Electric wire manufacturing method, and electric wire

Abstract

To provide a manufacturing method capable of manufacturing an electric wire having a coating layer with a uniform thickness, which maintains a uniformity of the coating layer thickness even when heated.SOLUTION: There is provided a manufacturing method for an electric wire having a conductor and a coating layer containing a thermoplastic resin by using an extruder equipped with a cylinder, a screw, a nipple and a die, the method comprising: forming the coating layer by coating with the thermoplastic resin in the die on the conductor that is fed through a nipple passageway in the die; directly contacting the conductor with the thermoplastic resin with each other in the die; and controlling a ratio (L2 / D) of a distance L2 that is a smallest cross-sectional area and that is a part parallel to the die with a maximum length D of an opening of the die into 4.0 or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing an electric wire and an electric wire. [Background technology]

[0002] Patent document 1 describes an electric cable including a metal conductor and a fluoropolymer insulation surrounding and directly adhering to the metal conductor, wherein the fluoropolymer insulation has a recrystallized region at the interface with the conductor and a non-recrystallized region on the opposite side to the recrystallized region. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2016-516608 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present disclosure is to provide a manufacturing method capable of manufacturing an electric wire having a coating layer with a uniform thickness, in which the uniformity of the thickness of the coating layer is maintained even when heated. Another object of the present disclosure is to provide an electric wire in which the thickness of the coating layer remains uniform even when heated. [Means for solving the problem]

[0005] According to the present disclosure, there is provided a method for manufacturing an electric wire using an extrusion molding machine equipped with a cylinder, a screw, a nipple, and a die to manufacture an electric wire having a coating layer containing a conductor and a thermoplastic resin, wherein the coating layer is formed by coating the thermoplastic resin in the die on the conductor fed out from a passage opening of the nipple contained in the die, and the conductor and the thermoplastic resin are in direct contact with each other in the die, and the ratio (L2 / D) of the distance L2 between the part of the die that has the smallest cross-sectional area and is parallel to the part of the die, to the maximum length D of the opening of the die, is 4.0 or more. [Effects of the Invention]

[0006] According to the present disclosure, it is possible to provide a manufacturing method capable of manufacturing an electric wire having a coating layer with a uniform thickness, in which the uniformity of the thickness of the coating layer is maintained even when heated. Furthermore, according to the present disclosure, it is possible to provide an electric wire in which the thickness of the coating layer remains uniform even when heated. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a nipple and a die. [Figure 2] FIG. 2 is a schematic diagram for explaining the maximum length D of the opening of the die. [Figure 3] FIG. 3 is a cross-sectional view showing an example of a nipple and a die. DETAILED DESCRIPTION OF THE INVENTION

[0008] Specific embodiments of the present disclosure will be described in detail below, but the present disclosure is not limited to the following embodiments.

[0009] Patent Document 1 describes a method for forming the insulating material of the above-mentioned electric cable, in which a molten fluoropolymer is extruded in the form of a cylinder through an extrusion die, and the cylinder of the molten fluoropolymer is made into a cone shape by vacuum drawing down, and the molten fluoropolymer is brought into contact with a conductor.

[0010] However, when a coating layer is formed by processing a polymer by melt drawdown extrusion, the coating layer tends to shrink when the molten polymer is brought into contact with a conductor and then cooled and solidified, resulting in a problem of uneven thickness of the coating layer.Furthermore, after the electric wire is manufactured, when the electric wire is heated during use, the coating layer tends to shrink, resulting in a problem of uneven thickness of the coating layer.

[0011] The manufacturing method of the present disclosure successfully solves these problems by using a die having a specific shape in the extrusion molding of the thermoplastic resin to form the coating layer, and the manufacturing method of the present disclosure makes it possible to manufacture an electric wire having a coating layer with a uniform thickness, which maintains its uniform thickness even when heated.

[0012] Furthermore, the electric wire of the present disclosure has a ratio of scattering intensity (longitudinal direction) to scattering intensity (horizontal axis direction) of 3.0 or less, which results in a coating layer with a uniform thickness that is maintained even when heated. Such an electric wire can be suitably manufactured by using the manufacturing method of the present disclosure.

[0013] Next, the manufacturing method and the electric wire of the present disclosure will be described in more detail.

[0014] (Manufacturing method) In the method for producing an electric wire according to the present disclosure, an extruder equipped with a cylinder, a screw, a nipple, and a die is used to produce an electric wire having a conductor and a coating layer containing a thermoplastic resin.

[0015] The manufacturing method of the present disclosure uses an extruder in which the tip of a nipple is housed in a die, and using this extruder, a conductor is fed through a nipple passage hole housed in the die and coated with molten thermoplastic resin inside the die.

[0016] Furthermore, in the manufacturing method of the present disclosure, the ratio (L2 / D) of the distance L2 between the smallest cross-sectional area and parallel dies to the maximum length D of the die opening is set to 4.0 or more, which makes it possible to manufacture an electric wire having a coating layer with a uniform thickness that remains uniform even when heated.

[0017] Length L2 is the length of land portion 16, i.e., the length of the portion of die 14 that has the smallest cross-sectional area and is parallel. FIG. 1 shows an example of a nipple and die provided in an extrusion molding machine for forming a coating layer on a conductor having a substantially circular cross section. The tip of nipple 11 shown in FIG. 1 is provided with a passage 12 for discharging conductor 13. The tip (passage 12) of nipple 11 shown in FIG. 1 is housed within die 14. Conductor 13 discharged from passage 12 of nipple 11 merges with molten thermoplastic resin in gently sloping conical gap 15, then passes through parallel land portions 16 of a constant diameter, and is discharged from die 14 through die opening 17. In the die shown in FIG. 1, length L1 is the distance from the tip of nipple (passage 12) to die opening 17.

[0018] The maximum length D of the die opening 17 is the longest opening length of the die opening, as shown in Figure 2. If the die opening is circular, as shown in Figure 2(a), the maximum length D is equal to the diameter of the circle. If the die opening is rectangular, as shown in Figure 2(b), the maximum length D is equal to the length of the diagonal of the rectangle. If the die opening is triangular, as shown in Figure 2(c), the maximum length D is equal to the length of the longest side of the triangle.

[0019] The diagram shown in Figure 2(a) schematically shows the cross section of an electric wire obtained when a die having an opening with a maximum length D is used to form a coating layer 14 having a circular cross section on a conductor 13 having a circular cross section. The diagram shown in Figure 2(b) schematically shows the cross section of an electric wire obtained when a die having an opening with a maximum length D is used to form a coating layer 14 having a rectangular cross section on a conductor 13 having a rectangular cross section. The diagram shown in Figure 3(c) schematically shows the cross section of an electric wire obtained when a die having an opening with a maximum length D is used to form a substantially triangular coating layer 21 on a conductor 13 having a substantially triangular cross section.

[0020] The ratio (L2 / D) of the distance L2 between the smallest cross-sectional area and parallel parts of the die to the maximum length D of the die opening is 4.0 or more, preferably 10 or more, more preferably 20 or more, even more preferably 30 or more, and preferably 150 or less, more preferably 125 or less, even more preferably 100 or less.

[0021] When the cross section of the electric wire is approximately circular, the ratio of L2 to D (L2 / D) is preferably 20 or more, more preferably 40 or more, even more preferably 80 or more, and preferably 150 or less, more preferably 125 or less.

[0022] When the cross section of the electric wire is approximately rectangular, the ratio of L2 to D (L2 / D) is preferably 20 or more, more preferably 30 or more, and preferably 50 or less, more preferably 40 or less.

[0023] In this way, by providing a parallel portion at the tip of the die that is long enough relative to the maximum length of the die opening, it is possible to produce an electric wire having a coating layer with a uniform thickness, and the uniformity of the coating layer thickness can be maintained even when heated. The reason for this is unclear, but it is presumed as follows: When a coating layer is formed by processing a polymer through melt draw-down extrusion, as in the manufacturing method described in Patent Document 1, the resin is likely to be stretched in the longitudinal direction of the electric wire, i.e., the direction in which the thermoplastic resin flows (MD), and thus oriented. As a result, the longitudinal length of the electric wire shrinks more than in the transverse direction of the electric wire, i.e., the direction perpendicular to the direction in which the thermoplastic resin flows (TD). On the other hand, when an electric wire is manufactured using the manufacturing method disclosed herein, the thermoplastic resin remains molten in the die for a relatively long time, which relieves stress acting on the resin. Therefore, even when the thermoplastic resin is extruded to form a coating layer on the conductor, excessive stretching stress due to the draw-down is not applied, and it is presumed that the orientation of the resin in the coating layer is likely to be relaxed.

[0024] In the die shown in Figure 1, the conductor 13 fed out from the tip of the nipple (passage opening 12) meets with the molten thermoplastic resin in a conical gap 15. Alternatively, as shown in Figure 3, the tip of the nipple 11 may be provided with a parallel tubular section 31 of a constant diameter through which the conductor 13 passes. In the die 14 shown in Figure 3, the conductor 13 fed out from the tip of the nipple meets with the molten thermoplastic resin in a land section 16 of the die. In the die 14 shown in Figure 3, the length L1 and the length L2 are the same (L1 = L2).

[0025] In one embodiment, the tip of the nipple is accommodated in the die so that length L1 is longer than length L2 (L1>L2). As a result, as shown in Figure 1, conductor 13 fed from the tip of the nipple (passage opening 12) meets the molten thermoplastic resin in the sloped gap 15. This configuration makes it possible to produce an electric wire having a coating layer with a more uniform thickness, which is better maintained even when heated, and further improves the adhesion between the conductor and the coating layer.

[0026] Furthermore, by making length L1 10 mm or more longer than length L2, the adhesion between the conductor and the coating layer can be further improved. The difference between length L1 and length L2 (L1-L2) is preferably 10 mm or more, more preferably 20 mm or more, even more preferably 30 mm or more, and preferably 60 mm or less, more preferably 50 mm or less, and even more preferably 40 mm or less.

[0027] The length L1 is preferably 40 mm or more, more preferably 50 mm or more, even more preferably 80 mm or more, and preferably 180 mm or less.

[0028] The length L2 is preferably 5 mm or more, more preferably 20 mm or more, even more preferably 50 mm or more, and preferably 150 mm or less.

[0029] When the cross section of the electric wire is approximately circular, the maximum length D is preferably 0.4 mm or more, more preferably 0.8 mm or more, and preferably 2.0 mm or less, more preferably 1.5 mm or less.

[0030] When the cross section of the electric wire is approximately rectangular, the maximum length D is preferably 2.0 mm or more, more preferably 3.0 mm or more, and preferably 5.0 mm or less, more preferably 4.0 mm or less.

[0031] In one embodiment, the gradient angle of the flow path of the thermoplastic resin in the die is 45° or less. The gradient angle of the flow path of the thermoplastic resin in the die refers to the angle of the gradient provided in the gently sloping gap 15 in the die of the extruder. In the die 14 shown in FIG. 1, the gradient angle is angle (θ). On the other hand, the gradient angle of the land portion 16 shown in FIG. 1 is 0°. However, a gradient angle necessary for manufacturing the die is also acceptable for the land portion 16. For example, a gradient angle of less than 5° is acceptable. The shape of the gap where the gradient is provided may be a cone, a pyramid, or the like.

[0032] The slope angle is preferably 45° or less, more preferably 40° or less, even more preferably 35° or less, preferably greater than 0°, more preferably 5° or more, even more preferably 10° or more, and even more preferably 15° or more.

[0033] By providing a gradual gradient toward the opening of the thermoplastic resin flow path in the die, it is possible to produce an electric wire with a coating layer having a more uniform thickness, and whose thickness uniformity is better maintained even when heated. The reason for this is not clear, but it is presumed that if the gradient angle is too large, a large shear stress is applied to the molten thermoplastic resin along the wall of the cavity in the die, whereas if the gradient angle is set within the above range, excessive shear stress is not applied to the molten thermoplastic resin.

[0034] The extrusion molding machine is not particularly limited as long as it has a die having the above-mentioned specific shape, but an extrusion molding machine having a cylinder, a screw, a nipple and a die can be used.

[0035] In one embodiment, a crosshead die is used as the die. By feeding the molten thermoplastic resin while passing the conductor through the crosshead die, it is possible to apply an appropriate and uniform pressure to the molten thermoplastic resin. This allows the production of an electric wire having a coating layer with a more uniform thickness, which maintains its thickness even when heated.

[0036] In one embodiment, from the viewpoint of uniforming the viscosity of the resin pressure or from the viewpoint of the degassing effect, a screw having a compression ratio of 2.0 to 4.0, preferably 2.5 to 3.5, and more preferably 2.8 to 3.2 is used. The compression ratio is the ratio of the spatial volume per screw in the feed section of the screw located directly below the hopper of the extrusion molding machine to the spatial volume per screw in the metering section (tip) of the screw. By using a screw having a compression ratio within the above range, the viscosity of the molten resin in the extruder becomes uniform, the resin pressure applied to the crosshead becomes constant, and an electric wire can be produced that has a coating layer with a more uniform thickness and that maintains its thickness uniformity even when heated. In addition, the gas degassing effect due to back pressure is easily achieved, preventing the generation of bubbles in the coating layer.

[0037] In one embodiment, a conductor at room temperature is coated with a thermoplastic resin molten in a die. In another embodiment, a heated conductor is coated with a thermoplastic resin molten in a die. The temperature of the conductor coated with the thermoplastic resin may be 10°C or higher, 100°C or higher, or 150°C or higher. The temperature of the conductor coated with the thermoplastic resin may be a temperature equal to or higher than the melting point of the thermoplastic resin. When using the manufacturing method of the present disclosure, the conductor and the coating layer can be sufficiently adhered to each other even at low conductor temperatures. Therefore, the temperature of the conductor coated with the thermoplastic resin may be a temperature equal to or lower than the temperature of the molten thermoplastic resin, or a temperature lower than the melting point of the thermoplastic resin. The temperature of the conductor can be determined, for example, by measuring the temperature of the conductor between the heating device and the extruder using a contact or non-contact thermometer.

[0038] The line speed during extrusion molding may be 0.1 to 50 m / min, and is preferably 20 m / min or less.

[0039] After the coating layer is formed, the electric wire can be cooled. The cooling method is not particularly limited, and may be water cooling, air cooling, etc. When the electric wire is cooled by air cooling, it can be cooled at an appropriate rate, and therefore the thickness of the coating layer tends to become uniform.

[0040] After the coating layer is formed, the electric wire may be subjected to an annealing treatment. The temperature of the annealing treatment is usually equal to or higher than the glass transition point of the thermoplastic resin, preferably equal to or higher than a temperature 15°C higher than the melting point of the thermoplastic resin, and preferably equal to or lower than a temperature 50°C higher than the melting point of the thermoplastic resin. In one embodiment, the electric wire of the present disclosure is an electric wire that has not been subjected to a heat treatment (annealing treatment) performed at 50°C or higher.

[0041] After forming the coating layer, a material for forming another layer may be extruded onto the coating layer containing a thermoplastic resin to form another layer, or a simultaneous multilayer melt extrusion method may be used to form a coating layer containing a thermoplastic resin and at the same time form another layer on the coating layer containing a thermoplastic resin.

[0042] (Electric wire) The electric wire of the present disclosure includes a conductor and a coating layer containing a thermoplastic resin. In one embodiment, the electric wire of the present disclosure includes a conductor and a coating layer containing a fluororesin. The electric wire of the present disclosure can be preferably manufactured by the manufacturing method of the present disclosure described above.

[0043] The electric wire of the present disclosure has a ratio of scattering intensity (longitudinal direction) to scattering intensity (horizontal axis direction) of 3 or less. Ratio = Scattering intensity (longitudinal direction) / Scattering intensity (horizontal axis direction) Scattering intensity (longitudinal direction): Scattering intensity obtained by small-angle X-ray scattering measurement of the coating layer, measured by scanning the transmitted scattering of X-rays along the longitudinal direction of the wire (scattering vector q = 0.3 nm -1 ) Scattering intensity (horizontal axis): Scattering intensity obtained by small-angle X-ray scattering measurement of the coating layer, measured by scanning the transmission scattering of X-rays along the horizontal axis of the wire (scattering vector q = 0.3 nm -1 )

[0044] The inventors have found through their studies that the thickness uniformity of the coating layer can be maintained even when heated by adjusting the ratio of the scattering intensity (longitudinal direction) to the scattering intensity (lateral direction) of the coating layer within the above range. The ratio of the scattering intensity (longitudinal direction) to the scattering intensity (lateral direction) is 3.0 or less, preferably 2.7 or less, more preferably 2.5 or less, even more preferably 2.3 or less, and preferably 0.1 or more, more preferably 0.3 or more, even more preferably 0.6 or more.

[0045] By using the manufacturing method of the present disclosure, the ratio of the scattering intensity (longitudinal direction) to the scattering intensity (horizontal axis direction) of the coating layer can be adjusted to fall within the above range.

[0046] The scattering intensity of the coating layer can be measured by the method described in the Examples.

[0047] From the viewpoint of insulating properties, the average thickness of the coating layer is preferably 30 to 400 μm, more preferably 40 μm or more, even more preferably 50 μm or more, more preferably 300 μm or less, even more preferably 200 μm or less.

[0048] By using the manufacturing method of the present disclosure, an electric wire having a coating layer with a uniform thickness can be manufactured. In one embodiment, the electric wire has a coating layer in which the difference between the maximum thickness and the minimum thickness of the coating layer is less than 5.0% of the average thickness. The difference between the maximum thickness and the minimum thickness of the coating layer is preferably 4.0% or less, more preferably 3.0% or less, even more preferably 2.5% or less, still more preferably 1.7% or less, particularly preferably 1.25% or less, and may be 0.1% or more.

