JP2022122338A - Electric wire and cable - Google Patents

Abstract

To provide an electric wire and a cable having high performance in fire retardancy and electrical insulation performance.SOLUTION: An electric wire 10 comprises: a conductor 11; an insulation layer (first insulation layer) 12 provided with a polyolefin-containing base polymer and coating the conductor 11; and an insulation layer (second insulation layer) 13 provided with a polyolefin-containing base polymer and coating the insulation layer 12. In the insulation layer 12, 130-200 pts.mass of aluminum hydroxide is added to 100 pts.mass of polyolefin. A surface area of the aluminum hydroxide per unit volume of a resin composition of the insulation layer 12 is 3.7 m2/ml or larger. In the insulation layer 13 being a non-halogen resin composition containing an acetic acid/vinyl copolymer as the main component of polyolefin, 150-250 pts.mass of magnesium hydrate is added to 100 pts.mass of polyolefin. The insulation layer 12 and the insulation layer 13 are each crosslinked.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to an electric wire and a cable using the same.

For example, railroad vehicles use a large number of cables such as power lines for motors and control lines for controlling operation. These cables are required to have high flame retardancy and electrical insulation performance.

In order to obtain high flame retardancy, for example, there is a method of blending a large amount of metal hydroxide into a polyolefin resin (see, for example, Patent Documents 1 and 2).

Japanese Patent Application Laid-Open No. 2004-186011 JP 2014-53247 A

The inventors of the present application have studied techniques for improving flame retardancy or electrical insulation performance in electric wires and cables using the same. For example, in Patent Document 1 described above, an insulating layer to which a styrene elastomer or ethylene propylene rubber is added is described as a material constituting the outer insulating layer, but the formulation described in Patent Document 1 is sufficient. oil resistance is not obtained. Also, an insulating layer containing magnesium hydroxide is described as the inner insulating layer, but magnesium hydroxide tends to contain many impurity ions, which may cause deterioration of the electrical properties of the electric wire. Moreover, when an ethylene-acrylic acid copolymer having a high polarity is used as the base polymer of the inner insulating layer, the hygroscopicity is high, which may cause deterioration of the electrical properties of the electric wire. Further, as described in the above-mentioned patent document, for example, when a vinyl acetate copolymer containing 30% or more of acetic acid is used as a base polymer for an insulating layer, the tackiness of the wire surface is too strong. , the cross-linking treatment by electron beam irradiation may become difficult.

SUMMARY OF THE INVENTION An object of the present invention is to provide electric wires and cables with high characteristics in terms of flame retardancy and electrical insulation performance.

An electric wire according to one embodiment includes: [1] a conductor, a base polymer containing polyolefin, a first insulating layer covering the conductor, and a base polymer containing polyolefin, covering the first insulating layer and a second insulating layer. For the first insulating layer, 130 to 200 parts by mass of aluminum hydroxide is added to 100 parts by mass of polyolefin. The surface area of aluminum hydroxide per unit volume of the resin composition of the first insulating layer is 3.7 m ² /ml or more. The second insulating layer is a non-halogen resin composition containing 150 to 250 parts by mass of magnesium hydroxide with respect to 100 parts by mass of polyolefin and containing an ethylene-vinyl acetate copolymer as the main component of the polyolefin. Each of the first insulating layer and the second insulating layer is crosslinked.

[2] For example, in [1], the first insulating layer contains polyethylene having a melting point of 110°C or higher as a main component of polyolefin, and vinyl acetate copolymer and ethylene acrylic acid copolymer as secondary components. Not included.

[3] For example, in [1] or [2], the first insulating layer contains acid-modified polyolefin as a subcomponent of polyolefin. The acid-modified polyolefin includes at least one of polyethylene, ethylene-α-olefin, and ethylene acrylic acid copolymer.

[4] For example, in any one of [1] to [3], the aluminum hydroxide contained in the first insulating layer has an electrical conductivity of 20 μS/cm or less when suspended in pure water.

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

In another embodiment, a cable has [6] a plurality of electric wires and a sheath that collectively covers the plurality of electric wires, and at least a part of the plurality of electric wires includes [ 1] to [5].

Exemplary embodiments of the present invention provide wires and cables with high properties in flame retardancy and electrical insulation performance.

It is a sectional view showing an example of structure of an electric wire which is one embodiment. FIG. 2 is a cross-sectional view showing a structural example of a cable including the electric wire shown in FIG. 1;

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

<Example of basic structure of wire and cable>
FIG. 1 is a cross-sectional view showing a structural example of an electric wire according to one embodiment. FIG. 2 is a cross-sectional view showing a structural example of a cable including the electric wires shown in FIG.

The electric wire 10 shown in FIG. 1 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 electric wire 10 is a double-layer insulated electric wire having two insulating layers. As will be described later, each of insulating layers 12 and 13 is crosslinked. The electric wire 10 can be said to be a two-layer bridging insulated electric wire. Insulation layers 12 and 13 of electric wire 10 each contain a flame retardant, as will be described later. The electric wire 10 can be rephrased as a two-layer cross-linked flame-retardant insulated electric wire.

