Insulated wire and cable

Abstract

The invention provides an insulated wire and a cable in which an insulator is easy to remove during end processing. An insulated wire (1) is provided with a conductor (2) and an insulator (3) that covers the periphery of the conductor (2), and the insulator (3) is configured from a resin composition in which particles comprising a crosslinked fluororesin are dispersed in a base resin.

Description

Technical Field

[0001] The present invention relates to insulated wire and cable. Background Art

[0002] In the past, there is known an insulated wire in which an insulator is coated around a conductor by solid extrusion. For example, Patent Document 1 discloses an insulated wire in which an insulator composed of a tetrafluoroethylene polymer (PTFE) is coated around a conductor by solid extrusion to improve the adhesion between the conductor and the insulator.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2015-69950 Summary of the invention

[0006] Problems to be solved by the invention

[0007] However, when the close contact between the conductor and the insulator increases as in Patent Document 1, it becomes difficult to remove the insulator when processing the end of the insulated wire to remove the insulator and expose the conductor. Therefore, part of the insulator is likely to remain on the surface of the conductor. In addition, if the insulator is to be completely removed, the blade of the removal tool that forms a crack on the insulator will come into contact with the conductor, which may cause damage to the surface of the conductor. In addition, if the insulator is difficult to remove, the conductor will be forcibly stretched in the length direction when the insulator is removed, and the conductor may be elongated. If the conductor is elongated, electrical properties such as conductivity will decrease, and the connection reliability to the connected component will be impaired.

[0008] It should be noted that it is also possible to facilitate the removal of the insulator 3 by placing a separator such as a tape between the conductor and the insulator, but if a separator is provided, the flexibility (softness) of the insulated wire will be reduced. In addition, the work of removing the separator is added during the terminal processing.

[0009] Therefore, an object of the present invention is to provide an insulated wire and a cable whose insulation can be easily removed during terminal processing.

[0010] Methods for solving problems

[0011] The present invention aims to solve the above-mentioned problems and provides an insulated wire comprising a conductor and an insulator covering the periphery of the conductor, wherein the insulator is composed of a resin composition in which particles composed of a cross-linked fluororesin are dispersed in a base resin.

[0012] In order to solve the above-mentioned problems, the present invention provides a cable including one or more of the above-mentioned insulated wires.

[0013] Effects of the Invention

[0014] According to the present invention, it is possible to provide an insulated wire and a cable whose insulation can be easily removed during terminal processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A cross-sectional view and a partially enlarged view showing a cross section perpendicular to the longitudinal direction of an insulated wire according to an embodiment of the present invention.

[0016] Figure 2 This is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of a multi-core cable as a cable according to one embodiment of the present invention.

[0017] Figure 3 A cross-sectional view and a partially enlarged view showing a cross section perpendicular to the longitudinal direction of a coaxial cable as a cable according to one embodiment of the present invention.

[0018] Figure 4 The present invention is a cross-sectional view and a partially enlarged view showing a cross section perpendicular to the longitudinal direction of a working signal transmission cable as a cable according to an embodiment of the present invention.

[0019] Explanation of symbols

[0020] 1…insulated wire, 2…conductor, 3…insulator, 4…space, 10…cable. DETAILED DESCRIPTION

[0021] [Implementation Method]

[0022] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0023] Figure 1 1 is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of the insulated wire 1 of the present embodiment and a partially enlarged view thereof. Figure 1 As shown, the insulated wire 1 includes a conductor 2 and an insulator 3 covering the conductor 2 .

[0024] (Conductor 2)

[0025] The conductor 2 is composed of a stranded conductor obtained by twisting a plurality of metal wires 2a composed of annealed copper wires, copper alloy wires, etc. The surface of the metal wires 2a may be plated with tin, silver, etc.

[0026] (Insulator 3)

[0027] In the insulated wire 1 of the present embodiment, the insulator 3 is composed of a resin composition in which particles composed of a cross-linked fluororesin are dispersed in a base resin. The particles composed of the cross-linked fluororesin are composed of a fluororesin having a cross-linked structure that is cross-linked by irradiation with ionizing radiation. The insulator 3 is formed around the conductor 2 by extrusion molding. The extrusion molding is solid extrusion or tube extrusion. If the insulator 3 is formed around the conductor 2 by solid extrusion, the adhesion with the conductor 2 can be improved compared to the case of forming by tube extrusion.

