Non-halogen flame-retardant resin composition, insulated wire, and cable

Abstract

To provide a non-halogen flame-retardant resin composition that, while being non-halogen, has high tear strength, can maintain excellent oil resistance, and has good flexibility, and an insulated wire and a cable using the non-halogen flame-retardant resin composition.SOLUTION: A non-halogen flame-retardant resin composition comprises a base polymer (A) obtained by mixing (a1) an ethylene polymer having a melting point of 115°C or higher and (a2) an ethylene polymer having a melting point of lower than 115°C, and a metal hydroxide (B), wherein the content of the metal hydroxide (B) is from 150 pts.mass to 200 pts.mass per 100 pts.mass of the base polymer (A), and the base polymer (A) does not contain an ethylene-vinyl acetate copolymer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a non-halogen flame-retardant resin composition, an insulated wire, and a cable. In particular, the present invention relates to a non-halogen flame-retardant resin composition having excellent tear strength, oil resistance, and flexibility, and an insulated wire and a cable using the non-halogen flame-retardant resin composition. [Background technology]

[0002] Electric wires and cables used in vehicles such as railway cars and automobiles are required to have high tear strength, oil resistance, flexibility, and the like depending on the environment in which they are used.

[0003] It is known that halogen-based flame retardants and phosphorus-based flame retardants such as red phosphorus are added to impart high flame retardancy. However, halogen-based flame retardants generate halogen gases during combustion, and their use lacks consideration for the growing environmental issues worldwide. Furthermore, phosphorus-based flame retardants such as red phosphorus also have problems such as generating phosphine during combustion and phosphoric acid during disposal, which can contaminate groundwater veins.

[0004] On the other hand, metal hydroxides used as flame retardants do not cause the above-mentioned problems compared to halogen-based flame retardants and phosphorus-based flame retardants, but they need to be highly loaded to achieve the desired flame retardancy.

[0005] It is also known that the use of polar polymers such as ethylene-vinyl acetate copolymers is effective in achieving high oil resistance (fuel resistance) (see, for example, Patent Documents 1 and 2). However, when ethylene-vinyl acetate copolymers are highly loaded with magnesium hydroxide, a flame retardant, the mechanical properties are significantly reduced, making it difficult to obtain high tear strength in particular.

[0006] Furthermore, resin compositions containing a specific ethylene-α-olefin block copolymer and a metal hydroxide in an attempt to improve oil resistance and cold resistance, as well as electric wires and cables having an insulating layer or covering layer formed therefrom, are known (see, for example, Patent Document 3). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 5907015 [Patent Document 2] Patent No. 5733352 [Patent Document 3] Japanese Patent Application Laid-Open No. 2015-00913 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention aims to provide a halogen-free, flame-retardant resin composition that has high tear strength, excellent oil resistance, and good flexibility, and an insulated wire and cable that use the halogen-free, flame-retardant resin composition. Other objects and novel features will become apparent from the description and accompanying drawings of this specification. [Means for solving the problem]

[0009] One embodiment of the halogen-free flame-retardant resin composition is a halogen-free flame-retardant resin composition containing a base polymer (A) which is a mixture of (a1) an ethylene-based polymer having a melting point of 115°C or more and (a2) an ethylene-based polymer having a melting point of less than 115°C, and a metal hydroxide (B), wherein the metal hydroxide (B) is present in an amount of 150 parts by mass or more and 200 parts by mass or less per 100 parts by mass of the base polymer (A), and the base polymer (A) does not contain an ethylene-vinyl acetate copolymer.

[0010] An insulated wire according to one embodiment has a conductor and an insulating layer provided around the conductor, wherein the insulating layer is made of a halogen-free flame-retardant resin composition containing a base polymer (A) that is a mixture of (a1) an ethylene-based polymer having a melting point of 115°C or more and (a2) an ethylene-based polymer having a melting point of less than 115°C, and a metal hydroxide (B), wherein the metal hydroxide (B) is present in an amount of 150 parts by mass or more and 200 parts by mass or less per 100 parts by mass of the base polymer (A), and the base polymer (A) does not contain an ethylene-vinyl acetate copolymer.

