JPH11172057A - Semiconducting resin composition having good water-crosslinkability and power cable made by using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconducting resin composition which has good water- crosslinkability, does not undergo premature crosslinking and produces no gel, with the result of giving a smooth and projection-free interface between a semiconducting layer and an insulating layer, and a power cable made by using the composition. SOLUTION: This composition contains (A) 100 pts.wt. ethylene/ethylenically unsaturated silane compound copolymer obtained by copolymerizing ethylene and an ethylenically unsaturated silane compound by using high-pressure polyethylene production equipment and having a melt index of 0.5-10 g/10 min and a content of the ethylenically unsaturated silane compound of 0.5-5 wt.%, (B) 15-85 pts.wt. conductive carbonaceous material, and (C) 0.01-3.0 pts.wt. silanol condensation catalyst. The power cable comprises an electrical cable having an inside semiconducting layer, an electrical insulating layer, an outside semiconducting layer and a shielding layer formed in order around a conductor, wherein at least one semiconducting layer comprising the inside or outside semiconducting layer is formed from a water-crosslinked material obtained by using the semiconducting resin composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductive resin composition having good water crosslinkability, and to a power cable manufactured using the same. More specifically, a water-crosslinkable semiconductive resin composition that does not cause early crosslinking and that does not generate gel and that has a smooth interface between the semiconductive layer and the insulating layer and has no protrusions, Further, the present invention relates to a power cable manufactured using the same without generating an electric tree or a water tree.

[0002]

2. Description of the Related Art A power cable generally has a structure in which an inner semiconductive layer, an electric insulating layer, an outer semiconductive layer, a metal shielding layer, and an anticorrosion layer are sequentially coated around a conductor. The inner semiconductive layer fills the gap between the conductor and the electrical insulating layer, and functions to suppress partial discharge or alleviate the electric field on the conductor surface.The outer semiconductive layer functions as an external shield. It functions to fill the gap between the layer and the insulator, to suppress partial discharge, or to reduce the electric field on the surface of the external shielding layer. Therefore, the semiconductive layers such as the inner semiconductive layer and the outer semiconductive layer need to have an appropriate conductivity. Usually, conductive carbon black is blended in the resin component. In this case, a polyethylene resin is usually used as the resin component, but the polyethylene resin causes plastic flow at a high temperature, so that the required characteristics as a power cable cannot be sufficiently satisfied. Have.

As a means for solving this problem, a method of cross-linking a polyethylene resin with an organic peroxide has heretofore been performed. However, this method not only requires a high equipment cost but also increases the carbon cost. In a semi-conductive resin composition containing a large amount of black, premature crosslinking is likely to occur, and projections are generated on the surface of the semi-conductive layer, and electric and water trees are generated due to the projections. As a result, there is a problem that the life of the power cable is significantly shortened.

[0004] In order to solve this problem, the following method of cross-linking with water using a silane-grafted polyethylene has been developed. That is, this method uses a polyethylene resin, for example, a high-pressure polyethylene, an ethylene-vinyl acetate copolymer, an ethylene-ethyl acrylate copolymer, a linear low density polyethylene (LLDPE), a very low density polyethylene (VLDPE), and the like. Then, an ethylenically unsaturated silane compound such as vinyltriethoxysilane or vinyltrimethoxysilane is grafted with an organic peroxide to obtain a water-crosslinkable silane-grafted polyethylene, which is then mixed with carbon black and a silanol condensation catalyst. Then, a semiconductive resin composition is prepared, and then coated on a conductor or an electric insulating layer. Finally, the coating layer is brought into contact with moisture to cause a water crosslinking reaction, whereby the water-crosslinked This is for forming a conductive layer. The method of using the water-crosslinkable silane-grafted polyethylene, compared to the conventional method of crosslinking with an organic peroxide, eliminates the need for expensive power cable cross-linking equipment, so that not only can the equipment cost be reduced, A similar effect could be achieved. Techniques for forming a semiconductive layer by these water bridges include, for example, Japanese Patent Publication No. 55-41657, Japanese Patent Publication No. 57-41048,
JP-A-59-60904, JP-A-2-236912
JP-A-2-2555731, JP-A-4-29394
No. 5, etc.

However, the technique of forming a semiconductive layer using the water-crosslinkable silane-grafted polyethylene still has some problems, particularly when an ethylenically unsaturated silane is grafted onto polyethylene, an organic peroxide. Therefore, not only the silane grafting reaction but also the cross-linking reaction between polyethylene molecules occur simultaneously,
The premature cross-linking phenomenon occurs, gels are generated, and protrusions are easily generated on the surface of the semiconductive layer. These protrusions cause electric trees and water trees, which significantly shorten the life of the power cable. It was short. Under such circumstances, by eliminating the above-mentioned problems of the technology for forming a semiconductive layer using a water-crosslinkable silane-grafted polyethylene, early crosslinking does not occur and gelling does not occur. An interface between the conductive layer and the insulating layer is smooth, and a semi-conductive resin composition having good water crosslinking properties without protrusions,
There has been a strong demand for the emergence of a power cable manufactured by using the same without generating an electric tree or a water tree.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the conventional water-crosslinkable silane-grafted polyethylene, so that premature crosslinking does not occur and gelling does not occur. An object of the present invention is to provide a semiconductive resin composition having a smooth interface between a semiconductive layer and an insulating layer and having no protrusions and good water crosslinkability, and a power cable manufactured using the same.

