Foam-coated pipe, and method for manufacturing the same

Abstract

To provide a technology capable of reducing a shrinkage percentage of a foam-coated portion while maintaining high quality of a resin pipe, in a foam-coated pipe.SOLUTION: This technology is a foam-coated pipe in which an outer periphery of a resin pipe is covered with a foam sheet, where a dynamic friction coefficient of a resin pipe measured in accordance with JIS K7125:1999 is 0.13 or more, and a dynamic friction coefficient of a surface of the foam sheet measured in accordance with JIS K7125:1999 is 0.10 to 1.0.SELECTED DRAWING: None

Description

Technical Field

[0001] The present technology relates to a foam-coated pipe. More specifically, it relates to a foam-coated pipe in which the outer circumference of a resin pipe is coated with a foam sheet, and a method for manufacturing the foam-coated pipe.

Background Art

[0002] For hot water supply pipes, hot water pipes for floor heating, etc., resin pipes are often used from the viewpoints of heat resistance, durability, and corrosion resistance. For example, Patent Document 1 discloses that by using a crosslinked product of a resin composition (X) containing a specific amount of high-density polyethylene (A-1) having a specific MFR and density, high-density polyethylene (A-2) having a specific MFR and density, and linear low-density polyethylene (B) having a specific MFR and density, a pipe having high flexibility and high creep strength and suitable for use in hot water, etc. is manufactured.

[0003] In cold regions, etc., in order to improve heat insulation, a method of coating the above resin pipe with a foam is also used. As a method of coating a resin pipe with a foam, for example, a method is used in which a sheet-like foam is curved into a cylindrical shape while covering the resin pipe, and both end portions in the width direction of the foam sheet are heat-sealed in a hollow die and continuously pulled using a take-up machine or the like.

[0004] When pulling a foam-coated pipe from a die, the foam-coated pipe is stretched by the pulling force of a take-up machine or the like. In particular, when coating with a foam sheet having a small pipe diameter size or a thickness compared to the pipe diameter size, it is easily stretched. The foam-coated portion of the stretched foam-coated pipe contracts in the pipe longitudinal direction after passing through the take-up machine. The resin pipe portion that is exposed due to the contraction of the foam-coated portion will be cut and discarded.

[0005] In order to reduce the shrinkage of the foam-coated portion as much as possible, various techniques are being developed. For example, in Patent Document 2, a sheet-shaped foam material is covered around a pipe while being squeezed into a circular shape, the sheet ends facing each other are melted before the foam material is wrinkled, and a liner is arranged on the outer surface of the circularly squeezed foam material and passed through a hollow die having a diameter slightly smaller than the diameter after coating to fuse the melted sheet ends together, and in a method for manufacturing a pipe with a foam material in which the pipe with the foam material with the sheet ends fused together is continuously drawn out from the hollow die, the liner is provided with an anti-slip layer on the foam material side of the liner body, and the friction coefficient μ0 between the die and the foam material > the friction coefficient μ1 between the die and the liner body, the friction coefficient μ2 between the foam material and the liner body < the friction coefficient μ3 between the foam material and the anti-slip layer, and the friction coefficient μ3 between the foam material and the anti-slip layer > the friction coefficient μ1 between the die and the liner body, and a technique for suppressing the shrinkage of the coated foam material is disclosed by satisfying these conditions.

[0006] Also, in Patent Document 3, a resin pipe and a foam material sheet are continuously fed into a former, the foam material sheet is rolled up to surround the resin pipe, and after the side ends in the width direction of the foam material sheet are heated and melted, the side ends are fusion-bonded to each other in the former, and in a method for manufacturing a foam-coated pipe for continuously coating a resin pipe, a feeder for feeding the resin pipe at a constant speed before passing it through a cylindrical former, a first speedometer for measuring the feeding speed of the resin pipe between the feeder and the cylindrical former, and a second speedometer for measuring the feeding speed of the foam-coated pipe fed out from a take-up machine on the outer surface of the coating material are installed, and by making the difference between the speed of the foam-coated pipe measured by the second speedometer and the speed of the resin pipe measured by the first speedometer within 2%, a technique for suppressing the shrinkage of the coated foam material is disclosed.

[0007] Further, in Patent Document 4, a polyolefin-based resin foam having a dimensional change rate of 5% or less in absolute value at 140°C, which is produced by extruding a melt of a resin composition containing 20 to 80% by weight of a polyolefin-based resin having a melting point in the range of 140 to 180°C and 80 to 20% by weight of a thermoplastic elastomer having a melting point in the range of 140 to 180°C, a nucleating agent, and carbon dioxide as a foaming agent, is used as a heat insulating cover for a pipe.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0009] As described above, technologies for reducing the shrinkage rate of the foam-coated portion of a foam-coated pipe are being developed. However, for example, in Patent Document 3, the reduced shrinkage rate of the foam-coated portion is still 4%, and the fact is that the true solution has not been achieved.

[0010] Further, technologies for improving the heat resistance and durability of resin pipes have also been developed as in Patent Document 1. However, when a hard resin pipe is used to improve the heat resistance and durability, there is also a problem that the shrinkage rate of the foam-coated portion with respect to the pipe becomes even larger.

[0011] Therefore, the main object of the present technology is to provide a technology capable of reducing the shrinkage rate of the foam-coated portion while maintaining the high quality of the resin pipe in a foam-coated pipe.

Means for Solving the Problems

[0012] In order to solve the above problems, the present inventor conducted intensive research and found that by using a resin pipe having a specific coefficient of kinetic friction and a foam sheet having a specific coefficient of kinetic friction, it was possible to reduce the shrinkage rate of the foam-coated portion while maintaining the quality of the resin pipe, and thus the present technology was completed.

