Resin pipe, method for manufacturing the same, connection method, and connection structure of resin pipe

Abstract

To provide a resin pipe excellent in identifiability and appearance.SOLUTION: A resin pipe to be connected to an electro-fusion fitting, comprising: a cylindrical main body; and at least one identification layer integrally formed on an outer surface of the main body and extending in a pipe axis direction of the main body, wherein a color tone of the identification layer is different from a color tone of the main body, and the identification layer is not provided in a portion in contact with the electro-fusion fitting when the resin pipe is connected to the electro-fusion fitting. The first plastic of the body and the second plastic of the discrimination layer are preferably the same or different by one type as shown in the appendix of JISK6922 1:1997.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a resin pipe, a method for manufacturing the same, a connecting method, and a connecting structure for a resin pipe. [Background technology]

[0002] Conventionally, plastic pipes such as polyethylene pipes (polyethylene plastic pipes) have been widely used for a wide variety of purposes, including water pipes and gas pipes. For this reason, plastic pipes are color-coded according to their intended use. As the number of uses for plastic pipes increases, the colors of each pipe tend to become similar even when trying to distinguish them by color tone alone. This creates a problem in that it becomes difficult to distinguish the purpose of a plastic pipe by appearance. It is particularly difficult to distinguish the purpose of a plastic pipe by color tone in dark places.

[0003] To address these issues, for example, Patent Document 1 discloses a plastic pipe with a line-shaped marking layer molded integrally with the outer surface of the body. This marking layer contains a luminescent material and a metallic material. By providing an identification layer such as a marking layer, the invention of Patent Document 1 makes the plastic pipe more visible in dark places and detectable by a metal detector. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-188757 Summary of the Invention [Problem to be solved by the invention]

[0005] However, simply forming an identification layer such as a line-shaped marking layer on the outer surface of the body can result in distortion of the identification layer, resulting in a poor appearance. Furthermore, the identification layer is prone to peeling off from the body. Peeling off of the identification layer from the body can damage the appearance of the plastic pipe. Therefore, an object of the present invention is to provide a polyethylene resin pipe that is excellent in identifiability and appearance. [Means for solving the problem]

[0006] To form an identification layer on the outer surface of the main body, a resin pipe can be manufactured by co-extrusion molding. As a result of extensive investigations, the present inventors have made the following findings. If the resin of the main body and the resin of the identification layer flow differently in the mold of the co-extrusion molding machine, the thickness and width of the identification layer will be uneven, making it difficult to achieve a smooth surface. In addition, the resin of the main body and the resin of the identification layer will be less compatible, making it easy for the identification layer to peel off from the main body. The present invention has been completed based on the above findings and has the following aspects.

[0007] <1> A resin pipe to be connected to an electric fusion joint, The container comprises a cylindrical body and one or more discrimination layers integrally formed on an outer surface of the body and extending in a tube axis direction of the body, The color tone of the identification layer is different from the color tone of the main body, A resin pipe that does not have the discrimination layer in a portion that comes into contact with the electrofusion joint when connected to the electrofusion joint. <2> The first resin constituting the main body and the second resin constituting the discrimination layer are the same or different by one class as shown in the appendix of JIS K 6922-1:1997. <1> The resin pipe described in <3> The thickness d2 of the discrimination layer is 0.02 mm or more and 2.0 mm or less. <1> or <2> The resin pipe described in <4> The ratio (d2 / d1) of the thickness d2 of the identification layer to the thickness d1 of the main body is 3.0×10 -6 Over 3.0 x 10 - 2 Below is the <1> ~ <3> The resin pipe according to any one of the preceding items. <5> <1> ~ <4> A method for manufacturing a resin pipe according to any one of the above, A method for manufacturing a resin pipe, wherein the main body and the discrimination layer are formed by co-extrusion molding. <6> <1> ~ <4> A method for connecting a resin pipe and an electric fusion joint according to any one of the above, a connecting method in which the discrimination layer is removed by cutting, and then the resin tube is connected to the electric fusion joint. <7> <1> ~ <4> A resin pipe connection structure comprising the resin pipe according to any one of the above and the electric fusion joint. The present invention also has the following aspects. [1] A cylindrical body and one or more discrimination layers integrally formed on the outer surface of the body and extending in the axial direction of the body; A polyethylene resin pipe, wherein a first resin constituting the main body and a second resin constituting the discrimination layer satisfy any one of the following (1), (2), and (3): (1) The first resin and the second resin are low-density polyethylene. (2) The first resin and the second resin are medium density polyethylene. (3) The first resin and the second resin are high-density polyethylene. [2] The polyethylene resin pipe according to [1], wherein the first resin and the second resin are of the same type or one type different as shown in Appendix Table 2 of JIS K 6922-1:1997. [3] A method for producing a polyethylene resin pipe according to [1] or [2], wherein the main body and the discrimination layer are formed by co-extrusion molding. [Effects of the Invention]

