CN115274205B

CN115274205B - LAN cable

Info

Publication number: CN115274205B
Application number: CN202211030107.1A
Authority: CN
Inventors: 木部有; 岩崎周; 梶山元治; 大桥守
Original assignee: Bomeilicheng Co ltd
Current assignee: Bomeilicheng Co ltd
Priority date: 2017-05-02
Filing date: 2018-02-07
Publication date: 2024-02-09
Anticipated expiration: 2038-02-07
Also published as: CN115274205A; CN108806861A; JP6829819B2; JP2018190585A

Abstract

The invention provides a LAN cable with high flame retardance. The LAN cable is characterized by comprising: an insulated wire having an insulating layer on the outer periphery of a conductor, and a sheath covering the outer periphery of the insulated wire, wherein an intermediate layer is provided between the sheath and the insulated wire, the mass reduction rate of the intermediate layer at 800 ℃ is 80 mass% or less, and the sheath is formed of a crosslinked product having a mass reduction rate at 800 ℃ of 60 mass% or less.

Description

LAN cable

The present application is a divisional application of the invention patent application with the application number 20181012598. X, the application date 2018, 2/7, and the name "LAN cable".

Technical Field

The present invention relates to LAN cables.

Background

LAN cables are used to construct LANs (Local Area Network, local area networks). The LAN cable includes a structure including a sheath for covering the outer periphery of an insulated wire having an insulating layer formed on the outer periphery of a conductor, and a halogen-free flame-retardant resin composition is sometimes used for the sheath (for example, refer to patent document 1).

For LAN cables, in order to maintain the transmission characteristics, the addition of a flame retardant to the insulating layer should be avoided, and thus a flame retardant method using a halogen-free flame retardant resin composition highly filled with a flame retardant for the sheath is employed.

Prior art literature

Patent literature

Patent document 1: japanese patent application laid-open No. 2015-4025

Disclosure of Invention

Problems to be solved by the invention

However, such conventional flame-retardant methods cannot achieve high flame retardancy required in flame retardancy tests represented by overseas standards, and there is room for further improvement.

Accordingly, an object of the present invention is to provide a LAN cable having high flame retardancy.

Means for solving the problems

In order to achieve the above object, according to the present invention, the following LAN cable is provided.

[1] A LAN cable comprising: an insulated wire having an insulating layer on the outer periphery of a conductor, and a sheath covering the outer periphery of the insulated wire, wherein an intermediate layer is provided between the sheath and the insulated wire, the mass reduction rate of the intermediate layer at 800 ℃ is 80 mass% or less, the sheath is formed of a crosslinked product that is a halogen-free flame-retardant resin composition having a mass reduction rate at 800 ℃ of 60 mass% or less.

[2] The LAN cable according to [1], wherein the sheath contains 150 parts by mass or more of a flame retardant per 100 parts by mass of the polyolefin-based polymer.

[3] The LAN cable according to [1] or [2], characterized in that the intermediate layer comprises a polyimide film.

[4] The LAN cable according to [2], characterized in that the flame retardant comprises magnesium hydroxide or aluminum hydroxide.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a LAN cable having high flame retardancy can be provided.

Drawings

Fig. 1 is a cross-sectional view of a LAN cable according to an embodiment of the present invention.

Symbol description

1: a LAN cable; 3: a sheath; 5: an insulated wire; 7: an intermediate layer; 9: a resin tape; 11: a braiding layer; 13: a conductor; 15: an insulating layer.

Detailed Description

< one embodiment of the invention >

An embodiment of the present invention will be described below.

LAN cable

The LAN cable according to an embodiment of the present invention includes: an insulated wire having an insulating layer on the outer periphery of a conductor, and a sheath covering the outer periphery of the insulated wire, wherein an intermediate layer is provided between the sheath and the insulated wire, the mass reduction rate of the intermediate layer at 800 ℃ is 80 mass% or less, the sheath is formed of a crosslinked product of a halogen-free flame-retardant resin composition, and the mass reduction rate of the halogen-free flame-retardant resin composition at 800 ℃ is 60 mass% or less.

Conventional flame-retardant methods, in which the sheath is highly filled with a flame retardant, cannot achieve high flame retardancy required in flame-retardant tests represented by overseas standards such as EN45545 and NFPA 130.

Accordingly, the present inventors focused on the fact that the combustion of the insulating layer cannot be suppressed by the above conventional flame retardant method, and focused on the fact that it is necessary to suppress the escape of the combustible gas generated from the insulating layer to the combustion site during combustion.

Then, the present inventors considered that in order to suppress the escape of the combustible gas generated by the insulating layer to the burning site, it is necessary that the intermediate layer maintains its shape when burning, and if the sheath is dropped during burning, the intermediate layer burns in the presence of oxygen, so that it is necessary that the sheath is not dropped during burning to form the charred layer.

Accordingly, the present invention employs an intermediate layer having a mass reduction rate of 80 mass% or less at 800 ℃ between the sheath and the insulated wire, and a sheath formed of a crosslinked product of a halogen-free flame-retardant resin composition having a mass reduction rate of 60 mass% or less at 800 ℃.

1.1 intermediate layer

The intermediate layer is arranged between the sheath and the insulated wire. The mass reduction rate of the intermediate layer at 800 ℃ is 80 mass% or less, more preferably 60 mass% or less. The mass reduction rate of the intermediate layer was measured using a thermogravimetric detector (TGA) under a nitrogen atmosphere at a temperature rise rate of 10 ℃/min, and the change rate of the mass before and after heating was measured. By providing the intermediate layer having the above characteristics, the shape at the time of combustion can be maintained, and the escape of the combustible gas generated by the insulating layer to the combustion site can be suppressed, and high flame retardancy can be satisfied.

Examples of the material of the intermediate layer include metals and organic substances. The metal may be copper or the like. In addition, if an organic material is used as the material of the intermediate layer, the flexibility of the LAN cable can be further improved. The organic substance may be polyimide, mica, or the like, and polyimide is preferable.

The position of the intermediate layer in the LAN cable may be appropriately selected, but is preferably a position immediately below the sheath. It is considered that, in the case of the sheath being immediately below, the sheath is brought into close contact with the intermediate layer, and thus, since no air exists between the sheath and the intermediate layer, the sheath charres at the time of combustion, and the effect of suppressing the combustion of the intermediate layer in an oxygen atmosphere is further improved.

Examples of the form of the intermediate layer include a form in which a film is wound. The intermediate layer may be formed by winding a plurality of films around a plurality of portions. The winding method of the film is not particularly limited, and examples thereof include transverse winding, longitudinal winding, and the like. By using the film winding method as the transverse winding, the flexibility of the LAN cable can be further improved. In the case of transverse winding, for example, a portion of a film having a predetermined width may be wound while being overlapped. The amount of overlap is preferably 1/4 or more of the film width.

1.2 sheath

The sheath is a crosslinked product composed of a halogen-free flame-retardant resin composition having a mass reduction rate at 800 ℃ of 60 mass% or less, more preferably 52 mass% or more and 58 mass% or less, 52 mass% or more and 56 mass% or less, and 52 mass% or more and 54 mass% or less. The mass reduction rate of the jacket was measured using a thermogravimetric detector (TGA) under a nitrogen atmosphere at a temperature rise rate of 10 ℃/min, and the mass change rate before and after heating was measured. The sheath having the above characteristics prevents the sheath from dripping during combustion, and the intermediate layer is in an anoxic state, thereby satisfying flame retardancy.

The sheath is not particularly limited as long as it is crosslinked, and a material having a gel fraction of 80% by mass or more can be preferably used. The gel fraction was measured by immersing the sheath in xylene at 110℃for 24 hours according to the method for measuring the degree of crosslinking of item 4.25 in JIS C3005, and the value was calculated from the weight ratio before and after immersion.

Polyolefin polymers can be used for the sheath. The polyolefin-based polymer is preferably used as a base polymer for the sheath. Examples of the polyolefin-based polymer include Low Density Polyethylene (LDPE), linear Low Density Polyethylene (LLDPE), linear ultra low density polyethylene (VLDPE), high Density Polyethylene (HDPE), polypropylene (PP), ethylene-ethyl acrylate copolymer (EEA), ethylene-vinyl acetate copolymer (EVA), ethylene-styrene copolymer, ethylene-glycidyl methacrylate copolymer, ethylene-1-butene copolymer, ethylene-butene-hexene terpolymer, ethylene-propylene-diene terpolymer (EPDM), ethylene-octene copolymer (EOR), ethylene-copolymerized polypropylene, ethylene-propylene copolymer (EPR), poly-4-methyl-1-pentene, maleic acid grafted low density polyethylene, hydrogenated styrene-butadiene copolymer (H-SBR), maleic acid grafted linear low density polyethylene, copolymer of ethylene and alpha olefin having 4 to 20 carbon atoms, ethylene-styrene copolymer, maleic acid grafted ethylene-methyl acrylate copolymer, maleic acid grafted ethylene-vinyl acetate copolymer, ethylene-maleic anhydride copolymer, ethylene-ethyl acrylate copolymer, and maleic anhydride-1-butene copolymer. The polyolefin polymer is preferably EVA, and particularly preferably EVA having a VA content of 20 to 50 mass%. Any EVA may be used alone or 2 or more EVA may be used in combination as the polyolefin polymer.

