CASTING APPARATUS FOR MANUFACTURING POLYMER FILM

Abstract

A film casting apparatus includes a die which has a non-zero angled discharge direction relative to a horizontal plane. A chill roll is positioned downstream of the die. A film displacement device is positioned proximate to the chill roll and is configured to position the molten polymer on the chill roll and establish the thickness of the film. The non-zero discharge angle is of a predetermined magnitude to gravity assist delivery of the molten polymer to the chill roll. The chill roll is positioned to gravity support the polymer film along a first length of a first side of the polymer film. A first polishing roll is positioned downstream of the chill roll and engages and cools a second length of a second side of the polymer film which is opposite the first side. The first length is substantially equal to the second length.

Claims

1. A casting apparatus for manufacturing polymer film, the casting apparatus comprising: a die for discharging a molten polymer, the die having a discharge direction oriented at a non-zero discharge angle offset from a horizontal reference plane; a chill roll positioned downstream of the die; a film displacement device positioned proximate to the chill roll, the film displacement device being configured to position the molten polymer on the chill roll and establish the thickness of the film at an initial point of contact on the chill roll; the non-zero discharge angle of the discharge direction of the die being of a predetermined magnitude to gravity assist delivery of the molten polymer to the chill roll; the chill roll being positioned to gravity support the polymer film along a first length of a first side of the polymer film; a first polishing roll positioned downstream of the chill roll, the first polishing roll engaging and cooling a second length of a second side of the polymer film, the second side being opposite the first side; and the first length being substantially equal to the second length.

2. The casting apparatus of claim 1, wherein the film displacement device comprises one of a fluid impingement device and a vacuum device.

3. The casting apparatus of claim 1, further comprising a second gap between the first polishing roll and the chill roll wherein the first length extends between the initial point of contact and the second gap.

4. The casting apparatus of claim 1, further comprising a second polishing roll positioned downstream of the first polishing roll and a third gap between the first polishing roll and the second polishing roll, the second length extending between the second gap and the third gap.

5. The casting apparatus of claim 1, further comprising a third polishing roll positioned downstream of the second polishing roll and a fourth gap between the second polishing roll and the third polishing roll, the first side of the polymer film engaging and extending a third length on the second polishing roll, between the third gap and the fourth gap.

6. The casting apparatus of claim 1, wherein the second side of the polymer film engages and extends a fourth length on the third polishing roll.

7. The casting apparatus of claim 5, wherein the first length, the second length and the third length are substantially equal.

8. The casting apparatus of claim 6, wherein the first length, the second length, the third length and the fourth length are substantially equal.

9. The casting apparatus of claim 5, wherein the first length and the second length are established by positioning of at least one of the film displacement device, the second chill roll and the first polishing roll, relative to one another.

10. The casting apparatus of claim 6, wherein the first length, the second length, the third length and the fourth length are established by positioning of at least one of the film displacement device, the second chill roll, the first polishing roll, the second polishing roll and the third polishing roll, relative to one another.

11. The casting apparatus of claim 5, wherein the first length and the second length are established by a second diameter defined by the chill roll and a third diameter defined by the first polishing roll.

12. The casting apparatus of claim 6, wherein the third length and the fourth length are established by a third diameter defined by the second polishing roll and a fourth diameter defined by the third polishing roll.

13. The casting apparatus of claim 5, wherein at least two of the second chill roll, the first polishing roll, the second polishing roll and the third polishing roll are aligned along a common plane oriented at a non-zero tilt angle offset from the horizontal reference plane.

14. The casting apparatus of claim 6, wherein at least one of the film displacement device and the second chill roll are rotationally mounted on a frame and the frame comprises a system for moving the frame relative to the die.

