JPS629609Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of an ant-proof cable.

Recently, most power cables or communication cables are installed underground.

Cables laid underground in this way often suffer from damage from termites living underground, especially the Japanese termite. That is, termites attach to the outer surface of the cable underground and bite through the cable sheath, causing damage. Water from the ground enters through the damaged parts,
This significantly shortened the life of the cable. In some cases, they would penetrate the sheath and even damage the insulator layer, leading to accidents such as dielectric breakdown.

In order to protect cables from termite damage, the following various methods have been proposed.

(1) A method in which a powerful chemical that kills termites is mixed into the sheath material and extruded to coat it, or mixed into a paint and applied to the sheath surface.

(2) Nylon resin, which is known to be resistant to termite damage, is coated on the outermost layer of the cable, or between the internal layers of the cable (for example, between the sheath and the insulation layer), either alone or A method in which metal is laminated with tape, etc.

(3) The inner part of the polyvinyl chloride sheath has a molecular weight of approx.
A method in which more than 3,000 polyester plasticizers are blended to provide anti-termite properties.

(4) A method in which copper tape, a metal that termites dislike, is placed between the internal layers of the cable.

(5) A method in which the cable sheath is formed from tape or pipe made of various metals (iron, brass, etc.) that are not susceptible to termite damage, and a protective rubber or plastic layer is placed on top of this.

However, since the method (1) above uses a powerful chemical, there is a risk of harm to workers during production, which is undesirable from a sanitary standpoint. Furthermore, during installation, there is a risk that the material will be leached into the ground, causing soil contamination problems, which is also undesirable. Furthermore, in the methods (2) to (5) above, each requires an independent termite-proofing layer that is separate from the essential constituent layers of the cable, which increases costs in terms of materials and manufacturing. In particular, the above
Not only when metal tapes or pipes (4) and (5) are used, but also when using nylon (2) above, it is possible for small diameter ones, but extrusion coating is necessary for large diameter ones. Since it is almost impossible to do so, it must be rolled up or attached vertically, which increases the number of manufacturing steps and increases costs. In addition, in method (2) above, nylon resin has weak mechanical strength, water resistance, acid resistance, alkali resistance, etc., as well as poor flexibility and flammability, compared to polyvinyl chloride, which is a general sheath material. and expensive. Therefore, if this nylon is coated as the outermost layer of the cable, it is ideal in terms of its anti-termite effect because the termite-proof layer is located on the surface that is in direct contact with the underground soil, but it is easily damaged. There is a problem that the anti-termite effect is lost due to numerous scratches during handling or severe damage due to moisture under various conditions such as acidity or alkalinity underground. Furthermore, if the coating layer is made too thick, it loses flexibility and is inconvenient to handle. In addition, portions that are partially exposed above the ground are inferior in terms of flame resistance and combustion resistance. The thicker the material, the more expensive it is. For this reason, an anti-termite layer is generally used.
As mentioned above, it is often provided between the internal layers of the cable. That is, in many cases, some form of sheath or protective layer is provided on the anti-termite layer. In some cases, the nylon layer is made considerably thinner by laminating it with metal tape. With this structure, it is possible to obtain a termite-proof cable that is flexible and has the same sheath characteristics as a normal cable, but from the point of view of termite-proofing effect, it is difficult to obtain a termite-proof cable that has not been subjected to any termite-proofing treatment. Because it is in direct contact with the underground soil, the sheath part is also subject to damage by termites. During this initial feeding damage, termites are prevented from advancing once they reach the inner termite-proof layer, but once a feeding damage passage is formed in the sheath, moisture in the ground The termite-proofing effect of nylon is significantly reduced due to the infiltration of termites, and there is a risk that the termite-proofing effect of the nylon will be destroyed by another attack by termites on this feeding damage passage site. Therefore, the long-term termite-proofing effect is still incomplete. This is especially true if the nylon layer is thin. Even in the case of lamination with metal tape, if the thin layer of nylon is damaged by moisture, the metal will corrode and become weak, so there is a risk of it being torn by termites in the same way as above. Also, in method (3),
Since polyvinyl chloride containing a polyester plasticizer is easily hydrolyzed, once the ordinary polyvinyl chloride on the outside is eaten by termites and a damage passage is formed, the same situation as described above occurs. If the sheath is corroded as described above, the electrical balance of the entire cable will be disrupted, which may adversely affect the electrical properties of the cable, particularly the withstand voltage properties. In addition, in methods (4) and (5) above, using metal tape or pipes
In the case of low-voltage cables, this method is impractical because it requires unnecessary metal shielding. In addition, as in the case described above, these metal tapes or pipes are covered with sheaths, rubber, or plastic layers that are not treated with anti-termite treatment. As the metal corrodes and breaks due to infiltration, the anti-termite effect is significantly reduced and there is a risk that it will break.

The present invention has been made in view of the conventional circumstances as described above. The purpose is to provide a termite-proof cable that is harmless, inexpensive, easy to manufacture, and exhibits an ideal termite-proofing effect.

The present invention achieves this object by incorporating powder of a plastic resin known not to be damaged by termites, a so-called termite-resistant plastic resin, such as the above-mentioned nylon powder, into the cable sheath material. Copper powder, which is repellent to termites, is blended and extruded using an extruder to form a termite-proof sheath.

In other words, the above-mentioned resin powder uniformly mixed in the sheath material acts as a hard resin that inhibits termite chewing and prevents damage, and at the same time, when used in combination with copper powder, the copper metal has a physiological effect on termites. This prevents termites from approaching and progressing, thereby preventing feeding damage.

