Insulated wire, coil, and motor

Abstract

An insulated wire comprising a conductor and a coating film that contains a thermoplastic polyimide resin, the insulated wire being wound with a winding diameter that is at least ten times the wire diameter of the insulated wire.

Description

Insulated wires, coils, and motors

[0001] This disclosure relates to insulated wires, coils, and motors.

[0002] Polyimide resin is widely used as an insulating material in various components for industrial materials, automobiles, electrical and electronic applications, and other industrial uses due to its excellent heat resistance, electrical insulation properties, and mechanical properties.

[0003] Patent Document 1 discloses an insulated wire in which an insulating film is formed by extruding a thermoplastic polyimide onto the outer circumference of a conductor.

[0004] Patent Document 1: International Publication No. 2014 / 084063

[0005] Insulated wires (magnet wires) are typically transported and distributed after manufacturing, wound onto bobbins (packaging). The inventors of this invention have conducted diligent research and found that after a predetermined period of time, crazing can occur in the insulating coating of insulated wires coated with thermoplastic polyimide resin while wound onto bobbins, indicating room for improvement.

[0006] One embodiment of this disclosure aims to solve the problem of providing insulated wires, coils, and motors in which the occurrence of crazing is suppressed.

[0007] The means for solving the above problems include the following embodiments: <1> An insulated wire comprising a conductor and a coating containing a thermoplastic polyimide resin, wherein the insulated wire is wound with a winding diameter of 10 times or more the diameter of the wire. <2> An insulated wire comprising a conductor and a coating containing a thermoplastic polyimide resin, wherein the elongation rate of the coating calculated by the following formula (A) is 9.5% or less. Elongation rate of coating (%) = [d / (D + d)] × 100 (d: wire diameter, D: winding diameter) (A) <3> The insulated wire according to <1> or <2>, wherein the thermoplastic polyimide resin comprises a structural unit represented by the following formula (1). In equation (1) above, X is a direct bond, -SO ２ -, -CO-, -C(CH ３ ) ２ -, -C (CF ３ )２ The group is - or -S-, where R1, R2, R3, and R4 are each independently a hydrogen atom, an alkyl group, an alkoxy group, a halogenated alkyl group, a halogenated alkoxy group, or a halogen atom, and Y is a group selected from the group consisting of four groups represented by any of the following formulas (2-1) to (2-4). In the following formulas (2-1) to (2-4), * represents the bond position, and the hydrogen atom of the aromatic ring may be substituted. Also, the position of the bond group whose bond position has not been determined in formula (1) is either the para or meta position relative to the position to which the oxygen atom is bonded. <4> The insulated wire according to <3>, wherein the thermoplastic polyimide resin includes a structural unit represented by the following formula (3). <5> An insulated wire according to any one of <1> to <4>, wherein the aspect ratio of the cross-section of the insulated wire is 1.5 or less. <6> An insulated wire according to any one of <1> to <5>, wherein the wire diameter of the insulated wire is 0.5 mm to 3.0 mm. <7> An insulated wire according to any one of <1> to <6>, wherein the thickness of the coating is 0.05 mm to 0.15 mm. <8> An insulated wire according to any one of <1> to <7>, wound with a winding diameter of 10 mm to 150 mm. <9> An insulated wire according to any one of <1> to <8>, wherein the coating is a single layer. <10> An insulated wire according to any one of <1> to <9>, wherein the coating mainly contains the thermoplastic polyimide resin. <11> A coil comprising an insulated wire according to any one of <1> to <10>. <12> A motor comprising the coil according to <11>.

[0008] According to one embodiment of the present disclosure, insulated wires, coils, and motors are provided in which the occurrence of crazing is suppressed.

[0009] Figure 1 is a schematic diagram showing an example of an apparatus used in the manufacture of insulated wires according to this disclosure.

[0010] The embodiments of this disclosure are described below. The description is illustrative and does not limit the scope of this disclosure.

[0011] In this disclosure, numerical ranges indicated using "~" represent a range that includes the numerical values ​​before and after "~" as the minimum and maximum values, respectively. In numerical ranges described in stages within an embodiment, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in numerical ranges described within an embodiment, the upper or lower limit of that numerical range may be replaced with the values ​​shown in the example.

[0012] In this disclosure, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, as long as their intended purpose is achieved.

[0013] In this disclosure, each component may contain multiple of the corresponding substances. When referring to the amount of each component in a composition in this disclosure, if there are multiple substances corresponding to each component in the composition, it means the total amount of those multiple substances present in the composition unless otherwise specified.

[0014] In this disclosure, the term "wire diameter" means, when the conductor is a rectangular wire, the length of the longer side of the rectangular cross-section perpendicular to the longitudinal direction of the insulated wire. When the conductor is a round wire, it means the length of the longer axis of the circular or elliptical cross-section perpendicular to the longitudinal direction of the insulated wire.

[0015] In this disclosure, the term "aspect ratio" means, when the conductor is a rectangular wire, the ratio of the length of the long side to the length of the short side of a rectangular cross-section perpendicular to the longitudinal direction of the insulated wire (length of the long side of the rectangular cross-section / length of the short side of the rectangular cross-section). When the conductor is a round wire, the term "aspect ratio" means, when the conductor is a rectangular wire, the ratio of the length of the long axis to the length of the short axis of a circular or elliptical cross-section perpendicular to the longitudinal direction of the insulated wire (length of the long axis of the circular or elliptical cross-section / length of the short axis of the circular or elliptical cross-section).

[0016] In this disclosure, the term "winding diameter" means, when the insulated wire is wound on a bobbin (packaging), the diameter (outer diameter) of the body (winding core) of the bobbin used when winding a long length of insulated wire, and when the insulated wire is wound on a core in a coil, twice the minimum radius of curvature of the cross-section of the portion of the core on which the insulated wire is wound. Furthermore, in the manner in which the insulated wire is wound according to this disclosure, for example, in the case of an insulated wire with a rectangular cross-section (or circular or elliptical), the wire is wound in such a way that the surface including the short side (or short axis) is in contact with the winding core and the surfaces including the short sides (or single axis) are in contact with each other.

