Electric wire

Abstract

The present invention provides an electric wire which comprises a conductor and a cover layer that covers the outer surface of the conductor, wherein: the cover layer contains a polyolefin resin and a biomass material; and the content ratio of the biomass material among the polyolefin resin and the biomass material is 45% by mass or less.

Description

electric wire

[0001] The present disclosure relates to electrical wires.

[0002] This application claims priority based on Japanese Application No. 2021-122964, filed on July 28, 2021, and incorporates by reference all of the contents of the aforementioned Japanese application.

[0003] Patent Document 1 discloses an insert for electric wires and cables, which includes a core wire made of paper and having a circular cross section, and a bioplastic layer covering the entire periphery of the core wire.

[0004] JP 2010-027387 A

[0005] The electric wire of the present disclosure has a conductor and a coating layer covering an outer surface of the conductor, the coating layer containing a polyolefin resin and a biomass raw material, and a content of the biomass raw material in the polyolefin resin and the biomass raw material is 45 mass% or less.

[0006] FIG. 1 is a cross-sectional view of an electric wire according to one embodiment of the present disclosure taken along a plane perpendicular to the longitudinal direction thereof.

[0007] [Problem to be solved by the present disclosure]

[0008] In recent years, environmental issues have become a major concern, and as a result, electronic components using bioplastics and the like have been investigated to reduce the environmental impact, such as the electronic cable interposer disclosed in Patent Document 1.

[0009] However, there have been no reports on electric wires using biomass materials for the coating layer or the like.

[0010] Therefore, an object of the present disclosure is to provide an electric wire made from biomass raw materials.

[0011] According to the present disclosure, an electric wire using biomass raw materials can be provided.

[0012] [Description of the embodiments of the present disclosure] First, the embodiments of the present disclosure will be listed and described. In the following description, the same or corresponding elements will be denoted by the same reference numerals, and the same description will not be repeated.

[0013] (1) An electric wire according to one aspect of the present disclosure includes a conductor and a coating layer covering an outer surface of the conductor, the coating layer containing a polyolefin resin and a biomass raw material, and a content of the biomass raw material in the polyolefin resin and the biomass raw material is 45 mass% or less.

[0014] Biomass raw materials are organic resources derived from plants and animals, and do not include petroleum-derived materials. Biomass raw materials are sometimes simply called biomass.

[0015] Biomass raw materials are not exhaustible resources, and therefore, by including biomass raw materials in the coating layer of the electric wire according to one embodiment of the present disclosure and reducing the content of petroleum-derived resin components, the environmental load can be reduced.

[0016] Furthermore, the carbon dioxide generated by incinerating biomass raw materials is carbon dioxide that has been absorbed and fixed during the growth process of the biomass raw materials, and therefore does not increase the amount of carbon dioxide in the atmosphere.

[0017] Therefore, by providing a coating layer containing a biomass raw material and using a reduced amount of resin component, it is possible to suppress an increase in the amount of carbon dioxide in the atmosphere even when the coating layer portion is incinerated when the electric wire including the coating layer is disposed of, etc. Therefore, from this viewpoint as well, the electric wire according to one embodiment of the present disclosure can suppress the environmental load.

[0018] However, when biomass raw materials are added to the coating layer, the coating layer may not have sufficient elongation properties, which may result in damage to the coating layer when the electric wire having the coating layer containing biomass raw materials is bent or otherwise attached to various devices.

[0019] However, by setting the content of the biomass raw material in the polyolefin resin and the biomass raw material to 45% by mass or less, the elongation characteristics of the coating layer can be sufficiently improved, and even when the electric wire is bent, etc., to attach it to various devices, the coating layer can be prevented from being damaged, etc. Therefore, by setting the content of the biomass raw material in the polyolefin resin and the biomass raw material in the coating layer to 45% by mass or less, it is possible to obtain an electric wire that has sufficient performance while suppressing the environmental load.

[0020] (2) The polyolefin resin may not be crosslinked.

[0021] When the polyolefin resin is not crosslinked, the elongation properties of the coating layer can be particularly improved, which allows the content of biomass raw materials in the coating layer to be increased, thereby particularly reducing the environmental impact.

[0022] (3) The polyolefin-based resin may be crosslinked, and a content of the biomass raw material in the polyolefin-based resin and the biomass raw material may be 38 mass % or less.

[0023] Crosslinking the polyolefin resin can improve the heat resistance of the electric wire. However, when the polyolefin resin is crosslinked, the elongation properties of the coating layer tend to decrease, so it is preferable to reduce the content of the biomass raw material. Furthermore, by setting the content of the biomass raw material between the polyolefin resin and the biomass raw material to 38% by mass or less, the elongation properties of the coating layer can be particularly improved, and damage to the coating layer can be prevented even when the electric wire is bent, for example, to attach to various devices. Therefore, when the polyolefin resin is crosslinked, setting the content of the biomass raw material between the polyolefin resin and the biomass raw material between the polyolefin resin and the biomass raw material for the coating layer to 38% by mass or less can reduce the environmental impact while providing an electric wire with excellent heat resistance and sufficient performance.

[0024] (4) The coating layer may further contain a flame retardant, and the content of the biomass raw material among the polyolefin resin, the biomass raw material, and the flame retardant may be 15 mass % or less.

[0025] The inclusion of a flame retardant in the coating layer can improve the flame retardancy of the electric wire. However, when the coating layer contains a flame retardant, the elongation characteristics of the coating layer are likely to decrease, so it is preferable to reduce the content of the biomass raw material. Furthermore, by setting the content of the biomass raw material among the polyolefin resin, biomass raw material, and flame retardant to 15% by mass or less, the elongation characteristics of the coating layer can be particularly improved. Therefore, even when the electric wire is bent, for example, to attach it to various devices, damage to the coating can be prevented. Therefore, when the coating layer contains a flame retardant, by setting the content of the biomass raw material among the polyolefin resin, biomass raw material, and flame retardant in the coating layer to 15% by mass or less, an electric wire can be obtained that has excellent flame retardancy and sufficient performance while reducing the environmental impact.

[0026] (5) The biomass raw material may be rice.

[0027] Rice is easier to obtain and handle than other biomass materials, so using rice as a biomass material can increase productivity and reduce production costs.

[0028] (6) The particle diameter of the biomass raw material may be 500 μm or less.

[0029] By setting the particle size of the biomass raw material to 500 μm or less, it is possible to improve the mechanical strength and electrical properties of the electric wire containing the biomass raw material in the coating layer, and in particular to improve the elongation properties of the coating layer.

[0030] [Details of the embodiment of the present disclosure] Specific examples of an electric wire according to one embodiment of the present disclosure (hereinafter referred to as "the present embodiment") will be described below with reference to the drawings. Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. [Electric wire] Fig. 1 shows an example of the cross-sectional configuration of an electric wire according to this embodiment, taken perpendicular to the longitudinal direction. The direction perpendicular to the paper surface in Fig. 1 is the longitudinal direction of the electric wire.

[0031] As shown in Fig. 1, the electric wire 10 of this embodiment can have a conductor 11 and a coating layer 12 that coats the outer surface of the conductor 11. (1) Components Contained in the Electric Wire The components contained in the electric wire of this embodiment will be described. (1-1) Conductor The conductor 11 can be composed of a single metal wire or multiple metal wires. When the conductor 11 has multiple metal wires, the multiple metal wires can be twisted together. That is, when the conductor 11 has multiple metal wires, the conductor 11 can also be a twisted wire of multiple metal wires.

[0032] The material of the conductor 11 is not particularly limited, but may be one or more conductive materials selected from the group consisting of copper, annealed copper, silver-plated annealed copper, nickel-plated annealed copper, and tin-plated annealed copper.

[0033] The outer diameter D11 of the conductor 11 is not particularly limited, but is preferably, for example, 0.12 mm or more and 5.20 mm or less. (1-2) Coating Layer The coating layer 12 can coat the outer surface of the conductor 11, specifically the outer surface along the longitudinal direction of the electric wire 10, as shown in Fig. 1. The coating layer 12 can contain a polyolefin resin, which is a resin component described below, and a biomass raw material.

[0034] The outer diameter D12 of the coating layer 12 is not particularly limited, but can be, for example, 0.2 mm or more and 8 mm or less. (1-2-1) Resin Component The coating layer 12 can contain a resin component. From the perspective of suppressing the generation of dioxins and other emissions during incineration and thereby particularly reducing the environmental impact, the coating layer 12 preferably contains a reduced amount of halogen components, and more preferably does not contain any halogen components, i.e., is halogen-free. Note that "free of halogen components" means that halogen-containing components are not intentionally added, but does not exclude their inclusion as unavoidable components. For this reason, the resin component also preferably contains a reduced amount of halogen components, and more preferably does not contain any halogen components. Therefore, the coating layer 12 preferably contains a polyolefin-based resin as a resin component. Note that the coating layer 12 can also contain only polyolefin-based resin as a resin component.

