JP6799963B2 - Resin pipes, resin pipe manufacturing methods, and piping structures - Google Patents

Description

The present invention relates to a flexible resin pipe made of polybutene, cross-linked polyethylene, or the like, a method for producing the resin pipe, and a piping structure using the resin pipe.

In recent years, flexible resin pipes made of polybutene, cross-linked polyethylene, etc. are wrapped in an annular shape over a length of several tens of meters (meters) and packed, unlike inflexible metal pipes and vinyl chloride pipes. It can be stored and transported in the state of being in the state, and when it is used at the construction site, it has advantages such as being able to cut it to a desired length and bend it in a desired direction for piping. It is often used in piping structures for water supply or hot water supply (for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2001-65008

However, in the flexible resin pipe as described above, when the pipe is bent at a steep angle (and thus with a small radius of curvature), after a long period of use, the bent portion of the pipe is used. Cracks are likely to occur on the inner peripheral surface, and if cracks occur, the cracks may penetrate the peripheral wall of the pipe and cause water leakage. The mechanism of this crack generation will be described in detail with reference to FIG.

FIG. 4A shows a flexible resin pipe (hereinafter, simply referred to as “pipe”) 100 in an initial state in which no external force is applied before piping. FIG. 4B shows a state in which the pipe 100 of FIG. 4A is bent at a steep angle and piped. As shown in FIG. 4B, when viewed in a cross section along the central axis O of the pipe 100, the bent portion of the piped pipe 100 has a center of curvature C with respect to the central axis O of the pipe 100. A stress load in the compression direction is applied to the peripheral wall portion on the side, and a stress load in the tensile direction is applied to the peripheral wall portion on the side opposite to the center of curvature C with respect to the central axis O. On the other hand, in general, an antioxidant is added to the resin constituting the tube 100 in order to suppress deterioration due to oxidation of the resin, and the antioxidant is conveyed from the inner peripheral side of the tube 100. It flows out into the fluid. In addition, tap water generally contains chlorine for disinfection, and chlorine has an effect of accelerating deterioration due to oxidation of the resin. As described above, due to the gradual decrease of the antioxidant in the resin constituting the pipe 100, the constant exposure of the pipe 100 to chlorine contained in the water in the pipe 100, and the like, with the passage of time. , The pipe 100 gradually deteriorates from the inner peripheral side. When the deterioration of the inner peripheral side of the pipe 100 progresses to some extent, a stress load in the tensile direction is always applied, and the inner peripheral surface portion on the side opposite to the center of curvature C with respect to the central axis O is substantially along the circumferential direction. Crack 101 is likely to occur.

By the way, as in the example of FIG. 4A, when the conventional pipe 100 is used at a construction site, it is in a state of being taken out of the packing material (an initial state in which no external force is applied before piping). ) Has a so-called curl that curves in a certain direction with a radius of curvature of about 400 mm. Such a curl is imparted to the tube 100 during the production of the tube 100, after being formed into a tubular shape by extrusion molding of a resin and then being cured in a wound state. Then, as in the example of FIG. 4, when the pipe 100 is bent in the direction opposite to the bending direction (winding habit direction) of the pipe 100 in the initial state, the pipe 100 is assumed to be in the initial state. Since the stress load acting on the pipe 100 is larger than that in the case where the pipe is bent in the same direction as the bending direction of the pipe 100, cracks are more likely to occur.
In order to suppress the occurrence of cracks as much as possible, it is ideal not to pipe the pipe 100 in a state of being bent in the direction opposite to the direction of bending in the initial state of the pipe 100 at the construction site. Or, when connecting under the water heater after penetrating it through the skeleton, it is often piped in a state of being bent in the opposite direction. In addition, it is difficult in reality because it limits the degree of freedom in arranging the water supply equipment in the building and the layout of the pipes.

As described above, the conventional flexible resin pipe has been required to have improved durability.

The present invention is for solving the above-mentioned problems, and is a resin pipe having improved durability, a method for manufacturing a resin pipe capable of obtaining a resin pipe having improved durability, and improved durability. It is an object of the present invention to provide a pipe structure.

