Communication cable

Abstract

A communication cable (10) includes: a wire bundle (4) including a plurality of insulated wires (3) each having an electrical conductor (1) and a coating layer (2) covering the electrical conductor (1); a sheath layer (5) that covers the outer periphery of the wire bundle; and an intermediate layer (6) that is interposed between the wire harness and the sheath layer and covers the outer periphery of the wire harness. The intermediate layer is in close contact with the coating layer of each insulated wire, and the sheath layer has a solid structure in which the sheath layer is arranged in close contact with the intermediate layer. The melting point of the base resin constituting the intermediate layer is at least 20 DEG C lower than the melting point of the base resin constituting the coating layer and the sheath layer. The base resin constituting the intermediate layer is at least one of a polyethylene resin or a polyethylene copolymer, and the base resin constituting the cover layer and the sheath layer is a polypropylene resin.

Description

Technical Field

[0001] This invention relates to a communication cable. Background Technology

[0002] Traditionally, communication cables have been developed to enable the high level of electrical communication required for autonomous vehicles. JP2021-136105A discloses a communication cable comprising a signal wire having multiple insulated wires and a solid sheath covering the outer periphery of the signal wires. Each insulated wire has an electrical conductor and an insulating sheath covering the outer periphery of the conductor. The material constituting the sheath has a melt flow rate of 0.25 g / 10 min or higher, measured at 200°C and a load of 2.16 kg.

[0003] JP2017-188431A discloses a communication wire having stranded wires and an insulating sheath. The stranded wires are formed by stranding a pair of insulated wires, which are made of conductors with a tensile strength of 400 MPa or more, and the insulating sheath covers the outer periphery of the conductors. The characteristic impedance of the communication wire is in the range of 100 ± 10 Ω, and the capacitance difference of the insulated wires forming the stranded wires is 25 pF / m or less. Furthermore, the communication wire has a sheath made of insulating material that covers the outer periphery of the stranded wires. A gap exists between the sheath and the insulated wires forming the stranded wires.

[0004] The communication wire disclosed in JP2021-136105A has a solid structure, in which there is essentially no gap between the signal wire and the sheath, and the material forming the sheath is in close contact with the surfaces of the insulated wires forming the signal wire. Meanwhile, the communication wire disclosed in JP2017-188431A has a tubular structure, in which there are gaps between the sheath and the insulated wires. Summary of the Invention

[0005] As mentioned above, JP2021-136105A discloses a material having a melt flow rate of 0.25 g / 10 min or higher as a material for constituting the sheath. However, even if such a material is used as a material for constituting the sheath, it may be difficult to peel off the sheath because the sheath and the insulation sheath of each insulated wire are fused together when the sheath is extruded.

[0006] Furthermore, because the communication wire disclosed in JP2017-188431A has a tubular structure, its sheath has excellent stripping properties. However, in communication wires, the insulated wires are not constrained by the sheath. Therefore, the structure of the stranded wires is easily altered, such as by the collapse of the strand spacing and changes in the distance between the wires. Consequently, the communication characteristics of the communication wire disclosed in JP2017-188431A may be affected by splicing to the outer material or bending when the communication wire is installed in a vehicle.

[0007] In view of past problems, the present invention has been completed. The object of the present invention is to provide a communication cable that has stable communication characteristics even when the communication cable is installed in a vehicle, and that has a sheath layer with excellent peelability.

[0008] A communication cable according to an aspect of the invention comprises: a wire harness including a plurality of insulated wires, each insulated wire having an electrical conductor and a sheath covering the electrical conductor; a sheath covering the outer periphery of the wire harness; and an intermediate layer between the wire harness and the sheath, covering the outer periphery of the wire harness. The intermediate layer is in close contact with the sheath of each insulated wire, and the sheath has a solid structure, wherein the sheath is arranged to be in close contact with the intermediate layer. The melting point of the base resin constituting the intermediate layer is at least 20°C lower than the melting point of the base resin constituting the sheath and the sheath. The base resin constituting the intermediate layer is at least one of polyethylene resin or polyethylene copolymer, and the base resin constituting the sheath and the sheath is polypropylene resin.

[0009] According to the present invention, a communication cable can be provided that has stable communication characteristics even when the communication cable is installed in a vehicle and has a sheath layer with excellent peelability. Attached Figure Description

[0010] Figure 1 This is a cross-sectional view showing an example of a communication cable according to this embodiment.

[0011] Figure 2 This is a cross-sectional view showing an example of a communication cable according to this embodiment. Detailed Implementation

[0012] The communication cable according to this embodiment will now be described in detail with reference to the accompanying drawings. For ease of explanation, the dimensions in the drawings are exaggerated and may differ from the actual scale.

[0013] like Figure 1 As shown, the communication cable 10 according to this embodiment includes a wire harness 4 and a sheath layer 5. The wire harness 4 is composed of multiple insulated wires 3, each insulated wire 3 having an electrical conductor 1 and a covering layer 2 covering the outer periphery of the electrical conductor 1, and the sheath layer 5 covers the outer periphery of the wire harness 4. Figure 1 In the communication cable 10 shown, the wire harness 4 includes two insulated wires 3. The communication cable 10 also includes an intermediate layer 6 inserted between the wire harness 4 and the sheath layer 5 and covering the outer periphery of the wire harness 4.