[0007]

DISCLOSURE OF THE INVENTION The present inventors have developed ethylene and ethylenically unsaturated silane compounds as water-crosslinkable polyethylene resins which have not been employed in semiconductive resin compositions for power cables. Pay attention to the copolymer with
As a result of intensive studies using this, it was found that good results were obtained. The present invention has been completed based on these findings.

That is, according to the present invention, (A) ethylene and an ethylenically unsaturated silane compound are copolymerized in a high-pressure polyethylene production apparatus, and have a melt index of 0.5 to 10 g / 10 min. 100 parts by weight of an ethylene-ethylenically unsaturated silane compound copolymer having a content of the unsaturated silane compound of 0.5 to 5% by weight, (B) 15 to 85 parts by weight of the conductive carbon, and (C) a silanol condensation catalyst A semi-conductive resin composition having good water crosslinkability, characterized by containing 0.01 to 3.0 parts by weight.

Further, according to the present invention, in an electric cable comprising a conductor, an inner semiconductive layer, an electrical insulating layer, an outer semiconductive layer, and a shield layer in this order, an inner semiconductive layer or an outer semiconductive layer is provided. Wherein the at least one semiconductive layer is made of a water crosslinked body obtained from the above semiconductive resin composition having good water crosslinkability.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

1. Ethylene-ethylenically unsaturated silane compound copolymer (A) The ethylene-ethylenically unsaturated silane compound used in the present invention is obtained by copolymerizing ethylene and an ethylenically unsaturated silane compound in a high-pressure polyethylene production apparatus. It is a thing.

In this method, for example, usually, for example, ethylene as a monomer and an ethylenically unsaturated silane compound are pumped into a tubular or tank-shaped reactor using a high-pressure pump, and the mixture is heated at a high temperature (polymerization peak temperature of 200). ~ 330 ° C), high pressure (1
After the copolymerization using a radical generating catalyst such as an organic peroxide under the conditions of 50 to 300 MPa), the copolymerization and the unreacted monomer are separated in a high-pressure separator. At the time of copolymerization, a chain transfer agent may be used to promote a chain transfer reaction.

The ethylenically unsaturated silane compound used in the present invention is a silane compound having an olefinically unsaturated bond copolymerizable with ethylene and a hydrolyzable alkoxy group in the molecule, and represented by the general formula R ¹ SiR ² _n (O
R ³ ) _3-n (wherein, R ¹ is an ethylenically unsaturated hydrocarbon group such as vinyl, allyl, butenyl, cyclohexenyl, γ- (meth) acryloxypropyl, and R ² and R ³ are , Each independently, methyl, ethyl, propyl, butyl, butyl, pentyl, hexyl, heptyl,
An aliphatic saturated hydrocarbon group such as octyl, and n is 0,
Indicates 1 or 2. ). Specific examples of the ethylenically unsaturated silane compound include vinyltrimethoxysilane, vinyldimethoxymethylsilane, vinylmethoxydimethylsilane, vinyltriethoxysilane, vinyldiethoxyethylsilane, vinylethoxydiethylsilane,
γ-methacryloyloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropyl-tris- (2-methoxyethoxy) silane, vinyl-tris (n-butoxy) silane, vinyl-tolyl (n -Pentoxy) silane, vinyl-tris (n-hexoxy) silane, vinyl-tris (n-heptoxy) silane, vinyl-tris (n-octoxy) silane, vinyl-tris (n-dodecyloxy) silane, vinyl-bis ( n-butoxy) methylsilane, vinyl-bis (n-hexoxy) methylsilane, vinyl- (n-butoxy) dimethylsilane, vinyl- (n-pentoxy) dimethylsilane, β-methacryloxyethyl-tris (n-butoxy) silane, γ-
Methyloxypropyl-tris (n-dodecyl) silane and the like. The ethylenically unsaturated silane compound is used in an amount of 0.01 to 10% based on 100 parts by weight of ethylene.
0 parts by weight, preferably 2.0 to 7.0 parts by weight.

