JP5811359B2 - Halogen-free flame-retardant resin composition and cable using the same - Google Patents

Description

  The present invention relates to a halogen-free flame retardant resin composition and a cable using the same. More specifically, the present invention relates to a halogen-free resin composition that is excellent in flame retardancy, oil resistance / fuel resistance, and low temperature characteristics, and can be used for a railway vehicle, and has a low toxicity in combustion gas, and a cable using the same. .

  Examples of moving cables used in railway vehicle cables and cranes include chloroprene rubber blends and chlorosulfonated polyethylene that are balanced in oil and fuel resistance, low temperature characteristics, flame resistance, flexibility, and cost. Halogen-based rubber blends such as blends, chlorinated polyethylene blends, and fluororubber blends are used (see, for example, Patent Document 1). However, these halogen-containing substances generate a large amount of toxic and harmful gases during combustion, and generate extremely toxic dioxins depending on the incineration conditions. For this reason, cables using a halogen-free material that does not contain a halogen substance as a covering material have become widespread from the viewpoint of safety at the time of fire and reduction of environmental burden. However, the halogen-free material has a problem that it is inferior in oil resistance / fuel resistance and flame retardancy due to the difference in chemical structure of the base polymer as compared with a conventional halogen-containing material.

  In particular, cables used for railway vehicles have the risk of leading to major accidents due to their malfunctions. Therefore, the standards (EN50264, etc.), high flame resistance, oil / fuel resistance, low temperature at -40 ° C There is a need to use halogen-free materials with properties.

  In order to increase the flame retardancy of halogen-free materials, make the side chain of the base polymer have a structure that generates incombustible gas during combustion, or add halogen-free flame retardants such as metal hydroxides and nitrogen compounds. Can be mentioned. However, having a structure that generates incombustible gas in the side chain of the base polymer leads to an increase in the polarity of the base polymer, deteriorating the low temperature characteristics, and it is necessary to add a large amount when adding a halogen-free flame retardant. There is a problem that flexibility and other mechanical properties are greatly reduced.

  Oil resistance and fuel resistance can be improved by increasing the crystallinity of the base polymer, increasing the polarity of the base polymer, or increasing the degree of crosslinking of the base polymer. A material in which the crystallinity of the base polymer is increased is inferior in flexibility and has poor wiring properties. In addition, a material with increased crystallinity and poor flexibility has a risk of cracking due to adhesion of chemicals or vibration. A highly polar base polymer is excellent in flexibility but has a problem that it is inferior in low-temperature characteristics as described above.

  Therefore, it is conceivable to increase the degree of crosslinking of the base polymer. As a method of crosslinking the polyolefin material described above, for example, generally, vulcanization with sulfur, peroxide crosslinking using an organic peroxide, electron beam crosslinking using an electron beam, a silane coupling agent is previously added to a base polymer. Examples thereof include silane water crosslinking which is grafted and crosslinked by dehydration condensation.

  In the case of vulcanization with sulfur, only a diene polymer having a double bond in the base polymer main chain or a polymer intentionally copolymerized with a diene component such as EPDM is possible. However, a diene polymer having a double bond in the main chain is inferior in heat resistance, and EPDM is inferior in oil resistance and fuel resistance. In addition, the S—S bond that becomes a cross-linked chain also has a problem that the bond is weak and heat resistance is poor.

  In the case of electron beam crosslinking, a thick material with a large outer diameter has a problem that crosslinking is insufficient because the electron beam does not reach the inside.

  In the case of silane crosslinking, it is necessary to crosslink by contacting with warm water or water vapor and air. Since a relatively long period of cross-linking is required, it is necessary to wind the cable once. For this reason, a soft base polymer that is deformed before crosslinking cannot be used. Therefore, a hard base polymer with high crystallinity (a base polymer with high green strength) is used. However, since the base polymer becomes hard, a cable having a large outer diameter is inferior in flexibility. Further, when a high amount of a flame retardant such as a metal hydroxide is filled in order to ensure flame retardancy, there is a problem that workability is deteriorated, scorching is likely to occur, and molding becomes difficult.

