JPH1110713A - Method and device for manufacture of thermoplastic resin tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of outer appearance generated by the volatilization of an admixture having low melting point added to a resin such as calcium stearate and the adhesion of it on a tube inner wall at the time of extrusion molding. SOLUTION: A manufacturing device for a thermoplastic resin tube for extruding a tube shaped thermoplastic molten body is provided, and a suction hole 71 for sucking volatile gas V remaining on the inner side of an extruded tubular thermoplastic resin molten body P and an air feed hole 17 for blowing cooled air flows on the inner face of the extruded tubular thermoplastic resin molten body P are opened on the end side of a mandrel 15 in the manufacturing device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for manufacturing a thermoplastic resin tube.

[0002]

2. Description of the Related Art When extruding a thermoplastic resin tube,
A resin or a compounded composition comprising a resin and additives is melted and kneaded in an extruder, passed through a resin passage between an outer mold and a mandrel, extruded as a tubular thermoplastic resin melt, and cooled. After cooling and hardening, it is cut into a predetermined length by a cutting machine to obtain a product.

By the way, low melting point additives such as calcium stearate and lead stearate are added to a resin or a compounded composition for the purpose of improving thermal stability, moldability, and tube properties. May be. These low-melting-point additives have low melting points, and due to high temperatures in extruders and extrusion dies, some volatilize and form fine bubbles, but melt due to high resin temperature and pressure. When it is present in the resin and passes through the resin passage of the extrusion mold and is extruded as a tubular thermoplastic resin melt, the pressure of the molten resin is rapidly removed, and the temperature of the molten resin is reduced. As the resin lowers and the resin hardens and shrinks, the volatile gas of the low-melting-point additive that has been present as bubbles is released.

The volatile gas of the low-melting-point additive adheres to the inner wall of the tube and solidifies to stain the inner surface of the tube, deteriorating the appearance,
There was a problem that hygiene was reduced.

[0005] As means for solving such a problem, conventionally, as shown in Japanese Utility Model Application Laid-Open No. 61-81723, a gas that has accumulated in the inner surface of a tubular thermoplastic resin melt immediately after extrusion is removed by an extrusion molding die. It is disclosed that an exhaust device is provided which sucks through an intake hole opened at the tip of the mandrel and discharges the same through the inside of the extrusion mold. Also,
Japanese Patent Laid-Open Publication No. Sho 62-140816 discloses that an air supply hole is provided at the tip of a mandrel of an extrusion mold in order to smooth the inner surface of a thermoplastic resin tube, and a cooling air flow is blown from the air supply hole. Cooling is disclosed.

[0006]

[Problems to be Solved by the Invention]
In the apparatus described in the publication, the extruded thermoplastic resin melt is long and continuous to the cutting machine, and the thermoplastic resin melt is gradually cooled. The temperature of the plastic resin melt decreases, and volatile gas is released. For this reason, there is a problem that the volatile gas released at a position distant from the mandrel cannot be sucked from the suction hole provided at the tip of the mandrel of the extrusion molding die. The present invention has been made in view of the above-described conventional problems, and solves the problems of the conventional method, and prevents the volatile gas from adhering to the inner wall of the tube and preventing the inner surface of the tube from becoming dirty and deteriorating the appearance. It is intended for that purpose.

[0007]

In order to achieve the above object, according to the first aspect of the present invention, a thermoplastic resin to which a low melting point additive is added is passed through a passage between an outer mold and a mandrel. A method of manufacturing a thermoplastic resin tube, in which a cooling air flow is supplied from an air supply hole to cool and shrink the thermoplastic resin by cooling the inner surface of the tubular thermoplastic resin, thereby forming a low melting point additive gas. It is characterized in that the gas of the low-melting-point additive released is sucked in from the suction hole and discharged out of the tube. The invention according to claim 2 is characterized in that the air supply hole and the air intake hole according to claim 1 are provided so as to open at the tip end side of the mandrel, and the air supply hole is provided on the mandrel side from the air intake hole. The invention according to claim 3 is an apparatus for producing a thermoplastic resin tube having a mold comprising an outer mold and a mandrel, wherein an air supply hole for supplying a cooling air flow is opened to a tip side of the mandrel. An air supply device is provided, which is provided with an intake hole for inhaling gas in the thermoplastic resin tube opened to the tip side of the mandrel, and the air supply hole is provided on the mandrel side from the intake hole, and supplies a cooling airflow to the air supply hole. Is provided, and a discharge device that discharges gas from the intake hole is provided.

