Composition for wire coating material, insulated wire and cable harness

Abstract

Composition for a wire coating material, comprising: (A) a silane-grafted polyolefin, which is a polyolefin grafted with a silane adhesion promoter; (B) an unmodified polyolefin; (C) a modified polyolefin with one or more functional groups selected from the group consisting of a carboxyl group, an ester group, an acid anhydride group, an amino group and an epoxy group; (D) a flame retardant; and (E) a crosslinking catalyst, wherein the polyolefin of (A), the silange-grafted polyolefin, has a density of 0.855 to 0.890 g / cm³ 3 in an ungrafted state and has a melting point of 80°C or higher, and where (B), the unmodified polyolefin, has a density of 0.855 to 0.950 g / cm³ 3exhibits a flexural modulus of 3 to 200 MPa and is one or more selected from the group consisting of a very low density polyethylene, a linear low density polyethylene and a low density polyethylene.

Description

Technical field

[0001] The present invention relates to a composition for a wire coating material, an insulated wire and a cable harness. Technical background

[0002] Insulated wires used in motor vehicles are sometimes located in areas exposed to high temperatures, such as near an engine, requiring high heat resistance. Crosslinked polyvinyl chloride resin and crosslinked polyolefin resin have traditionally been used as coating materials for these insulated wires. Known methods for crosslinking these resins include electron beam irradiation (see patent reference 1) and silane crosslinking (see patent reference 2).Furthermore, a flame-retardant composition and an insulated wire using the same are known in the prior art, wherein the flame-retardant composition comprises a polymer component containing a silane-modified ethylene polymer, a non-silane-modified ethylene polymer and a polypropylene polymer, a metal hydroxide, a phenolic antioxidant, a metal deactivator and a silane crosslinking catalyst, and the silane-modified ethylene polymer has a density of 0.875 g / cm³. 3 or less (see patent literature 3). Citation list for patent literature Patent literature 1: JP 2000 - 294 039 A Patent literature 2: JP 2000 - 212 291 A Patent literature 3: JP 2015 - 193 689 A Summary of the invention Problems to be solved by the invention

[0003] Silane crosslinking, also known as water crosslinking, is promoted by atmospheric moisture. Therefore, a method for metering and mixing a silane-modified resin, a crosslinking catalyst, and other components was employed to prevent the progression of unintended crosslinking reactions and the production of partially cured products. Since the crosslinking catalyst and other components are added to an uncrosslinked resin, concerns arose regarding the potential reduction in the overall resin's degree of crosslinking, heat resistance, and mechanical properties.

[0004] In recent years, the proliferation of hybrid vehicles has necessitated the use of electrical wires capable of handling high voltage and current, leading to the widespread adoption of large-diameter wires. Large-diameter insulated electrical wires require flexible coating materials to ensure workability during assembly. However, if these coating materials are made flexible, raw material beads and uncrosslinked insulated wires can fuse together, and the coating material of the electrical wire can deform upon heating.

[0005] An object of the present invention is to provide a composition for a wire coating material comprising a silane-crosslinked polyolefin, with excellent flame retardancy, melting resistance and heat resistance, as well as an insulated wire and a cable harness comprising the composition. Solution to the problem

[0006] The composition for a wire coating material according to the present invention comprises (A) a silange-grafted polyolefin, which is a polyolefin grafted with a silane adhesion promoter, (B) an unmodified polyolefin, (C) a modified polyolefin with one or more functional groups selected from the group consisting of a carboxyl group, an ester group, an acid anhydride group, an amino group, and an epoxy group, (D) a flame retardant, and (E) a crosslinking catalyst. The polyolefin of the silange-grafted polyolefin (A) in an ungrafted state has a density of 0.855 to 0.890 g / cm³. 3 and a melting point of 80°C or higher. The unmodified polyolefin (B) has a density of 0.855 to 0.950 g / cm³. 3and a flexural modulus of 3 to 200 MPa and is one or more selected from the group consisting of a very low density polyethylene, a linear low density polyethylene and a low density polyethylene.

[0007] It is preferred that the polyolefin of the silange-grafted polyolefin (A) has a density of 0.865 to 0.880 g / cm³ in the ungrafted state. 3 , has a melt flow rate of 0.5 to 5 g / 10 min at 190°C under a load of 2.16 kg, a Shore A hardness of 55 to 70, a flexural modulus of 3 to 50 MPa, and a melting point of 100°C or higher. Furthermore, it is preferred that the unmodified polyolefin (B) has a melt flow rate of 0.5 to 5 g / 10 min at 190°C under a load of 2.16 kg and a melting point of 65°C or higher.

[0008] It is preferred that the amount of the silange-grafted polyolefin (A) is 30 to 90 parts by mass, the total amount of the unmodified polyolefin (B) and the modified polyolefin (C) is 10 to 70 parts by mass, the flame retardant (D) contains, in relation to 100 parts by mass of the total amount of components (A), (B) and (C), at least one of (D-1) 10 to 100 parts by mass of a metal hydroxide and (D-2) 10 to 40 parts by mass of a bromine-containing flame retardant and 5 to 20 parts by mass of antimony trioxide, and the amount of the crosslinking catalyst (E) is 0.01 to 1 part by mass in relation to 100 parts by mass of the total amount of components (A), (B) and (C).

[0009] Furthermore, it is preferred that the composition contains, in relation to 100 parts by mass of the total amount of components (A), (B) and (C), 1 to 10 parts by mass of an antioxidant (F), 1 to 10 parts by mass of a metal deactivator (G) and 1 to 10 parts by mass of a lubricant (H).

[0010] It is also preferred that the composition further contains, in relation to 100 parts by mass of the total amount of components (A), (B) and (C), either (I-1) 1 to 15 parts by mass of zinc oxide and 1 to 15 parts by mass of an imidazole compound or (I-2) 1 to 15 parts by mass of zinc sulfide.

[0011] It is preferred that the polyolefin forming the silange-grafted polyolefin (A) is one or more from the group consisting of a very low density polyethylene, a linear low density polyethylene and a low density polyethylene.

[0012] An insulated wire according to the present invention contains a cross-linked product of the above composition for a wire coating material.

[0013] A cable harness according to the present invention includes the aforementioned insulated wire. Advantageous effects of the invention

[0014] The composition for a wire coating material according to the present invention is a composition containing a silange-grafted polyolefin which has excellent flexibility, melt resistance and heat resistance as well as excellent flame retardancy.

[0015] In general, a polyolefin with a lower density exhibits higher flexibility but tends to have a lower melting point. Therefore, it is difficult to achieve both melt resistance and heat resistance while maintaining flexibility. The insulated wire according to the present invention exhibits excellent flexibility, melt resistance, and heat resistance by incorporating components whose densities and melting points are set within suitable ranges. Description of embodiments

[0016] Next, the present invention will be described in more detail with reference to embodiments.

[0017] The composition for a wire coating material (hereinafter sometimes referred to as the present protective composition) comprises (A) a silange-grafted polyolefin, (B) an unmodified polyolefin, (C) a modified polyolefin, (D) a flame retardant, and (E) a crosslinking catalyst. Furthermore, the present composition preferably comprises (F) an antioxidant, (G) a metal deactivator, (H) a lubricant, and (I) a zinc-based stabilizer. Each component is to be described in detail as below.

[0018] A silange-grafted polyolefin (A) is obtained by introducing a silange-grafted chain into a polyolefin serving as the main chain by grafting modification with a silane adhesion promoter.

[0019] The polyolefin of the silange-grafted polyolefin (A) has a density of 0.855 to 0.890 g / cm³. 3 , preferably a density of 0.860 to 0.885 g / cm³ 3and preferably a density of 0.865 to 0.880 g / cm³ 3 The polyolefin, which has a lower density, can be more easily grafted with a silane adhesion promoter and exhibits greater flexibility. However, if the density of the polyolefin is lower than 0.855 g / cm³ 3 The melting point could be too low, causing material granules and a shaped product to fuse before crosslinking and deform upon heating. Furthermore, the wire's heat resistance and wear resistance could be low, and the resin could be too soft, reducing its malleability. On the other hand, if the polyolefin's density is higher than 0.890 g / cm³ 3 If this is the case, the grafting rate, crosslinking density, and flexibility could be low. The density of the polyolefin can be measured according to ASTM D790.