The sheath may be made of a polyolefin polymer containing a flame retardant. Examples of the flame retardant include metal hydroxides such as magnesium hydroxide, aluminum hydroxide and calcium hydroxide, amorphous silica, zinc compounds such as zinc stannate, zinc hydroxystannate, zinc borate and zinc oxide, boric acid compounds such as calcium borate, barium borate and barium metaborate, nitrogen-based flame retardants such as phosphorus-based flame retardants and melamine cyanurate, and intumescent flame retardants formed from a mixture of a component which foams during combustion and a cured component. The flame retardant is preferably a metal hydroxide, and particularly preferably magnesium hydroxide. In the case of containing magnesium hydroxide and/or aluminum hydroxide as a flame retardant, the flame retardancy of LAN cables is further improved.

Any one of the above flame retardants may be used alone, or two or more of them may be used in combination. For example, magnesium hydroxide and aluminum hydroxide may be used in admixture. The flame retardant may be a flame retardant surface-treated with a silane coupling agent, a titanate coupling agent, a fatty acid such as stearic acid or calcium stearate, a fatty acid metal salt, or the like.

The amount of the flame retardant to be added is 150 parts by mass or more per 100 parts by mass of the polyolefin polymer. When the amount is 150 parts by mass or more, the flame retardancy of the LAN cable is improved. The upper limit of the amount of the flame retardant to be added is not particularly limited, but is preferably 250 parts by mass or less. By controlling the amount of the flame retardant to be added, the elongation of the sheath at low temperature can be further increased. The amount of the flame retardant to be added is more preferably 150 to 220 parts by mass, 180 to 200 parts by mass, based on 100 parts by mass of the polyolefin polymer.

The jacket may further contain additives such as antioxidants, metal deactivators, crosslinking agents, crosslinking aids, lubricants, inorganic fillers, compatibilizers, stabilizers, carbon black, colorants, and the like, as needed. The sheath may be crosslinked with an organic peroxide or with radiation such as electron beam.

The antioxidant is not particularly limited, and examples thereof include phenol-based, sulfur-based, amine-based, and phosphorus-based antioxidants. The phenol-based antioxidant is not particularly limited, and examples thereof include dibutylhydroxytoluene (BHT), pentaerythritol tetrakis [3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate ], 1,3, 5-tris (3, 5-di-t-butyl-4-hydroxy-benzyl) -S-triazine-2, 4,6- (1 h,3h,5 h) trione, thiodiethylenebis [3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate ], and the like, more preferably pentaerythritol tetrakis [3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate ].

Examples of the sulfur-based antioxidant include, but are not particularly limited to, didodecyl 3,3' -thiodipropionate, ditridecyl 3,3' -thiodipropionate, dioctadecyl 3,3' -thiodipropionate, tetrakis [ methylene-3- (dodecylthio) propionate ] methane, and the like, and more preferably tetrakis [ methylene-3- (dodecylthio) propionate ] methane. These antioxidants may be used singly or in combination of two or more.

The metal deactivator has an effect of stabilizing metal ions by forming chelate and suppressing oxidative degradation. The structure of the metal deactivator is not particularly limited, and examples thereof include N- (2H-1, 2, 4-triazol-5-yl) salicylamide, dodecanedioic acid bis [ N2- (2-hydroxybenzoyl) hydrazide ], 2', 3-bis [ [3- [3, 5-di-t-butyl-4-hydroxyphenyl ] propionyl ] ] propionyl hydrazide, and the like, and more preferably 2', 3-bis [ [3- [3, 5-di-t-butyl-4-hydroxyphenyl ] propionyl ] ] propionyl hydrazide.

