WO2025052983A1 - Imide group-containing epoxy resin and curable epoxy resin composition containing same - Google Patents

Abstract

The present invention provides: an imide group-containing epoxy resin which has excellent fluidity and enables the achievement of a cured product that is excellent in terms of uniformity and heat resistance even under relaxed curing conditions (for example, curing temperature conditions of 200°C or lower); and a curable epoxy resin composition which uses the same. The present invention relates to an imide group-containing epoxy resin which contains a diimide dicarboxylic acid-based compound represented by a specific general formula and a bifunctional epoxy resin, wherein the diimide dicarboxylic acid-based compound and the bifunctional epoxy resin are ester-bonded to each other, and the epoxy equivalent is 1,000 or less.

Description

Imide group-containing epoxy resin and curable epoxy resin composition containing the same

The present invention relates to an imide group-containing epoxy resin having an imide skeleton and a curable epoxy resin containing the same.

Hardenable resins such as epoxy resins have excellent heat resistance, mechanical properties, and electrical properties, and are widely used industrially, primarily as electrical and electronic materials such as insulating materials for printed wiring boards and semiconductor encapsulation materials.

In recent years, there has been active development of materials for electronics components to accommodate the large capacity and high speed communication demands. For example, rising junction temperatures due to the high performance of semiconductor elements and increased heat generation due to improved efficiency have increased the need for high performance epoxy resin materials, requiring higher heat resistance than ever before.

In addition, in the field of power semiconductors, as typified by automotive power modules, there is a demand for even higher current, smaller size, and higher efficiency, and the transition to silicon carbide (SiC) semiconductors is progressing. Because SiC semiconductors can operate under higher temperature conditions than conventional silicon (Si) semiconductors, the semiconductor encapsulation materials used for SiC semiconductors are required to have higher heat resistance than ever before.

On the other hand, methods such as cast molding and transfer molding are used to seal power semiconductors and semiconductor elements, but these do not use solvents and must flow and harden at the molding temperature (200°C or less) to achieve sufficient performance.

For example, Patent Document 1 discloses a cured product made from an epoxy resin that contains a compound having an imide structure.

International Publication No. 2021/117686 Brochure

However, the cured product in Patent Document 1 was produced using a solvent, and the curing conditions were high, at 300°C. If Patent Document 1 was cured at 200°C without using a solvent, there were problems with poor fluidity, reduced uniformity, and insufficient heat resistance.

The present invention aims to provide an imide group-containing epoxy resin with excellent fluidity, which can give a cured product with excellent uniformity and heat resistance even under moderate curing conditions (e.g., curing temperature conditions of 200°C or less), and a curable epoxy resin composition using the same.

As a result of extensive research into the above-mentioned problems, the inventors discovered that the above-mentioned objectives could be achieved by reacting a bifunctional epoxy resin with a specific diimidedicarboxylic acid compound in advance, leading to the invention.

（式（１）中、Ｘ^１およびＸ^２は、それぞれ独立して、芳香族無水トリカルボン酸成分、脂環族無水トリカルボン酸成分、または脂肪族無水トリカルボン酸成分に由来する構造を表す；Ｒ^１は、芳香族ジアミン成分、または脂環族ジアミン成分に由来する構造を表す。）
＜２＞　前記二官能型エポキシ樹脂は、ビスフェノールＡ型エポキシ樹脂、ナフタレン型エポキシ樹脂、ビフェニル型エポキシ樹脂、およびアントラセン型エポキシ樹脂からなる群から選択される１種以上のエポキシ樹脂である、＜１＞に記載のイミド基含有エポキシ樹脂。
＜３＞　前記二官能型エポキシ樹脂は、ナフタレン型エポキシ樹脂、およびビフェニル型エポキシ樹脂からなる群から選択される１種以上のエポキシ樹脂であり、
　前記エポキシ当量が５００以下である、＜１＞または＜２＞に記載のイミド基含有エポキシ樹脂。
＜４＞　前記二官能型エポキシ樹脂は、ナフタレン型エポキシ樹脂、およびビフェニル型エポキシ樹脂からなる群から選択される１種以上のエポキシ樹脂であり、
　前記エポキシ当量は２５０～３５０である、＜１＞～＜３＞のいずれかに記載のイミド基含有エポキシ樹脂。
＜５＞　前記イミド基含有エポキシ樹脂は、前記ジイミドジカルボン酸系化合物１分子の両端の各々に前記二官能型エポキシ樹脂１分子がエステル結合を介して結合された構造を有する、＜１＞～＜４＞のいずれかに記載のイミド基含有エポキシ樹脂。
＜６＞　ジイミドジカルボン酸系化合物を二官能型エポキシ樹脂と、リン系化合物の存在下、反応させる、イミド基含有エポキシ樹脂の製造方法。
＜７＞　前記ジイミドジカルボン酸系化合物の配合量は、該ジイミドジカルボン酸系化合物の官能基当量が二官能型エポキシ樹脂のエポキシ当量に対して、０．０１～０．６当量比となるような量である、＜６＞に記載のイミド基含有エポキシ樹脂の製造方法。
＜８＞　前記二官能型エポキシ樹脂は、ナフタレン型エポキシ樹脂、およびビフェニル型エポキシ樹脂からなる群から選択される１種以上のエポキシ樹脂であり、
　前記ジイミドジカルボン酸系化合物の配合量は、該ジイミドジカルボン酸系化合物の官能基当量が二官能型エポキシ樹脂のエポキシ当量に対して、０．０５～０．３５当量比となるような量である、＜６＞または＜７＞に記載のイミド基含有エポキシ樹脂の製造方法。
＜９＞　前記二官能型エポキシ樹脂は、ナフタレン型エポキシ樹脂、およびビフェニル型エポキシ樹脂からなる群から選択される１種以上のエポキシ樹脂であり、
　前記ジイミドジカルボン酸系化合物の配合量は、該ジイミドジカルボン酸系化合物の官能基当量が二官能型エポキシ樹脂のエポキシ当量に対して、０．１５～０．２５当量比となるような量である、＜６＞～＜８＞のいずれかに記載のイミド基含有エポキシ樹脂の製造方法。
＜１０＞　＜１＞～＜５＞のいずれかに記載のイミド基含有エポキシ樹脂を製造する、＜６＞～＜９＞のいずれかに記載のイミド基含有エポキシ樹脂の製造方法。
＜１１＞　＜１＞～＜５＞のいずれかに記載のイミド基含有エポキシ樹脂と硬化剤とを含む硬化性エポキシ樹脂組成物。
＜１２＞　＜１１＞に記載の硬化性エポキシ樹脂組成物の硬化物。
＜１３＞　＜１２＞に記載の硬化物を含む電気絶縁材料。
＜１４＞　＜１２＞に記載の硬化物を含む封止材。
＜１５＞　パワー半導体モジュールに用いる＜１４＞に記載の封止材。
＜１６＞　＜１２＞に記載の硬化物を含むプリント配線基板。 That is, the gist of the present invention is as follows.
<1> A diimide dicarboxylic acid compound represented by general formula (1) and a bifunctional epoxy resin,
the diimide dicarboxylic acid compound and the bifunctional epoxy resin are bonded by an ester bond,
An imide group-containing epoxy resin having an epoxy equivalent of 1,000 or less.

