JP2021173306A - Multilayer pipe - Google Patents

Abstract

To provide a multilayer pipe that prevents interlayer peeling even when high-temperature liquid is passed therethrough.SOLUTION: A multilayer pipe has an inner layer, an outer layer, and an adhesive layer disposed between the inner layer and the outer layer. The inner layer contains a polypropylene resin, the outer layer contains a hard polyvinyl chloride resin, and the adhesive layer contains a polyester resin and a polyolefin resin having a polar group introduced thereto. The adhesive layer has a sea-island structure having a sea part and an island part.SELECTED DRAWING: Figure 1

Description

The present invention relates to a multilayer tube.

Resin multi-layer pipes are widely used as pipes through which liquids flow inside water supply pipes, drainage pipes, and the like.

For example, Patent Document 1 below includes a first layer and a second layer laminated on the outer surface of the first layer, and the first layer is a non-ionic layer having a hydrophilic group. The second layer contains a sex component and has a recess on the inner surface on the side of the first layer having a maximum depth of 3 μm or more, and the first layer is the second layer. A multilayer tube having a convex portion in the concave portion is disclosed.

In Patent Document 2 below, the first layer, the second layer laminated so as to contact the first layer, and the second layer laminated so as to contact the second layer are laminated in the direction from the axial center to the outer periphery. A multilayer tube having a ten-point average roughness Rz of 30 μm or more at least one of the interface between the first layer and the second layer and the interface between the second layer and the third layer. Is disclosed.

JP-A-2018-003859 Japanese Unexamined Patent Publication No. 2016-055561

Generally, a low temperature liquid to a high temperature liquid is passed through the inside of the multilayer tube. In the multilayer tube described in Patent Documents 1 and 2, since the interface between specific layers has irregularities, peeling between layers can be suppressed to some extent. However, in the multilayer tubes described in Patent Documents 1 and 2, when a high-temperature liquid is passed through the tubes, delamination may occur between the layers.

An object of the present invention is to provide a multilayer tube capable of preventing delamination between layers even when a high-temperature liquid is passed through the liquid.

According to a broad aspect of the present invention, the inner layer is provided with an inner layer, an outer layer, and an adhesive layer arranged between the inner layer and the outer layer, the inner layer contains a polypropylene resin, and the outer layer is a hard polyvinyl chloride. Provided is a multilayer tube containing a vinyl-based resin, wherein the adhesive layer contains a polyester-based resin and a polyolefin-based resin into which a polar group has been introduced, and the adhesive layer has a sea-island structure having a sea portion and an island portion. Will be done.

In certain aspects of the multilayer tube according to the present invention, the melting temperature of the adhesive layer is 95 ° C. or higher.

In certain aspects of the multilayer pipe according to the present invention, the multilayer pipe is a drainage pipe.

The multilayer tube according to the present invention includes an inner layer, an outer layer, and an adhesive layer arranged between the inner layer and the outer layer. The inner layer contains a polypropylene resin, and the outer layer is a hard polyvinyl chloride. The adhesive layer contains a polyester resin and a polyolefin resin into which a polar group has been introduced, and the adhesive layer has a sea-island structure having a sea portion and an island portion. Since the multilayer tube according to the present invention has the above configuration, it is possible to prevent delamination from occurring even when a high-temperature liquid is passed through the tube.

FIG. 1 is a cross-sectional view schematically showing a multilayer tube according to an embodiment of the present invention. 2 (a) and 2 (b) are scanning electron micrographs of the cross section of the multilayer tube obtained in Example 1.

Hereinafter, the present invention will be described in detail.

The multilayer tube according to the present invention includes an inner layer, an outer layer, and an adhesive layer arranged between the inner layer and the outer layer. The inner layer contains a polypropylene resin, and the outer layer is a hard polyvinyl chloride. The adhesive layer contains a polyester resin and a polyolefin resin into which a polar group has been introduced, and the adhesive layer has a sea-island structure having a sea portion and an island portion.

Since the multilayer tube according to the present invention has the above configuration, it is possible to prevent delamination from occurring even when a high-temperature liquid is passed through the tube. In the multilayer tube according to the present invention, for example, even when a liquid having a temperature of 60 ° C. or higher is passed through the tube, it is possible to prevent peeling between layers.

