JP4465092B2 - Composite resin pipe joint structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a joint structure of a composite resin pipe having a high internal pressure resistance.
[0002]
[Prior art]
As is well known, when an internal pressure P acts on a pipe having a thickness t and an inner diameter φD, a tensile stress δ (δ = DP / 2t) is generated in the circumferential direction of the pipe and is mechanically balanced.
Conventionally, as a composite resin pipe, a steel tape winding intermediate layer is provided on a resin inner layer and a resin outer layer is provided on the intermediate layer (Japanese Patent Laid-Open No. 10-19174).
However, in this composite resin pipe, if the intermediate layer and the inner and outer resin layers are bonded together so that a tensile stress that balances the inner pressure of the steel tape is effectively generated in the steel tape winding intermediate layer, the composite resin pipe can be used. On the other hand, if the flexibility is ensured by allowing the intermediate layer and the inner and outer resin layers to slide between each other, it is difficult to generate tensile stress on the wound steel tape, and effective internal pressure resistance It becomes difficult to achieve an increase in strength.
[0003]
Therefore, the applicant of the present invention stated that “a composite material having a polyolefin-based resin inner layer, a stretched polyolefin-based resin sheet winding intermediate layer, and a polyolefin-based resin outer layer, and by bonding the inner and outer layers to the intermediate layer. Has already been proposed (Japanese Patent Application No. 11-95451).
In this composite pipe, the stretched polyolefin resin sheet winding intermediate layer is bonded to the inner and outer layers, and the elastic modulus of the stretched polyolefin resin sheet intermediate layer is larger than the elastic modulus of the inner and outer layers. Therefore, a sufficiently large internal pressure component can be assigned to the intermediate layer sheet, and the internal pressure resistance of the composite resin tube can be increased. Further, since the intermediate layer sheet is made of resin in the same manner as the inner and outer resin layers and is sufficiently flexible, it is possible to ensure the same bending rigidity and therefore flexibility as the single layer resin pipe.
[0004]
[Problems to be solved by the invention]
The composite resin pipe proposed by the present applicant structurally satisfies the requirements for high internal pressure resistance and flexibility.
However, according to the results of intensive studies by the present inventors, it has been found that when the internal pressure is actually applied, the rate of increase in the internal pressure strength is lower than expected.
As a result of exploring the cause, a stretchable polyolefin resin sheet winding intermediate layer may form a water intrusion path, and water may enter the composite pipe end face through this path. It became clear that.
[0005]
An object of the present invention is to effectively exhibit the inherent excellent internal pressure resistance of the composite resin pipe proposed by the applicant. Moreover, it is in enabling relaxation of the manufacturing conditions of the composite resin pipe.
[0006]
[Means for Solving the Problems]
The joint structure of the composite resin pipe according to the present invention has a polyolefin resin inner layer, a stretched polyolefin resin sheet winding intermediate layer, and a polyolefin resin outer layer, and the inner / outer layer and the intermediate layer are bonded to each other. What junction structure der composite tube comprising Te, stretched polyolefin resin sheet - a plurality bets winding layer number, shea composite tube end face - - sheet of the winding interim layer fusing preparative winding layer Thus, the composite pipe end face is sealed.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a composite resin pipe to which the present invention is applied.
In FIG. 1, 11 is a polyolefin resin inner layer. Reference numeral 12 denotes a stretched polyolefin resin sheet wound intermediate layer, which is bonded to the inner 11 layers. Reference numeral 13 denotes a polyolefin-based resin outer layer, which is bonded to the intermediate layer 12.
The internal pressure resistance and creep resistance of the composite resin pipe are guaranteed by the inner layer 11 and the intermediate layer 12, and the outer layer 13 is mainly used as a mechanical protective layer for the intermediate layer 12.
The stretched polyolefin-based resin sheet winding intermediate layer 12 is for improving the internal pressure resistance and creep resistance, and the sheet is stretched in the longitudinal direction to increase the elastic modulus and tensile strength of the sheet. The internal pressure strength is effectively enhanced by increasing the resistance, and the creep resistance is effectively enhanced by the cross-linking of the sheet.
The reason why this sheet is made of polyolefin resin is to adhere to the inner and outer layers. In addition, there is an advantage that it is possible to recycle the material generated from the fragments and used composite resin pipes produced during the production.
