JP7479877B2 - Multilayer Pipe - Google Patents

Description

The present invention relates to a multi-layer pipe.

Multi-layer pipes made of resin are used as air conditioning drain pipes. Air conditioning drain pipes are required to have high insulation properties. To improve insulation properties, air conditioning drain pipes with a foam layer are sometimes used.

The following Patent Document 1 discloses an air conditioning drain pipe that includes a cylindrical foamed layer containing a vinyl chloride resin (B) and a non-foamed outer layer that is provided on the outer surface of the foamed layer and contains a vinyl chloride resin (A). In this air conditioning drain pipe, the foamed layer has an expansion ratio of 3.5 times or more, and the vinyl chloride resin (A) is a mixture of vinyl chloride resin and elastomer resin, or a graft polymer in which an elastomer resin is graft polymerized onto vinyl chloride resin. Patent Document 1 also describes that the foamed layer may contain a thermoplastic resin other than the vinyl chloride resin (B).

The following Patent Document 2 discloses an insulated pipe comprising an organic polymer pipe having an outer diameter of 50 to 180 mm, a foamed polyurethane insulation layer disposed on the outer surface of the pipe, and a sheath of at least 3 mm thickness made of polyvinyl chloride or polyethylene disposed on the outer surface of the foamed polyurethane insulation layer. The foamed polyurethane insulation layer has a foaming degree of 10 to 50 times, a thickness of 30 to 60 mm, and is a continuous foam layer.

JP 2018-059633 A Japanese Utility Model Application Publication No. 60-24998

When a foam layer is formed using only vinyl chloride resin as the resin by the method described in Patent Document 1, it is difficult to increase the foaming ratio and closed cell ratio of the foam layer because the viscosity of the vinyl chloride resin is relatively high, and as a result, the insulation of the air conditioning drain pipe may not be sufficiently improved. Also, when a foam layer is formed using vinyl chloride resin (B) and a thermoplastic resin other than vinyl chloride resin (B) as the resin by the method described in Patent Document 1, it is difficult to obtain a good foam layer because the compatibility between the vinyl chloride resin and the thermoplastic resin is low, and as a result, the insulation may not be sufficiently improved.

In the thermal insulation pipe described in Patent Document 2, the inner layer, foam layer, and outer layer are made of different materials, so an extrusion device is required to mold each layer, resulting in poor manufacturing efficiency. In addition, because the molding temperatures of each layer are different, adjustments are required when laminating each layer, making it difficult to obtain a good foam layer, and as a result, it may not be possible to sufficiently improve the thermal insulation.

When a multi-layer pipe with insufficient insulation is used as an air conditioning drain pipe, condensation may form on the outer surface of the air conditioning drain pipe due to the temperature difference between the liquid flowing inside and the outside air.

The object of the present invention is to provide a multi-layer pipe that can improve thermal insulation.

According to a broad aspect of the present invention, there is provided a multi-layer pipe comprising an inner layer, a foamed layer disposed on the outside of the inner layer, and an outer layer disposed on the outside of the foamed layer, the inner layer containing a vinyl chloride resin, the foamed layer containing a resin different from the vinyl chloride resin, the outer layer containing a vinyl chloride resin, and the specific gravity of the foamed layer being 0.1 or more and 0.5 or less.

In a particular aspect of the multi-layer pipe of the present invention, the resin contained in the foam layer is a polyethylene-based resin, a polyurethane-based resin, a polystyrene-based resin, or a polyacrylic-based resin.

In a particular aspect of the multi-layer pipe of the present invention, the material of the foam layer contains a pyrolytic foaming agent.

In a particular aspect of the multi-layer tube of the present invention, the material of the foam layer contains thermally expandable microcapsules.

In a particular aspect of the multi-layer pipe of the present invention, the multi-layer pipe is an air conditioning drain pipe.

The multi-layer pipe according to the present invention comprises an inner layer, a foam layer disposed on the outside of the inner layer, and an outer layer disposed on the outside of the foam layer, the inner layer contains a vinyl chloride resin, the foam layer contains a resin different from the vinyl chloride resin, the outer layer contains a vinyl chloride resin, and the specific gravity of the foam layer is 0.1 or more and 0.5 or less. The multi-layer pipe according to the present invention has the above configuration, and therefore can improve thermal insulation.

FIG. 1 is a cross-sectional view showing a multi-layer tube according to one embodiment of the present invention. FIG. 2 is a plan view showing a schematic diagram of a manufacturing apparatus used for manufacturing a multi-layer pipe according to one embodiment of the present invention. FIG. 3 is a front view showing a schematic diagram of a manufacturing apparatus used for manufacturing a multi-layer pipe according to an embodiment of the present invention. FIG. 4 is an enlarged cross-sectional view showing a mold portion and a tube portion for forming an outer surface of a pipe in a manufacturing apparatus.

The present invention is described in detail below.

The multi-layer pipe according to the present invention comprises an inner layer, a foamed layer disposed on the outside of the inner layer, and an outer layer disposed on the outside of the foamed layer, the inner layer contains a vinyl chloride resin, the foamed layer contains a resin different from the vinyl chloride resin, the outer layer contains a vinyl chloride resin, and the specific gravity of the foamed layer is 0.1 or more and 0.5 or less.

The multi-layer pipe of the present invention has the above-mentioned configuration, and therefore can improve thermal insulation. The multi-layer pipe of the present invention is preferably used as an air conditioning drain pipe. The multi-layer pipe of the present invention is preferably used as an air conditioning drain pipe. When the multi-layer pipe of the present invention is used as an air conditioning drain pipe, condensation can be made less likely to occur on the outer surface.

The multi-layer pipe of the present invention can be well bonded to joints using adhesive, which improves workability. The multi-layer pipe of the present invention can be bonded to polyvinyl chloride resin joints using the TS (Taper sized solvent welding method) using adhesive.

The multi-layer pipe includes, from the center to the outside, an inner layer, a foam layer, and an outer layer in this order. The multi-layer pipe may have a three-layer structure of an inner layer, a foam layer, and an outer layer, or may have a structure of four or more layers. The inner layer may be the innermost layer, or it may not be the innermost layer. Another layer may be disposed inside the inner layer. However, it is preferable that the inner layer is the innermost layer. The outer layer may be the outermost layer, or it may not be the outermost layer. Another layer may be disposed outside the outer layer. However, it is preferable that the outer layer is the outermost layer. Another layer may be disposed between the inner layer and the foam layer, or between the outer layer and the foam layer. However, it is preferable that another layer is not disposed between the inner layer and the foam layer, and between the outer layer and the foam layer.

Specific embodiments of the present invention will be described below with reference to the drawings. Note that in the following drawings, the size, thickness, shape, etc. may differ from the actual size, thickness, shape, etc. for the sake of convenience of illustration.

Figure 1 is a cross-sectional view showing a multi-layer pipe according to one embodiment of the present invention. Figure 1 shows a cross-sectional view along the radial direction of the multi-layer pipe.

The multi-layer pipe 10 shown in FIG. 1 comprises an inner layer 1, a foam layer 2, and an outer layer 3. The multi-layer pipe 10 has a three-layer structure. The foam layer 2 is disposed on the outside of the inner layer 1. The outer layer 3 is disposed on the outside of the foam layer 2. The foam layer 2 is disposed on the outer surface of the inner layer 1 and is laminated thereon. The outer layer 3 is disposed on the outer surface of the foam layer 2 and is laminated thereon. The inner layer 1 is the innermost layer and is a surface layer. The foam layer 2 is an intermediate layer. The outer layer 3 is the outermost layer and is a surface layer. The inner layer 1, the foam layer 2, and the outer layer 3 are each tubular.

The inner layer 1 contains a vinyl chloride resin. The foam layer 2 contains a resin different from the vinyl chloride resin. The outer layer 3 contains a vinyl chloride resin.

(Inner and outer layers)
The inner layer contains a vinyl chloride resin. The outer layer contains a vinyl chloride resin. The vinyl chloride resin contained in the inner layer and the vinyl chloride resin contained in the outer layer may be the same or different. Furthermore, the material of the inner layer and the material of the outer layer may be the same or different. From the viewpoint of increasing production efficiency and reducing the number of extruders, it is preferable that the material of the inner layer and the material of the outer layer are the same.

As the vinyl chloride resin, conventionally known vinyl chloride resins can be used. Examples of the vinyl chloride resin include (1) a homopolymer of a vinyl chloride monomer, (2) a copolymer of a vinyl chloride monomer and a monomer having an unsaturated bond copolymerizable with the vinyl chloride monomer, and (3) a graft polymer in which vinyl chloride is graft-polymerized onto a polymer or copolymer other than vinyl chloride. Only one type of the vinyl chloride resin may be used, or two or more types may be used in combination.

