Resin composition, resin coating material, insulated wire, method for manufacturing insulated wire, wire harness for automobile, and method for manufacturing wire harness for automobile

Abstract

To provide a resin composition which is used for formation of an insulation film (resin coating material layer) of an insulated wire, and thereby makes the obtained insulated wire excellent in all of extrusion appearance, mechanical characteristics, flexibility and terminal workability, while sufficiently maintaining excellent characteristics (insulation property, compound workability, etc.) of a conventional resin coating material; a resin coating material using the resin composition; an insulated wire having a layer of the resin coating material and a method for manufacturing the same, and a wire harness for an automobile including the insulated wire and a method for manufacturing the same.SOLUTION: A resin composition contains the following components (A) to (E): (A) a low-density polyethylene resin; (B) a hydrogenated elastomer; (C) millable silicone rubber; (D) an antioxidant; and (E) a crosslinking auxiliary, wherein in the total content of the components (A) to (C), 50 to 80 mass% of the component (A), 10 to 40 mass% of the component (B) and 5 to 20 mass% of the component (C) are contained.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin composition, a resin coating material, an insulated wire, a method for producing an insulated wire, an automotive wire harness, and a method for producing an automotive wire harness. [Background technology]

[0002] In recent years, the development of environmentally friendly automobiles has been progressing rapidly around the world, with a focus on electric vehicles (EVs). Conventionally, resin coating materials for insulated electric wires used in automobiles have been made of materials with a density of 0.910 g / cm3 from the viewpoint of flexibility. 3 More than 0.930g / cm 3 Low-density polyethylene of less than 1000 kJ / cm2 has generally been used. However, as the need for environmental friendliness increases, there is a demand for even more flexible resin coating materials to accompany the increase in the diameter of electric wires, in order to accommodate the increased current required for hybrid and electric vehicles, as well as to facilitate easier wiring management and space saving.

[0003] To improve the flexibility of the resin coating material, the density is set to 0.900 g / cm 3 Resin compositions have been developed that can improve the flexibility of the resulting resin coating material by using the following ethylene-α-olefin copolymer resins (e.g., ultra-low density polyethylene) or by blending an ethylene copolymer or ethylene propylene diene rubber (EPDM) into the base resin. For example, Patent Document 1 discloses a resin composition containing (A) a low-density polyethylene resin and (B) an ethylene-vinyl acetate copolymer resin, and also containing at least one of (C) a thioether compound and (D) a fluororubber, in which, per 100 parts by mass of the total content of components (A) and (B), the proportion of component (A) is 5 to 40 parts by mass and the proportion of component (B) is 60 to 95 parts by mass, the total content of components (C) and (D) is 0.05 to 1 part by mass per 100 parts by mass of the total content of components (A) and (B), and the proportion of vinyl acetate in component (B) is 40% by mass or less. The low-density polyethylene described in Patent Document 1 has a density of 0.929 g / cm 3 The following polyethylene resins: [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-187970 Summary of the Invention [Problem to be solved by the invention]

[0005] When blending an ethylene copolymer into the base resin, increasing the comonomer content of the ethylene copolymer can improve the flexibility of the resin coating, but increasing the polar component ratio can strengthen adhesion to the conductor, which could impair the ease of terminating the wire.In addition, because EPDM is a non-polar, amorphous rubber, it can improve the insulation and flexibility of the resin coating, but it is inferior to polyethylene resin in terms of strength and heat resistance. Furthermore, while the flexibility of resin coating materials can be improved by reducing the density of ethylene-alpha-olefin copolymer resins, these resins have a low melting point, so when cross-linked by radiation (electron beams), the heat generated by the material causes the coated insulation to soften, which can lead to stronger adhesion to the conductor and compromise the ease of terminating the wire. Furthermore, because ethylene-alpha-olefin copolymer resins are produced by polymerization using a metallocene catalyst, they have excellent physical properties such as tensile strength, but their narrow molecular weight and composition distributions make them inferior in extrusion processability.

[0006] The present invention aims to provide a resin composition that, when used to form an insulating coating (resin coating layer) for an insulated electric wire, can provide the resulting insulated electric wire with excellent extrusion appearance, mechanical properties, flexibility, and terminal processability while fully maintaining the excellent properties (insulation, compound processability, etc.) of conventional resin coating materials. Another objective of the present invention is to provide a resin coating material using the resin composition, an insulated electric wire having a layer of this resin coating material and a method for producing the same, and an automotive wire harness including the insulated electric wire and a method for producing the same. [Means for solving the problem]

[0007] As a result of investigations aimed at solving the above-mentioned problems, the present inventors have found that by preparing a resin composition using a base resin containing a specific blend of low-density polyethylene resin, a hydrogenated elastomer, and a millable silicone rubber, and then forming a resin coating layer using this resin composition, it is possible to obtain an insulated wire that has the desired excellent properties and characteristics in all aspects of extrusion appearance, mechanical properties, flexibility, and terminal processability while fully maintaining the excellent properties of conventional resin coating materials. Based on these findings, the present inventors have conducted further investigations and have now completed the present invention.