[0035] The polyolefin resin is not particularly limited, but examples of the polyolefin resin include polyethylene (PE), ethylene acrylate ester copolymers such as ethylene-vinyl acetate copolymer (EVA) and ethylene-ethyl acrylate copolymer (EEA), ethylene-α-olefin copolymer, ethylene methyl acrylate copolymer, ethylene butyl acrylate copolymer, ethylene methyl methacrylate copolymer, ethylene acrylic acid copolymer, partially saponified EVA, maleic anhydride-modified polyolefin, ethylene acrylic ester maleic anhydride copolymer, etc. One selected from these resins may be used alone, or two or more may be used in combination.

[0036] The polyolefin resin that is the resin component may be crosslinked or may not be crosslinked.

[0037] However, when the polyolefin resin is not crosslinked, i.e., when it is non-crosslinked, the elongation property of the coating layer can be particularly improved, which allows the content of the biomass raw material described below in the coating layer to be increased, thereby particularly reducing the environmental load.

[0038] Furthermore, when the polyolefin resin is crosslinked, the heat resistance of the electric wire 10 can be improved. Therefore, when the electric wire 10 is used in an application requiring heat resistance, it is preferable that the polyolefin resin is crosslinked. (1-2-2) Biomass Raw Materials The coating layer 12 can contain biomass raw materials. Biomass raw materials are organic resources derived from plants and animals and do not include petroleum-derived materials. Biomass raw materials are sometimes simply called biomass.

[0039] Biomass raw materials are not exhaustible resources, so by including biomass raw materials in the coating layer 12 and reducing the content of petroleum-derived resin components, the environmental load can be reduced.

[0040] Furthermore, the carbon dioxide generated by incinerating biomass raw materials is carbon dioxide that has been absorbed and fixed during the growth process of the biomass raw materials, and therefore does not increase the amount of carbon dioxide in the atmosphere.

[0041] Therefore, by including the coating layer 12 in a biomass raw material and reducing the amount of resin component used, it is possible to reduce an increase in the amount of carbon dioxide in the atmosphere even when the coating layer 12 is incinerated when the electric wire 10 including the coating layer 12 is disposed of, etc. Therefore, from this viewpoint as well, the electric wire 10 of the present embodiment can reduce the environmental load.

[0042] The biomass raw material is not particularly limited, and may be one or more selected from the group consisting of rice, rice husks, rice straw, wheat straw, coffee beans, wood, buckwheat husks, bamboo, etc. In particular, rice is preferably used as the biomass raw material. Rice is easier to obtain and easier to handle than other biomass raw materials. Therefore, using rice as the biomass raw material can increase the productivity of electric wires and reduce production costs.

[0043] In the electric wire 10 of this embodiment, the biomass material can be used in its original form without being converted into other compounds. That is, instead of using bioplastics or other plastics produced from biomass materials, for example, if the biomass material is rice, the rice can be used in its original form. Therefore, the electric wire of this embodiment can eliminate the energy required to convert the biomass material into bioplastics or other materials, thereby reducing the environmental impact. The size of the biomass material may be adjusted or selected by pulverizing or sieving, as needed. The particle size of the biomass material is not particularly limited, but is preferably below a certain value. Specifically, for example, the particle size of the biomass material is preferably 500 μm or less. By using a biomass material with a particle size of 500 μm or less, the mechanical strength and electrical properties of an electric wire containing a biomass material in a coating layer can be particularly improved, and the elongation characteristics of the coating layer can be particularly improved. However, if a biomass material with an excessively small particle size is sought, larger particle sizes will have to be removed, resulting in a decrease in the amount of usable biomass material. From this point of view, it is preferable that the particle diameter of the biomass raw material is 1 μm or more.

[0044] In this specification, the particle size refers to a particle size measured by a laser diffraction / scattering method.

[0045] However, when biomass raw materials are added to the coating layer, the coating layer may not have sufficient elongation properties, which may result in damage to the coating layer when the electric wire having the coating layer containing biomass raw materials is bent or otherwise attached to various devices.

[0046] Therefore, the inventors of the present invention conducted research and found that the elongation characteristics of the coating layer can be sufficiently improved by setting the content ratio of biomass raw material within a certain range, and thus completed the present invention.

[0047] In the coating layer 12 of the electric wire 10 of this embodiment, the content of the biomass raw material in the polyolefin resin and the biomass raw material is preferably 45% by mass or less, and more preferably 40% by mass or less. By setting the content of the biomass raw material in the polyolefin resin and the biomass raw material to 45% by mass or less, the elongation characteristics of the coating layer are sufficiently improved, and even when the electric wire is bent, for example, to attach to various devices, the coating layer 12 can be prevented from being damaged. Therefore, by setting the content of the biomass raw material in the polyolefin resin and the biomass raw material in the coating layer 12 to 45% by mass or less, the electric wire 10 can be provided with sufficient performance while reducing the environmental impact.

[0048] Of the polyolefin resin and the biomass raw material, the content of the biomass raw material being 45% by mass or less means that the content of the biomass raw material is 45% by mass or less when the total content of the polyolefin resin and the biomass raw material is 100% by mass.

[0049] When the polyolefin resin contained in the coating layer 12 is not cross-linked and does not contain a flame retardant, and the content of the biomass raw material is within the above range, the coating layer 12 exhibits sufficient elongation characteristics. Therefore, when the electric wire 10 is bent, for example, to attach it to various devices, the coating layer 12 can be reliably prevented from being damaged. However, when the polyolefin resin is cross-linked or when the coating layer 12 contains a flame retardant, the elongation characteristics of the coating layer 12 may be reduced.

[0050] As described above, the polyolefin resin, which is a resin component, may be crosslinked. When the polyolefin resin is crosslinked, the content of the biomass raw material in the polyolefin resin and the biomass raw material is preferably 38% by mass or less, more preferably 35% by mass or less. Crosslinking the polyolefin resin can improve the heat resistance of the electric wire 10. However, when the polyolefin resin is crosslinked, the elongation characteristics of the coating layer 12 tend to decrease, so the content of the biomass raw material is preferably reduced. Furthermore, by setting the content of the biomass raw material in the polyolefin resin and the biomass raw material to 38% by mass or less, the elongation characteristics of the coating layer 12 can be particularly improved, and even when the electric wire 10 is bent to attach it to various devices, the coating layer 12 can be prevented from being damaged. Therefore, when the polyolefin resin is crosslinked, setting the content of the biomass raw material in the coating layer 12 to 38% by mass or less can reduce the environmental impact while providing an electric wire with excellent heat resistance and sufficient performance.

[0051] As described below, the coating layer 12 may also contain a flame retardant. That is, the coating layer 12 may also contain a polyolefin resin, a biomass raw material, and a flame retardant. When the coating layer 12 contains a flame retardant, the content of the biomass raw material among the polyolefin resin, the biomass raw material, and the flame retardant is preferably 15% by mass or less, and more preferably 10% by mass or less. The inclusion of a flame retardant in the coating layer 12 can enhance the flame retardancy of the electric wire. However, when the coating layer 12 contains a flame retardant, the elongation characteristics of the coating layer 12 are likely to decrease, so the content of the biomass raw material is preferably suppressed. Furthermore, by setting the content of the biomass raw material among the polyolefin resin, the biomass raw material, and the flame retardant to 15% by mass or less, the elongation characteristics of the coating layer 12 can be particularly improved. Therefore, even when the electric wire 10 is bent, for example, to be attached to various devices, the coating layer 12 can be prevented from being damaged. Therefore, when the coating layer 12 contains a flame retardant, by setting the content of biomass raw materials in the coating layer among the polyolefin resin, biomass raw materials, and flame retardant to 15 mass% or less, it is possible to obtain an electric wire that has excellent flame retardancy and sufficient performance while reducing the environmental load.

[0052] When the coating layer 12 contains a flame retardant, the coating layer 12, specifically the polyolefin resin that is the resin component, may or may not be crosslinked.

[0053] Of the polyolefin resin, biomass raw material, and flame retardant, the content of biomass raw material being 15% by mass or less means that the content of biomass raw material is 15% by mass or less when the total content of the polyolefin resin, biomass raw material, and flame retardant is 100% by mass.

