Method for manufacturing insulated wire and insulated wire

Abstract

To provide a method for manufacturing an insulated wire which achieves both heat resistance and low dielectric constant of an insulation film, and is also excellent in adhesion of the insulation film.SOLUTION: A method for manufacturing an insulated wire includes the steps of: preparing a conductor; coating a varnish containing a polyimide resin having a polycondensation unit of a tetracarboxylic acid dianhydride containing a pyromellitic acid anhydride and a 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, and diamine containing 4,4'-diaminodiphenyl ether and 2,2-bis[4-(4-aminophenoxy)phenyl]propane; and forming an insulation film. The ratio of the pyromellitic acid anhydride to the 3,3',4,4'-biphenyltetracarboxylic acid dianhydride is 50 mol:50 mol to 80 mol:20 mol. The ratio of the 4,4'-diaminodiphenyl ether to the 2,2-bis[4-(4-aminophenoxy)phenyl]propane is 80 mol:20 mol to 95 mol:5 mol.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for producing an insulated wire and an insulated wire. [Background technology]

[0002] Motors mounted on electronic devices and the like use windings. The windings have a conductor and an insulating coating disposed around the conductor, and are wound into a coil shape. The motor generates heat during use. Therefore, the windings used in motors are required to be flexible and heat resistant (see, for example, Patent Documents 1 and 2).

[0003] Patent Document 1 describes an insulated wire having a conductor and an insulating layer containing polyimide. The polyimide has a polycondensation unit containing tetracarboxylic acid including 3,3',4,4'-benzophenonetetracarboxylic anhydride and pyromellitic anhydride, and diamine including 4,4'-diaminodiphenyl ether.

[0004] Patent Document 2 describes an insulating coated electrical conductor having a conductor and an insulating coating layer containing a polyamide-imide resin. The polyamide-imide resin has a polycondensation unit containing trimellitic anhydride and diphenylmethane-4,4'-diisocyanate. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2018-45890 A [Patent Document 2] JP 2005-78934 A Summary of the Invention [Problem to be solved by the invention]

[0006] The insulated wire described in Patent Document 1 is said to have excellent flexibility and heat resistance, while the insulated electric conductor described in Patent Document 2 is said to have excellent heat resistance. However, there is room for improvement in heat resistance in the insulated wire of Patent Document 1 and the insulated coated electric conductor of Patent Document 2. In addition, since there is a trade-off between heat resistance and a low dielectric constant, the insulating layer in the insulated wire of Patent Document 1 and the insulating coating layer in the insulated coated electric conductor of Patent Document 2 need to maintain a balance between heat resistance and a low dielectric constant. Furthermore, in a high-temperature environment such as during TIG welding, the insulating layer or insulating coating layer may swell and peel off from the conductor.

[0007] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide an insulated wire and a method for producing the same, which achieves both heat resistance and a low dielectric constant for the insulating coating and also provides an insulated wire with excellent adhesion to the insulating coating. [Means for solving the problem]

[0008] In order to solve the above problem, according to one aspect of the present invention, A method for producing an insulated wire having a conductor and an insulating coating covering the conductor, comprising the steps of: providing the conductor; A step of applying a varnish containing a polyimide resin having polycondensation units of a tetracarboxylic dianhydride containing pyromellitic anhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride, and a diamine containing 4,4'-diaminodiphenyl ether and 2,2-bis[4-(4-aminophenoxy)phenyl]propane, around the conductor; baking the varnish applied to the conductor to form the insulating coating; Including, The ratio of the pyromellitic anhydride to the 3,3',4,4'-biphenyltetracarboxylic dianhydride is within a range of 50 mol:50 mol to 80 mol:20 mol, The ratio of the 4,4'-diaminodiphenyl ether to the 2,2-bis[4-(4-aminophenoxy)phenyl]propane is within a range of 80 mol:20 mol to 95 mol:5 mol. A method for making an insulated wire is provided.

