Resin composition, resinous coating material, insulated electric wire, automotive wire harness, and method for producing insulated electric wire for use in automotive wire harness

Abstract

A resin composition including an ethylene / vinyl acetate copolymer resin as a resin component and containing an imidazole compound, a phenol compound, and a thioether compound as antioxidants and a bromine compound and an antimony compound as flame retardants, wherein the content of the imidazole compound is 14-24 parts by mass, the content of the phenol compound is 1.0-2.0 parts by mass, the content of the thioether component is 0.3-0.9 parts by mass, the content of the bromine compound is 15-30 parts by mass, and the content of the antimony compound is 5-15 parts by mass, per 100 parts by mass of the total content of the resin component in the resin composition.

Description

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

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

[0002] Flame-retardant insulated wires are widely used in various home appliances, office automation equipment, and the like. Furthermore, insulated wires used in automobiles and the like are also required to have various properties, such as flame retardancy, heat resistance, flexibility, and mechanical properties. Resin compositions that can be used as conductor covering materials to achieve insulated wires with flame retardancy, heat resistance, flexibility, and mechanical properties have been investigated and many reports have been published. Resin compositions based on resins such as polyethylene and ethylene-vinyl acetate copolymers are widely used as resin compositions for constituting insulated wires with such desired properties.

[0003] For example, Patent Document 1 describes that by preparing a resin composition containing an ethylene-vinyl acetate copolymer, a specific flame retardant, specific types of antioxidants, a copper inhibitor, and a cross-linking aid in specific amounts, the composition is less likely to adhere to a processing machine during preparation of the resin composition (excellent processing adhesion), and the amount of composition remaining in the processing machine can be reduced; and that by applying the composition to the surface of a conductor or the like and cross-linking it, an insulated wire can be obtained that exhibits desired excellent properties in all of flexibility, hardness, degree of cross-linking, abrasion resistance, flame retardancy, cold resistance, and heat resistance. This resin composition contains, relative to 90 to 100 parts by mass of ethylene-vinyl acetate copolymer, 15 to 30 parts by mass of a bromine-based flame retardant, 5 to 15 parts by mass of antimony trioxide, 6 to 12 parts by mass of a benzimidazole-based antiaging agent, 2 to 4 parts by mass of a phenol-based antiaging agent, 2 to 4 parts by mass of a thioether-based antiaging agent, 0.5 to 2 parts by mass of a copper inhibitor, and 3 to 6 parts by mass of a cross-linking aid.

[0004] Patent Document 2 describes a flame-retardant resin composition that, when used as a coating material for a conductor, can produce an insulated electric wire that has excellent heat resistance, flame retardancy, and compatibility with polyvinyl chloride (PVC) and that does not cause problems such as elution of heavy metal compounds or generation of large amounts of smoke or corrosive gases when disposed of by landfilling, incineration, etc. This flame-retardant resin composition contains 50 to 160 parts by mass of a metal hydrate, 2 to 10 parts by mass of a phenolic antioxidant, 10 to 25 parts by mass of a benzimidazole antioxidant, and 0 to 10 parts by mass of a thioether antioxidant per 100 parts by mass of an ethylene-vinyl acetate copolymer or a mixture of an ethylene-vinyl acetate copolymer and a polyolefin, each having a vinyl acetate content of 10% to less than 40% by mass.

[0005] Patent Document 3 describes an insulated wire that has excellent flame retardancy, tensile properties, heat resistance, and electrical properties, and that does not elute heavy metal compounds or emit large amounts of smoke or corrosive gases when disposed of by landfilling, incineration, etc. This insulated wire has a conductor coated with a crosslinked product of a composition that contains 150 to 300 parts by mass of a metal hydrate, 1 to 6 parts by mass of a phenolic antioxidant, and 12 to 30 parts by mass of a thioether antioxidant, relative to 100 parts by mass of a base resin containing an ethylene-vinyl acetate copolymer, and the vinyl acetate content of the base resin is 40% by mass or more.

[0006] Patent Document 4 describes a non-halogen flame-retardant electric wire / cable that has excellent durability against corrosive gases such as NOx and SOx. This non-halogen flame-retardant electric wire / cable is characterized in that the insulator or sheath contains a non-halogen flame retardant, and the insulator or sheath is a composition obtained by mixing 300 parts by weight or less of the non-halogen flame retardant with 100 parts by weight of rubber or plastic, and adding 0.1 to 10 parts by weight each of a hindered phenol-based antioxidant and a thioether-based antioxidant.