[0049] In one embodiment, the electric wire has a coating layer having an average thickness of 30 to 100 μm, and the difference between the maximum thickness and the minimum thickness of the coating layer is less than 5.0% of the average thickness. In one embodiment, the electric wire has a coating layer having an average thickness of more than 100 μm and not more than 200 μm, and the difference between the maximum thickness and the minimum thickness of the coating layer is not more than 2.5% of the average thickness. In one embodiment, the electric wire has a coating layer having an average thickness of more than 200 μm and not more than 300 μm, and the difference between the maximum thickness and the minimum thickness of the coating layer is not more than 1.7% of the average thickness. In one embodiment, the electric wire has a coating layer having an average thickness of more than 300 μm and equal to or greater than 400 μm, and the difference between the maximum thickness and the minimum thickness of the coating layer is 1.25% or less of the average thickness.

[0050] By using the manufacturing method of the present disclosure, it is possible to manufacture an electric wire having a coating layer whose thickness remains uniform even when heated. In one embodiment, the electric wire has a coating layer whose longitudinal length shrinkage rate is less than 7% even when heated at 200°C for 3 hours. The shrinkage rate of the coating layer is preferably 6% or less, more preferably 5% or less, even more preferably 4% or less, and even more preferably 3% or less, and may be 0.1% or more. An electric wire whose shrinkage rate is within the above range is unlikely to deform due to heat, and therefore maintains thickness uniformity even when heated.

[0051] The shrinkage rate can be calculated by the following formula. Shrinkage rate (%) = [(length before heating) - (length after heating)] / (length before heating) x 100 Length before heating: Length of the coating layer in the longitudinal direction (mm) Length after heating: The length (mm) of the coating layer in the longitudinal direction measured after heating the coating layer at 200°C for 3 hours and then cooling it sufficiently to room temperature

[0052] By using the manufacturing method of the present disclosure, it is possible to manufacture an electric wire having a coating layer that maintains a uniform thickness even when heated. In one embodiment, the electric wire has a coating layer that maintains an average thickness of 90% or more even when heated at 200°C for 3 hours. The average thickness maintenance rate of the coating layer is preferably 95% or more and may be 100% or less.

[0053] The average thickness maintenance rate can be calculated by the following formula. Retention rate (%) = (average thickness after heating) / (average thickness before heating) x 100 Average thickness before heating: Average thickness of coating layer (μm) The long-average thickness (μm) of the coating layer measured after heating the coating layer at 200°C for 3 hours and then cooling it to room temperature.

[0054] By using the manufacturing method of the present disclosure, it is possible to manufacture an electric wire in which the conductor and the coating layer are firmly adhered to each other. In one embodiment, the electric wire is characterized in that, in an adhesion test conducted in accordance with JIS C3216-3, when a test piece prepared from the electric wire is stretched to an elongation rate of 10%, no lifting of the coating layer occurs. The adhesion test can be conducted by the method described in the examples.

[0055] By using the manufacturing method of the present disclosure, it is possible to manufacture an electric wire in which the conductor and the coating layer are firmly adhered to each other. In one embodiment, the electric wire is characterized by a pull-out strength of 5 N / mm or more. A pull-out test can be carried out by the method described in the Examples. The pull-out strength is preferably 7.5 N / mm, more preferably 10 N / mm or more, and even more preferably 15 N / mm. The upper limit is not particularly limited, but may be 50 N / mm or less. The pull-out strength is calculated using the following formula. Pull-out strength (N / mm) = Maximum point stress (N) / Conductor circumference (mm) In one embodiment, the above-mentioned pull-out strength is the pull-out strength of an electric wire that has not been heated to 50°C or higher.

[0056] By using the manufacturing method of the present disclosure, it is possible to manufacture an electric wire having a coating layer that maintains strong adhesion to the conductor even when heated. In one embodiment, the electric wire is characterized in that the rate of change in the pull-out strength of the electric wire before and after heating is less than 10%. The rate of change in the pull-out strength of the electric wire before and after heating is preferably 9% or less, more preferably 8% or less, even more preferably 7% or less, and even more preferably 6% or less. The lower limit is not particularly limited, but may be 0.1% or more. Change rate (%) = [(pull-out strength before heating) - (pull-out strength after heating)] / (pull-out strength before heating) x 100 Pull-out strength before heating: The pull-out strength (N / mm) is calculated using the maximum point stress (N) measured by pulling the coating layer from the conductor of an electric wire that has not been heated to 50°C or higher and the outer circumference of the conductor (mm) according to the following formula. Pull-out strength after heating: An electric wire that has not been heated to 50°C or higher is heated at 200°C for 3 hours, cooled to below 50°C, and then the coating layer is pulled out from the conductor of the electric wire. The maximum point stress (N) measured and the outer circumference (mm) of the conductor are used to calculate the pull-out strength (N / mm) using the following formula. Pull-out strength (N / mm) = Maximum point stress (N) / Conductor circumference (mm)

[0057] In the present disclosure, an electric wire that has not been heated to 50°C or higher means an electric wire that has not been heated to 50°C or higher after being manufactured by forming a thermoplastic resin coating layer on a conductor and cooling it to room temperature. Therefore, an electric wire that has been manufactured at room temperature and then heated to 50°C or higher (an annealed electric wire) is not included in the electric wire that has not been heated to 50°C or higher. In one embodiment, the electric wire of the present disclosure is an electric wire that has not been subjected to a heat treatment (annealing treatment) at 50°C or higher.

[0058] The pull-out strength is the maximum tensile stress measured when the coating layer is pulled out from the conductor in the longitudinal direction over a distance of 30 mm at a speed of 50 mm / min.

[0059] As will be described later, the cross-sectional shape of the conductor of the electric wire may be either substantially rectangular or substantially circular. When the cross-sectional shape of the conductor of the electric wire is substantially rectangular, the peel strength measured by peeling the coating layer from the conductor is preferably 0.30 N / mm or more, more preferably 0.50 N / mm or more, even more preferably 1.00 N / mm or more, still more preferably 1.50 N / mm or more, and particularly preferably 3.00 N / mm or more. The upper limit of the peel strength is not limited, but may be, for example, 10.00 N / mm.

[0060] The peel strength is the maximum tensile stress measured when peeling the coating layer from the conductor in the longitudinal direction over a distance of 30 mm at a speed of 100 mm / min.

[0061] In addition, an electric wire having a substantially rectangular cross section usually has a flat surface on the conductor that is wide enough to measure the peel strength, whereas an electric wire having a substantially circular cross section usually does not have a flat surface on the conductor that is wide enough to measure the peel strength, and in this respect, the electric wire having a substantially rectangular cross section differs from the electric wire having a substantially circular cross section.

[0062] In the manufacturing method of the present disclosure, an annealing treatment may or may not be performed after the electric wire is manufactured. The manufacturing method of the present disclosure can manufacture an electric wire with a coating layer of uniform thickness even without annealing, where the uniformity of the coating layer thickness is maintained even when heated, and where the rate of change in pull-out strength and peel strength is small. Therefore, by using the manufacturing method of the present disclosure, an electric wire can be manufactured that includes a conductor whose surface is not oxidized and whose inherent electrical conductivity is not impaired.

[0063] In one embodiment, the electric wire is characterized in that the difference Δ(AB) between the L* value (A) of the conductor and the L* value (B) of the conductor after surface oxide film removal treatment is 20 or less.

[0064] The surface oxide film removal treatment can be performed by the method described in the Examples. The L* value of a conductor can be measured using a colorimeter with an optical system conforming to or equivalent to JIS Z 8722. If the conductor of an electric wire does not have a surface large enough to measure the L* value, the L* value of the conductor of the electric wire can be estimated by heating a rectangular conductor made of the same material as the conductor of the electric wire and having a surface large enough to measure the L* value, so that it has a thermal history equivalent to the manufacturing conditions of the electric wire, and measuring the L* value.

[0065] (conductor) The conductor may be a single wire, a stranded wire, a twisted wire, etc., but is preferably a single wire. The cross-sectional shape of the conductor may be either substantially rectangular or substantially circular.

[0066] The conductor is not particularly limited as long as it is made of a conductive material, but may be made of copper, copper alloy, aluminum, aluminum alloy, iron, silver, nickel, or other materials, with copper, copper alloy, aluminum, or aluminum alloy being preferred. Conductors plated with silver or nickel may also be used. As copper, oxygen-free copper, low-oxygen copper, copper alloy, etc. may be used.

[0067] When the conductor has a substantially rectangular cross section, i.e., when the conductor is a rectangular conductor, the width of the conductor cross section may be 1 to 75 mm, and the thickness of the conductor cross section may be 0.1 to 30 mm. The perimeter of the conductor may be 6.5 mm or more and 200 mm or less. Furthermore, the ratio of width to thickness may be greater than 1 and less than 30.

[0068] When the cross section of the conductor is approximately circular, that is, when the conductor is a round conductor, the diameter of the conductor is preferably 0.1 to 10 mm, and more preferably 0.3 to 3 mm.

[0069] The surface roughness Sz of the conductor is preferably 0.2 to 12 μm, more preferably 1 μm or more, even more preferably 5 μm or more, and more preferably 10 μm or less, since this allows for stronger adhesion between the conductor and the coating layer.

