Electric wire

Abstract

This electric wire comprises a conductor and a coating that covers the conductor, wherein: the coating includes a first layer; the first layer contains as a main component a crosslinked resin body of which the resin component is two or more polymers selected from the group consisting of ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, and tetrafluoroethylene-propylene copolymer; and the silica particle content in the first layer is between 2% and 40% inclusive by volume.

Description

electric wire

[0001] The present disclosure relates to electrical wires.

[0002] BACKGROUND ART Conventionally, "electric wires having a conductor and a coating that covers the conductor" have been used for various device applications (Patent Document 1).

[0003] JP 2013-168313 A

[0004] The electric wire of the present disclosure is an electric wire including a conductor and a coating covering the conductor, wherein the coating includes a first layer, and the first layer contains, as a main component, a crosslinked resin body having two or more polymers selected from the group consisting of ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, and tetrafluoroethylene-propylene copolymer as resin components, and the content of silica particles in the first layer is 2% by volume or more and 40% by volume or less.

[0005] Fig. 1 is a schematic perspective view of an electric wire according to an embodiment of the present disclosure. Fig. 2 is a schematic cross-sectional view taken along II-II in Fig. 1. Fig. 3 is a schematic view illustrating a part of an evaluation method for a heat resistance evaluation test. Fig. 4 is a schematic view illustrating a part of an evaluation method for a tensile test.

[0006] [Problem to be Solved by the Present Disclosure] Conventionally, when electric wires are used for various purposes such as automobiles, electronic / electrical devices, spacecraft, etc., the conditions under which the electric wires are used have been severe in some cases. In particular, when electric wires are used in spacecraft (in other words, when used in space), the conditions under which the electric wires are used tend to be severer than when the electric wires are used in automobiles, electronic / electrical devices, etc. (in other words, when used on the ground). When electric wires are used in space, it is particularly required to improve the heat resistance, radiation resistance, atomic oxygen resistance, and elongation of the coating of the electric wire.

[0007] Fluorine resins are sometimes used as raw materials for the coating of electric wires because of their excellent heat resistance. For example, perfluoropolymers such as polytetrafluoroethylene (PTFE) resin, fluorinated ethylene propylene (FEP) resin, and perfluoroalkoxyalkane (PFA) resin have been used as fluororesins. However, because these fluororesins have low radiation resistance, when electric wires using these fluororesins as raw materials for the coating are used in space, the radiation resistance of the electric wires may be insufficient. In electric wires using these fluororesins as raw materials for the coating, the elongation of the coating may be insufficient.

[0008] Alternatively, polymers such as ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, or tetrafluoroethylene-propylene copolymer have sometimes been used as raw materials for the coating of electric wires in order to provide radiation resistance. However, while these polymers have high radiation resistance, they have low atomic oxygen resistance, and therefore electric wires using such polymers as coating materials sometimes have insufficient atomic oxygen resistance.

[0009] For these reasons, in an "electric wire including a conductor and a coating covering the conductor," it has sometimes been difficult to achieve excellent heat resistance, excellent radiation resistance, excellent atomic oxygen resistance, and excellent elongation of the coating.

[0010] Effect of the Present Disclosure According to the present disclosure, it is possible to provide an electric wire that has excellent heat resistance, excellent radiation resistance, excellent atomic oxygen resistance, and excellent coating elongation.

[0011] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described. (1) An electric wire according to the present disclosure is an electric wire including a conductor and a coating covering the conductor, wherein the coating includes a first layer, and the first layer contains, as a main component, a crosslinked resin body having two or more polymers selected from the group consisting of ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, and tetrafluoroethylene-propylene copolymer as resin components, and the content of silica particles in the first layer is 2% by volume or more and 40% by volume or less.

[0012] According to the present disclosure, it is possible to provide an electric wire that has excellent heat resistance, excellent radiation resistance, excellent atomic oxygen resistance, and excellent coating elongation.

[0013] (2) In the above (1), the silica particles may have an average particle size of 0.1 μm or more and 40 μm or less, thereby providing an electric wire having better heat resistance, better radiation resistance, better atomic oxygen resistance, and better elongation of the coating.

[0014] (3) In the above (1) or (2), the crosslinked resin may contain two resin components, an ethylene-tetrafluoroethylene copolymer and a tetrafluoroethylene-propylene copolymer, and the parts by mass of the ethylene-tetrafluoroethylene copolymer may be 50 parts by mass or more and 90 parts by mass or less, relative to 100 parts by mass of the total of the parts by mass of the ethylene-tetrafluoroethylene copolymer and the parts by mass of the tetrafluoroethylene-propylene copolymer. This makes it possible to provide an electric wire that has better heat resistance, better radiation resistance, better atomic oxygen resistance, and better elongation of the coating.

[0015] (4) In any one of the above (1) to (3), the first layer may have a thickness of 0.05 mm or more and 3 mm or less, thereby providing an electric wire having better heat resistance, better radiation resistance, better atomic oxygen resistance, and better elongation of the coating.