The polyolefin-based resin is not particularly limited. For example, low-density polyethylene, linear low-density polyethylene, high-density polyethylene, homopolypropylene, propylene random copolymer, propylene block copolymer, poly (4-methyl- 1-pentene) and the like. In particular, it is preferable to use polyethylene having particularly high elastic modulus after stretching, particularly high-density polyethylene having high crystallinity.
In addition to the crosslinking agent and the crosslinking aid, the polyolefin-based resin can be blended with a crystal nucleating agent, a lubricant, a filler, a pigment, a different polyolefin-based resin, a low-molecular-weight polyolefin wax, or the like, if necessary.
The purpose of adding the crosslinking agent and crosslinking aid is to partially crosslink the molecular chain of the polyolefin resin to improve the elastic modulus, tensile strength, creep properties, and heat resistance of the crosslinked stretched polyolefin resin sheet. Examples of the crosslinking agent include photopolymerization initiators such as benzophenone, thioxanthone, and acetophenone. Examples of the crosslinking assistant include triallyl cyanurate, trimethylolpropane triacrylate. And polyfunctional monomers such as diallyl phthalate.
The purpose of adding the crystalline nucleic acid is to increase the degree of crystallinity, and examples of the crystalline nucleic acid include calcium carbonate and titanium oxide.
The crosslinking can be performed by heating in addition to crosslinking by electron beam irradiation or ultraviolet irradiation. For crosslinking by electron beam irradiation or ultraviolet irradiation, the above-mentioned crosslinking agent or crosslinking aid is added to the polyolefin resin, and the electron beam is 1 to 20 Mrad, preferably 3 to 10 Mrad, or 50 to 800 mW / cm @ 2, preferably 100. It can be performed by irradiating with ~ 500 mW / cm2.
The crosslinking by the electron beam irradiation or the ultraviolet irradiation can be performed in the same or subsequent to the stretching process, and the crosslinking by heating can be performed before the stretching process.
[0008]
The raw material of the polyolefin resin sheet can be obtained, for example, by extrusion molding by a T-die method, roll molding by a calendar method, or the like.
In the stretching process, for example, a sheet is heated and passed between rolls with different speeds, or the heated sheet is squeezed between rolls rotating in different directions to reduce the thickness. However, it is possible to use a method of stretching in the length direction (rolling method) or the like, which may be either a single treatment or a multistage treatment. In the case of a multistage treatment, a plurality of stretching methods can be used. In the case of a thick wall, it is preferable to carry out subsequent stretching after processing by the rolling method.
The thickness of the original fabric before stretching is set according to the sheet thickness and the stretching ratio to be finally obtained, and is not particularly limited. Usually, the thickness of the stretched polyolefin resin sheet as the final product is 50 to 1000 μm. Correspondingly, it is 0.5 to 15 mm.
The width of the stretched polyolefin resin sheet is selected according to the diameter of the pipe, the winding angle, the winding method, etc. When using a relatively narrow stretched polyolefin resin sheet, a wide sheet is used. The slit may be slit to a predetermined width.
The stretch ratio of the stretched polyolefin resin sheet is set according to the elastic modulus and tensile strength to be obtained, and is usually 10 times or more, preferably 20 times or more. If it is less than 10 times, it is difficult to obtain a desired elastic modulus and tensile strength. Further, the stretching in the sheet width direction is preferably eliminated as much as possible because the stretching in the sheet longitudinal direction is suppressed.
In the stretched polyolefin resin sheet, a physical or chemical surface treatment can be applied as necessary to enhance the adhesiveness. For example, surface roughening by sandblasting or the like, fine embossing, and surface unevenness treatment by alternating non-uniform local heating can be performed. An adhesive sheet can be laminated on the surface of the stretched polyolefin resin sheet. Examples of the adhesive sheet include linear low density polyethylene, modified polyethylene, and ethylene-vinyl acetate copolymer. Can be mentioned.
[0009]
As the polyolefin resin of the inner layer, the same kind of resin, for example, a low density polyethylene, a linear low density polyethylene, a high density polyethylene, a homopolypropylene, a propylene random copolymer, is used for adhesion to the stretched polyolefin resin sheet. Polymer, propylene block copolymer, poly (4-methyl-1-pentene) and the like, and in particular, the melting point is 110 ° C to 135 ° C, and the melt index (JISK6760, unit g / 10 min). It is preferable to use 0.04 to 7.0. If it exceeds 7.0, the fluidity of the molten resin becomes too high, and if it is less than 0.04, the extrusion pressure becomes too high and shaping becomes difficult.
[0010]
Also in the polyolefin resin of the outer layer, the same kind of resin, for example, low density polyethylene, linear low density polyethylene, high density polyethylene, homopolypropylene, propylene random copolymer, is used for adhesion to the stretched polyolefin resin sheet. Polymer, propylene block copolymer, poly (4-methyl-1-pentene), and the like. In particular, the melting point is 110 ° C to 135 ° C, and the melt index is 0.04 to 10.0. Are preferably used. The reason why the upper limit of the melt index is set higher than that of the inner-layer polyolefin resin is that it is advantageous for filling a fine gap or a step generated on the outer surface of the stretched polyolefin-based resin sheet winding intermediate layer.
[0011]
The composite resin tube can be manufactured by a manufacturing apparatus shown in the figure.
In FIG. 2, 21 is a resin extruder, 22 is an extrusion die, 23 is an outer diameter sizing die, 24 is a sheet winding machine, 25 is a heating device, and 26 is a crosshead type outer layer extrusion. , 261 is a head, 27 is a cooling water tank, 28 is a take-up machine, and 29 is a regular cutting machine. To manufacture the above composite resin pipe, the polyolefin resin is extruded with an extruder, the outer diameter is regulated with a sizing mold, the inner layer is formed, and the stretched polyolefin resin sheet is usually in the same direction with a sheet wrapping machine. The two layers are wound so as to have substantially the same angle in the opposite direction, and heated and pressurized with a heating device to fuse the stretched polyolefin resin sheet wound layer to the inner layer.
The heating temperature is in the range from the softening point to the melting point of the inner layer resin, and the pressurization is preferably ² kgf / cm ² or more. For the pressurization, a method of performing from the outer surface of the tube, a method of performing from the inner surface of the tube, a method utilizing the heat shrinkage of the stretched polyolefin resin sheet, and the like can be used. Examples of the method of applying pressure from the inner surface of the pipe include air-pressurization and a method of expanding the diameter within the elastic range of the inner layer by a mandrel.
In this way, after the intermediate layer is bonded to the inner layer, the outer layer is formed by extrusion coating of a polyolefin resin by passing it through the die of a crotch head extruder, cooled in a water tank, and then cut with a take-up machine while taking a fixed size. I will do it.
For the inner layer, a polyolefin-based resin pipe already molded in a separate line can also be used. The outer layer can also be formed by a method in which a preformed polyolefin resin sheet is longitudinally attached and a method in which a preformed polyolefin resin tube is inserted and fused.
[0012]
The diameter of the composite resin pipe is not particularly limited, from a small diameter of 10 mm to 30 mm inside diameter to a large diameter of 300 mm to 500 mm inside diameter. In the former case, the drum can be wound and transported without performing the above-described regular cutting.
The cross-sectional shape of the composite resin tube is usually circular, but it may be non-circular, for example, a square with a corner and an alarm.
[0013]
In the composite resin pipe shown in FIG. 1, the internal pressure is substantially supported by the inner layer and the intermediate layer, the inner layer thickness is t, the intermediate layer thickness is Δt, the inner layer elastic modulus is Ea, and the intermediate layer 12 elastic modulus is If Eb, the inner diameter of the composite resin pipe is D ′, the pipe internal pressure is P, and the average tensile stress acting on the inner layer is τ,
P = 2τ [(EbΔt) / Ea + t] / D ′ (1)
If the allowable stress of the resin inner / outer pipe is τ ₀ , the allowable internal pressure P ₀ is
P ₀ = 2τ ₀ [(EbΔt) / Ea + t] / D ′ (2)
Given in.
Thus, since the elastic modulus Eb of the stretched polyolefin resin sheet is larger than the elastic modulus Ea of the polyolefin resin in the inner and outer layers, the internal pressure resistance can be improved.
[0014]
The stretched polyolefin resin sheet winding intermediate layer is usually two layers. When each layer is a butt winding, if the sheet width is W and the inner layer outer diameter is Dφ, the winding angle θ of the sheet is
[Equation 3]
θ = tan ^-1 (πD / W) (3)
Given in.
The sheet winding by the sheet winding machine is usually performed by rotating the sheet pad around the traveling pipe while feeding the sheet, and the pipe take-up speed is V and the rotation speed is Assuming N, the sheet winding angle ψ controlled by these V and N is:
ψ = 2πN / V (4)
V and N are given by
N / V = tan ^-1 (πD / W) (5)
It is controlled to satisfy.
[0015]
When the tensile strength in the longitudinal direction of the stretched polyolefin resin sheet is s, the thickness of the sheet winding layer is t, and the inner diameter of the inner layer is D ', the maximum internal pressure P "that can be supported by the sheet winding intermediate layer" Is [Equation 6]
P ″ = 2stsinψ / πD ′ (6)
The maximum tensile force Y in the tube axis direction that can be supported by the sheet winding intermediate layer is given by
Y = 2πsD'tcosψ (7)
Given in.
In the composite resin pipe according to the present invention, the purpose is to improve the resistance to internal pressure, so that P ″ in the formula (6) is set as high as 30 ° to 90 °, preferably 45 ° to 70 °. The
[0016]
In the present invention, N and D are controlled so as to satisfy the equation (4) under such a sheet winding angle, but the equation (3) based on the accuracy of the winding machine, the variation in the take-up speed, etc. ), It is inevitable that gaps or wraps will occur in the winding of the stretched polyolefin resin sheet.
As a result, the water running capacity of the passage through which the water can enter the stretched polyolefin resin sheet winding intermediate layer can be increased. However, according to the joint structure of the composite resin pipe according to the present invention, even under such conditions, In addition, it is possible to prevent water from entering and effectively exhibit the excellent internal pressure resistance of the composite resin tube.
[0017]
(A) to (e) of FIG. 3 show different reference examples and examples of the joint structure of the composite resin pipe according to the present invention.
In FIG. 3, reference numeral 1 denotes a composite resin pipe composed of the polyolefin resin inner layer 11, the stretched polyolefin resin sheet winding intermediate layer 12, and the polyolefin resin outer layer 13, between the inner layer and the outer layer on the pipe end face. Is sealed. 3 is a resin pipe joint, and the inner surface of the joint and the outer surface of the composite resin pipe are bonded together by fusion or an adhesive.
The resin pipe joint 3 uses an EF sleeve (Electrofusion sleeve) in which a heating wire is embedded in the inner peripheral surface of a resin sleeve of the same material as the polyolefin resin outer layer of the composite resin pipe. It is desirable that the composite resin tube end portion outer surface is fused by heating with heating wire.
According to the joint structure of the composite resin pipe according to the present invention, water can enter along the interface between the inner layer and the intermediate layer of the composite resin pipe, the sheet winding layer in the intermediate layer, and the interface between the intermediate layer and the outer layer. Even if a simple passage is formed, the end surface of the composite resin tube is sealed with respect to the passage, so that the inherent excellent resistance to internal pressure of the composite resin tube can be effectively exhibited.
[0018]
As shown in FIG. 3A, at least one of the inner layer resin 11 or the outer layer resin 12 is melted, and the molten resin covers the space between the inner layer and the outer layer of the end surface to cool and solidify the end surface of the composite resin tube. It is. In this case, the inner / outer layer resins 11 and 13 and the intermediate layer sheet 12 can also be melted.
For melting the inner layer resin or the outer layer resin, and further the intermediate layer sheet, as shown in FIG. 4, a heating wire 42 is stretched on a C-type insulating holder 41 and heated by energization. A wire-type cutter that melts the composite resin tube can be used.
Moreover, it is also possible to use a wire cutter for the above-mentioned regular cutting machine at the time of manufacturing the composite resin pipe, and to perform the sealing process of the end face of the composite resin pipe at the time of standard cutting.
[0019]
As shown in FIG. 3 (b), a curable resin liquid a, for example, a two-component reactive resin liquid, is applied and cured so as to cover between the inner layer and the outer layer of the end face of the composite resin tube. The end surfaces are sealed, and it is preferable to apply the two-component reactive resin liquid after roughening the end surfaces with an organic solvent such as acetone, toluene, xylene or the like. In this case, use a fast volatile solvent and apply after a sufficient solvent volatilization time so that the resin liquid is applied after the solvent is completely volatilized and scattered so as not to prevent the curing failure of the curable resin liquid. It is effective.
[0020]
As shown in FIG. 3C, the composite resin pipe end face is sealed by applying and solidifying hot melt resin b so as to cover between the inner layer and the outer layer of the composite resin pipe end face. When the tube is thick, the heat capacity of the tube end is increased and the hot-melt resin is solidified too quickly and the adhesive force is likely to be insufficient, so it is effective to preheat the composite resin tube end.
