JP2004230657A - Method for joining crosslinked polyethylene tube to joint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for joining a crosslinked polyethylene tube to a joint with the advantages that even a sleeve not crosslinked at all unexpectedly proves to be heat-resistant as a result of the study to find how the heat resistance and fusing strength of joint parts of the tube and the joint part change by the material, rotating velocity and the like of the sleeve and the frictional fusion joining of sufficient strength of the joint surface between the tube and the joint can be realized by setting the rotating velocity of the sleeve at the joint surface within a specified range. <P>SOLUTION: In this method, a frictional fusion layer of both joint parts of the joining member of is a polyethylene layer with a density of 0.93×10<SP>3</SP>to 0.95×10<SP>3</SP>kgf/m<SP>3</SP>and a melt flow rate of 0.1 to 10 g/10 min. The crosslinked polyethylene tube and the joint are forced into both joint parts of the joining member which rotate at a rotary velocity of 0.35 to 0.8 m/s and thus both tube and joint are joined together by frictional fusion. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for joining a crosslinked polyethylene pipe and a crosslinked polyethylene joint by rotational friction melting of a joining member.
[0002]
[Prior art]
For piping for gas, water supply, hot and cold water supply, hot springs, sprinklers, etc., thermoplastic resin piping materials having excellent corrosion resistance are used. Among them, olefin resins are widely used in these applications because they are lightweight, have excellent workability, and are ductile and have excellent earthquake resistance.
Further, since the olefin-based resin has a low melting point, the reliability of the entire pipe can be improved as compared with mechanical joining by forming a seamless pipe by using a fusion method.
As the fusion method, a butt fusion method of melting and bonding the joint surface of the piping material using a hot plate or a heating wire is built in the joint inner surface, and the joint and tube are melted by heat transfer and joined by energization. A so-called electrofusion method using an electrofusion joint is generally used.
[0003]
However, since the butt fusion method is fusion bonding by heat transfer, there are disadvantages that the time required for bonding is extremely long, and there are many methods for extruding a skin layer formed in a step of removing a hot plate. There is a drawback that a molten resin is required, and in the electric fusion method, it is difficult to recycle because the heating wire is built into the joint, and the joint becomes complicated, so that the cost is high and the joining time is long. There was a problem.
[0004]
The fusion between the resins is caused by the entanglement of the molecules, but the resin molecules generate a diffusion motion by applying heat, and the two resin molecules enter each other at the joint surface, and molecules having a length of one molecule or more are generated. By entanglement, high-strength fusion is developed.
Incidentally, the above-mentioned piping material is often subjected to crosslinking in order to improve heat resistance. In this case, the resin having a gel fraction of less than 50% contains many molecules that freely interdiffuse, so that as long as heat is applied, the resin is fused with high strength by any fusion method. However, there is a problem in that a resin having a gel fraction of 50% or more has few molecules that can freely diffuse into each other, so that simply applying heat does not result in high-strength fusion.
[0005]
On the other hand, as a method of joining the pipe members, the pipe members are pressed and held at both ends of a sleeve having an inner diameter smaller than the outer diameter, and by rotating the sleeve, the frictional heat causes the two pipe members to be in contact with each other. A so-called friction welding method for fusing the sleeve with the sleeve has been proposed.
Further, a sleeve having a joint having an inner diameter smaller than the outer diameter of the pipe and a joint having an outer diameter larger than the inner diameter of the joint is rotated, and the pipe and the joint are pressed and inserted into both joints of the rotating sleeve. Accordingly, it has been proposed to friction-weld the pipe and the joint.
