阅读说明：本技术 绝缘电线及电缆 (Insulated wire and cable ) 是由 木部有 岩崎周 梶山元治 桥本充 于 2020-01-22 设计创作，主要内容包括：本发明提供一种绝缘电线以及电缆,其使用了阻燃性、耐油性、耐燃料性、低温特性良好的无卤树脂组合物。绝缘电线(11)具有导体(11a)、内层(11b)以及外层(11c),内层由包含第1基础聚合物和填充剂的树脂组合物形成,外层由包含第2基础聚合物和金属氢氧化物的树脂组合物形成。而且,第2基础聚合物包含乙酸乙烯酯含量(VA量)为60％以上的乙烯-乙酸乙烯酯共聚物(EVA)和熔点为85℃以上的聚烯烃系聚合物的至少两种聚合物,两种聚合物占据第2基础聚合物的80％以上,以相对于第2基础聚合物100重量份为150～250重量份的比例包含金属氢氧化物。(The invention provides an insulated wire and a cable, which use a halogen-free resin composition with good flame retardance, oil resistance, fuel resistance and low-temperature property. The insulated wire (11) has a conductor (11a), an inner layer (11b) formed from a resin composition containing a1 st base polymer and a filler, and an outer layer (11c) formed from a resin composition containing a2 nd base polymer and a metal hydroxide. The 2 nd base polymer comprises at least two polymers of an ethylene-vinyl acetate copolymer (EVA) having a vinyl acetate content (VA amount) of 60% or more and a polyolefin polymer having a melting point of 85 ℃ or more, wherein the two polymers account for 80% or more of the 2 nd base polymer, and the metal hydroxide is contained in a proportion of 150 to 250 parts by weight relative to 100 parts by weight of the 2 nd base polymer.)

1. An insulated wire having a conductor, a1 st insulating layer covering the conductor, and a2 nd insulating layer covering the 1 st insulating layer,

the 1 st insulating layer is formed of a1 st halogen-free resin composition comprising a1 st base polymer and a filler,

the 2 nd insulating layer is formed of a2 nd halogen-free resin composition comprising a2 nd base polymer and a metal hydroxide,

the 2 nd base polymer comprises at least two polymers of an ethylene-vinyl acetate copolymer (EVA) having a vinyl acetate content (VA amount) of 60% or more and a polyolefin-based polymer having a melting point of 85 ℃ or more, the two polymers occupying 80% or more of the 2 nd base polymer,

the metal hydroxide is contained in a ratio of 150 to 250 parts by weight with respect to 100 parts by weight of the 2 nd base polymer.

2. The insulated electric wire according to claim 1,

the 1 st base polymer comprises 50% or more of polyethylene having a melting point of 110 ℃ or higher,

the filler is contained in a proportion of 150 parts by weight or less with respect to 100 parts by weight of the 1 st base polymer.

3. The insulated wire according to claim 2, wherein the filler is calcined clay or talc.

4. The insulated electric wire according to claim 2,

a tensile strength after crosslinking of 10MPa or more and an elongation of 150% or more,

the tensile strength change rate after immersion in IRM903 oil at 70 ℃ for 168 hours is within + -30%, and the elongation change rate is within + -40%.

5. The insulated electric wire according to claim 2,

the 1 st base polymer is mixed with an acid-modified polyolefin.

6. The insulated electric wire according to claim 2,

the 2 nd base polymer is mixed with an acid-modified polyolefin,

the acid-modified polyolefin has a glass transition temperature Tg of-55 ℃ or lower,

the mass ratio of the two polymers to the acid-modified polyolefin is 80: 20-99: 1.

7. The insulated electric wire according to claim 2,

the metal hydroxide comprises magnesium hydroxide or aluminum hydroxide,

the polyolefin polymer having a melting point of 85 ℃ or higher is ethylene-vinyl acetate copolymer (EVA).

8. A cable having an insulated wire and a sheath covering the insulated wire,

the insulated wire according to any one of claims 1 to 7 is provided.

