Aminosilane-modified colloidal silica dispersion and method of manufacturing same

Abstract

The aminosilane-modified colloidal silica dispersion contains colloidal silica particles having surfaces to which there are bound a first silyl group represented by the following formula (1): R.sup.1.sub.aSi(OR.sup.2).sub.3-aO and a second silyl group represented by the following formula (2): R.sup.3.sub.bSi(OR.sup.4).sub.3-bO and, as a dispersion medium, a mixed solvent formed of a polar solvent S1 having a dielectric constant at 20 C. of 15 or higher and lower than 60 and a non-polar solvent S2 having a dielectric constant at 20 C. of 1 or higher and lower than 15, at a mass ratio (S1/S2) of 0.3 to 6.

Claims

1. An aminosilane-modified colloidal silica dispersion comprising: colloidal silica particles having surfaces to which there are bound a first silyl group represented by the following formula (1):
R.sup.1.sub.aSi(OR.sup.2).sub.3-aO(1) wherein R.sup.1 represents a C1 to C10 substituted or non-substituted alkyl group or a phenyl group; R.sup.2 represents a C1 to C4 alkyl group or a C1 to C4 alkoxyalkyl group; a is 1 to 3; a plurality of R.sup.1s may be identical to or different from one another; and a plurality of OR.sup.2s may be identical to or different from one another, and a second silyl group represented by the following formula (2):
R.sup.3.sub.bSi(OR.sup.4).sub.3-bO(2) wherein R.sup.3 represents a C1 to C4 alkyl group, a phenyl group, or a C1 to C3 alkyl group which is substituted with one or more groups selected from an amino group, an aminoalkyl group, and an alkylamino group; at least one R.sup.3 is a C1 to C3 alkyl group which is substituted with any of the groups selected from an amino group, an aminoalkyl group, and an alkylamino group; R.sup.4 represents a C1 to C4 alkyl group; b is 1 or 2; a plurality of R.sup.3s may be identical to or different from one another; a plurality of OR.sup.4s may be identical to or different from one another; and no salt is formed from the amino group, the aminoalkyl group, and the alkylamino group with acid groups; and, as a dispersion medium, a mixed solvent formed of a polar solvent S1 having a dielectric constant at 20 C. of 15 or higher and lower than 60 and a non-polar solvent S2 having a dielectric constant at 20 C. of 1 or higher and lower than 15, at a mass ratio (S1/S2) of 0.3 to 6, wherein a silica concentration in the aminosilane-modified colloidal silica dispersion is in a range of 8 mass % to 50 mass %.

2. An aminosilane-modified colloidal silica dispersion according to claim 1, wherein the amount of the first silyl group is 0.05 to 5 mmol/g with respect to the mass of silica, and the amount of the second silyl group is 0.02 to 3 mmol/g with respect to the mass of silica.

3. An aminosilane-modified colloidal silica dispersion according to claim 1, wherein the first silyl group is at least one member selected from the group consisting of a methyldimethoxysilyl group, a methyldiethoxysilyl group, a dimethylmethoxysilyl group, a dimethylethoxysilyl group, a trimethylsilyl group, a phenyldimethoxysilyl group, a phenyldiethoxysilyl group, a phenylmethylmethoxysilyl group, a phenylmethylethoxysilyl group, a phenyldimethylsilyl group, a -methacryloxypropyldimethoxysilyl group, a -methacryloxypropyldiethoxysilyl group, a -methacryloxypropylmethylmethoxysilyl group, a -methacryloxypropylmethylethoxysilyl group, a -acryloxypropyldimethoxysilyl group, a hexyldimethoxysilyl group, a hexyldiethoxysilyl group, a hexylmethylmethoxysilyl group, a hexyldimethylsilyl group, a decyldimethoxysilyl group, a decyldiethoxysilyl group, a decylmethylmethoxysilyl group, a decylmethylethoxysilyl group, and a decyldimethylsilyl group.

4. An aminosilane-modified colloidal silica dispersion according to claim 1, wherein the second silyl group is at least one member selected from the group consisting of an N-(2-aminoethyl)-3-aminopropylmethylmethoxysilyl group, an N-(2-aminoethyl)-3-aminopropyldimethoxysilyl group, an N-(2-aminoethyl)-3-aminopropylmethylethoxysilyl group, an N-(2-aminoethyl)-3-aminopropyldiethoxysilyl group, a 3-aminopropyldimethoxysilyl group, a 3-aminopropyldiethoxysilyl group, an N-methylaminopropyltdimethoxysilyl group, an N-methylaminopropyldiethoxysilyl group, an N,N-dimethyl-3-aminopropyldimethoxysilyl group, an N-ethyl-3-aminopropyldimethoxysilyl group, an N,N-diethyl-3-aminopropyldimethoxysilyl group, and an N-phenyl-3-aminopropyldimethoxysilyl group.

5. An aminosilane-modified colloidal silica dispersion according to claim 1, wherein the colloidal silica particles have a mean primary particle size D in a range of from 5 to 500 nm.

6. An aminosilane-modified colloidal silica dispersion according to claim 1, wherein an amount of water content in the aminosilane-modified colloidal silica dispersion is in a range of from 0.17 mol to 1.5 mol with respect to 1 mol of the second silyl groups.

7. A method for producing an aminosilane-modified colloidal silica dispersion, wherein the method comprises: preparing a primary dispersion of colloidal silica being dispersed in a primary solvent which is one of a polar solvent S1 having a dielectric constant at 20 C. of 15 or higher and lower than 60 or a non-polar solvent S2 having a dielectric constant at 20 C. of 1 or higher and lower than 15, wherein colloidal silica particles contained therein having surfaces to which is bound a first silyl group represented by the following formula (1):
R.sup.1.sub.aSi(OR.sup.2).sub.3-aO(1) wherein R.sup.1 represents a C1 to C10 substituted or non-substituted alkyl group or a phenyl group; R.sup.2 represents a C1 to C4 alkyl group or a C1 to C4 alkoxyalkyl group; a is 1 to 3; a plurality of R.sup.1s may be identical to or different from one another; and a plurality of OR.sup.2s may be identical to or different from one another, and adding, as an additional solvent, a counter solvent member different from the primary solvent which is one of the polar solvent S1 or the non-polar solvent S2 contained in the primary dispersion; and a subsequent addition of an aminosilane compound represented by the following formula (3):
R.sup.3.sub.bSi(OR.sup.4).sub.4-bO(3) wherein R.sup.3 represents a C1 to C4 alkyl group, a phenyl group, or a C1 to C3 alkyl group which is substituted with one or more groups selected from an amino group, an aminoalkyl group, and an alkylamino group; at least one R.sup.3 is a C1 to C3 alkyl group which is substituted with any of the groups selected from an amino group, an aminoalkyl group, and an alkylamino group; R.sup.4 represents a C1 to C4 alkyl group; b is 1 or 2; a plurality of R.sup.3s may be identical to or different from one another; and a plurality of OR.sup.4s may be identical to or different from one another, to thereby form colloidal silica, wherein the silica particles have surfaces to which are bound the first silyl group and a second silyl group represented by the following formula (2):
R.sup.3.sub.bSi(OR.sup.4).sub.3-bO(2) wherein R.sup.3 represents a C1 to C4 alkyl group, a phenyl group, or a C1 to C3 alkyl group which is substituted with one or more groups selected from an amino group, an aminoalkyl group, and an alkylamino group; at least one R.sup.3 is a C1 to C3 alkyl group which is substituted with any of the groups selected from an amino group, an aminoalkyl group, and an alkylamino group; R.sup.4 represents a C1 to C4 alkyl group; b is 1 or 2; a plurality of R.sup.3s may be identical to or different from one another; and a plurality of OR.sup.4s may be identical to or different from one another.

