JP2013149425A - Halogen-free flame-retardant insulated wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a halogen-free flame-retardant insulated wire capable of reducing leakage current at high voltage while satisfying the required characteristics of flame retardancy and heat resistance suitable for a railroad vehicle, and having sufficient insulation characteristics for a high voltage current even with a thin insulation layer, and useful for reduction of the environmental load.SOLUTION: A halogen-free flame-retardant insulated wire comprises a conductor, a first insulation layer covering the conductor, and a second insulation layer covering the first insulation layer. The conductor has a cross-sectional area of 0.5-5.5 mm. The first insulation layer comprises a resin composition containing 5-70 pts.mass of nitrogen-based flame retardants based on 100 pts.mass of resin component containing 20-50 pts.mass of polyester resin, 20-50 pts.mass of polyphenylene ether-based resin, and 30-60 pts.mass of styrene-based elastomer. Total thickness of the first and second insulation layers to the conductor diameter is 15-65%, and the thickness ratio of the first and second insulation layers is 4:1-5:2.

Description

  The present invention relates to a halogen-free flame-retardant insulated wire, which is excellent in heat resistance and flame retardancy, has a relatively thin insulating layer, and is suitably used for vehicles (especially railway vehicles). Regarding electric wires.

  A vehicular electric wire used in a vehicle such as a train is used for a wiring path for supplying high-voltage power such as 600V or 1500V. In a conventional representative electric wire for a vehicle, a separator is covered around a conductor formed by a tin-plated annealed copper flexible strand, and an insulator having a predetermined thickness is covered around the conductor. Vehicle wires are required to have flame retardancy, light weight, and space saving.

  As an insulated wire that is required not only for vehicles but also for flame retardancy, Patent Document 1 discloses flame retardancy containing ultra-low density polyethylene polymerized with a single-site metallocene catalyst, a halogen flame retardant, and zinc white. An insulated wire using a resin composition as an insulating layer is disclosed. The flame retardant resin composition used for the insulating layer has a low dielectric constant of less than 3.3, and the leakage current of high voltage current can be reduced even if the thickness of the insulating layer is reduced.

  On the other hand, in order to meet the demand for reducing the environmental burden, a halogen-free insulated wire that does not contain a halogen element is required. This is because when the insulated wire contains a halogen element, a toxic gas such as hydrogen chloride may be generated when the insulated wire after use is incinerated.

  Generally, as a coating material for halogen-free electric wires, a resin composition that is flame-retardant by blending a polyolefin-based resin such as polypropylene with a metal hydroxide such as magnesium hydroxide or aluminum hydroxide is used. For example, Patent Document 2 discloses an insulated wire using a flame retardant resin composition in which magnesium hydroxide is blended as a flame retardant in an ethylene-vinyl acetate copolymer (EVA) as an insulating layer. However, in order to pass the vertical combustion test called the VW-1 test, which is a strict standard for flame retardancy evaluation, it is necessary to blend a large amount of metal hydroxide in the polyolefin resin. As a result, the dielectric constant of the insulating layer increases, and the leakage current increases in high voltage applications. There is also the problem of reduced flexibility.

  In order to reduce the weight of an insulated wire for vehicles and save space, there has been an increasing demand for reducing the thickness of the insulating layer of the wire. However, when the thickness of the insulating layer is reduced to, for example, 0.4 mm or less and a metal hydrate is blended, there is a problem that the cut-through resistance of the insulated wire is significantly reduced. Patent Document 3 discloses a thin-walled flame-retardant insulated wire that has excellent cut-through resistance and does not generate toxic corrosive gas during combustion.

