JPH0430685B2 - - Google Patents

Description

[Detailed description of the invention]

<Technical Field of the Invention> The present invention relates to a crosslinked polyethylene cable having an easily peelable outer semiconductive layer and a method for manufacturing the same. <Background of the Invention> Conventionally, in a crosslinked polyethylene cable having an outer semiconducting layer, when the outer semiconducting layer is to be easily peeled from the crosslinked polyethylene insulating layer, the outer semiconducting layer is made of polyethylene. Mixtures of vinyl chloride-vinyl acetate copolymers, chlorinated polyethylene-vinyl acetate copolymers, and the like mixed with conductivity-imparting agents such as carbon black have been used. However, the outer semiconducting layer using the above-mentioned conventional admixtures has satisfactory peelability when crosslinked at temperatures below 200°C, but when crosslinked at temperatures above, e.g. 230°C, , did not have satisfactory peelability. Although the cause is not clear, it is thought that the material of the outer semiconducting layer deteriorates due to thermal decomposition, and its tensile breaking force decreases relative to the peeling force. Therefore, it was not possible to increase the production speed by increasing the crosslinking temperature above 230°C, and there was a limit to productivity. <Objective and Structure of the Invention> The present invention was made in view of the above-mentioned current situation, and provides a crosslinked polyethylene cable having an outer semiconductive layer that is easily peeled off even when crosslinked at a temperature of 200°C or higher, and a method for manufacturing the same. The purpose is to provide. The purpose is to increase the vinyl acetate content (hereinafter referred to as "vinyl acetate content") in the outer semiconducting layer.
A semiconductive product made by blending a mixture of 35 to 55% ethylene vinyl acetate, 10 to 90 parts by weight, and 90 to 10 parts by weight of a polar polymer made of polyamide or polyester as the main resin, and adding a conductivity imparting agent to this mixture. This is achieved by using an admixture. The amount of vinyl acetate of ethylene vinyl acetate in the base resin mixture must be in the range of 35 to 55%. If the amount of vinyl acetate is less than 35%, heat at 200℃ or higher, e.g.
When crosslinked at 230°C, the resulting semiconductive layer is difficult to peel off from the crosslinked polyethylene insulating layer and breaks immediately, making it impossible to obtain a semiconductive layer that is easy to peel off, and the temperature exceeds 55%. In some cases, the elongation is less than 200%, and if it is made into a cable, it cannot be used due to its flexibility. As long as the amount of vinyl acetate is 35 to 55%, ethylene vinyl acetate from any manufacturer can be used without any problem. As a general commercial product, for example, Mitsui Polychemical Co., Ltd. EVATUREX 45× (vinyl acetate amount
45%), Evaflex 40 (vinyl acetate amount 41%), etc. The polar polymer in the above main resin mixture is
Refers to a polymer having an amide group or an ester group,
Specifically, the polyamides used include Nopamid 1010 manufactured by Mitsubishi Kasei Corporation and Macromelt manufactured by Henkel Japan.
6030, and examples of the polyester include Pylon GM900 manufactured by Toyobo Co., Ltd. and PES110H manufactured by Toagosei Kagaku Co., Ltd. Examples of the conductivity imparting agent to be added to the main resin include metal powder, graphite, various carbon blacks, etc., but conductive carbon black is the most preferred in terms of ease of mixing and economic efficiency. Commonly used. The amount of the conductivity imparting agent to be blended depends on its type, but in order to obtain the conductivity required for the external semiconductive layer of the crosslinked polyethylene cable, for example, in the case of conductive carbon black, it should be 10 to 100 parts by weight. Enough. A crosslinked polyethylene cable having an easily peelable outer semiconducting layer according to the present invention includes an inner semiconducting layer, an insulating layer made of an uncrosslinked polyethylene composition, and an outer semiconducting layer made of the semiconducting blend of the present invention on the outside of the conductor. It can be produced by extrusion coating each of these layers one after another or simultaneously extrusion coating two or more layers thereof, and then heating the mixture to 230° C. or higher. Note that the heating atmosphere may or may not be an inert gas atmosphere, such as a nitrogen gas atmosphere. Further, the heating source may be water vapor, infrared rays, heated silicone oil, or the like. Next, the structure of the crosslinked polyethylene cable according to the present invention will be explained with reference to FIG. In FIG. 1, 1 is a conductor. The conductor 1 is usually made by twisting together a plurality of wires made of copper, aluminum, or an alloy thereof. On the outside of the conductor 1, an insulating layer 3 made of cross-linked polyethylene is applied directly with or without an internal semiconducting layer 2.
is provided. Note that the internal semiconducting layer 2
is often provided especially in products used for relatively high voltage (6KV or higher). Internal semiconducting layer 2
may be formed from a known semiconductive mixture that has been widely used in the past, or may be formed from an external semiconductive mixture according to the present invention. In addition, the crosslinked polyethylene constituting the insulating layer 3 is made of a crosslinking agent (for example, dicumyl peroxide 0.5
~5 parts by weight) is heated to a high temperature (usually 150°C or higher). An outer semiconducting layer 4 is provided on the outside of the crosslinked polyethylene insulating layer 3. This outer semiconducting layer 4 must be formed from a semiconducting compound according to the invention. A crosslinking agent (for example, 0.3 to 3 parts by weight of dicumyl peroxide) may be added to the semiconducting wire mixture. Note that, normally, a sheath (protective coating) 5 may be provided on the outside of the external semiconductive layer 4, if necessary, in order to prevent mechanical or chemical damage. <Example> A semiconductive mixture having the composition shown in Table 1 below was formed into a sheet with a thickness of 1 mm, and a sheet with a thickness of 2 mm prepared separately was formed.
A bonded sample was obtained by stacking each on a non-crosslinked polyethylene sheet of mm in diameter and heating under predetermined crosslinking conditions (200°C, 230°C, 250°C). The peeling force was measured using a tensilon tester at a tensile speed of 500 mm/min. Note that the sample width was 12.5 mm.

