Resin pipe

Abstract

To provide a resin pipe that suppresses a decrease in mechanical strength on an outer peripheral side of a curved part.SOLUTION: A resin pipe 10 having a tubular fiber-reinforced resin layer 11 containing resin and fibers has a spiral molding mark centering on an axis of the resin pipe 10 on an inner surface 10a of the resin pipe 10. In a plan view of an arbitrary region of the resin pipe 10, when one of an axial direction of the resin pipe 10 is 0° and one of a direction perpendicular to the axial direction is 90° and the other is -90°, an angle θ1 on the acute angle side from among angles formed by the axial direction and the molding mark is more than 0° and less than 90° and an orientation angle θ2 of the fiber F which is an angle on the acute angle side from among angles formed by the axial direction and the fiber F, is oriented between 60° and 73° in an arbitrary region (α) of an outer surface 11b of the fiber-reinforced resin layer 11, and the resin pipe 10 is bent at an arbitrary angle θ3.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a resin pipe.

Background Art

[0002] Conventionally, in a synthetic resin bend pipe made of polyolefin obtained by secondary processing (for example, see Patent Document 1), a curved portion is formed by bending the middle portion by secondary molding. Therefore, on the outer peripheral side of the curved portion, the thickness of the resin bend pipe becomes thin, so that the performance such as mechanical strength is lowered as compared with the portions other than the curved portion. Further, a high-performance polyethylene pipe for air-conditioning piping (for example, see Patent Document 2) having higher strength than the above synthetic resin pipe contains glass fibers. In this high-performance polyethylene pipe for air-conditioning piping, at the time of secondary molding, the thickness on the outer peripheral side of the curved portion becomes thin, and the glass fibers on the outer peripheral side of the curved portion are stretched and torn, and the mechanical strength on the outer peripheral side of the curved portion may be lowered. Therefore, the above high-performance polyethylene pipe for air-conditioning piping could not be used in the field of high-pressure fire extinguishing and hot water supply piping.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the above synthetic resin bend pipe or the high-performance polyethylene pipe for air-conditioning piping is bent into a bend shape, the resin is stretched due to the stretching of the outer peripheral side of the bent portion, resulting in a decrease in the thickness of the outer peripheral side of the bent portion, or the glass fibers are cut, and the mechanical strength decreases on the outer peripheral side of the bent portion. Therefore, there has been a problem that the above synthetic resin bend pipe and the high-performance polyethylene pipe for air-conditioning piping cannot be used in the high-pressure fire extinguishing and hot water supply piping fields where high performance is required. In addition, the angles of the bend processing in the bend pipe include 11 1 / 4°, 22 1 / 2°, 45°, and 90°. In particular, when the angle is 90°, there has been a problem that the decrease in the mechanical strength on the outer peripheral side of the bent portion is significant as described above.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a resin pipe in which a decrease in mechanical strength on the outer peripheral side of a bent portion is suppressed.

Means for Solving the Problems

[0006] The present invention has the following aspects. [1] A resin pipe including a tubular fiber-reinforced resin layer containing a resin and fibers, having a spiral molding mark on the inner surface of the resin pipe with the axis of the resin pipe as the axis, and in a plan view of an arbitrary region of the resin pipe, when one of the axial directions of the resin pipe is set to 0°, one of the directions perpendicular to the axial direction is set to 90°, and the other is set to -90°, the acute angle θ1 of the angles formed by the axial direction and the molding mark is greater than 0° and less than 90°, and the orientation angle θ2 of the following fiber F, which is the acute angle of the angles formed by the axial direction and the following fiber F, is oriented at 60° or more and 73° or less in an arbitrary region (α) of the outer surface of the fiber-reinforced resin layer, and the resin pipe is bent at an arbitrary angle θ3. Fiber F: Let the average fiber diameter of the fiber itself be the average fiber diameter D. Let the distance in the length direction of each cross-section of the fiber observed in the cross-section along the axial direction of the fiber-reinforced resin layer be the distance L. Among the fibers observed in the cross-section along the axial direction of the fiber-reinforced resin layer, the fiber with the distance L being 2 times or more of the average fiber diameter D is defined as fiber F. [2] The resin pipe according to [1], wherein the angle θ3 is more than 0° and less than or equal to 90°. [3] The resin pipe according to [1] or [2], wherein the fiber is a glass fiber. [4] The resin pipe according to any one of [1] to [3], wherein at least one of the inner surface and the outer surface of the fiber-reinforced resin layer is coated with a resin layer containing a resin. [5] The resin pipe according to [4], wherein the resins contained in the fiber-reinforced resin layer and the resin layer are polyolefin resins.

Advantages of the Invention

[0007] According to the present invention, it is possible to provide a resin pipe in which a decrease in mechanical strength on the outer peripheral side of the curved portion is suppressed.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments of the resin pipe of the present invention will be shown and described. However, the present invention is not limited to the following embodiments.

[0010] FIG. 1 is a diagram showing a resin pipe according to an embodiment of the present invention. FIG. 1(a) is a cross-sectional view, FIG. 1(b) is a cross-sectional view along the line I-I shown in (a), and FIG. 1(c) is a plan view. FIG. 2 is a plan view showing a resin pipe according to an embodiment of the present invention. FIG. 3 is a diagram for explaining the orientation angle of the fibers in the fiber-reinforced resin layer of the resin pipe according to an embodiment of the present invention. FIG. 4 is a diagram for explaining the inclination angle of the spiral molding marks in the second resin layer of the resin pipe according to an embodiment of the present invention. In addition, the drawings used in the following description may, for the sake of clarity of their features, show the characteristic parts enlarged for convenience, and the dimensional ratios of each component may be different from the actual ones.

[0011] As shown in FIG. 1, the resin pipe 10 of the present embodiment includes a tubular fiber-reinforced resin layer 11 containing resin and fibers 14. In the resin pipe 10, the inner surface 11a of the fiber-reinforced resin layer 11 is covered with a resin layer 12 containing resin, and the outer surface 11b of the fiber-reinforced resin layer 11 is covered with a resin layer 13 containing resin. Further, as shown in FIG. 2, the resin pipe 10 has a bent portion 15 bent at an arbitrary angle θ3. In the present embodiment, the resin layer 12 disposed on the inner surface 11a of the fiber-reinforced resin layer 11 is also referred to as the "first resin layer 12", and the resin layer 13 disposed on the outer surface 11b of the fiber-reinforced resin layer 11 is also referred to as the "second resin layer 13". That is, the resin pipe 10 is a multilayer pipe including a first resin layer 12, a fiber-reinforced resin layer 11, and a second resin layer 13. In this example, the first resin layer 12 is the innermost layer (the innermost surface layer), and is the surface layer. The fiber-reinforced resin layer 11 is the intermediate layer. The second resin layer 13 is the outermost layer (the outermost surface layer), and is the surface layer. The first resin layer 12, the fiber-reinforced resin layer 11, and the second resin layer 13 are each tubular. In FIGS. 1(b) and (c), one fiber 14 is schematically shown.

[0012] As shown in FIG. 1(b), the resin pipe 10 has a spiral molding mark on the inner surface 10a with the axis of the resin pipe 10 as the axis. In the present embodiment, the inner surface 10a of the resin pipe 10 is the inner surface 12a of the first resin layer 12.

