Resin composition and coated wire

Abstract

To provide a resin composition which is excellent in flame retardancy and heat resistance, and can suppress moisture absorption and bleeding, without using a bromine-based flame retardant having a concern of an environmental regulation control.SOLUTION: A resin composition contains polyolefin, zeolite, an antioxidant, and a metal hydroxide, wherein the resin composition contains 0.1 pts.mass or more and 3.5 pts.mass or less of the zeolite with respect to 100 pts.mass of the polyolefin, and 1 pts.mass or more and 6.5 pts.mass or less of the antioxidant with respect to 100 pts.mass of the polyolefin, and a mass ratio of the zeolite to the antioxidant is 0.08 or more and 3 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a resin composition and a coated electric wire. [Background technology]

[0002] Conventionally, it is known that insulated electric wires routed in automobiles are provided with a coating layer made of a resin composition containing a thermoplastic resin. Furthermore, in order to impart flame retardancy suitable for practical use to thermoplastic resins such as polyolefins, flame retardants are appropriately added to the resin composition.

[0003] Brominated flame retardants are known as highly flame-retardant flame retardants. Patent Document 1 discloses a resin composition containing a thermoplastic resin, a brominated flame retardant, and a zeolite with a pore size of 8 Å or less.

[0004] On the other hand, non-brominated flame retardants, such as metal hydroxides, are also known as flame retardants. Patent document 2 discloses a non-halogen wire in which a conductor is coated with a material containing a resin component and a metal hydroxide. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-15812 [Patent Document 2] Japanese Patent Publication No. 2008-84833 [Overview of the project] [Problems that the invention aims to solve]

[0006] The resin composition described in Patent Document 1 exhibits good heat resistance while maintaining high flame retardancy. However, some brominated flame retardants, such as polybrominated biphenyls (PBBs) and polybrominated diphenyl ethers (PBDEs), are regulated by environmental laws. Therefore, other brominated flame retardants may also become subject to environmental laws in the future. If environmental laws are enacted, the use of resin compositions containing brominated flame retardants may be restricted.

[0007] Furthermore, in the non-halogen wire described in Patent Document 2, in order to achieve flame retardancy equivalent to that of brominated flame retardants, it is necessary to fill it with a large amount of metal hydroxide. However, such metal hydroxides may accelerate the oxidative degradation of the resin components. Therefore, when a large amount of metal hydroxide is filled, the heat resistance of the resin composition may decrease.

[0008] This invention has been made in view of the problems of the prior art. The object of this invention is to provide a resin composition and coated wire that are excellent in flame retardancy and heat resistance, and that can suppress moisture absorption and bleeding, without using brominated flame retardants, which are a concern under environmental laws and regulations. [Means for solving the problem]

[0009] A resin composition according to an aspect of the present invention contains a polyolefin, a zeolite, an antioxidant, and a metal hydroxide. The resin composition contains 0.1 parts by mass or more and 3.5 parts by mass of zeolite per 100 parts by mass of polyolefin. The resin composition contains 1 part by mass or more and 6.5 parts by mass of antioxidant per 100 parts by mass of polyolefin. The mass ratio of zeolite to antioxidant is 0.08 or more and 3 or less.

[0010] Another embodiment of the present invention provides a covered electric wire comprising a conductor and a covering layer that covers the conductor and is formed of the above-mentioned resin composition. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a resin composition and a coated electric wire that are excellent in flame retardancy and heat resistance, can suppress moisture absorption and bleeding, without using brominated flame retardants that are a concern in environmental regulations.

Brief Description of the Drawings

[0012] [Figure 1] It is a cross-sectional view showing an example of a coated electric wire according to an embodiment.

Mode for Carrying Out the Invention

[0013] Hereinafter, the resin composition, coated electric wire, and wire harness according to this embodiment will be described in detail with reference to the drawings. Note that the dimensional ratios in the drawings are exaggerated for convenience of explanation and may differ from the actual ratios.

[0014] [Resin Composition] The resin composition according to this embodiment contains a polyolefin, a zeolite, an antioxidant, and a metal hydroxide. Hereinafter, each component will be described in detail.

