Insulated electric wire and cable

Abstract

The present application provides an insulated electric wire and cable, the insulated electric wire has a conductor, a first insulating layer and a second insulating layer, the first insulating layer is formed by a first halogen-free resin composition containing a first base polymer and a filler, the second insulating layer is formed by a second halogen-free resin composition containing a second base polymer and a metal hydroxide, the second base polymer contains two polymers of EVA with a VA amount of 60% or more and ethylene-vinyl acetate copolymer with a melting point of 85 DEG C or more, the two polymers account for 80% or more of the second base polymer, the metal hydroxide is contained in a proportion of 150-250 parts by weight per 100 parts by weight of the second base polymer, the first base polymer contains 50% or more of polyethylene with a melting point of 110 DEG C or more, the filler is contained in a proportion of 150 parts by weight or less per 100 parts by weight of the first base polymer, and an acid-modified polyolefin is mixed in the first base polymer.

Description

[0001] This application is a divisional application of Chinese patent application filed on January 22, 2020, with application number 202010075770.8 and invention title "Insulated Wires and Cables". Technical Field

[0002] This invention relates to insulated wires and cables using halogen-free resin compositions. Background Technology

[0003] Due to the active global efforts in environmental protection in recent years, halogen-free materials that do not produce toxic gases when burned and cause minimal environmental pollution during disposal are rapidly gaining popularity. For example, Patent Document 1 (Japanese Patent Application Publication No. 2010-97881) discloses an insulated wire comprising a conductor, an insulating inner layer covered with the conductor and containing ethylene ethyl acrylate copolymer (EEA), and an outer layer covered with the inner layer and containing ethylene vinyl acetate copolymer (EVA) and a halogen-free flame retardant. The outer layer is cross-linked to have oil resistance and flame retardancy.

[0004] However, halogen-free materials generally have poorer flame retardancy compared to halogenated materials. Therefore, to impart high flame retardancy, a high filler content of flame retardant is required. For example, to meet the very stringent flame retardancy requirements of standards such as EN45545 and NFPA130, approximately 200 parts by weight or more of flame retardant needs to be added. This method of adding flame retardant tends to improve flame retardancy but also reduces other properties of the material, such as elongation and low-temperature performance.

[0005] In addition, flame retardants such as metal hydroxides are highly hygroscopic, so adding large amounts can sometimes lead to a decrease in electrical properties, making it difficult to maintain the required insulation performance.

[0006] On the other hand, insulated wires and cables used in railway vehicles, etc., require not only high flame retardancy and electrical insulation, but also fuel resistance, depending on the environment in which they are used. For example, in the fuel resistance test specified in EN60811-2-1, the material is immersed in IRM903 oil at 70°C, and the change rate of tensile strength and elongation of the material is measured.

[0007] As a method that combines high flame retardancy, electrical insulation, and fuel resistance, a method was considered that makes the outer layer a layer with high flame retardancy and fuel resistance, and the inner layer a layer with high electrical insulation.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2010-97881 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] The inventors of this invention are engaged in the research and development of coating materials such as the outer sheath of cables and the insulation layer of wires. As polymers for coating materials, they have studied resin compositions with good flame retardancy, oil resistance, fuel resistance, and low-temperature properties, using halogen-free materials.

[0013] In particular, insulated wires and cables used in railway vehicles and other applications, in addition to high flame retardancy and electrical insulation, are also required to have fuel resistance and other properties, depending on the environment in which they are used.

[0014] To improve fuel resistance, it is effective to use polymers that do not melt at the test temperature of 70°C, or polymers that are incompatible with IRM903 oil. While using the former type of polymer does improve fuel resistance, the addition of flame retardants and other additives significantly reduces elongation and other properties. Under stringent requirements such as EN45545 and NFPA130, it is difficult to simultaneously achieve both flame retardancy and elongation.

[0015] As for polymers incompatible with IRM903 oil, those with high polarity are effective. However, as mentioned above, high-melting-point polymers are difficult to possess simultaneously with flame retardancy and elongation properties. Examples of low-melting-point and highly polar polymers include high-VA EVA and high-EA EVA. Considering market availability, it is appropriate to have many grades of high-VA EVA available on the market. However, high-VA EVA generally lacks tensile strength, and the polymers fuse strongly together, making it unsuitable for use alone.

[0016] The present invention was made in view of the above-mentioned problems, and its object is to provide insulated wires and cables using a halogen-free resin composition with good flame retardancy, oil resistance, fuel resistance and low temperature characteristics.

[0017] Methods for solving problems

[0018] (1) An insulated wire according to one aspect of the present invention has a conductor, a first insulating layer covering the conductor, and a second insulating layer covering the first insulating layer. The first insulating layer is formed from a first halogen-free resin composition comprising a first base polymer and a filler. The second insulating layer is formed from a second halogen-free resin composition comprising a second base polymer and a metal hydroxide. The second base polymer comprises at least two polymers: an ethylene-vinyl acetate copolymer (EVA) with a vinyl acetate content (VA content) of 60% or more and a polyolefin polymer with a melting point of 85°C or more. The two polymers account for more than 80% of the second base polymer. The metal hydroxide is contained in a proportion of 150 to 250 parts by weight relative to 100 parts by weight of the second base polymer.

