JPH0154806B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for producing watertight stranded conductors with excellent environmental stress cracking resistance.

In order to solve the problem of so-called environmental stress cracking (SCC), where the twisted conductors of insulated wires that are used outdoors for long periods of time are broken due to water entering between the twisted conductor strands, organic polymers have been developed. It has been proposed to fill the gaps between the strands of a twisted conductor to make it watertight. However, in order to fill organic polymer between the twisted conductor wires, it is necessary to heat the organic polymer to melt it and apply it to the conductor while applying pressure. There is a problem in that it is difficult to sufficiently fill the gap near the center of the conductor.

According to the research conducted by the present inventors, water that has entered a stranded conductor tends to concentrate in the center of the stranded conductor, and as a result, the conductor strands at or near the center are weaker than the strands in the periphery. Therefore, it is important to make the gap near the center of the twisted conductor watertight.

The present invention is based on the above-described shortcomings of the conventional method and new findings, and also proposes a manufacturing method that can easily produce watertight stranded conductors with excellent SCC resistance.
With one or more conductor wires pre-coated with an organic polymer being present at or near the center of a large number of conductor wire aggregates to be twisted, the temperature is higher than the melting point or softening point of the organic polymer. The above-mentioned assembly is twisted together, and the gaps between the conductor strands near the center of the twisted conductor are filled with the organic polymer by compressive force during the twisting.

The above-mentioned organic polymers include various types of raw rubber, regardless of their chemical structure, as long as they can flow under the pressure of the conductor wires when twisted at room temperature or high temperature and fill the gaps between the conductor wires. , such as natural rubber, butyl rubber, chloroprene rubber, EPDM rubber, EP rubber, 1,4- and 1,2-polybutadiene, silicone rubber, styrene-butadiene rubber, polyisoprene rubber, thermoplastic polymers such as polyethylene, ethylene-vinyl acetate. Copolymers, ethylene/ethyl acrylate copolymers, etc., or thermoplastic elastomers such as polyolefin thermoplastic elastomers, hydrogenated styrene-butadiene thermoplastic elastomers, etc. are used.

The organic polymer can be made to exist at or near the center of the conductor wire assembly by various methods. for example,
Methods include using wires that have a coating layer of organic polymer in advance as the center wire of the twisted conductor, or twisting the conductor wires together using an appropriate number of organic polymer strings at appropriate intervals. It can be harvested. The pressure during twisting causes the organic polymer to flow and deform, filling the gap near the center of the twisted conductor. If the amount of organic polymer used is sufficient, the remaining portion moves from the center toward the periphery and also fills the gaps in the periphery.

When the organic polymer is raw rubber or a thermoplastic material that is easily deformed at the temperature of the twisting operation, e.g., room temperature to 100°C, especially at room temperature, the twisting pressure is applied while the organic polymer is present at one location near the center. In this case, the gap near the center is sufficiently filled. On the other hand, organic polymers that require large pressure to deform are preferably used in a form where they are dispersed in small amounts in the vicinity of the center. The method of using the organic polymer may be appropriately determined in consideration of the ease of deformation of the organic polymer to be used, the magnitude of the twisting pressure, and the like.

The organic polymer used in the present invention may be cross-linked with various compounding agents, cross-linking agents such as sulfur, cross-linking aids, etc., as long as the inter-strand filling properties due to the flow caused by the pressure during twisting are not impaired. It may be sexual.

A particularly preferred organic polymer is benzotriazole or other metal deactivator per 100 parts (parts by weight, hereinafter the same) of the organic polymer.
It contains about 0.05 to 10 parts. If the space between the wires is filled with an organic polymer containing a metal deactivator, the surface of the wire will be inactivated by water due to the metal deactivator migrating from the organic polymer, so twisting will be difficult. The SCC resistance of the conductor is improved.

As mentioned above, in a twisted conductor, the conductor strands in the center are most susceptible to SCC, and therefore, in the present invention, it is important to fill the gaps between the strands in this part with an organic polymer. Furthermore, if the gap is filled with an organic polymer, the SCC resistance of the twisted conductor is improved.

