Electric wire and cable

Abstract

An electric wire according to the present disclosure is provided with: a conductor formed of a single wire or a conductor obtained by twisting together a plurality of wires; and an insulation layer coating the outer circumference of the conductor. The insulation layer contains: a resin component; and magnesium hydroxide or aluminum hydroxide. The resin component contains an acid-modified polyethylene and a polypropylene which is the main component. The mass ratio of the acid-modified polyethylene with respect to the polypropylene is 0.05-0.82. The mass ratio of the magnesium hydroxide or the aluminum hydroxide with respect to the acid-modified polyethylene is 2.0-20.0. In the insulation layer, the thermal conductivity at 25°C is 0.5 W / m·K or more, and the volume specific resistivity is 1×1013 Ω·cm or more.

Description

Wire and Cable

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to electrical wires and cables.

[0002] In recent years, there has been a demand for ever greater capacity and speed in information transmission for electric wires and cables. Conventional cables generally include a core material (core wire) formed by twisting together a plurality of insulated electric wires (core electric wires), and an outer jacket layer that covers the core material (see Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2018-139177

[0004] The electric wire of the present disclosure includes a conductor formed of a single wire or a conductor formed by twisting a plurality of wires together, and an insulating layer covering the outer periphery of the conductor, wherein the insulating layer contains a resin component and magnesium hydroxide or aluminum hydroxide, the resin component contains acid-modified polyethylene and polypropylene as a main component, the mass ratio of the acid-modified polyethylene to the polypropylene is 0.05 or more and 0.82 or less, and the mass ratio of the magnesium hydroxide or aluminum hydroxide to the acid-modified polyethylene is 2.0 or more and 20.0 or less, and the insulating layer has a thermal conductivity of 0.5 W / m K or more at 25°C and a volume resistivity of 1×10 １３ It is Ω·cm or more.

[0005] Fig. 1 is a schematic cross-sectional view showing an electric wire according to one embodiment, Fig. 2 is a schematic cross-sectional view showing a cable according to one embodiment, and Fig. 3 is a schematic cross-sectional view showing a cable according to another embodiment.

[0006] [Problem to be Solved by the Present Disclosure] In recent years, the amount of information has increased, leading to an increase in power consumption. Therefore, when a current flows through an electric wire or cable that supplies power, the temperature of the conductor rises, which increases the conduction resistance and makes it prone to power loss. In addition, electric wires and cables that supply power are required to have further improvements in deformation resistance at high temperatures, mechanical strength, and high oil resistance.

[0007] The present disclosure has been made based on the above circumstances, and aims to provide an electric wire having an insulating layer that has excellent heat dissipation properties, as well as deformation resistance at high temperatures, high insulation properties, good mechanical strength, and high oil resistance.

[0008] Effect of the Present Disclosure According to the present disclosure, it is possible to provide an electric wire including an insulating layer that has excellent heat dissipation properties, as well as deformation resistance at high temperatures, high insulation properties, good mechanical strength, and high oil resistance.

[0009] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described.

[0010] The electric wire of the present disclosure includes: (1) a conductor formed of a single wire or a conductor formed by twisting a plurality of wires together; and an insulating layer covering the outer periphery of the conductor, wherein the insulating layer contains a resin component and magnesium hydroxide or aluminum hydroxide, the resin component contains acid-modified polyethylene and polypropylene as a main component, the mass ratio of the acid-modified polyethylene to the polypropylene is 0.05 or more and 0.82 or less, the mass ratio of the magnesium hydroxide or aluminum hydroxide to the acid-modified polyethylene is 2.0 or more and 20.0 or less, and the thermal conductivity of the insulating layer at 25°C is 0.5 W / m K or more and the volume resistivity is 1×10 １３ It is Ω·cm or more.