[0019] (2) For example, the first base polymer contains more than 50% polyethylene with a melting point of more than 110°C, and contains the filler in a proportion of less than 150 parts by weight relative to 100 parts by weight of the first base polymer.

[0020] (3) For example, the filler mentioned above is sintered clay or talc.

[0021] (4) For example, the cross-linked tensile strength is above 10 MPa and the elongation is above 150%. After being immersed in IRM903 oil at 70°C for 168 hours, the tensile strength change rate is within ±30% and the elongation change rate is within ±40%.

[0022] (5) For example, the first base polymer described above contains an acid-modified polyolefin.

[0023] (6) For example, the second base polymer is mixed with an acid-modified polyolefin, the glass transition temperature (Tg) of the acid-modified polyolefin is below -55°C, and the mass ratio of the two polymers to the acid-modified polyolefin is 80:20 to 99:1.

[0024] (7) For example, the metal hydroxides mentioned above include magnesium hydroxide or aluminum hydroxide, and the polyolefin polymers with a melting point of 85°C or above are ethylene-vinyl acetate copolymers (EVA).

[0025] (8) One aspect of the present invention is a cable having the above-mentioned insulated wires and a sheath covering the above-mentioned insulated wires.

[0026] (9) One aspect of the present invention is a cable having an insulated wire and a sheath covering the insulated wire, the sheath being formed of a halogen-free resin composition comprising a second base polymer and a metal hydroxide, wherein the second base polymer comprises at least two polymers, namely an ethylene-vinyl acetate copolymer (EVA) having a vinyl acetate content (VA content) of 60% or more and a polyolefin polymer having a melting point of 85°C or more, the two polymers comprising 80% or more of the second base polymer, and the metal hydroxide comprising in a proportion of 150 to 250 parts by weight relative to 100 parts by weight of the second base polymer.

[0027] (10) For example, the cross-linked tensile strength is 10 MPa or more and the elongation is 150% or more. After being immersed in IRM903 oil at 70°C for 168 hours, the tensile strength change rate is within ±30% and the elongation change rate is within ±40%.

[0028] The effects of the invention

[0029] According to one aspect of the present invention, insulated wires and cables using a halogen-free resin composition can improve flame retardancy, oil resistance, fuel resistance, and low-temperature properties. Attached Figure Description

[0030] Figure 1 A cross-sectional view showing an example of the structure of an insulated wire.

[0031] Figure 2 A cross-sectional view showing an example of cable construction.

[0032] Symbol Explanation

[0033] 11 Insulated wire, 11a Conductor, 11b Inner layer, 11c Outer layer, 12 Cable, 12d Sheath. Detailed Implementation

[0034] (Implementation Method 1)

[0035] Figure 1 This is a cross-sectional view showing an example of the structure of the insulated wire in this embodiment. Figure 1 The insulated wire 11 shown has a conductor 11a, an inner layer 11b, and an outer layer 11c.

[0036] As conductor 11a, metallic wires can be used, such as copper wire, copper alloy wire, aluminum wire, gold wire, silver wire, etc. Alternatively, conductors with tin, nickel, or other metal plating on the outer periphery of the metallic wire can also be used. Multiple metallic wires can be used as conductor 11a; twisted wires can also be used.

[0037] As the inner layer (insulating layer) 11b, a resin composition containing a first base polymer, fillers, and other additives can be used.

[0038] (First basic polymer)

[0039] Polyethylene (polyolefin), a polymer with excellent electrical insulation properties, can be used as the first base polymer. Preferably, polyethylene with a melting point of 110°C or higher is used. The melting point can be determined using differential scanning calorimetry (DSC). If the melting point is below 110°C, the crystals melt during the oil resistance test, making it difficult to prevent oil diffusion within the polymer, and increasing the rate of change in tensile properties.

[0040] To improve crystallinity, it is preferable to add crystalline polyethylene (polyolefin) with a melting point above 120°C.

[0041] Examples of polyethylene with a melting point of 110°C or higher include low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, and high-density polyethylene. The proportion of polyethylene with a melting point of 110°C or higher in the first base polymer is preferably 50% (50% by weight) or more, more preferably 60% to 80%. Thus, the first base polymer contains polyethylene with a melting point of 110°C or higher as a main component.

[0042] If filler acceptability is taken into consideration, it is preferable to include a rubber component in the first base polymer. That is, through the rubber component, the interface between polyethylene (polyolefin) and the filler is tightly bonded, which can prevent the polyethylene (polyolefin) from peeling off from the filler.

