JP3011302B2 - Coated electrical conductor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an electric conductor,
It is insulated and insulated by a heat-resistant film having a heat-resistant adhesive layer containing (a) a soluble polyimide siloxane, (b) an epoxy compound having an epoxy group, and (c) an epoxy curing agent in a specific composition as a resin component. To a coated electrical conductor. The electric conductor according to the present invention has no swelling or peeling of the adhesive layer and no cracks even in a high-temperature environment or a low-temperature environment, and has an appropriate strength as well as an adhesive strength. And coated electric conductors used in particle accelerators and the like.

[0002]

2. Description of the Related Art Conventionally, as a method for insulating a linear electric conductor, a method in which a tape-like polyimide film is wound around and coated, a method in which an adhesive is applied to the polyimide film and wound, and the like are used. In many cases, epoxy resin, urethane resin, or the like is used as the adhesive. However, electrical conductors manufactured using known adhesives, when exposed to high temperatures, cause blistering or peeling in the adhesive layer, or when exposed to low temperatures such as liquid nitrogen or liquid helium. In addition, there is a problem that cracks occur or the material becomes brittle, and improvement thereof has been desired.

In order to improve such disadvantages, imide resin-based adhesives such as N, N '-(4,
4'-diphenylmethane) bismaleimide and 4,4'-
Precondensates consisting of diaminodiphenylmethane have been proposed. However, since the precondensate itself is brittle, it is not suitable as an insulating coating for a linear electric conductor requiring flexibility. Also, for example, see JP-A-62-2324.
No. 75 and Japanese Patent Application Laid-Open No. 62-235382,
A thermosetting adhesive film formed from a resin composition in which an aromatic polyimide obtained from benzophenonetetracarboxylic acid and an aromatic diamine is mixed with polybismaleimide has been proposed.

However, the above-mentioned adhesive film has a softening temperature of 180 ° C. or higher, and requires a high temperature of about 250 ° C. for curing, which is a problem in terms of practicality.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems caused by the known adhesives.
An object of the present invention is to provide a coated electric conductor which is free from swelling, peeling and cracking of an adhesive layer even in a severe environment, and has excellent flexibility and insulation properties.

[0006]

According to the present invention, the electric conductor comprises (a) an aromatic tetracarboxylic acid component having a biphenyltetracarboxylic acid as a main component and a general formula (1)

[0007]

Embedded image

(Wherein R represents a divalent hydrocarbon residue, R ₁ , R ₂ , R ₃ and R ₄ represent a lower alkyl group or a phenyl group, and n represents an integer of 3 to 60) (B) 100 parts by weight of a soluble polyimide siloxane obtained from 10 to 80 mol% of a diaminopolysiloxane and 20 to 90 mol% of an aromatic diamine, and (b) an epoxy compound 15 having an epoxy group. ~ 2
The present invention relates to a coated electric conductor characterized by being covered and insulated by a heat-resistant film having a heat-resistant adhesive layer containing 50 parts by weight of an epoxy curing agent (c) as a resin component.

In the present invention, the aromatic tetracarboxylic acid component mainly composed of biphenyltetracarboxylic acids includes 3,3 ′, 4,4′-biphenyltetracarboxylic acid and 2,3,3 ′, 4′- Biphenyltetracarboxylic acid or a biphenyltetracarboxylic acid such as an acid dianhydride or an ester thereof is used in an amount of 60 mol% or more, particularly 80 mol% or more.
An aromatic tetracarboxylic acid component containing about 100 mol% is used. Among these, 2,3,3 ', 4'
-Biphenyltetracarboxylic dianhydride is preferred because it has excellent solubility of the above-mentioned polyimide siloxane in an organic polar solvent, compatibility with an epoxy compound, and the like.

