JPH10162650A - Cross-linked polyolefin-insulated power cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively suppress the deterioration of the electric insulation performance by the water generated by the decomposition of a cross-linking agent and the occurrence of a water tree by containing a triazole compound in a specific range in a cross-linked polyolefin insular cross-linked by dicumyl peroxide as the cross-linking agent. SOLUTION: A triazole compound inthe range of 0.01-1 phr (pts. M./resin 100 pts.wt.) is contained in a cross-linked polyolefin insulating material cross- linked by DCP(dicumyl peroxide). The triazole compound has the action to prevent the production of water in the cross-linked polyolefin insulater and blocks the progress of the secondary decomposition reaction of cumyl alcohol. Benzotriazole or substituted benzotriazole is used for the triazole compound. The deterioration of the electric insulation performance by the water produced by the decomposition of a cross-linking agent and the occurrence of a water tree can be prevented under all operating conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cross-linked polyolefin insulated power cable using dicumyl peroxide as a cross-linking agent for an insulator. Water is generated
The present invention relates to a crosslinked polyolefin insulated power cable in which electric insulation performance is prevented from deteriorating and water trees are prevented from being generated.

[0002]

2. Description of the Related Art An electric wire or a power cable using a crosslinked polyethylene as an insulator is widely used as a crosslinked polyolefin insulated cable. The cross-linking of this polyethylene is usually performed using dicumyl peroxide (hereinafter referred to as “DCP”) as a cross-linking agent. However, when the insulator crosslinked by this method is heated at the time of assembling a cable connection portion or by a heat cycle during actual use, water is generated inside the insulator to deteriorate electrical insulation performance, or so-called water. Such as generating a tree,
This can cause major impairments in cable characteristics.

Therefore, a method for suppressing the generation of water in the insulator has been sought. It has been found that water generated in the crosslinked polyolefin insulator is generated by decomposition of DCP. That is, upon crosslinking, DCP is decomposed to generate cumyloxy radicals, and hydrogen is extracted from polyethylene to promote crosslinking, and to generate acetophenone, methane, cumyl alcohol, and the like. The produced cumyl alcohol, when heated, causes a secondary decomposition reaction to produce α-methylstyrene and water.

[0004]

As a method for removing this water, for example, Japanese Patent Application Laid-Open No. 4-342731 discloses a method of heating water to a temperature of 75 ° C. or less at which the secondary decomposition reaction of cumyl alcohol is suppressed. A method has been proposed in which the moisture content in the insulator is reduced in advance, and the insulator is heated again to 85 to 95 ° C. However, this method is intended to prevent a temporary increase and accumulation of water, and is not efficient in that a long drying time is required. Further, Japanese Patent Application Laid-Open No. 4-35501
By heating and drying the crosslinked insulator,
A method for volatilizing and removing decomposition products of DCP, which is a substance that causes water generation, is described. However, this method is also inefficient in that it requires a long additional heat drying step to remove decomposition products and generated water.

[0005] As a method without adding a step of removing cumyl alcohol and / or produced water by heating for a long time,
A method has been proposed in which a basic antioxidant such as an aliphatic amine or an isocyanate ester is added to an insulator to suppress the secondary decomposition reaction (JP-A-1-243306, JP-A-1-243306, respectively). See JP-A-63-289715). However, these antioxidants expire relatively quickly, and when mixed in large amounts, they also impair the insulation performance of the cable. SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and accordingly, has as its object the purpose of the present invention is to provide a crosslinked polyolefin in which deterioration of electric insulation performance and generation of water trees due to water generated by decomposition of a crosslinking agent are effectively suppressed. It is to provide an insulated power cable.

[0006]

The object of the present invention is to provide a crosslinked polyolefin insulator crosslinked with DCP containing a triazole compound in the range of 0.01 phr (parts by weight / 100 parts by weight of resin) to 1 phr. The problem can be solved by providing a crosslinked polyolefin insulated power cable.

[0007] It has been found that triazole-based compounds have an effect of preventing the formation of water in a crosslinked polyolefin insulator. Although the mechanism is not always clear, it is thought to prevent the progress of the secondary decomposition reaction of cumyl alcohol. The content of the triazole compound is 0.01 phr
If it is less than 1 phr, no effect is exhibited, and if it exceeds 1 phr, there is a possibility of blooming. This triazole-based compound is preferably a benzotriazole or a substituted benzotriazole. Benzotriazole and 5-methylbenzotriazole are easily available and are particularly preferred triazole compounds.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described specifically with reference to examples. In each of the following examples, each of the power cable samples used was obtained by extruding a polyethylene insulator compound having the following composition to a thickness of 25 mm on a conductor having a diameter of 60 mm and cross-linking at 200 ° C.

Example 1 The composition of the polyethylene insulator compound used is shown below: Low density polyethylene (specific gravity 0.92); 100 parts by weight Crosslinking agent (DCP); 2 parts by weight Antioxidant (4,4) '-Thiobis (3-methyl-6-t-butylphenol)); 0.3 parts by weight Triazole compound (benzotriazole); 0.10 parts by weight

Example 2 Example 2 was repeated in the same manner as in Example 1 except that the triazole compound of Example 1; 0.10 parts by weight was changed to a triazole compound (benzotriazole); 0.20 parts by weight. Power cable samples were obtained.

(Comparative Example) For the purpose of comparative evaluation, a composition obtained by removing the triazole compound from the composition of Example 1 was used.
Other than that, the power cable sample of the comparative example was obtained in the same manner as in Example 1.

From each of the above power cable samples, an insulator portion was cut into a sheet having a thickness of 5 mm, sealed with aluminum foil, and left in a 180 ° C. air oven for 2 hours.
After taking out and cooling, the amount of water generated in each sheet-like sample was measured by the Karl Fischer method. Table 1 shows the results.

[0013]

[Table 1]

From the results shown in Table 1, it is clear that the triazole compound effectively suppresses the generation of moisture after heating.

[0015]

According to the crosslinked polyolefin insulated power cable of the present invention, the crosslinked polyolefin insulator crosslinked using DCP as a crosslinker has a triazole compound content of 0.01 p
Since it is contained within the range of hr to 1 phr, it is possible to prevent deterioration of the electric insulation performance and generation of water trees due to water generated by decomposition of the crosslinking agent under all use conditions.

Claims (1)

[Claims] 1. A cross-linked polyolefin insulator, wherein the cross-linked polyolefin insulator cross-linked using dicumyl peroxide as a cross-linking agent comprises a triazole compound in a range of 0.01 phr (parts by weight / 100 parts by weight of resin) to 1 phr. Power cable.