JP2021193094A - Imide group-containing compound, imide group-containing curing agent, and epoxy resin cured product and electric insulating material using the same - Google Patents

Abstract

To provide a curing agent (in particular, imide group-containing compound) which sufficiently prevents local accumulation of electric charges under high temperature and high electric field, and produces an electric insulating epoxy resin cured product sufficiently excellent in heat resistance and dielectric characteristics.SOLUTION: An imide group-containing compound is selected from the group consisting of a diimidodicarboxylic acid-based compound, a diimidotetracarboxylic acid-based compound and a monoimidotricarboxylic acid-based compound.SELECTED DRAWING: None

Description

The present invention relates to an imide group-containing compound, an imide group-containing curing agent, an epoxy resin cured product, and an electrically insulating material using the same.

Epoxy resin cured products composed of epoxy resins and their curing agents have excellent thermal, mechanical and electrical properties, and are widely used industrially mainly for electrical and electronic materials. As the curing agent for producing the epoxy resin cured product, for example, a phenol-based curing agent, an acid anhydride-based curing agent, an amine-based curing agent and the like are used.

In recent years, in the field of power devices represented by in-vehicle power modules, further increase in current, miniaturization, and high efficiency are required, and the shift to silicon carbide (SiC) semiconductors is progressing. Since SiC semiconductors can operate under higher temperature conditions than conventional silicon (Si) semiconductors, semiconductor encapsulants used in SiC semiconductors are also required to have higher heat resistance than ever before. (For example, Patent Document 1). In addition, power devices are used under high temperature and high electric field due to miniaturization and high output. Under high temperature and high electric field, electric charge is accumulated in the insulating material, the electric field inside the semiconductor is distorted, and the resistance of the semiconductor element is reduced. Reduce the voltage. Therefore, in order to improve the performance of power devices, it is necessary to develop a material that does not cause charge accumulation under high temperature and high electric field in order to improve the withstand voltage at high temperature.

Further, in the field of power transmission lines, insulators made of pottery or ceramic have been conventionally used, but since the insulators are heavy and brittle, insulators using a polymer as a part are being studied (for example, Patent Document 2). ). In recent years, the voltage of insulators has been increasing, and along with this, the polymer used for insulators has a lower dielectric constant than conventional products in order to prevent charge accumulation, and can withstand high voltages. Highly insulating materials are required so that they can be used.

Further, in the field of electric vehicles, an insulating electric wire covering material is used for electric wires constituting electric devices such as motors (for example, Patent Document 3). In recent years, the output of motors has been increased, and the influence of partial discharge due to inverter surges is increasing. Along with this, the wire coating material used for motors is required to have a lower dielectric constant than conventional products in order to prevent inverter surges from occurring, and a highly insulating material that can withstand high output. There is.

Japanese Unexamined Patent Publication No. 2007-305962 Japanese Unexamined Patent Publication No. 2013-234311 Japanese Unexamined Patent Publication No. 2012-224714

When the inventor of the present invention uses a conventional material (particularly an epoxy resin cured product manufactured by using a conventional curing agent) as an electrically insulating material, electric charges are locally accumulated under a high temperature and high electric field. It was found that sufficient insulation cannot be obtained because it may lead to dielectric breakdown. For example, in the field of power devices, conventional insulating materials have a possibility that electric charges are locally accumulated due to a high temperature and high electric field environment, leading to dielectric breakdown.

The present invention provides a cured epoxy resin and a curing agent (particularly an imide group-containing compound) for producing the cured epoxy resin, in which local accumulation of electric charges is sufficiently prevented under high temperature and high electric field. The purpose is.

The present invention is also for producing an epoxy resin cured product having sufficiently excellent heat resistance and dielectric properties, and an epoxy resin cured product, in which local accumulation of electric charges is sufficiently prevented under a high temperature and high electric field. It is an object of the present invention to provide a curing agent (particularly an imide group-containing compound).

In the present specification, the local accumulation of electric charge is the uneven distribution of electric charge generated inside the electrically insulating material under a high temperature and high electric field, and can be observed by measuring the charge density distribution over time. It is an electrical phenomenon that can occur. The high temperature and high electric field is, for example, an environment having a temperature of 120 ° C. or higher (particularly 130 to 150 ° C.) and an electric field of 40 to 120 kV / mm (particularly 80 to 120 kV / mm). Electrical insulation and insulation include the property that local accumulation of electric charge is sufficiently prevented under such high temperature and high electric field.
In general, the dielectric constant and the dielectric loss tangent may be evaluated as being superior when it is high or as being superior when it is low, depending on the purpose. In particular, is the performance in which both the permittivity and the dielectric loss tangent can be sufficiently reduced.

As a result of diligent studies to solve such problems, the present inventors have found that a cured product composed of a specific imide group-containing curing agent and an epoxy resin has all the properties of heat resistance, dielectric properties and insulating properties. We found it to be excellent and arrived at the present invention.

That is, the gist of the present invention is as follows.
<1> An imide group-containing compound selected from the group of diimide dicarboxylic acid-based compounds, diimide tetracarboxylic acid-based compounds, and monoimide tricarboxylic acid-based compounds.
<2> An imide group-containing curing agent selected from the imide group-containing compounds described in <1>.
<3> An epoxy resin cured product comprising the imide group-containing curing agent according to <2> and an epoxy resin.
<4> The cured epoxy resin according to <3>, wherein the epoxy resin has two or more epoxy groups in one molecule.
<5> The epoxy resin cured product according to <3> or 4, wherein the imide group-containing curing agent has a molecular weight of 200 to 1100.
<6> The epoxy resin cured product according to any one of <3> to <5>, wherein the imide group-containing curing agent has a functional group equivalent of 50 to 500.
<7> An electrically insulating material containing the cured epoxy resin according to any one of <3> to <6>.
<8> A sealing material containing the cured epoxy resin according to any one of <3> to <6>.
<9> The encapsulant according to <8>, which is for a power semiconductor module.
<10> An insulator containing the epoxy resin cured product according to any one of <3> to <6>.
<11> The insulator according to <10> for transmission lines.
<12> An electric wire coating material containing the cured epoxy resin according to any one of <3> to <6>.
<13> The electric wire covering material according to <12> for electric vehicles.
<14> A printed wiring board containing the epoxy resin cured product according to any one of <3> to <6>.

According to the present invention, an electrically insulating epoxy resin cured product having excellent heat resistance, dielectric properties and insulating properties and suitable for use in, for example, encapsulants (particularly semiconductor encapsulants), insulators, electric wire coating materials and the like. And a curing agent (particularly an imide group-containing compound) for producing the cured epoxy resin can be provided.
The electrically insulating epoxy resin cured product of the present invention has sufficiently excellent insulating properties, that is, the local accumulation of electric charges is sufficiently prevented, especially under a high temperature and high electric field.

FIG. 1 is a chart showing changes over time in the charge density distribution of the cured epoxy resin products of Examples A-1, B-1, B-2 and C-1. FIG. 2 is a chart showing changes over time in the charge density distribution of the cured epoxy resin of Comparative Examples 1 to 3.

The imide group-containing compound of the present invention is useful as a curing agent (particularly, a curing agent for epoxy resins). When the imide group-containing compound of the present invention is used as a curing agent (particularly, a curing agent for an epoxy resin), it is also referred to as an "imide group-containing curing agent". Hereinafter, the cured product of the electrically insulating epoxy resin of the present invention will be described in detail, and in the above description, the imide group-containing compound will be described in detail as an imide group-containing curing agent.

<Electrically insulating epoxy resin cured product>
The electrically insulating epoxy resin cured product of the present invention is composed of an imide group-containing curing agent and an epoxy resin.