[0008] That is, the above problems were solved by the following means. [1] It contains the following components (A) to (E): (A) low-density polyethylene resin, (B) hydrogenated elastomer, (C) Millable silicone rubber, (D) antioxidants, (E) crosslinking coagent, A resin composition containing 50 to 80 mass % of component (A), 10 to 40 mass % of component (B), and 5 to 20 mass % of component (C) in the total content of components (A) to (C). [2] The resin composition according to [1] above, wherein the component (B) contains a hydrogenated styrene-based elastomer and / or a hydrogenated olefin-based elastomer. [3] The resin composition according to [1] or [2], wherein the component (B) comprises at least one of a styrene-ethylene / butylene-styrene block copolymer, a styrene-ethylene / ethylene-propylene-styrene block copolymer, a hydrogenated styrene / butadiene rubber, a styrene-ethylene / propylene-styrene block copolymer, a styrene-ethylene / butylene-olefin crystalline block copolymer, and an olefin crystalline-ethylene / butylene-olefin crystalline block copolymer. [4] The resin composition according to any one of [1] to [3] above, wherein the component (B) has a Duro A hardness of 30 to 80, and the component (C) has a Duro A hardness of 10 to 80. [5] The resin composition according to any one of [1] to [4] above, for forming a resin coating material for an insulated electric wire that constitutes an automotive wiring harness. [6] A resin coating material obtained by crosslinking the resin composition according to any one of [1] to [5] above. [7] An insulated wire, the insulating coating of which has the resin coating material according to [6]. [8] An automotive wire harness comprising the insulated wire according to [7]. [9] A method for producing an insulated wire, comprising the steps of extrusion coating a conductor with the resin composition according to any one of [1] to [5] to provide a layer of the resin composition, and irradiating the layer of the resin composition with an electron beam.

[10] A method for producing an automotive wire harness, comprising a step of bundling insulated wires obtained by the method for producing an insulated wire according to [9] above, and attaching connectors to the ends of the bundled insulated wires. [Effects of the Invention]

[0009] When the resin composition of the present invention is used to form an insulating coating (resin coating layer) for an insulated wire, an insulated wire can be obtained that exhibits desired excellent properties and characteristics in all of extrusion appearance, mechanical properties, flexibility, and terminal processability while fully maintaining the excellent properties of conventional resin coating materials. The automotive wire harness of the present invention also has an insulated wire that exhibits the above-mentioned excellent properties and characteristics. Furthermore, the manufacturing method for an automotive wire harness of the present invention also allows for the production of an automotive wire harness that has an insulated wire that exhibits the above-mentioned excellent properties and characteristics. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Resin composition] The resin composition of the present invention contains (A) a low-density polyethylene resin (also referred to as component (A)), (B) a hydrogenated elastomer (also referred to as component (B)), (C) a millable silicone rubber (also referred to as component (C)), (D) an antioxidant (also referred to as component (D)), and (E) a cross-linking aid. In the present invention, "containing components (A) to (E)" is synonymous with "composed of components (A) to (E)." Components (A) to (E) and the optional components described below may each be used alone or in combination of two or more. The total content of components (A) to (C) in the resin composition of the present invention is preferably 40 to 90% by mass, more preferably 50 to 80% by mass, and even more preferably 60 to 70% by mass. The resin composition of the present invention contains components (A) to (C) as a base resin. When low-density polyethylene is blended into the base resin, the resulting resin coating material has excellent flexibility and mechanical strength, but the adhesion strength is too strong, resulting in poor terminal workability for insulated electric wires and a poor extrusion appearance. Furthermore, when millable silicone rubber is blended into the base resin, the adhesion strength between the resin coating material and the conductor can be controlled within an appropriate range, resulting in excellent terminal workability for insulated electric wires, but the extrusion appearance and mechanical strength tend to be poor. Furthermore, when a hydrogenated elastomer is blended into the base resin, the resulting insulated electric wire has excellent extrusion appearance, but the mechanical strength and terminal workability tend to be poor. The resin composition of the present invention blends components (A) to (C) in combination and controls their blending amounts, thereby enabling the resulting insulated electric wire to have excellent extrusion appearance, mechanical properties, flexibility, and terminal workability. The components contained in the resin composition of the present invention will be described below.

[0011] <(A) Low-density polyethylene resin> In the present invention, the term "low density polyethylene resin" refers to a polyethylene resin having a density of 0.929 g / cm 3The term "polyethylene resin" refers to the following polyethylene resins. Examples of such polyethylene resins include low-density polyethylene (LLDPE) and very low-density polyethylene (VLDPE). These may also be, for example, high-pressure radical low-density polyethylene or metallocene-catalyzed linear low-density polyethylene. For examples of such polyethylene, see, for example, the description of Japanese Patent Application No. 2016-072380. Furthermore, component (A) used in the present invention may be a modified polyethylene (for example, an acid-modified polyethylene). The density range of the component (A) is preferably 0.870 to 0.929 g / cm 3 From the viewpoint of further improving flexibility, the density of component (A) is 0.900 g / cm 3 Less than 0.890 g / cm is more preferable. 3 More preferably, 0.880 g / cm 3 The following is more preferable: The density of polyethylene can be determined in accordance with JIS K7112 (2023).

[0012] The melt flow rate (MFR) of the component (A) is preferably 0.1 to 100 g / 10 min (load: 2.16 kg, temperature: 190°C), more preferably 0.1 to 20 g / 10 min, and even more preferably 0.2 to 10 g / 10 min. By setting the melt flow rate of the component (A) within the above preferred range, the load on the kneading equipment and extruder during preparation of the resin composition or during production of the insulated wire can be further reduced, and the dispersibility of each component in the resin composition can be further improved. The melt flow rate (MFR) can be measured using an extrusion type plastometer (melt indexer) specified in JIS K6760 (1995) as a testing machine, using a method in accordance with JIS K7210 (2014).

