JP2021021451A - Piping - Google Patents

Abstract

To provide piping which is excellent in durability, and small in a linear expansion coefficient.SOLUTION: Piping 10 comprises a tubular fiber-reinforced resin layer 11 including resin and fibers 14, and satisfies the following conditions (A) to (C) when setting an alignment angle of a specific fiber out of the fibers to θ1. The condition (A): in an arbitrary region of an outer surface of the fiber-reinforced resin layer, the fibers which are aligned at θ1=45°±25° is 50% or higher with respect to the total number of the fibers included in the region. The condition (B): in an arbitrary region of a center part of the fiber-reinforced resin layer in a thickness direction, the fibers which are aligned at θ1=45°±25° is 50% or higher with respect to the total number of the fibers included in the region. The condition (C): in an arbitrary region of an inner surface of the fiber-reinforced resin layer, the fibers which are aligned at θ1=45°±25° is 50% or higher with respect to the total number of the fibers included in the region.SELECTED DRAWING: Figure 1

Description

The present invention relates to piping.

High-pressure water flows through cold / hot water pipes in the air conditioning / sanitary field, cooling water pipes, and cleaning liquid pipes in the plant field during use, and temperature changes are likely to occur. Therefore, conventionally, as a pipe, a metal pipe having a small coefficient of linear expansion and high pressure resistance or a metal pipe coated with a resin has been used.
In recent years, there has been an increasing demand for alternatives from metal pipes to resin pipes from the viewpoints of corrosion, workability (weight), earthquake resistance, and the like.

As a means for achieving a desired coefficient of linear expansion and pressure resistance in a resin tube, a method of combining a metal with a resin tube and a method of combining fibers with a resin tube are known.
An aluminum multi-layer tube is known as a resin tube in which a metal is composited (see, for example, Non-Patent Document 1).
As a method of synthesizing the fibers, a method of wrapping a woven fabric of long fibers around the outer surface of a resin tube (see, for example, Patent Documents 1 to 4) and a method of blending short fibers with a resin and aligning them in the axial direction of the resin tube (see Patent Documents 1 to 4) For example, Patent Document 5), a method of blending short fibers with a resin and orienting the resin tube in the circumferential direction (see, for example, Patent Document 6) are known.

Japanese Patent No. 5006355 Japanese Patent No. 5415995 Japanese Unexamined Patent Publication No. 2009-30387 JP 2015-34591 Japanese Unexamined Patent Publication No. 2016-196122 Japanese Unexamined Patent Publication No. 2016-196914

"Eslon Super Eslometax Series Catalog", Sekisui Chemical Co., Ltd., February 2019, Revised 1st Edition, Page 7

However, the method of compounding a metal with a resin tube is not only costly, but is not suitable for producing a resin tube having an outer diameter of 60.5 mm (50 A) or more.
In the case of the method of winding the long fiber woven fabric around the outer surface of the resin tube, the long fiber woven fabric is expensive and therefore costly. Further, since the long fiber woven fabric is difficult to be integrated with the resin constituting the resin tube in a molten state, the coefficient of linear expansion cannot always be reduced.
In the case of the method of orienting the short fibers in the axial direction of the resin pipe, although there is a reinforcing effect in the axial direction, there is no reinforcing effect in the circumferential direction which contributes to the pressure resistance performance, so the resin pipe needs to have a certain thickness. Become. Therefore, it is not suitable for manufacturing a large-diameter resin tube having an outer diameter of 267.4 mm (250 A) or more.
In the case of the method of orienting the short fibers in the circumferential direction of the resin tube, the pressure resistance can be increased to some extent, but the resin tube is required to be further improved in pressure resistance.

An object of the present invention is to provide a pipe having excellent pressure resistance and a small coefficient of linear expansion.

The present invention has the following aspects.
[1] A pipe provided with a tubular fiber-reinforced resin layer containing a resin and fibers having an average fiber length of 15 mm or less.
The inner surface of the pipe has a spiral molding mark about the axis of the pipe.
In a plan view of an arbitrary region of the pipe, when one of the axial directions of the pipe is 0 °, one of the directions perpendicular to the axial direction is 90 °, and the other is −90 °, the axial direction is set. Of the angles formed by the molding marks and the molding marks, the acute angle θ1 is more than 0 ° and less than 90 °.
A pipe in which the orientation angle θ1 of the following fiber F, which is the angle formed by the axial direction and the following fiber F, which is the acute angle, satisfies the following conditions (A), (B), and (C).
Condition (A): In an arbitrary region (α) on the outer surface of the fiber reinforced resin layer, the fibers F oriented at θ1 = 45 ° ± 25 ° are the total number of fibers F contained in the region (α). It is 50% or more with respect to the number.
Condition (B): In an arbitrary region (β) at the center of the fiber reinforced resin layer in the thickness direction, the fiber F oriented at θ1 = 45 ° ± 25 ° is included in the region (β). It is 50% or more with respect to the total number of fibers F.
Condition (C): In an arbitrary region (γ) on the inner surface of the fiber reinforced resin layer, the fibers F oriented at θ1 = 45 ° ± 25 ° are the total number of fibers F contained in the region (γ). It is 50% or more with respect to the number.
Fiber F: The average fiber diameter of the fiber itself is defined as the average fiber diameter D. The distance L in the length direction in each cross section of the fiber observed in the cross section of the fiber reinforced resin layer along the axial direction is defined as the distance L. Among the fibers observed in the cross section of the fiber reinforced resin layer along the axial direction, the fiber whose distance L is at least twice the average fiber diameter D is defined as the fiber F.
[2] The pipe according to [1], wherein the aspect ratio represented by the average fiber length of the fiber / the average fiber diameter of the fiber is 20 or more.
[3] The pipe according to [1] or [2], wherein the fiber is glass fiber.
[4] The 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 pipe according to [4], wherein the fiber-reinforced resin layer and the resin contained in the resin layer are polyolefin resins.

According to the present invention, it is possible to provide a pipe having excellent pressure resistance and a small coefficient of linear expansion.

It is a figure which shows typically the piping which concerns on one Embodiment of this invention, (a) is a sectional view, (b) is a sectional view which follows line Ii shown in (a), (c). Is a plan view. It is a figure for demonstrating the orientation angle of the fiber in the fiber reinforced resin layer of a pipe. It is a figure for demonstrating the inclination angle of the spiral molding mark in the 1st resin layer of a pipe. It is a figure for demonstrating the inclination angle of the spiral molding mark in the 2nd resin layer of a pipe. It is a schematic block diagram which shows an example of the manufacturing apparatus of a pipe.

Hereinafter, the piping of the present invention will be described with reference to embodiments. However, the present invention is not limited to the following embodiments.

FIG. 1 is a diagram showing a pipe according to an embodiment of the present invention. 1 (a) is a cross-sectional view, FIG. 1 (b) is a cross-sectional view taken along line II shown in (a), and FIG. 1 (c) is a plan view.
In addition, in the drawings used in the following description, in order to make the features easy to understand, the featured parts may be enlarged and shown, and the dimensional ratios of each component may differ from the actual ones. There is.

