JP2024016303A - Resin composition for insulative coating material, and metal coating material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin composition for insulative coating materials that has superior processability, high heat resistance and flex resistance, as well as superior wear resistance, and a metal coating material that includes the resin composition for insulative coating materials.

SOLUTION: A resin composition for an insulative coating material comprises a solvent, a polyimide resin precursor and/or a polyimide resin, as well as an additive, wherein the polyimide resin precursor and/or the polyimide resin includes a compound having a functional group that reacts with a terminal ring-closure product thereof, and the difference between the solubility parameter (SP value) of the additive and the solubility parameter of the solvent is 0.1(cal/cm³)^1/2 or more and 20(cal/cm³)^1/2 or less.

SELECTED DRAWING: None

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a resin composition for insulation coating materials that has high heat resistance, flexibility, abrasion resistance, and excellent workability, and a metal coating material using this resin composition for insulation coating materials.

Conventionally, polyimide, which has excellent heat resistance, electrical insulation properties, abrasion resistance, chemical resistance, mechanical properties, etc., has been widely used in the fields of electricity, electronic parts, transportation equipment, space, aircraft, etc.
In insulating coatings, which are a typical use of polyimide, as the performance of final products increases, even higher performance is required of insulating resins.

For example, insulation coating materials for various electric wires used in automobiles require high heat resistance due to the higher output of automobiles, and high flexibility to cope with the bending of electric wires and friction between wires due to higher wiring density. properties and mechanical strength are required.
On the other hand, as devices become smaller in flexible printed circuit boards (FPCs), high flexibility is required in order to fit them into the device housing. , flexibility is required to prevent breakage during bending. Furthermore, since FPCs undergo a solder reflow process when electronic components are mounted, heat resistance against the heat of the solder reflow process is also required.

In order to meet these demands for higher performance, when polyimide is made to have a high molecular weight, the polyimide solution used to form the insulating film becomes highly viscous, causing problems such as uneven film thickness and a large amount of residual solvent remaining in the film. . If the polyimide concentration is lowered in order to achieve a viscosity with excellent coating properties, a thick film cannot be obtained with one coating, and multiple coatings are required to thicken the film, which may reduce productivity. It has become a challenge.

In order to address these issues, efforts have been made to use isocyanates and alcohols to oligomerize the polyimide resin in the solution state and lower the viscosity of the varnish (Patent Documents 1 and 2).
)

Japanese Patent Application Publication No. 9-137118 Japanese Patent Application Publication No. 2016-151020

The present inventor discovered the problem in Patent Document 1 that when an isocyanate reacts with anything other than an acid anhydride, bonds other than imide bonds are formed, resulting in a decrease in the rigidity of the molecular chain and a decrease in mechanical properties. Ta. Furthermore, in Patent Document 2, molecular weight elongation does not proceed sufficiently during calcination,
We have found a problem in that the mechanical properties are lower than when fired from a high molecular weight polyimide resin solution.

The present invention is intended to solve the above-mentioned problems, and an object of the present invention is to provide a resin composition for an insulating coating material that has good processability, high heat resistance, bending resistance, and excellent abrasion resistance, An object of the present invention is to provide a metal coating material using a resin composition for materials.

As a result of intensive research to solve the above problems, the present inventors have developed a compound represented by the following formula (0) and/or a compound represented by the following formula (0'), and a compound represented by the following formula (0). Polyimide resin and/or its precursor (hereinafter referred to as polyimide resin and its precursor) containing a compound having a functional group that reacts with the terminally closed compound of the compound represented by the formula (0') and/or the compound represented by the following formula (0') When certain additives are added to polyimide resins (together referred to as "polyimide resins"), they can be used for insulation coating materials that maintain workability and have excellent heat resistance, bending resistance, and abrasion resistance. It has been found that a resin composition can be obtained, and that even better effects can be achieved by controlling the imidization rate to a specific level or by introducing a specific structure into the repeating units of polyimide resins, This led to the present invention.
That is, the gist of the present invention is as follows.

[1] A composition containing a solvent, a polyimide resin precursor and/or a polyimide resin,
The polyimide resin precursor and/or polyimide resin is a compound represented by the following formula (0) and/or a compound represented by the following formula (0'), and a compound represented by the following formula (0) and/or Or a compound having a functional group that reacts with the terminally closed ring product of the compound represented by the following formula (0'),
The difference in SP value from the solvent is 0.1 (cal/cm ³ ) ^1/2 or more 20 (cal/cm ³ ) ¹
A resin composition for an insulating coating material, comprising an additive having an additive content of ^/2 or less.

(In the above formulas (0) and (0'), R' each independently represents a hydrogen atom or an alkyl group, R ^a represents a tetracarboxylic acid residue, and R ^b represents a diamine residue. p and q represent arbitrary integers.)

[2] The resin composition for an insulating coating material according to [1], wherein the boiling point of the additive is 10° C. or more higher than the boiling point of the solvent.
[3] The polyimide resin precursor and/or polyimide resin has at least one of a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2),
The insulating coating resin composition according to [1] or [2].

[4] The insulating coating material according to any one of [1] to [3], wherein the polyimide resin precursor and/or the fired film of the polyimide resin has a glass transition temperature (Tg) of 250°C or more and 400°C or less. Resin composition.

[5] The resin for insulation coating material according to any one of [1] to [4], wherein the polyimide resin precursor and/or the polyimide resin has a structural unit represented by the following formula (3). Composition.

(In the above formula (3), R ¹ to R ⁸ may be the same or different from each other, and include a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, and a fluoroalkyl group having 1 to 4 carbon atoms. or a hydroxyl group; , n is an integer from 0 to 4.)

[6] The polyimide resin precursor and/or polyimide resin is -NH-, =NH, -
C(O)NH-, -NHC(O)O-, -NHC(O)NH-, -NHC(S)NH-,
-NH ₂ , -OH, -C(O)OH, -SH, -C(O)N(OH)-, -(O)S(O
)-, -C(O)-, and -C(O)SH, the insulating coating according to any one of [1] to [5], having a repeating unit containing at least one structure selected from the group consisting of -, -C(O)-, and -C(O)SH. Resin composition for materials.

[7] The resin composition for an insulating coating material according to [6], wherein the polyimide resin precursor and/or the polyimide resin has a repeating unit containing a -C(O)NH- structure.

[8] The resin composition for an insulating coating material according to [7], wherein the -C(O)NH- structure is a structure derived from 4,4'-diaminobenzanilide.

[9] A metal coating material having at least a resin layer containing the resin composition for an insulating coating material according to any one of [1] to [8].

According to the present invention, there are provided a resin composition for an insulation coating material that has high heat resistance, flexibility resistance, abrasion resistance, and excellent workability, and a metal coating material using this resin composition for an insulation coating material. .

Embodiments of the present invention will be described in detail below, but the following description is an example of the embodiments of the present invention, and the present invention is limited to the following description unless it exceeds the gist thereof. isn't it. Note that when the expression "~" is used in this specification, it is used as an expression that includes numerical values or physical property values before and after it.

≪Resin composition for insulation coating material≫
The resin composition for insulation coating material of the present invention is a composition containing a solvent, a polyimide resin precursor and/or a polyimide resin, and the polyimide resin precursor and/or polyimide resin is represented by the following formula (0). and/or a compound represented by the following formula (0') (hereinafter these may be referred to as "compounds (0), (0')"), and a compound represented by the following formula (0) Contains a compound having a functional group that reacts with the compound and/or the terminally closed ring product of the compound represented by the following formula (0'), and has an SP value difference of 0.1 (cal/cm ³ ) ^1/2 or more with the solvent. 20 (cal/c
The present invention relates to a resin composition for an insulating coating material, characterized in that it contains an additive having an amount of m ³ ) ^1/2 or less.

(In the above formulas (0) and (0'), R' each independently represents a hydrogen atom or an alkyl group, R ^a represents a tetracarboxylic acid residue, and R ^b represents a diamine residue. p and q represent arbitrary integers.)

The polyimide resin composition for insulation coating material or the polyimide resin precursor composition described below may be referred to as "the composition of the present invention". Furthermore, hereinafter, the term "polyimide resin coating" refers to a polyimide coating obtained by firing the resin composition for an insulation coating material of the present invention.

[Mechanism of action]
The insulation coating material obtained from the resin composition for insulation coating materials of the present invention maintains workability,
Although the details of the reason for maintaining heat resistance and mechanical properties are not clear, it is presumed as follows.
That is, when baking the coating film etc. of the resin composition for insulation coating material of the present invention, the compounds (0) and (0'
), water and/or alcohol are removed from the ring-opened tetracarboxylic acid terminal, and the ring-closed acid anhydride reacts with the functional group (reactive group) that reacts with the acid anhydride in the composition, resulting in a highly Forms a molecular body. By forming such a mechanism, it becomes possible to lower the molecular weight of the resin composition for insulation coating material, and the viscosity can be lowered, thereby improving processability. However, when fired for a short time, the molecular weight cannot be fully extended, and the molecular weight after firing tends to decrease. Therefore, by adding specific additives and prolonging the time during which the molecules are highly mobile, it is assumed that the reaction will be accelerated and the molecular weight can be increased, resulting in better heat resistance, bending resistance, and abrasion resistance. be done. Furthermore, since polyimide has a rigid structure, it may inhibit intermolecular packing, but in this case, the additive acts as a plasticizer and promotes molecular orientation, resulting in improved heat resistance, flexibility, It is thought that wear resistance is maintained.
Furthermore, for specific additives, the difference in SP value from the solvent is 0.1 (cal/cm ³ ) ^1/
By being between ² and 20 (cal/cm ³ ) ^1/2 or less, it has good compatibility with solvents and polyimide resins, and it is possible to obtain a uniform film with high surface smoothness, so it has good heat resistance, It is thought that it has even better bending resistance, abrasion resistance, and workability.