[0013] The component (A) can be synthesized by a conventional method, or a commercially available product can be used, such as ENGAGE 8452 manufactured by The Dow Chemical Company and NUC-9060 manufactured by ENEOS NUC Corporation.

[0014] The content of component (A) in the resin composition of the present invention is 50 to 80 mass% of the total content of components (A) to (C). From the viewpoint of further improving mechanical properties such as breaking strength, the content of component (A) in the total content of components (A) to (C) is preferably 52 mass% or more, more preferably 55 mass% or more. Furthermore, from the viewpoint of improving the extrusion appearance and improving the terminal processability of the insulated wire (controlling the adhesion strength to a more appropriate value), the content is preferably 75 mass% or less, more preferably 70 mass% or less. The preferred range is preferably 52 to 75 mass%, more preferably 55 to 70 mass%.

[0015] <(B) Hydrogenated elastomer> The hydrogenated elastomer (hydrogenated diene elastomer) can be obtained by adding hydrogen to a diene elastomer. The component (B) is preferably a hydrogenated styrene elastomer and / or a hydrogenated olefin elastomer. The durometer hardness (Type A) of component (B) (hereinafter also referred to as "Duro A hardness") is preferably 80 or less. The Duro A hardness of component (B) is preferably 10 or more, more preferably 20 or more, and even more preferably 30 or more. In terms of the preferred range, the Duro A hardness is preferably 10 to 80, more preferably 20 to 80, and even more preferably 30 to 80. The Duro A hardness is determined by a method in accordance with ISO 7619 2010.

[0016] (hydrogenated styrene elastomer) Hydrogenated styrene elastomers are copolymer blocks of components derived from aromatic vinyl compounds and conjugated diene compounds, and / or hydrogenated block copolymers or random copolymers primarily composed of components derived from the above compounds. Examples of aromatic vinyl compounds include one or more of styrene, α-methylstyrene, vinyltoluene, and p-tert-butylstyrene, with styrene being preferred. Examples of conjugated diene compounds include one or more of butadiene, isoprene, 1,3-pentadiene, and 2,3-dimethyl-1,3-butadiene, with butadiene and / or isoprene being preferred. In the hydrogenated styrene-based elastomer, the content of a component derived from an aromatic vinyl compound (preferably a styrene component) is preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less. The content is preferably 10% by mass or more. The content can be determined, for example, by measuring the UV absorption spectrum with a UV spectrophotometer using a chloroform solution.

[0017] The hydrogenated styrene elastomer is preferably a binary or ternary block copolymer composed of a polystyrene block and a polyolefin block. Examples of such hydrogenated styrene elastomers include styrene-ethylene / butylene-styrene block copolymer (SEBS), styrene-ethylene / ethylene-propylene-styrene block copolymer (SEEPS), hydrogenated styrene / butadiene rubber (HSBR), styrene-ethylene / propylene-styrene block copolymer (SEPS), styrene-ethylene / butylene-olefin crystalline block copolymer (SEBC), and styrene-ethylene / propylene block copolymer. The hydrogenated styrene elastomer preferably contains at least one of SEBS, SEEPS, HSBR, SEPS, and SEBC, and more preferably contains at least one of SEBS, SEEPS, and HSBR. Examples of commercially available hydrogenated styrene elastomers include SEPTON (brand: 2063, type: SEPS, styrene content: 13% by mass) and SEEPS (brand: 4033, type: SEEPS, styrene content: 30% by mass) manufactured by Kuraray Co., Ltd., and DYNARON (brand: 1321P, type: HSBR, styrene content: 10% by mass) manufactured by ENEOS Materials Corporation.

[0018] (hydrogenated olefin elastomer) Hydrogenated olefin elastomers are copolymer blocks of components derived from olefin compounds and conjugated diene compounds, and / or hydrogenated products of block copolymers or random copolymers mainly composed of components derived from the above compounds. Examples of the olefin compounds include crystalline olefins, with crystalline ethylene being more preferred. Examples of the conjugated diene compounds include one or more of butadiene, isoprene, 1,3-pentadiene, and 2,3-dimethyl-1,3-butadiene, with butadiene and / or isoprene being preferred.

[0019] The hydrogenated olefin elastomer is preferably a binary or ternary block copolymer composed of an olefin crystalline block and an elastomer block having a polyolefin structure. Examples of such an olefin elastomer include a crystalline olefin-ethylene / butylene-crystalline olefin block copolymer (CEBC), and more preferably contains CEBC. An example of a commercially available hydrogenated olefin elastomer is DYNARON (brand: 6200P, type: CEBC) manufactured by ENEOS Materials Corporation.

[0020] The content of component (B) in the resin composition of the present invention is 10 to 40 mass% of the total content of components (A) to (C). From the viewpoint of further suppressing defects in the appearance (extrusion appearance) of the surface of the insulated wire, the content of component (B) in the total content of components (A) to (C) is preferably 20 to 40 mass%, more preferably 20 to 35 mass%.