[0070] However, when used in high-frequency communication applications, a large surface roughness Sz of the conductor increases transmission loss due to the skin effect, so a small surface roughness Sz of the conductor is preferable. In this case, the surface roughness Sz of the conductor may be 1 μm or less, less than 1 μm, less than 0.50 μm, less than 0.20 μm, or 0.01 μm or more. In the electric wire of the present disclosure, even when the surface roughness Sz of the conductor is small, the conductor and the coating layer are sufficiently adhered to each other.

[0071] The surface roughness of the conductor can be adjusted by surface treatment of the conductor using a surface treatment method such as etching, blasting, or laser treatment. Furthermore, the surface of the conductor may be provided with irregularities by surface treatment. The smaller the distance between the irregularities between the convex portions, the better, for example, 5 μm or less. Furthermore, the size of the irregularities is, for example, 1 μm when the area of ​​each concave portion when the convex portion is cut from the unprocessed surface. 2 The uneven shape may be a single crater-shaped uneven shape, or may be branched like an ant's nest.

[0072] (covering layer) In one embodiment, the coating layer contains a thermoplastic resin, such as a fluororesin, a polyaryletherketone (PAEK) resin, a thermoplastic polyimide resin, a thermoplastic polyamideimide resin, a polyamide resin, a polyolefin resin, a modified polyolefin resin, a polyvinyl resin, a polyester, an ethylene / vinyl alcohol copolymer, a polyacetal resin, a polyurethane resin, a polyphenylene oxide resin, a polycarbonate resin, an acrylic resin, a styrene resin, an acrylonitrile / butadiene / styrene resin (ABS), a vinyl chloride resin, a cellulose resin, a polysulfone resin, a polyethersulfone resin (PES), a polyetherimide resin, or a polyphenylene sulfide resin.

[0073] In one embodiment, the coating layer contains a fluororesin. The fluororesin is preferably a melt-processable fluororesin. In the present disclosure, melt-processable means that the polymer can be melted and processed using conventional processing equipment such as an extruder or an injection molding machine. Therefore, the melt-processable fluororesin typically has a melt flow rate of 0.01 to 500 g / 10 min, as measured by the measurement method described below.

[0074] The melt flow rate of the fluororesin is preferably 1 to 100 g / 10 min, and the upper limit of the melt flow rate is more preferably 90 g / 10 min or less, and even more preferably 80 g / 10 min or less. A melt flow rate of 100 g / 10 min or less is preferred in that cracks can be suppressed when an electric wire coated with the resin is bent. The lower limit of the melt flow rate is preferably 10 g / 10 min or more, and more preferably 15 g / 10 min or more. A melt flow rate of 10 g / 10 min or more is preferred in that melt fracture can be suppressed when the resin is coated and molded. When the melt flow rate of the fluororesin is within the above range, the coating layer can be easily formed, and the resulting coating layer has excellent mechanical strength and appearance.

[0075] In the present disclosure, the melt flow rate of a fluororesin is a value obtained in accordance with ASTM D1238 using a melt indexer (manufactured by Yasuda Seiki Seisakusho Co., Ltd.) as the mass of polymer flowing out per 10 minutes (g / 10 min) from a nozzle with an inner diameter of 2.1 mm and a length of 8 mm under a load of 5 kg at 372°C.

[0076] The melting point of the fluororesin is preferably 200 to 322°C, more preferably 210°C or higher, even more preferably 220°C or higher, particularly preferably 240°C or higher, and more preferably 320°C or lower.

[0077] The melting point can be measured using a differential scanning calorimeter (DSC).

[0078] Examples of melt-processable fluororesin include tetrafluoroethylene (TFE) / fluoroalkyl vinyl ether (FAVE) copolymer, tetrafluoroethylene (TFE) / hexafluoropropylene (HFP) copolymer, TFE / ethylene copolymer [ETFE], TFE / ethylene / HFP copolymer, ethylene / chlorotrifluoroethylene (CTFE) copolymer [ECTFE], polychlorotrifluoroethylene [PCTFE], CTFE / TFE copolymer, polyvinylidene fluoride [PVdF], TFE / vinylidene fluoride (VdF) copolymer [VT], polyvinyl fluoride [PVF], TFE / VdF / CTFE copolymer [VTC], and TFE / HFP / VdF copolymer.

[0079] As the fluororesin, at least one selected from the group consisting of TFE / FAVE copolymer and TFE / HFP copolymer is preferred, as it has excellent heat resistance, moldability, and electrical properties and provides stronger adhesion between the conductor and the coating layer.

[0080] TFE / FAVE copolymers are copolymers containing tetrafluoroethylene (TFE) units and fluoroalkyl vinyl ether (FAVE) units.

[0081] The FAVE constituting the FAVE unit is represented by the general formula (1): CF2=CFO(CF2CFY 1 O) p -(CF2CF2CF2O) q -Rf (1) (In the formula, Y 1 represents F or CF3, and Rf represents a perfluoroalkyl group having 1 to 5 carbon atoms. p represents an integer of 0 to 5, and q represents an integer of 0 to 5.) and a monomer represented by general formula (2): CFX=CXOCF2OR 1 (2) (wherein X may be the same or different and represents H, F or CF3; R 1represents a linear or branched fluoroalkyl group having 1 to 6 carbon atoms which may contain 1 to 2 atoms of at least one type selected from the group consisting of H, Cl, Br and I, or a cyclic fluoroalkyl group having 5 or 6 carbon atoms which may contain 1 to 2 atoms of at least one type selected from the group consisting of H, Cl, Br and I.

[0082] Among the FAVEs, a monomer represented by general formula (1) is preferred, and at least one selected from the group consisting of perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether) (PEVE) and perfluoro(propyl vinyl ether) (PPVE) is more preferred, and at least one selected from the group consisting of PEVE and PPVE is even more preferred, with PPVE being particularly preferred.

[0083] The content of FAVE units in the TFE / FAVE copolymer is preferably 1.0 to 30.0 mol % of all monomer units, in order to further strengthen the adhesion between the conductor and the coating layer, more preferably 1.2 mol % or more, even more preferably 1.4 mol % or more, still more preferably 1.6 mol % or more, particularly preferably 1.8 mol % or more, more preferably 3.5 mol % or less, even more preferably 3.2 mol % or less, still more preferably 2.9 mol % or less, and particularly preferably 2.6 mol % or less.

[0084] The content of TFE units in the TFE / FAVE copolymer is preferably 99.0 to 70.0 mol % of all monomer units, in order to further strengthen the adhesion between the conductor and the coating layer, more preferably 96.5 mol % or more, even more preferably 96.8 mol % or more, still more preferably 97.1 mol % or more, particularly preferably 97.4 mol % or more, more preferably 98.8 mol % or less, even more preferably 98.6 mol % or less, still more preferably 98.4 mol % or less, and particularly preferably 98.2 mol % or less.

[0085] In the present disclosure, the content of each monomer unit in the copolymer is 19 Measured by F-NMR.

[0086] The TFE / FAVE copolymer may also contain monomer units derived from a monomer copolymerizable with TFE and FAVE. In this case, the content of the monomer copolymerizable with TFE and FAVE is preferably 0 to 29.0 mol %, more preferably 0.1 to 5.0 mol %, and even more preferably 0.1 to 3.0 mol %, based on the total monomer units of the TFE / FAVE copolymer.

[0087] Monomers that can be copolymerized with TFE and FAVE include HFP and CZ 1 Z 2 =CZ 3 (CF2) n Z 4 (In the formula, Z 1 , Z 2 and Z 3 are the same or different and represent H or F, and Z 4 represents H, F or Cl, and n represents an integer of 2 to 10.) and a vinyl monomer represented by CF2=CF-OCH2-Rf 1 (In the formula, Rf 1 represents a perfluoroalkyl group having 1 to 5 carbon atoms. Examples include alkyl perfluorovinyl ether derivatives represented by the following formula: and monomers having a functional group. Of these, HFP is preferred.

[0088] The TFE / FAVE copolymer is preferably at least one selected from the group consisting of copolymers consisting only of TFE units and FAVE units and the above-mentioned TFE / HFP / FAVE copolymers, and more preferably a copolymer consisting only of TFE units and FAVE units.

[0089] From the viewpoint of heat resistance and stress crack resistance, the melting point of the TFE / FAVE copolymer is preferably 240 to 322° C., more preferably 285° C. or higher, more preferably 320° C. or lower, even more preferably 315° C. or lower, and particularly preferably 310° C. or lower. The melting point can be measured using a differential scanning calorimeter (DSC).

[0090] The glass transition temperature (Tg) of the TFE / FAVE copolymer is preferably 70 to 110° C., more preferably 80° C. or higher, and more preferably 100° C. or lower. The glass transition temperature can be measured by dynamic viscoelasticity measurement.

[0091] From the viewpoint of electrical properties, the relative dielectric constant of the TFE / FAVE copolymer is preferably 2.4 or less, more preferably 2.1 or less, and although there is no particular lower limit, it is preferably 1.8 or more. The relative dielectric constant is a value obtained by measuring the changes in resonant frequency and electric field strength at a temperature of 20 to 25°C using a network analyzer HP8510C (manufactured by Hewlett-Packard Co.) and a cavity resonator.

