Flat wire and manufacturing method thereof

Abstract

A flat wire provided with a flat conductor having a rectangular cross-section in a direction perpendicular to the axial direction, and a coating film of an insulating coating material formed by extrusion molding directly covering the entire circumferential direction of the flat conductor, the insulating coating material having a melt flow rate at 297 DEG C of 13-150 g / 10 minutes and a melt flow rate at 297 DEG C of 10-30 g / 10 minutes. The average thickness of the coating film of the insulating coating material is 10-1000 [mu] m, the unbiased standard deviation of the thickness of the coating film of the insulating coating material in the axial direction of the flat wire is less than 0.06 mm, and the insulating coating material contains a fluorine-containing copolymer having tetrafluoroethylene-based units and ethylene-based units. In the flat wire, the film of the insulating coating material is not peeled off from the flat conductor in a winding test according to a 5.1. 2 flat wire of JIS 3216-3: 2011.

Description

Technical Field

[0001] The present invention relates to a flat wire and a method for manufacturing the same. This application claims the benefit of Japanese Patent Application No. 2022-200429, filed in Japan on December 15, 2022, the contents of which are incorporated herein by reference. Background Art

[0002] Vehicles used in automobiles, railways, and aircraft are increasingly being miniaturized and lightweight. Consequently, thinner films are being required for the insulating coatings used in insulated wires in these vehicles. Furthermore, as the power and voltage of electrical equipment continue to increase, these insulating coatings are being required to not only provide excellent insulation but also maintain strong adhesion to the conductor.

[0003] By making the conductors of electric wires rectangular, the coil space ratio is increased compared to round wire, saving space for the coil as a whole and contributing to the miniaturization of electrical equipment. However, rectangular conductors have the problem of being more difficult to form a uniform insulating coating than round wires, resulting in insufficient insulation properties.

[0004] Patent Document 1 discloses a method for manufacturing a flat wire in which a powder having an average particle size of 0.02 μm to 150 μm is applied to a flat conductor to form an insulating coating having a thickness of 10 to 150 μm on the outer periphery of the flat conductor. The powder comprises a melt-moldable fluororesin having a melting point of 100°C to 325°C and at least one functional group selected from the group consisting of a carbonyl group, a hydroxyl group, an epoxy group, and an isocyanate group. Prior art literature Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2017-204410 Summary of the Invention Technical problem to be solved by the invention

[0006] However, the production method described in Patent Document 1 requires a calcination step after powder preparation and powder coating, resulting in low productivity. Furthermore, the powder coating process reduces the surface smoothness of the insulating coating. Furthermore, the insulating coating has poor conformability to the rectangular conductor, and bending deformation of the rectangular wire can lead to wrinkles in the insulating coating and peeling of the insulating coating from the rectangular conductor.

[0007] The technical problem of the present invention is to provide a flat wire and a method for producing the same with high productivity, excellent surface smoothness of the insulating coating and excellent followability of the insulating coating to the flat conductor during bending deformation. Means of solving technical problems

[0008] The present invention has the following aspects. [1] A flat wire comprising: a flat conductor having a rectangular cross-section in a direction perpendicular to an axial direction; and a film of an insulating coating material formed by extrusion molding so as to directly cover the entire circumference of the flat conductor, wherein the insulating coating material has a melt flow rate at 297°C of 13 to 150 g / 10 minutes, the average thickness of the insulating coating material film is 10 to 1000 μm, the unbiased standard deviation of the thickness of the insulating coating material film in the axial direction of the flat wire is less than 0.06 mm, the insulating coating material comprises a fluorinated copolymer having units based on tetrafluoroethylene and units based on ethylene, and the insulating coating material film does not peel off from the flat conductor in a winding test in accordance with "5.1.2 Flat Wire of JIS 3216-3:2011". [2] The flat wire according to [1], wherein the cross-sectional area of the flat conductor is 2.6 mm 2 above. [3] The flat wire according to [1] or [2], wherein the insulating coating material contains a cross-linking auxiliary agent having a plurality of unsaturated carbon bonds. [4] The flat wire according to [3], wherein the insulating coating material is a cross-linked product having a cross-linked structure formed by the cross-linking auxiliary agent. [5] The flat wire according to [4], wherein the scratch abrasion test according to ISO 6722-1 is performed 2000 times or more. [6] A method for manufacturing a flat wire, the method comprising: a flat conductor having a rectangular cross-section in a direction perpendicular to an axial direction; and a film of an insulating coating material formed by extrusion molding directly covering the entire circumference of the flat conductor, wherein the manufacturing method comprises: using an extruder having a die head to melt a fluorinated copolymer, extruding the molten fluorinated copolymer from the die head around the flat conductor, thereby coating the molten fluorinated copolymer around the flat conductor to form the insulating coating material, the insulating coating material having a melt flow rate of 13 to 150 g / 10 minutes at 297° C., the insulating coating material having an average thickness of 10 to 1000 μm, the unbiased standard deviation of the thickness of the insulating coating material film in the axial direction of the flat wire being less than 0.06 mm, the fluorinated copolymer having units based on tetrafluoroethylene and units based on ethylene, and the flat wire being formed in accordance with “JIS In the winding test of "5.1.2 Flat Wire" of 3216-3:2011, the film of the insulating coating material does not peel off from the rectangular conductor. [7] The method for producing a flat wire according to [6], wherein the draw ratio DDR calculated by the following formula 1 is greater than or equal to 0.5 and less than 10.0, DDR=(D A -C A ) / (F A -C A ) Formula 1 In the above formula 1, D A is the opening area of the die (mm 2 ), C A is the cross-sectional area of the flat conductor in the direction perpendicular to the axial direction (mm 2 ), F A is the cross-sectional area of the flat wire in the direction perpendicular to the axial direction (mm 2 ). [8] The method for manufacturing a flat wire according to [6] or [7], wherein the cross-sectional area of the flat conductor is 2.6 mm 2 above. [9] The flat wire or the method for producing a flat wire according to any one of [1] to [8], wherein the insulating coating material has a melt flow rate of 15 to 130 g / 10 min at 297°C.

[10] The flat wire or the method for producing a flat wire according to any one of [1] to [8], wherein the insulating coating material has a melt flow rate of 20 to 110 g / 10 min at 297°C.

