Wires and Cables

Abstract

The electric wire according to the present disclosure comprises a conductor formed from a single wire or a conductor formed from multiple intertwined strands and an insulating layer covering the outer periphery of the conductor, wherein: the insulating layer contains a resin component, a first filler, and a second filler; the resin component contains an olefinic resin and a resin incompatible with the olefinic resin; the olefinic resin and the resin incompatible with the olefinic resin form a sea-island structure; the first filler is formed from graphite; the second filler is formed from a metal oxide, a metal hydroxide, or a combination of these ingredients; the first filler has a mass ratio of 10 / 100 to 80 / 100 with respect to the resin component; and the insulating layer has a thermal conductivity of 0.5 W / m·K or greater at 25˚C and a volume resistivity of 1 x 1013 Ω·cm or greater.

Description

[Technical field]

[0001] The present disclosure relates to electrical wires and cables.

[0002] In recent years, there has been a demand for ever-increasing capacity and speed in information transmission for information wires and cables. Conventional cables generally have a core material (core wire) made of multiple twisted insulated wires (core wires) and an outer sheath layer that covers the core material (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-139177 A Summary of the Invention

[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, the insulating layer containing a resin component, a first filler, and a second filler, the resin component containing an olefin-based resin and a resin incompatible with the olefin-based resin, the olefin-based resin and the resin incompatible with the olefin-based resin forming a sea-island structure, the first filler is made of graphite, and the second filler is made of a metal oxide, a metal hydroxide, or a combination thereof, a mass ratio of the first filler to the resin component is 10 / 100 or more and 80 / 100 or less, and the insulating layer has a thermal conductivity at 25°C of 0.5 W / m K or more and a volume resistivity of 1×10 13 Ω·cm or more. [Brief description of the drawings]

[0005] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an electric wire according to one embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing a cable according to one embodiment. [Diagram 3]FIG. 3 is a schematic cross-sectional view showing a cable according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] [Problem that this disclosure aims to solve] In recent years, the amount of power consumption has increased along with the increase in the amount of information. Therefore, when a current flows through an electric wire or cable that supplies electric power, the temperature of the conductor rises, the conduction resistance increases, and power loss is likely to occur.

[0007] The present disclosure has been made in light of the above circumstances, and has an object to provide an electric wire including an insulating layer that has excellent heat dissipation properties, as well as high insulation properties, mechanical strength, and high oil resistance.

[0008] [Effects of this 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 high insulation properties, mechanical strength, and high oil resistance.

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

[0010] An electric wire according to one embodiment of the present disclosure includes a conductor formed of a single wire or a conductor formed by twisting a plurality of elemental wires together, and an insulating layer covering an outer periphery of the conductor, the insulating layer containing a resin component, a first filler, and a second filler, the resin component containing an olefin-based resin and a resin incompatible with the olefin-based resin, the olefin-based resin and the resin incompatible with the olefin-based resin forming a sea-island structure, the first filler being made of graphite, the second filler being made of a metal oxide, a metal hydroxide, or a combination thereof, a mass ratio of the first filler to the resin component being 10 / 100 or more and 80 / 100 or less, the insulating layer having a thermal conductivity of 0.5 W / m K or more at 25° C. and a volume resistivity of 1×10 13 Ω·cm or more.

[0011] The present inventors have focused on the fact that the heat dissipation of the covering material used in conventional electric wires is low, and therefore the heat of the conductor cannot be released when the temperature rises. Therefore, they have intensively studied ways to improve the thermal conductivity of the covering material and suppress the temperature rise of the conductor, and have completed the present invention. The insulating layer of the electric wire is excellent in tensile strength and oil resistance because it contains an olefin-based resin with a large amount of crystalline components as the resin component. In addition, the insulating layer contains the first filler made of graphite and the second filler made of a metal oxide, a metal hydroxide, or a combination thereof, and the mass ratio of the first filler to the resin component is 10 / 100 or more and 80 / 100 or less. The thermal conductivity of the insulating layer at 25°C is 0.5 W / m·K or more, and the insulating layer has high thermal conductivity, so that the heat of the conductor is released to the outside, and the effect of suppressing the temperature rise of the conductor is high. In addition, the volume resistivity is 1×10 13 By having a resistivity of Ω·cm or more, the insulating properties of the insulating layer can be improved. Furthermore, by the resin component containing an olefin resin and a resin incompatible with the olefin resin forming a sea-island structure, the first filler, which is difficult to disperse in the olefin resin, can be unevenly distributed on the incompatible resin side, thereby further improving the heat dissipation properties of the insulating layer. Therefore, in the electric wire, the insulating layer has excellent heat dissipation properties, which can suppress the temperature rise of the conductor and reduce power loss, and also has high insulation properties, mechanical strength, and high oil resistance.

[0012] The above-mentioned "volume resistivity" means an electrical resistance value measured by a double ring electrode method based on JIS-K6271:2008. The above-mentioned "resin incompatible with olefin resin" means a resin incompatible with olefin resin, and can be confirmed, for example, by observing a cross section of the insulating layer perpendicular to the longitudinal direction of the electric wire using a transmission electron microscope (TEM). A sea-island structure is observed when a cross section of a resin incompatible with olefin resin is observed using an electron microscope. By adopting such a dispersed state of the sea-island structure, the physical property behaviors originating from both the olefin resin and the resin incompatible with this olefin resin appear independently, and the mutual incompatibility allows the properties of both resins to be fully exhibited.

[0013] It is preferable that the mass ratio of the second filler to the resin component is 30 / 100 or more and 200 / 100 or less. In the electric wire, by having the mass ratio of the second filler to the resin component be 30 / 100 or more and 200 / 100 or less, both insulation properties and tensile elongation can be well achieved.

[0014] The average particle size ratio of the first filler to the second filler is preferably 1.1 or more. By having the average particle size ratio of the first filler to the second filler be 1.1 or more, the heat dissipation property of the insulating layer of the electric wire can be further improved.

[0015] The above-mentioned "average particle size" refers to the median size (D50) which is the value at which the volume-based cumulative distribution calculated in accordance with JIS-Z-8819-2:2001 is 50%. Specifically, the median size (D50) can be measured by the following method. Measurement is performed using a laser diffraction particle size distribution measuring device as the measuring device. A scattering measurement mode is adopted, and a laser beam is irradiated onto a wet cell in which a dispersion liquid in which particles of the measurement sample are dispersed in a dispersion solvent is circulated, and a scattered light distribution is obtained from the measurement sample. The scattered light distribution is then approximated by a log-normal distribution, and the particle size at which the cumulative degree is 50% (D50) is taken as the median size.

[0016] It is preferable that the incompatible resin is a styrene copolymer, the olefin resin is polypropylene, and the mass ratio of the styrene copolymer to the polypropylene is 20 / 80 or more and 80 / 20 or less. When the olefin resin is polypropylene, the tensile strength and oil resistance of the insulation layer of the electric wire can be further improved. When the incompatible resin is a styrene copolymer, the tensile elongation of the insulation layer of the electric wire can be improved, and the dispersibility of the first filler is increased, thereby improving the heat dissipation. When the mass ratio of the styrene copolymer to the polypropylene is 20 / 80 or more and 80 / 20 or less, the tensile properties, heat dissipation, and oil resistance of the insulation layer of the electric wire can be further improved.

[0017] The polypropylene is preferably a random polypropylene or a block polypropylene. When the polypropylene is a random polypropylene or a block polypropylene, the tensile strength and oil resistance of the insulating layer can be further improved.

[0018] The content of structural units derived from styrene in the styrene-based copolymer is preferably 5% by mass or more and 40% by mass or less. On the other hand, when the content of structural units derived from styrene in the styrene-based copolymer is 5% by mass or more and 40% by mass or less, the tensile elongation and oil resistance of the insulating layer can be further improved.

[0019] A cable according to another embodiment of the present disclosure includes the one or more electric wires and an outer sheath layer disposed around the one or more electric wires. The cable includes the above-mentioned electric wire as a core electric wire constituting a core wire, and therefore has excellent heat dissipation properties, high insulation properties, mechanical strength, and high oil resistance.

[0020] [Details of the embodiment of the present disclosure] Hereinafter, an electric wire according to an embodiment of the present disclosure will be described in detail with reference to the drawings as appropriate.

[0021] <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 an embodiment of the present disclosure. The electric wire 1 in Fig. 1 includes a conductor 2 made of a single wire or a conductor line 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.

[0022] [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-sectional shape, a rectangular wire having a rounded square cross-sectional shape, and a rectangular wire having a rounded rectangular cross-sectional shape. The conductor 2 may be a single linear body as shown in Figs. 1 and 2, or a twisted wire body in which multiple thin wires are twisted together.

[0023] The material for the conductor 2 may be, for example, a metal such as copper, aluminum, nickel, silver, or iron, or an alloy thereof, and from the viewpoints of electrical conductivity and workability, it is preferable to use copper or aluminum. The conductor 2 may also have a multi-layer structure in which a coating made of another metal is laminated on the outer circumferential surface of a metal linear body.

[0024] The lower limit of the average cross-sectional area (including the gaps between the wires) of the conductor 2 is 2 mm 2 is preferred, 8 mm 2 is more preferable, and 14 mm 2 On the other hand, the upper limit of the average cross-sectional area of ​​the conductor 2 is 600 mm 2 is preferable, and 500 mm 2 is more preferable, and 400 mm 2 is more preferable. If the average cross-sectional area of ​​the conductor 2 is less than the above lower limit, there is a risk that the current cannot be sufficiently passed. If the average cross-sectional area of ​​the conductor 2 exceeds the above upper limit, there is a risk that sufficient bending resistance cannot be obtained. Here, the "average cross-sectional area" refers to the average value of values ​​measured at any 10 points on the cross section.

[0025] [Insulation layer] The insulating layer 3 contains a resin component, a first filler, and a second filler.

[0026] The average thickness of the insulating layer 3 is not particularly limited, but the lower limit of the average thickness is, for example, preferably 0.8 mm, more preferably 1.0 mm. On the other hand, the upper limit of the average thickness of the insulating layer 3 is preferably 10 mm, more preferably 7 mm. If the average thickness of the insulating layer 3 is less than the above lower limit, the insulating properties of the insulating layer 3 may be insufficient. If the average thickness of the insulating layer 3 exceeds the above upper limit, flexibility may be impaired. Here, the "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.

[0027] (Resin component) The resin component contains an olefin resin and a resin incompatible with the olefin resin. The olefin resin and the resin incompatible with the olefin resin form a sea-island structure. The resin component contains an olefin resin and a resin incompatible with the olefin resin, and these form a sea-island structure, so that the first filler, which is difficult to disperse in the olefin resin, can be unevenly distributed toward the incompatible resin, thereby further improving the heat dissipation property of the insulating layer 3.

[0028] <Olefin Resin> The insulating layer 3 contains an olefin-based resin as a resin component, and thus has excellent tensile strength and oil resistance. Examples of the olefin-based resin include polyethylene (PE) and polypropylene (PP).

[0029] Examples of polyethylene include high density polyethylene (PE), very low density polyethylene (VLDPE), low density polyethylene, linear low density polyethylene (LLDPE), ethylene-α-olefin copolymer, acid-modified polyethylene modified with unsaturated carboxylic acid or a derivative thereof, etc. Examples of 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.

[0030] Examples of polypropylene include homopolypropylene, random polypropylene, block polypropylene, and acid-modified polypropylene modified with unsaturated carboxylic acid or a derivative thereof. Examples of random polypropylene include propylene-α-olefin copolymers, which are copolymers of propylene and ethylene or α-olefins having 4 to 20 carbon atoms. Block polypropylene is a resin composed of homopolypropylene as a main component, random copolymer elastomer as a copolymer component, and an ethylene polymer as an optional component.

