JP7277216B2 - Joint structure - Google Patents

Description

The present invention relates to pipe joints and joint structures.

2. Description of the Related Art Conventionally, a pipe joint provided with a heat insulating layer has been known, as shown in Patent Document 1 below.
Since this pipe joint is provided with a heat insulating layer, it is possible to suppress the formation of condensation on the outer peripheral surface of the receptacle when, for example, cold water flows inside.

JP-A-11-201382

However, conventional pipe joints have room for improvement in suppressing dew condensation at the socket.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pipe joint capable of reliably suppressing condensation.

In order to solve the above problems, the present invention proposes the following means.
A pipe joint according to the present invention is a pipe joint provided with a heat-insulating layer, comprising a plurality of sockets to which pipes are connected, and having a size L (mm) in the axial direction along the central axis of the sockets. , and the size F (mm) of the heat insulating layer in the axial direction in the socket satisfies the following formula (1).
0.03<F/L<0.5 (1)

In this case, the axial size L of the socket portion and the axial size F of the heat insulating layer in the socket portion satisfy the expression (1).
That is, since F/L is larger than 0.03, it is possible to reliably suppress dew condensation in the socket by ensuring the size of the heat insulating layer in the socket. On the other hand, if F/L is 0.03 or less, dew condensation is likely to occur at the socket.

Further, since F/L is smaller than 0.5, the strength of the socket can be ensured by suppressing the size of the heat insulating layer in the socket from becoming too large. On the other hand, if F/L is 0.5 or more, there is a concern that the strength of the socket may be weakened due to an increase in the size of the heat insulating layer in the socket.

Further, in the pipe joint according to the present invention, even if the size L (mm) and the thickness T (mm) of the socket portion in the radial direction perpendicular to the central axis satisfy the following expression (2): good.
4<L/T<13 (2)

In this case, the axial size L of the socket portion and the radial thickness T of the socket portion satisfy the expression (2). That is, since L/T is larger than 4, the strength of the socket can be ensured by ensuring the thickness of the socket. On the other hand, if L/T is 4 or less, there is a concern that the strength of the socket may be weakened.

In addition, since L/T is less than 13, it is possible to prevent the thickness of the socket portion from becoming too thick, thereby suppressing the occurrence of sink marks in the socket portion due to molding shrinkage. On the other hand, if L/T is 13 or more, the thickness of the receptacle portion becomes too thick, which may cause sink marks due to variations in the amount of shrinkage during molding.

Further, the receptacle portion in the pipe joint according to the present invention may be transparent to such an extent that the pipe connected to the receptacle portion can be visually recognized from the outside.
In this case, since the receptacle is transparent, the state of the pipe connected to the receptacle can be visually recognized from the outside of the receptacle, so that the pipe can be reliably connected to the receptacle.

Further, the pipe joint according to the present invention includes a joint body that connects the plurality of receptacle portions, and of the outer peripheral portion of the joint body, a connection portion with the receptacle portion has a radial direction perpendicular to the central axis. A stepped portion may be formed to protrude from the edge.

In this case, a stepped portion projecting in the radial direction is formed at the portion of the joint main body that is connected to the receptacle portion. Therefore, the resin can easily flow into the receptacle through the stepped portion during molding, and the moldability of the pipe joint can be ensured.

Further, a joint structure according to the present invention is a joint structure including a pipe provided with a tubular foam layer and a pipe joint provided with a heat insulating layer to which the pipe is connected, wherein the pipe joint comprises: A plurality of sockets to which the pipes are connected may be provided, and the heat insulating layer and the foam layer may be arranged overlapping each other in a radial direction perpendicular to the central axis of the sockets.

In this case, the heat insulating layer in the socket and the foam layer in the pipe are arranged so as to overlap in the radial direction. Therefore, it is possible to ensure the heat insulating performance of the pipe connecting portion of the pipe joint, and to reliably suppress the formation of dew condensation on the pipe joint and the pipe.

ADVANTAGE OF THE INVENTION According to this invention, it can suppress reliably that dew condensation arises in a pipe joint.

1 is a perspective view showing an air conditioner in which the joint structure of the present invention is used; FIG. BRIEF DESCRIPTION OF THE DRAWINGS It is a longitudinal cross-sectional view which shows the joint structure which concerns on 1st Embodiment of this invention. FIG. 3 is a diagram showing a first modification of the pipe joint shown in FIG. 2; 3 is a view showing a second modification of the pipe joint shown in FIG. 2; FIG. 3 is a view showing a third modification of the pipe joint shown in FIG. 2; FIG. It is a figure which shows the pipe joint which concerns on 2nd Embodiment of this invention. It is a figure which shows the pipe joint based on 3rd Embodiment of this invention. FIG. 8 is a view showing a first modification of the pipe joint shown in FIG. 7; FIG. 8 is a view showing a second modification of the pipe joint shown in FIG. 7; It is a figure which shows the state before a compression process of the pipe joint which concerns on 4th Embodiment of this invention. It is a figure which shows the pipe joint based on 4th Embodiment of this invention. FIG. 10 is a diagram showing a state of a pipe before a depressurization process according to a fifth embodiment of the present invention; It is a figure which shows the pipe joint based on 5th Embodiment of this invention. 1 is a front view showing an apparatus for measuring fusion bonding strength; FIG. It is a schematic block diagram which shows an example of the manufacturing apparatus which manufactures the piping material of three-layer structure. 16 is a cross-sectional view showing an example of a mold provided in the manufacturing apparatus of FIG. 15; FIG. 16 is a schematic diagram showing an example of a vacuum sizing device provided in the manufacturing apparatus of FIG. 15. FIG. FIG. 3 is a side view showing a joint structure for a stretching fatigue test;

(First embodiment)
A joint structure 1 according to a first embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG.
As shown in FIG. 1, a joint structure 1 according to this embodiment includes a pipe 10 and a pipe joint 20 to which the pipe 10 is connected.
The joint structure 1 is connected to, for example, an air conditioner 100, and low-temperature drain water from the air conditioner 100 flows therein.

[Tube 10]
As shown in FIG. 2, the pipe 10 includes a cylindrical foam layer 11 containing vinyl chloride resin, a non-foamed inner layer 12 provided on the inner surface of the foam layer 11 and containing vinyl chloride resin, and a foam layer 11. and a non-foamed outer layer 13 provided on the outer surface and containing vinyl chloride resin.
The coefficient of linear expansion of the tube 10 is preferably 5×10 −5 /° C. or more and less than 7×10 −5 /° C. or less. When the coefficient of linear expansion of the pipe 10 is large, the expansion of the pipe 10 increases the stress applied to the socket portion 21 of the pipe joint 20, which will be described later, and the socket portion 21 may crack.

The pipe 10 is cut to an arbitrary length at the construction site and connected by inserting the end into the receptacle 21 of the pipe joint 20 . The pipe 10 and the pipe joint 20 constitute an air conditioning pipe. Therefore, inside the socket portion 21 of the pipe joint 20 , the foam layer 11 , the non-foam inner layer 12 , and the non-foam outer layer 13 are exposed on the end face (cut surface) of the pipe 10 .

The foam layer 11 of the pipe 10 has a high closed cell rate, and the drain water flowing down inside the pipe 10 is difficult to permeate. It is not necessary to provide an annular elastic body (packing) inside the joint 20 .
The pipe joint 20 according to the present embodiment has a heat insulating layer 25 in the socket portion 21 as described later. Therefore, it is difficult to confirm (visually recognize) that the adhesive has been applied. Therefore, the adhesive is preferably an adhesive containing a fluorescent agent that emits fluorescence when irradiated with ultraviolet rays.

