Non-halogen flame-retardant resin compositions, electric wires and cables

Abstract

To provide a non-halogen fire retardant resin composition that can have high fire retardancy and further have excellent flexibility and breaking elongation as well as an electric wire using the non-halogen fire retardant resin composition and a cable.SOLUTION: A cable 20 constituted of a non-halogen fire retardant resin composition that includes: an electric wire 10, a shield layer 22 having a separator 21 provided on an outside thereof, and a coating layer 23 on an outside of the shield layer 22, wherein the coating layer 23 is constituted of a non-halogen fire retardant resin composition containing (a) a mixed resin of an ethylene acetic acid vinyl copolymer having a content of vinyl acetate of 60 mass% or more and an ethylenic polymer having a melting point of 115°C or more (excluding acid-modified polyolefin), and (b) a base polymer containing acid-modified polyolefin, and a fire retardant agent including aluminum hydroxide.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a non-halogen flame-retardant resin composition that has high flame retardancy and excellent flexibility and elongation at break, as well as electric wires and cables using the non-halogen flame-retardant resin composition. [Background technology]

[0002] Electric wires and cables used in vehicles such as railway cars and automobiles require high flame retardancy, excellent flexibility, and elongation at break, depending on the environment in which they are used.

[0003] It is known that halogenated flame retardants or phosphorus-based flame retardants such as red phosphorus are added to impart high flame retardancy. However, halogenated flame retardants generate halogen gas during combustion, which is a lack of consideration for the growing environmental problem worldwide. Furthermore, phosphorus-based flame retardants such as red phosphorus also have problems, such as the generation of phosphine during combustion and the production of phosphoric acid during disposal, which contaminates groundwater.

[0004] On the other hand, metal hydroxides used as flame retardants do not cause the aforementioned problems compared to halogen-based or phosphorus-based flame retardants. However, in order to achieve the desired flame retardancy, a high concentration is required, which may lead to deterioration of mechanical properties, low-temperature properties, and even electrical properties.

[0005] To address these problems, electric wires and cables are known in which an insulating layer or coating layer is constructed using a resin composition in which a metal hydroxide is blended as a flame retardant into a base polymer having a predetermined composition (see, for example, Patent Documents 1-2). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2014-67657 [Patent Document 2] Japanese Patent Publication No. 2021-125396 [Overview of the project] [Problems that the invention aims to solve]

[0007] The present invention aims to provide a non-halogen flame-retardant resin composition that is halogen-free, yet possesses high flame retardancy, as well as excellent flexibility and elongation at break, and electric wires and cables using this non-halogen flame-retardant resin composition.

[0008] Other challenges and novel features will become apparent from the description and accompanying drawings in this specification. [Means for solving the problem]

[0009] One embodiment of the non-halogen flame-retardant resin composition is a base polymer containing (a) an ethylene vinyl acetate copolymer with a vinyl acetate content of 60% by mass or more and an ethylene-based polymer (excluding acid-modified polyolefins) with a melting point of 115°C or higher, and (b) an acid-modified polyolefin, and a flame retardant containing aluminum hydroxide, wherein the mass ratio of the (a) mixed resin to the (b) polyolefin is (a):(b) = 95:5 to 70:30, and the density of the ethylene-based polymer with a melting point of 115°C or higher is 0.9 g / cm³. 3 The amount is less than 100 parts by mass of the total of the (a) mixed resin and the (b) polyolefin, and contains 150 to 180 parts by mass of the flame retardant.

[0010] One embodiment of an electric wire is an electric wire having a conductor and an insulating layer provided around the conductor, wherein the insulating layer is a non-halogen flame-retardant resin composition containing (a) a mixed resin of an ethylene vinyl acetate copolymer having a vinyl acetate content of 60% by mass or more and an ethylene-based polymer (excluding acid-modified polyolefin) having a melting point of 115°C or higher and (b) an acid-modified polyolefin, and a flame retardant containing aluminum hydroxide, wherein the mass ratio of the mixed resin (a) to the polyolefin (b) is (a):(b) = 95:5 to 70:30, and the density of the ethylene-based polymer with a melting point of 115°C or higher is 0.9 g / cm³ 3 The composition is a non-halogen flame-retardant resin composition containing 150 to 180 parts by mass of the flame retardant with respect to a total of 100 parts by mass of the (a) mixed resin and the (b) polyolefin.