[0016] [Details of the embodiment of the present disclosure] A specific example of an electric wire according to one embodiment of the present disclosure (hereinafter also referred to as "the present embodiment") will be described below with reference to the drawings. In the drawings of the present disclosure, the same reference symbols represent the same or corresponding parts. Furthermore, dimensional relationships such as length, width, thickness, and depth have been changed as appropriate for clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

[0017] In the present disclosure, the expression "A to B" means the upper and lower limits of a range (i.e., A or more and B or less), and when no unit is specified for A and a unit is specified only for B, the units of A and B are the same.

[0018] In the present disclosure, when a compound or the like is represented by a chemical formula, unless the atomic ratio is particularly limited, it is intended to include any conventionally known atomic ratio, and should not necessarily be limited to only those within the stoichiometric range.

[0019] [Embodiment 1: Electric Wire] An electric wire according to an embodiment of the present disclosure will be described with reference to Figures 1 and 2. Figure 1 is a schematic perspective view of an electric wire according to an embodiment of the present disclosure. Figure 2 is a schematic cross-sectional view taken along II-II in Figure 1. One embodiment of the present disclosure (hereinafter also referred to as "the present embodiment") is an electric wire 1 including a conductor 2 and a coating 5 that coats the conductor 2, wherein the coating 5 includes a first layer 3, and the first layer 3 contains, as a main component, a crosslinked resin whose resin components are two or more polymers selected from the group consisting of ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, and tetrafluoroethylene-propylene copolymer, and the content of silica particles in the first layer 3 is 2% by volume or more and 40% by volume or less.

[0020] According to the present disclosure, it is possible to provide an electric wire 1 that has excellent heat resistance, excellent radiation resistance, and excellent atomic oxygen resistance. The reason for this is presumed to be as follows.

[0021] (a) In the electric wire 1 of this embodiment, the first layer 3 contains, as a main component, a crosslinked resin body having, as resin components, two or more polymers selected from the group consisting of an ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, and a tetrafluoroethylene-propylene copolymer. This allows the electric wire 1 to have improved heat resistance, radiation resistance, and elongation of the coating, since a combination of multiple types of partially fluorinated resins is used as the resin components.

[0022] (b) Ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, and tetrafluoroethylene-propylene copolymer have low atomic oxygen resistance, so when these components are used, it has sometimes been difficult to impart excellent atomic oxygen resistance to the electric wire.

[0023] In the electric wire 1 of the present embodiment, the content of silica particles in the first layer 3 is 2% by volume or more and 40% by volume or less. This allows the electric wire 1 to have improved atomic oxygen resistance due to the atomic oxygen shielding effect of silica.

[0024] <Electric Wire> The equivalent circle diameter of a cross section perpendicular to the longitudinal direction of the electric wire 1 may be 1 mm or more and 5 mm or less, or 1.5 mm or more and 3 mm or less. Note that the longitudinal direction here can be rephrased as a "first direction" described later.

[0025] The circle-equivalent diameter of the cross section perpendicular to the longitudinal direction of the electric wire 1 can be determined by the following method. First, the average cross-sectional area of ​​the electric wire 1 is determined in the same manner as the average cross-sectional area of ​​the conductor 2, except that the object of measurement is the electric wire 1. Next, the circle-equivalent diameter of the cross section perpendicular to the longitudinal direction of the electric wire 1 can be determined by calculating the square root of "[4 × (average cross-sectional area of ​​the electric wire 1)] / π".

[0026] It has been confirmed that, as long as the same electric wire 1 is measured by the above method, there is no variation in the measurement results even if the measurement location is changed arbitrarily.

[0027] <Conductor> The electric wire 1 includes a conductor 2. The material of the conductor 2 can be a metal material with high electrical conductivity and high mechanical strength. Examples of such metal materials include copper, copper alloys, aluminum, aluminum alloys, nickel, silver, mild steel, steel, and stainless steel. The conductor 2 can be a wire material formed from a single metal material. The conductor 2 can also have a multilayer structure in which the wire material is coated with another metal by a technique such as plating. Examples of the conductor 2 having a multilayer structure include tin-plated copper wire, nickel-plated copper wire, silver-plated copper wire, copper-plated aluminum wire, and copper-plated steel wire.

[0028] The shape of the conductor 2 is not particularly limited, and any conventionally known shape can be used. Examples of the shape of the conductor 2 include a round wire having a circular cross section, a rectangular wire having a square cross section, a rectangular wire having a rectangular cross section, and a twisted wire formed by twisting together a plurality of wires.

[0029] The equivalent circle diameter of a cross section perpendicular to the longitudinal direction of the conductor 2 may be 0.8 mm or more and 4.8 mm or less, or 1.3 mm or more and 2.8 mm or less. Here, the longitudinal direction can be rephrased as the "first direction" described later.

[0030] The equivalent circle diameter of a cross section perpendicular to the longitudinal direction of the conductor 2 can be determined in the same manner as the equivalent circle diameter of a cross section perpendicular to the longitudinal direction of the wire 1, except that the object of measurement is the conductor 2.

