JP2021070827A - Acid anhydride-dispersed alumina sol, use therefor and method for producing the same - Google Patents

Abstract

To provide a dispersion in which alumina particles are satisfactorily dispersed in a dispersion medium containing an acid anhydride as a dispersoid, and a method for producing the same.SOLUTION: The present disclosure provides a dispersion in which dispersoid particles containing alumina coated with a titanate coupling agent and/or an aluminate coupling agent are dispersed in a dispersion medium that contains an alicyclic or aliphatic carboxylic acid anhydride of a specific structure that is liquid at 20°C.SELECTED DRAWING: None

Description

The present invention uses dispersed particles containing alumina particles surface-coated with a titanate-based or aluminate-based coupling agent as a dispersoid, and is dispersed in a dispersion medium containing an acid anhydride. Regarding the method.

Alumina is chemically stable, has high hardness, electrical insulation, and high thermal conductivity, and is therefore widely used in electrical and electronic component materials, machine component materials, building materials, and the like in the industrial field. In particular, it has been proposed to use alumina as an insulating filler because it has high chemical resistance to _{sulfur hexafluoride (SF 6} ) as a medium for gas-insulated switching equipment in substations and power plants.
When alumina is used for such an insulating member, a cured product obtained by curing an epoxy resin composition in which alumina particles are mixed with an epoxy resin or the like is generally used. For example, a one-component epoxy resin composition in which alumina powder is added to an epoxy resin composition using a polybasic carboxylic anhydride as a curing agent is disclosed (Patent Document 1).

However, since the viscosity of the epoxy resin composition may increase in the one-component type and a problem may occur in handling, it has been proposed to use a two-component epoxy resin composition composed of a main component and a curing component. In this case, the alumina particles are blended with the main agent component containing an epoxy resin, the curing agent component containing an acid anhydride or the like, or both. If the alumina particles settle or form aggregates in the resin composition, the electrical properties of the obtained cured product may deteriorate, or the mechanical strength may become insufficient. Therefore, it is required that alumina is well dispersed in each component. In particular, from the viewpoint of ease of handling, a cured component in which alumina is well dispersed in an acid anhydride or the like is required.
For example, a liquid A containing an epoxy resin surface-treated with an alumina, an epoxy group-containing silane coupling agent, and acrylic resin particles, and an alumina and an acid anhydride not surface-treated with a coupling agent. A two-component epoxy resin composition comprising a liquid B containing the above is disclosed. (Patent Document 2)

Further, from the main agent component containing an epoxy resin, unsurface-treated alumina particles, a silane coupling agent, silica fine particles, and a curing accelerator, and a curing agent component containing an acid anhydride and unsurface-treated alumina particles. A two-component epoxy resin composition (Patent Document 3), a first solution containing an epoxy resin and an electrofusion alumina, and a second solution containing an acid anhydride and a curing accelerator surface-treated with aminosilane are blended. A two-component epoxy resin composition is also disclosed (Patent Document 4).

Japanese Unexamined Patent Publication No. 61-171725 Japanese Unexamined Patent Publication No. 2012-188611 Japanese Unexamined Patent Publication No. 2014-88498 Japanese Unexamined Patent Publication No. 2009-67884

In recent years, higher insulation performance and mechanical strength have been required for insulating members and the like, and alumina-dispersed epoxy resins having both insulating properties such as dielectric breakdown resistance and mechanical strength at a higher level have been strongly demanded. .. In order to meet such demands, the dispersed state of the alumina-containing particles is important, and it is effective to use a dispersion in which the alumina-containing particles are well dispersed in the curing agent component.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a dispersion liquid in which alumina-containing particles are well dispersed in a dispersion medium containing an acid anhydride as a dispersoid, and a method for producing the same. ..

As a result of diligent studies on the above problems, the present inventors have surface-coated the alumina-containing dispersoid particles with a titanate-based or aluminate-based coupling agent, whereby alumina is placed in a dispersion medium containing a specific acid anhydride. We have found that the dispersibility of the contained particles is dramatically improved, and based on this finding, we have completed the present invention.

（式中、Ｒ^１、及びＲ^２は炭素原子数１から３のアルキル基を示し、Ｒ^３は炭素原子数２から１２のアルケニル基を示し、ｎ_１及びｎ_２は０から１の整数を示す。）。
［２］
前記カルボン酸無水物（Ｉ）が、前記分散液の分散媒中に５質量％以上含まれる［１］に記載の分散液。
［３］
前記アルミナがα−アルミナ、β−アルミナ、γ−アルミナ、θ−アルミナ、及びアルミナ水和物からなる群より選ばれる少なくとも一種である［１］又は［２］に記載の分散液。
［４］
前記チタネート系カップリング剤（ＩＩ）が、式（２ａ）又は式（２ｂ）で示される構造を有する、［１］乃至［３］のいずれか１項に記載の分散液：

（式（２ａ）中、Ｒ^５はそれぞれ独立に炭素原子数１から１２のアルコキシ基、オキシ酢酸残基、又はエチレングリコール残基を示し、Ｘはそれぞれ独立にカルボキシル基、ホスフェート基、ピロホスフェイト基、ホスファイト基、スルホニル基、又はアミノエチル基、を示し、Ｒ^６はそれぞれ独立に炭素原子数１から１３のアルキル基、又はアリール基を示し、Ｙはヒドロキシル基を示す。ｎ_１、及びｎ_３はそれぞれ独立に０又は１の整数、ｎ_２は１、ｎ_４はそれぞれ独立に０から２の整数、ｍは１から３の整数を示す。）；

（式（２ｂ）中、Ｒ^７は炭素原子数１から１２のアルコキシ基、Ｚはホスフェート基、又はホスファイト基を示し、ｓは１から４の整数を示す。）。
［５］
前記チタネート系カップリング剤（ＩＩ）が、式（３ａ）、又は式（３ｂ）で示される構造を有する、［１］乃至［４］のいずれか１項に記載の分散液：

（式（３ａ）中、ｎ_５は１から３の整数を示す。）。
［６］
前記アルミネート系カップリング剤（ＩＩＩ）が、式（４）で示される構造を有する、［１］乃至［５］のいずれか１項に記載の分散液：

［７］
前記分散質粒子がさらに、式（５ａ）、又は式（５ｂ）で示される構造を有する加水分解性シランで表面被覆された、［１］乃至［６］のいずれか１項に記載の分散液：

（式（５ａ）、及び式（５ｂ）中、Ｒ^８及びＲ^１１は、それぞれ独立にアルキル基、フェニル基、ビニル基、アクリロキシ基、メタクリロキシ基、エポキシ基、イソシアネート基、メルカプト基、ウレイド基、アミノ基、若しくは酸無水物基、又はそれら官能基のいずれかを含む炭素原子数１から１０のアルキレン基であって、且つＳｉ−Ｃ結合によりケイ素原子と結合しているものであり、Ｒ^９及びＲ^１２は、それぞれ独立にアルコキシ基、アシルオキシ基、及びハロゲン基からなる群より選ばれる加水分解性基を示す。Ｙはアルキレン基、アリーレン基、ＮＨ基又は酸素原子を示す。ａは１から３の整数を示し、ｄはそれぞれ独立に０から２の整数を示し、ｅは０又は１の整数を示す。）。
［８］
前記分散質粒子の平均粒子径が２０ｎｍ乃至１０００ｎｍである［１］乃至［７］のいずれか１項に記載の分散液。
［９］
前記分散質粒子を、Ａｌ_２Ｏ_３の質量換算で０．１から５０質量％含有する［１］乃至［８］のいずれか１項に記載の分散液。
［１０］
［１］乃至［９］のいずれか１項に記載の分散液、及びエポキシ樹脂成分を含むエポキシ樹脂組成物。
［１１］
さらに平均粒子径１μｍ〜２０μｍの無機酸化物又は金属酸化物粒子を含む［１０］に記載のエポキシ樹脂組成物。
［１２］
前記エポキシ樹脂成分１等量に対して、前記カルボン酸無水物（Ｉ）を１．５から２．５等量の等量割合にて含有してなる、［１０］又は［１１］に記載のエポキシ樹脂組成物。
［１３］
さらに硬化促進剤を含む［１０］乃至［１２］のいずれか１項に記載のエポキシ樹脂組成物。
［１４］
［１０］乃至［１３］のいずれか１項に記載のエポキシ樹脂組成物の硬化物であるエポキシ樹脂硬化物。
［１５］
［１４］に記載のエポキシ樹脂硬化物を用いた絶縁部材。
［１６］
アルミナを含む分散質粒子とチタネート系カップリング剤（ＩＩ）、及び／又はアルミネート系カップリング剤（ＩＩＩ）とを、カルボン酸無水物（Ｉ）を含む分散媒中にて分散処理する工程を含む［１］乃至［９］のいずれか１項に記載の分散液の製造方法。
［１７］
前記分散処理する工程を、粉砕装置を用いて行う［１６］に記載の分散液の製造方法。
［１８］
前記粉砕装置が、ボールミル、ビーズミル、又はサンドミルである［１７］に記載の分散液の製造方法。 That is, the present invention and its embodiments are as follows.
[1]
Disperse particles containing alumina coated with the titanate-based coupling agent (II) and / or the aluminate-based coupling agent (III) are represented by the formula (1a), the formula (1b), or the formula (1c). Dispersion liquid dispersed in a dispersion medium containing a carboxylic acid anhydride (I) having a structure of the above and liquid at 20 ° C .:

(In the formula, R ¹ and R ² indicate an alkyl group having 1 to 3 carbon atoms, R ³ indicates an alkenyl group having 2 to 12 carbon atoms, and n ₁ and n ₂ represent an integer of 0 to 1. Show.).
[2]
The dispersion liquid according to [1], wherein the carboxylic acid anhydride (I) is contained in the dispersion medium of the dispersion liquid in an amount of 5% by mass or more.
[3]
The dispersion according to [1] or [2], wherein the alumina is at least one selected from the group consisting of α-alumina, β-alumina, γ-alumina, θ-alumina, and alumina hydrate.
[4]
The dispersion liquid according to any one of [1] to [3], wherein the titanate-based coupling agent (II) has a structure represented by the formula (2a) or the formula (2b):

