JPS58168519A - Cooler for inflation molding - Google Patents

Abstract

PURPOSE:To increase the cooling effect of fused resin tubular body and to increase the inflation molding speed, by arranging a heat pipe equipped with an evaporation part on the inner peripheral surface of the fused resin tubular body just after being extruded from extrusion die. CONSTITUTION:In the inflation molding apparatus wherein the resin tubular body 6A of fused state extruded from the annular slit 4 of the extrusion die 1 is made the resin bubble 6C by the expansion and thinning wall of it and it is winded after completely solidification by cooling, the cooling heat pipe 10 is provided in the gas-filled tube 9 installed by penetrating the central part of the extrusion die 1. The evaporation part 10A of heat pipe 10 is formed to be of the column having about the same height as that of the expansion part 6B of resin tubular body 6 and the same diameter as that of the tubular body 6A just after extrusion. The condensation part 10B of heat pipe 10 is arranged at a fixed height in the resin bubble 6C and a heat dissipation fin is provided on the outer peripheral part near the upper end of it.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inflation cooling device that cools a tubular resin extruded into a tubular shape from a pressing die from the inside.
In particular, it relates to improvements in its cooling capacity.

In inflation molding of thermoplastic resins, there is an increasing demand for high-speed molding to improve productivity, or even if extruders and extrusion dies are capable of high-speed extrusion, in order to achieve high-speed molding, extrusion 1-- It is difficult to cool down the tubular resin to be used unless it can be sufficiently cooled. Furthermore, in order to improve the physical properties of the formed film, it is necessary to sufficiently cool the molten resin evenly inside and outside.

By the way, a method of blowing cooling air onto the outer peripheral surface of an extruded tubular resin using one or more near rings is widely used, but in order to improve the cooling effect, melting by increasing the flow rate of cooling air Since the molding stability of resins with low tension is significantly impaired, there is a natural limit to the improvement of the cooling effect only when cooling from the outside of the tubular resin.

Therefore, in order to cool the tubular resin not only from the outside but also from the inside, a method has been devised in which a cooling air bag is circulated from the outside inside the tubular resin. but,
In these four methods, the tubular resin requires rapid cooling especially for the molten resin tubular body immediately after being extruded from the extrusion die, but on the other hand, the resin that has burst into bubbles through the expansion part,
Although the Q pool does not necessarily require rapid cooling, it only cools the entire tubular resin approximately uniformly, and the quenched seedlings of the saturated resin tubular body are particularly cooled. Therefore, even if such a method was adopted alone, a sufficient cooling effect to achieve high-speed molding could not be obtained.

According to Japanese Patent Application Laid-Open No. 56-75829, a cooling device in which an evaporating section of heat and soybean is buried in the center of a mandrel has been proposed, but this cooling device that has already been proposed has Since the evaporation section cools the core, and the cooled core further cools the molten resin tubular body, the heat transfer efficiency is not necessarily sufficient, and the heat nozzle is not necessarily sufficient. Since the evaporating part and the core of the eve are constructed as separate bodies, the structure is also complicated.

An object of the present invention is to provide a cooling device for forming a blown film that has a large cooling effect and a simple structure.

The present invention comprises a cooling device for inflation molding using a beat nozzle in which an evaporating section is positioned in contact with or close to the inner circumferential surface of a molten resin tubular body immediately after being extruded from an extrusion die, and The object is to be achieved by cooling the molten resin from the inside using the evaporation section.

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows the main parts of an inflation molding apparatus to which a first embodiment of the cooling apparatus for inflation molding according to the present invention is applied.

In this figure, the extrusion die l consists of a die body 2 having a cylindrical hollow part, and a die mandrel 3 fitted into the hollow part of the die body 2, and an annular slit at the upper end of the fitting part. 4 is constructed, and the molten resin 5 supplied into the extrusion die 1 is extruded into a tubular shape through the annular slit 4 to form a tubular resin 6.

Immediately after the tubular resin 6 is extruded from the extrusion die 1, it becomes a molten resin tubular body 6A in a molten state. After the resin bubble 6C is completely cooled and solidified, the resin bubble 6C is linearized and flattened by nip rolls (not shown), and then continuously wound up.

In the center of the extrusion die 1, a penetration pipe 9 having an external cock 8 is formed so as to penetrate into the tubular resin 6 and reach a predetermined height position of the resin bubble 6C. A heat tube 10 serving as a cooling device for molding is held at the center of the extrusion die 1 along the resin extrusion direction, with the enclosing tube 9 inserted through the center.

Evaporation section of the heat worm 10] (IA is the expansion section 6
It is formed in a cylindrical shape with a predetermined diameter and has approximately the same height position as B, and the outer circumferential surface of the lower half portion along the longitudinal direction is in contact with the inner circumferential surface of the molten resin tubular body 6A. While being approached, the lower end of the evaporation section 1()A and the extrusion die 1
A predetermined interval is provided between the upper end surface of the encapsulating tube 9 and a communication port 11 located within this interval.