The pipe 10 of this example includes a tubular fiber-reinforced resin layer 11 containing resin and fibers 14, and the inner and outer surfaces of the fiber-reinforced resin layer 11 are coated with resin layers 12 and 13 containing resin. ..
In the present invention, the resin layer 12 arranged on the inner surface of the fiber reinforced resin layer 11 is also referred to as a "first resin layer 12", and the resin layer 13 arranged on the outer surface of the fiber reinforced resin layer 11 is referred to. It is also referred to as "second resin layer 13".
That is, the pipe 10 is a multi-layer 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 (innermost layer) and is a surface layer. The fiber reinforced resin layer 11 is an intermediate layer. The second resin layer 13 is the outermost layer (outermost layer) and is a surface layer. The first resin layer 12, the fiber-reinforced resin layer 11, and the second resin layer 13 are each tubular.
In addition, in FIGS. 1 (b) and 1 (c), one fiber 14 is schematically shown.

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

<Fiber reinforced plastic layer>
The fiber reinforced resin layer 11 contains the resin and the fibers 14.
Among the fibers 14 contained in the fiber reinforced resin layer 11, the fibers satisfying the following configurations are referred to as "fibers F".
Fiber F: The average fiber diameter of the fiber itself is defined as the average fiber diameter D. Let the distance L be the distance in the length direction in each cross section of the fibers observed in the cross section of the fiber reinforced plastic layer along the axial direction of the pipe. Among the fibers observed in the cross section of the fiber reinforced resin layer along the axial direction, the fiber whose distance L is at least twice the average fiber diameter D is defined as the fiber F.

FIG. 2 is a diagram for explaining the orientation angle of the fibers 14 in the fiber reinforced resin layer.
Among the fibers 14 contained in the fiber-reinforced resin layer, the fibers 141 and 142 observed in the cross section of the fiber-reinforced resin layer along the axial direction of the pipe are shown in the upper part of FIG.
The fiber 141 has one end 141a and the other end 141b. In the fiber 141, the distance L (distance between one end 141a and the other end 141b) in the length direction in the cross section of the fiber reinforced resin layer along the axial direction of the pipe is twice or more the average fiber diameter D of the fiber itself. It is a fiber. That is, the fiber 141 is the fiber F.
The fiber 142 has one end 142a and the other end 142b. The fiber 142 is a fiber in which the distance L (distance between one end 142a and the other end 142b) in the length direction in the cross section of the fiber reinforced resin layer along the axial direction of the pipe 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 along the axial direction of the pipe can be classified into either fiber 141 (fiber F) or fiber 142.

The lower part of FIG. 2 shows the axial direction and circumferential direction of the pipe, the spiral direction in the spiral molding mark, and the orientation angle of the fibers contained in the fiber reinforced resin layer when an arbitrary region of the fiber reinforced resin layer is viewed in a plan view. It is shown.
X is the axial direction of the pipe.
Y is the direction perpendicular to the axial direction X, that is, the circumferential direction of the pipe.
L1 is the orientation direction of the fiber F.
L2 is the spiral direction in the spiral forming mark formed on the inner surface of the pipe. The spiral direction in the spiral molding mark means a 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 fiber F, that is, the angle formed by the axial direction X and the orientation direction L1 of the fiber F, whichever is the acute angle, and θ1 is defined as the orientation angle of the fiber F. ..
θ2 is the angle formed by the axial direction X and the molding mark, that is, the angle formed by the axial direction X and the spiral direction L2, which is the acute angle, and θ2 is a spiral formed on the inner surface of the pipe. The inclination angle of the molding mark of.

As shown in FIG. 2, in a plan view of an arbitrary region of the pipe, one of the axial directions X of the pipe is 0 °, one of the directions Y perpendicular to the axial direction is 90 °, and the other is −90 °. Occasionally, the inclination angle θ2 of the spiral molding mark formed on the inner surface of the pipe is more than 0 ° and less than 90 °. This means that the inclination angle θ2 of the spiral forming mark is positive in the plan view of an arbitrary region of the pipe.
The spiral molding marks formed on the inner surface of the pipe will be described in the first resin layer 12.

The orientation angle θ1 of the fiber F satisfies the following conditions (A), (B) and (C).
Condition (A): In an arbitrary region (α) on the outer surface of the fiber reinforced resin layer, the fibers F oriented at θ1 = 45 ° ± 25 ° are the total number of fibers F contained in the region (α). It is 50% or more with respect to.
Condition (B): In an arbitrary region (β) at the center of the fiber reinforced resin layer in the thickness direction, the fiber F oriented at θ1 = 45 ° ± 25 ° is included in the region (β). It is 50% or more of the total number of Fs.
Condition (C): In an arbitrary region (γ) on the inner surface of the fiber reinforced resin layer, the fibers F oriented at θ1 = 45 ° ± 25 ° are the total number of fibers F contained in the region (γ). It is 50% or more with respect to.

If the fiber orientation angle θ1 satisfies the conditions (A), (B) and (C), the pressure resistance of the pipe is improved. In addition, the coefficient of linear expansion of the pipe becomes smaller.
Under the condition (A), the fiber F oriented at θ1 = 45 ° ± 25 ° is preferably 55% or more, more preferably 55% or more of the total number of fibers F contained in the region (α). It is 60% or more, and the closer it is to 100%, the more preferable. Further, it is preferable that 50% or more of the fibers F contained in the region (α) are oriented at θ1 = 45 ± 10 °, and more preferably at θ1 = 45 ± 5 °.
Under the condition (B), the fiber F oriented at θ1 = 45 ° ± 25 ° is preferably 55% or more, more preferably 55% or more of the total number of fibers F contained in the region (β). It is 60% or more, and the closer it is to 100%, the more preferable. Further, it is preferable that 50% or more of the fibers F contained in the region (β) are oriented at θ1 = 45 ± 10 °, and more preferably at θ1 = 45 ± 5 °.
Under the condition (C), the fiber F oriented at θ1 = 45 ° ± 25 ° is preferably 55% or more, more preferably 55% or more of the total number of fibers F contained in the region (γ). It is 60% or more, and the closer it is to 100%, the more preferable. Further, it is preferable that 50% or more of the fibers F contained in the region (γ) are oriented at θ1 = 45 ± 10 °, and more preferably at θ1 = 45 ± 5 °.

The orientation angle θ1 of the fiber F can be controlled by adjusting the twist angle when twisting the multilayer tubular body in the circumferential direction, the take-up speed of the tubular body, and the like in the manufacturing process of the pipe. For example, when the twist angle is increased, the orientation angle θ1 of the fiber F tends to be increased.
When the orientation angle θ1 of the fiber F is 0 °, the orientation direction L1 of the fiber F coincides with the axial direction X of the pipe.
When the orientation angle θ1 of the fiber F is 90 °, the orientation direction L1 of the fiber F coincides with the circumferential direction of the pipe (the direction Y perpendicular to the axial direction X).

