JPH05298927A - Highly insulating body made of ethylene-based copolymer or its composition and electric cable using thereof - Google Patents

Abstract

PURPOSE:To heighten the electric insulation resistance greatly by specifying a dibasic acid anhydride unit and a monomer unit having specified polar groups regarding an ethylene-based copolymer or its composition mixed with another polyolefine-based resin. CONSTITUTION:An ethylene-based copolymer or a composition of the ethylene- based copolymer and another polyolefine-based resin is prepared wherein the copolymer is obtained by grafting a dibasic acid adhydride to a copolymer practically consisting of ethylene and at least one kind of monomers having carbonyl, nitryl, and nitro group and prepared by high pressure radical polymerization. A highly insulating material is made of the ethylene-based copolymer or ethylene-based copolymer composition containing 0.001-0.05wt.% of dibasic acid anhydride unit and 0.002-0.2wt.% in total of dibasic acid anhydride unit and the polar group unit. In this case, the electric insulation resistance is greatly heightened by specifying the dibasic acid anhydride unit and the monomer unit having the specified polar groups.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high insulator made of an ethylene copolymer or a composition thereof, which is excellent in high voltage characteristics and workability, and a high voltage power cable using the same.

[0002]

2. Description of the Related Art Conventionally, high-voltage polyethylene and cross-linked polyethylene have been widely used as insulators for high-voltage power cables because of their excellent electrical characteristics. One of the problems of high voltage power cables is power loss during high voltage power transmission, and reducing it is an important issue. One means of reducing this power loss can be achieved by increasing the high voltage characteristics of the insulating material, especially the electrical insulation resistance.
As a method for improving the high voltage characteristics of the insulating material, a method of grafting maleic anhydride onto low-pressure polyethylene has been proposed (for example, JP-A-2-10610).
However, when low-pressure polyethylene is used as an insulator for high-voltage power cables, it has a problem that it is inferior in flexibility as compared with high-pressure radical-polymerized polyethylene, and metal compounds that adversely affect electric properties remain as catalyst residues. ..
Further, a power cable having an insulating layer of a composition in which 100 parts by weight of polyethylene is mixed with 2 to 40 parts by weight of maleic anhydride grafted polyethylene having a maleic anhydride graft amount of 0.5 to 10% by weight has been proposed ( JP 63
-150811).

[0003]

DISCLOSURE OF THE INVENTION As a result of intensive studies in view of the above problems, the present invention is obtained by copolymerizing ethylene and a small amount of a monomer having a specific polar group by a high pressure radical polymerization method. By using an ethylene copolymer grafted with a small amount of a dibasic acid anhydride on the copolymer, or a composition of the ethylene copolymer and another polyolefin resin, the electrical insulation resistance characteristics can be significantly improved. It was made by finding that improvements were made, and the first
The object is to provide a high insulator made of an ethylene-based copolymer having an extremely high electrical insulation resistance, and the second object is to provide a high voltage power cable using the same, which has an extremely high electrical insulation resistance.

[0004]

The first invention of the present invention is a copolymer of substantially ethylene obtained by a high pressure radical polymerization method and at least one of monomers having a carbonyl group, a nitrile group and a nitro group. An ethylene-based copolymer grafted with a dibasic acid anhydride, or a composition of the ethylene-based copolymer and another polyolefin-based resin, wherein the ethylene-based copolymer or the ethylene-based copolymer 0.001 wt% to 0.05 wt% of the basic acid anhydride unit, and 0.002% of the total amount of the dibasic acid anhydride unit and the polar group unit.
It is a high insulator composed of an ethylene-based copolymer or its composition in an amount of from 0.2 to 0.2% by weight.

A second aspect of the present invention is a dibasic acid anhydride obtained by using a copolymer of substantially ethylene and at least one monomer having a carbonyl group, a nitrile group and a nitro group, which is obtained by a high pressure radical polymerization method. An ethylene-based copolymer grafted with a product, or a composition of the ethylene-based copolymer and another polyolefin-based resin, wherein the ethylene-based copolymer or the dibasic acid anhydride unit in the composition is 0.0
Insulating ethylene-based copolymer or its composition in which 01 wt% to 0.05 wt% and the total of dibasic acid anhydride unit and the polar group unit is 0.002 wt% to 0.2 wt% It is a power cable characterized by being used as. The present invention will be described in detail below.