A cable 20 shown in FIG. 2 has a plurality of electric wires 10 and a sheath (insulating layer, third insulating layer) 21 that collectively covers the plurality of electric wires 10 . The example shown in FIG. 2 shows an example in which the sheath 21 covers two electric wires 10 . However, the number of wires 10 in the sheath 21 is not limited to two, and may be three or more, for example. Moreover, as shown in FIG. 2, it is preferable that all the electric wires covered by the sheath 21 are the electric wires 10. may be covered with

The features of the electric wire 10 will be described below separately for the insulating layer 12 that is the inner layer and the insulating layer 13 that is the outer layer.

<Insulating layer 12>
The insulating layer 12, which is the inner layer, is mainly composed of polyolefin as a base polymer (50% by weight or more of the base polymer is polyolefin). The insulating layer 12 preferably contains aluminum hydroxide as a flame retardant. Metal hydroxides commonly used as flame retardants include magnesium hydroxide. Magnesium hydroxide tends to have a large amount of impurity ions, which may cause deterioration of the electrical properties of the electric wire. On the other hand, when aluminum hydroxide is used as the flame retardant, the electrical properties of the electric wire 10 can be improved as compared with the case of using magnesium hydroxide.

However, the surface area of aluminum hydroxide per unit volume of the resin composition (composition including base polymer and filler) forming the insulating layer 12 must be 3.7 m ² /ml or more. The amount of aluminum hydroxide to be added should be 130 to 200 parts by mass (130 parts by mass or more and 200 parts by mass or less) when the polyolefin contained in the insulating layer 12 is 100 parts by mass.

It is believed that the smaller the area of the interface between the base polymer and the filler (in other words, the surface area of the filler), the more likely it is that moisture can be prevented from entering. Based on this idea, the smaller the amount of filler added, the better, and the smaller the surface area of the filler, the better. However, according to the study of the inventor of the present application, when the amount of aluminum hydroxide added exceeds 100 parts by mass when the polyolefin contained in the insulating layer 12 is 100 parts by mass, the surface area of aluminum hydroxide is reduced to 3 parts by mass. When the surface area of aluminum hydroxide is less than 0.7 ^{m 2 /} ml, dielectric breakdown may occur. Although this mechanism has not been clarified completely, it can be considered as follows. That is, the dielectric breakdown caused by the aluminum hydroxide filler is considered to be affected by the element of electrolytic strain in addition to the element of insulation resistance of the resin composition. As the amount of aluminum hydroxide added to the insulating layer ¹² increases, the insulation resistance of the resin composition decreases. Since it becomes small, it is thought that dielectric breakdown can be prevented.

In addition, from the viewpoint of imparting sufficient flame retardancy to the insulating layer 12, the amount of aluminum hydroxide added should be 130 parts by mass or more when the polyolefin contained in the insulating layer 12 is 100 parts by mass. be. For example, if the amount of aluminum hydroxide added is less than 100 parts by mass, dielectric breakdown of the insulating layer 12 does not occur, but flame retardancy is insufficient. However, if the amount of aluminum hydroxide added exceeds 200 parts by mass, dielectric breakdown may occur even if the surface area of aluminum hydroxide is 3.7 m ² /ml or more. In addition, if the amount of aluminum hydroxide added exceeds 200 parts by mass, the mechanical properties such as elongation properties of the insulating layer 12 are deteriorated. Therefore, the amount of aluminum hydroxide to be added should be 130 to 200 parts by mass when the polyolefin contained in the insulating layer 12 is 100 parts by mass.

Moreover, from the viewpoint of improving the electrical properties of the electric wire 10, the following configuration is preferable. That is, the aluminum hydroxide contained in the insulating layer 12 preferably has an electric conductivity of 20 μS/cm or less when suspended in pure water. Also, as a modification, aluminum hydroxide can be subjected to a surface treatment. For example, when the surface of aluminum hydroxide is silane-treated, the adhesion between the base polymer and the aluminum hydroxide filler is improved, which is preferable in terms of improving electrical properties. Note that if attention is paid to the improvement of the electrical properties, it is conceivable to replace the aluminum hydroxide filler with a filler such as clay or talc. However, in the case of the present embodiment, from the viewpoint of improving the flame retardancy of the insulating layer 12, aluminum hydroxide is used as the filler filled in the base polymer.

Moreover, from the viewpoint of appropriately conducting an oil resistance test for evaluating the oil resistance of the electric wire 10, the following configuration is preferable. That is, the insulating layer 12 preferably contains polyethylene having a melting point of 110° C. or higher as a main component of polyolefin. As a representative method of the oil resistance test, the tensile properties are measured before and after 72 hours of immersion in test oil (IRM902 test oil) heated to 100°C, and the degree of change in tensile properties before and after immersion is evaluated. . At this time, the melting point of the main component (base) of the polyolefin, which is the base polymer of the sample, is preferably 110° C. or higher by differential scanning calorimetry (DSC method). The above-described main component (base) of polyolefin refers to a component that accounts for 50 parts by mass or more with respect to 100 parts by mass of polyolefin. If the melting point of the main component of the polyolefin is below 110°C, the crystals of the base polymer will melt during the oil resistance test, making it difficult to prevent the oil from diffusing. In this case, the rate of change in tensile properties increases due to diffusion of the test oil, making it difficult to accurately evaluate oil resistance.