[0008] The polyethylene resin pipe of the present invention has excellent distinguishability and appearance. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view of a polyethylene resin pipe according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Polyethylene resin pipe] The polyethylene resin pipe of the present invention (hereinafter, sometimes simply referred to as a resin pipe) comprises a cylindrical main body and a discrimination layer formed on the outer surface of the main body. Hereinafter, a polyethylene resin pipe according to one embodiment will be described with reference to the drawings.

[0011] The resin pipe 1 in FIG. 1 includes a cylindrical main body 10 and four discrimination layers 20. The discrimination layer 20 is located on the outer surface of the main body 10. The discrimination layer 20 is strip-shaped. The discrimination layer 20 extends in the tube axis O1 direction of the main body 10. The discrimination layer 20 is formed integrally with the main body 10. As shown in FIG. 2, the four discrimination layers 20 are positioned in an annular shape at 90° intervals around the tube axis O1 of the main body 10.

[0012] The length of the main body 10 is determined depending on the application of the resin pipe 1, and is preferably, for example, 2 m or more and 10 m or less. The length of the main body 10 is the distance from one open end to the other open end. The inner diameter R1 of the main body 10 is determined depending on the application of the resin pipe 1, and is preferably, for example, 10 mm or more and 600 mm or less. The thickness d1 of the main body 10 (that is, the length in the radial direction of the resin pipe 1) is determined depending on the use of the resin pipe 1, and is preferably, for example, 1 mm or more and 50 mm or less.

[0013] The color tone of the main body 10 is not particularly limited and is determined appropriately depending on the application and purpose.

[0014] The first resin constituting the main body 10 is polyethylene. The content of polyethylene in the main body 10 is 100 parts by mass relative to 100 parts by mass of the resin. Polyethylene is a homopolymer of ethylene (homopolyethylene), a copolymer of ethylene with up to 5 mol% of 1-olefin monomers, or a copolymer of ethylene with up to 1 mol% of non-olefin monomers whose functional groups contain only carbon, hydrogen, and hydrogen atoms.

[0015] The first resin may be low-density polyethylene, medium-density polyethylene, or high-density polyethylene. Among these, high-density polyethylene is preferred as the first resin. The types of polyethylene are shown in Annex Tables 1 and 2 of JIS K 6922-1:1997. Low-density polyethylene meets the requirements of any of Class 1, Category 1 to Category 6 in Annex 2. The density of low-density polyethylene is 910 kg / m 3 More than 930kg / m 3 is less than. Medium density polyethylene meets the requirements of any of Class 2, Class 1 to Class 5 in Annex 2. The density of medium density polyethylene is 930 kg / m 3 More than 942kg / m 3 is less than. High density polyethylene meets the requirements of any of Class 3, Class 1 to Class 5 in Annex 2. The density of high density polyethylene is 942 kg / m 3 That's all. As shown in Annex Tables 1 and 2, types of polyethylene are classified by a combination of "type" and "class," such as "●type●class."

