JPH0914568A - Protector for underground buried pipe - Google Patents

Abstract

PURPOSE: To provide a protector wherein plastic waste is reutilized to a maximum limit and capable of recycling. CONSTITUTION: This underground buried pipe use protector 10 comprises a semicylinder part 12 half split with a cylindrical unit and a linear part 14 extended in a tangential direction from both side edges of the half cylinder part, to be formed in a substantially half cylindrical member of U-shaped section. In this protector, an underground buried pipe, for instance, a polyethylene- made corrugated flexible electric wire protecting pipe or flat type electric wire protecting pipe is coated from upward, so as to protect mechanical strength of the electric wire protecting pipe. This protector is formed by extrusion molding or compression molding using a material mixed with at least one kind of high/intermediate/low density polyethylene in cross-linked polyethylene so as to obtain 5 to 35wt.% mixing ratio of cross-linked polyethylene. In this way, polyethylene recovered from a used article is used, and the underground buried pipe use protector, having excellent shock resistance and heating compressibility and high mechanical strength, can be realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protector for underground pipes, and more particularly to a protector which is suitable for covering an upper portion of an electric wire protection tube to protect the electric wire protection tube from mechanical damage, and more particularly to recycled plastic. The present invention relates to a protector for an underground pipe, which is formed by using a material.

[0002]

2. Description of the Related Art In the case of burying an electric wire or a cable (hereinafter collectively referred to as a cable) in the ground, a plastic or metal tube generally called an electric wire protection tube is buried in the ground, and The cable runs through the pipe.
This is because if the cable is directly buried in the ground, it may be damaged by mechanical external force, for example, by a pickaxe at the time of re-digging, or by a load from above, so the cable is damaged from the external force. This is because it needs to be protected. As the electric wire protection tube, a plastic electric wire protection tube is often used. This is because the electric wire protection tube made of plastic is more flexible than the electric wire protection tube made of metal and can be easily installed, and is economical.

By the way, the electric wire protection tube made of plastic is shipped from the factory in the form of being wound around a drum or in the form of being directly wound for the convenience of storage and transportation. Therefore, there is a limit to increase the wall thickness of the pipe, and the pressure-resistant strength of the electric wire protection pipe and the pickaxe resistance during re-digging are lacking. Here, the pickaxe strength of the wire protection tube means the strength of the wire protection tube when the tip of the pickaxe hits the wire protection tube when excavating using the pickaxe and taking out the cable. It is representative of the impact strength of the tool. In particular, a corrugated flexible polyethylene pipe (a cable pipe line corresponding to JIS C3653 Annex 1) has a pipe inside as shown in FIG. 2 (indicated by 16 in FIG. 2) in order to have flexibility. The outer surface is corrugated, and the wall thickness is relatively thin to facilitate molding. On the other hand, for a flexible tube with corrugation, on the other hand, without corrugation in FIG.
The smooth tube 18 as shown in FIG. 3 is also used as a wire protection tube, but it has poor flexibility and is not suitable for protecting large-diameter cable wiring.

Therefore, in order to make up for such a lack of mechanical strength of a plastic wire protection tube, a semi-cylindrical protector having a relatively thick cross section and a semi-circular cross section is usually prepared, and the wire protection tube is mounted on the wire protection tube. It is covered with a protector so as to match the cylindrical shape. Conventionally, protectors used for such applications have been molded using new plastics such as hard polyvinyl chloride and high-density polyethylene.

[0005]

By the way, the garbage problem,
Or, with increasing concern about environmental issues, the disposal of plastic products has become a problem. Therefore, as one of the attempts to reduce the amount of waste as much as possible, it is of interest to reuse plastic waste to produce a protector. In order to respond to such circumstances and contribute to the reduction of the amount of plastic waste, an object of the present invention is to provide a protector in which plastic waste is reused to the maximum extent and which can be repeatedly recycled.

