WO2006134842A1

WO2006134842A1 - Composite pipe and air-conditioning piping system comprising composite pipe

Info

Publication number: WO2006134842A1
Application number: PCT/JP2006/311623
Authority: WO
Inventors: Kojiro Inamori; Hiroyuki Yamazaki; Toshiyuki Andoh; Isamu Sakuma
Original assignee: The Furukawa Electric Co., Ltd.
Priority date: 2005-06-13
Filing date: 2006-06-09
Publication date: 2006-12-21
Also published as: JP2006348976A

Abstract

A composite pipe which comprises a pipe, a foamed resin layer with which the outer surface of the pipe is covered, and a protective layer with which the foamed resin layer is covered. The composite pipe has marring resistance and weatherability. Also provided is a process for producing the composite pipe.

Description

Specification

Composite pipe and air conditioning piping system using composite pipe

Technical field

TECHNICAL FIELD [0001] The present invention relates to a composite pipe, and more particularly to a composite pipe having excellent weather resistance used as a cooling medium piping for an air conditioner and an air conditioning piping system using the composite pipe.

Background art

In general, an air conditioning piping system is composed of an outdoor unit installed on the roof of a building, an indoor unit installed in the building, and a cooling medium piping connecting them. The cooling medium piping includes a portion laid outside.

Composite pipes that have been coated with highly heat-insulated resin foam around pipes have been used as the cooling medium piping. However, the resin foam alone is not resistant to trampling by people, scratching crows, etc. In addition, the weather resistance to solar ultraviolet rays was insufficient.

For this reason, the portion of the cooling medium piping exposed to the outside is covered with a protective cover or protected with a tape (see Patent Document 1). However, since the protective cover is retrofitted after the pipe is laid, there is a problem in that the delay of the period and the cost increase are caused. Patent Document 1: JP 2002-310382 A

Disclosure of the invention

[0003] An object of the present invention is to provide a composite pipe and an air conditioning piping system that are excellent in scratch resistance and weather resistance.

[0004] According to the present invention, the following means are provided:

(1) The outer surface of the pipe is covered with a resin foam layer, and the resin foam layer is covered with a protective layer.

(2) Place the composite tube on a horizontal surface, and place a stainless indenter in the shape of a tip of R0.25 whose diameter is reduced by 2 mm from the tip of a cylinder with a diameter of 2 mm on the surface of the protective layer. When a pulling force test is performed by pulling 10 cm horizontally at a speed of 2 cm / s while keeping the indenter perpendicular to the composite tube with a load of 800 g in the vertical downward direction standing vertically Depth force of the wound is less than Slmm tube,

(3) Expose the composite tube for 1000 hours under the conditions that the black panel temperature is 63 ° C and the rainfall time is 18 minutes out of 120 minutes with a sunshine weatherometer. Stand still, and on the surface of the protective layer, a stainless indenter with an R0.25 protruding end whose diameter has decreased from a point 2 mm away from the tip of a cylinder with a diameter of 2 mm is set up vertically and vertically downward. while applying a load 800 g, when performing speed-out bow I one force pulling 10cm horizontally test 2 cm / _S while keeping perpendicular to the indenter composite pipe, the resulting bow I one Chikaraki scratch depth The composite pipe as set forth in (1), wherein the force is lmm or less,

(4) Item (1) characterized in that the tube is a metal tube or a resin tube, the resin foam layer is made of polyolefin resin, and the protective layer is made of polyolefin resin. The composite tube described,

(5) The air conditioning piping system using the composite pipe according to any one of (1) to (4),

(6) The air conditioning piping system according to (5), comprising an outdoor unit, an indoor unit, and a composite pipe, wherein at least a part of the composite pipe is exposed outdoors.

(7) The method for producing a composite tube according to any one of (1) to (4), wherein the protective layer is a tube having a resin foam layer coated thereon and passed through a bellows tube forming apparatus. A method of manufacturing a composite pipe, characterized by comprising a step of coating with

(8) The method for manufacturing a composite pipe according to any one of (1) to (4), wherein the protective layer is formed by converting a pipe coated with a resin foam layer into a pre-formed protective pipe. A method for producing a composite pipe, comprising a step of being covered by passing the film.

[0005] The above and other features and advantages of the present invention will become apparent from the following descriptive power when considered in conjunction with the accompanying drawings.

