JP2005322474A - Cross-linked damage-resistant flame-retardant insulated wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flame-resistant flame-retardant insulated electric wire that is non-halogen, highly flame-retardant, and excellent in scratch resistance.
SOLUTION: Hydroxylation surface-treated with a silane coupling agent with respect to 100 parts by mass of a base resin composed of 45 to 55 parts by mass of EVA, 35 to 45 parts by mass of AEM and 5 to 10 parts by mass of a styrene / ethylene / butylene copolymer elastomer. The flame retardant resin composition to which 250 to 300 parts by mass of magnesium is added is used as an inner layer, and 60 to 80 parts by mass of EVA, 15 to 25 parts by mass of styrene / ethylene / ethylene propylene / styrene copolymer, 5 to 10 parts by mass of AEM, and maleic acid A trauma-resistant resin composition in which 60 to 100 parts by mass of a flame retardant comprising 50 to 100 parts by mass of magnesium hydroxide and 10 to 30 parts by mass of melamine cyanurate is blended with 100 parts by mass of a base resin consisting of 5 to 10 parts by mass of modified LLDPE. The object is provided as an outer layer with a thickness of 100 μm or less, and electron beam irradiation crosslinking By Rukoto, it is resolved.
[Selection figure] None

Description

  The present invention relates to a cross-linked flame-retardant insulated wire that has excellent trauma resistance and is cross-linked by electron beam irradiation.

  In recent years, coating materials for flame-retardant insulated wires have been switched to so-called halogen-free coating materials that do not generate halogen gas during combustion in place of conventional PVC and halogen-based flame retardants due to environmental problems. ing. As such a halogen-free coating material, a polyolefin-based homopolymer, an ethylene-based copolymer, ethylene / acrylic rubber or the like is used as a base resin component, and magnesium hydroxide, aluminum hydroxide, hydrated aluminum silicate, etc. A compound containing a metal hydrate flame retardant is known. However, since the resin component such as the polyolefin polymer has essentially no flame retardancy, a large amount of a metal hydrate flame retardant is blended when trying to make it highly flame retardant. As a result, there is a problem in that the flexibility and mechanical properties of the coating material are lowered, or the coating material becomes brittle and is easily damaged by the friction between the wires and the contact with a hard container.

  In order to improve the above-mentioned problems, it is intended to improve flame retardancy, mechanical properties, and electrical insulation properties by using a resin composition containing a polyolefin resin and a metal hydrate surface-treated with a fatty acid and a silane coupling agent. A proposal is described in Patent Document 1. In addition, an ethylene copolymer such as an ethylene / vinyl acetate copolymer, an ethylene / vinyl acetate copolymer suspended at least partially, and an unsaturated carboxylic acid-modified polyolefin resin are used as a base resin, and a crosslinkable silane is used as the base resin. Patent Document 2 describes a proposal to improve the flame retardancy and mechanical properties of an insulated wire by blending and coating a metal hydrate surface-treated with a coupling agent and a melamine cyanurate compound. . Furthermore, as a resin composition, a proposal is made to improve mechanical properties by mixing styrene elastomer or acrylic rubber with ethylene copolymer, and to improve flame retardancy with metal hydrate and melamine cyanurate compound. Is described in Patent Document 3.

The coating composition and insulated wire described in the above patent document have flame retardancy conforming to the VW-1 standard of the vertical combustion test of UL standard 1581, and have mechanical properties such as elongation at break and tensile strength at break. It is said that it can be satisfied. However, each of the coating composition and the insulated wire described here is obtained by blending 100 to 250 parts by mass or 150 to 280 parts by mass of a metal hydrate flame retardant with respect to 100 parts by mass of the base resin. Although a large amount of such a metal hydrate flame retardant is effective for improving flame retardancy, it causes a decrease in flexibility and an increase in brittleness. There is a problem that the coating layer is liable to be damaged by contact with a hard container or the like, which is inferior in so-called trauma resistance.
JP 2000-195336 A JP 2000-294036 A JP 2001-60414 A

  Therefore, the problem to be solved by the present invention is excellent in resistance to trauma, which can prevent scratches caused by rubbing and abrasion between wires, contact with hard objects, etc., and whitening due to scratches, especially during processing or wiring. A thin outer layer on an inner layer made of a non-halogen coated flame retardant resin composition having excellent flame resistance and mechanical properties. It is intended to provide a cross-linked trauma-resistant flame-retardant insulated wire that is non-halogen and excellent in high flame retardancy and trauma resistance.

