CN114728903B

CN114728903B - Imide group-containing compound, imide group-containing curing agent, epoxy resin cured product, and electrical insulating material using same

Info

Publication number: CN114728903B
Application number: CN202080080567.8A
Authority: CN
Inventors: 谷中爱步; 中井诚; 田洼由纪
Original assignee: Unitika Ltd
Current assignee: Unitika Ltd
Priority date: 2019-12-10
Filing date: 2020-12-07
Publication date: 2023-04-28
Anticipated expiration: 2040-12-07
Also published as: TW202128620A; JP6960705B1; CN114728903A; WO2021117686A1; KR20220114525A; JP2021193094A; TWI829983B; JPWO2021117686A1

Abstract

The present invention provides a curing agent (particularly an imide group-containing compound) for producing an electrically insulating epoxy resin cured product which sufficiently prevents local accumulation of charges under a high-temperature and high-electric field and is excellent in heat resistance and dielectric characteristics. The present invention relates to an imide group-containing compound selected from the group consisting of a diimide dicarboxylic acid-based compound, a diimide tetracarboxylic acid-based compound, and a monoimide tricarboxylic acid-based compound.

Description

Imide group-containing compound, imide group-containing curing agent, epoxy resin cured product, and electrical insulating material using same

Technical Field

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.

Background

An epoxy resin cured product comprising an epoxy resin and a curing agent thereof is excellent in thermal characteristics, mechanical characteristics and electrical characteristics, and is widely used in industry mainly for electric and electronic materials. As the curing agent used for producing the epoxy resin cured product, for example, a phenol curing agent, an acid anhydride curing agent, an amine curing agent, and the like are used.

In recent years, in the field of power equipment typified by in-vehicle power modules, further large-current, small-sized, and high-efficiency power equipment is demanded, and a transition to a silicon carbide (SiC) semiconductor is made. Since SiC semiconductors can operate at a higher temperature than conventional silicon (Si) semiconductors, semiconductor packaging materials used for SiC semiconductors are also required to have higher heat resistance than heretofore (for example, patent document 1). In addition, although power devices are used in high-temperature and high-electric fields with miniaturization and high output, electric charges are accumulated in insulating materials in high-temperature and high-electric fields, and electric fields in semiconductors are distorted, so that withstand voltages of semiconductor elements are lowered. Therefore, in order to improve the performance of a power device, it is necessary to develop a material that does not cause charge accumulation under high temperature and high electric field in order to improve withstand voltage at high temperature.

In the field of power transmission lines, insulators made of ceramics or ceramics have been conventionally used, but since the insulators are heavy and brittle, some insulators using polymers have been studied (for example, patent literature 2). In recent years, the voltage of insulators has been increased, and accordingly, polymers used for insulators are required to be materials having a dielectric property lower than that of conventional products and a high insulation property that can withstand even when the voltage is increased so as not to cause charge accumulation.

In the field of electric vehicles, an insulating wire coating material is used for electric wires constituting electric devices such as motors (for example, patent literature 3). In recent years, the motor has been increased in output, and the influence of partial discharge due to inverter surge has been increased. Accordingly, a wire coating material used for a motor is required to have a dielectric lower than that of conventional products and a high insulation property which can be tolerated even when the output is high, in order to prevent the occurrence of an inverter surge.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2007-305962

Patent document 2: japanese patent laid-open publication No. 2013-234311

Patent document 3: japanese patent application laid-open No. 2012-224714

Disclosure of Invention

The inventors of the present invention have found that when a conventional material (particularly an epoxy resin cured product produced using a conventional curing agent) is used as an electrically insulating material, electric charges are locally accumulated at a high temperature and a high electric field to such an extent that the insulation is broken, and thus sufficient insulation properties cannot be obtained. For example, in the field of power devices, conventional insulating materials may have a degree of breakdown of insulation due to local accumulation of charges in a high-temperature and high-electric-field environment.

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

The present invention also provides an epoxy resin cured product which sufficiently prevents localized accumulation of charges under a high-temperature and high-electric field and is excellent in heat resistance and dielectric characteristics, and a curing agent (particularly an imide group-containing compound) for producing the epoxy resin cured product.

In the present specification, the local accumulation of electric charge means a bias of electric charge generated in the electrically insulating material under a high temperature and high electric field, and is an electrical phenomenon that can be observed by measuring a charge density distribution over time. The high-temperature high-electric field means, for example, a temperature of 120℃or higher (particularly 130 to 150 ℃) and an electric field environment of 40 to 120kV/mm (particularly 80 to 120 kV/mm). The electrical insulation property and the insulation property include a characteristic of sufficiently preventing local accumulation of electric charges under such a high-temperature and high-electric field.

In general, the higher dielectric constant and the dielectric loss tangent are evaluated as excellent for the purpose, and the lower dielectric constant and the dielectric loss tangent are evaluated as excellent for the purpose, and in the present invention, the dielectric characteristics mean, in particular, the performance that both the dielectric constant and the dielectric loss tangent can be sufficiently reduced.

The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that a cured product composed of a specific imide group-containing curing agent and an epoxy resin is excellent in all of heat resistance, dielectric characteristics and insulation properties, and have completed the present invention.

Namely, the gist of the present invention is as follows.

< 1 > an imide group-containing compound selected from the group consisting of a diimide dicarboxylic acid-based compound, a diimide tetracarboxylic acid-based compound and a monoimide tricarboxylic acid-based compound.

< 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 described in < 2 > and an epoxy resin.

The cured epoxy resin product according to < 4 > to < 3 >, wherein the epoxy resin has 2 or more epoxy groups in 1 molecule.

The epoxy resin cured product according to < 5 > to < 3 > or 4, wherein the imide group-containing curing agent has a molecular weight of 200 to 1100.

The cured epoxy resin of any one of < 3 > - < 5 >, wherein the imide group-containing curing agent has a functional group equivalent of 50 to 500.

An electrically insulating material comprising the cured epoxy resin of any one of < 3 > - < 6 >.

An encapsulating material containing the cured epoxy resin of any one of < 3 > - < 6 >.

< 9 > the encapsulating material according to < 8 > is used for a power semiconductor module.

An insulator comprising the cured epoxy resin of any one of < 3 > - < 6 >.

The insulator is used for power transmission lines according to the following condition of < 11 > and < 10 >.

A wire coating material comprising the cured epoxy resin of any one of < 3 > - < 6 >.

< 13 > the wire coating material according to < 12 > is used for an electric vehicle.

A printed wiring board comprising the cured epoxy resin of any one of < 3 > - < 6 >.

According to the present invention, it is possible to provide an electrically insulating cured epoxy resin which is excellent in heat resistance, dielectric properties and insulation properties and is suitable for use in, for example, packaging materials (particularly, semiconductor packaging materials), insulators, wire coating materials, and the like, and a curing agent (particularly, an imide group-containing compound) for producing the cured epoxy resin.

The electrically insulating epoxy resin cured product of the present invention has excellent insulating properties, particularly, sufficient prevention of local accumulation of charges under high-temperature and high-electric fields.

Drawings

FIG. 1 is a graph showing the change with time in charge density distribution of the cured epoxy resins of examples A-1, B-2 and C-1.

Fig. 2 is a graph showing the change with time of the charge density distribution of the epoxy resin cured products of comparative examples 1 to 3.

Detailed Description

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 "imide group-containing curing agent". The electrically insulating epoxy resin cured product of the present invention will be described in detail below, but in this description, an 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 comprises 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 a diimide dicarboxylic acid-based compound, a diimide tetracarboxylic acid-based compound, and a monoimide tricarboxylic acid-based compound. The imide group-containing curing agent may be 1 or more types of imide group-containing curing agents selected from them. From the viewpoint of further improving heat resistance, dielectric characteristics and insulation properties, the imide group-containing curing agent is preferably at least 1 type of imide group-containing curing agent selected from the group consisting of bisimide dicarboxylic acid compounds.

