JP2002234067A - Method for manufacturing resin tube having excellent shape memory properties and inner surface resin lining steel tube using the resin tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a resin tube having excellent shape memory characteristics. SOLUTION: The method for manufacturing the resin tube having the excellent shape memory characteristics comprises the steps of extruding a thermoplastic resin from a double annular die by an extruder to a tubular element, thereafter contacting an outside of the element with an inside of a tapered sizing die attached to an input side of a vacuum cooling tank where cooling water is injected in a shower state, and passing the element therethrough. The element arrives at a tapered part before the element is sufficiently solidified, radially contracted or enlarged while being cooled to impart a residual stress necessary for the shape memory properties, and its outer diameter is fixed at a parallel part of the element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin pipe and a method for manufacturing an inner resin-lined steel pipe using the same. The present invention relates to a method for manufacturing an inner resin-lined steel pipe suitable for a steel pipe.

[0002]

2. Description of the Related Art In recent years, an inner resin-lined steel pipe having a resin layer on the inner surface of a steel pipe has been used for the purpose of corrosion prevention and the like. After being inserted into the inside of the steel pipe, a method is used in which the resin pipe is expanded to adhere to the inner surface of the steel pipe.

In this case, the shape-memory resin tube is restored to the stored outer diameter by heating. Although a method of spraying powder onto the inner surface of a steel pipe is also employed, the productivity is poor and it is hard to say that this method is suitable for obtaining a thick lining layer.

[0004] Like a general resin tube which does not show shape memory, the shape memory resin tube first fixes the outer diameter of the tube.
After extruding the molten resin from the die of the extruder, it is guided to a vacuum water tank, and the outer diameter of the tube is fixed by a sizing die arranged at the entrance of the vacuum water tank. A plurality of vacuum water tanks are arranged according to desired cooling.

[0005] Next, in order to impart shape memory, as a secondary process, the tube whose shape is fixed is reheated to reduce the diameter. Thereafter, the shape is fixed by cooling again. The diameter reduction may be performed by causing a difference in the take-up speed between the two take-up machines. By such a process, the manufactured tube has a high residual stress, and when heated, exhibits a property of relieving the residual stress and returning to the shape before tensile deformation: shape memory. In some cases, the molten resin is extruded from an extruder and subjected to a series of steps up to tensile deformation for imparting residual stress.

[0006]

However, the method of reducing the diameter by reheating in order to impart a residual stress to the once cooled pipe by the above-described method has a poor thermal efficiency, and the molten resin is extruded from the extruder. When extruding and performing tensile deformation to impart residual stress in a series of steps, a long facility space is required. The present invention has been made in order to solve these problems. A sizing die having a tapered portion reduces the diameter while performing solidification of a molten resin, thereby imparting residual stress, thereby improving thermal efficiency and production efficiency. It is an object of the present invention to provide a method for producing a resin tube having excellent shape memory properties and excellent properties.

[0007]

Means for Solving the Problems The present inventors diligently studied a method for imparting residual stress, and focused on a sizing die which was conventionally provided at the entrance of a vacuum water tank for fixing the outer shape of a tube. However, it has been found that in a sizing die, when a taper is provided inside the resin comes into contact with the resin, a residual stress sufficient to impart shape memory to the tube can be given.

The present invention has been made by further studying these findings. That is, the present invention provides: A method for producing a resin tube, comprising extruding a thermoplastic resin from an extrusion die, and passing the thermoplastic resin through a sizing die having a tapered portion to reduce the diameter to impart shape memory.

[0009] 2. An inner resin-lined steel pipe in which the inner surface of the steel pipe is lined with a resin layer, the resin pipe having the outer diameter smaller than the inner diameter of the steel pipe according to the method described in 1 is disposed inside the steel pipe, and thereafter, the resin pipe is heated to manufacture. Inner surface resin lined steel pipe.

[0010] 3. 0.7% radially after lining
3. The inner resin-lined steel pipe according to 2, excellent in surface properties, having a resin lining layer that expands as described above.

[0011]

FIG. 1 shows an example of a process for extruding a resin tube for carrying out the present invention. The molten resin is extruded from an extruder 1 using a double ring die 2 or the like so as to form a tubular body 3. Thereafter, the tubular body 3 is guided to a vacuum cooling tank 5 in which a sizing die 4 is installed. I will The sizing die 4 is provided with a tapered portion, and by passing through the tapered portion, the tubular body 3 is reduced in diameter while being cooled, and a residual stress is applied. Then, the tubular body 3
Are parallel portions, the outer diameter of which is fixed, and the resin tube 7 has a predetermined size. After being further cooled, the resin pipe 7 coming out of the sizing die 4 is taken up by a take-up machine 6.

FIG. 2 is a schematic view showing a sizing die provided with a tapered portion. The sizing die 4 has parallel portions on the entrance side and the exit side with the tapered portion interposed therebetween. The tubular body 3 is
From the left side of the sizing die 4, it proceeds in a molten state to a parallel portion on the entry side, and is reduced in diameter while solidifying at a tapered portion.
Thereafter, the outer diameter is fixed at the outlet side parallel portion.

In the present invention, the resin used is not specified. Styrene butadiene copolymer with excellent shape memory, polyurethane, polynorbornene, etc.
Polyolefin resins such as polymethylpentene, polybutene, ionomer, polystyrene, polycarbonate,
It is possible to apply to engineering plastics and the like.

In the present invention, it is not necessary to define properties such as density, MFR and molecular weight. Additives such as a plasticizer, a pigment, a filler, a flame retardant, an antioxidant, an ultraviolet absorber, a charging material, a lubricant, and a tackifier may be added, and a blend resin containing other resins may be used.

Using the shape memory resin tube according to the present invention,
Manufacture of inner surface resin-lined steel pipe is possible. The inner lining inserts a shape-memory resin tube having an outer diameter smaller than the inner diameter of the steel tube into the steel tube, and then heats the resin tube to a melting point or higher. The resin pipe expands in the radial direction due to shape memory, and sticks to the inner surface of the steel pipe.

Incidentally, after the lining, if the fragments cut out from the lining layer expand further by 0.7% or more in the radial direction by reheating, a lining layer having particularly excellent surface properties was obtained.

The steel pipe used for the inner resin-lined steel pipe is as follows:
The inner surface may be plated, chemically treated, or treated with a primer, while the outer surface of the shape memory resin tube may be coated with an adhesive.

[0018]

EXAMPLES (Example 1) High density polyethylene (melting point 12
8 °) was manufactured using a tapered sizing die. The extrusion die used is a double ring die,
Outer inner diameter 32mmΦ, mandrel outer diameter 29mmΦ
And The extruder was used to extrude the molten resin from a double-ring die into a tubular body at an extrusion temperature of 180 ° C.

The tubular body moves inside the tapered sizing die attached to the entrance side of the vacuum cooling tank in which the cooling water at a water temperature of 20 ° C. is sprayed in a shower shape, and the cooling body proceeds. Before sufficiently solidifying, the tubular body reaches the tapered portion, is reduced in diameter while being cooled, and then reaches the parallel portion, and the outer diameter is fixed.

The resin tube (tubular body) coming out of the vacuum cooling tank is
It was picked up by a pick-up machine. The sizing die has an inner diameter of a parallel part on the entrance side: 32 mmφ, a length: 30 mm, a length of a taper part: 50 mm, an inner diameter of a parallel part on the exit side: 26.5 mmφ,
Length: 30 mm was used.

FIG. 2 shows the change over time in the expansion coefficient when the obtained resin tube is poured into silicone oil heated to 140 ° C. The resin tube expands in the radial direction with the passage of time. Remarkable shape memory was observed. However, expansion rate (%) = (outside diameter after heating−outside diameter before heating) / outside diameter before heating × 1
00.

The obtained resin pipe (outer diameter: about 26 mmφ) is inserted into a steel pipe (inner diameter: 27.3 mmφ), and the steel pipe surface temperature becomes 1
It heated under various conditions so that it might be 00-350 degreeC. By heating, the internal resin pipe was restored to its shape before being reduced in diameter, and adhered to the inner surface of the steel pipe. After cooling, the resin pipe protruding from the end of the steel pipe was cut.