[Imide group-containing curing agent]
Examples of the imide group-containing curing agent include imide group-containing compounds such as diimide dicarboxylic acid-based compounds, diimide tetracarboxylic acid-based compounds, and monoimide tricarboxylic acid-based compounds. The imide group-containing curing agent may be one or more imide group-containing curing agents selected from these groups. From the viewpoint of further improving heat resistance, dielectric properties and insulating properties, the preferred imide group-containing curing agent is one or more imide group-containing curing agents selected from the group consisting of diimide dicarboxylic acid compounds.

The molecular weight of the imide group-containing curing agent is not particularly limited, and is preferably 200 to 1100, more preferably 300 to 1000, still more preferably 300 to 300, from the viewpoint of further improving heat resistance, dielectric properties and insulating properties. It is 700, most preferably 400 to 600.

The functional group equivalent of the imide group-containing curing agent is not particularly limited, and is preferably 50 to 500, more preferably 800 to 400, still more preferably 800 to 400, from the viewpoint of further improving heat resistance, dielectric properties and insulating properties. It is 100 to 400, most preferably 200 to 350. The functional group equivalent is a value calculated by dividing the molecular weight by the number of functional groups (for example, carboxyl groups) that the imide group-containing curing agent has per molecule.

The blending amount of the imide group-containing curing agent contained in the curing agent is not particularly limited, and is preferably 50% by mass or more with respect to the total amount of the curing agent from the viewpoint of further improving heat resistance, dielectric properties and insulating properties. It is more preferably 80% by mass or more, further preferably 90% by mass or more, and most preferably 100% by mass. When the blending amount of the imide group-containing curing agent is 100% by mass with respect to the total amount of the curing agent, it means that the curing agent is composed of only the imide group-containing curing agent. When two or more kinds of imide group-containing curing agents are blended, the total blending amount thereof may be within the above range.

(Diimidedicarboxylic acid compound)
The diimide dicarboxylic acid compound is a compound having two imide groups and two carboxyl groups in one molecule. Diimide dicarboxylic acid compounds do not have an amide group. Using a tricarboxylic acid anhydride component and a diamine component as raw material compounds, it is possible to produce an amidoic acid-based compound by reacting functional groups with each other, and to produce a diimidedicarboxylic acid-based compound by advancing the imidization reaction. can. Here, the reaction between the functional groups may be carried out in a solution or in a solid phase state, and the production method is not particularly limited.

A diimide dicarboxylic acid-based compound using a tricarboxylic acid anhydride component and a diamine component is a compound formed by reacting one molecule of the diamine component with two molecules of the tricarboxylic acid anhydride component to form two imide groups. ..

In the production of a diimidedicarboxylic acid-based compound using a tricarboxylic acid anhydride component and a diamine component, the diamine component is usually about 0.5 times the molar amount, for example 0.1 to 0.7 times, the amount of the tricarboxylic acid anhydride component. It is used in a molar amount, 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.

The tricarboxylic acid anhydride component that can constitute the diimide dicarboxylic acid compound is not particularly limited, and for example, further the heat resistance, dielectric property and insulating property of the diimide dicarboxylic acid compound and the cured epoxy resin obtained by using the diimide dicarboxylic acid compound. From the viewpoint of improvement, an aromatic tricarboxylic acid anhydride component containing an aromatic ring, particularly trimellitic acid anhydride, is preferable. As the tricarboxylic acid anhydride component that can constitute a diimide dicarboxylic acid compound, one kind may be used alone, or two or more kinds may be used as a mixture.

The diamine component that can constitute the diimide dicarboxylic acid compound is not particularly limited, and for example, the heat resistance, dielectric property, insulating property, and solubility of the diimide dicarboxylic acid compound and the cured epoxy resin obtained by using the diamine dicarboxylic acid compound are not particularly limited. From the viewpoint of further improvement of the above, aromatic diamine components containing an aromatic ring, particularly m-xylylenediamine, p-xylylenediamine, 4,4'-diaminodiphenyl ether, and dimerdiamine are preferable. As the diamine component that can constitute a diimide dicarboxylic acid compound, one kind may be used alone, or two or more kinds may be used as a mixture.

(Diimidetetracarboxylic acid compound)
The diimide tetracarboxylic dian compound is a compound having two imide groups and four carboxyl groups in one molecule. A tetracarboxylic acid dianhydride component and a monoaminodicarboxylic acid component are used as a raw material compound, and an amidic acid-based compound is produced by reacting functional groups with each other, and the imidization reaction is promoted to carry out the diimide tetracarboxylic acid. A system compound can be produced. Here, the reaction between the functional groups may be carried out in a solution or in a solid phase state, and the production method is not particularly limited.

In a diimide tetracarboxylic acid-based compound using a tetracarboxylic acid dianhydride component and a monoaminodicarboxylic acid component, two molecules of the monoaminodicarboxylic acid component react with one molecule of the tetracarboxylic acid dianhydride component. It is a compound in which two imide groups are formed.

In the production of a diimidetetracarboxylic acid-based compound using a tetracarboxylic acid dianhydride component and a monoaminodicarboxylic acid component, the monoaminodicarboxylic acid component is usually about twice as much as that of the tetracarboxylic acid dianhydride component. The molar amount, for example, 1.5 to 10.0 times molar amount, preferably 1.8 to 2.2 times molar amount, more preferably 1.9 to 2.1 times molar amount, still more preferably 1.95 to 2 times molar amount. Used in 0.05 times the molar amount.

The tetracarboxylic acid dianhydride component that can constitute the diimide tetracarboxylic acid-based compound is not particularly limited, and for example, the heat resistance and dielectric properties of the diimide tetracarboxylic acid-based compound and the cured epoxy resin obtained by using the diimide tetracarboxylic acid-based compound. Aromatic tetracarboxylic acid dianhydride components containing an aromatic ring and / or an aliphatic tetracarboxylic acid dian containing neither an aromatic ring nor an alicyclic ring, from the viewpoint of further improving insulation and solubility and versatility. Anhydrous components, especially 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride, 4,4'-(hexafluoroisopropylidene) diphthalic acid anhydride, 1,2,3,4-butanetetracarboxylic Acid dianhydride is preferred. As the tetracarboxylic dianhydride component that can constitute a diimide tetracarboxylic dianhydride compound, one kind may be used alone, or two or more kinds may be used as a mixture.

The monoaminodicarboxylic acid component that can constitute the diimidetetracarboxylic acid-based compound is not particularly limited, and for example, the heat resistance, dielectric property, and insulation of the diimidetetracarboxylic acid-based compound and the cured epoxy resin obtained by using the diimidetetracarboxylic acid-based compound are limited. From the viewpoint of further improving the property and solubility, aromatic monoaminodicarboxylic acid components containing an aromatic ring, particularly 2-aminoterephthalic acid, 2-aminoisophthalic acid, 4-aminoisophthalic acid, 5-aminoisophthalic acid, 3-Aminophthalic acid and 4-aminophthalic acid are preferable. As the monoaminodicarboxylic acid component that can constitute a diimidetetracarboxylic acid compound, one kind may be used alone, or two or more kinds may be used as a mixture.

(Monoimide tricarboxylic acid compound)
The monoimide tricarboxylic acid compound is a compound having one imide group and three carboxyl groups in one molecule. Using a tricarboxylic acid anhydride component and a monoaminodicarboxylic acid component as a raw material compound, an amic acid-based compound is produced by reacting functional groups with each other, and a monoimide tricarboxylic acid-based compound is produced by advancing the imidization reaction. Can be manufactured. Here, the reaction between the functional groups may be carried out in a solution or in a solid phase state, and the production method is not particularly limited.

In a monoimide tricarboxylic acid compound using a tricarboxylic acid anhydride component and a monoaminodicarboxylic acid component, one molecule of the monoaminodicarboxylic acid component reacts with one molecule of the tricarboxylic acid anhydride component, and one imide group is formed. It is a compound formed.

In the production of a monoimide tricarboxylic acid-based compound using a tricarboxylic acid anhydride component and a monoaminodicarboxylic acid component, the monoaminodicarboxylic acid component is usually about 1-fold in molar amount with respect to the tricarboxylic acid anhydride component, for example, 0. 5 to 5.0 times the molar amount, preferably 0.8 to 1.2 times the molar amount, more preferably 0.9 to 1.1 times the molar amount, still more preferably 0.95 to 1.05 times the molar amount. used.

The anhydrous tricarboxylic acid component that can constitute the monoimide tricarboxylic acid compound is not particularly limited, and for example, the heat resistance, dielectric property and insulating property of the monoimide tricarboxylic acid compound and the cured epoxy resin obtained by using the monoimide tricarboxylic acid compound are not particularly limited. From the viewpoint of further improvement, an aromatic tricarboxylic acid anhydride component containing an aromatic ring, particularly trimellitic acid anhydride, is preferable. As the tricarboxylic acid anhydride component that can constitute a monoimide tricarboxylic acid compound, one type may be used alone, or two or more types may be used as a mixture.

The monoaminodicarboxylic acid component that can constitute the monoimide tricarboxylic acid compound is not particularly limited, and for example, the heat resistance, dielectric property and insulation of the monoimide tricarboxylic acid compound and the cured epoxy resin obtained by using the monoimide tricarboxylic acid compound are not particularly limited. From the viewpoint of further improving the properties, aromatic monoaminodicarboxylic acid components containing an aromatic ring, particularly 2-aminoterephthalic acid, 2-aminoisophthalic acid, 4-aminoisophthalic acid, 5-aminoisophthalic acid, 3-aminophthalic acid Acids and 4-aminophthalic acids are preferred. As the monoaminodicarboxylic acid component that can constitute a monoimide tricarboxylic acid compound, one kind may be used alone, or two or more kinds may be used as a mixture.

[Manufacturing method of imide group-containing curing agent]
The imide group-containing curing agent can be produced in a solvent or in the absence of a solvent, but the production method is not particularly limited.

As a method for producing in a solvent, for example, a predetermined raw material (for example, tricarboxylic acid anhydride component, diamine component, tetracarboxylic acid dianhydride component, monoaminodicarboxylic acid) is added to an aprotic solvent such as N-methyl2-pyrrolidone. There is a method of imidizing after adding (acid component) and stirring at 80 ° C.

The imidization method is not particularly limited, for example, a heating imidization method performed by heating to 250 ° C. to 300 ° C. in a nitrogen atmosphere, a dehydration cyclization reagent such as a mixture of a carboxylic acid anhydride and a tertiary amine. It may be a chemical imidization method carried out by treating with.

Examples of the method for producing without a solvent include a method utilizing a mechanochemical effect. The method utilizing the mechanochemical effect is a method for obtaining an organic compound by expressing the mechanochemical effect by utilizing the mechanical energy generated when the raw material compound used for the reaction is crushed.

The mechanochemical effect is formed by crushing a raw material compound that is in a solid state under a reaction environment by applying mechanical energy (compressive force, shearing force, impact force, grinding force, etc.) to the raw material compound. It is the effect (or phenomenon) that activates the crushed interface. This causes a reaction between the functional groups. Reactions between functional groups usually occur between two or more raw compound molecules. For example, the reaction between functional groups may occur between two raw material compound molecules having different chemical structures, or may occur between two raw material compound molecules having the same chemical structure. Reactions between functional groups do not only occur between a limited set of two source compound molecules, but usually also between another set of two source compound molecules. A new reaction between functional groups may occur between the compound molecule generated by the reaction between the functional groups and the raw material compound molecule. The reaction between the functional groups is usually a chemical reaction, whereby a binding group (particularly a covalent bond) is formed between the two raw material compound molecules by the functional group of each raw material compound molecule, and another one. Compound molecules are produced.

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, an environment inside the apparatus. Being in a solid state in a reaction environment means being in a solid state in an environment where mechanical energy is applied (eg, under temperature and pressure in an apparatus). The raw material compound in the solid state under the reaction environment may usually be in the solid state at normal temperature (25 ° C.) and normal pressure (101.325 kPa). The raw material compound in the solid state under the reaction environment may be in the solid state at the start of the application of mechanical energy. In the present invention, a raw material compound in a solid state under a reaction environment is in a liquid state (for example, in a molten state) during a reaction (or a process) due to an increase in temperature and / or pressure due to continuous application of mechanical energy. ), But from the viewpoint of improving the reaction rate, it is preferable to be in a continuous solid state during the reaction (or treatment).

The details of the mechanochemical effect are not clear, but it is considered to follow the following principle. When mechanical energy is applied to one or more kinds of raw material compounds in a solid state to cause pulverization, the pulverized interface is activated by absorption of the mechanical energy. It is considered that a chemical reaction occurs between the two raw material compound molecules due to the surface active energy of such a pulverized interface. Grinding means that when mechanical energy is applied to the raw material compound particles, the particles absorb the mechanical energy, cracks occur in the particles, and the surface is renewed. Renewing the surface means forming a pulverized interface as a new surface. In the mechanochemical effect, the new surface condition formed by surface renewal is not particularly limited as long as the activation of the crushed interface by pulverization occurs, and may be in a dry state or in a wet state. May be good. The new surface wet state due to surface renewal is due to the raw material compound in a liquid state different from the raw material compound in the solid state.

Mechanical energy is applied to a raw material mixture containing one or more raw material compounds that are in a solid state under the reaction environment. The state of the raw material mixture is not particularly limited as long as the raw material compound in the solid state is pulverized by applying mechanical energy. For example, the raw material mixture may be in a dry state due to the fact that all the raw material compounds contained in the raw material mixture are in a solid state. Further, for example, the raw material mixture may be in a wet state due to the fact that 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 kind of raw material compound, the one kind of raw material compound is in a solid state. Further, for example, when the raw material mixture contains two kinds of raw material compounds, the two kinds of raw material compounds may both be in a solid state, or one raw material compound is in a solid state and the other raw material compound is a liquid. It may be in a state.

In a method utilizing the mechanochemical effect, a functional group is a monovalent group (atomic group) that can cause reactivity in the molecular structure, and is not a carbon-carbon double bond, a carbon-carbon triple bond, or the like. It shall be used in the concept excluding saturated bond groups (for example, radically polymerizable groups). A functional group is a group containing a carbon atom and a heteroatom. Heteroatoms are one or more atoms selected from the group consisting of oxygen atoms, nitrogen atoms and sulfur atoms, particularly the group consisting of oxygen atoms and nitrogen atoms. The functional group may further contain a hydrogen atom. The functional groups subjected to the reaction are usually two functional groups, and the structure of the raw material compound molecule having one functional group and the raw material compound molecule having the other functional group may be different from each other. , Or they may be the same. By the reaction, a bond (particularly a covalent bond) between two raw material compound molecules is formed, and their monomolecular formation is achieved. Small molecules such as water, carbon dioxide, and / or alcohol may or may not be by-produced by the reaction between the functional groups.

The reaction between the functional groups may be a reaction between any functional group (particularly a monovalent functional group) capable of chemically reacting with each other, for example, a carboxyl group and its halide (group), an acid anhydride group, an amino group. , An isocyanate group, a reaction of two functional groups selected from the group consisting of a hydroxyl group and the like. The two functional groups are not particularly limited as long as a chemical reaction occurs, and may be, for example, two functional groups having different chemical structures or two functional groups having the same chemical structure.

Examples of the reaction between the functional groups include a condensation reaction, an addition reaction, or a composite reaction thereof.

The condensation reaction is a reaction in which binding or ligation between the raw material compound molecules is achieved with the elimination of small molecules such as water, carbon dioxide, and alcohol between the raw material compound molecules. Examples of the condensation reaction include a reaction in which an amide group is generated (amidization reaction), a reaction in which an imide group is generated (imidization reaction), a reaction in which an ester group is generated (esteration reaction), and the like.