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

The functional group equivalent of the imide group-containing curing agent is not particularly limited, but is preferably 50 to 500, more preferably 800 to 400, still more preferably 100 to 400, and most preferably 200 to 350 from the viewpoint of further improving heat resistance, dielectric characteristics and insulation properties. The functional group equivalent is a value calculated by dividing the molecular weight by the number of functional groups (for example, carboxyl groups) of the imide group-containing curing agent per 1 molecule.

The blending amount of the imide group-containing curing agent contained in the curing agent is not particularly limited, but is preferably 50% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and most preferably 100% by mass based on the total amount of the curing agent, from the viewpoint of further improving heat resistance, dielectric characteristics and insulation properties. The blending amount of the imide group-containing curing agent being 100 mass% with respect to the total amount of the curing agent means that the curing agent is composed of only the imide group-containing curing agent. When 2 or more imide group-containing curing agents are blended, the total amount of these agents is within the above range.

(diimide dicarboxylic acid-based Compound)

The diimine dicarboxylic acid compound is a compound having 2 imide groups and 2 carboxyl groups in 1 molecule. The diimine dicarboxylic acid compound does not have an amide group. The imide dicarboxylic acid compound can be produced by reacting a tricarboxylic anhydride component and a diamine component as raw material compounds to produce an amic acid compound, and then imidizing the obtained amic acid compound. Here, the reaction between functional groups may be performed in a solution or in a solid phase, and the production method is not particularly limited.

The diimine dicarboxylic acid compound using the tricarboxylic anhydride component and the diamine component is a compound in which 2 molecules of tricarboxylic anhydride component react with 1 molecule of diamine component to form 2 imide groups.

In the production of the diimide dicarboxylic acid compound using the tricarboxylic acid anhydride component and the diamine component, the diamine component is usually used in an amount of about 0.5-fold molar amount, for example, 0.1 to 0.7-fold molar amount, preferably 0.3 to 0.7-fold molar amount, more preferably 0.4 to 0.6-fold molar amount, and still more preferably 0.45 to 0.55-fold molar amount, relative to the tricarboxylic acid anhydride component.

The tricarboxylic acid anhydride component constituting the diimine dicarboxylic acid compound is not particularly limited, and for example, an aromatic tricarboxylic acid anhydride component containing an aromatic ring is preferable, and trimellitic anhydride is particularly preferable from the viewpoint of further improving heat resistance, dielectric characteristics and insulation properties of the diimine dicarboxylic acid compound and an epoxy resin cured product obtained by using the same. The tricarboxylic anhydride component constituting the diimide dicarboxylic acid compound may be used alone or in a mixture of 1 or more than 2 kinds.

The diamine component constituting the diimine dicarboxylic acid compound is not particularly limited, but, for example, an aromatic diamine component containing an aromatic ring is preferable from the viewpoint of further improving heat resistance, dielectric characteristics, insulation properties and solubility of the diimine dicarboxylic acid compound and an epoxy resin cured product obtained by using the same, and m-xylylenediamine, p-xylylenediamine, 4' -diaminodiphenyl ether and dimer diamine are particularly preferable. The diamine component constituting the diimide dicarboxylic acid compound may be used alone or in combination of 1 or more than 2 kinds.

(imide tetracarboxylic acid compound)

The diimide tetracarboxylic acid compound is a compound having 2 imide groups and 4 carboxyl groups in 1 molecule. The tetracarboxylic dianhydride component and the monoaminodicarboxylic acid component are used as raw material compounds, and the functional groups are reacted with each other to produce an amic acid compound, and the imidization reaction is performed to produce an imide tetracarboxylic acid compound. Here, the reaction between functional groups may be performed in a solution or in a solid phase, and the production method is not particularly limited.

The diimine tetracarboxylic acid compound using the tetracarboxylic dianhydride component and the monoaminodicarboxylic acid component is a compound in which 2 molecules of the monoaminodicarboxylic acid component react with 1 molecule of the tetracarboxylic dianhydride component to form 2 imide groups.

In the production of the imide tetracarboxylic acid compound using the tetracarboxylic dianhydride component and the monoaminodicarboxylic acid component, the monoaminodicarboxylic acid component is used in an amount of usually about 2 times by mol, for example, 1.5 to 10.0 times by mol, preferably 1.8 to 2.2 times by mol, more preferably 1.9 to 2.1 times by mol, and still more preferably 1.95 to 2.05 times by mol, based on the tetracarboxylic dianhydride component.

The tetracarboxylic dianhydride component constituting the imide tetracarboxylic compound is not particularly limited, and for example, from the viewpoint of further improving the heat resistance, dielectric characteristics, insulation properties, solubility and versatility of the imide tetracarboxylic compound and the epoxy resin cured product obtained by using the same, aromatic tetracarboxylic dianhydride components containing an aromatic ring and/or aliphatic tetracarboxylic dianhydride components not containing an aromatic ring and aliphatic rings are preferable, and 3,3', 4' -benzophenone tetracarboxylic dianhydride, 4' - (hexafluoroisopropylidene) diphthalic anhydride and 1,2,3, 4-butane tetracarboxylic dianhydride are particularly preferable. The tetracarboxylic dianhydride component constituting the imide tetracarboxylic acid compound may be used alone or in combination of 1 or more than 2 kinds.

The monoaminodicarboxylic acid component constituting the imide tetracarboxylic acid compound is not particularly limited, and from the viewpoint of further improving the heat resistance, dielectric characteristics, insulation properties and solubility of the imide tetracarboxylic acid compound and the cured epoxy resin obtained by using the same, for example, an aromatic monoaminodicarboxylic acid component containing an aromatic ring is preferable, and 2-amino terephthalic acid, 2-amino isophthalic acid, 4-amino isophthalic acid, 5-amino isophthalic acid, 3-amino phthalic acid and 4-amino phthalic acid are particularly preferable. The monoaminodicarboxylic acid component constituting the imide tetracarboxylic acid compound may be used alone or in combination of 1 or more than 2.

(Monoimide tricarboxylic acid series Compound)

The monoimide tricarboxylic acid compound is a compound having 1 imide group and 3 carboxyl groups in 1 molecule. The method can be used to produce an amic acid compound by reacting functional groups with each other using a tricarboxylic anhydride component and a monoaminodicarboxylic acid component as raw material compounds, and to produce a monoimide tricarboxylic acid compound by imidizing. Here, the reaction between functional groups may be performed in a solution or in a solid phase, and the production method is not particularly limited.

The monoimide tricarboxylic acid compound using the tricarboxylic acid anhydride component and the monoaminodicarboxylic acid component is a compound in which 1 molecule of monoaminodicarboxylic acid component reacts with 1 molecule of tricarboxylic acid anhydride component to form 1 imide group.

In the production of a monoimide tricarboxylic acid compound using a tricarboxylic acid anhydride component and a monoaminodicarboxylic acid component, the monoaminodicarboxylic acid component is used in an amount of usually about 1 time by mol, for example, 0.5 to 5.0 times by mol, preferably 0.8 to 1.2 times by mol, more preferably 0.9 to 1.1 times by mol, and still more preferably 0.95 to 1.05 times by mol, relative to the tricarboxylic acid anhydride component.