[0013] <Fiber-reinforced resin layer> The fiber-reinforced resin layer 11 contains resin and fibers 14. Among the fibers 14 included in the fiber-reinforced resin layer 11, the fibers that satisfy the following configuration are defined as "fiber F". Fiber F: Let the average fiber diameter of the fiber itself be the average fiber diameter D. Let the distance in the length direction of each cross-section of the fiber observed in the cross-section of the fiber-reinforced resin layer 11 along the axial direction of the resin pipe be the distance L. Among the fibers observed in the cross-section of the fiber-reinforced resin layer 11 along the axial direction, the fibers with the distance L being 2 times or more of the average fiber diameter D are defined as fiber F.

[0014] In the upper part of FIG. 3, among the fibers 14 included in the fiber-reinforced resin layer 11, the fibers 141 and 142 observed in the cross-section of the fiber-reinforced resin layer 11 along the axial direction of the resin pipe 10 are shown. The fiber 141 has one end 141a and the other end 141b. The fiber 141 is a fiber in which the distance L (the distance between one end 141a and the other end 141b) in the length direction in the cross-section of the fiber-reinforced resin layer 11 along the axial direction of the resin pipe 10 is 2 times or more of the average fiber diameter D of the fiber itself. That is, the fiber 141 is the above-mentioned fiber F. The fiber 142 has one end 142a and the other end 142b. The fiber 142 is a fiber in which the lengthwise distance L (the distance between the one end 142a and the other end 142b) in the cross-section of the fiber-reinforced resin layer 11 along the axial direction of the resin pipe 10 is less than twice the average fiber diameter D. The fiber 142 is different from the fiber F. The fiber 14 observed in the cross-section of the fiber-reinforced resin layer 11 along the axial direction of the resin pipe 10 can be classified into either one of the fiber 141 (fiber F) and the fiber 142.

[0015] In the lower part of FIG. 3, when any region of the fiber-reinforced resin layer 11 is viewed in plan, the axial direction and circumferential direction of the resin pipe 10, the spiral direction in the spiral-shaped molding mark, and the orientation angle of the fiber 14 included in the fiber-reinforced resin layer 11 are shown. X is the axial direction of the resin pipe 10. Y is the direction perpendicular to the axial direction X, that is, the circumferential direction of the resin pipe 10. L1 is the spiral direction in the spiral-shaped molding mark formed on the inner surface 10a of the resin pipe 10. The spiral direction in the spiral-shaped molding mark means the tangential direction with respect to the spiral-shaped molding mark in any region. L2 is the orientation direction of the fiber F. θ1 is the angle formed by the axial direction X and the molding mark, that is, the smaller of the two angles formed by the axial direction X and the spiral direction L1, and θ1 is defined as the inclination angle of the spiral-shaped molding mark formed on the inner surface 10a of the resin pipe 10. θ2 is the angle formed by the axial direction X and the fiber F, that is, the smaller of the two angles formed by the axial direction X and the orientation direction L2 of the fiber F, and θ2 is defined as the orientation angle of the fiber F.

[0016] As shown in FIG. 3, in a plan view of an arbitrary region of the resin pipe 10, when one of the axial directions X of the resin pipe 10 is set to 0°, one of the directions Y perpendicular to the axial direction is set to 90°, and the other is set to -90°, the acute angle of the angles formed by the axial direction and the molding marks, that is, the inclination angle θ1, is greater than 0° and less than 90°. Further, the orientation angle θ2 of the fiber F, which is the acute angle of the angles formed by the axial direction and the fiber F, is oriented at 60° or more and 73° or less in an arbitrary region (α) of the outer surface 11b of the fiber reinforced resin layer 11. The orientation angle θ2 is preferably 61° or more and 73° or less, and more preferably 67° or more and 73° or less, in an arbitrary region (α) of the outer surface 11b of the fiber reinforced resin layer 11. The spiral molding marks formed on the inner surface 10a of the resin pipe 10 will be described in the first resin layer 12.

[0017] The orientation angle θ2 of the fiber F can be controlled by adjusting the twist angle when twisting the multi-layer tubular body in the circumferential direction, the pulling speed of the tubular body, etc. in the manufacturing process of the resin pipe 10. For example, when the twist angle is increased, the orientation angle θ2 of the fiber F increases on the inner surface 11a and the outer surface 11b of the fiber reinforced resin layer 11, and tends to decrease at the center in the thickness direction of the fiber reinforced resin layer 11. When the orientation angle θ2 of the fiber F is 0°, the orientation direction L1 of the fiber F coincides with the axial direction X of the resin pipe 10. When the orientation angle θ2 of the fiber F is 90°, the orientation direction L1 of the fiber F coincides with the circumferential direction of the resin pipe 10 (the direction Y perpendicular to the axial direction X). When the orientation angle θ2 is 67° or more and 73° or less near the upper limit value of the angle, the inclination angle θ1 is preferably 65° or more and 80° or less, and the inclination angle θ4 described later is preferably 65° or more. When the orientation angle θ2 is 61° or more and 73° or less near the lower limit value of the angle, the inclination angle θ1 is preferably 60° or more and 80° or less, the inclination angle θ4 is preferably 60° or more, and the angle θ3 described later is preferably 61° or more.

[0018] The orientation angle θ2 of the fiber F can be obtained as follows. In an arbitrary region of the resin pipe 10, the resin pipe 10 is sliced axially from the outer surface 10b (the outer surface 13a of the second resin layer 13) until the outer surface 11b of the fiber-reinforced resin layer 11 is exposed, and a cross-section (arbitrary region (α)) obtained using a scanning electron microscope (SEM) is photographed. Using image analysis software, only the fibers F in which the distance L between one end and the other end is 2 times or more the average fiber diameter D of the fiber itself among the fibers photographed in the micrograph are selected, and the orientation angle θ2 is determined for each of the fibers F. In the measurement of the orientation angle θ2, for those in which the orientation rate of the fiber F is less than 50%, it is regarded as a defective product because the orientation angle θ2 is not oriented due to molding troubles or the like. Note that "until the outer surface 11b of the fiber-reinforced resin layer 11 is exposed" means until reaching a region within 1 mm from the outer surface 11b of the fiber-reinforced resin layer 11. "Until reaching the central part in the thickness direction of the fiber-reinforced resin layer 11" means until reaching a region within ±1 mm from the center in the thickness direction of the fiber-reinforced resin layer. "Until reaching the inner surface of the fiber-reinforced resin layer" means until reaching a region within 1 mm from the inner surface of the fiber-reinforced resin layer. Examples of the photographing conditions with a scanning electron microscope include conditions such as a vapor deposition thickness of 10 nm, an acceleration voltage of 15 kV, and a magnification of 25 times.

[0019] The thickness of the fiber-reinforced resin layer 11 is preferably 40% or more and 80% or less of the thickness of the resin pipe 10, and more preferably 50% or more and 70% or less. If the thickness of the fiber-reinforced resin layer 11 is equal to or greater than the above lower limit value, the pressure resistance of the resin pipe 10 can be further enhanced. In addition, the linear expansion coefficient of the resin pipe 10 becomes smaller. If the thickness of the fiber-reinforced resin layer 11 is equal to or less than the above upper limit value, the dimensional stability becomes even better. Note that the thickness of the fiber-reinforced resin layer 11 represents the average thickness, and the average thickness is calculated including the part where the molding marks exist.

[0020] Examples of the resin contained in the fiber reinforced resin layer 11 include polyolefin resins and vinyl chloride resins. Among these, from the viewpoints of further enhancing the pressure resistance of the resin pipe 10 and reducing the weight of the resin pipe 10, polyolefin resins are preferred.