[0014] The electrical conductor 1 may consist of a single element wire, or it may be a clustered stranded wire composed of multiple element wires bundled together. Furthermore, the electrical conductor 1 may consist of a single stranded wire, or it may be a composite stranded wire composed of multiple clustered stranded wires bundled together. Additionally, the electrical conductor 1 may be a compressed conductor or an uncompressed conductor. There are no particular limitations on the material constituting the electrical conductor 1, but it is preferably at least one conductive metal material selected from the group consisting of copper, copper alloys, aluminum, and aluminum alloys.

[0015] There is no particular limitation on the outer diameter of the electrical conductor 1, but it is preferably 0.435 mm or more, and more preferably 0.440 mm or more. Since the outer diameter of the electrical conductor 1 has the above-mentioned value, the resistance of the electrical conductor 1 can be reduced. Furthermore, although there is no particular limitation on the outer diameter of the electrical conductor 1, it is preferably 0.465 mm or less, and more preferably 0.460 mm or less.

[0016] The thickness of the coating layer 2 is not particularly limited, but it is preferably 0.15 mm or more, and more preferably 0.18 mm or more. Because the thickness of the coating layer 2 has the above-mentioned values, it can effectively protect the electrical conductor 1. Furthermore, although the thickness of the coating layer 2 is not particularly limited, it is preferably 0.32 mm or less.

[0017] The coating layer 2 covers the entire outer periphery of the electrical conductor 1. Figure 1 In the communication cable 10 shown, the sheath 2 is in close contact with the entire surface of the electrical conductor 1.

[0018] The wire harness 4 has multiple insulated wires 3, each insulated wire 3 having an electrical conductor 1 and a sheath 2, and forming a signal line. The multiple insulated wires 3 can be twisted together to form a stranded wire. Alternatively, the multiple insulated wires 3 can be parallel to each other without twisting. However, if the multiple insulated wires 3 are used as stranded wires, the insulated wires 3 are less susceptible to external noise and the likelihood of noise from the insulated wires 3 affecting the outside is lower compared to when the insulated wires 3 are parallel to each other. Therefore, preferably, the multiple insulated wires 3 in the wire harness 4 are used as stranded wires.

[0019] The sheath layer 5 covers the outer periphery of the wire bundle 4, and therefore functions to protect the insulated wires 3 and also to stabilize the relative positions of the multiple insulated wires 3 within the wire bundle 4. The sheath layer 5 has a solid structure, wherein there are essentially no gaps between the sheath layer 5 and the intermediate layer 6, and the material forming the sheath layer 5 is in close contact with the surface of the intermediate layer 6. As will be described later, the intermediate layer 6 covers the entire outer periphery of the wire bundle 4 and further is in close contact with the entire surface of the wire bundle 4. Therefore, the solid structure of the sheath layer 5 and the intermediate layer 6 enables the stabilization of the relative positions of the multiple insulated wires 3. Preferably, there are no gaps between the intermediate layer 6 and the sheath layer 5, but a small number of gaps may exist between them when the relative positions of the multiple insulated wires 3 remain substantially unchanged.

[0020] In the communication cable 10, an intermediate layer 6 is located between the wire harness 4 and the sheath layer 5, and further covers the entire surface of the wire harness 4. The presence of this intermediate layer 6 facilitates the stripping of the sheath layer 5.

[0021] The resin compositions constituting the coating layer 2 and sheath layer 5 of each insulated wire 3 contain a base resin as a main component. Similarly, the resin composition constituting the intermediate layer 6 contains a base resin as a main component. In this specification, the amount of base resin contained in the resin compositions constituting each layer is 50% by mass or more.

[0022] The base resins constituting the coating layer 2 and the sheath layer 5 can be the same. However, the base resins constituting the coating layer 2 and the sheath layer 5 are different from the base resin constituting the intermediate layer 6. Because the base resin constituting the coating layer 2 is different from the base resin constituting the intermediate layer 6, resin fusion is unlikely. Similarly, because the base resin constituting the sheath layer 5 is different from the base resin constituting the intermediate layer 6, resin fusion is unlikely. Therefore, when a load is applied to the sheath layer 5 to peel it off, peeling occurs between the coating layer 2 and the intermediate layer 6 and / or between the sheath layer 5 and the intermediate layer 6, and voids are easily formed. As a result, the sheath layer 5 can be easily separated from the coating layer 2 and / or the intermediate layer 6.

[0023] Furthermore, the melting point of the base resin constituting the intermediate layer 6 is preferably 20°C lower than the melting point of the base resin constituting the coating layer 2 and the sheath layer 5. As will be described later, the sheath layer 5 and the intermediate layer 6 can be formed on the outer periphery of the wire harness 4 by extruding the resin composition of the sheath layer 5 and the resin composition of the intermediate layer 6 onto the outer periphery of the wire harness 4. At this time, since the melting point of the base resin constituting the intermediate layer 6 is 20°C lower than the melting point of the base resin constituting the coating layer 2 and the sheath layer 5, the melting point of the coating layer 2 is higher than the melting point of the intermediate layer 6. Therefore, it is unlikely that the coating layer 2 will melt due to the heat generated in the intermediate layer 6 during extrusion molding. As a result, since the thickness of the coating layer 2 is unlikely to be partially reduced, the conductor 1 can be effectively protected by the coating layer 2.

