Electromagnetic wire and coil

Abstract

An electromagnetic wire is provided, which has a conductor and an insulating coating formed on the periphery of the conductor, wherein the insulating coating contains a copolymer comprising tetrafluoroethylene units and fluoroalkyl vinyl ether units, the melt flow rate of the copolymer is 10 g / 10 min to 60 g / 10 min, and the content of fluoroalkyl vinyl ether units in the copolymer is 6.2% by mass to 8.0% by mass relative to all monomer units.

Description

Technical Field

[0001] This invention relates to electromagnetic wires and coils. Background Technology

[0002] Previously, enameled wires were known as electromagnetic wires, which were obtained by baking resins such as polyesterimide resin, polyamideimide resin, and polyimide resin onto a conductor.

[0003] For example, Patent Document 1 describes a heat-resistant flat insulated wire, which is obtained as follows: a polyisocyanate block block blocked by polyesterimide resin and phenolic compound is added to a polyetherimide resin having a specific structure, and the block block is dissolved in an organic solvent to form an insulating coating. The insulating coating is then applied to a conductor, baked, and calendered into a flat shape, thereby obtaining the aforementioned heat-resistant flat insulated wire.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 62-58519 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] The purpose of this invention is to provide an electromagnetic wire with an attractive appearance and uniform thickness of insulation coating, which is not prone to expansion and cracking.

[0009] Methods for solving problems

[0010] According to the present invention, an electromagnetic wire is provided, which is an electromagnetic wire having a conductor and an insulating coating formed on the outer periphery of the conductor, wherein the insulating coating contains a copolymer comprising tetrafluoroethylene units and fluoroalkyl vinyl ether units, the melt flow rate of the copolymer being 10 g / 10 min to 60 g / 10 min, and the content of fluoroalkyl vinyl ether units in the copolymer being 6.2% by mass to 8.0% by mass relative to all monomer units.

[0011] The electromagnetic wire of the present invention is preferably a flat electromagnetic wire having a flat conductor and an insulating coating formed on the outer periphery of the flat conductor.

[0012] The aforementioned insulation coating is preferably a cross-linked insulation coating.

[0013] The aforementioned insulating coating is preferably an insulating coating that has been irradiated with radiation.

[0014] The aforementioned insulation coating is preferably an insulation coating that has been irradiated with radiation doses of 20 kGy or more but less than 100 kGy at an irradiation temperature of 160°C to 280°C.

[0015] The copolymers described above preferably have functional groups, and the number of functional groups in the copolymers relative to each 10 6 There are 5 to 1000 carbon atoms in a single carbon atom.

[0016] The thickness of the above-mentioned insulating coating is preferably 30μm to 100μm.

[0017] In addition, according to the present invention, a coil is provided which has the above-described electromagnetic wire.

[0018] The effects of the invention

[0019] According to the present invention, an electromagnetic wire can be provided having an attractive appearance and a uniformly thick insulating coating that is not prone to expansion or cracking. Furthermore, according to the present invention, a flat electromagnetic wire can be provided having an attractive appearance and a uniformly thick insulating coating that, even when bent along a flattened direction, is not prone to expansion or cracking of the insulating coating on the outer periphery of the bend. Attached Figure Description

[0020] Figure 1 This is a cross-sectional view showing an example of a flat electromagnetic wire.

[0021] Figure 2 This is a schematic diagram of the bending fixture used in the flat bending process test. Detailed Implementation

[0022] The specific embodiments of the present invention will be described in detail below, but the present invention is not limited to the following embodiments.

[0023] The electromagnetic wire of the present invention is a wire used to carry current when electrical energy and magnetic energy are converted into each other in an electrical device. The electromagnetic wire of the present invention can be an electromagnetic wire (round wire) having a circular conductor with a substantially circular cross-section and an insulating coating formed on the outer periphery of the circular conductor, or it can be a flat electromagnetic wire having a flat conductor and an insulating coating formed on the outer periphery of the flat conductor. Compared with a round wire, a flat electromagnetic wire can increase the duty cycle of the coil. Hereinafter, a flat electromagnetic wire as an embodiment of the present invention will be described.

[0024] Figure 1 This is a cross-sectional view showing an example of a flat electromagnetic wire. (As shown) Figure 1 As shown, a flat electromagnetic wire 1 according to one embodiment of the present invention includes a flat conductor 10 and an insulating coating 11 formed on the outer periphery of the flat conductor.

[0025] As for the flat conductor 10, there are no particular limitations as long as it is made of a conductive material. It can be made of materials such as copper, copper alloy, aluminum, aluminum alloy, iron, silver, nickel, etc., but copper or copper alloy is preferred. Alternatively, conductors that have been plated with silver, nickel, or other platings can also be used.