The monomer having an unsaturated bond copolymerizable with the vinyl chloride monomer is not particularly limited, and examples thereof include α-olefin compounds such as ethylene, propylene, and butylene; compounds having a vinyl group such as allyl chloride and acrylonitrile; vinyl ester compounds such as vinyl acetate and vinyl propionate; vinyl ether compounds such as butyl vinyl ether and cetyl vinyl ether; (meth)acrylic acid ester compounds such as methyl (meth)acrylate, ethyl (meth)acrylate, and butyl (meth)acrylate; aromatic vinyl compounds such as styrene and α-methylstyrene; dicarboxylic acid compounds such as maleic anhydride; and N-substituted maleimide compounds such as N-phenylmaleimide and N-cyclohexylmaleimide. The monomer having an unsaturated bond copolymerizable with the vinyl chloride monomer may be used alone or in combination of two or more.

The copolymer may be a random copolymer, a block copolymer, or a graft copolymer.

The above-mentioned polymers and copolymers to be graft-copolymerized with vinyl chloride are not particularly limited, and examples thereof include ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-carbon monoxide copolymer, ethylene-ethyl acrylate copolymer, and ethylene-butyl acrylate-carbon monoxide copolymer. The above-mentioned polymers and copolymers to be graft-copolymerized with vinyl chloride may be used alone or in combination of two or more kinds.

In the vinyl chloride resin, the content of structural units derived from vinyl chloride is preferably 50% by weight or more.

The degree of polymerization of the vinyl chloride resin is preferably 400 or more, and preferably 1500 or less. If the degree of polymerization of the vinyl chloride resin is equal to or more than the lower limit, the long-term performance such as thermal stability and fatigue properties is unlikely to be impaired. If the degree of polymerization of the vinyl chloride resin is equal to or less than the upper limit, high temperatures are not required during molding, and processability is further improved.

The vinyl chloride resin may be a chlorinated vinyl chloride resin.

From the viewpoint of further improving flame retardancy and heat deformation resistance, the vinyl chloride resin contained in the inner layer is preferably a chlorinated vinyl chloride resin.

From the viewpoint of further improving flame retardancy and heat distortion resistance and facilitating connection to joints, the vinyl chloride resin contained in the outer layer is preferably a chlorinated vinyl chloride resin.

In the inner layer (100% by weight), the content of the vinyl chloride resin is preferably 80% by weight or more, and more preferably 90% by weight or more.

In the outer layer (100% by weight), the content of the vinyl chloride resin is preferably 80% by weight or more, and more preferably 90% by weight or more.

The thickness of the inner layer is preferably 1 mm or more, more preferably 1.5 mm or more, and preferably 3 mm or less, more preferably 2 mm or less. If the thickness of the inner layer is equal to or greater than the lower limit and equal to or less than the upper limit, the strength of the multilayer pipe can be increased.

The thickness of the outer layer is preferably 1 mm or more, more preferably 1.2 mm or more, and preferably 3 mm or less, and more preferably 2 mm or less. When the thickness of the outer layer is equal to or greater than the lower limit and equal to or less than the upper limit, the surface hardness of the multi-layer pipe can be increased, surface scratches can be effectively suppressed, and adhesive strength can be increased.

The thickness of the inner layer and the outer layer can be measured using a caliper or the like.

(Foam layer)
The foam layer contains a resin (hereinafter, may be referred to as "resin A") different from the vinyl chloride resin. The foam layer contains resin A. Only one type of resin A may be used, or two or more types may be used in combination.

Examples of the resin A include polyethylene-based resins, polyurethane-based resins, polystyrene-based resins, polyacrylic-based resins, and polypropylene-based resins.

Examples of the polyethylene resin include polyethylene resin and ethylene-vinyl acetate copolymer.

The polyurethane resin may be a thermoplastic polyurethane resin or a thermoplastic polyurethane elastomer.

Examples of the polystyrene-based resin include polystyrene resin, MS resin (methyl methacrylate-styrene copolymer), and α-methylstyrene resin.

Examples of the polyacrylic resin include polymethyl methacrylate resin and polymethyl acrylate resin.

Since the melting temperature is relatively high and the moldability is poorer than that of vinyl chloride resins, it is preferable that the above resin A is a resin different from polypropylene resins. In other words, it is preferable that the above resin A is a resin different from both vinyl chloride resins and polypropylene resins.

The resin A is preferably a polyethylene resin, a polyurethane resin, a polystyrene resin, or a polyacrylic resin. These resins are easier to foam than vinyl chloride resins, can achieve a good foaming ratio, and have a melting temperature relatively close to that of vinyl chloride resins. Therefore, a good foam layer can be obtained, and as a result, the insulation properties of the multi-layer pipe can be further improved.

It is most preferable that the foam layer does not contain a vinyl chloride resin. If the foam layer contains a vinyl chloride resin, that is, if the material of the foam layer contains a vinyl chloride resin, the compatibility between the vinyl chloride resin and resin A may decrease, making it impossible to obtain a good foam layer.

