JPH05318591A - Connecting method for synthetic resin tube - Google Patents

Abstract

PURPOSE:To obtain a predetermined connecting quality of a synthetic resin tube and to simultaneously prevent adherence of molten resin to a heating plate by shortening a nonfoaming time of an end of the tube and eliminating an irregularity in a molten state in the case of butt connecting the tube. CONSTITUTION:A sealed vessel 1 in which ends of two synthetic resin tubes P1, P2 are contained is evacuated to an atmospheric pressure or less. Ends of the tubes are so heated as not to be brought into contact with a heater 6 to be non-foamed, then melted, and pressed in a tube axial direction in butted state of the ends of the tubes to be fusion-bonded.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for butt-joining (butt-joining) a synthetic resin pipe such as a thermoplastic resin.

[0001]

2. Description of the Related Art Pipes made of synthetic resin such as polyethylene, polypropylene, polyvinylidene fluoride, polyether ether ketone, and polyphenylene sulfide are often used as fluid transport pipes such as water pipes, drainage pipes and gas pipes. As a method of joining such synthetic resin pipes, a butt joint (butting) in which both pipe ends to be joined are heated and melted, and then the pipe ends are pressed against each other and pressed in the axial direction of the pipe Joining) is widely practiced.

As a method of heating the tube ends in this case, a method has been generally used in which the left and right tube ends are brought into contact with a heated hot plate from both sides to heat by heat conduction. In this case, a hot plate coated with a highly non-adhesive fluorine-based resin such as ethylene tetrafluoride (PTFE) is used to prevent the molten resin from adhering.

However, when joining pipes of highly heat-resistant polyetheretherketone, polyphenylene sulfide, etc., since the melting temperature of ethylene tetrafluoride is lower than those resins, ethylene tetrafluoride is used as a hot plate. The coating on is not effective in preventing the adhesion of molten resin. Therefore, in such a case, heating is performed by convection and radiation in a state where the tube end is separated so as not to contact the heating body.

Further, such a high heat resistant engineering resin generally has a high water absorption and contains a large amount of water and volatile matter, and these water and volatile matter are foamed by heating, and air bubbles are entrapped in the joining portion and joined. The strength may be significantly reduced. Therefore, as a countermeasure against this, Japanese Patent Application Laid-Open No. 1-1237
As disclosed in Japanese Unexamined Patent Publication No. 28-28, the vicinity of the joint is preheated and subjected to non-foaming treatment, and then fusion-bonded.

[0005]

However, in the case of heating in the atmosphere as in the above-mentioned prior art, the heating condition, that is, the molten state is varied due to the influence of the outside air temperature and the air flow, and uniform bonding strength is obtained. Absent. Further, since the non-foaming treatment requires a long time of 1 to 3 hours at 200 to 240 ° C., there is a problem that the joining work becomes remarkably inefficient.

The present invention has been made in view of the problems of the prior art as described above, and when performing butt joining of synthetic resin pipes, work is performed by shortening the non-foaming treatment time of the pipe end portion. The purpose is to efficiently perform, to obtain stable joining quality by eliminating variations in the molten state, and to prevent molten resin from adhering to the hot plate or the decomposed resin being caught in the joint. .

[0007]

In order to achieve the above object, the method for joining synthetic resin pipes of the present invention is such that two pipe ends of two synthetic resin pipes are heated and melted and then the two pipe ends are butted. In the method for joining synthetic resin pipes that are fused by fusion, the pipe ends are defoamed by heating so that they do not come into contact with the heating body in a state where the pipe ends are depressurized to atmospheric pressure or less, and then the pipe ends are abutted after being melted. The gist of the invention is to press and fuse in the tube axial direction in this state.

The material of the synthetic resin pipe used in the present invention is a crystalline or amorphous thermoplastic engineering such as polyether ether ketone, polyphenylene sulfide, polyether sulfone, polyethylene terephthalate, polysulfone, polyvinylidene fluoride. Examples include resins, polyvinyl chloride, polyethylene, polypropylene, general-purpose thermoplastic resins such as ABS, and composite materials and polymer alloys in which fillers and the like are added to the above resins, and particularly polyether ether ketone, polyphenylene sulfide, poly It is suitable for joining synthetic resin pipes made of highly heat-resistant engineering resin such as ether sulfone, polyethylene terephthalate, polysulfone, and polyvinylidene fluoride.

