Insulated wires, coils, and electrical and electronic equipment

Abstract

This insulated electrical wire has a conductor and an insulation film covering the conductor, and at least one of the insulation layers constituting the insulation film contains a thermosetting resin A and a resin B having a lower triboelectric series rank than the thermosetting resin A. The preferred thermosetting resin A is polyimide, and the preferred resin B is a fluororesin, a silicone resin, or a polypropylene resin. In at least the outermost layer of the insulation film, it is preferable that the thermosetting resin A constitutes a continuous phase, the resin B constitutes a dispersed phase, the area occupancy of the resin B in the outermost surface of the insulation film is 10% or greater, and the preferred tensile elongation of break of the insulation film is 30% or greater.

Description

[Technical field]

[0001] The present invention relates to an insulated wire, a coil, and an electric / electronic device. [Background technology]

[0002] Insulated wire (enameled wire) with an insulating resin coating (insulating film) formed around the conductor is used as magnet wire for inverter-related equipment (high-speed switching elements, inverter motors, coils for electric and electronic equipment such as transformers, etc.).

[0003] In recent years, with the spread of hybrid cars and electric cars, there is a demand for improved motor efficiency, and motor operation and inverter control at high voltages are required. When insulated wires are used under such high voltages, partial discharges (corona discharges) occur on the surface of the insulating coating, inducing deterioration of the insulating coating. To suppress this partial discharge, resins with low dielectric constants are used as the constituent material of the insulating coating. Summary of the Invention [Problem to be solved by the invention]

[0004] Thus, the insulated wire is required to have a high degree of insulation durability under high voltage conditions. In addition, there is an increasing demand for smaller size and higher output of rotating electrical machines such as automobile motors, which requires winding the insulated wire around a small bobbin, winding it at a high density, and fitting as many bent insulated wires as possible into a limited space such as a stator slot. Therefore, the insulated wires are required to have not only high insulation durability but also high flexibility and excellent elongation properties.

[0005] An object of the present invention is to provide an insulated wire having excellent insulation durability as well as excellent elongation characteristics and flexibility, and a coil and an electric / electronic device using the insulated wire. [Means for solving the problem]

[0006] The present inventors have conducted extensive research in light of the above problems and have found that by using a thermosetting resin and a resin (charge-adjusting resin) that is lower in the triboelectric series (easier to be negatively charged) than the thermosetting resin as the resin material constituting at least one layer of the insulating coating, the insulation durability can be effectively improved without substantially impairing the elongation and flexibility of the thermosetting resin.The present invention was completed based on this finding and through further research.

[0007] The above-mentioned object of the present invention has been achieved by the following means. [1] An insulated wire having a conductor and an insulating coating covering the conductor, an insulated wire, wherein at least one of the insulating layers constituting the insulating coating contains a thermosetting resin A and a resin B lower in the triboelectric series than the thermosetting resin A. [2] The insulated wire according to [1], wherein the thermosetting resin A contains a polyimide resin. [3] The insulated wire according to [1] or [2], wherein, in at least an outermost layer of the insulating coating, the thermosetting resin A constitutes a continuous phase and the resin B constitutes a dispersed phase, and the area occupancy rate of the resin B on the outermost surface of the insulating coating is 10% or more. [4] The insulated wire according to [3], wherein the thermosetting resin A and the resin B are incompatible with each other. [5] The insulated wire according to any one of [1] to [4], wherein the resin B contains resin particles having a particle size of 0.2 to 10 μm. [6] The insulated wire according to any one of [1] to [5], wherein the resin B contains core-shell particles and / or hollow particles. [7] The insulated wire according to any one of [1] to [6], wherein the resin B includes at least one of a fluororesin, a silicone resin, and a polypropylene resin. [8] The insulated wire according to any one of [1] to [7], wherein the insulating coating has a tensile elongation at break of 30% or more. [9] A coil having the insulated wire according to any one of [1] to [8].

[10] An electric / electronic device having the coil described in [9].

[0008] In the present invention, a numerical range expressed using "to" means a range including the numerical values ​​before and after it as the lower limit and upper limit. In the present invention, when an insulating coating contains "thermosetting resin A," it means that thermosetting resin A is contained in the insulating coating in a cured state. Effect of the Invention

[0009] The insulated wire of the present invention is excellent in insulation durability, elongation property and flexibility. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic cross-sectional view showing one embodiment of an insulated wire of the present invention. [Diagram 2] FIG. 2 is a schematic perspective view showing a preferred embodiment of a stator used in the electric / electronic device of the present invention. [Diagram 3] FIG. 3 is a schematic exploded perspective view showing a preferred embodiment of a stator used in an electric / electronic device of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] [Insulated wire] An example of the insulated wire of the present invention will be described with reference to the drawings. However, the insulated wire of the present invention is not limited to the form shown in the drawings. For example, the insulated wire of the present invention is preferably an insulated wire having a multi-layered insulating coating, or an insulated wire having a square, circular, elliptical, or other conductor cross section coated with an insulating coating. An insulated wire 1, the cross-sectional view of which is shown in FIG.

[0012] <Conductor> The conductor used in the present invention may be any conductor that has been used in conventional insulated wires without any particular limitation, and examples of such conductors include metal conductors such as copper wires and aluminum wires.

[0013] As a preferred example of a conductor used in the present invention, FIG. 1 shows a conductor having a rectangular cross section (flat angle shape). In order to suppress partial discharge from the corners, the rectangular conductor preferably has four chamfered corners (with a radius of curvature r) as shown in Fig. 1. The radius of curvature r is preferably 0.6 mm or less, and more preferably 0.2 to 0.4 mm. The size of the conductor is not particularly limited, but in the case of a rectangular conductor, the width (long side) of the rectangular cross-sectional shape is preferably 1 to 5 mm, more preferably 1.4 to 4.0 mm, and the thickness (short side) is preferably 0.4 to 3.0 mm, more preferably 0.5 to 2.5 mm. The ratio of the width (long side) to the thickness (short side) (thickness:width) is preferably 1:1 to 1:4. On the other hand, in the case of a conductor with a circular cross-sectional shape, the diameter is preferably 0.3 to 3.0 mm, more preferably 0.4 to 2.7 mm.

