Flame-retardant wire

Abstract

To provide a flame-retardant electric wire which is excellent in characteristics such as mechanical characteristic, oil resistance, cold resistance, thermal aging resistance, flexibility and handleability required for a flame-retardant electric wire, and comprises a halogen-free insulating layer.SOLUTION: A flame-retardant electric wire 1 has an electric conductor 2, and an insulating layer 3 which covers the outer periphery of the electric conductor 2 and is composed of a resin composition. The resin composition includes 130-180 pts.mass of a flame retarder, 7 pts.mass or more of an antioxidant, and 1 pts.mass or more of a copper inhibitor, with respect to 100 pts.mass of a base polymer. The base polymer includes 45-60 mass% of an amount of vinyl acetate, 50-90 pts.mass of an ethylene-vinyl acetate copolymer, and 10-50 pts.mass of an ethylene-α-olefin copolymer. The flame retarder is composed of a magnesium hydroxide and / or an aluminum hydroxide surface-treated with a silane coupling agent and has a BET specific surface area of 6 m2 / g or less. The resin composition is crosslinked.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a flame-retardant wire, and more particularly to a flame-retardant wire having a halogen-free insulating layer.

Background Art

[0002] Conventionally, as a material for the insulating layer of wires used in railway vehicles, automobiles, electrical equipment, and electronic equipment, a polyolefin resin having a good balance of oil resistance, fuel resistance, cold resistance, and flame retardancy has been used. Further, in order to further enhance the flame retardancy, a material obtained by adding a halogen-based flame retardant to a polyolefin resin has been used. The polyolefin resin is, for example, polyvinyl chloride, polychloroprene rubber, chlorosulfonated polyethylene, chlorinated polyethylene, fluororubber, fluororesin, or polyethylene.

[0003] However, these materials containing a large amount of halogen generate a large amount of toxic and harmful gases during combustion, and generate highly toxic dioxin depending on the combustion conditions. Therefore, from the viewpoints of safety in the event of a fire and reduction of environmental load, halogen-free materials that do not contain halogen have begun to be used as the covering material of wires.

[0004] Furthermore, in wires used in railway vehicles and automobiles, in order to save power and improve fuel efficiency, reduction in diameter and weight are required. When the cross-sectional area of the conductor is reduced with the same current capacity to reduce the diameter and weight of the wire, the conductor becomes hot, so the covering material is required to have high heat aging resistance.

[0005] When the conductor becomes hot, a fluororubber or fluororesin having excellent heat aging resistance is often used as the covering material of the wire. As described above, these fluorine-based materials contain halogen. Therefore, as a halogen-free covering material, a flame-retardant silicone rubber having excellent heat aging resistance is used following the fluorine-based materials.

[0006] In silicone rubber, since the base rubber itself is flame retardant, it is not necessary to mix a large amount of flame retardant in order to achieve the high flame retardancy required for electric wires used in, for example, railway vehicles. Therefore, silicone rubber is an excellent material with both flame retardancy and electrical insulation properties.

[0007] For example, in Patent Document 1, a composition containing 50 to 200 parts by mass of a metal hydroxide, 0.5 part by mass or more of silicone raw rubber, 1 to 10 parts by mass of a hydroxybenzoyl isocyanurate compound, and 1 to 10 parts by mass of a sulfur-containing ester compound with respect to 100 parts by mass of a polyolefin is applied as a coating material for a flame retardant electric wire.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] Silicone rubber is known to be inferior in mechanical properties compared to other resins or rubbers. In particular, it is known that the tear strength of silicone rubber is low. For example, when using an electric wire or cable with silicone rubber as a coating material, silicone rubber will tear immediately when it receives an impact, so it is difficult to use silicone rubber in an environment where it is easily damaged.

[0010] Therefore, in Japanese Industrial Standards, for electric wires using silicone rubber (for example, C3323, C3315), when the tear strength of the silicone rubber as the coating material is 25 kN / m or less, it is stipulated that a reinforcing layer such as a glass fiber braid should be provided outside the silicone rubber.