The radical generating catalyst used in the present invention comprises:
A conventional catalyst used in the production of polyethylene by a high-pressure method may be used, and examples thereof include organic peroxides, azo compounds, and oxygen. Specifically, organic peroxides include di-tert-butyl peroxide, tert-butyl benzonide, dodecanol peroxide, lauryl peroxide, diacetyl peroxide, dipropyl peroxide, tertiary butyl peroxy acetate, tertiary butyl Peroxyisobutyrate, dicumyl peroxide, tertiary butyl peroxypivalate, tertiary butyl peroxyisopropyl carbonate, di (tertiary butylperoxy) adipate, tertiary butyl peroxylaurate, etc. Examples of the azo compound include azobisisobutyronitrile and the like. The used amount of the radical generating catalyst is 1 to 100 ppm by weight, preferably 5 to 30 ppm by weight of the total amount of the raw materials supplied to the reactor.

The chain transfer agent used in the present invention may be a conventional chain transfer agent used in the production of polyethylene by a high-pressure method, for example, α-olefins, alcohols,
Ketones and aldehydes are exemplified. In particular,
As α-olefins, propylene, butene-1,
Hexene-1, 3-methylbutene-1, 4-methylpentene-1, octene-1, decene-1, etc., and alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n- Butyl alcohol, isobutyl alcohol, pentyl alcohol, hexyl alcohol, octyl alcohol, etc., further, as ketones, acetone, diethyl ketone, diamyl ketone, diisobutyl ketone,
Methyl ethyl ketone, methyl isopropyl ketone, ethyl butyl ketone, ethyl propyl ketone, diisoamyl ketone and the like, and further, as aldehydes, formaldehyde, acetaldehyde, n-butyraldehyde, isobutyraldehyde, n-valeraldehyde, isovaleraldehyde, n -Caprolaldehyde, n-caprylaldehyde and the like. The amount of the chain transfer agent used is 0.2 to 0.2% based on the total amount of the raw materials supplied to the reactor.
It is 10 mol%, preferably 0.5 to 5 mol%.

In the present invention, the physical properties of the ethylene-ethylenically unsaturated silane compound copolymer obtained by the above method are those having a melt index of 0.5 to 10 g / 10.
Minutes, the ethylenically unsaturated silane compound content is 0.5 to
It needs to be 5% by weight. If the melt index is less than 0.5 g / 10 minutes, extrudability is poor,
Protrusions are formed at the interface between the semiconductive layer and the electrical insulating layer, which results in the generation of electrical trees and water trees, which shortens the life of the power cable, and is undesirable, while the melt index exceeds 10 g / 10 min. In this case, the mechanical properties are weakened, which is not desirable. On the other hand, if the content of the ethylenically unsaturated silane compound in the copolymer is less than 0.5% by weight, the shape retention characteristics at high temperatures and the heat deformation rate deteriorate, which is undesirable. Exceeding not only deteriorates the moldability but also increases the cost because a large amount of expensive silane compounds are used, which is not desirable.

In the present invention, in addition to the above-mentioned ethylene-ethylenically unsaturated silane compound copolymer, a polymer component usually used for a semiconductive resin composition for a power cable is blended within a range not to impair the object of the present invention. can do. The polymer components to be blended include ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, high-pressure low-density polyethylene, linear low-density polyethylene, ultra-low-density linear polyethylene, ionomer, and styrene-butadiene copolymer. Examples thereof include a polymer and an acrylonitrile-butadiene copolymer. The compounding amount is usually 100 parts by weight or less based on 100 parts by weight of the ethylene-ethylenically unsaturated silane compound copolymer. The amount is 1
If the amount exceeds 00 parts by weight, mechanical properties and heat resistance deteriorate, which is not desirable.

2. Conductive Carbon (B) The carbon black used in the present invention may be any conductive carbon used in a semiconductive resin composition for a power cable. Examples of such carbon black include Ketchum black, furnace black, and acetylene black. No.
Among them, acetylene black is preferable because the interface between the semiconductive layer and the electrical insulating layer can be particularly smoothed.
The amount of the carbon black is 15 to 85 parts by weight based on 100 parts by weight of the ethylene-ethylenically unsaturated silane compound copolymer (100 parts by weight of the resin component when the other polymer is blended). Range. If the amount is less than 15 parts by weight, the volume-specific low pressure value required for the semiconductive layer of the power cable is 100 Ω · cm or more, which is undesirable. , Flexibility, elongation, etc. are undesirably deteriorated.

3. Silanol Condensation Catalyst (C), etc. The silanol condensation catalyst used in the present invention is -Si- which hangs as a pendant group on the long chain of an ethylene-ethylenically unsaturated silane compound copolymer in the presence of water.
(OR) — promotes a reaction of dehydrating and condensing groups, for example, dibutyltin dilaurate, dibutyltin diacetate, dibutyl chain dioleate, acetic acid
Tin, lead naphthenate, cobalt naphthenate, zinc caprylate, iron 2-ethylhexanoate, titanate, tetrabutyl titanate, tetranonyl titanate, bis (acetylacetonitrile), di-isopropyltitanium, ethylamine, Hexylamine, dibutylamine, pyridine and the like can be mentioned. The amount of the silanol condensation catalyst used is 0.001 to 3 parts by weight based on 100 parts by weight of the ethylene-ethylenically unsaturated silane compound copolymer. If the amount used is less than 0.001 part by weight, the water crosslinking reaction is not promoted. On the other hand, if the amount used exceeds 3 parts by weight, not only does the electrical property of the resin layer deteriorate, but also the cost increases. Not so desirable. In the present invention, in addition to the above-mentioned components, additives and auxiliary materials usually used in the semiconductive resin composition for power cables may be blended as long as the object of the present invention is not impaired. These various additives and auxiliary materials include antioxidants, ultraviolet absorbers, light stabilizers,
Examples include an antistatic agent, a lubricant, a processability improver, a filler, a dispersant, a copper damage inhibitor, a neutralizing agent, a foaming agent, an air bubble inhibitor, a colorant, and a pigment.

