JP3242463B2 - Method and apparatus for manufacturing resin tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for manufacturing a resin tube having a highly smooth inner surface by an extrusion molding method.

[0002]

2. Description of the Related Art A mold used for extruding a resin tube has a mandrel in the outer die concentrically with the outer die. In order to smooth the inner surface of the resin tube, the mandrel is used. Heaters have been incorporated to heat the mandrel in the land. For example, as shown in FIG. 2, a mold is known in which a cylindrical casting heater C is embedded at the tip of a mandrel B, and an air ejection tube E is attached to the tip of the mandrel B. A band heater is usually attached to the outer periphery of the outer mold A, but is not shown.

[0003] Then, the hose E ₁ for sending the air to the conduction cord C ₁ and the air ejection cylinder E for energizing the heater C are both mandrel B, drawn out through the spider D and outer mold A, Each is connected to a power supply and a blower.

[0004]

Even when the above-mentioned mold is used, the smoothness of the inner surface of the resin tube is not always sufficient, and for example, it is even smoother as a pipe material for passing ultrapure water. Is required.

In the above-mentioned mold, the energizing cord C
₁ and the hose E ₁ are to be bored in the mandrel B, the spider D and the outer mold A to pass through,
The structure of the mold becomes more complicated, and the mandrel B
Is extrusion since become very hot during molding such as a hose E ₁ is exposed to high temperatures, easily damaged by heat deterioration, once damaged, through a very narrow space, such as a small hole drilled in the spider D Because of the piping, the repair took a lot of time and labor, such as disassembling the mold.

Particularly, in a mold for a resin pipe having a small diameter (for example, 25 mm or less), the mandrel has a small diameter, and a hole for passing a heater cord and a blower pipe cannot be formed therein. Without adding, a heater was simply embedded in the tip of the mandrel and heated.

[0007] In view of the above, it is an object of the present invention to provide a method for manufacturing a resin tube with further improved inner surface smoothness, and an apparatus for manufacturing such a resin tube.

[0008]

According to a method for manufacturing a resin tube of the present invention, a resin tube is extruded from a mold having a mandrel attached to the tip of an extruder .
The temperature of the inner peripheral surface of the tubular resin passing therethrough is first heated to a temperature higher than the resin temperature of the core, and then the temperature of the resin pipe of the mandrel is increased .
In the cooling part of the heat pipe buried inside the tip in the extrusion direction
It is characterized in that it is cooled to a temperature lower than the resin temperature of the core and extruded.

Further, in the resin pipe manufacturing apparatus of the present invention, a die having a mandrel is attached to the tip of the extruder, and a heating device and a heat pipe are mounted on the mandrel of the land portion of the die .
The cooling section is embedded in this order in the extrusion direction of the resin pipe, and the heating section of the heat pipe is provided so as to protrude from the tip of the mandrel .

[0010] In the above apparatus, the heating device embedded in the land portion on the inner side of the mandrel is a rod-shaped or plate-shaped heater,
For example, a sheathed heater is used, which is not different from a conventional one buried in a mandrel. Further, it is preferable that the heating device and the heat pipe are insulated through a heat insulating material.

In the method of manufacturing a resin tube according to the present invention, the temperature of the resin on the inner peripheral surface of the tubular resin passing through the land portion of the mold is first made higher than the temperature of the core portion. The resin on the peripheral surface is sufficiently melted to be smooth along the outer peripheral surface of the mandrel. Then the inner peripheral surface of the tubular resin is said mandrel
Heat pipe buried inside the tip of the resin tube in the extrusion direction
In the cooling part, the core is cooled to a temperature lower than the core temperature and fixed, so the smoothness of the inner peripheral surface is maintained without being affected by the behavior of the unmelted part of the core, and the core is extruded from the open end of the mold. You.