9. A cable having an insulated wire and a sheath covering the insulated wire,

the sheath is formed of a halogen-free resin composition comprising a2 nd base polymer and a metal hydroxide,

the 2 nd base polymer comprises at least two polymers of an ethylene-vinyl acetate copolymer (EVA) having a vinyl acetate content (VA amount) of 60% or more and a polyolefin-based polymer having a melting point of 85 ℃ or more, the two polymers occupying 80% or more of the 2 nd base polymer,

the metal hydroxide is contained in a ratio of 150 to 250 parts by weight with respect to 100 parts by weight of the 2 nd base polymer.

10. The electrical cable as set forth in claim 9,

a tensile strength after crosslinking of 10MPa or more and an elongation of 150% or more,

the tensile strength change rate after immersion in IRM903 oil at 70 ℃ for 168 hours is within + -30%, and the elongation change rate is within + -40%.

Technical Field

The present invention relates to an insulated wire and a cable using a halogen-free resin composition.

Background

Since the recent activity for environmental protection has been actively developed worldwide, halogen-free materials that do not generate toxic gases when burned and cause little environmental pollution when disposed of have been rapidly spread. For example, patent document 1 (jp 2010-97881 a) discloses an insulated wire including a conductor, an inner layer having insulation and covering the conductor and including an ethylene ethyl acrylate copolymer (EEA), and an outer layer covering the inner layer and including an ethylene vinyl acetate copolymer (EVA) and a halogen-free flame retardant, the outer layer being crosslinked to have oil resistance and flame retardancy.

However, since halogen-free materials generally have inferior flame retardancy compared to halogen materials, it is necessary to highly fill the flame retardant in order to impart high flame retardancy. For example, in order to satisfy the standard requiring very high flame retardancy such as EN45545 and NFPA130, the flame retardant needs to be added in an amount of about 200 parts by mass or more. By adding the flame retardant in this way, although the flame retardancy is improved, other properties such as elongation property and low temperature property of the material tend to be lowered.

Further, since flame retardants such as metal hydroxides have high hygroscopicity, the addition of a large amount of them may cause a decrease in electrical characteristics, and it may be difficult to maintain desired insulation performance.

On the other hand, insulated wires and cables used in railway vehicles and the like are required to have high flame retardancy and electrical insulation, and also required to have fuel resistance and the like depending on the environment in which they are used. For example, in the fuel resistance test defined in EN60811-2-1, the material was immersed in IRM903 oil at 70 ℃ to measure the rate of change in tensile strength and elongation.

As a method of achieving high flame retardancy, electrical insulation, and fuel resistance at the same time, a method of forming an outer layer as a layer having high flame retardancy and fuel resistance and forming an inner layer as a layer having high electrical insulation is considered.

Disclosure of Invention

Problems to be solved by the invention

The present inventors have conducted research and development on coating materials such as a coating layer of a cable and an insulating layer of an electric wire, and have studied a resin composition which uses a halogen-free material and is excellent in flame retardancy, oil resistance, fuel resistance, low-temperature characteristics, and the like as a polymer of the coating material.

In particular, insulated wires and cables used in railway vehicles and the like are required to have high flame retardancy and electrical insulation properties, and also fuel resistance properties and the like depending on the environment in which they are used.

In order to improve the fuel resistance, it is effective to use a polymer that does not melt at 70 ℃ as the test temperature, or a polymer that is hardly compatible with IRM903 oil. In the case of using the former polymer, although it is effective for improving fuel resistance, the reduction in elongation characteristics and the like accompanying the addition of a flame retardant and the like is remarkable, and in the case where extremely high flame retardancy is required such as EN45545 and NFPA130, it is difficult to achieve both of physical properties such as flame retardancy and elongation characteristics.

