Methods and devices for processing polymer films

• US 20040099993A1
• Filed: 11/27/2002
• Published: 05/27/2004
• Est. Priority Date: 11/27/2002
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Merrill, William Ward, Ruff, Andrew T., Jackson, Jeffery N., Thompson, Desiree L.
• Granted Patent: US 6,936,209 B2
• Time in Patent Office: Days
• US Class Current: 264/290.2
• CPC Class Codes: B29C 55/08 transverse to the direction of feed
• CPC Class Codes: B29C 55/165 Apparatus therefor
• CPC Class Codes: Y10S 425/041 Reshape

Abstract

Stretched polymeric films can be used in a variety of applications, including optical applications. The stretching conditions and shape of the stretching tracks in a stretching apparatus can determine or influence film properties. Take-away systems can be used to receive the film after stretching. The configuration of the take-away system can, in at least some instances, influence final film properties.

Claims

1. An apparatus for processing a film, the apparatus comprising:

a conveyor configured and arranged to convey the film along a machine direction within the apparatus, the conveyor comprising gripping members that are configured and arranged to hold opposing edge portions of the film, a portion of the conveyor is configured and arranged to provide diverging paths along which the gripping members move to stretch the film; and

an isolated take-away system that receives the film from the conveyor after stretching the film, the take-away system comprising opposing tracks and gripping members configured and arranged to grasp opposing take-away regions of the film after a desired amount of stretching and convey the opposing take-away regions of the film along the opposing tracks, wherein the opposing tracks define a region in which at least a portion of the opposing tracks are angled toward each other.

2. The apparatus of claim 1, wherein the opposing tracks are angled toward each other along an entire length of the opposing tracks.

3. The apparatus of claim 1, wherein each of the opposing tracks comprises at least a first track section and a second track section, wherein the first track sections of the opposing tracks are angled toward each other.

4. The apparatus of claim 1, wherein each of the opposing tracks comprises at least a first track section and a second track section, wherein the second track sections of the opposing tracks are angled toward each other.

5. The apparatus of claim 1, wherein the portions of the opposing tracks are each angled toward each other at an angle of no more than 3°

relative to the direction along which the film is conveyed.

6. The apparatus of claim 1, wherein take-away system is disposed at an angle relative to the direction along which the film is conveyed.

7. A method of processing a film, the method comprising:

holding opposing edge portions of a film using gripping members;

conveying the film along diverging paths and in a machine direction within a stretching region of a stretching apparatus to stretch the film;

receiving the film after stretching in an isolated take-away system by grasping opposing take-away regions of the films using opposing gripping members of the take-away system; and

conveying the film through a portion of the take-away system in which the opposing gripping members are angled toward each other.

8. The method of claim 7, wherein the opposing gripping members are angled toward each other along an entire length of the take-away system.

9. The method of claim 7, wherein the take-away system comprises at least a first set of opposing gripping members and a second set of opposing gripping members, wherein the first set of opposing gripping members are angled toward each other.

10. The method of claim 7, wherein the take-away system comprises at least a first set of opposing gripping members and a second set of opposing gripping members, wherein the second set of opposing gripping members are angled toward each other.

11. The method of claim 7, wherein the portion of the opposing gripping members are angled toward each other at an angle of no more than 3°

relative to the direction along which the film is conveyed.

12. An apparatus for processing a film, the apparatus comprising:

a conveyor comprising gripping members that hold opposing edge portions of the film and convey, under influence of a drive member, the film along a machine direction within the apparatus, wherein a portion of the conveyor is configured and arranged to provide diverging paths along which the gripping members move to stretch the film; and

an isolated take-away system that receives the film from the conveyor after stretching the film, the take-away system comprising a first set of opposing tracks, a second set of opposing tracks, a plurality of first gripping members configured and arranged to grasp opposing first take-away regions of the film after a desired amount of stretching and convey the film along the first set opposing tracks, and a plurality of second gripping members configured and arranged to grasp opposing second take-away regions of the film and convey the film along the second set of opposing tracks, wherein the second take-away regions are nearer a center of the film than the first take-away regions.

13. The apparatus of claim 12, wherein the second gripping members are configured and arranged to move from a first position disposed at least partially between the first gripping members and a second position in which the second gripping members are not partially disposed between the first gripping members.