[0021] <(C) Millable Silicone Rubber> Millable silicone rubber (HCR, High Consistency Rubber) is a compound made by blending a reinforcing agent (usually silica) with a linear organopolysiloxane (uncrosslinked) as the main raw material (silicone raw rubber).While liquid silicone rubber is primarily composed of a linear polymer with a degree of polymerization of about 100 to 2000, millable silicone rubber is primarily composed of a highly polymerized linear polymer with a degree of polymerization of about 3000 to 10,000, so it remains solid at room temperature (25°C) and is easy to process in mixers and extruders. The Duro A hardness of component (C) is preferably 80 or less, may be 70 or less, or may be 60 or less. The Duro A hardness of component (C) is also preferably 10 or more, more preferably 20 or more, and even more preferably 30 or more. In terms of the preferred range, the Duro A hardness is preferably 10 to 80, more preferably 20 to 80, and even more preferably 30 to 80, and may be 30 to 70 or 30 to 60.

[0022] Examples of the linear organopolysiloxane include methylvinylpolysiloxane, methylphenylvinylpolysiloxane, and methylfluoroalkylpolysiloxane. The fluoroalkyl is not particularly limited, and examples thereof include a 3,3,3-trifluoropropyl group. The terminal group of the organopolysiloxane is not particularly limited, and examples thereof include an alkyl group (methyl group), a vinyl group, and a hydroxyl group.

[0023] Millable silicone rubber contains a reinforcing agent (filler). The reinforcing agent is not particularly limited, and examples thereof include various types of silica such as fumed silica (also called fumed silica or dry silica), precipitated silica, diatomaceous earth, and quartz powder, as well as surface-treated silica thereof. As the reinforcing agent, fumed silica is preferred from the viewpoints of moldability, appearance of the molded product, insulation resistance, etc. The BET specific surface area of ​​the reinforcing agent is not particularly limited, and may be, for example, 50 to 300 m 2The BET specific surface area is preferably about 1 / g. The BET specific surface area can be measured, for example, in accordance with the method specified in Japanese Industrial Standards (JIS) Z8830 (2013), by adsorbing gas molecules with a known adsorption area, such as nitrogen gas, onto the surface of powder particles, and determining the specific surface area of ​​the sample from the amount of gas molecules adsorbed (BET method).

[0024] The content of the reinforcing agent in the millable silicone rubber is not particularly limited and can be set appropriately depending on the application, required properties, etc. For example, the content of the reinforcing agent in the millable silicone rubber can be, for example, 10 to 40 mass %, preferably 12 to 38 mass %, and more preferably 14 to 35 mass %, based on 100 mass % of the millable silicone rubber. The millable type silicone rubber may contain fillers, dispersion promoters and other additives other than the reinforcing agent.

[0025] Millable silicone rubber may be prepared by mixing the above-mentioned additives in addition to the organopolysiloxane and reinforcing agent, or a commercially available product (a compound that does not contain a crosslinking agent (curing agent)) may be used. Examples of commercially available products include XIAMETER RBB6630-30 and XIAMETER RBB2070-60 manufactured by Dow Chemical Toray.

[0026] The content of component (C) in the resin composition of the present invention is 5 to 20 mass% of the total content of components (A) to (C). From the viewpoint of further improving the terminal processability of the insulated wire, the content of component (C) in the total content of components (A) to (C) is preferably 7.5 to 20 mass%, more preferably 10 to 20 mass%.

[0027] <(D) Antioxidants> The resin composition of the present invention contains an antioxidant (D). Examples of such component (D) include phenol compounds (phenol-based antioxidants), imidazole compounds (imidazole-based antioxidants), and thioether compounds (thioether-based antioxidants), and these may be used alone or in combination. From the viewpoint of improving heat resistance, the resin composition of the present invention preferably contains 10 to 30 parts by mass, and more preferably 14 to 22 parts by mass, of component (D) (when the resin composition contains multiple antioxidants, the total amount of antioxidants) per 100 parts by mass of the total amount of components (A) to (C).

[0028] (phenolic antioxidant) Examples of the phenolic antioxidant that can be used in the resin composition of the present invention include triethylene glycol-bis(3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate), 1,6-hexanediol-bis(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate), pentaerythritol-tetrakis(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate), octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, Examples include tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate and isooctyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate. Among these, from the viewpoint of imparting high heat resistance to automotive wire harnesses, those having two or more 3,5-di-t-butyl-4-hydroxyphenyl groups or 3,5-di-t-butyl-4-hydroxybenzyl groups are preferred, and tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate and pentaerythritol-tetrakis(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate) are particularly preferred. In the present invention, commercially available phenolic antioxidants may be used, such as Irganox 1010 (trade name, manufactured by BASF).

[0029] When the resin composition of the present invention contains a phenolic antioxidant, from the viewpoint of improving heat resistance, the resin composition preferably contains 1 to 8 parts by mass, and more preferably 2 to 6 parts by mass, of the phenolic antioxidant per 100 parts by mass of the total content of components (A) to (C).

[0030] (imidazole antioxidant) Examples of imidazole-based antioxidants that can be used in the resin composition of the present invention include 2-sulfanylbenzimidazole, 2-sulfanylmethylbenzimidazole, 4-sulfanylmethylbenzimidazole, 5-sulfanylmethylbenzimidazole, and zinc salts thereof, with 2-sulfanylbenzimidazole and its zinc salt being preferred. In the present invention, commercially available imidazole antioxidants may be used, such as Nocrac MBZ (trade name, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.).