[0026] The shape of a flat conductor is not particularly limited as long as its cross-section is approximately rectangular. The corners of the cross-section of a flat conductor can be right angles or rounded. In addition, as long as the entire cross-section of the flat conductor is approximately rectangular, it can also be a single wire, a bundled wire, a stranded wire, etc., with a single wire being preferred.

[0027] The width of the flat conductor cross-section can range from 1 mm to 75 mm, and the thickness can range from 0.1 mm to 10 mm. In addition, the width-to-thickness ratio can exceed 1 and be less than 30.

[0028] The insulating coating 11 formed on the outer periphery of the flat conductor 10 is formed of a copolymer containing tetrafluoroethylene units and fluoroalkyl vinyl ether units. The copolymer has a melt flow rate of 10 g / 10 min to 60 g / 10 min and the content of fluoroalkyl vinyl ether units in the copolymer is 6.2% to 8.0% by mass relative to all monomer units.

[0029] In the fields of electrical and electronic equipment, there is a growing trend towards higher performance, smaller size, and greater energy efficiency. This necessitates miniaturization and higher performance in coils, inductors, and various motors. Miniaturization is particularly evident in automotive inductors and motors, where compact winding of flat electromagnetic wires is driving miniaturization. However, in electric vehicle motors, there is a tendency to increase the operating voltage from around 400V to around 1000V for the purpose of miniaturization and higher performance. Therefore, when using existing flat electromagnetic wires such as enameled wire, partial discharge can occur between the windings, potentially leading to insulation breakdown. The flat electromagnetic wire of this embodiment, with its insulation coating formed from the aforementioned copolymer, is less prone to partial discharge even at high motor operating voltages.

[0030] Furthermore, flat-coil coils are formed by bending and longitudinally winding flat electromagnetic wire along the flat direction (the width direction of the flat electromagnetic wire). Flat-coil coils offer advantages in miniaturization and efficiency due to the high duty cycle of the conductor. However, when bending the flat electromagnetic wire along the flat direction, the insulation coating covering the outer periphery of the bend stretches more than the insulation coating covering the inner periphery of the bend, making it prone to peeling off from the flat conductor and causing expansion or cracking. Expansion or cracking reduces insulation properties. For example, in enameled wire where polyimide resin is baked onto the conductor, cracking or expansion sometimes occurs at the outer periphery of the bend. In this embodiment, because the insulation coating of the flat electromagnetic wire is formed from the aforementioned copolymer, even when bent along the flat direction, the insulation coating covering the outer periphery of the bend is less prone to expansion and cracking.

[0031] Furthermore, since the insulation coating of the flat electromagnetic wire of this embodiment is formed from the aforementioned copolymer, the insulation coating of the flat electromagnetic wire of this embodiment does not suffer from defects such as melt cracking, foaming, or whitening that may occur during molding or radiation exposure. In addition, the thickness of the insulation coating is also uniform. Therefore, the flat electromagnetic wire of this embodiment has an attractive appearance.

[0032] The melt flow rate of the copolymer is 10 g / 10 min to 60 g / 10 min, preferably 15 g / 10 min or more, more preferably 25 g / 10 min or more, further preferably 30 g / 10 min or more, preferably 50 g / 10 min or less, and more preferably 40 g / 10 min or less. By keeping the melt flow rate of the copolymer within the above range, a flat electromagnetic wire with a uniformly thick insulating coating can be obtained. Furthermore, a flat electromagnetic wire with an insulating coating that exhibits excellent stress crack resistance even with a small thickness and is less prone to expansion and cracking can be obtained.

[0033] Furthermore, the melt flow rate of the copolymer when the thickness of the insulating coating is 60 μm to 100 μm is preferably 15 g / 10 min or more, more preferably 25 g / 10 min or more, even more preferably 30 g / 10 min or more, and preferably 40 g / 10 min or less. By keeping the melt flow rate of the copolymer within the above range, a flat electromagnetic wire with a uniformly thick insulating coating can be obtained. Additionally, a flat electromagnetic wire with an insulating coating exhibiting excellent stress crack resistance and being less prone to expansion and cracking can be obtained.

[0034] Furthermore, for copolymers with an insulating coating thickness of 30 μm or more and less than 60 μm, the melt flow rate is preferably more than 40 g / 10 min, more preferably 45 g / 10 min or more, even more preferably 50 g / 10 min or more, preferably 60 g / 10 min or less, and more preferably 55 g / 10 min or less. By keeping the melt flow rate of the copolymer within the above range, a flat electromagnetic wire with a uniformly thick insulating coating can be obtained. Additionally, a flat electromagnetic wire with an insulating coating exhibiting excellent stress crack resistance and being less prone to expansion and cracking can be obtained.

