LAN cable

Abstract

To provide a LAN cable which can be made smaller in diameter, and can secure high flame retardancy.SOLUTION: A LAN cable includes a stranded pair cable formed by stranding two insulated wires, a collectively stranded wire formed by stranding the plurality of stranded pair cables, and a sheath coating the outer periphery of the collectively stranded wire, wherein the LAN cable has its outer diameter of 8.8 mm or less, the sheath is composed of a non-halogen flame-retardant resin composition containing a base polymer, a metal hydroxide and carbon black, 180 to 190 pts.mass of the metal hydroxide is contained with respect to 100 pts.mass of the base polymer, 15 to 20 pts.mass of the carbon black is contained with respect to 100 pts.mass of the base polymer, the outer diameter of the insulated wire is 1.5 mm or less, and the outer diameter of the collectively stranded wire is 6.5 mm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a LAN cable. [Background technology]

[0002] LAN cables are cables used to construct LANs (Local Area Networks). These LAN cables are configured with a sheath that covers the outer periphery of an insulated wire, which has an insulating layer formed around the outer periphery of a conductor. Some LAN cables use a non-halogen flame-retardant resin composition for the sheath.

[0003] In particular, LAN cables for railway vehicles are required to have extremely high flame retardancy, meeting the European unified standard for fire safety (single-wire flame retardancy test) of the EN standard, and also to satisfy physical properties such as cable strength, elongation, and low-temperature characteristics.

[0004] When such high flame retardancy is required, it is generally considered to add a large amount of flame retardant, but if the amount of flame retardant added is too high, the physical properties of the sheath will deteriorate, making it difficult to provide a LAN cable that satisfies these properties using only the sheath.

[0005] Therefore, a LAN cable that satisfies the above-mentioned characteristics is known, which has a flame-retardant tape such as a polyimide film between the insulated wire and the sheath that covers its outer periphery, and the sheath has a predetermined degree of cross-linking, so that the LAN cable as a whole satisfies the above-mentioned characteristics (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-64623 Summary of the Invention [Problem to be solved by the invention]

[0007] In recent years, there has been a growing demand for thinner LAN cables. However, because high flame retardancy must be ensured for the above applications, the flame retardant tape placed between the sheath and the insulated wire cannot be omitted, and there has been a limit to how thin the cables can be.

[0008] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a LAN cable that can be made thinner and that can ensure high flame retardancy. [Means for solving the problem]

[0009] In one embodiment, a LAN cable comprises a twisted pair wire formed by twisting two insulated wires together, a bunched stranded wire formed by twisting multiple twisted pair wires together, and a sheath covering the outer circumference of the bunched stranded wire, wherein the LAN cable has an outer diameter of 8.8 mm or less, the sheath is made of a halogen-free flame-retardant resin composition containing a base polymer, a metal hydroxide, and carbon black, the metal hydroxide being contained in an amount of 180 to 190 parts by mass per 100 parts by mass of the base polymer, and the carbon black being contained in an amount of 15 to 20 parts by mass per 100 parts by mass of the base polymer, the insulated wire having an outer diameter of 1.5 mm or less, and the bunched stranded wire having an outer diameter of 6.5 mm or less.

[0010] In one embodiment, a LAN cable comprises a bunched stranded wire formed by twisting together a plurality of insulated wires, and a sheath covering the outer circumference of the bunched stranded wire, wherein the LAN cable has an outer diameter of 8.8 mm or less, the sheath is made of a halogen-free flame-retardant resin composition containing a base polymer, a metal hydroxide, and carbon black, the metal hydroxide being contained in an amount of 180 to 190 parts by mass per 100 parts by mass of the base polymer, and the carbon black being contained in an amount of 15 to 20 parts by mass per 100 parts by mass of the base polymer, the insulated wire having an outer diameter of 2.5 mm or less, and the bunched stranded wire having an outer diameter of 5.5 mm or less. [Effects of the Invention]

[0011] According to the LAN cable of one embodiment, it is possible to provide a LAN cable that can be made thinner and that can ensure high flame retardancy. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic cross-sectional view of a LAN cable according to an embodiment of the present invention; [Figure 2] FIG. 10 is a schematic cross-sectional view of a test cable according to another embodiment. [Figure 3] FIG. 2 is a schematic cross-sectional view of a LAN cable according to a modified example of FIG. [Figure 4] FIG. 2 is a schematic cross-sectional view of a LAN cable according to another modified example of FIG. [Figure 5] FIG. 3 is a schematic cross-sectional view of a LAN cable according to a modified example of FIG. 2. [Figure 6] FIG. 3 is a schematic cross-sectional view of a LAN cable according to another modified example of FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A LAN cable according to the present invention will be described below with reference to embodiments.

[0014] In all the drawings for explaining the embodiments, the same components are generally designated by the same reference numerals, and repeated explanations thereof will be omitted. In order to make the drawings easier to understand, hatching may be omitted even in cross-sectional views. Similarly, hatching may be added even in plan views.

[0015] In the following explanation, the terms insulated wire, twisted pair wire, and bunched twisted wire are used. An insulated wire is a wire in which a linear conductor is covered with an insulating layer. A twisted pair wire is a wire in which two (in other words, a pair) insulated wires are twisted together. A bunched twisted wire is a wire in which two or more twisted pair wires or three or more insulated wires are twisted together. A conductor is a wire made of a conductive material. As will be described later, conductors may be solid wires, or may have a twisted wire structure in which multiple strands are twisted together, or may have a plating film formed on the surface of a solid wire or strand.