Japanese Patent No. 3279206 JP 2000-211981 JP-A-11-219626

As described above, in a flame retardant resin composition using a metal hydroxide as a non-halogen flame retardant, increasing the compounding amount of the metal hydroxide to satisfy the flame retardancy increases the dielectric constant and increases the leakage current. Become. On the other hand, if the compounding amount of the metal hydroxide is reduced in order to lower the dielectric constant, the flame retardancy cannot be satisfied.
Moreover, the thin-walled flame-retardant insulated wire disclosed in Patent Document 3 is not sufficient in terms of flame retardancy in the evaluation at the 60 ° C. incline flame retardancy test, and is also evaluated for heat resistance required for railway vehicles. Is not shown.
In view of these circumstances, the present invention can reduce the leakage current at a high voltage and satisfy the required characteristics of flame retardancy and heat resistance suitable for railway vehicles. It is an object of the present invention to provide a halogen-free flame-retardant insulated wire that has excellent insulation characteristics and is useful for reducing environmental burden.

As a result of intensive studies, the present inventors have found that the above problems can be solved by the following means.
(1) A halogen-free flame-retardant insulated electric wire having a conductor, a first insulating layer covering the conductor, and a second insulating layer covering the first insulating layer,
The conductor has a cross-sectional area of 0.5 to 5.5 mm ² ;
A nitrogen-based flame retardant with respect to 100 parts by mass of a resin component in which the first insulating layer contains 20 to 50 parts by mass of a polyester resin, 20 to 50 parts by mass of a polyphenylene ether resin, and 30 to 60 parts by mass of a styrene elastomer. A resin composition containing 5 to 70 parts by mass of
The total thickness of the first insulating layer and the second insulating layer with respect to the conductor diameter is 15 to 65%;
A halogen-free flame-retardant insulated wire, wherein the thickness ratio of the first insulating layer to the second insulating layer is 4: 1 to 5: 2.

(2) The resin component of the resin composition constituting the first insulating layer is a polybutylene terephthalate 20 to 30 parts by mass, a modified polyphenylene ether 20 to 30 parts by mass, and a styrene ethylene butylene styrene copolymer 45 to 55 parts by mass. The halogen-free flame-retardant insulated electric wire according to (1), which is contained in a ratio of parts.

  According to the present invention, the leakage current at high voltage can be reduced, the required characteristics of flame retardancy and heat resistance can be satisfied, and even a thin insulating layer has sufficient insulation characteristics against high voltage current, and the environment It is possible to provide a halogen-free flame-retardant insulated wire that is useful for reducing the load.

Hereinafter, the present invention will be described in detail.
Halogen-free flame燃絶edge wire (hereinafter simply referred to as "insulated wire") of the present invention the conductor cross-sectional area is wire size of 0.5mm ² ~5.5mm ^2. Used for signal transmission, power supply, etc. within and between devices. The resin composition constituting the first insulating layer (hereinafter also simply referred to as “first resin composition”) is 20 to 50 parts by mass of a polyester resin, 20 to 50 parts by mass of a polyphenylene ether-based resin, and a styrene-based resin. The nitrogen-based flame retardant is contained in an amount of 5 to 70 parts by mass with respect to 100 parts by mass of the resin component containing 30 to 60 parts by mass of the elastomer.
The first resin composition can have a dielectric constant of 3.2 or less by the above composition. By using the first resin composition, which is a low dielectric constant material of 3.2 or less, for the first insulating layer (inner layer) portion in contact with the conductor, the leakage current can be effectively reduced.
In addition, the first resin composition also has a certain degree of flame retardancy due to the synergistic effect of the polyphenylene ether (PPE) resin, the nitrogen flame retardant, and the polyester resin.

  A resin composition containing a polyphenylene ether resin and a styrene elastomer is a polymer alloy having a sea-island structure in which a hard polyphenylene ether resin having a high elastic modulus at normal temperature is used as an island and a styrene elastomer having a large elongation is used as a sea. It is estimated to be. If a polyester resin is further added thereto, a three-component polymer alloy is obtained. The polyester resin is a crystalline resin, and can maintain an appropriate elastic modulus and maintain flexibility and extensibility even at a temperature higher than the glass transition temperature. Moreover, if the compatibility with a styrene-type elastomer is comparatively high and it can disperse | distribute uniformly in a styrene-type elastomer, tensile strength and tensile strength will be expressed as a whole. By including a nitrogen-based flame retardant in such a resin component, flexibility can be exhibited, the dielectric constant is low, and a certain degree of flame retardancy can be imparted.

