JP2006132639A - Joining part of polyolefin pipe with solvent penetration preventing layer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a joining part of a polyolefin pipe with a solvent penetration preventing layer capable of eliminating the pollution of service water caused by an organic solvent and capable of joining the polyolefin pipe with the organic solvent penetration preventing layer used for a service water pipe by an electric fusion joint or a butt-welding and joining method. <P>SOLUTION: The electric fusion joint 1 having an inner end and a whole outer surface covered with a solvent penetration preventing layer 14 and the end of the pipe having a solvent penetration preventing layer 24 on the outer surface of a polyolefin pipe body are joined by the fusion of the polyolefin of a joint body and the polyolefin of the pipe body, and a solvent penetration preventing layer part 141 of the inner end of the electric fusion joint and a solvent penetration preventing layer part 241 of the pipe end are fused. A fusion joining interface between the polyolefin of the joint body and the plyolefin of the pipe body exists inside the fusion part, and thereby the intrusion of the organic solvent to the fusion joining interface can be prevented. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a connecting portion of a polyolefin tube with a solvent penetration preventing layer, for example, a polyethylene tube with a polyamide outer layer.

Conventionally, polyolefin pipes such as polyethylene pipes, polypropylene pipes and polybutene pipes have been used for water pipes, but organic solvents such as gasoline are likely to penetrate into the polyolefin pipes.
For this reason, when a polyolefin pipe is used as a water pipe in an area where soil is contaminated, such as an urban area where industrialization has advanced, there is a possibility that the water is polluted by the permeation of the organic solvent.
As a countermeasure, it is known to provide a solvent permeation preventive layer on the outer surface of the polyolefin pipe, and a composite pipe having an organic solvent permeation preventive structure has been proposed. (See Patent Document 1)
JP 2004-35595 A

Conventionally, as a joining structure of polyolefin pipes, those using an electric fusion joint and those using a butt fusion method are known.
FIG. 7-1 shows a process of joining a polyolefin pipe by an electric fusion joint. As shown in FIG. 7-1 (a), the polyolefin pipe 1 ′ having a heating wire 12 ′ embedded on the inner surface side is connected to the polyolefin pipe 2 ′. Insert the end, and then melt the polyolefin part including the contact interface a between the inner surface of the joint near the heating wire and the outer surface of the tube end as shown in FIG. After that, it is cooled and the interface is fused.
In this case, the melted resin is based on thermal expansion because the other part maintains a solid phase state against melting of the polyolefin part near the heating wire including the contact interface between the joint inner surface and the pipe end outer surface. As a result of being pressurized, a part is released in the direction of the arrow, and in this state, the molten polyolefin is cooled and contracted. As a result, a vertical tensile stress tends to remain at the interface.

  In the butt fusion bonding of polyolefin pipes, the ends of the polyolefin pipe ends are heated and softened to butt, the resin is deformed into a bowl shape by the butt force, and then cooled and solidified. When the heat softened resin is cooled and solidified In this case, too, the pipe axis direction tensile stress tends to remain at the butt joint interface.

  It is known as a so-called environmental stress cracking phenomenon that a polyolefin is easily cracked in a stress direction when contacting with an organic solvent in the presence of residual stress.

As described above, it has been proposed to provide an organic solvent permeation preventive layer on the outer surface of a polyolefin pipe as a countermeasure for preventing the organic solvent of tap water in a water pipe using the polyolefin pipe.
Even if this polyolefin pipe with an organic solvent permeation prevention layer is joined by an electrofusion joint or a butt joining method, the length of the joint is significantly shorter than the length of the pipe. Since the surface area is negligibly small compared to the organic solvent permeation surface area of the tube, no measures for preventing the organic solvent permeation at the joint are taken.
However, as described above, the joint interface is susceptible to stress environment cracks due to the organic solvent, and there is a problem that there is a concern about the intensive intrusion of the organic solvent from the cracked portion.

  In view of the above-mentioned points, the object of the present invention is to remove the organic solvent contamination of clean water from the polyolefin pipe with an organic solvent permeation preventive layer used as a water pipe by an electric fusion joint or a butt fusion joining method. An object of the present invention is to provide a joint portion of a polyolefin pipe with a solvent penetration preventing layer that can be joined.