[0009] According to another aspect of the present invention, An insulated wire having a conductor and an insulating coating covering the conductor, the insulating coating contains a polyimide resin having a polycondensation unit of a tetracarboxylic dianhydride, including pyromellitic anhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride, and a diamine, including 4,4'-diaminodiphenyl ether and 2,2-bis[4-(4-aminophenoxy)phenyl]propane; The ratio of the pyromellitic anhydride to the 3,3',4,4'-biphenyltetracarboxylic dianhydride is within a range of 50 mol:50 mol to 80 mol:20 mol, The ratio of the 4,4'-diaminodiphenyl ether to the 2,2-bis[4-(4-aminophenoxy)phenyl]propane is within a range of 80 mol:20 mol to 95 mol:5 mol. An insulated wire is provided. Effect of the Invention

[0010] According to the present invention, there are provided a method for producing an insulated wire in which an insulating coating has both good heat resistance and a low dielectric constant, and in which the insulating coating has excellent adhesion, and an insulated wire are provided. [Brief description of the drawings]

[0011] [Figure 1] 1A and 1B are cross-sectional views of an insulated wire according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a flowchart of a method for producing an insulated wire according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an insulated wire and a method for producing an insulated wire according to an embodiment of the present invention will be described with reference to the accompanying drawings. The insulated wire produced by the method for producing an insulated wire according to the embodiment of the present invention can be used, for example, as a winding for an in-vehicle motor. In this specification, the term "to" indicating a range of values ​​means that the upper and lower limits are included in the range.

[0013] (Insulated Wire Structure) 1A and 1B are schematic diagrams showing the configuration of an insulated wire.

[0014] As shown in FIGS. 1A and 1B, the insulated wire 1 has a conductor 3 and an insulating coating 5. The conductor 3 is the same as that in a conventional insulated wire, and is preferably a copper wire. The copper in the copper wire may be a tough pitch material, but is preferably low-oxygen copper having an oxygen content of 30 ppm or less, more preferably low-oxygen copper or oxygen-free copper having an oxygen content of 20 ppm or less, and particularly preferably oxygen-free copper having an oxygen content of 10 ppm or less (MiDIP (registered trademark); SWCC Corporation). When the copper is low-oxygen copper or oxygen-free copper, voids that cause electrical resistance are unlikely to occur when the conductors 3 of multiple insulated wires 1 are welded together. The conductor 3 may be an aluminum wire or an aluminum alloy wire. When a high current value is required for the insulated wire 1, the conductor 3 is preferably made of pure aluminum with a purity of, for example, 99.00% or more.

[0015] The cross-sectional shape of the conductor 3 is not particularly limited and is appropriately selected depending on the application. As shown in FIG. 1A, the cross-section of the conductor 3 may be circular, and as shown in FIG. 1B, the cross-section of the conductor 3 may be rectangular. The cross-sectional shape of the conductor 3 may be other than these shapes, for example, hexagonal. When the cross-section is rectangular, it is preferable that the corners are chamfered. The size of the cross-section of the conductor 3 is appropriately selected depending on the application. When the cross-section is circular, the diameter is usually within the range of 0.3 mm to 3 mm. When the cross-section is rectangular, the long side is usually within the range of 1 mm to 8 mm, and the short side is usually within the range of 0.4 mm to 3 mm.

[0016] The insulating coating 5 is a layer that covers the conductor 3 and is disposed around the conductor 3. The insulating coating 5 contains a polyimide resin. The insulating coating 5 is a film obtained by applying and baking a varnish, which will be described in the manufacturing method described later, i.e., a cured varnish film. The polyimide resin has a polycondensation unit of a tetracarboxylic dianhydride and a diamine.

[0017] The tetracarboxylic acid includes pyromellitic anhydride (PMDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA). The ratio of PMDA to BPDA is within the range of 50 mol:50 mol to 80 mol:20 mol.

[0018] If the ratio of PMDA to BPDA is within the above range, the flexibility and heat resistance can be improved and the occurrence of delamination can be suppressed. Specifically, when PMDA is 50 moles or more, the flexibility and heat resistance are excellent. When BPDA is 20 moles or more, the adhesion between the layers constituting the insulating coating 5 (interlayer adhesion) is high, so that delamination is suppressed. On the other hand, when BPDA is more than 50 moles, the adhesion between the conductor 3 and the insulating coating 5 is high, so that there is a risk of so-called co-cracks occurring, in which cracks occur in the insulating coating 5 and the conductor 3 also crack.

[0019] The diamine includes 4,4'-diaminodiphenyl ether (DDE) and 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP). The ratio of DDE to BAPP is within the range of 80 mol:20 mol to 95 mol:5 mol, and preferably within the range of 90 mol:10 mol to 95 mol:5 mol. If the amount of 4,4'-diaminodiphenyl ether (DDE) increases too much, the heat resistance improves but the dielectric constant increases. If the amount of 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) increases, the heat resistance decreases but the dielectric constant decreases.