  Examples of the polyester resin used in the first resin composition include PET (polyethylene terephthalate) resin and PBT (polybutylene terephthalate) resin. In particular, PBT resin has a melting point close to the glass transition temperature of polyphenylene ether and has good extrudability. It also has excellent flame retardancy.

The polyphenylene ether resin used for the first resin composition will be described.
Polyphenylene ether is an engineering plastic obtained by oxidative polymerization of 2,6-xylenol synthesized using methanol and phenol as raw materials. In order to improve the moldability of polyphenylene ether, various materials are commercially available as modified polyphenylene ether resins in which polystyrene is blended with polyphenylene ether. As the polyphenylene ether resin used in the present invention, any of the above-mentioned polyphenylene ether resin alone and a modified polyphenylene ether resin obtained by melt blending polystyrene can be used, but a modified polyphenylene ether resin is preferred. Moreover, what introduce | transduced carboxylic acid, such as maleic anhydride, can also be blended suitably and used.

  In such a polyphenylene ether resin, the deflection temperature under load changes depending on the blend ratio of polystyrene. However, when a resin with a deflection temperature under load of 95 ° C. or higher is used, the tensile properties of the wire coating are improved and the mechanical strength is high. An insulating layer is obtained, and it is preferable because it has excellent thermal deformation characteristics. The deflection temperature under load is a value measured at a load of 1.80 MPa by the method of ISO75-1,2.

  A polyphenylene ether resin not blended with polystyrene can also be used as the polyphenylene ether resin. In this case, if a low-viscosity polyphenylene ether resin is used, the resin pressure during extrusion can be reduced while maintaining the mechanical strength. The intrinsic viscosity of the polyphenylene ether resin is preferably 0.1 to 0.6 dl / g, and more preferably 0.3 to 0.5 dl / g.

  Styrene elastomers used in the first resin composition include styrene / ethylene / butylene / styrene (SEBS) copolymers, styrene / ethylene propylene / styrene copolymers, and styrene / ethylene / ethylene propylene / styrene copolymers. , Styrene / butylene / styrene copolymers, etc., and examples thereof include hydrogenated polymers and partially hydrogenated polymers. Moreover, what introduce | transduced carboxylic acid, such as maleic anhydride, can also be blended suitably and used. Among these, styrene ethylene butylene styrene copolymer is preferable.

  Use of a block copolymer elastomer of styrene and a rubber component is preferable from the viewpoints of improving extrudability, improving tensile elongation at break, and improving impact resistance. Block copolymers include hydrogenated styrene / butylene / styrene block copolymers, triblock copolymers such as styrene / isobutylene / styrene copolymers, styrene / ethylene copolymers, styrene / ethylene propylene, etc. It is preferable that the triblock component in the styrene elastomer is contained in an amount of 50% by mass or more because the strength and hardness of the electric wire coating is improved.

Also, those having a styrene content of 20% by mass or more contained in the styrene elastomer can be suitably used from the viewpoint of mechanical properties and flame retardancy.
Further, the melt flow rate (abbreviated as “MFR”; measured at 230 ° C. × 2.16 kgf in accordance with JIS K 7210) serving as an index of molecular weight is preferably in the range of 0.8 to 15 g / 10 min. If the melt flow rate is 0.8 g / 10 min or more, the extrusion processability is improved, and if it is 15 g / 10 min or less, the mechanical strength is improved.

  Furthermore, it is preferable to contain a styrene elastomer having a functional group as a part of the styrene elastomer. The styrenic elastomer having a functional group acts as a compatibilizing agent, and the polyester resin and the styrenic elastomer can be mixed well to improve adhesion, high temperature characteristics, and tensile elongation characteristics. Examples of the functional group include an epoxy group, an oxazoline group, an acid anhydride group, and a carboxyl group, which can be appropriately selected according to the type of resin. The content of the styrenic elastomer having a functional group is preferably 1 to 20 parts by mass with respect to 100 parts by mass of the resin component, and more preferably 1 to 10 parts by weight.