In 100% by weight of the foam layer, the content of the resin A is preferably 90% by weight or more, more preferably 95% by weight or more, and even more preferably 99% by weight or more.

The foaming method for forming the foam layer is not particularly limited, and any conventionally known foaming method can be used. Examples of the foaming method include a chemical foaming method and a physical foaming method.

When the foam layer is formed by the chemical foaming method, the material of the foam layer preferably contains a thermally decomposable foaming agent. By using the thermally decomposable foaming agent, the resin A can be foamed well, and the specific gravity of the resulting foam layer can be effectively reduced. The thermally decomposable foaming agent may be used alone or in combination of two or more kinds.

The above-mentioned thermal decomposition type foaming agents include baking soda (sodium bicarbonate)-based foaming agents, ADCA (azodicarbonamide), DPT (N,N'-dinitrosopentamethylenetetramine), and OBSH (4,4'-oxybis(benzenesulfonylhydrazide)).

From the viewpoint of increasing the closed cell ratio, it is preferable that the thermal decomposition type foaming agent contains ADCA.

The content of the thermally decomposable foaming agent in the material of the foam layer is not particularly limited, and can be appropriately changed depending on the desired foaming ratio, molding conditions such as the manufacturing equipment and molding temperature, the type of resin A used, etc. In 100% by weight of the material of the foam layer, the content of the thermally decomposable foaming agent is preferably 0.1% by weight or more, more preferably 0.2% by weight or more, preferably 2% by weight or less, more preferably 1.5% by weight or less. When the content of the thermally decomposable foaming agent is equal to or more than the lower limit and equal to or less than the upper limit, the foaming ratio can be improved and cell breakage can be effectively suppressed, resulting in further improved insulation of the multilayer pipe.

The content of the thermally decomposable foaming agent is preferably 0.2 parts by weight or more, more preferably 0.4 parts by weight or more, preferably 2.0 parts by weight or less, more preferably 1.5 parts by weight or less, relative to 100 parts by weight of the resin contained in the material of the foam layer. When the content of the thermally decomposable foaming agent is equal to or more than the lower limit and equal to or less than the upper limit, the foaming ratio can be improved and cell breakage can be effectively suppressed, resulting in further improved insulation of the multilayer pipe.

When the foam layer is formed by the physical foaming method, the material of the foam layer preferably contains thermally expandable microcapsules (tiny plastic spheres). By using the thermally expandable microcapsules, the resin A can be foamed well, and the specific gravity of the resulting foam layer can be effectively reduced. Only one type of the thermally expandable microcapsules may be used, or two or more types may be used in combination. The thermally decomposable foaming agent and the thermally expandable microcapsules may be used in combination.

The thermally expandable microcapsules are preferably thermally expandable microcapsules that encapsulate low-boiling-point hydrocarbons. The thermally expandable microcapsules preferably have a shell made of a thermoplastic resin and low-boiling-point hydrocarbons as encapsulants. The volatilization temperature of the low-boiling-point hydrocarbons is preferably 140°C or higher and preferably 210°C or lower.

Commercially available products of the above-mentioned thermally expandable microcapsules include "Advancell" manufactured by Tokuyama Sekisui Kogyo Co., Ltd.

The content of the thermally expandable microcapsules in the material of the foam layer is not particularly limited, and can be appropriately changed depending on the desired expansion ratio, molding conditions such as the manufacturing equipment and molding temperature, the type of resin A used, etc. In 100% by weight of the material of the foam layer, the content of the thermally expandable microcapsules is preferably 1% by weight or more, more preferably 2% by weight or more, preferably 5% by weight or less, more preferably 4% by weight or less. When the content of the thermally expandable microcapsules is equal to or more than the lower limit and equal to or less than the upper limit, the expansion ratio can be improved, and as a result, the insulation properties of the multilayer pipe can be further improved.

The content of the thermally expandable microcapsules is preferably 1.0 part by weight or more, more preferably 1.5 parts by weight or more, preferably 6.0 parts by weight or less, more preferably 5.0 parts by weight or less, relative to 100 parts by weight of the resin contained in the material of the foam layer. When the content of the thermally expandable microcapsules is equal to or more than the lower limit and equal to or less than the upper limit, the foaming ratio can be improved, and as a result, the insulation properties of the multilayer pipe can be further improved.

The specific gravity of the foam layer is 0.1 or more and 0.5 or less. If the specific gravity of the foam layer is less than 0.1, the foam layer is excessively foamed, which may cause unevenness on the inner surface of the multilayer pipe or make it difficult to take it up by a take-up machine during production, making it difficult to obtain a good multilayer pipe. If the specific gravity of the foam layer exceeds 0.5, the insulation properties are likely to decrease. The specific gravity of the foam layer is preferably 0.15 or more and preferably 0.4 or less. If the specific gravity of the foam layer is equal to or less than the upper limit, the insulation properties can be further improved.

The specific gravity of the foam layer is measured as follows:

The multilayer pipe is cut to a specified length. The inner and outer layers are cut and removed from the cut multilayer pipe to obtain a test piece consisting only of the foamed layer. The specific gravity of the obtained test piece is measured with an electronic specific gravity meter and is taken as the specific gravity of the foamed layer.

The foaming ratio of the foam layer is preferably 2 times or more, more preferably 3 times or more, preferably 8 times or less, more preferably 6 times or less, and even more preferably 5 times or less. When the foaming ratio is equal to or greater than the lower limit, the heat insulating properties can be further improved. When the foaming ratio is equal to or less than the upper limit, the bubble diameter can be made uniform, and the closed cell ratio can be increased. When the closed cell ratio is high, for example, when water penetrates into the foam layer from the end of the multilayer tube due to capillary action or the like, the risk of water permeating the entire foam layer through the bubbles can be reduced. Therefore, the deterioration of the heat insulating performance can be suppressed.

The expansion ratio of the foam layer is measured as follows:

The multi-layer pipe is cut to an axial length of 50 mm. The cut multi-layer pipe is then cut axially so as to divide it into four equal parts in the circumferential direction, and the inner and outer layers are then cut away to produce four 50 mm long plate-shaped test pieces composed only of the foamed layer. Using a water displacement specific gravity measuring device, the apparent density of each of the four test pieces at 23°C ± 2°C is determined to three decimal places in accordance with JIS K7112:1999. The expansion ratio for one test piece is calculated using the following formula (X), and the average of the expansion ratios of the four test pieces is taken as the expansion ratio of the foamed layer.

m = γo/γ ... (X)

In the above formula (X), m represents the expansion ratio, γ represents the apparent density (g/cm ³ ) of the test piece, and γo represents the density (g/cm ³ ) of the material of the foamed layer. γo is the density of the material of the foamed layer before the foamed layer is formed, and is the density when unfoamed.

The density (γo) of the foam layer material may vary from the density of resin A by about 0.1 g/ ^cm3 when the foam layer material contains components (additives) other than resin A. As the density (γo) of the foam layer material, for example, the density of the resin listed in the Chemistry Handbook (Applied Chemistry II, Materials Edition) may be used.

The thickness of the foam layer is preferably 4 mm or more, more preferably 4.3 mm or more, and preferably 6 mm or less, more preferably 5.8 mm or less. If the thickness of the foam layer is equal to or greater than the lower limit and equal to or less than the upper limit, the insulation properties can be further improved and the inner diameter of the multilayer pipe can be improved.

The thickness of the foam layer can be measured using a caliper or similar.

(Other details of the inner layer, foam layer and outer layer)
The inner layer, the foam layer and the outer layer may each contain various additives as necessary. Examples of the additives include stabilizers, stabilization aids, lubricants, processing aids, impact modifiers, heat resistance improvers, antioxidants, ultraviolet absorbers, light stabilizers, fillers, pigments and plasticizers. The additives may be used alone or in combination of two or more.

The stabilizer is not particularly limited, and examples thereof include heat stabilizers and heat stabilization assistants. The heat stabilizer is not particularly limited, and examples thereof include organotin stabilizers, lead stabilizers, calcium-zinc stabilizers, barium-zinc stabilizers, and barium-cadmium stabilizers. The organotin stabilizers include dibutyltin mercapto, dioctyltin mercapto, dimethyltin mercapto, dibutyltin mercapto, dibutyltin maleate, dibutyltin maleate polymer, dioctyltin maleate, dioctyltin maleate polymer, dibutyltin laurate, and dibutyltin laurate polymer. The stabilizers may be used alone or in combination of two or more. The heat stabilization assistant is not particularly limited, and examples thereof include epoxidized soybean oil, phosphate esters, polyols, hydrotalcite, and zeolites. The heat stabilization assistant may be used alone or in combination of two or more.

The lubricant is not particularly limited, and examples thereof include internal lubricants and external lubricants. The internal lubricant is used to reduce the flow viscosity of the molten resin during molding and to prevent frictional heat generation. The internal lubricant is not particularly limited, and examples thereof include butyl stearate, lauryl alcohol, stearyl alcohol, epoxy soybean oil, glycerin monostearate, stearic acid, and bisamide. The external lubricant is used to increase the sliding effect between the molten resin and the metal surface during molding. The external lubricant is not particularly limited, and examples thereof include paraffin wax, polyolefin wax, ester wax, and montanic acid wax. The lubricants may be used alone or in combination of two or more.