In the present invention, in order to bring the end of the pipe into a state of being depressurized below atmospheric pressure, the end of the pipe is hermetically sealed in a sealed container whose pressure is reduced below atmospheric pressure, and the pipe is sealed so that the inside of the sealed container does not communicate with outside air. Also, it is achieved by providing a sealing means such as a sealing plug, and connecting the sealed container to the suction port of the vacuum pump to suck.

The closed container has a structure capable of withstanding negative pressure, airtightness, and heat insulation, and has a structure that can be opened and closed in order to put the pipe end in and out. For this reason, the material is preferably stainless steel, pressure-resistant glass, etc., and a sealing means such as an elastic packing or gasket is provided around the opening / closing part and the through hole of the synthetic resin pipe, and the pressure between the inner case and the outer case is reduced. It is preferable to use one that can be used, or one that is filled with a heat insulating material between the inner box and the outer box.

It is preferable that the pressure in the closed container is as low as atmospheric pressure and as low as possible, but 0.2 to 0.5 in absolute pressure.
It may be kg / cm ² .

As the heating element, a plate-shaped element is suitable so that the end surface of the tube can be heated. Examples of heating means include a heating wire heater, circulating oil heating, a halogen lamp, and a far infrared heater. It is assumed that the heating element can adjust the distance from the end surface of the tube, and can be removed from the end of the tube when the tube is pressed in the axial direction of the tube to be fused.

[0013]

[Operation] Since the end of the pipe is heated under atmospheric pressure, the water and volatile components are removed more quickly than in the atmosphere and defoamed without being affected by outside temperature or wind. Since it is heated mainly by radiant heat, a constant molten state is obtained. Further, since the tube end portion does not come into contact with the heating body, the molten resin or the thermal decomposition product thereof does not adhere to the heating body and the thermal decomposition product is not caught in the joint portion.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings. 1 to 3 are explanatory views showing an embodiment of the present invention, FIG. 1 is a state in which a tube end is heated to defoam, and FIG. 2 is a state in which a tube end is heated and melted. 3 shows a state in which the melted pipe ends are butted against each other and fused.

As shown in FIG. 1, the closed container 1 has a double structure of an outer case 1a made of stainless steel and having a pressure resistant structure, and an inner case 1b made of stainless steel. The outer case 1a and the inner case 1b have a double structure. A heat insulating material 1c is filled in between. The airtight container 1 is formed in two parts that can be opened and closed downward, and the joint surface of the two parts is provided with a sealing packing made of fluororubber, which is not shown in the figure, and the synthetic resin pipes P ₁ , P ₂ A sealing packing 2 made of fluororubber is also provided in the peripheral portion of the pipe insertion hole for accommodating the pipe end portion. The closed container 1 is provided with an exhaust port 3 connected to an intake port of a vacuum pump (not shown), and a valve 4 at the tip of the exhaust port 3. Further, a sealing plug 5 made of polypropylene resin, heat-resistant rubber or the like is fitted to the outer end portion of the joined synthetic resin pipes P ₁ and P ₂ protruding outside the closed container 1, And the outside air is shut off. In addition, in the central part of the closed container 1,
A plate-shaped heating body 6 provided with a nichrome wire heater is erected, and synthetic resin pipes P ₁ and P ₂ are held by a movable pipe clamp device 7, and the movable pipe clamp device 7 is moved in the pipe axial direction. The distance to the heating element 6 can be adjusted by moving the heating element 6 to.

In joining the synthetic resin pipes P ₁ and P ₂ , first, the valve 4 is opened and the vacuum pump is driven to discharge the air in the closed container 1 to reduce the pressure to below atmospheric pressure. The end is heated at a position slightly separated from the heating body 6 to defoam the end of the tube.

After defoaming for a certain period of time, the closed container 1
With the inside kept in a depressurized state, as shown in FIG. 2, the movable tube clamp device 7 is moved toward the center of the closed container 1, and the tube ends are brought close to each other so as not to come into contact with the heating body 6. It is heated to a molten state suitable for fusing.