In the present invention, examples of the aromatic tetracarboxylic acid component which can be used together with the biphenyltetracarboxylic acids include 3,3 ′, 4,4′-benzophenonetetracarboxylic acid, 3,3 ′, 4, 4'-
Diphenyl ether tetracarboxylic acid, bis (3,4-
Dicarboxyphenyl) methane, 2,2-bis (3,4
-Dicarboxyphenyl) propane, pyromellitic acid,
Alternatively, acid dianhydrides and esterified products thereof can be preferably mentioned. However, if the amount of these is too large, the polyimide siloxane becomes insoluble in an organic polar solvent or the compatibility with an epoxy resin deteriorates, which is not suitable.

In the present invention, as the diaminopolysiloxane represented by the general formula (1), R in the formula is selected from "a plurality of methylene groups" having 2 to 6 carbon atoms, particularly 3 to 5 carbon atoms, or phenylene group. A divalent hydrocarbon residue represented by R ₁
-R ₄ has 1 carbon atom such as a methyl group, an ethyl group and a propyl group
5 to lower alkyl groups or phenyl groups, and n is particularly preferably 5 to 20, more preferably 5 to 1
It is preferably about 5. If the number of carbon atoms of R and R _{1 to} R ₄ is too large, or if the number of n is too large, the reactivity is reduced, the heat resistance is deteriorated, the molecular weight of the obtained polyimide siloxane is reduced, and the solubility in an organic solvent is reduced. Is lower or the compatibility with other organic compounds deteriorates, so that the above-mentioned degree is appropriate.

Specific examples of the diaminopolysiloxane represented by the general formula (1) include ω, ω′-bis (2-aminoethyl) polydimethylsiloxane and ω, ω′-bis (3
-Aminopropyl) polydimethylsiloxane, ω, ω '
-Bis (4-aminophenyl) polydimethylsiloxane, ω, ω'-bis (4-amino-3-methylphenyl) polydimethylsiloxane, ω, ω'-bis (3-aminopropyl) polydiphenylsiloxane and the like are preferable. Can be listed.

The aromatic diamine used together with the diaminopolysiloxane is generally an aromatic diamine compound having two or more, especially 2 to 5, aromatic rings such as a benzene ring, for example, biphenyl diamine compounds, diphenyl ether Diamine compound, benzophenone diamine compound, diphenyl sulfone diamine compound,
Diphenylmethane diamine compound, diphenylpropane diamine compound, diphenylthioether diamine compound, bis (phenoxy) benzene diamine compound, bis (phenoxyphenyl) sulfone diamine compound, bis (phenoxy) diphenylsulfone diamine compound, bis (phenoxyphenyl) A) hexafluoropropane-based diamine compound, bis (phenoxyphenyl) propane-based diamine compound, and the like.
They can be used alone or as a mixture.

Specific examples of the aromatic diamine include:
Diphenyl ether diamine compounds such as 4,4'-diaminodiphenyl ether and 3,3'-diaminodiphenyl ether, 1,3-bis (3-diaminophenoxy) benzene, 1,4-bis (4-aminophenoxy)
Bis (phenoxy) benzene diamine compounds such as benzene, bis-bis [4- (4-aminophenoxy) phenyl] propane, and bis-bis [4- (3-aminophenoxy) phenyl] propane such as 2,2-bis [4- (3-aminophenoxy) phenyl] propane (Phenoxyphenyl) propane-based diamine compound, bis [4- (4-
Aminophenoxy) phenyl] sulfone, bis [4-
Aromatic diamine compounds having 2 to 5 aromatic rings, such as bis (phenoxyphenyl) sulfone-based diamine compounds such as (3-aminophenoxy) phenyl] sulfone, are preferred.

In the present invention, the diaminopolysiloxane and the aromatic diamine are preferably 10 to 80 mol%, preferably 15 to 70 mol%, more preferably 20 to 65 mol%, and the latter 20 to 90 mol%. Is 30-85
Mol%, more preferably 35 to 80 mol%. If either component is too large or too small, and deviates from these ranges, the solubility of the polyimidesiloxane in the organic solvent will decrease, the compatibility with other organic compounds will deteriorate, and the elastic modulus will increase. Is not appropriate.