[0028] Cross-linked fluororesin is a non-melting resin that does not show melt fluidity even when heated to above its melting point, and has the characteristics of being difficult to agglomerate and having very high dispersibility. Therefore, by using particles composed of a fluororesin having a cross-linked structure, it is easy to evenly disperse the particles in the base resin. Moreover, by evenly dispersing the particles composed of the non-melting cross-linked fluororesin in the base resin, fine and uniform concavoconvexities can be formed on the surface of the insulator 3 after molding. As a result, even if the insulator 3 is formed by solid extrusion in a manner that enters between the metal wires 2a constituting the conductor 2, the adhesion of the insulator 3 to the conductor 2 can be reduced due to the presence of a tiny gap between the surface of the conductor 2 (metal wire 2a) and the insulator 3. As a result, the insulator 3 can be easily peeled off from the conductor 2 during the terminal processing. The tiny gap between the surface of the conductor 2 (metal wire 2a) and the insulator 3 is, for example, a size of less than 10 μm in terms of the straight-line distance from the surface of the conductor 2 to the inner surface of the insulator 3.

[0029] In the insulator 3, the arithmetic mean roughness Ra of at least the inner surface (inner circumference) thereof can be greater than 1 μm and less than 10 μm. Thus, the outer diameter variation of the insulator 3 can be suppressed, and the closeness of the insulator 3 relative to the conductor 2 can be reduced, and the insulator 3 can be easily removed during the end processing. The insulator 3 is preferably formed by tube extrusion, but can also be formed by solid extrusion. Even in the case of solid extrusion, by including particles composed of a cross-linked fluororesin, the resin can be prevented from flowing into the fine gaps between the metal wires 2a of the conductor 2, so that the closeness of the insulator 3 relative to the conductor 2 can be reduced compared to the case where the particles composed of the cross-linked fluororesin are not included.

[0030] In addition, the insulator 3 may have fine concavo-convex on its outer surface (peripheral surface), and the arithmetic mean roughness Ra of the outer surface may be 1 μm or more and 10 μm or less. Thus, even if the insulated wire 1 contacts other components, the insulator 3 is not easily worn, and the wear resistance is improved. In addition, water and dirt are difficult to adhere to the outer surface of the insulator 3, and even if they adhere, they can be easily wiped off.

[0031] The particles composed of cross-linked fluororesin are formed by irradiating uncross-linked fluororesin formed into a sheet shape with ionizing radiation to cross-link the sheet, and then crushing the sheet into particles with a particle size of 25 μm or less, more preferably 20 μm or less. That is, the particle size of the particles composed of cross-linked fluororesin used in the present embodiment is 25 μm or less, more preferably 20 μm or less. It should be noted that in the present embodiment, since the thickness of the insulator 3 is about 100 μm, if particles with a particle size greater than 25 μm are included, the outer diameter of the insulator 3 changes too much, which is not preferred.

[0032] The uncrosslinked fluororesin used for crosslinking fluororesin is composed of, for example, tetrafluoroethylene polymer (PTFE), tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), and tetrafluoroethylene / ethylene copolymer (ETFE). In the present embodiment, PTFE is used as the uncrosslinked fluororesin used for crosslinking fluororesin. When crosslinking the uncrosslinked fluororesin, the crosslinking treatment may be performed by irradiating ionizing radiation at a temperature higher than the melting point of the uncrosslinked fluororesin in an inactive gas atmosphere with an oxygen concentration of 100 torr or less (more preferably 10 torr or less).

[0033] The content of perfluorinated compounds (PFCA) with 8 carbon atoms in the cross-linked fluororesin can be 10 ppb or less. In addition, the content of each PFCA with 9 to 21 carbon atoms in the cross-linked fluororesin can be 25 ppb or less. In this embodiment, by performing a heat treatment under prescribed conditions after cross-linking, the content of PFCA known as an environmental load substance is reduced. As a result, an insulated wire 1 with less load on the environment can be achieved. As a heat treatment, for example, it can be carried out in a temperature range that is higher than the melting point of the cross-linked fluororesin and 100°C or less than the melting point of the cross-linked fluororesin.