[0020] Insulation coating 5 may contain components other than polyimide resin as necessary. Examples of components other than polyimide resin include an adhesion improver.

[0021] The insulated wire 1 preferably has, for example, the following characteristics.

[0022] The dielectric constant of the insulating coating 5 is preferably within the range of 3.0 to 3.3. If the dielectric constant of the insulating coating 5 is within the above range, the insulation properties can be adequately ensured. The dielectric constant of the insulating coating 5 can be measured, for example, by the following method. Silver is pasted on both ends of the insulated electric wire 1 from which the insulating coating 5 has been removed, to create two measurement electrodes and two guard electrodes. Then, the electrostatic capacitance between the conductor 3 and the measurement electrodes is measured with an LCR meter, and the dielectric constant εr is calculated from the following formula. (Formula)εr=(C / 2Πε0L)×ln(R2 / R1) Here, C represents the capacitance, ε0 represents the dielectric constant of a vacuum, L represents the distance between the measurement electrodes, R1 represents the outer diameter of the conductor, and R2 represents the outer diameter of the insulated wire.

[0023] The elastic modulus of the insulating film 5 at 325°C is preferably 0.7 GPa or more, more preferably 1.0 GPa or more. If the elastic modulus of the insulating film 5 at 325°C is less than 0.7 GPa, the insulating film may crack if it is exposed to a high temperature environment for a long time in a bent state. The elastic modulus of the insulating film 5 at 325°C can be measured, for example, by the following method. First, an insulating film piece with a width of 0.9 mm, a length of 60 mm, and a thickness of 0.09 mm is prepared. A viscoelasticity measuring device DSM6100 (Seiko Instruments Inc.) is used for the measurement. In addition, the strain amplitude is 5 μm and the frequency is 1.0 Hz. The temperature conditions are that the temperature is raised from 23°C to 500°C at a rate of 10°C / min, and the elastic modulus calculated based on the stress and strain at 325°C is the elastic modulus of the insulating film 5.

[0024] The insulated wire 1 preferably has rapid extensibility. The rapid extensibility can be examined, for example, by the following method. After the gauge length of the insulated wire 1 having a length of 35 cm is set to 200 to 250 mm, the wire is rapidly elongated to breakage or to a specified value. The test is performed using a rapid elongation tester or a device capable of elongation at a tensile speed of 4 m / sec, and then the presence or absence of cracks and lifting of the insulating coating 5 is examined. However, the area up to 2 mm from the breaking point is not examined. If there are no cracks or lifting of the insulating coating 5, it is understood that the adhesion of the insulating coating 5 to the conductor 3 is high.

[0025] The insulated wire 1 preferably has peel twisting property. In this embodiment, the peel twisting property may be 45 times or more. The peel twisting property can be examined, for example, by the following method. For each of three 35 cm insulated wires 1, the insulating coating 5 is removed from one end of the insulated wire 1, and the wire is twisted until the insulating coating 5 peels off, and the number of twists is recorded. It can be seen that the greater the number of twists, the higher the adhesion of the insulating coating 5 to the conductor 3.

[0026] The insulating coating 5 of the insulated wire 1 is preferably softening-resistant. In this embodiment, the softening resistance is preferably 460°C or higher. The softening resistance can be examined, for example, by the following method. Two insulated wires 1 are arranged so as to be perpendicular to each other, and 0.7 kg is placed on the intersection, and then the wires are placed in a thermostatic chamber to measure the softening resistance temperature. In the test, an AC voltage of 100V having a waveform close to a sine wave of 50 or 60Hz is applied to the conductor, and the temperature is raised in this state at a rate of about 2°C per minute to measure the temperature at which the wire shorts out. The short-circuit current sensitivity is 5 to 20mA.

