JPH06143389A - Manufacture of fluorocarbon resin tube - Google Patents

Abstract

PURPOSE:To provide a method of manufacturing a high quality fluorocarbon resin tube having a small diameter and thin wall thickness and having no curls or diameter variation of the tube. CONSTITUTION:In a manufacture of fluorocarbon resin tube for forming a resin admixture consisting of fluorocarbon resin or having fluorocarbon resin as a base into a tube shape, temperature of air around the tube passing therethrough is kept at 30 deg.C or higher over the range from the die lip of die 2 of an extrusion machine main body 1 to the solidification of the tube 5 by a method of arranging, e.g. a cooling cylinder 3 provided with a water cooling pipe 4.

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 fluororesin tube, and more particularly to a method for producing a high-quality fluororesin tube which is thin and thin and has no curl or diameter fluctuation.

[0002]

2. Description of the Related Art Fluororesin tubes are extremely excellent in electrical insulation, heat resistance, chemical resistance, antithrombogenicity, etc., so that demand for them in various applications is increasing. There is a strong demand for thinner tubes, especially in the fields of electronic devices. Conventionally, in the production of these fluororesin tubes by extrusion molding, a molten resin is extruded from a die into a tube shape, and then cooled and solidified by a water cooling method of passing through a water tank to produce a product.

However, in this method, the tube has a small diameter.
In the case of a thin wall, there is a problem that the tube after cooling causes a curl phenomenon in which the tube bends. This is because in a thin-walled tube, uneven flow is likely to occur when the molten resin is extruded from the die, and the thin resin is rapidly cooled while the unevenness remains. In the case of a fluororesin, the melting point is 200 ° C or higher, so even if the temperature of the cooling water is raised to near 100 ° C, the temperature difference of 100 ° C or more is rapidly cooled, and as long as the water cooling method is used, such curl The phenomenon cannot be prevented. It is also possible to heat using silicone oil or the like as a refrigerant to reduce the temperature difference, but especially in medical applications, such impurities are not allowed to remain, and tube cleaning must be performed strictly. It will not be worth the cost.

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for producing a high-quality fluororesin tube which has a small diameter and a thin wall and has no variation in the wall thickness or the diameter.

The object of the present invention is to manufacture a fluororesin tube by melt-extruding a fluororesin or a resin mixture based on the fluororesin to form a tube, from the die lip until the tube is cooled and solidified. This can be solved by setting the temperature of the air in the vicinity of the passage of the tube to 30 ° C. or higher over the period.

The method for producing the fluororesin tube of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a diagram showing an example of an apparatus suitable for carrying out the manufacturing method of the present invention. In the figure, reference numeral 1 is an extruder body, and a tube molding die 2 is attached to the tip of the extruder body 1. A cooling cylinder 3 is provided in front of the die 2. The cooling cylinder 3 has a cylindrical shape, and is arranged such that its central axis coincides with the center die lip of the die 2. A water cooling pipe 4 is spirally wound around the outer peripheral wall of the cooling cylinder 3.

As the extruder main body 1, an apparatus used for ordinary extrusion molding can be used as it is. Also, die 2
As the material, a commonly used material can be used, but it is preferable to use a material made of a heat and corrosion resistant alloy. Also, the water cooling pipe 4
Is connected to a cooling water supply device (not shown) so that cooling water of a predetermined temperature is guided to the water cooling pipe 4. Further, the cooling cylinder 3 is a fluororesin tube 5 that is extruded.
It is preferable that the inner diameter is at least 2 cm or more larger than the outer diameter and the length is at least the distance from the die lip to the point where the molten resin is cooled and solidified to a temperature at which the molten resin is not deformed.

A specific manufacturing method of the present invention will be described using such an apparatus. First, constant temperature water at a predetermined temperature is circulated through the water cooling pipe 4 attached around the cooling cylinder 3 to
The temperature in the vicinity where the internal fluororesin tube 5 passes is 3
Adjust so that the temperature is 0 ° C or higher. In the present invention, the vicinity where the tube passes shall mean a range within at least 2 cm from the surface of the tube.

Next, a fluororesin as a raw material is charged into the hopper of the extruder main body 1 and heated to a predetermined temperature to melt the resin. The molten fluororesin is extruded from the inside of the cylinder through the die lip of the die 2 into a tube shape. Extrusion conditions differ depending on the properties of the fluororesin used as the material,
The conditions generally used for extrusion molding of fluororesin tubes are used.

The molten resin extruded is stored in the cooling cylinder 3 inside
While passing through the region kept at a temperature of 0 ° C. or higher, it is gradually cooled by releasing heat to the surrounding air, and when it leaves the cooling cylinder 3, it is cooled and solidified to a temperature at which it does not deform. The cooled and solidified fluororesin tube 5
It is transferred to a cutting device or the like through the take-up roll 6 and commercialized.

The fluororesin or the fluororesin-based resin mixture used as the raw material for the fluororesin tube 5 may be any fluororesin which can be molded by ordinary extrusion molding. For example, polytetrafluoroethylene-peroxide may be used. Examples thereof include fluorovinyl ether copolymer (PFA), polytetrafluoroethylene-6-fluoropropylene copolymer (FEP), and polytetrafluoroethylene-ethylene copolymer (ETFE). Also, a mixture of two or more of these and a mixture of resins other than fluororesin can be used.