8. An aminosilane-modified colloidal silica dispersion production method according to claim 7, which comprises: (a) adding a polar solvent S1 having a dielectric constant at 20 C. of 15 or higher and lower than 60 to a colloidal silica in which silica particles are dispersed in a non-polar solvent S2 having a dielectric constant at 20 C. of 1 or higher and lower than 15, and the silica particles have surfaces to which is bound a first silyl group represented by the following formula (1):
R.sup.1.sub.aSi(OR.sup.2).sub.3-aO(1) wherein R.sup.1 represents a C1 to C10 substituted or non-substituted alkyl group or a phenyl group; R.sup.2 represents a C1 to C4 alkyl group or a C1 to C4 alkoxyalkyl group; a is 1 to 3; a plurality of R.sup.1s may be identical to or different from one another; and a plurality of OR.sup.2s may be identical to or different from one another, in an amount of 0.05 to 5 mmol/g with respect to the mass of silica, such that the mass ratio (S1/S2) is adjusted to 0.3 to 6; and subsequently, mixing the colloidal silica with an aminosilane compound represented by the following formula (3):
R.sup.3.sub.bSi(OR.sup.4).sub.4-bO(3) wherein R.sup.3 represents a C1 to C4 alkyl group, a phenyl group, or a C1 to C3 alkyl group which is substituted with one or more groups selected from an amino group, an aminoalkyl group, and an alkylamino group; at least one R.sup.3 is a C1 to C3 alkyl group which is substituted with any of the groups selected from an amino group, an aminoalkyl group, and an alkylamino group; R.sup.4 represents a C1 to C4 alkyl group; b is 1 or 2; a plurality of R.sup.3s may be identical to or different from one another; and a plurality of OR.sup.4s may be identical to or different from one another, in an amount of 0.02 to 3.0 mmol/g with respect to the mass of silica; (b) adjusting the water content of the mixture to a mole ratio of 0.05 to 1.8 with respect to the aminosilane compound; and (c) thermally treating the colloidal silica dispersion obtained in (b) at 20 to 200 C.

9. A method for producing a surface-treated colloidal silica dispersion containing silica particles having surfaces to which a functional group having a radical-generation site has been introduced, wherein the method comprises: (a), (b), and (c) employed in claim 8; and subsequently: (d) adding, to the aminosilane-modified colloidal silica dispersion obtained in (c), a compound represented by the following formula (4):
XY(4) wherein X represents a halo-carbonyl group, a carboxyl group, an aldehyde group, an isocyanate group, a thioisocyanate group, or an active ester group including a succinimido group; and Y represents an acetophenone derivative, an acyl phosphine oxide derivative, a titanocene derivative, a triazine derivative, a bisimidazole derivative, an O-acyloxime derivative, a benzophenone derivative, a thioxanthone derivative, an -diketone derivative, an anthraquinone derivative, an azo compound derivative, or a peroxide derivative, in an equivalent of 0.05 to 100 with respect to the amount by mole of the aminosilane compound employed in (a); and heating the mixture at 20 to 200 C.

10. A method according to claim 9 for producing a surface-treated colloidal silica dispersion containing silica particles having surfaces to which a functional group having a radical-generation site has been introduced, which method comprises, in (d), adding at least one condensing agent selected from the group consisting of a triazine-type condensing agent, an imidazole-type condensing agent, a phosphonium salt-type condensing agent, a carbodiimide-type condensing agent, a uronium-type condensing agent, and a succinimide-type condensing agent to a compound represented by the following formula (4):
XY(4) wherein X represents a halo-carbonyl group, a carboxyl group, an aldehyde group, an isocyanate group, a thioisocyanate group, or an active ester group including a succinimido group; and Y represents an acetophenone derivative, an acyl phosphine oxide derivative, a titanocene derivative, a triazine derivative, a bisimidazole derivative, an O-acyloxime derivative, a benzophenone derivative, a thioxanthone derivative, an -diketone derivative, an anthraquinone derivative, an azo compound derivative, or a peroxide derivative, in an equivalent of 0.01 to 100 with respect to the amount by mole of the compound (4).

11. A method for producing a surface-treated colloidal silica dispersion containing silica particles having polymer-grafted surfaces, wherein the method comprises adding a polymerizable monomer to surface-treated colloidal silica dispersion comprising silica particles having surfaces to which a functional group having a radical-generation site has been introduced and produced through a method as recited in claim 9, and performing radical polymerization via an activate energy ray or heat.

12. An aminosilane-modified colloidal silica dispersion production method according to claim 7, which method comprises: (e) adding a non-polar solvent S2 having a dielectric constant at 20 C. of 1 or higher and lower than 15 to a colloidal silica in which silica particles are dispersed in a polar solvent S1 having a dielectric constant at 20 C. of 15 or higher and lower than 60, and the silica particles have surfaces to which a first silyl group represented by the following formula (1):
R.sup.1.sub.aSi(OR.sup.2).sub.3-aO(1) wherein R.sup.1 represents a C1 to C10 substituted or non-substituted alkyl group or a phenyl group; R.sup.2 represents a C1 to C4 alkyl group or a C1 to C4 alkoxyalkyl group; a is 1 to 3; a plurality of R.sup.1s may be identical to or different from one another; and a plurality of OR.sup.2s may be identical to or different from one another, is bound in an amount of 0.05 to 5 mmol/g with respect to the mass of silica, such that the mass ratio (S1/S2) is adjusted to 1 to 6; and subsequently, mixing the colloidal silica with an aminosilane compound represented by the following formula (3):
R.sup.3.sub.bSi(OR.sup.4).sub.4-bO(3) wherein R.sup.3 represents a C1 to C4 alkyl group, a phenyl group, or a C1 to C3 alkyl group which is substituted with one or more groups selected from an amino group, an aminoalkyl group, and an alkylamino group; at least one R.sup.3 is a C1 to C3 alkyl group which is substituted with any of the groups selected from an amino group, an aminoalkyl group, and an alkylamino group; R.sup.4 represents a C1 to C4 alkyl group; b is 1 or 2; a plurality of R.sup.3s may be identical to or different from one another; and a plurality of OR.sup.4s may be identical to or different from one another, in an amount of 0.02 to 3.0 mmol/g with respect to the mass of silica; (f) adjusting the water content of the mixture to a mole ratio of 0.4 to 5 with respect to the aminosilane compound; and (g) thermally treating the colloidal silica dispersion obtained in (f) at 20 to 200 C.