[0027] The insulated wire 1 preferably has a wet heat BDV (breakdown voltage) property. In this embodiment, the wet heat BDV property is preferably a retention rate of 80% or more. The wet heat BDV property can be examined, for example, by the following method. The wet heat BDV property is evaluated by measuring the BDV of a two-ply insulated wire at room temperature and using the BDV (initial value). After dropping 0.2 wt % of water into a test tube, the two-ply insulated wire is placed in the test tube and sealed. The test tube is left in a thermostatic chamber at 180° C. for 120 hours, and the BDV (after wet heat) of the insulated wire is then measured. The retention rate can be calculated by the following formula. The evaluation criteria are as follows. Retention rate (%) = (BDV (after moist heat) / BDV (initial value)) x 100

[0028] (Insulated Wire Manufacturing Method) Next, a method for producing the insulated wire 1 will be described.

[0029] The method for producing insulated wire 1 includes a step of preparing conductor 3 (S110), a step of annealing conductor 3 (S120), a step of applying varnish (S130), and a step of baking the varnish (S140).

[0030] In the step (S110) of preparing the conductor 3, the above-mentioned conductor 3 is prepared. The conductor 3 may be one manufactured by any known method, and may be one adjusted to a desired shape and size by wire drawing.

[0031] In the step (S120) of annealing the conductor 3, the conductor 3 obtained by wire drawing is annealed in a steam bright furnace at 500° C. for 10 to 30 seconds.

[0032] In the step (S130) of applying varnish, varnish is applied around the conductor 3. The varnish contains a polyimide resin and a solvent. Examples of the solvent include aprotic polar organic solvents such as N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, and γ-butyrolactone. The solvent may be one type or two or more types. There is no particular limitation on the method of preparing the varnish, and a varnish containing pyromellitic anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, and a solvent is prepared. The ratio of pyromellitic anhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride in the polycondensation unit of the polyimide resin is within the range of 50 mol:50 mol to 80 mol:20 mol, and the ratio of 4,4'-diaminodiphenyl ether and 2,2-bis[4-(4-aminophenoxy)phenyl]propane in the diamine is within the range of 80 mol:20 mol to 95 mol:5 mol. In this case, it is preferable to perform stirring or dispersion so that the solvent is uniformly dispersed. The varnish can be applied by a known method. An example of the method of applying the varnish includes a method in which the conductor 3 is inserted into a die having an opening slightly larger than the cross section of the conductor 3 and having a shape approximately similar to the cross section of the conductor 3, and the varnish is applied in the die while the conductor 3 is moved in one direction.

[0033] In the step of baking the varnish (S140), the varnish is applied and then baked. The baking of the varnish can be performed by a known method, and may be performed by heating in a vertical furnace or a horizontal furnace. The baking temperature is appropriately selected according to the resin in the varnish, and may be a temperature at which the solvent in the varnish can be removed. The baking time is appropriately selected according to the type of resin and the amount of solvent in the varnish. The thickness of the film formed by one application and baking of the varnish is preferably within a range of 1 μm to 6 μm, and the insulating film 5 is preferably formed by applying and baking the varnish multiple times (for example, 10 times or more) until the desired thickness is reached.

[0034] (effect) As described above, in the insulated wire of the present embodiment, an insulating coating is formed using a polyimide resin containing polycondensation units in which pyromellitic anhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-diaminodiphenyl ether and 2,2-bis[4-(4-aminophenoxy)phenyl]propane are each within a specified range, and therefore the insulating film can achieve both heat resistance, low dielectric constant and adhesion. EXAMPLES

[0035] The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited by these examples, and the embodiments can be modified without departing from the spirit of the present invention.

[0036] [Insulated wire manufacturing] (Insulated Wire 1) As the conductor, a round wire conductor (oxygen-free copper, MiDIP (registered trademark); SWCC Corporation) having a circular cross-sectional shape (diameter: about 1.0 mm) was prepared. Into a flask equipped with a stirrer, a nitrogen inlet pipe, and a heating and cooling device, pyromellitic anhydride (PMDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) were placed as tetracarboxylic acids, 4,4'-diaminodiphenyl ether (DDE) and 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) were placed as diamines, and N-methyl-2-pyrrolidone was placed as a solvent. The mixture was allowed to react for 2 hours with stirring under a nitrogen atmosphere to obtain a varnish. The tetracarboxylic acid contained 60 moles of pyromellitic anhydride (PMDA) and 40 moles of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA). The diamine contained 95 moles of 4,4'-diaminodiphenyl ether (DDE) and 5 moles of 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP). The amounts of the tetracarboxylic acid and diamine added were each 1.00 mole. The amount of the solvent added was 400 parts by mass relative to 100 parts by mass of the total of the tetracarboxylic acid and diamine. The conductor was inserted into a die for applying varnish, and while the conductor was moved in one direction, varnish was applied inside the die and baked at 400° C. The application of varnish and baking were repeated 10 to 15 times to obtain an insulated wire 1 having an insulating coating having a thickness of 34 μm (0.034 mm).