In the present invention, the polyimide siloxane (a) is produced by the following method. (A ₁₎ an aromatic tetracarboxylic acid component and a diaminopolysiloxane and diamine component aromatic diamines, continuously and substantially equimolar used in an organic polar solvent temperature 15 to 2
A method of obtaining polyimide siloxane by polymerization and imidization at 50 ° C.

(A ₂ ) The diamine component is separated, and an excess amount of the aromatic tetracarboxylic acid component and diaminopolysiloxane are polymerized and imidized in an organic polar solvent at a temperature of 15 to 250 ° C. to obtain an average degree of polymerization. An imidosiloxane oligomer having an acid or acid anhydride group at about 1 to 10 terminals is prepared. Separately, an aromatic tetracarboxylic acid component and an excess amount of an aromatic diamine are mixed in an organic polar solvent at a temperature of 15 to 250.
C., polymerization and imidation to prepare an imide oligomer having an amino group at a terminal having an average degree of polymerization of about 1 to 10, and then mixing both so that the acid component and the diamine component are substantially equimolar. And reacting at a temperature of 15 to 60 ° C., and further raising the temperature to 130 to 250 ° C. to obtain a block type polyimide siloxane.

(A ₃ ) An aromatic tetracarboxylic acid component, a diaminopolysiloxane component and an aromatic diamine component are used in approximately equimolar amounts, and are first heated to 20 to 80 ° C. in an organic polar solvent.
There is a method in which a polyamic acid is once obtained by polymerization at a temperature of ° C. and then imidized to obtain a polyimide siloxane.

Examples of the organic polar solvent used in the production of polyimidesiloxane in the present invention include N, N-dimethylacetamide, N, N-diethylacetamide,
Contains amide solvents such as N, N-dimethylformamide, N, N-diethylformamide, N-methyl-2-pyrrolidone, and sulfur atoms such as dimethylsulfoxide, diethylsulfoxide, dimethylsulfone, diethylsulfone, and hexamethylsulfonamide. Solvent, cresol,
Examples thereof include phenol solvents such as phenol and xylenol, solvents having an oxygen atom in the molecule such as acetone, methanol, ethanol, ethylene glycol, dioxane and tetrahydrofuran, and other solvents such as pyridine and tetramethylurea. Further, if necessary, aromatic hydrocarbon solvents such as benzene, toluene and xylene, and other kinds of organic solvents such as solvent naphtha and benzonitrile can be used in combination.

In the present invention, as the polyimide siloxane, those obtained by any of the above methods (a ₁ ) to (a ₃ ) may be used. What can be dissolved at a high concentration of at least 3% by weight or more, particularly about 5 to 40% by weight is preferable since an adhesive having good bonding operation and bonding performance can be obtained.

The imidation ratio of the polyimide siloxane is as follows:
The imidation ratio is 9 as measured by infrared absorption spectrum analysis.
0% or more, especially 95% or more is preferred. In the infrared absorption spectrum analysis, a high imidization ratio is obtained such that substantially no absorption peak relating to the amide-acid bond of the polymer is found and only the absorption peak relating to the imide ring bond is observed. Preferably, there is.

The polyimide siloxane has its logarithmic viscosity (measurement concentration: 0.5 g / 100 ml solvent, solvent: N-methyl-2-pyrrolidone, measurement temperature: 30 ° C.,
Viscometer: Cannon-Fenske viscometer)
4, more preferably about 0.1 to 3.

Further, the above-mentioned polyimidesiloxane has an elastic modulus of 250 kg / m2 when formed into a film.
m ² or less, especially 0.5 to 200 kg / mm ² ,
Thermal decomposition initiation temperature is 250 ° C. or higher, particularly 300 ° C. or higher, and secondary rearrangement temperature is −10 ° C. or higher, particularly 10 to 250 ° C.
It is preferred that it is about.