[0011] One embodiment of the cable is a cable having a conductor, an insulating layer formed around the conductor, and a coating layer formed around the insulating layer, wherein the coating layer is made of a halogen-free flame-retardant resin composition containing a base polymer (A) that is a mixture of (a1) an ethylene-based polymer having a melting point of 115°C or more and (a2) an ethylene-based polymer having a melting point of less than 115°C, and a metal hydroxide (B), wherein the metal hydroxide (B) is present in an amount of 150 parts by mass or more and 200 parts by mass or less per 100 parts by mass of the base polymer (A), and the base polymer (A) does not contain ethylene-vinyl acetate copolymer. [Effects of the Invention]

[0012] According to one embodiment, it is possible to obtain a halogen-free flame-retardant resin composition that is halogen-free yet has high tear strength, and furthermore, can maintain excellent oil resistance and flame retardancy, and has good flexibility, as well as an electric wire and a cable using the same. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view showing a structural example of an insulated wire according to an embodiment. [Figure 2] 1 is a cross-sectional view showing an example of the structure of a cable according to an embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0014] An embodiment of the present invention will be described below with reference to the drawings. In all the drawings for explaining the embodiment, components having the same functions are designated by the same reference numerals, and repeated explanations thereof will be omitted. Furthermore, in the following embodiment, explanations of identical or similar parts will not be repeated unless specifically required.

[0015] <Halogen-free flame-retardant resin composition> The halogen-free flame-retardant resin composition of this embodiment will be described in detail below.

[0016] As described above, the halogen-free flame-retardant resin composition according to this embodiment contains a base polymer (A) which is a mixture of (a1) an ethylene polymer having a melting point of 115°C or higher and (a2) an ethylene polymer excluding the component (a1), and a metal hydroxide (B). The amount of the metal hydroxide (B) is 150 parts by mass or more and 200 parts by mass or less per 100 parts by mass of the base polymer (A). The base polymer (A) does not contain an ethylene-vinyl acetate copolymer.

[0017] First, the configuration of the halogen-free flame-retardant resin composition in this embodiment will be described.

[0018] [Base polymer (A)] The base polymer (A) used in this embodiment is a base polymer made of a mixed resin obtained by mixing (a1) an ethylene polymer having a melting point of 115°C or higher and (a2) an ethylene polymer other than the component (a1). The (a1) ethylene polymer having a melting point of 115°C or higher is preferably the main component of the base polymer (A). In this embodiment, the (a2) ethylene polymer other than the component (a1) is an ethylene polymer having a melting point of less than 115°C. However, the base polymer (A) does not contain ethylene vinyl acetate copolymer (EVA). Here, "the base polymer (A) does not contain ethylene vinyl acetate copolymer (EVA)" means that the amount of ethylene vinyl acetate copolymer (EVA) contained in the base polymer (A) is 0.1 parts by mass or less per 100 parts by mass of the base polymer (A). Each component will be described below. (a1) The expression "main component" as an ethylene polymer having a melting point of 115°C or higher means the component that is contained in the base polymer (A) in the largest amount by mass, and includes the case where the content of the ethylene polymer is the same as that of other polymer components.

[0019] (a1) Ethylene polymer having a melting point of 115°C or higher The halogen-free flame-retardant resin composition of this embodiment has a base polymer containing, as a main component, an ethylene polymer having a melting point of 115°C or higher. The main component (a1) ethylene polymer having a melting point of 115°C or higher has a melting point of 115°C or higher, as described above. The (a1) ethylene polymer having a melting point of 115°C or higher does not necessarily contain EVA, and multiple ethylene polymers having melting points of 115°C or higher may be mixed. In this specification, unless otherwise specified, melting point refers to a value measured by differential scanning calorimetry (DSC).

[0020] Ethylene polymers with high melting points have a large amount of crystals, which prevents the IRM902 or IRM903 test oil used in oil resistance tests from penetrating between polymer molecules, thereby suppressing changes in the physical properties of the halogen-free flame-retardant resin composition.

