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

Abstract

To provide an imide group-containing epoxy resin with excellent fluidity and a curable epoxy resin composition employing the same, which are able to form a cured product excellent in uniformity and heat resistance even under relaxed curing conditions (e.g., a condition of curing temperature equal to or lower than 200°C).SOLUTION: An imide group-containing epoxy resin comprises a diimide dicarboxylic acid based compound represented by a specific general formula, and a bifunctional epoxy resin, where the diimide dicarboxylic acid based compound and the bifunctional epoxy resin are ester-bonded, and the epoxy equivalent is 1000 or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an imide group-containing epoxy resin having an imide skeleton and a curable epoxy resin containing the same. [Background technology]

[0002] Curable 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.

[0003] In recent years, the development of materials for electronics components has become more active in order to support large capacity and high speed communication. For example, the rise in junction temperature due to the high performance of semiconductor elements and the increase in heat generation due to improved efficiency have increased the need for high performance epoxy resin materials, and higher heat resistance than ever before is required.

[0004] Furthermore, 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.Since 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.

[0005] On the other hand, methods such as cast molding and transfer molding are used to encapsulate power semiconductors and semiconductor elements, but these do not use solvents and must flow and harden at the molding temperature (200°C or lower) to exhibit sufficient performance.

[0006] For example, Patent Document 1 discloses a cured product obtained by using a compound having an imide structure in an epoxy resin. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2021 / 117686 Brochure Summary of the Invention [Problem to be solved by the invention]

[0008] However, the cured product of Patent Document 1 is produced using a solvent, and is cured at a high temperature of 300° C. If Patent Document 1 is cured at 200° C. without using a solvent, there are problems in that the flowability is poor, the uniformity is reduced, and sufficient heat resistance is not exhibited.

[0009] An object of the present invention is to provide an imide group-containing epoxy resin having excellent flowability, which can give a cured product having excellent uniformity and heat resistance even under mild curing conditions (for example, a curing temperature condition of 200°C or less), and a curable epoxy resin composition using the same. [Means for solving the problem]

[0010] As a result of intensive research into the above-mentioned problems, the present inventors have found that the above-mentioned object can be achieved by reacting a specific bifunctional epoxy resin with a specific diimidedicarboxylic acid compound in advance, thereby completing the present invention.

[0011] That is, the gist of the present invention is as follows. <1> The present invention relates to a diimide dicarboxylic acid compound represented by the general formula (1) and a bifunctional epoxy resin, the diimide-dicarboxylic acid compound and the bifunctional epoxy resin are bonded by an ester bond, The bifunctional epoxy resin is an imide group-containing epoxy resin which is a polycyclic aromatic hydrocarbon type epoxy resin or a biphenyl type epoxy resin. [ka] (In formula (1), X 1 and X 2R each independently represents a structure derived from an aromatic tricarboxylic anhydride component, an alicyclic tricarboxylic anhydride component, or an aliphatic tricarboxylic anhydride component; 1 represents a structure derived from an aromatic diamine component or an alicyclic diamine component. <2> The epoxy equivalent is 1000 or less. <1> The imide group-containing epoxy resin according to claim 1. <3> The bifunctional epoxy resin is one or more epoxy resins selected from the group consisting of naphthalene epoxy resins and biphenyl epoxy resins, The epoxy equivalent is 500 or less. <1> or <2> The imide group-containing epoxy resin according to claim 1. <4> The bifunctional epoxy resin is one or more epoxy resins selected from the group consisting of naphthalene epoxy resins and biphenyl epoxy resins, The epoxy equivalent is 250 to 350. <1> ~ <3> 2. The imide group-containing epoxy resin according to claim 1 . <5> The imide group-containing epoxy resin has a structure in which one molecule of the diimide dicarboxylic acid compound is bonded to each end of the difunctional epoxy resin via an ester bond. <1> ~ <4> 2. The imide group-containing epoxy resin according to claim 1 . <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 amount of the diimidedicarboxylic acid compound is such that the functional group equivalent of the diimidedicarboxylic acid compound is 0.01 to 0.6 equivalent ratio relative to the epoxy equivalent of the bifunctional epoxy resin. <6> 2. A method for producing the imide group-containing epoxy resin according to claim 1 . <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 amount of the diimidedicarboxylic acid compound is such that the functional group equivalent of the diimidedicarboxylic acid compound is 0.05 to 0.35 equivalent ratio relative to the epoxy equivalent of the bifunctional epoxy resin. <6> or <7> 2. A method for producing the imide group-containing epoxy resin according to claim 1 . <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 amount of the diimidedicarboxylic acid compound is such that the functional group equivalent of the diimidedicarboxylic acid compound is 0.15 to 0.25 equivalent ratio relative to the epoxy equivalent of the bifunctional epoxy resin. <6> ~ <8> 2. A method for producing the imide group-containing epoxy resin according to claim 1 , <10> <1> ~ <5> The imide group-containing epoxy resin according to any one of claims 1 to 5 is produced. <6> ~ <9> 2. A method for producing the imide group-containing epoxy resin according to claim 1 , <11> <1> ~ <5> 2. A curable epoxy resin composition comprising the imide group-containing epoxy resin according to claim 1 and a curing agent. <12> <11> A cured product of the curable epoxy resin composition according to claim 1. <13> <12> An electrical insulating material comprising the cured product according to claim 1. <14> <12> An encapsulant comprising the cured product according to claim 1. <15> Used in power semiconductor modules <14> The sealing material according to claim 1. <16> <12> A printed wiring board comprising the cured product according to claim 1. Effect of the Invention