In general, even if a layer containing a polypropylene-based resin and a layer containing a hard polyvinyl chloride-based resin are adhered with an adhesive or the like, peeling is likely to occur at the interface thereof, and peeling is more likely to occur in a high temperature environment. Therefore, as a multilayer tube through which a high-temperature liquid can pass, a multilayer tube including a layer containing a polypropylene-based resin and a layer containing a hard polyvinyl chloride-based resin is not generally used.

On the other hand, in the multilayer tube according to the present invention, the inner layer containing the polypropylene-based resin and the outer layer containing the hard polyvinyl chloride-based resin are adhered by a specific adhesive layer, so that a high-temperature liquid can pass through. Even if this is the case, it is possible to prevent peeling between layers. In the present invention, the polyester resin in the adhesive layer enhances the adhesive force between the adhesive layer and the outer layer. Further, the main chain portion of the polyolefin resin into which the polar group is introduced in the adhesive layer enhances the adhesive force between the adhesive layer and the inner layer, and the polar group portion provides a region containing the polyester resin (sea part or sea portion or The affinity between the island part) and the region containing the polyolefin resin into which the polar group has been introduced (island part or sea part) is enhanced. As a result, the inner layer and the outer layer are satisfactorily adhered to each other via the adhesive layer, and it is possible to prevent peeling between the layers.

The multilayer tube includes an inner layer, an adhesive layer, and an outer layer in this order from the center to the outside. The multilayer tube may have a three-layer structure of an inner layer, an adhesive layer, and an outer layer, or may have a structure of four or more layers. The inner layer may be the innermost layer and may not be the innermost layer. Another layer may be arranged inside the inner layer. However, the inner layer is preferably the innermost layer. The outer layer may be the outermost layer and may not be the outermost layer. Another layer may be arranged outside the outer layer. However, the outer layer is preferably the outermost layer.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. In the drawings below, the size, thickness, shape, etc. may differ from the actual size, thickness, shape, etc. for convenience of illustration.

FIG. 1 is a cross-sectional view schematically showing a multilayer tube according to an embodiment of the present invention. In FIG. 1, a cross-sectional view taken along the radial direction of the multilayer tube is shown.

The multilayer tube 10 shown in FIG. 1 includes an inner layer 1, an outer layer 2, and an adhesive layer 3. The multilayer tube 10 has a three-layer structure. The inner layer 1 is arranged inside the adhesive layer 3. The outer layer 2 is arranged on the outside of the adhesive layer 3. The adhesive layer 3 is arranged between the inner layer 1 and the outer layer 2. The inner layer 1 is arranged on the inner surface of the adhesive layer 3 and is laminated. The outer layer 2 is arranged on the outer surface of the adhesive layer 3 and is laminated. The adhesive layer 3 adheres the inner layer 1 and the outer layer 2. The inner layer 1 and the outer layer 2 are adhered to each other via the adhesive layer 3. The inner layer 1 is the innermost layer and is a surface layer. The outer layer 2 is the outermost layer and is a surface layer. The adhesive layer 3 is an intermediate layer. The inner layer 1, the outer layer 2, and the adhesive layer 3 are each tubular.

The inner layer 1 contains a polypropylene-based resin. The outer layer 2 contains a hard polyvinyl chloride resin. The adhesive layer 3 contains a polyester-based resin and a polyolefin-based resin into which a polar group has been introduced. The adhesive layer 3 has a sea-island structure.

(Inner layer)
The inner layer contains a polypropylene resin. The inner layer is obtained by molding a material of the inner layer containing a polypropylene-based resin. Only one kind of the polypropylene resin may be used, or two or more kinds may be used in combination.

As the polypropylene-based resin, a conventionally known polypropylene-based resin can be used. Examples of the polypropylene-based resin include (1) a homopolymer of propylene (homopolypropylene), and (2) a copolymer of propylene and a monomer copolymerizable with propylene.

Examples of the monomer copolymerizable with propylene include α-olefin compounds. Therefore, examples of the polypropylene-based resin include a copolymer of propylene and an α-olefin compound. Examples of the α-olefin compound include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene and 1-octene. As the monomer copolymerizable with propylene, only one kind may be used, or two or more kinds may be used in combination.

In the above-mentioned copolymer of propylene and α-olefin compound, the content of the structural unit derived from the α-olefin compound in 100 mol% of the structural unit of the copolymer is preferably less than 10 mol%, more preferably. It is 9 mol% or less.

