Air conditioning drain pipe and method for manufacturing air conditioning drain pipe

Abstract

To provide an air conditioning drain pipe capable of easily preventing water from penetrating into a foam layer. [Solution] An air conditioning drain pipe comprising a cylindrical foamed layer containing a vinyl chloride resin (B), a non-foamed inner layer provided on the inner surface of the foamed layer and containing a vinyl chloride resin (A), and a non-foamed outer layer provided on the outer surface of the foamed layer and containing a vinyl chloride resin (C), wherein the foamed layer has an expansion ratio of 3.5 to 10 times, the foamed layer has a closed cell ratio of 45% or more, the fusion strength between the foamed layer and the non-foamed inner layer is 1.5 MPa or more, and the foamed layer has an average cell diameter of 30 μm to 400 μm.

Description

Technical Field

[0001] The present invention relates to a pipe for air conditioner drain.

Background Art

[0002] As a pipe for air conditioner drain, one with excellent heat insulation properties is required. As such a pipe for air conditioner drain, a pipe containing polyvinyl chloride and having a foamed layer and a non-foamed inner layer laminated on the inner surface thereof is preferably used. However, in conventional pipes for air conditioner drain, since the end of the foamed layer is exposed at the pipe joint portion, there is a problem that water easily penetrates from the end. When water penetrates into the foamed layer, the heat exchange rate increases and the heat insulation effect decreases.

[0003] In Patent Document 1, a method of preventing water from penetrating into the foamed layer by applying an adhesive to the end of the foamed layer to cover the end has been proposed. In Patent Document 2, a method of preventing water from penetrating into the foamed layer by using an annular elastic body has been proposed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the method of Patent Document 1, it is necessary to apply the adhesive uniformly, and the work is complicated. Also, in the method of Patent Document 2, it is necessary to use a special member, and the work is complicated.

[0006] An object of the present invention is to provide a pipe for air conditioner drain that can easily prevent water from penetrating into the foamed layer.

Means for Solving the Problems

[0007] The inventors of the present application have found that the above problems can be solved by setting the expansion ratio, closed cell ratio, average cell diameter, and fusion strength of the foam layer within specific numerical ranges. The present invention has the following aspects. [1] A pipe for air-conditioning drain, comprising: And a tin-based stabilizer and a decomposition-type foaming agent a tubular Thermoplastic resin composition for foam layer foam layer, and molded a non-foamed inner layer provided on the inner surface of the foam layer and containing vinyl chloride resin (A), wherein the expansion ratio of the foam layer is 3.5 times or more stacked and 8 times or less, Furthermore, a thermoplastic resin composition for a non-foaming layer that does not contain a foaming agent was molded. the closed cell ratio of the foam layer is 45% or more, and, the fusion strength between the foam layer and the non-foamed inner layer is 1.5 MPa or more, and the average cell diameter of the foam layer is 6 times 10 μm or more and 100 μm or less. 95% or less 100 250 [2] A foamed layer formed by molding a thermoplastic resin composition for foamed layers, which includes a vinyl chloride resin (B), a tin-based stabilizer, and a heat-expandable capsule, into a cylindrical shape, An air conditioning drain pipe comprising: a non-foamed inner layer laminated on the inner surface of the foamed layer, and molded from a thermoplastic resin composition for non-foamed layers containing a vinyl chloride resin (A) but without a foaming agent; The foaming ratio of the foamed layer is 3.5 times or more and 6 times or less. The closed-cell ratio of the foamed layer is 45% or more and 95% or less. The fusion strength between the foamed layer and the non-foamed inner layer is 1.5 MPa or more. An air conditioning drain pipe having an average bubble diameter of 100 μm or more and 250 μm or less in the foamed layer. [3] A method for manufacturing an air conditioning drain pipe comprising a cylindrical foamed layer containing a vinyl chloride resin (B), and a non-foamed inner layer provided on the inner surface of the foamed layer and containing a vinyl chloride resin (A), A thermoplastic resin composition for a non-foaming layer, which does not contain a foaming agent, is melt-kneaded and extruded by an extruder to form the aforementioned non-foaming inner layer. A thermoplastic resin composition for a foamed layer, which contains one or more foaming agents selected from decomposition-type foaming agents and thermally expandable capsules, and a tin-based stabilizer, is melt-kneaded and extruded using an extruder. The thermoplastic resin composition for the non-foamed layer and the thermoplastic resin composition for the foamed layer are injected into a mold and combined inside the mold to form an uncured air conditioning drain pipe. A method for manufacturing an air conditioning drain pipe, characterized by cooling the uncured air conditioning drain pipe and molding it to a predetermined size. [4] The method for manufacturing an air conditioning drain pipe according to [3], wherein the foaming agent comprises the decomposing foaming agent and the thermally expandable capsule. [5] The method for manufacturing an air conditioning drain pipe according to [3] or [4], wherein the thermoplastic resin composition for the foam layer comprises polyvinyl chloride having an average degree of polymerization of 600 or more and 800 or less. [6] A method for producing an air conditioning drain pipe according to any one of [3] to [5], wherein the thermoplastic resin composition for the foamed layer comprises an acrylic polymer compound.