[0011] The inventors of the present invention focused on the fact that the coating materials used in conventional electric wires have poor heat dissipation properties, preventing heat from being released from heated conductors. Therefore, they conducted extensive research into improving the thermal conductivity of the coating materials to suppress temperature increases in the conductor, and completed the present invention. The insulating layer of the electric wire contains polypropylene as the main resin component, thereby providing the insulating layer with excellent tensile strength and oil resistance. Furthermore, the insulating layer contains acid-modified polyethylene and magnesium hydroxide or aluminum hydroxide as resin components, which forms a crosslinked structure with the magnesium hydroxide or aluminum hydroxide, thereby improving the insulating layer's resistance to deformation at high temperatures. By setting the mass ratio of the acid-modified polyethylene to the polypropylene to between 0.05 and 0.82, the insulating layer can achieve excellent tensile strength, oil resistance, and resistance to deformation at high temperatures. Furthermore, by setting the mass ratio of the magnesium hydroxide or aluminum hydroxide to the acid-modified polyethylene to between 2.0 and 20.0, the insulating layer can achieve both excellent insulation properties and excellent resistance to deformation at high temperatures. The insulating layer has a thermal conductivity of 0.5 W / m·K or more at 25°C, and has high thermal conductivity, so that heat from the conductor is released to the outside, and the effect of suppressing the temperature rise of the conductor is high. １３ The insulation layer has excellent heat dissipation properties, which can suppress the temperature rise of the conductor and reduce power loss, and the wire has deformation resistance at high temperatures, high insulation properties, good mechanical strength, and high oil resistance.

[0012] The "volume resistivity" refers to the electrical resistance value measured by the double ring electrode method in accordance with JIS-K6271: 2008. The "major component" refers to the component with the highest content, preferably 60% by mass or more.

[0013] (2) In the above (1), the acid-modified polyethylene may be an acid-modified very low density polyethylene. In the electric wire, the acid-modified polyethylene being an acid-modified very low density polyethylene can improve insulation properties and tensile elongation.

[0014] (3) In the above (1) or (2), the magnesium hydroxide and aluminum hydroxide may be surface-treated with a vinyl silane coupling agent. By surface-treating the magnesium hydroxide and aluminum hydroxide with a vinyl silane coupling agent, the cross-linked structure between the acid-modified polyethylene and the magnesium hydroxide or aluminum hydroxide becomes stronger, thereby improving deformation resistance at high temperatures. Furthermore, the increased compatibility with the acid-modified polyethylene improves the dispersibility of the magnesium hydroxide and aluminum hydroxide, thereby further improving the deformation resistance of the insulating layer at high temperatures.

[0015] (4) In any of (1) to (3) above, the insulating layer may further contain a black pigment. If the insulating layer contains a large amount of magnesium hydroxide or aluminum hydroxide, the surface of the insulating layer tends to be easily whitened. By further containing the black pigment in the insulating layer, whitening of the insulating layer surface due to magnesium hydroxide or aluminum hydroxide can be suppressed.

[0016] (5) A cable according to another aspect of the present disclosure includes one or more of the electric wires and an outer jacket layer disposed around the one or more electric wires. The cable includes the above-described electric wire as a core electric wire constituting a core wire, and therefore has excellent heat dissipation properties, deformation resistance at high temperatures, high insulation properties, good mechanical strength, and high oil resistance.

[0017] [Details of Embodiments of the Present Disclosure] Hereinafter, electric wires and cables according to embodiments of the present disclosure will be described in detail with appropriate reference to the drawings.

[0018] <Electric wire> The electric wire includes a conductor made of a single wire or a conductor made of multiple stranded wires, and an insulating layer that covers the outer periphery of the conductor. Fig. 1 shows an electric wire according to one embodiment of the present disclosure. The electric wire 1 in Fig. 1 includes a linear conductor 2 made of a single wire or a conductor made of multiple stranded wires, and an insulating layer 3 that covers the outer periphery of the conductor 2. In the electric wire, an additional layer such as a primer treatment layer may be provided between the conductor and the insulating layer.

[0019] [Conductor] The conductor 2 is a metal linear body that is responsible for electrical conduction of the electric wire 1. Examples of the conductor 2 include a round wire having a circular cross section, a rectangular wire having a rounded square cross section, and a rectangular wire having a rounded rectangular cross section. The conductor 2 may be a single linear body as shown in Fig. 1, or a twisted wire body formed by twisting together multiple thin wires.

[0020] The conductor 2 may be made of a metal such as copper, aluminum, nickel, silver, or iron, or an alloy thereof, but may be made of copper or aluminum from the viewpoints of electrical conductivity and workability. The conductor 2 may also have a multilayer structure in which a coating made of another metal is laminated on the outer surface of a metal linear body.