[0034] As the base resin used in the insulator 3, nylon, fluororesin such as ETFE, engineering plastics such as PEEK (polyetheretherketone), polyimide, polyethylene, polypropylene, etc. can be used. For example, when ETFE is used as the base resin, by including particles composed of a cross-linked fluororesin, the heat resistance of the insulator 3 can be improved. Therefore, the thickness of the insulator 3 can be reduced, and the insulated wire 1 suitable as a wiring material for space saving can be obtained.

[0035] From the viewpoint of reducing the environmental load, as the base resin used in the insulator 3, it is also possible to use non-fluorine resins such as nylon instead of fluororesin. As in the present embodiment, by dispersing particles composed of cross-linked fluororesin in the base resin, sufficient wear resistance can be achieved even if fluororesin is not used as the base resin. For example, when nylon is used as the base resin, by including particles composed of cross-linked fluororesin, wear resistance equivalent to ETFE can be achieved. Therefore, as a substitute for ETFE, a resin composition in which particles composed of cross-linked fluororesin are dispersed in nylon can be used for the insulator 3, the amount of fluororesin used can be suppressed, and the load on the environment can be further suppressed. Similarly, when polyimide is used as the base resin, by including particles composed of cross-linked fluororesin, the relative dielectric constant of the insulator 3 can be reduced, and the partial discharge starting voltage can be improved.

[0036] The insulator 3 may contain 10% by mass or more and 20% by mass or less of particles composed of a cross-linked fluororesin. That is, the mass ratio of the base resin to the particles composed of the cross-linked fluororesin (base resin: particles composed of the cross-linked fluororesin) may be in the range of 90:10 to 80:20. If the particles composed of the cross-linked fluororesin are less than 10% by mass, the effect of suppressing the adhesion of the insulator 3 to the conductor 2 cannot be fully obtained. In addition, when the particles composed of the cross-linked fluororesin are more than 20% by mass, the fluidity is reduced, and extrusion molding of the insulator 3 becomes difficult.

[0037] (cable 10)

[0038] Next, a cable 10 using the insulated wire 1 is described. The cable 10 is, for example, a movable part cable used in a movable part of an industrial robot or the like, a signal transmission cable wired inside an electronic device or the like. The cable 10 only needs to include one or more insulated wires 1 of the present embodiment, and may have various structures.

[0039] The cable 10 may also be a multi-core cable 11 . Figure 2 1 is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of the multi-core cable 11. The multi-core cable 11 includes a cable core 11a formed by twisting a plurality of (here, six) insulated wires 1, a belt member 11b spirally wound around the cable core 11a, a shielding layer 11c provided to cover the belt member 11b, and a sheath 11d provided to cover the shielding layer 11c.

[0040] The cable core 11a is formed by twisting a plurality of (six in this case) insulated wires 1 and a fiber interlayer 11e made of nylon or the like. It should be noted that the fiber interlayer 11e can be omitted. Since the insulated wires 1 have fine irregularities on their outer surfaces, even if the multi-core cable 11 is repeatedly subjected to bending, twisting, and other actions, it is possible to suppress the wear of the insulator 3 caused by the friction between adjacent insulated wires 1 or the friction between the insulated wires 1 and the belt member 11b. Therefore, the insulation performance of the insulator 3 is not easily reduced with respect to repeated bending, twisting, U-shaped sliding, and other actions.

[0041] The belt member 11b is made of, for example, a resin belt, and is wound in a spiral shape so that a portion of the belt is overlapped in the width direction. The shielding layer 11c is made of a braided shielding member made by braiding a plurality of metal wires, a transversely wound shielding member made by winding a plurality of metal wires in a spiral shape, a plated shielding member made by plating a metal such as copper, or a combination of a plurality of these. It should be noted that the shielding layer 11c can be omitted depending on the application. The sheath 11d is made of, for example, a polyvinyl chloride resin.

