Resin composition and power cable

Abstract

To provide a resin composition for an external semiconducting layer to enable improvements in both of the peelability of the external semiconducting layer and the productivity of a power cable.SOLUTION: A resin composition comprises: an ethylene vinyl acetate of 100 pts.wt., with a vinyl acetate content of 20 wt.% or more and 40 wt.% or less; acrylonitrile butadiene rubber of 5 pts.wt. or more and 30 pts.wt. or less; sulfur as a crosslinker of 0.01 pt.wt. or more and 1.0 pt.wt. or less; and conductive carbon black of 20 pts.wt. or more and 150 pts.wt. or less, in weight ratio.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a resin composition containing ethylene vinyl acetate as a base resin, and a power cable having a semiconductive layer made of the resin composition. [Background technology]

[0002] Power cables have been proposed in the past, each having a structure in which a conductor core wire is covered in multiple layers, such as semiconductive layers and insulating layers. For example, one conventional power cable has a structure in which a conductor core wire is covered in multiple layers, in this order, with an inner semiconductive layer, an insulating layer, an outer semiconductive layer, an electromagnetic shielding layer, and a sheath (see, for example, Patent Documents 1 to 3). Note that the inner semiconductive layer is generally provided for the purpose of reducing minute gaps that may occur between the conductor core wire and the insulating layer, thereby preventing localized corona discharges (so-called partial discharges) from occurring in such minute gaps during power transmission and damaging the insulating layer. The same applies to the outer semiconductive layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-302856 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-141877 [Patent Document 3] Patent No. 6347415 Summary of the Invention [Problem to be solved by the invention]

[0004] When the conventional power cable described above is actually used, the outer semiconductive layer and the layers outside it are generally peeled off from the insulating layer at the end of the power cable before connection to the other end is performed. From the viewpoint of improving the workability of such processing, it is preferable that the outer semiconductive layer can be easily peeled off from the insulating layer.

[0005] To make it easier to peel the outer semiconductive layer from the insulating layer (hereinafter also referred to as "improving the peelability" of the outer semiconductive layer), it is possible to consider, for example, increasing the degree of cross-linking of the resin that constitutes the outer semiconductive layer. As an example, in the above-mentioned conventional power cable (see Patent Document 3), after the outer semiconductive layer is extrusion-molded to cover the insulating layer, a separate cross-linking step is carried out under a predetermined vapor pressure to increase the degree of cross-linking of the resin that constitutes the outer semiconductive layer.

[0006] However, if the above-mentioned step for increasing the degree of cross-linking is included in the power cable manufacturing process, the productivity of the power cable will be reduced by the time and processing required for the step. Thus, it has been difficult to achieve both an improvement in the peelability of the outer semiconductive layer and an improvement in the productivity of the power cable.

[0007] One object of the present invention is to provide a resin composition for a semiconductive layer that can improve both the peelability of the semiconductive layer and the productivity of the power cable, and a power cable using the resin composition. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, the resin composition according to the present invention has the following characteristics.

[0009] 100 parts by weight of ethylene vinyl acetate having a vinyl acetate content of 20% by weight or more and 40% by weight or less, 5 parts by weight or more and 30 parts by weight or less of acrylonitrile butadiene rubber, Sulfur as a crosslinking agent is 0.01 parts by weight or more and 1.0 parts by weight or less, The conductive carbon black is contained in a weight ratio of 20 parts by weight or more and 150 parts by weight or less. It is a resin composition.

[0010] Furthermore, in order to achieve the above-mentioned object, the power cable according to the present invention has the following features.