[0007] JP 2019-14794 A JP 2009-286903 A JP 2002-42574 A JP 2002-324442 A

[0008] With the recent advances in the development of hybrid vehicles and other vehicles, insulated wires used in automobiles and other vehicles are increasingly required to have superior properties, such as flexibility, hardness, degree of cross-linking, abrasion resistance, flame retardancy, cold resistance, and heat resistance. Regarding heat resistance, wires are required to meet the heat resistance class 150°C specified in the JASO D624 (2015) automotive standard or the heat resistance class D specified in ISO 6722 (2006). Furthermore, from the perspective of terminal sealing properties (preventing water from entering the connection from the outside), it is known that the wire coating is compressively deformed using rubber or other materials to ensure its watertightness. To ensure such watertightness, a high degree of cross-linking (gel fraction) is required. In particular, many resins tend to have a high thermal deformation rate in high-temperature environments. If the insulation coating of an insulated wire is crushed (deformed) under these conditions, it can impair its sealing properties with the connector. Furthermore, in general, when processing wire harnesses and assembling harnesses, harness processing such as processing cable terminals, inserting connectors, and routing cables is often done manually. In particular, when processing harnesses during times when the ambient environment changes significantly, such as summer, the ease of passing wires through wire harness components and electric cables or between electric wires is important from the standpoints of work efficiency, worker load, and assembly accuracy.

[0009] In view of the above circumstances, an object of the present invention is to provide a resin composition that, when used to form an insulating coating (resin coating layer) for an insulated electric wire, can provide an insulated electric wire that has excellent heat resistance, excellent cross-linking properties within the insulating coating, and excellent wire-passability (ease of sliding) between the resulting insulated electric wires in a high-temperature environment. Another object of the present invention is to provide a resin coating material using the resin composition, an insulated electric wire having the resin coating material around a conductor, an automotive wire harness having the insulated electric wire, and a method for producing an insulated electric wire for use in an automotive wire harness.

[0010] As a result of intensive research aimed at solving the above problems, the present inventors have found that by using an ethylene-vinyl acetate copolymer resin as a base resin, blending specific amounts of an imidazole compound, a phenol compound, and a thioether compound, and further blending specific amounts of a bromine compound and an antimony compound, the resulting resin composition can be used to form an insulating coating for an insulated wire, thereby providing an insulated wire that is excellent in heat resistance, high crosslinkability, and ease of wire threading.The present invention was completed through further research based on these findings.

[0011] That is, the above-mentioned problems have been solved by the following means. <1> A resin composition containing an ethylene-vinyl acetate copolymer resin as a resin component, the resin composition containing an imidazole compound, a phenol compound, and a thioether compound as antioxidants, and a bromine compound and an antimony compound as flame retardants, wherein the content of the imidazole compound is 14 to 24 parts by mass, the content of the phenol compound is 1.0 to 2.0 parts by mass, the content of the thioether compound is 0.3 to 0.9 parts by mass, the content of the bromine compound is 15 to 30 parts by mass, and the content of the antimony compound is 5 to 15 parts by mass, relative to 100 parts by mass of the total amount of the resin components in the resin composition. <2> The resin composition according to <1>, wherein the resin composition further contains 0.5 to 6.0 parts by mass of a dispersant, relative to 100 parts by mass of the total amount of the resin components in the resin composition. <3> The resin composition according to <1> or <2>, wherein the resin component contains a maleic acid-modified polyethylene resin and / or a low-density polyethylene resin. <4> The resin composition according to any one of <1> to <3>, wherein the ethylene-vinyl acetate copolymer resin has a vinyl acetate component content of 30% by mass or less. <5> The resin composition according to any one of <1> to <4>, wherein the total content of the antioxidants is 20 to 26 parts by mass per 100 parts by mass of the total content of the resin components in the resin composition. <6> The resin composition according to any one of <1> to <5>, wherein the resin composition contains at least one of a cross-linking aid and a processing aid. <7> The resin composition according to any one of <1> to <6>, which is used for an automotive wire harness. <8> A resin coating material obtained by crosslinking the resin composition according to any one of <1> to <7>. <9> An insulated electric wire, an insulating coating of which comprises the resin coating material according to <8>. <10> An automotive wire harness comprising the insulated electric wire according to <9>. <11> A method for producing an insulated wire used for an automotive wire harness, comprising the steps of extrusion coating a conductor with the resin composition according to any one of <1> to <7> to provide a layer of the resin composition, and irradiating the layer of the resin composition with an electron beam of 80 to 250 kGy.

[0012] In the present invention, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after it as the lower and upper limits.

[0013] By using the resin composition of the present invention to form an insulating coating (resin coating material layer) for an insulated electric wire, an insulated electric wire can be obtained that has excellent heat resistance, excellent cross-linking ability within the insulating coating, and excellent wire-passing ability between the resulting insulated electric wires. By using the resin coating material of the present invention as a constituent material for the insulating coating of an insulated electric wire, an insulated electric wire that exhibits the desired excellent properties described above can be obtained. In the automotive wire harness of the present invention, the insulated electric wire that constitutes the automotive wire harness has the above-mentioned resin coating material in its insulating coating, and has excellent heat resistance, excellent cross-linking ability within the insulating coating, and excellent wire-passing ability even in high-temperature environments. By using the method of the present invention for producing an insulated electric wire for use in an automotive wire harness, an insulated electric wire having the above-mentioned excellent properties can be obtained.