  The joint part of the polyolefin pipe with a solvent penetration preventing layer according to claim 1 is an electromelting method in which a heating wire is embedded on the inner surface side of the polyolefin joint main body, and a solvent permeation prevention layer is coated on the inner surface end and all outer surfaces of the joint main body. The welded joint and the end of the pipe having a solvent permeation preventive layer on the outer surface of the polyolefin pipe main body are joined by fusion of the polyolefin of the joint main body and the polyolefin of the pipe main body. The permeation preventing layer portion and the solvent permeation preventing layer portion at the end of the pipe are fused.

  The joint portion of the polyolefin pipe with a solvent permeation preventive layer according to claim 2 is a butt joint between polyolefin pipe main bodies or a polyolefin pipe main body and a polyolefin electrofusion joint. And the joint is surrounded by a solvent penetration preventing cover, and the end of the cover is fused to the solvent penetration preventing layer at the end of the tube.

  In the joint portion of the polyolefin pipe with a solvent permeation preventive layer according to claim 1, the solvent permeation preventive layer portion at the inner end of the electrofusion joint and the solvent permeation preventive layer portion at the end of the pipe with the organic solvent permeation preventive layer are Since the fusion-bonded interface exists between the polyolefin of the joint body and the polyolefin of the pipe body inside the fusion-bonded portion, the penetration of the organic solvent into the fusion-bonded interface can be eliminated.

  In the joint part of the polyolefin pipe with a solvent permeation preventive layer according to claim 2, the end part of the solvent permeation preventive cover that surrounds the joint part by the electric fusion joint or the butt fusion method is the pipe with the organic solvent permeation preventive layer. Therefore, it is possible to eliminate the penetration of the organic solvent into the fusion bonded interface by the electric fusion joint or the butt fusion method.

  Therefore, in any of the claims, even if tensile stress remains at the fusion-bonding interface and the fusion-bonding interface is in a state of being susceptible to environmental stress cracking, it is ensured that the solvent enters the fusion-bonding interface. It is possible to block, and it is possible to stably hold the joint portion of the polyolefin pipe with a solvent permeation preventive layer by an electric fusion joint or a butt fusion joining method with respect to the organic solvent.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1-1 shows an example of an electric fusion joint 1 used in claim 1.
In FIG. 1-1, 11 is a polyolefin joint main body, for example, a polyethylene joint main body, and the heating wire 12 is embedded so as to spirally exist on the inner surface excluding both ends and the center of the inner surface of the joint main body. Reference numeral 13 denotes a heating wire terminal, which is implanted on both ends of the outer surface of the joint. 14 is an organic solvent permeation preventive layer for gasoline or the like, which is made of a material having a solvent permeation amount smaller than that of polyolefin, for example, polyethylene (so-called nylon), and covers both ends of the inner surface of the joint body and the entire outer surface. Has been. The polyamide layer 14 has a thickness of usually 0.1 to 0.2 mm, preferably 0.15 mm. Reference numeral 15 denotes a protective layer coated on the organic solvent permeation preventive layer except for the solvent permeation preventive portions 141 at both ends of the inner surface of the joint main end, and can be a polyethylene layer, for example.

The electric fusion joint can be manufactured, for example, as follows.
First, the polyethylene inner layer is molded on the mandrel in advance. A spiral groove for heating wire is formed in the inner layer portion. Further, the heating wire is wound by rotating the mandrel. Further, the inner layer portion wound with the heating wire is incorporated into the injection mold together with the mandrel, the terminals at both ends of the heating wire are fitted into the inner concave portion of the outer die, and the polyethylene outer portion is injection molded. Next, the polyamide layer is coated, and further the polyethylene layer is coated.
The coating of the polyamide layer 14 is performed by adhering a polyamide thin-walled case divided into two in the longitudinal direction formed in advance to the joint with an adhesive, cutting the joint so that the inner end portions and the entire outer face of the joint can be neatly wrapped, and The cut polyamide film can be attached to the joint via an adhesive, and the overlapped cuts can be heat sealed by high frequency fusion, ultrasonic fusion, heat scissors, or the like.
The polyethylene protective layer 15 can also be provided in the same manner as the polyamide layer 14. In this case, an adhesive is interposed between the polyethylene protective layer 15 and the polyamide layer 14.

FIG. 1-2 shows an embodiment of a joint portion of a polyolefin pipe with a solvent penetration preventing layer according to claim 1.
In FIG. 1-2, 2 is a polyolefin tube with a solvent penetration preventing layer, for example, a polyethylene tube having a polyamide outer layer 24. The thickness of the polyamide outer layer 24 is usually 0.1 like the polyamide layer 14 of the electrofusion joint 1. It is set to -0.2 mm, preferably 0.15 mm. Reference numeral 25 denotes a protective layer provided on the organic solvent permeation preventive layer 24, for example, a polyethylene layer.
1 is a polyolefin electrofusion joint with a solvent permeation preventive layer as described above, for example, a polyethylene electrofusion joint with a polyamide layer. The contact interface a with the polyolefin is fused, and the solvent permeation preventive layer portion 141 at the end of the joint inner surface and the solvent permeation preventive layer portion 241 at the end of the polyolefin tube with the solvent permeation preventive layer are fused.

In order to form the joint shown in FIG. 1-2, the solvent permeation preventive layer 24 is peeled off from the end of the polyolefin tube 1 with the solvent permeation preventive layer 1 so as to obtain a predetermined polyolefin fusion allowance, and further the peel length Then, the protective layer 25 is peeled off and the polyolefin pipe end portion with the solvent permeation preventive layer thus treated is inserted into the polyolefin electrofusion joint 1 with the solvent permeation preventive layer, and the heating wire 12 of the joint 1 is energized. Heat is generated to melt the polyolefin portion near the contact interface between the joint and the pipe end. Since the joint polyolefin and the pipe end polyolefin other than the molten polyolefin portion are maintained in a solid state, an internal pressure is generated in the molten polyolefin, and the internal pressure is shown in FIG. As shown in the enlarged view in the dotted frame in (a)], it acts as an interface clamping pressure on the contact interface between the solvent permeation preventing layer portion 141 at the inner end of the joint and the solvent permeation preventing layer 241 at the pipe end.
In particular, in the polyolefin electrofusion joint 1 with the solvent penetration preventing layer, the thickness of the solvent penetration preventing layer 142 on the outer surface side is sufficiently thick and can effectively contribute to the generation of the internal pressure. Can be expensive.

  The material of the solvent permeation preventive layers 14 and 24 has the same melting point as that of the polyolefin, and the solvent permeation preventive layer portion 141-contacted simultaneously with melting of the polyolefin portion near the contact interface between the joint and the pipe end portion. 241 is also melted, and the contact interface of the solvent permeation preventive layer is also fused together with the fusion of the polyolefin contact interface. When the polyolefin is polyethylene and the solvent permeation preventive layer is polyamide, the two contact interfaces can be fused at a heating temperature of approximately 200 ° C. with a heating wire.

  In order to more firmly fuse the solvent permeation preventive layer portion in contact with each other, as shown by 121 in FIG. 1-3, even if a heating wire is present in the vicinity of the solvent permeation preventive layer portion on the inner surface of the joint. Good.

In FIG. 1-2, the vertical tensile stress remains at the fusion-bonding interface a between the polyolefin of the joint body and the polyolefin of the pipe body, and the fusion-bonded interface is susceptible to environmental stress cracking. The solvent permeation preventive layer portion 141 at the inner surface end of the joint 1 and the solvent permeation preventive layer portion 241 at the end of the pipe 2 with the organic solvent permeation preventive layer are fused together, and the polyolefin is fused inside the fused portion. Since the adhesive bonding interface a exists, the penetration of the solvent into the fusion interface can be reliably blocked, and the fusion interface between polyolefins can be stably maintained against environmental stress cracks.

