Electrical wire and multicore cable

Abstract

This electrical wire is provided with a conductor and a coating that covers the conductor. The coating includes a first layer and a second layer formed on the first layer. The first layer includes a fluororesin as a main component and the second layer includes a silsesquioxane as a main component. The silsesquioxane is a polymer having (RSiO3 / 2) as a structural unit, R is a polymerizable group, and the thickness of the second layer is 0.1 μm or more and 100 μm or less.

Description

Wires and multi-core cables

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

[0002] Conventionally, "electric wires having a conductor and a coating that covers the conductor" and "multi-core cables having an electric wire" have been used for various purposes such as automobiles, aircraft, rockets, artificial satellites, industrial robots, electrical equipment, and thermal equipment (Patent Documents 1 to 5).

[0003] Japanese Patent Laid-Open No. 9-288914 Japanese Utility Model Laid-Open No. 4-61808 Japanese Patent Laid-Open No. 2000-30535 Japanese Patent Laid-Open No. 8-255513 Japanese Patent Laid-Open No. 2016-192374

[0004] The electric wire of the present disclosure is an electric wire including a conductor and a coating covering the conductor, the coating including a first layer and a second layer formed on the first layer, the first layer including a fluororesin as a main component, the second layer including a silsesquioxane as a main component, and the silsesquioxane being (RSiO ３／２ ) as a structural unit, R is a polymerizable group, and the thickness of the second layer is 0.1 μm or more and 100 μm 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 line II-II in Fig. 1. Fig. 3 is a schematic view illustrating a part of the evaluation methods of Evaluation Tests 1 to 3.

[0006] [Problem to be Solved by the Present Disclosure] When electric wires are used in various applications such as automobiles, aircraft, rockets, artificial satellites, industrial robots, electrical equipment, and thermal equipment, the conditions under which the electric wires are used can be severe. In particular, when the temperature conditions among the conditions under which the electric wires are used are severe, it is required to prevent oxidative degradation due to oxygen, ozone, atomic oxygen, etc., and to impart excellent heat resistance to the electric wires. Note that oxidative degradation progresses when oxygen in the air reacts with a polymer. Oxidative degradation tends to be accelerated as the temperature increases. This is because the higher the temperature, the more easily oxygen molecules diffuse within the polymer, facilitating the reaction between the polymer and oxygen. By suppressing oxidative degradation under severe temperature conditions, it is possible to suppress deterioration of the electric wire due to heating (in other words, it is possible to improve the heat resistance of the electric wires).

[0007] Therefore, an object of the present disclosure is to provide an electric wire having excellent heat resistance and a multi-core cable including the electric wire.

[0008] Effect of the Present Disclosure According to the present disclosure, it is possible to provide an electric wire having excellent heat resistance and a multi-core cable including the electric wire.

[0009] [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 a second layer formed on the first layer, the first layer contains a fluororesin as a main component, and the second layer contains silsesquioxane as a main component, and the silsesquioxane is (RSiO ３／２ ) as a structural unit, R is a polymerizable group, and the thickness of the second layer is 0.1 μm or more and 100 μm or less.

[0010] According to the present disclosure, it is possible to provide an electric wire having excellent heat resistance and a multi-core cable including the electric wire.

[0011] (2) In the above (1), the fluororesin of the first layer may be at least one fluororesin selected from the group consisting of perfluoroalkoxyalkane resin, fluorinated ethylene propylene resin, ethylene tetrafluoroethylene copolymer resin, and crosslinked ethylene tetrafluoroethylene copolymer resin, thereby making it possible to provide an electric wire having superior heat resistance and a multi-core cable including the electric wire.

[0012] (3) In the above (1), the fluororesin of the first layer may be a resin modified with a first functional group, and the first functional group may have a carboxyl group or an ether group. This makes it possible to provide an electric wire having superior heat resistance and a multi-core cable including the electric wire.

[0013] (4) In the above (3), the first functional group may be at least one functional group selected from the group consisting of a carboxyl group, a maleic anhydride group, and an epoxy group, thereby providing an electric wire having superior heat resistance and a multi-core cable including the electric wire.

[0014] (5) In the above (1), the fluororesin of the first layer may be a resin that has been subjected to a hydrophilic surface treatment, thereby making it possible to provide an electric wire having superior heat resistance and a multi-core cable including the electric wire.

[0015] (6) In the above (5), the hydrophilic surface treatment may be at least one surface treatment selected from the group consisting of corona treatment, plasma treatment, ozone treatment, and etching treatment with active sodium, thereby providing an electric wire having superior heat resistance and a multi-core cable including the electric wire.

[0016] (7) In any one of the above (1) to (6), the coating may further include a third layer formed between the first layer and the second layer, and the third layer may contain a fluororesin as a main component. This makes it possible to provide an electric wire having superior heat resistance and a multi-core cable including the electric wire.

[0017] (8) In the above (7), the fluororesin of the third layer may be at least one fluororesin selected from the group consisting of perfluoroalkoxyalkane resin, fluorinated ethylene propylene resin, ethylene tetrafluoroethylene copolymer resin, and crosslinked ethylene tetrafluoroethylene copolymer resin, thereby making it possible to provide an electric wire having superior heat resistance and a multi-core cable including the electric wire.

[0018] (9) In the above (7), the fluororesin of the third layer may be a resin modified with a second functional group, and the second functional group may have a carboxyl group or an ether group. This makes it possible to provide an electric wire having superior heat resistance and a multi-core cable including the electric wire.

[0019] (10) In the above (9), the second functional group may be at least one functional group selected from the group consisting of a carboxyl group, a maleic anhydride group, and an epoxy group, thereby providing an electric wire having superior heat resistance and a multi-core cable including the electric wire.

[0020] (11) In any one of the above (1) to (10), the polymerizable group may be a radically polymerizable group or a cationically polymerizable group, thereby making it possible to provide an electric wire having superior heat resistance and a multi-core cable including the electric wire.

