JPS5828098B2 - Method for manufacturing grooved tetrafluoroethylene resin tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing grooved tetrafluoroethylene resin tubes, and in particular, a method for continuously and economically producing tubes with spiral grooves to improve flexibility. It concerns the method of doing so.

For general corrugated resin tubes, the dimensions to be corrugated are engraved into a mold, and a resin tube with a temperature higher than the melting point is loaded into this mold, which is heated to near the melting point of the resin.At the same time, pressure is applied from inside, and the crystalline melting point of the resin tube is heated. It is manufactured using a method of cooling and then removing it from the mold.

For this reason, it has disadvantages such as (1) it is impossible to obtain a corrugated tube with a small diameter, and (2) productivity is low.

The present invention makes it possible to continuously manufacture grooved tetrafluoroethylene resin tubes, which can be applied not only to thick inner diameter tubes but also to thin inner diameter tubes, with high productivity using a small jig without using a large mold. The present invention provides a method.

In the method according to the present invention, a tetrafluoroethylene resin tube is extruded by a so-called paste method, the liquid lubricant is removed, and the tube is heated and sintered to a temperature of 327°C or higher.As it begins to cool, crystals begin to precipitate, but all the crystals are not formed. It is characterized in that when the temperature reaches a temperature range of up to 100 mL, a concave groove is formed by closely contacting a protruding object that matches the shape of the groove, and then the groove is rapidly cooled and fixed so that it does not recover.

The contact object may have not only one protrusion but also a plurality of protrusions, and by rotating the contact object, a spiral groove can be formed.

Furthermore, by changing the state of close contact between the protruding surface of the contacting object and the tube over time, including the state of no close contact, it is also possible to continuously and alternately produce tubes with grooved portions and non-grooved portions. Become.

The drawings are shown to further explain the invention.

In FIG. 1, a tube 2 is heated to a temperature higher than the crystalline melting point of the resin by a furnace 1 and then comes out.

The resin begins to cool as it exits the furnace 1, but a contact object 3 with protrusions is installed at a position in the range from the temperature at which crystal precipitation begins to the temperature at which all crystals precipitate, and the resin is tightly connected to the tube 2. By bringing them into close contact, a recess is created, and at this time, by moving the tube 2 in the length direction, a recess groove 9 is continuously formed on the wall surface of the tube 2.

The state of close contact between the tube 2 and the contactable object 3 is adjusted by a rotary gear 5 with the support base 4 as a fulcrum.

Although not shown in the figure, a signal is given to the motor to rotate the rotating gear 5 at regular intervals, thereby making it possible to vary the contact state over time.

Therefore, it is possible to set a state in which the contact object no longer comes into close contact with each other at regular intervals.

On the other hand, the support assembly 4 is fixed to the center of a rotary table 6 via a bolt 7, and the rotary table 6 can be set at an arbitrary rotation speed by a gear 8 connected to a motor (not shown).

Therefore, when the rotary table 6 is stopped, only complete vertical grooves can be formed, and as the rotational speed increases, it becomes possible to form more spiral grooves.

At this time, the number of contactable objects 3 having protrusions may be one or two or more, but it is usually most preferable to use two.

FIG. 2 shows a side view of the tube 2 provided with a helical groove 9. FIG.

FIG. 3 is a side view of the tube 2 with the same spiral groove 9, but the state of close contact with the contacting object 3 is varied by the rotating gear 5, and a state in which it is not completely in close contact is created for a short period of time. This represents a state in which the spiral groove 9 has completely disappeared from the circumference of the tube 2.

FIG. 4 shows a preferred embodiment of an extrusion device for the tube 2 supplied to the furnace 1.

A mixture 11 of liquid lubricant and tetrafluoroethylene resin loaded into a die and cylinder 10 has an inner diameter defined by a central mandrel 12 and is forced into a tube 2 by a descending ram 13.

More preferably, the central mandrel 12 is rotated in one direction during extrusion so that the fiber orientation of the resin has a component perpendicular to the extrusion direction.

This rotation during extrusion reduces the deflection of the tube 2,
And the tear resistance in the longitudinal direction increases.