In the apparatus of the present invention, a heating device and a cooling section of a heat pipe are buried in a mandrel of a land portion in the extrusion direction of a resin pipe in this order, and the heating section of the heat pipe projects from the tip of the mandrel. First, the tubular resin passing through the land of the mold is heated so that the resin temperature on the inner peripheral surface is higher than the temperature of the core, and then cooled so as to be lower than the temperature of the core. Can be done. As a result, the resin tube extruded from the opening end of the mold has no unevenness on the inner peripheral surface and has excellent smoothness.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing a synthetic resin tube and an apparatus therefor according to the present invention will be described with reference to the drawings.

FIG. 1 is a partially cutaway front view of an embodiment of a mold used in the apparatus for manufacturing a synthetic resin pipe of the present invention. In FIG. 1, 1 is an outer mold, 2 is a mandrel, 3 is a land portion, 4 is a heater, 5 is a heat pipe, 52
Denotes a cooling unit of the heat pipe 5, and 51 denotes a heating unit of the heat pipe 5.

The mandrel 2 is inserted into the outer mold 1, is supported concentrically with the outer mold 1 by a spider 7, and the gap between the outer mold 1 and the mandrel 2 is an annular resin passage. The land portion 3 is the parallel resin passage portion on the opening end side.
A band heater attached to the outer periphery of the outer mold 1 for heating the outer mold 1 is omitted in the drawing.

A rod-shaped heater 4 and a heat pipe 5 are provided at a portion of the mandrel 2 located at the land 3 at the tip end.
It is buried in the opening end direction (the direction in which the resin tube is extruded) in this order. The heat pipe 5 has a cooling part 52 embedded in a hole at the tip of the mandrel 2, and a heating part 51 of the heat pipe 5 protrudes from the tip of the mandrel 2. Heat transfer grease is applied to the outer periphery of the cooling portion 52 in the embedded portion of the heat pipe 5 so that heat transfer from the mandrel 2 is performed more efficiently. In addition, heater 4
A heat insulating material 6 is provided between the heat pipe 5 and the heat pipe 5 for heat insulation. Reference numeral 41 denotes a power supply cord, which is connected to the heater 4 through holes provided in the outer mold 1, the mandrel 2 and the spider 7, respectively.

The resin heated by an extruder (not shown) is transferred through the respective molds to the annular resin passage, sent to the land portion 3 where it is rectified, and extruded from the opening end as a resin tube. By the way, the resin transported while being rectified in the land portion 3 is first heated by the mandrel 2 whose inner peripheral surface is heated by the heater 4 and is sufficiently melted to eliminate the unmelted portion. As a result, the inner peripheral surface of the resin is smoothed along the outer peripheral surface of the mandrel 2. The resin on the inner peripheral surface that has been sufficiently melted and smoothed is subsequently cooled by the cooling unit 52 of the heat pipe 5 to be at a temperature lower than the resin temperature of the core, and is in a stable state. For this reason, the inner peripheral surface of the extruded resin tube is not irregularized without following the behavioral stress of the molten or unmelted resin in the core of the tube wall, and is smooth.

Next, using the mold having the structure described above,
A specific example in which a rigid vinyl chloride pipe is extruded will be described.

As the mold of the present invention, a mandrel having a 20 mm outer diameter and a land length of about 130 mm for a rigid polyvinyl chloride pipe is used, and a hole of about 10 mm is formed in the mandrel to a depth of about 100 mm from the front end face. A rod-shaped heater (length 50 mm) was inserted into the back of the hole, heat insulating material was inserted, and a heat pipe (outer diameter 10 mm, length 100 m) was inserted.
The cooling unit (approximately 50 mm) of half of m) was coated with heat transfer grease on its outer peripheral surface and inserted.