[0017] <Insulated Wire> A first aspect of the insulated wire of this disclosure comprises a conductor and a coating containing a thermoplastic polyimide resin, and is a winding with a winding diameter of 10 times or more the diameter of the insulated wire. A second aspect of the insulated wire of this disclosure comprises a conductor and a coating containing a thermoplastic polyimide resin, wherein the elongation rate of the coating, calculated by the following formula (A), is 9.5% or less. Elongation rate of coating (%) = [d / (D + d)] × 100 (d: wire diameter, D: winding diameter) (A)

[0018] The insulated wire of this disclosure can suppress the occurrence of crazing by winding the insulated wire with a winding diameter of 10 times or more its wire diameter, as described above, or by having an elongation rate of 9.5% or less of the coating on the insulated wire.

[0019] The insulated wires of the first embodiment and the insulated wires of the second embodiment will be described in detail below. The contents common to the insulated wires of the first embodiment and the second embodiment will generally be simply referred to as "the insulated wires of this disclosure."

[0020] (Conductor) As the conductor, metals with excellent electrical conductivity such as copper, copper alloys, nickel-plated copper, copper-clad aluminum, and aluminum can be used. Among these, copper wire is preferred from the viewpoint of excellent electrical conductivity and cost.

[0021] The shape of the conductor is not particularly limited, but from the viewpoint of improving the space factor when applied to a motor, a rectangular cross-section is preferable. In other words, the conductor is preferably a rectangular wire.

[0022] From the viewpoint of improving adhesion with the coating, the paraffin used during manufacturing of the conductor may be degreased with alcohol. Furthermore, the surface of the conductor may be plated or otherwise treated to prevent the formation of an oxide film.

[0023] The conductor may be surface-modified to improve adhesion with the coating. Examples of surface modification treatments include mechanical treatments such as blasting, polishing, and embossing; physical treatments such as laser treatment, corona treatment, plasma treatment, and dry etching; electrochemical treatments such as plating and anodizing; and chemical treatments such as chemical etching (wet etching) and surface coating.

[0024] In blasting, particulate or finely powdered media is sprayed onto a conductor and impacted, creating irregularities on the conductor's surface. This increases the surface roughness of the conductor, making it easier for the coating to adhere due to frictional resistance (anchor effect). Therefore, the adhesion between the conductor and the coating can be improved. Furthermore, blasting can also remove oxide films formed on the conductor's surface, which further contributes to improved adhesion with the coating, making it a suitable method. Examples of media that can be used include those composed of metal particles, carbon particles, oxide particles, carbide particles, nitride particles, and the like.

[0025] Corona treatment modifies (makes hydrophilic) the conductor surface through corona discharge. Chemical interactions can improve the adhesion between the conductor and the coating.

[0026] In the plating process, the conductor is coated with a plating material. From the viewpoint of cost and productivity, wet plating is preferred. Furthermore, electrolytic plating is more preferred. Examples of plating materials include nickel plating and silver plating. The plating thickness is preferably 0.1 μm to 10 μm, and more preferably 0.5 μm to 5 μm.

[0027] In surface coating, a coating agent is applied or sprayed onto the conductor. Coating prevents surface oxidation of the conductor, and chemical interactions improve the adhesion between the coated conductor and the coating film. Silane coupling agents can be used as the coating agent.

[0028] Examples of silane coupling agents include vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2-(aminoethyl)- 3-aminopropylmethyldimethoxysilane, N-2(aminoethyl)3-aminopropyltrimethoxysilane, N-2(aminoethyl)3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, hexamethyldisilazane, 3-(2-aminoethylaminopropyl)dimethoxymethylsilane, 3-(2-aminoethylaminopropyl)trimethoxysilane, 2-(2-aminoethylthioethyl)diethoxymethylsilane, 2-(2-aminoethylthioethyl)triethoxysilane, 3-[2-(2-aminoethylaminoethylamino)propyl]trimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride, 3-ureidopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-isocyanatetopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis(triethoxysilylpropyl)tetrasulfide, imidazolylalkyl-trialkoxysilane, diphenyldimethoxysilane, hexyltrimethoxysilane, decyltrimethoxysilane, trifluoropropyltrimethoxysilane, tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, dimethyltriethoxysilane, phenyltriethoxysilane, 3-trimethoxysilylpropyl succinic anhydride, etc. can be used. Among the silane coupling agents listed above, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 3-glycidoxypropyltrimethoxysilane are preferred. Commercially available silane coupling agents can be used, such as KBE-903, KBM-602, KBM-603, KBM-903, KBE-402, KBE-403, KBM-303, KBM-402, and KBM-403 (all manufactured by Shin-Etsu Chemical Co., Ltd.).

[0029] (Coating Containing Thermoplastic Polyimide Resin) The insulated wire of the present disclosure includes a coating containing a thermoplastic polyimide resin. From the viewpoint of improving the electrical properties and heat resistance of the coating, the coating preferably contains a thermoplastic polyimide resin as a main component. The expression "contains a thermoplastic polyimide resin as a main component" means that the content of the thermoplastic polyimide resin in the coating is 51% by mass or more. The coating may be a single layer or a multilayer, but is preferably a single layer from the viewpoint of production cost. When the coating is a multilayer, at least one of the plurality of layers only needs to contain a thermoplastic polyimide resin, and the other layers do not need to contain a thermoplastic polyimide resin. When the coating is a single layer, in the insulated wire, the layer containing the thermoplastic polyimide resin is in direct contact with the conductor. The coating may have a thickness of 0.05 mm to 0.15 mm.

[0030] —Thermoplastic Polyimide Resin— Examples of the thermoplastic polyimide resin include a thermoplastic polyimide resin (a1) having a structural unit represented by the following chemical formula (1), a thermoplastic polyimide resin (a1)' having a structural unit represented by the following chemical formula (1)', a thermoplastic polyimide resin (a2) having a structural unit represented by the following chemical formula (3), a thermoplastic polyimide copolymer resin (a3) having structural units represented by the following chemical formula (4) and the following chemical formula (5), a thermoplastic polyimide resin (a4) having a structural unit represented by the following chemical formula (6), and a thermoplastic polyimide copolymer resin (a5) having a structural unit represented by the following chemical formula (6) and a structural unit represented by the following chemical formula (7).

[0031]

[0032] In chemical formula (1), X is a direct bond, -SO ２ -, -CO-, -C(CH ３ ) ２ -, -C(CF ３ ) ２-, or -S-, and R1, R2, R3, and R4 each independently represent a hydrogen atom, an alkyl group, an alkoxy group, a halogenated alkyl group, a halogenated alkoxy group or a halogen atom, and Y is a tetravalent aromatic group selected from any of the following linking group groups (2-1) to (2-4). In addition, in the above-mentioned formula (1), the bonding position of the bonding group whose bonding position is not determined is para or meta with respect to the bonding position of the oxygen atom.

[0033]

[0034] In the above formula (1), the bonding position of the bonding group whose bonding position is not determined is preferably meta with respect to the bonding position of the oxygen atom. That is, the formula (1) is preferably represented by the following formula (1)', and the thermoplastic polyimide preferably contains a structural unit represented by the following formula (1)'.

[0035]

[0036] From the viewpoint of suppressing a decrease in dielectric breakdown voltage, Y is preferably a group represented by formula (2-1) or formula (2-3), and more preferably a group represented by formula (2-1).

[0037] As the substituents that the aromatic rings in formulas (2-1) to (2-4) may have, an optionally substituted alkyl group, an optionally substituted alkoxy group, an optionally substituted halogenated alkyl group, an optionally substituted halogenated alkoxy group, or a halogen atom are preferred. When the aromatic ring in any of formulas (2-1) to (2-4) has a plurality of substituents, the substituents may be the same as or different from each other.

[0038]

[0039]

[0040] Here, n in chemical formula (4) and m in chemical formula (5) represent the copolymerization ratio of the polyimide copolymer, n / m is in the range of 4 to 99 (mol% / mol%), n / m is more preferably 5 to 50, still more preferably 6 to 20, particularly preferably 7 to 15, and most preferably 9.

[0041]

[0042] However, p in formula (6) and q in formula (7) represent the copolymerization ratio of the thermoplastic polyimide copolymer, where p / q (mol% / mol%) is preferably 0.01 to 100, more preferably 0.1 to 50, even more preferably 0.3 to 10, particularly preferably 0.5 to 3, and most preferably 1.

[0043] Each of the above thermoplastic polyimide resins (a1) to (a5) can be produced by reacting an aromatic diamine compound and an aromatic tetracarboxylic dianhydride, which form the structural units shown in each chemical formula, as raw materials, in the presence or absence of an organic solvent, and imidizing the resulting polyamic acid. Known methods for producing polyimides can be used for production. At least one of the above aromatic diamine compound and the above aromatic tetracarboxylic dianhydride may be a biomass-derived compound, in which at least a portion of the raw materials are derived from biomass. That is, the above thermoplastic polyimide may be a biomass-derived thermoplastic polyimide.

[0044] To give a more specific example, a thermoplastic polyimide resin (a1)' having a structural unit represented by chemical formula (1)' is used, and an aromatic diamine compound represented by the following chemical formula (8) and an aromatic tetracarboxylic dianhydride represented by the following chemical formula (9) are used as raw materials.

[0045]

[0046] In chemical formula (8), X and R1-R4 are the same as X and R1-R4 in chemical formula (1)'.

[0047]

[0048] In chemical formula (9), Y is the same as Y in chemical formula (1)'.

[0049] In chemical formulas (1), (1)', and (8), specific examples of R1, R2, R3, and R4 include a hydrogen atom, alkyl groups such as a methyl group and an ethyl group; alkoxy groups such as a methoxy group and an ethoxy group; halogenated alkyl groups such as a fluoromethyl group and a trifluoromethyl group; halogenated alkoxy groups such as a fluoromethoxy group; and halogen atoms such as a chlorine atom and a fluorine atom; preferably, a hydrogen atom.

[0050] In chemical formulas (1), (1)', and (9), Y is a tetravalent aromatic group selected from the above-mentioned linking group group (2-1) to (2-4), and is preferably a benzene ring. In that case, the aromatic tetracarboxylic dianhydride of chemical formula (9) is a pyromellitic dianhydride.

[0051] The thermoplastic polyimide resin is preferably thermoplastic polyimide resin (a1), thermoplastic polyimide resin (a1)', thermoplastic polyimide resin (a2), thermoplastic polyimide copolymer resin (a3), thermoplastic polyimide resin (a4), or thermoplastic polyimide copolymer resin (a5).

[0052] The thermoplastic polyimide preferably contains the structural unit represented by the above chemical formula (1), and more preferably consists of the structural unit represented by the above chemical formula (1). By containing the structural unit represented by the above chemical formula (1), the electrical properties and heat resistance of the coating containing the thermoplastic polyimide resin are improved.

[0053] The thermoplastic polyimide more preferably contains the structural unit represented by the above chemical formula (1)', and even more preferably consists of the structural unit represented by the above chemical formula (1)'. By containing the structural unit represented by the above chemical formula (1)', the electrical properties and heat resistance of the coating containing the thermoplastic polyimide resin are improved.

[0054] The thermoplastic polyimide is more preferably composed of the structural unit represented by the above chemical formula (3), and even more preferably composed of the structural unit represented by the above chemical formula (3). By including the structural unit represented by the above chemical formula (3), the electrical properties and heat resistance of the coating containing the thermoplastic polyimide resin are improved. By being composed of the structural unit represented by the above chemical formula (3), the adhesion between the conductor and the coating containing the thermoplastic polyimide resin is improved.

[0055] In manufacturing thermoplastic polyimide resins, copolymerization can be carried out using one or more other aromatic diamine compounds or aromatic tetracarboxylic dianhydrides as raw materials, to the extent that the issues of this disclosure are not impaired.