[0035] In this invention, the melt flow rate is obtained as follows: according to ASTM D1238, using a melt flow index tester (manufactured by Yasuda Seiki Co., Ltd.), in the form of the mass (g / 10 min) of polymer flowing out of a nozzle with an inner diameter of 2.1 mm and a length of 8 mm every 10 minutes under a load of 5 kg at 372 °C.

[0036] The content of fluoroalkyl vinyl ether (FAVE) units in the copolymer is 6.2% to 8.0% by mass, preferably 6.5% by mass or more, and more preferably 7.5% by mass or less, relative to all monomer units. By keeping the content of FAVE units in the copolymer within the above range, a flat electromagnetic wire with a uniform insulation coating can be obtained. Furthermore, a flat electromagnetic wire with an insulation coating that exhibits excellent stress crack resistance even with a small thickness and is not prone to expansion and cracking can be obtained.

[0037] The content of tetrafluoroethylene (TFE) units in the copolymer is preferably 82.0% to 93.8% by mass, more preferably 92.0% by mass or more, further preferably 92.5% by mass or more, particularly preferably 93.0% by mass or more, more preferably 93.8% by mass or less, further preferably 93.5% by mass or less, and particularly preferably 93.2% by mass or less, relative to all monomer units. By keeping the content of TFE units in the copolymer within the above range, a flat electromagnetic wire with a uniform insulation coating can be obtained. Furthermore, a flat electromagnetic wire with an insulation coating that exhibits excellent stress crack resistance even with a small thickness and is less prone to expansion and cracking can be obtained.

[0038] In this invention, the content of each monomer unit in the copolymer is determined by... 19 The determination was performed using F-NMR.

[0039] The copolymer that forms the insulating coating is a melt-processable fluoropolymer. Melt processability means that the polymer can be melted and processed using existing processing equipment such as extruders and injection molding machines.

[0040] As a FAVE constituting the above-mentioned FAVE unit, at least one of the groups consisting of the monomers shown in general formula (1) and the monomers shown in general formula (2) can be cited.

[0041] CF2 = CFO(CF2CFY) 1 O) p -(CF2CF2CF2O) q -Rf (1)

[0042] (where Y) 1 (This indicates F or CF3, Rf indicates a perfluoroalkyl group with 1 to 5 carbon atoms. p represents an integer from 0 to 5, q represents an integer from 0 to 5.)

[0043] CFX = CXOCF2OR 1 (2)

[0044] (In the formula, X being the same or different represents H, F, or CF3, R) 1 This refers to a straight-chain or branched fluoroalkyl group having 1 to 6 carbon atoms, containing or not containing 1 to 2 atoms selected from the group consisting of H, Cl, Br, and I; or a cyclic fluoroalkyl group having 5 or 6 carbon atoms, containing or not containing 1 to 2 atoms selected from the group consisting of H, Cl, Br, and I.

[0045] Among them, the monomer represented by general formula (1) is preferred as the FAVE, more preferably at least one of the group consisting of perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether) (PEVE) and perfluoro(propyl vinyl ether) (PPVE), further preferably at least one of the group consisting of PEVE and PPVE, and particularly preferably PPVE.

[0046] The copolymer may also contain monomer units from monomers capable of copolymerizing with TFE and FAVE. In this case, the content of monomers capable of copolymerizing with TFE and FAVE is preferably 0 to 10% by mass, more preferably 0.1% to 1.8% by mass, relative to all monomer units of the copolymer.

[0047] Monomers capable of copolymerizing with TFE and FAVE include hexafluoropropylene (HFP) and CZ. 1 Z 2 =CZ 3 (CF2) n Z 4 (where Z) 1 Z 2 and Z 3 Same or different, represented by H or F, Z 4Vinyl monomers (represented by H, F, or Cl, where n represents an integer from 2 to 10) and CF2=CF-OCH2-Rf 1 (where Rf) 1 Alkyl perfluorovinyl ether derivatives (representing perfluoroalkyl groups with 1 to 5 carbon atoms) are preferred.

[0048] As a copolymer, it is preferably selected from at least one of the group consisting of copolymers composed only of TFE units and FAVE units and the above-mentioned TFE / HFP / FAVE copolymers, and more preferably copolymers composed only of TFE units and FAVE units.

[0049] From the perspective of heat resistance and stress cracking resistance, the melting point of the copolymer is preferably 280°C to 322°C, more preferably 290°C or higher, even more preferably 315°C or lower, and even more preferably 305°C or lower. The melting point can be determined using a differential scanning calorimeter (DSC).

