Insulated wire

Abstract

To provide an insulated wire which is excellent in adhesion / adhesiveness between a conductor and a coating material, prevents generation of a gap therebetween, and is excellent in followability of the coating material to external stress change, and accordingly is excellent in heat resistance and a partial discharge start voltage.SOLUTION: An insulated wire has a conductor and a coating material coating its outer periphery, wherein the coating material is made of a polyarylene sulfide resin composition containing 5 to 45 pts.wt. of a saponified ethylene-vinyl acetate copolymer (B) and 10 to 50 pts.wt. of high pressure process low density polyethylene (C), with respect to 100 pts.wt. of a polyarylene sulfide resin (A).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an insulated wire, and in particular to an insulated wire that is highly manufacturable and that uses a polyarylene sulfide resin composition as a coating or exterior material. The polyarylene sulfide resin composition has excellent adhesion and bonding between a conductor and a coating material, making it difficult for gaps and the like to occur between them, and also has excellent compliance of the coating material with changes in external stress. The polyarylene sulfide resin composition has excellent breakdown voltage resistance, dielectric properties, and toughness such as impact resistance. [Background technology]

[0002] The automotive industry is working to develop core technologies for increasing the efficiency, size, and weight of the motors and generators used in hybrid and electric vehicles. One method for achieving higher output is to increase the coil space within the stator core. One way to increase the coil space is to use rectangular wire instead of the round wire that has traditionally been used for coils.

[0003] In this case, the insulating wire coating material is required to have a high dielectric breakdown strength, especially a high partial discharge inception voltage, and it is known that the relationship between the partial discharge inception voltage and the relative dielectric constant is expressed by the following formula (1) (Dakin's formula) (see, for example, Non-Patent Document 1). According to formula (1), in order for the wire to have a high partial discharge inception voltage, the insulating wire coating material is required to have a low relative dielectric constant relative to the resin composition. V=163(t / εr) 0.46 (1) (Here, V is the partial discharge inception voltage (Vrms), t is the thickness of the insulating layer (μm), and εr is the relative dielectric constant of the insulating layer.) Furthermore, electric wires used for such applications are continuously formed by extrusion molding, followed by bending, and the end faces of the electric wires are electrically connected by spot welding to form a single long wire. In addition to insulating performance, the resin composition used as the insulating coating is also required to have flexibility during bending of the electric wire and adhesion to the conductor.

[0004] The resin composition used here is proposed to contain a polyphenylene sulfide resin (A) and a resin (B) made of an olefin copolymer resin consisting of at least one member selected from the group consisting of ethylene copolymers (B1) composed of polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, and ethylene glycidyl methacrylate copolymer, resins (B2) composed of isotactic polypropylene, syndiotactic polypropylene, and polymethylpentene, and resins (B3) obtained by modifying the resins (B2) with maleic anhydride or glycidyl methacrylate (see, for example, Patent Document 1).

[0005] Also proposed is an insulated wire having an insulating coating layer composed of two or more resin layers, with at least one inner thermosetting resin layer and at least one outer thermoplastic resin layer, the thermosetting resin being selected from polyamideimide and polyimide, and the thermoplastic resin containing polyether ether ketone or polyphenylene sulfide (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5516303 [Patent Document 2] Patent No. 6839695 [Non-patent literature]

[0007] [Non-Patent Document 1] Furukawa Electric Times No. 133 (2014) p11-18. Summary of the Invention [Problem to be solved by the invention]

[0008] However, the isotactic polypropylene, syndiotactic polypropylene, and polymethylpentene proposed in Patent Document 1 are all polymers made from hydrocarbons. While they have excellent dielectric constants and partial discharge inception voltages, their low polarity and chemical stability result in poor chemical interaction with copper wires and poor adhesion. Therefore, when extrusion-molded into electric wires, gaps may form between the copper wire and the thermoplastic resin layer due to molding shrinkage and differences in the coefficient of linear expansion, potentially reducing the breakdown voltage. Furthermore, since the thickness of the insulation layer of electric wires with internal gaps cannot be determined by simple dimensional measurement alone, quality assurance on the production line becomes difficult.

[0009] The proposal in Patent Document 2 proposes a structure in which the insulating coating layer of an electric wire is composed of two or more layers, with an inner layer of a thermosetting resin that adheres well to the copper wire to prevent gaps from forming between the copper wire and the outer thermoplastic resin layer. However, in the manufacturing process of electric wires using thermosetting resin, a monomer is dissolved or dispersed in an organic solvent, and the coating and baking processes are repeated multiple times to create a defect-free coating layer. This requires a large amount of thermal energy and dedicated equipment to heat and evaporate the organic solvent and cause the monomer to undergo a thermosetting reaction. Furthermore, volatilizing the solvent creates a poor working environment and requires exhaust equipment, which is disadvantageous in terms of CO2 emissions and energy costs during production. For this reason, continuous extrusion molding of a single layer of thermoplastic resin with high insulating properties is desired as a manufacturing method for insulated electric wires that is the most cost-effective, environmentally friendly, and requires minimal workload.