[Table] <Effects of the Invention> As is clear from Table 1, the semiconductive mixture of the present invention whose main resin is an ethylene vinyl acetate polar polymer with a vinyl acetate content of 35 to 55% can be heated to 200°C. It is easy to peel off even if cross-linked at higher temperatures (e.g. 230℃ or higher), but if the amount of vinyl acetate in ethylene vinyl acetate is 35 to 55
If the main resin is outside the range of
When cross-linked at 230°C or higher, it broke during peeling, resulting in failure to peel.

[Table] Furthermore, if the method of the present invention is implemented, as shown in Table 2 above, the crosslinking temperature is higher than that of the conventional method (230°C).
As described above, a cross-linked polyethylene cable having an external semiconductive layer with excellent peelability can be manufactured.
The higher the temperature, the higher the manufacturing speed, which is industrially advantageous, and the cables obtained also have excellent construction efficiency because the connections and terminations are easy to make.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a crosslinked polyethylene cable according to the present invention. DESCRIPTION OF SYMBOLS 1...Conductor, 2...Inner semiconducting layer, 3...Crosslinked polyethylene insulating layer, 4...Outer semiconducting layer, 5...
…sheath.

Claims (1)

[Scope of Claims] 1. A cross-linked polyethylene cable in which a cross-linked polyethylene insulating layer and an outer semi-conducting layer are sequentially provided directly on the outside of a conductor with or without an inner semi-conducting layer, wherein the outer semi-conducting layer contains acetic acid. The main resin is a mixture consisting of 10 to 90 parts by weight of ethylene vinyl acetate with a vinyl content of 35 to 55% and 90 to 10 parts by weight of a polar polymer made of polyamide or polyester, and a semi-finished material made of a mixture containing a conductivity imparting material. A cross-linked polyethylene cable characterized by using a conductive mixture. 2. A method for producing a crosslinked polyethylene cable in which an inner semiconducting layer, an insulating layer made of an uncrosslinked polyethylene composition, and an outer semiconducting layer are sequentially or simultaneously extruded and coated on the outside of a conductor, and then crosslinked and heated, A method for producing a crosslinked polyethylene cable, comprising using the following semiconducting mixture in the outer semiconducting layer, and heating to 230° C. or higher as the crosslinking heating. The main resin is a mixture consisting of 10 to 90 parts by weight of ethylene vinyl acetate with a vinyl acetate content of 35 to 55% and 90 to 10 parts by weight of a polar polymer made of polyamide or polyester, and a conductivity imparting material is blended with this. Semiconducting mixture.