The processing aid is not particularly limited, and examples thereof include acrylic processing aids. Examples of the acrylic processing aids include alkyl acrylate-alkyl methacrylate copolymers having a weight average molecular weight of 100,000 to 2,000,000, and specific examples thereof include n-butyl acrylate-methyl methacrylate copolymers and 2-ethylhexyl acrylate-methyl methacrylate-butyl methacrylate copolymers. Only one type of the processing aids may be used, or two or more types may be used in combination.

The impact modifier is not particularly limited, and examples thereof include methyl methacrylate-butadiene-styrene copolymer (MBS), chlorinated polyethylene, and acrylic rubber. The impact modifier may be used alone or in combination of two or more kinds.

The heat resistance improver is not particularly limited, and examples thereof include α-methylstyrene-based resins and N-phenylmaleimide-based resins. Only one type of the heat resistance improver may be used, or two or more types may be used in combination.

The antioxidant is not particularly limited, and examples thereof include phenol-based antioxidants. The antioxidants may be used alone or in combination of two or more.

The above-mentioned UV absorbers are not particularly limited, and examples thereof include salicylic acid ester-based UV absorbers, benzophenone-based UV absorbers, benzotriazole-based UV absorbers, and cyanoacrylate-based UV absorbers. The above-mentioned UV absorbers may be used alone or in combination of two or more kinds.

The light stabilizer is not particularly limited, and examples thereof include hindered amine light stabilizers. Only one type of the light stabilizer may be used, or two or more types may be used in combination.

The filler is not particularly limited, and examples thereof include calcium carbonate and talc. Only one type of the filler may be used, or two or more types may be used in combination.

The pigments are not particularly limited, and examples thereof include organic pigments and inorganic pigments. Examples of the organic pigments include azo-based organic pigments, phthalocyanine-based organic pigments, threne-based organic pigments, and dye lake-based organic pigments. Examples of the inorganic pigments include oxide-based inorganic pigments, molybdenum chromate-based inorganic pigments, sulfide/selenide-based inorganic pigments, and ferrocyanide-based inorganic pigments. Only one type of the pigments may be used, or two or more types may be used in combination.

The plasticizer may be added to improve processability during molding. The addition of a plasticizer may reduce the heat resistance of the molded body, so it is preferable to add a small amount of plasticizer. The plasticizer is not particularly limited, and examples include dibutyl phthalate, di-2-ethylhexyl phthalate, and di-2-ethylhexyl adipate. The plasticizer may be used alone or in combination of two or more.

(Manufacturing method of multi-layer pipe)
Fig. 2 is a plan view showing a manufacturing apparatus used to manufacture a multi-layer pipe according to an embodiment of the present invention. Fig. 3 is a front view showing a manufacturing apparatus used to manufacture a multi-layer pipe according to an embodiment of the present invention. Figs. 2 and 3 are schematic views showing a manufacturing apparatus for manufacturing a multi-layer pipe 10.

The manufacturing device 20 includes an inner/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/outer layer extruder 11 and the foam layer extruder 12. The cooling water tank 15 is connected to the mold 13. The take-up machine 16 is connected to the cooling water tank 15. The cutter 17 is connected to the take-up machine 16.

The materials for the inner layer and the outer layer are fed from a hopper, melted and mixed in the inner and outer layer extruder 11, and extruded into the die 13.

The foam layer material is added from a hopper, melted and kneaded in the foam layer extruder 12, and extruded into the die 13.

An uncured multi-layer tube with a three-layer structure is extruded from the outlet of the mold 13.

A tube for forming the outer surface of the pipe 14 is attached to the cooling water tank 15 to form the uncured multi-layer pipe to a specified dimension, and the outer surface of the uncured multi-layer pipe is cooled while in contact with the tube for forming the outer surface of the pipe 14.

Figure 4 is an enlarged cross-sectional view of the mold portion of the manufacturing device and the tube portion used to mold the outer surface of the tube.

As shown in FIG. 4, the inner layer material 21 and the outer layer material 23 melt-kneaded by the inner and outer layer extruder 11 and the foam layer material 22 melt-kneaded by the foam layer extruder 12 are injected into a mold 13 to form an uncured multi-layer pipe 10X. The inner layer material 21 and the outer layer material 23 contain vinyl chloride resin. The foam layer material 22 contains resin A and a pyrolysis type foaming agent or thermally expandable microcapsules. The uncured multi-layer pipe 10X comprises an uncured inner layer 31, an uncured outer layer 33, and a layer formed by the foam layer material 22.