The tricarboxylic acid anhydride component constituting the monoimide tricarboxylic acid compound is not particularly limited, and for example, from the viewpoint of further improving heat resistance, dielectric characteristics and insulation properties of the monoimide tricarboxylic acid compound and an epoxy resin cured product obtained by using the same, an aromatic tricarboxylic acid anhydride component containing an aromatic ring is preferable, and trimellitic anhydride is particularly preferable. The tricarboxylic acid anhydride component constituting the monoimide tricarboxylic acid compound may be used alone in an amount of 1 or 2 or more.

The monoaminodicarboxylic acid component constituting the monoimide tricarboxylic acid compound is not particularly limited, and for example, from the viewpoint of further improving heat resistance, dielectric characteristics and insulation properties of the monoimide tricarboxylic acid compound and an epoxy resin cured product obtained by using the same, an aromatic monoaminodicarboxylic acid component containing an aromatic ring is preferable, and 2-amino terephthalic acid, 2-amino isophthalic acid, 4-amino isophthalic acid, 5-amino isophthalic acid, 3-amino phthalic acid and 4-amino phthalic acid are particularly preferable. The monoaminodicarboxylic acid component constituting the monoimide tricarboxylic acid compound may be used alone in an amount of 1 or 2 or more.

[ method for producing imide group-containing curing agent ]

The imide group-containing curing agent may be produced in a solvent or without a solvent, and the production method is not particularly limited.

As a method for producing the polymer in a solvent, there is a method in which a predetermined raw material (for example, a tricarboxylic anhydride component, a diamine component, a tetracarboxylic dianhydride component, and a monoaminodicarboxylic acid component) is added to an aprotic solvent such as N-methyl 2-pyrrolidone, and the mixture is stirred at 80 ℃ and then imidized.

The imidization method is not particularly limited, and may be, for example, a thermal imidization method by heating to 250 to 300 ℃ under a nitrogen atmosphere, or a chemical imidization method by treating with a dehydrative cyclization agent such as a mixture of a carboxylic anhydride and a tertiary amine.

Examples of the method for producing the polymer in the absence of a solvent include a method utilizing mechanochemical effect. The method using the mechanochemical effect refers to a method of obtaining an organic compound by using mechanical energy generated when pulverizing a raw material compound used in a reaction to exhibit the mechanochemical effect.

The mechanochemical effect is an effect (or phenomenon) of pulverizing a raw material compound in a solid state by imparting mechanical energy (compressive force, shearing force, impact force, grinding force, etc.) to the raw material compound under a reaction environment, thereby activating the resulting pulverizing interface. Thereby, the reaction of the functional groups with each other occurs. The reaction of the functional groups with each other usually occurs between 2 or more molecules of the starting compound. For example, the reaction of the functional groups with each other may occur between 2 starting compound molecules having different chemical structures, or may occur between 2 starting compound molecules having the same chemical structure. The reaction of the functional groups with each other takes place not only between the defined 1 group of 2 starting compounds, but generally also between the other groups of 2 starting compounds. New reactions of functional groups with each other can occur between the compound molecules generated by the reactions of functional groups with each other and the raw material compound molecules. The reaction of the functional groups with each other is usually a chemical reaction, whereby a bond group (particularly a covalent bond) is formed between 2 molecules of the raw material compound by using the functional group of each raw material compound molecule, and another 1 molecule of the compound is generated.

The reaction environment refers to an environment in which the raw material compound is subjected to mechanical energy for the reaction, and may be, for example, an environment within the apparatus. By solid state in the reaction environment is meant that it is in a solid state in the environment to which mechanical energy is imparted (e.g., at the temperature and pressure within the device). The starting material compound in a solid state in the reaction environment is usually only required to be in a solid state at ordinary temperature (25 ℃) and normal pressure (101.325 kPa). The starting material compound in a solid state in the reaction environment may be in a solid state at the start of application of mechanical energy. The raw material compound in a solid state in the reaction environment of the present invention may be changed to a liquid state (for example, a molten state) during the reaction (or during the treatment) due to an increase in temperature, pressure, or the like accompanying the continuous application of mechanical energy, but is preferably continuously in a solid state during the reaction (or during the treatment) from the viewpoint of improving the reaction rate.

The details of the mechanochemical effect are not yet clear, but are considered to follow the following principles. When mechanical energy is applied to 1 or more solid-state raw material compounds to cause pulverization, the pulverization interface is activated by the absorption of the mechanical energy. It is considered that the chemical reaction occurs between 2 molecules of the raw material compound by utilizing the surface activity of the crushing interface. The pulverization means that mechanical energy is applied to the raw material compound particles to cause the particles to absorb the mechanical energy, and thus the particles are cracked and the surface is updated. Surface renewal refers to the formation of a crushed interface as a new surface. In the mechanochemical effect, the state of the new surface formed by the surface renewal is not particularly limited as long as activation of the pulverization interface occurs by pulverization, and may be in a dry state or may be in a wet state. The wet state of the new surface formed by the surface renewal is caused by the raw material compound in a liquid state, which is different from the raw material compound in a solid state.

Mechanical energy is imparted to a raw material mixture containing 1 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 pulverization of the raw material compound in a solid state occurs by applying mechanical energy. For example, since all the raw material compounds contained in the raw material mixture are in a solid state, the raw material mixture may be in a dry state. In addition, for example, since at least 1 of the raw material compounds contained in the raw material mixture is in a solid state and the remaining raw material compounds are in a liquid state, the raw material mixture may be in a wet state. Specifically, for example, when the raw material mixture contains only 1 raw material compound, the 1 raw material compound is in a solid state. In addition, for example, when the raw material mixture contains 2 raw material compounds, all of the 2 raw material compounds may 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.

In the method using mechanochemical effect, a functional group is a 1-valent group (atomic group) that can cause reactivity in a molecular structure, and is used in a concept of excluding unsaturated bond groups (for example, radical polymerizable groups) such as an inter-carbon double bond and an inter-carbon triple bond. The functional group is a group containing a carbon atom and a heteroatom. The hetero atom is an atom selected from the group consisting of an oxygen atom, a nitrogen atom and a sulfur atom, and particularly 1 or more of an oxygen atom and a nitrogen atom. The functional group may further contain a hydrogen atom. The functional groups to be reacted are usually 2 functional groups, and the structures of the starting compound molecule having one functional group and the starting compound molecule having another functional group may be different from each other or may be the same. The reaction forms bonds (in particular covalent bonds) of 2 molecules of the starting compound, and thus 1-molecules thereof are obtained. By the reaction of the functional groups with each other, small molecules such as water, carbon dioxide and/or alcohol may be by-produced, or no by-product may be produced.

The reaction of the functional groups with each other may be a reaction of all functional groups (particularly, 1-valent functional groups) that can undergo a chemical reaction with each other, for example, a reaction of 2 functional groups selected from a carboxyl group and a halide (group) thereof, an acid anhydride group, an amino group, an isocyanate group, a hydroxyl group, and the like. The 2 functional groups are not particularly limited as long as they are chemically reacted, and may be, for example, 2 functional groups having different chemical structures or 2 functional groups having the same chemical structure.

Examples of the reaction between functional groups include a condensation reaction, an addition reaction, and a combination reaction of these reactions.

The condensation reaction is a reaction in which the molecules of the raw material compound are bound or connected to each other by the detachment of small molecules such as water, carbon dioxide, and alcohol. Examples of the condensation reaction include a reaction for producing an amide group (amidation reaction), a reaction for producing an imide group (imidization reaction), and a reaction for producing an ester group (esterification reaction).