[0031] It has been confirmed that, as long as measurements are made on the same conductor 2 using the above method, there is no variation in the measurement results even if the measurement location is changed arbitrarily.

[0032] The average cross-sectional area of ​​the conductor 2 is not particularly limited and can be appropriately selected depending on the application. ２ 5.3mm or more ２ It may be 0.8 mm or less, ２ 3.3mm or more ２In the present disclosure, the average cross-sectional area of ​​the conductor 2 is measured as follows: One conductor 2 is stretched in a straight line, cut along a plane normal to a first direction connecting one end of the conductor 2 to the other, the cross section is exposed, and the cross-sectional area is measured. For one conductor 2, the conductor 2 is cut along a plane normal to the first direction at any five locations, the cross-sectional areas are measured, and an average value is calculated. The average value corresponds to the average cross-sectional area of ​​the conductor 2.

[0033] <Coating> The electric wire 1 includes a coating 5 that coats the conductor 2. The coating 5 includes a first layer 3. The coating 5 may consist of only the first layer 3, or may further include other layers described below in addition to the first layer 3.

[0034] The thickness of the coating 5 may be 0.05 mm or more and 3 mm or less. If the thickness of the coating 5 is less than 0.05 mm, the coating 5 tends to be easily damaged. If the thickness of the coating 5 exceeds 3 mm, the electric wire 1 tends to be hard and difficult to bend, and the cost tends to be high. The thickness of the coating 5 may be 0.07 mm or more and 2 mm or less.

[0035] In the present disclosure, the thickness of the coating 5 can be determined by the following method. The electric wire 1 is stretched in a straight line and cut along a plane normal to a first direction connecting one end of the electric wire 1 to the other end of the electric wire 1, thereby exposing a cross section. The thickness of the coating 5 is measured at three arbitrary locations on the cross section, and the average value is calculated. The electric wire 1 is cut along a plane normal to the first direction at a total of five arbitrary locations to determine the average values, and the thickness of the coating 5 is determined by calculating the average value. Note that it has been confirmed that, as long as the same electric wire 1 is measured by the above method, there is no variation in the measurement results even if the measurement locations are arbitrarily changed.

[0036] <First Layer> <Composition> <Cross-linked Resin> The first layer 3 contains, as a main component, a cross-linked resin whose resin components are two or more polymers selected from the group consisting of ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, and tetrafluoroethylene-propylene copolymer. This can improve the heat resistance, radiation resistance, and elongation of the coating in the electric wire 1. Here, "containing a cross-linked resin as a main component" means that the cross-linked resin accounts for 50% by mass or more.

[0037] In the electric wire 1, the fact that "the first layer 3 contains, as a main component, a crosslinked resin body having, as resin components, two or more polymers selected from the group consisting of an ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, and a tetrafluoroethylene-propylene copolymer" can be identified by combining an analysis of the chemical bonding state based on measurements of the infrared absorption spectrum by nuclear magnetic resonance (NMR) spectrum and Fourier transform infrared spectroscopy (FT-IR) with measurements of the crystalline melting temperature and the heat of crystalline fusion by a differential scanning calorimeter.

[0038] The crosslinked resin product contains two resin components, an ethylene-tetrafluoroethylene copolymer and a tetrafluoroethylene-propylene copolymer, and the parts by mass of the ethylene-tetrafluoroethylene copolymer may be 50 parts by mass or more and 90 parts by mass or less, relative to a total of 100 parts by mass of the parts by mass of the ethylene-tetrafluoroethylene copolymer and the parts by mass of the tetrafluoroethylene-propylene copolymer. This allows the heat resistance, radiation resistance, and elongation of the coating of the electric wire 1 to be further improved. The lower limit of the parts by mass of the ethylene-tetrafluoroethylene copolymer relative to the total of 100 parts by mass may be 50 parts by mass or more, 52 parts by mass or more, or 54 parts by mass or more. The upper limit of the parts by mass of the ethylene-tetrafluoroethylene copolymer relative to the total of 100 parts by mass may be 90 parts by mass or less, 85 parts by mass or less, or 80 parts by mass or less. The parts by mass of the ethylene-tetrafluoroethylene copolymer relative to the total of 100 parts by mass may be 52 parts by mass or more and 85 parts by mass or less, or 54 parts by mass or more and 80 parts by mass or less.

[0039] The crosslinked resin product contains two resin components, an ethylene-tetrafluoroethylene copolymer and polyvinylidene fluoride, and the parts by mass of the ethylene-tetrafluoroethylene copolymer may be 50 parts by mass or more and 90 parts by mass or less, relative to a total of 100 parts by mass of the parts by mass of the ethylene-tetrafluoroethylene copolymer and the parts by mass of the polyvinylidene fluoride. This allows the heat resistance, radiation resistance, and elongation of the coating of the electric wire 1 to be further improved. The lower limit of the parts by mass of the ethylene-tetrafluoroethylene copolymer relative to the total of 100 parts by mass may be 50 parts by mass or more, 52 parts by mass or more, or 54 parts by mass or more. The upper limit of the parts by mass of the ethylene-tetrafluoroethylene copolymer relative to the total of 100 parts by mass may be 90 parts by mass or less, 85 parts by mass or less, or 80 parts by mass or less. The parts by mass of the ethylene-tetrafluoroethylene copolymer relative to the total of 100 parts by mass may be 52 parts by mass or more and 85 parts by mass or less, or 54 parts by mass or more and 80 parts by mass or less.

