JPS5939524A - Chamber for forming inflation film - Google Patents

Abstract

PURPOSE:To provide the titled chamber capable of stably forming a uniform film excellent in transparency and luster at a high speed while enhancing cooling efficiency, by making a height freely changeable, and providing with a ring form guide plate parallel with a die surface, whose inside diameter can be freely changed. CONSTITUTION:A thermoplastic resin melted and extruded through an annular die 1 is applied with an internal pressure by compressed air to form a bubble 4, which is then cooled by cooling air blown from an air ring 2. Cooling air having been used for precooling is again blown to the bubble 4 by using the chamber 3 having a height capable of being freely changed and provided with the ring form guide plate 3a parallel with the surface of the die 1 the inside diameter of which plate 3a can be freely changed. Accordingly, the bubble 4 is rapidly cooled, a solidification line 5 is formed, and an inflation film is obtained. The guide plate 3a may be comprised of, for example, a mechanism wherein a plurality of blade plates 8 overlap with each other in a closable ring form so that the inside diameter of the guide plate 3a can be freely changed.

Description

Detailed Description of the Invention The present invention improves cooling efficiency in molding blown films of thermoplastic resins such as high-density polyethylene, low-density polyethylene, and polypropylene, and improves film haze (haze) and cross (gloss). The present invention relates to a chamber suitable for stably forming a homogeneous film at high speed and with a high degree of hardness.

Conventionally, in order to mold a film from thermoplastic resin by the inflation method, the raw material 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 the resin. 9.The paper passes through a folding device and is folded and collected.

Transparent, i.e., low haze due to the inflation method.
In order to obtain a homogeneous film with a high cross-sectional area, it is necessary to cool the film as quickly as possible. When cooling an blown film using fluid, a second air ring is added above the first air ring. The most advanced technology is to direct the outlet upward or diagonally upward. However, even with this technology, in addition to the disadvantages of energy loss and the complexity of the device due to blowing out air in two stages, increasing the number of second air bubbles causes the bubbles to oscillate, causing sagging, crackling, and uneven thickness. Failure to slow down the pick-up speed will result in defective products.

Furthermore, since the diameter of the second air ring is fixed, it is impossible or inappropriate to expand or reduce the diameter of the bubble during molding, and it is necessary to stop molding and replace the second air ring. There was the problem of the hassle of restarting and the inevitable loss.

The purpose of the present invention is to solve the above-mentioned problems and to stably obtain a blown film with good transparency and gloss. This is a chamber for forming a blown film, characterized in that the chamber has a height that can be expanded and contracted.

The chamber bar for blown film molding of the present invention will be explained with reference to the drawings. FIG. 1 is a schematic sectional view of an embodiment of a blown film forming apparatus to which the present invention is applied. The resin melt-kneaded in an extrusion mode (not shown) is melt-extruded into a tubular shape from an annular die 1, and internal pressure is applied to air forced through an air blowing port (not shown) to form bubbles 4.

The formed bubble 4 is cooled by cooling air blown out from the air ring 2. The cooling air that has completed preliminary cooling is
A cylindrical chamber 3 that is extendable in height and has a double slide type locking device, and a ring-shaped guide plate 3a whose inner diameter can be increased and decreased is blown onto the bubble 4 again and the solidification line 5 is formed into the bubble 4. to form. The solidification line 5 can be identified as a line that changes from opaque to transparent, and the bubble 4 that has been cooled and solidified is folded by a guide plate 6 and taken out by a nip row and a lure.

The position of the guide plate 3a of the chamber can be approximately aligned with the position of the solidification line 5 of the bubble 4 by adjusting the height of the chamber 3, which improves transparency.
The distance between the inner edge of the bottom of a and the upper edge of the air ring outlet is B
Then, B has 1 win if it is 200% or more, and 9 wins if it is less than 200, indicating poor bubble stability. However, B
It is natural that B differs depending on the bubble diameter A, and B is 0.5 A~
4. A range of OA is preferred. Note that when the air ring outlet is not a horizontal plane but an inclined plane or a vertical plane, the center position is considered to be the upper end. Further, the horizontal distance between the bubble 4 and the guide plate 3a of the chamber is preferably in the range of 5 to 100% by adjusting the inner diameter of the guide plate 3a, and more preferably in the range of 10 to 50%. If it is less than , 5'X, there is a risk of contact, and if it exceeds 100%, the quenching effect will be insufficient.

The internal length C in the radial direction of the guide plate 3a is preferably 30% or more, and more preferably 50% or more, since air is blown almost perpendicularly to the bubbles to rapidly cool them. Further, the vertical distance E between the inner end of the bottom surface of the guide plate 3a and the solidification line 5 is 0 to
It is preferably in the range of 100%, especially 0 to 50
% is more preferred.

Note that the solidification line 5 may be formed before or after the bottom surface of the guide plate 3a. If the distance is too long, for example if the air volume is small, the die temperature is high, or if the distance E is long and the solidification line 5 is formed far past the position of the guide plate 3a, slow cooling will cause the film to deteriorate. Transparency is not achieved. Conversely, if the hardening line 5 is formed by rapid cooling far before the inner end of the bottom surface of the guide plate 3a, even if transparency is obtained, blow-up is difficult and the film strength in MD and TD becomes unbalanced.

On the other hand, being almost parallel to the die surface is for rapidly cooling the bubble, and the angle formed by the center line of the bubble on the guide plate 3a is 90°±20°.
It is preferably within the range of 90°±5°.

As shown in Fig. 2a, in the case of a conventional chamber without a guide plate, the diameter of the bubble expands immediately after exiting the annular die, but in the case of using the chamber of the present invention as shown in Fig. 2b, the bubble inside is cooled. Perhaps due to the high pressure caused by the wind, the diameter of the bubble expands rapidly after it leaves the annular die.

This rapid expansion ψ is carried out at a lower temperature than conventional ones, resulting in h'Vr D orientation, preventing vertical tearing due to conventional bias toward MD orientation, and providing a film with balanced MD and TD. Furthermore, according to the chamber of the present invention, by adjusting the inner diameter and height of the guide plate, the cooling air is concentrated near the gap between the guide plate and the bubble, producing a rapid cooling effect and improving the transparency of the film, that is, haze. ) is small, the gloss (gloss) is high, and since the chamber surrounds the bubble, the fluctuation of the bubble is small and a homogeneous film can be obtained even at high speeds.

In order to freely increase or decrease the inner diameter of the guide plate, a mechanism can be adopted in which a large number of blade plates 8, similar to the nine apertures of a camera, overlap each other and close in a ring shape, as shown in the plan view of Fig. 3. .

The chamber for forming a blown film of the present invention is not limited to the above-mentioned configuration, and for example, the shape of the chamber 3 may be polygonal in plan view.

Furthermore, although the air ring 2 in the embodiment shown in FIG. This includes all cases such as a shape with a cylindrical object attached, a shape that blows out some air from other than the outlet at the tip, an air ring outlet with two or more layers, an air ring shape with a Venturi effect, etc. . Further, in the embodiment shown in FIG. 1, the dice face upward, but of course the chamber of the present invention can be implemented even when the dice face downward.

In order to obtain a sufficiently transparent film in the chamber of the present invention, it is preferable to use a cooling air of such a degree that the bubble in the solidification line has a concave shape, since this improves the quenching effect in the vicinity of the guide plate.

In some cases, an air hole may be provided in the wall of the chamber to reduce the amount of cooling air. As shown in the above examples, basically the use of the chamber of the present invention falls within the scope of the present invention.

The main synthetic resins of the present invention are polyolefin polymer resins, including homopolymers and copolymers of ethylene, propylene, butene-1, etc., such as high-pressure polyethylene, medium-low pressure polyethylene, polypropylene, and polybutene-1. A mixture thereof, etc.

Further, the method of forming a blown film to which the present invention is directed includes not only a method of forming a single layer blown film but also a method of forming a multilayer blown film such as two layers or three layers.

Next, the method of the present invention will be explained with reference to examples and comparative examples, but the present invention is not limited to these examples in any way as long as the gist thereof is not exceeded.

Examples 1 to 7, Comparative Examples 1 to 3 Using a 65M0 extruder and a 15omO annular die, a 30μ thick blown film was formed using high density polyethylene or low density polyethylene as a raw material resin under the conditions shown in Table 1, and bubbles were formed. The stability, haze and cross of the film were investigated. The results are also shown in Table 1, and the use of the chamber and guide plate of the present invention results in good bubble stability and
Excellent transparency and high gloss were obtained, while Comparative Examples 1 to 3
When the chamber and guide plate of the present invention are not used, the stability of the bubble is poor and the transparency is poor.
Low gloss.

In Table 1, 1) 1...High density polyethylene 11 with density 0.940 El/cri, tart index 0.3 g/10+/I+...density 0.9209/ad, melt index 2.0. ! i'/10m low density polyethylene (ethylene-butene-1 copolymer) 2) ◎...Very good ○...Good but slightly vibrated △...Poor ×...Very poor 3) ASTM D, 1003-61 4) JIS Z8741-1962 5) Guide plate Type 6 rowing plate shown in Figure 3. Inner diameter 500cm, thickness 5mm.

Distance with information board 100 wins

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing an example of a blown film forming apparatus to which the present invention is applied, FIG. 2a is a conventional bubble shape, and FIG. 2b is a side view showing a bubble shape to which the present invention is applied. Figure 3 is a plan view of the guide plate of the present invention;
The figure is a schematic cross-sectional view showing another example of a blown film forming apparatus to which the present invention is applied. 1; annular die 21 air ring 3; chamber 3a; air guide plate 4 on top of the chamber; bubble 5; solidification line 6; guide plate 7; nip roll 8; vane plate 9; rectifier plate 10;

Claims (1)

[Claims] A blown film forming chamber characterized by having a ring-shaped guide plate that is almost parallel to the die surface and whose inner diameter can be freely increased or decreased, and whose height can be expanded or contracted.