JPS6297206A - Power cable - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] (a) Industrial application field The present invention uses a cross-linked ethylene copolymer with excellent dielectric strength and heat resistance, or an ethylene nail band aggregate mainly composed of the copolymer, as an insulating layer. It concerns power cables.

(B) Prior Art Conventionally, various plastic materials have been used as insulating materials for power cables. In particular, low-density polyethylene produced by high-pressure radical polymerization is inexpensive, has low induction loss, has good processability, and can improve heat resistance through crosslinking. Since it has many advantages such as less concern about tree phenomenon, it is widely used for 1-ton cables.

One of the problems with such cross-linked polyethylene power cables is the lack of dielectric strength, which results in thickening of the insulation layer of high-voltage power cables, that is, an increase in the outer diameter of the cables, making it difficult to transport and install the cables. This poses a major obstacle.

Moreover, in the crosslinking treatment for improving heat resistance, the crosslinkability of polyethylene is insufficient. Therefore, the development of highly crosslinkable, ie highly heat resistant, materials is desired.

(c) Problems to be Solved by the Invention The present invention is directed to a novel ethylene copolymer that is highly crosslinkable and capable of improving dielectric strength, or an ethylene copolymer containing the copolymer as a main component. This method improves the above drawbacks by using it as an insulating layer for power cables.
The present invention provides a power cable that maintains high dielectric strength and high heat resistance.

(d) Means for solving the problems The present invention has at least two carbon-carbon double bonds in one molecule.
In the presence of an aromatic compound, ethylene or a mixture of ethylene and other monomers is polymerized at a pressure of 500 to 400.
00Kg/ci, a copolymer obtained by high-pressure radical polymerization at a polymerization temperature of 50 to 400°C, or a copolymer containing the copolymer as the main component and units derived from the aromatic compound.
, oos to 1 mol % of an ethylene polymer for an insulating layer.

The aromatic compound in the present invention is a compound having a monocyclic or polycyclic non-fused or fused aromatic ring and at least two carbon-carbon double bonds, and is a hydrocarbon compound or its oxygen, It is a derivative containing sulfur, nitrogen, halogen, etc.

Examples of monocyclic compounds include those whose side chains are derived from cyclic aromatic compounds such as benzene or indene,
Specifically, 1-phenyl-1,3-butadiene: 9-phenyl-2,6-nonadiene; 3-methyl-8-phenyl-1,5-J phtadiene; allylstyrene; 4-styryl-1-butene; allyl Representative examples include hydrocarbons such as indene, and oxygen-containing compounds such as vinyl cinnamate, vinylallylphenyl ether, and 7lylbenzyl (meth)acrylate.

Examples of the polycyclic compound include diarylalkane derivatives, biphenyl derivatives, naphthalene derivatives, etc. Specifically, 1-phenyl-1-(4'-vinylphenyl)1-dylene:1,1-diphenylbutadiene;2, 4-diphenyl-1,3-penkdione; bis(4-isopropenylphenylmethane): 1,2- or 1,1-bis(4
-isopropenylphenyl)ethane: 1.1-his(vinylphenyl)methane; 1.1-bis(vinylphenyl)ethane; 2.2' -divinylhyphenyl: 4.4'
-diisopropenylbiphenyl: 4゜4'-diallylbiphenyl: divinylnaphthalene: diallylnaphthalene;
Examples include diisopropenylnaphthalene.

Further, these aromatic compounds may be used alone or as a mixture of two or more thereof, or may be used as a mixture with by-products derived from the production of the aromatic compounds.

The ethylene copolymer used in the couple of the present invention is produced by a radical polymerization method under high pressure. In other words, the radical polymerization method under high pressure means that the polymerization pressure is 50
9/-1 to 0-4000, preferably 1000-3500
Kg/d, reaction temperature 50-400℃, preferably 1
Ethylene and aromatics, and optionally other monomers, are co-coupled in a seed or tubular reactor in the presence of free radical catalysts and chain transfer agents and, if necessary, auxiliaries, at temperatures between 00 and 350°C. or a method of contacting and polymerizing in stages. When the aromatic compound is solid, it is supplied after being dissolved in an appropriate solvent.

The free radical catalysts include customary initiators such as peroxides, hydroperoxides, azo compounds, amine oxide compounds, oxygen, and the like.

