JP2002264202A - Method for manufacturing thermoplastic resin tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a thermoplastic resin tube capable of manufacturing the resin tube having a smooth inner peripheral surface even with a plural-layer tube having an excellent dimensional accuracy and entirely made of a foamed thermoplastic resin or containing the foamed thermoplastic resin. SOLUTION: The method for manufacturing the thermoplastic resin tube comprises the steps of continuously extruding the tube 12 of a soft state by an extrusion mold 11 by using the heat foamable thermoplastic resin as a raw material, introducing the tube into a forming tube 14 while foaming the tube 12, and cooling and forming the tube. The method further comprises the steps of contacting the outer peripheral surface of a disc 17 extended from the mold 11 side via a bar-like element 15 with the inner peripheral surface of the tube 12 at the radially inside position of the tube 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thermoplastic resin tube having a plurality of layers, which is entirely made of a foamed thermoplastic resin or contains a foamed thermoplastic resin.

[0002]

2. Description of the Related Art Conventionally, foam molding of a thermoplastic resin is frequently performed because of its performance such as light weight and heat insulation. For example, as described in JP-A-61-103085, a multilayer plastic pipe having a foamed resin layer provided inside a pipe wall of the plastic pipe is disclosed.

[0003] When a foamed resin layer is provided as an intermediate layer and a non-foamed resin layer is provided in the inner and outer layers as in this multilayer pipe,
The appearance can be kept beautiful, the fluid flowing inside the product does not penetrate into the foamed resin layer, and the foamed resin layer is not exposed outside except at the end of the tube, so you do not have to worry about the appearance There is an advantage that recycled materials can be used.

However, when manufacturing a thermoplastic resin tube which is entirely made of a foamed thermoplastic resin or has a plurality of layers containing the foamed thermoplastic resin, the obtained thermoplastic resin tube has poor dimensional stability. However, there is a problem that the use of recycled materials is even more problematic. In both physical and chemical foaming, foaming of thermoplastics begins at the extrusion die outlet and increases in thickness with the foaming, and the wall thickness is determined when the parison is cooled and foaming is completed. To do that. In addition, since the foam layer has heat insulation properties and is difficult to cool, there is a problem that the width of the variation becomes large.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned conventional problems, is excellent in dimensional accuracy, and is entirely made of a foamed thermoplastic resin or contains a plurality of foamed thermoplastic resins. An object of the present invention is to provide a method of manufacturing a thermoplastic resin tube capable of manufacturing a thermoplastic resin tube having a smooth inner peripheral surface despite having layers.

[0006]

The invention according to claim 1 of the present application (Invention 1) uses a heat-expandable thermoplastic resin as a raw material to continuously extrude a softened tube from an extrusion die. A method for producing a thermoplastic resin tube, which comprises a step of performing cooling and forming by introducing the tube into a forming tube while foaming the tube, wherein a position inside the forming tube in the radial direction is from an extrusion die side. This is a method for producing a thermoplastic resin tube in which an outer peripheral surface of a disk extended through a rod-like body is brought into contact with an inner peripheral surface of the tube.

The invention described in claim 2 of the present application (the present invention 2)
Using a heat-foamable thermoplastic resin, continuously extrude a multilayered tube in a softened state from a crosshead extrusion mold, conduct foaming of the multilayered tube, and guide it into a forming tube to perform cooling and forming. A method for manufacturing a thermoplastic resin tube having a step, wherein at the radially inner position of the forming tube, the outer peripheral surface of a disk extended from a side of an extrusion die via a rod-like body, the multilayer This is a method for producing a thermoplastic resin tube to be brought into contact with the inner peripheral surface of the tube.

The invention described in claim 3 of the present application (the present invention 3)
The present invention 1 or the present invention, wherein a plurality of rotating bodies that rotate with the progress of the tube or the multilayer tube are provided on the outer peripheral surface of the disc that contacts the inner peripheral surface of the tube or the multilayer tube. It is a manufacturing method of the thermoplastic resin pipe of invention 2.

The invention described in claim 4 of the present application (Invention 4)
An air outlet is provided in the vicinity of the outer peripheral surface of the disk contacting the inner peripheral surface of the pipe or the multi-layer pipe, and cooling / forming is performed while blowing air from the outlet to reduce frictional resistance. This is a method for producing the thermoplastic resin pipe of the present invention 1 or 2 of the present invention.