[0015] (Polyolefin) Polyolefin is a resin obtained by polymerizing monomers of olefins or alkenes. The polyolefin may be, for example, a polymer obtained by polymerizing a monomer containing at least one of ethylene and propylene. Specifically, the polyolefin may contain at least one resin selected from the group consisting of, for example, polyethylene, ethylene copolymer, and polypropylene. Also, the polyolefin may be an olefin-based thermoplastic elastomer (TPO).

[0016] Polyethylene may include at least one selected from the group consisting of high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and very low-density polyethylene (VLDPE). Polyethylene may also be a copolymer containing a small amount of comonomer. Polyethylene may be a homopolymer of ethylene monomers, a copolymer of ethylene monomers and 5 mol% or less of α-olefin monomers, or a copolymer of ethylene monomers and 1 mol% or less of non-olefin monomers having only carbon, oxygen, or hydrogen atoms in their functional groups.

[0017] The ethylene copolymer may be a polymer obtained by polymerizing two or more monomers. The ethylene copolymer may be a copolymer of an ethylene monomer and an olefin monomer other than the ethylene monomer in an amount of more than 5 mol%, or a copolymer of an ethylene monomer and a non-olefin monomer in an amount of more than 1 mol%. The ethylene copolymer may contain at least one selected from the group consisting of, for example, ethylene-butene copolymer, ethylene-octene copolymer, ethylene-vinyl ester copolymer, ethylene-α,β-unsaturated carboxylic acid, alkyl ester copolymer of ethylene-α,β-unsaturated carboxylic acid, ethylene-vinyl acetate copolymer (EVA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-butyl acrylate copolymer (EBA), and ethylene-vinyl acetate-ethyl acrylate copolymer.

[0018] Polypropylene may contain propylene as the main component and α-olefins other than propylene. The term "main component" here means that propylene monomers make up 50% or more of the total monomers used to polymerize the polypropylene. Polypropylene may contain at least one of block copolymers and random copolymers. Polypropylene may contain at least one selected from the group consisting of propylene homopolymers, propylene-ethylene random copolymers, propylene-α-olefin random copolymers, and propylene·ethylene-α-olefin random copolymers.

[0019] The polyolefin content in the resin component contained in the resin composition may be 90% by mass or more, 95% by mass or more, 99% by mass or more, or 100% by mass.

[0020] Polyolefins may be crosslinked. Crosslinking polyolefins can improve the mechanical properties of the resin composition. For example, polyolefins may contain at least one of polyethylene and ethylene copolymers. Such polyolefins are suitable for use as insulation layers for electric wires due to their high flexibility.

[0021] (Zeolite) The resin composition contains zeolite. Adding zeolite to the resin composition can improve its heat resistance. Zeolite is a type of aluminosilicate, with the general formula M x / n ·[(AlO2) x (SiO2) y It can be represented as ]·zH2O. In the general formula, M is a cation with valency n, x+y is the number of tetrahedra per unit cell, z is the number of moles of water, and y is a value greater than x. Examples of cation species with valency 1 include Li + kaNa + , K + Examples include Ca 2+ Mg 2+ Ba2+ Examples include the following.

[0022] The resin composition contains 0.1 to 3.5 parts by mass of zeolite with respect to 100 parts by mass of polyolefin. By setting the content of zeolite to 0.1 part by mass or more, the heat resistance can be improved. Further, by setting the content of zeolite to 3.5 parts by mass or less, moisture absorption by zeolite can be suppressed. The content of zeolite may be 0.3 part by mass or more, 0.5 part by mass or more, 1 part by mass or more, 1.5 parts by mass or more, 2 parts by mass or more, 2.5 parts by mass or more, or 3 parts by mass or more. Also, the content of zeolite may be 3 parts by mass or less, 2.5 parts by mass or less, 2 parts by mass or less, 1.5 parts by mass or less, 1 part by mass or less, 0.8 part by mass or less, or 0.5 part by mass or less.

