JPH0365779B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to an air cooling device for tubular film forming (extruding resin from a die into a cylindrical shape to form a tubular resin product).

[Prior art and its problems]

Conventionally, to form a film tube from thermoplastic resin by the inflation method, the raw resin is heated and melted and extruded through an annular slit in a die to form bubbles, while air is blown from an air cooling ring to cool and crystallize. It is then passed through a folding device to be folded and taken out. The transparency of the film tube obtained by such an inflation method depends on the degree of cooling of the bubble. However, if the air volume of the air ring is increased and the bubbles are rapidly cooled, a film with good transparency can be obtained, but for polyethylene, etc., which has a low melt tension, increasing the air volume increases the vibration of the bubbles, making wrinkles more likely to occur. The problem was that it was not possible to obtain high-quality products.

Therefore, some attempts have been made to provide air rings in two stages, upper and lower, to intensively cool the area near the solidification line (for example, Japanese Patent Application Laid-Open No. 146764/1983).
If only a plurality of air rings are provided in this manner, it is not possible to quickly respond to changes in film size or expansion, and the cooling air volume and temperature cannot be adjusted as desired, and furthermore, the cooling efficiency is poor.

To solve this problem, a cylindrical chamber is added to the bottom annular air ring, and an iris (a ring-shaped guide plate whose inner diameter can be increased or decreased) is used on the end plate to effectively cool the air with a small amount of air while changing the inner diameter. Therefore, there is a device that can cope with changes in the size and expansion ratio of the film tube without changing the air ring, for example, as disclosed in Japanese Patent Application Laid-Open No. 59-39524.

This has the advantage that the chamber can be expanded and contracted in the height direction, and the upper end of the chamber can be aligned approximately with the solidification line of the bubble. Because the chamber is formed only by a space, the cooling air blown from the bottom air ring is heated and heated by the high temperature molten resin extruded from the die, and the molten resin in the cylinder and film tube forming the chamber is heated and heated. Rapid cooling was insufficient near the frost line (solidification line), which causes convection to flow through the space, greatly affecting high-speed moldability and physical properties of the product. This causes problems in that the transparency and gloss of the film are poor during high-speed molding, and the impact strength of the film is reduced.

[Purpose of the invention]

The purpose of the present invention is to eliminate the disadvantages of the conventional example,
When cooling efficiently with a small amount of air by using a chamber, the cooling air is divided into primary air and secondary air.
It is possible to divide the air into the following types of air and obtain it in all the necessary places, and the direction and volume of each air, as well as the cooling temperature, can be freely controlled.
It is an object of the present invention to provide an air cooling device for tubular membrane formation, which can increase the take-up speed while maintaining the physical properties of the film, and can freely change the blow-up ratio without reducing the physical properties of the film.

[Key points of the invention]

However, according to the present invention, when an air cooling chamber is provided surrounding the tube-shaped resin discharged from the die, the chamber is provided with a plurality of chambers so as to supply primary air and secondary or more cooling air. Each chamber has a sliding double wall with a slidable side wall so that it can expand and contract in the height direction, and is connected to each other with the iris as the boundary, and has a chamber for supplying primary air. In this case, another iris is arranged in parallel with the iris, and an exhaust chamber is provided between these irises in which the direction and volume of the air can be controlled. This is achieved by providing an air supply chamber between the irises that can control the wind direction and volume.

[Specific examples of the invention]

Hereinafter, specific examples of the present invention will be described in detail with reference to the drawings.

Fig. 1 is a schematic vertical cross-sectional side view showing an air cooling device for tubular film forming of the present invention, Fig. 2 is a plan view of the iris part, and in the figure, 1 is an annular die for discharging resin melted and kneaded by an extruder (not shown). , 2 is the die 1
Shows the air ring installed above that blows out cooling air.

Furthermore, 3 in the figure is a tube that is melted and extruded from the die 1 into a tubular shape, and internal pressure is applied to it by air pumped from an air outlet (not shown). A shaped chamber 4 is provided.

In the device of the present invention, the chamber 4 includes a first chamber 4a for supplying primary air located above the air ring 2, and a second chamber 4b for supplying secondary air located above the first chamber 4a. It was divided into 2 and formed into multiple sets.

Both the first chamber 4a and the second chamber 4b are configured with a double wall whose side walls are slidable, so that they can be expanded and contracted in the height direction, and are continuous with each other with the iris 5 as a boundary.

Furthermore, the first chamber 4a has an exhaust chamber 6 in its upper part that communicates with the exhaust port 7, and the second chamber 4b has an air supply chamber 8 in its lower part that communicates with the air supply port 9; The air supply chamber 8 has an iris 5 and an iris 10 arranged in parallel below the iris 5, and an iris 11 arranged in parallel above the iris 5, the size of which can be changed. Further, the iris 12 is also used on the upper end plate of the second chamber 4b.

