JPS58183222A - Cooling device for inflatable film molding - Google Patents

Abstract

PURPOSE:To improve a cooling effect, and to enhance stability in molding by adiabatically expanding air supplied from an air feed pipe once in an expansion chamber, cooling air and blowing air off into a tubular resin. CONSTITUTION:Air for cooling at comparatively low pressure is supplied from a first air feed pipe 16, is supplied to the lower end side of a core 11 through a ventilating hole 22, and flows to the resin bubble 6C side. Consequently, a melted resin tubular body 6A not only is cooled from the outside by an air cylinder 8 but also is cooled from the inside. Air for cooling at comparatively high pressure is supplied from the second air feed pipe 17, ejected into the expansion chamber 23 in an adiabatic expansion manner once from outflow ports 24 and cooled, and adiabatically expanded secondarily from blow-off ports 25 and cooled again, and blown against a resin expanding section 6B. Accordingly, the resin expanding section 6B is cooled effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cooling device for inflation molding that cools a tubular resin extruded into a tubular shape from an extrusion die from an internal part 1, and particularly relates to an improvement in its cooling capacity.

In inflation molding of thermoplastic resins, there is an increasing demand for high extrusion per mold and high speed molding to improve productivity, but in order to achieve high extrusion per mold and high speed molding, the extruder and extrusion die must be Even if high-speed extrusion is possible, it is necessary to be able to sufficiently cool the extruded tubular resin. In addition, in order to improve the film properties such as the mechanical strength and film appearance of the formed film, 4
, 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 nearings is widely adopted, but if the nearing IT is increased in order to improve the cooling effect, for example, For resins with low melt tension such as ^density polyethylene, ethylene-α-olefin copolymer, and I-propylene, the molding stability is significantly inhibited, so molding is performed only from the outside of the tubular resin. With cooling, there was naturally a limit to the improvement of the cooling effect.

Furthermore, a method is known in which a core (mandrel) used as a stabilizer for the tubular resin is cooled by water cooling or the like and brought into contact with the molten resin tubular body. (1) (It only cools the molten resin tubular body, and does not effectively cool the entire tubular resin. Furthermore, it also has the disadvantage that temperature control is extremely difficult.

In addition, while keeping the internal pressure of the tubular resin constant, a supply/discharge mechanism is provided to supply cooling air into the tubular resin while discharging hot air heated inside the tubular resin from inside the tubular resin. A method has been devised to maintain the temperature at a constant low temperature. However, in this conventional method,
If the internal air supply and exhaust speed was increased in an attempt to increase the cooling effect from the inside of the tubular resin, it would become difficult to maintain the internal pressure of the tubular resin at a constant level, which would impede molding stability. . Another possibility is to cool the air supplied to the inside of the tubular resin to an extremely low temperature on the outside in advance, but this method is difficult to adopt because it tends to complicate and enlarge the equipment. there were. In any case, conventional cooling equipment has a very complicated structure, which not only makes the equipment expensive, but also makes it technically impossible to apply it to high blow-ag ratio molding using small-diameter gouimandrels. Atsuku.

The purpose of the present invention is to have high cooling effect and excellent molding stability,
Moreover, K provides a cooling device for inflation molding with a simple structure.

The present invention provides a round air supply pipe and an air discharge pipe for supplying and discharging the internal air of the tubular resin, and the air supplied from the air supply pipe is once adiabatically expanded and cooled in an expansion chamber, and then the air is inside the tubular resin. The purpose is to achieve the above object by effectively cooling the tubular resin from the inside by blowing the resin out.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the main parts of a blown film molded lid to which the first embodiment is applied.

In this figure, from the annular slit 4 of the extrusion die 1,
The molten resin 5 supplied into the extrusion die 1 is continuously extruded, and a tubular resin 6 is formed above the extrusion die 1.

The tubular resin 6 becomes a molten resin tubular body 6A in a molten state when the blood is extruded from the extrusion die 1, but a predetermined temperature is reached in the resin expansion part 6B. He is #stretched at the low-fat ratio, thinned and becomes a resin bubble 6C, and a resin bubble 6C.
After being completely cooled and solidified, it is linched and flattened by nip rolls (not shown), and then continuously wound up. Here, the resin expansion portion 6B is a region where the molten resin tubular body 6A starts stretching, that is, a region that starts at the stretching point and ends near the frist line of the resin bubble 6C.

An external cooling device is provided on one end surface side of the extrusion die 1.

A near ring 8 is arranged, and cooling air is discharged from an annular air discharge slit 9 of the near ring 8 toward the outer peripheral surface of the tubular resin 6.

