JP2000053815A - Electrical insulating resin composition and electric wire and cable using the composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrical insulating resin composition which has good electrical properties even under high electrical fields and exerts a good flexibility and a power cable using this. SOLUTION: This electrical insulating resin composition comprises as resin components 20 to 90 wt.% low-density polyethylene and 80 to 10 wt.% ethylene/ propylene/diene terpolymer having a propylene content of 20 to 50 wt.% which is copolymerized using a single site catalyst and/or an ethylene/α-olefin copolymer having a density of 0.840 to 0.910 g/cm3 which is copolymerized using a single site catalyst. Furthermore, an electric wire or cable has an insulator layer comprising the electrical insulating resin composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrically insulating resin composition having good electrical properties even under a high electric field and having good flexibility, and an electric wire / cable using the same.

[0002]

2. Description of the Related Art Polyethylene is being applied to an insulating layer of electric wires and cables because of its excellent electrical insulation. For example, a cross-linked polyethylene insulated power cable (mainly a CV cable) using a cross-linked polyethylene formed by cross-linking low-density polyethylene as an insulating layer has various electrical properties, excellent heat resistance, and easy handling and maintenance. Due to its advantages, it is dominant in transmission or distribution cables.

However, a cross-linked polyethylene insulated power cable using cross-linked polyethylene for the insulator layer has high bending rigidity and is inferior in flexibility of the cable. Therefore, there is a problem that workability is inferior at the time of cable laying and construction.

As a means for improving the flexibility of a cable, an elastomer or a plastomer material such as an ethylene / α-olefin copolymer or an ethylene / propylene / diene copolymer is blended with low-density polyethylene of a cable insulator layer. Means are conceivable. However, elastomers or plastomer materials such as ethylene-α-olefin copolymers and ethylene-propylene-diene copolymers have poorer electrical properties than low-density polyethylene, and these elastomers or plastomer materials are mixed with low-density polyethylene. The cable using the resin composition as the insulator layer is required for high-voltage, extra-high-voltage power cables,
There is a problem that sufficient electric characteristics cannot be obtained under a high electric field. Further, since tan δ is high, the insulator layer generates heat and power loss increases, so that there is a problem that the usable voltage class is limited.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been made to solve such a problem, and an electric insulating resin composition having good electric characteristics even under a high electric field and having good flexibility. An object and a power cable using the same are provided.

[0006]

Means for Solving the Problems The inventors of the present invention have studied a decrease in electric characteristics caused when an elastomer or a plastomer material such as an ethylene / α-olefin copolymer or an ethylene / propylene / diene copolymer is blended with low-density polyethylene. Examination of the cause revealed that a large amount of catalyst (Ziegler catalyst, etc.) used in the polymerization of ethylene / α-olefin copolymer or ethylene / propylene / diene copolymer remained in the resin. I found that. As a result of further studies, it was found that ethylene-α-olefin copolymers and ethylene-propylene-diene copolymers polymerized using a single-site catalyst had a small amount of residual catalyst and had good electrical properties. Obtained.

The present invention has been made on the basis of these findings and is based on ethylene-polymer having a propylene content of 20 to 50% by weight, which is obtained by copolymerizing 20 to 90% by weight of low-density polyethylene with a single-site catalyst. Density of 0.840 to 0.910 g / cm3 obtained by copolymerization using propylene / diene terpolymer and / or single-site catalyst
An electrical insulating resin composition comprising 80 to 10% by weight of an ethylene / α-olefin copolymer as a resin component.
Further, the present invention provides an electric wire / cable having an insulator layer made of the electric insulating resin composition.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The low-density polyethylene used in the electrical insulating resin composition of the present invention is not particularly limited as long as it is a low-density polyethylene used for an insulator of a power cable. Synthetic low density polyethylene is preferred. In particular, those having a melt flow rate (MFR) of 0.1 to 10 g / 10 min and a density of 0.910 to 0.935 g / cm ³ are preferable because of good workability.