[0043] Examples of rubber components include ethylene-propylene copolymer rubber (EPR), ethylene-propylene-diene terpolymer rubber (EPDM), nitrile rubber (NBR), hydrogenated NBR (HNBR), acrylic rubber, ethylene-acrylate copolymer rubber, ethylene-octene copolymer rubber (EOR), ethylene-vinyl acetate copolymer rubber, ethylene-1-butene copolymer rubber (EBR), butadiene-styrene copolymer rubber (SBR), isobutylene-isoprene copolymer rubber (IIR), block copolymer rubber containing polystyrene blocks, and polyurethane rubber. Among these, EOR and EBR, lacking double bonds, eliminate the risk of scorching during extrusion. Furthermore, their lack of polarity allows for the acquisition of high electrical properties. Therefore, EOR and EBR are preferred rubber components.

[0044] Furthermore, to obtain high electrical properties, acid-modified polyolefins (products of polyolefins modified with acid) are preferred. Examples of acids that can be used as acid-modified polyolefins include maleic acid, maleic anhydride, and fumaric acid. Examples of polyolefins that can be used as acid-modified polyolefins include polyethylene, ethylene-α-olefin, ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, and vinyl acetate copolymer. Among these, acid-modified polyolefins with a glass transition temperature (Tg) of -55°C or lower are preferred.

[0045] (filler)

[0046] A filler is added to the first base polymer. Here, in this specification, a filler refers to an inorganic substance added to the base polymer, and is a component added at least 20 parts by weight relative to 100 parts by weight of the first base polymer. However, if the amount of filler is too large, the elongation at break will decrease; therefore, the amount of filler added relative to 100 parts by weight of the first base polymer is preferably 150 parts by weight or less.

[0047] Fillers may be omitted, but adding fillers reduces the proportion of organic matter in the resin composition. Because the proportion of organic matter (polymer, rubber components) is reduced, toxic gases such as carbon monoxide and carbon dioxide produced during combustion are reduced. The amount of filler added is more preferably 20 to 130 parts by weight, and even more preferably 50 to 100 parts by weight, relative to 100 parts by weight of the first base polymer.

[0048] Examples of fillers include silicates such as kaolinite, kaolin clay, calcined clay, talc, mica, wollastonite, and pyrophyllite; oxides such as silicon dioxide, aluminum oxide, zinc oxide, titanium oxide, calcium oxide, and magnesium oxide; carbonates such as calcium carbonate, zinc carbonate, and barium carbonate; and hydroxides such as calcium hydroxide, magnesium hydroxide, and aluminum hydroxide. These materials can be used alone or in combination of two or more.

[0049] Among the aforementioned materials, hydrophobic sintered clay and talc not only exhibit high electrical properties but also, due to their carbon-free nature, suppress carbon monoxide production, making them preferred as fillers. Furthermore, surface-treated materials can be used as fillers. For example, the aforementioned materials can utilize fillers that have undergone surface treatment of silanes. By surface-treating the silanes, the bond between the filler and the polymer becomes stronger, thereby improving insulation performance.

[0050] (Other additives)

[0051] The resin composition may contain crosslinking aids, flame retardants, ultraviolet absorbers, light stabilizers, softeners, lubricants, colorants, reinforcing agents, surfactants, plasticizers, metal passivators, foaming agents, compatibilizers, processing aids, stabilizers, etc., as needed.

[0052] As the outer layer (insulating layer) 11c, a halogen-free resin composition containing a second base polymer, fillers, and other additives can be used.

[0053] (Second basic polymer)

[0054] The second basic polymer comprises two polymers: an ethylene-vinyl acetate copolymer (EVA) with a vinyl acetate content (VA) of 60% or more, and a polyolefin polymer with a melting point of 85°C or higher. Here, "two polymers" refers to a group of polymers. The ethylene-vinyl acetate copolymer (EVA) with a vinyl acetate content (VA) of 60% or more can include multiple polymers. Similarly, the polyolefin polymer with a melting point of 85°C or higher can also include multiple polymers. Furthermore, the polyolefin polymer with a melting point of 85°C or higher can also be an ethylene-vinyl acetate copolymer (EVA).

[0055] As for the aforementioned EVA, there are no particular limitations if the VA content is 60% or more. However, since low-temperature properties tend to decrease as the VA content increases, it is preferable to have a VA content of 60-80%, more preferably 60-70%, when low-temperature properties are required. "VA content [%)" refers to the vinyl acetate content in the ethylene-vinyl acetate copolymer. This VA content can be determined based on JIS K7192.

[0056] As for the aforementioned polyolefin polymers, there are no particular limitations as long as the melting point is above 85°C. Examples include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), linear ultra-low-density polyethylene (VLDPE), high-density polyethylene (HDPE), polypropylene (PP), ethylene-ethyl acrylate copolymer (EEA), and ethylene-vinyl acetate copolymer (EVA). Among these, EVA with a melting point above 85°C is preferred. However, since higher crystallinity leads to a decrease in physical properties such as elongation with the addition of fillers, EVA with a VA content of about 17% and a melting point of about 89°C is more preferred.