In addition, as a chain transfer agent, hydrogen, propylene, butene-1
, C to C20 again. is higher than saturated aliphatic hydrocarbons and halogen-substituted hydrocarbons, such as methane, ethane,
Propane, butane, isobutane, n-hexane, n-hebutane, cycloparaffins, hydrogen chloride and carbon tetrachloride, saturated aliphatic alcohols of C1-C2° or higher, such as methanol, ethanol, propatool and isopropane. Patur, C-C2o or higher saturated aliphatic carbonyl compounds, such as carbon dioxide,
Mention may be made of acetone and methyl ethyl ketone as well as other aromatic compounds such as toluene, diethylbenzene and xylene.

Further, the above-mentioned ethylene copolymer may contain other unsaturated monomers in addition to ethylene, and examples of the unsaturated monomer include propylene, butene-1-pentene-1
, hexene-1,4-methylpentene-1, octene-
Examples include 1, decene-1, vinyl acetate, ethyl acrylate, methacrylic acid or its ester, and mixtures thereof.

The content of unsaturated monomers in the ethylene copolymer is preferably 0 to 3 mol%, particularly 1 mol% or less.

The density of the above ethylene polymer is 0.890 to 0.95
0! ? /α3 is preferable. Further, the melt index (hereinafter abbreviated as MT) is preferably 0.05 to 5.
0g/10 min, more preferably 0.1-20g/10
range of minutes.゛In the ethylene copolymer, the content of units derived from the hemianoptic compound to be contained as a polymer component is 0.
．． 005-1.07%, preferably 0.01-1.07%
It is 0.1 mol%. If it is less than 0.005'Ele%, almost no improvement effect is observed, and if it exceeds 1.0'Ele%, the impulse rupture strength is actually lower than when it does not contain units derived from the aromatic compound. Not only that, but it is also uneconomical due to the large consumption of high-pressure radical polymerization initiators and the use of large amounts of expensive aromatic compounds. The molecular weight of the polymer decreases significantly, making the polymer unsuitable as an electrical insulating material.

In the present invention, an ethylene polymer containing no other aromatic units may be blended with the above ethylene copolymer. Compositions containing other ethylene-based monomers are also preferred embodiments of the present invention, and the impulse rupture strength of the composition is improved by having the aromatic unit content in the composition within the range 1-1. be done.

Other ethylene polymers to be blended with the ethylene copolymer used in the cable of the present invention include ethylene homopolymer, 1-dylene and pyrene, butene-1, pentene-1, hexene-1,4 -Methylbenzone-1, Octene-1, Dehin-1 copolymer with α-rufin having 3 to 12 carbon atoms, ethylene and vinyl acetate, acrylic acid, ethyl acrylate, methacrylic acid, ethyl methacrylate, maleic acid , polar group-containing upper materials such as maleic anhydride
copolymers with ethylene, or polymers obtained by modifying the above-mentioned ethylene homopolymers or ethylene and α-olefin copolymers with unsaturated carboxylic acids such as acrylic acid and maleic acid, or derivatives thereof, and their predecessors. It will be done.

゛ The characteristics of the ethylene copolymer used in the couple of the present invention or the ethylene polymer mainly composed of the ethylene copolymer are that Therefore, double bonds that did not participate in copolymerization remain in the polymer chain, resulting in 1. 31 Always excellent in crosslinking properties.

Therefore, when this material is used for the insulation layer of a power cable, an insulation layer with a fast crosslinking reaction (crosslinking efficiency) and a high crosslinking rate (gel fraction) is formed, and high heat resistance is maintained. . Furthermore, high dielectric strength is maintained for the following reasons. In other words, polyethylene, which has traditionally been widely used as an insulating material for power cables, etc., has a lower crystallinity, which lowers its breakdown strength against stiffness voltage (impulse breakdown strength). It has the disadvantage that when the value is increased, workability deteriorates. It is generally known that when other components are added to the polyethylene chain, the degree of crystallinity decreases due to steric hindrance.

However, the present inventors have found that when the intermediates derived from specific □aromatic compounds are incorporated into the polymer chain in the specific ratio as described above, the crystallinity decreases and the impulse rupture strength of -C also increases. He discovered that there is a range of things that people can turn their backs on. The present invention is based on the unexpected finding that an improvement in impulse rupture strength can be achieved by introducing and covering an extremely small amount of aromatic units into an ethylene polymer.

