JPH07245014A - Electrical insulation composition and electric wire / cable - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to provide a novel electrical insulation capable of preventing the generation of a water tree even in a wet or flooded atmosphere and preventing a decrease in electrical insulation. To provide a composition and an electric wire / cable. [Structure] The present invention comprises polyethylene, an ethylene-based copolymer, or a mixture thereof, and 3,3-bis (3-tert-butyl-4-hydroxyphenyl) butyrate.
It is characterized by adding ethylene ester.

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 having excellent water tree resistance, and particularly excellent in bowtie resistance, and electric wires and cables.

[0002]

2. Description of the Related Art Conventionally, among polyolefins, so-called cross-linked polyethylene, which is obtained by cross-linking polyethylene, has been widely used as an insulating material for electric wires and cables because of its excellent electric insulation and heat resistance.

[0003]

By the way, in this crosslinked polyethylene insulated wire / cable, when the crosslinked polyethylene is used in a wet or flooded atmosphere, a water tree is generated in the insulator, and the excellent electrical insulating property of the insulating material is obtained. There is a problem of a large drop.

That is, the general structure of an insulated cable for high voltage is, as shown in FIG. 1, that an inner semiconductor layer 2 is formed on a conductor 1, an insulator 3 is formed on the outer periphery thereof, and this insulator is further formed. The outer semiconductor layer 4 is provided on the outer periphery of the insulator 3. However, under the conditions as described above, a bowtie-shaped water tree is generated inside the insulator 3, and the inner semiconductor layer 2 or the outer semiconductor layer is further formed. An interfacial water tree is generated at 4, and in the worst case, this may penetrate the insulator 3 and cause dielectric breakdown.

Therefore, the present invention has been devised in order to effectively solve the above-mentioned problems, and its purpose is to suppress the generation of water trees even in a wet or flooded atmosphere and to provide electrical insulation. The present invention provides a novel electrical insulating composition and an electric wire / cable capable of preventing deterioration of the property.

[0006]

This water tree is generated by condensing water on a high electric field portion such as a void in the insulator, a foreign substance, and an irregularity at 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 resins and improvements in electric wire and cable manufacturing techniques have improved the effect of suppressing the generation of water trees. ing. However, despite the efforts made in various fields, it has not reached the stage where the above water trees can be completely eliminated, and studies are being earnestly conducted to prevent the occurrence of such water trees.

In order to solve the above-mentioned problems, the present invention provides polyethylene, an ethylene-based copolymer or a mixture thereof with butyric acid 3,3-bis (3-tert-butyl-4-hydroxyphenyl) ethylene ester. It is an electric insulating composition added and an electric wire / cable using the electric insulating composition as an insulator.

In the present invention, butyric acid 3,3-bis (3-tert-butyl-4-hydroxyphenyl) ethylene ester means a structural unit as shown in FIG.

As the base resin constituting the electric insulating composition, low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-propylene copolymer, etc. , And polyolefins containing ethylene in the majority are applicable, and any one of them may be used, or two or more kinds may be used in combination.

A resin composition obtained by adding a hydroaromatic hydrocarbon to such polyethylene or ethylene copolymer or a mixture thereof is coated on the outer periphery of the conductor directly or through a semiconductive layer, and is crosslinked or non-crosslinked. Form a cross-linked electrically insulating layer. In the case of cross-linking, it is general to heat-crosslink using peroxides represented by dicumyl peroxide and 2,5-dimethyl-2,5- (t-butylperoxy) hexyne-3.

In addition, a so-called silane water bridge obtained by grafting an organic silane such as vinyltriethoxysilane to a polymer and contacting 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.

In addition, addition of lubricants, colorants, fillers, cross-linking accelerators and the like may be added if necessary.

[0013]

The electric wire / cable of the present invention greatly improves the water tree resistance, particularly the bow tie tree resistance in a wet or flooded atmosphere environment, by using the electric insulating composition having the above-mentioned structure as an insulator. can do.
Therefore, even if there are defects such as voids, foreign matter in the insulator, and irregularities at the interface between the insulator and the semiconductive layer, the generation of water trees can be suppressed, and the deterioration of electrical insulation can be prevented. You can In addition, the influence of water on the bow tie tree is extremely large, and the vault tie tree has been found in a cable that is electrically charged in the air or a cable that is shielded by a metal sheath. These are not due to the water infiltrated from the outside, but due to the small amount of water contained inside the cross-linked polyethylene at the time of manufacturing the cable. The insulating property of the present invention is effective also for such a bowtie tree.

[0014]

EXAMPLES Preferred examples and comparative examples of the present invention will be described below.

Compositions of the formulations shown in Table 1 were prepared in the amount of 12
The mixture was kneaded with a hot roll of 0 ° C. to form a sheet, and pelletized with a pelletizer. Then, the pellets are introduced into an extruder and, as shown in FIG. 1, are extruded as a 2 mm thick insulator 3 together with a 0.5 mm thick inner semiconductor layer 2 and an outer semiconductor layer 4 on a copper conductor 1 having an outer diameter of 3 mm. did. After this, immediately cross-link in a dry cross-linking tube using nitrogen gas as a thermal catalyst,
After that, it was made into a cable by pressure cooling, and the number of occurrence of bowtitley and the bloom of the additive were evaluated for each of these cable samples. In addition, each sample was evaluated as
Immerse in warm water of 0 ℃, AC3kV 50 between conductor and water
After applying for 0 days, this was sliced thinly, boiled and dyed with an aqueous solution of methylene blue, and the presence or absence of occurrence of votitley and the number (0.2 mm or more) were examined using an optical microscope. As a method of evaluating the bloom of the additive, the surface of the sample after the completion of charging was visually observed and analyzed by an infrared absorption spectrum method to examine the presence or absence of the additive.

[0016]

[Table 1]

As a result, as is clear from Table 1, each of the samples of Examples 1 to 5 had good anti-bowtite resistance and no precipitation of additives was observed. On the other hand, in Comparative Example 1 in which the amount of the additive added was equal to or more than the specified amount of the present invention, the additive was precipitated and a large number of bowtitley occurred, and the amount of the added additive was less than the specified amount of the present invention Comparative Example 2 and Comparative Example 3 in which no additive is added
In each of the above cases, a large amount of bowtitley was generated, and in all of them, the anti-bowtitley resistance of the additive was insufficient.

[0018]

As described in detail above, according to the present invention, the water tree resistance, particularly the bowtley resistance, in a wet or flooded atmosphere environment is greatly improved. Even if a defect such as an irregularity at the interface between the insulator and the semiconductive layer is generated, it is possible to suppress the generation of water trees, and it is possible to prevent deterioration of the electrical insulation property in advance.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of an electric wire / cable according to the present invention.

FIG. 2 is a structural formula diagram showing a structure of an additive used in the present invention.

[Explanation of symbols]

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

Claims (3)

[Claims] 1. A method comprising adding butyric acid 3,3-bis (3-tert-butyl-4-hydroxyphenyl) ethylene ester to polyethylene, an ethylene-based copolymer, or a mixture thereof. Electrical insulation composition. 2. To 100 parts by weight of polyethylene or an ethylene copolymer or a mixture thereof, 3,3-bis (3-tert-butyl-4-hydroxyphenyl) butyric acid ethylene ester is added in an amount of 0.01-3. An electrical insulating composition comprising 0 part by weight. 3. An electric wire / cable, characterized in that a conductor is coated with the electrical insulating composition according to claim 1 or 2.