(In formula (1), ^X1 and ^X2 each independently represent a structure derived from an aromatic tricarboxylic anhydride component, an alicyclic tricarboxylic anhydride component, or an aliphatic tricarboxylic anhydride component; ^R1 represents a structure derived from an aromatic diamine component, or an alicyclic diamine component.)
<2> The imide group-containing epoxy resin according to <1>, wherein the bifunctional epoxy resin is one or more epoxy resins selected from the group consisting of bisphenol A type epoxy resins, naphthalene type epoxy resins, biphenyl type epoxy resins, and anthracene type epoxy resins.
<3> The bifunctional epoxy resin is one or more epoxy resins selected from the group consisting of naphthalene-type epoxy resins and biphenyl-type epoxy resins,
The imide group-containing epoxy resin according to <1> or <2>, wherein the epoxy equivalent is 500 or less.
<4> The bifunctional epoxy resin is one or more epoxy resins selected from the group consisting of naphthalene-type epoxy resins and biphenyl-type epoxy resins,
The imide group-containing epoxy resin according to any one of <1> to <3>, wherein the epoxy equivalent is 250 to 350.
<5> The imide group-containing epoxy resin according to any one of <1> to <4>, wherein the imide group-containing epoxy resin has a structure in which one molecule of the diimidedicarboxylic acid compound is bonded to each end of the difunctional epoxy resin via an ester bond.
<6> A method for producing an imide group-containing epoxy resin, comprising reacting a diimidedicarboxylic acid compound with a bifunctional epoxy resin in the presence of a phosphorus compound.
<7> The method for producing an imide group-containing epoxy resin according to <6>, wherein the diimide dicarboxylic acid compound is blended in an amount such that the functional group equivalent of the diimide dicarboxylic acid compound is in an equivalent ratio of 0.01 to 0.6 relative to the epoxy equivalent of the bifunctional epoxy resin.
<8> The bifunctional epoxy resin is one or more epoxy resins selected from the group consisting of naphthalene epoxy resins and biphenyl epoxy resins,
The method for producing an imide group-containing epoxy resin according to <6> or <7>, wherein the amount of the diimide dicarboxylic acid compound is such that the functional group equivalent of the diimide dicarboxylic acid compound is 0.05 to 0.35 equivalent ratio relative to the epoxy equivalent of the bifunctional epoxy resin.
<9> The bifunctional epoxy resin is one or more epoxy resins selected from the group consisting of naphthalene epoxy resins and biphenyl epoxy resins,
The method for producing an imide group-containing epoxy resin according to any one of <6> to <8>, wherein the amount of the diimide dicarboxylic acid compound is such that the functional group equivalent of the diimide dicarboxylic acid compound is 0.15 to 0.25 equivalent ratio relative to the epoxy equivalent of the bifunctional epoxy resin.
<10> A method for producing an imide group-containing epoxy resin according to any one of <6> to <9>, comprising producing the imide group-containing epoxy resin according to any one of <1> to <5>.
<11> A curable epoxy resin composition comprising the imide group-containing epoxy resin according to any one of <1> to <5> and a curing agent.
<12> A cured product of the curable epoxy resin composition according to <11>.
<13> An electrical insulating material comprising the cured product according to <12>.
<14> An encapsulant comprising the cured product according to <12>.
<15> The encapsulating material according to <14>, which is used for a power semiconductor module.
<16> A printed wiring board comprising the cured product according to <12>.

According to the present invention, it is possible to provide a highly fluid imide group-containing epoxy resin having an imide skeleton, which can give a cured product having excellent uniformity and heat resistance even when the curing conditions are relaxed, and a curable epoxy resin composition using the same.
The cured product obtained by curing the curable epoxy resin composition of the present invention can be suitably used for electrical insulating materials, sealing materials, and printed wiring boards.

<Imide Group-Containing Epoxy Resin>
The imide group-containing epoxy resin of the present invention is a reaction product of a diimide dicarboxylic acid compound and a bifunctional epoxy resin. In detail, the imide group-containing epoxy resin of the present invention contains a diimide dicarboxylic acid compound and a bifunctional epoxy resin, and the diimide dicarboxylic acid compound and the bifunctional epoxy resin are ester-bonded. More specifically, the structure of the imide group-containing epoxy resin of the present invention is not particularly limited as long as it has an epoxy equivalent weight as described below, and may be, for example, one structure selected from the group consisting of the following structures (A), (B) and (C), or the imide group-containing epoxy resin of the present invention may be a mixture of two or more structures selected from the group.

Structure (A): A structure in which one molecule of a diimidedicarboxylic acid compound is bonded to each end of the molecule via an ester bond. In Structure (A), more specifically, one of the two carboxyl groups in the diimidedicarboxylic acid compound forms an ester bond by reacting with one of the two epoxy groups in the bifunctional epoxy resin. The other carboxyl group forms an ester bond by reacting with one of the two epoxy groups in another bifunctional epoxy resin.

Structure (B): A structure in which one molecule of a diimidedicarboxylic acid compound is bonded to each end of one molecule of a bifunctional epoxy resin via an ester bond In Structure (B), more specifically, one of the two epoxy groups in the bifunctional epoxy resin forms an ester bond by reacting with one of the two carboxyl groups in the diimidedicarboxylic acid compound, and the other epoxy group forms an ester bond by reacting with one of the two carboxyl groups in the other diimidedicarboxylic acid compound.

Structure (C): Oligomer Structure In Structure (C), specifically, a diimidedicarboxylic acid compound and a bifunctional epoxy resin are repeatedly bonded via ester bonds, and the number of repeating units is usually 10 or less, particularly 5 or less, and from the viewpoint of further improving the fluidity of the imide group-containing epoxy resin and the uniformity and heat resistance of the obtained cured product, is preferably 3 or less, more preferably 2. The lower limit of the number of repeating units is not particularly limited, and may be, for example, 2.

In structures (A) to (C), when an ester bond is formed, a hydroxyl group is generated by opening the epoxy ring. Each of these hydroxyl groups may independently react with a carboxyl group of another diimidedicarboxylic acid compound to form an ester bond, or may react with an epoxy group of another bifunctional epoxy resin to form an ether bond, or may not react with any group at all.

The imide group-containing epoxy resin of the present invention preferably has structure (A) from the viewpoint of further improving the fluidity of the imide group-containing epoxy resin and the uniformity and heat resistance of the resulting cured product. In particular, from the same viewpoint as above, the imide group-containing epoxy resin of the present invention preferably contains an imide group-containing epoxy resin having structure (A).

In this specification, the term "fluidity" refers to the fluidity of the imide group-containing epoxy resin, and is a property relating to a lower viscosity at 140° C. The imide group-containing epoxy resin needs to flow during molding, and a lower viscosity is preferable.
The uniformity refers to the uniformity of the cured product of the imide group-containing epoxy resin and the curing agent, and is a characteristic related to the fact that the cured product contains less insoluble components. The insoluble components are foreign matter that inhibit the transparency of the cured product, and may be generated during the manufacturing process of the cured product due to a decrease in the compatibility between the imide group-containing epoxy resin and the curing agent and/or the presence of unreacted imide dicarboxylic acid compounds. The presence of insoluble components leads to poor curing and/or a decrease in physical properties, so it is desirable to cure uniformly.
The heat resistance refers to the heat resistance of the cured product of the imide group-containing epoxy resin and the curing agent, and is a property related to the higher glass transition temperature of the cured product. Since the cured product needs to operate under high temperature conditions, it is better for the glass transition temperature to be higher.

The epoxy equivalent of the imide group-containing epoxy resin of the present invention must be 1000 or less (particularly 100 to 1000), and from the viewpoint of further improving the fluidity of the imide group-containing epoxy resin and the uniformity and heat resistance of the resulting cured product, it is preferably 800 or less (particularly 150 to 800), more preferably 500 or less (particularly 200 to 500), and more preferably 250 to 350. If the epoxy equivalent exceeds 1000, the fluidity and uniformity will decrease.

In this specification, the epoxy equivalent is the molecular weight of the epoxy resin per epoxy group, and is the value measured by nuclear magnetic resonance spectroscopy.

The viscosity (140°C) of the imide group-containing epoxy resin of the present invention is usually 1000 Pa·s or less, and from the viewpoint of further improving the fluidity, it is preferably 500 Pa·s or less, more preferably 200 Pa·s or less, even more preferably 100 Pa·s or less, sufficiently preferably 10 Pa·s or less, and even more preferably 5 Pa·s or less. There is no particular lower limit to the viscosity, and the viscosity is usually 0.01 Pa·s or more, particularly 0.05 Pa·s or more, and from the viewpoint of further improving the fluidity and heat resistance of the cured product, it is preferably 0.5 Pa·s or more, more preferably 1 Pa·s or more.

In this specification, the viscosity is the value at 140°C determined by dynamic viscoelasticity measurement.

[Diimidedicarboxylic acid compounds]
The diimidedicarboxylic acid compound is a compound having two imide groups and two carboxyl groups in one molecule. The diimidedicarboxylic acid compound does not have an amide group. A tricarboxylic anhydride component and a diamine component are used as raw material compounds, and a reaction between functional groups is carried out to produce an amide acid compound, and an imidization reaction is carried out to produce a diimidedicarboxylic acid compound. The reaction between functional groups may be carried out in a solution or in a solid phase, and the production method is not particularly limited.

A diimidedicarboxylic acid compound using a tricarboxylic anhydride component and a diamine component is a compound in which two molecules of the tricarboxylic anhydride component react with one molecule of the diamine component to form two imide groups, and more specifically, is a diimidedicarboxylic acid compound having the structure of general formula (1).

In the general formula (1), ^X1 and ^X2 each independently represent a structure derived from a tricarboxylic acid anhydride component (e.g., an aromatic tricarboxylic acid anhydride component, an alicyclic tricarboxylic acid anhydride component, or an aliphatic tricarboxylic acid anhydride component) described below. In more detail, ^X1 and ^X2 each independently may be a residue derived from the above components.
^R1 represents a structure derived from a diamine component (for example, an aromatic diamine component or an alicyclic diamine component) described below. Specifically, ^R1 may be a residue derived from the above components.

When producing a diimidedicarboxylic acid compound using a tricarboxylic anhydride component and a diamine component, the diamine component is usually used in a molar amount of about 0.5 times, for example 0.1 to 0.7 times, preferably 0.3 to 0.7 times, more preferably 0.4 to 0.6 times, and even more preferably 0.45 to 0.55 times, relative to the tricarboxylic anhydride component.

