Wires and cables

Abstract

Provided is an electric wire and cable having high properties in flame retardancy and electric insulation. An electric wire (10) has a conductor (11), an insulating layer (first insulating layer) (12) having a base polymer containing a polyolefin and covering the conductor (11), and an insulating layer (second insulating layer) (13) having a base polymer containing a polyolefin and covering the insulating layer (12). The insulating layer (12) has 130 to 200 parts by mass of aluminum hydroxide added per 100 parts by mass of the polyolefin. The surface area of the aluminum hydroxide in the resin composition per unit volume of the insulating layer (12) is 3.7 m 2 / ml or more. The insulating layer (13) is a halogen-free resin composition having 150 to 250 parts by mass of magnesium hydroxide added per 100 parts by mass of the polyolefin and containing a vinyl acetate copolymer as a main component of the polyolefin. The insulating layer (12) and the insulating layer (13) are crosslinked, respectively.

Description

Technical Field

[0001] This invention relates to wires and cables using the same. Background Technology

[0002] For example, railway vehicles use multiple cables, such as power lines and control lines for motors and other components. These cables require high flame retardancy and electrical insulation properties.

[0003] To obtain high flame retardancy, for example, there are methods that incorporate a large amount of metal hydroxide into polyolefin resins (see, for example, Patent Document 1 and Patent Document 2).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2004-186011

[0007] Patent Document 2: Japanese Patent Application Publication No. 2014-53247 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] The inventors of this application have researched techniques to improve the flame retardancy and electrical insulation properties of wires and cables using them. For example, Patent Document 1 described above discloses an insulation layer in which a styrene-based elastomer and ethylene propylene rubber are added as materials constituting the outer insulation layer; however, the formulation described in Patent Document 1 cannot achieve sufficient oil resistance. Furthermore, an insulation layer containing magnesium hydroxide is also described as the inner insulation layer; however, magnesium hydroxide tends to contain many impurity ions, which can sometimes cause a decrease in the electrical properties of the wire. In addition, when a highly polar ethylene acrylate copolymer is used as the base polymer for the inner insulation layer, its high hygroscopicity can sometimes cause a decrease in the electrical properties of the wire. Furthermore, as described in the aforementioned patent documents, when a vinyl acetate copolymer with an acetic acid content of 30% or more is used as the base polymer for the insulation layer, the excessive adhesiveness of the wire surface sometimes makes cross-linking treatment by electron beam irradiation difficult.

[0010] The purpose of this invention is to provide wires and cables with high properties in terms of flame retardancy and electrical insulation.

[0011] Methods for solving problems

[0012] As one embodiment of the wire, [1] it has a conductor, a first insulating layer comprising a base polymer containing a polyolefin and covering the conductor, and a second insulating layer comprising a base polymer containing a polyolefin and covering the first insulating layer. The first insulating layer contains 130 to 200 parts by mass of aluminum hydroxide relative to 100 parts by mass of polyolefin. The surface area of ​​aluminum hydroxide in each unit volume of the resin composition of the first insulating layer is 3.7 m². 2 / ml or more. The second insulating layer is a halogen-free resin composition containing 150-250 parts by weight of magnesium hydroxide added per 100 parts by weight of polyolefin, and having ethylene-vinyl acetate copolymer as the main component of the polyolefin. The first insulating layer and the second insulating layer are crosslinked separately.

[0013] [2] For example, in [1], the first insulating layer contains polyethylene with a melting point of 110°C or higher as the main component of the polyolefin, and does not contain vinyl acetate copolymer and ethylene acrylic acid copolymer as minor components.

[0014] [3] For example, in [1] or [2], the first insulating layer contains an acid-modified polyolefin as a minor component of the polyolefin. The acid-modified polyolefin contains one or more of polyethylene, ethylene-α-olefin and ethylene-acrylic acid copolymer.

[0015] [4] For example, in any of [1] to [3], the conductivity of the aluminum hydroxide contained in the first insulating layer when suspended in pure water is less than 20 μS / cm.

[0016] [5] For example, in any of [1] to [3], the second insulating layer contains an ethylene-vinyl acetate copolymer with a melting point of 80°C or higher as the main component of the polyolefin.

[0017] In addition, in another embodiment of the cable, [6] there are multiple wires and a sheath covering the multiple wires, at least a portion of which are wires as described in any one of [1] to [5].

[0018] Invention Effects

[0019] According to representative embodiments of the present invention, wires and cables with high properties in flame retardancy and electrical insulation can be obtained. Attached Figure Description

[0020] Figure 1 A cross-sectional view showing a structural example of an electrical wire as one embodiment.

[0021] Figure 2 To display including Figure 1 A cross-sectional view of the cable structure of the wire shown.

[0022] Symbol Explanation

[0023] 10: Wire; 11: Conductor; 12: Insulation layer (first insulation layer); 13: Insulation layer (second insulation layer). Detailed Implementation

[0024] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0025] <Example of basic structure of wires and cables>

[0026] Figure 1 A cross-sectional view showing a structural example of an electrical wire as one embodiment. Figure 2 To display including Figure 1 A cross-sectional view of the cable structure of the wire shown.