The addition reaction is an addition reaction between functional groups, and is a reaction in which binding or ligation between raw material compound molecules is achieved without desorption of small molecules between raw material compound molecules. Examples of the addition reaction include a reaction in which a urea group is generated, a reaction in which a urethane group is generated, and a reaction in which a cyclic structure is opened (that is, a ring-opening reaction). In the ring-opening reaction, in a raw material compound having a cyclic structure (for example, an acid anhydride group-containing compound, a cyclic amide compound, a cyclic ester compound, an epoxy compound), a part of the cyclic structure is cleaved, and the cleaved site and other parts thereof. A reaction in which a bond or linkage with a functional group of a raw material compound is achieved. The ring-opening reaction produces, for example, an amide group, a carboxyl group, an ester group, and an ether group. In particular, in the ring-opening reaction of an acid anhydride group in an acid anhydride group-containing compound as a raw material compound, the acid anhydride group is opened and bonded to another raw material compound molecule (amino group or hydroxyl group). Or the consolidation is achieved. As a result, for example, an amide group or an ester group and a carboxyl group are simultaneously generated.

More specifically, the reaction between functional groups may be, for example, one or more reactions selected from the group consisting of the following reactions:
(A) A reaction in which an acid anhydride group reacts with an amino group to form (a1) an amide group and a carboxyl group, (a2) an imide group, (a3) an isoimide group or (a4) a mixed group thereof;
(B) A reaction in which an imide group is generated by a reaction between an acid anhydride group and an isocyanate group;
(C) A reaction in which an amide group is generated by a reaction between a carboxyl group or a halide (group) thereof and an amino group or an isocyanate group;
(D) A reaction in which an ester group is generated by a reaction between a carboxyl group or a halide (group) thereof and a hydroxyl group;
(E) A reaction in which a urea group is generated by a reaction between an isocyanate group and an amino group;
(F) A reaction in which a urethane group is generated by a reaction between an isocyanate group and a hydroxyl group; and (G) a reaction in which an ester group and a carboxyl group are generated by a reaction between an acid anhydride group and a hydroxyl group.

When the above-mentioned imide group-containing curing agent is produced from the above-mentioned raw material compounds, the reaction between the functional groups corresponds to the above-mentioned reaction (A). In the method for producing without a solvent, after carrying out the method utilizing the mechanochemical effect, imidization may be carried out by the same method as the imidization method in the method for producing in a solvent.

[Epoxy resin]
The epoxy resin used in the present invention is not particularly limited as long as it is an organic compound having two or more epoxy groups in one molecule. Specific examples of the epoxy resin include, for example, bisphenol A type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, naphthalene type epoxy resin, bisphenyl type epoxy resin, dicyclopentadiene type epoxy. Examples thereof include resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, isocyanurate type epoxy resins, alicyclic epoxy resins, acrylic acid modified epoxy resins, polyfunctional epoxy resins, brominated epoxy resins, and phosphorus modified epoxy resins. The epoxy resin may be used alone or in combination of two or more. The epoxy group may be a glycidyl group. Epoxy resins are available as commercial products.

The epoxy equivalent of the epoxy resin is usually 100 to 3000, preferably 150 to 300.

[Additive]
The cured epoxy resin of the present invention may further contain additives such as a curing accelerator, a thermosetting resin, an inorganic filler, an antioxidant, and a flame retardant.

The curing accelerator is not particularly limited, but for example, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, and the like imidazoles; 4-dimethylaminopyridine, benzyldimethylamine, 2- (dimethylaminomethyl). ) Tertiary amines such as phenol, 2,4,6-tris (dimethylaminomethyl) phenol; organic phosphines such as triphenylphosphine and tributylphosphine. The curing accelerator may be used alone or in combination of two or more.

The blending amount of the curing accelerator is not particularly limited, and is, for example, 0.01 to 2% by mass with respect to the total amount of the epoxy resin solution described later, further improving the heat resistance, dielectric properties and insulating properties of the epoxy resin cured product. From the viewpoint of the above, it is preferably 0.01 to 1% by mass, and more preferably 0.05 to 0.5% by mass.

The thermosetting resin is not particularly limited, and examples thereof include cyanate resin, isocyanate resin, maleimide resin, polyimide resin, urethane resin, and phenol resin. The thermosetting resin may be used alone or in combination of two or more.

Examples of the inorganic filler include silica, glass, alumina, talc, mica, barium sulfate, aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, magnesium oxide, titanium oxide, silicon nitride, boron nitride and the like. The inorganic filler may be used alone or in combination of two or more. Further, the inorganic filler is preferably surface-treated with a surface treatment agent such as an epoxy silane coupling agent or an amino silane coupling agent. The inorganic filler may be used alone or in combination of two or more.

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

The flame retardant is not particularly limited, and a non-halogen flame retardant is preferable from the viewpoint of the influence on the environment. Examples of the flame retardant include phosphorus-based flame retardants, nitrogen-based flame retardants, silicone-based flame retardants, and the like. The flame retardant may be used alone or in combination of two or more.

<Manufacturing method of electrically insulating epoxy resin cured product>
The electrically insulating epoxy resin cured product of the present invention can be produced by heating an epoxy resin solution, which will be described in detail later, containing an imide group-containing curing agent and an epoxy resin.
For example, the electrically insulating epoxy resin cured product of the present invention can be produced by applying an epoxy resin solution to a substrate, drying and curing the substrate by heating. After curing, the cured product may be peeled off from the substrate and used. The method for applying the epoxy resin solution is not particularly limited, and examples thereof include a casting method and a dipping method. A cured epoxy resin can be obtained in the form of a sheet, a film, or the like by applying an epoxy resin solution to a substrate, drying and curing the substrate, and then peeling the epoxy resin solution from the substrate.

Further, for example, the electrically insulating epoxy resin cured product of the present invention can be produced by molding, drying and curing the epoxy resin solution while pouring it into a mold. The molding method of the epoxy resin solution is not particularly limited, and examples thereof include a transfer molding method and an injection molding method.

By heating the coating film, the film and its laminate, and the molded product thereof (that is, the molded product) obtained by using the epoxy resin solution of the present invention, the imide group-containing curing agent and the epoxy resin are reacted to complete the curing. Can be achieved. The heating temperature (curing temperature) is usually 80 to 350 ° C, preferably 130 to 300 ° C. The heating time (curing time) is usually 1 minute to 20 hours, preferably 5 minutes to 10 hours.

The epoxy resin cured product of the present invention may have any size. When the cured epoxy resin of the present invention has, for example, a film, a plate, a film, a sheet, or the like, the thickness of the cured product may be usually 1 μm to 100 mm.

[Epoxy resin solution]
The epoxy resin solution is made by mixing at least an imide group-containing curing agent and an epoxy resin with an organic solvent. Preferably, in the epoxy resin solution, the imide group-containing curing agent and the epoxy resin are dissolved in the organic solvent, and at least the imide group-containing curing agent, the epoxy resin and the organic solvent are uniformly mixed at the molecular level. Dissolution means that the solute is uniformly mixed in the solvent at the molecular level. A solution is a state in which a solute is uniformly mixed in a solvent at the molecular level. For example, at normal temperature (25 ° C.) and normal pressure (101.325 kPa), the solute is used as a solvent with the naked eye. It is a mixed liquid that is dissolved to the extent that it looks transparent. The epoxy resin solution may further contain the above-mentioned additives.

The organic solvent used in the epoxy resin solution is not particularly limited as long as the curing agent and the epoxy resin can be uniformly dissolved, and a non-halogenated solvent is preferable from the viewpoint of the influence on the environment. Examples of such a non-halogenated solvent include amide compounds such as N, N-dimethylformamide, N, N-dimethylacetamide, and N-methyl-2-pyrrolidone. All of these non-halogenated solvents are useful as general purpose solvents. The organic solvent may be used alone or in combination of two or more.