[0011] Also, EN50264-3-1 (thin cross-linked elastomer insulated single-core cable), which is the European regional standard for electric wires for railway vehicles, and EN50382-2 (120℃ / 150℃ rated silicone rubber insulated single-core cable) have the same rated voltage. However, in EN50382-2, which uses silicone rubber, the mechanical properties (tear strength, tensile strength, and breaking elongation) are ensured by making the insulation layer thicker. In addition, in the case of EN50382-2 with a sheath, the mechanical properties are ensured by making the sheath thicker.

[0012] However, as stipulated by the Japanese Industrial Standards, providing a glass fiber braid as a reinforcing layer requires processing the glass fiber braid when processing the ends of the electric wire, which makes the processing of the ends complicated. Furthermore, short glass fibers that are generated when the glass fiber braid is cut may get mixed into the connection, increasing the insulation resistance of the connection and causing abnormal heat generation.

[0013] Furthermore, even if the thickness of the covering material is increased, as in the case of electric wires for railway vehicles, if the silicone rubber is damaged, the cracks that occur in the silicone rubber will quickly grow regardless of the thickness of the covering material. Therefore, it is difficult to say that these methods are essential solutions.

[0014] The main object of the present application has been made in consideration of the above problems, and is to provide a flame-retardant electric wire which has excellent properties required for a flame-retardant electric wire, such as mechanical properties, oil resistance, cold resistance, heat aging resistance, flexibility, and handleability, and which is provided with a halogen-free insulating layer.

[0015] Other objects and novel features will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0016] The flame-retardant electric wire according to one embodiment has a conductor and a first insulating layer that covers the outer periphery of the conductor and is made of a first resin composition. The first resin composition contains 130 to 180 parts by mass of a flame retardant, 7 parts by mass or more of an antioxidant, and 1 part by mass or more of a copper damage inhibitor with respect to 100 parts by mass of a base polymer. The base polymer consists of an ethylene vinyl acetate copolymer having a vinyl acetate content of 45 to 60% by mass and 50 to 90 parts by mass, and 10 to 50 parts by mass of an ethylene α-olefin copolymer. The flame retardant is surface-treated with a silane coupling agent and consists of magnesium hydroxide and / or aluminum hydroxide having a BET specific surface area of 6 m 2 / g or less. The first resin composition is crosslinked.

Advantages of the Invention

[0017] According to one embodiment, it is possible to provide a flame-retardant electric wire that is excellent in properties required for flame-retardant electric wires such as mechanical properties, oil resistance, cold resistance, heat aging resistance, flexibility, and handleability, and has a halogen-free insulating layer.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0019] Hereinafter, embodiments will be described in detail with reference to the drawings. In all the drawings for explaining the embodiments, members having the same function are denoted by the same reference numerals, and repeated explanations thereof are omitted. In the following embodiments, explanations of the same or similar parts are not repeated in principle unless particularly necessary.

[0020] In the following description, when an expression defining a numerical range such as "1 to 10 parts by mass" is used, "1 to 10 parts by mass" means "1 part by mass or more and 10 parts by mass or less". The same applies to other numerical ranges and other units.

[0021] Hereinafter, the flame-retardant electric wire (flame-retardant cable) 1 in the present embodiment will be described.

[0022] As shown in FIG. 1, the flame-retardant electric wire 1 has a conductor 2 and an insulating layer 3 covering the outer periphery of the conductor 2. The conductor 2 may be a single-strand conductive wire or a stranded wire composed of a plurality of twisted conductive wires. Such a conductive wire is made of a metal material such as copper or a copper alloy. Further, a plating layer made of a metal material such as tin or nickel may be formed on the surface of the conductive wire.

[0023] In the present application, an expression such as "the insulating layer 3 covering the outer periphery of the conductor 2" means that the insulating layer 3 is located around the conductor 2. And the above expression includes the case where the conductor 2 and the insulating layer 3 are in direct contact, and also includes the state where a space or other structure exists between the conductor 2 and the insulating layer 3, and the conductor 2 and the insulating layer 3 are adjacent via the above space or the above other structure.