[0021] (12) In any one of the above (1) to (10), the polymerizable group may be one type of polymerizable group selected from the group consisting of an acryloyl group, a methacryloyl group, and an oxetanyl group, thereby making it possible to provide an electric wire having superior heat resistance and a multi-core cable including the electric wire.

[0022] (13) A multi-core cable of the present disclosure includes the electric wires described in (1) to (12) above.

[0023] According to the present disclosure, a multi-core cable including electric wires with excellent heat resistance can be provided.

[0024] [Details of the embodiment of the present disclosure] Specific examples of electric wires and multi-core cables 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.

[0025] In the present disclosure, the notation in the form of "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.

[0026] 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.

[0027] [Embodiment 1: Electric Wire] An electric wire according to an embodiment of the present disclosure will be described with reference to Figs. 1 and 2. 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. 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 a second layer 4 formed on the first layer 3, the first layer 3 containing a fluororesin as a main component, and the second layer 4 containing a silsesquioxane as a main component, the silsesquioxane being (RSiO ３／２ ) as a structural unit, R is a polymerizable group, and the thickness of the second layer 4 is 0.1 μm or more and 100 μm or less.

[0028] According to the present disclosure, it is possible to provide an electric wire 1 having excellent heat resistance and a multi-core cable including the electric wire 1. The reason for this is presumed to be as follows.

[0029] In the electric wire 1 of this embodiment, the coating 5 includes a first layer 3 and a second layer 4 formed on the first layer 3. The first layer 3 contains a fluororesin as a main component, and the second layer 4 contains a silsesquioxane as a main component. The silsesquioxane is (RSiO ３／２ ) as a structural unit, R is a polymerizable group, and the thickness of the second layer 4 is 0.1 μm or more and 100 μm or less. Since the second layer 4 serves as a dense protective film, oxidation degradation due to oxygen in the air can be prevented, and therefore, an electric wire 1 having excellent heat resistance and a multi-core cable including the electric wire 1 can be provided.

[0030] <Electric Wire> The equivalent circle diameter of a cross section perpendicular to the longitudinal direction of the electric wire 1 may be 0.1 mm or more and 50 mm or less, 0.2 mm or more and 20 mm or less, or 0.5 mm or more and 10 mm or less. Note that the longitudinal direction here can be rephrased as the "first direction" described later.

[0031] 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 by the same method 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 is calculated based on the "average cross-sectional area of ​​the electric wire 1," thereby making it possible to determine the circle-equivalent diameter of the cross section perpendicular to the longitudinal direction of the electric wire 1.

[0032] 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.

[0033] <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.

[0034] 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.

[0035] The equivalent circle diameter of a cross section perpendicular to the longitudinal direction of the conductor 2 may be 0.05 mm to 30 mm, 0.1 mm to 15 mm, or 0.3 mm to 8 mm. Here, the longitudinal direction can be rephrased as the "first direction" described later.

[0036] 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.

[0037] 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.

[0038] The average cross-sectional area of ​​the conductor 2 is not particularly limited and can be appropriately selected depending on the application. ２ Over 550mm ２ It may be 0.006 mm or less, ２ Over 140mm ２ It may be 0.05 mm or less. ２ Over 40mm 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.

[0039] <Coating> The electric wire 1 includes a coating 5 that coats the conductor 2. The coating 5 includes a first layer 3 and a second layer 4 formed on the first layer 3. The coating 5 may consist of only the first layer 3 and the second layer 4 formed on the first layer 3, or may further include a third layer formed between the first layer 3 and the second layer 4, or may further include other layers described below in addition to the first layer 3 and the second layer 4 formed on the first layer 3.

[0040] The thickness of the coating 5 may be 0.025 mm or more and 10 mm or less. If the thickness of the coating 5 is less than 0.025 mm, the coating 5 tends to be easily damaged. If the thickness of the coating 5 exceeds 10 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 0.050 mm or more and 2.5 mm or less, or 0.150 mm or more and 1 mm or less.

[0041] 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 to expose 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.

[0042] 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.

[0043] <First Layer> The first layer 3 contains a fluororesin as a main component. Here, "containing a fluororesin as a main component" means that the fluororesin is contained in an amount of, for example, 50% by mass or more. The first layer 3 may be made of a fluororesin. "The first layer 3 may be made of a fluororesin" means that the first layer 3 may be made of only a fluororesin, or may contain other components (such as first inevitable impurities) in addition to the fluororesin, as long as the effects of the present disclosure are not impaired. Examples of the first inevitable impurities include cross-linking aids (such as triallyl isocyanurate and trimethylpentene trimethacrylate), 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), and flame retardants (such as bromine-based flame retardants, antimony trioxide, melamine cyanurate, magnesium hydroxide, and aluminum hydroxide).

[0044] The fluororesin of the first layer 3 may be at least one fluororesin selected from the group consisting of perfluoroalkoxyalkane resin, fluorinated ethylene propylene resin, ethylene tetrafluoroethylene copolymer resin, and cross-linked ethylene tetrafluoroethylene copolymer resin. This makes it possible to provide an electric wire 1 with superior heat resistance and a multi-core cable including the electric wire 1. In the present disclosure, perfluoroalkoxyalkane resin can be rephrased as PFA resin, fluorinated ethylene propylene resin can be rephrased as FEP resin, ethylene tetrafluoroethylene copolymer resin can be rephrased as ETFE resin, and cross-linked ethylene tetrafluoroethylene copolymer resin can be rephrased as cross-linked ETFE resin.