The resin component of the first resin composition contains 20 to 50 parts by mass of the polyester resin, 20 to 50 parts by mass of a polyphenylene ether resin, and 30 to 60 parts by mass of a styrene elastomer. When the content of the polyphenylene ether-based resin exceeds 50 parts by mass, the extrudability decreases, and when the content is less than 20 parts by weight, the mechanical strength and flame retardancy are decreased. Similarly, when the content of the polyester resin exceeds 50 parts by mass, the extrudability is lowered, and when it is less than 20 parts by mass, the mechanical strength and flame retardancy are lowered. The more preferable content of the polyester resin is 25 to 40 parts by mass.
The resin component of the first resin composition may be contained in a proportion of 20 to 30 parts by mass of polybutylene terephthalate, 20 to 30 parts by mass of modified polyphenylene ether, and 45 to 55 parts by mass of a styrene ethylene butylene styrene copolymer. preferable.

  Furthermore, as said resin component, it is possible to mix various resin in the range which does not impair the meaning of this invention.

  Examples of the nitrogen-based flame retardant used in the first resin composition include melamine resin and melamine cyanurate. Nitrogen-based flame retardants do not generate toxic gases such as hydrogen halides even when incinerated after use, and can reduce the environmental burden. When melamine cyanurate is used as a nitrogen-based flame retardant, it is preferable in terms of heat stability at the time of mixing and a flame retardant improvement effect. Melamine cyanurate can also be used after surface treatment with a silane coupling agent or a titanate coupling agent.

  Content of the said nitrogen-type flame retardant is 5-70 mass parts with respect to 100 mass parts of resin components of a 1st resin composition. This is because if the amount is less than 5 parts by mass, the flame resistance of the insulated wire is insufficient, and if it exceeds 70 parts by mass, the elongation and extrusion processability are deteriorated. As for content of a nitrogen-type flame retardant, 10-40 mass parts is further more preferable.

Furthermore, the first resin composition can contain a crosslinking aid. By containing a crosslinking aid, a plasticizing effect of the resin is obtained, and the extrusion processability is improved. Moreover, the crosslinking efficiency at the time of irradiation of ionizing radiation increases. As the crosslinking aid, a polyfunctional monomer having a plurality of carbon-carbon double bonds in the molecule such as trimethylolpropane trimethacrylate, triallyl cyanurate, triallyl isocyanurate and the like can be preferably used. Moreover, it is preferable that a crosslinking adjuvant is a liquid at normal temperature. This is because when it is a liquid, it can be easily mixed with a polyphenylene ether resin or a styrene elastomer. In particular, trimethylolpropane trimethacrylate as a crosslinking aid is preferable because it has good compatibility with the resin and can be easily mixed. It is preferable to contain 0.1-10 mass parts of trimethylolpropane trimethacrylate with respect to 100 mass parts of resin components.
In order to improve flame retardancy, a phosphorus-based flame retardant may be added. Examples of the phosphorus-based flame retardant include phosphate esters.

The insulated wire of the present invention has a second insulating layer that covers the first insulating layer.
The resin composition constituting the second insulating layer (hereinafter also simply referred to as “second resin composition”) does not contain a halogen-based flame retardant or the like, does not contain a so-called halogen element, and functions of the first insulating layer. As long as it does not decrease the thickness, it is not particularly limited and may be appropriately selected according to the purpose and application.

  Among them, as an example, the outer second insulating layer may include a form using a resin composition containing a certain proportion of a metal hydroxide having a high flame retardant effect with an emphasis on flame retardancy. The form will be described below.

  In the case of the second insulating layer focusing on the above flame retardancy, the dielectric constant of the second resin composition is increased, but as described above, the dielectric constant of the first insulating layer as the inner layer is lowered. The leakage current of the insulated wire itself can be reduced. By adopting such a configuration, it is possible to achieve both reduction in leakage current at high voltage and flame retardancy.