[0024] The insulating layer 3 is made of a resin composition formed without halogen. The above resin composition uses a polyolefin having better mechanical properties (tear strength, tensile strength, and elongation at break) than silicone rubber as a base polymer. The base polymer has a vinyl acetate content of 45 to 60% by mass and contains 50 to 90 parts by mass of an ethylene vinyl acetate copolymer and 10 to 50 parts by mass of an ethylene α-olefin copolymer.

[0025] The properties of the ethylene-vinyl acetate copolymer vary depending on the amount of vinyl acetate. When the amount of vinyl acetate is high, flexibility and oil resistance are improved, but cold resistance deteriorates, and it is known that handling becomes difficult due to stickiness. For example, when the amount of vinyl acetate is less than 45% by mass, the flexibility and oil resistance of the ethylene-vinyl acetate copolymer deteriorate, and when the amount of vinyl acetate is more than 60% by mass, the cold resistance of the ethylene-vinyl acetate copolymer deteriorates.

[0026] Ethylene-vinyl acetate copolymers with a vinyl acetate content of 45% by mass or more do not have crystals, so as described above, flexibility and oil resistance are improved and cold resistance is maintained, but handling during or after molding becomes difficult due to stickiness. Therefore, by mixing an ethylene-α-olefin copolymer into the ethylene-vinyl acetate copolymer, the difficulty in handling due to stickiness is eliminated.

[0027] On the other hand, when the amount of the ethylene-α-olefin copolymer is less than 10 parts by mass, stickiness is not improved. Also, when the amount of the ethylene-α-olefin copolymer is more than 50 parts by mass, the properties of the entire base polymer deteriorate and oil resistance cannot be satisfied.

[0028] The hardness of the ethylene-α-olefin copolymer is not particularly specified, but in order to obtain flexibility, it is desirable that the durometer A hardness of the ethylene-α-olefin copolymer is 60 or less. Thereby, the durometer A hardness of the flame-retardant wire 1 can be made 80 or less.

[0029] Also, if the ethylene-α-olefin copolymer is a block copolymer and the melting point of the crystals of the ethylene-α-olefin copolymer is 110°C or higher, the oil resistance of the flame-retardant wire 1 can be further improved.

[0030] Moreover, by introducing or grafting an organic acid such as maleic acid, maleic anhydride, fumaric acid, or carboxylic acid to a part of the ethylene-α-olefin copolymer at the end of the base polymer, the mechanical properties and cold resistance of the flame-retardant wire 1 can be improved.

[0031] Also, when the ethylene α-olefin copolymer is an acid-modified ethylene α-olefin copolymer obtained by copolymerizing an organic acid such as maleic acid, maleic anhydride, fumaric acid or carboxylic acid, the mechanical properties and cold resistance of the flame-retardant wire 1 can be improved.

[0032] 130 to 180 parts by mass of a flame retardant is added to 100 parts by mass of the base polymer. Thereby, a high flame retardancy that passes the vertical tray flame retardancy test defined in IEEE1202 or IEC60332 can be imparted to the flame-retardant wire 1. Further, in order to impart oil resistance to the flame-retardant wire 1, it is effective to perform surface treatment with a silane coupling agent. By strongly bonding the particles of the flame retardant and the base polymer with the silane coupling agent, the oil absorption amount of the resin composition can be reduced, and oil resistance can be imparted to the flame-retardant wire 1.

[0033] The flame retardant is, for example, magnesium hydroxide and / or aluminum hydroxide surface-treated with a silane coupling agent. When the amount of the flame retardant is less than 130 parts by mass, the flame retardancy deteriorates, and when the amount of the flame retardant is more than 180 parts by mass, the mechanical properties, flexibility and cold resistance deteriorate.

[0034] The type of the silane coupling agent is not particularly defined. However, when crosslinking is performed using ionizing radiation or an organic peroxide, in order to facilitate bonding with the base polymer, the functional group of the silane coupling agent is preferably, for example, a vinyl group, a methacrylic group or an acryloyl group.