Advantages of the Invention

[0008] ​​​​​According to the present invention, it is possible to provide an air conditioning drain pipe that can easily prevent water from penetrating into the foam layer. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view showing an example of an air conditioning drain pipe according to the present invention. [Figure 2] This is a front view showing an apparatus for measuring fusion strength. [Figure 3] This is a plan view of a manufacturing apparatus for producing air conditioning drain pipes. [Figure 4] This is a front view of a manufacturing apparatus for producing air conditioning drain pipes. [Figure 5] This is a diagram showing the mold and tube used for forming the outer surface of air conditioning drain pipes in a manufacturing apparatus. [Figure 6] This is a front view showing a schematic of the full-water test apparatus. [Modes for carrying out the invention]

[0010] ≪Air conditioning drain pipe≫ The air conditioning drain pipe of the present invention comprises a cylindrical foamed layer containing a vinyl chloride resin (B), a non-foamed inner layer containing a vinyl chloride resin (A) provided on the inner surface of the foamed layer, and a non-foamed outer layer containing a vinyl chloride resin (C) provided on the outer surface of the foamed layer. Figure 1 is a cross-sectional view showing an example of an air conditioning drain pipe according to the present invention. As shown in Figure 1, the air conditioning drain pipe 10' comprises a cylindrical foamed layer 2, a non-foamed inner layer 1 laminated on the inner surface of the foamed layer 2, and a non-foamed outer layer 3 laminated on the outer surface of the foamed layer 2.

[0011] The air conditioning drain pipe 10' is cut to any desired length at the construction site and connected by inserting the end of the air conditioning drain pipe 10' into the socket of a pipe fitting (not shown), such as a socket, elbow, or tee. The air conditioning drain pipe 10' and the pipe fitting constitute the air conditioning drain piping. Therefore, inside the socket of the pipe fitting, the non-foamed inner layer 1, foamed layer 2, and non-foamed outer layer 3 are exposed at the end face (cut surface) of the air conditioning drain pipe 10'. The air conditioning drain pipe 10' has a high percentage of closed cells in the foam layer 2, making it difficult for drain water flowing down the inside of the pipe to penetrate. Therefore, it is not necessary to uniformly apply adhesive to the end of the air conditioning drain pipe or to provide an annular elastic body inside the pipe joint, as in conventional designs.

[0012] The outer diameter of the air conditioning drain pipe 10' is preferably, for example, 32 mm to 100 mm. The inner diameter of the air conditioning drain pipe 10' is preferably, for example, 19 mm to 80 mm. The combined thickness of the air conditioning drain pipe 10', consisting of the non-foamed inner layer 1, foamed layer 2, and non-foamed outer layer 3, is preferably, for example, 6 mm to 10 mm.

[0013] The Young's modulus of the air conditioning drain pipe 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 keeping the Young's modulus within the above numerical range, when the air conditioning drain pipe 10' is subjected to an external force, bending and elongation deformation can be suppressed, and the pipe can flexibly follow these external forces, preventing the air conditioning drain pipe 10' from being destroyed. The Young's modulus, also known as the modulus of elasticity or Young's modulus, is determined from the tensile stress and tensile strain obtained by a tensile test, according to JIS K 7161-1:2014. The Young's modulus can be adjusted by factors such as the degree of polymerization of the vinyl chloride resin, the foaming ratio of the foamed layer, and the thicknesses of the non-foamed inner layer 1, foamed layer 2, and non-foamed outer layer 3.

[0014] <Non-foamed inner layer> The non-foamed inner layer 1 contains a vinyl chloride resin (A). The vinyl chloride resin (A) may be a homopolymer of vinyl chloride monomers (polyvinyl chloride), or a copolymer of a vinyl chloride monomer and another monomer copolymerizable with the vinyl chloride monomer. Other monomers copolymerizable with the vinyl chloride monomer mentioned above include, for example, ethylene, propylene, allyl chloride, acrylic acid, methacrylic acid, acrylic acid esters, methacrylic acid esters, vinyl acetate, maleic anhydride, and acrylonitrile. These may be used individually or in combination of two or more. The vinyl chloride resin (A) may be used alone, or two or more types may be used in combination. The non-foamed inner layer 1 may contain a thermoplastic resin other than the vinyl chloride resin (A). Examples of such thermoplastic resins 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 individually or in combination of two or more types. In the non-foamed inner layer 1, the content of vinyl chloride resin (A) relative to the total mass of the resin is preferably 80% by mass or more and 95% by mass or less, and more preferably 85% by mass or more and 90% by mass or less.