[0011] A power cable comprising a conductor core, an insulating layer, and a semiconductive layer, the insulating layer is disposed so as to surround the outer periphery of the conductor core wire, The semiconductive layer is made of the resin composition according to any one of claims 1 to 3, and is disposed so as to be in close contact with the insulating layer and to surround the outer periphery of the insulating layer. It is a power cable. [Effects of the Invention]

[0012] According to experiments and considerations by the inventors, when a semiconductive layer is formed by extrusion molding the resin composition according to the present invention so as to adhere closely to an insulating layer of a power cable (for example, a resin layer made of cross-linked polyethylene), the semiconductive layer has the following properties. First, by having the vinyl acetate content in the ethylene vinyl acetate be 20% by weight or more and 40% by weight or less, appropriate releasability suitable for the peeling operation can be obtained when peeling the semiconductive layer from the insulating layer. Second, by having the weight ratio of acrylonitrile-butadiene rubber to 100 parts by weight of ethylene vinyl acetate be 5 parts by weight or more and 30 parts by weight or less, and the weight ratio of sulfur as a cross-linking agent to 100 parts by weight of ethylene vinyl acetate be 0.01 part by weight or more and 1.0 part by weight or less, it is possible to maintain good extrusion processability during extrusion molding while preventing deterioration of releasability due to insufficient cross-linking of the acrylonitrile-butadiene rubber, and to prevent deterioration of the appearance of the semiconductive layer due to premature cross-linking. Third, by setting the weight ratio of conductive carbon black to 100 parts by weight of ethylene vinyl acetate to 20 parts by weight or more and 150 parts by weight or less, the semiconductive layer can have appropriate conductivity while maintaining good extrusion processability during extrusion molding.

[0013] Furthermore, according to experiments and considerations by the inventors, when the resin composition according to the present invention is extruded, the acrylonitrile-butadiene rubber is crosslinked by sulfur inside the extruder, etc., and a semiconductive layer having an appropriate degree of crosslinking as a whole is obtained. Therefore, when the resin composition according to the present invention is used, there is no need to carry out a separate step for increasing the degree of crosslinking, as is employed in the above-mentioned conventional power cables.

[0014] Therefore, by forming a semiconductive layer of a power cable using the resin composition according to the present invention, it is possible to improve both the peelability of the semiconductive layer and the productivity of the power cable. In other words, the power cable according to the present invention can improve both the peelability of the semiconductive layer and the productivity of the power cable.

[0015] The present invention has been briefly described above. The details of the present invention will become clearer by reading the following detailed description of the invention (hereinafter referred to as "embodiments") with reference to the accompanying drawings. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a cross-sectional view of a power cable according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, a resin composition and a power cable 1 according to an embodiment of the present invention will be described with reference to the drawings.

[0018] <Cable configuration> 1, a power cable 1 according to this embodiment includes a conductor core wire 10, an inner semiconductive layer 11 in close contact with the conductor core wire 10 and surrounding the outer periphery of the conductor core wire 10, an insulating layer 12 in close contact with the inner semiconductive layer 11 and surrounding the outer periphery of the inner semiconductive layer 11, an outer semiconductive layer 13 in close contact with the insulating layer 12 and surrounding the outer periphery of the insulating layer 12, a shielding layer 14 in close contact with the outer semiconductive layer 13 and surrounding the outer periphery of the outer semiconductive layer 13, and a sheath 15 surrounding the shielding layer 14. The outer semiconductive layer 13 corresponds to the "semiconductive layer" in the present invention.

[0019] In this example, the conductor core wire 10 is made of a metal conductor. The conductor core wire 10 may be made of, for example, copper, copper alloy, aluminum, or aluminum alloy. The internal semiconductive layer 11 is made of a conductive resin material. The internal semiconductive layer 11 may be made of a resin composition in which conductive carbon is added to a polyolefin resin base material such as polyethylene, ethylene-propylene copolymer, ethylene-α-olefin copolymer, ethylene-vinyl acetate copolymer, or ethylene-acrylic acid ester copolymer. The insulating layer 12 is made of cross-linked polyethylene. The insulating layer 12 may be made of polyethylene to which a heat-activated cross-linking agent such as an organic peroxide (e.g., dicumyl peroxide) is added. The external semiconductive layer 13 is made of a resin composition containing ethylene-vinyl acetate as a base resin, as will be described in detail later. The shielding layer 14 is made of a shielding metal tape. The shielding layer 14 may be made of, for example, copper tape.