[0016] [LAN cable] A LAN cable according to the present embodiment will be described with reference to the drawings. Fig. 1 is a schematic cross-sectional view of the LAN cable according to the embodiment. As shown in Fig. 1, the LAN cable according to the present embodiment is a LAN cable 10 including a twisted pair 8 formed by twisting together a pair of insulated wires 3, each of which has an insulating layer 2 around the outer periphery of a conductor 1, a braid 4 provided so as to cover the outer periphery of the twisted pair 8, and a sheath 5 that further covers the braid 4. This LAN cable 10 is configured as a bunched twisted wire 7 formed by twisting together a plurality of twisted pair wires 8, and a shield 6 is provided around the outer periphery of each of the plurality of twisted pair wires 8.

[0017] In such LAN cables, the high flame retardancy required for flame retardancy tests such as those in the overseas standard EN45545 has traditionally been achieved by providing a specified flame retardant layer such as flame retardant tape between the sheath 5 and the insulated wire 3 (directly below the sheath 5). However, the inclusion of this flame retardant tape results in a larger diameter cable.

[0018] In contrast, the LAN cable 10 of this embodiment can achieve flame retardancy that meets the above standards without using such flame-retardant tape, and the cable can be made thinner, making it a LAN cable that is particularly suitable for use in railway vehicles.

[0019] [Insulated wire] The insulated wire 3 is configured by providing an insulating layer 2 on the outer periphery of a conductor 1. The material of the conductor 1 is not particularly limited, and any known conductor can be used, such as copper or a copper alloy. The configuration of the conductor 1 is also not particularly limited, but in consideration of the flexibility of the cable, it is preferable to adopt a stranded wire structure in which multiple wires are twisted together, in addition to a single wire. The conductor can also be appropriately plated, for example, with tin plating.

[0020] The material of the insulating layer 2 is not particularly limited, but is preferably polyethylene, more preferably polyethylene with a dielectric constant of 2.5 or less. When the dielectric constant of polyethylene is 2.5 or less, the capacitance of the insulating layer is reduced, thereby further improving the transmission characteristics of the LAN cable. The dielectric constant of the entire insulating layer is preferably 2.5 or less. In this case, the transmission characteristics of the LAN cable are further improved. The dielectric constant of the entire insulating layer is more preferably 1.9 to 2.3, and even more preferably 1.9 to 2.1.

[0021] Examples of polyethylene include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), linear very low-density polyethylene (VLDPE), and high-density polyethylene (HDPE), and more preferably low-density polyethylene having a density of 0.930 or less and an MFR (melt flow rate) of 0.30 or less. Any one of the above polyethylenes may be used alone, or two or more may be blended and used.

[0022] The insulating layer 2 may further contain an antioxidant, a copper inhibitor, a colorant, etc. Although there are no particular limitations on the amounts of antioxidant, copper inhibitor, colorant, etc. added, an amount that results in a dielectric constant of the entire insulating layer 2 of 2.5 or less is preferred. The amount of colorant, etc. added is preferably 5 mass % or less, and more preferably 2 mass % or less. Furthermore, the insulating layer 2 may not contain a flame retardant. By using a sheath having the properties described below, it is possible to achieve a LAN cable 10 that has high flame retardancy, even if the insulating layer 2 is made of a resin composition that does not contain a flame retardant.

[0023] The polyethylene may be foamed using a known method. For example, the polyethylene can be foamed using an inert gas such as nitrogen or a chemical foaming agent such as ADCA (azodicarbonamide). The foaming degree of the polyethylene is preferably 15% by mass or more.

[0024] [Twisted pair wire] The twisted pair wire 8 is formed by twisting two insulated wires 3 together. As described above, this LAN cable 10 is characterized by having twisted pair wires 8. The LAN cable 10 shown in FIG. 1 shows an example in which it has four sets of twisted pair wires 8, each made up of two insulated wires 3.

[0025] In this case, the outer diameter r1 of the insulated wires 3 constituting the twisted pair wire 8 is small, for example, 1.5 mm or less, and a shield 6 is provided around the core. The outer diameter r1 of the insulated wires 3 is preferably 1.43 mm or less. In this embodiment, the sheath 5 is made of a resin composition with sufficient flame retardancy. Therefore, in order to achieve another objective of reducing the diameter of the LAN cable 10, the inventors have found that by reducing the outer diameter r1 of the insulated wires 3 as described above, it is possible to ensure the flame retardancy of the LAN cable even when the outer diameter of the LAN cable is reduced. This makes it possible to obtain a LAN cable 10 that is both small in diameter and highly flame-retardant, something that has not been achieved before. Furthermore, reducing the outer diameter r1 of the insulated wires 3 also reduces the amount of flammable insulating layer used in the insulated wires 3, which also has a positive effect on ensuring the flame retardancy of the LAN cable 10.

[0026] The shield 6 is formed by wrapping around the twisted pair wires 8, and can be, for example, a shielding tape having a base layer made of a resin such as polyethylene terephthalate formed into a tape shape, and a metal layer made of an aluminum sheet attached to the surface of the base layer.

[0027] Although the insulating layer 2 may be a foam layer in the above description, it may also be a multilayer insulating layer including a foam layer. For example, when the insulating layer 2 has a three-layer structure consisting of an inner layer, an intermediate layer, and an outer layer from the conductor 1 side, the inner and outer layers are preferably configured as skin layers, and the intermediate layer is preferably a foam layer. Alternatively, a two-layer structure may be used, with the inner layer being a foam layer and the outer layer being a skin layer. By combining a skin layer and a foam layer in this way, the outer diameter of the insulated wire 3 can be reduced, allowing for a thinner LAN cable. Furthermore, since the insulating layer 2 has a structure including such a foamed portion (air), the dielectric constant can also be improved.

[0028] As described above, this insulating layer 2 can be formed, for example, from a polyethylene material. For example, the inner and outer layers can be made of polyethylene skin layers, and the middle layer can be made of polyethylene foam layer, so that the inner, middle and outer layers are all made of polyethylene.