<Polyimide resin concentration>
The concentration of the polyimide resin precursor and/or polyimide resin, that is, polyimide resins, in the resin composition for insulation coating material of the present invention is preferably 15% by weight or more and less than 30% by weight. This concentration is more preferably 16% by weight or more, still more preferably 18% by weight or more, and preferably 25% by weight or less. By controlling the concentration of the polyimide resin within such a range, productivity tends to improve while maintaining film formability.

Incidentally, the concentration of the polyimide resin in the composition of the present invention can be appropriately confirmed using a conventionally known method. For example, it can be determined from the weight ratio before and after distilling off the solvent and other components of the composition using a method such as vacuum drying. Moreover, it can also be calculated|required from the charged weight of the resin composition for insulation coating materials.

<Viscosity>
The viscosity of the resin composition for insulation coating material of the present invention is preferably 10,000 cP or less. This viscosity is preferably 8,000 cP or less, more preferably 6,000 cP or less. Further, although there is no particular lower limit to the viscosity, it is, for example, 10 cP or more.
When the viscosity of the resin composition for insulation coating material is 10,000 cP or less, it tends to be possible to suppress unevenness of the coating film and deterioration of coating properties. In particular, when coating a linear or rod-shaped object such as an electric wire, the coating thickness tends to be uneven, and the above viscosity is preferable. The resin composition for an insulating coating material of the present invention tends to suppress an increase in viscosity and has excellent processability by containing a compound having a specific structure.
There are no particular restrictions on the method of measuring viscosity, but the viscosity here refers to the measurement method using an E-type viscometer,
The rotational viscosity at 0°C was measured.

[solvent]
The resin composition for an insulating coating material according to the present invention contains a solvent. As the solvent, solvents that are normally used in compositions containing polyimide resins can be used.
Specifically, hydrocarbon solvents such as hexane, cyclohexane, heptane, benzene, naphtha, toluene, xylene, mesitylene, anisole; carbon tetrachloride, methylene chloride, chloroform, 1,2-dichloroethane, chlorobenzene, dichlorobenzene, fluorocarbon Halogenated hydrocarbon solvents such as benzene; Ether solvents such as diethyl ether, tetrahydrofuran, 1,4-dioxane, and methoxybenzene; Ketone solvents such as acetone, methyl ethyl ketone, cyclohexanone, and methyl isobutyl ketone; ethylene glycol monomethyl ether, ethylene glycol Glycol solvents such as monoethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, propylene glycol monomethyl ether acetate; Amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone; dimethyl Sulfonic solvents such as sulfoxide; Heterocyclic solvents such as pyridine, picoline, lutidine, quinoline, and isoquinoline; Phenolic solvents such as phenol and cresol; Lactone solvents such as γ-butyrolactone, γ-valerolactone, and δ-valerolactone ; etc. One type of these solvents may be used alone, or two or more types may be used in any ratio and combination.
Among these, amide solvents and lactone solvents are preferred, and N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and γ-butyrolactone are more preferred because they tend to increase the solubility of polyimide.

The content of the solvent in the resin composition for insulation coating material is not particularly limited, but the content of the solvent in the entire composition is 10
If it is 0% by weight, it is preferably 35% by weight or more, more preferably 40% by weight or more. Further, it is preferably 90% by weight or less, more preferably 80% by weight or less. Within the above range, the solubility of polyimide resins can be ensured and a film with a smooth surface tends to be obtained.

[Additive]
The resin composition for insulation coating material according to the present invention has a solubility parameter (SP value) difference with the solvent of 0.1 (cal/cm ³ ) ^1/2 or more and 20 (cal/cm ³ ) ^1/2 or less. Contains certain additives.
In the present invention, the solubility parameter is a value defined by the regular solution theory introduced by Hildebrand, and the SP value described in the present invention is a value defined by the canonical solution theory introduced by Hildebrand.
gineering and Science, February, 1974, Vol.
14, No. It is a value calculated by the Fedors method described in 2,147-154, and is calculated by the following formula.
SP value = (△H/V) ^1/2
(ΔH: molar heat of vaporization (cal), V: molar volume (cm ³ ))

The additive of the present invention has a difference in SP value of 0.1 from the solvent used in the resin composition for insulation coating material.
(cal/cm ³ ) ^1/2 or more and 20 (cal/cm ³ ) ^1/2 or less. Preferably 0
．． 15) Cal/cm ³ ) ^1/2 or more, more preferably 0.2 cal/cm ³ ) ^1
/2 or more, particularly preferably 0.25 (cal/cm ³ ) ^1/2 or more. Also,
It is preferably 19 (cal/cm ³ ) ^1/2 or less, more preferably 18 (cal/cm 3 ) 1/2 or less, and more preferably 18 (cal/cm 3 ) 1/2 or less.
m ³ ) ^1/2 or less, particularly preferably 17 (cal/cm ³ ) ^1/2 or less. Within these ranges, molecular mobility during firing is improved, and a film with good heat resistance, bending resistance, and abrasion resistance and a smooth surface tends to be obtained.

The additive of the present invention is not particularly limited as long as the difference in SP value from the solvent is within the above specific range, but examples include N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone. Sulfonic solvents such as dimethyl sulfoxide; Heterocyclic solvents such as pyridine, picoline, lutidine, quinoline, and isoquinoline; Phenolic solvents such as phenol and cresol; γ-butyrolactone, γ-valerolactone, δ- Lactone solvents such as valerolactone; Amide catalysts such as N,N-dimethylethanolamine, dimethylaminopyridine, triethanolamine; polyvinylpyrrolidone, polyvinylpyridine, polyvinylpyrrole, polyvinylporphyrin, polyvinylindole, polyvinylphthalimide, polyvinylthiophene, etc. Examples include water-soluble polymers. Among them, N-methyl-2-pyrrolidone, propylene carbonate, dimethylaminopyridine, and polyvinylpyrrolidone are preferred because they have high compatibility with polyimide resins.

The additive of the present invention preferably has a boiling point higher than the boiling point of the solvent in the resin composition for insulation coating material by 10° C. or more. When containing multiple additives, it is sufficient that one of them is a liquid or solid whose boiling point is 10°C or more higher than the boiling point of the solvent in the resin composition for insulation coating materials, and the resin composition for insulation coating materials When a plurality of solvents are contained in the additive, it is sufficient that the boiling point of the additive is 10° C. or more higher than the boiling point of one of the solvents.
In addition, if the additive is solid and has a boiling point higher than the melting point and the boiling point cannot be specified, it is preferable that the melting point of the additive is 10° C. or more higher than the boiling point of the solvent in the resin composition for insulation coating material. That is, since the boiling point of the additive is higher than the melting point, the difference between the melting point of the additive and the boiling point of the solvent is at least the temperature difference between the boiling point and the boiling point.
The boiling point of the additive is more preferably 12°C or more higher than the boiling point of the solvent in the resin composition for insulation coating material, and even more preferably 15°C or more higher. When the above-mentioned additive is solid and has a boiling point higher than the melting point and the boiling point cannot be specified, it is more preferable that the melting point of the additive is 12° C. or more higher than the solvent, and even more preferably 15° C. or more higher.
Further, the difference between the boiling point of the additive and the boiling point of the solvent in the resin composition for insulation coating material is preferably 120°C or less, more preferably 100°C or less. If the above-mentioned additive is solid and has a boiling point higher than the melting point and the boiling point cannot be determined, the difference between the melting point of the additive and the boiling point of the solvent in the resin composition for insulation coating material should be 300°C or less. The temperature is preferably 290°C or lower, and more preferably 290°C or lower.
Within the above range, a film with good heat resistance, bending resistance, and abrasion resistance and a smooth surface tends to be obtained.

The content of additives in the resin composition for insulation coating materials of the present invention is not particularly limited, but is preferably 0.01 to 50 parts by weight based on 100 parts by weight of the total amount of the solvent and additives. When the content of the additive is 0.01 parts by weight or more, it tends to be possible to sufficiently improve the bending resistance and abrasion resistance by incorporating the additive. In addition, by keeping the solubility of polyimide resins at 50 parts by weight or less, it is possible to prevent the film from becoming rough and to suppress the residual solvent in the polyimide resin coating, thereby achieving the desired flexibility and wear resistance. It becomes easier to obtain sex.
The additive content in the resin composition for insulation coating material of the present invention is the total amount of solvent and additives of 100
The amount is more preferably 0.01 to 40 parts by weight.
The resin composition for an insulating coating material of the present invention containing additives in the above ratio is produced by mixing the additives with a polyimide resin composition produced by the method described below.

