JP6152802B2 - Radiation-resistant halogen-free resin composition and electric wire / cable using the same - Google Patents

Description

  The present invention relates to a radiation-resistant halogen-free resin composition that can be used in a radiation environment, particularly in a nuclear power plant, and an electric wire / cable using the same.

  In nuclear power plants, fast breeder reactors, nuclear fuel reprocessing facilities, particle accelerator facilities, etc., radiation such as γ rays exists in the usage environment. For this reason, electric wires and cables used for power supply and signal transmission to each facility / equipment are required to withstand deterioration due to radiation.

  In particular, electric wires and cables used in nuclear power plants are used for heat, radiation and hot water or superheated steam that are expected in the event of a loss of coolant accident (hereinafter referred to as LOCA), in addition to heat and radiation generated during steady operation. Even when exposed, it must be possible to maintain the specified electrical insulation for a certain period of time. Furthermore, in the unlikely event of a fire, a high level of flame retardancy simulating a cable fire laid on a vertical tray is required.

  On the other hand, halogen-free wires and cables that do not contain halogen elements such as chlorine and do not generate harmful gases during combustion are desired from the viewpoint of safety and environmental considerations in the event of fire. . In response to this demand, in recent years, electric wires and cables such as those defined in JISC3605 and JISC3401 that use “eco-material” as a covering material for building equipment cables have become widespread.

  Eco-materials include ethylene-ethyl acrylate (EEA), ethylene-vinyl acetate copolymer (EVA), ethylene-α olefin copolymer, etc., soft ethylene polymer, metal hydroxide such as magnesium hydroxide and aluminum hydroxide. It is a general term for halogen-free flame retardant resin compositions formed by mixing physical flame retardants.

  However, resin compositions used for electric wires and cables using ecomaterials undergo main chain scission and cross-linking due to oxidative degradation due to irradiation, and mechanical properties such as elongation and tensile strength are significantly reduced. In addition, the coating material is cracked due to oxidative deterioration, and electrical insulation cannot be maintained.

  For example, Patent Document 1 contains a metal hydrate and a melamine / cyanurate compound in a specific mass ratio with respect to a resin component such as ethylene / propylene rubber, and 50% by mass or more of the metal hydrate is a silane coupling agent. An insulating resin composition having a specific physical property value and flame retardancy is disclosed.

  Patent Document 2 discloses a radiation-resistant composition comprising an ethylene / propylene / diene rubber having an iodine value of 1 to 10 and a process oil (naphthene or aromatic).

  Patent Document 3 describes a radiation-resistant resin composition obtained by adding a salicylate-based, benzotriazole-based, and triazine-based ultraviolet absorber to a polyolefin-based resin.

JP 2002-42552 A JP-A-4-268350 JP 2009-84571 A

  However, Patent Document 1 does not describe radiation resistance, and when the resin composition is used in a radiation environment, it is difficult to maintain electrical insulation particularly when LOCA occurs.

  In addition, the radiation resistance of the invention described in Patent Document 2 is only 0.8 to 1 MGy class, and in recent years, a higher level of radiation resistance is required.

  Although the radiation resistance of the invention described in Patent Document 3 has 2.5 MGy class radiation resistance, exposure to hot water and superheated steam at the time of occurrence of LOCA is not assumed, and electrical insulation should be provided in the event of an accident. May not be retained.

  Accordingly, an object of the present invention is to provide a halogen-free resin composition having high radiation resistance capable of maintaining electrical insulation even when exposed to hot water or superheated steam when LOCA occurs, and an electric wire / cable using the same. It is to be.

  In order to achieve the above object, according to the present invention, the following radiation-resistant halogen-free resin composition and an electric wire / cable using the same are provided.