[0010] Therefore, there is a need for insulated wires with a coating made of thermoplastic resin, which has excellent electrical insulation properties, flexibility for bending, and excellent adhesion between the coating and the conductor, making it suitable for motors and / or generators. [Means for solving the problem]

[0011] As a result of extensive research into solving the above problems, the present inventors have discovered that by using a resin composition containing polyarylene sulfide resin (hereinafter sometimes referred to as PAS resin), saponified ethylene-vinyl acetate copolymer (hereinafter sometimes referred to as saponified EVA), and high-pressure low-density polyethylene (hereinafter sometimes referred to as LDPE) as a coating material, an insulated wire can be obtained that has a certain low relative dielectric constant and excellent adhesion between the conductor and the coating material, and have thus completed the present invention.

[0012] That is, the present invention relates to an insulated wire having a conductor and a covering material covering the conductor, characterized in that the covering material is made of a PAS resin composition containing 100 parts by weight of PAS resin (A), 5 to 45 parts by weight of saponified EVA (B), and 10 to 50 parts by weight of LDPE (C).

[0013] The present invention will be described in detail below.

[0014] The insulated wire of the present invention is an insulated wire having a conductor and a covering material covering the outer surface of the conductor, and is an insulated wire in which the outer surface of the conductor is covered with a PAS resin composition containing 100 parts by weight of PAS resin (A), 5 to 45 parts by weight of saponified EVA (B), and 10 to 50 parts by weight of LDPE (C).The insulated wire can be produced, for example, by covering the outer surface of the conductor with the PAS resin composition by wire extrusion coating molding.

[0015] The PAS resin (A) constituting the PAS resin composition in this case may be any resin that falls within the category generally referred to as a PAS resin. Examples of such PAS resins include homopolymers or copolymers composed of p-phenylene sulfide units, m-phenylene sulfide units, o-phenylene sulfide units, phenylene sulfide sulfone units, phenylene sulfide ketone units, phenylene sulfide ether units, and biphenylene sulfide units. Specific examples of such PAS resins include poly(p-phenylene sulfide) (hereinafter sometimes simply referred to as PPS), polyphenylene sulfide sulfone, polyphenylene sulfide ketone, and polyphenylene sulfide ether. Of these, PPS is preferred because it results in a PAS resin composition and insulated wire that are particularly excellent in heat resistance and chemical resistance.

[0016] The PAS resin (A) can be produced by a method known for producing PAS resins, for example, by polymerizing an alkali metal sulfide salt and a polyhaloaromatic compound in a polar solvent. Examples of polar organic solvents include N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, cyclohexylpyrrolidone, dimethylformamide, and dimethylacetamide. Examples of alkali metal sulfide salts include anhydrous or hydrated sodium sulfide, rubidium sulfide, and lithium sulfide. The alkali metal sulfide salt may also be a product of reacting an alkali metal hydrosulfide salt with an alkali metal hydroxide. Examples of polyhaloaromatic compounds include p-dichlorobenzene, p-dibromobenzene, p-diiodobenzene, m-dichlorobenzene, m-dibromobenzene, m-diiodobenzene, 4,4'-dichlorodiphenyl sulfone, 4,4'-dichlorobenzophenone, 4,4'-dichlorodiphenyl ether, and 4,4'-dichlorodiphenyl.

[0017] Examples of PAS resin (A) include linear PAS resins, PAS resins that have been heat-treated in oxygen to introduce crosslinks or branching, PAS resins that have been polymerized with a small amount of a trihalogen or higher polyhalogen compound to introduce a slight crosslinking or branching, PAS resins in which part of the molecular chain and / or the terminals have been modified with functional groups such as carboxyl groups, carboxy metal salts, alkyl groups, alkoxy groups, amino groups, and nitro groups, and PAS resins that have been heat-treated in a non-oxidizing inert gas such as nitrogen. Mixtures of these PAS resins are also acceptable. Among these, PAS resins in which part of the molecular chain has been modified with amino groups are preferred because they have excellent interaction with saponified EVA containing polar groups, and excellent reactivity with reactive compounds, particularly copolymers of ethylene-meth(acrylic acid ester) containing reactive functional groups, making it easier to obtain PAS resin compositions with excellent toughness, including impact resistance. The PAS resin may be one in which impurities such as sodium atoms, PAS oligomers, table salt, and sodium salt of 4-(N-methyl-chlorophenylamino)butanoate have been reduced by washing with an acid, alkali, hot water, or an organic solvent such as acetone or methyl alcohol.

[0018] The PAS resin preferably has a melt viscosity of 400 to 3,000 poise, as measured using a high-speed flow tester equipped with a die having a diameter of 1 mm and a length of 2 mm, at a measurement temperature of 315°C and a load of 10 kg, in order to provide excellent moldability and productivity for insulated wires when made into a PAS resin composition.

