JP4487591B2 - Resin pipe having shape memory characteristics and inner surface resin-lined steel pipe using the resin pipe - Google Patents

Description

  The present invention relates to a resin tube having shape memory characteristics and a manufacturing method thereof. The present invention also relates to an inner surface resin-lined steel pipe obtained by lining the resin pipe on the inner surface of the steel pipe.

  In recent years, for the purpose of corrosion prevention, for example, an inner surface resin-lined steel pipe in which a resin lining layer is formed on the inner surface of a steel pipe used for water supply, hot water supply, air conditioning, drainage, and the like has been used. As a method of forming a resin lining layer on the inner surface of a steel pipe, there is a method of spraying resin powder onto the inner surface of the steel pipe. However, this method is poor in productivity and is not a suitable method for obtaining a thick lining layer. .

  Therefore, as a lining layer forming method with higher productivity, a resin tube having an outer diameter slightly smaller than the inner diameter of the steel pipe and having a shape memory characteristic that expands outside the inner diameter of the steel pipe by heating is placed in the steel pipe and then heated. Thus, a method is used in which the resin tube is expanded and attached to the inner surface of the steel tube. In this case, the resin tube recovers to the memorized outer diameter by heating.

  A resin tube having shape memory characteristics is manufactured by the following method. First, in the same manner as general resin pipes that do not have shape memory characteristics, the molten resin is extruded from a die of an extruder, led to a vacuum cooling tank, and a sizing die arranged at the inlet of the vacuum cooling tank is used to remove the resin pipe. Fix the diameter. A plurality of vacuum cooling tanks are arranged according to the desired cooling. Next, in order to impart shape memory characteristics, the resin tube having a fixed outer diameter is reheated, subjected to diameter reduction processing, and then cooled again to fix the shape. The resin tube manufactured by such a process has a high residual stress, and when the resin tube is heated, the resin tube exhibits a property (shape memory characteristic) of releasing the residual stress and returning to the shape before the diameter reduction processing.

In the diameter reduction processing, there is a method of reducing the diameter of a resin pipe by causing a difference in take-up speed between two take-up machines (hereinafter referred to as Prior Art 1). As an alternative method, Patent Document 1 provides a taper sizing die immediately after the extruder on the entrance side of a vacuum cooling tank (shower type vacuum cooling tank) in which cooling water is sprayed in a shower shape. A method of reducing the diameter of the resin tube by passing through the resin tube while cooling the resin tube and applying a residual stress necessary for imparting shape memory characteristics has been proposed (hereinafter, Prior Art 2).
JP 2002-234067 A (page 3)

  However, in prior art 1, since the diameter is reduced only by the speed difference between the two take-up machines, a larger drawing ratio is required in the axial direction in order to obtain a desired diameter reduction ratio. The resin pipe to which shape memory characteristics are imparted by this method requires a larger axial shrinkage in order to obtain a desired outer diameter expansion. Therefore, in the lining process, the resin pipe is caused to shrink in the axial direction due to resistance caused by friction with the inner surface of the steel pipe. Since the required time becomes longer and the time for expanding the outer diameter also becomes longer, there is a problem that the productivity of the lining process cannot be increased as a result.

  Further, the method described in Prior Art 2 has a problem that the resin tube is easily clogged by the tapered portion of the tapered sizing die when the diameter is reduced, and the productivity of the process of imparting shape memory characteristics to the resin tube is lowered. is there.

The present invention solves the above problems, has no problem of reducing productivity in the process of imparting shape memory characteristics to the resin pipe, and improves the productivity in the lining process when lining the resin pipe to the inner surface of the steel pipe. inner surface plastic lined steel pipe with plastic pipe and its tree fat tube having a can shape memory properties is to provide.

  The gist of the present invention for solving the above problems is as follows.

The first invention is extruded from an extruder, water-cooled, brought into close contact with a sizing die by vacuum drawing, cooled and cured, and further heated to a predetermined shape memory characteristic imparting temperature in a heating furnace, to a tapered sizing die surface close contact allowed to cool, while being cured, reduced diameter to a shape resin tube storage characteristics are imparted, the radial expansion ratio Rd at the time of re-heated to 60 seconds held in the predetermined shape memory properties imparted temperature 1 to 30%, axial shrinkage R1 is 30% or less, and the ratio Rd / R1 of the radial expansion coefficient Rd and the axial shrinkage ratio R1 is 0.8 or more. It is a resin tube having memory characteristics.
However,
Rd = (da−ds) / da × 100 (%)
Rl = (La−Ls) / La × 100 (%)
ds: outer diameter of resin tube before reheating to shape memory property imparting temperature da: outer diameter of resin tube after holding for 60 seconds at shape memory property imparting temperature Ls: resin tube before reheating to shape memory property imparting temperature Length La: Length of the resin tube after holding for 60 seconds at the shape memory property imparting temperature

A second invention is an inner surface resin-lined steel pipe characterized in that a resin layer formed by heating the resin pipe of the first invention is coated on the inner surface of the steel pipe.

A third invention is an inner surface resin-lined steel pipe whose inner surface is covered with a resin layer , the resin pipe according to the first invention having an outer diameter smaller than the inner diameter of the outer steel pipe disposed in the steel pipe , and then the resin pipe It is an inner surface resin-lined steel pipe manufactured by heating the tube and expanding its outer diameter to coat the inner surface of the steel pipe.

According to the first shot bright resin pipe, the axial shrinkage is small when the inflated outside diameter by heating the resin tube, the productivity in the lining process when lining the resin pipe inner surface of the steel pipe Can be improved.

By lining the first shot Ming resin pipe inner surface of the steel pipe, the productivity in manufacturing the inner surface plastic lined steel pipe is improved (the second invention, the third invention).

  The present inventors paid attention to the fact that the resin pipe provided with shape memory characteristics using a tapered sizing die is excellent in productivity when manufacturing an inner surface resin-lined steel pipe, and using the tapered sizing die. A method for solving the problem of Prior Art 2 when manufacturing a resin pipe having shape memory characteristics was examined. As a result, when imparting shape memory characteristics by reducing the diameter with a tapered sizing die, Prior Art 2 showers the cooling water in order to efficiently reduce the diameter while solidifying the molten resin. Although the resin tube is directly cooled by spraying in the shape of a tube, if the resin tube is not directly cooled with cooling water, it is found that the clogging of the resin tube in the taper portion can be prevented, and further investigation results. The present inventors have also found a resin pipe having shape memory characteristics that is excellent in productivity when manufacturing a resin pipe having the above and also has excellent productivity in a lining process when manufacturing an inner surface resin-lined steel pipe. The present invention is based on this finding.

  Hereinafter, the reasons for limitation of the present invention will be described.

Resin tube having shape memory properties according to the present invention, the radial expansion ratio when reheated to 60 seconds held in a predetermined shape memory characteristic applying temperature Rd is less than 30% 1%, the axial shrinkage Rl 30% or less, and the ratio Rd / Rl of the radial expansion rate Rd and the axial shrinkage rate Rl is 0.8 or more.
However,
Rd = (da−ds) / da × 100 (%)
Rl = (La−Ls) / La × 100 (%)
ds: outer diameter of resin tube before reheating to shape memory property imparting temperature da: outer diameter of resin tube after holding for 60 seconds at shape memory property imparting temperature Ls: resin tube before reheating to shape memory property imparting temperature length La: length of the resin tube after shape memory properties imparted temperature 60 seconds hold in the present invention, by reheating the radial expansion of the resin tube Rd and the axial shrinkage Rl shape memory properties imparted temperature The reason why it is defined by the numerical value when held for 60 seconds is as follows.

The shape memory property imparting temperature is a temperature at which the resin tube is heated when the shape memory property is imparted to the resin tube. In order to impart a good shape restoration property, the shape memory property imparting temperature is Teg or higher, Teg + 50 It is preferable to set it as below ℃. Where Teg is the glass transition end temperature of the resin. In the temperature range above the glass transition start temperature and below the glass transition end temperature (Teg), the resin is in the process of changing from the glass state to the rubber state. not obtained a stable shape recovery properties when reheated imparting resin tube. Moreover, when it exceeds Teg + 50 ° C., the rubber elastic modulus is lowered, and when the resin tube is heated, a good shape restoring property cannot be obtained. A more preferable temperature of the shape memory property imparting temperature is Teg or more and Teg + 10 ° C. or less.

In the lining process in which the resin pipe is lined on the inner surface of the steel pipe, the heating temperature of the resin pipe is usually set to a temperature equal to or higher than the shape memory characteristic imparting temperature. Therefore, by evaluating the radial expansion ratio Rd at the time of re-heating the resin tube shape memory imparted temperature and axial shrinkage Rl, the shape recovery property in the lining process can be properly evaluated. The reason for setting the heating time to 60 seconds is that the evaluation result at this heating time was able to appropriately evaluate the shape restoration property in the lining process.