[0024] The base resin constituting the coating layer 2 and the sheath layer 5 is preferably polypropylene resin. Furthermore, the base resin constituting the intermediate layer 6 is preferably at least one of polyethylene resin or polyethylene copolymer. Polypropylene resin, polyethylene resin, and polyethylene copolymer exhibit excellent instantaneous heat resistance due to their relatively high melting points. Therefore, the coating layer 2, sheath layer 5, and intermediate layer 6 can be easily formed by extrusion molding.

[0025] Examples of polypropylene resins include homopolymer polypropylene (homogeneous PP), atactic polypropylene (random PP), block polypropylene (block PP), and copolymers with other olefins that can copolymerize with propylene. Examples of other olefins that can copolymerize with propylene include α-olefins such as ethylene, 1-butene, isobutene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3,4-dimethyl-1-butene, 1-heptene, and 3-methyl-1-hexene. Examples of polyethylene resins include high-density polyethylene resin (HDPE), low-density polyethylene resin (LDPE), and linear low-density polyethylene resin (LLDPE). Examples of polyethylene copolymers include ethylene-vinyl acetate copolymers, ethylene-propylene copolymers, ethylene-propylene-butene-1 copolymers, ethylene-butene-1 copolymers, ethylene-hexene-1 copolymers, ethylene-4-methylpentene-1 copolymers, ethylene-octene-1 copolymers, and mixtures thereof.

[0026] The base resin constituting the coating layer 2 and the sheath layer 5 can be polypropylene resin with a melting point of 160°C or higher. Furthermore, the base resin constituting the intermediate layer 6 can be at least one of polyethylene resin or polyethylene copolymer, and the polyethylene resin and polyethylene copolymer have a melting point of 140°C or lower. Even with this structure, instantaneous heat resistance is enhanced. Therefore, the coating layer 2, sheath layer 5, and intermediate layer 6 can be easily formed by extrusion molding.

[0027] To enhance the flexibility of the communication cable 10, the coating layer 2 and the sheath layer 5 may contain a flexible resin in addition to the base resin. As a flexible resin, the following can be used: chlorinated polyolefins, such as chlorinated polyethylene resin; acrylic rubbers, such as nitrile rubber (NBR); or one or more olefin thermoplastic elastomers or one or more styrene thermoplastic elastomers as described in the following paragraphs. The flexible resin may or may not be modified with maleic acid, etc.

[0028] Olefin thermoplastic elastomers comprise hard segments made of olefin resins and soft segments made of rubber. A typical example of an olefin thermoplastic elastomer is a polymer alloy in which the soft segments are finely dispersed as domains within a matrix of hard segments. Copolymers of hard and soft segments can also be used as olefin thermoplastic elastomers. Examples of olefin resins that can be used include polyethylene resins and polypropylene resins. Examples of rubbers that can be used include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), ethylene-propylene rubber (EPM), and ethylene-propylene-diene rubber (EPDM). One of these rubbers can be used alone, or a mixture of several rubbers can be used.

[0029] Examples of styrene thermoplastic elastomers are block copolymers or random copolymers having hard segments made of aromatic vinyl polymers and soft segments made of conjugated diene polymers. The monomers forming the aromatic vinyl polymers can be: α-alkyl-substituted styrene, such as styrene, α-methylstyrene, α-ethylstyrene, and α-methyl-p-methylstyrene; and aromatic alkyl-substituted styrene, such as o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, 2,4,6-trimethylstyrene, o-tert-butylstyrene, p-tert-butylstyrene, and p-cyclohexylstyrene. The conjugated diene polymers can be copolymers of at least one of butadiene or isoprene, as well as substances formed by a portion of a hydrogenated copolymer.

[0030] Styrene thermoplastic elastomers can be at least one block copolymer selected from the group consisting of polystyrene-polybutadiene-polystyrene (SBS), polystyrene-polyisoprene-polystyrene (SIS), polystyrene-polyisobutylene-polystyrene (SIBS), styrene-ethylene-butene-styrene block copolymer (SEBS), polystyrene-poly(ethylene-butene)-crystalline polyolefin (SEBC), and polystyrene-poly(ethylene-propylene)-polystyrene (SEPS).

[0031] The sheath layer 5 may contain 0 to 49 parts by weight of flexible resin relative to 51 to 100 parts by weight of the base resin. That is, the amount of flexible resin may be more than 0 parts by weight and less than 49 parts by weight relative to the total amount of 100 parts by weight of base resin and flexible resin. Since the amount of flexible resin is less than 49 parts by weight, abrasion resistance can be maintained while enhancing the flexibility of the resin composition.

