JP3451401B2 - Heat-fusible laminated film for superconducting wire coating - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a heat-fusible laminated film for wire rod coating BACKGROUND OF THE, more particularly suitable for the coating of such superconducting (superconducting) wire material excellent in workability, flexibility and adhesion properties, in particular, for wire coating excellent in radiation resistance regarding heat fusible laminated film.

[0002]

2. Description of the Related Art Polyimide films are widely used as materials for electrical and electronic equipment because they have excellent heat resistance, low temperature characteristics, chemical resistance, and electrical characteristics. ing. However, since polyimide used in the form of a film is generally insoluble and infusible, when it is used as a coating material for metal wires or the like, a polyimide film is laminated with a resin layer having a heat-fusible property.

Further, with the recent progress of elementary particle physics, construction of an accelerator for generating higher energy is progressing. In order to generate this high energy, a magnet that can carry a large current and generate a strong magnetic field is required.Recently, the number of cases where a superconducting magnet using a superconducting wire is used as the wire of the magnet is increasing. ing. An oxide containing copper as a main component is often used as a material for this superconducting wire, but if a thermosetting adhesive is used to coat this superconducting wire with an insulating coating material, heat can be applied by applying heat. The rate of oxidation of the superconducting wire changes, and the characteristics of the magnet deteriorate. Therefore, low temperature curing for such applications,
The use of adhesives to adhere is essential.

An accelerator is a device for accelerating elementary particles such as protons and protons, electrons and electrons, colliding and collapsing them, and investigating the particles generated from them. However, a large amount of radiation is generated by its nature. Therefore, the insulating coating material and the adhesive used for the superconducting magnet are required to have excellent radiation resistance.

Among them, a polyimide film laminated with a thermosetting resin containing an epoxy resin as a main component has been used for coating a superconducting wire used at extremely low temperatures. However, in this case, it takes a high temperature and a long time to cure the epoxy resin, which causes a problem of deterioration of the wire. Epoxy resin does not show sufficient radiation resistance, and since it is expected that the amount of radiation generated will increase as the size of the accelerator increases in the future, adhesives that bond at low temperatures and have excellent radiation resistance Was required.

In order to solve this problem, a low temperature curing type adhesive can be used to prevent the deterioration of the wire. However, in this case, since the curing at room temperature also proceeds relatively quickly, the adhesive B stage It has a short life (shelf life) and cannot be used in the market as a laminated film.

From the above point of view, in view of the above situation, the development of a heat-fusible laminated film for coating a wire rod, which does not cause deterioration of the wire rod and has excellent flexibility and adhesiveness, is awaited. Was there.

[0008]

As a result of intensive studies to solve the above problems, the present inventors have found a heat-fusible laminated film for coating wire according to the present invention.

The gist of the heat-fusible laminated film for coating a superconducting wire according to the present invention is that a polyimide film and a fusible agent layer containing a thermoplastic resin as a main component are laminated.

In the heat-fusible laminated film for coating a superconducting wire according to the present invention, the thermoplastic resin is 22
Has a softening point of 0 ° C. or lower and has the general formula (1) 4

[Chemical 4] (In the formula, Ar ₁ , Ar ₂ , Ar ₄ and Ar ₆ are divalent organic groups, Ar ₃ and Ar
₅ represents a tetravalent organic group. In addition, l, m, and n are 0 or a positive integer of 1 or more, the sum of l and m is 1 or more, and t represents a positive integer of 1 or more. ) Is a polyimide resin represented by.

Further, the polyimide film is

[Chemical 5] And at least one or more acid dianhydride represented by

[Chemical 6] It consists in making at least 1 type or more diamine represented by.

[0012]

The heat-fusible laminated film for coating a wire according to the present invention comprises a polyimide film, in particular a predetermined polyimide film, and a fusing agent layer containing a thermoplastic resin as a main component, in particular a thermoplastic resin having a softening point of 220 ° C. or less. And a fusion agent layer containing as a main component are laminated. Therefore, after the laminated film is wound around the wire material with the adhesive layer inside, it is heated at a temperature exceeding the softening point of the adhesive layer. By heating at a temperature exceeding the softening point, the fusion agent layer of the heat-fusible laminated film for coating a wire melts and bonds to the wire. At that time, the heating temperature is a temperature exceeding the softening point of 220 ° C. or less, and the wire or the like is not significantly affected by the heating and is not deteriorated. in this way,
The heat-fusible laminated film for coating a wire according to the present invention is a polyimide film having excellent heat resistance, low temperature characteristics, chemical resistance, and electrical characteristics, has excellent flexibility and adhesiveness, and is fused at low temperatures. By laminating the fusing agent layers that can be formed, it is configured to have comprehensively excellent properties, and this is particularly suitable for coating superconducting wires and the like.