[0035] The variation in oil resistance in the flame-retardant wire 1 is often caused by the swelling of the resin composition due to oil absorption and the accompanying mechanical properties (tensile strength and elongation at break) of the resin composition. In the resin composition of the present application, the elongation at break may decrease after the oil resistance test. Regarding swelling and tensile strength, a treatment is performed to minimize oil absorption into the resin composition, but regarding the decrease in elongation at break, other treatments are required.

[0036] Regarding the decrease in elongation at break in oil resistance, the inventors of the present application focused on the BET specific surface area of the flame retardant (magnesium hydroxide and / or aluminum hydroxide surface-treated with a silane coupling agent). Although the exact reason cannot be asserted, it was found that by using a flame retardant with a BET specific surface area of 6 m 2 / g or less, the decrease in elongation at break can be suppressed.

[0037] The BET specific surface area described here is measured by the nitrogen gas adsorption method in which the specific surface area is calculated using the BET equation from the isothermal absorption curve of nitrogen gas at liquid nitrogen temperature (77 K). The BET equation was proposed by S. Brunauer, P. H. Emmett, E. Teller, etc., and is represented by the following "Equation 1". Vm is the volume of gas adsorbed in the first layer, V is the volume of adsorbed gas, P is the pressure in the sample cell, and P 0 is the saturated vapor pressure.

[0038] P / V(P 0 -P)=(1 / VmC)+((C - 1) / VmC)×P / P 0 Equation 1

[0039] This "Equation 1" is applied in the range where P / P 0 is 0.05 to 0.35. When P / P 0 is taken on the horizontal axis and P / V(P 0 -P) is taken on the vertical axis and plotted, a straight line is obtained. Vm is obtained from the intercept and slope of this straight line. And the BET specific surface area is obtained by the following "Equation 2". SA is the surface area of the sample, Vm is the volume of gas adsorbed in the first layer, N is Avogadro's constant, and Am is the area occupied by one molecule of nitrogen gas (0.162 nm 2 ).

[0040] SA = Vm×N×Am Equation 2

[0041] The lower limit of the BET specific surface area is not particularly defined. However, the average particle diameter of the flame retardant particles correlated with the BET specific surface area (the average particle diameter of magnesium hydroxide and / or aluminum hydroxide particles surface-treated with a silane coupling agent) is preferably about 1 to 2 μm. When the average particle diameter is less than 1 μm, the dispersibility deteriorates, the particles aggregate, the processability deteriorates, and the elongation at break decreases. When the average particle diameter is greater than 2 μm, the cold resistance deteriorates and the elongation at break decreases.

[0042] The use of the flame-retardant electric wire 1 in this embodiment assumes a case where a high heat aging resistance with a rated temperature of 120°C or higher is required. Therefore, the resin composition constituting the insulating layer 3 preferably retains 50% of the elongation at break after a heat aging test equivalent to 20,000 hours at 140°C in the long-term heat aging test defined in EN50305.

[0043] In order to impart a high heat aging resistance comparable to silicone rubber to the flame-retardant electric wire 1, an antioxidant of 7 parts by mass or more is added to the resin composition per 100 parts by mass of the base polymer. The antioxidant is preferably a phenolic antioxidant or a sulfur-based antioxidant, or a mixture thereof.

[0044] When the antioxidant is less than 7 parts by mass, it is not possible to retain 50% of the elongation at break after a heat aging test equivalent to 20,000 hours at 140°C. The upper limit of the addition amount of the antioxidant is not particularly defined. However, when the antioxidant is more than 10 parts by mass, crosslinking inhibition occurs when crosslinking is performed using ionizing radiation or an organic peroxide, and the bled-out antioxidant may damage the appearance of the flame-retardant electric wire 1. Therefore, when crosslinking the resin composition, it is most preferable to add 7 to 10 parts by mass of the antioxidant to the resin composition per 100 parts by mass of the base polymer.

[0045] In order to further improve the heat aging resistance of the flame-retardant wire 1, a copper corrosion inhibitor in an amount of 1 part by mass or more is added to 100 parts by mass of the base polymer in the resin composition. The copper corrosion inhibitor is preferably bis(dodecanedioic acid) (for example, CDA-6 [N2-(2-hydroxybenzoyl)hydrazide] manufactured by ADEKA Corporation), or bis(isophthalic acid) (for example, Curenox AX [2-phenoxypropionylhydrazide] manufactured by Mitsui Chemicals Fine Chemicals Co., Ltd.), or a mixture thereof.