The orientation angle θ1 and the number ratio of the fibers F can be obtained as follows.
In any region of the pipe, the pipe is sliced axially from the outer surface until the outer surface of the fiber reinforced resin layer is exposed, and a cross section obtained using a scanning electron microscope (SEM) (arbitrary region (α)). ) Is taken. Using image analysis software, among the fibers photographed in the micrograph, only the fibers F whose distance L between one end and the other end is at least twice the average fiber diameter D of the fibers themselves are selected and oriented with respect to the fibers F. Find the angle θ1 respectively. The ratio of the number of fibers F oriented at θ1 = 45 ° ± 25 ° to the total number of fibers F (100%) is calculated.
Next, the fiber-reinforced resin layer is sliced in the axial direction of the pipe until it reaches the central portion in the thickness direction of the fiber-reinforced resin layer, and the cross section (arbitrary region (β)) obtained by using SEM is photographed. Using image analysis software, only the fiber F is selected, and the orientation angle θ1 is obtained for each fiber F. The ratio of the number of fibers F oriented at θ1 = 45 ° ± 25 ° to the total number of fibers F (100%) is calculated.
Next, the fiber-reinforced resin layer is sliced in the axial direction of the pipe until it reaches the inner surface of the fiber-reinforced resin layer, and the cross section (arbitrary region (γ)) obtained by using SEM is photographed. Using image analysis software, only the fiber F is selected, and the orientation angle θ1 is obtained for each fiber F. The ratio of the number of fibers F oriented at θ1 = 45 ° ± 25 ° to the total number of fibers F (100%) is calculated.
In addition, "until the outer surface of the fiber reinforced resin layer is exposed" means until it reaches a region within 1 mm inside from the outer surface of the fiber reinforced resin layer. "Until reaching the center in the thickness direction of the fiber reinforced resin layer" 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 inside from the inner surface of the fiber reinforced resin layer.
Examples of the imaging conditions with the 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.

The thickness of the fiber reinforced resin layer 11 is preferably 40 to 80%, more preferably 50 to 70% of the thickness of the pipe. When the thickness of the fiber reinforced resin layer 11 is at least the above lower limit value, the pressure resistance of the pipe can be further increased. In addition, the coefficient of linear expansion of the pipe becomes smaller. When the thickness of the fiber reinforced resin layer 11 is not more than the above upper limit value, the dimensional stability is further improved.
The thickness of the fiber reinforced resin layer 11 represents the average thickness, and the average thickness is calculated including the portion where the molding mark is present.

Examples of the resin contained in the fiber reinforced resin layer 11 include a polyolefin resin and a vinyl chloride resin. Among these, polyolefin resin is preferable from the viewpoint of further increasing the pressure resistance of the pipe and reducing the weight of the pipe.

Examples of the polyolefin resin include polyethylene, polypropylene, polybutene, ethylene-vinyl acetate copolymer, ethylene-α-olefin copolymer and the like. Among these, polyethylene or polypropylene is preferable from the viewpoint of further increasing the pressure resistance of the pipe and reducing the weight of the pipe.
Only one type of these polyolefin resins may be used, or two or more types may be used in combination.

The polyethylene may be low density polyethylene, linear low density polyethylene, high density polyethylene, or antiheat resistant polyethylene (PE-RT).
Examples of polyethylene include a homopolymer of ethylene and a copolymer of a monomer containing ethylene. When polyethylene is a copolymer, it may be a random copolymer or a block copolymer.
With respect to the total mass of all the monomer units constituting polyethylene, 50% by mass or more is preferably ethylene units, more preferably 80% by mass or more, and further preferably 90% by mass or more.

Examples of polypropylene include homopolymers of propylene and copolymers of monomers containing propylene. When polypropylene is a copolymer, it may be a random copolymer or a block copolymer.
With respect to the total mass of all the monomer units constituting polypropylene, 50% by mass or more is preferably propylene units, more preferably 80% by mass or more, and further preferably 90% by mass or more.

The resin content is preferably 50% by mass or more, more preferably 65% by mass or more, based on the total mass of the fiber-reinforced resin layer 11. Further, the resin content is preferably 90% by mass or less, more preferably 85% by mass or less, based on the total mass of the fiber-reinforced resin layer 11. When the resin content is within the above range, the pressure resistance of the pipe can be further increased.

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

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, glass fiber is preferable from the viewpoint of further increasing the pressure resistance of the pipe.

The average fiber length of the fibers is preferably 100 μm or more, more preferably 200 μm or more, and further preferably 300 μm or more. The average fiber length of the fibers is 15 mm or less, preferably 1.5 mm or less, more preferably 1 mm or less, and further preferably 500 μm or less. When the average fiber length of the fiber is at least the above lower limit value, the pressure resistance of the pipe can be further improved. When the average fiber length of the fibers is equal to or less than the above upper limit value, the fibers can be easily arranged in a specific direction.

The average fiber diameter of the fibers is preferably 5 μm or more, more preferably 7 μm or more, still more preferably 10 μm or more. The average fiber diameter of the fibers is preferably 17 μm or less, more preferably 13 μm or less. When the average fiber diameter of the fibers is at least the above lower limit value, the pressure resistance of the pipe can be further improved. When the average fiber diameter of the fibers is equal to or less than the above upper limit value, the fibers can be easily arranged in a specific direction.

The average fiber length and average fiber diameter of the fibers can be obtained as follows.
First, in any region of the pipe, the pipe is sliced along the axial direction from the outer surface until the fiber reinforced resin layer is exposed. Next, the exposed fiber-reinforced resin layer is photographed using SEM, and the fiber length and fiber diameter of one fiber are obtained from the photographed micrograph. The fiber length and fiber diameter are measured for each of 5000 arbitrarily selected fibers, and the average value is calculated.
The "fiber length" is the distance between one end and the other end of the fiber when the fiber is straightened. "Until the fiber-reinforced resin layer is exposed" means until it reaches an arbitrary position in the thickness direction of the fiber-reinforced resin layer.
Examples of the imaging conditions with the 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.

The aspect ratio represented by the average fiber length of the fiber / the average fiber diameter of the fiber is preferably 20 or more, more preferably 25 or more, and further preferably 30 or more. The aspect ratio is preferably 100 or less, more preferably 80 or less, still more preferably 70 or less, particularly preferably 50 or less, and most preferably 35 or less. When the aspect ratio is at least the above lower limit value, the pressure resistance of the pipe can be further improved. When the aspect ratio is equal to or less than the above upper limit value, the fibers can be easily arranged in a specific direction.

The fiber content is preferably 10% by mass or more, more preferably 15% by mass or more, still more preferably 20% by mass or more, based on the total mass of the fiber-reinforced resin layer 11. Further, the fiber content is preferably 40% by mass or less, more preferably 30% by mass or less, based on the total mass of the fiber-reinforced resin layer 11. When the fiber content is within the above range, the pressure resistance of the pipe can be further increased.

The fiber reinforced resin layer 11 may contain various additives, if necessary.
Additives include compatibilizers, stabilizers, stabilizers, lubricants, processing aids, impact modifiers, heat improvers, antioxidants, UV absorbers, light stabilizers, fillers, pigments and plasticizers. Examples include agents. Among these, a compatibilizer is preferable.
Only one of these additives may be used, or two or more of these additives may be used in combination.

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

The stabilizer is not particularly limited, and examples thereof include a heat stabilizer and a heat stabilization aid.
The heat stabilizer is not particularly limited, and examples thereof include an organic tin-based stabilizer, a lead-based stabilizer, a calcium-zinc-based stabilizer, a barium-zinc-based stabilizer, and a barium-cadmium-based stabilizer.
Examples of organic tin stabilizers include dibutyl tin mercapto, dioctyl tin mercapto, dimethyl tin mercapto, dibutyl tin mercapto, dibutyl tin malate, dibutyl tin malate polymer, dioctyl tin malate, dioctyl tin malate polymer, dibutyl tin laurate, and dibutyl tin. Laurate polymer and the like can be mentioned.
Only one kind of these heat stabilizers may be used, or two or more kinds thereof may be used in combination.