The polypropylene-based resin may be homopolypropylene, block polypropylene, or random polypropylene.

From the viewpoint of exerting the effects of the present invention even more effectively, the polypropylene-based resin is preferably homopolypropylene or random polypropylene.

The content of the polypropylene-based resin in 100% by weight of the inner layer is preferably 90% by weight or more, more preferably 95% by weight or more. When the content of the polypropylene-based resin is at least the above lower limit, the effect of the present invention can be exhibited even more effectively.

The elastic modulus of the inner layer at 23 ° C. is preferably 1900 MPa or less, more preferably 1400 MPa or less, still more preferably 1000 MPa or less. When the elastic modulus is not more than the upper limit, the effect of the present invention can be exhibited even more effectively.

The elastic modulus is measured under the condition of 23 ° C. according to JIS K7161.

Linear expansion coefficient of the inner layer is preferably ¹⁰ × 10 ^-5 / ℃ or more, preferably 15 × ^{10 -5} / ℃ less, more preferably 14 × ^{10 -5} / ℃ less, more preferably 13 × ^{10 -5} It is / ° C. or lower, particularly preferably 12 × ^10-5 / ° C. or lower. When the coefficient of linear expansion is equal to or higher than the lower limit and lower than the upper limit, the effect of the present invention can be exhibited even more effectively. The coefficient of linear expansion of the inner layer ^{may be 7 × 10 −5} / ° C. or less.

The coefficient of linear expansion is measured according to ASTM D696.

(Outer layer)
The outer layer contains a rigid polyvinyl chloride resin. The outer layer is obtained by molding a material of the outer layer containing a hard polyvinyl chloride resin. Since the outer layer contains a hard polyvinyl chloride resin, the workability of the multilayer pipe can be improved. For example, it is possible to satisfactorily connect a multilayer pipe and a member to be connected such as a joint without performing electrical fusion. Only one kind of the hard polyvinyl chloride resin may be used, or two or more kinds thereof may be used in combination.

As the hard polyvinyl chloride resin, a conventionally known hard polyvinyl chloride resin can be used. Examples of the hard polyvinyl 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 capable of copolymerizing with the vinyl chloride monomer, and (3). ) Examples thereof include polymers other than vinyl chloride and graft polymers in which vinyl chloride is graft-polymerized on a copolymer.

The monomer having an unsaturated bond copolymerizable with the vinyl chloride monomer is not particularly limited, and is an α-olefin compound such as ethylene, propylene or butylene; a compound having a vinyl group such as allyl chloride or acrylonitrile; vinyl acetate or propion. Vinyl ester compounds such as vinyl acid acid; Vinyl ether compounds such as ethyl vinyl ether, butyl vinyl ether and cetyl vinyl ether; (meth) such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate and hydroxyethyl (meth) acrylate. Acrylic acid ester compounds; 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 can be mentioned. As the monomer having an unsaturated bond copolymerizable with the vinyl chloride monomer, only one kind may be used, or two or more kinds may be used in combination.

In a copolymer of a vinyl chloride monomer and a monomer having an unsaturated bond copolymerizable with the vinyl chloride monomer, a monomer having an unsaturated bond copolymerizable with the vinyl chloride monomer in 100% by weight of the copolymer. The content of is preferably 40% by weight or less.

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

The polymer and copolymer for graft-copolymerizing vinyl chloride are not particularly limited, and are ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-carbon monoxide copolymer, ethylene-ethyl acrylate copolymer, and ethylene. Examples thereof include -butyl acrylate-carbon monoxide copolymer, ethylene-methyl methacrylate copolymer, ethylene-propylene copolymer, acrylonitrile-butadiene copolymer, polyurethane, chlorinated polyethylene, and chlorinated polypropylene. As the polymer and copolymer for graft-copolymerizing vinyl chloride, only one kind may be used, or two or more kinds may be used in combination.

In the graft polymer, the content of the polymer and the copolymer that graft-copolymerizes the vinyl chloride in 100% by weight of the graft polymer is preferably 40% by weight or less.

The content of the structural unit derived from vinyl chloride in 100% by weight of the hard polyvinyl chloride resin is preferably 60% by weight or more, more preferably 75% by weight or more, still more preferably 80% by weight or more, and particularly preferably 80% by weight or more. It is 90% by weight or more, preferably 98% by weight or less, and more preferably 95% by weight or less. When the content of the structural unit derived from vinyl chloride is at least the above lower limit, the flame retardancy can be further enhanced. When the content of the structural unit derived from vinyl chloride is not more than the above upper limit, the moldability can be improved and the thermal decomposition of vinyl chloride can be suppressed at the time of molding. The content of the structural unit derived from vinyl chloride in 100% by weight of the hard polyvinyl chloride resin may be 100% by weight (total amount).

The hard polyvinyl chloride resin is preferably a hard chlorinated polyvinyl chloride resin obtained by post-chlorinating the vinyl chloride resin. In this case, since the chlorine content can be increased, the flame retardancy and heat resistance can be further improved. Therefore, the multilayer tube of the present invention can be preferably used as the multilayer tube through which a liquid having a temperature of 80 ° C. or higher (preferably 90 ° C. or higher) is passed.

The chlorine content of the hard chlorinated polyvinyl chloride resin is preferably 60% by weight or more, more preferably 64% by weight or more, further preferably 66% by weight or more, particularly preferably 67% by weight or more, and preferably 71. It is less than% by weight. When the chlorine content is at least the above lower limit, flame retardancy and heat resistance can be further enhanced. When the chlorine content is not more than the above upper limit, the moldability can be improved.

The chlorine content means the chlorine content measured by neutralization titration by the oxygen flask combustion method in accordance with JIS K7229.

The average degree of polymerization of the hard polyvinyl chloride resin is preferably 600 or more, more preferably 800 or more, and preferably 1400 or less. When the average degree of polymerization is at least the above lower limit, the mechanical strength of the multilayer tube can be increased. When the average degree of polymerization is not more than the above upper limit, it is not necessary to keep the temperature at a high temperature during molding, and the workability is further improved.

The average degree of polymerization is measured as follows. A hard polyvinyl chloride resin is dissolved in tetrahydrofuran (THF), and insoluble components are removed by filtration. THF in the obtained filtrate is dried and removed to obtain a resin. Using the obtained resin as a sample, the average degree of polymerization is measured according to the vinyl chloride resin test method of JIS K-6721.

The content of the rigid polyvinyl chloride resin in 100% by weight of the outer layer is preferably 80% by weight or more, more preferably 85% by weight or more, preferably 98% by weight or less, and more preferably 95% by weight or less. .. When the content of the hard polyvinyl chloride resin is not less than the above lower limit and not more than the above upper limit, the effect of the present invention can be exhibited even more effectively.

The coefficient of linear expansion of the outer layer is preferably 5 × ^10-5 / ° C. or higher, more preferably 6 × ^10-5 / ° C. or higher, still more preferably 6.5 × ^10-5 / ° C. or higher, preferably 7.5. ^{It is x10-5} / ° C or less. When the coefficient of linear expansion is equal to or higher than the lower limit and lower than the upper limit, the effect of the present invention can be exhibited even more effectively. In general, the smaller the coefficient of linear expansion of the outer layer (the difference from the coefficient of linear expansion of the inner layer is larger), the more likely it is that the layers are separated. Even when the coefficient of expansion is relatively small, it is possible to prevent peeling between layers.

The coefficient of linear expansion is measured according to ASTM D696.

(Adhesive layer)
The adhesive layer has a sea-island structure having a sea part (first region) and an island part (second region). The adhesive layer has a phase-separated structure. The adhesive layer contains a polyester-based resin and a polyolefin-based resin into which a polar group has been introduced. As the polyester resin and the polyolefin resin into which the polar group is introduced, only one type may be used, or two or more types may be used in combination.

Examples of the polyester-based resin include polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate.

Examples of the polyolefin-based resin in the polyolefin-based resin into which the polar group has been introduced include polyethylene, polypropylene, and polybutene.

Examples of the polar group in the polyolefin resin into which the polar group has been introduced include a hydroxyl group, a carboxyl group, and an amino group. The polar group is preferably introduced into the main chain of the polyolefin resin.

In the adhesive layer, the sea portion may contain a relatively large amount of polyester resin, and the island portion may contain a relatively large amount of polyolefin resin into which a polar group has been introduced. In the adhesive layer, the sea portion may contain a relatively large amount of a polyolefin-based resin into which a polar group has been introduced, and the island portion may contain a relatively large amount of a polyester-based resin.

The total content of the polyester resin and the polyolefin resin into which the polar group is introduced is preferably 80% by weight or more, more preferably 90% by weight or more in 100% by weight of the adhesive layer. When the total content is equal to or higher than the above lower limit, the effect of the present invention can be exhibited even more effectively.

The melting temperature of the adhesive layer is preferably 95 ° C. or higher, more preferably 100 ° C. or higher, still more preferably 130 ° C. or higher, particularly preferably 150 ° C. or higher, and most preferably 160 ° C. or higher. When the melting temperature is at least the above lower limit, the effect of the present invention can be exhibited more effectively, and the multilayer tube of the present invention can be preferably used as an application for passing a high-temperature liquid. The melting temperature of the adhesive layer may be 200 ° C. or lower, or 180 ° C. or lower.

The melting temperature is measured by DSC (Differential Scanning Calorimetry) in accordance with the C method of JIS K6824 under the condition that the temperature is raised at 10 ° C./min.

(Other ingredients)
The inner layer, the outer layer, and the adhesive layer may contain various additives, if necessary. Examples of the additive include stabilizers, stabilizing aids, lubricants, impact modifiers, heat resistance improvers, antioxidants, ultraviolet absorbers, light stabilizers, fillers, pigments, plasticizers and the like. Only one kind of the above-mentioned additive may be used, or two or more kinds thereof may be used in combination.

The stabilizer is not particularly limited, and examples thereof include a heat stabilizer and a heat stabilization aid. The heat stabilizer is not particularly limited, and examples thereof include an organic tin-based stabilizer, a lead-based stabilizer, a calcium-zinc-based stabilizer, a barium-zinc-based stabilizer, and a barium-cadmium-based stabilizer. Examples of the organic tin stabilizer include dibutyl tin mercapto, dioctyl tin mercapto, dimethyl tin mercapto, dibutyl tin mercapto, dibutyl tin malate, dibutyl tin malate polymer, dioctyl tin malate, dioctyl tin malate polymer, dibutyl tin laurate, and the like. Examples thereof include dibutyltin laurate polymer. The heat stabilizing aid is not particularly limited, and examples thereof include epoxidized soybean oil, phosphoric acid ester, polyol, hydrotalcite, and zeolite. Only one kind of the above stabilizer may be used, or two or more kinds may be used in combination.

Examples of the lubricant include an internal lubricant and an external lubricant. The internal lubricant is used for the purpose of lowering the flow viscosity of the molten resin during molding and preventing 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 for the purpose of enhancing the sliding effect between the molten resin and the metal surface during the molding process. The external lubricant is not particularly limited, and examples thereof include paraffin wax, polyolefin wax, ester wax, and montanic acid wax. Only one kind of the above-mentioned lubricant may be used, or two or more kinds 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. Only one type of the impact modifier may be used, or two or more types may be used in combination.

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

The antioxidant is not particularly limited, and examples thereof include phenolic antioxidants. Only one kind of the above-mentioned antioxidant may be used, or two or more kinds may be used in combination.

The ultraviolet absorber is not particularly limited, and examples thereof include a salicylate ester-based ultraviolet absorber, a benzophenone-based ultraviolet absorber, a benzotriazole-based ultraviolet absorber, and a cyanoacrylate-based ultraviolet absorber. Only one kind of the above-mentioned ultraviolet absorber may be used, or two or more kinds may be used in combination.

The light stabilizer is not particularly limited, and examples thereof include hindered amine-based light stabilizers. Only one kind of the above-mentioned light stabilizer may be used, or two or more kinds thereof may be used in combination.

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

The pigment is 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, slene-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 / selenium-based inorganic pigments, and ferrosinide-based inorganic pigments. Only one kind of the above pigment may be used, or two or more kinds may be used in combination.

The plasticizer may be added for the purpose of improving processability at the time of molding. The plasticizer is not particularly limited, and examples thereof include dibutyl phthalate, di-2-ethylhexyl phthalate, and di-2-ethylhexyl adipate. Only one type of the above-mentioned plasticizer may be used, or two or more types may be used in combination.

From the viewpoint of increasing the mechanical strength of the multilayer tube, it is preferable that the content of the plasticizer contained in the inner layer, the outer layer and the adhesive layer is small. The content of the plasticizer contained in the inner layer, the outer layer and the adhesive layer is preferably less than 10 parts by weight, respectively, with respect to 100 parts by weight of the resin contained in the inner layer, the outer layer and the adhesive layer. It is more preferably 5 parts by weight or less, further preferably 2 parts by weight or less, and most preferably 0 parts by weight (not compounded).