[0011] One embodiment of the cable comprises a single-core / multi-core stranded wire formed by twisting together one or more single-layer or multi-layered wires, a shield braid or shield braid having a separator provided on the outside thereof, and a covering layer covering the outside of the shield braid, wherein the covering layer is a non-halogen flame-retardant resin composition containing (a) a mixed resin of an ethylene vinyl acetate copolymer with a vinyl acetate content of 60% by mass or more and an ethylene-based polymer (excluding acid-modified polyolefin) with a melting point of 115°C or higher, and (b) an acid-modified polyolefin, and a flame retardant containing aluminum hydroxide, wherein the mass ratio of the mixed resin (a) to the polyolefin (b) is (a):(b) = 95:5 to 70:30, and the density of the ethylene-based polymer with a melting point of 115°C or higher is 0.9 g / cm³ 3 The composition is a non-halogen flame-retardant resin composition containing 150 to 180 parts by mass of the flame retardant with respect to a total of 100 parts by mass of the (a) mixed resin and the (b) polyolefin. [Effects of the Invention]

[0012] According to one embodiment, a non-halogenated flame-retardant resin composition that is non-halogenated, has high flame retardancy, and can have excellent oil resistance and low-temperature characteristics, as well as an electric wire and a cable using the same, can be obtained.

Brief Description of the Drawings

[0013] [Figure 1] It is a cross-sectional view showing a structural example of an electric wire according to one embodiment. [Figure 2] It is a cross-sectional view showing a structural example of a cable according to one embodiment.

Modes for Carrying Out the Invention

[0014] Hereinafter, one embodiment of the present invention will be described with reference to the drawings. In all the drawings for explaining the embodiment, members having the same function are denoted by the same reference numerals, and the repeated description thereof will be omitted. In the following embodiments, the description of the same or similar parts will not be repeated in principle unless particularly necessary.

[0015] <Non-halogenated Flame-retardant Resin Composition> Hereinafter, the non-halogenated flame-retardant resin composition of the present embodiment will be described in detail.

[0016] The non-halogenated flame-retardant resin composition according to the present embodiment contains a base polymer containing (a) a mixed resin of an ethylene vinyl acetate copolymer having a vinyl acetate content of 60% by mass or more and an ethylene-based polymer having a melting point of 115°C or more and (b) an acid-modified polyolefin, and a flame retardant containing aluminum hydroxide.

[0017] First, the configuration of the non-halogenated flame-retardant resin composition in the present embodiment will be described.

[0018] [Base Polymer] The base polymer used in this embodiment contains (a) a mixed resin of an ethylene vinyl acetate copolymer with a vinyl acetate content of 60% by mass or more and an ethylene-based polymer with a melting point of 115°C or more, and (b) an acid-modified polyolefin. Hereinafter, each component will be described.

[0019] (a) Mixed resin The mixed resin used here is a mixed resin comprising (a1) an ethylene vinyl acetate copolymer (EVA) with a vinyl acetate content (VA amount) of 60% by mass or more and (a2) an ethylene-based polymer with a melting point of 115°C or more. This mixed resin may be mixed with other polyolefins. However, it does not contain the acid-modified polyolefin which is the component (b) described later.

[0020] (a1) EVA with a VA amount of 60% by mass or more can impart excellent oil resistance to the resin composition by setting the VA amount to 60% by mass or more. It also has an effect of improving the elongation characteristics by improving the filler acceptability in the resin composition.

[0021] (a2) The ethylene-based polymer with a melting point of 115°C or more has a melting point of 115°C or more as described. By including an ethylene-based polymer with a melting point of 115°C or more, excellent oil resistance can be ensured. That is, for example, since the heating temperature of the test oil used in the oil resistance test is 70°C, by adopting an ethylene-based polymer with a melting point of 115°C or more as a polymer with a melting point higher than the heating temperature of the test oil, excellent oil resistance can be ensured. Here, the ethylene-based polymer may be a polymer containing ethylene as a monomer, and in addition to polyethylene, it includes ethylene-based copolymers containing ethylene and other monomers. The ethylene-based copolymer is preferably a copolymer composed of ethylene and an α-olefin as structural units.

[0022] The blending ratio of the above components (a1) and (a2) is not particularly limited, but based on mass, the ratio of (a1):(a2)=1:2 to 2:1 is good, and 2:3 to 3:2 is more preferable.

[0023] Using only EVA with a VA content of 60% by mass or more as the base polymer is undesirable because it degrades low-temperature properties. Furthermore, the amount of EVA with a VA content of 60% by mass or more added is preferably 40% by mass or less when the total of the above-mentioned (a) mixed resin and the polyolefin described below (b) is taken as 100% by mass. Adding more than this amount may degrade low-temperature properties.