[0032] like Figure 1 and Figure 2 As shown, when there are two insulated wires 3 in the wire bundle 4, the thickness of the intermediate layer 6 is preferably 20% to 80% of the thickness of the sheath layer 5. Since the thickness of the intermediate layer 6 is more than 20% of the thickness of the sheath layer 5, as will be described later, when the intermediate layer 6 and the sheath layer 5 are extruded, the melting of the coating layer 2 of each insulated wire 3 is suppressed. Therefore, partial reduction in the thickness of the coating layer 2 can be prevented. Furthermore, since the thickness of the intermediate layer 6 is less than 80% of the thickness of the sheath layer 5, the deterioration of the flame retardancy of the communication cable 10 can be suppressed. The thickness value of the sheath layer 5 is the average of the thicknesses of four portions: the thicknesses A and B of two portions perpendicular to the center line passing through the centers of the two conductors 1 and along the joint surface of the two insulated wires 3, and the thicknesses C and D of two portions along the center line passing through the centers of the two conductors, as shown below. Figure 1 As shown. Furthermore, the thickness of the intermediate layer 6 is the average thickness of four portions, namely, the thicknesses E and F of two portions perpendicular to the center line passing through the centers of the two conductors 1 and along the joint surface of the two insulated wires 3, and the thicknesses G and H of two portions along the center line passing through the centers of the two conductors 1, as shown. Figure 2 As shown.

[0033] In addition to the base resin and flexible resin, appropriate amounts of various additives can be added to the resin composition forming the coating layer 2, the sheath layer 5, and the intermediate layer 6 to a degree that does not inhibit the effects of this embodiment. Examples of additives include antioxidants, copper inhibitors, flame retardants, processing aids, crosslinking agents, metal passivators, anti-aging agents, fillers, reinforcing agents, ultraviolet absorbers, stabilizers, plasticizers, pigments, dyes, colorants, antistatic agents, foaming agents, etc.

[0034] When the sheath layer 5 has a solid structure, it is necessary to maintain a low dielectric constant for the insulated wire 3. Therefore, it is preferable to minimize the amount of additives added to the base resin of the coating layer 2. However, when copper or copper alloys are used for the conductor 1, oxidative degradation of the coating layer 2, known as copper damage, may occur due to the contact between the coating layer 2 and the conductor 1. Therefore, it is preferable to add antioxidants and copper inhibitors to the base resin forming the coating layer 2 so that the communication characteristics are not degraded.

[0035] Antioxidants inhibit the oxidation of coating layer 2. Known antioxidants used in thermoplastic resins, etc., can be used as antioxidants, including: free radical chain inhibitors, such as phenolic antioxidants, hindered phenolic antioxidants, and amine antioxidants; peroxide decomposers, such as phosphorus-based antioxidants and sulfur-based antioxidants; and metal passivators, such as hydrazine-based antioxidants and amine antioxidants. One antioxidant can be used alone, or a mixture of multiple antioxidants can be used.

[0036] The amount of antioxidant can be adjusted by considering its effects on antioxidant properties and its impact on communication characteristics. The amount of antioxidant in the resin composition constituting the coating layer 2 is preferably in the range of 0.1 to 5.0 parts by mass relative to 100 parts by mass of polypropylene resin. Since the amount of antioxidant is 0.1 parts by mass or more, heat resistance can be enhanced. Furthermore, since the amount of antioxidant is 5.0 parts by mass or less, its impact on communication characteristics can be suppressed.

[0037] A copper inhibitor suppresses oxidative degradation of the coating layer 2, known as copper damage, which is caused by the contact between the coating layer 2 and the conductor 1 (copper or copper alloy). As a copper inhibitor, for example, a salicylic acid-based copper inhibitor or a hydrazine-based copper inhibitor is used. The amount of the copper inhibitor in the resin composition constituting the coating layer 2 is preferably in the range of 0.1 to 3.0 parts by weight relative to 100 parts by weight of polypropylene resin. Since the amount of the copper inhibitor is 0.1 parts by weight or more, it can effectively impart a copper damage prevention effect. Furthermore, since the amount of the copper inhibitor is 3.0 parts by weight or less, it can suppress the impact on communication characteristics.

[0038] It is preferable to add a flame retardant to the resin composition constituting the sheath layer 5 to ensure the flame retardancy required for the characteristics of the wire. In addition, it is preferable to add an antioxidant or the like to the resin composition constituting the sheath layer 5 in the same manner as the coating layer 2, to a degree that does not inhibit communication characteristics.

[0039] Flame retardants enhance the flame retardancy of the sheath layer 5. By enhancing the flame retardancy of the sheath layer 5, even if a fire occurs inside the vehicle, the spread of fire within the sheath layer 5 can be suppressed.

[0040] Flame retardants can be, for example, at least one of organic or inorganic flame retardants. As organic flame retardants, examples include halogen-based flame retardants such as brominated and chlorinated flame retardants; and phosphorus-based flame retardants such as phosphate esters, condensed phosphate esters, cyclic phosphorus compounds, and red phosphorus. As inorganic flame retardants, at least one metal hydroxide selected from the group consisting of aluminum hydroxide, magnesium hydroxide, and calcium hydroxide can be used. One flame retardant can be used alone or in a mixture of multiple flame retardants. Flame retardants can include, for example, organic and inorganic flame retardants.