[0029] In this case, the thickness of the intermediate layer is preferably 0.25 mm to 0.4 mm, more preferably 0.25 mm to 0.37 mm. Furthermore, the total thickness of the two-layer structure is preferably 0.35 mm to 0.45 mm, or the total thickness of the three-layer structure is preferably 0.35 mm to 0.45 mm.

[0030] [Braid] The braid 4 is made by braiding a plurality of metal wires together, and is provided to reduce noise in the LAN cable 10 and to improve the strength of the LAN cable 10. The braid 4 is, for example, a cross braid. The metal wires that make up the braid 4 can be made of copper, copper alloy, or the like.

[0031] 〔sheath〕 The sheath 5 is made of a halogen-free resin composition containing a base polymer, a metal hydroxide, and carbon black. In this embodiment, these components are blended in specific ratios, and each component will be described in detail below.

[0032] (Base polymer) The base polymer includes polyolefin, maleic anhydride modified polyolefin, and ethylene vinyl acetate copolymer.

[0033] (1) Polyolefin The polyolefin used here has a melting point of 110°C or higher. The melting point can be determined by differential scanning calorimetry (DSC). By using this polyolefin having a melting point of 110°C or higher, the oil resistance of the sheath 5 can be improved.

[0034] One method of oil resistance testing is to immerse a test piece in IRM902 test oil heated to 100°C for 72 hours, then examine the tensile properties to see how much the tensile properties have changed after immersion compared to the tensile properties before immersion. For example, if the melting point is below 110°C, the crystals will melt during the oil resistance test, making it difficult to prevent the oil from diffusing, and the rate of change in tensile properties will increase.

[0035] Examples of polyolefins with a melting point of 110°C or higher include low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, and polypropylene. However, high-density polyethylene has too high a degree of crystallinity and therefore low elongation at break, while polypropylene is prone to collapse when crosslinked by electron beam irradiation or the like. To achieve a balance of properties, it is preferable to use low-density polyethylene, and it is more preferable to use linear low-density polyethylene.

[0036] (2) Maleic anhydride modified polyolefin Maleic anhydride modified polyolefin is a polyolefin modified with maleic anhydride.

[0037] Examples of polyolefins that can be used as the material to be modified include ethylene-α-olefins such as low-density polyethylene, linear low-density polyethylene, very low-density polyethylene, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-butene-1 copolymer, ethylene-hexene-1 copolymer, and ethylene-octene-1 copolymer.

[0038] The method for modifying a polyolefin with maleic anhydride is not limited, and the polyolefin can be obtained by a reaction using heat alone. Furthermore, the maleic anhydride in the maleic anhydride-modified polyolefin may be graft copolymerized or block copolymerized.

[0039] The amount of maleic anhydride-modified polyolefin added is 10 to 35 parts by mass per 100 parts by mass of the base polymer. If it is less than 10 parts by mass, the required low-temperature properties cannot be satisfied, and if it is more than 35 parts by mass, the initial elongation at break becomes insufficient.

[0040] In order to obtain even better low-temperature properties, it is more preferable to add the maleic anhydride-modified polyolefin in an amount of 25 to 35 parts by mass per 100 parts by mass of the base polymer.

[0041] (3) Ethylene vinyl acetate copolymer By using ethylene vinyl acetate copolymer as the base polymer, an endothermic reaction occurs due to deacetylation during combustion, improving flame retardancy. The amount of acetic acid (CH3COO - By making the amount of (amount of) 2.3 mass % or more, high flame retardancy can be obtained.

[0042] (metal hydroxide) The metal hydroxide used here is a flame retardant. Examples of metal hydroxides that can be used include aluminum hydroxide, magnesium hydroxide, and calcium hydroxide. Among these, aluminum hydroxide and magnesium hydroxide are preferred. The endothermic heat during decomposition of calcium hydroxide is approximately 1000 J / g, whereas the endothermic heat of aluminum hydroxide and magnesium hydroxide is 1500 to 1600 J / g, which is a large endothermic heat. Therefore, adding aluminum hydroxide or magnesium hydroxide improves flame retardancy.

[0043] Furthermore, it is preferable to use magnesium hydroxide, which has a higher decomposition temperature than aluminum hydroxide, and therefore improves molding processability.

[0044] The metal hydroxide may be surface-treated with a silane coupling agent, a titanate coupling agent, a fatty acid such as stearic acid, or the like to improve dispersibility.

[0045] The metal hydroxide is added in an amount of 180 to 190 parts by mass per 100 parts by mass of the base polymer. If the amount is less than 180 parts by mass, sufficient flame retardancy cannot be obtained, and if the amount is more than 190 parts by mass, the elongation at break decreases.

[0046] (carbon black) The carbon black used here is a flame retardant aid. There are no particular restrictions on the type of carbon black to be added, but in consideration of elongation at break and the like, it is preferable to use FT or MT class carbon.

[0047] To ensure a certain level of flame retardancy, a large amount of metal hydroxide must be added as a flame retardant. However, adding a large amount of flame retardant may impair the mechanical properties of the resin composition. Therefore, carbon black is added as a flame retardant aid. The amount of carbon black added is 15 to 20 parts by mass per 100 parts by mass of the base polymer. The greater the amount of carbon black added, the better the flame retardancy can be. However, if the amount is more than 20 parts by mass, the carbon black will aggregate to form coarse particles, which will reduce the initial elongation at break and low-temperature properties.

[0048] (Other additives) In addition to the above materials, crosslinking agents, crosslinking aids, ultraviolet absorbers, light stabilizers, softeners, lubricants, colorants, reinforcing agents, surfactants, inorganic fillers, antioxidants, plasticizers, metal chelating agents, foaming agents, compatibilizers, processing aids, stabilizers, etc. may be added.