  The problem to be solved, as described in claim 1, is 45 to 55 parts by mass of an ethylene / vinyl acetate copolymer, 35 to 45 parts by mass of an ethylene / acrylic rubber, and a styrene / ethylene / butylene copolymer elastomer. A flame-retardant resin composition in which 250 to 300 parts by mass of magnesium hydroxide surface-treated with a silane coupling agent is added to 100 parts by mass of a base resin consisting of 5 to 10 parts by mass is coated on the conductor as an inner layer. 60-80 parts by mass of ethylene / vinyl acetate copolymer, 15-25 parts by mass of styrene / ethylene / ethylene propylene / styrene copolymer, 5-10 parts by mass of ethylene / acrylic rubber, and maleic acid-modified linear low density Magnesium hydroxide 50-100 quality with respect to 100 parts by mass of base resin consisting of 5-10 parts by mass of polyethylene And a flame retardant composed of 10 to 30 parts by weight of a melamine cyanurate is provided as an outer layer having a thickness of 100 μm or less, and is crosslinked by electron beam irradiation. It is solved by using a traumatic flame-retardant insulated wire.

  As described above, the base resin is composed of 45 to 55 parts by mass of ethylene / vinyl acetate copolymer, 35 to 45 parts by mass of ethylene / acrylic rubber and 5 to 10 parts by mass of styrene / ethylene / butylene copolymer elastomer. On the other hand, a coating layer of a flame retardant resin composition that is non-halogen, highly flame retardant and excellent in mechanical properties, containing 250 to 300 parts by mass of magnesium hydroxide surface-treated with a silane coupling agent is formed on the conductor. Further, 60-80 parts by mass of ethylene / vinyl acetate copolymer, 15-25 parts by mass of styrene / ethylene / ethylenepropylene / styrene copolymer, 5-10 parts by mass of ethylene / acrylic rubber, and maleic acid-modified Magnesium hydroxide 50-10 with respect to 100 parts by mass of the base resin composed of 5-10 parts by mass of the chain low density polyethylene. Cross-linked cross-linked damage resistant by providing a thin layer of a flame-retardant resin composition having excellent trauma resistance, which is formed by blending 60 to 100 parts by mass of a flame retardant comprising 10 parts by mass and 10 to 30 parts by mass of melamine cyanurate Because it is a flammable insulated wire, it has a scratch resistance that does not cause scratches due to friction between the wires or contact with hard objects, or whitening caused by it, and is non-halogenous. In addition to having a high degree of flame retardancy that passes one test, it has an inner layer that is also excellent in mechanical properties such as tensile strength at break and elongation at break. Furthermore, chemical resistance, heat resistance, and the like are improved by crosslinking by electron beam irradiation, so that a crosslinked trauma-resistant flame-retardant insulated electric wire that is preferable for use in wiring of electronic devices and the like can be obtained.

  The present invention is described in detail below. The present invention according to claim 1 is a base comprising 45 to 55 parts by mass of an ethylene / vinyl acetate copolymer, 35 to 45 parts by mass of an ethylene / acrylic rubber and 5 to 10 parts by mass of a styrene / ethylene / butylene copolymer elastomer. A flame retardant resin composition in which 250 to 300 parts by mass of magnesium hydroxide surface-treated with a silane coupling agent is added to 100 parts by mass of the resin is coated on the conductor as an inner layer, on which ethylene / vinyl acetate is coated. 60-80 parts by mass of a blend, 15-25 parts by mass of styrene / ethylene / ethylene propylene / styrene copolymer, 5-10 parts by mass of ethylene / acrylic rubber, and 5-10 parts by mass of maleic acid-modified linear low density polyethylene Magnesium hydroxide 50-100 parts by mass and melamine cyanurate with respect to 100 parts by mass of the base resin A trauma-resistant resin composition obtained by blending 60 to 100 parts by mass of a flame retardant consisting of 0 to 30 parts by mass is provided as an outer layer with a thickness of 100 μm or less, and is cross-linked trauma-resistant flame retardant obtained by electron beam irradiation crosslinking. It is an insulated wire.