(In the formula (2a), R ⁵ independently represents an alkoxy group having 1 to 12 carbon atoms, an oxyacetic acid residue, or an ethylene glycol residue, and X independently represents a carboxyl group, a phosphate group, and a pyrophosphate. It represents a group, a phosphite group, a sulfonyl group, or an aminoethyl group, where R ⁶ independently represents an alkyl or aryl group having 1 to 13 carbon atoms, and Y represents a hydroxyl group, n ₁ and. n ₃ is an independently integer of 0 or 1, n ₂ is 1, n ₄ is an independent integer of 0 to 2, and m is an integer of 1 to 3.);

(In formula (2b), R ⁷ represents an alkoxy group having 1 to 12 carbon atoms, Z represents a phosphate group or a phosphate group, and s represents an integer of 1 to 4).
[5]
The dispersion liquid according to any one of [1] to [4], wherein the titanate-based coupling agent (II) has a structure represented by the formula (3a) or the formula (3b):

(In equation (3a), n ₅ represents an integer from 1 to 3).
[6]
The dispersion liquid according to any one of [1] to [5], wherein the aluminate-based coupling agent (III) has a structure represented by the formula (4):

[7]
The dispersion according to any one of [1] to [6], wherein the dispersoid particles are further surface-coated with a hydrolyzable silane having a structure represented by the formula (5a) or the formula (5b). :

(In the formulas (5a) and (5b), R ⁸ and R ¹¹ are independently alkyl groups, phenyl groups, vinyl groups, acryloxy groups, metharoxy groups, epoxy groups, isocyanate groups, mercapto groups, ureido groups, respectively. It is an alkylene group having 1 to 10 carbon atoms containing any of an amino group, an acid anhydride group, or a functional group thereof, and is bonded to a silicon atom by a Si—C bond, and is R ⁹ And R ¹² represent a hydrolyzable group independently selected from the group consisting of an alkoxy group, an acyloxy group, and a halogen group, respectively. Y represents an alkylene group, an arylene group, an NH group, or an oxygen atom. An integer of 3 is indicated, d is an integer of 0 to 2 independently, and e is an integer of 0 or 1.).
[8]
The dispersion liquid according to any one of [1] to [7], wherein the average particle size of the dispersoid particles is 20 nm to 1000 nm.
[9]
The dispersion liquid according to any one of [1] to [8], which contains the dispersoid particles in _{an amount of 0.1 to 50% by mass in terms of mass of Al 2} O _3.
[10]
An epoxy resin composition containing the dispersion liquid according to any one of [1] to [9] and an epoxy resin component.
[11]
The epoxy resin composition according to [10], further comprising inorganic oxide or metal oxide particles having an average particle diameter of 1 μm to 20 μm.
[12]
[10] or [11], wherein the carboxylic acid anhydride (I) is contained in an equal amount of 1.5 to 2.5 equal amounts with respect to 1 equal amount of the epoxy resin component. Epoxy resin composition.
[13]
The epoxy resin composition according to any one of [10] to [12], which further contains a curing accelerator.
[14]
An epoxy resin cured product which is a cured product of the epoxy resin composition according to any one of [10] to [13].
[15]
An insulating member using the cured epoxy resin according to [14].
[16]
A step of dispersing disperse particles containing alumina and a titanate-based coupling agent (II) and / or an aluminate-based coupling agent (III) in a dispersion medium containing a carboxylic acid anhydride (I). The method for producing a dispersion according to any one of [1] to [9].
[17]
The method for producing a dispersion liquid according to [16], wherein the step of performing the dispersion treatment is performed using a pulverizer.
[18]
The method for producing a dispersion liquid according to [17], wherein the pulverizer is a ball mill, a bead mill, or a sand mill.

According to the present invention, by surface-coating the dispersoid particles containing alumina with a titanate-based or aluminate-based coupling agent, the alumina-containing particles are satisfactorily dispersed in the dispersion medium containing a specific acid anhydride. A dispersion can be obtained. Further, by preparing an epoxy resin composition using the dispersion, a cured epoxy resin having excellent properties such as high insulation and excellent mechanical properties such as high bending strength at a high level. Can be produced.

Hereinafter, preferred embodiments of the present invention will be described. However, the following embodiments are examples for explaining the present invention, and the present invention is not limited to the following embodiments.

式中、Ｒ^１、及びＲ^２は炭素原子数１から３のアルキル基を示し、Ｒ^３は炭素原子数２から１２のアルケニル基を示し、ｎ_１及びｎ_２は０から１の整数を示す。 In the present invention, disperse particles containing alumina particles surface-coated with a titanate-based coupling agent (II) and / or an aluminate-based coupling agent (III) have a specific chemical structure and are liquid at 20 ° C. It is a dispersion liquid dispersed in a dispersion medium containing the carboxylic acid anhydride (I) of the above, and the dispersion medium may also contain an organic solvent described later. Then, as an optional component, a pH adjuster, a viscosity adjuster, a curing accelerator and the like can be included.
Hereinafter, each element constituting the dispersion liquid of the present invention will be described in detail.
The carboxylic acid anhydride (I) is a compound represented by the following formula (1a), (1b), or (1c), and one of these may be used alone or a mixture of two or more kinds may be used. You may use it.

In the formula, R ¹ and R ² indicate an alkyl group having 1 to 3 carbon atoms, R ³ indicates an alkenyl group having 2 to 12 carbon atoms, and n ₁ and n ₂ indicate an integer of 0 to 1. ..

Specific examples of the carboxylic acid anhydride represented by the above formula (1a) include 2-methylhexahydrophthalic anhydride represented by the following formula (6a) and 4-methylhexahydro represented by the following formula (6b). Phthalic anhydride, 2-methylbicyclo [2.2.1] heptane-2,3-dicarboxylic acid anhydride represented by the following formula (6c), 4-methylbicyclo [2.2] represented by the following formula (6d). .1] Heptane-2,3-dicarboxylic acid anhydride and the like can be mentioned.

Specific examples of the carboxylic acid anhydride represented by the above formula (1b) are 2-methyl-1,2,3,6-tetrahydrophthalic anhydride represented by the following formula (7a) and represented by the following formula (7b). 4-Methyl-1,2,3,6-tetrahydrophthalic anhydride, 2-methyl-3,6 endomethylene-1,2,3,6-tetrahydrophthalic anhydride represented by the following formula (7c), described below. Examples thereof include 4-methyl-3,6 endomethylene-1,2,3,6-tetrahydrophthalic anhydride represented by the formula (7d).

これらのカルボン酸無水物は、１種類を単独で使用してもよく、２種類以上の混合物として使用してもよい。また、上記式（１ａ）、式（１ｂ）、又は式（１ｃ）で表される構造を有さないカルボン酸無水物と混合して使用してもよい。 Specific examples of the carboxylic acid anhydride represented by the above formula (1c) include tetrapropenyl succinic anhydride represented by the following formula (8a) and octenyl succinic anhydride represented by the following formula (8b).

These carboxylic acid anhydrides may be used alone or as a mixture of two or more. Further, it may be mixed with a carboxylic acid anhydride having no structure represented by the above formula (1a), formula (1b), or formula (1c).

Formula (1a), formula (1a), formula in the carboxylic acid anhydride mixture when used in combination with a carboxylic acid anhydride having no structure represented by the formula (1a), the formula (1b), or the formula (1c). The total content of the carboxylic acid anhydride having the structure represented by (1b) or the formula (1c) is 1% by mass to 95% by mass, preferably 20% by mass to 90% by mass, and more preferably 50% by mass. It can be% to 90% by mass.
The total content of the carboxylic acid anhydride in the dispersion medium can be 5% by mass to 90% by mass, preferably 30% by mass to 90% by mass, and more preferably 50% by mass to 90% by mass.

The titanate-based coupling agent (II) is an organic titanium compound having a hydrolyzable group and a hydrophobic functional group.
The number of hydrolyzable groups and hydrophobic functional groups contained in the titanate-based coupling agent (II) is not particularly limited, but 1 to 4 hydrolyzable groups and hydrophobic functional groups per titanium atom. It is preferable to have 1 to 3 groups.
As the hydrolyzable group, an alkoxy group, an oxyacetic acid residue, an ethylene glycol residue and the like are preferable, and when a plurality of hydrolyzable groups are present, they may be the same or different from each other.
As the hydrophobic functional group, a carboxyl group, a phosphate group, a pyrophosphate group, a phosphite group, a sulfonyl group, an aminoethyl group and the like are preferable, and when a plurality of the hydrophobic functional groups are present, they may be the same or different from each other.

式（２ａ）中、Ｒ^５はそれぞれ独立に炭素原子数１から１２のアルコキシ基、オキシ酢酸残基、又はエチレングリコール残基を示し、Ｘはそれぞれ独立にカルボキシル基、ホスフェート基、ピロホスフェイト基、ホスファイト基、スルホニル基、又はアミノエチル基、を示し、Ｒ^６はそれぞれ独立に炭素原子数１から１３のアルキル基、又はアリール基を示し、Ｙはヒドロキシル基を示す。ｎ_１、及びｎ_３はそれぞれ独立に０又は１の整数、ｎ_２は１、ｎ_４はそれぞれ独立に０から２の整数、ｍは１から３の整数を示す。
すなわち、Ｒ^５、Ｘ、及び／又はＲ^６が複数存在するときは、それらは同一であってもよく、互いに異なっていてもよい。同様に、４−ｍが２以上であるとき（式（２ａ）右辺の構造が複数存在するとき）は、複数のｎ_１、ｎ_３、及び／又はｎ_４は、同一であってもよく、互いに異なっていてもよい。

式（２ｂ）中、Ｒ^７はそれぞれ独立に炭素原子数１から１２のアルコキシ基、Ｚはそれぞれ独立にホスフェート基、又はホスファイト基を示し、ｓは１から４の整数を示す。
すなわち、Ｒ^７、及び／又はＺが複数存在するときは、それらは同一であってもよく、互いに異なっていてもよい。 Preferred examples of the titanate-based coupling agent (II) include compounds represented by the formula (2a) or the formula (2b).