15. A casting apparatus for manufacturing polymer film, the casting apparatus comprising: a die for discharging a molten polymer, the die having a discharge direction oriented at a non-zero discharge angle offset from a horizontal reference plane; at least one chill roll positioned downstream of the die; the non-zero discharge angle of the discharge direction of the die being of a predetermined magnitude to gravity assist delivery of the molten polymer; the at least one chill roll being positioned to gravity support the polymer film along a first length of a first side of the polymer film; a first polishing roll positioned downstream of the at least one chill roll, the first polishing roll engaging and cooling a second length of a second side of the polymer film, the second side being opposite the first side; and the first length being substantially equal to the second length.

16. The casting apparatus of claim 15, further comprising a second gap between the first polishing roll and the chill roll wherein the first length extends between the initial point of contact and the second gap.

17. The casting apparatus of claim 15, further comprising a second polishing roll positioned downstream of the first polishing roll and a third gap between the first polishing roll and the second polishing roll, the second length extending between the second gap and the third gap.

18. The casting apparatus of claim 15, further comprising a third polishing roll positioned downstream of the second polishing roll and a fourth gap between the second polishing roll and the third polishing roll, the first side of the polymer film engaging and extending a third length on the second polishing roll, between the third gap and the fourth gap.

19. The casting apparatus of claim 15, wherein the second side of the polymer film engages and extends a fourth length on the third polishing roll.

20. The casting apparatus of claim 18, wherein the first length, the second length and the third length are substantially equal.

21. The casting apparatus of claim 19, wherein the first length, the second length, the third length and the fourth length are substantially equal.

22. The casting apparatus of claim 16, wherein the first length and the second length are established by positioning of at least one of the chill roll and the first polishing roll, relative to one another.

23. The casting apparatus of claim 19, wherein the first length, the second length, the third length and the fourth length are established by positioning of at least one of the chill roll, the first polishing roll, the second polishing roll and the third polishing roll, relative to one matter.

24. The casting apparatus of claim 16, wherein the first length and the second length are established by a second diameter defined by the chill roll and a third diameter defined by the first polishing roll.

25. The casting apparatus of claim 19, wherein the third length and the fourth length are established by a third diameter defined by the second polishing roll and a fourth diameter defined by the third polishing roll.

26. The casting apparatus of claim 16, wherein at least two of the chill roll, the first polishing roll, the second polishing roll and the third polishing roll are aligned along a common plane oriented at a non-zero tilt angle offset from the horizontal reference plane.

27. The casting apparatus of claim 15, wherein the chill roll is rotationally mounted on a frame and the frame comprises a system for moving the frame relative to the die.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] FIG. 1A is a schematic side view of a portion of a prior art vertical downstack polymer film casting system;

[0052] FIG. 1B is a schematic side view of a portion of a prior art horizontal polymer film casting system;

[0053] FIG. 1C is a schematic side view of a portion of a prior art vertical upstack polymer film casting system;

[0054] FIG. 1D is a schematic side view of a portion of a prior art offset vertical upstack polymer film casting system;

[0055] FIG. 1E is a schematic side view of a portion of a prior art offset vertical upstack polymer film casting system with additional horizontal chill rolls;

[0056] FIG. 1F is a schematic side view of a portion of a prior art offset vertical downstack polymer film casting system;

[0057] FIG. 2 is an enlarged view of the prior art offset vertical upstack polymer film casting system of FIG. 1E;

[0058] FIG. 3A is a schematic side view of a portion of a polymer film casting apparatus of the present invention;

[0059] FIG. 3B is a schematic side view of a portion of a polymer film casting apparatus of the present invention having an air impingement device;

[0060] FIG. 3C is a schematic side view of a portion of a polymer film casting apparatus of the present invention having a vacuum device;

[0061] FIG. 4 is a side view of the polymer film casting apparatus of FIG. 3A shown installed in a frame in an open configuration;

[0062] FIG. 5 is a perspective view of the polymer film casting apparatus of FIG. 4; and

[0063] FIG. 6 is a rear perspective view of the polymer film casting apparatus of FIG. 5.