[0014] [Resin Composition] The resin composition of the present invention contains an ethylene-vinyl acetate copolymer resin as a base resin, an imidazole compound, a phenol compound, or a thioether compound as an antioxidant, and a bromine compound or an antimony compound as a flame retardant, each in a specific amount. Each of the above components and the optional components described below may be used alone or in combination of two or more. Each component contained in the resin composition of the present invention will be described below.

[0015] <Ethylene-vinyl acetate copolymer resin> The resin composition of the present invention contains at least an ethylene-vinyl acetate copolymer resin as a resin component constituting the base resin. The polymerization form of the ethylene-vinyl acetate copolymer resin used in the present invention may be any of block, random, and graft polymerization.

[0016] The content of the vinyl acetate component constituting the ethylene-vinyl acetate copolymer is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less, in terms of adhesion between the resin coating material and the conductor, and ease of passing (slipperiness) between the wire harness member and the electric cable or between the electric wires. From the same viewpoints as above, the content of the vinyl acetate component is preferably 7% by mass or more, more preferably 9% by mass or more. Furthermore, by keeping the content of the vinyl acetate component within the above range, the resin coating material produced using the resin composition of the present invention can acquire sufficient mechanical properties such as tensile strength and tensile elongation, and further improve the flame retardancy of the insulated wire. The content of the vinyl acetate component can be determined, for example, from the mass ratio of the raw materials (monomers) used in synthesis.

[0017] The melt flow rate (MFR) of the ethylene-vinyl acetate copolymer resin used in the present invention is preferably 0.1 to 10 g / 10 min (load 2.16 kg, temperature 190°C), more preferably 0.5 to 5 g / 10 min. By setting the melt flow rate of the ethylene-vinyl acetate copolymer resin within the above preferred range, the load on the kneading equipment and extruder can be further reduced during the preparation of the resin composition and the production of the insulated wire or wiring harness, and the dispersibility of each component in the resin composition can also be further improved. The melt flow rate (MFR) can be measured by a method in accordance with JIS K 7210:2014.

[0018] The ethylene-vinyl acetate copolymer resin used in the present invention can be synthesized by a conventional method, or a commercially available product may be used, such as Evaflex V5274 and Evaflex V422 (both trade names) manufactured by DuPont-Mitsui Polychemicals Co., Ltd.

[0019] In terms of improving flame retardancy and crosslinkability, the content of the ethylene-vinyl acetate copolymer resin among the resin components constituting the resin composition of the present invention is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more. Furthermore, all of the resin components contained in the resin composition of the present invention may be ethylene-vinyl acetate copolymer resins.

[0020] <Polyethylene Resin> In addition to the ethylene-vinyl acetate copolymer resin, the resin composition of the present invention may contain a polyethylene resin as a resin component other than the ethylene-vinyl acetate copolymer resin. Examples of such polyethylene resins include maleic acid-modified polyethylene resins and low-density polyethylene resins. Such polyethylene resins may be used alone or in combination of two or more. Among the resin components constituting the resin composition of the present invention, the content of the polyethylene resin is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 12% by mass or less, and may be 1 to 10% by mass, 2 to 8% by mass, or 3 to 5% by mass.

[0021] (Maleic Acid-Modified Polyethylene Resin) When the resin composition of the present invention contains a maleic acid-modified polyethylene resin component as a resin component, the content of the maleic acid-modified polyethylene resin in the resin components constituting the resin composition of the present invention is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 12% by mass or less, and may be 1 to 10% by mass, 2 to 8% by mass, or even 3 to 5% by mass. By setting the content of the maleic acid-modified polyethylene resin within the above-mentioned preferred range, sufficient flexibility can be imparted to an insulated wire having a resin coating material produced using the resin composition of the present invention. Furthermore, since the resin composition is less likely to adhere to a processing machine (excellent processing adhesion), the amount of composition remaining in the processing machine can be reduced. Furthermore, the compatibility between the resin component and fillers in the composition can be improved, thereby further improving the abrasion resistance of the resulting insulated wire.

[0022] (Low-density polyethylene resin) In the present invention, the term "low-density polyethylene resin" refers to a polyethylene having a density of 0.929 g / cm ３ The term "low-density polyethylene resin" as used herein refers to the following polyethylene resin. Therefore, the term "low-density polyethylene resin" in the present invention includes not only "low-density polyethylene (LDPE)" but also "very low-density polyethylene (VLDPE)". The low-density polyethylene resin used in the present invention preferably has a density range of 0.870 to 0.929 g / cm. ３ and more preferably in the density range of 0.910 to 0.929 cm ３ The density of the polyethylene resin can be determined in accordance with JIS K 7112:1999. The low-density polyethylene resin may be, for example, a high-pressure radical method (high-pressure method) low-density polyethylene resin or a metallocene-catalyzed linear low-density polyethylene resin. For details of such polyethylene resins, see, for example, the description of Japanese Patent Application No. 2016-072380.

[0023] When the resin composition of the present invention contains a low-density polyethylene resin as a resin component, the content of the low-density polyethylene resin in the resin components constituting the resin composition of the present invention is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 12% by mass or less, and can be 1 to 10% by mass, 2 to 8% by mass, or 3 to 5% by mass.