The method for producing the epoxy resin solution is not particularly limited, and may be, for example, an individual dissolution method, a batch dissolution method, or the like. The individual dissolution method is preferable from the viewpoint of obtaining a uniform resin solution in a short time. The individual dissolution method is a method in which an imide group-containing curing agent and an epoxy resin are mixed and dissolved in an organic solvent in advance, and then they are mixed. The batch dissolution method is a method in which an imide group-containing curing agent and an epoxy resin are simultaneously mixed with an organic solvent and dissolved. In the individual melting method and the batch melting method, the mixing temperature is not particularly limited and may be, for example, 80 to 180 ° C., particularly 100 to 160 ° C. The heating for achieving the mixing temperature may be, for example, reflux heating of an organic solvent.

In the epoxy resin solution, the amount of the imide group-containing curing agent blended is such that the functional group equivalent of the imide group-containing curing agent is the epoxy resin from the viewpoint of further improving the heat resistance, dielectric properties and insulating properties of the obtained epoxy resin cured product. The amount is preferably 0.5 to 1.5 equivalents, more preferably 0.7 to 1.3 equivalents, relative to the epoxy equivalent. The functional group equivalent of the imide group-containing curing agent corresponds to the equivalent calculated from the content of the hydroxy group or the carboxyl group.

In the epoxy resin solution, the total amount of the imide group-containing curing agent and the epoxy resin is not particularly limited, and the total amount of the epoxy resin solution is set from the viewpoint of further improving the heat resistance, dielectric properties and insulating properties of the obtained epoxy resin cured product. On the other hand, it is preferably 30 to 90% by mass, more preferably 40 to 80% by mass, and further preferably 50 to 70% by mass.

The epoxy resin solution usually has a viscosity of 10 to 70 Pa · s, particularly 30 to 70 Pa · s, preferably 40 to 60 Pa · s, and does not have a so-called gel form. A gel does not have a viscosity and is generally a solid state having no fluidity. Specifically, the epoxy resin solution, when mixed with a further solvent, is easily compatible with each other and is uniformly mixed at the molecular level as a whole. However, even when the gel is mixed with a further solvent, it does not dissolve with each other and remains in a lump form, and is not uniformly mixed at the molecular level as a whole. Mixing for determining compatibility is usually with 100 g of solution or gel and 100 g of additional solvent, even under stirring conditions at room temperature (25 ° C.), normal pressure (101.325 kPa) and 100 rpm. good. At this time, the "further solvent" is a solvent that is compatible with the solvent contained in the solution or gel, and is, for example, a solvent represented by the same structural formula as the solvent contained in the solution or gel. The viscosity of the epoxy resin solution is the viscosity at 30 ° C. measured by a Brookfield digital viscometer.

In the epoxy resin solution, since the epoxy resin is unlikely to react unexpectedly, it may have a relatively low viscosity as described above. Therefore, a cured product can be produced with sufficient workability by using the epoxy resin solution. Specifically, the epoxy resin solution usually has a reaction rate of 10% or less. The reaction rate is the ratio of the number of glycidyl groups reacted in the epoxy resin solution to the total number of glycidyl groups contained in the epoxy resin.

<Use of electrically insulating epoxy resin cured product>
The cured epoxy resin of the present invention is useful in all applications that require at least one of heat resistance, dielectric properties and electrical insulation (preferably properties including at least electrical insulation). Specifically, the cured epoxy resin of the present invention can be preferably used as any electrically insulating material. Such electrically insulating materials include, for example, encapsulants (for example, encapsulants for power semiconductor modules), insulators (particularly insulator covering materials) (for example, insulators for transmission lines (particularly insulator covering materials for transmission lines)). , Electric wire covering materials (for example, electric wire covering materials for electric vehicles), insulating materials for printed wiring boards, and the like.

Use as a sealant for hardened electrically insulating epoxy resin:
When the electrically insulating epoxy resin cured product of the present invention is used as a sealing material, for example, after producing a power semiconductor module, the epoxy resin solution is filled in a mold in which the module is set, and dried and cured. Therefore, the cured epoxy resin of the present invention can be used as a sealing material for a power semiconductor module.

Use of hardened electrically insulating epoxy resin as insulator coating material:
When the electrically insulating epoxy resin cured product of the present invention is used as an insulator coating material, for example, an epoxy resin solution is used to coat the outer peripheral portion (particularly the outer peripheral surface) of the insulator core to form a layer, and then dried and dried. By curing, the cured epoxy resin of the present invention can be used as an insulator coating material. Examples of the core include glass fiber reinforced plastics such as glass fiber reinforced epoxy resin and glass fiber reinforced phenol resin, which are usually formed into various shapes such as a cylindrical shape or a columnar shape. The thickness of the cured epoxy resin as a coating material formed on the outer peripheral portion of the core can be changed according to the size and shape of the obtained polymer insulator (for example, the presence or absence of a bulk portion and its shape, size, and spacing). However, from the viewpoint of further improving heat resistance, dielectric properties, insulating properties, etc., the thinnest portion is preferably 1 mm or more, and more preferably 2 mm or more. When the cured product of the electrically insulating epoxy resin of the present invention is used as the insulator coating material, the thickness of the coating material is usually 1 to 100 mm, preferably 2 to 50 mm. When the cured epoxy resin of the present invention is used as an insulator coating material, the cured epoxy resin of the present invention has an insulating property (particularly, an insulating property that more sufficiently prevents dielectric breakdown due to local accumulation of charge). It is especially useful as an insulator covering material for power transmission lines.

Use of hardened electrically insulating epoxy resin as a wire coating material:
When the electrically insulating epoxy resin cured product of the present invention is used as an electric wire coating material, the epoxy resin cured product of the present invention is obtained by applying an epoxy tree solution to the surface of a conductor and baking (that is, drying and curing). It can be used as an electric wire covering material. Examples of the conductor include copper and copper alloys. The coating method and the baking method can be carried out according to the same methods and conditions as the coating method and the baking method in the conventional wire coating forming method. The coating and baking may be repeated twice or more. The epoxy resin solution may be mixed with other resins and used. The thickness of the wire covering material is preferably 1 to 100 μm, more preferably 10 to 50 μm from the viewpoint of protecting the conductor. When the cured epoxy resin of the present invention is used as a wire coating material, the cured epoxy resin of the present invention has an insulating property (particularly, an insulating property that more sufficiently prevents dielectric breakdown due to local accumulation of charge). It is particularly useful as an electric wire covering material for electric vehicles.

Use as an insulating material for printed wiring boards of electrically insulating epoxy resin cured products:
The printed wiring board usually contains an electrically insulating epoxy resin cured product, and may further contain a glass cloth. When the electrically insulating epoxy resin cured product of the present invention is used as an insulating material for a printed wiring board, the epoxy resin cured product of the present invention is dried and cured after impregnating or applying an epoxy resin solution to a glass cloth. Can be used as an insulating material for printed wiring boards. It may be a printed wiring board. Wiring (conductors) may be arranged on and / or inside the printed wiring board, and / or electronic components may be attached to the printed wiring board. The thickness of the printed wiring board is not particularly limited.

The cured epoxy resin of the present invention is an electric / electronic material for other uses, for example, a mold material for a bushing transformer, a mold material for a solid insulating switchgear, an electric penetration for a nuclear power plant, an electric / electronic material such as a build-up laminate. Can also be suitably used.

Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited thereto. The evaluation and measurement were carried out by the following methods.

A. Evaluation and measurement [Method and evaluation method for producing imide group-containing curing agent]
(1) Method for producing imide group-containing curing agent 150 g of a sample in which an acid component and an amine component are mixed at the ratios shown in the table is pulverized by Wonder Crusher (Osaka Chemical Co., Ltd.) WC-3C at a rotation speed of about 9000 rpm for 1 minute. The mechanochemical treatment was performed by repeating the mixing and crushing three times.
The treated sample was transferred to a glass container, and an imidization reaction was carried out in an inert oven (Yamato Scientific Co., Ltd.) DN411I under a nitrogen atmosphere at a firing temperature of 300 ° C. and a firing time of 2 hours.
The identification of the imide group-containing curing agent was performed based on the fact that the molecular weight is the same as the molecular weight of the target structure and that there is absorption derived from the imide group in infrared spectroscopy.