[0042] The cable 10 may also be a coaxial cable 12. It may also be a multi-core cable 11. Figure 3 It is a cross-sectional view and a partially enlarged view showing a cross section perpendicular to the length direction of the coaxial cable 12. The coaxial cable 12 is formed by sequentially arranging a shielding layer 12a and a sheath 12c around the insulated wire 1. The shielding layer 12a is composed of a braided shielding member formed by braiding a plurality of metal wires, a transversely wound shielding member formed by winding a plurality of metal wires into a spiral shape, a plated shielding member formed by plating a metal such as copper, or a combination of a plurality of them. It should be noted that in the case where the shielding layer 12a is composed of a plated shielding member, it is preferred that a crack suppression layer composed of polyethylene or the like and used to suppress cracks in the plated shielding member is provided between the insulator 3 and the shielding layer 12a. The sheath 12b is composed of, for example, a polyvinyl chloride resin or the like. The sheath 12b can also be formed by winding a resin tape composed of polyethylene, polyimide, or the like.

[0043] exist Figure 3In the example, the conductor 2 of the insulated wire 1 is composed of a compressed stranded conductor obtained by compressing a stranded conductor into a circular cross-section. By forming the conductor 2 from a compressed stranded conductor, the gap between the metal wires 2a can be reduced and the conductor resistance of the conductor 2 can be greatly suppressed, the electrical characteristics such as attenuation and characteristic impedance matching can be improved, and a conductor 2 with excellent bending resistance can be achieved. In particular, in a coaxial cable 12 used for high-speed transmission in a high-frequency band such as 25 GHz, a compressed stranded conductor is preferably used as the conductor 2. The compressed stranded conductor is formed by, for example, passing a stranded conductor formed by concentrically twisting 7 metal wires 2a through a die having a smaller diameter than the stranded conductor and a circular outlet multiple times and compressing it. It should be noted that by passing through the die for compression, strain can be applied to the metal wire 2a, thereby reducing the conductivity, but thereafter, by performing a heat treatment (annealing treatment), the strain can be removed and a conductivity of 99% IACS or more can be achieved. The filling rate of the compressed stranded conductor (the ratio of the cross-sectional area of ​​the metal wire portion to the cross-sectional area of ​​the outer circumference of the compressed conductor) may be 95% or more and less than 100%. Figure 1 As shown, the conductor 2 can also be an uncompressed stranded conductor.

[0044] In the coaxial cable 12, in order to match the characteristic impedance, it is sometimes desirable to increase the thickness of the insulator 3 (for example, to make the thickness of the insulator 3 the same as the outer diameter of the conductor 2). In such a case, the insulator 3 is difficult to be peeled off during the terminal processing, and when the insulator 3 is peeled off, the conductor 2 is forcibly stretched in the length direction, and the conductor 2 may be elongated. In contrast, in the present embodiment, since fine concavoconvexities are formed on the inner surface of the insulator 3, the adhesion force of the interface between the insulator 3 and the conductor 2 can be reduced, and the insulator 3 can be easily peeled off even when the insulator 3 is thickened. Therefore, a coaxial cable 12 with easy terminal processing can be realized.

[0045] Furthermore, by having fine irregularities on the inner and outer surfaces of the insulator 3, it is possible to form minute gaps 4 between the conductor 2 and the insulator 3, and between the insulator 3 and the shielding layer 12a. Therefore, it is possible to suppress the reduction of electrical characteristics (particularly attenuation) without foaming the insulator 3. By not foaming the insulator 3, it is also possible to suppress the reduction of electrical characteristics caused by the flattening of the insulator 3. However, the insulator 3 does not necessarily have to be non-foamed, and the insulator 3 may be formed of a foamed resin.

[0046] Figure 4 1 is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of the coaxial cable 12 and a partially enlarged view thereof. Figure 4As shown, the cable 10 may be a differential signal cable 13 in which a pair of conductors 2 arranged in parallel are covered with an insulator 3 and a shield layer 13a and a sheath 13b are sequentially provided around the insulator 3. In this case, as in the above-mentioned coaxial cable 12, the insulator 3 can be easily peeled off from the conductor 2 to facilitate the terminal processing. In addition, by forming the gap 4 on the surface of the insulator 3, the insulator 3 is prevented from foaming and the reduction of the electrical characteristics (particularly the attenuation) can be suppressed. When the insulator 3 is peeled off from the conductor 2, the insulator 3 formed between the adjacent conductors 2 (that is, the insulator 3 formed in the center of the cable) is easily peeled off.