The epoxy compound (b) having an epoxy group used in the present invention is used in an amount of 15 to 250 parts by weight per 100 parts by weight of the polyimide siloxane.
When the amount is too large or too small, the uncured adhesive is sticky and lacks flexibility after curing, or the softening point of the uncured adhesive is too high. Therefore, the adhesive properties after curing may be deteriorated.

The epoxy compound having an epoxy group used in the present invention includes an epoxy compound having one or more epoxy groups, for example, a bisphenol A type or a bisphenol F type epoxy resin (trade name: manufactured by Yuka Shell Co., Ltd.) Epicoat 807, 828, etc.), phenol novolak type epoxy resin, alkyl polyphenol type epoxy resin (Nippon Kayaku Co., Ltd., RE701,
RE550S etc.), polyfunctional epoxy resin (Sumitomo Chemical Co., Ltd., ELM-100 etc.), glycidyl ether type epoxy resin, glycidyl ester type epoxy resin, glycidylamine type epoxy resin (Mitsubishi Gas Chemical Co., Ltd., trade name: Tetrad X, etc.) can be used alone or in combination. If the melting point of the epoxy compound is too high, the softening point of the uncured adhesive increases, so
0 ° C. or less, especially about 0 to 80 ° C., or 3
Those which are liquid at a temperature of 0 ° C. or lower are preferred.

The epoxy curing agent (c) used in the present invention includes curing agents known per se, for example, curing catalysts such as imidazoles, tertiary amines and triphenylphosphine, dicyandiamides, and the like. Polyaddition-type curing agents such as hydrazines, aromatic diamines, and phenol novolak-type curing agents having a hydroxyl group (manufactured by Meiwa Kasei Co., Ltd., phenol novolak: H-1, H-5, etc.);
Organic peroxides and the like can be mentioned. The curing agent is appropriately used together with a known curing accelerator.

The amount of the epoxy curing agent used is generally 0.01 to 110 parts by weight, preferably 0.03 to 100 parts by weight, per 100 parts by weight of the epoxy compound.

The heat-resistant adhesive used in the present invention is prepared by uniformly stirring and mixing predetermined amounts of the above-mentioned polyimide siloxane (a), epoxy compound (b) having an epoxy group, and epoxy curing agent (c). Can be easily obtained. When mixed with an organic polar solvent, a solution composition of the heat-resistant adhesive is obtained. As the organic polar solvent, an organic polar solvent that can be used for obtaining the polyimide siloxane, for example, a solvent having an oxygen atom in a molecule such as dioxane or tetrahydrofuran or an amide-based solvent such as N-methyl-2-pyrrolidone is preferably used. Is done.

The concentration of the solution composition of the heat-resistant adhesive is from 3 to
50% by weight, preferably 5-40% by weight,
The solution viscosity (30 ° C.) is 0.1 to 10,000 poise, particularly 0.2 to 5000 poise, and more preferably 0.3 to 1 poise.
It is preferably about 000 poise.

The heat-resistant adhesive used in the present invention may contain fine inorganic fillers such as silicon dioxide, aluminum oxide and titanium oxide. An appropriate amount of addition is 0.2 to 5 parts by weight based on 100 parts by weight of the polyimide siloxane.

The heat-resistant adhesive used in the present invention has a softening temperature (a temperature at which softening starts on a hot plate) of the composition containing only the uncured resin component of 150 ° C. or less, especially 140 ° C.
C. or lower, more preferably about 0 to 130C.

In the present invention, the heat-resistant film having the heat-resistant adhesive layer comprises a solution composition of the heat-resistant adhesive in which the above-mentioned resin component is dissolved in an organic polar solvent, an aromatic polyimide film, a polyamide film, Apply on one or both sides of a heat-resistant film such as polyetheretherketone, polyethersulfone,
By drying at a temperature of ~ 200 ° C for 20 seconds to 100 minutes, the solvent is substantially removed to 1% by weight or less (preferably, the residual ratio of the solvent is 0.5% by weight or less). Heat-resistant adhesive thin film (thickness about 1 to 200 μm
(A dry film or sheet) or a method of transferring this thin film to another heat-resistant film.