Therefore, as mentioned above, the crystallinity of the ethylene copolymer or the ethylene copolymer mainly composed of the ethylene copolymer is also an important factor for improving the dielectric strength. It is preferable that the crystallinity by diffraction is within a range of 30% or less compared to the crystallinity of an ethylene homopolymer containing no aromatic rings obtained under substantially the same condition.

The upper limit of the crystallinity is naturally determined to be equal to or lower than the crystallinity of an ethylene homopolymer obtained under substantially the same conditions as the ethylene copolymer.

In the present invention, olefin polymers (including copolymers) other than the above-mentioned loose ethylene polymer, polyacrylonitrile, polyamide, etc. , polycarbonate, △.

BS resin, polybrene, polyphenylene oxide,
Thermoplastic resins such as polyvinyl alcohol resin, vinyl chloride resin, vinylidene chloride resin, polyester resin, petroleum resin, coumaron-indene resin, ethylene-
propylene copolymer rubber (El)R, El)DM, etc.)
, SBR, NBR, butadiene rubber, IIR, chloroprene rubber, isoprene rubber, synthetic rubber such as sobrene-butadiene-styrene rubber zero-tension copolymer, or natural rubber. can.

On the other hand, in the present invention, antioxidants, lubricants, ultraviolet inhibitors,
Dispersant, copper damage inhibitor, neutralizing agent, plasticizer, anti-bubble agent, n
Nine additives such as a repellent, a crosslinking agent, a flowability improver, a weld strength improver, and a nucleating agent may be added to the extent that they do not significantly impair the effects of the present invention.

The above-mentioned crosslinking method for producing a crosslinked power resin using an ethylene copolymer may be a generally widely used chemical crosslinking method or a radiation crosslinking method.

(e) Function and Effect of the Invention Mizumoto Ill's air capeple is an insulating layer made of a novel ethylene copolymer present in the m-combined chain with an aromatic compound capable of improving crosslinking properties and dielectric strength as described above. Ultra-high voltage electrical cables with high crosslinking rate and crosslinking efficiency, high heat resistance, high dielectric strength, and excellent impulse breakdown strength.
This is a pull.

(f) Examples 1 to 3 Next, examples will be described in comparison with comparative examples.

Tomato 5-U: U: Nitrogen and J: Fully substituted with ethylene, and the internal volume was 38 g.
Approximately 1.70 in a metal autoclave type reaction chamber with a stirrer.
JJ's ethylene, aromatic compound d3 shown in Table 1,
J: and a predetermined amount of n-hexane, and further injected di-turn 11-butyl peroxide, which is a polymerization initiator, at a temperature of 170°C and a table pressure of 1600 kg/cM.
Polymerization was carried out for 60 minutes to prepare various 1-brene-based polymers containing units of 'l'i spaced metal compounds as shown in Table 1.

A part of the produced polymer was dissolved in heated carbon tetrachloride, and reprecipitated by pouring it into acetone of 1 ff). After purification by repeating this operation for 1 ff, it was vacuum-dried.

Table 1 shows the properties of the obtained copolymer.

The copolymer is mixed with a predetermined amount of an organic peroxide crosslinking agent and an anti-aging agent to form an insulating compound.

Conductor area 32! Apply 1 of the above compound on the im2 conductor.
Extrusion coating was carried out at a temperature of 20°C to an insulation thickness of 11NR. An extruded semiconductive layer was applied directly above the conductor and on the surface of the insulator. After extrusion coating, the cable was introduced into high-temperature heated oil and cross-linked to obtain a power cable having a cross-section MA''Ih as shown in FIG.

The impulse breaking strength (measured by a conventional method), gel fraction (crosslinking rate), and thermal deformation rate (heat resistance) of the obtained cable were measured and are shown in Table 1.

Example 4 In place of the aromatic compound used in Example 1, 4-ethyl-1-isopropenylbenzene and 1-isopropenylbenzene prepared when producing 1-isopropenyl-4-vinylbenzene were used.
Polymerization was carried out in the same manner as in Example 1 using an aromatic compound consisting of a mixture of isopropyl-4-vinylbenzene (4/1/2 molar ratio).

Using the above copolymer, a power cable was fabricated in the same manner as in Example 1, and the results of evaluation are shown in Table 1.