Brief Description of Drawings

[0006] FIG. 1 is a schematic explanatory view showing an example of a method of coating a resin foam layer on a pipe in the method for producing a composite pipe of the present invention.

FIG. 2 is a schematic explanatory view showing another example of a method of coating a resin foam layer on a pipe in the method for producing a composite pipe of the present invention.

[FIG. 3] In the method for producing a composite pipe of the present invention, a protective layer is coated on the outer periphery of the resin foam layer. It is a schematic explanatory drawing which shows an example of the method to do.

FIG. 4 is a schematic explanatory view showing another example of a method for coating the outer periphery of a resin foam layer with a protective layer in the method for producing a composite pipe of the present invention.

FIG. 5 is a schematic explanatory view showing still another example of a method for coating a protective layer on the outer periphery of a resin foam layer in the method for producing a composite pipe of the present invention. FIG. 5 (a) is a perspective view showing a resin foam coated tube and a protective layer, and FIG. 5 (b) is a perspective view showing a composite tube.

FIG. 6 is a schematic explanatory view showing a method of measuring a pulling scratch on the composite pipe of the present invention. Fig. 6 (a) is a front view showing the outline of the whole measuring method, and Fig. 6 (b) is an enlarged view of the tip of the indenter.

BEST MODE FOR CARRYING OUT THE INVENTION

[0007] As a result of intensive studies, the inventors of the present invention have improved scratch resistance and weather resistance by coating a tube with a resin foam layer and then coating a protective layer on the outer periphery of the resin foam layer. I found it to improve.

[0008] A composite pipe suitable as an outdoor exposure pipe of the present invention includes a pipe, a resin foam layer coated on the outer surface thereof, and a protective layer coated on the outer periphery of the resin foam layer. Become.

[0009] As the pipe, a metal pipe such as copper or iron can be used. In the case of a resin tube, polyethylene, polybutene, polypropylene, or a cross-linked material is used as a material for forming the tube, but is not limited thereto.

[0010] In the present invention, any material can be used as the material constituting the resin foam depending on the purpose, but polyolefin resin is preferable from the viewpoint of extrusion stability and ease of increasing the expansion ratio. .

Examples of polyolefin resin include low-density polyethylene, linear low-density polyethylene, high-density polyethylene, polypropylene, ethylene propylene rubber, ethylene propylene terpolymer, styrene butadiene rubber, and ethylene acetate butyl copolymer. Examples thereof include, but are not limited to, ethylene butyl alcohol resin, ethylene ethyl acrylate resin, and ethylene acrylic acid resin. Furthermore, modified products such as silane modification and carboxylic acid modification of each of the above resins can be used, and these resins can be used alone or as a mixture of two or more.

[0011] The resin foam layer may be cross-linked. When cross-linking, electron beam cross-linking, chemical Either a bridge or a water bridge method may be used.

Polypropylene is more preferable as a material constituting the resin foam from the viewpoint of high heat resistance. When polypropylene is used, considering the extrudability and foamability, the melt flow rate (MFR) (230 ° C, 2.16 kgi) of rosin is preferably 0.05-10.0 g / 10 min 0.5-3.0 g / lOmin is more preferred.

[0012] For the resin foam, if necessary, cell nucleating agent, heat stabilizer, processing aid, lubricant, impact modifier, filler, antioxidant, UV absorber, light stabilizer, pigment, etc. May be added as appropriate.

Throughout this specification, the expansion ratio represents the average value of the entire tubular foam configured as an aggregate of rod-shaped foams. The expansion ratio φ of the resin foam is expressed by the following formula (1) when the density of the unfoamed resin composition is p (g / cm ³ ) and the density of the resin foam is pf (g / cm ³ ). Defined by

[0013] [Equation 1] φ ^{= ρ} c Equation (1)

[0014] The expansion ratio of the resin foam is preferably in the range of 5 to 30 times. If the expansion ratio of the resin foam is less than 5 times, the heat insulating property of the composite pipe may not be sufficient, and if it exceeds 30 times, the convective heat transfer will increase and the heat insulating property may also be lowered. In view of heat insulation, the expansion ratio of the resin foam is more preferably in the range of 5 to 20 times, and more preferably 10 to 15 times.

[0015] The foamed resin layer of the composite pipe of the present invention is preferably formed by coating the outer surface of the pipe with a resin foam by an extrusion foaming method. The extrusion foaming method is a method in which a foaming agent is supplied to the extruder together with the resin and the die force is pushed out and foamed at the same time. According to this method, the resin is foamed and coated on the pipe at the same time. it can.

