JPH08339717A - Electric insulating composition and electric wire-cable - Google Patents

Abstract

PURPOSE: To improve water resistant tree performance even if a defect is caused in an insulator by blending a styrene-maleic anhydride copolymer by a prescribed quantity with a polyethylene or ethylene type copolymer or the like. CONSTITUTION: A styrene-maleic anhydride copolymer is blended with a polyethylene or ethylene type copolymer or a mixture of these grafted so that the content of maleic anhydride becomes 0.02wt.% to 5wt.%, so that the content of styrene becomes 0.05wt.% to 10wt.%, and an electric insulating composition is obtained. Since this composition is used, even if there exists a defect such as a void in insulation, a foreign matter and nonuniformity of an interface between an insulator and a semiconductive layer, water resistant tree performance, particularly, bow-tie tree performance is improved while having an electric characteristic equal to or more than usual.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric insulating composition and an electric wire / cable using the same as an insulator.

[0002]

2. Description of the Related Art Polyolefin, especially so-called cross-linked polyethylene obtained by cross-linking polyethylene, has been widely used as an insulating material for electric wires / cables and their accessories because of its excellent electric insulation and heat resistance.

However, the electric wire / cable coated with this cross-linked polyethylene has a drawback that when used in a wet or flooded atmosphere, water trees are generated in the insulator, and the excellent electric insulation performance of the material is greatly deteriorated. There is. That is, the general structure of an insulated cable for high voltage using this crosslinked polyethylene is as shown in FIG.
The inner semiconductive layer 2 is formed on the upper part of the, the insulator 3 is formed on the outer circumference of the inner semiconductive layer 2, and the outer semiconductive layer 4 is formed on the outer circumference of the insulator 3. However, a bowtie-shaped water tree is generated in the insulator 3, and an interfacial water tree is generated from the inner semiconductive layer 2 or the outer semiconductive layer 4, and in the worst case, it penetrates the insulator 3 to cause dielectric breakdown. Can even lead to.

The water tree is a void in the insulator, foreign matter,
It is also caused by water agglomeration in a locally high electric field portion such as irregularity of the interface between the insulator and the semiconductive layer. For this reason, much effort has been made to eliminate these defects in electric wires and cables, and the quality control of the resin and improvement of the electric wire and cable manufacturing technology have improved the effect of suppressing the generation of water trees. I'm doing it.

[0005]

However, in spite of the efforts and researches for suppressing the generation of water trees in such various fields, it is possible to significantly reduce the generation of water trees. Is not reached yet.

Therefore, the present invention has been devised to solve the above-mentioned problems, and its object is to prevent water tree, particularly resistance to defects, even if defects such as voids, foreign matters, irregularities, etc. occur in the insulator. It is an object of the present invention to provide a novel electrical insulating composition and an electric wire / cable capable of significantly improving the bowtie tree.

[0007]

The first invention for achieving the above object is to provide a maleic anhydride content of 0.02 w.
Polyethylene or ethylene-based copolymer or a mixture thereof, which is grafted so as to have a content of t% to 5 wt%,
A second aspect of the present invention is an electrical insulating composition comprising a styrene / maleic anhydride copolymer compounded so that the content of styrene is 0.05 wt% to 10 wt%. A polymer grafted with maleic anhydride is blended with the mixture or a mixture thereof so that the content of maleic anhydride is 0.02 wt% to 5 wt%, and the styrene-maleic anhydride copolymer is further added with styrene. The electrical insulating composition is compounded so that the amount is 0.05 wt% to 10 wt%. The third invention is an electric wire / cable in which a conductor is coated with such an electric insulating composition.

In the present invention, the amount of maleic anhydride in the maleic anhydride grafted polymer and the amount of maleic anhydride in the resin blended with the maleic anhydride grafted polymer are set to 0.05 wt% to 5 wt%. 0.05 wt%
If it is less than 5, the styrene / maleic anhydride copolymer to be compounded will be precipitated, and the effect of the anti-bottley resistance will not be obtained.
This is because if it exceeds wt%, the electrical characteristics deteriorate.

A typical example of the styrene / maleic anhydride copolymer is as follows.

[0010]

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Here, the content of styrene is 0.05 wt%
The reason for defining -10 wt% is that if the content is less than 0.05 wt%, the effect of anti-bowtie resistance is not obtained.
This is because if it exceeds 0 wt%, the electrical characteristics deteriorate.

A resin composition obtained by adding a styrene / ethylene butylene olefin crystal block copolymer to polyethylene or an ethylene copolymer or a mixture thereof is coated on the outer periphery of the conductor directly or through a semiconductive layer, and then crosslinked or Form a non-crosslinked electrical insulation. When cross-linked, dicumyl peroxide, 2,5-dimethyl-2,5- (t-butylperoxy) hexyne-3
It is common to heat-crosslink with a peroxide represented by.

