Resin composition and coated electric wire

Abstract

This resin composition contains a polyolefin, a zeolite, an antioxidant, and a metal hydroxide. The resin composition contains 0.1-3.5 parts by mass of the zeolite per 100 parts by mass of the polyolefin. The resin composition contains 1-6.5 parts by mass of the antioxidant per 100 parts by mass of the polyolefin. Additionally, the mass ratio of the zeolite to the antioxidant is 0.08-3.

Description

Resin composition and coated wire

[0001] The present invention relates to a resin composition and a coated electric wire.

[0002] It has been known that a coating layer formed of a resin composition containing a thermoplastic resin is provided on a coated electric wire to be installed in an automobile. In addition, a flame retardant is appropriately added to the resin composition of a thermoplastic resin such as polyolefin to impart flame retardancy suitable for practical use.

[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 having a pore size of 8 Å or less.

[0004] On the other hand, non-bromine-based flame retardants such as metal hydroxides are also known as flame retardants. Patent Document 2 discloses a halogen-free electric wire in which a conductor is coated with a material containing a resin component and a metal hydroxide.

[0005] Japanese Patent Application Laid-Open No. 2020-15812

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

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

[0008] The present invention has been made in view of the problems inherent in the prior art, and an object of the present invention is to provide a resin composition and a coated electric wire that are excellent in flame retardancy and heat resistance and are capable of suppressing moisture absorption and bleeding, even without using a brominated flame retardant that is subject to environmental regulations.

[0009] A resin composition according to an embodiment 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 or less of the zeolite per 100 parts by mass of the polyolefin. The resin composition contains 1 part by mass or more and 6.5 parts by mass or less of the antioxidant per 100 parts by mass of the polyolefin. The mass ratio of the zeolite to the antioxidant is 0.08 to 3.

[0010] A coated electric wire according to another aspect of the present invention includes a conductor and a coating layer that coats the conductor and is formed from the resin composition.

[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 and can suppress moisture absorption and bleeding, even without using a brominated flame retardant that is subject to environmental regulations.

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

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

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

[0015] (Polyolefin) Polyolefin is a resin obtained by polymerizing an olefin or alkene monomer. 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 polyethylene, ethylene copolymer, polypropylene, etc. The polyolefin may also be an olefin-based thermoplastic elastomer (TPO).

[0016] The 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). The polyethylene may be a copolymer containing a small amount of comonomer. The polyethylene may be a homopolymer of ethylene monomer, a copolymer of ethylene monomer and 5 mol% or less of an α-olefin monomer, or a copolymer of ethylene monomer and 1 mol% or less of a non-olefin monomer having only carbon, oxygen, or hydrogen atoms as functional groups.

[0017] The ethylene copolymer may be a polymer obtained by polymerizing two or more types of monomers. The ethylene copolymer may be a copolymer of ethylene monomer and more than 5 mol% of an olefin monomer other than ethylene monomer, or a copolymer of ethylene monomer and more than 1 mol% of a non-olefin monomer. 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, ethylene-α,β-unsaturated carboxylic acid alkyl ester copolymer, 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] The polypropylene may contain propylene as a main component and an α-olefin other than propylene. Here, "main component" means that propylene monomer accounts for 50% or more of all the monomers used to polymerize the polypropylene. The polypropylene may contain at least one of a block copolymer and a random copolymer. The polypropylene may contain at least one selected from the group consisting of a propylene homopolymer, a propylene-ethylene random copolymer, a propylene-α-olefin random copolymer, and a propylene-ethylene-α-olefin random copolymer.

[0019] The content of polyolefin 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] The polyolefin may be crosslinked. Crosslinking the polyolefin can improve the mechanical properties of the resin composition. The polyolefin may contain, for example, at least one of polyethylene and an ethylene copolymer. Such polyolefins are highly flexible and therefore suitable for use as a coating layer for electric wires.