[0021] The (a1) ethylene polymer having a melting point of 115°C or higher may be a polymer containing ethylene as a monomer and having a melting point of 115°C or higher. The (a1) ethylene polymer having a melting point of 115°C or higher includes polyethylene as well as ethylene copolymers containing ethylene and other monomers. The ethylene copolymer is preferably a copolymer having ethylene and an α-olefin as a constituent unit. Specific examples of the (a1) ethylene polymer having a melting point of 115°C or higher include low-density polyethylene (LDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), linear very low-density polyethylene (VLDPE), 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 (EO), and the like. Examples of the polymer include ethylene copolymer polypropylene, ethylene-propylene copolymer (EPR), poly-4-methyl-pentene-1, hydrogenated styrene-butadiene copolymer (H-SBR), copolymers of ethylene and an α-olefin having 3 to 30 carbon atoms, ethylene-styrene copolymers, ethylene-butene-1 copolymers such as ethylene-propylene-butene-1 terpolymers containing butene-1 as the main component, ethylene-α-olefin copolymers such as ethylene-hexene-1 copolymers and ethylene-octene-1 copolymers, and olefin block copolymers.

[0022] The ethylene polymer (a1) having a melting point of 115°C or higher used herein is an ethylene polymer having a density of 0.9 g / cm 3 It is preferable that the ethylene polymer be less than 100%. This can improve the flexibility and oil resistance of the halogen-free flame-retardant resin composition. As described above, EVA is not contained because EVA has low tear strength and may reduce the tear strength that is the target of this embodiment.

[0023] Among these, specific examples of olefin block copolymers include D9000, D9007, D9100, D9107, D9500, D9507, D9530, D9807, and D9817 of the INFUSE series, a trade name of Dow Chemical Company.

[0024] (a2) Ethylene-based polymer The (a2) ethylene polymer does not necessarily contain ethylene-vinyl acetate copolymer (EVA), and may contain a mixture of multiple other ethylene polymers. Note that the (a2) component does not include the aforementioned (a1) ethylene polymer having a melting point of 115°C or higher.

[0025] The (a2) ethylene polymer used here preferably has a melting point of less than 115° C. That is, the (a2) ethylene polymer is preferably an ethylene polymer having a melting point of less than 115° C. Such an ethylene polymer having a low melting point has a small amount of crystals, and therefore has excellent acceptability for fillers such as flame retardants and is highly flexible.

[0026] The (a2) ethylene-based polymer may be any polymer containing ethylene as a monomer. The (a2) ethylene-based polymer includes polyethylene as well as ethylene-based copolymers containing ethylene and other monomers. The ethylene-based copolymer is preferably a copolymer having ethylene and an α-olefin as structural units. Specific examples of (a2) ethylene polymers include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), linear very low-density polyethylene (VLDPE), 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 copolymerized polypropylene, ethylene-propylene copolymer (EPR), poly-4-methyl-pentene-1, hydrogenated styrene-butadiene copolymer (H-SBR), copolymers of ethylene and an α-olefin having 3 to 30 carbon atoms, ethylene-styrene copolymer, ethylene-butene-1 copolymers such as ethylene-propylene-butene-1 terpolymers containing butene-1 as the main component, ethylene-α-olefin copolymers such as ethylene-hexene-1 copolymer and ethylene-octene-1 copolymer, and olefin block copolymers.

[0027] The ethylene polymer (a2) used here has a density of 0.9 g / cm 3 It is preferable that the ethylene polymer is an ethylene polymer having a molecular weight of less than 1000. This can improve the flexibility of the halogen-free flame-retardant resin composition.

[0028] Furthermore, by using (a1) an ethylene polymer having a melting point of 115°C or higher as the main component, the amount of crystals contained in the base polymer (A) can be increased, which results in high tear strength and flexibility while minimizing changes in the physical properties of the halogen-free flame-retardant resin composition in oil resistance tests.

[0029] The base polymer (A) of the halogen-free flame-retardant resin composition of the present embodiment contains the above-mentioned components (a1) and (a2) as essential components, and may further contain the next described component (a3) ​​as necessary.