  First, the flame retardant resin composition coated on the conductor as the inner layer of the cross-linked damage resistant flame retardant insulated wire will be described. This flame retardant resin composition comprises 45 to 55 parts by mass of an ethylene / vinyl acetate copolymer (hereinafter EVA), 35 to 45 parts by mass of ethylene / acrylic rubber (hereinafter AEM) and a styrene / ethylene / butylene copolymer elastomer 5. It is a flame retardant resin composition in which 250 to 300 parts by mass of magnesium hydroxide surface-treated with a silane coupling agent is added to 100 parts by mass of a base resin consisting of 10 parts by mass to 10 parts by mass.

  The EVA used as one of the base resins preferably has a high vinyl acetate content from the viewpoint of flame retardancy, but is appropriately selected from the balance with mechanical properties. As an example, EVA having a vinyl acetate content of 22 to 47% by mass, preferably 25 to 42% by mass and an MFR (melt flow rate) of 0.1 to 20 g / 10 min, preferably 0.1 to 3. Examples of such EVA include trade name EV180 manufactured by Mitsui DuPont Polychemical Co., Ltd. And EVA is mix | blended in 45-55 mass parts in base resin. If the blending amount is less than 45 parts by mass, the mechanical strength is insufficient, and if it exceeds 55 parts by mass, the flame retardancy is insufficient, which is not preferable.

  The amount of AEM used as the base resin is 35 to 45 parts by mass. If the amount is less than 35 parts by mass, the flame retardancy is insufficient, and if it exceeds 45 parts by mass, the mechanical strength is insufficient. . Furthermore, the blending amount of the styrene / ethylene / butylene copolymer elastomer used as the base resin is 5 to 10 parts by mass. If the blending amount is less than 5 parts by mass, the mechanical strength is insufficient. Is not preferable because of lack of. Such a styrene / ethylene / butylene copolymer elastomer preferably has a styrene content of 15 to 35% by mass. As a specific example, there is a trade name Dynalon 4630P manufactured by Nippon Synthetic Rubber.

  And in order to improve flame retardancy in the aforementioned base resin, it is excellent in flame retardancy by blending 250 to 300 parts by mass of magnesium hydroxide surface-treated with a silane coupling agent with respect to 100 parts by mass of the base resin. It can be set as the flame retardant resin composition for the inner layer of the bridge | crosslinking flame-resistant flame-retardant insulated wire. Examples of magnesium hydroxide include natural magnesium hydroxide and synthetic magnesium hydroxide. Among these, synthetic magnesium hydroxide is preferably used. The particle diameter is not particularly limited, but the particle diameter is preferably 5 μm or less and the average particle diameter is 0.7 to 4 μm from the viewpoint of dispersibility with respect to the resin. Further, as silane coupling agents, vinyltrimethoxysilane, vinyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxy Propyltriethoxysilane, N-2 (aminoethyl) 3-aminopropylmethyldimethoxysilane, N-2 (aminoethyl) 3-aminopropyltrimethoxysilane, N-2 (aminoethyl) 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane or the like can be used, but the surface treatment of magnesium hydroxide particularly added to the flame retardant resin composition is made of vinyltrimethoxysilane, vinyltriethoxysilane, or methacrylic silane. Functional group is preferably used a silane coupling agent vinyl groups. As the surface treatment method, it can be carried out by mixing or kneading magnesium hydroxide and a silane coupling agent. Moreover, it is preferable to use the said silane coupling agent in 0.1-5 mass% with respect to magnesium hydroxide. Such surface-treated magnesium hydroxide not only improves the dispersibility in the base resin and improves mechanical properties, but can further enhance flame retardancy.

  Such a flame-retardant resin composition is dry-blended with a predetermined amount of each constituent component, melt-kneaded with a commonly used kneader such as a twin-screw kneading extruder, a Banbury mixer, a kneader, or a roll, and then usually used. The inner layer of the insulated wire is formed by extrusion coating on the conductor using an extruder. In addition, the flame retardant resin composition may contain, for example, an ultraviolet absorber, an antioxidant, an anti-aging agent, a copper damage inhibitor, a pigment, a lubricant, a compatibilizing agent, and the like, if necessary. If necessary, other flame retardant aids (red phosphorus, polyphosphoric acid compound, zinc hydroxytinate, etc.) may be used in combination. And on the inner layer, the following trauma-resistant resin composition is provided as an outer layer with a thickness of 100 μm or less, cross-linked trauma-resistant flame-retardant insulated wire for electronic devices and the like subjected to electron beam irradiation cross-linking and Become.