[0050] The glass transition temperature (Tg) of the copolymer is preferably 70°C to 110°C, more preferably 80°C or higher, and even more preferably 100°C or lower. The glass transition temperature can be determined by dynamic viscoelasticity measurement.

[0051] From the perspective of partial discharge resistance, the relative permittivity of the copolymer is preferably 2.10 or less, more preferably 2.08 or less, and the lower limit is not particularly limited, but preferably 1.80 or more. The relative permittivity is obtained by measuring the changes in resonant frequency and electric field strength using a network analyzer HP8510C (manufactured by Hewlett-Packard) and a cavity resonator at a temperature of 20°C to 25°C.

[0052] The copolymers used in this invention have functional groups, and the number of functional groups in the copolymers is preferably relative to the number of 10 6 Each carbon atom can range from 5 to 1000. Relative to every 10... 6 The number of functional groups is more preferably 50 or more, further preferably 100 or more, particularly preferably 200 or more, more preferably 800 or less, further preferably 700 or less, and particularly preferably 500 or less. By keeping the number of functional groups in the copolymer within the above range, the adhesion between the conductor and the insulating coating is improved, or the effect of suppressing expansion and cracking caused by radiation irradiation of the insulating coating becomes more significant.

[0053] The aforementioned number of functional groups refers to the number of functional groups in the copolymer contained in the insulating coating before radiation irradiation. By irradiating an insulating coating containing copolymers with the aforementioned number of functional groups, even when bent along a flattened direction, a flat electromagnetic wire can be obtained where the outer periphery of the bent coating is less prone to expansion and cracking. This is presumably because irradiation of the insulating coating causes a cross-linking reaction between the functional groups of the copolymer. Furthermore, when the number of functional groups in the copolymer is within the aforementioned range, even at relatively low irradiation temperatures, expansion and cracking can be further suppressed, thus also preventing radiation-induced adverse effects such as foaming, whitening, and conductor detachment from the insulating coating.

[0054] The aforementioned functional groups are functional groups present at the ends of the main chain or side chains of the copolymer, as well as functional groups present in the main chain or side chains. Preferably, the aforementioned functional groups are selected from at least one of the group consisting of -CF=CF2, -CF2H, -COF, -COOH, -COOCH3, -CONH2, and -CH2OH.

[0055] The identification of the types of functional groups and the determination of the number of functional groups can be performed using infrared spectrophotometry.

[0056] Specifically, the number of functional groups was determined using the following method. First, the copolymer was melted at 330°C–340°C for 30 minutes and then compressed to form a film with a thickness of 0.25 mm–0.3 mm. The film was analyzed using Fourier transform infrared spectroscopy to obtain the infrared absorption spectrum of the copolymer, resulting in a differential spectrum compared to the background spectrum of a fully fluorinated copolymer devoid of functional groups. Based on the following formula (A), the number of functional groups per 1 × 10⁻⁶ functional groups in the copolymer was calculated from the absorption peaks of specific functional groups appearing in this differential spectrum. 6 The number of functional groups N per carbon atom.

[0057] N = I × K / t (A)

[0058] I: Absorbance

[0059] K: Correction coefficient

[0060] t: Membrane thickness (mm)

[0061] For reference, the absorption frequencies, molar absorptivity, and correction factors for the functional groups in this invention are shown in Table 1. Furthermore, the molar absorptivity was determined using FT-IR measurement data from low-molecular-weight model compounds.

[0062] [Table 1]

[0063] Table 1

[0064]

[0065] It should be noted that the absorption frequencies of -CH2CF2H, -CH2COF, -CH2COOH, -CH2COOCH3, and -CH2CONH2 are tens of Kaiser (cm) lower than those of -CF2H, -COF, -COOH free and -COOH bonded, -COOCH3, and -CONH2 shown in the table. -1 ).

[0066] Therefore, for example, the number of functional groups in -COF is determined by the absorption frequency of -CF2COF, which is 1883 cm⁻¹. -1 The number of functional groups determined from the absorption peak and the absorption frequency at 1840 cm⁻¹ due to -CH₂COF are also relevant. 1 The total number of functional groups obtained from the absorption peaks.

[0067] The number of functional groups mentioned above can be the total number of -CF=CF2, -CF2H, -COF, -COOH, -COOCH3, -CONH2 and -CH2OH.

[0068] The aforementioned functional groups are introduced into the copolymer, for example, through chain transfer agents or polymerization initiators used in the manufacturing of the copolymer. For instance, when an alcohol is used as a chain transfer agent or a peroxide having a -CH2OH structure is used as a polymerization initiator, -CH2OH is introduced into the ends of the copolymer's main chain. Alternatively, the aforementioned functional groups can be introduced into the ends of the copolymer's side chains by polymerizing monomers having functional groups.