4. Power cable The power cable of the present invention is obtained by coating and forming an inner semiconductive layer, an electrically insulating layer, an outer semiconductive layer, and a shield layer on a conductor. The conductor, the electrical insulation layer, and the shield layer may be any of those conventionally used in AC power cables. For example, as the conductor, a solid conductor or a stranded conductor made of soft copper, hard copper, hard aluminum or the like is preferably used. On the other hand, the electrical insulation layer is to insulate high voltage current flowing through the conductor and measure safety, and the material is a high-pressure low-density polyethylene, a linear low-density ethylene-α-olefin copolymer,
Ethylene-propylene rubber, butyl rubber and the like are used. At that time, to improve properties such as heat resistance, mechanical strength, heat aging resistance, heat deformation resistance, dielectric breakdown resistance, environmental stress crack resistance, etc., by crosslinking with organic peroxide, grafting vinyl silane compound It is desirable to form a water bridge, a bridge by electron beam irradiation, or the like. The shield layer is provided to stabilize the electrical characteristics of the current flowing through the cable, and is made of carbon paper, semiconductive cloth tape, aluminum tape, copper tape, or the like. On the other hand, as described above, the inner semiconductive layer and the outer semiconductive layer were obtained by copolymerizing ethylene and an ethylenically unsaturated silane compound with a high-pressure polyethylene manufacturing apparatus, and had a melt index of 0.5 to 0.5. 10g / 10
And the content of the ethylenically unsaturated silane compound is 0.5 to 5
It comprises the semiconductive resin composition of the present invention containing the ethylene-ethylenically unsaturated silane compound copolymer (A), the conductive carbon (B), and the silanol condensation catalyst (C) by weight.

The method of coating each of these layers on the conductor may be any method conventionally employed in the production of AC power cables. For example, first, an inner semiconductive layer is coated on a conductor, and A method of coating an electrically insulating layer and then an outer semiconductive layer thereon, a method of first coating an inner semiconductive layer on a conductor, and then simultaneously coating the electrically insulating layer and an outer semiconductive layer, There is a method in which a semiconductive layer, an electric insulating layer and an external semiconductive layer are simultaneously coated by coextrusion.
In the case of co-extrusion, a tandem extruder in which three extruders are connected in tandem or a common three-layer extruder is used. As a result, the adhesion between the layers is improved, and furthermore, no protrusion is generated at the interface, and no water tree or electric tree is generated. As a result, the life of the electric wire can be extended. The formed water-crosslinkable insulating layer is then immersed in a usual method, for example, immersed in a hot water bath at a temperature of 50 to 90 ° C, or in air containing water vapor (temperature is room temperature to 110 ° C).
The water-crosslinking is carried out by causing a condensation reaction between the alkoxy groups of the vinyl silane grafted on the polyethylene in the presence of a silanol condensation catalyst.

The power cable of the present invention does not generate water trees or electric trees, and as a result, the life of the electric wires can be maintained for a long time. It is widely used as a means for transmitting electricity of medium pressure or high pressure between cities, factories, buildings, and the like, or within these.

[0023]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited to these examples.