[0020] The present composition can be crosslinked by steam exposure. To prevent fusing between formed products, the melting point of the polyolefin comprising the silange-grafted polyolefin is 80°C or higher, preferably 100°C or higher, and more preferably 120°C or higher. If the melting point of the polyolefin is below 80°C, material granules and a formed product could fuse prior to crosslinking and be deformed by heating. An upper limit for the melting point is not specifically defined. If a polyolefin exhibits excellent properties such as flexibility, its melting point is often 135°C or lower. The melting point of a polyolefin can be measured according to JIS K7121.

[0021] In general, a polyolefin with more and longer branched chains in the polymer chain has a lower density and higher flexibility. On the other hand, such a polyolefin has a lower melting point. A polyolefin containing both more and less crystalline parts serves as a polyolefin with a suitable density and melting point. The more crystalline parts contain fewer branched chains and have a very dense structure, while the less crystalline parts contain more long branched chains and have a lower density structure. Such a polyolefin can therefore exhibit satisfactory melting and heat resistance while maintaining flexibility.

[0022] The polyolefin from which the silange-grafted polyolefin (A) is composed preferably has a melt flow rate (hereinafter sometimes referred to as "MFR") of 0.5 to 5 g / 10 min and more preferably of 1.0 to 3.0 g / 10 min at 190°C under a load of 2.16 kg. If the polyolefin has an MFR of 0.5 g / 10 min or higher, it exhibits excellent extrusion forming properties and thus offers excellent productivity. Conversely, if the polyolefin has an MFR of 5 g / 10 min or lower, it effectively retains a specific shape during forming and thus offers excellent productivity. The MFR of a polyolefin can be measured according to ASTM D1238.

[0023] The polyolefin of which the silange-grafted polyolefin (A) is composed preferably has a Shore A hardness of 55 to 70. Furthermore, the polyolefin of which the silange-grafted polyolefin (A) is composed preferably has a flexural modulus of 3 to 50 MPa. If both the Shore A hardness and the flexural modulus are within the aforementioned ranges, the polyolefin exhibits excellent flexibility and mechanical properties such as wear resistance. Shore A hardness can be measured according to ASTM D2240 and flexural modulus can be measured according to ASTM D790.

[0024] Examples of the polyolefin used to produce the silange-grafted polyolefin (A) are homopolymers of ethylene and propylene and a copolymer of ethylene or propylene and an α-olefin. These can be used individually or in combination. It is preferred to use at least one selected from polyethylene, polypropylene, ethylene-butene copolymer, and ethylene-octene copolymer.

[0025] Preferably, the polyethylene described above consists of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), very low-density polyethylene (VLDPE), and metallocene low-density polyethylene. These can be used individually or in combination. When using this type of low-density polyethylene, the flexibility of the electrical wire is particularly excellent, and extrusion productivity is improved.

[0026] Furthermore, a polyolefin-based elastomer can be used instead of the polyolefin described above. Using a polyolefin elastomer can impart flexibility to the coating material. Examples of polyolefin elastomers include thermoplastic polyolefin-based elastomers (TPO), such as polyethylene-based elastomers (PE elastomers) and polypropylene-based elastomers (PP elastomers), ethylene propylene rubber (EPM or EPR), and ethylene propylene diene copolymer (EPDM or EPT).

[0027] A silane adhesion promoter used in the manufacture of the silange-grafted polyolefin (A) is not particularly limited. Examples of such a promoter include vinyl alkoxysilanes such as vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltributoxysilane, vinyltriacetoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacryloxypropylmethyldimethoxysilane. These can be used individually, or any two of them can be used in combination.

[0028] To avoid excessive crosslinking, the graft quantity of the silane adhesion promoter is preferably 15 wt% or less, more preferably 10 wt% or less, and even more preferably 5 wt% or less. In contrast, the graft quantity of the silane adhesion promoter is preferably 0.1 wt% or more, more preferably 1.0 wt% or more, and even more preferably 1.5 wt% or more. When the graft quantity of the silane adhesion promoter is 0.1 wt% or more, the present composition is sufficiently crosslinked and provides a wire coating material with excellent heat resistance and mechanical strength through crosslinking. Here, the graft quantity represents a percentage of the mass of the grafted silane adhesion promoter relative to the mass of the polyolefin before silane grafting.

[0029] When the silange-grafted polyolefin (A) is crosslinked by the crosslinking catalyst, the silange-grafted polyolefin preferably has a gel fraction of 85 wt% or more and more preferably 90 wt% or more. When the gel fraction is 85 wt% or more, the present composition is sufficiently crosslinked and exhibits excellent heat resistance and mechanical strength upon crosslinking.

[0030] The gel fraction of the silange-grafted polyolefin described above is obtained, for example, by a measurement method described below.

[0031] A material obtained by adding 0.5 parts by mass of the crosslinking catalyst to 100 parts by mass of the silange-grafted polyolefin is mixed for 5 minutes at 200°C, and the resulting bulk material is subjected to compression pressing at 200°C for 3 minutes to form it into a 1 mm thick sheet. The sheet is then crosslinked in a thermostatic bath at 60°C and 95% relative humidity for 12 hours, and subsequently dried at room temperature.

[0032] A test piece weighing approximately 0.1 g is taken from the resulting mold plate and immersed in a xylene solvent at 120°C. After 20 hours, the test piece is removed from the solvent and dried. The dried test piece is weighed. The mass of the test piece after immersion in xylene, expressed as a percentage of its mass before immersion, is defined as the gel fraction. If a substance other than the silange-grafted polyolefin is present in the crosslinked product both before and after immersion of the test piece in xylene, the gel fraction of the silange-grafted polyolefin can be calculated by removing the mass of the other substance.For example, it is assumed that the crosslinking catalyst is still present in the crosslinked product even after immersion in xylene, and as described below, if the crosslinking catalyst is diluted with a binder resin that is a non-crosslinking component, the gel fraction can be calculated assuming that the entire amount of the binder resin is eluted into xylene after immersion.

[0033] The silane-grafted polyolefin (A) can be produced by adding a free radical inducer to a polyolefin and a silane adhesion promoter, and mixing the material, for example, with a twin-screw extrusion kneader or a single-screw extrusion kneader. Alternatively, a process can be used in which a silane adhesion promoter is added when a polyolefin is produced by polymerization.

[0034] At this stage, the material preferably contains the silane adhesion promoter in an amount of 0.5 to 5 parts by mass, based on 100 parts by mass of the polyolefin, and more preferably in an amount of 3 to 5 parts by mass. If the amount of the silane adhesion promoter is 0.5 parts by mass or more, the polyolefin is sufficiently grafted with the agent. If, on the other hand, the amount of the silane adhesion promoter is 5 parts by mass or less, no excessive crosslinking reaction occurs during mixing, thereby suppressing the formation of gel-like substances and achieving excellent productivity and processability.

[0035] Examples of free radical generating agents include organic peroxides such as dicumyl peroxide (DCP), benzoyl peroxide, dichlorobenzoyl peroxide, di-tert-butyl peroxide, butyl peracetate, tert-butyl perbenzoate, and 2,5-dimethyl-2,5-di(tert-butyl peroxide)hexane. Dicumyl peroxide (DCP) is a preferred free radical generating agent.

[0036] When dicumyl peroxide (DCP) is used as a free radical generating agent, the mixing temperature during the graft modification of the polyolefin with the silane adhesion promoter is preferably set to 120°C or higher.