[0024] The above-mentioned ethylene-based polymers with a melting point of 115°C or higher include low-density polyethylene (LDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), linear ultra-low-density polyethylene (VLDPE), ethylene vinyl acetate copolymer (EVA, excluding those with a VA content of 60% by mass or more), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate copolymer (EMA), ethylene-glycidyl methacrylate copolymer (EGMA), ethylene-butene-hexene terpolymer, ethylene-propylene-diene terpolymer (EPDM), ethylene-octene copolymer (EOR), ethylene copolymer polypropylene, and ethylene-propylene copolymer (EPR). Examples include poly-4-methyl-pentene-1, maleic acid grafted low-density polyethylene, hydrogenated styrene-butadiene copolymer (H-SBR), maleic acid grafted linear low-density polyethylene, copolymers of ethylene and α-olefins with 3 to 30 carbon atoms, ethylene-styrene copolymers, maleic acid grafted ethylene-methyl acrylate copolymers, maleic acid grafted ethylene-vinyl acetate copolymers, ethylene-maleic anhydride copolymers, ethylene-ethyl acrylate-maleic anhydride terpolymers, ethylene-butene-1 copolymers such as ethylene-propylene-butene-1 terpolymers mainly composed of butene-1, ethylene-hexene-1 copolymers, and olefin block copolymers.

[0025] The density of this (a2) ethylene polymer is 0.9 g / cm³. 3 Less than 0.9 g / cm³ is preferable. 3 If the value is less than this, the flexibility and oil resistance imparted to the resin composition will be good.

[0026] In particular, specific examples of olefin block copolymers include Dow Chemical's INFUSE series products D9000, D9007, D9100, D9107, D9500, D9507, D9530, D9807, and D9817.

[0027] Furthermore, EVA (excluding component (a1)) and ethylene-α-olefin copolymers with a melting point of 115°C or higher, as described above, can be mixed individually or in combination. When mixing multiple copolymers, using EVA is preferable because it has good compatibility with EVA with a VA content of 60% by mass or more (a1), and using EVA with a melting point of 85°C or higher is preferable as it also provides good oil resistance. In this case, since ethylene-α-olefin copolymers with a melting point of 115°C or higher (a2) are blended in, the oil resistance of the resin composition can be further improved, which is preferable.

[0028] (b) Acid-modified polyolefins The (b) acid-modified polyolefin used here is a polyolefin that has been modified with acid. Ethylene-α-polyolefin is preferred as this polyolefin, as it has excellent flexibility in low-temperature environments, and when modified with acid, its adhesion to metal hydroxides can be strengthened, thereby improving the low-temperature properties of the resin composition.

[0029] Examples of polyolefins before modification include low-density polyethylene, linear low-density polyethylene, ultra-low-density polyethylene, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-butene-1 copolymer, ethylene-hexene-1 copolymer, and ethylene-octene-1 copolymer. Among these, ethylene-butene-1 copolymer, ethylene-hexene-1 copolymer, and ethylene-octene-1 copolymer are preferred because they have few crystals, can accept fillers in the resin composition, and provide flexibility at low temperatures. Examples of acids used for modification include maleic acid, maleic anhydride, and fumaric acid.

[0030] The above components (a) and (b) are used to form a base polymer. In these base polymers, the mass ratio of the (a) mixed resin to the (b) acid-modified polyolefin is preferably (a):(b) = 95:5 to 70:30, and more preferably (a):(b) = 90:10 to 80:20. For example, when the total mass of components (a) and (b) is 100 parts by mass, including 5 parts by mass or more of component (b) results in good low-temperature properties, and including 30 parts by mass or less ensures appropriate adhesion to the filler and results in good elongation at break properties of the resin composition.

[0031] [Flame retardant] In this embodiment, aluminum hydroxide is used as the flame retardant. Furthermore, other metal hydroxides can also be added, such as magnesium hydroxide and calcium hydroxide.

[0032] Furthermore, in cable structures using shielding braids, which will be discussed later, it is also important to prevent the propagation of flames to the separator and wires directly beneath the braid. When aluminum hydroxide is applied as a sheath material to such cable structures, it exhibits a dramatic flame-retardant effect. The mechanism is not entirely clear, but compared to magnesium hydroxide, it can be considered as follows.