[0012] According to the present invention, it is possible to provide a highly fluid imide group-containing epoxy resin having an imide skeleton, which is capable of giving 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. The imide group-containing epoxy resin of the present invention and a 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. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] <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. More specifically, 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 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.

[0014] Structure (A): A structure in which one molecule of a diimide dicarboxylic acid compound is bonded to each end of the molecule with one molecule of a bifunctional epoxy resin 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, and the other carboxyl group forms an ester bond by reacting with one of the two epoxy groups in another bifunctional epoxy resin.

[0015] Structure (B): A structure in which one molecule of a diimide dicarboxylic 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 another diimidedicarboxylic acid compound.

[0016] Structure (C): Oligomer structure In Structure (C), specifically, the diimidedicarboxylic acid compound and the 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.

[0017] In the 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.

[0018] 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 obtained cured product. More specifically, the imide group-containing epoxy resin of the present invention preferably contains an imide group-containing epoxy resin having structure (A) from the same viewpoint as above.

[0019] In this specification, the 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 homogeneity 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. Insoluble components are foreign matters that impair the transparency of the cured product, and can occur during the production 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 heat resistance refers to the heat resistance of a cured product of an imide group-containing epoxy resin and a curing agent, and is a property related to a higher glass transition temperature of the cured product.

[0020] The epoxy equivalent of the imide group-containing epoxy resin of the present invention is preferably 1500 or less, more preferably 1000 or less (particularly from 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 obtained cured product, is even more preferably 800 or less (particularly from 150 to 800), still more preferably 500 or less (particularly from 200 to 500), and most preferably 250 to 350. If the epoxy equivalent exceeds 1000, the fluidity and uniformity decrease.

[0021] In this specification, the epoxy equivalent is the molecular weight of an epoxy resin per epoxy group, and the value is measured by a nuclear magnetic resonance method.

[0022] 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 limitation on the lower limit of 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.

[0023] In this specification, the viscosity is a value at 140° C. determined by dynamic viscoelasticity measurement.

[0024] [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 functional groups are reacted with each other to produce an amide acid compound, which is then subjected to an imidization reaction 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.

[0025] A diimidedicarboxylic acid-based compound using a tricarboxylic acid anhydride component and a diamine component is a compound in which two molecules of the tricarboxylic acid anhydride component react with one molecule of the diamine component to form two imide groups, and more specifically, is a diimidedicarboxylic acid compound having a structure represented by the general formula (1).

[0026] [ka]

[0027] In general formula (1), X 1 and X 2 Each of X independently represents a structure derived from a tricarboxylic acid anhydride component (for example, an aromatic tricarboxylic acid anhydride component, an alicyclic tricarboxylic acid anhydride component, or an aliphatic tricarboxylic acid anhydride component) described later. 1 and X 2 may each independently be a residue derived from the above moieties. R 1 represents a structure derived from a diamine component (e.g., an aromatic diamine component or an alicyclic diamine component) described later. 1 may be a residue derived from the above moieties.

[0028] When producing a diimidedicarboxylic acid compound using a tricarboxylic anhydride component and a diamine component, the diamine component is usually used in an amount of about 0.5 times by molar, for example, 0.1 to 0.7 times by molar, preferably 0.3 to 0.7 times by molar, more preferably 0.4 to 0.6 times by molar, and even more preferably 0.45 to 0.55 times by molar, relative to the tricarboxylic anhydride component.

[0029] The tricarboxylic anhydride component that can constitute the diimide dicarboxylic acid compound includes an aromatic tricarboxylic anhydride component containing an aromatic ring, an alicyclic tricarboxylic anhydride component containing an aliphatic ring but not an aromatic ring, and an aliphatic tricarboxylic anhydride component containing neither an aromatic ring nor an alicyclic ring. The tricarboxylic anhydride component may contain an ether group and / or a thioether group, and / or one or more hydrogen atoms may be substituted with a halogen atom (e.g., a fluorine atom, a chlorine atom, a bromine atom). The tricarboxylic anhydride component may be an acid halide component. The 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.

