Magnet wire and method for manufacturing magnet wire

Abstract

A magnet wire according to the present disclosure is provided with: a conductor; and an insulating layer that is superposed on the surface of the conductor, and is composed of a plurality of layers. The insulating layer includes a crosslinked layer that is superposed on the surface of the conductor, and a non-crosslinked layer that is superposed on the surface of the crosslinked layer. The main component of the non-crosslinked layer is a non-crosslinked fluororesin. The main component of the crosslinked layer is a crosslinked body of a tetrafluoroethylene-hexafluoropropylene copolymer, a crosslinked body of a polytetrafluoroethylene, or a crosslinked body of a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer. The content of the perfluoroalkyl vinyl ether unit in the tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer is 1.0% by mass to 6.0% by mass inclusive with respect to all monomer units.

Description

Magnet wire and method for manufacturing the same

[0001] This disclosure relates to a magnet wire and a method for manufacturing the magnet wire. This application claims priority to Japanese Application No. 2023-172938, filed October 4, 2023, and incorporates by reference all of the contents of the above-mentioned Japanese application.

[0002] 2. Description of the Related Art Known insulated wires (magnet wires) used for coil windings include wires in which an insulating layer made of a resin such as fluororesin, polyesterimide, polyamideimide, or polyimide is laminated on a conductor.

[0003] As such magnet wire, a prior art insulated electric wire has been proposed in which a coating layer made of a crosslinked melt-soluble fluorine resin composition is provided on a conductor, and a baked coating layer of a heat-resistant insulating paint is provided on the outside of the coating layer, thereby providing excellent inter-wire adhesion (see Patent Document 1).

[0004] Japanese Utility Model Application Publication No. 63-168923

[0005] The magnet wire of the present disclosure comprises a conductor and an insulating layer consisting of a plurality of layers laminated on the surface of the conductor, the insulating layer having a cross-linked layer laminated on the surface of the conductor and a non-cross-linked layer laminated on the surface of the cross-linked layer, the non-cross-linked layer comprising a non-cross-linked fluororesin as a main component, the cross-linked layer comprising a cross-linked product of tetrafluoroethylene-hexafluoropropylene copolymer, a cross-linked product of polytetrafluoroethylene, or a cross-linked product of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and the tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer has a content of perfluoroalkyl vinyl ether units of 1.0 mass % or more and 6.0 mass % or less based on all monomer units.

[0006] Fig. 1 is a schematic cross-sectional view showing a magnet wire according to a first embodiment of the present disclosure, and Fig. 2 is a schematic cross-sectional view showing a magnet wire according to a second embodiment of the present disclosure.

[0007] [Problem to be Solved by the Present Disclosure] By using a cross-linked fluororesin as the material for the insulating layer, the insulating performance of the magnet wire and its adhesion to the conductor can be improved. However, cross-linking the fluororesin inherently reduces the elongation of the insulating layer, which may result in a decrease in bending workability.

[0008] An object of the present disclosure is to provide a magnet wire that has good bending workability and good adhesion between the conductor and the insulating layer.

[0009] [Effects of the Present Disclosure] According to the present disclosure, it is possible to provide a magnet wire that has good bending workability and good adhesion between the conductor and the insulating layer.

[0010] [Description of Embodiments of the Present Invention] First, embodiments of the present disclosure will be listed and described.

[0011] (1) A magnet wire according to the present disclosure comprises a conductor and an insulating layer consisting of a plurality of layers laminated on the surface of the conductor, the insulating layer having a cross-linked layer laminated on the surface of the conductor and a non-cross-linked layer laminated on the surface of the cross-linked layer, the non-cross-linked layer comprising a non-cross-linked fluororesin as a main component, the cross-linked layer comprising a cross-linked product of tetrafluoroethylene-hexafluoropropylene copolymer, a cross-linked product of polytetrafluoroethylene, or a cross-linked product of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and the tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer has a perfluoroalkyl vinyl ether unit content of 1.0% by mass or more and 6.0% by mass or less based on all monomer units.

[0012] The magnet wire includes an insulating layer having a crosslinked layer laminated on the surface of a conductor and a non-crosslinked layer laminated on the surface of the crosslinked layer and composed primarily of a non-crosslinked fluororesin, the main component of the crosslinked layer being a crosslinked product of tetrafluoroethylene-hexafluoropropylene copolymer, a crosslinked product of polytetrafluoroethylene, or a crosslinked product of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and the content of perfluoroalkyl vinyl ether units in the tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer is 1.0% by mass or more and 6.0% by mass or less relative to all monomer units, thereby improving adhesion between the conductor and the insulating layer and maintaining good elongation of the insulating layer. Therefore, the magnet wire has good bending workability and good adhesion between the conductor and the insulating layer. In the present disclosure, "main component" means the component with the largest content in terms of mass, for example, a component that accounts for 90% by mass or more.