[0045] The fluororesin of the first layer 3 is a resin modified with a first functional group, and the first functional group may have a carboxyl group or an ether group. This makes it possible to provide the electric wire 1 and a multi-core cable including the electric wire 1 having superior heat resistance. Examples of resins modified with a first functional group include resins obtained by modifying PFA resin with maleic anhydride groups, resins obtained by modifying PFA resin with carboxyl groups, resins obtained by modifying PFA resin with epoxy groups, resins obtained by modifying FEP resin with maleic anhydride groups, resins obtained by modifying FEP resin with carboxyl groups, resins obtained by modifying FEP resin with epoxy groups, resins obtained by modifying ETFE resin with maleic anhydride groups, resins obtained by modifying ETFE resin with carboxyl groups, resins obtained by modifying ETFE resin with epoxy groups, resins obtained by modifying cross-linked ETFE resin with maleic anhydride groups, resins obtained by modifying cross-linked ETFE resin with carboxyl groups, and resins obtained by modifying cross-linked ETFE resin with epoxy groups. The state of being "modified with a first functional group" means a state in which the first functional group is graft-bonded to a terminal or non-terminal of a polymer molecular chain, or a state in which the first functional group is copolymerized in a polymer molecular chain.

[0046] The first functional group may be at least one functional group selected from the group consisting of a carboxyl group, a maleic anhydride group, and an epoxy group, thereby making it possible to provide an electric wire 1 and a multi-core cable including the electric wire 1 having superior heat resistance.

[0047] The fluororesin of the first layer 3 may be a resin that has been subjected to a hydrophilic surface treatment, thereby making it possible to provide an electric wire having superior heat resistance and a multi-core cable including such an electric wire.

[0048] The hydrophilic surface treatment may be at least one surface treatment selected from the group consisting of corona treatment, plasma treatment, ozone treatment, and etching treatment with active sodium, thereby providing an electric wire and a multi-core cable including the electric wire with superior heat resistance.

[0049] The composition of the first layer 3 can be identified by a combination of an analysis of the chemical bonding state based on measurements of the infrared absorption spectrum by nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared spectroscopy (FT-IR), and measurements of the crystalline melting temperature and the heat of crystalline melting by a differential scanning calorimeter.

[0050] The weight-average molecular weight of the fluororesin of the first layer 3 may be 10,000 or more and 5,000,000 or less, 50,000 or more and 2,000,000 or less, or 100,000 or more and 1,000,000 or less. The weight-average molecular weight of the fluororesin of the first layer 3 can be determined by measurement using gel permeation chromatography (GPC) in accordance with JIS-K7252-1:2008 "Plastics -- Determination of average molecular weight and molecular weight distribution of polymers by size exclusion chromatography -- Part 1: General rules."

[0051] The thickness of the first layer 3 may be 0.025 mm or more and 10 mm or less. This can impart better heat resistance to the electric wire 1. Furthermore, the electric wire 1 can be made easier to bend. The lower limit of the thickness of the first layer 3 may be 0.025 mm or more, 0.050 mm or more, 0.100 mm or more, or 0.200 mm or more. The upper limit of the thickness of the first layer 3 may be 10 mm or less, 2.5 mm or less, 1 mm or less, or 0.500 mm or less. The thickness of the first layer 3 may be 0.050 mm or more and 2.5 mm or less, or 0.100 mm or more and 1 mm or less.

[0052] 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.

[0053] 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.

[0054] <Third Layer> The coating 5 further includes a third layer (not shown) formed between the first layer 3 and the second layer 4, and the third layer may include a fluororesin as a main component. This can impart better heat resistance to the electric wire 1. Here, "including a fluororesin as a main component" means that the fluororesin is contained in an amount of, for example, 50% by mass or more. The third layer may be made of a fluororesin. "The third layer may be made of a fluororesin" means that the third layer may be made of only a fluororesin, or may include other components (such as a third inevitable impurity) in addition to the fluororesin, as long as the effects of the present disclosure are not impaired. Examples of the third unavoidable impurities include crosslinking aids (triallyl isocyanurate, trimethylpentene trimethacrylate, etc.), fillers (silica, talc, calcium carbonate, clay, zinc oxide, etc.), lubricants (oleic acid amide, erucic acid amide, stearic acid, zinc stearate, etc.), coloring pigments (inorganic pigments such as titanium oxide, organic pigments, carbon, etc.), and flame retardants (bromine-based flame retardants, antimony trioxide, melamine cyanurate, magnesium hydroxide, aluminum hydroxide, etc.).

[0055] The fluororesin of the third layer may be at least one fluororesin selected from the group consisting of perfluoroalkoxyalkane resin, fluorinated ethylene propylene resin, ethylene tetrafluoroethylene copolymer resin, and crosslinked ethylene tetrafluoroethylene copolymer resin, thereby making it possible to provide an electric wire 1 and a multi-core cable including the electric wire 1 having superior heat resistance.

[0056] The fluororesin of the third layer is a resin modified with a second functional group, which may have a carboxyl group or an ether group, thereby making it possible to provide the electric wire 1 and a multi-core cable including the electric wire 1 having superior heat resistance. Examples of resins modified with a second functional group include resins obtained by modifying PFA resin with maleic anhydride groups, resins obtained by modifying PFA resin with carboxyl groups, resins obtained by modifying PFA resin with epoxy groups, resins obtained by modifying FEP resin with maleic anhydride groups, resins obtained by modifying FEP resin with carboxyl groups, resins obtained by modifying FEP resin with epoxy groups, resins obtained by modifying ETFE resin with maleic anhydride groups, resins obtained by modifying ETFE resin with carboxyl groups, resins obtained by modifying ETFE resin with epoxy groups, resins obtained by modifying cross-linked ETFE resin with maleic anhydride groups, resins obtained by modifying cross-linked ETFE resin with carboxyl groups, and resins obtained by modifying cross-linked ETFE resin with epoxy groups. The state of being "modified with a second functional group" means a state in which the second functional group is graft-bonded to a terminal or non-terminal of the polymer molecular chain, or a state in which the second functional group is copolymerized in the polymer molecular chain.