[0016] As the foaming agent, a gas foaming agent, an evaporating foaming agent, a chemical foaming agent, or the like can be used. Nitrogen gas, carbon dioxide gas, etc. can be used as the gas blowing agent, butane, pentane, methanol, water, etc. can be used as the evaporation type blowing agent, and azodicarbonamide, azo Bisisobutyronitrile, Ν, Ν-dinitrosopentamethylentetramine, ρ-toluenesulfurhydrazide, ρ, ρ, monooxybis (benzenesulfo- Force capable of using hydrazide) and the like is not limited thereto. Among the above foaming agents, in consideration of the influence on the environment, nitrogen gas, which is preferred as a gas blowing agent, or carbon dioxide gas, which is preferred over a carbon dioxide power, is particularly preferred.

In the present invention, any material can be used as the material constituting the protective layer depending on the purpose, but considering the ease of molding, it is preferable to use polyolefin resin. As the polyolefin resin, the resin exemplified as the polyolefin resin used in the material constituting the above-mentioned resin foam can be used. As the polyolefin resin constituting the protective layer, ethylene acetate bur resin is also preferred because of its ability to bend easily during construction and improve the cutting ability.

[0018] The protective layer may be foamed, but the compressive strength described in JIS K 7181 must be higher than that of the resin foam layer.

A weathering agent may be added to the protective layer. There are various weathering agents to be added depending on the resin, and any of ultraviolet absorbers, ultraviolet reflectors, antioxidants and light stabilizers may be used alone or in combination. The content of the weathering agent is not particularly limited. For example, when polyolefin resin is used as the material constituting the protective layer, 0.1 to 5% by mass is preferable with respect to the resin.

[0019] Further, the protective layer has an action of protecting the foamed layer from damage during construction and ultraviolet rays.

In the present invention, the thickness of the protective layer is preferably from 0.3 to 2 mm, more preferably from 0.5 to 1 mm.

Further, the hardness of the protective layer is preferably 70 or more according to Shore A of JIS K 6253.

[0020] A method for manufacturing a composite pipe of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic explanatory view (perspective view) showing an example of a method for coating a resin foam layer on a pipe in the method for producing a composite pipe of the present invention. In Fig. 1, the tube is coated with a resin foam layer by extrusion foaming. In FIG. 1, the resin can be supplied to the hopper 12 of the extruder 10, and the resin foam can be extruded from the crosshead 11 and simultaneously coated on the tube 14 to obtain the resin foam-coated tube 16. Reference numeral 15 denotes a resin foam layer. As a method of supplying foaming agent, chemical foaming agent may be supplied from hopper 12 together with the resin! Alternatively, a gas foaming agent or an evaporative foaming agent may be injected directly from the gas supply port 13. [0021] When the resin foam layer is coated on the pipe by the extrusion foaming method, the extruder 10 may be either a single screw extruder or a twin screw extruder, or a tandem extrusion system combining both. System may be used. From the viewpoint of increasing the expansion ratio, it is preferable to use a tandem extrusion system capable of highly cooling the resin.

[0022] When the resin foam layer is coated on the pipe by the extrusion foaming method, the die outlet shape of the extruder may be either an annular shape or a plurality of holes. From the viewpoint of improving the expansion ratio, it is preferable to use a perforated die in which a plurality of holes having a circular cross section with the smallest ratio of the surface area to the cross sectional area is arranged.

In the present invention, surface irregularities can be smoothed by passing a sizing die (not shown) immediately after the resin foam layer-coated tube exits the die. As the sizing die, a cylindrical metal with an inner diameter adjusted to be equal to the outer diameter of the target composite pipe can be used, but this is not a limitation!

[0024] Fig. 2 is a schematic explanatory view (perspective view) showing another example of a method for coating a resin foam layer on a pipe in the method for producing a composite pipe of the present invention. In the method shown in FIG. 2, first, a strip-like resin foam sheet 22 is passed through a foam sheet fusion machine 20 to fuse the ends of the foam sheets, and then the fused resin foam 23 is joined to a tube 21. It is possible to obtain the resin foam-coated tube 24 by coating the resin.

As a method for firmly adhering the end portions of the foam, other than the method of melting the end portions with heat and pressing the ends together, an adhesive may be used.

