Insulated wire and cable

Abstract

To provide: an insulated wire whose insulator is easy to remove while being unprocessed; and a cable.SOLUTION: An insulated wire 1 includes a conductor 2 and an insulator 3 that covers surrounding of the conductor 2. The insulator 3 is composed of a resin composition in which particles composed of cross-linked fluororesin are dispersed in a base resin.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an insulated wire and a cable. [Background technology]

[0002] Conventionally, an insulated wire in which an insulator is coated around a conductor by solid extrusion has been known. For example, Patent Document 1 discloses an insulated wire in which an insulator made of tetrafluoroethylene polymer (PTFE) is coated around a conductor by solid extrusion, thereby increasing the adhesion between the conductor and the insulator. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-69950 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the adhesion between the conductor and the insulator is strong as in Patent Document 1, there is a problem in that the insulator is difficult to remove during terminal processing at the end of the insulated wire to remove the insulator and expose the conductor. As a result, some of the insulator tends to remain on the surface of the conductor. Furthermore, when attempting to completely remove the insulator, the blade of the removal tool used to cut the insulator may come into contact with the conductor, potentially damaging the conductor's surface. Furthermore, if the insulator is difficult to remove, the conductor may be forcibly pulled longitudinally when removing the insulator, potentially stretching the conductor. Stretching the conductor reduces electrical properties such as conductivity, impairing the reliability of the connection to the connected member.

[0005] It is possible to make it easier to remove the insulator 3 by placing a separator such as tape between the conductor and the insulator, but providing a separator reduces the flexibility (softness) of the insulated wire. Also, the work of removing the separator is added when processing the terminals.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an insulated wire and a cable from which the insulation can be easily removed during terminal processing. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the present invention provides an insulated wire comprising a conductor and an insulator covering the conductor, wherein the insulator is made of a resin composition in which particles made of cross-linked fluororesin are dispersed in a base resin.

[0008] Furthermore, in order to solve the above-mentioned problems, the present invention provides a cable including one or more of the above-mentioned insulated wires. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an insulated wire and a cable from which the insulation can be easily removed during terminal processing. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of an insulated wire according to an embodiment of the present invention, and an enlarged view of a portion thereof; [Figure 2] 1 is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of a multi-core cable according to an embodiment of the present invention. [Figure 3] 1A and 1B are a cross-sectional view showing a cross section perpendicular to the longitudinal direction of a coaxial cable according to an embodiment of the present invention, and an enlarged view of a portion thereof; [Figure 4] 1 is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of a cable for transmitting an operating signal, which is a cable according to an embodiment of the present invention, and a partially enlarged view thereof. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Embodiment Mode] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0012] 1 is a cross-sectional view perpendicular to the longitudinal direction of an insulated wire 1 according to the present embodiment, and an enlarged view of a portion thereof. As shown in FIG. 1, the insulated wire 1 includes a conductor 2 and an insulator 3 that covers the conductor 2.

[0013] (Conductor 2) The conductor 2 is a stranded conductor formed by stranding together a plurality of metal wires 2a made of annealed copper wire, copper alloy wire, etc. The surfaces of the metal wires 2a may be plated with tin, silver, or the like.

[0014] (Insulator 3) In the insulated wire 1 according to this embodiment, the insulator 3 is made of a resin composition in which particles made of cross-linked fluororesin are dispersed in a base resin. The particles made of cross-linked fluororesin are made of 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 method is solid extrusion or tube extrusion. When the insulator 3 is formed around the conductor 2 by solid extrusion, adhesion to the conductor 2 can be improved compared to when the insulator 3 is formed by tube extrusion.