[0040] The crosslinked resin product contains two resin components, polyvinylidene fluoride and a tetrafluoroethylene-propylene copolymer, and the parts by mass of polyvinylidene fluoride may be 50 parts by mass or more and 90 parts by mass or less, relative to a total of 100 parts by mass of the parts by mass of polyvinylidene fluoride and the parts by mass of the tetrafluoroethylene-propylene copolymer. This allows the heat resistance, radiation resistance, and elongation of the coating of the electric wire 1 to be further improved. The lower limit of the parts by mass of polyvinylidene fluoride relative to the total of 100 parts by mass may be 50 parts by mass or more, 52 parts by mass or more, or 54 parts by mass or more. The upper limit of the parts by mass of polyvinylidene fluoride relative to the total of 100 parts by mass may be 90 parts by mass or less, 85 parts by mass or less, or 80 parts by mass or less. The amount of polyvinylidene fluoride relative to the total of 100 parts by mass may be 52 parts by mass or more and 85 parts by mass or less, or may be 54 parts by mass or more and 80 parts by mass or less.

[0041] The crosslinked resin body contains three resin components: an ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, and a tetrafluoroethylene-propylene copolymer. The parts by mass of the ethylene-tetrafluoroethylene copolymer, the parts by mass of the polyvinylidene fluoride, and the parts by mass of the tetrafluoroethylene-propylene copolymer, relative to a total of 100 parts by mass of the ethylene-tetrafluoroethylene copolymer, the parts by mass of the polyvinylidene fluoride, and the parts by mass of the tetrafluoroethylene-propylene copolymer, may be 50 parts by mass or more and 90 parts by mass or less, and the parts by mass of the polyvinylidene fluoride relative to the total of 100 parts by mass may be 1 part by mass or more and 40 parts by mass or less. This allows the heat resistance, radiation resistance, and elongation of the coating of the electric wire 1 to be further improved. The lower limit of the parts by mass of the ethylene-tetrafluoroethylene copolymer relative to the total of 100 parts by mass may be 50 parts by mass or more, 52 parts by mass or more, or 54 parts by mass or more. The upper limit of the parts by mass of the ethylene-tetrafluoroethylene copolymer per 100 parts by mass of the total may be 90 parts by mass or less, 85 parts by mass or less, or 80 parts by mass or less. The parts by mass of the ethylene-tetrafluoroethylene copolymer per 100 parts by mass of the total may be 52 parts by mass or more and 85 parts by mass or less, or 54 parts by mass or more and 80 parts by mass or less. The lower limit of the parts by mass of polyvinylidene fluoride per 100 parts by mass of the total may be 1 part by mass or more, 3 parts by mass or more, or 5 parts by mass or more. The upper limit of the parts by mass of polyvinylidene fluoride per 100 parts by mass of the total may be 40 parts by mass or less, 35 parts by mass or less, or 30 parts by mass or less. The parts by mass of polyvinylidene fluoride per 100 parts by mass of the total may be 3 parts by mass or more and 35 parts by mass or less, or 5 parts by mass or more and 30 parts by mass or less.

[0042] In the electric wire 1, the composition of the resin component in the crosslinked resin body can be identified by a combination of an analysis of the chemical bonding state based on measurements of the NMR spectrum and the infrared absorption spectrum by FT-IR, and measurements of the crystalline melting temperature and the heat of crystalline fusion by a differential scanning calorimeter.

[0043] <Silica Particles> The content of silica particles in the first layer 3 is 2 vol% or more and 40 vol% or less. This can improve the atomic oxygen resistance of the electric wire 1. The lower limit of the content of silica particles in the first layer 3 may be 3 vol% or more, 4 vol% or more, or 5 vol% or more. The upper limit of the content of silica particles in the first layer 3 may be 35 vol% or less, 30 vol% or less, or 25 vol% or less. The content of silica particles in the first layer 3 may be 3 vol% or more and 35 vol% or less, 4 vol% or more and 30 vol% or less, or 5 vol% or more and 25 vol% or less.

[0044] The content of silica particles in the first layer 3 can be determined by combining an analysis of the chemical bonding state based on infrared absorption spectrum measurement by FT-IR, an analysis of the elements contained in the material, and specific gravity measurement. As long as the same first layer 3 is measured using the above method, it has been confirmed that there is no variation in the measurement results even if the measurement location is changed arbitrarily.

[0045] The average particle size of the silica particles may be 0.1 μm or more and 40 μm or less. This allows the electric wire 1 to have better atomic oxygen resistance. The lower limit of the average particle size of the silica particles may be 0.1 μm or more, 0.2 μm or more, or 0.5 μm or more. The upper limit of the average particle size of the silica particles may be 40 μm or less, 35 μm or less, or 30 μm or less.