[0021] (Zeolite) The resin composition contains zeolite. Adding zeolite to the resin composition can improve heat resistance. Zeolite is a type of aluminosilicate and is represented by the general formula M ｘ／ｎ [(AlO ２ ) ｘ (SiO ２ ) ｙ ]・zH ２ In the general formula, M is a cation with a valence of 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 cationic species with a valence of 1 include Li ＋ , Na ＋ , K. ＋ Examples of cationic species with a valence of 2 include Ca ２＋ , Mg ２＋ , Ba ２＋Examples include:

[0022] The resin composition contains 0.1 parts by mass or more and 3.5 parts by mass or less of zeolite per 100 parts by mass of polyolefin. By setting the zeolite content to 0.1 parts by mass or more, heat resistance can be improved. Furthermore, by setting the zeolite content to 3.5 parts by mass or less, moisture absorption by the zeolite can be suppressed. The zeolite content may be 0.3 parts by mass or more, 0.5 parts 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. Furthermore, the zeolite content 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 parts by mass or less, or 0.5 parts by mass or less.

[0023] Generally, zeolites are porous and have pores. Zeolites can adsorb molecules smaller than the pore size, but cannot accommodate molecules larger than the pore size, and are therefore known to have a molecular sieve effect and ion exchange function. The pore size of zeolites is derived from the crystalline structure of zeolites. The pore size of zeolites may be, for example, 1 Å or more and 10 Å or less. The pore size of zeolites 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. The pore size of zeolites may also 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 size of zeolites can be measured, for example, by the Horvath-Kawazoe method.

[0024] The molar ratio of silica to alumina in the zeolite (SiO ２ / Al ２ O ３ The silica / alumina ratio is not particularly limited. The silica / alumina ratio may be, for example, 1 or more and 10,000 or less. The silica / alumina ratio may be 2 or more, 5 or more, 20 or more, 80 or more, 500 or more, or 1,000 or more. The silica / alumina ratio may also be 2,000 or less, 1,000 or less, 200 or less, 50 or less, 30 or less, 10 or less, or 4 or less.

[0025] The pore diameter of the zeolite may be 6.5 Å or less, or the pore diameter of the zeolite may be 6.6 Å or more and 9.0 Å or less, and the molar ratio of silica to alumina in the zeolite may be not more than 10. A resin composition containing such a zeolite is particularly excellent in heat resistance.

[0026] Zeolites include natural zeolites, synthetic zeolites, and artificial zeolites. Natural zeolites are characterized by being produced in nature and being inexpensive. Synthetic zeolites are made from highly pure chemical substances as raw materials and are characterized by high purity. Artificial zeolites are made from unused resources such as coal ash as raw materials and are characterized by being more pure than natural zeolites and less expensive than artificial zeolites. Of these, it is preferable that the zeolite is at least one of synthetic zeolites and artificial zeolites. These zeolites have a more uniform structure than natural zeolites.

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

[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. 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 a value calculated by observing a cross section of a resin composition using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM) and averaging the particle sizes of particles observed within several to several tens of fields of view.

[0029] The cation species of the zeolite is not particularly limited, and examples thereof include hydrogen ions (H ＋ ), potassium ions (K ＋ ), calcium ions (Ca ２＋ ) and ammonium ion (NH ４ ＋ ) may be at least one selected from the group consisting of

[0030] (Antioxidant) The antioxidant suppresses oxidative degradation of polyolefins. As the antioxidant, known antioxidants used for polyolefins can be used, such as radical chain inhibitors such as phenol-based antioxidants and amine-based antioxidants, peroxide decomposers such as phosphorus-based antioxidants and sulfur-based antioxidants, and metal deactivators such as hydrazine-based antioxidants and amine-based antioxidants. The antioxidants may be used alone or in combination.