The ethylene-based copolymer or the composition thereof in the first invention of the present invention means ethylene obtained by grafting a dibasic acid anhydride onto a copolymer of ethylene and the above-mentioned monomer having a specific polar group. It is a composition in which another polyolefin resin is added to the ethylene copolymer or the ethylene copolymer, and the ethylene copolymer or the composition thereof,
0.001 wt% to 0.05 wt% of the dibasic acid anhydride unit, and 0.002 wt% to 0.2 wt% of the total of the dibasic acid anhydride unit and the monomer unit having the polar group. % Included. The ethylene-based copolymer is a copolymer of ethylene and at least one monomer having a polar group consisting of a carbonyl group, a nitrile group and a nitro group (hereinafter, referred to as a polar group) by a high-pressure radical polymerization method, It can be produced by grafting a dibasic acid anhydride.

The high-pressure radical polymerization method for producing the copolymer of substantially ethylene and the monomer having the polar group used in the present invention is, for example, ethylene 93 to 99.95.
% By weight, 0.05 to 7% by weight of the above polar group-containing monomer
Of the mixture based on the total weight of all those monomers.
Polymerization pressure in the presence of 0001 to 1% by weight of a radical polymerization initiator is 500 to 4000 kg / cm ² , preferably 100 to
This is a method of contacting or polymerizing the monomers simultaneously or stepwise in a tank or tube reactor in the presence of a chain transfer agent and, if necessary, an auxiliary agent at 350 ° C. Examples of the radical polymerization initiator include conventional initiators such as peroxides, hydroperoxides, azo compounds, amine oxide compounds and oxygen. Examples of the chain transfer agent include hydrogen, propylene, butene-1, C1 to C20 or higher saturated aliphatic hydrocarbons and halogen-substituted hydrocarbons such as methane, ethane, propane, butane, isobutane, n-hexane and n-hexane. Mention may be made of heptane, cycloparaffins, chloroform, and carbon tetrachloride, aromatic compounds such as toluene, diethylbenzene and compounds such as xylene. When copolymerizing the polar group-containing monomer with ethylene, another unsaturated monomer may be further copolymerized, if necessary. Examples of the other unsaturated monomer include propylene,
Butene-1, hexene-1, decene-1, octene-
1, olefins such as styrene.

In the present invention, the grafting method of grafting the dibasic acid anhydride onto the copolymer of ethylene and the above polar group-containing monomer may be carried out by a generally well known method.
That is, a method of reacting an ethylene / monomer copolymer having a polar group and a dibasic acid anhydride obtained by high-pressure radical polymerization under melt-kneading using a crosslinking agent such as an organic peroxide, A method in which these are dissolved in an appropriate solvent to carry out a graft reaction in a solution state, the ethylene / monomer copolymer having a polar group is dispersed in water, and a dibasic acid anhydride and a reaction initiator are supplied. However, various methods such as a method of carrying out a graft reaction can be carried out. However, the melt-kneading method is preferable from the viewpoint of practicality.

The dibasic acid anhydride usable in the graft reaction in the present invention includes maleic anhydride, itaconic anhydride,
Hymic anhydride, methyl maleic anhydride, dimethyl maleic anhydride, phenyl maleic anhydride, diphenyl maleic anhydride, chloromaleic anhydride, dichloromaleic anhydride, fluoromaleic anhydride, difluoromaleic anhydride, bromomaleic anhydride, dibromo Maleic anhydride etc. can be mentioned. Among these, maleic anhydride can be mentioned as a particularly preferable one.

The polar group-containing monomer that can be used for copolymerization with ethylene in the present invention includes (a) a carbonyl group-containing monomer, (b) a nitrile group-containing monomer, and c) The monomer which has a nitro group can be mentioned. Examples of the (a1) carbonyl group-containing monomer include:
Unsaturated carboxylic acid esters derived from α, β-unsaturated carboxylic acid esters can be mentioned, and specific examples thereof include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, acrylic acid. Propyl, propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, acrylic acid-n-
Butyl, n-butyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, maleic acid monomethyl ester, maleic acid monoethyl ester, maleic acid diethyl ester, fumar Examples thereof include unsaturated carboxylic acid esters such as acid monomethyl ester, glycidyl acrylate and glycidyl methacrylate. Among these, (meth) acrylic acid alkyl ester is particularly preferable. More preferably, methyl acrylate and ethyl acrylate can be mentioned.