[0021] Examples of the polyolefin resin include polyethylene, polypropylene, polybutene, ethylene-vinyl acetate copolymer, and ethylene-α-olefin copolymer. Among these, from the viewpoints of further enhancing the pressure resistance of the resin pipe 10 and reducing the weight of the resin pipe 10, polyethylene or polypropylene is preferably used. These polyolefin resins may be used alone or in combination of two or more.

[0022] The polyethylene may be low density polyethylene, linear low density polyethylene, high density polyethylene, or heat-resistant polyethylene (PE-RT). Examples of the polyethylene include a homopolymer of ethylene and a copolymer of a monomer containing ethylene. When the polyethylene is a copolymer, it may be a random copolymer or a block copolymer. Preferably, 50% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more of the total mass of all monomer units constituting the polyethylene are ethylene units.

[0023] Examples of the polypropylene include a homopolymer of propylene and a copolymer of a monomer containing propylene. When the polypropylene is a copolymer, it may be a random copolymer or a block copolymer. Preferably, 50% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more of the total mass of all monomer units constituting the polypropylene are propylene units.

[0024] Preferably, the resin content is 50% by mass or more, more preferably 65% by mass or more, based on the total mass of the fiber-reinforced resin layer 11. Also, preferably, the resin content is 90% by mass or less, more preferably 85% by mass or less, based on the total mass of the fiber-reinforced resin layer 11. If the resin content is within the above range, the pressure resistance of the resin pipe 10 can be further enhanced.

[0025] The fiber 14 contained in the fiber-reinforced resin layer 11 may be an inorganic fiber or an organic fiber. Only one type of fiber 14 may be used, or two or more types may be used in combination.

[0026] Examples of the inorganic fiber include glass fiber, carbon fiber, silicon-titanium-carbon composite fiber, boron fiber, metal fiber, basalt fiber, and the like. Examples of the organic fiber include aramid fiber, vinylon fiber, polyester fiber, polyamide fiber, and the like. Among these, from the viewpoint of further enhancing the pressure resistance of the resin pipe 10, glass fiber is preferable.

[0027] Preferably, the average fiber length of the fiber 14 is 100 μm or more, more preferably 200 μm or more, and even more preferably 300 μm or more. Also, preferably, the average fiber length of the fiber 14 is 15 mm or less, more preferably 1.5 mm or less, even more preferably 1 mm or less, and particularly preferably 500 μm or less. If the average fiber length of the fiber 14 is at least the above lower limit value, the pressure resistance of the resin pipe 10 can be further enhanced. If the average fiber length of the fiber 14 is at most the above upper limit value, the fiber 14 is likely to be arranged in a specific direction.

[0028] The average fiber diameter of the fiber 14 is preferably 5 μm or more, more preferably 7 μm or more, and even more preferably 10 μm or more. Also, the average fiber diameter of the fiber 14 is preferably 17 μm or less, more preferably 13 μm or less. If the average fiber diameter of the fiber 14 is at least the above lower limit value, the pressure resistance of the resin pipe 10 can be further enhanced. If the average fiber diameter of the fiber 14 is at most the above upper limit value, the fiber 14 is likely to be arranged in a specific direction.

[0029] The average fiber length and average fiber diameter of the fiber 14 can be determined as follows. First, in an arbitrary region of the resin pipe 10, the resin pipe 10 is sliced along the axial direction from the outer surface 10b until the fiber reinforced resin layer 11 is exposed. Next, the exposed fiber reinforced resin layer 11 is photographed using SEM, and the fiber length and fiber diameter of one fiber 14 are determined from the photographed micrograph. The fiber length and fiber diameter are measured for 5000 arbitrarily selected fibers 14, and the average values are calculated. Note that the "fiber length" is the distance between one end and the other end of the fiber 14 when the fiber 14 is made linear. "Until the fiber reinforced resin layer 11 is exposed" means until an arbitrary position in the thickness direction of the fiber reinforced resin layer 11 is reached. Examples of the photographing conditions with a scanning electron microscope include conditions such as a vapor deposition thickness of 10 nm, an acceleration voltage of 15 kV, and a magnification of 25 times.

[0030] The aspect ratio represented by the average fiber length of the fiber 14 / the average fiber diameter of the fiber is preferably 20 or more, more preferably 25 or more, and even more preferably 30 or more. Also, the aspect ratio is preferably 100 or less, more preferably 80 or less, even more preferably 70 or less, particularly preferably 50 or less, and most preferably 35 or less. If the aspect ratio is at least the above lower limit value, the pressure resistance of the resin pipe 10 can be further enhanced. If the aspect ratio is at most the above upper limit value, the fiber 14 is likely to be arranged in a specific direction.

[0031] With respect to the total mass of the fiber-reinforced resin layer 11, the content of the fiber 14 is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more. Also, with respect to the total mass of the fiber-reinforced resin layer 11, the content of the fiber 14 is preferably 40% by mass or less, and more preferably 30% by mass or less. If the content of the fiber 14 is within the above range, the pressure resistance of the resin pipe 10 can be further enhanced.

[0032] The fiber-reinforced resin layer 11 may contain various additives as necessary. Examples of the additives include compatibilizers, stabilizers, stabilization aids, lubricants, processing aids, impact modifiers, heat resistance improvers, antioxidants, ultraviolet absorbers, light stabilizers, fillers, pigments, plasticizers, and the like. Among these, compatibilizers are preferred. Only one kind of these additives may be used, or two or more kinds may be used in combination.

[0033] The compatibilizer is not particularly limited, and examples include maleic acid-modified polyolefin, silane-modified polyolefin, chlorinated polyolefin, and the like. Note that these compatibilizers are not included in the above polyolefin resin. Only one kind of these compatibilizers may be used, or two or more kinds may be used in combination.

[0034] The stabilizer is not particularly limited, and examples include heat stabilizers, heat stabilization aids, and the like. The heat stabilizer is not particularly limited, and examples include organotin-based stabilizers, lead-based stabilizers, calcium-zinc-based stabilizers, barium-zinc-based stabilizers, barium-cadmium-based stabilizers, and the like. Examples of the organotin-based stabilizer include dibutyltin mercapto, dioctyltin mercapto, dimethyltin mercapto, dibutyltin mercapto, dibutyltin maleate, dibutyltin maleate polymer, dioctyltin maleate, dioctyltin maleate polymer, dibutyltin laurate, dibutyltin laurate polymer, and the like. Only one kind of these heat stabilizers may be used, or two or more kinds may be used in combination.

[0035] The heat stabilizer is not particularly limited, and examples thereof include epoxidized soybean oil, phosphate ester, polyol, hydrotalcite, zeolite and the like. Only one kind of these heat stabilizers may be used, or two or more kinds may be used in combination.

[0036] The lubricant is not particularly limited, and examples thereof include internal lubricants and external lubricants. The internal lubricant is used for the purpose of reducing the flow viscosity of the molten resin during the molding process and preventing frictional heat generation. The internal lubricant is not particularly limited, and examples thereof include butyl stearate, lauryl alcohol, stearyl alcohol, epoxidized soybean oil, glycerin monostearate, stearic acid, bisamide and the like. The external lubricant is used for the purpose of enhancing the sliding effect between the molten resin and the metal surface during the molding process. The external lubricant is not particularly limited, and examples thereof include paraffin wax, polyolefin wax, ester wax, montanic acid wax and the like. Only one kind of these lubricants may be used, or two or more kinds may be used in combination.