The outer diameter of the tube 10 is preferably 32 mm or more and 100 mm or less, for example. The inner diameter of the tube 10 is preferably 19 mm or more and 80 mm or less, for example. The combined thickness of the tube 10 including the foamed layer 11, the non-foamed inner layer 12, and the non-foamed outer layer 13 is preferably, for example, 6 mm or more and 10 mm or less.

The longitudinal elastic modulus of the tube 10 is preferably 400 MPa or more and 1500 MPa or less, more preferably 500 MPa or more and 1300 MPa or less, and even more preferably 600 MPa or more and 1000 MPa or less.
By setting the modulus of longitudinal elasticity within the above numerical range, when the pipe 10 receives an external force, deformation such as bending and elongation is suppressed, and the pipe 10 is prevented from being broken by following these external forces flexibly. can be done.

The longitudinal elastic modulus is also called longitudinal elastic modulus or Young's modulus, and is obtained from tensile stress and tensile strain obtained by a tensile test according to JIS K 7161-1:2014.
The modulus of longitudinal elasticity can be adjusted by the degree of polymerization of the vinyl chloride resin, the expansion ratio of the foamed layer, the thickness of each of the foamed layer 11, the non-foamed inner layer 12, the non-foamed outer layer 13, and the like.

<Non-foaming inner layer>
The non-foamed inner layer 12 contains vinyl chloride resin. The vinyl chloride resin may be a homopolymer of a vinyl chloride monomer (polyvinyl chloride), or a vinyl chloride monomer and another monomer copolymerizable with the vinyl chloride monomer. It may be a copolymer.
Other monomers copolymerizable with the vinyl chloride monomer include, for example, ethylene, propylene, allyl chloride, acrylic acid, methacrylic acid, acrylic acid ester, methacrylic acid ester, vinyl acetate, maleic anhydride, acrylonitrile. and other monomers. These may be used alone, or two or more of them may be used in combination.

A vinyl chloride-based resin may be used alone, or two or more of them may be used in combination.
The non-foamed inner layer 12 may contain a thermoplastic resin other than vinyl chloride resin. Examples of the thermoplastic resin include polyethylene, polypropylene, polystyrene, polybutene, chlorinated polyethylene, ethylene-propylene copolymer, ethylene-ethyl acrylate copolymer, polyethylene terephthalate, ABS resin and acrylic resin. These may be used alone, or two or more of them may be used in combination.
In the non-foamed inner layer 12, the content of the vinyl chloride resin with respect to the total mass of the resin is preferably 80% by mass or more and 95% by mass or less, more preferably 85% by mass or more and 90% by mass or less.

The thickness of the non-foamed inner layer 12 is preferably 1.0 mm or more and 5.0 mm or less, more preferably 1.5 mm or more and 3.5 mm or less. By setting the thickness of the non-foamed inner layer 12 within the above numerical range, the pipe 10 having excellent heat insulation can be obtained without the risk of permeation of the drain water flowing inside into the foamed layer 11 .
On the other hand, when the closed cell rate of the foam layer 11 is high, the thickness of the non-foam inner layer 12 may be 0.6 mm or more and 1.5 mm or less because the foam layer 11 itself prevents permeation of drain water. It can be made lightweight. Moreover, since the thickness of the foam layer 11 can be increased, the pipe 10 can be made excellent in heat insulation.

<Foam layer>
The foam layer 11 is formed by foaming a thermoplastic resin composition for a foam layer containing a resin containing a vinyl chloride resin and a foaming agent. The vinyl chloride resin may be a homopolymer of a vinyl chloride monomer (polyvinyl chloride), or a vinyl chloride monomer and another monomer copolymerizable with the vinyl chloride monomer. It may be a copolymer.

Other monomers copolymerizable with the vinyl chloride monomer include, for example, ethylene, propylene, allyl chloride, acrylic acid, methacrylic acid, acrylic acid ester, methacrylic acid ester, vinyl acetate, maleic anhydride, acrylonitrile. and other monomers. These may be used alone, or two or more of them may be used in combination.

A vinyl chloride-based resin may be used alone, or two or more of them may be used in combination.
The foam layer 11 may contain a thermoplastic resin other than the vinyl chloride resin. Examples of the thermoplastic resin include polyethylene, polypropylene, polystyrene, polybutene, chlorinated polyethylene, ethylene-propylene copolymer, ethylene-ethyl acrylate copolymer, polyethylene terephthalate, ABS resin and acrylic resin. These may be used alone, or two or more of them may be used in combination.
In the foam layer 11, the content of the vinyl chloride resin relative to the total mass of the resin is preferably 70% by mass or more and 80% by mass or less, more preferably 70% by mass or more and 75% by mass or less.

The mass average molecular weight of the vinyl chloride resin is preferably 37,500 or more and 70,000 or less, and more preferably 37,500 or more and 44,000 or less.
The weight average molecular weight is a value measured by gel permeation chromatography using polyethylene glycol as a standard substance.
When the vinyl chloride resin is polyvinyl chloride, the average degree of polymerization of polyvinyl chloride is preferably 600 or more and 800 or less, more preferably 600 or more and 700 or less.
The average degree of polymerization can be calculated by dividing the mass average molecular weight by the molecular weight of chloroethylene.
The vinyl chloride resin may be the same as or different from the vinyl chloride resin.

The foam layer 11 preferably contains acrylic acid, methacrylic acid, acrylic acid ester, or methacrylic acid ester (collectively referred to as an acrylic polymer compound) as a thermoplastic resin other than vinyl chloride resin. . By containing the acrylic polymer, the closed cell ratio can be improved and the cell diameter can be made finer.

The mass average molecular weight of the acrylic polymer compound is preferably 3 million or more and 6 million or less, more preferably 4 million or more and 5 million or less.
When the foam layer 11 contains an acrylic polymer compound, the content of the acrylic polymer compound is preferably 10 parts by mass or more and 50 parts by mass or less, and 12 parts by mass or more and 36 parts by mass with respect to 100 parts by mass of the vinyl chloride resin. It is more preferably 18 parts by mass or more and 24 parts by mass or less.
The thickness of the foam layer 11 is preferably 4.0 mm or more and 10 mm or less.

As the foaming agent, either a volatile foaming agent or a decomposable foaming agent may be used.
Volatile foaming agents include, for example, aliphatic hydrocarbons, alicyclic hydrocarbons, halogenated hydrocarbons, ethers, ketones and the like. Of these, aliphatic hydrocarbons include propane, butane (normal butane, isobutane), pentane (normal pentane, isopentane, etc.), and alicyclic hydrocarbons include cyclopentane, cyclohexane, and the like. mentioned. Examples of halogenated hydrocarbons include one or more of halogenated hydrocarbons such as trichlorofluoromethane, trichlorotrifluoroethane, tetrafluoroethane, chlorodifluoroethane, and difluoroethane. Examples of ethers include dimethyl ether and diethyl ether, and examples of ketones include acetone and methyl ethyl ketone.

Examples of decomposition-type foaming agents include inorganic foaming agents such as sodium bicarbonate (sodium hydrogen carbonate), sodium carbonate, ammonium bicarbonate, ammonium nitrite, azide compounds, sodium borohydride, azodicarbonamide, and barium azodicarboxylate. and dinitrosopentamethylenetetramine.

