JP2001315193A - Method for manufacturing synthetic resin pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a synthetic resin pipe excellent in dimensional stability and roundness without generating a stripe or the like on the outer peripheral surface of the synthetic resin pipe. SOLUTION: In the method for manufacturing the synthetic resin pipe by passing the synthetic resin pipe, which is extruded from the cap of an extruder in a molten state, through a cooling water tank while shaping the molten resin pipe by a sizing die to cool the same, a shaping die is arranged to the leading end part of the sizing die and hot water is circulated to the cavity formed in the shaping die to heat the shaping die and allowing a part of hot water to flow out from the inner peripheral surface of the shaping die to form a water film between the outer peripheral surface of the synthetic resin pipe and the inner peripheral surface of the shaping die when the synthetic resin pipe is passed through the shaping die.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a synthetic resin pipe having excellent dimensional stability and roundness without causing streaks on the outer peripheral surface of the synthetic resin pipe.

[0002]

2. Description of the Related Art Conventionally, when a synthetic resin pipe is extruded, a synthetic resin pipe melt-extruded from a die of an extruder is shaped by a sizing die and cooled by passing through a cooling water tank or a shower cooling section. That is, when the synthetic resin pipe passes through the inside of the sizing die, its outer peripheral surface is suction-contacted to the inner peripheral surface of the sizing die to be shaped, and then cooled and solidified by passing through a cooling water tank or a shower cooling section.

[0003]

However, in the case of this conventional manufacturing method, foreign matter of the molten resin may adhere to the tip of the sizing die, and the foreign matter comes into contact with the outer peripheral surface of the synthetic resin pipe, thereby causing the pipe to become inaccessible. Streaks and the like continuous in the axial direction may occur on the outer peripheral surface. In particular, since the tip of the conventional sizing die is maintained at a low temperature by circulating cooling water, foreign matter is likely to be generated due to rapid cooling when the outer peripheral surface of the synthetic resin pipe in a high temperature state contacts. there were.

[0004]

The object of the present invention is to provide a method of manufacturing a synthetic resin pipe which has solved the above-mentioned problems. The gist of the present invention is to form a synthetic resin pipe melt-extruded from a die of an extruder with a sizing die. In the method for manufacturing a synthetic resin pipe that cools by passing through a cooling water tank, a shaping die is disposed at the tip of the sizing die, and hot water is circulated through a cavity formed inside the shaping die to form the shaping die. While warming, a part of the hot water overflows from the inner peripheral surface of the shaping die, and when the synthetic resin pipe passes through the shaping die, the space between the outer peripheral surface of the synthetic resin pipe and the inner peripheral surface of the shaping die is increased. And a method of manufacturing a synthetic resin pipe in which hot water at 60 to 90 ° C. is circulated in the cavity of the shaping die.

[0005]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an overall schematic sectional view showing an embodiment of an apparatus used in the present invention, and FIG. 2 is an enlarged partial sectional view of a sizing die used in the present invention.

In FIG. 1, reference numeral 1 denotes a die of an extruder, and a synthetic resin pipe P melt-extruded from the die is:
It is shaped by the sizing die 2, cooled while passing through the cooling water tank 3, and then cut by the cutting machine 5 to a predetermined length while being continuously drawn by the pulling machine 4.

[0007] The cooling water tank 3 is provided with a first circulating cooling water.
The sizing die 2 is disposed in the first water tank 3a which is composed of a water tank 3a and a second water tank 3b and is located on the extruder side. A vacuum pump or the like (not shown) is connected to the first water tank 3a.
It is set to ~ 55 kPa. Meanwhile, sizing die 2
As shown in FIG. 2, a large number of through holes 2 penetrating the inner and outer surfaces are provided.
When the synthetic resin pipe P passes through the inside of the sizing die 2, its outer peripheral surface is
It moves while attracting and sticking to the inner peripheral surface of.

[0008] A shaping die 2a is provided at the tip of the sizing die 2 on the extruder side. The shaping die 2
A cavity 22 for circulating warm water at 60 to 90 ° C., preferably about 80 ° C. is formed inside a, and an inflow pipe 23 and an outflow pipe 24 are connected to the cavity 22. The shaping die 2a is heated by hot water circulating in the cavity 22, and is provided with a through hole 25 communicating from the cavity 22 to the inner peripheral surface of the shaping die 2a. It overflows to the inner peripheral surface of 2a. A fine spiral groove is provided on the inner peripheral surface of the shaping die 2a.
The hot water that has overflowed through flows into and forms a water film on the inner peripheral surface of the shaping die 2a.

When the synthetic resin pipe P extruded from the die 1 of the extruder passes through the shaping die 2a, the pipe P
The resistance is reduced by the water film formed between the outer peripheral surface of the sizing die 2a and the shaping die 2a, so that the water passes through the sizing die 2 smoothly. Further, the outer peripheral surface of the synthetic resin pipe P is brought into close contact with the inner peripheral surface of the sizing die 2 and shaped into a predetermined shape and size while sequentially moving. The first water tank 3a at this time
The cooling water temperature is in the range of 40 to 60 ° C., and by selecting the optimum temperature in this temperature range according to the outer diameter, wall thickness, etc. of the synthetic resin pipe P, the manufactured synthetic resin pipe has a shape, dimensions and trueness. Products with excellent circularity can be obtained.

Next, the synthetic resin pipe P sent out from the sizing die 2 is sufficiently cooled while passing through the second water tank 3b, and then continuously taken by the take-up machine 4 to have a predetermined length by the cutting machine 5. Is cut off.

[0011]

As described above in detail, according to the present invention, the shaping die disposed at the tip of the sizing die is heated.
The outer surface of the synthetic resin pipe extruded from the die of the extruder is not rapidly cooled. As a result, since the foreign matter of the molten resin does not adhere to the tip of the sizing die, it is possible to obtain a synthetic resin pipe having no streaks on the outer peripheral surface of the manufactured pipe. In addition, since a water film is formed between the outer peripheral surface of the synthetic resin pipe and the shaping die, the synthetic resin pipe smoothly passes through the inside of the sizing die. No defect occurs.

[Brief description of the drawings]

FIG. 1 is an overall schematic sectional view showing one embodiment of an apparatus used in the present invention.

FIG. 2 is an enlarged partial cross-sectional view of a sizing die used in the present invention. DESCRIPTION OF SYMBOLS 1 Extruder base 2 Sizing die 2a Shaping die 22 Cavity 3 Cooling water tank 4 Take-off machine 5 Cutting machine

Claims (2)

[Claims] 1. A method for manufacturing a synthetic resin pipe which is cooled by passing through a cooling water tank while shaping a synthetic resin pipe melt-extruded from a die of an extruder with a sizing die. Arranged, warm water is circulated through the cavity formed inside the shaping die to heat the shaping die, and a part of the hot water overflows from the inner peripheral surface of the shaping die. A water film is formed between the outer peripheral surface of the synthetic resin pipe and the inner peripheral surface of the shaping die when passing through the synthetic resin pipe. 2. The method for producing a synthetic resin pipe according to claim 1, wherein hot water at 60 to 90 ° C. is circulated through the cavity of the shaping die.