[0014] <Insulating film> At least one of the insulating layers constituting the insulating coating contains a thermosetting resin A and a resin B (charge adjusting resin) that is lower (more negative) in the triboelectric series (triboelectric series) than the thermosetting resin A. The insulating layer constituting the insulating coating means the insulating coating itself when the insulating coating is a single layer as shown in Fig. 1, or means each layer constituting the multi-layer structure when the insulating coating has a multi-layer structure.

[0015] In the present invention, even if an insulating coating is formed by applying and baking multiple times, if the constituent materials of adjacent insulating layers are the same and the content ratio of the constituent materials is also the same, the adjacent insulating layers are considered to be combined as one layer. In the present invention, when adjacent insulating layers constituting an insulating coating are made of different resin materials, or when the resin materials are the same but the content ratios of the resin materials are different, the two adjacent insulating layers are considered to be different layers. In addition, air bubbles may be contained in one or both of the adjacent insulating layers constituting the insulating coating, and either or both of the thermosetting resin A and the resin B may contain air bubbles (hollow portions), and in any case, as described above, it is sufficient that the resin B (charge control resin) is lower (negative) in the triboelectric series (triboelectric series) than the thermosetting resin A. Here, the triboelectric series is an order indicating whether a material is likely to be charged positively or negatively when two types of materials are slid and rubbed against each other, and the negative side means that when a film of the thermosetting resin A and a film containing the resin B (charge control resin) described below are slid and rubbed against each other as described below, the film of the thermosetting resin A is positively charged and the film containing the resin B is negatively charged. The thickness of the insulating coating (when the insulating coating has a multi-layer structure, the thickness of the entire multi-layer structure) is preferably set to 1 to 200 μm, more preferably 5 to 100 μm, even more preferably 10 to 50 μm, and particularly preferably 20 to 40 μm.

[0016] The insulated wire of the present invention preferably has an insulating layer that contains thermosetting resin A and resin B that is lower in the triboelectric series than thermosetting resin A occupying 20% ​​or more of the thickness of the insulating coating, and more preferably has an insulating layer that contains thermosetting resin A and resin B that is lower in the triboelectric series than thermosetting resin A occupying 40% or more (preferably 50% or more, more preferably 60% or more, even more preferably 70% or more, and particularly preferably 80% or more) of the thickness of the insulating coating. Furthermore, when the insulating coating of the insulated wire of the present invention has a multi-layer structure, it is preferable that at least the outermost layer contains thermosetting resin A and resin B that is lower in the triboelectric series than thermosetting resin A, and it is also preferable that a layer other than the insulating layer in contact with the conductor contains thermosetting resin A and resin B that is lower in the triboelectric series than thermosetting resin A. Furthermore, all of the insulating layers constituting the insulating coating of the insulated wire of the present invention may be made to contain thermosetting resin A and resin B which is lower than thermosetting resin A in the triboelectric series.

[0017] In an insulating layer containing a thermosetting resin A and a resin B lower in the triboelectric series than the thermosetting resin A, the content of the thermosetting resin A is preferably 40 volume % or more, more preferably 50 volume % or more, and even more preferably 60 volume % or more. The content of the thermosetting resin A is usually 90 volume % or less. The content of the resin B in the insulating layer is preferably 10 volume % or more, more preferably 15 volume % or more. The content of the resin B is usually 60 volume % or less. In addition, when a hollow portion exists in the thermosetting resin A and / or the resin B, the above volume % is the volume % including the hollow portion.

[0018] The thermosetting resin A blended in the insulating film can be a wide variety of thermosetting resins used as a constituent material of the insulating film of an insulated electric wire. Specific examples of the thermosetting resin A include polyimide resin (PI), polyamideimide resin (PAI), polyetherimide resin (PEI), polyesterimide resin (PEsI), polyurethane resin, polyester resin (PEst), polybenzimidazole resin, melamine resin, and epoxy resin. Among these, it is preferable to use one or more of polyimide resin, polyamideimide resin, polyetherimide resin, polyesterimide resin, polyurethane resin, and polyester resin, and among these, a thermosetting resin having an imide bond is more preferable. Examples of the thermosetting resin A having an imide bond include polyimide resin, polyamideimide resin, polyetherimide resin, and polyesterimide resin, and it is preferable to use one or more of these. In particular, polyimide resin, polyamide-imide resin, and polyester-imide resin are excellent materials for forming enameled wires because of their high heat resistance. It is more preferable that thermosetting resin A contains polyimide resin, and it is even more preferable that thermosetting resin A is polyimide resin.

[0019] The resin B is lower in the triboelectric series than the thermosetting resin A. In other words, when the resin B is triboelectrically charged with the thermosetting resin A, the resin B is more negatively charged than the thermosetting resin A. In the present invention, the relationship in the triboelectric series between the thermosetting resin A and the resin B is determined in accordance with JIS C 61340-2-2:2013. Specifically, film A is made of thermosetting resin A molded into a square shape with a length of 100 mm, width of 100 mm, and thickness of 0.05 mm, and film B is made of a mixture of 50 parts by mass of thermosetting resin A and 50 parts by mass of resin B molded into a square shape with a length of 100 mm, width of 100 mm, and thickness of 0.05 mm. The two films are overlapped with each other with the squares aligned in the atmosphere under conditions of a temperature of 25°C and a relative humidity of 50%. While keeping the two films in contact, film B is slid 50 mm along the length of film A at a speed of 50 mm / sec, and then slid back to the original position at the same speed. This is counted as one round trip, and five round trips are repeated to frictionally charge both films. After that, the surface potential of film B is promptly measured with a potential meter. If the measured surface potential of film A is a positive value and the surface potential value (V) of film B is a negative value (-0.1 V or less) with an absolute value of 0.1 V or more, then resin B is determined to be lower in the triboelectric series than thermosetting resin A. The surface potential value (V) of film B measured after the above-mentioned frictional charging is preferably -5 V or less, more preferably -10 V or less, and also preferably -20 V or less. The surface potential value (V) of film B measured after the above-mentioned frictional charging is usually -200 V or more, and also preferably -150 V or more.

[0020] As a preferred combination of thermosetting resin A and resin B, when thermosetting resin A is selected from polyimide resin, polyamideimide resin, and polyesterimide resin, resin B can be selected from silicone resin and fluororesin. When thermosetting resin A is a polyimide resin, resin B can be selected from polyethylene resin, polypropylene resin, and polyvinyl chloride resin, and polypropylene resin is preferably used. Among them, it is preferable to adopt the following combinations (a) to (i) of the thermosetting resin A and the resin B.

[0021] (Thermosetting resin A) (Resin B) (a) Polyimide resin Silicone resin (b) Polyimide resin Fluorine resin (c) Polyamide-imide resin Silicone resin (d) Polyamide-imide resin Fluorine resin (e) Polyesterimide resin Silicone resin (f) Polyesterimide resin Fluorine resin (g) Polyimide resin Polyethylene resin (h) Polyimide resin Polypropylene resin (i) Polyimide resin Polyvinyl chloride resin

[0022] In the present invention, a silicone resin suitable for use as resin B is a compound having a polysiloxane structure. In the polysiloxane structure, the difference in electronegativity between O and Si constituting the siloxane bond is relatively large, and it is considered that Si, which is positively charged during friction, attracts electrons from the other party in friction, causing the silicone resin as a whole to become negatively charged. Similarly, it is thought that atoms in fluororesin, which are positively charged due to the electrons being attracted by F with high electronegativity, then attract electrons from the other party in friction, causing the fluororesin or the entire body to become negatively charged. Examples of fluororesin include polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), and perfluoroethylenepropene copolymer (FEP). Similarly, polyvinyl chloride resin is considered to be negatively charged as a whole due to Cl, which has a large electronegativity, in the same manner as above.

[0023] In the present invention, the thermosetting resin A may be one type of thermosetting resin or two or more types of thermosetting resin. One or two or more types of resins can also be used as the resin B. When the thermosetting resin A is made of two or more types of thermosetting resins, it is preferable that the two or more types of thermosetting resins are mutually compatible. Also, when the resin B is made of two or more types of resins, it is preferable that the two or more types of resins are mutually compatible. "Mutually compatible" means that no phase separation occurs (no sea-island structure is formed) when mixed (blended).

[0024] It is preferable that the thermosetting resin A and the resin B are mutually incompatible. "Mutually incompatible" means that when mixed (blended), phase separation occurs (a sea-island structure is formed). In this case, it is preferable that the thermosetting resin A constitutes the continuous phase, and the resin B constitutes the dispersed phase. The resin B can also be blended as resin particles (including hollow particles and core-shell particle forms). The core-shell particles are not limited to specific ones as long as they have a core-shell structure. Examples of the core-shell particles include those having a crosslinked polymethyl methacrylate as the core and a polymethylsilsesquioxane as the shell. When the resin B is present as resin particles, the particle diameter of the dispersed resin particles is preferably 0.1 to 20 μm, more preferably 0.2 to 10 μm, further preferably 0.5 to 10 μm, and particularly preferably 1.0 to 8.0 μm. This particle diameter is the average particle diameter, and is published by the manufacturer or distributor. When the particle diameter published by the manufacturer is unknown, the above particle diameter is the median diameter (d50) based on volume. In this manner, a state in which resin B is dispersed in thermosetting resin A is also considered in the present invention to be a form in which thermosetting resin A constitutes a continuous phase and resin B constitutes a dispersed phase. In a preferred embodiment of the insulated wire of the present invention, the thermosetting resin A forms a continuous phase and the resin B forms a dispersed phase in at least the outermost layer of the insulating coating (the insulating coating if the insulating coating has a single layer structure). In this embodiment, the area occupancy of the resin B on the outermost surface of the insulating coating (the surface of the outermost layer of the insulating coating) (the ratio of the area of ​​the resin B constituting the outermost surface to the area of ​​the outermost surface of the insulating coating when the outermost surface is made flat) is preferably 10% or more. This allows the insulated wire to have a longer voltage-applied life and improved durability. The reason for this is not yet clear, but it is believed to be due to the fact that by making the area occupancy of the resin B 10% or more, the surface of the insulating coating can be charged more negatively, and when a sine wave AC voltage is applied, the negative voltage can be effectively reduced, and as a result, the negative voltage of the sine wave AC voltage can be made smaller than the breakdown voltage that damages the insulating coating, and the breakdown voltage applied to the insulating coating is narrowed to the positive side, thereby reducing the frequency of application of the breakdown voltage. In addition, it is presumed that the charge charged on the outermost surface of the insulating coating under AC voltage acts on (mitigates) the electric field of the air layer in contact with the insulating coating, and as a result, partial discharge is suppressed, thereby lengthening the voltage-applied life. The area occupancy rate of the resin B on the outermost surface of the insulating coating is preferably 12% or more, and more preferably 14% or more, and is usually 50% or less, preferably 40% or less, and more preferably 35% or less.

[0025] The area occupancy rate can be determined as follows. The conductor is removed from the insulated wire, and the resulting tubular insulating coating is cut into a flat plate. With the outermost surface of the insulating coating (the surface opposite to the surface of the insulating coating that was in contact with the conductor) facing up, elemental analysis is performed using SEM-EDX, and the area occupancy rate of resin B is calculated using image analysis software. Even if the outermost surface of the insulating coating has some irregularities, the area occupancy of resin B in the entire outermost surface of the insulating coating can be determined by elemental analysis using SEM-EDX. That is, in the present invention, the area occupancy is the area occupancy in a plan view.

