JPH11320655A - Method and mold for extrusion molding of thermoplastic resin tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a temperature difference between the surface of a mandrel and an outer die from becoming large. SOLUTION: In a method for extrusion molding of a thermoplastic resin tube wherein thermoplastic resin is extruded in the shape of the tube from a circular gap between a mandrel 12 and an outer die 11, a mold 1 for extrusion molding which is equipped with the mandrel 12 provided with a through hole 121 located in proximity to the outer surface of the mandrel 12, one end of the through hole 121 of the mandrel 12 being made to communicate with a pass hole 131 provided in a spider 13 and the other end being opened in the end face of the mandrel 12, is used and the mandrel 12 is cooled by making a fluid flow through the through hole 121 thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for extruding a thermoplastic resin tube and a mold for extruding a thermoplastic resin tube, and more particularly to a heat-resistant thermoplastic resin tube such as a chlorinated vinyl chloride resin. It is suitable for use in molding.

[0002]

2. Description of the Related Art Conventionally, as described in, for example, Japanese Utility Model Laid-Open No. 23578/1993, a thermoplastic resin tube is extruded from an annular gap between an inner surface of an outer mold and a surface of a mandrel to form a thermoplastic resin tube. It is known to mold.

In the case of molding a heat-resistant thermoplastic resin tube such as a chlorinated vinyl chloride resin, it is necessary to mold at a temperature higher by about 15 ° C. ± 5 ° C. than that of a usual vinyl chloride resin. Further, during kneading and melting in the barrel of the extruder, heat is stored in the extrusion mold due to rapid heat generation.

[0004] Therefore, the heating temperature of the extrusion mold is lower than the temperature of the thermoplastic resin by one to prevent the decomposition of the thermoplastic resin.
Usually, the temperature is set lower by about 5 ° C. ± 5 ° C.

[0005]

However, the surface temperature of the mandrel depends on the temperature of the outer mold that is gradually released from the shear heat of the passing thermoplastic resin and accumulated in the mandrel. The temperature difference increases, the so-called slip stick phenomenon occurs, and the inner surface of the molded thermoplastic resin tube is blurred or uneven,
There is a drawback that a thermoplastic resin tube having excellent inner surface smoothness cannot be formed.

When the difference between the surface temperature of the mandrel and the temperature of the outer mold is large, the difference in cooling rate when cooling after molding is also large, and the tensile stress generated on the inner surface of the molded thermoplastic resin tube is increased. As a result, stress concentration occurs at the spider passage portion where the strength of the thermoplastic resin tube is relatively weak, which causes a problem that the impact strength is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the conventional method of extrusion molding a thermoplastic resin pipe, and an object of the present invention is to solve the above-mentioned problems and to provide a mandrel. An object of the present invention is to provide a method for extruding a thermoplastic resin tube and a mold for extruding a thermoplastic resin tube in which the difference in temperature between the surface temperature and the outer mold does not increase.

[0008]

According to a first aspect of the present invention, there is provided a method for forming a thermoplastic resin tube, comprising: forming a thermoplastic resin between an outer surface of a mandrel and an inner surface of an outer mold; A method for extruding a thermoplastic resin tube extruded from a gap into a tube, comprising a mandrel provided with a through hole close to the outer surface of the mandrel, one end of the through hole of the mandrel is communicated with a through hole provided in the spider. The other end of the through hole is characterized in that the mandrel is cooled by flowing a fluid through the through hole of the mandrel by using an extrusion mold opened to the end face of the mandrel.

According to a second aspect of the present invention, there is provided a method for molding a thermoplastic resin tube according to the first aspect, wherein the temperature of the surface of the mandrel is controlled with respect to the temperature of the inner surface of the outer mold. Is controlled within a range of ± 15 ° C.

According to a third aspect of the present invention, there is provided a mold for extrusion molding of a thermoplastic resin tube, wherein a mandrel is provided in an outer mold, and a spider is provided between the outer mold and the mandrel. A tube extrusion molding die, wherein a mandrel is provided with a through hole close to the outer surface of the mandrel, one end of the through hole communicates with a through hole provided in the spider, and the other end of the through hole is an end surface of the mandrel. It is characterized in that it is opened to the user.

In the present invention, as the thermoplastic resin,
Although not particularly limited, for example, vinyl chloride resin, chlorinated vinyl chloride resin, polyethylene, polypropylene, polycarbonate and the like can be used.

