JP2828595B2 - Method and apparatus for producing thermoplastic film - Google Patents

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 a T-die method.
In particular, the present invention relates to a method and an apparatus for manufacturing the plastic film having a degassing box on a side of a 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 provided with a vacuum box as a degassing box on the side of a T-die, as shown in FIG. The film 4 is cooled by a cooling roll 5 and wound up by a winder (not shown) via a guide roll 9 to form a product.

On the side of the T-die 3, a vacuum box 12 having a suction port at the tip is provided.
Is sucked by the vacuum pump 11 so that the cooling roll 5
Air is sucked from the gap between the contact portion of the molten film 4 and the cooling roll 5 to prevent the entrainment of the air and improve the close contact between the molten film 4 and the cooling roll 5.

However, in such a conventional configuration, air flows in through a gap between both ends of the molten film 4 and the cooling roll 5. The amount of air flowing in through the gaps at both ends is large, and in order to achieve a vacuum degree of about 200 to 300 ° Aq, the capacity of the vacuum pump 11 is increased, or otherwise, the gaps at the ends are reduced. It was necessary to cover with the sealing 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 sealing, the sealing member is worn out, and its maintenance is troublesome. In addition, the surface of the cooling roll is worn out by foreign substances such as seal members and dust clogging there, and streaks are formed.
Also, when the surface is matte finish, the matte finish pattern often disappears.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a novel structure that replaces the conventional vacuum box, vacuum pump, and seal member is used to reduce the pressure between the molten film and the cooling roll. It is another object of the present invention to prevent 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-mentioned object, a method for producing a thermoplastic plastic film is described in which the direction of rotation of a cooling roll is adjacent to a T-die for extruding a molten film of thermoplastic plastic. Air is pumped to the degassing box provided on the opposite side, and air is blown out from the tip and both ends of the nozzle member provided at the lower part of the degassing box on the side opposite to the T-die. In this method, air is discharged from the gap to make the gap between the molten film and the cooling roll a negative pressure to produce a thermoplastic film. In addition, in addition to this, an air knife provided on the rotation direction side of the cooling roll adjacent to the T die,
Preferably, the molten film is pressed against a chill roll.

The degassing box provided adjacent to the T-die comprises a main body connected to a compressed air blower and a nozzle member provided at a lower portion of the main body, and the nozzle member is provided at a lower portion thereof. A hollow plate having a bottom curved along the periphery of the cooling roll, one end of which is extended to a position near the extrusion port of the molten film of the T-die and closed, and the other end is extended to the side opposite to the T-die and is closed. An outlet nozzle is provided at the tip, and outlet nozzles are provided at both ends of the nozzle member. Further, on both sides of the bottom of the nozzle member on the T-die side, a seal member may be provided in the vicinity of the cooling roll.

An apparatus for producing a thermoplastic plastic film includes an extruder for a thermoplastic plastic, a T-die connected to the extruder via an adapter, a cooling roll provided below the T-die, The air knives are provided adjacent to the die on the rotation direction side of the cooling roll and press the molten film against the cooling roll, and the above-described degassing box.

[0010]

The air is pumped into the degassing box constructed as described above, and the air is blown out from the blowing nozzles provided at the tip and both ends opposite to the T-die of the nozzle member provided at the lower part of the degassing box. Then, by 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 set to a negative pressure. Also, on both sides of the bottom of the nozzle member on the T-die side,
By providing a sealing member near the cooling roll, the negative pressure can be increased. In addition, by providing an air knife adjacent to the T-die on the side of the cooling roll in the rotation direction, air entrapment is prevented in association with the deaeration by the negative pressure.

[0011]

An embodiment will be described with reference to the drawings. Parts that are the same as or equivalent to the conventional example will be described using the same reference numerals.

In FIG. 1 and FIG. 2, a T-die 3 is attached via an adapter 2 to the tip of an extruder 1 for thermoplastics. The molten film 4 formed by the T die 3 is cooled by a cooling roll 5 provided below the T die 3.
Extruded on the surface. A pressurizing box 6 is provided adjacent to the T-die 3 on the side opposite to the rotation direction of the cooling roll 5 as a degassing box. The pressurizing box 6 is connected to the pressurized air blower 8. 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 a cooling roll 5. The cooled film 4 is wound by a winder (not shown) via a guide roll 9 and the like.

The pressure box 6 has substantially the same width as the T-die 3 and comprises a main body 6a connected to the compressed air blower 8 and a nozzle member 6b formed below the main body 6a. The nozzle member 6b is a hollow plate having a bottom curved along the periphery of the cooling roll 5, one end of which extends to the vicinity of the molten film 4 extrusion port of the T die 3, and is closed at the other end. And a blowing nozzle 6c is provided at the tip. In addition, blowing nozzles 6c are also provided at both ends of the nozzle member 6b. It is desirable that the blowing nozzle 6c 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 sealing member 7 may be provided on both sides of the bottom of the nozzle member 6b on the side of the T die 3 near the cooling roll 5.

Next, the operation of the above embodiment will be described. Blowing nozzle 6c opened in nozzle member 6b of pressurizing box 6
When the air from the compressed air blower 8 is blown out, air flows out of 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.
Generates a negative pressure. Also, the air is blown out from the blowing nozzle 6c opened at both ends of the nozzle member 6b, so that the air flows out from the gap A on both sides to generate a negative pressure, and it is possible to prevent the air from flowing in at the same time. Further, the negative pressure can be freely changed by changing the air velocity and the gap A from the blowing nozzle 6c, so that the molten film 4 can be brought into close contact with the cooling roll 5 according to the operating conditions.

[0015]

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

Air is blown out from blowing nozzles provided at the tip and both ends of the nozzle member.
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.
The electric motor of the compressed air blower can be reduced in capacity.

On both sides of the bottom of the nozzle member on the T-die side,
By providing a sealing member near the cooling roll, the negative pressure can be increased. If the conventional sealing member was not brought into contact with the cooling roll, a negative pressure was not sufficiently generated. However, if the degassing box according to the present invention was used, a sufficient negative pressure was generated even without bringing the sealing member into contact with the cooling roll. Therefore, maintenance like a conventional sealing member is not required.

Also, the velocity of the air blown from the blow nozzle,
Since the negative pressure can be freely changed by changing the gap between the bottom of the nozzle member and the cooling roll, the molten film can be brought into close contact with the cooling roll according to the operating conditions. As an additional effect, since air is pumped from the degassing box along the surface of the cooling roll, it is possible to clean oligomers and the like generated on the roll surface during film cooling by raising the temperature of the blown air. Now you can.

Further, a film is formed by a degassing box provided adjacent to the T-die and on the opposite side to the rotation direction of the cooling roll, and an air knife provided on the rotation direction side of the cooling roll and pressing the molten film against the cooling roll. Since the manufacturing equipment is configured, the molten film adheres well to the cooling roll,
A film of good quality, especially transparency, was obtained.

[Brief description of the 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]

 REFERENCE SIGNS LIST 1 extruder 2 adapter 3 T die 4 molten film 5 cooling roll 6 deaeration box (pressure 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 Clearance between bottom of member and cooling roll B Clearance between molten film and cooling roll

Continuation of the front page (56) References JP-A-53-6367 (JP, A) JP-A-61-146520 (JP, A) JP-A-1-97621 (JP, A) JP-A-4-14426 (JP) JP-A-7-329143 (JP, A) JP-A-52-15556 (JP, A) JP-A-4-82726 (JP, A) JP-A-5-286019 (JP, A) 5-305646 (JP, A) Japanese Utility Model 4-20423 (JP, U) Japanese Utility Model 4-115635 (JP, U) Japanese Utility Model 4-137820 (JP, U) Japanese Utility Model 4-30921 (JP, U) U) Japanese Utility Model Hei 4-89320 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) B29C 47/00-47/96

Claims (5)

(57) [Claims] 1. A degassing box (6) provided adjacent to a T-die (3) for extruding a molten film (4) of a thermoplastic plastic and opposite to a rotation direction of a cooling roll (5). Air is fed under pressure, and air is blown out from the tip and both ends of the nozzle member (6b) provided at the lower part of the degassing box (6) on the side opposite to the T-die (3), and the nozzle member (6) is blown.
b) air flows out from the gap (A) between the bottom 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 rotation direction side of the cooling roll (5).
The method according to claim 1, wherein the molten film (4) is pressed against a cooling roll (5). 3. A degassing box (6) provided adjacent to a T-die (3) for extruding a molten film (4) of a thermoplastic plastic and opposite to a rotation direction of a cooling roll (5). Body (6a) connected to the compressed air blower (8)
And a nozzle member (6) provided below the main body (6a).
b), wherein the nozzle member (6b) is a hollow plate having a bottom curved along the periphery of the cooling roll (5) provided thereunder, and one end of which is a molten film of a T-die (3). (4) extending to the vicinity of the extrusion port and being closed,
The other end extends to the side opposite to the T-die (3), and has a blowing nozzle 6c at its tip, and also has blowing nozzles 6c at both ends of the nozzle member (6b). Degassing box for die (3). 4. A sealing member (7) is provided on both sides of the bottom of the nozzle member (6b) on the side of the T die (3), close to the cooling roll (5). 3. The degassing box according to 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) Film (4) provided adjacent to the cooling roll (5) in the direction of rotation of the cooling roll (5)
Air knife (10) for pressing the roll against the cooling roll (5)
And a degassing box (6) according to claim 3 or 4.