Also, a thermally expandable capsule in which the above hydrocarbon is encapsulated in a thermoplastic resin may be used.
In addition, gases such as carbon dioxide, nitrogen, and air may be used as foaming agents.
These may be used alone, or two or more of them may be used in combination.
The amount of the foaming agent used is preferably 1 part by mass or more and 8 parts by mass or less, more preferably 2 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the vinyl chloride resin.

The foam layer 11 may contain known stabilizers such as lead compounds (lead-based stabilizers), CaZn compounds (CaZn-based stabilizers), and tin compounds (tin-based stabilizers). In particular, the inclusion of a stabilizer containing a tin compound facilitates enhancing the thermal stability of the resin. Mercapto-based, laurate-based, and malate-based tin compounds are preferred.

The presence and content of these compounds are confirmed by inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma atomic emission spectrometry (ICP-AES), gas chromatograph mass spectrometry (GC-MS), and the like. be able to. In the case of ICP-AES, it can be measured according to EN ISO17353:2004.
The foam layer 11 may contain a lubricant. By containing a lubricant, it becomes easier to maintain the lubricity on metal surfaces and the lubricity between resins. Ester-based, polyethylene-based, and polyethylene oxide-based lubricants are preferable as lubricants.

[Expansion ratio]
The foaming ratio of the foam layer 11 is 3.5 times or more and 10 times or less, preferably 4.0 times or more and 8 times or less, and more preferably 4.5 times or more and 6.0 times or less.
By setting the foaming ratio within the above numerical range, high heat insulating properties can be imparted. Further, by setting the foaming ratio within the above numerical range, the weight of the tube 10 can be reduced.
The expansion ratio can be adjusted by the type or amount of resin, the type or amount of foaming agent, manufacturing conditions, and the like.

The foaming ratio can be measured by the following method.
[Method for measuring expansion ratio]
A section of 10 mm or more in the circumferential direction and 50 mm in the axial direction was cut from the pipe 10, the non-foamed inner layer 12 and the non-foamed outer layer 13 were cut with a milling machine, and only the foamed layer 11 was processed into a plate with a length of about 50 mm. and In addition, four test pieces shall be prepared centering on points which are evenly divided into four in the inner circumferential direction.
According to JIS K 7112:1999, the apparent density of the test piece is determined to three digits after the decimal point at 23° C.±2° C. with a water displacement type specific gravity meter, and the foaming ratio is calculated by the following formula (1).
m=γc/γ (1)
[In formula (1), m is the expansion ratio, γ is the apparent density (g/cm ³ ) of the foam layer 11, and γc is the unfoamed density (g/cm ³ ) of the foam layer 11. . ]

The foam layer 11 has a closed cell rate of 45% or more, preferably 60% or more, and more preferably 80% or more. The upper limit of the closed cell ratio is not particularly limited, and is practically 95% or less, and may be 100% or 90% or less.
By setting the closed cell ratio within the above numerical range, it is possible to improve heat insulating properties while suppressing costs, prevent permeation of water into the foam layer 11, and prevent condensation from occurring on the surface of the socket portion 21 of the pipe joint 20. can be prevented. Further, when the closed cell ratio of the foamed layer 11 is within the above numerical range, even if the thickness of the non-foamed outer layer 13, which will be described later, is reduced, it is difficult for water to permeate from the outside, and there is a low possibility that the heat insulating properties will deteriorate.
In addition, a closed-cell rate is measured based on JISK7138:2006. The pipe 10 is cut to a length of 30 mm, cut in the circumferential direction so as to have a circumferential length of 20 mm, and a cutter is used to remove the non-foamed inner layer 12 and the non-foamed outer layer 13 to obtain a test piece. The volume of the test piece is measured with an air comparison type hydrometer at a temperature of 23°C ± 2°C. According to JIS K 7112:1999, the volume of the test piece is measured with a water displacement hydrometer at a temperature of 23°C ± 2°C. The closed cell ratio is calculated by the following formula (2).
Cc=(Va/Vaq)×100 (2)
[In formula (2), Cc is the closed cell ratio (%), Va is the air comparison formula volume (cm ³ ), and Vaq is the water displacement method volume (cm ³ ). ]
The closed cell content can be adjusted by the type or amount of resin, the type or amount of foaming agent, production conditions, and the like.

[Weld strength]
The fusion strength between the foamed layer 11 and the non-foamed inner layer 12 is 1.0 MPa or higher, preferably 1.5 MPa or higher, and more preferably 2.0 MPa or higher.
By setting the fusion bonding strength within the above range, it is possible to prevent separation between the foamed layer 11 and the non-foamed inner layer 12 .

The fusion bond strength can be measured by the following method.
[Method for measuring fusion bond strength]
A universal testing machine 50 shown in FIG. 14 was prepared. The universal testing machine 50 includes a random punching jig 51 and two compression plates (not shown). The punching jig 51 includes a pedestal portion 51a and a pushing portion 51b arranged above the pedestal portion 51a. The punching jig 51 is sandwiched between two compression plates (not shown).
Next, a test piece was obtained by cutting the tube 10 into a tubular shape having a width of 20 mm in the tube axial direction. The test piece P has a non-foamed inner layer 12, a foamed layer 11, and a non-foamed outer layer 13 (not shown in FIG. 14).
The test piece P is set between the pedestal portion 51a and the push-in portion 51b of the universal testing machine 50 under conditions of a temperature of 23° C.±2° C. and normal humidity (45 to 85%). The test piece P is compressed in the direction of the tube axis at a rate of 10 mm/min±2 mm/min per minute using two compression plates. The maximum load at which the fused surfaces of the non-foamed inner layer 12 and the foamed layer 11 separate is obtained, and the fusion strength is calculated by the following equations (3) and (4).
F=W/S (3)
S=3.14×d×L (4)
[In formulas (3) and (4), F is the fusion bond strength (MPa), W is the maximum load (N), S is the fusion bond area (cm ² ), and d is the non-foamed inner layer 12 is the average outer diameter (cm), and L is the length of the test piece P (cm). ]
The fusion bonding strength can be adjusted by the type or amount of resin, the type or amount of foaming agent, manufacturing conditions, and the like.

[Average bubble diameter]
The average cell diameter of the foam layer 11 is 30 μm or more and 400 μm or less, preferably 50 μm or more and 400 μm or less, more preferably 50 μm or more and 250 μm or less, and even more preferably 60 μm or more and 200 μm or less.
By setting the average cell diameter within the above numerical range, it is possible to improve heat insulation and prevent water from penetrating into the foam layer 11 . Even if the cells are not completely closed cells (closed cell ratio is 100%) and the cell walls are partially connected and water can permeate, the average cell diameter is within the above numerical range and the closed cell ratio is is within the above numerical range, water does not permeate deep into the foam layer 11, and there is no problem with the heat insulation performance in practical use.
The average cell diameter can be adjusted by the type or amount of resin, the type or amount of foaming agent, production conditions, and the like.

Incidentally, the average bubble diameter can be measured by the following method.
[Measurement of average bubble diameter]
Any of the photographs obtained on the circumferential cross-sectional image of the foam layer 11 of the air conditioning drain pipe taken with a scanning electron microscope (SEM) at a magnification of 50 times with reference to the method described in JIS K 6402 4 straight lines with a length of 9 cm (corresponding to 1,800 μm in the actual cross section) are drawn at the position of , and the average value of the number of bubbles crossed by each straight line is obtained. The average bubble diameter is calculated by dividing 1,800 μm by the average number of crossed bubbles.

<Non-foaming outer layer>
The non-foamed outer layer 13 contains vinyl chloride resin. The vinyl chloride resin may be a homopolymer of a vinyl chloride monomer (polyvinyl chloride), or a vinyl chloride monomer and another monomer copolymerizable with the vinyl chloride monomer. It may be a copolymer.
Other monomers copolymerizable with the vinyl chloride monomer include, for example, ethylene, propylene, allyl chloride, acrylic acid, methacrylic acid, acrylic acid ester, methacrylic acid ester, vinyl acetate, maleic anhydride, acrylonitrile. and other monomers. These may be used alone, or two or more of them may be used in combination.

A vinyl chloride-based resin may be used alone, or two or more of them may be used in combination.
The non-foamed outer layer 13 may contain a thermoplastic resin other than vinyl chloride resin. Examples of the thermoplastic resin include polyethylene, polypropylene, polystyrene, polybutene, chlorinated polyethylene, ethylene-propylene copolymer, ethylene-ethyl acrylate copolymer, polyethylene terephthalate, ABS resin and acrylic resin. These may be used alone, or two or more of them may be used in combination.
In the non-foamed outer layer 13, the content of the vinyl chloride resin with respect to the total mass of the resin is preferably 80% by mass or more and 95% by mass or less, more preferably 85% by mass or more and 90% by mass or less.

The thickness of the non-foamed outer layer 13 is preferably 0.6 mm or more and 1.5 mm or less, more preferably 1.0 mm or more and 1.3 mm or less. By making the thickness of the non-foamed outer layer 13 equal to or greater than the above lower limit, the tube 10 can be made resistant to impact from the outside. By making the thickness of the non-foamed outer layer 13 equal to or less than the above upper limit, the weight of the tube 10 can be reduced. Moreover, since the thickness of the foam layer 11 can be increased, the pipe 10 can be made excellent in heat insulation.
In the case of strengthening by impact from the outside, the thickness of the non-foamed outer layer 13 is preferably 1.0 mm or more and 5.0 mm or less, more preferably 1.5 mm or more and 3.5 mm or less.
The non-foamed outer layer 13 may contain a pigment. Appearance can be improved by containing a pigment.

[Manufacturing method of tube 10]
The pipe 10 having a three-layer structure consisting of the non-foamed outer layer 13, the foamed layer 11, and the non-foamed inner layer 12 is manufactured using a manufacturing apparatus 60 shown in FIG. 15, for example.
A manufacturing apparatus 60 in this example includes a first extruder 61 , a second extruder 62 , a vacuum sizing device 63 , a take-up machine 64 and a cutting machine 65 .

The first extruder 61 includes a first extruder 68 for kneading, heating and melting the resin composition supplied from the hopper 66 and extruding it. The second extruder 62 includes a second extruder 69 for kneading, heating and melting the resin composition supplied from the hopper 67 and for extruding the resin composition. A mold 70 is attached to the outlets of the first extruder 68 and the second extruder 69 . A hopper 66 of the first extruder 61 is supplied with the resin composition (B-2) that constitutes the non-foamed outer layer 13 and the non-foamed inner layer 12 of the tube 10 . A hopper 67 of the second extruder 62 is supplied with the resin composition (B-1) forming the foam layer 11 . At least the resin composition (B-1) contains a vinyl chloride resin and a foaming agent, and the resin composition (B-2) contains a vinyl chloride resin.

As shown in FIG. 16, the mold 70 is a three-layer extrusion mold and includes a confluence section 71 and a molding section 72 . In the confluence portion 71, the molten resin introduced from the first extruder 68 (melted resin composition (B-2)) 73 and the molten resin introduced from the second extruder 69 (melted resin composition (B -1)) 74 are merged, and these are stacked in the vicinity of the outlet of the confluence portion 71 . The laminated molten resins 73 and 74 are expanded in diameter in the laminated state in the molding portion 72 to form a tubular shape. A die ring 75 and a mandrel 76 provided at the tip of the molding portion 72 regulate the outer and inner circumferences to an appropriate size to some extent, and extruded as a continuous tube (hereinafter referred to as “continuous tube”) 77 . be
In addition, the resin composition constituting the non-foamed outer layer 13 and the non-foamed inner layer 12 may not be the same. The material may be extruded and fed to the forming section 72 for lamination.

At this time, the temperature (molding temperature) for molding with the mold 70 is preferably 130° C. or higher and 180° C. or lower, more preferably 140° C. or higher and 170° C. or lower, and even more preferably 140° C. or higher and 160° C. or lower. By setting the molding temperature within the above range, it is possible to improve the adhesion between the well-kneaded foam layer 11, the non-foamed outer layer 13 and the non-foamed inner layer 12, and to improve the closed cell ratio. can.
If the molding temperature is lower than 170° C., the kneading state of the resin composition (B-1) and the resin composition (B-2) is poor, resulting in poor adhesion. If the molding temperature exceeds 180° C., the cells formed by the foaming agent expand too much up to the mold 70, and the cells become interconnected during shaping in the vacuum sizing step, which will be described later, and the closed cell ratio decreases.

Next, the continuous tube 77 extruded from the mold 70 is introduced into the vacuum sizing device 63 . The vacuum sizing device 63 is for shaping the outer surface of the continuous tube 77 and for cooling it. As shown in FIG. 17, the vacuum sizing device 63 has a body 78 extending in the extrusion direction of the continuous tube 77 . An inlet 79 and an outlet 80 of the body 78 are formed at one longitudinal end and the other longitudinal end of the body 78 . A vacuum chamber 82 to which a vacuum pump 81 is connected is provided on the inlet 79 side in the main body 78 . A sizing sleeve 83 is arranged in the vacuum chamber 82 . One end of sizing sleeve 83 is connected to inlet 79 . A cooling chamber 84 is provided between the vacuum chamber 82 and the outlet 80 , and a water spray pipe 85 is arranged over the entire length of the vacuum chamber 82 and the cooling chamber 84 .
The atmospheric pressure (degree of vacuum) in the vacuum chamber 82 is preferably −2 kPa or less and −100 kPa or more. If the air pressure is higher than −2 kPa (low vacuum), the pressure applied from the air in the tube 10 is weak, the fusion strength between the non-foamed inner layer 12 and the foamed layer 11 is inferior, and the cells expand too much and become independent. Low bubble rate. If the atmospheric pressure is less than -100 kPa (high degree of vacuum), the cells in the foam layer 11 will be crushed and the expansion ratio will decrease.

When the continuous tube 77 is supplied to the vacuum sizing device 63 , the continuous tube 77 is expanded by the negative pressure of the vacuum pump 81 . The outer surface of the continuous tube 77 is brought into close contact with the inner surface of the sizing sleeve 83 to shape the continuous tube 77 , and the non-foamed outer layer 13 and the non-foamed inner layer 12 of the continuous tube 77 and the foamed layer 11 are brought into close contact. Further, the sized continuous pipe 77 is cooled and hardened by the cooling water sprayed from the water spray pipe 85 .

Returning to FIG. 15, the take-up device 64 is for taking the continuous tube 77 at a constant speed. The take-up machine 64 comprises a plurality of take-up rollers 86 pressed against the bottom and top of the continuous tube 77 . A motor (not shown) is connected to at least one of the take-up rollers 86, and the take-up speed of the continuous tube 77 is adjusted by controlling the number of rotations of the motor.

The cutting machine 65 is for cutting the continuous tube 77 to a predetermined length. The cutting machine 65 includes a sensor 87 that detects the position of the tip of the continuous tube 77 and a cutting blade 88 that is driven in conjunction with the sensor 87 . When the tip of the continuous tube 77 pushes the sensor 87, the cutting blade 88 is driven to cut the continuous tube 77, thereby obtaining the tube 10 of a predetermined length. The pipe 10 is cut to any length, for example, at the construction site, as described above.

