JP5639010B2 - Semiconductive resin composition and power cable - Google Patents

Description

  The present invention relates to a semiconductive resin composition and a power cable using the same, and more specifically, a semiconductive layer capable of forming an external semiconductive layer excellent in peelability from an insulating layer in a room temperature to high temperature (50 ° C.) region. The present invention relates to a conductive resin composition.

  High-voltage power cables cover the surface of the conductor with an insulating layer to electrically insulate it from the outside, but this insulating layer also generates a discharge when there are fine irregularities on the surface. A semiconductive layer is provided on the surface to smooth the surface potential and prevent discharge. Therefore, as illustrated in FIG. 1, in the high-voltage power cable 1, the inner semiconductive layer 5 is coated on the conductor 3, and then the insulating layer 7 is coated thereon, and further on the insulating layer 7. It has a multilayer structure in which the outer semiconductive layer 9 is covered.

  And as base resin of the semiconductive resin composition which comprises the internal semiconductive layer 5 and the external semiconductive layer 9, generally an ethylene homopolymer, ethylene-alpha-olefin (C3-C12) copolymer weight Polymers, ethylene-α, β-unsaturated carboxylic acid (or ester derivatives thereof) copolymers, ethylene carboxylic acid vinyl ester copolymers, and the like are used alone or as a mixture of two or more. And carbon black is mix | blended with these base resins, electroconductivity is provided, and it is set as the said semiconductive resin composition. This semiconductive resin composition generally has good adhesion to a resin such as cross-linked polyethylene constituting the insulating layer 7.

  However, in such a power cable 1, it is necessary to easily peel off the external semiconductive layer 9 from the insulating layer 7 in order to easily and satisfactorily perform the terminal processing work performed when connecting the cables. There is also. Therefore, it has been proposed to improve the stripping property by blending various compounds with the base resin of the resin composition constituting the outer semiconductive layer 9. Examples of such compounds include chlorinated polyethylene (Patent Document 1) and styrene-modified ethylene-vinyl acetate copolymer obtained by grafting a styrene monomer to an ethylene-vinyl acetate copolymer (Patent Document 2). ) And nitrile butadiene rubber (Patent Document 3).

  Among the compounds proposed above, chlorinated polyethylene and styrene-modified ethylene-vinyl acetate copolymer are quite expensive, and it is preferable to add nitrile butadiene rubber from the viewpoint of price, but there are many nitrile butadiene rubbers. When it mix | blends, there existed a problem that heat resistance fell.

  On the other hand, the temperature of a power cable laid outside increases in direct sunlight. In summer, this temperature may reach 50 ° C on the surface of the outer semiconductive layer. In order to carry out the terminal treatment work on site easily and satisfactorily, good peeling will occur even in such a temperature environment. It is required to maintain the take-off performance. Therefore, it has been proposed to ensure heat resistance while ensuring peelability by blending hydrogenated nitrile butadiene rubber (Patent Document 4).

JP 56-0667109 Japanese Patent Laid-Open No. 09-111089 JP 56-0667108 A Japanese Patent Laid-Open No. 04-079105

  However, since hydrogenated nitrile butadiene rubber is an expensive material, there is no merit in using it as compared with the case of using chlorinated polyethylene or styrene-modified ethylene-vinyl acetate copolymer as a base resin. End up. Therefore, any semiconductive resin composition that is excellent in stripping property and can be used for a power cable laid outdoors has become expensive.

  The present invention has been made in view of the above-described problems, and the object of the present invention is to provide excellent power stripping from an insulating layer in a temperature range from room temperature to high temperature (50 ° C.), which is relatively inexpensive. It is to obtain a semiconductive resin composition for a cable.

  As a result of intensive studies to achieve the above object, the present inventors have secured heat resistance by adding an oxidation type polyethylene (PE) wax to the base material of the semiconductive resin composition, It has been found that the insulating layer and the semiconductive layer are easily peeled off. The present invention has been made based on this finding.