[Polyimide resins]
<Formula (0), (0')>
The polyimide resins according to the present invention are compounds represented by the following formula (0) and/or the following formula (
0').

(In the above formulas (0) and (0'), R' each independently represents a hydrogen atom or an alkyl group, R ^a represents a tetracarboxylic acid residue, and R ^b represents a diamine residue. p and q represent arbitrary integers.)

(R')
R' each independently represents a hydrogen atom or an alkyl group. The number of carbon atoms in the alkyl group is not particularly limited, but is preferably 10 or less, more preferably 5 or less, and even more preferably 2 or less. If it is below the above upper limit, the alcohol tends to be easily eliminated and vaporized due to terminal ring closure during firing. The alkyl group may be linear or branched, or may form a ring. Moreover, it may have a substituent.
R' in the above formulas (0) and (0') may be the same or different.

(p, q)
p and q represent arbitrary integers. Although not particularly limited, the range includes, for example, the number of repetitions of each formula corresponding to a suitable weight average molecular weight (Mw) of the polyimide resin precursor and polyimide resin described below.

(R ^a )
R ^a in formulas (0) and (0') represents a structure derived from tetracarboxylic dianhydride, and formula (0)
, (0') may be the same or ^different .

Examples of the tetracarboxylic dianhydride constituting R ^a include chain aliphatic tetracarboxylic dianhydride, alicyclic tetracarboxylic dianhydride, aromatic tetracarboxylic dianhydride, and the like. One type of these compounds may be used alone, or two or more types may be used in any ratio and combination.

Examples of chain aliphatic tetracarboxylic dianhydrides include ethylenetetracarboxylic dianhydride, butanetetracarboxylic dianhydride, meso-butane-1,2,3,4-tetracarboxylic dianhydride, and the like. can be mentioned.

Examples of the alicyclic tetracarboxylic dianhydride include 3,3',4,4'-biscyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1 , 2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,4,5-
Cyclohexanetetracarboxylic dianhydride, 1,2,3,4-tetramethyl-1,2,3
, 4-cyclobutanetetracarboxylic dianhydride, 5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-11,2-dicarboxylic anhydride, tricyclo[6.4.0.0 ^2,7 ] Dodecane-1,8:2,7-tetracarboxylic dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 4
-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic anhydride, 1,1'-bicyclohexane-3,3',4
, 4'-tetracarboxylic dianhydride, and the like.

Examples of the aromatic tetracarboxylic dianhydride include pyromellitic dianhydride, 1,2
, 3,4-benzenetetracarboxylic dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3-dicarboxyphenyl)methane dianhydride, ,4-dicarboxyphenyl)methane dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2 , 2-bis(2,3-dicarboxyphenyl)propane dianhydride, bis(3,4
-dicarboxyphenyl) sulfone dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, bis(2,3-dicarboxyphenyl)ether dianhydride, 3,3',
4,4'-benzophenonetetracarboxylic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 4,4'-oxydiphthalic dianhydride, 4,4-(p-
phenylenedioxy)diphthalic dianhydride, 4,4-(m-phenylenedioxy)diphthalic dianhydride, 2,2',6,6'-biphenyltetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)-1,1,1, 3, 3, 3
-hexafluoropropane dianhydride, 2,2'-bis(trifluoromethyl)-4,4'
, 5,5'-biphenyltetracarboxylic dianhydride, 4,4'-(hexafluorotrimethylene)-diphthalic dianhydride, 4,4'-(octafluorotetramethylene)-diphthalic dianhydride, 4,4'-oxydiphthalic anhydride, 1,2,5,6-naphthalene dicarboxylic dianhydride, 1,4,5,8-naphthalene dicarboxylic dianhydride, 2,3,6,7-
Naphthalene dicarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride Examples include acid dianhydrides.

( ^Rb )
R ^b in formula (0), (0') represents a structure derived from a diamine compound, and R b in formula (0), (0')
Each R ^b therein may be the same or different.

Examples of the diamine compound constituting R ^b include aromatic diamine compounds, chain aliphatic diamine compounds, alicyclic diamine compounds, and the like. One type of these compounds may be used alone, or two or more types may be used in any ratio and combination.

Examples of aromatic diamine compounds include 1,4-phenylenediamine, 1,2-phenylenediamine, 1,3-phenylenediamine, 4,4'-(biphenyl-2,5-diylbisoxy)bisaniline, 4, 4'-Diamino diphenyl ether, 3,4'-diaminodiphenyl ether, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 2,2-bis(4-(4 -aminophenoxy)phenyl)propane, bis(4-(4-aminophenoxy)phenyl)sulfone, bis(4
-(3-aminophenoxy)phenyl)sulfone, 1,3-bis(4-aminophenoxy)neopentane, 4,4'-diamino-3,3'-dimethylbiphenyl, 4,4'-diamino-2,2' -dimethylbiphenyl, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-diamino-3,3'-dihydroxybiphenyl, bis(4-amino-3
-carboxyphenyl)methane, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfide, N-(4-aminophenoxy)-4-aminobenzamine, 2, 2'-bis(trifluoromethyl)-4
, 4'-diaminobiphenyl, bis(3-aminophenyl) sulfone, norbornanediamine, 4,4'-diamino-2-(trifluoromethyl)diphenyl ether, 5-trifluoromethyl-1,3-benzenediamine, 2, 2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane, 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl, 2,2-bis[4-{4-amino -2-(trifluoromethyl)phenoxy}phenyl]hexafluoropropane, 2-trifluoromethyl-p-phenylenediamine, 2,2-bis(3-amino-4-methylphenyl)hexafluoropropane, 4,4' -(9-fluorenylidene) dianiline, 2,7-diaminofluorene, 1,5-diaminonaphthalene, and 3,7-diamino-2,8-dimethyldibenzothiophene 5,5-dioxide.

Examples of chain aliphatic diamine compounds include 1,2-ethylenediamine, 1,2-diaminopropane, 1,3-diaminopropane, 1,4-diaminobutane, 1,6-hexamethylenediamine, and 1,5-diaminopropane. Examples include diaminopentane, 1,10-diaminodecane, 1,2-diamino-2-methylpropane, 2,3-diamino-2,3-butanediamine, and 2-methyl-1,5-diaminopentane.

Examples of the alicyclic diamine compound include 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1,4-diaminocyclohexane,
4,4'-methylenebis(cyclohexylamine), and 4,4'-methylenebis(2-
methylcyclohexylamine).

Among the polyimide resins contained in the resin composition for insulation coating material of the present invention, compound (0),
The amount of (0') is preferably 10% by weight or more, more preferably 20% by weight or more,
Particularly preferred is 30% by weight or more. Further, it is preferably 90% by weight or less, more preferably 80% by weight or less, and particularly preferably 70% by weight or less. Within these ranges, the molecular weight increases and a coating film with excellent heat resistance, bending resistance, and abrasion resistance tends to be obtained.

<Compound having a functional group that reacts with the terminally closed ring product of compound (0) and (0')>
The polyimide resins according to the present invention are compounds having a functional group that reacts with the terminally closed product of compounds (0) and (0') (hereinafter referred to as "compounds having a functional group that reacts with the terminally closed product"). ).
The functional group that reacts with the terminally closed ring product of compounds (0) and (0') is not particularly limited, and examples thereof include an amino group, an isocyanate group, a hydroxyl group, a thiol group, and a glycidyl group. In particular, amino groups and isocyanate groups form imide bonds after firing and molding, and are therefore preferable in terms of heat resistance, bending resistance, and abrasion resistance.
The compound having a functional group that reacts with the terminally closed product is not particularly limited as long as it has the functional group, but polyvalent compounds may be mentioned.

Among the polyimide resins contained in the resin composition for insulation coating materials of the present invention, the amount of the compound having a functional group that reacts with the terminal closed product is preferably 10% by weight or more, more preferably 20% by weight or more. , 30% by weight or more is particularly preferred. Further, it is preferably 90% by weight or less,
It is more preferably 80% by weight or less, particularly preferably 70% by weight or less. Within these ranges, the molecular weight increases and a coating film with excellent heat resistance, bending resistance, and abrasion resistance tends to be obtained.
In the polyimide resins according to the present invention, the ratio of the content of compounds (0), (0') and the compound having a functional group that reacts with the terminal ring-closing product is not particularly limited, but molecular cleavage due to exchange reaction is unlikely to occur. Therefore, from the viewpoint of molecular weight extension, it is preferable that the compound having a functional group that reacts with the terminally closed ring product and the compounds (0) and (0') are present in about the same amount.

[Compound with amino group]
As the compound having a functional group that reacts with the terminally closed compound, a compound having an amino group is preferable, and a compound having an amine terminal structure (amine-terminated compound) is particularly preferable. Amine-terminated compounds are polyimide resins, and both terminal structures are amines.