[0047] Figure 2 to Figure 4 The structure of the cable 10 shown is just an example, and the present invention can be applied to cables 10 having various structures.

[0048] (Functions and Effects of Implementation Methods)

[0049] As described above, in the insulated wire 1 of the present embodiment, the insulator 3 is composed of a resin composition in which particles composed of a cross-linked fluororesin are dispersed in a base resin. The particles composed of the cross-linked fluororesin are non-fusible and have low cohesion and are easily dispersed. Therefore, the particles composed of the cross-linked fluororesin are uniformly dispersed in the base resin, and fine concavo-convex shapes are uniformly formed on the surface of the insulator 3, thereby suppressing the adhesion to the conductor 2 and making it easy to remove the insulator 3 during terminal processing.

[0050] In addition, since fine concavo-convex shapes are also formed on the outer surface of the insulator 3, wear caused by friction with other components can be suppressed, and wear resistance is improved. In addition, by forming fine concavo-convex shapes on the outer surface of the insulator 3, liquids such as water and dirt are difficult to adhere to the surroundings of the insulated wire 1, and even if they are attached, they can be easily wiped off.

[0051] Furthermore, according to this embodiment, even if fluororesin is not used in the base resin, wear resistance and the like equivalent to that of the case where fluororesin is used can be achieved. Therefore, the amount of fluororesin used in the insulator 3 can be reduced, further reducing the load on the environment. In addition, by reducing the amount of fluororesin used in the insulator 3, costs can also be reduced.

[0052] (Summary of Implementation Methods)

[0053] Next, the technical ideas grasped from the above-described embodiments are described by referring to the symbols in the embodiments. However, the symbols in the following description do not limit the constituent elements in the claims to the members specifically shown in the embodiments.

[0054] [1] An insulated wire (1) comprising a conductor (2) and an insulator (3) covering the conductor (2), wherein the insulator (3) is composed of a resin composition in which particles composed of a cross-linked fluororesin are dispersed in a base resin.

[0055] [2] The insulated wire (1) according to [1], wherein the insulator (3) contains 10% by mass or more and 20% by mass or less of the particles composed of the cross-linked fluororesin.

[0056] [3] The insulated wire (1) according to [1], wherein the insulator (3) has an arithmetic mean roughness Ra of at least the inner surface thereof of not less than 1 μm and not more than 10 μm.

[0057] [4] The insulated wire (1) according to [1], wherein the cross-linked fluororesin contains a perfluoro compound having 8 carbon atoms in a content of 10 ppb or less, and a perfluoro compound having 9 to 21 carbon atoms in a content of 25 ppb or less.

[0058] [5] The insulated wire (1) according to [1], wherein the base resin is composed of a non-fluorine resin.

[0059] [6] A cable (10) comprising one or more insulated wires (1) according to any one of [1] to [5].

[0060] (Note)

[0061] The embodiments of the present invention are described above, but the embodiments described above do not limit the invention involved in the claims. In addition, it should be noted that all combinations of the features described in the embodiments are not necessary for solving the invention problems. In addition, the present invention can be implemented by appropriate deformation within the scope of its purpose.

Claims

1. An insulated wire comprising a conductor and an insulator covering the periphery of the conductor, The insulator is composed of a resin composition in which particles composed of a cross-linked fluororesin are dispersed in a base resin.

2. The insulated wire according to claim 1, wherein The insulator contains 10% by mass or more and 20% by mass or less of the particles composed of the cross-linked fluororesin.

3. The insulated wire according to claim 1, wherein In the insulator, at least an inner surface thereof has an arithmetic mean roughness Ra of 1 μm or more and 10 μm or less.

4. The insulated wire according to claim 1, wherein In the cross-linked fluororesin, the content of the perfluoro compound having 8 carbon atoms is 10 ppb or less, and the content of each perfluoro compound having 9 to 21 carbon atoms is 25 ppb or less.

5. The insulated wire according to claim 1, wherein The base resin is composed of a non-fluorine resin. 6 . A cable comprising one or more insulated wires according to claim 1 .

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