FIG. 2-1 shows a polyolefin electrofused joint 1 with a solvent penetration preventing layer used in an embodiment different from the above embodiment of the joint according to claim 1.
In FIG. 2-1, 11 is a single-piece type polyolefin joint main body, for example, a single-piece type polyethylene joint main body, so that the heating wire 12 spirally exists on the inner surface of the receiving port except for the end on the inlet side. Buried. Reference numeral 13 denotes a heating wire terminal. Reference numeral 14 denotes an organic solvent permeation preventive layer for gasoline or the like, which is made of a material having a solvent permeation amount smaller than that of polyolefin. For example, it is made of polyamide (so-called nylon) for polyethylene, and extends over the inlet side end of the receiving port and the entire outer surface. It is covered. The thickness of this polyamide layer is usually 0.1 to 0.2 mm, preferably 0.15 mm. Reference numeral 15 denotes a protective layer coated on the organic solvent permeation preventive layer 14 except for the solvent permeation preventive portions 141 at both ends of the inner surface of the joint main end, and can be, for example, a polyethylene layer.
Similarly to the above, the heating wire 12 can also be present in the vicinity of the solvent permeation preventing layer portion 141 at the inlet side end of the receiving port.

FIG. 2-2 shows an embodiment different from the above-described embodiment of the joint according to claim 1.
In FIG. 2-2, 2 is a polyolefin tube with a solvent penetration preventing layer 24, for example, a polyethylene tube having a polyamide outer layer 24. The thickness of the polyamide outer layer 24 is usually 0.1 to 0.2 mm, preferably 0.15 mm. The Reference numeral 25 denotes a protective layer provided on the organic solvent permeation preventive layer 24, for example, a polyethylene layer.
1 is a polyolefin electrofusion joint with a solvent permeation preventive layer, for example, a polyethylene electrofusion joint with a polyamide layer, and the joint polyolefin in the vicinity of the electrothermal layer and the end of the polyolefin tube with a solvent permeation preventive layer are energized by the heating wire 12. The contact interface a with the polyolefin is fused, and the solvent permeation preventive layer portion 141 at the inlet side end of the inlet of the joint 1 and the solvent permeation preventive layer portion 241 at the end of the polyolefin tube 2 with the solvent permeation preventive layer, Are fused.

  The joint portion of the polyolefin pipe with a solvent permeation preventive layer according to claim 1 can be applied to a branch joint portion or a bent joint portion. In this case, the polyolefin electrofusion joint with a solvent permeation preventive layer has the joint shown in the figure. A cheese having a receiving port similar to the receiving port or a bent joint having the receiving port is used.

3-1 (a) is an example of a joint part of a polyolefin tube with a solvent penetration preventing layer according to claim 2, and (b) in FIG. 3-1 is a dotted frame in (a) in FIG. 3-1. Each enlarged view is shown.
In FIG. 3-1, 10 is a polyolefin electrofusion joint, for example, a polyethylene electrofusion joint, and the heating wire 12 is embedded in the vicinity of the inner surface to be fused in a spiral manner. 13 is a heating wire terminal.
Reference numeral 2 denotes a polyolefin tube with a solvent penetration preventing layer, for example, a polyethylene tube having a polyamide outer layer 24. The thickness of the polyamide outer layer 24 is usually 0.1 to 0.2 mm, preferably 0.15 mm. Reference numeral 25 denotes a protective layer provided on the organic solvent permeation preventive layer 24, for example, a polyethylene layer.
The solvent permeation preventive layer is peeled from the end of the polyolefin tube with the solvent permeation preventive layer by a predetermined length, the protective layer is peeled beyond the peel length to expose the polyolefin fusion allowance, and the exposed polyolefin portion And the portion to be fused on the inner surface of the joint are melted by energizing heat generated by the heating wire of the joint, and then cooled and fused. A shows the joint formed by this fusion.
Reference numeral 140 denotes a cover made of the same material as the solvent permeation preventive layer 24, for example, a polyamide cover, and a protective layer 15, for example, a polyethylene layer, is provided on the outer surface. The thickness of the polyethylene protective layer 15 is sufficiently thick, for example, 0.5 to 2.0 mm.
The joint A is surrounded by the solvent permeation preventive cover 140, and the polyamide at the cover end 141 is fused to the solvent permeation preventive layer 24 at the end of the polyolefin tube 2 with the solvent permeation preventive layer.