[0013] That is, in the present technology, first, a foam-coated pipe in which the outer periphery of a resin pipe is coated with a foam sheet, wherein the coefficient of kinetic friction measured in accordance with JIS K7125:1999 of the resin pipe is 0.13 or more, and the coefficient of kinetic friction measured in accordance with JIS K7125:1999 of the surface of the foam sheet is 0.10 to 1.0, is provided. The foam-coated pipe according to the present technology, can be manufactured by covering the outer periphery of the resin pipe with a foam sheet and pulling it out in a state where both end portions in the width direction of the foam sheet are heat-sealed in a hollow die. In the manufacturing method of the foam-coated pipe according to the present technology, the feeding of the resin pipe and the foam sheet into the hollow die can be performed by pulling from the downstream of the hollow die.

Brief Description of the Drawings

[0014]

Figure 1

Embodiments for Carrying Out the Invention

[0015] Hereinafter, preferred embodiments for carrying out the present technology will be described. The embodiments described below show an example of a typical embodiment of the present technology, and any of the embodiments can be combined. Also, the scope of the present technology is not construed narrowly thereby.

[0016] 1. Foam-coated pipe The foam-coated pipe according to the present technology is a foam-coated pipe in which the outer periphery of a resin pipe is coated with a foam sheet. Details will be described below.

[0017] (1) Resin pipe [Coefficient of kinetic friction] The resin pipe used in the present technology is characterized in that the coefficient of kinetic friction is 0.13 or more. When the coefficient of kinetic friction of the resin pipe is less than 0.13, when manufacturing the foam-coated pipe, the friction between the resin pipe and the foam sheet described later becomes too small, and the coated portion formed of the foam sheet is easily stretched. As a result, the shrinkage rate of the foam-coated portion of the manufactured foam-coated pipe becomes high. On the other hand, in the present technology, by using a resin pipe with a coefficient of kinetic friction of 0.13 or more, an appropriate friction is generated between the resin pipe and the foam sheet. Therefore, the elongation rate of the coated portion during the manufacture of the foam-coated pipe is reduced, and as a result, the shrinkage rate of the foam-coated portion of the manufactured foam-coated pipe is successfully reduced.

[0018] The lower limit of the coefficient of kinetic friction of the resin pipe used in the present technology can sufficiently exhibit the effects of the present technology as long as it is 0.13 or more, but preferably 0.14 or more, more preferably 0.15 or more, still more preferably 0.16 or more, even more preferably 0.17 or more, and particularly preferably 0.18 or more. By setting the lower limit of the coefficient of kinetic friction of the resin pipe used in the present technology within this range, the shrinkage rate of the foam-coated portion of the foam-coated pipe can be further reduced, contributing to the reduction of the process of cutting the exposed resin pipe and the reduction of material loss.

[0019] The upper limit of the coefficient of kinetic friction of the resin pipe used in the present technology can be freely set as long as the functions and effects of the present technology are not impaired. As the upper limit of the coefficient of kinetic friction of the resin pipe, for example, it is 0.5 or less, preferably 0.3 or less, and more preferably 0.25 or less. By setting the upper limit of the coefficient of kinetic friction of the resin pipe used in the present technology within this range, when manufacturing the foamed coating pipe, it is possible to prevent the peeling of the fused portion of the foamed sheet due to excessive friction between the resin pipe and the foamed sheet described later.

[0020] In the present technology, the coefficient of kinetic friction of the resin pipe is a value measured in accordance with JIS K7125:1999.

[0021] [Tensile yield strength] The tensile yield strength of the resin pipe used in the present technology is not particularly limited as long as the functions and effects of the present technology are not impaired. For example, it is 15 MPa or more, preferably 17 MPa or more, and more preferably 20 MPa or more. If the resin pipe has a tensile yield strength within this range, it can sufficiently meet the durability needs in various applications. The upper limit of the tensile yield strength of the resin pipe is not particularly limited in the present technology and can be, for example, 35 MPa or less.

[0022] In the present technology, the tensile yield strength of the resin pipe is a value measured in accordance with JIS K6769:2014.

[0023] [Degree of crosslinking] The degree of crosslinking of the resin pipe used in the present technology is not particularly limited as long as the functions and effects of the present technology are not impaired. For example, it is 50% or more, preferably 60% or more, and more preferably 65% or more. If the resin pipe has a degree of crosslinking within this range, it can sufficiently meet the durability needs in various applications. The upper limit of the degree of crosslinking of the resin pipe is not particularly limited in the present technology and can be, for example, 90% or less.

[0024] In the present technology, the degree of crosslinking of the resin pipe is a value measured in accordance with JIS K6769:2014.

[0025] [Hot internal pressure creep test] The resin pipe used in this technology preferably has a time to failure of 800 hours or more, more preferably 900 hours or more, and even more preferably 1000 hours or more in the hot internal pressure creep test conducted at 90°C. If the resin pipe has a result in the hot internal pressure creep test within this range, it can sufficiently meet the heat resistance needs in various applications.

[0026] In this technology, the hot internal pressure creep test of the resin pipe is a test conducted in accordance with JIS K6769:2014.

[0027] [Inner diameter] The inner diameter of the resin pipe used in this technology can be freely set as long as the functions and effects of this technology are not impaired. The lower limit of the inner diameter of the resin pipe is, for example, 10 mm or more, preferably 13 mm or more, more preferably 14 mm or more, and even more preferably 15 mm or more. By setting the lower limit of the inner diameter of the resin pipe within this range, the moldability can be improved.

[0028] The upper limit of the inner diameter of the resin pipe is, for example, 80 mm or less, preferably 70 mm or less, and more preferably 65 mm or less. By setting the inner diameter of the resin pipe within this range, the resin pipe can have an appropriate thickness, and the heat resistance and durability can be improved.