[1] 3 to 10 parts by weight of an aromatic amine-based antioxidant, 5 to 20 parts by weight of an aromatic process oil, and 10 to 30 melamine / cyanurate compounds with respect to 100 parts by weight of a base polymer mainly composed of an ethylene polymer. The ethylene-based polymer contains ethylene-propylene-diene copolymer and ethylene-α-olefin copolymer, or ethylene-vinyl acetate copolymer and ethylene-. A radiation-resistant halogen-free resin composition comprising any one of α-olefin copolymers and an ethylene polymer modified with a polar functional group.
[2] The radiation-resistant halogen-free resin composition according to [1], wherein the polar functional group is an epoxy group, a carboxyl group, or a maleic anhydride group.
[3] The radiation-resistant halogen-free resin composition according to [1] or [2], wherein the ethylene polymer modified with the polar functional group is an ethylene-α-olefin copolymer. .
[4] An electric wire characterized by using the radiation-resistant halogen-free resin composition according to any one of [1] to [3] as a coating material.
[5] A cable using the radiation-resistant halogen-free resin composition according to any one of [1] to [3] as a coating material.

  ADVANTAGE OF THE INVENTION According to this invention, the halogen-free resin composition which has high radiation resistance which can hold | maintain an electrical insulation even if it exposes to the hot water or superheated steam at the time of LOCA generation, and an electric wire and a cable using the same are provided. .

It is a cross-sectional view of the electric wire which concerns on embodiment of this invention. It is a cross-sectional view of a cable according to an embodiment of the present invention. It is a figure which shows the conditions (temporal change of temperature and pressure) in a radiation resistance test (high pressure steam exposure test).

[Radiation-resistant halogen-free resin composition]
The radiation-resistant halogen-free resin composition according to the embodiment of the present invention includes 3 to 10 parts by weight of an aromatic amine antioxidant, 100 parts by weight of an aromatic process, and 100 parts by weight of an aromatic process. 5 to 20 parts by weight of oil, 10 to 30 parts by weight of a melamine / cyanurate compound, and 100 to 200 parts by weight of metal hydrate, and the ethylene polymer comprises an ethylene-propylene-diene copolymer and an ethylene-α-olefin copolymer. Either a polymer or an ethylene-vinyl acetate copolymer and an ethylene-α olefin copolymer, and an ethylene polymer modified with a polar functional group are included.

(Base polymer based on ethylene polymer)
The base polymer used in the embodiment of the present invention is mainly composed of an ethylene-based polymer. The ethylene polymer includes any one of an ethylene-propylene-diene copolymer and an ethylene-α olefin copolymer, or an ethylene-vinyl acetate copolymer and an ethylene-α olefin copolymer. The content of the ethylene-based polymer in the base polymer is preferably 60% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and most preferably 100% by mass. As long as the effects of the present invention are exhibited, other types of polymers may be included.

  Examples of the ethylene polymer used in the embodiment of the present invention include high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and linear ultra-high density polyethylene (LDPE). Low density polyethylene, high density polyethylene (HDPE), ethylene-methyl methacrylate copolymer (EMMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-butyl acrylate (EBA), ethylene-vinyl acetate copolymer (EVA) ), Ethylene-glycidyl methacrylate copolymer, ethylene-butene-1 copolymer, ethylene-butene-hexene terpolymer, ethylene-propylene-diene terpolymer (EPDM), ethylene-octene copolymer (EOR), ethylene copolymer polypropylene , Ethylene-propylene copolymer (EPM), poly-4 methyl-pentene-1, maleic acid grafted low density polyethylene, hydrogenated styrene-butadiene copolymer (H-SBR), maleic acid grafted linear low density Polyethylene, maleic acid grafted linear ultra-low density polyethylene, ethylene-α olefin copolymer (especially a copolymer of ethylene and α-olefin having 4 to 20 carbon atoms is preferred), ethylene-styrene copolymer, malee Acid grafted ethylene-styrene copolymer, maleic acid grafted ethylene-methyl acrylate copolymer, maleic acid grafted ethylene-vinyl acetate copolymer, ethylene-maleic anhydride copolymer, ethylene-ethyl acrylate-maleic anhydride ternary Copolymer, ethylene-propylene containing butene-1 as the main component Emissions - like butene-1 terpolymer. These may be used alone or in combination of two or more.

