JPH08258117A - Film molding apparatus - Google Patents

Abstract

PURPOSE: To provide a film forming apparatus in which the contact with an air chamber is prevented, no damage or cut occurs on the surface, and the film having excellent surface roughness is obtained by uniformly cooling. CONSTITUTION: A film forming apparatus 1 winds a film F extruded from a mold 11 on the lower half of a cooling roll 12, and diffuses the air from an air chamber 13 provided near the roll 12 to cool the film F while uniformly pressing the film F to the roll 12 to continuously draw it by a drawing unit, and the chamber 13 is formed in a box air duct state of a flat upper plate 13a and a lower plate 13b arranged substantially in parallel and side plates 13c. The distance between the upper plate edge 13d of the chamber 13 and the roll 12 is shorter than the distance between the lower plate edge 13e and the roll 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film forming apparatus provided with an air chamber for cooling a film for uniformly cooling and taking the film.

[0002]

2. Description of the Related Art In a conventional film forming apparatus, as shown in FIG. 2, a film f extruded downward from a mold 10 is wound around a cooling roll 20 to be continuously cooled, and the cooling roll 20 is also used. Cooling air is blown from a box-shaped wind tunnel-shaped air chamber 30 constituted by a flat upper plate and a lower plate provided on the lower side surface of the film, and a surface of the film f wound around the cooling roll 20. , It is designed to be picked up by a take-up machine while effectively cooling.

[0003]

However, in the above-described conventional film forming apparatus, the distance between the cooling roller 20 and the edges of the upper plate 30a and the lower plate 30b of the air chamber 30 on the air blowing side is appropriate. If not maintained, the film f is insufficiently cooled, or uneven cooling is caused, which is called air unevenness, a phenomenon in which a so-called surface becomes rough and the appearance is deteriorated, and the film f and the air chamber 30 are not. However, there is a problem in that the surface of the film f is scratched or broken.

The present invention has been made in view of the above problems, and an object of the present invention is to solve these problems, prevent contact with an air chamber, and improve the surface. It is intended to provide a film forming apparatus capable of obtaining a film having a good surface roughness by being uniformly cooled without causing scratches or breaks.

[0005]

In the film forming apparatus of the present invention, a film extruded from a mold is wound around a cooling roll, and air is blown out from an air chamber provided near the cooling roll to form the film. A film forming apparatus which is adapted to be cooled while being uniformly pressed against a cooling roll and to be continuously drawn by a take-up machine, wherein the air chamber is a flat upper plate and a lower plate, and a side plate having substantially parallel arrangement. Is configured in a box-shaped wind tunnel, and the distance between the upper plate edge of the air chamber and the cooling roll is shorter than the distance between the lower plate edge and the cooling roll.

The air chamber of the film forming apparatus of the present invention is provided in order to prevent a large amount of air from being blown out between the cooling rolls of the upper plate and the lower plate to cause air unevenness. The air from the blower arranged at the rear of the air chamber is compressed and used, and the static pressure of the air in the air chamber is the water column 20.
mm to 100 mm is preferable.

In the position where the air chamber is provided, it is preferable that the edge of the upper plate of the air chamber on the air blowing side is below the contact position between the cooling roll and the film.

The distance between the upper plate edge of the air chamber and the roll must be shorter than the distance between the lower plate edge and the roll, and the distance between the upper plate edge and the roll must be shorter than the lower plate edge. If it is longer than the distance from the roll, the air that is not cooled will come into contact with the air more strongly, causing uneven cooling, which is not preferable. Therefore, the distance between the edge of the upper plate on the air blowing side and the cooling roll is preferably 0.1 mm to 5 mm, more preferably 1 mm to 2 mm.

If the distance is shorter than the above range, the film may come into contact with the edge of the upper plate to be scratched or cut, and if it is longer than the above range, the edge of the upper plate may be damaged. The amount of air blown out between the cooling roll and the cooling roll becomes too large, which causes the film before solidification to flutter and cause air unevenness.

The distance between the edge of the lower plate on the air blowing side and the cooling roll is preferably 3 mm to 10 mm, more preferably 5 mm to 7 mm. If this distance is shorter than the above range, the amount of air blown out will be too large and air unevenness may occur even if the distance between the edge of the upper plate of the air chamber and the cooling roll is short. On the other hand, if the length is longer than the above range, the amount of air blown out from between the edge of the lower plate and the cooling roll becomes too large, and the effect of pressing the film against the cooling roll decreases.

The cooling roll is made of steel and has a diameter of 50.
mm-100 mm is preferably used, and has a structure in which cooling water for cooling is circulated. Further, it is preferable that the so-called lip portion at the tip of the die from which the film F is extruded is provided at a position slightly higher than the outer circumference of the cooling roll and closer to the center.

[0012]

In the film forming apparatus of the present invention, the flat upper and lower plates in which the air chambers are arranged substantially in parallel,
Since the distance between the upper plate edge of the air chamber and the cooling roll is set to be shorter than the distance between the lower plate end edge and the cooling roll, the air chamber of the film is connected to the air chamber of the film. Is prevented, no scratches or breaks are generated on the surface, the film is cooled uniformly without air unevenness, and a film having good surface roughness is obtained.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The film forming apparatus of the present invention will be described below with reference to the drawings. FIG. 1 is a side view showing an example of the film forming apparatus of the present invention. In FIG. 1, reference numeral 1 is a film forming apparatus. In the film forming apparatus 1, an extrusion die 11 is provided above the film forming apparatus 1.
A cooling roll 12 is disposed below the cooling roll 1.

The film F continuously extruded from the lip portion 11a at the tip of the extrusion die 11 runs downward and is wound around the lower half portion of the cooling roll 12, and obliquely upward from the opposite side as shown in the figure. It is designed to be taken up by a take-up machine via a guide roll (not shown).

Reference numeral 13 is an air chamber, and the air chamber 13 is disposed on the side surface of the film F on the side where the film F has descended. This air chamber 13
A flat upper plate 13a and a lower plate 13b, which are arranged substantially parallel to each other,
And side plates 13c and 13c on both sides form a box-shaped wind tunnel. The position of the edge 13d of the upper plate 13a on the air blowing side is located slightly below the contact position 12a of the cooling roll 12 of the film F.

Further, the upper plate 13a of the air chamber 13
The distance between the edge 13d of the sheet and the cooling roll 12 is equal to the lower plate 13b.
It is provided to be shorter than the distance between the edge 13e and the cooling roll 12.

The air blown to the film F in the direction of the arrow in the figure is supplied from an air blower (not shown) provided in the rear of the air chamber 13 and in communication with the air chamber 13, and continuously runs. The film F is blown onto the surface of the film F so as to uniformly cool the film F in the width direction and further in the flow direction.

The diameter of the cooling roll of the film forming apparatus was set to 60 mm, the vertical distance from the lip of the mold to the inside of the cooling roll was set to 30 mm, and the static pressure of the air chamber was set to 60 mm of water column. Molding of F was carried out.

[Example 1] Using a mold by the T-die method,
The height of the upper plate of the air chamber is set so that it is vertically 2 mm below the central axis position of the cooling roll, and the distance between the edge of the upper plate of the air chamber and the cooling roll is 1 mm.
Further, the distance between the edge of the lower plate of the air chamber and the cooling roll was set to 5 mm, and a film of 60 μm was formed from low density polyethylene (LK-30 manufactured by Mitsubishi Petrochemical Co., Ltd.). The results were evaluated from the external haze as shown in Table 1, and the surface condition was good.

[Embodiment 2] Using a die by the T-die method,
Set the height of the upper plate of the air chamber so that it is vertically 2 mm below the center axis position of the cooling roll, and the distance between the edge of the upper plate of the air chamber and the cooling roll is 1.5 m.
In addition, the distance between the edge of the lower plate of the air chamber and the cooling roll was set to 5.5 mm, and a 60 μm film was formed from low density polyethylene (LK-30 manufactured by Mitsubishi Petrochemical Co., Ltd.). The results were evaluated from the external haze as shown in Table 1, and the surface condition was good.

[Embodiment 3] Using a die by the T-die method,
The height of the upper plate of the air chamber is set so that it is vertically 2 mm below the central axis position of the cooling roll, and the distance between the edge of the upper plate of the air chamber and the cooling roll is 5 mm.
Further, the distance between the edge of the lower plate of the air chamber and the cooling roll was set to 7 mm, and a film of 60 μm was formed from low density polyethylene (LK-30 manufactured by Mitsubishi Petrochemical Co., Ltd.). The results were evaluated from the external haze as shown in Table 1, and the surface condition was good to some extent.

[Comparative Example 1] Using a mold by the T-die method,
The height of the upper plate of the air chamber is set to be 2 mm vertically below the central axis position of the cooling roll, and the distance between the edge of the upper plate of the air chamber and the cooling roll is 8 mm.
In addition, the distance between the edge of the lower plate of the air chamber and the cooling roll was set to 3 mm, and a 60 μm film was formed from low density polyethylene (LK-30 manufactured by Mitsubishi Petrochemical Co., Ltd.). The results were evaluated from the external haze as shown in Table 1, and the surface condition was poor.

In the above-mentioned Examples and Comparative Examples, the surface roughness of the film was measured by the external haze value (JISK7105-198).
It was evaluated from 1). Further, the external haze value (%) was measured at three points in the film flow direction and taken as an average value.

[0024]

[Table 1]

From the results of the above Examples and Comparative Examples, the distance between the edge of the upper plate of the air chamber and the cooling roll and the distance between the edge of the lower plate and the cooling roll were determined as follows. It was confirmed that a good film was obtained by setting as in the apparatus.

[0026]

In the film forming apparatus of the present invention,
The air chamber is composed of a flat upper plate and a lower plate, which are arranged substantially in parallel, and a side plate in a box-shaped wind tunnel shape, and the distance between the upper edge of the air chamber and the cooling roll is the same as the lower edge. Since it is set shorter than the distance from the cooling roll,
The film is prevented from coming into contact with the air chamber, the surface is free from scratches and breaks, and the film is cooled uniformly without air unevenness to obtain a film having a good surface roughness. Therefore, it is preferably used as a film forming apparatus.

[Brief description of drawings]

FIG. 1 is a side view showing an example of a film forming apparatus of the present invention.

FIG. 2 is a side view of a conventional film forming apparatus.

[Explanation of reference numerals] 1 film forming apparatus 11 mold 11a lip portion 12 cooling roll 12a contact position 13 air chamber 13a upper plate 13b lower plate 13c side plate 13d upper plate edge 13e lower plate edge F film

Claims (1)

[Claims] 1. A film extruded from a mold is wound around a cooling roll, and air is blown out from an air chamber provided in the vicinity of the cooling roll to uniformly press the film against the cooling roll to continuously cool the film. A film forming apparatus adapted to be taken up by a take-up machine, wherein the air chamber is formed in a box-like wind tunnel shape by a flat upper plate, a lower plate, and side plates arranged substantially parallel to each other. A film forming apparatus, wherein the distance between the plate edge and the cooling roll is shorter than the distance between the lower plate edge and the cooling roll.