JPH1064339A - Electric insulating composite, and wire and cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep excellent electric characteristics and improve water tree resistance, particularly, bowtie tree resistance by covering a conductor with an insulator formed of a specified electric insulating composite. SOLUTION: A conductor 1 formed of a soft copper stranded wire is covered with an insulator 3 together with an internal semiconductive layer 2 and an external semiconductivelayer 4. The resin composite constituting the insulator 3 is formed of an electric insulating composite obtained by mixing 0.05-3 parts by weight of dialkyl disulfide to 100 parts by weight of a polyethylene or ethylene copolymer, or a mixture thereof. Thus, since water tree resistance, particularly, bowtie tree resistance is significantly improved even if a defect such as void, foreign matter, irregularities or the like is caused in the insulator, excellent electric performance can be kept over a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art So-called cross-linked polyethylene obtained by cross-linking polyolefin, particularly polyethylene, has been widely used as an insulating material for electric wires and cables because of its excellent electric insulation and heat resistance.

[0003] However, the wires and cables coated with the cross-linked polyethylene have a disadvantage that when used in a wet or submerged atmosphere, water trees are generated in the insulator and the excellent electrical insulation performance of the material is greatly reduced.

[0004] The water tree that causes the deterioration of the electric insulation performance is formed by condensation of water on voids and foreign matters in the insulator and defects such as local high electric field portions such as irregularities in the interface between the insulator and the semiconductive layer. It is known that this is caused by things. For this reason, much effort has been made to eliminate these defects in wires and cables, for example,
Improvement of resin quality and improvement of manufacturing technology of electric wires and cables have improved the effect of suppressing the generation of water trees.

[0005]

However, despite efforts to suppress the generation of water trees over various areas, the generation of water trees can be greatly reduced. At present, it has not reached the stage.

Accordingly, the present invention has been devised in order to effectively solve such a problem, and an object of the present invention is to provide a water resistant tree even if a defect such as a void, a foreign substance, or irregularity occurs in an insulator. It is intended to provide a novel electric insulating composition and a wire / cable capable of greatly improving the properties, particularly the bow titley resistance.

[0007]

According to the present invention, 0.05 to 3 parts by weight of a dialkyl disulfite is blended with 100 parts by weight of polyethylene or an ethylene copolymer or a mixture thereof. An electric insulating composition characterized by comprising: an electric insulating composition; and an electric wire or cable obtained by coating an insulator made of the electric insulating composition on a conductor.

As a result, excellent electrical properties are maintained, and the water-resistant tree, especially the bow titley resistance, is improved.

[0009]

Next, a preferred embodiment of the present invention will be described.

FIG. 1 is an enlarged sectional view showing an embodiment of an electric cable according to the present invention, in which 1 is a conductor made of annealed copper or the like, 2 is an internal semiconductive layer, and 3 is a resin composition. The insulator 4 is an external semiconductive layer.

The resin composition constituting the insulator 3 is an electric insulating material obtained by mixing 0.05 to 3 parts by weight of dialkyl disulfite with 100 parts by weight of polyethylene or ethylene copolymer or a mixture thereof. It is made of a composition, and can exhibit excellent electrical properties and properties excellent in water-resistant tree, particularly, excellent bow-tree resistance.

The dialkyl disulphide is a non-saponified long-chain, aliphatic disulfide and can be represented by the following formula. Examples include dihexadecyl disulfide, diheptadecyl disulfide, dioctadecyl disulfide, dinonadecyl disulfide,
Examples thereof include dieicosyl disulfide, dipheneicosyl disulfide, didecosyl disulfide, ditricosyl disulfide, ditetradicosyl disulfide, and ditricontil disulfide.

[0013]

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Here, the reason why the addition amount is specified in the range of 0.05 to 3 parts by weight is that if the amount is less than the specified amount, the bow title tree is not effectively controlled, and if the added amount exceeds the specified amount, the electric properties, especially This is because the dielectric loss tangent deteriorates.

The polyethylene or ethylene copolymer of the present invention includes low-density polyethylene, medium-density polyethylene, linear low-density polyethylene, high-density polyethylene, ethylene-propylene copolymer, and ethylene-ethyl acrylate copolymer. , Ethylene-vinyl acetate copolymer,
Polyolefins containing ethylene in a majority, such as ethylene-styrene copolymers, furthermore, those obtained by grafting maleic anhydride or vinyl silane to these polyethylenes, and these can be used alone or in combination of two or more. is there.