[0037] The free radical inducer is preferably used in an amount of 0.025 to 0.1 parts by mass per 100 parts by mass of the polyolefin to be silane-grafted. If the amount of free radical inducer is 0.025 parts by mass or more, the grafting reaction proceeds sufficiently. Conversely, if the amount of free radical inducer is 0.1 parts by mass or less, the progression of an excessive grafting reaction is suppressed, and the silane-grafted target polyolefin is sufficiently preserved.

[0038] The free radical generating agent can be added to the materials in the form diluted with an inert substance such as talc or calcium carbonate, or in the form of a pellet in which the agent is diluted with a polymer such as ethylene propylene rubber, ethylene propylene diene rubber, and polyolefin.

[0039] An unmodified polyolefin (B) is a polyolefin consisting of a hydrocarbon into which no modifying group is introduced, for example by graft polymerization or copolymerization.

[0040] According to the present invention, the unmodified polyolefin (B) is one or more selected from the group consisting of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and very low-density polyethylene (VLDPE). These can be used individually or in combination. With these low-density polyethylenes, the electrical wire exhibits particularly excellent flexibility and extrusion productivity.

[0041] The unmodified polyolefin (B) can be the same as or different from the polyolefin used for the main chain of the silange-grafted polyolefin (A). Using the same type of polyolefin provides excellent compatibility.

[0042] The unmodified polyolefin (B) has a density of 0.855 to 0.950 g / cm³ 3 and preferably a density of 0.860 to 0.940 g / cm³ 3on. If the density of the unmodified polyolefin is lower than 0.855 g / cm³ 3 If the melting point is too low, the pellets and the formed product could easily fuse before crosslinking, leading to deformation due to heating. Furthermore, the resin could be too soft to maintain sufficient malleability. On the other hand, if the density of the unmodified polyolefin (B) is 0.950 g / cm³ 3 If the limit is exceeded, flexibility may be limited.

[0043] The melting point of the unmodified polyolefin (B) is preferably 65°C or higher, more preferably 80°C or higher, and even more preferably 100°C or higher. If the melting point of the unmodified polyolefin is 65°C or higher, component (B) exhibits excellent melting and heat resistance. If a polyolefin with a sufficiently high melting point than that of the silange-grafted polyolefin (A) is used as the crosslinkable component, the melting point of the unmodified polyolefin (B) may be lower than that of the polyolefin of the silange-grafted polyolefin (A). The melting point of a polyolefin may be measured according to JIS K7121.

[0044] The microflow rate (MFR) of the unmodified polyolefin is preferably in the range of 0.5 to 5.0 g / 10 min and more preferably in the range of 1.0 to 3.0 g / 10 min. When the MFR is 0.5 g / 10 min or higher, the composition exhibits excellent extrusion properties and improved productivity. Conversely, when the MFR is 5 g / 10 min or lower, the resin shape is effectively retained, and the composition exhibits improved productivity. The MFR can be measured according to ASTM D1238.

[0045] According to the present invention, the flexural modulus of the unmodified polyolefin (B) is in the range of 3 to 200 MPa, and preferably in the range of 10 to 100 MPa. If the flexural modulus is within the range described above, the composition exhibits excellent flexibility. The flexural modulus can be measured according to ASTM D790.

[0046] A modified polyolefin (C) has one or more functional groups selected from the group consisting of a carboxyl group, an ester group, an acid anhydride group, an amino group, and an epoxy group. In the modified polyolefin (C), a functional group can be introduced by grafting a polymerizable compound with the functional group described above onto an unmodified base polyolefin consisting of one or more α-olefins, or by copolymerizing a polymerizable compound with the functional group described above and an olefin polymerizable with the polymerizable compound. It should be noted that a polyolefin modified with a silanol derivative such as methacryloxyalkylsilane is not classified as the modified polyolefin (C) but as the silange-grafted polyolefin (A).

[0047] Since the modified polyolefin (C) has one or more functional groups selected from the group consisting of a carboxyl group, an ester group, an acid anhydride group, an amino group, and an epoxy group, component (C) exhibits a high degree of interaction with an inorganic component. Furthermore, since component (C) has a polyolefin chain, it exhibits a high degree of interaction with the resin component, such as the silange-grafted polyolefin (A) and the unmodified polyolefin (B). Thus, the modified polyolefin (C) can be used as a compatibilizing agent between the resin component and the inorganic component, offering excellent dispersibility and adhesion to the inorganic component.

[0048] A polymerizable compound with a carboxyl group is not particularly limited, as long as the polymerizable compound contains both a carboxyl group and a polymerizable group such as a carbon-carbon double bond in one molecule. Examples of polymerizable compounds include acrylic acid, methacrylic acid, crotonic acid, α-chloroacrylic acid, itaconic acid, butenetricarboxylic acid, maleic acid, fumaric acid, and derivatives that contain these as part of their molecular structures. If the acid forms an acid anhydride, an acid anhydride group can be introduced through the acid hydride.

[0049] A polymerizable compound containing an ester group can be an ester compound obtained by reacting the polymerizable compound containing a carboxyl group described above with an alcohol. Alternatively, the ester compound can be obtained by reacting an alcohol containing a carbon-carbon double bond with any carboxylic acid. Examples of compounds containing an ester group are vinyl acetate and vinyl propionate.

[0050] A polymerizable compound containing an amino group is not particularly limited, as long as the polymerizable compound has a polymerizable group, such as a carbon-carbon double bond, and an amino group in one molecule. An example of a polymerizable compound containing an amino group is esters, which are obtained by a reaction between the polymerizable compounds with the carboxyl group described above, an alkanolamine, and another compound such as vinylamine and allylamine, as well as derivatives that incorporate these as part of their molecular structures.

[0051] A polymerizable compound with an epoxy group is not particularly limited as long as the polymerizable compound contains a polymerizable group, such as a carbon-carbon double bond, and an epoxy group in one molecule. Examples of polymerizable compounds with an epoxy group include acidic glycidyl esters, which are obtained by a reaction between the polymerizable compounds with a carboxyl group described above and glycidyl alcohol, glycidyl ethers such as vinyl glycidyl ether, allyl glycidyl ether, glycidyloxyethyl vinyl ether, and styrene p-glycidyl ether, as well as p-glycidylstyrene and derivatives that contain these as part of their molecular structures.

[0052] A polymerizable monomer that is copolymerizable with the polymerizable compound containing the functional group described above is not particularly restricted, as long as the monomer has a polymerizable group, such as a carbon-carbon double bond. For example, an olefin monomer that does not have a functional group, such as ethylene and propylene, or a polymerizable monomer that has a functional group other than a carboxyl group and an epoxy group, can be used. They can be used individually or in combination.

[0053] The present composition preferably contains the modified polyolefin (C) in an amount of 3 to 15 parts by mass, and more preferably in an amount of 4 to 10 parts by mass, relative to 100 parts by mass of the total amount of components (A), (B), and (C). When the present composition contains the modified polyolefin (C) in an amount of 3 parts by mass or more, the present composition exhibits a high affinity between the resin component and the inorganic component.

[0054] Regarding the ratio of the resin components (A), (B), and (C) described above, the present composition preferably contains the silange-grafted polyolefin (A) in an amount of 30 to 90 parts by mass and the unmodified polyolefin (B) and the modified polyolefin (C) in a combined amount of 10 to 70 parts by mass, based on 100 parts by mass of the total amount of components (A), (B), and (C). When the present composition contains the resin components within the ranges described above, it exhibits excellent flexibility and sufficient crosslinking density. Sufficient crosslinking density results in excellent heat resistance and wear resistance.

[0055] Examples of a flame retardant (D) are a metal hydroxide and a bromine-containing flame retardant. The metal hydroxide can provide flame retardancy on its own, while the bromine-containing flame retardant, when used with antimony trioxide as a flame retardant additive, enhances the flame-retardant effect. The metal hydroxide-containing or the bromine-containing flame retardant can each be used individually or in combination as the flame retardant (D). The metal hydroxide is preferred as a flame retardant due to its low cost and excellent heat resistance.