[0030] 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, particularly 1 to 2. In particular, naphthalene rings are counted as containing two aromatic rings in one molecule.

[0031] Examples of the alicyclic tricarboxylic anhydride component 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, particularly 1 to 2.

[0032] Examples of the aliphatic tricarboxylic anhydride component include 3-carboxymethylglutaric anhydride, 1,2,4-butanetricarboxylic acid-1,2-anhydride, cis-propene-1,2,3-tricarboxylic acid-1,2-anhydride, etc. These may be used alone or in combination of two or more.

[0033] 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, the tricarboxylic acid anhydride component of the diimidedicarboxylic acid compound preferably contains an aromatic tricarboxylic acid anhydride component and / or an alicyclic tricarboxylic acid anhydride component, and more preferably contains an aromatic tricarboxylic acid anhydride component.

[0034] 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.

[0035] The diamine components that can constitute the diimide dicarboxylic acid compound include aromatic diamine components that contain an aromatic ring, and alicyclic diamine components that contain an aliphatic ring but no aromatic ring. The diamine component may contain an ether group and / or a thioether group, and / or one or more of the hydrogen atoms may be substituted with a halogen atom (e.g., a fluorine atom, a chlorine atom, a bromine atom). The diamine component may have a side chain.

[0036] Examples of aromatic diamine components include 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, particularly 1 to 2. In particular, a fluorene ring is counted as containing 2 aromatic rings in one molecule.

[0037] Examples of the alicyclic diamine component 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.

[0038] 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, 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.

[0039] 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.

[0040] The diimidedicarboxylic acid compound can be produced in a solvent or without a solvent, but the production method is not particularly limited.

[0041] As a method for producing in a solvent, for example, predetermined raw materials (e.g., tricarboxylic anhydride component, diamine component, tetracarboxylic dianhydride component, monoaminodicarboxylic acid component) are added to an aprotic solvent such as N-methyl-2-pyrrolidone, stirred at 80°C, and then imidized to obtain the product.

[0042] The imidization method is not particularly limited, and may be, for example, a thermal imidization method carried out by heating at 250° C. to 350° C. (particularly 280 to 320° C.) for 1 to 10 hours (particularly 1 to 3 hours) under a nitrogen atmosphere, or a chemical imidization method carried out by treating with a dehydration / cyclization reagent such as a mixture of a carboxylic acid anhydride and a tertiary amine.

[0043] An example of a method for producing an organic compound without a solvent is a method utilizing a mechanochemical effect, which is a method for obtaining an organic compound by utilizing the mechanical energy generated when the raw material compound used in the reaction is pulverized to produce a mechanochemical effect.

[0044] 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 formed. This causes a reaction between functional groups. The reaction between functional groups usually occurs between two or more raw material compound molecules. For example, the 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. The 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 the compound molecule generated by the reaction between functional groups and the raw material compound molecule. The reaction between functional groups is usually a chemical reaction, and as a result, a bond group (particularly a covalent bond) is formed between the two raw material compound molecules by the functional groups of each raw material compound molecule, generating another compound molecule.

[0045] The reaction environment means an environment in which the raw material compound is placed for the reaction, that is, an environment in which mechanical energy is applied, and may be, for example, the environment in 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 in 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 during processing) due to an increase in temperature and / or pressure, etc., accompanying the continued application of mechanical energy, but from the viewpoint of improving the reaction rate, it is preferable that the raw material compound is in a solid state continuously during the reaction (or during processing).

[0046] Although the details of the mechanochemical effect are not clear, it is believed to follow the following principle. When mechanical energy is applied to one or more solid-state raw material compounds to cause pulverization, the absorption of the mechanical energy activates the pulverized interface. It is believed that a chemical reaction occurs between two raw material compound molecules due to the surface activation energy of the pulverized interface. Pulverization 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 pulverized interface as a new surface. In the mechanochemical effect, the state of the new surface formed by the renewal of the surface is not particularly limited as long as the activation of the pulverized interface occurs due to the pulverization, and may be in a dry state or a wet state. The wet state of the new surface due to the renewal of the surface is due to the raw material compound in a liquid state separate from the solid-state raw material compound.

[0047] Mechanical energy is applied to a raw material mixture containing one or more raw material compounds in a solid state under a reaction environment. The state of the raw material mixture is not particularly limited as long as the application of mechanical energy causes the pulverization of the raw material compounds in a solid state. 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. 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. 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.

[0048] The mechanochemical effect of such mechanical energy is utilized 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 to produce an imide group.