The addition reaction is an addition reaction between functional groups, and is a reaction in which intermolecular bonding or connection of the raw material compound is achieved without detachment of small molecules between the molecules of the raw material compound. Examples of the addition reaction include a reaction for producing a urea group, a reaction for producing a urethane group, and a reaction for opening a cyclic structure (i.e., a ring opening reaction). The ring-opening reaction is a reaction in which a part of the cyclic structure is cleaved in a raw material compound having a cyclic structure (for example, a compound containing an acid anhydride group, a cyclic amide compound, a cyclic ester compound, an epoxy compound), and the cleavage site is bonded or linked to a functional group of another raw material compound. For example, amide groups, carboxyl groups, ester groups, ether groups are formed by ring opening reaction. In particular, in the ring-opening reaction of an acid anhydride group in a compound containing an acid anhydride group as a raw material compound, the acid anhydride group is ring-opened to bond or link with other raw material compound molecules (amino group or hydroxyl group). As a result, for example, an amide group or an ester group, and a carboxyl group are simultaneously formed.

More specifically, the reaction between functional groups may be, for example, 1 or more reactions selected from the following reactions:

(A) A reaction of an acid anhydride group with an amino group to form (a 1) an amide group and a carboxyl group, (a 2) an imide group, (a 3) an isoprimide group, or (a 4) a mixture thereof;

(B) A reaction of forming an imide group by a reaction of an acid anhydride group with an isocyanate group;

(C) A reaction of forming an amide group by a reaction of a carboxyl group or a halide (group) thereof with an amino group or an isocyanate group;

(D) A reaction of forming an ester group by a reaction of a carboxyl group or a halide (group) thereof with a hydroxyl group;

(E) A reaction to form an ureido group by a reaction of an isocyanate group with an amino group;

(F) A reaction to form a urethane group by reaction of an isocyanate group with a hydroxyl group; and

(G) The reaction of the acid anhydride group with the hydroxyl group to form an ester group and a carboxyl group.

In the case of producing the imide group-containing curing agent from the raw material compounds, the reaction between functional groups corresponds to the reaction of (A). In the method of producing in the absence of a solvent, after the method utilizing the mechanochemical effect is carried out, imidization can be carried out by the same method as that of imidization in the method of 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 2 or more epoxy groups in 1 molecule. Specific examples of the epoxy resin include bisphenol a type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, naphthalene type epoxy resin, bisphenol type epoxy resin, dicyclopentadiene type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, isocyanurate type epoxy resin, alicyclic epoxy resin, acrylic modified epoxy resin, polyfunctional epoxy resin, brominated epoxy resin, and phosphorus modified epoxy resin. The epoxy resin may be used alone or in combination of 2 or more. The epoxy group may be a glycidyl group. The epoxy resin may be obtained in the form of a commercially available product.

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

[ additive ]

The epoxy resin cured product 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, and examples thereof include imidazoles such as 2-methylimidazole, 2-ethyl-4-methylimidazole and 2-phenylimidazole; tertiary amines such as 4-dimethylaminopyridine, benzyl dimethylamine, 2- (dimethylaminomethyl) phenol, 2,4, 6-tris (dimethylaminomethyl) phenol, and the like; triphenylphosphine, tributylphosphine, and other organic phosphines. The curing accelerator may be used alone or in combination of 2 or more.

The blending amount of the curing accelerator is not particularly limited, but is, for example, preferably 0.01 to 1% by mass, more preferably 0.05 to 0.5% by mass, based on the total amount of the epoxy resin solution to be described later, from the viewpoint of further improving the heat resistance, dielectric characteristics and insulation properties of the epoxy resin cured product.

The thermosetting resin is not particularly limited, and examples thereof include cyanate resins, isocyanate resins, maleimide resins, polyimide resins, urethane resins, phenolic resins, and the like. The thermosetting resin may be used alone or in combination of 2 or more kinds.

Examples of the inorganic filler include silica, glass, alumina, talc, mica, barium sulfate, aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium oxide, titanium oxide, silicon nitride, and boron nitride. The inorganic filler may be used alone or in combination of 2 or more kinds. The inorganic filler is preferably one surface-treated with a surface-treating agent such as an epoxy silane coupling agent or an aminosilane coupling agent. The inorganic filler may be used alone or in combination of 2 or more kinds.

Examples of the antioxidant include hindered phenol antioxidants, phosphorus antioxidants, and thioether antioxidants. The antioxidant may be used alone or in combination of 2 or more.

The flame retardant is not particularly limited, and a non-halogen flame retardant is preferable from the viewpoint of environmental impact. Examples of the flame retardant include phosphorus flame retardants, nitrogen flame retardants, and silicone flame retardants. The flame retardant may be used alone or in combination of 2 or more.

Method for producing 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 containing an imide group-containing curing agent and an epoxy resin, which will be described in detail below.

For example, the electrically insulating epoxy resin cured product of the present invention can be produced by applying an epoxy resin solution onto a substrate, and drying and curing the epoxy resin solution by heating. After curing, the cured product may be peeled off from the substrate and used. The method of applying the epoxy resin solution is not particularly limited, and examples thereof include a casting method and an impregnation method. The epoxy resin solution is applied to a substrate, dried and cured, and then peeled off from the substrate to obtain an epoxy resin cured product in the form of a sheet, a film, or the like.

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

The coating film, film and laminate thereof obtained by using the epoxy resin solution of the present invention, and a molded article (i.e., molded article) thereof can be heated to react the imide group-containing curing agent with the epoxy resin to complete curing. The heating temperature (curing temperature) is usually 80 to 350℃and preferably 130 to 300 ℃. 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 a form of, for example, a film, a plate, a film, a sheet, etc., the thickness of the cured epoxy resin may be usually 1 μm to 100mm.

[ epoxy resin solution ]

The epoxy resin solution is obtained by mixing at least an imide group-containing curing agent and an epoxy resin in an organic solvent. Preferably, in the epoxy resin solution, the imide group-containing curing agent and the epoxy resin are dissolved in an organic solvent, and at least the imide group-containing curing agent, the epoxy resin and the organic solvent are uniformly mixed at a molecular level. Dissolution refers to the solute being homogeneously mixed at the molecular level in the solvent. The solution is a mixed liquid in which a solute is uniformly mixed in a solvent at a molecular level, and for example, the solute is dissolved in the solvent to such an extent that the solute is transparent to the naked eye at normal temperature (25 ℃) and normal pressure (101.325 kPa). 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 it can uniformly dissolve the curing agent and the epoxy resin, and a non-halogenated solvent is preferable from the viewpoint of environmental impact. Examples of such a non-halogenated solvent include amide compounds such as N, N-dimethylformamide, N-dimethylacetamide, and N-methyl-2-pyrrolidone. These non-halogenated solvents are all useful as general purpose solvents. The organic solvents may be used alone or in combination of 2 or more.

The method for producing the epoxy resin solution is not particularly limited, and may be, for example, a separate dissolution method or a simultaneous dissolution method. From the viewpoint of obtaining a uniform resin solution in a short time, the individual dissolution method is preferable. The individual dissolution method is a method in which an imide group-containing curing agent and an epoxy resin are mixed in advance, dissolved in an organic solvent, and then mixed. The co-dissolution method is a method in which an imide group-containing curing agent and an epoxy resin are simultaneously mixed and dissolved in an organic solvent. In the individual dissolution method and the simultaneous dissolution method, the mixing temperature is not particularly limited, and may be, for example, 80 to 180 ℃, particularly 100 to 160 ℃. The heating for achieving the above-mentioned mixing temperature may be, for example, reflux heating of the organic solvent.

The amount of the imide group-containing curing agent blended in the epoxy resin solution is preferably an amount of 0.5 to 1.5 equivalents, more preferably 0.7 to 1.3 equivalents, relative to the epoxy equivalent of the epoxy resin, from the viewpoint of further improving the heat resistance, dielectric characteristics and insulation properties of the resulting epoxy resin cured product. The equivalent of the functional group of the imide group-containing curing agent corresponds to the equivalent calculated from the content of the hydroxyl group or carboxyl group.