Radial expansion coefficient Rd: 1% or more and 30% or less When the radial expansion coefficient Rd is less than 1%, it becomes difficult to insert the resin pipe into the steel pipe in the lining process. On the other hand, in order to increase the radial expansion coefficient Rd to more than 30%, it is necessary to increase the processing degree of the diameter reduction processing at the time of manufacturing the resin pipe. As a result, clogging or folding is likely to occur at the tapered portion during the production of the resin tube, making it difficult to produce the resin tube. The radial expansion coefficient Rd is more preferably 3% or more and 25% or less.

Axial shrinkage rate Rl: 30% or less When the axial shrinkage rate Rl is 30% or less, the productivity of the lining process is excellent. When the axial shrinkage ratio Rl exceeds 30%, the resistance due to friction with the inner surface of the steel pipe increases in the lining process, and time is required for axial contraction and time is required for expansion of the outer diameter. The productivity of the lining process is reduced. The axial shrinkage ratio Rl is more preferably 25% or less.

Ratio of radial expansion rate Rd and axial contraction rate Rl (Rd / Rl): 0.8 or more In the case of diameter reduction by simple pulling using two take-up machines, the ratio of radial deformation to axial deformation (Radial deformation / axial deformation) is constant (determined by Poisson's ratio for each material) and is usually less than 0.8. By setting Rd / Rl to 0.8 or more, it becomes a resin pipe that can be restored in the radial direction while suppressing shrinkage in the axial direction, and the productivity of the lining process can be improved. In the present invention, Rd / Rl can be made 0.8 or more by reducing the diameter of a resin tube through a tapered sizing die at a predetermined shape memory characteristic application temperature to give the shape memory characteristic. In order to further improve the productivity in the lining process, it is more preferable that Rd / Rl is 1.0 or more.

  The resin species targeted by the present invention is not particularly defined. It is possible to use polystyrene, polycarbonate, engineering plastics (for example, polysulfone, polycarbonate, modified polyphenylene ether, etc.) having poor shape memory characteristics, such as styrene-butadiene copolymers having excellent shape memory characteristics, polyurethane, and pororbornene. .

  In the present invention, it is not necessary to define characteristics such as resin density, MFR, and molecular weight. Additives such as plasticizers, pigments, fillers, flame retardants, antioxidants, ultraviolet absorbers, charging agents, lubricants, and tackifiers may be added, and blend resins may be added with other resins.

  Next, the manufacturing method of the resin pipe | tube which has the shape memory characteristic of this invention is demonstrated.

  FIG. 1 is a diagram showing a configuration example of a resin pipe manufacturing facility used for manufacturing a resin pipe having shape memory characteristics of the present invention. In FIG. 1, 1 is an extruder, 2 is a resin tube, 3 is a vacuum cooling tank, 4 is a first take-up machine, 5 is a heating furnace, 6 is a tapered sizing die, 7 is a dry vacuum tank, 8 is a cooling tank, 9 is a second take-up machine.

  The vacuum cooling tank 3 is provided with a shower device (not shown) on the inlet side for cooling by spraying cooling water directly on the outer surface of the tube in a shower shape. A sizing die 3a is disposed at the entrance of the vacuum cooling bath. The sizing die 3a includes a water cooling jacket in which cooling water is supplied. Between the heating furnace 5 and the dry vacuum tank 7, the shower apparatus which cools by injecting cooling water directly on the resin pipe 2 surface is not arrange | positioned. In addition, in this specification, a dry vacuum tank means the vacuum tank which does not have the water shower equipment which water-cools a resin pipe | tube directly.

  FIG. 2 is an enlarged cross-sectional view illustrating the detailed structure of the dry vacuum chamber 7 and the cooling bath 8 arranged in the facility of FIG. The tapered sizing die 6 is disposed in the dry vacuum chamber 7 and has parallel portions 6a and 6c on the entry side and the exit side, respectively, across the taper portion 6b.

  The tapered sizing die 6 is provided with a plurality of suction holes 16 that lead from the resin tube passage portion to the vacuum chamber 15 of the dry vacuum chamber 7. By sucking the atmosphere in the vacuum chamber 15 with the vacuum pump 17, the resin tube 2 passing through the tapered sizing die 6 is evacuated and brought into close contact with the surface of the tapered sizing die 6, and is cooled and cured.