[0037] The processing aid is not particularly limited, and examples thereof include acrylic processing aids and the like. Examples of the acrylic processing aid include alkyl acrylate-alkyl methacrylate copolymers having a mass average molecular weight of 100,000 to 2,000,000. Specific examples of the acrylic processing aid include n-butyl acrylate-methyl methacrylate copolymer, 2-ethylhexyl acrylate-methyl methacrylate-butyl methacrylate copolymer and the like. Only one kind of these processing aids may be used, or two or more kinds may be used in combination.

[0038] The impact modifier is not particularly limited, and examples thereof include methyl methacrylate-butadiene-styrene copolymer (MBS), chlorinated polyethylene, acrylic rubber and the like. Only one kind of these impact modifiers may be used, or two or more kinds may be used in combination.

[0039] The heat resistance improver is not particularly limited, and examples thereof include α-methylstyrene resins, N-phenylmaleimide resins, and the like. Only one kind of these heat resistance improvers may be used, or two or more kinds may be used in combination.

[0040] The antioxidant is not particularly limited, and examples thereof include phenolic antioxidants and the like. Only one kind of these antioxidants may be used, or two or more kinds may be used in combination.

[0041] The ultraviolet absorber is not particularly limited, and examples thereof include salicylic acid ester-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, and the like. Only one kind of these ultraviolet absorbers may be used, or two or more kinds may be used in combination.

[0042] The light stabilizer is not particularly limited, and examples thereof include hindered amine-based light stabilizers and the like. Only one kind of these light stabilizers may be used, or two or more kinds may be used in combination.

[0043] The filler is not particularly limited, and examples thereof include calcium carbonate, talc, and the like. Only one kind of these fillers may be used, or two or more kinds may be used in combination.

[0044] The pigment is not particularly limited, and examples thereof include organic pigments and inorganic pigments. Examples of the organic pigment include azo-based organic pigments, phthalocyanine-based organic pigments, perylene-based organic pigments, and dye lake-based organic pigments. Examples of the inorganic pigment include oxide-based inorganic pigments, molybdenum chromate-based inorganic pigments, sulfide / selenide-based inorganic pigments, and ferrocyanide-based inorganic pigments. Only one kind of these pigments may be used, or two or more kinds may be used in combination.

[0045] The plasticizer may be added for the purpose of enhancing the processability during molding. Since the addition of the plasticizer may reduce the heat resistance of the molded body, it is preferable that the amount of the plasticizer added be small. The plasticizer is not particularly limited, and examples thereof include dibutyl phthalate, di-2-ethylhexyl phthalate, di-2-ethylhexyl adipate, and the like. These plasticizers may be used alone or in combination of two or more.

[0046] <The first resin layer> The first resin layer 12 contains a resin. As shown in FIG. 1(b), the first resin layer 12 has a spiral molding mark on the inner surface 12a with the axis of the resin pipe 10 as the axis. The spiral molding mark in the first resin layer 12 is formed by a convex portion 12b extending in a spiral shape. The spiral molding mark in the first resin layer 12 is a molding mark that can be formed by twisting a multi-layered tubular body in the circumferential direction during the manufacturing process of the resin pipe 10, and is mainly generated by the unevenness derived from the wall thickness deviation of the resin pipe 10. The spiral molding mark in the first resin layer 12 is distinguishable by visual inspection. The first resin layer 12 may have a convex portion or the like that does not form a spiral molding mark on the inner surface 12a. In addition, in FIG. 1(a), the convex portion 12b is not shown.

[0047] The convex portion 12b is preferably a ridge and may also be in a band shape. In the first resin layer 12, the spiral molding marks may be continuous as a whole in the spiral direction or may be partially interrupted.

[0048] From the viewpoint of further enhancing the pressure resistance of the resin pipe 10, the average height of the convex portion 12b preferably exceeds 0 mm and is 2 mm or less, more preferably 1.5 mm or less, and even more preferably 1 mm or less. The average height of the convex portion 12b may exceed 2 mm, but the smaller the average height of the convex portion 12b, the more preferable.

[0049] The height of the convex portion 12b is measured at the maximum height position in the direction orthogonal to the spiral direction. The height of the convex portion 12b is measured only at the portion where the convex portion 12b is present. The average height of the convex portion 12b can be obtained, for example, by measuring the heights of the convex portion 12b at 50 or more positions arbitrarily selected at intervals in the spiral direction and calculating the average value. The height of the entire convex portion 12b may be measured and the average value may be calculated. The height of the convex portion 12b can be measured using a non-contact three-dimensional measuring machine.

[0050] FIG. 4 is a diagram for explaining the inclination angle of the spiral molding mark in the first resin layer 12. In the upper part of FIG. 4, a cross-sectional view of the first resin layer 12 along the line I-I shown in FIG. 1(a) is shown. Note that the fiber-reinforced resin layer 11 and the second resin layer 13 are not shown. In the lower part of FIG. 4, when any region of the first resin layer 12 is viewed in plan, the axial direction and the circumferential direction of the resin pipe 10, and the spiral direction in the spiral molding mark are shown. X is the axial direction of the resin pipe 10. Y is the direction perpendicular to the axial direction X, that is, the circumferential direction of the resin pipe 10. L1 is the spiral direction in the spiral molding mark formed on the inner surface 12a of the first resin layer 12 (that is, the inner surface 10a of the resin pipe 10). The spiral direction in the spiral molding mark means the tangential direction with respect to the spiral molding mark in an arbitrary region. θ1 is the angle formed by the axial direction X and the molding mark, that is, the smaller of the two angles formed by the axial direction X and the spiral direction L1, and θ1 is defined as the inclination angle of the spiral molding mark formed on the inner surface 12a of the first resin layer 12. When the spiral molding marks with the inclination angle θ1 are not uniform, it is considered that the molding conditions during molding are unstable and that molding has not been performed at a constant inclination angle θ1, and the product is regarded as a defective product.

[0051] As shown in FIG. 4, in a plan view of an arbitrary region of the first resin layer 12, when one of the axial directions X of the resin pipe 10 is set to 0°, one of the directions Y perpendicular to the axial direction is set to 90°, and the other is set to -90°, the inclination angle θ1 of the spiral molding mark is greater than 0° and less than 90°. This means that in a plan view of an arbitrary region of the first resin layer 12, the inclination angle θ1 of the spiral molding mark is positive. From the viewpoint of enhancing pressure resistance, the average value of the inclination angle θ1 of the spiral molding mark is preferably 40° or more and 80° or less, more preferably 60° or more and 80° or less, and even more preferably 65° or more and 80° or less. The closer the average value of the inclination angle θ1 of the spiral molding mark is to 65°, the more preferable it is. The inclination angle θ1 of the spiral molding mark can be controlled by adjusting the torsion angle when twisting the multilayer tubular body in the circumferential direction, the drawing speed of the tubular body, etc. in the manufacturing process of the resin pipe 10. For example, when the torsion angle is increased, the inclination angle θ1 of the spiral molding mark tends to increase. When the inclination angle θ1 is 65° or more and 80° or less near the upper limit value of the angle, the orientation angle θ2 is preferably 67° or more and 73° or less, and the inclination angle θ4 is preferably 65° or more. When the inclination angle θ1 is 60° or more and 80° or less near the lower limit value of the angle, the orientation angle θ2 is preferably 61° or more and 73° or less, the inclination angle θ4 is preferably 60° or more, and the angle θ3 is preferably 61° or more.

