JPS629610Y2 - - 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 insulation 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, partially exposed areas such as above ground are inferior in terms of flame resistance and combustion resistance. The thicker the material, the more expensive it is. For this reason, a termite-proofing layer is generally provided between the inner layers of the cable as described above. 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, etc., it is impractical because it requires unnecessary metal shielding. In addition, as in the case mentioned 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 objective by incorporating a glass powder, which is known not to be damaged by termites, into the cable sheath material, or by combining this glass powder with the glass powder, which is also known not to be damaged by termites. A hard plastic resin (such as nylon), so-called anti-termite plastic resin powder, and copper powder are appropriately combined and extruded using an extruder to form a sheath with anti-termite properties.

That is, the glass powder uniformly mixed in the sheath material acts as a hard substance that inhibits termites from biting off and prevents feeding damage. In addition, when this glass powder is used in combination with a hard resin such as nylon or copper powder, the resin inhibits termites from biting off, just like the glass powder mentioned above.
Copper powder utilizes the physiological action of copper metal against termites to prevent termites from approaching and progressing, thereby preventing feeding damage.

The shape of the glass powder used here may be, for example, flaky or granular as finely pulverized glass, and its size is preferably about 100 to 1000 μm. In other words, if it is too small (less than 100 μm),
It is no longer possible to expect an inhibitory effect on the chewing of termites, and conversely, if the particle size exceeds 1000 μm, the above-mentioned inhibitory effect can no longer be expected because the spacing between powders is too large, and at the same time, compatibility deteriorates and the sheath properties deteriorate. This is because it may cause a decrease in
Regarding the ratio of glass powder to the sheath material, from the standpoint of termite prevention, it is better to have a larger amount of glass powder. It takes a lot of effort. Therefore, according to research by the present inventors, the range within which the anti-termite effect is not lost and the sheath properties are reasonable is as follows:
A range of 10 parts to 100 parts is preferred.

In order to make the sheath properties reasonable by reducing the amount of the glass powder, etc., it is necessary to use plastic resins such as the above-mentioned nylon, which are hard materials like the glass powder, and the above-mentioned copper powder, which is disliked by termites. They may be used in combination as appropriate. In other words, by using these powders together, the amount of glass powder etc. can be relatively reduced,
Even in that case, a sufficient anti-termite effect can be obtained due to the synergistic effect of these powders. In the case of resin powder and copper powder as well, their shape may be flaky or granular, and their size is preferably about 100 to 1000 μm for the same reason as the above-mentioned glass powder. In addition to nylon, the termite-proof plastic resin used here includes, for example, polycarbonate, hard polyvinyl chloride, high-density polyethylene, Teflon (trade name, manufactured by Dupont),
Polyester, etc.

Next, embodiments of the present invention will be described with reference to the drawings.
Figure 1 shows an example in which the above-mentioned glass powder that is not damaged by termites is mixed into the sheath material, and Figure 2 shows an example in which plastic resin powder and copper powder are combined in addition to this glass powder. shows. 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 glass powder 4 in a general sheath material 3, such as polyvinyl chloride, and the sheath 1' in the case of FIG. and copper powder 6 are uniformly mixed. 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 resin 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 contains an appropriate combination of glass powder or this powder that is not damaged by termites, and hard plastic resin powder or copper powder that is repellent to termites. This is extruded using an extruder to form a termite-proof sheath, which 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. Further, since the glass 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 appropriate combination with plastic resin powder or copper powder, the amount of glass powder blended may be relatively small, making it possible to obtain the desired anti-termite effect without stressing the sheath properties. becomes possible.

(c) Of course, what is mixed into the sheath material is
Since it is made of glass powder, 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, glass powder, plastic resin powder, copper powder, etc. using an extruder, so that it is necessary to form a termite-proof layer as an essential component of the cable 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. Can be done.

[Brief explanation of the drawing]

FIGS. 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...
...Glass powder, 5...Plastic resin powder,
6...Copper powder.

Claims (1)

[Claims for Utility Model Registration] (1) An anti-termite cable characterized in that a sheath is formed by blending glass powder into the sheath material of the cable and extruding it. (2) When blending the glass powder, at least one of a termite-resistant plastic resin powder such as nylon and copper powder is simultaneously blended. ant cable.