[0057] The second functional group may be at least one functional group selected from the group consisting of a carboxyl group, a maleic anhydride group, and an epoxy group, thereby making it possible to provide an electric wire 1 and a multi-core cable including the electric wire 1 having superior heat resistance.

[0058] The composition of the third layer can be determined by a method similar to the method for measuring the "composition of the first layer 3," except that the measurement target is the "third layer."

[0059] The weight average molecular weight of the fluororesin of the third layer may be 10,000 or more and 5,000,000 or less, 50,000 or more and 2,000,000 or less, or 100,000 or more and 1,000,000 or less. The weight average molecular weight of the fluororesin in the third layer can be determined by measurement using gel permeation chromatography (GPC) in accordance with JIS-K7252-1:2008 "Plastics -- Determination of average molecular weight and molecular weight distribution of polymers by size exclusion chromatography -- Part 1: General rules."

[0060] The thickness of the third layer may be 0.025 mm or more and 10 mm or less. This can impart better heat resistance to the electric wire 1. Furthermore, the electric wire 1 can be made easier to bend. The lower limit of the thickness of the third layer may be 0.025 mm or more, 0.050 mm or more, 0.100 mm or more, or 0.200 mm or more. The upper limit of the thickness of the third layer may be 10 mm or less, 2.5 mm or less, 1 mm or less, or 0.500 mm or less. The thickness of the third layer may be 0.050 mm or more and 2.5 mm or less, or 0.100 mm or more and 1 mm or less.

[0061] The thickness of the third layer can be determined in the same manner as the thickness of the coating 5, except that the measurement target is the third layer.

[0062] 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.

[0063] <Second Layer> The second layer 4 contains silsesquioxane as a main component. Here, "containing silsesquioxane as a main component" means that the second layer 4 contains silsesquioxane in an amount of, for example, 50 mass % or more. Silsesquioxane is (RSiO ３／２) as a structural unit, where R is a polymerizable group. These can impart excellent heat resistance to the electric wire 1. The second layer 4 may be made of silsesquioxane. "The second layer 4 may be made of silsesquioxane" means that the second layer 4 may be made of only silsesquioxane, or may contain other components (such as second inevitable impurities) in addition to silsesquioxane as long as the effects of the present disclosure are not impaired. Examples of the second inevitable impurities include photoradical polymerization initiators, thermal polymerization initiators, acrylic monomers, organic solvents, lubricants, and pigments.

[0064] Silsesquioxane may contain at least one structure selected from the group consisting of a random structure, a ladder structure, a complete cage structure, and an incomplete cage structure. Here, the "random structure" means a structure represented by formula 1, the "ladder structure" means a structure represented by formula 2, the "complete cage structure" means a structure represented by formula 3 or a structure represented by formula 4, and the "incomplete cage structure" means a structure represented by formula 5 or a structure represented by formula 6. The structure represented by formula 3 is "T ８ ", and the structure represented by formula 4 can be expressed as "T １０ " can be rephrased as "

[0065]

[0066]

[0067]

[0068] The polymerizable group may be a radically polymerizable group or a cationically polymerizable group. These polymerizable groups have excellent polymerization reactivity, particularly photopolymerization reactivity, and therefore can provide an electric wire 1 and a multi-core cable including the electric wire 1 having superior heat resistance.

[0069] The polymerizable group may be one selected from the group consisting of an acryloyl group, a methacryloyl group, and an oxetanyl group. These polymerizable groups have excellent polymerization reactivity, particularly photopolymerization reactivity, and therefore can provide an electric wire 1 and a multi-core cable including the electric wire 1 having superior heat resistance.

[0070] The composition of the second layer 4 can be identified by a combination of an analysis of the chemical bonding state based on measurements of infrared absorption spectra by nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared spectroscopy (FT-IR) and measurements of the ash content by thermogravimetry (TG).

[0071] The thickness of the second layer 4 is 0.1 μm or more and 100 μm or less. This allows the second layer 4 to fully exhibit its heat resistance effect, making it possible to provide an electric wire 1 having excellent heat resistance and a multi-core cable including the electric wire 1. The lower limit of the thickness of the second layer 4 may be 0.1 μm or more, 0.5 μm or more, 1 μm or more, or 2 μm or more. The upper limit of the thickness of the second layer 4 may be 100 μm or less, 50 μm or less, 20 μm or less, or 10 μm or less. The thickness of the second layer 4 may be 0.5 μm or more and 50 μm or less, or 1 μm or more and 20 μm or less.

[0072] The thickness of the second layer 4 can be determined in the same manner as the thickness of the coating 5, except that the measurement target is the second layer 4.

[0073] It has been confirmed that, as long as the same second layer 4 is measured by the above method, there is no variation in the measurement results even if the measurement location is changed arbitrarily.

[0074] <Other Layers> The coating 5 may further include other layers. Examples of such other layers include a surface layer and an intermediate layer. The surface layer is a layer located on the surface of the coating 5. The intermediate layer is a layer located between the conductor 2 and the first layer 3 or between the first layer 3 and the second layer 4.

[0075] <<Method for Manufacturing Electric Wire>> In a case where the coating 5 does not include a third layer formed between the first layer 3 and the second layer 4, the method for manufacturing the electric wire 1 of this embodiment includes, for example, Step 1 of preparing the conductor 2, a compound for forming the first layer 3, and a varnish for forming the second layer 4, in this order; Step 2 of forming the first layer 3 on the outer peripheral surface of the conductor 2; and Step 3 of forming the second layer 4 on the surface of the first layer 3. In a case where the coating 5 further includes a third layer formed between the first layer 3 and the second layer 4, the method for manufacturing the electric wire 1 of this embodiment further includes, for example, Step 2A between Step 2 and Step 3. The first step includes Step 1A of preparing the conductor 2, Step 1B of preparing the compound for forming the first layer 3, and Step 1C of preparing the varnish for forming the second layer 4. In the case where the coating 5 further includes a third layer formed between the first layer 3 and the second layer 4, the first step further includes a first step D of preparing a varnish for forming the third layer. The method for producing the electric wire 1 of this embodiment may further include a "step of forming other layers." The "step of forming other layers" may be performed by a conventionally known method.