Further, a so-called silane water bridge obtained by grafting an organic silane such as vinyltriethoxysilane onto a polymer and contacting it with water to condense the silane with a silanol condensation catalyst, or an ionizing property such as an electron beam. Crosslinking by irradiation with radiation may be used.

Here, the addition amount of the styrene / ethylene butylene olefin crystal block copolymer is from 1 part by weight to 1 part.
The amount of 0 parts by weight is used because if the amount is less than 1 part by weight, sufficient bowtley properties are not exhibited, and if the amount exceeds 10 parts by weight, the dielectric properties adversely affect.

In addition, if necessary, a lubricant, a coloring agent, a filler, a crosslinking accelerator, etc. may be added.

[0016]

Since the present invention uses the electric insulating composition as described above, even if there are defects such as voids, foreign matters in the insulator, and irregularities at the interface between the insulator and the semiconductive layer, they are equal to or more than the conventional one. While having electrical characteristics, the water tree resistance, especially the bowtley resistance, is greatly improved. In addition, the influence of water on the bow tie tree is extremely large, and it has been found that the cable is electrically charged in the air or the cable is shielded by a metal sheath. These are not due to water infiltrated from the outside, but due to a small amount of water contained in the cross-linked polyethylene at the time of manufacturing the cable. Needless to say, the insulator of the present invention is also effective for such a bowtie tree. Is.

[0017]

EXAMPLES Examples of the present invention will be described in detail below.

The composition having the composition shown in Table 1 was kneaded with a hot roll at 120 ° C. to prepare a sheet, which was pelletized with a pelletizer. Then, the pellets were introduced into an extruder, and as shown in FIG.
As shown in (3), a 2 mm thick insulator 3 was extruded together with a 1.5 mm thick inner semiconductive layer 2 and an outer semiconductive layer 4 onto a copper conductor 1 having an outer diameter of 3 mm. Immediately thereafter, the cable 5 is completed by crosslinking in a dry crosslinking tube using nitrogen gas as a heat medium, and then pressure cooling to obtain 8 types of samples (Examples 1 to 5 and Comparative Examples 1 to 3). Then, each of these samples was evaluated with respect to the anti-bowtley resistance and the electrical characteristics. As the method for evaluating the anti-bowtley resistance, each of the above samples was immersed in warm water of 90 ° C., AC3 kV was applied between the conductor and water for 500 days, and this was sliced into thin pieces and boiled and dyed with an aqueous solution of methylene blue. Then, using an optical microscope, the presence or absence of occurrence of votitley and the number (0.2 mm) were examined. On the other hand, as a method for evaluating the electrical characteristics, a Schering bridge is used, the electric field related to the cable insulator is set to 10 kV / mm, the dielectric loss tangent at that time is measured, and if the value of the dielectric loss tangent is 0.05% or less, ,
Those exceeding that were evaluated as x.

[0019]

[Table 1]

As a result, as is clear from Table 1, each of the samples of Examples 1 to 5 according to the present invention has a good anti-bowtley resistance and a good dielectric property. It was On the other hand, in Comparative Example 1 in which the maleic anhydride graft polymer was not used, the number of occurrence of bowtitley was very large and the resistance to bowtitley was greatly deteriorated. Further, in Comparative Example 2 in which the concentration of maleic anhydride exceeds 5%, the number of occurrence of bowtitley is large and the resistance to bowtitley is poor. Further, in Comparative Example 3 in which the concentration of styrene exceeded the specified amount of the present invention, not only the anti-bowtie tree characteristics but also the dielectric loss tangent deteriorated.

[0021]

In summary, according to the present invention, the water tree resistance, in particular, the bowtley resistance is greatly improved while maintaining the electrical characteristics equal to or higher than those of the conventional ones. It has excellent effects such as being able to maintain it.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view showing an embodiment of the present invention.

[Explanation of symbols]

 1 conductor 2 inner semiconductive layer 3 insulator 4 outer semiconductive layer

Claims (3)

[Claims] 1. The content of maleic anhydride is 0.02 wt.
% To 5 wt% grafted polyethylene or ethylene-based copolymer or a mixture thereof with styrene / maleic anhydride copolymer so that the content of styrene is 0.05 wt% to 10 wt% An electrical insulating composition comprising: 2. A polymer obtained by grafting maleic anhydride onto polyethylene or an ethylene-based copolymer or a mixture thereof has a maleic anhydride content of 0.02 wt% to
Blended to be 5 wt%, and
Maleic anhydride copolymer with a styrene content of 0.05
An electrical insulating composition characterized by being blended so as to be 10 wt% to 10 wt%. 3. An electric wire / cable, comprising a conductor coated with an insulator comprising the electrical insulating composition according to claim 1.