High impact strength film containing single site catalyzed copolymer

• US 6,514,583 B1
• Filed: 09/17/1997
• Issued: 02/04/2003
• Est. Priority Date: 11/13/1992
• Status: Expired due to Term

• Current Assignee: Cryovac Incorporated (Sealed Air)
• Original Assignee: Cryovac Incorporated (Sealed Air)
• Inventors: Childress, Blaine C., Moffitt, Ronald D., Shah, Gautam P., Herran, Vincent W., Ahlgren, Kelly R., Babrowicz, Robert, Wofford, George D., Bekele, Solomon, Havens, Marvin R.
• Primary Examiner(s): TARAZANO, DONALD LAWRENCE
• Application Number:
  US08/932,946
• Time in Patent Office: 1,966 Days
• Field of Search: 428/34.1, 428/34.9, 428/35.2, 428/36.6, 428/36.7, 428/36.9, 428/36.91, 428/36.92, 428/347, 428/515, 428/516, 428/518, 428/520, 428/35.4, 428/332, 428/337, 526/348.1, 526/348.5, 525/240, 525/285, 525/221, 525/222, 525/74
• US Class Current: 428/34.9
• CPC Class Codes: B32B 2307/31 Heat sealable
• CPC Class Codes: B32B 2307/72 Density
• CPC Class Codes: B32B 2307/736 Shrinkable
• CPC Class Codes: B32B 27/08 of synthetic resin
• CPC Class Codes: B32B 27/304 comprising vinyl halide (co)polymers, e.g. PVC, PVDC, PVF, PVDF
• CPC Class Codes: B32B 27/306 comprising vinyl acetate or vinyl alcohol (co)polymers
• CPC Class Codes: B32B 27/308 comprising acrylic (co)polymers
• CPC Class Codes: B32B 27/32 comprising polyolefins comprising vinyl (co)polymers or acrylic (co)polymers B32B27/30
• CPC Class Codes: B32B 27/34 comprising polyamides
• CPC Class Codes: C08J 2323/08 Copolymers of ethene C08J2323/16 takes precedence
• CPC Class Codes: C08J 5/18 Manufacture of films or sheets
• CPC Class Codes: C08L 2205/02 containing two or more polymers of the same C08L -group
• CPC Class Codes: C08L 2205/03 containing three or more polymers in a blend
• CPC Class Codes: C08L 23/0815 Copolymers of ethene with aliphatic 1-olefins
• CPC Class Codes: C08L 2314/06 Metallocene or single site catalysts
• CPC Class Codes: C08L 2666/02 Organic macromolecular compounds, natural resins, waxes or and bituminous materials
• CPC Class Codes: C08L 2666/06 Homopolymers or copolymers of unsaturated hydrocarbons; Derivatives thereof
• CPC Class Codes: Y10S 526/943 Polymerization with metallocene catalysts
• CPC Class Codes: Y10T 428/1328 Shrinkable or shrunk [e.g., due to heat, solvent, volatile agent, restraint removal, etc.]
• CPC Class Codes: Y10T 428/1334 Nonself-supporting tubular film or bag [e.g., pouch, envelope, packet, etc.]
• CPC Class Codes: Y10T 428/1341 : Contains vapor or gas barrier, polymer derived from vinyl chloride or vinylidene chloride, or polymer containing a vinyl alcohol unit
• CPC Class Codes: Y10T 428/26 : Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
• CPC Class Codes: Y10T 428/266 : of base or substrate
• CPC Class Codes: Y10T 428/2826 : Synthetic resin or polymer
• CPC Class Codes: Y10T 428/31855 : Of addition polymer from unsaturated monomers
• CPC Class Codes: Y10T 428/31909 : Next to second addition polymer from unsaturated monomers
• CPC Class Codes: Y10T 428/31913 : Monoolefin polymer
• CPC Class Codes: Y10T 428/31928 : Ester, halide or nitrile of addition polymer
• CPC Class Codes: Y10T 428/31938 : Polymer of monoethylenically unsaturated hydrocarbon

Abstract

A heat-shrinkable film containing a homogeneous ethylene/alpha-olefin copolymer has a high impact strength and a high free shrink. The film can be a monolayer film or multilayer film, with the homogeneous ethylene/alpha-olefin copolymer present alone or in a blend, and in one or more film layers. The film is especially suited for use in heat-shrinkable bags, which can be used for the packaging of various products, especially meat.