The heat stabilizing aid is not particularly limited, and examples thereof include epoxidized soybean oil, phosphoric acid ester, polyol, hydrotalcite, and zeolite.
Only one of these heat stabilizing aids may be used, or two or more thereof may be used in combination.

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

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

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

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

The antioxidant is not particularly limited, and examples thereof include phenolic antioxidants.
Only one of these antioxidants may be used, or two or more of these antioxidants may be used in combination.

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

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

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

The pigment is not particularly limited, and examples thereof include organic pigments and inorganic pigments.
Examples of the organic pigment include an azo-based organic pigment, a phthalocyanine-based organic pigment, a slene-based organic pigment, and a dye lake-based organic pigment.
Examples of the inorganic pigments include oxide-based inorganic pigments, molybdenum chromate-based inorganic pigments, sulfide / selenium-based inorganic pigments, and ferrosinized inorganic pigments.
Only one of these pigments may be used, or two or more of these pigments may be used in combination.

The plasticizer may be added for the purpose of improving processability at the time of molding. Since the heat resistance of the molded product may decrease due to the addition of the plasticizer, it is preferable that the amount of the plasticizer added is small.
The plasticizer is not particularly limited, and examples thereof include dibutyl phthalate, di-2-ethylhexyl phthalate, and di-2-ethylhexyl adipate.
Only one of these plasticizers may be used, or two or more of these plasticizers may be used in combination.

<First resin layer>
The first resin layer 12 contains a resin.
As shown in FIG. 1B, the first resin layer 12 has spiral molding marks on the inner surface about the axis of the pipe 10.
The spiral molding marks in the first resin layer 12 are formed by the convex portions 12a extending in a spiral shape. As will be described later, the spiral molding marks in the first resin layer 12 are molding marks formed by twisting a multilayer tubular body in the circumferential direction in the manufacturing process of the pipe 10, and are mainly derived from the uneven thickness of the pipe. It is caused by the unevenness of. The spiral molding marks on the first resin layer 12 are visually identifiable.
The first resin layer 12 may have a convex portion or the like on the inner surface that does not form a spiral molding mark.
In FIG. 1A, the convex portion 12a is not shown.

The convex portion 12a is preferably a ridge, and may be strip-shaped.
In the first resin layer 12, the spiral molding marks may be wholly continuous or partially interrupted in the spiral direction.

From the viewpoint of further increasing the pressure resistance of the pipe 10, the average height of the convex portion 12a is more than 0 mm, preferably 2 mm or less, more preferably 1.5 mm or less, still more preferably 1 mm or less. The average height of the convex portion 12a may exceed 2 mm, but it is preferable that the average height of the convex portion 12a is smaller.

The height of the convex portion 12a is measured at the maximum height position in the direction orthogonal to the spiral direction. The height of the convex portion 12a is measured only in the portion where the convex portion 12a is located. The average height of the convex portion 12a can be obtained, for example, by measuring the height of the convex portion 12a at 50 or more positions arbitrarily selected apart from each other in the spiral direction and calculating an average value. The height of the entire convex portion 12a may be measured and an average value may be calculated.
The height of the convex portion 12a can be measured using a non-contact coordinate measuring machine.

FIG. 3 is a diagram for explaining the inclination angle of the spiral molding mark in the first resin layer 12. The upper part of FIG. 3 shows a cross-sectional view of the first resin layer 12 along the line II shown in FIG. 1 (a). The fiber reinforced resin layer and the second resin layer are not shown. The lower part of FIG. 3 shows the axial direction and the circumferential direction of the pipe, and the spiral direction in the spiral molding mark when an arbitrary region of the first resin layer is viewed in a plan view.
X is the axial direction of the pipe.
Y is the direction perpendicular to the axial direction X, that is, the circumferential direction of the pipe.
L2 is the spiral direction in the spiral molding mark formed on the inner surface of the first resin layer (that is, the inner surface of the pipe). The spiral direction in the spiral molding mark means a tangential direction with respect to the spiral molding mark in an arbitrary region.
θ2 is the angle formed by the axial direction X and the molding mark, that is, the angle formed by the axial direction X and the spiral direction L2, which is the acute angle, and θ2 is formed on the inner surface of the first resin layer. The inclination angle of the spiral molding mark is used.

As shown in FIG. 3, in a plan view of an arbitrary region of the first resin layer, one of the axial directions X of the pipe is 0 °, one of the directions Y perpendicular to the axial direction is 90 °, and the other is −. When 90 °, the inclination angle θ2 of the spiral molding mark is more than 0 ° and less than 90 °. This means that the inclination angle θ2 of the spiral molding mark is positive in the plan view of an arbitrary region of the first resin layer.
From the viewpoint of increasing the pressure resistance, the average value of the inclination angle θ2 of the spiral molding mark is preferably 40 to 80 °, more preferably 60 to 80 °, and further preferably 65 to 80 °. The average value of the inclination angle θ2 of the spiral molding mark is preferably closer to 65 °.
The inclination angle θ2 of the spiral molding mark can be controlled by adjusting the twist angle when twisting the multilayer tubular body in the circumferential direction, the take-up speed of the tubular body, and the like in the manufacturing process of the pipe. For example, when the twist angle is increased, the inclination angle θ2 of the spiral molding mark tends to increase.

The inclination angle θ2 of the spiral molding mark and its average value can be obtained as follows.
Draw a line horizontally from any point on the inner surface of the pipe with respect to the axial direction of the pipe. This line is set to 0 °, and the inclination angle θ2 of an arbitrary spiral molding mark is periodically measured using a protractor having curvable flexibility. The inclination angle θ2 is measured for each specified production amount (for example, 4 m), and the average value is calculated.

The thickness of the first resin layer 12 is preferably 10 to 30%, more preferably 15 to 25% of the thickness of the pipe. When the thickness of the first resin layer 12 is at least the above lower limit value, the creep performance and the dimensional stability are further improved. When the thickness of the first resin layer 12 is not more than the above upper limit value, the pressure resistance of the pipe can be further increased by increasing the proportion of the fiber reinforced resin layer. In addition, the coefficient of linear expansion of the pipe becomes smaller.
The thickness of the first resin layer 12 represents the average thickness, and the average thickness is calculated including the portion where the molding mark is present.

Examples of the resin contained in the first resin layer 12 include polyolefin resins and vinyl chloride resins. Among these, polyolefin resin is preferable from the viewpoint of further increasing the pressure resistance of the pipe and reducing the weight of the pipe.
Examples of the polyolefin resin include the polyolefin resin exemplified above in the description of the fiber reinforced resin layer.
The resin contained in the first resin layer 12 and the resin contained in the fiber reinforced resin layer may be of the same type or different types.

The content of the resin is preferably 80% by mass or more, more preferably 90% by mass or more, based on the total mass of the first resin layer 12. Further, the resin content is preferably 100% by mass or less with respect to the total mass of the first resin layer 12. When the resin content is within the above range, the pressure resistance of the pipe can be further increased.