[0013] (2) In the above (1), the average thickness of the crosslinked layer may be 5 μm or more and 100 μm or less. By setting the average thickness of the crosslinked layer to 5 μm or more and 100 μm or less, the adhesion between the conductor and the insulating layer can be improved and the elongation of the insulating layer can be maintained. Here, the "average thickness" refers to the average value of thicknesses measured at any ten points.

[0014] (3) In the above (1) or (2), the non-crosslinked layer may have an average thickness of 20 μm or more and 200 μm or less. By having the average thickness of the non-crosslinked layer be 20 μm or more and 200 μm or less, the elongation of the insulating layer can be further improved, and the bending workability of the magnet wire can be improved.

[0015] (4) In any of the above (1) to (3), the non-crosslinked layer may contain a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer or a tetrafluoroethylene-hexafluoropropylene copolymer as a main component. When the non-crosslinked layer contains the above component as a main component, the magnet wire has good elongation and can have better extrusion processability and bending processability.

[0016] (5) In any of (1) to (4) above, the insulating layer may further have an outermost layer laminated on the surface of the non-crosslinked layer, and the main component of the outermost layer may be polyimide, polyamideimide, polyether ether ketone, polyphenylene sulfide, a crosslinked product of tetrafluoroethylene-hexafluoropropylene copolymer, a crosslinked product of polytetrafluoroethylene, or a crosslinked product of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer. Generally, when manufacturing a coil using magnet wire, the magnet wire is wound around a core, and then an impregnating varnish is infiltrated into the gaps between the magnet wires and the gaps between the magnet wire and the core to bond the magnet wires together and the magnet wire and the core together. Having the main component of the outermost layer be one of the above components can improve the adhesive strength between the outermost layer and the impregnating varnish. Furthermore, in winding processes using concentrated winding or winding processes using segment coil bending, wear is likely to occur when the fluorine coating material is subjected to large shear during winding processes. In response to this, abrasion resistance can be imparted by providing a resin layer with high strength and elastic modulus or a crosslinked fluorine layer as the outermost layer.

[0017] (6) Furthermore, the method for manufacturing a magnet wire of the present disclosure includes a step of laminating an insulating layer consisting of a plurality of layers on the surface of a conductor, and the step of laminating the insulating layer includes a step of laminating a cross-linked layer on the surface of the conductor and a step of laminating a non-cross-linked layer on the surface of the cross-linked layer, wherein the non-cross-linked layer is mainly composed of a non-cross-linked fluororesin, the cross-linked layer is mainly composed of a cross-linked product of tetrafluoroethylene-hexafluoropropylene copolymer, a cross-linked product of polytetrafluoroethylene, or a cross-linked product of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and the content of perfluoroalkyl vinyl ether units in the tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer is 1.0 mass% or more and 6.0 mass% or less with respect to all monomer units.

[0018] In the method for producing the magnet wire, the step of laminating an insulating layer comprises a step of laminating a cross-linked layer on the surface of a conductor and a step of laminating a non-cross-linked layer on the surface of the cross-linked layer, the non-cross-linked layer being mainly composed of a non-cross-linked fluororesin, the cross-linked layer being mainly composed of a cross-linked product of tetrafluoroethylene-hexafluoropropylene copolymer, a cross-linked product of polytetrafluoroethylene, or a cross-linked product of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and the content of perfluoroalkyl vinyl ether units in the tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer is 1.0 mass % or more and 6.0 mass % or less with respect to all monomer units, thereby enabling the production of a magnet wire having good bending workability and good adhesion between the conductor and the insulating layer.

[0019] [Details of Embodiments of the Present Disclosure] Magnet wires and methods for manufacturing magnet wires according to embodiments of the present disclosure will be described in detail below.

[0020] <Magnet Wire> [First Embodiment] The magnet wire of the present disclosure is an insulated wire used for winding a coil. The magnet wire 10 of the first embodiment shown in Fig. 1 includes a conductor 1 and an insulating layer 7 made up of multiple layers and laminated on the surface of the conductor 1. The insulating layer 7 has a cross-linked layer 2 laminated on the surface of the conductor 1 and a non-cross-linked layer 3 laminated on the surface of the cross-linked layer 2.

[0021] The cross-sectional shape of the magnet wire 10 is not particularly limited, and examples thereof include a circular shape (round wire), an elliptical shape, a square shape (rectangular wire), and a rectangular shape (flat wire). In the case of a square cross-section wire and a rectangular cross-section wire, the corners of the cross-section may be rounded. The cross-section of the magnet wire 10 may be a square cross-section wire. When the magnet wire 10 is a rectangular wire, the magnet wire 10 can be wound at a high density during coil processing.

[0022] When the cross section of the magnet wire 10 is a square wire, the length of one side of the cross section of the magnet wire 10 may be 0.25 mm or more and 4.0 mm or less, or 0.45 mm or more and 3.6 mm or less.

[0023] (Conductor) A linear conductor can be used as the conductor 1. Examples of the linear conductor include metal wires such as copper wire, tin-plated copper wire, aluminum wire, aluminum alloy wire, steel-core aluminum wire, copper fly wire, nickel-plated copper wire, silver-plated copper wire, and copper-clad aluminum wire.