[0092] TFE / HFP copolymer is a copolymer containing tetrafluoroethylene (TFE) units and hexafluoropropylene (HFP) units.

[0093] The content of HFP units in the TFE / HFP copolymer is preferably 0.1 to 30.0 mol % of all monomer units, more preferably 0.7 mol % or more, even more preferably 1.4 mol % or more, and more preferably 10.0 mol % or less, in order to further strengthen the adhesion between the conductor and the coating layer.

[0094] The content of TFE units in the TFE / HFP copolymer is preferably 70.0 to 99.9 mol %, more preferably 90.0 mol % or more, more preferably 99.3 mol % or less, and even more preferably 98.6 mol %, based on all monomer units, in order to further strengthen the adhesion between the conductor and the coating layer.

[0095] The TFE / HFP copolymer may also contain monomer units derived from a monomer copolymerizable with TFE and HFP. In this case, the content of the monomer copolymerizable with TFE and HFP is preferably 0 to 29.9 mol%, more preferably 0.1 to 5.0 mol%, and even more preferably 0.1 to 1.0 mol%, based on the total monomer units of the TFE / HFP copolymer.

[0096] Monomers that can be copolymerized with TFE and HFP include FAVE and CZ 1 Z 2 =CZ 3 (CF2) n Z 4 (In the formula, Z 1 , Z 2 and Z 3 are the same or different and represent H or F, and Z 4 represents H, F or Cl, and n represents an integer of 2 to 10.) and a vinyl monomer represented by CF2=CF-OCH2-Rf 1 (In the formula, Rf 1 represents a perfluoroalkyl group having 1 to 5 carbon atoms. Examples include alkyl perfluorovinyl ether derivatives represented by the following formula: and monomers having a functional group. Among these, FAVE is preferred.

[0097] The melting point of the TFE / HFP copolymer is preferably 200 to 322°C, more preferably 210°C or higher, even more preferably 220°C or higher, particularly preferably 240°C or higher, more preferably 320°C or lower, even more preferably lower than 300°C, and particularly preferably 280°C or lower.

[0098] The glass transition temperature (Tg) of the TFE / HFP copolymer is preferably 60 to 110°C, more preferably 65°C or higher, and more preferably 100°C or lower.

[0099] The fluororesin preferably has a functional group, which allows the conductor and the coating layer to adhere more firmly to each other.

[0100] The functional group is preferably at least one selected from the group consisting of a carbonyl group-containing group, an amino group, a hydroxy group, a -CF2H group, an olefin group, an epoxy group, and an isocyanate group.

[0101] The carbonyl group-containing group is a group that contains a carbonyl group (—C(═O)—) in its structure. Examples of the carbonyl group-containing group include: Carbonate group [-OC(=O)-OR 3 (In the formula, R 3 is an alkyl group having 1 to 20 carbon atoms or an alkyl group having 2 to 20 carbon atoms and containing an ether-bonding oxygen atom); Acyl group [-C(=O)-R 3 (In the formula, R 3 is an alkyl group having 1 to 20 carbon atoms or an alkyl group having 2 to 20 carbon atoms and containing an ether-bonded oxygen atom. Haloformyl group [-C(=O)X 5 , X 5 is a halogen atom], formyl group [-C(=O)H], Formula:-R 4 -C(=O)-R 5 (In the formula, R 4 is a divalent organic group having 1 to 20 carbon atoms, and R 5 is a monovalent organic group having 1 to 20 carbon atoms), Formula: -OC(=O)-R 6 (In the formula, R 6 is an alkyl group having 1 to 20 carbon atoms or an alkyl group having 2 to 20 carbon atoms containing an ether-bonding oxygen atom), Carboxyl group [-C(=O)OH], Alkoxycarbonyl group [-C(=O)OR 7 (In the formula, R 7 is a monovalent organic group having 1 to 20 carbon atoms); Carbamoyl group [-C(=O)NR 8 R 9 (In the formula, R 8 and R 9may be the same or different and are a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms); Acid anhydride bond [-C(=O)-OC(=O)-], Examples include:

[0102] R 3 Specific examples of R include a methyl group, an ethyl group, a propyl group, an isopropyl group, and a butyl group. 4 Specific examples of R include a methylene group, a -CF2- group, and a -C6H4- group. 5 Specific examples of R include a methyl group, an ethyl group, a propyl group, an isopropyl group, and a butyl group. 7 Specific examples of R include a methyl group, an ethyl group, a propyl group, an isopropyl group, and a butyl group. 8 and R 9 Specific examples of include a hydrogen atom, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, and a phenyl group.

[0103] A hydroxy group is a group represented by -OH or a group containing a group represented by -OH. In this disclosure, the -OH constituting a carboxyl group is not included in the hydroxy group. Examples of the hydroxy group include -OH, a methylol group, and an ethylol group.

[0104] An olefinic group is a group having a carbon-carbon double bond. Examples of the olefinic group include those represented by the following formula: -CR 10 =CR 11 R 12 (In the formula, R 10 , R 11 and R 12 may be the same or different and are a hydrogen atom, a fluorine atom, or a monovalent organic group having 1 to 20 carbon atoms. ) is a functional group, and at least one selected from the group consisting of -CF=CF2, -CH=CF2, -CF=CHF, -CF=CH2, and -CH=CH2 is preferred.

[0105] The isocyanate group is a group represented by -N=C=O.

[0106] The functional group can also include a non-fluorinated or partially fluorinated alkyl group such as a -CH3 group or a -CFH2 group.

[0107] The number of functional groups in the fluororesin is set to 10 carbon atoms, which allows for stronger adhesion between the conductor and the coating layer. 6 The number of functional groups is preferably 5 to 2000 per carbon atom. 6 More preferably, the number is 10 or more, even more preferably 20 or more, particularly preferably 30 or more, more preferably 1,500 or less, even more preferably 1,000 or less, particularly preferably 800 or less, and most preferably 500 or less.

[0108] In addition, the number of functional groups of the fluororesin is set to 10 carbon atoms, which allows the formation of a coating layer with excellent electrical properties. 6 There may be less than 5 per piece.

[0109] The functional groups are those present at the main chain terminal or side chain terminal of the copolymer (fluororesin), and those present in the main chain or side chain, preferably at the main chain terminal. Examples of the functional groups include -CF=CF2, -CF2H, -COF, -COOH, -COOCH3, -CONH2, -OH, and -CH2OH. At least one selected from the group consisting of -CF2H, -COF, -COOH, -COOCH3, and -CH2OH is preferred. -COOH includes a dicarboxylic acid anhydride group (-CO-O-CO-) formed by the bonding of two -COOH groups.

[0110] Infrared spectroscopy can be used to identify the type of functional group and measure the number of functional groups.

[0111] The number of functional groups is specifically measured by the following method. First, the copolymer is melted at 330 to 340°C for 30 minutes and compression molded to produce a film with a thickness of 0.20 to 0.25 mm. This film is analyzed by Fourier transform infrared spectroscopy to obtain an infrared absorption spectrum of the copolymer, and a difference spectrum is obtained from the base spectrum, which is completely fluorinated and has no functional groups. From the absorption peaks of specific functional groups that appear in this difference spectrum, the number of carbon atoms in the copolymer (1 x 10) is calculated according to the following formula (A): 6 Calculate the number of functional groups per molecule, N. N=I×K / t (A) I: Absorbance K: Correction coefficient t: film thickness (mm)

[0112] For reference, the absorption frequencies, molar absorption coefficients, and correction factors for the functional groups in this disclosure are shown in Table 1. The molar absorption coefficients were determined from FT-IR measurement data of low molecular weight model compounds.

[0113] [Table 1]

[0114] The absorption frequencies of -CH2CF2H, -CH2COF, -CH2COOH, -CH2COOCH3, and -CH2CONH2 are shown in the table, and are expressed as a few tens of Kaiser (cm) from the absorption frequencies of -CF2H, -COF, -COOH free and -COOH bonded, -COOCH3, and -CONH2. -1 ) becomes lower. Therefore, for example, the number of functional groups of -COF is the absorption frequency of 1883 cm due to -CF2COF. -1 The number of functional groups determined from the absorption peak of -CH2COF and the absorption frequency of 1840 cm -1 The number of functional groups is the sum of the number of functional groups determined from the absorption peaks of the compounds.

[0115] The number of functional groups may be the total number of -CF=CF2, -CF2H, -COF, -COOH, -COOCH3, -CONH2 and -CH2OH, or may be the total number of -CF2H, -COF, -COOH, -COOCH3 and -CH2OH.

[0116] The functional group is introduced into the fluororesin (copolymer) by, for example, a chain transfer agent or a polymerization initiator used in producing the fluororesin. For example, when an alcohol is used as a chain transfer agent or a peroxide having a -CHOH structure is used as a polymerization initiator, -CHOH is introduced into the main chain terminal of the fluororesin. Alternatively, the functional group is introduced into the side chain terminal of the fluororesin by polymerizing a monomer having a functional group. The fluororesin may contain units derived from a monomer having a functional group.