[0031] When the resin composition of the present invention contains an imidazole-based antioxidant, from the viewpoint of improving heat resistance, the resin composition preferably contains 8 to 16 parts by mass, and more preferably 10 to 14 parts by mass, of the imidazole-based antioxidant per 100 parts by mass of the total content of components (A) to (C).

[0032] (Thioether antioxidant) Thioether antioxidants that can be used in the resin composition of the present invention include dilauryl 3,3'-thiodipropionate, dimyristyl 3,3'-thiodipropionate, distearyl 3,3'-thiodipropionate, 2,2-bis{[3-(dodecylthio)-1-oxopropoxy]methyl}propane-1,3-diyl bis[3-(dodecylthio)propionate] (also known as 2,2-bis[[3-(dodecylthio)-1-oxopropyloxy]methyl]-1,3-propanediyl bis[3-(dodecylthio)propionic acid]). Among these, 2,2-bis{[3-(dodecylthio)-1-oxopropoxy]methyl}propane-1,3-diyl bis[3-(dodecylthio)propionate] is preferred from the viewpoints of long-term thermal stability and improved extraction resistance. The resin composition of the present invention may contain a commercially available thioether antioxidant, such as Adekastab AO-412S (trade name, manufactured by ADEKA Corporation).

[0033] When the resin composition of the present invention contains a thioether-based antioxidant, from the viewpoint of improving heat resistance, the thioether-based antioxidant is preferably contained in an amount of 0.5 to 4 parts by mass, and more preferably 1 to 3 parts by mass, per 100 parts by mass of the total content of components (A) to (C).

[0034] <(E) Crosslinking Coagent> The resin composition of the present invention contains a crosslinking aid (E). Component (E) may be a polyfunctional compound, preferably a compound having two or more (preferably three or more, more preferably three to six) ethylenically unsaturated bonds (carbon-carbon double bonds) in the molecule. Specific examples of component (E) include (meth)acrylate compounds such as polypropylene glycol diacrylate and trimethylolpropane triacrylate, allyl compounds such as triallyl cyanurate, maleimide compounds, and divinyl compounds. In the present invention, a commercially available crosslinking aid may be used as component (E). An example of a commercially available product is Ogmont T200 (trade name, manufactured by Shin-Nakamura Chemical Co., Ltd.). From the viewpoint of improving heat resistance and chemical resistance, the resin composition of the present invention preferably contains 1 to 8 parts by mass, and more preferably 2 to 6 parts by mass, of component (E) per 100 parts by mass of the total content of components (A) to (C).

[0035] <Other ingredients> In addition to the above components (A) to (E), the resin composition of the present invention may contain other components such as the following flame retardants, processing aids, and additives, as long as the effects of the present invention are not impaired.

[0036] <Flame retardant> The present invention can contain a flame retardant to the extent that the effects of the present invention are not impaired. Examples of such flame retardants include bromine-based flame retardants and antimony-based flame retardants. The present invention preferably contains at least one of a bromine-based flame retardant or an antimony-based flame retardant, and more preferably contains both a bromine-based flame retardant and an antimony-based flame retardant. Furthermore, the mixing ratio of the bromine-based flame retardant and the antimony-based flame retardant is preferably within a range such that the molar ratio of bromine element to antimony element contained in the resin composition is 2 to 5 times the molar amount of bromine element. In other words, it is preferable to contain a bromine-based flame retardant whose molar amount is 2 to 5 times the molar amount of antimony-based flame retardant. When the resin composition of the present invention contains a flame retardant, it preferably contains a total amount of 35 to 45 parts by mass of the flame retardant per 100 parts by mass of the total content of components (A) to (C).

[0037] (Brominated flame retardants) The brominated flame retardant is preferably a bromine-containing compound. That is, the resin composition of the present invention preferably contains a bromine-containing compound as a flame retardant. Examples of brominated flame retardants that can be used include brominated N,N'-ethylenebisphthalimide or compounds derived therefrom (collectively referred to as "brominated N,N'-ethylenebisphthalimide compounds"), N,N'-bis(bromophenyl)terephthalamide or compounds derived therefrom (collectively referred to as "N,N'-bis(bromophenyl)terephthalamide compounds"), brominated bisphenol or compounds derived therefrom (collectively referred to as "brominated bisphenol compounds"), and 1,2-bis(bromophenyl)alkanes and other organic bromine-containing flame retardants. Among these, brominated N,N'-ethylenebisphthalimide and / or 1,2-bis(pentabromophenyl)ethane are preferred. By using brominated N,N'-ethylenebisphthalimide and / or 1,2-bis(bromophenyl)alkane as a flame retardant, it is possible to form a resin coating material that hardly causes bleeding. The brominated flame retardant used in the resin composition of the present invention may be a commercially available brominated flame retardant, such as Cytex 8010 (trade name, manufactured by Albemarle).

[0038] When the resin composition of the present invention contains a brominated flame retardant, it preferably contains 20 to 40 parts by mass, and more preferably 25 to 35 parts by mass, of the brominated flame retardant per 100 parts by mass of the total content of components (A) to (C).