[0054] There is no particular lower limit for the content of biomass raw material in the coating layer 12, and it is sufficient that the content of biomass raw material in the polyolefin resin and biomass raw material is greater than 0% by mass. However, from the perspective of reducing environmental impact in particular, the content of biomass raw material in the polyolefin resin and biomass raw material is preferably 5% by mass or more, and more preferably 10% by mass or more.

[0055] Even when the coating layer 12 contains a flame retardant, the lower limit of the biomass raw material content is not particularly limited. The biomass raw material content of the polyolefin resin, biomass raw material, and flame retardant may be greater than 0% by mass, preferably 5% by mass or greater, and more preferably 10% by mass or greater. (1-2-3) Additives In addition to the resin components and biomass raw material, the coating layer 12 may also contain various additives. The coating layer 12 may contain additives such as a flame retardant. (Flame Retardant) The flame retardant is not particularly limited. However, as mentioned above, it is preferable that the halogen content of the coating layer 12 be reduced, and more preferably that the coating layer 12 does not contain any halogen components. For this reason, it is preferable to use a non-halogen flame retardant rather than a halogen-based flame retardant.

[0056] For this reason, the coating layer 12 may contain, for example, one or more flame retardants selected from phosphorus-based flame retardants, nitrogen-based flame retardants, and metal hydroxides or metal oxides such as magnesium hydroxide, aluminum hydroxide, and antimony trioxide. (Other Additives) The coating layer 12 may be composed only of the polyolefin resin and biomass raw material described above, or only of the polyolefin resin, biomass raw material, and flame retardant. However, the coating layer 12 may also contain further additives, such as antioxidants, anti-degradants, colorants, crosslinking aids, tackifiers, lubricants, softeners, fillers, processing aids, and coupling agents that are commonly incorporated into coating layers.

[0057] Examples of antioxidants include phenol-based antioxidants, amine-based antioxidants, sulfur-based antioxidants, and phosphite-based antioxidants.

[0058] Examples of the deterioration inhibitor include HALS (hindered amine light stabilizers), ultraviolet absorbers, metal deactivators, and hydrolysis inhibitors.

[0059] Examples of colorants include carbon black, titanium white, other organic pigments, inorganic pigments, etc. These can be added for identification or for absorbing ultraviolet light.

[0060] When crosslinking the resin component of the coating layer 12, i.e., the polyolefin resin, in order to increase crosslinking efficiency, a crosslinking aid can be added in a proportion of 1 part by mass to 10 parts by mass per 100 parts by mass of the resin component contained in the coating layer 12. Examples of crosslinking aids include triallyl isocyanurate, triallyl cyanurate, trimethylolpropane trimethacrylate, N,N'-metaphenylene bismaleimide, ethylene glycol dimethacrylate, zinc acrylate, and zinc methacrylate.

[0061] Examples of tackifiers include coumarone-indene resin, polyterpene resin, xylene formaldehyde resin, and hydrogenated rosin. Examples of lubricants include fatty acids, unsaturated fatty acids, their metal salts, fatty acid amides, and fatty acid esters. Examples of softeners include mineral oil, vegetable oil, and plasticizers. Examples of fillers include calcium carbonate, talc, clay, silica, zinc oxide, and molybdenum oxide. Examples of coupling agents include silane coupling agents and titanate-based coupling agents such as isopropyl triisostearoyl titanate and isopropyl tri(N-aminoethyl-aminoethyl) titanate, and the like, can also be added as needed.

[0062] Specific examples will be described below, but the present invention is not limited to these examples. (Evaluation Method) First, the evaluation method for the electric wires produced in the following experimental examples will be described. (1) Outer Diameter of Conductor and Outer Diameter of Coating Layer The outer diameter D11 of the conductor 11 and the outer diameter D12 of the coating layer 12 were measured using a micrometer.

[0063] Specifically, in the case of the outer diameter D11 of the conductor 11, the outer diameter of the conductor 11 was measured with a micrometer along two orthogonal diameters of the electric wire 10 in any one cross section perpendicular to the longitudinal direction of the electric wire 10. The average value of the measured values ​​was then taken as the outer diameter D11 of the conductor 11 of the electric wire 10. The outer diameter D12 of the coating layer 12 was also measured and calculated in the same manner.