According to such a manufacturing method, the molten resin extruded from the die 2 gradually releases heat to the air having a low thermal conductivity in the cooling cylinder 3 kept at a temperature of 30 ° C. or higher. On the other hand, it is cooled and solidified while alleviating the bias of the stress remaining during the extrusion. Therefore, no curling phenomenon is observed, and cleaning after molding is not necessary. Moreover, there is no variation in the outer diameter or inner diameter of the tube due to the local temperature distribution, and there is a problem that the tube is hit with air flow, wind, etc. until it is cooled and solidified, resulting in uneven thickness and variation in diameter. Does not occur.

In the above description, as a constant temperature means for keeping the temperature of the air in the vicinity of the tube at 30 ° C. or higher from the die lip until the tube is cooled and solidified, the water cooling spirally formed on the outer circumference. Although a cooling cylinder having a pipe was used, the constant temperature means is not particularly limited in shape, material and the like as long as it meets the purpose, and various ones can be used.

For example, the cooling cylinder itself may be a double cylinder, and a water cooling section may be provided between the inner cylinder and the outer cylinder, or a spiral water cooling pipe may be densely wound so that there is no space between the inner cylinder and the outer cylinder. It may be used as described. Further, a ceramic heater or a rubber heater having a shape surrounding the region through which the tube passes may be used. In any case, it is preferable that the tube is provided so as to surround the tube so that airflow, dust, etc. do not hit the tube before being cooled and solidified.

Further, temperature detecting means may be provided inside the constant temperature means, and means for adjusting the temperature of the water to be circulated and the electric power supplied to the heater according to the output thereof may be provided. Further, the constant temperature means is arranged at a position where the molten resin extruded from the die 2 immediately enters the inside, and may be directly fixed to the extruder, or other fixing means may be used. You may fix it.

The production method of the present invention will be described below with reference to specific examples. (Example 1) A nipple having an outer diameter of 2 mm and an inner diameter of 3 m is used in an extruder.
m tube forming die was attached. Outer diameter 15 cm,
A cooling cylinder was prepared by spirally winding an iron water-cooled pipe around an iron pipe having an inner diameter of 10 cm and a length of 1 m, and the cooling cylinder was fixed to an extruder so that the center line of the cylinder approximately coincided with the resin extrusion direction.
By circulating water at 15 ° C through the water cooling pipe of the cooling cylinder,
The temperature was adjusted to 0 ° C. PFA in the hopper of the extruder
, And the Siranda temperature is 360 ° C and the head temperature is 38
It was heated to melt at 0 ° C. The molten resin was extruded at a rate of 50 g / min, passed through the inside of the cooling cylinder, and taken into a take-out machine. The formed tube was vertically cut at an appropriate position, and the cross-section tube outer diameter was measured with a loupe. Similarly, F
A tube was molded using EP and ETFE, and the outer diameter of the cross section was measured. The results are shown in Table 1.

[0016]

[Table 1]

(Embodiment 2) The temperature of the water flowing through the water cooling pipe is set to 45
The same experiment as in Example 1 was carried out except that the temperature was adjusted so that the temperature inside the cooling cylinder was 60 ° C. The results are shown in Table 2.

[0018]

[Table 2]

(Comparative Example 1) The temperature of the water flowing through the water cooling tube was adjusted to 10
The same experiment as in Example 1 was performed except that the temperature was adjusted so that the temperature inside the cooling cylinder was 20 ° C. The results are shown in Table 3.

[0020]

[Table 3]

(Comparative Example 2) The cooling cylinder was removed from the apparatus of Example 1 and the temperature was not controlled.
A tube was molded under the same conditions as above, cut and the tube outer diameter was measured. The results are shown in Table 4.

[0022]

[Table 4]

As is clear from the above results, in any of the fluororesins, when the temperature of the cooling cylinder was 20 ° C., the cooling rate was too high and the tube curled like the one rapidly cooled in water. Therefore, in the case where the cooling cylinder is not provided, a large fluctuation in outer diameter occurs. On the other hand, 3
When the cooling cylinder maintained at a temperature of 0 ° C. or higher is provided, the tube does not curl and the outer diameter hardly changes.

[0024]

According to the method for producing a fluororesin tube of the present invention, since the molten resin is extruded from the die and then air-cooled in the cooling cylinder maintained at a temperature of 30 ° C. or higher, air having a low thermal conductivity is obtained. While gradually releasing heat in the tube, it cools and solidifies while alleviating the bias of the stress remaining in the tube. Therefore, the curl phenomenon is not observed and cleaning after molding is not necessary. Moreover,
There is no variation in the outer diameter or inner diameter of the tube due to the local temperature distribution, and there is also a problem that the tube is hit with air flow, wind, etc. before it is cooled and solidified, causing uneven thickness and fluctuation in diameter. do not do. Therefore, it is possible to manufacture a high-quality tube with almost no diameter variation. Moreover, since an ordinary extrusion molding machine can be applied as it is, there is no cost such as equipment cost.

[0025]

[Brief description of drawings]

FIG. 1 is a schematic configuration view of an example of an apparatus suitable for carrying out the manufacturing method of the present invention when viewed from the side.

[Explanation of symbols]

1 ... Extruder, 2 ... Die, 3 ... Cooling tube, 4 ... Water cooling tube, 5 ...
Fluororesin tube, 6 ... Take-up machine

Claims (1)

[Claims] 1. A method for producing a fluororesin tube in which a fluororesin or a resin mixture containing a fluororesin as a base is melt-extruded to form a tube shape, in the vicinity of the passage of the tube from the die lip until the tube is cooled and solidified. The method for producing a fluororesin tube, characterized in that the temperature of the air is kept at 30 ° C. or higher.