[0031] Examples of the unsaturated carboxylic acid in the acid used for the acid modification include acrylic acid, methacrylic acid, maleic acid, itaconic acid, fumaric acid, etc. Examples of the derivatives of unsaturated carboxylic acids include maleic acid monoesters, maleic anhydride, itaconic acid monoesters, itaconic anhydride, fumaric acid monoesters, fumaric anhydride, etc. Among these, derivatives of unsaturated carboxylic acids are preferred, and maleic anhydride is more preferred.

[0032] Examples of the propylene-α-olefin copolymer include an ethylene-propylene copolymer, a propylene-acrylic acid copolymer, a propylene-methacrylic acid copolymer, a propylene-acrylate ester copolymer, and a propylene-methacrylate ester copolymer.

[0033] The olefin resin is preferably polypropylene, more preferably random polypropylene or block polypropylene. By using the olefin resin as random polypropylene or block polypropylene, it is possible to improve the tensile strength and oil resistance while suppressing a significant decrease in tensile elongation.

[0034] <Resins incompatible with olefin-based resins> By including a resin incompatible with the olefin resin in the resin component, the first filler, which is difficult to disperse in the olefin resin, can be unevenly distributed toward the resin incompatible with the olefin resin, thereby further improving the heat dissipation of the insulating layer. Examples of resins incompatible with the olefin resin include styrene copolymers, polyvinyl chloride resins, polyurethanes, fluororesins, fluororubbers, and silicones. Among these, styrene copolymers, which have good dispersibility of the first filler and can improve the tensile elongation of the insulating layer, are more preferable. The incompatible resin may include one or more types.

[0035] Examples of styrene-based copolymers include styrene-ethylene block copolymer (SE), styrene / ethylene-butylene / ethylene block copolymer (SEBE) or its hydrogenated products, styrene / ethylene-butylene / styrene block copolymer (SEBS) or its hydrogenated products, styrene / ethylene-propylene / styrene block copolymer (SEPS), styrene / ethylene-ethylene-propylene-styrene block copolymer (SEEPS), hydrogenated styrene butadiene rubber (HSBR), etc.

[0036] The lower limit of the content of the structural unit derived from styrene in the styrene-based copolymer is preferably 5% by mass, more preferably 8% by mass. The upper limit of the content of the structural unit derived from styrene is preferably 40% by mass, more preferably 38% by mass. By setting the content of the structural unit derived from styrene in the above range, the tensile elongation and oil resistance of the insulating layer can be further improved.

[0037] When the incompatible resin is a styrene copolymer and the olefin resin is a polypropylene, the lower limit of the mass ratio of the styrene copolymer to the polypropylene is preferably 20 / 80, more preferably 30 / 70. The upper limit of the mass ratio of the styrene copolymer to the polypropylene is preferably 80 / 20 or less, more preferably 70 / 30. When the mass ratio of the styrene copolymer to the polypropylene is within the above range, the tensile properties, heat dissipation properties, and oil resistance of the insulating layer of the electric wire can be further improved.

[0038] The insulating layer 3 may contain a resin other than the olefin resin and the resin incompatible with the olefin resin, such as polyvinyl chloride resin, polyurethane, fluororesin, fluororubber, silicone, and polyester resin.

[0039] (First filler) The first filler is made of graphite. When the insulating layer contains the first filler made of graphite, the electrical conductivity of the insulating layer can be increased, and the heat dissipation properties can be improved.

[0040] The lower limit of the mass ratio of the first filler to the resin component is 10 / 100, preferably 20 / 100, and more preferably 25 / 100. The upper limit of the mass ratio of the first filler to the resin component is 80 / 100, preferably 75 / 100, and more preferably 70 / 100. By setting the mass ratio of the first filler to the resin component within the above range, it is possible to achieve both heat dissipation and insulation properties in the insulating layer.