When the uncured multi-layer pipe 10X is ejected from the mold 13, the foam layer material 22 foams, forming an uncured foam layer 32. The uncured multi-layer pipe 10X is inserted into the tube 14 for molding the outer surface of the pipe, and the uncured multi-layer pipe 10X is cooled in the cooling water tank 15 while being molded to a specified dimension.

Next, as shown in Figures 2 and 3, a take-up machine 16 is used to take up the multi-layer pipe 10 that has been cooled in the cooling water tank 15, and a cutter 17 is used to cut the multi-layer pipe 10 sent from the take-up machine 16 to a predetermined length. In this way, a multi-layer pipe 10 having a predetermined length is obtained.

The heating temperature in the mold 13 is preferably 140°C or higher, more preferably 160°C or higher, and preferably 200°C or lower, more preferably 190°C or lower. The heating time in the mold 13 is preferably 10 minutes or higher, preferably 30 minutes or lower, more preferably 20 minutes or lower.

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

Example 1
Inner layer material and outer layer material:
As the materials for the inner layer and the outer layer, materials having the following compositions were prepared.

Polyvinyl chloride resin (Tokuyama Sekisui Kogyo Co., Ltd. "TS-1000R", melting temperature: 180°C to 200°C) 100 parts by weight Organotin stabilizer (Nitto Kasei Co., Ltd. "TVS-8832") 3 parts by weight MBS resin (Kaneka Corporation "B-564") 5 parts by weight Acrylic resin with molecular weight of 3 million or more (Kaneka Corporation "PA-20") 1 part by weight Lubricant (Mitsui Chemicals Inc. "Hiwax 220MP") 1 part by weight Lubricant (Emery Oleochemicals Japan Co., Ltd. "Roxiol 259") 1 part by weight Calcium carbonate (Shiraishi Kogyo Co., Ltd. "CCR") 2 parts by weight

Foam layer material:
As the material for the foam layer, a material having the following composition was prepared.

Polyethylene resin (Novatec LL UE320 manufactured by Japan Polyethylene Corporation, melting temperature: 160°C to 190°C) 100 parts by weight ADCA (Vinihol AC#3 manufactured by Eiwa Chemical Industry Co., Ltd.) 0.4 parts by weight

Manufacturing of multi-layer pipes (air conditioning drain pipes):
A manufacturing apparatus including an inner and outer layer extruder, a foaming layer extruder, a mold, a cooling water tank equipped with a tube for molding the outer surface of the pipe, a take-up machine, and a cutter was used. The mold temperature was set to 185° C., and extrusion molding was performed to obtain a multi-layer pipe (air conditioning drain pipe) with an outer diameter of 48 mm.

Example 2
A multi-layer pipe (air conditioning drain pipe) was obtained in the same manner as in Example 1, except that the amount of ADCA used in the foam layer material was changed as shown in Table 1.

Example 3
A multi-layer pipe (air conditioning drain pipe) was obtained in the same manner as in Example 1, except that the polyethylene resin used for the foam layer material was changed to the following ethylene-vinyl acetate copolymer.

Ethylene-vinyl acetate copolymer (Novatec EVA LV211A, manufactured by Japan Polyethylene Corporation, melting temperature: 150°C to 190°C)

Example 4
A multi-layer pipe (air conditioning drain pipe) was obtained in the same manner as in Example 3, except that the amount of ADCA used in the foam layer material was changed as shown in Table 1.

Example 5
A multi-layer pipe (air conditioning drain pipe) was obtained in the same manner as in Example 1, except that the polyvinyl chloride resin used in the material of the inner layer and the material of the outer layer was changed to the following chlorinated polyvinyl chloride resin and the set temperature of the mold was changed as shown in Table 1.

Chlorinated polyvinyl chloride resin (Tokuyama Sekisui Kogyo Co., Ltd. "HA-58K", melting temperature: 190°C to 210°C)

Example 6
A multi-layer pipe (air conditioning drain pipe) was obtained in the same manner as in Example 5, except that the amount of ADCA used in the foam layer material was changed as shown in Table 1.

(Example 7)
A multi-layer pipe (air conditioning drain pipe) was obtained in the same manner as in Example 1, except that the ADCA used as the material for the foam layer was changed to the following thermally expandable microcapsules and the blending amounts were changed as shown in Table 1.