Peroxide crosslinking with less restrictions on materials is promising, but when peroxide crosslinking is performed, it is necessary to increase the temperature to a level at which the peroxide can be decomposed without oxygen and to perform crosslinking. As the heat source, saturated steam that is excellent in heat transfer efficiency and can realize an oxygen-free state is used. Since saturated steam has a unique temperature and pressure, the pressure increases as the temperature increases. When the sheath material of a cable having a plurality of cores (a plurality of electric wires) is crosslinked, the insulator is deformed by the pressure of the steam, so that the crosslinking temperature cannot be increased. Also, when a cable with a large outer diameter is cross-linked, it is difficult to cross-link at the same time as extrusion molding. Therefore, a metal or a hard resin (for example, polymethylpentene) having a high melting point is coated on the outside of the coating and wound around a drum. Put in a pot and crosslink.
Also in this case, since the kettle becomes quite large, it is difficult to raise the above temperature for safety.

  Generally, the crosslinking temperature of peroxide crosslinking is determined with reference to the half-life temperature of the organic peroxide. In general, an organic peroxide cross-linking agent having a high half-life temperature has a high cross-linking efficiency, and a composition having a high cross-linking density can be obtained. On the other hand, peroxide crosslinking agents with a low half-life temperature often have low crosslinking efficiency. When the crosslinking temperature cannot be raised, a crosslinking aid such as triallyl isocyanurate can be added to increase the crosslinking density in order to obtain a composition having a high crosslinking density by organic peroxide crosslinking.

JP 2011-144286 A

  However, in the case of a cable having a plurality of cores and a cable having a large outer diameter, a crosslinking aid described later is added to increase the crosslinking density, but a crosslinking aid effective for increasing the crosslinking density contains nitrogen. Even if the crosslink density can be increased to improve oil resistance and fuel resistance, burning the composition may generate harmful gases such as NOx and cyanide compounds. is there.

  The present invention has been made in view of the above-described problems. In particular, the present invention is excellent in flame retardancy, oil resistance / fuel resistance, and low-temperature characteristics that can be used for railway vehicles, and combustion gas has low toxicity. An object is to provide a halogen-free flame-retardant resin composition and a cable using the same.

  In order to achieve the above object, the present invention, etc., has conducted extensive research focusing on organic peroxide cross-linking agents having different half-life temperatures and cross-linking efficiencies. As a result, a predetermined cross-linking efficiency ( %)) Was blended and crosslinked by heating to find that the desired halogen-free flame retardant resin composition was obtained, and the present invention was completed. That is, according to the present invention, the following halogen-free flame-retardant resin composition and a cable using the same are provided.

[1] A base polymer containing an ethylene-vinyl acetate copolymer having a vinyl acetate amount of 40% by mass or more alone or in a mixture with one or more other polyolefins, and 130 parts by mass with respect to 100 parts by mass of the base polymer. The crosslinking efficiency represented by the following formula (1) obtained by crosslinking for 45 minutes with a metal hydroxide compounded at a ratio of ˜220 parts by mass and saturated steam with a saturated steam pressure of 0.4 MPa (145 ° C.) is 39% or more. It contains an organic peroxide, a, and Ri Na is crosslinked by heating, the organic peroxide, t- butyl peroxy-2-ethylhexyl carbonate, or t- butyl halogen-free is peroxybenzoate flame retardant Resin composition.
Cross-linking efficiency (%) = [amount of n-pentadecane dimer (mol) / amount of organic peroxide (mol)] × 100 (1)

[ 2 ] The halogen-free flame-retardant resin composition according to [1 ], which is crosslinked at a crosslinking temperature of 140 to 160 ° C.

[ 3 ] An electric wire having a conductor and an insulator formed on the outer periphery of the conductor, and the halogen-free flame retardancy according to any one of [1] or [2] formed on the outer periphery of the insulator of the electric wire And a sheath made of a resin composition.

[ 4 ] The cable according to [ 3 ], wherein the sheath is formed on an outer periphery of two or more electric wires.

[ 5 ] The cable according to [ 4 ], which has an outer diameter of 12.5 mm or more.

  According to the present invention, a halogen-free flame-retardant resin composition having excellent flame retardancy, oil resistance / fuel resistance, and low-temperature characteristics, particularly low-toxicity for combustion gas, and the like, which can be used for railway vehicles, and the like A cable using can be provided.

It is sectional drawing which shows typically the cable which concerns on embodiment of this invention.