Comparative Examples 1 to 3 Under the same polymerization conditions as in Example 1, copolymers of ethylene homopolymers and comonomers outside the scope of the present invention as shown in Table 1 were subjected to WJ! ! A. A kaesol was produced in the same manner as in Example 1, and its physical properties were evaluated. The results are shown in Table 1.

(g) Evaluation results As is clear from Table 1, Examples 1 to 4 failed.

This shows that the dielectric strength and heat resistance of the power cable using the light ethylene copolymer for the insulating layer are superior to those of the conventional crosslinked polyethylene power cable (Comparative Example 1).

- On the other hand, when the aromatic inclusion was set outside the scope of the present invention in Comparative Example 2.3, no improvement effect was observed.

The test method is as follows.

1) Gel fraction: Grind the molded product into a 20 mesh bath and wash it with xylene at 120
C. for 10 hours, and the residual rate was determined.

2) Heat modification rate The sample was pressurized with a load of 2.64 g in an oil bath at 120°C, and the deformation rate after 30 minutes was determined.

3) Crystallinity X [11 Based on diffraction method.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of the cable of the present invention. 1... Conductor 2... Internal semiconducting layer 3...
・Insulating layer 4...Outer half 39 electrical layer Patent applicant Nippon Petrochemical Co., Ltd. Tewa V Ne city official book 1986 2ri ≦ - day 1, i (S &amp; showing 1988 1h correction request No. 235022 2, Name of the invention in the sky 3, Relationship with EIXfl with amendments Applicant name Nippon Raura Chemical Co., Ltd. 4 Agent address 111-1-5, Minami-Aoyama-cho, Minato-ku, Tokyo 107 , the date of the amendment order) (Send the date) Ill sum <[month/day Specifications 1, Name of the invention Power cable 2, Claims (1) Carbon-carbon double viscosity in one molecule In the presence of an aromatic compound having at least two combinations, ethylene or a mixture of ethylene and other monocamellia is heated under a combined pressure of 500 to 400.
The main component is a copolymer obtained by high-pressure radical polymerization at a polymerization temperature of 50 to 400 °C, and has 0 to 1 mol% of units derived from the aromatic compound. A power cable characterized by having an insulating layer made of cross-linked Brene polymer. (2) The power cable according to claim 1, wherein the aromatic compound is at least one selected from the group of allylstyrene, 4-styryl-1-butene, and 1-phenyl-1-styrylethylene. . (3) The crystallinity of the copolymer determined by X-ray diffraction is within 30% of the crystallinity of an ethylene homopolymer containing no aromatic rings obtained under substantially the same conditions. The power cable according to claim 1 or 2, characterized in that: 3. Detailed description of the invention (a) Industrial application field The present invention relates to an insulation made by crosslinking a crosslinked ethylene copolymer having excellent dielectric strength and heat resistance, or an ethylene polymer mainly composed of the copolymer. The present invention relates to power cables using layers. (B) Prior Art Conventionally, various plastic materials have been used as insulating materials for power cables. In particular, low-density polyethylene produced by high-pressure radical polymerization is inexpensive, has low dielectric loss, has good processability, and can be crosslinked to improve heat resistance. It is widely used for power cables because it has many advantages such as less concern about the tree phenomenon. One of the problems with such cross-linked polyethylene power cables is the lack of electrical dielectric strength, which leads to the thickening of the insulation layer of the back piezoelectric cable, which means an increase in the outer diameter of the cable, making it difficult to transport and install the cable. It becomes a big obstacle. Moreover, in the crosslinking treatment for improving heat resistance, the crosslinkability of polyethylene is insufficient. Therefore, the development of highly crosslinkable, ie highly heat resistant, materials is desired. (c) Problems to be Solved by the Invention The present invention is directed to crosslinking a novel ethylene copolymer that has extremely high crosslinking properties and can improve dielectric strength, or an ethylene polymer containing the copolymer as a main component. By using it as an insulating layer of a power cable, the above-mentioned drawbacks are improved, and a power cable that maintains high dielectric strength and high heat resistance is provided. (d) Means for solving the problems The present invention provides at least two carbon-carbon double-width bonds in one molecule.
