JPS63301427A - Manufacture of plastic power cable - Google Patents

Abstract

PURPOSE:To improve the insulating property by forming an inner semiconductive layer, an outer semiconductive layer, and an insulating layer by the three-layer simultaneous extrusion, heating in a dry heating, and mixing 1 to 4 wt.% of bridging agent tor executing the bridging in the insulating layer. CONSTITUTION:A copolymer of a styrene type monomer shown in the general formula 0.01 to 1 mol to ethylene 1 mol, or mixture of polymers of the two compounds is used, and by using the substance as the insulating layer as it is, or by making it to the insulating layer after bridging, it can be given an insulation of an excellent impulse breaking strength. In order to make it into a cable to exercise an excellent performance, an inner semiconductive layer, an outer semiconductive layer, and an insulating layer are formed by three-layer simultaneous extrusion. As the heating means for the heat-formation or bridging heat-formation, a dry heating is used, and when a bridging agent is used, a bridging agent whose temperature after a half-life period of 10 hours is 110 deg.C or more is mixed to the insulating layer at 1 to 4 wt.%. In such a way, the insulating performance can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a plastic electrical cable, particularly an electrical cable with improved insulation properties.

[Prior Art] [Problems to be Solved by the Invention] Conventionally, ciboethylene insulating capacitors have been widely used.
In recent years, CV cables have become ultra-high voltage, and AC300KVC
Even the V cable is about to be put into practical use.

In addition, the cable outer diameter is limited due to various problems, and therefore,
The insulation thickness cannot be increased in proportion to the voltage, and the working stress of the cable gradually increases, making insulation performance more difficult.

Therefore, there was a need for materials with excellent insulation properties, and certain plastics were found to be promising for this purpose.

However, even though it is an excellent material, the conditions for manufacturing cables are completely unknown, so at present no electric cable has been manufactured that takes advantage of this material.

[Means to eliminate the problem]

The present invention was developed as a result of various studies regarding this point, and the outline thereof will be described below.

0.01 to 1 mol of a styrene-based heptamer copolymer represented by the general formula or a mixture of the respective polymers is used per 1 mol of polyethylene,
It was discovered that by using this directly as an insulating layer or by crosslinking it to form an insulating layer, insulation with extremely excellent impulse breakdown strength could be obtained. Moreover, the conditions for making this into a cable and exhibiting excellent characteristics were established. The following findings were obtained.

■ Forming the inner semiconducting layer, the outer semiconducting layer, and the insulating layer by interlayer extrusion.

■ Use dry heating as a heating means for thermoforming or crosslinking thermoforming.

(2) When using a crosslinking agent, 1 to 4% by weight of the crosslinking agent having a 10 hour half-life of 110° C. or more should be incorporated into the insulating layer.

[Effect]

The above effects will be described below.

Polyethylene, which has been conventionally used as an insulating material, has a lower impulse breakdown strength against impact voltage when the degree of crystallinity is lowered, and a decrease in workability when the degree of crystallinity is increased, but the plastic insulating material used in the present invention By having an aromatic compound (styrene component) having a specific structure as described above, when copolymerized in a predetermined amount, the crystallinity does not decrease and the impulse rupture strength increases.

The blending range of the styrene yarn thread picker is preferably 0001 to 1 mol. If it is less than 0.01 mol., there is hardly any improvement effect on impulse rupture strength, and if it exceeds 1 mol. In contrast, the impulse rupture strength also decreases. The reason for this is that the crystallinity of the styrenic polymer is significantly reduced by containing a large amount of aromatic components, making the polymer unsuitable for use as an electrical insulating material. Furthermore, it is uneconomical to consume a large amount of initiator for radical polymerization and to use a large amount of expensive aromatic compounds.

The styrenic monomer in the present invention may contain other unsaturated monomers in addition to styrene, and these unsaturated monomers include propylene, butene-1, pentene-1,
Examples include 1, hexene-1, vinyl acetate, acrylic acid ether, methacrylic acid or its ester, and mixtures thereof.