  The tapered sizing die 6 includes a cooling jacket 13 to which cooling water is supplied. In this apparatus, since the resin tube is not directly cooled by water in the water shower, the temperature of the cooling water supplied to the cooling jacket 13 of the tapered sizing die 6 is lowered to cool the tapered sizing die 6, and the surface temperature thereof is lower than a predetermined temperature. Keep it at a low temperature. The cooling water is cooled to a predetermined temperature by a temperature adjusting device (not shown), supplied from the cooling water supply port 12 to the water cooling jacket 13 of the tapered sizing die 6, and discharged from the cooling water discharge port 14.

  In the cooling tank 8, the resin tube is submerged and cooled, or the resin tube is cooled by a water shower.

  1, the extruded resin is extruded from the extruder 1 so as to form a tubular shape, and the extruded tubular resin is directly water-cooled by a shower device (not shown) on the inlet side of the vacuum cooling tank. Guided to the vacuum cooling bath 3. It is cooled and hardened by being vacuumed in the vacuum cooling tank 3 and closely contacting the surrounding sizing die 3a, and cooled to a temperature at which there is no problem in taking up the resin tube, usually about 20 ° C. or lower. Taken by the machine 4.

  Next, it is heated to a predetermined shape memory characteristic imparting temperature in the heating furnace 5 and guided to a dry vacuum chamber 7 in which a tapered sizing die 6 is installed.

  The resin tube 2 passes through the tapered portion 6b of the tapered sizing die 6 of the dry vacuum chamber 7 while being held in a temperature range suitable for imparting shape memory characteristics. During this time, the diameter is reduced in the radial direction while the axial stretching rate is suppressed, and residual stress is applied. Further, by sucking the atmosphere in the vacuum chamber 15 with the vacuum pump 17, the resin tube passing through the tapered sizing die 6 is evacuated and brought into close contact with the surface of the tapered sizing die 6, and the resin tube 2 is cooled and cured. Is done.

  In the apparatus according to the present embodiment, since the shower device is not provided on the entry side of the dry vacuum chamber 7, the resin tube is cooled in a dry state while the diameter is reduced in the entry side of the dry vacuum chamber 7 and the dry vacuum chamber 7. The In the present invention, the dry state means that the resin tube is not directly cooled with a water shower. In this section, the resin tube 2 is indirectly cooled by a tapered sizing die 6 having a cooling jacket. By cooling the resin tube 2 in a dry state, the resin tube 2 can be prevented from being clogged with the tapered portion 6b. The reason that the clogging of the resin tube 2 at the taper portion 6b can be prevented is because the resin tube 2 is no longer directly cooled by the cooling water, so that the resin tube 2 is not locally cooled below the glass transition temperature. It is done.

  In the apparatus according to the present embodiment, the tapered sizing die 6 has parallel portions 6a and 6c in front and rear of the taper portion 6b, so that the resin tube 2 can ensure the stability of the outer diameter before and after the diameter reduction. The Further, as a result of the diameter reduction processing of the resin tube 2 in a state where the resin tube 2 is held at a predetermined shape memory characteristic application temperature in the tapered portion 6b, fluctuations in the applied shape memory characteristics are reduced.

  From the viewpoint of enhancing the ability to cool the resin pipe passing through the tapered sizing die 6, the die surface temperature (mold surface temperature) of the tapered sizing die 6 is preferably 50 ° C. or less, more preferably 20 ° C. or less. . By adjusting the temperature of the cooling water supplied to the cooling jacket 13, the temperature of the tapered sizing die 6 can be easily adjusted.

  The resin pipe 2 that has passed through the tapered sizing die 6 passes through the adjacent cooling tank 8 and is cooled to a temperature that is not hindered by the downstream second take-up machine 9 and is usually about 20 ° C. or lower. The outer diameter is fixed, the resin pipe 2 has a predetermined size, and is taken up by the second take-up machine 9.

  In the present invention, a gas such as air may be blown onto the resin tube as necessary from the viewpoint of improving the cooling capacity within a range not impairing the effects of the present invention. Further, from the viewpoint of improving lubricity, a self-lubricating material may be coated on the resin tube, and a lubricant may be supplied to the surface of the resin tube or the tapered sizing die.