The tricarboxylic anhydride components that can constitute the diimide dicarboxylic acid-based compound include aromatic tricarboxylic anhydride components that contain an aromatic ring, alicyclic tricarboxylic anhydride components that contain an aliphatic ring but no aromatic ring, and aliphatic tricarboxylic anhydride components that contain neither an aromatic ring nor an alicyclic ring. The tricarboxylic anhydride components may contain ether groups and/or thioether groups, and/or one or more of the hydrogen atoms may be substituted with halogen atoms (e.g., fluorine atoms, chlorine atoms, bromine atoms). The tricarboxylic anhydride components may be acid halide components. An acid halide component is a compound in which the OH group of the carboxyl group in the tricarboxylic anhydride component is substituted with a halogen atom.

Examples of aromatic tricarboxylic anhydride components include trimellitic anhydride and 1,2,4-naphthalene tricarboxylic anhydride. These may be used alone or in a mixture of two or more. The number of aromatic rings contained in one molecule of the aromatic tricarboxylic anhydride component is not particularly limited, and may be, for example, 1 to 4, and particularly 1 to 2. In particular, naphthalene rings are counted as containing two aromatic rings in one molecule.

Examples of alicyclic tricarboxylic anhydride components include 1,2,3-cyclohexane tricarboxylic anhydride and 1,2,4-cyclohexane tricarboxylic anhydride. These may be used alone or in a mixture of two or more. The number of alicyclic rings contained in one molecule of the alicyclic tricarboxylic anhydride component is not particularly limited, and may be, for example, 1 to 4, and particularly 1 to 2.

Examples of the aliphatic tricarboxylic anhydride component include 3-carboxymethylglutaric anhydride, 1,2,4-butanetricarboxylic acid-1,2-anhydride, and cis-propene-1,2,3-tricarboxylic acid-1,2-anhydride. These may be used alone or in a mixture of two or more.

The tricarboxylic anhydride component of the diimidedicarboxylic acid compound preferably contains an aromatic tricarboxylic anhydride component and/or an alicyclic tricarboxylic anhydride component, and more preferably contains an aromatic tricarboxylic anhydride component, from the viewpoint of the heat resistance of the diimidedicarboxylic acid compound, the imide group-containing epoxy resin obtained using the same, and the cured product obtained using the same.

From the viewpoint of the solubility of the diimidedicarboxylic acid compound, it is preferable to use, among the above-mentioned tricarboxylic acid anhydride components, an alicyclic tricarboxylic acid anhydride component and/or an aliphatic tricarboxylic acid anhydride component as the tricarboxylic acid anhydride component of the diimidedicarboxylic acid compound.
From the viewpoint of further improving the solubility of the diimidedicarboxylic acid-based compound, it is preferable to use only an alicyclic tricarboxylic acid anhydride component and/or an aliphatic tricarboxylic acid anhydride component among the above-mentioned tricarboxylic acid anhydride components as the tricarboxylic acid anhydride component of the diimidedicarboxylic acid-based compound.

Diamine components that can form diimide dicarboxylic acid compounds include aromatic diamine components that contain aromatic rings, and alicyclic diamine components that contain aliphatic rings but no aromatic rings. The diamine components may contain ether groups and/or thioether groups, and/or one or more of the hydrogen atoms may be substituted with halogen atoms (e.g., fluorine atoms, chlorine atoms, bromine atoms). The diamine components may have side chains.

Aromatic diamine components include, for example, m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminobenzanilide, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, bis(4-aminophenyl)sulfone, 9,9-bis(4-aminophenyl)fluorene, metaxylenediamine, 4,4'-bis(3-aminophenoxy)biphenyl, 4,4'-bis(4-aminophenoxy)biphenylbis[4-(4-aminophenoxy)phenyl]sulfone, and analogs of the above diamines. These may be used alone or in a mixture of two or more. The number of aromatic rings contained in one molecule of the aromatic diamine component is not particularly limited, and may be, for example, 1 to 4, and particularly 1 to 2. In particular, a fluorene ring is counted as containing two aromatic rings in one molecule.

Examples of alicyclic diamine components include trans-1,4-cyclohexanediamine, 4,4'-methylenebis(cyclohexylamine), and 1,4-bis(aminomethyl)cyclohexane. These may be used alone or in a mixture of two or more. The number of alicyclic rings contained in one molecule of the alicyclic diamine component is not particularly limited, and may be, for example, 1 to 4, and particularly 1 to 2.

The diamine component of the diimidedicarboxylic acid compound preferably contains an aromatic diamine component and/or an alicyclic diamine component, and more preferably contains an aromatic diamine component, from the viewpoint of the heat resistance of the diimidedicarboxylic acid compound, the imide group-containing epoxy resin obtained using the same, and the cured product obtained using the same.

From the viewpoint of the solubility of the diimidedicarboxylic acid compound, it is preferable to use, among the above diamine components, a diamine component having an ether group, a thioether group, a sulfonyl group, a sulfonic acid group, a methyl group, a methylene group, an isopropylidene group, a phenyl group, a fluorene structure, a halogen atom (or a halogen atom-containing substituent), or a siloxane bond as the diamine component of the diimidedicarboxylic acid compound.
From the viewpoint of further improving the solubility of the diimidedicarboxylic acid compound, it is preferable to use only diamine components having an ether group, a thioether group, a sulfonyl group, a sulfonic acid group, a methyl group, a methylene group, an isopropylidene group, a phenyl group, a fluorene structure, a halogen atom (or a halogen atom-containing substituent), or a siloxane bond among the above diamine components.

The diimidedicarboxylic acid compound can be produced in a solvent or without a solvent, but the production method is not particularly limited.

As a method for producing in a solvent, for example, predetermined raw materials (e.g., tricarboxylic anhydride components, diamine components, tetracarboxylic dianhydride components, monoaminodicarboxylic acid components) are added to an aprotic solvent such as N-methyl 2-pyrrolidone, stirred at 80°C, and then imidized to obtain the product.

The method of imidization is not particularly limited, and may be, for example, a thermal imidization method performed by heating at 250°C to 350°C (particularly 280°C to 320°C) for 1 to 10 hours (particularly 1 to 3 hours) in a nitrogen atmosphere, or a chemical imidization method performed by treating with a dehydration/cyclization reagent such as a mixture of a carboxylic anhydride and a tertiary amine.

One example of a method for producing organic compounds without using a solvent is a method that utilizes the mechanochemical effect. This method utilizes the mechanical energy generated when the raw compound used in the reaction is pulverized to produce a mechanochemical effect, thereby obtaining an organic compound.

The mechanochemical effect is an effect (or phenomenon) in which mechanical energy (compressive force, shear force, impact force, grinding force, etc.) is applied to a raw material compound in a solid state in a reaction environment, thereby pulverizing the raw material compound and activating the pulverized interface that is formed. This causes a reaction between functional groups. A reaction between functional groups usually occurs between two or more raw material compound molecules. For example, a reaction between functional groups may occur between two raw material compound molecules with different chemical structures, or between two raw material compound molecules with the same chemical structure. A reaction between functional groups does not occur only between a limited set of two raw material compound molecules, but usually occurs between two raw material compound molecules of other sets. A new reaction between functional groups may occur between a compound molecule generated by a reaction between functional groups and a raw material compound molecule. A reaction between functional groups is usually a chemical reaction, in which a bond group (particularly a covalent bond) is formed between two raw material compound molecules by the functional groups of each raw material compound molecule, generating another compound molecule.

The reaction environment means the environment in which the raw material compound is placed for the reaction, i.e., the environment in which mechanical energy is applied, and may be, for example, the environment inside the apparatus. Being in a solid state in the reaction environment means being in a solid state in the environment in which mechanical energy is applied (for example, under the temperature and pressure inside the apparatus). The raw material compound in a solid state in the reaction environment may usually be in a solid state at room temperature (25°C) and normal pressure (101.325 kPa). The raw material compound in a solid state in the reaction environment may be in a solid state at the start of the application of mechanical energy. The present invention does not prevent the raw material compound in a solid state in the reaction environment from changing to a liquid state (for example, a molten state) during the reaction (or processing) due to an increase in temperature and/or pressure, etc., accompanying the continued application of mechanical energy, but it is preferable for the raw material compound to be in a solid state continuously during the reaction (or processing) from the viewpoint of improving the reaction rate.

The details of the mechanochemical effect are not clear, but it is thought to follow the following principle. When mechanical energy is applied to one or more solid raw material compounds to cause grinding, the grinding interface is activated by absorbing the mechanical energy. It is thought that a chemical reaction occurs between the two raw material compound molecules due to the surface activation energy of the grinding interface. Grinding refers to the application of mechanical energy to raw material compound particles, which causes the particles to absorb the mechanical energy, resulting in cracks in the particles and renewal of the surface. The renewal of the surface means the formation of a grinding interface as a new surface. In the mechanochemical effect, the state of the new surface formed by surface renewal is not particularly limited as long as the activation of the grinding interface occurs due to grinding, and it may be in a dry state or a wet state. The wet state of the new surface due to surface renewal is due to the raw material compounds in a liquid state separate from the solid raw material compounds.