[0049] In the method of production without a solvent, after carrying out a method utilizing the mechanochemical effect, imidization may be carried out by a method similar to the imidization method in the method of production in a solvent (particularly a thermal imidization method).

[0050] [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.

[0051] The bifunctional epoxy resin must be a polycyclic aromatic hydrocarbon epoxy resin or a biphenyl epoxy resin. Examples of the polycyclic aromatic hydrocarbon epoxy resin include naphthalene epoxy resin and anthracene epoxy resin. From the viewpoint of further improving the flowability of the imide group-containing epoxy resin and the uniformity and heat resistance of the resulting cured product, naphthalene epoxy resin and biphenyl epoxy resin are preferred. The epoxy resin may be one of the above alone or two or more of them may be used in combination.

[0052] 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 the general formula (E1). [ka] (In formula (E1), 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.)

[0053] 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 the general formula (E2). [ka] (In formula (E2), n is an integer of 0 to 3. The hydrogen atoms bonded to the carbon atoms constituting the anthracene ring may each be independently substituted with a methyl group.)

[0054] 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 (E3). [ka] (In formula (E3), 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.)

[0055] Difunctional epoxy resins are commercially available or can be prepared by known methods.

[0056] 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 obtained 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.

[0057] <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.

[0058] 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 obtained cured product, the heating temperature is preferably 130 to 200°C, and particularly preferably 150 to 200°C.

[0059] 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 obtained cured product, it is preferably 0.5 to 5 hours, and more preferably 0.5 to 2 hours.

[0060] 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 flowability of the imide group-containing epoxy resin and the uniformity and heat resistance of the obtained cured product, the amount of the diimide dicarboxylic acid compound is preferably 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 may be within the above range.

[0061] 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, more preferably 0.2 to 0.5 parts by mass, based on 100 parts by mass of the total amount of the diimide dicarboxylic acid compound and the bifunctional functional group. When two or more phosphorus-based compounds are used, the total amount of the compounds may be the above amount. When a catalyst other than the 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.

[0062] 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 (particularly tri-tert-butylphosphine), tri-n-octylphosphine); aromatic phosphonium salts (e.g., tetraphenylphosphonium bromide, n-butyltriphenyl Examples of the phosphorus-based compound include phosphonium salts such as phosphonium bromide, methyl triphenyl phosphonium bromide, ethyl triphenyl phosphonium bromide, (methoxymethyl) triphenyl phosphonium chloride, benzyl triphenyl phosphonium chloride, tetraphenyl phosphonium tetraphenyl borate, tetraphenyl phosphonium tetra-p-tolylborate, triphenylborane-triphenylphosphine, tri-tert-butyl phosphonium tetraphenyl borate, and aliphatic phosphonium salts (e.g., tetrabutyl phosphonium bromide).) The phosphorus-based compound may be used alone or in combination of two or more kinds. The phosphorus-based compound is commercially available.

[0063] 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, the phosphorus-based compound is preferably an organic phosphine, more preferably an aromatic organic phosphine, and even more preferably triphenylphosphine.

[0064] <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.

[0065] 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 them, 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.

[0066] Examples of imidazoles include 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, 1-(2-cyanoethyl)-2-undecylimidazole, Examples of the imidazole include 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, and 4-methyl-2-phenyl-5-hydroxymethyl-1H-imidazole.

[0067] 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.

[0068] Examples of the amine-based curing agent include 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), and the like.

[0069] The amount of these hardeners to be mixed varies depending on the type of hardener. If hardeners are classified as Class A hardeners and Class B hardeners, the amounts to be mixed are as follows:

[0070] The A-type curing agent is a curing agent belonging to dicyandiamides and imidazoles. The amount of the A-type curing agent is preferably 1 to 10 parts by mass, more preferably 1 to 3 parts by mass, relative to 100 parts by mass of the imide group-containing epoxy resin. The A-type curing agent may be used alone or in combination of two or more kinds. When two or more kinds are used in combination, it is preferable that the total amount is within the above range.

[0071] The B-type curing agent is a curing agent belonging to the phenol-based curing agent, thiol-based curing agent, amine-based curing agent, acid anhydride-based curing agent, cyanate-based curing agent, and active ester-based curing agent. The blending amount of the B-type curing agent is preferably an amount that is an equivalent ratio of 0.5 to 1.5, more preferably an equivalent ratio of 0.7 to 1.3, relative to the epoxy equivalent of the imide group-containing epoxy resin. The B-type curing agent 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 blending amount of the B-type curing agent is within the above range in total.