Examples of the crosslinking aid include, but are not particularly limited to, trimethylolpropane trimethacrylate (TMPT) and triallyl isocyanurate (TAIC). The lubricant is not particularly limited, and examples thereof include fatty acids, fatty acid metal salts, fatty acid amides, and the like, and specifically, zinc stearate. These lubricants may be used singly or in combination of two or more.

The carbon black is not particularly limited, and examples thereof include rubber carbon black (N900-N100: ASTM D1765-01) and the like. The colorant is not particularly limited, and examples thereof include a halogen-free color master batch.

1.3 insulated wire

The insulated wire includes an insulating layer on an outer periphery of the conductor. The material of the conductor is not particularly limited, and copper or copper alloy, aluminum or aluminum alloy may be used. The conductor is not particularly limited to this, and a twisted structure formed by twisting a plurality of bare wires is preferably used in view of flexibility of the cable, in addition to a single wire. Further, it is also possible to suitably plate the substrate, for example, tin plating or the like may be applied.

The material of the insulating layer is not particularly limited, and is preferably polyethylene, and more preferably polyethylene having a dielectric constant of 2.5 or less. Since the dielectric constant of polyethylene is 2.5 or less, the electrostatic capacity of the insulating layer becomes small. Thereby, the transmission characteristics of the LAN cable are further improved. 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. More preferably, the dielectric constant of the entire insulating layer is 1.9 to 2.3, 1.9 to 2.1.

Examples of the polyethylene include Low Density Polyethylene (LDPE), linear Low Density Polyethylene (LLDPE), linear ultra low density polyethylene (VLDPE), and High Density Polyethylene (HDPE), and the like, and more preferably low density polyethylene, particularly preferably low density polyethylene having a density of 0.930 or less and an MFR of 0.30 or less. Any one of the above polyethylenes may be used alone, or two or more thereof may be used in combination.

The insulating layer may further contain an antioxidant, a copper inhibitor, a colorant, and the like. The amount of the antioxidant, copper inhibitor, colorant, etc. to be added is not particularly limited, but is preferably an amount such that the dielectric constant of the entire insulating layer is 2.5 or less. The amount of the colorant and the like to be added is preferably 5% by mass or less, more preferably 2% by mass or less. In addition, the insulating layer may contain no flame retardant. By using the intermediate layer having the above-described characteristics and the sheath having the above-described characteristics, a LAN cable satisfying high flame retardancy can be realized even if the insulating layer is a resin composition containing no flame retardant.

The polyethylene may be foamed using known methods. For example, polyethylene can be foamed by a method using an inert gas such as nitrogen or using a chemical foaming agent such as ADCA. The polyethylene preferably has a foaming degree of 15 mass% or more.

1.4LAN cable

Fig. 1 is a cross-sectional view of a LAN cable according to an embodiment of the present invention. The LAN cable 1 includes a sheath 3, an insulated wire 5, an intermediate layer 7, a resin tape 9, and a braid 11. The insulated wire 5 includes a conductor 13 and an insulating layer 15 located on the outer periphery of the conductor 13. That is, the outer periphery of the conductor 13 is covered with the insulating layer 15. An intermediate layer 7 is located between the sheath 3 and the insulated wire 5. The resin tape 9 and the braid 11 are located between the insulated wire 5 and the intermediate layer 7. The material of the resin tape 9 is not limited, and an aluminum laminated PET tape may be used. Here, as the insulated wire, the same materials as those of the insulated wire described above can be used. The material of the braid 11 is not particularly limited, and copper or a copper alloy may be used.

Examples

The present invention will be described in further detail based on examples, but the present invention is not limited to these examples.

Example 1

(1) Manufacture of LAN cable 1

The LAN cable 1 is manufactured as follows. First, materials of the insulating layer and the sheath were prepared according to the formulations shown in table 1.

In the formulation, pellets kneaded at a starting temperature of 40℃and a finishing temperature of 190℃by a pressure kneader were used as materials for the insulating layer and the sheath. Then, the insulating layer was coated with a material having a thickness of 0.4mm on a conductor having an outer diameter of 0.78mm, and crosslinked by an irradiation dose of 7MRad, to produce an insulated wire.

Next, an aluminum laminate PET tape was wound on a twisted wire formed by twisting 4 of the insulated wires by an overlap amount of 1/4 of the film width. Next, a copper braid is sleeved. Next, the polyimide tape was wound transversely in an overlap amount of 1/4 of the film width to form an intermediate layer. Next, the material of the sheath was coated with a thickness of 1.1mm, and irradiation crosslinking was performed with an irradiation dose of 13MRad, to produce a LAN cable.

