JPH081756A - Method for and apparatus for manufacture of thermoplastic plastic film - Google Patents

Abstract

PURPOSE:To manufacture a high quality thermoplastic plastic film at a high speed by a method wherein a gap between a molten film extruded from a T-die and a cooling roll provided below the T-die is made negative in pressure, and besides air is prevented from flowing in from outside. CONSTITUTION:Air is fed by pressure to a deaerating box 6 provided adjacent to a T-die 3 extruding a thermoplastic plastic molten film 4 on an opposed side to a revolving direction of a cooling roll 5. Air is blown off from a blow-off nozzle 6c bored at a tip opposed to the T-die 3 of a nozzle component 6b provided below the deaerating box 6 and at its both ends to make air flow out from a gap A between a bottom part of the nozzle component 6b and the cooling roll 5. A gap B between the molten film 4 and the cooling roll 5 is made negative in pressure thereby.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing a thermoplastic film by the T-die method,
In particular, it relates to a method and apparatus for producing the plastic film having a degassing box on the side of the T-die. As the plastic film, unstretched polypropylene (C
PP), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), soft vinyl chloride (SP)
VC) monolayer and multilayer films.

[0002]

2. Description of the Related Art In a conventional film manufacturing apparatus in which a vacuum box is provided as a deaeration box on the side of a T-die, resin melted by an extruder (not shown) is melted by a T-die 3 as shown in FIG. The film 4 is cooled by a cooling roll 5 and wound by a winder (not shown) via a guide roll 9 to obtain a product.

A vacuum box 12 having a suction port at its tip is provided on the side of the T-die 3.
By sucking the air with the vacuum pump 11,
Air is sucked through the gap between the contact portion between the molten film 4 and the film 4 to prevent the air from being entrained, and the melted film 4 and the cooling roll 5 are closely attached.

However, in such a conventional configuration, air flows in through the gap between the molten film 4 and the cooling roll 5 at both ends. The amount of air flowing in from the gaps at both ends is large, and in order to achieve a vacuum degree of about 200 to 300 〓Aq, the vacuum pump 11 should have a large capacity, or else the gaps at both ends should be made larger. It was necessary to close it with the seal member 7.

[0005]

Since the above-mentioned sealing member is provided in contact with the outer peripheral surface of the cooling roll in order to improve the hermetical sealing, the sealing member is worn and it takes time to maintain it. Also, the surface of the chill roll may be worn due to foreign matter such as dust or the like that is clogged in the seal member, causing streaks,
Further, when the surface has a matte finish, the matte finish pattern often disappears.

The present invention has been made in order to solve the above problems and has a novel structure in place of the conventional vacuum box, vacuum pump and sealing member, which creates a negative pressure in the gap between the molten film and the cooling roll. In addition, it is intended to prevent the inflow of air from the outside and to produce a high quality thermoplastic film at a high speed.

[0007]

In order to achieve the above object, a method for producing a thermoplastic film is such that the direction of rotation of a cooling roll is adjacent to a T die for extruding a molten film of thermoplastic. Air is pressure-fed to the deaeration box provided on the opposite side, and air is blown from the tip and both ends of the nozzle member provided at the lower part of the deaeration box on the side opposite to the T die, and the bottom of the nozzle member and the cooling roll This is a method for producing a thermoplastic film by letting out air from the gap and setting a negative pressure in the gap between the molten film and the cooling roll. In addition to this, with an air knife provided adjacent to the T-die on the rotation direction side of the cooling roll,
It is preferred to press the molten film against a chill roll.

The deaeration box provided adjacent to the T-die comprises a main body connected to the compressed air blower and a nozzle member provided at the lower part of the main body, and the nozzle member is provided at the lower part. A hollow plate having a curved bottom along the periphery of a cooling roll, one end of which extends to the vicinity of the extrusion opening of the molten film of the T die and is closed, and the other end of which extends to the opposite side of the T die and A blowing nozzle is opened at the tip, and blowing nozzles are also opened at both ends of the nozzle member. Further, a seal member may be provided on both side surfaces of the bottom portion of the nozzle member on the T-die side, in proximity to the cooling roll.

An apparatus for producing a thermoplastic film comprises an extruder for thermoplastics, a T-die connected to the extruder via an adapter, a cooling roll provided under the T-die, and a T-die. The air knife is provided adjacent to the die on the rotation direction side of the cooling roll to press the molten film against the cooling roll, and the degassing box.

[0010]

The air is sent under pressure to the deaeration box configured as described above, and the air is blown out from the nozzles provided at the bottom of the deaeration box on the opposite side to the T-die and at the blowing nozzles provided at both ends. Then, due to the so-called Venturi effect, air flows out from the gap between the bottom of the nozzle member and the cooling roll, and the gap between the molten film and the cooling roll is made negative pressure. Also, on both sides of the bottom of the nozzle member on the T die side,
The negative pressure can be increased by providing the seal member in the vicinity of the cooling roll. In addition, an air knife is provided adjacent to the T-die on the rotation direction side of the cooling roll to prevent air entrapment due to degassing due to the negative pressure.

[0011]

EXAMPLES Examples will be described with reference to the drawings. In addition, the same or equivalent portions as those of the conventional example will be described using the same reference numerals.

In FIGS. 1 and 2, a T-die 3 is attached to the tip of an extruder 1 for thermoplastics via an adapter 2. The molten film 4 formed by the T-die 3 is cooled by the cooling roll 5 provided below the T-die 3.
Is extruded on the surface of. Adjacent to the T-die 3, a pressure box 6 is provided as a deaeration box on the side opposite to the rotation direction of the cooling roll 5. The pressurizing box 6 is connected to the compressed air blower 8. Further, an air knife 10 is provided adjacent to the T die 3 on the rotation direction side of the cooling roll 5,
The molten film 4 formed by the T die 3 is pressed against the cooling roll 5. The cooled film 4 is wound by a winder (not shown) via the guide roll 9 and the like.

The pressure box 6 has substantially the same width as the T-die 3, and is composed of a main body 6a connected to the compressed air blower 8 and a nozzle member 6b formed under the main body 6a. The nozzle member 6b is a hollow plate having a curved bottom along the periphery of the cooling roll 5, one end of which extends to the vicinity of the melt film 4 extrusion port of the T die 3 and is closed, and the other end of which is the T die 3 A blow-out nozzle 6c is opened at the tip end of the blow-out nozzle 6c. In addition, blowing nozzles 6c are opened at both ends of the nozzle member 6b. The blowing nozzle 6c preferably has a slit shape or a round hole shape. A gap A is provided between the bottom of the nozzle member 6b and the cooling roll 5. If necessary, a seal member 7 may be provided on both side surfaces of the bottom of the nozzle member 6b on the T die 3 side in close proximity to the cooling roll 5.

Next, the operation of the above embodiment will be described. Blow-out nozzle 6c opened in the nozzle member 6b of the pressure box 6
As a result, when air is blown out from the compressed air blower 8, the air flows out from the gap A due to the so-called Venturi effect, and the gap B formed between the molten film 4 and the surface of the cooling roll 5 is formed.
A negative pressure is generated in. Further, even when the air is blown out by the blowout nozzles 6c formed at both ends of the nozzle member 6b, the air flows out from the gap A on both side surfaces to generate a negative pressure, and at the same time, the inflow of air can be prevented. Further, since the negative pressure can be freely changed by changing the speed of air blown from the blow nozzle 6c and the gap A, the molten film 4 can be closely adhered to the cooling roll 5 depending on the operating conditions.

[0015]

Since the present invention is constructed as described above, it has the following effects.

Air is blown out from blowout nozzles provided at the tip and both ends of the nozzle member, and by the Venturi effect,
Air flows out from the gap between the bottom of the nozzle member and the cooling roll, and the gap between the molten film and the cooling roll is set to a negative pressure, so there is less inflow of air than the conventional degassing box,
It is possible to reduce the capacity of the air blower electric motor.

On both sides of the bottom of the nozzle member on the T-die side,
The negative pressure can be increased by providing the seal member in the vicinity of the cooling roll. Negative pressure was not sufficiently generated unless the conventional sealing member was brought into contact with the cooling roll, but when the deaeration box according to the present invention was used, sufficient negative pressure was generated even if the sealing member was not brought into contact with the cooling roll. Therefore, maintenance such as the conventional seal member is unnecessary.

Further, the velocity of the air blown from the blow nozzle,
The negative pressure can be freely changed by changing the bottom of the nozzle member and the gap between the cooling rolls, so that the molten film can be closely adhered to the cooling roll depending on the operating conditions. In addition, as an additional effect, since air is pumped from the deaeration box along the surface of the cooling roll, oligomers or the like generated on the roll surface during film cooling can be cleaned by raising the temperature of the blown air. I can do it now.

The degassing box is provided adjacent to the T-die on the side opposite to the rotating direction of the cooling roll, and the air knife is provided on the rotating direction side of the cooling roll to press the molten film against the cooling roll. Since the manufacturing equipment is configured, the molten film adheres well to the cooling roll,
A film with a particularly good quality was obtained.

[Brief description of drawings]

FIG. 1 is a schematic front view showing a film manufacturing apparatus according to the present invention.

FIG. 2 is a top view of FIG.

FIG. 3 is a schematic view of a conventional film manufacturing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Extruder 2 Adapter 3 T die 4 Molten film 5 Cooling roll 6 Degassing box (pressurizing box) 6a Main body 6b Nozzle member 6c Blow-out nozzle 7 Sealing member 8 Compressed air blower 9 Guide roll 10 Air knife 11 Vacuum pump 12 Vacuum box A Nozzle Gap between bottom of member and cooling roll B Gap between molten film and cooling roll

Claims (5)

[Claims] 1. A deaeration box (6) provided adjacent to a T-die (3) for extruding a molten film (4) of a thermoplastic and opposite to the direction of rotation of a cooling roll (5). Air is sent under pressure to blow air from the tip and both ends of the nozzle member (6b) provided in the lower part of the deaeration box (6) on the side opposite to the T die (3), and the nozzle member (6
Air that flows out from the gap (A) between the bottom of b) and the cooling roll (5), and the gap (B) between the molten film (4) and the cooling roll (5) is set to a negative pressure. A method for producing a plastic film. 2. An air knife (10) provided adjacent to the T-die (3) on the rotational side of the cooling roll (5).
2. The method for producing a thermoplastic film according to claim 1, wherein the molten film (4) is pressed against the cooling roll (5). 3. A deaeration box (6) provided adjacent to the T-die (3) for extruding the molten film (4) of thermoplastic, and on the side opposite to the rotating direction of the cooling roll (5). , Body (6a) connected to the compressed air blower (8)
And a nozzle member (6) provided at the bottom of the body (6a).
b) and the nozzle member (6b) is a hollow plate having a curved bottom portion along the peripheral edge of the cooling roll (5) provided at the lower portion thereof, one end of which is a molten film of the T die (3). It extends to the vicinity of the extrusion port of (4) and is closed,
The other end extends to the side opposite to the T-die (3), and a blowing nozzle 6c is opened at the tip thereof, and blowing nozzles 6c are also opened at both ends of the nozzle member (6b). Degassing box for the die (3). 4. A seal member (7) is provided on both sides of the bottom of the nozzle member (6b) on the T-die (3) side, in proximity to the cooling roll (5). The deaeration box described in 3. 5. Extruder for thermoplastics (1)
A T-die (3) connected to the extruder (1) via an adapter (2); a cooling roll (5) provided below the T-die (3); and the T-die (3). A melted film (4) provided on the rotation direction side of the cooling roll (5) adjacent to
Air knife (10) that presses against the cooling roll (5)
And a deaeration box (6) according to claim 3 or 4, characterized in that it comprises a thermoplastic film manufacturing apparatus.