[0029] [Outer diameter] The outer diameter of the resin pipe used in this technology can be freely set as long as the functions and effects of this technology are not impaired. The lower limit of the outer diameter of the resin pipe used in this technology is, for example, 30 mm or more, preferably 35 mm or more, more preferably 45 mm or more, and even more preferably 50 mm or more. By setting the lower limit of the outer diameter of the resin pipe used in this technology within this range, the resin pipe used in this technology can have an appropriate thickness, and the heat resistance and durability can be improved.

[0030] The upper limit of the outer diameter of the resin pipe is, for example, 100 mm or less, preferably 90 mm or less, more preferably 80 mm or less. By setting the outer diameter of the resin pipe within this range, the moldability can be improved.

[0031] [Thickness] The thickness of the resin pipe used in the present technology can be freely set as long as the functions and effects of the present technology are not impaired. In the present technology, the lower limit of the thickness of the resin pipe is, for example, 2 mm or more, preferably 3 mm or more, more preferably 4 mm or more. By setting the lower limit of the thickness of the resin pipe within this range, the heat resistance and durability can be improved.

[0032] The upper limit of the thickness of the resin pipe is, for example, 20 mm or less, preferably 17 mm or less, more preferably 15 mm or less. By setting the thickness of the resin pipe within this range, the moldability can be improved.

[0033] [Raw material] The resin pipe used in the present technology is characterized by its physical properties, and its raw material is not particularly limited as long as the functions and effects of the present technology are not impaired. The raw materials used for the production of general resin pipes can be freely combined in one kind or two or more kinds to produce a resin pipe.

[0034] For example, the resin pipe used in the present technology can be produced by crosslinking and forming into a cylindrical shape a resin composition for producing a resin pipe (hereinafter also referred to as "the resin composition") containing a resin component, a crosslinking agent, a catalyst, and other components as required. Hereinafter, the components of the resin composition for producing a resin pipe used in the present technology will be described in detail.

[0035] (A) Resin component As the resin component that can be used in the resin composition, one or more common resins that can be used in resin pipes can be freely selected and used within the range that does not impair the object and effects of the present technology. For example, thermoplastic resins such as polyolefin-based resins, polystyrene-based resins, polyamide-based resins, and polyester-based resins; thermoplastic elastomers such as olefin-based thermoplastic elastomers and styrene-based thermoplastic elastomers; synthetic rubbers such as ethylene-propylene rubber (EPDM), and thermosetting elastomers such as natural rubber can be mentioned. Among these, in the present technology, it is preferable to use polyolefin-based resins or olefin-based thermoplastic elastomers.

[0036] The polyolefin-based resin that can be used in the present technology is a resin mainly composed of olefin component units. A resin mainly composed of olefin component units is a resin containing 50% by mass or more of olefin component units. In the present technology, the content of olefin component units in the resin is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and it is particularly preferable that the resin component is composed only of polyolefin-based resins.

[0037] The olefin-based thermoplastic elastomer that can be used in the present technology is a thermoplastic elastomer having a polyolefin-based resin as a hard segment and a rubber component as a soft segment.

[0038] Examples of the polyolefin-based resin that can be used in the present technology include polyethylene-based resins, polypropylene-based resins, polybutene, polypentene, and copolymers of olefin-based monomers and monomers copolymerizable with the olefin-based monomers. These can also be used alone or in combination of two or more.

[0039] Examples of the polyethylene resin include homopolymers of ethylene such as high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and very-low-density polyethylene (VLDPE); ethylene-propylene random copolymers, ethylene-propylene block copolymers, ethylene-butene block copolymers, ethylene-butene random copolymers, ethylene-vinyl acetate copolymers (EVA), and ethylene-methyl methacrylate copolymers.

[0040] Examples of the polypropylene resin include homopolymers of propylene such as isotactic polypropylene, syndiotactic polypropylene, and atactic polypropylene; propylene-ethylene random copolymers, propylene-ethylene block copolymers, propylene-butene random copolymers, propylene-butene block copolymers, propylene-ethylene-butene terpolymers, propylene-acrylic acid copolymers, and propylene-maleic anhydride copolymers.

[0041] Among these, it is preferable to use a polyethylene resin such as high-density polyethylene (HDPE) for the resin pipe used in this technology.

[0042] In addition, in this technology, a resin derived from biomass can also be used as part or all of the resin component. In this technology, the resin derived from biomass refers to a renewable resin made from animals and plants excluding fossil fuels such as petroleum.

[0043] The resin used in this technology may contain a recycled resin regenerated from waste such as the resin moldings described above. In this technology, the recycled resin is a resin produced from a resin composition that has been crosslinking-depolymerized using a general method. That is, in this technology, the recycled resin is not simply a resin pulverized product obtained by pulverizing a used resin molding or the like, but a resin in a crosslinking-depolymerized state obtained by performing pulverization, shearing, melt-kneading, etc. on a used resin molding or the like.

[0044] (B) Crosslinking agent The resin pipe used in this technology is preferably a crosslinked product. By performing crosslinking during the production of the resin pipe used in this technology, heat resistance and durability can be improved.

[0045] The resin pipe used in this technology can be crosslinked by irradiation with ionizing radiation, or can also be chemically crosslinked using a crosslinking agent. As the crosslinking agent that can be used in this technology, one or more crosslinking agents that can be used in the production of resin pipes can be freely selected and used as long as the objectives and effects of this technology are not impaired.

[0046] Examples of the crosslinking agent that can be used in this technology include crosslinking agents having chemical structures such as silane groups, peroxides, hydroxyl groups, amide groups, and ester groups. Among these, in this technology, it is preferable to use a silane coupling agent or an organic peroxide as the crosslinking agent.

[0047] Examples of the silane coupling agent include vinyltrimethoxysilane, vinyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, tris-(trimethoxysilylpropyl)isocyanurate, and the like. Among these, in this technology, it is preferable to use vinyltrimethoxysilane as the crosslinking agent.

[0048] Examples of the organic peroxide include dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, di-t-butyl peroxide, di-t-butylperoxy-3,3,5-trimethylcyclohexane, and t-dibutyl hydroperoxide. Among these, in this technology, it is preferable to use 2,5-dimethyl-2,5-di(t-butylperoxy)hexane as the crosslinking agent.

[0049] The amount of the crosslinking agent used in the production of the resin pipe used in this technology can be freely set as long as the functions and effects of this technology are not impaired. In this technology, as the content of the crosslinking agent relative to 100 parts by mass of the resin component in the resin composition, for example, it is 0.2 part by mass or more, preferably 0.4 part by mass or more, and more preferably 0.6 part by mass or more. By setting the content of the crosslinking agent in the resin composition within this range, the degree of crosslinking can be improved, and the mechanical properties such as heat resistance and durability of the produced resin pipe can be improved.

[0050] In this technology, as the content of the crosslinking agent relative to 100 parts by mass of the resin component in the resin composition, for example, it is 4.0 parts by mass or less, preferably 3.0 parts by mass or less, and more preferably 2.0 parts by mass or less. By setting the content of the crosslinking agent in the resin composition within this range, the moldability can be improved.

[0051] (C) Catalyst In the production of the resin pipe used in this technology, a catalyst can be used. As the catalyst that can be used in this technology, as long as the functions and effects of this technology are not impaired, one or more catalysts that can be used in the production of the resin pipe can be freely selected and used.

[0052] Examples of the catalyst include metal-based catalysts (organometallic catalysts) such as tin compounds (dibutyltin dilaurate, dibutyltin diacetate, dibutyltin dioctate, dioctyltin dilaurate, tin(II) octoate, stannous acetate, tin naphthenate, etc.), iron compounds (iron acetylacetonate, etc.), nickel compounds (nickel acetylacetonate, nickel octoate, nickel naphthenate, etc.), bismuth compounds (bismuth octoate, bismuth naphthenate, etc.), lead compounds (lead octoate, lead naphthenate, etc.), cobalt compounds (cobalt acetylacetonate, cobalt octoate, cobalt naphthenate, etc.), zirconium compounds (zirconium acetylacetonate, etc.), zinc compounds, etc.; amine-based catalysts such as triethylamine, triethylenediamine (TEDA), tetramethylguanidine, diethanolamine, bis(2-dimethylaminoethyl) ether, N,N,N′,N″,N″-pentamethyldiethylenetriamine, imidazole-based compounds, piperazine-based amines such as dimethylpiperazine, N-methyl-N'-(2-dimethylamino)ethylpiperazine, N-methyl-N'-(2-hydroxyethyl)piperazine, morpholine-based amines such as N-methylmorpholine, N-ethylmorpholine, and amines such as 1,8-diazabicyclo-[5,4,0]-undecene-7 (DBU), 1,5-diazabicyclo-[4,3,0]-nonene-5 (DBN), 1,8-diazabicyclo-[5,3,0]-decene-7 (DBD), 1,4-diazabicyclo-[3,3,0]octene-4 (DBO) which are referred to as DBU homologues. Among these, in this technology, it is preferable to use a metal-based catalyst, and among the metal-based catalysts, it is more preferable to use a tin compound.

[0053] The amount of the catalyst in the resin composition used for manufacturing the resin pipe used in the present technology can be freely set as long as the functions and effects of the present technology are not impaired. In the present technology, the lower limit of the catalyst content in the resin composition is, for example, 0.01 part by mass or more, preferably 0.05 part by mass or more, more preferably 0.1 part by mass or more, based on 100 parts by mass of the resin component. By setting the lower limit of the catalyst content in the resin composition within this range, the crosslinking reaction during manufacturing can be promoted to improve the degree of crosslinking. As a result, mechanical properties such as heat resistance and durability of the manufactured resin pipe can be improved.

[0054] In the present technology, the upper limit of the catalyst content in the resin composition is, for example, 3.0 parts by mass or less, preferably 2.0 parts by mass or less, more preferably 1.0 part by mass or less, based on 100 parts by mass of the resin component. By setting the upper limit of the catalyst content in the resin composition within this range, destabilization of various reactions during manufacturing can be prevented. As a result, a resin pipe with excellent mechanical properties and appearance can be obtained.

[0055] In the present technology, the catalyst can be used as a masterbatch in which the catalyst is dispersed in the above-described resin component. By using the catalyst masterbatch, the dispersibility in the resin component can be improved.

[0056] (D) Other components For manufacturing the resin pipe used in the present technology, as long as the objects and effects of the present technology are not impaired, as other components, various components that can be used for manufacturing the resin pipe can be freely selected and used one kind or two or more kinds according to the purpose.

[0057] Examples of the components that can be used for manufacturing the resin pipe used in the present technology include inorganic fillers, flame retardants, stabilizers, plasticizers, colorants, antioxidants, dispersants, ultraviolet absorbers, and the like.

[0058] [Manufacturing method] The resin pipe used in this technology is characterized by its physical properties, and its manufacturing method is not particularly limited as long as the functions and effects of this technology are not impaired. A general resin pipe manufacturing method can be freely combined with one or more types to manufacture a resin pipe.

[0059] In this technology, it is preferable to perform extrusion molding. Specifically, for example, a resin as a raw material and, if necessary, additives such as a crosslinking agent and a catalyst are supplied to an extruder, heated and mixed to prepare a molten resin composition, introduced into an annular die provided on the downstream side of the extruder, and extruded from the tip of the annular die, whereby a resin pipe can be manufactured.

