JPH058529B2 - - 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 electric wires and cables that are underground or in conduits, including these termite-proof electric wires and cables, damage, trauma, deterioration, deterioration, etc. may occur to the electric wires and cables after the installation work of the electric wires and cables 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 providing such metal electrodes along the entire length of the cable is not only economically problematic, 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 wire/cable of the present invention is made by providing a nylon layer on the outer periphery of a plastic or rubber sheath, and further adding carbon black to a mixture containing alcohol-soluble nylon and an epoxy compound on the outer periphery. It is characterized by being coated with conductive paint.

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.

Alcohol-soluble nylons include those that are soluble in lower aliphatic alcohols such as methanol and ethanol, and mixtures of these and chlorinated hydrocarbons such as trichlene.

Alcohol-soluble nylon is produced by copolymerizing raw materials,
It is made by tertiary copolymerization etc., for example,
There are 6/66/610, 6/66/11, 6/66/12, etc.
Furthermore, low molecular weight nylons such as nylon 11 and 12 are also soluble in alcohol.

In addition to such copolymers, alcohol-soluble nylons such as N-alkoxymethyl-modified nylons are also used in which nylon is reacted with formalin and alcohol to replace hydrogen in amide groups.

In short, the composition of nylon is not limited as long as it is soluble in a solvent mainly composed of alcohol.

Examples of epoxy compounds include bisphenol A type epoxy Epicote 828 (trade name of Schiel Chemical Co., Ltd.), novolac epoxy DER-438 (trade name of Dow Chemical Co.), and tetrafunctional epoxy Araldite.
One example is MI-720 (product name of Ciba Geigy).

The mixing ratio of alcohol-soluble nylon and epoxy compound is not particularly limited, but is between 8:2 and 2:2.
Values up to 8 are particularly good.

Examples of the carbon black for imparting conductivity include channel black, furnace black, acetylene black, and the like. The amount thereof is preferably about 50 to 300 parts by weight per 100 parts by weight of the mixture of alcohol-soluble nylon and epoxy compound.

A composition containing alcohol-soluble nylon, an epoxy compound, and carbon black is used as a paint by dissolving it in a suitable solvent such as ethyl alcohol or a mixed solution of ethyl alcohol and trichlene.

[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, 10 parts by weight of acetylene black was added to a mixture consisting of 6 parts by weight of ternary copolymerized nylon consisting of nylon 6/66/610 and 4 parts by weight of bisphenol A type epoxy, and this was mixed with 80 parts by weight of ethyl alcohol. A diluted conductive paint was applied.

The conductivity of the conductive layer was 85 Ω-cm, which was sufficient for use as an external electrode for measuring the withstand voltage and insulation resistance of the sheath.

This cable's aluminum sheath and 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 metal ethyl ketone and perchlorethylene 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 nylon layer is provided on the outer periphery of the plastic or rubber sheath of the electric wire/cable, and a conductive paint made by adding carbon black to a mixture containing alcohol-soluble nylon and an epoxy compound is coated on the outer periphery. Ant-proof wires and cables.