In formula (2a), R ⁵ independently represents an alkoxy group, an oxyacetic acid residue, or an ethylene glycol residue having 1 to 12 carbon atoms, and X independently represents a carboxyl group, a phosphate group, or a pyrophosphate group, respectively. , Phosphite group, sulfonyl group, or aminoethyl group, R ⁶ independently represents an alkyl group or an aryl group having 1 to 13 carbon atoms, and Y represents a hydroxyl group. n ₁ and n ₃ independently indicate an integer of 0 or 1, n ₂ indicates an integer of 1, n ₄ independently indicates an integer of 0 to 2, and m indicates an integer of 1 to 3.
That is, when there are a plurality of ^{R 5} , X, and / or R ^{6, they may be the same or different from each other.} Similarly, when 4-m is 2 or more (when there are a plurality of structures on the right side of the equation (2a)), the plurality of n ₁ , n ₃ , and / or n ₄ may be the same. They may be different from each other.

In formula (2b), R ⁷ independently represents an alkoxy group having 1 to 12 carbon atoms, Z independently represents a phosphate group or a phosphite group, and s represents an integer of 1 to 4.
That is, when the R ^7, and / or Z there are multiple, they may be the same or may be different from each other.

式（３ａ）中、ｎ_５は１から３の整数を示す。 Specific examples of the titanate-based coupling agent represented by the above formula (2a) or the formula (2b) include isopropyltriisostealloy titanate represented by the following formula (3a) (available as Plenact TTS from Ajinomoto Fine-Techno Co., Ltd.). ), Tetraoctyl-bis (ditridecylphosphite) titanate represented by the following formula (3b) (available from Ajinomoto Fine-Techno Co., Ltd. as Plenact 46B), Tetra (2,2-) represented by the following formula (3c). Examples thereof include dialyloxymethyl-1-butyl) -bis (ditridecylphosphite) titanate and tetraisopropyl-bis (dioctylphosphite) titanate represented by the following formula (3d).

In equation (3a), n ₅ represents an integer from 1 to 3.

The aluminate-based coupling agent (III) is an organoaluminum compound having a hydrolyzable group and a hydrophobic functional group.
The number of hydrolyzable groups and hydrophobic functional groups contained in the aluminum-based coupling agent (III) is not particularly limited, but 1 to 4 hydrolyzable groups and 1 to 4 hydrolyzable groups per aluminum atom. It preferably has 1 to 3 hydrophobic functional groups.
As the hydrolyzable group, an alkoxy group, an oxyacetic acid residue, an ethylene glycol residue and the like are preferable, and when a plurality of hydrolyzable groups are present, they may be the same or different from each other.
As the hydrophobic functional group, a carboxyl group, a phosphate group, a pyrophosphate group, a phosphite group, a sulfonyl group, an aminoethyl group and the like are preferable, and when a plurality of groups are present, they may be the same or different from each other. ..

Examples of the aluminate-based coupling agent (III) include alkylacetoacetate aluminum diisopropyrate represented by the formula (4).

The dispersoid particles containing alumina may be only alumina or may contain other components. Other components include, for example, Li, Be, Na, Mg, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Sr, Y, Zr. Included are at least one metal oxide selected from the group. The forms of these oxides include Li ₂ O, BeO, Na ₂ O, MgO, Si ₂ O, K ₂ O, Ca ₂ O, Sc ₂ O ₃ , TiO ₂ , V ₂ O ₅ , CrO, MnO, and so on. Examples thereof include Fe ₂ O ₃ , CoO, NiO, CuO, ZnO ₂ , Ga ₂ O ₃ , GeO ₂ , SrO, Y ₂ O ₃ , and ZrO _2. These metal oxides can be used alone or in combination of two or more.
When alumina and other components such as other metal oxides are present, both may be uniformly distributed in the form of a mixture or a composite oxide, or the alumina portion and the other component portion may be uniformly distributed. , May be separated. In the latter case, substantially only alumina may form the particles.
The higher the purity of alumina, the higher the insulation performance can be realized. Therefore, in applications where insulation performance is required, high-purity alumina particles can be selected. Specifically, the amount of metal impurities is preferably 20 ppm or less for Si, 10 ppm or less for Fe, 10 ppm or less for Na, 10 ppm or less for Mg, and 10 ppm or less for Cu. In particular, Na is preferably 10 ppm or less.

The alumina constituting the dispersoid particles containing alumina may have a crystal structure such as α-type, β-type, γ-type, or θ-type. Further, it may be alumina hydrate. Further, it may be a mixture of two or more of these.
When the dispersoid particles containing alumina contain a component other than alumina as an oxide, the combination method includes a method of mixing the above alumina with one or more kinds of metal oxides, or one or two kinds of the above alumina. Examples thereof include a method of compounding the above metal oxides, a method of solidifying one or more kinds of metal oxides with the above alumina into a solid solution at the atomic level, and the like.
Alumina content of dispersoid particles comprising the alumina is preferably 50 to 100 mass% in terms _{of Al} 2 _{O 3,} more preferably 60 wt% or more, particularly preferably 80 mass% or more. By setting the alumina content to 50 to 100% by mass or more, improvement in insulating properties can be expected in a cured product obtained by curing a resin composition containing these particles.

The dispersoid particles containing alumina can be produced by a known method. For example, the Bayer method, the thermal decomposition method of ammonium aluminium, the thermal decomposition method of ammonium aluminum carbonate, the underwater spark discharge method of aluminum, the gas phase oxidation method, the hydrolysis method of aluminum alkoxide, the spraying method of alumina powder and the like can be mentioned. .. These aluminas can be obtained from, for example, Sumitomo Chemical Co., Ltd. and Denka Co., Ltd. (Also, the solid content obtained by drying a solvent dispersion of commercially available dispersoid particles containing alumina may be used as the dispersoid particles.)
Here, the "total metal oxide concentration" in the dispersoid particles in the present specification is a concentration including metal oxides such _{as Al 2} O ₃ and inorganic oxides such as _{SiO 2 contained in the dispersoid particles.} Defined as (mass basis).

The surface coating amount of the titanate-based coupling agent (II) and / or the aluminate-based coupling agent (III) with respect to the disperse particles containing alumina is not particularly limited, but the total metal oxide mass in the dispersoid particles is used. On the other hand, the total amount of these coupling agents is 0.1% by mass to 30% by mass, preferably 0.1% by mass to 20% by mass, and more preferably 0.1% by mass to 10% by mass. desirable.
Further, by adjusting the type of the titanate-based coupling agent (II) and / or the aluminate-based coupling agent (III) in this dispersion and the amount of coating on the dispersoid particles containing alumina, the dispersoid can be obtained. The average particle size of the particles can be appropriately adjusted to obtain a desired particle size.

式（５ａ）、式（５ｂ）中、Ｒ^８及びＲ^１１は、それぞれ独立にアルキル基、フェニル基、ビニル基、アクリロキシ基、メタクリロキシ基、エポキシ基、イソシアネート基、メルカプト基、ウレイド基、アミノ基、酸無水物基又はそれら官能基のいずれかを含む炭素原子数１から１０のアルキレン基であって、且つＳｉ−Ｃ結合によりケイ素原子と結合しているものであり、Ｒ^９及びＲ^１２は、それぞれ独立にアルコキシ基、アシルオキシ基、及びハロゲン基からなる群より選ばれる加水分解性基を示す。Ｙはアルキレン基、アリーレン基、ＮＨ基又は酸素原子を示す。ａは１から３の整数を示し、ｄはそれぞれ独立に０から２の整数を示し、ｅは０又は１の整数を示す。
すなわち、Ｒ^８、Ｒ^９、Ｒ^１１、Ｒ^１２、及び／又はｄが複数存在するときは、それらは同一であってもよく、互いに異なっていてもよい。 The dispersoid particles containing the alumina particles surface-coated with the titanate-based coupling agent (II) and / or the aluminate-based coupling agent (III) in the present embodiment are further surface-coated with the silane coupling agent. Can be done. The silane coupling agent in this case is preferably a hydrolyzable silane having at least a part thereof having a structure represented by the formula (5a) or the formula (5b).

In formulas (5a) and (5b), R ⁸ and R ¹¹ are independently alkyl groups, phenyl groups, vinyl groups, acryloxy groups, metharoxy groups, epoxy groups, isocyanate groups, mercapto groups, ureido groups and amino groups, respectively. , An alkylene group having 1 to 10 carbon atoms containing either an acid anhydride group or one of these functional groups, which is bonded to a silicon atom by a Si—C bond, and R ⁹ and R ¹² are , Each independently represents a hydrolyzable group selected from the group consisting of an alkoxy group, an acyloxy group, and a halogen group. Y represents an alkylene group, an arylene group, an NH group or an oxygen atom. a indicates an integer of 1 to 3, d indicates an integer of 0 to 2 independently, and e indicates an integer of 0 or 1.
That ^{is, when a plurality of R 8} , R ⁹ , R ¹¹ , R ¹² , and / or d exist, they may be the same or different from each other.

The alkyl group is preferably an alkyl group having 1 to 10 carbon atoms, for example, a methyl group, an ethyl group, an n-propyl group, an i-propyl group, a cyclopropyl group, an n-butyl group, an i-butyl group, and the like. s-butyl group, t-butyl group, cyclobutyl group, 1-methyl-cyclopropyl group, 2-methyl-cyclopropyl group, n-pentyl group, 1-methyl-n-butyl group, 2-methyl-n-butyl Group, 3-methyl-n-butyl group, 1,1-dimethyl-n-propyl group, 1,2-dimethyl-n-propyl group, 2,2-dimethyl-n-propyl group, 1-ethyl-n- Propyl group, cyclopentyl group, 1-methyl-cyclobutyl group, 2-methyl-cyclobutyl group, 3-methyl-cyclobutyl group, 1,2-dimethyl-cyclopropyl group, 2,3-dimethyl-cyclopropyl group, 1-ethyl -Cyclopropyl group, 2-ethyl-cyclopropyl group, n-hexyl group, 1-methyl-n-pentyl group, 2-methyl-n-pentyl group, 3-methyl-n-pentyl group, 4-methyl-n -Pentyl group, 1,1-dimethyl-n-butyl group, 1,2-dimethyl-n-butyl group, 1,3-dimethyl-n-butyl group, 2,2-dimethyl-n-butyl group, 2, 3-Dimethyl-n-butyl group, 3,3-dimethyl-n-butyl group, 1-ethyl-n-butyl group, 2-ethyl-n-butyl group, 1,1,2-trimethyl-n-propyl group 1,2,2-trimethyl-n-propyl group, 1-ethyl-1-methyl-n-propyl group, 1-ethyl-2-methyl-n-propyl group, cyclohexyl group, 1-methyl-cyclopentyl group, 2-Methyl-cyclopentyl group, 3-methyl-cyclopentyl group, 1-ethyl-cyclobutyl group, 2-ethyl-cyclobutyl group, 3-ethyl-cyclobutyl group, 1,2-dimethyl-cyclobutyl group, 1,3-dimethyl- Cyclobutyl group, 2,2-dimethyl-cyclobutyl group, 2,3-dimethyl-cyclobutyl group, 2,4-dimethyl-cyclobutyl group, 3,3-dimethyl-cyclobutyl group, 1-n-propyl-cyclopropyl group, 2 -N-propyl-cyclopropyl group, 1-i-propyl-cyclopropyl group, 2-i-propyl-cyclopropyl group, 1,2,2-trimethyl-cyclopropyl group, 1,2,3-trimethyl-cyclo Propyl group, 2,2,3-trimethyl-cyclopropyl group, 1-ethyl-2-methyl-cyclopropyl group, 2-ethyl-1-methyl-cy Examples thereof include a clopropyl group, a 2-ethyl-2-methyl-cyclopropyl group and a 2-ethyl-3-methyl-cyclopropyl group.

The alkoxy group is preferably an alkoxy group having 1 to 10 carbon atoms, for example, a methoxy group, an ethoxy group, an n-propoxy group, an i-propoxy group, an n-butoxy group, an i-butoxy group, or an s-butoxy group. , T-butoxy group, n-pentyroxy group, 1-methyl-n-butoxy group, 2-methyl-n-butoxy group, 3-methyl-n-butoxy group, 1,1-dimethyl-n-propoxy group, 1 , 2-Dimethyl-n-propoxy group, 2,2-dimethyl-n-propoxy group, 1-ethyl-n-propoxy group, n-hexyloxy group, 1-methyl-n-pentyroxy group, 2-methyl-n- Pentyroxy group, 3-methyl-n-pentyroxy group, 4-methyl-n-pentyroxy group, 1,1-dimethyl-n-butoxy group, 1,2-dimethyl-n-butoxy group, 1,3-dimethyl-n -Butoxy group, 2,2-dimethyl-n-butoxy group, 2,3-dimethyl-n-butoxy group, 3,3-dimethyl-n-butoxy group, 1-ethyl-n-butoxy group, 2-ethyl- n-butoxy group, 1,1,2-trimethyl-n-propoxy group, 1,2,2-trimethyl-n-propoxy group, 1-ethyl-1-methyl-n-propoxy group and 1-ethyl-2- Methyl-n-propoxy group, etc., and cyclic alkoxy groups include cyclopropoxy group, cyclobutoxy group, 1-methyl-cyclopropoxy group, 2-methyl-cyclopropoxy group, cyclopentyroxy group, 1-methyl-cyclo. Butoxy group, 2-methyl-cyclobutoxy group, 3-methyl-cyclobutoxy group, 1,2-dimethyl-cyclopropoxy group, 2,3-dimethyl-cyclopropoxy group, 1-ethyl-cyclopropoxy group, 2-ethyl -Cyclopropoxy group, cyclohexyloxy group, 1-methyl-cyclopentyroxy group, 2-methyl-cyclopentyroxy group, 3-methyl-cyclopentyroxy group, 1-ethyl-cyclobutoxy group, 2-ethyl-cyclobutoxy Group, 3-ethyl-cyclobutoxy group, 1,2-dimethyl-cyclobutoxy group, 1,3-dimethyl-cyclobutoxy group, 2,2-dimethyl-cyclobutoxy group, 2,3-dimethyl-cyclobutoxy group, 2,4-Dimethyl-cyclobutoxy group, 3,3-dimethyl-cyclobutoxy group, 1-n-propyl-cyclopropoxy group, 2-n-propyl-cyclopropoxy group, 1-i-propyl-cyclopropoxy group, 2-i-propyl-cyclopropoxy group 1,2, 2-trimethyl-Cyclopropoxy group, 1,2,3-trimethyl-cyclopropoxy group, 2,2,3-trimethyl-cyclopropoxy group, 1-ethyl-2-methyl-cyclopropoxy group, 2-ethyl-1- Examples thereof include a methyl-cyclopropoxy group, a 2-ethyl-2-methyl-cyclopropoxy group and a 2-ethyl-3-methyl-cyclopropoxy group.

The acyloxy group is preferably an acyloxy group having 1 to 10 carbon atoms, for example, a methylcarbonyloxy group, an ethylcarbonyloxy group, an n-propylcarbonyloxy group, an i-propylcarbonyloxy group, an n-butylcarbonyloxy group. , I-butylcarbonyloxy group, s-butylcarbonyloxy group, t-butylcarbonyloxy group, n-pentylcarbonyloxy group, 1-methyl-n-butylcarbonyloxy group, 2-methyl-n-butylcarbonyloxy group , 3-Methyl-n-butylcarbonyloxy group, 1,1-dimethyl-n-propylcarbonyloxy group, 1,2-dimethyl-n-propylcarbonyloxy group, 2,2-dimethyl-n-propylcarbonyloxy group , 1-ethyl-n-propylcarbonyloxy group, n-hexylcarbonyloxy group, 1-methyl-n-pentylcarbonyloxy group, 2-methyl-n-pentylcarbonyloxy group, 3-methyl-n-pentylcarbonyloxy group Group, 4-methyl-n-pentylcarbonyloxy group, 1,1-dimethyl-n-butylcarbonyloxy group, 1,2-dimethyl-n-butylcarbonyloxy group, 1,3-dimethyl-n-butylcarbonyloxy group Group, 2,2-dimethyl-n-butylcarbonyloxy group, 2,3-dimethyl-n-butylcarbonyloxy group, 3,3-dimethyl-n-butylcarbonyloxy group, 1-ethyl-n-butylcarbonyloxy group Group, 2-ethyl-n-butylcarbonyloxy group, 1,1,2-trimethyl-n-propylcarbonyloxy group, 1,2,2-trimethyl-n-propylcarbonyloxy group, 1-ethyl-1-methyl Examples thereof include an -n-propylcarbonyloxy group, a 1-ethyl-2-methyl-n-propylcarbonyloxy group, a phenylcarbonyloxy group, and a tosylcarbonyloxy group.

Examples of the halogen group include fluorine, chlorine, bromine and iodine.

Specific examples of the hydrolyzable silane represented by the above formulas (5a) and (5b) include compounds represented by the following formulas (10a) to (10i).

In the above formula, R ¹⁵ independently represents a hydrolyzable group selected from the group consisting of an alkoxy group, an acyloxy group, or a halogen group.
These can be obtained as silanes and silane coupling agents of Shin-Etsu Chemical Co., Ltd.

The compound of the formula (5b) contains a trimethylsilylating agent, and examples thereof include hexamethyldisiloxane and hexamethyldisilazane. These silylating agents can be obtained from Tokyo Chemical Industry Co., Ltd.

The silane coupling agent used for the surface coating of the dispersoid particles containing alumina can include a hydrolyzable silane of the formula (5a) and / or a hydrolyzable silane of the formula (5b). The hydrolyzable silane of the formula (5a) and the hydrolyzable silane of the formula (5b) can be used in combination with other hydrolyzable silanes, and the hydrolyzable silane of the formula (5a) and / or the formula. The mass ratio of the hydrolyzable silane of (5b) to the other hydrolyzable silane is preferably in the range of 1: 0.1 to 1.0, more preferably 1: 0.5 to 1.0. it can.

The amount of hydrolyzable silane added is preferably 0.5 to 50% by mass, more preferably 1 to 30% by mass, and particularly preferably 5 to 20% by mass with respect to 100 parts by mass of the dispersoid particles containing alumina. It can be added in a range.

The method for surface treatment of the dispersoid particles containing alumina with hydrolyzable silane is not particularly limited, and for example, the carboxylic acid anhydride of the dispersoid particles containing the alumina particles surface-coated with a titanate or an aluminate-based coupling agent. A hydrolyzable silane containing the hydrolyzable silane of the formula (5a) and / or the formula (5b) can be added to the dispersion to hydrolyze and surface coat. Further, when the dispersoid particles containing alumina particles and the titanate-based or aluminate-based coupling agent are dispersed in a dispersion medium containing a liquid carboxylic acid anhydride or a mixture thereof at 20 ° C., Hydrolyzable silanes can be added for hydrolysis and surface coating.

For the hydrolysis of the alkoxysilyl group, the acyloxysilyl group, or the halogenated silyl group, 0.5 to 100 mol, preferably 1 to 10 mol, of water can be used per 1 mol of the hydrolyzable group.
Further, 0.001 to 10 mol, preferably 0.001 to 1 mol, of a hydrolyzable catalyst can be used per mol of the hydrolyzable group.
The reaction temperature for hydrolysis and condensation is usually 20-80 ° C.
Hydrolysis may be complete hydrolysis or partial hydrolysis. That is, the hydrolyzate or the monomer may remain in the hydrolyzate condensate.

A catalyst can be used when hydrolyzing and condensing. As the hydrolysis catalyst, a chelate compound, an organic acid, an inorganic acid, an organic base, or an inorganic base can be used alone or in combination. More specifically, for example, an aqueous hydrochloric acid solution, an acetic acid solution, an aqueous ammonia solution, or the like can be used.