Claims

1. A heat-shrinkable film comprising homogeneous linear ethylene/C_6-10 alpha-olefin copolymer, the heat-shrinkable film having an impact strength of from about 40 to 200 pounds and a total free shrink, at 185°

F., of from about 80 to 150 percent.

2. The heat-shrinkable film according to claim 1, wherein the heat-shrinkable film has an impact strength of from about 40 to 90 pounds.

3. The heat-shrinkable film according to claim 2, wherein the heat-shrinkable film has a total thickness of from about 1 to 3 mils.

4. The heat-shrinkable film according to claim 3, wherein the heat-shrinkable film has a total free shrink at 185°

F., of from about 80 to 120 percent.

5. The heat-shrinkable film according to claim 1, wherein the heat-shrinkable film is a monolayer film.

6. The heat-shrinkable film according to claim 1, wherein the heat-shrinkable film is a multilayer heat-shrinkable film, and the layer comprising the homogeneous ethylene/alpha olefin copolymer is an inner layer.

7. The heat-shrinkable film according to claim 6, wherein the homogeneous ethylene/alpha olefin copolymer is present in the inner layer in an amount of from about 60 to 100 weight percent, based on the weight of the inner layer, and wherein the inner layer has a thickness of about 1 to 3 mils.

8. The heat-shrinkable film according to claim 7, wherein the homogeneous ethylene/alpha olefin copolymer is present in the inner layer in an amount of about 80 to 100 weight percent, based on the weight of the inner layer, and wherein the inner layer has a thickness of about 1 to 2.5 mils.

9. The heat-shrinkable film according to claim 8, wherein the homogeneous ethylene/alpha olefin copolymer is present in the inner layer in an amount of about 90 to 100 weight percent, based on the weight of the inner layer.

10. The heat-shrinkable film according to claim 7, wherein the homogeneous ethylene/alpha olefin copolymer is a first component present in a composition which further comprises a second component comprising least one member selected from the group consisting of another ethylene/alpha-olefin copolymer, ethylene/vinyl acetate copolymer, ethylene/vinyl ester copolymer, ethylene/acrylic acid copolymer, propylene/ethylene copolymer, polyethylene homopolymer, polypropylene homopolymer, and ionomer, wherein the second component is present in the composition in an amount of from about 1 to 40 weight percent, based on the weight of the composition.

11. The beat-shrinkable film according to claim 10, wherein the first component and the second component are in a uniform blend.

12. The heat-shrinkable film according to claim 11, wherein the homogeneous ethylene/alpha olefin copolymer is present in a composition which further comprises at least one member selected from the group consisting of a maleic anhydride grafted ethylene/alpha-olefin copolymer, maleic anhydride grafted ethylene/vinyl acetate copolymer, maleic anhydride grafted ethylene/vinyl ester copolymer, maleic anhydride grafted ethylene/acrylic acid copolymer, maleic anhydride grafted propylene/ethylene copolymer, maleic anhydride grafted polyethylene homopolymer, maleic anhydride grafted polypropylene homopolymer, and maleic anhydride grafted ionomer.

13. The heat-shrinkable film according to claim 6, wherein the multilayer heat-shrinkable film further comprises a barrier layer and an outer sealant layer.

14. The heat-shrinkable film according to claim 13, wherein the outer sealant layer is a first outer layer, and an outer abuse layer is a second outer layer.

15. The heat-shrinkable film according to claim 13, further comprising at least one tie layer between the barrier layer and the first outer layer.