Mechanical energy is applied to a raw material mixture containing one or more raw material compounds that are in a solid state in a reaction environment. The state of the raw material mixture is not particularly limited as long as the application of mechanical energy causes the raw material compounds in a solid state to be pulverized. For example, the raw material mixture may be in a dry state because all raw material compounds contained in the raw material mixture are in a solid state. Also, for example, the raw material mixture may be in a wet state because at least one raw material compound contained in the raw material mixture is in a solid state and the remaining raw material compounds are in a liquid state. Specifically, for example, when the raw material mixture contains only one raw material compound, the one raw material compound is in a solid state. Also, for example, when the raw material mixture contains two raw material compounds, the two raw material compounds may both be in a solid state, or one raw material compound may be in a solid state and the other raw material compound may be in a liquid state.

The mechanochemical effect of this mechanical energy is used to cause a reaction between functional groups. More specifically, a reaction occurs between the acid anhydride group of the tricarboxylic acid anhydride component and the amino group of the diamine component, producing an imide group.

In the method of manufacturing without a solvent, after carrying out the method utilizing the mechanochemical effect, imidization may be carried out by a method similar to the imidization method in the method of manufacturing in a solvent (particularly the thermal imidization method).

[Bifunctional epoxy resin]
A bifunctional epoxy resin has a structure having two epoxy groups in one molecule. If a multifunctional epoxy resin having three or more epoxy groups in one molecule is used, the reaction between the epoxy resin and the diimide dicarboxylic acid compound does not proceed sufficiently, leaving unreacted material, making it impossible to produce an imide group-containing epoxy resin. As a result, the uniformity of the epoxy resin cured product using a curing agent decreases, and sufficient heat resistance cannot be obtained.

Examples of bifunctional epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, naphthalene type epoxy resins, bisphenyl type epoxy resins, and anthracene type epoxy resins. Among them, from the viewpoint of further improving the fluidity of the imide group-containing epoxy resin and the uniformity and heat resistance of the resulting cured product, bisphenol A type epoxy resins, naphthalene type epoxy resins, bisphenyl type epoxy resins, and anthracene type epoxy resins are preferred, bisphenol A type epoxy resins, naphthalene type epoxy resins, and bisphenyl type epoxy resins are more preferred, naphthalene type epoxy resins and bisphenyl type epoxy resins are even more preferred, and naphthalene type epoxy resins are sufficiently preferred. The epoxy resins may be used alone or in combination of two or more types.

（式（Ｅ１）中、ｎは０～３の整数である。ベンゼン環を構成する炭素原子に結合している水素原子は、それぞれ独立して、メチル基によって置換されていてもよい。） The bisphenol A type epoxy resin is a compound having a bisphenol A skeleton and two epoxy groups in one molecule, and may be, for example, an epoxy resin represented by the general formula (E1).

(In formula (E1), n is an integer of 0 to 3. The hydrogen atoms bonded to the carbon atoms constituting the benzene ring may each be independently substituted with a methyl group.)

（式（Ｅ２）中、ｎは０～３の整数である。ナフタレン環を構成する炭素原子に結合している水素原子は、それぞれ独立して、メチル基によって置換されていてもよい。） The naphthalene type epoxy resin is, for example, a compound having a naphthalene skeleton and two epoxy groups in one molecule, and may be an epoxy resin represented by general formula (E2).

(In formula (E2), n is an integer of 0 to 3. The hydrogen atoms bonded to the carbon atoms constituting the naphthalene ring may each be independently substituted with a methyl group.)

（式（Ｅ３）中、ｎは０～３の整数である。アントラセン環を構成する炭素原子に結合している水素原子は、それぞれ独立して、メチル基によって置換されていてもよい。） The anthracene type epoxy resin is a compound having an anthracene skeleton and two epoxy groups in one molecule, and may be, for example, an epoxy resin represented by general formula (E3).

(In formula (E3), n is an integer of 0 to 3. Each hydrogen atom bonded to a carbon atom constituting the anthracene ring may be independently substituted with a methyl group.)

（式（Ｅ４）中、ｎは０～３の整数である。ベンゼン環を構成する炭素原子に結合している水素原子は、それぞれ独立して、メチル基によって置換されていてもよい。） The biphenyl type epoxy resin is, for example, a compound having a biphenyl skeleton and two epoxy groups in one molecule, and may be an epoxy resin represented by general formula (E4).

(In formula (E4), n is an integer of 0 to 3. The hydrogen atoms bonded to the carbon atoms constituting the benzene ring may each be independently substituted with a methyl group.)

Bifunctional epoxy resins are commercially available or can be produced by known methods.

The epoxy equivalent of the bifunctional epoxy resin is not particularly limited and may be, for example, 100 to 1000 g/eq. From the viewpoint of further improving the fluidity of the imide group-containing epoxy resin and the uniformity and heat resistance of the resulting cured product, it is preferably 100 to 500 g/eq, more preferably 100 to 300 g/eq, and even more preferably 150 to 250 g/eq.

<Method of producing imide group-containing epoxy resin>
The method for producing the imide group-containing epoxy resin of the present invention is not particularly limited, and may be, for example, a method of heating and mixing under a nitrogen atmosphere. In detail, a diimide dicarboxylic acid compound is heated and mixed with a bifunctional epoxy resin in the presence of a phosphorus compound to react with each other. Such a treatment for producing an imide group-containing epoxy resin may be considered as a pretreatment of the epoxy resin, which is carried out before the epoxy resin is reacted with a cured product.

The heating temperature during mixing is not particularly limited and may be, for example, 100 to 250°C. From the viewpoint of further improving the fluidity of the imide group-containing epoxy resin and the uniformity and heat resistance of the resulting cured product, it is preferably 130 to 200°C, and more preferably 150 to 200°C.

The reaction time (mixing time) is not particularly limited and may be 0.1 to 10 hours, but from the viewpoint of further improving the fluidity of the imide group-containing epoxy resin and the uniformity and heat resistance of the resulting cured product, it is preferably 0.5 to 5 hours, and more preferably 0.5 to 2 hours.

In the imide group-containing epoxy resin, the amount of the diimide dicarboxylic acid compound is not particularly limited, and may be, for example, an amount such that the functional group equivalent of the diimide dicarboxylic acid compound is 0.01 to 0.6 equivalent ratio relative to the epoxy equivalent of the bifunctional epoxy resin. From the viewpoint of further improving the fluidity of the imide group-containing epoxy resin and the uniformity and heat resistance of the resulting cured product, the amount of the diimide dicarboxylic acid compound is preferably an amount such that the functional group equivalent of the diimide dicarboxylic acid compound is 0.05 to 0.5 equivalent ratio, preferably 0.05 to 0.35 equivalent ratio, more preferably 0.15 to 0.25 equivalent ratio relative to the epoxy equivalent of the bifunctional epoxy resin. The functional group equivalent of the diimide dicarboxylic acid compound corresponds to the equivalent calculated from the content of carboxyl groups. In detail, in the present invention, since both the diimide dicarboxylic acid compound and the bifunctional epoxy resin are bifunctional, the functional group equivalent of the diimide dicarboxylic acid compound corresponds to the molar amount of the diimide dicarboxylic acid compound relative to 1 mole of the bifunctional epoxy resin. When two or more diimidedicarboxylic acid compounds are used, the total amount of them should be the above blend amount.

Since the phosphorus-based compound acts as a catalyst, the amount of the compound is preferably 0.1 to 1 part by mass, more preferably 0.1 to 0.5 parts by mass, and more preferably 0.2 to 0.5 parts by mass, per 100 parts by mass of the total amount of the diimidedicarboxylic acid compound and the bifunctional functional group. When two or more phosphorus-based compounds are used, the total amount of the compounds should be the above amount. If a catalyst other than a phosphorus-based compound is used as a catalyst, gelation occurs during the synthesis of the imide group-containing epoxy resin, and the viscosity increases. As a result, the compatibility of the imide group-containing epoxy resin and the curing agent decreases during the production of the cured product, and these components behave as insoluble components, resulting in a decrease in the uniformity (transparency) of the cured product.