[0015] Cross-linked fluororesin is a non-melt resin that does not exhibit melt fluidity even when heated above its melting point. It is characterized by its resistance to aggregation and excellent dispersibility. Therefore, using particles made of fluororesin with a cross-linked structure makes it easier to uniformly disperse the particles in the base resin. Furthermore, uniform dispersion of particles made of non-melt cross-linked fluororesin in the base resin makes it possible to form fine and uniform irregularities on the surface of the insulator 3 after molding. As a result, even if the insulator 3 is formed by solid extrusion so as to penetrate between the metal strands 2a constituting the conductor 2, minute voids exist between the surface of the conductor 2 (metal strands 2a) and the insulator 3, thereby reducing the adhesion of the insulator 3 to the conductor 2. This makes it easy to peel the insulator 3 from the conductor 2 during terminal processing. The minute voids existing between the surface of the conductor 2 (metal strands 2a) and the insulator 3 are, for example, 10 μm or less in linear distance from the surface of the conductor 2 to the inner surface of the insulator 3.

[0016] The insulator 3 preferably has an arithmetic mean roughness Ra of at least its inner surface (inner peripheral surface) of 1 μm or more and 10 μm or less. This makes it possible to reduce the adhesion of the insulator 3 to the conductor 2 while suppressing fluctuations in the outer diameter of the insulator 3, making it easier to remove the insulator 3 during terminal processing. The insulator 3 is preferably formed by tube extrusion, but may also be formed by solid extrusion. Even in the case of solid extrusion, the insulator 3 contains particles made of cross-linked fluororesin, which prevents the resin from flowing into the small gaps between the metal wires 2a of the conductor 2. This reduces the adhesion of the insulator 3 to the conductor 2 compared to when the insulator 3 does not contain particles made of cross-linked fluororesin.

[0017] The insulator 3 also preferably has fine irregularities on its outer surface (peripheral surface), with the arithmetic mean roughness Ra of the outer surface being 1 μm or more and 10 μm or less. This makes the insulator 3 less susceptible to wear even when the insulated wire 1 comes into contact with other members, improving its abrasion resistance. Furthermore, water and dirt are less likely to adhere to the outer surface of the insulator 3, and even if they do adhere, they can be easily wiped off.

[0018] The particles made of crosslinked fluororesin are formed by irradiating uncrosslinked fluororesin formed into a sheet with ionizing radiation to crosslink it, and then pulverizing the sheet into particles having a particle size of 25 μm or less, more preferably 20 μm or less. That is, the particle size of the particles made of crosslinked fluororesin used in this embodiment is 25 μm or less, more preferably 20 μm or less. In this embodiment, since the thickness of the insulator 3 is about 100 μm, including particles having a particle size larger than 25 μm would result in excessive fluctuation in the outer diameter of the insulator 3, which is not preferable.

[0019] The uncrosslinked fluororesin used for the crosslinked fluororesin may be, for example, a tetrafluoroethylene polymer (PTFE), a tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer (PFA), a tetrafluoroethylene / hexafluoropropylene copolymer (FEP), or a tetrafluoroethylene / ethylene copolymer (ETFE). In this embodiment, PTFE is used as the uncrosslinked fluororesin used for the crosslinked fluororesin. When crosslinking the uncrosslinked fluororesin, the crosslinking treatment may be performed by irradiating the uncrosslinked fluororesin with ionizing radiation in an inert gas atmosphere with an oxygen concentration of 100 torr or less (more preferably 10 torr or less) at a temperature higher than the melting point of the uncrosslinked fluororesin.

[0020] The cross-linked fluororesin preferably has a content of 10 ppb or less of perfluorocarbon compounds (PFCAs) having 8 carbon atoms. The cross-linked fluororesin preferably has a content of 25 ppb or less of each of PFCAs having 9 to 21 carbon atoms. In this embodiment, the content of PFCAs, which are known to be environmentally hazardous substances, is reduced by performing a heat treatment under predetermined conditions after cross-linking. This allows for the realization of an insulated wire 1 with even less environmental impact. The heat treatment may be performed, for example, at a temperature higher than the melting point of the cross-linked fluororesin and 100°C lower than the melting point of the cross-linked fluororesin.