DETAILED DESCRIPTION

[0064] As best shown in FIG. 3A, a casting apparatus for manufacturing polymer film is generally designated by the numeral 10. The casting apparatus 10 includes a die 19 for discharging a molten polymer MP. The die 19 is an elongate member that extends in a generally horizontal plane and is in communication with an extruder that supplies the molten polymer MP to the die 19. The die 19 has a discharge slit 19X and is oriented such that the discharge slit 19X has a discharge direction oriented at a non-zero discharge angle 2 that is offset from a horizontal reference plane H2. In one embodiment, the non-zero discharge angle 2 is from 10 to 45 degrees.

[0065] The casting apparatus 10 includes a pair of initial film receiving chill rolls (e.g., cylindrical rolls configured with a heat removal system), for example, a first chill roll 12 having a first diameter D12 and a second chill roll 13 having a second diameter D13. The second diameter D13 is greater than the first diameter D12. In one embodiment, the second diameter D13 is about two to three times greater than the first diameter D12. The first chill roll 12 and the second chill roll 13 are positioned downstream of the die 19. As shown in FIGS. 4-6, the first chill roll 12 and the second chill roll 13 are rotationally secured to a frame 20 (e.g., a roll stand) about respective center lines C12 and C13, by respective bracket and bearing assemblies 12B and 13B. The chill roll 12 is moveably mounted relative to the frame 20 to allow of adjustment of the position thereof relative to the second chill roll 13.

[0066] A first gap N12 is provided between the first chill roll 12 and the second chill roll 13. The first gap N12 is adjustable between a fully open position (e.g., as shown in FIG. 4 that is used during initial set up of the casting apparatus 10 and for maintenance) and during operation. During operation of the casting apparatus the gap N12 is reduced to a predetermined range of magnitudes to create a nip (e.g., a nip, adjustable during operation of the casting apparatus 10) for controlling the thickness of the molten polymer MP that cools into a polymer film F.

[0067] The non-zero discharge angle 2 of the discharge direction of the die 19 is of a predetermined magnitude to gravity assist delivery of the molten polymer MP to the first gap N1. For example, the discharge direction points downwardly at the non-zero discharge angle 2 to allow the force of gravity to urge the molten polymer into the gap N1 for sizing. Thus, employing the non-zero discharge angle 2 mitigates or eliminates the problems of the prior art polymer film casting devices, such as sagging of the molten polymer that can cause flutter, and intermittent and premature contact of the molten polymer with the chill roll 2, before sizing.

[0068] As shown in FIG. 3A, the second chill roll 13 is positioned to cool and gravity support the film F exiting the first gap N1 along a first length L13 of a first side F1 of the polymer film F. For example, the first side F1 of the first length L13 of the polymer film F, engages an exterior quadrant surface of the second chill roll 13 that is generally upward facing, from the 12 o'clock position (i.e., at the first gap N12) to the 3 o'clock position (i.e., at the second gap N13) on the second chill roll 13. Since the exterior quadrant surface of the second chill roll 13 is generally upward facing the first length L13 of the polymer film F tends to be pressed against the exterior quadrant surface by the force of gravity.

[0069] While the casting apparatus 10 is shown in FIG. 3A to include the first chill roll 12 and the second chill roll 13, the present invention is not limited in this regard as the first chill roll 12 may be eliminated and replaced with an film displacement device 55 (e.g., a vessel or box) that has an elongate discharge slit 56 therein. The second chill roll 13 and the film displacement device 55 are positioned downstream of the die 19. The die 19 and orientation thereof shown in FIG. 3B are configured similar to the die 19 shown in FIG. 3A. In one embodiment, the film displacement device 55 is a fluid impingement device (e.g., an air knife) that is in communication with a fluid supply source 57 (e.g., air compressor, air tank, nitrogen supply, liquid supply or pump) via a suitable conduit 58. A linear jet 59 is discharged from the slit 56 and impinges and controls and establishes the thickness, of the molten polymer MP that cools into a polymer film F on the second chill roll 13. The linear jet 59 controls and establishes the initial point of contact N12 of the molten polymer on the second chill roll 13. The linear jet 59 is positioned so that the first length L13 is equal to the second length L14. In one embodiment, the first length L13, the second length L14 and the third length L15 are substantially equal. In one embodiment, the first length L13, the second length L14, the third length L15 and the fourth length L16 are substantially equal.