[0039] (Antimony-based flame retardant) Examples of antimony-based flame retardants include antimony trioxide, antimony tetroxide, antimony pentoxide, and sodium antimonate. Antimony reacts with chlorine (halogen), and the generated gas is thought to block oxygen, promoting the formation of a carbonized layer and trapping free radicals (stopping the pyrolysis chain reaction). Among these, in the present invention, it is preferable to add antimony trioxide from the viewpoint of forming a more stable carbonized layer. In the present invention, commercially available antimony trioxide may be used, for example, PATOX-C (trade name, manufactured by Nippon Seiko Co., Ltd.).

[0040] When the resin composition of the present invention contains an antimony-based flame retardant, it preferably contains 5 to 15 parts by mass, and more preferably 7 to 13 parts by mass, of the antimony-based flame retardant per 100 parts by mass of the total content of components (A) to (C).

[0041] (Other flame retardants) The resin composition of the present invention may contain, in addition to the above-mentioned bromine-based flame retardant and antimony-based flame retardant, a flame retardant that can be commonly used in the insulating coating of an insulated electric wire. Examples of such flame retardants include metal hydroxides (hydroxide-based flame retardants) such as magnesium hydroxide and aluminum hydroxide. When the resin composition of the present invention contains a hydroxide-based flame retardant, the hydroxide-based flame retardant is preferably contained in an amount of 5 parts by mass or less, more preferably 3 parts by mass or less, per 100 parts by mass of the total content of components (A) to (C).

[0042] <Processing aids> The resin composition of the present invention preferably contains a processing aid within a range that does not impair the effects of the present invention. Preferred examples of the processing aid include metal soaps (lubricants). Examples of metal soaps (lubricants) that can be used in the resin composition of the present invention include calcium stearate, zinc stearate, and magnesium stearate. In the present invention, commercially available metal soaps may be used, such as Shinaka Red ZS-101 (trade name, manufactured by Shinagawa Kako Co., Ltd.).

[0043] When the resin composition of the present invention contains a metal soap, it preferably contains 0.5 to 2 parts by mass of the metal soap per 100 parts by mass of the total content of components (A) to (C).

[0044] <Additives> The resin composition of the present invention may contain various additives, such as copper inhibitors, ultraviolet absorbers, dispersants, plasticizers, fillers, pigments, etc., as needed, within the range that does not impair the effects of the present invention.

[0045] [Method of producing resin composition] The resin composition of the present invention can be obtained by blending the above-mentioned components (A) to (E) and, if necessary, the above-mentioned optional components, and melt-kneading them in a commonly used kneading device such as a batch kneader, a roll, a kneader, a Banbury mixer, or the like, or a twin-screw extruder.

[0046] [Insulated wire] The insulated wire of the present invention has a layer made of a resin coating material obtained by crosslinking the resin composition of the present invention on the surface of a conductor (including a conductor bundle and a fiber core). The insulated wire may have an intermediate layer or a shielding layer between the conductor and the layer made of the resin coating material. The conductor may be a single wire or a twisted wire, and may be a bare wire or a tin-plated or enamel-coated wire. Examples of metal materials for forming the conductor include soft copper, copper alloys, and aluminum. The thickness of the resin coating material formed around the conductor is not particularly limited, but is usually about 0.15 to 5 mm. There are no particular restrictions on the diameter of the conductor, the material of the conductor, the thickness of the coating layer, etc., and these may be determined appropriately depending on the purpose and application.

[0047] [Insulated wire manufacturing method] The insulated wire of the present invention can be obtained by extrusion coating a conductor with the resin composition of the present invention to form a resin composition layer, and then irradiating the resin composition layer with an electron beam, which causes a crosslinking reaction in the resin composition layer to form a resin coating layer. The conditions for extrusion molding the resin composition of the present invention are not particularly limited as long as the resin composition of the present invention can be extruded, but the extrusion temperature (head) is preferably 100 to 230°C, more preferably 120 to 200°C, from the viewpoint of reducing the load on the extruder (extrusion molding machine) and ensuring shape retention. Other conditions for extrusion molding can be appropriately set depending on the purpose. The screw configuration of the extruder is not particularly limited, and a conventional full-flighted screw, double-flighted screw, tip double-flighted screw, Maddock screw, etc. can be used.

[0048] The crosslinking reaction by electron beam irradiation is not particularly limited and can be carried out by a conventional method and conditions. The irradiation conditions for electron beam irradiation are preferably a dose of 50 to 450 kGy, more preferably 80 to 250 kGy, further preferably 80 to 200 kGy, and particularly preferably 80 to 160 kGy. The acceleration voltage is preferably 300 to 5000 keV, more preferably 500 to 3000 keV.

[0049] [Automotive wire harnesses and manufacturing methods for automotive wire harnesses] The automotive wire harness of the present invention includes the insulated wire of the present invention. In the automotive wire harness of the present invention, components other than the insulated wire are not particularly limited, and may include components typically used in automotive wire harnesses. For example, connectors, terminals, etc. The automotive wire harness of the present invention can be obtained through a process of bundling insulated wires and attaching connectors to the ends of the bundled insulated wires. [Example]

[0050] The present invention will be described in more detail based on the following examples and comparative examples, but the present invention is not limited to these.

[0051] [Examples 1 to 6 and Comparative Examples 1 to 12] The materials used to prepare the resin compositions of Examples 1 to 6 and Comparative Examples 1 to 12 are shown in Table 1 below. Details of the materials used are as follows.

