JP2002150846A - Aerial electric cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aerial electric cable with an excellent heat resistant property, disusing the process of winding an antirust tape on the conduction body, not changing the working circumstances for the worse, which is formed by covering a conduction body with an insulation body, made of bridged polyethylene having a permanently stable antirust property, by an extrusion. SOLUTION: The polyethylene, bridged by an aqueous bridging reaction, does not need to make react at high temperature like a chemical bridging when reacting, but enabled to carry out a bridging reaction at room temperature. The above obtains the aerial electric cable, which does not cause a blooming during bridging process even if a volatile antirust reagent is added to the polyethylene, surely containing the added antirust reagent in the polyethylene, with a permanently stable antirust property and an excellent heat resistant property.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overhead distribution line in which a conductor is coated with polyethylene by extrusion.
Particularly, the present invention relates to an overhead distribution line having excellent heat resistance and a long-lasting rust-preventing effect.

[0002]

2. Description of the Related Art Overhead power distribution lines installed outdoors have overhead conductors (hereinafter also referred to as OE wires) in which polyethylene is coated on a conductor as an insulator, and cross-linked polyethylene is coated on a conductor as an insulator. There is an overhead distribution line (hereinafter also referred to as an OC line). In recent years, as the demand for electric power has increased, it has been desired to increase the electric current capacity, that is, to improve the heat resistance of electric wires, and the demand for OC lines, which are superior in heat resistance to OE lines, to overhead distribution lines, has increased. are doing.

[0003] In an overhead distribution line installed outdoors, the tensile stress applied to the conductor and the corrosion of the conductor caused by the installation environment are correlated, and an abnormal disconnection accident, so-called stress corrosion cracking, may become a problem. As a measure to prevent such a disconnection accident occurring in an overhead distribution line installed outdoors, a separator tape containing a rust inhibitor is wound on a conductor, and a cross-linked polyethylene is coated thereon as an insulator. A manufacturing process has been implemented. This manufacturing process requires a winding process and a coating process, which takes a long time.

[0004] Comparing the production cost of the OE wire with the production cost of the OC wire, the production cost of the OC wire which requires the winding and cross-linking step of the separator tape containing the rust preventive is higher. However, as power demand has increased, manufacturing costs of OC wires have been reduced by improving manufacturing methods and the like.

[0005] As a countermeasure for preventing an abnormal disconnection accident, for example, as disclosed in Japanese Patent Application Laid-Open No. 9-27217, a method of covering a conductor with polyethylene containing a rust preventive agent as an insulator has been disclosed for OE wire. I have. One is a method of adding an ethylene-α-olefin and a sublimable rust inhibitor using a single-site catalyst to low-density polyethylene coated on a conductor. The other is a method of adding an ultra-low-density polyethylene having a density of 0.900 g / cm3 or less and a sublimable rust inhibitor to be coated on the conductor.
In the case of these methods, an OE wire having rust prevention performance can be produced without a step of winding a separator tape containing a rust inhibitor such as an OC wire. There is a problem that the polyethylene itself becomes soft under the influence of the addition of α-olefin or ultra-low-density polyethylene, and is easily damaged when laid.

Benzotriazole (hereinafter also referred to as BTA), which is generally used as a rust preventive for copper conductors, has poor compatibility with polyethylene and high sublimability. Worsens the environment. for that reason,
Worker health is impaired, and equipment for maintaining a good working environment is required.

In the case of producing an OC wire that requires a crosslinking step, the temperature required for crosslinking polyethylene is about 16 in chemical crosslinking, which is one of the methods for crosslinking polyethylene.
Because it is as high as 0 ° C or higher, the compatibility with polyethylene is poor,
BTA having high sublimability causes blooming (transfer to the surface layer) during the crosslinking process. As a result, there has been a problem that the added BTA is not sufficiently contained in the polyethylene, and the desired effect of the rust prevention performance cannot be obtained. Also, even if the rust prevention performance is good in the pre-shipment inspection,
There is a problem that rust prevention performance is remarkably reduced.

[0008]

SUMMARY OF THE INVENTION The present invention does not require a step of winding a tape having rust-preventive performance on a conductor, can be manufactured without deteriorating the working environment, and has a long-term stable rust-preventive performance. The present invention provides an overhead distribution line in which a crosslinked polyethylene insulator having the following is coated on a conductor by extrusion molding.