The heat-resistant film having the heat-resistant adhesive layer is usually used in the form of a slit tape.

In the present invention, the electric conductor to be coated and insulated may be any conductive material, for example, a metal or alloy such as iron, aluminum, copper, or brass, or even niobium-titanium. Superconducting materials. The shape of the electric conductor is not particularly limited, but generally, a wire is suitably used. The wire may have a round bar shape or a polygonal bar shape.

The coated electric conductor insulated and insulated with the heat-resistant film having the heat-resistant adhesive layer of the present invention is, for example,
It is obtained by bundling one or more wires, winding the wire once or more times with the tape while partially overlapping the tape, and then heating to cure the adhesive layer. Although there is no need to pressurize during heating, the pressure can increase the adhesion.
The tape may be one having an adhesive layer on one side, one having both sides, or two or more tapes.

[0036]

The present invention will be described below in further detail with reference to examples. In the following examples, logarithmic viscosity (η)
Is prepared by uniformly dissolving polyimide siloxane in N-methyl-2-pyrrolidone so that the concentration becomes 0.5 g / 100 ml of a solvent, and preparing the solution using a Cannon-Fenske viscometer. Viscosity and viscosity of solvent are 30
It is a value calculated from the following formula when measured at ° C.

[0037]

(Equation 1)

The softening temperature of the polyimide siloxane film is a value obtained by measuring the tan δ (high temperature side) of a viscoelastic peak in a viscoelastic test using a mechanical spectrometer RDS-2 manufactured by Rheometrics.

The modulus of elasticity of the polyimide siloxane is a result of measurement using a tensile tester manufactured by Intesco Corporation at a tensile speed of 5 mm / min.

The adhesive strength was measured at a peeling rate of 50 mm / min and a measuring temperature of 25 ° C. using a tensile tester manufactured by Intesco Corporation.
The results are obtained by conducting a 180 ° peel test at 90 ° and a measurement temperature of 180 ° C, and performing a 180 ° shear test at a measurement temperature of 25 ° C and -196 ° C.

[Production of Imidosiloxane Oligomer] Reference Example 1 2, 3, 3 ′, 4 ′ was placed in a 500 ml glass flask equipped with a thermometer, a charging / discharging port, and a stirrer.
-Biphenyltetracarboxylic dianhydride (a-BPD
A) 0.054 mol, ω, ω′-bis (3-aminopropyl) polydimethylsiloxane (manufactured by Shin-Etsu Silicon Co., Ltd., X-22-161AS, n: 9) 0.027 mol,
And 160 g of N-methyl-2-pyrrolidone (NMP) were added, the temperature was raised to 50 ° C. in a stream of nitrogen, and the mixture was stirred at this temperature for 2 hours to form an amic acid oligomer. Temperature, and at that temperature
After stirring for an hour, an imide siloxane oligomer having an anhydride group at the terminal (A-1 component, average degree of polymerization: 1) was produced.

REFERENCE EXAMPLES 2-3 The same procedures as in Reference Example 1 were repeated except that the amounts of a-BPDA, diaminopolysiloxane (X-22-161AS) and NMP shown in Table 1 were used, and the anhydride group was added to the terminal. Having imidosiloxane oligomer (A-2, average degree of polymerization:
2 and A-3, average degree of polymerization: 6) were produced, respectively.

[Production of imide oligomer] Reference Example 4 The amount of a-BPDA, 2,2-bis [4-
(4-Aminophenoxy) phenyl] propane (BAP
P) and NPA were charged in the same manner as in Reference Example 1 and stirred at 50 ° C. for 2 hours in a nitrogen stream to produce an amic acid oligomer. Then, the reaction solution was heated to 200 ° C. The mixture was stirred for 3 hours to produce an imide oligomer having an amino group at a terminal, component B-1 (average degree of polymerization: 1).