The phosphorus-based compound is not particularly limited, and examples thereof include organic phosphines such as aromatic organic phosphines (e.g., triphenylphosphine, tri(o-tolyl)phosphine, tri(m-tolyl)phosphine, tri(p-tolyl)phosphine, tris(4-methoxyphenyl)phosphine, diphenylcyclohexylphosphine), alicyclic organic phosphines (e.g., tricyclohexylphosphine), aliphatic organic phosphines (e.g., tributylphosphine (especially tri-tert-butylphosphine), tri-n-octylphosphine); aromatic phosphonium salts (e.g., tetraphenylphosphonium bromide, n-butyltriphenylphosphonium bromide, Examples of phosphorus-based compounds include phosphonium salts such as methyltriphenylphosphonium bromide, ethyltriphenylphosphonium bromide, (methoxymethyl)triphenylphosphonium chloride, benzyltriphenylphosphonium chloride, tetraphenylphosphonium tetraphenylborate, tetraphenylphosphonium tetra-p-tolylborate, triphenylborane-triphenylphosphine, tri-tert-butylphosphonium tetraphenylborate, and aliphatic phosphonium salts (e.g., tetrabutylphosphonium bromide). Phosphorus-based compounds may be used alone or in combination of two or more. Phosphorus-based compounds are commercially available.

From the viewpoint of further improving the fluidity of the imide group-containing epoxy resin and the uniformity and heat resistance of the resulting cured product, the phosphorus-based compound is preferably an organic phosphine, more preferably an aromatic organic phosphine, and even more preferably triphenylphosphine.

<Curable Epoxy Resin Composition>
The curable epoxy resin composition of the present invention comprises a mixture of at least an imide group-containing epoxy resin and a curing agent.

Examples of the curing agent include imidazoles, dicyandiamides, phenol-based curing agents, thiol-based curing agents, amine-based curing agents, acid anhydride-based curing agents, cyanate-based curing agents, and active ester-based curing agents. Among these, imidazoles, acid anhydride-based curing agents, and amine-based curing agents are preferred. The curing agent may be used alone or in combination of two or more of the above.

Imidazoles include, for example, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-heptadecylimidazole, 2-undecylimidazole, 1,2-dimethylimidazole, 4-methyl-2-phenylimidazole, N-benzyl-2-methylimidazole, 2-phenyl-1-benzyl-1H-imidazole, and 1-(2-cyanoethyl)-2-undecylimidazole. , 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole, 1-(2-cyanoethyl)-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 2,4-diamino-6-[2-methylimidazolyl-(1)]ethyl-s-triazine, 4,5-di(hydroxymethyl)-2-phenyl-1H-imidazole, 4-methyl-2-phenyl-5-hydroxymethyl-1H-imidazole, etc.

Examples of acid anhydride curing agents include 4-methylcyclohexane-1,2-dicarboxylic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, hydrogenated methylnadic anhydride, trialkyltetrahydrophthalic anhydride, methylcyclohexenetetracarboxylic dianhydride, phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenonetetracarboxylic dianhydride, ethylene glycol bisanhydrotrimellitate, glycerin bis(anhydrotrimellitate) monoacetate, and dodecenyl succinic anhydride.

Amine-based hardeners include, for example, aliphatic polyamines (e.g., diethylenetriamine, triethylenetetramine, tetraethylenepentamine, m-xylenediamine, trimethylhexamethylenediamine, 2-methylpentamethylenediamine, diethylaminopropylamine), alicyclic polyamines (e.g., isophoronediamine, 1,3-bisaminomethylcyclohexane, bis(4-aminocyclohexyl)methane, norbornenediamine, 1,2-diaminocyclohexane), aromatic polyamines (e.g., 4,4-diaminodiphenylmethane, metaphenylenediamine, diaminodiphenylsulfone), etc.

The amounts of these hardeners used vary depending on the type of hardener. If hardeners are classified as Class A hardeners and Class B hardeners, the amounts to be used are as follows:

　Class A hardeners are hardeners belonging to the dicyandiamide and imidazole classes. The amount of Class A hardener blended is preferably 1 to 10 parts by mass, more preferably 1 to 3 parts by mass, per 100 parts by mass of the imide group-containing epoxy resin. Class A hardeners may be used alone or in combination of two or more types. When two or more types are used in combination, it is preferable that the total amount blended is within the above range.

　Class B curing agents are curing agents that belong to the following categories: phenol-based curing agents, thiol-based curing agents, amine-based curing agents, acid anhydride-based curing agents, cyanate-based curing agents, and active ester-based curing agents. The amount of Class B to be blended is preferably an equivalent ratio of 0.1 to 1.0, more preferably 0.1 to 0.5, relative to the epoxy equivalent of the imide group-containing epoxy resin. Class B curing agents may be used alone or in combination of two or more of the above. When two or more types are used in combination, it is preferable that the total amount is within the above range.

　Class A curing agent and Class B curing agent may be used in combination. When used in combination, it is sufficient to use one or more types of Class A curing agent and Class B curing agent. For example, one Class A curing agent and one Class B curing agent may be used, one Class A curing agent and two Class B curing agents may be used, or two Class A curing agents and one Class B curing agent may be used. When used in combination, for example, the amount of Class A curing agent is 0.1 parts by mass or more relative to 100 parts by mass of the imide group-containing epoxy resin, and the amount of Class B curing agent is 0.5 equivalent ratio or more relative to the epoxy equivalent of the imide group-containing epoxy resin. When used in combination, the Class A curing agent is preferably in an amount of 0.1 to 1.0 parts by mass, more preferably 0.1 to 0.5 parts by mass, relative to 100 parts by mass of the imide group-containing epoxy resin. In this case, when two or more Class A curing agents are used, it is preferable that the total amount of them is in the above range. When used in combination, the amount of the B-type curing agent is preferably 0.5 to 1.5 equivalent ratio, more preferably 0.7 to 1.3 equivalent ratio, relative to the epoxy equivalent of the imide group-containing epoxy resin. In this case, when two or more types of B-type curing agents are used, it is preferable that the total amount of them is in the above range.

Other additives such as curing accelerators, inorganic fillers, antioxidants, flame retardants, organic solvents, etc. may be added to the curable epoxy resin composition of the present invention as long as they do not impair the effects of the present invention.

Examples of the curing accelerator include tertiary amines such as 4-dimethylaminopyridine, benzyldimethylamine, 2-(dimethylaminomethyl)phenol, and 2,4,6-tris(dimethylaminomethyl)phenol; and organic phosphines such as triphenylphosphine and tributylphosphine. The curing accelerator may be used alone or in combination of two or more. When a curing accelerator is used, the amount of the curing accelerator is preferably 0.01 to 2.0% by mass relative to the curable epoxy resin composition. Since the heat resistance and dielectric properties of the resulting cured product are improved, the amount is preferably 0.01 to 1% by mass, and more preferably 0.05 to 0.5% by mass.

Examples of inorganic fillers include silica, barium sulfate, alumina, aluminum nitride, boron nitride, silicon nitride, glass powder, glass frit, glass fiber, carbon fiber, and inorganic ion exchangers. The inorganic fillers may be used alone or in combination of two or more. When using inorganic fillers, the average particle size of the inorganic filler is preferably 50 nm to 4 μm, and more preferably 100 nm to 3 μm, as this provides better coatability and processability.

Examples of antioxidants include hindered phenol-based antioxidants, phosphorus-based antioxidants, and thioether-based antioxidants. The antioxidants may be used alone or in combination of two or more.

Flame retardants include non-halogen flame retardants, phosphorus-based flame retardants, nitrogen-based flame retardants, and silicone-based flame retardants. Among these, non-halogen flame retardants are preferred from the viewpoint of environmental impact. The flame retardants may be used alone or in combination of two or more of the above.

The organic solvent is an organic solvent capable of dissolving the imide group-containing epoxy resin and the curing agent. Examples of such organic solvents include cyclohexanone, γ-butyrolactone, dimethylacetamide, dimethylformamide, and N-methyl-2-pyrrolidone.

The curable epoxy resin composition of the present invention preferably does not contain a solvent (particularly an organic solvent). This is because the curable epoxy resin composition of the present invention can have excellent fluidity even without containing a solvent, based on the excellent fluidity of the imide group-containing epoxy resin. The content of the solvent (particularly an organic solvent) is not particularly limited, and is, for example, 10 mass % or less, preferably 5 mass % or less, more preferably 1 mass % or less, even more preferably 0.1 mass % or less, and particularly preferably 0 mass % or less, based on the total amount of the curable epoxy resin composition.

The content of the solvent (particularly the organic solvent) can be calculated from the mass before and after the curable epoxy resin composition is subjected to a heat treatment (i.e., drying treatment) at 80 to 250°C for 1 minute to 20 hours. In detail, the content of the solvent (particularly the organic solvent) can be calculated based on the formula: {(X-Y)/X} x 100 (%), where Xg is the mass before the drying treatment and Yg is the mass after the drying treatment.

The method for producing the curable epoxy resin composition of the present invention is not particularly limited, but examples include a method in which an imide group-containing epoxy resin, a curing agent, and other additives that are added as necessary are mixed using a mixer such as a homodisper, a universal mixer, a Banbury mixer, or a kneader.

