JPS6046761B2 - crosslinked polyethylene cable - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high voltage cable having an easily peelable outer conductive layer.

Conventionally, materials obtained by mixing polyethylene, ethylene vinyl acetate polymer, or ethylene-ethyl acrylate copolymer with conductive carbon black have often been used as external conductive materials for high voltage cables.

However, since these materials are completely in close contact with the adjacent crosslinked polyethylene insulation layer, there was a problem in that it was extremely difficult to separate the two layers when connecting the cable or creating the termination. As a solution to this problem, cables having an easily peelable outer conductive layer made of PVC-EVA copolymer, chlorinated polyethylene, etc. have been announced. On the other hand, currently there are approximately 200 cross-linked polyethylene cables.
Although crosslinking is often achieved by heating to °C, it is clear that heating at a higher temperature is economically advantageous. It is desirable to raise the heating temperature to near the thermal decomposition point of polyethylene. However, near the thermal decomposition point of polyethylene, the material undergoes thermal decomposition. Especially 12Tm, 207
Cables with a wall thickness of 500 ft (m) are subject to severe deterioration during vulcanization because they are heated for a long time. In view of the above points, we have conducted various studies to find conductive materials that are easy to peel off, and we have found that we mainly use acrylic rubber or acrylic rubber, as well as SBR) nitrile rubber, butyl rubber, ethylene-vinyl acetate copolymer, and ethylene-acrylate. It has been found that a material such as a copolymer can be used as the outer conductive layer.

The amount of carbon added here depends on the type of carbon, but it is sufficient to provide the necessary conductivity for a normal semiconducting layer.
The amount may be 10 to 1 part by weight. Further, the amount of the substance added to the acrylic rubber is desirably 5 parts or less. Examples of the present invention will be described below. After preforming (pressing at 120°C for 5 minutes) an lwrm sheet of the conductive material and crosslinked polyethylene shown in Table 1 (pages 4 and 5), the crosslinked polyethylene sheet (pressing at 120°C for 5 minutes) and the external conductive material were heated to 270°C. The layers were heated together in a press for 1 minute at ℃. Thereafter, the peel strength was measured using an Instron tester. At that time, the sample width was 25.4wr! n, and the pulling speed is 200 m/
It's a minute. Next, these mixtures were extruded into rod-shaped samples with a diameter of 5 Tm using a 257 rlmφ extruder, and the surfaces were observed.
The results are shown in Table 1. As is clear from the above results, the external conductive material of the present invention is stable even when heated to high temperatures and is easily peeled off.

Therefore, since the cable having the conductive layer of the present invention can be vulcanized at high temperatures, the vulcanization speed can be increased, which is industrially advantageous, and it is also easier to create connections and terminations of the finished cable. Construction efficiency will also improve.

Table 1 Peel strength and extrusion appearance

Claims (1)

[Scope of Claims] 1. A cross-linked polyethylene cable characterized in that it has an outer conductive layer made of acrylic rubber or a mixture mainly composed of acrylic rubber to which carbon necessary to obtain conductivity is added. 2. The crosslinked polyethylene cable according to claim 1, in which 2-mercaptobenzothiazole zinc salt or dibenzothiazyl disulfide is added as a vulcanizing agent.