(Other details of multi-layer tube)
The ratio of the thickness of the inner layer to the thickness of the multilayer tube (thickness of the inner layer / thickness of the multilayer tube) is preferably 0.06 or more, preferably 0.45 or less, more preferably 0.3 or less, still more preferably. It is 0.2 or less. When the ratio (thickness of the inner layer / thickness of the multilayer tube) is equal to or greater than the above lower limit and equal to or lower than the above upper limit, the effect of the present invention can be exhibited even more effectively.

The ratio of the thickness of the outer layer to the thickness of the inner layer (thickness of the outer layer / thickness of the inner layer) is preferably more than 1, more preferably 2 or more, still more preferably 2.5 or more, particularly preferably 3 or more. It is preferably 3.5 or more, preferably 7 or less. When the above ratio (thickness of outer layer / thickness of inner layer) is equal to or higher than the above lower limit, the rigidity of the multilayer pipe can be increased, and as a result, the rigid polyvinyl chloride type is used from the viewpoint of gradient management, the number of construction members, man-hours, and the like. Workability closer to that of a resin pipe can be obtained. When the above ratio (thickness of the outer layer / thickness of the inner layer) is not more than the above upper limit, the effect of the present invention can be more effectively exhibited while maintaining the thickness of the inner layer.

The thickness of the inner layer can be appropriately changed depending on the nominal diameter of the target multilayer tube. The thickness of the inner layer is preferably 0.3 mm or more, preferably 2.2 mm or less, more preferably 2 mm or less, still more preferably 1 mm or less. When the thickness of the inner layer is not less than the above lower limit and not more than the above upper limit, the effect of the present invention can be exhibited even more effectively.

The thickness of the outer layer can be appropriately changed depending on the nominal diameter of the target multilayer tube, the thickness of the inner layer, and the like. The thickness of the outer layer is preferably 2.5 mm or more, more preferably 3 mm or more, and preferably 4 mm or less. When the thickness of the outer layer is at least the above lower limit, workability closer to that of a rigid polyvinyl chloride resin pipe can be obtained. When the thickness of the outer layer is not more than the upper limit, the weight of the multilayer tube can be reduced.

The thickness of the adhesive layer is preferably 0.05 mm or more, more preferably 0.1 mm or more, still more preferably 0.3 mm or more, particularly preferably 0.4 mm or more, preferably 1.0 mm or less, and more preferably 0. It is 8 mm or less. When the thickness of the adhesive layer is not less than the above lower limit and not more than the above upper limit, the effect of the present invention can be exhibited even more effectively.

The nominal diameter (inner diameter) of the multilayer tube is preferably 20 mm or more, more preferably 40 mm or more, preferably 200 mm or less, more preferably 150 mm or less, still more preferably 100 mm or less, and particularly preferably 50 mm or less.

The multilayer tube can be manufactured by a conventionally known method for manufacturing a multilayer tube. The multi-layer tube can be manufactured, for example, by multi-layer extrusion molding as shown below. An extrusion molding machine according to the number of layers and a mold for a multi-layer pipe having a resin inlet corresponding to the number of layers are prepared. The material of each layer is kneaded with an extrusion molding machine, and the material of each layer is injected into the mold from the resin inflow port. The materials of each layer are merged and laminated in the mold, and then the cooled tubular material is taken up by a take-up machine to obtain a multi-layer tube.

The multi-layer pipe is preferably used as a drain pipe. The multi-layer pipe is preferably a drain pipe. The multi-layer pipe is preferably used as a drainage pipe for high temperature drainage. The maximum temperature of the liquid passed through the multilayer tube (maximum temperature of the high-temperature liquid) is preferably 60 ° C. or higher, more preferably 80 ° C. or higher, still more preferably 85 ° C. or higher, particularly preferably 87 ° C. or higher. It is preferably 90 ° C. or higher, preferably 100 ° C. or lower, more preferably 95 ° C. or lower, and further preferably 93 ° C. or lower. The maximum temperature of the liquid passed through the multilayer tube may be 90 ° C. or lower.