[0015] The thickness of the non-foamed inner layer 1 is preferably 1.0 mm to 5.0 mm, and more preferably 1.5 mm to 3.5 mm. By setting the thickness of the non-foamed inner layer 1 within the above numerical range, there is no risk of the drain water flowing inside penetrating into the foamed layer 2, resulting in an air conditioning drain pipe 10' with excellent heat insulation properties. On the other hand, if the closed-cell ratio of the foam layer 2 is high, the foam layer 2 itself prevents the penetration of drain water, so the thickness of the non-foamed inner layer 1 may be 0.6 mm to 1.5 mm, making the air conditioning drain pipe 10' lighter. Also, since the thickness of the foam layer 2 can be increased, the air conditioning drain pipe 10' can be made to have excellent heat insulation properties.

[0016] <Foam layer> The foamed layer 2 is formed by foaming a thermoplastic resin composition for foamed layers, which contains a resin including a vinyl chloride resin (B) and a foaming agent. The vinyl chloride resin (B) may be a homopolymer of vinyl chloride monomers (polyvinyl chloride), or a copolymer of a vinyl chloride monomer and another monomer copolymerizable with the vinyl chloride monomer. Other monomers copolymerizable with the vinyl chloride monomer mentioned above include, for example, ethylene, propylene, allyl chloride, acrylic acid, methacrylic acid, acrylic acid esters, methacrylic acid esters, vinyl acetate, maleic anhydride, and acrylonitrile. These may be used individually or in combination of two or more. The vinyl chloride resin (B) may be used alone, or two or more types may be used in combination. The foamed layer 2 may contain a thermoplastic resin other than the vinyl chloride resin (B). Examples of such thermoplastic resins 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 individually or in combination of two or more types. In the foamed layer 2, the content of vinyl chloride resin (B) relative to the total mass of the resin is preferably 70% by mass or more and 80% by mass or less, and more preferably 70% by mass or more and 75% by mass or less.

[0017] The mass-average molecular weight of the vinyl chloride resin (B) is preferably 37,500 to 70,000, and more preferably 37,500 to 44,000. The mass-average molecular weight was measured by gel permeation chromatography using polyethylene glycol as the standard substance. When the vinyl chloride resin (B) is polyvinyl chloride, the average degree of polymerization of the polyvinyl chloride is preferably 600 to 800, and more preferably 600 to 700. 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 (B) may be the same as or different from the vinyl chloride resin (A).

[0018] Preferably, the foamed layer 2 contains a thermoplastic resin other than the vinyl chloride resin (B), such as acrylic acid, methacrylic acid, acrylic acid ester, or methacrylic acid ester (collectively referred to as acrylic polymer compounds). The inclusion of acrylic polymers improves the closed-cell ratio and further refines the cell diameter. The mass-average molecular weight of the acrylic polymer compound is preferably 3 million to 6 million, and more preferably 4 million to 5 million. When foam layer 2 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, more preferably 12 parts by mass or more and 36 parts by mass or less, and even more preferably 18 parts by mass or more and 24 parts by mass or less, per 100 parts by mass of vinyl chloride resin (B). The thickness of the foam layer 2 is preferably 4.0 mm or more and 10 mm or less.

[0019] Either a volatile foaming agent or a decomposing foaming agent may be used as the foaming agent. Examples of volatile foaming agents include aliphatic hydrocarbons, alicyclic hydrocarbons, halogenated hydrocarbons, ethers, and ketones. Examples of aliphatic hydrocarbons include propane, butane (n-butane, isobutane), and pentane (n-pentane, isopentane, etc.), while examples of alicyclic hydrocarbons include cyclopentane and cyclohexane. Examples of halogenated hydrocarbons include one or more 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 blowing agents include inorganic blowing agents such as sodium bicarbonate, sodium carbonate, ammonium bicarbonate, ammonium nitrite, azide compounds, and sodium boride, as well as organic blowing agents such as azodicarbonamide, barium azodicarboxylate, and dinitrosopentamethylenetetramine. Alternatively, a thermally expandable capsule in which the above-mentioned hydrocarbon is encapsulated within a thermoplastic resin may be used. In addition, gases such as carbon dioxide, nitrogen, and air may be used as blowing agents. These may be used individually, or two or more may be used in combination. The amount of foaming agent used is preferably 1 to 8 parts by mass, and more preferably 2 to 5 parts by mass, per 100 parts by mass of vinyl chloride resin (B).