That is, in an overhead distribution line in which a polyethylene insulating layer is coated on a conductor by extrusion molding, the polyethylene is polyethylene cross-linked by a water cross-linking reaction, and a rust inhibitor is added to the polyethylene. It is an overhead distribution line characterized by the following.

The above-mentioned polyethylene comprises one of low-density polyethylene (hereinafter also referred to as LDPE), linear low-density polyethylene (hereinafter also referred to as LLDPE) and polyethylene polymerized with a metallocene catalyst (hereinafter also referred to as Me-PE). An overhead distribution line characterized by being polyethylene.

The overhead distribution line is characterized in that the rust preventive added to the polyethylene is an alkyl derivative of benzotriazole.

The overhead distribution line is characterized in that the polyethylene is a polyethylene polymerized with a metallocene catalyst, and the polyethylene is added with an alkyl derivative of benzotriazole.

[0013]

DETAILED DESCRIPTION OF THE INVENTION Polyethylene cross-linked by a water cross-linking reaction has a high temperature (eg, 180 ° C.) at the time of cross-linking, such as chemical cross-linking.
C), and a cross-linking reaction is possible at around room temperature (for example, after extrusion molding, it is left at room temperature to cause a cross-linking reaction with moisture in the air). As a result, blooming does not occur during the cross-linking step even if a rust preventive that is easily volatilized is added, and the added rust preventive is reliably contained in polyethylene, so that long-term stable rust preventive performance can be obtained.

A silane compound is used as a cross-linking agent for the water cross-linking reaction, and specifically, trimethoxyvinylsilane and the like are used. A preferable addition amount of the silane compound is 1.0 to 2.5 parts by weight based on 100 parts by weight of the polyethylene. If the amount is less than 1.0 part by weight, the polyethylene cannot be sufficiently crosslinked. If the amount is more than 2.5 parts by weight, the unreacted silane compound lowers the insulation performance of polyethylene as an insulator.

One of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and polyethylene (Me-PE) polymerized with a metallocene catalyst is applied as the base polyethylene to be subjected to the water crosslinking reaction. Polyethylene (Me-PE) polymerized with a metallocene catalyst is preferred in view of compatibility with a rust agent and addition of a large amount of filler such as carbon. Metallocene is a non-electrolyte complex of bis (synchropentadiniel) intermetallic compounds, in which two cyclopentadiniel rings have a regular pentagonal structure and face each other in parallel, with a metal atom sandwiched between them. It is a synonym for one consisting of molecules with a sandwich structure. The metal atoms are Zr, Ti, V, Cr, Fe, C
o, Ni, Ru, Pd and the like.
r is most preferred.

Since cross-linking is carried out by a water cross-linking reaction which does not require a high temperature unlike chemical cross-linking, the added rust preventive has poor compatibility with polyethylene, and BTA having high sublimability can be applied. Preferably, an alkyl derivative of benzotriazole having better compatibility with polyethylene than BTA, low sublimability, and little influence on the working environment is preferably used. Specifically, 1- (N, N-di (2-ethylhexyl) amino) methyl-1H-benzotriazole,
1- (N, N-di (2-ethylhexyl) amino) methyl-1H-methylbenzotriazole, carboxybenzotriazole and the like are applied. One or more rust preventives may be added, and a preferable amount of the rust preventive is 0.5 to 1.5 parts by weight based on 100 parts by weight of polyethylene. If the amount is less than 0.5 part by weight, the long-term rust prevention is insufficient, and if the amount is more than 1.5 part by weight, the rust inhibitor acts as a lubricant and the extrudability becomes unstable.

The crosslinked polyethylene further contains an initiator for grafting the silane compound to the polyethylene, dibutyltin dilaurate (hereinafter also referred to as DBTDL) as a catalyst for water crosslinking, an antioxidant (for example, Irganox), Carbon (for example, acetylene black or furnace-based carbon black) or the like can be appropriately added.

[0018]

EXAMPLES Polyethylene having the composition shown in Tables 1 and 2 was extruded on a conductor, and the polyethylene was subsequently crosslinked to produce an overhead distribution line coated as a crosslinked polyethylene insulator layer. With respect to this overhead distribution line, the following methods were used to evaluate the rust prevention effect and the blooming of the rust prevention agent. The results are shown in Tables 1 and 2.