[0020] The power cable 1 is manufactured, for example, as follows: First, the inner semiconductive layer 11, the insulating layer 12, and the outer semiconductive layer 13 are extruded in this order to cover the conductor core wire 10. These extrusions may be performed sequentially or all at once. Next, the shielding layer 14 is wrapped around the outer periphery of the outer semiconductive layer 13. After that, the sheath 15 is extruded to cover the shielding layer 14, thereby obtaining the power cable 1.

[0021] More specifically, the outer semiconductive layer 13 is formed by extruding a resin composition containing 100 parts by weight of ethylene vinyl acetate (EVA) with a vinyl acetate (VA) content of 20 to 40% by weight, 5 to 30 parts by weight of acrylonitrile butadiene rubber (NBR), 0.01 to 1.0 part by weight of sulfur as a crosslinking agent, and 20 to 150 parts by weight of conductive carbon black in a weight ratio of 100 to 40% by weight, so as to surround the insulating layer 12. This extrusion is performed using an extruder to heat and knead the resin composition while extruding the cylindrical outer semiconductive layer 13 surrounding the outer periphery of the insulating layer 12 from an extrusion nozzle with a predetermined extrusion torque. By extruding this resin composition, the acrylonitrile butadiene rubber is crosslinked (vulcanized) by sulfur inside the extruder, etc., and an outer semiconductive layer 13 having an appropriate degree of crosslinking as a whole is obtained.

[0022] The composition of the resin composition that constitutes the outer semiconductive layer 13 and the properties of the outer semiconductive layer 13 obtained from the resin composition will be described in more detail below.

[0023] When the vinyl acetate content in the ethylene vinyl acetate is 20% by weight or more, it is possible to prevent the outer semiconductive layer 13 from being excessively adhered to the insulating layer 12. On the other hand, when the vinyl acetate content in the ethylene vinyl acetate is 40% by weight or less, it is possible to prevent the outer semiconductive layer 13 from being excessively easily peeled off from the insulating layer 12.

[0024] Furthermore, by setting the weight ratio of the acrylonitrile-butadiene rubber to 5 parts by weight or more, the degree of crosslinking of the outer semiconductive layer 13 as a whole becomes excessively small, and it is possible to prevent the heat treatment applied during extrusion molding from excessively reducing the releasability of the outer semiconductive layer 13. On the other hand, by setting the weight ratio of the acrylonitrile-butadiene rubber to 30 parts by weight or less, it is possible to maintain good extrusion processability during extrusion molding (i.e., it is possible to prevent an excessive increase in extrusion torque).

[0025] Furthermore, by setting the weight ratio of sulfur as a cross-linking agent to 0.01 part by weight or more, it is possible to prevent the degree of cross-linking of the acrylonitrile butadiene rubber from becoming excessively small, and to prevent the peelability of the outer semiconductive layer 13 from becoming excessively low due to the heat treatment applied during extrusion molding. On the other hand, by setting the weight ratio of sulfur as a cross-linking agent to 1.0 part by weight or less, it is possible to prevent the appearance of the outer semiconductive layer 13 from being impaired.

[0026] Furthermore, when the weight ratio of the conductive carbon black is 20 parts by weight or more, the outer semiconductive layer 13 has sufficient conductivity. On the other hand, when the weight ratio of the conductive carbon black is 150 parts by weight or less, good extrusion processability can be maintained during extrusion molding.

[0027] It is more preferable that the ethylene vinyl acetate contained in the resin composition described above has a vinyl acetate content of 20% by weight or more and 33% by weight or less, from the viewpoint of further improving the releasability from the insulating layer 12. Furthermore, it is more preferable that the resin composition described above contains conductive carbon black in a weight ratio of 20 parts by weight or more and 70 parts by weight or less, from the viewpoint of further improving the conductivity of the outer semiconductive layer 13 and further improving the ease of extrusion molding.

[0028] The resin composition constituting the outer semiconductive layer 13 may contain a vulcanization accelerator, a lubricant, an antioxidant, and the like, as needed.