[0057] Both of the above polymers are necessary. As for their ratio, there is no particular limitation. The ratio of EVA with a VA content of 60% or more to polyolefin polymer with a melting point of 85°C or more is preferably 1:2 to 2:1 (the former is about 33% to 66% and the latter is about 66% to 33%), more preferably 4:6 to 6:4 (the former is 40% to 60% and the latter is 60% to 40%).

[0058] The second base polymer may include other polymers. These other polymers can be added within a specified range. That is, since the second base polymer contains at least 80% of the two essential polymers—ethylene-vinyl acetate copolymer (EVA) with a vinyl acetate content (VA) of at least 60% and a polyolefin polymer with a melting point of at least 85°C—other polymers can be included within the remaining range of less than 20%, provided they do not overlap with the aforementioned two polymers. Examples of other polymers include, for instance, low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), linear ultra-low-density polyethylene (VLDPE), high-density polyethylene (HDPE), polypropylene (PP), ethylene-ethyl acrylate copolymer (EEA), ethylene-vinyl acetate copolymer (EVA), ethylene-styrene copolymer, ethylene-glycidyl methacrylate copolymer, ethylene-1-butene copolymer, ethylene-butene-hexene terpolymer, ethylene-propylene-diene terpolymer (EPDM), and ethylene-octene copolymer (EOR). Ethylene copolymer polypropylene, ethylene-propylene copolymer (EPR), poly4-methyl-1-pentene, maleic acid-grafted low-density polyethylene, hydrogenated styrene-butadiene copolymer (H-SBR), maleic acid-grafted linear low-density polyethylene, copolymer of ethylene with α-olefins having 4 to 20 carbon atoms, ethylene-styrene copolymer, maleic acid-grafted ethylene-methyl acrylate copolymer, maleic acid-grafted ethylene-vinyl acetate copolymer, ethylene-maleic anhydride copolymer, ethylene-ethyl acrylate-maleic anhydride terpolymer, ethylene-propylene-1-butene terpolymer with 1-butene as the main component, etc.

[0059] In addition, acid-modified polyolefins (polymers in which polyolefins have been modified with acid) can be used as other polymers. Acid-modified polyolefins with a glass transition temperature of -55°C or lower are particularly preferred. The glass transition temperature refers to the glass transition temperature determined by DSC. Acid-modified polyolefins are products obtained by grafting or copolymerizing polyolefins with acids such as maleic anhydride. Examples of polyolefins that can be used as acid-modified polyolefins include natural rubber, butyl rubber, ethylene-propylene rubber, ethylene-α-olefin copolymers, styrene-butadiene rubber, nitrile rubber, acrylic rubber, silicone rubber, polyurethane rubber, polyethylene, polypropylene, ethylene-vinyl acetate copolymers, polyvinyl acetate, ethylene-ethyl acrylate copolymers, ethylene-acrylate copolymers, polyurethane, ultra-low density polyethylene, ethylene-methyl acrylate copolymers, ethylene-ethyl acrylate copolymers, ethylene-1-butene copolymers, ethylene-1-hexene copolymers, and ethylene-1-octene copolymers. Ethylene-propylene rubber, ethylene-α-olefin copolymers, and ethylene-ethyl acrylate copolymers are particularly preferred.

[0060] In addition to maleic anhydride, other acids used as materials for acid-modified polyolefins include maleic acid and fumaric acid. These acid-modified polyolefins can be added alone or in combination with two or more.

[0061] Furthermore, the preferred mass ratio of the two polymers to the acid-modified polyolefin is 80:20 to 99:1.

[0062] (Metal hydroxides)

[0063] The second base polymer contains a metal hydroxide. The metal hydroxide acts as a flame retardant. Examples of metal hydroxides include magnesium hydroxide, aluminum hydroxide, and calcium hydroxide. Magnesium hydroxide is preferred. Furthermore, the aforementioned metal hydroxides can be used alone or in combination. Additionally, metal hydroxides that have undergone surface treatment using silane coupling agents, titanate coupling agents, fatty acids such as stearic acid or calcium stearate, or fatty acid metal salts can also be used.

[0064] The amount of metal hydroxide added relative to 100 parts by weight of the second base polymer is preferably 150 to 250 parts by weight, more preferably 180 to 220 parts by weight. When it is less than 150 parts by weight, sufficient flame retardancy cannot be obtained, and if it is more than 250 parts by weight, elongation characteristics and other properties are reduced.

[0065] (Other additives)

[0066] In the second base polymer, other additives may be added as needed. Examples of other additives include antioxidants, metal passivators, flame retardants other than the aforementioned metal hydroxides, crosslinking agents, crosslinking aids, lubricants, fillers other than the aforementioned fillers, compatibilizers, stabilizers, carbon black, and colorants.

[0067] Examples of antioxidants include phenolic, sulfur-based, amine-based, and phosphorus-based antioxidants.