Ethylene-ethylenically unsaturated silane compound
Preparation of Copolymer (Polymerization Example 1) In ethylene, 8.3 mol% of vinyltrimethoxysilane, methyl ethyl ketone (chain transfer agent)
7 mol% and 22 wt ppm of di-t-butyl peroxide (radical generating catalyst) were added. The mixture was pumped into the tubular reactor using a high pressure pump and the reaction pressure was 25
Polymerized under the conditions of 0 MPa and a reaction peak temperature of 225 ° C.
An ethylene-vinyltrimethoxysilane copolymer having a melt index of 2.3 g / 10 minutes and a vinyltrimethoxysilane content of 1.3% by weight was obtained. (Polymerization Example 2) 6.7 mol% of vinyldiethoxyethylsilane, 3.2 mol% of isopropyl alcohol (chain transfer agent), and 55 ppm by weight of dipropionyl peroxide (radical generation catalyst) were added to ethylene. The mixture was pumped into a tubular reactor using a high-pressure pump, and polymerized under the conditions of a reaction pressure of 280 MPa and a reaction peak temperature of 220 ° C., a melt index of 4.5 g / 10 min, and a vinyldiethoxyethylsilane content of 0.9 wt. % Ethylene-vinyldiethoxyethylsilane copolymer was obtained. (Polymerization Comparative Example 1) 1.3 mol% of vinyltriethoxysilane, 0.8 mol% of propylene (chain transfer agent), and 23 ppm by weight of tertiary butyl peroxyacetate (radical generating catalyst) were added to ethylene. . This mixture was pumped into a tubular reactor using a high-pressure pump, and polymerized under the conditions of a reaction pressure of 300 MPa and a reaction peak temperature of 230 ° C., a melt index of 0.3 g / 10 min, and a vinyltriethoxysilane content of 0.2% by weight. Of ethylene-vinyltriethoxysilane copolymer was obtained. (Polymerization Comparative Example 2) 13.5 mol% of γ-methacryloyloxypropyltrimethoxysilane in ethylene, n
3.8 mol% of -butyraldehyde (chain transfer agent) and 58 ppm by weight of tertiary butyl peroxyisopropyl carbonate (radical generating catalyst) were added. This mixture was pumped into a tank reactor using a high-pressure pump, and polymerized under the conditions of a reaction pressure of 245 MPa and a reaction peak temperature of 260 ° C., and a melt index of 6.3 g / 10 min.
An ethylene-γ-methacryloyloxypropyltrimethoxysilane copolymer having a methacryloyloxypropyltrimethoxysilane content of 6.3% by weight was obtained.

Preparation of water-crosslinkable internal semiconductive resin composition (water-crosslinkable internal semiconductive resin composition 1) Ethylene-vinyltrimethoxysilane copolymer 10 prepared in Polymerization Example I
The antioxidant pentaerythritol tetrakis [3- (2,5-di-tert-butyl-4-) was added to 0 parts by weight.
(Hydroxyphenyl) propionate] (trade name Irganox 1010), 0.5 part by weight, 65 parts by weight of acetylene black, and 0.1 part by weight of dibutyltin laurate which is a silanol condensation catalyst, were mixed at 130 ° C. for 10 minutes. After kneading with a mixer, 3m in diameter
m, a columnar pellet having a height of 3 mm. (Water-crosslinkable internal semiconductive resin composition 2) With respect to 100 parts by weight of the ethylene-vinyltrimethoxyethylsilane copolymer prepared in Polymerization Example 2, pentaerythritol tetrakis [3- (2, 5-di-t-butyl-4-hydroxyphenyl) propionate] (trade name Irganox 1010) in an amount of 0.5 part by weight and furnace black in an amount of 80 parts by weight.
After kneading with a Banbury mixer for 0 minutes, 3 mm in diameter,
A cylindrical pellet having a height of 3 mm was obtained. Separately, 1 part by weight of dibutyltin laurate, which is a silanol condensation catalyst, is blended with 100 parts by weight of ethylene-vinyl acetate copolymer (EVA) having a vinyl acetate (VA) content of 26%,
This was kneaded at 130 ° C. for 10 minutes with a Banbury mixer to obtain a cylindrical pellet having a diameter of 3 mm and a height of 3 mm. These pellets were mixed so that the former: the latter = 9/1. (Water-crosslinkable internal semiconductive resin composition 3 (for comparison)) To 100 parts by weight of the ethylene-vinyltriethoxysilane copolymer prepared in Comparative Example 1, pentaerythritol tetrakis [3 -(2,5-di-t
-Butyl-4-hydroxyphenyl) propionate]
(Irganox 1010 (trade name)) 0.5 part by weight, 60 parts by weight of acetylene black, and 0.1 part by weight of dibutyltin laurate which is a silanol condensation catalyst were mixed and kneaded with a Banbury mixer at 130 ° C. for 10 minutes. , And 3 mm in diameter and 3 mm in height as a cylindrical pellet. (Water-crosslinkable internal semiconductive resin composition 4 (for comparison)) An antioxidant is used with respect to 100 parts by weight of the ethylene-γ-methacryloyloxypropyltrimethoxysilane copolymer prepared in Comparative Example 2. 0.5 parts by weight of pentaerythritol tetrakis [3- (2,5-di-t-butyl-4-hydroxyphenyl) propionate] (trade name: Irganox 1010), 30 parts by weight of acetylene black, and dibutyl as a silanol condensation catalyst 0.1 parts by weight of tin laurate was blended and kneaded with a Banbury mixer at 130 ° C. for 10 minutes.
mm cylindrical pellets.