Examples of polyolefins having 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 the polyolefin, polyethylene is preferable as the main component of the polyolefin because the polypropylene collapses when subjected to cross-linking treatment by electron beam irradiation.

In addition, it is preferable that vinyl acetate copolymer and ethylene-acrylic acid copolymer are not contained as subcomponents of polyolefin (components less than 50 parts by mass with respect to 100 parts by mass of polyolefin). Since the vinyl acetate copolymer and the ethylene acrylic acid copolymer are hygroscopic, the elimination of these components can prevent deterioration of electrical properties due to moisture.

However, an acid-modified ethylene-acrylic acid copolymer can increase the adhesion of the polymer. When an acid-modified ethylene-acrylic acid copolymer is included as a secondary component of the polyolefin, the adhesion of the base polymer is improved to suppress the intrusion of moisture and improve the electrical properties of the electric wire 10. can be done. Examples of acids include maleic acid, maleic anhydride, and fumaric acid. Examples of acid-modified polyolefin include polyethylene, ethylene-α-olefin, and ethylene-acrylic acid copolymer. As the subcomponent of the polyolefin, one kind of the plurality of components described above may be contained singly, and two or more kinds of the plurality of components described above may be contained.

Further, the resin composition forming the insulating layer 12 of the electric wire 10 shown in FIG. 1 may contain subcomponents other than those described above. Materials added to the resin composition constituting the insulating layer 12 as subcomponents other than the above are functionally exemplified. , coloring agents, reinforcing agents, surfactants, plasticizers, metal chelating agents, foaming agents, compatibilizers, processing aids, stabilizers, and the like.

<Insulating layer 13>
The insulating layer 13, which is an outer layer, is mainly composed of polyolefin as a base polymer (50% by weight or more of the base polymer is polyolefin). The insulating layer 13 is made of a resin composition in which a flame retardant filler or the like is mixed with a base polymer. The insulating layer 13 is a non-halogen resin composition that does not generate halogen gas when burned. Moreover, the insulating layer 13 contains magnesium hydroxide as a flame retardant. Flame retardants for non-halogen resin compositions include phosphorus-based flame retardants such as red phosphorus and triazine-based flame retardants such as melamine cyanurate. This is adopted because it does not generate

From the viewpoint of improving the flame retardancy of the insulating layer 13, it is preferable that 150 parts by mass or more of magnesium hydroxide is added to 100 parts by mass of polyolefin, which is the base polymer of the insulating layer 13, and 160 parts by mass or more. It is particularly preferred that magnesium hydroxide is added. In addition, from the viewpoint of preventing deterioration of mechanical properties such as elongation properties of the insulating layer 13, 250 parts by mass or less of magnesium hydroxide is added to 100 parts by mass of polyolefin, which is the base polymer of the insulating layer 13. It is particularly preferable that 200 parts by mass or less of magnesium hydroxide is added.

Polyolefin, which is the base polymer of the insulating layer 13, contains a vinyl acetate copolymer as a main component (50 parts by mass or more with respect to 100 parts by mass of polyolefin). In particular, an ethylene-vinyl acetate copolymer is preferable because it undergoes an endothermic reaction due to deacetic acid during combustion. Vinyl acetate copolymer contributes to the improvement of flame retardancy due to the endothermic effect of deacetic acid. For this reason, the polyolefin of the insulating layer 13 must contain a vinyl acetate copolymer as a main component, and it is particularly preferable to contain an ethylene-vinyl acetate copolymer having a melting point of 80° C. or higher as a main component of the polyolefin. When an ethylene-vinyl acetate copolymer having a melting point of 80° C. or higher is used as the main component, the effect of suppressing the tackiness of the electric wire 10 is obtained. Moreover, when conducting an oil resistance test using a test oil (IRM903 test oil) on the electric wire 10, the test temperature is 70°C. For this reason, the melting point of the polyolefin of the insulating layer 13 is increased, so that the evaluation accuracy of the oil resistance test can be improved.

Moreover, the ethylene-vinyl acetate copolymer may be used alone, but may be used in combination with a plurality of types of vinyl acetate copolymers for the purpose of improving the properties of the insulating layer 13 . For example, from the viewpoint of improving the elongation property of the insulating layer 13, it may be mixed with a vinyl acetate copolymer having a melting point of less than 80° C. (for example, a vinyl acetate copolymer having no crystals). The effect of improving the elongation property is particularly likely to be exhibited when the proportion of the vinyl acetate copolymer having a low melting point is 60% or more. Moreover, as the polyolefin of the insulating layer 13, a vinyl acetate copolymer and other polyolefin may be mixed as needed. For example, when the polyolefin of the insulating layer 13 contains acid-modified ethylene-α-olefin, the low temperature properties of the insulating layer 13 can be improved.

