JP2001256832A - Composition for electrical insulation and electric wire and cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composition for a high voltage electrical insulation showing good water-proof tree, especially bowtightly. SOLUTION: The composition for electrical insulation consists of 1 to 80 parts by weight of polyethylene or ethylene copolymer or a mixture of these, 1 to 20 parts by weight of elastomer having a styrene component in its molecule, and 0.1 to 2 pants by weight of hydrophilic polymer capable of restraining a local moisture concentration. An electric wire and cable use the composition as an insulating layer. A copolymer of styrene, maleic anhydride and allyl ether, or a polyethylene glycol with a molecular weight of 10,000 or more is used as the hydrophilic polymer.

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 relates to a crosslinked polyolefin electric insulating composition and a wire / cable obtained by coating the crosslinked polyolefin electric insulating composition on a conductor.

[0002]

2. Description of the Related Art Polyolefins have excellent electrical properties because they have no polar group which deteriorates electrical properties. For this reason, polyolefins such as polyethylene and polypropylene are widely used as electric insulating materials for electric wires and cables.

A disadvantage of polyolefins is that they have poor heat resistance. Crosslinked polyolefins obtained by crosslinking the polyolefins also have good heat resistance. For this reason, crosslinked polyolefins have come to be widely used as electrical insulating materials for high-voltage insulated wires and high-voltage power cables that also require heat resistance.

However, when this cross-linked polyethylene is used for a long period of time in a wet or submerged atmosphere and under a high voltage, a water tree,
For example, a bow title tree is generated, and as a result, the excellent electrical properties of the crosslinked polyethylene insulating layer are greatly impaired. That is, the bow title part generated inside the crosslinked polyethylene insulating layer becomes an electric defect part, and as a result, electric breakdown or the like occurs at the electric defect part of the bow title part.

On the other hand, in high-voltage cross-linked polyethylene insulated wires and high-voltage cross-linked polyethylene power cables, foreign matter, amber, voids, etc., inside the cross-linked polyethylene insulating layer generated during the extrusion coating work of these cross-linked polyethylene insulations are also electrical defects. We know that it will be a department. In other words, the high-voltage cross-linked polyethylene insulated wire and high-voltage cross-linked polyethylene power cable having foreign matter, amber, voids, etc. inside the cross-linked polyethylene insulating layer were used for a long time under the condition that almost no moisture was present and under the voltage. Sometimes, such foreign matters, amber, voids and the like become a starting point of electrical insulation breakdown. The fact that such a portion becomes the starting point of electrical breakdown has been confirmed by a precursor cutoff test or the like in which the voltage is cut off immediately after partial discharge starts as a sign of dielectric breakdown.

For this reason, wire / cable manufacturers have been working to prevent these electrical defects from being formed inside the cross-linked polyethylene insulation layer of high-voltage cross-linked polyethylene insulated wires and high-voltage cross-linked polyethylene power cables. Every effort has been made. For example, strict control and improvement of quality control of polyethylene as a main raw material resin of cross-linked polyethylene, production control of cross-linkable polyethylene composition, extrusion coating / cross-linking technology of cross-linkable polyethylene composition and the like.

[0007]

Due to such hard efforts, the reliability of recent high-voltage cross-linked polyethylene insulated wires and high-voltage cross-linked polyethylene power cables has been highly enhanced.

[0008] Nevertheless, it is very difficult to completely eliminate foreign matter, voids, invars and the like inside the cross-linked polyethylene insulating layer of the high-voltage cross-linked polyethylene insulated wire and the high-voltage cross-linked polyethylene power cable. I know that.

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 provide a high-voltage crosslinked polyethylene insulated wire or a high-voltage crosslinked polyethylene power cable. Even if foreign matter, amber, voids and other electrical defects occur inside the cross-linked polyethylene insulation layer of the above, the electrical insulation composition and the electric wire / cable which can exhibit remarkably excellent water tree resistance, particularly bow resistance.
To provide a cable.

[0010]

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

(1) 1 to 80 parts by weight of polyethylene or an ethylene copolymer or a mixture thereof, 1 to 20 parts by weight of a mixture of one or more elastomers having a styrene component in the molecule, and An electrically insulating composition comprising 0.1 to 2 parts by weight of a hydrophilic polymer capable of suppressing concentration.

(2) In an electric wire or cable having an insulating layer on a conductor directly or via a semiconductive layer, the insulating layer is composed of 1 to 80 parts by weight of polyethylene or an ethylene copolymer or a mixture thereof, and An electrically insulating composition comprising 1 to 20 parts by weight of a mixture of one or more kinds of elastomers having a styrene component and 0.1 to 2 parts by weight of a hydrophilic polymer capable of suppressing local concentration of water. An electric wire or cable characterized by the following.