[0030] (a3) Acid-modified ethylene polymer The (a3) ​​acid-modified ethylene polymer used here is an ethylene polymer that has been acid-modified and is an optional component. Blending such an acid-modified ethylene polymer is preferred because it can strengthen adhesion to fillers such as flame retardants and improve mechanical properties such as tensile strength. The (a3) ​​acid-modified ethylene polymer should also be free from EVA-derived components. In other words, the (a3) ​​acid-modified ethylene polymer does not include an acid-modified ethylene-vinyl acetate copolymer.

[0031] The ethylene-based polymer before modification used here may be any polymer containing ethylene as a monomer. The ethylene-based polymer before modification includes polyethylene as well as ethylene-based copolymers containing ethylene and other monomers. The ethylene-based copolymer is preferably a copolymer having ethylene and an α-olefin as a constituent unit. Specific examples of the ethylene-based polymer before modification include low-density polyethylene (LDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), linear very low-density polyethylene (VLDPE), 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-octene copolymer (ECR ... Examples of such copolymers include ethylene copolymer polypropylene, ethylene-propylene copolymer (EPR), poly-4-methyl-pentene-1, hydrogenated styrene-butadiene copolymer (H-SBR), copolymers of ethylene and an α-olefin having 3 to 30 carbon atoms, ethylene-styrene copolymers, ethylene-butene-1 copolymers such as ethylene-propylene-butene-1 terpolymers containing butene-1 as the main component, ethylene-α-olefin copolymers such as ethylene-hexene-1 copolymers and ethylene-octene-1 copolymers, and olefin block copolymers.

[0032] Among these, ethylene-butene-1 copolymer, ethylene-hexene-1 copolymer, and ethylene-octene-1 copolymer are preferred because they have a small amount of crystallinity, can accept fillers, and can provide flexibility.

[0033] The acid used for modification includes maleic acid, maleic anhydride, fumaric acid, and the like.

[0034] In this embodiment, the base polymer (A) contains the components (a1) and (a2), and optionally the component (a3), as described above. The blending ratio of the components (a1) and (a2) in the base polymer (A) is not particularly limited, but is preferably in the range of 1:1 to 5:1, and more preferably 1:1 to 3:1, by mass.

[0035] Since component (a3) ​​is an optional component, it does not matter whether or not component (a3) ​​is added, but adding component (a3) ​​is preferable because it is expected to improve mechanical properties. When component (a3) ​​is added, the blending ratio of component (a2) to component (a3) ​​is not particularly limited, but a range of (a2):(a3)=1:1 to 10:1 on a mass basis is preferred, and a range of 4:1 to 9:1 is more preferred.

[0036] [Metal hydroxide (B)] In this embodiment, a metal hydroxide (B) is used as the flame retardant. There are no particular limitations on the metal hydroxide (B) as long as it can be used as a flame retardant.

[0037] Specific examples of the metal hydroxide used here include magnesium hydroxide, aluminum hydroxide, calcium hydroxide, etc., and among these, magnesium hydroxide and aluminum hydroxide are preferred. Among the metal hydroxides, magnesium hydroxide has a decomposition temperature close to that of the polymer, and therefore can effectively exhibit high flame retardancy.

[0038] The amount of metal hydroxide (B) added is preferably 150 parts by mass or more and 200 parts by mass or less per 100 parts by mass of the base polymer (A). By adding 150 parts by mass or more, sufficient flame retardancy can be obtained, and by adding 200 parts by mass or less, appropriate elongation at break and the like can be ensured.

[0039] Taking into consideration dispersibility, etc., the metal hydroxide (B) can be surface-treated with a silane coupling agent, a titanate coupling agent, a fatty acid such as stearic acid, etc. Among these, a metal hydroxide silane-treated with a silane coupling agent is preferred because of its excellent reinforcing effect and aging properties.

[0040] The metal hydroxide (B) is added in particulate form. The particle size of the metal hydroxide (B) is preferably small. Here, the particle size refers to the average particle size. For example, it is preferable to use particles with an average particle size D50 in the range of 0.6 to 1.5 μm. In this specification, the average particle size refers to the particle size at 50% of the cumulative value in the particle size distribution determined by a laser diffraction / scattering method.