As the above-mentioned nylon as a plastic resin which is not damaged by termites, for example, nylon 66, nylon 6, nylon 12, nylon 11, etc. can be used. Examples of other resins include polycarbonate, hard polyvinyl chloride, high-density polyethylene, Teflon (trade name, manufactured by DuPont), polyester, and the like.

When blended, the powder shape may be finely pulverized nylon or the like, for example, in the form of flakes or granules, and the size thereof is preferably about 100 to 1000 μm. In other words, if the powder is too small (less than 100 μm), no inhibitory effect on termite chewing can be expected, and conversely, if it exceeds 1000 μm, the spacing between the powders is too large and the above inhibitory effect cannot be expected. This is because the compatibility may deteriorate and the sheath properties may deteriorate. Regarding the blending ratio of powder such as nylon to the sheath material, from the standpoint of termite prevention effect, the greater the blending ratio of powder such as nylon, the better. ,
(decreased water resistance, chemical resistance, flexibility, increased flammability, etc.), which puts stress on the sheath. Therefore, according to research by the present inventors, the preferable range is 10 parts to 100 parts per 100 parts of the sheath material, as long as the anti-termite effect is not lost and the sheath properties are not unreasonable.

In order to reduce the blending amount of the nylon powder and the like so that the sheath properties are not unreasonable, it is preferable to use the above-mentioned copper powder, which is disliked by termites, in combination with the nylon powder. That is, by using copper powder in combination, the amount of nylon powder etc. can be relatively reduced, and even in that case, a sufficient anti-termite effect can be obtained due to the synergistic effect of these two powders.
In the case of copper powder as well, its shape may be flaky or granular, and its size is preferably about 100 to 1000 μm for the same reason as the above-mentioned nylon powder.

Next, embodiments of the present invention will be described with reference to the drawings.

Figure 1 shows an example in which the above-mentioned plastic resin powder that is not damaged by termites is mixed into the sheath material, and Figure 2 shows an example in which copper powder is used in addition to this plastic resin powder. show. In each figure, 1 and 1' indicate the cable sheath, and 2 indicates the inside of the cable sheath. The sheath 1 in the case of FIG. 1 contains a general sheath material 3, for example, nylon powder 4 in polyvinyl chloride, and the sheath 1' in the case of FIG. 2 contains copper powder 5 in addition to the nylon powder 4. , were mixed uniformly.
This uniform mixing is carried out in the screw or crosshead of the extruder when coating the sheaths 1, 1'. At this time, it is necessary that the melting point of the nylon powder to be mixed is higher than that of the sheath material.

As explained above, according to the termite-proof cable of the present invention, the sheath material is made of a plastic resin that is not damaged by termites, such as nylon powder, or this powder is mixed with copper powder, which is repellent to termites. Since it is extruded to form a termite-proof sheath, it has the following effects.

(b) When installed underground, the sheath, which is the surface that comes into direct contact with the soil, is treated with anti-termite treatment.
It is possible to obtain an ideal termite-proof cable that is completely free from termite damage. In other words, in the past, a termite-proofing layer was provided between the inner layers of the cable, and the outermost layer was often covered with a normal sheath that had not been treated with termite-proofing. However, once a feeding damage passage was formed in the sheath part, there was a risk that the termite-proof layer would be destroyed by moisture in the ground and subsequent attack by termites. , can provide complete termite-proof cable. Furthermore, since the sheath is not corroded at all, the electrical properties of the cable, especially the voltage resistance properties, can be maintained as they were at the initial stage of manufacture over a long period of time.

(b) The sheath has termite-proofing properties and, at the same time, the sheath material, such as polyvinyl chloride, has the same properties as a general sheath. As such, it has low mechanical strength and will not get scratched during handling, and it is not susceptible to water, acid, alkali, etc., so it will not be damaged by moisture in the ground.
That is, sufficient mechanical strength, water resistance, acid resistance,
Has alkali resistance etc. Furthermore, since the plastic resin powder is uniformly mixed and dispersed in the sheath material, the flexibility is not so poor, the handleability is good, and the sheath material can be made nonflammable. In particular, when used in combination with copper powder, the amount of plastic resin powder to be blended may be relatively small, so it is possible to obtain the desired termite prevention effect without imposing undue stress on the sheath properties.

(c) Of course, what is mixed into the sheath material is
Since it is made of plastic resin powder and copper powder, there are no problems in handling it during manufacturing, and it does not contaminate the soil during installation.

(d) In addition, during manufacturing, it is only necessary to uniformly mix and extrude the sheath material, plastic resin powder, copper powder, etc. using an extruder, so it can be used as an essential constituent layer of the cable as an anti-termite layer as in the past. Since there is no need to provide a layer with an independent structure, the number of manufacturing steps can be reduced accordingly, making it extremely economical. In this case, no special mixing device is required, and extrusion can be carried out using a normal extruder. In addition, in terms of materials, since only the appropriate amount is required, manufacturing is extremely inexpensive compared to the conventional methods of rolling tapes, laminates, or attaching them vertically, or using metal tapes or pipes. I can do it.

[Brief explanation of the drawing]

1 and 2 are longitudinal sectional end views showing each embodiment of the termite-proof cable according to the present invention. 1,1'...sheath, 3...sheath material, 4...
...Plastic resin powder, 5...Copper powder.

Claims (1)

[Scope of utility model registration request] This termite-proof cable is characterized in that the sheath is formed by blending powder of termite-proof plastic resin such as nylon or powder of said termite-proof plastic resin and copper powder into the sheath material of the cable and extruding the blend.