[11] The flat wire or the method for producing a flat wire according to any one of [1] to [8], wherein the insulating coating material has a melt flow rate of 30 to 90 g / 10 min at 297°C.

[12] The flat wire or the method for producing a flat wire according to any one of [1] to

[11] , wherein the insulating coating material has a melt flow rate of 40 to 500 g / 10 min at 350°C.

[13] The flat wire or the method for producing a flat wire according to any one of [1] to

[11] , wherein the insulating coating material has a melt flow rate of 60 to 300 g / 10 min at 350°C.

[14] The flat wire or the method for producing a flat wire according to any one of [1] to

[11] , wherein the insulating coating material has a melt flow rate of 80 to 210 g / 10 min at 350°C.

[15] The flat wire or the method for producing a flat wire according to any one of [1] to

[14] , wherein the average thickness of the film of the insulating coating material is 20 to 500 μm.

[16] The flat wire or the method for producing a flat wire according to any one of [1] to

[14] , wherein the average thickness of the film of the insulating coating material is 50 to 200 μm.

[17] The flat wire or the method for manufacturing a flat wire according to any one of [1] to

[16] , wherein the unbiased standard deviation of the thickness of the film of the insulating coating material in the axial direction of the flat wire is 0.03 mm or less.

[18] The method for producing a flat wire according to any one of [1] to

[17] , wherein the draw ratio DDR is 0.5 to 5.

[19] The method for producing a flat wire according to any one of [1] to

[17] , wherein the draw ratio DDR is 0.8 to 1.5. Effects of the Invention

[0009] According to the present invention, a flat wire and a method for producing the same can be provided, which have high productivity and are excellent in surface smoothness of the insulating coating and in the ability of the insulating coating to follow the flat conductor during bending deformation. DETAILED DESCRIPTION

[0010] Melt flow rate (MFR) is the melt mass flow rate specified in JIS K 7210-1:2014 (corresponding to the international standard ISO 1133-1:2011). Hereinafter, the melt flow rate is also referred to as MFR. The MFR is measured at a temperature of 297°C and a load of 49N, or at a temperature of 350°C and a load of 49N. The average thickness of the insulating coating was determined by measuring the thickness of the insulating coating on the long side of a rectangular cross section perpendicular to the axial direction of a 5-meter flat wire every 100 mm and taking the arithmetic mean. The unbiased standard deviation of the thickness of the insulating coating material in the axial direction of the flat wire is obtained by measuring the thickness of the insulating coating material on the long side of a rectangular cross section perpendicular to the axial direction of 5 m of the flat wire every 100 mm. The shear stress of the insulating coating material is a value measured using a known formula corresponding to the die provided in the extrusion molding apparatus (e.g., JIS K7199:1999). In this specification, the value is measured using a capillary die. Specifically, the value is measured using the method described in paragraphs

[0073] to

[0075] and

[0079] to

[0081] of Japanese Patent Application Laid-Open No. 2015-086364.

[0011] A unit of a polymer is a portion of a monomer formed by polymerization of the monomer (polymerized unit). A unit may be formed directly by polymerization or by converting a portion of the unit into another structure by treating the polymer. In this specification, a unit based on a monomer is also referred to as a monomeric unit.

[0012] Flatline The flat wire comprises a rectangular conductor having a rectangular cross-section perpendicular to the axial direction, and an insulating coating formed by extrusion molding that directly covers the entire circumference of the flat conductor. The flat wire of this embodiment exhibits no peeling of the insulating coating from the flat conductor during a winding test in accordance with JIS 3216-3:2011, 5.1.2 Flat Wire.

[0013] <Flat conductor> A rectangular conductor is the core wire of a flat wire, and has a rectangular cross-section perpendicular to the axial direction. The rectangular conductor can be made of any material commonly known for core wires in electrical wires, such as copper, tin, silver, gold, aluminum, and alloys thereof. Copper is preferred for ease of forming the rectangular conductor. The thickness of the rectangular conductor is, for example, 0.5 mm to 3.0 mm. The width of the rectangular conductor is, for example, 1.0 mm to 5.0 mm. Furthermore, the ratio of the thickness to the width of the rectangular conductor (thickness / width) is preferably 0.1 to 3.0. The thickness of the flat conductor is the short side of the rectangular cross section in a direction perpendicular to the axial direction, and the width of the flat conductor is the long side of the rectangular cross section in a direction perpendicular to the axial direction.

[0014] The cross-sectional area of the flat conductor is preferably 2.6 mm 2 More than, more preferably 3.0mm 2 The upper limit of the cross-sectional area of the rectangular conductor is not particularly limited, and is, for example, 15 mm 2 . The cross-sectional area of a rectangular conductor is the area of the cross section in a direction perpendicular to the axial direction. If the insulating coating has poor conformability to the flat conductor during bending, a larger cross-sectional area of the flat conductor increases the likelihood of wrinkles forming on the insulating coating or separation from the flat conductor during bending. The flat wire of this embodiment has excellent conformability to the insulating coating during bending, so a larger cross-sectional area of the flat conductor increases the advantage.

[0015] <Film of Insulation Coating Material> The average thickness of the film of the insulating coating material is 10 to 1000 μm, preferably 20 to 500 μm, and more preferably 50 to 200 μm. When the average film thickness is above the lower limit, excellent tracking resistance is achieved. When the average film thickness is below the upper limit, the overall thickness of the flat wire can be reduced, which, when formed into a coil, can save space for the entire coil, contributing to the miniaturization of electrical equipment.

[0016] The unbiased standard deviation (hereinafter referred to as "thickness variation") of the thickness of the insulating coating material in the axial direction of the flat wire is less than 0.06 mm, preferably 0.03 mm or less, and more preferably 0.01 mm or less. When the thickness variation of the coating is less than (or below) the above upper limit, the crack resistance and tracking resistance during bending deformation are excellent. The smaller the variation in thickness of the film, the better, and it may be 0. From the viewpoint of ease of production and yield, the variation in thickness of the film is preferably 0.001 mm or more. The above lower limit value and the above upper limit value may be combined as appropriate.

[0017] The MFR of the insulating coating material at 297° C. is 13 to 150 g / 10 minutes, preferably 15 to 130 g / 10 minutes, more preferably 20 to 110 g / 10 minutes, and further preferably 30 to 90 g / 10 minutes.

[0018] The MFR of the insulating coating material at 350° C. is preferably 40 to 500 g / 10 minutes, more preferably 60 to 300 g / 10 minutes, and even more preferably 80 to 210 g / 10 minutes.

[0019] When the MFR of the insulating coating material at 297°C or 350°C is above the lower limit, the surface smoothness of the insulating coating film and the ability of the insulating coating film to conform to the rectangular conductor during bending deformation are improved. When the MFR of the insulating coating material at 297°C or 350°C is below the upper limit, the strength of the insulating coating film is improved.

[0020] The shear stress of the insulating coating material is preferably 0.1 to 105 kPa, more preferably 1 to 75 kPa, and even more preferably 5 to 50 kPa. When the shear stress of the insulating coating material is above the lower limit, the thickness uniformity of the insulating coating material is improved. When the shear stress of the insulating coating material is below the upper limit, the insulating coating material has improved adhesion to the conductor.

[0021] The insulating coating material includes a fluorinated copolymer having units based on tetrafluoroethylene (hereinafter also referred to as "TFE") and units based on ethylene (hereinafter also referred to as "E"). The insulating coating material may contain other components in addition to the fluorinated copolymer as long as its properties are not seriously impaired.

[0022] The content of the fluorinated copolymer is preferably at least 50 mass%, more preferably at least 70 mass%, and may be 100 mass%, based on the total mass of the insulating coating material.

[0023] (Fluorinated copolymer) The fluorinated copolymer has TFE units and E units. The fluorinated copolymer may be a fluorinated copolymer composed only of TFE units and E units, or may be a fluorinated copolymer having TFE units, E units, and other units.

[0024] Examples of other units include units u1 based on fluorine-containing monomers other than TFE units, units u2 based on functional group-containing monomers (excluding fluorine-containing monomers), and units u3 based on non-fluorine-containing monomers other than E units (excluding functional group-containing monomers).

[0025] As the fluorinated monomer of unit u1, a fluorinated compound having one polymerizable carbon-carbon double bond is preferred. For example, fluoroolefins (vinyl fluoride, vinylidene fluoride, trifluoroethylene, hexafluoropropylene (hereinafter also referred to as "HFP"), chlorotrifluoroethylene, hexafluoroisobutylene, etc., but excluding TFE), perfluoro(alkyl vinyl ether) (hereinafter also referred to as "PAVE"), CF2=CFOR f2 SO2X 1 (Among them, R f2 is a perfluoroalkylene group having 1 to 10 carbon atoms and optionally containing oxygen atoms between carbon atoms, X 1 is a halogen atom or a hydroxyl group), CF2=CFOR f3 CO2X2(where R f3is a perfluoroalkylene group having 1 to 10 carbon atoms and optionally containing oxygen atoms between carbon atoms, X 2 is a hydrogen atom or an alkyl group with 1 to 3 carbon atoms), CF2=CF(CF2) p OCF=CF2 (wherein p is 1 or 2), fluoroalkylethylene (hereinafter also referred to as "FAE"), fluorinated monomers having a ring structure (perfluoro(2,2-dimethyl-1,3-dioxole), 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole, perfluoro(2-methylene-4-methyl-1,3-dioxolane), etc. The fluorinated monomers may be used alone or in combination of two or more.

[0026] As the fluorinated monomer of unit u1, from the viewpoint of excellent moldability of the fluorinated copolymer, at least one selected from HFP, PAVE and FAE is preferred. From the viewpoint of excellent electrical properties (dielectric constant, dielectric loss tangent) and heat resistance, HFP and FAE are more preferred, and FAE is particularly preferred.

[0027] As PAVE, for example, CF2=CFOR can be mentioned. f1 (Among them, R f1 It is a perfluoroalkyl group having 1 to 10 carbon atoms and optionally containing an oxygen atom between carbon atoms. Specific examples of PAVE include CF2=CFOCF2CF3, CF2=CFOCF2CF2CF3 (hereinafter also referred to as "PPVE"), CF2=CFOCF2CF2CF2CF3, and CF2=CFO(CF2)6F. As PAVE, PPVE is preferred.

[0028] As FAE, for example, CH2=CX 3 (CF2) q X 4 (where X 3 is a hydrogen atom or a fluorine atom, q is an integer from 2 to 10, X 4 is a hydrogen atom or a fluorine atom). Specific examples of FAE include CH2=CF(CF2)2F, CH2=CF(CF2)3F, CH2=CF(CF2)4F, CH2=CF(CF2)5F, CH2=CF(CF2)6F, CH2=CF(CF2)2H, CH2=CF(CF2)3H, CH2=CF(CF2)4H, CH2=CF(CF2)5H, CH2=CF( CF2)6H, CH2=CH(CF2)2F, CH2=CH(CF2)3F, CH2=CH(CF2)4F, CH2=CH(CF2)5F, CH2=CH(CF2 )6F, CH2=CH(CF2)2H, CH2=CH(CF2)3H, CH2=CH(CF2)4H, CH2=CH(CF2)5H, CH2=CH(CF2)6H. As FAE, CH2=CH(CF2) is preferred q1 X 4 (wherein q1 is 2 to 6, preferably 2 to 4), more preferably CH2=CH(CF2)2F, CH2=CH(CF2)3F, CH2=CH(CF2)4F, CH2=CF(CF2)3H, CH2=CF(CF2)4H, and particularly preferably CH2=(CF2)4F, CH2=(CF2)2F.

[0029] Examples of the functional group-containing monomer of unit u2 include carboxyl group-containing monomers (maleic acid, itaconic acid, citraconic acid, undecylenic acid, etc.); acid anhydride group-containing monomers (itaconic anhydride (hereinafter also referred to as "IAH"), citraconic anhydride (hereinafter also referred to as "CAH"), 5-norbornene-2,3-dicarboxylic anhydride (hereinafter also referred to as "NAH"), maleic anhydride, etc.); hydroxyl group- and epoxy group-containing monomers (hydroxybutyl vinyl ether, glycidyl ether, etc.). The functional group-containing monomers may be used alone or in combination of two or more.

[0030] The functional group-containing monomer of unit u2 is preferably an acid anhydride group-containing monomer, preferably one or more selected from IAH, CAH, and NAH, more preferably IAH or NAH, and even more preferably IAH. The use of one or more selected from IAH, CAH, and NAH makes it possible to easily produce an acid anhydride group-containing fluorinated copolymer without requiring the special polymerization method required when using maleic anhydride (see Japanese Patent Application Laid-Open No. 11-193312).

[0031] As the fluorine-free monomer of unit u3, a fluorine-free compound having one polymerizable carbon-carbon double bond is preferred, and examples thereof include olefins (propylene, 1-butene, etc., but excluding E) and vinyl esters (vinyl acetate, etc.). The fluorine-free monomer may be used alone or in combination of two or more.

[0032] Preferred contents and ratios of the respective units in the fluorinated copolymer are as follows. The content of the TFE unit is preferably from 30 to 70 mol %, more preferably from 35 to 65 mol %, further preferably from 40 to 60 mol %, based on the total amount of the constitutional units of the fluorinated copolymer.

[0033] The content of the E unit is preferably from 20 to 60 mol %, more preferably from 25 to 55 mol %, further preferably from 30 to 50 mol %, based on the total amount of the constitutional units of the fluorinated copolymer.

[0034] The total content of the TFE unit and the E unit is preferably 80 to 100 mol %, more preferably 85 to 99.5 mol %, further preferably 90 to 99 mol %, based on the total amount of the constitutional units of the fluorinated copolymer.

[0035] In the fluorinated copolymer, the molar ratio of TFE unit / E unit is preferably from 40 / 60 to 70 / 30, more preferably from 45 / 55 to 65 / 35, further preferably from 50 / 50 to 60 / 40.

[0036] When the fluorinated copolymer contains the unit u1, the content of the unit u1 is preferably from 0.5 to 15 mol%, more preferably from 1 to 10 mol%, based on the total amount of the constitutional units of the fluorinated copolymer. When the fluorinated copolymer contains the units u2, the content of the units u2 is preferably from 0.05 to 1 mol %, more preferably from 0.1 to 0.5 mol %, based on the total amount of the constitutional units of the fluorinated copolymer. When the fluorinated copolymer contains the unit u3, the content of the unit u3 is preferably 0 mol % based on the total amount of the constitutional units of the fluorinated copolymer from the viewpoint of heat resistance. When the unit u3 is contained, the content is preferably 0.001 to 1 mol %, more preferably 0.01 to 0.1 mol %. When the fluorinated copolymer contains any one of the units u1 to u3, the total content of the units u1 to u3 is preferably from 0.5 to 15 mol%, more preferably from 1 to 10 mol%, based on the total amount of the constitutional units of the fluorinated copolymer. When the fluorinated copolymer contains any one of units u1 to u3, the total content of TFE units, E units and units u1 to u3 is preferably 90 mol % or more, more preferably 95 mol % or more, further preferably 100 mol % based on the total amount of the constituent units of the fluorinated copolymer.

[0037] When the content and ratio of each unit are within the above ranges, the surface smoothness of the insulating coating film in the obtained rectangular wire and the ability of the insulating coating film to follow the rectangular conductor during bending deformation are improved.

[0038] The ratio of each unit can be calculated by melt NMR analysis, fluorine content analysis, infrared absorption spectrum analysis, and the like of the fluorinated copolymer.

[0039] In fluorinated copolymers, some of the acid anhydride groups in unit u2 may hydrolyze, resulting in the inclusion of units based on dicarboxylic acids corresponding to the anhydride-containing cyclic hydrocarbon monomer (e.g., itaconic acid, citraconic acid, 5-norbornene-2,3-dicarboxylic acid, maleic acid, etc.). When units based on such dicarboxylic acids are included, these units are referred to as unit u2.

[0040] Preferred specific examples of fluorine-containing copolymers include TFE / E / HFP copolymers, TFE / E / CH2=CH(CF2)2F copolymers, TFE / E / CH2=CH(CF2)4F copolymers, TFE / E / CH2=CH(CF2)2F / CH2=CH(CF2)4F copolymers, TFE / E / HFP / IAH copolymers, TFE / E / CH2=CH(CF2)2 / IAH copolymers, TFE / E / CH2=CH(CF2)4 / IAH copolymers, TFE / E / CH2=CH(CF2)2F / CH2=CH(CF2)4F / IAH copolymers, and the like.

[0041] The MFR of the fluorinated copolymer at 297°C is preferably from 13 to 300 g / 10 min, more preferably from 15 to 150 g / 10 min, further preferably from 20 to 100 g / 10 min.

[0042] The MFR of the fluorinated copolymer at 350°C is preferably from 25 to 350 g / 10 min, more preferably from 50 to 300 g / 10 min, further preferably from 80 to 250 g / 10 min.

[0043] The fluorinated copolymer may be produced by a known production method or a commercially available one. Examples of known production methods include those described in International Publication Nos. 2015 / 182702, 2016 / 006644, and 2016 / 017801.

[0044] (Other ingredients) The insulating coating material of the present invention may further contain other components as needed. Examples of other components that may be included in the insulating coating material include fluorinated polymers other than fluorinated copolymers having TFE units and E units, fluorine-free polymers, crosslinking aids, antioxidants, fillers, plasticizers, flame retardants, pigments, and other additives. These other components may be used alone or in combination of two or more. Specific examples of fillers include fibrous fillers such as glass fiber, carbon fiber, boron fiber, aramid fiber, liquid crystal polyester fiber, and stainless steel microfiber; and powdered fillers such as talc, mica, graphite, molybdenum disulfide, polytetrafluoroethylene, calcium carbonate, silica, silica alumina, aluminum oxide, and titanium dioxide. Furthermore, hydrotalcites and metal oxides such as zinc oxide, magnesium oxide, titanium oxide, and lead oxide may be used. At least one inorganic filler may be used. Examples of the pigment include coloring pigments such as organic pigments and inorganic pigments. Specific examples include carbon black (black pigment), iron oxide (red pigment), aluminum cobalt oxide (blue pigment), copper phthalocyanine (blue pigment, green pigment), perylene (red pigment), and bismuth vanadate (yellow pigment).

[0045] [Crosslinking aid] The crosslinking aid has two or more unsaturated bonds in one molecule. Examples of the crosslinking aid include triallyl cyanurate, triallyl isocyanurate, bismaleimide, ethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, trihydroxypropyl propane trimethacrylate, and divinylbenzene. Among them, triallyl isocyanurate, also known as TAIC, is preferred due to its high thermal stability.

[0046] The cross-linking auxiliary agent is preferably added in an amount of 0.5 to 20 parts by mass, more preferably 2 to 8 parts by mass, per 100 parts by mass of the fluororesin.

[0047] The insulating coating material may contain an antioxidant having at least one of a phenol group and a phosphorus atom and a molecular weight of 600 or more. The antioxidant preferably has both a phenolic group and a phosphorus atom. Preferred examples of antioxidants are listed below. Two of these antioxidants may be selected and used in any combination.

[0048] Examples of antioxidants having both a phenol group and a phosphorus atom include 2-tert-butyl-6-methyl-4-[3-(2,4,8,10-tetra-tert-butylbenzo[d][1,3,2]benzodioxaphosphin-6-yl)oxypropyl]phenol and phosphorus-modified novolac-type phenolic resins. Among them, 2-tert-butyl-6-methyl-4-[3-(2,4,8,10-tetra-tert-butylbenzo[d][1,3,2]benzodioxaphosphin-6-yl)oxypropyl]phenol is preferred from the viewpoint of excellent thermal stability.

[0049] Examples of the antioxidant having a phenol group include bisphenol A, bisphenol AF, phenol, cresol, p-phenylphenol, m-phenylphenol, o-phenylphenol, allylphenol, p-hydroxybenzoic acid, ethyl p-hydroxybenzoate, and hindered phenols.

[0050] Examples of the hindered phenol include octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, octyl 3-(4-hydroxy-3,5-diisopropylphenyl)propionate, and 1,3-diylbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate][2,2-bis[[1-oxo-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propoxy]methyl]propane].

[0051] As the antioxidant having a phosphorus atom, a phosphorus compound having a trivalent phosphorus atom is preferable. Trivalent phosphorus atoms exist in the molecule as phosphine groups or phosphonate groups. Trivalent phosphorus atoms undergo self-oxidation to pentavalent phosphorus atoms, which then exhibit antioxidant properties through the peroxide decomposition effect (elimination of free radicals generated by peroxides).

[0052] Examples of the antioxidant having a trivalent phosphorus atom include trioctyl phosphite, trilauryl phosphite, tridecyl phosphite, (octyl) diphenyl phosphite, tris(2,4-di-tert-butylphenyl) phosphite, triphenyl phosphite, tris(butoxyethyl) phosphite, tris(nonylphenyl) phosphite, distearyl pentaerythritol diphosphite, tetra(tridecyl)-1,1,3-tris(2-methyl-5-tert-butyl-4-hydroxyphenyl)butane diphosphite, tetra(C12-C15 mixed phosphite), alkyl)-4,4'-isopropylidene diphenyl diphosphite, tetra(tridecyl)-4,4'-butylidene bis(3-methyl-6-tert-butylphenol) diphosphite, tris(3,5-di-tert-butyl-4-hydroxyphenyl) phosphite, tris(mono- and di-mixed nonylphenyl) phosphite, hydrogenated 4,4'-isopropylidene diphenol polyphosphite, bis(octylphenyl)bis[4,4'-butylidene bis(3-methyl-6-tert-butylphenol)]-1,6-hexanediol diphosphite, phenyl(4 ,4'-isopropylidene diphenol) pentaerythritol diphosphite, distearyl pentaerythritol diphosphite, tris[4,4'-isopropylidene bis(2-tert-butylphenol)] phosphite, di(isodecyl)phenyl phosphite, 4,4'-isopropylidene bis(2-tert-butylphenol)bis(nonylphenyl) phosphite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, bis(2,4-di-tert-butyl-6-methylphenyl)ethyl phosphite, 2-[{2,4,8,10- Tetra-tert-butyldibenzo[d,f][1.3.2]-dioxaphosphin-6-yl}oxy]-N,N-bis[2-[{2,4,8,10-tetra-tert-butyldibenzo[d,f][1.3.2]-dioxaphosphin-6-yl}oxy]ethyl]ethanamine, 6-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-tert-butyldibenzo[d,f][1.3.2]-dioxaphosphine, bis(dialkylphenyl)pentaerythritol diphosphite.

[0053] Commercially available antioxidants having a trivalent phosphorus atom may also be used. Examples of commercially available antioxidants include Irgafos 168 (registered trademark, manufactured by Ciba Specialty Chemicals), Irgafos 12 (registered trademark, manufactured by Ciba Specialty Chemicals), Irgafos 38 (registered trademark, manufactured by Ciba Specialty Chemicals), ADEKA 329K (registered trademark, manufactured by Asahi Denka Co., Ltd.), ADEKA PEP 36 (registered trademark, manufactured by Asahi Denka Co., Ltd.), ADEKA PEP-8 (registered trademark, manufactured by Asahi Denka Co., Ltd.), Sandstab P-EPQ (registered trademark, manufactured by Clariant), WESTON 618 (registered trademark, manufactured by GE), WESTON 619G (registered trademark, manufactured by GE), Ultranox 626 (registered trademark, manufactured by GE), and Sumilizer GP (registered trademark, manufactured by Sumitomo Chemical Co., Ltd.).

[0054] The molecular weight of the antioxidant is not less than 600. The molecular weight of the antioxidant is preferably 600 to 50,000, more preferably 600 to 3,000. When the molecular weight of the antioxidant is 600 or more, excellent thermal stability is achieved. When the molecular weight of the antioxidant is below the preferred upper limit, excellent dispersibility in other polymer components is achieved.

[0055] The antioxidant is preferably added in an amount of 0.001 to 20 parts by mass, more preferably 0.01 to 5 parts by mass, per 100 parts by mass of the fluorinated copolymer contained in the insulating coating material. When the antioxidant content is above the preferred lower limit, excellent thermal stability is achieved. When the antioxidant content is below the preferred upper limit, excellent mechanical properties are achieved.

[0056] Specific examples of additives such as fillers, plasticizers, and flame retardants include the components described in paragraphs

[0042] to

[0048] of International Publication No. 2019-198771.

[0057] Furthermore, as other components, fluororesins or fluoroelastomers other than fluoropolymers having TFE units and E units (hereinafter also referred to as "ETFE") may be included, preferably in an amount less than 50% by mass, more preferably less than 35% by mass, relative to ETFE.

[0058] Examples of fluororesins other than ETFE include TFE / HFP copolymers (copolymers containing TFE units and HFP units, the same below), TFE / HFP / PAVE copolymers, TFE / PAVE copolymers [PFA], E / TFE / HFP copolymers, polychlorotrifluoroethylene [PCTFE], CTFE / TFE copolymers, CTFE / TFE / PAVE copolymers, E / CTFF copolymers, TFE / VDF copolymers, VDF / HFP / TFE copolymers, VDF / HFP copolymers, polyvinylidene fluoride (PVDF), and polyvinyl fluoride (PVF).

[0059] The fluorine-containing elastomer may, for example, be a TFE / propylene (P) copolymer, an HFP / VDF copolymer or a TFE / PAVE copolymer. Among them, TFE / P copolymer, HFP / VDF copolymer, and TFE / PAVE copolymer are preferred as fluorine-containing elastomers.

[0060] The flat wire of the present invention may be crosslinked, if necessary, with an insulating coating material containing a crosslinking aid. Specifically, the insulating coating material is irradiated with ionizing radiation such as gamma rays, electron beams, or X-rays. Electron beams are preferred from the perspective of the device.

[0061] The cross-linking conditions also depend on the shape, thickness, etc. of the molded body and therefore cannot be generalized, but it is preferably carried out at least once in a temperature atmosphere below the melting point of ETFE, preferably below the glass transition temperature, and at least once in a temperature atmosphere above the melting point of ETFE. By crosslinking by electron beam irradiation in an atmosphere at a temperature lower than the melting point of ETFE, the insulating coating material can maintain its shape without melting or deformation even if it is heated to a temperature higher than the melting point of ETFE during the second irradiation. The radiation dose is preferably 1 to 5000 kGy, more preferably 10 to 200 kGy, and even more preferably 30 to 100 kGy. In the flat wire of the present invention, when the insulating coating material containing a crosslinking auxiliary agent is crosslinked, the evaluations of the MFR, shear stress, winding test, etc. are performed after crosslinking.

[0062] Manufacturing method of flat wire The above-mentioned flat wire can be produced by melting a fluorinated copolymer using an extruder having a die, extruding the molten fluorinated copolymer from the die onto a flat conductor, thereby coating the flat conductor with the molten fluorinated copolymer to form the above-mentioned insulating coating material. In addition to the fluorinated copolymer, the above-mentioned other components may be added to the extruder.

[0063] Examples of the extruder include a twin-screw extruder and a single-screw extruder, and a twin-screw extruder is preferred. The opening face of the die head is rectangular in shape. The barrel temperature and die temperature of the extruder are set according to the type of fluorinated copolymer. The barrel temperature of the extruder is preferably 50 to 450°C, more preferably 80 to 440°C, and further preferably 90 to 430°C. The die temperature is preferably 100 to 420°C, more preferably 120 to 400°C, and further preferably 150 to 380°C. When the barrel temperature and die temperature of the extruder are above the above lower limit, the miscibility of the mixed material is good. When the barrel temperature and die temperature of the extruder are below the above upper limit, it is easy to suppress the degradation of the fluorinated copolymer due to heat. The residence time in the extruder is preferably 10 seconds or more and 30 minutes or less. The screw speed of the extruder is preferably 0.5 to 100 rpm.

[0064] The rectangular conductor is preferably preheated. The temperature of the preheated rectangular conductor is preferably 50 to 400°C, more preferably 80 to 250°C. The preheating method is not particularly limited, and examples thereof include light heating, hot air heating, radiation heating, gas burner heating, and induction heating.

[0065] (Stretching ratio) In the method for producing a flat wire of the present embodiment, the draw ratio (hereinafter also referred to as "DDR") calculated by the following formula 1 is preferably 0.1 or more and less than 10.0, more preferably 0.5 to 5, and even more preferably 0.8 to 1.5. When the DDR is above the lower limit, a flat wire having excellent surface smoothness of the insulating coating film is easily obtained. When the DDR is below the upper limit (or below the upper limit), a flat wire having excellent surface smoothness of the insulating coating film and excellent conformability of the insulating coating film to the rectangular conductor during bending deformation is easily obtained.

[0066] DDR=(D A -C A ) / (F A -C A ) Formula 1 In the above formula 1, D A is the opening area of the die head (mm 2 ), C A The cross-sectional area of the flat conductor in the direction perpendicular to the axial direction (mm 2 ), F A is the cross-sectional area of the flat wire in the direction perpendicular to the axial direction (mm 2 ).

[0067] D AIt can be obtained by the following formula 2. D A =D L ×D S Formula 2 In the above formula 2, D L D is the inner dimension of the long side of the rectangular opening of the die head (mm). S It is the inner dimension (mm) of the short side of the rectangular opening of the die head.

[0068] C A It can be obtained by the following formula 3. C A =C L ×C S Formula 3 In the above formula 3, C L C is the long side of the rectangular cross section of the flat conductor in the direction perpendicular to the axial direction (mm), S It is the short side (mm) of the rectangular cross section of the flat conductor in a direction perpendicular to the axial direction.

[0069] F A It can be obtained by the following formula 4. F A =F L ×F S Formula 4 In the above formula 4, F L F is the long side of the rectangular cross section of the flat wire in the direction perpendicular to the axial direction (mm), S It is the short side (mm) of the rectangular cross section of the flat wire in a direction perpendicular to the axial direction.

[0070] In this embodiment, a so-called press forming method, in which the insulating coating is formed under pressure, is preferably employed. Using press forming facilitates achieving a DDR below (or below) the aforementioned upper limit compared to conventional tube forming methods. This results in a flat wire with excellent surface smoothness of the insulating coating and excellent conformability of the insulating coating to the flat conductor during bending deformation.

[0071] (use) The flat wire of the present invention can be used in applications such as insulating amplifiers, insulating transformers, automotive alternators, hybrid vehicles, electric ships, electric aircraft, and electric vertical take-off and landing (EVTL) motors. Furthermore, it can be used as various electrical wires (wrap wires, automotive wires, and robotics wires) and coil windings (magnet wires). Example

[0072] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples. In the following examples, Examples 1, 3, 5, 7, 11 to 15 are examples, and Examples 2, 4, 6, 8 to 10 are comparative examples.