That is, the present invention provides the following inventions.
(1) 100 mass of base resin in which 90 to 95 mass parts of ethylene-vinyl acetate copolymer containing 10 to 40 mass% of vinyl acetate monomer and 5 to 10 mass parts of nitrile butadiene rubber containing 40 mass% or less of acrylonitrile are blended. A semiconductive resin composition for an external semiconductive layer of a power cable, which contains 5 to 15 parts by mass of an oxidized type polyethylene wax and carbon black with respect to the part.
(2) The semiconductive resin composition for an external semiconductive layer for a power cable according to (1), comprising 30 to 100 parts by mass of carbon black with respect to 100 parts by mass of the base resin.
(3) A power cable having an external semiconductive layer made of the semiconductive resin composition according to (1) or (2).

  According to the present invention, it is possible to obtain a semiconductive resin composition that is excellent in heat resistance and can be peeled off well in a normal temperature to high temperature region without using an expensive hydrogenated nitrile butadiene rubber.

The perspective view which shows typically the structure of the power cable which concerns on this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
<1. Semiconductive resin composition>
The semiconductive resin composition of the present invention comprises 90 to 95 parts by mass of an ethylene-vinyl acetate copolymer containing 10 to 40% by mass of a vinyl acetate monomer and 5 to 10 parts by mass of nitrile butadiene rubber containing 40% by mass or less of acrylonitrile. It is characterized by containing 5 to 15 parts by mass of an oxidized polyethylene wax containing a carbonyl group in the molecular structure and 30 to 100 parts by mass of carbon black with respect to 100 parts by mass of the base resin. Below, each component and its content are demonstrated.

(Ethylene-vinyl acetate copolymer)
The ethylene-vinyl acetate copolymer (EVA) is a main material of the semiconductive resin composition of the present invention and occupies 90 to 95 parts by mass of the base resin. As this ethylene-vinyl acetate copolymer, various types are used alone or in combination of two or more kinds so that the content of vinyl acetate monomer (EA) is 10 to 40% by mass, preferably 15 to 25% by mass. It can be used as a mixture. If the content of the vinyl acetate monomer is less than 10% by mass, the external semiconductive layer adheres well to the insulating layer, making it difficult to remove. On the other hand, if it exceeds 40% by mass, the softening temperature of the resin composition is lowered, so that, for example, mechanical properties in a high temperature region around 50 ° C. are weakened, and it becomes difficult to remove.

(Nitrile butadiene rubber)
Nitrile butadiene rubber is blended in the base resin for the purpose of improving the peelability from the insulating layer. As the nitrile butadiene rubber, one containing 15 to 40% by mass of acrylonitrile can be used. Nitrile butadiene rubber having an acrylonitrile content of 15% by mass or less is generally not sold and is difficult to obtain. A semiconductive resin composition containing nitrile butadiene rubber containing acrylonitrile in excess of 40% by mass is not preferable because the peelability from an insulating layer made of crosslinked polyethylene deteriorates at high temperatures.
Nitrile butadiene rubber is blended in an amount of 5 to 10 parts by mass in the base resin. Since nitrile butadiene rubber has low heat resistance, the amount of nitrile butadiene rubber needs to be 10 parts by mass or less in order to ensure sufficient heat resistance of the semiconductive resin composition. Moreover, since the effect which improves peelability is not fully acquired when there are few compounding quantities, and peelability at high temperature falls, it is preferable to set it as 5 mass parts or more.

(Polyethylene wax)
In the present invention, an oxidation type polyethylene wax is used in combination with a nitrile butadiene rubber to realize a semiconductive resin composition having heat resistance and sufficient peelability even at high temperatures.
Polyethylene wax is a polyethylene having a small molecular weight, and the affinity with a resin or metal varies depending on the acid value. When the non-oxidized type polyethylene wax is used, it is necessary to use an oxidized type because it is compatible with the crosslinked polyethylene constituting the insulating layer and is difficult to peel off. As the oxidation type polyethylene wax, various types can be used as long as a carbonyl group (C═O) is introduced into the polyethylene structure. For example, low density oxidation type, high density oxidation type, and oxidative copolymerization type polyethylene can be used, but it is preferable to use low density oxidation type polyethylene wax. For example, an oxidation type polyethylene wax having an acid value of 1 to 40 mgKOH / g and an average molecular weight of 10,000 or less can be used. The addition amount of the oxidation type polyethylene wax is suitably 5 to 15 parts by mass with respect to 100 parts by mass of the base resin. If the added amount is less than 5 parts by mass, sufficient effect for improving the peelability is not seen and it becomes difficult to separate from the insulating layer, and if it exceeds 15 parts by weight, slip occurs when mixing (compounding) the raw materials. This makes it difficult to obtain a compound, which is not preferable.