[0049] Flame retardant auxiliaries other than carbon black may also be added. Examples of flame retardant auxiliaries include phosphorus-based flame retardant auxiliaries such as red phosphorus and triazine-based flame retardant auxiliaries such as melamine cyanurate. However, these auxiliaries may generate phosphine gas or cyanide gas, so care must be taken when handling them. Other flame retardant auxiliaries may also be used, such as clay, silica, zinc stannate, zinc borate, calcium borate, dolomide hydroxide, and silicone.

[0050] (gel fraction) Gel fraction is a method for confirming the degree of cross-linking of a polymer. We will explain how to measure gel fraction. First, weigh the sample (W1) and immerse it in xylene heated to 110°C for 24 hours. After immersion, leave it at 20°C under atmospheric pressure for 3 hours, and then vacuum dry it at 80°C for 4 hours. The weight ratio of the sample's weight after this (W2) to its weight before immersion in xylene (W1) ((W2 / W1) x 100, unit [%]) is defined as the gel fraction. If the gel fraction is less than 85%, it cannot be said that the oil resistance is sufficient.

[0051] The crosslinking treatment may be chemical crosslinking using an organic peroxide, a sulfur compound, or silane, or the like; irradiation crosslinking using an electron beam, radiation, or the like; or chemical crosslinking using other chemical reactions, and any of these crosslinking methods is applicable. Among these, irradiation crosslinking using an electron beam is more versatile than other irradiation crosslinking methods and does not involve the risk of scorching during extrusion molding as occurs with chemical crosslinking, and is therefore preferably used as the crosslinking treatment in this embodiment.

[0052] [Outer diameter of cable] In addition, in this embodiment, the LAN cable 10 is characterized in that its outer diameter is 8.8 mm or less. After careful consideration of the configuration of this highly flame-retardant cable, it was found that the thinner the outer diameter of the cable, the more likely it is to burn in a flame-retardant test such as EN45545.

[0053] The inventors have discovered for the first time that even under such conditions, a highly flame-retardant LAN cable that meets the flame retardancy requirements in the above-mentioned flame retardancy test can be obtained without using flame-retardant tape and by reducing the cable diameter.

[0054] In this case, the thickness of the sheath 5 is preferably 0.68 mm to 0.92 mm, more preferably 0.72 mm to 0.88 mm. If this thickness exceeds 0.92 mm, it is easy to ensure flame retardancy, but it becomes difficult to achieve the thin diameter required in this embodiment, and if it is less than 0.68 mm, there is a risk that sufficient flame retardancy cannot be ensured.

[0055] [LAN cable manufacturing method] The LAN cable 10 of this embodiment is manufactured, for example, as follows. First, a resin composition that will become the insulating layer 2 of the insulated wire 3 is prepared, and then the conductor 1 is prepared. Then, the resin composition for the insulating layer is extruded using an extrusion molding machine so as to cover the periphery of the conductor 1, thereby forming the insulating layer 2 of a predetermined thickness. In this manner, the insulated wire 3 can be manufactured.

[0056] The insulating layer 2 can be formed using a general-purpose material, preferably a halogen-free polymer, such as polyolefins such as high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, very low-density polyethylene, and ethylene-acrylic acid ester copolymer.

[0057] In this embodiment, after the insulated wire 3 is produced, the resin composition that forms the insulating layer 2 can be crosslinked by, for example, an electron beam crosslinking method.

[0058] When the electron crosslinking method is used, the resin composition is molded into the insulating layer 2 of the insulated wire 3, and then crosslinked by irradiating it with an electron beam of, for example, 1 to 30 MRad.

[0059] Two of the obtained insulated wires 3 are twisted together to form a twisted pair wire 8, and four twisted pair wires 8 having a shield 6 obtained by wrapping a shielding tape around the twisted pair wires 8 are twisted together, and then a braid 4 is formed by a known method to cover the braid 4. Furthermore, the resin composition of this embodiment is extruded around the outer periphery of the braid 4 thus obtained to form a sheath (coating layer) 5 of a predetermined thickness. In this manner, the LAN cable 10 of this embodiment can be manufactured.

[0060] Next, the structure of a LAN cable according to an embodiment will be described. FIG. 1 is a schematic cross-sectional view of a LAN cable according to one embodiment. As shown in FIG. 1, a LAN cable 10 includes a bunched twisted wire 7, a braid 4 covering the outer periphery of the bunched twisted wire 7, and a sheath 5 covering the outer periphery of the braid 4. The outer periphery of the braid 4 is in contact with the sheath 5. The bunched twisted wire 7 includes four twisted pairs 8. The four twisted pairs 8 are twisted together. The twisted pairs 8 include two insulated wires 3. The two insulated wires 3 are twisted together. The two insulated wires 3 are in contact with each other. The insulated wire 3 includes a conductor 1 and an insulating layer 2 covering the outer periphery of the conductor 1. The LAN cable 10 shown in FIG. 1 does not have a flame-retardant tape between the twisted pairs 8 and the sheath 5.

[0061] In the example shown in FIG. 1 , the bunched wire 7 further includes four shields 6. One shield 6 covers the outer circumference of one twisted pair 8. In other words, the bunched wire 7 includes four pairs of a shield 6 and a twisted pair 8 covered by the shield 6. The four pairs of twisted pairs 8, each covered by a shield 6, are twisted together. The shield 6 is in contact with the braid 4. The shield 6 is in contact with the twisted pairs 8.