[0056] Examples of metal hydroxides include magnesium hydroxide, aluminum hydroxide, and zirconium hydroxide. In the materials described above, magnesium hydroxide is preferred due to its low cost and excellent heat resistance. Magnesium hydroxide can be obtained by chemical synthesis or by grinding natural minerals.

[0057] The metal hydroxide preferably has an average particle size of 0.1 to 10 µm and more preferably of 0.5 to 5 µm. When the average particle size of the metal hydroxide is 0.1 µm or larger, particle aggregation is difficult, whereas with an average particle size of 10 µm or smaller, the metal hydroxide particles are easily dispersed. Furthermore, to improve dispersibility, the metal hydroxide can be treated with a surface treatment agent such as a silane adhesion promoter, a higher fatty acid, and a polyolefin wax. Without the surface treatment, the metal hydroxide compound exhibits excellent dispersibility because the present composition contains the modified polyolefin (C).

[0058] Examples of bromine-containing flame retardants include bromine-containing flame retardants with a phthalimide structure, such as ethylenebistetrabromophthalimide and ethylenebistribromophthalimide, ethylenebispentabromophenyl, tetrabromobisphenol A (TBBA), hexabromocyclododecane (HBCD), TBBA carbonate oligomer, TBBA epoxy oligomer, brominated polystyrene, TBBA bisdibromopropyl ether, poly(dibromopropyl ether), and hexabromobenzene (HBB). These can be used individually or in combination. Due to their high melting point and excellent heat resistance, it is preferred to use at least one or more of the phthalimide-containing flame retardants, ethylenebispentabromophenyl, or its derivatives.

[0059] Antimony trioxide, a flame-retardant additive, enhances flame retardancy when used in conjunction with a bromine-containing flame retardant. It is preferred to use antimony trioxide with a purity of 99% or higher. The antimony trioxide is produced as a mineral. The mineral can be crushed and micronized for use as a flame-retardant additive. The antimony trioxide preferably has an average particle size of 3 µm or less, and more preferably 1 µm or less. When the average particle size of the antimony trioxide is 3 µm or less, the particles exhibit excellent interfacial strength with resins. Furthermore, to improve dispersibility, the antimony trioxide can be treated with a surface treatment agent, such as a silane adhesion promoter, a higher fatty acid, and a polyolefin wax.

[0060] When the metal hydroxide is used individually, it is preferably present in an amount of 10 to 100 parts by mass of the total amount of resin components (A), (B), and (C). When the metal hydroxide is present in an amount of 10 parts by mass or more, the present composition exhibits excellent flame retardancy. Conversely, when the metal hydroxide is present in an amount exceeding 100 parts by mass, no further improvement in flame retardancy can be expected. Considering this, and also the need for excellent flexibility, the upper limit of the amount of flame retardant is preferably 100 parts by mass.

[0061] When the bromine-containing flame retardant and the inorganic flame retardant additive are used together as a flame retardant component, the ratio of the bromine-containing flame retardant to the inorganic flame retardant additive (the bromine-containing flame retardant : the inorganic flame retardant) is preferably in a stoichiometric ratio in the range of 3:1 to 2:1.

[0062] When the bromine-containing flame retardant and the inorganic flame retardant auxiliary are used as flame retardants, the bromine-containing flame retardant is preferably present in an amount of 10 to 40 parts by mass and the antimony trioxide in an amount of 5 to 20 parts by mass per 100 parts by mass of the total amount of resin components (A), (B), and (C). When the bromine-containing flame retardant is present in an amount of 10 parts by mass or more, the present composition exhibits excellent flame retardancy. On the other hand, when the bromine-containing flame retardant is present in an amount of more than 40 parts by mass, no further improvement in flame retardancy can be expected. From this perspective, and considering the need for excellent flexibility, the upper limit of the amount of the bromine-containing flame retardant is preferably 100 parts by mass.

[0063] When the metal hydroxide and the bromine-containing flame retardant are used together as a flame retardant, the amounts of each added can be reduced. With respect to 100 parts by mass of the total amount of resin components (A), (B) and (C), it is particularly preferred that the metal hydroxide be present in an amount of 10 to 50 parts by mass, the bromine-containing flame retardant in an amount of 5 to 20 parts by mass, and the antimony trioxide in an amount of 5 to 20 parts by mass.

[0064] A crosslinking catalyst (E) is a silanol condensation catalyst for the silane crosslinking of the silange-grafted polyolefin (A). Examples of crosslinking catalysts include carboxylates of metals such as tin, zinc, iron, lead, and cobalt; titanate esters; organic bases; inorganic acids; and organic acids. Specific examples include dibutyltin dilaurate, dibutyltin dimaleate, dibutyltin bisisooctylthioglycol ester salt, dibutyltin β-mercaptopropionate, dibutyltin diacetate, dioctyltin dilaurate, tin(II) acetate, tin(II) caprylate, lead naphthenate, cobalt naphthenate, barium stearate, calcium stearate, tetrabutyl titanate, tetranonyl titanate, dibutylamine, hexylamine, pyridine, sulfuric acid, hydrochloric acid, toluenesulfonic acid, acetic acid, stearic acid, and maleic acid. The crosslinking catalyst preferably contains dibutyltin dilaurate, dibutyltin dimaleate, dibutyltin bisisooctylthioglycol ester salt or dibutyltin β-mercaptopropionate.

[0065] When the crosslinking catalyst (E) is mixed with the silange-grafted polyolefin (A), a crosslinking reaction occurs. Therefore, the crosslinking catalyst is preferably mixed with the composition immediately before coating an electrical wire. To improve the dispersibility of the crosslinking catalyst, it is preferably pre-mixed with a binder resin and produced in the form of a crosslinking batch. When the crosslinking catalyst is produced in the form of a crosslinking batch, an unexpected crosslinking reaction of the silange-grafted polyolefin (A) can be prevented. The crosslinking catalyst then exhibits excellent dispersibility and sufficiently promotes the crosslinking reaction. Furthermore, when the crosslinking catalyst is used as a crosslinking catalyst batch, it is easy to control the amount of crosslinking catalyst added.

[0066] The polyolefins listed above in (A) to (C) can be used as binder resins for producing the crosslinking catalyst batch. In particular, low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), very low-density polyethylene (VLDPE), and metallocene low-density polyethylene are preferred. When these low-density polyethylenes are used, the electrical wire exhibits favorable flexibility and excellent extrudability, and productivity can be improved. For example, a portion of the unmodified polyolefin (B) can be used as the binder resin.

[0067] The crosslinking catalyst batch preferably contains the crosslinking catalyst in an amount of 0.5 to 5 parts by mass per 100 parts by mass of the binder resin, and more preferably in an amount of 1 to 5 parts by mass. If the batch contains the crosslinking catalyst in an amount of 0.5 parts by mass or more, the crosslinking reaction proceeds readily. Conversely, if the batch contains the catalyst in an amount of 5 parts by mass or less, the catalyst exhibits excellent dispersibility.

[0068] The present composition preferably contains the crosslinking catalyst (E) in an amount of 0.01 to 1.0 parts by mass and more preferably in an amount of 0.02 to 0.9 parts by mass per 100 parts by mass of the total amount of resin components (A), (B), and (C). If the present composition contains the catalyst in an amount of 0.01 parts by mass or more, the crosslinking reaction can proceed readily. Conversely, if the present composition contains the catalyst in an amount of 1.0 parts by mass or less, excessive crosslinking can be prevented.