  Next, the trauma resistant resin composition for forming the outer layer coated on the inner layer of the crosslinked trauma resistant flame retardant insulated wire will be described. This trauma resistant resin composition is composed of a base resin having excellent trauma resistance and a flame retardant. EVA used as one of the base resins preferably has a high vinyl acetate content from the viewpoint of flame retardancy, but is appropriately selected from the balance with mechanical properties. As an example, EVA having a vinyl acetate content of 22 to 47% by mass, preferably 25 to 42% by mass and an MFR (melt flow rate) of 0.1 to 20 g / min, preferably 0.1 to 3 is used. Examples of such EVA include trade name EV180 manufactured by Mitsui DuPont Polychemical Co., Ltd. And EVA is blended in the range of 60 to 80 parts by mass in the base resin. If the blending amount is less than 60 parts by mass, the mechanical strength is insufficient, and if it exceeds 80 parts by mass, the flame retardancy is insufficient. Since the flexibility is also lowered, the above range is set.

  The styrene / ethylene / ethylene propylene / styrene copolymer (hereinafter referred to as SEEPS) used as one of the base resins preferably has a styrene content of 20% by mass or more. A specific example of such SEEPS is Kuraray's trade name Septon 4033. And the compounding quantity of SEEPS shall be 15-25 mass parts in base resin. If the blending amount is less than 15 parts by mass, the mechanical strength is insufficient, and if it exceeds 25 parts by mass, the flame retardancy is insufficient.

  Further, AEM used as a base resin is a block polymer composed of an ethylene polymer block and a methyl acrylate polymer block, and examples thereof include trade name VAMAC DP manufactured by Mitsui DuPont Polychemical Co., Ltd. And the compounding quantity of AEM shall be 5-10 mass parts in base resin. When the blending amount is less than 5 parts by mass, the flame retardancy is insufficient and the flexibility is lowered. On the other hand, if the amount exceeds 10 parts by mass, the mechanical strength is insufficient, so the above range is adopted.

One of the base resins, maleic acid-modified linear low-density polyethylene (hereinafter maleic acid-modified LLDPE) has a density such as linear low-density polyethylene (LLDPE) and linear ultra-low-density polyethylene (LVLDPE). Polyethylene of 0.93 g / cm ³ or less is modified with maleic acid, maleic anhydride, or the like, and among them, LLDPE is preferably modified with maleic acid. An example of a method for producing such maleic acid-modified LLDPE is a method of melt kneading polyethylene and maleic acid in the presence of an organic peroxide. The maleic acid concentration at the time of modification is usually about 0.5 to 10% by mass. And the compounding quantity of maleic acid modification | denaturation LLDPE is the range of 5-10 mass parts in 100 mass parts of base resins, and if the compounding quantity is less than 5 mass parts, the improvement effect of the dispersibility in the base resin of magnesium hydroxide is effective. It cannot be expected to improve the mechanical properties. On the other hand, if it exceeds 10 parts by mass, the elongation at break will be insufficient, the flexibility will be lowered, the adhesiveness with the conductor will be too strong, and the lead-out property such as the connecting work of the insulated wire will be deteriorated.

  In order to improve the flame retardancy of the above base resin, 60-100 mass parts of a flame retardant in a ratio range of magnesium hydroxide 50-100 mass parts and melamine cyanurate 10-30 mass parts with respect to 100 mass parts of the base resin. Partly blended to make a flame resistant resin composition with improved flame retardancy. Magnesium hydroxide is natural magnesium hydroxide, synthetic magnesium hydroxide or the like, and among them, it is preferable to use synthetic magnesium hydroxide from the uniformity of particles. The particle diameter is not particularly limited, but the maximum particle diameter is preferably 5 μm or less and the average particle diameter is preferably 0.7 to 4 μm from the viewpoint of dispersibility with respect to the resin. And if the compounding quantity of magnesium hydroxide is less than 50 mass parts, a flame retardance is not enough, and when it exceeds 100 mass parts, a trauma-resistant resin composition will become hard too much and the trauma resistance as an outer layer will be reduced. It becomes like this. Moreover, the melamine cyanurate used together with magnesium hydroxide is mix | blended in the range of 10-30 mass parts. If the blending amount is less than 10 parts by mass, a flame retardant effect cannot be expected. Thus, by using together magnesium hydroxide and melamine cyanurate, compared with the case where magnesium hydroxide is mix | blended independently, the higher flame retarding effect is acquired by the mixing | blending of the same number of parts. Moreover, both are mix | blended so that it may become 60-100 mass parts with respect to 100 mass parts of base resins in each compounding quantity range. The reason why such a blending amount is used is that when the amount is less than 60 parts by mass, the trauma resistance is good but the flame retardancy is inferior, and when it exceeds 100 parts by mass, the trauma resistance is inferior. . In addition, it is preferable to surface-treat this magnesium hydroxide with a silane coupling agent similarly to the magnesium hydroxide added to the flame-retardant resin composition for inner layers. That is, the dispersibility in the trauma resistant resin composition is improved, and the extrudability during coating as the outer layer can be improved.