  In the above case, as the resin component used in the second resin composition, in addition to the resin used in the first resin composition, polyolefin resins such as polyethylene and polypropylene, ethylene vinyl acetate copolymer, ethylene Any resin such as an ethylene α-olefin copolymer such as a methyl acrylate copolymer, an ethylene ethyl acrylate copolymer, and an ethylene meryl methacrylate copolymer can be used. In particular, an ethylene vinyl acetate copolymer can be preferably used from the viewpoints of extrudability and flexibility when a resin composition is used.

  Examples of the metal hydroxide used as the flame retardant include aluminum hydroxide, magnesium hydroxide, calcium hydroxide and the like. Among these, from the viewpoint of extrusion processability, magnesium hydroxide having a particle size in the range of 0.1 to 3 μm is preferable.

  Although content of a metal hydroxide is not specifically limited, The range of 150-250 mass parts is preferable with respect to 100 mass parts of resin components. If it is 150 mass parts or more, the flame retardance of an insulated wire will improve more, and if it is 250 mass parts or less, elongation and extrusion processability will improve more. A more preferable range is 150 to 200 parts by mass.

  In the present invention, the first resin composition and the second resin composition include an antioxidant, an anti-aging agent, a lubricant, a processing stabilizer, a colorant, a heavy metal inactivating material, a foaming agent, if necessary. A polyfunctional monomer or the like can be appropriately mixed. These materials are mixed using a known melt mixer such as a short-shaft extrusion mixer, a pressure kneader, or a Banbury mixer to produce a resin composition.

  The insulated wire of the present invention is obtained by coating a conductor with the first insulating layer made of the first resin composition, and coating the first insulating layer with the second insulating layer made of the second resin composition. is there. A known extruder can be used to form the first insulating layer and the second insulating layer. In order to simplify the manufacturing process, it is preferable that the first insulating layer and the second insulating layer are simultaneously coated by extrusion.

  Furthermore, it is preferable that the first insulating layer and the second insulating layer are crosslinked by irradiation with ionizing radiation from the viewpoint of improving heat resistance and mechanical strength. Examples of ionizing radiation sources include accelerating electron beams, gamma rays, X-rays, α rays, ultraviolet rays, and the like. Lines are most preferably available.

In the insulated wire of the present invention, the thicknesses of the first insulating layer and the second insulating layer are such that the total thickness of the first insulating layer and the second insulating layer is 15 to 65% with respect to the conductor diameter described later. It is. The ratio of the thickness of the insulating layer to the conductor diameter varies depending on the value of the conductor diameter. When the conductor cross-sectional area is 0.5 mm ² (conductor diameter of about 0.8 mm), the ratio of the total thickness of the insulating layer to the conductor diameter is about 65%, and the conductor cross-sectional area is 5.5 mm ² (conductor diameter of about 2. mm). In the case of 8 mm), the ratio of the total thickness of the insulating layer to the conductor diameter is about 15%. If the total thickness of the first insulating layer and the second insulating layer is too small with respect to the conductor diameter, the leakage current at a high voltage cannot be sufficiently reduced, and sufficient flame retardancy and heat resistance can be obtained. I can't. In addition, if the total thickness of the first insulating layer and the second insulating layer is too large with respect to the conductor diameter, the flexibility is deteriorated, and the insulating layer is thinned for the purpose of weight reduction and space saving. Therefore, the technical content of the present invention that the first resin composition is used for the first insulating layer of the present invention becomes meaningless.

  Moreover, the insulated wire of this invention WHEREIN: The ratio of the thickness of a 1st insulating layer and a 2nd insulating layer is 4: 1-5: 2. If the thickness of the first insulating layer is smaller than this ratio, the leakage current at a high voltage cannot be sufficiently reduced. Further, even if the thickness of the first insulating layer is larger than this ratio, the effect of the present invention accompanying this cannot be obtained.

The conductor used in the insulated wire of the present invention is not particularly limited as long as it has excellent conductivity and a cross-sectional area of 0.5 to 5.5 mm ² corresponding to the standard for railway vehicles. Copper wire, aluminum wire, etc. can be used.