[Pipe joint 20]
As shown in FIG. 2, the pipe joint 20 includes a plurality of receptacles 21 to which the pipes 10 are connected, and a joint main body 22 that connects the plurality of receptacles 21 .
The receptacle part 21 has a tubular shape. In the following description, the direction along the central axis O of the socket portion 21 is called the axial direction, and the direction perpendicular to the axial direction is called the radial direction.
The joint main body 22 has an L-shaped elbow shape. Two receptacles 21 are connected to the joint body 22 . The central axes O of the two receptacles 21 are orthogonal to each other.

The joint main body 22 and the receptacle portion 21 are integrally formed by injection molding of a synthetic resin material.
As a method of integrally forming the joint main body 22 and the receptacle portion 21 by injection molding of a synthetic resin material, the manufacturing method described in JP-A-11-201382 can be referred to.
Specifically, after injecting a non-foaming resin from a gate for supplying resin to a cavity (space) for forming the joint main body 22 provided in the mold, the foaming resin that becomes the heat insulating layer 25 is injected. is injected into the mold.
As a result, the foaming resin enters the inside of the non-foaming resin by the injection pressure and/or the foaming pressure of the foaming resin, filling the non-foaming resin to the tip of the cavity, and the non-foaming resin on the outer surface of the cavity (metal inside the mold). By cooling and hardening both resins in the mold, the non-foaming resin and the foaming resin are integrally formed.

A stopper 23 having a restricting surface 23A facing in the axial direction is formed in a portion of the joint main body 22 located inside the receptacle portion 21 . The stopper 23 has a cylindrical shape and is arranged coaxially with the central axis O. As shown in FIG. The end of the tube 10 is in contact with the restricting surface 23A.
The radial thickness of the stopper 23 is the same as the thickness of the tube 10 . The inner diameter of the socket portion 21 and the outer diameter of the tube 10 are the same. Also, the inner diameter of the pipe 10 and the inner diameter of the joint body 22 are the same.

A stepped portion 24 projecting in the radial direction is formed at a portion of the outer peripheral portion 32 of the joint body 22 that is connected to the receptacle portion 21 . The stepped portion 24 is formed with an inclined surface 24</b>A that gradually extends outward in the radial direction from the joint main body 22 side toward the receptacle portion 21 side.

A heat insulating layer 25 is provided on the pipe joint 20 .
In the joint main body 22, the heat insulating layer 25 is arranged over the entire area in the direction in which the joint main body 22 extends. In other words, the heat insulating layer 25 extends along the L-shaped flow path formed by the joint main body 22 in cross-sectional view of the joint main body 22 . In the illustrated example, the heat insulating layer 25 in the joint body 22 is formed between the inner peripheral portion 31 and the outer peripheral portion 32 of the joint body 22 .
In the receptacle portion 21 , the heat insulating layer 25 is arranged only in the connection portion with the joint main body 22 . In the illustrated example, the heat insulating layer 25 in the socket portion 21 is also formed between the inner peripheral portion 31 and the outer peripheral portion 32 of the socket portion 21 .

The heat insulating layer 25 of the joint main body 22 and the heat insulating layer 25 of the receptacle portion 21 are integrally formed of the same heat insulating layer 25 . The heat insulating layer 25 is integrally formed inside each of the joint main body 22 and the receptacle portion 21 . The heat insulating layer 25 is made of expandable resin.

Of the joint main body 22 and the receptacle portion 21, portions other than the heat insulating layer 25 (hereinafter referred to as non-foaming portions) are made of non-foaming resin. Non-foamable resins include, for example, polyvinyl chloride resins, ABS resins, AES resins, polyethylene resins, polypropylene resins, and acrylic resins. ABS resin and AES resin are particularly preferable from the viewpoint of transparency. On the other hand, polyvinyl chloride resin, polyethylene resin, and polypropylene resin are particularly preferable from the viewpoint of chemical resistance.

ABS resin and AES resin are resins obtained by polymerizing an aromatic vinyl monomer and a vinyl cyanide monomer in the presence of a rubber component. The rubber component refers to a monomer component that is a raw material for diene rubber such as polybutadiene and polyisoprene.
Examples of rubber components include butadiene, isoprene, ethylene, and propylene. Examples of aromatic vinyl monomers include styrene and α-methylstyrene.
Vinyl cyanide monomers include acrylonitrile, methacrylonitrile, and the like.

In the non-foaming resin composed of ABS resin and/or AES resin, the content of units derived from vinyl cyanide monomer is preferably 10% by mass or more and 50% by mass or less with respect to the total mass of the first resin. , more preferably 15% by mass or more and 45% by mass or less.
Tensile strength can be improved as content of the unit derived from a vinyl cyanide monomer is more than the said lower limit. Impact strength can be improved as content of the unit derived from a vinyl cyanide monomer is below the said upper limit.

The content of the rubber component in the non-foamable resin composed of ABS resin and/or AES resin is not particularly limited, and is preferably 1% by mass or more and 20% by mass or less based on the total mass of the non-foamable resin.
In the non-foaming resin composed of ABS resin and/or AES resin, the content of units derived from aromatic vinyl monomers is preferably 15% by mass or more and 60% by mass or less with respect to the total mass of the non-foaming resin. , more preferably 20% by mass or more and 50% by mass or less.
When the content of the unit derived from the aromatic vinyl monomer is at least the above lower limit, the indentation hardness can be improved. Impact strength can be improved as content of the unit derived from an aromatic vinyl monomer is below the said upper limit.

The content of each component in the non-foaming resin is determined by pyrolysis gas chromatography mass spectrometry (
It is determined by analysis using PGC/MS).
A method for calculating the content of each component in the first resin by PGC/MS measurement will be described.

First, each component constituting the first resin is thermally decomposed and separated by pyrolysis gas chromatography to obtain a thermal decomposition pattern (pyrogram) in which each component is recorded as a peak. Next, for each peak of the thermal decomposition pattern, each component of acrylonitrile, rubber component, and styrene is specified by mass spectrum obtained by a mass spectrometer.
Here, acrylonitrile, rubber component, and styrene each have a different depolymerization rate (the rate at which the polymer decomposes into monomers) due to thermal decomposition, so the peak area (X) of each component is The peak area (Z) of each component is obtained by dividing by the depolymerization rate (Y) of the component. The depolymerization rate (Y) of each component is acrylonitrile: 0.15, rubber component: 0.10, and styrene: 1.0.

Then, the ratio (Z/T) to the total sum (T) of the peak areas (Z) of each component in the thermal decomposition pattern is defined as the content of each component in the first resin.
The same material as the non-foaming resin can be used for the foaming resin forming the heat insulating layer 25, and the heat insulating layer 25 and the non-foaming portion are preferably made of the same resin.

The socket portion 21 is preferably transparent to the extent that the drain pipe 10 connected to the socket portion 21 can be visually recognized from the outside. In other words, the heat insulating layer 25 is not formed on the portion of the receptacle portion 21 other than the connection portion with the joint main body 22 . This non-foamed portion is transparent to the extent that the drain pipe 10 connected to the socket portion 21 can be visually recognized from the outside. In addition, it does not necessarily have to be transparent, and may be colored with a pigment to be opaque.

In this embodiment, the axial size L (mm) of the socket portion 21 and the axial size F (mm) of the heat insulating layer 25 in the socket portion 21 satisfy the expression (1). there is
Here, the axial size L of the socket portion 21 and the axial size F of the heat insulating layer 25 in the socket portion 21 respectively refer to the axial size of the stopper 23 from the restricting surface 23A.
0.03<F/L<0.5 (1)

Further, F/L is preferably greater than 0.05 and less than 0.4, more preferably greater than 0.08 and less than 0.36.
In addition, the size L of the socket portion 21 in the axial direction is, for example, 15 mm or more and 40 mm or less. The axial dimension F of the heat insulating layer 25 is, for example, 1 mm or more and 8 mm or less, preferably 3 mm or more and 8 mm or less.

Further, the axial size L of the socket portion 21 and the radial thickness T (mm) of the socket portion 21 satisfy the following formula (2).
4<L/T<13 (2)
Further, L/T is preferably greater than 5 and less than 10, more preferably greater than 6 and less than 9. The radial thickness T of the socket portion 21 is 2.5 mm or more and 6 mm or less. Here, the radial thickness T of the receptacle portion 21 refers to the thickness of the portion of the receptacle portion 21 that is the smallest in the radial direction (the thinnest portion).
Also, the heat insulating layer 25 and the foam layer 11 of the pipe 10 are arranged so as to overlap each other in the radial direction.

Next, modified examples of the pipe joint 20 will be described.
Like the pipe joint 20B of the first modified example shown in FIG. 3, the inclined surface 24A formed on the stepped portion 24 of the outer peripheral portion 32 may be made gentler than the pipe joint 20 described above.
Specifically, the axial position of the portion of the inclined surface 24A connected to the outer peripheral portion 32 of the joint main body 22 is closer to the joint main body 22 than the heat insulating layer 25 disposed inside the flow path of the joint main body 22. In this case, the distance from the axial position of the portion of the joint body 22 connected to the outer peripheral portion 32 to the restricting surface 23A of the stopper 23 is greater than the radial thickness T of the socket portion 21, This makes it easier for the expandable resin forming the heat insulating layer 25 to reach the socket portion 21 .

Further, the shape of the joint body 22 in the pipe joint 20 is not limited to an elbow shape. For example, like a joint body 22C of a pipe joint 20C according to a second modification shown in FIG. 4, it may be cheese-shaped.
The pipe joint 20</b>C includes a T-shaped joint main body 22</b>C and three receptacles 21 .

Further, for example, like a joint body 22D of a pipe joint 20D according to a third modified example shown in FIG. 5, it may have a socket shape.
The pipe joint 20D includes a straight cylindrical joint body 22D and two sockets 21 arranged coaxially.

As described above, according to the pipe joint 20 according to the present embodiment, the axial size L of the socket portion 21 and the axial size F of the heat insulating layer 25 in the socket portion 21 are (1) satisfy the formula.
That is, since F/L is larger than 0.03, the size of the heat insulating layer 25 in the receptacle 21 is ensured, so that dew condensation in the receptacle 21 can be reliably suppressed. Accordingly, there is no need to provide an annular elastic body at the connecting portion between the tube 10 and the socket portion 21 . On the other hand, if F/L is 0.03 or less, dew condensation is likely to occur in the receptacle portion 21 .

Further, since F/L is smaller than 0.5, the strength of the socket portion 21 can be ensured by suppressing the size of the heat insulating layer 25 in the socket portion 21 from becoming too large. On the other hand, if F/L is 0.5 or more, there is a concern that the heat insulating layer 25 in the receptacle portion 21 will become large and the strength of the receptacle portion 21 will be weakened.

In addition, the axial size L of the socket portion 21 and the radial thickness T of the socket portion 21 satisfy the expression (2). That is, since L/T is larger than 4, the strength of the socket portion 21 can be ensured by ensuring the thickness of the socket portion 21 . On the other hand, if L/T is 4 or less, there is a concern that the strength of the receptacle portion 21 may be weakened.

In addition, since L/T is less than 13, it is possible to prevent the socket portion 21 from becoming too thick and to suppress the occurrence of sink marks in the socket portion 21 due to molding shrinkage. On the other hand, if L/T is 13 or more, the thickness of the receptacle portion 21 becomes too thick, and there is a risk that the amount of shrinkage during molding will vary and sink marks will occur. If sink marks occur, a gap is formed at the connecting portion between the pipe 10 and the socket portion 21, and dew condensation is likely to occur in the gap. By suppressing the occurrence of sink marks as described above, it is possible to suppress the occurrence of such dew condensation.

Further, since the socket part 21 is transparent, the state of the pipe 10 connected to the socket part 21 can be visually recognized from the outside of the socket part 21, so that the pipe 10 can be reliably connected to the socket part 21. - 特許庁
A stepped portion 24 projecting in the radial direction is formed at the connecting portion between the joint main body 22 and the socket portion 21 . Therefore, the resin can easily flow into the receptacle portion 21 through the stepped portion 24 during molding, and the moldability of the pipe joint 20 can be ensured.

Also, the heat insulating layer 25 in the socket portion 21 and the foam layer 11 in the pipe 10 are arranged to overlap in the radial direction. Therefore, it is possible to ensure the heat insulating performance of the connection portion of the pipe 10 in the pipe joint 20, and to suppress the formation of dew condensation in the pipe joint 20.
Specifically, when the pipe 10 is cut obliquely with respect to the pipe axis, the plane passing through the cross section of the pipe 10 is no longer parallel to the restricting surface 23A of the stopper 23 of the pipe joint 20 . As a result, a gap is generated between the stopper 23 and the cross section of the pipe, and a portion where the foam layer 11 of the pipe 10 and the heat insulating layer 25 of the pipe joint 20 are not continuous is generated. Become.
Even in such a state, in the present embodiment, the heat insulating layer 25 inside the receptacle portion 21 and the foam layer 11 inside the pipe 10 overlap in the radial direction. As a result, the length F of the heat insulating layer 25 in the receptacle portion 21 is set longer than the gap that occurs when the pipe 10 is obliquely cut, thereby suppressing the occurrence of dew condensation.

(Second embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. In addition, the same code|symbol is attached|subjected about the same structure as 1st Embodiment mentioned above in this embodiment, and the description is abbreviate|omitted. Also, the description of the same action will be omitted.
As shown in FIG. 6, in the pipe joint 20E according to this embodiment, a part of the receptacle portion 21E is formed of a separate member. In other words, the receptacle portion 21E includes a first receptacle 41 integrally formed with the joint main body 22E and a second receptacle 42 formed separately from the joint main body 22E and connected to the first receptacle 41. there is

For this embodiment, the manufacturing method described in JP-A-2011-2012 can be referred to.
Specifically, the second receptacle 42 made of a non-foamable resin that has been injection-molded in advance is set in the cavity forming the joint main body 22 or in the inner core that forms the receptacle space of the mold, and then the mold is A non-foaming resin and a foaming resin are injected into the cavity of the. Thereby, the joint main body 22E and the heat insulating layer 25 can be integrally formed.

Here, in general, the cavity forming the socket is thin, and it is difficult to fill the non-foaming resin and the foaming resin. can be reliably formed, and the transparency of the receptacle can be improved by using a highly transparent resin.

(Third Embodiment)
Next, a third embodiment of the present invention will be described with reference to FIGS. 7 to 9. FIG. In addition, the same code|symbol is attached|subjected about the same structure as 1st Embodiment mentioned above in this embodiment, and the description is abbreviate|omitted. Also, the description of the same action will be omitted.
As shown in FIG. 7, a pipe joint 20F according to the present embodiment is formed by two-color molding of a heat insulating layer 25F made of expandable resin and non-expandable resin.

For this embodiment, the manufacturing method described in JP-A-2012-214021 can be referred to. Specifically, foaming resin is injected into the first cavity of the mold and cooled to form the heat insulating layer 25F, and then the mold around the heat insulating layer 25F is used to form the joint main body 22F and the receptacle portion 21F. Replace the mold with a second cavity for
By injecting a non-foamable resin between the heat insulating layer 25F and the second cavity, the joint main body 22F and the receptacle portion 21F can be formed so as to surround the heat insulating layer 25F.

At this time, the non-foaming resin injected into the second cavity is kept at a temperature higher than the glass transition point of the foaming resin constituting the heat insulating layer 25, so that the surface of the heat insulating layer 25 melts, and the joint main body 22F, socket portion 21F, and heat insulating layer 25 can be integrally molded.
The temperature of the non-foaming resin can be adjusted by setting the mold having the second cavity or the injection temperature of the non-foaming resin to a temperature higher than the glass transition point of the foaming resin forming the heat insulating layer 25. Adjustable.

In addition, although the case where the heat insulation layer 25 was formed first was demonstrated, it does not restrict to this. That is, the joint main body 22F and the receptacle portion 21F may be formed by the first cavity first.
After that, the mold on the inner surface of the joint main body 22F and the socket portion 21F is replaced with a mold having a second cavity for forming the heat insulating layer 25, and the joint main body 22F and the socket portion 21F and the second mold are replaced. The joint main body 22F and the receptacle portion 21F may be formed so as to surround the heat insulating layer 25F by injecting a foamable resin between them and the cavity.
In this case, the foaming resin is injected at a temperature higher than the glass transition point of the non-foaming resin forming the joint main body 22F and the socket portion 21F.

As shown in FIG. 7, the portion from the outer peripheral portion 32 of the joint body 22F to the receptacle portion 21F is formed of non-foamable resin. On the other hand, from the inner peripheral portion 31 of the joint main body 22F to the inner peripheral portions of the stopper 23 and the receptacle portion 21F, a heat insulating layer 25F is integrally formed.

Further, as a first modification of the pipe joint 20F according to the present embodiment, the entire joint main body 22G may be formed of the heat insulating layer 25G, like the pipe joint 20G shown in FIG.
As a second modification, as in a pipe joint 20H shown in FIG. 9, a heat insulating layer 25H may be formed integrally from the outer peripheral portion 32 of the joint main body 22H to the outer peripheral portions of the stopper 23 and the receptacle portion 21F.

The structures shown in FIGS. 7 to 9 use a first cavity and a second cavity, but are not limited to this. The peripheral portion 31 and the stopper 23 may also be made of a non-foaming resin so that the heat insulating layer 25F is not exposed to the outside.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described with reference to FIGS. 10 and 11. FIG. In addition, the same code|symbol is attached|subjected about the same structure as 1st Embodiment mentioned above in this embodiment, and the description is abbreviate|omitted. Also, the description of the same action will be omitted.
As shown in FIG. 11, the pipe joint 20I according to this embodiment includes a compressed portion 26 that is pressurized during molding and changes from a foamed layer to a non-foamed layer.

As shown in FIG. 10, when molding the pipe joint 20I, an intermediate member 20J is first formed in a cavity of a mold with a foamable resin. The compressed portion 26 of the intermediate member 20J is formed on the inner peripheral portion of the socket portion 21J. The compressed portion 26 has a cylindrical shape and is arranged coaxially with the socket portion 21J. That is, the compressed portion 26 protrudes radially inward at the stage of the intermediate member 20J. Further, in order to maintain the molten state of the intermediate material 20J, the temperature of the mold around the intermediate material 20J is set to a temperature higher than the glass transition point of the foamable resin.
Then, as shown in FIG. 11, by compressing the compressed portion 26 of the intermediate member 20J in the mold radially outward, the foam layer of the compressed portion 26 is compressed, and the air bubbles inside are crushed. It changes into a non-foamed layer having light transmission properties. Along with this, light is scattered by the bubbles, and the opaque foam layer changes to a transparent state.
Thereafter, by cooling the pipe joint 20I in this state, the pipe joint 20I in which the joint main body and the transparent receptacle portion 21J are integrated can be formed.
Note that the compressed portion 26 may be provided on the outer surface of the socket so as to compress the intermediate member 20J from the outside to the inside in the radial direction.

(Fifth embodiment)
Next, a fifth embodiment of the present invention will be described with reference to FIG. In addition, the same code|symbol is attached|subjected about the same structure as 1st Embodiment mentioned above in this embodiment, and the description is abbreviate|omitted. Also, the description of the same action will be omitted.
As shown in FIG. 13, the pipe joint 20K according to this embodiment includes a pressure-reduced portion 27 that is decompressed during molding and changes from a non-foamed layer to a foamed layer.

As shown in FIG. 12, when forming the pipe joint 20K, the intermediate member 20L is first integrally formed from a non-foaming resin. The pressure-reduced portion 27 of the intermediate member 20L is formed over the entire outer peripheral portion 32 of the joint main body 22K.
Then, by widening a portion of the mold corresponding to the outer peripheral portion 32 of the joint main body 22K, the outer peripheral portion 32 is decompressed and the depressurized portion 27 is formed. The non-foamed layer of the depressurized portion 27 becomes a foamed layer by being decompressed and expanded to generate bubbles inside. Along with this, the non-foamed layer, which was transparent, scatters light due to the generated air bubbles and changes to an opaque state.

The technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

For example, in the above-described embodiments, the configuration in which the pipe joint is used in the air conditioner is shown, but the configuration is not limited to this. The pipe joint may be used for equipment other than air conditioners.
Moreover, although the pipe|tube 10 showed the structure which is a drain pipe, it is not restricted to such an aspect. Pipe 10 may be used in applications other than drain pipes.

In addition, it is possible to appropriately replace the constituent elements in the above-described embodiment with well-known constituent elements without departing from the spirit of the present invention, and the modifications described above may be combined as appropriate.

EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

Examples 1-1 to 1-3 and Comparative Examples 1-1 and 1-2 were prepared in relation to the tube 10 described above. In relation to the joint structure 1, Examples 2-1 to 2-5, Comparative Examples 2-1 and 2-2, and Reference Examples 1-1 and 1-2 were prepared.

(Example 1-1)
As the resin composition constituting the foam layer 11, 100 parts by mass of a vinyl chloride resin (polymerization degree 640, manufactured by Tokuyama Sekisui Kogyo Co., Ltd., trade name “TS-640M”) and a tin-based stabilizer (Daikyo Kasei Kogyo Co., Ltd. 2 parts by mass of baking soda (manufactured by Eiwa Kasei Kogyo Co., Ltd., trade name “STX-80”) and 2.2 parts by mass of sodium bicarbonate (manufactured by Eiwa Kasei Kogyo Co., Ltd., trade name “Celbon SC-855”). Resin composition (B-1 ) was prepared.
As the resin composition constituting the non-foamed inner layer 12 and the non-foamed outer layer 13, 100 parts by mass of a vinyl chloride resin (polymerization degree 1000, manufactured by Tokuyama Sekisui Kogyo Co., Ltd., trade name "TS-1000R"), a tin stabilizer ( A resin composition (B-2) was prepared by mixing 2 parts by mass of STX-80 (trade name, manufactured by Daikyo Kasei Kogyo Co., Ltd.).
The resin composition (B-2) was supplied to the hopper 66 of the first extruder 61 shown in FIG. 15, and the resin composition (B-1) was supplied to the hopper 67 of the second extruder 62. The resin temperatures in the first extruder 68 and the second extruder 69 were set to 140° C., and each resin was supplied from the first extruder 68 and the second extruder 69 to the mold 70 . The molding temperature in the mold 70 is set to 160° C., and the product is extruded into a tubular shape. A tube 10 having a three-layer structure was manufactured by cutting to a predetermined length at 65 . The tube 10 has an outer diameter of 48 mm, is composed of the resin composition (B-2), is composed of a non-foamed inner layer 12 with a thickness of 2.0 mm, and is composed of the resin composition (B-2), and has a thickness of 0. A non-foamed outer layer 13 having a thickness of .5 mm, and a foamed layer 11 having a thickness of 6.0 mm formed between the non-foamed inner layer 12 and the non-foamed outer layer 13 and formed of the resin composition (B-1). It was a three-layer tube.