[0027] Figure 1 The wire 10 shown has a conductor 11, an insulating layer (first insulating layer) 12 covering the conductor 11, and an insulating layer (second insulating layer) 13 covering the insulating layer 12. The wire 10 is a double-insulated wire with two insulating layers. As described below, insulating layers 12 and 13 are cross-linked. The wire 10 can be referred to as a double-cross-linked insulated wire. Furthermore, as described below, insulating layers 12 and 13 of the wire 10 each contain a flame retardant. The wire 10 can be referred to as a double-cross-linked flame-retardant insulated wire.

[0028] Figure 2 The cable 20 shown has multiple wires 10 and a sheath (insulation layer, third insulation layer) 21 covering the multiple wires 10. Figure 2 The example shown illustrates a case where the sheath 21 covers two wires 10. However, the number of wires 10 within the sheath 21 is not limited to two; for example, there may be three or more. Furthermore, it is preferable to... Figure 2 As shown, all the wires covered by the sheath 21 are wires 10; as a variation, there are cases where wires with different structures from wires 10 are covered by the sheath 21 together with wires 10.

[0029] The features of the wire 10 will be described below as an inner insulating layer 12 and an outer insulating layer 13.

[0030] <Insulation Layer 12>

[0031] In the inner insulating layer 12, the base polymer is mainly composed of polyolefin (50% by weight or more of the base polymer is polyolefin). The insulating layer 12 preferably contains aluminum hydroxide as a flame retardant. Magnesium hydroxide is a commonly used metal hydroxide as a flame retardant. Magnesium hydroxide tends to contain many impurity ions, which can sometimes cause a decrease in the electrical properties of the wire. On the other hand, using aluminum hydroxide as a flame retardant improves the electrical properties of the wire 10 compared to using magnesium hydroxide.

[0032] Specifically, the surface area of ​​aluminum hydroxide per unit volume in the resin composition (composition containing a base polymer and fillers) constituting the insulating layer 12 must be 3.7 m². 2 / ml or more. In addition, when the polyolefin contained in the insulating layer 12 is set to 100 parts by weight, the amount of aluminum hydroxide added must be 130 to 200 parts by weight (more than 130 parts by weight and less than 200 parts by weight).

[0033] It is generally believed that a smaller interface area between the base polymer and the filler (in other words, the surface area of ​​the filler) better prevents moisture intrusion. Following this logic, the less filler added and the smaller the filler surface area, the better. However, according to the inventors' research, when the polyolefin content in the insulating layer 12 is set to 100 parts by mass, even with an aluminum hydroxide addition exceeding 100 parts by mass, the surface area of ​​the aluminum hydroxide is less than 3.7 m². 2 At a concentration of / ml, insulation failure may occur; the surface area of ​​aluminum hydroxide is 3.7m². 2 At concentrations above a certain level (e.g., 1 ml), insulation failure is not considered to occur. The mechanism is not fully understood, but the following can be hypothesized: It is believed that insulation failure caused by aluminum hydroxide filler is influenced not only by the insulation resistance of the resin composition but also by electrolytic strain. It is also believed that if the amount of aluminum hydroxide added to the insulating layer 12 increases, the insulation resistance of the resin composition decreases, but the surface area of ​​aluminum hydroxide is 3.7 m². 2 When the value is above / ml, the electrolytic strain also decreases, thus preventing insulation failure.

[0034] Furthermore, from the viewpoint of imparting sufficient flame retardancy to the insulation layer 12, when the polyolefin contained in the insulation layer 12 is set to 100 parts by mass, the amount of aluminum hydroxide added needs to be at least 130 parts by mass. For example, if the amount of aluminum hydroxide added is less than 130 parts by mass, although insulation failure of the insulation layer 12 will not occur, the flame retardancy will be insufficient. However, if the amount of aluminum hydroxide added exceeds 200 parts by mass, even if the surface area of ​​the aluminum hydroxide is 3.7 m², there is a risk of insufficient flame retardancy. 2Insulation failure can also occur if the amount of aluminum hydroxide added exceeds 200 parts by mass. Furthermore, if the amount of aluminum hydroxide added exceeds 200 parts by mass, the mechanical properties of the insulation layer 12, such as its elongation characteristics, decrease. Therefore, when the polyolefin contained in the insulation layer 12 is set to 100 parts by mass, the amount of aluminum hydroxide added should be 130 to 200 parts by mass.

[0035] Furthermore, from the viewpoint of improving the electrical properties of the wire 10, the following configuration is preferred: the conductivity of the aluminum hydroxide contained in the insulation layer 12 when suspended in pure water is preferably 20 μS / cm or less. Additionally, as a variation, the aluminum hydroxide may be surface-treated. For example, when the surface of the aluminum hydroxide is treated with silane, the adhesion between the base polymer and the aluminum hydroxide filler is improved, thus improving electrical properties, which is preferable. It should be noted that if improving electrical properties is of interest, the aluminum hydroxide filler can be replaced with fillers such as clay or talc. However, in this embodiment, from the viewpoint of improving the flame retardancy of the insulation layer 12, aluminum hydroxide is used as the filler in the base polymer.