13. A method for producing a surface-treated colloidal silica dispersion containing silica particles having surfaces to which a functional group having a radical-generation site has been introduced, wherein the method comprises: (e), (f), and (g) employed in claim 12; and subsequently: (h) adding, to the aminosilane-modified colloidal silica dispersion obtained in (g), a compound represented by the following formula (4):
XY(4) wherein X represents a halo-carbonyl group, a carboxyl group, an aldehyde group, an isocyanate group, a thioisocyanate group, or an active ester group including a succinimido group; and Y represents an acetophenone derivative, an acyl phosphine oxide derivative, a titanocene derivative, a triazine derivative, a bisimidazole derivative, an O-acyloxime derivative, a benzophenone derivative, a thioxanthone derivative, an -diketone derivative, an anthraquinone derivative, an azo compound derivative, or a peroxide derivative, in an equivalent of 0.05 to 100 with respect to the amount by mole of the aminosilane compound employed in (e); and heating the mixture at 20 to 200 C.

14. A method according to claim 13 for producing a surface-treated colloidal silica dispersion containing silica particles having surfaces to which a functional group having a radical-generation site has been introduced, wherein the method includes, in (h), adding at least one condensing agent selected from the group consisting of a triazine-type condensing agent, an imidazole-type condensing agent, a phosphonium salt-type condensing agent, a carbodiimide-type condensing agent, a uronium-type condensing agent, and a succinimide-type condensing agent to a compound represented by the following formula (4):
XY(4) wherein X represents a halo-carbonyl group, a carboxyl group, an aldehyde group, an isocyanate group, a thioisocyanate group, or an active ester group including a succinimido group; and Y represents an acetophenone derivative, an acyl phosphine oxide derivative, a titanocene derivative, a triazine derivative, a bisimidazole derivative, an O-acyloxime derivative, a benzophenone derivative, a thioxanthone derivative, an -diketone derivative, an anthraquinone derivative, an azo compound derivative, or a peroxide derivative, in an equivalent of 0.01 to 100 with respect to the amount by mole of the compound (4).

15. A method for producing a multi-branched-polymer-modified colloidal silica dispersion, wherein the method comprises: obtaining the aminosilane-modified colloidal silica dispersion produced by the method of claim 7; (i) adding an ,-unsaturated carbonyl compound to the aminosilane-modified colloidal silica dispersion, and heating the mixture at 10 to 200 C.; and (j) adding a diamine compound to the dispersion obtained in (i), and heating the mixture at 10 to 200 C.; and repeating (i) and (j) 2 to 10 times.

16. A method for producing an aminosilane-modified colloidal silica dispersion, the dispersion medium being only a polar solvent S1 having a dielectric constant at 20 C. of 15 or higher and lower than 60; wherein the method comprises: obtaining the aminosilane-modified colloidal silica dispersion produced by the method of claim 7; (k) heating the dispersion at 50 to 200 C. under a pressure of 10 to 760 Torr, while adding to the mixture a polar solvent S1 having a dielectric constant at 20 C. of 15 or higher and lower than 60, to thereby remove a non-polar solvent S2 having a dielectric constant at 20 C. of 1 or higher and lower than 15.

Description

EXAMPLES

(1) The present invention will next be described in detail by way of the Examples and the Comparative Examples. However, the Examples should not be construed as limiting the invention thereto.

(2) <Measurement of the Amount of Introduced Aminosilane>

(3) The amount of aminosilane introduced into the aminosilane-modified colloidal silica dispersion was obtained by centrifuging the formed aminosilane-modified colloidal silica dispersion at 5,000 rpm for 30 minutes, to thereby remove aminosilane remaining in the dispersion; drying the precipitates at 60 C. for 4 hours under reduced pressure; and measuring the nitrogen concentration by means of an element analyzer (PE2400 Series II CHNS/O Analyzer, product of Perkin Elmer).

Example 1

(4) To a 300-mL eggplant-shaped flask, a colloidal silica dispersion (in toluene) (particle size: 12 nm, silica concentration: 40 mass %, water content: 0.027 mass %, product of Nissan Chemical Industries, Ltd.) (100 g) was added, and then methanol (30 mass % with respect to non-polar solvent, product of Kanto Kagaku) (18 g) and 3-aminopropyltrimethoxysilane (KBM-903, product of Shin-Etsu Chemical Co., Ltd., 0.28 mmol/g with respect to silica) (2 g) were added. Pure water (0.17 g) was added to the above mixture so that the water content was adjusted to a mole ratio of 1.0 mole with respect to aminosilane. The resultant mixture was maintained at 65 C. for 3 hours under stirring, to thereby yield 120.17 g of an aminosilane-modified colloidal silica dispersion. The thus-obtained aminosilane-modified colloidal silica dispersion was found to have a silica concentration of 33.3 mass %, a toluene concentration of 50.0 mass %, a methanol concentration of 14.9 mass %, and a water content of 0.14 mass %, and was in a favorable dispersion state. The amount of aminosilane introduced into silica was 0.21 mmol/g as obtained through element analysis.

Example 2

(5) The procedure of Example 1 was repeated, except that methanol (100 mass % with respect to non-polar solvent) (60 g) was added as a polar solvent, to thereby yield 162.17 g of an aminosilane-modified colloidal silica dispersion. The thus-obtained aminosilane-modified colloidal silica dispersion was found to have a silica concentration of 24.7 mass %, a toluene concentration of 37.0 mass %, a methanol concentration of 37.0 mass %, and a water content of 0.12 mass %, and was in a favorable dispersion state. The amount of aminosilane introduced into silica was 0.19 mmol/g.

Example 3

(6) The procedure of Example 1 was repeated, except that methanol (300 mass % with respect to non-polar solvent) (180 g) was added as a polar solvent, to thereby yield 282.17 g of an aminosilane-modified colloidal silica dispersion. The thus-obtained aminosilane-modified colloidal silica dispersion was found to have a silica concentration of 14.2 mass %, a toluene concentration of 21.3 mass %, a methanol concentration of 63.8 mass %, and a water content of 0.07 mass %, and was in a favorable dispersion state. The amount of aminosilane introduced into silica was 0.16 mmol/g.

Example 4

(7) The procedure of Example 1 was repeated, except that methanol (500 mass % with respect to non-polar solvent) (300 g) was added as a polar solvent, to thereby yield 402.17 g of an aminosilane-modified colloidal silica dispersion. The thus-obtained aminosilane-modified colloidal silica dispersion was found to have a silica concentration of 9.9 mass %, a toluene concentration of 14.9 mass %, a methanol concentration of 74.6 mass %, and a water content of 0.05 mass %, and was in a favorable dispersion state. The amount of aminosilane introduced into silica was 0.20 mmol/g.

Example 5

(8) The procedure of Example 1 was repeated, except that methanol. (166.7 mass % with respect to non-polar solvent (180 g) was added as a polar solvent, and heating was performed at 50 C. for about 15 hours, to thereby yield 202.17 g of an aminosilane-modified colloidal silica dispersion. The thus-obtained aminosilane-modified colloidal silica dispersion was found to have a silica concentration of 19.8 mass %, a toluene concentration of 29.7 mass %, a methanol concentration of 49.5 mass %, and a water content of 0.10 mass %, and was in a favorable dispersion state. The amount of aminosilane introduced into silica was 0.19 mmol/g.

Example 6

(9) The procedure of Example 1 was repeated, except that isobutyl alcohol (166.7 mass % with respect to non-polar solvent) (100 g) was added as a polar solvent, and heating was performed at 50 C. for about 15 hours, to thereby yield 202.17 g of an aminosilane-modified colloidal silica dispersion. The thus-obtained aminosilane-modified colloidal silica dispersion was found to have a silica concentration of 19.8 mass %, a toluene concentration of 29.7 mass %, an isobutyl alcohol concentration of 49.5 mass %, and a water content of 0.10 mass %, and was in a favorable dispersion state. The amount of aminosilane introduced into silica was 0.25 mmol/g.