The base polyethylenes in Tables 1 and 2 are as follows. Low density polyethylene (LDPE): density 0.92 g / cm3, melt index 1.1 g /
10 min, linear low density polyethylene (LLDP
E): Density 0.92 g / cm3, melt index 0.8 g / 10 min, polyethylene (Me-PE) polymerized with a metallocene catalyst: density 0.92 g / cm3, melt index 2.3 g / 10 min.

The additives in Table 1 are as follows. Trimethoxyvinylsilane which is a silane compound as a cross-linking agent, 1- (N, N-di (2-ethylhexyl) amino) methyl-1H-benzotriazole as a rust inhibitor A, 1- (N, N- Di (2-ethylhexyl)
Amino) methyl-1H-methylbenzotriazole, carboxybenzotriazole as rust inhibitor C, rust inhibitor D
2-undecyl-1H-imidazole (trade name: thiolite T-869), benzotriazole (BTA) as rust inhibitor E, furnace carbon black as carbon, 4,4'-thiobis (3methyl-6) as antioxidant T-butylphenol, DC as initiator
P, a catalyst for water crosslinking DBTDL was used.

The base polyethylene and the additives are kneaded, and the feeder below the hopper is extruded at a temperature of 100 ° C. or less and about 230 ° C. in the vicinity of the crosshead. It was coated by extrusion molding to a thickness of 0.5 mm, wound up on a drum or the like after a cooling step. After that, the wire was left at room temperature for 14 days to undergo a water crosslinking reaction with water in the air to obtain an electric wire.

As a comparative example, in an overhead distribution line in which a polyethylene insulator layer is coated on a conductor by extrusion molding, the polyethylene is a polyethylene cross-linked by a chemical cross-linking reaction, and a rust inhibitor is added to the polyethylene. Table 2 shows the composition of the overhead distribution lines and the evaluation results.

The base polyethylene and additives (rust inhibitor, chemical cross-linking agent, initiator, antioxidant, DBTDL, carbon) are kneaded, and the feeder under the hopper is kept at 100 ° C. or less, and at about 230 ° C. near the crosshead. With an extruder set at such a temperature, a copper conductor having a cross-sectional area of 60 mm2 was coated by extrusion molding to a thickness of 2.5 mm, then passed through a tubular furnace maintained at 180 ° C, crosslinked, cooled, and cooled to a drum. It was a winding wire.

The rust-preventive effect was evaluated by visually observing the copper conductor for discoloration after leaving the overhead distribution line in a steam atmosphere for two months. The presence of discoloration was evaluated as x, the absence of discoloration was evaluated as ○, and the copper conductor evaluated as ○ was measured for the thickness of the oxide film formed on the surface of the copper conductor by a cathode reduction method.
Those thinner than 0 ° were evaluated as ◎.

Evaluation of the occurrence of blooming of the rust preventive agent
5 With the overhead distribution line after production completed wound around the drum
After standing for a month, the surface coated with the polyethylene insulating layer was visually observed to see whether the rust inhibitor had precipitated or not.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

As is apparent from the above description, the overhead distribution line obtained by adding a rust inhibitor to the polyethylene cross-linked by the water cross-linking reaction of the present invention and coating the conductor on the conductor by extrusion molding has a rust-proof tape on the conductor. Thus, an overhead power distribution line having stable rust prevention performance over a long period of time and excellent heat resistance can be obtained without requiring a step of winding the wire.

Claims (4)

[Claims] An overhead distribution line in which polyethylene is coated on a conductor by extrusion molding, wherein the polyethylene is a polyethylene cross-linked by a water cross-linking reaction, and a rust preventive is added to the polyethylene. And overhead distribution lines. 2. The method according to claim 1, wherein the polyethylene is a low density polyethylene,
2. The overhead distribution line according to claim 1, wherein the low-density polyethylene is one of a linear low-density polyethylene and a polyethylene polymerized with a metallocene catalyst. 3. The overhead distribution line according to claim 1, wherein the rust preventive is an alkyl derivative of benzotriazole. 4. The overhead distribution line according to claim 1, wherein said polyethylene is polyethylene polymerized with a metallocene catalyst, and said polyethylene is added with an alkyl derivative of benzotriazole.