  The radiation-resistant halogen-free resin composition according to an embodiment of the present invention includes an ethylene-propylene-diene copolymer (EPDM), an ethylene-α-olefin copolymer, an ethylene-vinyl acetate copolymer among the ethylene polymers. 1 type or more chosen from coalescence (EVA) is included. As a result, even if a large amount of melamine / cyanurate compound or metal hydrate is added, these ethylene polymers accept the additive and do not deteriorate the mechanical properties.

  In particular, when the resin composition is used as an insulator material for electric wires and cables, an ethylene-propylene-diene copolymer (EPDM), ethylene-α, which has good radiation resistance because it can retain electrical insulation. An olefin copolymer is preferably included, and when used as a cable sheath material, an ethylene-vinyl acetate copolymer (EVA) having flame retardancy is preferably included.

  The content of one or more selected from ethylene-propylene-diene copolymer (EPDM), ethylene-α olefin copolymer, ethylene-vinyl acetate copolymer (EVA) in the ethylene polymer constituting the base polymer is: It is preferable that it is 70-97 mass%, More preferably, it is 75-96 mass%, More preferably, it is 80-95 mass%, Most preferably, it is 85-95 mass%.

  Moreover, the radiation-resistant halogen-free resin composition according to the embodiment of the present invention includes an ethylene polymer modified with a polar functional group. As the ethylene polymer to be modified, those described above can be used, but an ethylene-α olefin copolymer is preferred. Thereby, it is excellent in mechanical characteristics and can have radiation resistance that maintains electrical insulation even when exposed to hot water or superheated steam generated when LOCA occurs after deterioration. This is because the polar functional group in the polymer is electrostatically adsorbed with the hydroxyl group on the surface of the additive particle, improving the adhesion between the polymer and the particle surface, suppressing the ingress of moisture, and maintaining the electrical insulation. It is considered a thing.

  As the polar functional group, an epoxy group, a carboxyl group, and a maleic anhydride group are preferable. In particular, it is preferable to use an ethylene-α olefin copolymer modified with maleic anhydride.

  The content of the ethylene polymer modified with the polar functional group in the ethylene polymer constituting the base polymer is preferably 2 to 20% by mass, more preferably 3 to 18% by mass, and still more preferably 5 It is -15 mass%, Most preferably, it is 7-12 mass%.

  In order to improve the heat resistance of the base polymer, it is preferable to perform crosslinking according to a conventional method such as addition of a sulfur compound or an organic peroxide, electron beam irradiation, or silane graft water crosslinking. In the present embodiment, since an ethylene polymer is used, electron beam irradiation and crosslinking with an organic peroxide are preferable, and in order to increase the degree of crosslinking, crosslinking with an organic peroxide is particularly preferable.

(Aromatic amine antioxidant)
The radiation-resistant halogen-free resin composition according to the embodiment of the present invention includes 3 to 10 parts by mass of an aromatic amine-based antioxidant with respect to 100 parts by mass of the base polymer.

  When radiation (mainly γ-rays) is applied to an ethylene-based polymer, hydrogen is extracted from the polymer at room temperature and radicals are generated even at room temperature, and the radicals combine with oxygen to cause oxidative degradation of the polymer. Arise. As a result, cross-linking and molecular cutting of the polymer occur, and the mechanical properties of the resin composition are drastically lowered. As countermeasures against this deterioration phenomenon, it is important to quickly capture radicals generated in the polymer and to prevent chain oxidative deterioration by changing the hydroperoxide generated in the polymer due to oxidative deterioration to a stable alcohol, We have found that aromatic amine antioxidants are effective against deterioration.

  Aromatic amine antioxidants include compounds that are commercially available as rubber and plastic antioxidants, such as monoamine compounds such as diphenylamine compounds, quinoline compounds, and naphthylamine compounds, phenylenediamine compounds, and benzimidazoles. And diamine compounds such as a series compound.