[0068] Examples of phenolic antioxidants include butylated hydroxytoluene (BHT), pentaerythritol tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-triazine-2,4,6-(1H,3H,5H)trione, and thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. Pentaerythritol tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] is preferred among these.

[0069] Examples of sulfur-based antioxidants include di(dodecyl)-3,3'-thiodipropionate, di(tetranyl)-3,3'-thiodipropionate, di(octadecyl)-3,3'-thiodipropionate, and tetra[methylene-3-(dodecylthio)propionate]methane. Tetra[methylene-3-(dodecylthio)propionate]methane is preferred among these.

[0070] These antioxidants can be added individually or in combination with two or more.

[0071] Metal passivating agents stabilize metal ions through chelation formation, thus inhibiting oxidative degradation. Examples of metal passivating agents include N-(2H-1,2,4-triazol-5-yl)salicylic acid amide, dodecanoic acid bis[N2-(2-hydroxybenzoyl)hydrazide], and 2',3-bis[[3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionyl]]propionylhydrazide. 2',3-bis[[3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionyl]]propionylhydrazide is preferred.

[0072] Other flame retardants besides metal hydroxides include zinc compounds such as amorphous silica, zinc stannate, zinc hydroxystannate, zinc borate, and zinc oxide; borate compounds such as calcium borate, barium borate, and barium metaborate; phosphorus-based flame retardants; nitrogen-based flame retardants such as melamine cyanurate; and intumescent flame retardants formed from a mixture of components that foam during combustion and components that solidify.

[0073] As crosslinking aids, preferred materials include, for example, trimethylolpropane trimethacrylate (TMPT) and triallyl isocyanurate (TAIC).

[0074] Examples of lubricants include fatty acids, fatty acid metal salts, and fatty acid amides. Specifically, zinc stearate can be used. These lubricants can be added individually or in combination with more than one type.

[0075] As carbon black, for example, rubber-grade carbon black (N900-N100: ASTM D 1765-01) can be used.

[0076] As a colorant, a color masterbatch for the outer 11c layer can be used, for example.

[0077] (crosslinking)

[0078] The inner layer 11b and outer layer 11c used in the aforementioned insulated wire are obtained by crosslinking the mixture of the aforementioned materials (resin composition). As a crosslinking method, an irradiation crosslinking method can be mentioned, in which the mixture of the aforementioned materials (resin composition) is molded and then irradiated with electron beams, radiation, etc., to crosslink it. In the case of implementing the irradiation crosslinking method, a crosslinking aid can be added to the mixture of the aforementioned materials (resin composition) beforehand. Alternatively, a chemical crosslinking method can be used, in which crosslinking is achieved by heating. In the case of implementing the chemical crosslinking method, a crosslinking agent can be added to the mixture of the aforementioned materials (resin composition) beforehand. As a crosslinking agent, an organic peroxide can be used. Examples of organic peroxides include 1,3-bis(2-tert-butylperoxyisopropyl)benzene and dicumyl peroxide (DCP).

[0079] Alternatively, the inner layer 11b and the outer layer 11c can be cross-linked simultaneously. In addition, after the inner layer 11b is cross-linked, the outer layer 11c can be formed on its periphery for cross-linking.

[0080] (Application Example 1)

[0081] Figure 1 The example shown depicts conductor 11a covered with a two-layer insulation layer (inner layer 11b and outer layer 11c), but a configuration where conductor 11a is covered with a single-layer insulation layer is also possible. Even in this case, by using the same material as the outer layer 11c described above to construct a single-layer insulation layer, it is possible to obtain an insulated wire with excellent properties.

[0082] (Application Example 2)

[0083] Figure 1 As in Application Example 1 above, a halogen-free resin composition applied to insulated wires was used as an example, but the halogen-free resin composition of this embodiment can also be used as a cable sheath.

[0084] Figure 2 A cross-sectional view showing the configuration of the cable in Application Example 2. Figure 2 The cable 12 shown has two insulated wires 11 twisted together (see reference). Figure 1 The cable 12 consists of a sheath (outer sheath, coating layer) 12d located outside the twisted wires. The sheath 12d can be made of the same material as the outer layer 11c described above. Furthermore, the cable 12 may contain one insulated wire 11, or three or more. Additionally, a spacer or shielding braid may be provided between the two twisted insulated wires 11 and the sheath 12d. The material of the spacer is not particularly limited and can be provided inside or outside the shielding braid.

[0085] The aforementioned insulated wires and cables can be used as halogen-free insulated wires or halogen-free cables. For example, applications in railway vehicles can be considered. That is, they can be used as halogen-free insulated wires and halogen-free cables for railway vehicles.

[0086] [Example]

[0087] The following examples will be used to further illustrate the insulated wires using the halogen-free resin composition of this embodiment.

[0088] Insulated wires made using halogen-free resin compositions are manufactured as follows.

[0089] (Material Name)

[0090] The materials used in the examples and comparative examples are shown in Tables 1 and 3. The specific material names are as follows.