[0037] (Insulated Wire 2) An insulated wire 2 was obtained in the same manner as in the production of the insulated wire 1, except that the amount of 4,4'-diaminodiphenyl ether (DDE) was 90 mol and the amount of 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) was 10 mol.

[0038] (Insulated Wire 3) An insulated wire 3 was obtained in the same manner as in the production of the insulated wire 1, except that the amount of 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) was 20 mol and the amount of 4,4'-diaminodiphenyl ether (DDE) was 80 mol.

[0039] (Insulated Wire 4) An insulated wire 4 was obtained in the same manner as in the production of the insulated wire 1, except that the amount of 4,4'-diaminodiphenyl ether (DDE) was 60 mol and the amount of 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) was 40 mol.

[0040] [evaluation] (Evaluation of adhesion (rapid elongation)) To evaluate rapid extensibility, first, 35 cm long insulated electric wires 1 to 4 were stretched at a tensile speed of 4 m / s until breakage, with the gauge length (area to check for lifting) set to 200 mm. After stretching, the presence or absence of lifting of the insulation coating was checked. However, the area up to 2 mm from the breaking point was not included. The test was performed on three insulated electric wires, and the presence or absence of lifting of the insulation coating was checked and evaluated according to the following criteria. Evaluation criteria Good: Not a single piece had any insulating film peeling off. Poor: One or more insulated wires are loose.

[0041] (Evaluation of Adhesion (Peel Twisting)) The peel twistability was evaluated by peeling off the insulating coating 5 at one end of each of three 35 cm insulated electric wires 1 with a cutter, twisting the wire until the insulating coating 5 peeled off, and recording the number of twists. The evaluation criteria were as follows: Evaluation criteria Pass: 45 or more twists Fail: Less than 45 twists

[0042] (Evaluation of softening resistance) To evaluate the softening resistance, two insulated electric wires 1 to 4 were arranged so that they crossed each other at right angles, and 0.7 kg was placed on the intersection point. The wires were then placed in a thermostatic chamber to measure the softening resistance temperature. In the test, an AC voltage of 100 V with a waveform close to a sine wave of 50 or 60 Hz was applied between the two conductors, and the temperature was raised at a rate of about 2°C per minute under this condition, and the temperature at which the wires shorted was measured. The short circuit current sensitivity was 5 to 20 mA. The evaluation criteria were as follows: Evaluation criteria Pass: 460℃ or higher Fail: Less than 460℃

[0043] (Evaluation of humidity and heat BDV properties) The wet heat BDV property was evaluated by measuring the BDV of the two-ply insulated electric wires 1 to 4 at room temperature, and this was taken as the BDV (initial value). After 0.2 wt% water was dropped into a test tube, the two-ply insulated electric wires 1 to 4 were placed in the test tube and sealed. The test tube was left in a thermostatic chamber at 180°C for 120 hours, after which the BDV (after wet heat) of the insulated electric wires 1 to 4 was measured. The remaining percentage was calculated using the following formula. The evaluation criteria were as follows: Retention rate (%) = (BDV (after moist heat) / BDV (initial value)) x 100 Retention rate evaluation criteria Pass: Remaining rate 80% or more Failed: Less than 80% remaining

[0044] (Evaluation of dielectric constant) The dielectric constant was evaluated by pasting silver on both ends of the insulated electric wires 1 to 4 from which the insulating film had been removed to prepare a measurement electrode and a guard electrode. The capacitance of the conductor 3 and the measurement electrode was then measured with an LCR meter, and the dielectric constant (εr) was calculated from the following formula and evaluated according to the following criteria. (Formula)εr=(C / 2Πε0L)×ln(R2 / R1) Here, C represents the capacitance, ε0 represents the dielectric constant of a vacuum, L represents the distance between the measurement electrodes, R1 represents the outer diameter of the conductor, and R2 represents the outer diameter of the insulated wire. Evaluation criteria Pass: Dielectric constant is 3.0~3.3 Fail: Dielectric constant less than 3.0 or greater than 3.3