[0069] The antioxidant (F) is preferably a flame retardant based on hindered phenol and particularly preferably a hindered phenol with a melting point of 200°C or higher. Examples of the hindered phenol-based antioxidant include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], thiodiethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, N,N'-(hexane-1,6-diyl)bis[3-(3,5-di-tert-butyl)-4-hydroxyphenyl)propionamide], 2,4-dimethyl-6-(1-methylpentadecyl)phenol, and diethyl[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]methylphosphonate. 3,3',3'',5,5',5''-Hexa-tert-butyl-a,a',a''-(mesitylene-2,4,6-tolyl)tri-p-cresol, Calcium diethyl bis[[[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate], 4,6-Bis(octylthiomethyl)-o-cresol, Ethylene bis(oxyethylene)-bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], Hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-Tris[(4-tert-butyl-3-hydroxy-2,6-xylyl)methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 2,6-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazine-2-ylamino)phenol, 2,6-Di-tert-butyl-4-methylphenol, 2,2'-methylenebis-(4-methyl-6-tert-butylphenol), 4,4'-butylidenebis(3-methyl-6-tert-butylphenol), 4,4'-Thiobis(3-methyl-6-tert-butylphenol), 3,9-Bis[2-(3-(3-tert-butyl-4-hydroxy-5-methylphenyl)-propynoxy)-1,1-dimethylethyl]-2,4,8, 10-tetraoxaspiro(5,5)-undecane. These can be used individually, or two or more of them can be used in combination. Examples of the hindered phenol-based antioxidant with a melting point of 200°C or higher are 3,3',3'',5,5',5''-hexa-tert-butyl-a,a',a''-(mesitylene-2,4,6-tolyl)tri-p-cresol and 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione.

[0070] The present composition preferably contains the antioxidant (F) in an amount of 1 to 10 parts by mass and more preferably in an amount of 1 to 5 parts by mass per 100 parts by mass of the total amount of resin components (A), (B) and (C). When the amount is within the range described above, the present composition exhibits excellent antioxidant properties and suppresses blooming.

[0071] A metal deactivator (G) can be a copper deactivator or a chelating agent that can prevent oxidation caused by contact with a heavy metal such as copper. Examples of metal deactivators are hydrazide derivatives such as 2,3-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]-propionohydrazide and salicylic acid derivatives such as 3-(N-salicyloyl)amino-1,2,4-triazole. The metal deactivator preferably contains salicylic acid derivatives such as 3-(N-salicyloyl)amino-1,2,4-triazole.

[0072] The present composition preferably contains the metal deactivator (G) in an amount of 1 to 10 parts by mass and more preferably in an amount of 1 to 5 parts by mass per 100 parts by mass of the total amount of resin components (A), (B) and (C). When the amount is within the range described above, the present composition exhibits excellent antioxidant properties and suppresses blooming.

[0073] The choice of lubricant (H) is not particularly limited, and either an internal or external lubricant can be used. Examples of lubricants include hydrocarbons such as liquid paraffin, paraffin wax, and polyethylene wax; higher alcohols; fatty acids such as stearic acid, oleic acid, and erucic acid; fatty acid amides such as stearamide, oleamide, erucamide, and methylenebisstearamide; alkylene fatty acid amides such as ethylenebisstearamide; metal soaps such as metal stearates; and ester lubricants such as stearic acid monoglyceride, stearyl stearate, and hydrogenated oil. From the perspective of compatibility with the resin components, derivatives of fatty acids such as erucic acid, oleic acid, and stearic acid, or polyethylene-based waxes, are preferably used as lubricants.

[0074] The present composition preferably contains the lubricant in an amount of 1 to 10 parts by mass and more preferably in an amount of 1 to 5 parts by mass per 100 parts by mass of the total amount of resin components (A), (B) and (C). If the amount is within the range described above, the present composition exhibits sufficient lubricating properties.

[0075] Component (I) consists of a combination (I-1) of zinc oxide and an imidazole compound or (I-2) of zinc sulfide, used as an additive to improve heat resistance and long-term heat resistance. Adding only zinc sulfide (I-2) or only the combination (I-1) of zinc oxide and the imidazole compound can achieve a similar effect.

[0076] The zinc oxide described above is obtained, for example, by adding a reducing agent, such as coke, to a zinc ore and oxidizing zinc vapor generated during firing with air, or by using zinc sulfate or zinc chloride as raw material. The method for producing the zinc oxide is not particularly limited; any method for producing zinc oxide can be used. Zinc sulfide produced by a known process can also be used. The average particle size of the zinc oxide and the zinc sulfide is preferably 3 µm or less, and more preferably 1 µm or less. As the average particle size of the zinc oxide and the zinc sulfide decreases, the interfacial strength increases with the resin, and the dispersibility also increases.

[0077] The imidazole compound described above is preferably a mercaptobenzimidazole. Examples of mercaptobenzimidazole are 2-mercaptobenzimidazole, 2-mercaptomethylbenzimidazole, 4-mercaptomethylbenzimidazole, 5-mercaptomethylbenzimidazole, and the zinc salts of these compounds. 2-Mercaptobenzimidazole and its zinc salt are particularly preferred because the compounds have high melting points and cause little sublimation upon mixing.

[0078] The present composition preferably contains as component (I) the combination (I-1) of zinc oxide and the imidazole compound, each in an amount of 1 to 15 parts by mass, or zinc sulfide (I-2) in an amount of 1 to 15 parts by mass, based on 100 parts by mass of the total amount of resin components (A), (B), and (C). When the amounts of the components are within the ranges described above, the present composition exhibits excellent heat resistance and long-term heat stability, and the particles are less likely to aggregate and exhibit excellent dispersibility.

[0079] The composition for a wire coating material according to the present invention may contain various additives, provided that the additives do not impair the object of the present invention. Examples of such additives are an inorganic filler, a pigment, and a silicone oil.

[0080] For example, if an inorganic filler is added to the existing composition, the hardness of the resin can be adjusted by adding the filler, and the melting resistance and heat resistance of the composition can be improved by adding the filler.

[0081] The present composition contains the inorganic filler preferably in an amount of 30 parts by mass or less with regard to resin strength in relation to 100 parts by mass of the total amount of resin components (A), (B) and (C).

[0082] The composition for a wire coating material according to the present invention can be prepared by mixing components (A) to (E) and the various additives, which are added as required, and by kneading the mixture with a twin-screw extruder. When the silange-grafted polyolefin and the crosslinking catalyst are mixed, the crosslinking reaction proceeds due to atmospheric humidity. Therefore, to prevent the crosslinking reaction and other unintended reactions during storage of the composition, the components are preferably mixed with the composition immediately before coating an electrical wire. As such a method, it is preferred to prepare and pelletize a silange-grafted batch, a flame-retardant batch, and a crosslinking catalyst batch separately beforehand.

[0083] The silange-grafted batch is a batch containing the silange-grafted polyolefin (A). The flame-retardant batch is a batch containing the unmodified polyolefin (B), the modified polyolefin (C), and the flame-retardant (D). The crosslinking catalyst batch is a batch containing the crosslinking catalyst (E) and the binder resin. The silange-grafted batch, the flame-retardant batch, and the crosslinking catalyst batch may contain components (F) to (I) and various additives, which are added as required, provided that this does not impair the object of the present invention.

[0084] An insulated wire and a cable harness according to the present invention are described below.

[0085] In the insulated wire according to the present invention, a conductor is coated with an insulating layer of a coating material for electrical wire (also simply referred to as the coating material), which is obtained by crosslinking the composition for the electrical wire coating material described above. The conductor of the insulated wire is not particularly limited by the conductor diameter and the conductor material, so that the conductor can be selected accordingly, for example, depending on the application of the insulated wire. Examples of the conductor material are copper, copper alloy, aluminum, and aluminum alloy. From the perspective of reducing the weight of the electrical wire, the conductor is preferably made of aluminum or an aluminum alloy.The insulating layers of the coating material for the electrical wire can have a single layer or multiple layers consisting of two or more layers.

[0086] In the insulated wire according to the present invention, the degree of cross-linking of the cross-linked coating material, expressed as the gel fraction, is preferably 50% or more, and, from the perspective of heat resistance, more preferably 60% or more. The gel fraction of the coating material for the insulated wire is generally used as an index of the cross-linked state of an electrical wire. The gel fraction of the coating material can be measured according to JASO D608-92.