[0029] <Evaluation of the characteristics of the outer semiconductive layer> The properties of the outer semiconductive layer 13 will be evaluated below from the viewpoints of the peelability of the outer semiconductive layer 13 from the insulating layer 12, the conductivity of the outer semiconductive layer 13, and the appearance of the outer semiconductive layer 13. Specifically, the inventors produced power cable 1 samples as test samples using outer semiconductive layers 13 made of each of the resin compositions (Examples 1 to 10 and Comparative Examples 1 to 25) having the compositions shown in Tables 1 to 4 below, and evaluated the peelability, conductivity, and appearance described above. Note that the units of the numerical values ​​representing each composition in Tables 1 to 4 are parts by weight.

[0030] In each sample, the thickness of the outer semiconductive layer 13 was 0.7 mm. Furthermore, due to the nature of the test to evaluate the above-mentioned properties of the outer semiconductive layer 13, the shielding layer 14 and the sheath 15 were not provided in each sample.

[0031] [Table 1]

[0032] [Table 2]

[0033] [Table 3]

[0034] [Table 4]

[0035] Regarding the ethylene vinyl acetate (EVA) listed in Tables 1 to 4, the EVA with a vinyl acetate (VA) content of 32% is Evaflex (registered trademark) product number V523 manufactured by Dow Mitsui Polychemicals Co., Ltd., the EVA with a vinyl acetate (VA) content of 20% is Ultrathene (registered trademark) product number 684 manufactured by Tosoh Corporation, the EVA with a vinyl acetate (VA) content of 42% is Ultrathene (registered trademark) product number 760 manufactured by Tosoh Corporation, and the EVA with a vinyl acetate (VA) content of 19% is Ultrathene (registered trademark) product number 636 manufactured by Tosoh Corporation. The acrylonitrile butadiene rubber (NBR) listed in Tables 1 to 4 is Nipol (registered trademark) product number DN3380 manufactured by Zeon Corporation. The conductive carbon black listed in Tables 1 to 4 is Denka Black (registered trademark) manufactured by Denka Company, Limited. The sulfur listed in Tables 1 to 4 is SULFAX (registered trademark) 200S manufactured by Tsurumi Chemical Industry Co., Ltd.

[0036] For each sample (Examples 1 to 10 and Comparative Examples 1 to 25), the appearance of the outer semiconductive layer 13 extrusion-molded on the outer periphery of the insulating layer 12 was visually observed. The pass / fail of the appearance was determined by checking whether or not there were any irregularities, roughness, or bubbles on the surface of the outer semiconductive layer 13. If there were no irregularities, it was judged as pass (◯), and if there were any irregularities, it was judged as fail (×).

[0037] As shown in Table 1, the appearances of all of Examples 1 to 10 were acceptable (◯). On the other hand, as shown in Tables 2 to 4, the appearances of Comparative Examples 1 to 9, 12 to 15, and 18 to 25 were acceptable (◯), while the appearances of Comparative Examples 10, 11, 16, and 17 were unacceptable (×). In particular, comparisons between Example 5 and Comparative Example 10, between Example 6 and Comparative Example 11, between Example 9 and Comparative Example 16, and between Example 10 and Comparative Example 17 revealed that the appearance of outer semiconducting layer 13 was good when the weight ratio of sulfur was 1.0 part by weight or less.

[0038] Furthermore, each sample (Examples 1 to 10 and Comparative Examples 1 to 25) was evaluated for extrusion processability when extruding the outer semiconductive layer 13. The extrusion processability was evaluated as pass (◯) if there was no excessive increase in extrusion torque during the process of extruding the outer semiconductive layer 13, and as fail (×) if there was an excessive increase in extrusion torque.

[0039] As shown in Table 1, the extrusion processability of all of Examples 1 to 10 was acceptable (◯). On the other hand, as shown in Tables 2 to 4, the extrusion processability of Comparative Examples 1 to 19 was acceptable (◯), and the extrusion processability of Comparative Examples 20 to 25 was unacceptable (×). In particular, a comparison between Examples 1 and 2 and Comparative Example 20, and a comparison between Examples 3 and 4 and Comparative Example 21 revealed that the extrusion processability was good when the weight ratio of conductive carbon black was 150 parts by weight or less.