[0033] The dehydration temperature of magnesium hydroxide ranges from 340 to 420°C, peaking around 400°C. The decomposition temperature of the base polymer is also around 400°C, resulting in high flame retardancy. The dehydration temperature of aluminum hydroxide involves three stages of dehydration reactions, occurring at 245°C, 320°C, and 550°C, with 320°C being the main stage. During the dehydration of aluminum hydroxide, the base polymer does not reach its decomposition point, and the coating layer expands significantly. This expansion is thought to provide a high thermal insulation effect, suppressing heat transfer to the separator and wires, and thus resulting in high flame retardancy.

[0034] The amount of this flame retardant added is preferably 150 to 180 parts by mass per 100 parts by mass of the total of the mixed resin (a) and the polyolefin (b) above. Adding 150 parts by mass or more provides sufficient flame retardancy, while adding 180 parts by mass or less ensures adequate elongation at break and flexibility.

[0035] This flame retardant can be surface-treated with silane coupling agents, titanate coupling agents, fatty acids such as stearic acid, etc., taking into consideration dispersibility, but metal hydroxides treated with silane coupling agents are preferred because they have improved reinforcing effects and low-temperature properties.

[0036] The metal hydroxide is added in particulate form, and it is preferable that the particle size is fine. For example, it is preferable to use particles with an average particle size in the range of 0.6 to 1.5 μm at D50. In this specification, the average particle size refers to the particle size at 50% of the integrated value of the particle size distribution determined by laser diffraction-scattering.

[0037] Furthermore, a larger specific surface area of ​​metal hydroxide particles can be expected to provide a reinforcing effect to the resin composition, resulting in high dynamic cut-through properties. Specifically, a specific surface area of ​​4 m² obtained by the BET method. 2 It is preferable that the amount is 1 / g or more.

[0038] Flame retardants can be supplemented with flame retardant additives to enhance their flame-retardant effect. However, phosphorus-based flame retardants such as red phosphorus and triazine-based flame retardants such as melamine cyanurate are unsuitable because they generate phosphine gas and cyanide gas, which are harmful to the human body. Other flame retardant additives are applicable, such as clay, silica, zinc stannate, zinc borate, calcium borate, dolomide hydroxide, and silicone.

[0039] In addition to the components described above, the resin composition of this embodiment may optionally contain crosslinking agents, crosslinking aids, ultraviolet absorbers, light stabilizers, softeners, lubricants, colorants, reinforcing agents, surfactants, inorganic fillers, antioxidants, plasticizers, metal chelating agents, foaming agents, compatibilizers, processing aids, stabilizers, and the like.

[0040] When the resin composition described above is used as an insulating layer for electric wires or a coating layer for cables, it is preferable that it is crosslinked. Crosslinking is an important component for ensuring oil resistance. The degree of crosslinking can be defined by the gel fraction. The gel fraction can be calculated, for example, as follows.

[0041] To measure the gel fraction, the material to be used should be weighed beforehand. Next, the material is immersed in xylene heated to 110°C for 24 hours. After immersion, it is left at atmospheric pressure at 20°C for 3 hours, then vacuum-dried at 80°C for 4 hours. The mass of the treated material is then weighed, and the gel fraction can be calculated as the ratio (percentage) of the mass after immersion (before treatment) to the mass before immersion (before treatment). Sufficient oil resistance cannot be obtained unless the gel fraction is 80% or higher.

[0042] Crosslinking treatments include chemical crosslinking using organic peroxides, sulfur compounds, or silanes, irradiation crosslinking using electron beams, radiation, etc., and crosslinking using other chemical reactions. There are no particular limitations, and any crosslinking method can be applied.

[0043] <Electric wire> Next, an electric wire, which is one embodiment of this design, will be described using Figure 1. Figure 1 is a cross-sectional view showing the structure of the electric wire according to this embodiment.

[0044] As shown in Figure 1, the electric wire 10 according to this embodiment has a conductor 11 and an insulating layer 12 that covers the conductor 11. The insulating layer 12 may be a single layer or a multilayer structure of two or more layers.

[0045] As the conductor 11, commonly used metal wires such as copper wire and copper alloy wire can be used, as well as aluminum wire, gold wire, silver wire, etc. Alternatively, the conductor 11 may be a metal wire with a metal plating of tin, nickel, or other metal. Furthermore, the conductor 11 may be a single-wire structure, or a stranded conductor made by twisting metal wires together can be used. As for the stranded conductor, concentric stranded wire, bundled stranded wire, or composite stranded wire made by further concentrically twisting these can be used. Additionally, lightly compressed conductors, which are made by compressing these stranded wires, are preferable because they allow for a thinner wire diameter.