[0076] <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.

[0077] <Step 1B: Step of Preparing 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 fluororesin is prepared as a raw material. In addition to the fluororesin, for example, a cross-linking aid, a lubricant, a filler, etc. may also be prepared as raw materials. Next, the raw materials are kneaded to prepare the compound for forming the first layer 3.

[0078] Examples of fluororesins include perfluoroalkoxyalkane resins, fluorinated ethylene propylene resins, ethylene tetrafluoroethylene copolymer resins, crosslinked ethylene tetrafluoroethylene copolymer resins, and resins obtained by modifying these resins with maleic anhydride groups, carboxyl groups, or epoxy groups.

[0079] The weight average molecular weight of the fluororesin may be 10,000 or more and 5,000,000 or less, 50,000 or more and 2,000,000 or less, or 100,000 or more and 1,000,000 or less.

[0080] The kneading can be carried out using rolls heated to, for example, 280° C. or more and 350° C. or less. The kneading time can be 5 minutes or more and 30 minutes or less.

[0081] <Step 1C: Step of Preparing Varnish for Forming Second Layer> In step 1C, a varnish for forming the second layer 4 is prepared. For example, the varnish for forming the second layer 4 can be prepared by the following method. First, a silsesquioxane derivative is prepared as a raw material. The silsesquioxane derivative may be prepared by manufacturing it using a conventionally known method, or may be prepared by purchasing a commercially available product. In addition to the silsesquioxane derivative, for example, a photoradical polymerization initiator, an acrylic monomer, a solvent, etc. may also be prepared as raw materials. Next, the photoradical polymerization initiator, etc., can be added to the silsesquioxane derivative and stirred to prepare the varnish for forming the second layer 4.

[0082] The stirring speed may be, for example, 10 rpm or more and 1000 rpm or less. The temperature during stirring may be 10° C. or more and 40° C. or less. The temperature during stirring may be room temperature. The stirring time may be 5 minutes or more and 30 minutes or less.

[0083] <Step 1D: Step of Preparing Varnish for Forming Third Layer> In Step 1D, a compound for forming the third layer is prepared. Step 1D is performed in the same manner as Step 1B, except that "compound for forming the first layer" is replaced with "compound for forming the third layer."

[0084] <Second Step> In the second step, 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 300°C or higher and 350°C or lower and the cylinder set to 280°C or higher and 320°C or lower. Next, the compound for forming the first layer 3 is extrusion-coated onto the outer peripheral surface of the conductor 2. When the fluororesin of the first layer is a cross-linked ETFE resin, the extrusion-coated compound for forming the first layer 3 may be irradiated with electron beams at 0.1 kGy or higher and 500 kGy or lower. In this manner, the first layer 3 can be formed on the outer peripheral surface of the conductor 2.

[0085] In step 2A, a third layer is formed on the surface of the first layer 3. For example, the third layer can be formed by the following method. First, a compound for forming the third layer is pressure-loaded into an extruder with the head set to 300°C or higher and 350°C or lower and the cylinder set to 280°C or higher and 320°C or lower. Next, the compound for forming the third layer is extrusion-coated onto the surface of the first layer 3. When the fluororesin of the third layer is a cross-linked ETFE resin, the extrusion-coated compound for forming the third layer may be irradiated with an electron beam at 0.1 kGy or higher and 500 kGy or lower. In this manner, the third layer can be formed on the surface of the first layer 3.

[0086] <Third Step> When the method for producing the electric wire 1 of this embodiment does not include Step 2A between Step 2 and Step 3, in Step 3, the second layer 4 is formed on the surface of the first layer 3. For example, the second layer 4 can be formed by the following method. First, a varnish for forming the second layer 4 is applied to the surface of the first layer 3. Next, the varnish for forming the second layer 4 applied to the surface of the first layer 3 is subjected to a photo-curing treatment under the following conditions, thereby forming the second layer 4 on the surface of the first layer 3. Note that Step 3 may be repeatedly performed until the second layer 4 reaches a predetermined thickness. (Photo-curing Treatment Conditions) Light source: high-pressure mercury lamp (input power: 10 W / cm to 300 W / cm) Lamp height: 1 cm to 50 cm Conveyor speed: 1 m / min to 10 m / min Integrated light intensity per pass: 1,000 mJ / cm２ 30,000mJ / cm or more ２ Number of passes: 1 to 10 Atmosphere: Air

[0087] When the method for producing the electric wire 1 of this embodiment further includes a step 2A between the second step and the third step, the second layer 4 is formed on the surface of the third layer in the third step. For example, the second layer 4 can be formed by the following method. First, a varnish for forming the second layer 4 is applied to the surface of the third layer. Next, the varnish for forming the second layer 4 applied to the surface of the third layer is subjected to a photo-curing treatment under the following conditions, thereby forming the second layer 4 on the surface of the third layer. Note that the third step may be repeated until the second layer 4 reaches a predetermined thickness. (Photo-curing treatment conditions) Light source: high-pressure mercury lamp (input power: 10 W / cm to 300 W / cm) Lamp height: 1 cm to 50 cm Conveyor speed: 1 m / min to 10 m / min Integrated light intensity per pass: 1,000 mJ / cm ２ 30,000mJ / cm or more ２ Number of passes: 1 to 10 Atmosphere: Air

[0088] [Embodiment 2: Multi-core cable] A multi-core cable of this embodiment includes the electric wire according to embodiment 1.

[0089] According to the present disclosure, a multi-core cable including electric wires with excellent heat resistance can be provided.

[0090] The multi-core cable according to the present embodiment is not particularly limited as long as it includes the electric wires described in embodiment 1. In the present disclosure, a multi-core cable refers to a cable including a plurality of electric wires. "The multi-core cable according to the present embodiment includes the electric wires described in embodiment 1" means that at least one of the plurality of electric wires included in the multi-core cable according to the present embodiment is the electric wire described in embodiment 1.

[0091] <<Method for Manufacturing Multi-Core Cable>> The method for manufacturing the multi-core cable according to this embodiment can be carried out in the same manner as a conventionally known method, except that the electric wire according to the first embodiment is used.

[0092] The present embodiment will be described in more detail with reference to examples, although the present embodiment is not limited to these examples.

[0093] <<Preparation of Electric Wires>> Electric wires according to Samples 1 to 19 and 101 to 112 were prepared as follows.

[0094] <Step 1> The conductors shown in Tables 11 and 12 were prepared by purchasing commercially available products (Step 1A). Furthermore, the raw materials shown in Tables 1 and 2 were kneaded in the compositions shown in Tables 1 and 2 using rolls heated to the temperatures shown in Tables 1 and 2 for the times shown in Tables 1 and 2 to prepare compounds for forming the first layer (Step 1B). The fluororesin used was a resin shown in the "Composition" column of the "First Layer" column of Tables 11 and 12, except when the "Composition" column of the "First Layer" column in Tables 11 and 12 lists crosslinked ETFE resin, crosslinked ETFE resin (modified with maleic anhydride groups), crosslinked ETFE resin (modified with carboxyl groups), or crosslinked ETFE resin (modified with epoxy groups). The PFA resin used was "P-63P" (trademark) manufactured by AGC, the FEP resin used was "9494" (trademark) manufactured by Chemours, and the ETFE resin used was "C-55AXP" (trademark) manufactured by AGC. When the "Composition" column of the "First Layer" column in Tables 11 and 12 states "crosslinked ETFE resin," "crosslinked ETFE resin (modified with maleic anhydride groups)," "crosslinked ETFE resin (modified with carboxyl groups)," or "crosslinked ETFE resin (modified with epoxy groups)," AGC's "C-55AXP" (trademark) was used as the fluororesin. The crosslinking aid used was "EBECRYL" (trademark) manufactured by Allnex. The "unsaturated monomer having a maleic anhydride group" used maleic anhydride manufactured by Tokyo Chemical Industry Co., Ltd. The "unsaturated monomer having a carboxyl group" used acrylic acid manufactured by Tokyo Chemical Industry Co., Ltd. As the "unsaturated monomer having an epoxy group", allyl glycidyl ether manufactured by Tokyo Chemical Industry Co., Ltd. was used.

[0095] Furthermore, the raw materials listed in Tables 3 and 4 (in other words, raw materials other than the silsesquioxane derivative) were added to the silsesquioxane derivative so as to obtain the composition listed in Tables 3 and 4, and the mixture was stirred under the conditions listed in Tables 3 and 4 to prepare a varnish for forming a second layer (Step 1C). Note that if "-" is entered in all columns in the "Step 1C" column, this means that "Step 1C" was not performed. Note that the silsesquioxane derivatives listed in Tables 15 and 16 were used as the "silsesquioxane derivatives." As the silsesquioxane derivative in which R (polymerizable group) is an acryloyl group (radical polymerizable group), "AC-SQ TA-100" (trademark) manufactured by Toagosei Co., Ltd. was used; as the silsesquioxane derivative in which R (polymerizable group) is a methacryloyl group (radical polymerizable group), "MAC-SQ TM-100" (trademark) manufactured by Toagosei Co., Ltd. was used; and as the silsesquioxane derivative in which R (polymerizable group) is an oxetanyl group (cationically polymerizable group), "QX-SQ SI-20" (trademark) manufactured by Toagosei Co., Ltd. was used. As the photoradical polymerization initiator, "BLUESIL PI 2074" (trademark) manufactured by ELKEM was used.

[0096] Furthermore, the raw materials shown in Tables 5 and 6 were kneaded in the compositions shown in Tables 5 and 6 using rolls heated to the temperatures shown in Tables 5 and 6 for the times shown in Tables 5 and 6 to prepare compounds for forming a third layer (step 1D). Note that, as the fluororesin, the resins shown in the "Composition" column of the "Third Layer" column in Tables 13 and 14 were used, except when the "Composition" column of the "Third Layer" column in Tables 13 and 14 states crosslinked ETFE resin, crosslinked ETFE resin (modified with maleic anhydride groups), crosslinked ETFE resin (modified with carboxyl groups), or crosslinked ETFE resin (modified with epoxy groups). In Tables 13 and 14, when the "Composition" column of the "Third Layer" column states "crosslinked ETFE resin," "crosslinked ETFE resin (modified with maleic anhydride groups)," "crosslinked ETFE resin (modified with carboxyl groups)," or "crosslinked ETFE resin (modified with epoxy groups)," the fluororesin used was "C-55AXP" (trademark) manufactured by AGC. In addition, when "-" is entered in all columns of the "Step 1D" column, it means that "Step 1D" was not performed.

[0097] <Second Step> First, the compound for forming the first layer was pressed into an extruder whose head was set to the temperature shown in Tables 7 and 8 and whose cylinder was set to the temperature shown in Tables 7 and 8. 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 Tables 11 and 12. Next, the extrusion-coated compound for forming the first layer was irradiated with an electron beam at a dose shown in Tables 7 and 8, except when "0" is listed in the "Electron beam [kGy]" column in the "Second Step" column. In this way, a first layer was formed on the outer periphery of the conductor.

[0098] <Step 2A> First, the compound for forming the third layer was pressed into an extruder whose head was set to the temperature shown in Tables 7 and 8 and whose cylinder was set to the temperature shown in Tables 7 and 8. Next, the compound for forming the third layer was extrusion-coated onto the outer periphery of the conductor so that the thickness of the third layer was as shown in Tables 13 and 14. Next, the extrusion-coated compound for forming the third layer was irradiated with electron beams at the doses shown in Tables 7 and 8, except when "-" or "0" is listed in the "Electron beam [kGy]" column of the "Step 2A" column. In this way, the third layer was formed on the surface of the first layer. Note that when "-" is listed in all columns of the "Step 2A" column, it means that "Step 2A" was not performed.

[0099] <Third Step> First, when Step 2A was not performed, the second layer-forming varnish was applied to the surface of the first layer. When Step 2A was performed, the second layer-forming varnish was applied to the surface of the third layer. Next, when Step 2A was not performed, the second layer-forming varnish applied to the surface of the first layer was photocured under the following conditions to form a second layer on the surface of the first layer. When Step 2A was performed, the second layer-forming varnish applied to the surface of the third layer was photocured under the following conditions to form a second layer on the surface of the third layer. The application of the second layer-forming varnish and the photocuring treatment were repeated until the thickness of the second layer reached the thickness listed in Table 2. Note that if "-" is entered in all columns in the "Third Step" column, it means that "Third Step" was not performed. (Photo-curing treatment conditions) Light source: high-pressure mercury lamp (input power [W / cm] as shown in Tables 9 and 10) Lamp height: as shown in Tables 9 and 10 Conveyor speed: as shown in Tables 9 and 10 Integrated light intensity per pass: as shown in Tables 9 and 10 Number of passes: as shown in Tables 9 and 10 Atmosphere: air

[0100] In this manner, electric wires according to Samples 1 to 19 and 101 to 112 were produced.

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[0119] <Evaluation of Electric Wire Properties> <Composition of First Layer> For each electric wire sample, the composition of the first layer was determined by the method described in Embodiment 1. The results obtained are shown in the "Composition" column of the "First Layer" column in Tables 11 and 12. When a component name is listed in the "Composition" column of the "First Layer" column in Tables 11 and 12, this means that the first layer contains, as a main component, the component listed in the "Composition" column of the "First Layer" column in Tables 11 and 12. For example, when "PFA resin" is listed in the "Composition" column of the "First Layer" column in Tables 11 and 12, this means that the first layer contains, as a main component, a fluororesin, which is a perfluoroalkoxyalkane resin.

[0120] <Composition of Second Layer> For each sample of the electric wire, the composition of the second layer was determined by the method described in Embodiment 1. The results obtained are shown in the "Composition" column of the "Second Layer" column in Tables 15 and 16. When a component name is listed in the "Composition" column of the "Second Layer" column in Tables 15 and 16, this means that the second layer contains the component listed in the "Composition" column of the "Second Layer" column in Tables 15 and 16 as a main component. For example, when "Silsesquioxane" is listed in the "Composition" column of the "Second Layer" column in Tables 15 and 16 and "Acryloyl group (radical polymerizable group)" is listed in the "R" column of the "Second Layer" column in Tables 15 and 16, this means that the second layer contains silsesquioxane as a main component, and the silsesquioxane is (RSiO ３／２ ) as a constituent unit, and R is a polymerizable group, which is a radical polymerizable group and an acryloyl group.

[0121] <Composition of Third Layer> For each sample electric wire, the composition of the third layer was determined by the method described in Embodiment 1. The results obtained are shown in the "Composition" column of the "Third Layer" column in Tables 13 and 14. When a component name is listed in the "Composition" column of the "Third Layer" column in Tables 13 and 14, it means that the third layer contains the component listed in the "Composition" column of the "Third Layer" column in Tables 13 and 14 as a main component. For example, when "PFA resin" is listed in the "Composition" column of the "Third Layer" column in Tables 13 and 14, it means that the third layer contains a fluororesin as a main component, and the fluororesin is a perfluoroalkoxyalkane resin.

[0122] <Coating Thickness> The coating thickness of each sample electric wire was determined by the method described in Embodiment 1. The obtained results are shown in the "Thickness [μm]" column of the "Coating" column in Tables 15 and 16.

[0123] <Circle-equivalent diameter of cross section perpendicular to the longitudinal direction of electric wire> For each sample electric wire, the circle-equivalent diameter of the cross section perpendicular to the longitudinal direction of the electric wire was determined by the method described in embodiment 1. The obtained results are shown in the "Circle-equivalent diameter [mm]" column of the "Electric wire" column in Tables 15 and 16.

[0124] <Evaluation Test 1> 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 85±2°C, 100±2°C, 125±3°C, 150±3°C, 175±3°C, 200±3°C, 225±4°C, and 250±4°C for 3,000 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 a winding speed of 1 s was performed. －１ The wire was wound twice at two locations at room temperature (FIG. 3). 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. A voltage of 1 kV was applied to the wire for 1 minute. The wire was then visually observed to determine whether the coating had been broken. The heat resistance of the wire was evaluated based on the following evaluation criteria. The results are shown in the "Evaluation Test 1" column of Tables 17 and 18. The closer the evaluation result is to H, the better the heat resistance of the wire. Note that the heat resistance of electric wires differs depending on the type of fluororesin in the first layer (in other words, depending on the composition of the first layer), and therefore, samples using the same resin listed in the "Composition" column of the "First Layer" column in Tables 11 and 12 were compared. (Evaluation criteria) A: No breakdown of the coating when the temperature of the thermostatic bath is 85±2°C or less B: No breakdown of the coating when the temperature of the thermostatic bath is 100±2°C or less C: No breakdown of the coating when the temperature of the thermostatic bath is 125±3°C or less D: No breakdown of the coating when the temperature of the thermostatic bath is 150±3°C or less E: No breakdown of the coating when the temperature of the thermostatic bath is 175±3°C or less F: No breakdown of the coating when the temperature of the thermostatic bath is 200±3°C or less G: No breakdown of the coating when the temperature of the thermostatic bath is 225±4°C or less H: No breakdown of the coating when the temperature of the thermostatic bath is 250±4°C or less