In the most preferred embodiment, the direction in which the contact object 3 with the protrusion for forming the groove 9 on the tube surface is rotated by the rotating table 6 and the direction in which the central mandrel 12 is rotated during extrusion are opposite to each other. In other words, the direction of fiber orientation during extrusion of the tube intersects the direction of the grooves 9 on the tube surface at an angle close to a right angle, resulting in strong resistance to repeated bending fatigue. This is because even if elongation and compression forces are applied, the stress in the direction of fiber orientation is greater than that, so the occurrence of cracks is extremely reduced.

The shape of the protrusion at the tip of the contactable object can be arbitrarily selected, and the width, depth, etc. of the groove can also be arbitrarily selected accordingly.

In extreme cases, three contacting objects can cause a triangular tube to
It is also possible to form a square tube with four contact objects.

The inner diameter of the support base holding the contact object must be equal to or larger than the diameter of the sintered tube, but if it is not about three times the diameter of the tube, the tube will not protrude from the contact object. Sometimes I run away from the club.

Therefore, each time the diameter of the extruded tube changes, it is necessary to select a support base and a contacting object with an inner diameter corresponding to the change in diameter.

On the other hand, even if the contact object and its support are integrated into a die shape, the same purpose can be achieved by providing an inner diameter that changes the shape of the tube.

In this case, if the inner diameter is made completely circular, tubes with different inner diameters can be obtained, and if the inner diameter is made circular and a protrusion is provided, a grooved tube can be obtained.

Of course, by rotating it, it is possible to create a spiral groove.

Next, the temperature conditions of the tube in close contact with the contactable object will be described in detail.

The tube may be already sintered, but
It is usually preferable to take advantage of the temperature range that occurs during sintering of the green tube in a furnace and simultaneous cooling of the green tube.

Even if the material has already been sintered, by heating it again above the sintering temperature, it becomes a transparent glass-like Q-tube. When it comes out of the furnace, the tube begins to cool, crystal particles begin to precipitate, and it becomes cloudy. There are parts.

On the other hand, when all the crystal grains have precipitated, a completely white and opaque area can be seen, and it is necessary to install a contact object with protrusions in this intermediate area.

These parts can be easily determined by visual inspection, and at the same time, it can be easily determined whether or not they are appropriate by placing them and bringing a contact object into close contact with them.

The above is a case where the tube is moved continuously, but it is of course also possible to fix a fixed short tube and move the contact object while adjusting the ambient temperature.
It is not intended to limit the scope of the invention.

[Brief explanation of the drawing]

Figure 1 is a longitudinal front view showing the arrangement of a furnace and contacting object for forming grooves on a tube, Figure 2 is a front view of a tube with spiral grooves, and Figure 3 shows the part where the spiral grooves have disappeared. FIG. 4 is a longitudinal sectional front view of a ram extruder suitable for extruding the tube. 1 is a furnace, 2 is a tube, 3 is a contact object, 4 is a support stand,
5 is a rotating gear, 6 is a rotating table, 7 is a bolt, 8 is a gear,
9 is a concave groove, 10 is a die and cylinder, 11 is a resin,
12 is a mandrel, and 13 is a ram.

Claims (1)

[Claims] 1. A tetrafluoroethylene resin mixture containing a liquid lubricant is extruded into a tube using a ram extruder, the liquid lubricant is removed, and the mixture is heated to a temperature higher than the sintering temperature of the resin. Subsequently, a contactable object with protrusions is brought into close contact with the tube, which is being cooled from the temperature at which crystals begin to precipitate to a temperature range at which all crystals precipitate, and the tube or contactable object is moved. A method for producing a grooved tetrafluoroethylene resin tube, which comprises forming grooves on the tube surface and then cooling the tube to room temperature. 2. The manufacturing method according to claim 1, wherein the tube wall is deformed by rotating a contacting object having protrusions that come in close contact with each other to form a spiral groove. 3. When extruding the tetrafluoroethylene resin mixture into a tube using a ram extruder, a central mandrel that defines the inner diameter of the tube is rotated to add fiberization in a direction perpendicular to the extrusion direction. The manufacturing method according to claim 1 or 2, characterized in that: 4. Claim 3, characterized in that the direction of rotation of the contacting object having protrusions in close contact with each other is opposite to the direction of rotation of the central mandrel that defines the inner diameter of the tube.
Manufacturing method of section. 5. Claims 1, 2, 3, or 4 characterized in that the state of close contact between the contacting object having a protrusion and the tube changes over time, including the state where the tube does not come into close contact. Production method.