[0046] By using such a copper corrosion inhibitor, copper ions migrating from the conductor 2 can be captured, and deterioration of the conductor 2 due to oxidation can be suppressed. In order to capture metal ions contained as impurities in the antioxidant, it is also necessary to add a copper corrosion inhibitor to the resin composition. The upper limit of the addition amount of the copper corrosion inhibitor is not particularly defined. However, since the copper corrosion inhibitor is expensive, it is preferable that the addition amount of the copper corrosion inhibitor be as small as possible.

[0047] The resin composition is preferably crosslinked in order to prevent deformation due to heating and improve mechanical properties. The crosslinking agent and the crosslinking method are not particularly limited, but peroxide crosslinking using an organic peroxide crosslinking agent, radiation crosslinking using ionizing radiation, or silane hydrosilylation crosslinking in which a silane coupling agent is grafted onto the base polymer with an organic peroxide and crosslinked by hydrothermal treatment is preferable. In particular, peroxide crosslinking and radiation crosslinking are most preferable.

[0048] If necessary, additives such as a lubricant, a flame retardant aid, a crosslinking agent, a crosslinking aid, a crosslinking accelerator, a surfactant, a compatibilizer, an ultraviolet absorber, or a hindered amine light stabilizer (HALS) can be appropriately added to the resin composition. In particular, when high flame retardancy is required, a phosphorus-based flame retardant typified by, for example, red phosphorus, a phosphate ester derivative, an intumescent flame retardant; a nitrogen-based flame retardant typified by a melamine cyanurate derivative mixture; a polyhydric phenol compound such as catechol or a gallic acid derivative; or a silicone-based flame retardant is preferably added to the resin composition as a flame retardant aid.

[0049] (Modification example) FIG. 2 shows a flame-retardant electric wire 1 in a modified example of the present embodiment.

[0050] In the modified example, as shown in FIG. 2, the insulating layer 3 is composed of a plurality of layers. In FIG. 2, the outermost first insulating layer 3a and the second insulating layer 3b provided between the first insulating layer 3a and the conductor 2 are shown, but the insulating layer 3 may be composed of three or more layers.

[0051] The outermost first insulating layer 3a is made of the same resin composition as the insulating layer 3 described in the embodiment. The inner second insulating layer 3b may be composed of the same composition as the resin composition of the first insulating layer 3a, or may be composed of a composition different from the resin composition of the first insulating layer 3a, such as a flame-retardant silicone rubber or a polyolefin-based composition with high electrical insulation.

[0052] That is, assuming that the flame-retardant electric wire 1 is exposed to a harsh external environment, it is preferable that the first insulating layer 3a, which is excellent in properties such as mechanical properties, oil resistance, cold resistance, and heat aging resistance, is provided on the outermost periphery. Thus, among the plurality of layers of insulating layers, the above resin composition is applied to at least the outermost first insulating layer 3a.

[0053] (Example) Hereinafter, with reference to FIGS. 3 and 4, Examples 1 to 9 and Comparative Examples 1 to 11 of the flame-retardant electric wire 1 will be described, and with reference to FIG. 5, the pass / fail determination thereof will be described.

[0054] As shown in FIG. 3, in Examples 1 to 9, the compounding ratios of the respective compounding agents for forming the insulating layer 3 (resin composition) are assigned so as to fall within the following numerical ranges. Amount of vinyl acetate: 45 to 60% by mass Ethylene-vinyl acetate copolymer: 50 to 90 parts by mass Ethylene-α-olefin copolymer: 10 to 50 parts by mass Magnesium hydroxide (flame retardant): 130 to 180 parts by mass Antioxidant: 7 parts by mass or more Copper corrosion inhibitor: 1 part by mass or more

[0055] On the other hand, as shown in FIG. 4, in Comparative Examples 1 to 11, at least one of the compounding ratios of the respective compounding agents for forming the insulating layer 3 (resin composition) is assigned to be outside the above numerical range. Regarding the compounding ratios of carbon, crosslinking assistant, and crosslinking agent, they are equally assigned in Examples 1 to 9 and Comparative Examples 1 to 11.