[0052] <Materials used> (Component (A): Low-density polyethylene resin) ENGAGE 8452 (VLDPE, Mooney viscosity at 121°C: 11, density: 0.875 g / cm 3 , MFR: 3.0g / 10min, Crystallinity: 20%, Melting point: 66℃, Duro A hardness: 74, manufactured by Dow Chemical Co.) ·NUC-9060(LLDPE, density: 0.921g / cm 3 , MFR: 1.3g / 10min, crystallinity: 50-60%, melting point: 112℃, manufactured by ENEOS NUC (EPDM: other rubber) EP51 (EPDM, Mooney viscosity at 125°C: 23, density: 0.89 g / cm 3 , manufactured by JSR Corporation)

[0053] (Component (B): Hydrogenated elastomer) Septon 2063 (SEPS, styrene content: 13%, Duro A hardness: 36, manufactured by Kuraray) DYNARON 1321P (HSBR, styrene content: 10%, density: 0.89 g / cm 3 , Duro A hardness: 41, manufactured by ENEOS Materials Co., Ltd.) DYNARON 6200P (CEBC, styrene content: 0%, density: 0.89 g / cm 3 , Duro A hardness: 66, manufactured by ENEOS Materials Co., Ltd.) Septon 4033 (SEEPS, styrene content: 30%, Duro A hardness: 76, manufactured by Kuraray)

[0054] (Component (C): Millable silicone rubber) ·XIAMETER RBB6630-30 Base(HCR, density: 1.11g / cm 3 , Duro A hardness: 30, manufactured by Dow Toray ·XIAMETER RBB2070-60 Base(HCR, Density: 1.18g / cm 3 , Duro A hardness: 60, manufactured by Dow Toray (LSR: Liquid Silicone Rubber) XIAMETER RBL-9117 POLYMER (Vinyl-terminated dimethyl (siloxane and silicone), liquid polymer, density: 0.97 g / cm 3 , kinematic viscosity: 2000mm 2 / s, manufactured by Dow-Toray)

[0055] (Component (D): Antioxidant) Phenolic antioxidant: pentaerythritol-tetrakis(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate), phenolic antioxidant, Irganox 1010 (trade name), manufactured by BASF Imidazole antioxidant: zinc salt of 2-mercaptobenzimidazole, Nocrac MBZ (trade name), manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Thioether antioxidant: 2,2-bis{[3-(dodecylthio)-1-oxopropoxy]methyl}propane-1,3-diyl bis[3-(dodecylthio)propionate], Adeka Stab AO-412S (trade name), manufactured by ADEKA Corporation

[0056] (Component (E): Crosslinking aid) Multifunctional polymer: Trimethylolpropane trimethacrylate, Ogmont T200 (trade name), manufactured by Shin-Nakamura Chemical Co., Ltd.

[0057] (Flame retardant) Brominated flame retardants: 1,2-bis(pentabromophenyl)ethane, Cytex 8010 (trade name), manufactured by Albemarle Antimony-based flame retardant: Antimony trioxide, PATOX-C (trade name), manufactured by Nihon Seiko Co., Ltd.

[0058] (processing aids) Metal soap: zinc stearate, Sinaka Red ZS-101 (product name), manufactured by Shinagawa Chemical Industry Co., Ltd.

[0059] <Production of resin composition and insulated wire> According to the composition shown in Table 1 below, the materials were melt-kneaded at 180°C using a 75-liter Banbury mixer, and the mixture (compound) was discharged and granulated through an extruder to obtain resin composition pellets. Each resin composition pellet obtained above was extrusion coated onto a conductor at a linear speed of 30 m / min, 60 m / min, and 100 m / min using an extruder set at a temperature of 90 to 190°C. The formed resin composition layer was subjected to a cross-linking reaction by electron beam irradiation. 2 An insulated wire was obtained with a 0.7 mm thick insulating coating around a copper conductor (≒3 sq.). Crosslinking using an electron beam was performed under the conditions of an acceleration voltage of 800 keV and a dose of 160 kGy. Regarding the following performance evaluations, the insulated wires obtained at a wire speed of 30 m / min were used for evaluation of mechanical properties, flexibility, and terminal processability.

[0060] [Performance evaluation] <Extruded appearance> The surface condition of the resin coating material of the insulated wires obtained under each of the above drawing speed conditions was visually observed and evaluated based on the following evaluation criteria. -Evaluation criteria- A: The surfaces of the resin coating materials of the insulated wires obtained at wire speeds of 30 m / min, 60 m / min, and 100 m / min are all smooth. B: The surface of the resin coating material of the insulated wire obtained at a wire speed of 100 m / min is clearly rough when visually observed, but the surfaces of the resin coating material of the insulated wire obtained at wire speeds of 30 m / min and 60 m / min are smooth. C: The surface of the resin coating material of the insulated wire obtained at a wire speed of 60 m / min and 100 m / min is clearly rough when visually observed, but the surface of the resin coating material of the insulated wire obtained at a wire speed of 30 m / min is smooth. D: Roughness was clearly observed on the surface of the resin coating material of all the insulated wires obtained at wire speeds of 30 m / min, 60 m / min, and 100 m / min by visual inspection.