[Summary of embodiment]
The halogen-free flame retardant resin composition of the present embodiment contains a base polymer, a flame retardant, and a crosslinking agent. In the crosslinked halogen-free flame retardant resin composition, the vinyl acetate content is 40% by mass or more. Metallic water blended in a proportion of 130 to 220 parts by mass with respect to 100 parts by mass of the base polymer containing the ethylene-vinyl acetate copolymer alone or in a mixture with one or more other polyolefins Containing an oxide and an organic peroxide having a crosslinking efficiency of 39% or more represented by the following formula (1) crosslinked with saturated water vapor at a saturated water vapor pressure of 0.4 MPa (145 ° C.) for 45 minutes , and heated Ri Na being crosslinked by the organic peroxide, a halogen-free flame is t- butyl peroxy-2-ethylhexyl carbonate, or t- butyl peroxybenzoate RESIN composition.

  Cross-linking efficiency (%) = [amount of n-pentadecane dimer (mol) / amount of organic peroxide (mol)] × 100 (1)

  The above formula (1) shows that the amount of n-pentadecane dimer generated (mol) relative to the amount of organic peroxide used (mol) when the organic peroxide was completely decomposed at 15 minutes half-life temperature in n-pentadecane. ) Is shown as a percentage.

  The cable according to the present embodiment includes a conductor and an electric wire having an insulator formed on the outer periphery of the conductor, and the halogen-free flame-retardant resin composition described above formed on the outer periphery of the insulator of the electric wire. And a sheath which is made.

[Embodiment]
1. Halogen-free flame-retardant resin composition The halogen-free flame-retardant resin composition according to the present embodiment is an ethylene-vinyl acetate copolymer having a vinyl acetate content of 40% by mass or more, or one or more other types. Base polymer contained in a mixture with polyolefin, metal hydroxide blended at a ratio of 130 to 220 parts by mass with respect to 100 parts by mass of the base polymer, and saturated water vapor with a saturated water vapor pressure of 0.4 MPa (145 ° C.) in cross-linking efficiency shown in 45 minutes crosslinked allowed the following equation (1) contains an organic peroxide is 39% or more, and Ri Na is crosslinked by heating, the organic peroxide, t- butyl Peroxy-2-ethylhexyl carbonate or t-butyl peroxybenzoate .

  Cross-linking efficiency (%) = [amount of n-pentadecane dimer (mol) / amount of organic peroxide (mol)] × 100 (1)

  The above formula (1) shows that the amount of n-pentadecane dimer generated (mol) relative to the amount of organic peroxide used (mol) when the organic peroxide was completely decomposed at 15 minutes half-life temperature in n-pentadecane. ) Is shown as a percentage.

(1) Base polymer The base polymer used in the present embodiment includes an ethylene-vinyl acetate copolymer having a vinyl acetate content of 40% by mass or more alone or in a mixture with one or more other polyolefins.

  The vinyl acetate (VA) content of the ethylene-vinyl acetate copolymer (EVA) in the present embodiment means the vinyl acetate content defined in JIS K 7192.

  The reason why EVA having a VA amount of 40% by mass or more is adopted as the base polymer is to make the material balanced in flame retardancy, flexibility, oil resistance / fuel resistance.

  The oil resistance in the present embodiment refers to ASTM No. 2 refers to resistance to oil, and fuel resistance refers to ASTM No. 3 means resistance to oil. Since these are all mineral oils and have low polarity, they swell the base polymer with low polarity. In order to prevent swelling, it is preferable to use a highly polar base polymer. In particular, in order to satisfy the high fuel resistance as defined in EN50264, the EVA VA content is preferably 60% or more. On the other hand, when the VA amount is less than 40% by mass, crystallinity appears in the base polymer, so that the flexibility is poor and the polarity is low, so that satisfactory oil resistance and fuel resistance cannot be obtained.

  If necessary, it can be mixed with one or more other polyolefins. Examples of other polyolefins include polyolefins modified with maleic anhydride and ethylene-α-olefins. In particular, by mixing polyolefin modified with maleic anhydride, the adhesion with the flame retardant to be added can be improved and the low temperature characteristics can be improved.

(2) Metal hydroxide In this embodiment, in addition to the above-mentioned base polymer, a metal hydroxide is blended as a flame retardant at a ratio of 130 to 220 parts by mass with respect to 100 parts by mass of the base polymer. Is done.

