JP2001256833A - Composition for electrical insulation and electric wire and cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel composition for electrical insulation capable of effectively alleviating the electric field of a defective portion containing voids and foreign matter in an insulating layer of an insulated cross-linked polyethylene electric wire for voltage and a high voltage power cable, thereby remarkably improving water-proof tree, especially bowtightly as well as an electric wire and cable using the same. SOLUTION: The composition for electrical insulation contains 0.05 to 5 parts by weight of copolymer of styrene, maleic anhydride, and allyl ether against 100 parts by weight of polyethylene or ethylene copolymer or a mixture of these. The electric wire and cable are coated with the insulating layer directly on a conductor or through a semi-conductive layer.

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 electric wires and cables. More specifically, the present invention provides a polyolefin-based electrical insulating composition based on polyethylene or an ethylene copolymer or a mixture thereof and a polyolefin-based electrical insulating composition coated on a conductor directly or via a semiconductive layer. Related to electric wires and cables.

[0002]

2. Description of the Related Art Polyolefins, particularly polyethylene, have excellent electrical properties because they are typical hydrocarbon plastic materials. For this reason, polyolefins such as polyethylene are widely used as electric insulating materials for electric wires and cables.

The only drawback of polyolefins such as polyethylene is their low heat resistance. Therefore, a crosslinked polyolefin such as a crosslinked polyethylene having improved heat resistance, which is a difficult point, has come to be used as an electrical insulating material for insulated wires for high voltage and power cables for high voltage.

However, when this cross-linked polyethylene is used in a wet or submerged atmosphere under a high voltage for a long period of time, water trees are generated in the cross-linked polyethylene insulating layer, and the locations where the water trees are generated have electrical defects. We know that it will be a department.

[0005] Further, such a water tree is formed by voids, foreign matter, and amber (partially having a high degree of polymerization or being crosslinked to have a high molecular weight) in the crosslinked polyethylene insulating layer.
It is also known that water is aggregated at a defective portion such as a local high electric field portion.

Further, it is known that when a high-voltage insulated wire or a high-voltage power cable is placed in an atmosphere in which almost no moisture is present, electrical insulation breakdown occurs when various adverse conditions are overlapped. It has also been found that the starting point of the electrical breakdown occurring in an atmosphere where almost no moisture is present is an electrical defect such as a void, a foreign substance, or an invar in the crosslinked polyethylene insulating layer. Such a phenomenon has been confirmed by a precursor cutoff test or the like in which the voltage is cut off immediately after the partial discharge starts as a sign of dielectric breakdown.

[0007] For this reason, wire and cable manufacturers have found that voids, foreign matter, and the like are present in the cross-linked polyethylene insulating layer of cross-linked polyethylene-based insulated wires and high-voltage power cables.
Efforts have been made to prevent the formation of electrical defects such as amba. For example, quality control, compounding control, extrusion coating technology, cross-linking technology and the like of polyethylene base resin.

[0008] Due to these hard efforts, the electrical reliability of crosslinked polyethylene-based insulated wires for voltage and power cables for high voltage has been highly enhanced.

[0009]

On the other hand, the operating voltage of crosslinked polyethylene-based insulated electric wires and high-voltage power cables tends to be higher and higher, and the operating environment is severe, such as high temperature and high humidity. It is getting down.

Under such a background, in the case of a crosslinked polyethylene-based insulated electric wire or a high-voltage power cable, it is required to further reduce electrical defects such as voids, foreign matter, and amber in the crosslinked polyethylene insulating layer. It is becoming.

However, at this stage, it is difficult to completely remove foreign matter and voids in the crosslinked polyethylene insulating layer from electrical defects such as voids, foreign matter, and amber.

The present invention has been made in view of such a point, and an object of the present invention is to solve the above-mentioned disadvantages of the prior art and to form a crosslinked polyethylene-based insulated electric wire or a high-voltage power cable. Even if electrical defects such as voids and foreign matter occur in the insulator in the polyethylene insulating layer, the electric field at those electrical defects can be effectively relaxed, thereby providing water tree resistance, especially bow tie resistance. An object of the present invention is to provide a novel electric insulating composition and a wire / cable capable of significantly improving a tree.

[0013]

The gist of the present invention lies in the following two points.

(1) A styrene-maleic anhydride-allyl ether copolymer is added in an amount of 0.05 to 100 parts by weight of polyethylene or an ethylene copolymer or a mixture thereof.
An electrical insulating composition characterized by being blended in an amount of up to 5 parts by weight.