Example 7

(10) The procedure of Example 1 was repeated, except that dimethyl sulfoxide (166.7 mass % with respect to non-polar solvent) (100 g) was added as a polar solvent, and heating was performed at 50 C. for about 15 hours, to thereby yield 202.17 g of an aminosilane-modified colloidal silica dispersion. The thus-obtained aminosilane-modified colloidal silica dispersion was found to have a silica concentration of 19.8 mass %, a toluene concentration of 29.7 mass %, a dimethyl sulfoxide concentration of 49.5 mass %, and a water content of 0.10 mass %, and was in a favorable dispersion state. The amount of aminosilane introduced into silica was 0.24 mmol/g.

Example 8

(11) The procedure of Example 1 was repeated, except that N-methylpyrrolidone (100 mass % with respect to non-polar solvent) (60 g) was added as a polar solvent, to thereby yield 162.17 g of an aminosilane-modified colloidal silica dispersion. The thus-obtained aminosilane-modified colloidal silica dispersion was found to have a silica concentration of 24.7 mass %, a toluene concentration of 37.0 mass %, an N-methylpyrrolidone concentration of 37.0 mass %, and a water content of 0.12 mass %, and was in a favorable dispersion state. The amount of aminosilane introduced into silica was 0.24 mmol/g.

Comparative Example 1

(12) The procedure of Example 1 was repeated, except that methanol serving as a polar solvent was not added, but 3-aminopropyltrimethoxysilane (2 g) was added. As a result, the mixture was gelled immediately after the addition, failing to form an aminosilane-modified colloidal silica dispersion.

Comparative Example 2

(13) The procedure of Example 1 was repeated, except that tetrahydrofuran was used instead of methanol. The amount of tetrahydrofuran was adjusted to 100 g (i.e., 166.7 mass % with respect to non-polar solvent), and 3-aminopropyltrimethoxysilane (2 g) was added. As a result, the mixture was gelled immediately after the addition, failing to form an aminosilane-modified colloidal silica dispersion.

Example 9

(14) To a 300-mL eggplant-shaped flask, a colloidal silica dispersion (in methyl isobutyl ketone) (particle size: 12 nm, silica concentration: 30 mass % and water content: 0.070 mass %, product of Nissan Chemical Industries, Ltd.) (100 g) was added, and then methanol (product of Kanto Kagaku) (21 g) and 3-aminopropyltrimethoxysilane (KBM-903, product of Shin-Etsu Chemical Co., Ltd., 0.28 mmol/g with respect to silica) (1.5 g) were added. Pure water (0.08 g) was added to the above mixture so that the water content was adjusted to a mole ratio of 1.0 mole with respect to aminosilane. The resultant mixture was maintained at 65 C. for 3 hours under stirring, to thereby yield 122.58 g of an aminosilane-modified colloidal silica dispersion. The thus-obtained aminosilane-modified colloidal silica dispersion was found to have a silica concentration of 24.5 mass %, a methyl isobutyl ketone concentration of 49.0 mass %, a methanol concentration of 17.0 mass %, and a water content of 0.12 mass % was in a favorable dispersion state. The amount of aminosilane introduced into silica was 0.20 mmol/g.

Comparative Example 3

(15) To a 300-mL eggplant-shaped flask, a colloidal silica dispersion (in methanol) (particle size: 12 nm, silica concentration: 30.5 mass %, water content: 0.20 mass %, product of Nissan Chemical Industries, Ltd.) (100 g) was added, and then 3-aminopropyltrimethoxysilane (KBM-903, product of Shin-Etsu Chemical Co., Ltd., 0.28 mmol/g with respect to silica) (1.5 g) was added. As a result, the mixture was gelled immediately after the addition, failing to form an aminosilane-modified colloidal silica dispersion.

Example 10

(16) The procedure of Example 1 was repeated, except that no pure water was added, to thereby yield 120 g of an aminosilane-modified colloidal silica dispersion. The thus-obtained aminosilane-modified colloidal silica dispersion was found to have a silica concentration of 33.3 mass %, a toluene concentration of 50.0 mass %, a methanol concentration of 14.9 mass %, and a water content of 0.022 mass %, and was in a favorable dispersion state. The amount of aminosilane introduced into silica was 0.23 mmol/g.

Example 11

(17) The procedure of Example 1 was repeated, except that pure water (0.27 g) was added so as to adjust the water content (by mole ratio) with respect to aminosilane to 1.5, to thereby yield 120.27 g of an aminosilane-modified colloidal silica dispersion. The thus-obtained aminosilane-modified colloidal silica dispersion was found to have a silica concentration of 33.3 mass %, a toluene concentration of 49.9 mass %, a methanol concentration of 14.9 mass %, and a water content of 0.25 mass %, and was in a favorable dispersion state. The amount of aminosilane introduced into silica was 0.23 mmol/g.

Comparative Example 4

(18) The procedure of Example 1 was repeated, except that pure water (0.37 g) was added, so as to adjust the mole ratio thereof to 2.0, with respect to aminosilane. As a result, the mixture was gelled during the heating treatment, failing to form an aminosilane-modified colloidal silica dispersion.

Example 12

(19) The procedure of Example 1 was repeated, except that heating was performed at 23 C. for 5 days, to thereby yield 120.17 g of an aminosilane-modified colloidal silica dispersion. The thus-obtained aminosilane-modified colloidal silica dispersion was found to have a silica concentration of 33.3 mass %, a toluene concentration of 50.0 mass %, a methanol concentration of 14.9 mass %, and a water content of 0.14 mass %, and was in a favorable dispersion state. The amount of aminosilane introduced into silica was 0.21 mmol/g.

Example 13

(20) The procedure of Example 1 was repeated, except that heating was performed at 40 C. for 6 hours, to thereby yield 120.17 g of an aminosilane-modified colloidal silica dispersion. The thus-obtained aminosilane-modified colloidal silica dispersion was found to have a silica concentration of 33.3 mass %, a toluene concentration of 50.0 mass %, a methanol concentration of 14.9 mass %, and a water content of 0.14 mass %, and was in a favorable dispersion state. The amount of aminosilane introduced into silica was 0.23 mmol/g.

Example 14

(21) The procedure of Example 1 was repeated, except that heating was performed at 65 C. for 30 minutes, to thereby yield 120.17 g of an aminosilane-modified colloidal silica dispersion. The thus-obtained aminosilane-modified colloidal silica dispersion was found to have a silica concentration of 33.3 mass %, a toluene concentration of 50.0 mass %, a methanol concentration of 14.9 mass %, and a water content of 0.14 mass %, and was in a favorable dispersion state. The amount of aminosilane introduced into silica was 0.23 mmol/g.

