JPH044936B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical Field of the Invention) The present invention relates to a termite-proof heat-shrinkable tube used, for example, to prevent termite damage to buried plastic pipes, electric wires and cables, or their connections. (Background of the Invention) Electric wires and cables are exposed to various usage conditions and expropriation environments, and their lifespans are usually determined by electrical and mechanical deterioration of their jackets and insulators. Among these, many accidents have been reported in which electricity and communication suddenly become unavailable due to damage caused by termites, rats, bat moths, etc. In addition, termite damage also occurs to plastic pipes installed for water supply or sewage. Although there are slight differences in termite prevention methods for electric wires and cables depending on the type of termites, environment, etc., the basic methods are (a) imparting termite-proofing properties to the electric wires and cables themselves, and (b)
It can be roughly divided into two types: providing termite protection around the installation of electric wires and cables. In other words, method (a) involves devising the structure and materials of the wires and cables, providing a layer containing termiticides, or applying termiticides, and method (b). One method is to apply anti-termite treatment to the soil along the installation route. Among these methods, from the viewpoint of processing of electric wires and cables and mainly from the viewpoint of cost, the method of adding a termiticide to the sheath material of electric wires and cables has been most commonly adopted. In particular, so-called dorin-based drugs such as aldrin, deirdrin, and endrin were mainly used, but it has become clear that they are harmful to humans and animals and cause environmental pollution, and are now being used.
Its use is prohibited (Cabinet Order of October 2, 1981)
No. 302). Therefore, instead of using drugs, more and more measures are now being taken from the viewpoint of structural design and material design.
That is, methods such as protecting the cable itself with a metal sheath or adding a coating layer such as nylon on the cable sheath are beginning to be adopted. However, no matter which of the cable structures mentioned above, the connecting parts of electric wires and cables must be independently treated for termites. That is, cable connections are usually covered with lead tape or the like, and although they are fairly termite-proof, they are not perfect. Therefore, applying an anti-corrosion tube containing an anti-termite agent to the outermost sheath of the cable connection part is effective in making the anti-termite property more complete. In particular, if the anti-corrosion tube is heat-shrinkable, it will be easier to apply the coating. That is, the heat-shrinkable tube can be heat-shrinked by simply heating it with a gas burner, torch lamp, etc. after being inserted into the cable connection part, and can completely and reliably cover the cable connection part. Here, a heat-shrinkable tube is a tube molded product made of a thermoplastic resin composition that is expanded and deformed under heating and then cooled and solidified while maintaining the deformation strain.For example, it is made as follows. . A tube molded product made from a thermoplastic resin composition such as cross-linked polyethylene is heated to a temperature higher than its softening point or crystal melting point, and is expanded by applying an external force such as internal pressure. Cool to below melting point temperature. The deformation strain imparted to the tube by this operation is fixed, and even if external forces such as internal pressure are removed, the tube hardly returns to its original shape and maintains its expanded shape. After inserting this into a plastic pipe, electric wire, cable, etc., the tube is heated to a temperature above its softening point or crystal melting point using a heating device such as a gas burner or torch lamp, and the deformation strain frozen and fixed inside is eliminated. Recovers to almost its original shape. In order to impart termite-proofing properties to the heat-shrinkable tube as described above, a termite-proofing agent may be added to the thermoplastic resin composition used. Plastic containing extract of Japanese cypress wood as a thermoplastic resin composition that can be used for termite-proof heat-shrinkable tubes (Japanese Utility Model Publication No. 34623/1983)
Plastics containing 10% by weight or more of creosote oil (Japanese Patent Publication No. 57-30787), PVC containing polyester plasticizers (molecular weight 3000 or more) (Japanese Patent Publication No. 8810/1983), X is B _r m=1 to 4 Y is a C ₁ to C ₄ alkylidene group or A resin composition containing 5 to 50 parts by weight of one or more of the following compounds (Japanese Utility Model Publication No. 57-140016), mixed with fenitrothion, phoxim, or chlorpyrifos, and zinc octylate or zinc versatate, etc. PVC (JP-A-58-25012, JP-A-58-142927, JP-A-58-169810) and the like are known. The termiticide used in heat-shrink tubes for corrosion protection at the connections of electric wires and cables must have excellent long-lasting anti-termite effects, as plastic pipes, electric wires and cables are used for long periods of time. In particular, volatilization during material mixing, tube extrusion, and expansion processing under heating is extremely low, and specifically, it has thermal stability even under conditions of several minutes to one hour at temperatures of about 160 to 220 degrees Celsius. is desirable. It is desirable that no blooming occurs even after molding. Excellent thermal stability is required even when heat-shrinking with a burner or the like during construction.
In the case of cable connections, it is of course undesirable for the mechanical properties, electrical properties and other properties of the base material to be impaired after installation. However, there has not been a heat-shrinkable tube for corrosion protection that satisfies the above characteristics and contains a termiticide that is also excellent in termitproofing effects. (Disclosure of the Invention) As a result of various studies, the present inventors have discovered that a specific organic phosphorus agent that has an excellent anti-termite effect and has low thermal decomposition properties especially at high temperatures can be used for plastic pipe materials, electric wires, etc.
When blended with vinyl chloride resin (PVC), which is widely used in cable joint materials, it was found that blooming did not occur, and based on this knowledge, the termite-resistant heat-shrinkable tube of the present invention was completed. That is, the present invention provides isopropyl 2-
This is a termite-proof heat-shrinkable tube containing [ethoxy(isopropylamino)thiophosphoryloxy]benzoate. In addition, isopropyl 2-[ethoxy(isopropylamino)thiophosphoryloxy] according to the present invention
Benzoate is commonly referred to as isofenphos. In the present invention, this isofenphos is added to the thermoplastic resin composition of the heat-shrinkable tube in an amount of usually 0.01 to
The content is 10% by weight, preferably 0.05 to 5% by weight. Mixing with the resin can be carried out by conventional methods (for example, by calender roll, Banbury, etc.). In the present invention, as a base resin for the thermoplastic resin composition, for example, in addition to PVC, polyolefins such as polyethylene, ethylene-α-olefin copolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, etc. Union,
Alternatively, a composition may be used in which isofenphos is easily mixed by blending chlorinated polyethylene or other various synthetic rubbers. After the thermoplastic resin composition is extruded to obtain a tube molded product, chemical crosslinking or electron beam irradiation crosslinking is performed. When crosslinking PVC with electron beam irradiation, it is advisable to add a required amount (for example, 2 to 10 parts by weight) of a polyfunctional monomer in advance. The thermoplastic resin composition may contain pigments, fillers, stabilizers, crosslinking agents, and the like, if necessary. The crosslinked tube molded product is heated to a temperature higher than the softening point or crystal melting point of the resin composition to mechanically expand the diameter of the tube molded product. Next, the expanded state is cooled to room temperature to obtain the heat-shrinkable tube of the present invention. The termite-proof heat-shrinkable tube of the present invention, which is made by blending isofenphos into the tube material, is superior to those using other termiticides in terms of not only its termite-proofing effect, but also the electric power required for electric wires and cables. The following experiment shows that it also has excellent physical properties. (Test termiticide) Table 1 shows the substances used as the test termiticide.

[Table] Nhosu


Regarding the termiticide properties of the drugs themselves shown in Table 1, the following termicidal efficacy test was conducted, and the results shown in Table 2 were obtained. Anticide efficacy test (knockdown test) (a) Diluent: acetone drug concentration 0.1% and 1%
And so. (b) Test termites: Termite worker ants (c) Test method: The termiticidal activity of the drug was evaluated based on the mortality rate after 24 hours (at 25°C) according to the method specified by the Japan Termite Countermeasures Association.

[Table] (Test sheet) PVC (degree of polymerization: approx. 1100-1300) 100 parts Plasticizer (phthalate ester) 50 parts Filler (heavy calcium carbonate) 30 parts Stabilizer (tribasic lead sulfate) From 5 parts The termiticide shown in Table 1 was mixed with a plasticizer into a PVC compound, mixed with a roll at 160℃ for about 10 minutes, taken out into a 1mm thick sheet, and further
Preheated at 160℃ for 10 minutes and pressed for 10 minutes,
A 13 cm x 17 cm sample sheet containing 3% termiticide was obtained. This 1 mm thick PVC sheet was covered on a 30 mm square pine sapwood, the overlapping portions and end portions were completely sealed with adhesive tape with metal tape, and the sheet was subjected to a field test. Field tests were conducted for three years,
The results are shown in Table 3.

[Table] Table 4 also shows the electrical properties (insulation resistance) of the PVC sheets obtained in the same manner.

【table】

[Table] First, it can be seen from Table 3 that Prothiophos has sufficient anti-termitic and termiticidal properties as a drug itself, but in a field test, it was found that PVC with 3% added
Even a sheet with a thickness of 1mm was penetrated. Therefore, no anti-termite effect can be expected even if it is mixed into electrical wire/cable coatings. As shown in Table 4, chlorpyrifos has an insulation resistance value of approximately 1/143 of that of a non-additive PVC sheet with 3% additive.
3 (a decrease of more than 3 digits), making it unsuitable as a corrosion-proofing material for electric wires and cables. In this respect, for isofenphos and fenitrothion, the decrease is only in the double digit range, and the resistance of 10 ¹² Ω·cm, which is generally required as an anticorrosion material for electric wires and cables, can be maintained. (Tube extrusion test) A PVC compound with the same composition as the test sheet was extruded using an extruder as a tube material to obtain a tube, which was then crosslinked by electron beam irradiation.
This was heated to expand the diameter of the tube approximately twice, and while maintaining the expanded state, it was cooled to room temperature to obtain a heat-shrinkable tube. An appropriate amount of sample was taken from this heat-shrinkable tube, and the remaining amount of the added termiticide in the PVC was determined. The results are shown in Table 5.

[Table] As shown in Table 5, most of the added amount of fenitrothion decomposes and evaporates, making it impractical. Although it is possible to improve the survival rate to some extent by lowering the material temperature during extrusion as much as possible, it is necessary to suppress the heat generation in the extruder, so the screw rotation speed must be lowered. First, the extrusion speed decreases, and the extrusion processing time increases, that is, the extrusion processing cost inevitably increases. On the other hand, isofenphos was added
Most of the PVC compounds remain,
From this point of view as well, it can be seen that it is an extremely effective termiticide. Isofenphos does not cause blooming from the tube surface even after molding. As mentioned above, the heat-shrink tube made of a thermoplastic resin composition containing isofenphos as an active ingredient not only has an excellent termite-proofing effect, but also prevents the volatilization and decomposition of the termiticide during extrusion processing and heat shrinkage. This is extremely rare.

Claims (1)

[Scope of Claims] 1. A termite-proof heat-shrinkable tube containing isopropyl 2-[ethoxy(isopropylamino)thiophosphoryloxy]benzoate.