Although the method of the present invention sufficiently fills the gaps between the twisted conductors, it goes without saying that it is desirable to completely fill the gaps between the outermost layers of the twisted conductors in order to improve SCC resistance. . In this case, it is sufficient to use a sufficiently large amount of organic polymer that is pre-existing at or near the center of the conductor, but it is also possible to make the entire gap by making the organic polymer exist not only near the center but also outside the center. can be filled with.

Alternatively, the gaps between the strands in the periphery of the stranded conductor can be easily filled by applying a filler from the outside of the stranded conductor even after the stranding, so only the center part can be filled by the above-described method of the present invention. After laying and twisting, the outer peripheral gap may be filled with a suitable filler. In this case, a room temperature or high temperature curing liquid such as silicone rubber, urethane rubber, epoxy resin, etc. is used as a filler and applied to the stranded conductor by dropping, dipping, brushing, etc.
It is preferable to harden the filler. It is more preferable to use a filler containing a metal deactivator such as benzotriazole in an amount similar to that described above.

The present invention will be explained in more detail with reference to Examples below.

Example 1 Outdoor cross-linked polyethylene insulated wire (OC) with a nominal cross-sectional area of 38 mm ² is made by twisting 7 hard copper wires with a wire diameter of 2.6 mm.
When twisting the conductors for use, 1.2 to 1.3 mm thick ethylene/
Vinyl acetate copolymer (Mitsui Petrochemical Co., Ltd., EVAFLEX 150, VA content 33 wt.%, melt index 30 g/10 minutes) was coated by extrusion, and then six hard copper wires with a diameter of 2.6 mm were coated around it at room temperature. After twisting them together, they were passed through a die with an inner diameter of 8.0 mm heated to 120°C to remove excess polymer, and the outer periphery was finished in a circular shape. When the thus obtained twisted conductor was cut and its cross section was observed with the naked eye, it was confirmed that all the gaps between the twisted wires were filled with the polymer.

Example 2 When twisting 19 hard copper wires with a wire diameter of 2.3 mm to form an OC conductor with a nominal cross-sectional area of 80 mm ² , a 2.2 mm thick olefin-based thermoplastic elastomer ( Thermolan 3600 (manufactured by Japan Synthetic Rubber Co., Ltd.) was extruded coated, and then six hard copper wires of 2.3 mm in diameter were twisted around it at 100℃, and then 12 wires of 2.3 mm in diameter were twisted as a third layer. After twisting hard copper wires at 100℃, the inner diameter is removed to remove excess polymer.
The outer periphery was finished into a circular shape through an 11.7 mm die heated to 100°C.

When the thus obtained twisted conductor was cut and its cross section was visually observed, it was found that all the gaps between the twisted wires were filled with the polymer.

Example 3 When twisting the same conductors as in Example 2, ethylene propylene rubber (manufactured by Sumitomo Chemical Co., Ltd., Espren 301) to which 0.3 parts by weight of benztriazole was added was used as the coating material for the central wire, and the coating thickness was Sao
The nominal cross-sectional area is 80 mm ² in the same way except that it is 2.0 mm.
After twisting the OC conductors at room temperature, apply room temperature curing liquid silicone rubber (SH9140 manufactured by Toray Silicone) to the outer periphery of the conductors, wrap a 100 μm thick polyester tape around the outermost layer, and leave it for 24 hours. After the liquid silicone rubber was cured, the polyester tape was removed. When the thus obtained conductor was cut and its cross section was observed, it was confirmed that the internal cavity and the outer circumference were completely filled with polymer.

Claims (1)

[Claims] 1. With one or more conductor wires pre-coated with an organic polymer being present at or near the center of a large number of conductor wire aggregates to be twisted, A method for producing a watertight stranded conductor, which comprises twisting the above aggregate at temperature, and filling at least the gaps between the conductor strands near the center of the stranded conductor with the organic polymer using compressive force during the twisting. .