Japanese Patent Application Laid-Open No. Sho 62-140816 describes that the inner surface of a pipe is melted near an outlet of a mandrel, and a cooling air flow is blown to the inner surface in the molten state to smooth the inner surface. However, it does not disclose curing and shrinking the resin to release the gas of the low melting point additive.

[0009] Some extrusion molding dies have and do not have an auxiliary mandrel. In the case of an extrusion molding die having an auxiliary mandrel, the suction hole and the air supply hole are
Provided on the tip of the mandrel or on the auxiliary mandrel,
In the case of an extrusion mold having no auxiliary mandrel, the air intake hole and the air supply hole are provided at the tip of the mandrel.

One of the flow path from the intake hole to the exhaust device and the flow path from the air supply hole to the supply device is a tubular body (hose) passed through an extrusion mold, and the other is an extrusion mold. Or both may be tubular bodies (hoses) passed through an extrusion mold. Examples of the thermoplastic resin include hard vinyl chloride, polyethylene, and polypropylene, but any thermoplastic resin may be used as long as it can be extruded.

(Action) In the method and apparatus for manufacturing a thermoplastic resin pipe of the present invention, a tubular thermoplastic resin molten body surface is formed by an air supply hole opened at the tip end side of a mandrel of an extrusion mold. Blow cooling air. Therefore, near the tip of the mandrel, the temperature of the inner surface of the tubular thermoplastic resin melt decreases, the resin hardens and shrinks, and the volatile gas of the low-melting-point additive, which was present as bubbles, is discharged from the tip of the mandrel. Emitted near. Then, the volatile gas of the low-melting-point additive is sucked through an intake hole provided at the tip of the mandrel of the extrusion molding die. Further, when the air supply hole is provided on the mandrel side from the air intake hole, the air can be taken in from the air intake hole after being cooled by the cooling airflow from the air supply hole, so that the volatile gas can be efficiently taken in.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing one embodiment of a manufacturing apparatus used in a method for manufacturing a thermoplastic resin tube according to the present invention. The extrusion mold 1 includes a main body 11, a rear portion 12, a torpedo 13, an outer mold 18, a mandrel 15, and an auxiliary mandrel 16. These components are assembled as shown in FIG. 1 by bolts and nuts (not shown) or screw connections between them. Further, the main body 11 is integrally formed with a main body outer mold 111, a main body inner mold 112, and a plurality of spiders 113 connecting between them. The extrusion die 1 has a rear portion 12 attached to the tip of the extruder.

At the tip of the auxiliary mandrel 16, a baffle plate 8 supported by the support rod 7 is provided. The support rod 7 is provided with an intake hole 71, and the baffle plate 8 is also provided with an intake hole 71. ing. An auxiliary mandrel hole 2 is opened at the tip of the auxiliary mandrel 16, and the intake hole 2 penetrates through the auxiliary mandrel 16, the mandrel 15, and the central portion of the main body inner mold 112 in the axial direction. The pores 3 and the center of the inner mold 112 are connected to the air pipe 4 which is penetrated in the radial direction through the spider 113 and the outer mold 111 and connected to the exhaust device 6 such as a vacuum pump or a blower. Have been.

On the outer peripheral surface of the auxiliary mandrel 16, a plurality of air supply holes 17 are opened. The air supply hole 17 communicates with the air supply hose 14 passed through the through hole 3 that passes through the mandrel 15 and the center of the main body inner mold 112 in the axial direction, and is connected to the air supply device 9.