[0046] The insulating layer 12 is composed of the resin composition described above. In this case, it is preferable to use a resin composition that has undergone crosslinking treatment as described above. The thickness of the insulating layer 12 is not particularly limited, but 0.15 to 2 mm is preferred.

[0047] The electric wire 10 of this embodiment is manufactured, for example, as follows. First, a base polymer consisting of (a) a mixed resin, (b) a polyolefin, and a metal hydroxide which is a flame retardant is melt-kneaded to obtain the resin composition of this embodiment.

[0048] Next, the conductor 11 is prepared. Then, the resin composition of this embodiment is extruded using an extrusion molding machine to cover the conductor 11 and form an insulating layer 12 of a predetermined thickness. In this way, the electric wire 10 can be manufactured.

[0049] Furthermore, in this embodiment, after manufacturing the electric wire 10, the flame-retardant resin composition constituting the insulating layer 12 can be crosslinked, for example, by electron beam crosslinking or chemical crosslinking. In the electric wire 10 of this embodiment, such crosslinking is not essential, but it is preferable because it improves the oil resistance of the insulating layer 12 made of the flame-retardant resin composition.

[0050] When using the electronic crosslinking method, the resin composition is molded as the insulating layer 12 of the electric wire 10, and then crosslinked by irradiation with an electron beam of, for example, 1 to 30 MRad. When using the chemical crosslinking method, a crosslinking agent is added to the flame-retardant resin composition in advance, and after molding this flame-retardant resin composition as the insulating layer 12 of the electric wire 10, it is heat-treated to crosslink.

[0051] <Cable> One embodiment of the present invention is a cable in which a single-core or multi-core stranded wire, formed by twisting one or more insulated wires together, is provided with a shield braid on the outside, and a covering layer is applied to the outside of the shield braid. However, the separator can be freely installed and can be used either on the inside or outside while in contact with the shield braid. The material of the separator is not particularly limited. Furthermore, in the present invention, the separator may be omitted.

[0052] This cable, which is one embodiment of this design, will be described in detail with reference to Figure 2. Figure 2 is a cross-sectional view showing the structure of the cable according to this embodiment.

[0053] As shown in Figure 2, the cable 20 according to this embodiment is provided with a stranded wire made by twisting two electric wires 10 together, and a separator 21 provided around this stranded wire, with a braided shield layer 22 provided on the outside of the separator 21. Here, there is flexibility in the positioning of the separator 21, and for example, it can be placed inside or outside the shield layer 22 while in contact with the shield layer 22. The material of the separator 21 is not particularly limited.

[0054] On the other hand, the shield layer 22 is made of a conductive material, such as a metal, in order to exert a shielding effect. For example, the material of the braided shield layer 22 can be the same as the material of the conductor 11. In this case, the braiding density is 50% to 99%. The wire diameter is 0.05 mm to 0.3 mm, and preferably 0.1 mm to 0.2 mm. Subsequently, as shown in Figure 2, a covering layer (sheath) 23 is provided on the outside of the shield layer 22. This covering layer 23 is made of the resin composition described above.

[0055] The cable 20 of this embodiment is manufactured, for example, as follows. First, two electric wires 10 are manufactured using the method described above. Then, the two electric wires 10 are twisted together with intermediaries such as rayon yarn, paper tape, or jute, and then a separator 21 and a shield layer 22 are formed in that order using known methods to cover them. Furthermore, the resin composition of this embodiment is extruded onto the outer circumference of the shield layer 22 obtained in this way, in the same manner as the electric wire manufacturing method described above, to form a covering layer (sheath) 23 of a predetermined thickness. In this way, the cable 20 of this embodiment can be manufactured.

[0056] In this embodiment, the cable 20 was described as having a two-core stranded wire made by twisting two electric wires 10 together as core wires, but the core wire may be a single core (one wire), or a multi-core stranded wire other than two cores. Also, there may be no intervening material between the electric wire 10 and the covering layer 23.

[0057] Furthermore, although the above description used the example of using the aforementioned electric wire 10 in the cable 20 of this embodiment, it is not limited to this, and electric wires using general-purpose materials for the insulating layer can also be used.

[0058] When general-purpose materials are used for the insulating layer 12, it is preferable to include a flame retardant in the insulating layer 12 to obtain higher flame retardancy. However, the flame retardant must be a non-halogen material, and even among non-halogen flame retardants, it is preferable not to add phosphorus-based flame retardants such as red phosphorus or triazine-based flame retardants such as melamine cyanurate.