16. The heat-shrinkable film according to claim 15, wherein the tie layer between the barrier layer and the first outer layer is a first tie layer, and a second tie layer is between the barrier layer and the second outer layer.

17. The heat-shrinkable film according to claim 1, wherein the film is a multilayer heat-shrinkable film, and the film layer comprising the homogeneous ethylene/alpha-olefin copolymer is a first outer film layer.

18. The heat-shrinkable film according to claim 17, wherein the homogeneous ethylene/alpha-olefin copolymer in the first outer film layer is a first homogeneous ethylene/alpha-olefin copolymer, and wherein the film further comprises a second outer film layer comprising a second homogeneous ethylene/alpha-olefin copolymer.

19. The heat-shrinkable film according to claim 18, wherein the first homogeneous ethylene/alpha-olefin copolymer is identical to the second homogeneous ethylene/alpha-olefin copolymer.

20. The heat-shrinkable film according to claim 18, the first and second outer layers are identical in chemical composition and thickness, and the heat-shrinkable film is symmetrical.

21. The heat-shrinkable film according to claim 19, wherein:

the heat-shrinkable film comprises a first inner layer, a second inner layer, and a third inner layer;

the first inner layer is a first tie layer, the second inner layer is an O₂-barrier layer, and the third inner layer is a second tie layer;

the first and second outer layers are identical in chemical composition and thickness;

the first and second tie layers are identical in chemical composition and thickness; and

the heat-shrinkable film is symmetrical.

22. The heat-shrinkable film according to claim 1, wherein the ethylene/alpha-olefin copolymer is a copolymer of ethylene and an alpha-olefin comprising hexene or octene.

23. The heat-shrinkable film according to claim 1, wherein the homogeneous ethylene/alpha-olefin copolymer has a density of from 0.90 to 0.93 g/cm³.

24. A heat-shrinkable film comprising homogeneous linear ethylene/C_6-10 alpha-olefin copolymer, the heat-shrinkable film having a thickness of from 1 to 3 mils, an impact strength of from about 80 to 250 pounds, and a total free shrink, at 185°

F., of from about 30 to 150 percent.

25. The heat-shrinkable film according to claim 24, wherein the heat-shrinkable film has an impact strength of from about 80 to 200 pounds, and a total free shrink, at 185°

F., of from about 50 to 120 percent.

26. The heat-shrinkable film according to claim 24, wherein the heat-shrinkable film is a monolayer film.

27. The heat-shrinkable film according to claim 24, wherein the heat-shrinkable film is a multilayer heat-shrinkable film, and the layer comprising the homogeneous ethylene/alpha olefin copolymer is an inner layer.

28. The heat-shrinkable film according to claim 24, wherein the ethylene/alpha-olefin copolymer is a copolymer of ethylene and an alpha-olefin comprising hexene or octene.

29. The heat-shrinkable film according to claim 24, wherein the homogeneous ethylene/alpha-olefin copolymer has a density of from 0.90 to 0.93 g/cm³.

30. An article comprising a heat-shrinkable film comprising a film layer comprising homogeneous linear ethylene/C_6-10 alpha-olefin copolymer, wherein the heat-shrinkable film has an impact strength of from about 40 to 200 pounds and a total free shrink, at 185°

F., of from about 80 to 150 percent, and wherein the article is a member selected from the group consisting of a bag and a casing.

31. The heat-shrinkable film according to claim 30, wherein the ethylene/alpha-olefin copolymer is a copolymer of ethylene and an alpha-olefin comprising hexene or octene.

32. The heat-shrinkable film according to claim 30, wherein the homogeneous ethylene/alpha-olefin copolymer has a density of from 0.90 to 0.93 g/cm³.

37. The heat-shrinkable film according to claim 32, wherein the homogeneous ethylene/alpha-olefin copolymer is present in an outer film layer.

45. The heat-shrinkable film according to claim 30, wherein the heat-shrinkable film is biaxially oriented.

46. The heat-shrinkable film according to claim 45, wherein the film is a multilayer film with the homogeneous ethylene/alpha-olefin copolymer present in a first layer, the film further comprising a second layer comprising an O₂-barrier layer.