The structure of the amine-terminated compound is not particularly limited, and examples include structures represented by the following formulas (5) and (6).

(In the above formulas (5) and (6), R ^c represents a tetracarboxylic acid residue, R ^d represents a diamine residue. t and u represent arbitrary integers.)

(t, u)
t and u represent arbitrary integers. Although not particularly limited, the range includes, for example, the number of repetitions of each formula corresponding to a suitable weight average molecular weight (Mw) of the polyimide resins described below.

( ^Rc )
R ^c in formulas (5) and (6) represents a structure derived from tetracarboxylic dianhydride, and formula (5),
Each R ^c in (6) may be the same or different. Specifically, the above formula (
0) and (0'), and the preferred ^ranges are also the same. Moreover, in the resin composition for an insulating coating material of the present invention, R ^a and R ^c may be the same or different.

( ^Rd )
R ^d in formulas (5) and (6) represents a structure derived from a diamine compound, and each R ^d in formulas (5) and (6) may be the same or different. Specifically, the equations (0) and (0
') has the same meaning as each R ^b , and the preferred ranges also have the same meaning. Moreover, in the resin composition for an insulating coating material of the present invention, R ^b and R ^d may be the same or different.

<Other ingredients>
The resin composition for an insulating coating material of the present invention may contain polyimide resins having other structures in addition to compounds (0), (0'), and compounds having a functional group that reacts with the terminally closed product. Although polyimide resins having other structures are not particularly limited, examples thereof include compounds represented by the following formulas (a) and (b).

In the above formulas (a) and (b), R ^a and R ^b have the same meanings as R ^a and R ^b in formulas (0) and (0').
r and s represent arbitrary integers, and are synonymous with p and q in formulas (0) and (0').

In the production of polyimide resins, depending on the purpose, compounds having ethynyl groups, vinyl groups, allyl groups, cyano groups, isocyanate groups, etc. that serve as crosslinking points (hereinafter sometimes referred to as "other monomers") may be used. may also be used.

<Preferable aspect 1>
From the viewpoint of heat resistance and productivity, the polyimide resin used in the present invention preferably has at least one of a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2). By including the structures represented by the following formulas (1) and (2), the reactivity during polymerization and the solubility in the solvent of polyimide resins are both good, and the heat-resistant material has a rigid skeleton. A polyimide resin coating with excellent properties can be obtained.

The structural units represented by the above formulas (1) and (2) may be derived from tetracarboxylic dianhydride or from a diamine compound, but usually tetracarboxylic acid Introduced into polyimide resins by means of dianhydrides. Therefore, the polyimide resins used in the present invention use at least pyromellitic dianhydride and/or 3,3',4,4'-biphenyltetracarboxylic dianhydride as the raw material tetracarboxylic dianhydride. Preferably, it is manufactured by

In addition, the polyimide resins used in the present invention are of the following formula (3) from the viewpoint of improving heat resistance and productivity.
) is preferable.

In the above formula (3), R ¹ to R ⁸ may be the same or different, and may be a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a fluoroalkyl group having 1 to 4 carbon atoms, or It is a hydroxyl group. Among these, a hydrogen atom or a methyl group is preferred since both the reactivity during polymerization and the solubility of the polyimide resin in a solvent are improved.

In the above formula (3),
It is an ester group or a secondary amino group. Among these, direct bonds, oxygen atoms, sulfur atoms, and alkylene groups having 1 to 4 carbon atoms are preferred because the polyimide resin coating obtained by heating and baking has good bending resistance, abrasion resistance, and heat resistance. , a sulfonyl group or an amide group are preferred, and an oxygen atom is particularly preferred.

In the above formula (3), n is an integer from 0 to 4. n is preferably an integer from 1 to 4.

In addition, in the structural unit represented by formula (3) in one entire molecule of polyimide resins, R
¹ to R ⁸ , X, and n do not necessarily all have to be the same. In particular, when n is an integer greater than or equal to 2, X may have a different structure.

Among the structural units represented by formula (3), those represented by any of the structural units represented by formulas (3-1) to (3-6) below are polyimide obtained by heating and baking. This is preferable because the resin coating has good bending resistance, abrasion resistance, and heat resistance. Note that one molecule of polyimide resin may contain only one type of these structural units or a combination of multiple types.

The structural unit represented by the above formula (3) may be derived from a tetracarboxylic dianhydride or a diamine compound, but it is usually introduced into polyimide resins with a diamine compound. be done.

Therefore, the polyimide resins used in the present invention are preferably manufactured using at least a diamine compound represented by the following formula (4) as the diamine compound.

In the above formula (4), R ¹ ' to R ⁸ ' are defined in the same way as R ¹ to R ⁸ in the above formula (3), and X' is defined in the same way as X. Further, n' is defined similarly to n.

Examples of the diamine compound represented by the above formula (4) include 4,4'-diaminodiphenyl ether, 2,2'-dimethyl-4,4'-diaminobiphenyl, 1,4-bis(4
-aminophenoxy)benzene, 2,2-bis(4-(4-aminophenoxy)phenyl)propane, 2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane, 2,2-bis[ 4-(4-aminophenoxy)phenyl]propane, 4,4'-
Bis(4-aminophenoxy)biphenyl, 2,2'-bis(trifluoromethyl)-4
, 4'-diaminobiphenyl, 4,4'-diaminobenzoylanilide, 4-aminophenyl-4-aminobenzoate, bis(4-aminophenyl) terephthalate, bis(4
-(4-aminophenoxy)phenyl)sulfone, bis(4-amino-3-carboxyphenyl)methane and the like. Among these, 4,4'-diaminodiphenyl ether, 2,2'-dimethyl-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl and the like are preferred.

The polyimide resins used in the present invention may have structural units other than the structural unit represented by the above formula (1) or (2) and the structural unit represented by the above formula (3), but the above-mentioned In order to effectively obtain the above-mentioned effects of the structural unit represented by the formula (1) or (2) and the structural unit represented by the formula (3), the tetracarboxylic dianhydride constituting the polyimide resin 80 mol% or more of the structural units represented by formulas (1) and/or (2), especially 90 to 1
It is preferable that the polyimide resin contains 80 mol% or more, particularly 90 to 100 mol%, of the structural unit represented by formula (3) in all the structural units derived from the diamine compound constituting the polyimide resin.

<Preferred aspect 2>
The polyimide resins used in the present invention are -NH-
(imino bond; sometimes called imino group), =NH (imino group), -C(O)NH-(
Amide bond; sometimes called amide group), -NHC(O)O- (urethane bond; sometimes called urethane group), -NHC(O)NH- (urea bond; sometimes called urea group) ), -NHC(S)NH- (thiourea bond; sometimes referred to as thiourea group), -N
H ₂ (amino group), -OH (hydroxyl group), -C(O)OH (carboxy group), -SH (thiol group), -C(O)N(OH)-(hydroxyamide group), -(O )S(O)-(sulfonyl group), -C(O)-(carbonyl group), and -C(O)SH(thiocarboxy group)
It is preferable to have a repeating unit containing at least one type of structure selected from the group consisting of (hereinafter, these structures may be referred to as "hydrogen bond forming structure").

This is due to the following reasons.
It is known that connecting molecular chains with chemical bonds increases the elastic modulus. Chemical bonds include covalent bonds and non-covalent bonds, but when molecular chains are linked by covalent bonds, the elastic modulus increases (that is, wear resistance improves), but mechanical flexibility (elongation) increases. ) decreases. That is, the bending resistance decreases. Normally, when polyimide resins are fired above a certain temperature, the ends of the molecules react with other molecules or specific sites within the molecule to form covalent bonds, which reduces flexibility, but By having a repeating unit containing a structure that forms a bond, intermolecular and/or
Or, non-covalent bonds (hereinafter simply referred to as "non-covalent bonds") are formed with specific sites within the molecule, and due to intermolecular interactions, it has an appropriate elastic modulus and has wear resistance and bending resistance. It is possible to achieve both.

Examples of non-covalent bonds include ionic bonds, π-π stacking, and hydrogen bonds. Hydrogen Bonding is preferred, and in preferred embodiment 2 of the present invention, the above-mentioned hydrogen bond-forming structure, which is particularly effective in forming hydrogen bonds, is introduced into polyimide resins.

Among the above hydrogen bond forming structures, -C(O)NH- (amide bond), -NHC(O
)NH- (urea bond) and -OH (hydroxyl group) are preferred, and -C(O)NH- (amide bond) is particularly preferred from the viewpoint of the excellent introduction effect described above.

There is no particular limit to the content of hydrogen bond-forming structures in polyimide resin molecules, but
In the case of a polyimide resin precursor, if all the repeating units in the polyimide resin precursor each contain one hydrogen bond forming structure is defined as 100%, it is usually larger than 0%, preferably 2%.
The content is more preferably 5% or more, usually less than 100%, preferably 75% or less, and more preferably 50% or less. Also, in the case of polyimide resins, if all repeating units contain one structure that forms a non-covalent bond as 100%, it is usually larger than 0%, preferably 2% or more, more preferably 5% or more. , usually less than 100%, preferably 75% or less, more preferably 50% or less. When the content of the hydrogen bond-forming structure is within this range, the polyimide resin coating can have better bending resistance such as tensile modulus and elongation, and better abrasion resistance.
The content of hydrogen bond-forming structures in polyimide resin molecules is usually determined by NMR, IR,
It can be determined by Raman, titration, mass spectrometry, etc.