[0125] <Evaluation Test 2> 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 110±2°C, 125±3°C, 150±3°C, 175±3°C, 200±3°C, 225±4°C, 250±4°C, and 275±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 five times the equivalent circle diameter of a cross section perpendicular to the longitudinal direction of the electric wire 12, and the winding speed was 1 s. －１ The wire was wound twice around two locations at room temperature (FIG. 3). 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. A voltage of 1 kV was applied to the wire for 1 minute. The wire was then visually observed to determine whether the coating had been damaged. The heat resistance of the wire was evaluated based on the following evaluation criteria. The results are shown in the "Evaluation Test 2" column of Tables 17 and 18. The closer the evaluation result is to H', the better the heat resistance of the wire. Note that the heat resistance of the wire differs depending on the type of fluororesin in the first layer (in other words, depending on the composition of the first layer), and therefore, samples in which the resin listed in the "Composition" column of the "First Layer" column in Tables 11 and 12 was the same were compared. (Evaluation criteria) A': No breakdown of the coating when the temperature of the thermostatic bath is 110±2°C or lower B': No breakdown of the coating when the temperature of the thermostatic bath is 125±3°C or lower C': No breakdown of the coating when the temperature of the thermostatic bath is 150±3°C or lower D': No breakdown of the coating when the temperature of the thermostatic bath is 175±3°C or lower E': No breakdown of the coating when the temperature of the thermostatic bath is 200±3°C or lower F': No breakdown of the coating when the temperature of the thermostatic bath is 225±4°C or lower G': No breakdown of the coating when the temperature of the thermostatic bath is 250±4°C or lower H': No breakdown of the coating when the temperature of the thermostatic bath is 275±4°C or lower

[0126] <Evaluation Test 3> 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 for 6 hours in a thermostatic oven 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. Next, the electric wires were removed from the thermostatic oven 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 winding speed was 1 s. －１ The wire was wound twice at two locations at room temperature (FIG. 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 the coating had been broken. Next, the heat resistance of the wire was evaluated based on the following evaluation criteria. The obtained results are shown in the "Evaluation Test 3" column of Tables 17 and 18. The closer the evaluation result is to H", the better the heat resistance of the wire. Note that the heat resistance of electric wires varies depending on the type of fluororesin in the first layer (in other words, depending on the composition of the first layer), so a relative comparison was made between samples in which the same resin was listed in the "Composition" column of the "First Layer" column in Tables 11 and 12. (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

[0127] The electric wires according to Samples 1 to 19 correspond to Examples. The electric wires according to Samples 101 to 112 correspond to Comparative Examples. The results in Tables 17 and 18 show that the electric wires according to Samples 1 to 19 have superior heat resistance compared to the electric wires according to Samples 101 to 112.

[0128] From the above, it was found that the electric wires according to Samples 1 to 19 had excellent heat resistance.

[0129] 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.

[0130] 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.

[0131] 1 Electric wire, 2 Conductor, 3 First layer, 4 Second layer, 5 Coating, 11 Mandrel, 12 Electric wire, 13 Weight

Claims

1. An electric wire comprising a conductor and a coating covering the conductor, the coating including a first layer and a second layer formed on the first layer, the first layer including a fluororesin as a main component, the second layer including a silsesquioxane as a main component, and the silsesquioxane being (RSiO ３／２ ) as a constituent unit, R is a polymerizable group, and a thickness of the second layer is 0.1 μm or more and 100 μm or less.

2. The electric wire according to claim 1, wherein the fluororesin of the first layer is at least one fluororesin selected from the group consisting of perfluoroalkoxyalkane resin, fluorinated ethylene propylene resin, ethylene tetrafluoroethylene copolymer resin, and crosslinked ethylene tetrafluoroethylene copolymer resin.

3. The electric wire according to claim 1, wherein the fluororesin of the first layer is a resin modified with a first functional group, and the first functional group has a carboxyl group or an ether group.

4. The electric wire according to claim 3, wherein the first functional group is at least one functional group selected from the group consisting of a carboxyl group, a maleic anhydride group, and an epoxy group.

5. The electric wire according to claim 1, wherein the fluororesin of the first layer is a resin that has been subjected to a hydrophilic surface treatment.

6. The electric wire according to claim 5, wherein the hydrophilic surface treatment is at least one type of surface treatment selected from the group consisting of corona treatment, plasma treatment, ozone treatment, and etching treatment with active sodium.

7. The electric wire according to any one of claims 1 to 6, wherein the coating further includes a third layer formed between the first layer and the second layer, and the third layer includes a fluororesin as a main component.

8. The electric wire according to claim 7, wherein the fluororesin of the third layer is at least one fluororesin selected from the group consisting of perfluoroalkoxyalkane resin, fluorinated ethylene propylene resin, ethylene tetrafluoroethylene copolymer resin, and crosslinked ethylene tetrafluoroethylene copolymer resin.

9. The electric wire according to claim 7, wherein the fluororesin of the third layer is a resin modified with a second functional group, and the second functional group has a carboxyl group or an ether group.

10. The electric wire according to claim 9, wherein the second functional group is at least one functional group selected from the group consisting of a carboxyl group, a maleic anhydride group, and an epoxy group.

11. The electric wire according to any one of claims 1 to 10, wherein the polymerizable group is a radically polymerizable group or a cationic polymerizable group.

12. The electric wire according to any one of claims 1 to 10, wherein the polymerizable group is one type of polymerizable group selected from the group consisting of an acryloyl group, a methacryloyl group, and an oxetanyl group.

13. A multi-core cable comprising an electric wire according to any one of claims 1 to 12.

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