[0024] Examples of the cross-sectional shape of the conductor 1 include a circle, an ellipse, a square, and a rectangle. It is preferable that the cross-sectional shape of the magnet wire 10 and the cross-sectional shape of the conductor 1 are the same type of shape. For example, when the magnet wire 10 is a rectangular wire, the cross-sectional shape of the conductor 1 may be rectangular, and the corners of the rectangle may be arc-shaped.

[0025] The lower limit of the average cross-sectional area of ​​the conductor 1 is 0.01 mm ２ 0.1 mm ２ The upper limit of the average cross-sectional area is 15 mm ２ 10 mm ２ may be.

[0026] (Insulating Layer) The insulating layer 7 is composed of a plurality of layers. The insulating layer 7 is laminated on the surface of the conductor 1 so as to cover the conductor 1. The insulating layer 7 has a cross-linked layer 2 laminated on the surface of the conductor, and a non-cross-linked layer 3 laminated on the surface of the cross-linked layer 2. Of the insulating layer 7, the cross-linked layer 2 is the layer laminated at the innermost position (on the surface of the conductor).

[0027] The average thickness of the entire insulating layer 7 is not particularly limited and can be, for example, 25 μm or more and 300 μm or less. The lower limit of the average thickness of the entire insulating layer 7 may be 25 μm, 30 μm, or 50 μm. On the other hand, the upper limit of the average thickness may be 300 μm, 250 μm, or 200 μm. By having the average thickness be 25 μm or more and 300 μm or less, durability, elasticity, adhesion, and insulation properties can be improved.

[0028] <Crosslinked Layer> The crosslinked layer 2 is laminated on the surface of the conductor 1. The main component of the crosslinked layer 2 is a crosslinked body of tetrafluoroethylene-hexafluoropropylene copolymer (FEP), a crosslinked body of polytetrafluoroethylene (PTFE), or a crosslinked body of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA). When the main component of the crosslinked layer 2 is a crosslinked body of FEP, a crosslinked body of PTFE, or a crosslinked body of PFA, the adhesion between the conductor and the insulating layer is improved and the elongation of the insulating layer can be maintained well. The main component of the crosslinked layer 2 may be a crosslinked body of PTFE or a crosslinked body of FEP, from the viewpoint of better bending processability.

[0029] The content of perfluoroalkyl vinyl ether units in the tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer is 1.0% by mass or more and 6.0% by mass or less, or may be 2.0% by mass or more and 5.0% by mass or less, or 2.5% by mass or more and 4.5% by mass or less, or may be 3.0% by mass or more and 4.0% by mass or less, based on the total monomer units.

[0030] The cross-linked layer 2 may contain components other than the above-mentioned main components. Examples of such components include fillers such as silica, alumina, magnesium oxide, beryllium oxide, silicon carbide, titanium carbide, boron carbide, tungsten carbide, boron nitride, and silicon nitride. Heat-resistant engineering plastics with a melting point of 250°C or higher, such as polyether ether ketone (PEEK), polyetherimide (PEI), and polyethersulfone (PES), can also be mixed. By mixing a heat-resistant engineering plastic, the elongation of the insulating layer 7 can be maintained and adhesion to the conductor can be improved.

[0031] The lower limit of the average thickness of the crosslinked layer 2 may be 5 μm, 8 μm, or 10 μm. The upper limit of the average thickness of the crosslinked layer 2 may be 100 μm, 80 μm, 60 μm, or 50 μm. When the average thickness of the crosslinked layer is 5 μm or more and 100 μm or less, the adhesion between the conductor and the insulating layer can be improved and the elongation of the insulating layer can be maintained.

[0032] <Non-crosslinked layer> The non-crosslinked layer 3 is laminated on the surface of the crosslinked layer 2. By providing the magnet wire 10 with the non-crosslinked layer 3, the elongation of the insulating layer 7 can be improved, and bending workability can be improved.

[0033] The main component of the non-crosslinked layer 3 is a non-crosslinked fluororesin. When the main component of the non-crosslinked layer 3 is a non-crosslinked fluororesin, the insulating layer 7 can be made to have good elongation.

[0034] The term "fluororesin" refers to a polymer in which at least one hydrogen atom bonded to a carbon atom forming a repeating unit of the polymer chain is substituted with a fluorine atom or an organic group having a fluorine atom (hereinafter also referred to as a "fluorine atom-containing group"). A fluorine atom-containing group is a linear or branched organic group in which at least one hydrogen atom is substituted with a fluorine atom, and examples thereof include a fluoroalkyl group, a fluoroalkoxy group, and a fluoropolyether group. Examples of fluororesins include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene-ethylene copolymer (ETFE), and chlorotrifluoroethylene-ethylene copolymer (ECTFE). Among these, the fluororesin that is the main component of the non-crosslinked layer 3 may be FEP or PFA, due to their good elongation and ease of extrusion and bending processability.