  EVA with a large amount of VA has flame retardancy in itself, but does not have flame retardance that can be used for railway vehicles. In order to provide flame retardancy that satisfies EN 50264, it is necessary to add a metal hydroxide as a flame retardant.

  If the compounding amount of the metal hydroxide is less than 130 parts by mass with respect to 100 parts by mass of the base polymer, high flame retardancy cannot be obtained, and the amount of carbon monoxide generated during combustion increases. not appropriate. By adding an inorganic filler such as a metal hydroxide to some extent, the amount of carbon in the entire composition is reduced, so that the amount of carbon monoxide generated during combustion is also reduced. If it exceeds 220 parts by mass, mechanical properties such as elongation at break and tensile strength are remarkably deteriorated, and the interface between the base polymer and the particles is increased, so that the low temperature properties are also deteriorated.

  In order to obtain high flame retardancy, the metal hydroxide is preferably magnesium hydroxide and / or aluminum hydroxide whose dehydration temperature is close to the decomposition temperature of the base polymer, and is surface-treated with a fatty acid or an organosilane. It is more preferable because the adhesion between the base polymer particles is reinforced and the oil resistance / fuel resistance and low temperature characteristics can be improved. In particular, organosilane coupling agent surface-treated aluminum hydroxide is particularly preferable from the viewpoint of oil resistance and fuel resistance.

(3) Organic peroxide In the present embodiment, an organic peroxide is blended in addition to the above-described base polymer and metal hydroxide.

  This organic peroxide is produced by the above-described crosslinking efficiency (the n-type produced with respect to the amount (mole) of organic peroxide used when the organic peroxide is completely decomposed in n-pentadecane at a half-life temperature of 15 minutes. The ratio of the amount of pentadecane dimer (mol) expressed in percentage) is 39% or more, and is used for performing peroxide crosslinking by heating described later.

The organic peroxide used in the present embodiment, t - butyl peroxy-2-ethylhexyl carbonate, using t- butyl peroxybenzoate Agent bets.

  In the present embodiment, the crosslinking efficiency represents hydrogen abstraction ability from the base polymer, and the higher the crosslinking efficiency, the more easily radicals are generated in the base polymer. If the crosslinking efficiency is less than 39%, crosslinking is insufficient.

  The amount of organic peroxide is generally determined based on the theoretical active oxygen amount. In the case of this embodiment, the blending amount of the organic peroxide crosslinking agent is not particularly limited, but is preferably 1 to 5 parts by mass in consideration of characteristics and scorch.

(4) Crosslinking by heating The halogen-free flame retardant resin composition according to the present embodiment is obtained by crosslinking a compound containing the above-mentioned base polymer, metal hydroxide and organic peroxide by heating. is there.

  As described above, the selection of the organic peroxide is often determined by the crosslinking temperature. In general, ± 15 ° C. of the 1 minute half-life temperature of the organic peroxide is preferred. In the present embodiment, it is preferably crosslinked at a crosslinking temperature of 140 to 160 ° C.

  The halogen-free flame retardant resin composition obtained in the present embodiment can provide a halogen-free cable that can satisfy the cable standard (EN50264).

  In particular, the cable defined in EN50264-3-2 is suitable for a sheath material having a plurality of cores. As described above, in the case of having a plurality of wire cores, the insulator is deformed by pressure when crosslinked with high-temperature steam. For this reason, it is preferable to crosslink at 160 ° C. or lower. Moreover, it is not preferable to perform crosslinking at less than 140 ° C. because the crosslinking time becomes enormous. An organic peroxide having a too low half-life temperature is likely to be scorched, so that the crosslinking temperature is preferably from 140 ° C to 160 ° C.

  The crosslinking time is preferably within 1 hour at the longest in terms of production efficiency.

  When the crosslinking temperature is relatively low at 140 to 160 ° C., the organic peroxide that can be selected from the half-life temperature of the organic peroxide is limited, and as a whole, the crosslinking agent used in that temperature range is a sufficient theory. Although it is the amount of active oxygen, the crosslinking efficiency is low. Although it is conceivable to increase the blending amount in order to increase the crosslinking density by using an organic peroxide having a low crosslinking efficiency, even if the blending amount was increased, a great effect could not be obtained. Furthermore, there is a problem that increasing the amount of the crosslinking agent tends to cause scorch.