<Cured Product>
The present invention also provides a cured product. The cured product of the present invention is a cured product of the above-mentioned curable epoxy resin composition of the present invention. By heating the curable epoxy resin composition of the present invention, the imide group-containing epoxy resin and the curing agent are reacted to obtain a cured product. The heating temperature (curing temperature) is preferably 80 to 350°C, more preferably 130 to 220°C, and more preferably 130 to 200°C. The heating time (curing time) is preferably 1 minute to 24 hours, more preferably 5 minutes to 10 hours, and more preferably 1 to 5 hours.

<Applications of the cured product>
The cured product of the present invention is excellent in heat resistance, uniformity, and mechanical properties, and therefore can be suitably used as an electrical insulating material. Specifically, the cured product of the present invention can be suitably used as an electrical insulating material for sealing materials (e.g., sealing materials for power semiconductor modules), printed wiring boards, molding materials (e.g., molding materials for bushing transformers, molding materials for solid insulating switch gears), electrical penetration for nuclear power plants, build-up laminates, powder coatings, and the like. Among these, the cured product of the present invention can be suitably used for sealing materials and printed wiring boards.

When the cured product of the present invention is used as an insulating material for sealing materials, it can be used, for example, by producing a power semiconductor module, filling the mold in which the module is set with the curable epoxy resin composition of the present invention, and curing it.

For example, when the cured product of the present invention is used as an insulating material for printed wiring boards, a solvent is often used. In this case, the solution of the curable epoxy resin composition of the present invention can be used by impregnating or coating a glass cloth with the solution and then curing it. The solution of the curable epoxy resin composition of the present invention is the same as the solution of the curable epoxy resin composition when the cured product of the present invention is used as an insulating material for sealing materials. An insulating material for printed wiring boards refers to an insulating material that constitutes a printed wiring board.

The curable epoxy resin composition of the present invention can also be used for purposes other than electrical insulation materials. Specifically, the curable epoxy resin composition of the present invention can be used for adhesives and CFRP.

The present invention will be explained in detail below with reference to examples, but the present invention is not limited to these.

A. Raw Materials The raw materials used in the examples and comparative examples are shown below.
(A) Bifunctional epoxy resin/bisphenol A type epoxy resin: manufactured by Tokyo Chemical Industry Co., Ltd., epoxy equivalent 170 g/eq
Naphthalene type epoxy resin: "HP-4032D" manufactured by DIC Corporation, epoxy equivalent 141 g/eq
Anthracene type epoxy resin "YX8800" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent 180 g/eq
Biphenyl type epoxy resin: "YX4000H" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent 191 g/eq.

(B) Multifunctional epoxy resin/cresol novolac type epoxy resin: "N-660" manufactured by DIC Corporation, epoxy equivalent 209 g/eq

(C) Diimidedicarboxylic acid compounds: Diimidedicarboxylic acid X
A mechanochemical treatment was carried out by mixing and grinding 52.3 parts by mass of 4,4'-diaminodiphenyl ether and 100 parts by mass of trimellitic anhydride at a rotation speed of 9000 rpm for 1 minute three times using a Wonder Crusher WC-3C manufactured by Osaka Chemical Co., Ltd. The treated sample was transferred to a glass container and subjected to an imidization reaction at 300°C for 2 hours in a nitrogen atmosphere using an inert oven DN411I manufactured by Yamato Scientific Co., Ltd., to obtain diimidedicarboxylic acid X.
Diimidedicarboxylic acid X was confirmed by ¹ H-NMR to be a trimer composed of trimellitic acid-4,4′-diaminodiphenyl ether-trimellitic acid. Mass spectrometry revealed that diimidedicarboxylic acid X had a number average molecular weight of 549 and was a solid at room temperature.

Diimide dicarboxylic acid Y
Diimidedicarboxylic acid Y was obtained in the same manner as diimidedicarboxylic acid X, except that 52.3 parts by mass of 4,4'-diaminodiphenyl ether was used in place of 107.2 parts by mass of 2,2-bis[4-(4-aminophenoxy)phenyl]propane.
Diimidedicarboxylic acid Y was confirmed by ^1H -NMR to be a trimer composed of trimellitic acid-2,2-bis[4-(4-aminophenoxy)phenyl]propane-trimellitic acid. Mass spectrometry revealed that the number average molecular weight of diimidedicarboxylic acid Y was 759 and that it was a solid at room temperature.

Diimidedicarboxylic acid Z
Diimidedicarboxylic acid Z was obtained in the same manner as diimidedicarboxylic acid X, except that 52.3 parts by mass of 4,4'-diaminodiphenyl ether was used instead of 29.8 parts by mass of trans-1,4-cyclohexanediamine.
Diimidedicarboxylic acid Z was confirmed by ¹ H-NMR to be a trimer composed of trimellitic acid-trans-1,4-cyclohexanediamine-trimellitic acid. Mass spectrometry revealed that diimidedicarboxylic acid Z had a number average molecular weight of 462 and was a solid at room temperature.

(D) Phosphorus compounds, triphenylphosphine: manufactured by Tokyo Chemical Industry Co., Ltd. (E) Other catalysts, N,N-dimethylbenzylamine: manufactured by Tokyo Chemical Industry Co., Ltd.

(F) Hardener 2-ethyl-4-methylimidazole: manufactured by Tokyo Chemical Industry Co., Ltd. 4-methylcyclohexane-1,2-dicarboxylic anhydride: manufactured by Tokyo Chemical Industry Co., Ltd. 4,4-diaminodiphenylmethane: manufactured by Tokyo Chemical Industry Co., Ltd.

B. Evaluation Methods The compounds (imide group-containing epoxy resins) and cured products obtained in the examples and comparative examples were evaluated as follows.

[Evaluation method of imide group-containing epoxy resin]
(1) Confirmation of Esterification Reaction The imide group-containing epoxy resins obtained in the Examples and Comparative Examples were measured and identified by infrared spectroscopy (IR) under the following conditions.

<Measurement conditions>
Apparatus: Nicolet iS5 FT-IR, iD7 ATR accessory, manufactured by Thermo Fisher Scientific Method: ATR method Number of scans: 64 (resolution 4 cm-1)
The presence or absence of absorption near 1680 cm ⁻¹ due to the carboxyl group of the diimidedicarboxylic acid compound was confirmed.
<Evaluation criteria>
⊚: The esterification reaction proceeded sufficiently; the peak derived from the carboxyl group disappeared;
×: Esterification reaction did not proceed sufficiently; peaks derived from carboxyl groups remained

(2) Epoxy Equivalent Weight The imide group-containing epoxy resins obtained in the Examples and Comparative Examples were measured by nuclear magnetic resonance (NMR) under the following conditions, and the epoxy equivalent weight was calculated.
The imide group-containing epoxy resins obtained in the examples and comparative examples were subjected to ^1H -NMR analysis using a high-resolution nuclear magnetic resonance apparatus (JNM-ECA500 NMR manufactured by JEOL Ltd.) to determine the resin composition from the peak intensity of each copolymerization component (resolution: 500 MHz, solvent: deuterated dimethyl sulfoxide, temperature: 25°C).

<Measurement conditions>
Equipment: JNM-ECA500 NMR manufactured by JEOL Ltd.
Resolution: 500MHz
Solvent: Deuterated dimethyl sulfoxide Temperature: 25°C
Method: Internal standard method (sodium 3-(trimethylsilyl)propionate-2,2,3,3-d4 (TSP-d4); purity 99.8%)
The epoxy equivalent was calculated from the peak intensity of the internal standard and each component.
<Evaluation criteria>
◎: 250≦epoxy equivalent≦350 (best);
○: 200≦epoxy equivalent<250 or 350<epoxy equivalent≦500 (good);
Δ: Epoxy equivalent < 200 or 500 < epoxy equivalent ≦ 1000 (no problem in practical use);
×: Epoxy equivalent > 1000 (problems in practical use).

(3) Evaluation of fluidity (viscosity measurement)
The imide group-containing epoxy resins obtained in the examples and comparative examples were subjected to dynamic viscoelasticity measurement under the following conditions, and the viscosity was calculated.

<Measurement conditions>
Apparatus: TA Instruments ARESG2 Rheometer Measurement temperature range: 25 to 200°C
Temperature rise rate: 5° C./min Angular frequency: 10 rad/s
The viscosity at 140°C was calculated.
<Evaluation criteria>
◎: Viscosity ≦10 Pa·s (best);
○: 10 Pa·s<viscosity≦100 Pa·s (good);
△: 100 Pa·s<viscosity≦1000 Pa·s (no problem in practical use);
×: Viscosity < 1000 Pa·s (problems in practical use).

[Evaluation method of the cured product]
(1) Evaluation of Uniformity (Transparency) The presence or absence of insoluble components in the cured products obtained in the Examples and Comparative Examples was visually confirmed to judge the uniformity. Insoluble components impair the uniformity and transparency of the cured product.