[0073] Evaluation Method (MFR of fluorinated copolymer and insulation coating material) After preheating the insulating coating material for 5 minutes, the MFR at 49N was measured according to JIS K 7210-1:2014. The measurement was performed at 297°C and 350°C. In Table 1, MFR1 indicates the result of measurement at 297°C, and MFR2 indicates the result of measurement at 350°C.

[0074] (Shear stress of insulation coating material) The measurement was performed in accordance with JIS K 7199: 1999. Specifically, the measurement was performed according to the method described in paragraphs

[0073] to

[0075] and

[0079] to

[0081] of JP-A-2015-086364 (using a capillary die).

[0075] (Average thickness and thickness variation of the film) A 5-meter-long flat wire was taken and the thickness of the insulating coating material film on the long side of the rectangular cross section perpendicular to the axial direction was measured every 100 mm (only the side in contact with the upper inner surface of the die during molding). The arithmetic mean of the measured values (mm) is the average thickness. The unbiased standard deviation of the measured values (mm) is the thickness variation.

[0076] (Winding test) The flat wire was evaluated according to the winding test of "5.1.2 Flat Wire of JIS 3216-3:2011." The cross section of the flat wire was visually observed and evaluated according to the following criteria. A: The film of the insulating coating material was not peeled off from the rectangular conductor. B: The film of the insulating coating material peels off from the rectangular conductor.

[0077] (Followability) The flat wire was bent in both the edgewise and flatwise directions at an angle of 90±10°. The surface of the insulating coating material at the bent portion and the cross-section of the flat wire were then observed, and the following criteria were used to evaluate the following properties. A: No wrinkles were generated on the surface of the film of the insulating coating material during the bending, and the film of the insulating coating material was not peeled off from the rectangular conductor. B: During the bending, wrinkles are generated on the surface of the film of the insulating coating material, or the film of the insulating coating material is peeled off from the rectangular conductor.

[0078] Surface smoothness The surface roughness (Ra) of the flat wire was measured using a digital microscope (HRX-1 manufactured by Hirox Co., Ltd.) at a magnification of 80 times and a measurement length of 4 mm. A: Surface roughness is less than 10μm B: Surface roughness greater than 10μm and less than 45μm C: Surface roughness is greater than 45 μm.

[0079] <Scratch wear test> A 2m long sample specimen was cut from the resulting flat wire and subjected to a scratch wear test using a "MAGNET WIRE Abrasion Tester (Reciprocating)" manufactured by Yasuda Seiki Co., Ltd., according to a test method compliant with ISO 6722-1. Specifically, the test was conducted under the following conditions: a grinding needle diameter of 0.45±0.01mm, a grinding needle material of SUS316 (according to JIS K-G7602), a wear distance of 15.5±1mm, a wear rate of 55±5 times / minute, a load of 7N, and a test environment of 23±1°C. The wear resistance is expressed as the number of reciprocating motions of the grinding needle required until the conductor is exposed from the insulating film. A higher wear resistance (number of reciprocating motions) indicates a better wear resistance of the insulating layer.

[0080] (Materials used) Fluorinated copolymer 1: Fluorinated copolymer having a molar ratio of TFE unit:E unit:HFP unit:C4 unit:IAH unit = 47.5:43.4:8.3:0.6:0.3 (MFR at 297°C = 70 g / 10 min, MFR at 350°C = 246.2 g / 10 min) Fluorinated copolymer 2: Fluorinated copolymer having a molar ratio of TFE unit:E unit:C2 unit:C4 unit:IAH unit = 58.1:38.8:0.4:2.6:0.1 (MFR at 297°C = 25 g / 10 min, MFR at 350°C = 93.7 g / 10 min) Fluorinated copolymer 3: Fluorinated copolymer having a molar ratio of TFE unit:E unit:C4 unit = 60:40:3.3 (MFR at 297°C = 25 g / 10 min, MFR at 350°C = 113.8 g / 10 min) Fluorinated copolymer 4: Fluorinated copolymer having a molar ratio of TFE unit:E unit:C4 unit = 54:46:1.4 (MFR at 297°C = 33 g / 10 min, MFR at 350°C = 157 g / 10 min) Fluorinated copolymer 5: Fluorinated copolymer having a molar ratio of TFE unit:E unit:C4 unit = 53.5:45.6:0.9 (MFR at 297°C = 7 g / 10 min, MFR at 350°C = 20.8 g / 10 min) Among them, the C2 unit is CH2=CH(CF2)2F, and the C4 unit is CH2=CH(CF2)4F. Crosslinking aid: Triallyl isocyanurate (TAIC), manufactured by Mitsubishi Chemical Corporation Antioxidant A: Sumilizer GP (Sumilizer GP) manufactured by Sumitomo Chemical Co., Ltd. Antioxidant B: Irganox 1010 manufactured by BASF

[0081] (Example 1) Fluorinated copolymer 1 was subjected to wire extrusion molding under the following conditions to produce a flat wire. DDR was 1. For wire extrusion molding, a so-called press molding method was employed in which the insulating coating material is formed under pressure. Die temperature: 270℃. Barrel temperature: 160~270℃. Flat conductor: Flat copper wire with a thickness of 1.5 mm and a width of 2.3 mm. Preheating temperature of flat conductors: 185°C. Film thickness (set value): 0.18mm.

[0082] (Example 2) A flat wire was produced in the same manner as in Example 1 except that the DDR was 15. However, the wire extrusion molding employed a so-called tube forming method in which the insulating coating material is formed substantially under normal pressure.

[0083] (Example 3) Fluorinated copolymer 2 was subjected to wire extrusion molding under the following conditions to produce a flat wire. DDR was 1. For wire extrusion molding, a so-called press molding method was employed in which the insulating coating material is formed under pressure. Die temperature: 350℃. Barrel temperature: 210~350℃. Flat conductor: Flat copper wire with a thickness of 1.5 mm and a width of 2.3 mm. Preheating temperature of flat conductors: 195°C. Film thickness (set value): 0.18mm.

[0084] (Example 4) A flat wire was produced in the same manner as in Example 3 except that the DDR was 15. However, the wire extrusion molding employed a so-called tube forming method in which the insulating coating material is formed substantially under normal pressure.