  Therefore, although the half-life temperature is somewhat different from the crosslinking temperature, an organic peroxide having a high crosslinking efficiency was added to crosslink the composition. The organic peroxide cross-linking agent with the same amount of theoretical active oxygen at the same cross-linking temperature and cross-linking time was blended, but organic cross-linking agents with low half-life temperature and low cross-linking efficiency were used. Compared to the reacted composition, the use of an organic peroxide having a high crosslinking efficiency results in a composition having a higher crosslinking density, although the half-life temperature is high and the crosslinking agent has not reacted. It turns out that it is obtained.

  This makes it possible to obtain a composition having a high crosslinking density without using a crosslinking aid that generates harmful gases, and has excellent non-halogen flame resistance with low toxicity during combustion and excellent oil and fuel resistance. A resin composition can be obtained.

(5) Other additives In addition, the halogen-free flame retardant resin composition according to the present embodiment includes an antioxidant, a silane coupling agent, a flame retardant / a flame retardant auxiliary (for example, hydroxytin) as necessary. Phosphate flame retardants such as acid salts, calcium borate, ammonium polyphosphate, red phosphorus, and phosphate esters, silicone flame retardants such as polysiloxane, nitrogen flame retardants such as melamine cyanurate and cyanuric acid derivatives, zinc borate Boric acid compounds, molybdenum compounds, etc.), lubricants, surfactants, softeners, plasticizers, inorganic fillers, carbon black, compatibilizers, stabilizers, metal chelators, UV absorbers, light stabilizers, coloring It is preferable to add an additive such as an agent.

2. As shown in FIG. 1, the cable according to the present embodiment includes a copper conductor 1 (in FIG. 1, a case where a copper conductor (specifically, a tin-plated copper conductor) 1 is used as a conductor) is shown. And an electric wire having an insulator 3 formed on the outer periphery of the copper conductor 1 via the PET tape 2 (in FIG. 1, a case where three electric wires are twisted together), a PET tape 4 and a metal braid 5 are And a sheath 6 made of the above-described halogen-free flame-retardant resin composition formed on the outer periphery of the insulator 3 of the three electric wires.

  The cable of the present embodiment can exert its effect particularly when the sheath is formed on the outer periphery of two or more electric wires (having a large outer diameter).

  In addition, the cable of the present embodiment can exert its effect particularly when it has an outer diameter of 12.5 mm or more (thick outer diameter).

  As a material of the insulator 3 used in the present embodiment, a resin composition generally used for a halogen-free cable can be used, and an engineering plastic may be used if it is halogen-free. In particular, if electrical characteristics are important, polyolefins such as ethylene-α-olefin copolymer, HDPE, LDPE, LLDPE, VLDPE, EPDM, EVA, EEA, EMA are used as the base polymer, and inorganic fillers such as talc and clay If the flame retardancy is important, a mixture of the above-mentioned polyolefin and a halogen-free flame retardant such as a metal hydroxide is preferable.

  The copper conductor 1, the PET tape 2, the PET tape 4, and the metal braid 5 are not particularly limited, and general-purpose materials and general-purpose forming methods can be used.

  Hereinafter, the halogen-free flame-retardant resin composition of the present invention and a cable using the same will be described more specifically with reference to examples. Note that the present invention is not limited in any way by the following examples.

(Example 1)
As shown in Table 1, 40 parts by mass of an ethylene-α-olefin copolymer (manufactured by Mitsui Chemicals, trade name: Toughma A4070), EVA1 (manufactured by Mitsui DuPont Polychemicals, trade name: EV45X) : VA amount 46%) 60 parts by mass, magnesium hydroxide (manufactured by Kamishima Chemical Co., Ltd., trade name: Magsees S4) 180 parts by mass, composite antioxidant (made by ADEKA, trade name: AO-18) 3 parts by mass, and A blend of 2 parts by mass of a cross-linking agent 1 (manufactured by NOF Corporation, trade name: Perbutyl P) was used.