  Moreover, the insulated wire of this invention can be used conveniently for railway vehicles. The electric wire that can be suitably used for a railway vehicle has flame retardancy and heat resistance suitable for the railway vehicle. The flame retardancy suitable for a railway vehicle means a level that can pass the material combustion test for railway vehicles of the Japan Railway Vehicle Machinery Association. It is also required to pass an accelerated aging test at 150 ° C.

Next, the best mode for carrying out the invention will be described by way of examples. The examples are not intended to limit the scope of the invention.
[Example 1]
(Preparation of resin composition 1)
Using a twin-screw mixer (26 mmφ, L / D = 48), melt-mixed at a cylinder temperature of 230 ° C. and a screw rotation speed of 200 to 400 rpm, melt-extruded into a strand, and then cooled and cut the molten strand to produce pellets. Produced. A blending example is shown in Table 1.

In Table 1 above, the numerical values indicate parts by mass.
Crosslinking aid: Trimethylolpropane trimethacrylate (TMPTMA)
Anti-aging agent: Irganox 1010 manufactured by Ciba Specialty Chemicals Co., Ltd.
Lubricant: Nippon Kasei Co., Ltd. SLIPAX O
Copper damage inhibitor: ADK STAB CDA-1 manufactured by Asahi Denka Kogyo Co., Ltd.

(Preparation of resin composition 2)
Each component was mixed according to the formulation shown in Table 2 below. After mixing at 130 to 160 ° C. using an open roll machine having a diameter of 12 inches, the stripped sample was pelletized using a pelletizer.

In Table 2 above, the numerical values indicate parts by mass.
EVA1: ethylene vinyl acetate copolymer with 70% vinyl acetate EVA2: ethylene vinyl acetate copolymer with 32% vinyl acetate Magnesium hydroxide: average particle size 0.7μm, stearic acid surface treatment zinc stannate: Nippon Light Metal ( FlammardH manufactured by Co., Ltd.
Clay: Shiraishi Calcium Co., Ltd., Burgess # 30
Calcium carbonate: White Shiraka CCR (stearic acid treatment), manufactured by Shiraishi Calcium Co., Ltd.
Anti-aging agent: Irganox 1010 manufactured by Ciba Specialty Chemicals Co., Ltd.
Lubricant 1: Nippon Kasei Co., Ltd. SLIPAX O
Lubricant 2: Sripax E, manufactured by Nippon Kasei Co., Ltd.
Copper damage inhibitor: ADK STAB CDA-1 manufactured by Asahi Denka Kogyo Co., Ltd.

(Production of insulated wires)
A 50-stranded tin-plated copper wire (outer diameter 1.47 mm) was used as the conductor. The thickness of the first insulating layer (inner layer) made of the resin composition 1 was 0.45 mm, and the thickness of the second insulating layer (outer layer) made of the resin composition 2 was 0.15 mm. The extrusion conditions were conductor preheating 60 ° C., cylinder and die temperatures were set to 190-200 ° C., and the line linear velocity was 25 m / min. Each insulated wire was irradiated with an accelerating electron beam so that the irradiation amount was 120 kGray.

[Example 2]
An insulated wire was produced in the same manner as in Example 1 except that the conductor was changed to an outer diameter of 1.82 mm.

[Comparative Example]
As the insulating layer resin composition, a single layer using an antimony trioxide, a chlorine-based flame retardant and a cross-linking agent added to an ethylene vinyl acetate copolymer having a vinyl acetate content of 15% as a base resin. An insulated wire was produced in the same manner as in Examples 1 and 2 except that the insulating layer was used. However, the outer diameter of the conductor in Comparative Example 1 is 1.47 mm and the insulating coating layer is 0.85 mm, the outer diameter of the conductor in Comparative Example 2 is 1.82 mm, and the thickness of the insulating coating layer is 0.85 mm.

  The following items were evaluated for the manufactured insulated wires. The evaluation results are shown in Table 3 below.

(Evaluation of coating layer: tensile properties)
A conductor was extracted from the produced electric wire, and a tensile test of the coating layer was performed. The test conditions were tensile speed = 500 mm / min, distance between marked lines = 25 mm, temperature = 23 ° C., tensile strength (tensile strength) and tensile elongation at break were measured with three samples each, and the average value was obtained. . Those having a tensile strength (tensile strength) of 7 MPa or more and a tensile elongation at break of 350% or more were judged as “pass”.