As the latter polymer incompatible with IRM903 oil, a polymer having a high polarity is effective. However, as described above, it is difficult for a polymer having a high melting point to have both of the physical properties such as flame retardancy and elongation properties. The polymer having a low melting point and a high polarity includes EVA having a high VA content, EEA having a high EA content, and the like, and it is appropriate to market EVA having a high VA content in many grades in consideration of availability in the market. However, high VA EVA generally lacks tensile strength and the polymers fuse strongly to each other and are not suitable for use alone.

The present invention has been made in view of the above problems, and an object thereof is to provide an insulated wire and a cable using a halogen-free resin composition having excellent flame retardancy, oil resistance, fuel resistance, and low-temperature characteristics.

Means for solving the problems

(1) An insulated wire according to one embodiment of the present invention includes a conductor, a1 st insulating layer covering the conductor, and a2 nd insulating layer covering the 1 st insulating layer, wherein the 1 st insulating layer is formed of a1 st halogen-free resin composition including a1 st base polymer and a filler, the 2 nd insulating layer is formed of a2 nd halogen-free resin composition including a2 nd base polymer and a metal hydroxide, the 2 nd base polymer includes at least two polymers of an ethylene-vinyl acetate copolymer (EVA) having a vinyl acetate content (VA content) of 60% or more and a polyolefin polymer having a melting point of 85 ℃ or more, the two polymers occupy 80% or more of the 2 nd base polymer, and the metal hydroxide is included in an amount of 150 to 250 parts by weight based on 100 parts by weight of the 2 nd base polymer.

(2) For example, the 1 st base polymer contains 50% or more of polyethylene having a melting point of 110 ℃ or higher, and the filler is contained in an amount of 150 parts by weight or less based on 100 parts by weight of the 1 st base polymer.

(3) For example, the filler is calcined clay or talc.

(4) For example, the tensile strength after crosslinking is 10MPa or more and the elongation is 150% or more, and the tensile strength change rate after immersion in IRM903 oil at 70 ℃ for 168 hours is within. + -.30% and the elongation change rate is within. + -.40%.

(5) For example, the 1 st base polymer is mixed with an acid-modified polyolefin.

(6) For example, the 2 nd base polymer is mixed with an acid-modified polyolefin, the acid-modified polyolefin has a glass transition temperature (Tg) of-55 ℃ or lower, and the mass ratio of the two polymers to the acid-modified polyolefin is 80:20 to 99: 1.

(7) For example, the metal hydroxide includes magnesium hydroxide or aluminum hydroxide, and the polyolefin polymer having a melting point of 85 ℃ or higher is an ethylene-vinyl acetate copolymer (EVA).

(8) A cable according to an embodiment of the present invention is a cable including the insulated wire and a sheath covering the insulated wire.

(9) The cable according to one embodiment of the present invention is a cable having an insulated wire and a sheath covering the insulated wire, wherein the sheath is formed from a halogen-free resin composition containing a2 nd base polymer and a metal hydroxide, the 2 nd base polymer contains at least two polymers of an ethylene-vinyl acetate copolymer (EVA) having a vinyl acetate content (VA amount) of 60% or more and a polyolefin polymer having a melting point of 85 ℃ or more, the two polymers occupy 80% or more of the 2 nd base polymer, and the metal hydroxide is contained in a proportion of 150 to 250 parts by weight with respect to 100 parts by weight of the 2 nd base polymer.

(10) For example, the tensile strength after crosslinking is 10MPa or more and the elongation is 150% or more, and the tensile strength change rate after immersion in IRM903 oil at 70 ℃ for 168 hours is within. + -.30% and the elongation change rate is within. + -.40%.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the insulated wire and cable using the halogen-free resin composition according to one embodiment of the present invention, flame retardancy, oil resistance, fuel resistance, and low-temperature characteristics can be improved.

Drawings

Fig. 1 is a sectional view showing an example of the structure of an insulated wire.

Fig. 2 is a cross-sectional view showing an example of the configuration of the cable.

Description of the symbols

11 insulated wire, 11a conductor, 11b inner layer, 11c outer layer, 12 cable, 12d sheath.