[0041] The lower limit of the average particle size of the graphite is preferably 0.5 μm, more preferably 1 μm, and more preferably 5 μm. On the other hand, the upper limit of the average particle size is preferably 100 μm, more preferably 50 μm, and more preferably 30 μm. If the average particle size of the graphite is less than 0.5 μm, the thermal conductivity at 25° C. may decrease. On the other hand, if the average particle size of the graphite is more than 100 μm, the tensile elongation may decrease. By having the average particle size of the graphite in the above range, the heat dissipation property can be further improved.

[0042] (Second filler) The insulating layer 3 contains a second filler made of a metal oxide, a metal hydroxide, or a combination thereof. When the insulating layer 3 contains a second filler made of a metal oxide, a metal hydroxide, or a combination thereof, the heat dissipation property and insulating property of the insulating layer can be improved.

[0043] Examples of the metal oxide include magnesium oxide, zinc oxide, aluminum oxide, titanium oxide, and calcium oxide.

[0044] Examples of the metal hydroxide include magnesium hydroxide, aluminum hydroxide, and calcium hydroxide.

[0045] The lower limit of the mass ratio of the second filler to the resin component is preferably 30 / 100, more preferably 50 / 100. The upper limit of the mass ratio of the second filler to the resin component is preferably 200 / 100, more preferably 180 / 100. In the electric wire, by having the mass ratio of the second filler to the resin component in the above range, both insulation properties and tensile elongation can be achieved well.

[0046] The lower limit of the average particle size ratio of the first filler to the second filler is preferably 1.1 times, and more preferably 5 times. When the average particle size ratio of the first filler to the second filler is 1.1 times or more, the heat dissipation property of the insulation layer of the electric wire can be further improved. The upper limit of the average particle size ratio of the first filler to the second filler is not particularly limited, but may be, for example, 100 times or less, from the viewpoint that the tensile elongation decreases when the particle size of graphite is too large.

[0047] The insulating layer 3 may contain other additives as necessary. Examples of such additives include flame retardants, flame retardant assistants, antioxidants, lubricants, colorants, reflectivity imparting agents, opacifying agents, processing stabilizers, and plasticizers.

[0048] The lower limit of the thermal conductivity of the insulating layer 3 at 25° C. is 0.5 W / m·K, preferably 0.6 W / m·K, and more preferably 0.7 W / m·K. By setting the lower limit of the insulating layer 3 to 0.5 W / m·K, the heat dissipation property of the insulating layer 3 can be improved.

[0049] The lower limit of the volume resistivity of the insulating layer 3 is 1×10 13 Ω cm, 1×10 14 Ω cm is preferred, 1×10 15 It is more preferable that the volume resistivity of the insulating layer 3 is 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.

[0050] [Wire manufacturing method] The method for producing the electric wire is not particularly limited, but may include, for example, the following steps. (1) A step of preparing a resin composition for forming an insulating layer (hereinafter also referred to as a resin composition) for forming an insulating layer (a resin composition preparation step) (2) A step of coating a conductor with a resin composition for forming an insulating layer (resin composition coating step)

[0051] (1) Resin composition preparation process In the resin composition preparation step, the resin composition for forming an insulating layer is prepared by mixing the resin components of the resin composition for forming an insulating layer, the first filler, the second filler, and other additives as necessary, using a melt mixer, etc. As the melt mixer, a known one, for example, an open roll, a Banbury mixer, a pressure kneader, a single-shaft mixer, a multi-shaft mixer, etc. can be used. The resin composition of the present disclosure may be subjected to a crosslinking treatment by any of chemical crosslinking, silane crosslinking, and radiation crosslinking.

[0052] (2) Resin composition coating process In the resin composition coating process, for example, the resin composition for forming an insulating layer can be extruded onto the 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 according to the application.

[0053] <Cable> A cable according to another embodiment 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.