[0021] The lower limit of the average cross-sectional area (including the gaps between the wires) of the conductor 2 is 2 mm ２ 8 mm ２ 14 mm ２ On the other hand, the upper limit of the average cross-sectional area of ​​the conductor 2 is 600 mm ２ 500 mm ２ 400 mm ２ If the average cross-sectional area of ​​the conductor 2 is less than the above-mentioned lower limit, there is a risk that a sufficient current will not flow. On the other hand, if the average cross-sectional area of ​​the conductor 2 exceeds the above-mentioned upper limit, there is a risk that sufficient bending resistance will not be obtained. Here, the "average cross-sectional area" refers to the average value of values ​​measured at any 10 points on the cross section.

[0022] [Insulating Layer] The insulating layer 3 contains a resin component and magnesium hydroxide or aluminum hydroxide.

[0023] The average thickness of the insulating layer 3 is not particularly limited, but the lower limit of the average thickness may be, for example, 0.8 mm or 1.0 mm. On the other hand, the upper limit of the average thickness of the insulating layer 3 may be 10 mm or 7 mm. If the average thickness of the insulating layer 3 is less than the above-mentioned lower limit, the insulating properties of the insulating layer 3 may be insufficient. Furthermore, if the average thickness of the insulating layer 3 exceeds the above-mentioned upper limit, flexibility may be impaired. Here, "average thickness" refers to the average value of thicknesses measured at any ten points. Note that the same definition is used hereinafter when referring to "average thickness" for other members, etc.

[0024] (Resin Component) The resin component contains acid-modified polyethylene and polypropylene as the main component. Since the insulating layer 3 contains polypropylene as the main component of the resin component, the insulating layer 3 has excellent tensile strength and oil resistance. Furthermore, since the insulating layer 3 contains acid-modified polyethylene as the resin component, a crosslinked structure is formed with magnesium hydroxide or aluminum hydroxide, which improves the deformation resistance of the insulating layer 3 at high temperatures.

[0025] <Polypropylene> Examples of polypropylene (PP) include homopolypropylene, random polypropylene, block polypropylene, and acid-modified polypropylene modified with an unsaturated carboxylic acid or its derivative. Examples of random polypropylene include propylene-α-olefin copolymers, which are copolymers of propylene with ethylene or an α-olefin having 4 to 20 carbon atoms. Block polypropylene is a resin composed of homopolypropylene as the main component, a random copolymer elastomer as a copolymer component, and an ethylene polymer as an optional component. Examples of the propylene-α-olefin copolymer include ethylene-propylene copolymers, propylene-acrylic acid copolymers, propylene-methacrylic acid copolymers, propylene-acrylate ester copolymers, and propylene-methacrylate ester copolymers.

[0026] Among these, the polypropylene may be a random polypropylene or a block polypropylene. When the polypropylene is a random polypropylene or a block polypropylene, it is possible to improve the tensile strength and oil resistance while suppressing a significant decrease in tensile elongation.

[0027] The lower limit of the polypropylene content in the resin component may be 60% by mass or 65% by mass. The upper limit of the polypropylene content may be 95% by mass or 90% by mass. When the polypropylene content in the resin component is within the above range, the insulating layer 3 can have good tensile strength and oil resistance while also achieving compatibility with other properties.

[0028] <Acid-Modified Polyethylene> Acid-modified polyethylene (PE) is polyethylene modified with an unsaturated carboxylic acid or its derivative. Examples of the polyethylene include high-density polyethylene, very low-density polyethylene (VLDPE), low-density polyethylene, linear low-density polyethylene (LLDPE), and ethylene-α-olefin copolymer. Examples of the ethylene-α-olefin copolymer include ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate copolymer (EMA), ethylene-butyl acrylate copolymer (EBA), ethylene-methyl methacrylate copolymer, ethylene-acrylic acid copolymer, and ethylene-methacrylic acid copolymer. Among these, the acid-modified polyethylene may be acid-modified very low-density polyethylene. In the electric wire, when the acid-modified polyethylene is acid-modified very low-density polyethylene, the insulation properties and tensile elongation can be improved.

[0029] Examples of unsaturated carboxylic acids used in the acid modification include acrylic acid, methacrylic acid, maleic acid, itaconic acid, and fumaric acid. Examples of derivatives of unsaturated carboxylic acids include maleic acid monoesters, maleic anhydride, itaconic acid monoesters, itaconic anhydride, fumaric acid monoesters, and fumaric anhydride. Among these, derivatives of unsaturated carboxylic acids may be used, or maleic anhydride may be used.