[0117] Examples of monomers having a functional group include cyclic hydrocarbon monomers having a dicarboxylic acid anhydride group (-CO-O-CO-) and a polymerizable unsaturated group in the ring, as described in JP 2006-152234 A, and monomers having a functional group (f) as described in WO 2017 / 122743 A. Examples of monomers having a functional group include monomers having a carboxy group (maleic acid, itaconic acid, citraconic acid, undecylenic acid, etc.); monomers having an acid anhydride group (itaconic anhydride, citraconic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, maleic anhydride, etc.); and monomers having a hydroxyl group or an epoxy group (hydroxybutyl vinyl ether, glycidyl vinyl ether, etc.).

[0118] The fluororesin can be produced by a conventionally known method, for example, by appropriately mixing monomers that are the constituent units of the fluororesin and additives such as a polymerization initiator, followed by emulsion polymerization or suspension polymerization.

[0119] The coating layer may contain other components as needed. Examples of such other components include crosslinking agents, antistatic agents, heat stabilizers, foaming agents, foam nucleating agents, antioxidants, surfactants, photopolymerization initiators, anti-wear agents, surface modifiers, various organic and inorganic pigments, copper inhibitors, anti-foaming agents, adhesion promoters, lubricants, processing aids, colorants, phosphorus-based stabilizers, lubricants, release agents, sliding materials, UV absorbers, dyes and pigments, reinforcing materials, anti-drip agents, fillers, curing agents, UV curing agents, and flame retardants. The content of such other components in the coating layer is preferably less than 30% by mass, more preferably less than 10% by mass, and even more preferably 5% by mass or less, relative to the mass of the thermoplastic resin (fluororesin) in the coating layer. The lower limit is not particularly limited, but may be 0% by mass or more. That is, the coating layer need not contain any other components.

[0120] The coating layer may contain additives and fillers for the purpose of improving mechanical properties, improving moldability, etc. Examples of such additives and fillers include fibrous fillers such as glass fiber, carbon fiber, carbon milled fiber, carbon nanotube, carbon nanohorn, metal fiber, asbestos, rock wool, ceramic fiber, slag fiber, potassium titanate whisker, boron whisker, aluminum borate whisker, calcium carbonate whisker, titanium oxide whisker, wollastonite, palygorskite, sepiolite, aramid fiber, alumina fiber, silicon carbide fiber, ceramic fiber, asbestos fiber, gypsum fiber, metal fiber, polyimide fiber, and polybenzthiazole fiber; Examples include laren, talc, wollastonite, zeolite, mica, clay, pyrophyllite, graphite, silica, bentonite, asbestos, silicates such as alumina silicate, metal compounds such as silicon oxide, magnesium oxide, calcium oxide, alumina, zirconium oxide, titanium oxide, and iron oxide, carbonates such as calcium carbonate, magnesium carbonate, and dolomite, sulfates such as calcium sulfate and barium sulfate, hydroxides such as calcium hydroxide and aluminum hydroxide, glass beads, glass flakes, glass powder, boron nitride, silicon carbide, carbon black, and graphite.

[0121] To improve dielectric constant, it is also effective to introduce bubbles into the coating layer. Examples of inorganic foaming nucleating agents include boron nitride, talc, zeolite, mica, aluminum silicate, calcium silicate, calcium carbonate, dolomite, magnesium oxide, magnesium hydroxide, aluminum oxide, aluminum hydroxide, antimony trioxide, titanium oxide, and iron oxide. Bubbles can be obtained by injecting an inert gas, such as nitrogen, carbon dioxide, argon, or helium, into the coating material during wire processing to cause foaming. Bubbles can also be obtained by incorporating fine hollow particles, hollow capsules, hollow balloons, hollow polymer particles, or the like into the material. Examples include acrylic hollow particles, silica hollow particles, alumina hollow particles, ceramic hollow particles, glass balloons, and glass hollow particles. The size of the hollow particles is preferably 10 μm or less, more preferably less than 1 μm, and even more preferably 500 nm or less. The lower limit is not particularly limited, but may be 30 nm or more.

[0122] (Other layers) The electric wire of the present disclosure may further include another layer formed on the outer periphery of the coating layer.

[0123] In a preferred embodiment of the present disclosure, the coating layer does not include any other layers and is formed solely from a layer containing a thermoplastic resin. In a preferred embodiment of the present disclosure, the coating layer does not include any other layers and is formed solely from a layer containing a fluororesin. Even if the electric wire of the present disclosure does not include a layer for adhering the conductor and the coating layer, such as a primer layer, the conductor and the coating layer are sufficiently adhered to each other, so the coating layer can be a single layer. Furthermore, since the thickness of the coating layer of the electric wire of the present disclosure is maintained uniform, the electric wire has sufficient insulating properties even when it has a single coating layer.

[0124] In one embodiment of the electric wire of the present disclosure, the conductor and the covering layer are adhered to each other with sufficient strength, and therefore, there is no other layer between the conductor and the covering layer, and the conductor and the covering layer are in direct contact with each other.

[0125] The other layer may be a layer formed on the outer periphery of the coating layer and containing a thermoplastic resin, such as a fluororesin, a thermoplastic polyimide resin, a thermoplastic polyamideimide resin, a polyamide resin, a polyolefin resin, a modified polyolefin resin, a polyvinyl resin, a polyester, an ethylene / vinyl alcohol copolymer, a polyacetal resin, a polyurethane resin, a polyphenylene oxide resin, a polycarbonate resin, an acrylic resin, a styrene resin, an acrylonitrile / butadiene / styrene resin (ABS), a vinyl chloride resin, a cellulose resin, a polysulfone resin, a polyethersulfone resin (PES), a polyetherimide resin, a polyphenylene sulfide, or a polyethylene terephthalate.

[0126] The electric wire of the present disclosure can be suitably used for, for example, LAN cables, USB cables, Lightning cables, HDMI (registered trademark) cables, QSFP cables, aerospace electric wires, underground power transmission cables, submarine power cables, high-voltage cables, superconducting cables, wrapped electric wires, automotive electric wires, wire harnesses and electrical components, electric wires for robots and factory automation (FA), electric wires for office automation equipment, electric wires for information equipment (optical fiber cables, LAN cables, HDMI cables, Lightning cables, audio cables, etc.), internal wiring for communication base stations, internal wiring for large currents (inverters, power conditioners, storage battery systems, etc.), internal wiring for electronic devices, wiring for small electronic devices and mobile devices, wiring for moving parts, internal wiring for electrical equipment, internal wiring for measuring instruments, power cables (for construction, wind / solar power generation, etc.), control and instrumentation wiring cables, motor cables, etc.

[0127] The electric wire of the present disclosure can be wound and used as a coil. The electric wire and coil of the present disclosure can be suitably used in electric or electronic devices such as motors, generators, and inductors. Furthermore, the electric wire and coil of the present disclosure can be suitably used in on-vehicle electric or electronic devices such as on-vehicle motors, on-vehicle generators, and on-vehicle inductors.

[0128] The electric wire of the present disclosure can be suitably used particularly as a motor stator. The motor stator can be used in an inverter motor. The electric wire of the present disclosure has the above-described configuration, and therefore has a high partial discharge inception voltage. In one embodiment, the partial discharge inception voltage is higher than a surge voltage that occurs during motor operation.

[0129] Although the embodiments have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the claims.

[0130] <1> According to a first aspect of the present disclosure, A method for producing an electric wire comprising: using an extruder equipped with a cylinder, a screw, a nipple, and a die to produce an electric wire having a conductor and a coating layer containing a thermoplastic resin, The conductor is fed through a passage opening of the nipple housed in the die, and the thermoplastic resin is coated in the die to form the coating layer. A manufacturing method is provided in which the conductor and the thermoplastic resin are in direct contact within the die, and the ratio (L2 / D) of the distance L2 between the part of the die that has the smallest cross-sectional area and is parallel to the maximum length D of the opening of the die is 4.0 or more. <2> According to a second aspect of the present disclosure, A manufacturing method according to a first aspect is provided in which the relationship between the length L1 from the tip of the nipple, where the conductor and the thermoplastic resin come into direct contact with each other within the die, to the die opening and the length L2 satisfies L1 > L2. <3> According to a third aspect of the present disclosure, A manufacturing method according to the first or second aspect is provided, in which the relationship between the length L1 from the tip of the nipple where the conductor and the thermoplastic resin come into direct contact with each other within the die to the die opening and the length L2 is L1-L2>10 (mm). <4> According to a fourth aspect of the present disclosure, There is provided a manufacturing method according to any one of the first to third aspects, wherein the die is a crosshead type die. <5> According to a fifth aspect of the present disclosure, According to any one of the first to fourth aspects, there is provided a production method in which the thermoplastic resin is a fluororesin. <6> According to a sixth aspect of the present disclosure, The present invention provides an electric wire comprising a conductor and a coating layer containing a fluororesin, the ratio of scattering intensity (longitudinal direction) to scattering intensity (horizontal axis direction) being 3.0 or less. Ratio = Scattering intensity (longitudinal direction) / Scattering intensity (horizontal axis direction) Scattering intensity (longitudinal direction): Scattering intensity obtained by small-angle X-ray scattering measurement of the coating layer, measured by scanning X-rays along the longitudinal direction of the wire (scattering vector q = 0.3 nm -1 ) Scattering intensity (horizontal axis direction): Scattering intensity obtained by small-angle X-ray scattering measurement of the coating layer, measured by scanning X-rays along the horizontal axis of the wire (scattering vector q = 0.3 nm -1 ) <7> According to a seventh aspect of the present disclosure, In accordance with a sixteenth aspect, there is provided an electric wire in which the covering layer is a single layer. <8> According to an eighth aspect of the present disclosure, According to a sixth or seventh aspect, there is provided an electric wire, wherein the surface roughness Sz of the conductor is 1 μm or less. <9> According to a ninth aspect of the present disclosure, There is provided an electric wire according to any one of the sixth to eighth aspects, in which, when a test piece made from the electric wire is stretched to an elongation rate of 10% in an adhesion test conducted in accordance with JIS C3216-3, no lifting of the coating layer occurs. <10> According to a tenth aspect of the present disclosure, There is provided an electric wire according to any one of the sixth to ninth aspects, which has a pull-out strength of 5 N / mm or more. Pull-out strength (N / mm) = Maximum point stress (N) / Conductor circumference (mm) Maximum point stress: The maximum point stress (N) measured by pulling the covering layer off the conductor of the wire <11> According to an eleventh aspect of the present disclosure, According to any one of the sixth to tenth aspects, there is provided an electric wire, wherein the rate of change in the pull-out strength of the electric wire before and after heating is less than 10%. Change rate (%) = [(pull-out strength before heating) - (pull-out strength after heating)] / (pull-out strength before heating) x 100 Pull-out strength before heating: The pull-out strength (N / mm) is calculated using the maximum point stress (N) measured by pulling the coating layer from the conductor of an electric wire that has not been heated to 50°C or higher and the outer circumference of the conductor (mm) according to the following formula. Pull-out strength after heating: An electric wire that has not been heated to 50°C or higher is heated at 200°C for 3 hours, cooled to below 50°C, and then the coating layer is pulled out from the conductor of the electric wire. The maximum point stress (N) measured and the outer circumference (mm) of the conductor are used to calculate the pull-out strength (N / mm) using the following formula. Pull-out strength (N / mm) = Maximum point stress (N) / Conductor circumference (mm) <12> According to a twelfth aspect of the present disclosure, The cross-sectional shape of the conductor is substantially rectangular, There is provided an electric wire according to any one of the sixth to eleventh aspects, wherein the peel strength measured by peeling the coating layer from the conductor is 0.30 N / mm or more. <13> According to a thirteenth aspect of the present disclosure, There is provided an electric wire according to any one of the sixth to twelfth aspects, wherein the difference Δ(AB) between the L* value (A) of the conductor and the L* value (B) of the conductor after surface oxide film removal treatment is 20 or less. <14> According to a fourteenth aspect of the present disclosure, According to any one of the sixth to thirteenth aspects, there is provided a stator for a motor including the electric wire. <15> According to a fifteenth aspect of the present disclosure, According to a fourteenth aspect, there is provided an inverter motor including a motor stator. <16> According to a sixteenth aspect of the present disclosure, According to a fifteenth aspect, there is provided an inverter motor, wherein the partial discharge inception voltage of the electric wire is higher than a surge voltage generated during operation of the motor. [Example]

[0131] Next, embodiments of the present disclosure will be described with reference to examples, but the present disclosure is not limited to these examples.

[0132] The values ​​in the examples were measured by the following methods.

[0133] (Fluororesin Composition) 19 Measurement was performed by F-NMR.

[0134] (Number of functional groups) The fluororesin was melted at 330-340°C for 30 minutes and compression molded to produce a film with a thickness of 0.20-0.25 mm. This film was scanned 40 times using a Fourier transform infrared spectrometer (FT-IR (trade name: Model 1760X, manufactured by PerkinElmer)) to obtain an infrared absorption spectrum, and a difference spectrum was obtained from the base spectrum, which was completely fluorinated and had no functional groups. From the absorption peaks of specific functional groups appearing in this difference spectrum, the carbon atoms in the fluororesin were determined according to the following formula (A): 6 The number of functional groups per molecule, N, was calculated.

[0135] N=I×K / t (A) I: Absorbance K: Correction coefficient t: film thickness (mm)

[0136] For reference, the absorption frequencies, molar absorption coefficients, and correction factors for the functional groups in this disclosure are shown in Table 2. The molar absorption coefficients were determined from FT-IR measurement data of low molecular weight model compounds.

[0137] [Table 2]

[0138] (Melt flow rate (MFR)) According to ASTM D1238, the mass (g / 10 min) of the copolymer flowing out from a nozzle with an inner diameter of 2.1 mm and a length of 8 mm at 372°C under a load of 5 kg per 10 min was determined using a melt indexer (manufactured by Yasuda Seiki Seisakusho Co., Ltd.).

[0139] (Surface roughness Sz) 8000μm using a laser microscope (Keyence) 2 The surface roughness Sz in the field of view was measured.

[0140] (Scattering intensity) The following equipment was used: Device name: Rigaku RINT2500 Radiation source: CuKα ray (λ=1.5418Å) Output: 50kV / 300mA Detector: Scintillation counter Measurement angle θ:0°~2°

[0141] The coating layer was recovered from the electric wire produced in the example, and the recovered coating layer was cut to prepare test pieces measuring 50 mm in the longitudinal direction of the electric wire and 2 to 3 mm in the transverse direction. The prepared test piece was placed on a sample holder so that the longitudinal direction was horizontal, and the sample was irradiated with X-rays. The intensity of the scattered X-rays on the equator (scattering intensity (longitudinal direction)) was measured while the detector was moved horizontally. The prepared test piece was placed in a sample holder so that the horizontal axis was horizontal, and the sample was irradiated with X-rays. The intensity of the scattered X-rays on the equator (scattering intensity (horizontal axis direction)) was measured while the detector was moved horizontally. Scattering vector q is 0.3 nm -1 Scattering intensity (longitudinal direction) when the scattering vector q is 0.3 nm -1 The ratio (scattering intensity (longitudinal direction) / scattering intensity (lateral direction)) of the scattering intensity (lateral direction) in the case of

[0142] (Coating layer thickness) The thickness of the coating layer was measured by cross-sectional measurement using a Keyence VHX-5000 digital microscope. The measurement was performed at a magnification of 50x, and the cross-section was polished to remove any irregularities.

[0143] The average thickness was calculated by measuring the thickness of the coating layer at eight equally spaced locations on each cross section of five different samples, and averaging the 40 measurements for each sample. For example, in the case of a roughly rectangular sample, measurements were taken at eight locations on each cross section, including the centers of the four sides and the corners of the rectangle.

[0144] The maximum measured value (maximum thickness (μm)) was the average of the maximum thicknesses of the five measured cross sections, and the maximum value (maximum thickness (μm)) of that sample was taken as the maximum value (maximum thickness (μm)).

[0145] The minimum measured value (minimum thickness (μm)) was the average of the minimum thicknesses of the five measured cross sections, and this was taken as the minimum value (minimum thickness (μm)) of that sample.

[0146] The percentage (%) of the difference between the maximum and minimum thicknesses relative to the average thickness was calculated from the maximum measurement value (maximum thickness (μm)), the minimum measurement value (minimum thickness (μm)), and the average thickness (μm) according to the following formula. Percentage of difference between maximum and minimum thickness (%) = [(maximum thickness) - (minimum thickness)] / (average thickness) x 100

[0147] (shrinkage rate) The coating layer was peeled off from the conductor of the electric wire produced in the example to prepare a test piece having a length of approximately 10 cm in the longitudinal direction. The test piece was heated at 200°C for 3 hours and then sufficiently cooled to room temperature. The longitudinal length of the test piece before and after heating was measured, and the shrinkage rate (%) was calculated according to the following formula. Shrinkage rate (%) = [(length before heating) - (length after heating)] / (length before heating) x 100

[0148] (Adhesion test) An adhesion test was conducted in accordance with JIS C3216-3. A test specimen was prepared by cutting the wire to a length of 150 mm, and a slit was made around the entire circumference of the coating layer at approximately the center of the specimen, reaching the conductor. Using a tensile tester, the test specimen was stretched at a speed of 50 mm / sec with a chuck distance of 100 mm, and the elongation rate was measured when lift occurred at the slit in the coating layer.