<Evaluation criteria>
◎ (Uniform): No insoluble matter. Completely transparent.
△ (almost uniform): some insoluble components present, but transparent.
× (uneven): Contains insoluble components and is opaque.

(2) Glass transition temperature of the cured product (heat resistance)
The cured products obtained in the examples and comparative examples were measured using a differential scanning calorimeter (DSC) under the following conditions.
<Measurement conditions>
Apparatus: Perkin Elmer DSC 6000
Temperature rise rate: 10° C./min. The temperature was raised from 25° C. to 300° C., and the starting temperature of the discontinuous change resulting from the transition temperature in the obtained temperature rise curve was determined as the glass transition temperature.

<Evaluation criteria>
◎: Tg≧200° C. (best);
○: 200° C.>Tg≧180° C. (good);
Δ: 180° C.>Tg≧150° C. (no problem in practical use);
×: 150° C.>Tg (bad) (problematic in practical use).

[comprehensive evaluation]
A comprehensive evaluation was made based on the evaluation results of the fluidity of the imide group-containing epoxy resin, as well as the uniformity and heat resistance of the cured product.
<Evaluation criteria>
: All evaluation results were rated as .
◯: Of all the evaluation results, the lowest evaluation result was ◯.
Δ: Of all the evaluation results, Δ was the lowest evaluation result.
×: Of all the evaluation results, the lowest evaluation result was ×.

Example 1
(Imide Group-Containing Epoxy Resin A)
100 parts by mass of naphthalene-type epoxy resin, 19 parts by mass of diimidedicarboxylic acid X, and 0.3 parts by mass of triphenylphosphine were charged into a reaction vessel equipped with a heating mechanism and a stirring mechanism. The mixture was then heated to 150° C. with stirring and reacted for 1 hour under normal pressure in a nitrogen stream to obtain an imide group-containing epoxy resin A.
The imide group-containing epoxy resin A was confirmed by IR to have undergone a sufficient esterification reaction, and the imide group-containing epoxy resin A had an epoxy equivalent of 216 according to ¹ H-NMR, and was a viscous solid at room temperature.
From these results and the charged amounts, it was confirmed that the imide group-containing epoxy resin A has a structure in which one molecule of a diimidedicarboxylic acid compound is bonded to each end of the molecule via an ester bond.

(Cured product)
The obtained imide group-containing epoxy resin A and a curing agent were mixed to obtain the composition shown in Table 1, and the mixture was heated at 200° C. in a nitrogen atmosphere to carry out a curing reaction for 3 hours to obtain a cured product.

Example 2
(Imide group-containing epoxy resin B)
An imide group-containing epoxy resin B was obtained in the same manner as in Example 1, except that 19 parts by mass of diimidedicarboxylic acid X was used in place of 39 parts by mass.
Incidentally, IR analysis of imide group-containing epoxy resin B confirmed that the esterification reaction had progressed sufficiently, and ¹ H-NMR analysis revealed that imide group-containing epoxy resin B had an epoxy equivalent of 309 and was solid at room temperature.
From these results and the charged amounts, it was confirmed that the imide group-containing epoxy resin B has a structure in which one molecule of a diimidedicarboxylic acid compound is bonded to each end of the molecule via an ester bond.

The obtained imide group-containing epoxy resin B was used to prepare a cured product in the same manner as in Example 1, except that the blending amounts were changed to obtain the composition shown in Table 1.

Examples 3 to 5
(Imide group-containing epoxy resin C)
An imide group-containing epoxy resin C was obtained in the same manner as in Example 1, except that 58 parts by mass of diimidedicarboxylic acid X was used instead of 19 parts by mass.
Incidentally, IR analysis of imide group-containing epoxy resin C confirmed that the esterification reaction had progressed sufficiently, and ¹ H-NMR analysis revealed that imide group-containing epoxy resin C had an epoxy equivalent of 400 and was solid at room temperature.
From these results and the charged amounts, it was confirmed that the imide group-containing epoxy resin C has a structure in which one molecule of a diimidedicarboxylic acid compound is bonded to each end of the molecule via an ester bond.

The obtained imide group-containing epoxy resin C was used to prepare a cured product in the same manner as in Example 1, except that the amounts were changed to obtain the composition shown in Table 1.

Example 6
(Imide group-containing epoxy resin D)
An imide group-containing epoxy resin D was obtained in the same manner as in Example 1, except that 78 parts by mass of diimidedicarboxylic acid X and 0.4 parts by mass of triphenylphosphine were used instead of 19 parts by mass and 0.3 parts by mass, respectively.
Incidentally, IR analysis of imide group-containing epoxy resin D revealed that the esterification reaction had progressed sufficiently, and ¹ H-NMR analysis revealed that imide group-containing epoxy resin D had an epoxy equivalent of 543 and was solid at room temperature.
From these results and the charged amounts, it was confirmed that imide group-containing epoxy resin D has a structure in which one molecule of a diimidedicarboxylic acid compound is bonded to each end of the molecule via an ester bond.

The obtained imide group-containing epoxy resin D was used to prepare a cured product in the same manner as in Example 1, except that the blending amounts were changed to obtain the composition shown in Table 1.

Example 7
(Imide group-containing epoxy resin E)
An imide group-containing epoxy resin E was obtained in the same manner as in Example 1, except that the naphthalene type epoxy resin was replaced with the bisphenol A type epoxy resin and the 19 parts by mass of diimidedicarboxylic acid X was replaced with 48 parts by mass.
The esterification reaction of the imide group-containing epoxy resin E was confirmed by IR spectroscopy, and it was found to have progressed sufficiently. Furthermore, the epoxy equivalent of the imide group-containing epoxy resin E was found to be 441 by ¹ H-NMR spectroscopy, and the resin was a solid at room temperature.
From these results and the charged amounts, it was confirmed that the imide group-containing epoxy resin E has a structure in which one molecule of a diimidedicarboxylic acid compound is bonded to each end of the molecule via an ester bond.

The obtained imide group-containing epoxy resin E was used to prepare a cured product in the same manner as in Example 1, except that the blending amounts were changed to obtain the composition shown in Table 1.

Example 8
(Imide group-containing epoxy resin F)
An imide group-containing epoxy resin F was obtained in the same manner as in Example 1, except that the naphthalene type epoxy resin was replaced with an anthracene type epoxy resin and 19 parts by mass of diimidedicarboxylic acid X was replaced with 46 parts by mass.
It should be noted that IR analysis confirmed that the esterification reaction had progressed sufficiently for the imide group-containing epoxy resin F. Furthermore, ¹ H-NMR analysis revealed that the epoxy equivalent of the imide group-containing epoxy resin E was 375, and the resin was solid at room temperature.
From these results and the charged amounts, it was confirmed that imide group-containing epoxy resin F has a structure in which one molecule of a diimidedicarboxylic acid compound is bonded to each end of the molecule via an ester bond.

The obtained imide group-containing epoxy resin F was used to prepare a cured product in the same manner as in Example 1, except that the compounding amounts were changed to obtain the composition shown in Table 1.

Example 9
(Imide group-containing epoxy resin G)
An imide group-containing epoxy resin G was obtained in the same manner as in Example 1, except that the naphthalene type epoxy resin was replaced with a biphenyl type epoxy resin and 19 parts by mass of diimidedicarboxylic acid X was replaced with 43 parts by mass.
Incidentally, IR analysis of imide group-containing epoxy resin G revealed that the esterification reaction had progressed sufficiently, and ¹ H-NMR analysis revealed that imide group-containing epoxy resin G had an epoxy equivalent of 412 and was solid at room temperature.
From these results and the charged amounts, it was confirmed that the imide group-containing epoxy resin G has a structure in which one molecule of a diimidedicarboxylic acid compound is bonded to each end of the molecule via an ester bond to one molecule of a bifunctional epoxy resin.

The obtained imide group-containing epoxy resin G was used to prepare a cured product in the same manner as in Example 1, except that the blending amounts were changed to obtain the composition shown in Table 1.

Example 10
(Imide group-containing epoxy resin H)
An imide group-containing epoxy resin H was obtained in the same manner as in Example 1, except that 81 parts by mass of diimidedicarboxylic acid Y was used in place of 19 parts by mass of diimidedicarboxylic acid X, and 0.4 parts by mass of triphenylphosphine was used in place of 0.3 parts by mass.
Incidentally, IR analysis of imide group-containing epoxy resin H confirmed that the esterification reaction had progressed sufficiently, and ¹ H-NMR analysis revealed that imide group-containing epoxy resin H had an epoxy equivalent of 450 and was solid at room temperature.
From these results and the charged amounts, it was confirmed that imide group-containing epoxy resin H has a structure in which one molecule of a diimidedicarboxylic acid compound is bonded to each end of the molecule via an ester bond.

