TWI639504B - Resin tube, method for manufacturing resin tube, and piping structure - Google Patents

Abstract

An object of the present invention is to provide a resin tube having improved durability, a method for manufacturing a resin tube capable of obtaining a resin tube having improved durability, and a piping structure having improved durability.

The resin tube of the present invention is a flexible resin tube 10, and in the initial state without external force, the radius of curvature R1 of the peripheral surface portion on the side of the center of curvature C1 with respect to the center axis O of the bent tube is 750 mm In the above, when the tube is bent from the initial state to the direction opposite to the bending direction of the tube in the initial state, and the radius of curvature R2 of the peripheral surface portion on the side of the center of curvature C2 with respect to the center axis becomes the minimum predetermined for the tube In the bending state of the bending radius, the strain of the inner peripheral surface portion 20 on the side of the center of curvature C1 with respect to the initial state of the central axis becomes 8.5% or less.

Description

Resin tube, method for manufacturing resin tube, and piping structure

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

In recent years, flexible resin pipes made of polybutene, cross-linked polyethylene, etc. are different from non-flexible metal pipes or vinyl chloride pipes, etc., and can cover lengths of tens of meters (meters). It can be stored or transported in a state of being wound down in a ring shape, and it can be cut to a desired length and bent into a desired direction to form a pipe when used at the construction site. These advantages Therefore, it is often used as a piping structure for water supply or hot water supply in buildings (for example, Patent Document 1).

Prior art literature

Patent Document 1 Japanese Patent Laid-Open No. 2001-65008

However, when the flexible resin tube is formed at a large angle (and further with a small radius of curvature) to form a piping, after a long period of use, the inner peripheral surface of the bent portion is prone to cracking. In the case of cracking, the crack may penetrate the peripheral wall of the pipe and cause leakage. The mechanism of this crack occurrence can be described in detail with reference to FIG. 4.

FIG. 4 (a) shows a flexible resin tube (hereinafter simply referred to as a “tube”) 100 in an initial state where no external force is applied before piping. Fig. 4 (b) shows a state where the pipe 100 of Fig. 4 (a) is bent at a large angle to form a pipe. As shown in FIG. 4 (b), when viewed in a cross section along the central axis O of the pipe 100, the bent portion of the pipe 100 forming the piping is located on the side of the center of curvature C with respect to the central axis O of the pipe 100 The peripheral wall part will form a stress load in the compression direction, and the curvature is relative to the central axis O The peripheral wall portion on the opposite side of the center C will cause a stress load in the tensile direction. On the other hand, generally, an antioxidant is added to the resin constituting the tube 100 to suppress the deterioration of the resin due to oxidation, but the antioxidant flows out from the inner peripheral side of the tube 100 into the transport fluid. In general, tap water contains chlorine for disinfection purposes, but chlorine has the effect of promoting deterioration due to resin oxidation. In this way, as the antioxidant in the resin constituting the tube 100 gradually decreases, or the tube 100 is continuously exposed to the chlorine contained in the water in the tube 100, the tube 100 gradually deteriorates from the inner peripheral side with the passage of time. Once the deterioration of the inner peripheral side of the tube 100 progresses to a certain degree, stress load in the tensile direction is often maintained, and the inner peripheral surface portion on the opposite side of the center of curvature O with respect to the center axis O easily occurs along the approximate circumference The direction of the crack 101.

On the other hand, as shown in the example of FIG. 4 (a), when the conventional pipe 100 is used at the construction site, it will be maintained at 400mm in a certain direction under the state of being taken out from the packaging material (the initial state without external force before piping). The degree of curvature radius is so-called winding inertia. Such a winding inertia is a material that is given to the tube 100 after being hardened in a wound state after being formed into a tube shape by extrusion of a resin during the production of the tube 100. In addition, in the example of FIG. 4, when the pipe 100 is bent in a direction opposite to the bending direction (winding inertia direction) of the pipe 100 in the initial state, the pipe is compared with the pipe 100 in the initial state. The bending direction is a case where the pipe is bent in the same direction, and the stress load acting on the pipe 100 becomes larger, so cracking is more likely to occur. In order to suppress the occurrence of cracks as much as possible, it is ideal at the construction site to avoid piping the pipe 100 in a state where the bending direction of the pipe 100 is in the opposite direction to the initial state of the pipe 100. This is the case where the body is connected behind the supply water heater, and the frequency of piping is high when the pipe is bent in the opposite direction. In addition, the degree of freedom in the location of the water appliances and the pipe layout in the building will be limited, which is actually difficult.