[0036] Furthermore, from the viewpoint of appropriately conducting an oil resistance test to evaluate the oil resistance of the wire 10, the following configuration is preferred: The insulation layer 12 preferably contains polyethylene with a melting point of 110°C or higher as the main polyolefin component. A representative method for the oil resistance test is as follows: measuring the tensile properties before and after immersion in test oil (IRM902 test oil) heated to 100°C for 72 hours, and evaluating the degree of change in tensile properties before and after immersion. In this case, the melting point of the main polyolefin component (base) of the base polymer of the sample is preferably 110°C or higher using differential scanning calorimetry (DSC). The aforementioned main polyolefin component (base) refers to a component that comprises 50 parts by mass or more of polyolefin per 100 parts by mass. If the melting point of the main polyolefin component is lower than 110°C, the crystals of the base polymer will melt (dissolve) during the oil resistance test, making it difficult to prevent oil diffusion. In this case, due to the diffusion of the test oil, the rate of change in tensile properties becomes larger, making it difficult to accurately evaluate the oil resistance.

[0037] Examples of polyolefins with a melting point of 110°C include low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, and polypropylene. However, when polypropylene is used as the main component of a polyolefin, it will degrade during cross-linking treatment using electron beam irradiation. Therefore, polyethylene is preferred as the main component of a polyolefin.

[0038] Furthermore, as a minor component of the polyolefin (less than 50 parts by mass relative to 100 parts by mass of polyolefin), it is preferable to exclude vinyl acetate copolymers and ethylene acrylate copolymers. Vinyl acetate copolymers and ethylene acrylate copolymers are hygroscopic, and therefore, by excluding these components, it is possible to prevent a decline in electrical properties due to moisture.

[0039] However, acid-modified ethylene-acrylic acid copolymers can improve the polymer's adhesion. When an acid-modified ethylene-acrylic acid copolymer is included as a minor component of a polyolefin, it can inhibit moisture intrusion by improving the adhesion of the base polymer, thereby improving the electrical properties of the wire 10. Examples of acids include maleic acid, maleic anhydride, or fumaric acid. Furthermore, examples of acid-modified polyolefins include polyethylene, ethylene-α-olefin, or ethylene-acrylic acid copolymers. As a minor component of the polyolefin, there are cases where only one of the above components is contained, and cases where two or more of the above components are contained.

[0040] In addition, constituting Figure 1 The resin composition of the insulation layer 12 of the wire 10 shown may sometimes also contain minor components other than those described above. Examples of minor components other than those described above, exemplified by their function, that can be added to the resin composition constituting the insulation layer 12 include, for example, crosslinking aids, flame retardants, ultraviolet absorbers, light stabilizers, softeners, lubricants, colorants, reinforcing materials, surfactants, plasticizers, metal chelating agents, foaming agents, compatibilizers, processing aids, and stabilizers.

[0041] <Insulation Layer 13>

[0042] In the outer insulating layer 13, the base polymer is primarily composed of polyolefin (50% by weight or more of the base polymer is polyolefin). The insulating layer 13 is composed of a resin composition in which flame retardants, fillers, etc., are mixed into the base polymer. The insulating layer 13 is a halogen-free resin composition that does not produce halogen gases during combustion. Furthermore, the insulating layer 13 contains magnesium hydroxide as a flame retardant. Flame retardants used in halogen-free resin compositions include phosphorus-based flame retardants such as red phosphorus and triazine-based flame retardants such as melamine cyanurate. Since magnesium hydroxide does not produce harmful phosphorus or cyanide gases during combustion, it is used.

[0043] From the viewpoint of improving the flame retardancy of the insulation layer 13, it is preferable to add 150 parts by mass or more of magnesium hydroxide, and particularly preferable to add 160 parts by mass or more of magnesium hydroxide, relative to 100 parts by mass of the polyolefin used as the base polymer of the insulation layer 13. Furthermore, from the viewpoint of preventing a decrease in the mechanical properties of the insulation layer 13, such as its elongation characteristics, it is preferable to add 250 parts by mass or less of magnesium hydroxide, and particularly preferable to add 200 parts by mass or less of magnesium hydroxide, relative to 100 parts by mass of the polyolefin used as the base polymer of the insulation layer 13.

[0044] Furthermore, the polyolefin used as the base polymer of the insulation layer 13 contains vinyl acetate copolymer as a main component (50 parts by mass or more per 100 parts by mass of polyolefin). In particular, the ethylene-vinyl acetate copolymer exhibits an endothermic reaction due to deacetic acidification during combustion, which is preferred. The endothermic effect of the vinyl acetate copolymer due to deacetic acidification contributes to improved flame retardancy. Therefore, it is necessary for the polyolefin of the insulation layer 13 to contain vinyl acetate copolymer as a main component, and it is especially preferable to contain ethylene-vinyl acetate copolymer with a melting point of 80°C or higher. Using ethylene-vinyl acetate copolymer with a melting point of 80°C or higher as the main component can suppress the stickiness of the wires 10 to each other. Furthermore, when conducting an oil resistance test on the wires 10 using test oil (IRM903 test oil), the test temperature is 70°C. Therefore, by increasing the melting point of the polyolefin in the insulation layer 13, the evaluation accuracy of the oil resistance test can be improved.