(2) In an electric wire or cable in which an electric insulating layer is coated on a conductor directly or via a semiconductive layer, the electric insulating layer is based on 100 parts by weight of polyethylene or an ethylene copolymer or a mixture thereof. Styrene-maleic anhydride-allyl ether copolymer in an amount of 0.05 to 5
Electric wires characterized by being blended in parts by weight
cable.

That is, the present inventors have conducted intensive studies on the mechanism of water tree generation inside a crosslinked polyethylene insulating layer of a high-voltage insulated wire or a high-voltage power cable, and have found that polyethylene or an ethylene copolymer or a mixture thereof can be obtained. ,
The inventors have found that a compound having three groups of a styrene group, a maleic anhydride group, and an alkylene glycol group in the molecule is effective, and have reached the present invention.

It is considered that the combination of the three groups is effective because each group has the following effects.

First, since the maleic anhydride group has an adhesive property to a defect such as a foreign substance, peeling of the interface with the foreign substance is prevented.

The aromatic ring of the styrene group can form a resonance structure by trapping electrons.

Furthermore, the alkylene glycol group is hydrophilic, so that local concentration of water is prevented.

These elements act synergistically to effectively alleviate the electric field at the electrically defective portion of the crosslinked polyethylene-based insulated electric wire or high-voltage power cable,
Thereby, the water tree resistance, particularly the bow titley resistance, can be remarkably improved.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the electric insulating composition and the electric wires / cables of the present invention will be described.

In the present invention, examples of the polyethylene include low-density polyethylene, medium-density polyethylene, straight-shaped low-density polyethylene, and high-density polyethylene. Further, those obtained by grafting maleic anhydride, vinyl silane, or the like to these polyethylenes may be used.

In the present invention, the ethylene copolymer is a polyolefin containing ethylene in a majority, for example, ethylene-propylene copolymer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, ethylene-styrene copolymer. It is a polymer or the like.

In the present invention, these polyethylenes, polyethylene grafted with maleic anhydride, vinyl silane, etc.,
Ethylene copolymers can be used alone or in combination of two or more.

In the present invention, the styrene-maleic anhydride-allyl ether copolymer has a structure as shown in Chemical formula 1.

[0027]

Embedded image

In the present invention, the blending amount of the styrene-maleic anhydride-allyl ether copolymer is set to 0.05 to 5 parts by weight. When the amount is less than 0.05 part by weight, the effect of relaxing the electric field and the effect of suppressing bow titleries are obtained. On the other hand, when the content is 5 parts by weight or more, the electrical characteristics rapidly deteriorate.

In the present invention, examples of the alkylene glycol group include an ethylene glycol group and a propylene glycol group.

In the present invention, a method of crosslinking polyethylene, a polyethylene grafted with maleic anhydride, vinyl silane, or the like, an ethylene copolymer alone or a blend of two or more of them includes chemical crosslinking with an organic peroxide,
Any of silane water crosslinking using silanes such as vinyltrimethoxysilane and irradiation crosslinking by ionizing radiation such as electron beam may be used.

Here, the organic peroxide used for the chemical crosslinking is dicumyl peroxide, 1- (2-t-butylperoxyisopropyl) -1-isopropylbenzene, 1- (2-t-butylperoxyisopropyl).
-3-isopropylbenzene, 1,3-bis- (t-butylperoxy-isopropyl) benzene, 2,5-dimethyl-2,5-di (t-perperoxy) hexane, 2,5-dimethyl-2,5 -(T-butylperoxy) -hexin-3 and the like. These organic peroxides can be used alone or as a blend of two or more.

Further, together with such an organic peroxide,
It is also possible to use an unsaturated dimer of α-aromatic-substituted-α-methylalkene which has an effect of preventing scorch during extrusion.

Here, the unsaturated dimer is α
-Methylstyrene, para-methyl-α-methylstyrene, para-isopropyl-α-methylstyrene, meta-
Ethyl-α-methylstyrene, meta-methyl-α-methylstyrene, ar-dimethyl-α-methylstyrene, a
r-chloro-α-methylstyrene, ar-chloro-ar
-Methyl-α-methylstyrene, ar-diethyl-α-
Methylstyrene, ar-methyl-ar-isopropyl-
Unsaturated dimers such as α-methylstyrene are included. A specific example of such a compound is 2,4-diphenyl-4-methyl-1-pentene which is a dimer of α-methylstyrene.

In the present invention, an antioxidant, a lubricant, a coloring agent, an antioxidant and the like may be added as necessary in addition to the above-mentioned compounding agents.

