JPH058530B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to electric wires and cables provided with termite resistance.

[Conventional technology] Electrical wires and cables for control, power, communication, etc. that are buried underground in termite habitats or installed underground conduits are damaged by termites, causing major problems in energy and information transmission. An accident is occurring.

As a measure against such accidents, termite-proof electric wires and cables having a structure in which nylon is provided in the outermost sheath of electric wires and cables have been put into practical use in recent years.

Nylon's termite resistance is said to be due to its physical hardness rather than its chemical composition; in fact, epoxy,
Rigid plastics such as polycarbonate and polyacetal have been proven to have excellent termite resistance.

In this way, the termite-proofing properties of nylon are certain.
This nylon is applied as the outermost sheath of electric wires and cables by extrusion or tape wrapping.

On the other hand, for underground wires and cables, including these termite-proof wires and cables, damage, trauma, deterioration, deterioration, etc. may occur after the wire and cable installation work is completed or during actual use. Withstanding voltage tests and insulation resistance tests are increasingly being performed not only on the insulator, but also on the sheath, in order to confirm the integrity of the cable.

Among these, in particular, it is necessary to measure the withstand voltage and insulation resistance characteristics of the sheath portion by providing appropriate electrodes inside and outside the sheath. The electrodes within the sheath can generally utilize a metal layer as the outer shielding layer of the cable;
As the external electrode outside the sheath, metal tape or metal braid can be considered, but it is not only economically viable to provide such metal electrodes over the entire length of the cable, but also poses problems in terms of handling and installation workability. Up until now, vinyl and polyethylene sheaths have been coated with conductive paint or extruded with a conductive compound.

[Problems to be solved by the invention] For electric wires and cables with a nylon sheath on the outermost layer, compounds or paints that can be used as external electrodes have not yet been developed or put into practical use. The problem is that it is not possible to measure the withstand voltage or insulation resistance of wires and cable sheaths.

In particular, in electric wires and cables that use high-density polyethylene for the sheath and have a nylon termite layer on top, it is extremely difficult to understand the integrity of the sheath, as high-density polyethylene has some concerns about thermal or environmental stress cracking. important, and an electrode material suitable for nylon is desired.

The present invention is based on the above, and provides a novel termite-proof wire and cable provided with a conductive layer that functions as an external electrode to enable measurement of the withstand voltage or insulation resistance of the sheath of a termite-proof wire/cable having a nylon sheath.・The purpose is to provide cables.

[Means for Solving the Problems] The electric wires and cables of the present invention include a nylon layer provided on the outer periphery of a plastic or rubber sheath, and further coated with a conductive paint made of acrylonitrile-butadiene rubber to which carbon black is added. It is characterized by:

The sheath material of the present invention includes plastic,
Any rubber may be used, and examples thereof include polyethylene, polyvinyl chloride, chloroprene, ethylene propylene, and the like.

Examples of nylon include nylon 6, 66, 610, and nylon 11 and 12, with nylon 11 and 12 being preferred in consideration of termite resistance, processability, moisture absorption, and handleability.

Of course, as long as it is mainly composed of nylon, it may be a copolymer or a blend.

The thickness of the nylon layer varies depending on the size of the cable, but it is generally about 1 mm thick, and may be thinner for small cables and thicker for large cables. be.

Acrylonitrile-butadiene rubber is used for adhesion to the carbon black binder and nylon sheath layer.

The properties of acrylonitrile-butadiene rubber change depending on the amount of acrylonitrile, but it is 15 to 50% by weight.
It has been confirmed that amounts of acrylonitrile up to

The molecular weight ranges from liquid with a molecular weight of 10,000 to so-called rubber and so-called molecular weight, and any of these can be used.

It is advantageous to add small amounts of antidegradants to the polymer, such as 4,4'-thiobis-(6-tert-butyl-3-methylphenol).

The carbon black for imparting conductivity may be one such as channel black, furnace black, acetylene black, etc. that can be added to acrylonitrile-butadiene rubber to impart conductivity.

The amount is acrylonitrile-butadiene rubber
It is preferably about 50 to 300 parts by weight per 100 parts by weight.

A composition containing acrylonitrile-butadiene rubber and carbon black is used as a paint by dissolving it in a suitable solvent such as methyl ethyl ketone.

The paint contains 400 parts by weight of acrylonitrile-butadiene rubber and carbon black composition.
A preferred range is 2000 parts by weight.

[Example] Example An OF in which a 1000 mm ² copper conductor is wrapped with insulating paper, an aluminum sheath is applied to the periphery of the core impregnated with insulating oil, and the outer periphery is covered with a polyvinyl chloride sheath with a thickness of 7 mm.
used cable.

The outer periphery of the polyvinyl chloride sheath was extruded and coated with nylon 11 to a thickness of 1.0 mm.

Next, acrylonitrile-butadiene rubber 10
A conductive paint consisting of 10 parts by weight of acetylene black and 80 parts by weight of methyl ethyl ketone was applied.

The conductivity of the conductive layer was 70 Ω-cm, which was sufficient for use as an external electrode for measuring the withstand voltage and insulation resistance of the sheath.

The aluminum sheath of this cable is the conductive layer (ground)
As with the withstand voltage test between the two electrodes, the insulation resistance calculated back from the leakage current was measured, and sufficient electrode action was confirmed. On the other hand, when the cable was subjected to an abrasion test 20 times each using a dry cloth tape and a lubricated cloth tape, no peeling of the paint or friction occurred with either tape.

Comparative example The same OF cable as in the example was used.

Nylon 11 is placed around the outer circumference of the PVC sheath.
It was applied to 1.0mm.

Subsequently, a conductive paint consisting of 10 parts by weight of vinyl chloride-vinyl acetate copolymer, 10 parts by weight of acetylene black, and 80 parts by weight of a 2:1 mixed solvent of methyl ethyl ketone and perchloroethylene was applied.

The conductivity of the conductive layer was 60 Ω-cm, and it was confirmed that it could be used as an external electrode.

However, in the dry cloth tape and wet cloth tape abrasion tests, the paint layer on the nylon sheath disappeared after 6 and 4 times, respectively.

[Effect of the invention] As explained above, according to the present invention, manufacturing,
It becomes possible to provide termite-proof wires and cables coated with a conductive paint that is extremely advantageous for finding defects, abnormalities, etc. in sheaths after transportation and installation.

Claims (1)

[Claims] 1. A termite-proof electric wire/cable, characterized in that a nylon layer is provided on the outer periphery of a plastic or rubber sheath of the electric wire/cable, and a conductive paint made of acrylonitrile-butadiene rubber added with carbon black is coated on the outer periphery. .