[0045] Furthermore, ethylene-vinyl acetate copolymers can be used alone, or they can be mixed with various vinyl acetate copolymers to improve the properties of the insulating layer 13. For example, from the viewpoint of improving the elongation properties of the insulating layer 13, it is sometimes mixed with vinyl acetate copolymers with a melting point below 80°C (e.g., vinyl acetate copolymers without crystals). The effect of improving elongation properties is particularly evident when the proportion of low-melting-point vinyl acetate copolymers is 60% or more. In addition, depending on the needs, there are cases where vinyl acetate copolymers are mixed with other polyolefins as the polyolefin of the insulating layer 13. For example, when the polyolefin of the insulating layer 13 contains acid-modified ethylene-α-olefins, the low-temperature properties of the insulating layer 13 can be improved.

[0046] In addition, constituting Figure 1 The resin composition of the insulation layer 13 of the wire 10 shown may sometimes contain minor components other than those described above. Examples of minor components other than those described above, exemplified by their function, that can be added to the resin composition constituting the insulation layer 13 include, for example, crosslinking aids, flame retardants, ultraviolet absorbers, light stabilizers, softeners, lubricants, colorants, reinforcing materials, surfactants, plasticizers, metal chelating agents, foaming agents, compatibilizers, processing aids, and stabilizers.

[0047] <About crosslinking>

[0048] From the viewpoint of suppressing dripping (the phenomenon of a portion of the resin composition melting and dripping) during the combustion of the wire 10, it is preferable that the insulation layer 12 and the insulation layer 13 are both cross-linked. As a cross-linking treatment method, there are chemical cross-linking using organic peroxides, sulfur compounds, or silanes, irradiation cross-linking using energy beams such as electron beams or radiation, or cross-linking methods utilizing other chemical reactions; any cross-linking method can be applied. Among the methods of cross-linking using electron beam irradiation, the cross-linking treatment can be carried out at near room temperature, thus it is particularly advantageous in terms of ease of processing and the minimal change in the glass transition temperature and melting temperature of the polymer crystals before and after the cross-linking treatment.

[0049] <Evaluation>

[0050] Next, make Figure 1 Examples of the wire 10 shown and some comparative examples of the examples are evaluated, and the results are explained. Table 1 shows the mixing ratios and evaluation results of Examples 1 to 7. Table 2 shows the mixing ratios and evaluation results of Comparative Examples 1 to 5.

[0051] The various embodiments shown in Table 1 and the various comparative examples shown in Table 2 respectively employ the following steps to achieve the same level of... Figure 1 The wire 10 shown is manufactured using the same structural method. The conductor 11 is, for example, a tin-plated conductor made by stranding 37 bare copper wires together. The diameter of the conductor 11 is, for example, 0.18 mm. Insulation layers 12 and 13 are respectively formed by mixing the formulations shown in Tables 1 and 2 using 14-inch open rolls and granulating them using a granulator. Then, the conductor 11 is covered by bilayer extrusion molding using a 40 mm extruder with insulation layer 12 having a thickness of 0.3 mm and insulation layer 13 having a thickness of 0.47 mm. The resulting wire 10 is cross-linked by irradiating it with electron beams.

[0052] The items listed as "surface area" in Tables 1 and 2 represent the surface area of ​​aluminum hydroxide or magnesium hydroxide as flame retardants per unit volume in the resin composition of insulating layer 12. "Surface area" represents the specific surface area relative to 1 cc of the resin composition, calculated using the formula: "(surface area) = (surface area obtained by the BET method) × specific gravity × weight of flame retardant ÷ total weight of the resin composition".

[0053] In the tensile test, the tube from which the conductor 11 was removed from the fabricated wire 10 was used, and the tensile test was carried out at a displacement speed of 250 mm / min to determine the tensile strength and elongation characteristics. As evaluation indicators, samples with an elongation of 150% or more were set as 0, samples with an elongation of less than 150% but more than 120% were set as △, and samples with an elongation of less than 120% were set as ×.

[0054] In the oil resistance test, the tube after removing conductor 11 from wire 10 is immersed in test oil (IRM902) heated to 100°C for 72 hours. Then, it is left at room temperature for 16 hours, and a tensile test is performed under the same conditions as the tensile test described above to determine tensile strength and elongation characteristics. The measured results are compared with the results of the tensile test described above, and the rate of change of tensile strength and elongation characteristics before and after heating with the test oil is calculated. As evaluation indicators, samples with an absolute value of less than 30% change in tensile strength are designated as 0, and samples with a change of more than 30% are designated as △. Similarly, samples with an absolute value of less than 40% change in elongation characteristics are designated as 0, and samples with a change of more than 40% are designated as △.

