JPH04135731A - Manufacture of thermoplastic resin pipe - Google Patents

Abstract

PURPOSE:To enable a molten resin pipe to be cooled effectively from its inner and outer surface and thus prevent distortion from occurring in its pipe wall by disposing a contact material that elastically comes into contact with the pipe inner peripheral surface on the inner peripheral side of a molten resin pipe extruded from a mouth piece, and allowing a coolant to be passed forcibly through the gap between the contact material and the pipe inner peripheral surface. CONSTITUTION:When a coolant is introduced from a supplying pipe 3 into a bag 6, the outer peripheral surface of the bag 6 comes elastically into contact with the inner peripheral surface of a molten resin pipe 2. As the coolant spouts from a number of small holes 61 made on the outer peripheral surface of the bag 6, a uniform gap is formed throughout the peripheral direction between the inner peripheral surface of the molten resin pipe 2 and the outer peripheral surface of the bag 6, wherein the inner peripheral surface is cooled by the coolant that energically passes through this narrow gap. Meanwhile, the temperature-risen and used coolant is discharged via a duct 4 from a through hole 62 provided on the rear side of the bag 6. At the same time, the molten resin pipe 2 is cooled such that the outer peripheral surface comes into contact with cooling water in a bath during passing through a cooling water bath 8, and since it is cooled in a state wherein each temperature of the inner surface and outer surface is approximately equal, any distortion never occurs in its pipe wall.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides a thermoplastic resin tube that effectively cools a molten resin tube extruded from a die from its inner and outer circumferential surfaces to prevent distortion from occurring in the tube wall. This invention relates to a method for manufacturing resin pipes.

(Conventional technology and its problems) Generally, when manufacturing thermoplastic resin pipes such as vinyl chloride resin and polyethylene resin, the molten resin pipe extruded from the mouthpiece is submerged in a cooling water tank and the outer peripheral surface is cooled with cooling water. things are being done.

However, simply cooling the molten resin pipe from the outer circumferential side is not enough.
Since the temperature difference between the inner and outer circumferential surfaces of the tube is large, a temperature gradient is created in the thickness direction of the tube wall. For this reason, there have been problems in that the tube wall of the molded thermoplastic resin tube is strained in the wall thickness direction, causing the tube to deform, and that the tube is easily damaged when external forces such as vibrations and shocks are applied. .

Therefore, various methods have been proposed in which the molten resin tube extruded from the die is not only cooled from the outer periphery of the tube, but also from the inner periphery of the tube to prevent distortion from occurring in the tube wall.

For example, Japanese Patent Application Laid-Open No. 50-112462 proposes a method in which a molten resin tube extruded from a die is forcibly cooled from the inner circumferential side of the tube, as shown in a longitudinal cross-sectional view in FIG. To briefly explain this based on the same figure, a supply pipe 3a is arranged on the inner peripheral side of the molten resin pipe extruded from the nozzle, and a predetermined interval is arranged in the axial direction on the outer peripheral surface of the supply pipe 3a. A plurality of disks 31a are provided. Further, a large number of small holes 32a are provided on the outer circumferential surface of the supply pipe 3a, and a refrigerant such as water or air ejected from the small holes 32a flows between the inner circumferential surface of the molten resin pipe and the outer circumferential surface of the disk 31a. After passing through, it is discharged through a conduit 4a inserted into the supply pipe 3a. In this cooling method, the refrigerant such as water or air passes vigorously between the inner peripheral surface of the molten resin pipe and the outer peripheral surface of the disk, so the refrigerant is simply circulated on the inner peripheral side of the molten resin pipe. Although it was expected that the cooling effect would be better than in the conventional case, it was not sufficient.

The present invention solves this problem and provides a method for manufacturing a thermoplastic resin tube that can effectively cool a molten resin tube from the inner and outer circumferential surfaces and that does not cause distortion in the tube wall. be.

(Means for Solving the Problems) The present invention provides a contact member that elastically contacts the inner circumferential surface of the tube on the inner circumferential side of the molten resin tube extruded from the mouthpiece, and the contact member and the inner circumferential surface of the tube. The inner circumferential surface of the molten resin tube is cooled by forcing a refrigerant to pass between the tube and the tube, and the outer circumferential surface is cooled with cooling water by submerging the resin tube into a cooling water tank. be.

(Function) When refrigerant is forced to pass between the inner peripheral surface of the molten resin pipe extruded from the mouthpiece and the contact member that is in elastic contact with the inner peripheral surface of the pipe, the inner peripheral surface of the pipe and An almost constant gap is created in the circumferential direction between the contact member and the refrigerant, which passes vigorously through this narrow gap, cooling the inner circumferential surface of the molten resin tube, and at the same time cooling the outer circumference of the molten resin tube. The surface is cooled by cooling water.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings. 1st
The figure is a longitudinal cross-sectional view showing one embodiment of the manufacturing apparatus used in the present invention, and FIGS. 2 and 3 are main part cross-sectional views showing other embodiments. First, to explain the outline of the apparatus shown in FIG. 1, reference numeral 1 in the figure is a die, and the die 1 is a tie that constitutes a six-rod metal 1 provided at the tip of an extruder II (not shown). An annular resin passage 13 is provided between the ring 11 and the mandrel 12, and the molten resin tube 2 is extruded from the resin passage 13.