  In order to form the joint portion of the polyolefin pipe with a solvent penetration preventing layer shown in FIG. 3A, a cylindrical solvent penetration prevention cover 140 is inserted into one of the polyolefin pipes with the solvent penetration prevention layer to be joined. The pipes are joined by the electric fusion joint 10, and then the solvent permeation prevention cover 140 is pulled back so as to surround the electric fusion joint 10, and each end of the cover 140 is connected to the end of each pipe. Overlaid on the solvent permeation preventive layer, next, as shown in (b) of FIG. 3-1, the clamp-type heating jig 3, for example, a crack ring in which the heating wire 32 is embedded on the inner peripheral surface is overlaid. The protective layer portion 151 that adheres to the inner surface and contacts the inner surface of the ring, for example, the polyethylene layer portion, is melted by the heat generated by the ring 3, and the expansion pressure due to the melting and the end of the solvent penetration preventing cover and the tube end Solvent penetration prevention layer, for example The contact interface with melting of both polyamide 141, 241 of the cover and a solvent permeation preventing layer are fused.

  The solvent permeation prevention cover 140 has a cylindrical shape, and its end portion is squeezed by the crack ring 3 and is brought into contact with the solvent permeation prevention layer portion 241 at the pipe end portion. As shown in (a), it is a left and right split type consisting of reduced-type split pieces, each split piece is inserted in advance into each polyolefin penetration-attached polyolefin pipe, and both pipes are joined by an electrofusion joint. After that, each cover divided piece is pulled back, and the divided pieces are fused together by high frequency fusion, ultrasonic fusion, heat filing, etc., as shown in (b) of FIG. 3-2, both ends are reduced. The cover is divided into upper and lower parts of a semicircular cross section, and both pipes are joined by an electric fusion joint. Then, the cover division pieces are joined to the joint, and the division pieces are mutually joined by high-frequency fusion, ultrasonic fusion, and heat welding. It is also possible to fuse them by means of, for example.

FIG. 4-1 shows an embodiment different from the above of the joint portion of the polyolefin pipe with a solvent penetration preventing layer according to claim 2.
In FIG. 4-1, 100 is a cheese type polyolefin electrofusion joint, for example, a cheese type polyethylene electrofusion joint, and as shown in FIG. It is embedded so as to be spirally present in the vicinity of the inner surface to be fused, a terminal 131 for the heating wire 102 is provided, and another heating wire 122 is spiral in the vicinity of the inner surface to be fused on the inner surface of the branch leg 102. And a terminal 132 for the heating wire 122 is provided.
In FIG. 4A, reference numeral 2 denotes a polyolefin tube with a solvent permeation preventive layer 24, for example, a polyethylene having a polyamide outer layer 24. Reference numeral 25 denotes a protective layer provided on the organic solvent permeation preventive layer, for example, a polyethylene layer.
The solvent permeation preventive layer 24 is peeled off by a predetermined length from the ends of the polyolefin pipes 1,... With these solvent permeation preventive layers, the protective layer 25 is peeled off at a longer length, and the polyolefin fusion allowance is exposed. The exposed polyolefin portion and the portion to be fused on each joint inner surface of the joint 100 are melted by energization heat generation of the heating wire of the joint 100, and then cooled and fused. A shows a branch joint formed by this fusion.
Reference numeral 140 denotes a T-type cover made of the same material as the solvent penetration preventing layer, for example, a polyamide T-type cover, and a protective layer 15 such as a polyethylene layer is provided on the outer surface. The thickness of the polyethylene protective layer 15 is sufficiently thick as described above, and is, for example, 0.5 to 2.0 mm.
The branch joint A is surrounded by the solvent permeation preventive T-type cover 140, and each end 140 of the cover is fused to the solvent permeation preventive layer 24 at the end of each polyolefin tube 1 with the solvent permeation preventive layer. .