[0091] ・PE 1 Prime Polymer's "Evolue SP1510" (melting point 117°C)

[0092] ・PE 2 Prime Polymer's "Evolue SP4030" (melting point 127°C)

[0093] EBR 3 ): Mitsui Chemicals Co., Ltd.'s "Tafmer DF840"

[0094] • Acid-modified polyolefins 4 ): Mitsui Chemicals Co., Ltd. "Tafmer MH7020" (glass transition temperature (Tg) ≤ -55℃)

[0095] • Firing clay 5 ): BASF's "Translink 37"

[0096] • Antioxidants 6 ): AO-18 manufactured by Adico Corporation

[0097] Copper damage prevention agent 7 ): CDA-6 manufactured by Adico Corporation

[0098] Lubricant 8 Zinc stearate manufactured by Nitto Kasei Corporation

[0099] EVA 9 Lanxess "Levapren 600" (VA content: 60%, melting point: none)

[0100] EVA 10Lanxess "Levapren 800" (VA content: 80%, melting point: none)

[0101] EVA 11 ): EVAFLEX V5274 manufactured by Mitsui-DuPont Polymer Chemicals Co., Ltd.

[0102] (VA content: 17%, melting point: 89℃)

[0103] EVA 12 ): EVAFLEX P1007 manufactured by Mitsui-DuPont Polymer Chemicals Co., Ltd.

[0104] (VA content: 10%, melting point: 94℃)

[0105] •EEA 13 ): REXPEARL A1150 manufactured by Japan Polyethylene Co., Ltd.

[0106] (EA content: 15%, melting point: 100℃)

[0107] • Acid-modified polyolefins 14 ): Mitsui Chemicals Co., Ltd. "Tafmer MH7020" (glass transition temperature (Tg) ≤ -55℃)

[0108] Magnesium hydroxide 15 ): MAGSEEDS S4, manufactured by Shinjima Chemical Industry Co., Ltd.

[0109] • Antioxidants 16 ): AO-18 manufactured by Adico Corporation

[0110] • Carbon black 17 ): Asahi Carbon Corporation's "FT Carbon"

[0111] Lubricant 18 Zinc stearate manufactured by Nitto Kasei Corporation

[0112] ・PE 19 Prime Polymer's "Evolue SP0510" (melting point 98°C)

[0113] EVA 20 ): EVAFLEX V9000 manufactured by Mitsui-DuPont Polymer Chemicals.

[0114] (VA content: 41%, melting point: none)

[0115] EVA 21 ): EVAFLEX EV260 manufactured by Mitsui-DuPont Polymer Chemicals.

[0116] (VA content: 28%, melting point: 72℃)

[0117] (Making Insulated Wires)

[0118] In Examples 1-10, the inner and outer layers were manufactured using the formulations shown in Table 1. Furthermore, in Comparative Examples 1-7, the inner and outer layers were manufactured using the formulations shown in Table 3 (see Table 3). Figure 1 That is, the compounding materials for the inner layer or the compounding materials for the outer layer shown in Tables 1 and 3 are mixed using a pressure kneader at a starting temperature of 40°C and an ending temperature of 190°C, so that the mixture becomes granular. The granular resin composition is then used to form insulated wires.

[0119] Here, a 40mm extruder is used to extrude two layers around a conductor consisting of 37 tin-plated conductors with a diameter of 0.18mm, forming an inner layer of 0.3mm thickness and an outer layer of 0.47mm thickness, thus simultaneously forming the inner and outer layers. Then, the inner and outer layers are cross-linked by irradiation with 7.5MRad electron beams.

[0120] (1) Tensile test

[0121] The conductor is pulled out of the insulated wire, and a tube consisting of an inner and outer layer is made. The tube is cut to obtain a test piece with markings spaced at predetermined intervals. At room temperature (25°C), the test piece is stretched at a displacement speed of 250 mm / min, and the load and elongation at break are measured. The tensile strength (in MPa) is calculated from the load. Furthermore, the elongation at break ((Lb-La / La)×100%) is calculated from the initial length (marking distance) La and the elongation (length between marks at break) Lb. A tensile strength of 10 MPa or more and an elongation of 150% or more are considered as... (qualified).

[0122] (2) Fuel resistance test

[0123] The conductor is pulled out of the insulated wire, and a tube consisting of an inner and outer layer is made. The tube is cut to obtain test pieces marked with predetermined intervals. The test pieces are immersed in IRM903 test oil heated to 70°C for 168 hours, then left at room temperature for approximately 16 hours. The test pieces are then stretched at a displacement speed of 250 mm / min, and the load and elongation at break are measured. The change rate of tensile strength against fuel ((A2-A1) / A1)×100 [%) and the change rate of elongation at break against fuel ((B2-B1) / B1)×100 [%) are calculated from the tensile strength (A1) and elongation at break (B1) of the test piece before immersion in the test oil, and from the tensile strength (A2) and elongation at break (B2) of the test piece after immersion in the test oil. A decrease in tensile strength or elongation at break after immersion is marked as "- (negative)". If the rate of change of tensile strength in fuel-resistant materials (tensile strength retention rate) is within ±30%, then it is set as... (Qualified) If the change rate of elongation at break (residual elongation at break) is within ±40%, then it is set as qualified. (qualified).