Examples of (a2) another monomer having a carbonyl group include vinyl ester. Specific examples thereof include vinyl propionate, vinyl acetate,
Examples thereof include vinyl ester monomers such as vinyl caproate, vinyl caprylate, vinyl laurate, vinyl stearate and vinyl trifluoroacetate. Among these, vinyl acetate is particularly preferable.

(A3) Examples of other monomers having a carbonyl group include carbon monoxide, methyl vinyl ketone, isopropenyl vinyl ketone, ethyl vinyl ketone, phenyl vinyl ketone, t-butyl vinyl ketone, isopropyl vinyl ketone, Methyl propenyl ketone, methyl isopropenyl ketone, cyclohexyl vinyl ketone, etc. can be mentioned.

(B) Monomers having a nitrile group include acrylonitrile, methacrylonitrile, α-methoxyacrylonitrile, vinylidene cyanide, cinnamonitrile, crotononitrile, α-phenylcrotononitrile, fumaronitrile, allylacetonitrile, 2 −
Butene nitrile, 3-butene nitrile, etc. can be mentioned.

Examples of the monomer (c) having a nitro group include
2,4-dinitrophenyl acrylate, 2-nitrostyrene, 3-nitrostyrene, 4-nitrostyrene, p
-Nitrophenyl methacrylate, m-nitrophenyl methacrylate, 2,4-dinitrophenyl methacrylate, 2,4,6-trinitrophenyl methacrylate and the like can be mentioned.

Specific examples of the ethylene-based polymer obtained by grafting a dibasic acid anhydride onto the copolymer of substantially ethylene and the above-mentioned monomer having a polar group obtained by the high pressure radical polymerization method used in the present invention are as follows: , Ethylene / maleic anhydride / VA or carbon monoxide copolymer, ethylene / maleic anhydride / methyl vinyl ketone copolymer, ethylene / maleic anhydride / ethyl vinyl ketone copolymer, ethylene /
Maleic anhydride / acrylonitrile copolymer, ethylene / maleic anhydride / methacrylonitrile copolymer, ethylene / maleic anhydride / allyl acetonitrile copolymer, ethylene / maleic anhydride / 2-nitrostyrene copolymer, ethylene / anhydrous Maleic acid / m-nitrostyrene copolymer, ethylene / maleic anhydride / p-nitrophenyl methacrylate copolymer, ethylene / maleic anhydride / methyl isopropenyl ketone copolymer, ethylene / maleic anhydride / EA or one Carbon oxide copolymer etc. can be mentioned.

In the present invention, other polyolefin resins to be added to the above ethylene copolymer include homopolymers such as low density, medium density and high density polyethylene, ethylene-propylene copolymer, ethylene-butene- 1 copolymer, ethylene-hexene-1 copolymer, ethylene-
Linear low-density polyethylene, ultra-low-density polyethylene composed of a copolymer with other α-olefins containing ethylene as a main component, such as 4-methylpentene-1 copolymer and ethylene-octene-1 copolymer. Examples thereof include ethylene-propylene copolymer rubber and ethylene-propylene-diene copolymer rubber. Among these, high-pressure radical polymerization polyethylene is preferably used. As a method for melt-mixing these compositions, a kneading machine that is commonly used, such as a Banbury mixer, a pressure kneader, a kneading extruder, a twin-screw extruder, or a roll, can be used.

In the present invention, the ethylene-based copolymer described above may be used as an insulator, or a composition prepared by mixing the ethylene-based copolymer with another polyolefin resin may be used as an insulator. Content of the dibasic acid anhydride unit in the system copolymer or its composition is 0.00
1 to 0.05% by weight, preferably 0.003 to 0.03
The total amount of dibasic acid anhydride units and other monomer units having a specific polar group is 0.002% by weight to
0.2% by weight, preferably 0.005-0.15% by weight
It is essential that the above range be satisfied, and by adjusting the dibasic acid anhydride unit and the monomer unit having a specific polar group to a specific range, it is possible to dramatically improve the electric insulation resistance.