The through holes provided in the mandrel may be provided continuously and annularly along the surface of the mandrel, or a plurality of through holes may be provided intermittently.

According to the first aspect of the present invention, there is provided a method for molding a thermoplastic resin pipe according to the present invention, comprising a mandrel provided with a through-hole close to the outer surface of the mandrel, and one end of the through-hole of the mandrel is provided with an outer mold and an outer mold. The other end of the through hole communicates with the through hole provided in the spider, and the other end of the through hole uses an extrusion molding die opened on the end face of the mandrel, and fluid flows from the through hole provided in the spider to the through hole of the mandrel. By cooling the mandrel, the temperature difference between the outer mold and the mandrel can be reduced.

In the method for molding a thermoplastic resin tube according to the present invention, the temperature of the surface of the mandrel is controlled within a range of ± 15 ° C. with respect to the temperature of the inner surface of the outer mold. The temperature difference between the outer mold and the mandrel can be reduced.

According to a third aspect of the present invention, there is provided a mold for extruding a thermoplastic resin tube, wherein the mandrel is provided with a through hole close to the outer surface of the mandrel, and one end of the through hole is formed in the outer mold and the spider. Since the other end of the through hole is opened to the end face of the mandrel, the mandrel can be cooled by flowing a fluid from the through hole provided in the spider to the through hole of the mandrel. it can.

[0016]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view showing one embodiment of the method for forming a thermoplastic resin tube of the present invention, and FIG. 2 is a right side view of one embodiment of the method for forming a thermoplastic resin tube of the present invention shown in FIG.

1 and 2, reference numeral 1 denotes a mold for extrusion molding of a thermoplastic resin, 11 denotes an outer mold of the extrusion mold 1, 12 denotes a mandrel provided in the outer mold 11, and 13 denotes an outer mold 11 A spider connecting the mandrel 12 and the outer mold 11
It is a torpedo provided inside.

Reference numeral 15 denotes a bolt. One end of the bolt 15 is attached to the torpedo 14, and the other end of the bolt 15 is protruded from the front end surface of the mandrel 12. A nut 151 is screwed into the mandrel 12, the spider 13, and the torpedo 14. Are combined.

.. Are a plurality of through holes intermittently provided along the surface at a position close to the surface of the mandrel 12, and the through holes 121, 121,. It communicates with the through hole 131.

Reference numeral 2 denotes a suction pump / blowing pump provided outside the spider 13. One end of a suction / blowing pipe 21 is connected to the suction pump / blowing pump 2.
1 is connected to the inlet of the through hole 131, and the through holes 121, 121 are operated by the operation of the suction pump and the blowing pump 2.
・ ・ Air is circulated to the air.

Next, an embodiment in which a thermoplastic resin tube is molded by the method of the present invention using the thermoplastic resin tube molding die 1 shown in FIGS.

The mold 1 is extruded from an extruder (not shown).
The thermoplastic resin 3 in the molten state introduced into the inside is branched by the tip of the torpedo 14, passes through the annular gap between the inner surface of the outer mold 11 and the surface of the torpedo 14, and
Through the annular gap between the inner surface of the outer mold 11 and the surface of the mandrel 12 and is formed into a tubular shape.

The through holes 121 of the mandrel 12
・ The through-hole 1 is activated by the operation of the suction pump and the blower pump 2.
The surface of the mandrel 12 is cooled by the flow of air through 21, 121.

Therefore, even if heat is stored in the mandrel 12, the temperature difference between the outer mold 11 and the outer mold 11 is small, and the thermoplastic resin 3 extruded from the annular gap between the inner surface of the outer mold 11 and the surface of the mandrel 12 has a so-called so-called “diffusion”. The slip stick phenomenon does not occur, and the inner surface of the extruded thermoplastic resin tube 31 is smooth.

FIG. 3 is a side view showing another example of the extrusion molding die. In the extrusion molding die 1a shown in FIG. 3, as shown in FIGS. Instead of providing the through holes 121 intermittently, an annular through hole 121a is provided. Incidentally, in FIG.
Reference numeral 2 denotes a reinforcing member provided at regular intervals in the annular through hole 121a.

FIG. 4 is an explanatory view showing another embodiment of the method for molding a thermoplastic resin tube of the present invention. In the embodiment shown in FIG. 4, the control device 4 is provided in the suction pump / blowing pump 2, the temperature sensor 41 is embedded in the mandrel 12, and the temperature data detected by the temperature sensor 41 is transmitted to the control device via the lead wire 42. 4 and the output of the control device 4 is transmitted to the suction pump / blowing pump 2 through the lead wire 43.