Example 15

(22) The procedure of Example 1 was repeated, except that dimethyl sulfoxide (166.7 mass % with respect to non-polar solvent) (100 g) was added as a polar solvent, and heating was performed at 120 C. for 3 hours, to thereby yield 202.17 g of an aminosilane-modified colloidal silica dispersion. The thus-obtained aminosilane-modified colloidal silica dispersion was found to have a silica concentration of 19.8 mass %, a toluene concentration of 29.7 mass %, a dimethyl sulfoxide concentration of 49.5 mass %, and a water content of 0.10 mass %, and was in a favorable dispersion state. The amount of aminosilane introduced into silica was 0.24 mmol/g.

Example 16

(23) The procedure of Example 1 was repeated, except that 3-aminopropyltrimethoxysilane was added in an amount of 4 g (0.56 mmol/g with respect to silica), and no pure water was added, to thereby yield 122 g of an aminosilane-modified colloidal silica dispersion. The thus-obtained aminosilane-modified colloidal silica dispersion was found to have a silica concentration of 32.8 mass %, a toluene concentration of 49.2 mass %, a methanol concentration of 14.8 mass %, and a water content of 0.022 mass %, and was in a favorable dispersion state. The amount of aminosilane introduced into silica was 0.21 mmol/g.

Example 17

(24) The procedure of Example 1 was repeated, except that 3-aminopropyltrimethoxysilane was added in an amount of 20 g (2.8 mmol/g with respect to silica), and no pure water was added, to thereby yield 138 g of an aminosilane-modified colloidal silica dispersion. The thus-obtained aminosilane modified colloidal silica dispersion was found to have a silica concentration of 29.0 mass %, a toluene concentration of 43.5 mass %, a methanol concentration of 13.0 mass %, and a water content of 0.019 mass %, and was in a favorable dispersion state. The amount of aminosilane introduced into silica was 0.41 mmol/g.

Example 18

(25) To a 300-mL, eggplant-shaped flask, a surface-treated colloidal silica dispersion (in methanol) (particle size: 12 nm, silica concentration: 30 mass %, water content: 0.60 mass %, product of Nissan Chemical Industries, Ltd.) (100 g). Subsequently, toluene (166.7 mass % (polar solvent non-polar solvent), product of Kanto Kagaku) (42 g) as a non-polar solvent and 3-aminopropyltrimethoxysilane (KBM-903, product of Shin-Etsu Chemical Co., Ltd., 0.28 mmol/g with respect to silica) (1.51 g) were added, and the mixture was agitated. The water content was 3.91 by mole ratio, with respect to aminosilane. Subsequently, the resultant mixture was heated at about 50 C. for about 15 hours, to thereby yield 143.51 g of an aminosilane-modified colloidal silica dispersion. The thus-obtained aminosilane-modified colloidal silica dispersion was found to have a silica concentration of 20.9 mass %, a methanol concentration of 48.8 mass %, a toluene concentration of 48.8 mass %, and a water content of 0.41 mass %, and was in a favorable dispersion state. The amount of aminosilane introduced into silica was 0.20 mmol/g.

Example 19

(26) The procedure of Example 18 was repeated, except that the amount of toluene was changed to 70.1 g (100 mass % (polar solvent/non-polar solvent)), to thereby yield 171.61 g of an aminosilane-modified colloidal silica dispersion. The water content was 3.98 by mole ratio, with respect to aminosilane. The thus-obtained aminosilane-modified colloidal silica dispersion was found to have a silica concentration of 17.5 mass %, a methanol concentration of 40.8 mass %, a toluene concentration of 40.8 mass %, and a water content of 0.35 mass %, and was in a favorable dispersion state. The amount of aminosilane introduced into silica was 0.19 mmol/g.

Comparative Example 5

(27) The procedure of Example 18 was repeated, except that a surface-treated colloidal silica (dispersed in methanol, water content: 1.24 mass %, particle size: 12 nm, silica concentration: 30 mass %, product of Nissan Chemical Industries, Ltd.) was used. As a result, the mixture was gelled immediately after addition of 3-aminopropyltrimethoxysilane, failing to form an aminosilane-modified colloidal silica dispersion. Notably, water content was 8.18 by mole ratio, with respect to aminosilane.

Comparative Example 6

(28) The procedure of Example 18 was repeated, except that surface-non-treated colloidal silica (dispersed in methanol, particle size: 12 nm, silica concentration: 30 mass %, water content: 0.60 mass %, product of Nissan Chemical Industries, Ltd.) (50 g) was used, and the amount of toluene was changed to 116.7 g (30 mass % (polar solvent/non-polar solvent)). When 3-aminopropyltrimethoxysilane (0.75 g, 0.28 mmol/g with respect to silica) was added to the mixture, the mixture was gelled immediately after addition, failing to form an aminosilane-modified colloidal silica dispersion. Notably, the water content was 3.98 by mole ratio, with respect to aminosilane.

Synthesis Example 1

(29) To a 100-mL round-bottom flask, 4,4-azobis(4-cyanovaleric acid) (hereinafter abbreviated as ACVA) (5 g (0.0178 mol)), N,N-dimethyl-4-aminopyridine (hereinafter abbreviated as DMAP) (0.128 g), tetrahydrofuran (hereinafter abbreviated as THF) (50 mL), and n-propanol (1.07 g (0.0178 mol, equivalent to ACVA)) were added, and the mixture was stirred at 0 C. N,N-Dicyclohexylcarbodiimide (hereinafter abbreviated as DCC) (3.67 g (0.0178 mol)) serving as a condensing agent and dissolved in dichloromethane (20 mL) was gradually added to the stirred mixture by means of a burette, and then, the mixture was allowed to stand at 0 C. for 12 hours. Subsequently, by-products were removed through filtration under reduced pressure, and the filtrate was concentrated under reduced pressure by means of an evaporator, to thereby remove THF. Dichloromethane (50 mL) was added to the concentrated product, and the mixture was transferred to a separatory funnel. The mixture was thrice subjected to liquid separation by use of saturated brine, to thereby remove unreacted ACVA. The thus-recovered organic layer was transferred to a beaker, and an appropriate amount of magnesium sulfate was added thereto for dehydration. Magnesium sulfate was removed through filtration under reduced pressure, and the filtrate was concentrated again by means of an evaporator, to thereby synthesize ACVA-MP in which one end carboxyl group of ACVA was protected with n-propanol.

Synthesis Example 2

(30) The procedure of Synthesis example 1 was repeated, except that ACVA (3 g (0.011 mol), DMAP (0.077 g), benzyl alcohol (1.13 g (0.0105 mol)) (instead of n-propanol (1.07 g)), and DCC (2.27 g (0.011 mol)) were employed, to thereby synthesize ACVA-Bz in which one end carboxyl group of ACVA was protected with benzyl alcohol.

Synthesis Example 3

(31) To a 100-mL round-bottom flask, ACVA (1 g (0.00357 mol)), N-hydroxysuccinimide (hereinafter abbreviated as NHS) (0.41 g (0.00357 mol)), THF (50 mL), and acetonitrile (25 mL) were added, and the mixture was stirred at 0 C. Water-soluble carbodiimide (hereinafter abbreviated as WSC) (0.68 g (0.00357 mol) serving as a condensing agent was added to the stirred mixture, and the resultant mixture was stirred at 25 C. for 24 hours in the dark. Subsequently, the solvent was removed through concentration under reduced pressure by means of an evaporator. Ion-exchange water was added to the concentrated product under stirring, to thereby form white precipitates. The white precipitates were separated, to thereby synthesize ACVA-NHS in which one end carboxyl group of ACVA was activated with NHS.