[0052] The inclination angle θ1 of the spiral molding mark and its average value can be obtained as follows. Draw a line horizontally from an arbitrary point on the inner surface 10a of the resin pipe 10 with respect to the axial direction of the resin pipe 10. Using this line as 0°, use a protractor with bendable flexibility to periodically measure the inclination angle θ1 of an arbitrary spiral molding mark. Measure the inclination angle θ1 every specified production volume (for example, 4 m), and calculate the average value.

[0053] The thickness of the first resin layer 12 is preferably 10% or more and 30% or less, more preferably 15% or more and 25% or less, of the thickness of the resin pipe 10. If the thickness of the first resin layer 12 is equal to or greater than the above lower limit, the creep performance and dimensional stability will be even better. If the thickness of the first resin layer 12 is equal to or less than the above upper limit, the proportion of the fiber-reinforced resin layer 11 increases, so that the pressure resistance of the resin pipe 10 can be further enhanced. In addition, the linear expansion coefficient of the resin pipe 10 becomes smaller. Note that the thickness of the first resin layer 12 represents the average thickness, and the average thickness is calculated including the portion where the molding marks exist.

[0054] Examples of the resin contained in the first resin layer 12 include polyolefin resins and vinyl chloride resins. Among these, from the viewpoint of further enhancing the pressure resistance of the resin pipe 10 and the viewpoint of making the resin pipe 10 lighter, polyolefin resins are preferred. Examples of the polyolefin resin include the polyolefin resins exemplified above in the description of the fiber-reinforced resin layer 11. The resin contained in the first resin layer 12 and the resin contained in the fiber-reinforced resin layer 11 may be of the same type or different types.

[0055] With respect to the total mass of the first resin layer 12, the resin content is preferably 80% by mass or more, more preferably 90% by mass or more. Also, with respect to the total mass of the first resin layer 12, the resin content is preferably 100% by mass or less. If the resin content is within the above range, the pressure resistance of the resin pipe 10 can be further enhanced.

[0056] The first resin layer 12 may contain fibers and various additives as necessary. Examples of the fibers and additives include the fibers and additives exemplified above in the description of the fiber-reinforced resin layer 11.

[0057] <The second resin layer> The second resin layer 13 contains resin. As shown in Fig. 1(c), the second resin layer 13 has a spiral molding mark on the outer surface 13a with the axis of the resin pipe 10 as the axis. The spiral molding mark in the second resin layer 13 is formed by a convex portion 13b extending spirally. As will be described later, the spiral molding mark in the second resin layer 13 is a molding mark formed by twisting a multi-layer tubular body in the circumferential direction in the manufacturing process of the resin pipe 10, and is mainly caused by transfer marks during molding (for example, unevenness in the mold, unevenness at the tip of the mold, unevenness of forming, scratches due to friction at the forming inlet, scratches due to friction with members such as rollers in the cooling water tank, etc.). The spiral molding mark in the second resin layer 13 is visually distinguishable. The second resin layer 13 may have convex portions or the like on the outer surface 13a that do not form a spiral molding mark. In addition, in Figs. 1(a) and (b), the convex portion 13b is not shown.

[0058] The convex portion 13b is preferably a ridge, and may also be strip-shaped. In the second resin layer 13, the spiral molding mark may be continuous as a whole in the spiral direction, or may be partially interrupted.

[0059] The average height of the convex portion 13b forming the spiral molding mark in the second resin layer 13 is preferably more than 0 mm and 0.2 mm or less, more preferably 0.1 mm or less, and even more preferably 0.05 mm or less. The average height of the convex portion 13b may exceed 0.2 mm, but the smaller the average height of the convex portion 13b, the more preferable, and it is most preferable that it is substantially 0 mm. The average height of the convex portion 13b may be larger than, the same as, or smaller than the average height of the convex portion 12b. The spiral forming mark in the second resin layer 13 may be visually recognized, for example, as the degree of scratch. The height of the convex portion 13b is measured in the same manner as the height of the convex portion 12b.

[0060] FIG. 5 is a diagram for explaining the inclination angle of the spiral molding marks in the second resin layer 13. The upper part of FIG. 5 shows a plan view of the resin pipe 10. The lower part of FIG. 5 shows the axial direction and circumferential direction of the resin pipe 10 and the spiral direction of the spiral molding marks when any region of the second resin layer 13 is viewed in plan. X is the axial direction of the resin pipe 10. Y is the direction perpendicular to the axial direction X, that is, the circumferential direction of the resin pipe 10. L4 is the spiral direction of the spiral molding marks formed on the outer surface 13a of the second resin layer 13 (that is, the outer surface 10b of the resin pipe 10). The spiral direction of the spiral molding marks means the tangential direction with respect to the spiral molding marks in any region. θ4 is the angle formed by the axial direction X and the molding marks, that is, the acute angle among the angles formed by the axial direction X and the spiral direction L4. θ4 is defined as the inclination angle of the spiral molding marks formed on the outer surface 13a of the second resin layer 13. If the spiral molding marks with the inclination angle θ4 are not uniform, it is considered that the molding conditions during molding are unstable and the product is regarded as a defective product because it cannot be molded at a constant inclination angle θ4.

[0061] As shown in FIG. 5, in the plan view of any region of the second resin layer 13, when one of the axial directions X of the resin pipe 10 is set to 0°, one of the directions Y perpendicular to the axial direction is set to 90°, and the other is set to -90°, the inclination angle θ4 of the spiral molding marks is greater than 0° and less than 90°. This means that the inclination angle θ4 of the spiral molding marks is positive in the plan view of any region of the second resin layer 13. From the viewpoint of enhancing pressure resistance, the average value of the inclination angle θ4 of the spiral molding marks is preferably 30° or more, more preferably 60° or more, and even more preferably 65° or more. The larger the average value of the inclination angle θ4 of the spiral molding marks, the more preferable. The inclination angle θ4 of the spiral forming mark can be controlled by adjusting the twist angle when twisting the multi-layer tubular body in the circumferential direction, the pulling speed of the tubular body, etc. in the manufacturing process of the resin pipe 10. For example, when the twist angle is increased, the inclination angle θ4 of the spiral forming mark tends to increase. When the inclination angle θ4 is 65° or more near the upper limit value of the angle, the inclination angle θ1 is preferably 65° or more and 80° or less, and the orientation angle θ2 is preferably 67° or more and 73° or less. When the inclination angle θ4 is 60° or more near the lower limit value of the angle, the inclination angle θ1 is preferably 60° or more and 80° or less, the orientation angle θ2 is preferably 61° or more and 73° or less, and the angle θ3 is preferably 61° or more.

[0062] From the viewpoint of further enhancing the pressure resistance of the pipe, the absolute value of the difference between the average value of the inclination angle θ1 of the spiral forming mark in the first resin layer 12 and the average value of the inclination angle θ4 of the spiral forming mark in the second resin layer 13 is preferably 5° or less, more preferably 3° or less, still more preferably 1° or less, and particularly preferably 0°. That is, it is particularly preferable that the average value of the inclination angle θ1 and the average value of the inclination angle θ4 coincide.