[0041] Flame retardants can be supplemented with flame retardant synergists to enhance their flame retardancy. However, phosphorus-based flame retardants such as red phosphorus and triazine-based flame retardants such as melamine cyanurate are not suitable because they may generate phosphine gas and cyanide gas, which are harmful to humans. Other flame retardant synergists can be used, such as clay, silica, zinc stannate, zinc borate, calcium borate, dolomide hydroxide, and silicone.

[0042] Furthermore, in addition to the components described above, the resin composition according to the present embodiment may contain, as necessary, a crosslinking agent, a crosslinking aid, an ultraviolet absorber, a light stabilizer, a softener, a lubricant, a colorant, a reinforcing agent, a surfactant, an inorganic filler, an antioxidant, a plasticizer, a metal chelating agent, a foaming agent, a compatibilizer, a processing aid, a stabilizer, and the like.

[0043] In this embodiment, when the resin composition described above is used for the insulating layer of an insulated wire or the covering layer of a cable, it is preferable that the resin composition is crosslinked. In other words, it is preferable that the resin composition has a crosslinked structure. This is because 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.

[0044] Before measuring the gel fraction, the material to be used is weighed. Next, the material is immersed in xylene heated to 110°C for 24 hours. After immersion, the material is left at atmospheric pressure at 20°C for 3 hours and 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 (after treatment) to the mass before immersion in xylene (before treatment). A gel fraction of 80% or more is insufficient to achieve sufficient oil resistance. In other words, a gel fraction of less than 80% is insufficient to achieve sufficient oil resistance. Furthermore, a gel fraction of 90% or more is preferable, with 95% or more being more preferable.

[0045] The crosslinking treatment may be chemical crosslinking using an organic peroxide, a sulfur compound, or a silane, or the like; irradiation crosslinking using an electron beam, radiation, or the like; or crosslinking using other chemical reactions; and any crosslinking method can be applied without any particular limitation.

[0046] <Insulated wire> Next, an insulated wire according to one embodiment will be described with reference to Fig. 1. Fig. 1 is a cross-sectional view showing the structure of the insulated wire according to this embodiment.

[0047] 1, an insulated wire 11 according to this embodiment includes a conductor 11a and an insulating layer 11b that covers the conductor 11a. The insulating layer 11b may have a single layer structure or a multilayer structure having two or more layers.

[0048] The conductor 11a can be a commonly used metal wire, such as a copper wire or a copper alloy wire, or an aluminum wire, gold wire, or silver wire. The conductor 11a can also be a metal wire plated with a metal such as tin or nickel. The conductor 11a can have a single wire structure, or a stranded conductor formed by twisting metal wires together. Examples of stranded conductors that can be used include concentric stranded wires, bunched stranded wires, and composite stranded wires formed by twisting these concentrically. Lightly compressed conductors formed by compressing these stranded wires are preferred because they allow the insulated wire to have a smaller diameter.

[0049] The insulating layer 11b is made of the resin composition described above. That is, the halogen-free flame-retardant resin composition according to this embodiment can be used for the insulating layer 11b. In this case, it is preferable to use a resin composition that has been subjected to a crosslinking treatment as described above. That is, it is preferable to use a resin composition having a crosslinked structure. The thickness of this insulating layer 11b is not particularly limited, but is preferably 0.5 to 3.5 mm.

[0050] The insulated wire 11 of this embodiment is produced, for example, as follows: First, materials containing the components (a1) to (a3) ​​that form the base polymer (A) and the metal hydroxide (B) that serves as the flame retardant are melt-kneaded to obtain the resin composition of this embodiment.

[0051] Thereafter, the conductor 11a is prepared. Then, the resin composition of the present embodiment is extruded using an extrusion molding machine so as to cover the periphery of the conductor 11a, thereby forming the insulating layer 11b of a predetermined thickness. In this manner, the insulated wire 11 can be manufactured.