[0031] The resin composition contains 1 part by mass or more and 6.5 parts by mass or less of an antioxidant per 100 parts by mass of polyolefin. By setting the antioxidant content to 1 part by mass or more, it is possible to suppress deterioration of polyolefin and the like due to oxidation. Furthermore, by setting the antioxidant content to 6.5 parts by mass or less, it is possible to suppress bleed-out. Furthermore, by setting the antioxidant content to 6.5 parts by mass or less, it is possible to suppress a decrease in the degree of crosslinking of the resin composition due to reaction of the antioxidant during crosslinking treatment, or a decrease in smoke generation characteristics when electricity is applied to the electric wire. In this embodiment, since the addition of zeolite improves heat resistance, it is expected that the effect will be exhibited with a smaller amount than 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 0.08 or more and 3 or less. By setting the mass ratio of zeolite to antioxidant within the above range, heat resistance can be improved. The mass ratio may be 0.1 or more, or 0.3 or more. Furthermore, the mass ratio may be 2 or less, 1 or less, or 0.7 or less.

[0033] (Metal hydroxide) Metal hydroxide functions as a flame retardant. Metal hydroxide is less likely to be subject to environmental regulations compared to brominated flame retardants. Therefore, in the resin composition according to the present embodiment, a metal hydroxide is used as a flame retardant for the resin composition.

[0034] The metal hydroxide may include at least one of a salt of a metal ion and a hydroxide ion and a hydrate of a metal oxide. The metal hydroxide may be, for example, magnesium hydroxide (Mg(OH) ２ ), aluminum hydroxide (Al(OH) ３ ), calcium hydroxide (Ca(OH) ２ ), basic magnesium carbonate (mMgCO ３ Mg(OH) ２ ・nH ２ O), hydrated aluminum silicate (aluminum silicate hydrate, Al ２ O ３ 3SiO ２ ・nH ２ O), and hydrated magnesium silicate (magnesium silicate pentahydrate, Mg ２ Si ３ O ８ ・5H ２ O), etc. Specifically, the metal hydroxide may include magnesium hydroxide.

[0035] These metal hydroxides are preferably surface-treated in consideration of compatibility with resin materials, but can also be used without surface treatment as long as their physical properties are not impaired. The surface treatment of the metal hydroxide is preferably carried out using a silane coupling agent, a titanate coupling agent, a fatty acid such as stearic acid, or a fatty acid metal salt such as calcium stearate.

[0036] The resin composition may contain 40 parts by mass or more and 130 parts by mass or less of a metal hydroxide per 100 parts by mass of polyolefin. In the resin composition according to this embodiment, as described above, the blending ratio of the zeolite and the antioxidant is optimized, so the content of the metal hydroxide can be within the above-mentioned range. Furthermore, by setting the metal hydroxide content to 40 parts by mass or more, flame retardancy can be further improved. Furthermore, by setting the metal hydroxide content to 130 parts by mass or less, the hardness of the resin composition can be increased, thereby improving wear resistance. The content of the metal hydroxide may be 50 parts by mass or more, or may be 60 parts by mass or more. Furthermore, the content of the 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 be substantially free of brominated flame retardants. Brominated flame retardants are organic compounds containing at least one halogen, which can capture hydroxyl radicals and suppress 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. Because the resin composition according to this embodiment contains a metal hydroxide, the resin composition has flame retardancy even if it does not substantially contain a brominated flame retardant. Note that "the resin composition is 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. Note that the resin composition may 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 within the range that does not impair the effects of this embodiment. Examples of additives include crosslinking aids, flame retardant aids, metal deactivators, copper inhibitors, antioxidants, 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 appropriately depending on the purpose.

[0039] The Shore D hardness of the resin composition may be less than 45. By making the Shore D hardness of the resin composition less than 45, the abrasion resistance of the resin composition can be improved. The Shore D hardness of the resin composition is 0 or more, and may be 10 or more. 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 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 or less of the zeolite per 100 parts by mass of the polyolefin. The resin composition contains 1 part by mass or more and 6.5 parts by mass or less 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.

[0041] Therefore, the resin composition according to this embodiment has excellent flame retardancy and heat resistance, and can suppress moisture absorption and bleeding, even without using a brominated flame retardant, which is a concern under environmental regulations.

[0042] The resin composition according to the present embodiment has a blending ratio of zeolite and antioxidant within a predetermined range, which is thought to lengthen the time it takes for the antioxidant to be consumed during heat treatment, resulting in excellent heat resistance. Furthermore, the resin composition according to the present embodiment has a blending ratio of zeolite and antioxidant within a predetermined range, which allows the amounts of zeolite and antioxidant to be kept low.

[0043] The resin composition according to this embodiment can be used with flexible conductors and thin-wall specifications that comply with ISO 19642, and it is also possible to reduce costs by filling a large amount of filler.

[0044] [Coated Electric Wire] Next, a coated electric wire 1 according to this embodiment will be described with reference to Fig. 1. As shown in Fig. 1, the coated electric wire 1 according to this embodiment includes a conductor 2 and a coating layer 3 that coats the conductor 2 and is formed from the resin composition. As described above, the resin composition according to this embodiment has excellent flame retardancy and heat resistance and can suppress moisture absorption and bleeding, even without using a brominated flame retardant that is subject to environmental regulations. Therefore, the coated electric wire 1 can be preferably used, for example, as a coated electric wire 1 for automobiles.

[0045] The conductor 2 may be composed of a single wire or a bundle of multiple wires. The diameter of the conductor 2 and the diameter of the wire are not particularly limited and can be determined appropriately depending on the application. The conductor 2 may be made of copper, aluminum, or an alloy containing these metals.

[0046] The resin composition forming the coating layer 3 is prepared by melt-kneading the above-mentioned resin composition, and this can be done by any known method. For example, the resin composition can be obtained by pre-blending the resin composition in advance using a high-speed mixer such as a Henschel mixer, and then kneading it using a known kneader such as a Banbury mixer, a kneader, or a roll mill.

[0047] The method for covering the conductor 2 with the covering layer 3 can also be known, and for example, the covering 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. The covering layer 3 covering the outer periphery of the conductor 2 can be formed by extruding a molten resin and covering the outer periphery of the conductor 2 with the molten resin composition.

[0048] As described above, in the coated electric wire 1 of this embodiment, the coating layer 3 can be formed by extrusion molding in the same manner as in the case of a general resin composition for electric wires. Note that, in order to improve the strength of the coating layer 3, after the coating layer 3 is formed on the outer periphery 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 resin composition onto the coating layer 3, radicals are generated in the molecules, and these radicals couple with each other to form intermolecular cross-links. As a result, it is possible to improve the strength of the coating layer 3. Note that the strength of the coating layer 3 can be further improved by further blending a cross-linking agent that is activated by radiation into the coating layer 3.

[0050] Regarding the method of processing the resin composition, the method of kneading the resin composition, the method of coating the conductor 2, and the method of crosslinking the resin composition, the optimum method can be selected depending on the purpose, and there are no particular limitations.

[0051] As described above, the covered electric wire 1 according to this embodiment includes the conductor 2 and the covering layer 3 that covers the conductor 2 and is formed from the above-described resin composition. The resin composition has excellent flame retardancy and heat resistance and can suppress moisture absorption and bleeding, even without using a brominated flame retardant, which is subject to environmental regulations. Therefore, the covered electric wire 1 can be preferably used, for example, as a covered electric wire 1 for automobiles. Furthermore, because the resin composition contains polyolefin, a covered electric wire 1 that is less expensive than a silicone rubber electric wire can be provided.

[0052] [Wire Harness] Next, a wire harness according to the present embodiment will be described. The wire harness according to the present embodiment includes the above-described covered electric wire 1. The covering layer 3 of the covered electric wire 1 is formed from a resin composition, which has excellent flame retardancy and heat resistance and can suppress moisture absorption and bleeding even without using a brominated flame retardant that is subject to environmental regulations. Therefore, the wire harness according to the present embodiment can be preferably used as a wire harness to be installed in a vehicle such as an electric vehicle.