Moreover, the resin composition forming the insulating layer 13 of the electric wire 10 shown in FIG. 1 may contain subcomponents other than those described above. Materials added to the resin composition constituting the insulating layer 13 as subcomponents other than the above are functionally exemplified. , coloring agents, reinforcing agents, surfactants, plasticizers, metal chelating agents, foaming agents, compatibilizers, processing aids, stabilizers, and the like.

<About cross-linking>
From the viewpoint of suppressing drip (phenomenon in which a part of the resin composition melts down) when the electric wire 10 is burned, it is preferable that each of the insulating layers 12 and 13 is crosslinked. Examples of cross-linking methods include chemical cross-linking using organic peroxides, sulfur compounds, silanes, etc., irradiation cross-linking using energy beams such as electron beams and radiation, and cross-linking methods using other chemical reactions. However, any cross-linking method is applicable. In the case of the method of cross-linking by irradiating an electron beam, the cross-linking treatment can be performed at around room temperature, so the ease of processing, or the fact that the glass transition temperature and melting temperature of the polymer crystals do not easily change before and after the cross-linking treatment. It is a particularly advantageous method.

<Evaluation>
Next, examples of the electric wire 10 shown in FIG. 1 and several comparative examples for the examples were produced, and evaluation results for each will be described. Table 1 shows the blending ratios and evaluation results of Examples 1 to 7. Table 2 shows the blending ratios and evaluation results of Comparative Examples 1 to 5.

Each of the plurality of examples shown in Table 1 and the plurality of comparative examples shown in Table 2 was manufactured to have the same structure as the electric wire 10 shown in FIG. 1 by the following procedure. The conductor 11 is, for example, a tin-plated conductor in which tin-plated copper wires are used as strands and 37 strands are twisted. The diameter of the conductor 11 is, for example, 0.18 mm. Each of the insulating layer 12 and the insulating layer 13 was formed by kneading the compositions shown in Tables 1 and 2 with a 14-inch open roll and pelletizing with a granulator. After that, two-layer extrusion molding was performed using a 40 mm extruder so that the thickness of the insulating layer 12 was 0.3 mm and the thickness of the insulating layer 13 was 0.47 mm, and the conductor 11 was covered. A cross-linking treatment was performed by irradiating the obtained electric wire 10 with an electron beam.

The item described as “surface area” in Tables 1 and 2 indicates the surface area value of aluminum hydroxide or magnesium hydroxide, which is the flame retardant, per unit volume of the resin composition of the insulating layer 12 . "Surface area" indicates the specific surface area for 1 cc of the resin composition, and is calculated by the formula: (Surface area) = (Surface area by BET method) x Specific gravity x Weight of flame retardant / Weight of entire resin composition.

In the tensile test, a tube obtained by extracting the conductor 11 from the produced electric wire 10 was used, and the tensile test was performed at a displacement rate of 250 mm/min to measure tensile strength and elongation characteristics. As an evaluation index, ◯ indicates that the elongation is 150% or more, Δ indicates that the elongation is less than 150% and 120% or more, and x indicates that the elongation is less than 120%.

In the oil resistance test, the tube obtained by extracting the conductor 11 from the electric wire 10 was immersed in test oil (IRM902) heated to 100° C. for 72 hours. Then, it was allowed to stand at room temperature for 16 hours, and a tensile test was performed under the same conditions as the tensile test described above to measure tensile strength and elongation properties. The obtained measurement results were compared with the results of the tensile test described above to calculate the rate of change in tensile strength and elongation properties before and after heating with the test oil. As an evaluation index, ◯ indicates that the absolute value of the rate of change in tensile strength is less than 30%, and Δ indicates that it is 30% or more. In addition, when the absolute value of the rate of change in the elongation property was less than 40%, it was evaluated as ◯, and when it was 40% or more, it was evaluated as Δ.

As a flame retardancy test, the following evaluations were performed according to the European standard (EN45545-2). That is, after applying the flame of the burner to the wire supported vertically for 1 minute, the flame is removed, and the distance between the upper fixed part and the carbonized upper end is 50 mm or more, and the distance between the upper fixed part and the carbonized part lower end is 540 mm. Those less than 0 were designated as 0, and others were designated as x.

As an electrical test, a 1500 V direct current stability test was performed according to European standard EN50305.6.7. A sample that did not short-circuit for 240 hours was rated as ◯, and a sample that short-circuited in less than 240 hours was rated as x.

For evaluation of electric conductivity, 2 g of flame retardant was added to 100 ml of pure water, stirred, and heated at 85° C. for 20 hours. The filtered suspension was then measured with a conductivity meter.

As a comprehensive evaluation, ⊚ indicates that all evaluation items are 〇, and ⊚ indicates that one or more △ is included. Moreover, the thing containing x was set to x.