[0035]

EXAMPLES Next, examples of the electric insulating composition and electric wires / cables of the present invention and conventional comparative examples will be described.

(Manufacturing Method of Crosslinked Polyethylene Insulated Wire for High Voltage) First, the manufacturing procedure of the electrical insulating compositions and the wires and cables of the examples and comparative examples will be described.

First, the materials of the electric insulating composition were weighed and collected as shown in Table 1 in Examples and Comparative Examples.

Preparation of Electric Insulating Composition Sheet Next, the materials of the electric insulating compositions of the Examples and Comparative Examples weighed and collected as described above are kneaded with a hot roll at 120 ° C., and then the Examples and Comparative Examples are compared with the hot roll. Example electrical insulating composition sheets were prepared.

Preparation of Electrical Insulating Composition Pellets Next, the electrical insulating composition sheets of the examples and comparative examples obtained above were each pelletized by a pelletizer.

Production of cross-linked polyethylene insulated wire for uncross-linked high voltage Next, the electric insulating composition pellets of the examples and comparative examples obtained above were put into a hopper of a 150 mm extruder in which the cylinder temperature was set to 140 ° C. I put it in.

Then, an internal semiconductive layer having a thickness of 0.7 mm on a soft copper wire stranded conductor having a conductor cross-sectional area of 100 mm ² , an electrical insulating composition layer having a thickness of 6 mm on the internal semiconductive layer, and an electrical insulating composition thereof An uncrosslinked high voltage crosslinked polyethylene insulated wire was manufactured by simultaneously extruding a 0.7 mm thick external semiconductive layer on the layer.

The inner semiconductive layer and the outer semiconductive layer used herein were 100 parts by weight of ethylene vinyl acetate copolymer, 65 parts by weight of acetylene plaque as a conductivity-imparting agent,
The composition is obtained by mixing 0.5 parts by weight of α-α′-bis (t-butylperoxy-m-isopropyl) benzene as an organic peroxide.

Production of Crosslinked Polyethylene Insulated Wire for High Voltage Next, the uncrosslinked crosslinked polyethylene insulated wires for high voltage obtained in Examples and Comparative Examples obtained above were immediately heated at 280 ° C. for 10 minutes.
Cross-linking was performed by passing through a dry-type cross-linking tube in a nitrogen gas atmosphere at atmospheric pressure, and then a cross-linked polyethylene insulated wire for high voltage was obtained by passing through a cooling bath.

FIG. 1 is a cross-sectional view of the high-voltage crosslinked polyethylene insulated wire of Example 1 thus obtained.

In FIG. 1, 1 is a soft copper wire stranded conductor, 2 is an inner semiconductive layer, 3 is a crosslinked polyethylene insulating layer, and 4 is an outer semiconductive layer.

As can be seen from FIG. 1, the crosslinked polyethylene insulated wire for high voltage of Example 1 has an inner semiconductive layer 2 extruded and coated on a soft copper wire stranded conductor 1, and The crosslinked polyethylene insulating layer 3 is formed by extrusion-coating, and the outer semiconductive layer 4 is extruded and coated on the crosslinked polyethylene insulating layer 3.

In the present invention, the external semiconductive layer 4 can be omitted as shown in FIG.

Further, in the present invention, the inner semiconductive layer 2 and the outer semiconductive layer 4 can be omitted as shown in FIG.

Further, in the present invention, a sheath layer, an armoring layer and the like may be provided on the outermost layer of the crosslinked polyethylene insulated wire for high voltage shown in FIGS. 1, 2 and 3.

(Method of Testing Properties) Next, a method of testing the properties of the high-voltage crosslinked polyethylene insulated wires of Examples and Comparative Examples obtained above will be described.

As a characteristic test of the crosslinked polyethylene insulated wire for high voltage, measurement of an AC breakdown voltage, a bow titley resistance test, and a dielectric loss tangent measurement test were performed.

A. AC Breakdown Voltage Test First, the high-voltage crosslinked polyethylene insulated wires of Examples and Comparative Examples obtained above were heated to 90 ° C., respectively.

Next, an AC voltage of 170 kV / 10 minutes was applied while heating to 90 ° C., and then the voltage was increased at a rate of 5 kV / 10 minutes to measure the dielectric breakdown voltage.

B. First, the high-voltage crosslinked polyethylene insulated wires of Examples and Comparative Examples obtained above were immersed in warm water at 90 ° C., and then an AC voltage of 50 Hz and 9 kV was applied between the conductor and the water. Was applied for 500 days.

Next, a cross-linked polyethylene insulating layer was obtained from each of the high-voltage cross-linked polyethylene insulated wires of Examples and Comparative Examples to which an AC voltage was applied for 500 days.