[0035] The resins that are the main components of the crosslinked layer 2 and the non-crosslinked layer 3 may be the same or different. The main component of the crosslinked layer 2 may be a crosslinked product of tetrafluoroethylene-hexafluoropropylene copolymer or a crosslinked product of polytetrafluoroethylene, and the main component of the non-crosslinked layer 3 may be a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer or a tetrafluoroethylene-hexafluoropropylene copolymer. When the main components of the crosslinked layer 2 and the non-crosslinked layer 3 are the above-mentioned components, the magnet wire can have improved bending processability and adhesion between the conductor and the insulating layer.

[0036] The non-crosslinked layer 3 may contain components other than the above-mentioned main components. Examples of the other components include fillers such as silica, alumina, magnesium oxide, beryllium oxide, silicon carbide, titanium carbide, boron carbide, tungsten carbide, boron nitride, and silicon nitride. Heat-resistant engineering plastics with a melting point of 250°C or higher, such as the above-mentioned polyether ether ketone (PEEK), polyetherimide (PEI), and polyethersulfone (PES), may also be mixed.

[0037] The lower limit of the average thickness of the non-crosslinked layer 3 may be 20 μm, 25 μm, or 50 μm. The upper limit of the average thickness of the non-crosslinked layer 3 may be 200 μm, 150 μm, or 120 μm. When the average thickness of the non-crosslinked layer 3 is 20 μm or more and 200 μm or less, the elongation of the insulating layer 7 can be improved, and the bending workability of the magnet wire 1 can be improved.

[0038] The magnet wire of the first embodiment has good bending workability and good adhesion between the conductor and the insulating layer.

[0039] <Method for Manufacturing Magnet Wire of First Embodiment> The method for manufacturing the magnet wire of the first embodiment includes a step of laminating an insulating layer made up of a plurality of layers on the surface of a conductor.

[0040] (Step of Laminating an Insulating Layer) In this step, an insulating layer consisting of multiple layers is laminated on the surface of the conductor. More specifically, this step includes a step of laminating a cross-linked layer on the surface of the conductor and a step of laminating a non-cross-linked layer on the surface of the cross-linked layer.

[0041] <Step of Laminating Crosslinked Layer> In this step, a crosslinked layer is laminated. Specifically, first, a resin composition for forming a crosslinked layer is applied to the surface of a conductor.

[0042] The resin composition for forming a crosslinked layer is mainly made of tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polytetrafluoroethylene (PTFE), or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and the content of perfluoroalkyl vinyl ether units in the tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer is 1.0% by mass or more and 6.0% by mass or less based on all monomer units. When the resin composition for forming a crosslinked layer is mainly made of FEP, PTFE, or PFA, bending processability is good, and when the resin composition is made of FEP or PTFE, bending processability can be made even better.

[0043] When the resin composition for forming a crosslinked layer is applied to the surface of a conductor, a coating material in which the resin composition for forming a crosslinked layer is dispersed in a solvent is applied to the surface of the conductor. As the solvent, a petroleum-based solvent capable of efficiently dispersing the resin composition for forming a crosslinked layer, such as naphtha, toluene, or xylene, can be used. The coating method is not particularly limited, and various methods such as spray coating, flow coating, and dip coating can be used.

[0044] Next, the conductor coated with the paint is placed in a heating furnace and heated to evaporate the solvent in the paint and bake the coating film. The baking temperature for the coating film can be, for example, 250° C. to 800° C. The baking time is not particularly limited, but can be, for example, 5 seconds to 1 minute.

[0045] The apparatus used for the firing is not particularly limited, and for example, a cylindrical baking furnace that is long in the direction of travel of the conductor can be used. The heating method is not particularly limited, and known methods such as hot air heating, infrared heating, and high-frequency heating can be used.

[0046] After baking the coating film, it is irradiated with radiation in a low-oxygen atmosphere at a constant temperature. Examples of radiation used for irradiation and crosslinking include electron beams (β rays) and γ rays. This irradiation causes the fluororesin of the resin composition for forming the crosslinked layer to have a crosslinked structure. By laminating a layer having a crosslinked structure on the surface of the conductor, the adhesion between the conductor and the insulating layer can be improved.

[0047] When the main component of the resin composition for forming the crosslinked layer is polytetrafluoroethylene or a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, the heating temperature during electron beam irradiation is, for example, 280° C. or higher and 420° C. or lower.

[0048] When the main component of the resin composition for forming the crosslinked layer is a tetrafluoroethylene-hexafluoropropylene copolymer, it has a low melting point and can be irradiated at a low temperature, for example, from 180°C to 265°C, thereby enabling energy savings.

[0049] The average thickness of the crosslinked layer may be 5 μm or more and 100 μm or less. By making the average thickness of the crosslinked layer 5 μm or more and 100 μm or less, the adhesion between the conductor and the insulating layer can be improved and the elongation of the insulating layer can be maintained, so that a magnet wire having good bending workability and good adhesion between the conductor and the insulating layer can be produced.