Next, the suction by the vacuum pump is stopped to close the valve, and the closed container 1 is opened to remove the heating body as shown in FIG. 3, and the clamp device 7 is further moved toward the center of the closed container 1. Then, the pipe ends in the molten state are brought into a butted state with each other and pressed in the pipe axial direction to be fused. In the example shown in FIG. 3, the hermetically sealed container 1 was opened prior to the fusing and the fusing was performed under the atmospheric pressure. However, even if the fusing is performed under a reduced pressure and the fusing is performed after the fusing is performed. Good.

As described above, the heating is performed in the closed container 1 under a reduced pressure below the atmospheric pressure and under stable conditions without being affected by the outside air temperature, wind, etc. The time is drastically shortened, a constant molten state is always obtained, and the quality of joining is improved.

4 and 5 are explanatory views showing another embodiment of the present invention. FIG. 4 is a state in which the tube end is heated to be non-foamed or melted, and FIG. 5 is a tube end. The state where they are butted against each other and fused is shown. As shown by the solid line in FIG. 4, a doughnut-shaped heating body 8 is erected at the center of the closed container 1 in a depressurized state in the same manner as in the previous embodiment, and a position slightly separated from the heating body 8. A state in which the pipe ends of the synthetic resin pipes P ₁ and P ₂ are held, and an inner surface support 9 made of fluororubber having an outer diameter slightly smaller than the inner diameter of the pipe is connected to the inner pipe surfaces of both pipe ends. Insert with. Plates 10 and 11 having an outer diameter smaller than the inner diameter of the pipe are arranged at both ends of the inner support 9, and the inner support 9 is axially moved by strongly pulling a wire 12 connected to the plate 11. The outer peripheral surface is pressed against the inner wall of the pipe.

In this state, the tube end is heated by the heating body 8 to make it non-foamed, and then the tube end is brought close to the heating body 8 as shown by the dotted line to heat and melt it.

Then, as shown in FIG. 5, the closed container 1 is opened, the heating body 8 is removed from the tube ends, and the molten tube ends are brought into abutment with each other and pressed in the axial direction of the tube for fusion. To do. After cooling the fused portion, the wire 12
Is loosened to restore the inner support 9 to a reduced diameter, and is pulled out of the synthetic resin pipe P ₁ . In addition, in the case of the present embodiment, since the inner surface support 9 blocks the invasion of the outside air into the closed container 1, it is not necessary to use the sealing plug 5 shown in FIG.

According to the method of this embodiment, as described in the previous embodiment, the time required for non-foaming can be greatly shortened, a constant molten state can be obtained, and the molten resin does not enter the pipe. The generation of beads on the inner surface of the pipe is prevented.

[0024]

As is apparent from the above description, according to the method for joining synthetic resin pipes of the present invention, the time required for non-foaming of the pipe end portion is greatly shortened as compared with the conventional method. In addition, a constant molten state of the pipe end is always obtained, and the quality of joining is improved. Further, the molten resin does not adhere to the heating body, and the thermally decomposed product of the molten resin is not caught in the joint portion, so that stable joining work can be performed.

[0025]

[Brief description of drawings]

FIG. 1 is an explanatory view showing a state in which a tube end portion is not foamed in an embodiment of the present invention.

FIG. 2 is an explanatory view showing a state in which a pipe end portion is melted in the embodiment of the present invention.

FIG. 3 is an explanatory view showing a state in which the tube end portion is fused in the embodiment of the present invention.

FIG. 4 is an explanatory view showing a state in which a tube end portion is defoamed or melted in another embodiment of the present invention.

FIG. 5 is an explanatory view showing a state in which a pipe end portion is fused in another embodiment of the present invention.

[Explanation of Codes] 1 airtight container 1a outer box 1b inner box 2 sealing packing 4 valve 5 sealing plug 6,8 heating body 7 movable tube clamp device 9 inner surface support body 10, 11 plate body 12 wire P ₁ , P ₂ Synthetic resin pipe

Claims (1)

[Claims] 1. A method for joining synthetic resin pipes in which the pipe ends of two synthetic resin pipes are heated and melted, and then both pipe ends are abutted and fused to each other, with the pipe ends being depressurized to atmospheric pressure or lower. A method for joining synthetic resin pipes, characterized in that the synthetic resin pipes are heated so that they do not come into contact with a heating body to be non-foamed, then melted, and then pressed in the pipe axial direction in a state where the pipe ends are abutted against each other to be fused.