[0149] (Pull-out strength) Measurements were performed using an AGS-X Autograph (5 kN) (Shimadzu Corporation). The wire was cut to 70 mm and the insulation was stripped off from only the first 20 mm. A jig with a hole wider than the conductor diameter but narrower than the wire diameter was attached to the upper chuck. The stripped conductor was then passed through the jig and secured to the lower chuck. The device was then moved in the pulling direction to pull out only the coating. The pull-out strength was calculated using the maximum stress at the time of pulling at 50 mm / min until the travel distance reached 30 mm and the circumference of the conductor cross section using the following formula. Table 1 shows the pull-out strength before heating. Pull-out strength before heating (N / mm) = Maximum point stress (N) / conductor circumference (mm)

[0150] In addition, the electric wire was heated at 200°C for 3 hours, and after being sufficiently cooled to room temperature, the pull-out strength of the electric wire after heating was measured using the method described above, and the pull-out strength was calculated using the obtained maximum point stress and the circumference of the conductor cross section using the following formula. Pull-out strength after heating (N / mm) = Maximum point stress (N) / Periphery of conductor cross section (mm)

[0151] Furthermore, the rate of change in pull-out strength before and after heating was calculated according to the following formula. Change rate (%) = [(pull-out strength before heating) - (pull-out strength after heating)] / (pull-out strength before heating) x 100

[0152] (peel strength) The peel strength of the coating layer on the main surface of the conductor (rectangular wire) of an electric wire was measured using an AGS-J Autograph (50N) (manufactured by Shimadzu Corporation). Here, of the two opposing surfaces of the rectangular wire, the surface with the larger width dimension of the conductor (the long side surface perpendicular to the longitudinal direction of the conductor) was defined as the main surface, and the surface conductor perpendicular to the main surface (the short side surface perpendicular to the longitudinal direction) was defined as the side surface. The width dimension of the conductor on the main surface was larger than the width dimension of the conductor on the side surface. Two approximately parallel incisions were made in the coating layer on one of the main surfaces along the longitudinal direction of the electric wire, and two further incisions perpendicular to the longitudinal direction were made 50 mm apart. The ends of the incised coating layer were peeled from the conductor, leaving a 10 mm grip. The electric wire was fixed to a jig with the other main surface facing downward, and the gripping area was clamped in an upper chuck and folded back 90 degrees. A moving jig was used so that the angle between the wire fixed to the jig and the coating layer was maintained at 90 degrees. The coating layer was peeled off 30 mm at a pulling rate of 100 mm / min, the tensile stress was measured, and the maximum stress was taken as the peel strength. In the table, "break" means that the coating layer broke during peeling.

[0153] (L* value of conductor) Using a CMS-35FS (sensor head φ1.6 mm) manufactured by Murakami Color Research Laboratory, the coating layer was peeled off from the electric wire produced in the example, and the surface of the remaining conductor was measured to obtain the L* value (A) of the conductor.

[0154] (L* value of conductor after surface oxide film removal treatment) The coating layer was peeled off from the electric wires produced in the examples, and the surface was polished to a depth of 0.3 mm or more. The treated surface was used as the surface from which the oxide layer had been removed, and the L* value (B) of the conductor after the surface oxide layer removal treatment was measured using a CMS-35FS (sensor head φ1.6 mm) manufactured by Murakami Color Research Laboratory.

[0155] (Outer diameter stable after annealing) The thickness of the coating layer before annealing was measured by cross-sectional measurement using a Keyence VHX-5000 digital microscope. The measurement was performed at a magnification of 50x, and the cross-section was polished to remove any irregularities.

[0156] The average thickness (A) before annealing was calculated by measuring the thickness of the coating layer at eight equally spaced locations on each cross section at five different locations for each sample, and averaging the 40 measurements for each sample. For example, in the case of a roughly rectangular sample, measurements were taken at eight locations on each cross section, including the centers of the four sides and the corners of the rectangle.

[0157] The annealing treatment was carried out by heating the electric wire at 200° C. for 3 hours, and after sufficient cooling to room temperature, the average thickness (B) after the annealing treatment was calculated by the method described above.

[0158] The obtained average thickness was calculated as the rate of change in average film thickness before and after annealing according to the following formula. Change rate (%) = [(average film thickness after annealing) / (average film thickness before annealing)] × 100

[0159] In the examples and comparative examples, the following thermoplastic resins were used. PFA1: Fluorine resin (TFE / PPVE copolymer, TFE / PPVE = 97.6 / 2.4 (mol%), functional groups: 173 / 10 6 C, MFR28g / 10min) FEP1: Fluorine resin (TFE / HFP / PPVE copolymer, TFE / HFP / PPVE = 91.7 / 7.9 / 0.4 (mol%), functional groups: 517 / 10 6 C, MFR25g / 10min) PFA2: Fluorine resin (TFE / PPVE copolymer, TFE / PPVE = 97.3 / 2.7 (mol%), functional groups 799 / 10 6 C, MFR68g / 10min)

[0160] In the examples and comparative examples, the following conductors were used. Conductor 1: Copper round wire with a roughly circular cross section, diameter 1.0 mm, surface roughness 0.16 μm, circumference 3.14 mm Conductor 2: Copper flat wire with a roughly rectangular cross section, thickness (short side) 2.0 mm, width (long side) 3.4 mm, surface roughness 0.31 μm, circumference 10.80 mm

[0161] Examples and Comparative Examples Electric wires were produced by extruding thermoplastic resins onto conductors using an extrusion molding machine equipped with dies having shapes shown in Tables 3 to 5. The various physical properties of the obtained electric wires were measured using the methods described above. The results are shown in Tables 3 to 5.

[0162] [Table 3]

[0163] [Table 4]

[0164] [Table 5]

Claims

1. A method for producing an electric wire using an extruder equipped with a cylinder, a screw, a nipple, and a die, the method comprising: The conductor is fed through a passage opening of the nipple housed in the die, and the thermoplastic resin is coated in the die to form the coating layer. The distance L between the conductor and the thermoplastic resin in the die, the smallest cross-sectional area in the die, and the parallel dies ２ and the ratio D of the maximum length of the opening of the die (L ２ / D) is 4.0 or more.

2. The length L from the tip of the nipple where the conductor and the thermoplastic resin come into direct contact within the die to the die opening １ and the length L ２ The relationship between １ >L ２ The method according to claim 1, wherein

3. The length L from the tip of the nipple where the conductor and the thermoplastic resin come into direct contact within the die to the die opening １ and the length L ２ The relationship between １ -L ２ The manufacturing method according to claim 1 or 2, wherein the thickness is greater than 10 (mm).

4. 3. The manufacturing method according to claim 1, wherein the die is a crosshead die.

5. 3. The method according to claim 1, wherein the thermoplastic resin is a fluororesin.

6. An electric wire comprising a conductor and a coating layer containing a fluororesin, wherein the ratio of scattering intensity (longitudinal direction) to scattering intensity (horizontal axis direction) is 3.0 or less. Ratio = Scattering intensity (longitudinal direction) / Scattering intensity (horizontal axis direction) Scattering intensity (longitudinal direction): Scattering intensity obtained by small-angle X-ray scattering measurement of the coating layer, measured by scanning X-rays along the longitudinal direction of the electric wire (scattering vector q = 0.3 nm －１ ) Scattering intensity (horizontal axis direction): Scattering intensity obtained by small-angle X-ray scattering measurement of the coating layer, measured by scanning X-rays along the horizontal axis of the electric wire (scattering vector q = 0.3 nm －１ )

7. The electric wire according to claim 6, wherein the coating layer is a single layer.

8. 8. The electric wire according to claim 6, wherein the surface roughness Sz of the conductor is 1 μm or less.

9. The electric wire according to claim 6 or 7, wherein when a test piece made from the electric wire is stretched to an elongation rate of 10% in an adhesion test conducted in accordance with JIS C3216-3, no lifting of the coating layer occurs.

10. The electric wire according to claim 6 or 7, which has a pull-out strength of 5 N / mm or more. Pull-out strength (N / mm) = maximum point stress (N) / outer circumference of conductor (mm) Maximum point stress: Maximum point stress (N) measured by pulling the coating layer off the conductor of the wire

11. 8. The electric wire according to claim 6, wherein a rate of change in pull-out strength of the electric wire before and after heating is less than 10%. Change rate (%) = [(pull-out strength before heating) - (pull-out strength after heating)] / (pull-out strength before heating) x 100 Pull-out strength before heating: The pull-out strength (N / mm) is calculated according to the following formula from the maximum point stress (N) measured by pulling out the coating layer from the conductor of an electric wire that has not been heated to 50°C or higher and the outer circumference (mm) of the conductor. Pull-out strength after heating: An electric wire that has not been heated to 50°C or higher is heated at 200°C for 3 hours, cooled to below 50°C, and then the coating layer is pulled out from the conductor of the electric wire. The pull-out strength (N / mm) is calculated according to the following formula from the maximum point stress (N) measured and the outer circumferential length (mm) of the conductor. Pull-out strength (N / mm) = maximum point stress (N) / outer circumference of conductor (mm)

12. The cross-sectional shape of the conductor is substantially rectangular, 8. The electric wire according to claim 6, wherein a peel strength measured by peeling the coating layer from the conductor is 0.30 N / mm or more.

13. The electric wire according to claim 6 or 7, wherein the difference Δ(A−B) between the L* value (A) of the conductor and the L* value (B) of the conductor after the surface oxide film removal treatment is 20 or less.

14. A stator for a motor, comprising the electric wire according to claim 6 or 7.

15. An inverter motor comprising the motor stator according to claim 14.

16. 16. The inverter motor according to claim 15, wherein a partial discharge inception voltage of the electric wire is higher than a surge voltage generated during operation of the motor.

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