Detailed Description

(embodiment mode 1)

Fig. 1 is a sectional view showing an example of the structure of an insulated wire according to the present embodiment. The insulated wire 11 shown in fig. 1 has a conductor 11a, an inner layer 11b, and an outer layer 11 c.

As the conductor 11a, a metal wire, for example, a copper wire, a copper alloy wire, an aluminum wire, a gold wire, a silver wire, or the like can be used. Further, a conductor plated with a metal such as tin or nickel on the outer periphery of the metal wire may be used. As the conductor 11a, a plurality of wires may be used, or a twisted wire may be used.

As the inner layer (insulating layer) 11b, a resin composition containing the 1 st base polymer, a filler, and other additives can be used.

(1 st base Polymer)

As the 1 st base polymer, polyethylene (polyolefin) which is a polymer having excellent electrical insulation properties can be used. As the polyethylene, polyethylene having a melting point of 110 ℃ or higher is preferably used. The melting point can be measured by a Differential Scanning Calorimetry (DSC) method. If the melting point is less than 110 ℃, the crystals melt in the oil resistance test, and it becomes difficult to prevent the oil from diffusing in the polymer, and the rate of change in tensile properties increases.

In order to increase the crystallinity, crystalline polyethylene (polyolefin) having a melting point of 120 ℃ or higher is preferably added.

Examples of the polyethylene having a melting point of 110 ℃ or higher include low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, and high-density polyethylene. The ratio of the polyethylene having a melting point of 110 ℃ or higher in the 1 st base polymer is preferably 50% by weight or more, more preferably 60 to 80%. Thus, the 1 st base polymer contains polyethylene having a melting point of 110 ℃ or higher as a main component.

In consideration of the acceptability of the filler, it is preferable to include a rubber component in the 1 st base polymer. That is, the interface between the polyethylene (polyolefin) and the filler is closely adhered by the rubber component, and the polyethylene (polyolefin) and the filler can be prevented from peeling off.

Examples of the rubber component include ethylene-propylene copolymer rubber (EPR), ethylene-propylene-diene terpolymer rubber (EPDM), nitrile rubber (NBR), hydrogenated NBR (hnbr), acrylic rubber, ethylene-acrylate copolymer rubber, ethylene octene copolymer rubber (EOR), ethylene-vinyl acetate copolymer rubber, ethylene-1-butene copolymer rubber (EBR), butadiene-styrene copolymer rubber (SBR), isobutylene-isoprene copolymer rubber (IIR), block copolymer rubber containing a polystyrene block, and urethane rubber. Among them, EOR and EBR have no double bond and therefore have no risk of scorching during extrusion, and further, have no polarity and therefore can obtain high electrical characteristics. Thus, EOR and EBR are preferably used as the rubber component.

In addition, in order to obtain high electrical characteristics, it is preferable to use an acid-modified polyolefin (a product obtained by modifying a polyolefin with an acid). Examples of the acid to be a material of the acid-modified polyolefin include maleic acid, maleic anhydride, fumaric acid, and the like. Examples of the polyolefin as a material of the acid-modified polyolefin include polyethylene, ethylene- α -olefin, ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, and vinyl acetate copolymer. Among them, acid-modified polyolefins having a glass transition temperature (Tg) of-55 ℃ or lower are preferably used.

(Filler)

A filler is added to the 1 st base polymer. Herein, the filler means an inorganic substance added to the base polymer, and is a component added in an amount of at least 20 parts by weight based on 100 parts by weight (parts by mass) of the 1 st base polymer. However, if the amount of the filler is too large, the elongation at break is lowered, and therefore the amount of the filler added is preferably 150 parts by weight or less with respect to 100 parts by weight of the 1 st base polymer.

The filler may not be added, but the proportion of organic substances in the resin composition can be reduced by adding the filler. Since the proportion of organic matter (polymer, rubber component) is reduced, it is possible to reduce toxic gases such as carbon monoxide and carbon dioxide generated during combustion. The amount of the filler added is more preferably 20 to 130 parts by weight, and still more preferably 50 to 100 parts by weight, based on 100 parts by weight of the 1 st base polymer.