  Examples of diphenylamine compounds include p- (p-toluenesulfonylamide) -diphenylamine (trade name: NOCRACK TD, etc.), 4,4 ′-(α, α-dimethylbenzyl) diphenylamine (trade names: NOCRACK CD, NAUGARD 445). Others) 4,4′-dioctyl diphenylamine derivatives (trade names: Nocrack ODA-N, Antage OD-P, Antage DDP, etc.) and the like.

  Examples of the quinoline compound include 2,2,4-trimethyl 1,2-dihydroquinoline polymer (trade name: NOCRACK 224; JIS abbreviation TMDQ).

  Examples of naphthylamine compounds include phenyl-α-naphthylamine (trade name: Nocrack PA and others; JIS abbreviation PAN), N, N′-di-2-naphthyl-p-phenylenediamine (trade name Nocrack White and others: JIS abbreviation DNPD). Etc.

  Examples of phenylenediamine compounds include N, N′-diphenyl-p-phenylenediamine (trade name: Nocrack DP and others; JIS abbreviation DPPD), N-isopropyl-N′-phenyl-p-phenylenediamine (Antege 3C, Nocrack 810NA). Others: JIS abbreviation IPPD), N-phenyl-N ′-(3-methacryloyloxy-2-hydroxypropyl) -p-phenylenediamine (trade name: Nocrack G-1 and others), N-phenyl-N ′-(1 , 3-dimethylbutyl) -p-phenylenediamine (ANTAGE 6C, NOCRACK 6C, etc.), N, N′-diphenyl-p-phenylenediamine (trade name: NOCRACK DP, etc .; JIS abbreviation DPPD) (trade name: NOCRACK) 500, Antage DP2 and others), diaryl-p-phenylenediamine derivative A conductor or a mixture thereof (trade name: Nocrack 630, Antage ST1, etc.) can be used.

  Examples of the benzimidazole compound include 2-mercaptobenzimidazole (trade name: Antage MB, etc .; JIS abbreviation MBI), 2-mercaptomethylbenzimidazole (trade name, Nocrack MMB, etc.), zinc salt of 2-mercaptobenzimidazole (trade name) : Nocrack MBZ, etc .; JIS abbreviation ZnMBI), zinc salt of 2-mercaptomethylbenzimidazole (trade name: Nocrack MMBZ, etc.) and the like.

  These aromatic amine antioxidants can be used alone or in combination of two or more. In particular, diphenylamine compounds and quinoline compounds are suitable for capturing radicals, and benzimidazole compounds are suitable for stabilizing hydroperoxide in addition to capturing radicals. For this reason, the combined use of a diphenylamine compound, a quinoline compound and a benzimidazole compound is preferred.

  The addition amount of the aromatic amine-based antioxidant is 3 to 10 parts by mass with respect to 100 parts by mass of the base polymer. Preferably, it is 5-8 mass parts. When the addition amount is less than 3 parts by mass, the effect of preventing deterioration under a radiation environment is small, and when it exceeds 10 parts by mass, the radicals necessary for crosslinking are crosslinked when the composition is crosslinked with an electron beam or an organic peroxide. Is trapped by the antioxidant, which causes cross-linking inhibition and mechanical properties are deteriorated.

(Aromatic process oil)
The radiation-resistant halogen-free resin composition according to the embodiment of the present invention includes 5 to 20 parts by mass of aromatic process oil with respect to 100 parts by mass of the base polymer.

  The addition of aromatic process oil further improves radiation resistance. The cause of this is not clear, but it is considered that the π-shared electrons contained in the aromatic compound in the aromatic process oil resonance-stabilizes the energy received from radiation.

  The addition amount of the aromatic process oil is 5 to 20 parts by mass with respect to 100 parts by mass of the base polymer. Preferably, it is 5-15 mass parts. When the amount is less than 5 parts by mass, the radiation resistance is not significantly observed, and when the amount exceeds 20 parts by mass, the tensile strength is lowered.