[0024] The polyethylene resins such as maleic acid-modified polyethylene resins and low-density polyethylene resins that can be used in the present invention can be synthesized by conventional methods, or commercially available products can be used. Specific examples of commercially available products include Petrothene 180R, Petrothene 170R, and Petrothene 173R manufactured by Tosoh Corporation, Sumikathene F218-0, Sumikathene F200, and Sumikathene G401 manufactured by Sumitomo Chemical Co., Ltd., Novatec UE320, Novatec LF443, Novatec LF280H, Novatec LF448K1, and Adtex L6100M manufactured by Japan Polyethylene Co., Ltd., NUC-9060 and ENGAGE-8100 manufactured by NUC Corporation, and NUCG-5130 manufactured by Dow Estramers (all trade names).

[0025] The total content of the resin components contained in the resin composition of the present invention is usually 30 to 80% by mass, but can also be 40 to 75% by mass, or can also be 50 to 75% by mass.

[0026] <Antioxidant> The resin composition of the present invention contains specific amounts of an imidazole compound (imidazole antioxidant), a phenolic compound (phenolic antioxidant), and a thioether compound (thioether antioxidant) as antioxidants (antiaging agents). By incorporating specific amounts of each of these antioxidants, the heat resistance, crosslinkability, and slip properties of the resulting resin coating material can be further improved while suppressing the occurrence of bleeding. Each of the above antioxidants is described below.

[0027] (Imidazole Compound) Examples of imidazole compounds (compounds having a benzimidazole skeleton) 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. Commercially available imidazole compounds may also be used in the present invention. An example of a commercially available product is Nocrac MBZ (trade name, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.). The content of the imidazole compound is 14 to 24 parts by mass per 100 parts by mass of the total content of the resin components constituting the resin composition of the present invention. From the viewpoint of further improving heat resistance and crosslinkability, and from the viewpoint of dispersibility in the resin and suppressing the occurrence of bleeding, the content is preferably 16 to 24 parts by mass, and more preferably 16 to 20 parts by mass.

[0028] (Phenol Compound) Examples of the phenol compound (a compound having a phenol skeleton) 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), pentaerythrityl-tetrakis(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate), octadecyl methyl ester, ... Examples include 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, 1,3,5-tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanuric acid, and isooctyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, and one or more of these can be used. 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 1,3,5-tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanuric acid and pentaerythrityl-tetrakis(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate) are particularly preferred. Note that, even among compounds having a phenol skeleton (phenolic antioxidants), those that fall under the category of triazole compounds, N,N'-diacylhydrazine compounds, or dihydrazide compounds and are used as copper inhibitors, as described below, are treated as copper inhibitors in the present invention, rather than as phenol compounds. Commercially available phenolic compounds may be used in the present invention. Commercially available products include, for example, Irganox 1010 (trade name, manufactured by BASF) and Adekastab AO-20 (trade name, manufactured by ADEKA Corporation). The content of the phenol compound is 1.0 to 2.0 parts by mass relative to 100 parts by mass of the total content of the resin components constituting the resin composition of the present invention. From the viewpoint of further improving heat resistance and crosslinkability, and from the viewpoint of suppressing the occurrence of bleeding, the content is preferably 1.5 to 2.0 parts by mass.

[0029] (Thioether Compound) Examples of the thioether compound (compound having a thioether bond) used in the resin composition of the present invention include thioether compounds used as antioxidants for wire coating materials. Examples 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-dodecylthiopropionate] (also known as 2,2-bis[[3-(dodecylthio)-1-oxopropyloxy]methyl]-1,3-propanediyl bis[3-(dodecylthio)propionic acid]), and the like. One or more of these may be used. Among these, 2,2-bis{[3-(dodecylthio)-1-oxopropoxy]methyl}propane-1,3-diyl bis[3-dodecylthiopropionate] is preferred from the viewpoint of long-term thermal stability. Commercially available thioether compounds may also be used in the resin composition of the present invention. Examples of commercially available thioether compounds include Adeka Stab AO-412S (trade name, manufactured by ADEKA Corporation).

[0030] The content of the thioether compound is 0.3 to 0.9 parts by mass per 100 parts by mass of the total content of the resin components constituting the resin composition of the present invention. Insulated wires containing a resin composition containing a high content of a thioether compound tend to bleed the thioether compound onto the surface of the insulating coating. When such an insulated wire is stored at high temperatures, the slipperiness is significantly impaired (the dynamic friction coefficient increases significantly), hindering the assembly of the wire. Therefore, by setting the content of the thioether compound within the above range, a resin composition with excellent heat resistance and slipperiness can be obtained. Furthermore, from the viewpoints of improving heat resistance, improving slipperiness, and suppressing crosslinking inhibition, the content is preferably 0.3 to 0.6 parts by mass.