Example X1

(32) The procedure of Example 1 was repeated, except that the amount of colloidal silica (dispersed in toluene) was changed to 5 g, and the reaction scale (including the reactor) was reduced, to thereby form an aminosilane-modified colloidal silica dispersion. To the dispersion, added were a solution containing ACVA-MP synthesized in Synthesis example 1 (0.17 g (0.95 mole equivalents with respect to the used aminosilane compound)) and 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (hereinafter abbreviated as DMT-MM) (0.15 g (1 mole equivalent with respect to ACVA-MP)) serving as a condensing agent which were dissolved in a mixed solvent of toluene (6.6 mL) and methanol (2 mL), and the resultant mixture was allowed to react at 35 C. for 6 hours under stirring, to thereby yield a surface-treated colloidal silica dispersion in which ACVA-MP was bound to surface amino groups of colloidal silica particles via amido bonds, and azo groups were introduced as radical-generation sites. The thus-obtained dispersion underwent no gelation and maintained high dispersibility.

Example X2

(33) The procedure of Example X1 was repeated, except that ACVA-Bz synthesized in Synthesis example 2 was used instead of ACVA-MP, and ACVA-Bz (1.0 g (4.84 mole equivalents with respect to the used aminosilane compound)) and DMT-MM (0.75 g (1 mole equivalent with respect to ACVA-Bz)) were dissolved in a mixed solvent of toluene (16.6 mL) and methanol (5 mL), to thereby yield a surface-treated colloidal silica dispersion in which ACVA-Bz was bound to surface amino groups of colloidal silica particles via amido bonds, and azo groups were introduced as radical-generation sites. The thus-obtained dispersion underwent no gelation and maintained high dispersibility.

Comparative Example X1

(34) The procedure of Example X1 was repeated, except that ACVA was used instead of ACVA-MP, in an amount of 0.15 g (0.96 mole equivalents with respect to the used aminosilane compound). In this case, the dispersion was gelled before addition of ACVA and heating, thereby failing to produce a surface-treated colloidal silica dispersion in which azo groups were introduced as radical-generation sites.

Example X3

(35) The procedure of Example 7 was repeated, except that the reaction scale (including the reactor) was reduced; the amount of colloidal silica (dispersed in toluene) was changed to 3 g; the amount of toluene was changed to 3 mL; the amount of dimethyl sulfoxide was changed to 5 mL; and heating was performed at 65 C. for 3 hours, to thereby form an aminosilane-modified colloidal silica dispersion. To the dispersion, added were a solution containing ACVA-MP synthesized in Synthesis example 1 (0.16 g (1.44 mole equivalents with respect to the used aminosilane compound)) and DMT-MM (0.13 g (1 mole equivalent to ACVA-MP)) serving as a condensing agent which were dissolved in a mixed solvent of toluene (3 mL) and dimethyl sulfoxide (3 mL), and the resultant mixture was allowed to react at 35 C. for 6 hours under stirring, to thereby yield a surface-treated colloidal silica dispersion in which ACVA-MP was bound to surface amino groups of colloidal silica particles via amido bonds, and azo groups were introduced as radical-generation sites. The thus-obtained dispersion underwent no gelation and maintained high dispersibility.

(36) In Example X3, the surface-treated colloidal silica dispersion in which azo groups were introduced as radical-generation sites was subjected to thermogravimetric analysis. As a result, the azo group introduction amount was determined to 0.11 mmol/g with respect to silica.

Example X4

(37) The procedure of Example X3 was repeated, except that ACVA-Bz was used instead of ACVA-MP, in an amount of 0.18 g (1.43 mole equivalents with respect to the used aminosilane compound), to thereby yield a surface-treated colloidal silica dispersion in which ACVA-Bz was bound to surface amino groups of colloidal silica particles via amido bonds, and azo groups were introduced as radical-generation sites. The thus-obtained dispersion underwent no gelation and maintained high dispersibility.

(38) In Example X4, the surface-treated colloidal silica dispersion in which azo groups were introduced as radical-generation sites was subjected to thermogravimetric analysis. As a result, the azo group introduction amount was determined to 0.10 mmol/g with respect to silica.

Example XX1

(39) The procedure of Example X3 was repeated, except that N-methylpyrrolidone was used instead of dimethyl sulfoxide, and ACVA-Bz was used instead of ACVA-MP, in an amount of 0.18 g (1.43 mole equivalents with respect to the used aminosilane compound), to thereby yield a surface-treated colloidal silica dispersion in which ACVA-Bz was bound to surface amino groups of colloidal silica particles via amido bonds, and azo groups were introduced as radical-generation sites. The thus-obtained dispersion underwent no gelation and maintained high dispersibility. Notably, the surface-treated colloidal silica dispersion in which azo groups were introduced as radical-generation sites was subjected to thermogravimetric analysis. As a result, the azo group introduction amount was determined to 0.15 mmol/g with respect to silica. Thus, the azo group introduction amount was found to be enhanced by using N-methylpyrrolidone instead of dimethyl sulfoxide as a reaction solvent.

Example X5

(40) The procedure of Example X3 was repeated, except that ACVA-NHS synthesized in Synthesis example 3 was added instead of ACVA-MP, in an amount of 0.18 g (1.43 mole equivalents with respect to the used aminosilane compound), and no condensing agent was used. In this case, NHS groups were eliminated. As a result, there was obtained a surface-treated colloidal silica dispersion in which ACVA was bound to surface amino groups of colloidal silica particles via amido bonds, and azo groups were introduced as radical-generation sites. The thus-obtained dispersion underwent no gelation and maintained high dispersibility.

(41) In Example X5, the surface-treated colloidal silica dispersion in which azo groups were introduced as radical-generation sites was subjected to thermogravimetric analysis. As a result, the azo group introduction amount was determined to 0.17 mmol/g with respect to silica. Also, in preparation of the surface-treated colloidal silica dispersion having azo groups introduced as radical-generation sites by means of amino groups on the surface of the colloidal silica particles, the azo group introduction amount was found to be increased through activating terminal carboxylic groups to be reacted with amino groups by use of NHS without using a condensing agent.

Example XX2

(42) The procedure of Example X3 was repeated, except that N-methylpyrrolidone was used instead of dimethyl sulfoxide, and ACVA-NHS was used instead of ACVA-MP; that ACVA-NHS in an amount of 0.18 g (1.43 mole equivalents with respect to the used aminosilane compound) was used; and no condensing agent was used. As a result, NHS groups were eliminated, and ACVA formed amido bonds with surface amino groups of the colloidal silica, to thereby yield a surface-treated colloidal silica dispersion in which azo groups were introduced as radical-generation sites. The thus-obtained dispersion underwent no gelation and maintained high dispersibility. Through thermogravimetric analysis, the azo group introduction amount was determined to 0.20 mmol/g with respect to silica. Thus, the azo group introduction amount was found to be enhanced by using N-methylpyrrolidone instead of dimethyl sulfoxide as a reaction solvent.