In the presence of an aromatic compound, ethylene or a mixture of ethylene and other monopolymers is polymerized at a pressure of 500 to 4
ooo*y/C14, a copolymer obtained by high-pressure radical polymerization at a polymerization temperature of 50 to 400°C, or a unit mainly composed of the copolymer and derived from the aromatic compound o, oos~1 The present invention provides a power cable characterized by using an insulating layer formed by crosslinking an ethylene polymer having a mol %. The aromatic compound in the present invention is a compound having a monocyclic or polycyclic non-fused or fused aromatic ring and at least two carbon-carbon double bonds, and is a hydrocarbon compound or its oxygen, It is a derivative containing sulfur, nitrogen, halogen, etc. Examples of monocyclic compounds include those whose side chains are derived from cyclic aromatic compounds such as benzene or indene,
Specifically, 1-7enyl-1,3-butane; 9-phenyl-2,6-nonadiene; 3-methyl-8-phenyl-1,5-octadiene; allylstyrene; 4-styryl-1-butene ; hydrocarbons such as allyl indene;
Vinyl cinnamate, vinyl allyl phenyl ether, 1-
Representative examples include oxygen-containing compounds such as isopropenyl-4-vinylbenzene and allylbenzyl (meth)acrylate. Examples of the polycyclic compound include diarylalkane i 1, biphenyl derivatives, naphthalene derivatives, and specifically 1-phenyl-1-(4'-vinylphenyl)ethylene;1,1-diphenylbutadiene; .4-Schiff I-1,3-pentadiene: bis(4-isopropenylphenylmethane): 1.2- or 1.1-bis(
4-isopropenylphenyl)ethane; 1,1-bis(
vinylphenyl)methane; 1,1-bis(vinylphenyl)ethane: 2.2'-divinylbiphenyl: 4.4
'-Diimpropenylbiphenyl;4°4'-diallylhyphenyl;divinylnaphthalene; diallylnaphthalene diisopropenylnaphthalene and the like. Further, these aromatic compounds may be used alone or in a mixture of two or more thereof, or may be used as a mixture with by-products derived from the production of the aromatic compounds. The ethylene copolymer used in the cable of the present invention is produced by a radical polymerization method under high pressure. However, the radical polymerization method under high pressure, polymerization pressure 50
0 to 4000 to 9/c#i, preferably t to 1000
~3500Kg/crA, reaction temperature 50~400℃,
Ethylene and aromatics, and optionally other monomers, in a vessel wall or in a tubular reactor in the presence of a free radical catalyst and a chain transfer agent, if necessary auxiliaries, preferably at a temperature of 100 to 350°C. A method of contacting and polymerizing simultaneously or stepwise. When the aromatic compound is solid, it is supplied after being dissolved in an appropriate solvent. Examples of the above-mentioned "iIi leaving group catalysts include peroxides, droperoxides, azo compounds, amine oxide compounds, and conventional initiators such as oxygen. Chain transfer agents include hydrogen, propylene, butene-1, etc.
, C to C2o or higher, such as methane, ethane, propane, butane, isobutane, n-hexane, n-hebutane, cycloparaffins, chloroform and carbon tetrachloride, Saturated aliphatic alcohols of C1 to C20 or higher, such as methanol, ethanol, propatool and isopropanofur, saturated aliphatic carbonyl compounds of C1 to C20 or higher, such as carbon dioxide, acetone and medyl edyl ketone, and the above. Examples include other young group compounds such as toluene, diethylbenzene, and xylene. Further, the above-mentioned ethylene copolymer may contain other unsaturated type suspensions in addition to ethylene, and examples of the unsaturated monomer include propylene, butene-1-pentene-1
, heni-1cene-1,4-methylpentene-1, octene-1, decene-1, vinyl acetate, ethyl acrylate, methacrylic acid or its ester, and mixtures thereof. The content of unsaturated monomers in the ethylene copolymer is O~3'
[l-le %, particularly preferably 1 mol % or less. The density of the above ethylene polymer is 0.890 to 0.9
A range of 50 J/cm3 is preferred. Further, the null 1-index (hereinafter abbreviated as Ml) is preferably 0
05-5JJ/10 minutes, more preferably 0.1-20
It is in the range of U/10 minutes. The content of units derived from the aromatic compound to be contained as an assembly component in the ethylene copolymer is 0.
．． 00!1 to 1.0 mol%, preferably (yo001