<Example 1>
In the insulating layer 13 shown in FIG. 1, 45 parts by mass of EVA (V5274, manufactured by DuPont Mitsui Chemicals), 40 parts by mass of EVA (Levabun 600, manufactured by Lanxess), and 15 parts by mass of modified polyolefin (Tafuma MH7020, manufactured by Mitsui Chemicals) , 180 parts by mass of magnesium hydroxide (Kamishima Chemical Co., Ltd., Magshees S4) as a flame retardant, and 8 parts by mass of additives shown in Table 3 as other additives were kneaded.

As the insulating layer 12 shown in FIG. 1, 70 parts by mass of polyethylene (SP1510, manufactured by Prime Polymer), 26 parts by mass of EBR (Tafuma DF840, manufactured by Mitsui Chemicals), 4 parts by mass of modified polyolefin (Bondyne LX4110, manufactured by Arkema), 130 parts by mass of aluminum hydroxide (OL107ZO manufactured by Huber) as a flame retardant and 5 parts by mass of other additives shown in Table 4 were kneaded.

Using the above materials, the electric wire shown in FIG. 1 was produced and irradiated with an electron beam of 5 Mrad to crosslink the insulating layers 12 and 13. After that, various evaluations shown in Table 1 were carried out. As shown in Table 1, all the evaluation items were judged to be ◯, so the overall evaluation was ⊚.

<Example 2>
In the insulating layer 13 shown in FIG. 1, 45 parts by mass of EVA (V5274, manufactured by DuPont Mitsui Chemicals), 40 parts by mass of EVA (Levabun 600, manufactured by Lanxess), and 15 parts by mass of modified polyolefin (Tafuma MH7020, manufactured by Mitsui Chemicals) , 180 parts by mass of magnesium hydroxide (Kamishima Chemical Co., Ltd., Magshees S4) as a flame retardant, and 8 parts by mass of additives shown in Table 3 as other additives were kneaded.

As the insulating layer 12 shown in FIG. 1, 70 parts by mass of polyethylene (SP1510, manufactured by Prime Polymer), 26 parts by mass of EBR (Tafuma DF840, manufactured by Mitsui Chemicals), 4 parts by mass of modified polyolefin (Bondyne LX4110, manufactured by Arkema), 150 parts by mass of aluminum hydroxide (OL107ZO manufactured by Huber) as a flame retardant and 5 parts by mass of other additives shown in Table 4 were kneaded.

Using the above materials, the electric wire shown in FIG. 1 was produced and irradiated with an electron beam of 5 Mrad to crosslink the insulating layers 12 and 13. After that, various evaluations shown in Table 1 were carried out. As shown in Table 1, all the evaluation items were judged to be ◯, so the overall evaluation was ⊚.

<Example 3>
In the insulating layer 13 shown in FIG. 1, 45 parts by mass of EVA (V5274, manufactured by DuPont Mitsui Chemicals), 40 parts by mass of EVA (Levabun 600, manufactured by Lanxess), and 15 parts by mass of modified polyolefin (Tafuma MH7020, manufactured by Mitsui Chemicals) , 180 parts by mass of magnesium hydroxide (Kamishima Chemical Co., Ltd., Magshees S4) as a flame retardant, and 8 parts by mass of additives shown in Table 3 as other additives were kneaded.

As the insulating layer 12 shown in FIG. 1, 70 parts by mass of polyethylene (SP1510, manufactured by Prime Polymer), 26 parts by mass of EBR (Tafuma DF840, manufactured by Mitsui Chemicals), and 4 parts by mass of modified polyolefin (Tafuma MH7020, manufactured by Mitsui Chemicals). , 150 parts by mass of aluminum hydroxide (OL107ZO manufactured by Huber) as a flame retardant, and 5 parts by mass of other additives shown in Table 4 were kneaded.

Using the above materials, the electric wire shown in FIG. 1 was produced and irradiated with an electron beam of 5 Mrad to crosslink the insulating layers 12 and 13. After that, various evaluations shown in Table 1 were carried out. As shown in Table 1, all the evaluation items were judged to be ◯, so the overall evaluation was ⊚.

<Example 4>
In the insulating layer 13 shown in FIG. 1, 45 parts by mass of EVA (V5274, manufactured by DuPont Mitsui Chemicals), 40 parts by mass of EVA (Levabun 600, manufactured by Lanxess), and 15 parts by mass of modified polyolefin (Tafuma MH7020, manufactured by Mitsui Chemicals) , 180 parts by mass of magnesium hydroxide (Kamishima Chemical Co., Ltd., Magshees S4) as a flame retardant, and 8 parts by mass of additives shown in Table 3 as other additives were kneaded.

As the insulating layer 12 shown in FIG. 1, 70 parts by mass of polyethylene (SP1510, manufactured by Prime Polymer), 26 parts by mass of EBR (Tafuma DF840, manufactured by Mitsui Chemicals), and 4 parts by mass of modified polyolefin (Tafuma MH7020, manufactured by Mitsui Chemicals). , 180 parts by mass of aluminum hydroxide (OL107ZO manufactured by Huber) as a flame retardant, and 5 parts by mass of other additives shown in Table 4 were kneaded.