Next, the operation of the apparatus for manufacturing a thermoplastic resin pipe will be described. The hard vinyl chloride and the compounded composition melted and kneaded in the extruder are heated and melted, and some of the low melting point additives such as calcium stearate and lead stearate contained therein are volatilized. However, due to the high temperature and pressure of the resin, they are present in the form of fine bubbles in the molten resin.

Next, the molten resin is sent to the extrusion mold 1, between the rear part 12 and the torpedo 13, and outside the main body part mold 111.
A plurality of air supply holes formed by opening the inner surface of the extruded parison P to the outer peripheral surface of the auxiliary mandrel 16 through a resin passage formed between the outer mold 18 and the mandrel 15 between the inner mold 112 and the outer mold 18. A cooling air flow is blown from 17 to cool the cooling air. As the temperature of the tubular thermoplastic resin melt decreases and the resin hardens and shrinks, the volatile gas of the low melting point additive that was present as bubbles was released near the mandrel tip or near the auxiliary mandrel. You.

The volatile gas V of the low-melting-point additive released from the inner surface of the tubular thermoplastic resin melt P is supplied to the baffle plate 8.
Is sucked from the auxiliary mandrel hole 2 of the auxiliary mandrel 16 together with the airflow sucked through the ventilation hole 81 of the support rod 7 and the air flow sucked through the intake hole 71 of the support rod 7, and is quickly discharged to the outside through the through hole 3 of the extrusion mold 1. You.

[0018]

As is apparent from the above description, according to the method and apparatus for manufacturing a thermoplastic resin pipe of the present invention, a cooling air flow is blown onto the inner surface of a tubular thermoplastic resin melt so that the vicinity of the tip of the mandrel can be obtained. As a result, the volatile gas of the low-melting-point additive is released, and the volatile gas of the low-melting-point additive can be efficiently discharged out of the pipe from the air inlet provided at the end of the mandrel. Thermoplastic resin melt extruded from the mold,
In the extrusion method that is long and continuous to the cutting machine, the volatile gas of the low-melting-point additive can be efficiently sucked, and the appearance of the inner wall of the pipe can be prevented from being deteriorated. When the air supply hole is provided on the mandrel side from the air intake hole,
After being cooled by the cooling airflow from the air supply hole, the air can be taken in from the intake hole, and the volatile gas can be taken in efficiently.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a thermoplastic resin pipe manufacturing apparatus according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 mold 11 main body 15 mandrel 16 auxiliary mandrel 17 air supply hole 18 outer mold 2 auxiliary mandrel hole 3 through hole 4 vacuum hose 6 exhaust device 71 intake hole 8 baffle plate 9 air supply device P tubular thermoplastic resin melt

Claims (3)

[Claims] 1. A method for producing a thermoplastic resin tube through which a thermoplastic resin to which a low-melting-point additive is added is passed through a passage between an outer mold and a mandrel, wherein a cooling air flow is supplied from an air supply hole. By cooling the inner surface of the tubular thermoplastic resin to cure and shrink the thermoplastic resin, releasing the low-melting-point additive gas, inhaling the released low-melting-point additive gas from the intake hole, A method for producing a thermoplastic resin tube, wherein the thermoplastic resin tube is discharged outside the tube. 2. The thermoplastic resin pipe according to claim 1, wherein the air supply hole and the air intake hole according to claim 1 are provided so as to open at a tip end side of the mandrel, and the air supply hole is provided on the mandrel side from the air intake hole. Production method. 3. An apparatus for manufacturing a thermoplastic resin tube having a mold comprising an outer mold and a mandrel, wherein an air supply hole for supplying a cooling air flow is provided to be open at a tip side of the mandrel, An intake hole for inhaling gas in the thermoplastic resin pipe is provided to be open at the tip side of the mandrel, and an air supply hole is provided on the mandrel side from the intake hole, and an air supply device for supplying a cooling air flow to the air supply hole is provided. And a discharge device for discharging gas from an intake hole.