The content of the dibasic acid anhydride unit is 0.001
If the total amount of the dibasic acid anhydride unit and the monomer unit having the polar group is less than 0.002% by weight, the effect of improving the electrical insulation resistance is small, and the dibasic acid anhydride unit of When the content exceeds 0.05% by weight and the total amount of the dibasic acid anhydride unit and the monomer unit having the polar group exceeds 0.2% by weight, the electrical insulation resistance is high but the dielectric It is not preferable because it increases the tangent (tan δ). The dielectric loss tangent value monotonically increases as the amount of the dibasic acid anhydride unit and the amount of the monomer unit having the polar group increase. In order to use it as an insulating material for power cables, it is desirable that the dielectric loss tangent value be 5 × 10 ^-4 or less at the maximum,
Therefore, the amount of the dibasic acid anhydride unit is 0.05% by weight or less, and the total amount of the dibasic acid anhydride unit and the monomer unit having the polar group is 0.002% by weight to 0.2% by weight. It is limited to%.

The density of the above ethylene copolymer is generally applied in the range of 0.91 to 0.94 g / cm ³ . Further, regarding the melt index (hereinafter abbreviated as MI), considering the extrudability into a cable, it is 0.05 to
20 g / 10 minutes is desirable.

The above-mentioned ethylene-based copolymer of the present invention or a composition thereof is not only used as an insulating layer for a usual electric wire / power cable, but also alone or blended with another synthetic resin, rubber or the like. , Film or sheet,
It is processed into tapes, yarns, etc., and if necessary, laminated with other base materials, and is utilized for insulating films and sheets, insulating tapes, insulating covers, insulating garments, etc.

The power cable according to the second aspect of the present invention means an inner semiconductive layer and / or an outer semiconductive layer formed by extrusion, or an outer metal shielding layer such as copper, aluminum, or lead, or an aluminum tape if desired. It has an insulating layer made of the above-mentioned ethylene-based copolymer or its composition together with a coating layer such as a wound water-impermeable layer which is usually provided in a power cable.

The insulating layer may be a crosslinked body or an uncrosslinked body. In addition, in the crosslinking, in addition to peroxide, sulfur, etc., a usual method such as silane crosslinking, electron beam crosslinking, etc. can be used.

In the present invention, other synthetic resins or rubbers or antioxidants, within the range not departing from the gist of the present invention,
It is possible to add usual additives such as an anti-UV agent, a pigment, a dye, a lubricant, a foaming agent, a flame retardant and a filler.

[0024]

EXAMPLES The present invention will be described in more detail by way of examples, which should not be construed as limiting the invention. Example 1 n-Hexane 380 g ethyl acrylate (abbreviated as EA) 0.4 g and ditertiary butyl peroxide as a polymerization initiator were added to an autoclave equipped with a stirrer and having an internal capacity of 3.8 liters, which was replaced with nitrogen. Then, after charging 1,700 g of ethylene, polymerization pressure of 1,600 kg
Polymerization was carried out at a f / cm ² temperature of 190 ° C. and a polymerization time of 1 hour. An ethylene-ethyl acrylate copolymer was obtained by this polymerization. After reprecipitation purification with a toluene-acetone solvent, analysis by an infrared spectrophotometer revealed that ethyl acrylate was 0.1% by weight. 500 g of this ethylene-ethyl acrylate copolymer and 0.08 maleic anhydride
After dry blending 4 g and 0.02 g of 2,5-demethyl-2,5-de (t-butylperoxy) hexane,
Single screw extruder with cylinder temperature set at 230 ° C (L / D
= 26, C.I. R. = 3.0), and extruded and then granulated. The granulated ethylene polymer was purified by reprecipitation with a toluene-acetone solution and analyzed by an infrared spectrophotometer. Maleic anhydride was 0.01% by weight and ethyl acrylate was 0.1% by weight. % By weight. When the electrical characteristics of this copolymer were measured, the volume resistance was 20 times that of the low density polyethylene of Comparative Example 1. The dielectric loss tangent was 5 × 10 ⁻⁴ or less.

Example 2 The electrical characteristics of an ethylene polymer (maleic anhydride: 0.04% by weight, ethyl acrylate: 0.1% by weight) obtained by the same production method as in Example 1 were measured. As a result, the volume resistance was 50 as compared with the low density polyethylene of Comparative Example 1.
It was doubled. The dielectric loss tangent was 5 × 10 ⁻⁴ or less.