[0013]

EXAMPLES Next, examples of the wire-covered heat-fusible laminated film according to the present invention will be described together with the manufacturing method thereof.

The heat-fusible laminated film for coating a wire according to the present invention is formed by laminating a polyimide film and a fusing agent layer containing a thermoplastic resin as a main component. Of these, a predetermined polyimide resin having a softening point of 220 ° C. or lower is more preferably used as the thermoplastic resin. Therefore, a method for producing a predetermined polyimide resin which is a thermoplastic resin will be described.

First, in an atmosphere of an inert gas such as argon or nitrogen, the general formula (2) H ₂ N—Ar ₇ —NH ₂ (2) (in the formula, Ar ₇ represents a divalent organic group). The diamine represented by is dissolved or diffused in an organic solvent. In this solution, the compound of the general formula (3) 7

[Chemical 7] (In the formula, Ar ₈ represents a divalent organic group), or only the ester dianhydride represented by the formula (4)

[Chemical 8] (In the formula, Ar ₉ represents a tetravalent organic group.) A mixture with at least one kind of organic tetracarboxylic dianhydride represented by the following is added in the form of a solid or a solution prepared by dissolving it in an organic solvent, A polyamic acid solution which is a precursor of polyimide can be obtained.

Alternatively, another method for producing a polyamic acid solution is as follows: in an atmosphere of an inert gas such as argon or nitrogen,
General formula (5)

[Chemical 9] (In the formula, Ar ₁₀ represents a divalent organic group.) Only an ester diamine represented by the formula or a mixture of the ester diamine and at least one diamine represented by the general formula (2) is used as an organic solvent. Dissolve or diffuse in. In this solution, only the ester acid dianhydride represented by the above general formula (3), or at least one organic tetracarboxylic acid dianhydride represented by the above general formula (4), or these ester acid dianhydrides It is possible to obtain a polyamic acid solution, which is a precursor of polyimide, by adding a mixture of an organic tetracarboxylic acid dianhydride and a solid or an organic solvent in the form of a solution.

In this reaction, contrary to the above, first, an ester acid dianhydride represented by the general formula (3) or at least one organic tetracarboxylic dianhydride represented by the general formula (4) is used. Or a solution of a mixture of these ester acid dianhydrides and organic tetracarboxylic acid dianhydrides is prepared, and the diamine represented by the general formula (2) or the general formula (5) is added to the solution. Only the ester diamine represented, or this ester diamine and the general formula (2)
A solution or slurry of a mixture of at least one diamine represented by the above with a solid or organic solvent may be added.

The reaction temperature at this time is preferably -10 to 50 ° C, more preferably -5 ° C to 20 ° C. The reaction time is 30 minutes to 6 hours. By this reaction, the compound represented by the general formula (1)

[Chemical 10] (In the formula, Ar ₁ , Ar ₂ , Ar ₄ and Ar ₆ are divalent organic groups, A
r ₃ and Ar ₅ represent a tetravalent organic group. Further, l, m, and n are 0 or a positive integer of 1 or more, and the sum of l and m is 1.
Above, t represents a positive integer of 1 or more. The polyamic acid polymer which is the precursor of the polyimide resin which is the main component of the fusion agent layer represented by the above) is produced.

Examples of the organic solvent used in the reaction for producing the polyamic acid polymer solution include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, N, N-dimethylformamide, N, N-diethylformamide. Formamide solvent such as N, N-
Examples thereof include acetamide-based solvents such as dimethylacetamide and N, N-diethylacetamide. These may be used alone or as a mixed solvent of two or three or more. Further, it can be used as a mixed solvent with a non-solvent of polyamic acid such as acetone, methanol, ethanol, isopropanol, and benzenemethylcellosolve together with these polar solvents.