[0124] (3) Oil resistance test

[0125] The conductor is pulled out of the insulated wire, and a tube consisting of an inner and outer layer is made. The tube is cut to obtain test pieces marked with predetermined intervals. The test pieces are immersed in IRM902 test oil heated to 100°C for 72 hours, then left at room temperature for approximately 16 hours. The test pieces are then stretched at a displacement speed of 250 mm / min, and the load and elongation at break are measured. The oil-resistant tensile strength change rate ((A2-A1) / A1)×100 [%) and the oil-resistant elongation at break change rate ((B2-B1) / B1)×100 [%) are calculated from the tensile strength (A1) and elongation at break (B1) of the test piece before immersion in the test oil, and from the tensile strength (A2) and elongation at break (B2) of the test piece after immersion in the test oil. A decrease in "tensile strength" or "elongation at break" after immersion is marked as "- (negative)". If the rate of change of oil-resistant tensile strength (residual tensile strength) is within ±30%, then it is set as (Qualified) If the change rate of oil-resistant elongation at break (residual elongation at break) is within ±40%, then it is set as qualified. (qualified).

[0126] (4) Low temperature test

[0127] The conductor is pulled out of the insulated wire, and a tube consisting of an inner and outer layer is made. The tube is cut to obtain a test piece marked with predetermined intervals. The test piece is held at -40°C and stretched at a displacement speed of 30 mm / min in an atmosphere at -40°C, and the elongation (L2) until fracture is measured. The low-temperature elongation ((L2 / L1)×100 [%)) is calculated from the initial length L1 and the elongation L2. A low-temperature elongation of 30% or more is considered... (qualified).

[0128] (5) Flame retardancy test

[0129] (5-1) Vertical Burning Test

[0130] As part of the flame retardancy test according to EN60332-1-2, a vertical burning test (VFT) was conducted. A 600mm length of insulated wire was cut as a test piece. The test piece was held vertically, and a flame was brought close for 60 seconds before the flame was removed. The fire extinguished within 60 seconds under this condition was considered extinguished. (Pass) If the fire is not extinguished within 60 seconds, it will be marked as × (Fail).

[0131] (5-2) Vertical bracket combustion test

[0132] A vertical bracket burning test (VTFT) according to EN50266-2-4 was conducted. Seven 3.5m long insulated wires were prepared, twisted into one core bundle, and arranged vertically at equal intervals. After burning for 20 minutes from the bottom, the wires were allowed to self-extinguish, and the charred length from the bottom was measured. Cases with a charred length of less than 2.5m were considered as... (Pass) Cases with a carbonization length exceeding 2.5m are marked as × (Fail). Additionally, cases with a carbonization length of less than 1.5m are marked as... (excellent).

[0133] (6) Insulation test

[0134] DC stability tests were conducted according to EN50305 6.7. The condition where no insulation breakdown occurred was considered... (Pass) indicates that insulation breakdown has occurred, and (Fail) indicates that the condition has been marked as ×.

[0135] The test results of Examples 1 to 10 are shown in Table 2, and the test results of Comparative Examples 1 to 7 are shown in Table 4.

[0136] [Table 1]

[0137]

[0138] [Table 2]

[0139]

[0140] [Table 3]

[0141]

[0142] [Table 4]

[0143]

[0144] (Inspection)

[0145] The following matters were examined based on the above embodiments and comparative examples.

[0146] As shown in Tables 1 and 2, it was confirmed that in Examples 1 to 10, while maintaining high flame retardancy, fuel resistance, insulation properties, and other properties (tensile properties, oil resistance, low-temperature properties, etc.) were also good.

[0147] Compared to Example 1, in Examples 2 and 4, where the amount of inner filler (inorganic filler) added is higher, the tensile strength is improved with the increase in the amount of filler added. Furthermore, in Example 4, where the amount of filler added is increased to 150 parts by weight, the vertical burning test (VFT) result in terms of flame retardancy is... (Pass), Vertical Bracket Flammability Test (VTFT) result is: (Excellent), a good result was achieved.

[0148] Compared to Example 1, in Example 3, where a high-melting-point PE (melting point 127°C) was used as the first base polymer (polymer) for the inner layer, oil resistance was improved.

[0149] In Examples 5 and 6, where an outer flame retardant was added at amounts of 150 or 250 parts by weight, all properties were good. Comparison with other examples and comparative examples shows that the amount of metal hydroxide added can be increased or decreased within the range of 150 to 250 parts by weight. This indicates a tendency for lower amounts of metal hydroxide to improve elongation and low-temperature properties, and a tendency for higher amounts to improve flame retardancy.