[0055] As part of the flame retardancy test, the following evaluation is conducted according to the European standard (EN45545-2). Specifically, after the burner flame is brought into contact with the vertically supported electrical wire for 1 minute, the flame is removed. Samples where the distance between the upper fixing part and the upper charred part is 50 mm or more, and the distance between the upper fixing part and the lower charred part is less than 540 mm, are marked as 0. All other cases are marked as ×.

[0056] As an electrical test, a 1500V DC stability test was conducted according to the European standard EN50305.6.7. Samples that did not short-circuit after 240 hours were marked as 0, and samples that short-circuited in less than 240 hours were marked as ×.

[0057] For conductivity evaluation, 2g of flame retardant was added to 100ml of pure water and stirred, then heated at 85℃ for 20 hours. The solution was then filtered, and the conductivity of the suspension was measured using a conductivity meter.

[0058] For comprehensive evaluation, samples with all evaluation items rated 0 are marked as ◎, and samples containing more than one △ are marked as ◎. In addition, samples containing × are marked as ×.

[0059] [Table 1]

[0060]

[0061] [Table 2]

[0062]

[0063] [Table 3]

[0064] Table 3. Details of other additives used in the outer layer.

[0065]

[0066] [Table 4]

[0067] Table 4. Details of other additives used in the inner layer

[0068] AO-18 ADEKA 1.5 SZ-P (Zinc Stearate) Sakai Chemical 0.5 TMPT (Trimethylolpropane triacrylate) Shin-Nakamura Chemical 3

[0069] <Example 1>

[0070] Figure 1 In the insulation layer 13 shown, 45 parts by mass of EVA (Mitsui DuPont Chemicals, V5274), 40 parts by mass of EVA (Lanxess, Lewabane 600), 15 parts by mass of modified polyolefin (Mitsui Chemicals, Tafmer MH7020), 180 parts by mass of magnesium hydroxide as a flame retardant (Kamishima Chemical Industry, Magseeds S4), and 8 parts by mass of other additives as shown in Table 3 are compounded.

[0071] As Figure 1 The insulating layer 12 shown is compounded with 70 parts by weight of polyethylene (Pryman Polymer, SP1510), 26 parts by weight of EBR (Mitsui Chemicals, Tafmer DF840), 4 parts by weight of modified polyolefin (Arkema, Bondine LX4110), 130 parts by weight of aluminum hydroxide as a flame retardant (Huber, OL107ZO), and 5 parts by weight of other additives shown in Table 4.

[0072] Made using the above materials Figure 1 The wire shown was subjected to crosslinking of insulation layers 12 and 13 by irradiating it with 5Mrad electron beams, and then various evaluations as shown in Table 1 were performed. As shown in Table 1, all evaluation items were rated as 0, therefore the overall evaluation is ◎.

[0073] <Example 2>

[0074] Figure 1 In the insulation layer 13 shown, 45 parts by mass of EVA (Mitsui DuPont Chemicals, V5274), 40 parts by mass of EVA (Lanxess, Lewabane 600), 15 parts by mass of modified polyolefin (Mitsui Chemicals, Tafmer MH7020), 180 parts by mass of magnesium hydroxide as a flame retardant (Kamishima Chemical Industry, Magseeds S4), and 8 parts by mass of other additives as shown in Table 3 are compounded.

[0075] As Figure 1The insulating layer 12 shown is compounded with 70 parts by weight of polyethylene (Pryman Polymer, SP1510), 26 parts by weight of EBR (Mitsui Chemicals, Tafmer DF840), 4 parts by weight of modified polyolefin (Arkema, Bondine LX4110), 150 parts by weight of aluminum hydroxide as a flame retardant (Huber, OL107ZO), and 5 parts by weight of other additives shown in Table 4.

[0076] Made using the above materials Figure 1 The wire shown was subjected to crosslinking of insulation layers 12 and 13 by irradiating it with 5Mrad electron beams, and then various evaluations as shown in Table 1 were performed. As shown in Table 1, all evaluation items were rated as 0, therefore the overall evaluation is ◎.

[0077] <Example 3>

[0078] Figure 1 In the insulation layer 13 shown, 45 parts by mass of EVA (Mitsui DuPont Chemicals, V5274), 40 parts by mass of EVA (Lanxess, Lewabane 600), 15 parts by mass of modified polyolefin (Mitsui Chemicals, Tafmer MH7020), 180 parts by mass of magnesium hydroxide as a flame retardant (Kamishima Chemical Industry, Magseeds S4), and 8 parts by mass of other additives as shown in Table 3 are compounded.

[0079] As Figure 1 The insulating layer 12 shown is compounded with 70 parts by weight of polyethylene (Pryman Polymer, SP1510), 26 parts by weight of EBR (Mitsui Chemicals, Tafmer DF840), 4 parts by weight of modified polyolefin (Mitsui Chemicals, Tafmer MH7020), 150 parts by weight of aluminum hydroxide as a flame retardant (Huber, OL107ZO), and 5 parts by weight of other additives shown in Table 4.

[0080] Made using the above materials Figure 1 The wire shown was subjected to crosslinking of insulation layers 12 and 13 by irradiating it with 5Mrad electron beams, and then various evaluations as shown in Table 1 were performed. As shown in Table 1, all evaluation items were rated as 0, therefore the overall evaluation is ◎.