Example 3 A copolymer obtained by the same production method as in Example 1 (0.15% by weight of maleic anhydride and 0.1% by weight of ethyl acrylate).
(5 wt%) 40 g and low-density polyethylene 2000 g were dry-blended and then fed to a single-screw extruder (L / D = 26, CR = 3.0) set to a cylinder temperature of 200 ° C., and after extrusion , Granulated. The granulated ethylene copolymer composition was purified by reprecipitation with a toluene-acetone solution and analyzed by an infrared spectrophotometer. As a result, maleic anhydride was 0.003% by weight and ethyl acrylate was 0%. ．
It was 003% by weight. When the electrical characteristics of this copolymer composition were measured, the volume resistance was 10 times that of the low density polyethylene of Comparative Example 1. The dielectric loss tangent was 5 × 10 ⁻⁴ or less.

Example 4 A copolymer obtained by the same production method as in Example 1 (0.15% by weight of maleic anhydride and 0.1% by weight of ethyl acrylate).
5% by weight) 500 g and low-density polyethylene 2000 g, and an ethylene copolymer composition obtained by the same production method as in Example 3 (maleic anhydride: 0.03% by weight; ethyl acrylate: (0.03% by weight), the volume resistance was 40 times that of the low density polyethylene of Comparative Example 1. The dielectric loss tangent was 5 × 10 ⁻⁴ or less.

Example 5 By the same production method as in Example 3, 60 g of a copolymer (0.4% by weight of maleic anhydride and 0.2% by weight of ethyl acrylate) and 2000 g of low-density polyethylene were used. Ethylene copolymer composition obtained by blending (0.01% by weight of maleic anhydride and 0.0% by weight of ethyl acrylate)
(06% by weight) had a volume resistance 25 times that of the low density polyethylene of Comparative Example 1. Dielectric loss tangent is 5
It was less than × 10 ^-4 .

Example 6 10 g of a copolymer (0.2% by weight of maleic anhydride and 7% by weight of ethyl acrylate) obtained by the same production method as in Example 1 and 2000 g of low-density polyethylene were used. The ethylene copolymer composition (maleic anhydride: 0.001% by weight, ethyl acrylate: 0.03% by weight) obtained by the same production method as in Example 3 was used. The volume resistance was 10 times that of low-density polyethylene. The dielectric loss tangent was 5 × 10 ⁻⁴ or less.

Example 7 A copolymer obtained by the same production method as in Example 1 (the content of maleic anhydride is 0.01% by weight, vinyl acetate (abbreviated as VA)).
0.5% by weight) 10 g and 100 g of low-density polyethylene, and an ethylene copolymer composition obtained by the same production method as in Example 3 (maleic anhydride is 0.001% by weight,
VA was 0.05% by weight), the volume resistance was 13 times that of the low density polyethylene of Comparative Example 1. The dielectric loss tangent was 5 × 10 ⁻⁴ or less.

Example 8 A copolymer obtained by the same production method as in Example 1 (the amount of maleic anhydride was 0.01% by weight, methyl vinyl ketone (MVK
0.5% by weight) and 10 g of low-density polyethylene and 100 g of low-density polyethylene, and an ethylene copolymer composition (maleic anhydride: 0.005) obtained by the same production method as in Example 3 was used.
1% by weight, MVK is 0.05% by weight) is Comparative Example 1
The volume resistance was 10 times higher than that of the low density polyethylene. The dielectric loss tangent was 5 × 10 ⁻⁴ or less.

Example 9 A copolymer obtained by the same production method as in Example 1 (0.01% by weight of maleic anhydride and 0.1% by weight of acrylonitrile (abbreviated as AN)) was as low as 10 g. Density polyethylene 1
The ethylene copolymer composition (maleic anhydride is 0.001% by weight and AN is 0.01% by weight) obtained by the same production method as in Example 3 using The volume resistance was 20 times higher than that of the low density polyethylene. The dielectric loss tangent was 5 × 10 ⁻⁴ or less.

Example 10 A copolymer obtained by the same production method as in Example 1 (maleic anhydride: 0.01% by weight: 2-nitrostyrene (NSt:
0.1% by weight) and 10 g of low-density polyethylene (100 g), and an ethylene copolymer composition (maleic anhydride: 0.005) obtained by the same production method as in Example 3.
1 wt%, NSt is 0.01 wt%) is Comparative Example 1
The volume resistance was 18 times that of the low density polyethylene. The dielectric loss tangent was 5 × 10 ⁻⁴ or less.

Comparative Example 1 Low-density polyethylene (trade name: Nisseki Lexron W2000, manufactured by Nippon Petrochemical Co., Ltd.) manufactured by the high pressure radical method, which is currently on the market, was used as Comparative Example 1.

