Method for making permeable film

• US 6,427,419 B2
• Filed: 02/12/2001
• Issued: 08/06/2002
• Est. Priority Date: 11/24/1998
• Status: Expired due to Fees

• Current Assignee: Cryovac Incorporated (Sealed Air)
• Original Assignee: Cryovac Incorporated (Sealed Air)
• Inventors: Owensby, Joseph E.
• Primary Examiner(s): Rada, Rinaldi I
• Assistant Examiner(s): Tawfik, Sameh
• Application Number:
  US09/781,717
• Publication Number:
  US 20010005970A1
• Time in Patent Office: 540 Days
• Field of Search: 219/384, 264/154, 264/41, 534/41, 533/96
• US Class Current: 53/396
• CPC Class Codes: B29C 55/005 characterised by the choice of materials
• CPC Class Codes: B29K 2105/04 cellular or porous
• CPC Class Codes: B29K 2105/16 Fillers

Abstract

In a method for making a permeable film, a physical force is applied to a film of a first material containing particles of a second material which is different from the first material. The second material has a higher susceptibility to the physical force than does the first material. Applying the physical force to the film affects the particles which in turn affect the first material of the film, thereby increasing permeability of the film.

Claims

1. A method of increasing the permeability of a film comprising:

providing a film having

a thickness of from about 0.3 mil to about 9.8 mils;

at least one layer comprising a first material comprising a polymeric material selected from the group consisting of olefinic resins, poly(vinyl chloride), ionomers, nylons, and homo- and co-polymers of ethylene; and

a plurality of solid particles incorporated into the at least one layer, wherein the solid particles;

comprise a second material different from the first material; and

have a higher susceptibility than the first material to a selected physical force selected from the group consisting of spark discharge, inductive heating, infrared heating, magnetic force, ultrasonic excitation, microwave irradiation, e-beam irradiation, and laser irradiation; and

applying the selected physical force to affect the particles and create perforations in the at least one layer, whereby the permeability of the at least one layer is increased.

2. The method of claim 1 wherein the selected physical force comprises inductive heating.

3. The method of claim 1 wherein the selected physical force comprises magnetic force.

4. The method of claim 1 wherein the selected physical force comprises ultrasonic excitation.

5. The method of claim 1 wherein the selected physical force comprises microwave irradiation.

6. The method of claim 1 wherein the selected physical force comprises e-beam irradiation.

7. The method of claim 1 wherein the selected physical force comprises laser irradiation.

8. The method of claim 1 wherein:

the film comprises a multiple layer film; and

at least one of the layers is an oxygen-barrier layer incorporating the plurality of solid particles in an amount of between about 0.4% and about 4% based on the weight of the film, wherein the particles have a diameter of between about 2.5 μ

m and about 25 μ

m.

9. The method of claim 1 wherein the film comprises at least two layers.

10. The method of claim 1 wherein:

the film comprises at least two layers; and

the plurality of solid particles are incorporated into only one layer of the at least two layers.

11. The method of claim 1 wherein:

the film comprises at least two layers; and

at least one of the layers is an oxygen-barrier layer incorporating the plurality of solid particles.

12. The method of claim 1 wherein the film comprises a peelable film.

13. The method of claim 1 wherein the film has a Young'"'"'s modulus as measured by ASTM D882 of at least about 200 MPa.

14. The method of claim 1 wherein the film comprises an oriented film.

15. The method of claim 1 wherein the film comprises a heat-shrinkable film having a total free shrink of from about 5% to about 150% at 85°

C. in accordance with ASTM D2732.

16. The method of claim 1 wherein the at least one layer incorporates the particles in an amount of between about 0.4% and about 4% based on the weight of the film.

17. The method of claim 1 wherein the at least one layer incorporates the particles in an amount of between about 0.6% and about 3% based on the weight of the film.

18. The method of claim 1 wherein the second material comprises metal.

19. The method of claim 1 wherein the second material comprises metal and the selected physical force comprises inductive heating.

20. The method of claim 1 wherein the second material comprises iron and the selected physical force comprises inductive heating.

21. The method of claim 1 wherein the second material comprises carbon black.

22. The method of claim 1 wherein the second material comprises carbon black and the selected physical force comprises infrared heating.

23. The method of claim 1 wherein the second material comprises ferromagnetic material and the selected physical force comprises magnetic force.

24. The method of claim 1 wherein the selected physical force is applied while the film is under tension.

25. The method of claim 1 wherein the selected physical force is applied to create the perforations while the film is under tension and further comprising subsequently releasing the film from the tension to reduce the size of the perforations.

26. The method of claim 1 wherein the particles have a diameter of between about 2.5 μ

m and about 25 μ

m.

27. The method of claim 1 wherein the particles have a diameter of between about 5 μ

m and about 18 μ

m.

28. The method of claim 1 wherein the particles have a diameter of less than about 5 μ

m.

29. The method of claim 1 wherein the particles have a diameter of less than or equal to the film thickness.

30. The method of claim 1 wherein the particles have a diameter substantially the same as the film thickness.

31. The method of claim 1 wherein the at least one layer has a thickness of less than or equal to about 2 mils.

32. The method of claim 1 further comprising forming a package comprising the film before applying the physical force to the film.

33. The method of claim 1 further comprising forming a package comprising the film and enclosing a product, before applying the physical force to the film.

34. The method of claim 1 further comprising forming a package comprising the film and enclosing a meat product, before applying the physical force to the film.

35. The method of claim 1 wherein the selected physical force removes the particles from the at least one layer to create the perforations.