Example X6

(43) The surface-treated colloidal silica dispersion in produced in Example X3 in which azo groups were introduced as radical-generation sites was subjected to centrifugation at 20,000 rpm for 6 hours, whereby the solvent was removed from the solid content. Unreacted products were also removed along with the solvent. Subsequently, toluene (15 mL) and dimethyl sulfoxide (4.5 mL) were added to the solid content, and the mixture was ultrasonicated, so as to re-disperse the solid content, to thereby prepare a surface-treated colloidal silica dispersion in which azo groups were introduced as radical-generation sites. To the thus-prepared dispersion, methyl methacrylate (hereinafter abbreviated as MMA) (5 mL) was added, and the mixture was heated at 70 C. for 24 hours under stirring for polymerization. MMA was polymerized by the mediation of the radicals generated from the introduced azo groups, to thereby form a PMMA-grafted surface-treated colloidal silica dispersion. The thus-obtained dispersion was not gelled, assumed yellow, and maintained high dispersibility. Separately, the solid content was centrifuged with a solvent at 20,000 rpm for 12 hours, and the separated solid was washed, to thereby recover a new solid. The solid was dried and subjected to thermogravimetric analysis (TGA), to thereby calculate a PMMA grafting ratio (percent). As a result, the percent PMMA grafting ratio was 26% based on the weight of silica.

Example X7

(44) The procedure of Example X6 was repeated, except that the surface-treated colloidal silica dispersion obtained in Example X4 in which dispersion azo groups were introduced as radical-generation sites was used. In this case, MMA was polymerized by the mediation of the radicals generated from the introduced azo groups, to thereby form a PMMA-grafted surface-treated colloidal silica dispersion. The thus-obtained dispersion was not gelled, assumed yellow, and maintained high dispersibility. Notably, the percent PMMA grafting ratio was 14% based on the weight of silica.

Example XX3

(45) The procedure of Example X6 was repeated, except that the surface-treated colloidal silica dispersion obtained in Example XX1 in which dispersion azo groups were introduced as radical-generation sites was used, and that N-methylpyrrolidone was used instead of dimethyl sulfoxide. In this case, MMA was polymerized by the mediation of the radicals generated from the introduced azo groups, to thereby form a PMMA-grafted surface-treated colloidal silica dispersion. The thus-obtained dispersion was not gelled, and maintained high dispersibility. Notably, the percent PMMA grafting ratio was 52% based on the weight of silica. Thus, the percent PMMA grafting ratio was found to be enhanced by use of N-methylpyrrolidone as a solvent for PMMA grafting, instead of dimethyl sulfoxide.

Example XX4

(46) The procedure of Example X6 was repeated, except that the surface-treated colloidal silica dispersion obtained in Example XX2 in which dispersion azo groups were introduced as radical-generation sites was used, and that N-methylpyrrolidone was used instead of dimethyl sulfoxide. In this case, MMA was polymerized by the mediation of the radicals generated from the introduced azo groups, to thereby form a PMMA-grafted surface-treated colloidal silica dispersion. The thus-obtained dispersion was not gelled, and maintained high dispersibility. Notably, the percent PMMA grafting ratio was 67% based on the weight of silica. In preparation of the surface-treated colloidal silica dispersion having azo groups introduced as radical-generation sites, the azo group introduction amount was found to be increased through activating terminal carboxylic groups to be reacted with amino groups by use of NHS without using a condensing agent. In addition, the final percent PMMA grafting ratio was found to be enhanced.

Example XX5

(47) Poly(methyl methacrylate) powder (av. mol. weight (Mw) of 15,000, product of Wako Pure Chemical Industries, Ltd.) (0.5 g) was dissolved in a mixed solvent of N-methylpyrrolidone (6.0 mL) and ethylene glycol monobutyl ether (0.6 mL). Separately, the PMMA-grafted surface-treated colloidal silica dispersion obtained in Example XX4 was subjected to centrifugation at 20,000 rpm for 12 hours, and the solid was separated and washed, to thereby form PMMA-grafted surface-treated colloidal silica particles (0.5 g (as silica), 0.84 g as PMMA-grafted silica particles). The silica particles were added to the above mixture, to thereby prepare a coating solution. The coating solution was added dropwise to a glass substrate, and the applied coating solution was spread by means of a spin coater at 1,000 rpm for 30 seconds. The coating solution was dried, to thereby form a composite thin film formed of a PMMA-grafted surface-treated colloidal silica and PMMA. The thus-obtained composite thin film was smooth and transparent. Also, the thin film was uniformed, such that no aggregates having dimensions of some tens of micrometers were identified through observation under a digital microscope (500).

Comparative Example XX1

(48) The procedure of Example XX5 was repeated, except that the colloidal silica dispersion (in toluene) (particle size: 12 nm, product of Nissan Chemical Industries, Ltd.) was used instead of the PMMA-grafted surface-treated colloidal silica dispersion, to thereby prepare a composite thin film of colloidal silica and PMMA. The thus-obtained composite thin film was smooth and transparent. However, some aggregates having such dimensions of 10 to 20 m were detected through observation under a digital microscope (500). Thus, microscopic uniformity was poor.

Example X8

(49) The procedure of Example 7 was repeated, except that the reaction scale (including the reactor) was reduced; the amount of colloidal silica (dispersed in toluene) was changed to 5 g; the amount of toluene was changed to 1.6 mL; the amount of dimethyl sulfoxide was changed to 5 mL; and heating was performed at 65 C. for 3 hours, to thereby form an aminosilane-modified colloidal silica dispersion. To the colloidal silica dispersion, added were 2-benzoylbenzoic acid (hereinafter abbreviated as BBA) (1.18 g (1.43 mole equivalents with respect to the used aminosilane compound) and DMT-MM (0.22 g (1 mole equivalent with respect to BBA)) serving as a condensing agent which were dissolved in a mixed solvent of toluene (3 mL) and dimethyl sulfoxide (3 mL). The resultant mixture was allowed to react at 60 C. for 6 hours under stirring, to thereby yield a surface-treated colloidal silica dispersion in which BBA was bound to surface amino groups of colloidal silica particles via amido bonds, and BBA groups were introduced as radical-generation sites. The thus-obtained dispersion underwent no gelation and maintained high dispersibility.

Example X9

(50) The surface-treated colloidal silica dispersion in produced in Example X8 in which BBA was introduced as a radical-generation site was subjected to centrifugation at 20,000 rpm for 6 hours, whereby the solvent was removed from the solid content. Unreacted products were also removed along with the solvent. Subsequently, toluene (15 mL) and dimethyl sulfoxide (4.5 mL) were added to the solid content, and the mixture was ultrasonicated, so as to re-disperse the solid content, to thereby prepare a surface-treated colloidal silica dispersion in which BBA was introduced as a radical-generation site. To the thus-prepared dispersion, methyl methacrylate (hereinafter abbreviated as MMA) (5 mL) was added, and the mixture was stirred with a stirrer for 24 hours under irradiation with UV for polymerization. MMA was photo-polymerized by the mediation of the radicals generated from introduced BBA, to thereby form a PMMA-grafted surface-treated colloidal silica dispersion. The thus-obtained dispersion was not gelled, assumed yellow, and maintained high dispersibility. Separately, the solid content was centrifuged with a solvent at 20,000 rpm for 12 hours, and the separated solid was washed, to thereby recover a new solid. The solid was dried and subjected to thermogravimetric analysis (TGA), to thereby calculate a percent PMMA grafting ratio. As a result, the percent PMMA grafting patio was 6.9% based on the weight of silica.