Comparative Example 2 A copolymer obtained by the same production method as in Example 1 (0.04% by weight of maleic anhydride and 0.2% of ethyl acrylate).
(% By weight), the volume resistance was 60 times that of the low density polyethylene of Comparative Example 1, but the dielectric loss tangent was 5 × 10 ⁻⁴ or more. , Is not suitable as an insulator for electric cables.

Comparative Example 3 A copolymer obtained by the same production method as in Example 1 (0.15% by weight of maleic anhydride and 0.1% by weight of ethyl acrylate).
10% by weight) and 2000 g of low-density polyethylene, and an ethylene copolymer composition obtained by the same production method as in Example 3 (maleic anhydride is 0.0007% by weight, ethyl acrylate is 0% by weight). 0.0005% by weight is the comparative example 1
No significant improvement in volume resistance is observed as compared with the low density polyethylene of the above.

Comparative Example 4 60 g of a copolymer (0.2% by weight of maleic anhydride and 7% by weight of ethyl acrylate) obtained by the same production method as in Example 1 and 2000 g of low-density polyethylene were used. An ethylene copolymer composition obtained by the same production method as in Example 3 (0.01% by weight of maleic anhydride and 0.2% by weight of ethyl acrylate) was prepared as in Comparative Example 1. The volume resistance is 20 times that of low density polyethylene, but the dielectric loss tangent is 5 × 10 ^-4 or more,
Not suitable as an insulator for electric cables.

Comparative Example 5 10 g of a copolymer (0.4% by weight of maleic anhydride and 10% by weight of ethyl acrylate) obtained by the same production method as in Example 1 and 2000 g of low-density polyethylene were used. An ethylene copolymer composition (maleic anhydride: 0.02 wt%, ethyl acrylate: 0.05 wt%) obtained by the same production method as in Example 3 was used. No significant improvement in volume resistance is observed as compared to low density polyethylene. The results are summarized in (Table 1).

(Test method) Insulation resistance (volume specific resistance); applied voltage 3 kV, time 10
Min, and the sample thickness was 0.3 mm. Dielectric loss tangent (tan δ) ...; Using YHP4194A impedance analyzer manufactured by Yokogawa Hewlett-Packard Co., sample thickness 1 mm, 100 kHz.

[0040]

[Table 1]

[0041]

As described above, the ethylene-based copolymer prepared by the high-pressure radical polymerization method of the present invention, which is composed of ethylene / a monomer having a specific polar group, is grafted with a dibasic acid anhydride. The composition of a polymer or its ethylene-based copolymer and other polyolefin-based resin makes the electrical insulation resistance leap by specifying a dibasic acid anhydride unit and a monomer unit having a specific polar group. When it is used as an insulating layer of a power cable, it is possible to reduce power loss during high-voltage power transmission without thickening the insulating layer.

(72) Inventor Hideo Kawabata 3-35-2, Okubo, Konan-ku, Yokohama-shi, Kanagawa Prefecture (72) Junichi Yokoyama 2-25-26 Takafunedai, Kanazawa-ku, Yokohama-shi, Kanagawa Prefecture

Claims (2)

[Claims] 1. An ethylene-based polymer obtained by grafting a dibasic acid anhydride onto a copolymer of substantially ethylene obtained by a high-pressure radical polymerization method and at least one of monomers having a carbonyl group, a nitrile group and a nitro group. A copolymer, or a composition of the ethylene-based copolymer and another polyolefin-based resin, wherein the dibasic acid anhydride unit in the ethylene-based copolymer or the composition is 0.001% by weight to 0.0
A high insulator comprising an ethylene-based copolymer or a composition thereof in an amount of 5% by weight and the total amount of the dibasic acid anhydride unit and the polar group unit is 0.002% by weight to 0.2% by weight. 2. An ethylene-based copolymer obtained by grafting a dibasic acid anhydride onto a copolymer of substantially ethylene obtained by a high-pressure radical polymerization method and at least one of monomers having a carbonyl group, a nitrile group and a nitro group. A copolymer, or a composition of the ethylene-based copolymer and another polyolefin-based resin, wherein the dibasic acid anhydride unit in the ethylene-based copolymer or the composition is 0.001% by weight to 0.0
An ethylene-based copolymer having a dibasic acid anhydride unit content and a polar group unit content of 0.002% by weight to 0.2% by weight or a composition thereof is used as an insulator. And power cable.