From the lining layer of the inner resin-lined steel pipe manufactured as described above, a piece was sampled, immersed in hot water at 85 ° C., and examined to what extent the lining further expanded after lining in the radial direction. As a result, in the case of the lining layer expanded 0.7% or more, the inner lining layer was excellent in surface properties without deformation such as wrinkles and shrinkage.

Example 2 Ionomer (melting point 94 °)
Was manufactured using a tapered sizing die. The extrusion die used was a double ring die with an outer inner diameter of 32 mmΦ and a mandrel outer diameter of 29 mmΦ.
It was extruded at an extrusion temperature of 160 ° C. by an extruder so as to form a tubular body from the double ring die.

The tubular body moves inside the tapered sizing die attached to the entrance side of the vacuum cooling tank in which cooling water at a water temperature of 20 ° C. is sprayed in a shower shape, and the cooling proceeds. Before sufficiently solidifying, the tubular body reaches the tapered portion, is reduced in diameter while being cooled, and then reaches the parallel portion, and the outer diameter is fixed. The resin tube (tubular body) coming out of the vacuum cooling tank was taken by a take-up machine. In addition, the sizing die having the same dimensions as in Example 1 was used.

FIG. 2 also shows the change over time in the expansion coefficient when the obtained resin tube was poured into silicone oil heated to 140 ° C., together with Example 1. It expanded in the radial direction, and remarkable shape memory was observed.

The obtained resin pipe (outer diameter about 26 mmφ) was inserted into a steel pipe (inner diameter 27.3 mmφ), and the steel pipe surface temperature was 9 mm.
It heated under various conditions so that it might be 4-250 degreeC. By heating, the internal resin tube is restored to the shape before diameter reduction,
It adhered to the inner surface of the steel pipe. After cooling, the resin pipe protruding from the end of the steel pipe was cut.

From the lining layer of the inner resin-lined steel pipe manufactured as described above, a piece was sampled, immersed in hot water of 85 ° C., and even after the lining, the extent of further expansion in the radial direction was examined. As a result, in the case of the lining layer expanded by 0.7% or more, the inner lining layer was excellent in surface properties without deformation such as wrinkles and shrinkage.

[0029]

As described above, in the method of manufacturing a shape memory resin tube of the present invention, the residual stress required for the shape memory property is applied by the tapered portion provided on the sizing die.
It is excellent in productivity and equipment space, and is extremely effective industrially.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a resin tube manufacturing process for carrying out the present invention.

FIG. 2 is a sectional view showing an example of a tapered sizing die of the present invention.

FIG. 3 is a view showing a shape memory characteristic of a resin tube according to the present invention.

[Description of Signs] 1 ... Extruder, 2 ... Double ring die, 3 ... Tube body, 4 ... Sizing die, 5 ... Vacuum cooling tank 6 ... Retractor, 7 ... Resin pipe.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuhiro Harada 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Akihiko Furuta 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Sun F-term (reference) in this steel pipe company 4F207 AA05 AG08 AH43 AH46 AR06 KA01 KA17 KK54 KK56 KK76 KW41 4F211 AD12 AG03 AG08 AH43 AH46 AR06 SC03 SD04 SG01 SH18 SP21

Claims (3)

[Claims] 1. A method for producing a resin tube, comprising: extruding a thermoplastic resin from an extrusion die, and then passing the thermoplastic resin through a sizing die having a tapered portion to reduce the diameter to impart shape memory. 2. An inner resin-lined steel pipe in which an inner surface of the steel pipe is lined with a resin layer, wherein the resin pipe according to the method of claim 1 having an outer diameter smaller than the inner diameter of the steel pipe is disposed inside the steel pipe. An inner resin-lined steel pipe manufactured by heating a resin pipe. 3. The inner-surface resin-lined steel pipe according to claim 2, wherein the inner-surface resin tube has excellent surface properties, further comprising a resin lining layer which expands in the radial direction by 0.7% or more after lining.