(Carbon black)
Carbon black is added to impart conductivity to the base resin. The compounding quantity of carbon black can be suitably determined according to desired electroconductivity, for example, can be 30-100 mass parts with respect to 100 mass parts of base resins, Preferably it can be 40-80 mass parts. . When the blending amount of carbon black is less than 30 parts by mass, the necessary conductivity as a semiconductive resin composition cannot be obtained, and when it exceeds 100 parts by mass, the extrusion characteristics and mechanical properties in the case of a semiconductive layer are obtained. This is not preferable because the characteristics are insufficient. There is no restriction | limiting in particular as carbon black, Well-known various carbon black can be used. Examples thereof include furnace black, acetylene black, and ketjen black. Carbon black can be used alone or in combination of two or more.

(Other compounds)
In the semiconductive resin composition of the present invention, in addition to the above materials, various additives can be blended as necessary within a range not impairing the object of the present invention. Examples of such additives include stabilizers, anti-aging agents, cross-linking agents, processing aids, and the like.
For example, as the anti-aging agent, a commonly used anti-aging agent can be appropriately selected and blended. However, it is preferable to use a phenol-based, phosphite-based, or thioether-based anti-aging agent. 4,4′-thiobis (3-methyl-6-tert-butylphenol) is preferable in that it has an effect of inhibiting the crosslinking reaction of the resin composition during extrusion.

(Effect of semiconductive resin composition)
Since the semiconductive resin composition of the present invention has both releasability from the resin material and heat resistance, it is composed of a crosslinked polyethylene or the like not only at room temperature but also at a high temperature range of about 50 ° C., for example. A semiconductive resin composition having excellent peelability from the insulating layer is provided. Moreover, since expensive materials such as chlorinated polyethylene, styrene-modified ethylene-vinyl acetate copolymer, and hydrogenated nitrile butadiene rubber are not required, they can be obtained at a relatively low cost. Furthermore, since it also has extrusion moldability, it can be suitably used, for example, as a material for a coating layer (semiconductive layer) of a power cable.

<2. Power cable>
Next, the power cable of the present invention will be described with reference to FIG. The power cable 1 of the present invention has a structure including an internal semiconductive layer 5, an insulating layer 7 and an external semiconductive layer 9 in order from the inside on a conductor 3, and the conductor 3 is composed of the internal semiconductive layer 5, the insulating layer 7, and the external It is covered with a semiconductive layer 9. The power cable 1 electrically insulates the conductor 3 from the outside by the insulating layer 7, and the internal semiconductive layer 5 and the external semiconductive layer are formed on the boundary surface between the conductor 3 and the insulating layer 7 and the outer surface of the insulating layer 7, respectively. By providing the conductive layer 9, external discharge from fine irregularities on the surface of the insulating layer 7 is also prevented. Although not shown in FIG. 1, the power cable 1 may be configured to include, for example, a metal shielding layer or a sheath on the outer surface of the external semiconductive layer 9 as necessary.
And in this invention, the external semiconductive layer 9 consists of said semiconductive resin composition of this invention, It is characterized by the above-mentioned. About the conductor 3, the internal semiconductive layer 5, and the insulating layer 7, it can select from a well-known various material suitably, and can use it.

  The power cable of the present invention can be manufactured by a conventional method. For example, a metal strand is twisted to form a conductor 3, on which a resin composition that becomes the inner semiconductive layer 5, an uncrosslinked polyethylene that becomes the insulating layer 7, and an outer semiconductive layer 9 of the present invention. The semiconductive resin composition is simultaneously coated by extrusion coating, and then the uncrosslinked polyethylene is crosslinked by heating under pressure. Then, if necessary, for example, a power cable can be manufactured by forming a shielding layer or a sheath.

(Effect of power cable)
Since the power cable 1 of the present invention uses the above semiconductive resin composition as the external semiconductive layer 9, the external semiconductive layer 9 is peeled off from the insulating layer 7 even in a high temperature range from room temperature to about 50 ° C. Easy to take. Furthermore, the power cable 1 of the present invention is provided at a relatively low cost.

Hereinafter, the present invention will be specifically described using examples and comparative examples.
(Manufacture of semiconductive resin composition)
In the formulations shown in Examples 1 to 7 and Comparative Examples 1 to 8 in Table 1 and Table 2 below, each material was put into a Banbury mixer and melt-kneaded at 160 to 170 ° C. for 5 minutes. The pellets were granulated to produce a semiconductive resin composition as a compound. Note that the annotations * 1 to * 13 in Table 2 are the same as those in Table 1. Moreover, about the compounding quantity of PE-WAX, acetylene black, Nocrack 300R, Trigonox T, and a calcium stearate, it means how many mass parts were added with respect to 100 mass parts of base resins which mixed EVA and NBR.

* 1 EVA1: Ethylene-vinyl acetate copolymer (Mitsui DuPont Polychemical Co., Ltd., EVAFLEX P1007, EA content: 10 wt%)
* 2 EVA2: Ethylene-vinyl acetate copolymer (Mitsui / DuPont Polychemical Co., Ltd., EVAFLEX EV45LX, EA content: 46 wt%)
* 3 EVA3: Ethylene-vinyl acetate copolymer (Mitsui / DuPont Polychemical Co., Ltd., EVAFLEX 150, EA content: 33 wt%)
* 4 EVA4: Ethylene-vinyl acetate copolymer (Mitsui DuPont Polychemical Co., Ltd. EVAFLEX V523, EA content: 33 wt%)
* 5 EVA5: Ethylene-vinyl acetate copolymer (Novatec EVA LV244A, EA content: 7 wt%, manufactured by Nippon Polyethylene Corporation)
* 6 NBR1: nitrile butadiene rubber (Nipol 1041, acrylonitrile content: 40 wt%, manufactured by Nippon Zeon Co., Ltd.)
* 7 NBR2: nitrile butadiene rubber (N260S manufactured by JSR Corporation, acrylonitrile content: 15 wt%)
* 8 NBR3: nitrile butadiene rubber (N215SL manufactured by JSR Corporation, acrylonitrile content: 48 wt%)
* 9 Oxidized polyethylene wax (A-C polyethylene (acid value 15-40 mgKOH / g) manufactured by Honeywell)
* 10 Non-oxidizing polyethylene wax (LC polyethylene made by Toshin Yushi)
* 11 Carbon black (Denka Black manufactured by Denki Kagaku Kogyo)
* 12 Anti-aging agent (made by Ouchi Shinsei Chemical)
* 13 Cross-linking agent (manufactured by Kayaku Akzo Corporation)

(Manufacture of power cables)
Using the obtained semiconductive resin composition, a power cable 1 having the structure shown in FIG. 1 was produced. As a procedure for manufacturing the power cable 1, an inner semiconductive layer 5 having a thickness of 1.0 mm, an insulating layer 7 having a thickness of 3.0 mm, and a thickness are sequentially formed on the surface of the conductor 3 having a cross-sectional area of 100 mm ² from the inside. Three external semiconductive layers 9 having a thickness of 1.0 mm are simultaneously extrusion-coated, guided to a heated crosslinking zone, and subjected to a crosslinking reaction by applying pressure and heating in a nitrogen gas at a pressure of 10 kg / cm ² at a temperature of 260 ° C. Was completed.
A commercially available semiconductive compound (NUCV-9563 manufactured by Nihon Unicar Co., Ltd.) is used for the inner semiconductive layer 5, and a commercially available insulating compound (NUCV-9253 manufactured by Nihon Unicar Co., Ltd.) is used for the insulating layer 7. For the layer 9, the semiconductive resin composition prepared above was used.
Next, a metal shielding layer and an anticorrosion layer were provided by a conventional method to produce a power cable.

(Evaluation of semiconductive resin composition and power cable)
About the obtained electric power cable, the peelability of the external semiconductive layer from the insulating layer was examined by the following method for normal temperature and when affected by a high temperature environment.
(1) Peel test A peel test was performed on the external semiconductive layer of the manufactured power cable. Using a cutter knife, place a 0.5-inch wide cut in the length direction of the external semiconductive layer to a depth that does not reach the insulating layer, and perform the lead-out operation from one end to make the external semiconductive layer an insulating layer. Peeled off. In the peel test, both a room temperature peel test at 25 ° C. and a high temperature peel test at 50 ° C. were performed.