The obtained imide group-containing epoxy resin H was used to prepare a cured product in the same manner as in Example 1, except that the compounding amounts were changed to obtain the composition shown in Table 1.

Example 11
(Imide group-containing epoxy resin I)
An imide group-containing epoxy resin I was obtained in the same manner as in Example 1, except that 19 parts by mass of diimidedicarboxylic acid X was used in place of 49 parts by mass of diimidedicarboxylic acid Z.
Incidentally, IR analysis confirmed that the esterification reaction had progressed sufficiently for the imide group-containing epoxy resin I. Furthermore, ¹ H-NMR analysis revealed that the imide group-containing epoxy resin I had an epoxy equivalent of 380 and was solid at room temperature.
From these results and the charged amounts, it was confirmed that the imide group-containing epoxy resin I has a structure in which one molecule of a diimidedicarboxylic acid compound is bonded to each end of the molecule via an ester bond.

The obtained imide group-containing epoxy resin I was used to prepare a cured product in the same manner as in Example 1, except that the amounts were changed to obtain the composition shown in Table 1.

Comparative Example 1
(Imide group-containing epoxy resin J)
An imide group-containing epoxy resin J was obtained in the same manner as in Example 1, except that 19 parts by mass of diimidedicarboxylic acid X was replaced with 58 parts by mass, and triphenylphosphine was used in place of N,N-dimethylbenzylamine.
Incidentally, IR analysis of imide group-containing epoxy resin J confirmed that the esterification reaction had progressed sufficiently, and ¹ H-NMR analysis revealed that imide group-containing epoxy resin J had an epoxy equivalent of 1,500 and was a solid at room temperature.
From these results, it was confirmed that the imide group-containing epoxy resin J has a polymer structure in which a diimidedicarboxylic acid compound and a bifunctional epoxy resin are repeatedly bonded via ester bonds.

The obtained imide group-containing epoxy resin J was used to prepare a cured product in the same manner as in Example 1, except that the blending amounts were changed to obtain the composition shown in Table 1.

Comparative Example 2
(Imide group-containing epoxy resin K)
An imide group-containing epoxy resin K was obtained in the same manner as in Example 1, except that the naphthalene type epoxy resin was replaced with a cresol novolac type epoxy resin and 19 parts by mass of diimide dicarboxylic acid X was replaced with 39 parts by mass.
When the imide group-containing epoxy resin K was examined by IR, it was found that the esterification reaction had not progressed sufficiently and some unreacted material remained.
From these results, it was confirmed that the imide group-containing epoxy resin K was simply a mixture of a diimidedicarboxylic acid compound and a polyfunctional epoxy resin.

The obtained imide group-containing epoxy resin K was used to prepare a cured product in the same manner as in Example 1, except that the blending amounts were changed to obtain the composition shown in Table 1.

Comparative Example 3
100 parts by mass of bisphenol A type epoxy resin and 163 parts by mass of diimidedicarboxylic acid X were mixed at room temperature to obtain a mixture.
When the mixture was examined by IR, it was found that the esterification reaction had not progressed sufficiently.
From these results, it was confirmed that the mixture was simply a mixture of a diimidedicarboxylic acid compound and a bifunctional epoxy resin.

The obtained mixture was used to prepare a cured product in the same manner as in Example 1, except that the compounding amounts were changed to obtain the composition shown in Table 1.

The composition of the imide group-containing epoxy resin and the evaluation results of the resulting cured product are shown in Table 1.

The symbols in the table are as follows.
-: Not blended.
*: Value relative to the epoxy equivalent of difunctional epoxy resin.
＊＊: Not measured.
***: The acid anhydride and amine curing agent are charged at an equivalent ratio of 1/0.25 to the imide group-containing epoxy resin, while the imidazole is charged by parts by mass regardless of the equivalent ratio.

In Examples 1 to 11, all of the compounds contained a bifunctional epoxy resin and a diimidedicarboxylic acid compound, which were bonded by ester bonds and had an epoxy equivalent of 1000 or less, so imide group-containing epoxy resins with excellent fluidity could be obtained. In particular, the use of a bifunctional epoxy resin and a phosphorus-based compound as a catalyst allowed for control of fluidity. In addition, all of the cured products were homogenized, and because an imidedicarboxylic acid compound was used, they had excellent heat resistance.

In Comparative Example 1, the catalyst was changed from a phosphorus-based compound to a tertiary amine, and synthesis was performed. As a result, gelation occurred during synthesis of the imide group-containing epoxy resin, and the viscosity increased. This reduced the compatibility of the imide group-containing epoxy resin with the curing agent, and these components behaved as insoluble components, resulting in a decrease in the uniformity (transparency) of the cured product.

In Comparative Example 2, the bifunctional epoxy resin was changed to a multifunctional epoxy resin, and an imide group-containing epoxy resin was synthesized. As a result, the reaction between the epoxy resin and diimidedicarboxylic acid did not proceed sufficiently, and some unreacted material remained. As a result, the uniformity of the cured product was poor.

In Comparative Example 3, the raw materials were simply mixed and cured, so the product did not become an imide group-containing epoxy resin, had high viscosity, and had poor uniformity in the cured product. It did not exhibit sufficient heat resistance.

The imide group-containing epoxy resin of the present invention and the cured product using the same are useful as electrical insulating materials such as sealing materials, printed wiring boards, molding materials, electrical penetration for nuclear power plants, and build-up laminates.

Claims (16)

The present invention relates to a diimide dicarboxylic acid compound represented by general formula (1) and a bifunctional epoxy resin,
the diimide dicarboxylic acid compound and the bifunctional epoxy resin are bonded by an ester bond,
An imide group-containing epoxy resin having an epoxy equivalent of 1,000 or less.

(In formula (1), ^X1 and ^X2 each independently represent a structure derived from an aromatic tricarboxylic anhydride component, an alicyclic tricarboxylic anhydride component, or an aliphatic tricarboxylic anhydride component; ^R1 represents a structure derived from an aromatic diamine component, or an alicyclic diamine component.) The imide group-containing epoxy resin according to claim 1, wherein the bifunctional epoxy resin is one or more epoxy resins selected from the group consisting of bisphenol A type epoxy resins, naphthalene type epoxy resins, biphenyl type epoxy resins, and anthracene type epoxy resins. The bifunctional epoxy resin is one or more epoxy resins selected from the group consisting of naphthalene type epoxy resins and biphenyl type epoxy resins,
2. The imide group-containing epoxy resin according to claim 1, wherein the epoxy equivalent is 500 or less. The bifunctional epoxy resin is one or more epoxy resins selected from the group consisting of naphthalene type epoxy resins and biphenyl type epoxy resins,
The imide group-containing epoxy resin according to claim 1, wherein the epoxy equivalent is 250 to 350. The imide group-containing epoxy resin according to claim 1, wherein the imide group-containing epoxy resin has a structure in which one molecule of the difunctional epoxy resin is bonded to each end of one molecule of the diimide dicarboxylic acid compound via an ester bond. A method for producing an imide group-containing epoxy resin by reacting a diimide dicarboxylic acid compound with a bifunctional epoxy resin in the presence of a phosphorus compound. The method for producing an imide group-containing epoxy resin according to claim 6, wherein the amount of the diimide dicarboxylic acid compound is such that the functional group equivalent of the diimide dicarboxylic acid compound is 0.01 to 0.6 equivalent ratio relative to the epoxy equivalent of the bifunctional epoxy resin. The bifunctional epoxy resin is one or more epoxy resins selected from the group consisting of naphthalene type epoxy resins and biphenyl type epoxy resins,
The method for producing an imide group-containing epoxy resin according to claim 6, wherein the diimide dicarboxylic acid compound is blended in an amount such that the functional group equivalent of the diimide dicarboxylic acid compound is 0.05 to 0.35 equivalent ratio relative to the epoxy equivalent of the bifunctional epoxy resin. The bifunctional epoxy resin is one or more epoxy resins selected from the group consisting of naphthalene type epoxy resins and biphenyl type epoxy resins,
The method for producing an imide group-containing epoxy resin according to claim 6, wherein the diimide dicarboxylic acid compound is blended in an amount such that the functional group equivalent of the diimide dicarboxylic acid compound is 0.15 to 0.25 equivalent ratio relative to the epoxy equivalent of the bifunctional epoxy resin. The method for producing the imide group-containing epoxy resin according to claim 6, which produces the imide group-containing epoxy resin according to any one of claims 1 to 5. A curable epoxy resin composition comprising the imide group-containing epoxy resin according to any one of claims 1 to 5 and a curing agent. A cured product of the curable epoxy resin composition according to claim 11. An electrical insulating material comprising the cured product according to claim 12. A sealant comprising the cured product according to claim 12. The encapsulant according to claim 14, which is used in a power semiconductor module. A printed wiring board comprising the cured product according to claim 12.