  Moreover, what was mix | blended as shown in Table 2 as a material of the sheath of a cable (as the halogen-free flame-retardant resin composition of this invention) was used. That is, EVA2 (product name: YX-21: VA amount 41%) 100 parts by mass as a base polymer, magnesium hydroxide (product name: Magseeds S4, manufactured by Kamishima Chemical Co.) 180 as a metal hydroxide. 1 part by mass of a phenolic antioxidant (manufactured by BASF, trade name: Irganox 1010) and 2 parts by weight of a composite antioxidant (trade name: AO-18, manufactured by ADEKA) As a colorant, 2 parts by mass of carbon black (thermal carbon), as a lubricant, 2 parts by mass of zinc stearate, and as an organic peroxide (peroxide crosslinking agent), a crosslinking agent 3 (manufactured by Kayaku Akzo) Product name: Kayabutyl B, 1 minute half-life temperature: 169 ° C., crosslinking efficiency: 49%, theoretical active oxygen content: 8.24%) 2.5 parts by mass were used.

  Among the insulator material and the sheath material described above, components other than the cross-linking agent are kneaded by a 75 L pressure kneader, the insulator material (shown in Table 1) is formed into pellets, and the sheath material (shown in Table 2). ) Was striped. Thereafter, the pellet-like insulator material was impregnated with a predetermined amount of a crosslinking agent by a mixer, and the sheath material was kneaded with a 25 L pressure kneader.

  The kneaded insulator material was extrusion coated at a extrusion temperature of 110 ° C. onto a 50SQ tin-plated copper conductor wrapped with PET tape, and continuously crosslinked with saturated water vapor with a saturated water vapor pressure of 1.8 MPa (205 ° C.). The insulated wire has a thickness of 1.0 mm and an outer diameter of 11.7 mm. Three insulated wires are twisted together, wound with PET tape, knitted with a metal braid, and a sheath material kneaded at an extrusion temperature of 90 ° C. is extruded and coated at a thickness of 1.6 mm. At the same time, polymethylpentene Was coated on the sheath material and wound on a drum. Put the drum around which the cable is wound into a kettle, crosslink with saturated water vapor with a saturated water vapor pressure of 0.4 MPa (145 ° C.) for 45 minutes, peel off the polymethylpentene, and connect the cable with an outer diameter of 30.1 mm shown in FIG. Obtained.

(Examples 2 to 6)
A cable was obtained in the same manner as in Example 1 except that the resin composition was changed to that shown in Table 2 in Example 1.

(Comparative Examples 1-5)
A cable was obtained in the same manner as in Example 1 except that the resin composition was changed to that shown in Table 3 in Example 1.

In Tables 1 to 3, specifically, those shown below were used.
(1) Ethylene-α-olefin copolymer (manufactured by Mitsui Chemicals, trade name: Toughma A4070)
(2) EVA1 (Mitsui DuPont Polychemical Co., Ltd., trade name: EV45X: VA amount 46%)
(3) Magnesium hydroxide (trade name: Magseeds S4, manufactured by Kamishima Chemical Co., Ltd.)
(4) Composite antioxidant (trade name: AO-18, manufactured by ADEKA)
(5) Crosslinking agent 1 (trade name: Perbutyl P, manufactured by NOF Corporation)
(6) EVA2 (Mitsui DuPont Polychemical Co., Ltd., trade name: EV45X: VA amount 46%)
(7) EVA3 (manufactured by LANXESS, product name: Revaprene 600: VA amount 60%)
(8) Maleic acid-modified polyolefin (Mitsui Chemicals, trade name: Toughma MH5040)
(9) Phenol-based antioxidant (trade name: Irganox 1010, manufactured by BASF)
(10) Carbon black (thermal carbon)
(11) Crosslinking agent 2 (manufactured by Kayaku Akzo, trade name: Trigonox 117, 1 minute half-life temperature: 156 ° C., crosslinking efficiency: 39.5%, theoretical active oxygen content: 6.49%)
(12) Crosslinking agent 3 (manufactured by Kayaku Akzo, trade name: Kayabutyl B, 1 minute half-life temperature: 169 ° C., crosslinking efficiency: 49%, theoretical active oxygen content: 8.24%)
(13) EVA4 (Mitsui DuPont Polychemical Co., Ltd., trade name: EV170)
(14) Crosslinking agent 4 (manufactured by Kayaku Akzo, trade name: Trigonox 22-70E, 1 minute half-life temperature: 151 ° C., crosslinking efficiency: 24%, theoretical active oxygen content: 8.6%)

[Evaluation test]
The obtained cable was subjected to the following evaluation test. The test method was carried out according to EN50264 3-2. Those satisfying all the standards were accepted. The results are shown in Tables 4 and 5.