[0016] The melt flow rate (MFR) of the first resin is, for example, preferably 0.01 g / 10 min or more and 200 g / 10 min or less, more preferably 0.1 g / 10 min or more and 100 g / 10 min or less, even more preferably 0.2 g / 10 min or more and 50 g / 10 min or less, and particularly preferably 0.3 g / 10 min or more and 10 g / 10 min or less. The melt flow rate (MFR) of the first resin is a value measured in accordance with 4.1 (melt flow rate) of Appendix 1 of JIS K 6922-2:2010 at a test temperature of 190°C and a test load of 21.18N.

[0017] The tensile strength of the first resin is preferably 5.9 MPa or more, more preferably 19.6 MPa or more, and even more preferably 25 MPa or more. The upper limit of the tensile strength of the first resin is usually 100 MPa. The tensile strength of the first resin is a value measured in accordance with 4.3 (tensile test) of the appendix of JIS K 6922-2:2010.

[0018] The tensile elongation at break of the first resin is preferably 100% or more, more preferably 350% or more, and even more preferably 500% or more. The upper limit of the tensile elongation at break of the first resin is usually 1200%. The tensile elongation at break of the first resin is a value measured in accordance with 4.3 (tensile test) of the appendix of JIS K 6922-2:2010.

[0019] The durometer hardness of the first resin is 30H D D or higher is preferable, 60H D D or higher is more preferable, 65H D The upper limit of the durometer hardness of the first resin is usually 200H D It's D. The durometer hardness of the first resin is a value measured in accordance with 4.4 (Durometer D hardness test) of Appendix 1 of JIS K 6922-2:2010.

[0020] The Vicat softening point of the first resin is preferably 65°C or higher, more preferably 90°C or higher, and even more preferably 100°C or higher. The upper limit of the Vicat softening point of the first resin is usually 150°C. The Vicat softening point of the first resin is a value measured in accordance with JIS K 6922-2:2010, Appendix 4.5 (Vicat softening point test).

[0021] The mass average molecular weight of the first resin is 0.5×10 5 Over 10.0 x 10 5 Less than 1.5 x 10 is preferable. 5 Over 3.0 x 10 5 The following is more preferable: If the mass average molecular weight is within the above range, the fluidity of the resin becomes appropriate, and productivity can be increased. The mass average molecular weight of the first resin is measured in accordance with JIS K 7252-1:2008.

[0022] The number average molecular weight of the first resin is 0.1×10 4 Over 2.0 x 10 4Less than 0.5 x 10 is preferable. 4 Over 1.0 x 10 4 The following is more preferable: If the number average molecular weight is within the above range, the fluidity of the resin becomes appropriate, and productivity can be increased. The number average molecular weight of the first resin is measured in accordance with JIS K 7252-1:2008.

[0023] The glass transition point of the first resin is preferably −140° C. or higher and −90° C. or lower, and more preferably −120° C. or higher and −100° C. If the glass transition point is within the above range, the resin has appropriate fluidity, which increases productivity. The glass transition point of the first resin is a value measured by a differential scanning calorimeter (DSC).

[0024] The melting point of the first resin is preferably 110° C. or higher and 130° C. or lower, and more preferably 120° C. or higher and 125° C. or lower. If the melting point is within the above range, the resin has appropriate fluidity, which increases productivity. The melting point of the first resin is a value measured by a differential scanning calorimeter (DSC).

[0025] The crystallinity of the first resin is preferably 60% to 80%, more preferably 65% ​​to 70%. If the crystallinity is within the above range, the resin has appropriate fluidity, which increases productivity. The crystallinity of the first resin is a value measured by DSC.

[0026] The pencil hardness of the first resin is preferably HB or more and 7B or less, and more preferably HB or more and 6B or less. If the pencil hardness is within the above range, the resin is less susceptible to scratches and the appearance can be further improved. The pencil hardness of the first resin is a value measured in accordance with JIS K 5600-5-4:1999.