47. The heat-shrinkable film according to claim 45, wherein the homogeneous ethylene/alpha-olefin copolymer is a metallocene-catalyzed ethylene/alpha-olefin copolymer.

33. A heat-shrinkable film comprising homogeneous linear ethylene/C_6-10 alpha-olefin copolymer, the heat-shrinkable film having an impact strength of from about 40 to 200 pounds and a total free shrink, at 185°

F., of from about 80 to 150 percent, wherein the film is biaxially oriented.

34. The heat-shrinkable film according to claim 33, herein the ethylene/alpha-olefin copolymer is a copolymer of ethylene and an alpha-olefin comprising hexene or octene.

35. The heat-shrinkable film according to claim 33, wherein the homogeneous ethylene/alpha-olefin copolymer has a density of from 0.90 to 0.93 g/cm³.

36. The heat-shrinkable film according to claim 33, wherein the film is a multilayer film with homogeneous ethylene/alpha-olefin copolymer present in a first layer, the film further comprising a second layer comprising an O₂-barrier layer.

38. The heat-shrinkable film according to claim 36, wherein the homogeneous ethylene/alpha-olefin copolymer is present in an inner film layer.

39. The heat-shrinkable film according to claim 33, wherein the homogeneous ethylene/alpha-olefin copolymer is a metallocene-catalyzed ethylene/alpha-olefin copolymer.

40. The heat-shrinkable film according to claim 33, wherein the heat-shrinkable film has an impact strength of from about 40 to 90 pounds.

41. The heat-shrinkable film according to claim 40, wherein the heat-shrinkable film has a total thickness of from about 1 to 3 mils.

42. The heat-shrinkable film according to claim 41, wherein the heat-shrinkable film has a total free shrink at 185°

F., of from about 80 to 120 percent.

43. The heat-shrinkable film according to claim 42, wherein the homogeneous ethylene/alpha-olefin copolymer is a first component present in a composition which further comprises a second component comprising at least one member selected from the group consisting of another ethylene/alpha-olefin copolymer, ethylene/vinyl acetate copolymer, ethylene/vinyl ester copolymer, ethylene/acrylic acid copolymer, propylene/ethylene copolymer, polyethylene homopolymer, polypropylene homopolymer, and ionomer, wherein the second component is present in the composition in an amount of from about 1 to 40 weight percent, based on the weight of the composition.

44. The heat-shrinkable film according to claim 42, wherein the homogeneous ethylene/alpha-olefin copolymer is present in a composition which further comprises at least one member selected from the group consisting of a maleic anhydride grafted ethylene/alpha-olefin copolymer, maleic anhydride grafted ethylene/vinyl acetate copolymer, maleic anhydride grafted ethylene/vinyl ester copolymer, maleic anhydride grafted ethylene/acrylic acid copolymer, maleic anhydride grafted propylene/ethylene copolymer, maleic anhydride grafted polyethylene homopolymer, maleic anhydride grafted polypropylene homopolymer, and maleic anhydride grafted ionomer.

48. A heat-shrinkable film comprising a homogeneous linear ethylene/C_6-10 alpha-olefin copolymer having a melt index of 1 g/10 min, shrink at 200°

F. of at least 38% shrink in each direction and exhibiting a peak instrumented impact of at least 31 pounds.

49. A heat-shrinkable film comprising a homogeneous linear ethylene/alpha-olefin copolymer, the film having a free shrink at 200°

F. of from 13% to 55% in the longitudinal direction and from 10% to 53% in the transverse direction, and a peak impact strength of from 31 to 86.8 pounds.

50. The heat-shrinkable film according to claim 49, wherein the alpha-olefin has from 6 to 10 carbon atoms.

51. The heat-shrinkable film according to claim 50, wherein the homogeneous linear ethylene/alpha-olefin copolymer has a density of from 0.898 to 0.922 g/cm³.