[0064] The thickness of the coating layer 12 was determined by subtracting the outer diameter D11 of the conductor 11 from the outer diameter D12 of the coating layer 12 and dividing the result by 2. (2) Elongation The conductor was removed from the produced electric wire, and a tensile test of the coating layer was performed based on 4.16 (tensile strength of insulator and sheath) of JIS C 3005 (2014), and the elongation was calculated.

[0065] The test conditions were a tensile speed of 500 mm / min, a gauge length of 25 mm, and a temperature of 23°C. The elongation was measured for 10 samples prepared under the same conditions in each experimental example, and the average of the measured values ​​for the 10 samples was taken as the elongation of the coating layer in that experimental example.

[0066] The higher the elongation value, the better the elongation characteristics. A coating layer with an elongation of 95% or higher is considered to have suitable elongation characteristics for use in electric wires, and a coating layer with an elongation of 100% or higher is considered to have sufficient elongation characteristics. (3) Flame Retardancy Test: The VW-1 vertical flame test specified in UL Standard 2556 was conducted on five samples prepared under the same conditions for each electric wire in each experimental example. Each sample was ignited for 15 seconds five times. A sample was considered to have passed if it extinguished within 60 seconds, if the absorbent cotton placed underneath was not ignited by falling flames, and if the kraft paper attached to the top of the sample was not burned or scorched. Five samples were evaluated, and if all five passed, they were rated A. If any one failed, they were rated B. In the following experimental examples, if a rating of B was given, all five failed. The evaluation results are shown in the "Flame Retardancy" column of Tables 1 to 3. (4) Heat Resistance Test Evaluation was performed by a test conforming to the 90°C condition of UL Standard 758. Specifically, a sample (length: approximately 100 mm) consisting of only the coating layer of the electric wire produced in each experimental example was heat-treated in a gear oven under the 90°C condition of the UL Standard. Then, the tensile strength retention rate (%) and elongation retention rate (%) were calculated from the initial tensile strength and elongation of the sample that had not been heat-treated and the tensile strength and elongation after the heat treatment using the following formulas (1) and (2).

[0067] Electric wires with a calculated tensile strength retention of 70% or more and an elongation retention of 70% or more were evaluated as A. Electric wires with either or both of a tensile strength retention and an elongation retention of 70% or more were evaluated as B.

[0068] Tensile strength retention (%) = 100 × (tensile strength after heat treatment) / (initial tensile strength) (1) Elongation retention (%) = 100 × (elongation after heat treatment) / (initial elongation) (2) A rating of A indicates excellent heat resistance, while a rating of B indicates poor heat resistance. The evaluation results are shown in the "Heat Resistance" column of Tables 1 to 3. (5) Electrical Properties (5-1) Insulation Resistance Insulation resistance was measured at a temperature of 40°C and an electric field strength of 60 kV / mm according to a method in accordance with JIS C 3005 (2014) 4.7 (insulation resistance). (5-2) Underwater Pressure Resistance Testing was performed under conditions of 3 kVAC for 1 minute according to a method in accordance with JIS C 3005 (2014) 4.6 (voltage resistance). Three samples were evaluated, and the number of samples that passed was counted. The evaluation results for the samples evaluated are shown in the "Voltage resistance" column of Table 4.

[0069] The breakdown voltage was measured by increasing the voltage. The evaluation results for the samples are shown in the "Breakdown Voltage" column of Table 4.

[0070] The electric wires used in each experimental example will be described below.

[0071] (Experimental Example 1) Electric wires of Experimental Examples 1-1 to 1-9 were fabricated and evaluated as described above. Experimental Examples 1-1 to 1-3, 1-5, 1-7, and 1-9 are examples, while Experimental Examples 1-4, 1-6, and 1-8 are comparative examples. [Experimental Example 1-1] In Experimental Example 1-1, an insulated electric wire was fabricated that included a conductor 11 and a coating layer 12 covering the outer surface of the conductor 11, as shown in FIG. 1 in a cross section perpendicular to the longitudinal direction. (Conductor) The conductor 11 was a stranded wire formed by twisting together seven tin-plated annealed copper wires with a wire diameter of 0.254 mm. The outer diameter D11 of the conductor 11 was 0.76 mm. Note that conductors of the same configuration and size were used in the other experimental examples described below. (Coating Layer) The coating layer 12 was formed by feeding LDPE (low-density polyethylene), a resin component, and rice, a biomass material, into an extruder, kneading the mixture, and molding it to cover the outer surface of the conductor 11. The rice used was previously crushed to a particle diameter of 500 μm or less. The resin components used are listed in the mixed resin column in Table 1. The outer diameter D12 of the coating layer 12 was 1.3 mm, and the thickness of the coating layer 12 was 0.270 mm. The outer diameter D12 and thickness of the coating layer 12 of the electric wires 10 fabricated in the following other Experimental Examples 1-2 to 1-9, Experimental Example 2, and Experimental Example 3 were also the same.