  The constituent carbon of the aromatic process oil is divided into carbon in the aromatic ring, carbon in the naphthalene ring, and carbon in the paraffin chain. The more carbon in the aromatic ring, the more effective the radiation protection, preferably 25 It is contained by mass% or more.

(Melamine / Cyanurate Compound)
The radiation-resistant halogen-free resin composition according to the embodiment of the present invention contains 10 to 30 parts by mass of a melamine / cyanurate compound (addition product of melamine and cyanuric acid) with respect to 100 parts by mass of the base polymer.

  Melamine / cyanurate compounds are widely known as flame retardants, but they have been found to be able to impart not only flame resistance but also radiation resistance when used in combination with the aromatic process oil. Although the cause of this is not clear, the melamine cyanurate compound has a property of absorbing ultraviolet rays having a wavelength of about 200 to 230 nm. Gamma rays are radiation with a wavelength of about 10 pm, which is even shorter. However, if the gamma rays collide with some atoms in the composition and the wavelength is expected to increase due to the Compton effect, It is considered that the melamine cyanurate compound absorbs and can suppress deterioration. In addition, dispersibility of melamine / cyanurate is improved by using an aromatic process oil having π-shared electrons in the same way as melamine / cyanurate compounds, and π-shared electrons of aromatic process oil and melamine / cyanurate compounds are stacked. This is considered to have strengthened the action of resonance stabilization of the energy received from the radiation.

  The addition amount of the melamine cyanurate compound is 10 to 30 parts by mass with respect to 100 parts by mass of the base polymer. Preferably, it is 15-25 mass parts. When the amount is less than 10 parts by mass, radiation resistance is not exhibited. When an amount exceeding 30 parts by mass is added, dispersibility is deteriorated and tensile properties are deteriorated. Therefore, deterioration in a radiation environment is likely to occur.

(Metal hydrate)
The radiation-resistant halogen-free resin composition according to the embodiment of the present invention includes 100 to 200 parts by mass of a metal hydrate with respect to 100 parts by mass of the base polymer.

  Examples of the metal hydrate include magnesium hydroxide, aluminum hydroxide, hydrotalcite and the like. Of these, magnesium hydroxide and aluminum hydroxide have the greatest flame retardant effect. Considering the dispersibility of these particles and the adhesion between the particle surface and the polymer, fatty acids, fatty acid metal salts, silane coupling agents, titanate coupling agents, acrylic resins, phenol resins, silicone resins, silicone elastomers, cations It is also possible to carry out a surface treatment with a water-soluble resin having a property or nonionic property. In particular, surface treatment with a silane coupling agent is preferred.

  The addition amount of the metal hydrate is 100 to 200 parts by mass with respect to 100 parts by mass of the base polymer. Preferably, it is 120-160 mass parts. If the addition amount of the metal hydrate is less than 100 parts by mass, high flame retardancy that can pass the vertical tray flame retardant test cannot be obtained. If the addition amount exceeds 200 parts by mass, the mechanical properties are remarkably deteriorated.

(Other additives)
In addition to the above additives, the resin composition according to the embodiment of the present invention, if necessary, flame retardant aids, antioxidants, lubricants, surfactants, softeners, plasticizers, inorganic fillers, Additives such as compatibilizers, stabilizers, metal chelating agents (copper damage inhibitors), crosslinking agents, ultraviolet absorbers, light stabilizers (hindered amine compounds), and colorants can be added. It is particularly preferred to add a flame retardant aid. Examples of the flame retardant aid include phosphorus flame retardants such as red phosphorus and phosphate ester compounds, silicone flame retardants, nitrogen flame retardants, boric acid compounds and stannic acid compounds.

〔Electrical wire〕
The electric wire according to the embodiment of the present invention is characterized in that the radiation-resistant halogen-free resin composition according to the embodiment of the present invention is used as a coating material (insulator).