[0025] Fig. 3 is a schematic explanatory view (perspective view) showing an example of a method for covering the resin foam-coated layer-coated tube with a protective layer in the method for producing a composite tube of the present invention. In Fig. 3, the protective layer is covered with an extruder. In this method, the resin foam-coated tube in which the tube 33 is coated with the resin foam layer 34 is supplied to the crosshead 31 of the extruder 30, and the protective layer 35 is coated to obtain the composite tube 36. it can. 32 indicates a hopper.

FIG. 4 is a schematic explanatory view (perspective view) showing another example of a method for covering the resin foam-coated tube with a protective layer in the method for producing a composite tube of the present invention. In Fig. 4, the protective layer is covered with a bellows tube forming device. In this method, the bellows tube is coated as the protective layer 43 by supplying the resin foam layer-coated tube 42 in which the tube 41 is coated with the resin foam to the bellows tube forming device 40. A composite tube 44 is obtained.

FIG. 5 is a schematic explanatory view (perspective view) showing still another example of a method for covering a resin foam-coated tube with a protective layer in the method for producing a composite tube of the present invention. In this method, as shown in FIG. 5 (a), a resin foam layer-coated tube 53 in which a tube 51 is coated with a resin foam layer 52 is passed through a protective layer (protective tube) 50 formed in advance. Thus, the composite tube 54 can be obtained as shown in FIG. The surface shape of the protective layer may be smooth as long as the protective layer is soft enough to be bent by hand, and if it is hard, it may be bent into an accordion shape to facilitate bending.

[0028] The above manufacturing methods are examples for carrying out the present invention, and the present invention is not particularly limited to the present description as long as the present invention can be realized.

Further, there are no particular limitations on the foam sheet fusion machine, the bellows tube forming apparatus and the like, and any conventionally used one can be used as appropriate.

[0029] In addition, the pulling strength of the covering portion including the resin foam layer (62) and the protective layer (63) in the present invention is shown in a schematic explanatory view (front view) of FIG. Measure according to the test method. First, as shown in FIG. 6 (a), the composite pipe 60 is allowed to stand on the horizontal plane 68, and a stainless indenter 64 is vertically placed on the surface of the protective layer 63 of the composite pipe 60, and a load of 800 g is applied in the vertical downward direction 66. Call. FIG. 6 (b) is an enlarged view of the tip portion of the indenter 64 (a shape having a protruding end portion of R0.25, the diameter of which decreases from the point of the tip force of 2mm of the cylinder having a diameter of 2mm). In the figure, 61 is a pipe of the composite pipe (60), and 65 is a support for supporting the indenter (64). Subsequently, with the load being applied, the indenter 64 is pulled 10 cm in the horizontal direction 67 at a speed of 2 cm / s while being kept perpendicular to the composite tube 60. Then, it is confirmed whether or not the composite pipe 60 has a pulling scratch having a depth of 1 mm or more. This test is performed three times with different specimens, and the conditions of the present invention are satisfied when the depth of the bow I scuff is 1 mm or less.

[0030] In the present invention, it is preferable that the depth of the pulling scratches generated by the pulling force test described above is 1 mm or less. Here, the above-mentioned value of 800 g load is almost the same value as that considered to be the load in piercing with a crow, which is considered to be the most severe load in practical use. This is because if the depth force S lmm of the pulling scratch is exceeded, the possibility of further tearing from the scratch or accumulation of water or debris in the scratch and deterioration of appearance will increase. The depth of the flaw is preferably 0.5 mm or less, and more preferably 0.3 mm or less. The depth of the wound In order to make it lmm or less, it can carry out by using a hard protective layer, for example.

[0031] In addition, the composite tube is exposed for 1000 hours under conditions of a black panel temperature of 63 ° C and a rainfall time of 120 minutes using a sunshine user meter (eg, Suga Test Instruments, product name S80). Even after the accelerated exposure test, the depth of the pulling scratch is preferably lmm or less. In this case, even if the composite tube is exposed to the field for a long period of time, it means that there is a low possibility that the composite tube will be torn or that it will not look good due to accumulation of dust in the wound. The depth of the flaw is preferably 0.5 mm or less, more preferably 0.3 mm or less. To reduce the depth of scratches to 1 mm or less after the above accelerated exposure test, for example, use a hard protective layer and mix a weathering agent into the protective layer to prevent the hardness of the protective layer from being reduced by ultraviolet rays. This can be done by scolding.

[0032] The air conditioning piping system of the present invention uses the above composite pipe. The air-conditioning piping system of the present invention preferably includes the above-mentioned composite pipe as an outdoor unit, an indoor unit, and a cooling medium piping, and at least a part of the composite pipe is exposed to the outdoors. It is. The outdoor unit and indoor unit that can be used in the present invention are not limited, and any known outdoor unit or indoor unit of an air conditioner can be used.

[0033] Since the composite pipe of the present invention is excellent in scratch resistance and weather resistance, an air-conditioning piping system using the composite pipe has an advantage that a man-hour and cost can be reduced without requiring a protective cover for outdoor exposed piping.

In addition, the composite pipe of the present invention has an advantage that the protective layer is extremely strong, so that there is little fear of breakage.

In the production method in which the protective layer of the composite tube is coated by passing a tube coated with the resin foam layer through a pre-formed protective tube, the coating of the resin foam layer on the tube and the resin This has the advantage that the protective layer can be applied to the foam layer separately without changing the existing equipment.

Example

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. [0035] Example 1

The extrusion foaming method shown in Fig. 1 was used to coat the resin foam layer on the pipes of outdoor exposed pipes. At this time, the tandem extrusion system (φ40mm single screw extruder for the first stage extruder, φ65mm single screw extruder for the second stage extruder) is used as the extruder 10, and the cylinder temperature of the first stage extruder is set to 1 70 Set the temperature of the second stage extruder to 175 ° C to 220 ° C and the die temperature to 170 ° C at ~ 220 ° C, 7 pieces.

[0036] Next, 100 parts by weight of polypropylene (made by Sanalomer: SD632 (trade name) MFR = 3.0 g / lOmin (230 ° C; 2.16 kgf)) and talc (made by Japan Talc: talc MG (product) Name)) A material consisting of 1 part by weight was supplied, and the gas supply valve force provided on the side of the first-stage extruder was also supplied at a rate of 3.2% by weight with respect to the total extrusion amount.

A copper tube having a diameter of 15.9 mm and a wall thickness of 1 mm was supplied to the crosshead 11 as the tube 14, and the resin foam layer was also extruded with a die force and coated on the copper tube. Here, a die having an annular (inner diameter: 18 mm, outer diameter: 20 mm) cross section was used.

The copper tube coated with the resin foam layer was supplied to a sizing die (not shown) having an inner diameter of 26 mm to obtain a copper tube coated with the resin foam layer having a foam thickness of 5 mm and a foaming ratio of 10.1.

[0037] The method shown in Fig. 3 was used to coat the protective layer on the copper tube coated with the resin foam layer. A single screw extruder with a diameter of 40 mm was used as the extruder 30, and the set temperature of the cylinder of the extruder was set to 170 to 190 ° C. As a protective layer material, 100 parts by weight of polyethylene is extruded into a resin composition containing 5 parts by weight of acid zinc oxide, which acts as a weathering agent to reflect ultraviolet rays, and is thickened around the resin foam layer. Covered with lmm. In this way, a composite pipe in which the resin foam layer and the protective layer were coated around the copper pipe was obtained. The resulting composite pipe was incorporated into an air-conditioning pipe system as an outdoor exposure pipe.

[0038] Example 2

The method shown in Fig. 2 was used to coat the resin foam layer on the pipes of outdoor exposed pipes. Here, a copper tube having a diameter of 15.9 mm and a wall thickness of 1 mm is used as the tube 21, and this copper tube and a cross-linked foamed polyethylene sheet 22 (foaming magnification 19.8 times, thickness 10 mm) cut into a strip shape are used as a foam sheet fusion machine. By supplying to 20, a tube 24 coated with the resin foam layer (23) was obtained. The resulting composite pipe was incorporated into an air-conditioning piping system as outdoor exposure piping. Next, the method shown in FIG. 5 was used to coat the protective layer. Here, the composite pipe 54 was obtained by passing the pipe 53 coated with the resin foam layer 52 through a pre-formed protective pipe 50 (polyethylene bellows pipe (thickness 2 mm)). The resulting composite pipe was incorporated into an air-conditioning pipe system as an outdoor exposure pipe.

[0040] Comparative Example 1

The composition of the pipe and the foamed resin layer and the coating method were the same as in Example 1. A composite pipe without a protective layer was prepared and incorporated into an air-conditioning pipe system as an outdoor exposure pipe.