  As this T-shaped cover, a cover divided into three at the intersection as shown in FIG.

  In order to form the joint portion of the polyolefin tube with a solvent permeation preventive layer shown in FIG. 4-1, each divided piece of the cover for solvent permeation prevention is inserted into each polyolefin tube with a solvent permeation preventive layer to be joined. Then, three polyolefin pipes with a solvent penetration preventing layer to be joined are joined by the cheese type electrofusion joint 100, and then each cover piece is pulled back so as to surround the electrofusion joint 100 and divided into three parts. The cover cracks are heat-sealed by ultrasonic fusion or the like, and each end of each cover segment is overlaid on the solvent permeation preventive layer at each tube end. And the polyamide of the solvent permeation preventing layer at the end of each tube are fused together.

As shown in (b) of FIG. 4-3, the straight portion 1401 of the T-shaped cover 140 is released, and the T-shaped leg portion 1402 of this cover is inserted in advance into the branch pipes of the three-way joined pipes. Then, after joining the three pipes to be joined by the cheese type electrofusion joint, pull the cover back and turn the release straight part of the cover into the straight part of the cheese type electrofusion joint. It is also possible to heat-seal the superposed layers by ultrasonic fusion or the like.
Also, the T-shaped cover is divided up and down so as to have a semicircular cross-section, and after joining the three pipes to be joined by a cheese-type electric fusion joint, the upper and lower divided covers are joined to this branch connection part, It is also possible to superimpose the divided edges of the divided pieces and heat seal them by ultrasonic fusion or the like.

FIG. 5 shows another embodiment of the joint portion of the polyolefin pipe with a solvent permeation preventive layer according to claim 2, which is different from the above, and is a polyolefin electrofused joint having a planned fusion portion on both inner surfaces, for example, polyethylene electrofusion. A polyolefin pipe with a solvent penetration preventing layer, for example, a polyethylene pipe 2, 2 with a polyamide outer layer, is joined by a bending joint 1000, and a cylindrical solvent penetration prevention cover with a protective layer, such as polyethylene, inserted in advance into one pipe. The polyamide cover 140 with the protective layer 15 is pulled back on the bent joint against the bending moment reaction force caused by the bending, and the polyamide inner layer portion 141 at the end of the cover is overlapped with the end polyamide layer portion 241 of each pipe, In the same manner as above, the overlapping portion is fused.
Also in this embodiment, it is possible to divide the cover into two parts with respect to the length as in the embodiment shown in FIG.

  In any of the examples shown in FIGS. 2-1, FIG. 3-1, FIG. 4-1, and FIG. 5, similar to the example described with reference to FIG. A part is released due to the pressure based on the thermal expansion, and the molten polyolefin is cooled and shrunk without returning the escaped part, so that a tensile stress remains on the joint pipe surface. Environmental stress cracks occur when polyolefins with residual tensile stress come into contact with organic solvents, but in any of the previous examples, the ends melt into the solvent penetration prevention layer at the end of the polyolefin tube with the solvent penetration prevention layer. Since the solvent permeation preventing cover is prevented from entering the bonding interface, the bonding interface can be stably held against the solvent.

FIG. 6 shows an embodiment different from the above-described embodiment of the joint portion of the polyolefin pipe with a solvent penetration preventing layer according to claim 2.
In FIG. 6, reference numeral 1 denotes a polyolefin pipe with a solvent permeation preventive layer, for example, a polyethylene pipe having a polyamide outer layer 24 and a polyethylene protective layer 25, and the pipe end faces are butt-joined.
In this butt joint, the polyamide layer is peeled from the pipe end by a predetermined length, the polyethylene protective layer is peeled beyond this peel length, and the very tip of the pipe end is heated with a suitable heating jig to melt and soften. Both ends are butted together with a predetermined force and swelled into a bowl shape, and the molten polyolefin is cooled in a state where both pipes are fixed. A tensile stress is applied to the joint interface due to thermal contraction during cooling. It remains.
In FIG. 6, reference numeral 140 denotes a cylindrical solvent penetration preventing cover made of the same material as the solvent penetration preventing layer,
For example, it is a polyamide cover, has a polyethylene protective layer 15 having a sufficient thickness, preferably 0.5 to 2.0 mm, and the polyamide portion 141 at the end of the cover becomes a polyamide outer layer portion 241 at the end of the tube in the same manner as described above. It is firmly fused.