Using the above materials, the electric wire shown in FIG. 1 was produced and irradiated with an electron beam of 5 Mrad to crosslink the insulating layers 12 and 13. After that, various evaluations shown in Table 1 were carried out. As shown in Table 1, all the evaluation items were judged to be ◯, so the overall evaluation was ⊚.

<Example 5>
In the insulating layer 13 shown in FIG. 1, 45 parts by mass of EVA (V5274, manufactured by DuPont Mitsui Chemicals), 40 parts by mass of EVA (Levabun 600, manufactured by Lanxess), and 15 parts by mass of modified polyolefin (Tafuma MH7020, manufactured by Mitsui Chemicals) , 180 parts by mass of magnesium hydroxide (Kamishima Chemical Co., Ltd., Magshees S4) as a flame retardant, and 8 parts by mass of additives shown in Table 3 as other additives were kneaded.

As the insulating layer 12 shown in FIG. 1, 70 parts by mass of polyethylene (SP1510, manufactured by Prime Polymer), 26 parts by mass of EBR (Tafuma DF840, manufactured by Mitsui Chemicals), and 4 parts by mass of modified polyolefin (Tafuma MH7020, manufactured by Mitsui Chemicals). , 200 parts by mass of aluminum hydroxide (OL107ZO manufactured by Huber) as a flame retardant, and 5 parts by mass of other additives shown in Table 4 were kneaded.

Using the above materials, the electric wire shown in FIG. 1 was produced and irradiated with an electron beam of 5 Mrad to crosslink the insulating layers 12 and 13. After that, various evaluations shown in Table 1 were carried out. As shown in Table 1, the elongation at break was 130%, so the evaluation was made as Δ. All other evaluation items were evaluated as 0, so the overall evaluation was 0.

<Example 6>
In the insulating layer 13 shown in FIG. 1, 45 parts by mass of EVA (V5274, manufactured by DuPont Mitsui Chemicals), 40 parts by mass of EVA (Levabun 600, manufactured by Lanxess), and 15 parts by mass of modified polyolefin (Tafuma MH7020, manufactured by Mitsui Chemicals) , 180 parts by mass of magnesium hydroxide (Kamishima Chemical Co., Ltd., Magshees S4) as a flame retardant, and 8 parts by mass of additives shown in Table 3 as other additives were kneaded.

As the insulating layer 12 shown in FIG. 1, 70 parts by mass of polyethylene (SP1510, manufactured by Prime Polymer), 26 parts by mass of EBR (Tafuma DF840, manufactured by Mitsui Chemicals), 4 parts by mass of modified polyolefin (Bondyne LX4110, manufactured by Arkema), 180 parts by mass of aluminum hydroxide (OL104ZO manufactured by Huber) as a flame retardant and 5 parts by mass of other additives shown in Table 4 were kneaded.

Using the above materials, the electric wire shown in FIG. 1 was produced and irradiated with an electron beam of 5 Mrad to crosslink the insulating layers 12 and 13. After that, various evaluations shown in Table 1 were carried out. As shown in Table 1, all the evaluation items were judged to be ◯, so the overall evaluation was ⊚.

<Example 7>
In the insulating layer 13 shown in FIG. 1, 45 parts by mass of EVA (V5274, manufactured by DuPont Mitsui Chemicals), 40 parts by mass of EVA (Levabun 600, manufactured by Lanxess), and 15 parts by mass of modified polyolefin (Tafuma MH7020, manufactured by Mitsui Chemicals) , 180 parts by mass of magnesium hydroxide (Kamishima Chemical Co., Ltd., Magshees S4) as a flame retardant, and 8 parts by mass of additives shown in Table 3 as other additives were kneaded.

As the insulating layer 12 shown in FIG. 1, 70 parts by mass of polyethylene (SP0510, manufactured by Prime Polymer), 26 parts by mass of EBR (Tafuma DF840, manufactured by Mitsui Chemicals), 4 parts by mass of modified polyolefin (Bondyne LX4110, manufactured by Arkema), 150 parts by mass of aluminum hydroxide (OL107ZO manufactured by Huber) as a flame retardant and 5 parts by mass of other additives shown in Table 4 were kneaded.

Using the above materials, the electric wire shown in FIG. 1 was produced and irradiated with an electron beam of 5 Mrad to crosslink the insulating layers 12 and 13. After that, various evaluations shown in Table 1 were carried out. As shown in Table 1, the absolute value of the rate of change in oil-resistant tensile strength and the absolute value of the rate of change in oil-resistant elongation at break were each greater than 30%, so the evaluation was given as Δ. All other evaluation items were evaluated as 0, so the overall evaluation was 0.

<Comparative Example 1>
In the insulating layer 13 shown in FIG. 1, 45 parts by mass of EVA (V5274, manufactured by DuPont Mitsui Chemicals), 40 parts by mass of EVA (Levabun 600, manufactured by Lanxess), and 15 parts by mass of modified polyolefin (Tafuma MH7020, manufactured by Mitsui Chemicals) , 180 parts by mass of magnesium hydroxide (Kamishima Chemical Co., Ltd., Magshees S4) as a flame retardant, and 8 parts by mass of additives shown in Table 3 as other additives were kneaded.