[0041] Preferably, the resin composition contains at least a halogenated flame retardant as an organic flame retardant. The halogenated flame retardant is capable of capturing hydroxyl radicals that promote the combustion of the base resin constituting the sheath layer 5 and inhibiting the combustion of the base resin. The halogenated flame retardant can be a compound in which one or more halogens are substituted in an organic compound. Examples of halogenated flame retardants include fluorinated flame retardants, chlorinated flame retardants, brominated flame retardants, and iodine flame retardants. The halogenated flame retardant is preferably a brominated flame retardant.

[0042] The preferred resin composition contains at least a metal hydroxide as an inorganic flame retardant. Metal hydroxides are commonly used as flame retardants, and their cost is relatively lower than that of brominated flame retardants. Furthermore, since the dielectric constant of metal hydroxides is higher than that of general polyolefin resins, they act as dielectric constant modifiers. Therefore, the sheath layer 5 of this embodiment preferably contains a metal hydroxide. As the metal hydroxide, one or more metal compounds having hydroxyl groups or water of crystallization can be used, such as magnesium hydroxide (Mg(OH)2), aluminum hydroxide (Al(OH)3), calcium hydroxide (Ca(OH)2), basic magnesium carbonate (mMgCO3·Mg(OH)2·nH2O), hydrated aluminum silicate (alumina silicate hydrate, Al2O3·3SiO2·nH2O), and hydrated magnesium silicate (magnesium silicate pentahydrate, Mg2Si3O8·5H2O). Among these, magnesium hydroxide is particularly preferred as the metal hydroxide.

[0043] The amount of flame retardant in the resin composition constituting the sheath layer 5 is preferably in the range of 60 to 150 parts by weight, relative to the total amount of 100 parts by weight of polypropylene resin and flexible resin. Since the amount of flame retardant is 60 parts by weight or more, the flame retardancy of the sheath layer 5 can be enhanced. Furthermore, since the amount of flame retardant is 150 parts by weight or less, it is possible to maintain the mechanical properties of the sheath layer 5 while avoiding the use of more flame retardant than required. This reduces the manufacturing cost of the sheath layer 5.

[0044] As an antioxidant included in the sheath layer 5, an antioxidant, for example, that used in the coating layer 2, can be used.

[0045] The amount of added antioxidant can be adjusted by considering its effect on antioxidant properties and its impact on communication characteristics. The amount of antioxidant in the resin composition constituting the sheath layer 5 is preferably 0.1 to 5.0 parts by mass relative to the total amount of 100 parts by mass of polypropylene resin and flexible resin. Since the amount of antioxidant is 0.1 parts by mass or more, heat resistance can be enhanced. Furthermore, since the amount of antioxidant is 5.0 parts by mass or less, its impact on communication characteristics can be suppressed.

[0046] The communication cable 10 of this embodiment can be manufactured by the following method. First, a resin composition constituting the coating layer 2, the sheath layer 5, and the intermediate layer 6 is prepared. These resin compositions are manufactured by melt-mixing the raw materials of the above-mentioned resin compositions, and known methods can be used. The resin composition can be obtained by premixing the raw materials with a high-speed mixer such as a Henschel mixer, and then mixing the raw materials with a known mixer such as a Banbury mixer, a kneading mill, or a tumbler.

[0047] Next, the conductor 1 is covered with the coating layer 2 to obtain each insulated wire 3. There are no particular limitations on the method used to cover the conductor 1 with the coating layer 2, but a general extrusion molding method can be used, for example. As the extrusion molding machine, a single-screw extruder or a twin-screw extruder can be used, and an extruder having a screw, baffle plate, crosshead, distributor, nozzle or die can be used.

[0048] Next, the obtained multiple insulated wires 3 are bundled together to obtain a wire bundle 4. At this point, the multiple insulated wires 3 can be twisted together to form a stranded wire.

[0049] Then, a sheath layer 5 and an intermediate layer 6 are formed around the periphery of the wire harness 4. While the method for forming the sheath layer 5 and the intermediate layer 6 is not particularly limited, the sheath layer 5 and the intermediate layer 6 can be formed by twin-screw extrusion molding of the resin composition of the sheath layer 5 and the resin composition of the intermediate layer 6. At this time, the extrusion molding conditions are adjusted so that the sheath layer 5 has a solid structure.

[0050] When the sheath layer 5 and the intermediate layer 6 are formed by twin-screw extrusion molding, the resin composition of the sheath layer 5 and the resin composition of the intermediate layer 6 are extruded simultaneously. Therefore, the intermediate layer 6 is in close contact with the sheath layer 5. Consequently, when the sheath layer 5 is peeled off, the intermediate layer 6 can be peeled off along with the sheath layer 5. This improves operational efficiency.

[0051] The communication cable 10 of this embodiment can be obtained by this method.