[0062] The cross-sectional shape of the LAN cable 10, i.e., the cross-sectional shape of the sheath 5, is circular. The cross-sectional shape of the shield 6 is also circular. In the example shown in FIG. 1, the cross-sectional shape of the sheath 5 and the cross-sectional shape of each of the four shields 6 are perfect circles. However, the cross-sectional shapes of the sheath 5 and the shield 6 include cases where they are perfect circles, as well as cases where they can be considered substantially circular (where the difference in the length of two perpendicularly intersecting diameters is negligibly small). The four shields 6 have rotational symmetry with the center Q1 of the circle formed by the cross-sectional shape of the LAN cable 10 as the axis of rotation. For example, in the example shown in FIG. 1, the shape formed by the four shields 6 overlaps with itself when rotated 90 degrees around the center Q1, so it has four-fold symmetry. The two shields 6 are arranged point-symmetrically with respect to the center Q1 of the circle. As shown in FIG. 1, the bunched twisted wire 7 has two pairs of two shields 6 arranged point-symmetrically. In this embodiment, the LAN cable 10 has two or more twisted-pair wires 8. Within the LAN cable 10, each of the four shields 6 is twisted together to form a spiral in the longitudinal direction. That is, when a cross section of the LAN cable 10 perpendicular to the longitudinal direction is continuously changed in the longitudinal direction of the LAN cable 10, the position of the shield 6 rotates in a circular fashion around the center Q1 of the circle. The two insulated wires 3 included in the twisted pair wire 8 have a double-helix structure. In this embodiment, the outer diameter r1 of the insulated wires 3 is 1.5 mm or less, and the outer diameter r2 of the bunched wires 7 is 6.5 mm or less. The outer diameter r2 of the bunched wires 7 is the diameter of a circle formed when the shield 6 is rotated around the center Q1 of the circle. In the example shown in FIG. 1 , the outer diameter r2 of the bunched wires 7 is the diameter of a circle inscribed with each of the multiple shields 6. The outer diameter r2 of the bunched wires 7 can be measured, for example, by measuring the outer diameters r2 of the bunched wires 7 at three different cross sections of the LAN cable 10 and averaging the measured values.

[0063] A LAN cable according to another embodiment will be described. In all the drawings used to explain the embodiment, the same components are generally designated by the same reference numerals, and repeated explanations may be omitted.

[0064] FIG. 2 is a schematic cross-sectional view of a test cable according to another embodiment. The test cable 50 shown in FIG. 2 differs from the LAN cable 10 shown in FIG. 1 in that it does not have a twisted pair. The test cable 50 shown in FIG. 2 has four insulated wires 3. The four insulated wires 3 are twisted together. The test cable 50 must have two or more insulated wires 3. The test cable 50 preferably has three or more insulated wires 3. The insulated wires 3 are in contact with the braid 4. The four insulated wires 3 have rotational symmetry with respect to the center Q1 of the circle formed by the cross-sectional outline of the test cable 50 as the rotation axis. For example, in the example shown in FIG. 2, the shape formed by the four insulated wires 3 overlaps itself when rotated 90 degrees around the center Q1, and therefore has four-fold symmetry. Two of the four insulated wires 3, which are arranged on opposite sides of the center Q1, are arranged point-symmetrically with respect to the center Q1 of the circle. As shown in FIG. 2 , the bunched strand 7 has two pairs of two insulated wires 3 arranged point-symmetrically. Each of the four insulated wires 3 is twisted to form a spiral in the longitudinal direction. When a cross section perpendicular to the longitudinal direction of the test cable 50 is continuously changed in the longitudinal direction of the test cable 50, the positions of the insulated wires 3 rotate in a circular pattern about a center Q1 of the circle. In this embodiment, the outer diameter r1 of the insulated wires 3 is 2.5 mm or less, and the outer diameter r2 of the bunched strand 7 is 5.5 mm or less. The outer diameter r2 of the bunched strand 7 is the diameter of a circle formed when the insulated wires 3 are rotated about the center Q1 of the circle. In the example shown in FIG. 2 , the outer diameter r2 of the bunched strand 7 is the diameter of a circle inscribed with the four insulated wires 3. The outer diameter r2 of the bunched strands 7 can be measured by measuring the outer diameter r2 of the bunched strands 7 at three different cross sections of the test cable 50 and averaging the measured values.

[0065] FIG. 3 is a schematic cross-sectional view of a LAN cable according to another embodiment. The LAN cable 10A shown in FIG. 3 further differs from the LAN cable 10 shown in FIG. 1 in that it includes a twisted tape 11, a separator 12, a shielding tape 13, and a filler 14. The bunched stranded wires 7 of the LAN cable 10A shown in FIG. 3 also differ from the LAN cable 10 shown in FIG. 1 in that they do not include a shield 6. The insulated wires 3 of each of the multiple (four in FIG. 3) twisted pairs 8 form a double helix structure within the LAN cable 10A. Each of the multiple (four in FIG. 3) twisted pairs 8 forms a helical shape in its longitudinal direction. When a cross section of the LAN cable 10A perpendicular to the longitudinal direction is continuously changed in the longitudinal direction of the LAN cable 10A, the position of the insulated wires 3 rotates in a circular motion. The area through which the insulated wires 3 pass as they rotate in a circular motion is the area P1 surrounded by the dotted line in FIG. 3. In addition, all of the insulated wires 3 of the twisted pairs 8 are arranged side by side in the same direction. In the example shown in Fig. 3, the insulated wires 3 of two of the twisted pairs 8 that face each other across the center Q1 of the circle formed by the outline of the cross section of the LAN cable 10A are arranged side by side in a direction extending outward from the center Q1 of the circle. Meanwhile, the insulated wires 3 of the other two of the twisted pairs 8 that face each other across the center of the LAN cable 10A are arranged side by side in a direction perpendicular to the direction extending outward from the center Q1 of the circle. The outer diameter r2 of the bunched twisted wire 7 is the diameter of the circle formed when the twisted pairs 8 are rotated about the center Q1 of the circle.