Preparation of Resin Composition for Electrical Insulating Layer (Resin Composition 1 for Electrical Insulating Layer) 100 parts by weight of the ethylene-vinyltrimethoxysilane copolymer of Polymerization Example 1 was added to 4,4'- Thiobis- (6-t-butyl-
m-cresol) (trade name Seanox BCS) 0.2
Parts by weight, and 0.1 part by weight of dibutyltin laurate as a silanol condensation catalyst were blended.
After kneading with a Banbury mixer for 3 minutes, a cylindrical pellet having a diameter of 3 mm and a height of 3 mm was obtained. (Resin composition 2 for electric insulating layer) 100 parts by weight of the ethylene-vinyldiethoxyethylsilane copolymer of Polymerization Example 2
4,4'-thiobis- (6-t-butyl-m-cresol) which is an antioxidant (trade name: Seanox BCS)
0.2 part by weight and 1 part by weight of dibutyltin laurate, which is a silanol condensation catalyst, were mixed.
After kneading with a Banbury mixer for 0 minutes, 3 mm in diameter,
A columnar pellet having a height of 3 mm was obtained. (Resin Composition 3 for Electric Insulating Layer) Density 0.923 g / cm
³ , 4,4′-thiobis- (6-t-butyl-m-cresol) (trade name: Seanox) as an antioxidant with respect to 100 parts by weight of high-pressure low-density polyethylene having a melt index of 3.5 g / 10 min. BCS) 0.2 part by weight was mixed and kneaded at 130 ° C. for 10 minutes, and then 3 m in diameter was obtained.
m, a columnar pellet having a height of 3 mm. Next, 3.5 parts by weight of dicumyl peroxide, which is an organic peroxide, was added to the pellets, and the mixture was slowly stirred at 68 ° C. for 5 hours to uniformly impregnate the organic peroxide into the inside of the pellets, thereby obtaining electricity. Insulating layer resin composition 3 was obtained.

Preparation of resin composition for water-crosslinkable external semiconductive layer (water-crosslinkable external semiconductive resin composition 1) Ethylene-vinyltrimethoxysilane copolymer 10 prepared in Polymerization Example 1
0 parts by weight, high-pressure method ethylene-vinyl acetate copolymer (vinyl acetate content 28% by weight, melt index 7 g / 1
0 minutes) 50 parts by weight and an acrylonitrile content of 30
Pentaerythritol tetrakis [3- (2,5-di-tert-butyl-4-hydroxyphenyl) propionate] (trade name: Irganox 1010) was added to 10 parts by weight of an acrylonitrile butadiene block copolymer in an amount of 10% by weight. 0.5 parts by weight, acetylene black 70
Parts by weight and 1 part by weight of dibutyltin laurate, which is a silanol condensation catalyst, were kneaded with a Banbury mixer at 130 ° C. for 10 minutes, and then 3 mm in diameter and 3 mm in height.
mm cylindrical pellets. (Water crosslinkable external semiconductive resin composition 2) 100 parts by weight of the ethylene-vinyldiethoxyethylsilane copolymer prepared in Polymerization Example 2 and a high-pressure ethylene-ethyl acrylate copolymer (ethyl acrylate content 26% by weight) , A melt index of 9 g / 10 min) and 20 parts by weight of the kneaded product of ethylene-ethyl acrylate copolymer (EEA) -organopolysiloxane were added to pentaerythritol tetrakis [3- (2,5- Jee
t-butyl-4-hydroxyphenyl) propionate] (trade name Irganox 1010) 0.5 part by weight,
70 parts by weight of acetylene black and 1 part by weight of dibutyltin laurate, which is a silanol condensation catalyst, were blended and kneaded at 130 ° C. for 10 minutes using a Banbury mixer to obtain columnar pellets having a diameter of 3 mm and a height of 3 mm. (Water crosslinkable external semiconductive resin composition 3 (for comparison)) 100 parts by weight of the ethylene-vinyltrimethoxysilane copolymer prepared in Comparative Example 1 and a high-pressure method ethylene-vinyl acetate copolymer (containing vinyl acetate) Pentaerythritol tetrakis [3] in an amount of 28% by weight, a melt index of 7 g / 10 minutes) of 30 parts by weight, and a high-pressure kneaded product of ethylene-vinyl acetate copolymer (EVA) -organopolysiloxane of 20 parts by weight. -(2,5-di-tert-butyl-4-hydroxyphenyl) propionate] (trade name Irganox 1010) 0.5 parts by weight, acetylene black 70 parts by weight, and dibutyltin laurate 1 part by weight as a silanol condensation catalyst Is mixed with 130
After kneading with a Banbury mixer for 10 minutes at
mm, and a columnar pellet having a height of 3 mm. (Water-crosslinkable external semiconductive resin composition 4 (for comparison)) 100 parts by weight of the ethylene-γ-methacryloyloxypropyltrimethoxysilane copolymer prepared in Comparative Example 2 and a high-pressure ethylene-ethylacrylic copolymer Combined (ethyl acrylate content 26% by weight, melt index 9
g / 10 minutes) 30 parts by weight, 20 parts by weight of a high-pressure kneaded product of ethylene-ethylacryl copolymer (EEA) -organopolysiloxane, and pentaerythritol tetrakis [3- (2,5-di- t-butyl-4-hydroxyphenyl) propionate] (trade name Irganox 1010) 0.5 part by weight, acetylene black 7
0 parts by weight and 1 part by weight of dibutyltin laurate, which is a silanol condensation catalyst, were mixed and kneaded at 130 ° C. for 10 minutes with a Banbury mixer to obtain cylindrical pellets having a diameter of 3 mm and a height of 3 mm.