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

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

[0055] [Polyolefin] ENGAGE (registered trademark) 7256 (manufactured by Dow), ethylene-butene copolymer, polyolefin elastomer

[0056] [Zeolite] (1) Type A zeolite, pore diameter 3 Å, SiO ２ / Al ２ O ３ = 2, cationic species K ＋ , Zeolum (registered trademark) A-3 (product model number) (manufactured by Tosoh Corporation) (2) A-type zeolite, pore diameter 4 Å, SiO ２ / Al ２ O ３ = 2, cation species Na ＋ , Zeolum (registered trademark) A-4 (product model number) (manufactured by Tosoh Corporation) (3) A-type zeolite, pore diameter 5 Å, SiO ２ / Al ２ O ３ = 2, cation species Ca ２＋ , Zeolum (registered trademark) A-5 (product model number) (manufactured by Tosoh Corporation) (4) ZSM-5 type zeolite, pore diameter 5.8 Å, SiO ２ / Al ２ O ３ = 40, cationic species H ＋ , HSZ (registered trademark) 840HOA (product model number) (manufactured by Tosoh Corporation) (5) ZSM-5 type zeolite, pore diameter 5.8 Å, SiO ２ / Al ２ O ３ = 1500, cationic species H ＋ , HSZ (registered trademark) 891HOA (product model number) (manufactured by Tosoh Corporation) (6) Beta type zeolite, pore diameter 6.5 Å, SiO ２ / Al ２ O３ = 40, cationic species H ＋ , HSZ (registered trademark) 940HOA (product model number) (manufactured by Tosoh Corporation) (7) Y-type zeolite, pore diameter 9.0 Å, SiO ２ / Al ２ O ３ = 5.5, cationic species H ＋ , HSZ (registered trademark) 320HOA (product model number) (manufactured by Tosoh Corporation) (8) Y-type zeolite, pore diameter 9.0 Å, SiO ２ / Al ２ O ３ = 100, cationic species H ＋ , HSZ (registered trademark) 385HUA (product model number) (manufactured by Tosoh Corporation)

[0057] [Antioxidant] Irganox (registered trademark) 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 acid, KISUMA (registered trademark) 5A (Kyowa Chemical Industry Co., Ltd.)

[0059] [Evaluation] The flame retardancy, heat resistance, moisture absorption, bleeding properties and hardness of the resin compositions prepared as described above were evaluated as follows.

[0060] (Flame retardancy) According to JIS K7201-2, the oxygen index of a 3 mm thick resin composition that had been subjected to a crosslinking treatment was measured, and the flame retardancy was evaluated. An oxygen index of 21.0 or more was rated as "Good", and an oxygen index of less than 21.0 was rated as "Poor".

[0061] (Heat Resistance) The crosslinked resin composition was molded into a resin sheet having a thickness of 1 mm, and then punched into a dumbbell-shaped No. 3 sheet as specified in JIS K6251:2010. The punched 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 allowed to stand at room temperature (approximately 23°C) for 12 hours. The sheet was then cooled to room temperature and used as a test sample. A tensile test was performed at room temperature (23°C) at a tensile speed of 200 mm / min. Heat resistance was evaluated as "Good" when the elongation of the test sample was 100% or more, and as "Poor" when the elongation of the test sample was less than 100%.

[0062] (Moisture absorption) Pellets were prepared from the crosslinked resin composition, and the pellets were vacuum degassed at 40°C using a vacuum dryer. They were then left to stand for 168 hours at room temperature (23°C) and a humidity of 40% to 60%. The moisture content of the test sample was measured by Method A (anhydrous methanol extraction method) specified in JIS K7251:2002. Moisture absorption was evaluated by assigning "Good" when the moisture content was less than 1,500 ppm and "Poor" when the moisture content was 1,500 ppm or more.