The dispersion liquid of the present invention may contain an organic solvent for the purpose of imparting fluidity and adjusting the solid content concentration, viscosity and the like. The solvent used is not limited as long as it is an acid anhydride or a solvent in which each component can be dispersed, and for example, alcohols, ethers, ketones, esters, amides, hydrocarbons, nitriles and the like can be used. It can be exemplified as an organic solvent.

Alcohols include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, isobutyl alcohol, 2-butanol, ethylene glycol, glycerin, prepylene glycol, triethylene glycol, polyethylene glycol, benzyl alcohol, 1,5. -Pentanediol, diacetone alcohol and the like can be mentioned.
Examples of ethers include diethyl ether, dibutyl ether, tetrahydrofuran, dioxane, ethylene glycol monomethyl ether, ethylene glycol monopropyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether and the like. Can be mentioned.
Examples of the ketones include acetone, methyl ethyl ketone, 2-pentanone, 3-pentanone, methyl isobutyl ketone, 2-heptanone, cyclohexanone and the like.
Examples of the esters include ethyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate and the like.
Examples of amides include acetamide, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone and the like.
Examples of hydrocarbons include n-hexane, cyclohexane, benzene, toluene, xylene, solvent naphtha, styrene and the like, and examples of halogenated hydrocarbons include dichloromethane, trichlorethylene and the like.
Examples of nitriles include acetonitrile, glutaronitrile, methoxynitrile, propionitrile, benzonitrile and the like.
Other organic solvents include dimethyl sulfoxide.
One of these organic solvents may be used alone, or two or more thereof may be mixed and used.

The content of the organic solvent in the dispersion medium can be adjusted as appropriate, but is preferably 0.01% by mass to 20% by mass, and more preferably 0.01% by mass to 10% by mass. The average particle size of the dispersoid particles containing alumina coated with the titanate-based or aluminate-based coupling agent constituting the acid separation solution is not particularly limited, but is preferably 20 nm to 1000 nm, more preferably 50 nm to. It is 600 nm, particularly preferably 50 nm to 200 nm. The average particle size can be measured by a dynamic light scattering method or a laser diffraction method, and more specifically, for example, by the method described in the examples of the present application.
By using disperse particles having such a specific particle size, it is possible to produce a particularly excellent alumina-dispersed epoxy resin in which insulating properties such as dielectric breakdown resistance and mechanical strength are compatible at a particularly high level. Further, the dispersion liquid of the present invention can be particularly preferably used for dispersing such alumina-containing dispersoid particles having a specific particle size in a good dispersed state.

One embodiment of the present invention is an epoxy resin composition containing the dispersion liquid of the present invention and an epoxy resin component. As the epoxy resin composition in the present embodiment, as the epoxy resin component, a polymerizable compound having an epoxy ring, a polymerizable compound such as a polymerizable compound having an oxetane ring, or a resin obtained by polymerizing them is preferably used. be able to. The resin obtained by polymerizing the polymerizable compound has polymerizable functional groups at the ends and side chains, and can be further polymerized by utilizing them.

As the polymerizable compound having an epoxy ring, a compound having 1 to 6 epoxy rings can be preferably used. The polymerizable compound having 1 to 6 epoxy rings is composed of, for example, a compound having two or more hydroxyl groups or a carboxyl group such as a diol compound, a triol compound, a dicarboxylic acid compound and a tricarboxylic acid compound, and a glycidyl compound such as epichlorohydrin. Examples thereof include compounds having two or more glycidyl ether structures or glycidyl ester structures that can be produced.

Specific examples of the polymerizable compound having an epoxy ring include 1,4-butanediol diglycidyl ether, 1,2-epoxy-4- (epoxyethyl) cyclohexane, glycerol triglycidyl ether, diethylene glycol diglycidyl ether, 2,6. -Diglycidylphenyl glycidyl ether, 1,1,3-tris [p- (2,3-epoxypropoxy) phenyl] propane, 1,2-cyclohexanedicarboxylic acid diglycidyl ester, 4,4'-methylenebis (N, N) − Diglycidyl aniline), 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, trimethylol ethane triglycidyl ether, triglycidyl-p-aminophenol, tetraglycidyl metaxylene diamine, tetraglycidyl diaminodiphenylmethane, tetra Glycidyl-1,3-bisaminomethylcyclohexane, bisphenol-A-diglycidyl ether, bisphenol-S-diglycidyl ether, pentaerythritol tetraglycidyl ether resorcinol diglycidyl ether, diglycidyl phthalate, neopentyl glycol diglycidyl ether, Polypropylene glycol diglycidyl ether, tetrabromobisphenol-A-diglycidyl ether, bisphenol hexafluoroacetone diglycidyl ether, pentaerythritol diglycidyl ether, hydride bisphenol-A-diglycidyl ether, tris- (2,3-epoxypropyl) Isocyanurate, 1- {2,3-di (propionyloxy)} -3,5-bis (2,3-epoxypropyl) -1,3,5-triazine-2,4,6. (1H, 3H, 5H) -Trione, 1,3-bis {2,3-di (propionyloxy)}-5- (2,3-epoxypropyl) -1,3,5-triazine-2,4,6 · (1H, 3H, 5H) -trione, monoallyl diglycidyl isocyanurate, diglycerol polydiglycidyl ether, pentaerythritol polyglycidyl ether, 1,4-bis (2,3-epoxypropoxyperfluoroisopropyl) cyclohexane, sorbitol polyglycidyl ether, tri Methylolpropan polyglycidyl ether, resorcindiglycidyl ether, 1,6-hexanediol diglycidyl ether, polyethylene glycol di Glysidyl ether, phenyl glycidyl ether, p-tersary butyl phenyl glycidyl ether, diglycidyl ether adipate, diglycidyl ether o-phthalate, dibromophenyl glycidyl ether, 1,2,7,8-diepoxyoctane, 1,6 -Dimethylol perfluorohexane diglycidyl ether, 4,4'-bis (2,3-epoxypropoxyperfluoroisopropyl) diphenyl ether, 2,2-bis (4-glycidyloxyphenyl) propane, 3,4-epoxycyclohexylmethyl -3', 4'-epoxycyclohexanecarboxylate, 3,4-epoxycyclohexyloxylane, 2- (3,4-epoxycyclohexyl) -3', 4'-epoxy-1,3-dioxane-5-spirocyclohexane, 1,2-ethylenedioxy-bis (3,4-epoxycyclohexylmethane), 4', 5'-epoxy-2'-methylcyclohexylmethyl-4,5-epoxy-2-methylcyclohexanecarboxylate, ethylene glycol- Examples thereof include bis (3,4-epoxycyclohexanecarboxylate), bis- (3,4-epoxycyclohexylmethyl) adipate, and bis (2,3-epoxycyclopentyl) ether.

式（１１）中、Ｒ_1６及びＲ_１７は、それぞれ独立して、アルキル基、アルケニル基、アルキニル基、アリール基、アラルキル基、複素環基、又はそれらのハロゲン化、アミノ化、若しくはニトロ化誘導体を表す。 Further, as another preferable example of the polymerizable compound having an epoxy ring, a portion (i) having a functional group represented by the following formula (11) in the molecule and a moiety (ii) having a glycidyl group in the molecule are included. Ester-modified epoxy compounds can be used.

In formula (11), R ₁₆ and R ₁₇ are independently alkyl groups, alkenyl groups, alkynyl groups, aryl groups, aralkyl groups, heterocyclic groups, or halogenated, amination, or nitrated derivatives thereof. Represents.

As the polymerizable compound having an oxetane ring, a compound having 1 to 6 oxetane rings can be preferably used. Preferred specific examples of the compound are 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3- (phenoxymethyl) oxetane, 3,3-diethyloxetane, and 3-ethyl-3- (2-ethylhexyloxy). Methyl) oxetane, 1,4-bis (((3-ethyl-3-oxetanyl) methoxy) methyl) benzene, di ((3-ethyl-3-oxetanyl) methyl) ether, and pentaerythritol tetrakis ((3-ethyl) -3-oxetanyl) methyl) ether and the like can be mentioned.

In the epoxy resin composition of the present embodiment, the carboxylic acid anhydride (I) is contained in an equal amount ratio of 1.5 to 2.5 equal amounts with respect to 1 equal amount of the epoxy resin component. Is preferable, and it is more preferable that the carboxylic acid anhydride (I) is contained in an equal amount ratio of 1.5 to 2.0 equal amounts.
As long as the above equal ratio is realized, the mass ratio of the carboxylic acid anhydride (I) and the epoxy resin component is not particularly limited, but practically, with respect to 100 parts by mass of the carboxylic acid anhydride (I). It is often preferable to contain 80 to 120 parts by mass of the epoxy resin component.
By adjusting the blending amount ratio of the epoxy resin component and the carboxylic acid anhydride (I) and the concentration of the dispersoid particles in the epoxy resin composition, the transparency and insulating property of the cured product obtained from the epoxy resin composition are adjusted. Can be adjusted.

In the epoxy resin composition of the present embodiment, the specific carboxylic acid anhydride (I) functions as a curing agent for the epoxy resin component.
The epoxy resin composition of the present embodiment contains the epoxy resin component, the dispersion liquid of the present invention (dispersible particles containing alumina having undergone a specific coating treatment, and a specific carboxylic acid anhydride (I)). It may or may not contain other components, but for example, a reactive diluent, a curing accelerator, a plasticizer, an anti-settling agent, and the like can be contained.
Preferably, as a curing accelerator, tertiary aliphatic amines, hybrid amines, organic phosphorus compounds and the like can be contained.

Examples of tertiary aliphatic amines include trimethylamine, triethylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, triisobutylamine, tri-sec-butylamine, tripentylamine and tricyclopentylamine. , Trihexylamine, tricyclohexylamine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, tridodecylamine, tricetylamine, N, N, N', N'-tetramethylmethylenediamine, N, Examples thereof include N, N', N'-tetramethylethylenediamine, N, N, N', N'-tetramethyltetraethylenepentamine and the like.
Examples of the mixed amines include dimethylethylamine, methylethylpropylamine, benzylamine, phenethylamine, benzyldimethylamine and the like.
Examples of the organophosphorus compounds include triphenylphosphine, tri-p-trilphosphine, diphenylcyclohexylphosphine, tricyclohexylphosphine, tetra-n-butylphosphonium bromide, tetra-n-butylphosphonium laurate, and the like. Bis (Tetratetra-n-Butylphosphonium) Pyromericate, Ethyltriphenylphosphonium bromide, n-butyltriphenylphosphonium bromide, benzyltriphenylphosphonium chloride, triphenylphosphine triphenylborane, tetraphenylphosphonium tetraphenylborate, tetraphenylphosphonium tetra Examples thereof include -p-trilbolate, 1,4-bis (diphenylphosphine) butane, 1,2-bis (diphenylphosphino) acetylene and the like.
These may be used alone or in combination of two or more.