The resin tube of the present invention is a flexible resin tube, and in the initial state where no external force is applied, the radius of curvature of the outer peripheral surface portion on the curvature center C1 side with respect to the central axis of the curved tube. R1 is 750 mm or more, curves in the direction opposite to the direction of curvature of the tube in the initial state from the initial state, and the radius of curvature of the outer peripheral surface portion on the curvature center C2 side with respect to the central axis. When the pipe is bent into a bent state such that R2 has a predetermined minimum bending radius for the pipe, the inner peripheral surface located on the curvature center C1 side with respect to the central axis in the initial state. It is characterized in that the distortion of the portion is 8.5% or less.
According to the resin tube of the present invention, durability can be improved.

It is preferable that the resin tube of the present invention is maintained in a wound state by a packing material.
According to this, the pipe can be protected from scratches and the like.
In the resin pipe of the present invention, the length of the pipe may be 10 m or more.

The method for producing a resin tube of the present invention is the method for producing the above-mentioned resin tube, which comprises an extrusion molding step of forming a thermoplastic resin into a tubular body by extrusion molding, and after the extrusion molding step, the tubular body. After the curing step and the curing step of curing the tubular body in a linearly extending state, the tubular body is wound and the tubular body is maintained in a wound state by a packing material, whereby the resin tube is formed. It is characterized by including a packing process and the like.
According to the method for producing a resin tube of the present invention, the durability of the tube can be improved.

The piping structure of the present invention is a piping structure for water supply or hot water supply arranged in a building using the above resin pipe.
According to the piping structure of the present invention, durability can be improved.

According to the present invention, it is possible to provide a resin pipe having improved durability, a method for manufacturing a resin pipe capable of obtaining a resin pipe having improved durability, and a piping structure having improved durability. ..

It is sectional drawing along the central axis of the pipe for demonstrating one Embodiment of the resin pipe of this invention, FIG. 1 (a) shows the pipe in the initial state, and FIG. 1 (b) bends the pipe. Shown in state. It is a graph which shows the result of the durability test of a resin pipe. It is a figure for demonstrating the process until one Embodiment of the resin tube of this invention is obtained. It is sectional drawing along the central axis of the pipe for demonstrating the problem of the conventional resin pipe, FIG. 4A shows the pipe in the initial state, and FIG. 4B shows the pipe bent and piped. It is shown in the state of.

Hereinafter, the resin pipe, the method for manufacturing the resin pipe, and the embodiment of the pipe structure according to the present invention will be illustrated and described with reference to the drawings.

FIG. 1 shows a resin pipe (hereinafter, also simply referred to as “tube”) 10 according to an embodiment of the present invention. The pipe 10 of the present embodiment is a flexible resin pipe made of a thermoplastic resin such as polybutene or cross-linked polyethylene (PEX), for example, in a piping structure for water supply or hot water supply arranged in a building. It is preferably used. The nominal diameter of the tube 10 is, for example, 10 to 25 or the like. However, the pipe 10 of the present embodiment can also be used for a pipe structure for a fluid (liquid or gas) other than water.
Here, "flexible" means that the material has an elastic modulus of 200 to 900 MPa and does not break even if there is a material strain of about 5%.

The pipe 10 of the present embodiment is maintained in a state of being wound in an annular shape over a length of about 10 m or more (for example, 30 m or 60 m) by a packing material after the pipe is manufactured through an extrusion molding step and a curing step. It is stored and transported, and then taken out of the packing material when it is used at a construction site.

FIG. 1A shows a state when the pipe 10 of the present embodiment is in an initial state in which no external force acts on the pipe 10. In the initial state, the pipe 10 of the present embodiment is an outer peripheral surface portion of the pipe 10 on the curvature center C1 side with respect to the central axis O of the curved pipe 10 when viewed in a cross section passing through the central axis O of the pipe 10. The radius of curvature R1 is 750 mm or more. Here, the radius of curvature R1 of the tube 10 in the initial state is a radius of curvature caused only by the winding habit attached to the tube 10. As described above, the radius of curvature R1 of the resin pipe 10 of the present embodiment in the initial state is made larger than that of the conventional resin pipe described above. In other words, the curl of the resin pipe 10 of the present embodiment is smaller than that of the conventional resin pipe.
As a result, the amount of deformation (and thus distortion) of the pipe when the pipe is bent from the initial state to a predetermined bending state in which the pipe is curved in the direction opposite to the direction of curvature (direction of curl) in the initial state. , Can be reduced compared to conventional resin pipes. Therefore, if the pipe 10 is piped in a state of being bent in the direction opposite to the direction of the curl, the stress load acting on the pipe 10 can be reduced, and eventually cracks are generated in the bent portion. Can be suppressed. Thereby, the durability of the pipe 10 (and the pipe structure using the pipe 10) can be improved.
The curl of the tube 10 can be reduced by appropriately adjusting the manufacturing method described later.
From the viewpoint of improving durability, the smaller the curl of the tube 10, the better. Therefore, in the initial state, it is preferable that the radius of curvature R1 of the outer peripheral surface portion on the curvature center C1 side with respect to the center axis O of the tube 10 is 900 mm or more when viewed in a cross section passing through the center axis O of the tube 10. Is.

