Heat sealable films and articles made therefrom

• US 5,530,065 A
• Filed: 05/25/1995
• Issued: 06/25/1996
• Est. Priority Date: 01/07/1992
• Status: Expired due to Term

• Current Assignee: Exxon Chemical Patents Inc. (Exxon Mobil Corporation)
• Original Assignee: Exxon Chemical Patents Inc. (Exxon Mobil Corporation)
• Inventors: Farley, James M., Trudell, Barry C., Stehling, Ferdinand C., Kurtzman, Myron B., Meka, Prasadarao
• Primary Examiner(s): Seidleck, James J.
• Assistant Examiner(s): Truong, Duc
• Application Number:
  US08/449,870
• Time in Patent Office: 397 Days
• Field of Search: 525/191, 525/192, 525/195, 525/240, 525/242, 428/34.1, 428/35.7, 428/349, 428/500, 428/515, 428/516, 156/308.4
• US Class Current: 525/240
• CPC Class Codes: C08J 2323/04 Homopolymers or copolymers of ethene
• CPC Class Codes: C08J 5/18 Manufacture of films or sheets
• CPC Class Codes: C08L 23/0815 Copolymers of ethene with aliphatic 1-olefins
• CPC Class Codes: C08L 2314/02 Ziegler natta catalyst
• CPC Class Codes: C08L 2314/06 Metallocene or single site catalysts
• CPC Class Codes: C08L 2666/06 Homopolymers or copolymers of unsaturated hydrocarbons; Derivatives thereof
• CPC Class Codes: Y10T 428/13 Hollow or container type article [e.g., tube, vase, etc.]
• CPC Class Codes: Y10T 428/1352 Polymer or resin containing [i.e., natural or synthetic]
• 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

Abstract

Heat sealed articles and heat sealable films comprising a polymer blend of a first polymer having a narrow molecular weight and composition distribution and a second polymer having a broad molecular weight distribution and composition distribution. The articles and films have significantly improved physical characteristics and remarkably low heat seal initiation temperatures, high seal strength, high hot tack and therefore provide improved processibility and higher line speeds on commercial heat sealing equipment.

Claims

1. A polymer blend comprising from about 40 to about 99 weight percent of at least one first ethylene interpolymer produced using a metallocene catalyst system, said first ethylene interpolymer having a molecular weight distribution of 3 or less and a composition distribution breadth index greater than 50 percent and from about 1 to about 60 weight percent of at least one second ethylene interpolymer produced using a Ziegler-Natta catalyst system, said second ethylene interpolymer having a molecular weight distribution greater than 3 and a composition distribution breadth index less than 50 percent.

2. The interpolymer blend of claim 1 wherein the first polymer has a composition distribution breadth index greater than 60%.

3. The interpolymer blend of claim 1 wherein the first polymer has a composition distribution breadth index greater than 70%.

4. The polymer blend of claim 1 wherein said polymer blend comprises from about 60 to 99 weight percent of said first interpolymer.

5. The polymer blend of claim 1 wherein said polymer blend comprises 60 to 90 weight percent of said first interpolymer.

6. The polymer blend of claim 1 wherein said polymer blend comprises 60 to 90 weight percent of said first interpolymer of said first component.

7. The interpolymer blend of claim 1 wherein said first polymer has a molecular weight distribution less than about 2.5.

8. The interpolymer blend of claim 1 wherein said first polymer has a density in the range of about 0.875 g/cm³ to about 0.96 g/cm³.

9. The polymer blend of claim 1 wherein said first interpolymer is a copolymer of ethylene.

10. The interpolymer blend of claim 1 wherein said second polymer is a LLDPE.

11. The polymer blend of claim 1 wherein said blend has a density in the range of 0.88 to 0.94 g/cm³ and a melt index of 0.5 to 20 dg/min.

12. A film comprising at least one layer of from about 40 to about 99 weight percent of an ethylene copolymer or terpolymer produced using a metallocene catalyst system, said ethylene copolymer or terpolymer having a molecular weight distribution less than about 3 and a composition distribution breadth index greater than 50 percent and from about 1 to 60 weight percent of an ethylene interpolymer produced using a Ziegler-Natta catalyst system, said ethylene interpolymer having a molecular weight distribution greater than 3 and a composition distribution breadth index less than 50 percent.

13. The film of claim 12 wherein the ethylene copolymer or terpolymer has a composition distribution breadth index greater than 60%.

14. The film of claim 12 wherein said polymer blend comprises from about 60 to 98 weight percent of said ethylene copolymer or terpolymer.

15. The film of claim 12 wherein said ethylene interpolymer is a LLDPE.

16. The film of claim 12 wherein said film has at least one additional resin layer selected from at least one of the group consisting of LLDPE, LDPE, HDPE, PP or the like or a blend thereof.