The epoxy resin composition of the present embodiment may further contain inorganic oxide or metal oxide particles having an average particle diameter of 1 μm to 20 μm for the purpose of improving the mechanical strength and electrical properties of the cured product. By using the inorganic oxide or metal oxide particles having an average particle diameter of 1 μm to 20 μm in combination with the dispersoid particles (containing alumina) constituting the dispersion liquid of the present invention, favorable effects such as improvement of mechanical strength can be obtained. It can be realized.
Further, by using the inorganic oxide or metal oxide particles having an average particle diameter of 1 μm to 20 μm in combination with the dispersoid particles (containing alumina) constituting the dispersion liquid of the present invention, the thermal conductivity of the cured product can be improved. It is possible to reduce the CTE.
Examples of suitable inorganic oxide or metal oxide particles here include silica, alumina, zirconia, and the like, and composite particles thereof. Alumina particles are preferable.
The average particle size of the inorganic oxide or metal oxide particles, preferably alumina particles, is preferably 1 μm to 10 μm, more preferably 1 μm to 3 μm.
The content of the inorganic oxide or metal oxide particles, preferably alumina particles, is preferably 1% by mass to 30% by mass, and 1% by mass to 20% by mass, based on the total mass of the epoxy resin composition. More preferably, it is by mass%. When these inorganic oxide or metal oxide particles are alumina particles, they may have a crystal structure such as α-type, β-type, γ-type, or θ-type, or may be alumina hydrate. Further, these inorganic oxide or metal oxide particles, preferably alumina particles, can be obtained from, for example, Sumitomo Chemical Co., Ltd. or Denka Co., Ltd. The inorganic oxide or metal oxide particles, preferably alumina particles, have a surface coating treatment similar to that of the dispersoid particles constituting the dispersion liquid of the present invention, for example, a coupling agent treatment, preferably the titanate-based coupling agent (preferably the above-mentioned titanate-based coupling agent). Surface treatment with II), an aluminate-based coupling agent (III), and / or a silane coupling agent may be performed.

By curing the epoxy resin composition of the present embodiment, a cured epoxy resin can be produced. In the epoxy resin cured product of the embodiment, disperse particles containing alumina are present in a well-dispersed state, so that the insulating property such as dielectric breakdown resistance and the mechanical strength are balanced at a higher level than in the prior art. (Compatible), good epoxy resin cured product.
The dielectric breakdown resistance of the cured epoxy resin is preferably equivalent to or higher than that of the epoxy resin derived from the epoxy resin component and the curing agent used, and specifically, 25 kV / mm or more, preferably 30 kV. It is more preferably / mm or more.
The bending strength of the cured epoxy resin is also preferably equivalent to or higher than that of the epoxy resin derived from the epoxy resin component and the curing agent used, specifically, 140 MPa or more, and 150 MPa. Is more preferable.
An insulating member can be manufactured by coating a base material with the epoxy resin composition of the present embodiment and heating the base material.
Here, as the base material, metals such as aluminum, copper, stainless steel, and silicon, glass, plastic, glass cloth, and the like can be preferably used.
The coating method on the base material is not particularly limited, but it can be applied by using a coating method such as spin coating, bar coating, potting, casting, and impregnation. The film thickness of the coated film can be, for example, 100 nm to 5 mm. The applied film can be cured by heating at, for example, 50 to 500 ° C.

The epoxy resin composition of the present embodiment and the epoxy resin cured product obtained from the epoxy resin composition are used for electronic materials such as semiconductor encapsulant materials, adhesives for electronic materials, printed wiring substrate materials, interlayer insulating film materials, and encapsulants for power modules. It can be suitably used as an insulating member, a generator coil, a transformer coil, an insulating member used for high-voltage equipment such as a gas-insulated switchgear, and the like.

In producing the dispersion liquid of the present invention, a dispersoid particle containing alumina particles and a titanate-based coupling agent (II) or an aluminate-based coupling agent (III) are liquid carboxylic acid anhydride (I) at 20 ° C. A wet medium stirring mill using a pulverizer can be mentioned as a preferable method for dispersion treatment in a dispersion medium containing).
The wet medium stirring mill can perform the dispersion treatment by putting the raw material liquid into a container filled with the media and stirring the media and the raw material liquid together using a stirring device. In the present embodiment, the container filled with the media and the device for stirring the media are collectively defined as a crushing device. When a dedicated container is attached to the device for stirring the media in the commercially available crushing device, the commercially available container can be used depending on the volume of the raw material liquid and the like.
Specific examples of the crushing device that can be used here include a ball mill, a bead mill, and a sand mill.
Examples of the ball mill include a universal ball mill (Yamato Scientific Co., Ltd.) and an attritor (manufactured by Nippon Coke Co., Ltd.). Examples of the bead mill include a bead mill (manufactured by Ashizawa Finetech Co., Ltd.) and an apex mill (manufactured by Kotobuki Kogyo Co., Ltd.).
Examples of the sand mill include a sand grinder (manufactured by Imex Co., Ltd.) and the like.

The material and particle size of the media, the rotation speed of the device for stirring the media, the reaction time, and the like may be appropriately adjusted according to the desired particle size and the like. Further, it is also possible to appropriately adjust the rotation speed and reaction time of the apparatus in order to prevent the reaggregation of the particles in the dispersion medium.
Further, an organic solvent can be added for the purpose of imparting fluidity during the dispersion treatment step, adjusting the solid content concentration, adjusting the viscosity, and the like. Examples of the organic solvent include organic solvents such as alcohols, ethers, ketones, esters, amides, hydrocarbons, and nitriles.
In the production of the dispersion liquid of the present invention, a step of removing the solvent added in the dispersion treatment step can be added, if necessary, after the dispersion treatment step. As the removal method, a known method such as a vacuum distillation method, an atmospheric distillation method, or an ultrafiltration method can be used.

Hereinafter, the present invention will be described in more detail with reference to Production Examples, Examples and Comparative Examples, but the present invention is not limited to these Examples and the like.
The evaluation method of physical properties, characteristics, etc. in Examples and the like is as follows.

上記式により算出した中和価をゾル中の酸無水物の酸価とした。算出された酸価に基づいて、エポキシ１等量に対して酸無水物が１．８等量になるように、エポキシ樹脂と配合した。 [Evaluation of dispersion]
(viscosity)
The measurement was performed using a B-type rotational viscometer (manufactured by Toki Sangyo Co., Ltd.).
(Alumina concentration)
The sol was taken in a crucible and calcined at 1000 ° C. for 1 hour, and the calcined residue was measured to calculate the ratio of alumina to the mass of the sol.
(Average particle size (dynamic light scattering method))
The dispersion sol was diluted with a dispersion solvent, and the average particle size (DLS diameter) by a dynamic light scattering method was measured with a dynamic light scattering method measuring device (manufactured by Malvern) using alumina and solvent parameters.
(Median diameter of particles (laser diffraction method))
For the dispersion sol having a DLS diameter of 150 nm or more, the dispersion sol was diluted with a dispersion solvent, and the median diameter (SALD-D50) was measured by a laser diffraction method with a laser diffraction measuring device (manufactured by Shimadzu Corporation). .. Here, from the particle size distribution calculated with reference to the theoretical refractive index of alumina, the refractive index having a high degree of agreement with the measured light intensity distribution was selected.
(Storage stability)
The dispersion (acid anhydride-dispersed alumina sol) was stored at 50 ° C. for 4 weeks, the viscosity and the average particle diameter (or median diameter) were measured, and the storage stability was evaluated by comparing with the initial values according to the following criteria. ..
〇: The average particle size (or median diameter) (nm) was less than the initial value + 20%, and the viscosity (mPa · s) was less than the initial value + 20%.
Δ: Either the average particle diameter (or median diameter) (nm) or viscosity (mPa · s) is + 20% or more of the initial value, and the average particle diameter (or median diameter) (nm) and viscosity (mPa · s) All of s) were less than the initial value + 35%.
X: The average particle size (or median diameter) (nm) was + 35% or more of the initial value, and / or the viscosity (mPa · s) was + 35% or more of the initial value.
(Measurement of neutralization value)
Weigh 1.5 g of the dispersion sol into a 250 mL Erlenmeyer flask with a stopper, add 20 mL of thymolphthalein-pyridine solution as an indicator to dissolve it, add 30 mL of distilled water, and shake until uniform. It was titrated with a 5N potassium hydroxide solution. The neutralization value was calculated by the following formula, with the point where the last drop turned blue as the end point.

The neutralization value calculated by the above formula was used as the acid value of the acid anhydride in the sol. Based on the calculated acid value, the epoxy resin was blended so that the amount of acid anhydride was 1.8 equivalents with respect to 1 equivalent of epoxy.