[0072] The resin component and the biomass raw material were fed to an extruder and kneaded so that the content of the biomass raw material was 40% by mass. The content of the biomass raw material among the resin component and the biomass raw material is shown in the "Biomass Raw Material Ratio" column in Table 1.

[0073] As can be seen from the "No" column for crosslinking and the "No" column for flame retardant in Table 1, crosslinking of the resin component was not performed and no flame retardant was added to the coating layer 12.

[0074] The obtained electric wires were subjected to elongation, flame retardancy, and heat resistance tests. The evaluation results are shown in Table 1. [Experimental Examples 1-2 to 1-4] Electric wires were produced and evaluated in the same manner as in Experimental Example 1-1, except that the content ratio of the biomass raw material among the resin component and biomass raw material supplied to the extrusion molding machine was changed to the value shown in Table 1. The evaluation results are shown in Table 1.

[0075] For Experimental Example 1-3, electrical properties were also evaluated. The evaluation results are shown in Table 4. [Experimental Examples 1-5 and 1-6] Electric wires were produced and evaluated in the same manner as in Experimental Example 1-1, except that ethylene-vinyl acetate copolymer (EVA) was used as the resin component, and the resin component and biomass raw material were supplied to the extruder and kneaded so that the content ratio of the biomass raw material was the ratio shown in Table 1. The evaluation results are shown in Table 1. [Experimental Examples 1-7 and 1-8] Ethylene-ethyl acrylate copolymer (EEA) was used as the resin component, and the resin component and biomass raw material were supplied to the extruder and kneaded so that the content ratio of the biomass raw material was the ratio shown in Table 1. Except for the above, electric wires were produced and evaluated in the same manner as in Experimental Example 1-1. The evaluation results are shown in Table 1. [Experimental Example 1-9] Electric wires were produced and evaluated under the same conditions as in Experimental Example 1-1, except that the particle diameter of the biomass raw material was set to 600 μm or less. The evaluation results are shown in Table 1.

[0076] According to Table 1, when a polyolefin resin is used as the resin component, regardless of the type of resin, the coating layer exhibits sufficient elongation of 95% or more by setting the biomass raw material content to 45% by mass or less. Furthermore, by setting the particle diameter of the biomass raw material to 500 μm or less, the elongation characteristics of the coating layer can be improved, and the coating layer exhibits sufficient elongation of 100% or more. Therefore, it was confirmed that such electric wires can prevent damage to the coating layer even when bent when attached to various devices, and also reduce environmental impact. (Experimental Example 2) Electric wires of Experimental Examples 2-1 to 2-6 were fabricated and evaluated as described above. Experimental Examples 2-1 to 2-6 are examples, and Experimental Example 2-5 is a comparative example. [Experimental Examples 2-1 to 2-5] The content ratio of biomass raw material among the resin component and biomass raw material supplied to the extruder was changed to the value shown in Table 2. In addition, a coating layer was formed using an extrusion molding machine to cover the outer surface of the conductor 11, and then the resin component was crosslinked by irradiating it with an electron beam. Except for the above points, an electric wire was produced in the same manner as in Experimental Example 1-1 and evaluated. The evaluation results are shown in Table 2.

[0077] For Experimental Example 2-3, the electrical properties were also evaluated. The evaluation results are shown in Table 4. [Experimental Example 2-6] An electric wire was produced and evaluated in the same manner as in Experimental Example 2-1, except that ethylene-vinyl acetate copolymer (EVA) was used as the resin component, and the resin component and biomass raw material were fed to the extruder and kneaded so that the content of the biomass raw material was 35 mass%. The evaluation results are shown in Table 2.

