JP4902404B2 - Blown film production equipment - Google Patents

Description

  The present invention relates to an inflation film manufacturing apparatus for continuously manufacturing a synthetic resin film by an inflation method.

  As a method of forming a synthetic resin into a film, an inflation method that can be produced with relatively simple equipment and is advantageous in terms of cost is often used.

  The inflation method is a method for obtaining a synthetic resin film by blowing cooling air from the surroundings to a resin bubble formed by extruding a molten resin from a die lip in a tube shape and pulling it upward while cooling.

  In order to increase productivity in the inflation method, it is necessary to increase the pulling speed of the resin bubbles. However, when the pulling speed of the resin bubbles is increased, the air volume of the cooling air must be increased. However, when the air volume of the cooling air is too large, the resin bubble is shaken and becomes unstable. Therefore, for example, Patent Document 1 discloses an apparatus in which the cooling air is cooled by maintaining the temperature of the air ring main body that discharges the cooling air at a low temperature to increase the cooling efficiency of the resin bubbles.

  In the inflation method, in order to produce a film having a uniform thickness, there has been proposed an apparatus provided with means for adjusting the thickness deviation immediately after being extruded from the die lip (see Patent Documents 2 to 5).

Japanese Patent Laid-Open No. 5-104623 JP-A-8-267572 Japanese Patent Laid-Open No. 10-80948 JP 11-262948 A Japanese Patent Laid-Open No. 11-300827

  It is an object of the present invention to provide a production apparatus capable of producing a synthetic resin film with good productivity by stabilizing the resin bubble better in the production of a synthetic resin film by an inflation method and pulling up the resin bubble at a higher speed. Furthermore, it is providing the manufacturing apparatus which can manufacture the synthetic resin film which reduced uneven thickness with sufficient productivity.

The present invention provides an apparatus for producing an inflation film in which cooling air is blown and cooled from a ring-shaped air ring surrounding the resin bubble to a resin bubble formed by extruding a molten resin in a tube shape from a die lip.
In the air ring having at least three stages of the air ring, the first stage, the second stage, and the third stage from the side close to the die lip,
The second stage air volume is 1.5 to 10 times the first stage air volume, the third stage air volume is 3 to 15 times the second stage air volume,
If the vertical distance between the first stage air outlet and the second stage air outlet is t2, and the vertical distance between the first stage air outlet and the third stage air outlet is t2, t2 is 5 to 15 times t1,
The inside of the first stage air ring has a plurality of independent air supply paths extending radially from the vicinity of the die lip toward the outside, and the amount of cooling air discharged from each air supply path toward the resin bubble and An apparatus for producing an inflation film , wherein at least one of the temperatures is controlled independently for each supply path .

  In the present invention, by providing three or more air rings for blowing out the cooling air, it is possible to carry out the dispersion adjustment, cooling, and stabilization of the resin bubbles in each stage of the air ring. Each action can be easily controlled.

  Furthermore, in the present invention, by increasing the air volume of the cooling air in order from the side closer to the die lip, the cooling efficiency is good and the resin bubble is also stabilized. Therefore, the line speed (resin bubble pulling speed) is increased and the productivity is increased. Can be improved.

  Further, in the present invention, the first-stage air ring close to the die lip and the second-stage air ring are placed close to each other, and the second-stage air ring and the third-stage air ring are separated from each other. The resin bubble is less susceptible to the influence of cooling air due to the air ring up to the stage, and the resin bubble can be stabilized.

  Therefore, according to the present invention, it is possible to produce a synthetic resin film with high productivity by pulling up the resin bubbles at a higher speed than before.

  Furthermore, in the present invention, as the first stage air ring, by providing a plurality of supply paths radially and individually controlling the air volume and temperature of the cooling air, the thickness adjustment of the resin bubble immediately after being extruded from the die lip is adjusted. Can be carried out with high accuracy. In the present invention, since the resin bubble is stabilized by adjusting the air volume of the air rings in a plurality of stages and further adjusting the gap between the air rings, the resin bubble in which the uneven thickness is adjusted by the plurality of supply passages. Even if it is pulled up at a high speed, the resin bubbles adjusted for uneven thickness are efficiently cooled, and a synthetic resin film with reduced uneven thickness can be produced with high productivity.

  The manufacturing apparatus of the present invention will be described with reference to preferred embodiments.