In the present invention, as the ethylene / propylene / diene copolymer or ethylene / α-olefin copolymer to be mixed with the low-density polyethylene, those polymerized using a single-site catalyst are used. Single-site catalysts have uniform active sites, resins made with single-site catalysts have a relatively narrow molecular weight distribution, and have a more controlled crystal structure than those polymerized with multi-site catalysts. It has the characteristic of being easy. Examples of the single-site catalyst include a metallocene catalyst.

[0010] As described above, the ethylene-α-olefin copolymer and ethylene-propylene-diene copolymer polymerized using these single-site catalysts have a small amount of the catalyst remaining in the resin, and therefore have poor electrical characteristics. It is favorable, and by blending it with low-density polyethylene, it is possible to obtain an electrical insulating resin composition which is less likely to inhibit the electrical properties of low-density polyethylene and has improved flexibility.

The ethylene / propylene / diene copolymer used in the present invention has a propylene content of 20 to 50% by weight. If the propylene content is less than 20% by weight, the mechanical strength of the obtained electrically insulating resin composition tends to be insufficient, and if it exceeds 50%, the crystallinity becomes high and good flexibility cannot be obtained.

Specific examples of the diene component include dicyclopentadiene, 1,4 hexadiene, cyclooctadiene, methylene norbornene, and ethylidene norbornene.

In the present invention, the ethylene / α-olefin copolymer has a density of 0.840 to 0.91 g / cm.
^Three are preferred. If the density is less than 0.840 g / cm ³ , the mechanical strength of the obtained electrically insulating resin composition tends to be insufficient. If it exceeds 0.91 g / cm ³ , the crystallinity tends to be high, and good flexibility tends not to be obtained.

The α-olefin component includes 3 carbon atoms.
More than 10 or less α-olefins are preferred, and specifically,
Examples thereof include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, and 1-decene. Particularly preferred is a copolymer of ethylene and octene.

In the present invention, the ethylene / α-olefin copolymer or ethylene / propylene / diene copolymer used in the low-density polyethylene may be used alone or in combination.

The low-density polyethylene and the ethylene / α-olefin copolymer in the electric insulating resin composition of the present invention,
The blending ratio of the ethylene / propylene / diene copolymer is 20 to 90% by weight of the low density polyethylene, and 80 to 10% by weight of the ethylene / propylene / diene copolymer and / or the ethylene / α-olefin copolymer. Preferably,
50 to 90% by weight of low density polyethylene, 50 to 10% by weight of ethylene / propylene / diene copolymer and / or ethylene / α-olefin copolymer. ethylene·
Propylene-diene copolymer and / or ethylene
If the amount of the α-olefin copolymer exceeds 80% by weight, the electrical properties of the electrically insulating resin composition tend to be insufficient, and tan δ tends to be high. If the content is less than 10% by weight, the effect of improving flexibility tends not to be exhibited. ethylene·
When both the propylene / diene copolymer and the ethylene / α-olefin copolymer are blended, the amount ratio is not particularly limited, and an arbitrary amount ratio is possible.

The electric insulating resin composition of the present invention may contain an inorganic filler, a softening agent and the like, if necessary, as long as the electric properties are not affected. As inorganic fillers, calcium carbonate, hydrotalcite, talc, kaolinite,
Examples include clay, alumina, silica, titania, zeolite, magnesium oxide, molybdenum oxide, antimony oxide, aluminum hydroxide, and magnesium hydroxide. Examples of the softener include process oil, liquid paraffin, paraffin, petroleum asphalt, petrolatum, lubricating oil, castor oil, linseed oil and the like. In addition, in addition to the above components, various antioxidants, lubricants, dispersants, coloring agents, copper antioxidants, etc., as necessary, are compounded with various compounding agents which are effective in insulating layers of electric wires and cables. it can.

The electric wire / cable of the present invention is one wherein the insulator layer is constituted by the above-mentioned electric insulating resin composition. The electrically insulating resin composition of the insulator layer may be non-crosslinked or crosslinked. For example, in the case of a power cable for high-capacity current transmission, the temperature may be high during operation, and a cross-linked body having excellent characteristics at high temperatures may be selected as appropriate according to the type of electric wire or cable.

As a crosslinking method, a chemical crosslinking method of heating an electric insulating resin composition containing a crosslinking agent, a silane compound,
A silane crosslinking method in which an electrically insulating resin composition containing an organic peroxide is crosslinked in the presence of a silanol condensation catalyst, and an ionizing radiation irradiation crosslinking method in which the electrically insulating resin composition is irradiated with ionizing radiation and crosslinked. .

The organic peroxide compounded in the chemical crosslinking method includes benzoyl peroxide, t-butylperoxybenzoate, dicumyl peroxide, t-butylcumyl peroxide, di-t-butyl peroxide, 2,5 -Dimethyl-2,5-di-t-butylperoxyhexene, 2,4-dichloro-benzoyl peroxide and the like. The amount is about 0.01 to 5 parts by weight based on 100 parts by weight of the resin component.

The silane compound to be compounded in the silane cross-linking method is not limited as long as it can form a silane cross-link. Vinyl methoxy silane, vinyl triethoxy silane, vinyl methyl dimethoxy silane, vinyl tris (β
-Methoxyethoxy) silane and the like.
The amount of the silane compound is about 0.5 to 10 parts by weight based on 100 parts by weight of the resin component. The organic peroxide is not particularly limited, and for example, the organic peroxides exemplified above can be used. The amount of the organic peroxide is about 0.01 to 5 parts by weight based on 100 parts by weight of the resin component. The silanol condensation catalyst is not particularly limited as long as it is used for silane crosslinking, and dibutyltin dilaurate, stannous acetate,
Stannous octoate, lead naphthenate, zinc caprate, 2
Carboxylic acid salts such as -ethylhexane iron and cobalt naphthenate; tetrabutyl titanate, tetranonyl titanate; and titanate esters such as bis (acetylacetonitrile) diisopropyl titanate. The silanol condensation catalyst is usually previously blended with the resin. The amount of the silanol condensation catalyst is usually about 0.001 to 5 parts by weight based on 100 parts by weight of the resin component.

The dose of ionizing radiation in the ionizing radiation irradiation crosslinking method is appropriately adjusted according to the type of ionizing radiation such as electron beam and γ-ray, the type of insulator layer, and the thickness of the insulator layer. Is done.

In any of the above-mentioned cross-linking methods, a cross-linking aid such as trimethylolpropane triacrylate or divinylbenzene can be blended if necessary.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments. (Examples 1 to 17) (Comparative Examples 1 to 12) Thickness 0.8 of an ethylene / vinyl acetate copolymer obtained by adding carbon black on a conductor having a cross-sectional area of 100 mm ^2.
mm internal semiconductive layer, a 5.5 mm thick insulator layer composed of an electrically insulating resin composition having the composition (unit: parts by weight) shown in Tables 1 to 4, and further formed of the same material as the internal semiconductive layer. After forming an outer semiconductive layer having a thickness of 0.7 mm by extrusion coating, a metal shielding layer and a sheath layer were formed by coating in a conventional manner to prepare a power cable. Examples 10 to 1
7. In Comparative Examples 7 to 12, after the inner semiconductive layer, the insulator layer, and the outer semiconductive layer were extrusion-coated, a crosslinking treatment was performed to crosslink the inner semiconductive layer, the insulator layer, and the outer semiconductive layer.

