JPS6290806A - Power cable - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power cable having a semiconducting layer on either a conductor or an insulator.

[Prior art] The internal and external semiconductive layers of a cross-linked polyethylene cable include
Extruded semiconducting layers are often used to prevent irregularities at the interface with insulators.

Ethylene copolymers, particularly ethylene/vinyl acetate copolymers, are preferred as materials for the extruded semiconductor T and layer in view of extrusion processability and conductive carbon black filling properties.

[Problems to be Solved by the Invention] However, the ethylene/vinyl acetate copolymer generates acetic acid under the action of heat and moisture, which tends to discolor and corrode copper.

For this reason, there is a problem that the copper conductor and the steel tape for shielding the insulator are easily discolored and corroded due to the crosslinking process using high temperature and high pressure steam during cable manufacturing or when the cable is used in a humid atmosphere.

The present invention aims to provide a power cable that can prevent discoloration and corrosion of copper conductors and insulator shielding steel tapes caused by semiconductors T and H mainly composed of ethylene/vinyl acetate copolymer. It is something.

[Means for Solving the Problems] The power cable of the present invention is a power cable in which a semiconducting layer is formed on a conductor or an insulator, and the semiconducting layer is formed with an ethylene-vinyl acetate copolymer and a conductive material. carbon black as a main component, and a mixture of zinc oxide and lead oxide is added to 100 parts by weight of the ethylene/vinyl acetate copolymer.
．． It is characterized in that it is formed from a resin composition containing 5 to 10 parts by weight.

The base polymer in the semiconducting composition of the present invention is an ethylene/vinyl acetate copolymer, and in addition to this, polyethylene, polypropylene, polybutene, ethylene/ethyl acrylate copolymer, ethylene/methyl acrylate copolymer, ethylene/vinyl acetate copolymer, etc. Propylene rubber, ethylene/vinyl acetate copolymer graft-polymerized with an aromatic monomer such as styrene, etc. may be used in combination.

Conductive carbon black is generally acetylene black or furnace black, and the amount added is 20 to 1 part per 10011 parts of ethylene/vinyl acetate copolymer.
00 parts by weight is common.

Zinc oxide (ZnO) and lead oxide (PbO or Pb
3otf) is used as an inhibitor of discoloration and corrosion of copper.

The amount of zinc oxide and lead oxide added must be in the range of 5 to 10 parts by weight, based on the ethylene/vinyl acetate copolymer]00IiJlaB, and is 0.5! If it is less than 1 part by weight, there is no effect of inhibiting discoloration or corrosion of copper, and if it exceeds 10 parts by weight, the extruded appearance of the semiconductive layer will deteriorate.

Further, the mixing ratio of zinc oxide and lead oxide is 1/2 to 2/I in rim ratio of zinc oxide/lead oxide, preferably 1/I.
It is 1.

In this way, the reason why discoloration and corrosion of steel can be suppressed by using zinc oxide and lead oxide together is that they react with acetic acid, which causes discoloration and corrosion, and convert it into a substance that does not have a negative effect on copper. It is thought that this is because of this.

In the present invention, crosslinking agents, antioxidants, lubricants, etc. are appropriately blended.

As a crosslinking agent, dicumyl peroxide, l.

3-bis-(t-butylperoxy-isoprobyl)-
Benzene, 2,5-dimethyl-2,5-di(1-butylperoxy)-hexane, 2,5-dimethyl-2,5
-di(t-butylperoxy)-hexyne-3 and the like.

Examples of antioxidants include 4,4'-thiobis(3-methyl-6-t-butylphenol), 2,2°4-trimethyl-dihydroquinoline polymer, and N.

Examples include N'-diphenyl-p-phenylenediamine, 2-mercabutobenzimidazole and its zinc salt.

Examples of lubricants include stearic acid, metal salts thereof, and paraffin wax.

[Example] The compositions shown in Example 6 in Table 1 were kneaded in a Banbury mixer, and then a crosslinking agent was added to prepare a conductive composition.

The above conductive composition was extrusion coated on a copper stranded conductor having a conductor area of 150+am' to a thickness of 1III11 to form an internal semiconductive layer, and then O low density polyethylene (density 0.9203/am', melt Index 1.0) 100 parts by weight O dicumyl peroxide 2. OMWL Department 04.
An insulator composition consisting of 0.2 parts by weight of 4'-thiobis-(3-methyl-6-butylphenol) was coated by extrusion, and the above semiconductive composition was further coated with a thickness of 1+mC:pH on the outer periphery. Then, an external semiconductor M layer was formed.

Following these extrusions, thermal crosslinking was performed, and a copper tape for shielding the insulator, a vinyl sheath, etc. were applied to produce a crosslinked polyethylene insulated capeple.

The evaluation results for the cables produced in this manner are shown in the lower column of Table 1.

Note that the evaluation was performed as follows.

Corrosion of copper conductors and copper tape for shielding insulators can be prevented by cutting the cable to a specified length, sealing both ends, energizing the cable, and subjecting it to a heat cycle from room temperature to 105°C (conductor temperature) for 4 hours at 0N. The test was repeated 100 times with -4 hours OFF, then the cable was disassembled and judged by visual observation. Note that the surface temperature of the outer semiconducting layer was 75°C when the conductor temperature was 105°C.

Volume resistivity was measured at room temperature for the outer semiconducting layer before and after the heat cycle described above.

In Examples 1-4 within the scope of the present invention, there was no discoloration or corrosion of the copper conductor or copper tape, and practically sufficient results were obtained in terms of volume resistivity and extrusion appearance.

In Comparative Example 1 in which zinc oxide was used alone, Comparative Example 2 in which lead oxide was used alone, and Comparative Example 3 in which zinc oxide and lead oxide were used together in a small amount, discoloration and corrosion were observed. In Comparative Example 4, in which the content of zinc oxide and lead oxide was higher than the specified value of the present invention, the extrusion appearance was poor.

[Effects of the Invention] As explained above, the present invention prevents discoloration and corrosion of copper conductors and copper tapes for shielding insulators caused by the ethylene-vinyl acetate copolymer used as the main component of the semiconductive layer. This makes it possible to improve the long-term reliability of power cables.

Claims (1)

[Claims] (1) In a power cable in which a semiconductive layer is formed on a conductor or an insulator, the semiconductive layer is mainly composed of an ethylene/vinyl acetate copolymer and conductive carbon black, A power cable comprising a resin composition containing 0.5 to 10 parts by weight of a mixture of zinc oxide and lead oxide based on 100 parts by weight of the copolymer.