Examples of the filler include silicates such as kaolinite, kaolin, calcined clay, talc, mica, wollastonite, and pyrophyllite; oxides such as silica, alumina, zinc oxide, titanium oxide, calcium oxide, and magnesium oxide; carbonates such as calcium carbonate, zinc carbonate, and barium carbonate; hydroxides such as calcium hydroxide, magnesium hydroxide, and aluminum hydroxide. These materials may be used alone or in combination of two or more.

Among the above materials, hydrophobic calcined clay and talc exhibit high electrical characteristics and contain no carbon, and therefore can suppress the generation of carbon monoxide, and are preferably used as fillers. Further, as the filler, a material subjected to surface treatment may be used. For example, a filler obtained by surface-treating silane may be used as the material. By surface treatment of silane, adhesion between the filler and the polymer can be enhanced, and the insulating performance can be improved.

(other additives)

The resin composition may contain, as necessary, a crosslinking aid, a flame retardant aid, an ultraviolet absorber, a light stabilizer, a softener, a lubricant, a colorant, a reinforcing agent, a surfactant, a plasticizer, a metal deactivator, a foaming agent, a compatibilizer, a processing aid, a stabilizer, and the like.

As the outer layer (insulating layer) 11c, a halogen-free resin composition containing the 2 nd base polymer, a filler, and other additives can be used.

(2 nd base Polymer)

The 2 nd base polymer comprises two polymers of an ethylene-vinyl acetate copolymer (EVA) having a vinyl acetate content (VA amount) of 60% or more and a polyolefin-based polymer having a melting point of 85 ℃ or more. The "two polymers" herein means a group of polymers, and may include a plurality of polymers as an ethylene-vinyl acetate copolymer (EVA) having a vinyl acetate content (VA amount) of 60% or more, and may also include a plurality of polymers as a polyolefin-based polymer having a melting point of 85 ℃ or more. The polyolefin polymer having a melting point of 85 ℃ or higher may be an ethylene-vinyl acetate copolymer (EVA).

The EVA is not particularly limited if the VA content is 60% or more, but tends to lower the low-temperature characteristics as the VA content increases, and therefore, when the low-temperature characteristics are required, the VA content is preferably 60 to 80%, more preferably 60 to 70%. "amount of VA [% ]" is the content of vinyl acetate in the ethylene-vinyl acetate copolymer. This VA amount can be measured based on JISK 7192.

The polyolefin-based polymer is not particularly limited as long as the melting point is 85 ℃ or higher, and examples thereof include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), linear very low-density polyethylene (VLDPE), high-density polyethylene (HDPE), polypropylene (PP), ethylene-ethyl acrylate copolymer (EEA), ethylene-vinyl acetate copolymer (EVA), and the like. Among them, EVA having a melting point of 85 ℃ or higher is preferably used. However, since the higher the crystallinity, the lower the physical properties such as elongation and the like with the addition of the filler, it is more preferable to use EVA having a VA content of about 17% and a melting point of about 89 ℃.

The ratio of the above-mentioned two polymers is not particularly limited, but the ratio of EVA having a VA content of 60% or more to the polyolefin polymer having a melting point of 85 ℃ or more is preferably 1:2 to 2:1 (about 33% to 66% for the former and about 66% to 33% for the latter), and more preferably 4:6 to 6:4 (40% to 60% for the former and 60% to 40% for the latter).

The 2 nd base polymer may comprise other polymers. Other polymers can be added within the specified ranges. That is, since the second base polymer 2 includes ethylene-vinyl acetate copolymer (EVA) having a vinyl acetate content (VA amount) of 60% or more, which is two essential polymers, and a polyolefin polymer having a melting point of 85 ℃ or more, the remaining amount of the ethylene-vinyl acetate copolymer (EVA) is less than 20%, and other polymers may be included in a range not overlapping with the two polymers. Examples of the other polymer include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), linear very 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), and the like, Maleic acid-grafted linear low-density polyethylene, a copolymer of ethylene and an alpha-olefin having 4 to 20 carbon atoms, an ethylene-styrene copolymer, a maleic acid-grafted ethylene-methyl acrylate copolymer, a maleic acid-grafted ethylene-vinyl acetate copolymer, an ethylene-maleic anhydride copolymer, an ethylene-ethyl acrylate-maleic anhydride terpolymer, an ethylene-propylene-1-butene terpolymer containing 1-butene as a main component, and the like.

Further, as another polymer, an acid-modified polyolefin (a polymer in which a polyolefin is modified with an acid) can be used. Particularly, an acid-modified polyolefin having a glass transition temperature of-55 ℃ or lower is preferably used. The glass transition temperature refers to a glass transition temperature measured by a DSC method. The acid-modified polyolefin is obtained by grafting or copolymerizing an acid such as maleic anhydride with a polyolefin. Examples of the polyolefin as a material of the acid-modified polyolefin include natural rubber, butyl rubber, ethylene-propylene rubber, ethylene- α -olefin copolymer, styrene-butadiene rubber, nitrile rubber, acrylic rubber, silicone rubber, urethane rubber, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, polyvinyl acetate, ethylene-ethyl acrylate copolymer, ethylene-acrylic ester copolymer, polyurethane, ultra-low density polyethylene, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-1-butene copolymer, ethylene-1-hexene copolymer, ethylene-1-octene copolymer, and the like. Particularly, ethylene-propylene rubber, ethylene- α -olefin copolymer, and ethylene-ethyl acrylate copolymer are preferably used.

Examples of the acid of the material of the acid-modified polyolefin include maleic acid and fumaric acid in addition to the above maleic anhydride. These acid-modified polyolefins may be added alone or in combination of two or more.

In addition, the mass ratio of the two polymers to the acid-modified polyolefin is preferably 80:20 to 99: 1.

(Metal hydroxide)

The 2 nd base polymer is added with a metal hydroxide. The metal hydroxide has a function as a flame retardant. Examples of the metal hydroxide include magnesium hydroxide, aluminum hydroxide, and calcium hydroxide. Among them, magnesium hydroxide is preferably used. The metal hydroxide may be used alone or in combination of two or more. As the metal hydroxide, a metal hydroxide surface-treated with a silane coupling agent, a titanate coupling agent, a fatty acid such as stearic acid or calcium stearate, or a fatty acid metal salt can be used.

The amount of the metal hydroxide added is preferably 150 to 250 parts by weight, more preferably 180 to 220 parts by weight, based on 100 parts by weight of the No. 2 base polymer. When the amount is less than 150 parts by weight, sufficient flame retardancy cannot be obtained, and when the amount is more than 250 parts by weight, elongation properties and the like are deteriorated.

(other additives)

To the 2 nd base polymer, other additives are added as necessary. Examples of the other additives include antioxidants, metal deactivators, flame retardants other than the above-mentioned metal hydroxides, crosslinking agents, crosslinking aids, lubricants, fillers other than the above-mentioned fillers, compatibilizers, stabilizers, carbon black, colorants, and the like.

Examples of the antioxidant include phenol-based, sulfur-based, amine-based, and phosphorus-based antioxidants.

Examples of the phenolic antioxidant 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- (1H,3H,5H) trione, and thiodiethylene bis [3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate ]. Among them, pentaerythritol tetrakis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ] is preferably used.

Examples of the sulfur-based antioxidant include didodecyl-3, 3 ' -thiodipropionate, ditridecyl-3, 3 ' -thiodipropionate, dioctadecyl-3, 3 ' -thiodipropionate, and tetrakis [ methylene-3- (dodecylthio) propionate ] methane. Among them, tetrakis [ methylene-3- (dodecylthio) propionate ] methane is preferably used.

These antioxidants may be added singly or in combination of two or more.