The total amount of the imide group-containing curing agent and the epoxy resin to be mixed in the epoxy resin solution is not particularly limited, but is preferably 30 to 90% by mass, more preferably 40 to 80% by mass, and even more preferably 50 to 70% by mass, based on the total amount of the epoxy resin solution, from the viewpoint of further improving the heat resistance, dielectric characteristics and insulation properties of the resulting epoxy resin cured product.

The epoxy resin solution generally 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. Gels are not substances having a viscosity, but are generally solid substances that do not have flowability. Specifically, when the epoxy resin solution is mixed with a further solvent, the epoxy resin solution is easily compatible with each other, and the epoxy resin solution is uniformly mixed on a molecular level throughout. However, even if the gel is mixed with a further solvent, the gel is not compatible with each other and remains in a block form, and the whole gel cannot be uniformly mixed at a molecular level. Mixing at the time of determining miscibility, 100g of the solution or gel and 100g of the further solvent may be mixed under stirring at room temperature (25 ℃), normal pressure (101.325 kPa) and 100 rpm. In this case, the "further solvent" is a solvent 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 was determined by a brookfield digital viscometer at 30 ℃.

In the epoxy resin solution, the epoxy resin is difficult to react unexpectedly, and thus can have a low viscosity as described above. Therefore, a cured product can be produced with sufficient workability using the epoxy resin solution. In detail, the epoxy resin solution generally 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 epoxy resin cured product of the present invention is useful in all applications requiring at least one of heat resistance, dielectric properties and electrical insulation properties (preferably, properties including at least electrical insulation properties). In detail, the epoxy resin cured product of the present invention can be preferably used as all electrical insulating materials. Examples of such an electrically insulating material include a sealing material (e.g., a sealing material for a power semiconductor module), an insulator (particularly, an insulator-coated material) (e.g., an insulator for a power transmission line (particularly, an insulator-coated material for a power transmission line)), an electric wire-coated material (e.g., an electric wire-coated material for an electric vehicle), an insulating material for a printed wiring board, and the like.

Use of an electrically insulating epoxy resin cured product as an encapsulating material:

when the electrically insulating cured epoxy resin of the present invention is used as a packaging material, for example, after the power semiconductor module is manufactured, the power semiconductor module can be packaged with an epoxy resin solution in a mold provided with the module, and then dried and cured, whereby the cured epoxy resin of the present invention is used as a packaging material for a power semiconductor module.

Use of an electrically insulating epoxy resin cured product as an insulator coating material:

when the electrically insulating cured epoxy resin of the present invention is used as an insulator-coating material, for example, an epoxy resin solution may be used to coat the outer peripheral portion (particularly, the outer peripheral surface) of the core of an insulator to form a layer, and the layer may be dried and cured, thereby using the cured epoxy resin of the present invention as an insulator-coating material. The core is usually a glass fiber reinforced plastic such as a glass fiber reinforced epoxy resin or a glass fiber reinforced phenolic resin molded into various shapes such as a cylinder or a cylinder. The thickness of the cured epoxy resin material as the coating material formed on the outer periphery of the core may be changed depending on the size or shape of the resulting polymer insulator (for example, the presence or absence of the umbrella portion, its shape, size, and interval), but from the viewpoint of further improving heat resistance, dielectric characteristics, insulation, and the like, the portion having the thinnest thickness is preferably 1mm or more, more preferably 2mm or more. When the electrically insulating epoxy resin cured product of the present invention is used as an insulator-coating material, the thickness of the coating material is usually 1 to 100mm, preferably 2 to 50mm. When the epoxy resin cured product of the present invention is used as an insulator coating material, the epoxy resin cured product of the present invention is particularly useful as an insulator coating material for power transmission lines from the viewpoint of insulation (particularly, insulation that sufficiently prevents dielectric breakdown due to local accumulation of charges).

Use of an electrically insulating epoxy resin cured product 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 can be used as an electric wire coating material by applying an epoxy resin solution to the surface of a conductor and sintering (i.e., drying and curing). Examples of the conductor include copper and copper alloy. The coating method and the sintering method can be performed in the same manner and under the same conditions as the coating method and the sintering method in the conventional wire coating forming method. The coating and sintering may be repeated more than 2 times. The epoxy resin solution may be used in combination with other resins. From the viewpoint of protecting the conductor, the thickness of the wire coating material is preferably 1 to 100 μm, more preferably 10 to 50 μm. When the epoxy resin cured product of the present invention is used as a wire coating material, the epoxy resin cured product of the present invention is particularly useful as a wire coating material for electric vehicles from the viewpoint of insulation properties (particularly, insulation properties that further sufficiently prevent dielectric breakdown due to accumulation of charges).

Use of an electrically insulating epoxy resin cured product as an insulating material for a printed wiring board:

The printed wiring board generally contains an electrically insulating epoxy resin cured product, and may further contain 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 may be used as an insulating material for a printed wiring board by impregnating or coating a glass cloth with an epoxy resin solution and then drying and curing the same. May be a printed wiring board. The printed wiring board may be provided with wiring (conductors) on its surface and/or inside, and/or may also mount electronic components. The thickness of the printed wiring board is not particularly limited.

The epoxy resin cured product of the present invention can be suitably used as an electrical and electronic material for other applications, for example, a mold material for a bushing transformer, a mold material for a solid insulation switching device, an electrical penetration assembly for a nuclear power plant, a laminate by a lamination method, and the like.

Examples

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

A. Evaluation and measurement

[ method for producing imide group-containing curing agent and method for evaluating the same ]

(1) Preparation method of curing agent containing imide group

The mechanochemical treatment was performed by mixing and pulverizing 150g of a sample obtained by mixing an acid component and an amine component at the ratios described in the table using Wonder Crusher (Osaka chemical Co., ltd.) WC-3C at a rotation speed of about 9000rpm for 1 minute, and repeating the above operation 3 times.

The treated sample was transferred to a glass container, and imidization was performed at a calcination temperature of 300℃for a calcination time of2 hours in a nitrogen atmosphere by using an inert oven (DN 411I, manufactured by Yamadup scientific Co., ltd.).

The identification of the imide group-containing curing agent was performed by having the same molecular weight as that of the target structure and having the imide group-derived absorption by infrared spectrometry, as described below.

(2) Molecular weight of imide group-containing curing agent

The molecular weight was determined by measurement using a high performance liquid chromatography mass spectrometer (LC/MS) under the following conditions.

Sample: curing agent/DMSO solution containing imide groups (200. Mu.g/mL)

The device comprises: microTOF2-kp manufactured by Bruker Daltonics

Column: cadenza CD-C18 μm 2mm by 150mm

Mobile phase: (mobile phase A) 0.1% formic acid aqueous solution, (mobile phase B) methanol

Gradient (B conc.): 0min (50%) -5,7min (60%) -14.2min (60%) -17min (100%) -21.6min (100%) -27.2min (50%) -34min (50%)

Ionization method: ESI (electronic service provider interface)

Detection conditions: negative mode

(3) Confirmation of reaction

The identification was performed by infrared spectroscopy (IR) under the following conditions.

Infrared spectroscopy (IR)

The device comprises: perkin Elmer System 2000 infrared spectroscopy device

The method comprises the following steps: KBr process

Cumulative number of times: 64 scans (resolution 4 cm) ^-1 )

Confirm whether or not 1778cm derived from imide group was present ^-1 Nearby and 1714cm ^-1 Nearby absorption.