[0046] The average particle size of silica particles can be determined by the following method. First, a 20 mm electric wire 1 obtained by cutting the electric wire 1 along a plane perpendicular to the longitudinal direction is embedded in resin. Next, one of the cut surfaces of the resin-embedded electric wire 1 is pre-finished by mechanical polishing, and then a cross-section polisher (CP) is used with an Ar ion beam under the following conditions to obtain a polished cut surface. Next, CP-SEM (Scanning Electron Microscopy) is performed on the polished cut surface using a high-resolution scanning electron microscope "SU8020" manufactured by Hitachi High-Tech Corporation, and a 5000x magnification image is obtained so that the entire polished cut surface is included in one field of view. Next, energy dispersive X-ray spectroscopy (EDX) elemental analysis is performed on the image to identify the silica particles. Next, the particle size of each silica particle is calculated using the following formula (1), and the average (in other words, the arithmetic mean) is taken as the average particle size of the silica particles. (Particle size of silica particle) = {(Width of silica particle) + (Height of silica particle)} / 2 (1) Here, "width of silica particle" means the maximum distance between two points located on the outer edge of the silica particle to be measured, where an imaginary line passing through the two points is perpendicular to the thickness direction of the coating. "Height of silica particle" means the maximum distance between two points located on the outer edge of the silica particle to be measured, where an imaginary line passing through the two points is parallel to the thickness direction of the coating. The number of silica particles to be measured is 10 randomly selected in one field of view of the same first layer, and the number of fields of view is 20. Note that one field of view is a rectangle with a length of 12 μm and a width of 9.6 μm. (CP conditions) Acceleration voltage: 1.0 kV Inclination: 0°

[0047] It has been confirmed that as long as the measurement is performed on the same first layer 3, there is no variation in the measurement results even if the measurement location is arbitrarily selected.

[0048] <Other Components> The first layer 3 may be composed of a crosslinked resin product containing, as resin components, two or more polymers selected from the group consisting of an ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, and a tetrafluoroethylene-propylene copolymer, and silica particles, and may further contain other components in addition to the crosslinked resin product and the silica particles, as long as the effects of the present disclosure are not impaired. Examples of other components include at least one component selected from the group consisting of crosslinking aids (such as triallyl isocyanate (TAIC) and trimethylolpropane trimethacrylate (TMPTMA)), fillers (such as silica, talc, calcium carbonate, clay, and zinc oxide), lubricants (such as oleic acid amide, erucic acid amide, stearic acid, and zinc stearate), coloring pigments (such as inorganic pigments such as titanium oxide, organic pigments, and carbon), flame retardants (such as bromine-based flame retardants, antimony trioxide, melamine cyanurate, magnesium hydroxide, and aluminum hydroxide), antioxidants (such as phenol-based antioxidants, sulfur-based antioxidants, and phosphorus-based antioxidants), and metal deactivators.

[0049] <Thickness> The thickness of the first layer 3 may be 0.05 mm or more and 3 mm or less. This makes it possible to provide an electric wire that has better heat resistance, better radiation resistance, better atomic oxygen resistance, and better elongation of the coating. The lower limit of the thickness of the first layer 3 may be 0.05 mm or more, 0.1 mm or more, or 0.2 mm or more. The upper limit of the thickness of the first layer 3 may be 3 mm or less, 2.5 mm or less, or 2.0 mm or less. The thickness of the first layer 3 may be 0.1 mm or more and 2.5 mm or less, or 0.2 mm or more and 2.0 mm or less.

[0050] The thickness of the first layer 3 can be determined in the same manner as the thickness of the coating 5, except that the measurement target is the first layer 3. It has been confirmed that, as long as the same electric wire 1 is measured by the above-mentioned method, there is no variation in the measurement results even if the measurement location is changed arbitrarily.

[0051] <<Atomic oxygen resistance>> Using an atomic oxygen generator using a laser detonation method, the collision speed of atomic oxygen to one point on the surface of the coating of an electric wire was 7.4 km / s, and the flow rate of atomic oxygen was 5 × 10 ２０ atoms / cm ２ and the irradiation area is 0.78 cm ２ After a test in which atomic oxygen is irradiated under the conditions, the erosion depth of the coating of the electric wire may be 10 μm or less. This allows the electric wire to have better atomic oxygen resistance. The upper limit of the depth may be 9 μm or less, 8 μm or less, or 7 μm or less. The lower limit of the depth is not particularly limited, and may be, for example, 0 μm or more, 1 μm or more, or 2 μm or more. The depth may be 0 μm or more and 10 μm or less, 0 μm or more and 9 μm or less, 0 μm or more and 8 μm or less, or 0 μm or more and 7 μm or less. In the present disclosure, "atomic oxygen resistance" refers to the resistance of the electric wire 1 to deterioration caused by an oxidation reaction by atomic oxygen. The depth can be determined by observing, with an SEM, a cross section obtained by cutting the electric wire along a plane normal to the direction from one end of the electric wire to the other end and passing through the center of gravity at the one location. It has been confirmed that there is no variation in the measurement results even if the above one location is changed arbitrarily.