[0040] Furthermore, comparisons between Examples 1 and 3 and Comparative Example 22, between Examples 2 and 4 and Comparative Example 23, and between Examples 7 and 8 and Comparative Examples 24 and 25 revealed that when the amount of NBR (acrylonitrile butadiene rubber) is 30 parts by weight or less, the extrusion processability is good.

[0041] Furthermore, for each sample (Examples 1 to 10 and Comparative Examples 1 to 25), the conductivity of the outer semiconductive layer 13 was evaluated by a four-terminal method using a digital ohmmeter R-506 manufactured by Kawaguchi Electric Works Co., Ltd. The conductivity was judged to be acceptable or unacceptable when the measured resistance value was 1.0×10 4 If the resistance is less than Ωcm, it is judged as pass (○), and the measured resistance is 1.0 × 10 4 If it was greater than Ωcm, it was judged as unacceptable (×).

[0042] As shown in Table 1, the conductivity of all of Examples 1 to 10 was acceptable (◯). On the other hand, as shown in Tables 2 to 4, the conductivity of Comparative Examples 1 to 13 and 15 to 25 was acceptable (◯), while the conductivity of Comparative Example 14 was unacceptable (×). In particular, a comparison between Example 1 and Comparative Example 14 revealed that the conductivity of outer semiconductive layer 13 was good when the weight ratio of conductive carbon black was 20 parts by weight or more.

[0043] Furthermore, the releasability at room temperature was evaluated for each sample (Examples 1 to 10 and Comparative Examples 1 to 25). The releasability at room temperature was evaluated by making a strip-shaped peel piece (i.e., a notch) 12.7 mm wide in the outer semiconductive layer 13, peeling this peel piece from the insulating layer 12 at a speed of 500 mm / min using a tensile tester, and determining whether the measured peel force was 10 N or more and 40 N or less as pass (◯), and determining whether the measured peel force was less than 10 N or more than 40 N as fail (×).

[0044] As shown in Table 1, the releasability at room temperature for all of Examples 1 to 10 was acceptable (◯). On the other hand, as shown in Tables 2 to 4, the releasability for Comparative Examples 9 to 25 was acceptable (◯), while the releasability for Comparative Examples 1 to 8 was unacceptable (×). In particular, a comparison between Example 7 and Comparative Example 1, a comparison between Example 8 and Comparative Example 2, a comparison between Examples 5 and 9 and Comparative Example 3, and a comparison between Examples 6 and 10 and Comparative Example 4 revealed that the releasability at room temperature of the outer semiconductive layer 13 was good when the vinyl acetate content in the ethylene vinyl acetate was 40 wt % or less. Furthermore, a comparison between Example 7 and Comparative Example 5, a comparison between Example 8 and Comparative Example 6, a comparison between Example 9 and Comparative Example 7, and a comparison between Example 10 and Comparative Example 6 revealed that the releasability at room temperature of the outer semiconductive layer 13 was good when the vinyl acetate content in the ethylene vinyl acetate was 20 wt % or more.

[0045] Furthermore, the releasability after heating was evaluated for each sample (Examples 1 to 10 and Comparative Examples 1 to 25). The releasability after heating was evaluated by heating each sample in an environment at 120°C for 96 hours, then leaving it in an environment at 50°C for 1 hour. The releasability after heating was evaluated by making a strip-shaped peelable piece (i.e., an incision) 12.7 mm wide in the outer semiconductive layer 13, and if the tester could peel this peelable piece by hand, it was judged as passed (◯). If the tester could not peel this peelable piece by hand because the outer semiconductive layer 13 was fused to the insulating layer 12, for example, it was judged as failed (×).

[0046] As shown in Table 1, the releasability after heating of all Examples 1 to 10 was acceptable (◯). On the other hand, as shown in Tables 2 to 4, the releasability after heating of Comparative Examples 1 to 8, 10, 11, 14, 16, 17, and 20 to 25 was acceptable (◯), while the releasability after heating of Comparative Examples 9, 12, 13, 15, 18, and 19 was unacceptable (×). In particular, a comparison between Example 5 and Comparative Example 12, a comparison between Example 5 and Comparative Example 13, a comparison between Example 7 and Comparative Example 9, a comparison between Example 7 and Comparative Example 15, a comparison between Example 9 and Comparative Example 18, and a comparison between Example 10 and Comparative Example 19 revealed that the releasability after heating of outer semiconductive layer 13 was good when the weight ratio of acrylonitrile butadiene rubber was 5 parts by weight or more and the weight ratio of sulfur was 0.01 parts by weight or more.