And (3) the following materials: (reaction proceeds) in some cases;

x: (reaction did not proceed) none.

[ evaluation method of epoxy resin cured product ]

(1) Reactivity of

The epoxy resin cured products obtained in the examples and comparative examples were subjected to measurement of the infrared absorption spectrum (IR) under the following conditions to determine the absorbance ratio of the glycidyl groups.

Typically 900-950 cm ^-1 The wavenumber region of (2) detects the absorption from the glycidyl group. The absorbance was calculated using a line obtained by linearly connecting the base parts on both sides of the absorption peak detected at these wave numbers as a base line and a length from the intersection point when the peak was perpendicularly connected to the base line to the peak point of the peak as absorbance.

Infrared spectroscopy (IR)

The device comprises: perkin Elmer System 2000 infrared spectroscopy device

The method comprises the following steps: KBr process

Cumulative number of times: 64 scans (resolution 4 cm) ^-1 )

Next, details of the calculation method of the reaction rate of the glycidyl group will be described

First, the epoxy resin solutions obtained in examples and comparative examples were mixed with KBr powder to prepare a sample for IR measurement, and measurement was performed. The intensity of the peak showing the highest absorbance in the obtained spectrum was confirmed to fall within the range of absorbance 0.8 to 1.0, and the absorbance α of the glycidyl group was obtained. Next, the sample was subjected to heat treatment with an oven at a temperature of 300 ℃ for 2 hours under a nitrogen stream to complete the curing reaction. The cured sample was subjected to IR measurement by the same method to determine the absorbance α' of the wave number due to the glycidyl group. The reaction rate of the glycidyl groups before the curing reaction was set to 0%, and the reaction rate of the sample at this time was determined by the following formula.

Reaction rate (%) = {1- (α'/α) } ×100

And (3) the following materials: 90% -100% (optimal);

o: 80% or more and less than 90% (good);

delta: 70% or more and less than 80% (no problem in practice);

x: less than 70% (which is practically problematic).

(2) Glass transition temperature (Tg) (Heat resistance)

The measurement was performed by a Differential Scanning Calorimeter (DSC) under the following conditions, and the identification was performed.

The device comprises: DSC 7 of Perkin Elmer

Heating rate: 20 ℃/min

After the temperature was raised from 25 ℃ to 300 ℃, the temperature was lowered, and then the temperature was raised again from 25 ℃ to 300 ℃, and the starting temperature from the discontinuous change of the transition temperature in the obtained temperature-raising curve was regarded as the glass transition temperature (Tg).

Using "jER828: bisphenol A epoxy resin "manufactured by Mitsubishi chemical corporation as the epoxy resin

And (3) the following materials: tg (optimum) at 190 ℃ or less;

o: tg is more than or equal to 170 ℃ and less than 190 ℃ (good);

delta: tg is more than or equal to 140 ℃ and less than 170 ℃ (no problem in practice);

x: tg < 140 ℃ (practically problematic).

Use "EOCN-1020-55: in the case of o-cresol novolak type epoxy resin "manufactured by Japanese chemical Co., ltd., as an epoxy resin

And (3) the following materials: tg (optimum) at 200 ℃ or less;

o: tg is more than or equal to 180 ℃ and less than 200 ℃ (good);

delta: tg is more than or equal to 150 ℃ and less than 180 ℃ (no problem in practice);

x: tg < 150 ℃ (practically problematic).

(3) Insulation (measurement of Charge Density distribution)

The charge density distribution was measured by a pulse electrostatic stress (PEA) measurement system for high temperature measurement on the epoxy resin cured product obtained in each of the examples and comparative examples under the following conditions, and the maximum electric field in the obtained samples was evaluated. The epoxy resin cured product sample was set in a state immersed in silicone oil in a high voltage application unit, heated to 140 ℃, and after reaching 140 ℃, controlled to be maintained at 140 ℃ for 30 minutes, and applied with a dc voltage. In view of acoustic characteristic impedance of the test piece, a commercially available sheet of conductive PEEK (polyether ether ketone) was used for the anode (anode), and an aluminum plate was used for the cathode (cathode). The epoxy resin cured product (sample) had a film shape and was sandwiched between an anode and a cathode. When applying a DC voltage, a DC voltage corresponding to an average electric field of 20kV/mm was applied for 10 minutes, followed by short-circuiting for 5 minutes, and a pulse voltage (5 ns, 200V) was applied at 1ms intervals (1 kHz) during the voltage application and short-circuiting, taking into account the thickness of the sample, and the resulting waveforms were averaged 1000 times to obtain a 1 waveform. The measurement interval was 10 seconds. After the measurement of the 20kV/mm applied neutralization short circuit was completed, the applied DC voltage was increased so that the average applied electric field became 40kV/mm, and a series of measurements similar to those described above were performed, and the measurements were repeated in sequence under average applied electric fields corresponding to 60, 80, 100 and 120 kV/mm. The charge density distribution thus measured over time is shown in fig. 1 and 2. FIG. 1 is a graph showing the change with time in charge density distribution of the epoxy resin cured products of examples A-1, B-2 and C-1 (particularly, epoxy resin cured products using bisphenol A type epoxy resins). Fig. 2 is a graph showing the change with time of the charge density distribution of the epoxy resin cured products of comparative examples 1 to 3 (particularly, epoxy resin cured products using bisphenol a type epoxy resin). The smaller the maximum electric field (in particular, the ratio of the maximum electric field to the applied electric field), the more excellent the insulation.

The device comprises: high voltage external unit

Sample size: length 50mm x width 50mm x thickness 100 μm-150 μm

An external electric field: 20. 40, 60, 80, 100, 120kV/mm

Measuring temperature: 140 DEG C

And (3) the following materials: the ratio of the maximum electric field to the externally applied electric field in the sample is maximally 1.1 or less (optimally);

o: the ratio of the maximum electric field to the externally applied electric field in the sample is maximally more than 1.1 and less than 1.3 (good);

delta: the ratio of the maximum electric field to the externally applied electric field in the sample is maximally more than 1.3 and less than 1.5 (no problem in practical use);

x: the ratio of the maximum electric field to the applied electric field in the sample is at most greater than 1.5 (which is practically problematic).

And (3) the following materials: the ratio of the maximum electric field to the externally applied electric field in the sample is maximally 1.2 or less (optimally);

o: the ratio of the maximum electric field to the externally applied electric field in the sample is maximally more than 1.2 and less than 1.4 (good);

delta: the ratio of the maximum electric field to the externally applied electric field in the sample is maximally more than 1.4 and less than 1.6 (no problem in practical use);

X: the ratio of the maximum electric field to the applied electric field in the sample is maximally greater than 1.6 (which is practically problematic).

(4) Dielectric characteristics (dielectric constant, dielectric loss tangent)

The impedance was measured and evaluated under the following conditions.

Impedance analyzer

The device comprises: agilent Technologies E4991ARF impedance/Material Analyzer sample size: length 20 mm. Times.width 20 mm. Times.thickness 150. Mu.m

Frequency: 1GHz (1 GHz)

Measuring temperature: 23 DEG C

Test environment: 23 ℃ + -1 ℃, 50%RH+ -5%RH

And (3) the following materials: the dielectric constant is less than or equal to 2.6 (best);

o: dielectric constant is more than 2.6 and less than or equal to 3.0 (good);

delta: the dielectric constant is more than 3.0 and less than or equal to 3.3 (no problem in practical use);

x: 3.3 < dielectric constant (practically problematic).