  The above-mentioned trauma-resistant resin composition is obtained by dry blending a predetermined amount of each base resin and flame retardant, and melt-kneading with a commonly used kneader such as a twin-screw kneading extruder, a Banbury mixer, a kneader, or a roll. can get. The trauma resistant resin composition may contain other additives such as UV absorbers, antioxidants, antioxidants, copper damage inhibitors, pigments, lubricants, compatibilizers, etc. as necessary. As long as the object of the invention is not impaired, it may be blended as appropriate, and in some cases, other flame retardant aids (red phosphorus, polyphosphate compound, zinc hydroxytinate, etc.) may be used in combination.

  The trauma resistant resin composition is provided as an outer layer having a thickness of 100 μm or less on an inner layer made of the flame retardant resin composition provided on a conductor. That is, it is formed by extrusion coating in tandem on the inner layer or by co-extrusion with the inner layer. In addition, the thickness of the outer layer is set to 100 μm or less when the cable is formed with a coating layer made of only the scratch-resistant resin composition, for example, flame retardance that passes the VW-1 test of UL standard 1581 cannot be obtained. However, when the coating thickness of the flame retardant resin composition on the conductor is 250 μm or more, the UL test can be passed by setting the thickness of the trauma resistant resin composition to 100 μm or less. . The trauma-resistant flame-retardant insulated wire is then subjected to crosslinking. Crosslinking is preferably performed by irradiation with an electron beam, since the mechanical properties are greatly improved as compared with other crosslinking methods, and heat resistance and damage resistance can be improved. And the irradiation amount in that case is performed by about 1-30 Mrad. The cross-linked trauma-resistant flame-retardant insulated electric wire having such a configuration functions integrally with high flame retardance and mechanical properties due to the inner layer and excellent trauma resistance due to the outer layer. It becomes useful as a traumatic flame-retardant insulated wire.

  The effects of the present invention will be described below with reference to examples and comparative examples. Each component shown in Table 1 and Table 2 is blended and melt-kneaded at 160 to 190 ° C. using a Banbury mixer to produce a flame retardant resin composition for the inner layer and a trauma resistant resin composition for the outer layer, respectively. did. Next, a 0.36 mm-thick coating layer made of the flame retardant resin composition is formed on a 0.48 mmφ copper conductor, and a 50 μm-thick coating layer is formed on the outer periphery of the coating layer. Then, it was crosslinked by electron beam irradiation of 3 Mrad to produce a crosslinked trauma-resistant flame-retardant insulated wire.

  In addition, the compounding component used for preparation of each of the above cross-linked damage resistant flame retardant insulated wires is a flame retardant resin composition for an inner layer. (1) EVA is a product name EV180 manufactured by Mitsui DuPont Chemical Co., Ltd. (2) AEM is a product name VAMAC DP manufactured by Mitsui DuPont Chemical Co., Ltd. (3) A styrene / ethylene / butylene copolymer elastomer is a product name Dynalon 4630P manufactured by Nippon Synthetic Rubber Co., Ltd. (4) Silane cup As the magnesium hydroxide surface-treated with a ring agent, trade names Kisma 5P and Kisma 5L manufactured by Kyowa Chemical Co., Ltd. were used. However, in the comparative example, the trade name Kisuma 5P was used. In addition, in the outer layer-resistant trauma-resistant resin composition, EVA and AEM are the same as those for the inner layer, (5) SEEPS is a product name Septon 4033 manufactured by Kuraray, and (6) acid-modified LLDPE is Japan. (7) Magnesium hydroxide is treated with silane coupling agent, Kyowa Chemical Co., Ltd. product name Kisuma 5P, (8) Melamine Cyanurate is a product name manufactured by Nissan Chemical Co., Ltd. MC-860 was used, respectively, and (9) the antioxidant used for the inner layer and outer layer was trade name Irganox 1010 manufactured by Ciba Specialty Chemicals.