[0030] The lower limit of the mass ratio of the acid-modified polyethylene to the polypropylene is 0.05, and may be 0.11 or 0.18. The upper limit of the mass ratio of the acid-modified polyethylene to the polypropylene is 0.82, and may be 0.67 or 0.54. When the mass ratio of the acid-modified polyethylene to the polypropylene is 0.05 or more and 0.82 or less, the insulating layer 3 can better achieve both tensile strength, oil resistance, and deformation resistance at high temperatures.

[0031] The insulating layer 3 may contain a resin other than the polypropylene and the acid-modified polyethylene, such as polyvinyl chloride, polyurethane, fluororesin, fluororubber, silicone, or polyester.

[0032] (Magnesium hydroxide and aluminum hydroxide) The insulating layer 3 contains magnesium hydroxide or aluminum hydroxide. When the insulating layer 3 contains magnesium hydroxide or aluminum hydroxide, a crosslinked structure is formed between the acid-modified polyethylene and the magnesium hydroxide or aluminum hydroxide, thereby improving the deformation resistance of the insulating layer 3 at high temperatures.

[0033] The magnesium hydroxide and aluminum hydroxide may be surface-treated with a vinyl silane coupling agent. By surface-treating the magnesium hydroxide and aluminum hydroxide with a vinyl silane coupling agent, the cross-linked structure between the acid-modified polyethylene and the magnesium hydroxide or aluminum hydroxide becomes stronger, thereby further improving deformation resistance at high temperatures. The vinyl silane coupling agent is a silane coupling agent having a vinyl group as the organic functional group. Examples of the vinyl silane coupling agent include vinyltrialkoxysilane coupling agents such as vinyltrimethoxysilane and vinyltriethoxysilane, and styrylsilane coupling agents such as p-styryltrimethoxysilane.

[0034] The lower limit of the mass ratio of magnesium hydroxide or aluminum hydroxide to the acid-modified polyethylene is 2.0, and may be 2.2. The upper limit of the mass ratio of magnesium hydroxide or aluminum hydroxide to the acid-modified polyethylene is 20.0, and may be 19.5, and may be 19.0. In the electric wire 1, when the mass ratio of magnesium hydroxide or aluminum hydroxide to the acid-modified polyethylene is within the above range, both the insulating properties of the insulating layer 3 and deformation resistance at high temperatures can be achieved satisfactorily.

[0035] (Black Pigment) The insulating layer 3 may further contain a black pigment. If the insulating layer 3 contains a large amount of magnesium hydroxide or aluminum hydroxide, the surface of the insulating layer tends to be easily whitened. By further containing a black pigment in the insulating layer 3, whitening of the insulating layer surface due to magnesium hydroxide or aluminum hydroxide can be suppressed.

[0036] Examples of the black pigment include carbon black, titanium-based black pigments, and iron tetroxide. Examples of the titanium-based black pigment include titanium / titanium oxide sintered products, low-order titanium oxides, and titanium nitride. These may be used alone or in combination of two or more.

[0037] The lower limit of the mass ratio of the black pigment to the resin component may be 0.03 or 0.05. The upper limit of the mass ratio of the black pigment to the resin component may be 0.25 or 0.20. When the mass ratio of the black pigment to the resin component is within the above range, both the whitening suppression effect and the insulating properties in the insulating layer 3 can be satisfactorily achieved.

[0038] (Thermally conductive filler) The insulating layer 3 may further contain a thermally conductive filler. When the insulating layer 3 further contains a thermally conductive filler, the electrical conductivity of the insulating layer 3 can be increased, and the heat dissipation properties can be improved. Examples of the thermally conductive filler include boron nitride, alumina, aluminum nitride, zinc oxide, graphite, magnesium oxide, silicon carbide, silica, iron carbonate, boehmite, chromium oxide, nickel oxide, copper oxide, zirconium oxide, indium oxide, and calcium carbonate.

[0039] The lower limit of the mass ratio of the thermally conductive filler to the resin component may be 0.10, 0.15, or 0.20. The upper limit of the mass ratio of the thermally conductive filler to the resin component may be 0.60, 0.55, or 0.50. When the mass ratio of the thermally conductive filler to the resin component is within the above range, the heat dissipation and insulation properties of the insulating layer 3 can be improved.

[0040] The insulating layer 3 may contain other additives as needed, such as a flame retardant, a flame retardant assistant, an antioxidant, a lubricant, a colorant, a reflectivity imparting agent, a masking agent, a processing stabilizer, and a plasticizer.