[0021] The base resin used for the insulator 3 may be nylon, a fluororesin such as ETFE, an engineering plastic such as PEEK (polyether ether ketone), polyimide, polyethylene, polypropylene, or the like. For example, when ETFE is used as the base resin, the heat resistance of the insulator 3 can be improved by including particles made of cross-linked fluororesin. This allows the thickness of the insulator 3 to be thin, resulting in an insulated wire 1 suitable for use as a wiring material in a small space.

[0022] From the viewpoint of reducing environmental impact, it is preferable to use a non-fluororesin such as nylon as the base resin for the insulator 3, rather than a fluororesin. By dispersing particles made of cross-linked fluororesin in the base resin, as in the present embodiment, it is possible to achieve sufficient abrasion resistance, etc., without using a fluororesin as the base resin. For example, when nylon is used as the base resin, adding particles made of cross-linked fluororesin makes it possible to achieve abrasion resistance equivalent to that of ETFE. Therefore, as an alternative to ETFE, a resin composition in which particles made of cross-linked fluororesin are dispersed in nylon can be used for the insulator 3, thereby reducing the amount of fluororesin used and further reducing the environmental impact. Similarly, when polyimide is used as the base resin, adding particles made of cross-linked fluororesin can reduce the relative dielectric constant of the insulator 3 and increase the partial discharge inception voltage.

[0023] The insulator 3 preferably contains particles made of cross-linked fluororesin in an amount of 10 mass% to 20 mass%. That is, the mass ratio of the base resin to the particles made of cross-linked fluororesin (base resin:particles made of cross-linked fluororesin) is preferably within a range of 90:10 to 80:20. If the particles made of cross-linked fluororesin are less than 10 mass%, the effect of suppressing the adhesion of the insulator 3 to the conductor 2 cannot be sufficiently obtained. On the other hand, if the particles made of cross-linked fluororesin are more than 20 mass%, the fluidity decreases, making it difficult to extrude the insulator 3.

[0024] (Cable 10) Next, a cable 10 using the insulated wire 1 will be described. The cable 10 is, for example, a cable for moving parts used in moving parts of industrial robots, etc., a signal transmission cable wired inside electronic devices, etc. The cable 10 may have various structures as long as it includes one or more insulated wires 1 according to the present embodiment.

[0025] The cable 10 may be a multi-core cable 11. Fig. 2 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 together a plurality of (six in this case) insulated wires 1, a tape member 11b wound spirally around the cable core 11a, a shielding layer 11c provided so as to cover the periphery of the tape member 11b, and a sheath 11d provided so as to cover the shielding layer 11c.

[0026] The cable core 11a is formed by twisting together a plurality of insulated wires 1 (six in this example) and a fiber interposer 11e made of nylon or the like. The fiber interposer 11e can be omitted. The insulated wires 1 have minute irregularities on their outer surfaces, which can suppress wear of the insulator 3 due to friction between adjacent insulated wires 1 or between the insulated wires 1 and the tape member 11b, even when the multi-core cable 11 is repeatedly bent, twisted, or otherwise subjected to other operations. This makes it difficult for the insulating performance of the insulator 3 to deteriorate due to repeated bending, twisting, U-shaped sliding, and other operations.

[0027] The tape member 11b is made of, for example, a resin tape, and is spirally wound so that parts of it overlap in the width direction. The shielding layer 11c is made of a braided shield made of multiple braided metal wires, a horizontally wound shield made of multiple spirally wound metal wires, a plated shield plated with a metal such as copper, or a combination of these. The shielding layer 11c can be omitted depending on the application. The sheath 11d is made of, for example, polyvinyl chloride resin.