[0056] First, each compounding agent is weighed according to the compounding ratios shown in FIGS. 3 and 4, and these are kneaded by a 75L pressure kneader to form a kneaded product. Next, the kneaded product is extruded into strands, and after the extruded kneaded product is cooled, the cooled kneaded product is processed into pellets.

[0057] Next, a predetermined amount of liquid crosslinking agent heated to 40°C is prepared. Next, the pelletized kneaded product and the crosslinking agent are stirred by a blender, and the pelletized kneaded product is impregnated with the crosslinking agent to form a pelletized resin composition.

[0058] Next, the conductor 2 is prepared. The conductor 2 may be a single-strand conductive wire or a stranded wire formed by twisting a plurality of conductive wires. Such a conductive wire is made of a metal material such as copper or a copper alloy. Further, if necessary, a plating layer made of a metal material such as tin or nickel may be formed on the surface of the conductive wire. The cross-sectional area of the conductor 2 formed in this way is, for example, 70 mm 2 and the outer diameter of the conductor 2 (the diameter of the outer periphery of the conductor 2) is, for example, 11 mm.

[0059] Next, in order to prevent the resin composition from penetrating into the conductor 2, a film tape made of polyethylene terephthalate is wound around the outer periphery of the conductor 2. The thickness of the film tape is, for example, 0.15 mm. In FIG. 1, the illustration of the film tape is omitted. Next, using an extruder, the outer periphery of the conductor 2 is coated with the resin composition via the film tape so that the thickness of the resin composition becomes, for example, 3.6 mm.

[0060] Next, with the internal pressure set at 1.8 MPaG, the resin composition is heated in a chamber filled with saturated steam for, for example, 5 minutes. As a result, the resin composition is crosslinked, and the flame-retardant electric wire 1 shown in FIG. 1 is formed. The outer diameter of the flame-retardant electric wire 1 (the diameter of the outer circumference of the flame-retardant electric wire 1) is, for example, 18.5 mm.

[0061] The evaluation items of the flame-retardant electric wire 1 and the evaluation methods thereof will be described below.

[0062] <Initial Tensile Test> First, the conductor 2 was removed, and the insulation layer 3 was separated from the conductor 2 to disassemble the flame-retardant electric wire 1. Next, the insulation layer 3 was ground so that the inner peripheral side thereof was smooth, and the thickness of the insulation layer 3 was adjusted to approximately 1 mm. Next, the ground insulation layer 3 was punched into a dumbbell shape shown in IEC60811-1-1 to obtain a test sample. The sample was pulled at a speed of 250 mm / min by a tensile testing machine, and the tensile strength and elongation at break were measured.

[0063] <Oil Resistance> An oil resistance test was carried out in accordance with item 10 of EN60811-2-1. First, a dumbbell-shaped sample was prepared in the same manner as in the initial tensile test, and the sample was immersed in IRM903 oil at 70°C for 168 hours. Next, the sample was pulled at a speed of 250 mm / min by a tensile testing machine, and the tensile strength and elongation at break were measured. Next, the change rate between the results of the initial tensile test and the results of the oil resistance test was calculated. Samples with a change rate of within ±30% for the tensile strength and within ±40% for the elongation at break were considered qualified.

[0064] <Measurement of Durometer A Hardness> A type A durometer specified in JIS K6253-3 is pressed against the produced flame-retardant electric wire 1, and after 3 seconds, the durometer A hardness is measured by the durometer. The flame-retardant electric wire 1 with a durometer A hardness of 80 or less was considered qualified.

[0065] <Cold Resistance at -50°C> In accordance with item 8.3 of EN60811-1-4, a cold resistance test was carried out. First, dumbbell-shaped samples were prepared in the same manner as the initial tensile test, and the samples were cooled at minus 50 °C for 4 hours or more. Next, using a tensile testing machine, the samples were pulled at a speed of 25 mm / min at minus 50 °C, and samples with an elongation at break of 30% or more were considered qualified.