[0063] The inclination angle θ4 of the spiral forming mark and its average value can be obtained as follows. Draw a line horizontally from an arbitrary point on the outer surface 10b of the resin pipe 10 with respect to the axial direction of the resin pipe 10. Taking this line as 0°, use a protractor with bendable flexibility to periodically measure the inclination angle θ4 of an arbitrary spiral forming mark. Measure the inclination angle θ4 every specified production volume (for example, 4 m), and calculate the average value.

[0064] The thickness of the second resin layer 13 is preferably 10% or more and 30% or less of the thickness of the resin pipe 10, and more preferably 15% or more and 25% or less. If the thickness of the second resin layer 13 is equal to or greater than the above lower limit value, the creep performance and workability will be further improved. If the thickness of the second resin layer 13 is equal to or less than the above upper limit value, the proportion of the fiber-reinforced resin layer 11 increases, so that the pressure resistance of the resin pipe 10 can be further enhanced. In addition, the linear expansion coefficient of the resin pipe 10 becomes smaller. In addition, the ratio of the thickness of the first resin layer 12 to the thickness of the second resin layer 13 (first resin layer 12: second resin layer 13) is preferably 1:5 to 5:1, more preferably 1:3 to 3:1, and even more preferably 1:2 to 2:1. Note that the thickness of the second resin layer 13 represents the average thickness. When the second resin layer 13 has a molding mark, the average thickness is calculated including the portion where the molding mark exists.

[0065] Examples of the resin contained in the second resin layer 13 include polyolefin resins and vinyl chloride resins. Among these, from the viewpoints of further enhancing the pressure resistance of the resin pipe 10 and reducing the weight of the resin pipe 10, polyolefin resins are preferred. Examples of the polyolefin resin include the polyolefin resins exemplified above in the description of the fiber-reinforced resin layer. The resin contained in the second resin layer 13 and the resin contained in the fiber-reinforced resin layer 11 may be of the same type or different types. Also, the resin contained in the second resin layer 13 and the resin contained in the first resin layer 12 may be of the same type or different types.

[0066] With respect to the total mass of the second resin layer 13, the resin content is preferably 80% by mass or more, and more preferably 90% by mass or more. Also, with respect to the total mass of the first resin layer 12, the resin content is preferably 100% by mass or less. If the resin content is within the above range, the pressure resistance of the resin pipe 10 can be further enhanced.

[0067] The second resin layer 13 may contain fibers and various additives as needed. Examples of the fibers and additives include the fibers and additives exemplified above in the description of the fiber-reinforced resin layer.

[0068] <Bending portion> As shown in FIG. 2, the resin pipe 10 has a bending portion 15 bent at an arbitrary angle θ3. The angle θ3 indicating the degree of bending of the bending portion 15 is the angle formed by the axis of the resin pipe 10 (i.e., the line C1 that becomes the central axis of the resin pipe 10 at one end face 10c of the resin pipe 10) and the axis of the resin pipe 10 at the other end face (the end face of the other opening) 10d of the resin pipe 10 (i.e., the line C2 that becomes the central axis of the resin pipe 10 at the other end face 10d of the resin pipe 10) at one end face 10c of the resin pipe 10. The angle θ3 is preferably more than 0° and less than or equal to 90°, more preferably 11° or more and 90° or less, and even more preferably 45° or more and 90° or less. If the angle θ3 is within the above range, the bent pipe can be molded at the same angle as the bent pipe products of the PE pipes existing in off-the-shelf products. When the orientation angle θ2 is 67° or more and 73° or less near the upper limit value of the angle, the inclination angle θ1 is preferably 65° or more and 80° or less, and the inclination angle θ4 is preferably 65° or more. When the orientation angle θ2 is 61° or more and 73° or less near the lower limit value of the angle, the inclination angle θ1 is preferably 60° or more and 80° or less, the inclination angle θ4 is preferably 60° or more, and the angle θ3 is preferably 61° or more.

[0069] <sdr> The SDR (outer diameter of the resin pipe 10 / thickness (wall thickness) of the resin pipe 10) of the resin pipe 10 is preferably 8 or more, more preferably 10 or more, and even more preferably 11 or more. Also, the SDR of the resin pipe 10 is preferably 15 or less, and even more preferably 13.5 or less. If the SDR of the resin pipe 10 is within the above range, the pressure resistance of the resin pipe 10 can be maintained, the flow rate inside the resin pipe 10 can be ensured, and furthermore, the weight reduction of the resin pipe 10 can be achieved. Note that the larger the SDR of the resin pipe 10, the thinner the resin pipe 10.

[0070] <Manufacturing Method> Hereinafter, an example of a manufacturing method of a resin pipe according to the present invention will be described. FIG. 6 is a schematic configuration diagram showing an example of a manufacturing apparatus for a resin pipe. The manufacturing apparatus 20 shown in FIG. 6 includes a mold 21, a first water tank 22, a second water tank 23, a rotary take-up machine 24, and a cutting machine 25. The mold 21 is a multi-layer mold capable of forming a multi-layer tubular body. The rotary take-up machine 24 is a device that can take up the multi-layer tubular body extruded from the mold 21 and can twist the multi-layer tubular body in the circumferential direction by rotating the take-up portion in the circumferential direction.

[0071] The manufacturing method of the resin pipe 10 shown in FIG. 1 includes a first molding step of supplying a first resin composition for forming the first resin layer 12, a second resin composition for forming the fiber-reinforced resin layer 11, and a third resin composition for forming the second resin layer 13 to the mold 21 to obtain a multi-layer tubular body, a second molding step of twisting the multi-layer tubular body in the circumferential direction using the rotary take-up machine 24 installed on the downstream side of the mold 21, and a third molding step of bending the multi-layer tubular body at an arbitrary angle. The first resin composition and the third resin composition are compositions containing resin, and may contain fibers and optional components as necessary. The second resin composition is a composition containing resin and fibers, and may contain optional components as necessary.

[0072] In the first molding step, after supplying the first resin composition, the second resin composition, and the third resin composition to the mold 21, a multilayer tubular body can be molded by melt extrusion. In the multilayer tubular body before twisting, it is preferable that the fibers (fiber orientation direction) contained in the fiber-reinforced resin layer are oriented along the axial direction of the multilayer tubular body, that is, the extrusion direction, in the fiber-reinforced resin layer. Further, it is preferable that the fibers (fiber orientation direction) are not inclined from the axial direction of the multilayer tubular body toward the circumferential direction of the multilayer tubular body in the fiber-reinforced resin layer. When the fibers (fiber orientation direction) are inclined from the axial direction of the multilayer tubular body toward the circumferential direction of the multilayer tubular body, the inclination angle is preferably less than 45°, more preferably less than 15°, still more preferably 10° or less, and particularly preferably 5° or less.

[0073] Examples of the method for orienting the fiber orientation direction along the axial direction of the multilayer tubular body or the method for controlling the inclination angle of the fibers in the multilayer tubular body within the above range include the following methods. (1) A method of making the inner diameter of the forming tube installed at the inlet of the first water tank 22 smaller than the outer diameter of the tubular body extruded from the mold 21. (2) A method of controlling the fiber orientation direction by twisting the tube before the molten resin extruded from the mold 21 is cooled and solidified in the forming tube of the cooling water tank.

[0074] In the first molding step, the temperature of the mold 21 can be appropriately changed depending on the type of resin used.