And (3) the following materials: dielectric loss tangent is less than or equal to 0.0175 (best);

o: dielectric loss tangent of 0.0175 < 0.020 (good);

delta: dielectric loss tangent of 0.020 < 0.030 (no problem in practice);

x: dielectric loss tangent 0.030 < dielectric loss tangent (practically problematic).

And (3) the following materials: the dielectric constant is less than or equal to 2.8 (best);

o: the dielectric constant is more than 2.8 and less than or equal to 3.2 (good);

delta: the dielectric constant is more than 3.2 and less than or equal to 3.4 (no problem in practical use);

x: 3.4 < dielectric constant (practically problematic).

And (3) the following materials: dielectric loss tangent is less than or equal to 0.0195 (best);

o: 0.0195 < dielectric loss tangent is less than or equal to 0.030 (good);

delta: dielectric loss tangent of 0.030 < 0.042 (no problem in practice);

x: 0.042 < dielectric loss tangent (practically problematic).

(5) Comprehensive evaluation

Comprehensive evaluation was performed based on the evaluation results of heat resistance, dielectric properties and insulation properties.

And (3) the following materials: all the evaluation results were excellent.

O: the lowest evaluation result was o among all the evaluation results.

Delta: the lowest evaluation result among all the evaluation results was Δ.

X: of all the evaluation results, the lowest evaluation result was x.

[ evaluation method of epoxy resin solution ]

(1) Viscosity of epoxy resin solution

The epoxy resin solutions obtained in examples and comparative examples were measured for viscosity at 30℃using a Brookfield digital viscometer (Dong machine industry TVB-15M) (Pa.s).

(2) Solubility of imide group-containing curing agent contained in epoxy resin solution

The presence or absence of dissolved residual components (residues) in the epoxy resin solutions obtained in the examples and comparative examples was visually observed.

Very good (solubility): no dissolution residue; completely dissolved within 10 minutes after mixing at 150 ℃.

O (with solubility): no dissolution residue; mixing at 150 ℃ for more than 10 minutes to dissolve completely (time is required until dissolution).

X (no solubility): there is a dissolution residue; there is a dissolution residue in the resulting epoxy resin solution.

B. Raw materials

(1) Imide group-containing curing agent

[ production of diimide dicarboxylic acid ]

Synthesis example A-1

The "method for producing an imide group-containing curing agent" is based on the above-mentioned method for producing an imide dicarboxylic acid. The detailed procedure is as follows.

521 parts by mass of granular trimellitic anhydride and 479 parts by mass of 4,4' -diaminodiphenyl ether were added to a pulverizing vessel, and mixed and pulverized.

Thereafter, the mixture was transferred to a glass container, and imidization was performed at 300℃for 2 hours in a nitrogen atmosphere by using an inert oven to prepare a curing agent containing imide groups.

[ production of imide tetracarboxylic acid ]

Synthesis example B-1

The "method for producing an imide group-containing curing agent" is based on the above-mentioned method for producing an imide tetracarboxylic acid. The detailed procedure is as follows.

To the pulverization tank were added 471 parts by mass of granular 3,3', 4' -benzophenone tetracarboxylic dianhydride and 529 parts by mass of 2-amino terephthalic acid, followed by mixing and pulverization.

Synthesis example B-2

The same procedure as in Synthesis example B-1 was conducted except that the acid dianhydride composition and the monoamine composition were changed, to obtain a curing agent containing an imide group.

[ production of Monoimide tricarboxylic acid ]

Synthesis example C-1

The monoimide tricarboxylic acid is produced based on the above-mentioned "method for producing a curing agent containing an imide group". The detailed procedure is as follows.

To the pulverizing tank, 515 parts by mass of granular trimellitic anhydride and 485 parts by mass of 2-aminoterephthalic acid were added, followed by mixing and pulverizing.

(2) Epoxy resin

jER828: bisphenol A type epoxy resin, epoxy equivalent 184-194 g/eq

EOCN-1020-55: o-cresol novolak type epoxy resin produced by Japanese chemical Co., ltd., epoxy equivalent 195g/eq

(3) Curing agents other than imide-based curing agents

PHENOLITE TD-2131: a novolac-type phenolic resin, a curing agent containing no imide group; the curing agent has the following structural formula.

HN-2200: an alicyclic acid anhydride-free curing agent made by Hitachi chemical Co., ltd; the curing agent has the following structural formula.

jERcure113: modified alicyclic amine, curing agent containing no imide group.

Example A-1

To 60 parts by mass of a sample obtained by mixing the imide group-containing curing agent obtained in Synthesis example A-1 with an epoxy resin (jER 828) at a ratio of 1.0/1.1 (equivalent ratio), 0.2 parts by mass of a curing accelerator (2-ethyl-4-methylimidazole, manufactured by Tokyo chemical industry Co., ltd.) and 39.8 parts by mass of Dimethylformamide (DMF) were mixed at room temperature (i.e., 20 ℃ C.), and reflux heating was performed at 150 ℃ C. For 0.5 hours to obtain an epoxy resin solution.

The epoxy resin solution obtained in this example had a viscosity of 50 Pa.s and had very good workability.

The resulting epoxy resin solution was applied to an aluminum substrate at a thickness of 300 μm, and the resulting coating film was dried under a nitrogen atmosphere at 180℃for 2 hours and then at 300℃for 2 hours by an inert oven to conduct desolvation and curing reactions. The aluminum substrate was removed from the obtained sample with aluminum substrate, and an epoxy resin cured product was obtained. The average thickness of the cured epoxy resin (cured epoxy resin using the epoxy resin "jER 828") was 112 μm. In the present specification, the average thickness is an average value of thicknesses at arbitrary 10 points.

An epoxy resin solution and an epoxy resin cured product were produced in the same manner as the above-described method in this example, except that "EOCN-1020-55" (o-cresol novolak type epoxy resin manufactured by Japanese chemical Co., ltd.) was used as the epoxy resin instead of "jER 828". The epoxy resin solution had a viscosity of 50 Pa.s and had very good workability. The average thickness of the epoxy resin cured product (the epoxy resin cured product using the epoxy resin "EOCN-1020-55") was 103. Mu.m.

Examples B-1, B-2 and C-1 and comparative example 1

An epoxy resin solution and an epoxy resin cured product were produced in the same manner as in example A-1, except that the imide group-containing curing agent or curing agent "PHENOLITE TD-2131" obtained in Synthesis example B-1, B-2 or C-1 was used. The curing agent containing an imide group used in each example was the curing agent obtained in the synthesis example having the same number as that of the example.

The epoxy resin solutions obtained in examples B-1, B-2 and C-1 and comparative example 1 all had a reaction rate of glycidyl groups of 10% or less.

The epoxy resin solutions obtained in examples B-1, B-2 and C-1 and comparative example 1 all had viscosities of 30 to 70 Pa.s, and had very good workability.

The average thickness of the cured epoxy resin is as follows.

Average thickness of epoxy resin cured product using epoxy resin "jER 828:

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

The alicyclic acid anhydride curing agent HN-2200, epoxy resin (jER 828) and curing accelerator (2, 4, 6-tris (dimethylaminomethyl) phenol, mitsubishi chemical Co., ltd.) were mixed at a ratio of 100/80/1 (weight ratio) at room temperature (i.e., 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 very good workability.

The resulting epoxy resin solution was applied to an aluminum substrate at a thickness of 300. Mu.m, and the resulting coating film was dried at 120℃for 5 hours under a nitrogen atmosphere by an inert oven, followed by drying at 150℃for 15 hours, and a curing reaction was carried out. The aluminum substrate was removed from the obtained sample with aluminum substrate, and an epoxy resin cured product was obtained. The average thickness of the cured epoxy resin (cured epoxy resin using the epoxy resin "jER 828") was 133 μm.