Methods for introducing hydrogen bond-forming structures into repeating units of polyimide resins include methods of polymerizing monomers having hydrogen bond-forming structures when producing polyimide resins, and methods of forming hydrogen bond-forming structures through polymerization reactions. In particular, a method in which a monomer having one or more types of hydrogen bond-forming structures is used as a raw material for producing polyimide resins and polymerized is preferred.

Examples of monomers having one or more hydrogen bond-forming structures (hereinafter sometimes referred to as "hydrogen bond-forming monomers") include tetracarboxylic dianhydrides and diamine compounds having one or more hydrogen bond-forming structures. .

Specifically, examples of the tetracarboxylic dianhydride include 3,3',4,4'-benzophenone tetracarboxylic dianhydride, and examples of the diamine compound include 4,4'-
Diaminobenzanilide, 4,4'-bis(4-aminobenzamide)-3,3'-dihydroxybiphenyl, 2,2'-bis(3-amino-4-hydroxyphenyl)sulfone, 2,2'-bis( Examples include 3-amino-4-hydroxyphenyl)propane, 4'-diamino-3,3'-dihydroxybiphenyl polyamic acid, and bis(4-amino-3-carboxyphenyl)methane. These hydrogen bond-forming monomers may be used alone or in combination of two or more in any ratio.
Among these, it is particularly preferable to use 4,4'-diaminobenzanilide because of its excellent introduction effect.

The amount of these hydrogen bond-forming monomers introduced is not particularly limited, but in the case of a polyimide resin precursor, it is usually 0.5 mol% or more, based on the total repeating units of the polyimide resin precursor.
The content is preferably 5 mol% or more, more preferably 10 mol% or more, and usually 50 mol% or less, preferably 40 mol% or less, and more preferably 30 mol% or less. Also, in the case of polyimide resin, it is usually 0.5 mol% or more, preferably 5 mol% or more, more preferably 10 mol% or more, and usually 50 mol% or less, preferably 40 mol% or less, more preferably, in all repeating units of the polyimide resin. is 30 mol% or less. By introducing the amount of the hydrogen bond forming monomer within this range, it is easy to obtain a polyimide resin coating that has both high elasticity and high elongation. Hereinafter, this amount of hydrogen bond-forming monomer introduced will be referred to as "the amount of hydrogen bond-forming monomer introduced."

Note that the polyimide resins used in the present invention may have only the requirements of the above-mentioned preferred embodiment 1, or may have only the requirements of preferred embodiment 2, or may have the requirements of both preferred embodiments 1 and 2. It may be prepared.

<Manufacturing method>
There are no particular limitations on the method for producing polyimide resins, and conventionally known imidization methods can be used. For example, in the presence of a reaction solvent, the above-mentioned tetracarboxylic dianhydride and diamine compound are subjected to an imidization reaction using heat dehydration or a dehydrating reagent, and in the presence of a reaction solvent, the tetracarboxylic dianhydride and diamine compound are amidated Examples include a method in which a polyimide resin precursor obtained by reaction is obtained, and then the precursor is subjected to an imidization reaction by heating and dehydrating or using a dehydrating reagent. By allowing the above-mentioned hydrogen bond-forming monomer to exist in a necessary amount in this reaction system, an insulating coating material having a repeating unit containing a hydrogen bond-forming structure can be manufactured. Furthermore, the reaction may be carried out in the presence of other monomers mentioned above in this reaction system.
Further, the compounds (0) and (0') and the compound having a functional group that reacts with the terminally closed product may be produced simultaneously in the reaction system, or may be obtained individually and then mixed.
By the reaction in the presence of a reaction solvent, polyimide resins are obtained as a polyimide resin composition.

Hereinafter, the tetracarboxylic dianhydride, diamine compound, hydrogen bond forming monomer, and other monomers will be collectively referred to as "raw materials for tetracarboxylic dianhydride, diamine compound, etc.".

As the dehydration reagent, conventionally known reagents can be used, and examples thereof include acid anhydrides such as acetic anhydride, propionic anhydride, benzoic anhydride, trifluoroacetic anhydride, and chloroacetic anhydride.

The method of reacting raw materials such as tetracarboxylic dianhydride and diamine compound in a solvent is not particularly limited. Furthermore, the order and method of adding raw materials such as tetracarboxylic dianhydride and diamine compound are not particularly limited. For example, by ring-opening the terminal of tetracarboxylic dianhydride with water or alcohol and then reacting with a diamine compound, a compound having a functional group that reacts with the compound represented by the formula (0) and the terminal ring-closing product can be obtained. Compound (compound represented by the above formula (5), etc.)
There are methods for obtaining polyimide resin precursors such as The amount of these compounds can be adjusted as appropriate by adjusting the ratio of the tetracarboxylic dianhydride and diamine compound, the amount of alcohol, etc.

Examples of the above alcohol include methanol, ethanol, 1-propanol, 2-propanol,
Propanol, tert-butyl alcohol, 1-butanol, 2-methylpropanol, 1-pentanol, 1-hexanol, 1-heptanol, 2-ethyl-1-hexanol, 1-octanol, 1-decanol, diacetone alcohol, etc. Monohydric aliphatic alcohol; ethylene glycol, propylene glycol, trimethylene glycol, butanediol, hexamethylene glycol, 1,5-pentanediol, 2-butene-1,
Dihydric aliphatic alcohols such as 4-diol and 2-methyl-2,4-pentanediol;
Examples include trihydric aliphatic alcohols such as glycerol and 1,2,6-hexanetriol. In particular, methyl alcohol and ethyl alcohol are preferred from the viewpoint of elimination during firing.
These alcohols may be used alone, or two or more of water and alcohol may be used in any ratio and combination.

In order to increase the reactivity of the tetracarboxylic dianhydride with water, alcohol, etc., N,N-dimethylethanolamine or the like may be used as a catalyst, as described below, if necessary.

The amount of the diamine compound used in the reaction is usually 0.7 mol or more, preferably 0.8 mol or more, more preferably 0.9 mol or more, and usually 1.3 mol or less, preferably is 1.2 mol or less, more preferably 1.1
It is less than mol. By setting the amount of the diamine compound within such a range, polyimide resins with a high degree of polymerization can be obtained, and film forming properties and film forming properties tend to be improved.

The concentration of raw materials such as tetracarboxylic dianhydride and diamine compound in the solvent can be appropriately set depending on the reaction conditions and the viscosity of the resulting polyimide resin composition.

The total concentration of raw materials such as tetracarboxylic dianhydride and diamine compounds is not particularly limited, but is usually 1% by weight or more based on the total amount of the solution containing raw materials such as tetracarboxylic dianhydride and diamine compounds and the solvent. , preferably 5% by weight or more, usually 70% by weight or less, preferably 50% by weight or less. By carrying out polymerization within this concentration range, polyimide resins that are uniform and have a high degree of polymerization can be obtained. By performing polymerization at a total concentration of 1% by weight or more of raw materials such as tetracarboxylic dianhydride and diamine compounds, the degree of polymerization of polyimide resins becomes sufficiently high, and the strength of the final polyimide resin coating can be obtained. There is a tendency. On the other hand, when the content is 70% by weight or less, increase in solution viscosity is suppressed and stirring tends to become easier.

When obtaining a polyimide resin in a solution, the temperature at which raw materials such as tetracarboxylic dianhydride and a diamine compound are reacted in a solvent is not particularly limited as long as the reaction proceeds;
Usually 20°C or higher, preferably 40°C or higher, and usually 240°C or lower, preferably 220°C
It is as follows.
The reaction time is usually 1 hour or more, preferably 2 hours or more, and usually 100 hours or less, preferably 42 hours or less. By carrying out the process under such conditions, it is likely that a polyimide resin can be obtained at low cost and in good yield.
The pressure during the reaction may be normal pressure, increased pressure, or reduced pressure. The atmosphere may be air or an inert atmosphere, but an inert atmosphere is preferable from the viewpoint of the polyimide resin obtained and the bending followability of the metal coating material of the present invention.

When obtaining a polyimide resin precursor in a solution, the temperature at which raw materials such as tetracarboxylic dianhydride and diamine compounds are reacted in a solvent is not particularly limited as long as the reaction proceeds, but is usually 0°C. above, preferably 20°C or higher, usually 120°C or lower, preferably 10°C
The temperature is below 0°C.
The reaction time is usually 1 hour or more, preferably 2 hours or more, and usually 100 hours or less, preferably 42 hours or less. By carrying out the process under such conditions, it is likely that a polyimide resin precursor can be obtained at low cost and in good yield.
The pressure during the reaction may be normal pressure, increased pressure, or reduced pressure. The atmosphere may be air or an inert atmosphere, but an inert atmosphere is preferable from the viewpoint of the polyimide resin obtained and the bending followability of the metal coating material of the present invention.