[0075] In the second molding step, the multilayer tubular body is twisted in the circumferential direction between the mold 21 and the first water tank 22. From the viewpoint of effectively enhancing the pressure resistance, it is preferable to twist while taking up the multilayer tubular body. In the multilayer tubular body immediately after being extruded from the mold 21, the fibers are generally oriented along the axial direction of the multilayer tubular body in the fiber-reinforced resin layer 11. That is, the orientation angle θ2 of the fiber F is generally 0°. By twisting this multilayer tubular body in the circumferential direction, the orientation angle θ2 of the fiber F changes and becomes larger than 0°.

[0076] In the second molding step, considering the molding diameter, flow rate, and the take-up speed of the tubular body, the rotation angle (twist angle) of the rotary take-up machine 24 is set so that the inclination angles θ1 and θ4 of the above-described spiral molding marks and the orientation angle θ2 of the fiber F are within the above ranges. Here, the "twist angle" is the angle with respect to the ratio of the circumference of the center of the wall thickness of the tubular body and the two sides of the pitch obtained from the linear velocity and the take-up rotation speed, and specifically, it is obtained from the following formula (1). Twist angle = tan -1 [{π(D - t)}n] / V (1) In formula (1), "D" is the diameter of the tubular body, "t" is the thickness of the tubular body, "n" is the take-up rotation speed, and "V" is the linear velocity. Note that the pitch is obtained by V / n.

[0077] Also, when an orientation ring is installed between the land and the core of the mold, that is, in the flow path of the resin composition, a uniform shear stress is applied to each resin composition between the land and the orientation ring and between the orientation ring and the core. As a result, the fibers tend to be oriented in one direction in the axial direction in the fiber-reinforced resin layer 11. When the multi-layer tubular body in this state is twisted in the circumferential direction, the fibers are likely to be oriented at θ2 = 45° ± 25° on the outer surface, the central portion in the thickness direction, and the inner surface of the fiber-reinforced resin layer 11 (that is, in any part of the fiber-reinforced resin layer 11). Instead of the orientation ring, a mesh, a baffle plate, or a spiral strip member may be installed between the land and the core. Also, by once narrowing and then widening the clearance difference between the land and the core of the mold, a uniform shear stress can be applied to each resin composition between the land and the core.

[0078] The multi-layer tubular body twisted in the circumferential direction is cooled and solidified in the first water tank 22 and the second water tank 23. Then, the multi-layer tubular body passes through the rotary take-up machine 24 and is cut to a predetermined length by the cutting machine 25. As a result, a multi-layer tubular body of a predetermined length with the inclination angles θ1 and θ4 of the spiral molding marks and the orientation angle θ2 of the fiber F within the above ranges is obtained.

[0079] In the third molding step, the multi-layer tubular body is bent at an arbitrary angle. The heated multi-layer tubular body is pressure-molded by a mold having a curvature radius smaller than a predetermined angle θ3 and a bend angle larger than a predetermined bend angle θ3. After cooling the curved multi-layer rod-shaped body to an intermediate temperature between the heating temperature and room temperature and then demolding, pressure processing is performed by a mold having a curvature radius and a bend angle equal to the curvature radius and the bend angle of θ3. As a result, a multi-layer resin pipe 10 having a curved portion 15 bent at an arbitrary angle θ3 is obtained.

[0080] In the resin pipe 10 of the present embodiment, in a plan view of an arbitrary region of the resin pipe 10, when one of the axial directions of the resin pipe 10 is set to 0°, one of the directions perpendicular to the axial direction is set to 90°, and the other is set to -90°, among the angles formed by the axial direction and the molding mark, the acute angle θ1 is greater than 0° and less than 90°. The orientation angle θ2 of the fiber F, which is the acute angle among the angles formed by the axial direction and the fiber F, is oriented at 60° or more and 73° or less in an arbitrary region (α) of the outer surface 11b of the fiber-reinforced resin layer 11. The resin pipe 10 is bent at an arbitrary angle θ3. Therefore, in the resin pipe 10 of the present embodiment, the fibers 14 are oriented not only in the axial direction but also in the circumferential direction. Therefore, in the resin pipe 10 of the present embodiment, it is considered that the stretching of the fibers 14 is relaxed by the orientation of the fibers 14 in the circumferential direction. Therefore, the resin pipe 10 of the present embodiment can suppress a decrease in mechanical strength on the outer peripheral side of the curved portion. In the relationship of θ1 to θ4, when the orientation angle θ2 is 61° or more and 73° or less near the angle lower limit value, the inclination angle θ1 is preferably 60° or more and 80° or less, and the inclination angle θ4 is preferably 60° or more. When the orientation angle θ2 is 67° or more and 73° or less near the angle upper limit value, the inclination angle θ1 is preferably 65° or more and 80° or less, and if the inclination angle θ4 is 65° or more, when the resin pipe 10 is processed at an arbitrary angle θ3 of 0° or more and 90° or less, a decrease in mechanical strength on the outer peripheral side of the curved portion 15 in the resin pipe 10 of the present embodiment can be suppressed.

[0081] As described above in detail with reference to the drawings, the embodiments are merely illustrative of the present invention. Therefore, the present invention is not limited only to the configurations of the embodiments, and it goes without saying that the present invention includes design changes and the like within the scope not departing from the gist of the present invention. Further, for example, when a plurality of configurations are included in each embodiment, it goes without saying that possible combinations of these configurations are included even without specific description. Also, when a plurality of examples and modification examples are disclosed as those of the present invention in the embodiments, it goes without saying that possible combinations of configurations across these are included even without specific description. Also, regarding the configurations depicted in the drawings, it goes without saying that they are included even without specific description. Furthermore, when the term "etc." is used, it is used in the sense of including equivalents.

Example

[0082] Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples.

[0083] [Example 1] As the first resin composition for forming the first resin layer (innermost layer), high-density polyethylene (A) was used. As the second resin composition for forming the fiber-reinforced resin layer (intermediate layer), a mixed material obtained by mixing high-density polyethylene (A) and glass fiber (a) was used. As the third resin composition for forming the second resin layer (outermost layer), high-density polyethylene (A) was used.

[0084] Using the manufacturing apparatus 20 shown in FIG. 6, a resin pipe was manufactured as follows. The first resin composition, the second resin composition, and the third resin composition were supplied to a mold 21 capable of obtaining a three-layer tubular molded body. The mold 21 was set at a temperature of about 200°C. Next, by extrusion molding each resin composition at an extrusion rate of 120 kgf / h, a three-layer tubular body was obtained in which the first resin layer and the second resin layer contained high-density polyethylene, the fiber-reinforced resin layer contained high-density polyethylene and glass fibers, and the glass fibers were not inclined from the axial direction of the tubular body toward the circumferential direction of the tubular body. The obtained three-layer tubular body had an SDR of about 11 and a nominal diameter of 100A. The rotary take-up machine 24 was operated under the conditions of a linear velocity and a rotational speed such that the torsional angle with respect to the axis was 67°, and the three-layer tubular body was taken up and molded while being twisted in the circumferential direction. Next, the three-layer tubular body was cooled and solidified in the first water tank 22 and the second water tank 23 to obtain a three-layer resin pipe. Next, it was bent at an angle of 90°.