[0047] <Actions and Effects> As described above, in the power cable 1 according to this embodiment, the outer semiconductive layer 13 is composed of a resin composition containing, in weight ratios of 100 parts by weight of ethylene vinyl acetate having a vinyl acetate content of 20% by weight or more and 40% by weight or less, 5 parts by weight or more and 30 parts by weight or less of acrylonitrile butadiene rubber, 0.01 parts by weight or more and 1.0 parts by weight or less of sulfur as a cross-linking agent, and 20 parts by weight or more and 150 parts by weight or less of conductive carbon black.

[0048] First, by setting the vinyl acetate content in the ethylene vinyl acetate to 20% by weight or more and 40% by weight or less, appropriate releasability suitable for peeling the outer semiconductive layer 13 from the insulating layer 12 is obtained. Second, by setting the weight ratio of the acrylonitrile butadiene rubber to 100 parts by weight of the ethylene vinyl acetate to 5 parts by weight or more and 30 parts by weight or less, and by setting the weight ratio of the sulfur as a crosslinking agent to 100 parts by weight of the ethylene vinyl acetate to 0.01 parts by weight or more and 1.0 parts by weight or less, it is possible to maintain good extrusion processability during extrusion molding while preventing deterioration of releasability due to insufficient crosslinking of the acrylonitrile butadiene rubber, and to prevent deterioration of the appearance of the outer semiconductive layer 13 due to premature crosslinking. Third, by setting the weight ratio of the conductive carbon black to 100 parts by weight of the ethylene vinyl acetate to 20 parts by weight or more and 150 parts by weight or less, it is possible to maintain appropriate electrical conductivity of the outer semiconductive layer 13 while maintaining good extrusion processability during extrusion molding.

[0049] Furthermore, when the resin composition having the above-described composition is extruded, the acrylonitrile-butadiene rubber is crosslinked by sulfur inside the extruder or the like, and an outer semiconducting layer 13 having an appropriate degree of crosslinking as a whole is obtained. Therefore, when the above-described resin composition is used, there is no need to carry out a separate step for increasing the degree of crosslinking, as is employed in the above-described conventional power cables.

[0050] Therefore, by using the resin composition having the above-described composition to form the outer semiconductive layer 13 of the power cable 1, it is possible to improve both the peelability of the outer semiconductive layer 13 and the productivity of the power cable 1. In other words, it is possible to improve both the peelability of the outer semiconductive layer 13 and the productivity of the power cable 1.

[0051] <Other aspects> It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be adopted within the scope of the present invention. For example, the present invention is not limited to the above-described embodiments, and modifications, improvements, etc. are possible as appropriate. In addition, the material, shape, dimensions, number, location, etc. of each component in the above-described embodiments are arbitrary and not limited as long as the present invention can be achieved.

[0052] Here, the characteristics of the resin composition according to the present invention and the power cable 1 described above will be briefly summarized and listed below in [1] to [4].

[0053] [1] 100 parts by weight of ethylene vinyl acetate having a vinyl acetate content of 20% by weight or more and 40% by weight or less, 5 parts by weight or more and 30 parts by weight or less of acrylonitrile butadiene rubber, Sulfur as a crosslinking agent is 0.01 parts by weight or more and 1.0 parts by weight or less, The conductive carbon black is contained in a weight ratio of 20 parts by weight or more and 150 parts by weight or less. Resin composition.

