, silica concentration: 40% by mass) dispersed in a mixed solvent of methanol and n-butanol (mixing proportions=4:6).

[0133] Step (B): To the silica sol was added 7.90 g of decyltrimethoxysilane (i.e., the aforementioned silane coupling agent) (product name: KBM-3103C, available from Shin-Etsu Chemical Co., Ltd.). The resultant mixture was maintained at 65° C. for three hours with stirring.

[0134] Step (C): Subsequently, the solvent was replaced by Isoper G with a rotary evaporator, to thereby prepare a silica sol (average primary particle diameter: 85 nm, silica concentration: 40% by mass) dispersed in a mixed solvent of methanol, n-butanol, and Isoper G (mixing proportions=2:13:15).

[0135] Step (D): Thereafter, 32.4 g of hexamethyldisilazane as a trimethylsilyl group (product name: SZ-31, available from Shin-Etsu Chemical Co., Ltd.) was added to the silica sol, and the resultant mixture was heated at 65° C. for five hours. The silica sol was found to contain silica particles containing a silicon atom containing a decyl group and a silicon atom containing a methyl group in proportions by mole of 1:13.3 in terms of silicon atom.

[0136] Step (E): After completion of the reaction, the silica sol was transferred to a 1 L eggplant-shaped flask, and the solvent was replaced by Isoper G, to thereby produce a silica sol dispersed in Isoper G (solid content (in terms of SiO.sub.2): 50% by mass, average particle diameter as measured by dynamic light scattering: 58 nm, Ostwald viscosity at 20° C. (specific gravity: 0.866, solid content: 20% by mass): 1.49 mPa.Math.s, Ostwald viscosity at 20° C. (specific gravity: 1.034, solid content: 30% by mass): 2.04 mPa.Math.s, Ostwald viscosity at 20° C. (specific gravity: 1.132, solid content: 50% by mass): 4.08 mPa.Math.s, n-butanol content of the dispersion medium: 1.0% by mass, balance: Isoper G).

[0137] The Isoper G solvent was found to have an Ostwald viscosity at 20° C. (specific gravity: 0.743) of 1.12 mPa.Math.s. The viscosity of the resultant sol was 1.33 times (solid content: 20% by mass), 1.82 times (solid content: 30% by mass), and 3.64 times (50% by mass) the viscosity of Isoper G.

Comparative Example 1

[0138] Step (A): A 500 mL three-necked round-bottom flask was charged with 300 g of a silica sol dispersed in isopropanol (product name: IPA-ST, average primary particle diameter: 12 nm as measured by observation with a transmission electron microscope, silica concentration: 30% by mass, available from Nissan Chemical Corporation).

[0139] Step (B): To the silica sol was added 13.8 g of decyltrimethoxysilane (i.e., the aforementioned silane coupling agent) (product name: KBM-3103C, available from Shin-Etsu Chemical Co., Ltd.). The resultant mixture was maintained at 65° C. for three hours with stirring.

[0140] Step (C): Subsequently, the solvent was replaced by Exxsol DSP145/160 with a rotary evaporator, to thereby prepare a silica sol (average primary particle diameter: 12 nm, silica concentration: 30% by mass) dispersed in a mixed solvent of isopropanol and Exxsol DSP145/160 (mixing proportions=3:2).

[0141] Step (D): Thereafter, 56.7 g of hexamethyldisilazane as a trimethylsilyl group (product name: SZ-31, available from Shin-Etsu Chemical Co., Ltd.) was added to the silica sol, and the resultant mixture was heated at 65° C. for five hours. The silica sol was found to contain silica particles containing a silicon atom containing a decyl group and a silicon atom containing a methyl group in proportions by mole of 1:13.3 in terms of silicon atom.

[0142] Step (E): After completion of the reaction, the silica sol was transferred to a 500 mL eggplant-shaped flask, and the solvent was replaced by Exxsol DSP145/160, to thereby produce a silica sol dispersed in Exxsol DSP145/160.

[0143] This procedure produced a silica sol dispersed in Exxsol DSP145/160 (solid content (in terms of SiO2): 50% by mass, average particle diameter as measured by dynamic light scattering: 39 nm, viscosity (measured by a B-type viscometer) at 20° C. (specific gravity: 1.140, solid content: 50% by mass): 41 mPa.Math.s, isopropanol content of the dispersion medium: 1.0% by mass, balance: Exxsol DSP145/160).

[0144] The Exxsol DSP145/160 solvent was found to have an Ostwald viscosity at 20° C. (specific gravity: 0.760) of 0.81 mPa.Math.s.

[0145] The viscosity of the resultant sol was 50.6 times (solid content: 50% by mass) the viscosity of Exxsol DSP145/160 at 20° C. This physical property was unsatisfactory.