[0023] Generally, zeolite is porous and has pores. Zeolite can adsorb molecules smaller than the pore diameter, but molecules larger than the pore diameter cannot enter the pores, so it is known to have a molecular sieve effect and an ion exchange function. The pore diameter of zeolite is derived from the crystal structure of zeolite. The pore diameter of zeolite may be, for example, 1 Å or more and 10 Å or less. The pore diameter of zeolite may be 2 Å or more, 3 Å or more, 4 Å or more, 5 Å or more, 6 Å or more, 7 Å or more, or 8 Å or more. Also, the pore diameter of zeolite may be 9 Å or less, 8 Å or less, 7 Å or less, 6 Å or less, 5 Å or less, 4 Å or less, or 3 Å or less. The pore diameter of zeolite can be measured, for example, by the Horvath-Kawazoe method or the like.

[0024] The molar ratio of silica to alumina (SiO2 / Al2O3 ratio) in zeolite is not particularly limited. The silica / alumina ratio may be, for example, 1 or more and 10000 or less. The silica / alumina ratio may be 2 or more, 5 or more, 20 or more, 80 or more, 500 or more, or 1000 or more. Also, the silica / alumina ratio may be 2000 or less, 1000 or less, 200 or less, 50 or less, 30 or less, 10 or less, or 4 or less.

[0025] The pore size of the zeolite may be 6.5 Å or less, or 6.6 Å to 9.0 Å, and the molar ratio of silica to alumina in the zeolite may be 10 or less. Resin compositions containing such zeolite exhibit particularly excellent heat resistance.

[0026] Zeolites include natural zeolites, synthetic zeolites, and artificial zeolites. Natural zeolites are characterized by being naturally occurring and often inexpensive. Synthetic zeolites are characterized by being made from highly purified chemical substances and thus having high purity. Artificial zeolites are characterized by being made from unused resources such as coal ash and having higher purity than natural zeolites and being less expensive than artificial zeolites. Among these, it is preferable that the zeolite be at least one of synthetic zeolites or artificial zeolites. These zeolites have a more uniform structure compared to natural zeolites.

[0027] The structure of the zeolite is not particularly limited and may be, for example, type A, type beta, MCM-22, ZSM-5, ferrielite, and mordenite.

[0028] The average particle size of the zeolite is not particularly limited and may be 0.1 μm or more, 1 μm or more, or 5 μm or more. Alternatively, the average particle size of the zeolite may be 50 μm or less, 30 μm or less, or 20 μm or less. The average particle size of the zeolite is calculated as the average value of the particle sizes of particles observed in several to tens of fields of view by observing the cross-section of the resin composition using observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0029] The cation species of zeolite are not particularly limited, for example, hydrogen ions (H + ), potassium ions (K + ), calcium ions (Ca 2+ ) and ammonium ions (NH4 + ) may be selected from the group consisting of at least one of the following.

[0030] (Antioxidant) Antioxidants suppress oxidative degradation of polyolefins. Known antioxidants used with polyolefins can be used, including radical chain inhibitors such as phenolic and amine antioxidants, peroxide decomposers such as phosphorus and sulfur antioxidants, and metal deactivators such as hydrazine and amine antioxidants. Antioxidants may be used individually or in combination of multiple types.

[0031] The resin composition contains 1 to 6.5 parts by mass of antioxidant per 100 parts by mass of polyolefin. By including 1 part by mass or more of antioxidant, degradation of polyolefin due to oxidation can be suppressed. Furthermore, by including 6.5 parts by mass or less of antioxidant, bleed-out can be suppressed. Also, by including 6.5 parts by mass or less of antioxidant, it is possible to suppress the reaction of the antioxidant during crosslinking treatment, which reduces the degree of crosslinking of the resin composition, and the reduction of smoke emission characteristics when current is passed through the wire. In this embodiment, since the heat resistance is improved by the addition of zeolite, it is expected that the effect can be achieved with a smaller amount compared to when the antioxidant is used alone. Furthermore, the antioxidant content may be 6 parts by mass or less, 4 parts by mass or less, or 2 parts by mass or less.

[0032] The mass ratio of zeolite to antioxidant (zeolite / antioxidant) is between 0.08 and 3. By setting the mass ratio of zeolite and antioxidant within the above range, heat resistance can be improved. The above mass ratio may be 0.1 or higher, or 0.3 or higher. Furthermore, the above mass ratio may be 2 or lower, 1 or lower, or 0.7 or lower.