In addition, this plastic contains organic and inorganic fisi-1.
Antioxidants, lubricants, pigments, ultraviolet inhibitors, dispersants, copper inhibitors, neutralizing agents, plasticizers, crosslinking agents, and the like may be added.

In the present invention, the reason why the inner semiconducting layer, the outer semiconducting layer, and the insulating layer are simultaneously extruded using 3W is that no protrusions are observed on the inner and outer conductors.

Inert gas such as nitrogen gas or argon gas is used for heating, but since heating means uses oil such as silicone oil and does not use water vapor or air, there are problems such as generation of water trees and air oxidation deterioration of materials. Don't let it happen! /) In particular, since the product of the present invention contains substances with polar groups such as aromatic compounds, it is greatly affected by moisture.

In addition, in the present invention, when a crosslinking agent is blended into the material and crosslinked, the insulating material has a melting point of about 100°C and has a half-life of 10 hours to prevent the progress of crosslinking during extrusion processing (120°C to 130°C). A crosslinking agent having a temperature of 110° C. or higher is used, and examples of the crosslinking agent are as follows.

Di-t-butyl peroxide, di-t-amyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, 2,5-dimethyl 2,5-di(1-butylperoxy)hexyne, α-α '-Bis(t-7'
The optimal amount of these is 1 to 4% by weight, and if it is less than 1% by weight, crosslinking will not be achieved to a sufficient degree, and if it exceeds 10% by weight, unnecessary waste will be produced for the crosslinking reaction. The inclusion of a crosslinking agent is also considered to be a cause of early vulcanization during extrusion.

Example A polymer made by copolymerizing 1 mole of ethylene with 0.3 mole of styrene monomer was used as an insulating layer on a stranded copper wire conductor with a conductor diameter of 7 m, and a material made of the same material with carbon black was used as the inner and outer semiconductive layers. , coated by three-layer coextrusion method.

(Outer diameter: 37 ff) (However, 3 weights of dicumyl peroxide was mixed into the insulating layer.) Then, this was introduced into silicone oil and crosslinked by heating to obtain a cable of the present invention.

Comparative Example 1 An insulating layer made of polyethylene mixed with 3% by weight of dicumyl peroxide, and an inner and outer semiconductive layer made of the same material containing carbon black, were extruded simultaneously. An electric cable as a comparative example was manufactured in exactly the same manner.

Comparative Example 2 Comparative Example 1 except that steam vulcanization was used as the crosslinking method
An electric cable of a comparative example was manufactured in exactly the same manner as described above.

Comparative Example 3 Example 1 except that steam vulcanization was used as the crosslinking method.
A comparative example-type capsule was produced in exactly the same manner as above.

Comparative Example 4 An electrical cable was manufactured in exactly the same manner as in Example except that the inner and outer semiconductive layers and the insulating layer were individually extruded and coated.

The results of a comparative test for the above Comparative Examples and Examples are as follows.

Effects of the invention It can be seen from the comparative test that the present invention ζ;
It is extremely easy to obtain an electrical cable that uses an insulating material that is essentially superior to polyethylene, and that can effectively exhibit its original properties without reducing its properties in the slightest. This new improvement can contribute to the realization of ultra-high voltage cables.

Claims (1)

[Claims] For 1 mole of ethylene, styrenic monomer represented by the general formula ▲ Numerical formula, chemical formula, table, etc. ▼ (where R represents a straight chain or branched alkyl group having 4 or less carbon atoms) 0 .01 to 1 mol % of a copolymer or a mixture of each polymer as an insulating layer as it is or cross-linked; (1) an inner semiconducting layer, an outer semiconducting layer and The insulating layer is formed by simultaneous extrusion of three layers, (2) dry heating is performed as a heating means for thermoforming or crosslinking thermoforming, and (3) the crosslinking agent used for crosslinking has a half-life of 110 hours.
A method for manufacturing a plastic power cable, characterized in that 1 to 4% by weight of a crosslinking agent with a temperature of 100°C or higher is mixed into the insulating layer, and the process is carried out under these conditions.