[Epoxy cured product evaluation]
Using the dispersion liquid (acid anhydride-dispersed alumina sol) prepared in Examples / Comparative Examples, an epoxy resin cured product was prepared according to the following procedure, and various physical properties were measured and evaluated.
As an epoxy resin, 24.4 g of jER-828 (manufactured by Mitsubishi Chemical Co., Ltd., epoxy equivalent 187 g / eq) was prepared in Examples / Comparative Examples so that the amount of acid anhydride was 1.8 equivalents with respect to 1 equivalent of epoxy. A dispersion (acid anhydride-dispersed alumina sol) was added, and 0.2 g of dimethylbenzylamine (manufactured by Tokyo Kasei Co., Ltd.) was mixed as a reaction accelerator to obtain a curable epoxy resin composition.
Next, the curable epoxy resin composition was poured into a casting plate made of a 3 mm thick glass plate treated with a fluorine-based mold release agent (product name: Optool DSX, manufactured by Daikin Industries, Ltd.), and the mixture was poured at 70 ° C. for 2 hours. Heat treatment was carried out under the curing conditions of 90 ° C. for 2 hours and 150 ° C. for 8 hours to obtain an epoxy resin cured product.
(Dielectric breakdown voltage)
The measurement was performed using a dielectric breakdown tester based on JIS-C2110-1.
As the dielectric breakdown tester, a YST-243-100RHO type manufactured by Yamayo Tester Co., Ltd. was used. A sheet-shaped test piece having a size of 70 mm × 70 mm × 1 mm is prepared from a cured epoxy resin, sandwiched between cylindrical electrodes (φ25 mm), boosted at 2 kV / sec in mineral oil at 23 ° C, and subjected to dielectric breakdown. Was measured. The detected current value at the time of dielectric breakdown was set to 10 mA. The test was measured at n = 3 to 4, and the voltage (kV) obtained in the dielectric breakdown test was divided by the thickness (mm) of the test piece to calculate the dielectric breakdown voltage (kV / mm).
Based on the calculated breakdown voltage value, the insulation property was evaluated according to the following criteria.
A: The value of the dielectric breakdown voltage is 33.0 or more and shows excellent insulation.
B: The value of the dielectric breakdown voltage is 32.5 or more and less than 33.0, and shows good insulation.
C: The value of the dielectric breakdown voltage is 30.5 or more and less than 32.5, and shows sufficient insulation.
(Measurement of bending strength of cured epoxy resin)
It was measured using a tensile tester based on JIS K-6911.
The height and width of the test piece were measured, the test piece was supported, a load was applied to the center of the test piece with a pressure wedge, the load when the test piece was broken was measured, and the bending strength (σ) was calculated according to the following formula. ..
σ = (3PL) / (2Wh ² )
In the above formula
σ: Bending strength: (MPa) {kgf / mm ² }
P: Load when the test piece is broken (N) {kgf},
L: Distance between fulcrums (mm)
W: Width of test piece (mm)
h: Height of test piece (mm)
And said.
(Measurement of flexural modulus of cured epoxy resin)
It was measured using a tensile tester based on JIS K-6911.
More specifically, the same method as the method for measuring the bending strength was performed, and the flexural modulus (E) was calculated from the load-deflection curve obtained by the measurement according to the following equation.
E = (L ³ /4Wh ³ ) × (ΔF / Δs)
In the above formula
E: Flexural modulus (MPa) {kgf / mm ² }
L: Distance between fulcrums (mm)
W: Width of test piece (mm)
h: Specimen thickness (mm)
ΔF: Change in bending load (N) {kgf}
Δs: Change in deflection (mm)
Based on the calculated flexural modulus, evaluation was performed according to the following criteria.
Excellent: Those with excellent flexural modulus.
Good: Those with a good flexural modulus.
Possible: Those with sufficient flexural modulus.

(Example 1)
In an 800 mL sand grinder container (manufactured by Imex Co., Ltd.), 50 g of AKP-G07 (manufactured by Sumitomo Chemical Co., Ltd., BET specific surface area 72.9 m ² / g) as a θ-type high-purity alumina powder, and Plenact as a titanate-based coupling agent. 2.5 g of TTS (manufactured by Ajinomoto Fine Techno Co., Ltd.), ARADUR HY925 (manufactured by HUNTSMAN ADVANCED MATERIALS, 60 to 100 parts by mass of tetrahydromethylphthalic anhydride, 2,2-dimethylpropane-1,3-diylcyclohexyl) as an acid anhydride 447.5 g of tetrahydromethylphthalic anhydride (about 80% by mass), a mixture containing 13 to 30 parts by mass of sir-4-ene-1,2-dicarboxylate, methyl ethyl ketone (manufactured by Kanto Chemical Co., Ltd.) ), And 375 g of zirconia beads having a diameter of 1 mm were added. Next, it was mounted on a sand grinder (manufactured by Imex Co., Ltd.) and subjected to a wet dispersion treatment at a rotation speed of 1000 rpm for 18 hours to obtain an intermediate solution of an acid anhydride-dispersed alumina sol.
Next, 600 g of the obtained intermediate solution of the acid anhydride-dispersed alumina sol was taken in a 1000 mL eggplant-shaped flask, and then, as 3-trimethoxysilylpropyl succinic anhydride, X-12-967C (Shinetsu Chemical Industry Co., Ltd.) 7.6 g of (manufactured by the company) was added, and then the methyl anhydride ketone was distilled off at 300 to 50 Torr under nitrogen bubbling at a bath temperature of 80 ° C. using an evaporator to obtain an acid anhydride-dispersed alumina sol.
The obtained acid anhydride-dispersed alumina sol had an alumina concentration of 10% by mass, an average particle size (DLS diameter) of 125.3 nm, and a B-type viscosity of 1150 mPa · s.
Table 1 shows the evaluation results of the acid anhydride-dispersed alumina sol and the epoxy cured product obtained from the alumina sol.

(Example 2)
Examples except that KBM-103 (manufactured by Shin-Etsu Chemical Industry Co., Ltd.) was used as phenyltrimethoxysilane in an amount of 15% by mass based on the solid content instead of 3-trimethoxysilylpropyl succinic anhydride. An acid anhydride-dispersed alumina sol was prepared in the same manner as in 1, and then an epoxy cured product was prepared and evaluated. The results are shown in Table 1.

(Example 3)
Examples except that KBM-1003 (manufactured by Shin-Etsu Chemical Industry Co., Ltd.) was used as vinyl trimethoxysilane in an amount of 15% by mass based on the solid content instead of 3-trimethoxysilylpropyl succinic anhydride. An acid anhydride-dispersed alumina sol was prepared in the same manner as in 1, and then an epoxy cured product was prepared and evaluated. The results are shown in Table 1.

(Example 4)
KBM-403 (manufactured by Shin-Etsu Chemical Industry Co., Ltd.) was used as 3-glycidoxypropyltrimethoxysilane, which was also 15% by mass based on the solid content, instead of 3-trimethoxysilylpropyl succinic anhydride. In addition to the above, an acid anhydride-dispersed alumina sol was prepared in the same manner as in Example 1, and then an epoxy cured product was prepared and evaluated. The results are shown in Table 1.

(Example 5)
An acid anhydride-dispersed alumina sol was prepared in the same manner as in Example 1, except that no acid anhydride silane was used and no other silane-based coupling agent was used, and then an epoxy cured product was prepared. ,evaluated. The results are shown in Table 1.

(Comparative Example 1)
Powder kneading was performed instead of the wet dispersion treatment using the same starting materials as in Example 1 except that no acid anhydride silane was used and no other silane-based coupling agent was used.
An epoxy cured product was prepared using the obtained kneaded product and evaluated. The results are shown in Table 1.
Since an acid anhydride-dispersed alumina sol was not obtained, evaluations other than the alumina concentration were not performed at the kneading stage.

(Example 6)
Except for the fact that 447.5 g of MHHPA (4-methylhexahydrophthalic anhydride, manufactured by Tokyo Ohka Kogyo Co., Ltd.) was used instead of ARADUR HY925 as the carboxylic acid anhydride.
An acid anhydride-dispersed alumina sol was prepared in the same manner as in Example 5, and then an epoxy cured product was prepared and evaluated. The results are shown in Table 1.

(Comparative Example 2)
Except that Plenact TTS was not used and no other titanate-based coupling agent was used, an acid anhydride-dispersed alumina sol was prepared in the same manner as in Example 6, and then an epoxy cured product was prepared and evaluated. did. The results are shown in Table 1.

(Example 7)
An acid anhydride-dispersed alumina sol was prepared in the same manner as in Example 2, except that 2.5 g of Plenact 46B (manufactured by Ajinomoto Fine-Techno Co., Ltd.) was used instead of Plenact TTS as the titanate-based coupling agent. An epoxy cured product was then prepared and evaluated. The results are shown in Table 1.

(Example 8)
An acid anhydride-dispersed alumina sol was prepared in the same manner as in Example 7, except that phenyltrimethoxysilane was not used and no other silane-based coupling agent was used, and then an epoxy cured product was prepared. ,evaluated. The results are shown in Table 1.

(Example 9)
An acid anhydride-dispersed alumina sol was prepared in the same manner as in Example 2, except that 2.5 g of an aluminate-based coupling agent AL-M (manufactured by Ajinomoto Fine-Techno Co., Ltd.) was used instead of Plenact TTS. Then, an epoxy cured product was prepared and evaluated. The results are shown in Table 1.

(Example 10)
In a 500 mL polypropylene container, 20 g of CERALOX ALUMINA UHPA-G-AFS (manufactured by sasol, BET specific surface area: 135 m ² / g) as γ-type alumina powder, and Plenact TTS (Ajinomoto Fine Techno Co., Ltd.) as a titanate-based coupling agent. 2 g of MHHPA (4-methylhexahydrophthalic anhydride, manufactured by Tokyo Ohka Kogyo Co., Ltd.), 60 g of methyl ethyl ketone (manufactured by Kanto Chemical Co., Ltd.), and 300 g of φ1 mm zirconia beads were added as acid anhydrides. .. Then, it was placed on a ball mill turntable and subjected to a wet dispersion treatment at a rotation speed of 350 rpm for 69 hours to obtain an intermediate solution of an acid anhydride-dispersed alumina sol.
Next, 260 g of the intermediate solution of the obtained acid anhydride-dispersed alumina sol was taken in a 500 mL eggplant-shaped flask, and then KBM-103 (Shinetsu Chemical Industry Co., Ltd.) was used as phenyltrimethoxysilane in an amount of 15% by mass based on the solid content. An acid anhydride-dispersed alumina sol was obtained by adding (manufactured by the company) and then distilling off methyl ethyl ketone using an evaporator at 300 to 50 Torr under nitrogen bubbling at a bath temperature of 80 ° C.
The obtained acid anhydride-dispersed alumina sol had an alumina concentration of 10% by mass, an average particle size (DLS diameter) of 179.7 nm, and a B-type viscosity of 650 mPa · s.
Table 1 shows the evaluation results of the acid anhydride-dispersed alumina sol and the epoxy cured product obtained from the alumina sol.