17. The film of claim 12 wherein said film when used as a seal layer has a seal initiation temperature less than 100°

C.

18. The film of claim 12 wherein said film when used as a seal layer has a plateau-on-set temperature less than 120°

C.

19. The film of claim 12 wherein said film is a single layer.

20. The film of claim 12 wherein said film at a sealing temperature of about 95°

C. has a seal strength at room temperature greater than about 3N/cm.

21. The film of claim 12 wherein said film at a sealing temperature of about 100°

C. has a seal strength at room temperature greater than about 5N/cm.

22. A heat sealable film comprising a polymer blend of from about 60 to about 99 weight percent of the total weight of the polymer blend of at least one first ethylene interpolymer produced using a metallocene catalyst system, said first ethylene interpolymer having a molecular weight distribution less than about 3 and a composition distribution breadth index greater than 50 percent and from about 1 to about 40 weight percent of the total weight of the polymer blend of at least one second interpolymer produced using a Ziegler-Natta catalyst system, said second ethylene interpolymer having a molecular weight distribution greater than 3 and a composition distribution breadth index less than 50 percent.

23. The film of claim 22 wherein said film when used as a seal layer has a seal initiation temperature less than 100°

C.

24. The film of claim 22 wherein said film has at least one additional resin layer selected from at least one of the group consisting of LLDPE, LDPE, HDPE, PP or the like or a blend thereof.

25. A method of forming an article of manufacture comprising the step of:

pressing at least two portions or the same portion of said article together to form a seal at a temperature sufficient to soften at least one portion of said article wherein said softened portion comprises a polymer blend of from about 40 to about 99 weight percent of a first ethylene interpolymer produced using a metallocene catalyst system, said first ethylene interpolymer having a molecular weight distribution less than about 3 and a composition distribution breadth index greater than 50 percent and from about 1 to about 40 weight percent of a second ethylene interpolymer produced using a Ziegler-Natta catalyst system, said second ethylene interpolymer having a molecular weight distribution greater than 3 and a composition distribution breadth index less than 50 percent.

26. The method of claim 25 wherein said temperature is below about 110°

C.

27. The method of claim 25 wherein said temperature is less than 100°

C.

28. The method of claim 25 wherein said first component comprises from about 60 to 90 weight percent of the first ethylene interpolymer.

29. The method of claim 25 wherein the first polymer has a composition distribution breadth index greater than 60%.

30. The method of claim 25 wherein said polymer blend at a sealing temperature of 95°

C. has a seal strength of about 3N/cm.

31. An article of manufacture comprising a seal layer, said seal layer comprising from about 60 to about 99 weight percent of a first ethylene interpolymer produced using a metallocene catalyst system, said first ethylene interpolymer having a molecular weight distribution less than about 3 and a composition distribution breadth index greater than 50 percent and from about 1 to about 40 weight percent of a second ethylene interpolymer produced using a Ziegler-Natta catalyst system, said second ethylene interpolymer having a molecular weight distribution greater than 3 and a composition distribution breadth index less than 50 percent.

32. The article of claim 31 wherein said film when used as a seal layer has a seal initiation temperature less than 100°

C.

33. The article of claim 31 wherein the first ethylene interpolymer has a composition distribution breadth index greater than 70%.

34. The article of manufacture 31 claim 32 wherein said article further comprises additional layers.

35. The article of manufacture 31 claim 32 is a container wherein said seal layer comprises from about 60 to about 90 weight percent of the first ethylene interpolymer and from about 10 to about 40 weight percent of the second ethylene interpolymer.

36. A container comprising a body and a sealing member wherein said member comprises a seal layer, said seal layer comprising a polymer blend of from about 40 to about 99 weight percent of a first ethylene interpolymer produced using a metallocene catalyst system, said first ethylene interpolymer having a molecular weight distribution less than about 3 and a composition distribution breadth index greater than 50 percent and from about 1 to about 60 weight percent of a second ethylene interpolymer produced using a Ziegler-Natta catalyst system, said second ethylene interpolymer having a molecular weight distribution greater than 3 and a composition distribution breadth index less than 50 percent.

37. The container of claim 36 wherein said sealing member is sealed to said body.

38. The container of claim 36 wherein said seal layer comprises from about 50 to about 99 weight percent of said first ethylene interpolymer.

39. The container of claim 36 wherein said seal layer comprises from about 60 to about 98 weight percent of said first component.

40. The container of claim 36 wherein said seal layer at a sealing temperature of about 95°

C. has a seal strength of greater than 3N/cm.

41. The container of claim 36 wherein said seal layer has a composition distribution breadth index greater than about 60%.

42. The container of 36 37 wherein said seal layer comprises LLDPE as said second ethylene interpolymer.