[0020] The foam layer 2 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 makes it easier to improve the thermal stability of the resin. Mercapto-based, laurate-based, and maleate-based tin compounds are preferred. The presence and content of these compounds can be confirmed by inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma atomic emission spectrometry (ICP-AES), gas chromatography-mass spectrometry (GC-MS), etc. In the case of ICP-AES, measurement can be performed in accordance with EN ISO 17353:2004. The foamed layer 2 may contain a lubricant. The inclusion of a lubricant makes it easier to maintain slipperiness with metal surfaces and between resins. Ester-based, polyethylene-based, and polyethylene oxide-based lubricants are preferred.

[0021] The foaming ratio of foam layer 2 is 3.5 times or more and 10 times or less, and preferably 4.5 times or more and 6.0 times or less. By keeping the foaming ratio within the above numerical range, high thermal insulation can be provided. Furthermore, by keeping the foaming ratio within the above numerical range, the weight of the air conditioning drain pipe 10' can be reduced. The foaming ratio can be adjusted by the type or amount of resin, the type or amount of foaming agent, manufacturing conditions, etc. The expansion ratio can be measured using the following method. [Method for measuring foaming ratio] A section of the air conditioning drain pipe 10' is cut circumferentially for at least 10 mm and axially for 50 mm. The non-foamed inner layer 1 and non-foamed outer layer 3 are milled, and only the foamed layer 2 is processed into a plate approximately 50 mm long to serve as the test specimen. Four test specimens are prepared, centered around four equally divided points in the inner circumference. The apparent density of the test specimen is determined to three decimal places using a water displacement type specific gravity analyzer at 23°C ± 2°C in accordance with JIS K 7112:1999, and the expansion ratio is calculated using the following formula (1). m = γc / γ ... (1) [In equation (1), m is the foaming ratio, and γ is the apparent density of foam layer 2 (g / cm³). 3 ) and γc is the density of the unfoamed foam layer 2 (g / cm³). 3 )

[0022] The closed-cell ratio of foam layer 2 is 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 in practice it is 95% or less, but it may also be 100% or 90% or less. By keeping the closed-cell ratio within the above numerical range, it is possible to improve insulation performance while keeping costs down and preventing water from penetrating into the foam layer 2. Furthermore, if the closed-cell ratio of the foam layer 2 is within the above numerical range, even if the thickness of the non-foamed outer layer 3 (described later) is reduced, water is less likely to penetrate from the outside, and there is a low risk of a decrease in insulation performance. The closed-cell ratio is measured in accordance with JIS K 7138:2006. The closed-cell ratio can be adjusted by the type or amount of resin, the type or amount of foaming agent, manufacturing conditions, etc.

[0023] The fusion strength between the foamed layer 2 and the non-foamed inner layer 1 is 1.5 MPa or higher, and preferably 2.0 MPa or higher. By keeping the fusion strength within the above range, it is possible to prevent the foamed layer 2 and the non-foamed inner layer 1 from separating. The bonding strength can be adjusted by the type or amount of resin, the type or amount of foaming agent, manufacturing conditions, etc.

[0024] The average bubble diameter of the foamed layer 2 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 keeping the average cell diameter within the above numerical range, the thermal insulation performance can be improved, and water penetration into the foam layer 2 can be prevented. Even if the cells are not completely closed cells (100% closed cell ratio) and some cell walls are connected, allowing water penetration, as long as the average cell diameter and the closed cell ratio are within the above numerical range, water will not penetrate deep into the foam layer 2, and thermal insulation performance will not be a problem in practical use. The method for measuring the average bubble diameter will be described later. The average bubble diameter can be adjusted by the type or amount of resin, the type or amount of foaming agent, manufacturing conditions, etc.

[0025] <Non-foamed outer layer> The non-foamed outer layer 3 contains a vinyl chloride resin (C). The vinyl chloride resin (C) may be a homopolymer of vinyl chloride monomers (polyvinyl chloride), or a copolymer of a vinyl chloride monomer and another monomer copolymerizable with the vinyl chloride monomer. Other monomers copolymerizable with the vinyl chloride monomer mentioned above include, for example, ethylene, propylene, allyl chloride, acrylic acid, methacrylic acid, acrylic acid esters, methacrylic acid esters, vinyl acetate, maleic anhydride, and acrylonitrile. These may be used individually or in combination of two or more. The vinyl chloride resin (C) may be used alone, or two or more types may be used in combination. The non-foamed outer layer 3 may contain a thermoplastic resin other than vinyl chloride resin (C). Examples of such thermoplastic resins 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 individually or in combination of two or more types. In the non-foamed outer layer 3, the content of vinyl chloride resin (C) relative to the total mass of the resin is preferably 80% by mass or more and 95% by mass or less, and more preferably 85% by mass or more and 90% by mass or less. The vinyl chloride resin (C) may be the same as or different from the vinyl chloride resin (A). The vinyl chloride resin (C) may be the same as or different from the vinyl chloride resin (B). The thickness of the non-foamed outer layer 3 is preferably 0.6 mm to 1.5 mm, and more preferably 1.0 mm to 1.3 mm. By making the thickness of the non-foamed outer layer 3 equal to or greater than the lower limit, the air conditioning drain pipe 10' can be made more resistant to external impacts. By making the thickness of the non-foamed outer layer 3 equal to or less than the upper limit, the air conditioning drain pipe 10' can be made lighter. In addition, since the thickness of the foamed layer 2 can be increased, the air conditioning drain pipe 10' can be made to have excellent heat insulation properties. To increase resistance to external impacts, the thickness of the non-foamed outer layer 3 is preferably 1.0 mm or more and 5.0 mm or less, and more preferably 1.5 mm or more and 3.5 mm or less. The non-foaming outer layer 3 may contain pigment. The inclusion of pigment can improve the appearance.