[0072] The A-type curing agent and the B-type curing agent may be used in combination. When used in combination, one or more types of A-type curing agent and one or more types of B-type curing agent may be used. For example, one A-type curing agent and one B-type curing agent may be used, one A-type curing agent and two B-type curing agents may be used, or two A-type curing agents and one B-type curing agent may be used. When used in combination, for example, the amount of the A-type 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 the B-type 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 A-type 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 types of A-type curing agents are used, it is preferable that the total amount of them is in the above range. The amount of the B-type curing agent used in combination is preferably 0.1 to 1.0 equivalent ratio, more preferably 0.1 to 0.5 equivalent ratio, relative to the epoxy equivalent of the imide group-containing epoxy resin. In this case, when two or more B-type curing agents are used, the total amount of them is preferably within the above range.

[0073] To the curable epoxy resin composition of the present invention, other additives such as a curing accelerator, an inorganic filler, an antioxidant, a flame retardant, an organic solvent, etc. may be added as long as the effects of the present invention are not impaired.

[0074] 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 of the above. When using a curing accelerator, the blending amount is preferably 0.01 to 2.0% by mass relative to the curable epoxy resin composition, and is preferably 0.01 to 1% by mass, more preferably 0.05 to 0.5% by mass, since the heat resistance and dielectric properties of the obtained cured product are improved.

[0075] 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 an inorganic filler, the average particle size of the inorganic filler is preferably 50 nm to 4 μm, and more preferably 100 nm to 3 μm because of superior coating properties and processability.

[0076] Examples of the antioxidant include hindered phenol-based antioxidants, phosphorus-based antioxidants, and thioether-based antioxidants. The antioxidant may be used alone or in combination of two or more thereof.

[0077] Examples of the flame retardant include non-halogen flame retardants, phosphorus flame retardants, nitrogen flame retardants, and silicone flame retardants. Among them, non-halogen flame retardants are preferred from the viewpoint of environmental impact. The flame retardant may be used alone or in combination of two or more of the above.

[0078] The organic solvent is an organic solvent capable of dissolving the imide group-containing epoxy resin and the curing agent, and examples of such organic solvents include cyclohexanone, γ-butyrolactone, dimethylacetamide, dimethylformamide, and N-methyl-2-pyrrolidone.

[0079] 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 due to 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, further preferably 0.1 mass% or less, and particularly preferably 0 mass% or less, based on the total amount of the curable epoxy resin composition.

[0080] 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., a 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: {(XY) / X}×100 (%), where Xg is the mass before the drying treatment and Yg is the mass after the drying treatment.

[0081] The method for producing the curable epoxy resin composition of the present invention is not particularly limited, and examples thereof include a method in which the imide group-containing epoxy resin, the curing agent, and other additives to be added as necessary are mixed using a mixer such as a homodisper, a universal mixer, a Banbury mixer, or a kneader.

[0082] <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.

[0083] <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.

[0084] When the cured product of the present invention is used as an insulating material for an encapsulant, for example, after a power semiconductor module is produced, the curable epoxy resin composition of the present invention can be filled into a mold in which the module is set, and then cured.

[0085] For example, when the cured product of the present invention is used as an insulating material for a printed wiring board, a solvent is often used, and 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 a sealant. The insulating material for a printed wiring board is an insulating material that constitutes a printed wiring board.

[0086] The curable epoxy resin composition of the present invention can be used for purposes other than electrical insulating materials. Specifically, the curable epoxy resin composition of the present invention can be used for adhesives and CFRP. EXAMPLES

[0087] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0088] A. Raw materials The raw materials used in the examples and comparative examples are shown below. (A) Polycyclic aromatic hydrocarbon type epoxy resin or biphenyl type epoxy resin Naphthalene-type epoxy resin: DIC "HP-4032D", epoxy equivalent 141g / eq Anthracene type epoxy resin: Mitsubishi Chemical Corporation "YX8800", epoxy equivalent: 180 g / eq Biphenyl type epoxy resin: Mitsubishi Chemical Corporation "YX4000H", epoxy equivalent 191g / eq

[0089] (B) Other epoxy resins Cresol novolac epoxy resin: DIC Corporation "N-660", epoxy equivalent 209g / eq Bisphenol A epoxy resin: Tokyo Chemical Industry Co., Ltd., epoxy equivalent 170g / eq

[0090] (C) Diimidedicarboxylic acid compounds Diimidedicarboxylic acid X 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. The diimide dicarboxylic acid X is 1 When confirmed by H-NMR, it was a trimer composed of trimellitic acid-4,4'-diaminodiphenyl ether-trimellitic acid. Furthermore, according to mass spectrometry, the number average molecular weight of the diimidedicarboxylic acid X was 549, and it was a solid at room temperature.