[0045] (Evaluation of elastic modulus) To evaluate the elastic modulus, first, an insulating film piece with a width of 0.9 mm, a length of 60 mm, and a thickness of 0.09 mm was prepared. A viscoelasticity measuring device (DMS; Seiko Instruments Inc.) was used. The strain amplitude was 5 μm and the frequency was 1.0 Hz. The temperature was raised from 23°C to 500°C at a rate of 10°C / min, and the elastic modulus calculated from the stress and strain at 325°C was taken as the elastic modulus of the insulating film, and it was evaluated according to the following criteria. Pass: 0.7GPa or higher Fail: Less than 0.7GPa

[0046] Table 1 shows the insulated wire numbers, the sizes of the insulated wires, and the evaluation results.

[0047] [Table 1]

[0048] As shown in Table 1, insulated wires 1 to 3, in which the ratio of 4,4'-diaminodiphenyl ether (DDE) to 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) was within the range of 80 mol:20 mol to 95 mol:5 mol, had good heat resistance, adhesion and dielectric constant. This is thought to be due to the appropriate ratio of 4,4'-diaminodiphenyl ether (DDE) and 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP). In addition, insulated wires 1 and 2 in which the ratio of 4,4'-diaminodiphenyl ether (DDE) to 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) was within the range of 90 mol:10 mol to 95 mol:5 mol, showed particularly good heat resistance, adhesion and dielectric constant.

[0049] On the other hand, as shown in Table 1, insulated wire 4, in which the ratio of 4,4'-diaminodiphenyl ether (DDE) to 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) was 60 mol:40 mol, had poor heat resistance, adhesion and dielectric constant. [Industrial Applicability]

[0050] The insulated wire obtained by the present invention is useful, for example, for windings of vehicle motors. [Explanation of symbols]

[0051] 1. Insulated wire 3 Conductors 5. Insulation film

Claims

1. A method for producing an insulated wire having a conductor and an insulating coating covering the conductor, comprising the steps of: providing the conductor; A step of applying a varnish containing a polyimide resin having polycondensation units of a tetracarboxylic dianhydride containing pyromellitic anhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride, and a diamine containing 4,4'-diaminodiphenyl ether and 2,2-bis[4-(4-aminophenoxy)phenyl]propane, around the conductor; baking the varnish applied to the conductor to form the insulating coating; Including, The ratio of the pyromellitic anhydride to the 3,3',4,4'-biphenyltetracarboxylic dianhydride is within a range of 50 mol:50 mol to 80 mol:20 mol; The ratio of the 4,4'-diaminodiphenyl ether to the 2,2-bis[4-(4-aminophenoxy)phenyl]propane is within the range of 80 mol:20 mol to 95 mol:5 mol. A method for manufacturing insulated electric wire.

2. The method for producing an insulated wire according to claim 1, The ratio of the 4,4'-diaminodiphenyl ether to the 2,2-bis[4-(4-aminophenoxy)phenyl]propane is within a range of 90 mol:10 mol to 95 mol:5 mol. A method for manufacturing insulated electric wire.

3. An insulated wire having a conductor and an insulating coating covering the conductor, the insulating coating contains a polyimide resin having polycondensation units of tetracarboxylic dianhydrides, including pyromellitic anhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride, and diamines, including 4,4'-diaminodiphenyl ether and 2,2-bis[4-(4-aminophenoxy)phenyl]propane; The ratio of the pyromellitic anhydride to the 3,3',4,4'-biphenyltetracarboxylic dianhydride is within a range of 50 mol:50 mol to 80 mol:20 mol; The ratio of the 4,4'-diaminodiphenyl ether to the 2,2-bis[4-(4-aminophenoxy)phenyl]propane is within the range of 80 mol:20 mol to 95 mol:5 mol. Insulated wire.

4. The insulated wire according to claim 3, The ratio of the 4,4'-diaminodiphenyl ether to the 2,2-bis[4-(4-aminophenoxy)phenyl]propane is within a range of 90 mol:10 mol to 95 mol:5 mol. Insulated wire.

5. The insulated wire according to claim 4, The dielectric constant of the insulating coating is 3.0 to 3.

3. Insulated wire.

6. The insulated wire according to claim 5 , The elastic modulus of the insulating coating at 325°C is 0.7 GPa or more. Insulated wire.

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