[0056] The thermoplastic polyimide resins preferably used in this disclosure, or other polyimide resins, may be optionally polymer-blended to the extent that they do not impair the issues addressed in this disclosure.

[0057] The weight-average molecular weight (Mw) of thermoplastic polyimide is preferably 20,000 or more from the viewpoint of heat resistance. The weight-average molecular weight (Mw) of thermoplastic polyimide is preferably 35,000 or less from the viewpoint of adhesion. The weight-average molecular weight (Mw) of thermoplastic polyimide is preferably 20,000 to 40,000, more preferably 22,000 to 35,000, and even more preferably 25,000 to 30,000.

[0058] In this disclosure, the weight-average molecular weight (Mw) of thermoplastic polyimide refers to the value measured using gel permeation chromatography (GPC), and the measurement method is as follows. When two or more types of thermoplastic polyimide are used in combination, the weight-average molecular weight (Mw) value of the thermoplastic polyimide shall be the value of the mixture of the two or more types of thermoplastic polyimide. Add 1.5 mL of 4-chlorophenol to 5 mg of the sample, stir gently at 130°C to 140°C, and after the resulting solution has been air-cooled to room temperature, add 3.5 mL of chloroform. Then, filter the solution using a 0.2 μm filter to prepare the sample solution, and measure the prepared sample solution under the following conditions.

[0059] Detector: Differential refractive index detector RI (Tosoh Corporation, RI-8020) Column: TSKgel GMHXL x 2, G2500HXL x 1 (Tosoh Corporation, 7.8 mm I.D. x 300 mm) Column temperature: 23°C Solvent: 4-chlorophenol / chloroform (3 / 7) (volt / volt) Flow rate: 0.8 mL / min, Sample concentration: 1 mg / ml, Injection volume: 0.3 mL Standard sample: Monodisperse polystyrene (Tosoh Corporation)

[0060] The melt flow rate (MFR) of thermoplastic polyimide resin, measured under conditions of 400°C and a 1.05 kg load in accordance with JIS K7210-1:2014, is not particularly limited, but is preferably 2 g / 10 min to 30 g / 10 min, and more preferably 4 g / 10 min to 20 g / 10 min. When two or more types of thermoplastic polyimide are used in combination, the MFR of the thermoplastic polyimide shall be the value of the mixture of the two or more types of thermoplastic polyimide contained in the coating. The MFR of thermoplastic polyimide resin is not particularly limited, but can be measured using a melt indexer (manufactured by Toyo Seiki Seisakusho Co., Ltd., model number: A-371401705).

[0061] The logarithmic viscosity of the thermoplastic polyimide resin is not particularly limited, but is preferably 0.1 dl / g to 3.0 dl / g, more preferably 0.2 dl / g to 2.0 dl / g, even more preferably 0.3 dl / g to 1.5 dl / g, and particularly preferably 0.4 dl / g to 1.0 dl / g. When the logarithmic viscosity is 0.1 dl / g to 3.0 dl / g, the molecular weight of the thermoplastic polyimide resin is appropriate. Therefore, the coating containing the thermoplastic polyimide resin has excellent mechanical strength, and the thermoplastic polyimide resin has excellent fluidity for manufacturing the coating by injection molding or extrusion molding. When two or more types of thermoplastic polyimide are used in combination, the logarithmic viscosity of the thermoplastic polyimide is the value of the mixture of the two or more types of thermoplastic polyimide contained in the coating.

[0062] Logarithmic viscosity is measured by heating a 0.5 g / 100 ml solution of parachlorophenol / phenol (90 / 10 weight ratio) to 200°C and then cooling it to 35°C. The definition of logarithmic viscosity is described on page 58 of the 1995 first edition of the 'Polymer Handbook' published by Asakura Shoten, Japan Society for Analytical Chemistry.

[0063] The glass transition temperature Tg of the thermoplastic polyimide resin is not particularly limited, but from the viewpoint of heat resistance, it is preferably 200°C or higher, more preferably 210°C or higher, even more preferably 220°C or higher, and particularly preferably 230°C or higher. The glass transition temperature Tg of the thermoplastic polyimide resin is not particularly limited, but is preferably 300°C or lower, more preferably 290°C or lower, even more preferably 280°C or lower, and particularly preferably 260°C or lower.

[0064] The glass transition temperature Tg can be determined using a differential scanning calorimeter (DSC220C model, manufactured by Seiko Instruments Inc.). Approximately 5 mg of the material is sealed in a measuring aluminum pan, placed in the differential scanning calorimeter, heated from room temperature to 450°C at a rate of 10°C / min, held at 450°C for 5 minutes to completely melt the resin, then cooled to 30°C at a rate of 10°C / min, left at 30°C for 5 minutes, and then heated a second time to 450°C at a rate of 10°C / min. The displacement point corresponding to the glass transition is then determined as the glass transition temperature (Tg).

[0065] The melting point of thermoplastic polyimide resin is not particularly limited, but from the viewpoint of heat resistance, it is preferably 340°C or higher, more preferably 350°C or higher, even more preferably 360°C or higher, even more preferably 370°C or higher, and particularly preferably 380°C or higher. The melting point of thermoplastic polyimide resin is not particularly limited, but from the viewpoint of moldability, it is preferably 420°C or lower, more preferably 410°C or lower, even more preferably 400°C or lower, and particularly preferably 390°C or lower. Compared to other thermoplastic resins, thermoplastic polyimide resin has a higher melting point, so it is presumed that the temperature difference with the ambient temperature after coating is large, leading to large thermal shrinkage and the possibility of crazing. The melting point can be measured by a differential scanning calorimeter (DSC) (DSC220C model, manufactured by Seiko Instruments).

[0066] A commercially available thermoplastic polyimide resin having the repeating structural unit of the above chemical formula (1)' is AURUM PL400C ("AURUM" is a registered trademark, manufactured by Mitsui Chemicals, Inc., glass transition temperature 250°C, melting point 388°C).