[0027] The content of the first resin is preferably 90% by mass or more and 99.99999% by mass or less with respect to the total mass of the main body 10.

[0028] The body 10 may contain additives such as colorants, antioxidants, ultraviolet absorbers (UVA), hindered amine light stabilizers (HALS), and the like. The content of the additive in the main body 10 is determined taking into consideration the type of additive. The content of the additive per 100 parts by mass of the first resin is 1.0×10 -5 Parts by mass or more and 10 parts by mass or less are preferred, and 1.0 × 10 -3 Parts by mass or more and 1.0 parts by mass or less are more preferable.

[0029] The length of the identification layer 20 is the same as the length of the main body 10. The length of the identification layer 20 may be the same as or different from the length of the main body 10. The length of the identification layer 20 is preferably the same as the length of the main body 10.

[0030] The width w2 of the identification layer 20 (i.e., the length in the circumferential direction of the resin pipe 1) is determined appropriately depending on the purpose of the identification layer 20, and is, for example, 2 mm to 50 mm, and preferably 4 mm to 40 mm. Furthermore, the ratio of the width w2 to the outer circumference of the resin pipe 1 (the circumferential length around the pipe axis O1) (w2 ratio) is, for example, 5% to 30%, and preferably 7% to 25%. If the width w2 is equal to or greater than the above-mentioned lower limit, the identification layer 20 is easy to see. If the width w2 is equal to or less than the above-mentioned upper limit, the color tone of the main body 10 is easy to see in a side view. The w2 ratio is calculated by [width w2 of the discrimination layer 20]÷[circumferential length of the resin pipe 1]×100.

[0031] The thickness d2 of the identification layer 20 (i.e., its length in the radial direction of the plastic pipe 1) is determined appropriately according to the thickness d1 of the main body 10, and is preferably, for example, 0.02 mm or more and 2.0 mm or less, and more preferably 0.1 mm or more and 0.5 mm or less. If the thickness d2 is equal to or greater than the above-mentioned lower limit, the strength of the identification layer 20 can be increased. If the thickness d2 is equal to or greater than the above-mentioned lower limit, the color tone of the identification layer 20 can be easily distinguished regardless of the color darkness of the identification layer 20. If the thickness d2 is equal to or less than the above-mentioned upper limit, the thickness of the main body 10 is not too thin at the position of the identification layer 20, and the strength of the main body 10 can be increased. If the thickness d2 is equal to or less than the above-mentioned upper limit, the identification layer 20 is removed by cutting the surface of the plastic pipe 1 when connecting with an electric fusion joint, and it is easy to confirm that cutting has been performed. The thickness ratio, d2 / d1, is 3.0 x 10 -6 Over 3.0 x 10 -2 Less than 3.0 x 10 is preferred -5 Over 3.0 x 10 -3 The following is more preferred:

[0032] The color tone of the identification layer 20 is not particularly limited, but is preferably different from the color tone of the main body 10. When the color tone of the identification layer 20 is different from the color tone of the main body 10, a striped pattern appears on the outer periphery of the plastic pipe 1. Furthermore, by combining the colors of the identification layer 20 and the main body 10, the color coding variations of the plastic pipe 1 are increased.

[0033] The second resin constituting the discrimination layer 20 is a polyethylene resin. The content of the polyethylene resin in the discrimination layer 20 is 100 parts by mass relative to 100 parts by mass of the resin. The second resin species is the same as the first resin species. That is, the first resin and the second resin satisfy any one of the following conditions (1), (2), and (3). (1) The first resin and the second resin are low-density polyethylene. (2) The first resin and the second resin are medium density polyethylene. (3) The first resin and the second resin are high-density polyethylene. That is, the first resin and the second resin are the same "type" of polyethylene in Annex Table 2 of JIS K 6922-1:1997. Since the first resin and the second resin are of the same type, they are easily compatible with each other, and therefore the discrimination layer 20 adheres closely to the main body 10. In addition, if the first resin and the second resin are the same type, the fluidity of both resins will be equivalent. This makes the discrimination layer 20 less likely to warp. Furthermore, since the fluidity of the first resin and the second resin is equivalent, the surface of the discrimination layer 20 will be as smooth as the surface of the main body 10. This will result in a good appearance of the resin pipe 1.

[0034] The first resin and the second resin preferably have the same "type" or a difference of one type in Appendix Table 2 of JIS K 6922-1:1997. For example, if the first resin is Type 3, Type 1, the second resin is preferably Type 3, Type 1 or Type 1, Type 2. Furthermore, if the first resin is Type 3, Type 3, the second resin is preferably Type 3, Type 2, Type 3, Type 3, or Type 3, Type 4. In particular, it is preferable that the first resin and the second resin have the same "type" and "type."

[0035] The MFR of the second resin is the same as that of the first resin. The difference between the MFR of the second resin and the MFR of the first resin is preferably 0 g / 10 min or more and 1 g / 10 min or less, more preferably 0 g / 10 min or more and 0.3 g / 10 min or less. If the difference in MFR between the first resin and the second resin is within the above range, the appearance of the identification layer 20 can be made better.

[0036] The tensile strength of the second resin is the same as that of the first resin. The difference between the tensile strength of the second resin and that of the first resin is preferably 0 MPa or more and 10 MPa or less, more preferably 0 MPa or more and 5 MPa or less. If the difference in tensile strength between the first resin and the second resin is within the above range, the appearance of the identification layer 20 can be made better.

[0037] The tensile elongation at break of the second resin is the same as that of the first resin. The difference between the tensile elongation at break of the second resin and the tensile elongation at break of the first resin is preferably 0% or more and 100% or less, and more preferably 0% or more and 50% or less. If the difference in tensile elongation at break between the first resin and the second resin is within the above range, the appearance of the discrimination layer 20 can be made better.

[0038] The durometer hardness of the second resin is the same as the durometer hardness of the first resin. The difference between the durometer hardness of the second resin and the durometer hardness of the first resin is 0H. D D or more 30H D D or lower is preferable, 0H D D or more 15H D D or lower is more preferable. If the difference in durometer hardness between the first resin and the second resin is within the above range, the appearance of the identification layer 20 can be made better.

[0039] The Vicat softening point of the second resin is the same as that of the first resin. The difference between the Vicat softening points of the second resin and the first resin is preferably 0° or more and 10°C or less, more preferably 0° or more and 5°C or less. If the difference in Vicat softening point between the first resin and the second resin is within the above range, the appearance of the discrimination layer 20 can be made better.

[0040] The mass average molecular weight of the second resin is the same as that of the first resin. The difference between the mass average molecular weight of the second resin and the mass average molecular weight of the first resin is 0 to 1.0 × 10 3 The following is preferable, 0 to 0.5 × 10 3 The following is more preferred: If the difference in mass average molecular weight between the first resin and the second resin is within the above range, the appearance of the discrimination layer 20 can be made better.

[0041] The number average molecular weight of the second resin is the same as that of the first resin. The difference between the number average molecular weight of the second resin and the number average molecular weight of the first resin is 0 to 1.0 × 10 3 The following is preferable, 0 to 0.5 × 10 3 The following is more preferred: If the difference in number average molecular weight between the first resin and the second resin is within the above range, the appearance of the discrimination layer 20 can be made better.

[0042] The glass transition point of the second resin is the same as that of the first resin, and the difference between the glass transition points of the second resin and the first resin is preferably 0°C or higher and 10°C or lower, more preferably 0°C or higher and 5°C or lower. If the difference in glass transition point between the first resin and the second resin is within the above range, the appearance of the identification layer 20 can be made better.

[0043] The melting point of the second resin is the same as that of the first resin, and the difference between the melting points of the second resin and the first resin is preferably 0°C or higher and 10°C or lower, more preferably 0°C or higher and 5°C or lower. If the difference in melting point between the first resin and the second resin is within the above range, the appearance of the identification layer 20 can be made better.

[0044] The crystallinity of the second resin is the same as that of the first resin, and the difference between the crystallinity of the second resin and that of the first resin is preferably 0% or more and 10% or less, and more preferably 0% or more and 5% or less. If the difference in crystallinity between the first resin and the second resin is within the above range, the appearance of the identification layer 20 can be made better.

[0045] The pencil hardness of the second resin is the same as that of the first resin. The difference in pencil hardness between the second resin and the first resin is preferably 0 or more and 2B or less, more preferably 0 or more and 1B or less. If the difference in hardness between the first resin and the second resin is within the above range, the appearance of the identification layer 20 can be made better.

[0046] The content of the second resin relative to the total mass of the discrimination layer 20 is preferably 90% by mass or more and 99.99999% by mass or less.

[0047] The identification layer 20 may contain an additive. The additive contained in the identification layer 20 is the same as the additive contained in the main body 10. The additive in the main body 10 and the additive in the identification layer 20 may be the same or different. The content of the additive in the discrimination layer 20 is determined taking into consideration the type of additive. The content of the additive per 100 parts by mass of the second resin is 1.0 × 10 -5 Parts by mass or more and 10 parts by mass or less are preferred, and 1.0 × 10 -3 Parts by mass or more and 1.0 parts by mass or less are more preferable.

[0048] [Manufacturing method of resin pipes] The method for manufacturing the resin pipe 1 includes a step of forming the main body 10 and the discrimination layer 20 by co-extrusion molding. An example of a manufacturing device for the resin pipe 1 is a manufacturing device including an extrusion molding machine, a sizing die, a cooling tank, and a cutting machine. The extruder is a co-extrusion-capable extruder having at least two feed ports. The sizing die is a cylindrical member whose diameter decreases as it moves downstream. The cooling tank is a device that cools the reduced diameter resin pipe and hardens the resin. Examples of the cooling tank include a water-cooled cooling tank.

[0049] An example of a method for manufacturing a resin pipe using the above manufacturing apparatus will be described below. A first resin and, if necessary, additives (the first resin and additives may be collectively referred to as the first resin composition) are fed into one feed port of the extruder. A second resin and, if necessary, additives (the second resin and additives may be collectively referred to as the second resin composition) are fed into the other feed port of the extruder. The first resin composition is heated to a temperature above the melting point of the first resin and kneaded. The second resin composition is heated to a temperature above the melting point of the second resin and kneaded. The first resin composition and the second resin composition are then extruded into a cylindrical shape using the extruder. The first resin composition and the second resin composition flow through separate flow paths and then merge, with the second resin composition forming the discrimination layer 20. In this case, since the first resin and the second resin are the same "species," the first resin composition and the second resin composition have equivalent fluidity. Because the second resin composition flows in the same way as the first resin composition, distortion of the discrimination layer 20 is suppressed and the surface of the discrimination layer 20 is smooth. In addition, the first resin and the second resin are easily compatible with each other, making it difficult for the identification layer 20 to peel off from the main body 10 . As a result, a cylindrical molded body is obtained in which the discrimination layer 20 is integrally formed on the outer surface of the main body 10.

[0050] Next, the cylindrical molded body is inserted into a sizing die. As the cylindrical molded body passes through the sizing die, it becomes the desired diameter. The cylindrical molded body adjusted to the desired diameter is inserted into a cooling tank. The cooling tank cools the cylindrical molded body and hardens the resin. The hardened cylindrical molded body is cut to the desired length to form a resin pipe 1.

[0051] The heating temperature for the first resin composition in the extruder is, for example, preferably 170° C. or higher and 250° C. or lower, and more preferably 180° C. or higher and 220° C. or lower. When the heating temperature is within the above range, good fluidity can be obtained while suppressing thermal decomposition of the first resin. The heating temperature for the second resin composition in the extruder is the same as the heating temperature for the first resin composition.

[0052] The temperature of the cooling water in the cooling tank is preferably, for example, from 20° C. to 30° C. If the temperature of the cooling water is within the above range, the cylindrical molded body can be sufficiently cured.

[0053] The cylindrical molded body that has passed through the cooling tank is cut to a desired length by a cutter to form a resin pipe 1.

[0054] According to the resin pipe of this embodiment, the outer surface of the body is provided with a discrimination layer. In addition, the first resin and the second resin are the same type. Therefore, the resin pipe has excellent discrimination properties and appearance.

[0055] The present invention is not limited to the above-described embodiments. The above-described embodiment includes four identification layers. However, the present invention is not limited to this, and the number of identification layers may be three or less, or five or more. In particular, the number of identification layers is preferably four or more, more preferably four to eight, and even more preferably four to six, so that the identification layers can be seen from all angles.

[0056] In the above-described embodiment, the four discrimination layers are positioned at 90° intervals around the tube axis. That is, the four discrimination layers are equally spaced. However, the present invention is not limited to this, and the intervals between the discrimination layers may be different. However, it is preferable that the discrimination layer is positioned so that it can be seen when the resin pipe is rotated around the pipe axis.

[0057] In the above-described embodiment, the linear band-shaped identification layer extends over the entire length of the body (from one open end to the other open end). However, the present invention is not limited to this, and each identification layer may be a broken line. Furthermore, the identification layer may be non-linear, such as wavy or zigzag. However, from the viewpoint of increasing the fluidity of the second resin in the extruder and obtaining a more aesthetically pleasing identification layer, a linear band-shaped identification layer is preferred. [Example]

[0058] (Raw materials used) Resin A: High-density polyethylene, type 3, category 1. Density: 942 kg / m 3 , MFR=0.39g / 10min, Durometer hardness=65H D D, Vicat softening point = 120°C. Resin B: High-density polyethylene, type 3, category 2. Density: 943 kg / m 3 , MFR=0.59g / 10min, Durometer hardness=80H D D, Vicat softening point = 125°C. Resin C: Medium density polyethylene, type 2, category 1. Density: 935 kg / m 3 , MFR=1.6g / 10min, Durometer hardness=50H D D, Vicat softening point = 100°C. Resin D: High-density polyethylene, type 3, category 1. Density: 950 kg / m 3 , MFR=0.11g / 10min, Durometer hardness=67H D D, Vicat softening point = 125°C. Resin E: High-density polyethylene, type 3, category 2. Density: 951 kg / m 3 , MFR=0.80g / 10min, Durometer hardness=62H D D, Vicat softening point = 122°C.

[0059] Examples 1 to 4 According to the description in Table 1, 100 parts by mass of the first resin and 7.0 × 10 -4 parts by mass and antioxidant 3.0 x 10 -4 parts by mass and ultraviolet absorber (UVA) 1.5 x 10 -4 The parts by weight were fed into an extruder. According to the description in Table 1, 100 parts by mass of the second resin and 7.0 × 10 -4 parts by mass and antioxidant 3.0 x 10 -4 parts by mass and ultraviolet absorber (UVA) 1.5 x 10 -4 The parts by weight were fed into an extruder. The supplied resin was melted at 190°C and extruded while kneading to obtain a cylindrical molded body. The cylindrical molded body was cooled with cooling water at 23°C for 60 minutes. The cooled cylindrical molded body was cut to obtain a resin tube with an inner diameter R1 of 87 mm, a length of 5 m, a thickness d1 of 13.3 mm, a thickness d2 of 0.1 mm, and a width w2 of 20 mm. The obtained resin tube had four linear discrimination layers. The appearance, creep properties and tensile strength of the obtained resin pipe were measured. The results are shown in Table 1.

[0060] (Comparative Example 1) A resin pipe was obtained in the same manner as in Example 1, except that Resin C was used as the resin constituting the discrimination layer. The appearance, creep properties and tensile strength of the obtained resin pipe were measured. The results are shown in Table 1.