Above the center of the extrusion die 1, there is disposed an integral core 11 in the form of a substantially cylindrical body as a tubular super fat stabilizer, and this core 11 holds the molten resin tubular body 6A on the inner peripheral surface side. We are providing more guidance. The diameter of the core 11 is usually about 0.7 to 1.3 times the diameter of the annular slit 4, but when forming a thin film, the diameter of the core 11 is slightly larger than the diameter of the annular slit 4. The size is preferable. Also, center core 1
1 is formed with a cylindrical hollow part 12 through which the core 11 passes in a V along the longitudinal direction, and the upper end of the core 11 reaches a position sufficiently higher than the stretching point of the tubular resin 6. has reached.

On the other hand, a cylindrical center hole 15 through which the extrusion die It passes is bored in the center of the extrusion die 1, and this center hole 15 and An
The hollow portions 12 are configured such that their center line positions are 1 with each other.

Inside this center hole 15 are the first air mooring Q#16, the second
2P air supply t3 pipe 17 and air discharge pipe 18 are connected to this M
t: M/, IIJIntroduction 9) With a triple tube structure in which the inner side is the inner side, the tube is penetrated and supported via a duck heating material (not shown). The first and second air supply pipes 16° and 17 that constitute this triple armature,
The air discharge pipes 18 are branched from each other at the lower part l111 of the extrusion die 1 so that each pipe has an independent single pipe structure, and cocks 19, 20, and 21 are provided, respectively.

The first air supply pipe 16 has a specific gravity from the upper end surface of the extrusion die l.
It protrudes by a predetermined length corresponding to the target size, and the core 11 is supported at the upper end of the supply receptacle 16 . In addition, a number of communication holes 2 are provided on the circumferential surface of the first air supply pipe 16 located between the lower end 5111 of the core 11 and the end side of the extrusion die l.
2 is bored, and the air supplied from the supply pipe 16 is supplied to the lower end side of the core 11 through the communication hole 22.
1 and rises to the resin bubble 6C@ through the gap between the outer circumferential surface of the resin bubble 1 and the bath melt resin tubular body 6A.

The second air supply pipe 17 protrudes upward from the first air supply pipe 6 and penetrates the hollow portion 12, and then protrudes further upward from the center core 11 to form the boundary between the resin expansion portion 6B and the resin bubble 6C. It ends nearby.

An expansion chamber 23 is provided in a predetermined range near the upper end of the second air supply pipe 17 and located within the resin expansion section 6B. The RFT expansion chamber 23 is formed into a hollow cylindrical shape in which the second air supply pipe 17 is located in the center, and an initial number of air outlets [ ] 25 are provided on the circumferential surface toward the outside in the radial direction. ing. In addition, an air outlet 24 is bored on the circumference of the second air supply pipe 170 located inside the air supply room 23, and the air supplied from the second air supply pipe 17 is passed through the outlet 24. After flowing out into the expansion chamber 23 and being adiabatically expanded and cooled in the expansion chamber 23, it is secondarily expanded through the outlet 25, cooled secondarily, and blown onto the resin expansion section 613. It is configured like this.

Further, the air exhaust pipe 18 projects beyond the expansion chamber 23 by a predetermined length and is open at the upper end, so that the internal air inside the tubular resin 6 is sucked from the front P opening, and the air inside the tubular resin 6 is sucked from the front P opening. It is designed to be discharged to the outside 1LII.

Next, the operation of this embodiment will be explained.

At the start of operation, the first and second air supply pipes 16.
Air is sealed in the tubular resin 6 through at least one of the tubes 17 and 18, and internal pressure is applied to the tubular resin 6 to cause it to expand and form a resin bubble 6C.

During stable operation, that is, during production, cooling air is supplied into the tubular resin 6 from the first and second air supply pipes 16 and 17, while the air is supplied from the air exhaust pipe 18 to the tubular resin 6.
The hot air heated inside is discharged to the outside of the tubular resin 6, and the amount of supply and exhaust is adjusted to keep the internal pressure of the tubular resin 6 constant.

Relatively low-pressure cooling air is supplied from the first air supply pipe 16 , and this cooling air is supplied to the lower end side of the core 11 through the communication hole 22 . It flows through the gap between the outer peripheral surface and the inner peripheral surface of the molten resin tubular body 6A to the resin bubble 6C side, and as a result, the bath molten resin tubular body 6A is not only cooled from the outside by the near ring 8, but also cooled from the inside. The molten resin tubular body 6A and the core 11 are also cooled.
This prevents adhesion.

Relatively high-pressure cooling air is supplied from the second air supply pipe 17, and this cooling air is once blown out from the outlet 24 into the expansion chamber 23 in an adiabatic expansion manner, cooled, and then further blown out. The resin is secondarily adiabatically expanded from the outlet 25, cooled again, and blown onto the resin expansion section 6B. Therefore, the resin expansion part 6B is effectively cooled, and is heated by the molten resin tubular body 6A while increasing the relationship between the inner circumferential surface of the molten resin tubular body 6A and the outer circumferential surface of the core 11. Since the air flow is rejected from the vicinity of the inner circumferential surface of the resin expansion part 6B by the cooling air blown from the outlet 25 to the resin expansion part 6B, the resin expansion part 6B can be cooled more effectively. becomes. Note that the second air supply pipe 17
Since the cooling air supplied from
Since it acts as a shock band, the resin # and tension part 6BK act to cause breathing, etc., which inhibits molding stability.
'There is no such thing.