[0021]
As shown in FIG. 3D, the composite resin pipe end face is sealed by fusing a single-layer short pipe c to the composite pipe end face by butt welding or the like. It is desirable to use a polyolefin resin of the same material as the inner and outer layers of the tube.
[0022]
As shown in FIG. 3E, the composite resin is obtained by melting and integrating the polyolefin resin inner layer 11 at the end of the composite tube, the stretched polyolefin resin sheet winding intermediate layer 12 and the polyolefin resin outer layer 13. The tube end face is sealed, and this fusion integration can also be performed at the time of standard cutting in the composite resin tube manufacturing process.
Further, as shown in FIG. 5, in the composite resin pipe manufacturing process, the polyolefin resin inner layer 11 and the stretched polyolefin resin at the local portion of the pipe are heated by a heating ring 290 that holds the pipe at regular intervals on the upstream side of the fixed cut portion 29. The sheet winding intermediate layer 12 and the polyolefin-based resin outer layer 13 can be melted and integrated, and this portion can be used as a fixed cut portion.
[0023]
When the stretched polyolefin resin sheet winding intermediate layer is two layers and the interface between the intermediate layer and the inner layer and the interface between the intermediate layer and the outer layer are securely bonded, the sheet winding of the intermediate layer Only the interlayer serves as a water intrusion passage.
In the joint structure of the composite resin pipe according to claim 1 , when the number of sheet winding layers of the stretched polyolefin resin sheet winding intermediate layer is plural, sealing of the composite resin pipe end face is performed on the composite pipe end face. This is done by fusing the sheet winding layer.
[0024]
【Example】
[Example 1]
The stretched polyolefin resin sheet used for the intermediate layer of the composite resin pipe is as follows.
A composition in which 3% by weight of triallyl cyanurate (crosslinking aid) and 3% by weight of benzophenone (photocrosslinking initiator) is blended with high density polyethylene having a melting point of 135 ° C and a melt index of 1 at 200 ° C. The 3 mm-thick original fabric sheet formed by the T-die method is passed through a heating furnace at 120 ° C. with a feed speed of 1 m / min and a pinch roll take-up speed of 30 m / min, and a draw ratio of 30 times and a thickness of 0.15 mm A stretched polyolefin resin sheet was obtained, and this sheet was crosslinked by irradiation with a high-pressure mercury lamp for 10 seconds. Then, two pairs of pinchrollers having one temperature of 200 ° C. and the other temperature of 50 ° C. were paired. Then, it passes through a roughening roll device arranged upside down at a speed of 20 m / min to process fine irregularities with a centerline surface roughness Ra of 2 μm, and further has a thickness of 0.025 mm, a melting point of 123 ° C. on one side, Melt inde Laminating a linear polyethylene adhesive film Box 0.8 - it is obtained by preparative.
The composite resin tube consists of an extruded inner layer of high-density polyethylene (extrusion temperature: about 200 ° C) with a melting point of 135 ° C and a melt index of 0.5, and two layers of the above-mentioned stretched polyolefin resin sheet with a width of 90mm. With the film facing inward, the second layer facing the adhesive film outward, and with each layer slightly wrapped, the surface of the wound layer was heated to 130 ° C., and then the melting point was 125 ° C. and the melt index was 0.5. A linear low-density polyethylene was extruded (extrusion temperature about 200 ° C.), and further cooled in a cooling water bath to form an outer layer. The outer diameter was 63 mmφ, and the thickness was 4.0 mm.
A plate heater having a heating temperature of 200 ° C. was lightly pressed against the tube end surface of the composite resin tube for 30 seconds to seal the tube end surface, and then the composite resin tube was joined with a predetermined polyethylene EF pipe joint.
[0025]
[ Reference Example 2]
The tube end surface of the composite resin tube was roughened with acetone, and then the same as Example 1 except that a two-component reactive epoxy resin was applied and sealed.
[0026]
[ Reference Example 3]
The tube end face of the composite resin tube is heated by contacting a plate heater having a heating temperature of 100 ° C. for 10 seconds, and then an ethylene-vinyl acetate copolymer hot melt heated to 200 ° C. is applied and sealed. The same as Example 1 except that.
[0027]
[Comparative Example 1]
The high-density polyethylene inner layer used in Example 1 was joined with a predetermined polyethylene EF pipe joint.
[0028]
[Comparative Example 2]
The same as Example 1 except that the pipe end face of the composite resin pipe was not sealed. In order to evaluate the internal pressure performance of these examples and comparative examples, the following test was performed.
[0029]
(1) Internal pressure fracture test Each of the composite resin tube subjected to the same tube end surface sealing treatment as that of each example, the inner layer tube, and the composite resin tube not subjected to the tube end surface sealing treatment is shown in FIG. Thus, both ends of the sample tube P were sealed with the measurement jig 51, the tube end surface was not in contact with the jig, and the internal pressure was increased by the pump 52 at a rate of 5 kgf / min, and the fracture internal pressure was measured (pressure increase) The internal pressure at the time when impossibility or high pressure was taken as the internal pressure at break)
(2) Internal pressure creep fracture test An internal pressure of 12 kgf / cm ² was continuously imposed at an external temperature of 80 ° C. and a water temperature of 80 ° C., and the internal pressure holding time was measured.
(3) Pipe end water stop test Compared to the internal pressure fracture test of (1), the pipe length is 200 mm, a spacer is interposed between the pipe end surface and the jig end surface to ensure a sufficient gap, and composite resin The presence or absence of water intrusion between layers in the pipe was judged from the condition of the outer surface of the pipe.
[0030]
These measurement results are shown in Table 1.
[Table 1]
Internal pressure at break (kgf / cm ² ) Internal pressure retention time (hr) Pipe end water blocking Example 1 evaluation 70 200 or more ○
Reference Example 2 Evaluation 70 200 or more ○
Reference Example 3 Evaluation 70 200 or more ○
Comparative Example 1 Evaluation 40 25 ○
Comparative Example 2 Evaluation 60 30 ×
[0031]
From the measurement results of Table 1, according to the joint structure of the composite resin pipe according to the present invention, it has a polyolefin-based resin inner layer, a stretched polyolefin-based resin sheet winding intermediate layer, and a polyolefin-based resin outer layer. -Even if a composite resin pipe formed by bonding the outer layer and the intermediate layer is formed with a passage that allows water to enter between the layers, water penetration into the passage is eliminated for sealing at the pipe end surface. It can be confirmed that pinging and the like can be prevented and the excellent internal pressure resistance inherent in the composite resin tube can be exhibited.
[0032]
【The invention's effect】
According to the joint structure of the composite resin pipe according to the present invention, it has a polyolefin resin inner layer, a stretched polyolefin resin sheet winding intermediate layer, a polyolefin resin outer layer, and an inner / outer layer and an intermediate layer. The inherent excellent internal pressure resistance of the bonded composite resin tube can be exhibited.
In addition, due to the take-up speed at the time of manufacturing the composite resin pipe and the accuracy of the sheet winding machine, there is some deficiency in the winding state of the stretched polyolefin resin sheet, and the intermediate layer in the composite resin pipe causes water intrusion. Even in the easy state, the excellent internal pressure resistance inherent in the composite resin pipe can be exhibited, so that the manufacturing conditions such as the take-up speed and the sheet winding speed can be relaxed, and the take-up machine and the sheet It is also possible to reduce the cost of the composite resin pipe by simplifying the winding machine.
[Brief description of the drawings]
FIG. 1 is a drawing showing a composite resin pipe to be joined according to the present invention.
FIG. 2 is a view showing an apparatus for manufacturing the composite resin pipe.
FIG. 3 is a drawing showing different reference examples and examples of the joint structure of the composite resin pipe according to the present invention.
FIG. 4 is a drawing showing an example of a cutter used for joining composite resin pipes according to the present invention.
FIG. 5 is a drawing showing an example of a tube end face sealing method in joining composite resin pipes according to the present invention.
6 is a drawing showing a test apparatus for evaluating internal pressure resistance of a joint structure of composite resin pipes according to the present invention. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Composite resin pipe 11 Polyolefin resin inner layer 12 Stretched polyolefin resin sheet winding intermediate layer 13 Polyolefin resin outer layer 3 Pipe joint a Curable resin b Hot melt resin c Single-layer short tube

Claims (1)

And a polyolefin resin inner layer, stretched polyolefin resin sheet - and the winding interim layer has a polyolefin resin outer layer, yet the inner and outer layer and the intermediate layer I junction structure der composite tube formed by bonding,
The number of sheet wound layers of the stretched polyolefin resin sheet wound intermediate layer is plural,
A composite resin pipe joining structure , wherein the composite pipe end face is sealed by fusing a sheet winding layer of the composite pipe end face.

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