[0070] While the film displacement device 55 of FIG. 3B is shown and described as being the fluid impingement device (e.g., an air knife) that is in communication with the fluid supply source 57 (e.g., air compressor, air tank, nitrogen supply, liquid supply or pump) via the suitable conduit 58, the present invention is not limited in this regard as other configurations may be employed. For example, as shown in FIG. 3C, the first chill roll 12 may be eliminated and replaced with a film displacement device 65 (e.g., a vessel or box) that has an elongate discharge slit 66 therein. The second chill roll 13 and the film displacement device 65 are positioned downstream of the die 19. The die 19 and orientation thereof shown in FIG. 3C are configured similar to the die 19 shown in FIG. 3A. In one embodiment, the film displacement device 65 is a vacuum device (e.g., a vacuum chamber) that is in communication with a vacuum source 67 (e.g., vacuum pump) via a suitable conduit 68. A linear jet 69 is suctioned into the slit 66 and controls and establishes the thickness of the molten polymer MP that cools into a polymer film F on the second chill roll 13. The linear jet 69 controls and establishes the initial point of contact of the molten polymer on the second chill roll 13 by pulling the film onto the second chill roll 13. The linear jet 69 is positioned so that the first length L13 is equal to the second length L14. In one embodiment, the first length L13, the second length L14 and the third length L15 are substantially equal. In one embodiment, the first length L13, the second length L14, the third length L15 and the fourth length L16 are substantially equal.

[0071] A polishing stage 30 is positioned downstream of the pair of initial film receiving chill rolls 12 and 13. The polishing stage 30 (e.g., cylindrical rolls configured with a heat removal system) is employed to further cool, size and uniformly finish the polymer film F. The polishing stage 30 includes a first polishing roll 14 positioned downstream of the pair of initial film receiving chill rolls 12 and 13. A second gap N13 (e.g., a nip, adjustable during operation of the casting apparatus 10) is located between the first polishing roll 14 and the second chill roll 13. The polishing stage 30 includes a second polishing roll 15 positioned downstream of the first polishing roll 14. A third gap N14 is located between the first polishing roll 14 and the second polishing roll 15. The polishing stage 30 includes a third polishing roll 16 positioned downstream of the second polishing roll 15. A fourth gap N15 (e.g., a nip, adjustable during operation of the casting apparatus 10) is located between the second polishing roll 15 and the third polishing roll 16. As shown in FIGS. 4-6, the first polishing roll 14, the second polishing roll 15 and the third polishing roll 16 are rotatably mounted to the frame 20, about respective center lines C14, C15 and C16, by respective bracket and bearing assemblies 14B, 15B and 16B.

[0072] The first polishing roll 14, the second polishing roll 15 and the third polishing roll 16 are moveably mounted to the frame 20 to allow of adjustment of the position thereof relative to each other and the second chill roll 13. The movability of the first polishing roll 14, the second polishing roll 15 and the third polishing roll 16 allows for adjustment of the size of the gaps N13, N14 and N15 to create respective nips at each gap N13, N14 and N15 for controlling the thickness of the polymer film F, during operation of the casting apparatus 10.

[0073] While the polishing stage 30 is shown and described as having the first polishing roll 14, the second polishing roll 15 and the third polishing roll 16, the present invention is not limited in this regard as more or less polishing rolls may be employed.

[0074] As best shown in FIG. 3A, the second chill roll 13, the first polishing roll 14, the second polishing roll 15 and the third polishing roll 16 are aligned along a common plane oriented at a non-zero tilt angle 1 offset from the horizontal plane H1, which is parallel to the horizontal plane H2. In one embodiment, the non-zero tilt angle 1 is from 45 to 10 degrees. The first chill roll 12 and the second chill roll 13 are aligned along a common plane that is oriented at a non-zero tilt angle 3 offset from a vertical plane V. In one embodiment, the non-zero tilt angle 3 is from 10 to 45 degrees.

[0075] As shown in FIG. 3B, the linear jet 59 and/or the film displacement device 55 and the second chill roll 13 are aligned along a common plane that is oriented at a non-zero tilt angle 3 offset from a reference plane R. In one embodiment, the non-zero tilt angle 3 is from 10 to 45 measured counterclockwise from the reference plane R. In one embodiment, the non-zero tilt angle 3 is 0 to 90 degrees measured counterclockwise from the reference plane R.

[0076] As shown in FIG. 3A, the first polishing roll 14 engages and cools a second length L14 of a second side F2 of the polymer film F. The second side F2 is opposite the first side F1. The first length L13 is substantially equal to the second length L14. The first length L13 extends along an exterior surface of the second chill roll 13, between the first gap N12 and the second gap N13. The second length L14 extends along an exterior surface of the first polishing roll 14, between the second gap N13 and the third gap N14. The first side F1 of the polymer film F engages and extends a third length L15 on an exterior surface of the second polishing roll 15, between the third gap N14 and the fourth gap N15. The second side F2 of the polymer film F engages and extends a fourth length L16 on an exterior surface of the third polishing roll 16 between the fourth gap N15 and a line located opposite the fourth gap N15 (e.g., about 180 degrees around the third polishing roll 16). The location of the line located opposite the fourth gap N15 is determined by the angle of discharge of the polymer film F from the third polishing roll 16.

[0077] In one embodiment, the first length L13, the second length L14 and the third length L15 are substantially equal. In one embodiment, the first length L13, the second length L14, the third length L15 and the fourth length L16 are substantially equal. In one embodiment, the first length L13 and the second length L14 are established by relative positioning (e.g., positioning the rolls relative to one another) of the first chill roll 12, the second chill roll 13 and/or the first polishing roll 14. In one embodiment, the first length L13, the second length L14, the third length L15 and the fourth length L16 are established by relative positioning of the first chill roll 12, the second chill roll 13, the first polishing roll 14, the second polishing roll 15 and the third polishing roll 16.

[0078] In one embodiment, the first length L13 and the second length L14 are established by the second diameter D13 of the second chill roll and/or a third diameter D14 of the first polishing roll 14. In one embodiment, the third length L15 and/or the fourth length L16 are established by a third diameter D15 of the second polishing roll 15 and/or a fourth diameter D16 of the third

[0079] As shown in FIG. 4, the frame 20 includes a system 70 for vertical movement of the frame along an axis Y; horizontal movement of the frame 20 along an axis X, horizontal movement along an axis Z and angular movement co of horizontal plane H1 of the frame 20 relative to a base H4. The system 70 includes a set of roller jacks 72 (e.g., two shown in FIG. 4, and four shown in FIG. 5). Each of the roller jacks 72 has a roller device 74 rotationally secured thereto and a jacking device positioned to adjust the vertical position of the frame 20. The system 70 is configured to move the frame 20 relative to the die 19 to adjust the distance and angle of the frame 20, second chill roll 13 and first chill roll 12 relative to the die 19. The system 70 may also be employed to adjust the distance and angle of the frame 20, second chill roll 13 and film displacement device 55 and 65 (FIGS. 3B and 3C) relative to the die 19. The system 70 is operational and employed during setup of the casting apparatus 10 and the processing of the film during operation of the casting apparatus 10.

[0080] Although the present invention has been disclosed and described with reference to certain embodiments thereof, it should be noted that other variations and modifications may be made, and it is intended that the following claims cover the variations and modifications within the true scope of the invention.