Preparation of Common Three-Layer Extrusion Apparatus Three extruders each having a screen pack of 250 mesh or more installed on a die plate are prepared and connected to form an internal semiconductive layer extruder, an insulating layer extruder and The extruder had a common three-layer crosshead sequentially installed so as to be an external semiconductive layer extruder.

Production of Power Cable Example 1 Water-crosslinkable internal semiconductive resin composition 1, resin composition for electric insulating layer 1, and water-crosslinkable external semiconductive resin composition 1 prepared as described above. Was supplied to each extruder of the common three-layer extruder. These resin compositions were heated and kneaded at the following temperatures in each extruder. That is, the inner semiconductive layer extruder: 160 ° C., the insulating layer extruder: 150 ° C., and the outer semiconductive layer extruder: 160 ° C. Next, the kneaded resin composition was applied to the hard copper stranded wire conductor using a dice of a common three-layer crosshead, and the thickness of the inner semiconductive layer was 1 mm, the thickness of the insulating layer was 3 mm, and the thickness of the outer semiconductive layer. Was 1 mm at the same time, passed through 90 ° C. hot water, and left at room temperature for 30 days. Thereafter, the pressure was reduced at 70 ° C. (300 mm
It dried under Hg) for 30 days, and obtained the power cable. Observation of the obtained power cable showed that the surfaces of the inner semiconductive layer and the outer semiconductive layer were smooth, and that the interface between the semiconductive layer and the insulating layer was completely integrated, with no projections. Did not.

In addition, the power cable was subjected to a water tree generation experiment by the following method. As shown in Table 1, it was found that water tree generation was small and the life of the power cable was sufficient. (Water tree generation experiment) A water-crosslinkable internal semiconductive resin composition, a resin composition for an electrical insulating layer, and a water-crosslinkable external semiconductive resin composition are co-extruded with a three-layer common extruder,
A three-layer laminated sheet having a thickness of 1 mm for each layer is prepared. Next, the three-layer laminated sheet is heated in warm water at 90 ° C. for 1 hour, left at room temperature for 30 days, and crosslinked with water. Then 9
After drying at 0 ° C. and 300 mmHg for 2 days, 500 m
A sample is punched into a square of mx 500 mm. Then the first
As shown in the figure, the center part of the sample was sandwiched between glassware (1) having an inner diameter of 30 mm and tightened to prevent water leakage.
A 0.1 normal saline solution (2) is injected into each glass device (1) to form an electrode. Insert the high-voltage lead wire (3) and the ground wire (4) into one glass device (1),
KV, 5 KHz AC voltage is applied for one week by flooding. After the experiment is completed, a flooded part with a diameter of 30 mm is 20 × 20 × 3
Punched in mm to make a measurement sample. As shown in FIG. 2, a test piece (8) having a thickness of about 0.5 mm was cut out from the measurement sample with a microtome (7) and stained with a 2% aqueous solution of crystal violet for 10 minutes to make the water tree observable. Forty dyed specimens (3 x 20 x 0.5 mm) were prepared,
An arbitrary 20 of them are observed with a stereoscopic microscope of 30 times, and the portion where the water tree occurs most is photographed, and 20 microscopic photographs of 50 times are obtained. Using this photograph, the number of generated water trees is checked, and the rate of occurrence per 1 mm is calculated.
At that time, measure the length of the water tree and record the average and maximum values

Example 2 In Example 1, the water-crosslinkable internal semiconductive resin composition 1, the resin composition 1 for the electrical insulating layer, and the water-crosslinkable external semiconductive resin composition 1 were each replaced with the water-crosslinkable internal semiconductive resin composition. The same experiment as in Example 1 was performed, except that the semiconductive resin composition 2, the resin composition 2 for an electrical insulating layer, and the water-crosslinkable external semiconductive resin composition 2 were used. As in Example 1, good results were obtained.