14. The apparatus of claim 12, wherein the first gripping members are angled toward each other.

15. The apparatus of claim 12, wherein the second gripping members are angled toward each other.

16. An apparatus for processing a film, the apparatus comprising:

a conveyor comprising gripping members that hold opposing edge portions of the film and convey, under influence of a drive member, the film along a machine direction within the apparatus, wherein a portion of the conveyor is configured and arranged to provide diverging paths along which the gripping members move to stretch the film; and

an isolated take-away system that receives the film from the conveyor after stretching the film, the take-away system comprising opposing tracks and a plurality of gripping members configured and arranged to grasp opposing take-away regions of the film after a desired amount of stretching and convey the opposing take-away regions of the film along the opposing tracks, wherein the opposing tracks are disposed at an angle of at least 1°

with respect to the machine direction.

17. The apparatus of claim 16, wherein the at least a portion of the opposing tracks of the take-away system are angled toward each other.

18. The apparatus of claim 16, wherein the opposing tracks are disposed at different angles with respect to the machine direction.

19. The apparatus of claim 16, wherein the opposing tracks of the take-away system are configured and arranged to grasp the opposing take-away regions of the film at a position in which the opposing take-away regions of the film have a same transverse directional draw ratio.

20. The apparatus of claim 16, wherein the opposing tracks of the take-away system are configured and arranged to grasp the opposing take-away regions of the film at a position in which the opposing take-away regions of the film have different transverse directional draw ratios.

21. The apparatus of claim 16, wherein the diverging paths are configured and arranged to stretch the film so that a centerline of the film is angled with respect to a machine direction of the conveyor prior to stretching the film.

22. An apparatus for processing a film, the apparatus comprising:

a conveyor comprising gripping members that hold opposing edge portions of the film and convey, under influence of a drive member, the film along a machine direction within the apparatus, wherein a portion of the conveyor is configured and arranged to provide diverging paths along which the gripping members move to stretch the film; and

an isolated take-away system that receives the film from the conveyor after stretching the film, the take-away system comprising opposing tracks and a plurality of gripping members configured and arranged to grasp opposing take-away regions of the film after a desired amount of stretching and convey the opposing take-away regions of the film along the opposing tracks, wherein the apparatus is configured and arranged to allow selection of a final transverse direction draw ratio of the film by changing a position of the isolated take-away system with respect to a position of the conveyor.

23. An apparatus for processing a film, the apparatus comprising:

a conveyor configured and arranged to convey the film along a machine direction within the apparatus, the conveyor comprising gripping members that are configured and arranged to hold opposing edge portions of the film, a portion of the conveyor is configured and arranged to provide diverging paths along which the gripping members move to stretch the film; and

an isolated take-away system that receives the film from the conveyor after stretching the film, the take-away system comprising opposing tracks and gripping members configured and arranged to grasp opposing take-away regions of the film after a desired amount of stretching and convey the opposing take-away regions of the film along the opposing tracks, wherein the opposing tracks define a region in which at least a portion of the opposing tracks are angled away from each other.

24. The apparatus of claim 23, wherein the opposing tracks are angled away from each other along an entire length of the opposing tracks.

25. The apparatus of claim 23, wherein each of the opposing tracks comprises at least a first track section and a second track section, wherein the first track sections of the opposing tracks are angled away from each other.

26. The apparatus of claim 23, wherein each of the opposing tracks comprises at least a first track section and a second track section, wherein the second track sections of the opposing tracks are angled away from each other.

27. The apparatus of claim 23, wherein the portions of the opposing tracks are each angled away from each other at an angle of no more than 3°

relative to the direction along which the film is conveyed.

28. An apparatus for processing a film, the apparatus comprising:

a conveyor configured and arranged to convey the film along a machine direction, the conveyor comprising gripping members that are configured and arranged to hold opposing edge portions of the film;

a stretching region in which the gripping members are configured arranged to travel along diverging paths to stretch the film; and

a post-conditioning region disposed after the stretching region and comprising at least one zone in which the gripping members are configured and arranged to travel along converging paths.

29. The apparatus of claim 28, wherein the post-conditioning region comprises at least a first zone and a second zone, wherein the gripping members are configured and arranged to travel along paths converging at a first angle in the first zone and along paths converging at a second angle in the second zone, wherein the first and second angles are substantially different.

30. The apparatus of claim 29, wherein the first angle is no more than about 3°

and the second angle is at least about 15°

.

31. The apparatus of claim 28, wherein the converging paths in at least one zone of the post-conditioning region converge at an angle of no more than 3°

.

32. The apparatus of claim 28, wherein the converging paths in at least one zone of the post-conditioning region converge at an angle of at least 15°

.

33. The apparatus of claim 28, wherein the converging paths in at least one zone of the post-conditioning region converge at an angle of in the range of 20°

to 30°

.