[0067] While the above-mentioned commercially available thermoplastic polyimide resin may be used, thermoplastic polyimide resin can also be synthesized by the following method. Specifically, thermoplastic polyimide resin is obtained by dehydration cocondensation of a diamine represented by formula (10) and a tetracarboxylic dianhydride represented by formula (11).

[0068]

[0069]

[0070] A known imidation reaction can be applied to the method for producing thermoplastic polyimide resin. The amount of raw material compound used is usually 0.90 to 0.99 equivalents of tetracarboxylic dianhydride per equivalent of diamine. Preferably, the amount of raw material compound used is 0.93 to 0.985 equivalents, more preferably 0.95 to 0.98 equivalents. When the amount of raw material compound used is 0.90 to 0.99 equivalents, the molecular weight of the thermoplastic polyimide resin is sufficiently high, resulting in excellent mechanical properties of the coating containing the thermoplastic polyimide resin, as well as excellent fluidity of the thermoplastic polyimide resin.

[0071] In the synthesis of thermoplastic polyimide resins, it is preferable to encapsulate the reaction ends of the molecules with phthalic anhydride or the like. By encapsulating the reaction ends, the thermal stability of the thermoplastic polyimide resin is significantly improved.

[0072] The reaction is particularly preferably carried out in an organic solvent. Examples of organic solvents include N,N-dimethylformamide, N,N-diethylacetamide, N,N-dimethoxyacetamide, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, N-methylcaprolactam, 1,2-dimethoxyethane, bis(2-methoxyethyl) ether, 1,2-bis(2-methoxyethoxy)ethane, bis[2-(2-methoxyethoxy)ethyl] ether, tetrahydrofuran, 1,3-dioxane, 1,4-dioxane, pyrroline, picoline, dimethyl sulfoxide, dimethyl sulfone, tetramethylurea hexamethylphosphoramide, phenol, o-cresol, m-cresol, p-cresol, p-chlorophenol, anisole, benzene, toluene, xylene, etc. Organic solvents may be used individually or in mixtures of two or more types.

[0073] The reaction temperature is usually room temperature to 250°C, preferably 140°C to 200°C. The reaction pressure is not particularly limited and can be carried out at atmospheric pressure. The reaction time varies depending on the type of solvent and the reaction temperature, but is usually 4 to 24 hours. As for the imidation method, the desired polyimide resin can be obtained by imidizing the precursor polyamic acid by heating it to 100°C to 300°C, or by chemical imidation using an imidizing agent such as acetic anhydride.

[0074] A coating containing thermoplastic polyimide resin may contain components other than thermoplastic polyimide resin, such as additives, as long as at least one of the one or more layers contains thermoplastic polyimide resin. A coating containing thermoplastic polyimide resin may also include a coating composed of a resin composition containing thermoplastic polyimide resin. Furthermore, a coating containing thermoplastic polyimide resin may include a coating composed of multiple types of resins other than thermoplastic polyimide resin.

[0075] The additive may contain at least one from the group consisting of carbon fiber, glass fiber, potassium titanate fiber, aluminum borate fiber, metal fiber, ceramic fiber, boron fiber, silicon carbide fiber, asbestos fiber, rock wool fiber, and aramid fiber, within a range that does not impair the properties of the thermoplastic polyimide resin.

[0076] The additive may, if necessary, contain at least one filler, lubricant, release agent, stabilizer, colorant, or nucleating agent, such as mica, synthetic mica, wollastonite, talc, silicone oil, fluorinated oil, glass beads, molybdenum disulfide, clay, silica, alumina, diatom, soil, hydrated alumina, shirasu balloon, carbon nanotube, calcium carbonate, hydrotalcite, fluorine, or graphite (e.g., artificial graphite, natural graphite (e.g., flake graphite, scaly graphite, earthy graphite), etc.), to the extent that it does not impair the properties of the thermoplastic polyimide resin.

[0077] Resins other than thermoplastic polyimide resins may include various liquid crystal polymers, thermoplastic resins different from thermoplastic polyimide resins (e.g., fluororesins, polyetherimide, polyethernitrile, polyetherketone, polyetherketoneketone, polyetherketoneetherketoneketone, polyamideimide, polyethersulfone, polysulfone, polyarylate and / or polyphenylene sulfide), and thermosetting resins (e.g., epoxy resins, polybenzimidazole resins, polyimide resins, etc.).

[0078] When the coating contains additives, the content of the additives and the content of the thermoplastic polyimide resin are not particularly limited and are appropriately selected according to the type of additive, etc., and are preferably within the following ranges. The content of the additives is preferably 0% to 40% by mass relative to the total amount of the coating. The content of the thermoplastic polyimide resin is preferably 60% to 100% by mass relative to the total amount of the coating.

[0079] The insulated wire of this disclosure, taking into consideration the skin effect when an alternating current is passed through it, preferably has a wire diameter of 0.5 mm to 10 mm, more preferably 0.5 mm to 3.0 mm, and even more preferably 0.5 mm to 2.0 mm.

[0080] In the case of the insulated wire of the present disclosure, when the conductor is a rectangular wire, the length of the rectangular cross-section is preferably 0.5 mm to 3.0 mm, more preferably 1.0 mm to 2.5 mm, and even more preferably 1.0 mm to 1.5 mm.

[0081] In the case of the insulated wire of the present disclosure, when the conductor is a rectangular wire, the length of the shorter side of the rectangular cross-section is preferably 0.5 mm to 2.0 mm, more preferably 0.5 mm to 1.7 mm, and even more preferably 0.5 mm to 1.5 mm.

[0082] In the case of the insulated wire of this disclosure, if the conductor is a round wire, the circular or elliptical cross-section preferably has a major axis length of 0.5 mm to 3.0 mm, more preferably 1.0 mm to 2.5 mm, and even more preferably 1.0 mm to 1.5 mm.

[0083] In the case of the insulated wire of this disclosure, if the conductor is a round wire, the circular or elliptical cross-section preferably has a minor axis length of 0.5 mm to 2.0 mm, more preferably 0.5 mm to 1.7 mm, and even more preferably 0.5 mm to 1.5 mm.