~0.7 mol%. When the amount is less than 0005 mol%, almost no improvement effect is observed, and when it exceeds 10 mol%, when the unit does not contain units derived from the aromatic compound, the impulse rupture strength decreases to 1 Good. Not only that, but also the consumption of high-pressure radical initiator for undercarriage is large and high ti;'￥? It is uneconomical to use B f& compounds in multiple tanks, and the chain transfer reaction becomes intense, resulting in a significant decrease in the molecular weight of the ethylene copolymer, making it a very unsuitable polymer for electrical insulation materials 11. become. In the present invention, the above-mentioned ethylene copolymer can be blended with other ethylene polymers that do not contain aromatic monomer T18. Compositions containing other ethylene polymers are also preferred embodiments of the present invention, and when the aromatic compound m in the composition is within the above range, the impulse rupture strength of the composition is improved. Other ethylene polymers to be blended with the ethylene copolymer used in the cable of the present invention include ethylene homopolymer, ethylene and propylene, butene-1, pentene-1
, hexene-1,4-methylpentene-1, octene-
1. Copolymers with α-olefins having 3 to 12 carbon atoms such as decene-1, ethylene and vinyl acetate, acrylic acid, ethyl acrylate, methacrylic acid, ethyl methacrylate,
A copolymer with a polar group-containing monomer such as maleic acid or maleic anhydride, or the above ethylene homopolymer or ethylene and α-olefin copolymer with acrylic acid,
Examples include polymers modified with unsaturated carboxylic acids such as maleic acid or derivatives thereof, and mixtures thereof. The ethylene copolymer used in the cable of the present invention or the ethylene copolymer mainly composed of the ethylene copolymer is characterized by the use of an aromatic compound having a plurality of small amounts of carbon-carbon double bonds. Therefore, double bonds that did not participate in copolymerization remain in the polymer chain, resulting in extremely excellent crosslinking properties. Therefore, when this material is used for an insulating layer of a power cable, an insulating layer is formed that has a fast crosslinking reaction (crosslinking efficiency) and a high crosslinking rate (gel fraction), and maintains high heat resistance. Furthermore, high dielectric strength is maintained for the following reasons. In other words, polyethylene, which has traditionally been widely used as an insulating material for power cables, etc., has a lower crystallinity and a lower breakdown strength against impact voltage (impulse breakdown strength). It has the disadvantage of poor processability. It is generally known that when other components are introduced into the polyethylene chain, the degree of crystallinity decreases due to steric hindrance. However, the present inventors have discovered that when units derived from a specific aromatic compound are contained in the polymer chain at a specific ratio as described above, the range in which the impulse rupture strength increases even if the degree of crystallinity decreases is I discovered that it exists. The present invention is based on the unexpected finding that an improvement in impulse rupture strength can be achieved by introducing a very small amount of aromatic units into an ethylene polymer. Therefore, as mentioned above, the crystallinity of the ethylene copolymer or the ethylene polymer containing the ethylene copolymer as a main component is also an important factor for improving dielectric strength.
In the present invention, it is preferable that the crystallinity by X11 diffraction is within 30% of the crystallinity of an ethylene homopolymer containing no aromatic rings obtained under substantially the same conditions. . The upper limit of the crystallinity is naturally determined to be equal to or lower than the crystallinity of an ethylene homopolymer obtained under substantially the same conditions as the ethylene copolymer. In the present invention, olefin polymers (including copolymers) other than the other ethylene polymers, polyacrylonitrile, polyamide, etc. , thermoplastic resins such as polycarbonate, ABS resin, polystyrene, polyphenylene oxide, polyvinyl alcohol resin, vinyl chloride resin, vinylidene chloride resin, polyester resin, petroleum resin, coumaron-indene resin, ethylene-propylene copolymer Combined rubber (EpH,
EPDM, etc.), SBR, NBR, butadiene rubber, II
R, chloroprene rubber, isoprene rubber, styrene-butashiconine-styrene block copolymer, or other synthetic rubber or natural rubber. On the other hand, in the present invention, antioxidants, lubricants, ultraviolet inhibitors,
Dispersant, copper damage inhibitor, neutralizing agent, plasticizer, anti-bubble agent, flame retardant, crosslinking aid, flowability improver, weld strength improver,