[0033] (metal hydroxide) Metal hydroxides function as flame retardants. Compared to brominated flame retardants, metal hydroxides are less likely to be subject to environmental regulations. Therefore, in the resin composition according to this embodiment, metal hydroxides are used as the flame retardant of the resin composition.

[0034] The metal hydroxide may contain at least one of a salt of a metal ion and a hydroxide ion, or a hydrate of a metal oxide. The metal hydroxide may contain at least one selected from the group consisting of, for example, magnesium hydroxide (Mg(OH)2), aluminum hydroxide (Al(OH)3), calcium hydroxide (Ca(OH)2), basic magnesium carbonate (mMgCO3·Mg(OH)2·nH2O), hydrated aluminum silicate (aluminum silicate hydrate, Al2O3·3SiO2·nH2O), and hydrated magnesium silicate (magnesium silicate pentahydrate, Mg2Si3O8·5H2O). Specifically, the metal hydroxide may contain magnesium hydroxide.

[0035] These metal hydroxides are preferably surface-treated to improve their compatibility with resin materials, but they can be used even without surface treatment as long as their physical properties do not deteriorate. Surface treatment of the metal hydroxide is preferably carried out using silane coupling agents, titanate coupling agents, fatty acids such as stearic acid, or fatty acid metal salts such as calcium stearate.

[0036] The resin composition may contain 40 to 130 parts by mass of metal hydroxide per 100 parts by mass of polyolefin. In the resin composition according to this embodiment, as described above, the blending ratio of zeolite and antioxidant is optimized, so the content of metal hydroxide can be within the above range. Furthermore, by including 40 parts by mass or more of metal hydroxide, flame retardancy can be further improved. Furthermore, by including 130 parts by mass or less of metal hydroxide, the hardness of the resin composition can be increased, thereby improving wear resistance. The content of metal hydroxide may be 50 parts by mass or more, or 60 parts by mass or more. Also, the content of metal hydroxide may be 120 parts by mass or less, 110 parts by mass or less, 100 parts by mass or less, 90 parts by mass or less, 80 parts by mass or less, 70 parts by mass or less, or 60 parts by mass or less.

[0037] The resin composition may not substantially contain a brominated flame retardant. A brominated flame retardant is an organic compound having at least one halogen, which can capture hydroxyl radicals and suppress the combustion of the resin composition. However, brominated flame retardants may be subject to environmental regulations in the future. If environmental regulations are enacted, the use of resin compositions containing brominated flame retardants may be restricted. Since the resin composition according to this embodiment contains a metal hydroxide, the resin composition is flame retardant even if it does not substantially contain a brominated flame retardant. It should be noted that "substantially free of a brominated flame retardant" means that the resin composition contains 1 part by mass or less of a brominated flame retardant per 100 parts by mass of polyolefin. The resin composition may also contain 0.5 parts by mass or less, or 0.1 parts by mass or less, of a brominated flame retardant per 100 parts by mass of polyolefin.

[0038] The resin composition of this embodiment can contain various additives in appropriate amounts, as long as they do not interfere with the effects of this embodiment. Examples of additives include crosslinking aids, flame retardant aids, metal deactivators, copper damage inhibitors, anti-aging agents, lubricants, fillers, reinforcing agents, UV absorbers, stabilizers, plasticizers, pigments, dyes, colorants, antistatic agents, and foaming agents. The content of these additives is not particularly limited and can be determined as appropriate depending on the purpose.

[0039] The Shore D hardness of the resin composition may be less than 45. By setting the Shore D hardness of the resin composition to less than 45, the wear resistance of the resin composition can be improved. The Shore D hardness of the resin composition may be 0 or greater, and may also be 10 or greater. The Shore D hardness of the resin composition can be measured in accordance with JIS K7215:1986.

[0040] As described above, the resin composition according to this embodiment contains polyolefin, zeolite, an antioxidant, and a metal hydroxide. The resin composition contains 0.1 parts by mass to 3.5 parts by mass of zeolite per 100 parts by mass of polyolefin. The resin composition contains 1 part by mass to 6.5 parts by mass of antioxidant per 100 parts by mass of polyolefin. The mass ratio of zeolite to antioxidant is 0.08 to 3.