[0052] In this manner, the communication cable 10 of this embodiment includes: a wire harness 4 comprising a plurality of insulated wires 3, each insulated wire 3 having an electrical conductor 1 and a sheath 2 covering the electrical conductor; a sheath 5 covering the outer periphery of the wire harness; and an intermediate layer 6 situated between the wire harness 4 and the sheath 5 and covering the outer periphery of the wire harness. The intermediate layer 6 is in close contact with the sheath 2 of each insulated wire 3, and the sheath 5 has a solid structure, wherein the sheath 5 is arranged to be in close contact with the intermediate layer 6. The melting point of the base resin constituting the intermediate layer 6 is at least 20°C lower than the melting point of the base resin constituting the sheath 2 and the sheath 5. The base resin constituting the intermediate layer 6 is at least one of polyethylene resin or polyethylene copolymer, and the base resin constituting the sheath 2 and the sheath 5 is polypropylene resin.

[0053] Because the sheath layer 5 of the communication cable 10 has a solid structure, the relative positions of the multiple insulated wires 3 can be stabilized. Therefore, even when the communication cable 10 is installed in a vehicle, the communication characteristics can be stabilized. Furthermore, in the communication cable 10, the intermediate layer 6 is disposed between the covering layer 2 and the sheath layer 5 of each insulated wire 3. Therefore, since the sheath layer 5 is easy to detach, it can be easily peeled off.

[0054] In the communication cable 10, the wire harness 4 can be a stranded wire formed by twisting together multiple insulated wires 3. Stranded wires are not easily affected by external noise, and the noise from stranded wires is less likely to affect the outside. Therefore, since the wire harness 4 is a stranded wire, the functionality of the communication cable 10 can be further enhanced.

[0055] The base resin constituting the intermediate layer 6 in the communication cable 10 can be at least one of polyethylene resin or polyethylene copolymer with a melting point below 140°C. The base resin constituting the coating layer 2 and the sheath layer 5 can be polypropylene resin with a melting point above 160°C. With this structure, it is unlikely that the coating layer 2 will melt due to the heat generated in the intermediate layer 6 during extrusion molding. Therefore, the thickness of the coating layer 2 is unlikely to be partially reduced. Therefore, the electrical conductor 1 can be effectively protected by the coating layer 2.

[0056] Relative to 100 parts by weight of polypropylene resin, the coating layer 2 of the communication cable 10 may contain 0.1 to 5.0 parts by weight of an antioxidant and 0.1 to 3.0 parts by weight of a copper inhibitor. This configuration effectively imparts antioxidant and copper damage prevention effects to the coating layer 2.

[0057] The sheath layer 5 of the communication cable 10 may contain 0 to 49 parts by weight of flexible resin, relative to 51 to 100 parts by weight of polypropylene resin. Furthermore, relative to the total amount of 100 parts by weight of polypropylene resin and flexible resin, the sheath layer 5 may contain 0.1 to 5.0 parts by weight of antioxidant and 60 to 150 parts by weight of flame retardant. This structure effectively imparts both flexibility and antioxidant and flame-retardant properties to the sheath layer 5.

[0058] In the communication cable 10, when there are two insulated wires 3 in the wire bundle 4, the thickness of the intermediate layer 6 can be 20% to 80% of the thickness of the sheath layer 5. With this construction, it is unlikely that the coating layer 2 will melt due to the heat generated during extrusion molding of the intermediate layer 6. Therefore, the thickness of the coating layer 2 is unlikely to be partially reduced. Thus, the electrical conductor 1 can be effectively protected by the coating layer 2.

[0059] The present embodiment will now be described in more detail using examples, comparative examples, and reference examples, but the present embodiment is not limited to these examples.

[0060] [Preparation of test samples]

[0061] In order to manufacture the test samples of Examples 1 to 4, Comparative Example 1, and Reference Examples 1 and 2, the following materials were prepared as raw materials for the resin compositions used in the coating, sheath, and intermediate layers of each insulated wire.

[0062] • Polypropylene resin (PP): Prime Polypro (registered trademark) E-150GK, manufactured by Prime Polymer Co., Ltd., melting point 162℃

[0063] • Polyethylene resin (PE): Novatec (registered trademark) HE122R, high-density polyethylene resin, manufactured by Nippon Polypropylene Co., Ltd., melting point 128℃

[0064] • Ethylene-vinyl acetate copolymer (EVA): Evaflex (registered trademark) P1007, manufactured by DOW-MITSUIPOLYCHEMICALS CO.,LTD., melting point 94℃

[0065] • Styrene-ethylene-butene-styrene block copolymer (SEBS): Septon (registered trademark) 8007L, manufactured by Kuraray Co., Ltd.

[0066] • Phenol-based antioxidant: ADKSTAB (registered trademark) AO-60, pentaerythritol tetratetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], manufactured by ADEKA Corporation

[0067] Copper inhibitor: ADKSTAB (registered trademark) CDA-10, N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, manufactured by ADEKA Corporation

[0068] • Flame retardant: Magnesium hydroxide, manufactured by Konoshima Chemical Co., Ltd.

[0069] (Example 1)

[0070] First, weigh each raw material according to the blending amounts shown in Table 1, and then melt-blend the raw materials to prepare a resin composition constituting the coating layer, intermediate layer, and sheath layer.