[0091] Diimidedicarboxylic acid Y Diimidedicarboxylic acid Y was obtained in the same manner as for 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. The diimide dicarboxylic acid Y is 1 When confirmed by H-NMR, it was a trimer composed of trimellitic acid-2,2-bis[4-(4-aminophenoxy)phenyl]propane-trimellitic acid. In addition, according to mass spectrometry, the number average molecular weight of the diimidedicarboxylic acid Y was 759, and it was a solid at room temperature.

[0092] Diimidedicarboxylic acid Z Diimidedicarboxylic acid Z was obtained in the same manner as in the preparation of diimidedicarboxylic acid X, except that 52.3 parts by mass of 4,4'-diaminodiphenyl ether was used in place of 29.8 parts by mass of trans-1,4-cyclohexanediamine. The diimide dicarboxylic acid Z is 1 When confirmed by H-NMR, it was a trimer composed of trimellitic acid-trans-1,4-cyclohexanediamine-trimellitic acid. Furthermore, according to mass spectrometry, the number average molecular weight of the diimidedicarboxylic acid Z was 462, and it was a solid at room temperature.

[0093] (D) Phosphorus compounds Triphenylphosphine: Tokyo Chemical Industry Co., Ltd. (E) Other catalysts N,N-Dimethylbenzylamine: Tokyo Chemical Industry Co., Ltd.

[0094] (F) Hardener 2-Ethyl-4-methylimidazole: Tokyo Chemical Industry Co., Ltd. 4-Methylcyclohexane-1,2-dicarboxylic anhydride: Tokyo Chemical Industry Co., Ltd. 4,4-Diaminodiphenylmethane: manufactured by Tokyo Chemical Industry Co., Ltd.

[0095] B. Evaluation Methodology The compounds (imide group-containing epoxy resins) and cured products obtained in the examples and comparative examples were evaluated as follows.

[0096] [Evaluation method for imide group-containing epoxy resins] (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.

[0097] <Measurement conditions> Instrument: Thermo Fisher Scientific Nicolet iS5 FT-IR, iD7 ATR accessory Method: ATR method Accumulation count: 64 scans (resolution 4 cm-1) The 1680cm peak is due to the carboxyl group of diimidedicarboxylic acid compounds. -1 The presence or absence of absorption in the vicinity was confirmed. <Evaluation criteria> ◎: The esterification reaction proceeded sufficiently; the peak derived from the carboxyl group disappeared; ×: The esterification reaction did not proceed sufficiently; peaks derived from carboxyl groups remained.

[0098] (2) Epoxy equivalent 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 was calculated. The imide group-containing epoxy resins obtained in the examples and comparative examples were analyzed using a high-resolution nuclear magnetic resonance apparatus (JNM-ECA500 NMR manufactured by JEOL Ltd.). 1 The resin composition was determined from the peak intensity of each copolymer component by H-NMR analysis (resolution: 500 MHz, solvent: deuterated dimethyl sulfoxide, temperature: 25°C).

[0099] <Measurement conditions> Equipment: JNM-ECA500 NMR manufactured by JEOL Ltd. Resolution: 500MHz Solvent: Deuterated dimethyl sulfoxide Temperature: 25℃ 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); △: epoxy equivalent < 200 or 500 < epoxy equivalent ≦ 1000 (no problem in practical use); ×: Epoxy equivalent > 1000 (problems in practical use).

[0100] (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.

[0101] <Measurement conditions> Equipment: TA Instruments ARESG2 rheometer Measurement temperature range: 25~200℃ Heating rate: 5℃ / min Angular frequency: 10rad / 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).

[0102] [Evaluation method of the cured product] (1) Evaluation of uniformity (transparency) The presence or absence of insoluble matter in the cured products obtained in the Examples and Comparative Examples was visually confirmed to judge the uniformity. Insoluble matter impairs the uniformity and transparency of the cured product.

[0103] <Evaluation criteria> ◎ (Uniform): No insoluble components. Completely transparent. △ (almost uniform): Some insoluble components are present, but the solution is transparent. × (uneven): Contains insoluble components and is opaque.

[0104] (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 Heating rate: 10℃ / 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.

[0105] <Evaluation criteria> ◎: Tg≧200℃ (best); ○: 200℃>Tg≧180℃ (good); △: 180°C>Tg≧160°C (no practical problem); ×: 160° C.>Tg (bad) (problematic in practical use).

[0106] [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 ⊚. ○: Of all the evaluation results, the lowest evaluation result was ○. △: Of all the evaluation results, the lowest evaluation result was △. ×: Of all the evaluation results, the lowest evaluation result was ×.

[0107] 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 placed in 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 at normal pressure under a nitrogen stream to obtain an imide group-containing epoxy resin A. In addition, when the imide group-containing epoxy resin A was confirmed by IR, the esterification reaction had progressed sufficiently. 1 H-NMR revealed that the epoxy equivalent of imide group-containing epoxy resin A was 216, and it was a viscous solid at room temperature. From these results and the amounts charged, 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.