[0041] Comparative Example 2

The composition of the pipe and the foamed resin layer and the coating method were the same as in Example 2. A composite pipe without a protective layer was prepared and incorporated into an air-conditioning pipe system as an outdoor exposure pipe.

[0042] Comparative Example 3

The composition of the tube, the foamed resin layer, the coating method, and the coating method of the protective layer were the same as in Example 1, and only the protective layer composition was changed to a composition that does not contain an ultraviolet absorber, and an outdoor exposure pipe was prepared. As an air conditioning piping system.

[0043] In all the air-conditioning piping systems of the examples and comparative examples, the portion of the piping for the cooling medium that is not exposed to the outside has a foaming ratio of 20 times and a thickness of 10 mm around the copper tube. The one coated with cross-linked polyethylene (both ends of the strip-shaped foam was heat-fused into a pipe shape) was used.

[0044] The expansion ratio of the resin foam layer of the composite pipe obtained in Examples 1 and 2 and Comparative Examples 1 to 3, and the tensile strength of the coating layer including the resin foam layer and the protective layer The thickness was measured according to the method described above. The results are shown in Table 1.

[0045] [Table 1] table 1

As is clear from the results in Table 1, Examples 1 to 3 had excellent scratch resistance and weather resistance with a small depth of scratches before and after the accelerated exposure test. In contrast, in Comparative Examples 1 to 3, the pulling wound was deep. Comparative example 3 is a comparative example of the invention according to claim 3. Industrial applicability

[0047] Since the composite pipe of the present invention is excellent in scratch resistance and weather resistance, it can be suitably used as a cooling medium piping for an air conditioner, and can be suitably used for an air conditioning piping system, for example. Moreover, since the air-conditioning piping system of the present invention uses the composite pipe, it has excellent scratch resistance and weather resistance.

Furthermore, the method for producing a composite pipe of the present invention is suitable as a method for producing a composite pipe having excellent scratch resistance and weather resistance.

[0048] While this invention has been described in conjunction with its embodiments, we do not intend to limit our invention in any detail of the description unless otherwise specified. The spirit and scope of the invention as set forth in the appended claims I think that it should be interpreted widely without contradicting.

Claims

The scope of the claims

[1] A flaw- and weather-resistant composite pipe in which an outer surface of a pipe is covered with a resin foam layer, and the resin foam layer is covered with a protective layer.

[2] The composite tube is placed in a horizontal plane, and the surface of the protective layer is made of stainless steel with a shape having a tip of R0.25 with a diameter reduced from a point 2 mm from the tip of a cylinder with a diameter of 2 mm. When a pulling force test is performed in which the indenter is placed vertically and a load of 800 g is applied in the vertical downward direction and the indenter is held vertically to the composite tube and pulled 10 cm horizontally at a speed of 2 cm / s, 2. The composite pipe according to claim 1, wherein the depth force of the resulting pulling scratch is less than Slmm.

[3] Using a sunshine weatherometer, the composite tube was exposed for 1000 hours under conditions where the black panel temperature was 63 ° C and the rainfall was 18 minutes out of 120 minutes. Stand still, and on the surface of the protective layer, a stainless indenter with an R0.25 protruding end whose diameter has decreased from a point 2 mm away from the tip of a cylinder with a diameter of 2 mm is set up vertically and vertically downward. while applying a load 800 g, when performing speed-out bow I one force pulling 10cm horizontally test 2 cm / _S while keeping perpendicular to the indenter composite pipe, the resulting bow I one Chikaraki scratch depth The composite pipe according to claim 1, wherein the force is lmm or less.

[4] The tube according to claim 1, wherein the tube is a metal tube or a resin-made tube, the resin foam layer is made of polyolefin resin, and the protective layer is made of polyolefin resin. Composite pipe.

[5] An air conditioning piping system using the composite pipe according to any one of claims 1 to 4.

6. The air conditioning piping system according to claim 5, comprising an outdoor unit, an indoor unit, and a composite pipe, wherein at least a part of the composite pipe is exposed outdoors.

[7] The method of manufacturing a composite pipe according to any one of claims 1 to 4, wherein the protective layer is

A method for producing a composite pipe, comprising a step of coating a pipe coated with a resin foam layer through a bellows pipe forming apparatus.

[8] The method of manufacturing a composite pipe according to any one of claims 1 to 4, wherein the protective layer is

A method for producing a composite pipe, comprising a step of coating a pipe coated with a resin foam layer through a pre-formed protective pipe.