(Initial tension)
The sheath is peeled off, shaved so that the inside of the sheath becomes flat, and punched with dumbbell No. 6 described in JIS K 6251. The punched test sample was pulled with a tensile tester at a speed of 200 mm / min, and the tensile strength and elongation at break were measured. A tensile strength of 10 MPa or more and an elongation at break of 125% or more were regarded as acceptable.

(Oil resistance)
Similar to the initial tensile test, the sheath material was punched with dumbbell No. 6, and the punched test sample was ASTM No. 100 ° C. Soak in 2 oils for 72 hours. The test sample after immersion was pulled at a rate of 200 mm / min with a tensile tester, and the tensile strength and elongation at break were measured. From the results of the initial tensile test, those that fall within the range of 70 to 130% residual tensile strength and 60 to 140% residual elongation at break were regarded as acceptable.

(Fuel resistance)
Similar to the initial tensile test, the sheath material was punched with dumbbell No. 6, and the punched test sample was ASTM No. 100 ° C. Immerse in 3 oils for 168 hours. The test sample after immersion was pulled at a rate of 200 mm / min with a tensile tester, and the tensile strength and elongation at break were measured. From the results of the initial tensile test, those that fall within the range of 70 to 130% residual tensile strength and 60 to 140% residual elongation at break were regarded as acceptable.

(Low temperature characteristics)
As with the initial tensile test, the sheath material was punched with dumbbell No. 6, and the punched test sample was left in a thermostatic bath at −40 ° C. for 10 minutes. Those having an absolute value of breaking elongation of 30% or more were regarded as acceptable.

(Flame retardance)
A vertical tray combustion test was performed by the method described in EN50266-2, and a carbonization distance of 250 cm or less was accepted.

(toxicity)
It was carried out by the method described in EN50305.9.2, and an ITC value of 3 or less was accepted.

  As shown in Table 4, the cable using the halogen-free flame retardant resin composition obtained in Examples 1 to 6 as the sheath satisfies all the characteristics, and is oil / fuel resistant, low temperature characteristics, flame retardant It can be seen that it has excellent properties and low toxicity during combustion.

  On the other hand, as shown in Table 5, in Comparative Examples 1 and 2, since the VA amount of EVA of the base polymer is low, the oil resistance and fuel resistance are inferior. In the case of Comparative Example 3, the flame retardance is insufficient because the amount of metal hydroxide added is small. In the case of Comparative Example 4, the initial characteristics and the low temperature characteristics cannot be satisfied because the metal hydroxide is added too much. In the case of Comparative Example 5, although it seems that the crosslinking is completed, since it is a crosslinking agent having a low crosslinking efficiency, it is inferior in fuel resistance.

1 Copper conductor (tin-plated copper conductor)
2 PET tape 3 Insulator 4 PET tape 5 Metal braid 6 Sheath

Claims (5)

A base polymer comprising an ethylene-vinyl acetate copolymer having a vinyl acetate content of 40% by mass or more alone or in a mixture with one or more other polyolefins;
A metal hydroxide blended at a ratio of 130 to 220 parts by mass with respect to 100 parts by mass of the base polymer;
And an organic peroxide having a crosslinking efficiency of 39% or more shown in the following formula (1) crosslinked with saturated steam having a saturated steam pressure of 0.4 MPa (145 ° C.) for 45 minutes , and crosslinked by heating. Do Ri, the organic peroxide, t- butyl peroxy-2-ethylhexyl carbonate, or t- butyl halogen-free flame-retardant resin composition is a peroxy benzoate.
Cross-linking efficiency (%) = [amount of n-pentadecane dimer (mol) / amount of organic peroxide (mol)] × 100 (1) The halogen-free flame-retardant resin composition according to claim 1, which is crosslinked at a crosslinking temperature of 140 to 160 ° C. An electric wire having a conductor and an insulator formed on the outer periphery of the conductor; and a sheath made of the halogen-free flame-retardant resin composition according to claim 1 or 2 formed on the outer periphery of the insulator of the electric wire; , Having cable. The cable according to claim 3 , wherein the sheath is formed on an outer periphery of the two or more electric wires. The cable according to claim 4 , having an outer diameter of 12.5 mm or more.