[0026] The breaking elongation of the insulating coating of the present invention is preferably 30% or more. When the breaking elongation is 30% or more, the flexibility of the insulated electric wire is improved, and cracks and the like are less likely to occur in the insulating coating even when the insulated electric wire is pulled. This breaking elongation is the breaking elongation when a tubular insulating coating is prepared by removing the conductor from the insulated electric wire, and a tensile test is performed in the longitudinal direction at 10 mm / min using a tensile tester with a chuck distance of 30 mm in an atmosphere of 25°C and 50% relative humidity while still in the tubular form. Note that a breaking elongation of 30% or more means that the insulating coating breaks when it is stretched to 130% or more, with the length when not stretched being taken as 100%.

[0027] The insulating coating of the present invention may contain various additives, such as a bubble nucleating agent, an antioxidant, an antistatic agent, an ultraviolet protection agent, a light stabilizer, a fluorescent brightening agent, a pigment, a dye, a compatibilizer, a lubricant, a reinforcing agent, a flame retardant, a crosslinking agent, a crosslinking aid, a plasticizer, a thickener, a viscosity reducer, and an elastomer.

[0028] [Insulated wire manufacturing method] The insulated wire of the present invention can be produced in a conventional manner, except that, as described above, at least the outermost layer of the insulating coating contains thermosetting resin A and resin B that is lower in the triboelectric series than thermosetting resin A. For example, the insulating film can be obtained by dissolving or dispersing the thermosetting resin A and resin B, which are the constituent materials of the insulating film, in an organic solvent, mixing various additives as necessary to prepare a varnish, applying this varnish around the conductor or around the insulating layer formed around the conductor, and baking the varnish to form the insulating film. The solvent in the varnish is volatilized and removed by this baking. Examples of the organic solvent include amide-based solvents such as N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAC), and N,N-dimethylformamide (DMF); urea-based solvents such as N,N-dimethylethyleneurea, N,N-dimethylpropyleneurea, and tetramethylurea; lactone-based solvents such as γ-butyrolactone and γ-caprolactone; carbonate-based solvents such as propylene carbonate; ketone-based solvents such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester-based solvents such as ethyl acetate, n-butyl acetate, butyl cellosolve acetate, butyl carbitol acetate, ethyl cellosolve acetate, and ethyl carbitol acetate; glyme-based solvents such as diglyme, triglyme, and tetraglyme; hydrocarbon-based solvents such as toluene, xylene, and cyclohexane; phenol-based solvents such as cresol, phenol, and halogenated phenol; sulfone-based solvents such as sulfolane; and dimethyl sulfoxide (DMSO).

[0029] Specific baking conditions cannot be unambiguously described because they vary depending on the shape of the furnace used, but for a natural convection vertical furnace of approximately 10 m, examples of such conditions include a furnace temperature of 400 to 650°C and a passage time of 10 to 90 seconds.

[0030] [Coils and electrical / electronic devices] The insulated wire of the present invention can be used as a coil in fields requiring electrical properties (voltage resistance) and heat resistance, such as various electric and electronic devices. For example, the insulated wire of the present invention can be used in motors, transformers, etc. to configure high-performance electric and electronic devices. In particular, it is preferably used as a winding for the drive motors of hybrid vehicles (HVs) and electric vehicles (EVs). Thus, according to the present invention, it is possible to provide electric and electronic devices, such as drive motors for HVs and EVs, that use the insulated wire of the present invention as a coil.

[0031] The coil of the present invention may have any shape suitable for various electric and electronic devices, and examples of the coil include one formed by processing the insulated electric wire of the present invention into a coil, and one formed by bending the insulated electric wire of the present invention and then electrically connecting predetermined portions of the bent wire. The coil formed by coil processing the insulated electric wire of the present invention is not particularly limited, and may be a coil formed by winding a long insulated electric wire in a spiral shape. In such a coil, the number of turns of the insulated electric wire is not particularly limited. Usually, an iron core or the like is used to wind the insulated electric wire.

[0032] An example of a coil obtained by bending the insulated electric wire of the present invention and then electrically connecting predetermined portions thereof is a coil used in a stator of a rotating electric machine, etc. As shown in Fig. 3, for example, such a coil can be a coil 33 (see Fig. 2) produced by cutting the insulated electric wire of the present invention to a predetermined length, bending it into a U-shape or the like to produce a plurality of electric wire segments 34, and alternately connecting two open ends (terminals) 34a of the U-shape or the like of each electric wire segment 34.

[0033] The electric / electronic device using this coil is not particularly limited. A preferred embodiment of such an electric / electronic device is a transformer. Another example is a rotating electric machine (especially a drive motor for HV and EV) equipped with a stator 30 shown in FIG. 2. This rotating electric machine can have the same configuration as a conventional rotating electric machine, except that it is equipped with the stator 30. The stator 30 can have the same configuration as a conventional stator, except that the electric wire segment 34 is formed of the insulated electric wire of the present invention. That is, the stator 30 has a stator core 31 and a coil 33 formed by inserting an electric wire segment 34 made of the insulated electric wire of the present invention into a slot 32 of the stator core 31 and electrically connecting the open end 34a, as shown in FIG. 3, for example. The coil 33 is fixed by fixing adjacent fusion layers to each other or to the fusion layer and the slot 32. Here, the electric wire segment 34 may be inserted into the slot 32 by itself, but is preferably inserted as a pair as shown in FIG. 3. In the stator 30, the coil 33 formed by connecting the open end 34a, which is the two ends of the electric wire segment 34 bent as described above, alternately is inserted into the slot 32 of the stator core 31, and is inserted into the slot 32 of the stator core 31. At this time, the open end 34a of the wire segment 34 may be connected before being stored in the slot 32, or the insulating segment 34 may be stored in the slot 32 and then the open end 34a of the wire segment 34 may be bent and connected.