The metal deactivator has an effect of stabilizing metal ions by chelate formation and suppressing oxidative deterioration. Examples of the metal inactivator include N- (2H-1,2, 4-triazol-5-yl) salicylamide, dodecanedioic acid bis [ N2- (2-hydroxybenzoyl) hydrazide ], 2', 3-bis [ [3- [3, 5-di-tert-butyl-4-hydroxyphenyl ] propionyl ] ] propionylhydrazide and the like. Among them, 2', 3-bis [ [3- [3, 5-di-t-butyl-4-hydroxyphenyl ] propionyl ] ] propionylhydrazide is preferably used.

Examples of the flame retardant other than the metal hydroxide include amorphous silica, zinc stannate, zinc hydroxystannate, zinc borate, zinc oxide and other zinc compounds, calcium borate, barium metaborate and other boric acid compounds, phosphorus flame retardants, melamine cyanurate and other nitrogen flame retardants, and intumescent (インテュメッセント) flame retardants formed of a mixture of a component that foams during combustion and a component that solidifies.

As the crosslinking assistant, for example, trimethylolpropane trimethacrylate (TMPT) or Triallylisocyanurate (TAIC) is preferably used.

Examples of the lubricant include fatty acids, fatty acid metal salts, and fatty acid amides. Specifically, zinc stearate can be used. These lubricants may be added alone or in combination of two or more.

As the carbon black, for example, carbon black for rubber (N900-N100: ASTM D1765-01) can be used.

As the colorant, for example, a color masterbatch for the outer layer 11c can be used.

(Cross-linking)

The inner layer 11b and the outer layer 11c used for the insulated wire are obtained by crosslinking a mixture (resin composition) of the above materials. As a crosslinking method, there is an irradiation crosslinking method in which a mixture (resin composition) of the above materials is molded and then crosslinked by irradiation with an electron beam, a radiation, or the like. In the case of performing the irradiation crosslinking method, a crosslinking assistant may be added in advance to the mixture of the above materials (resin composition). Further, a chemical crosslinking method in which crosslinking is performed by heating may be used. In the case of performing the chemical crosslinking method, a crosslinking agent may be added in advance to a mixture of the above materials (resin composition). As the crosslinking agent, an organic peroxide can be used. Examples of the organic peroxide include 1, 3-bis (2-t-butylperoxyisopropyl) benzene, dicumyl peroxide (DCP), and the like.

The inner layer 11b and the outer layer 11c may be simultaneously crosslinked, or the outer layer 11c may be formed and crosslinked on the outer periphery thereof after the inner layer 11b is crosslinked.

(application example 1)

Fig. 1 shows an example in which the conductor 11a is covered with 2-layer insulating layers (an inner layer 11b and an outer layer 11c), but a configuration in which the conductor 11a is covered with a single-layer insulating layer may be employed. In this case as well, by forming a single-layer insulating layer using the same material as the outer layer 11c, an insulated wire having good characteristics can be obtained.

(application example 2)

In fig. 1 and application example 1, the halogen-free resin composition applied to the insulated wire is described as an example, but the halogen-free resin composition of the present embodiment may be used as a sheath of a cable.

Fig. 2 is a cross-sectional view showing an example of the cable configuration of application example 2. The cable 12 shown in fig. 2 includes 2 twisted insulated wires 11 (twisted wires, see fig. 1) and a sheath (outer coating layer, covering layer) 12d provided outside the twisted wires. As a material of the sheath 12d, the same material as the outer layer 11c can be used. The number of insulated wires 11 in the cable 12 may be 1, or 3 or more. Further, a spacer or a shield braid may be provided between the twisted 2 insulated wires 11 and the sheath 12 d. The spacer may be made of any material, and may be provided inside or outside the shield braid.

The insulated wire and cable described above can be used as a halogen-free insulated wire or a halogen-free cable. Specific applications include, for example, applications for railway vehicles. That is, the halogen-free insulated wire can be used as a halogen-free insulated wire for railway vehicles and a halogen-free cable for railway vehicles.