[0108] (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.

[0109] 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. In addition, when the imide group-containing epoxy resin B was confirmed by IR, the esterification reaction had progressed sufficiently. 1 H-NMR revealed that the epoxy equivalent of imide group-containing epoxy resin B was 309, and it was a solid at room temperature. From these results and the amounts charged, it was confirmed that 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.

[0110] Using the obtained imide group-containing epoxy resin B, a cured product was produced in the same manner as in Example 1, except that the blending amounts were changed so as to obtain the composition shown in Table 1.

[0111] 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 19 parts by mass of diimidedicarboxylic acid X was used in place of 58 parts by mass. In addition, when the imide group-containing epoxy resin C was confirmed by IR, the esterification reaction had progressed sufficiently. 1 H-NMR revealed that the imide group-containing epoxy resin C had an epoxy equivalent of 400 and was a solid at room temperature. From these results and the amounts charged, it was confirmed that 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.

[0112] Using the obtained imide group-containing epoxy resin C, a cured product was produced in the same manner as in Example 1, except that the blending amounts were changed so as to obtain the composition shown in Table 1.

[0113] 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. In addition, when the imide group-containing epoxy resin D was confirmed by IR, the esterification reaction had progressed sufficiently. 1 H-NMR analysis revealed that the epoxy equivalent of imide group-containing epoxy resin D was 543, and it was a solid at room temperature. From these results and the amounts charged, 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.

[0114] Using the obtained imide group-containing epoxy resin D, a cured product was prepared in the same manner as in Example 1, except that the blending amounts were changed so as to obtain the composition shown in Table 1.

[0115] 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 136 parts by mass of diimidedicarboxylic acid X and 0.5 parts by mass of triphenylphosphine were used in place of 19 parts by mass and 0.3 parts by mass, respectively. In addition, when the imide group-containing epoxy resin E was confirmed by IR, the esterification reaction had progressed. 1 H-NMR revealed that the imide group-containing epoxy resin E had an epoxy equivalent of 1,110 and was a solid at room temperature. From these results and the amounts charged, 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 to one molecule of a bifunctional epoxy resin.

[0116] Using the obtained imide group-containing epoxy resin E, a cured product was produced in the same manner as in Example 1, except that the blending amounts were changed so as to obtain the composition shown in Table 1.

[0117] 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. In addition, when the imide group-containing epoxy resin F was confirmed by IR, the esterification reaction had progressed sufficiently. 1 H-NMR revealed that the epoxy equivalent of imide group-containing epoxy resin F was 375, and it was a solid at room temperature. From these results and the amounts charged, 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.

[0118] Using the obtained imide group-containing epoxy resin F, a cured product was prepared in the same manner as in Example 1, except that the blending amounts were changed so as to obtain the composition shown in Table 1.

[0119] 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. In addition, when the imide group-containing epoxy resin G was confirmed by IR, the esterification reaction had progressed sufficiently. 1 H-NMR revealed that the epoxy equivalent of imide group-containing epoxy resin G was 412, and it was a solid at room temperature. From these results and the amounts charged, it was confirmed that 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.

[0120] Using the obtained imide group-containing epoxy resin G, a cured product was prepared in the same manner as in Example 1, except that the blending amounts were changed so as to obtain the composition shown in Table 1.

[0121] 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. In addition, when the imide group-containing epoxy resin H was confirmed by IR, the esterification reaction had progressed sufficiently. 1 H-NMR revealed that the epoxy equivalent of imide group-containing epoxy resin H was 450, and it was a solid at room temperature. From these results and the amounts charged, 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.

[0122] Using the obtained imide group-containing epoxy resin H, a cured product was prepared in the same manner as in Example 1, except that the blending amounts were changed so as to obtain the composition shown in Table 1.

[0123] 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. In addition, when the imide group-containing epoxy resin I was confirmed by IR, the esterification reaction had progressed sufficiently. 1H-NMR revealed that the epoxy equivalent of imide group-containing epoxy resin G was 380, and it was a solid at room temperature. From these results and the amounts charged, it was confirmed that 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.

[0124] Using the obtained imide group-containing epoxy resin I, a cured product was prepared in the same manner as in Example 1, except that the blending amounts were changed so as to obtain the composition shown in Table 1.

[0125] 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. In addition, when the imide group-containing epoxy resin J was confirmed by IR, the esterification reaction had progressed sufficiently. 1 H-NMR revealed that the epoxy equivalent of imide group-containing epoxy resin J was 1500 and that it was a solid at room temperature. From these results, it was confirmed that imide group-containing epoxy resin J has a polymer structure in which diimidedicarboxylic acid compounds and bifunctional epoxy resins are repeatedly bonded via ester bonds.