(2) Room temperature peeling test after high temperature treatment The manufactured power cable was stored in a thermostatic layer at 145 ° C. for 96 hours, and then the room temperature peeling test was performed on the external semiconductive layer. The test method was the same as (1).
The high temperature treatment was performed assuming that the power cable was used for a long time. By applying the high temperature treatment, the adhesive force of the external semiconductive layer to the insulating layer may be increased, which is a severer condition than a normal room temperature peeling test.
(3) Evaluation The above (1) and (2) were evaluated, and the results are shown in Table 3. ○ for the case where the external semiconductive layer could be easily peeled off from the insulating layer, peeling was difficult and part of the external semiconductive layer remained on the surface of the insulating layer, or the external semiconductive layer was removed during the peeling Those that were broken were marked with x.

  Examples 1-7 are 90-95 parts by mass of an ethylene-vinyl acetate copolymer having a vinyl acetate monomer content of 10-40% by mass, and a nitrile butadiene rubber 5-10 having an acrylonitrile content of 15-40% by mass. It is a semiconductive resin composition in which 5 to 15 parts by mass of an oxidation type polyethylene wax is blended with 100 parts by mass of a base resin consisting of parts by mass. Therefore, it was confirmed that a semiconductive resin composition having excellent heat resistance and showing good peelability in a room temperature to high temperature region was provided. In Example 3, mixing was performed so that the content of the vinyl acetate monomer was 40% by mass on average.

  On the other hand, in Comparative Example 1, since non-oxidizing type polyethylene wax was used and the compatibility of the insulating layer with the cross-linked polyethylene was improved, peeling at high temperature became difficult. In Comparative Example 2, since there was little oxidation type polyethylene wax, a part of the external semiconductive layer remained on the surface of the insulating layer in the high temperature peel test. In Comparative Example 3, because there was too much oxidation type polyethylene wax, slip was generated when the kneaded product of each component was put into the extruder at the time of production of the semiconductive resin composition, and a compound was obtained. I could not.

  In Comparative Example 4, since the blending amount of nitrile butadiene rubber was small, in the high temperature peel test, the outer semiconductive layer broke before being peeled from the insulating layer. In Comparative Example 5, since the nitrile butadiene rubber is blended in an amount exceeding 10 parts by mass, the heat resistance is inferior, the external semiconductive layer is deteriorated and hardened by the high temperature treatment, and is broken before peeling from the insulating layer. Oops. In Comparative Example 6, since nitrile butadiene rubber containing acrylonitrile in excess of 40% by mass was blended, it was difficult to peel off at high temperature.

  In Comparative Example 7, since an ethylene-vinyl acetate copolymer having a vinyl acetate monomer content of less than 10% by mass is blended, the external semiconductive layer adheres well to the insulating layer, making it difficult to remove. I have. In Comparative Example 8, since the ethylene-vinyl acetate copolymer having a vinyl acetate monomer content exceeding 40% by mass is blended, the softening temperature of the resin composition is lowered, and the mechanical properties around 50 ° C. are inferior. Peeling at high temperature was difficult.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the technical idea disclosed in the present application, and these are naturally within the technical scope of the present invention. Understood.

1 ......... Power cable 3 ......... Conductor 5 ......... Internal semiconductive layer 7 ......... Insulating layer 9 ......... External semiconductive layer

Claims (3)

For 100 parts by mass of a base resin in which 90 to 95 parts by mass of an ethylene-vinyl acetate copolymer containing 10 to 40% by mass of vinyl acetate monomer and 5 to 10 parts by mass of nitrile butadiene rubber containing 40% by mass or less of acrylonitrile are blended. And
A semiconductive resin composition for an external semiconductive layer of a power cable , comprising 5 to 15 parts by mass of an oxidation type polyethylene wax and carbon black. 2. The semiconductive resin composition for an external semiconductive layer of a power cable according to claim 1, comprising 30 to 100 parts by mass of carbon black with respect to 100 parts by mass of the base resin.   A power cable comprising an external semiconductive layer made of the semiconductive resin composition according to claim 1.

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