  In the facility shown in FIG. 1, the vacuum cooling tank 3, the first take-up machine 4, and the heating furnace 5 are disposed upstream of the dry vacuum tank 7. The resin extruded into a tubular shape may be introduced into the tapered sizing die 6 of the dry vacuum chamber 7 to impart shape memory characteristics.

By lining the resin pipe having shape memory characteristics according to the present invention on the inner surface of the steel pipe, it is possible to manufacture the inner surface resin-lined steel pipe. Disposing a first shot bright tree fat tube having an outer diameter smaller than the inner diameter of the steel pipe in the steel, then, the inner surface resin lining was coated on the steel tube surface to expand the outer diameter by heating the resin tube Manufacture steel pipes. Specifically, in accordance with the method for manufacturing a resin pipe of the present invention described above, after fixing the outer diameter of the resin pipe to an outer diameter larger than the inner diameter of the steel pipe, the diameter is reduced to an outer diameter smaller than the inner diameter of the steel pipe to obtain shape memory characteristics. The resin pipe which has is manufactured. The resin tube is inserted into the steel tube, and then heated within the range of the glass transition end temperature (Teg) of the resin tube to the shape memory property imparting temperature + 50 ° C. or less. The heated resin tube expands in the radial direction while being contracted in the length direction due to its shape memory characteristics, and sticks to the inside of the steel tube.

  The steel pipe used for the inner surface resin-lined steel pipe may be one whose inner surface is plated, chemically treated, or primed.

  A resin tube made of a modified polyphenylene ether resin (Teg: 170 ° C.) having an outer diameter of 32 mm and a wall thickness of 0.8 mm is provided with shape memory characteristics using a resin tube manufacturing facility including the tapered sizing die 6 shown in FIG. Temperature: A resin tube having a shape memory characteristic was produced by reducing the diameter after heating to 180 ° C. The cooling tank 8 used a water shower device. Table 1 shows the shape of the tapered sizing die 6. At that time, the temperature of the cooling water supplied to the cooling jacket for cooling the tapered sizing die 6 was adjusted to change the surface temperature (mold surface temperature) of the tapered sizing die 6 (cooling state: dry). For comparison, in the equipment shown in FIG. 1, a shower device was installed on the inlet side of the dry vacuum chamber 7 and the resin tube was directly water-cooled, and then a resin tube having shape memory characteristics was produced (cooled state). : Wet). The presence or absence of clogging with the tapered sizing die 6 during the production of the resin pipe was investigated. Resin pipes in which clogging did not occur were examined for shape memory characteristics. Table 2 shows the manufacturing conditions and the investigation results of the characteristics of the resin pipe to which the shape memory characteristics are imparted. For comparison, Table 2 also shows a case where the diameter is reduced by the method of the prior art 1 and shape memory characteristics are imparted to the resin pipe (conventional manufacturing method).

  The manufactured resin tube was inserted into the inner surface of a steel pipe having an inner diameter of φ27.5 mm and a wall thickness of 3.2 mm, and heated so that the temperature of the resin tube became 180 ° C., and the resin tube was lined on the inner surface of the steel pipe. The productivity evaluation results in the lining process are also shown in Table 2.

  In the comparative example, clogging of the resin tube occurred in the taper portion of the sizing die with taper, and the resin tube could not be manufactured. However, in the present invention example, there was no clogging and the resin tube could be manufactured without any problem. . The resin pipe of the present invention example has a smaller axial shrinkage than the conventional resin pipe, and Rd / Rl is 0.8 or more. Furthermore, the lining property (productivity) when the resin pipe of the present invention is lined on the inner surface of the steel pipe to produce the inner surface resin-lined steel pipe is manufactured by lining the resin pipe of the conventional example on the inner surface of the steel pipe. Compared to the conventional lining, the productivity is improved twice as much as the conventional example.