[0019] The saponified EVA (B) constituting the coating material may be any saponified EVA obtained by saponifying an ethylene-vinyl acetate copolymer. The hydroxyl groups contained in the saponified EVA are highly polar, and therefore exhibit excellent adhesion through interaction with the surface of the metal conductor. For example, if the conductor is made of copper, the saponified EVA exhibits excellent adhesion through interaction with the copper oxide on the copper surface, eliminating any gaps between the conductor and the coating material, resulting in an insulated wire with improved partial discharge inception voltage.

[0020] The saponified EVA (B) is preferably a saponified EVA having an ethylene content of 65 mol% to 90 mol% inclusive, since this provides a coating material with particularly excellent adhesion to the conductor and flexibility. The saponification degree of the saponified EVA (B) is preferably 60% by weight or more, and more preferably 80% by weight or more to 100% by weight in terms of the vinyl acetate content, calculated in accordance with JIS K7192 (1999), in order to provide an insulated wire with particularly excellent adhesion to the conductor.

[0021] Examples of commercially available saponified EVA (B) include (trade names) Mersen H6051 and Mersen H6960 (manufactured by Tosoh Corporation). In addition, commercially available EVA products, such as (trade names) Ultrathene 751 (vinyl acetate content: 28%) and Ultrathene 750 (vinyl acetate content: 32%) (manufactured by Tosoh Corporation), can be heat-treated with an aqueous sodium hydroxide solution or the like to produce saponified EVA having any desired degree of saponification.

[0022] Furthermore, the saponified EVA (B) preferably has a melt mass-flow rate of 100 g / 10 min or less as measured in accordance with JIS K6924-1 (under conditions of 190°C and a load of 2160 g) in order to provide a PAS resin composition that has an excellent balance between viscosity and melt tension and can be molded at high speed, thereby enabling the coating material to be made thinner.The saponified EVA may be one type alone or two or more types may be combined in order to adjust the amount of hydroxyl groups and viscosity.

[0023] The amount of saponified EVA to be blended is 5 to 45 parts by weight, preferably 10 to 35 parts by weight, of saponified EVA (B) per 100 parts by weight of PAS resin (A) to achieve both moldability of the coating material for the electric wire and adhesion to the conductor. If the amount of saponified EVA blended is less than 5 parts by weight, the resulting resin composition will have poor adhesion to the metal conductor, and gaps will form when the electric wire is made into it, resulting in insufficient insulation. On the other hand, if the amount of saponified EVA blended is more than 45 parts by weight, the resulting resin composition will have poor mechanical properties and heat resistance, and when made into an electric wire, it will have poor flexibility and heat degradation resistance.

[0024] The LDPE (C) constituting the insulation material may be what is known as high-pressure low-density polyethylene. LDPE obtained by high-pressure processing is known as low-density polyethylene with long-chain branching. Furthermore, for the purpose of adjusting the branching number, melt tension, molecular weight distribution, etc., it may be heat-adjusted by, for example, heating commercially available LDPE in the presence of oxygen at 130°C to 220°C using a twin-screw extruder or Banbury mixer, and melt-kneading. LDPE is characterized by its high melt tension, and LDPE that has undergone the aforementioned heat adjustment, in particular, exhibits high melt tension regardless of the mass flow rate (MFR). Furthermore, the PAS resin composition constituting the insulation material for insulated electric wires has improved melt tension, which allows for good moldability even under high-speed wire molding conditions, resulting in a thin, uniform insulation material. In particular, it is preferable that the LDPE (C) has a melt tension of 100 mN or more at 260°C as measured with a capillary viscometer, and a molecular weight distribution (hereinafter referred to as Mw / Mn), which is the ratio of weight average molecular weight (hereinafter referred to as Mw) to number average molecular weight (hereinafter referred to as Mn), of 9 or more. Such LDPE can be prepared, for example, by the methods described in Japanese Patent Nos. 6,047,953 and 6,115,130.

[0025] Melt tension can be measured by known methods. For example, the melt tension of LDPE and PAS resin compositions can be measured in a thermostatic chamber set to 23°C, at 260°C, by filling an 18 g sample into a capillary viscometer (manufactured by Toyo Seiki Seisakusho, product name: Capilograph) with a barrel diameter of 9.55 mm and equipped with a die having a length of 8 mm, a diameter of 2.095 mm, and an inlet angle of 90°, setting the piston descending speed to 10 mm / min, and the draw ratio to 4.7. The melt tension is measured as the load (mN) required for take-up. The Mw, Mn, and Mw / Mn of LDPE can be measured, for example, using gel permeation chromatography (GPC). The Mw / Mn of LDPE (C) in a PAS resin composition can be determined by heating and dissolving the PAS resin composition in an aprotic nonpolar solvent such as toluene or xylene, and then measuring the melt tension.

[0026] The blending amount of LDPE (C) is 10 to 50 parts by weight per 100 parts by weight of PAS resin (A), and 15 to 35 parts by weight is more preferred, as this results in an insulated wire with an excellent balance of moldability and low dielectric constant. Here, if the blending amount of LDPE is less than 10 parts by weight, the melt tension will be insufficient, and when coated under conditions of high wire coating molding speed, the wire will remain uncoated and will not function as an insulated wire. Alternatively, the coating thickness will become too thick, resulting in poor productivity. On the other hand, if the blending amount is more than 50 parts by weight, the melt tension will be too high, and the wire may remain partially uncoated during molding.

[0027] The PAS resin composition containing PAS resin (A), saponified EVA (B), and LDPE (C) may have any melt viscosity, as long as it can be melt-molded into a coating or sheathing material. To ensure excellent moldability during the manufacture of insulated wire, the PAS resin composition preferably has a melt viscosity of 1,000 to 10,000 poise, particularly 2,000 to 4,000 poise, as measured using a high-speed flow tester equipped with a die measuring 1 mm in diameter and 2 mm in length at a temperature of 290°C and a load of 10 kg. Furthermore, to ensure excellent dielectric properties and partial discharge inception voltage, the PAS resin composition preferably has a dielectric constant of 3.0 or less, particularly 2.8 or less, as measured using a 70 mm x 3 mm x 1 mm thick strip test piece in accordance with JIS C-2565 at a temperature of 23°C and a frequency of 2 GHz. Furthermore, since the PAS resin composition can be used to produce an insulated wire with excellent flexibility, it is preferable that the tensile breaking strain measured in accordance with JIS K7161 is 10% or more, particularly 15% or more.

[0028] Furthermore, since the PAS resin composition allows for fine dispersion of saponified EVA (B) and LDPE (C) in the PAS resin (A), it is preferable to further blend a modified polyolefin copolymer or polyolefin copolymer having reactive functional groups. This fine dispersion provides good moldability even under conditions of high wire molding speed, enabling the molding of thin, uniform insulation materials. Furthermore, the flexibility of the insulation material is increased, allowing it to conform to the conductor without peeling or cracking even when bending the wire after molding.

[0029] The modified polyolefin copolymer having a reactive functional group may be any polyolefin copolymer as long as it falls within that category, and among these, a PAS resin composition having excellent flexibility during bending after molding into an electric wire and excellent resistance to cold and heat shock, and an insulated electric wire, are preferably an ethylene-acrylic acid ester copolymer (D) or an ethylene-methacrylic acid ester copolymer (D) (hereinafter, sometimes collectively referred to as ethylene-(meth)acrylic acid ester copolymer (D)), which are copolymers having a low glass transition temperature, and for example, a reactive functional group-modified It belongs to the category of ethylene-α,β-unsaturated carboxylic acid alkyl ester copolymers, and examples of the α,β-unsaturated carboxylic acid alkyl ester residues constituting the copolymer include methyl acrylate units, ethyl acrylate units, propyl acrylate units, butyl acrylate units, hexyl acrylate units, octyl acrylate units, glycidyl acrylate units, methyl methacrylate units, ethyl methacrylate units, propyl methacrylate units, hexyl methacrylate units, octyl methacrylate units, glycidyl methacrylate units, etc. Furthermore, examples of the reactive functional groups include epoxy groups, maleic anhydride groups, carboxylic acid groups, amino groups, isocyanate groups, etc. The ethylene-a(meth)acrylic acid ester copolymer (D) is preferably a reactive functional group-modified ethylene-α,β-unsaturated carboxylic acid alkyl ester copolymer, since it can be used to produce a PAS resin composition and an insulated electric wire having particularly excellent impact resistance and flexibility. Examples of such copolymers include ethylene-α,β-unsaturated carboxylic acid alkyl ester-maleic anhydride copolymer, ethylene-α,β-unsaturated carboxylic acid glycidyl ester copolymer, ethylene-α,β-unsaturated carboxylic acid glycidyl ester-vinyl acetate copolymer, and ethylene-α,β-unsaturated carboxylic acid glycidyl ester-α,β-unsaturated carboxylic acid alkyl ester copolymer.

[0030] Examples of ethylene-a(meth)acrylic acid ester copolymers and maleic anhydride-modified ethylene-a(meth)acrylic acid ester copolymers include (trade names) Lotader AX8700 and AX8750 manufactured by SK Global Chemical Co., Ltd. and (trade names) Bondfast 7M and 7L manufactured by Sumitomo Chemical Co., Ltd. Examples of maleic anhydride-modified ethylene-a(meth)acrylic acid ester copolymers include (trade names) Lotader AX5500, (trade names) BONDINE AX8390, LX4110, and TX8030 manufactured by SK Global Chemical Co., Ltd.