Additives such as nucleating agents may be added to the extent that they do not significantly impair the effects of the present invention. The crosslinking method used when producing a crosslinked capeple using the ethylene copolymer described above may be chemical crosslinking, which is generally widely practiced, or radiation crosslinking. (e) Functions and Effects of the Invention The power cable of the present invention uses a novel ethylene copolymer in the insulating layer that has aromatic compounds present in the polymer chain that can improve crosslinking properties and dielectric strength. Therefore, the crosslinking rate and crosslinking efficiency are high, and the ultra-high voltage electrical cable has high heat resistance and high dielectric strength, that is, excellent impulse breakdown strength. (F) Examples 1 to 3 Next, examples are compared. Examples 1 to 3 A metal autoclave type reactor with an internal volume of 3.89 mL and equipped with a stirrer, which was sufficiently purged with nitrogen and ethylene, was heated with about 1.7 mL of water.
Ethylene No. 09, the aromatic compound shown in Table 1, and a predetermined amount of n-hexane were charged, and di-tertiary-butyl peroxide as a polymerization initiator was added, and the polymerization temperature was 110°C and the polymerization pressure was 160089/cm%. Polymerization was carried out for 60 minutes to prepare various ethylene polymers containing units derived from aromatic compounds as shown in Table 1. A part of the produced polymer was dissolved in heated carbon tetrachloride, and reprecipitated by pouring it into a large amount of acetone. This operation was repeated several times for purification, and then vacuum-dried. Table 1 shows the properties of the obtained copolymer. A predetermined amount of an organic peroxide crosslinking agent and an antiaging agent were blended with the copolymer to prepare a powder for insulators. The above compound was extrusion coated onto a conductor having a conductor area of 325 #11!2 at a temperature of 120° C. to an insulation thickness of 11 M. An extruded semiconductive layer was applied directly above the conductor and on the surface of the insulator. After extrusion coating, the cable was introduced into high-temperature heated oil and cross-linked to obtain a power cable having a cross-sectional structure as shown in FIG. The impulse breaking strength (measured according to the conventional method 2, gel fraction (crosslinking rate), and thermal deformation rate (heat resistance) of the obtained cable were measured and shown in Table 1. Example 4 Example 1 4-ethyl-1-isopropenylbenzene and 1-isopropyl-4-vinylbenzene (4/1/ Polymerization was carried out in the same manner as in Example 1 using an aromatic compound consisting of a mixture with a molar ratio of Comparative Examples 1 to 3 Ethylene homopolymers shown in Table 1 and copolymers with comonomer contents outside the range of the present invention were prepared under the same polymerization conditions as in Example 1. Manufacture cables to
The results of physical property evaluation are shown in Table 1. (g) Evaluation Results As is clear from Table 1, Examples 1 to 4 show that the dielectric strength and heat resistance of the power cables using the ethylene copolymer of the present invention in the insulation layer are higher than those of the conventional crosslinked polyethylene power cables. This shows that it is superior to that of Comparative Example 1). On the other hand, when the aromatic content was set outside the range of the present invention in Comparative Examples 2 and 3, no improvement effect was observed. The test method is as follows. 1) Gel fraction: Grind the molded product into a 20 mesh bath and wash it with xylene at 120
C. for 10 hours, and the residual rate was determined. 2) Heat denaturation rate The sample was heated in an oil bath at 120°C. G4 was pressurized at 9, and the deformation rate after 30 minutes was determined. 3) Crystallinity by X-ray diffraction method. 4. Brief Description of the Drawings FIG. 1 is a sectional view showing an example of the cable of the present invention.

Claims (3)

[Claims] (1) In the presence of an aromatic compound having at least two carbon-carbon double bonds in one molecule, ethylene or a mixture of ethylene and other monomers is polymerized at a polymerization pressure of 500 to 400.
The main component is a copolymer obtained by high-pressure radical polymerization under conditions of 0 Kg/cm^2 and a polymerization temperature of 50 to 400°C, and contains 0.005 to 1 mol% of units derived from the aromatic compound.
A power cable characterized in that an ethylene polymer having the following properties is used for an insulating layer. (2) The power cable according to claim 1, wherein the aromatic compound is at least one selected from the group of allylstyrene, 4-styryl-1-butene, and 1-phenyl-1-styrylethylene. . (3) The crystallinity of the copolymer determined by X-ray diffraction is within 30% of the crystallinity of an ethylene homopolymer containing no aromatic rings obtained under substantially the same conditions. The power cable according to claim 1 or 2, characterized in that: