JPH112383A - Cylindrical electric fusion joint for connecting crosslinked polyethylene resin pipes - Google Patents

Abstract

(57) [Summary] [Problem] Excellent pressure resistance, tensile resistance, hot water resistance, 40-
Provided is a tubular electric fusion joint for connecting a crosslinked polyethylene resin pipe which has a long service life even when used as a joint for hot water piping heated to 100 ° C. SOLUTION: A cylindrical body for connecting at least two crosslinked polyethylene resin pipes by inserting an end of a crosslinked polyethylene resin pipe into a cylinder, and an electric heater wire disposed on an inner wall surface of the cylindrical body. Tubular electric fusion for connecting a crosslinked polyethylene resin pipe, comprising: a heater terminal disposed on a side surface of the tubular body for connecting to both ends of the electric heater wire and connecting to a connector for energization. In the joint, the tubular electrofusion joint is formed of a crosslinked polyethylene resin,
A tubular electric fusion joint for connecting a crosslinked polyethylene resin pipe, wherein an electric heater wire disposed on an inner wall surface of the tubular body is covered with a heat-resistant insulating resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tubular electric fusion joint for connecting crosslinked polyethylene resin pipes which has excellent pressure resistance, tensile strength resistance and hot water resistance and has a long service life even when used as a joint for hot water piping. Things.

[0002]

2. Description of the Related Art Conventionally, as a tubular joint for connecting polyethylene resin pipes by electric fusion, a heating wire (electric heater wire) for heating is previously buried in the inner wall of the tubular joint made of polyethylene resin. A current flows through a heater terminal protruding from a side surface of the tubular joint, thereby causing the electric heater wire to generate heat, thereby fusing the tubular joint and the polyethylene resin tube. Fusion joints are known. On the other hand, compared with the above polyethylene resin pipes, crosslinked polyethylene resin pipes having excellent heat resistance, pressure resistance, etc. are widely used for piping of hot water for heating heated to 40 to 100 ° C., hot springs, geothermal water, and the like. However, in order to connect such crosslinked polyethylene resin pipes, generally, a special polyolefin resin adhesive is applied to the crosslinked polyethylene resin pipe, and a sleeve fusion method of connecting the adhesive as a binder is used. (See Japanese Patent Laid-Open No. 58-209524). Further, regarding the cylindrical electro-fusion joint for connecting the cross-linked polyethylene resin pipe, PLASTIC PIP
ES VIII (The PLASTIC AND
RUBBER INSTITUTE) Pages 21-24
September issue "CROSSLINKED" issued in 1992
POLYETHYLEN-EXTENDING THE
LIMITS OF PRESSURE PIPE
"SYSTEM PERFORMANCE" states that a crosslinked polyethylene resin pipe can also be connected by the above-mentioned non-crosslinked polyethylene resin tubular electric fusion joint. Therefore, as for the tubular electro-fusion joint for connecting the cross-linked polyethylene resin pipe, it is introduced that the connection is performed by using a normal tubular electro-fusion joint for connecting a polyethylene resin pipe.

[0003]

However, in the method of connecting a cross-linked polyethylene resin tube by sleeve fusion or butt fusion in which the above-mentioned adhesive is connected as a binder,
A good solvent of a polyethylene resin (benzene, toluene, xylene) is used as a solvent in the adhesive,
These good solvents for the polyethylene resin are difficult to completely remove in the drying treatment before fusing, and remain at the fusing interface, which may adversely affect the fusing, and the good solvent for the polyethylene resin is Steam also had problems in terms of safety and workability. In addition, the non-crosslinked polyethylene resin-made cylindrical electric fusion joint has low heat resistance, and can be used for a long time at room temperature. There is a disadvantage that leakage occurs. Therefore, pipes made of cross-linked polyethylene resin
Since it has a service life of 25 years or more even when used at a temperature of about 80 ° C., a tubular electrofusion joint made of a crosslinked polyethylene resin that can be easily connected has been desired. However, in order to connect a cross-linked polyethylene resin pipe using a tubular electro-fusion joint made of cross-linked polyethylene resin, the uncross-linked component (sol) of the cross-linked polyethylene resin pipe component must be melted. It is necessary to energize for a longer period of time and fuse at a higher temperature than in the case of melting a cylindrical electric fusion joint made of resin. Therefore, in the case of a conventional electric heater wire such as a non-crosslinked polyethylene resin tubular electric fusion joint, when the electric current is supplied, the electric heater wire starts dancing, and a short circuit occurs to make it impossible to heat, or the temperature becomes lower than the fusion temperature. As a result, a sufficient connection of the crosslinked polyethylene resin tube could not be made.

[0004]

Means for Solving the Problems The present inventor has conducted intensive studies in view of the above problems, and as a result, has found that the use of an electric fusion joint made of a crosslinked polyethylene resin in which an electric heater wire is covered with a heat-resistant insulating resin. It can be fused at high temperature, and it is possible to connect the cross-linked polyethylene resin pipe with an electric fusion joint made of cross-linked polyethylene resin, and it is excellent in pressure resistance, tensile strength resistance, hot water resistance, and for hot water piping The present invention has been completed based on the finding that a crosslinked polyethylene resin pipe having a long service life can be connected even when used as a joint. That is, the tubular electrofusion joint for crosslinked polyethylene resin pipe connection of the present invention is a tubular body for connecting at least two crosslinked polyethylene resin pipes by inserting the end of the crosslinked polyethylene resin pipe into the cylinder, An electric heater wire disposed on the inner wall surface of the tubular body, and a heater disposed on a side surface of the tubular body for connecting to both ends of the electric heater wire and connecting to a current-carrying connector. A tubular electric fusion joint for connecting a crosslinked polyethylene resin pipe comprising a terminal, wherein the tubular electric fusion joint is formed of a crosslinked polyethylene resin, and is disposed on an inner wall surface of the tubular body. Are coated with a heat-resistant insulating resin.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION

[I] Cylindrical electric fusion joint for connecting a crosslinked polyethylene resin pipe (1) Structure The structure of the cylindrical electric fusion joint 1 for connecting a crosslinked polyethylene resin pipe of the present invention is shown in FIGS. Similarly, a tubular body 3 for connecting at least two crosslinked polyethylene resin pipes 2 and 2 'by inserting the end 2a of the crosslinked polyethylene resin pipe 2 into the barrel, and an inner wall surface 3a of the tubular body 3 This is basically composed of an electric heater wire 6 covered with a heat-resistant insulating resin 4 and a polyethylene resin 5 and a heater terminal 7 disposed on a side surface portion 3b of the tubular body 3.

(A) Cylindrical body As shown in FIG. 2, the cylindrical body 3 is used to insert the ends 2a and 2'a of the crosslinked polyethylene resin pipes 2 and 2 'to be connected. It has an inner diameter slightly larger than the outer diameter of the resin pipes 2 and 2 ′, and a stopper 8 is provided at the center of the inner wall of the tubular body 3 so as to project toward the center. Only one of the inserted crosslinked polyethylene resin tubes 2, 2 'is provided so as not to be inserted more than necessary. In FIG. 2, the tubular body 3 is a tubular electro-fusion joint 1 for connecting a cross-linked polyethylene resin pipe for connecting two cross-linked polyethylene resin pipes 2 and 2 ′ in a straight line. Or a U-shaped cylindrical body 3, or three cross-linked polyethylene resin tubes 2, 2 ',
A T-shaped or Y-shaped tubular body for connecting the 2 ″ can be formed, and four or more tubular bodies 3 can be formed in substantially the same manner.

(B) Electric heater wire The electric heater wire 6 is a cross-linked polyethylene resin tube 2,
In order to fuse 2 ′, it is important to melt and fuse at a high temperature, so that it is important that the wire is covered with the heat-resistant insulating resin 4. However, if the heater wire 6 is used, the heater wires 6 may be short-circuited or fusion at a high temperature may not be performed. Heat-resistant insulating resin 4 covering the electric heater wire 6
Is formed on the outer periphery of the electric heater wire 6 with a thickness of generally about 10 to 1,000 μm, as shown in FIG.
In addition, generally 0.2 to 5 mm, preferably 0.5 to
Covered with polyethylene resin 5 having a thickness of about 3 mm,
In addition to providing electrical insulation, the outer polyethylene resin layer 5 is easily melted. The electric heater wire 6 covered with the heat-resistant insulating resin 4 and the polyethylene resin 5 has a mat layer 9 in which the coated medium-density polyethylene resin or high-density polyethylene resin 5 is continuously arranged as shown in FIG. Preferably, it is formed. The mat layer 9 of the electric heater wire 6 covered with the heat-resistant insulating resin 4 and the polyethylene resin 5
A concave portion 3c is formed in a part of the inner wall surface portion 3a, and is disposed in the concave portion 3c.

(C) Heater terminal The heater terminals 7, 7 'are arranged so as to protrude from the side surface 3b of the tubular body 3, as shown in FIGS. , 7 'on the base end side 7a, 7'a
Are connected to both ends of the electric heater wires 6, 6 '. The heater terminals 7, 7 ′ can be freely connected to a connector 13 connected to, for example, an AC 200 V power supply 10 via a controller 11 and a switch 12. Also, the peripheral portion 7 of the heater terminals 7, 7 '
b, 7'b, as shown in FIGS.
3, a terminal terminal wall 15 is formed so that the size determination terminal 14 is embedded or a connector 13 can be connected to the terminal terminal wall 15. After termination of energization, the terminal terminal wall 15 is covered with a cap 16 to prevent corrosion. Screw portion 17 is formed as described above.

(2) Material (a) Cross-linked polyethylene resin As the cross-linked polyethylene resin used as a material of the tubular electrofusion joint 1 for connecting a cross-linked polyethylene resin pipe of the present invention, a medium-density or high-density polyethylene resin is cross-linked. Specifically, a medium-density or high-density polyethylene resin is mixed with an organic peroxide such as dicumyl peroxide, and the organic peroxide is decomposed by heating to generate radicals and crosslink. A cross-linked polyethylene resin, a hydrogen atom is removed from a molecule excited by irradiation with γ-rays, an electron beam, or the like to generate free radicals of polyethylene and react with a molecular chain of another polyethylene, or The ethylene-vinylsilane compound graft copolymer obtained by graft-polymerizing a polyethylenevinylsilane compound Examples thereof include crosslinked polyethylene resins crosslinked by a condensation reaction below. Among these, it is preferable to use the crosslinked polyethylene resin described above. As the crosslinked polyethylene resin has a higher crosslink density, it is harder to melt and becomes harder, and a crosslinked polyethylene resin having a gel fraction of usually 20 to 85%, preferably 30 to 70, particularly preferably 40 to 60 is used. If the gel fraction is less than the above range, voids increase in order to obtain satisfactory fusion. On the other hand, if the ratio exceeds the above range, melting becomes difficult, and fusion must be performed at a high temperature. As a result, the void ratio increases, and thermal deterioration tends to occur.

(B) Electric heater wire Examples of the electric heater wire 6 include a nichrome wire, a copper wire, and a copper alloy (electric copper ingot JIS-H2121) wire. It is important that the surface of the electric heater wire 6 is covered with the heat-resistant insulating resin 4 so as to be insulative. If the electric heater wire 6 not covered with the heat-resistant insulating resin 4 is used, short-circuiting or fusion at a high temperature cannot be performed. The heat-resistant insulating resin 4 covering the electric heater wire 6 is applied to the outer periphery of the electric heater wire 6 or
It is formed with a thickness of about 0 to 1,000 μm to provide electrical insulation. The electric heater wire 6 is covered with a heat-resistant insulating resin 4, and further covered with a polyethylene resin 5. Then, the electric heater wire 6 covered with the heat-resistant insulating resin 4 and the polyethylene resin 5 and the like is wound around the inner cylinder without any gap and formed in a mat shape.
When a mat layer 9 of a medium-density polyethylene resin, a high-density polyethylene resin, or a silane-crosslinked polyethylene resin is formed and the electric heater wire 6 is energized, the medium-density polyethylene resin, the high-density polyethylene resin, or the silane The sol in the crosslinked polyethylene resin (uncrosslinked polyethylene resin) as the mat layer 9 of the crosslinked polyethylene resin melts
Is presumed to be mixed into the crosslinked polyethylene resin to penetrate into the network structure to form an integrated structure.

(C) Heat-resistant insulating resin The heat-resistant insulating resin 4 covering the electric heater wire 6 has a melting temperature of 250 ° C. or higher, preferably 300 to 40 ° C.
0 ° C, particularly preferably 350 to 400 ° C, and a dielectric strength of 2
00 kV / mm or more, preferably 250 to 350 kV /
mm. Specifically, polyimide resin, polyamide imide resin, polyether imide resin,
Examples thereof include a polyimide resin such as a polyesterimide resin, a polyetheretherketone resin, a polyethersulfone resin, and a fluorine resin. The thickness of the heat-resistant insulating resin 4 covering the electric heater wire 6 is generally 10 to
It is 1,000 μm, preferably about 20 to 500 μm.

(D) Mat layer The mat layer 9 of the electric heater wire 6 covered with the heat-resistant insulating resin 4 and the polyethylene resin 5 is usually made of a medium-density polyethylene resin, a high-density polyethylene resin or a silane cross-linked resin. Polyethylene resin
Preferably, a silane cross-linked polyethylene resin is used.
The thickness of the mat layer 9 is generally 0.2 to 5 m.
m, preferably about 0.3 to 3 mm.

(3) Crosslinked polyethylene resin pipes As the crosslinked polyethylene resin pipes 2 and 2 ′ that can be connected by the above tubular electric fusion joint 1 for connecting a crosslinked polyethylene resin pipe of the present invention, commercially available crosslinked polyethylene resin pipes For example, the gel fraction is 20 to 85%, preferably 30
It is preferred to use ~ 70%, particularly preferably 40-60, crosslinked polyethylene resin tubes. In addition, it is preferable to use a crosslinked polyethylene resin tube not covered with a non-crosslinked polyethylene resin for the crosslinked polyethylene resin tubes 2 and 2 ′.

[II] Connection Method Cylindrical electric fusion joint 1 for connecting the above crosslinked polyethylene resin pipe
In order to connect the cross-linked polyethylene resin pipes 2 and 2 ′, one end of the cross-linked polyethylene resin pipes 2 and 2 ′ is generally inserted into the inner cylindrical portion of the cylindrical electro-fusion joint 1, and then the cylindrical electro-fusion joint is connected. The connector 13 connected to the 200 V AC power supply 10 via the controller 11 and the switch 12 is connected to the heater terminals 7 and 7 ′ of the electric heater wire 6 arranged on the side surface portion 3 b of the first unit 3, and the switch 12 is turned on. Then, a predetermined amount of electric power is applied to the electric heater wire 6 to perform fusion. The amount of power to be given varies depending on the inner diameter and the fusion area of the crosslinked polyethylene resin pipes 2 and 2 'to be connected, and is usually the amount of power shown in Table 1 below.

[0015]

[Table 1]

More specifically, for example, a constant-voltage power supply 10 of 40 volts is connected to the electric heater wire 6 by 250 to 40 volts.
0 seconds, preferably for 300 to 375 seconds, 75
By applying electric energy of 0 to 1,150 J / cm ² , heat of 200 to 250 ° C. and pressure of 3 to 10 kgf / cm ² due to thermal expansion are generated on the fusion surface, and the heat of the mat layer 9 The polyethylene resin 5 is melted and pressure-bonded to the joint 1 and the cross-linked polyethylene resin pipes 2, 2 'softened due to the thermal expansion pressure. Impregnate inside. The reason why the polyethylene resin 5 of the mat layer 9 is impregnated in the crosslinked polyethylene structure is that, in the case of the silane crosslinked polyethylene, only about 85% is crosslinked (gelled) at most.
It is estimated that the remaining 15% can be fused by appropriately applying heat and pressure. Also,
The crosslinked polyethylene resin does not melt as freely as non-crosslinked polyethylene resin under high temperature and high pressure conditions generated in the tubular electrofusion joint 1 for crosslinked polyethylene resin pipe connection, but softens to the extent that molecules are entangled. I think that the. Also, a tubular electric fusion joint 1 for connecting a crosslinked polyethylene resin pipe.
The difference between the diameters of the crosslinked polyethylene resin pipes 2 and 2 'inserted into the cylinder varies depending on the thickness of the inserted crosslinked polyethylene resin pipes 2 and 2', but generally has a nominal diameter of 25 to
250 and 0.5 to 5.4 mm.

[III] Performance The tubular electrofusion joint for connecting a crosslinked polyethylene resin pipe of the present invention can be used to remove a crosslinked polyethylene pipe, particularly a crosslinked polyethylene resin pipe not coated with non-crosslinked polyethylene resin, at a peeling rate of 25%. % Or less, and a void ratio of 25% or less, preferably a peeling ratio of 20% or less, and a void ratio of 20% or less,
Particularly preferably, the peeling rate is 10% or less and the void rate is 1%.
Since it is fused at 5% or less, it is excellent in pressure resistance, tensile strength and hot water resistance, and has a long service life even when used as a joint for hot water piping.

[IV] Application The tubular electrofusion joint 1 for connecting a crosslinked polyethylene resin pipe of the present invention is used as a tubular electrofusion joint 1 for connecting a crosslinked polyethylene resin pipe for piping of hot water, hot chemical solution or the like. Not only can it be used as a tubular electro-fusion joint 1 for connecting non-crosslinked polyethylene resin pipes for piping of water, chemicals, etc., but in particular, heating hot water heated to 40 to 100 ° C., hot springs, It is preferable to use as the tubular electric fusion joint 1 for connecting a crosslinked polyethylene resin pipe for piping such as geothermal water.

[0019]

The present invention will be described more specifically with reference to the following experimental examples. [I] Evaluation method (1) Measurement of gel fraction It was measured according to JIS-K6769 “Method for measuring gel fraction of crosslinked polyethylene pipe”. (2) Measurement of peeling test As shown in FIG. 5 (a), a sample was manufactured by cutting the fused pipe and the joint axially at a thickness of about 2 mm evenly from the entire EF joint. After the entire sample was sandwiched and fixed at a position 1 mm below the interface between the mat and the joint of the joint portion of the sample, at room temperature, a force was applied to the fusion interface as shown in FIG. Pipe sections 90 whole forward
The operation of bending at 90 degrees backward and backward was repeated 10 times. After the operation was completed, the length (L1) peeled off at the boundary surface between the mat layer and the pipe and the total fusion length (L2) were measured. The peeling rate was calculated by the following equation. Peeling rate = (L1 / L2) × 100

(3) Measurement of void ratio The void ratio is the peel ratio of the joint and the mat as measured by the above-mentioned "(2) Measurement of peel test". Is obtained by measuring the total length of the length (L3) of the void portion generated by the entanglement of the joint and the length (L4) of the portion peeled off at the interface between the joint and the mat. Was used to calculate the void fraction. Void ratio = (L3 / L2) × 100 (4) Measurement of pressure resistance test (JIS-K6769) A water pressure of 17.5 kgf / cm ² was applied to the fused portion for 60 minutes, and leakage was confirmed.

(5) Measurement of tensile test (JIS-K676)
9) From a sample manufactured in the same manner as in the above-described peeling test, a sample having a thickness of about 2 mm and a width of 20 mm was cut, and a tensile tester AG-5000E manufactured by Shimadzu Corporation was used. It was measured at a pull rate of min. (6) Measurement of hot water resistance test Inner diameter 95.6 mm connected using six electrofusion joints
The hot water of 95 ° C. was constantly passed through the crosslinked polyethylene resin pipe at a pressure of 1 kgf / cm ² outdoors, and the time when an abnormality such as leakage occurred was measured.

[II] Experimental Examples Example 1 A 3.58-m-long copper alloy (electric copper JIS-JIS) coated with a polyimide resin to a thickness of 50 μm and further covered with a medium-density polyethylene resin to a thickness of 1.5 mm H21
21) is wound around the core of outer diameter 114.5 mm 17 times each, and 76.times.
A mat layer of an electric heater wire coated with a polyimide resin and a medium density polyethylene resin is formed with a length of 2 mm. next,
The core having the mat layer formed thereon is set in a mold having an outer diameter of 130 mm, an inner diameter of 114.5 mm, and a length of 155 mm,
A vinylsilane-grafted high-density polyethylene resin was injection-molded, and as shown in FIG.
An electrofusion joint having a length of 5 mm and a length of 155 mm was manufactured. At the side of the tubular body of the electric fusion joint, heater terminals to which the ends of the electric heater wires are connected are formed so as to protrude. This was left in the air to produce an electrofusion joint made of a silane-crosslinked high-density polyethylene resin having a gel fraction of 60%. An outer diameter of 114.0 m is provided on the inner cylinder portion of the silane-crosslinked high-density polyethylene resin electrofusion joint.
m, an inner diameter of 95.6 mm, and one end side of two hot spring piping made of crosslinked high density polyethylene resin having a gel fraction of 60% were inserted. Next, a connector connected to a 200 V AC power supply via a controller and a switch was connected to a heater terminal projecting from a side surface of the tubular body of the electrofusion joint. Then, the electric heater wire of the electric fusion joint is energized with a constant power supply of 40 volts for 350 seconds (about 900 J / cm ² ), and the cross-linked polyethylene resin pipe is connected to the electric fusion joint for connecting the cross-linked polyethylene resin pipe. did. The joints obtained were evaluated. As a result, the peeling rate was 5.5%, and the void rate was 8.8%. In the pressure test, no leakage occurred even when a water pressure of 17.5 kgf / cm ² was applied for 60 minutes. The tensile strength by the tensile test was 23.5 N / mm ² , and there was no leakage even after 416 days in the hot water resistance test.

Example 2 Example 2 was carried out in the same manner as in Example 1, except that the gel fraction of the electrofusion joint and the tube made of a crosslinked high-density polyethylene resin were changed to the materials shown in Table 2. Table 2 shows the results.

Example 3 The procedure of Example 1 was repeated, except that the current supply time was changed to 150 to 400 seconds, and the peeling rate and void rate of the obtained joint were measured. Table 3 shows the results.

Example 4 The procedure of Example 1 was repeated, except that the medium-density polyethylene resin coated with the heater wire was changed to a vinylsilane-grafted high-density polyethylene resin. The joints obtained were evaluated. As a result, the peeling rate was 4.7%, and the void rate was 5.2%.
In the pressure test, no leakage occurred even when a water pressure of 17.5 kgf / cm ² was applied for 60 minutes. Further, the tensile strength in the tensile test was 22.5 N / mm ² , and there was no leakage even after 416 days in the hot water resistance test.

Comparative Example 1 The procedure of Example 1 was repeated, except that an electric heater wire not coated with a polyimide resin was used as the electric heater wire. As a result, when the connector was connected and energized, a short circuit occurred 80 seconds after the energization, and a sufficient connection could not be made.

Comparative Example 2 A tubular electrofusion joint made of a crosslinked high-density polyethylene resin having a gel fraction of 60% used in Example 1 was replaced with a tube made of a non-crosslinked high-density polyethylene resin (gel fraction 0%). The hot spring piping made of cross-linked high-density polyethylene resin with a gel fraction of 60% was changed to a water pipe made of non-cross-linked high-density polyethylene resin (gel fraction 0%), The procedure was performed in the same manner as in Example 1 except that the energization time was changed to 150 to 400 seconds, and the peeling rate and the void rate of the obtained joint portion were measured. Table 3 shows the results.

Comparative Example 3 A tubular electrofusion joint made of a crosslinked high-density polyethylene resin having a gel fraction of 60% used in Example 1 was replaced with a tube made of a non-crosslinked high-density polyethylene resin (gel fraction 0%). The procedure was the same as in Example 1 except that the joint was changed to an electrofused joint and the energization time was changed to 150 to 400 seconds, and the peeling ratio and void ratio of the obtained joint were measured. Table 3 shows the results.

[0029]

[Table 2]

[0030]

[Table 3]

[0031]

As described above, the electric fusion joint for connecting a crosslinked polyethylene resin pipe of the present invention uses a crosslinked polyethylene resin as a material thereof, and uses an electric heater wire covered with a heat-resistant insulating resin. Polyethylene resin pipes can be connected with cross-linked polyethylene resin electric fusion joints,
It has excellent hot water resistance and can provide a connection with a long service life even when used as a joint for hot water piping.
It is extremely excellent for piping of hot water for heating, hot springs, geothermal water, etc.

[Brief description of the drawings]

FIG. 1 is a plan view of an electric fusion joint for connecting a crosslinked polyethylene resin pipe according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the electric fusion joint for connecting a crosslinked polyethylene resin pipe of FIG. 1 taken along the line AA.

FIG. 3 is a sectional view of the electric fusion joint for connecting a crosslinked polyethylene resin pipe shown in FIG. 2 taken along the line BB.

FIG. 4 is a cross-sectional view of a mat layer of an electric heater wire covered with a heat-resistant insulating resin and a polyethylene resin.

FIG. 5 (a) is a drawing method of a sample in a peeling test of a tubular electric fusion joint for connecting a crosslinked polyethylene resin pipe, and FIG. 4 (b) is an explanatory diagram relating to a bending operation in the peeling test. .

FIG. 6 is a diagram illustrating a measurement method in a tensile peel test.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylindrical electrofusion joint for crosslinked polyethylene resin pipe connection 2, 2 ', 2 "Crosslinked polyethylene resin pipe 2a, 2'a, 2" a End part 3 Cylindrical body 3a Inner wall surface part 3b Side surface part 3c Concave part 4 Heat resistant insulating resin 5 Polyethylene resin 6, 6 'Electric heater wire 7 Heater terminal 7a, 7'a Base end side 7b, 7'b Peripheral edge 8 Stopper 9 Mat layer 10 Power supply 11 Controller 13 Switch 13 Connector 14 Size determination terminal 15 Terminal terminal wall 16 Cap 17 Screw part

[Procedure amendment]

[Submission date] September 1, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

(A) Cylindrical Body As shown in FIG. 2, the cylindrical body 3 is used to insert the ends 2a, 2'a of the cross-linked polyethylene resin pipes 2, 2 'to be connected. It has an inner diameter slightly larger than the outer diameter of the resin pipes 2 and 2 ′, and a stopper 8 is provided at the center of the inner wall of the tubular body 3 so as to project toward the center. Only one of the inserted crosslinked polyethylene resin tubes 2, 2 'is provided so as not to be inserted more than necessary. In FIG. 2, the tubular body 3 is the cross-linked polyethylene resin pipe-connecting tubular electro-fusion joint 1 for connecting the two cross-linked polyethylene resin pipes 2 and 2 ′ in a straight line. Or a U-shaped cylindrical body 3 or three cross-linked polyethylene resin pipes 2, 2
It is possible to form a T-shaped or Y-shaped tubular body for connecting ', 2'', and to form four or more tubular bodies 3 in substantially the same manner.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction contents]

(B) Electric heater wire The electric heater wire 6 is a cross-linked polyethylene resin tube 2,
In order to fuse 2 ′, it is important to be melted and fused at a high temperature. Therefore, it is important that the wire 2 ′ is covered with the heat-resistant insulating resin 4 and the electric heater wire 6 not covered with the heat-resistant insulating resin 4. However, if the heater wire 6 is used, the heater wires 6 may be short-circuited or fusion at a high temperature may not be performed. Heat-resistant insulating resin 4 covering the electric heater wire 6
As shown in FIG. 4, is formed on the outer periphery of the electric heater wire 6 with a thickness of generally about 10 to 1,000 μm, and further thereon, generally 0.2 to 5 mm, preferably 0 to 5 μm. .
It is covered with a polyethylene resin 5 having a thickness of about 5 to 3 mm to provide electrical insulation, and the outer polyethylene resin layer 5 is in contact with an electric heater wire 6 covered with a heat-resistant insulating resin 4. Therefore, the electric heater wire 6
, The polyethylene resin 5 can be melted. The electric heater wire 6 covered with the heat-resistant insulating resin 4 and the polyethylene resin 5
As shown in FIG. 4, it is preferable that the coated medium-density polyethylene resin or high-density polyethylene resin 5 is continuously arranged to form the mat layer 9. The mat layer 9 of the electric heater wire 6 covered with the heat-resistant insulating resin 4 and the polyethylene resin 5 is provided on the inner wall surface 3 of the tubular body 3.
A concave portion 3c is formed in a part of “a” and is disposed in the concave portion 3c.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction contents]

(C) Heater terminal The heater terminals 7, 7 'are provided so as to protrude from the side surface 3b of the tubular body 3, as shown in FIGS. , 7 'on the base end side 7a, 7'a
Are connected to both ends of the electric heater wires 6, 6 '. The heater terminals 7, 7 ′ can be freely connected to a connector 13 connected to, for example, an AC 200 V power supply 10 via a controller 11 and a switch 12. Also, as shown in FIGS. 1 to 3, the terminal 14 for judging the size of the joint 1 is embedded in the peripheral portion of the heater terminals 7 and 7 ′, and the terminal terminal wall is formed so that the connector 13 can be freely connected. 15 are formed,
A screw portion 17 is formed on the terminal terminal wall 15 so that a cap is put on the terminal terminal wall 15 to prevent corrosion after the end of energization.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

(2) Material (a) Cross-linked polyethylene resin As the cross-linked polyethylene resin used as the material of the tubular electro-fusion joint 1 for connecting a cross-linked polyethylene resin pipe of the present invention, a medium-density or high-density polyethylene resin is cross-linked. Specifically, a medium-density or high-density polyethylene resin is mixed with an organic peroxide such as dicumyl peroxide, and the organic peroxide is decomposed by heating to generate radicals and crosslink. Cross-linked polyethylene resin, a hydrogen atom is released from a molecule excited by irradiating γ-ray, electron beam, etc., to generate a free radical of polyethylene and react with a molecular chain of another polyethylene, or The ethylene-vinylsilane compound graft copolymer obtained by graft-polymerizing a vinylsilane compound to polyethylene is And a cross-linked polyethylene resin cross-linked by a condensation reaction in the presence of water. Among these, it is preferable to use the crosslinked polyethylene resin described above. As the crosslinked polyethylene resin has a higher crosslink density, it is harder to melt and becomes harder, and a crosslinked polyethylene resin having a gel fraction of usually 20 to 85%, preferably 30 to 70, particularly preferably 40 to 60 is used. If the gel fraction is less than the above range, voids increase in order to obtain satisfactory fusion. On the other hand, if the ratio exceeds the above range, melting becomes difficult, and fusion must be performed at a high temperature. As a result, the void ratio increases, and thermal deterioration tends to occur.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction contents]

[II] Connection Method The above-mentioned tubular electric fusion joint 1 for connecting a crosslinked polyethylene resin pipe.
In order to connect the cross-linked polyethylene resin pipes 2 and 2 ′, one end of the cross-linked polyethylene resin pipes 2 and 2 ′ is generally inserted into the inner cylindrical portion of the cylindrical electro-fusion joint 1, and then the cylindrical electro-fusion joint is connected. The connector 13 connected to the 200 V AC power supply 10 via the controller 11 and the switch 12 is connected to the heater terminals 7 and 7 ′ of the electric heater wire 6 arranged on the side surface portion 3 b of the first unit 3, and the switch 12 is turned on. Then, a predetermined amount of electric power is applied to the electric heater wire 6 to perform fusion. The amount of power to be applied varies depending on the nominal diameter and the fusion area of the crosslinked polyethylene resin pipes 2 and 2 'to be connected, and is usually the power amount shown in Table 1 below.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

[0015]

[Table 1]

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction contents]

Specifically, for example, a pipe nominal diameter 1
00, a 40 volt constant control power supply 10 is applied to the electric heater wire 6 for 250 to 400 seconds, preferably 300
For 375 seconds, 750 to 1,150 J / cm ²
By applying electric energy, 200
Heat of ~ 250 ° C and 3 ~ 10kgf / cm due to thermal expansion
² is generated, and the heat melts the polyethylene resin 5 of the mat layer 9 and softens the joint 1 due to the thermal expansion pressure.
And it is pressure-bonded to the crosslinked polyethylene resin pipes 2 and 2 ', and a part is impregnated in the crosslinked polyethylene structure of the joint 1 and the crosslinked polyethylene resin pipes 2 and 2'. The polyethylene resin 5 of the mat layer 9 is impregnated in the crosslinked polyethylene structure in the case of silane crosslinked polyethylene at a maximum of 8%.
Only about 5% is cross-linked (gelled) and the remaining 15%
It is presumed that fusion can be achieved by appropriately applying heat and pressure. Also, the cross-linked polyethylene resin does not melt as freely as the non-cross-linked polyethylene resin under the high-temperature and high-pressure conditions generated in the tubular electro-fusion joint 1 for cross-linked polyethylene resin pipe connection, but softens to the extent that the molecules are entangled. It seems to do. The difference between the diameters of the tubular electric fusion joint 1 for connecting a cross-linked polyethylene resin pipe and the cross-linked polyethylene resin pipes 2 and 2 ′ inserted into the pipe is the difference between the cross-linked polyethylene resin pipes 2 ', But generally varies from 0.5 to 250 for nominal diameter of 25 to 250.
5.4 mm.

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction contents]

(3) Measurement of void ratio The void ratio is the peel ratio of the joint and the mat when measured according to the above-mentioned "(2) Measurement of peel test". Is obtained by measuring the total length of the length (L3) of the void portion generated by the entanglement of the joint and the length (L4) of the portion peeled off at the interface between the joint and the mat. Was used to calculate the void fraction. Void rate = {(L3 + L4) / L2} × 100 (4) Measurement of pressure resistance test A water pressure of 17.5 kgf / cm ² was applied to the fused portion for 60 minutes, and leakage was confirmed.

[Procedure amendment 9]

[Document name to be amended] Statement

[Correction target item name] Explanation of sign

[Correction method] Change

[Correction contents]

[Description of Signs] 1 Cylindrical electric fusion joint for connecting a cross-linked polyethylene resin pipe 2, 2 ', 2' 'Cross-linked polyethylene resin pipe 2a, 2'a, 2''a End 3 Cylindrical body 3a Inner wall 3b Side surface portion 3c Concave portion 4 Heat resistant insulating resin 5 Polyethylene resin 6,6 'Electric heater wire 7 Heater terminal 7a, 7'a Base end side 8 Stopper 9 Mat layer 10 Power supply 11 Controller 12 Switch 13 Connector 14 Size determination terminal 15 Terminal Terminal wall 17 Screw part

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hidehiro Nakajo Oita City, Oita Pref. 843--18 Kasugaura, Oji, Mitsui Kinzoku Engineering Co., Ltd. Pipe Division Oita Plant

Claims (11)

[Claims] 1. A tubular body for connecting at least two crosslinked polyethylene resin pipes by inserting an end of a crosslinked polyethylene resin pipe into a cylinder, and an electric heater disposed on an inner wall surface of the tubular body. A tubular electric fusion tube for connecting a cross-linked polyethylene resin pipe, comprising a wire and heater terminals disposed on the side surface of the tubular body for connection to both ends of the electric heater wire and to a connector for energization. In the fitting joint, the tubular electric fusion joint is formed of a cross-linked polyethylene resin, and an electric heater wire disposed on an inner wall surface of the tubular body is covered with a heat-resistant insulating resin. , A tubular electric fusion joint for connecting crosslinked polyethylene resin pipes. 2. A crosslinked polyethylene resin having a gel fraction of 20
The tubular electrofusion joint for connecting a crosslinked polyethylene resin pipe according to claim 1, which is a crosslinked polyethylene resin of up to 85%. 3. The tubular electric fusion joint for connecting a crosslinked polyethylene resin pipe according to claim 1, wherein the heat-resistant insulating resin is a resin having a melting temperature of 250 ° C. or higher. 4. The tubular electric fusion joint for connecting a crosslinked polyethylene resin pipe according to claim 1, wherein the heat-resistant insulating resin is a polyimide resin. 5. The tubular electric fusion joint for connecting a crosslinked polyethylene resin pipe according to claim 1, wherein the electric heater wire covered with the heat-resistant insulating resin is further covered with a polyethylene resin. . 6. The crosslinked polyethylene resin according to claim 1, wherein an electric heater wire covered with a heat-resistant insulating resin and a polyethylene resin is arranged in a mat shape on an inner wall surface of the tubular body. Cylindrical electric fusion joint for pipe connection. 7. The tubular electrofusion joint for connecting a crosslinked polyethylene resin pipe according to claim 5, wherein the polyethylene resin is a silane crosslinked polyethylene resin. 8. A crosslinked polyethylene resin tube and 250 to 2.5
00J / electrical energy cm ² is obtained by fusing through, crosslinked polyethylene resin pipe connecting tubular electric fusion coupling according to any one of claims 1 to 7. 9. The tubular electrofusion for connecting a crosslinked polyethylene resin tube according to claim 1, wherein the crosslinked polyethylene resin tube is a crosslinked polyethylene resin tube not coated with a non-crosslinked polyethylene resin. Fittings. 10. A crosslinked polyethylene resin tube having a peeling rate of 2
A tubular electric fusion joint for connecting a crosslinked polyethylene resin pipe fused at 5% or less and a void ratio of 25% or less. 11. The tubular electrofusion joint for connecting a crosslinked polyethylene resin pipe according to claim 10, wherein the crosslinked polyethylene resin pipe is a crosslinked polyethylene resin pipe that is not coated with a non-crosslinked polyethylene resin.