[0031] The amount of the modified polyolefin copolymer or polyolefin copolymer having a reactive functional group to be blended is preferably 15 to 50 parts by weight, particularly preferably 20 to 40 parts by weight, per 100 parts by weight of the PAS resin, since this makes it possible to obtain a coating material or exterior material that has an excellent balance between toughness such as impact resistance and heat resistance. Furthermore, the PAS resin composition constituting the coating material may contain fillers such as fibrous fillers and non-fibrous fillers, provided that the purpose of the present invention is not exceeded. Examples of fibrous fillers include whiskers such as glass fibers, silicon nitride whiskers, basic magnesium sulfate whiskers, barium titanate whiskers, potassium titanate whiskers, silicon carbide whiskers, boron whiskers, and zinc oxide whiskers; inorganic fibers such as zirconia, alumina silica, barium titanate, silicon carbide, alumina, silica, and blast furnace slag; organic fibers such as wholly aromatic polyamide fibers, phenolic resin fibers, and wholly aromatic polyester fibers; and mineral fibers such as wollastonite and magnesium oxysulfate. Examples of non-fibrous fillers include silicates such as wollastonite, zeolite, sericite, kaolin, mica, pyrophyllite, talc, and alumina silicate; oxides such as aluminum oxide, silicon oxide, magnesium oxide, zirconium oxide, titanium oxide, zinc oxide, and iron oxide; carbonates such as calcium carbonate, magnesium carbonate, and dolomite; sulfates such as calcium sulfate and barium sulfate; nitrides such as silicon nitride, boron nitride, and aluminum nitride; glass flakes, glass beads, etc. The fillers may also be surface-treated with an isocyanate compound, a silane coupling agent, a titanate coupling agent, an epoxy compound, etc.

[0032] Furthermore, the PAS resin composition may contain a silane coupling agent, which will provide it with excellent toughness and other properties. Examples of the silane coupling agent include silane coupling agents consisting of a trialkoxysilane coupling agent having a glycidyl group and / or a trialkoxysilane coupling agent having an amino group. Specific examples include 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, and N-2-(aminoethyl)-3-aminopropyltrimethoxysilane.

[0033] Furthermore, the PAS resin composition may contain a mold release agent to improve moldability and appearance when molded into a molded product. Examples of the mold release agent include polyethylene wax, polypropylene wax, and fatty acid amide wax. Commonly available polyethylene wax and polypropylene wax products can be used.

[0034] The PAS resin composition may be mixed with various additives within the scope of the present invention, for example, one or more conventional additives such as conventionally known plasticizers (e.g., polyalkylene oxide oligomer compounds, thioether compounds, ester compounds, and organic phosphorus compounds), antioxidants, heat stabilizers, ultraviolet inhibitors, and foaming agents. Furthermore, the PAS resin composition may be mixed with one or more thermoplastic resins (e.g., various thermosetting resins, thermoplastic elastomers without reactive functional groups, epoxy resins, cyanate ester resins, phenolic resins, polyimides, silicone resins, polyesters, polyamides, polyphenylene oxides, polycarbonates, polysulfones, polyetherimides, polyethersulfones, polyetherketones, polyetheretherketones, polyamideimides, and polyalkylene oxides).

[0035] The PAS resin composition can be produced by conventionally used melt-kneading methods. Examples include melt-kneading methods using a single-screw or twin-screw extruder, kneader, mill, or Brabender. Melt-kneading using a twin-screw extruder is particularly preferred, due to its excellent kneading capacity and productivity. Furthermore, a screw length (L1) to screw diameter (D1) ratio (L1 / D1) of 30 or greater is desirable, since this allows for sufficient kneading and reaction of the PAS resin (A), saponified EVA (B), and LDPE (C), and optionally additional compounding components, resulting in the easy production of a PAS resin composition with excellent suitability for coating materials. The cylinder temperature in the kneading zone of the extruder is preferably set to 260 to 330°C, and more preferably 260 to 300°C. The peripheral speed of the screw is preferably 50 to 400 mm / sec, and more preferably 150 to 300 mm / sec. The residence time of the molten resin in the extruder is preferably 30 to 100 seconds.

[0036] The conductor constituting the insulated wire of the present invention may be any known conductor, and is preferably made of, for example, tough pitch copper, pure copper, copper alloy, or aluminum.

[0037] The shape of the conductor constituting the insulated wire of the present invention is preferably a rectangular wire with a rectangular cross section in order to improve the coil occupancy rate of the motor. From the viewpoint of workability when bending the insulated wire into a coil, a rectangular wire with a short side of 0.8 mm to 5 mm and a long side of 1.4 mm to 8 mm is preferred. Alternatively, a round wire may be used, which is advantageous in terms of ease of quality control and cost. Similarly, from the viewpoint of workability when forming a coil, the size of the round wire is preferably a diameter of 0.5 mm to 5 mm.

[0038] The insulated wire of the present invention comprises the conductor coated with the PAS resin composition. The thickness of the coating layer is optional as long as the desired dielectric breakdown strength and partial discharge inception voltage are achieved. A thickness of 0.05 to 0.3 mm is preferred, as this provides an insulated wire with excellent conformability, dielectric breakdown strength, partial discharge inception voltage, and gas permeation resistance. The PAS resin composition can be coated using a conventional molding machine, such as an extrusion molding machine, an injection molding machine, a thermal compression molding machine, or a transfer molding machine. Among these, extrusion-based wire coating molding is preferred, as it allows continuous coating of conductors with lengths ranging from several hundred meters to several kilometers, making it a molding method with excellent continuous productivity for insulated wires.