[0071] Next, a stranded wire with an outer diameter of 0.45 mm is prepared. The copper alloy conductor is then used. A resin composition for coating is then extruded onto the outer periphery of the conductor to form a 0.2 mm thick coating. In this way, an insulated wire is obtained in which the entire outer periphery of the conductor is covered by the coating. Two insulated wires are then prepared and twisted together to obtain a wire bundle.

[0072] Next, the resin compositions for the intermediate layer and the sheath layer are twin-screw extruded onto the outer periphery of the wire harness to form the intermediate layer and the sheath layer. During extrusion molding, the thickness of the sheath layer is adjusted to 0.75 mm, the thickness of the intermediate layer is adjusted to have the values ​​shown in Table 1, and further, the sheath layer is adjusted to have a solid structure. In this way, the test sample of this embodiment is obtained, wherein the entire outer periphery of the wire harness is covered by the intermediate layer and the sheath layer. The outer diameter of the obtained test sample is... It is 3.2mm.

[0073] like Figure 1 As shown, the thickness of the sheath layer is set as the average thickness of four portions: thicknesses A and B of two portions perpendicular to the center line passing through the centers of the two conductors 1 and along the joint surface of the two insulated wires, and thicknesses C and D of two portions along the center line passing through the centers of the two conductors. Furthermore, as... Figure 2 As shown, the thickness value of the intermediate layer is set as the average of the thicknesses of four parts, namely the thicknesses E and F of two parts perpendicular to the center line passing through the center of the two electrical conductors 1 and along the joint surface of the two insulated wires, and the thicknesses G and H of two parts along the center line passing through the center of the two conductors.

[0074] (Examples 2 to 4)

[0075] Except for changing the raw materials and mixing amounts of the coating, intermediate layer and sheath layer as shown in Table 1, test samples of each embodiment were obtained by the same method as in Example 1.

[0076] (Comparative Example 1)

[0077] Except for the changes in the raw materials and mixing amounts of the coating and sheath layers as shown in Table 2, the test samples of this embodiment were obtained using the same method as in Example 1. In Comparative Example 1, no intermediate layer was formed, and the sheath layer had a solid structure, wherein the sheath layer was arranged to be in close contact with the coating layer of each insulated wire.

[0078] (Refer to Examples 1 and 2)

[0079] Except for changes in the raw materials and mixing amounts of the coating layer, intermediate layer, and sheath layer as shown in Table 2, test samples for each embodiment were obtained using the same method as in Example 1. During extrusion molding, the thickness of the sheath layer was adjusted to 0.75 mm, the thickness of the intermediate layer was adjusted to have the values ​​shown in Table 2, and the sheath layer was further adjusted to have a solid structure.

[0080] [Table 1]

[0081]

[0082] [Table 2]

[0083]

[0084] [evaluate]

[0085] Adhesion tests, structural tests, and flame retardant tests were performed on the test samples of the various embodiments obtained as described above.

[0086] (Adhesion test)

[0087] The load required to peel off a 20 mm long sheath layer at the end of the test sample in each embodiment was measured. As a result of the measurement, a load less than 50 N was rated "○", and a load greater than 50 N was rated "×". The measurement results are shown in Tables 1 and 2.

[0088] As can be seen from Tables 1 and 2, the test samples of Examples 1 to 4 exhibit excellent peel characteristics because the load required to peel off the sheath layer is less than 50 N. Specifically, in each of the test samples of Examples 1 to 4, the base resin of the interlayer is polyethylene resin or polyethylene copolymer, and the base resin of the coating layer and sheath layer is polypropylene resin, with a melting point difference of more than 20°C. Therefore, fusion between the coating layer and the interlayer is unlikely to occur, resulting in good peelability.

[0089] In contrast, it can be seen that the test sample of Comparative Example 1 exhibits poor peel characteristics because the load required to peel off the sheath layer is over 50 N. In other words, in the test sample of Comparative Example 1, there is no intermediate layer, the coating layer and the sheath layer are in close contact, and the base resin of both the coating layer and the sheath layer is polypropylene resin. Therefore, the coating layer and the sheath layer are fused together, and the peel characteristics of the sheath layer are deteriorated.

[0090] (Structural Testing)

[0091] The thickness of the coating of each insulated wire was measured by observing the cross-section of the test samples of each embodiment. Specifically, the thickness of the coating of each insulated wire was measured in four portions, and the thickness of a total of eight portions of the two coatings was measured. When the thickness of all eight portions was 0.16 mm or more, it was rated as "○", and if the thickness of any one of the eight portions was less than 0.16 mm, it was rated as "×". The measurement results are shown in Tables 1 and 2.

[0092] As can be seen from Tables 1 and 2, in the various test samples of Examples 1 to 4, the thickness of all eight portions of the coating is 0.16 mm or more. In other words, when manufacturing the test samples of each embodiment, insulated wires with a coating thickness of 0.2 mm were used, and an intermediate layer and a sheath layer were extruded onto the outer periphery of a wire bundle formed by twisting two insulated wires. If the thickness of the intermediate layer is insufficient, the coating layer melts during the extrusion of the intermediate layer and the sheath layer, and the thickness of the coating layer decreases.