Thermal expansion microcapsules (Tokuyama Sekisui Kogyo Co., Ltd. "Advancell EM504")

(Example 8)
A multi-layer pipe (air conditioning drain pipe) was obtained in the same manner as in Example 7, except that the amount of thermally expandable microcapsules used in the foam layer material was changed as shown in Table 1.

(Comparative Example 1)
A multi-layer pipe (air conditioning drain pipe) was obtained in the same manner as in Example 1, except that the polyethylene resin used for the foam layer material was changed to the following polyvinyl chloride resin and the set temperature of the mold was changed as shown in Table 2.

Polyvinyl chloride resin (Tokuyama Sekisui Kogyo Co., Ltd. "TS-1000R")

(Comparative Example 2)
A multi-layer pipe (air conditioning drain pipe) was obtained in the same manner as in Comparative Example 1, except that the amount of ADCA used in the foam layer material was changed as shown in Table 2.

(Comparative Example 3)
A multi-layer pipe (air conditioning drain pipe) was obtained in the same manner as in Example 7, except that the amount of thermally expandable microcapsules used in the foam layer material was changed as shown in Table 2, and the set temperature of the mold was changed as shown in Table 2.

(Comparative Examples 4 and 5)
A multi-layer pipe (air conditioning drain pipe) was obtained in the same manner as in Example 1, except that the amount of ADCA used in the foam layer material was changed as shown in Table 2, and the set temperature of the mold was changed as shown in Table 2.

In addition, in the multi-layer pipe obtained in Comparative Example 5, irregularities were observed in the foam layer and the inner layer, and a well-formed multi-layer pipe could not be obtained.

(Comparative Example 6)
Molding was performed in the same manner as in Example 1, except that the polyethylene resin used as the material for the foam layer was changed to the following polypropylene resin, the amount of ADCA was changed as shown in Table 2, and the set temperature of the mold was changed as shown in Table 2. However, it was not possible to extrude the mixture from the mold, and a multi-layer pipe could not be obtained.

Polypropylene resin (Japan Polypropylene "EA9", melting temperature: 220℃-250℃)

(evaluation)
(1) Specific Gravity of Foam Layer The multi-layer pipe obtained was cut into an axial length of 3 cm, and the inner and outer layers were removed by cutting to obtain a test piece. The specific gravity of the test piece obtained was measured using an electronic densitometer ("MD-300S" manufactured by Alpha Mirage).

(2) Thermal insulation (condensation)
The obtained 4 m multi-layer pipe was placed in a temperature and humidity chamber at a temperature of 20° C. and a relative humidity of 80% with a gradient of 1/50. After running tap water at 7° C. at 6 L/h through the inside of the multi-layer pipe for 1 hour, the presence or absence of condensation was confirmed by touching the lower part of the multi-layer pipe with a hand.

[Criteria for determining insulation (condensation)]
○: No condensation occurs ×: Condensation occurs

The structure and results of the multilayer pipe are shown in Tables 1 and 2.

Reference Signs List 1: inner layer 2: foam layer 3: outer layer 10: multi-layer pipe 10X: uncured multi-layer pipe 11: inner and outer layer extruder 12: foam layer extruder 13: mold 14: tube for molding outer surface of pipe 15: cooling water tank 16: take-up machine 17: cutting machine 20: manufacturing device 21: inner layer material 22: foam layer material 23: outer layer material 31: uncured inner layer 32: uncured foam layer 33: uncured outer layer

Claims (6)

The inner layer,
A foam layer disposed on the outer side of the inner layer;
and an outer layer disposed on an outer side of the foam layer.
The inner layer contains a vinyl chloride resin,
the foam layer contains a resin other than a vinyl chloride-based resin,
the outer layer comprises a vinyl chloride resin,
the resin other than the vinyl chloride-based resin contained in the foam layer is a polyethylene-based resin, a polyurethane-based resin, a polystyrene-based resin, or a polyacrylic-based resin;
The content of the resin other than the vinyl chloride resin in 100% by weight of the foam layer is 90% by weight or more,
A multi-layer pipe, wherein the specific gravity of the foamed layer is 0.1 or more and 0.5 or less. 2. The multi-layer pipe according to claim 1, wherein the resin different from the vinyl chloride resin contained in the foam layer is a polyethylene resin. The multi-layer pipe according to claim 1 or 2, wherein the foam layer does not contain a vinyl chloride resin. The multi-layer pipe according to any one of claims 1 to 3, wherein the material of the foam layer contains a pyrolytic foaming agent. The multi-layer pipe according to any one of claims 1 to 4, wherein the material of the foam layer contains thermally expandable microcapsules. The multilayer pipe according to any one of claims 1 to 5, which is an air conditioning drain pipe.

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