[0041] The lower limit of the thermal conductivity of the insulating layer 3 at 25° C. is 0.5 W / m·K, or may be 0.6 W / m·K or 0.7 W / m·K. By setting the lower limit of the insulating layer 3 to 0.5 W / m·K, the heat dissipation properties of the insulating layer 3 can be improved.

[0042] The lower limit of the volume resistivity of the insulating layer 3 is 1×10 １３ Ω cm, and 1×10 １４ It may be Ω cm, and 1×10１５ The volume resistivity of the insulating layer 3 may be 1×10 １３ By making the resistivity Ω·cm or more, the insulating properties and voltage resistance of the insulating layer 3 can be improved.

[0043] [Method for Producing Electric Wire] The method for producing the electric wire is not particularly limited, but may include, for example, the following steps: (1) a step of preparing an insulating layer-forming resin composition (hereinafter also referred to as a resin composition) for forming an insulating layer (resin composition preparation step); and (2) a step of coating a conductor with the insulating layer-forming resin composition (resin composition coating step).

[0044] (1) Resin Composition Preparation Step In the resin composition preparation step, the resin components of the resin composition for forming an insulating layer, magnesium hydroxide or aluminum hydroxide, and other additives as needed are mixed using a melt mixer or the like to prepare a resin composition for forming an insulating layer. Known melt mixers, such as open roll mixers, Banbury mixers, pressure kneaders, single-screw mixers, and multi-screw mixers, can be used. The resin composition of the present disclosure may be crosslinked by chemical crosslinking, silane crosslinking, or radiation crosslinking.

[0045] (2) Resin Composition Coating Step The resin composition coating step can be carried out by, for example, extruding the resin composition for forming an insulating layer onto a conductor using a melt extruder. This produces an extrusion-molded product corresponding to the insulating layer. The dimensions of the extrusion-molded product can be designed depending on the application, etc.

[0046] The electric wire has an insulating layer that has excellent heat dissipation properties, as well as resistance to deformation at high temperatures, high insulation properties, good mechanical strength, and high oil resistance.

[0047] <Cable> A cable according to another aspect of the present disclosure includes one or more of the electric wires and an outer jacket layer disposed around the one or more electric wires.

[0048] The outer diameter of the cable is designed appropriately depending on the application, but the lower limit of the outer diameter may be 10 mm or 15 mm, while the upper limit of the outer diameter of the cable may be 80 mm, 60 mm, or 50 mm.

[0049] [First embodiment] A cable according to a first embodiment of the present disclosure is shown in Fig. 2. A coaxial cable 5 according to the first embodiment includes an electric wire 1 including a conductor 2 and an insulating layer 3 covering the outer periphery of the conductor 2, and an outer jacket layer 4 disposed around the electric wire 1. That is, the coaxial cable 5 has a cross-sectional configuration in which the conductor 2, the insulating layer 3, and the outer jacket layer 4 are concentrically stacked. The cable being a coaxial cable 5 enables a reduction in diameter. The electric wire 1 is similar to the electric wire 1 in Fig. 1, and therefore the same reference numerals are used and a description thereof will be omitted.

[0050] The main component of the outer layer 4 is not particularly limited as long as it is a synthetic resin with excellent abrasion resistance, and examples thereof include polyvinyl chloride, polyethylene, cross-linked polyethylene, and chloroprene. The outer layer 4 may also be cross-linked.

[0051] The outer covering layer 4 may contain the additives exemplified for the insulating layer 3 .

[0052] The average thickness of the outer covering layer 4 may be 0.5 mm or more and 3.0 mm or less.

[0053] Second Embodiment A cable according to a second embodiment of the present disclosure is shown in Fig. 3. The cable 20 according to the second embodiment is a cable including a core wire formed by twisting together two of the electric wires 1 shown in Fig. 1, an inner coating layer 7 (intervening) disposed around the core wire, and an outer coating layer 10 disposed around the inner coating layer 7. The core wire is formed by twisting two electric wires 1 of the same diameter together. As shown in Fig. 3, the cable 20 may have a tape member 8 such as paper wound between the outer coating layer 10 and the inner coating layer 7 as a restraining member. The cable 20 can be suitably used, for example, as a power supply cable in the field of information and communications.

[0054] The main components of the inner coating layer 7 are, for example, polypropylene yarn, paper, or jute.

[0055] The lower limit of the outer diameter of the inner coating layer 7 may be 9.0 mm or 10 mm. On the other hand, the upper limit of the outer diameter of the inner coating layer 7 may be 75 mm or 60 mm.

