JPH0683328U - Thermoplastic resin pipe manufacturing equipment - Google Patents

Abstract

(57) [Summary] [Purpose] During extrusion molding of thermoplastic resin pipes, the volatile gas of the low melting point additive contained in the resin or compounded composition is discharged to the outside of the pipe so that it does not stay and adhere to the inner wall of the pipe. ,
Prevents contamination of the inner wall of the pipe due to gas adhesion and solidification. The end surface of the auxiliary mandrel 16 is provided with a plurality of air ejection holes 5 whose tip portion is inclined with respect to the axial direction of the extrusion molding die 1 and which is inclined and opened outward in the radial direction. The air that has been pressure-fed through the air supply pipe 4 that is inserted through the extrusion molding die 1 is ejected from the air ejection holes 5 to the inner surface of the parison P immediately after being extruded to generate a swirling flow, and this swirling is performed. A device for manufacturing a thermoplastic resin pipe, in which a volatile gas of a low melting point additive which is volatilized and released to the inner surface of the parison P by a flow is discharged to the outside of the pipe.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

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

[Prior art]

 When extruding a pipe made of a thermoplastic resin such as hard vinyl chloride, polyethylene, polypropylene, etc., the resin or a compounded composition consisting of the resin and additives is melted and kneaded in an extruder, and the tip of the resin passage of the extrusion molding die It is extruded as a hollow parison from the product, shaped into a specified shape and size by a sizing device, cooled and solidified by a cooling device, and cut into a specified length by a cutting machine to obtain a product.

By the way, a low melting point additive such as calcium stearate or lead stearate is added to a resin or a compounded composition for the purpose of improving thermal stability and moldability, and improving physical properties of a tube. Sometimes. These low melting point additives are melted uniformly in the resin due to the high temperature and pressure in the extruder and extrusion mold, but some are volatilized and melted in the form of fine bubbles. When the resin is present in the resin, passes through the resin passage of the extrusion mold, and is extruded as a parison, the pressure of the molten resin is rapidly removed, so that the low-melting-point additive that was present as bubbles was present. Volatile gas is emitted.

In this case, since the outer surface side of the parison is open to the atmosphere, the gas is released into the atmosphere without staying on the outer surface of the tube. However, on the inner surface side, since the parison and the pipe are continuous up to the cutting machine, the volatile gas between them stays on the inner surface. As the temperature decreases, the gaseous low-melting-point additive adheres to the inner wall of the pipe and solidifies to contaminate the inner surface of the pipe, deteriorating the appearance and deteriorating hygiene.

As a means for solving such a problem, a device for blowing air to the inner peripheral surface of a molten pipe immediately after extrusion as disclosed in Japanese Patent Application Laid-Open No. 62-140816 has been disclosed. . (However, the purpose of the device described in JP-A-62-140816 is to smooth the inner peripheral surface of the pipe, but it is the same in that the volatile gas of the low melting point additive is discharged to the outside of the pipe by blowing air. )

[0005]

[Problems to be solved by the device]

 However, since the length from the outlet of the resin passage of the mold to the pipe end is long, in the case of the device described in the above-mentioned JP-A-62-140816, the volatilized gas of the low melting point additive is blown out of the pipe by air. It takes quite a long time to discharge the gas into the air, and the temperature of the gas drops during that time, so the actual situation is that the gas is not sufficiently effective. Also, as the diameter of the pipe increases, a significantly large amount of air is required, which is considerably difficult to implement in the case of a pipe with a large diameter.

The present invention has been made in view of the problems of the conventional apparatus as described above, and the problems of the conventional apparatus are solved, and when the thermoplastic resin pipe is extrusion-molded, it is contained in the resin or the compounded composition. By discharging the low-melting-point additive volatile gas to the outside of the pipe while preventing it from adhering to the inner wall of the pipe, it is possible to prevent the gas from adhering to the inner wall of the pipe and solidifying to contaminate the inner surface of the pipe or deteriorate the appearance. The purpose is to do.

[0007]

[Means for Solving the Problems]

 In order to achieve the above object, the apparatus for producing a thermoplastic resin pipe of the present invention is provided with an air ejection hole that opens obliquely forward at the mandrel tip portion of the extrusion molding die or the auxiliary mandrel tip portion. The gist of the present invention is to have a means for feeding air to the air ejection holes through the extrusion molding die.

In the above description, the diagonally forward direction means that the extrusion direction of the thermoplastic resin pipe is the front, and with respect to this, it is inclined in the left-right direction or the up-down direction, or both the left-right direction and the up-down direction (both 90 ° or less). Say the direction to do.

There are two types of extrusion molding dies, one with and without an auxiliary mandrel. In the case of an extrusion dies with an auxiliary mandrel, an air ejection hole is provided at the tip of the auxiliary mandrel. In the case of an extrusion molding die that does not have an auxiliary mandrel, the air ejection hole is provided at the tip of the mandrel.

[Action]

 In the apparatus for manufacturing a thermoplastic resin pipe of the present invention, an air ejection hole that is opened obliquely forward is provided at the tip of the mandrel or the auxiliary mandrel of the extrusion molding die, and the air ejection hole is extruded into the air ejection hole. It has means for pumping air through the mold.

Therefore, the air pressure-fed through the extrusion molding die is ejected obliquely forward with respect to the extruding direction of the pipe from the air ejection hole provided in the tip of the mandrel or the tip of the auxiliary mandrel. Then, it collides with the inner wall surface of the parison with a velocity component in an oblique direction, that is, a tangential direction together with the extruding direction of the pipe, and advances in a swirling flow along the inner wall surface of the parison. (See Figure 2)

As a result, the air near the inner wall surface of the parison and the subsequent inner wall surface of the pipe are pushed forward while being swirled and stirred, so that the volatile gas from the low melting point additive contained in the resin or the compounded composition is It is discharged from the pipe end without staying near the parison and the inner wall surface of the pipe that follows it.

[0012]

【Example】

 Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is an enlarged explanatory view of an auxiliary mandrel portion. The extrusion molding die 1 is composed of a main body portion 11, a rear portion 12, a torpedo 13, a land 14, a mandrel 15, and an auxiliary mandrel 16. These components are assembled in the state shown in FIG. 1 by bolts and nuts (not shown) or screw connections between them. Further, the main body portion 11 is integrally formed with a main body portion outer die 111, a main body portion inner die 112, and a plurality of spiders 113 that connect between them. The extrusion mold 1 has a rear portion 12 attached to the tip of an extruder (not shown).

The extrusion molding die 1 includes an air pipe insertion hole 2 that radially penetrates from the outer surface of the main body outer die 111 to the center of the spider 113 and the main body inner die 112, and further, the central portion of the main body inner die 112. To the mandrel 15 is formed, and an air supply pipe 4 is inserted into the air supply pipe insertion holes 2 and 3, one end of which is opened in the auxiliary mandrel 16 and the other end is formed. Is connected to a compressed air supply source 6 such as a compressor or a roots blower installed outside the extrusion molding die 1.

As shown in FIG. 2, a plurality of air ejection holes 5 are formed in the end surface of the auxiliary mandrel 16 in close proximity to the inner wall surface of the parison P. At least the tip portion of the air ejection hole 5 is inclined obliquely forward with respect to the extrusion direction of the thermoplastic resin pipe, and is also inclined slightly outward in the radial direction.

Next, the operation of the thermoplastic resin pipe manufacturing apparatus configured as described above will be described. When the resin or compounded composition that is melted and kneaded in the extruder is heated and melted, some of the low-melting point additive contained in it volatilizes, but it melts because the pressure of the resin is high. It is present in the resin in the form of fine bubbles.

Next, the molten resin is sent to the extrusion molding die 1, and is formed between the rear part 12 and the torpedo 13, between the main body outer mold 111 and the main body inner mold 112, and between the land 14 and the mandrel 15. When the parison P is extruded through the passage, the resin pressure is rapidly removed, the bubbles are broken, and volatile gas is released from the inner and outer surfaces of the parison P.

However, as shown in FIG. 2, since the air ejection holes 5 as described above are provided on the end surface of the auxiliary mandrel 16, the air sent to the auxiliary mandrel 16 through the air supply pipe 4 is provided. Is ejected obliquely forward from the air ejection hole 5 with respect to the extruding direction of the pipe, collides with the inner wall surface of the parison P in an oblique direction, and advances as a swirling flow along the inner wall surface. Therefore, the volatile gas of the low-melting-point additive released from the inner surface of the parison P is swirled and stirred by this swirling flow, near the inner surface of the parison P and in front of it. Near the inner surface of the cooled pipe. Since the low melting point additive is discharged to the outside of the pipe without accumulating in it, the inner surface of the pipe is not contaminated due to the retention of volatile gas of the low melting point additive.

In the above embodiment, the tip portion of the air ejection hole 5 is inclined with respect to the axial direction of the extrusion molding die 1 and is inclined outward in the radial direction. It may be inclined with respect to the axial direction of the mold 1 and outward in the tangential direction.

Further, the air ejection holes may be opened on the outer peripheral surface of the tip end portion of the auxiliary mandrel 16, but may be fan-shaped or slit-shaped openings along the inner wall surface of the parison P.

Further, the air ejection hole may be formed by a pipe and a pipe joint instead of being formed in the auxiliary mandrel.

Further, in the above-mentioned embodiment, the air is passed through the air supply pipe 4 inserted in the air supply pipe insertion holes 2 and 3, but the air supply pipe is directly inserted without using the air supply pipe or the air ejection pipe. The structure may be such that air is passed through the holes 2 and 3.

[0022]

[Effect of device]

 As is clear from the above description, according to the thermoplastic resin pipe manufacturing apparatus of the present invention, the volatile gas of the low melting point additive generated during the thermoplastic resin pipe extrusion molding is the mandrel tip of the extrusion molding die. The air blown out from the air blowout holes provided at the tip or the tip of the auxiliary mandrel advances as a swirl flow along the inner wall surface, so the air in contact with the inner wall surface of the parison and the pipe inner wall surface that follows it is agitated forward. Is pushed to.

As a result, the volatile gas of the low-melting point additive contained in the resin or the compounded composition is discharged from the pipe end without staying near the inner wall surface. It does not adhere or solidify to contaminate the inner surface of the pipe, deteriorating the appearance or deteriorating hygiene.

Further, the amount of air required can be made smaller than that of the conventional device by the stirring effect of the swirling flow, so that the equipment cost and the operating cost can be reduced.

[Brief description of drawings]

FIG. 1 is a partially cutaway vertical sectional view showing an embodiment of the present invention.

2A and 2B are an enlarged explanatory view and an operational explanatory view of an auxiliary mandrel portion, in which FIG. (B) is a front view of the auxiliary mandrel.

[Explanation of symbols]

 1 Extrusion Mold 15 Mandrel 16 Auxiliary Mandrel 2,3 Air Pipe Insertion Hole 4 Air Pipe 5 Air Jet Hole 6 Compressed Air Supply Source P Parison

Claims (1)

[Scope of utility model registration request] 1. A means for pressure-feeding air to the air ejection hole passing through the inside of the extrusion molding die, wherein an air ejection hole opening obliquely forward is provided at the tip of the mandrel or the tip of the auxiliary mandrel of the extrusion molding die. An apparatus for manufacturing a thermoplastic resin tube, which comprises: