Resin composition and electrical wire

Abstract

This resin composition comprises a fluoropolymer as the primary ingredient. The heat of fusion of the resin composition is 2.0 J / g to 10.0 J / g. The stretch ratio of the resin composition is 10 or greater.

Description

Resin composition and electric wire

[0001] The present disclosure relates to a resin composition and an electric wire.

[0002] Conventionally, "electric wires having a conductor and a coating covering the conductor" have been used in automobiles and the like, and "resin compositions containing a fluoropolymer as a main component" have been used as the material for the coating (Patent Documents 1 to 4).

[0003] JP 2010-186585 A International Publication No. 2015 / 046176 JP 11-323053 A JP 2023-97077 A

[0004] The resin composition of the present disclosure is a resin composition containing a fluoropolymer as a main component, wherein the heat of fusion of the resin composition is 2.0 J / g or more and 10.0 J / g or less, and the elongation ratio of the resin composition is 10 times or more.

[0005] Fig. 1 is a schematic perspective view of an electric wire according to an embodiment of the present disclosure, and Fig. 2 is a schematic cross-sectional view taken along line II-II in Fig. 1.

[0006] [Problem to be Solved by the Present Disclosure] Electric wires including a conductor and a coating covering the conductor have been used in applications such as automobiles. When the coating is formed by extrusion molding, a resin composition containing a fluoropolymer as a main component is used to impart heat resistance and oil resistance to the coating. However, when a resin composition containing a fluoropolymer as a main component is used, increasing the flexibility of the resin composition can easily cause adhesion between any part of the formed coating and any other part of the coating, particularly when a thin film is formed by extrusion molding. The occurrence of this adhesion can reduce workability when using the electric wire, and when the adhered coatings peel off from each other, it can easily cause adverse effects such as poor appearance of the adhered surfaces and tearing of the coating. Therefore, there is a need to suppress the occurrence of this adhesion.

[0007] Furthermore, particularly when a thin film is formed by extrusion molding, the conductor is rapidly cooled during the extrusion molding, which tends to cause a temperature difference between the conductor side region of the coating and the surface side region of the coating, which can easily cause cracks in the coating. Therefore, there is a need to suppress the occurrence of cracks in the coating.

[0008] However, in conventional "resin compositions containing a fluoropolymer as a main component," it is necessary to blend a fluororubber into the resin composition in order to impart flexibility to the coating of an electric wire, and due to the properties of the fluororubber, it has sometimes been difficult to suppress both the occurrence of sticking and the occurrence of cracks in the coating, particularly when forming a thin film by extrusion molding.The present disclosure aims to provide a resin composition that, in the production of an electric wire including a conductor and a coating covering the conductor, can suppress the sticking of any part of the coating to any other part of the coating and can suppress the occurrence of cracks in the coating, and an electric wire including a coating that includes a layer made of the resin composition.

[0009] [Effects of the Present Disclosure] According to the present disclosure, in the manufacture of an electric wire including a conductor and a coating covering the conductor, it is possible to provide a resin composition that prevents any part of the coating from adhering to any other part of the coating and that makes it possible to suppress the occurrence of cracks in the coating, and an electric wire that includes a coating that includes a layer made of the resin composition.

[0010] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described. (1) A resin composition of the present disclosure is a resin composition containing a fluoropolymer as a main component, wherein the heat of fusion of the resin composition is 2.0 J / g or more and 10.0 J / g or less, and the elongation ratio of the resin composition is 10 times or more.

[0011] According to the present disclosure, in the manufacture of an electric wire including a conductor and a coating covering the conductor, it is possible to provide a resin composition that can prevent any part of the coating from adhering to any other part of the coating and prevent the occurrence of cracks in the coating, and an electric wire that has a coating that includes a layer made of the resin composition.

[0012] (2) In the above (1), the elastic modulus E1 of the resin composition at 25° C. may be 200 MPa or less, and a ratio E1 / E2 of the elastic modulus E1 of the resin composition at 25° C. to the elastic modulus E2 of the resin composition at 200° C. may be 25 or less. This makes it easier for the electric wire coated with the resin composition to maintain its routed state at room temperature.

[0013] (3) In the above (2), the resin composition may have a linear expansion coefficient C1 at 200° C. of 500 ppm / K or less, and a product C1×E2 of the linear expansion coefficient C1 at 200° C. and the elastic modulus E2 of the resin composition at 200° C. may be 4000 Pa / K or less. This makes it easier to prevent gaps from forming between a sealing part and the electric wire at high temperatures when the electric wire coated with the resin composition is attached to the sealing part.

[0014] (4) In the above (3), the linear expansion coefficient C2 of the resin composition at −40° C. may be 100 ppm / K or less. This makes it easier to prevent gaps from occurring between a sealing part and the electric wire at low temperatures when an electric wire coated with the resin composition is attached to the sealing part.

[0015] (5) In any one of the above (1) to (4), the volume resistivity of the resin composition at 200°C is 1 x 10 ９ The electrical resistance may be Ω·cm or more, which allows the resin composition to have good insulating properties even at high temperatures.

[0016] (6) In any of the above (1) to (5), the resin composition may further contain an inorganic filler, and the amount of the inorganic filler per 100 parts by mass of the fluoropolymer may be 10 parts by mass or more and 50 parts by mass or less. This makes it possible to provide a resin composition that, in the production of an electric wire including a conductor and a coating covering the conductor, can further suppress adhesion of any part of the coating to any other part of the coating and further suppress the occurrence of cracks in the coating, and an electric wire including a coating that includes a layer made of the resin composition.

[0017] (7) In the above (6), the specific surface area of ​​the inorganic filler is 0.3 m２ / g or more 50m ２ This makes it possible to provide a resin composition that, in the production of an electric wire including a conductor and a coating covering the conductor, can further suppress adhesion of any part of the coating to any other part of the coating and further suppress the occurrence of cracks in the coating, and an electric wire that is provided with a coating that includes a layer made of the resin composition.

[0018] (8) In the above (6) or (7), the inorganic filler may include a first inorganic filler, the mass ratio of the first inorganic filler to 100 mass parts of the fluoropolymer may be 5 mass parts or more, the first inorganic filler may be made of calcium carbonate, and the first inorganic filler may have an average particle size of 0.01 μm or more and 10 μm or less. This makes it possible to suppress a decrease in the insulating properties of the resin composition due to thin-wall molding of the resin composition.

[0019] (9) In any of the above (1) to (8), the fluoropolymer may be made of a fluororesin and a fluororubber. This makes it possible to further prevent any part of the coating from adhering to any other part of the coating and to further prevent cracks from occurring in the coating in the production of an electric wire including a conductor and a coating covering the conductor.

[0020] (10) In the above item (9), the ratio of the fluororesin to 100 parts by mass of the fluoropolymer may be 20 parts by mass or more and 40 parts by mass or less. This makes it possible, in the production of an electric wire including a conductor and a coating covering the conductor, to further prevent any part of the coating from adhering to any other part of the coating and to further prevent cracks from occurring in the coating.

[0021] (11) In the above (9) or (10), the fluororesin may be an ethylene-tetrafluoroethylene copolymer, and the fluororubber may be a tetrafluoroethylene-propylene copolymer. This makes it possible to provide a resin composition that, in the production of an electric wire including a conductor and a coating covering the conductor, can further suppress adhesion of any part of the coating to any other part of the coating and further suppress cracking of the coating, and an electric wire equipped with a coating including a layer made of the resin composition.

[0022] (12) In any one of the above (1) to (11), the resin composition may further contain an acrylic resin, the weight-average molecular weight of the acrylic resin being 800,000 or more and 4,500,000 or less, and the parts by mass of the acrylic resin per 100 parts by mass of the fluoropolymer being 0.5 parts by mass or more and 8 parts by mass or less. This makes it possible to further suppress cracking of the coating in the production of an electric wire including a conductor and a coating covering the conductor.

[0023] (13) In any of the above (1) to (12), the fluoropolymer may be crosslinked. This can further prevent any part of the coating from adhering to any other part of the coating in the production of an electric wire including a conductor and a coating covering the conductor. It can also improve the shape retention of the resin composition at temperatures above the melting point of the fluororesin. It can also improve the oil resistance of the resin composition.

[0024] (14) 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, the first layer is located on a surface of the coating, and the first layer is made of a resin composition described in (1) to (13) above.

[0025] According to the present disclosure, in the manufacture of an electric wire including a conductor and a coating covering the conductor, it is possible to provide an electric wire including a coating that includes a layer made of a resin composition that can prevent any part of the coating from adhering to any other part of the coating and can prevent the occurrence of cracks in the coating.

[0026] (15) In the above (14), the surface roughness Sa of the first layer may be 0.1 μm or more and 15 μm or less, thereby reducing friction between the electric wire and another member in an environment where the electric wire comes into contact with the other member.

[0027] [Details of the embodiment of the present disclosure] Specific examples of a resin composition and 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.

[0028] 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.

[0029] 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.

[0030] [Embodiment 1: Resin Composition] A resin composition according to one embodiment of the present disclosure will be described. One embodiment of the present disclosure (hereinafter also referred to as "the present embodiment") is a resin composition containing a fluoropolymer as a main component, wherein the heat of fusion of the resin composition is 2.0 J / g or more and 10.0 J / g or less, and the elongation ratio of the resin composition is 10 times or more.

[0031] According to the present disclosure, in the manufacture of an electric wire including a conductor and a coating covering the conductor, it is possible to provide a resin composition that can prevent any part of the coating from adhering to any other part of the coating and prevent the coating from cracking, and an electric wire that has a coating that includes a layer made of the resin composition. The reason for this is presumed to be as follows.

[0032] (a) In the resin composition of this embodiment, the heat of fusion of the resin composition is 2.0 J / g or more and 10.0 J / g or less. This suppresses molecular motion of the fluoropolymer due to the crystals, and therefore, in the production of an electric wire including a conductor and a coating covering the conductor, it is possible to suppress adhesion of any part of the coating to any other part of the coating.

[0033] (b) In the resin composition of the present embodiment, the elongation ratio of the resin composition is 10 or more. This makes it easier to suppress breakage of the insulator during extrusion molding (in other words, the first layer according to the second embodiment) due to strain caused by a temperature difference between the interface on the conductor side according to the second embodiment and the surface of the first layer according to the second embodiment. Therefore, in the production of an electric wire including a conductor and a coating covering the conductor, it is possible to suppress cracking of the coating.

[0034] <Heat of Fusion> The heat of fusion of the resin composition is 2.0 J / g or more and 10.0 J / g or less. This makes it possible to prevent any part of the coating from adhering to any other part of the coating in the production of an electric wire including a conductor and a coating covering the conductor. The heat of fusion of the resin composition may be 2.3 J / g or more and 9.2 J / g or less, 3.0 J / g or more and 9.0 J / g or less, 4.0 J / g or more and 8.0 J / g or less, or 5.0 J / g or more and 6.0 J / g or less.

[0035] The heat of fusion of a resin composition can be determined by the following method. 5 mg of the resin composition is heated in a nitrogen atmosphere from -50°C to 300°C at a heating rate of 10°C / min using a differential scanning calorimeter, and the sum of the areas of all endothermic peaks that appear at or above 100°C is determined as the heat of fusion of the resin composition. When the peak is multimodal, the sum of the areas of all the peaks is determined as the heat of fusion of the resin composition.

[0036] <Elongation ratio> The elongation ratio of the resin composition is 10 times or more. This makes it possible to suppress cracking of the coating during the production of an electric wire including a conductor and a coating covering the conductor. The lower limit of the elongation ratio of the resin composition may be 10 times or more, 15 times or more, or 25 times or more. The upper limit of the elongation ratio of the resin composition may be 100 times or less, 90 times or less, 80 times or less, or 45 times or less. The elongation ratio of the resin composition may be 10 times or more and 100 times or less, 15 times or more and 90 times or less, or 25 times or more and 80 times or less.

[0037] The elongation ratio of a resin composition can be determined by the following method. The resin composition is heated to 260°C, pressurized by a cylinder, and extruded through a die attached to the cylinder so that the resin composition takes the shape of a strand. The resin composition is continuously taken up by a take-up roller while being extruded from the die. While the resin composition is being extruded, the take-up linear speed during take-up is increased from 5 m / min, and the take-up linear speed at which the resin composition breaks is recorded. Next, the elongation ratio of the resin composition can be determined by calculating the following equation 1 based on the take-up linear speed at which the resin composition breaks, the cylinder speed (i.e., the value obtained by dividing the flow rate of the resin composition in the cylinder at which the resin composition breaks by the cross-sectional area of ​​the cylinder), the cylinder inner radius DC, and the die hole diameter DD. Elongation ratio = (DD) ２ ÷ [(DC) ２ × (cylinder speed) ÷ (pulling wire speed at break)] Formula 1

[0038] <Elastic Modulus> The elastic modulus E1 of the resin composition at 25°C may be 200 MPa or less. This makes the resin composition flexible, making it easier to route an electric wire coated with the resin composition. The elastic modulus E1 of the resin composition at 25°C may be 10 MPa or more and 200 MPa or less, 10 MPa or more and 191 MPa or less, 20 MPa or more and 150 MPa or less, or 50 MPa or more and 100 MPa or less.

[0039] The elastic modulus E1 of the resin composition at 25°C can be measured by a method conforming to the dynamic mechanical property test method described in JIS K7244-4:1999. More specifically, the elastic modulus E1 (in other words, the storage modulus) of the resin composition at 25°C is measured using a viscoelasticity measuring device under the conditions of tensile mode, strain of 0.08%, and frequency of 10 Hz. As the viscoelasticity measuring device, for example, "DVA-220" (trademark) manufactured by IT Measurement & Control Co., Ltd. can be used.

[0040] The elastic modulus E2 of the resin composition at 200°C may be 0.1 MPa or more and 15 MPa or less. When the elastic modulus E2 is 0.1 MPa or more, in the production of an electric wire including a conductor and a coating covering the conductor, adhesion of any part of the coating to any other part of the coating can be further suppressed. Furthermore, when the elastic modulus E2 is 15 MPa or less, cracking of the coating can be further suppressed. The elastic modulus E2 of the resin composition at 200°C may be 0.4 MPa or more and 13 MPa or less, or may be 1 MPa or more and 10 MPa or less.

[0041] The elastic modulus E2 of the resin composition at 200°C can be determined in the same manner as the measurement method for the "elastic modulus E1 of the resin composition at 25°C", except that the measurement is performed after the resin composition is heated from 25°C to 200°C at a heating rate of 10°C / min.

[0042] The ratio E1 / E2 of the elastic modulus E1 of the resin composition at 25°C to the elastic modulus E2 of the resin composition at 200°C may be 25 or less. This makes it possible to minimize changes in the flexibility of the resin composition due to temperature changes, making it easier to maintain an installed state of an electric wire coated with the resin composition at room temperature. The ratio E1 / E2 may be 1 or more and 25 or less, 3 or more and 25 or less, 5 or more and 20 or less, or 7 or more and 20 or less.

[0043] <Linear Expansion Coefficient> The linear expansion coefficient C1 of the resin composition at 200°C may be 500 ppm / K or less. This can prevent gaps from forming between a sealing component and the electric wire at high temperatures when an electric wire coated with the resin composition is attached to the sealing component. The lower limit of the linear expansion coefficient C1 of the resin composition at 200°C may be 100 ppm / K or more, 150 ppm / K or more, 200 ppm / K or more, or 280 ppm / K or more. The upper limit of the linear expansion coefficient C1 of the resin composition at 200°C may be 500 ppm / K or less, 475 ppm / K or less, 450 ppm / K or less, or 400 ppm / K or less. The linear expansion coefficient C1 of the resin composition at 200°C may be 100 ppm / K or more and 500 ppm / K or less, 150 ppm / K or more and 450 ppm / K or less, or 200 ppm / K or more and 400 ppm / K or less.

[0044] The linear expansion coefficient C1 of the resin composition at 200°C can be determined by the following method: It is measured in tension mode under the conditions of a temperature range of 25°C to 200°C, a heating rate of 10°C / min, a frequency of 10 Hz, and a strain of 0.08%, using a viscoelasticity measuring device (for example, "DVA-220" (trademark) manufactured by IT Measurement & Control Co., Ltd.), based on the dimensional change of a thin plate with respect to a temperature change, in accordance with the test method for dynamic mechanical properties described in JIS-K7244-4 (1999).

[0045] The linear expansion coefficient C2 of the resin composition at -40°C may be 100 ppm / K or less. This makes it possible to suppress the occurrence of gaps between a sealing component and an electric wire at low temperatures when an electric wire coated with the resin composition is attached to the sealing component. The lower limit of the linear expansion coefficient C2 of the resin composition at -40°C may be 5 ppm / K or more, 10 ppm / K or more, 11 ppm / K or more, or 15 ppm / K or more. The upper limit of the linear expansion coefficient C2 of the resin composition at -40°C may be 100 ppm / K or less, or 95 ppm / K or less. The linear expansion coefficient C2 of the resin composition at -40°C may be 5 ppm / K or more and 100 ppm / K or less, 10 ppm / K or more and 100 ppm / K or less, or 15 ppm / K or more and 100 ppm / K or less.

[0046] The linear expansion coefficient C2 of the resin composition at -40°C can be determined by a method similar to the measurement method for the "linear expansion coefficient C1 of the resin composition at 200°C", except that the temperature range is from -40°C to 25°C.

[0047] <Product of Linear Expansion Coefficient C1 and Elastic Modulus E2> The product C1 × E2 of the linear expansion coefficient C1 of the resin composition at 200°C and the elastic modulus E2 of the resin composition at 200°C may be 4000 Pa / K or less. This makes it possible to suppress the occurrence of gaps between a sealing component and an electric wire coated with the resin composition at high temperatures when the electric wire is attached to the sealing component. The lower limit of the product C1 × E2 may be 50 Pa / K or more, 100 Pa / K or more, 150 Pa / K or more, or 186 Pa / K or more. The upper limit of the product C1 × E2 may be 4000 Pa / K or less, 3926 Pa / K or less, 3500 Pa / K or less, or 3000 Pa / K or less. The product C1×E2 may be 50 Pa / K or more and 4000 Pa / K or less, 100 Pa / K or more and 3500 Pa / K or less, or 150 Pa / K or more and 3000 Pa / K or less.

[0048] <Volume resistivity> The volume resistivity of the resin composition at 200°C is 1 × 10 ９The volume resistivity of the resin composition at 200°C may be 1 × 10 or more. This allows the resin composition to have good insulating properties even at high temperatures. ９ It may be Ω cm or more, and may be 1×10 １０ It may be Ω cm or more, and may be 1×10 １１ The upper limit of the volume resistivity of the resin composition at 200°C is 1 × 10 １６ It may be Ω cm or less, and may be 1×10 １５ It may be Ω cm or less, and may be 1×10 １４ Ω cm or less, and may be 9×10 １１ The volume resistivity of the resin composition at 200°C may be 1×10 ９ Ω・cm or more 1×10 １６ It may be Ω cm or less, and may be 1×10 １０ Ω・cm or more 1×10 １５ It may be Ω cm or less, and may be 1×10 １１ Ω・cm or more 1×10 １４ It may be Ω·cm or less.

[0049] The volume resistivity of the resin composition at 200°C can be determined by the following method. First, a press sheet measuring φ150 mm x 1 mm thick is prepared from the resin composition as a test sample using a heat press. Next, the electrical resistance of the press sheet is measured using the double ring electrode method defined in JIS-K6271:2008 in a thermostatic chamber heated to 200°C. Next, the volume resistivity of the resin composition at 200°C can be determined by calculating the volume resistivity based on the measured electrical resistance.

[0050] <Composition> <Inorganic Filler> The resin composition may further contain an inorganic filler, and the mass ratio of the inorganic filler relative to 100 parts by mass of the fluoropolymer may be 10 parts by mass or more and 50 parts by mass or less. This makes it easier to adjust the heat of fusion of the resin composition and the elongation ratio of the resin composition within the desired range. Therefore, in the production of an electric wire including a conductor and a coating covering the conductor, adhesion of any part of the coating to any other part of the coating can be more effectively prevented, and cracking of the coating can be more effectively prevented. The mass ratio of the inorganic filler relative to 100 parts by mass of the fluoropolymer may be 15 parts by mass or more and 40 parts by mass or less, 18 parts by mass or more and 35 parts by mass or less, or 20 parts by mass or more and 30 parts by mass or less. The material of the inorganic filler is not particularly limited, and examples of inorganic filler materials include calcium carbonate and zinc oxide. In the present disclosure, when the fluoropolymer is crosslinked, the mass ratio of the fluoropolymer refers to the mass ratio of the fluoropolymer before crosslinking.

[0051] In the resin composition, the parts by mass of the inorganic filler relative to 100 parts by mass of the fluoropolymer can be determined by fluorescent X-ray analysis.

[0052] The specific surface area of ​​the inorganic filler is 0.3 m ２ / g or more 50m ２ / g or less. This makes it easier to set the elongation ratio of the resin composition within a desired range, and in the production of an electric wire including a conductor and a coating covering the conductor, it is possible to further suppress adhesion of any part of the coating to any other part of the coating, and to further suppress the occurrence of cracks in the coating. ２ / g or more 30m ２ / g or less, and ２ / g or more 20m ２ / g or less, and ２ / g or more 10m ２ / g or less.

[0053] The specific surface area of ​​the inorganic filler is 0.3 m ２ / g or more 50m ２ / g or less" makes it easier to keep the elongation ratio of the resin composition within the desired range. This is presumably because the fluoropolymer and inorganic filler in a molten state interact with each other, making it easier to improve the elongation ratio of the resin composition.

[0054] The specific surface area of ​​the inorganic filler in the resin composition can be determined by the following method. For example, first, the resin composition is heated at 600°C for 10 minutes to decompose the fluoropolymer and extract the inorganic filler. Next, the specific surface area of ​​the inorganic filler is measured using the Brunauer Emmett Teller (BET) method specified in JIS-K8830:2013.