[0050] <Step of Laminating Non-Crosslinked Layer> In this step, a non-crosslinked layer is laminated. A resin composition for forming a non-crosslinked layer is applied to the surface of the crosslinked layer. The resin composition for forming a non-crosslinked layer contains a fluororesin as a main component.

[0051] Examples of the fluororesin that is the main component of the resin composition for forming the non-crosslinked layer include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene-ethylene copolymer (ETFE), and chlorotrifluoroethylene-ethylene copolymer (ECTFE). The fluororesin that is the main component of the non-crosslinked layer 3 may be FEP or PFA because of its good elongation and easy extrusion processability and bending processability.

[0052] When the resin composition for forming a non-crosslinked layer is applied to the surface of the crosslinked layer, a coating material in which the resin composition for forming a non-crosslinked layer is dispersed in a solvent is applied to the surface of the crosslinked layer. As this solvent, the same solvent as that used for the resin composition for forming the crosslinked layer can be used. The coating method is not particularly limited, and the same method as that used in the step of laminating the crosslinked layer can be used.

[0053] Next, in the same manner as in the step of laminating the crosslinked layer, the coating film is baked to laminate the non-crosslinked layer.

[0054] The fluororesin that is the main component of the resin composition for forming the crosslinked layer may be the same as or different from the main component of the resin composition for forming the non-crosslinked layer. For example, the main component of the resin composition for forming the crosslinked layer may be a tetrafluoroethylene-hexafluoropropylene copolymer or polytetrafluoroethylene, and the main component of the resin composition for forming the non-crosslinked layer may be a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer or a tetrafluoroethylene-hexafluoropropylene copolymer. When the main components of the resin composition for forming the crosslinked layer and the main components of the resin composition for forming the non-crosslinked layer are the above-mentioned components, the magnet wire manufacturing method can produce a magnet wire that has improved bending processability and adhesion between the conductor and the insulating layer.

[0055] The non-crosslinked layer may have an average thickness of 20 μm or more and 200 μm or less. By making the average thickness of the non-crosslinked layer 20 μm or more and 200 μm or less, the elongation of the insulating layer can be improved, and the bending workability of the magnet wire can be improved.

[0056] According to the magnet wire manufacturing method of the first embodiment, the non-crosslinked layer is mainly composed of a non-crosslinked fluororesin, the crosslinked layer is mainly composed of a crosslinked tetrafluoroethylene-hexafluoropropylene copolymer, a crosslinked polytetrafluoroethylene, or a crosslinked tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and the content of perfluoroalkyl vinyl ether units in the tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer is 1.0 mass % or more and 6.0 mass % or less with respect to all monomer units, thereby making it possible to manufacture a magnet wire that has good bending workability and good adhesion between the conductor and the insulating layer.

[0057] [Second Embodiment] In a second embodiment of the magnet wire, the insulating layer further has an outermost layer laminated on the surface of the non-crosslinked layer. A magnet wire 20 of the second embodiment shown in FIG. 2 includes a conductor 1 and an insulating layer 17 consisting of multiple layers laminated on the surface of the conductor 1. The insulating layer 17 has a crosslinked layer 2 laminated on the surface of the conductor 1, a non-crosslinked layer 3 laminated on the surface of the crosslinked layer 2, and an outermost layer 4 laminated on the surface of the non-crosslinked layer 3. Since the insulating layer 17 further has the outermost layer 4 laminated on the surface of the non-crosslinked layer 3, the bending workability of the magnet wire can be further improved. Note that the configurations of the conductor 1, the crosslinked layer 2, and the non-crosslinked layer 3 are the same as those of the first embodiment described above, and therefore the same reference numerals are used and description thereof will be omitted.

[0058] <Outermost Layer> The outermost layer 4 is the layer of the insulating layer 17 that is stacked outermost with respect to the conductor 1 .

[0059] The main component of the outermost layer 4 may be polyimide (PI), polyamideimide (PAI), polyether ether ketone (PEEK), polyphenylene sulfide (PPS), a crosslinked tetrafluoroethylene-hexafluoropropylene copolymer, a crosslinked polytetrafluoroethylene, or a crosslinked tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer. Generally, when manufacturing a coil using magnet wire, the magnet wire is wound around a core, and then an impregnating varnish is applied to the gaps between the magnet wires and between the magnet wire and the core to bond the magnet wires together or to the core. Having the above-mentioned components as the main component of the outermost layer 4 can improve the adhesive strength between the outermost layer 4 and the impregnating varnish. Furthermore, during winding processing using concentrated winding or winding processing using bending in a segment coil, wear is likely to occur when the fluorine coating material is subjected to large shear during winding processing. In response to this, a resin layer with high strength and elastic modulus or a crosslinked fluorine layer can be provided as the outermost layer to impart wear resistance.