[0085] (Examples 5, 7, 9) A rectangular wire was produced in the same manner as in Example 3, except that the fluorinated copolymer described in Table 1 was used instead of the fluorinated copolymer 2 and the preheating temperature of the rectangular conductor was set at 200°C.

[0086] (Examples 6, 8, 10) A rectangular wire was produced in the same manner as in Example 4, except that the fluorinated copolymer described in Table 1 was used instead of the fluorinated copolymer 2 and the preheating temperature of the rectangular conductor was set at 200°C.

[0087] The above evaluations were performed on the insulating coating materials and the flat wires of the respective examples. The results are shown in Table 1.

[0088] [Table 1]

[0089] Examples 1, 3, 5, and 7 were all excellent in the winding test results (durability), the surface smoothness of the insulating coating film, and the ability of the insulating coating film to follow the rectangular conductor during bending deformation. On the other hand, in Examples 2, 4, 6, 8, and 10, where the DDR was 15, the winding test results (durability) and the ability of the insulating coating to follow the rectangular conductor during bending deformation were poor. In Example 9, where the MFR of the insulating coating material at 297°C was less than 13 g / 10 min, even though the DDR was 1, the surface smoothness of the insulating coating film and the ability of the insulating coating film to follow the rectangular conductor during bending deformation were poor.

[0090] (Examples 11~14) The fluorine-containing resin composition having the formulation shown in Table 2 was melt-kneaded using a twin-screw extruder (φ32, secondary extruder manufactured by Technovel Co., Ltd.) to obtain pellets. Kneading conditions were: barrel temperature of 280-300°C, die temperature of 300°C, and screw speed of 200 rpm. A rectangular wire was produced in the same manner as in Example 3 except that the above-mentioned pellets were used instead of the fluorinated copolymer 2 and the preheating temperature of the rectangular conductor was set at 200°C. The above-mentioned flat wires were irradiated with electron beams at the radiation doses shown in Table 2, thereby producing flat wires of Examples 11 to 14. The insulation coating materials and flat wires of each example were evaluated as described above. (Evaluations of properties such as MFR, shear stress, winding test, and followability were all performed after crosslinking.) The results are shown in Table 2.

[0091] (Example 15) The fluorine-containing resin composition having the formulation shown in Table 2 was melt-kneaded using a twin-screw extruder (φ32, secondary extruder manufactured by Technovel Corporation) to obtain pellets. The kneading conditions were: barrel temperature of 280-300°C, die temperature of 300°C, and screw speed of 200 rpm. A flat wire was produced in the same manner as in Example 3 except that the above-mentioned pellets were used instead of the fluorinated copolymer 2. The flat wire described above was irradiated with electron beams at the radiation doses shown in Table 2, thereby producing a flat wire of Example 15. The insulation coating material and the flat wire were evaluated as described above. (Evaluations of properties such as MFR, shear stress, winding test, and followability were all performed after crosslinking.) The results are shown in Table 2.

[0092] [Table 2]

[0093] Examples 1 to 11 were excellent in terms of the winding test results (durability), the surface smoothness of the insulating coating, and the ability of the insulating coating to follow the rectangular conductor during bending deformation, as well as the wear resistance. Industrial applicability

[0094] According to the present invention, a flat wire and a method for producing the same can be provided, which have high productivity and are excellent in surface smoothness of the insulating coating and in the ability of the insulating coating to follow the rectangular conductor during bending deformation.

Claims

1. A flat wire comprising: a flat conductor having a rectangular cross-section in a direction perpendicular to an axial direction; and a film of an insulating coating material formed by extrusion molding to directly cover the entire circumference of the flat conductor, wherein: The insulating coating material has a melt flow rate of 13 to 150 g / 10 minutes at 297° C., an average thickness of the film of the insulating coating material is 10 to 1000 μm, and an unbiased standard deviation of the thickness of the film of the insulating coating material in the axial direction of the flat wire is less than 0.06 mm. The insulating coating material comprises a fluorine-containing copolymer having units based on tetrafluoroethylene and units based on ethylene, In the rectangular wire, the film of the insulating coating material does not peel off from the rectangular conductor in a winding test in accordance with "5.1.2 Flat Wire of JIS 3216-3:2011".

2. The flat wire according to claim 1, wherein The cross-sectional area of the flat conductor is 2.6 mm 2 above.

3. The flat wire according to claim 1 or 2, wherein The insulating coating material includes a cross-linking auxiliary agent having a plurality of unsaturated carbon bonds.

4. The flat wire according to claim 3, wherein The insulating coating material is a cross-linked product having a cross-linked structure formed by the cross-linking auxiliary agent.

5. The flat wire according to claim 4, wherein The scratch abrasion test according to ISO6722-1 is more than 2000 times.

6. A method for producing a flat wire comprising: a flat conductor having a rectangular cross-section in a direction perpendicular to an axial direction; and a film of an insulating coating material formed by extrusion molding to directly cover the entire circumference of the flat conductor; The manufacturing method includes: using an extruder having a die to melt a fluorinated copolymer, extruding the molten fluorinated copolymer from the die to the periphery of the rectangular conductor, thereby coating the molten fluorinated copolymer around the rectangular conductor to form the insulating coating material; The insulating coating material has a melt flow rate of 13 to 150 g / 10 minutes at 297° C., an average thickness of the film of the insulating coating material is 10 to 1000 μm, and an unbiased standard deviation of the thickness of the film of the insulating coating material in the axial direction of the flat wire is less than 0.06 mm. The fluorine-containing copolymer has units based on tetrafluoroethylene and units based on ethylene, In the rectangular wire, the film of the insulating coating material does not peel off from the rectangular conductor in a winding test in accordance with "5.1.2 Flat Wire of JIS 3216-3:2011".

7. The method for producing a flat wire according to claim 6, wherein: The stretching ratio DDR calculated by the following formula 1 is greater than 0.5 and less than 10.0, DDR=(D A -C A ) / (F A -C A ) Equation 1 In the above formula 1, D A is the opening area of the die (mm 2 ), C A is the cross-sectional area of the flat conductor in the direction perpendicular to the axial direction (mm 2 ), F A is the cross-sectional area of the flat wire in the direction perpendicular to the axial direction (mm 2 ).

8. The method for producing a flat wire according to claim 6 or 7, wherein: The cross-sectional area of the flat conductor is 2.6 mm 2 above.

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