[0126] Using the obtained imide group-containing epoxy resin J, a cured product was prepared in the same manner as in Example 1, except that the blending amounts were changed so as to obtain the composition shown in Table 1.

[0127] 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 diimidedicarboxylic 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 imide group-containing epoxy resin K was simply a mixture of a diimidedicarboxylic acid compound and a multifunctional epoxy resin.

[0128] Using the obtained imide group-containing epoxy resin K, a cured product was prepared in the same manner as in Example 1, except that the blending amounts were changed so as to obtain the composition shown in Table 1.

[0129] 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.

[0130] 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 so as to obtain the composition shown in Table 1.

[0131] Comparative Example 4 (Imide group-containing epoxy resin L) An imide group-containing epoxy resin L 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. In addition, when the imide group-containing epoxy resin L was confirmed by IR, the esterification reaction had progressed sufficiently. 1 H-NMR revealed that the epoxy equivalent of imide group-containing epoxy resin L was 441, and it was a solid at room temperature. From these results and the amounts charged, it was confirmed that imide group-containing epoxy resin L has a structure in which one molecule of a diimidedicarboxylic acid compound is bonded to each end of the molecule via an ester bond.

[0132] Using the obtained imide group-containing epoxy resin L, a cured product was prepared in the same manner as in Example 1, except that the blending amounts were changed so as to obtain the composition shown in Table 1.

[0133] The composition of the imide group-containing epoxy resin and the evaluation results of the obtained cured product are shown in Table 1.

[0134] [Table 1]

[0135] 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 weight regardless of the equivalent ratio.

[0136] In Examples 1 to 11, all of the examples 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 that an imide group-containing epoxy resin with excellent fluidity could be obtained. In particular, the use of a bifunctional epoxy resin and a phosphorus compound as a catalyst allowed the fluidity to be controlled. In addition, all of the cured products were homogenized, and the use of an imidedicarboxylic acid compound provided excellent heat resistance.

[0137] 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.

[0138] In Comparative Example 2, the bifunctional epoxy resin was changed to a cresol novolac epoxy resin to synthesize an imide group-containing epoxy resin. As a result, the reaction between the epoxy resin and diimide dicarboxylic acid did not proceed sufficiently, and some unreacted material remained. Therefore, the uniformity of the cured product was poor.

[0139] In Comparative Example 3, the raw materials were mixed and then cured, so that the imide group-containing epoxy resin was not formed, the viscosity was high, and the uniformity of the cured product was poor. Sufficient heat resistance was not achieved.

[0140] In Comparative Example 4, the bifunctional epoxy resin was changed to a bisphenol type epoxy resin to synthesize an imide group-containing epoxy resin, and the cured product had poor heat resistance.

Claims

1. 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, The bifunctional epoxy resin is an imide group-containing epoxy resin which is a polycyclic aromatic hydrocarbon type epoxy resin or a biphenyl type epoxy resin. 【Chemistry 1】 (In formula (1), X １ and X ２ each independently represents a structure derived from an aromatic tricarboxylic anhydride component, an alicyclic tricarboxylic anhydride component, or an aliphatic tricarboxylic anhydride component; R １ represents a structure derived from an aromatic diamine component or an alicyclic diamine component.

2. 2. The imide group-containing epoxy resin according to claim 1, having an epoxy equivalent of 1,000 or less.

3. The bifunctional epoxy resin is at least one epoxy resin selected from the group consisting of naphthalene epoxy resins and biphenyl epoxy resins, 2. The imide group-containing epoxy resin according to claim 1, wherein the epoxy equivalent is 500 or less.

4. The bifunctional epoxy resin is at least one epoxy resin selected from the group consisting of naphthalene epoxy resins and biphenyl epoxy resins, The imide group-containing epoxy resin according to claim 1, wherein the epoxy equivalent is 250 to 350.

5. 2. 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 diimide dicarboxylic acid compound is bonded to each of both ends 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 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 0.01 to 0.6 equivalent ratio relative to the epoxy equivalent of the bifunctional epoxy resin.

8. The bifunctional epoxy resin is at least one epoxy resin 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 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.

9. The bifunctional epoxy resin is at least one epoxy resin 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 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.

10. A method for producing the imide group-containing epoxy resin according to claim 6, which comprises producing the imide group-containing epoxy resin according to any one of claims 1 to 5.

11. 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.

12. A cured product of the curable epoxy resin composition according to claim 11.

13. An electrical insulating material comprising the cured product according to claim 12.

14. A sealing material comprising the cured product according to claim 12.

15. The encapsulant according to claim 14, which is used in a power semiconductor module.

16. A printed wiring board comprising the cured product according to claim 12.

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