[0028] The cable 10 may be a coaxial cable 12 or a multi-core cable 11. FIG. 3 shows a cross-sectional view of the coaxial cable 12 taken perpendicular to its longitudinal direction, with a partial enlargement. The coaxial cable 12 is configured by sequentially providing a shield layer 12a and a sheath 12c around the insulated wire 1. The shield layer 12a may be a braided shield formed by braiding multiple metal wires, a horizontally wound shield formed by spirally winding multiple metal wires, a plated shield plated with a metal such as copper, or a combination of these. When the shield layer 12a is a plated shield, it is desirable to provide a crack-suppressing layer made of polyethylene or the like between the insulator 3 and the shield layer 12a to suppress cracks from occurring in the plated shield. The sheath 12b is made of, for example, polyvinyl chloride resin. The sheath 12b may also be configured by wrapping a resin tape made of polyethylene, polyimide, or the like around the shield layer.

[0029] In the example shown in FIG. 3, the conductor 2 of the insulated wire 1 is a compressed stranded conductor, which is a stranded conductor compressed to a circular cross section. By using a compressed stranded conductor for the conductor 2, the gaps between the metal strands 2a are reduced, significantly reducing the conductor resistance of the conductor 2, improving electrical characteristics such as attenuation and characteristic impedance matching, and achieving a conductor 2 with excellent flexibility. In particular, a compressed stranded conductor is desirable for a coaxial cable 12 used for high-speed transmission in a high-frequency band, such as 25 GHz. A compressed stranded conductor is formed by compressing a stranded conductor, for example, made by concentrically twisting seven metal strands 2a, through a die with a smaller diameter than the stranded conductor and a circular exit, multiple times. Note that compressing the metal strands 2a through the die imparts strain to the metal strands 2a, reducing their electrical conductivity. However, subsequent heat treatment (annealing) can remove the strain and achieve electrical conductivity of 99% IACS or higher. The packing ratio of the compressed stranded conductor (the ratio of the cross-sectional area of ​​the metal wires to the cross-sectional area of ​​the outer circumferential circle of the compressed conductor) is preferably 95% or more and less than 100%. Note that the conductor 2 may be a non-compressed stranded conductor as shown in FIG.

[0030] In the coaxial cable 12, it is sometimes desirable to increase the thickness of the insulator 3 (for example, to make the thickness of the insulator 3 approximately the same as the outer diameter of the conductor 2) in order to match the characteristic impedance. In such cases, the insulator 3 becomes difficult to strip during terminal processing, and the conductor 2 may be forcibly pulled in the longitudinal direction when the insulator 3 is stripped, resulting in the risk of stretching the conductor 2. In contrast, in the present embodiment, the inner surface of the insulator 3 is formed with minute irregularities, which reduces the adhesive force at the interface between the insulator 3 and the conductor 2, making it easier to strip the insulator 3 even when the insulator 3 is thick. This makes it possible to realize a coaxial cable 12 that is easy to process for terminal processing.

[0031] Furthermore, by providing minute irregularities on the inner and outer surfaces of the insulator 3, minute gaps 4 can be formed between the conductor 2 and the insulator 3, and between the insulator 3 and the shielding layer 12a. This makes it possible to suppress deterioration of electrical characteristics (particularly attenuation) without foaming the insulator 3. Not foaming the insulator 3 also makes it possible to suppress deterioration of electrical characteristics due to crushing of the insulator 3. However, it is not essential that the insulator 3 be non-foamed, and the insulator 3 may be made of foamed resin.

[0032] FIG. 4 shows a cross-sectional view of a coaxial cable 12 taken perpendicular to its longitudinal direction, and an enlarged view of a portion thereof. As shown in FIG. 4, the cable 10 may be a differential signal cable 13 in which a pair of parallel-arranged conductors 2 are collectively covered with an insulator 3, and a shielding layer 13a and a sheath 13b are sequentially provided around the insulator 3. In this case, as with the coaxial cable 12 described above, the insulator 3 can be easily stripped from the conductors 2, facilitating terminal processing. Furthermore, the formation of voids 4 on the surface of the insulator 3 prevents foaming of the insulator 3 and suppresses deterioration of electrical characteristics (particularly attenuation). When stripping the insulator 3 from the conductors 2, the insulator 3 formed between adjacent conductors 2 (i.e., the insulator 3 formed in the center of the cable) can be easily stripped.