[0055] The inorganic filler may include a first inorganic filler, and the mass ratio of the first inorganic filler per 100 parts by mass of the fluoropolymer may be 5 parts by mass or more. The first inorganic filler may be calcium carbonate, and the average particle size of the first inorganic filler may be 0.01 μm or more and 10 μm or less. This makes it possible to suppress a decrease in the insulating properties of the resin composition due to thin-wall molding of the resin composition. The mass ratio of the first inorganic filler per 100 parts by mass of the fluoropolymer may be 5 parts by mass or more and 45 parts by mass or less, 10 parts by mass or more and 45 parts by mass or less, 15 parts by mass or more and 40 parts by mass or less, or 20 parts by mass or more and 30 parts by mass or less.

[0056] The parts by mass of the first inorganic filler relative to 100 parts by mass of the fluoropolymer can be determined by fluorescent X-ray analysis.

[0057] <Fluoropolymer> The resin composition contains a fluoropolymer as a main component. This can improve the heat resistance of the coating when producing an electric wire including a conductor and a coating covering the conductor. Here, "containing a fluoropolymer as a main component" means that the resin composition contains 60% by mass or more of the fluoropolymer. The content of the fluoropolymer in the resin composition may be 65.4% by mass or more. In the present disclosure, when the fluoropolymer is crosslinked, the content of the fluoropolymer in the resin composition means the content of the fluoropolymer in the resin composition before crosslinking.

[0058] The fluoropolymer content in the resin composition can be determined by the following method. First, the fluorine atom concentration [mass%] of the resin composition is measured by combustion ion chromatography. Next, the mass ratio of each polymer constituting the fluoropolymer is determined by solid-state NMR. Based on the fluorine atom concentration and the mass ratio, the fluoropolymer content in the resin composition is calculated.

[0059] The fluoropolymer may be composed of a fluororesin and a fluororubber. This makes it possible to further prevent any part of the coating from adhering to any other part of the coating in the production of an electric wire including a conductor and a coating covering the conductor, and to further prevent cracks from occurring in the coating. The fluororubber improves the flexibility of the resin composition, and therefore contributes to preventing cracks from occurring in the coating. The fluororesin contributes to preventing the above-mentioned adhesion.

[0060] When the fluoropolymer is composed of a fluororesin and a fluororubber, the mass ratio of the fluororesin per 100 parts by mass of the fluoropolymer may be 20 to 40 parts by mass. This allows the resin composition to contain a good balance of the fluororubber, which contributes to the flexibility of the resin composition, and the fluororesin, which contributes to the suppression of cracking in the coating. This makes it easier to adjust the heat of fusion of the resin composition and the elongation ratio of the resin composition within the desired range. In the production of an electric wire comprising a conductor and a coating covering the conductor, this can further suppress adhesion of any part of the coating to any other part of the coating and further suppress cracking in the coating. Furthermore, this can further improve the flexibility of the resin composition, particularly at room temperature, and can further suppress cracking in the coating at room temperature. The mass ratio of the fluororesin per 100 parts by mass of the fluoropolymer may be 25 to 38 parts by mass, or may be 30 to 35 parts by mass.

[0061] The parts by mass of the fluororesin relative to 100 parts by mass of the fluoropolymer and the parts by mass of the fluororubber relative to 100 parts by mass of the fluoropolymer can each be determined by solid-state NMR (Nuclear Magnetic Resonance) measurement.

[0062] Examples of the fluororesin include at least one resin selected from the group consisting of ethylene tetrafluoroethylene copolymer (hereinafter also referred to as "ETFE"), polyvinylidene fluoride (hereinafter also referred to as "PVDF"), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and perfluoroalkoxyalkane (PFA).

[0063] The fluororesin may be an ethylene tetrafluoroethylene copolymer. This makes it possible to provide a resin composition that, in the production of an electric wire including a conductor and a coating covering the conductor, can further suppress adhesion of any part of the coating to any other part of the coating and further suppress the occurrence of cracks in the coating, and an electric wire equipped with a coating including a layer made of the resin composition. Furthermore, in the production of an electric wire including a conductor and a coating covering the conductor, the use of this resin composition has the advantages of improving the heat resistance of the coating, improving the processability of the resin composition, and reducing the cost of the resin composition.

[0064] In the resin composition, the type of fluororesin can be identified using infrared spectroscopy (IR).

[0065] Examples of fluororubbers include at least one rubber selected from the group consisting of tetrafluoroethylene propylene copolymer (hereinafter also referred to as "TFE-P") and vinylidene fluoride-hexafluoropyrene-tetrafluoroethylene rubber.

[0066] The fluororubber may be a tetrafluoroethylene propylene copolymer. This can further prevent any part of the coating from adhering to any other part of the coating in the production of an electric wire including a conductor and a coating covering the conductor, and can further prevent the coating from cracking. Furthermore, in the production of an electric wire including a conductor and a coating covering the conductor, this has the advantages of improving the heat resistance of the coating, improving the processability of the resin composition, and reducing the cost of the resin composition.

[0067] In the resin composition, the type of fluororubber can be identified using infrared spectroscopy (IR).

[0068] The fluoropolymer may be crosslinked. This can further prevent any part of the coating from adhering to any other part of the coating in the production of an electric wire including a conductor and a coating covering the conductor. Furthermore, the shape retention of the resin composition at temperatures above the melting point of the fluororesin is improved. Furthermore, the oil resistance of the resin composition can be improved.