FIG. 1B shows a state in which the pipe 10 of the present embodiment is bent so as to be curved in the direction opposite to the bending direction of the pipe 10 in the initial state. In the bending state shown in FIG. 1B, the radius of curvature R2 of the outer peripheral surface portion of the pipe 10 on the side of the center of curvature C2 with respect to the central axis O of the pipe 10 is set to the minimum bending radius predetermined for the pipe 10. Has been made. In the following, such a bent state is also simply referred to as a “bent state”. In this example, the predetermined minimum bending radius of the pipe 10 is 10 times the outer diameter D of the pipe 10 (that is, R2 = 10D).
The "predetermined minimum bending radius for a pipe" is recommended or specified by the manufacturer of the pipe, or by the association (for example, the Bridged Polyethylene Pipe Industry Association) or the standard related to the pipe. Refers to the minimum bending radius (minimum value of bending radius) when pipes are installed. For example, the Cross-Linked Polyethylene Pipe Industry Association has set recommended values (references) for the minimum bending radius of cross-linked polyethylene pipes for each nominal diameter of the pipe, but in any nominal diameter, the outer diameter D of the pipe The minimum bending radius equivalent to about 10 times is set (Technical data of Cross-Linked Polyethylene Pipe Industry Association Chapter 5 Construction Standards (5) Bending Pipe 1). For Polybutene pipes manufactured and sold by Bridgestone Corporation, the company recommends that the minimum bending radius be 10 times the outer diameter D of the pipe.

The pipe 10 of the present embodiment is viewed from the initial state of FIG. 1A to the bent state of FIG. 1B when the pipe 10 is bent and viewed in a cross section passing through the central axis O of the pipe 10. The distortion of the predetermined inner peripheral surface portion 20 located on the curvature center C1 side with respect to the central axis O of the pipe 10 in the initial state is 8.5% or less.
The above distortion can be obtained by the following equation (1):
Distortion = {(YX) / X} x 100 (%) ... (1)
Here, X in the equation (1) is arbitrarily selected in advance on the curvature center C1 side with respect to the central axis O of the tube 10 in the initial state when viewed in a cross section passing through the central axis O of the tube 10. It is the length of a predetermined inner peripheral surface portion 20. Y in the formula (1) is the predetermined inner peripheral surface portion (hereinafter, also referred to as “measurement target portion”) which is the measurement target in the initial state when viewed in a cross section passing through the central axis O of the pipe 10. 20 is the length when the pipe 10 is in the bent state. When the tube 10 is in the bent state, the measurement target portion 20 is located on the side opposite to the center of curvature C2 with respect to the central axis O of the tube 10.

The lengths X and Y in the formula (1) may be obtained by providing a strain gauge on the measurement target portion 20 and measuring, or may be obtained by partial calculation. As a method of obtaining the lengths X and Y by partial calculation, for example, when viewed in a cross section passing through the central axis O of the tube 10, a predetermined value located on the curvature center C1 side with respect to the measurement target portion 20 in the initial state. There is a method of measuring the lengths of the outer peripheral surface portion in the initial state and the bent state, respectively, and calculating using the measurement results. In that case, using the measurement result, the outer diameter D of the pipe 10, the thickness T of the peripheral wall, the radius of curvature R1 in the initial state, the radius of curvature R2 in the bent state (10D in this example), and the like, The lengths X and Y of the measurement target portion 20 can be calculated.

When the pipe 10 of the present embodiment is bent from the initial state to the above-mentioned bent state, the above-mentioned strain is 8.5% or less. Therefore, the pipe 10 is assumed to be in the direction opposite to the direction of the curl. When the pipe is piped in a bent state, the stress load acting on the pipe 10 can be reduced, and the occurrence of cracks in the bent portion can be suppressed. Thereby, the durability of the pipe 10 (and the pipe structure using the pipe 10) can be improved. Hereinafter, this effect will be described in more detail with reference to FIG.

FIG. 2 is a graph showing the results of a durability test carried out using a normal polybutene tube. In this durability test, 12 tubes are bent, 3 each, so that the strains obtained by the above formula (1) are 5.6%, 6.8%, 8.5%, and 9.7%. While maintaining the bent state, water was continuously passed through each pipe, and the time required for each pipe to break was measured. Each tube had the same dimensions, and the winding habit of the tube (the radius of curvature of the outer peripheral surface portion on the center of curvature side with respect to the central axis of the tube in the initial state) was the same. The strain of each pipe was adjusted to each value by adjusting the degree of bending (radius of curvature of the outer peripheral surface portion on the center of curvature side with respect to the central axis of the pipe in the bent state). During the test, the strain of each pipe, the temperature and pressure of water passing through the pipe, and the residual chlorine concentration (concentration of chlorine component in water) were controlled to be always constant.
As can be seen from the results of FIG. 2, when the strain of the pipe is 5.6%, 6.8%, and 8.5%, the strain of the pipe is 9.7%, until the pipe breaks. It took a lot of time.
As is supported by this test result, the pipe 10 of the present embodiment has good durability because the above-mentioned strain when the pipe 10 is bent from the above-mentioned initial state to the bent state is 8.5% or less. It is what you get.
Further, as can be seen from this test result, the lower the strain, the better the durability of the pipe. Therefore, it can be said that the strain is preferably 6.8% or less, and more preferably 5.6% or less.

Next, an example of a manufacturing method for obtaining the tube 10 of the present embodiment will be described with reference to FIG.
First, the thermoplastic resin (polybutene, cross-linked polyethylene, etc.) constituting the tube 10 is formed into a tubular body by extrusion molding (extrusion molding step).
Then, as shown in FIG. 3A, the formed tubular body is cured over a predetermined time in a state in which the formed tubular body is linearly extended over a length of, for example, about 10 m or more (for example, 30 m or 60 m). Let (curing process). As a result, a linear flexible resin tubular body having no curl can be obtained. Here, "curing" refers to a chemical reaction in which the resin becomes hard, for example, when the resin is polybutene, it refers to crystallization, and when the resin is cross-linked polyethylene, for example, it refers to a cross-linking reaction. ..
As described above, from the viewpoint of improving durability, the smaller the curl of the tube, the more preferable it is, and most ideally, there is no curl at all. However, when storing and transporting a pipe extending over about 10 m, it is practically difficult to maintain the pipe in a straightened state from the viewpoint of space restrictions.

Therefore, after the curing step, as shown in FIG. 3B, the cured tubular body is wound in an annular shape over a length of about 10 m or more (for example, 30 m or 60 m), and the packing material 40 is used to wind the tubular body. Maintain the rolled state (packing process). The tubular body will be stored and transported in a packaged state. Meanwhile, the packing material 40 protects the tubular body from scratches and the like. Further, the tubular body gradually becomes curled with the passage of time while the state of being wound in an annular shape by the packing material 40 is maintained.
Then, when the tubular body is taken out from the packing material 40 when used at a construction site or the like, the pipe 10 of the present embodiment is obtained.

In the curing step described above, when the tubular body obtained by the extrusion molding step is cured in a linearly extending state, if the tubular body is made of polyethylene, the time and temperature for crystallization should be adjusted. Further, when the tubular body is made of cross-linked polyethylene, the degree of cross-linking can be adjusted to prevent curling habits in the subsequent packing process. As a result, the curl of the tube obtained after the packing process can be reduced.

From the viewpoint of suppressing the winding habit attached to the pipe as much as possible, the annular shape of the pipe 10 maintained by the packing material 40 in the packing process has an inner diameter d1 of 700 mm or more and an outer diameter d2 of 900 mm or more. Suitable. Further, from the viewpoint of obtaining good transportability of the pipe 10 packed by the packing material 40, the annular shape of the pipe 10 maintained by the packing material 40 in the packing process has an inner diameter d1 of 900 mm or less and an outer diameter d2. However, it is preferable that it is 1100 m or less.
In the pipe 10 of the present embodiment, the radius of curvature R1 in the initial state can be made larger than the maximum radius of the packing material 40 (that is, half of the outer diameter d2 of the packing material 40). Therefore, while the pipe is wound by the packing material 40 in the packing process, the space required for storing or transporting the pipe can be reduced, and since it is easy to carry, the construction work can be lightened.

Further, from the viewpoint of suppressing the winding habit attached to the pipe as much as possible, it is preferable that the period in which the pipe 10 is kept wound by the packing material 40 after the packing process is within 3 months.

When storing and transporting a pipe with a length of about 10 m or more, it is practically difficult to carry out the pipe in a straightened state due to space restrictions, so it is necessary to carry out the pipe in a wound state. It becomes. Therefore, in the initial state, the pipe 10 of the present embodiment obtained after the packing step has an outer peripheral surface on the curvature center C1 side with respect to the central axis O of the pipe 10 when viewed in a cross section passing through the central axis O of the pipe 10. The radius of curvature R1 of the portion tends to be practically about 1800 mm or less. Further, from the same viewpoint, in the pipe 10 of the present embodiment obtained after the packing process, the above-mentioned distortion when the pipe 10 is bent from the initial state to the bent state tends to be practically about 3.0% or more. In the pipe 10 of the present embodiment obtained after the packing step, when the radius of curvature R1 in the initial state is 1800 mm, the strain when the pipe 10 is bent from the initial state to the bent state is 3.0. It becomes%.

In the packing process, the outer peripheral side of the pipe 10 may be covered with another tubular member. As another tubular member that covers the tube 10, for example, a tubular member for heat retention, cushioning, and scratch prevention is suitable.

As described above, in the above example, in the curing step, the tube is cured in a straight extending state, and after the curing is completed, the tube is wound in the packing process. Compared with the case where the tube is wound, the winding habit of the tube when it is taken out from the packing material can be significantly reduced. As a result, as described above, the tube 100 having less curl and improved durability can be obtained. Further, the durability of the water supply or hot water supply piping structure arranged in the building using the pipe 10 of the present embodiment is also improved.

Since the pipe 10 of the present embodiment has improved durability as described above, in other words, even if the pipe 10 is bent at a steeper angle than allowed by the conventional resin pipe, the conventional pipe 10 is used. It is possible to suppress the occurrence of cracks and breaks in the pipe for the same period as the resin pipe.
For example, when the nominal diameter of the pipe 10 of the present embodiment is 13 (that is, the outer diameter is 17 mm), even if the bending radius is reduced to 150 to 170 mm, the pipe cracks or cracks occur over the same period as the conventional resin pipe. Occurrence of breakage can be suppressed.

The resin pipe according to the present invention can be used, for example, for a flexible resin pipe made of polybutene or cross-linked polyethylene, which is used in a piping structure for water supply / hot water supply.

10, 100: Resin pipe, 20: Measurement target part (inner peripheral surface part), 40: Packing material, 101: Crack, C, C1, C2: Center of curvature, D: Outer diameter of pipe, O: Center axis

Claims (4)

A flexible resin tube
In the initial state in which no external force is applied, the radius of curvature R1 of the outer peripheral surface portion on the curvature center C1 side with respect to the central axis of the curved pipe is 750 mm or more.
From the initial state, the radius of curvature R2 of the outer peripheral surface portion on the curvature center C2 side with respect to the central axis is predetermined for the tube while being curved in the direction opposite to the direction of curvature of the tube in the initial state. When the pipe is bent to a bent state such as the minimum bending radius, the distortion of the inner peripheral surface portion located on the curvature center C1 side with respect to the central axis in the initial state is 8.5. % or less and Do Ri,
The pipe is a resin pipe that is maintained in a wound state by a packing material . The resin pipe according to claim 1 , wherein the length of the pipe is 10 m or more. The method for manufacturing a resin tube according to claim 1 or 2 .
An extrusion molding process in which a thermoplastic resin is formed into a tubular body by extrusion molding,
After the extrusion molding step, a curing step of curing the tubular body in a linearly extending state,
After the curing step, the tubular body is wound, and the tubular body is maintained in a wound state by a packing material, whereby the resin tube is obtained.
A method for producing a resin tube, which comprises. A piping structure for water supply or hot water supply arranged in a building using the resin pipe according to claim 1 or 2 .

Images