[0031] (Other Antioxidants) In addition to the imidazole compound, phenol compound, and thioether compound, the resin composition of the present invention may contain other antioxidants. Examples of such antioxidants include copper inhibitors and zinc compounds, and one or more of these can be used. Specific examples of zinc compounds include zinc sulfide and zinc oxide.

[0032] (Copper Inhibitor) Examples of copper inhibitors that can be used in the resin composition of the present invention include triazole compounds, N,N'-diacylhydrazine compounds, dihydrazide compounds, etc. Commercially available products include the heavy metal deactivators Adekastab CDA series (CDA-1, CDA-6, CDA-10 (all trade names)) manufactured by ADEKA Corporation and Irganox MD1024 (trade name) manufactured by BASF. When the resin composition of the present invention contains a copper inhibitor, the content of the copper inhibitor is preferably 0.5 to 2.0 parts by mass per 100 parts by mass of the total content of the resin components, from the viewpoint of preventing a decrease in heat resistance due to contact with metal ions such as copper.

[0033] (Zinc Compound) Examples of zinc compounds that can be used in the resin composition of the present invention include zinc sulfide and zinc oxide. Of these, the resin composition of the present invention preferably contains zinc sulfide and / or zinc oxide. Commercially available zinc sulfide and zinc oxide include, for example, Sachtolith HD-S (trade name) manufactured by Sachtleben Chemie GmbH and Zinc sulfide manufactured by Taizhou ATS Optical Material Co., Ltd. Note that, in the present invention and this specification, the term "zinc compound" does not include zinc salts of imidazole compounds used as imidazole compounds or zinc stearate used as a processing aid (lubricant). When the resin composition of the present invention contains a zinc compound, the content of the zinc compound is preferably 1.0 to 10 parts by mass, and more preferably 3.0 to 5.0 parts by mass, per 100 parts by mass of the total content of the resin components, from the viewpoint of heat resistance.

[0034] The total content of the antioxidants is preferably 10 to 35 parts by mass, more preferably 15 to 30 parts by mass, and even more preferably 20 to 26 parts by mass, relative to 100 parts by mass of the total content of the resin components constituting the resin composition of the present invention.

[0035] <Flame Retardant> The resin composition of the present invention contains a bromine compound (bromine-based flame retardant) and an antimony compound (antimony-based flame retardant) as flame retardants. The ratio of the bromine compound to the antimony compound in the resin composition is preferably such that the amount of bromine element is 2 to 5 times by mole per mole of antimony element. The total content of the flame retardants in the resin composition of the present invention is preferably 20 to 45 parts by mass, more preferably 30 to 45 parts by mass, and even more preferably 31 to 42 parts by mass, per 100 parts by mass of the total resin content.

[0036] (Bromine Compound) Examples of the bromine compound used as a flame retardant in the present invention include organic bromine-containing flame retardants such as 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)alkane. Among these, it is preferable to use brominated N,N'-ethylenebisphthalimide and / or 1,2-bis(bromophenyl)ethane. Commercially available bromine compounds may be used as the bromine compound in the resin composition of the present invention. An example of a commercially available product is Cytex 8010 (trade name, manufactured by Albemarle).

[0037] The content of the bromine compound in the resin composition of the present invention is 15 to 30 parts by mass per 100 parts by mass of the total content of the resin components. From the viewpoint of flame retardancy, the content is preferably 20 to 30 parts by mass, and more preferably 24 to 30 parts by mass.

[0038] (Antimony Compound) Examples of antimony compounds include antimony trioxide, antimony tetroxide, antimony pentoxide, and sodium antimonate. Antimony reacts with chlorine (halogen), and the generated gas is thought to block oxygen, thereby promoting the formation of a carbonized layer and trapping free radicals (stopping the pyrolysis chain reaction). Of these, in the present invention, it is preferable to contain antimony trioxide from the viewpoint of forming a more stable carbonized layer. Commercially available antimony trioxide may be used in the present invention. An example of a commercially available product is PATOX-C (trade name, manufactured by Nippon Seiko Co., Ltd.).

[0039] When the resin composition of the present invention contains an antimony compound, the content is 5 to 15 parts by mass relative to 100 parts by mass of the total content of the resin components. From the viewpoint of flame retardancy, the content is preferably 8 to 13 parts by mass, more preferably 9 to 12 parts by mass, and even more preferably 10 to 12 parts by mass.

[0040] (Other Flame Retardants) In addition to the bromine compound and antimony compound, the resin composition of the present invention may contain a flame retardant that can be commonly used in insulating coatings for insulated electric wires. 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 amount is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, per 100 parts by mass of the total content of the resin components.

[0041] <Other Components> In addition to the above components, the resin composition of the present invention may contain other components such as the following crosslinking aids and processing aids, as long as the effects of the present invention are not impaired. Furthermore, the resin composition may contain components such as plasticizers, fillers, and pigments, as necessary.