[0033] The structure of cable 10 shown in FIGS. 2 to 4 is merely an example, and the present invention is applicable to cables 10 with various structures.

[0034] (Actions and Effects of the Embodiments) As described above, in the insulated wire 1 according to this embodiment, the insulator 3 is made of a resin composition in which particles made of cross-linked fluororesin are dispersed in a base resin. Particles made of cross-linked fluororesin are non-melt-type and have low coagulation properties, making them easy to disperse. Therefore, by uniformly dispersing the particles made of cross-linked fluororesin in the base resin, fine irregularities are uniformly formed on the surface of the insulator 3, reducing adhesion to the conductor 2 and making it easier to remove the insulator 3 during terminal processing.

[0035] Furthermore, since the outer surface of the insulator 3 is also formed with fine irregularities, it is possible to suppress abrasion due to rubbing against other members, improving abrasion resistance. Furthermore, since the outer surface of the insulator 3 is also formed with fine irregularities, it becomes difficult for liquids such as water and dirt to adhere to the periphery of the insulated wire 1, and even if they do adhere, they can be easily wiped off.

[0036] Furthermore, according to this embodiment, it is possible to achieve abrasion resistance and the like equivalent to that achieved when a fluororesin is used as the base resin, even without using a fluororesin. This makes it possible to reduce the amount of fluororesin used in the insulator 3 and further reduce the burden on the environment. Furthermore, reducing the amount of fluororesin used in the insulator 3 also makes it possible to reduce costs.

[0037] (Summary of the embodiment) Next, the technical ideas grasped from the above-described embodiments will be described by using the reference numerals and the like in the embodiments. However, the reference numerals and the like in the following description do not limit the components in the claims to the members and the like specifically shown in the embodiments.

[0038] [1] An insulated wire (1) comprising a conductor (2) and an insulator (3) covering the conductor (2), the insulator (3) being made of a resin composition in which particles made of cross-linked fluororesin are dispersed in a base resin.

[0039] [2] The insulated wire (1) according to [1], wherein the insulator (3) contains particles made of the cross-linked fluororesin in an amount of 10 mass % to 20 mass %.

[0040] [3] The insulated wire (1) according to [1], wherein the insulator (3) has an arithmetic mean roughness Ra of at least its inner surface of 1 μm or more and 10 μm or less.

[0041] [4] The insulated wire (1) according to [1], wherein the cross-linked fluororesin contains 10 ppb or less of perfluoro compounds having 8 carbon atoms, and 25 ppb or less of each of perfluoro compounds having 9 to 21 carbon atoms.

[0042] [5] The insulated wire (1) according to [1], wherein the base resin is made of a non-fluorine resin.

[0043] [6] A cable (10) comprising one or more insulated wires (1) according to any one of [1] to [5].

[0044] (Addendum) Although the embodiments of the present invention have been described above, the invention according to the claims is not limited to the above-described embodiments. It should be noted that not all of the combinations of features described in the embodiments are necessarily essential to the means for solving the problems of the invention. Furthermore, the present invention can be appropriately modified and implemented within the scope of its spirit. [Explanation of symbols]

[0045] 1...Insulated wire 2...conductor 3...Insulator 4...Void 10...Cable

Claims

1. A conductor; and an insulator covering the conductor. The insulator is made of a resin composition in which particles made of a crosslinked fluororesin are dispersed in a base resin. Insulated wire.

2. The insulator contains particles made of the cross-linked fluororesin in an amount of 10 mass% or more and 20 mass% or less. The insulated wire according to claim 1 .

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

4. The crosslinked fluororesin is The content of perfluoro compounds having 8 carbon atoms is 10 ppb or less, The content of each of the perfluoro compounds having a carbon number of 9 to 21 is 25 ppb or less. The insulated wire according to claim 1 .

5. The base resin is made of a non-fluorine resin. The insulated wire according to claim 1 .

6. A wire comprising one or more insulated electric wires according to any one of claims 1 to 5. cable.

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