An epoxy resin solution and an epoxy resin cured product were produced in the same manner as the above-described method in this comparative example, except that "EOCN-1020-55" (o-cresol novolak type epoxy resin manufactured by Japanese chemical Co., ltd.) was used as the epoxy resin instead of "jER 828". The epoxy resin solution had a viscosity of 40 Pa.s and had very good workability. The average thickness of the epoxy resin cured product (the epoxy resin cured product using the epoxy resin "EOCN-1020-55") was 140. Mu.m.

Comparative example 3

The modified alicyclic amine curing agent jERcure113 and the epoxy resin (jER 828) were mixed at a ratio of 100/10 (weight ratio) at room temperature (i.e., 20 ℃) to obtain an epoxy resin solution.

The resulting epoxy resin solution was applied to an aluminum substrate at a thickness of 300. Mu.m, and the resulting coating film was dried in an inert oven at 80℃for 1 hour under a nitrogen atmosphere, followed by drying at 150℃for 3 hours, to effect a curing reaction. The aluminum substrate was removed from the obtained sample with aluminum substrate, and an epoxy resin cured product was obtained. The average thickness of the cured epoxy resin (cured epoxy resin using the epoxy resin "jER 828") was 139 μm.

An epoxy resin solution and an epoxy resin cured product were produced in the same manner as the above-described method in this comparative example, except that "EOCN-1020-55" (o-cresol novolak type epoxy resin manufactured by Japanese chemical Co., ltd.) was used as the epoxy resin instead of "jER 828". The epoxy resin solution had a viscosity of 40 Pa.s and had very good workability. The average thickness of the epoxy resin cured product (the epoxy resin cured product using the epoxy resin "EOCN-1020-55") was 123. Mu.m.

The characteristic values of the curing agents and the characteristic values of the cured epoxy resins in the examples and comparative examples are shown in tables 1 to 4.

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The cured epoxy resins of examples A-1 to C-1 satisfy the requirements of the present invention, and therefore are excellent in all of the physical properties of heat resistance, dielectric characteristics and insulation properties.

In these examples, only in example A-1 using the diimine dicarboxylic acid compound, all the results of evaluation of heat resistance, dielectric properties and insulation properties were excellent.

Since the epoxy resin cured products of comparative examples 1 to 3 used the curing agent containing no imide group, at least one of the heat resistance, dielectric characteristics and insulation properties was poor.

In particular, the following matters are apparent from the maximum electric field/applied electric field ratio and the time-dependent change charts of the charge density distribution of fig. 1 and 2 in each of the epoxy resin cured products of examples and comparative examples.

For the epoxy resin cured products of examples A-1, B-2 and C-1, the local accumulation of charges was sufficiently prevented under high temperature and high electric field;

with respect to the cured epoxy resin of comparative examples 1 to 3, localized accumulation of electric charges occurred under high temperature and high electric field.

The local accumulation phenomenon of charges observed from the time-dependent change chart of the charge density distribution is described in detail as follows:

according to FIG. 1, the epoxy resin cured products of examples A-1, B-2 and C-1 showed approximately the same charge density distribution between the anode and the cathode.

Referring to fig. 2, with respect to the cured epoxy resin of comparative examples 1 to 3, localized accumulation of charge (i.e., bias of charge) was observed between the anode and the cathode (in particular, in the vicinity of the cathode (cathode)). In fig. 2, a portion where local accumulation of electric charges occurs is shown surrounded by a solid line (elliptical shape).

Industrial applicability

The epoxy resin cured product of the present invention has excellent heat resistance, dielectric properties and insulation properties. Therefore, the epoxy resin cured product of the present invention can be suitably used for an encapsulating material for a power semiconductor module (particularly, a semiconductor encapsulating material), a mold material for a bushing transformer, a mold material for a solid insulation switching device, an insulator for a power transmission line, a wire coating material for an electric vehicle, an electrical penetration member for a nuclear power plant, an insulating material for a printed wiring board, an electrical and electronic material such as a laminate sheet of a lamination method, and the like.

Claims

1. An electrically insulating epoxy resin cured product comprising an imide group-containing curing agent selected from the group consisting of a bisimide dicarboxylic acid compound, a bisimide tetracarboxylic acid compound and a monosimide tricarboxylic acid compound, an epoxy resin and a curing accelerator,

the amount of the imide group-containing curing agent to be blended is an amount such that the equivalent of the functional group of the imide group-containing curing agent is 0.5 to 1.5 equivalent ratio to the equivalent of the epoxy resin,

the diimine dicarboxylic acid compound is a compound in which 2 molecules of tricarboxylic anhydride component react with 1 molecule of diamine component to form 2 imide groups,

the diimine tetracarboxylic acid compound is a compound formed by reacting 2 molecules of monoaminodicarboxylic acid component with 1 molecule of tetracarboxylic dianhydride component to form 2 imide groups,

the monoimide tricarboxylic acid compound is a compound in which 1 molecule of monoaminodicarboxylic acid component reacts with 1 molecule of tricarboxylic anhydride component to form 1 imide group,

the tricarboxylic anhydride component constituting the diimide dicarboxylic acid compound is trimellitic anhydride,

The diamine component constituting the diimide dicarboxylic acid compound may be 1 or 2 or more kinds of compounds selected from m-xylylenediamine, p-xylylenediamine, 4' -diaminodiphenyl ether and dimer diamine,

the tetracarboxylic dianhydride component constituting the imide tetracarboxylic compound is one or more than 2 selected from 3,3', 4' -benzophenone tetracarboxylic dianhydride, 4' - (hexafluoroisopropylidene) diphthalic anhydride and 1,2,3, 4-butane tetracarboxylic dianhydride,

the monoaminodicarboxylic acid component constituting the imide tetracarboxylic acid compound is one or more compounds selected from the group consisting of 2-aminoterephthalic acid, 2-aminoisophthalic acid, 4-aminoisophthalic acid, 5-aminoisophthalic acid, 3-aminophthalic acid, and 4-aminophthalic acid,

the tricarboxylic acid anhydride component which can constitute the monoimide tricarboxylic acid compound is trimellitic anhydride,

the monoaminodicarboxylic acid component constituting the monoimide tricarboxylic acid compound is at least one compound selected from the group consisting of 2-aminoterephthalic acid, 2-aminoisophthalic acid, 4-aminoisophthalic acid, 5-aminoisophthalic acid, 3-aminophthalic acid, and 4-aminophthalic acid,

The curing accelerator is 1 or more than 2 selected from imidazoles, tertiary amines and organic phosphines.

2. The cured product of an electrically insulating epoxy resin according to claim 1, wherein the epoxy resin has 2 or more epoxy groups in 1 molecule.

3. The electrically insulating epoxy resin cured product according to claim 1 or 2, wherein the imide group-containing curing agent has a molecular weight of 200 to 1100.

4. The electrically insulating epoxy resin cured product according to claim 1 or 2, wherein the imide group-containing curing agent has a functional group equivalent of 50 to 500.

5. An electrical insulating material comprising the cured epoxy resin of any one of claims 1 to 4.

6. An encapsulating material comprising the cured electrically insulating epoxy resin according to any one of claims 1 to 4.

7. The packaging material of claim 6, for a power semiconductor module.

8. An insulator comprising the cured electrically insulating epoxy resin according to any one of claims 1 to 4.

9. The insulator of claim 8 for a power transmission line.

10. An electric wire coating material comprising the cured electrically insulating epoxy resin according to any one of claims 1 to 4.

11. The wire coating material according to claim 10, for an electric vehicle.

12. A printed wiring board comprising the cured electrically insulating epoxy resin according to any one of claims 1 to 4.