[0069] Copolymers can be manufactured, for example, by suitably mixing monomers, polymerization initiators, and other additives that will become their structural units and carrying out emulsion polymerization, suspension polymerization, or other known methods.

[0070] In this embodiment, the insulation coating of the flat electromagnetic wire is preferably a cross-linked insulation coating. If the insulation coating is cross-linked, even when the flat electromagnetic wire is bent along its flat direction, the insulation coating at the outer periphery of the bend is less prone to expansion and cracking. Furthermore, by cross-linking the insulation coating, the stress cracking resistance of the insulation coating can be further improved, making it less prone to expansion and cracking. In particular, it is not easy to form an insulation coating with uniform thickness and excellent stress cracking resistance. However, by using a copolymer with a relatively high melt flow rate and cross-linking the insulation coating, it is easy to form an insulation coating with uniform thickness, while simultaneously improving the stress cracking resistance of the insulation coating. In addition, if the insulation coating is cross-linked, the heat resistance of the flat electromagnetic wire is also improved.

[0071] One method for crosslinking the insulating coating is to irradiate the insulating coating with radiation. Suitable radiation irradiation conditions are described below.

[0072] The presence or absence of cross-linked structures in the insulation coating can be determined as follows: using the method described on pages 338-339 of the following document... 19 F-NMR confirms the presence or absence of chemical shifts of F atoms on the tertiary carbon at the crosslinking point, thus confirming the presence or absence of chemical shifts.

[0073] Hitoshi Imamura, “Study on Radiation Crosslinking of Perfluorinated Fluoropolymer PFA”, Molding and Processing, China Society for Plastics Molding and Processing, 2017, Vol. 29, No. 9, pp. 336-343

[0074] The insulating coating of the flat electromagnetic wire in this embodiment is preferably an insulating coating irradiated with radiation. If the insulating coating is irradiated with radiation, even when the flat electromagnetic wire is bent along its flattened direction, the insulating coating at the outer periphery of the bend is less prone to expansion and cracking. Furthermore, irradiation with radiation further improves the stress cracking resistance of the insulating coating, making it less prone to expansion and cracking. In particular, forming an insulating coating with uniform thickness and excellent stress cracking resistance is not easy. However, by using a copolymer with a relatively high melt flow rate and irradiating the insulating coating with radiation, a uniformly thick insulating coating can be easily formed, while simultaneously improving the stress cracking resistance of the insulating coating. In addition, if the insulating coating is irradiated with radiation, the heat resistance of the flat electromagnetic wire is also improved.

[0075] The irradiation temperature of the radiation is preferably 160°C to 280°C, more preferably 180°C or higher, even more preferably 200°C or higher, preferably less than 280°C, more preferably less than 260°C, and even more preferably less than 250°C. By keeping the irradiation temperature of the radiation within the above range, it is possible to obtain a flat electromagnetic wire whose insulating coating on the curved outer periphery is less prone to expansion and cracking, and it is also possible to further suppress adverse conditions caused by radiation irradiation, such as blistering, whitening, and conductor detachment from the insulating coating.

[0076] There are no particular limitations on the adjustment of the irradiation temperature mentioned above, and it can be done using known methods. Specifically, examples include: maintaining the copolymer in a heating furnace at a specified temperature; placing it on a heating plate, energizing a heater built into the heating plate, or heating the heating plate using an external heating mechanism.

[0077] The radiation dose is preferably 20 kGy or more and less than 100 kGy, more preferably 95 kGy or less, even more preferably 80 kGy or less, more preferably 30 kGy or more, and even more preferably 40 kGy or more. By keeping the radiation dose within the above range, it is possible to obtain a flat electromagnetic wire whose insulating coating on the curved outer periphery is less prone to expansion and cracking, and it is also possible to further suppress adverse conditions caused by radiation irradiation, such as blistering, whitening, and conductor detachment from the insulating coating.

[0078] Examples of radiation include electron beams, ultraviolet rays, gamma rays, X-rays, neutron rays, and high-energy ions. Among these, electron beams are preferred due to their excellent penetrating power, high dose rate, and suitability for industrial production.

[0079] There are no particular limitations on the method of irradiation; methods using existing, known radiation irradiation devices can be cited as examples. There are no particular limitations on the number of irradiations; it can be once or multiple times. Radiation can be irradiated from one side of the flat electromagnetic wire, followed by further irradiation from the opposite direction.

[0080] There are no particular restrictions on the irradiation environment for radiation, but it is preferable to have an oxygen concentration of 1000 ppm or less, more preferably to be in the absence of oxygen, and even more preferably in a vacuum or in an atmosphere of inactive gases such as nitrogen, helium or argon.