[0087] To produce the insulated wire according to the present invention, the silange-grafted batch, flame-retardant batch, and crosslinking catalyst batch described above can be heated and kneaded, for example, using an ordinary kneading machine, such as a Banbury mixer, a pressure kneader, a kneading extruder, a twin-screw extruder, or a roller. The composition can then be extruded through an extrusion die to coat the outer circumference of the conductor and subsequently crosslinked.

[0088] The coating material is crosslinked in a process in which a coating layer of the coated wire is exposed to steam or water. The crosslinking reaction is preferably carried out at a temperature in the range of room temperature to 90°C and over a period of 48 hours, and more preferably at a temperature in the range of 50 to 80°C and over a period of 8 to 24 hours.

[0089] A wiring harness according to the present invention comprises the insulated wire described above. The wiring harness can be a single wire bundle in which only the wires described above are bundled together, or a mixed wire bundle in which the insulated wires described above and other insulated wires are bundled together in a mixed state. The wire bundle forms the wiring harness, and the wire bundle is bound with a wiring harness protective material such as corrugated tubing and a binding material such as adhesive tape.

[0090] The insulated wire according to the present invention can be used as various types of electrical wires in motor vehicles, appliances, information and communication systems, power supply systems, ships, and aircraft. In particular, it can be suitable as an electrical wire for motor vehicles.

[0091] According to the international standard ISO 6722, automotive wires are classified into classes A to E based on their permissible heat resistance temperature. Since the insulated wire according to the present invention is made from the wire coating material described above, it exhibits excellent heat resistance and is ideal for use in high-voltage battery cables. Thus, the insulated wire according to the present invention can possess the properties of class C with a heat resistance temperature of 125°C or class D with a heat resistance temperature of 150°C. Examples

[0092] The present invention will be described by means of examples, but the present invention is not limited to the examples. [Silane Grafted Polyolefin (A)]

[0093] Silange-grafted polyolefins (silange-grafted PE1 to PE3 and silange-grafted PP1) were prepared by kneading dry-mixed materials containing the polyolefins shown below (i.e., base PE1 to PE5 and base PP1) as the base polyolefins at 140°C using a single-screw extrusion kneader with an inner diameter of 25 mm. The dry-mixed materials also contained, per 100 parts by mass of each polyolefin, vinyltrimethoxysilane (“KBM1003”, manufactured by Shin-Etsu Chemical Co., Ltd.) at a rate of 1.5 parts by mass and dicumyl peroxide (“PERCUMYL D”, manufactured by NOF CORPORATION) at a rate of 0.15 parts by mass.

[0094] A crosslinking catalyst (“Linkron LZ015H”, manufactured by Mitsubishi Chemical Corporation) at a quantity of 5 parts by weight was added to 100 parts by weight of the silange-grafted polyolefins described above. The materials were kneaded for 5 minutes at 200°C using “LABO PLASTOMILL”, manufactured by Toyo Seiki Co., Ltd., and then the resulting mass-like substances were compressed and pressed for 3 minutes at 200°C to form the materials into sheets 1 mm thick. After crosslinking the resulting sheets for 12 hours in a thermostatic bath at 60°C and 95% humidity, the sheets were dried for 24 hours at room temperature.

[0095] From each of the obtained mold plates, a test piece weighing approximately 0.1 g was taken and then immersed in xylene for 20 hours at a temperature of 120°C. The sample was then removed from the xylene and dried for 6 hours at 100°C. The dried sample was then weighed. The mass of the silange-grafted polyolefin after immersion in xylene, expressed as a percentage of the mass before immersion, was defined as the gel fraction. The gel fraction is shown in Table 1. Gel fraction % = (mass after immersion in xylene / mass before immersion in xylene) × 100

[0096] It was assumed that the crosslinking catalyst in the crosslinking catalyst batch was still present in the crosslinked product even after immersion in xylene. Furthermore, the gel fraction was calculated under the assumption that the total amount of the binder resin was eluted in xylene after immersion.

[0097] The resin described below was used for the base polyolefins from which the silane-grafted polyolefins are composed. The density, melting point, melt flow rate (MFR) at 190°C under a load of 2.16 kg, flexural modulus, and Shore A hardness of each of the base polyolefins in the ungrafted state, as well as the gel fraction of the base polyolefin after silane grafting, are listed in Table 1. • Base PE1: “INFUSE9107”, manufactured by Dow Elastomers Co., Ltd. • Base PE2: “INFUSE9807”, manufactured by Dow Elastomers Co., Ltd. • Base PE3: “INFUSE9507”, manufactured by Dow Elastomers Co., Ltd. • Base PE4: VLDPE prototype • Base PE5: “ENGAGE7467”, manufactured by Dow Elastomers Co., Ltd. • Base PE6: “NOVATECH EC9”, manufactured by Japan Polypro Co., Ltd. [Table 1] silage-grafted PE1 silage-grafted PE2 silage-grafted PE3 silage-grafted PE4 silage-grafted PE5 silage-grafted PP1 Base polyolefin Basic PE1 Basic PE2 Basic PE3 Basic PE4 Basic PE5 Basic PP1 density g / cm 3 0,866 0,866 0,866 0,850 0,862 0,920 Melting point °C 121 118 119 <30 34 160 MFR g / 10 min 1 15 5 2,5 1 0,5 Bending modulus MPa 7 8 4 3 4 1000 Shore A hardness - 60 55 60 50 52 90 < Gel fraction % 92 91 94 96 95 58 [Unmodified polyolefin (B)]

[0098] The resins presented below were used as unmodified polyolefins (unmodified PE1 to PE4). Table 2 shows the density of each polyolefin. • Unmodified PE1: “ENGAGE 7467”, manufactured by Dow Elastomers Co., Ltd. • Unmodified PE2: “ENGAGE 7256” manufactured by Dow Elastomers Co., Ltd. • Unmodified PE3: “INFUSE 9107”, manufactured by Dow Elastomers Co., Ltd. • Unmodified PE4: “NOVATEC HDHY 331”, manufactured by Japan Polypro Co., Ltd. • PP elastomer: “NEWCON NAR 6”, manufactured by Japan Polypro Co., Ltd. [Table 2] unmodified PE1 unmodified PE2 unmodified PE3 unmodified PE4 PP elastomer density g / cm 3 0,862 0,885 0,866 0,951 0,890 Melting point °C 34 70 121 131 140 MFR g / 10 min 1 2,5 1 1 2,2 Bending modulus MPa 4 30 7 1050 550 [Modified polyolefin (C)]

[0099] The resins described below were used as modified polyolefins (modified PE1 to PE3 and modified PP1). Modified PE1 to PE3 contained polyethylene as the base polyolefin, while modified PP1 contained polypropylene as the base polyolefin. The polyolefins described below (i.e., modified PE1 to PE3 and modified PP1) each refer to resins prepared by reacting the compounds indicated in each bracket (i.e., maleic anhydride, glycidyl methacrylate, and methyl methacrylate) with the polyolefins. In this way, functional groups corresponding to the reacted compounds were introduced into the polyolefins. Some of the ester and acid anhydride groups may be present in the form of a carboxyl group after hydrolysis. • Modified PE1: “Modic AP512P” (modified maleic anhydride), manufactured by Mitsubishi Chemical Corporation • Modified PE2: “Bond First E” (modified glycidyl methacrylate), manufactured by Sumitomo Chemical Co., Ltd. • Modified PE3: “Acryft WH102” (modified methyl methacrylate), manufactured by Sumitomo Chemical Co., Ltd. • Modified PP1: “Admer QB550” (modified maleic anhydride), manufactured by Mitsui Chemicals Co., Ltd.