FIG. 1 is a cross-sectional view of an electric wire according to an embodiment of the present invention.
As shown in FIG. 1, the electric wire 10 according to the present embodiment includes a conductor 1 made of a general-purpose material, for example, pure copper, tin-plated copper, or the like, and an insulator 2 coated on the outer periphery of the conductor 1. The conductor 1 may be plural or one as shown in FIG.

  The insulator 2 is composed of the radiation-resistant halogen-free resin composition according to the embodiment of the present invention.

  In this embodiment mode, the insulator may be a single layer or a multilayer structure. Furthermore, you may give a separator, a braiding, etc. as needed.

〔cable〕
The cable according to the embodiment of the present invention is characterized by using the radiation-resistant halogen-free resin composition according to the embodiment of the present invention as a coating material (insulator and / or sheath).

FIG. 2 is a cross-sectional view of the cable according to the embodiment of the present invention.
As shown in FIG. 2, the cable 100 according to the present embodiment includes a three-core stranded wire obtained by twisting together three electric wires in which a conductor 1 is coated with an insulator 2 together with an interposition 4 such as paper, and a three-core stranded wire. A press-wound tape 5 is provided on the outer periphery, and a sheath 3 is extrusion-coated on the outer periphery. The electric wire may be a single core or a multi-core stranded wire other than a three-core wire.

  The insulator 2 and the sheath 3 are composed of the radiation-resistant halogen-free resin composition according to the embodiment of the present invention. Only either the insulator 2 or the sheath 3 may be composed of the above radiation-resistant halogen-free resin composition, but both are preferable.

  In the present embodiment, the sheath may be composed of a single layer or a multilayer structure. Furthermore, you may give a separator, a braiding, etc. as needed.

[Effect of the embodiment of the present invention]
As described above, according to the embodiment of the present invention, it is possible to obtain a halogen-free resin composition having high radiation resistance that can maintain electrical insulation even when exposed to hot water or superheated steam at the time of occurrence of LOCA. I can do it. The radiation-resistant halogen-free resin composition according to the embodiment of the present invention does not generate harmful gas at the time of combustion, and is less deteriorated in mechanical properties even when used in a radiation environment. In addition, by using the resin composition as an insulator and / or sheath, it has high flame resistance that passes the vertical tray combustion test, does not generate harmful gas during combustion, and has high radiation resistance. In addition, it is possible to obtain an electric wire / cable that can maintain the prescribed electrical insulation for a certain time even when LOCA occurs.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

  The electric wire 10 having the structure shown in FIG. 1 was produced by the following method.

  Various components are blended in the blending ratios shown in Examples 1 to 10 in Table 1 and Comparative Examples 1 to 11 in Table 2, and a compounding agent other than organic peroxide is started at 40 ° C. and finished by a 25 L pressure kneader. After kneading at 180 ° C., the kneaded product was pelletized. Then, the kneaded material was impregnated with an organic peroxide with a blender to obtain a resin composition used as an insulator.

  The obtained resin composition was extruded on a copper conductor having a conductor cross-sectional area of 3.5 SQ at a thickness of 0.8 mm and a set temperature of 130 ° C., and then crosslinked with saturated steam at about 200 ° C. to obtain the electric wire shown in FIG.

  Evaluation of the produced electric wire was determined by the method shown below. The evaluation results are shown in Tables 1 and 2.

(1) Initial tensile test (mechanical property test)
About the produced electric wire, the tension test was implemented based on IEC60881-1. Tensile strength (Tb) was determined to be less than 9 MPa, and 9 MPa or higher. The elongation at break (Eb) was determined to be less than 200%, and 200% or more.

(2) Combustion test About the produced electric wire, the vertical tray combustion test based on IEEE Std.383 (2003) was done, and the carbonization length was set to 150 cm or less as the pass.