[0056] The outer layer 10 has the same configuration as the outer layer 4 in FIG. 2, and therefore a description thereof will be omitted.

[0057] <Cable Manufacturing Method> The cable can be obtained by a manufacturing method including a step of covering one or more electric wires with an outer covering layer (outer covering layer covering step). If the cable includes multiple electric wires, the manufacturing method may include a step of twisting the multiple electric wires together. Furthermore, if the cable includes an inner covering layer or a tape member around one or more electric wires, the manufacturing method may include a step of forming an inner covering layer or a step of winding a tape member.

[0058] In the outer covering layer covering step, a resin composition for forming an outer covering layer is extruded onto the outside of one or more electric wires formed using, for example, a melt extrusion molding machine, thereby coating the outside of one or more electric wires with an outer covering layer.

[0059] The cable is then cooled after coating to harden the jacket layer, and the cable is then wound up and collected.

[0060] The method for producing the cable may further include a step of crosslinking the resin component of the jacket layer (crosslinking step). This crosslinking step may be performed before or after coating the exterior of one or more electric wires with the composition that forms the jacket layer (after the jacket layer is formed).

[0061] The cable includes the above-described electric wire as a core electric wire constituting the core wire, and therefore has excellent heat dissipation properties, as well as deformation resistance at high temperatures, high insulation properties, good mechanical strength, and high oil resistance.

[0062] [Other Embodiments] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is not limited to the configurations of the above-described embodiments, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0063] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0064] <Insulating Layers No. 1 to No. 23> Insulating layers No. 1 to No. 23, each consisting of a single layer, were formed by the following procedure.

[0065] [Resin Component] 1. Polypropylene The following resins were used as polypropylenes in the resin component. (1) Random polypropylene (random PP) MFR 1.3 (g / 10 min), flexural modulus 950 MPa (2) Block polypropylene (block PP) MFR: 2.0 (g / 10 min), flexural modulus 790 MPa The melt flow rate (MFR) is a value measured using a melt indexer at a measurement temperature of 230°C and a load of 2.16 kg according to a method in accordance with JIS-K7210-1:2014 (Method A: Mass Measurement Method). The flexural modulus is a value measured according to a method in accordance with JIS-K7171:2016. 2. Acid-modified polyethylene (1) Acid-modified very low density polyethylene (acid-modified VLDPE) Maleic anhydride-modified very low density polyethylene Density 0.87 g / cm ３ (2) Acid-modified high-density polyethylene (acid-modified HDPE) Maleic anhydride-modified high-density polyethylene Density 0.94 g / cm ３

[0066] [Inorganic Particles] The following five types of fillers were used as inorganic particles. (1) Magnesium hydroxide: surface untreated (average particle size 0.8 μm) (2) Magnesium hydroxide: treated with a vinyl silane coupling agent (average particle size 0.8 μm) (3) Aluminum hydroxide: surface untreated (average particle size 1.5 μm) (4) Aluminum hydroxide: surface untreated (average particle size 10.0 μm) (5) Carbon black: furnace black The "average particle size" refers to the median diameter (D50), which is the value at which the volume-based cumulative distribution calculated in accordance with JIS-Z-8819-2:2001 is 50%. The median diameter (D50) can be measured using the following method. Measurements were performed using a laser diffraction particle size distribution analyzer. A scattering measurement mode was employed, and a laser beam was irradiated onto a wet cell through which a dispersion liquid in which particles of the sample to be measured are dispersed in a dispersion solvent is circulated, and the scattered light distribution from the measurement sample was obtained. The scattered light distribution is then approximated by a log-normal distribution, and the particle diameter at a cumulative degree of 50% (D50) is taken as the median diameter.

[0067] The resin composition for forming an insulating layer was prepared using the above resin components and inorganic particles. The composition and content of the insulating layer are shown in Tables 1 and 2. "-" indicates that the corresponding component was not used.

[0068] [Production of insulating layer] The insulating layer was produced by extrusion molding using the resin composition for forming the insulating layer. An extrusion die was used for extrusion molding. The extrusion molding was carried out at a die temperature of 180°C and a linear speed of 5 m / min to obtain insulating layers No. 1 to No. 23 with an average thickness of 2.5 mm. The insulating layers were used to produce insulating layers with a cross-sectional area of ​​14 mm. ２ An electric wire was prepared by covering the outer periphery of a (14SQ) conductor.