Next, in order to obtain a polyimide resin from a polyamic acid polymer solution which is a precursor of the polyimide resin, a method of thermally and / or chemically performing dehydration ring closure (imidization) may be used.

A method for dehydrating and ring-closing the polyamic acid polymer solution will be specifically described. First, in the method of thermally dehydrating and ring-closing, a solution of the above polyamic acid polymer is added to a supporting plate and PET.
An organic film, etc., or a support such as a drum or an endless belt is cast or coated to form a film, and then dried to obtain a film having self-supporting property. This drying is 10
It is preferable to carry out at a temperature of 0 ° C. or lower for about 5 to 90 minutes.
Next, this is further heated and dried to imidize to obtain a polyimide film made of the polyimide resin of the present invention. The heating temperature for imidization is preferably in the range of 100 to 350 ° C, particularly preferably 150 to 300 ° C. There is no limitation on the rate of temperature increase during heating, but it is preferable that the maximum temperature reaches the above temperature by gradually heating. The heating time depends on the film thickness and maximum temperature,
Generally, a range of 10 seconds to 30 minutes after reaching the maximum temperature is preferable. When the film having self-supporting properties is heated, it is preferable to peel it off from the support, fix the ends in this state and heat it, since a polyimide polymer having a small linear expansion coefficient can be obtained.

Further, in the method of chemically dehydrating and ring-closing, the same method as in the case of thermally dehydrating by adding a stoichiometric or more stoichiometric dehydrating agent and a catalytic amount of a tertiary amine to the solution of the polyamic acid polymer. To obtain the desired polyimide adhesive.

Comparing the thermal imidization method and the chemical imidization method, the chemical method has the advantage that the obtained polyimide has a higher mechanical strength and a smaller coefficient of linear expansion. . In addition, it is also possible to use the method of thermally imidizing and the method of chemically imidizing together. By such a method, the polyimide resin represented by the general formula (1) can be obtained. By thermocompression-bonding this polyimide resin to an insulating organic film such as a polyimide film made of another kind of polyimide resin, a heat-fusible laminated film for covering a wire having desired insulation properties can be obtained. Further, the above-mentioned polyamic acid polymer may be directly cast on an insulating material such as a polyimide film instead of the support to be imidized to obtain a target heat-fusible laminated film for coating a wire.

By the way, as the ester dianhydride represented by the above general formula (3) used in the present invention, ester dianhydrides having any structure can be used. In the general formula (3), Specific examples of the divalent organic group Ar ₈ group are shown below.

[Chemical 11] Can be mentioned.

As the organic tetracarboxylic dianhydride represented by the above general formula (4) used in the present invention, organic tetracarboxylic dianhydrides having any structure can be used. The Ar ₉ group in the general formula (4) is a tetravalent organic group, and specifically exemplifying this Ar ₉ group is

[Chemical 12] Can be mentioned. You may use these organic tetracarboxylic dianhydride individually or in combination of 2 or more types.

Further, as the ester diamine represented by the above general formula (5) used in the present invention, ester diamine having any structure can be used. The general formula (5) Ar ₁₀ groups in is a divalent organic group, specific examples of the Ar ₁₀ radical, of 13

[Chemical 13] Can be mentioned.

In addition, essentially any divalent organic group can be used as Ar ₇ in the diamine compound represented by the above general formula (2), and specifically, divalent aromatic groups can be used. The basic formula 14

[Chemical 14] Etc. can be mentioned.

Next, the number of repeating block units 1, m, and n in the polyimide resin represented by the general formula (1) is 0.
Alternatively, it may be a positive integer of 1 or more, and the sum of l and m may be 1 or more, but the number of repetitions l, m, and n is particularly preferably 15 or less. Because the number of repetitions l, m
This is because if the number of repetitions n exceeds 15 times the sum, the copolymerization ratio will be biased and the effect of polymerization will be small, and specifically, low temperature adhesiveness will be difficult to recognize. Further, there may be units having different values of l, m and n in one molecule of the polymer, but it is particularly preferable that the values of l, m and n are constant.

Further, the number t of repeating blocks of the polyimide resin represented by the general formula (1) may be a positive integer of 1 or more, and the molecular weight of the polyimide resin is not particularly limited, but is generated. In order to maintain the strength of the obtained polyimide resin, the number average molecular weight is preferably 10,000 or more.