[0084] The insulated wire of this disclosure preferably has an aspect ratio of 1.5 or less, more preferably 1.3 or less, and even more preferably 1.0 or less. If the aspect ratio of the insulated wire is greater than 1.5, there may be areas where localized force is applied to the coating when the insulated wire is wound up, which may lead to the occurrence of crazing.

[0085] The winding diameter of the insulated wire in this disclosure will be described later.

[0086] <Coils and Motors> The insulated wires of this disclosure are preferably used as windings (magnet wires) for forming coils. Coils equipped with the insulated wires of this disclosure have excellent durability because the occurrence of crazing in the insulated wires is suppressed. The "winding diameter" in a coil means twice the minimum radius of curvature in the cross-section of the portion of the core around which the insulated wire is wound. That is, it is twice the radius of curvature at the point with the greatest curvature in the cross-section of the portion of the core around which the insulated wire is wound.

[0087] Furthermore, it is preferable that the coil is provided in the motor. A motor equipped with the coil has excellent durability because the occurrence of crazing in the insulated wire is suppressed by using the insulated wire as a winding.

[0088] <Method for manufacturing insulated wire> The method will be explained using the case where the coating is a single layer and is coated with thermoplastic polyimide resin as an example. The insulated wire of this disclosure is obtained by preheating a conductor, extruding the preheated conductor with thermoplastic polyimide resin, and then winding it onto a bobbin with a predetermined winding diameter.

[0089] Figure 1 is a schematic diagram showing an example of an apparatus used in the manufacture of an insulated electric wire according to the present disclosure. The apparatus 100 includes a feeding unit 30 for feeding out a conductor 20, a preheating unit 40 for preheating the conductor 20 fed out from the feeding unit 30, an extrusion coating unit 50 for extruding a thermoplastic polyimide resin onto the preheated conductor 20 to form an insulated electric wire 10, a cooling unit 60 for cooling the formed insulated electric wire 10, and a winding unit 70 for winding up the cooled insulated electric wire 10.

[0090] The conductor 20 is fed out from the dispensing section 30, preheated in the preheating section 40, enters the extrusion coating section 50, is coated with thermoplastic polyimide resin, and is wound onto a bobbin in the winding section 70 while running through the cooling section 60, and recovered as an insulated wire. The winding section 70 consists of a bobbin (winding core) and a drive motor that transmits rotational force to the bobbin via a shaft that passes through the bobbin's cavity.

[0091] (Preheating) Preheating is preferably performed so that the conductor reaches a temperature higher than 250°C and 400°C or lower. Preheating is preferably performed so that the conductor reaches a temperature higher than 250°C and below the melting point of the thermoplastic polyimide resin, and more preferably so that the conductor reaches a temperature higher than 250°C and below the melting point of the thermoplastic polyimide resin. Specifically, preheating is preferably performed so that the conductor reaches a temperature higher than 250°C and 388°C or lower, and more preferably so that the conductor reaches a temperature higher than 250°C and below 388°C. By preheating the conductor within the above temperature range, the temperature difference between the conductor and the molten thermoplastic polyimide resin is reduced during extrusion coating, and stress strain is relieved, thereby improving the adhesion between the conductor and the coating. Furthermore, because the temperature difference is small, the time that the molten thermoplastic polyimide resin remains in contact with the surface of the conductor in a molten state can be extended. As a result, the thermoplastic polyimide resin can be impregnated into the fine irregularities formed on the surface of the conductor, improving the adhesion between the conductor and the coating. Furthermore, by preheating the conductor to a temperature below the melting point of the thermoplastic polyimide resin, the fluidity of the thermoplastic polyimide resin extruded onto the conductor during the extrusion coating process can be moderately reduced, thereby improving adhesion while also improving the uniformity of the coating thickness.

[0092] The preheating method is not particularly limited and may be a contact heating method in which a heat source or flame heated to a high temperature is brought into direct contact with the conductor, or a non-contact heating method using microwaves, high frequencies, etc. When preheating using a non-contact heating method, induction heating using high frequencies is preferred from the viewpoint of preheating at a high temperature. The preheating section may be provided integrally with the dispensing section. Alternatively, the winding core (bobbin) of the dispensing section around which the conductor is wound may be heated.

[0093] When the conductor is a copper wire and it is a high-frequency induction heating device, the preheating time is preferably 0.1 seconds to 5 minutes, more preferably 0.1 seconds to 1 minute.

[0094] (Extrusion Coating) Extrusion coating can be performed in the extrusion coating section (see Figure 1). In the extrusion coating section, a thermoplastic polyimide resin, supplied from the hopper and melted at a predetermined temperature, is extruded onto the preheated conductor fed out from the preheating section. The extrusion coating may be performed so that the coating has a thickness of, for example, 0.05 mm to 0.15 mm.

[0095] The shape of the screw is not particularly limited when extruding the coating. For example, it can be appropriately selected from full-flight shape, rapid compression shape, slow compression shape, barrier-flight shape, mixing-flight shape, etc.

[0096] The effective screw length L may be, for example, 625 mm. The screw diameter D may be, for example, φ25 mm. The ratio of the effective screw length L to the screw diameter D (L / D) may be, for example, 25. The screw compression ratio (ratio of the flight groove depths of cylinder sections C-1 and C-3) may be, for example, 3.0. The screw rotation speed may be, for example, 3.0 rpm.

[0097] The heating temperature of the extruder is, for example, 390°C to 400°C in cylinder section C-1, 410°C to 420°C in cylinder section C-2, 420°C to 430°C in cylinder section C-3, 420°C to 430°C in the neck section, 420°C to 430°C in the head section, and 410°C to 420°C in the die section.

[0098] A standard crosshead die can be used for the die. The die diameter may be, for example, φ7.2 mm. The die tip may have a diameter of φ6.0 mm and a length of 9.0 mm.

[0099] The land length of the die is not particularly limited. A longer land is preferable from the viewpoint of allowing the molten thermoplastic polyimide resin to flow well and increasing the back pressure to improve the adhesion between the conductor and the coating.