[0059] The polymer used in this insulating layer 12 is not particularly limited as long as it is halogen-free. Examples include polyolefins such as high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, ultra-low-density polyethylene, and ethylene-acrylic acid ester copolymers.

[0060] Rubber materials are also applicable, including ethylene-propylene copolymer rubber, ethylene-propylene-diene ternary copolymer rubber, acrylic rubber, ethylene-acrylic acid ester copolymer rubber, ethylene-octene copolymer rubber, ethylene-acrylic acid ester copolymer rubber, ethylene-octene copolymer rubber, ethylene-vinyl acetate copolymer rubber, ethylene-butene-1 copolymer rubber, butadiene-styrene copolymer rubber, isobutylene-isoprene copolymer rubber, and block copolymer rubber having polystyrene blocks.

[0061] Furthermore, engineering plastics can also be applied, including polyethylene terephthalate, polybutylene terephthalate, polyphenylene ether, polycarbonate, polyamide, polyphenyl sulfide, polyether ether ketone, polyethylene naphthalate, polybutylene naphthalate, and polyether sulfone, and these thermoplastic elastomers can also be used. The base polymer of this insulating layer 12 may be a single polymer or a blend of two or more polymers.

[0062] In the insulating layer 12, the resin composition made up of these materials may optionally contain crosslinking agents, crosslinking aids, flame retardant aids, ultraviolet absorbers, light stabilizers, softeners, lubricants, colorants, reinforcing agents, surfactants, inorganic fillers, plasticizers, metal chelating agents, foaming agents, compatibilizers, processing aids, stabilizers, and the like.

[0063] Crosslinking is necessary for oil resistance, and crosslinking treatments include chemical crosslinking using organic peroxides or silane compounds, irradiation crosslinking using electron beams or radiation, and crosslinking using other chemical reactions. Any of these crosslinking methods is applicable.

[0064] Furthermore, the insulating layer 12 and coating layer 23 described above must be crosslinked to ensure oil resistance. In this case, the degree of crosslinking can be defined by the gel fraction. Crosslinking treatments include chemical crosslinking using organic peroxides, sulfur compounds, or silanes, irradiation crosslinking using electron beams, radiation, etc., and crosslinking using other chemical reactions, but there is no particular limit, and any crosslinking method can be applied.

[0065] The thickness of the coating layer 23 is not particularly limited, but a thickness of 0.2 to 1.5 mm is particularly likely to produce the above effects. [Examples]

[0066] Next, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0067] [Manufacturing of insulated wires] First, as the conductor, a tin-plated conductor with 19 strands / 0.18 mm (wire diameter) was prepared. Next, 25 parts by mass of ethylene-methyl acrylate copolymer (Elbaroy 1125AC, manufactured by Nippon Polyethylene Co., Ltd.), 10 parts by mass of high-density polyethylene (Hyzex 5305E, manufactured by Prime Polymer Co., Ltd.), 25 parts by mass of maleic anhydride-modified high-density polyethylene (Fusabond E265, manufactured by DuPont), 10 parts by mass of maleic anhydride-modified ethylene-α-olefin copolymer (Tafma MH7020, manufactured by Mitsui Chemicals, Inc.), and ethylene-ethyl acrylate-maleic anhydride ternary copolymer (Bondine LX4110, manufactured by Arkema, Inc.) were used. 30 parts by mass of [material], 150 parts by mass of magnesium hydroxide (manufactured by Kyowa Chemical Co., Ltd., product name: Kisma 5L), 2 parts by mass of Irganox 1010 (manufactured by BASF) as an antioxidant, 8 parts by mass of TMPT (trimethylolpropane trimethacrylate) (manufactured by Shin Nakamura Chemical Co., Ltd.) as a crosslinking aid, 1 part by mass of zinc stearate as a metal soap, 2 parts by mass of magnesium 12-hydroxythrearate (manufactured by Katsuta Chemical Co., Ltd., EMS-6), and 3 parts by mass of a metal chelating agent (manufactured by Adeka Co., Ltd., CDA-6) were kneaded in a 25L kneader and pelletized in a granulator. The resulting pellets were extruded in a 65mm extruder to coat the outer circumference of the conductor, and a single-layer wire was produced in which the conductor was covered with an insulating layer. Furthermore, this wire was crosslinked by irradiation with a 10Mrad electron beam.