[0063] (Bleeding property) The resin composition was molded into a resin sheet having a thickness of 0.5 mm and a width of 50 mm, and cut into a length of 200 mm. This resin sheet was subjected to a crosslinking treatment, and any bleeding on the resin sheet was wiped off using acetone. Thereafter, the resin sheet was left for 1,000 hours under conditions of room temperature (23°C) and humidity of 40% to 60%. Thereafter, any bleeding on the resin sheet was wiped off again using acetone. The weight difference between the sample weight before the first wiping and the sample weight after the second wiping was calculated as the bleeding amount of the bleeding out on the surface of the resin sheet. The bleeding amount was converted to mass per unit area from the length and width of the resin sheet. When the bleeding amount was 0.150 mg / cm ２ If the bleeding amount is less than 0.150 mg / cm, the mark is "Good"; ２ In the above cases, the bleeding property was evaluated as "X".

[0064] (Hardness) The crosslinked resin composition was molded into a resin sheet having a thickness of 2 mm, and then punched out to the size specified in JIS K7215:1986 to prepare a test sample. Three or more punched test samples were stacked so that the thickness was 6 mm or more. The Shore D hardness of this sample was measured using a Type D durometer. The hardness was evaluated as "Good" when the Shore D hardness was less than 45, and as "Poor" when the Shore D hardness was 45 or more.

[0065]

[0066]

[0067]

[0068] As shown in Tables 1 and 2, the resin compositions of Examples 1 to 19 were excellent in flame retardancy, heat resistance, moisture absorption, and bleeding properties. Furthermore, the resin compositions of Examples 1 to 18 contained 130 parts by mass or less of a metal hydroxide, and therefore had higher hardness than the resin composition of Example 19, which contained 140 parts by mass of a metal hydroxide.

[0069] On the other hand, as shown in Table 3, the resin composition of Comparative Example 1, which did not contain zeolite, did not achieve sufficient heat resistance. The resin composition of Comparative Example 2 contained 4 parts by mass of zeolite, and the mass ratio of zeolite to antioxidant was 4, so the moisture absorption rating was "×". The resin composition of Comparative Example 3 contained a mass ratio of zeolite to antioxidant of 0.07, so the bleeding rating was "×". The resin composition of Comparative Example 4, like Comparative Example 2, contained 4 parts by mass of zeolite, and the mass ratio of zeolite to antioxidant was 4, so the moisture absorption rating was "×". The resin composition of Comparative Example 5, which did not contain magnesium hydroxide, so the flame retardancy rating was "×".

[0070] The entire contents of Japanese Patent Application No. 2023-213094 (filing date: December 18, 2023) are incorporated herein by reference.

[0071] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims.

[0072] 1 coated wire 2 conductor 3 coating layer

Claims

1. A resin composition comprising a polyolefin, a zeolite, an antioxidant, and a metal hydroxide, wherein the resin composition contains 0.1 parts by mass or more and 3.5 parts by mass or less of the zeolite per 100 parts by mass of the polyolefin, the resin composition contains 1 part by mass or more and 6.5 parts by mass or less of the antioxidant per 100 parts by mass of the polyolefin, and a mass ratio of the zeolite to the antioxidant is 0.08 or more and 3 or less.

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

3. The resin composition according to claim 1, wherein the zeolite has a pore size of 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. A resin composition according to any one of claims 1 to 3, wherein the polyolefin is crosslinked, and the polyolefin comprises at least one of polyethylene and an ethylene copolymer.

5. A resin composition according to any one of claims 1 to 4, wherein the metal hydroxide comprises magnesium hydroxide, and the resin composition comprises 40 parts by mass or more and 130 parts by mass or less of the metal hydroxide per 100 parts by mass of the polyolefin.

6. A resin composition according to any one of claims 1 to 5, wherein the resin composition has a Shore D hardness of less than 45.

7. The resin composition according to any one of claims 1 to 6, wherein the resin composition is substantially free of a brominated flame retardant.

8. A coated electric wire comprising: a conductor; and a coating layer coating the conductor and formed from the resin composition according to any one of claims 1 to 7.

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