[0052] In the present embodiment, after the insulated wire 11 is produced, the flame-retardant resin composition constituting the insulating layer 11b is crosslinked, for example, by electron beam crosslinking or chemical crosslinking. This crosslinking allows the insulating layer 11b to have a crosslinked structure. This type of crosslinking is preferable because it improves the oil resistance of the insulating layer 11b made of the flame-retardant resin composition.

[0053] When using the electron beam crosslinking method, the resin composition is molded into the insulating layer 11b of the insulated wire 11, 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 the flame-retardant resin composition to which the crosslinking agent has been added is molded into the insulating layer 11b of the insulated wire 11, and then crosslinked by heat treatment.

[0054] <Cable> A cable according to one embodiment of the present invention is a cable in which a single-core or multi-core stranded wire formed by twisting together one or more insulated electric wires is covered with a covering layer. The cable according to one embodiment will be described in detail with reference to Fig. 2. Fig. 2 is a cross-sectional view showing the structure of a cable according to this embodiment.

[0055] As shown in Fig. 2, cable 12 according to this embodiment includes an insulated wire having an insulating layer 12b disposed around a conductor 12a, and a covering layer (sheath) 12c disposed around the insulated wire. That is, covering layer (sheath) 12c is disposed around insulating layer 12b. Covering layer 12c is made of the resin composition described above. That is, covering layer 12c preferably uses the halogen-free flame-retardant resin composition according to this embodiment.

[0056] If necessary, the resin composition constituting the coating layer 12c may contain added crosslinking agents, crosslinking aids, flame retardant aids, ultraviolet absorbers, light stabilizers, softeners, lubricants, colorants, reinforcing materials, surfactants, inorganic fillers, plasticizers, metal chelating agents, foaming agents, compatibilizers, processing aids, stabilizers, etc.

[0057] From the viewpoint of oil resistance, it is preferable to crosslink the coating layer 12c. As described above for the insulating layer, the crosslinking treatment can be chemical crosslinking using organic peroxides or silane compounds, irradiation crosslinking using electron beams or radiation, or crosslinking using other chemical reactions, and any crosslinking method can be applied. By crosslinking, the coating layer 12c can have a crosslinked structure.

[0058] Here, the thickness of the coating layer 12c is not particularly limited, but a thickness of 0.5 to 2 mm is preferable in terms of achieving the effects of the present invention.

[0059] In the present embodiment, the cable 12 has been described as having a single insulated wire as the core wire, but the core wire may be a two-core twisted wire in which two insulated wires are twisted together, or a multi-core twisted wire other than a two-core twisted wire.

[0060] In the case of a multi-core stranded wire in which two or more insulated wires are twisted together, the wires are twisted together with staple yarn, paper tape, jute, or the like, and then the resin composition of this embodiment is extruded to cover the twisted wire in the same manner as in the above-described method for producing an insulated wire, thereby forming a coating layer (sheath) 12c of a predetermined thickness. Note that known layer structures such as a separator and a shielding layer may also be provided.

[0061] In addition, in the cable 12 of this embodiment, the resin composition of this embodiment may be used as the insulating layer 12b, or an insulated wire obtained by using a general-purpose material for the insulating layer may be used. When the resin composition of this embodiment is used, the obtained cable 12 has a configuration in which a covering layer (sheath) 12c is provided on the outer periphery of the insulated wire 11.

[0062] Furthermore, when a general-purpose material is used for the insulating layer 12b, adding a flame retardant to the insulating layer 12b is preferable because it can provide higher flame retardancy. However, the flame retardant must be a halogen-free material, and even if a halogen-free flame retardant is used, it is preferable not to add a phosphorus-based flame retardant such as red phosphorus or a triazine-based flame retardant such as melamine cyanurate.

[0063] The polymer used for the insulating layer 12b is not particularly limited as long as it is a halogen-free resin, and examples thereof include polyolefins such as high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, very low-density polyethylene, and ethylene-acrylic acid ester copolymer.

[0064] Furthermore, a rubber material can also be used for the insulating layer 12b, such as ethylene-propylene copolymer rubber, ethylene-propylene-diene terpolymer rubber, acrylic rubber, ethylene-acrylate copolymer rubber, ethylene-octene copolymer rubber, ethylene-acrylate 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 a polystyrene block.