By the way, it is often difficult to directly measure the molecular weight of the polyimide polymer. In such a case, an indirect method is used to make a speculative measurement. For example, when the polyimide polymer is synthesized from polyamic acid,
The value corresponding to the molecular weight of polyamic acid is the molecular weight of polyimide.

The above-obtained polyimide resin used in the present invention has both excellent low temperature adhesiveness and radiation resistance. That is, such a polyimide resin has a clear glass transition point between 100 ° C. and 220 ° C. depending on its composition, and can be directly adhered to a polyimide film or the like by laminating at a temperature close to the glass transition point. Further, it has been confirmed that the obtained polyimide resin exhibits excellent characteristics in radiation resistance. Therefore, by using the obtained polyimide resin having adhesiveness, the superconducting wire can be coated with the insulating coating material without impairing the characteristics of the superconducting wire.

Here, as the thermoplastic resin used in the present invention, a polyimide resin such as the above-mentioned adhesive polyimide resin, a polyamide resin, a polyester resin, a polyethylene resin, a butyral resin, a polyurethane resin, Various materials such as polyetherimide resins can be used alone or as a mixture of two or more, but a polyimide resin is preferably used from the viewpoint of property balance.
Of these, a polyimide resin having a softening point of 250 ° C. or lower, and more preferably 220 ° C. or lower is particularly preferable. When the heat-fusible laminated film for coating a wire according to the present invention is used for fusion bonding with a superconducting wire, the thermoplastic resin does not deteriorate the superconducting wire, so that its softening point is approximately 145 ° C or lower. Is preferred.

Further, it is essential that the fusion agent layer in the present invention contains the above-mentioned thermoplastic resin and has it as a main component, but in addition to this, it may contain other substances such as an inorganic filler. .

The fusing agent layer of the present invention is formed to have a thickness of 1 μm to 50 μm, preferably 5 μm to 20 μm. If the thickness of this fusion agent layer is thicker than this, not only there is a processing problem, such as the fusion agent layer protruding from the edge of the polyimide film during fusion, but it is possible to take full advantage of the excellent properties of the polyimide film. There is a characteristic problem that it is not possible. Further, if the thickness is smaller than this, sufficient adhesive force cannot be obtained.

On the other hand, the polyimide film used in the present invention contains various acid anhydride components such as pyromellitic dianhydride, biphenyltetracarboxylic dianhydride and benzophenonetetracarboxylic dianhydride. Polyamide acid obtained by polymerization reaction with various diamine components such as diamine, diaminodiphenyl ether, paraphenylenediamine, bis (aminophenoxyphenyl) propane, etc. is formed into a film in a solution state and then dehydrated and ring-closed. can get.

Further, a quasi-imide material such as polyamide-imide or polyether-imide can be used, and the polyimide film in the present invention is a concept including a film made of these. Further, polyimide is preferable, and especially polyimide film is

[Chemical 15] And at least one or more acid dianhydride represented by:

[Chemical 16] It is preferable that at least one diamine represented by

The thickness of the polyimide film is 5 to 150 μm.
It is possible to use a material having a thickness of about m, but practically 10
It is preferably about 125 μm, and more preferably about 10 to 75 μm when it is used for coating a wire. When the thickness of the polyimide film is thinner than this, not only is it difficult to form a laminate, but also the laminate film is easily broken during use. If the thickness is thicker than this, it becomes difficult to wind the wire.

The heat-fusible laminated film for coating a wire according to the present invention is formed by laminating a polyimide film and a fusing agent layer containing a thermoplastic resin as a main component. There are the following methods for obtaining the heat-fusible laminated film. That is, this fusing agent layer , a thermoplastic resin or the like dissolved in a solvent is applied on a polyimide film,
It is formed by drying.

In this forming method, when the thermoplastic resin or the like dissolved in a solvent is applied to a predetermined thickness and dried, the thickness of the fusion agent layer is set. For example, a polyamic acid solution that is a precursor of an adhesive polyimide resin can be cast on a polyimide film to imidize it to obtain a heat-fusible laminated film for coating a wire. Further, another method for forming the fusing agent layer can also be obtained by laminating a heat-fusible resin film, which is once formed into a film on a support, onto a polyimide film. More specifically, for example, a polyimide film, a polyimide resin having adhesiveness formed in a film shape,
Alternatively, the release paper can be peeled off after the release paper is overlaid and thermocompression-bonded to obtain a heat-fusible laminated film for wire coating.