[0060] (2) Foamed sheet [Coefficient of kinetic friction] The foamed sheet used in this technology is characterized in that the coefficient of kinetic friction of its surface is 0.10 to 1.0. When the coefficient of kinetic friction of the foamed sheet is less than 0.10, when manufacturing a foamed-coated pipe, the friction between the resin pipe and the foamed sheet becomes too small, and the coated portion formed by the foamed sheet is easily stretched. As a result, the shrinkage rate of the foamed-coated portion of the manufactured foamed-coated pipe becomes high. On the other hand, in this technology, by using a foamed sheet with a coefficient of kinetic friction of 0.10 or more, an appropriate friction occurs between the resin pipe and the foamed sheet. Therefore, the elongation rate of the foamed-coated portion when manufacturing a foamed-coated pipe is reduced, and as a result, the shrinkage rate of the foamed-coated portion of the manufactured foamed-coated pipe is successfully reduced.

[0061] In addition, when the coefficient of kinetic friction of the foam sheet exceeds 1.0, the friction with the inner surface of the hollow die used to thermally fuse both ends in the width direction of the foam sheet increases when manufacturing the foam-coated pipe. As a result, the coated portion formed of the foam sheet is easily stretched, and the shrinkage rate of the foam-coated portion of the manufactured foam-coated pipe becomes high. On the other hand, in the present technology, by using a foam sheet with a coefficient of kinetic friction of 1.0 or less, the friction between the foam-coated portion and the inner surface of the hollow die can be reduced. Therefore, the elongation rate of the foam-coated portion when manufacturing the foam-coated pipe is reduced, and as a result, the shrinkage rate of the foam-coated portion of the manufactured foam-coated pipe is successfully reduced.

[0062] If the lower limit of the coefficient of kinetic friction of the foam sheet used in the present technology is 0.10 or more, the effects of the present technology can be sufficiently exhibited. Preferably, it is 0.15 or more, more preferably 0.20 or more, still more preferably 0.25 or more. By setting the lower limit of the coefficient of kinetic friction of the resin pipe used in the present technology within this range, the shrinkage rate of the foam-coated portion of the foam-coated pipe can be reduced, contributing to the reduction of the process of cutting the exposed resin pipe and the reduction of material loss.

[0063] If the upper limit of the coefficient of kinetic friction of the foam sheet used in the present technology is 1.0 or less, the effects of the present technology can be sufficiently exhibited. Preferably, it is 0.9 or less, more preferably 0.8 or less, still more preferably 0.7 or less, even more preferably 0.6 or less, and particularly preferably 0.5 or less. By setting the upper limit of the coefficient of kinetic friction of the foam sheet used in the present technology within this range, the shrinkage rate of the foam-coated portion of the foam-coated pipe can be further reduced, contributing to the reduction of the process of cutting the exposed resin pipe and the reduction of material loss.

[0064] In the present technology, the coefficient of kinetic friction of the foam sheet is a value measured in accordance with JIS K7125:1999.

[0065] [25% Compressive Stress Strain] The 25% compression stress strain of the foam sheet used in the present technology is not particularly limited as long as the functions and effects of the present technology are not impaired. For example, it is 15 kPa or more, preferably 20 kPa or more, more preferably 25 kPa or more. A foam sheet with a 25% compression stress strain within this range has an appropriate hardness, so when heat-sealing both ends in the width direction of the foam sheet during the production of the foam-coated pipe, it can prevent the foam sheet from deforming and improve the heat-sealing property.

[0066] The upper limit of the 25% compression stress strain of the foam sheet used in the present technology is not particularly limited as long as the functions and effects of the present technology are not impaired. For example, it is 70 kPa or less, preferably 60 kPa or less, more preferably 50 kPa or less. A foam sheet with a 25% compression stress strain within this range has an appropriate softness, so it can improve the heat-sealing property when heat-sealing both ends in the width direction of the foam sheet during the production of the foam-coated pipe.

[0067] In the present technology, the 25% compression stress strain of the foam sheet is a value measured in accordance with JIS K6767:1999.

[0068] [Density] The density of the foam sheet used in the present technology is not particularly limited as long as the functions and effects of the present technology are not impaired. For example, it is 10 kg / m 3 or more, preferably 15 kg / m 3 or more, more preferably 20 kg / m 3 or more. A foam sheet with a density within this range has an appropriate hardness, so when heat-sealing both ends in the width direction of the foam sheet during the production of the foam-coated pipe, it can prevent the foam sheet from deforming and improve the heat-sealing property.

[0069] The upper limit of the density of the foam sheet used in the present technology is not particularly limited as long as the functions and effects of the present technology are not impaired. For example, it is 60 kg / m 3 or less, preferably 55 kg / m 3 or less, more preferably 50 kg / m 3The following is the case. Since the foam sheet having a density within this range has appropriate softness, the fusibility when heat-sealing both end portions in the width direction of the foam sheet during the production of the foam-coated pipe can be improved.

[0070] In addition, in this technology, the density of the foam sheet is a value measured in accordance with JIS K6767:1999.

[0071] [Raw materials] The foam sheet used in this technology is characterized by its physical properties, and the raw materials thereof are not particularly limited as long as the functions and effects of this technology are not impaired. The raw materials used for the production of general foam sheets can be freely combined in one kind or two or more kinds to produce a foam sheet.

[0072] For example, the foam sheet used in this technology can be produced by crosslinking and foaming a foamable resin composition for producing a foam sheet (hereinafter also referred to as "the foamable resin composition") containing a resin component, a foaming agent, a crosslinking agent, and other components as required, and then molding it into a sheet shape. Hereinafter, the components of the foamable resin composition for producing the foam sheet used in this technology will be described in detail.

[0073] (A) Resin component As the resin component that can be used in the foamable resin composition, one kind or two or more kinds of general resins that can be used in the foam sheet can be freely selected and used within the range that does not impair the purpose, functions, and effects of this technology. Since the specific examples of the resin component are the same as the resins that can be used for the resin pipes described above, the description is omitted here.

[0074] For the foam sheet used in this technology, it is preferable to use polyethylene-based resins such as high-density polyethylene (HDPE), low-density polyethylene (LDPE), and ethylene-vinyl acetate copolymer (EVA).

[0075] (B) Foaming agent The foaming resin composition for producing the foam sheet used in the present technology can contain a foaming agent. As the foaming agent that can be used in the present technology, one or more foaming agents that can be used in the foam sheet can be freely selected and used as long as the effects and functions of the present technology are not impaired.

[0076] In the present technology, either a physical foaming agent or a chemical foaming agent can be used. Examples of chemical foaming agents include organic chemical foaming agents and inorganic chemical foaming agents, and examples of physical foaming agents include inorganic physical foaming agents and organic physical foaming agents. In the present technology, any of them can be used.

[0077] Examples of organic chemical foaming agents include azo compounds such as azodicarbonamide (ADCA), metal salts of azodicarboxylic acid (such as barium azodicarboxylate), azobisisobutyronitrile (AIBN), nitroso compounds such as N,N'-dinitrosopentamethylenetetramine (DPT), hydrazodicarbonamide, hydrazine derivatives such as 4,4’-oxybis(benzenesulfonylhydrazide), toluenesulfonylhydrazide (TSH), semicarbazide compounds such as toluenesulfonyl semicarbazide, and the like.

[0078] Examples of inorganic chemical foaming agents include ammonium carbonate, sodium carbonate, ammonium bicarbonate, sodium bicarbonate, ammonium nitrite, sodium borohydride, monosodium anhydrous citrate, and the like.

[0079] Examples of inorganic physical foaming agents include nitrogen, carbon dioxide, oxygen, air, water, etc. Examples of organic physical foaming agents include aliphatic hydrocarbons such as isobutane, propane, normal butane, normal pentane, isopentane, normal hexane, isohexane, alicyclic hydrocarbons such as cyclopentane, cyclohexane, chlorinated hydrocarbons such as methyl chloride, ethyl chloride, fluorinated hydrocarbons such as 1,1,1,2 - tetrafluoroethane, 1,1 - difluoroethane, ethers such as dimethyl ether, methyl ethyl ether, and alcohols such as methanol, ethanol. In this technology, among these, it is preferable to use isobutane.

[0080] Among these, for the foam sheet used in this technology, it is preferable to use an organic foaming agent, and among the organic foaming agents, it is preferable to use azodicarbonamide (ADCA).

[0081] The amount of the foaming agent in the foam resin composition used for manufacturing the foam sheet used in this technology can be freely set as long as the functions and effects of this technology are not impaired. In this technology, the lower limit of the content of the foaming agent in the foam resin composition is, for example, 0.7 parts by mass or more, preferably 2.0 parts by mass or more, more preferably 4.0 parts by mass or more, based on 100 parts by mass of the resin component. By setting the content of the foaming agent in the foamable resin composition within this range, the foamability during the production of the foam sheet can be improved, and the physical properties of the produced foam sheet can be improved.

[0082] In this technology, the upper limit of the content of the foaming agent in the foam resin composition is, for example, 25 parts by mass or less, preferably 20 parts by mass or less, more preferably 15 parts by mass or less, based on 100 parts by mass of the resin component. By setting the content of the foaming agent in the foamable resin composition within this range, it is possible to suppress formation defects due to excessive foaming and also contribute to cost reduction.

[0083] In this technology, the foaming agent can be used as a masterbatch in which the foaming agent is dispersed in the resin component described above. By using the foaming agent masterbatch, the dispersibility in the resin component can be improved.

[0084] (C) Crosslinking agent The foam sheet used in this technology is preferably a crosslinked body. By performing crosslinking during the production of the foam sheet used in this technology, the viscosity of the foamable resin composition (kneaded product) before foaming can be improved, and the foamability can be improved. In addition, the physical properties of the produced foam sheet can be improved. Specific examples of the crosslinking method of the foam sheet used in this technology and specific examples of the crosslinking agent are the same as the crosslinking methods and crosslinking agents that can be used for the resin pipe described above, so the description is omitted here.

[0085] During the production of the foam sheet used in this technology, it is preferable to select a method of chemically crosslinking using a crosslinking agent. As the crosslinking agent to be used, it is preferable to use an organic peroxide, and among the organic peroxides, it is more preferable to use dicumyl peroxide.

[0086] The amount of the crosslinking agent used in the production of the foam sheet used in this technology can be freely set as long as the functions and effects of this technology are not impaired. In this technology, as the content of the crosslinking agent with respect to 100 parts by mass of the resin component in the foamable resin composition, for example, it is 0.2 parts by mass or more, preferably 0.4 parts by mass or more, and more preferably 0.6 parts by mass or more. By setting the content of the crosslinking agent in the foamable resin composition within this range, the viscosity of the foamable resin composition (kneaded product) before foaming can be improved, and the foamability can be improved. In addition, the mechanical properties such as heat resistance and durability of the produced foam sheet can be improved.

[0087] In this technology, the content of the crosslinking agent with respect to 100 parts by mass of the resin component in the foaming resin composition is, for example, 4.0 parts by mass or less, preferably 3.0 parts by mass or less, more preferably 2.0 parts by mass or less. By setting the content of the crosslinking agent in the foaming resin composition within this range, it is possible to prevent tearing or the like from occurring during foaming and improve the moldability.