[0039] A cross-sectional view of an exemplary insulated electric wire of the present invention is shown in Fig. 1. In Fig. 1, reference numeral 1 denotes an insulated electric wire with a rectangular cross section having an insulating coating material 2 on the outer periphery of a rectangular conductor 2, and reference numeral 4 denotes an insulated electric wire with a round cross section having an insulating coating material 6 on the outer periphery of a round conductor 5.

[0040] As long as the insulated wire of the present invention has a coating material made of the PAS resin composition on the outer periphery of the conductor, it may be a single layer made of the PAS resin composition or a multilayer including another thermoplastic resin layer, a rubber layer, a thermoplastic elastomer layer, or a thermosetting resin layer. In particular, it may have a water vapor or oxygen barrier layer, a heat-resistant coating layer, etc., and in order to achieve a high breakdown voltage, it is preferable to use a multilayer coating material according to the purpose.

[0041] The insulated wire of the present invention can be used for general purposes. In particular, when applied to motors, generators, reactors, and the like, the insulated wire can improve motor efficiency, output, and power generation efficiency, thereby contributing to energy conservation, miniaturization, and weight reduction of electric vehicles and hybrid vehicles. [Effects of the Invention]

[0042] The insulating electric wire of the present invention is excellent in heat resistance, dielectric breakdown strength, thermal shock cycle resistance, and toughness while ensuring the adhesion between the conductor and the coating layer, which has been a technical problem in the prior art. By using this insulating electric wire, the motor efficiency and power generation efficiency of motors, generators, reactors, etc. can be improved. It has a great effect on energy saving, miniaturization, and weight reduction of electric vehicles and hybrid vehicles.

Brief Description of the Drawings

[0043] [Figure 1] ; Cross-sectional view schematically showing the insulating electric wire of the present invention.

Examples

[0044] Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

[0045] The PAS resin (A), saponified EVA (B), LDPE (C), conductor, etc. used in the examples and comparative examples are shown below.

[0046] <PAS resin (A)> Poly(p-phenylene sulfide) (hereinafter referred to as PPS (A-1)): melt viscosity 1120 poise.

[0047] [[ID=३०]]<Saponified EVA (B)> Partially saponified EVA (B-1); manufactured by Tosoh Corporation, (trade name) Melsene H69๖0 (vinyl acetate content before saponification treatment 19 mol%, saponification degree of vinyl acetate component is 90 wt%, MFR 40 g / 10 min). Saponified EVA (B-2); manufactured by Tosoh Corporation, (trade name) Melsene H6051K (vinyl acetate content before saponification treatment 28 mol%, saponification degree of vinyl acetate component is 96 wt%, MFR 7 g / 10 min).

[0048] <EVA (B’)> EVA (B’-3); manufactured by Tosoh Corporation, (trade name) Ultrasen 751 (vinyl acetate content 28 mol%, MFR 8 g / 10 min).

[0049] <LDPE(C)> The preparation was carried out based on the method described in Japanese Patent No. 6047953. The kneading machine used was a counter-rotating twin-screw extruder (manufactured by Toyo Seiki Seisakusho, trade name: Labo Plastomill 2D25S type), with a melt mass flow rate of 1.6 g / 10 min and a density of 919 kg / m 3 The LDPE (manufactured by Tosoh Corporation, trade name Petrothene 360; melt tension 75 mN) was melt-kneaded under the conditions of a kneading temperature of 160°C, a discharge rate of 1.7 kg / hour, a screw rotation speed of 60 rpm, an oxygen concentration of 21%, and a filling rate of 80%, extruded into a strand shape, and cut into LDPE pellets (C-1) using a strand cutter (manufactured by Seiwa Iron Works Co., Ltd.). The screw used was a multi-flight type with reverse lead (2S25R type). The Mw / Mn value was 10.0 and the melt tension was 172 mN. LLDPE (C'-2): Commercially available linear low-density polyethylene (LLDPE) (manufactured by Tosoh Corporation, trade name Nipolon-L M50; melt tension 9 mN, melt mass-flow rate 3.0 g / 10 min, density 936 kg / m 3 The Mw / Mn value was 3.5.

[0050] <Ethylene-(meth)acrylate copolymer (D)> Ethylene-ethyl acrylate-maleic anhydride copolymer (D-1): SK Global Chemical Co., Ltd., (trade name) Bondine AX8390, reactive group: maleic anhydride, ethylene residue unit: α,β-unsaturated carboxylic acid ethyl residue unit: maleic anhydride residue unit (weight ratio) = 69.7:29:1.3.

[0051] <conductor> A rectangular copper wire (manufactured by Tanaka Electric Wire Co., Ltd.) made of tough pitch copper with a rectangular cross section of 3.2 mm long and 1.6 mm short, and a length of over 500 m.

[0052] The evaluation and measurement methods for the obtained PAS resin composition and insulated wire are shown below.