[0061] (Evaluation method) <Appearance> The resin pipe of each example was visually inspected and evaluated according to the following evaluation criteria. <Evaluation Criteria> ◯: No cracks, bubbles or irregularities were observed on the surface of the resin pipe. ×: Cracks, bubbles or irregularities are observed on the surface of the resin pipe.

[0062] <Creep performance> Creep performance tests were conducted in accordance with the Japan Water Works Association standard JWWA K 144. For each example of resin pipe, a tubular test piece with a length at least three times the outer diameter of the resin pipe was cut and used as the sample. Both ends of the sample were fixed with a water pressure test jig or similar. Water was used as the test medium both inside and outside the test piece. The test was conducted using the test pressure calculated using equation (1).

[0063] P = 2σ / (SDR-1) (1) P: Test pressure (MPa). σ: Circumferential stress of the pipe (MPa).

[0064] The test temperature was 20°C (+3°C to -1°C) for room temperature internal pressure creep, and 80°C (±1°C) for hot internal pressure creep and long-term hot internal pressure creep. The test time was 100 hours for room temperature internal pressure creep, 165 hours for hot internal pressure creep, and 1000 hours for long-term hot internal pressure creep. Creep tests were conducted at the above test temperatures and test times. If no cracks or fractures occurred in any of the room temperature internal pressure creep, hot internal pressure creep, and long-term hot internal pressure creep tests (i.e., if no fractures occurred at each test temperature for longer than the test time), the test was marked with an "O"; if cracks or fractures occurred in any of the tests, the test was marked with an "X."

[0065] <Tensile strength> The tensile elongation at break of each resin pipe was determined in accordance with JIS K 6922-2, and the obtained values ​​were evaluated according to the following evaluation criteria. <Evaluation Criteria> ◯: Tensile elongation at break is 500% or more. △: Tensile elongation at break is 100% or more and less than 500%. ×: Tensile elongation at break is less than 100%.

[0066] [Table 1]

[0067] As shown in Table 1, Example 1 to which the present invention was applied was evaluated as "good" or "fair" in terms of appearance, creep performance, and tensile strength performance. On the other hand, Comparative Example 1, in which the first resin was Type 3, Class 1 and the second resin was Type 2, Class 1, was evaluated as "poor" in terms of appearance and creep performance. [Explanation of symbols]

[0068] 1 Polyethylene resin pipe 10 Main Unit 20 Identification Layer O1 tube shaft

Claims

1. A resin pipe to be connected to an electric fusion joint, The container comprises a cylindrical body and one or more discrimination layers integrally formed on an outer surface of the body and extending in a tube axis direction of the body, The color tone of the identification layer is different from the color tone of the main body, A resin pipe that does not have the discrimination layer in a portion that comes into contact with the electrofusion joint when connected to the electrofusion joint.

2. The first resin constituting the main body and the second resin constituting the discrimination layer are the same or different by one type according to the appendix of JIS K 6922-1:1997. The resin pipe according to claim 1.

3. The resin pipe according to claim 1 or 2, wherein the discrimination layer has a thickness d2 of 0.02 mm or more and 2.0 mm or less.

4. The ratio (d2 / d1) of the thickness d2 of the identification layer to the thickness d1 of the main body is 3.0 × 10 －６ Above 3.0 x 10 － ２ The resin pipe according to any one of claims 1 to 3, wherein:

5. A method for manufacturing a resin pipe according to any one of claims 1 to 4, A method for manufacturing a resin pipe, wherein the main body and the discrimination layer are formed by co-extrusion molding.

6. A method for connecting a resin pipe and an electric fusion joint according to any one of claims 1 to 4, a connecting method in which the discrimination layer is removed by cutting, and then the resin tube is connected to the electric fusion joint.

7. A resin pipe connection structure comprising the resin pipe according to any one of claims 1 to 4 and the electric fusion joint.

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