Further, the condensing section 10B of the heat ejector 10 is arranged at a predetermined height position within the resin bubble 6C, and a heat radiation fin 12 is provided on the outer circumference near the upper end of the condensing section 10B. At this point, the enclosure tube 9 is opened.

[Evaporation section of Heat Tsuquib 1 ()] A wick 13 is provided on almost the entire inner circumferential surface of the OA, and this wick 13
The condensate 14 of the working fluid is moved through the inside, while the vapor flow of the working fluid flows through the inner wall portion of the heat nosoid 10.
is raised. Furthermore, a near ring 16 is arranged on the extrusion die 1 .

Next, the operation of this embodiment will be explained.

The molten resin 5 in the extrusion die 1 is continuously extruded through the annular slit 4 to form a tubular resin 6. Air at a constant pressure is introduced into the tubular resin 6 from the sealed tube 9 at the start of operation. The sealed molten resin tubular body 6A of the tubular resin 6 is expanded by the internal pressure at a blow-up ratio of Flf in the expansion section 6B, thereby forming a resin bubble 6C.

The molten resin tubular body 6A is cooled from the outside by the near ring 16, and the #valve part 1 of the heat pipe 10
It is also cooled from the inside by 0A. That is, the evaporation section 10A functions as a core that improves the stability of the bath melt resin tubular body 6A, and also absorbs heat from the inside of the evaporation section 10A, in other words, cools the evaporation section 10A. In this case, the condensate 14 evaporates.

The evaporated condensate 14 rises in the heat pipe 10 along with the vapor flow 15, and is condensed in the condensing section 10B to form the condensate 1.
4 and is moved to the evaporation section 10A.

As described above, the molten resin tubular body 6A is constantly rapidly cooled in the evaporation section 10A due to the circulation of the working fluid in the heat exchanger 10, and the expansion section 6B is also located close to the evaporation section 10A. The internal air in contact with the expansion section 6B is also cooled, and the expansion section 6B is also cooled.

On the other hand, in the condensing section 10B, heat is released into the resin bubbles 6C, or the condensing section 10B is arranged at a position where the resin bubbles 6C are completely cooled and solidified.
It is clear that the heat dissipation at B has an adverse effect on the fat bubble 6C.

Note that when the bath molten resin 5 is a resin with low melt tension such as polyethylene sieve, the stability of the molten resin tubular body 6A is relatively low. It is desirable to bring the molten resin into contact with the inner circumferential surface of the molten resin tubular body 6A to increase stability and further enhance the quenching effect. In the case of polymers, polypropylene, etc., it is not particularly necessary to bring the outer circumferential surface of the evaporator 10A into contact with the inner circumferential surface of the molten resin tubular body 6A, and it is sufficient to simply bring them close to each other. After the empty resin bubble 6C is introduced into the encapsulation tube 9 from the upper opening of the insertion tube 9, it flows out from the flow hole 11 to the lower end of the evaporation section 10A, and this flowed air is evaporated. Since the gap between the outer peripheral surface of the section 10A and the inner peripheral surface of the six molten resin tubular bodies flows toward the fat bubble 6C, the molten resin tubular body 6A is not welded to the evaporation section 10A. Stable molding will be ensured.

According to this embodiment, since the molten resin tubular body 6A is directly cooled by the evaporation section 10A of the Heat Nomi Eve 10, the quenching effect is large, and therefore high extrusion and high speed inflation molding can be performed completely stably. You will be able to do this. In addition, the increase in the quenching effect, together with the fact that the tubular resin 6 is cooled not only from the outside but also from the inside, can improve the physical properties of the formed film, such as improving the stretching effect.

Since the evaporation section 10A of the heat pipe 10 also serves as a nopuru stabilizer, that is, a core, the structure is simple and assembly is easy.

Furthermore, since there is no internal cooling means such as circulating cooling air between the inside and outside of the tubular resin 6 or cooling the core with cooling water, the structure is simple and small. It can also be applied to extrusion dies of any diameter, and can be operated easily.

Next, examples other than the above will be described.
The same reference numerals are used for parts that are the same as or similar to those in the embodiment, and the description thereof will be simplified or omitted.

A second embodiment is shown in FIG. 2, in which the insertion tube 9 terminates at the lower end surface of the heat pipe 10 and is closed. It's a trench, Eve 10's evaporation section 10A is in the heat.
, there is a communication passage 21 that communicates the upper and lower ends of this evaporation section 10A.
Two communicating pipes 22 are arranged (see Fig. 3), and internal air on the resin nozzle 6C side is introduced into the lower end side of the evaporating section 10A through the communicating passage 21, and the introduced air The resin flows back through the gap between the evaporator 10A and the molten resin tubular body 6A and flows back into the resin bubble 6C side.

In this way, the same operations and effects as in the first embodiment can be obtained also in this embodiment.