[0053] (1) Cross-section observation of insulated wire The resulting insulated wire was cut to a length of 1 cm, embedded in colored phenolic resin, and polished with waterproof abrasive paper (#240 to #2000) and buffed to a mirror finish (#8000) to create a sample for cross-sectional observation. The film thickness on all four sides was measured using an optical microscope at approximately 3000x magnification, and the average value was taken as the film thickness. The interface between the copper and the coating material was observed, and the maximum value of the gap on all four sides was taken as the "gap (μm)."

[0054] (2) Evaluation of bending workability of insulated wire Using a 5mm diameter half-moon-shaped bending jig (made of carbon steel), the insulated wire was bent at an angle of 180 degrees relative to the short side, and the appearance of the insulating coating after bending was observed visually or with a magnifying glass. N=5 tests were conducted, and specimens in which the appearance of the insulating coating after bending was good were rated as "good." In contrast, specimens in which one or more cracks appeared in the insulating coating outside the arc of the wire after bending were rated as "cracked."

[0055] (3) Judgment of insulated wire Insulated wires that had no gaps between the coating material and the conductor in the cross section and did not develop cracks during the bending workability evaluation were deemed suitable for use in motors and generators and were given a "Good" rating. Wires that did not satisfy either of these criteria were deemed unsuitable for use as wires and were given a "Poor" rating.

[0056] (4) Melt tension measurement The melt tensions of the LDPE and PAS resin compositions were measured by a known method. In a thermostatic chamber set to 23°C, the temperature was set to 260°C, and 18 g of sample was filled into a capillary viscometer (manufactured by Toyo Seiki Seisakusho, product name: Capilograph) with a barrel diameter of 9.55 mm and equipped with a die having a length of 8 mm, a diameter of 2.095 mm, and an inlet angle of 90°. The piston descending speed was set to 10 mm / min, and the draw ratio was set to 4.7, and the load (mN) required for take-up was measured as the melt tension.

[0057] (5) Measurement of Mw and Mn The Mw, Mn, and Mw / Mn of LDPE were measured using gel permeation chromatography (GPC). After weighing a measurement sample, the sample was added to a solvent of HPLC-grade 1,2,4-trichlorobenzene (Wako Pure Chemical Industries, Ltd.) containing 0.1% BHT (Wako Pure Chemical Industries, Ltd.) as an antioxidant, and the mixture was shaken at 140°C for 1 hour to dissolve the sample solution. The measurement system used was a Tosoh Corporation (trade name) HLC-8121 GPC / HT, and three connected TSKgel GMHHR-H(20)HT columns (Tosoh Corporation, 7.8 mm inner diameter, 30 cm length) were used as separation columns. The mobile phase consisted of HPLC-grade 1,2,4-trichlorobenzene (Wako Pure Chemical Industries, Ltd.) supplemented with 0.05% BHT (Wako Pure Chemical Industries, Ltd.) as an antioxidant. The mobile phase was maintained at 140 °C and moved through the separation column at a flow rate of 1.0 ml / min. 0.3 ml of sample solution adjusted to a concentration of 1.0 mg / ml was injected into the mobile phase, and the separated sample components were detected using a differential refractometer. A fifth-order approximation curve prepared using standard polystyrene (Tosoh Corporation) was used as a calibration curve to calculate Mn, Mw, and Mw / Mn.

[0058] Synthesis Example 1 A 50-liter autoclave equipped with a stirrer was charged with 6214 g of flake sodium sulfide (Na2S·2.9H2O) and 17,000 g of N-methyl-2-pyrrolidone. The mixture was gradually heated to 205°C while stirring under a nitrogen stream, and 1,355 g of water was distilled off. After cooling to 140°C, 7,278 g of p-dichlorobenzene, 11.7 g of 3,5-dichloroaniline, and 5,000 g of N-methyl-2-pyrrolidone were added and sealed under a nitrogen stream. The mixture was heated to 225°C over 2 hours and polymerized at 225°C for 2 hours. The temperature was then raised to 250°C over 30 minutes and further polymerized at 250°C for 3 hours. After polymerization, the mixture was cooled to room temperature and the polymer was isolated by centrifugation. The solid polymer was repeatedly washed with warm water and dried overnight at 100°C to obtain an amino group-substituted poly(p-phenylene sulfide) with a melt viscosity of 400 poise. The dried amino group-substituted poly(p-phenylene sulfide) was then loaded into a batch rotary kiln-type calciner and cured for 2 hours at 240°C in an air atmosphere to obtain PPS (A-1) with a melt viscosity of 1120 poise and an amino group content of 0.1 mol% relative to the phenyl groups.

[0059] Preparation Example 1 100 parts by weight of the PPS (A-1) obtained in Synthesis Example 1, 8 parts by weight of saponified EVA (B-1), and 30 parts by weight of LDPE (C-1) were homogeneously mixed in advance and charged into the hopper of a twin-screw extruder (manufactured by The Japan Steel Works, Ltd., product name TEX-25αIII, cylinder diameter 25 mm, L1 / D1 = 55) equipped with three kneading zones. The kneading zone cylinder temperature was heated to 290°C, and the mixture was melt-kneaded at a raw material supply rate of 12 kg / h and a screw rotation speed of 250 rpm (circumferential speed 327 mm / sec). The molten composition flowed out of the die after a residence time of approximately 60 seconds. The composition was water-cooled, cut with a rotary cutter, and dried in a constant-temperature bath at 80°C for approximately 3 hours to produce pellets of a PPS resin composition.