[0052] <Other Layers> The coating 5 may further include other layers. Examples of such other layers include an underlayer, an intermediate layer, and a surface layer. The underlayer is a layer that contacts the conductor 2. The intermediate layer is a layer (not shown) that is located between the conductor 2 and the first layer 3. The surface layer is a layer that is located on the surface of the coating 5.

[0053] <<Method for Manufacturing Electric Wire>> The method for manufacturing the electric wire 1 of this embodiment includes, for example, a first step of preparing the conductor 2 and a compound for forming the first layer 3, and a second step of forming the coating 5 on the outer peripheral surface of the conductor 2, in this order. The first step includes a 1A step of preparing the conductor 2 and a 1B step of preparing the compound for forming the first layer 3. The second step includes a 2A step of forming the first layer 3 on the outer peripheral surface of the conductor 2. The second step can further include a "step of forming another layer on the outer peripheral surface of the conductor 2." Note that the "step of forming another layer on the outer peripheral surface of the conductor 2" can be performed by a conventionally known method.

[0054] <Step 1> <Step 1A: Step of Preparing a Conductor> In Step 1A, a conductor 2 is prepared. The conductor 2 may be prepared by manufacturing using a conventionally known method, or may be prepared by purchasing a commercially available product.

[0055] <Step 1B: Step of Preparing a Compound for Forming First Layer> In step 1B, a compound for forming the first layer 3 is prepared. For example, the compound for forming the first layer 3 can be prepared by the following method. First, a base resin, a crosslinking aid, and silica particles are prepared as raw materials. Further raw materials, such as a lubricant and a filler, may also be prepared. These raw materials may be prepared by manufacturing using a conventionally known method, or may be purchased as commercially available products. Next, the raw materials are kneaded to prepare the compound for forming the first layer 3.

[0056] The base resin is prepared from two or more polymers selected from the group consisting of ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, and tetrafluoroethylene-propylene copolymer. The mass ratio of the base resin to 100 mass of the compound for forming the first layer 3 is 50 parts by mass or more and 99.5 parts by mass or less. The mass ratio of the base resin to 100 mass of the compound for forming the first layer 3 may be 55 parts by mass or more and 99 parts by mass or less, or may be 60 parts by mass or more and 98.5 parts by mass or less.

[0057] The cross-linking aid may be triallyl isocyanate (TAIC), trimethylolpropane trimethacrylate (TMPTMA), or both. The amount of the cross-linking aid relative to 100 parts by mass of the compound for forming the first layer 3 may be 0.1 parts by mass or more and 5 parts by mass or less, 0.2 parts by mass or more and 4 parts by mass or less, or 0.3 parts by mass or more and 3 parts by mass or less.

[0058] The amount of silica particles per 100 parts by mass of the compound for forming the first layer 3 is 2.5 parts by mass or more and 46 parts by mass or less. The amount of silica particles per 100 parts by mass of the compound for forming the first layer 3 may be 3.7 parts by mass or more and 40 parts by mass or less, or 4.8 parts by mass or more and 35 parts by mass or less. The average particle size of the silica particles as raw materials may be 0.1 μm or more and 40 μm or less. Here, the average particle size of the silica particles as raw materials means the particle size determined as the median diameter of the 50% cumulative value using a laser diffraction particle size distribution analyzer.

[0059] The kneading can be carried out using rolls heated to, for example, 200° C. or more and 280° C. or less. The kneading time can be 5 minutes or more and 30 minutes or less.

[0060] <Step 2> <Step 2A> In Step 2A, the first layer 3 is formed on the outer peripheral surface of the conductor 2. For example, the first layer 3 can be formed by the following method. First, a compound for forming the first layer 3 is pressure-loaded into an extruder with the head set to 200°C or higher and 300°C or lower and the cylinder set to 170°C or higher and 280°C or lower. Next, the compound for forming the first layer 3 is extrusion-coated onto the outer peripheral surface of the conductor 2. Next, the extrusion-coated compound for forming the first layer 3 is irradiated with an electron beam at 0.1 kGy or higher and 500 kGy or lower, thereby forming the first layer 3 on the outer peripheral surface of the conductor 2.

[0061] <Features of the Method for Producing an Electric Wire According to the Present Embodiment> The method for producing an electric wire according to the present embodiment is carried out by, in step 1B, preparing, as the base resin, two or more polymers selected from the group consisting of ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, and tetrafluoroethylene-propylene copolymer, preparing, as the cross-linking aid, triallyl isocyanate (TAIC), trimethylolpropane trimethacrylate (TMPTMA), or both, and setting the parts by mass of silica particles relative to 100 parts by mass of the compound for forming the first layer 3 to 2.5 parts by mass or more and 46 parts by mass or less. These make it possible to manufacture "an electric wire 1 including a conductor 2 and a coating 5 covering the conductor 2, wherein the coating 5 includes a first layer 3, the first layer 3 containing, as a main component, a crosslinked resin body having as its resin component two or more polymers selected from the group consisting of ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, and tetrafluoroethylene-propylene copolymer, and the content of silica particles in the first layer 3 is 2% by volume or more and 40% by volume or less." This was discovered by the present inventors as a result of extensive research.