As the insulating layer 12 shown in FIG. 1, 70 parts by mass of polyethylene (SP1510, manufactured by Prime Polymer), 26 parts by mass of EBR (Tafuma DF840, manufactured by Mitsui Chemicals), 4 parts by mass of modified polyolefin (Bondyne LX4110, manufactured by Arkema), 160 parts by mass of aluminum hydroxide (OL104ZO manufactured by Huber) as a flame retardant and 5 parts by mass of other additives shown in Table 4 were kneaded.

Using the above materials, the electric wire shown in FIG. 1 was produced and irradiated with an electron beam of 5 Mrad to crosslink the insulating layers 12 and 13. After that, various evaluations shown in Table 2 were carried out. As shown in Table 2, the aluminum hydroxide had a surface area of less than 3.7 m ² /ml (3.5 m ² /ml) and failed the direct current stability test. Therefore, the overall evaluation was x.

<Comparative Example 2>
In the insulating layer 13 shown in FIG. 1, 45 parts by mass of EVA (V5274, manufactured by DuPont Mitsui Chemicals), 40 parts by mass of EVA (Levabun 600, manufactured by Lanxess), and 15 parts by mass of modified polyolefin (Tafuma MH7020, manufactured by Mitsui Chemicals) , 180 parts by mass of magnesium hydroxide (Kamishima Chemical Co., Ltd., Magshees S4) as a flame retardant, and 8 parts by mass of additives shown in Table 3 as other additives were kneaded.

As the insulating layer 12 shown in FIG. 1, 70 parts by mass of polyethylene (SP1510, manufactured by Prime Polymer), 26 parts by mass of EBR (Tafuma DF840, manufactured by Mitsui Chemicals), 4 parts by mass of modified polyolefin (Bondyne LX4110, manufactured by Arkema), 120 parts by mass of aluminum hydroxide (OL104ZO manufactured by Huber) as a flame retardant and 5 parts by mass of other additives shown in Table 4 were kneaded.

Using the above materials, the electric wire shown in FIG. 1 was produced and irradiated with an electron beam of 5 Mrad to crosslink the insulating layers 12 and 13. After that, various evaluations shown in Table 2 were carried out. As shown in Table 2, the aluminum hydroxide had a surface area of less than 3.7 m ² /ml (2.9 m ² /ml) and failed the direct current stability test. It also failed the combustion test. Therefore, the overall evaluation was x.

<Comparative Example 3>
In the insulating layer 13 shown in FIG. 1, 45 parts by mass of EVA (V5274, manufactured by DuPont Mitsui Chemicals), 40 parts by mass of EVA (Levabun 600, manufactured by Lanxess), and 15 parts by mass of modified polyolefin (Tafuma MH7020, manufactured by Mitsui Chemicals) , 180 parts by mass of magnesium hydroxide (Kamishima Chemical Co., Ltd., Magshees S4) as a flame retardant, and 8 parts by mass of additives shown in Table 3 as other additives were kneaded.

As the insulating layer 12 shown in FIG. 1, 70 parts by mass of polyethylene (SP1510, manufactured by Prime Polymer), 26 parts by mass of EBR (Tafuma DF840, manufactured by Mitsui Chemicals), and 4 parts by mass of modified polyolefin (Tafuma MH7020, manufactured by Mitsui Chemicals). 210 parts by mass of aluminum hydroxide (OL107ZO manufactured by Huber) as a flame retardant and 5 parts by mass of other additives shown in Table 4 were kneaded.

Using the above materials, the electric wire shown in FIG. 1 was produced and irradiated with an electron beam of 5 Mrad to crosslink the insulating layers 12 and 13. After that, various evaluations shown in Table 2 were carried out. As shown in Table 2, the elongation at break was 120% and was unacceptable because the amount of aluminum hydroxide added was too large. Also, the DC stability test failed. Therefore, the overall evaluation was x.

<Comparative Example 4>
In the insulating layer 13 shown in FIG. 1, 45 parts by mass of EVA (V5274, manufactured by DuPont Mitsui Chemicals), 40 parts by mass of EVA (Levabun 600, manufactured by Lanxess), and 15 parts by mass of modified polyolefin (Tafuma MH7020, manufactured by Mitsui Chemicals) , 180 parts by mass of magnesium hydroxide (Kamishima Chemical Co., Ltd., Magshees S4) as a flame retardant, and 8 parts by mass of additives shown in Table 3 as other additives were kneaded.

As the insulating layer 12 shown in FIG. 1, 70 parts by mass of polyethylene (SP1510, manufactured by Prime Polymer), 26 parts by mass of EBR (Tafuma DF840, manufactured by Mitsui Chemicals), 4 parts by mass of modified polyolefin (Bondyne LX4110, manufactured by Arkema), 150 parts by mass of magnesium hydroxide (manufactured by Huber, H10A) as a flame retardant and 5 parts by mass of other additives shown in Table 4 were kneaded.