The details of the resin composition used in this example are as follows. Low density polyethylene: high pressure method low density polyethylene, NU
C-9025 (manufactured by Nippon Unicar, MFR 3.2 g / 10
min, density 0.922 g / cm ³ ) Ethylene / propylene / diene copolymer A1: Ethylene / propylene / diene copolymer using single site catalyst, Nodel IP NDX3725P (Dupont Dow Elastomers, propylene content 26.5% by weight) , Diene component: ethylidene norbornene) ethylene / propylene / diene copolymer A2: ethylene / propylene / diene copolymer using a single site catalyst, Nordel IP NDX4770P (manufactured by Dupont Dow Elastomers, propylene content: 25% by weight, diene component: ethylidene) Norbornene) Ethylene / propylene / diene copolymer A3: Conventional ethylene / propylene / diene copolymer EP-51 (produced by Nippon Synthetic Rubber, propylene content: 26% by weight, diene component: ethylidene norbornene) Tylene / α-olefin copolymer B1: Ethylene / α-olefin copolymer using single-site catalyst, Engage EG8100 (manufactured by Dupont Dow Elastomers, α
Olefin component: octene, density 0.870 g / c
m ³ ) Ethylene / α-olefin copolymer B2: Ethylene / α-olefin copolymer using single-site catalyst, EXAC
T4011 (manufactured by Exxon Chemical, α-olefin component:
Butene, density 0.885 g / cm ³ ) Ethylene / α-olefin copolymer B3: Conventional ethylene / α-olefin copolymer, EP02P (manufactured by Japan Synthetic Rubber, α-olefin component: propylene, density 0.860 g)
/ Cm ³ ) Antioxidant: Irganox 1010 (manufactured by Ciba Geigy) Organic peroxide: dicumyl peroxide Silane compound: vinylmethoxysilane Silanol condensation catalyst: dibutyltin dilaurate

The power cables of Examples 1 to 17 and Comparative Examples 1 to 12 were subjected to the following performance evaluations (1) and (2). The results are shown in Tables 1 to 4. (1) Tan δ measurement Take a sample with an effective length of 10 m from a power cable, apply an AC voltage with an average electric field of 5 kV / mm between the conductor and the metal shielding layer, and apply room temperature and 90 ° C. by the Schering bridge method.
The tan δ was measured with. When tan δ is 0.3% or more, the insulator layer generates heat and power loss increases, which is not preferable as an insulator for a power cable for high-voltage and extra-high-voltage applications.

(2) One-sided deflection test A sample of 50 cm length was taken from the power cable,
A 0 cm portion was fixed, a load of 10 kg was applied to the opposite end, and the amount of deflection at that time was measured. It is preferable that the amount of deflection is 15 cm or more in terms of ease of handling during construction.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

[Table 3]

[0031]

[Table 4]

As apparent from Tables 1 and 2, Example 1
The power cables of Comparative Examples 1 to 12 have low tan δ and good flexibility, whereas the power cables of Comparative Examples 1 to 12 have ethylene-propylene-diene copolymer or ethylene-α polymerized using a single-site catalyst. The tan δ or the flexibility was inferior because the olefin copolymer was not used, or even if used, the compounding amount was inappropriate.

[0033]

The electrical insulating resin composition of the present invention uses an ethylene / propylene / diene copolymer or an ethylene / α-olefin copolymer polymerized using a specific catalyst, so that it can be used even under a high electric field. It has excellent electrical properties and flexibility. In addition, electric wires and cables in which an insulator layer is composed of the electric insulating resin composition have good electric characteristics and workability even under a high electric field.

Claims (3)

[Claims] 1. Low-density polyethylene 20 to 90% by weight
And a density of 0.1 obtained by copolymerization using an ethylene-propylene-diene terpolymer having a propylene content of 20 to 50% by weight and / or a single-site catalyst. 840 to 0.910
g / cm ³ ethylene / α-olefin copolymer 80-1
An electrically insulating resin composition comprising 0% by weight of a resin component. 2. The electrically insulating resin composition according to claim 1, wherein the ethylene / α-olefin copolymer is a copolymer of ethylene and octene. 3. An electric wire or cable comprising an insulator layer made of the electric insulating resin composition according to claim 1 or 2.