[0062] The present embodiment will be described in more detail with reference to examples, although the present embodiment is not limited to these examples.

[0063] <<Preparation of Electric Wires>> Electric wires according to Samples 1 to 16 and 101 to 106 were prepared as follows.

[0064] <First step> The metal material is copper (Cu) and the average cross-sectional area is 0.8 mm ２A commercially available conductor having the formula (1A) was prepared (Step 1A). Furthermore, the raw materials listed in Table 1 were kneaded in the composition listed in Table 1 using a roll heated to the temperature listed in Table 1 for the time listed in Table 1 to prepare a compound for forming the first layer (Step 1B). The blending ratios of the polymers (i.e., resin components) constituting the base resin were adjusted to be as listed in Table 3. The ethylene-tetrafluoroethylene copolymer (ETFE) used was Fluon C-88AXP (trademark) manufactured by AGC. The polyvinylidene fluoride (PVdF) used was Kynar Flex 2800-00 (trademark) manufactured by Arkema. The tetrafluoroethylene-propylene copolymer (TFE-P) used was Aflas 150E (trademark) manufactured by AGC. The fluorinated ethylene propylene (FEP) resin used was "Teflon (registered trademark) 130-J" (trademark) manufactured by Mitsui DuPont Fluorochemicals Co., Ltd. The silica particles used had an average particle size equal to the average particle size listed in Table 3.

[0065] <Second Step> The compound for forming the first layer was pressed into an extruder whose head and cylinder were set to the temperatures shown in Table 2. Next, the compound for forming the first layer was extrusion coated onto the outer periphery of the conductor so that the thickness of the first layer was as shown in Table 3. Next, the extrusion-coated compound for forming the first layer was irradiated with an electron beam at a dose shown in Table 2, thereby forming a first layer on the outer periphery of the conductor.

[0066] As described above, electric wires according to Samples 1 to 16 and 101 to 106 were produced, each electric wire including a conductor and a coating covering the conductor, wherein the coating included a first layer, and the first layer included, as a main component, a crosslinked resin body having the polymer listed in Table 3 as a resin component.

[0067] <Evaluation of Electric Wire Properties> <Silica Particle Content in First Layer> The silica particle content in the first layer of each sample electric wire was determined by the method described in Embodiment 1. The obtained results are shown in the "Content [volume %]" column of the "Silica Particles" column in Table 3.

[0068] <Average particle size of silica particles in first layer> The average particle size of silica particles in the first layer of each sample electric wire was determined by the method described in embodiment 1. The obtained results are shown in the "Average particle size [μm]" column of the "Silica particles" column in Table 3.

[0069] <Heat Resistance Evaluation Test> First, eight electric wires (length: 350 mm) for each sample were prepared. Next, the coating was stripped from both ends of the electric wires in the region between the end and a position 25 mm away from the end in the longitudinal direction of the electric wire. Next, each of the eight electric wires (length: 350 mm) for each sample was left in a thermostatic chamber at temperatures of 135±3°C, 150±3°C, 175±3°C, 200±3°C, 225±4°C, 250±4°C, 275±4°C, and 300±4°C for 240 hours. Next, the electric wires were removed from the thermostatic chamber and left at room temperature for 16 hours. Next, a weight 13 having a mass of 5 kg was placed on a mandrel 11 having a diameter 1.5 times the equivalent circle diameter of a cross section perpendicular to the longitudinal direction of the electric wire 12, and the wire was wound at a winding speed of 1 s. －１The wire was wound twice at two locations at room temperature (Figure 3). Next, after visually confirming that the conductor of each sample wire was not exposed, the wire was immersed in salt water (3% by mass) for 10 minutes. Next, a voltage of 1 kV was applied to the wire for 1 minute. Next, the wire was visually observed to determine whether or not the coating (in other words, the first layer) of the wire had been damaged. Next, the heat resistance of the wire was evaluated based on the following evaluation criteria. The obtained results are shown in the "Heat Resistance Evaluation Test" column in Table 4. An evaluation result of E, F, G, or H means that the wire has excellent heat resistance. (Evaluation criteria) A: No breakdown of the coating when the temperature of the thermostatic bath is 135±3°C or less B: No breakdown of the coating when the temperature of the thermostatic bath is 150±3°C or less C: No breakdown of the coating when the temperature of the thermostatic bath is 175±3°C or less D: No breakdown of the coating when the temperature of the thermostatic bath is 200±3°C or less E: No breakdown of the coating when the temperature of the thermostatic bath is 225±4°C or less F: No breakdown of the coating when the temperature of the thermostatic bath is 250±4°C or less G: No breakdown of the coating when the temperature of the thermostatic bath is 275±4°C or less H: No breakdown of the coating when the temperature of the thermostatic bath is 300±4°C or less