The solvent used when reacting raw materials such as tetracarboxylic dianhydride and diamine compounds is not particularly limited, but examples include hexane, cyclohexane, heptane, benzene,
Hydrocarbon solvents such as naphtha, toluene, xylene, mesitylene, anisole; halogenated hydrocarbon solvents such as carbon tetrachloride, methylene chloride, chloroform, 1,2-dichloroethane, chlorobenzene, dichlorobenzene, fluorobenzene; diethyl ether, tetrahydrofuran , 1,4-dioxane, methoxybenzene and other ether solvents; acetone, methyl ethyl ketone, cyclohexanone, methyl isobutyl ketone and other ketone solvents; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, propylene glycol Glycol solvents such as monomethyl ether acetate; Amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone; Sulfonic solvents such as dimethyl sulfoxide; Pyridine, picoline, lutidine, Examples include heterocyclic solvents such as quinoline and isoquinoline; phenolic solvents such as phenol and cresol; lactone solvents such as γ-butyrolactone, γ-valerolactone, and δ-valerolactone; and the like. Among these, glycol-based solvents, amide-based solvents, and lactone-based solvents are preferable because they have high solubility for polyimide resins and tend to have composition viscosity that is easy to handle with normal manufacturing equipment.
One type of these solvents may be used alone, or two or more types may be used in any ratio and combination.

An organic amine compound may be used as a catalyst in order to increase the reactivity of raw materials such as tetracarboxylic dianhydride and a diamine compound. Examples of organic amine compounds include trimethylamine,
Tertiary alkylamines such as triethylamine, tripropylamine, and tributylamine; alkanolamines such as triethanolamine, N,N-dimethylethanolamine, and N,N-diethylethanolamine; alkylene diamines such as triethylenediamine; Examples include pyridines such as pyridine; pyrrolidines such as N-methylpyrrolidine and N-ethylpyrrolidine; piperidines such as N-methylpiperidine and N-ethylpiperidine; imidazoles such as imidazole; and quinolines such as quinoline and isoquinoline. It will be done. These are 1
A species may be used alone or two or more species may be used in any ratio and combination.

The obtained polyimide resins can also be collected in a solid state by adding them to a poor solvent.
In this case, the poor solvent used is not particularly limited and can be appropriately selected depending on the type of polyimide resin; ether solvents such as diethyl ether or diisopropyl ether; ketone solvents such as acetone, methyl ethyl ketone, isobutyl ketone, and methyl isobutyl ketone. ;
Examples include alcoholic solvents such as methanol, ethanol, and isopropyl alcohol. Among these, alcoholic solvents such as methanol and isopropyl alcohol are preferred because they tend to yield a precipitate efficiently and have a low boiling point, making drying easy. These solvents are 1
A species may be used alone or two or more species may be used in any ratio and combination.

Polyimide resins obtained by precipitation in a poor solvent can also be redissolved in a solvent and used as a resin composition for insulation coating materials.

<Weight average molecular weight>
The weight average molecular weight (Mw) of the polyimide resin used in the present invention is not particularly limited, but is usually 1,000 or more, preferably 3,000 or more, more preferably 5,000 or more in terms of polystyrene. Moreover, it is usually 200,000 or less, preferably 150,000 or less, and more preferably 100,000 or less. This range is preferable because the viscosity of the composition tends to be easily handled by manufacturing equipment. Note that the weight average molecular weight in terms of polystyrene can be determined by gel permeation chromatography (GPC).

<Imidization rate>
Among the polyimide resins in the resin composition for insulation coating materials of the present invention, when they become insoluble in solvents due to imidization, the imidization rate calculated by ¹ H-NMR is usually 1 mol% or more, preferably is 3 mol% or more, more preferably 5 mol% or more, particularly preferably 8 mol%
1% or more, and usually 35 mol% or less, preferably 30 mol% or less, more preferably 25 mol% or less, particularly preferably 20 mol% or less. By controlling the imidization rate within the above-mentioned preferred range, a polyimide resin with a good balance between elastic modulus and elongation at break can be obtained. On the other hand, if imidization does not result in insolubility in the solvent, the imidization rate is not particularly limited, but is usually 90 mol% or more.

[Polymer having a heterocycle in the side chain]
The resin composition for insulation coating material of the present invention may contain the following polymer having a heterocycle in the side chain, and by including the polymer having a heterocycle in the side chain, the resulting polyimide resin coating The bending resistance of the material can be improved.
The polymer having a heterocyclic side chain used in this case is usually a polymer of a heterocyclic compound having a vinyl group, and may be a homopolymer (homopolymer) or a copolymer.

Examples of the heterocyclic compound having a vinyl group, which is a monomer component constituting a polymer having a heterocycle in a side chain, include vinylpyrrolidone, vinylpyridine, vinylpyrrole, vinylporphyrin, vinylindole, vinylphthalimide, vinylthiophene, etc. ,
A heterocyclic compound containing a nitrogen atom is preferred because it has excellent compatibility with polyimide resins. Further, a 5-membered ring and/or 6-membered ring heterocyclic compound is preferable from the viewpoint of solubility in a solvent.

Homopolymers made of these heterocyclic compounds include polyvinylpyrrolidone, polyvinylpyridine, polyvinylpyrrole, polyvinylporphyrin, polyvinylindole,
Examples include polyvinylphthalimide and polyvinylthiophene.

A polymer having a heterocyclic ring in the side chain is a copolymer of two or more types of these heterocyclic compounds having a vinyl group, or a copolymer of one or more types of heterocyclic compounds having a vinyl group and another vinyl monomer. It may be a copolymer of one type or two or more types, and examples of copolymers of a heterocyclic compound having a vinyl group and other vinyl monomers include polyvinylpyridine-polystyrene copolymer, polyvinylpyrrolidone-polyvinyl alcohol. Examples include copolymers.

Among the polymers having a heterocycle in the side chain, those in which the heterocycle is composed of a nitrogen atom and a carbon atom are particularly preferable, and polyvinylpyrrolidone, polyvinylpyridine, or vinylpyrrolidone and/or vinylpyridine are used as a copolymer component. Polyvinylpyrrolidone and polyvinylpyridine are particularly preferred. In addition, the copolymer containing vinylpyrrolidone and/or vinylpyridine as a copolymerization component has 50 mol of structural units derived from vinylpyrrolidone and/or vinylpyridine for all structural units derived from the monomers constituting the copolymer. % or more is preferable.

The polymer having a heterocycle in the side chain used in the present invention has a molecular weight of 5,000 to 2,000,
000 is preferable, those with a molecular weight of 10,000 to 2,000,000 are more preferable, those with a molecular weight of 20,000 to 1,800,000 are still more preferable, and those with a molecular weight of 3
Particularly preferred are those between 0,000 and 1,500,000. When the molecular weight is within the above range, the function of weakening the intermolecular force of the polyimide tends to be sufficiently obtained when it is coordinated between the molecules of the polyimide resin. In addition, the "molecular weight" here refers to a weight average molecular weight (Mw), and is a polystyrene equivalent value measured by gel permeation chromatography (GPC).

These polymers having a heterocycle in the side chain may be used alone or in combination of two or more in any ratio.

When the resin composition for insulation coating material of the present invention contains a polymer having a heterocycle in the side chain, the content of the polymer having a heterocycle in the side chain is 0.1 to 7 parts by weight based on 100 parts by weight of the polyimide resin.
Parts by weight are preferred. The content of the polymer having a heterocycle in the side chain is 0.1 parts by weight or more based on 100 parts by weight of the polyimide resin, thereby improving the bending resistance by blending the polymer having a heterocycle in the side chain. It tends to be quite effective. Also,
When the amount is 7 parts by weight or less, molecular cleavage of the polymer having a heterocycle in the side chain due to heat during coating molding with the polyimide resin is suppressed, and the desired bending resistance can be easily obtained.
The content of the polymer having a heterocycle in the side chain in the resin composition for insulation coating material of the present invention is more preferably 0.5 to 5 parts by weight based on 100 parts by weight of the polyimide resin.

The resin composition for an insulation coating material of the present invention containing a polymer having a heterocycle in a side chain in the above proportion is obtained by adding a polymer having a heterocycle in a side chain to a polyimide resin composition produced by the method described above. Manufactured by mixing.

[Other ingredients]
The resin composition for insulation coating materials of the present invention contains surfactants, antifoaming agents, colorants such as organic pigments, antioxidants, and ultraviolet absorbers from the viewpoint of imparting coating properties, imparting processing characteristics, and imparting various functions. , stabilizers such as hindered amine light stabilizers, antistatic agents, lubricating oils, antistatic agents, flame retardants, plasticizers,
It may contain a mold release agent, a leveling agent, etc. Further, other resins, inorganic fillers, or organic fillers may be contained within a range that does not impair the purpose of the present invention.