[0042] <Crosslinking Auxiliary Agent> The resin composition of the present invention preferably contains a crosslinking auxiliary. Examples of crosslinking auxiliary agents include polyfunctional compounds, and compounds having two or more (preferably three or more, more preferably three to six) ethylenically unsaturated bonds (carbon-carbon double bonds) in the molecule are preferred. Specific examples of crosslinking auxiliary agents include (meth)acrylate compounds such as polypropylene glycol di(meth)acrylate and trimethylolpropane tri(meth)acrylate, allyl compounds such as triallyl cyanurate, maleimide compounds, and divinyl compounds. Commercially available crosslinking auxiliary agents may also be used in the present invention. An example of a commercially available product is Ogmont T200 (trade name, manufactured by Shin-Nakamura Chemical Co., Ltd.). The resin composition of the present invention preferably contains 2 to 6 parts by mass, and more preferably 3 to 5 parts by mass, of the crosslinking auxiliary per 100 parts by mass of the total content of the resin components.

[0043] <Processing Aid> The resin composition of the present invention preferably contains a processing aid. A preferred example of the processing aid is a metal soap (lubricant). 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. Commercially available metal soaps may also be used in the present invention. An example of a commercially available product is Sinaka Red ZS-101 (trade name, manufactured by Shinagawa Chemical Industry Co., Ltd.).

[0044] When the resin composition of the present invention contains a lubricant, it is preferable that the lubricant content be 0.5 to 2 parts by mass per 100 parts by mass of the total content of the resin components.

[0045] <Dispersant> The resin composition of the present invention preferably contains a dispersant. By incorporating a dispersant into the resin composition of the present invention, it is possible to prevent re-agglomeration of additives such as flame retardants and antioxidants, improve the dispersibility of each component in the polymer, and thereby achieve excellent processability in compound production using a feeder rudder or twin-screw extruder, as well as further enhance heat resistance. The dispersant that can be used in the present invention is not particularly limited, and dispersants that are typically incorporated into resin compositions can be used. From the perspective of further suppressing re-agglomeration of additives, the dispersant is preferably a wetting dispersant. A wetting dispersant is an additive that combines the functions of a wetting agent that acts as a surfactant to increase the wettability of dispersoids to the resin component and the functions of preventing dispersoid aggregation through actions such as electrical repulsion and steric hindrance. The function of wetting agent is typically performed by chains compatible with the resin component, while the function of preventing dispersoid aggregation is typically performed by groups that are adsorptive to the dispersoid. Commercially available wetting and dispersing agents include, for example, BYK-MAX D4221 and BYK-MAX P4102 (both trade names, manufactured by BYK Japan KK).

[0046] When the resin composition of the present invention contains a dispersant, from the viewpoint of further improving heat resistance and suppressing the occurrence of bloom and crosslinking inhibition, the dispersant is preferably contained in an amount of 0.5 to 6.0 parts by mass, and more preferably 1.0 to 6.0 parts by mass, per 100 parts by mass of the total content of the resin components.

[0047] <Additives> Various additives, such as ultraviolet absorbers, plasticizers, fillers, and pigments, may be appropriately blended into the resin composition of the present invention as needed, within the range that does not impair the effects of the present invention.

[0048] [Method of producing resin composition] The resin composition of the present invention can be obtained by blending each component such as a resin, an antioxidant, a flame retardant, and the like, and further, 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.

[0049] [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 of the present invention may have an intermediate layer or a shielding layer between the conductor and the layer made of the resin coating material.

[0050] The shape and material of the conductor may be any conductor as long as they are of the shape and material commonly used in insulated wires for automotive wiring harnesses. The conductor may be a solid wire or a stranded 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 layer of resin coating material formed around the conductor is not particularly limited, but is typically about 0.15 to 5 mm. The use of the resin composition of the present invention has the advantage that an insulated wire having excellent flexibility, hardness, degree of cross-linking, flame retardancy, cold resistance, and heat resistance can be obtained even if the thickness of the resin coating layer is thin.

[0051] [Automotive Wire Harness] In the present invention and this specification, an automotive wire harness is a general term for a bundle of electric wires arranged in various locations of a vehicle, such as the engine compartment, the instrument panel, and inside the doors, in accordance with environmental performance. The automotive wire harness of the present invention includes the insulated electric wire of the present invention. The resin composition of the present invention has excellent appearance and also has excellent flame retardancy and mechanical properties. Therefore, a wire harness incorporating an insulated electric wire having a layer made of a resin coating material crosslinked with the resin composition of the present invention can be suitably used for automotive applications. Hereinafter, the automotive wire harness may also be simply referred to as a "wire harness."

[0052] [Method for Manufacturing Insulated Wire for Automotive Wiring Harness] The insulated wire for use in the automotive wiring harness of the present invention can be obtained by extrusion coating the resin composition of the present invention onto a conductor to form a resin composition layer, and then irradiating the resin composition layer with 80 to 250 kGy of electron beams. This electron beam irradiation causes a crosslinking reaction in the resin composition layer, forming a resin coating material layer. The crosslinking reaction by electron beam irradiation can be carried out using conventional methods and conditions. The electron beam irradiation conditions are preferably a dose of 80 to 200 kGy, more preferably 80 to 160 kGy. The acceleration voltage is preferably 300 to 3000 keV, more preferably 500 to 2500 keV. Furthermore, a multilayer structure may be employed, such as providing an intermediate layer or a shielding layer between the conductor and the coating layer, or between the coating layers.