In the present invention, the thermoplastic resin includes:
For example, polyethylene, polypropylene, polybutene,
Extrudable materials such as polystyrene and polyvinyl chloride are used.

In the present invention, the foaming method of the thermoplastic resin is not particularly limited. Physical foaming such as carbon dioxide injection or chemical foaming using a pyrolytic foaming agent such as baking soda or azodicarbonamide can be used. But it doesn't matter.

[0012]

The method of manufacturing a thermoplastic resin pipe according to the first aspect of the present invention is characterized in that, at a position radially inward of the forming tube, the outer peripheral surface of a disk extended from a side of an extrusion die via a rod-like body is formed. The softened pipe guided into the forming tube by being brought into contact with the inner circumferential surface of the pipe is positioned at a position radially inside the tubular body of the forming tube. Is pressed against the inner peripheral surface of the tube, so that the tube has an intended outer diameter corresponding to the inner diameter of the tubular body of the forming tube, and the inner peripheral surface also has the expected inner diameter corresponding to the outer diameter of the disk. It is cooled and formed so as to have a smooth inner peripheral surface state in spite of being made of a foamed thermoplastic resin.

The method for producing a thermoplastic resin tube according to the second aspect of the present invention comprises:
At a position radially inward of the forming tube, an outer peripheral surface of a disk extended from a side of an extrusion die via a rod-like body is brought into contact with an inner peripheral surface of the multilayer tube, thereby forming an inside of the forming tube. Since the outer peripheral surface of the multilayer tube is pressed against the inner peripheral surface of the cylindrical member of the forming tube at the position radially inside the cylindrical member of the forming tube, The tube has an intended outer diameter corresponding to the inner diameter of the tubular body of the forming tube, and its inner peripheral surface also has an expected inner diameter corresponding to the outer diameter of the disk, and contains a foamed thermoplastic resin. Nevertheless, it is cooled and formed so as to have a smooth inner peripheral surface state.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram illustrating steps of an example of a method for manufacturing a thermoplastic resin tube of the present invention.

In this method of manufacturing a thermoplastic resin tube, FIG.
As shown in (1), a heat-expandable thermoplastic resin is supplied to an extruder (not shown), and a continuously softened tube 12 is continuously extruded from an extrusion die 11. While leaving the extrusion die 11, the pipe 12 is foamed and guided into a forming tube 14 provided at an inlet of a cooling water tank 13 to perform cooling and forming. The forming tube 14 is provided in the cooling water tank 1.
3 is a cylindrical portion 14 extending along the traveling direction of the pipe 12.
1 and a flange portion 142 provided along the outer peripheral surface at the base end of the cylindrical portion 141 and fixed to the inlet of the cooling water tank 13.

A base end of a rod 15 extending from the outlet of the extrusion die 11 into the softened pipe 12 is fixed to the extrusion die 11. The distal end of the rod 15 extends substantially up to the distal end of the cylindrical portion 141 of the forming tube 14. A first disk 16 is fixed to a substantially central portion of the rod 15. The outer diameter of the disk 16 is slightly larger than the inner diameter of the thermoplastic resin tube to be molded. The second disk 17 is fixed to the distal end portion of the rod 15 at a position radially inside the cylindrical portion 141 of the forming tube 14.
The outer diameter of the second disk 17 is equal to the inner diameter of the thermoplastic resin tube to be molded.

The tube 12 that has exited the extrusion die 11 proceeds toward the forming tube 14 provided at the inlet of the cooling water tank 13 while foaming. When the outer peripheral surface of the first disk 16 comes into contact with the first disk 16, the state becomes slightly expanded. Thereafter, the tube 12 is formed into a tubular body 141 of the forming tube 14.
And the inner peripheral surface thereof contacts the outer peripheral surface of the second disk 17 at a position radially inside the cylindrical body 141.
At this time, the outer peripheral surface of the tube 12 is pressed against the inner peripheral surface of the tubular body 141 of the forming tube 14. Accordingly, the tube 12 has an intended outer diameter corresponding to the inner diameter of the tubular body 141 of the forming tube 14, and the inner peripheral surface also has an expected inner diameter corresponding to the outer diameter of the second disk 17. It is cooled and formed so as to have a smooth inner peripheral surface state despite being made of a foamed thermoplastic resin.