[0054] When the resin composition having the configuration [1] above is extrusion-molded to form a semiconductive layer so as to adhere closely to an insulating layer of a power cable (for example, a resin layer made of cross-linked polyethylene), the semiconductive layer has the following properties. First, the vinyl acetate content in the ethylene vinyl acetate is 20% by weight or more and 40% by weight or less, so that appropriate releasability suitable for the peeling operation can be obtained when peeling the semiconductive layer from the insulating layer. Second, the weight ratio of acrylonitrile-butadiene rubber to 100 parts by weight of ethylene vinyl acetate is 5 parts by weight or more and 30 parts by weight or less, and the weight ratio of sulfur as a cross-linking agent to 100 parts by weight of ethylene vinyl acetate is 0.01 part by weight or more and 1.0 part by weight or less, so that good extrusion processability can be maintained during extrusion molding while preventing deterioration of releasability due to insufficient cross-linking of the acrylonitrile-butadiene rubber, and deterioration of the appearance of the semiconductive layer due to premature cross-linking can be prevented. Third, by setting the weight ratio of conductive carbon black to 100 parts by weight of ethylene vinyl acetate to 20 parts by weight or more and 150 parts by weight or less, the semiconductive layer can have appropriate conductivity while maintaining good extrusion processability during extrusion molding.

[0055] Furthermore, when the resin composition is extruded, the acrylonitrile-butadiene rubber is crosslinked by sulfur inside the extruder, etc., and a semiconductive layer having an appropriate degree of crosslinking as a whole is obtained, so that there is no need to carry out a separate step for increasing the degree of crosslinking, as is employed in the conventional power cables described above.

[0056] Therefore, by using the above-mentioned resin composition to form the semiconductive layer of the power cable, it is possible to improve both the peelability of the semiconductive layer and the productivity of the power cable.

[0057] [2] In the resin composition described in [1] above, The vinyl acetate content in the ethylene vinyl acetate is 20% by weight or more and 33% by weight or less. Resin composition.

[0058] If the semiconductive layer is formed using the resin composition having the above configuration [2], the peelability of the semiconductive layer from the insulating layer can be further improved.

[0059] [3] In the resin composition according to the above [1] or [2], Contains conductive carbon black in a weight ratio of 20 parts by weight or more and 70 parts by weight or less, Resin composition.

[0060] If the semiconductive layer is formed using the resin composition having the above configuration [3], the conductivity of the semiconductive layer can be further improved and the ease of extrusion molding can be further improved.

[0061] [4] A power cable (1) comprising a conductor core (10), an insulating layer (12), and a semiconductive layer (13), The insulating layer (12) is disposed so as to surround the outer periphery of the conductor core wire (10), The semiconductive layer (13) is made of the resin composition according to any one of [1] to [3] above, and is disposed so as to be in close contact with the insulating layer (12) and surround the outer periphery of the insulating layer (12). Power cable (1).

[0062] According to the power cable having the configuration [4], it is possible to improve both the peelability of the semiconductive layer and the productivity of the power cable, as described above with respect to the effect of the resin composition having the configuration [1]. If necessary, another layer (for example, an internal semiconductive layer) may be provided between the insulating layer and the conductor core. [Explanation of symbols]

[0063] 1 Cable (power cable) 10 Conductor core wire 11 Internal semiconducting layer 12 Insulating layer 13 Outer semiconductive layer (semiconductive layer)

Claims

1. 100 parts by weight of ethylene vinyl acetate having a vinyl acetate content of 20% by weight or more and 40% by weight or less; 5 parts by weight or more and 30 parts by weight or less of acrylonitrile butadiene rubber, sulfur as a crosslinking agent in an amount of 0.01 part by weight or more and 1.0 part by weight or less; The conductive carbon black is contained in a weight ratio of 20 parts by weight or more and 150 parts by weight or less. Resin composition.

2. The resin composition according to claim 1, The vinyl acetate content in the ethylene vinyl acetate is 20% by weight or more and 33% by weight or less. Resin composition.

3. The resin composition according to claim 1 or claim 2, Contains conductive carbon black in a weight ratio of 20 parts by weight or more and 70 parts by weight or less, Resin composition.

4. A power cable comprising a conductor core, an insulating layer, and a semiconductive layer, the insulating layer is disposed so as to surround the outer periphery of the conductor core wire, The semiconductive layer is made of the resin composition according to any one of claims 1 to 3, and is disposed so as to be in close contact with the insulating layer and to surround the outer periphery of the insulating layer. Power cable.

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