Example 2

In example 2, a LAN cable was produced in the same manner as in example 1, except that the foaming degree of the insulator was 15 mass% and the dielectric constant of the insulator was 2.1.

Example 3

In example 3, a LAN cable was produced in the same manner as in example 1, except that the foaming degree of the insulator was 15 mass%, the dielectric constant of the insulator was 1.9, and the irradiation amount of the sheath was 10 Mrad.

Example 4

In example 4, a LAN cable was produced in the same manner as in example 1, except that two polyimide films were used.

Example 5

In example 5, a LAN cable was produced in the same manner as in example 1, except that the foaming degree of the insulator was 15 mass%, the dielectric constant of the insulator was 2.1, the blending amounts of magnesium hydroxide (one) and magnesium hydroxide (two) were 60 mass parts and 90 mass parts, respectively, and the mass reduction rate of the sheath was 58 mass%.

Example 6

In example 6, a LAN cable was produced in the same manner as in example 1, except that the foaming degree of the insulator was 15 mass%, the dielectric constant of the insulator was 2.1, the blending amounts of magnesium hydroxide (one) and magnesium hydroxide (two) were 80 mass parts and 120 mass parts, respectively, and the mass reduction rate of the sheath was 54 mass%.

Example 7

In example 7, a LAN cable was produced in the same manner as in example 1, except that the foaming degree of the insulator was 15 mass%, the dielectric constant of the insulator was 2.1, the blending amounts of magnesium hydroxide (one) and magnesium hydroxide (two) were 90 mass parts and 130 mass parts, respectively, and the mass reduction rate of the sheath was 52 mass%.

Example 8

In example 8, a LAN cable was produced in the same manner as in example 1, except that 60 parts by mass of EVA having a VA content of 17% and an MFR of 0.8 was used instead of EVA having a VA content of 28% and an MFR of 6.0.

Example 9

A LAN cable was produced in the same manner as in example 1, except that in example 9, 10 parts by mass of EVA having a VA content of 28% and an MFR of 6.0 and 60 parts by mass of EVA having a VA content of 33% and an MFR of 1.0 were used.

Example 10

In example 10, a LAN cable was produced in the same manner as in example 1, except that 10 parts by mass of LDPE was used instead of 33 parts by mass of EVA having a VA content and an MFR of 1.0.

Comparative example 1

A LAN cable was produced in the same manner as in example 1, except that a polyimide film was not used in comparative example 1.

Comparative example 2

A LAN cable was produced in the same manner as in example 1, except that a PET film was used instead of the polyimide film in comparative example 2.

Comparative example 3

In comparative example 3, a LAN cable was produced in the same manner as in example 1, except that the sheath was not crosslinked.

Comparative example 4

In comparative example 4, a LAN cable was produced in the same manner as in example 1, except that the blending amounts of magnesium hydroxide (i) and magnesium hydroxide (ii) were 40 parts by mass and 80 parts by mass, respectively, and the mass reduction rate of the sheath was 62% by mass.

Table 1 (amount of the additive is in parts by mass)

Table 2 (amount of the additive is in parts by mass)

Table 3 (amount of the additive is in parts by mass)

The polyimide films in tables 1 to 3 were Kapton 200H (Toli-Du Bangzhi). The maleic acid-modified polyolefin A in tables 1 to 3 was TAFUMA MH7020 (Sanjing chemical Co., ltd.). Magnesium hydroxide (one) in tables 1 to 3 is Magnifin H10A (manufactured by yabao). Magnesium hydroxide (II) in tables 1 to 3 is Magnifin H10C (manufactured by Yabao). The mass reduction rate of the polyimide films shown in tables 1 to 3 was 24 mass% at 600℃and 65 mass% at 800 ℃. The mass reduction rate of the PET film shown in Table 3 was 100% by mass at 600℃and 100% by mass at 800 ℃.

(1) Sheath property test

The following tests were performed for examples and comparative examples. The test results are shown in tables 1 to 3.

(1-1) tensile test of sheath

Only the sheath was removed from the LAN cable, and a No. 6 dumbbell test piece was punched. Next, using the test piece, a tensile test was performed under the condition of a tensile speed of 200mm/min in accordance with JIS C3005. Regarding the elongation, the elongation was set to be x (failure) when the elongation was less than 125%, and to be o (failure) when the elongation was 125% or more.