As such, an improvement in durability is required for conventional flexible resin pipes.

This invention is made to solve the said subject, The objective is to provide the resin pipe with improved durability, the manufacturing method of the resin pipe which can obtain the resin pipe with improved durability, and the piping structure which improved durability.

The resin tube of the present invention is a flexible resin tube. In the initial state without external force, the radius of curvature R1 of the peripheral surface portion of the center axis of the tube after the center of curvature of the tube after bending is 750 mm or more; When bending the tube from this initial state to the bend of the tube towards this initial state When the bending direction is opposite to the bending direction, and the radius of curvature R2 of the peripheral surface portion on the side of the center of curvature C2 with respect to the center axis is a bending state of the minimum bending radius predetermined for the pipe, the The strain on the inner peripheral surface of the center axis located on the side of the center of curvature C1 becomes 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 uses a sack packing material to maintain the wound state.

This prevents damage to the tube and the like.

In the resin tube of the present invention, the length of the tube may be 10 m or more.

The method for manufacturing a resin tube of the present invention is used to manufacture the above-mentioned resin tube, and includes the following processes: an extrusion molding process, which forms a thermoplastic resin into a tubular body by extrusion molding; a hardening process, which is based on the extrusion molding process Thereafter, the tubular body is hardened in a state where the tubular body is linearly extended; and a wrapping process is performed after the hardening process, the tubular body is wound and the tubular body is maintained in a wound state by a wrapping material, Thereby, this resin tube was obtained.

According to the method for manufacturing 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 supplying water or supplying hot water to a building using the resin pipe described above.

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 having improved durability, and a piping structure having improved durability.

10,100‧‧‧resin tube

20‧‧‧Measurement target part (inner peripheral surface part)

40‧‧‧ 梱 Packaging materials

101‧‧‧crack

C, C1, C2 ‧‧‧ Curvature Center

D‧‧‧ tube outside diameter

O‧‧‧center axis

FIG. 1 is a cross-sectional view along a central axis of a tube for explaining an embodiment of a resin tube of the present invention. FIG. 1 (a) shows an initial state of the tube, and FIG. 1 (b) shows a bent state of the tube.

Fig. 2 is a graph showing the results of a durability test of a resin tube.

FIG. 3 is a process diagram for explaining one embodiment of obtaining the resin tube of the present invention.

Fig. 4 is a cross-sectional view along the central axis of the pipe for explaining the problems of conventional resin pipes. Fig. 4 (a) shows the initial state of the pipe, and Fig. 4 (b) shows the state after the pipe is bent into a pipe. .

Hereinafter, the embodiments of the resin tube, the method for manufacturing the resin tube, and the piping structure according to the present invention will be described by referring to the drawings.

FIG. 1 shows a resin tube (hereinafter also simply referred to as a “tube”) 10 according to an embodiment of the present invention. The pipe 10 of this embodiment is a flexible resin pipe made of a thermoplastic resin such as polybutene or cross-linked polyethylene (PEX), and can be applied to, for example, water supply or heat supply in a building. Water piping structure. The nominal diameter of the tube 10 is, for example, 10 to 25. However, the pipe 10 of this embodiment may be used as a pipe structure for a fluid (liquid, gas) other than water.

Here, the term "flexible" refers to a material composed of a material having an elastic modulus of 200 to 900 MPa and which does not break even if the material has a strain of about 5%.

After the tube 10 of this embodiment is manufactured through an extrusion molding process and a hardening process, it is maintained in a state of being wound into a ring shape by using a packing material to cover a length of about 10 m (for example, 30 m or 60 m). After being stored and transported, it is taken out from the packaging materials when it is used at the construction site.

Fig. 1 (a) shows the appearance of the tube 10 in this embodiment when it is in the initial state without being subjected to an external force. When the tube 10 of this embodiment is viewed in an initial state through a cross section of the central axis O of the tube 10, the radius of curvature R1 of the outer peripheral portion of the tube 10 in the bent state with respect to the central axis O on the center of curvature C1 side of the tube 10 It is 750mm or more. Here, the above-mentioned curvature radius R1 of the tube 10 in the initial state is a radius of curvature resulting from the winding inertia given to the tube 10 only. As such, in the initial state, the curvature radius R1 of the resin tube 10 of this embodiment is larger than that of the conventional resin tube described above. In other words, the winding inertia of the resin tube 10 of this embodiment is smaller than that of the conventional resin tube.