[0066] The insulating filler 14 includes a central filler 14a and outer fillers 14b. As shown in Fig. 3, the central filler 14a is surrounded by four twisted pairs 8. The outer fillers 14b are located between the bunched strands 7 and the twisted tape 11.

[0067] The twisted tape 11 circumferentially surrounds the bunched strands 7 and the filler 14. The twisted tape 11 contacts the bunched strands 7 and the outer filler 14b. The separator 12, which is a sheath arranged inside the braid 4, covers the twisted tape 11. The separator 12 contacts the outer periphery of the twisted tape 11. The shielding tape 13 covers the separator 12. The shielding tape 13 contacts the outer periphery of the separator 12. The braid 4 covers the shielding tape 13. The braid 4 contacts the outer periphery of the shielding tape 13.

[0068] In the example shown in FIG. 3, the central filler 14a is made of Kevlar (an insulating fiber material), and the outer filler 14b is made of PP yarn (an insulating fiber material). The twisted tape 11 is made of, for example, PET tape. The separator 12 is made of, for example, polyolefin. The shielding tape 13 has, for example, a two-layer structure. For example, of the two layers of the shielding tape 13, the layer in contact with the braid 4 is made of an aluminum sheet, and of the two layers of the shielding tape 13, the layer not in contact with the braid 4 is made of PET tape. The braid 4 is made of, for example, multiple Sn-plated annealed copper wires. The Sn-plated annealed copper wires have a thickness of, for example, 0.1 mm.

[0069] The LAN cable 10A shown in FIG. 3 has a separator 12, which ensures an under-shield diameter r4. This improves the impedance characteristics of the LAN cable 10A. Here, the under-shield diameter r4 is the distance below the shielding layer used for shielding. The shielding layer is made up of a braid 4 and a shielding tape 13. In other words, the under-shield diameter r4 is the inner diameter of the shielding tape 13.

[0070] FIG. 4 is a schematic cross-sectional view of a LAN cable according to another embodiment. The LAN cable 10B shown in FIG. 4 differs from the LAN cable 10A shown in FIG. 3 in that it does not have an interposer or a twisted ribbon. The LAN cable 10B also differs from the LAN cable 10A shown in FIG. 3 in that the insulated wires 3 of each of the four twisted pairs 8 are all aligned in a direction extending outward from the center Q1 of the circle defined by the cross-sectional outline of the LAN cable 10B. In the example shown in FIG. 4, the multiple insulated wires 3 are aligned radially from the center Q1 of the circle. The outer diameter r2 of the bunched twisted wire 7 is the diameter of a circle formed when the twisted pairs 8 are rotated about the center Q1 of the circle. In the example shown in FIG. 4, the outer diameter r2 of the bunched twisted wire 7 is the diameter of a circle inscribed in each of the multiple twisted pairs 8.

[0071] FIG. 5 is a schematic cross-sectional view of a LAN cable according to another embodiment. The LAN cable 50A shown in FIG. 5 further differs from the test cable 50 shown in FIG. 2 in that it includes a stranding tape 51 and a shielding tape 53. The stranding tape 51 circumferentially surrounds the bunched strands 7. The stranding tape 51 is in contact with the bunched strands 7. The stranding tape 51 includes a stranding tape 51a and a stranding tape 51b. The stranding tape 51a circumferentially surrounds the bunched strands 7. The stranding tape 51a is in contact with the bunched strands 7. The stranding tape 51b circumferentially surrounds the stranding tape 51a. The stranding tape 51b is in contact with the stranding tape 51a. The shielding tape 53 circumferentially surrounds the stranding tape 51. The shielding tape 53 is in contact with the stranding tape 51. The shielding tape 53 circumferentially surrounds the twisted upper tape 51b. The shielding tape 53 is in contact with the twisted upper tape 51b. The braid 4 circumferentially surrounds the shielding tape 53. The braid 4 is in contact with the shielding tape 53. The outer diameter r2 of the bunched stranded wire 7 is the diameter of a circle formed when the insulated wire 3 is rotated about the center Q1 of the circle. In the example shown in FIG. 5 , the outer diameter r2 of the bunched stranded wire 7 is the diameter of a circle inscribed with four insulated wires 3.

[0072] 5, twisted tape 51a is made of PET tape, and twisted tape 51b is made of LDPE. Shielding tape 53 has, for example, a two-layer structure. For example, of the two layers of shielding tape 53, the layer in contact with braid 4 is made of aluminum sheet, and the layer not in contact with braid 4 is made of PET tape.

[0073] The twisted tape 51a is, for example, a gap (spacing) winding. The gap (spacing) winding interval is, for example, 1 mm or less. The twisted tape 51b is, for example, a gap (spacing) winding. The gap (spacing) winding interval is, for example, 1 mm or less.

[0074] Fig. 6 is a schematic cross-sectional view of a LAN cable according to another embodiment. The LAN cable 50B shown in Fig. 6 further differs from the test cable 50 shown in Fig. 2 in that it includes a separator 52 and a shielding tape 53. The separator 52 circumferentially surrounds the bunched stranded wires 7. The separator 52 is in contact with the bunched stranded wires 7. The shielding tape 53 circumferentially surrounds the separator 52. The shielding tape 53 is in contact with the separator 52. The braid 4 circumferentially surrounds the shielding tape 53. The braid 4 is in contact with the shielding tape 53. [Example]

[0075] Next, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

[0076] [Sheath material production examples 1-3] The sheath material was prepared according to the formulations shown in Tables 1 and 2. These formulations were kneaded in a pressure kneader until the temperature reached 220° C., and pellets were produced as the sheath material.