The inside of the mandrel 12 is a cavity, and inside the cavity there is a supply pipe 3 for introducing a refrigerant such as water or air into the inner peripheral side of the molten resin pipe 2, and a supply pipe 3 for introducing a refrigerant such as water or air into the inner peripheral side of the molten resin pipe 2, and a supply pipe 3 for introducing a refrigerant such as water or air into the inner peripheral side of the molten resin pipe 2. A conduit 4 for discharging is installed. In addition, a shielding plate 5 for heat insulation and waterproofing is provided at the tip of the mandrel 12, and a cylindrical bag (a contact member )6 is provided. The outer diameter of the bag 6 is approximately the same as the inner diameter of the molten resin tube 2, and a large number of small holes 6 are formed on the outer peripheral surface of the bag 6.
1 is drilled. In addition, said bar 1. A shielding plate 7 is provided at the other end of the tube 6 in close contact with the inner circumferential surface of the molten resin tube 2 via a connecting member 71.

On the other hand, a cooling water tank 8 is provided on the outer peripheral side of the molten resin pipe 2, and while passing through the cooling water tank 8, the outer peripheral surface of the molten resin pipe 2 comes into contact with the cooling water in the tank and is cooled. It is now possible to do so.

In this embodiment, when the refrigerant is introduced into the bag 6 from the supply pipe 3, the outer peripheral surface of the bag 6 comes into elastic contact with the inner peripheral surface of the molten resin pipe 2. When the refrigerant is ejected from the large number of small holes 61 formed in the outer peripheral surface of the bag 6, a uniform gap is created in the circumferential direction between the inner peripheral surface of the molten resin pipe 2 and the outer peripheral surface of the bag 6. The inner circumferential surface of the molten resin tube 2 is cooled by the refrigerant passing through this narrow gap with force. On the other hand, the used refrigerant whose temperature has increased is discharged from a through hole 62 provided at the rear of the bag 6 via the conduit 4. At the same time, while the molten resin pipe 2 passes through the cooling water tank 8, its outer circumferential surface comes into contact with the cooling water in the tank and is cooled, so that the temperature of the inner and outer circumferential surfaces of the molten resin pipe 2 is almost the same. Since the tube is cooled in an even manner, no distortion occurs in the tube wall.

The apparatus shown in FIG.
A conduit 40 is provided connected to the conduit 40, and a large number of disks (contact members) 6a made of an elastic member such as rubber are protruded from the outer peripheral surface of the conduit 40 at predetermined intervals in the axial direction, and a shielding plate 7 is provided behind the disk. The outer peripheral surface of each disk 6a is in elastic contact with the inner peripheral surface of the molten resin tube 2. When the refrigerant is introduced from the supply pipe 3 to the inner peripheral side of the molten resin pipe 2, this refrigerant passes through the narrow gap between the inner peripheral surface of the molten resin pipe 2 and the outer peripheral surface of the disk 6a one after another. , the inner peripheral surface of the molten resin pipe 2 is efficiently cooled. On the other hand, the used refrigerant whose temperature has increased is discharged through the conduit 4 from a through hole 42 provided in the conduit 40 .

In the device shown in FIG. 3, a bullet-shaped back (abutting member) 6b made of an elastic member such as rubber is arranged on the inner circumferential side of the molten resin pipe 2, and a shielding plate 7 is provided behind it. When pressure fluid is introduced into the bag 6b from the conduit 9, its outer circumferential surface comes into elastic contact with the inner circumferential surface of the molten resin tube 2. Therefore, when the refrigerant is introduced into the molten resin pipe 2 from the supply pipe 3 and is forced to pass between the inner peripheral surface of the molten resin pipe 2 and the outer peripheral surface of the bag 6b, the inside of the molten resin pipe 2 is The used cooling medium is stored in the bag 6b, where the peripheral surface is efficiently cooled and the temperature does not rise.
It is discharged through a conduit 4 from a through hole 42 provided at the rear of the .

(Effects of the Invention) As detailed above, the present invention provides a contact member that elastically contacts the inner peripheral surface of the molten resin tube extruded from the mouthpiece, so that the molten resin tube is When refrigerant is forced to pass between the inner circumferential surface of the tube and the abutting member, an approximately constant gap is created in the circumferential direction between the inner circumferential surface of the tube and the abutting member, and the refrigerant passes by with great force. Therefore, the refrigerant having a high flow rate directly contacts the inner circumferential surface of the molten resin tube, and the inner circumferential surface of the molten resin tube is efficiently cooled. In addition, the outer circumferential surface of the molten resin tube is cooled by the cooling water while it passes through the cooling water tank, so the molten resin tube is effectively cooled from the inner and outer circumferential surfaces. A resin tube is obtained.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing a thermoplastic resin pipe manufacturing apparatus used in the present invention, FIGS. 2 and 3 are sectional views of main parts showing other embodiments of the present invention, and FIG. 4 is a conventional apparatus. FIG. 1...Bag 12...Man 3...Water pipe 6...Back (contact member) 7...Block plate 11... ...Die ring drell 2... Molten resin pipe 4... Conduit 5... Shield plate (contact member) 6a... Disc 6b...・・・・・・
Back (contact member) 1) Patent applicant Mitsubishi Plastics Co., Ltd. Patent attorney Hisami Kondo

Claims (1)

[Claims] When manufacturing a thermoplastic resin tube by cooling the molten resin tube extruded from the mouthpiece provided at the tip of the extruder from the inner and outer circumferential surfaces, a part is placed on the inner circumferential side of the molten resin tube to elastically contact the inner circumferential surface of the tube. A contacting member is disposed, and a refrigerant is forced to pass between the relevant contacting member and the inner circumferential surface of the pipe to cool the inner circumferential surface of the molten resin pipe, and the resin pipe is submerged in a cooling water tank to cool the outer circumference. A method for manufacturing a thermoplastic resin pipe, characterized by cooling the surface with cooling water.