[0069] In a resin composition, the "fluoropolymer is crosslinked" can be determined by measuring the storage modulus of the resin composition using a method conforming to the dynamic mechanical property test method described in JIS K7244-4:1999 and confirming that the storage modulus is 0.1 MPa or greater at a temperature 20°C higher than the melting point of the fluororesin in the resin composition. More specifically, the "method conforming to the dynamic mechanical property test method" is performed using a viscoelasticity measuring device under the conditions of tensile mode, strain 0.08%, frequency 10 Hz, and heating rate 10°C / min. As the viscoelasticity measuring device, for example, the "DVA-220" (trademark) manufactured by IT Measurement & Control Co., Ltd. can be used.

[0070] <Acrylic Resin> The resin composition further contains an acrylic resin, and the weight-average molecular weight of the acrylic resin may be 800,000 or more and 4,500,000 or less, and the parts by mass of the acrylic resin per 100 parts by mass of the fluoropolymer may be 0.5 parts by mass or more and 8 parts by mass or less. This makes it easier to set the elongation ratio of the resin composition within a desired range, and in the production of an electric wire including a conductor and a coating covering the conductor, it is possible to further suppress the occurrence of cracks in the coating. The parts by mass of the acrylic resin per 100 parts by mass of the fluoropolymer may be 1 part by mass or more and 6 parts by mass or more, or 2 parts by mass or more and 4 parts by mass or less.

[0071] The reason why the resin composition further contains an acrylic resin, the weight-average molecular weight of which is 800,000 or more and 4,500,000 or less, and the ratio of the acrylic resin to 100 parts by mass of the fluoropolymer is 0.5 or more and 8 parts by mass or less is presumably because the molecular chains of the acrylic resin are more likely to become entangled with the molecular chains of the fluoropolymer when melted. When the weight-average molecular weight of the acrylic resin is less than 800,000, the molecular chains of the acrylic resin tend to become less likely to become entangled with the molecular chains of the fluoropolymer when melted. When the weight-average molecular weight of the acrylic resin is more than 4,500,000, the mechanical properties of the coating tend to deteriorate when an electric wire is manufactured having a conductor and a coating covering the conductor. When the ratio of the acrylic resin to 100 parts by mass of the fluoropolymer is less than 0.5 parts by mass, the effect of suppressing cracking of the coating tends to deteriorate when an electric wire is manufactured having a conductor and a coating covering the conductor. If the ratio of the acrylic resin to 100 parts by mass of the fluoropolymer exceeds 8 parts by mass, the heat resistance of the coating tends to decrease in the production of an electric wire having a conductor and a coating covering the conductor.

[0072] In the resin composition, the parts by mass of the acrylic resin relative to 100 parts by mass of the fluoropolymer can be determined by solid-state NMR measurement.

[0073] The acrylic resin may be, for example, at least one resin selected from the group consisting of methacrylic acid ester, acrylic acid ester, and methacrylic acid ester-acrylic acid ester copolymer.

[0074] <Other Components> The resin composition may further contain other components, such as a flame retardant, a flame retardant aid, an antioxidant, a lubricant, a colorant, a reflectivity imparting agent, an opacifying agent, a processing stabilizer, a plasticizer, a processing agent, a crosslinking agent, a crosslinking aid, and an acid acceptor.

[0075] <<Method for Producing Resin Composition>> The method for producing the resin composition according to this embodiment can be carried out in the same manner as a conventionally known method, except that the above components are blended so as to have the above content. For example, the mass parts of the fluororesin relative to 100 mass parts of the fluoropolymer are adjusted to 20 mass parts or more, and the mass ratio is 0.3 m ２ / g or more 50m ２ By using an inorganic filler having a specific surface area of ​​1 / g or less, the acrylic resin described in embodiment 1, or both, and adjusting the parts by mass of the inorganic filler to 50 parts by mass or less per 100 parts by mass of the fluoropolymer, a resin composition having both the desired heat of fusion and the desired elongation ratio can be obtained.

[0076] [Embodiment 2: Electric Wire] An electric wire according to an embodiment of the present disclosure will be described with reference to Fig. 1 and Fig. 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.

[0077] 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 covering the conductor 2, wherein the coating 5 includes a first layer 3, the first layer 3 is located on the surface of the coating 5, and the first layer 3 is made of the resin composition described in embodiment 1.

[0078] According to the present disclosure, in the manufacture of an electric wire including a conductor and a coating covering the conductor, it is possible to provide an electric wire including a coating including a layer made of a resin composition that can prevent any part of the coating from adhering to any other part of the coating and can prevent the coating from cracking, the reason for which is presumably as described in (a) and (b) of embodiment 1.

[0079] <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.

[0080] 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".

[0081] 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.

[0082] <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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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 ２ In 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.

[0088] <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. The first layer 3 is located on the surface of the coating 5.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] <First Layer> The first layer 3 is made of the resin composition described in embodiment 1. This makes it possible, in the production of an electric wire including a conductor and a coating covering the conductor, to prevent any part of the coating from adhering to any other part of the coating and to prevent the coating from cracking.

[0093] 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.

[0094] The thickness of the first layer 3 may be 0.025 mm or more and 10 mm or less. This makes it possible to make the electric wire 1 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.

[0095] 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.

[0096] 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.

[0097] The surface roughness Sa of the first layer 3 may be 0.1 μm or more and 15 μm or less. This reduces friction between the electric wire and other members in an environment where the electric wire comes into contact with the other members. The surface roughness Sa may be 0.1 μm or more and 13 μm or less, 0.1 μm or more and 10 μm or less, or 0.1 μm or more and 7.5 μm or less.

[0098] The surface roughness Sa of the first layer 3 can be measured using a LEXT OLS4100 laser microscope manufactured by Olympus Corporation, and the arithmetic mean roughness defined in ISO 25178 is defined as the surface roughness Sa of the first layer 3.