(Example 1-2, Example 1-3, Comparative Example 1-1, Comparative Example 1-2)
A tube 10 was produced in the same manner as in Example 1-1 except that the molding temperature and degree of vacuum were set as shown in Table 1.

The closed cell ratio, foaming ratio, and fusion bonding strength were measured for each of the obtained pipes 10 (air conditioning drain pipes). The measurement results are shown in Table 1 above.
In Examples 1-1 to 1-3, both the foaming ratio and the fusion bond strength are within the preferred ranges of the tube 10 according to the above embodiment. In Comparative Example 1-1, although the foaming ratio is within the preferred range, the fusion bond strength is not within the preferred range. In Comparative Example 1-2, the fusion bond strength is within the preferred range, but the expansion ratio is not within the preferred range.

(Examples 2-1 to 2-5, Comparative Example 2-1, Comparative Example 2-2, Reference Example 2-1, Reference Example 2-2)
A transparent resin composition obtained by kneading poly(methyl methacrylate) into an ABS resin was used as a non-foaming resin composition. A foaming resin composition was prepared by mixing this non-foaming resin composition with azodicarbonamide as a foaming agent. With reference to the manufacturing method described in Japanese Patent Application Laid-Open No. 11-201382, resin is supplied from a gate for supplying resin to a cavity (space) for forming the joint main body 22 provided in a mold (not shown) into the cavity. A non-foaming resin composition, a foaming resin composition, and a non-foaming resin composition were injected in this order. As a result, the axial size L (mm) of the socket portion 21, the axial size F (mm) of the heat insulating layer 25 of the socket portion 21, and the radial thickness T (mm) of the socket portion 21 are shown in Table 2. , 3 were manufactured.

For each pipe joint 20 of Examples 2-1 to 2-5, Comparative Examples 2-1 and 2-2, and Reference Examples 2-1 and 2-2, Examples 1-1 to 1-3 and Comparative Example 1 A joint structure 1 was formed by applying either pipe 10 of -1 or 1-2. Combinations of fittings 20 and tubes 10 are shown in Tables 2 and 3 above.

In the joint structures 1 of Examples 2-1 to 2-3 and Comparative Examples 2-1 and 2-2, the pipe 10 is common to Example 1-1, but the pipe joint 20 is different. In Examples 2-1 to 2-3, F/L and L/T are all within the preferred ranges. In Comparative Example 2-1, L/T is within the preferred range, but F/L is not within the preferred range. In Comparative Example 2-2, F/L is within the preferred range, but L/T is not within the preferred range.

In the joint structures 1 of Examples 2-1, 2-4, 2-5 and Reference Examples 2-1 and 2-2, the pipe joint 20 is common, but the pipe 10 is different. The pipes 10 applied to Examples 2-1, 2-4, 2-5 and Reference Examples 2-1 and 2-2 are those of Examples 1-1, 1-2, 1-3 and Comparative Example 1- 1, 1-2. In any of the joint structures 1 of Examples 2-1, 2-4, 2-5 and Reference Examples 2-1, 2-2, the F/L and L/T of the pipe joint 20 are within the preferred ranges. there is

[Evaluation of stretching fatigue resistance]
As shown in FIG. 18, a hydraulic fatigue tester 300 (a serial fatigue tester EHF-ED10-70L manufactured by Shimadzu Corporation) was used. Adhesive was applied to the ends of the manufactured pipe 10 , and the joint structure 1 was formed by inserting and connecting to the receptacle 21 of the pipe joint 20 . The joint structure 1 was fixed to the fixing jig 90 and the fixing jig 92 . A stress F of 700 kg (6865 N) was applied once per second, and the pipe joint 20 was pulled vertically upward to perform an expansion fatigue test. The stretching fatigue test was performed until the pipe joint 20 stretched and fractured or the stress F was applied 1000 times, and the number of times the stress F was applied until the pipe joint 20 stretched and fractured was measured. Stretch fatigue resistance was evaluated according to the following evaluation criteria.
(Evaluation criteria)
○: 1000 times or more.
(triangle|delta): 200 times or more and less than 1000 times.
x: Less than 200 times.

[Evaluation of anti-condensation property]
An adhesive was applied to the ends of the two manufactured pipes 10 , and the joint structure 1 was formed by inserting and connecting the two receptacles 21 of the manufactured elbow-shaped pipe joint 20 . At this time, assuming the case where the pipe 10 is cut obliquely, the end face of one pipe 10 and the restricting surface 23A of the stopper 23 of the pipe joint 20 are connected with a gap of 1 mm. The joint structure 1 was installed in a constant temperature room (temperature 25° C., relative humidity 75%) so that the gradient of the single pipe 10 was 1/50. After the joint structure 1 was left in a constant temperature room for 1 hour, water with a water temperature of 10° C. was continued to flow for 1 hour at a flow rate of 3 L/hour, and the outer surface of the socket portion 21 of the pipe joint 20 was observed. The anti-condensation property was evaluated according to the following evaluation criteria.
(Evaluation criteria)
◯: No dew condensation occurred.
x: Dew condensation occurred.

Tables 2 and 3 show the evaluation of both the resistance to stretching fatigue and the anti-condensation property. In Examples 2-1 to 2-5, good evaluations were obtained in terms of anti-condensation properties as well as resistance to stretching fatigue.

REFERENCE SIGNS LIST 1 joint structure 10 pipe 20 pipe joint 21 socket 22 joint main body 24 stepped portion 25 heat insulating layer 31 inner peripheral portion 32 outer peripheral portion

Claims (4)

a tube comprising a tubular foam layer;
A joint structure provided with a heat insulating layer and a pipe joint to which the pipe is connected ,
The foam layer of the pipe has a closed cell ratio of 45% or more and 90% or less and an expansion ratio of 3.5 times or more and 10 times or less,
the pipe joint includes a plurality of receptacles to which the pipes are connected;
The axial size L (mm) along the central axis of the socket and the axial size F (mm) of the heat insulating layer in the socket satisfy the following formula (1) ,
The joint structure , wherein the heat insulating layer and the foam layer are arranged so as to overlap each other in a radial direction perpendicular to the central axis of the socket.
0.03<F/L<0.5 (1) The joint structure according to claim 1, wherein the size L and the thickness T (mm) of the socket portion in the radial direction perpendicular to the central axis satisfy the following formula (2). .
4<L/T<13 (2) 3. The joint structure according to claim 1, wherein the socket is transparent to the extent that the pipe connected to the socket is visible from the outside. comprising a joint body that connects the plurality of receptacles,
4. The joint body according to any one of claims 1 to 3, wherein a portion of the outer peripheral portion of the joint body that is connected to the receptacle portion is formed with a stepped portion projecting in a radial direction orthogonal to the central axis. The joint structure according to item 1.

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