[0053] 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, in order to reduce the load on the extruder (extrusion molding machine) and ensure shape retention. Other conditions for extrusion molding can be set appropriately 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.

[0054] 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.

[0055] [Examples 1 to 13 and Comparative Examples 1 to 12] The materials used to prepare the resin compositions of Examples 1 to 13 and Comparative Examples 1 to 12 are shown in Tables 1 and 2 below. Details of the materials used are as follows. Note that (1) to (14) below correspond to (1) to (14) in Tables 1 and 2 below.

[0056] <Materials Used> (Resins) (1): Ethylene-vinyl acetate copolymer 1, Evaflex V5274 (trade name), vinyl acetate content: 17% by mass, manufactured by DuPont-Mitsui Polychemicals (2): Ethylene-vinyl acetate copolymer 2, Evaflex V422 (trade name), vinyl acetate content: 20% by mass, manufactured by DuPont-Mitsui Polychemicals (3): Maleic acid-modified polyethylene, Adtex L6100M (trade name), manufactured by Japan Polyolefins (4): Linear low-density polyethylene (LLDPE), Novatec UE320 (trade name), density 0.922 g / cm ３ , manufactured by Japan Polyethylene Corporation

[0057] (Flame retardant) (5): 1,2-bis(pentabromophenyl)ethane, Cytex 8010 (trade name), manufactured by Albemarle Corporation (6): Antimony trioxide, PATOX-C (trade name), manufactured by Nippon Seiko Co., Ltd.

[0058] (Antioxidants) (7): Zinc salt of 2-mercaptobenzimidazole, Nocrac MBZ (trade name), manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (8): Pentaerythrityl-tetrakis(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate), Irganox 1010 (trade name), manufactured by BASF Corporation (9): 2,2-bis{[3-(dodecylthio)-1-oxopropoxy]methyl}propane-1,3-diyl bis[3-(dodecylthio)propionate], Adekastab AO-412S (trade name), manufactured by ADEKA Corporation (10): 2',3-bis{3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyl}propionohydrazide, Irganox MD1024 (trade name), manufactured by BASF Corporation (11): Zinc sulfide, Sachtolith HD-S (trade name), manufactured by Sachtleben Chemie GmbH (12): Zinc oxide, zinc oxide type 2, manufactured by Mitsui Mining & Smelting Co., Ltd.

[0059] (Crosslinking aid) (13): Trimethylolpropane trimethacrylate, Ogmont T200 (trade name), manufactured by Shin-Nakamura Chemical Co., Ltd.

[0060] (Lubricant) (14): Zinc stearate, Sinaka Red ZS-101 (trade name), manufactured by Shinagawa Chemical Industry Co., Ltd.

[0061] (Dispersant) (15): BYK-MAX D4221 (trade name), manufactured by BYK Japan

[0062] <Production of Resin Composition Sheets> According to the compositions shown in Tables 1 and 2 below, the resin compositions were melt-kneaded at 160°C using a 1.7-liter Banbury mixer, and the resulting mixture was molded into a sheet using a 6-inch roller. Each of the resulting resin composition sheets was pressed to a thickness of 1 mm using a pressure press set at 160°C, and the pressed molded sheet was crosslinked with an electron beam to obtain test samples (Examples 1 to 13, Comparative Examples 1 to 12). Crosslinking with an electron beam was performed at an acceleration voltage of 750 keV and a dose of 80 kGy or 120 kGy.

[0063] [Performance Evaluation] The test samples produced as described above were subjected to the following performance evaluations.

[0064] <Slipperiness Evaluation> Using each test sample (Examples 1 to 13, Comparative Examples 1 to 12), the dynamic friction coefficient was measured under the following conditions in accordance with the method of JIS K 7125:1999. Each test sample was cut to a size of 320 mm length x 200 mm width x 1 mm thickness, and a 100 mm square low-density polyethylene sheet (model number: UBEC130, manufactured by Ube Maruzen Polyethylene Co., Ltd.) was placed on top of the test sample. A 100 mm square acrylic plate was then placed on top of the low-density polyethylene sheet. A test load (30 N) was placed on the acrylic plate, and the low-density polyethylene sheet was pulled at a tensile speed of 100 mm / min. The friction force generated between each test sample and the low-density polyethylene sheet during a measurement distance of 80 mm was measured, and the dynamic friction coefficient (before heating) was determined. Furthermore, each test sample used for the measurement was heated at 50°C for 2 hours, then allowed to stand until the temperature of each test sample returned to room temperature, and the dynamic friction coefficient (after heating) was measured again under the same conditions. From the obtained dynamic friction coefficients (before heating and after heating), the ratio of the dynamic friction coefficient after heating to the dynamic friction coefficient before heating (dynamic friction coefficient after heating / dynamic friction coefficient before heating) was calculated, and the obtained value was applied to the following evaluation criteria to evaluate the slipperiness. A large value indicates that the slipperiness was reduced by heating. -Evaluation criteria- A: Less than 1.2 B: 1.2 or more but less than 1.5 C: 1.5 or more