That is, the temperature of the mandrel 12 is detected by the temperature sensor 41, and the operation of the suction pump / blowing pump 2 can be controlled by the control device 4 depending on the level of the temperature of the mandrel 12.

Therefore, in the embodiment of the thermoplastic resin tube molding method of the present invention shown in FIG. 4, when the temperature of the mandrel 12 is higher than the temperature of the outer mold 11, the control device 4
When the temperature of the mandrel 12 becomes substantially the same as the temperature of the outer mold 11, the controller 4 stops the operation of the suction pump / blowing pump 2. Things.

In the embodiment of the thermoplastic resin tube forming method of the present invention shown in FIG. 4, the temperature of the mandrel 12 can be automatically controlled, so that the temperature difference between the outer mold 11 and the surface of the mandrel 12 is automatically determined. Therefore, it is possible to form a thermoplastic resin tube having a smooth inner surface.

Although the embodiment of the present invention has been described with reference to the drawings, the configuration of the present invention is not limited to the illustrated embodiment, and any design change within the scope of the present invention is possible. Included in the present invention.

For example, instead of forming a thermoplastic resin tube having a circular cross section as in the illustrated embodiment, a thermoplastic resin tube having a square cross section may be formed. Also, instead of flowing air as in the illustrated embodiment, a liquid, for example, water may flow in the through-hole of the mandrel. However, in the case where water is circulated, it may be hindered if the water drips. Therefore, it is necessary to provide a circulation channel to circulate the water.

[0032]

According to the method for molding a thermoplastic resin pipe of the present invention, the temperature difference between the outer mold and the mandrel can be reduced, so that the so-called slip stick phenomenon does not occur. A thermoplastic resin tube having a smooth inner surface can be formed.

In the method for molding a thermoplastic resin tube according to the present invention, the temperature of the surface of the mandrel is controlled within a range of ± 15 ° C. with respect to the temperature of the inner surface of the outer mold. Since the temperature difference between the outer mold and the mandrel can be reduced, a so-called slip stick phenomenon does not occur, and a thermoplastic resin tube having a smooth inner surface can be formed.

According to the third aspect of the present invention, the mandrel is cooled by flowing a fluid from a through hole provided in the spider to a through hole of the mandrel. Therefore, the temperature difference between the outer mold and the mandrel can be reduced, so that a so-called slip stick phenomenon does not occur, and a thermoplastic resin tube having a smooth inner surface can be formed.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one embodiment of a method for extruding a thermoplastic resin tube according to the present invention.

FIG. 2 is a right side view of the embodiment shown in FIG.

FIG. 3 is a right side view showing another example of a mold for extrusion molding of a thermoplastic resin tube.

FIG. 4 is an explanatory view showing another embodiment of the extrusion molding method for a thermoplastic resin tube of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Extrusion mold 11 Outer mold 12 Mandrel 121 Through hole 13 Spider 131 Through hole 14 Torpedo 15 Bolt 151 Nut 2 Suction pump and blower pump 3 Thermoplastic resin 31 Thermoplastic resin pipe 4 Control device 41 Temperature sensor 42, 43 Lead line

Claims (3)

[Claims] 1. A method for extruding a thermoplastic resin tube into a tubular form by extruding a thermoplastic resin from an annular gap between a surface of a mandrel and an inner surface of an outer mold, wherein the mandrel is provided with a through hole close to an outer surface of the mandrel. One end of the through hole of the mandrel is communicated with a through hole provided in the spider, and the other end of the through hole uses an extrusion molding die opened on the end face of the mandrel, and a fluid flows into the through hole of the mandrel. The method for molding a thermoplastic resin tube, characterized in that the mandrel is cooled by allowing the mandrel to flow. 2. The method for molding a thermoplastic resin tube according to claim 1, wherein the temperature of the surface of the mandrel is controlled within a range of ± 15 ° C. with respect to the temperature of the inner surface of the outer die. 3. A mold for extruding a thermoplastic resin tube in which a mandrel is provided in an outer mold and a spider is provided between the outer mold and the mandrel, wherein the mandrel penetrates the mandrel close to the outer surface of the mandrel. A hole is provided, one end of the through hole is communicated with a through hole provided in the spider, and the other end of the through hole is opened at an end face of the mandrel. .