JP2003056758A - Synthetic resin double pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a synthetic resin double pipe having improved resistance to flame, impact and heat without impairing the advantages of a polyolefinic synthetic resin pipe. SOLUTION: The synthetic resin double pipe 10 is the polyolefinic synthetic resin pipe, for example, a polyethylene pipe 11 with its outer periphery coated with a polyvinyl chloride resin 12. For the polyvinyl chloride resin forming an outer layer, a chlorinated polyvinyl chloride resin composition is preferably used which contains 70-95 wt.pts. chlorinated polyvinyl chloride having an average polymerization degree of 500-1800 and a chloride content of 60-70 wt.%, and 5-30 wt.pts. vinyl chloride copolymer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic resin double-layer pipe, and more particularly to a synthetic resin double-layer pipe suitable as a gas transportation pipe.

[0002]

2. Description of the Related Art Heretofore, as a gas transportation pipe, a polyolefin synthetic resin pipe, for example, a polyethylene pipe has often been used because of its economical efficiency, handleability, and ease of joining. There is. However, since polyolefin synthetic resins such as polyethylene and polybutene have the drawbacks of being flammable and easily scratched, it is necessary to use a sheath pipe or the like depending on the installation site. Although it is possible to manufacture the entire pipe with a synthetic resin having excellent flame resistance, impact resistance, heat resistance, etc., it was limited to special applications because of problems in cost and joining. .

Therefore, an object of the present invention is to provide a two-layer synthetic resin tube which is excellent in flame resistance, impact resistance and heat resistance without impairing the advantages of the polyolefin synthetic resin tube. .

[0004]

In order to achieve the above object, the synthetic resin double-layer pipe of the present invention is characterized in that the outer periphery of a polyolefin synthetic resin pipe is coated with a polyvinyl chloride resin. In particular, the polyvinyl chloride resin is a chlorinated polyvinyl chloride resin having an average degree of polymerization of 500 to 1800 and a chlorine content of 60 to 70% by weight, and particularly an average degree of polymerization of 500 to 1800. And chlorine content of 60 to 70% by weight of chlorinated polyvinyl chloride 70 to
The composition is characterized by containing 95 parts by weight and 5 to 30 parts by weight of a vinyl chloride copolymer.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an end view showing an embodiment of a two-layer synthetic resin tube according to the present invention. The two-layer pipe 10 made of synthetic resin is a polyolefin synthetic resin pipe which is a pipe body, for example, a polyethylene pipe 11 whose outer periphery is coated with a polyvinyl chloride resin 12. Polyethylene pipe 11
Is formed into a pipe shape by the same extrusion molding method as the conventional one, and most of the strength of the synthetic resin double-layer pipe 10 as a pipe is the polyethylene pipe 1
1 is paying.

[0006] The polyvinyl chloride resin 12 is provided to supplement the drawbacks of the polyethylene pipe 11 such as flammability and lack of hardness, and to impart flame resistance and impact resistance. It is possible to use a general-purpose polyvinyl chloride resin as the polyvinyl chloride resin 12, and it is possible to improve the flame resistance and impact resistance of the two-layer pipe 10 made of synthetic resin by itself.

However, a general-purpose polyvinyl chloride resin does not have sufficient heat resistance and softens at 70 to 80 ° C. to cause thermal deformation. It is preferable to use a chlorinated polyvinyl chloride resin obtained by further chlorinating a vinyl chloride resin. This chlorinated polyvinyl chloride resin can further improve the heat resistance by increasing the degree of chlorination.

On the other hand, the chlorinated polyvinyl chloride resin has a drawback that if the chlorination degree is too high, the fluidity at the time of processing is lowered and the workability is deteriorated. From this, the outer layer of the synthetic resin double-layer tube 10 has an average degree of polymerization of 500 to 1800 and a chlorine content of 6 in consideration of workability and the like.
Preference is given to using 0 to 70% by weight of chlorinated polyvinyl chloride resin.

A lubricant for improving processability, such as stearic acid or its ester, can be added to the chlorinated polyvinyl chloride resin. Further, polypropylene, polyethylene, AB can be used as a modifying resin.
S, MBS, ethylene vinyl acetate copolymer, ethylene ethyl acrylate copolymer, acrylonitrile, polyolefin rubber, epichlorohydrin rubber and the like can also be added.

Further, by using the chlorinated polyvinyl chloride resin composition in which the chlorinated polyvinyl chloride resin and the vinyl chloride copolymer are mixed, the workability can be improved while maintaining the heat resistance. . This chlorinated polyvinyl chloride resin composition has an average degree of polymerization of 500 to 1800,
A composition containing 70 to 95 parts by weight of chlorinated polyvinyl chloride having a chlorine content of 60 to 70% by weight and 5 to 30 parts by weight of a vinyl chloride copolymer is most suitable.

When the average degree of polymerization of the chlorinated polyvinyl chloride resin is less than 500, the impact resistance is lowered and the average degree of polymerization is 180.
If it exceeds 0, the melt viscosity becomes high. Further, when the chlorine content of the chlorinated polyvinyl chloride resin is less than 60% by weight, the heat resistance decreases, and when the chlorine content exceeds 70% by weight, the melt viscosity becomes high.