Therefore, if the tube is bent in such a manner that the bending direction (the direction of winding inertia) from the initial state and the initial state is opposite to the initial state, the tube can be deformed (and further strained). ) Compared to the conventional resin tube. Accordingly, if the pipe 10 is bent in a state in which the pipe 10 is bent in a direction opposite to the winding inertia direction, the stress load acting on the pipe 10 can be reduced, and cracks at the bent portion can be suppressed. Thereby, the durability of the pipe 10 (and the piping structure using the pipe 10) can be improved.

The winding inertia of the tube 10 can be reduced by appropriately adjusting a manufacturing method described later.

In addition, from the viewpoint of improving the durability, the smaller the winding inertia of the tube 10 is, the better. Therefore, when viewed in an initial state in a cross section passing through the central axis O of the tube 10, the radius of curvature R1 of the peripheral surface portion on the side of the center of curvature C1 of the central axis O of the tube 10 is preferably 900 mm or more.

FIG. 1 (b) shows the appearance when the tube 10 of the present embodiment is bent in a state of being bent in a direction opposite to the bending direction of the tube 10 in the initial state. In the bent state shown in FIG. 1 (b), the radius of curvature R2 of the peripheral surface portion of the pipe 10 with respect to the center axis O of the pipe 10 on the side of the center of curvature C2 is set to be the minimum bend that is predetermined for the pipe 10. radius. In addition, the bending state as described below is also simply referred to as "bending state". In this example, the minimum bending radius predetermined for the tube 10 is 10 times the outer diameter D of the tube 10 (that is, R2 = 10D).

In addition, the so-called "minimum bending radius predetermined for a pipe" means that the pipe is recommended by the pipe manufacturer or the pipe association (such as the Cross-linked Polyethylene Pipe Industry Association) or the pipe recommended by the specifications. Minimum bending radius (minimum bending radius) during piping construction. For example, the cross-linked polyethylene pipe industry will set the recommended minimum bending radius (target) of the cross-linked polyethylene pipe according to the nominal diameter of each pipe, but all the nominal diameters are set to the equivalent of the pipe diameter. Minimum bending radius of approximately 10 times the outer diameter D (Technical Information of the Cross-linked Polyethylene Pipe Industry Association Chapter 5 Construction Standards (5) Bending Piping 1). In addition, for a pipe made of polybutene manufactured and sold by Bridgestone Corporation, the company recommends that the outer diameter D of the pipe be 10 times the minimum bending radius.

When the tube 10 of this embodiment is bent from the initial state of FIG. 1 (a) to the folded state of FIG. 1 (b) and viewed from a cross section passing through the central axis O of the tube 10, it is relative to the initial stage. The strain of the predetermined inner peripheral surface portion 20 of the central axis O of the tube 10 in the state on the side of the center of curvature C1 becomes 8.5% or less.

The above strain energy is calculated by the following formula (1): strain = {(Y-X) / X} × 100 (%) ‧‧‧ (1)

Here, X in the formula (1) is a predetermined inner peripheral surface arbitrarily selected in advance in the center of curvature C1 with respect to the center axis O of the tube 10 in the initial state when viewed in a cross section passing through the center axis O of the tube 10 Length of section 20. In the formula (1), Y is a predetermined inner peripheral surface portion (hereinafter also referred to as a “measuring object portion”) when viewed from a cross section passing through the central axis O of the tube 10 as the measurement object. 20 The length of the tube 10 when it is in a bent state. In addition, this measurement object When the tube 10 is in the bent state, the portion 20 is located on the opposite side from the center of curvature C2 of the tube 10.

The lengths X and Y in the formula (1) may be obtained by measuring by setting a strain gauge in the measurement target portion 20, or may be obtained by partial calculation. The method of obtaining the lengths X and Y by partial calculation is, for example, when looking at a cross section passing through the central axis O of the tube 10, for a predetermined outer peripheral surface portion located on the side of the center of curvature C1 with respect to the measurement target portion 20 in the initial state. The method of measuring the length of an initial state and a bending state, and using this measurement result to calculate. In this case, the measurement result can be calculated using the measurement result together with the outer diameter D of the tube 10, the thickness T of the peripheral wall, the radius of curvature R1 in the initial state, and the radius of curvature R2 in the bent state (10D in this example). 20 lengths X, Y.