A third embodiment is shown in FIG. 4, in which:
The enclosure tube 9 ends at the lower end surface of the heat pipe 10 and is closed, as in the second example 21oi, but a discharge tube 30 having an external cock 29 is inserted into the insertion tube 9. The discharge pipe 30 passes through the center of the heat pipe 10 and opens at the upper end of the heat pipe 10. An internal pipe 31 with a predetermined wall thickness is fitted into the exhaust pipe 30 in the evaporation section 10A of the heat zobe 10, and a plurality of communicating passages 32 are provided along the longitudinal direction of the internal pipe 31. They are arranged along a virtual circumference centered on the discharge pipe 30 (see FIG. 5, jf@, ). The upper ends of these communication passages 32 are bent toward the discharge pipe 30 and open at openings 33 bored at predetermined positions in the discharge pipe 30, and the lower ends of the communication passages 32 are located below the heat nozzle 10. It is open at the end.

Further, the enclosure tube 9 and the discharge tube 30 are connected to a linear air supply/discharge mechanism (not shown), and a cooling tube 9 is circulated within the tubular tube 6 so as to maintain a constant pressure. . Note that reference numeral 40 in FIG. 4 is a heat insulating material surrounding the encapsulating tube 9.

According to the third embodiment, although the structure of the entire device is complicated, since the cooling air is always in contact with the tubular resin 6 from the inside, the cooling effect of the tubular resin 6 is further promoted. Furthermore, since the area around the condensing section 10B of the Heat Tsuquib IO is always maintained at a low gA degree, heat dissipation in the condensing section 10H is always performed smoothly, and as a result, the quenching effect in the evaporating section 10A is also increased.

A fourth embodiment is shown in FIG. 6, in which:
The heat pipe 10 is composed of a spiral tubular evaporation section 10A with a relatively small pitch and a straight tubular condensation section 10B. The surfaces are brought into contact or close together. Further, the heat twig 10 does not need to be provided with a wick.

According to the fourth embodiment, the same effects as those of the first and second embodiments can be achieved, and furthermore, the internal air circulation that communicates both the upper and lower ends of the evaporator 10A is achieved. There is no need to provide a communication path etc. for
Since the contact points with the molten resin tubular body 6A are extremely limited, it is extremely difficult for the molten resin tubular body 6A to weld to the evaporation section 10A, resulting in the effect that stable formation is more likely to occur.

In each of the above-mentioned embodiments, the cooling device according to the present invention is applied to top-blown inflation molding, but it can also be applied to bottom-blown inflation molding. However, the condensing section 10B may be located outside the tubular resin 6 and connected to the evaporating section 10A via a transmission section that passes through the extrusion die 1. Furthermore, in the first to third embodiments, the wick 13 is provided over almost the entire inner circumferential surface of the evaporator 10A, but the wick 13 is provided over the entire inner circumferential surface of the heat tube 10. It may be something you have.

As described above, according to the present invention, it is possible to provide a cooling device for inflation molding which has a simple structure and a high cooling effect.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a first embodiment of the cooling malt for inflation molding according to the present invention, FIG. 2 is a sectional view showing the second embodiment, and FIG. 4 is a sectional view showing a third embodiment of the present invention; FIG. 5 is an enlarged sectional view taken along line v-v in FIG. 4;
FIG. 6 is a sectional view showing a fourth embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Extrusion die, 6... Tubular resin, 6A... Molten resin tubular body, 6B... Expansion part, 6C... Resin bubble, 10... Heat pipe as a cooling device for inflation molding , IOA... Evaporation section, IOB... Condensation section, 14... Condensate, 15... Vapor flow. Agent: Minoru Kinoshita, patent attorney. -14- Procedural amendment (voluntary) April 23, 1980 Haruki Shimada, Director General of the Japan Patent Office Patent Application No. 52822 ``3 Person making the amendment Name of patent applicant related to the case Name) Idemitsu Petrochemical Co., Ltd. Representative Yamato Kou 4, Agent 6 Number of inventions increased by amendment Contents of amendment (1) "Suppression die" in line 14 of page 1 of the specification is changed to "extrusion die". (2) "For inflation" on page 1, line 15 of the specification has been changed to "for inflation molding." (3) 1 on page 8, lines 7-8 of the specification -1 if it is high-density polyethylene
1. In the case of high-density polyethylene, etc., change it to ``1''. (4) Delete "The melt tension is not that low" on page 8, line 13 of the specification. (5) "Formation" on page 13, line 6 of the specification is changed to "1 formation." Above 2-

Claims (1)

[Claims] (1) A cooling device for inflation molding that cools from the inside a tubular resin that is extruded into a tubular shape from an extrusion die, expanded by internal pressure, cooled and assimilated, and then wound up, from the inside. 1. A cooling device for inflation molding, comprising a heat pipe in which an evaporating section is placed in contact with or close to the inner cylindrical surface of a molten resin tubular body immediately afterward.