The above-mentioned mold is attached to the tip of the extruder, and the mandrel temperature of that part is set to 216 ° C. by a heater, and the tip part is heated to 180 ° C. by a cooling part of a heat pipe.
Then, a rigid vinyl chloride resin tube having a diameter of 20 mm was extruded from the opening end of the mold. At this time, the temperature of the resin passing through the land heated by the heater is 213 ° C. at the maximum on the inner peripheral surface and 207 ° C. at the depth of 0.25 mm from the inner peripheral surface.
° C, 0.5 mm deep (center) is at most 201 ° C, and the resin temperature at the tip of the mandrel is 197 at the inner peripheral surface.
℃, 0.25mm deeper than the inner circumference 202 ° C, 0.5mm
The inside (center) was 201 ° C. The smoothness of the inner peripheral surface of the obtained rigid PVC pipe was measured by a roughness meter to a maximum value (RM).
AX) was 0.222 μm.

For comparison, the outer diameter of the mandrel is 20 mm
In a mandrel of a mold for a rigid vinyl chloride pipe having a land length of about 130 mm, a 10 mm hole is drilled 50 mm deep from the end face, and a mold having a 50 mm long heater inserted into the hole is used. To extrude a rigid vinyl chloride tube. At this time, the temperature at the back of the mandrel at the land of the mold is 195 ° C., the temperature at the tip (opening end) is 216 ° C., and the resin temperature at the land is 202 ° C. at maximum on the inner peripheral surface. A maximum of 201 ° C, 0.25 mm deep from the inner peripheral surface,
0.5 mm deep (center) is 198 ° C at the maximum, and the resin temperature at the mandrel tip is 213 ° C on the inner circumferential surface, 207 ° C at 0.25 mm deep from the inner circumferential surface, and 0.5 mm deep (center). Was 201 ° C.

The maximum value (R-MAX) of the smoothness of the inner peripheral surface of the obtained rigid vinyl chloride pipe measured by a roughness meter was 0.354 μm.

[0022]

As described above, in the method of manufacturing a synthetic resin tube according to the present invention, the inner peripheral surface of the resin passing through the land of the mold is first sufficiently heated and melted to be smoothed, and then the inner surface thereof is smoothed. Since the temperature is lower than the resin temperature and the resin is in a stable state, no irregularities are generated on the inner peripheral surface, and a resin pipe having a smooth inner peripheral surface is extruded.

In the apparatus for producing a synthetic resin according to the present invention,
The heating and cooling of the mandrel are efficiently performed by the heating device and the heat pipe, and the tubular resin passing through the land of the mold is first heated to a temperature higher than the temperature of the inner peripheral surface of the core, and Subsequently, it can be cooled to a temperature lower than the core temperature. Since the tip of the mandrel is cooled by the heat pipe, there is no need for piping such as a hose for guiding air as in the related art, and there is no fear of cutting the hose, thereby simplifying the structure of the mandrel.

[Brief description of the drawings]

FIG. 1 is an upper half cut front view of an example of a synthetic resin tube mold used in the method of the present invention.

FIG. 2 is an upper half cut front view of a synthetic resin tube mold used in a conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Outer type 2 Mandrel 3 Land part 4 Heating device (heater) 5 Heat pipe 6 Insulation material 7 Spider

Claims (2)

(57) [Claims] When extruding a resin tube from a mold having a mandrel attached to the tip of an extruder, the temperature of the inner peripheral surface of a tubular resin passing through a land portion of the mold is first measured by a resin at a core portion. Heat above the temperature, then
The heat pipe embedded in the tip of the resin tube in the extrusion direction
A method for manufacturing a resin pipe, comprising: extruding a resin at a temperature lower than a resin temperature of a core in a cooling unit . 2. A mold having a mandrel is attached to the tip of the extruder, and a heating device and a cooling part of a heat pipe are embedded in a mandrel of a land portion of the mold in the extrusion direction of the resin pipe in this order. Connect the heating part of the heat pipe to the mandrel
An apparatus for manufacturing a resin pipe, wherein the apparatus is provided so as to protrude from a tip end of a resin pipe.