The obtained heat-fusible laminated film for coating a wire according to the present invention is wound up as it is, or a film of polyethylene terephthalate, polypropylene, polyethylene or the like is fused to the heat-fusible laminated film for covering a wire. It is wound up by disposing it as a spacer on the agent layer side. The heat-fusible laminated film for coating a wire is appropriately formed into a predetermined width and used for coating the wire.

The coating of the heat-fusible laminated film for coating a wire onto the wire is usually carried out as follows. For example, as shown in FIG. 1, a wire-bonding heat-fusible laminated film 10 having a constant width is spirally wound around the outer periphery of the wire 12 so that both ends of the laminated film 10 overlap each other, and then heated to a predetermined temperature. The fusion agent layer 14 is melted and the polyimide film 16 is thermally fused to the wire 12. Further, as shown in FIG. 2, the heat-fusible laminated film 10 for coating a wire rod.
It is also possible to wind them so that both ends contact each other and do not overlap. Furthermore, as shown in FIG. 3, the width of the wire-bonding heat-fusible laminated film 10 is formed to be slightly longer than the outer circumference of the wire 12, so that the wire-bonding heat-fusible laminated film 10 is formed along the wire 12. You may wind it around. Although any of these methods may be used, it is most preferable to wind the wire-bonding heat-fusible laminated film 10 around the wire 12 by the method shown in FIG.

The wire coated with the heat-fusible laminated film for coating a wire according to the present invention may be a wire for superconductivity, or may be any wire such as a copper wire. In addition, the present invention can be carried out in a mode in which various improvements, modifications and variations are added based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the scope of the examples.

Example 1 In a 50 ml volumetric flask, 1.0 g of ethylene glycol bistrimellitic dianhydride (hereinafter referred to as TMEG) and dimethylformamide (hereinafter referred to as DM) were used.
It is called F. ) 10.0 g was taken and stirred by using a stirrer to be sufficiently dissolved. On the other hand, 500 with stirrer
2,2-bis (4-aminobenzyloxyphenyl) propane (hereinafter BABP
It is called P. ) 22.7 g and DMF 68.1 g are added,
The atmosphere in the flask was agitated while substituting with nitrogen to completely dissolve it. Next, 19.0 g of TMEG was sampled in a 100 ml eggplant-shaped flask and added to the BABPP solution in a solid state. Further, 21.5% of TMEG remaining adhered to the wall surface of the 100 ml eggplant flask was used.
Pour into a three neck flask with g DMF. After allowing to stand for about 1 hour while stirring, the TMEG solution in the 50 ml volumetric flask was gradually charged into the three-necked flask while paying attention to the viscosity of the solution in the three-necked flask.
After the maximum viscosity is reached, the TMEG solution addition is completed and 1
The mixture was left standing with stirring for a time to obtain a polyamic acid solution.

The film formation was performed as follows. First, 1
Isoquinoline 2.0 in a 00 ml volumetric flask
g and acetic anhydride 20.0 g were taken and stirred well. Next, this solution was added to the prepared polyamic acid solution and well stirred for 2 minutes. After degassing, apply on PET film,
After heating at 0 ° C. for 25 minutes, the PET film was peeled off. Then, the obtained polyamic acid film is treated with 150
The temperature was continuously raised from 200 ° C to 200 ° C, and after the temperature was raised, it was heated for 10 minutes for imidization to obtain a film-like polyimide resin having adhesiveness.

Further, a polyimide film (Apical (registered trademark), manufactured by Kanegafuchi Chemical Industry Co., Ltd.), a film of the obtained polyimide resin having adhesiveness, and a release paper are laminated in this order at 150 ° C. Lamination was performed at a speed of 2.2 cm / min to obtain a target heat-fusible laminated film for coating a wire. Further, after peeling the release paper from the heat-fusible laminated film for covering the wire material, a copper foil is placed thereon, and the temperature is 150 ° C.
Lamination was performed at a speed of 2 cm / min.

The glass transition point (° C.), peel strength (kg / cm) and water absorption (%) of the obtained film were examined.
The glass transition point is measured by TMA, and the peel strength is measured by JIS C 6481 (room temperature).
The water absorption rate was examined by ASTM D-570. The results are shown in Table 1. Furthermore, a radiation resistance test was performed by irradiation with 5 MGy using an electron beam of 2 MeV. As a result, there was no discoloration of the material and no deterioration of the material was observed.

[Table 1]

Example 2 A laminated film was obtained in the same manner as in Example 1 except that 13.3 g of 1,3-bis (4-aminophenoxy) -2,2-dimethylpropane was used instead of BABPP. .
The characteristics of the obtained laminated film were examined in the same manner as in Example 1. The results are shown in Table 1. Further, as a result of performing a radiation resistance test by irradiation with 5 MGy using an electron beam of 2 MeV as in Example 1, no discoloration of the material was observed and deterioration of the material was not recognized.

Comparative Example A laminated film was prepared in the same manner as in Example 1 except that an epoxy adhesive made of Epicoat 828 (trade name) manufactured by Yuka Shell Co., Ltd. was used instead of the polyimide resin having thermoplasticity (adhesiveness). Obtained. The characteristics of the obtained laminated film were examined in the same manner as in Example 1. The results are shown in Table 1.
Further, as in Example 1, 5M was obtained by using an electron beam of 2MeV.
As a result of the radiation resistance test by Gy irradiation, the laminated film turned black.

[0050]

As described above, the heat-fusible laminated film for coating a wire according to the present invention is a polyimide film excellent in various characteristics such as heat resistance, low temperature characteristics, chemical resistance, and electrical characteristics, and a thermoplastic resin. Since it is constituted by laminating a fusion agent layer containing as a main component, when coating a wire rod with such a wire-bonding heat-fusible laminated film, heating and melting are performed within a temperature range that hardly deteriorates the characteristics of the wire rod. Can be dressed. Therefore, the characteristics of the wire coated by the heat-fusible laminated film for wire coating according to the present invention, for example, when the wire is a superconducting wire, the film can be coated without impairing the superconducting characteristics. . Further, the wire-bonding heat-fusible laminated film according to the present invention is composed of a fusion-bonding agent layer containing a thermoplastic resin as a main component, so that it is distributed to the market as a laminated-film in which the fusion-bonding agent layer is laminated. Therefore, a manufacturer who coats the wire material can easily handle and work it, and the productivity is improved.

[0051] Further, as the thermoplastic resin, the general formula Re polyimide resin and its <br/> having adhesiveness of the formula (1) by using an insulating coating material and fusing agent layer, excellent low temperature Adhesiveness and radiation resistance can be realized.

[Brief description of drawings]

FIG. 1 is a perspective view for explaining a method for coating a wire with the heat-fusible laminated film for coating a wire according to the present invention.

FIG. 2 is a perspective view for explaining another method of coating a wire with the heat-fusible laminated film for coating a wire according to the present invention.

FIG. 3 is a perspective view for explaining still another method of coating the wire with the heat-fusible laminated film for coating a wire according to the present invention.

[Explanation of symbols]

10: Heat-fusible laminated film for coating wire 12; wire rod 14: Fusing agent layer 16; Polyimide film

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kosaku Nagano 2-1-2 Hiei Tsuji, Otsu City, Shiga Prefecture (56) References JP-A-2-272077 (JP, A) JP-A-4-202324 (JP, A) JP 2-142853 (JP, A) JP 63-117075 (JP, A) JP 60-235861 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) ) C09J 7/02 C08G 73/10 H01B 17/56 H01B 17/62

Claims (2)

(57) [Claims] And the polyimide film [1 claim], heat plasticity resin and fusing agent layer mainly composed Ri Na are laminated, the thermoplastic resin has a softening point of 220 ° C. or less, and the general formula (1 ) Chemical formula 1 (In the formula, Ar ₁ , Ar ₂ , Ar ₄ and Ar ₆ are divalent organic groups, Ar ₃ and Ar
₅ represents a tetravalent organic group. In addition, l, m, and n are 0 or a positive integer of 1 or more, the sum of l and m is 1 or more, and t represents a positive integer of 1 or more. ) A heat-fusible laminated film for coating a superconducting wire, which is a polyimide resin represented by 2. The polyimide film has the chemical formula: And at least one or more acid dianhydride represented by: The heat-fusible laminated film for coating a superconducting wire according to claim 1 , which comprises at least one diamine represented by