[0081] The thickness of the insulating coating is not particularly limited, but is preferably 30 μm to 100 μm, more preferably 50 μm to 100 μm. Even with a relatively thin insulating coating, the flat electromagnetic wire of this embodiment is less prone to expansion and cracking at the outer periphery of the curved portion. Furthermore, since the insulating coating contains the aforementioned copolymer, it exhibits sufficient insulating properties even when relatively thin. The thickness of the insulating coating can be 60 μm to 100 μm, or it can be 30 μm or more but less than 60 μm.

[0082] The insulating coating may include other components as needed. Examples of such components include crosslinking agents, antistatic agents, heat stabilizers, foaming agents, foaming nucleating agents, antioxidants, surfactants, photopolymerization initiators, abrasion inhibitors, surface modifiers, pigments, and other additives. The content of these other components in the insulating coating, relative to the mass of the copolymer, is preferably less than 1% by mass, more preferably less than 0.5% by mass, and even more preferably less than 0.1% by mass. The lower limit is not particularly limited and can be 0% by mass or more. That is, the insulating coating may not contain any other components.

[0083] Regarding the content of the copolymer in the insulating coating in this embodiment, from the perspective of partial discharge resistance, it is preferably more than 99% by mass, more preferably more than 99.5% by mass, and even more preferably more than 99.9% by mass, relative to the total polymer content in the insulating coating. There is no particular upper limit, and it can be less than 100% by mass. That is, the insulating coating may contain only the aforementioned copolymer as a polymer material, in which case the copolymer content is 100% by mass relative to the total polymer content in the insulating coating.

[0084] In this embodiment, the flat electromagnetic wire preferably has the conductor in contact with the insulating coating. Even without a base coat, the insulating coating of this flat electromagnetic wire does not easily float from the conductor, exhibiting excellent insulation properties. Since the dielectric constant is increased, the formation of a base coat is not preferred. Furthermore, the flat electromagnetic wire of this embodiment may further include other layers formed on the outer periphery of the insulating coating.

[0085] There are no particular limitations on the method for forming the insulating coating; it can be carried out according to existing known methods under various conditions. The insulating coating can be formed, for example, by a method such as melt-extruding a copolymer onto the surface of a conductor. After the insulating coating is formed around the conductor, it can be irradiated with radiation.

[0086] Alternatively, the insulating coating can be formed as follows: a copolymer is melt-extruded to form a tube, a conductor is inserted into the resulting tube, and the tube is further heated to shrink it, thereby forming the insulating coating. When the insulating coating is formed by thermally shrinking the tube, it is easier to suppress the formation of wrinkles in the insulating coating, and a flat electromagnetic wire with a curved outer periphery that is less prone to expansion and cracking can be obtained. The tube can be a stretched tube obtained by further stretching the tube obtained by melt extrusion. When irradiating the insulating coating with radiation, radiation can be applied to the tube before shrinkage or to the tube after shrinkage. Since the insulating coating in this embodiment has excellent resistance to stress cracking, it is preferably formed by melt extrusion molding. Insulating coatings formed by melt extrusion molding also include insulating coatings formed by thermally shrinking a tube after it has been formed by melt extrusion molding.

[0087] The flat electromagnetic wire of the present embodiment can be wound and used as a coil. The coil of the present embodiment only needs to be formed by winding the flat electromagnetic wire. The flat electromagnetic wire can be bent and wound along the flat-stand direction (width direction), or can be bent and wound along the flat-winding direction (thickness direction). Even when the flat electromagnetic wire of the present embodiment is bent along the flat-stand direction, the insulating coating covering the outer periphery of the bend is not likely to expand and crack. Therefore, the coil of the present embodiment is preferably a flat-stand coil formed by bending and winding the flat electromagnetic wire along the flat-stand direction. As the coil of the present embodiment, a coil wound with a flat electromagnetic wire having an insulating coating irradiated with radiation is preferred, and a coil wound with a flat electromagnetic wire having an insulating coating not irradiated with radiation may also be used. When winding the flat electromagnetic wire with an insulating coating, radiation can be irradiated to the insulating coating after winding the flat electromagnetic wire.

[0088] The flat electromagnetic wire and the coil of the present embodiment can be suitably used for electrical equipment or electronic equipment such as motors, generators, and inductors. In addition, the flat electromagnetic wire and the coil of the present embodiment can be suitably used for vehicle-mounted electrical equipment or vehicle-mounted electronic equipment such as vehicle-mounted motors, vehicle-mounted generators, and vehicle-mounted inductors.