Reference Examples 5 to 6 In the same manner as in Reference Example 4 except that a-BPDA, BAPP and NMP shown in Table 1 were used, respectively, an imide oligomer having an amino group at a terminal, B-2 (average polymerization) Degree: 2) and B-3 component (average degree of polymerization: 10) were produced.

[0045]

[Table 1]

[Production of Polyimide Siloxane] Reference Example 7 The imide siloxane oligomer (A-
3 components) 0.0025 mol of 20% by weight NMP solution and imide oligomer prepared in Reference Example 7 (component B-3)
A volume of 0.0025 mol of a 20% by weight NMP solution
Into a 0 ml glass flask, Reference Example 1
In the same manner as described above, in a nitrogen stream, the temperature was raised and stirred at 50 ° C. for 1 hour to generate a polyamic acid block polymer. Then, the temperature was raised and stirred at 200 ° C. for 3 hours to generate a polyimide siloxane (block polymer). I let it. This polyimide siloxane had an imidization ratio of 95% or more and an intrinsic viscosity of 0.45.

Reference Examples 8 to 9 Reference Examples 7 to 9 were conducted except that the oligomers prepared in the above Reference Examples 1 to 6 were used in the amounts and reaction conditions shown in Table 2.
In the same manner as in the above, polyimide siloxane (block polymer) was produced. Table 2 shows the logarithmic viscosities of each of the produced polyimide siloxanes, the elastic modulus when molded into a film, and the softening temperature.

[0048]

[Table 2]

Example 1 [Preparation of solution composition of heat-resistant adhesive] In a glass flask having a capacity of 500 ml, the polyimidesiloxane (block polymer, A-3
-B-3) 50 g, an epoxy resin [30 g of Epicoat 807 manufactured by Yuka Shell Epoxy Co., Ltd.], 20 g of a phenol novolak type hardener [H-1 manufactured by Meiwa Kasei Co., Ltd.] and a curing accelerator 2-phenylimidazole 0.005 g and 185 g of dioxane were charged and at room temperature (25 ° C.) about 2 g.
Stir for an hour to obtain a uniform heat-resistant adhesive solution composition (25 ° C
(Viscosity of 7 poise). This solution composition maintained a uniform solution state even when left at room temperature for one week.

[Production of a heat-resistant film having a heat-resistant adhesive layer] A solution composition of the above-mentioned heat-resistant adhesive was applied to a polyimide film (product name: UPILEX, manufactured by Ube Industries, Ltd.).
-S, thickness of 50 μm) and a thickness of 125 μm,
Then, the coated layer is heated at 50 ° C. for 30 minutes and
Heating and drying for 0 minutes, a heat resistant adhesive layer having a thickness of about 25 μm was formed on the polyimide film.

[Peel strength to metal] The polyimide film having the above-mentioned heat-resistant adhesive layer and the treated surface of copper foil (35 μm) are overlapped and passed through a laminate roll heated to 130 ° C. while applying pressure. The laminate was pressed at 100 ° C. for 1 hour at 120 ° C.
For 1 hour and at 160 ° C. for 10 hours to cure the heat-resistant adhesive layer to produce a laminate. The adhesive strength of the obtained laminate was measured, and the results are shown in Table 3.

[Strength of Adhesive Surface] A polyimide film having the above-mentioned heat-resistant adhesive was slit into a width of 10 mm to form a tape. The surfaces of the tapes to which the adhesive has been applied are overlapped with each other with a length of 5 mm (the area of the overlapped portion is 0. 0 mm).
5 cm ² ), pressure-bonded by passing between laminating rolls heated to 130 ° C. while applying pressure, and
1 hour at 120 ° C, 1 hour at 120 ° C and 10 hours at 160 ° C.
Heated for hours. The tensile shear strength of this sample was measured. Table 3 shows the results.