[0070] <Radiation Resistance Evaluation Test> First, two electric wires for each sample were prepared. Next, the first tensile elongation [mm] of each electric wire was determined before irradiating it with an electron beam of 300 kGy. Next, the second tensile elongation [mm] of each electric wire for each sample was determined after irradiating it with the electron beam. Next, the ratio of the second tensile elongation [mm] to the first tensile elongation [mm] was calculated as a percentage. The obtained results are shown in the "Radiation Resistance Evaluation Test [%]" column in Table 4. A ratio of 50% or more indicates excellent radiation resistance of the electric wire. The tensile elongation [mm] refers to the length of elongation between the gauge lines when a tensile test is performed on a sample with a gauge line distance of 20 mm set on a tensile tester at a tension speed of 25 mm / min, and can be determined by performing the tensile test.

[0071] <Atomic Oxygen Resistance Evaluation Test> The corrosion depth of the coating of the electric wire was determined by the method described in embodiment 1. The obtained results are shown in the "Atomic Oxygen Resistance Evaluation Test [μm]" column in Table 4. A corrosion depth of the coating of the electric wire of 10 μm or less means that the electric wire has excellent atomic oxygen resistance.

[0072] <Tensile Test> First, three test pieces were taken from each sample electric wire (length: 3 m) at 1 m intervals from the portion corresponding to the first layer of the electric wire. Next, the shape of each of the three test pieces was changed so that the thickness remained the same as the thickness of the first layer, and those with an inner diameter of less than 5 mm remained tubular, while the others were dumbbell-shaped. This resulted in three tubular samples or three dumbbell pieces 30 (see Figure 4) of type 3 specified in JIS K 6251:2004, Section 6.1. Next, the three samples (i.e., tubular samples or dumbbell pieces 30) were left to stand at room temperature for one hour. Next, the tubular samples were pulled from both ends at a rate of 25 mm / min, and the distance l between the gauge lines when the tubular samples were cut was measured. １ In addition, for the dumbbell pieces 30, each dumbbell piece 30 was pulled from the gripping portions 31 at both ends of the dumbbell piece 30 at a speed of 25 mm / min, and the distance l between the marked lines at the time of cutting each dumbbell piece 30 was measured. １ Next, the distance l between the marks when cutting each tubular sample or each dumbbell piece 30 was measured. １ [mm], distance l between the gauge lines before the test ０ [mm], and the formula "ε = {(l １ -l ０ ) / l ０} × 100". Next, the elongation ε [%] of the electric wire for each sample was determined by calculating the average value of the elongation ε of the three tubular samples or three dumbbell pieces 30. The obtained results are shown in the "Tensile test [%]" column in Table 4. An elongation [%] of 100% or more means that the electric wire has excellent elongation.

[0073]

[0074]

[0075]

[0076]

[0077] The electric wires according to Samples 1 to 16 correspond to Examples. The electric wires according to Samples 101 to 106 correspond to Comparative Examples. The results in Table 4 show that the electric wires according to Samples 1 to 16 exhibit superior effects, such as superior heat resistance, superior radiation resistance, superior atomic oxygen resistance, and superior elongation of the coating, compared to the electric wires according to Samples 101 to 106.

[0078] From the above, it was found that the electric wires according to Samples 1 to 16 had excellent heat resistance, excellent radiation resistance, excellent atomic oxygen resistance, and excellent coating elongation.

[0079] Although the embodiments and examples of the present disclosure have been described above, it is originally intended that the configurations of the above-described embodiments and examples may be appropriately combined or modified in various ways.

[0080] The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the embodiments and examples described above, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims.

[0081] 1 Electric wire, 2 Conductor, 3 First layer, 5 Coating, 11 Mandrel, 12 Electric wire, 13 Weight.

Claims

1. An electric wire comprising a conductor and a coating covering the conductor, wherein the coating includes a first layer, and the first layer contains, as a main component, a crosslinked resin body whose resin components are two or more polymers selected from the group consisting of ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, and tetrafluoroethylene-propylene copolymer, and the content of silica particles in the first layer is 2% by volume or more and 40% by volume or less.

2. The electric wire according to claim 1, wherein the average particle size of the silica particles is 0.1 μm or more and 40 μm or less.

3. The electric wire according to claim 1 or claim 2, wherein the resin crosslinked body contains two resin components, an ethylene-tetrafluoroethylene copolymer and a tetrafluoroethylene-propylene copolymer, and the parts by mass of the ethylene-tetrafluoroethylene copolymer are 50 parts by mass or more and 90 parts by mass or less relative to 100 parts by mass of the total of the parts by mass of the ethylene-tetrafluoroethylene copolymer and the parts by mass of the tetrafluoroethylene-propylene copolymer.

4. The electric wire according to any one of claims 1 to 3, wherein the thickness of the first layer is 0.05 mm or more and 3 mm or less.

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