Inorganic fillers include, for example, inorganic oxides such as silica, diatomaceous earth, beryllium oxide, pumice and pumice balloons; hydroxides such as aluminum hydroxide and magnesium hydroxide; calcium carbonate, magnesium carbonate, and basic magnesium carbonate. , metal carbonates such as dolomite and dawsonite; metal sulfates and sulfites such as calcium sulfate, barium sulfate, ammonium sulfate and calcium sulfite; talc, clay, mica, asbestos, glass fiber, glass balloon, glass beads, calcium silicate, Silicates such as montmorillonite and bentonite; powdered, granular, plate-like, or fibrous inorganic fillers such as molybdenum sulfide, zinc borate, barium metaborate, calcium borate, sodium borate, and boron fibers; silicon carbide; Examples include powdered, granular, fibrous, or whisker-shaped ceramic fillers such as silicon nitride, zirconia, aluminum nitride, titanium carbide, and potassium titanate.

Examples of organic fillers include husk fibers such as rice husks, wood flour, cotton, jute, paper strips,
Examples include cellophane pieces, aromatic polyamide fibers, cellulose fibers, nylon fibers, polyester fibers, polypropylene fibers, thermosetting resin powders, and rubber.
As the filler, a material processed into a flat plate such as a non-woven fabric may be used, or a mixture of a plurality of materials may be used.

These various fillers and additive components may be added at any stage of any process for producing the composition of the present invention.

Among other components, it is preferable to include a leveling agent since this tends to improve the smoothness of the polyimide resin coating formed. Examples of the leveling agent include silicone compounds. The silicone compound is not particularly limited, but examples include polyether-modified siloxane, polyether-modified polydimethylsiloxane, polyether-modified hydroxyl-containing polydimethylsiloxane, polyether-modified polymethylalkylsiloxane, polyester-modified polydimethylsiloxane, and polyester-modified hydroxyl group-containing polydimethylsiloxane. Examples include polydimethylsiloxane containing polydimethylsiloxane, polyester-modified polymethylalkylsiloxane, aralkyl-modified polymethylalkylsiloxane, highly polymerized silicone, amino-modified silicone, amino-derivative silicone, phenyl-modified silicone, and polyether-modified silicone.

[Glass transition temperature (Tg)]
The fired film of the resin composition for insulation coating material of the present invention has a glass transition temperature (Tg) measured by DMS (dynamic thermomechanical measuring device) of preferably 250°C or higher, more preferably 260°C or higher. , more preferably 270°C or higher, particularly preferably 280°C or higher. It is preferable from the viewpoint of heat resistance that the glass transition temperature is equal to or higher than the above lower limit. On the other hand, the upper limit of the glass transition temperature (Tg) is not particularly limited, but is usually 400° C. or lower, and some materials do not have Tg. Note that the glass transition temperature (Tg) measured by the DMS method can be measured by the method described in Examples below.

[Application]
The resin composition for an insulating coating material of the present invention can be used for display substrates, FPCs, electric wire coatings, thin film solar cell substrates, organic optical semiconductor lighting, LED mounting substrates, sensor substrates, switch substrates, and the like.
Furthermore, due to its high heat resistance, bending resistance, and further abrasion resistance properties, it can be used for insulation coating materials other than those mentioned above, metal coating materials such as metal wires and metal plates, polyimide films, polyimide laminates, etc. Note that insulation refers to cutting off current from flowing to peripheral parts and conductors in electrical machines and circuits.

In any of the uses, the composition of the present invention is usually formed into a film on a substrate and used for various purposes.

The method of forming a film using the resin composition for an insulating coating material of the present invention is not particularly limited, but examples include a method of coating it on a substrate or the like.
Examples of the coating method include die coating, spin coating, dip coating, screen printing, spraying, casting method, method using a coater, spraying method, dipping method, calendar method, and drooling method. These methods can be selected as appropriate depending on the coating area and the shape of the surface to be coated.

There is also no particular restriction on the method of volatilizing the solvent contained in the film formed by coating or the like. Usually, the solvent is evaporated by heating the carrier substrate coated with the composition. The heating method is not particularly limited, and includes, for example, hot air heating, vacuum heating, infrared heating, microwave heating, and heating by contact using a hot plate, hot roll, or the like.

As the heating temperature in the above case, a suitable temperature can be used depending on the type of solvent. The heating temperature is usually 40°C or higher, preferably 100°C or higher, more preferably 200°C or higher, particularly preferably 300°C or higher, usually 1000°C or lower, preferably 700°C or lower, even more preferably 600°C or lower, particularly preferably The temperature is below 500°C. It is preferable that the heating temperature is 40° C. or higher because the solvent is sufficiently volatilized. In addition, if the heating temperature is 300°C or higher,
Since the imidization reaction progresses quickly, short-time firing is possible. The atmosphere for heating may be air or an inert atmosphere and is not particularly limited, but when the polyimide is required to be colorless and transparent, it is preferable to heat it under an inert atmosphere such as nitrogen to suppress coloration. .

<Polyimide film>
When a polyimide film is formed and used using the resin composition for insulation coating materials of the present invention, the thickness of the polyimide film is usually 1 μm or more, preferably 2 μm or more, and usually 300 μm or less, preferably 200 μm. It is as follows. When the thickness is 1 μm or more, the polyimide film becomes a self-sustaining film with sufficient strength, and handling properties tend to improve. Further, by setting the thickness to 300 μm or less, the uniformity of the film tends to be easily ensured.

The performance required of the polyimide film depends on the application, but it is preferable that the polyimide film has the following mechanical strength.
The tensile modulus of the polyimide film is not particularly limited, but from the viewpoint of abrasion resistance it is preferably 2000 MPa or more, more preferably 2500 MPa or more, even more preferably 3000 MPa or more.
It is at least MPa, particularly preferably at least 3500 MPa, while from the viewpoint of bending resistance it is preferably at most 10 GPa, more preferably at most 5000 MPa.
Further, the tensile elongation is not particularly limited, but from the viewpoint of bending resistance, preferably 20% or more,
It is more preferably 30% or more, still more preferably 50% or more, and there is no particular upper limit from the viewpoint of bending followability, and higher elongation is preferred.

Because polyimide film has both such tensile modulus and tensile elongation, it has both high elastic modulus and high elongation, making it suitable for various uses such as surface protective layers, device substrates, insulating films, and wiring films. used. In addition, if the film satisfies such tensile modulus and tensile elongation when formed into a film, it can also be used as a metal coating material, which will be described later, to meet the recent demands for smaller motors and higher output. It satisfies the bending resistance and abrasion resistance commensurate with the standard.
Note that the tensile modulus and tensile elongation of the polyimide film are measured by the method described in the Examples section below.

A polyimide film made of the resin composition for insulation coating materials of the present invention can be prepared, for example, by applying the resin composition for insulation coating materials of the present invention on a base material serving as a support as described above, and then heating the substrate. It can be obtained by peeling the film from.
Although there are no particular limitations on the method for peeling the polyimide film from the support, physical peeling methods and laser peeling methods are preferred since they can be peeled off without impairing the performance of the film.

The physical peeling method includes, for example, a method in which a polyimide film is obtained by cutting off the peripheral edge of a laminate consisting of a polyimide film/support, a method in which a polyimide film is obtained by suctioning the peripheral edge, and a method in which the peripheral edge is fixed and the support is removed. Examples include a method of obtaining a polyimide film by moving the polyimide film.

<Polyimide laminate>
As mentioned above, after applying the resin composition for an insulating coating material of the present invention to a base material, it is heated to form a polyimide film on the base material, and this is integrated with the base material without being peeled off. It can be made into a polyimide laminate.

The base material is preferably hard and heat resistant. That is, it is preferable to use a material that does not deform under the temperature conditions required for the manufacturing process. Specifically, it is preferable that the base material is made of a material having a glass transition temperature of usually 200°C or higher, preferably 250°C or higher. Examples of such base materials include glass, ceramic, metal, and silicon wafers.

When glass is used as a base material, the glass used is not particularly limited, but includes, for example, blue plate glass (alkali glass), high silicate glass, soda lime glass, lead glass, aluminoborosilicate glass, and alkali-free glass. Examples include glass (borosilicate glass, Corning Eagle XG, etc.) and aluminosilicate glass.
When a metal is used as the base material, the metal used is not particularly limited, and examples thereof include gold, silver, copper, aluminum, and iron. These various alloys may also be used.

The shape of the base material is not particularly limited, and may be in the shape of a film, sheet, or plate. In this case, the base material may be flat, curved, or have steps. Further, the base material may be linear or rod-shaped.
There is no particular restriction on the form of polyimide resin coating on these base materials, and it can be formed as appropriate depending on the shape and purpose of the base material. For example, the entire surface, one surface, both surfaces, end surfaces, etc. of the substrate may be coated, or the entire surface or a portion of the substrate may be coated.
Further, the film may be a single layer or a multilayer.

<Metal coating material>
The metal coating material of the present invention has a resin layer made of the resin composition for insulation coating materials of the present invention, and is particularly suitable for electric wires and cables due to its high heat resistance, bending resistance, and wear resistance. It can be suitably used as an enamel coating material for insulation coatings, low temperature storage tanks, space insulation materials, integrated circuits, etc.

There is no particular restriction on the type of metal to be coated with the resin composition for insulation coating material of the present invention, but examples include gold, silver, copper, aluminum, iron, and alloys containing one or more of these metals. can be mentioned.