The first resin layer 12 may contain fibers and various additives, if necessary.
Examples of the fiber and the additive include the fiber and the additive exemplified above in the description of the fiber reinforced resin layer, respectively.

<Second resin layer>
The second resin layer 13 contains a resin.
As shown in FIG. 1 (c), the second resin layer 13 has spiral molding marks on the outer surface about the axis of the pipe 10.
The spiral molding marks in the second resin layer 13 are formed by the convex portions 13a extending in a spiral shape. As will be described later, the spiral molding marks on the second resin layer 13 are molding marks formed by twisting the multilayer tubular body in the circumferential direction in the manufacturing process of the pipe 10, and are mainly transfer marks during molding. (For example, unevenness in the mold, unevenness at the tip of the mold, unevenness in 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 marks on the second resin layer 13 are visually identifiable.
The second resin layer 13 may have a convex portion or the like on the outer surface that does not form a spiral molding mark.
In addition, in FIGS. 1A and 1B, the convex portion 13a is not shown.

The convex portion 13a is preferably a ridge, and may be strip-shaped.
In the second resin layer 13, the spiral molding marks may be entirely continuous in the spiral direction or may be partially interrupted.

The average height of the convex portion 13a forming the spiral molding mark in the second resin layer 13 exceeds 0 mm, preferably 0.2 mm or less, more preferably 0.1 mm or less, and further preferably 0. It is 05 mm or less. The average height of the convex portion 13a may exceed 0.2 mm, but the smaller the average height of the convex portion 13a is, the more preferable, and it is most preferably about 0 mm.
The average height of the convex portion 13a may be larger than the average height of the convex portion 12a, may be the same, or may be smaller.
The spiral formation marks on the second resin layer 13 may be visually recognized, for example, to the extent of scratches.
The height of the convex portion 13a is measured in the same manner as the height of the convex portion 12a.

FIG. 4 is a diagram for explaining the inclination angle of the spiral molding mark in the second resin layer 13. A plan view of the pipe is shown in the upper part of FIG. The lower part of FIG. 4 shows the axial direction and the circumferential direction of the pipe, and the spiral direction in the spiral molding mark when an arbitrary region of the second resin layer is viewed in a plan view.
X is the axial direction of the pipe.
Y is the direction perpendicular to the axial direction X, that is, the circumferential direction of the pipe.
L3 is the spiral direction in the spiral molding mark formed on the outer surface of the second resin layer (that is, the outer surface of the pipe). The spiral direction in the spiral molding mark means a tangential direction with respect to the spiral molding mark in an arbitrary region.
θ3 is the angle formed by the axial direction X and the molding mark, that is, the angle formed by the axial direction X and the spiral direction L3, which is the acute angle, and θ3 is formed on the outer surface of the second resin layer. The inclination angle of the spiral molding mark is used.

As shown in FIG. 4, in a plan view of an arbitrary region of the second resin layer, one of the axial directions X of the pipe is 0 °, one of the directions Y perpendicular to the axial direction is 90 °, and the other is −. When 90 °, the inclination angle θ3 of the spiral molding mark is more than 0 ° and less than 90 °. This means that the inclination angle θ3 of the spiral molding mark is positive in the plan view of an arbitrary region of the second resin layer.
From the viewpoint of increasing the pressure resistance, the average value of the inclination angle θ3 of the spiral molding mark is preferably 30 ° or more, more preferably 60 ° or more, and further preferably 65 ° or more. The larger the average value of the inclination angle θ3 of the spiral molding mark, the more preferable.
The inclination angle θ3 of the spiral molding mark can be controlled by adjusting the twist angle when twisting the multilayer tubular body in the circumferential direction, the take-up speed of the tubular body, and the like in the manufacturing process of the pipe. For example, when the twist angle is increased, the inclination angle θ4 of the spiral molding mark tends to increase.

From the viewpoint of further increasing the pressure resistance of the pipe, the average value of the inclination angle θ2 of the spiral molding mark in the first resin layer and the average value of the inclination angle θ3 of the spiral molding mark in the second resin layer. The absolute value of the difference is preferably 5 ° or less, more preferably 3 ° or less, further preferably 1 ° or less, and particularly preferably 0 °. That is, it is particularly preferable that the average value of the inclination angle θ2 and the average value of the inclination angle θ3 match.

The inclination angle θ3 of the spiral molding mark and its average value can be obtained as follows.
Draw a line horizontally from any point on the outer surface of the pipe with respect to the axial direction of the pipe. This line is set to 0 °, and the inclination angle θ3 of an arbitrary spiral molding mark is periodically measured using a protractor having curvable flexibility. The inclination angle θ3 is measured for each specified production amount (for example, 4 m), and the average value is calculated.

The thickness of the second resin layer 13 is preferably 10 to 30%, more preferably 15 to 25% of the thickness of the pipe. When the thickness of the second resin layer 13 is at least the above lower limit value, the creep performance and workability are further improved. When the thickness of the second resin layer 13 is not more than the above upper limit value, the pressure resistance of the pipe can be further increased by increasing the proportion of the fiber reinforced resin layer. In addition, the coefficient of linear expansion of the pipe becomes smaller.
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. It is 1: 3 to 3: 1, and more preferably 1: 2 to 2: 1.
The thickness of the second resin layer 13 represents the average thickness. When the second resin layer 13 has molding marks, the average thickness is calculated including the portion where the molding marks are present.

Examples of the resin contained in the second resin layer 13 include polyolefin resins and vinyl chloride resins. Among these, polyolefin resin is preferable from the viewpoint of further increasing the pressure resistance of the pipe and reducing the weight of the pipe.
Examples of the polyolefin resin include the polyolefin resin 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 may be of the same type or different types. Further, the resin contained in the second resin layer 13 and the resin contained in the first resin layer may be of the same type or different types.

The content of the resin is preferably 80% by mass or more, more preferably 90% by mass or more, based on the total mass of the second resin layer 13. Further, the resin content is preferably 100% by mass or less with respect to the total mass of the first resin layer 12. When the resin content is within the above range, the pressure resistance of the pipe can be further increased.

The second resin layer 13 may contain fibers and various additives, if necessary.
Examples of the fiber and the additive include the fiber and the additive exemplified above in the description of the fiber reinforced resin layer, respectively.

<SDR>
The SDR (outer diameter of the pipe / thickness of the pipe (thickness)) of the pipe 10 is preferably 8 or more, more preferably 10 or more, and further preferably 11 or more. The SDR of the pipe 10 is preferably 15 or less, more preferably 13.5 or less. When the SDR of the pipe 10 is within the above range, the flow rate in the pipe 10 can be secured while maintaining the pressure resistance of the pipe 10, and the weight of the pipe 10 can be reduced.
The larger the SDR of the pipe 10, the thinner the pipe 10.

<Manufacturing method>
Hereinafter, an example of a method for manufacturing a pipe according to the present invention will be described.
FIG. 5 is a schematic configuration diagram showing an example of a piping manufacturing apparatus.
The manufacturing apparatus 20 shown in FIG. 5 includes a mold 21, a first water tank 22, a second water tank 23, a rotary pick-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 pick-up machine 24 is a device capable of picking up a multi-layered tubular body extruded from the mold 21 and twisting the multi-layered tubular body in the circumferential direction by rotating the pick-up portion in the circumferential direction. ..