(2) Molecular weight of imide group-containing curing agent The molecular weight was determined by measuring under the following conditions with a high-performance liquid chromatograph mass spectrometer (LC / MS).
Sample: Imide group-containing curing agent / DMSO solution (200 μg / mL)
Equipment: Bruker Dartonics microTOF2-kp
Column: Cadenza CD-C18 3 μm 2 mm × 150 mm
Mobile phase: (Mobile phase A) 0.1% aqueous formic acid solution, (Mobile phase B) Methanol gradient (B Conc.): 0 min (50%) -5,7 min (60%) -14.2 min (60%)- 17min (100%) -21.6min (100%) -27.2min (50%) -34min (50%)
Ionization method: ESI
Detection condition: Negative mode

(3) Confirmation of reaction Measurement was performed under the following conditions by infrared spectroscopy (IR) for identification.

Infrared spectroscopy (IR)
Equipment: PerkinElmer System 2000 infrared spectroscope Method: KBr method Accumulation frequency: 64 scans (resolution 4 cm ^-1 )
To confirm the presence or absence of the absorption in the vicinity of 1778cm ^-1 and around 1714 cm ^-1 derived from an imide group.
⊚: If there is (reaction progresses);
×: When there is no (reaction is not progressing).

[Epoxy resin cured product evaluation method]
(1) Reactivity The transmitted infrared absorption spectrum (IR) of the cured epoxy resin obtained in each of the Examples and Comparative Examples was measured under the following conditions, and the absorbance ratio of the glycidyl group was determined.
Absorption derived from glycidyl groups is usually detected in the wavenumber region of ^{900-950 cm-1.} The line connecting the bases of both sides of the absorption peak detected in these wave numbers is used as the baseline, and the line is drawn from the apex of the peak to the apex of the peak when a line is drawn perpendicular to the baseline. The length was calculated as the absorbance.

Infrared spectroscopy (IR)
Equipment: PerkinElmer System 2000 infrared spectroscope Method: KBr method Accumulation frequency: 64 scans (resolution 4 cm ^-1 )

Next, the details of the method for calculating the reaction rate of the glycidyl group will be described. First, a sample for IR measurement was prepared and measured by mixing the epoxy resin solutions obtained in each of Examples and Comparative Examples with KBr powder. .. It was confirmed that the intensity of the peak showing the highest absorbance in the obtained spectrum was in the range of absorbance 0.8 to 1.0, and the absorbance α of the glycidyl group was determined. Next, this sample was heat-treated in an oven at a temperature of 300 ° C. under a nitrogen stream for 2 hours to allow the curing reaction to proceed completely. IR measurement was performed on this cured sample by the same method, and the absorbance α'of the wave number due to the glycidyl group was determined. At this time, the reaction rate of the sample was determined by the following formula, with the reaction rate of the glycidyl group before the curing reaction being 0%.
Reaction rate (%) = {1- (α'/ α)} x 100
⊚: 90% or more and 100% or less (best);
◯: 80% or more and less than 90% (good);
Δ: 70% or more and less than 80% (no problem in practical use);
X: Less than 70% (there is a problem in practical use).

(2) Glass transition temperature (Tg) (heat resistance)
The differential scanning calorimetry device (DSC) was used to measure and identify under the following conditions.

Equipment: PerkinElmer DSC 7
Temperature rise rate: 20 ° C / min
The temperature is raised from 25 ° C to 300 ° C, the temperature is lowered, and then the temperature is raised again from 25 ° C to 300 ° C. And said.

-When "jER828: Mitsubishi Chemical Corporation, bisphenol A type epoxy resin" is used as the epoxy resin ◎: 190 ° C ≤ Tg (best);
◯: 170 ° C ≤ Tg <190 ° C (good);
Δ: 140 ° C ≤ Tg <170 ° C (no problem in practical use);
X: Tg <140 ° C. (There is a problem in practical use).

-When "EOCN-1020-55: o-cresol novolac type epoxy resin manufactured by Nippon Kayaku Co., Ltd." is used as the epoxy resin ◎: 200 ° C. ≤ Tg (best);
◯: 180 ° C ≤ Tg <200 ° C (good);
Δ: 150 ° C ≤ Tg <180 ° C (no problem in practical use);
X: Tg <150 ° C (There is a problem in practical use).

(3) Insulation (measurement of charge density distribution)
For the epoxy resin cured products obtained in each of the examples and comparative examples, the charge density distribution was measured under the following conditions by a pulse electrostatic stress (PEA) measurement system for high temperature measurement, and the maximum electric field in the obtained sample was evaluated. Was done. The epoxy resin cured product sample is placed in a high voltage application unit in a state of being immersed in silicone oil, then heated to 140 ° C., after reaching 140 ° C., controlled to be constant at 140 ° C., and DC voltage after 30 minutes. Was applied. In consideration of the acoustic characteristic impedance of the sample, a commercially available conductive PEEK (polyetheretherketone) sheet was used for the anode, and an aluminum plate was used for the cathode. The cured epoxy resin (sample) has a film shape and is sandwiched between the anode and the cathode. When applying a DC voltage, in consideration of the thickness of the sample, a DC voltage corresponding to an average electric field of 20 kV / mm is applied for 10 minutes, then short-circuited for 5 minutes, and pulses are applied during and during the short circuit. A voltage (5 ns, 200 V) was applied at 1 ms intervals (1 kHz), and the obtained waveforms were added and averaged 1000 times to obtain one waveform. The measurement interval is 10 seconds. After the measurement during the application of 20 kV / mm and during the short circuit is completed, the DC voltage to be applied is increased so that the average applied electric field becomes 40 kV / mm, and a series of measurements similar to the above are performed. The measurements were sequentially repeated under average applied electric fields corresponding to 60, 80, 100 and 120 kV / mm. The charge density distributions thus measured over time are shown in FIGS. 1 and 2. FIG. 1 shows changes over time in the charge density distribution of the cured epoxy resin products of Examples A-1, B-1, B-2 and C-1 (particularly the cured epoxy resin products using bisphenol A type epoxy resin). It is a chart showing. FIG. 2 is a chart showing changes over time in the charge density distribution of the cured epoxy resin of Comparative Examples 1 to 3 (particularly the cured epoxy resin using bisphenol A type epoxy resin). The smaller the maximum electric field (particularly the ratio of the maximum electric field / applied electric field), the better the insulating property.

Equipment: High voltage application unit Sample dimensions: Length 50 mm x Width 50 mm x Thickness 100 μm or more and 150 μm or less Applied electric field: 20, 40, 60, 80, 100, 120 kV / mm
Measurement temperature: 140 ° C

-When "jER828: Mitsubishi Chemical Corporation, bisphenol A type epoxy resin" was used as the epoxy resin ◎: The ratio of the maximum electric field in the sample to the applied electric field was 1.1 or less at the maximum (best);
◯: The ratio of the maximum electric field in the sample to the applied electric field was greater than 1.1 at the maximum and 1.3 or less (good);
Δ: The ratio of the maximum electric field in the sample to the applied electric field was larger than 1.3 at the maximum and 1.5 or less (no problem in practical use);
X: The ratio of the maximum electric field in the sample to the applied electric field was larger than 1.5 at the maximum (there is a problem in practical use).