As a method for cross-linking the electrical insulating composition mainly composed of polyethylene, dicumyl peroxide, 1- (2-tert-butylperoxyisopropyl) -1-isopropylbenzene or 1- (2-
tert-butylperoxyisopropyl) -3-isopropylbenzene, 1,3-bis- (tert-butylperoxy-isopropyl) benzene, 2,5-dimethyl-2,
Chemical crosslinking with an organic peroxide such as 5- (tert-butylperoxy) -hexyne-3 can be mentioned, and these can be used alone or in combination of two or more.

Also, together with such an organic peroxide,
It is also possible to use an aromatic α-methylalkenyl dimer in combination. Here, such a dimer includes α-methylstyrene, para-methyl-α-methylstyrene,
Isopropyl-α-methylstyrene, meta-ethyl-α
-Methylstyrene, meta-methyl-α-methylstyrene, ar-dimethyl-α-methylstyrene, ar-chloro-α-methylstyrene, ar-chloro-ar-methyl-α-methylstyrene, ar-diethyl-α- Unsaturated dimers such as methylstyrene, ar-methyl-ar-isopropyl-α-methylstyrene are included.

Further, these dimers may be used alone or in combination of two or more. This dimer has a function of preventing cross-linking of polyethylene at the time of extrusion molding, can prevent scorch at the time of extrusion molding, and can obtain wires and cables having good appearance.

Other crosslinking methods include the following:
Silane water crosslinking using a silane such as vinyltriethoxysilane or irradiation crosslinking by ionizing radiation such as an electron beam can also be used.

[0020] In addition to the above components, additives such as an antioxidant, a lubricant, a coloring agent, a flame retardant, and a filler may be appropriately added to the electric insulating composition.

The effect of moisture on the bow title tree is extremely large, and a bow title tree has been found in a cable charged in the air or a cable shielded by a metal sheath or the like. It is considered that these are not due to moisture permeating from the outside, but to trace amounts of moisture contained inside the crosslinked polyethylene during cable production. It is needless to say that the present invention is also effective for such bow titles.

[0022]

EXAMPLES Hereinafter, specific examples of the present invention will be described in detail along with comparative examples.

First, 8 blended as shown in Table 1 below
Each composition (Examples 1 to 5 and Comparative Examples 1 to 3) was kneaded with a hot roll at 120 ° C. to form a sheet, and pelletized with a pelletizer. Next, each of these pellets was introduced into an extruder and, as shown in FIG. 1, a 4 mm-thick inner semiconductive layer 2 and an outer semiconductive layer 4 each having a thickness of 0.7 mm were placed on a conductor 1 made of a 60 mm ² soft copper stranded wire. After being extruded as an insulator 3, this was immediately cross-linked in a dry cross-linking tube using nitrogen gas as a medium, and then cooled to form cables.

These eight types of cables were used as samples, and the bow titley resistance and electrical characteristics of each sample were examined, and the respective characteristics were evaluated.

In order to evaluate the anti-bow titleile characteristics, the above sample was immersed in warm water of 90 ° C., and an AC voltage of 50 Hz and 9 kV was applied between the conductor and water for 500 days. Were sliced thinly and stained by boiling with an aqueous methylene blue solution, and the presence or absence and the number (200 μm or more) of bow titles were counted using an optical microscope. On the other hand, as a method for evaluating electric characteristics, a sharing bridge is used, and an electric field applied to the cable insulator is reduced by 10 k.
V / mm, and the dielectric loss tangent at that time was measured. If the value of the dielectric loss tangent was 0.05% or less, the result was marked as "O" if the value was acceptable, and "x" if it was not acceptable.

[0026]

[Table 1]

As a result, as is clear from Table 1, all of Examples 1 to 5 according to the present invention showed a small number of bow title trees and a good dielectric loss tangent.

On the other hand, in Comparative Example 1 in which only polyethylene was not added with dialkyl disulfite, and in Comparative Example 2 in which the amount of dialkyl disulfite added was less than the prescribed amount of the present invention, the number of bow title trees generated was all small. There were extremely many. In Comparative Example 3 in which the amount of the dialkyl disulfite exceeds the specified amount of the present invention, the dielectric loss tangent was deteriorated.

[0029]

In summary, according to the present invention, the water tree resistance, especially the bow titley resistance, is greatly improved irrespective of the occurrence of defects such as voids, foreign matters, irregularities, etc. in the insulator. Excellent effects such as excellent electric performance can be maintained over a long period of time.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of an embodiment of an electric wire / cable according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 conductor 2 inner semiconductive layer 3 insulator 4 outer semiconductive layer

Claims (2)

[Claims] 1. An electrical insulating composition comprising 0.05 to 3 parts by weight of a dialkyl disulphite with respect to 100 parts by weight of polyethylene or an ethylene copolymer or a mixture thereof. 2. An electric wire, comprising an insulator made of the electrical insulating composition according to claim 1 coated on a conductor.
cable.