In this way, the cooling air supplied into the tubular resin 6 from the first and second air supply pipes 16 and 17 is supplied to the molten resin tubular body 6 and the resin skin section 6, which are the parts that require particular cooling.
After being effectively cooled, it is heated and becomes hot air, and the temperature inside the tubular resin 6 tends to rise, but the internal air is always exhausted from the air exhaust pipe 18 and the air supply pipe 16.
Since cooling air is always supplied from 17, the internal air is always maintained at a low temperature.

According to this embodiment, since the inside of the tubular resin 6 can be kept at an extremely low temperature, high extrusion molding and high speed molding can be stably carried out over a long period of time. In addition, since the tubular resin can be rapidly cooled uniformly from the inside to the outside, there is an effect that the physical properties of the film, such as mechanical strength and film appearance, can be improved.

In addition, since the molten resin tubular body 6A and the resin expansion part 6B, which are parts of the tubular resin 6 that particularly require rapid cooling, can be effectively cooled.
From this point of view as well, it is suitable for high extrusion molding and high speed molding, and can be more effective in improving film physical properties.

Moreover, since the internal air can be maintained at a low temperature without particularly increasing the supply/exhaust speed of the internal air of the tubular resin 6, the molding stability is not hindered.
There is no particular need for equipment to previously cool cooling air on the outside of the tubular resin 6, and the structure of the expansion chamber 23 itself is extremely simple, so the structure as a whole is simple and easy to assemble.

Next, a second embodiment will be described. Parts that are the same as or similar to those in the first embodiment will be denoted by the same reference numerals, and the explanation will be simplified or omitted.

A second embodiment is shown in FIG. In the second embodiment, the expansion chamber 33 is formed in the same hollow cylindrical shape as in the first embodiment, but the air outlet 35 is formed along the outer peripheral surface of the expansion chamber 33 in the cylindrical direction. It consists of slits for the number of bales provided. This second embodiment also has the same functions and effects as the first embodiment, and furthermore, cooling air can be blown onto the resin expansion part 6B in an extremely uniform manner, resulting in stable molding. This is preferable from the viewpoint of improving properties and film properties.

In each of the above-mentioned embodiments, the expansion chamber 23° 33 is located within the resin expansion section 6B, but it may also be located within the resin bubble 6C, etc. Regarding .35, the expansion chamber 2 does not necessarily have to be directed toward the resin expansion section 6B, but the expansion chamber 2 is located inside the resin expansion section 6B.
3.33 is located and the blower outlet 25.35 is directed toward the resin expansion part 6B, there is an effect that the resin expansion part 6B, which particularly requires rapid cooling, can be effectively cooled.

Further, the shape of the expansion chamber 23.33 is not limited to a hollow cylindrical shape, but may be other shapes such as a hollow inverted cone shape or a shape substantially similar to the resin expansion part 6B. &i tube 17
It may also be one that rotates with the axis of rotation as the axis of rotation.

Furthermore, the first air supply pipe 16 is provided with a communication passage that communicates both the upper and lower ends of the inner core 11 in the thick wall part' of the inner core 11, and the internal air descending through this communication passage is It may be configured to raise the gap between the outer circumferential surface of the core 11 and the inner circumferential surface of the molten resin tubular body 6A.

Furthermore, the core 11 is not limited to a cylindrical integral type, but may also be of a multi-stage split type, a lip type, a spiral tube type, etc. Although the structure will be somewhat complicated, The core 11 may be configured to always have sufficient cooling capacity.

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

[Brief explanation of the drawing]

Figures 1 and 1!2 are cross-sectional views showing the first and eighty-second embodiments of the invention, respectively. l... Extrusion guide, 5... Molten resin, 6... Tubular resin 1.6A... Melt-resistant resin tubular body, 6B... Resin expansion part, 6C... Resin puzzle, 11...・Center core, 16.1
7...Air supply pipe, 18...Air discharge pipe, 23.3
3... Expansion chamber.

Claims (1)

[Claims] (1) An air supply pipe that supplies air to the inside of the tubular resin that is extruded into a tubular shape from an extrusion die, expanded by internal pressure, cooled and solidified, and then continuously wound up, and air supplied from the air supply pipe. -B An expansion chamber for adiabatic expansion and blowing out into the tubular resin, and an expansion chamber for discharging the air inside the tubular resin.
A cooling device for inflation molding, characterized in that it is equipped with an air discharge pipe. (2. In claim 1, the above-mentioned Bikhang room is
A cooling device for inflation molding, characterized in that the cooling device is configured to blow air toward a resin expansion part within a tubular resin.