[0041] Therefore, the resin composition according to this embodiment exhibits excellent flame retardancy and heat resistance, as well as suppressing moisture absorption and bleeding, without the need to use brominated flame retardants, which are a concern under environmental laws and regulations.

[0042] The resin composition according to this embodiment has a predetermined blending ratio of zeolite and antioxidant, which allows for a longer time for the antioxidant to be consumed during heat treatment, resulting in superior heat resistance. Furthermore, because the blending ratio of zeolite and antioxidant in the resin composition according to this embodiment is within a predetermined range, the amount of zeolite and antioxidant added can be kept low.

[0043] According to the resin composition of this embodiment, it can be used in flexible conductors and thin-walled specifications in accordance with ISO 19642, and it is also conceivable that costs can be reduced by filling with a large amount of filler.

[0044] [Insulated wire] Next, the insulated wire 1 according to this embodiment will be described with reference to Figure 1. As shown in Figure 1, the insulated wire 1 according to this embodiment comprises a conductor 2 and a coating layer 3 that covers the conductor 2 and is formed of the resin composition described above. As described above, the resin composition according to the above embodiment has excellent flame retardancy and heat resistance, and can suppress moisture absorption and bleeding, even without using brominated flame retardants, which are a concern under environmental laws and regulations. For this reason, the insulated wire 1 can be preferably used, for example, as an insulated wire 1 for automobiles.

[0045] The conductor 2 may consist of only one strand, or it may be composed of multiple strands bundled together. The diameter of the conductor 2 and the diameter of the strands are not particularly limited and can be determined as appropriate depending on the application. The conductor 2 may be copper, aluminum, or an alloy containing these metals.

[0046] The resin composition that forms the coating layer 3 is prepared by melt-kneading the above-mentioned resin composition, and known methods can be used for this. For example, the resin composition can be obtained by pre-blending using a high-speed mixing device such as a Henschel mixer, and then kneading it using a known kneader such as a Banbury mixer, kneader, or roll mill.

[0047] A known method can also be used to coat the conductor 2 with the coating layer 3; for example, the coating layer 3 may be formed by a general extrusion molding method. The extruder used in the extrusion molding method may include, for example, a single-screw extruder or a twin-screw extruder. By extruding molten resin and coating the outer circumference of the conductor 2 with the molten resin composition, a coating layer 3 covering the outer circumference of the conductor 2 can be formed.

[0048] Thus, in the coated wire 1 of this embodiment, the coating layer 3 can be formed by extrusion molding, similar to general resin compositions for electric wires. Furthermore, to improve the strength of the coating layer 3, after forming the coating layer 3 on the outer circumference of the conductor 2, the resin composition may be irradiated with radiation to crosslink the resin composition. As a result, the strength of the coating layer 3 can be improved.

[0049] For example, gamma rays or electron beams can be used as the radiation source. By irradiating the coating layer 3 with the resin composition, radicals are generated in the molecules, and these radicals couple to form intermolecular crosslinking bonds. As a result, the strength of the coating layer 3 can be improved. Furthermore, the strength of the coating layer 3 may be further improved by incorporating a radiation-activated crosslinking agent into the coating layer 3.

[0050] Regarding the processing method for the resin composition, the kneading method for the resin composition, the coating method for the conductor 2, and the crosslinking method for the resin composition can be selected to suit the purpose and are not particularly limited.

[0051] As described above, the coated wire 1 according to this embodiment comprises a conductor 2 and a coating layer 3 that covers the conductor 2 and is formed from the resin composition described above. The resin composition has excellent flame retardancy and heat resistance, and can suppress moisture absorption and bleeding, even without using brominated flame retardants, which are a concern under environmental laws and regulations. Therefore, the coated wire 1 can be preferably used, for example, as a coated wire 1 for automobiles. Furthermore, since the resin composition contains polyolefin, it is possible to provide a coated wire 1 that is cheaper than a silicone rubber wire.

[0052] [Wire harness] Next, the wire harness according to this embodiment will be described. The wire harness according to this embodiment comprises the insulated wire 1 described above. The coating layer 3 of the insulated wire 1 is formed of a resin composition, and the resin composition has excellent flame retardancy and heat resistance, and can suppress moisture absorption and bleeding, without using brominated flame retardants, which are a concern under environmental laws and regulations. For this reason, the wire harness according to this embodiment can be preferably used as a wire harness routed in vehicles such as electric vehicles. [Examples]

[0053] The resin compositions according to this embodiment will be described in more detail below with reference to examples and comparative examples, but the resin compositions according to this embodiment are not limited to these examples.