[0099] 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.

[0100] <Other Layers> The coating 5 may further include other layers. Examples of such other layers include an intermediate layer. The intermediate layer is a layer (not shown) located between the conductor 2 and the first layer 3.

[0101] <<Method for Manufacturing Electric Wire>> The method for manufacturing the electric wire 1 of the present embodiment can be carried out in the same manner as a conventionally known method, except that the resin composition described in embodiment 1 is used as the material for the first layer 3.

[0102] The present embodiment will be described in more detail with reference to examples, although the present embodiment is not limited to these examples.

[0103] <<Preparation of Resin Compositions>> Resin compositions according to Samples 1 to 22 and 101 to 104 were prepared as follows.

[0104] Mixtures were obtained by blending the components shown in Tables 3 to 8 (i.e., fluororubber, fluororesin, first inorganic filler, other inorganic fillers, acrylic resin, and other resins) to obtain the compositions shown in Tables 3 to 8. Next, the mixtures were kneaded for the times shown in Tables 1 and 2 using a pressure kneader heated to the temperatures shown in Tables 1 and 2, to prepare resin compositions for each sample. The components were prepared by purchasing commercially available products. In Tables 3 and 4, the first TFE-P represents a TFE-P having a specific gravity of 1.55, a Mooney viscosity ML1+10 (100°C) of 130, a glass transition point of -3°C, and no melting point. In Tables 3 and 4, the second TFE-P represents a TFE-P having a specific gravity of 1.55, a Mooney viscosity ML1+10 (121°C) of 120, a glass transition point of -3°C, and no melting point. In Tables 3 and 4, ETFE refers to an ethylene tetrafluoroethylene copolymer having a specific gravity of 1.78, a melt flow rate (MFR) of 25 g / 10 min, and a melting point of 225°C. In Table 3, PVDF refers to polyvinylidene fluoride having a specific gravity of 1.78, an MFR of 4 g / 10 min, and a melting point of 142°C. In Tables 5 and 6, zinc oxide refers to zinc oxide alone. In Table 8, the epoxy group-containing ethylene copolymer refers to an ethylene-methyl acrylate-glycidyl methacrylate copolymer (MFR: 7 g / 10 min, melting point: 52°C, specific gravity: 0.96). In Tables 7 and 8, "MAE" refers to a methacrylic acid ester, and "MAE-AAE copolymer" refers to a methacrylic acid ester-acrylic acid ester copolymer. The "parts by mass" of each component listed in Tables 3 to 8 means parts by mass relative to 100 parts by mass of the fluoropolymer.

[0105] <<Evaluation of Resin Composition Properties>> <Heat of Fusion> The heat of fusion of the resin composition of each sample was determined by the method described in Embodiment 1. The results obtained are shown in the “Heat of Fusion [J / g]” column of Tables 9 and 10.

[0106] <Elongation ratio> The elongation ratio of the resin composition for each sample was determined by the method described in embodiment 1. The obtained results are shown in the "Elongation ratio [times]" column of Tables 9 and 10.

[0107] <E1 and E2> The elastic modulus E1 of the resin composition for each sample was determined by the method described in embodiment 1. The results are shown in the "E1 [MPa]" column of Tables 9 and 10. The elastic modulus E2 of the resin composition for each sample was determined by the method described in embodiment 1. The results are shown in the "E2 [MPa]" column of Tables 9 and 10.

[0108] <C1 and C2> The linear expansion coefficient C1 of the resin composition for each sample was determined by the method described in embodiment 1. The results are shown in the "C1 [ppm / K]" column of Tables 9 and 10. The linear expansion coefficient C2 of the resin composition for each sample was determined by the method described in embodiment 1. The results are shown in the "C2 [ppm / K]" column of Tables 9 and 10.

[0109] <Volume Resistivity> The volume resistivity of the resin composition of each sample at 200°C was determined by the method described in Embodiment 1. The results obtained are shown in the "Volume Resistivity [Ω·cm]" column of Tables 9 and 10.

[0110] <<Preparation of Electric Wires>> Electric wires according to Samples 1 to 22 and 101 to 104 were prepared using the resin compositions according to the above-mentioned respective samples as follows.

[0111] First, a commercially available conductor was prepared. The conductor was a conductor wire having a cross section perpendicular to the longitudinal direction with a circular equivalent diameter of 1.8 mm and made of tin-plated copper.

[0112] Next, the resin composition of each sample was pressed into an extruder whose head was set to the temperature shown in Tables 1 and 2 and whose cylinder was set to the temperature shown in Tables 1 and 2. Next, the resin composition of each sample 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 resin composition of each sample was irradiated with an electron beam at a dose shown in Tables 1 and 2 to form a first layer (coating) on ​​the outer periphery of the conductor.

[0113] In this manner, electric wires according to Samples 1 to 22 and 101 to 104 were produced.

[0114] <Evaluation of Electric Wire Properties> <Surface Roughness Sa of First Layer> The surface roughness Sa of the first layer of each sample electric wire was determined by the method described in Embodiment 2. The obtained results are shown in the "Sa [μm]" column of Tables 11 and 12.

[0115] <Presence or Absence of Crosslinking> The presence or absence of crosslinking for the fluoropolymer of the resin composition 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 "Presence or Absence of Crosslinking" column in Tables 3 and 4.