[0066] <Heat resistance aging at 140 °C> Dumbbell-shaped samples were prepared in the same manner as the initial tensile test, and a long-term heat resistance aging test was carried out on the samples by the method specified in item 7.3 of EN50305. After the heat resistance aging test, an Arrhenius plot was obtained at the time when the elongation at break reached 50%. By extrapolating the plot, samples that reached 20,000 hours or more at 140 °C after the heat resistance aging test were considered qualified. That is, samples that maintained an elongation at break of 50% after a heat aging test equivalent to 20,000 hours at 140 °C were considered qualified.

[0067] <Flammability> For the prepared flame-retardant wire 1, a vertical tray combustion test in accordance with IEC60332-3 was carried out to determine the pass or fail of the flame-retardant wire 1.

[0068] <Stickiness> The operator palpated the prepared flame-retardant wire 1, and the flame-retardant wire 1 that was clearly judged to be sticky was considered unqualified.

[0069] As described above, a comprehensive judgment was made on the evaluation items related to oil resistance, durometer A hardness, cold resistance at minus 50 °C, heat resistance aging at 140 °C, flammability, and stickiness. Those that passed all the evaluation items were considered qualified.

[0070] As shown in Fig. 5, all of the flame-retardant electric wires 1 of Examples 1 to 9 passed the comprehensive judgment. On the other hand, all of the flame-retardant electric wires 1 of Comparative Examples 1 to 11 failed in some evaluation items, so they failed the comprehensive judgment. Therefore, it was found that the flame-retardant electric wire 1 of the present embodiment not only has a halogen-free insulating layer 3, but also is excellent in the characteristics required for the flame-retardant electric wire 1 such as mechanical properties, oil resistance, cold resistance, heat aging resistance, flexibility and handleability.

[0071] As described above, the present invention has been specifically described based on the above embodiments. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist thereof.

Explanation of Reference Numerals

[0072] 1 Flame-retardant electric wire 2 Conductor 3 Insulating layer 3a First insulating layer 3b Second insulating layer

Claims

1. A conductor, a first insulating layer covering the outer periphery of the conductor and made of a first resin composition, and having, the first resin composition contains 130 to 180 parts by mass of a flame retardant, 7 parts by mass or more of an antioxidant, and 1 part by mass or more of a copper damage inhibitor with respect to 100 parts by mass of a base polymer, the base polymer has a vinyl acetate content of 45 to 60% by mass and consists of 50 to 90 parts by mass of an ethylene vinyl acetate copolymer and 10 to 50 parts by mass of an ethylene α-olefin copolymer, The flame retardant is composed of magnesium hydroxide and / or aluminum hydroxide which is surface-treated with a silane coupling agent and has a BET specific surface area of 6 m ２ / g or less. the ethylene α-olefin copolymer is an acid-modified ethylene α-olefin copolymer obtained by copolymerizing maleic acid, maleic anhydride, fumaric acid or a carboxylic acid, the first resin composition is crosslinked, a flame-retardant electric wire.

2. In the flame-retardant electric wire according to Claim 1, the ethylene α-olefin copolymer is a block copolymer, and the melting point of the crystals of the ethylene α-olefin copolymer is 110°C or higher, a flame-retardant electric wire.

3. In the flame-retardant electric wire according to Claim 1, the average particle diameter of the particles of the flame retardant is 1 μm or more and 2 μm or less, a flame-retardant electric wire.

4. In the flame-retardant electric wire according to Claim 1, a second insulating layer is provided between the first insulating layer and the conductor, and the second insulating layer is composed of the same composition as the first resin composition or a composition different from the first resin composition, a flame-retardant electric wire.

5. In the flame-retardant electric wire according to Claim 1, the durometer A hardness of the flame-retardant electric wire is 80 or less, a flame-retardant electric wire.

6. In the flame-retardant electric wire according to Claim 1, the first insulating layer retains 50% of the elongation at break after a heat aging test equivalent to 20,000 hours at 140°C in the long-term heat aging test specified in EN50305, a flame-retardant electric wire.

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