  A resin tube made of a modified polyphenylene ether resin (Teg: 170 ° C.) having an outer diameter of φ59 mm and a wall thickness of 0.8 mm is provided with shape memory characteristics using a resin tube manufacturing facility including the tapered sizing die 6 shown in FIG. Temperature: A resin tube having a shape memory characteristic was produced by reducing the diameter after heating to 180 ° C. The cooling tank 8 used a water shower device. Table 3 shows the shape of the tapered sizing die 6. At that time, the temperature of the cooling water supplied to the cooling jacket for cooling the tapered sizing die 6 was adjusted to change the surface temperature (mold surface temperature) of the tapered sizing die 6 (cooling state: dry). For comparison, in the equipment shown in FIG. 1, a shower device was installed on the inlet side of the dry vacuum chamber 7 and the resin tube was directly water-cooled, and then a resin tube having shape memory characteristics was produced (cooled state). : Wet). The presence or absence of clogging with the tapered sizing die 6 during the production of the resin pipe was investigated. Resin pipes in which clogging did not occur were examined for shape memory characteristics. Table 4 shows the manufacturing conditions of the resin pipe to which the shape memory characteristics are imparted and the investigation results of the characteristics. For comparison, Table 4 also describes the case where the diameter is reduced by the method of the prior art 1 and shape memory characteristics are imparted to the resin pipe (conventional manufacturing method).

  The resin pipe produced above was inserted into the inner surface of a steel pipe having an inner diameter of 52.9 mm and a wall thickness of 3.8 mm, and heated so that the temperature of the resin pipe reached 180 ° C., and the resin pipe was lined on the inner surface of the steel pipe. The evaluation results of productivity in the lining process are also shown in Table 4.

  In the comparative example, clogging of the resin tube occurred in the taper portion of the sizing die with taper, and the resin tube could not be manufactured. However, in the present invention example, there was no clogging and the resin tube could be manufactured without any problem. . The resin pipe of the present invention example has a smaller axial shrinkage than the conventional resin pipe, and Rd / Rl is 0.8 or more. Furthermore, the lining property (productivity) when the resin pipe of the present invention is lined on the inner surface of the steel pipe to produce the inner surface resin-lined steel pipe is manufactured by lining the resin pipe of the conventional example on the inner surface of the steel pipe. It is superior to the conventional lining, and the productivity is more than twice that of the conventional example.

  The resin pipe manufacturing method of the present invention can be used as a method of manufacturing a resin pipe having a shape memory characteristic by reducing its diameter with a tapered sizing die.

  The resin pipe of the present invention and the resin pipe produced by the method of the present invention can be used as a resin pipe lining on the inner surface of an inner surface resin-lined steel pipe used for piping for water supply, hot water supply, air conditioning, drainage and the like.

It is a figure which shows one structural example of the resin pipe manufacturing equipment used for manufacture of the resin pipe which has the shape memory characteristic of this invention. It is a cross-sectional enlarged view explaining the detailed structure of the dry vacuum tank and cooling tank part arrange | positioned at the installation of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Extruder 2 Resin pipe 3 Vacuum cooling tank 3a Sizing die 4 First take-up machine 5 Heating furnace 6 Tapered sizing die 7 Dry vacuum tank 8 Cooling tank 9 Second take-up machine 12 Cooling water supply port 13 Cooling jacket 14 Cooling water discharge Outlet 15 Vacuum chamber 16 Suction hole 17 Vacuum pump

Claims (3)

Extruded from an extruder, cooled with water, cooled and hardened by being in close contact with a sizing die by vacuuming, and further heated in a heating furnace to a predetermined shape memory property imparting temperature, and in close contact with the surface of the tapered sizing die, cooling while being cured, a resin tube shape memory characteristics are imparted reduced in diameter, the radial expansion ratio Rd at the time of re-heated to 60 seconds held in the predetermined shape memory properties imparted temperature over 1% 30 % Or less, an axial shrinkage ratio R1 of 30% or less, and a ratio Rd / R1 of the radial expansion coefficient Rd and the axial shrinkage ratio R1 is 0.8 or more. tube.
However,
Rd = (da−ds) / da × 100 (%)
Rl = (La−Ls) / La × 100 (%)
ds: outer diameter of resin tube before reheating to shape memory property imparting temperature da: outer diameter of resin tube after holding for 60 seconds at shape memory property imparting temperature Ls: resin tube before reheating to shape memory property imparting temperature Length La: Length of the resin tube after holding for 60 seconds at the shape memory property imparting temperature An inner surface resin-lined steel pipe, wherein a resin layer formed by heating the resin pipe according to claim 1 is coated on the inner surface of the steel pipe. An inner surface resin-lined steel pipe whose inner surface is coated with a resin layer, the resin pipe according to claim 1 having an outer diameter smaller than the inner diameter of the outer steel pipe in the steel pipe , and then the resin pipe is heated to An inner surface resin-lined steel pipe produced by expanding its outer diameter and coating the inner surface of the steel pipe.

Images