[0116] <Presence or Absence of Cracks in First Layer> First, an 80x image was obtained using a microscope (Keyence Corporation's "VHX-8000" (trademark)) in a rectangular field of view of 3.75 mm x 2.80 mm at any one cross section of the outer circumferential surface of the first layer of each sample. Next, the presence or absence of cracks in the first layer was confirmed for that field of view on the outer circumferential surface of the first layer of each sample. Next, the presence or absence of cracks in the first layer was confirmed for 19 other cross sections of the outer circumferential surface of the first layer of each sample using the same method as above. Next, the degree of cracking in the first layer was evaluated based on the following evaluation criteria. The obtained results are shown in the "Crack Evaluation" column in Tables 11 and 12. An evaluation result of A or B means that the occurrence of cracks in the coating was suppressed. (Evaluation Criteria) A: No cracks in all 20 cross sections. B: Cracks present in one cross section. C: Cracks present in two or more cross sections.

[0117] <Presence or Absence of Sticking> First, two electric wires (length: 800 mm) for each sample were prepared. Next, each of the electric wires was wound 10 times around a mandrel (diameter: 20 mm). Next, one of the electric wires for each sample was left to stand at 25°C for 72 hours while wound around the mandrel. Similarly, the other electric wire for each sample was left to stand at 50°C for 72 hours while wound around the mandrel. Next, the electric wires were removed from the mandrel, and the presence or absence of sticking between any location on the coating (first layer) and any other location on the coating (first layer) was confirmed. Next, the degree of sticking between any location on the coating (first layer) and any other location on the coating (first layer) was evaluated based on the following evaluation criteria. The results obtained are shown in the "Stickness Evaluation" column of Tables 11 and 12. An evaluation result of A or B means that adhesion between any point on the coating and any other point on the coating was suppressed. (Evaluation Criteria) A: No adhesion at both 25°C and 50°C B: Adhesion at 50°C but not at 25°C C: Adhesion at both 25°C and 50°C

[0118]

[0119]

[0120]

[0121]

[0122]

[0123]

[0124]

[0125]

[0126]

[0127]

[0128]

[0129]

[0130] The electric wires of Samples 1 to 22 correspond to Examples. The electric wires of Samples 101 to 104 correspond to Comparative Examples. The results in Tables 11 and 12 show that the electric wires of Samples 1 to 22 exhibit superior effects to the electric wires of Samples 101 to 104 in that they suppress the occurrence of adhesion between any location of the coating and any other location of the coating and also suppress the occurrence of cracks in the coating.

[0131] From the above, it was found that in the electric wires according to samples 1 to 22, the occurrence of adhesion between any part of the coating and any other part of the coating was suppressed, and the occurrence of cracks in the coating was suppressed.

[0132] 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.

[0133] 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.

[0134] 1 Electric wire, 2 Conductor, 3 First layer, 5 Coating

Claims

1. A resin composition comprising a fluoropolymer as a main component, wherein the heat of fusion of the resin composition is 2.0 J / g or more and 10.0 J / g or less, and the elongation ratio of the resin composition is 10 times or more.

2. The resin composition according to claim 1, wherein the elastic modulus E1 of the resin composition at 25°C is 200 MPa or less, and the ratio E1 / E2 of the elastic modulus E1 of the resin composition at 25°C to the elastic modulus E2 of the resin composition at 200°C is 25 or less.

3. The resin composition according to claim 2, wherein the linear expansion coefficient C1 of the resin composition at 200°C is 500 ppm / K or less, and the product C1 x E2 of the linear expansion coefficient C1 of the resin composition at 200°C and the elastic modulus E2 of the resin composition at 200°C is 4000 Pa / K or less.

4. The resin composition according to claim 3, wherein the linear expansion coefficient C2 of the resin composition at -40°C is 100 ppm / K or less.

5. The volume resistivity of the resin composition at 200°C is 1 x 10 ９ The resin composition according to claim 1 , having a modulus of Ω·cm or more.

6. A resin composition according to any one of claims 1 to 5, wherein the resin composition further contains an inorganic filler, and the mass parts of the inorganic filler per 100 mass parts of the fluoropolymer is 10 mass parts or more and 50 mass parts or less.

7. The specific surface area of ​​the inorganic filler is 0.3 m ２ / g or more 50m ２ The resin composition according to claim 6, wherein the viscosity is 1000 kJ / g or less.

8. The resin composition according to claim 6 or 7, wherein the inorganic filler comprises a first inorganic filler, the mass parts of the first inorganic filler per 100 mass parts of the fluoropolymer are 5 mass parts or more, the first inorganic filler is made of calcium carbonate, and the average particle size of the first inorganic filler is 0.01 μm or more and 10 μm or less.

9. The resin composition according to any one of claims 1 to 8, wherein the fluoropolymer comprises a fluororesin and a fluororubber.

10. The resin composition according to claim 9, wherein the amount of the fluororesin per 100 parts by mass of the fluoropolymer is 20 parts by mass or more and 40 parts by mass or less.

11. The resin composition according to claim 9 or 10, wherein the fluororesin is an ethylene tetrafluoroethylene copolymer, and the fluororubber is a tetrafluoroethylene propylene copolymer.

12. A resin composition according to any one of claims 1 to 11, wherein the resin composition further contains an acrylic resin, the weight average molecular weight of the acrylic resin is 800,000 or more and 4,500,000 or less, and the parts by mass of the acrylic resin per 100 parts by mass of the fluoropolymer is 0.5 parts by mass or more and 8 parts by mass or less.

13. A resin composition according to any one of claims 1 to 12, wherein the fluoropolymer is crosslinked.

14. An electric wire comprising a conductor and a coating covering the conductor, wherein the coating includes a first layer, the first layer is located on the surface of the coating, and the first layer is made of a resin composition according to any one of claims 1 to 13.

15. The electric wire according to claim 14, wherein the surface roughness Sa of the first layer is 0.1 μm or more and 15 μm or less.

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