In the present invention, elastomers having a styrene component in the molecule include hydrogenated styrene butadiene styrene copolymer, hydrogenated styrene isoprene styrene copolymer, hydrogenated styrene butadiene rubber, hydrogenated styrene isobrene rubber, styrene ethylene butylene It is preferable to use one or more blends selected from olefin crystal block copolymers.

In the present invention, the hydrophilic polymer is preferably a styrene-maleic anhydride monoallyl ether copolymer or a polyethylene glycol having a molecular weight of 10,000 or more.

That is, the present inventors have conducted intensive studies on the improvement of the dielectric breakdown strength and the improvement of the water-tree resistance of the electric insulating composition and the electric wires and cables. It has been found that the present invention has been made.

[0016]

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, the polyethylene includes low-density polyethylene, medium-density polyethylene, linear low-density polyethylene, high-density polyethylene and the like.

In the present invention, the ethylene copolymer includes polyolefins containing ethylene in a majority such as ethylene-propylene copolymer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer and ethylene-styrene copolymer. Alternatively, those obtained by grafting maleic anhydride, vinyl silane, or the like to these polyolefins containing ethylene in a majority can also be used.

In the present invention, polyethylene, an ethylene copolymer, or a mixture thereof can be used alone, or two or more of them can be appropriately blended and used.

In the present invention, the elastomer having a styrene component in the molecule includes hydrogenated styrene butadiene styrene copolymer, hydrogenated styrene isoprene styrene copolymer, hydrogenated styrene butadiene rubber, hydrogenated styrene isoprene rubber, styrene It is a blend of one or more of ethylene propylene olefin crystal block copolymers.

In the present invention, the styrene-maleic anhydride-allyl ether copolymer includes, for example,
There is something like that shown in

[0022]

Embedded image

In the present invention, the alkylene glycol is an alkylene glycol, such as ethylene glycol or propylene glycol. These can be used alone or in combination of two or more.

In the present invention, when an elastomer having a styrene component in the molecule is blended with polyethylene, the water tree resistance, particularly the bow titley resistance, can be remarkably improved. First, electrons are trapped by the aromatic ring in the molecule. Secondly, to obtain a resonance structure and to stabilize it. Secondly, since it is an elastomer, it is tough against mechanical stress cracks.

In the present invention, styrene-
The reason that the blending of maleic anhydride-allyl ether copolymer or polyethylene glycol can significantly improve the water-tree resistance, particularly the bow-tree resistance, is because these are hydrophilic and effectively prevent local concentration of water. This is because it can be done.

In the present invention, these effects act synergistically to exhibit an excellent tree suppressing effect.

In the present invention, 1 to 20 parts by weight of one or more kinds of an elastomer having a styrene component in the molecule is added to 1 to 20 parts by weight of styrene, based on 100 parts by weight of polyethylene or an ethylene copolymer or a mixture thereof. Maleic anhydride-allyl ether copolymer or polyethylene glycol having a molecular weight of 10,000 or more
The reason why the amount is limited to 2 parts by weight is that if the amount is less than these limits, the electric field relaxation effect and the effect of suppressing bow titleries are poor, and if the amount is more than the above amount, the electrical characteristics deteriorate.

In the present invention, the method of crosslinking polyethylene, an ethylene copolymer or a mixture thereof includes chemical crosslinking with an organic peroxide, silane water crosslinking with a silane such as vinyltrimethoxysilane, ionizing radiation such as an electron beam. And irradiation crosslinking.

The crosslinking agent used in the organic peroxide crosslinking method is dicumyl peroxide, 1-
(2-t-butylperoxyisopropyl) -1-isopropylbenzene, 1- (2-t-butylperoxyisopropyl) -3-isopropylbenzene, 1,3-bis- (t-butylperoxy-isopropyl) benzene, , 5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5- (t-butylperoxy) hexyne-3 and the like. These can be used alone or in combination of two or more.

In the present invention, together with such an organic peroxide, an unsaturated dimer of α-aromatic-substituted α-methylalkene having an action of preventing scorch (burn due to premature crosslinking) at the time of extrusion molding is used. It is also possible to use them together.

Here, such unsaturated dimers include α-methylstyrene, para-methyl-α-methylstyrene, para-isopropyl-α-methylstyrene, meth-ethyl-α-methylstyrene, and meta-methyl-α. −
Methylstyrene, ar-dimethyl-α-methylstyrene, ar-chloro-α-methylstyrene, ar-chloro-ar-methyl-α-methylstyrene, ar-diethyl-α-methylstyrene, ar-methyl-ar-isopropyl There is a lower saturated dimer such as -α-methylstyrene. As a specific example, α-methylstyrene dimer 2,4
-Diphenyl-4-methyl-1pentene and the like.

In the present invention, in addition to the above, an antioxidant, a lubricant, a coloring agent, an antioxidant, a filler and the like can be added to the electric insulating composition as required.