[0093] However, in the test sample of Example 1, the thickness of the intermediate layer was 0.15 mm and the thickness of the sheath layer was 0.75 mm. Therefore, the thickness of the intermediate layer was 20% of the thickness of the sheath layer. Since the thickness of the intermediate layer was sufficiently ensured, it can be seen that the melting of the coating layer during extrusion molding was suppressed, and the reduction of the coating layer thickness was also suppressed.

[0094] In the test samples of Examples 2 and 3, the thickness of the intermediate layer was 0.15 mm and the thickness of the sheath layer was 0.75 mm. Therefore, the thickness of the intermediate layer was 20% of the thickness of the sheath layer. Furthermore, in the test sample of Example 4, the thickness of the intermediate layer was 0.6 mm and the thickness of the sheath layer was 0.75 mm. Therefore, the thickness of the intermediate layer was 80% of the thickness of the sheath layer. Thus, it can be seen that the reduction in the thickness of the coating layer can be suppressed in the test samples.

[0095] In contrast, since the test sample of Comparative Example 1 lacked an intermediate layer, the coating layer melted during extrusion molding of the sheath layer, and the thickness of the coating layer decreased. Furthermore, in the test sample of Reference Example 1, the thickness of the intermediate layer was 0.10 mm and the thickness of the sheath layer was 0.75 mm. Therefore, the thickness of the intermediate layer was 13% of the thickness of the sheath layer. Due to the insufficient thickness of the intermediate layer, the coating layer melted during extrusion molding, and the thickness of the coating layer decreased.

[0096] (Flame retardancy test)

[0097] For the test samples of each embodiment, a flame retardancy test according to ISO 19642 was performed on the wires. The flame retardancy test was conducted by arranging the test samples at a 45° angle. As a result of the flame retardancy test, if the flame extinguishes within 70 seconds and a test sample longer than 50 mm remains unburned, it is rated as "○", and if the flame lasts for more than 70 seconds or a test sample shorter than 50 mm remains unburned, it is rated as "×". The test results are shown in Tables 1 and 2.

[0098] According to Tables 1 and 2, the flame retardancy of the test sample in Reference Example 2 is poor. It is presumed that the flame retardancy is deteriorated because the thickness of the interlayer is greater than that of the test samples in other embodiments. In other words, in the test sample of Reference Example 2, the thickness of the interlayer is 0.65 mm, and the thickness of the sheath layer is 0.75 mm. Since the thickness of the interlayer is 87% of the thickness of the sheath layer, it is presumed that the flame retardancy of the test sample of Reference Example 2 is poor.

[0099] While specific embodiments have been described, these embodiments are disclosed by way of example only and are not intended to limit the scope of the invention. In fact, the novel embodiments described herein can be implemented in various other forms; furthermore, various omissions, substitutions, and changes can be made to the forms of the embodiments described herein without departing from the spirit of the invention. The appended claims and their equivalents are intended to cover such forms or modifications that fall within the scope and spirit of the invention.

Claims

1. A communication cable, comprising: A wire harness comprising a plurality of insulated wires, each of the insulated wires having an electrical conductor and a coating covering the electrical conductor; A sheath layer that covers the outer periphery of the wire harness; as well as An intermediate layer, which is located between the wire harness and the sheath layer and covers the outer periphery of the wire harness, wherein, The intermediate layer is in close contact with the sheathing layer of each of the insulated wires, and the sheath layer has a solid structure, wherein the sheath layer is arranged to be in close contact with the intermediate layer. The melting point of the base resin constituting the intermediate layer is more than 20°C lower than the melting point of the base resin constituting the coating layer and the sheath layer, and The base resin constituting the intermediate layer is at least one of polyethylene resin or polyethylene copolymer, and the base resin constituting the coating layer and the sheath layer is polypropylene resin.

2. The communication cable according to claim 1, wherein, The wire bundle is a stranded wire formed by twisting together multiple insulated wires.

3. The communication cable according to claim 1 or 2, wherein, The base resin constituting the intermediate layer is at least one of polyethylene resin or polyethylene copolymer with a melting point below 140°C, and The base resin constituting the coating layer and the sheath layer is polypropylene resin with a melting point of 160°C or higher.

4. The communication cable according to claim 1 or 2, wherein, The coating layer comprises, relative to 100 parts by weight of the polypropylene resin, 0.1 to 5.0 parts by weight of an antioxidant and 0.1 to 3.0 parts by weight of a copper inhibitor.

5. The communication cable according to claim 1 or 2, wherein, The sheath layer comprises 0 to 49 parts by weight of a flexible resin relative to 51 to 100 parts by weight of the polypropylene resin, and The sheath layer comprises 0.1 to 5.0 parts by weight of an antioxidant and 60 to 150 parts by weight of a flame retardant, relative to 100 parts by weight of the total amount of the polypropylene resin and the flexible resin.

6. The communication cable according to claim 1 or 2, wherein, When the number of insulated wires in the wire harness is two, the thickness of the intermediate layer is 20% to 80% of the thickness of the sheath layer.

Images