JPS60158504A - Electrically insulated 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 The present invention relates to an electrically insulated cable, and more particularly to an electrically insulated cable whose insulator is a blend of styrene-ethylene random copolymer and polyethylene.

Conventionally, the insulators of electrically insulated cables are polyethylene,
In particular, crosslinked products of low density polyethylene are likely to be used. Furthermore, electrically insulating resin compositions in which a styrene copolymer is blended with a polyolefin are also used. However, in both cases, the breakdown electric field decreases from one repeated impulse, so
It cannot be said to be ideal as an insulator.

In order to obtain an excellent insulating material for use in electrically insulated cables, the present inventors have conducted extensive research and found that by blending styrene-ethylene random copolymer with polyethylene, the breakdown electric field caused by one repeated impulse can be reduced. The inventors have discovered that an insulator with improved degradation can be obtained, and have completed the present invention.

The gist of the present invention is that the styrene content is 5% or more by market weight.
It consists in an electrically insulated cable whose insulator is a blend of ethylene random copolymer and polyethylene or a crosslinked product thereof.

Both the styrene-ethylene random copolymer and polyethylene used in the present invention may be those conventionally used.

If the amount of styrene in the styrene-ethylene random copolymer is less than the above, the object of the present invention will not be achieved.

The ratio of the styrene-ethylene random copolymer to polyethylene is preferably 50:50 to 5:95 (by weight).

If the content of polyethylene is less than 50% by weight, the AC breakdown value will decrease, which is not preferable.

Both polymers can be blended in a conventional manner, for example using a Banbury mixer.

The crosslinking may be carried out in accordance with the crosslinking of polyethylene.

The insulator of the present invention can similarly be used in place of cross-linked polyethylene in conventional cross-linked polyethylene insulated cables. Accordingly, additives used in polyethylene, such as anti-aging agents, fillers, etc., may be included in the blend.

Next, the present invention will be specifically explained with reference to Examples and Comparative Examples.

Examples 1-6 and Comparative Examples 1-6 The formulations shown in Table 1 were mixed in a Banbury mixer.

1mm single wire conductor with internal conductive layer (NUC0580゜thickness 0
．． 81 nm), and an insulating layer (1.5 mm thick) of the above mixture was formed around it. This cable was subjected to a long-term immersion voltage/snow impulse test (100 KV applied at approximately 5 minute intervals), and the AC breakdown value (voltage increased at 500 V/sec) was measured.

The results are shown in Table 1.

From these results, it was found that adding a styrene-ethylene random copolymer containing 6% by weight or more of styrene to polyethylene improves the repeated impulse rupture properties;
It is understood that the addition of 52% styrene-ethylene copolymer lowers the AC breakdown value. Further, even if a styrene-butadiene copolymer or a styrene-ethylene graft copolymer is blended with polyethylene I instead of the styrene-ethylene random copolymer, the repeated impulse characteristics are not improved.

Claims (2)

[Claims] (1) An electrically insulated cable using a blend of a styrene-ethylene random copolymer and polyethylene or a crosslinked product thereof as an insulator with a styrene content of 5 market weight < U. (2) The electrically insulated cable according to claim 1, wherein the blend contains 5 to 50% by weight of a styrene-ethylene random copolymer.