  About the said bridge | crosslinking damage-resistant flame-retardant insulated electric wire, the tensile breaking strength and breaking elongation were measured by UL specification 1581, tensile breaking strength was described above as 10.3 Mpa, breaking elongation as 150% or more as a pass. Further, regarding the scratch resistance, a scratch test was conducted with a diamond finger of R = 0.5 and a load of 100 g, and the presence or absence of whitening of the coating layer was determined. Further, as flame retardancy, the VW-1 test of the vertical combustion test of UL standard 1581 was conducted, and the test that passed this test was regarded as acceptable. The results of the examples are shown in Table 1, and the results of the comparative examples are shown in Table 2.

  As is clear from Table 1, the crosslinked trauma-resistant flame-retardant insulated wires described in Examples 1 to 14 were prepared using the flame-retardant resin composition and the trauma-resistant resin composition that met the requirements of the present invention. Therefore, no whitening due to scratches or scratches was observed in the trauma resistance, and all the tensile strength at break and elongation at break passed. In particular, it is a non-halogen, highly flame-retardant flame retardant resin composition formed as an inner layer, and thus exhibits excellent flame retardancy conforming to the VW-1 standard defined in the UL standard 1581, and is used in various applications. It is useful as a crosslinkable insulated wire.

  On the other hand, the crosslinked trauma-resistant flame-retardant insulated wire outside the scope of the present invention in Comparative Examples 1 to 8 shown in Table 2 fails in any of tensile rupture strength, rupture elongation, trauma resistance and flame retardancy. It has become. That is, in Comparative Example 1, the amount of Kisuma 5P added was not more than the lower limit of the present invention, so the flame retardancy was rejected. Moreover, since the EVA of an inner layer is more than the upper limit of this invention, and AEM is below a lower limit, the comparative example 4 is unsatisfactory in flame retardance. Furthermore, since the addition amount of Kisuma 5P exceeds 300 mass parts which is the upper limit of this invention, the comparative example 2 has failed fracture elongation. In Comparative Example 3, the tensile strength at break was rejected because EVA of the outer layer was not more than the lower limit of the present invention. In Comparative Example 5, since the blending amount of the styrene / ethylene / butylene copolymer elastomer exceeded the upper limit of the present invention, the elongation at break failed. In Comparative Example 6, EVA and AEM of the inner layer were not less than the upper limit values of the present invention, and no styrene / ethylene / butylene copolymer elastomer was added, so the tensile strength at break was unacceptable. Further, in Comparative Examples 7 and 8, since the blending amount of SEEPS is 10 parts by mass or less than the lower limit of the present invention, and the AEM amount of the outer layer exceeds 20 parts by mass and the upper limit of the present invention, whitening occurs. The trauma resistance was rejected.

  The crosslinked trauma-resistant flame-retardant insulated wire of the present invention is excellent in non-halogen flame retardancy and trauma resistance, and is particularly useful as wiring for electronic equipment and the like.

Claims (1)

  Silane coupling to 45 to 55 parts by mass of ethylene / vinyl acetate copolymer, 35 to 45 parts by mass of ethylene / acrylic rubber and 5 to 10 parts by mass of styrene / ethylene / butylene copolymer elastomer. A flame retardant resin composition to which 250 to 300 parts by mass of magnesium hydroxide surface-treated with an agent is added is coated on the conductor as an inner layer, on which 60 to 80 parts by mass of ethylene / vinyl acetate copolymer, styrene / ethylene Hydroxylation with respect to 100 parts by mass of base resin consisting of 15 to 25 parts by mass of ethylene propylene / styrene copolymer, 5 to 10 parts by mass of ethylene / acrylic rubber and 5 to 10 parts by mass of maleic acid-modified linear low density polyethylene Difficulty consisting of 50-100 parts by weight of magnesium and 10-30 parts by weight of melamine cyanurate External damage resin composition is provided as an outer layer with a thickness of 100 [mu] m, crosslinking external damage flame retardant insulated wire, characterized in that the electron beam irradiation crosslinking formed by 60 to 100 parts by mass of the agent.