The resin coating layer made of the resin composition for an insulating coating material of the present invention can be formed in the same manner as the method for forming a polyimide film described above, and is usually formed to have a thickness of about 1 to 200 μm.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. In addition, the values of various manufacturing conditions and evaluation results in the following examples have the meaning as preferable upper or lower limits in the embodiments of the present invention, and the preferable ranges are different from the above-mentioned upper or lower limits. , it may be a range defined by the values of the following examples or a combination of values of the examples.

〔Evaluation methods〕
The polyimide resin precursors, resin compositions for insulation coating materials, and polyimide films obtained in the following Examples and Comparative Examples were evaluated by the following methods.

[Imidization rate of polyimide resin precursor]
From ¹ H-NMR measurement of the polyimide resin precursor, the imidization rate was determined by quantifying the amide protons in the amic acid moiety and the aromatic protons in the main chain skeleton. Specifically, a solution in which a polyimide resin precursor was dissolved in DMSO- _d6 containing trimethylsilane (TMS) was used as a sample, and the imidization rate was calculated using the following formula using TMS as a reference peak (0 ppm). .
Imidization rate (mol%) = (B/2)/A x 100
(In the above formula, A is the value obtained by dividing the peak integral value of aromatic protons (7 to 8 ppm) by the number of aromatic protons contained in the repeating unit of polyamic acid, and B is the amide proton of the amic acid structural part. (This is an integral value of 10 to 11 ppm.)

[Viscosity of resin composition for insulation coating material]
The rotational viscosity at 30° C. was measured using a Brookfield E-type viscometer, DV-I+.

[Flexing resistance (tensile elongation) and abrasion resistance (tensile modulus) of polyimide film]
According to JIS K6301, a test piece of polyimide film in the form of a strip with a width of 9 mm, a length of 80 mm, and a thickness of about 15 μm was chucked using a tensile tester [manufactured by Orientech Co., Ltd., product name "Tensilon STB-1225L"]. A tensile test was carried out at a distance of 30 mm and a tensile speed of 10 mm/min, a stress-strain curve was created, the tensile modulus (MPa) was determined, and the elongation rate at the point when the test piece broke was measured. It was expressed as elongation (%). The higher the tensile modulus, the better the wear resistance. Moreover, it is evaluated that the greater the tensile elongation, the better the flexibility and bending resistance (bending followability).

[Heat resistance of polyimide film (glass transition temperature)]
Using a dynamic thermomechanical measurement device (manufactured by SII Nano Technology Co., Ltd., DMS/SS6100), the storage modulus and loss modulus of the sample against vibration load were measured under the following measurement conditions, and the glass transition was determined from the loss tangent. The temperature (Tg) was determined. That is, the peak top of the loss tangent (tan δ) obtained by dividing the storage modulus (E') of the polyimide film test piece by the loss modulus (E") was defined as the glass transition temperature (Tg). This glass transition temperature ( Tg) corresponds to the glass transition temperature (Tg) of the polyimide resin, and the higher the Tg, the better the heat resistance.
(DMS measurement conditions)
Measurement temperature range: 30°C to 500°C (heating rate: 5°C/min)
Tensile load: 5g
Test piece shape: 6mm x 20mm

[Raw materials used]
The raw materials used for producing the polyimide resin compositions in Examples and Comparative Examples are as follows.
3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA): manufactured by Mitsubishi Chemical Corporation 4,4'-diaminodiphenyl ether (ODA): manufactured by Wakayama Seika Kogyo Co., Ltd. 4,4'-diamino Benzanilide (DABA): Wakayama Seika Kogyo Co., Ltd. N,N-dimethylacetamide (DMAc): Mitsubishi Gas Chemical Co., Ltd. Polyvinylpyrrolidone K-30 (PVP K-30, molecular weight 45,000): Daiichi Kogyo Seiyaku Co., Ltd. N,N-dimethiaminopyridine (DMAP): manufactured by Tokyo Chemical Industry Co., Ltd. Methanol: manufactured by Wako Pure Chemical Industries, Ltd. N-methyl-2-pyrrolidone (NMP): manufactured by Tokyo Chemical Industry Co., Ltd. Propylene carbonate (PC) manufactured by Tokyo Chemical Industry Co., Ltd. : Diethylene glycol dimethyl ether (diglyme) manufactured by Tokyo Chemical Industry Co., Ltd. Hi-Solv BDM manufactured by Tokyo Chemical Industry Co., Ltd.: Manufactured by Tokyo Chemical Industry Co., Ltd.

[Synthesis examples, examples and comparative examples]
[Synthesis of polyimide pre-resin precursor]
<Synthesis example 1>
58.4 parts by weight of BPDA, 0.51 parts by weight of methanol, 0.049 parts by weight of DMAP, and 175 parts by weight of DMAc were added to a four-neck flask equipped with a nitrogen gas inlet tube, a condenser, and a stirrer, and the mixture was heated to 70 parts by weight while stirring. The reaction was carried out at ℃ for 8 hours. ODA 29.8 parts by weight, DABA
11.3 parts by weight and 118 parts by weight of DMAc were added thereto and reacted at 80° C. for 4 hours to obtain a polyimide resin precursor having a solid content concentration of 25% by weight.
Note that the solid content concentration here corresponds to the polyimide resin precursor concentration, and is determined based on the amount charged. The obtained polyimide resin precursor had a viscosity of 2000 cP and an imide content of 23%.
The same applies to the following synthesis examples.

[Preparation of resin composition for insulation coating material]
Resin compositions PI-1 to PI-4 (for examples) and PI-5 to PI-7 (for comparative examples) for insulation coating materials were prepared according to the formulation shown in Table 1. Note that the usage amounts of each component shown in Table 1 indicate parts by weight as solid content. Table 1 also shows the difference in solubility parameter (SP value), boiling point or melting point between the additive and the solvent (DMAc).
For the resin composition for insulation coating material, additives were prepared as shown in Table 1.

[Preparation of polyimide film]
The resin compositions for insulation coating materials of PI-1 to PI-7 are applied to a glass plate using a spin coater, heated for 6 minutes on a hot plate at 500°C to cure, and then the glass plate is coated with polyimide resin. The laminate was taken out from the drying oven. After the laminate was returned to room temperature, the laminate was immersed in hot water at 90°C to separate the glass and polyimide film.

By comparing Example 1-4 and Comparative Example 1-3, the solubility parameter with the solvent (SP value)
It has been shown that both tensile modulus and tensile elongation can be achieved by including additives whose difference is within a specific range.

Claims (9)

A composition containing a solvent, a polyimide resin precursor and/or a polyimide resin,
The polyimide resin precursor and/or polyimide resin is a compound represented by the following formula (0) and/or a compound represented by the following formula (0'), and a compound represented by the following formula (0) and/or Or a compound having a functional group that reacts with the terminally closed ring product of the compound represented by the following formula (0'),
A resin composition for an insulating coating material, comprising an additive having a solubility parameter (SP value) difference from the solvent of 0.1 (cal/cm ³ ) ^1/2 or more and 20 (cal/cm ³ ) ^1/2 or less thing.

(In the above formulas (0) and (0'), R' each independently represents a hydrogen atom or an alkyl group, R ^a represents a tetracarboxylic acid residue, and R ^b represents a diamine residue. p and q represent arbitrary integers.) The resin composition for an insulating coating material according to claim 1, wherein the boiling point of the additive is 10° C. or more higher than the boiling point of the solvent. Claim 1 or 2, wherein the polyimide resin precursor and/or polyimide resin has at least one of a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2). The insulating coating resin composition described above.

The glass transition temperature (Tg) of the fired film of the polyimide resin precursor and/or polyimide resin
) is 250°C or more and 400°C or less, the resin composition for an insulating coating material according to any one of claims 1 to 3. The resin composition for an insulating coating material according to any one of claims 1 to 4, wherein the polyimide resin precursor and/or the polyimide resin has a structural unit represented by the following formula (3).

(In the above formula (3), R ¹ to R ⁸ may be the same or different from each other, and include a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, and a fluoroalkyl group having 1 to 4 carbon atoms. or a hydroxyl group; , n is an integer from 0 to 4.) The polyimide resin precursor and/or polyimide resin contains -NH-, =NH, -C(O
)NH-, -NHC(O)O-, -NHC(O)NH-, -NHC(S)NH-, -NH
₂ , -OH, -C(O)OH, -SH, -C(O)N(OH)-, -(O)S(O)-,
The resin for insulating coating material according to any one of claims 1 to 5, which has a repeating unit containing at least one structure selected from the group consisting of -C(O)- and -C(O)SH. Composition. The resin composition for an insulating coating material according to claim 6, wherein the polyimide resin precursor and/or the polyimide resin has a repeating unit containing a -C(O)NH- structure. The resin composition for an insulating coating material according to claim 7, wherein the -C(O)NH- structure is a structure derived from 4,4'-diaminobenzanilide. A metal coating material comprising at least a resin layer containing the resin composition for an insulation coating material according to any one of claims 1 to 8.