The method for manufacturing the pipe 10 shown in FIG. 1 includes 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 second resin composition. The first molding step of supplying the third resin composition for forming the resin layer 13 of the above to the mold 21 to obtain a multi-layered tubular body, and the rotary pick-up installed on the downstream side of the mold 21. It includes a second molding step of twisting the multilayer tubular body in the circumferential direction using the machine 24.
The first resin composition and the third resin composition are compositions containing a resin, and may contain fibers and arbitrary components, if necessary. The second resin composition is a composition containing a resin and a fiber, and may contain an arbitrary component if necessary.

In the first molding step, the first resin composition, the second resin composition, and the third resin composition are supplied to the mold 21 and then melt-extruded to form a multilayer tubular body. be able to. In the multi-layered tubular body before twisting, the fibers (fiber orientation direction) contained in the fiber-reinforced resin layer are oriented in the fiber-reinforced resin layer along the axial direction of the multi-layered tubular body, that is, the extrusion direction. Is preferable. Further, it is preferable that the fibers (fiber orientation direction) are not inclined in the fiber reinforced resin layer from the axial direction of the multilayer tubular body toward the circumferential direction of the multilayer tubular body. 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 °. It is more preferably 10 ° or less, and particularly preferably 5 ° or less.

Examples of the method of aligning the fiber orientation direction along the axial direction of the multilayer tubular body and the method of controlling the inclination angle of the fiber in the multilayer tubular body within the above range include the following methods.
(1) A method in which the inner diameter of the forming tube installed at the entrance of the first water tank 22 is made smaller than the outer diameter of the tubular body extruded from the mold 21.
(2) A method of controlling the orientation direction of fibers by twisting the molten resin extruded from the mold 21 until the molten resin is cooled and solidified by the forming tube of the cooling water tank.

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

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 increasing the pressure resistance, it is preferable to twist the multilayer tubular body while taking it over. 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 θ1 of the fiber F is approximately 0 °. By twisting this multilayer tubular body in the circumferential direction, the orientation angle θ1 of the fiber F changes and becomes larger than 0 °.
In the second molding step, the molding diameter, the flow velocity, and the take-up speed of the tubular body are taken into consideration so that the inclination angles θ2 and θ3 of the spiral molding marks and the orientation angle θ1 of the fiber F are within the above ranges. Above, the rotation angle (twist angle) of the rotary take-up machine 24 is set. Here, the "torsion angle" is an angle with respect to the ratio of the circumference of the center of the wall thickness of the tubular body and the ratio of the two sides of the pitch obtained by the linear velocity and the take-up rotation speed. Obtained from equation (1).
Torsion angle = tan ^-1 [{π (Dt)} n] / V ・ ・ ・ (1)
In the 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. The pitch is obtained by V / n.

Further, when the alignment ring is installed between the land and the core of the mold, that is, in the flow path of the resin composition, uniform shear is applied to each resin composition between the land and the alignment ring and between the alignment ring and the core. Stress is applied. 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 multilayer tubular body is twisted in the circumferential direction in this state, θ1 is formed on the outer surface, the central portion and the inner surface in the thickness direction of the fiber reinforced resin layer 11 (that is, in any part of the fiber reinforced resin layer 11). = 45 ° ± 25 ° facilitates fiber orientation. Instead of the alignment ring, a mesh, baffle plate, or spiral strip may be installed between the land and the core.
Further, even if the clearance difference between the land and the core of the mold is narrowed and then widened, a uniform shear stress can be applied to each resin composition between the land and the core.

The multilayer tubular body twisted in the circumferential direction is cooled and solidified in the first water tank 22 and the second water tank 23. As a result, the multi-layered pipe 10 is obtained. After that, the pipe 10 passes through the rotary take-up machine 24 and is cut to a predetermined length by the cutting machine 25. As a result, a pipe 10 having a predetermined length is obtained, in which the inclination angles θ2 and θ3 of the spiral molding marks and the orientation angle θ1 of the fibers F are within the above ranges.

<Effect>
Since the pipe of the present embodiment includes a fiber-reinforced resin layer in which the fiber orientation angle θ2 satisfies the above-mentioned conditions (A), (B) and (C), the pressure resistance is excellent and the linear expansion coefficient is small. Specifically, in the piping of the present embodiment, for example, the breaking water pressure when the SDR is 11.0 tends to be 6.0 MPa or more, and the breaking water pressure when the SDR is 13.5 tends to be 5.0 MPa or more. High pressure fluid can flow. Further, the piping of the present embodiment tends to have a coefficient of linear expansion of 5.0 × ^10-5 / ° C. or less. The coefficient of linear expansion of the pipe is preferably less than 5.0 × ^10-5 / ° C.

The coefficient of linear expansion of the pipe is obtained by the following method.
The pipe is cut to an arbitrary length and cured in a constant temperature bath set to an arbitrary temperature (Hot) for 24 hours. After curing, the length of the pipe (Lhot) is measured. After that, the same pipe is cured for 24 hours in a constant temperature bath set to an arbitrary temperature (Tcool) lower than Hot, the length of the pipe (Lcool) is measured, and the coefficient of linear expansion of the pipe is calculated from the following formula (2). Ask.
Linear expansion coefficient = (Lhot-Lcool) / {Lcool (Photo-Tcool)} ... (2)

The pipe of the present embodiment can be suitably used as a constituent member of a pipe through which a fluid flows inside. Specifically, the piping of this embodiment is suitably used as a constituent member of cold / hot water piping in the air conditioning / sanitary field, cooling water piping, cleaning liquid piping in the plant field, fire extinguishing piping in the fire extinguishing field, drainage piping, chemical solution piping, and the like. Can be done. In particular, the piping of the present embodiment is suitable as piping through which high-pressure water flows during use (for example, withstand voltage of 1.5 MPa or more). Specifically, cold / hot water piping and cooling water in the fields of air conditioning and sanitation. It is suitable as a component of cleaning liquid piping in the field of piping and plants, and fire extinguishing piping in the field of fire extinguishing, and is particularly suitable as a component of cold / hot water piping.

<Other embodiments>
The pipe does not have to have a spiral molding mark on the outer surface of the second resin layer. The pipe does not have to have a visually identifiable spiral molding mark on the outer surface of the second resin layer. In the second molding step described above, after forming a spiral molding mark on the outer surface of the second resin layer of the obtained pipe along the axial direction of the pipe, the spiral molding mark on the second resin layer May be performed, or a step of thinning the spiral molding marks on the second resin layer may be performed. In the second molding step, a spiral molding mark is formed on the outer surface of the second resin layer of the obtained pipe along the axial direction of the pipe, and then the spiral molding mark on the second resin layer is scraped. By performing the process, the appearance of the pipe can be improved. Further, by polishing the outer surface of the obtained pipe (outer surface of the second resin layer) or applying a paint after polishing, spiral molding marks are formed on the outer surface of the second resin layer. It can be made indistinguishable visually.

The pipe may not include at least one of a first resin layer and a second resin layer. That is, the pipe may be a single-layer pipe made of a fiber-reinforced resin layer, a first resin layer and a fiber-reinforced resin layer, or a two-layer pipe made of a fiber-reinforced resin layer and a second resin layer.
When the pipe does not include the first resin layer, the inner surface of the pipe is the inner surface of the fiber reinforced resin layer. In this case, the inner surface of the fiber reinforced resin layer has spiral molding marks. The spiral molding marks on the inner surface of the fiber-reinforced resin layer are substantially the same as the spiral molding marks on the inner surface of the first resin layer described above.