The vinyl chloride copolymer has, for example, an average degree of polymerization of 5 having a vinyl chloride unit of 70 to 95% by weight and an N-substituted maleimide unit of 5 to 30% by weight.
It is preferable to use a vinyl chloride copolymer of 00 to 1500. 5% by weight of N-substituted maleimide unit
If it is less than the above range, the effect of improving the heat resistance of the vinyl chloride copolymer is small, and if it exceeds 30% by weight, the impact resistance is lowered and the melt viscosity is increased. Further, if the average degree of polymerization is less than 500, the impact resistance is lowered, and if the average degree of polymerization is more than 1500, the melt viscosity becomes high.

If the amount of chlorinated polyvinyl chloride in the chlorinated polyvinyl chloride resin composition is less than 70 parts by weight, the workability is lowered, and if it exceeds 95 parts by weight, heat resistance and impact resistance are lowered. When the chlorine content of the chlorinated polyvinyl chloride is low, the N-substituted maleic acid imide unit of the vinyl chloride copolymer is increased, and when the chlorine content of the chlorinated polyvinyl chloride is high, N- of vinyl chloride copolymer
By reducing the substituted maleic acid imide unit, the heat resistance, impact resistance, and moldability of the chlorinated polyvinyl chloride resin composition can be balanced.

The thickness of the polyvinyl chloride resin 12 constituting the outer layer of the synthetic resin double-layered pipe 10 is arbitrary, and the diameter and thickness of the pipe as a whole, the strength, and the characteristics of the polyethylene pipe 11 are not impaired. It can be set according to the conditions of the place of use, but normally 0.1
Appropriately about 1 mm.

A method of forming a layer of the polyvinyl chloride resin 12 on the outer circumference of the polyethylene pipe 11 is also arbitrary, and an appropriate method is adopted depending on the diameter and thickness of the entire pipe and the thickness of the polyvinyl chloride resin 12. can do. For example, it is also possible to perform extrusion molding using a conventionally used two-layer pipe die, and the polyvinyl chloride resin 12 is formed on the outer peripheral surface of the polyethylene pipe 11 which is molded in advance.
A film made of polyvinyl chloride resin 12 may be formed into a tubular shape.
A preformed polyethylene tube 11 may be inserted into this cylinder to shrink the tubular film.

Although the outer peripheral surface of the polyethylene pipe 11 and the polyvinyl chloride resin 12 may be firmly joined to each other, a layer of the polyvinyl chloride resin 12 is applied to the outer peripheral surface of the polyethylene pipe 11 with a light force. It is also possible to leave it ready for peeling. In this way, by allowing the polyvinyl chloride resin 12 to be peeled from the polyethylene pipe 11, the polyethylene pipe 1 which is the pipe body
The fusion joining of EF, HF, bat and the like similar to the conventional one can be performed for the joining of No. 1, and the piping work can be easily performed.

The synthetic resin two-layer pipe 10 in which a layer of the polyvinyl chloride resin 12 is formed on the outer layer of the pipe body made of the polyolefin synthetic resin in this way is more than the pipe of the polyolefin synthetic resin pipe alone. Since it becomes excellent in flame resistance, impact resistance, and heat resistance, for example, as shown in FIG.
It is possible to use the synthetic resin double-layer pipe 10 as a gas transportation pipe in the common groove 23 in which 2 is laid, and it is not necessary to separately perform a pipe burying work for gas, and the existing common groove 23 is used. Gas construction can be done easily.

[0018]

As described above, according to the synthetic resin double-layered pipe of the present invention, the outer periphery of the polyolefin synthetic resin pipe serving as the pipe body is coated with the polyvinyl chloride resin, so that the polyolefin synthetic resin is used. Flame resistance, impact resistance, and heat resistance can be significantly improved without impairing the advantages of the tube.

[Brief description of drawings]

FIG. 1 is an end view showing a form example of a two-layer synthetic resin tube of the present invention.

FIG. 2 is a longitudinal sectional view showing an example in which the synthetic resin double-layer pipe of the present invention is laid in a common groove in which a power cable is laid.

[Explanation of symbols]

10 ... Synthetic resin two-layer tube, 11 ... Polyethylene tube, 12
… Polyvinyl chloride resin, 21… Power cable protection tube,
22 ... Power cable, 23 ... Common groove

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // (C08L 27/24 C08L 27:06 27:06) F term (reference) 3H111 AA04 BA15 BA34 CB03 DB11 EA04 4F100 AK03A AK04 AK15B AK15J AL01B AL05B BA02 DA11 JA07B JJ03 4J002 BD032 BD052 BD181 EG016 EH026 FD176 GM00

Claims (3)

[Claims] 1. A double-layer pipe made of synthetic resin, characterized in that the outer periphery of the polyolefin synthetic resin pipe is coated with polyvinyl chloride resin. 2. The polyvinyl chloride-based resin is a chlorinated polyvinyl chloride resin having an average degree of polymerization of 500 to 1800 and a chlorine content of 60 to 70% by weight. Two-layer tube made of synthetic resin. 3. The polyvinyl chloride resin has an average degree of polymerization of 500 to 1800, a chlorine content of 60 to 70% by weight, and 70 to 95 parts by weight of chlorinated polyvinyl chloride, and a vinyl chloride copolymer. The synthetic resin double-layer pipe according to claim 1, which is a composition containing 5 to 30 parts by weight.