The tubular body 141 of the forming tube 14
After passing through the inside, the pipe 12 is further sprayed with water directly in the cooling water tank 13 and cooled, and then cut into a desired length by a cutting device (not shown) to have excellent dimensional accuracy and high heat generation. A thermoplastic resin tube having a smooth inner peripheral surface despite being made of a thermoplastic resin is manufactured.

FIG. 2 is a schematic diagram for explaining the steps of another example of the method for producing a thermoplastic resin tube of the present invention. As shown in FIG. 2, in the method for manufacturing a thermoplastic resin tube of this example, the base end of a rod 25 extending from the outlet of the extrusion die 21 into the softened tube 22 is fixed to the extrusion die 21. A pair of second second members is provided at the distal end of the rod-shaped body 25 at a position radially inside the cylindrical portion 241 of the forming tube 24.
Are fixed, and each of the second disks 27
Are provided on the outer peripheral surface thereof with a plurality of rotating bodies 271, 271... Which rotate as the pipe 22 advances (see FIG. 3). The outer diameter of each second disk 27 connecting the outer surfaces of the rotating bodies 271, 271... Is equal to the inner diameter of the thermoplastic resin pipe to be molded.

In the method of manufacturing a thermoplastic resin tube according to this embodiment, the tube 22 guided to the cylindrical body 241 of the forming tube 24 has its inner peripheral surface at a position radially inside the cylindrical body 241. Are provided on the outer peripheral surfaces of the pair of second disks 27, 27 in a state where the frictional resistance is reduced. At this time, the outer peripheral surface of the tube 22 is pressed against the inner peripheral surface of the tubular body 241 of the forming tube 24. Accordingly, the tube 22 has an intended outer diameter corresponding to the inner diameter of the tubular body 241 of the forming tube 24, and the inner peripheral surface thereof is also formed of a pair of second disks 27, 2.
It is cooled and formed so as to have an expected inner diameter corresponding to the outer diameter of No. 7 and to have a smooth inner peripheral surface state despite being made of a foamed thermoplastic resin. Other than the above,
Since this is the same as the case described with reference to FIG. 1, the corresponding drawing numbers are assigned and the detailed description is omitted.

FIG. 4 is a schematic diagram for explaining the steps of still another example of the method for producing a thermoplastic resin tube of the present invention. As shown in FIG. 4, in the method of manufacturing a thermoplastic resin tube of this example, the non-foamed thermoplastic resin is supplied from the inner surface layer forming channel 311 and the outer surface layer forming channel 312 of the crosshead extrusion die 31. An inner surface layer 321 and an outer surface layer 322 made of
The intermediate layer 323 made of a foamed thermoplastic resin is simultaneously extruded from the intermediate layer forming resin flow path 313, and the multilayer tube 32 in a continuously softened state is continuously extruded. After leaving the multi-layer tube 32 out of the crosshead extrusion mold 31, the intermediate layer 323 is formed.
While being foamed, is guided into a forming tube 34 provided at the entrance of the cooling water tank 33 to perform cooling and forming. The forming tube 34 includes a cylindrical portion 341 that extends in the cooling water tank 33 along the traveling direction of the multilayer tube 32.
And a flange portion 342 provided along the outer peripheral surface at the base end of the cylindrical portion 341 and fixed to the inlet of the cooling water tank 33.

The base end of a rod 35 extending from the outlet of the crosshead extrusion die 31 into the multilayer tube 32 in a softened state is fixed. The tip of the rod 35 is substantially
It extends to the tip of the cylindrical portion 341 of the forming tube 34. A first disk 36 is provided substantially at the center of the rod 35.
Has been fixed. The outer diameter of the disk 36 is slightly larger than the inner diameter of the thermoplastic resin tube to be molded. A pair of second discs 3 is provided at the distal end of the rod-shaped body 35 at a position radially inside the cylindrical portion 341 of the forming tube 34.
7, 37 are fixed. The outer diameter of each second disk 37 is equal to the inner diameter of the thermoplastic resin tube to be molded.

Each second disk 37 is provided with an air outlet 371 near the outer peripheral surface so that air can be blown through the crosshead extrusion die 31 and the rod 35. Has become.

The multi-layer tube 32 exiting the extrusion die 31 proceeds toward the forming tube 34 provided at the inlet of the cooling water tank 33 while foaming.
Before entering 4, the inner peripheral surface comes into contact with the outer peripheral surface of the first circular plate 36 to be in a slightly expanded state. After that, the multi-layer tube 32 is guided to the cylindrical body 341 of the forming tube 34, and at a position radially inward of the cylindrical body 341, its inner peripheral surface is formed by the pair of second disks 37, 37. Air is blown from the outlet 371 provided in the vicinity of the outer peripheral surface to make contact with the outer peripheral surface with reduced frictional resistance. At this time, tube 3
2 is a cylindrical body 341 of the forming tube 34
Is pressed against the inner peripheral surface of. Accordingly, the multi-layer tube 32 has an intended outer diameter corresponding to the inner diameter of the tubular body 341 of the forming tube 34, and its inner peripheral surface also corresponds to the outer diameter of the pair of second disks 37. It is cooled and formed so as to have an intended inner diameter and to have a smooth inner peripheral surface state despite containing a foamed thermoplastic resin.

The tubular body 341 of the forming tube 34
The multi-layer pipe 32 that has passed through the inside is further cooled by spraying water directly in the cooling water tank 33, and then cut to a desired length by a cutting device (not shown), so that the intermediate layer is foamed thermoplastic. In spite of being made of resin, a thermoplastic resin tube having excellent dimensional accuracy and having a smooth inner peripheral surface is manufactured.

[0026]

The method for producing a thermoplastic resin tube of the present invention comprises:
With the above configuration, it is possible to manufacture a thermoplastic resin tube having excellent dimensional accuracy and having a smooth inner peripheral surface despite containing a foamed thermoplastic resin.

[0027]

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a process of an example of a method for manufacturing a thermoplastic resin tube of the present invention.

FIG. 2 is a schematic diagram illustrating steps of another example of the method for manufacturing a thermoplastic resin tube of the present invention.

FIG. 3 is a front view illustrating a second disk portion used in the method of manufacturing a thermoplastic resin tube described with reference to FIG. 2;

FIG. 4 is a schematic view illustrating steps of still another example of the method for producing a thermoplastic resin tube of the present invention.

[Explanation of symbols]

 11, 21 Extrusion mold 31 Crosshead extrusion mold 12, 22 Tube 32 Multi-layer tube 13, 23, 33 Cooling water tank 14, 24, 34 Forming tube 15, 25, 35 Rod-shaped body 16, 26, 36 First circle Plates 17, 27, 37 Second disk 28, 38 Third disk 141, 241, 341 Cylindrical part 142, 242, 342 Flange part 271 Rotating body 371 Air outlet

Claims (4)

[Claims] 1. Using a heat-foamable thermoplastic resin as a raw material, continuously extruding a tube in a softened state from an extrusion die,
A method for producing a thermoplastic resin tube, which comprises a step of conducting cooling and forming by introducing the tube into a forming tube while foaming the tube, comprising: A method for producing a thermoplastic resin tube, wherein an outer peripheral surface of a disk extended through a body is brought into contact with an inner peripheral surface of the tube. 2. A multi-layer tube in a softened state is continuously extruded from a cross-head extrusion mold using a heat-foamable thermoplastic resin, and while the multi-layer tube is foamed, the multi-layer tube is guided into a forming tube for cooling and cooling. A method of manufacturing a thermoplastic resin tube having a step of performing forming, at a position radially inward of the forming tube, the outer peripheral surface of a disk extended from a side of an extrusion die via a rod-shaped body, A method for producing a thermoplastic resin tube, wherein the thermoplastic resin tube is brought into contact with an inner peripheral surface of the multilayer tube. 3. A method according to claim 1, wherein a plurality of rotating bodies are provided on an outer peripheral surface of said disk contacting an inner peripheral surface of said tube or multi-layer tube so as to rotate as said tube or multi-layer tube advances. The method for producing a thermoplastic resin tube according to claim 1 or 2, wherein 4. An air outlet is provided in the vicinity of the outer peripheral surface of the disk contacting the inner peripheral surface of the pipe or the multi-layer pipe, and air is blown out from the outlet to reduce frictional resistance. The method for producing a thermoplastic resin tube according to claim 1, wherein cooling and forming are performed.