[0069] [Evaluation] Insulating layers No. 1 to No. 23 were evaluated for thermal conductivity, volume resistivity, tensile strength, tensile elongation, tensile strength and tensile elongation after an oil resistance test, conductor temperature during current application, withstand voltage, modulus of elasticity at 200°C, and whitening suppression effect.

[0070] (Thermal Conductivity) A press sheet measuring φ150 mm x thickness 0.5 mm was prepared as a test sample from the resin composition for forming an insulating layer using a heat press machine, and the thermal conductivity at 25°C was measured in accordance with ISO-22007-3 (temperature wave method). A higher value of the thermal conductivity [W / (m K)] indicates higher heat dissipation properties of the insulating layer. A thermal conductivity of 0.50 [W / (m K)] or higher at 25°C can be said to have excellent heat dissipation properties.

[0071] (Volume Resistivity (Insulating Properties)) A press sheet measuring φ150 mm x 1 mm thick was prepared as a test sample from the resin composition for forming an insulating layer using a heat press machine, and electrical resistance was measured using the double ring electrode method specified in JIS-K6271:2008. The volume resistivity value was calculated from the measured value. A larger value of volume resistivity [Ω cm] means higher insulating properties of the insulating layer. A volume resistivity of 1×10 or more can be said to be excellent insulating properties of the insulating layer.

[0072] (Tensile Strength and Tensile Elongation) The tensile strength [MPa] and tensile elongation [%] of each insulating layer were measured in accordance with JIS-K-7162: 1994. When the tensile strength is 10 MPa or more and the tensile elongation is 300% or more, it can be said that the mechanical strength of the insulating layer is excellent.

[0073] (Tensile strength and tensile elongation after oil resistance test) After immersion for 4 hours at 70°C using JIS No. 2 test oil according to JIS-C3005:2014, the tensile strength [MPa] and tensile elongation [%] were measured to evaluate oil resistance. The tensile elongation [%] of the insulating layer was measured in accordance with JIS-K-7162:1994. The higher the tensile strength retention and tensile elongation retention after the oil resistance test, the better the oil resistance. When the tensile strength retention is 80% or more and the elongation retention is 60% or more, the insulating layer can be said to have excellent oil resistance.

[0074] (Conductor Temperature During Current Flow) To measure the conductor temperature during current flow, a current of 140 A was passed through each of electric wires having an outer diameter of 9.4 mm and a length of 3 m, each of which had an insulating layer No. 1 to No. 23 with an average thickness of 2.5 mm coated on the outer periphery of a 14SQ conductor with a conductor diameter of 4.4 mm, and the temperature of the conductor surface at the center of the electric wire was measured.

[0075] (Voltage Withstand Test) In accordance with JIS-C3605:2002, 2000 V was applied to each of the wires coated with the insulating layer No. 1 to No. 23, and the presence or absence of dielectric breakdown was evaluated. The evaluation was based on the following two levels. A rating of A indicates good effectiveness. A: No dielectric breakdown occurred. B: Dielectric breakdown occurred.

[0076] (Elastic modulus at 200°C) The elastic modulus at 200°C was measured to evaluate the resistance to deformation at high temperatures. Here, "elastic modulus" refers to the storage modulus measured using a dynamic viscoelasticity measuring device in accordance with JIS-K-0129 (2005). The storage modulus at 200°C was measured in the tensile mode of dynamic viscoelasticity measurement (DMA) in accordance with JIS-K-0129 (2005).

[0077] (Whitening suppression effect) Using a spectrophotometer ("CM-700d" manufactured by Konica Minolta, Inc.), the color difference ΔE between the rubbed area and the non-rubbed area was calculated to evaluate the whitening suppression effect. The evaluation was made according to the following two stages. Whitening suppression effect: Color difference ΔE is less than 10. Whitening suppression effect: Color difference ΔE is 10 or more.

[0078] The evaluation results of each of the insulating layers are shown in Tables 1 and 2.