Next, the crosslinked polyethylene insulating layers of the obtained examples and comparative examples were sliced by a slicing apparatus.

Next, the slices of the crosslinked polyethylene insulating layers of the examples and comparative examples were immersed in an aqueous methylene blue solution and subjected to boiling dyeing.

Next, the slices of the crosslinked polyethylene insulating layers of Examples and Comparative Examples which were dyed by boiling were observed with an optical microscope, and the number of bow title trees that had accumulated was counted.

C. First, the dielectric loss tangent of the crosslinked polyethylene insulated wires for high voltage obtained in the examples and the comparative examples obtained above was measured using a sharing bridge, and the electric field of the insulator was set to 10 kV / mm. .

The results were evaluated as ○ when the value of the dielectric loss tangent was 0.05% or less, and as X when the value was 0.05% or more.

(Characteristic test results) Table 1 shows the characteristic test results.

[0062]

[Table 1]

As can be seen from Table 1, the crosslinked polyethylene insulated wire for high voltage of Comparative Example 1 has a drawback that the number of accumulated bowties in the crosslinked polyethylene insulating layer is extremely large at 3 × 10 ⁴ .

The crosslinked polyethylene insulated wire for high voltage of Comparative Example 2 also has a drawback that the number of Bowtie trees accumulated in the crosslinked polyethylene insulating layer is as large as 1 × 10 ⁴ .

The crosslinked polyethylene insulated wire for high voltage of Comparative Example 3 also has a drawback that the number of Bowtie trees accumulated in the crosslinked polyethylene insulating layer is as large as 1 × 10 ⁴ .

In the crosslinked polyethylene insulated wire for high voltage of Comparative Example 4 in which the blending amount exceeds the limited amount, the number of Bowtie trees accumulated in the crosslinked polyethylene insulating layer is as small as 10 but the half-surface dielectric tangent is 0. And the dielectric loss tangent evaluation was x.

On the other hand, the crosslinked polyethylene insulated wire for high voltage of the present invention has a high dielectric breakdown voltage and a remarkably small cumulative number of bow titleries of 50 or less.
In addition, the dielectric loss tangent is 0.05% or less, and the dielectric loss tangent evaluation is ○.

Although the embodiment of the present invention has been described with reference to a cross-linked polyethylene insulated electric wire for high voltage, similar experiments have been carried out for a cross-linked polyethylene power cable for high voltage. Note that the results were obtained.

[0069]

Industrial Applicability The electrical insulating composition and electric wires and cables of the present invention have a high dielectric breakdown voltage, maintain a low dielectric loss tangent, and can exhibit remarkably excellent bow titley resistance. Even if it is used for a long time under a flooded atmosphere and under a high voltage, it can exhibit a high degree of electrical reliability and is industrially useful.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a high-voltage crosslinked polyethylene insulated wire according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a high-voltage crosslinked polyethylene insulated wire according to a first modified example of the present invention.

FIG. 3 is a cross-sectional view of a cross-linked polyethylene insulated wire for high voltage according to a second modified example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Annealed copper wire conductor 2 Inner semiconductive layer 3 Crosslinked polyethylene insulating layer 4 Outer semiconductive layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // (C08L 23/04 C08L 35:00) 35:00) H01B 7/28 EF term (Reference) 4J002 BB031 BB041 BB151 BE042 BH012 GQ01 5G305 AA02 AB05 AB06 BA12 BA13 CA01 CA02 CA04 CA06 CA07 CA51 CA54 CD04 5G313 FA02 FA09 FB03 FC10 FD01 FD03 FD04

Claims (4)

[Claims] 1. An electric machine comprising a styrene-maleic anhydride-allyl ether copolymer in an amount of 0.05 to 5 parts by weight per 100 parts by weight of polyethylene or an ethylene copolymer or a mixture thereof. Insulating composition. 2. The electrical insulating composition according to claim 1, wherein the styrene-maleic anhydride-allyl ether copolymer has an alkylene glycol group in a side chain. 3. An electric wire or cable comprising a conductor and an electric insulating layer coated directly or via a semiconductive layer, wherein the electric insulating layer is formed of polyethylene, an ethylene copolymer or a mixture thereof in an amount of 100 parts by weight. An electric wire or cable comprising 0.05 to 5 parts by weight of a styrene-maleic anhydride-allyl ether copolymer. 4. The electric wire / cable according to claim 3, wherein the styrene-maleic anhydride-allyl ether copolymer has an alkylene glycol group in a side chain.