Further, the pipe may include a first resin layer, a fiber reinforced resin layer, and a layer (another layer) different from the first resin layer. For example, the pipe may have another layer arranged between the first resin layer and the fiber reinforced resin layer or between the fiber reinforced resin layer and the second resin layer. Further, the pipe may have another layer arranged on the inner surface of the first resin layer. However, the first resin layer is preferably a surface layer. Further, it may have another layer arranged on the outer surface of the second resin layer, or the outer surface of the second resin layer may be coated with a paint and colored. However, the second resin layer is preferably a surface layer.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the following description.

[Example 1]
High-density polyethylene (PE100 grade third-generation polyethylene) was used as the first resin composition for forming the first resin layer (innermost layer).
As a second resin composition for forming the fiber-reinforced resin layer (intermediate layer), 80% by mass of high-density polyethylene (PE100 grade third-generation polyethylene) and glass fiber (average fiber length: 400 μm, average fiber diameter: A mixed material mixed with 13 μm and an aspect ratio of 30.8) 20% by mass was used.
High-density polyethylene (PE100 grade third-generation polyethylene) was used as the third resin composition for forming the second resin layer (outermost layer).

The pipe was manufactured as follows using the manufacturing apparatus 20 shown in FIG.
A first resin composition, a second resin composition, and a third resin composition were supplied to a mold 21 capable of obtaining a three-layer tubular molded body. The temperature of the mold 21 was set to 200 ° C. Further, an orientation ring was installed between the land and the core of the mold 21, that is, in the flow path of the resin composition. Next, by extrusion-molding each resin composition at an extrusion rate of 100 kgf / h, the first resin layer and the second resin layer contain high-density polyethylene, and the fiber-reinforced resin layer contains high-density polyethylene and glass fiber. A three-layered tubular body containing and having glass fibers not inclined from the axial direction of the tubular body toward the circumferential direction of the tubular body was obtained. The obtained three-layer tubular body had an SDR of 11 and a nominal diameter of 100.
The rotary take-up machine 24 was operated under the conditions of linear speed and rotation speed at which the twist angle was 45 ° with respect to the shaft, and the three-layer tubular body was taken over 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 pipe.

In the obtained pipe, a spiral molding mark was formed on the inner surface of the first resin layer by a convex portion along the axial direction of the pipe. Further, a spiral molding mark was formed on the outer surface of the second resin layer by a convex portion along the axial direction of the pipe.
The obtained pipe had an outer diameter of 114 mm and an SDR of 11. The thickness of the first resin layer is 18% of the thickness of the pipe, the thickness of the fiber reinforced resin layer is 67% of the thickness of the pipe, and the thickness of the second resin layer is that of the pipe. It was 15% of the thickness. That is, the ratio of the thickness of each layer (thickness of the first resin layer: thickness of the fiber reinforced resin layer: thickness of the second resin layer) was about 1: 4: 1.

With respect to the obtained pipe, the orientation angle (θ1) of the fiber F in an arbitrary region (α) on the outer surface of the fiber reinforced resin layer was measured as follows. In the region (α), the ratio of the fibers F oriented at θ1 = 45 ° ± 25 ° was determined. Similarly, the orientation angle (θ1) of the fiber F was measured for an arbitrary region (β) in the central portion in the thickness direction of the fiber reinforced resin layer and an arbitrary region (γ) on the inner surface. In the region (β), the ratio of the fibers F oriented at θ1 = 45 ° ± 25 ° was determined. In the region (γ), the ratio of the fibers F oriented at θ1 = 45 ° ± 25 ° was determined. The results are shown in Table 1.
Further, for the obtained pipe, the average values of the inclination angles θ2 and θ3 of the spiral molding marks were obtained as follows. The results are shown in Table 1.
In addition, the linear expansion coefficient and the breaking water pressure of the obtained pipe were measured as follows. The results are shown in Table 1.

[Example 2]
A pipe was manufactured and various measurements were carried out in the same manner as in Example 1 except that glass fibers having an average fiber length of 380 μm, an average fiber diameter of 10 μm and an aspect ratio of 38.0 were used. The results are shown in Table 1.

[Example 3]
Pipes were manufactured and various measurements were carried out in the same manner as in Example 1 except that glass fibers having an average fiber length of 350 μm, an average fiber diameter of 7 μm and an aspect ratio of 50.0 were used. The results are shown in Table 1.

[Example 4]
Pipes were manufactured and various measurements were carried out in the same manner as in Example 1 except that glass fibers having an average fiber length of 200 μm, an average fiber diameter of 13 μm and an aspect ratio of 15.4 were used. The results are shown in Table 1.

[Comparative Example 1]
Using glass fibers having an average fiber length of 200 μm, an average fiber diameter of 13 μm, and an aspect ratio of 15.4, the twist angle was set to 0 ° (that is, the three-layer tubular body was taken over without twisting. Except for the above), a pipe was manufactured in the same manner as in Example 1, and various measurements were performed. The results are shown in Table 1.
The thickness of the first resin layer is 15% of the thickness of the pipe, the thickness of the fiber reinforced resin layer is 67% of the thickness of the pipe, and the thickness of the second resin layer is that of the pipe. It was 18% of the thickness. That is, the ratio of the thickness of each layer (thickness of the first resin layer: thickness of the fiber reinforced resin layer: thickness of the second resin layer) was about 1: 4: 1.

[Comparative Example 2]
A pipe was manufactured in the same manner as in Example 1 except that glass fibers having an average fiber length of 200 μm, an average fiber diameter of 13 μm, and an aspect ratio of 15.4 were used and the twist angle was 70 °. , Various measurements were made. The results are shown in Table 1.

[Comparative Example 3]
Using glass fibers having an average fiber length of 350 μm, an average fiber diameter of 7 μm, and an aspect ratio of 50.0, the twist angle was set to 0 ° (that is, the three-layer tubular body was taken over without twisting. Except for the above), a pipe was manufactured in the same manner as in Example 1, and various measurements were performed. The results are shown in Table 1.

[Comparative Example 4]
A pipe was manufactured in the same manner as in Example 1 except that glass fibers having an average fiber length of 350 μm, an average fiber diameter of 7 μm, and an aspect ratio of 50.0 were used and the twist angle was 70 °. , Various measurements were made. The results are shown in Table 1.