Not only a high temperature liquid but also a low temperature liquid may be passed through the multilayer tube. The low-temperature liquid means a liquid that has not been heated, and is, for example, a liquid at 1 ° C. to 30 ° C. The multi-layer pipe is preferably a multi-layer pipe for passing a high-temperature liquid and a low-temperature liquid, and is a multi-layer pipe for repeatedly and alternately passing a high-temperature liquid and a low-temperature liquid. Is more preferable.

The multi-layer pipe is more preferably used as a drainage pipe for building piping (drainage pipe for construction). The multi-layer pipe is more preferably a drainage pipe for building piping (drainage pipe for construction). The drainage pipe for building piping is a pipe that constitutes an indoor drainage facility. Since the drainage pipe for building piping is installed near the drainage source, it is easily exposed to high-temperature liquid, and the temperature difference between the drained liquid is large. Among the drainage pipes for building piping, a higher temperature liquid (for example, 80 ° C. or higher) is drained to the drainage pipe for kitchen. Since the multi-layer pipe according to the present invention can make it difficult for delamination to occur even when a high-temperature liquid is passed through the multi-layer pipe, the multi-layer pipe of the present invention is preferably used as a drainage pipe for building piping. It can also be suitably used as a drainage pipe for a kitchen.

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

(Example 1)
The following materials were prepared.

Inner layer material:
Homopolypropylene (Homo PP, manufactured by HMC Polymers, elastic modulus at 23 ° C., 1800 MPa)

The elastic modulus is a value obtained by measuring in accordance with JIS K7161.

Outer layer material:
Hard chlorinated polyvinyl chloride resin (hard chlorinated polyvinyl chloride, manufactured by Tokuyama Sekisui Kogyo Co., Ltd.)

Adhesive layer material:
Material containing polyester resin and polyolefin resin with polar groups introduced ("Modic" manufactured by Mitsubishi Chemical Corporation)
Material containing copolyester (Sumitomo Chemical "VC-40")

(Example 1 and Comparative Example 1)
A multilayer tube was produced by multi-layer extrusion molding using the components shown in Table 1. The obtained multilayer tube was cut along the radial direction, and the dimensions were measured with a caliper. The results were as follows.

Multilayer tube thickness: 4 mm, inner layer thickness: 0.5 mm, outer layer thickness: 3.3 mm, adhesive layer thickness: 0.2 mm, nominal diameter (inner diameter): 40 mm

(evaluation)
(1) Presence or absence of sea-island structure The cross section of the obtained multilayer tube along the radial direction was observed with a scanning electron microscope (SEM) to confirm whether or not the adhesive layer had a sea-island structure. FIG. 2 is a scanning electron micrograph of a cross section of the multilayer tube obtained in Example 1. FIG. 2A is a photograph of the vicinity of the interface between the inner layer 1X and the adhesive layer 3X, and FIG. 2B is a photograph of the vicinity of the interface between the outer layer 2X and the adhesive layer 3X.

(2) Melting temperature of the adhesive layer The melting temperature of the adhesive layer was measured by DSC (Differential Scanning Calorimetry) in accordance with the C method of JIS K6824 under the condition that the temperature was raised at 10 ° C./min.

(3) Delamination (after passing a liquid at 90 ° C)
Water at 90 ° C. was passed through the obtained multilayer tube for 1 hour. After passing the liquid, the state of the inner surface of the multilayer tube was visually confirmed, and it was confirmed whether or not the inner layer was peeled off.

[Criteria for delamination (after passing liquid at 90 ° C)]
◯: No peeling of the inner layer is confirmed ×: Peeling of the inner layer is confirmed even slightly

Table 1 shows the configuration and results of the multi-layer pipe.

1,1X ... Inner layer 2,2X ... Outer layer 3,3X ... Adhesive layer 10 ... Multilayer tube

Claims (3)

The inner layer, the outer layer, and the adhesive layer arranged between the inner layer and the outer layer are provided.
The inner layer contains a polypropylene resin and contains
The outer layer contains a rigid polyvinyl chloride resin and contains
The adhesive layer contains a polyester-based resin and a polyolefin-based resin into which a polar group has been introduced.
A multi-layer pipe having a sea-island structure in which the adhesive layer has a sea part and an island part. The multilayer tube according to claim 1, wherein the melting temperature of the adhesive layer is 95 ° C. or higher. The multi-layer pipe according to claim 1 or 2, which is a drainage pipe.

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