[0060] Furthermore, since the main component of the outermost layer 4 is a cross-linked body of tetrafluoroethylene-hexafluoropropylene copolymer, a cross-linked body of polytetrafluoroethylene, or a cross-linked body of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, the insulating layer 17 can obtain good elongation, and therefore the bending processability of the magnet wire 20 can be further improved.

[0061] The outermost layer 4 may contain components other than the above-mentioned main components. Examples of such components include fillers such as silica, alumina, magnesium oxide, beryllium oxide, silicon carbide, titanium carbide, boron carbide, tungsten carbide, boron nitride, and silicon nitride. Heat-resistant engineering plastics with a melting point of 250°C or higher, such as polyetherimide (PEI) and polyethersulfone (PES), may also be mixed.

[0062] The lower limit of the average thickness of the outermost layer 4 may be 8 μm or 10 μm. The upper limit of the average thickness of the outermost layer 4 may be 30 μm or 25 μm. When the average thickness of the outermost layer 4 is 8 μm or more and 30 μm or less, the strength of the insulating layer 17 and the bending workability of the magnet wire 20 can be further improved.

[0063] According to the magnet wire of the second embodiment, the insulating layer further has an outermost layer laminated on the surface of the non-crosslinked layer, and the main component of the outermost layer is polyimide, polyamideimide, polyether ether ketone, polyphenylene sulfide, a crosslinked body of tetrafluoroethylene-hexafluoropropylene copolymer, a crosslinked body of polytetrafluoroethylene, or a crosslinked body of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, thereby improving the adhesive strength of the insulating layer with the impregnating varnish and imparting abrasion resistance.

[0064] <Method for Manufacturing Magnet Wire of Second Embodiment> The method for manufacturing a magnet wire of the second embodiment includes a step of laminating an insulating layer consisting of a plurality of layers on the surface of a conductor. The step of laminating the insulating layer includes a step of laminating a cross-linked layer on the surface of the conductor, a step of laminating a non-cross-linked layer on the surface of the cross-linked layer, and a step of laminating an outermost layer on the surface of the non-cross-linked layer. Note that the step of laminating a cross-linked layer on the surface of the conductor and the step of laminating a non-cross-linked layer on the surface of the cross-linked layer are the same as the method for manufacturing a magnet wire of the first embodiment described above, and therefore description thereof will be omitted.

[0065] <Step of Laminating Outermost Layer> In this step, the outermost layer is laminated on the surface of the non-crosslinked layer. Specifically, first, a resin composition for forming the outermost layer is applied to the surface of the conductor.

[0066] When the outermost layer contains polyimide (PI), polyamideimide (PAI), polyether ether ketone (PEEK), or polyphenylene sulfide (PPS) as a main component, the resin composition for forming the outermost layer also contains polyimide (PI), polyamideimide (PAI), polyether ether ketone (PEEK), or polyphenylene sulfide (PPS) as a main component.

[0067] Furthermore, when the main component of the outermost layer is a crosslinked product of tetrafluoroethylene-hexafluoropropylene copolymer, a crosslinked product of polytetrafluoroethylene, or a crosslinked product of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, the resin composition for forming the outermost layer contains a tetrafluoroethylene-hexafluoropropylene copolymer, polytetrafluoroethylene, or a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer as the main component. By using a crosslinked product of tetrafluoroethylene-hexafluoropropylene copolymer, a crosslinked product of polytetrafluoroethylene, or a crosslinked product of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer as the main component of the outermost layer, the insulating layer can maintain good elongation.

[0068] When the resin composition for forming the outermost layer is applied to the surface of the non-crosslinked layer, a coating material in which the resin composition for forming the outermost layer is dispersed in a solvent is applied to the surface of the non-crosslinked layer. The solvent may be the same as that used for the resin composition for forming the crosslinked layer. The coating method is not particularly limited, and the same method as that used in the process of laminating the crosslinked layer may be used. Alternatively, the outermost layer may be formed by extrusion.

[0069] Next, in the same manner as in the step of laminating the crosslinked layer, the coating film is baked to laminate the outermost layer.

[0070] When the main component of the outermost layer is a crosslinked product of tetrafluoroethylene-hexafluoropropylene copolymer, a crosslinked product of polytetrafluoroethylene, or a crosslinked product of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, after baking the coating film, radiation is irradiated in a low-oxygen atmosphere at a constant temperature, as in the step of laminating the crosslinked layer.

[0071] According to the magnet wire manufacturing method of the second embodiment, it is possible to manufacture a magnet wire that further has the above-mentioned outermost layer in which an insulating layer is laminated on the surface of the non-crosslinked layer, thereby improving the adhesive strength of the insulating layer with the impregnating varnish and obtaining a magnet wire that is wear-resistant.

[0072] [Other Embodiments] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is not limited to the configurations of the above-described embodiments, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0073] The surface of the conductor may be subjected to a silane treatment to further improve the adhesion between the conductor and the insulating layer.