(Evaluation of coating layer: Elongation residual ratio and tensile residual ratio after aging)
A tensile test similar to that described above was performed on a sample aged at 150 ° C. for 96 hours, and the tensile strength and tensile elongation at break were measured. The original numerical value was taken as 100, and the residual elongation rate and residual tensile strength rate were obtained. Those having a residual elongation rate of 70% or more and a tensile strength residual rate of 75% or more were judged as “pass”.

(Evaluation of electric wire: withstand voltage)
A DC voltage of 2.2 kV was applied for 1 minute between conductor insulations, and those without dielectric breakdown were judged as “pass”.

(Evaluation of electric wire: deformation after heating)
The sample preheated at 120 ° C. for 30 minutes was placed on a weight of 2.45 N and placed at 120 ° C. for 30 minutes, the thickness was measured, and the reduction rate was determined by the following formula.
(Thickness before heating−Thickness after heating) / Thickness before heating A reduction rate of 40% or less was determined as “pass”. The tip of the weight was a flat bottom with a diameter of 9.5 mm, and its edge was slightly rounded.

(Evaluation of electric wire: heat winding)
An electric wire aged at 150 ° C. for 96 hours was wound around a mandrel having the same diameter as the electric wire, and the presence or absence of a crack was visually observed. Those without cracks were judged as “pass”.
(Evaluation of electric wire: winding heating)
The electric wire was wound around a mandrel having the same diameter as the electric wire, aged at 150 ° C. for 96 hours, and visually observed for cracks. Those without cracks were judged as “pass”.
(Evaluation of electric wire: cold winding)
After placing the electric wire at a temperature of −25 ° C. for 1 hour, it was wound around a mandrel having the same diameter as the electric wire, and the presence or absence of a crack was visually observed. Those without cracks were judged as “pass”.

(Evaluation of electric wires: Railway vehicle material combustion test)
A material combustion test for railway vehicles was conducted at the Japan Railway Vehicle Machinery Association. The result was “flame retardant”.
(Scrape wear test)
A scrape wear test was performed according to the provisions of ISO 6722: 2006. Table 3 shows the number of reciprocating movements of the blade until the conductor is exposed.

  Although the electric wire of the example has a thin insulating layer and a small diameter compared to the electric wire of the comparative example, it has flame resistance and heat resistance suitable for a railway vehicle as well as the electric wire of the comparative example. Other characteristics such as wear were the same as or higher than those of the comparative example. In particular, it is excellent in tensile strength and heat deformation.

As an application example of the present invention, it is a halogen-free flame-retardant insulated electric wire, which is excellent in heat resistance and flame retardancy and has a thin insulating layer, and is suitably used for vehicles (particularly railway vehicles). .

Claims (2)

A halogen-free flame-retardant insulated electric wire having a conductor, a first insulating layer covering the conductor, and a second insulating layer covering the first insulating layer,
The conductor has a cross-sectional area of 0.5 to 5.5 mm ² ;
A nitrogen-based flame retardant with respect to 100 parts by mass of a resin component in which the first insulating layer contains 20 to 50 parts by mass of a polyester resin, 20 to 50 parts by mass of a polyphenylene ether resin, and 30 to 60 parts by mass of a styrene elastomer. A resin composition containing 5 to 70 parts by mass of
The total thickness of the first insulating layer and the second insulating layer with respect to the conductor diameter is 15 to 65%;
A halogen-free flame-retardant insulated wire, wherein the thickness ratio of the first insulating layer to the second insulating layer is 4: 1 to 5: 2.   The resin component of the resin composition constituting the first insulating layer is a ratio of polybutylene terephthalate 20 to 30 parts by mass, modified polyphenylene ether 20 to 30 parts by mass, and styrene ethylene butylene styrene copolymer 45 to 55 parts by mass. The halogen-free flame-retardant insulated wire according to claim 1, wherein