[0061] <Mechanical properties> The mechanical properties of insulated wires were evaluated by measuring the breaking strength of the resin coating material. Breaking strength was measured based on Japanese Industrial Standards (JIS) K7161 (2014). Specifically, tubular samples were prepared by removing the conductor from insulated wires that had been crosslinked using an electron beam. The tensile strength (breaking strength, MPa) at the time of breakage of the coating material was measured using a gripping distance of 60 mm, a gauge length of 20 mm, and a pulling speed of 200 mm / min (room temperature, 23°C). Based on the measurement results, the mechanical properties were evaluated according to the following evaluation criteria. -Evaluation criteria- A: Breaking strength is 15 MPa or more B: Breaking strength is 10 MPa or more and less than 15 MPa C: Breaking strength is less than 10 MPa

[0062] <Flexibility> The flexibility of insulated wires was evaluated by measuring the tensile stress (50% modulus) of the resin coating material. The tensile stress was measured based on Japanese Industrial Standards (JIS) K7161 (2014). Specifically, tubular samples were prepared by removing the conductor from insulated wires that had been crosslinked using an electron beam. These samples were then deformed with a gripping distance of 60 mm, a gauge length of 20 mm, and a pulling speed of 200 mm / min (room temperature, 23°C). The tensile stress (50% modulus) was measured when the tensile strain (the increase in the gauge length after pulling) divided by the gauge length (sample length before pulling) reached 50%, and the flexibility was evaluated according to the following criteria. -Evaluation criteria- A: 50% modulus is less than 3 MPa B: 50% modulus is 3 MPa or more and less than 4 MPa C: 50% modulus is 4 MPa or more

[0063] <Terminal processability> The termination workability of insulated wires was evaluated by measuring the adhesive strength between the resin coating and the conductor. The adhesive strength between the resin coating and the conductor was measured according to the Japanese Automotive Technical Standard JASO D618. Specifically, the resin coating was removed from the tip of a 75 mm insulated wire that had been crosslinked using an electron beam to expose the conductor. The conductor was then pulled at a pulling speed of 250 mm / min (room temperature, 23°C), and the tensile stress measured until the resin coating fell off the conductor was measured. The maximum value was taken as the adhesive strength. The termination workability was evaluated based on the adhesive strength according to the following criteria. -Evaluation criteria- A: Adhesion strength is 20N or more and less than 35N B: Adhesion strength is 35N or more and less than 50N C: Adhesion strength is 50N or more and less than 100N D: Adhesion strength is 100N or more

[0064] The results obtained from each of the above tests are shown in Table 1 below. The amounts listed in the table below are in parts by mass (mass ratio). Blank spaces indicate that the corresponding component was not included.

[0065] [Table 1-1]

[0066] [Table 1-2]

[0067] As is clear from Table 1, the insulated wires obtained using resin compositions (Comparative Examples 1 to 4, 6 to 9, 11, and 12) in which the contents of components (A), (B), and (C) were outside the ranges specified in the present invention were all inferior in at least one of extrusion appearance, mechanical properties, flexibility, and terminal processability. The insulated wire obtained using the resin composition of Comparative Example 5, which used EPDM instead of low-density polyethylene, was also inferior in extrusion appearance and mechanical properties. Furthermore, the insulated wire obtained using the resin composition of Comparative Example 10, which used liquid silicone rubber instead of millable silicone rubber, was also inferior in mechanical properties. In contrast, the insulated wires obtained using the resin compositions (Examples 1 to 6) that satisfied all of the requirements of the present invention were excellent in all of the extrusion appearance, mechanical properties, flexibility, and terminal processability. Furthermore, these resin compositions had sufficient insulation properties, flame retardancy, etc. as resin coating materials for insulated wires.

Claims

1. It contains the following components (A) to (E): (A) a low-density polyethylene resin; (B) a hydrogenated elastomer, (C) Millable type silicone rubber, (D) an antioxidant, (E) a crosslinking aid; A resin composition comprising 50 to 80 mass% of component (A), 10 to 40 mass% of component (B), and 5 to 20 mass% of component (C) in a total content of the components (A) to (C).

2. The resin composition according to claim 1 , wherein the component (B) comprises a hydrogenated styrene-based elastomer and / or a hydrogenated olefin-based elastomer.

3. The resin composition according to claim 2, wherein the component (B) comprises at least one of a styrene-ethylene / butylene-styrene block copolymer, a styrene-ethylene / ethylene-propylene-styrene block copolymer, a hydrogenated styrene / butadiene rubber, a styrene-ethylene / propylene-styrene block copolymer, a styrene-ethylene / butylene-olefin crystalline block copolymer, and an olefin crystalline-ethylene / butylene-olefin crystalline block copolymer.

4. The resin composition according to claim 3, wherein the component (B) has a Duro A hardness of 30 to 80, and the component (C) has a Duro A hardness of 10 to 80.

5. The resin composition according to any one of claims 1 to 4, for forming a resin coating material for an insulated wire that constitutes an automotive wiring harness.

6. A resin coating material obtained by crosslinking the resin composition according to any one of claims 1 to 4.

7. An insulated wire, the insulating coating of which comprises the resin coating material according to claim 6.

8. A wiring harness for an automobile, comprising the insulated wire according to claim 7.

9. A method for producing an insulated wire, comprising the steps of extrusion coating the resin composition according to any one of claims 1 to 4 onto a conductor to provide a layer of the resin composition, and irradiating the layer of the resin composition with an electron beam.

10. A method for producing an automotive wire harness, comprising a step of bundling insulated electric wires obtained by the method for producing an insulated electric wire according to claim 9 and attaching connectors to the ends of the bundled insulated electric wires.

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