[0077] [Table 1]

[0078] [Table 2]

[0079] [Sheath material] In Table 1, the materials used are as follows: (polymer) PE: Prime Polymer SP1510 (Tm 117°C) EVA: Evaflex EV45X, manufactured by Mitsui Dow Polychemicals Co., Ltd. Modified polyolefin: Toughma MH5040, manufactured by Mitsui Chemicals, Inc. (Flame retardant) Magnesium hydroxide: Konoshima Chemical Co., Ltd., Magsheath S4 Carbon black: Asahi Thermal manufactured by Asahi Carbon Co., Ltd.

[0080] [Evaluation of sheath materials] The resulting resin compositions were evaluated for the following properties.

[0081] (1-1) Flame retardancy of sheath material (VFT) The resulting resin composition was used to prepare a test cable for evaluating flame retardancy. This test cable was test cable 50 shown in Figure 2, which was covered with a sheath material to a thickness of 0.8 mm and cross-linked by irradiation with an irradiation dose of 5 MRad, resulting in a cable with an outer diameter of 5.8 mm.

[0082] The flame retardancy of the obtained test cables was evaluated by a vertical flame test in accordance with the standard EN60332-1-2, and those that passed were marked with "◯" and those that failed were marked with "X".

[0083] (1-2) Initial tensile test of sheath material The sheath was peeled off from the test cable having the configuration shown in Figure 2, obtained in the same manner as above, to prepare a dumbbell specimen. Next, a tensile test was conducted using the test specimen in accordance with EN60811-501 at a tensile speed of 250 mm / min. Regarding elongation, an elongation of less than 125% was evaluated as × (fail), and an elongation of 125% or more was evaluated as ○ (pass).

[0084] Regarding the tensile strength, if the tensile strength was less than 10 MPa, it was marked as × (fail), and if it was 10 MPa or more, it was marked as ○ (pass with a margin).

[0085] (1-3) Oil resistance test of sheath material Dumbbell specimens were prepared by stripping the sheath from the test cable (shown in Figure 2) obtained in the same manner. These specimens were then immersed in IRM902 oil heated to 100°C for 72 hours, in accordance with EN60811-404. The specimens were then stretched at a rate of 250 mm / min, and the load and elongation to break were measured. The tensile strength (A1) and elongation at break (B1) of the specimens before immersion in the test oil were used to calculate the percentage change in tensile strength (A2 / A1) × 100% and the percentage change in elongation at break ((B2 / B1) × 100%). Those with a tensile strength change rate of 75 to 125% and a breaking elongation change rate of 65 to 135% were rated as good (◯), and those with a tensile strength change rate of 70 to 75% or 125 to 130% and a breaking elongation change rate of 60 to 65% or 135 to 140% were rated as fair (△).

[0086] (1-4) Fuel resistance test of sheath material Dumbbell specimens were prepared by stripping the sheath from the test cable shown in Figure 2, obtained in the same manner as above. These specimens were then immersed in IRM903 oil heated to 70°C for 168 hours, and then subjected to tension at a displacement rate of 250 mm / min, according to EN 60811-404. The load and elongation to break were measured. The tensile strength (A1) and elongation at break (B1) of the specimen before immersion in the test oil were used to calculate the tensile strength change (A2 / A1) × 100% and the elongation at break change (B2 / B1) × 100%. Tests with a tensile strength change of 70% to 130% and a tensile elongation change of 60% to 140% were considered pass (good).

[0087] (1-5) Low-temperature property test of sheath material The above test cables were subjected to low-temperature bending tests in accordance with EN60811-504. Tests were conducted at -40°C and -50°C with N=2 for each condition, and cables that passed both tests (no cracks or breaks) were given a "○" and cables that passed only one test were given a "△".

[0088] [Example 1] Next, a LAN cable having the configuration shown in Figure 1 was fabricated as follows. A conductor with a diameter of 0.565 mm was coated with a 0.01 mm thick polyethylene layer as the inner layer, a 0.36 mm thick foamed polyethylene layer with a foaming degree of 30% as the intermediate layer, and a 0.05 mm thick polyethylene layer as the outer layer.

[0089] The above was subjected to irradiation and crosslinking at 22 Mrad to obtain an insulated wire having an outer diameter of 1.40 mm and an insulating layer of 0.42 mm thickness.

[0090] Next, two of these insulated wires were twisted together (one pair) and an aluminum-laminated PET tape was attached vertically to create four pairs. The four twisted pairs were then covered with a copper braid, and then coated with the sheath material of Preparation Example 1 shown in Table 1 to a thickness of 0.78 mm. The sheath material was then irradiated and cross-linked with an irradiation dose of 5 Mrad to obtain the LAN cable of Example 1 having the configuration shown in Figure 1.

[0091] [Example 2] Next, a conductor with a diameter of 0.565 mm was coated with a 0.01 mm polyethylene layer as an inner layer, a 0.30 mm foamed polyethylene layer with a foaming degree of 50% as an intermediate layer, and a 0.05 mm polyethylene layer as an outer layer.

[0092] The above was subjected to irradiation and crosslinking at 22 Mrad to obtain an insulated wire having an outer diameter of 1.30 mm and an insulating layer of 0.36 mm thickness.

[0093] Next, two of these insulated wires were twisted together (one pair) and an aluminum-laminated PET tape was attached vertically to create four pairs. After the four pairs were twisted together, a copper braid was placed over them, and the sheath material of Example 1 shown in Table 1 was then coated to a thickness of 0.78 mm. The sheath material was then irradiated and cross-linked at an irradiation dose of 5 Mrad, resulting in a LAN cable of Example 2 having the configuration shown in Figure 1.