[0089] In the above-described embodiment, the flat electromagnetic wire has a structure in which a flat conductor is provided. For example, a round conductor having a substantially circular cross-section can be used as the conductor. In the electromagnetic wire having a round conductor as the conductor, it is also preferred that the insulating coating contains the same copolymer as in the above-described embodiment. Thus, an electromagnetic wire having an insulating coating with a beautiful appearance, uniform thickness, and not likely to expand and crack can be obtained.

[0090] The embodiments have been described above, but it should be understood that various changes in the manner and details can be made without departing from the gist and scope of the claims.

[0091] Examples

[0092] Next, examples are given to illustrate the embodiments of the present invention, but the present invention is not limited to these examples.

[0093] The respective values in the examples were measured by the following methods.

[0094] <Melt Flow Rate (MFR)>

[0095] According to ASTM D1238, using a melt flow index measuring instrument (manufactured by Yasuda Seiki Co., Ltd.), the mass (g / 10 minutes) of the copolymer flowing out of a nozzle having an inner diameter of 2.1 mm and a length of 8 mm every 10 minutes at 372 °C under a load of 5 kg was determined.

[0096] <Content of PPVE Unit>

[0097] The content of perfluoro(propyl vinyl ether) (PPVE) units in the copolymer is determined by... 19 The determination was performed using F-NMR.

[0098] <Functional groups>

[0099] The copolymer was melted at 330°C–340°C for 30 minutes and then compressed to produce a film with a thickness of 0.25 mm–0.3 mm. The film was analyzed by performing 40 scans using a Fourier transform infrared spectroscopy (FT-IR) device (trade name: 1760X, manufactured by Perkin Elmer) to obtain the infrared absorption spectrum. The resulting differential spectrum was compared with the background spectrum of a fully fluorinated film devoid of functional groups. Based on the absorption peaks of specific functional groups appearing in this differential spectrum, the concentration of each functional group in the copolymer was calculated according to the following formula (A). 6 The number of functional groups N per carbon atom.

[0100] N = I × K / t (A)

[0101] I: Absorbance

[0102] K: Correction coefficient

[0103] t: Membrane thickness (mm)

[0104] For reference, the absorption frequencies, molar absorptivity, and correction factors for the functional groups in this invention are shown in Table 2. Furthermore, the molar absorptivity was determined using FT-IR measurements of low-molecular-weight model compounds.

[0105] [Table 2]

[0106] Table 2

[0107]

[0108] <Appearance evaluation of flat electromagnetic wires before radiation irradiation>

[0109] In the examples and comparative examples, the appearance of the flat electromagnetic wire obtained by melting and extruding the copolymer onto a flat copper wire before radiation irradiation was visually observed, and the appearance was evaluated according to the following criteria.

[0110] ×: Melt fracture was observed in the insulation coating.

[0111] 〇: No melt fracture was observed in the insulation coating.

[0112] Uniformity of insulation coating on flat electromagnetic wires

[0113] In the examples and comparative examples, the insulating coating was peeled off from the flat magnet wire before irradiation obtained by melt-extruding the copolymer onto a flat copper wire, and the thickness distribution was observed visually.

[0114] ×: The thickness of the insulating coating is uneven.

[0115] 〇: The thickness of the insulating coating is uniform.

[0116] <Measurement of MIT value>

[0117] The copolymers used in Examples 2 to 6, 8, and 12 were formed into sheets with a thickness of 0.2 mm. For the obtained sheets, electron beams were irradiated at the same irradiation temperature and radiation dose as in each example, and the MIT value of the sheet irradiated with electron beams was measured according to ASTM D2176. In addition, the copolymers used in Example 1 and 7 and Comparative Examples 1 to 3 were formed into sheets with a thickness of 0.2 mm, and the MIT value of the sheet not irradiated with electron beams was measured according to ASTM D2176. Specifically, test pieces (width 12.5 mm, length 130 mm, thickness 0.2 mm) were made from the sheets, and the obtained test pieces were installed on a MIT testing machine (model 12176, manufactured by Yasuda Seiki Seisakusho Co., Ltd.), and bent under the conditions of a load of 1.25 kg, a left and right bending angle of 135 degrees each, and a bending frequency of 175 times / minute, and the number of times until the test piece was cut off (MIT value) was measured.

[0118] The stress cracking resistance of the insulating coating formed from the copolymer that provides a sheet with a large MIT value is excellent, and when the flat magnet wire is bent, cracks are not easily generated in the bent outer peripheral portion of the insulating coating.

[0119] <Appearance evaluation of flat magnet wire after irradiation>

[0120] The flat magnet wires after irradiation produced in the examples were observed visually, and the presence or absence of foaming and the adhesion were evaluated according to the following criteria.