Using the above materials, the electric wire shown in FIG. 1 was produced and irradiated with an electron beam of 5 Mrad to crosslink the insulating layers 12 and 13. After that, various evaluations shown in Table 2 were carried out. As shown in Table 2, the DC stability test failed. The reason for this is thought to be that magnesium hydroxide was added in place of aluminum hydroxide. Therefore, the overall evaluation was x.

<Comparative Example 5>
In the insulating layer 13 shown in FIG. 1, 45 parts by mass of EVA (V5274, manufactured by DuPont Mitsui Chemicals), 40 parts by mass of EVA (Levabun 600, manufactured by Lanxess), and 15 parts by mass of modified polyolefin (Tafuma MH7020, manufactured by Mitsui Chemicals) , 180 parts by mass of magnesium hydroxide (Kamishima Chemical Co., Ltd., Magshees S4) as a flame retardant, and 8 parts by mass of additives shown in Table 3 as other additives were kneaded.

As the insulating layer 12 shown in FIG. 1, 70 parts by mass of polyethylene (SP1510, manufactured by Prime Polymer), 26 parts by mass of EBR (Tafuma DF840, manufactured by Mitsui Chemicals), 4 parts by mass of modified polyolefin (Bondyne LX4110, manufactured by Arkema), 100 parts by mass of magnesium hydroxide (manufactured by Huber, H10A) as a flame retardant and 5 parts by mass of other additives shown in Table 4 were kneaded.

Using the above materials, the electric wire shown in FIG. 1 was produced and irradiated with an electron beam of 5 Mrad to crosslink the insulating layers 12 and 13. After that, various evaluations shown in Table 2 were carried out. As shown in Table 2, the combustion test failed because the amount of flame retardant added was small. Also, the DC stability test failed. The reason for this is thought to be that magnesium hydroxide was added in place of aluminum hydroxide. Therefore, the overall evaluation was x.
<Evaluation results>
The evaluation results of the examples shown in Table 1 and the comparative examples shown in Table 2 reveal the following. First, by using aluminum hydroxide as the flame retardant added to the insulating layer 12, which is the inner layer, both flame retardancy and electrical properties can be achieved. The amount of aluminum hydroxide to be added to 100 parts by mass of polyolefin is preferably 130 parts by mass or more from the viewpoint of improving flame retardancy, and preferably 200 parts by mass or less from the viewpoint of improving breaking elongation properties. Also, if the surface area of aluminum hydroxide per unit volume of the resin composition of the insulating layer 12 is 3.7 m ² /ml or more, the electric wire 10 that passes the DC stability test can be obtained. However, from the results of Comparative Example 3, when the amount of aluminum hydroxide added exceeds 200 parts by mass, the surface area is 3.7 m ² /ml or more and the DC stability test fails.

The present invention is not limited to the above embodiments and examples, and can be modified in various ways without departing from the scope of the invention.

The invention is applicable to wires and cables.

10 Electric wire 11 Conductor 12 Insulating layer (first insulating layer, inner layer)
13 insulating layer (second insulating layer, outer layer)
20 cable 21 sheath

Claims (6)

a conductor;
a first insulating layer comprising a base polymer comprising polyolefin and covering the conductor;
a second insulating layer comprising a base polymer comprising polyolefin and covering the first insulating layer;
has
The first insulating layer contains 130 to 200 parts by mass of aluminum hydroxide added to 100 parts by mass of polyolefin,
The surface area of aluminum hydroxide per unit volume of the resin composition of the first insulating layer is 3.7 m ² /ml or more,
The second insulating layer is a non-halogen resin composition containing 150 to 250 parts by mass of magnesium hydroxide with respect to 100 parts by mass of polyolefin and containing an ethylene-vinyl acetate copolymer as the main component of the polyolefin,
The electric wire, wherein each of the first insulating layer and the second insulating layer is crosslinked. In claim 1,
The electric wire, wherein the first insulating layer contains polyethylene having a melting point of 110° C. or higher as a main component of polyolefin, and does not contain a vinyl acetate copolymer and an ethylene-acrylic acid copolymer as secondary components. In claim 1 or 2,
The first insulating layer contains acid-modified polyolefin as a secondary component of polyolefin,
The electric wire, wherein the acid-modified polyolefin includes one or more of polyethylene, ethylene-α-olefin, and ethylene-acrylic acid copolymer. In any one of claims 1 to 3,
The electric wire, wherein the aluminum hydroxide contained in the first insulating layer has an electrical conductivity of 20 μS/cm or less when suspended in pure water. In any one of claims 1 to 4,
The electric wire, wherein the second insulating layer contains an ethylene-vinyl acetate copolymer having a melting point of 80° C. or higher as a main component of polyolefin. having a plurality of electric wires and a sheath that collectively covers the plurality of electric wires,
A cable, wherein at least some of the plurality of electric wires are electric wires according to any one of claims 1 to 5.

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