[Measurement / evaluation]
(1) Method for measuring the orientation angle θ1 of the fiber F and the number ratio In an arbitrary region of the pipe, the pipe is sliced in the axial direction from the outer surface until the outer surface of the fiber-reinforced resin layer is exposed, and a scanning electron microscope (SEM) is used. , "JSM-6701F" manufactured by JEOL Ltd.), and a cross section (arbitrary region (α)) obtained was photographed. Using image analysis software, among the fibers photographed in the micrograph, only the fibers F whose distance L between one end and the other end is at least twice the average fiber diameter D of the fibers themselves are selected and oriented with respect to the fibers F. The angle θ1 was obtained respectively. The ratio of the number of fibers F oriented at θ1 = 45 ° ± 25 ° to the total number of fibers F (100%) was calculated.
Next, the fiber-reinforced resin layer was sliced in the axial direction of the pipe until it reached the central portion in the thickness direction of the fiber-reinforced resin layer, and the cross section (arbitrary region (β)) obtained by using SEM was photographed. Only the fiber F was selected using image analysis software, and the orientation angle θ1 was obtained for each fiber F. The ratio of the number of fibers F oriented at θ1 = 45 ° ± 25 ° to the total number of fibers F (100%) was calculated.
Next, the fiber-reinforced resin layer was sliced in the axial direction of the pipe until it reached the inner surface of the fiber-reinforced resin layer, and the cross section (arbitrary region (γ)) obtained by using SEM was photographed. Only the fiber F was selected using image analysis software, and the orientation angle θ1 was obtained for each fiber F. The ratio of the number of fibers F oriented at θ1 = 45 ° ± 25 ° to the total number of fibers F (100%) was calculated.
The imaging conditions in the SEM were a vapor deposition thickness of 10 nm, an acceleration voltage of 15 kV, and a magnification of 25 times.

(2) Method for measuring the average value of the inclination angles θ2 and θ3 of the spiral molding mark A line was drawn horizontally from an arbitrary point on the inner surface of the pipe in the axial direction of the pipe. This line was set to 0 °, and the inclination angle θ2 of an arbitrary spiral molding mark was periodically measured using a protractor having curvable flexibility. The inclination angle θ2 was measured for each specified production amount (for example, 4 m), and the average value was calculated.
A line was drawn horizontally from any point on the outer surface of the pipe with respect to the axial direction of the pipe. This line was set to 0 °, and the inclination angle θ3 of an arbitrary spiral molding mark was periodically measured using a protractor having curvable flexibility. The inclination angle θ3 was measured for each specified production amount (for example, 4 m), and the average value was calculated.

(3) Measurement of coefficient of linear expansion The pipe was cut to an arbitrary length and cured in a constant temperature bath set to an arbitrary temperature (Hot) for 24 hours. After curing, the length of the pipe (Lhot) was measured. After that, the same pipe is cured for 24 hours in a constant temperature bath set to an arbitrary temperature (Tcool) lower than Hot, the length of the pipe (Lcool) is measured, and the coefficient of linear expansion of the pipe is calculated from the following formula (2). It was calculated and evaluated according to the following evaluation criteria. Pass A.
Linear expansion coefficient = (Lhot-Lcool) / {Lcool (Hot-Tcool)} ... (2)
<Evaluation criteria>
A: The coefficient of linear expansion is 5.0 × 10 ^-5 / ° C or less.
B: The coefficient of linear expansion is more than 5.0 × ^10-5 / ° C.

(4) Measurement of breaking water pressure A water pressure was applied to the pipe at a boosting speed of 0.11 MPa / sec, and the breaking water pressure until the pipe cracked or cracked was determined and evaluated according to the following evaluation criteria. Pass A. The following evaluation criteria are evaluation criteria set on the assumption that the piping is used for piping through which high-pressure water flows during use (for example, the working pressure resistance is 1.5 MPa or more). For such pipes with high working pressure (for example, cold / hot water pipes in the air conditioning / sanitary field, cleaning liquid pipes in the cooling water pipe and plant fields, fire extinguishing pipes in the fire extinguishing field), a breaking water pressure standard of 4 times or more the maximum working pressure is required. Has been done. When the pipe according to the present invention is used as a pipe having a high pressure resistance, it is preferable that the breaking water pressure when a water pressure is applied at a boosting speed of 0.11 MPa / sec is 6.0 MPa or more, but it is used for other purposes. In some cases, the breaking water pressure may be less than 6.0 MPa. For example, when the pipe is used as a drainage pipe, a chemical liquid pipe, or the like, the breaking water pressure may be less than 6.0 MPa or less than 4.8 MPa.
<Evaluation criteria>
A: The breaking water pressure is 6.0 MPa or more.
B: The breaking water pressure is less than 6.0 MPa.

As shown in Table 1, the pipes obtained in each example had excellent pressure resistance even when thinned, and had a small coefficient of linear expansion.
On the other hand, the pipes obtained in each comparative example did not satisfy both the pressure resistance and the coefficient of linear expansion.

10 Piping 11 Fiber reinforced resin layer 12 Resin layer (first resin layer)
12a Convex part 13 Resin layer (second resin layer)
13a Convex 14 Fiber 141 A fiber whose distance L is at least twice the average fiber diameter D (fiber F).
142 Distance L is less than twice the average fiber diameter D Fiber X Piping axis direction Y Direction perpendicular to the piping axis direction (piping circumferential direction)
L1 Orientation direction of fiber F L2 Spiral direction in spiral molding mark L3 Spiral direction in spiral molding mark θ1 Of the angle formed by the axial direction and fiber F, the angle formed by the acute angle (orientation angle of fiber F)
θ2 The angle between the axial direction and the molding mark, which is the acute angle (tilt angle of the spiral molding mark)
θ3 The angle between the axial direction and the molding mark, which is the acute angle (tilt angle of the spiral molding mark)

Claims (5)

A pipe provided with a tubular fiber-reinforced resin layer containing a resin and fibers having an average fiber length of 15 mm or less.
The inner surface of the pipe has a spiral molding mark about the axis of the pipe.
In a plan view of an arbitrary region of the pipe, when one of the axial directions of the pipe is 0 °, one of the directions perpendicular to the axial direction is 90 °, and the other is −90 °, the axial direction is set. Of the angles formed by the molding marks and the molding marks, the acute angle θ1 is more than 0 ° and less than 90 °.
A pipe in which the orientation angle θ1 of the following fiber F, which is the angle formed by the axial direction and the following fiber F, which is the acute angle, satisfies the following conditions (A), (B), and (C).
Condition (A): In an arbitrary region (α) on the outer surface of the fiber reinforced resin layer, the fibers F oriented at θ1 = 45 ° ± 25 ° are the total number of fibers F contained in the region (α). It is 50% or more with respect to the number.
Condition (B): In an arbitrary region (β) at the center of the fiber reinforced resin layer in the thickness direction, the fiber F oriented at θ1 = 45 ° ± 25 ° is included in the region (β). It is 50% or more with respect to the total number of fibers F.
Condition (C): In an arbitrary region (γ) on the inner surface of the fiber reinforced resin layer, the fibers F oriented at θ1 = 45 ° ± 25 ° are the total number of fibers F contained in the region (γ). It is 50% or more with respect to the number.
Fiber F: The average fiber diameter of the fiber itself is defined as the average fiber diameter D. The distance L in the length direction in each cross section of the fiber observed in the cross section of the fiber reinforced resin layer along the axial direction is defined as the distance L. Among the fibers observed in the cross section of the fiber reinforced resin layer along the axial direction, the fiber whose distance L is at least twice the average fiber diameter D is defined as the fiber F. The pipe according to claim 1, wherein the aspect ratio represented by the average fiber length of the fiber / the average fiber diameter of the fiber is 20 or more. The pipe according to claim 1 or 2, wherein the fiber is glass fiber. The 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. The pipe according to claim 4, wherein the fiber-reinforced resin layer and the resin contained in the resin layer are polyolefin resins.

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