[0006]

Means and Action for Solving the Problems The present inventors have
Considering that the protector needs to have the characteristics capable of passing the impact resistance test and the heat compression test described below,
As a result of researching the conditions of the recovered plastic that can be used for the protector, the following has been found out. 1) A hard polyvinyl chloride-based material contains a halogen element, and is technically difficult to reuse. 2) High-density, medium-density, and low-density polyethylene-based materials can be easily collected in relatively large amounts, but they have poor pressurizing and compression characteristics in a heated state, and have a pickaxe resistance during digging work. Is insufficient. 3) Cross-linked polyethylene is excellent in heat resistance and mechanical strength and is easy to reuse, so it is most suitable as a recycled plastic material for protectors. However, it may be difficult to collect a large amount. Therefore, we conceived to mix cross-linked polyethylene with non-cross-linked high-density polyethylene, medium-density polyethylene, and low-density polyethylene to prepare materials with excellent properties suitable for protectors. A protector was prototyped and various experiments were accumulated to complete the present invention.

In order to achieve the above object, a protector for a buried underground pipe according to the present invention comprises a plate member having a wall surface curved in a direction orthogonal to the longitudinal direction and extending in the longitudinal direction, and is fitted to the curved wall. A protector for an underground pipe that covers an upper portion of the underground pipe by high density polyethylene, medium density polyethylene and low density polyethylene so that a mixing ratio of crosslinked polyethylene is 5% by weight to 35% by weight. It is characterized by being molded from a material obtained by mixing at least one of the above with crosslinked polyethylene.

The underground buried pipe protector (hereinafter simply referred to as protector) according to the present invention is not limited to the above-mentioned electric wire protection pipe, but mechanically protects underground buried pipes such as gas pipes and water pipes. Can be used as a protector. The cross-linked polyethylene used in the present invention generally has a gel fraction of 60% or more, and can be recovered from electric insulating coating materials such as electric wires and cables, high temperature specification pipes for hot water supply, and the like. The mixing ratio of the crosslinked polyethylene is 5% by weight to 35% by weight, preferably 1%.
It is 0% to 20% by weight. When it is 5% by weight or less,
When the heat compression property is unacceptable and the content is 35% by weight or more, the high-density polyethylene, the medium-density polyethylene and the low-density polyethylene are mixed with each other, resulting in difficulty in molding and poor impact resistance. In addition, the product quality is not uniform. High density polyethylene has a density of 0.9
40 to 0.965, medium density polyethylene has a density of 0.920 to 0.940, low density polyethylene has a density of 0.910 to 0.920, and is used for electrical insulation of electric wires, cables, etc. It can be recovered from covering materials and general packaging materials.

The shape of the protector is a plate-shaped member having a wall surface curved in a direction orthogonal to the longitudinal direction and extending in the longitudinal direction so as to cover the upper part of the underground buried pipe according to the shape. As long as there is no particular limitation. Preferably, the shape of the protector is such that a cylindrical body having an inner diameter slightly larger than the outer diameter of the underground buried pipe to be protected, for example, an electric wire protection pipe, is halved in the longitudinal direction, and further, tangentially from both side edges of the semicylindrical portion. It has a U-shape with a straight line extended. This U-shape has the advantage that the upper half of the wire protection tube can be reliably protected without coming off from the wire protection tube, and that it is easy to mold because it is semi-cylindrical. The protector according to the present invention usually has a wall thickness in the range of 10 mm to 25 mm.

By mixing with non-crosslinked polyethylene so that the mixing ratio of the crosslinked polyethylene falls within the range specified in the present invention, a molding material is prepared, and the prepared material is molded by extrusion molding or compression molding. Therefore, the protector according to the present invention can be obtained.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the accompanying drawings. Embodiment 1 FIG. 1 (a) is a perspective view of Embodiment 1 of the underground buried pipe protector according to the present invention, and FIG. 1 (b) is a sectional view taken along the line I--I. As shown in FIG. 1B, a protector 10 for a buried underground pipe of the present embodiment (hereinafter simply referred to as protector 10) is a semi-cylindrical portion obtained by dividing a cylinder having a wall thickness of 15 mm and a diameter of 107 mm into half. 12 and a straight portion 14 having a length of 30 mm extending tangentially from both side edges of the semi-cylindrical portion, and having a U-shaped cross section.
It is a substantially semi-cylindrical member having a character shape. As a result, the protector 10 has an inner diameter of 100 mm, an outer diameter of 130 mm, and a wall thickness of about 2.2 mm, which is shown in FIG.
As shown in (a) and (b), the electric wire protection tube 16 is covered.
The mechanical strength is protected. This protector 10
Is a mixture of cross-linked polyethylene of 8% by weight, high-density polyethylene of 50% by weight, and low-density polyethylene of 42% by weight. It is formed by extrusion molding. In this embodiment, the mixing ratio of low density polyethylene is a number including medium density polyethylene.

In order to evaluate the shock resistance and heat compression of the protector 10 of Example 1, the following shock resistance test and heat compression generally required by the electric power company, which is the largest consumer of electric wires, cables, etc. The test was conducted. In the impact resistance test, a length that can be freely rotated in a vertical plane about a horizontal arm axis 1
A tester equipped with a m-arm and having a 16.16 kg load (pickaxe-shaped tip) attached to the tip of the arm is used. First, a sample protector having a length of about 30 cm is left in the atmosphere of 80 ± 2 ° C for 1 hour or more in advance to adjust the condition. Next, the sample protector is quickly fixed in a direction perpendicular to the arm axis at a position about 1 m below the arm axis, and then the arm axis is naturally dropped from an angle of 95 ° to strike the sample protector. As a result, when the sample protector is not damaged such as cracking, the impact resistance is determined to be acceptable, and when the damage is generated, the impact resistance is determined to be unacceptable.

In the heat compression test, a plastic electric wire protection tube covered with a sample protector is integrally cut into a test piece having a length of 50 mm, and the test piece is left in an atmosphere of 80 ° C. or higher for 1 hour to adjust the condition. After that, this was sandwiched between flat plates of a tester (autograph), and the temperature of the test piece was 80
Five minutes after reaching ± 0.5 ° C, the test piece was compressed at a speed of 10 mm / min in the direction perpendicular to the longitudinal centerline of the test piece, and then 20.7
The flatness of the test piece when a load of kg is applied is measured.
When the flatness amount is 10% or less, the heat compression property is determined to be acceptable, and when the flatness amount is 10% or more, the heat compression property is determined to be unacceptable.

The protector 10 of Example 1 was subjected to an impact resistance test, and a heat compression test in combination with the corrugated flexible wire protection tube 16. The evaluation results are as shown in Table 1. In the evaluation of Table 1, ◯ means pass, and x means fail. As shown in FIG. 4, when the protector 10 protects the corrugated flexible wire protection tube 16, the combination with the wire protection tube is shown in Table 1 as "FIG. 4". Further, in Examples 2 to 5 and Comparative Examples 1 to 3 described later, Table 1 and Table 2
5 shown in combination with the electric wire protection tube of FIG. 5 shows a smooth electric wire protection tube 18 shown in FIG. 3 in place of the corrugated flexible electric wire protection tube 16 of FIG. And a case where the protector 10 is covered and protected as shown in (b).

[Table 1]

[0015] prepare a protector Examples 2-5 dimensions and composition shown in Example 2-5 Table 1, it is also shown in Table 1 "4" or wire protecting tube and combined in accordance with "5", for each Tests of impact resistance and heat compressibility were conducted. The results are as shown in Table 1.

Comparative Examples 1 to 3 As shown in Table 2, as shown in Table 2, except that molding was performed with a molding material that does not fall within the range of the mixing ratio specified in the present invention, the dimensions shown in Table 2 Comparative Example protectors 1 to 3 similar to Example 1 or Example 4 were manufactured, and the impact resistance test and the heat compression test were performed in the same manner as in Example 1, and the results are shown in Table 2.

[Table 2]

As is clear from the evaluation results of Examples 1 to 5, the protector using the materials in the mixing ratio range specified in the present invention is excellent in both impact resistance and heat compression. On the other hand, as is clear from the evaluation results of Comparative Examples 1 to 3, the protector using the material out of the range of the mixing ratio specified in the present invention fails in either impact resistance or heat compression property. In addition, the protector 10 according to the first to fifth embodiments.
Has a U-shaped cross section, it is difficult to separate from the corrugated flexible wire protection tube 16 or the smooth wire protection tube 18.
Since the upper half of the electric wire protection tubes is securely protected in strength, the electric wire protection tubes are not deformed flat due to the load from above, so that the cables therein are not damaged. Further, since the protector 10 of the first to fifth embodiments is made of recycled plastic, it helps to solve the dust problem and the material cost is low. In the first to fifth embodiments, as shown in FIG. 4B or FIG. 5B, the protector in which the linear portion 14 is relatively short is used, but the protector shown in FIG. 4C and FIG. As shown, it is also possible to use a protector in which the linear portion 14 is lengthened to almost the same depth as the bottom of the corrugated flexible electric wire protection tube 16 or the smooth type electric wire protection tube 18.

Although the protector according to the present invention has been described above by taking the electric wire protection tube as an example, the protector according to the present invention can be used as a protector for a buried underground pipe other than the electric wire protection pipe such as a gas pipe or a water pipe. You can also

[0019]

According to the constitution of the present invention, at least one of high-density polyethylene, medium-density polyethylene and low-density polyethylene is cross-linked so that the mixing ratio of cross-linked polyethylene is 5% by weight to 35% by weight. By molding the protector with a material obtained by mixing it with polyethylene, it is possible to realize a protector for a buried pipe which is satisfactory in mechanical strength. Moreover, by using polyethylene that can be easily recovered in large quantities from the electric insulation coating material of cables or general packaging materials, etc., a protector in which plastic waste is reused to the maximum extent is realized. Also,
Since polyethylene is used as the material instead of polyvinyl chloride, the underground pipe protector according to the present invention can be repeatedly recycled.

[Brief description of the drawings]

1 (a) is a perspective view of a first embodiment of a protector for an underground pipe according to the present invention, and FIG. 1 (b) is a line II of the protector for an underground pipe in FIG. 1 (a). FIG.

FIG. 2 is a partial sectional side view of a corrugated flexible electric wire protection tube.

FIG. 3 is a partial sectional side view of a smooth type electric wire protection tube.

4 (a) and 4 (b) are a partial cross-sectional side view and a transverse cross-sectional view taken along the line II-II showing a state in which a corrugated flexible electric wire protection tube is protected by a protector, respectively. FIG.
(C) is a cross-sectional view of a protector of a modified example.

5 (a) and 5 (b) are a partial cross-sectional side view and a cross-sectional view taken along the line III-III, respectively, showing a state in which the smooth type wire protection tube is protected by a protector. FIG. 5 (c)
[Fig. 6] is a cross-sectional view of a protector of a modified example.

[Explanation of symbols]

 10 Example 1 of protector for underground pipe according to the present invention 12 Semi-cylindrical part 14 Straight part 16 Flexible wire protection tube with wave 18 Smooth type wire protection tube

Claims (1)

[Claims] 1. A protector for an underground buried pipe, which comprises a plate-shaped member having a wall surface curved in a direction orthogonal to the longitudinal direction and extended in the longitudinal direction, and covers the upper part of the underground buried pipe according to the curved wall. A material obtained by mixing at least one of high-density polyethylene, medium-density polyethylene and low-density polyethylene with cross-linked polyethylene so that the mixing ratio of cross-linked polyethylene is 5% by weight to 35% by weight. Underground pipe protector characterized by being molded.