[0100] Components other than those described above were as follows: [Flame retardant (D)] • Metal hydroxide 1: “KISMA 5” (magnesium hydroxide), manufactured by Kyowa Chemical Industry Co., Ltd. • Metal hydroxide 2: “Magnifin H10” (magnesium hydroxide), manufactured by Albemarle Corporation • Metal hydroxide 3: “C305” (aluminum hydroxide), manufactured by Sumitomo Chemical Co., Ltd. • Bromine-containing flame retardant 1: “SAYTEX8010” (ethylenebispentabromenbenzene), manufactured by Albemarle Corporation • Bromine-containing flame retardant 2: “SAYTEXBT-93” (ethylenebistetrabromophthalimide), manufactured by Albemarle Corporation • Antimony trioxide: MSW quality, manufactured by Yamanaka & Co., Ltd. [Crosslinking catalyst (E)] • Batch of the crosslinking catalyst: “LINKLON LZ082”, manufactured by Mitsubishi Chemical Corporation [Antioxidant (F)] • Antioxidant 1: “Irganox1010”, manufactured by BASF JAPAN Co., Ltd. • Antioxidant 2: “Irganox3114”, manufactured by BASF JAPAN Co., Ltd. [Metal deactivator (G)] • Metal deactivator: “CDA-1”, manufactured by ADEKA CORPORATION [Lubricant (H)] • Lubricant: “ALFLOW P-10” (erucamide), manufactured by NOF CORPORATION [Component (I)] • Zinc oxide: manufactured by HAKUSUI TECH. Co., Ltd. • Imidazole compound: “ANTAGE MB” (2-Mercaptobenzimidazole), manufactured by Kawaguchi Chemical Industry Co., Ltd. • Zinc sulfide: “SACHTOLITH HD-S”, manufactured by Sachtleben Chemie GmbH (Production of the silage-grafted batch)

[0101] The silange-grafted polyolefins were produced as silange-grafted batches in pellet form. (Production of the batch of the crosslinking catalyst)

[0102] The crosslinking catalyst used was "Linklon LZ082," manufactured by Mitsubishi Chemical Corporation, which was supplied in advance as pellets. "Linklon LZ082" contains polyethylene (density: 0.91 g / cm³). 3 ) as a binder resin in a quantity of 99 parts by mass and a tin compound as a crosslinking catalyst in a quantity of 1 part by mass. (Production of the flame-retardant intermediate batch)

[0103] Flame-retardant batches were produced by kneading the components listed in Tables 3 and 4, with the exception of the silange-grafted polyolefin, the crosslinking catalyst, and the binder resin, at 200°C for 0.1 to 2 minutes using a twin-screw extruder to ensure sufficient dispersion. The resulting materials were then pelletized to form the flame-retardant batches. (Manufacturing of insulated wire)

[0104] The silage-grafted batches, the flame-retardant intermediate batches, and the crosslinking catalyst batches, prepared in the mixing ratios specified in Tables 3 and 4, were mixed in a hopper of an extruder and then extruded and shaped at a temperature of 200°C. In the extrusion process, insulators with a thickness of 0.7 mm were extruded onto conductors with an outer diameter of 2.4 mm to form coating materials (coating outer diameter: 3.65 mm). The coating materials were then crosslinked for 24 hours in a thermostat at a temperature of 65°C and a relative humidity of 95%. Insulated wires were thus obtained.

[0105] The resulting compositions for the wire coating material and the insulated wires were tested and evaluated with respect to melt resistance, ISO flame retardancy, gel fraction, ISO long-term heat resistance, ISO wear resistance, flexibility, and ISO thermal deformation. The evaluation results are presented in Tables 4 and 5. Each test procedure and evaluation criterion is described below. (Melting resistance)

[0106] Each of the previously produced insulated wires, before crosslinking, where the coating material was formed by extruding the insulator onto the conductor, was used as a test sample. The uncrosslinked insulated wire was wound 300 m long around an iron coil with an outer diameter of 30 mm.

[0107] The insulated wire was then crosslinked for 24 hours in a thermostatic bath at a temperature of 65°C and a relative humidity of 95%. After crosslinking, the insulated electrical wire was wound onto a plastic spool, and the presence of fusion marks, which occurred when one part of the wire fused to another, was assessed by visual observation. If no fusion marks were observed, the insulated wire was rated as "passed." Conversely, if a fusion mark was observed, the insulated wire was rated as "failed." (ISO flame retardant)

[0108] The flame retardancy of each cross-linked insulated wire was assessed according to ISO 6722. If the fire was extinguished within 70 seconds, the insulated wire was rated as "passed". If the fire was not extinguished within 70 seconds, the insulated wire was rated as "failed". (Gel fraction)

[0109] The gel fraction of each insulated wire was measured according to JASO D608-92. A sample weighing approximately 0.1 g was taken from the coating material of the cross-linked insulated wire. The sample was weighed. The sample was placed in a test tube, and then 20 ml of xylene was added to the test tube. The test tube was heated in an oil bath at 120°C for 24 hours. The sample was then removed from the test tube, dried in a dryer at 100°C for 6 hours, and then allowed to cool to room temperature. After this, the sample was weighed. The gel fraction was obtained by expressing the mass of the sample after the test as a percentage of the mass before the test. If the gel fraction was 50% or higher, the sample was rated as "pass," and if the gel fraction was 60% or higher, the sample was rated as "excellent."If the gel fraction was less than 50%, the sample was rated as "failed". (ISO long-term heat resistance)

[0110] The long-term heat resistance of the cross-linked material was assessed according to ISO 6722. The cross-linked insulated wire was immersed in a thermostatic bath at 125°C or 150°C for 3000 hours, followed by a voltage resistance test at 1 kV for 1 minute. If the insulated wire did not exhibit dielectric breakdown during the voltage resistance test after immersion in the thermostatic bath at 125°C, it was rated as "passed." Conversely, if the insulated wire did exhibit dielectric breakdown during the test, it was rated as "failed." Furthermore, the wire was rated as "excellent" if it did not exhibit dielectric breakdown during the voltage resistance test after immersion in the thermostatic bath at 150°C. (ISO wear resistance)

[0111] The wear resistance of the cross-linked insulated wire was evaluated according to ISO 6722. The insulated wire was pressed against an iron wire with an outer diameter of 0.45 mm under a load of 7 N, and the iron wire was reciprocated at a speed of 55 cycles / min. The number of reciprocations until the iron wire and the copper conductor were electrically connected was measured. If the number of reciprocations was 700 or more, the insulated wire was rated as "passed"; if the number of reciprocations was 1000 or more, the insulated wire was rated as "excellent"; and if the number of reciprocations was less than 700, the insulated wire was rated as "failed". (Flexibility)

[0112] In accordance with JIS K7171, the three-point bending flexibility of each insulated wire was evaluated using an Autograph AG-01, manufactured by Shimadzu Co., Ltd. The cross-linked insulated electrical wire was cut to a length of 100 mm. Three pieces of wire were placed side by side, and the wire ends were taped together with polyvinyl chloride tape to form a test specimen. The test specimen was placed on a clamping fixture with a pair of columns spaced 50 mm apart. The specimen was then pressed down at a rate of 1 mm / min at the center of the columns. The maximum load was measured during pressing.