[0074] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0075] <Magnet Wires No. 1 to No. 22> [Conductor] As the conductors, circular conductors (round wires) having a diameter of 2 mm and square conductors (rectangular wires) having sides of 2 mm, which conform to the annealed copper wire for electrical use specified in JIS-C3102:1984, were prepared, and the surfaces of the conductors were cleaned and annealed in a nitrogen atmosphere.

[0076] [Preparation of Resin Composition for Forming Insulating Layer] A resin composition for forming an insulating layer was prepared. The abbreviations for the materials are as follows: (Fluororesins) PTFE: Polytetrafluoroethylene PFA: Tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer FEP: Tetrafluoroethylene-hexafluoropropylene copolymer (Other resins) PEEK: Polyether ether ketone PI: Polyimide PAI: Polyamideimide

[0077] [Formation of Insulating Layer] (1) PTFE Layer The resin composition was prepared by dispersing PTFE (Daikin Corporation's "L-5") powder in water and stirring. After coating the resin composition, the coating was baked at 360°C for 30 minutes and then cooled, and a PTFE layer was laminated. The crosslinked layer was subjected to electron beam crosslinking under the conditions shown in Tables 1 to 3, with an oxygen concentration of 50 ppm or less, to form an insulating layer made of a crosslinked PTFE. (2) PFA Layer and FEP Layer FEP pellets (Mitsui Chemours' "9494X," melt flow rate 30) and PFA pellets (AGC's "P-61XP," with a perfluoroalkyl vinyl ether unit content of 3% by mass relative to total monomer units and a melt flow rate of 42) were extrusion molded. The melt flow rates of the FEP and PFA were determined in accordance with ASTM D1238 using a melt indexer (manufactured by Yasuda Seiki Seisakusho Co., Ltd.) as the mass of polymer (g / 10 min) flowing from a nozzle with an inner diameter of 2.1 mm and a length of 8 mm at 372°C under a load of 5 kg per 10 minutes. FEP was extruded at 300°C, and PFA at 340°C using an electric wire extruder. The crosslinked layer was subjected to electron beam crosslinking under the conditions shown in Tables 1 to 3, with an oxygen concentration of 50 ppm or less, to form an insulating layer made of a crosslinked PFA or FEP. (3) PEEK Layer: PEEK pellets (Victrex PEEK 450G) were extruded at 380°C, followed by water cooling, and the PEEK layer was laminated. (4) PI layer: A PI liquid composition diluted with a solvent was applied and then baked at 360° C. to form a PI layer. (5) PAI layer: A PAI liquid composition diluted with an aqueous solution was applied and then baked at 340° C. to form a PAI layer.

[0078] In this manner, insulating layers were formed by laminating each layer on the surface of the conductor so as to have the configurations shown in Tables 1 to 3 below, and magnet wires No. 1 to No. 22 were produced.

[0079] <Evaluation> The magnet wires prepared above were evaluated by the following methods. The results are shown in Tables 1 to 3 below.

[0080] [180° Bending Test] Bending workability was evaluated by a 180° bending test. The 180° bending test was performed under two conditions. (Condition 1) Two of the magnet wires prepared above were twisted together under a load of 1.5 kg to form a stranded wire. To evaluate the bending of the magnet wire, a tensile tester was used to perform a bending at a bending angle of 180° with three support points using three support rods with a beam length of 50 mm and a diameter of 4 mm, and the presence or absence of cracks was observed. The number of bendings was one. The presence or absence of cracks was evaluated according to the following three levels, with A and B being considered acceptable. A: No cracks were observed by microscopic observation. B: No cracks were observed by visual observation. C: Cracks were observed by visual observation. (Condition 2) Two of the magnet wires prepared above were twisted together under a load of 1.5 kg to form a stranded wire. To evaluate the bending of the magnet wire, a tensile tester was used to stretch the wire by 20%, and then the wire was bent 180° in the same manner as in Condition 1, and the presence or absence of cracks was observed. The sample was bent two times. The presence or absence of cracks was evaluated according to the following three levels, with A and B being considered acceptable. A: No cracks were observed under a microscope. B: No cracks were observed with the naked eye. C: Cracks were observed with the naked eye.

[0081] [Weldability Test] Using two of the magnet wires prepared above, TIG (Tungsten Inert Gas) welding was performed as a weldability test, and the presence or absence of bubbles on the welded surface was observed. TIG welding was performed at 100 A for welding times of 0.25 seconds and 0.50 seconds. The presence or absence of bubbles was evaluated on the following three levels, with A and B being considered acceptable. A: No abnormalities were observed visually, and no bubbles were observed on the cross section. B: No abnormalities were observed visually, and microbubbles were observed on the cross section. C: An abnormality was observed visually.

[0082] [Adhesion Test] The adhesion between the insulating layer and the conductor was evaluated by an adhesion test. The adhesion test was performed on the magnet wire produced above according to JIS-C3216-3, Section 5.5 Adhesion Test, in which a 300 mm long sample was stretched by 20% at a tensile speed of 5±1 mm / sec using a tensile tester, and the adhesion between the insulating layer and the conductor was evaluated based on the presence or absence of peeling. The adhesion between the insulating layer and the conductor was evaluated as pass if no peeling was observed, and as fail if peeling occurred.