[0026] ≪Manufacturing method for air conditioning drain pipes≫ Figures 3 and 4 are overall configuration diagrams of a manufacturing apparatus 20 for producing a three-layer air conditioning drain pipe 10'. The manufacturing apparatus 20 comprises an inner and outer layer extruder 11, a foam layer extruder 12, a mold 13, a cooling water tank 15, a take-up machine 16, and a cutting machine 17. The mold 13 is connected to the inner and outer layer extruder 11 and the foam layer extruder 12, and the cooling water tank 15 is connected to the mold 13. The take-up machine 16 is connected to the cooling water tank 15, and the cutting machine 17 is connected to the take-up machine 16. Furthermore, as shown in Figures 3 and 4, a gas cylinder 18 and a metering pump 19 may also be connected to the foam layer extruder 12. The gas cylinder 18 and the metering pump 19 supply the foaming agent gas through the vent hole of the foaming layer extruder 12. The inner and outer layer extruder 11 melts and kneads a thermoplastic resin composition for non-foamed layers that will form the non-foamed inner layer 1 and the non-foamed outer layer 3, and extrudes it into the mold 13. The foam extruder 12 melts and kneads the thermoplastic resin composition for the foam layer that will form the foam layer 2, and extrudes it into the mold 13. The mold 13 molds an uncured three-layer air conditioning drain pipe 100' from a thermoplastic resin composition for the non-foamed layer injected from the inner and outer layer extruder 11 and a thermoplastic resin composition for the foamed layer injected from the foamed layer extruder 12. The cooling water tank 15 is fitted with a tube 14 for forming the outer surface of the pipe, which is used to shape the uncured air conditioning drain pipe 100' to a predetermined size. The outer surface of the uncured air conditioning drain pipe 100', which has been molded in the mold 13, is cooled in contact with the tube 14. The collection unit 16 receives the air conditioning drain pipe 10' which has been cooled in the cooling water tank 15. The cutting machine 17 cuts the air conditioning drain pipe 10' sent from the collection machine 16 to a predetermined length.

[0027] First, the thermoplastic resin composition for the non-foamed layer is supplied to the inner and outer layer extruder 11 and melt-kneaded. Separately, the thermoplastic resin composition for the foamed layer is supplied to the foamed layer extruder 12 and melt-kneaded. When using gas as a blowing agent, the gas from the gas cylinder 18 is supplied through the vent hole by the pumping action of the metering pump 19 while the thermoplastic resin composition for the foamed layer is being melted and kneaded. When using a solid or liquid blowing agent, the blowing agent may be incorporated into the thermoplastic resin composition for the foamed layer beforehand.

[0028] Then, as shown in Figure 5, the thermoplastic resin composition 21 for the non-foamed layer, which has been melt-kneaded by the inner and outer layer extruder 11, and the thermoplastic resin composition 22 for the foamed layer, which has been melt-kneaded by the foamed layer extruder 12, are injected into the mold 13 and merged inside the mold 13 to form an uncured three-layer air conditioning drain pipe 100'. The uncured air conditioning drain pipe 100' consists of a non-foamed thermoplastic resin layer 31 formed from the thermoplastic resin composition 21 for the non-foamed layer, and a foamed thermoplastic resin layer 32 formed from the thermoplastic resin composition 22 for the foamed layer, which is located between the non-foamed inner layer 1 and the non-foamed outer layer 3.

[0029] Furthermore, when the uncured three-layered air conditioning drain pipe 100' is discharged from the mold 13, the resin of the foamed thermoplastic resin layer 32 foams up. The uncured air conditioning drain pipe 100' is inserted into the pipe outer surface molding tube 14, and the uncured air conditioning drain pipe 100' is molded to a predetermined size while being cooled in the cooling water tank 15 to become the air conditioning drain pipe 10'. Furthermore, the cooled and molded air conditioning drain pipe 10' is handed over to the take-up machine 16 and sent to the cutting machine 17, where it is cut to a predetermined length.

[0030] The temperature when molding in the mold 13 is preferably 140°C to 200°C, and more preferably 160°C to 190°C. The molding time in the mold is preferably 10 minutes or more and 30 minutes or less, and more preferably 10 minutes or more and 20 minutes or less. [Examples]

[0031] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited in any way by these examples.

[0032] The ingredients in the table are explained below. Note that the content of each component in the table is expressed in parts by mass when the polyvinyl chloride in the foamed layer is set at 100 parts by mass. <Vinyl chloride resin (B)> A-1: Polyvinyl chloride (degree of polymerization 640, manufactured by Tokuyama Sekisui Kogyo Co., Ltd., product name "TS-640M"). A-2: Polyvinyl chloride (degree of polymerization 800, manufactured by Tokuyama Sekisui Kogyo Co., Ltd., product name "TS-800E"). A-3: Polyvinyl chloride (500 degree of polymerization, manufactured by Taiyo Vinyl Chloride Co., Ltd., product name "TH-500"). A-4: Polyvinyl chloride (degree of polymerization 1000, manufactured by Tokuyama Sekisui Kogyo Co., Ltd., product name "TS-1000R"). <Acrylic polymer compounds> B-1: Acrylic polymer compound (mass-average molecular weight 3 million, manufactured by Mitsubishi Rayon Co., Ltd., product name "P-530A"). B-2: Acrylic polymer compound (mass-average molecular weight: 4 million, manufactured by Mitsubishi Rayon Co., Ltd., product name "P-531A"). B-3: Acrylic polymer compound (mass-average molecular weight: 5 million, manufactured by Kaneka Corporation, product name "PA-40"). B-4: Acrylic polymer compound (mass-average molecular weight: 1 million, manufactured by Kaneka Corporation, product name "PA-20"). B-5: Acrylic polymer compound (mass-average molecular weight: 8 million, manufactured by Kaneka Corporation, product name "PA-60"). <Foaming agent> C-1: Baking soda (manufactured by Eiwa Kasei Kogyo Co., Ltd., product name "Cellbon SC-855"). • C-2: Thermally expandable capsule (manufactured by Tokuyama Sekisui Kogyo Co., Ltd., product name "Advancell EM501"). C-3: Azodicarbonamide (manufactured by Eiwa Kasei Kogyo Co., Ltd., product name "Vinihole AC"). <Vinyl chloride resins (A) and (C)> • Polyvinyl chloride (degree of polymerization 1000, manufactured by Tokuyama Sekisui Kogyo Co., Ltd., product name "TS-1000R").

[0033] (Example 1) A thermoplastic resin composition for foamed layers was prepared by mixing 100 parts by mass of vinyl chloride resin (B)A-1, 2 parts by mass of tin-based stabilizer (manufactured by Daikyo Chemical Industries, Ltd., product name "STX-80"), 24 parts by mass of acrylic polymer compound B-1, and 2.2 parts by mass of sodium bicarbonate C-1. For the non-foamed layers used for the inner and outer layers, a thermoplastic resin composition was used, which consisted of 100 parts by mass of vinyl chloride resin (A) and (C) mixed with 2 parts by mass of a tin-based stabilizer (manufactured by Daikyo Chemical Industries, Ltd., product name "STX-80"). These compositions were extruded using a manufacturing apparatus consisting of an inner and outer layer extruder 11, a foam layer extruder 12, a mold 13, a cooling water tank 15 to which a tube for forming the outer surface of the pipe 14 is attached, a take-up machine 16, and a cutting machine 17, as shown in Figures 3 to 5. Specifically, a thermoplastic resin composition for the non-foamed layer was kneaded at 190°C in an inner and outer layer extruder 11 and injected into a mold 13 at an extrusion rate of 40 kg / h. A thermoplastic resin composition for the foamed layer was also kneaded at 190°C in a foamed layer extruder 12 and injected into the mold 13 at 60 kg / h. The mold 13 used had an outer diameter of 89 mm and an inner diameter of 77 mm. The composition extruded from the mold 13 was inserted into a tube 14 for pipe outer surface molding, cooled in a cooling water tank 15, taken up by a take-up machine 16, and then cut to a predetermined length by a cutting machine 17 to obtain a three-layer structured air conditioning drain pipe.

[0034] (Examples 2-8, Comparative Examples 1-6) A three-layer structured air conditioning drain pipe was obtained in the same manner as in Example 1, except that the components were changed as listed in Tables 1 and 2.

[0035] For each example of air conditioning drain pipe obtained, the closed-cell ratio, average cell diameter, flattening test, fusion strength, expansion ratio, Young's modulus, and full-water test were measured according to the following procedure.

[0036] [Measurement of closed-cell ratio] The air conditioning drain pipe was cut to a length of approximately 30 mm, then cut circumferentially to a circumference of approximately 20 mm, and the non-foamed inner and outer layers were removed using an NT cutter to create the test specimen. In accordance with JIS K 7138:2006, the volume was measured using an air-comparison hydrometer at 23°C ± 2°C, and in accordance with JIS K 7112:1999, the volume obtained using a water-displacement hydrometer at 23°C ± 2°C was measured, and the closed-cell ratio was measured using the following formula (2). Cc = (Va / Vaq) × 100 ... (2) [In equation (2), Cc is the percentage of closed cells (%), and Va is the volume of air compared to the standard volume (cm³). 3 ) and Vaq is the volume (cm³) of the water displacement method. 3 ) The results obtained are shown in Tables 1 and 2.

[0037] [Measurement of average bubble diameter] In accordance with JIS K 6400-1, a 1800 μm straight line was drawn on the circumferential cross-sectional image of an air conditioning drain pipe taken with a scanning electron microscope (SEM). The bubble diameter was calculated by dividing the value of the straight line by the number of bubbles on the straight line, and the average of the 8 straight lines and 8 data points was taken as the average bubble diameter.

[0038] [Flatness Test] A 50mm length of air conditioning drain pipe was cut and used as a test specimen. After adjusting the condition of the test specimen at 23°C ± 2°C for at least one hour, it was placed between two compression plates of a flattening tester and compressed at a compression rate of 10 mm / min in a direction perpendicular to the pipe axis until the flattening load reached 784 N (80 kgf) or more. The presence or absence of cracks or fissures in the test specimen was checked, and it was evaluated according to the following evaluation criteria. <Evaluation Criteria> ○: No cracks or fissures. ×: There are cracks or fissures. The results obtained are shown in Tables 1 and 2.

[0039] [Measurement of fusion strength] A 20mm tubular section cut along the axis of an air conditioning drain pipe was used as the test specimen. Under conditions of a temperature of 23°C ± 2°C and normal humidity (45-85%), the test specimen 43 was set in the punching jig 41 of the universal testing machine 40 shown in Figure 2, sandwiched between compression plates 42, and compressed at a speed of 10 mm / min ± 2 mm / min in a direction perpendicular to the pipe axis. The maximum load at which the fused surface between the non-foamed inner layer and the foamed layer delaminated was determined, and the fusion strength was calculated using the following equations (3) and (4). F = W / S ... (3) S = 3.14 × d × L ···(4) [In equations (3) and (4), F is the fusion strength (MPa), W is the maximum load (N), and S is the fusion area (cm²). 2 ) where d is the average outer diameter of the non-foamed inner layer (cm), and L is the length of the test specimen (cm). The results obtained are shown in Tables 1 and 2.

[0040] [Measurement of foaming ratio] A section of air conditioning drain pipe was cut circumferentially for at least 10 mm and axially for 50 mm. The non-foamed inner and outer layers were milled away, and only the foamed layer was processed into a plate approximately 50 mm long to serve as the test specimen. Four test specimens were prepared, each centered around one of four equally spaced points along the inner circumference. The apparent density of the test specimens was determined to three decimal places using a water displacement type specific gravity analyzer at 23°C ± 2°C in accordance with JIS K 7112:1999, and the expansion ratio was calculated using the following formula (1). m = γc / γ ... (1) [In equation (1), m is the foaming ratio and γ is the apparent density of the foamed layer (g / cm³). 3 ) and γc is the density of the foamed layer before foaming (g / cm³). 3 ) The average values ​​of the obtained results are shown in Tables 1 and 2.

[0041] [Young's modulus of elasticity] The Young's modulus was measured at a temperature of 15°C in accordance with JIS K 7161-1:2014. The results are shown in Tables 1 and 2.

[0042] [Full Water Test] Figure 6 shows a schematic diagram of the full-water test apparatus. A 10' air conditioning drain pipe was cut to a length L1 (L1 = 2000 mm) and used as a test specimen. A pipe fitting 50, with the other end closed, is connected to the lower end of the test specimen, and a pipe fitting 51 is also connected to the upper end of the test specimen. A cylinder 60 with a length L2 (L2 = 2000 mm) and a scale for checking the water level is connected to the top of the pipe fitting 51 to form a full-water test apparatus 70. No adhesive was applied to the end faces (cut surfaces) of both ends of the air conditioning drain pipe 10' of the test specimen. The full-water test apparatus 70 was fixed with the pipe joint 50 facing downwards and the pipe axis of the test specimen vertical. Then, water was added so that the water level from the lower end face of the test specimen was L1 + L2 (L1 + L2 = 4000 mm), and a hydrostatic pressure of L1 + L2 (L1 + L2 = 4000 mm) was applied to the lower end face of the test specimen. The amount of water level decrease (height of water level drop) after maintaining this condition for 120 minutes was measured and evaluated according to the following evaluation criteria. <Evaluation Criteria> ○: Water level decrease of 0 mm or more but less than 10 mm. △: Water level decrease of 10mm or more but less than 20mm. ×: Water level decrease of 20mm or more. The results obtained are shown in Tables 1 and 2.