These irises 5, 10, 11, and 12 all have the same structure. Taking the iris 5 as an example, as shown in FIG. 2, it slides on the inside of the rotary plate 5a.
This is a ring-shaped guide plate that utilizes a diaphragm mechanism in which a large number of arch-shaped blades 5b that can move forward and backward toward the center are superimposed in the circumferential direction.

In the illustrated example, the chamber 4 is divided into only two chambers, the first chamber 4a and the second chamber 4b, but the third chamber and subsequent chambers may be provided, such as tertiary air and quaternary air. In this case, all the secondary and higher air supply chambers have an air supply chamber like the second chamber 4b.

Next, the usage and operation of the device will be explained.

The cold air blown from the air ring 2 flows as primary cooling air in the first chamber 4a to form a tube-shaped resin bubble extruded from the die 1, and is discharged from the exhaust port 7 of the exhaust chamber 6. However, the exhaust volume and wind direction are determined by changing the opening diameter of the irises 5 and 10 based on the exhaust air temperature.
It is adjusted by adjusting the size of.

Further, the second chamber 4 is connected from the air supply port 9 to the air supply chamber 8.
The air forcedly blown or naturally sucked into the tube 3 rapidly cools the vicinity of the frost line 13 of the tube 3 as secondary cooling air, with the maximum amount not making the resin shape of the tube 3 unstable. This secondary air flows through tube 3 and iris 1.
However, the direction and volume of the air inside the second chamber 4b can be adjusted by appropriately adjusting the opening diameters of the irises 5 and 11 and the opening diameter of the iris 12.

In addition, the diameter of the film tube 3 and the iris 10
The difference in the opening diameter of tube 3 is 100 mm to 150 mm.
The difference between the diameter of the iris 5 and the aperture diameter of the iris 5 is desirably adjusted to 70 mm to 100 mm.

The main objects to be cooled in the device of the present invention are:
Commonly used thermoplastic resins such as low density polyethylene, medium density polyethylene,
High density polyethylene, polypropylene, poly1-
These include polyolefins such as budene, ethylene, and vinyl acetate copolymers, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyamide, and polyester.

The apparatus of the present invention can be used not only for tube forming using the above-mentioned inflation method, but also for other forming methods such as the deflation method, the bottom blowing method, the top blowing method, and the internal water cooling method. It is applicable to a certain extent.

〔Example〕

Linear low-density polyethylene (density = 0.924 g/cm ³ , MI = 1 g/10 min) using a 500 mm medium annular die
The total length of the cylinder that forms chamber 4 is
350mm, the inner diameter of the cylinder is 1000mm, the aperture diameter of iris 12 is 900mm, the aperture diameters of iris 11, 5, and 10 are 850mm, 680mm, and 700mm, respectively, and the height of iris 11, 5, and 10 is 200mm, 150mm, respectively.
100mm, bubble diameter 1100mm, blow-up ratio
2.2 An inflation film with a thickness of 30 μm was molded at a take-up speed of 100 m/min. The resulting film had a haze of 4.5% and good transparency.

For comparison, Iris 11, 5 and 1
When a blown film with a thickness of 30 μm was similarly molded without using 0, the haze was 9% at a take-up speed of 20 m/min.

〔Effect of the invention〕

As described above, when the tubular film forming air cooling device of the present invention is provided with an air cooling chamber that surrounds the tubular resin discharged from the die,
The cooling air is obtained by dividing it into primary and secondary cooling air, and the insufficient primary cooling air is supplemented with the secondary cooling air, and the primary air is superheated by the molten resin. By exhausting the heated material, the frost line can be efficiently and rapidly cooled, and by adjusting the diameter of the iris and the air volume of the blower, the direction and volume of each air stream, as well as the cooling temperature, can be freely controlled. As a result, it is possible to increase the take-up speed while maintaining the physical properties of the film, and without reducing the physical properties of the film.
The blow-up ratio can be changed freely.

[Brief explanation of drawings]

FIG. 1 is a schematic longitudinal sectional side view showing an embodiment of the tubular film forming air cooling device of the present invention, and FIG. 2 is a front view of the iris portion. 1... Dice, 2... Air ring, 3... Film tube, 4... Chamber, 4a... 1st
Room, 4b...2nd room, 5, 10, 11, 12...
Iris, 5a... rotating plate, 5b... vane, 6...
...Exhaust chamber, 7...Exhaust port, 8...Air supply chamber, 9...
Air supply port, 13...Frost line.

Claims (1)

[Claims] 1. When an air cooling chamber is provided to surround the tubular resin discharged from the die, the chamber is divided into multiple chambers to supply primary air and secondary or higher cooling air, and each chamber is The side wall is made up of a slidable double wall so as to be able to expand and contract in the height direction, and the iris is connected to each other with the iris as the boundary, and another iris is arranged in parallel to the iris in the primary air supply chamber. An exhaust chamber that can control the wind direction and air volume is provided between these irises, and other irises are similarly installed in parallel to the above-mentioned iris in the secondary and higher air supply chambers, and an exhaust chamber that can control the wind direction and air volume is provided between these irises. Tubular membrane air cooling device featuring an air chamber.