[0083] [Abrasion Test] Abrasion resistance was evaluated by an abrasion test. The abrasion test was conducted on the magnet wire prepared above in accordance with JIS-C3003-9. First, a piano wire with a diameter of 0.23 mm was placed perpendicular to the sample and a load was applied. Next, the test piece was moved in the longitudinal direction at a speed of 400 mm / min while simultaneously increasing the load, and the load was determined when the coating peeled off and the conductor came into contact with the piano wire. A load of 6 N or more was judged to be acceptable.

[0084]

[0085]

[0086]

[0087] As shown in Tables 1 to 3, magnet wires No. 1 to No. 16, in which the insulating layer had a crosslinked layer laminated on the surface of the conductor and a non-crosslinked layer laminated on the surface of the crosslinked layer, the non-crosslinked layer was mainly composed of a non-crosslinked fluororesin, the crosslinked layer was mainly composed of a crosslinked product of tetrafluoroethylene-hexafluoropropylene copolymer, a crosslinked product of polytetrafluoroethylene, or a crosslinked product of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and the content of perfluoroalkyl vinyl ether units in the tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer was 1.0 mass % or more and 6.0 mass % or less with respect to all monomer units, were excellent not only in bending workability and adhesion between the conductor and the insulating layer, but also in abrasion resistance and weldability.

[0088] Magnet wire No. 17, in which the average thickness of the cross-linked layer was less than 5 μm, was inferior in bending workability, adhesion between the conductor and the insulating layer, weldability at a welding time of 0.50 seconds, and abrasion resistance. Magnet wires No. 18, No. 21, and No. 22, in which the insulating layer had only a cross-linked layer laminated on the surface of the conductor and no non-cross-linked layer, were inferior in bending workability and adhesion between the conductor and the insulating layer. Magnet wires No. 19 and No. 20, in which the insulating layer had only a non-cross-linked layer laminated on the surface of the conductor, were inferior in bending workability, adhesion between the conductor and the insulating layer, weldability, and abrasion resistance.

[0089] The above results demonstrate that the magnet wire has good bending workability and good adhesion between the conductor and the insulating layer.

[0090] REFERENCE SIGNS LIST 1 Conductor 2 Cross-linked layer 3 Non-cross-linked layer 4 Outermost layer 7, 17 Insulating layer 10, 20 Magnet wire

Claims

1. A magnet wire comprising: a conductor; and an insulating layer consisting of a plurality of layers laminated on a surface of the conductor, wherein the insulating layer has a crosslinked layer laminated on the surface of the conductor and a non-crosslinked layer laminated on the surface of the crosslinked layer, wherein the main component of the non-crosslinked layer is a non-crosslinked fluororesin, and the main component of the crosslinked layer is a crosslinked product of tetrafluoroethylene-hexafluoropropylene copolymer, a crosslinked product of polytetrafluoroethylene or a crosslinked product of tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, and the content of perfluoroalkylvinyl ether units in the tetrafluoroethylene-perfluoroalkylvinyl ether copolymer is 1.0% by mass or more and 6.0% by mass or less based on all monomer units.

2. The magnet wire according to claim 1, wherein the average thickness of the cross-linked layer is from 5 μm to 100 μm.

3. A magnet wire according to claim 1 or 2, wherein the average thickness of the non-crosslinked layer is 20 μm or more and 200 μm or less.

4. A magnet wire according to any one of claims 1 to 3, wherein the main component of said non-crosslinked layer is a tetrafluoroethylene-perfluoroalkylvinyl ether copolymer or a tetrafluoroethylene-hexafluoropropylene copolymer.

5. A magnet wire as claimed in any one of claims 1 to 4, wherein the insulating layer further has an outermost layer laminated on a surface of the non-crosslinked layer, and the main component of the outermost layer is polyimide, polyamideimide, polyether ether ketone, polyphenylene sulfide, a crosslinked product of tetrafluoroethylene-hexafluoropropylene copolymer, a crosslinked product of polytetrafluoroethylene, or a crosslinked product of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer.

6. A method for manufacturing a magnet wire, comprising the step of laminating an insulating layer consisting of a plurality of layers on a surface of a conductor, wherein the step of laminating the insulating layer comprises the steps of laminating a cross-linked layer on the surface of the conductor and laminating a non-cross-linked layer on the surface of the cross-linked layer, wherein the main component of the non-cross-linked layer is a non-cross-linked fluororesin, and the main component of the cross-linked layer is a cross-linked product of tetrafluoroethylene-hexafluoropropylene copolymer, a cross-linked product of polytetrafluoroethylene or a cross-linked product of tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, and the content of perfluoroalkylvinyl ether units in the tetrafluoroethylene-perfluoroalkylvinyl ether copolymer is 1.0 mass% or more and 6.0 mass% or less with respect to all monomer units.

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