When the tube 10 of this embodiment is bent from the initial state to the above-mentioned folded state, the above-mentioned strain is 8.5% or less. Therefore, if the tube 10 is bent in a state in which the tube 10 is bent in a direction opposite to the winding inertia direction, the pipe can be reduced. The stress load acting on the pipe 10 can further suppress cracks in the bent portion. Thereby, the durability of the pipe 10 (and the piping structure using the pipe 10) can be improved. Hereinafter, this effect will be described in more detail with reference to FIG. 2.

FIG. 2 is a graph showing the results of durability tests performed using a general polybutene pipe. In this durability test, each of the 12 tubes was bent in such a manner that the strains obtained by the above formula (1) became 5.6%, 6.8%, 8.5%, and 9.7%, and maintained in a bent state, and Water was continuously passed through each tube, and the time taken for each tube to rupture was measured. The sizes of the tubes are the same, and the winding inertia of the tubes (in the initial state, the radius of curvature of the peripheral surface portion on the center of curvature side with respect to the center axis of the tube) is the same. The strain of each tube is adjusted to different values by adjusting the degree of bending (the radius of curvature of the outer peripheral surface portion on the center of curvature side of the center axis of the tube in the bent state). In the test, the strain of each tube and the temperature and pressure of the water passing through the tube, as well as the residual chlorine concentration (chlorine component concentration in water), were controlled so as to always be constant.

From the results in Figure 2, it can be seen that when the strain of the tube is 5.6%, 6.8%, 8.5%, compared to the case of the tube strain of 9.7%, the time taken until the tube ruptures is greatly lengthened.

This test result proves that the tube 10 of this embodiment can obtain good durability because the strain when the tube 10 is bent from the initial state to the bent state is 8.5% or less.

In addition, from the results of this test, it can be seen that the lower the strain, the more the durability of the tube can be improved. Therefore, the above 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 according to this embodiment will be described with reference to FIG. 3.

First, the thermoplastic resin (polybutene, cross-linked polyethylene, etc.) constituting the tube 10 is extruded into a tubular body (extrusion process).

After that, as shown in FIG. 3 (a), the formed tubular body is maintained at a length of, for example, about 10 m or more (for example, 30 m or 60 m), and is hardened for a predetermined period of time in a straight and straight state (hardening process) ). Thereby, a linear flexible resin tubular body having no winding inertia is obtained. The "hardening" referred to herein refers to a chemical reaction in which the resin becomes hard. For example, when the resin is polybutene, it means crystallization, and when the resin is a crosslinked polyethylene, it means a crosslinking reaction.

As described above, from the viewpoint of improving the durability, the smaller the winding inertia of the pipe, the better, and it is ideal that there is no winding inertia at all. However, in the case of storing and transporting tubes with a length of about 10m or more, it is practically difficult to maintain the tubes in a straight state from the viewpoint of saving space.

Therefore, after the hardening process, as shown in FIG. 3 (b), the hardened tubular body is rolled into a ring shape with a length of about 10 m or more (for example, 30 m or 60 m), and is maintained by the packing material 40 Winding state (packing process). The tubular system is stored and transported in a bagged state. In the meantime, the tubular body can be prevented from being damaged by the wrapping material 40. In addition, the tubular body is maintained in a state of being wound into a ring shape by the wrapping material 40, and is gradually given a winding inertia as time passes.

Then, at the time of use at a construction site or the like, the tubular body is taken out of the packing material 40 to obtain the tube 10 of this embodiment.

In addition, in the above-mentioned hardening process, when the tubular body obtained by the extrusion molding process is hardened in a linearly extended state, when the tubular body is made of polybutene, the crystallization time and temperature are adjusted by adjusting the crystallization time and temperature. For the case of cross-linked polyethylene, by adjusting the degree of cross-linking, it is not easy to impart winding inertia in the subsequent packaging process. Furthermore, the coiling inertia of the tube obtained after the packaging process can be reduced.

In addition, from the viewpoint of suppressing the winding inertia imparted to the pipe as much as possible, it is suitable that the ring shape of the tube 10 maintained by the packing material 40 in the packing process is an inner diameter d1 of 700 mm or more and an outer diameter d2 of 900 mm or more. In addition, the tube 10 wrapped by the packing material 40 is based on good transportation From the viewpoint of performance, it is suitable that the annular shape of the tube 10 maintained by the packing material 40 in the packing process is such that the inner diameter d1 is 900 mm or less and the outer diameter d2 is 1100 m or less.

In addition, the tube 10 of the present embodiment can make the above-mentioned curvature radius R1 of the initial state larger than the maximum radius of the packing material 40 (ie, one and a half of the outer diameter d2 of the packing material 40). Therefore, in the packaging process, the tube is wound by the packaging material 40, which not only reduces the space required for storage or transportation of the tube, but also saves construction work because it is easy to hold and transport.