[0078] According to Table 2, when a polyolefin resin is used as the resin component and crosslinking treatment is performed, it was confirmed that the coating layer exhibits sufficient elongation of 100% or more by setting the content of biomass raw materials to 38% by mass or less, regardless of the type of resin. Therefore, it was confirmed that such an electric wire can prevent damage to the coating layer even when it is bent when attached to various devices, and also that the environmental load can be reduced.

[0079] Furthermore, by performing a crosslinking treatment, the heat resistance rating was rated A, confirming that the electric wire had excellent heat resistance. (Experimental Example 3) Electric wires of Experimental Examples 3-1 to 3-3 were fabricated and evaluated as described above. Experimental Examples 3-1 and 3-2 are examples, and Experimental Example 3-3 is a comparative example. [Experimental Examples 3-1 to 3-3] Ethylene-vinyl acetate copolymer (EVA) was used as the resin component, and a flame retardant was further added in addition to the resin component and biomass raw material. A metal hydroxide was used as the flame retardant, and it was added at a ratio of 200 parts by mass per 100 parts by mass of the resin component. The resin component, biomass raw material, and flame retardant were supplied to the extrusion molding machine, and the content ratio of the biomass raw material was adjusted to the value shown in Table 3. In addition, a coating layer was formed using the extrusion molding machine to cover the outer surface of the conductor 11, and then the resin component was crosslinked by irradiating it with an electron beam. Except for the above points, electric wires were fabricated and evaluated in the same manner as in Experimental Example 1-1. The evaluation results are shown in Table 3.

[0080] The electrical characteristics of Experimental Example 3-1 were also evaluated. The evaluation results are shown in Table 4.

[0081] According to Table 3, when the coating layer contains a resin component, a biomass raw material, and a flame retardant and is subjected to a crosslinking treatment, it was confirmed that the coating layer exhibits sufficient elongation of 100% or more by setting the content of the biomass raw material among the resin component, the biomass raw material, and the flame retardant to 15% by mass or less. Therefore, it was confirmed that the coating layer of such an electric wire can be prevented from being damaged even when it is bent when attached to various devices, and that the environmental load can be reduced.

[0082] In addition, when the coating layer contains a flame retardant in addition to the resin component and the biomass raw material and is not crosslinked, the coating layer has better elongation properties than the above experimental example. Therefore, when the content of the biomass raw material among the resin component, the biomass raw material, and the flame retardant is 15 mass% or less, it can be said that the coating layer exhibits sufficient elongation of 100% or more.

[0083] Furthermore, it was confirmed that the heat resistance was evaluated as A by performing the crosslinking treatment, and the flame retardancy was evaluated as A by adding the flame retardant. In other words, it was confirmed that the electric wires of Experimental Examples 3-1 and 3-2 were excellent in heat resistance and flame retardancy.

[0084] According to the results shown in Table 4 for Experimental Examples 1-3, 2-3, and 3-1, the insulation resistance was sufficiently high, and all three samples used for evaluation passed the underwater pressure resistance test, confirming that the coating layer had sufficient insulating properties. Similarly, it was confirmed that the coating layer of the other experimental examples also had sufficient insulating properties.

[0085] 10 Electric wire 11 Conductor 12 Coating layer D11 Outer diameter of conductor D12 Outer diameter of coating layer

Claims

1. A conductor; a coating layer covering an outer surface of the conductor; The coating layer contains a polyolefin resin and a biomass raw material, The electric wire comprises the polyolefin resin and the biomass raw material, and the content of the biomass raw material is 45 mass% or less.

2. The polyolefin resin is not crosslinked, The electric wire according to claim 1 , wherein a content ratio of the biomass raw material in the polyolefin resin and the biomass raw material is 5 mass % or more.

3. The polyolefin resin is crosslinked, The polyolefin resin is made of either low-density polyethylene or ethylene-vinyl acetate copolymer, The electric wire according to claim 1 , wherein a content ratio of the biomass raw material in the polyolefin resin and the biomass raw material is 38 mass % or less.

4. The polyolefin resin is crosslinked, The coating layer further contains a flame retardant, The polyolefin resin is made of an ethylene-vinyl acetate copolymer, The electric wire according to claim 1 , wherein a content ratio of the biomass raw material among the polyolefin resin, the biomass raw material, and the flame retardant is 15 mass % or less.

5. The electric wire according to any one of claims 1 to 4, wherein the biomass raw material is rice.

6. The electric wire according to any one of claims 1 to 4, wherein the particle diameter of the biomass raw material is 500 µm or less.