[0088] (D) Other components For the production of the foam sheet used in this technology, as long as the object and effect of this technology are not impaired, as other components, various components that can be used in the production of the foam sheet can be freely selected and used singly or in combination of two or more according to the purpose.

[0089] Examples of the components that can be used in the production of the foam sheet used in this technology include a foaming aid, a crosslinking accelerator, an inorganic filler, a foam stabilizer, a flame retardant, a stabilizer, a plasticizer, a coloring agent, an antioxidant, a dispersant, an ultraviolet absorber, and the like.

[0090] [Production method] The foam sheet used in this technology is characterized by its physical properties, and its production method is not particularly limited as long as the action and effect of this technology are not impaired. A general production method of a foam sheet can be freely combined singly or in combination of two or more to produce a foam sheet.

[0091] In this technology, it is preferable to perform extrusion molding. Specifically, for example, a resin as a raw material and, if necessary, additives such as a crosslinking agent are supplied to an extruder and heated and mixed, and then a foaming agent is press-fitted and further kneaded to prepare a foaming resin composition. The prepared foaming resin composition is extruded from the extruder into a sheet shape in the atmosphere and further heated and foamed in an oven or the like to produce a foam sheet.

[0092] (3) Relationship between the coefficient of kinetic friction of the resin pipe and the coefficient of kinetic friction of the surface of the foam sheet If the dynamic friction coefficient of the resin pipe and the dynamic friction coefficient of the surface of the foam sheet are within the ranges described above, the effects of the present technology can be fully exhibited. However, it is preferable that the dynamic friction coefficient of the surface of the foam sheet is larger than the dynamic friction coefficient of the resin pipe.

[0093] Furthermore, it is more preferable that the relationship between the dynamic friction coefficient of the resin pipe and the dynamic friction coefficient of the surface of the foam sheet satisfies the following. Dynamic friction coefficient of resin pipe ≥ 1 / 2 × Dynamic friction coefficient of surface of foam sheet

[0094] By satisfying any of the above relationships between the dynamic friction coefficient of the resin pipe and the dynamic friction coefficient of the surface of the foam sheet, the shrinkage rate of the foam-coated portion of the foam-coated pipe can be further reduced, contributing to the reduction of the process of cutting the exposed resin pipe and the reduction of material loss.

[0095] (4) Shrinkage rate of the foam-coated portion with respect to the foam-coated pipe The foam-coated pipe according to the present technology is characterized in that the shrinkage rate of the foam-coated portion formed of the foam sheet with respect to the foam-coated pipe is low. The specific shrinkage rate is not limited as long as the functions and effects of the present technology are not impaired. For example, it is 4.0% or less, preferably 3.5% or less, and more preferably 3.0% or less. When the shrinkage rate of the foam-coated portion is within this range, it can contribute to the reduction of the process of cutting the exposed resin pipe and the reduction of material loss.

[0096] (5) Tensile strength of the heat-sealed portion of the foam-coated portion The tensile strength of the heat-sealed portion of the foam-coated portion formed of the foam sheet can be freely set according to the use of the foam-coated pipe and the like. For example, it is 10 N or more, preferably 12 N or more, and more preferably 15 N or more. When the tensile strength of the heat-sealed portion is within this range, the opening of the heat-sealed portion can be more reliably prevented, and the heat insulation performance and the like can be further improved.

[0097] The upper limit of the tensile strength of the heat-sealed portion is not particularly limited, but it can be set to, for example, 30 N or less.

[0098] In the present technology, the tensile strength of the heat-sealed portion is a value measured by the method described in the examples below.

[0099] 2. Method for manufacturing a foamed-coated pipe The method for manufacturing a foamed-coated pipe according to the present technology is a method for manufacturing a foamed-coated pipe by pulling out while covering the outer periphery of a resin pipe with a foamed sheet and heat-sealing both end portions in the width direction of the foamed sheet in a hollow die.

[0100] More specifically, while bending the foamed sheet into a cylindrical shape along the outer periphery of the resin pipe, the resin pipe and the foamed sheet are fed into a hollow die, and immediately before entering the hollow die, both end portions in the width direction of the foamed sheet are heated and melted, and both end portions are heat-sealed in the hollow die, thereby covering the outer periphery of the resin pipe with the foam. By pulling out the foamed-coated pipe in this state, the foamed-coated pipe can be manufactured.

[0101] The foamed-coated pipe and the foamed coating portion are not adhered to the resin pipe. Therefore, when pulling out the foamed-coated pipe from the hollow die during manufacturing, the foamed coating portion, which is softer than the resin pipe, may be stretched. Therefore, by using the resin pipe having the above-described coefficient of kinetic friction and the foamed sheet having the surface with the above-described coefficient of kinetic friction, the elongation rate of the coating portion during the manufacture of the foamed-coated pipe can be reduced, and as a result, the shrinkage rate of the foamed coating portion of the manufactured foamed-coated pipe can be reduced.

[0102] Feeding the resin pipe and the foam sheet into the hollow die from the upstream of the hollow die and controlling the feeding speed of the resin pipe and the foam sheet into the hollow die can also reduce the elongation rate of the coated portion when manufacturing the foam-coated pipe. In this technology as well, it is possible to adopt a method of feeding the resin pipe and the foam sheet into the hollow die from the upstream of the hollow die. However, in this technology, by using the resin pipe having the above-described coefficient of kinetic friction and the foam sheet having the surface with the above-described coefficient of kinetic friction, even when the feeding of the resin pipe and the foam sheet into the hollow die is performed by a method of pulling from the downstream of the hollow die, the elongation rate of the coated portion when manufacturing the foam-coated pipe can be reduced, and as a result, the shrinkage rate of the foam-coated portion of the manufactured foam-coated pipe can be reduced. By performing the feeding of the resin pipe and the foam sheet into the hollow die by a method of pulling from the downstream of the hollow die, it is not necessary to install a feeder, a speed measuring device, etc. upstream of the hollow die, and in addition to downsizing the apparatus and simplifying the manufacturing process, it is also possible to contribute to cost reduction in manufacturing.