[0068] (Examples 1-2, Comparative Examples 1-4) A multi-core stranded wire was prepared by twisting two of the obtained insulated wires together. A 32 μm polyethylene-terephthalate separator was wrapped around it, and a shield braid with a braiding density of 80% was applied using a 0.11 mm tin-plated conductor to obtain a core.

[0069] The obtained core was extruded using a 20 mm extruder to a thickness of 0.7 mm using a resin composition with the composition shown in Table 1. The resulting coating layer was irradiated with an electron beam to crosslink it, and a cable 20 with the configuration shown in Figure 2 was fabricated.

[0070] The materials used to form the coating layer are as follows:

[0071] [Materials] (Base Polymer) · Ethylene Vinyl Acetate Copolymer 1: Levapren (trade name, manufactured by Lanxess, VA content 60% by mass) · Ethylene Vinyl Acetate Copolymer 2: Evaflex EV5274 (manufactured by Mitsui DuPont Chemicals, melting point: 89 °C) · Polyolefin: INFUSE 9100 (manufactured by Dow, melting point: 120 °C, density: 0.877 g / cm 3 ) · Acid-Modified Ethylene-α-Olefin Copolymer: Toughma MA7020 (manufactured by Mitsui Chemicals)

[0072] (Flame Retardant) · Aluminum Hydroxide 1: OL104ZO (manufactured by HUBER, BET specific surface area: 4 m 2 / g) · Aluminum Hydroxide 2: OL107ZO (manufactured by HUBER, BET specific surface area: 7 m 2 / g) · Magnesium Hydroxide: Magsees S4 (manufactured by Kojima Chemical) · Others: Composition shown in Table 2

[0073] [Characteristic Tests] Also, in order to obtain mechanical properties, each resin composition with the composition shown in Table 1 was made into a 1 mm sheet, and a crosslinked sheet was obtained by electron beam irradiation. Using this crosslinked sheet, the following various characteristic tests were conducted, and the results are shown together with Table 1.

[0074] (Tensile Test) As the initial tensile test, the obtained crosslinked sheet was punched out into No. 6 dumbbell test pieces, and a tensile test was carried out at a displacement speed of 250 mm / min to measure the tensile strength, 100% modulus, and elongation at break. The tensile strength was considered qualified if it was 10 MPa or more and unqualified if it was less than that. The 100% modulus, which is an index indicating flexibility, was considered good (◎) if it was less than 11 MPa, acceptable (○) if it was 11 MPa or more and less than 14 MPa, and unacceptable (×) if it was 14 MPa or more. The elongation at break was considered good (◎) if it was 150% or more, acceptable (○) if it was 120% or more, and unacceptable (×) if it was less than 110%.

[0075] (Oil resistance test) For the oil resistance test, the obtained cross-linked sheet was punched out into No. 6 dumbbell test pieces, immersed in IRM903 test oil heated to 70°C for 168 hours, and then a tensile test was performed at a displacement rate of 250 mm / min to measure the tensile strength. The rate of change from the initial tensile strength was calculated, and it was judged as acceptable (○) if the rate of change in tensile strength was -30% or more, and unacceptable (×) if it was less than -30%.

[0076] (Low-temperature test) For the low-temperature test (low-temperature elongation), cross-linked sheets were punched out into No. 6 dumbbell test pieces and left in a low-temperature chamber at -40°C for more than 4 hours. The elongation at fracture was measured at a displacement rate of 25 mm / min. Elongations of 30% or more were rated as good (◎), those between 20% and 30% were rated as acceptable (○), and those below 20% were rated as unacceptable (×).

[0077] (Flame retardant) For flame retardancy evaluation, a 600mm long cable was held vertically and exposed to flames for 60 seconds. After removing the flames, a pass rate of 67% or higher was considered acceptable (○), while a pass rate below 67% was considered unacceptable (×).

[0078] (comprehensive evaluation) In the above testing method, the overall evaluation was rated as "acceptable" (○) if all evaluations were marked with ◎ or ○, and "unacceptable" (×) if any evaluation included ×.

[0079] [Table 1]

[0080] [Table 2]

[0081] Based on the above results, Examples 1 and 2 received either ◎ or ○ in all evaluations, so the overall evaluation was ○.

[0082] On the other hand, Comparative Examples 1 and 2 failed the 100% modulus test because they did not contain low-density polyolefins. Furthermore, Comparative Example 3 failed the test because it contained a large amount of flame retardant and had low elongation at break. Comparative Example 4 failed the flame retardancy test because it used magnesium hydroxide as the flame retardant.

[0083] Although the present invention has been described with reference to the above embodiments and examples, the present invention is not limited to the above embodiments and examples, and can be modified in various ways without departing from the spirit of the invention. [Industrial applicability]

[0084] The non-halogen flame-retardant resin composition of the present invention can be used not only for non-halogen and flame-retardant electric wires and cables, but also for sheets, films, panels, mats, pipes, protective materials, fillers, fibers, resin molded products, resin substrates, stationery, building materials, connectors, bushings, grommets, terminal blocks, and internal terminal insulators, etc., where halogen-free flame retardancy is required. [Explanation of Symbols]

[0085] 10 Electric wire 11 Conductors 12 Insulating layer 20 Cables 21 Separator 22 Shield Layer 23 Covering layer

Claims

1. A non-halogen flame-retardant resin composition comprising: (a) a mixed resin of an ethylene vinyl acetate copolymer having a vinyl acetate content of 60% by mass or more and an ethylene-based polymer having a melting point of 115°C or higher (excluding acid-modified polyolefins); and (b) a base polymer containing an acid-modified polyolefin; and a flame retardant containing aluminum hydroxide, The mass ratio of the (a) mixed resin to the (b) polyolefin is (a):(b) = 95:5 to 70:

30. The density of the ethylene polymer with a melting point of 115°C or higher is 0.9 g / cm³. ３ It is less than, A non-halogen flame-retardant resin composition containing 150 to 180 parts by mass of the flame retardant with respect to a total of 100 parts by mass of the mixed resin (a) and the polyolefin (b).

2. In the non-halogen flame-retardant resin composition according to claim 1, A non-halogen flame-retardant resin composition in which the content of the ethylene vinyl acetate copolymer is 40% by mass or less when the total of the mixed resin (a) and the polyolefin (b) is 100% by mass.

3. In the non-halogen flame-retardant resin composition according to claim 2, A non-halogen flame-retardant resin composition in which the aluminum hydroxide is aluminum hydroxide that has been treated with silane.

4. In the non-halogen flame-retardant resin composition according to claim 3, The aluminum hydroxide treated with the silane has a specific surface area (BET) of 4 m². ２ A non-halogen flame-retardant resin composition having a concentration of 1 / g or more.

5. A wire having a conductor and an insulating layer provided around the conductor, The insulating layer is a non-halogen flame-retardant resin composition containing (a) a mixed resin of an ethylene vinyl acetate copolymer having a vinyl acetate content of 60% by mass or more and an ethylene-based polymer with a melting point of 115°C or higher (excluding acid-modified polyolefins), and (b) an acid-modified polyolefin, and a flame retardant containing aluminum hydroxide. The mass ratio of the (a) mixed resin to the (b) polyolefin is (a):(b) = 95:5 to 70:

30. The density of the ethylene polymer with a melting point of 115°C or higher is 0.9 g / cm³. ３ It is less than, An electric wire comprising a non-halogen flame-retardant resin composition containing 150 to 180 parts by mass of the flame retardant per 100 parts by mass of the total of the (a) mixed resin and the (b) polyolefin.

6. In the electric wire described in claim 5, An electric wire in which the insulating layer is a crosslinked product of the non-halogen flame-retardant resin composition.

7. A cable comprising a single-core or multi-core stranded wire made by twisting together one or more single-layer or multi-layered wires, a shield braid or shield braid having a separator provided on the outside thereof, and a covering layer covering the outside of the shield braid, The coating layer is a non-halogen flame-retardant resin composition containing (a) a mixed resin of an ethylene vinyl acetate copolymer having a vinyl acetate content of 60% by mass or more and an ethylene-based polymer with a melting point of 115°C or higher (excluding acid-modified polyolefins), and (b) an acid-modified polyolefin as a base polymer, and a flame retardant containing aluminum hydroxide. The mass ratio of the (a) mixed resin to the (b) polyolefin is (a):(b) = 95:5 to 70:

30. The density of the ethylene polymer with a melting point of 115°C or higher is 0.9 g / cm³. ３ It is less than, A cable made from a non-halogen flame-retardant resin composition containing 150 to 180 parts by mass of the flame retardant per 100 parts by mass of the total of the (a) mixed resin and the (b) polyolefin.

8. In the cable according to claim 7, A cable in which the coating layer is a crosslinked product of the non-halogen flame-retardant resin composition.

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