[0043] [Table 1]

[0044] [Table 2]

[0045] As shown in Tables 1 and 2, the air conditioning drain pipes in Examples 1 to 8 had a closed-cell ratio of 45% or more and a small average bubble diameter, making them resistant to water penetration. The air conditioning drain pipe in Comparative Example 1 had a closed-cell ratio of 45% or more, but its average bubble diameter was large at 500 μm, making it prone to water penetration. The air conditioning drain pipes in Comparative Examples 2-5 had a closed-cell ratio of less than 45% and a high open-cell ratio, making them easily permeable to water. The air conditioning drain pipe in Comparative Example 6 had a high content of acrylic polymer compounds in the foamed layer, which prevented it from flexibly following external forces, resulting in cracks during the flattening test. From these results, it was found that the air conditioning drain pipe to which the present invention is applied can easily prevent water from penetrating into the foam layer. [Explanation of symbols]

[0046] 1. Non-foamed inner layer 2 Foam layer 3. Non-foamed outer layer 10' Air conditioning drain pipe

Claims

1. A foamed layer formed by molding a thermoplastic resin composition for foamed layers containing a vinyl chloride resin (B), a tin-based stabilizer, and a decomposition-type foaming agent into a cylindrical shape, An air conditioning drain pipe comprising: a non-foamed inner layer laminated on the inner surface of the foamed layer, and molded from a thermoplastic resin composition for non-foamed layers containing a vinyl chloride resin (A) and not containing a foaming agent; The foaming ratio of the foamed layer is 3.5 times or more and 5.5 times or less. The closed-cell ratio of the foamed layer is 48% or more and 95% or less. The fusion strength between the foamed layer and the non-foamed inner layer is 1.5 MPa or more. An air conditioning drain pipe in which, when a straight line of 1800 μm is drawn on a circumferential cross-sectional image of the air conditioning drain pipe taken with a scanning electron microscope (SEM), and the value obtained by dividing 1800 μm by the number of bubbles on the straight line is taken as the bubble diameter, the average bubble diameter of the foamed layer is 100 μm or more and 250 μm or less.

2. A foamed layer formed by molding a thermoplastic resin composition for foamed layers, which includes a vinyl chloride resin (B), a tin-based stabilizer, and a heat-expandable capsule, into a cylindrical shape, An air conditioning drain pipe comprising: a non-foamed inner layer laminated on the inner surface of the foamed layer, and molded from a thermoplastic resin composition for non-foamed layers containing a vinyl chloride resin (A) and not containing a foaming agent; The foaming ratio of the foamed layer is 3.5 times or more and 5.5 times or less. The closed-cell ratio of the foamed layer is 48% or more and 95% or less. The fusion strength between the foamed layer and the non-foamed inner layer is 1.5 MPa or more. An air conditioning drain pipe in which, when a straight line of 1800 μm is drawn on a circumferential cross-sectional image of the air conditioning drain pipe taken with a scanning electron microscope (SEM), and the value obtained by dividing 1800 μm by the number of bubbles on the straight line is taken as the bubble diameter, the average bubble diameter of the foamed layer is 100 μm or more and 250 μm or less.

3. A method for manufacturing an air conditioning drain pipe according to claim 1 or 2, A thermoplastic resin composition for a non-foaming layer, which does not contain a foaming agent, is melt-kneaded and extruded by an extruder to form the aforementioned non-foaming inner layer. A blowing agent comprising one or more selected from decomposition-type blowing agents and thermally expandable capsules, A thermoplastic resin composition for foamed layers, which has a tin-based stabilizer pre-mixed into it, is melt-kneaded and extruded using an extruder. The thermoplastic resin composition for the non-foamed layer and the thermoplastic resin composition for the foamed layer are injected into a mold and combined inside the mold to form an uncured air conditioning drain pipe. A method for manufacturing an air conditioning drain pipe, characterized by cooling the uncured air conditioning drain pipe and molding it to a predetermined size.

4. The method for manufacturing an air conditioning drain pipe according to claim 3, wherein the foaming agent comprises the decomposing foaming agent and the thermally expandable capsule.

5. The method for manufacturing an air conditioning drain pipe according to claim 3 or 4, wherein the thermoplastic resin composition for the foam layer contains polyvinyl chloride having an average degree of polymerization of 600 or more and 800 or less.

6. A method for manufacturing an air conditioning drain pipe according to any one of claims 3 to 5, wherein the thermoplastic resin composition for the foam layer contains an acrylic polymer compound.

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