JPH0124007B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a cable protection pipe for underground cables. BACKGROUND OF THE INVENTION It has become common practice to bury power distribution equipment underground for reasons of public safety, aesthetics, and the like. When burying power cables, steel pipes, fume pipes, asbestos pipes, vinyl chloride pipes, etc. are used as protective pipes to protect power cables. However, since steel pipes are heavy, they require heavy equipment for transportation and installation, and special tools are required for cutting and threading when making connections, making piping work difficult. Huium pipes are the heaviest among cable protection pipes, and are not as easy to transport and install as steel pipes.Also, because they are heavy and brittle materials, they have poor impact strength against falling objects and are prone to losses during transport and piping sites. Also, since the watertightness and connection strength of the joints are insufficient, it is necessary to tighten the joints with concrete. On the other hand, even after installation, cables are susceptible to impact from pickaxes and the like, and damage to the cables may impede the stable supply of power. Although asbestos-cement pipes are relatively lightweight, they have a high water absorption rate, so their physical properties change greatly and their strength is low. Therefore, they must be protected using the concrete shoring method, and the pipes must be protected during the concrete curing period. Since backfilling cannot be performed, it is not an appropriate material for urban areas, shopping streets, roads with heavy traffic, etc., as it will have a significant impact on surrounding residents and citizens' lives during the construction period. In addition, when ordinary PVC pipes are used as cable protection pipes for underground cables, the heat generated by the cables causes them to reach high temperatures of over 70°C.Under these conditions, the rigidity and flat compressive strength decrease, reducing the strength of the underground cables. It has the drawback that it is susceptible to damage such as cracking or penetration when subjected to impact from a sharp pickaxe or the like. In order to improve these drawbacks of general PVC pipes, post-chlorinated PVC resin, which has a higher heat distortion temperature than PVC resin, is used in combination with PVC resin, and a small amount (55%) of chlorinated polyethylene is added to this mixture. A vinyl chloride resin composition has been proposed that improves the impact strength without significantly reducing the heat resistance of the post-chlorinated vinyl chloride resin by adding (up to 10% by weight). however,
Tubes obtained by extrusion molding from such resin compositions have low impact strength at low temperatures, and cannot be used satisfactorily as cable protection tubes for underground cables, which require more severe performance. Ta. The objects of the present invention are that the pipe can be transported and installed manually, that the piping work is easy and does not require auxiliary construction methods such as concrete clamping, and that the pipe body temperature due to heat generated when energized is at least 80°C. It must be strong enough to withstand and not deform due to earth pressure or wheel loads, and must be strong enough to withstand construction by other companies such as water, sewage, gas, etc.
An object of the present invention is to provide a cable protection pipe for underground cables that is well-balanced in terms of workability, impact strength, and heat resistance, such as preventing the pipe from being destroyed by the impact load of a pickaxe or the like. The gist of the present invention is to add 12 parts by weight or more of chlorinated polyethylene to 100 parts by weight of post-chlorinated vinyl chloride resin or post-chlorinated vinyl chloride resin mixture containing 20% by weight or less of vinyl chloride resin, and The present invention relates to a cable protection tube for underground cables, which is made of a composition in which 20 parts by weight or less is added to 100 parts by weight of vinyl chloride resin. The post-chlorinated vinyl chloride resin used in the present invention is a vinyl chloride resin that has been subjected to post-chlorination treatment, and is not particularly limited, but preferably has a chlorine content of 64 to 68% by weight, More preferably, it is 65 to 67% by weight. The degree of polymerization is also not particularly limited, but is preferably 800 to 1,400. The vinyl chloride resin used in the present invention is not particularly limited and may be one commonly used for pipes, molded products, etc., but one synthesized by suspension polymerization and having a polymerization degree of 1000 to 1500 is preferable. . The chlorinated polyethylene used in the present invention is polyethylene that has been subjected to post-chlorination treatment, and is not particularly limited, but has a low chlorine content.
Preferably 30 to 40% by weight, more preferably
33-37% by weight. In the present invention, the chlorinated polyethylene is added to 100 parts by weight of the post-chlorinated vinyl chloride resin or the post-chlorinated vinyl chloride resin mixture containing 20% by weight or less of the vinyl chloride resin, and It is added in an amount of 20 parts by weight or less to 100 parts by weight of the post-chlorinated vinyl chloride resin, and the resulting composition is extruded to obtain a cable protection pipe for underground cables. If the content of vinyl chloride resin in the post-chlorinated vinyl chloride resin mixture exceeds 20% by weight, the heat distortion temperature will decrease and the flat compressive strength at high temperatures will decrease. It is set within a range of % by weight or less. In addition, if the amount of chlorinated polyethylene added is small, the impact resistance at low temperatures will decrease and it will break easily, while if the amount added is too large, the heat distortion temperature will decrease and the flat compressive strength at high temperatures will decrease. The chlorinated polyethylene is 12 parts by weight or more based on 100 parts by weight of the post-chlorinated vinyl chloride resin or the post-chlorinated vinyl chloride resin mixture containing 20% by weight or less of the vinyl chloride resin, and It is added in an amount of 20 parts by weight or less per 100 parts by weight of the resin. The structure of the composition used in the present invention is as described above, but stabilizers, lubricants, pigments, fillers, etc. may be added as appropriate. Further, in the present invention, the above composition is extruded into a pipe shape to produce a cable protection pipe for underground cables, but the extrusion method is not particularly limited, and any known method may be adopted. good. Furthermore, the wall thickness of the underground cable protection pipe is
The thicker the material, the more preferable it is from the viewpoint of properties such as impact strength and heat resistance strength at low and high temperatures, while the thinner it is from the viewpoint of properties such as transportation, installation, workability at piping sites, and cost. However, in the present invention, these In order to maintain a balance in terms of characteristics, this ratio D/t satisfies the condition of 16 or less (for example, when D = 130 mm, 130 /t≦16, that is, t≧130/16≈8.1 mm), the wall thickness of the underground cable protection pipe may be appropriately determined. The method of using the underground cable protection tube of the present invention obtained as described above is not particularly limited, and any known method may be employed. Since the underground cable protection pipe of the present invention has the above-mentioned configuration, the Young's modulus is 1.3×10 ⁴ Kg/cm ² or more even at 80°C or 85°C, and the flat compressive strength at 80°C or 85°C is also It has the strength to withstand the buried load even if it is buried underground and the temperature of the pipe reaches 80℃ or higher. It also has a high Shalpy impact value of 20Kg・cm/cm ² or more, and has excellent impact resistance without cracking or penetrating even when subjected to impact with a pickaxe, etc. In addition, after 100 hours of sunshine irradiation, the shear pea impact value is as high as 14.5 Kg・cm/cm ² or more, and the weather resistance is also excellent. Since it is mainly made of vinyl chloride resin, it is lighter than steel pipes and has good workability in piping and backfilling. Therefore, it is suitably used as a protective tube for underground cables, which has a good balance of workability, impact strength, and heat resistance. The present invention will be explained below with reference to Examples. Note that the term "parts" hereinafter simply means "parts by weight." Example 1 Predetermined amounts of vinyl chloride resin (polymerization degree 1000) shown in Table 1, post-chlorinated vinyl chloride resin (chlorine content
67% by weight) and chlorinated polyethylene (chlorine content
35% by weight), 2.5 parts of tin-based stabilizer, 1 part of calcium stearate, 1 part of stearic acid, and 1 part of paraffin wax were mixed uniformly and then extruded using a twin-screw extruder to form a product with an outer diameter of 147 mm and an inner diameter of 130 mm ( wall thickness
8.5mm) pipe was obtained. Using the obtained pipe, a flattening compression test (load at 2.5% flattening) was conducted at 80°C and 85°C in accordance with JISC-8430, and the results are shown in Table 1. or
Shalby impact strength was measured at 20℃ in accordance with JISK-7111, and at 0℃ and 80℃ in accordance with JISK-3801.
The results of the pickaxe test at 85°C are shown in Example 1.
It is shown in Table 1 as follows. JISC-3801 mentioned above stipulates the testing method for porcelain insulators used in electrical circuits.
Here, using a device similar to the impact tester described in section 7.1.4 Impact Load Resistance Test, 16.16 kg was applied to the tip to correspond to the impact energy when a worker swings the pickaxe from behind overhead. A test was conducted in which a 1 m long pendulum equipped with a terminal was swung up at an angle of 95 degrees, and the terminal was struck against a pipe. For comparison, the ratios of vinyl chloride resin, post-chlorinated vinyl chloride resin, and chlorinated polyethylene were changed and measurements were carried out in the same manner as in Example 1. The results are shown in Table 1 as Comparative Example 1. Indicated. Table 1 shows that the underground cable protection pipe of the present invention, which is made of a resin composition with a vinyl chloride resin content in the range of 10 to 20% by weight, has a flattened compressive strength (2.5% flattened) of 20.9 to 23.6 at 80°C. Kg/5cm width and required strength of 20.7
Kg/5cm width or more, so in a situation where a heat resistance temperature of 80℃ is required in practical use, for example, when increasing the number of piping lines from 2 rows and 2 tiers (4 lines) to 2 rows and 3 tiers (6 lines). Can be used in In addition, the underground cable protection pipe of the present invention, which is made of a resin composition with a vinyl chloride resin content of 10% by weight or less, or a post-chlorinated vinyl chloride resin alone, optimizes the amount of chlorinated polyethylene added. By this, the flat compressive strength at 85℃ (2.5%
(when flat) is 20.8~23.5Kg/5cm width and the required strength.
Since it is more than 20.7Kg/5cm wide, it can be used not only in the above-mentioned situation where a heat resistance temperature of 80℃ is required in practice, but also in situations where a heat resistance temperature of 85℃ is required in practice, for example, when the number of pipes is 3 rows and 3. It can be used in situations where it has increased to 9 stages. Example 2 10 parts of vinyl chloride resin (degree of polymerization 1000), 90 parts of post-chlorinated vinyl chloride resin (chlorine content 67% by weight), and 14 parts by weight of chlorinated polyethylene (chlorine content 35% by weight) and tin-based stabilizer Add 2.5 parts of calcium stearate, 1 part of stearic acid, and 1 part of paraffin wax, mix uniformly, and extrude with a twin screw extruder to make a product with an inner diameter of 130 mm and a wall thickness of 8.0, 8.5, 9.0, and 9.5 mm.
obtained each pipe. Using the obtained pipe, a flattening compression test (load at 2.5% flattening) was conducted at 80°C in accordance with JISC-8430, and the results are shown in Table 2 as Example 2.

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Claims (1)

[Claims] 1. 100 parts by weight of a post-chlorinated vinyl chloride resin or a post-chlorinated vinyl chloride resin mixture containing 20% by weight or less of a vinyl chloride resin, and 12 parts by weight of a post-chlorinated polyethylene.
1. A cable protection pipe for underground cables comprising a composition which is added in an amount of not less than 20 parts by weight and not more than 20 parts by weight per 100 parts by weight of the post-chlorinated vinyl chloride resin. 2 The chlorine content of the post-chlorinated vinyl chloride resin is 64-68
% by weight of the underground cable protection pipe according to claim 1. 3. The underground cable protection pipe according to claim 1 or 2, wherein the chlorine content of the chlorinated polyethylene is 30 to 40% by weight.