[0060] Preparation Examples 2 to 9 Pellets of PPS resin compositions were prepared in the same manner as in Preparation Example 1, except that the amounts of PAS resin (A), saponified EVA (B), LDPE (C), and ethylene-a(meth)acrylate copolymer (D) were changed to those shown in Table 1.

[0061] Example 1 The pelletized PPS resin composition obtained in Preparation Example 1 was placed in the hopper of a horizontal single-screw extruder (cylinder diameter 20 mm, cylinder length 500 mm; full-flight screw: compression ratio 3.2) and pressure-fed to the crosshead of a wire coating molding machine at a cylinder temperature of 290°C and a die temperature of 290°C. A rectangular tough-pitch copper wire (long side 3.2 mm, short side 1.6 mm, manufactured by Tanaka Electric Wire Co., Ltd.) was placed in a heating furnace under a nitrogen atmosphere, and the conductor preheated to approximately 180°C was introduced into the crosshead of the wire coating molding machine. The coating material was coated to a thickness of 130±10 μm and molded at a molding speed of 2 m / min to produce an insulated wire. The wire was cooled to below 60°C at room temperature and cut into approximately 50 cm sections to obtain insulated wires for evaluation.

[0062] The evaluation results of the insulated wires are shown in Table 1.

[0063] Examples 2 to 9 Insulated wires were obtained in the same manner as in Example 1, except that the pellet-shaped PPS resin compositions obtained in Preparation Examples 2 to 8 were used instead of the pellet-shaped PPS resin composition obtained in Preparation Example 1. The evaluation results are shown in Table 1.

[0064] [Table 1]

[0065] Preparation Examples 10-15 A pellet-shaped resin composition was prepared in the same manner as in Preparation Example 1, except that the amounts of PAS resin (A), saponified EVA (B), EVA (B'), and LDPE (C, C') were changed to the amounts shown in Table 2.

[0066] Comparative Examples 1 to 6 Insulated wires were obtained in the same manner as in Example 1, except that the pellet-shaped resin compositions obtained in Preparation Examples 10 to 15 were used instead of the pellet-shaped PPS resin composition obtained in Preparation Example 1. The evaluation results are shown in Table 2.

[0067] [Table 2] [Industrial Applicability]

[0068] The insulated wire of the present invention uses a specific PAS resin composition as the insulating layer covering material, thereby achieving excellent adhesion to the conductor and achieving heat resistance, dielectric breakdown strength, thermal shock cycle resistance, and toughness. This improves the productivity of the wires used in motors and generators, and also improves motor and power generation efficiency, contributing to energy savings, miniaturization, and weight reduction in electric and hybrid vehicles. [Explanation of symbols]

[0069] 1. Insulated wire with a rectangular cross section 2; conductor 3. Insulating coating material 4. Round cross-section insulated wire 5; conductor 6. Insulating coating material

Claims

1. An insulated wire having a conductor and a covering material covering the conductor, characterized in that the covering material is made of a polyarylene sulfide resin composition containing 100 parts by weight of a polyarylene sulfide resin (A), 5 to 45 parts by weight of a saponified ethylene-vinyl acetate copolymer (B), and 10 to 50 parts by weight of a high-pressure low-density polyethylene (C).

2. 2. The insulated wire according to claim 1, wherein the saponified ethylene-vinyl acetate copolymer (B) is a saponified ethylene-vinyl acetate copolymer having a degree of saponification of the vinyl acetate component in accordance with JIS K7192 (1999) of 60% by weight or more.

3. 2. The insulated wire according to claim 1, wherein the saponified ethylene-vinyl acetate copolymer (B) has an ethylene unit content of 65 mol % or more and 90 mol % or less.

4. 2. The insulated wire according to claim 1, wherein the high-pressure low-density polyethylene (C) is a high-pressure low-density polyethylene having a melt tension of 100 mN or more at 260°C and a molecular weight distribution determined by GPC of 9.0 or more.

5. 2. The insulated wire according to claim 1, wherein the covering material is made of a polyarylene sulfide resin composition further containing an ethylene-a(meth)acrylic acid ester copolymer (D).

6. 2. The insulated wire according to claim 1, wherein the covering material is a melt-extrusion-molded covering material.

7. 2. The insulated wire according to claim 1, wherein the covering material is a single layer having a thickness of 0.05 to 0.3 mm.

8. 2. The insulated wire according to claim 1, wherein the conductor is made of tough pitch copper and / or pure copper and has a rectangular cross section with short sides of 0.8 mm to 5 mm and long sides of 1.4 mm to 8 mm.

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