Comparative Example 2

[0146] The same procedure as in Example 1 was performed, except that the solvent was not replaced by n-butanol (special grade, available from Kanto Chemical Co., Inc.) in the step (A). In the step (C), difficulty was encountered in replacing the methanol solvent by Exxsol DSP145/160.

Comparative Example 3

[0147] The same procedure as in Example 1 was performed, except that decyltrimethoxysilane (product name: KBM-3103C, available from Shin-Etsu Chemical Co., Ltd.) was not added in the step (B).

[0148] This procedure produced a silica sol dispersed in Exxsol DSP145/160 (solid content (in terms of SiO.sub.2): 50% by mass, average particle diameter as measured by dynamic light scattering: 4,283 nm, viscosity (measured by a B-type viscometer) at 20° C. (specific gravity: 1.14, solid content: 50% by mass): 13,640 mPa.Math.s, n-butanol content of the dispersion medium: 1.0% by mass, balance: Exxsol DSP145/160).

[0149] The Exxsol DSP145/160 solvent was found to have an Ostwald viscosity at 20° C. (specific gravity: 0.760) of 0.81 mPa.Math.s.

[0150] The viscosity of the resultant sol was 16,840 times (solid content: 50% by mass) the viscosity of Exxsol DSP145/160 at 20° C. This physical property was unsatisfactory.

Comparative Example 4

[0151] The same procedure as in Example 1 was performed, except that hexamethyldisilazane (product name: SZ-31, available from Shin-Etsu Chemical Co., Ltd.) was not added in the step (D).

[0152] This procedure produced a silica sol dispersed in Exxsol DSP145/160 (solid content (in terms of SiO.sub.2): 50% by mass, average particle diameter as measured by dynamic light scattering: 1,469 nm, viscosity (measured by a B-type viscometer) at 20° C. (specific gravity: 1.14, solid content: 50% by mass): 113 mPa.Math.s, n-butanol content of the dispersion medium: 1.0% by mass, balance: Exxsol DSP145/160).

[0153] The Exxsol DSP145/160 solvent was found to have an Ostwald viscosity at 20° C. (specific gravity: 0.760) of 0.81 mPa.Math.s.

[0154] The viscosity of the resultant sol was 140 times (solid content: 50% by mass) the viscosity of Exxsol DSP145/160 at 20° C. This physical property was unsatisfactory.

[0155] The physical properties of the silica sols produced in Examples 1 to 9 and Comparative Examples 1 to 4 are shown below.

TABLE-US-00001 TABLE 1 Solid Specific DLS particle content (%) gravity Viscosity diameter (nm) Example 1 50 1.144 3.0 (Ost) 102 Example 2 50 1.143 6.0 (Ost) 117 Example 3 50 1.148 3.0 (Ost) 99 Example 4 50 1.142 2.9 (Ost) 110 Example 5 50 1.143 2.9 (Ost) 107 Example 6 50 1.141 2.9 (Ost) 101 Example 7 50 1.131 6.3 (Ost) 18 Example 8 30 1.024 3.1 (Ost) 44 Example 9 50 1.132 4.1 (Ost) 58 Comparative 50 1.140 41.0 (B) 39 Example 1 Comparative 50 Example 2 Comparative 50 13640 (B) 4283 Example 3 Comparative 50 113 (B) 1469 Example 4

[0156] In Table 1, “(Ost)” corresponds to the results of measurement with an Ostwald viscometer, and “(B)” corresponds to the results of measurement with a B-type viscometer. The Ostwald viscosity was measured with a capillary tube (inner diameter ϕ 0.75) made of borosilicate glass. The B-type viscosity was measured with VISCOMETER (BM-type) available from Toki Sangyo Co., Ltd. A viscosity of 10 mPa.Math.s or less was measured with an Ostwald viscometer, and a viscosity of more than 10 mPa.Math.s was measured with a B-type rotational viscometer.

[0157] In Table 1, “DLS particle diameter” corresponds to the results of particle diameter measurement by dynamic light scattering. The DLS particle diameter was measured with ZETASIZER NANO available from Malvern Panalytical Ltd.

[0158] The solid content was measured through the following procedure: a predetermined amount of each of the aforementioned sols was weighed and placed in a crucible made of alumina; the crucible was placed in an electric furnace available from Yamada Denki Co., Ltd. and heated to 1,000° C. and maintained for 30 minutes; and then the crucible was removed from the electric furnace, followed by calculation of the solid content based on the burnt residue. The specific gravity of a silica sol was measured with a standard gravimeter available from AS ONE Corporation.

INDUSTRIAL APPLICABILITY

[0159] The inorganic oxide sol of the present invention is a hydrophobic sol dispersed in a petroleum solvent, and can be used in, for example, an adhesive, a releasing agent, a semiconductor sealing material, an LED sealing material, a paint, a film internal additive, a hard coating agent, a photoresist material, a printing ink, a detergent, a cleaner, any resin additive, an insulating composition, an antirust, a lubricant, a metal processing oil, a film coating agent, or a peeling agent.