[Production of an electric conductor covered with a polyimide film having a heat-resistant adhesive layer and insulated] A rectangular wire (2 mm.times.10) in which superconducting wires made of niobium-titanium are bundled.
mm), the above-described tape slit to a width of 10 mm was wrapped around the side having the adhesive layer outside with a で overlap. The flat wire wound in this way is 10
The pieces were stacked and cured at a pressure of 10 kg / mm and a temperature of 160 ° C. for 1 hour to produce a block of an electric conductor covered and insulated with a polyimide film having a heat-resistant adhesive layer. This block was placed in liquid nitrogen from room temperature, held for 30 minutes, and then returned to room temperature. The cycle was repeated twice to test low temperature resistance. No defects such as cracks were observed in the blocks after the test.

Examples 2 to 4 As shown in Table 3, the polyimide siloxanes prepared in Reference Examples 8 and 9 were used, and the composition of each component was as shown in Table 3. In the same manner, a heat-resistant adhesive solution composition was prepared, respectively, to produce a polyimide film having a heat-resistant adhesive layer. Thereafter, in the same manner as in Example 1, the peel strength from the copper foil and the tensile shear strength when the polyimide films were bonded to each other were measured. Table 3 shows the results. An electric conductor block was manufactured in the same manner as in Example 1, and a low-temperature resistance test was performed in the same manner. No defect was found in the block.

[0055]

[Table 3]

Comparative Example 1 50 g of phenol novolak type epoxy resin [Yukaka Shell Co., Ltd., Epicoat 152], 30 g of phenol novolak [Meiwa Kasei Co., Ltd., H-1], imidazole curing catalyst (2PZ, manufactured by Shikoku Chemicals Co., Ltd.) ) 0.01 g,
A solution composition of a heat-resistant adhesive was prepared in the same manner as in Example 1, except that 200 g of dioxane and dioxane were used. Furthermore,
Using the above solution composition, a tape was formed in the same manner as in Example 1, and further a block was formed. When this block was subjected to a cycle test of room temperature and liquid nitrogen twice, cracks occurred in the adhesive layer of the block.

[0057]

The coated electric conductor insulated and covered with the heat-resistant film having the heat-resistant adhesive layer of the present invention has a blistering and peeling of the adhesive layer both in a high temperature environment and in a low temperature environment. Since it has no cracks or the like, and has a suitable flexibility as well as an adhesive strength, it can be suitably used even under severe conditions. For example, it is suitable as a coated electric conductor used in a nuclear fusion reactor or a particle accelerator. The heat-resistant adhesive used in the present invention can easily form an uncured and thin-layered heat-resistant adhesive layer by applying the solution composition on a support film and drying at a relatively low temperature. In addition, the thin heat-resistant adhesive layer has sufficient flexibility. Moreover, since the curing temperature is low, and the low-temperature characteristics are good as well as the high-temperature characteristics, the heat-resistant film having the heat-resistant adhesive layer has an excellent function as an insulating material of an electric conductor.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI H01B 3/40 H01B 3/40 P (56) References JP-A-2-255836 (JP, A) JP-A-3-177428 ( JP, A) JP-A-5-311143 (JP, A) JP-A-6-172716 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01B 3/46 H01B 3/40 C09J 7/02 C09J 163/00 C09J 179/08 C09J 183/04

Claims (1)

(57) [Claims] 1. An electric conductor comprising: (a) an aromatic tetracarboxylic acid component containing a biphenyltetracarboxylic acid as a main component and a general formula (1): (However, R in the formula represents a divalent hydrocarbon residue, and R ₁ ,
R ₂ , R ₃ and R ₄ represent a lower alkyl group or a phenyl group, and n represents an integer of 3 to 60. (B) 100 parts by weight of a soluble polyimide siloxane obtained from a diamine component consisting of 10 to 80 mol% of a diaminopolysiloxane and 20 to 90 mol% of an aromatic diamine, and (b) an epoxy compound having an epoxy group of 15 to 250.
(C) a coated electric conductor which is insulated and covered with a heat-resistant film having a heat-resistant adhesive layer containing an epoxy curing agent as a resin component.