-When "EOCN-1020-55: o-cresol novolac type epoxy resin manufactured by Nippon Kayaku Co., Ltd." is used as the epoxy resin ◎: The ratio of the maximum electric field in the sample to the applied electric field is 1.2 or less at the maximum. (Best);
◯: The ratio of the maximum electric field in the sample to the applied electric field was greater than 1.2 at the maximum and 1.4 or less (good);
Δ: The ratio of the maximum electric field in the sample to the applied electric field was larger than 1.4 at the maximum and 1.6 or less (no problem in practical use);
X: The ratio of the maximum electric field in the sample to the applied electric field was larger than 1.6 at the maximum (there is a problem in practical use).

(4) Dielectric characteristics (dielectric constant, dielectric loss tangent)
It was measured and evaluated by an impedance analyzer under the following conditions.

Impedance Analyzer Equipment: E4991A RF Impedance / Material Analyzer manufactured by Agilent Technologies, Ltd. Sample dimensions: Length 20 mm x Width 20 mm x Thickness 150 μm
Frequency: 1GHz
Measurement temperature: 23 ° C
Test environment: 23 ° C ± 1 ° C, 50% RH ± 5% RH

-When "jER828: Mitsubishi Chemical Corporation, bisphenol A type epoxy resin" is used as the epoxy resin ◎: Dielectric constant ≤ 2.6 (best);
◯: 2.6 <dielectric constant ≤ 3.0 (good);
Δ: 3.0 <dielectric constant ≤ 3.3 (no problem in practical use);
X: 3.3 <dielectric constant (there is a problem in practical use).
⊚: Dissipation factor ≤ 0.0175 (best);
◯: 0.0175 <dielectric loss ≤ 0.020 (good);
Δ: 0.020 <dielectric loss ≤ 0.030 (no problem in practical use);
X: 0.030 <dielectric loss tangent (there is a problem in practical use).

-When "EOCN-1020-55: o-cresol novolac type epoxy resin manufactured by Nippon Kayaku Co., Ltd." is used as the epoxy resin ◎: Dielectric constant ≤ 2.8 (best);
◯: 2.8 <dielectric constant ≤ 3.2 (good);
Δ: 3.2 <dielectric constant ≤ 3.4 (no problem in practical use);
X: 3.4 <dielectric constant (there is a problem in practical use).
⊚: Dissipation factor ≤ 0.0195 (best);
◯: 0.0195 <dielectric loss ≤ 0.030 (good);
Δ: 0.030 <dielectric loss ≤ 0.042 (no problem in practical use);
X: 0.042 <dielectric loss tangent (there is a problem in practical use).

(5) Comprehensive evaluation Comprehensive evaluation was performed based on the evaluation results of heat resistance, dielectric properties and insulating properties.
⊚: All evaluation results were ◎.
◯: Of all the evaluation results, the lowest evaluation result was ◯.
Δ: Of all the evaluation results, the lowest evaluation result was Δ.
X: Of all the evaluation results, the lowest evaluation result was ×.

[Epoxy resin solution evaluation method]
(1) Viscosity of Epoxy Resin Solution Viscosity (Pa · s) of the epoxy resin solutions obtained in each of the Examples and Comparative Examples at 30 ° C. using a Brookfield Digital Viscometer (Toki Sangyo TVB-15M). Was measured.

(2) Solubility of the imide group-containing curing agent contained in the epoxy resin solution The presence or absence of undissolved components (residues) in the epoxy resin solutions obtained in each of Examples and Comparative Examples was visually observed.
⊚ (with solubility): No undissolved residue; mixing at 150 ° C. Completely dissolved within 10 minutes.
○ (with solubility): No undissolved residue; mixed at 150 ° C. completely dissolved in more than 10 minutes (it takes time to dissolve).
X (no solubility): There was undissolved residue; there was undissolved residue in the obtained epoxy resin solution.

B. Raw Material (1) Imide Group-Containing Curing Agent [Preparation of Diimide Dicarboxylic Acid]
Synthesis example A-1
A diimide dicarboxylic acid was produced based on the above-mentioned "method for producing an imide group-containing curing agent". The details are as follows.
521 parts by mass of granular anhydrous trimellitic acid and 479 parts by mass of 4,4'-diaminodiphenyl ether were added to the crushing tank, and mixed pulverization was performed.
Then, the mixture was transferred to a glass container and subjected to an imidization reaction at 300 ° C. for 2 hours in a nitrogen atmosphere in an inert oven to prepare an imide group-containing curing agent.

[Preparation of diimidetetracarboxylic acid]
Synthesis example B-1
A diimide tetracarboxylic acid was prepared based on the above-mentioned "method for producing an imide group-containing curing agent". The details are as follows.
471 parts by mass of granular 3,3', 4,4'-benzophenonetetracarboxylic dianhydride and 529 parts by mass of 2-aminoterephthalic acid were added to the crushing tank, and mixed pulverization was performed.
Then, the mixture was transferred to a glass container and subjected to an imidization reaction at 300 ° C. for 2 hours in a nitrogen atmosphere in an inert oven to prepare an imide group-containing curing agent.

Synthesis example B-2
The same operation as in Synthesis Example B-1 was carried out except that the acid dianhydride composition and the monoamine composition were changed to obtain an imide group-containing curing agent.

[Preparation of monoimide tricarboxylic acid]
Synthesis example C-1
A monoimide tricarboxylic acid was produced based on the above-mentioned "method for producing an imide group-containing curing agent". The details are as follows.
515 parts by mass of granular anhydrous trimellitic acid and 485 parts by mass of 2-aminoterephthalic acid were added to the crushing tank, and mixed pulverization was performed.
Then, the mixture was transferred to a glass container and subjected to an imidization reaction at 300 ° C. for 2 hours in a nitrogen atmosphere in an inert oven to prepare an imide group-containing curing agent.

(2) Epoxy resin jER828: Mitsubishi Chemical Corporation, bisphenol A type epoxy resin, epoxy equivalent 184 to 194 g / eq
EOCN-1020-55: manufactured by Nippon Kayaku Co., Ltd., o-cresol novolac type epoxy resin, epoxy equivalent 195 g / eq

(3) Curing agent other than imide-based curing agent-PHENOLITE TD-2131: Novolac-type phenol resin manufactured by DIC, curing agent containing no imide group; The curing agent has the following structural formula.

HN-2200: manufactured by Hitachi Chemical Co., Ltd., alicyclic acid anhydride, imide group-free curing agent; the curing agent has the following structural formula.

-JERcure113: A curing agent manufactured by Mitsubishi Chemical Corporation that does not contain a modified alicyclic amine or an imide group.

Example A-1
The curing accelerator (2) was mixed with 60 parts by mass of the sample obtained by mixing the imide group-containing curing agent obtained in Synthesis Example A-1 and the epoxy resin (jER828) at a ratio of 1.0 / 1.1 (equivalent ratio). -Ethyl-4-methylimidazole, manufactured by Tokyo Chemical Industry Co., Ltd.) 0.2 parts by mass and 39.8 parts by mass of dimethylformamide (DMF) are mixed at room temperature (that is, 20 ° C.), and 0.5 at 150 ° C. Epoxy resin solution was obtained by reflux heating for a period of time.
The epoxy resin solution obtained in this example had a viscosity of 50 Pa · s and had sufficiently good workability.

The obtained epoxy resin solution was applied to an aluminum substrate to a thickness of 300 μm, and the produced coating film was dried in an inert oven at 180 ° C. for 2 hours and then at 300 ° C. for 2 hours in a nitrogen atmosphere. Desolvation and curing reactions were performed. The aluminum base material was removed from the obtained sample with an aluminum base material to obtain a cured epoxy resin. The average thickness of the cured epoxy resin (cured epoxy resin using the epoxy resin "jER828") was 112 μm. In the present specification, the average thickness is the average value of the thickness at any 10 points.

In addition, except that "EOCN-1020-55" (manufactured by Nippon Kayaku Co., Ltd., o-cresol novolac type epoxy resin) is used instead of "jER828" as the epoxy resin, the same method as described above in this example is used. , Epoxy resin solution and epoxy resin cured product were prepared. The epoxy resin solution had a viscosity of 50 Pa · s and had sufficiently good workability. The average thickness of the cured epoxy resin (cured epoxy resin using the epoxy resin "EOCN-1020-55") was 103 μm.