In addition, from the viewpoint of suppressing the winding inertia imparted to the tube as much as possible, the period during which the tube 10 is wound by the wrapping material 40 after the wrapping process is preferably within 3 months.

When storing and transporting a tube with a length of about 10m or more, in fact, from the viewpoint of space saving, it is difficult to store and transport the tube in a state where the tube extends straight, so it must be carried out while the tube is wound. Therefore, when the tube 10 of this embodiment obtained after the bundling process is viewed from the cross section of the central axis O of the tube 10 in the initial state, the radius of curvature R1 of the peripheral surface portion on the side of the center of curvature C1 with respect to the central axis O of the tube 10 is a fact. It is easy to become below about 1800mm. In addition, from the same point of view, the above-mentioned strain when the tube 10 of the present embodiment obtained after the bundling process is bent from the initial state to the folded state is actually likely to be about 3.0% or more. In addition, when the tube 10 of the present embodiment obtained after the baling process is in the initial state when the above-mentioned curvature radius R1 is 1800 mm, the above-mentioned strain when the tube 10 is bent from the initial state to the bent state becomes 3.0%.

In addition, in the packaging process, the outer peripheral side of the tube 10 may be covered with other tubular members. The other tubular members of the coating tube 10 are preferably, for example, tubular members for thermal insulation, buffering, and scratch prevention.

As such, in the above-mentioned example, the tube is hardened in the state where the tube is straightly extended in the hardening process. After the hardening is completed, the tube is wound in the ladle process, compared with the conventional method, the tube is made from the hardening process. In the wound state, the winding inertia of the tube in the state taken out from the packing material can be greatly reduced. This makes it possible to obtain the tube 100 having the aforementioned small winding inertia and improved durability. In addition, durability can also be improved by using the pipe structure of the water supply or hot water supply which the pipe 10 of this embodiment arrange | positions in a building.

In addition, the pipe 10 of the present embodiment has improved durability as described above. In other words, even when the pipe is bent at a larger angle than that allowed by conventional resin pipes, it can be suppressed in Conventional resin tubes are cracks, ruptures, and the like of tubes that occurred during the same period.

For example, when the nominal diameter of the tube 10 in this embodiment is set to 13 (that is, the outer diameter is 17 mm), even if the bending radius is reduced to 150 to 170 mm, it can still be prevented from occurring during the same period as the conventional resin tube. Cracks, ruptures, etc. of the tube.

The resin tube of the present invention can be used for flexible resin tubes made of polybutene or crosslinked polyethylene, for example, for use in piping structures for water supply and hot water supply.

Claims (6)

A flexible resin tube; the resin tube is a polybutene tube or a cross-linked polyethylene tube; in the initial state without external force, the center axis of the tube relative to the bent tube is on the side of the center of curvature C1 The radius of curvature R1 of the outer peripheral surface portion is 750 mm or more; when the tube is bent from the initial state to a direction opposite to the bending direction of the tube in the initial state, the outer peripheral surface is on the side of the center of curvature C2 with respect to the center axis When the partial curvature radius R2 is a bent state with respect to the minimum bending radius predetermined for the pipe, the strain on the inner peripheral surface portion on the C1 side of the center of curvature relative to the initial state of the central axis becomes 8.5% or less. For example, the resin tube of the scope of application for patent No. 1 wherein the tube system is maintained in a rolled state by the wrapping material. For example, the resin tube in the scope of patent application No. 1 or 2, in which the length of the tube is more than 10m. For example, the resin tube in the scope of patent application No. 1 or 2, wherein the tube is manufactured through the following process: extrusion molding process, polybutene or cross-linked polyethylene is formed into a tubular body by extrusion molding; The hardening process is performed after the extrusion molding process, and the tubular body is hardened in a linearly extended state. A method for manufacturing a resin tube, which is used to manufacture a resin tube as in any one of claims 1 to 4 of the scope of patent application; it includes the following processes: an extrusion molding process, which involves extruding polybutene or Polyethylene is formed into a tubular body; a hardening process is performed after the extruding process, and the tubular body is hardened in a linearly extended state; and a baling process is performed after the hardening process, and the tube is wound. The resin tube is obtained by maintaining the tubular body in a wound state with a wrapping material. A piping structure for water supply is obtained by using a resin pipe as set forth in any one of claims 1 to 4 in a patent application.