[0054] The following materials were melt-mixed using a resin mixer (manufactured by Toyo Seiki Seisakusho Co., Ltd.) in the proportions (parts by mass) shown in the table to prepare the resin compositions for each example. The resin compositions were crosslinked under the conditions of 750kV × 160kGy.

[0055] [Polyolefins] ENGAGE® 7256 (manufactured by Dow), ethylene-butene copolymer, polyolefin elastomer

[0056] [Zeolite] (1) Type A zeolite, pore size 3 Å, SiO2 / Al2O3=2, cation species K + Zeoram® A-3 (product model number) (manufactured by Tosoh Corporation) (2) Type A zeolite, pore size 4 Å, SiO2 / Al2O3=2, cation species Na + Zeoram® A-4 (product model number) (manufactured by Tosoh Corporation) (3) Type A zeolite, pore size 5 Å, SiO2 / Al2O3=2, cation species Ca 2+ Zeoram® A-5 (product model number) (manufactured by Tosoh Corporation) (4) ZSM-5 type zeolite, pore size 5.8 Å, SiO2 / Al2O3 = 40, cation species H +HSZ(registered trademark)840HOA(product model number)(manufactured by Tosoh Corporation) (5) ZSM-5 type zeolite, pore size 5.8 Å, SiO2 / Al2O3 = 1500, cation species H + HSZ(registered trademark)891HOA(product model number)(manufactured by Tosoh Corporation) (6) Beta-type zeolite, pore size 6.5 Å, SiO2 / Al2O3 = 40, cation species H + HSZ(registered trademark)940HOA(product model number)(manufactured by Tosoh Corporation) (7) Y-type zeolite, pore size 9.0 Å, SiO2 / Al2O3 = 5.5, cation species H + HSZ(registered trademark)320HOA(product model number)(manufactured by Tosoh Corporation) (8) Y-type zeolite, pore size 9.0 Å, SiO2 / Al2O3 = 100, cation species H + HSZ(registered trademark)385HUA(product model number)(manufactured by Tosoh Corporation)

[0057] [Antioxidant] Irganox® 1010 (manufactured by BASF), pentaerythritol tetrakis[3-[3,5-di(tert-butyl)-4-hydroxyphenyl]propionate]

[0058] [Metal hydroxide] Magnesium hydroxide surface-treated with higher fatty acids: KISUMA® 5A (Kyowa Chemical Industry Co., Ltd.)

[0059] [evaluation] The flame retardancy, heat resistance, hygroscopicity, bleedability, and hardness of the resin composition prepared as described above were evaluated as follows.

[0060] (Flame retardant) In accordance with JIS K7201-2, the oxygen index of a 3mm thick cross-linked resin composition was measured to evaluate its flame retardancy. An oxygen index of 21.0 or higher was marked as "○", and an oxygen index of 21.0 or lower was marked as "×".

[0061] (Heat resistance) The cross-linked resin composition was molded into a 1 mm thick resin sheet, and then punched out using the dumbbell-shaped die No. 3 specified in JIS K6251:2010. The punched-out dumbbell-shaped sheet was heated at 170°C for 150 hours in accordance with JIS K7212:1999. The heated sheet was removed from the oven and left at room temperature (approximately 23°C) for 12 hours. The sheet, which had cooled to room temperature, was then used as a test sample, and a tensile test was performed at a tensile speed of 200 mm / min at room temperature (23°C). Heat resistance was evaluated by marking "○" if the elongation rate of the test sample was 100% or more, and "×" if the elongation rate of the test sample was less than 100%.

[0062] (hygroscopicity) Pellets were prepared from the crosslinked resin composition, and these pellets were degassed using a vacuum dryer at 40°C. They were then left at room temperature (23°C) and humidity of 40% to 60% for 168 hours. The moisture content of these test samples was measured using Method A (anhydrous methanol extraction method) as specified in JIS K7251:2002. Hygroscopicity was evaluated as follows: "○" for moisture content less than 1,500 ppm, and "×" for moisture content 1,500 ppm or more.