Example

[0103] Hereinafter, the present technology will be described in more detail based on examples. Note that the examples described below show an example of typical examples of the present technology, and the scope of the present technology is not construed narrowly thereby.

[0104] (1) Manufacture of resin pipe The resin and raw materials shown in Table 1 below were supplied to a blender and heated and kneaded to prepare a molten resin composition. The prepared molten resin composition was supplied to an extruder, further introduced into an annular die provided on the downstream side of the extruder, and extruded from the lip portion at the tip of the annular die to manufacture a resin pipe.

[0105] (2) Measurement of physical properties, etc. of resin pipe [Tensile yield strength] The tensile yield strength of the manufactured resin pipe was measured in accordance with JIS K6769:2014.

[0106] [Coefficient of kinetic friction] Regarding the coefficient of kinetic friction of the surface portion of the manufactured resin pipe, a resin flat plate was manufactured using the same raw materials and the same method as the resin pipe, and the coefficient of kinetic friction of the manufactured resin flat plate was determined by measuring it in accordance with JIS K7125:1999.

[0107] [Hot internal pressure creep test] For the manufactured resin pipe, a hot internal pressure creep test was conducted at 90 °C in accordance with JIS K6769:2014. The time until rupture was 1000 hours or more was considered qualified, and less than 1000 hours was considered unqualified.

[0108] [Degree of crosslinking] Regarding the degree of crosslinking of the manufactured resin pipe, it was measured in accordance with JIS K6769:2014. A degree of crosslinking of 65% or more was considered qualified, and less than 65% was considered unqualified.

[0109]

Table 1

[0110] (3) Manufacture of the foam sheet The raw materials shown in Table 2 below were introduced into an extruder, melt-kneaded, and then extruded in a sheet form through a die attached to the tip of the extruder. The extruded sheet-like resin composition was heated in an oven to cause foaming, thereby producing a foam sheet with a thickness of 5 mm.

[0111] (4) Measurement of physical properties, etc. of the foam sheet [25% Compression stress strain] The 25% compression stress strain on the surface of the produced foam sheet was measured in accordance with JIS K6767:1999.

[0112] [Coefficient of kinetic friction] The coefficient of kinetic friction on the surface of the produced foam sheet was measured in accordance with JIS K7125:1999.

[0113] [Density] The density on the surface of the produced foam sheet was measured in accordance with JIS K6767:1999.

[0114]

Table 2

[0115] (5) Production of the foam-coated pipe Using the combination of the resin pipe and the foam sheet shown in Table 3 below, while covering the outer circumference of the resin pipe produced above with the foam sheet produced above, the foam-coated pipe was produced by pulling it out in a state where both end portions in the width direction of the foam sheet were heat-sealed inside a hollow die.

[0116] (6) Evaluation The shrinkage rate and fusion property of the foam-coated part formed of the foam sheet on the manufactured foam-coated pipe were evaluated by the following methods.

[0117] [Shrinkage rate] After the foam-coated pipe manufactured above was cured at 23°C for 1 day, the ratio of the shrinkage length of the foam sheet covering the resin pipe surface to the unit length of the resin pipe was defined as the shrinkage rate.

[0118] [Fusion property] After the foam-coated pipe manufactured above was cured at 23°C for 1 day, the foam sheet part covering the resin pipe surface was cut into 25-mm discs (see the dashed line part in Fig. 1A), the side opposite to the fused part was cut (see the dashed line part in Fig. 1B), and a tensile test was carried out with a tensile speed of 100 mm / min and a grip distance of 40 mm using a tensile testing machine. If the result of the tensile test was 15 N or more, it was evaluated as ○; if it was less than 15 N, it was evaluated as ×. In Fig. 1, the parts shown in light ink are the fused parts.

[0119] (7) Results The results are shown in Table 3 below.

[0120]

Table 3

[0121] (8) Discussion For the foam-coated pipes of Examples 1 to 4 manufactured using resin pipes 1 to 3 with a dynamic friction coefficient of 0.13 or more and foam sheet A or B with a surface dynamic friction coefficient of 0.10 to 1.0, both the shrinkage rate and the fusion property showed excellent results. On the other hand, in Comparative Example 1 using foam sheet C with a surface dynamic friction coefficient exceeding 1.0, the evaluation of the shrinkage rate was good, but the evaluation of the fusion property was inferior. In Comparative Examples 2 and 3 using resin pipes 4 or 5 with a dynamic friction coefficient of less than 0.13, although the evaluation of the fusion property was good, the shrinkage rate was high.

Claims

1. A foamed-coated pipe in which the outer circumference of a resin pipe is coated with a foamed sheet, wherein the coefficient of kinetic friction measured in accordance with JIS K7125:1999 of the resin pipe is 0.13 or more, and the coefficient of kinetic friction measured in accordance with JIS K7125:1999 of the surface of the foamed sheet is 0.10 to 1.

0.

2. A method for manufacturing the foamed-coated pipe according to Claim 1, which comprises drawing out while covering the outer circumference of a resin pipe with a foamed sheet and heat-sealing both end portions in the width direction of the foamed sheet in a hollow die.

3. The method for manufacturing the foamed-coated pipe according to Claim 2, wherein the resin pipe and the foamed sheet are fed into the hollow die by taking them out from the downstream of the hollow die.

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