Example XX6

(51) The surface-treated colloidal silica dispersion in produced in Example X8 in which BBA was introduced as a radical-generation site was subjected to centrifugation at 20,000 rpm for 6 hours, whereby the solvent was removed from the solid content. Unreacted products were also removed along with the solvent. Subsequently, the thus-recovered solid content (1.2 g as silica) and polyethylene glycol diacrylate having a molecular weight (Mn) of 700 (1.0 g) were added to N-methylpyrrolidone (1.0 mL) with mixing, to thereby prepare a varnish of a surface-treated colloidal silica dispersion in which BBA was introduced. The varnish was poured into a mold (20 mm30 mm1 made of Teflon plates and irradiated with UV (intensity: 100 W, wavelength: 312 to 577 nm) for 30 minutes, for bulk curing. As a result, BBA introduced to the colloidal silica worked as a photo-radical polymerization initiator, and a transparent bulk cure product was yielded.

Comparative Example XX2

(52) The procedure of Example XX6 was repeated, except that a colloidal silica (dispersed in toluene, particle size: 12 nm, product of Nissan Chemical industries, Ltd.) (3 g) was used instead of the surface-treated colloidal silica dispersion in which BBA was introduced as a radical-generation site. The varnish was tried to be bulk-cured, but no bulk cure product was yielded.

Example X10

(53) The procedure of Example 1 was repeated, except that the amount of the colloidal silica dispersion in toluene was changed to 5 g, and the reaction scale (including the reactor) was reduced, to thereby form an aminosilane-modified colloidal silica dispersion. To the dispersion, methyl acrylate (hereinafter abbreviated as MA) (5 mL) was added, and the mixture was heated at 50 C. for 24 hours under stirring by means of a stirrer, to thereby cause Michel reaction between MA and amino groups on the surfaces of colloidal silica particles. Thereafter, the reaction product was centrifuged at 20,000 rpm for 6 hours, whereby the solvent was removed from solid content. Unreacted MA was also removed along with the solvent. Subsequently, methanol (hereinafter abbreviated as MeOH) (10 mL) was added to the solid content, and the mixture was ultrasonicated, to thereby re-disperse the solid content. To the dispersion, ethylenediamine (hereinafter abbreviated as EDA) (5 mL) was added, and the mixture was heated at 50 C. for 24 hours under stirring by means of a stirrer, to thereby introduce amino groups to the terminals again. Thereafter, the reaction product was centrifuged at 20,000 rpm for 6 hours, whereby the solvent was removed from the solid content. Unreacted EDA was also removed along with the solvent. Again, MeOH (10 mL) was added to the solid content, and the mixture was ultrasonicated, to thereby re-disperse the solid content. Thus, a colloidal silica dispersion in which amidoamine (hereinafter abbreviated as AMAM) was introduced to the surfaces of colloidal silica particles (1st-generation) was formed. The sequential procedure including addition of MA, centrifugation, re-dispersion, addition of EDA, centrifugation, and re-dispersion was repeated five times, whereby colloidal silica dispersions in which polyamidoamine (hereinafter abbreviated as PAMAM)-grafted dendrimers were introduced to the surfaces of colloidal silica particles (2- to 5-generation) were formed. The percent grafting ratio of the 5-generation PAMAM dendrimer-grafted colloidal silica dispersion was calculated through thermogravimetric analysis (TGA). As a result, the percent grafting ratio was 45% based on the weight of silica. The thus-obtained dispersions in which 1- to 5-generation PAMAM dendrimer-grafted colloidal silica dispersion were not gelled in each step, and maintained high dispersibility. Also, such high re-dispersibility may be maintained even after removal of the solvent through centrifugation.

Example XX7

(54) In Example X10, the colloidal silica dispersion to which 5-generation PAMAM dendrimer was grafted to the surfaces of colloidal silica particles was subjected to a sequential procedure including addition of MA, centrifugation, re-dispersion, addition of EDA, centrifugation, and re-dispersion was repeated five times, whereby colloidal silica dispersions in which polyamidoamine (hereinafter abbreviated as PAMAM) dendrimers were grafted to the surfaces of colloidal silica particles (6- to 10-generation) were formed. The percent grafting ratio of the 10-generation PAMAM dendrimer-grafted colloidal silica dispersion was calculated through thermogravimetric analysis (TGA). As a result, the percent grafting ratio was 422% based on the weight of silica, and the amino group content was 23.8 mmol/g based on the weight of silica. The thus-obtained dispersions in which 6- to 10-generation PAMAM dendrimer-grafted colloidal silica dispersion were not gelled in each step, and maintained high dispersibility. Also, such high re-dispersibility may be maintained even after removal of the solvent through centrifugation.

Example XX8

(55) The colloidal silica dispersion produced in Example X10 to which 5-generation PAMAM dendrimer was grafted to the surfaces of colloidal silica particles was subjected to centrifugation at 20,000 rpm for 6 hours, whereby the solvent was removed from the solid content. The thus-recovered solid content (1.0 g as silica) was mixed with a bisphenol A epoxy resin (Epichlon 850-S product of DIC) (0.5 g), to thereby prepare an epoxy resin-based varnish of a 5-generation PAMAM dendrimer-grafted colloidal silica. The varnish was poured into a mold (20 mm30 mm1 mm) made of Teflon plates and heated at 120 C. for 3 hours, for bulk curing. As a result, terminal amino groups of the PAMAM dendrimer grafted to colloidal silica particles worked as an epoxy curing agent, to thereby yield a yellow, transparent bulk cure product. The pensile hardness, as measured in accordance with JIS K5600 1-4 (the scratch method), was 2H.

Comparative Example XX3

(56) The procedure of Example XX8 was repeated, except that the 5-generation PAMAM dendrimer-grafted colloidal silica dispersion was not used, and hexamethylenediamine (0.1 g) was used as a curing agent so as to perform bulk curing. As a result, a transparent bulk cure product was obtained. However, the pensile hardness of the product was F, which was lower than that of a similar cured product obtained from the 5-generation PAMAM dendrimer-grafted colloidal silica.

Comparative Example XX4

(57) The procedure of Example XX8 was repeated, except that the colloidal silica dispersion (in toluene) (particle size: 12 nm, product of Nissan Chemical Industries, Ltd.) (1.2 g (0.5 g as silica) was used instead of the 5-generation PAMAM dendrimer-grafted colloidal silica dispersion, and that hexamethylenediamine (0.1 g) was used as a curing agent so as to perform bulk curing. As a result, a transparent bulk cure product was obtained. However, the pensile hardness of the product was H, which was lower than that of a similar cured product obtained from the 5-generation PAMAM dendrimer-grafted colloidal silica.

Example X11

(58) The aminosilane-modified colloidal silica dispersion obtained in Example 7 (100 g) was placed into a 300-mL eggplant-shaped flask. While N-methylpyrrolidone was added to the flask under a reduced pressure of 150 to 120 Torr by means of a rotary evaporator, the mixture was heated at 115 to 125 C. on an oil bath so as to remove toluene via distillation, to thereby yield 100 g of an aminosilane-modified colloidal silica dispersion having a dispersion medium formed only of N-methylpyrrolidone as a polar solvent. The thus-obtained aminosilane-modified colloidal silica dispersion was in a favorable dispersion state, with a silica concentration of 24.7 mass %.