[0081] <Example 4>

[0082] Figure 1In the insulation layer 13 shown, 45 parts by mass of EVA (Mitsui DuPont Chemicals, V5274), 40 parts by mass of EVA (Lanxess, Lewabane 600), 15 parts by mass of modified polyolefin (Mitsui Chemicals, Tafmer MH7020), 180 parts by mass of magnesium hydroxide as a flame retardant (Kamishima Chemical Industry, Magseeds S4), and 8 parts by mass of other additives as shown in Table 3 are compounded.

[0083] As Figure 1 The insulating layer 12 shown is compounded with 70 parts by weight of polyethylene (Pryman Polymer, SP1510), 26 parts by weight of EBR (Mitsui Chemicals, Tafmer DF840), 4 parts by weight of modified polyolefin (Mitsui Chemicals, Tafmer MH7020), 180 parts by weight of aluminum hydroxide as a flame retardant (Huber, OL107ZO), and 5 parts by weight of other additives shown in Table 4.

[0084] Made using the above materials Figure 1 The wire shown was subjected to crosslinking of insulation layers 12 and 13 by irradiating it with 5Mrad electron beams, and then various evaluations as shown in Table 1 were performed. As shown in Table 1, all evaluation items were rated as 0, therefore the overall evaluation is ◎.

[0085] <Example 5>

[0086] Figure 1 In the insulation layer 13 shown, 45 parts by mass of EVA (Mitsui DuPont Chemicals, V5274), 40 parts by mass of EVA (Lanxess, Lewabane 600), 15 parts by mass of modified polyolefin (Mitsui Chemicals, Tafmer MH7020), 180 parts by mass of magnesium hydroxide as a flame retardant (Kamishima Chemical Industry, Magseeds S4), and 8 parts by mass of other additives as shown in Table 3 are compounded.

[0087] As Figure 1 The insulating layer 12 shown is compounded with 70 parts by weight of polyethylene (Pryman Polymer, SP1510), 26 parts by weight of EBR (Mitsui Chemicals, Tafmer DF840), 4 parts by weight of modified polyolefin (Mitsui Chemicals, Tafmer MH7020), 200 parts by weight of aluminum hydroxide as a flame retardant (Huber, OL107ZO), and 5 parts by weight of other additives shown in Table 4.

[0088] Made using the above materials Figure 1 The wire shown was subjected to various evaluations as shown in Table 1 after its insulation layers 12 and 13 were cross-linked by irradiation with 5Mrad electron beams. As shown in Table 1, the elongation at break was 130%, therefore the evaluation was set as △. All other evaluation items were rated as 0, therefore the overall evaluation was 0.

[0089] <Example 6>

[0090] Figure 1 In the insulation layer 13 shown, 45 parts by mass of EVA (Mitsui DuPont Chemicals, V5274), 40 parts by mass of EVA (Lanxess, Lewabane 600), 15 parts by mass of modified polyolefin (Mitsui Chemicals, Tafmer MH7020), 180 parts by mass of magnesium hydroxide as a flame retardant (Kamishima Chemical Industry, Magseeds S4), and 8 parts by mass of other additives as shown in Table 3 are compounded.

[0091] As Figure 1 The insulating layer 12 shown is compounded with 70 parts by weight of polyethylene (Pryman Polymer, SP1510), 26 parts by weight of EBR (Mitsui Chemicals, Tafmer DF840), 4 parts by weight of modified polyolefin (Arkema, Bondine LX4110), 180 parts by weight of aluminum hydroxide as a flame retardant (Huber, OL104ZO), and 5 parts by weight of other additives shown in Table 4.

[0092] Made using the above materials Figure 1 The wire shown was subjected to crosslinking of insulation layers 12 and 13 by irradiating it with 5Mrad electron beams, and then various evaluations as shown in Table 1 were performed. As shown in Table 1, all evaluation items were rated as 0, therefore the overall evaluation is ◎.

[0093] <Example 7>

[0094] Figure 1 In the insulation layer 13 shown, 45 parts by mass of EVA (Mitsui DuPont Chemicals, V5274), 40 parts by mass of EVA (Lanxess, Lewabane 600), 15 parts by mass of modified polyolefin (Mitsui Chemicals, Tafmer MH7020), 180 parts by mass of magnesium hydroxide as a flame retardant (Kamishima Chemical Industry, Magseeds S4), and 8 parts by mass of other additives as shown in Table 3 are compounded.

[0095] As Figure 1 The insulating layer 12 shown is compounded with 70 parts by weight of polyethylene (Pryman Polymer, SP0510), 26 parts by weight of EBR (Mitsui Chemicals, Tafmer DF840), 4 parts by weight of modified polyolefin (Arkema, Bondine LX4110), 150 parts by weight of aluminum hydroxide as a flame retardant (Huber, OL107ZO), and 5 parts by weight of other additives shown in Table 4.

