JPH08241624A - Semiconductor resin composition for power cable - Google Patents

Abstract

PURPOSE: To provide a power cable capable of restraining the generation of a water-tree in the semiconductive layer of a power cable and having high reliability, by blending conductive carbon black and also specific quantity of sulfur into polyolefine resin in a simiconductive resin composition. CONSTITUTION: A semiconductive resin composition for a power cable is a semiconductive resin composition including polyolefine resin and carbon black, and moreover, contains a sulfur of 1.0-3.0 wt. parts to a polyolefine resin of 100 wt. parts, besides can be blended with the adequate quantity of an additive such as a cross linking agent, or antioxidant and a processing aid. Acetylene black or conductive furnace black etc., can be used as conductive carbon black. In the carbon black, its particle diameter or a material characteristic value such as specific surface area is not limited in particular. Blended quantity in base polymer is also not limited in particular, and is appropriately adjusted by given conductivity and the kind of the conductive carbon black.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductive resin composition used for power cables, and more particularly, it can suppress the generation of water traces from the semiconductive layer and enhance the reliability of the power cable. It relates to a semiconductive resin composition.

[0002]

2. Description of the Related Art A cross-linked polyethylene insulation cable, which is a mainstream of electric power cables in recent years, has a cable conductor 1 and an insulation body as shown in FIG. 1 for the purpose of relaxing electric field concentration at the insulation body interface and preventing partial discharge. 3, the inner semiconductive layer 2 and the outer semiconductive layer 4 are provided on the boundary surface with the insulating layer 3 and the outer semiconductive layer 4, respectively, and the copper shielding layer 5 and the sheath layer 6 are provided on the outer surface of the outer semiconductive layer 4. Is a very general structure. The inner semiconductive layer 2 and the outer semiconductive layer 4 are made of a semiconductive resin composition in which polyolefin is used as a base resin and conductive carbon black is mixed in an appropriate amount to be semiconductive. It is co-extruded with the insulator 3 and formed on the cable conductor 1 and the insulator 3.

[0003]

However, in the above-mentioned semiconductive layer, a semiconductive layer tree such as an inner conductive tree or an outer conductive tree may be generated from the protrusions on the surface of the semiconductive layer after extrusion molding as starting points. is there. This water tree causes a dielectric breakdown of the power cable and is a factor that reduces the reliability of the power cable.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a resin composition for a semiconductive layer which suppresses the generation of water from the semiconductive layer and enhances the reliability of the power cable. To aim.

[0005]

The above object of the present invention is a semiconductive resin composition containing a polyolefin resin and carbon black, wherein 1.0 to 3.0% of sulfur is added to 100 parts by weight of the polyolefin resin. This is achieved by a resin composition for a semiconductive layer of a power cable, which is characterized by containing parts by weight.

The present invention will be described in more detail below. The polyolefin resin used as the base polymer of the semiconductive resin composition of the present invention may be a polyolefin resin conventionally used for power cables. For example, polyethylene or ethylene-based copolymers such as ethylene-vinyl acetate copolymer and ethylene-ethyl acrylate copolymer can be mentioned. In particular, ethylene-vinyl acetate copolymer is preferable. Further, it may be a blend polymer of a resin having compatibility with the polyolefin resin. The molecular weight of these polyolefin resins is not particularly limited, and may be in the range of the molecular weight of polyolefin resins conventionally used for electric power cables.

The semiconductive resin composition of the present invention is prepared by adding a proper amount of conductive carbon black to the base polymer to impart a predetermined conductivity. The type of conductive carbon black is not particularly limited, and commonly used acetylene black, conductive furnace black or the like can be used. In addition, physical properties such as particle size and specific surface area of these conductive carbon blacks are not particularly limited. Further, the blending amount in the base polymer is not particularly limited, and is appropriately adjusted depending on the conductivity to be imparted and the kind of the conductive carbon black.

The semiconductive resin composition of the present invention further comprises 1.0-3.
It is characterized by containing 0 part by weight of sulfur. here,
If the amount of sulfur added exceeds 3.0 parts by weight, blooming of sulfur will occur during molding and the appearance will be impaired, such being undesirable. On the other hand, if the amount is less than 1.0 part by weight, it is not possible to obtain a sufficient effect for suppressing the generation of water trees.
Further, sulfur is powdery and is added and kneaded to the base polymer together with the conductive carbon black.

The semiconductive layer resin composition of the present invention contains the above-mentioned polyolefin resin, conductive carbon black and sulfur as essential components, but other additives are added to the extent that the effects of the present invention are not impaired. You can also For example, a suitable amount of a crosslinking agent, an antioxidant, a processing aid, etc. can be added.

[0010]

EXAMPLES The semiconductive resin composition for a power cable according to the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. [Examples 1 and 2 and Comparative Examples 1 and 2] Ethylene-vinyl acetate copolymer, conductive carbon black, sulfur, a cross-linking agent and an antioxidant were mixed in the proportions (parts by weight) shown in Table 1 to give a semi-finished product. A conductive resin composition was prepared. Then, a disk-shaped sheet sample was prepared using the semiconductive resin composition, and was experimentally subjected to a high frequency accelerated water immersion voltage application test. That is, this semiconductive resin composition and low-density polyethylene to which a cross-linking agent as an insulator was added were separately preformed by hot pressing, and then both were combined and pressed at 175 ° C. for 20 minutes for cross-linking molding. . This was cut into a disk shape to obtain a sample. However, the thickness of the insulator is 1 mm,
The interface between the semiconductive layer and the insulator was roughened with a waterproof sandpaper. Next, 1 mol / liter of Na is applied to the semiconductive layer side.
It was immersed in a Cl aqueous solution and charged with a voltage of 6.9 kV and a frequency of 1000 Hz for 250 hours using a high frequency acceleration tester. The sample after charging was cut to a thickness of 300 μm with a microtome and stained with crystal violet, and the length and number of the water tree generated from the semiconductive layer of 30 μm or more were recorded by an optical microscope.

[0011]

[Table 1]

As is clear from Table 1, from the experiment using the disk-shaped sheet sample prepared by using the semiconductive resin composition of the present invention to which the specific amount of sulfur was added, the addition amount of sulfur was other than the specific amount of the present invention. It can be seen that the generation of water trees from the semiconductive layer is suppressed as compared with the case of using no addition at all.

[0013]

As described above, the semiconductive resin composition of the present invention suppresses the generation of water trees by blending the polyolefin resin with the conductive carbon black and a specific amount of sulfur. Therefore, a highly reliable power cable can be manufactured by using the semiconductive resin composition of the present invention.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts showing a typical configuration example of a power cable.

[Explanation of symbols]

 1 conductor 2 inner semiconductive layer 3 insulator 4 outer semiconductive layer 5 copper shielding layer 6 sheath

Claims (2)

[Claims] 1. A semiconducting resin composition containing a polyolefin resin and carbon black, which contains 1.0 to 3.0 parts by weight of sulfur with respect to 100 parts by weight of the polyolefin resin. Semi-conductive resin composition for cables. 2. The semiconductive resin composition for a power cable according to claim 1, wherein the polyolefin resin is polyethylene or an ethylene copolymer resin.