The tensile strength was set to be x (failed) when the tensile strength was less than 10MPa, and to be o (qualified and having a margin) when the tensile strength was 10MPa or more.

(1-2) Low temperature test of sheath

The test piece was set as in the case of the tensile test. Using the test piece, a tensile test was performed at a tensile speed of 25mm/min at-55℃in accordance with EN 60811-1-4. When the elongation characteristic is 30% or more, the test is "good" and when it is less than 30%, the test is "bad".

(2) Test of LAN Cable characteristics

For the examples and comparative examples, the following tests were performed. The test results are shown in tables 1 to 3.

(2-1) Low temperature test of LAN Cable

The bending test was carried out at-55℃on LAN cables according to EN 60811-1-4.8.1. When no crack occurred after winding, the test was set to be "good" and when a crack occurred, the test was set to be "bad".

(2-2) flame retardancy test of LAN cable

The VTFT test is performed in accordance with IEEE standard 1202. The damage distance of the LAN cable is equal to or less than 1.5m and greater than 1.0m, and is equal to or less than 1.0m, and is equal to or greater than 1.5 m.

(2-3) Transmission characteristics test of LAN Cable

The electrostatic capacity was measured in accordance with JIS X5150 and TIA-568-C, 2. The electrostatic capacity was set to be "good" when it was 5.6nF/100m or less, and set to be "bad" when it was more than 5.6nF/100 m.

Evaluation results

As shown in tables 1 and 2, the evaluation results of examples 1 to 10 were good in any test item. In particular, in example 4, the number of polyimide films was 2, and thus the flame retardancy was further improved.

In comparative example 1, the flame retardancy was tested as x. This is thought to be because the intermediate layer 7 is not provided.

In comparative example 2, the flame retardancy was tested as x. This is considered to be because the mass reduction rate of the PET film used for forming the intermediate layer 7 is larger than the predetermined range of the present invention.

In comparative example 3, the flame retardancy was tested as x. The reason for this is believed to be due to the fact that the sheath is not crosslinked.

In comparative example 4, the flame retardancy was tested as a result of X. This is considered to be because the mass reduction rate of the sheath is 62 mass% and is larger than the range defined in the present invention.

The embodiments of the present disclosure have been described above, but the present disclosure is not limited to the above embodiments and may be implemented with various modifications.

(1) The LAN cable may have a 2-core insulator structure or other structure, for example.

(2) The functions of 1 component in each of the above embodiments may be shared by a plurality of components, or the functions of a plurality of components may be exhibited by one component. In addition, a part of the constitution of each of the above embodiments may be omitted. At least a part of the constitution of each of the above embodiments may be added or replaced with the constitution of another of the above embodiments. All aspects encompassed by the technical idea that can be specified from the statements recited in the claims are embodiments of the present disclosure.

(3) The present invention can be realized by various means such as a method for manufacturing the LAN cable, in addition to the LAN cable described above.

Claims

1. A LAN cable is provided with:

insulated wire having insulating layer on outer periphery of conductor, and method for manufacturing same

A sheath covering the outer circumferences of the plurality of insulated wires,

an intermediate layer is provided between the sheath and the plurality of insulated wires at a position immediately below the sheath, the intermediate layer having a mass reduction rate of 80 mass% or less at 800 ℃, the intermediate layer being a polyimide film,

a metal layer is positioned between the plurality of insulated wires and the intermediate layer,

the sheath is formed of a crosslinked product which is a halogen-free flame-retardant resin composition, the mass reduction rate of the halogen-free flame-retardant resin composition at 800 ℃ is 60 mass% or less,

the electrostatic capacity obtained according to JIS-X5150 and TIA-568-C,2 is 5.6nF/100m or less,

the insulating layer is free of flame retardant, and the LAN cable has the following properties: when the VTFT test is performed according to IEEE standard 1202, the damage distance of the LAN cable is 1.5m or less.

2. The LAN cable of claim 1, said metal layer comprising a copper braid.

3. The LAN cable according to claim 1 or 2, wherein the sheath contains 150 parts by mass or more of the flame retardant per 100 parts by mass of the polyolefin-based polymer.

4. A LAN cable according to claim 3, wherein said flame retardant comprises magnesium hydroxide.