[0085] In the obtained resin pipe, spiral molding marks were formed by convex portions along the axial direction of the resin pipe on the inner surface of the first resin layer. Also, spiral molding marks were formed by convex portions along the axial direction of the pipe on the outer surface of the second resin layer. Further, the obtained resin pipe had an outer diameter of about 114 mm and an SDR of about 11. Also, the thickness of the first resin layer was about 25% of the thickness of the resin pipe, the thickness of the fiber-reinforced resin layer was about 50% of the thickness of the resin pipe, and the thickness of the second resin layer was about 25% of the thickness of the resin pipe. That is, the ratio of the thicknesses of the respective layers (thickness of the first resin layer: thickness of the fiber-reinforced resin layer: thickness of the second resin layer) was about 1:2:1.

[0086] Regarding the obtained resin pipe, the short-term strength was measured as follows. The results are shown in Table 1. As a method for measuring the short-term strength, after the above resin pipe was cured in a water tank at about 25°C for 1 hour, the inside of the resin pipe was pressurized at a constant rate, and the pressure until the above resin pipe broke was measured.

[0087] [Comparative Example 1] A resin pipe of Comparative Example 1 was obtained in the same manner as in Example 1, except that bending was not performed. In the same manner as in Example 1, the short-term strength of the resin pipe of Comparative Example 1 was measured. The results are shown in Table 1.

[0088] [Example 2] A resin pipe of Example 2 was obtained in the same manner as in Example 1, except that high-density polyethylene (B) was used instead of high-density polyethylene (A), glass fiber (b) was used, and the torsional angle was 73°. In the same manner as in Example 1, the short-term strength of the resin pipe of Example 2 was measured. The results are shown in Table 1.

[0089] [Comparative Example 2] A resin pipe of Comparative Example 2 was obtained in the same manner as in Example 2, except that bending was not performed. In the same manner as in Example 1, the short-term strength of the resin pipe of Comparative Example 2 was measured. The results are shown in Table 1.

[0090]

Table 1

[0091] From the results in Table 1, although the short-term strength is reduced by about 10% for those with bending compared to those without bending (straight pipes) due to bending, it is considered that the minimum required performance is satisfied in the short-term strength (destructive test).

[0092] [Example 3] The long-term strength of the resin pipe produced in Example 1 was measured as follows. The results are shown in Fig. 7. As a method for measuring the long-term strength, it was evaluated by hot internal pressure creep for evaluating the long-term durability of polyethylene pipes. The resin pipe was immersed in a hot water tank heated to 80°C, and a constant pressure was applied inside the resin pipe to load a constant stress on the resin pipe in the hot water tank at 80°C, and the long-term durability was estimated by extrapolation.

[0093] [Comparative Example 3] The long-term strength of the resin pipe produced in Comparative Example 1 was measured in the same manner as in Example 3. The results are shown in Fig. 7.

[0094] [Comparative Example 4] The long-term strength of the resin pipe produced in Comparative Example 2 was measured in the same manner as in Example 3. The results are shown in Fig. 7.

[0095] [Comparative Example 5] The long-term strength of the high-performance polyethylene pipe for air-conditioning piping (Kuuchou Hyper CH) produced as follows was measured in the same manner as in Example 3. The results are shown in Fig. 7. The high-performance polyethylene pipe for air-conditioning piping was manufactured by extrusion molding.

[0096] From the results in Fig. 7, it was found that although the long-term strength of Example 3 (the resin pipe produced in Example 1) was reduced by about 10% compared to Comparative Example 3 (the resin pipe produced in Comparative Example 1), it tended to maintain higher performance than the high-performance polyethylene pipe for air-conditioning piping.

[0097] [Example 4] A resin pipe was obtained in the same manner as in Example 1 except that the torsional angle was set to 60°. For the obtained resin pipe, the yield strain was measured as follows. The results are shown in Table 2. After cutting to about 400 mm, the resin pipe cured at about 25°C for 1 hour or more was fixed to a tensile testing machine (Tensilon 500 kN), and the yield strain was measured by applying a tensile load at a tensile speed of 100 mm / min until the resin pipe broke.

[0098] [Example 5] The yield strain of the resin pipe produced in Example 1 was measured in the same manner as in Example 4. The results are shown in Table 2.

[0099] [Example 6] A resin pipe was obtained in the same manner as in Example 1 except that the torsional angle was set to 71°. For the obtained resin pipe, the yield strain was measured in the same manner as in Example 4. The results are shown in Table 2.

[0100] [Comparative Example 6] A resin pipe was obtained in the same manner as in Example 1, except that the torsional angle was set to 0°. For the obtained resin pipe, the yield strain was measured in the same manner as in Example 4. The results are shown in Table 2.

[0101] [Table 2]

[0102] From the results in Table 2, it was found that a resin pipe without torsion reaches the yield strain at 5.25%, while a resin pipe with a torsional angle of 60° or more and 71° or less reaches the yield strain at about 12.5%. The larger the yield strain, the better the resin pipe stretches. When the torsional angle is 60°, it shows the same yield strain as when the torsional angle is 67° for which the short-term strength and long-term strength were measured. Therefore, when the torsional angle is 60°, it is also considered to be within the allowable range of bending processing.

Explanation of Reference Signs

[0103] 10 Resin pipe 11 Fiber-reinforced resin layer 12 Resin layer (first resin layer) 13 Resin layer (second resin layer) 14 Fiber X Axial direction of the pipe Y Direction perpendicular to the axial direction of the pipe (circumferential direction of the pipe) L1 Helical direction in the helical formed mark formed on the inner surface of the resin pipe (first resin layer) L2 Orientation direction of the fiber F L3 L4 Helical direction in the helical formed mark formed on the outer surface of the resin pipe (second resin layer) θ1 The smaller of the two angles formed by the axial direction and the formed mark on the inner surface of the resin pipe (first resin layer) θ2 The smaller of the two angles formed by the axial direction and the fiber F (orientation angle of the fiber F) θ3 Bend pipe angle Of the angles formed between the θ4 axis direction and the molding marks formed on the outer surface of the resin pipe (second resin layer), the acute angle< / sdr>

Claims

1. A resin pipe comprising a tubular fiber-reinforced resin layer containing a resin and fibers, having a spiral forming mark on the inner surface of the resin pipe with the axis of the resin pipe as the axis, in a plan view of any region of the resin pipe, when one of the axial directions of the resin pipe is set to 0°, one of the directions perpendicular to the axial direction is set to 90°, and the other is set to -90°, the acute angle θ1 of the angles formed by the axial direction and the forming mark is 60° or more and 80° or less, The orientation angle θ2 of the following fiber F, which is the acute angle of the angles formed by the axial direction and the following fiber F, is oriented at 60° or more and 73° or less in any region (α) of the outer surface of the fiber-reinforced resin layer, The resin pipe is bent at an angle θ3 of 61° or more. Fiber F: The average fiber diameter of the fiber itself is defined as the average fiber diameter D. The distance in the length direction of each cross-section of the fiber observed in the cross-section along the axial direction of the fiber-reinforced resin layer is defined as the distance L. Among the fibers observed in the cross-section along the axial direction of the fiber-reinforced resin layer, the fiber with the distance L being 2 times or more the average fiber diameter D is defined as the fiber F.

2. The resin pipe according to claim 1, wherein the angle θ3 is 90° or less.

3. The resin pipe according to claim 1 or 2, wherein the fiber is a glass fiber.

4. The resin pipe according to any one of claims 1 to 3, wherein at least one of the inner surface and the outer surface of the fiber-reinforced resin layer is coated with a resin layer containing a resin.

5. The resin pipe according to claim 4, wherein the resin contained in the fiber-reinforced resin layer and the resin layer is a polyolefin resin.

Images