[0113] If the maximum load was 3 N or less, the insulated wire was rated as "passed," and if the maximum load was 2 N or less, the insulated wire was rated as "excellent." However, if the maximum load was more than 3 N, the insulated wire was rated as "failed." (ISO heat deformation)

[0114] The thermal deformation of the cross-linked insulated wire was evaluated according to ISO 6722. The cross-linked insulated wire was pressed with a blade with a tip width of 0.7 mm under a load of 190 g and left in this state for 4 hours in a thermostat bath at 150°C. The dielectric strength test of the insulated wire was then performed at 1 kV for 1 min in a 1% saline solution. If the insulated wire did not exhibit dielectric breakdown during the dielectric strength test, it was rated as "passed". If, however, the insulated wire exhibited dielectric breakdown during the test, it was rated as "failed". If the wire was rated as "passed", the remaining percentage of the insulating coating was assessed.The remaining percentage was calculated as the ratio of the insulating coating thickness to the cumulative thickness in one direction (for example, if the thickness on one side was 0.7 mm, the cumulative thickness was 0.7 × 2 = 1.4 mm) after removal from the thermostat bath, relative to the thickness before insertion into the thermostat bath. If the remaining percentage was 75% or more, the insulated wire was rated as "excellent". [Table 3] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 silage-grafted PE1 60 60 85 silage-grafted PE2 60 70 silage-grafted PE3 60 60 silage-grafted PE4 silage-grafted PE5 silage-grafted PE6 unmodified PE1 30 20 10 unmodified PE2 30 30 30 unmodified PE3 30 unmodified PE4 PP elastomer 5 5 modified PE1 5 5 5 modified PE2 10 modified PE3 10 modified PP1 10 10 Metal hydroxide 1 70 Metal hydroxide 2 70 30 20 Metal hydroxide 3 80 Bromine flame hydroxide 1 30 15 20 Bromine flame hydroxide 2 15 10 Antimony trioxide 10 5 10 10 Antioxidant 1 2 3 3 1 2 1 Antioxidants 2 3 1 2 1 Metal deactivator 1 1 1 0,5 lubricant 0,5 0,8 0,4 0,5 0,6 1 0,3 zinc oxide 10 imidazole compound 10 Zinc sulfide 12 Binder resin 4,95 4,95 4,95 4,95 4,95 4,95 4,95 Crosslinking catalyst 0,05 0,05 0,05 0,05 0,05 0,05 0,05 Total quantity 178,5 179,8 189,4 169 169,6 165 137,3 Melting resistance P P P P P P P ISO flame retardancy test P P P P P P P Gel fraction E E E P P P P ISO long-term heat resistance test P P P E E P P ISO wear resistance test E P P P P P P flexibility E E E E E E E ISO heat deformation test E P E E E E P E: excellent, P: passed, F: failed

[0115] Examples 1 and 4 are non-inventive reference examples. [Table 4] Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Comparative example 5 Comparative example 6 silage-grafted PE1 60 silage-grafted PE2 60 silage-grafted PE3 silage-grafted PE4 60 silage-grafted PE5 60 silage-grafted PE6 60 60 unmodified PE1 30 35 unmodified PE2 30 unmodified PE3 30 30 unmodified PE4 30 PP elastomer 5 modified PE1 5 10 5 modified PE2 10 modified PE3 modified PP1 10 10 Metal hydroxide 1 70 70 Metal hydroxide 2 70 Metal hydroxide 3 80 100 Bromine flame hydroxide 1 Bromine flame hydroxide 2 Antimony trioxide Antioxidant 1 0,5 3 3 1 Antioxidants 2 3 0,5 1 Metal deactivator 1 1 1 0,5 0,2 lubricant 0,5 0,8 0,4 0,5 1 0,3 zinc oxide 10 imidazole compound 10 Zinc sulfide Binder resin 4,95 4,95 4,95 4,95 4,95 - Crosslinking catalyst 0,05 0,05 0,05 0,05 0,05 - Total quantity 177 179,8 189,4 199 106,7 202,3 Melting resistance F F P P F P ISO flame retardancy test P P P P F P Gel fraction E E F E P F ISO long-term heat resistance test P P P E P F ISO wear resistance test F P E E F P flexibility E E F F E E ISO heat deformation test E P F E F F E: excellent, P: passed, F: failed

[0116] As shown in Tables 3 and 4, the composition according to Comparative Examples 1, 2, and 5 led to fusion after crosslinking because the melting points of the polyolefins from which the silange-grafted polyolefins are made were below 80°C. The composition according to Comparative Example 3 resulted in a low gel fraction and reduced flexibility because the density of the polyolefin from which the silange-grafted polyolefin is made was higher than 0.890 g / cm³. 3 The composition according to comparative example 4 resulted in lower flexibility, as the density of the unmodified polyolefins was higher than 0.950 g / cm³. 3The composition according to Comparative Example 5 exhibited poorer flame retardancy because it did not contain a flame retardant. Furthermore, it exhibited poorer wear resistance because it contained an insufficient amount of the inorganic component. The composition according to Comparative Example 6 was not crosslinked because it did not contain the crosslinking catalyst.

[0117] Meanwhile, the composition according to the examples, which corresponded to the structure of the present invention, exhibited excellent flexibility, melting resistance, and deformation resistance. Furthermore, Examples 4 and 5, which contained component (I), showed excellent long-term heat resistance compared to the compositions that did not contain component (I).

Claims

[1] Composition for a wire coating material, comprising: (A) a silane-grafted polyolefin, which is a polyolefin grafted with a silane adhesion promoter; (B) an unmodified polyolefin; (C) a modified polyolefin with one or more functional groups selected from the group consisting of a carboxyl group, an ester group, an acid anhydride group, an amino group and an epoxy group; (D) a flame retardant; and (E) a crosslinking catalyst, wherein the polyolefin of (A), the silange-grafted polyolefin, has a density of 0.855 to 0.890 g / cm³ 3 in an ungrafted state and has a melting point of 80°C or higher, and where (B), the unmodified polyolefin, has a density of 0.855 to 0.950 g / cm³ 3exhibits a flexural modulus of 3 to 200 MPa and is one or more selected from the group consisting of a very low density polyethylene, a linear low density polyethylene and a low density polyethylene. [2] Composition according to claim 1, wherein the polyolefin of (A), the silange-grafted polyolefin, has a density of 0.865 to 0.880 g / cm³ in the ungrafted state. 3 , having a melt flow rate of 0.5 to 5 g / 10 min at 190°C under a load of 2.16 kg, a Shore A hardness of 55 to 70, a flexural modulus of 3 to 50 MPa and a melting point of 100°C or higher, and (B) the unmodified polyolefin having a melt flow rate of 0.5 to 5 g / 10 min at 190°C under a load of 2.16 kg and a melting point of 65°C or higher. [3] Composition according to claim 1 or claim 2, wherein the amount of (A), the silange-grafted polyolefin, is 30 to 90 parts by mass, the total amount of (B), the unmodified polyolefin, and (C), the modified polyolefin, is 10 to 70 parts by mass, (D) the flame retardant, in relation to 100 parts by mass of the total quantity of components (A), (B) and (C), comprises at least one of: (D-1) 10 to 100 parts by mass of a metal hydroxide; and (D-2) 10 to 40 parts by mass of a bromine-containing flame retardant and 5 to 20 parts by mass of an antimony trioxide, and the quantity of component (E), the crosslinking catalyst, is 0.01 to 1 part by mass in relation to 100 parts by mass of the total quantity of components (A), (B) and (C). [4] Composition according to any one of claims 1 to 3, wherein the composition further comprises, in relation to 100 parts by mass of the total quantity of components (A), (B) and (C): (F) 1 to 10 parts by mass of an antioxidant; (G) 1 to 10 parts by mass of a metal deactivator; and (H) 1 to 10 parts by mass of a lubricant [5] Composition according to any one of claims 1 to 4, wherein the composition is further defined in relation to 100 parts by mass of the total quantity of components (A), (B) and (C) as either: (I-1) 1 to 15 parts by mass of a zinc oxide and 1 to 15 parts by mass of an imidazole compound; or (I-2) 1 to 15 parts by mass of a zinc sulfide includes. [6] Composition according to any one of claims 1 to 5, wherein the polyolefin forming (A), the silange-grafted polyolefin, is one or more selected from the group consisting of a very low density polyethylene, a linear low density polyethylene and a low density polyethylene. [7] Insulated wire comprising an electrical wire coating material comprising a cross-linked product of the composition for a wire coating material according to any one of claims 1 to 6. [8] Wiring harness comprising the insulated wire according to claim 7.