[0150] This demonstrates that even in Examples 7-10, where the type and amount of the outer polymer were changed, the properties were good, and in Example 8, where the amount of acid-modified polyolefin added was as high as 20 parts by weight, the low-temperature properties were improved.

[0151] On the other hand, in Comparative Example 1, the inner layer did not contain polyethylene with a melting point of 110°C or higher, resulting in substandard oil resistance. From this and other examples and comparative examples, it is clear that the inner layer preferably contains polyethylene with a melting point of 110°C or higher. Furthermore, it is more preferable that the inner layer contains an acid-modified polyolefin.

[0152] In Comparative Example 2, no polyolefin (EVA) with a melting point above 85°C was added to the outer layer. 10 The tensile strength and low-temperature properties were unsatisfactory. Furthermore, in Comparative Example 2, after two-layer extrusion, fusion (adhesion) was observed between the insulated wires before cross-linking. In Comparative Example 3, the outer layer did not contain EVA with a VA content of 60% or more, resulting in unsatisfactory elongation and flame retardancy. Comparative Example 4, which did not contain either a polyolefin with a melting point of 85°C or higher and EVA with a VA content of 60% or higher, and Comparative Example 5, where the combined content of both was less than 80% of the polymer weight, showed unsatisfactory fuel resistance. From these observations, it is clear that the outer layer preferably uses a second base polymer in which at least two polymers—ethylene-vinyl acetate copolymer (EVA) with a vinyl acetate content (VA) of 60% or higher and a polyolefin polymer with a melting point of 85°C or higher—account for more than 80% of the total polymer content.

[0153] Furthermore, in Comparative Example 6, where the outer layer of metal hydroxide was as little as 120 parts by weight, the flame retardancy was unsatisfactory; and in Comparative Example 7, where the outer layer of metal hydroxide was as much as 280 parts by weight, the elongation and low-temperature properties were unsatisfactory. From these factors and other examples, it is clear that the outer layer of metal hydroxide is preferably set to 150 to 250 parts by weight.

[0154] This invention is not limited to the above-described embodiments and examples, and various modifications can be made without departing from its spirit. For example, the above embodiments were described using an insulated wire as an example, but a cable can also be manufactured for evaluation. For example, the internal structure of the cable sheath can be pulled out, and the same evaluation can be performed as in the case of the insulated wire.

Claims

1. An insulated wire, comprising a conductor, a first insulating layer covering the conductor, and a second insulating layer covering the first insulating layer. The first insulating layer is formed from a first halogen-free resin composition comprising a first base polymer and a filler. The second insulating layer is formed of a second halogen-free resin composition comprising a second base polymer and a metal hydroxide. The second basic polymer comprises two polymers: ethylene-vinyl acetate copolymer (EVA) with a vinyl acetate content (VA) of 60% or more, and ethylene-vinyl acetate copolymer with a melting point of 85°C or higher. These two polymers account for more than 80% of the second basic polymer. The metal hydroxide is contained in a proportion of 150 to 250 parts by weight relative to 100 parts by weight of the second base polymer. The first base polymer contains more than 50% polyethylene with a melting point of 110°C or higher. The filler is contained in a proportion of 150 parts by weight or less relative to 100 parts by weight of the first base polymer. The first base polymer contains an acid-modified polyolefin.

2. The insulated wire according to claim 1, wherein the filler is calcined clay or talc.

3. The insulated wire according to claim 1, The cross-linked tensile strength is above 10 MPa and the elongation is above 150%. The tensile strength change rate after immersion in IRM903 oil at 70°C for 168 hours is within ±30%, and the elongation change rate is within ±40%.

4. The insulated wire according to claim 1, The second base polymer contains an acid-modified polyolefin. The glass transition temperature (Tg) of the acid-modified polyolefin is below -55°C. The mass ratio of the two polymers to the acid-modified polyolefin is 80:20 to 99:

1.

5. The insulated wire according to claim 1, The metal hydroxide includes magnesium hydroxide or aluminum hydroxide.

6. A cable having insulated wires and a sheath covering the insulated wires, The insulated wire has any one of claims 1 to 5.

7. A cable having insulated wires and a sheath covering the insulated wires, The sheath is formed from a halogen-free resin composition comprising a second base polymer and a metal hydroxide. The second basic polymer comprises two polymers: ethylene-vinyl acetate copolymer (EVA) with a vinyl acetate content (VA) of 60% or more, and ethylene-vinyl acetate copolymer with a melting point of 85°C or higher. These two polymers account for more than 80% of the second basic polymer. The metal hydroxide is contained in a proportion of 150 to 250 parts by weight relative to 100 parts by weight of the second base polymer. The second base polymer contains an acid-modified polyolefin.

8. The cable according to claim 7, The cross-linked tensile strength is above 10 MPa and the elongation is above 150%. The tensile strength change rate after immersion in IRM903 oil at 70°C for 168 hours is within ±30%, and the elongation change rate is within ±40%.

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