[0096] Made using the above materials Figure 1The wire shown was subjected to crosslinking of insulation layers 12 and 13 by irradiating it with 5Mrad electron beams, and then various evaluations as shown in Table 1 were performed. As shown in Table 1, the absolute values ​​of the rate of change of oil-resistant tensile strength and the absolute values ​​of the rate of change of oil-resistant elongation at break were both greater than 30%, and therefore the evaluation was set as △. All other evaluation items were judged as 0, and therefore the overall evaluation was 0.

[0097] <Comparative Example 1>

[0098] Figure 1 In the insulation layer 13 shown, 45 parts by mass of EVA (Mitsui DuPont Chemicals, V5274), 40 parts by mass of EVA (Lanxess, Lewabane 600), 15 parts by mass of modified polyolefin (Mitsui Chemicals, Tafmer MH7020), 180 parts by mass of magnesium hydroxide as a flame retardant (Kamishima Chemical Industry, Magseeds S4), and 8 parts by mass of other additives as shown in Table 3 are compounded.

[0099] As Figure 1 The insulating layer 12 shown is compounded with 70 parts by weight of polyethylene (Pryman Polymer, SP1510), 26 parts by weight of EBR (Mitsui Chemicals, Tafmer DF840), 4 parts by weight of modified polyolefin (Arkema, Bondine LX4110), 160 parts by weight of aluminum hydroxide as a flame retardant (Huber, OL104ZO), and 5 parts by weight of other additives shown in Table 4.

[0100] Made using the above materials Figure 1 The wire shown was subjected to various evaluations as shown in Table 2 after its insulation layers 12 and 13 were cross-linked by irradiation with 5Mrad electron beams. As shown in Table 2, the surface area of ​​aluminum hydroxide was less than 3.7m². 2 / ml(3.5m 2 The DC stability test ( / ml) failed. Therefore, the overall evaluation is ×.

[0101] <Comparative Example 2>

[0102] Figure 1 In the insulation layer 13 shown, 45 parts by mass of EVA (Mitsui DuPont Chemicals, V5274), 40 parts by mass of EVA (Lanxess, Lewabane 600), 15 parts by mass of modified polyolefin (Mitsui Chemicals, Tafmer MH7020), 180 parts by mass of magnesium hydroxide as a flame retardant (Kamishima Chemical Industry, Magseeds S4), and 8 parts by mass of other additives as shown in Table 3 are compounded.

[0103] As Figure 1The insulating layer 12 shown is compounded with 70 parts by weight of polyethylene (Pryman Polymer, SP1510), 26 parts by weight of EBR (Mitsui Chemicals, Tafmer DF840), 4 parts by weight of modified polyolefin (Arkema, Bondine LX4110), 120 parts by weight of aluminum hydroxide as a flame retardant (Huber, OL104ZO), and 5 parts by weight of other additives shown in Table 4.

[0104] Made using the above materials Figure 1 The wire shown was subjected to various evaluations as shown in Table 2 after its insulation layers 12 and 13 were cross-linked by irradiation with 5Mrad electron beams. As shown in Table 2, the surface area of ​​aluminum hydroxide was less than 3.7m². 2 / ml(2.9m 2 The DC stability test ( / ml) failed. Furthermore, the combustion test also failed. Therefore, the overall evaluation is ×.

[0105] <Comparative Example 3>

[0106] Figure 1 In the insulation layer 13 shown, 45 parts by mass of EVA (Mitsui DuPont Chemicals, V5274), 40 parts by mass of EVA (Lanxess, Lewabane 600), 15 parts by mass of modified polyolefin (Mitsui Chemicals, Tafmer MH7020), 180 parts by mass of magnesium hydroxide as a flame retardant (Kamishima Chemical Industry, Magseeds S4), and 8 parts by mass of other additives as shown in Table 3 are compounded.

[0107] As Figure 1 The insulating layer 12 shown is compounded with 70 parts by weight of polyethylene (Pryman Polymer, SP1510), 26 parts by weight of EBR (Mitsui Chemicals, Tafmer DF840), 4 parts by weight of modified polyolefin (Mitsui Chemicals, Tafmer MH7020), 210 parts by weight of aluminum hydroxide as a flame retardant (Huber, OL107ZO), and 5 parts by weight of other additives shown in Table 4.

[0108] Made using the above materials Figure 1 The wire shown was subjected to various evaluations as shown in Table 2 after its insulation layers 12 and 13 were cross-linked by irradiation with 5Mrad electron beams. As shown in Table 2, the elongation at break was 120% due to excessive aluminum hydroxide addition, which is unacceptable. Furthermore, the DC stability test was also unacceptable. Therefore, the overall evaluation is ×.

[0109] <Comparative Example 4>

[0110] Figure 1In the insulation layer 13 shown, 45 parts by mass of EVA (Mitsui DuPont Chemicals, V5274), 40 parts by mass of EVA (Lanxess, Lewabane 600), 15 parts by mass of modified polyolefin (Mitsui Chemicals, Tafmer MH7020), 180 parts by mass of magnesium hydroxide as a flame retardant (Kamishima Chemical Industry, Magseeds S4), and 8 parts by mass of other additives as shown in Table 3 are compounded.