(3) Radiation resistance test The prepared electric wire was subjected to accelerated thermal degradation for 60 years in accordance with the Arrhenius rule, and then irradiated with γ-rays and exposed to vapor with the profile shown in FIG. FIG. 3 is a diagram showing conditions (temperature and pressure changes with time) in a radiation resistance test (high-pressure steam exposure test). During the vapor exposure period, the power must be applied at 600V AC and must not be short-circuited. After that, it was wound around a mandrel corresponding to 40 times the self-diameter of the electric wire, an AC 3200 V / mm, 5 minute immersion withstand voltage test was conducted, and a test piece that did not break was accepted. Irradiation with 2MGy was performed at a γ-ray irradiation dose rate of 5 kGy / h at room temperature.

(4) Comprehensive judgment In all the tests of (1) to (3), a pass was accepted, and even one failure was rejected.

  As shown in Table 1, the electric wire using the radiation-resistant halogen-free resin composition of Examples 1 to 10 as an insulator satisfies all the characteristics and is excellent in mechanical characteristics, flame retardancy, and radiation resistance. I understand that.

On the other hand, Comparative Examples 1 and 2 use any combination of ethylene-propylene-diene copolymer and ethylene-α olefin copolymer, or ethylene-vinyl acetate copolymer and ethylene-α olefin copolymer. Orazu, the elongation at break of the first period was unacceptable small. Moreover, the radiation resistance was insufficient.

  In Comparative Example 3, since no ethylene polymer modified with a polar functional group was added, the elongation at break after deterioration was sufficient, but passed the withstand voltage test after the vapor exposure test assuming a coolant loss accident. I couldn't.

  In Comparative Example 4, the amount of aromatic process oil added was small, and the radiation resistance was insufficient. Conversely, in Comparative Example 5, the amount of aromatic process oil added is large, and the initial tensile strength is not sufficient.

  In Comparative Examples 6 and 8, the addition amount of the melamine / cyanurate compound and the metal hydrate was insufficient, and the vertical tray combustion test could not be passed. In Comparative Example 6, both the amount of the aromatic process oil and the amount of the aromatic amine antioxidant were sufficient, but the radiation resistance was inferior.

  In Comparative Example 7, the amount of the melamine / cyanurate compound added was large, and the initial elongation at break was insufficient.

  In Comparative Example 9, the amount of metal hydrate added was large, the initial elongation at break was insufficient, and the withstand voltage test after deterioration also failed.

  In Comparative Example 10, the addition amount of the aromatic amine-based antioxidant is small, and the radiation resistance is insufficient. On the contrary, in Comparative Example 11, the addition amount of the aromatic amine-based antioxidant is too large, This was a result of causing inhibition and insufficient initial tensile strength.

1: conductor, 2: insulator, 3: sheath, 4: interposition, 5: presser winding tape 10: electric wire, 100: cable

Claims (5)

3 to 10 parts by weight of an aromatic amine antioxidant, 5 to 20 parts by weight of an aromatic process oil, 10 to 30 parts by weight of a melamine / cyanurate compound, with respect to 100 parts by weight of a base polymer mainly composed of an ethylene polymer. And 100 to 200 parts by mass of metal hydrate,
The ethylene polymer was modified with a polar functional group, either an ethylene-propylene-diene copolymer and an ethylene-α olefin copolymer, or an ethylene-vinyl acetate copolymer and an ethylene-α olefin copolymer . A radiation-resistant halogen-free resin composition comprising an ethylene polymer.   The radiation-resistant halogen-free resin composition according to claim 1, wherein the polar functional group is an epoxy group, a carboxyl group, or a maleic anhydride group.   The radiation-resistant halogen-free resin composition according to claim 1 or 2, wherein the ethylene polymer modified with the polar functional group is an ethylene-α olefin copolymer.   An electric wire characterized by using the radiation-resistant halogen-free resin composition according to any one of claims 1 to 3 as a coating material.   A cable comprising the radiation-resistant halogen-free resin composition according to claim 1 as a coating material.

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