[0094] The structural features of the obtained LAN cables are shown in Table 3, including the comparative examples described below.

[0095] [Comparative Example 1] As a conventional example, a LAN cable of Comparative Example 1 having the configuration shown in FIG. 1 was obtained using the sheath material of Example 1 as Preparation Example 3.

[0096] [Comparative examples A~C] In each of Examples 1 and 2 and Comparative Example 1, LAN cables were fabricated in which a flame-retardant polyimide tape was wound horizontally between the copper braid and the sheath in a 1 / 4 wrap, and these LAN cables were designated Comparative Examples A to C, respectively.

[0097] [Table 3]

[0098] [LAN cable evaluation] The LAN cables obtained in Examples 1 and 2, Comparative Example 1, and Comparative Examples A to C were evaluated for flame retardancy (VFT), initial tensile test, oil resistance test, fuel resistance test, and low-temperature characteristics test using the same procedures and evaluation criteria as those used to evaluate the sheath material. Tensile tests after aging were also conducted on the obtained LAN cables. The results are shown in Table 3.

[0099] (2-1) Tensile test of cable after aging The sheath was removed from the resulting cable to create a dumbbell specimen. The specimen was then heat-treated at 120°C for 240 hours, and then stretched at a rate of 250 mm / min to measure the load and elongation until breakage. The tensile strength (A1) and elongation at break (B1) of the specimen before heat treatment were used, and the tensile strength (A2) and elongation at break (B2) of the specimen after heat treatment were used to calculate the tensile strength change rate (A2 / A1) × 100 [%] and the elongation at break change rate ((B2 / B1) × 100 [%]). A tensile strength change rate of 70 to 130% and a tensile elongation change rate of 70 to 130% were evaluated as passing (○).

[0100] From the above results, it was found that in Examples 1 and 2, by providing a sheath made of a predetermined resin composition, high flame retardancy can be ensured even without the flame retardant tape provided between the sheath and the insulated wire, and a LAN cable can be obtained that satisfies physical properties such as sheath strength, elongation, and low-temperature characteristics.It was also confirmed that Example 2 is a cable that can be made even thinner.

[0101] On the other hand, in Comparative Example 1, it was found that sufficient flame retardancy for railway vehicles could not be obtained unless a flame retardant tape was used.

[0102] The invention made by the inventor has been specifically described above based on the embodiments thereof, but it goes without saying that the present invention is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit of the invention. [Explanation of symbols]

[0103] 1 conductor 2. Insulation layer 3. Insulated wire 4 braid 5 Sheath 6 Shield 10 LAN cable 50 Test Cable

Claims

1. A LAN cable comprising a twisted pair wire formed by twisting two insulated wires together, a bunched wire formed by twisting a plurality of twisted pairs together, and a sheath covering the outer periphery of the bunched wire, The LAN cable has an outer diameter of 8.8 mm or less, the sheath is made of a halogen-free flame-retardant resin composition containing a base polymer, a metal hydroxide, and carbon black; The metal hydroxide is contained in an amount of 180 to 190 parts by mass relative to 100 parts by mass of the base polymer, The carbon black is contained in an amount of 15 to 20 parts by mass relative to 100 parts by mass of the base polymer, The outer diameter of the insulated wire is 1.5 mm or less, the outer diameter of the bunched stranded wire is 6.5 mm or less; LAN cable.

2. 2. The LAN cable according to claim 1, A LAN cable having a braid between the twisted pair wires and the sheath.

3. 2. The LAN cable according to claim 1, The LAN cable contains 180 to 185 parts by mass of the metal hydroxide relative to 100 parts by mass of the base polymer, and 15 to 20 parts by mass of the carbon black relative to 100 parts by mass of the base polymer.

4. 2. The LAN cable according to claim 1, The insulated wire has a structure in which the insulating layer includes a foam layer.

5. 5. The LAN cable according to claim 4, the insulating layer has a three-layer structure, and the total thickness of the three-layer structure is 0.35 to 0.45 mm; or The LAN cable has a two-layer insulating layer, and the total thickness of the two-layer structure is 0.35 to 0.45 mm.

6. 2. The LAN cable according to claim 1, A LAN cable having no flame-retardant tape between the twisted pair wires and the sheath.

7. A LAN cable comprising a bunched stranded wire formed by twisting together a plurality of insulated wires and a sheath covering the outer periphery of the bunched stranded wire, The LAN cable has an outer diameter of 8.8 mm or less, the sheath is made of a halogen-free flame-retardant resin composition containing a base polymer, a metal hydroxide, and carbon black; The metal hydroxide is contained in an amount of 180 to 190 parts by mass relative to 100 parts by mass of the base polymer, The carbon black is contained in an amount of 15 to 20 parts by mass relative to 100 parts by mass of the base polymer, The outer diameter of the insulated wire is 2.5 mm or less, the outer diameter of the bunched stranded wire is 5.5 mm or less; LAN cable.

8. 8. The LAN cable according to claim 7, A LAN cable having a braid between the insulated wire and the sheath.

9. 8. The LAN cable according to claim 7, The LAN cable contains 180 to 185 parts by mass of the metal hydroxide relative to 100 parts by mass of the base polymer, and 15 to 20 parts by mass of the carbon black relative to 100 parts by mass of the base polymer.

10. 8. The LAN cable according to claim 7, The insulated wire has a structure in which the insulating layer includes a foam layer.

11. The LAN cable according to claim 10, the insulating layer has a three-layer structure, and the total thickness of the three-layer structure is 0.35 to 0.45 mm; or The LAN cable has a two-layer insulating layer, and the total thickness of the two-layer structure is 0.35 to 0.45 mm.

12. 8. The LAN cable according to claim 7, A LAN cable having no flame-retardant tape between the insulated wire and the sheath.

Images