[0034] The present invention will be described in more detail based on examples, but the present invention is not limited to these examples. EXAMPLES

[0035] [Example 1] <Conductor> A copper wire with a circular cross section (outer diameter of the cross section: 1 mm) was used as the conductor.

[0036] <Insulating paint> A polyimide (PI) resin varnish (product name: U-imide, manufactured by Unitika Ltd., NMP solution containing 25% by mass of PI resin component) was mixed with 20% by volume of silicone resin (product name: KMP590, manufactured by Shin-Etsu Chemical Co., Ltd., silicone resin particles with a particle size of 2.0 μm) relative to 80% by volume of PI resin component, and stirred for 3 hours. In this way, insulating coating 1 containing PI resin as thermosetting resin A and silicone resin as resin B was obtained. <Electric potential measurement> A PI resin film and a silicone resin-containing PI resin film were produced by molding a mixture of 50 parts by mass of the above-mentioned silicone resin and 50 parts by mass of the PI resin (both films had a square planar shape of 100 mm length, 100 mm width and 0.05 mm thickness). Both films were triboelectrically charged using the method described above, and the surface potential of the silicone resin-containing PI resin film was immediately measured with a potential meter (KSD-300, manufactured by Kasuga Electric Co., Ltd.). It was found that the surface potential of the silicone resin-containing PI resin film was -30 V, and that the triboelectric series of the silicone resin was lower than that of the PI resin, which had a positive surface potential.

[0037] <Insulated wire> The PI resin varnish was applied onto a conductor and baked at a furnace temperature of 520°C to form an insulating layer (polyimide resin layer) with a thickness of 4 μm. The insulating coating material 1 was applied onto this insulating layer and baked at a furnace temperature of 520°C, which was repeated several times to form a coating with a predetermined thickness, thereby obtaining the insulated wire of Example 1. The total thickness of the insulating coating (thickness including the insulating layer with a thickness of 4 μm) is shown in Table 1 below. The layer formed from the insulating coating material 1 had a structure in which silicone resin (dispersed phase) was dispersed in PI resin (continuous phase).

[0038] [Example 2] A polyamideimide (PAI) resin varnish (product name: HI-406, Hitachi Chemical Co., Ltd., NMP solution containing 32% by mass of resin component) was mixed with 25% by volume of silicone resin (product name: KMP590, Shin-Etsu Chemical Co., Ltd., silicone resin particles with a particle size of 2.0 μm) relative to 75% by volume of PAI resin component, and stirred for 3 hours. In this way, insulating coating material 2 containing PAI resin as thermosetting resin A and silicone resin as resin B was obtained. An insulated wire of Example 2 was obtained in the same manner as in Example 1, except that insulating varnish 2 was used instead of insulating varnish 1 in Example 1. The layer formed from insulating varnish 2 had a structure in which silicone resin (dispersed phase) was dispersed in PAI resin (continuous phase). Furthermore, in the same manner as in Example 1, a PAI resin film and a silicone resin-containing PAI resin film were prepared, and both films were triboelectrically charged by the method described above. The surface potential of the silicone resin-containing PAI resin film was quickly measured with a potential meter (KSD-300, manufactured by Kasuga Electric Co., Ltd.). It was confirmed that the surface potential of the silicone resin-containing PAI resin film was -45 V, and that the triboelectric series of the silicone resin was lower than that of the PAI resin, whose surface potential was a positive value.

[0039] [Example 3] Insulating varnish 3 was prepared by using 25% by volume of fluororesin (product name: Polymist F5A, manufactured by Solvay, PTFE particles with a particle size of 4.0 μm) relative to 75% by volume of PI resin component as resin B in insulating varnish 1 in Example 1, instead of 20% by volume of silicone resin relative to 80% by volume of PI resin component, and an insulated wire of Example 3 was obtained in the same manner as in Example 1, except that insulating varnish 3 was used instead of insulating varnish 1. The layer formed from insulating varnish 3 had a structure in which fluororesin (dispersed phase) was dispersed in PI resin (continuous phase). Furthermore, a PI resin film and a fluororesin-containing PI resin film were prepared in the same manner as in Example 1, and both films were triboelectrically charged by the method described above. The surface potential of the fluororesin-containing film was immediately measured with a potential meter (KSD-300, manufactured by Kasuga Electric Co., Ltd.). It was found that the surface potential of the fluororesin-containing PI resin film was −90 V, and that the triboelectric series of the fluororesin was lower than that of the PI resin, whose surface potential was a positive value.

[0040] [Example 4] Insulating paint 4 was prepared by using 25% by volume of a fluororesin (product name: Polymist F5A, manufactured by Solvay, PTFE particles with a particle size of 4.0 μm) relative to 75% by volume of the PAI resin component as resin B in insulating paint 2 in Example 2, instead of 25% by volume of a silicone resin relative to 75% by volume of the PAI resin component, and an insulated wire of Example 4 was obtained in the same manner as in Example 2, except that insulating paint 4 was used instead of insulating paint 2. The layer formed from insulating paint 4 had a structure in which a fluororesin (dispersed phase) was dispersed in a PAI resin (continuous phase). Furthermore, in the same manner as in Example 1, a PAI resin film and a fluororesin-containing PAI resin film were prepared, and both films were triboelectrically charged by the method described above. The surface potential of the fluororesin-containing PAI resin film was immediately measured with a potential meter (KSD-300, manufactured by Kasuga Electric Co., Ltd.). It was found that the surface potential of the fluororesin-containing PAI resin film was -95 V, and that the triboelectric series of the fluororesin was lower than that of the PAI resin, whose surface potential was a positive value.

[0041] [Example 5] Insulating paint 5 was prepared by using 35% by volume of silicone resin (product name: KMP590, manufactured by Shin-Etsu Chemical Co., Ltd., silicone resin particles with a particle size of 2.0 μm) relative to 65% by volume of PI resin component as resin B in insulating paint 1 in Example 1, instead of 20% by volume of silicone resin relative to 80% by volume of PI resin component, and an insulated wire of Example 5 was obtained in the same manner as in Example 1, except that insulating paint 3 was used instead of insulating paint 1. The layer formed from insulating paint 5 had a structure in which silicone resin (dispersed phase) was dispersed in PI resin (continuous phase).

[0042] [Example 6] Insulating varnish 6 was prepared by using 8 volume % silicone resin (product name: KNP590, manufactured by Shin-Etsu Chemical Co., Ltd., silicone resin particles with a particle size of 2 μm) relative to 92 volume % PI resin component as resin B in insulating varnish 1 in Example 1, instead of 20 volume % silicone resin relative to 80 volume % PI resin component, and an insulated wire of Example 6 was obtained in the same manner as in Example 1, except that insulating varnish 6 was used instead of insulating varnish 1. The layer formed from insulating varnish 6 had a structure in which silicone resin (dispersed phase) was dispersed in PI resin (continuous phase).

[0043] [Example 7] A polyesterimide resin varnish (product name: Neoheat 8600A, polyesterimide resin component 30 mass%, manufactured by Totoku Toryo Co., Ltd.) was mixed with 30 volume % fluororesin (product name: Polymist F5A, manufactured by Solvay, PTFE particles with a particle size of 4 μm) relative to 70 volume % polyesterimide resin component, and stirred for 3 hours. In this way, insulating coating material 7 containing polyesterimide resin as thermosetting resin A and fluororesin as resin B was obtained. An insulated wire of Example 7 was obtained in the same manner as in Example 1, except that insulating varnish 7 was used instead of insulating varnish 1 in Example 1. The layer formed from insulating varnish 7 had a structure in which a fluororesin (dispersed phase) was dispersed in a polyesterimide resin (continuous phase). In the same manner as in Example 1, a polyesterimide resin film and a fluororesin-containing polyesterimide resin film were prepared, and both films were triboelectrically charged by the method described above. The surface potential of the fluororesin-containing polyesterimide resin film was immediately measured with a potential meter (KSD-300, manufactured by Kasuga Electric Co., Ltd.). It was found that the surface potential of the fluororesin-containing polyesterimide resin film was −105 V, and the triboelectric series of the fluororesin was lower than that of the polyesterimide resin, whose surface potential was a positive value.

[0044] [Example 8] An insulated wire of Example 8 was obtained in the same manner as in Example 1, except that the thickness of the entire insulating coating (including the 4 μm-thick insulating layer) was changed as shown in the following Table 2. The layer formed from the insulating varnish 1 had a structure in which a silicone resin (dispersed phase) was dispersed in a PI resin (continuous phase).

[0045] [Example 9] Insulating paint 9 was prepared by using 25% by volume of silicone resin (product name: KMP590, manufactured by Shin-Etsu Chemical Co., Ltd., silicone resin particles with a particle size of 2.0 μm) relative to 75% by volume of PI resin component instead of 20% by volume of silicone resin relative to 80% by volume of PI resin component in insulating paint 1 in Example 1, and insulating paint 9 was used instead of insulating paint 1, and the thickness of the entire insulating coating (including the thickness of the 4 μm-thick insulating layer) was changed as shown in the following Table 2. An insulated wire of Example 9 was obtained in the same manner as in Example 1. The layer formed from insulating paint 9 had a structure in which silicone resin (dispersed phase) was dispersed in PI resin (continuous phase).

[0046] [Example 10] An insulated wire of Example 10 was obtained in the same manner as in Example 1, except that insulating paint 3 was used instead of insulating paint 1 in Example 1, and the thickness of the entire insulating coating (including the 4 μm insulating layer) was changed as shown in the following Table 2. The layer formed from insulating paint 3 had a structure in which a fluororesin (dispersed phase) was dispersed in a PI resin (continuous phase).

[0047] [Example 11] Insulating paint 11 was prepared by using 30% by volume of fluororesin (product name: Polymist F5A, manufactured by Solvay, PTFE particles with a particle size of 4 μm) relative to 70% by volume of PI resin component instead of 20% by volume of silicone resin relative to 80% by volume of PI resin component in insulating paint 1 in Example 1, and this insulating paint 11 was used instead of insulating paint 1, and the thickness of the entire insulating coating (including the thickness of the 4 μm-thick insulating layer) was changed as shown in the following Table 2. An insulated wire of Example 11 was obtained in the same manner as in Example 1. The layer formed from insulating paint 11 had a structure in which fluororesin (dispersed phase) was dispersed in PI resin (continuous phase).

[0048] [Example 12] In Example 1, instead of 20% by volume of silicone resin relative to 80% by volume of the PI resin component as resin B of the insulating varnish 1, 20% by volume of core-shell particles (product name: Silcrusta MK03, manufactured by Nikko Rica Corporation, particle size 3 μm) having a crosslinked polymethyl methacrylate core and a polymethylsilsesquioxane shell relative to 80% by volume of the PI resin component was used to prepare the insulating varnish 12, and the insulating varnish 12 was used instead of the insulating varnish 1, and the thickness of the entire insulating coating (including the thickness of the 4 μm-thick insulating layer) was changed as shown in Table 2 below. An insulated wire of Example 12 was obtained in the same manner as in Example 1. The layer formed from the insulating varnish 12 had a structure in which core-shell particles (dispersed phase) were dispersed in the PI resin (continuous phase). Furthermore, a PI resin film and a core-shell particle-containing PI resin film were prepared in the same manner as in Example 1, and both films were triboelectrically charged by the method described above. The surface potential of the core-shell particle-containing PI resin film was immediately measured with a potential meter (KSD-300, manufactured by Kasuga Electric Co., Ltd.). It was found that the surface potential of the core-shell particle-containing PI resin film was −25 V, and that the triboelectric series of the core-shell particles was lower than that of the PI resin, whose surface potential was a positive value.

[0049] [Example 13] In Example 1, instead of 20% by volume of silicone resin relative to 80% by volume of PI resin component as resin B of insulating varnish 1, 25% by volume of core-shell particles (product name: Silcrusta MK03, manufactured by Nikko Rica Corporation, particle size 3 μm) having crosslinked polymethylmethacrylate as a core and polymethylsilsesquioxane as a shell relative to 75% by volume of PI resin component was used to prepare insulating varnish 13, and insulating varnish 13 was used instead of insulating varnish 1. The thickness of the entire insulating coating (including the thickness of the 4 μm-thick insulating layer) was changed as shown in Table 2 below. An insulated wire of Example 13 was obtained in the same manner as in Example 1. The layer formed from insulating varnish 13 had a structure in which core-shell particles (dispersed phase) were dispersed in PI resin (continuous phase).

[0050] [Example 14] Insulating varnish 14 was prepared by using 20% ​​by volume of polypropylene resin (product name: PPW-5J, manufactured by Seishin Enterprise Co., Ltd., polypropylene (PP) particles with a particle size of 5 μm) relative to 80% by volume of PI resin components instead of 20% by volume of silicone resin relative to 80% by volume of PI resin components in insulating varnish 1 in Example 1, and insulating varnish 14 was used instead of insulating varnish 1, and the thickness of the entire insulating coating (thickness including the 4 μm-thick insulating layer) was changed as shown in Table 2 below. An insulated wire of Example 14 was obtained in the same manner as in Example 1. The layer formed from insulating varnish 14 had a structure in which polypropylene particles (dispersed phase) were dispersed in PI resin (continuous phase). In addition, a PI resin film and a polypropylene resin-containing PI resin film were prepared in the same manner as in Example 1, and both films were triboelectrically charged by the method described above. The surface potential of the polypropylene resin-containing PI resin film was immediately measured with a potential meter (KSD-300, manufactured by Kasuga Electric Co., Ltd.). It was found that the surface potential of the polypropylene-containing PI resin film was -10 V, and that the triboelectric series of polypropylene was lower than that of the PI resin, whose surface potential was a positive value.

[0051] [Comparative Example 1] The PI resin varnish was applied onto a conductor and baked at a furnace temperature of 520° C., which was repeated several times to form an insulating coating having a thickness of 27 μm, thereby obtaining an insulated wire of Comparative Example 1.

[0052] [Comparative Example 2] The PAI resin varnish was applied onto a conductor and baked at a furnace temperature of 520° C. repeatedly several times to form an insulating coating having a thickness of 27 μm, thereby obtaining an insulated wire of Comparative Example 2.

[0053] [Comparative Example 3] Comparative insulating varnish 3 was prepared by using 18% by volume of acrylic resin (product name: MX-150, manufactured by Soken Chemical & Engineering Co., Ltd., acrylic resin particles with a particle size of 1.5 μm) relative to 82% by volume of PI resin component as resin B in insulating varnish 1 in Example 1, instead of 20% by volume of silicone resin relative to 80% by volume of PI resin component, and an insulated wire of Comparative Example 3 was obtained in the same manner as in Example 1, except that comparative insulating varnish 3 was used instead of insulating varnish 1. The layer formed from comparative insulating varnish 3 had a structure in which acrylic resin (dispersed phase) was dispersed in PI resin (continuous phase). Furthermore, a PI resin film and an acrylic resin-containing PI resin film were prepared in the same manner as in Example 1, and both films were triboelectrically charged by the method described above. The surface potential of the acrylic resin-containing PI resin film was immediately measured with a potential meter (KSD-300, manufactured by Kasuga Electric Co., Ltd.). It was found that the surface potential of the acrylic resin-containing PI resin film was +20 V, and that the triboelectric series of the acrylic resin was higher than that of the PI resin.

[0054] [Comparative Example 4] Comparative insulating varnish 4 was prepared using 14 volume % metal oxide (product name: HT0210, manufactured by Toho Titanium Co., Ltd., titanium dioxide particles with a particle size of 2.1 μm) relative to 86 volume % PAI resin component as resin B of insulating varnish 2 in Example 2, instead of 25 volume % silicone resin relative to 75 volume % PAI resin component, and an insulated wire was obtained in the same manner as in Example 2, except that comparative insulating varnish 4 was used instead of insulating varnish 2. The layer formed from comparative insulating varnish 4 had a structure in which titanium dioxide (dispersed phase) was dispersed in the PAI resin (continuous phase). Furthermore, in the same manner as in Example 1, a PAI resin film and a titanium dioxide-containing PAI resin film were prepared, and both films were triboelectrically charged by the method described above. The surface potential of the titanium dioxide-containing PAI resin film was quickly measured with a potential meter (KSD-300, manufactured by Kasuga Electric Co., Ltd.). It was confirmed that the surface potential of the titanium dioxide-containing PAI resin film was +50 V, and that the triboelectric series of titanium dioxide was higher than that of the PAI resin.

[0055] [Comparative Example 5] The PI resin varnish was applied onto a conductor and baked at a furnace temperature of 520° C., which was repeated several times to form an insulating coating with a thickness of 80 μm, thereby obtaining an insulated wire of Comparative Example 5.

[0056] [Comparative Example 6] The PI resin varnish was applied onto a conductor and baked at a furnace temperature of 520° C. several times to form an insulating coating having a thickness of 200 μm, thereby obtaining an insulated wire of Comparative Example 6.

[0057] Various physical properties of each insulated wire were measured as follows. The methods for measuring these physical properties were as follows.

[0058] [Partial discharge inception voltage (PDIV)] A test piece was prepared by twisting two insulated wires together, and a 50 Hz sine wave AC voltage was applied between each conductor. The voltage was continuously increased while the voltage (effective value) when the discharge charge was 10 pC was measured at room temperature (20°C) using a partial discharge tester (Kikusui Electronics Co., Ltd., KPD2050). The test piece was evaluated according to the following criteria. -Evaluation criteria for partial discharge inception voltage- ○: 600Vrms or more ×: Less than 600Vrms

[0059] [Charging life] Two insulated wires were twisted together, and an AC voltage (sine wave 10 kHz) obtained by adding 10% of the PDIV value measured above was applied between each conductor, and the time until dielectric breakdown was measured at room temperature (20°C) and evaluated according to the following evaluation criteria. For example, if the measured PDIV value is 600 Vrms, the "AC voltage obtained by adding 10% of the PDIV value" is 660 Vrms. -Evaluation criteria for voltage life- ◎: 3000 minutes or more ○: 2000 to 3000 minutes ×: Less than 2000 minutes

[0060] [Tensile elongation at break] The conductor was removed from the insulated wire to obtain a tubular insulating coating with an inner diameter of 1.0 mm. While still in the tubular form, a tensile test was performed in the longitudinal direction at 10 mm / min with a chuck distance of 30 mm using a tensile tester in an atmosphere of 25°C and 50% relative humidity. The elongation at the time of break was measured and evaluated according to the following evaluation criteria. ◎: 30% or more ○: 15% to less than 30% ×: Less than 15%

[0061] [Flexibility] After stretching the insulated wire by 10% (stretching to 110% of the original length, with 100% being the original length), the insulated wire was wrapped tightly around itself 10 times so that the wires were in contact with each other. The presence or absence of cracks in the coating was then visually inspected and evaluated according to the following evaluation criteria. ○: No cracks ×: Cracks present

[0062] [Area occupancy rate of the resin B on the outermost surface of the insulating coating] The conductor was removed from the insulated wire, and the resulting tubular insulating coating was cut into a flat plate with the top surface facing up. The top surface was subjected to elemental analysis using a SEM (product name: SU8020, Hitachi High-Technologies Corporation)-EDX (product name: X-Max, Horiba, Ltd.). Silicon atoms were detected for silicone resin, fluorine atoms for fluororesin, silicon atoms for core-shell particles, and titanium atoms for metal oxide (titanium dioxide). Images obtained at 8 ekV and 5000x magnification were analyzed using image analysis software (product name: WinROOF, Mitani Shoji Co., Ltd.), and the area occupancy rate of resin B was calculated. For polypropylene and acrylic resin, nitrogen atoms that are absent in polypropylene and acrylic resin but present in polyimide resin were detected, and the area occupied by polypropylene and acrylic resin was calculated by subtracting the area of ​​the nitrogen atoms from the area of ​​the entire image.

[0063] The triboelectric series relationship between the thermosetting resin A and the resin B was determined as described above. A digital low potential meter (KSD-300 manufactured by Kasuga Electric Co., Ltd.) was used as a potential meter for measuring the surface potential. The results are shown in Tables 1 to 3 below.

[0064] [Table 1]

[0065] [Table 2]

[0066] [Table 3]

[0067] As shown in the above table, the insulated wires having an insulating coating in which the insulating layer did not contain a resin lower in the triboelectric series than thermosetting resin A had a short voltage application life (Comparative Examples 1 to 3, 5 and 6). In addition, an insulated wire having an insulating coating containing an insulating metal oxide (titanium dioxide) in an insulating layer had a long voltage application life and excellent insulation durability, but the flexibility (elongation, flexibility) of the insulating coating was poor (Comparative Example 4). In contrast, the insulated wires having an insulating coating satisfying the requirements of the present invention all exhibited sufficient elongation and flexibility, and the insulated wires having these insulating coatings had high PDIV and long voltage life (Examples 1 to 14).

[0068] Although the present invention has been described in conjunction with embodiments thereof, we do not intend to limit our invention to any of the details of the description unless specifically stated otherwise, and believe that the appended claims should be broadly construed without departing from the spirit and scope of the invention as set forth in the appended claims.

[0069] This application claims priority based on Japanese Patent Application No. 2019-212158, filed on November 25, 2019, the contents of which are incorporated herein by reference as part of the present specification. [Explanation of symbols]

[0070] 1. Insulated wire 11 Conductor 12 Insulation film 30 Stator 31 Stator core 32 Slots 33 Coil 34 Wire Segments 34a open end

Claims

1. An insulated wire having a conductor and an insulating coating covering the conductor, at least one of the insulating layers constituting the insulating coating contains a thermosetting resin A constituting a continuous phase and a resin B which is lower in the triboelectric series than the thermosetting resin A and constituting a dispersed phase.

2. The insulated wire according to claim 1 , wherein the thermosetting resin A contains a polyimide resin.

3. 3. The insulated wire according to claim 1, wherein in at least an outermost layer of the insulating coating, the thermosetting resin A forms a continuous phase and the resin B forms a dispersed phase, and an area occupancy rate of the resin B on the outermost surface of the insulating coating is 10% or more and 50% or less.

4. 4. The insulated wire according to claim 3, wherein the thermosetting resin A and the resin B are incompatible with each other.

5. The insulated wire according to any one of claims 1 to 4, wherein the resin B contains resin particles having a particle size of 0.2 to 10 µm.

6. The insulated wire according to any one of claims 1 to 5, wherein the resin B contains core-shell particles and / or hollow particles.

7. The insulated wire according to any one of claims 1 to 6, wherein the resin B contains at least one of a fluororesin, a silicone resin, and a polypropylene resin.

8. The insulated wire according to any one of claims 1 to 7, wherein the insulating coating has a tensile breaking elongation of 30% or more.

9. A coil comprising the insulated wire according to any one of claims 1 to 8.

10. An electric / electronic device comprising the coil according to claim 9.

Images