[0054] The outer diameter of the cable is appropriately designed depending on the application, but the lower limit of the outer diameter is preferably 10 mm, more preferably 15 mm, while the upper limit of the outer diameter of the cable is preferably 80 mm, more preferably 60 mm, and even more preferably 50 mm.

[0055] [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 having a conductor 2 and an insulating layer 3 covering the outer periphery of the conductor 2, and an outer jacket layer 4 arranged 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 stacked concentrically. The cable being a coaxial cable 5 allows for a reduction in diameter. The electric wire 1, the conductor 2, and the insulating layer 3 are the same as those of the electric wire 1 in Fig. 1, and therefore the same reference numerals are used and description thereof will be omitted.

[0056] The main component of the outer layer 4 is not particularly limited as long as it is a synthetic resin having excellent abrasion resistance, and examples thereof include polyvinyl chloride, polyethylene, cross-linked polyethylene, chloroprene, etc. Furthermore, the outer layer 4 may be cross-linked.

[0057] The outer covering layer 4 may contain the additives exemplified for the insulating layer 3 .

[0058] The average thickness of the outer covering layer 4 is preferably 0.5 mm or more and 3.0 mm or less.

[0059] [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 (interposed) arranged around the core wire, and an outer coating layer 10 arranged 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.

[0060] The main component of the inner coating layer 7 is, for example, PP yarn, paper, jute, or the like.

[0061] The lower limit of the outer diameter of the inner coating layer 7 is preferably 9.0 mm, and more preferably 10 mm. On the other hand, the upper limit of the outer diameter of the inner coating layer 7 is preferably 75 mm, and more preferably 60 mm.

[0062] The outer layer 10 has a similar configuration to the outer layer 4 in FIG. 2, and therefore a description thereof will be omitted.

[0063] <Cable manufacturing method> The cable can be obtained by a manufacturing method including a step of coating one or more electric wires with an outer coating layer (outer coating layer coating step). When the cable includes multiple electric wires, the manufacturing method may include a step of twisting the multiple electric wires together. When the cable includes an inner coating layer or a tape member around one or more electric wires, the manufacturing method may include a step of forming an inner coating layer or a step of winding a tape member.

[0064] (Outer layer coating process) In the outer jacket layer covering step, for example, a melt extruder is used to extrude a resin composition for forming an outer jacket layer onto the outside of one or more electric wires, thereby covering the outside of one or more electric wires with an outer jacket layer.

[0065] After coating with the jacket layer, the wire or wires are cooled to harden the jacket layer and obtain the cable, which is then wound and collected.

[0066] 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 composition forming the jacket layer on the outside of one or more electric wires (after the jacket layer is formed).

[0067] The cable includes the above-mentioned electric wire as a core electric wire constituting a core wire, and therefore has excellent heat dissipation properties, high insulation properties, mechanical strength, and high oil resistance.

[0068] [Other embodiments] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is not limited to the configurations of the above-described embodiments, but is indicated by the claims, and is intended to include all modifications within the meaning and scope of the claims. EXAMPLES

[0069] 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.

[0070] <Insulating layers No. 1 to No. 31> The insulating layers No. 1 to No. 31, each consisting of a single layer, were formed by the following procedure.

[0071] [Resin component] 1. Olefin resin As the olefin resin in the resin component, the following polypropylene was used. (1) Random polypropylene (random PP) MFR 1.3 (g / 10 min), flexural modulus 950MPa (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. Styrene copolymer The following styrene-based copolymer was used as a resin incompatible with the olefin-based resin in the resin component. (1) Styrene / ethylene-butylene / styrene block copolymer (SEBS) (styrene structural unit content: 12% by mass) Shore A hardness 42 (2) SEBS (styrene structural unit content: 18% by mass) Shore A hardness 67 (3) SEBS (styrene structural unit content: 35% by mass) Shore A hardness 49 (4) SEBS (styrene structural unit content: 43% by mass) Shore A hardness 96 (5) Hydrogenated styrene butadiene rubber (HSBR) (styrene structural unit content: 10% by mass) Shore A hardness 42 The term "Shore A hardness" refers to the hardness measured by a type A durometer based on JIS-K6253: 2012. The term "content of styrene structural units" refers to the content of structural units derived from styrene in the styrene-based copolymer.

[0072] [First filler] As the first filler, the following three types of graphite were used. (1) Thin graphite (average particle size 22 μm) (2) Spherical graphite (average particle size 20 μm) (3) Thin graphite (average particle size 5 μm)

[0073] [Second filler] As the second filler, the following five types of filler were used. (1) Magnesium hydroxide (average particle size 0.8 μm) (2) Aluminum hydroxide (average particle size 1.5 μm) (3) Aluminum hydroxide (average particle size 10.0 μm) (4) Zinc oxide type 1 (average particle size 0.75 μm) (5) Magnesium oxide (average particle size 4.5 μm)

[0074] A resin composition for forming an insulating layer was prepared using the above resin component, the first filler, and the second filler. The composition and content of the insulating layer are shown in Tables 1 to 3. "-" indicates that the corresponding component was not used.

[0075] [Insulating layer manufacturing] The insulating layer was produced by extrusion molding using the resin composition for forming the insulating layer. An extrusion die was used for the extrusion molding. The extrusion molding was performed at a die temperature of 180° C. and a linear speed of 5 m / min to obtain insulating layers No. 1 to No. 31 with an average thickness of 2.5 mm. The insulating layers were used to produce a cross-sectional area of ​​14 mm 2 The wire was made by coating the outer circumference of a (14SQ) conductor.

[0076] [evaluation] Insulation layers No. 1 to No. 31 were evaluated for thermal conductivity, volume resistivity, tensile strength, tensile elongation, tensile strength and tensile elongation after oil resistance test, conductor temperature when current is applied, withstand voltage, and the presence or absence of a sea-island structure in the cross section of the insulation layer.

[0077] (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 the 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). The higher the thermal conductivity [W / (m K)], the higher the heat dissipation 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.

[0078] (Volume resistivity (insulation)) A press sheet measuring φ150 mm and thickness 1 mm was prepared as a test sample from the resin composition for forming the insulating layer using a heat press machine, and electrical resistance was measured using the double ring electrode method defined in JIS-K6271:2008. The volume resistivity was calculated from the measured value. A higher volume resistivity [Ω·cm] value indicates higher insulating properties of the insulating layer. The volume resistivity is calculated based on a value of 1×10 13 In the above cases, it can be said that the insulating layer has excellent insulating properties.

[0079] (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 200% or more, it can be said that the mechanical strength of the insulating layer is excellent.

[0080] (Tensile strength and tensile elongation after oil resistance test) Based on JIS-C3005:2014, the tensile strength [MPa] and tensile elongation [%] were measured after immersion at 70°C for 4 hours using JIS No. 2 test oil, and the oil resistance was evaluated. 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 higher the oil resistance. If the tensile strength retention is 80% or more and the elongation retention is 60% or more, the oil resistance of the insulating layer can be said to be excellent.

[0081] (Conductor temperature when current is applied) The conductor temperature during current flow was measured by passing a current of 140A through each of the electric wires, each having an outer diameter of 9.4 mm and a length of 3 m, and consisting of a 14SQ conductor with a conductor diameter of 4.4 mm and an insulating layer of No. 1 to No. 31 with an average thickness of 2.5 mm coated on the outer circumference, and the temperature of the conductor surface at the center of the electric wire was measured.

[0082] (Voltage resistance) In accordance with JIS-C3605:2002, 2000V was applied to each of the wires covered with the insulating layer No.1 to No.31, and the presence or absence of dielectric breakdown was evaluated. The evaluation was made according to the following two stages. When the evaluation was A, the effect was good. A: No insulation breakdown has occurred. B: Dielectric breakdown occurred.

[0083] (Whether or not the insulating layer has an island structure) The presence or absence of a sea-island structure in the cross-section of the insulation layer was determined by preparing thin-film sections from the insulation layer taken from each electric wire using a freezing microtome method, staining the samples with ruthenium tetroxide, osmium tetroxide, tungsten phosphate, etc., and observing them under a transmission electron microscope and visually judging.

[0084] The evaluation results of each of the insulating layers are shown in Tables 1 to 3.

[0085] [Table 1]

[0086] [Table 2]

[0087] [Table 3]

[0088] From the results in Tables 1 to 3, it can be seen that the insulating layer contains an olefin resin and a resin incompatible with the olefin resin as resin components, the olefin resin and the incompatible resin form a sea-island structure, the insulating layer contains a first filler of graphite and a second filler of a metal oxide or metal hydroxide, the mass ratio of the first filler to the resin components is 10 / 100 or more and 80 / 100 or less, 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 The insulating layers of Test Nos. 1 to 22, which had a resistance of Ω·cm or more, showed good results in terms of heat dissipation, insulation, mechanical strength, and oil resistance.

[0089] On the other hand, the insulating layer of No. 23, which did not contain a resin incompatible with the olefin-based resin, exhibited a decreased tensile elongation. The insulating layer of No. 24, which did not contain an olefin-based resin, showed decreased tensile strength and tensile strength retention rate after the oil resistance test. The mass ratio of the first filler to the resin component is more than 80 / 100, and the volume resistivity is 1×10 13 The insulation layer of No. 25, which had a resistance of less than Ω·cm, experienced dielectric breakdown during the voltage withstand test. Volume resistivity is 1×10 13 The insulation layer of No. 26, which had a resistance of less than Ω·cm, experienced dielectric breakdown during the voltage withstand test. In the insulating layers of Nos. 27, 30, and 31, which had a mass ratio of the first filler to the resin component of less than 10 / 100 and a thermal conductivity of less than 0.5 W / m·K at 25°C, the conductor temperature was high when electricity was passed through them. The insulation layer of No. 28, which has a thermal conductivity of less than 0.5 W / m·K at 25°C, had a high conductor temperature when current was applied. The insulating layer of No. 29, which did not contain the second filler, experienced dielectric breakdown in the voltage resistance test.

[0090] The above results demonstrate that the electric wire has excellent heat dissipation properties, as well as high insulation properties, mechanical strength, and high oil resistance. [Explanation of symbols]

[0091] 1 electric wire 2 Conductors 3. Insulation layer 4, 10 Outer layer 5, 20 Cable 7 Inner coating layer 8 Tape material

Claims

1. A conductor made of a single wire or a conductor made of a plurality of stranded wires; an insulating layer covering the outer periphery of the conductor; It is equipped with the insulating layer contains a resin component, a first filler and a second filler, the resin component includes an olefin-based resin and a resin incompatible with the olefin-based resin, the olefin-based resin and a resin incompatible with the olefin-based resin form a sea-island structure, The first filler is made of graphite, The second filler is made of a metal oxide, a metal hydroxide, or a combination thereof; a mass ratio of the first filler to the resin component is 10 / 100 or more and 80 / 100 or less; 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 Ω cm or more, The mass ratio of the second filler to the resin component is 30 / 100 or more and 200 / 100 or less.

2. 2. The electric wire according to claim 1, wherein an average particle size ratio of the first filler to the second filler is 1.1 or more.

3. the incompatible resin is a styrene-based copolymer, The olefin resin is polypropylene, 2. The electric wire according to claim 1, wherein a mass ratio of the styrene-based copolymer to the polypropylene is 20 / 80 or more and 80 / 20 or less.

4. 4. The electric wire according to claim 3, wherein the polypropylene is a random polypropylene or a block polypropylene.

5. The electric wire according to claim 3, wherein the content of the structural units derived from styrene in the styrene-based copolymer is 5% by mass or more and 40% by mass or less.

6. One or more electric wires according to any one of claims 1 to 5; a jacket layer disposed around the one or more electric wires; A cable that is provided with:

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