[0121] (Presence or absence of foaming)

[0122] ×: Foaming is observed in the insulating coating.

[0123] 〇: No foaming is observed in the insulating coating.

[0124] (Adhesion)

[0125] ×: Lifting or whitening is observed in the insulating coating.

[0126] 〇: No lifting or whitening is observed in the insulating coating.

[0127] <Flat and vertical bending processing test>

[0128] As Figure 2 As shown, the flat electromagnetic wire 1 produced in the embodiments and comparative examples is placed on the V-block 21, with the short side of the cross-sectional shape of the flat electromagnetic wire 1 in contact with the V-block 21. The pressing member 22 is pressed onto the center of the flat electromagnetic wire 1 on the V-block 21, and a load is applied along the flat direction (width direction). The wire is bent at 90 degrees with a bending radius (inner diameter) of 3.50 mm (one diameter) to perform the flat bending process.

[0129] Visually inspect the curved outer periphery of the curved flat electromagnetic wire and evaluate it according to the following criteria.

[0130] (Expansion)

[0131] ×: Expansion was observed in the outer periphery.

[0132] 〇: No expansion was observed in the outer periphery.

[0133] (Cracked)

[0134] ×: Many cracks were observed on the outer periphery.

[0135] △: Some cracks were observed on the outer periphery.

[0136] 〇: No cracks were observed on the outer periphery.

[0137] Comparative Example 1

[0138] A tetrafluoroethylene (TFE) / perfluoro(propyl vinyl ether) (PPVE) copolymer having the MFR, PPVE content, and functional group number listed in Table 3 was extruded onto a flat copper wire (thickness: 1.95 mm, width: 3.36 mm) at 380°C using an extruder to obtain a flat electromagnetic wire with an insulating coating. The thickness of the insulating coating was 80 μm. The obtained flat electromagnetic wire was evaluated using the above method. Furthermore, the copolymer was molded into sheets, and the MIT value of the resulting sheets was measured using the above method. The evaluation results are shown in Table 3.

[0139] Compare Examples 2 and 3

[0140] The copolymer was changed to one having the properties described in Table 3, and flat electromagnetic wires were produced in the same manner as in Comparative Example 1. The evaluation results are shown in Table 3.

[0141] Examples 1 and 7

[0142] The copolymer was changed to one having the properties described in Table 3, and flat electromagnetic wires were produced in the same manner as in Comparative Example 1. The evaluation results are shown in Table 3.

[0143] Examples 2-6 and 8-14

[0144] The copolymer was changed to one having the properties described in Table 3, and flat electromagnetic wires were produced in the same manner as in Comparative Example 1. The evaluation results are shown in Table 3.

[0145] Next, the obtained flat electromagnetic wire was cut into 30cm pieces and placed in an electron beam irradiation container of an electron beam irradiation device (manufactured by NHC Corporation). Nitrogen gas was then added to create a nitrogen atmosphere inside the container. After the temperature inside the container stabilized at 25°C, the flat electromagnetic wire was irradiated with electron beams at the radiation doses listed in Table 3, under the conditions of irradiation temperature, electron beam accelerating voltage of 3000kV, and irradiation beam intensity of 20kGy / 5 minutes. The evaluation results are shown in Table 3.

[0146] It should be noted that “-” in Table 3 indicates that no evaluation or treatment was carried out.

[0147] [Table 3]

[0148]

[0149] Symbol Explanation

[0150] 1. Flat electromagnetic wire

[0151] 10 Flat conductors

[0152] 11 Insulation Covering

[0153] 21 V-blocks

[0154] 22 Pressing parts

Claims

1. A flat vertical coil, which is formed by bending and winding a flat electromagnetic wire having a flat conductor and an insulating coating formed on the outer periphery of the flat conductor in a flat vertical direction, wherein, The insulating coating contains only copolymers comprising tetrafluoroethylene units and fluoroalkyl vinyl ether units as polymer components. The melt flow rate of the copolymer is 10 g / 10 min to 60 g / 10 min. The content of fluoroalkyl vinyl ether units in the copolymer is 6.2% to 8.0% by mass relative to all monomer units. The copolymer has functional groups, and the number of functional groups in the copolymer is relative to the number of 10 6 Each carbon atom has 50 to 1000 atoms. The copolymer has a relative permittivity of 2.10 or less. The thickness of the insulating coating is 30μm to 100μm.

2. The flat vertical coil as described in claim 1, wherein, The insulation coating is a cross-linked insulation coating.

3. The flat vertical coil as described in claim 1 or 2, wherein, The insulating coating is an insulating coating that has been irradiated with radiation.

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