[0006]
Therefore, the applicant of the present application considered that when connecting the cross-linked resin tube and the cross-linked resin joint to perform friction fusion welding using a rotating sleeve, and as a result of an experiment, it was found that An outer surface of the first piping material and an inner surface of the sleeve, and an inner surface of the second piping material and an outer surface of the sleeve are joined by friction welding. The gel fraction of the resin in the portion exposed to the inner surface layer of the pipe is 50% or more, and at least one of the joining surface between the first piping member and the sleeve, and the joining between the second piping member and the sleeve It was confirmed that this was possible by using a thermoplastic resin tube connection structure characterized in that the gel fraction of the resin on at least one of the surfaces was less than 50%, and a patent application was filed. (For example, refer to Patent Document 1).
[0007]
[Patent Document 1]
JP-A-2002-103453
[Problems to be solved by the invention]
However, as described in Patent Document 1, the degree of cross-linking is adjusted so that the gel fraction of the resin on at least one of the joining surfaces is constant at less than 50% and uniform over the entire joining surface. It is very difficult to do so, and the degree of crosslinking will inevitably vary.
When the degree of cross-linking varies, even if friction fusion bonding is performed using a rotating sleeve, the fusion state changes due to the change in the fusion state due to the degree of cross-linking, resulting in a difference in the fusion strength, When the production lot of the piping material or the sleeve is different, there has been a problem that unless the rotation speed is adjusted, it is not possible to perform the fusion with the strength that can be used for a long period of time.
[0009]
In order to solve the above problems, the present invention provides a method of friction-welding a cross-linked polyethylene pipe and a cross-linked polyethylene joint by rotation of a sleeve. After examining how the heat resistance and fusion strength of the joint between the joint and the joint change, surprisingly, even if the sleeve is not cross-linked at all, it expresses heat resistance, The present invention has been completed by finding that by making the rotational speed at the joint surface between the pipe and the joint within a certain range, it is possible to perform friction welding with sufficient strength.
[0010]
[Means for Solving the Problems]
A method for joining a crosslinked polyethylene pipe and a joint according to claim 1 of the present application is a method for joining a crosslinked polyethylene pipe and a crosslinked polyethylene joint by rotational friction fusion welding of a joining member, wherein the joining member has an outer diameter of the crosslinked polyethylene pipe. It has a joint having a smaller inner diameter and a joint having an outer diameter larger than the inner diameter of the crosslinked polyethylene joint, and the friction-fused layers of both joints have a density of 0.93 × 10 ^{3 to} 0.95 × 10 ^3. kgf / m ³ , a polyethylene layer having a melt flow rate of 0.1 to 10 g / 10 min. The joining member is rotated at a joining portion rotating speed of 0.35 to 0.8 m / s. The pipe and the joint are pressed and inserted into both joint portions of the rotating joining member, and are joined by friction melting.
[0011]
The present invention is configured as described above, and in the rotational friction fusion welding of the joining member, the density and the melt flow rate of the polyethylene layer of the friction welding portion of both joining portions of the joining member are set to a specific range of the polyethylene layer. By setting the rotation speed of the friction-welded portion of the joining member at the time of rotational friction welding to a specific range, the joining member is rotated, and the two joining portions of the rotating joining member are cross-linked with the cross-linked polyethylene pipe. Just by pressing and inserting the polyethylene joint, the outer surface of the end of the cross-linked polyethylene pipe and the inner surface of the joining member, and the outer surface of the joining member and the inner surface of the cross-linked polyethylene joint are fitted and fused by friction melting. That is, to perform rotational friction fusion between a cross-linked polyethylene pipe and a cross-linked polyethylene joint, using exactly the same apparatus as that used for rotational friction fusion between a conventional non-cross-linked olefin resin pipe and a joint, the same method is used. By the operation, the heat resistance of the cross-linked polyethylene pipe was maintained, and fusion bonding with sufficient strength became possible.
[0012]
The method for joining a crosslinked polyethylene pipe and a joint according to claim 2 is the method according to claim 1, wherein the difference between the outer diameter of the crosslinked polyethylene pipe and the inside diameter of the joint member and the outside diameter of the crosslinked polyethylene joint and the joint member of the joint member. It is characterized in that the difference from the diameter is 0.4 to 1.6 mm.
With such a difference, it is possible to easily perform strong fusion bonding in which frictional fusion is reliable and strong.
[0013]
The joint used in the present invention may be, for example, an elbow, a cheese, a reducer, an increaser, a header, or an adapter having a metal screw insert on one side. .
[0014]
Further, the crosslinked polyethylene pipe and the joint are molded from a polyethylene resin, preferably a medium density polyethylene, a high density polyethylene, an ultra high molecular weight polyethylene or the like, and are crosslinked to have heat resistance. Crosslinking to a degree having heat resistance, particularly when applied to a pipeline used under high temperature such as hot water or hot spring, the gel fraction needs to be 65% or more. The gel fraction is measured according to JIS K6796, and is defined as a weight percentage.
[0015]
In order to crosslink the polyethylene pipe and the joint, an ordinary crosslinking method is employed, and examples thereof include a water crosslinking method, an electron beam crosslinking method, and a crosslinking method using a crosslinking agent such as a peroxide.
[0016]
The joining member used in the present invention may be a resin molded product having heat resistance or a member formed of metal. It is necessary to have a friction fusion layer which is a polyethylene layer having a 93 × 10 ^{3 to} 0.95 × 10 ³ kgf / m ³ and a melt flow rate of 0.1 to 10 g / 10 minutes.
The polyethylene layer may be formed in a layer shape as a frictional fusion layer at the joint of the joining member, or the entire joining member may be molded from the polyethylene resin.
The polyethylene layer only needs to have a thickness (for example, 0.5 mm) or more that melts during rotational friction melting.
[0017]
The method for manufacturing the joining member is not particularly limited. If there is no problem in terms of shape, it is preferable to manufacture by injection molding in terms of molding cost. Further, a resin molded product or a metal component having heat resistance may be subjected to insert injection molding.
[0018]
In the present invention, the above-mentioned joining member is rotated and held within a range of 0.35 to 0.8 m / s in the rotational speed of the joining portion, and the cross-linked polyethylene pipe and the joint are attached to the joining portion of the rotating joining member. Is pressed and inserted, and the joint inner surface and the tube outer surface and the joint outer surface and the joint inner surface of the joint member are friction-fused and joined.
In order for the cross-linked polyethylene pipe and the joint to be pressed and inserted into the joint of the rotating joining member, the joint inner surface and the tube outer surface, and the joint outer surface and the joint inner surface of the joint member frictionally melt, so that the joining is performed. The member has a joint having an inner diameter smaller than the outer diameter of the cross-linked polyethylene pipe and a joint having an outer diameter larger than the inner diameter of the cross-linked polyethylene joint. The contact surface is frictionally melted and inserted.
[0019]
To obtain sufficient fusion strength by pressing and inserting the pipe and the joint into the joint of the rotating joining member, the difference between the outside diameter of the cross-linked polyethylene pipe and the inside diameter of the joining member and the inside diameter of the cross-linked polyethylene joint When the difference between the outer diameter of the joint and the joining member is 0.4 to 1.6 mm, the welding strength is high, and furthermore, the pipe and the joint can be easily pressed and inserted into the joining member, and the joining operation can be easily performed. Therefore, it is preferable.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing an example of a joined product joined by a joining method of a crosslinked polyethylene pipe and a joint according to the present invention.
In FIG. 1, 1 is a cross-linked polyethylene pipe, 2 is a kind of cross-linked polyethylene joint, a header for distributing the pipe, and 3 is a joining member. The pipe 1 has been subjected to a crosslinking treatment after extrusion molding, and the header 2 and the joining member 3 have been subjected to a crosslinking treatment after injection molding.
[0021]
As shown in FIG. 1, the cross-linked polyethylene pipe 1 and the joining member 3 are joined by rotational friction fusion between the outer end portion 11 of the cross-linked polyethylene pipe 1 and the joining portion inner surface 31 of the joining member 3. The joining member outer surface 32 of the joining member 3 is joined by rotational friction fusion joining.
[0022]
FIG. 2 is a side view showing an example of a joining apparatus for press-inserting the crosslinked polyethylene pipe 1 and the header 2 of the present invention into the joining portion of the joining member 3 held in rotation, and performing rotational friction fusion joining. is there.
[0023]
This joining device is provided with a rotation holder 4 for the joining member 3 at a central position. The rotation holder 4 is provided with rotation supporting gears 42, 42 for rotating and holding the joining member 3 on a frame 41, and the joining member 3 is mounted between the frame 41 and a driving gear 44 rotated by a motor 43, and is held and rotated. It has become. A driven gear is provided on the outer periphery of the joining member 3, and the judo gear is held in mesh with the rotation supporting gears 42, 42, and is rotated by the driving gear 44. The driven gear provided on the joining member 3 may be formed integrally with the joining member 3, or may be one in which a split driven gear is attached to the outer periphery of the joining member 3. If the split driven gear is made of metal, the gear is not damaged by rotation and can be removed after fusion, so that a clean piping line can be formed.
[0024]
The cross-linked polyethylene tube 1 is held by a holder 45, and the header 2 is held by a holder 46, and is movable toward the joint of the joint member 3 by the operation of the air cylinders 47 and 48.
[0025]
In order to fuse and join the crosslinked polyethylene pipe 1 and the header 2 by rotating the joining member 3 using this joining device, first, the rotation supporting gears 42 and 42 of the rotating holder 4 and the driving gear 44 Are mounted so that the driven gears mesh with each other, and the cross-linked polyethylene pipe 1 and the header 2 are held by the holders 45 and 46 such that the joints are concentric.
Then, the motor 43 is activated to rotate the driving gear 44 and rotate the driven gear, whereby the joining member 3 is rotated. Next, the air cylinders 47 and 48 are operated to move the holders 45 and 46 toward the joining portion of the rotating joining member 3, and press the crosslinked polyethylene pipe 1 against the joining portion inner surface 31 of the rotating member 3. At the same time as the insertion, the joint outer surface 32 is pressed into the inner surface 21 of the header 2.
[0026]
Since the outer diameter of the cross-linked polyethylene pipe 1 is larger than the inner surface 31 of the joining member 3 and the inner diameter of the header 2 is smaller than the outer surface 32 of the joining member 3, the cross-linked polyethylene tube 1 and the header 2 When pressed against the rotating joining member 3, both surfaces fitted by frictional heat are melted and inserted. When a predetermined dimension is inserted, the movement of the holders 45 and 46 by the air cylinders 47 and 48 is stopped, and the motor 43 is stopped. Until the friction melting portion cools and solidifies, the stopped state is maintained and then removed from the joining device.
[0027]
[Examples and Comparative Examples]
The present invention will be described in more detail with reference to Examples and Comparative Examples.
(Example 1)
As the crosslinked polyethylene pipe 1, a product name “Eslopex 13A” (manufactured by Mitsubishi Chemical Corporation, silane crosslinkable polymer XHE740N: density 0.947 g / cm ³ , melt flow rate 0.35 g / 10 min, manufactured by Sekisui Chemical Co., Ltd.) Extrusion molding, molding, and water-crosslinking, which had been adjusted to a gel fraction of 67%, and an outer diameter D of 17.2 mm) were used.
The header 2 is made of the same raw material as the above crosslinked polyethylene pipe, and has the shape shown in FIG. 3 (D1 = 29 mm, D2 = 25.8 mm, D3 = 23.2 mm, D4 = 17.2 mm, D5 = 13.3 mm). (2 mm, L1 = 12 mm, L2 = 3 mm) were molded by injection molding, crosslinked with water, and adjusted to a gel fraction of 67%.
As the joining member 3, a medium density polyethylene (NZ4005M manufactured by Mitsui Chemicals, density 0.942 g / cm ³ , melting point 129 ° C., melt flow rate 0.20 g / 10 minutes) was used as the shape shown in FIG. D11 = 29 mm, D12 = 23.7 mm, D13 = 16.7 mm, L3 = 23 mm, L4 = 13 mm) were prepared by injection molding.
[0028]
Then, the crosslinked polyethylene pipe 1, the header 2, and the joining member 3 were attached to the joining device shown in FIG. 2, and the joining member 3 was rotated at 542 rpm. Next, the air cylinders 47 and 48 are operated to move the crosslinked polyethylene tube 1 and the header 2 toward the rotating joining member 3, and the crosslinked polyethylene tube 1 is pressed and inserted into the joint inner surface 31 of the joining member 3. Then, the inner surface 21 of the header 2 is pressed and inserted into the outer surface 32 of the joining portion of the joining member 3. When the air cylinders 47 and 48 are moved by a predetermined distance, the operation of the air cylinders 47 and 48 is stopped, the rotation is performed for 8 seconds, and then the motor 43 is stopped. After maintaining the stopped state for 60 seconds and solidifying the fusion bonded portion, the bonded product shown in FIG. 1 was obtained.
At this time, the outer diameter of the cross-linked polyethylene pipe 1 is set to be 0.5 mm larger than the inner diameter of the inner surface 31 of the joining portion of the joining member 3, the rotation speed at the joining surface is 0.49 m / s, and the inner diameter of the inner surface 21 of the header 2 is Was made 0.5 mm smaller than the outer diameter of the joint outer surface 32 of the joint member 3, and the rotation speed at the joint surface was 0.66 m / s.
[0029]
An internal pressure creep test at 95 ° C. was performed on the obtained bonded product. As a result, the final state was a creep rupture of the crosslinked polyethylene pipe 1, and no water leakage from the bonded portion was observed.
[0030]
(Comparative Example 1)
In Example 1, the cross-linked polyethylene tube 1 and the header 2 were formed under the same conditions as in Example 1 except that the joining member 3 was formed from polyethylene having a density of 0.948 g / cm ³ and a melt flow rate of 0.03 g / 10 minutes. And were subjected to friction fusion bonding.
When an internal pressure creep test at 95 ° C. was performed on the obtained joint at an internal pressure of 1.3 MPa, water leaked from the joint between the joint and the joint member in about 50 hours.
[0031]
(Comparative Example 2)
In Example 1, the cross-linked polyethylene tube 1 and the header 2 were separated under the same conditions as in Example 1 except that the joining member 3 was formed from polyethylene having a density of 0.943 g / cm ³ and a melt flow rate of 20 g / 10 minutes. Friction fusion welding was performed.
When an internal pressure creep test at 95 ° C. was performed on the obtained joint at an internal pressure of 1.3 MPa, water leaked from the joint between the joint and the joint member in about 50 hours.
[0032]
(Comparative Example 3)
In Example 1, the cross-linked polyethylene pipe 1 and the header 2 were manufactured under the same conditions as in Example 1 except that the joining member 3 was molded from polyethylene having a density of 0.914 g / cm ³ and a melt flow rate of 2.3 g / 10 minutes. And were subjected to friction fusion bonding.
When an internal pressure creep test at 95 ° C. was performed on the obtained joint at an internal pressure of 1.3 MPa, water leaked from the joint between the joint and the joint member in about 20 hours.
[0033]
(Comparative Example 4)
A cross-linked polyethylene tube 1 and a header 2 were manufactured under the same conditions as in Example 1 except that the joining member 3 was formed from polyethylene having a density of 0.961 g / cm ³ and a melt flow rate of 0.63 g / 10 minutes. And were subjected to friction fusion bonding.
When an internal pressure creep test at 95 ° C. was performed on the obtained joint at an internal pressure of 1.3 MPa, water leaked from the joint between the joint and the joint member in about 20 hours.
[0034]
【The invention's effect】
The present invention is configured as described above, and in the rotational friction fusion welding of the joining member, the density and the melt flow rate of the polyethylene layer of the friction-welded portion of both joining portions of the joining member are set to a specific range of the polyethylene layer. At the same time, by setting the rotation speed of the friction welding portion of the joining member at the time of rotational friction welding to a specific range, the joining member is rotated, and a cross-linked polyethylene pipe is attached to both joining portions of the rotating joining member. Just by pressing and inserting the crosslinked polyethylene joint, the outer surface of the end of the crosslinked polyethylene pipe and the inner surface of the joining member, and the outer surface of the joining member and the inner surface of the crosslinked polyethylene joint are fitted and fused by friction melting. That is, to perform rotational friction fusion between a cross-linked polyethylene pipe and a cross-linked polyethylene joint, using exactly the same apparatus as that used for rotational friction fusion between a conventional non-cross-linked olefin resin pipe and a joint, the same method is used. By the operation, the heat resistance of the crosslinked polyethylene pipe was maintained, and the fusion bonding with sufficient strength became possible.
[0035]
In addition, there is a difference between the diameters of the two joining portions of the joining member, and when the joining member is rotated, a difference occurs in the rotational speed at the two joining portions. However, in the present invention, by using a joining member of a specific polyethylene layer and performing rotational friction fusion joining at a particular rotational speed, joining having equal fusion strength at both joining portions of the joining member is performed. Can be.
[0036]
The method for joining a crosslinked polyethylene pipe and a joint according to claim 2 is the method according to claim 1, wherein the difference between the outer diameter of the crosslinked polyethylene pipe and the inside diameter of the joint member and the outside diameter of the crosslinked polyethylene joint and the joint member of the joint member. Since the difference between the diameter and the diameter is 0.4 to 1.6 mm, it is possible to easily perform firm fusion bonding with reliable frictional fusion.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a joined product joined by a joining method of a crosslinked polyethylene pipe and a joint according to the present invention.
FIG. 2 is a side view showing an example of a joining apparatus for realizing the method for joining a crosslinked polyethylene pipe and a joint according to the present invention.
FIG. 3 is a sectional view showing a shape of a header 2 used in Example 1 and Comparative Examples 1 to 4.
FIG. 4 is a cross-sectional view showing the shape of a joining member 3 used in Example 1 and Comparative Examples 1 to 4.
[Explanation of symbols]
1 Crosslinked polyethylene pipe 2 Crosslinked polyethylene joint (header)
3 joining member 11 outer surface 21 of cross-linked polyethylene pipe 1 inner surface 31 of header 2 joining inner surface 32 of joining member 3 joining outer surface of joining member 3

Claims (2)

A method of joining a cross-linked polyethylene pipe and a cross-linked polyethylene joint by rotational friction fusion welding of a joining member, wherein the joining member has a joint having an inner diameter smaller than the outer diameter of the cross-linked polyethylene pipe and an outer diameter larger than the inner diameter of the cross-linked polyethylene joint. And the frictional fusion layer of both the joints has a density of 0.93 × 10 ^{3 to} 0.95 × 10 ³ kgf / m ³ and a melt flow rate of 0.1 to 10 g / 10 min. The joint member is rotated at a rotational speed of the joint between 0.35 and 0.8 m / s, and the pipe and the joint are pressed against both joints of the rotating joint member. A method for joining a crosslinked polyethylene pipe and a joint, wherein the joint is inserted, friction-fused, and joined. The difference between the outside diameter of the cross-linked polyethylene pipe and the inside diameter of the joint at the joint member and the difference between the inside diameter of the cross-linked polyethylene joint and the outside diameter of the joint at the joint member are 0.4 to 1.6 mm. Of joining a crosslinked polyethylene pipe with a joint.

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