  FIG. 1 is a schematic partial sectional view in the vertical direction showing a preferred embodiment of the production apparatus of the present invention, in which 1 is a resin bubble, 3 is a die lip, 4 to 6 are air rings, and 4 a to 6 a are air rings 4. -6 air discharge ports, 8 an air supply port, 7, 9, 10 are inner peripheral walls of the air rings 4-6.

  In the present invention, like a conventional inflation film manufacturing apparatus, a molten resin is extruded from a die lip 3 to form a resin bubble 1, and the resin bubble 1 is pulled upward while enclosing the resin bubble 1. Cooling air is blown onto the resin bubble 1 from the air rings 4 to 6 to cool the resin bubble 1. The pulled-up resin bubble 1 is wound up by a winding device (not shown) at the top.

  The production apparatus of the present invention is characterized by having at least three air rings for cooling the resin bubble 1. The example of FIG. 1 is a configuration example in which three stages of air rings are provided, which are referred to as the first stage 4, the second stage 5, and the third stage 6 from the side close to the die lip 3.

  In the present invention, by providing three or more air rings as described above, the thickness adjustment of the resin bubble 1 is performed in the first stage air ring 4 having the highest resin temperature and easy thickness adjustment, and then 2 In the air ring 5 in the stage, the resin bubble 1 adjusted in thickness deviation is immediately cooled to maintain the state in which the thickness deviation is reduced, and further, the resin bubble 1 is prevented from shaking in the third stage air ring 6 and stabilized. This makes it possible to pull up the resin bubble 1 with the uneven thickness adjusted at high speed.

  In the present invention, in the three-stage air rings 4 to 6, the air volume of each air ring is adjusted so that the first stage 4 <the second stage 5 <the third stage 6 so as to increase the cooling efficiency and ensure the In addition, the resin bubble 1 can be stabilized. Preferably, the air volume of the second stage 5 is 1.5 to 10 times the air volume of the first stage 4, more preferably 2 to 5 times, and the air volume of the third stage 6 is 3 to 15 times the air volume of the second stage 4 Degree.

  In the three-stage air rings 4 to 6, the gap between adjacent air rings is larger in the second stage 5, the third stage 6, and the gap t2 than the gap t1 in the first stage 4 and the second stage 5. By being installed in such a manner, the resin bubble 1 can be satisfactorily stabilized at the third stage 6 without being affected by the cooling air up to the second stage 5. Preferably, t2 is 5 to 15 times t1.

  In the example shown in FIG. 1, the air discharge ports 4a, 5a, and 6a of the air rings at each stage blow air substantially vertically upward in structure, and in the air ring having such a structure, the air discharge ports 4a , 5a, 6a are parallel to the horizontal plane and have no height in the vertical direction. Therefore, the gap t1 between the first stage and the second stage is from the tip of the inner peripheral wall 7 where the first stage air discharge port 4a is located to the tip of the inner peripheral wall 9 where the second stage air discharge port 5a is located. The distance t2 between the second and third stages is a distance from the tip of the inner peripheral wall 9 where the second-stage air discharge port 5a is located to the tip of the inner peripheral wall 10 where the third-stage air discharge port 6a is located. Distance.

  Further, as shown in FIG. 3, when the air discharge port is inclined from the horizontal direction and the air is blown out inward from the vertical direction, the first-stage air discharge port 4a indicated by a broken line in the figure. From the upper end in the vertical direction to the lower end in the vertical direction of the second-stage air discharge port 5a is defined as a gap t1 between the first and second stages. That is, in FIG. 3, it is from the lower end of the inner peripheral wall 9 which comprises the air ring 5 to an upper end. Similarly, the gap t2 between the second stage and the third stage is the distance from the upper end in the vertical direction of the air discharge port 5a to the lower end in the vertical direction of the air discharge port 6a (not shown). In addition, in the example of FIG. 1, since each air ring discharge port 4a, 5a, 6a is parallel to a horizontal surface, it can be said that the vertical direction upper end and lower end correspond. Further, the inclination angle of the air discharge port from the horizontal plane indicated by θ1 and θ2 in FIG. 3 is 0 to 90 °, and FIG. 1 is a case of θ = 0 °. As the air discharge direction, it is preferable to blow out in the vertical direction as shown in FIG. Although the air ring discharge port 6a of the third stage air ring 6 is not shown in FIG. 3, the inclination angle from the horizontal plane is also 0 to 90 ° in the air ring discharge port 6a. It is preferable to blow out in the vertical direction as shown in FIG.

  Although it does not specifically limit as temperature of the cooling air supplied from the air rings 4-6, respectively, Usually, it is 0-60 degreeC. The temperature of the cooling air may be set individually for each air ring. However, the operation is complicated, and the film formation is improved by adjusting the air volume and setting the gap between the air rings as described above. In addition, the temperature of the cooling air is preferably set to a constant temperature since it can prevent uneven thickness of the film. Further, as will be described later, in the first stage air ring, it is preferable to form a plurality of supply paths so that the air volume and temperature can be adjusted in the circumferential direction, but even in such a case, the temperature is 1 It is preferable to set the same temperature as the second and second stages and adjust the air volume. Even when adjusting the temperature, the reference temperature should be the same as the first and second stages. desirable.

  Moreover, although the effect of the present invention can be obtained by using three stages of air rings, the present invention is not limited to this, and additional air rings may be installed after the third stage of FIG.

  In the present invention, the uneven thickness of the resin bubble 1 is adjusted by the first-stage air ring 4, and a preferred form of the air ring 4 is shown in FIG. FIG. 2 is a schematic view of the inside of the air ring as viewed from above.

  Each of the air rings 4 to 6 has a ring shape with a hollow center portion, and the die lip 3 is located in the hollow portion. As shown in FIG. As for the rings 4 to 6, the inner diameter of the hollow portion increases as the upper stage.

  In the air ring 4 shown in FIG. 2, the inside is radially divided by boundary walls 11 that radially extend from the vicinity of the inner peripheral wall 7 toward the outside, and a plurality of air supply paths 12 that are independent from each other are formed. The cooling air supply port 8 is provided on the outer peripheral side of each air supply path 12, and at least one of the air volume and the temperature is controlled independently for each air supply path 12. Therefore, since the air volume and temperature of the cooling air sprayed in the circumferential direction are selectively controlled in the resin bubble 1, the thickness adjustment can be performed with high accuracy. In addition, if the air ring is not formed with such a plurality of air supply paths, the air volume and temperature deviation in the circumferential direction generated in the air ring cannot be adjusted. For example, even when the cooling air is supplied at the same air volume and temperature, the air volume and temperature of the cooling air are controlled for each air supply path, so that an effect that the air volume and temperature in the circumferential direction are less likely to occur is obtained.

  In the air ring 4, more accurate thickness adjustment can be performed as the number of the air supply paths 12 is increased. However, the more the air supply paths 12, the more complicated the apparatus becomes and the control becomes difficult. It is preferable to select by.

  Further, when the inner end of the boundary wall 11 is too close to the inner peripheral wall 7, the air volume and temperature of the air hitting the resin bubble 1 are drastically changed when there is a difference in the air volume and temperature between the adjacent air supply paths 12. Since the area | region to change is formed and it becomes difficult to obtain the uneven thickness adjustment effect of the resin bubble 1, it is not preferable. Further, when the distance is too far, the effect of controlling the cooling air individually by providing a plurality of air supply passages 12 is reduced. Therefore, the inner end of the boundary wall 11 is preferably the inner diameter of the air ring, that is, the inner peripheral wall 7. It is preferable that the distance is 3 to 25% from the outer diameter (d3 in FIG. 2) in the horizontal direction. In other words, what is necessary is just to comprise so that the inner side edge part of the boundary wall 11 may be located on the concentric circle of the inner peripheral wall 7 which has the diameter d4 of 106-150% of the outer diameter d3 of the inner peripheral wall 7. FIG.

  The first-stage air ring 4 is preferably located immediately above the die lip 3 because the thickness of the molten resin can be adjusted while cooling the high-temperature molten resin. Further, the closer to the die lip 3, the more uneven thickness adjustment can be performed with a small amount of cooling air, which is preferable in terms of cost reduction. Therefore, the first-stage air ring 4 is provided as close to the die lip 3 as possible within a range where the inner peripheral wall 7 does not touch the resin bubble 1.

  As a specific method of adjusting the thickness deviation in the air ring 4 of FIG. 2, the thickness deviation of the obtained synthetic resin film is measured, the position of the air ring supply path 12 in the air ring 4 is specified, and the thick portion is the air volume Reduce the solidification rate by reducing the air flow, and increase the air volume in the thin part to increase the solidification rate. As a result, when the inner diameter of the resin bubble 1 is expanded while being pulled upward, the thicker portion is wider than the thinner portion, and the difference in thickness is reduced.

  Further, when the thickness of the cooling air in the air ring supply passage 12 is adjusted to adjust the uneven thickness, the temperature of the cooling air in the thick part of the resin bubble 1 is set higher than that in the thin part, so that the same as above. Thick portions are more spread out and the difference in thickness is reduced.

  The production apparatus of the present invention is preferably applied to an apparatus for producing a film having an outer diameter of the die lip 3 of about 70 to 300 mm and finally an outer diameter of about 600 to 3000 mm.

  A film having a thickness of 12 μm and an outer diameter of 2500 mm was manufactured using an inflation film manufacturing apparatus provided with a three-stage air ring having the structure of FIG. The configuration of the apparatus is as follows, and an ethylene / vinyl acetate copolymer (EVA; “Evaflex” manufactured by Mitsui DuPont Polychemical Co., Ltd.) was used as the resin material. For the first stage air ring, the same amount and temperature of air was supplied to 48 air supply paths.

Die lip 3 outer diameter d1: 200.00 mm
Inner diameter d2 of the inner peripheral wall 7 of the first stage air ring 4: 225.00 mm
The outer diameter d3 of the inner peripheral wall 7 of the first stage air ring 4 is 236.60 mm.
Air supply path 12 in the first stage air ring 4: 48 inner diameter d4 drawn by the inner end of the boundary wall 11: 256.00 mm
Gap t1: 19.00 mm between the first and second air rings 4 and 5
The gap t2 between the second and third air rings 5 and 6: 181.00 mm
Air discharge port 4a width w1: 4.20 mm
Air discharge port 5a width w2: 6.95 mm
Width w3 of air discharge port 6a: 10.00mm
Molten resin temperature: 200 ° C
Air temperature: 40 ° C

  Films were produced under the airflow conditions shown in Table 1, and the following evaluation was performed under each condition. The results are shown in Table 1.

[Film thickness accuracy]
Using an automatic film thickness meter (Yokogawa Electric Co., Ltd., “BallonGage”, model name: BG01F1A-J1-NN3-C2-L / B1A / Z), the maximum film thickness in the circumferential direction of the obtained film And the minimum difference (R) was measured and evaluated according to the following criteria. In addition, the measurement measured 10 points | pieces in the elongate direction of the film.
A: R is less than 2 μm B: R is 2 μm or more and less than 4 μm Δ: R is 4 μm or more −: Film cannot be formed

[Bubble stability]
The state of the resin bubble 1 during film formation was visually observed and judged.
A: The resin bubble hardly shakes.
○: Resin bubble slightly shakes.
Δ: Resin bubble shakes greatly.
-: Film cannot be formed

[Line speed]
The film winding speed at the time of film formation was changed, and the speed at which a film in substantially the same state was obtained was determined.
A: 100 m / min or more is possible.
A: 70 m / min or more and less than 100 m / min are possible.
Δ: Possible at less than 70 m / min.
-: Film cannot be formed

It is a fragmentary sectional view of the perpendicular direction of one Embodiment of the manufacturing apparatus of this invention. It is a top view which shows typically the structure inside the 1st step | paragraph air ring used by this invention. It is a fragmentary sectional view of the perpendicular direction of the air discharge port vicinity of the 1st step | paragraph and the 2nd step | paragraph air ring of other embodiment of the manufacturing apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Resin bubble 3 Die lip 4-6 Air ring 4a-6a Air discharge port 7, 9, 10 Air discharge port inner peripheral wall 8 Air supply port 11 Boundary wall 12 Air supply path

Claims (1)

In an apparatus for producing an inflation film for cooling by blowing cooling air from a ring-shaped air ring surrounding the resin bubble to a resin bubble formed by extruding a molten resin in a tube shape from a die lip,
In the air ring having at least three stages of the air ring, the first stage, the second stage, and the third stage from the side close to the die lip,
The second stage air volume is 1.5 to 10 times the first stage air volume, the third stage air volume is 3 to 15 times the second stage air volume,
If the vertical distance between the first stage air outlet and the second stage air outlet is t2, and the vertical distance between the first stage air outlet and the third stage air outlet is t2, t2 is 5 to 15 times t1,
The inside of the first stage air ring has a plurality of independent air supply paths extending radially from the vicinity of the die lip toward the outside, and the amount of cooling air discharged from each air supply path toward the resin bubble and An apparatus for producing an inflation film , wherein at least one of the temperatures is controlled independently for each supply path .

Images