Examples B-1, B-2 and C-1 and Comparative Example 1
The epoxy resin was subjected to the same operation as in Example A-1 except that the imide group-containing curing agent or the curing agent "PHENOLITE TD-2131" obtained in Synthesis Example B-1, B-2 or C-1 was used. A solution and a cured epoxy resin were prepared. The imide group-containing curing agent used in each example was obtained in a synthetic example having the same number as that of the example number.

The reaction rate of the glycidyl group in the epoxy resin contained in the epoxy resin solutions obtained in Examples B-1, B-2 and C-1 and Comparative Example 1 was 10% or less.
The viscosities of the epoxy resin solutions obtained in Examples B-1, B-2 and C-1 and Comparative Example 1 were all 30 to 70 Pa · s, and had sufficiently good workability.

The average thickness of the cured epoxy resin was as follows.
Average thickness of epoxy resin cured product using epoxy resin "jER828":
116 μm (Example B-1), 115 μm (Example B-2), 122 μm (Example C-1), 112 μm (Comparative Example 1).
Average thickness of epoxy resin cured product using epoxy resin "EOCN-1020-55":
120 μm (Example B-1), 104 μm (Example B-2), 114 μm (Example C-1), 106 μm (Comparative Example 1).

Comparative Example 2
100/80/1 (weight ratio) of alicyclic acid anhydride curing agent HN-2200, epoxy resin (jER828), and curing accelerator (2,4,6-trisdimethylaminomethylphenol, manufactured by Mitsubishi Chemical Co., Ltd.) The mixture was mixed at room temperature (that is, 20 ° C.) at the ratio of 1 to obtain an epoxy resin solution.
The epoxy resin solution obtained in this comparative example had a viscosity of 50 Pa · s and had sufficiently good workability.

The obtained epoxy resin solution was applied to an aluminum substrate to a thickness of 300 μm, and the produced coating film was dried in an inert oven at 120 ° C. for 5 hours and then at 150 ° C. for 15 hours in an inert oven. A curing reaction was carried out. The aluminum base material was removed from the obtained sample with an aluminum base material to obtain a cured epoxy resin. The average thickness of the cured epoxy resin (cured epoxy resin using the epoxy resin "jER828") was 133 μm.

In addition, except that "EOCN-1020-55" (manufactured by Nippon Kayaku Co., Ltd., o-cresol novolac type epoxy resin) is used instead of "jER828" as the epoxy resin, the same method as described above in this comparative example is used. , Epoxy resin solution and epoxy resin cured product were prepared. The epoxy resin solution had a viscosity of 40 Pa · s and had sufficiently good workability. The average thickness of the cured epoxy resin (cured epoxy resin using the epoxy resin "EOCN-1020-55") was 140 μm.

Comparative Example 3
The modified alicyclic amine curing agent jERcure113 and the epoxy resin (jER828) were mixed at a ratio of 100/10 (weight ratio) at room temperature (that is, 20 ° C.) to obtain an epoxy resin solution.
The epoxy resin solution obtained in this comparative example had a viscosity of 50 Pa · s and had sufficiently good workability.

The obtained epoxy resin solution was applied to an aluminum substrate to a thickness of 300 μm, and the produced coating film was dried in an inert oven at 80 ° C. for 1 hour and then at 150 ° C. for 3 hours in a nitrogen atmosphere. A curing reaction was carried out. The aluminum base material was removed from the obtained sample with an aluminum base material to obtain a cured epoxy resin. The average thickness of the cured epoxy resin (cured epoxy resin using the epoxy resin "jER828") was 139 μm.

In addition, except that "EOCN-1020-55" (manufactured by Nippon Kayaku Co., Ltd., o-cresol novolac type epoxy resin) is used instead of "jER828" as the epoxy resin, the same method as described above in this comparative example is used. , Epoxy resin solution and epoxy resin cured product were prepared. The epoxy resin solution had a viscosity of 40 Pa · s and had sufficiently good workability. The average thickness of the cured epoxy resin (cured epoxy resin using the epoxy resin "EOCN-1020-55") was 123 μm.

The characteristic values of the curing agent and the characteristic values of the epoxy resin cured product in each of Examples and Comparative Examples are shown in Tables 1 to 4.

Since the cured epoxy resin of Examples A-1 to C-1 satisfied the requirements of the present invention, they were sufficiently excellent in all physical properties of heat resistance, dielectric properties and insulating properties.

Among these examples, only in Example A-1 using the diimide dicarboxylic acid compound, all the evaluation results of heat resistance, dielectric property and insulating property achieved ⊚.

Since the cured epoxy resin of Comparative Examples 1 to 3 used a curing agent containing no imide group, it was inferior in at least one of heat resistance, dielectric property and insulating property.

In particular, regarding the insulating property, the following items are clear from the ratio of the maximum electric field / applied electric field in each of the cured epoxy resin products of Examples and Comparative Examples and the time-dependent change charts of the charge density distributions in FIGS. 1 and 2.
-In the epoxy resin cured products of Examples A-1, B-1, B-2 and C-1, local accumulation of electric charge was sufficiently prevented under high temperature and high electric field;
-In the epoxy resin cured products of Comparative Examples 1 to 3, local charge accumulation occurred under high temperature and high electric field.

The details of the observation of the local charge accumulation phenomenon from the time-dependent change chart of the charge density distribution are as follows;
From FIG. 1, the epoxy resin cured products of Examples A-1, B-1, B-2 and C-1 showed a substantially uniform charge density distribution between the anode and the cathode.
From FIG. 2, in the epoxy resin cured products of Comparative Examples 1 to 3, local accumulation of electric charges (that is, uneven distribution of electric charges) was observed between the anode and the cathode (particularly in the vicinity of the cathode (cathode)). .. In FIG. 2, the portion where the local accumulation of electric charge is often shown is surrounded by a solid line (elliptic shape).

The cured epoxy resin of the present invention has sufficiently excellent heat resistance, dielectric properties and insulating properties. Therefore, the cured epoxy resin of the present invention includes encapsulants for power semiconductor modules (particularly semiconductor encapsulants), mold materials for bushing transformers, mold materials for solid-insulated switch gears, insulators for power transmission lines, and the like. It can be suitably used for electric wire covering materials for electric vehicles, electric penetrations for nuclear power plants, insulating materials for printed wiring boards, and electrical and electronic materials such as build-up laminated boards.

Claims (14)

An imide group-containing compound selected from the group of diimide dicarboxylic acid compounds, diimide tetracarboxylic acid compounds and monoimide tricarboxylic acid compounds. An imide group-containing curing agent selected from the imide group-containing compounds according to claim 1. An epoxy resin cured product comprising the imide group-containing curing agent according to claim 2 and an epoxy resin. The cured epoxy resin according to claim 3, wherein the epoxy resin has two or more epoxy groups in one molecule. The epoxy resin cured product according to claim 3 or 4, wherein the imide group-containing curing agent has a molecular weight of 200 to 1100. The epoxy resin cured product according to any one of claims 3 to 5, wherein the imide group-containing curing agent has a functional group equivalent of 50 to 500. An electrically insulating material containing the cured epoxy resin according to any one of claims 3 to 6. A sealing material containing the cured epoxy resin according to any one of claims 3 to 6. The encapsulant according to claim 8, which is for a power semiconductor module. An insulator containing the cured epoxy resin according to any one of claims 3 to 6. The insulator according to claim 10, which is for a power transmission line. An electric wire coating material containing the cured epoxy resin according to any one of claims 3 to 6. The electric wire covering material according to claim 12, which is for an electric vehicle. A printed wiring board containing the cured epoxy resin according to any one of claims 3 to 6.

Images