[0065] Furthermore, engineering plastics can also be used for the insulating layer 12b, such as polyethylene terephthalate, polybutylene terephthalate, polyphenylene ether, polycarbonate, polyamide, polyphenyl sulfide, polyether ether ketone, polyethylene naphthalate, polybutylene naphthalate, polyether sulfone, etc. Thermoplastic elastomers of these can also be used. The base polymer of this insulating layer 12b can be a single polymer or a blend of two or more polymers. [Example]

[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] (Examples 1 to 3, Comparative Example 1) A resin composition was produced by mixing and kneading raw materials to obtain the composition shown in Table 1. The resulting resin composition was evaluated for the following various properties, and the results are also shown in Table 1. The materials used to form the coating layer were as follows:

[0068] [material] (Base polymer (A)) <Component (a1)> Ethylene polymer 1: INFUSE 9000 (manufactured by Dow, melting point: 120°C, density: 0.877 g / cm 3 )

[0069] <(a2) component> Ethylene polymer 2: Toughma DF740 (Mitsui Chemicals, Inc.; melting point: 55°C)

[0070] <(ca) component> Vinyl acetate copolymer: Evaflex EV45LX (Mitsui DuPont Chemical Co., Ltd.; no melting point)

[0071] <(a3) component> Acid-modified ethylene-α-olefin copolymer: Toughma MA7020 (Mitsui Chemicals)

[0072] (Metal hydroxide (B)) Magnesium hydroxide: Kisuma 5L (Kyowa Chemical Industry Co., Ltd.; surface treatment grade with silane coupling agent)

[0073] (additives) Crosslinking agent: Perbutyl P (NOF Corporation) Other: Compositions shown in Table 2

[0074] [Characteristics test] To obtain mechanical properties, each resin composition shown in Table 1 was kneaded in a 6-inch roll and then hot-pressed to produce 1 mm and 2 mm sheets, yielding crosslinked sheets. These crosslinked sheets were used to carry out the following various property tests, and the results are also shown in Table 1.

[0075] (Tensile test) For the initial tensile test, the obtained 1 mm crosslinked sheet was punched into No. 6 dumbbell test pieces and subjected to a tensile test at a displacement rate of 200 mm / min to measure the tensile strength and elongation at break. Tensile strength was rated as good (○) for 10 MPa or more, as fair (△) for less than 10 MPa and 8 MPa or more, and as poor (×) for less than 8 MPa.

[0076] (Fuel resistance test (IRM903, 168h)) For the fuel resistance test, the resulting 1 mm crosslinked sheet was punched into No. 6 dumbbell test pieces, which were immersed in IRM903 test oil heated to 70°C for 168 hours, and then subjected to a tensile test at a displacement rate of 200 mm / min to measure tensile strength. The rate of change from the initial tensile strength was calculated, and a rate of change of -30% or more was evaluated as acceptable (○), and a rate of change of less than -30% was evaluated as unacceptable (×).

[0077] (Tear test) For the tear test, the obtained crosslinked sheet was punched into a test piece conforming to CEI 20-34 10.1, and the tear strength was measured at a displacement rate of 500 mm / min. A test piece of 10 N / mm or more was rated as good (○), a test piece of less than 10 N / mm and 8 N / mm or more was rated as fair (△), and a test piece of less than 8 N / mm was rated as poor (×). The thickness of the crosslinked sheet was 1 mm in the examples and 2 mm in the comparative examples.

[0078] (Flexibility test) To evaluate flexibility, the obtained crosslinked sheets were cut into strip test pieces 30 mm wide and 80 mm long, and the maximum bending stress was measured at a support distance of 60 mm and a pressing speed of 50 mm / min. The bending stress was calculated using the formula [(3 × bending load × support distance) / (2 × thickness × width squared)]. A maximum bending stress of 3 MPa or less was evaluated as acceptable (○), and one exceeding 3 MPa was evaluated as unacceptable (×). The thickness of the crosslinked sheets was 1 mm in the examples and 2 mm in the comparative examples.