[0100] The cylinder may have a filter, and the filter mesh is preferably less than 200 mesh from the viewpoint of reducing resin pressure. For example, 30 mesh to 100 mesh. Multiple meshes may be combined.

[0101] (Winding) The insulated wire can be wound in the winding section 70. The insulated wire of this disclosure is wound onto a winding member (so-called bobbin) with a predetermined winding diameter after the preheated conductor is extruded and coated in the extrusion coating section. The winding diameter can be changed by replacing the bobbin located in the winding section 70 with a bobbin with a different diameter.

[0102] The insulated wire of the first aspect of this disclosure is wound with a winding diameter of 10 times or more the diameter of the insulated wire. The insulated wire of the second aspect of this disclosure comprises a conductor and a coating containing a thermoplastic polyimide resin, wherein the elongation rate of the coating, calculated by the following formula (A), is 9.5% or less. Elongation rate of coating (%) = [d / (D + d)] × 100 (d: wire diameter, D: winding diameter) (A) In formula (A), d represents the wire diameter (unit: mm) and D represents the winding diameter (unit: mm). The insulated wire of this disclosure, by being wound with a winding diameter of 10 times or more the diameter of the insulated wire, or by having an elongation rate of the coating of the insulated wire of 9.5% or less, can keep the tension (tensile stress) applied to the insulated wire below a threshold under the condition that the torque (N・m) applied by the drive motor is constant. This suppresses the orientation of molecular chains along the stretching direction in the coating of the insulated wire, thereby suppressing the occurrence of crazing on the surface of the coating of the insulated wire after it has been manufactured, shipped, inspected, and stored for a certain period of time for use. The aforementioned "threshold" represents the value at which the crazing occurrence rate is 15% or less.

[0103] The insulated wire of the first aspect of this disclosure is preferably wound with a winding diameter of 15 times or more, more preferably with a winding diameter of 20 times or more, and even more preferably with a winding diameter of 30 times or more, from the viewpoint of keeping the tension (tensile stress) applied to the insulated wire below a threshold and further suppressing the orientation of molecular chains in the coating of the insulated wire. There is no particular upper limit to the winding diameter, but from the viewpoint of the efficiency of transporting the insulated wire, it is preferably 100 times or less, more preferably 80 times or less, and even more preferably 50 times or less.

[0104] In the second aspect of the present disclosure, the insulated wire is preferably such that the tension (tensile stress) applied to the insulated wire is below a threshold, and the orientation of molecular chains in the coating of the insulated wire is further suppressed. From this viewpoint, the elongation rate of the coating is preferably 9.0% or less, more preferably 7.5% or less, and even more preferably 5.0% or less. There is no particular limit to the lower limit of the elongation rate of the coating, but from the viewpoint of the efficiency of transporting the insulated wire, it is preferably 0.5% or more, more preferably 1.0% or more, and even more preferably 2.0% or more.

[0105] Furthermore, the insulated wire of this disclosure is preferably wound with a winding diameter of 10 mm to 150 mm, from the viewpoint of ease of handling as an insulated wire product and preventing the occurrence of crazing.

[0106] When winding an insulated wire, a winding speed of 10 mm / min to 30 mm / min is preferable. A winding speed of 15 mm / min to 25 mm / min improves the winding condition, allows the torque to be controlled to a predetermined value or less, and keeps the tension (tensile stress) applied to the insulated wire below a threshold.

[0107] The material of the winding member (bobbin) for winding the insulated wire is not particularly limited, but from the viewpoint of preventing the coating from absorbing moisture from the bobbin, which has absorbed moisture in the storage environment, during storage of the insulated wire, and promoting the orientation of molecular chains in the coating, which can lead to the formation of crazing, a material with low water absorption is preferred. Examples of such materials include resins with a water absorption rate of less than 0.4% as measured according to JIS K 7209, and specifically, polypropylene, ABS (acrylonitrile butadiene styrene) resin, polycarbonate, etc.

[0108] Furthermore, from the viewpoint of preventing crazing from occurring due to the absorption of moisture in the storage environment by the coating during storage of insulated wires, which promotes the orientation of molecular chains, it is preferable that the relative humidity RH (%) in the storage environment of insulated wires be low. For example, 50% or less at 23°C. The storage environment of insulated wires may have a desiccant (e.g., silica gel) to reduce humidity, or it may be replaced with dry nitrogen or dry air. For similar purposes, insulated wires may be wrapped in aluminum bags or covered with polyethylene film.

[0109] An embodiment of this disclosure will be described in more detail below with reference to examples. The embodiments of this disclosure are not limited to the following examples.

[0110] - Preparation - The following materials were prepared: - Conductor: Flat rectangular wire A (flat rectangular copper wire, long side: 1.0 mm, short side: 1.0 mm, no Ni plating) - Thermoplastic polyimide resin or resin composition containing thermoplastic polyimide resin: Thermoplastic polyimide resin TPI1

[0111] The thermoplastic polyimide resin TPI1 was synthesized using the following procedure.

[0112] (Synthesis Example 1) Thermoplastic polyimide resin TPI1 containing the structural unit represented by formula (3) was synthesized by the following procedure. A container equipped with a stirrer, reflux condenser, water separator, and nitrogen inlet tube was prepared. 2.886 kg (7.8 mol) of 4,4'-bis(3-aminophenoxy)biphenyl, 1.604 kg (7.37 mol) of pyromellitic dianhydride, 0.148 kg (1.0 mol) of phthalic anhydride, and 21.53 kg of m-cresol were added to this container. The mixture was then heated to 200°C while stirring under a nitrogen atmosphere. During this time, approximately 350 ml of water was observed to distillate. The reaction was further carried out at 200°C for 6 hours. After that, the mixture was cooled to room temperature and 10.8 kg of toluene was added. The mixture was then filtered to obtain a yellow polyimide powder. After washing this polyimide powder with toluene, it was dried at 180°C for 24 hours to obtain 5.46 kg (yield 98.5%) of polyimide powder (thermoplastic polyimide). Using a 25 mmΦ extruder manufactured by Takayasu Co., Ltd., this polyimide powder was extruded at 400°C to obtain pellets.

[0113] <Example 1> An extruder equipped with a die (screw: 20 mm diameter, full flight, L / D = 24, compression ratio: 3.0) was prepared. The heating temperature in the cylinder section of the extruder was controlled by dividing it into three zones, C1, C2, and C3, in order from the material input side. The heating temperatures were set to 380°C for zone C1, 410°C for zones C2 and C3, and 420°C for the head section behind the cylinder of the extruder and the die at the front of the head section. The shape of the die holes was made similar to the cross-sectional shape of a conductor. A conductor (flat rectangular wire A) was prepared and heated to 380°C (preheating step). Pellets of thermoplastic polyimide resin TPI1 were supplied to the hopper, and nitrogen gas was further supplied to the hopper. Then, pellets of thermoplastic polyimide resin TPI1 were fed into an extruder along with nitrogen gas, and the molten TPI1 pellets were directly coated onto the outer circumference of a conductor (copper wire, flat wire A) preheated to 380°C (extrusion coating process). After water cooling in a water bath, the material was wound onto a bobbin (made of polypropylene) with the winding diameter shown in Table 1. This resulted in an insulated wire with a 0.1 mm thick thermoplastic polyimide resin coating. Preheating was performed using a preheater, and the temperature of the preheated copper wire was measured just before the crosshead. A traveling thermometer (MW-33E-TC1ASP, manufactured by Anritsu Instruments) was used to measure the preheating temperature.

[0114] The presence and degree of crazing in the obtained insulated wires were confirmed as follows: Insulated wires wound onto bobbins with a predetermined winding diameter were left for one week in a constant temperature and humidity chamber maintained at 23°C / 50%RH. After that, the presence or absence of crazing in the coating was checked visually or at a magnification of 6x or less. The evaluation was performed 20 times, and the crazing occurrence rate was calculated. If crazing occurred in 2 out of 20 samples, the crazing occurrence rate was set to 10%. In addition, the elongation rate of the coating was calculated using the following formula (A): Elongation rate of coating (%) = [d / (D + d)] × 100 (d: wire diameter, D: winding diameter) (A) The results are shown in Table 1.

[0115] <Examples 2 to 10 and Comparative Examples 1 to 8> Insulated wires were manufactured in the same manner as in Example 1, except that flat copper wires of the dimensions shown in Tables 1 and 2 were used and wound onto bobbins with the winding diameters shown in Tables 1 and 2. Measurements and evaluations were then performed. The results are shown in Tables 1 and 2. In Tables 1 and 2, the units for copper wire size and insulated copper wire size are "mm".

[0116]

[0117]

[0118] As shown in Tables 1 and 2, the insulated wires of Comparative Examples 1 to 8, where the winding diameter was less than 10 times the wire diameter of the insulated wire, had a high craze occurrence rate of 20% to 80%. Furthermore, the elongation rate (%) of the coating was also high, indicating that tensile stress during winding promoted molecular chain orientation, contributing to the occurrence of craze. On the other hand, the insulated wires of Examples 1 to 10, where the winding diameter was 10 times or more the wire diameter of the insulated wire, or where the elongation rate of the coating was 9.5% or less, had a low craze occurrence rate of 0% to 15%.

[0119] The disclosure of Japanese Patent Application No. 2025-057229, filed on 28 March 2025, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if the incorporation of each individual document, patent application, and technical standard were specifically and individually noted. [Explanation of Symbols]

[0120] 100 Insulated wire manufacturing apparatus 10 Insulated wire 20 Conductor 30 Feeding section 40 Preheating section 50 Extrusion coating section 51 Hopper 52 Cylinder 53 Die (crosshead die) 60 Cooling section 70 Winding section

Claims

1. An insulated wire comprising a conductor and a coating containing a thermoplastic polyimide resin, wherein the insulated wire is wound with a winding diameter of 10 times or more the diameter of the wire.

2. An insulated wire comprising a conductor and a coating containing a thermoplastic polyimide resin, wherein the elongation rate of the coating, calculated by the following formula (A), is 9.5% or less. Elongation rate of coating (%) = [d / (D + d)] × 100 (d: wire diameter, D: winding diameter) (A) 3. The insulated wire according to claim 1 or 2, wherein the thermoplastic polyimide resin includes a structural unit represented by the following formula (1). In equation (1) above, X is a direct bond, -SO ２ -, -CO-, -C(CH ３ ) ２ -, -C (CF ３ ) ２ The group is - or -S-, where R1, R2, R3, and R4 are each independently a hydrogen atom, an alkyl group, an alkoxy group, a halogenated alkyl group, a halogenated alkoxy group, or a halogen atom, and Y is a group selected from the group consisting of four groups represented by any of the following formulas (2-1) to (2-4). In the following formulas (2-1) to (2-4), * represents the bond position, and the hydrogen atom of the aromatic ring may be substituted. Also, the position of the bond group whose bond position has not been determined in formula (1) is either the para or meta position relative to the position to which the oxygen atom is bonded.

4. The insulated wire according to claim 3, wherein the thermoplastic polyimide resin includes a structural unit represented by the following formula (3).

5. The insulated wire according to claim 1 or 2, wherein the aspect ratio of the cross-section of the insulated wire is 1.5 or less.

6. The insulated wire according to claim 1 or 2, wherein the wire diameter of the insulated wire is 0.5 mm to 3.0 mm.

7. The insulated wire according to claim 1 or 2, wherein the thickness of the coating is 0.05 mm to 0.15 mm.

8. An insulated wire according to claim 1 or 2, wound with a winding diameter of 10 mm to 150 mm.

9. The insulated wire according to claim 1 or 2, wherein the coating is a single layer.

10. The insulated wire according to claim 1 or 2, wherein the coating mainly comprises the thermoplastic polyimide resin.

11. A coil comprising an insulated wire as described in claim 1 or 2.

12. A motor comprising the coil described in claim 11.

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