[0111] As Figure 1 The insulating layer 12 shown is compounded with 70 parts by weight of polyethylene (Pryman Polymer, SP1510), 26 parts by weight of EBR (Mitsui Chemicals, Tafmer DF840), 4 parts by weight of modified polyolefin (Arkema, Bondine LX4110), 150 parts by weight of magnesium hydroxide as a flame retardant (Huber, H10A), and 5 parts by weight of other additives shown in Table 4.

[0112] Made using the above materials Figure 1 The wire shown was subjected to various evaluations as shown in Table 2 after its insulation layers 12 and 13 were cross-linked by irradiation with 5Mrad electron beams. As shown in Table 2, the DC stability test failed. This is believed to be due to the addition of magnesium hydroxide instead of aluminum hydroxide. Therefore, the overall evaluation is ×.

[0113] <Comparative Example 5>

[0114] Figure 1 In the insulation layer 13 shown, 45 parts by mass of EVA (Mitsui DuPont Chemicals, V5274), 40 parts by mass of EVA (Lanxess, Lewabane 600), 15 parts by mass of modified polyolefin (Mitsui Chemicals, Tafmer MH7020), 180 parts by mass of magnesium hydroxide as a flame retardant (Kamishima Chemical Industry, Magseeds S4), and 8 parts by mass of other additives as shown in Table 3 are compounded.

[0115] As Figure 1 The insulating layer 12 shown is compounded with 70 parts by weight of polyethylene (Pryman Polymer, SP1510), 26 parts by weight of EBR (Mitsui Chemicals, Tafmer DF840), 4 parts by weight of modified polyolefin (Arkema, Bondine LX4110), 100 parts by weight of magnesium hydroxide as a flame retardant (Huber, H10A), and 5 parts by weight of other additives shown in Table 4.

[0116] Made using the above materials Figure 1The wire shown was subjected to various evaluations as shown in Table 2 after its insulation layers 12 and 13 were cross-linked by irradiation with 5Mrad electron beams. As shown in Table 2, the combustion test failed due to insufficient flame retardant addition. Furthermore, the DC stability test failed. This is believed to be due to the addition of magnesium hydroxide instead of aluminum hydroxide. Therefore, the overall evaluation is ×.

[0117] <Evaluation Results>

[0118] Based on the evaluation results of the examples shown in Table 1 and the comparative examples shown in Table 2, the following conclusions were drawn. First, by using aluminum hydroxide as the flame retardant added to the inner insulating layer 12, both flame retardancy and electrical properties can be achieved. Furthermore, when the polyolefin is set to 100 parts by mass, from the viewpoint of improving flame retardancy, the amount of aluminum hydroxide added is preferably 130 parts by mass or more; from the viewpoint of improving elongation at break, it is preferably 200 parts by mass or less. Additionally, if the surface area of ​​aluminum hydroxide in each unit volume of the resin composition of the insulating layer 12 is 3.7 m²... 2 If the amount of aluminum hydroxide added is above 200 parts by mass, a wire 10 that passes the DC stability test can be obtained. However, according to the results of Comparative Example 3, if the amount of aluminum hydroxide added exceeds 200 parts by mass, the surface area is 3.7 m². 2 If the value is above / ml, it will fail the DC stability test.

[0119] This invention is not limited to the above-described embodiments and examples, and various modifications may be made without departing from its spirit.

[0120] Industry availability

[0121] This invention can be applied to wires and cables.

Claims

1. An electrical wire, having: conductor, It comprises a base polymer containing a polyolefin and a first insulating layer covering the conductor, and A second insulating layer comprising a base polymer containing a polyolefin and covering the first insulating layer; In the first insulating layer, 130-200 parts by weight of aluminum hydroxide are added relative to 100 parts by weight of polyolefin. The surface area of ​​aluminum hydroxide in each unit volume of the resin composition of the first insulating layer is 3.7 m². 2 / ml or more, The second insulating layer is a halogen-free resin composition containing 150-250 parts by weight of magnesium hydroxide added to 100 parts by weight of polyolefin, and ethylene-vinyl acetate copolymer as the main component of polyolefin. The first insulating layer and the second insulating layer are cross-linked.

2. The wire according to claim 1, wherein, The first insulating layer contains polyethylene with a melting point of 110°C or higher as the main component of the polyolefin, and does not contain vinyl acetate copolymer and ethylene acrylic acid copolymer as minor components.

3. The wire according to claim 1 or 2, wherein, The first insulating layer contains acid-modified polyolefin as a minor component of the polyolefin. The acid-modified polyolefin contains one or more of acid-modified polyethylene, ethylene-α-olefin, and ethylene-acrylic acid copolymer.

4. The wire according to claim 1 or 2, wherein, The conductivity of the aluminum hydroxide contained in the first insulating layer when suspended in pure water is less than 20 μS / cm.

5. The wire according to claim 1 or 2, wherein, The second insulating layer contains an ethylene-vinyl acetate copolymer with a melting point above 80°C as the main component of the polyolefin.

6. A cable comprising a plurality of wires and a sheath covering the plurality of wires, At least a portion of the plurality of wires are wires as described in any one of claims 1 to 5.

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