[0079] (comprehensive evaluation) In the above test method, the overall evaluation was rated as "pass" (◯) when all evaluations were "◯" or "△", and "fail" (×) when any evaluation was "×".

[0080] [Table 1]

[0081] [Table 2]

[0082] From the above results, Examples 1 to 3 were rated as either good or fair in all evaluations, and therefore the overall evaluation was good.

[0083] On the other hand, Comparative Example 1, which is an example in which EVA was used, was rejected due to insufficient tear strength.

[0084] From the above, it was confirmed that the halogen-free flame-retardant resin composition of the present embodiment has excellent tear strength, oil resistance, and flexibility, and is useful for the insulating layer of an insulated wire or the covering layer of a cable.

[0085] 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 present invention. [Industrial Applicability]

[0086] The halogen-free flame-retardant resin composition of the present invention can be used not only for halogen-free, flame-retardant insulated 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 terminal internal insulators, all of which require halogen-free flame retardancy. [Explanation of symbols]

[0087] 11 Insulated wire 11a, 12a conductor 11b, 12b insulating layer 12 Cable 12c coating layer

Claims

1. A halogen-free flame-retardant resin composition comprising: a base polymer (A) which is a mixture of (a1) an ethylene polymer having a melting point of 115°C or higher and (a2) an ethylene polymer having a melting point of lower than 115°C; and a metal hydroxide (B), the content of the metal hydroxide (B) is 150 parts by mass or more and 200 parts by mass or less relative to 100 parts by mass of the base polymer (A); The base polymer (A) is a halogen-free flame-retardant resin composition that does not contain an ethylene-vinyl acetate copolymer.

2. The halogen-free flame-retardant resin composition according to claim 1, The halogen-free flame-retardant resin composition, wherein the base polymer (A) further contains (a3) ​​an acid-modified ethylene polymer.

3. The halogen-free flame-retardant resin composition according to claim 1, The halogen-free flame-retardant resin composition, wherein the metal hydroxide (B) is aluminum hydroxide or magnesium hydroxide, and has been subjected to a silane treatment.

4. The halogen-free flame-retardant resin composition according to claim 1, a blending ratio of the (a1) ethylene polymer having a melting point of 115°C or higher to the (a2) ethylene polymer having a melting point of lower than 115°C is (a1):(a2)=1:1 to 5:1 by mass.

5. The halogen-free flame-retardant resin composition according to claim 1, The halogen-free flame-retardant resin composition has a crosslinked structure, The halogen-free flame-retardant resin composition has a maximum bending stress of 3.0 MPa or less.

6. An insulated wire having a conductor and an insulating layer provided around the conductor, the insulating layer is composed of a halogen-free flame-retardant resin composition containing a base polymer (A) in which (a1) an ethylene-based polymer having a melting point of 115°C or more and (a2) an ethylene-based polymer having a melting point of less than 115°C are mixed, and a metal hydroxide (B); the content of the metal hydroxide (B) is 150 parts by mass or more and 200 parts by mass or less relative to 100 parts by mass of the base polymer (A); The insulated wire, wherein the base polymer (A) does not contain an ethylene vinyl acetate copolymer.

7. The insulated wire according to claim 6, The insulated wire comprises a halogen-free flame-retardant resin composition having a crosslinked structure and a maximum bending stress of 3.0 MPa or less.

8. A cable having a conductor, an insulating layer provided on the outer periphery of the conductor, and a coating layer provided on the outer periphery of the insulating layer, the coating layer is composed of a halogen-free flame-retardant resin composition containing a base polymer (A) in which (a1) an ethylene polymer having a melting point of 115°C or more and (a2) an ethylene polymer having a melting point of less than 115°C are mixed, and a metal hydroxide (B); the metal hydroxide (B) is present in an amount of 150 parts by mass or more and 200 parts by mass or less relative to 100 parts by mass of the base polymer (A); A cable, wherein the base polymer (A) does not contain an ethylene vinyl acetate copolymer.

9. 9. The cable of claim 8, The halogen-free flame-retardant resin composition has a crosslinked structure and a maximum bending stress of 3.0 MPa or less.

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