[0065] <Evaluation of Crosslinkability> 0.1 g of each test sample (Examples 1 to 13, Comparative Examples 1 to 12) was taken and used as a test sample. Tests were conducted based on the method specified in Japan Automotive Engineering Society Standard (JASO) D618 6.14.2. Specifically, the sample was placed in a test tube, 20 ml of xylene was added, and the sample was heated at 120°C for 24 hours. The sample was then removed and dried in a 100°C dryer for 6 hours, allowed to cool to room temperature (23°C), and then precisely weighed. The gel fraction was calculated as the percentage of the mass of the sample after xylene immersion and drying relative to the mass of the sample before xylene immersion ([mass of sample after xylene immersion and drying / mass of sample before xylene immersion] x 100), and the crosslinkability was evaluated according to the following criteria. -Evaluation Criteria- A: Gel fraction 70% or more B: Gel fraction 50% or more, but less than 70% C: Gel fraction less than 50%

[0066] <Heat Resistance Evaluation> Heat resistance was evaluated based on the continuous heat resistance temperature according to the method specified in Japan Automotive Engineering Society Standard (JASO) D618. Specifically, each test sample (Examples 1 to 13, Comparative Examples 1 to 12) was punched into a dumbbell-shaped No. 3 specimen as described in JIS K6251:2017, and an aging test was performed at temperatures of 170°C, 180°C, 190°C, and 200°C. The time until the specimen broke when the tensile elongation was 100% (100% is when the specimen was elongated twice) was determined, and the temperature at which the specimen broke when the tensile elongation was 100% after 10,000 hours was determined by Arrhenius plotting, and this temperature was taken as the heat resistance life temperature. The heat resistance life temperature was evaluated according to the following criteria. -Evaluation Criteria- A: 151°C or higher B: 150°C or higher but less than 151°C C: Less than 150°C

[0067] The results obtained are summarized in Tables 1 and 2 below.

[0068]

[0069]

[0070] The content of each component in the table is in parts by mass. "-" means that the corresponding component is not included.

[0071] As can be seen from Table 2, resin composition sheets using resin compositions that do not satisfy the requirements of the present invention were inferior in at least one of the evaluation items of slipperiness, crosslinkability, and heat resistance. In contrast, as can be seen from Table 1, resin composition sheets prepared using the resin compositions of the present invention were excellent in all evaluation items. This demonstrates that the resin composition of the present invention can achieve excellent properties as a resin coating material layer for automotive wire harnesses.

[0072] While the present invention has been described in connection with embodiments thereof, we do not intend to limit our invention to any of the details of the description unless otherwise specified, and believe that the claims should be construed broadly without departing from the spirit and scope of the invention as set forth in the appended claims.

[0073] This application claims priority based on Japanese Patent Application No. 2021-194495, filed in Japan on November 30, 2021, the contents of which are incorporated herein by reference as part of the present specification.

Claims

1. A resin composition containing an ethylene-vinyl acetate copolymer resin as a resin component, the resin composition contains an imidazole compound, a phenol compound, and a thioether compound as antioxidants, and a bromine compound and an antimony compound as flame retardants; a resin composition in which, relative to 100 parts by mass of the total amount of the resin components in the resin composition, the content of the imidazole compound is 14 to 24 parts by mass, the content of the phenol compound is 1.0 to 2.0 parts by mass, the content of the thioether compound is 0.3 to 0.9 parts by mass, the content of the bromine compound is 15 to 30 parts by mass, and the content of the antimony compound is 5 to 15 parts by mass.

2. The resin composition according to claim 1, wherein the resin composition contains 0.5 to 6.0 parts by mass of a dispersant relative to 100 parts by mass of the total content of the resin components in the resin composition.

3. The resin composition according to claim 1, comprising a maleic acid-modified polyethylene resin and / or a low-density polyethylene resin as the resin component.

4. 2. The resin composition according to claim 1, wherein the proportion of vinyl acetate components in the ethylene-vinyl acetate copolymer resin is 30% by mass or less.

5. 2. The resin composition according to claim 1, wherein a total content of the antioxidants in the resin composition is 20 to 26 parts by mass relative to 100 parts by mass of a total content of the resin components.

6. The resin composition according to claim 4, further comprising at least one of a crosslinking aid and a processing aid.

7. The resin composition according to any one of claims 1 to 6, which is used for an automobile wire harness.

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

9. An insulated wire, the insulating coating of which comprises the resin coating material according to claim 8.

10. A wiring harness for an automobile, comprising the insulated wire according to claim 9.

11. A method for producing an insulated wire used for an automotive wire harness, comprising the steps of extrusion coating the resin composition according to any one of claims 1 to 6 onto a conductor to provide a layer of the resin composition, and irradiating the layer of the resin composition with an electron beam of 80 to 250 kGy.