  In this embodiment as well, tensile stress remains on the joint pipe surface, but for the solvent penetration preventing cover whose end is fused to the solvent penetration preventing layer at the end of the polyolefin pipe with the solvent penetration preventing layer. Since the penetration of the solvent into the joining tube surface is well prevented, the joining interface can be stably maintained against the solvent.

  In the above, the material of the solvent penetration prevention layer of the polyolefin tube with the solvent penetration prevention layer and the solvent penetration prevention layer of the polyolefin electric fusion joint with the solvent penetration prevention layer of the same material as this solvent penetration prevention layer and the solvent penetration prevention cover are: The solvent permeation amount is sufficiently smaller than the polyolefin of the joint body and the pipe body, and the fusion temperature of the polyolefin may be any material that can be fused at, for example, a polyethylene fusion temperature of about 200 ° C. It is not limited.

  The protective layer on the solvent permeation preventive cover is the same as the protective layer on the solvent permeation preventive layer of the polyolefin pipe with the solvent permeation preventive layer and the protective layer on the outermost surface of the joint of the polyolefin electrofusion joint with the solvent permeation preventive layer. In addition to protecting the cover from lacerations due to external impacts, it is also responsible for pressurization during heat fusion by thermal expansion under a sufficient thickness as described above. What is necessary is just to have a thermal expansion coefficient, and it is not limited only to the said polyethylene.

It is drawing which shows an example of the electrical fusion joint used in Claim 1. It is drawing which shows one Example of Claim 1 which uses the electrical fusion joint of FIGS. 1-1. It is drawing which shows another example of the electric fusion joint used in Claim 1. It is drawing which shows one Example of Claim 1 which uses the electrical fusion joint of FIG. 2-1. It is drawing which shows one Example of Claim 2. FIG. It is drawing which shows the example from which the cover for solvent permeation prevention used in the Example of FIGS. 3-1 differs. It is drawing which shows the Example different from the above of Claim 2. It is drawing which shows an example of the electric fusion joint used in the Example of FIGS. It is drawing which shows the example from which the cover for solvent penetration prevention used in the Example of FIGS. 4-1 differs. It is drawing which shows the Example different from the above of Claim 2. It is drawing which shows the Example different from the above of Claim 2. It is drawing which shows the joining process of the polyolefin pipe | tube by an electrofusion joint.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrical fusion joint 10 Electrical fusion joint 100 Electrical fusion joint 1000 Electrical fusion joint 12 Heating wire 121 Heating wire 122 Heating wire 14 Solvent penetration prevention layer 15 Protective layer 2 Polyolefin pipe 24 with solvent penetration prevention layer Solvent penetration prevention layer 25 Protective layer 140 Cover for preventing solvent penetration

Claims (2)

Heat-bonded wires are embedded in the inner surface of the polyolefin joint body, and the electrofusion joint has a solvent penetration prevention layer coated on the outer surface of the polyolefin pipe body. The end of the pipe is joined by fusing the polyolefin of the joint body and the polyolefin of the pipe body, and the solvent permeation preventive layer portion at the inner surface end of the electrofused joint and the solvent permeation preventive layer portion at the pipe end are fused. A bonded portion of a polyolefin pipe with a solvent permeation preventive layer, characterized in that it is attached. A pipe having a solvent permeation preventive layer on the outer surface of the polyolefin pipe main body is joined by butt joining of the polyolefin pipe main bodies or by fusion of the polyolefin pipe main body and a polyolefin electric fusion joint, and the joint portion is a cover for preventing solvent permeation. A joint portion of a polyolefin tube with a solvent permeation preventive layer, characterized in that the end portion of the cover is fused to the solvent permeation preventive layer at the end of the tube.

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