Example 3 Water-crosslinkable internal semiconductive resin composition 2, resin composition 2 for electric insulating layer, and water-crosslinkable external semiconductive resin composition 2
Was supplied to each extruder of the common three-layer extruder. These resin compositions were heated and kneaded at the following temperatures in each extruder. That is, an inner semiconductive layer extruder: 170
° C, insulating layer extruder: 130 ° C, external semiconductive layer extruder: 1
60 ° C. Next, the kneaded resin composition was placed on a hard copper stranded conductor using a dice of a common three-layer crosshead, and the thickness of the inner semiconductive layer was 1 mm, the thickness of the insulating layer was 5 mm, and the thickness of the outer semiconductive layer. After extruding simultaneously so that is 1 mm,
The mixture is heated to 230 ° C. by a cross-linking tube located downstream thereof to perform a cross-linking reaction.
Left for 0 days. Thereafter, the pressure was reduced at 70 ° C. (300 mmH
g) and dried for 30 days to obtain a power cable. Observation of the obtained power cable showed that the surfaces of the inner semiconductive layer and the outer semiconductive layer were smooth, and that the interface between the semiconductive layer and the insulating layer was completely integrated, with no projections. Did not. In addition, a water tree generation experiment was performed on this power cable in the same manner as in Example 1. As shown in Table 1, it was found that water tree generation was small and the life of the power cable was sufficient. .

[0033]

[Table 1]

COMPARATIVE EXAMPLE 1 In Example 1, the water-crosslinkable internal semiconductive resin composition 1, the resin composition 1 for the electrical insulating layer and the water-crosslinkable external semiconductive resin composition 1 were each replaced with the water-crosslinkable internal semiconductive resin composition. The same experiment as in Example 1 was performed, except that the semiconductive resin composition 3, the resin composition 3 for an electric insulating layer, and the water-crosslinkable external semiconductive resin composition 3 were replaced. The obtained power cable was undesirably poor in shape retention characteristics at high temperatures and a heating deformation rate.

COMPARATIVE EXAMPLE 2 In Example 1, the water-crosslinkable internal semiconductive resin composition 1, the resin composition 1 for the electrical insulating layer, and the water-crosslinkable external semiconductive resin composition 1 were each replaced with the water-crosslinkable internal semiconductive resin composition. The same experiment as in Example 1 was performed, except that the semiconductive resin composition 4, the resin composition 4 for an electrical insulating layer, and the water-crosslinkable external semiconductive resin composition 4 were replaced. The obtained power cable was not desirable because of poor molding processability and increased cost.

Comparative Example 3 First, an ethylene-vinyl acetate copolymer (vinyl acetate content: 26% by weight, melt index: 8 g / 10 min) 10
0 parts by weight, 2 parts by weight of vinylmethoxysilane, and 0.5 parts by weight of dicumyl peroxide were mixed.
For 2 minutes to prepare a vinyltrimethoxysilane-grafted ethylene-vinyl acetate copolymer. Then
An ethylene-vinyltrimethoxysilane copolymer obtained by blending the vinyltrimethoxysilane-grafted ethylene-vinyl acetate copolymer into the water-crosslinkable internal semiconductive resin composition 1 and the water-crosslinkable external semiconductive resin composition 1; Instead, a semiconductive resin composition for internal and external use for Comparative Example 3 was obtained. Next, in place of the semiconductive resin composition for internal and external use of Example 1, Comparative Example 3 was used.
An experiment similar to that of Example 1 was performed using a semiconductive resin composition for internal and external use. Observation of the obtained power cable revealed that the surfaces of the inner and outer semiconductive layers were not smooth, the occurrence rate of water trees was high, and the life of the power cable was short, which was not desirable.

[0037]

According to the present invention, an ethylene-ethylenic copolymer obtained by copolymerizing at least one semiconductive layer of an inner semiconductive layer or an outer semiconductive layer forming a power cable with a high-pressure polyethylene manufacturing apparatus. By being composed of a saturated silane copolymer water cross-linked product and conductive carbon,
Compared to the conventional semiconductive layer, the surface is smooth and free of protrusions, and as a result, water trees are not generated in the insulating layer.
This has the effect of extending the life of the power cable.

[Brief description of the drawings]

FIG. 1 is a diagram showing the main points of an experimental apparatus for generating water trees.

FIG. 2 is a diagram showing a method of cutting out a test piece to observe a state of occurrence of a water tree after an experiment of generating a water tree.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass apparatus 2 Salt solution 3 High voltage lead wire 4 Earth wire 5 Semiconductive layer 6 Insulator layer 7 Microtome 8 Test piece

Claims (2)

[Claims] 1. A melt index obtained by copolymerizing (A) ethylene and an ethylenically unsaturated silane compound with a high-pressure polyethylene production apparatus, and having a melt index of 0.5 to 10 g / 10.
And the content of the ethylenically unsaturated silane compound is 0.5 to 5
100% by weight of an ethylene-ethylenically unsaturated silane compound copolymer, 15 to 85 parts by weight of (B) a conductive carbon, and 0.01 to 3.0 parts by weight of a (C) silanol condensation catalyst.
A semiconductive resin composition having good water crosslinkability, characterized by containing parts by weight. 2. An electric cable comprising an inner semiconductive layer, an electrically insulating layer, an outer semiconductive layer, and a shield layer around a conductor in the order of at least one of the inner semiconductive layer and the outer semiconductive layer. A power cable, characterized in that the layer is composed of a water crosslinked body obtained from the semiconductive resin composition having good water crosslinkability according to claim 1.