[0033]

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

(Manufacturing method of cross-linked polyethylene insulated wire for high voltage) First, the manufacturing procedure of the electric insulating composition and the wire / cable of the examples and comparative examples will be described.

Weighing and Sampling of Materials of Electrical Insulating Composition First, the materials of the electrical insulating compositions of Examples and Comparative Examples shown in Table 1 were weighed and collected.

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 heated with the hot roll. Example electrical insulating composition sheets were prepared.

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

Production of Crosslinked Polyethylene Insulated Wire for Uncrosslinked 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 inner 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 electrically insulating composition layer having a thickness of 6 mm on the inner semiconductive layer, and an electrically 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 here 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 non-crosslinked 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 shows a cross-sectional view of the high-voltage crosslinked polyethylene insulated wire of Example 1 thus obtained.

In FIG. 1, 1 is an annealed copper wire 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 extruded and coated, 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 for Testing Characteristics) Next, a method for testing the characteristics 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, a measurement of an AC dielectric breakdown voltage, a bow titley resistance test, and a measurement test of a dielectric loss tangent 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, and the breakdown voltage was measured.

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 example and the comparative example were sliced by a slicing apparatus.

Next, slices of the crosslinked polyethylene insulating layers of these Examples and Comparative Examples were dipped in an aqueous methylene blue solution and subjected to boiling dyeing.

Next, the slices of the crosslinked polyethylene insulating layers of the 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.

[0060]

[Table 1]

As can be seen from Table 1, the crosslinked polyethylene insulated wire for high voltage of Comparative Example 1 has the disadvantage that the number of accumulated bow titles in the crosslinked polyethylene insulating layer is extremely large at 30,000.

The crosslinked polyethylene insulated wire for high voltage of Comparative Example 2 also has a drawback that the number of accumulated bow titles in the crosslinked polyethylene insulating layer is as large as 200.

The crosslinked polyethylene insulated wire for high voltage of Comparative Example 3 also has a disadvantage that the number of accumulated bow titles in the crosslinked polyethylene insulating layer is as large as 400.

In the crosslinked polyethylene insulated wire for high voltage of Comparative Example 4 in which the compounding 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 title trees of 10 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 were carried out on a cross-linked polyethylene power cable for high voltage. Note that the results were obtained.

[0067]

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 53/00 C08L 53/00 53/02 53/02 71/02 71/02 H01B 7/282 H01B 9 / 00 A 9/00 7/28 EF term (reference) 4J002 AC11X BB03W BB04W BB15W BH01Y BP01X BP03X CH01Y GQ01 5G305 AA02 AB05 AB06 BA12 BA13 CA01 CA02 CA04 CA06 CA07 CA08 CA13 CA47 CA51 CA54 CD04 5G313 FA03 FD03 FB03 FD03 FD03

Claims (6)

[Claims] 1 to 80 parts by weight of polyethylene or an ethylene copolymer or a mixture thereof, 1 to 20 parts by weight of a mixture of one or more kinds of elastomers having a styrene component in a molecule, and An electrically insulating composition comprising 0.1 to 2 parts by weight of a hydrophilic polymer capable of suppressing concentration. 2. An elastomer having a styrene component in the molecule is a hydrogenated styrene butadiene styrene copolymer, a hydrogenated styrene isoprene styrene copolymer, a hydrogenated styrene butadiene rubber, a hydrogenated styrene isobrene rubber, a styrene ethylene butylene olefin. 2. The electrical insulating composition according to claim 1, wherein the composition is one or a blend of two or more selected from crystal block copolymers. 3. The hydrophilic polymer is a styrene-maleic anhydride-allyl ether copolymer or has a molecular weight of 10,000.
The electrical insulating composition according to claim 1, which is the above polyethylene glycol. 4. An electric wire or cable having an insulating layer directly on a conductor or via a semiconductive layer, wherein the insulating layer is made of polyethylene, an ethylene copolymer, or a mixture thereof.
To 80 parts by weight, 1 to 20 parts by weight of a mixture of one or more elastomers having a styrene component in the molecule, and 0.1 to 2 parts by weight of a hydrophilic polymer capable of suppressing local concentration of water And an electric insulating composition comprising: 5. An elastomer having a styrene component in the molecule is a hydrogenated styrene butadiene styrene copolymer, a hydrogenated styrene isoprene styrene copolymer, a hydrogenated styrene butadiene rubber, a hydrogenated styrene isoprene rubber, a styrene ethylene butylene olefin crystal. The electric wire / cable according to claim 4, wherein the electric wire / cable is one or a mixture of two or more selected from block copolymers. 6. The hydrophilic polymer is a styrene-maleic anhydride-allyl ether copolymer or has a molecular weight of 10,000.
The electric wire / cable according to claim 4, which is the above polyethylene glycol.