[0063] (Bleeding properties) The resin composition was molded into a 0.5 mm thick and 50 mm wide resin sheet and cut into 200 mm lengths. This resin sheet was subjected to a crosslinking treatment, and bleed material was wiped off using acetone. The sheet was then left at room temperature (23°C) and humidity of 40% to 60% for 1,000 hours. Afterward, the bleed material on the resin sheet was wiped off again using acetone. The weight difference between the sample weight before the first wipe and the sample weight after the second wipe was determined as the amount of bleed material that bled out onto the resin sheet surface. The bleed amount was converted to mass per unit area from the length and width of the resin sheet. A bleed amount of 0.150 mg / cm² was obtained. 2 If the value is less than 0.150 mg / cm³, mark it as "〇". 2 In the above cases, the breeding potential was evaluated as "×".

[0064] (hardness) After molding the crosslinked resin composition into a 2mm thick resin sheet, test samples were prepared by punching them out to the size specified in JIS K7215:1986. Three or more of these punched-out test samples were then stacked to a thickness of 6mm or more. The Shore D hardness of these samples was measured using a Type D durometer. Hardness was evaluated as "○" if the Shore D hardness was less than 45, and "×" if the Shore D hardness was 45 or higher.

[0065] [Table 1]

[0066] [Table 2]

[0067] [Table 3]

[0068] As shown in Tables 1 and 2, the resin compositions of Examples 1 to 19 exhibited excellent flame retardancy, heat resistance, hygroscopicity, and bleed resistance. Furthermore, because the resin compositions of Examples 1 to 18 contained 130 parts by mass or less of metal hydroxide, they had higher hardness compared to the resin composition of Example 19, which contained 140 parts by mass of metal hydroxide.

[0069] On the other hand, as shown in Table 3, the resin composition according to Comparative Example 1, which does not contain zeolite, did not provide sufficient heat resistance. Furthermore, the resin composition according to Comparative Example 2 contained 4 parts by mass of zeolite, and the mass ratio of zeolite to antioxidant was 4, resulting in a "×" evaluation for hygroscopicity. Similarly, the resin composition according to Comparative Example 3 had a mass ratio of zeolite to antioxidant of 0.07, resulting in a "×" evaluation for bleedability. Similarly, the resin composition according to Comparative Example 4 contained 4 parts by mass of zeolite, and the mass ratio of zeolite to antioxidant was 4, resulting in a "×" evaluation for hygroscopicity. Furthermore, the resin composition according to Comparative Example 5 did not contain magnesium hydroxide, resulting in a "×" evaluation for flame retardancy.

[0070] Although this embodiment has been described above, this embodiment is not limited to these, and various modifications are possible within the scope of the gist of this embodiment. [Explanation of Symbols]

[0071] 1. Insulated wire 2 conductors 3 Covering layer

Claims

1. Polyolefins and Zeolite and, Antioxidants, Metal hydroxides and A resin composition containing, The resin composition contains 0.1 to 3.5 parts by mass of the zeolite per 100 parts by mass of the polyolefin. The resin composition contains 1 to 6.5 parts by mass of the antioxidant per 100 parts by mass of the polyolefin. The mass ratio of the zeolite to the antioxidant is 0.08 or more and 3 or less. The aforementioned polyolefin is crosslinked, The resin composition wherein the polyolefin comprises at least one of polyethylene and ethylene copolymer.

2. The resin composition according to claim 1, wherein the pore size of the zeolite is 6.5 Å or less.

3. The resin composition according to claim 1, wherein the pore size of the zeolite is 6.6 Å or more and 9.0 Å or less, and the molar ratio of silica to alumina in the zeolite is 10 or less.

4. The aforementioned metal hydroxide includes magnesium hydroxide, The resin composition according to claim 1 or 2, wherein the resin composition contains 40 to 130 parts by mass of the metal hydroxide per 100 parts by mass of the polyolefin.

5. The resin composition according to claim 1 or 2, wherein the Shore D hardness of the resin composition is less than 45.

6. A conductor and A coating layer formed by the resin composition described in claim 1 or 2 covers the conductor, A covered electric wire equipped with this feature.

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