[0079]

[0080]

[0081] From the results in Tables 1 and 2, it can be seen that the insulating layer contains a resin component and magnesium hydroxide or aluminum hydroxide, the resin component contains acid-modified polyethylene and polypropylene as a main component, the mass ratio of the acid-modified polyethylene to the polypropylene is 0.05 or more and 0.82 or less, the mass ratio of the magnesium hydroxide or aluminum hydroxide to the acid-modified polyethylene is 2.0 or more and 20.0 or less, the thermal conductivity of the insulating layer at 25° C. is 0.5 W / m K or more, and the volume resistivity is 1×10 １３The insulating layers of Tests No. 1 to No. 14, which had a resistivity of Ω·cm or higher, achieved favorable results in all of the following: thermal conductivity, volume resistivity, tensile strength, tensile elongation, tensile strength and tensile elongation after oil resistance testing, conductor temperature during current application, voltage resistance testing, and modulus of elasticity at 200°C. A comparison of Tests No. 1 and No. 3 reveals that the insulating properties and tensile elongation of the insulating layer are improved by using acid-modified ultra-low-density polyethylene as the acid-modified polyethylene. A comparison of Tests No. 1 and No. 4 reveals that the surface treatment of magnesium hydroxide with a vinyl silane coupling agent improves the deformation resistance of the insulating layer at high temperatures. Furthermore, the insulating layers of Tests No. 11 to No. 13, which further contained a black pigment, exhibited suppressed whitening.

[0082] On the other hand, the insulating layer of Test No. 15, in which the insulating layer did not contain polypropylene, exhibited low values ​​for tensile strength, tensile strength and tensile elongation after the oil resistance test, and modulus of elasticity at 200°C. The insulating layer of Test No. 16, in which the insulating layer did not contain acid-modified polyethylene, exhibited a low modulus of elasticity at 200°C. The insulating layer of Test No. 17, in which the mass ratio of acid-modified polyethylene to polypropylene exceeded 0.82, exhibited low tensile strength. The insulating layer of Test No. 18, in which the mass ratio of magnesium hydroxide or aluminum hydroxide to acid-modified polyethylene exceeded 20.0, exhibited low tensile elongation. The insulating layer of Test No. 19, in which the mass ratio of magnesium hydroxide or aluminum hydroxide to acid-modified polyethylene was less than 2.0, exhibited a low modulus of elasticity at 200°C. Test No. 19, in which the insulating layer did not contain magnesium hydroxide or aluminum hydroxide and had a thermal conductivity of less than 0.5 W / m·K at 25°C, exhibited a low modulus of elasticity at 200°C. The insulating layer of Test No. 20 had a high conductor temperature when current was applied and a low modulus of elasticity at 200°C. The insulating layer of Test No. 21, in which the mass ratio of magnesium hydroxide or aluminum hydroxide to acid-modified polyethylene was less than 2.0 and the thermal conductivity at 25°C was less than 0.5 W / m K, had a high conductor temperature when current was applied. The insulating layer of Test No. 22, in which the mass ratio of acid-modified polyethylene to polypropylene was less than 0.05, had low values ​​for tensile elongation after the oil resistance test and modulus of elasticity at 200°C. A volume resistivity of 1×10１３ The insulating layer of Test No. 23, which had a resistance of less than Ω·cm, experienced dielectric breakdown in the withstand voltage test.

[0083] The above results demonstrate that the electric wire has excellent heat dissipation properties, as well as deformation resistance at high temperatures, high insulation properties, good mechanical strength, and high oil resistance.

[0084] REFERENCE SIGNS LIST 1 Electric wire 2 Conductor 3 Insulating layer 4, 10 Outer covering layer 5, 20 Cable 7 Inner covering layer 8 Tape member

Claims

1. A conductor comprising a single wire or a conductor twisted together with a plurality of wires, and an insulating layer covering the outer circumference of the conductor, wherein the insulating layer contains a resin component and magnesium hydroxide or aluminum hydroxide, the resin component contains acid-modified polyethylene and polypropylene as a main component, the mass ratio of the acid-modified polyethylene to the polypropylene is 0.05 or more and 0.82 or less, the mass ratio of the magnesium hydroxide or aluminum hydroxide to the acid-modified polyethylene is 2.0 or more and 20.0 or less, the thermal conductivity of the insulating layer at 25°C is 0.5 W / m K or more, and the volume resistivity is 1 x 10 １３ An electric wire with a resistance of Ω·cm or more.

2. The electric wire according to claim 1, wherein said acid-modified polyethylene is an acid-modified very low density polyethylene.

3. The electric wire according to claim 1 or 2, wherein said magnesium hydroxide and said aluminum hydroxide are surface-treated with a vinyl silane coupling agent.

4. The electric wire according to any one of claims 1 to 3, wherein the insulating layer further contains a black pigment.

5. A cable comprising one or more electric wires according to any one of claims 1 to 4, and an outer jacket layer arranged around said one or more electric wires.

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