(Example 11)
Except that phenyltrimethoxysilane was not used, no other silane coupling agent was used, and the amount of Plenact TTS used was changed as shown in Table 1, the same procedure as in Example 10 was performed. An acid anhydride-dispersed alumina sol was prepared, and then an epoxy cured product was prepared and evaluated.
The obtained acid anhydride-dispersed alumina sol had an alumina concentration of 10% by mass, an average particle size (DLS diameter) of 160.7 nm, and a B-type viscosity of 1660 mPa · s.
Table 1 shows the evaluation results of the acid anhydride-dispersed alumina sol and the epoxy cured product obtained from the alumina sol.

(Comparative Example 3)
In a 500 mL polypropylene container, 20 g of CERALOX ALUMINA UHPA-G-AFS (manufactured by sasol, BET specific surface area: 135 m ² / g) as γ-type alumina powder, and MHHPA (4-methylhexahydrophthalic acid anhydride) as acid anhydride. 180 g of the product (manufactured by Tokyo Ohka Kogyo Co., Ltd.), 60 g of methyl ethyl ketone (manufactured by Kanto Chemical Co., Ltd.), and 300 g of zirconia beads having a diameter of 1 mm were added. Next, the mixture was placed on a ball mill turntable and subjected to a wet dispersion treatment at a rotation speed of 350 rpm for 70 hours to obtain an intermediate solution of an acid anhydride-dispersed alumina sol.
Next, 260 g of the intermediate solution of the obtained acid anhydride-dispersed alumina sol was taken in a 500 mL eggplant-shaped flask, and then methyl ethyl ketone was retained at 300 to 50 Torr, nitrogen bubbling, and a bath temperature of 80 ° C. using an evaporator. By removing it, an acid anhydride-dispersed alumina sol was obtained.
The obtained acid anhydride-dispersed alumina sol had an alumina concentration of 10% by mass, an average particle size (DLS diameter) of 4045 nm, and a B-type viscosity of 1720 mPa · s.
Table 1 shows the evaluation results of the acid anhydride-dispersed alumina sol and the epoxy cured product obtained from the alumina sol.

(Example 12)
In addition to the acid anhydride-dispersed alumina sol obtained in the same manner as in Example 2, alumina powder LS-110F (average particle diameter 1.1 μm, manufactured by Nippon Light Metal Holdings Co., Ltd.) was further added as microparticles to 100 mass of the acid anhydride-dispersed alumina sol. An epoxy cured product was prepared and evaluated in the same manner as in Example 2, except that it was added so as to be 30 parts by mass with respect to the parts.
The results are shown in Table 2.

(Example 13)
In addition to the acid anhydride-dispersed alumina sol obtained in the same manner as in Example 5, alumina powder LS-110F (average particle diameter 1.1 μm, manufactured by Nippon Light Metal Holdings Co., Ltd.) was further added as microparticles to 100 mass of the acid anhydride-dispersed alumina sol. An epoxy cured product was prepared and evaluated in the same manner as in Example 5, except that it was added so as to be 30 parts by mass with respect to the parts.
The results are shown in Table 2.

From the comparison between Examples 1 to 6 and Comparative Example 2, the bending strength was significantly improved by using the dispersion liquid of the present invention while maintaining the same or slightly improved dielectric breakdown voltage, that is, more. It can be understood that both insulation and mechanical strength were achieved at a high level.
Similarly, from the comparison between Examples 1 to 5 and Comparative Example 1, it can be understood that the present invention has achieved both insulation and mechanical strength at a higher level than in the prior art. Since the titanate-based coupling agent itself is used in Comparative Example 1, in order to realize the effect of the present invention, the alumina particles coated with the coupling agent are dispersed, for example, as in Example 5. It can be understood that it is important that the particles are dispersed in the medium.

From the comparison of Examples 1 to 5 and Examples 7 to 9 using HY925 as the carboxylic acid anhydride and Comparative Example 1, the insulation which was equal to or slightly improved by using the dispersion liquid of the present invention. It can be understood that the bending characteristics such as bending strength and flexural modulus could be improved while maintaining the breakdown voltage.
Similarly, from the comparison between Example 6 and Comparative Example 2 in which MHHPA was used as the carboxylic acid anhydride and θ-alumina was used as the alumina, by using the dispersion liquid of the present invention, the same breakdown voltage and flexural modulus could be obtained. It can be understood that the bending strength could be improved while maintaining the bending strength. Further, from the comparison between Example 10 and Example 11 using γ-alumina as alumina and Comparative Example 3, by using the dispersion liquid of the present invention, a sufficient or higher dielectric breakdown voltage can be maintained. It can be understood that the bending characteristics such as bending strength and flexural modulus could be improved.
Further, in Examples 12 and 13 in which microparticles are used in combination with the acid anhydride-dispersed alumina sol of the present invention for the purpose of improving thermal conductivity and lowering CTE, sufficient insulating properties and excellent flexural modulus are exhibited. It can be confirmed that it is done.

Since the dispersion liquid of the present invention and the epoxy resin composition using the same can achieve both high insulating properties and excellent mechanical properties such as high bending strength at a high level, an insulating spacer for a gas switch can be used. It can be suitably used in various insulating members such as, and has high utility in each field of energy industry such as shipping electricity, electric / electronic industry, general machinery industry, transportation machinery industry, etc. Have.

Claims (18)

Disperse particles containing alumina coated with the titanate-based coupling agent (II) and / or the aluminate-based coupling agent (III) are represented by the formula (1a), the formula (1b), or the formula (1c). Dispersion liquid dispersed in a dispersion medium containing a carboxylic acid anhydride (I) having a structure of the above and liquid at 20 ° C .:

(In the formula, R ¹ and R ² indicate an alkyl group having 1 to 3 carbon atoms, R ³ indicates an alkenyl group having 2 to 12 carbon atoms, and n ₁ and n ₂ represent an integer of 0 to 1. Show.). The dispersion liquid according to claim 1, wherein the carboxylic acid anhydride (I) is contained in the dispersion medium of the dispersion liquid in an amount of 5% by mass or more. The dispersion liquid according to claim 1 or 2, wherein the alumina is at least one selected from the group consisting of α-alumina, β-alumina, γ-alumina, θ-alumina, and alumina hydrate. The dispersion according to any one of claims 1 to 3, wherein the titanate-based coupling agent (II) has a structure represented by the formula (2a) or the formula (2b).

(In the formula (2a), R ⁵ independently represents an alkoxy group having 1 to 12 carbon atoms, an oxyacetic acid residue, or an ethylene glycol residue, and X independently represents a carboxyl group, a phosphate group, and a pyrophosphate. It represents a group, a phosphite group, a sulfonyl group, or an aminoethyl group, where R ⁶ independently represents an alkyl or aryl group having 1 to 13 carbon atoms, and Y represents a hydroxyl group, n ₁ and. n ₃ is an independently integer of 0 or 1, n ₂ is 1, n ₄ is an independent integer of 0 to 2, and m is an integer of 1 to 3.);

(In formula (2b), R ⁷ independently represents an alkoxy group having 1 to 12 carbon atoms, Z independently represents a phosphate group or a phosphite group, and s represents an integer of 1 to 4). The dispersion according to any one of claims 1 to 4, wherein the titanate-based coupling agent (II) has a structure represented by the formula (3a) or the formula (3b).

(In equation (3a), n ₅ represents an integer from 1 to 3). The dispersion according to any one of claims 1 to 5, wherein the aluminate-based coupling agent (III) has a structure represented by the formula (4).

The dispersion liquid according to any one of claims 1 to 6, wherein the dispersoid particles are further surface-coated with a hydrolyzable silane having a structure represented by the formula (5a) or the formula (5b). :

(In the formulas (5a) and (5b), R ⁸ and R ¹¹ are independently alkyl groups, phenyl groups, vinyl groups, acryloxy groups, metharoxy groups, epoxy groups, isocyanate groups, mercapto groups, ureido groups, respectively. It is an alkylene group having 1 to 10 carbon atoms containing any of an amino group, an acid anhydride group, or a functional group thereof, and is bonded to a silicon atom by a Si—C bond, and is R ⁹ And R ¹² represent a hydrolyzable group independently selected from the group consisting of an alkoxy group, an acyloxy group, and a halogen group, respectively. Y represents an alkylene group, an arylene group, an NH group, or an oxygen atom. An integer of 3 is indicated, d is an integer of 0 to 2 independently, and e is an integer of 0 or 1.). The dispersion liquid according to any one of claims 1 to 7, wherein the average particle size of the dispersoid particles is 20 nm to 1000 nm. The dispersion liquid according to any one of claims 1 to 8, which contains the dispersoid particles in _{an amount of 0.1 to 50% by mass in terms of mass of Al 2} O _3. An epoxy resin composition containing the dispersion liquid according to any one of claims 1 to 9 and an epoxy resin component. The epoxy resin composition according to claim 10, further comprising inorganic oxide or metal oxide particles having an average particle diameter of 1 μm to 20 μm. The epoxy resin according to claim 10 or 11, wherein the carboxylic acid anhydride (I) is contained in an equal amount of 1.5 to 2.5 equal amounts with respect to 1 equal amount of the epoxy resin component. Composition. The epoxy resin composition according to any one of claims 10 to 12, further comprising a curing accelerator. An epoxy resin cured product which is a cured product of the epoxy resin composition according to any one of claims 10 to 13. An insulating member using the cured epoxy resin according to claim 14. A step of dispersing disperse particles containing alumina and a titanate-based coupling agent (II) and / or an aluminate-based coupling agent (III) in a dispersion medium containing a carboxylic acid anhydride (I). The method for producing a dispersion according to any one of claims 1 to 9, which comprises the above. The method for producing a dispersion liquid according to claim 16, wherein the step of performing the dispersion treatment is performed using a pulverizer. The method for producing a dispersion liquid according to claim 17, wherein the crushing device is a ball mill, a bead mill, or a sand mill.