Heat shrinkable multilayer film or tube that exhibits shrink stability after orientation

• US 20090029081A1
• Filed: 07/23/2007
• Published: 01/29/2009
• Est. Priority Date: 07/23/2007
• Status: Active Grant

• Current Assignee: Dow Global Technologies LLC (Dow, Inc.)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Lee, I-Hwa, Schenck, Heiko E.
• Granted Patent: US 8,202,590 B2
• Time in Patent Office: Days
• US Class Current: 428/34.900
• CPC Class Codes: B32B 1/08 Tubular products
• CPC Class Codes: B32B 2270/00 Resin or rubber layer containing a blend of at least two different polymers
• CPC Class Codes: B32B 2307/518 bi-axially
• CPC Class Codes: B32B 2307/71 Resistive to light or to UV
• CPC Class Codes: B32B 2307/7244 Oxygen barrier
• CPC Class Codes: B32B 2307/736 Shrinkable
• CPC Class Codes: B32B 2439/00 Containers; Receptacles
• CPC Class Codes: B32B 27/08 of synthetic resin
• CPC Class Codes: B32B 27/20 using fillers, pigments, thixotroping agents
• 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: B32B 27/36 comprising polyesters
• CPC Class Codes: Y10T 428/1328 Shrinkable or shrunk [e.g., due to heat, solvent, volatile agent, restraint removal, etc.]
• CPC Class Codes: Y10T 428/1341 Contains vapor or gas barrier, polymer derived from vinyl chloride or vinylidene chloride, or polymer containing a vinyl alcohol unit
• CPC Class Codes: Y10T 428/1352 Polymer or resin containing [i.e., natural or synthetic]
• CPC Class Codes: Y10T 428/31797 Next to addition polymer from unsaturated monomers
• CPC Class Codes: Y10T 428/31909 Next to second addition polymer from unsaturated monomers
• CPC Class Codes: Y10T 428/31928 : Ester, halide or nitrile of addition polymer

Abstract

Heat shrinkable oriented multilayer films are disclosed that comprise a structural layer, a heat sealing layer and a gas barrier layer. The structural layer comprises a polymer selected from the group consisting of copolymers of ethylene and a C₃ to C₈, -ethylenically unsaturated carboxylic acid, ionomers of the copolymers, polyesters, and blends thereof. The heat sealing layer comprises a polymer selected from the group consisting of ethylene vinyl acetate copolymers, ethylene alkyl acrylate copolymers, ethylene alkyl methacrylate copolymers, polyethylene, and blends thereof. The barrier layer, which is positioned between the structural and heat sealing layer, comprises at least one ethylene vinyl alcohol copolymer that has from about 2 to about 8 mol % 1,2-glycol structural units incorporated in the copolymer backbone chain. The films are particularly suitable for use in manufacture of shrinkbags.

Claims

1. A multilayer oriented heat shrinkable film comprising:

A) a structural layer comprising a polymer selected from the group consisting of copolymers of ethylene and a C₃ to C₈ α

,β

-ethylenically unsaturated carboxylic acid, ionomers of said copolymers, polyesters, and blends thereof;

B) a heat sealing layer comprising a polymer selected from the group consisting of ethylene vinyl acetate copolymers, ethylene alkyl acrylate copolymers, ethylene alkyl methacrylate copolymers, polyethylene, and blends thereof; and

C) a gas barrier layer comprising at least one ethylene vinyl alcohol copolymer, said ethylene vinyl alcohol copolymer having from about 2 to about 8 mol % 1,2 glycol structural units present in the polymer chain and said gas barrier layer being positioned between said structural layer and said heat sealing layer;

characterized in that said film is capable of shrinking to a size that is at least 25% less than its original size on initial exposure of said film to a temperature of 85°

C. for at least one minute.

2. A multilayer heat shrinkable film of claim 1 that is biaxially oriented.

3. A multilayer heat shrinkable film of claim 1 wherein said C₃ to C₈ α

,β

-ethylenically unsaturated carboxylic acid is acrylic acid or methacrylic acid.

4. A multilayer heat shrinkable film of claim 1 wherein said copolymer of ethylene and a C₃ to C₈ α

,β

-ethylenically unsaturated carboxylic acid additionally comprises copolymerized units of at least one other comonomer.

5. A multilayer heat shrinkable film of claim 1 wherein the structural layer comprises an ionomer of a copolymer of ethylene and a C₃ to C₈ α

,β

-ethylenically unsaturated carboxylic acid.

6. A multilayer heat shrinkable film of claim 1 wherein the structural layer comprises a polyester.

7. A multilayer heat shrinkable film of claim 1 wherein the structural layer comprises an ionomer.

8. A multilayer heat shrinkable film of claim 1 wherein the heat sealing layer comprises an ethylene vinyl acetate copolymer.

9. A multilayer heat shrinkable film of claim 1 wherein the heat sealing layer comprises a copolymer selected from the group consisting of ethylene alkyl acrylate copolymers and ethylene alkyl methacrylate copolymers.

10. A multilayer heat shrinkable film of claim 1 wherein the heat sealing layer comprises a polyethylene.

11. A multilayer heat shrinkable film of claim 1 additionally comprising an adhesive layer wherein said adhesive layer comprises:

1) at least one functionalized polymer component selected from the group consisting of a) anhydride-modified polymers, b) copolymers comprising copolymerized units of ethylene and a comonomer selected from the group consisting of C₄-C₈ unsaturated anhydrides, monoesters of C₄-C₈ unsaturated acids having at least two carboxylic acid groups, diesters of C₄-C₈ unsaturated acids having at least two carboxylic acid groups and c) mixtures thereof,

2) an ethylene copolymer, chemically distinct from said functionalized polymer component, comprising copolymerized units of ethylene and a comonomer selected from the group consisting of vinyl acetate, alkyl acrylates, alkyl methacrylates and mixtures thereof, said alkyl groups having from 1 to 10 carbon atoms; and

optionally

3) a tackifier resin.

12. A multilayer heat shrinkable film of claim 11 that is biaxially oriented;

13. A multilayer heat shrinkable film of claim 1 comprising additional layers.

14. A multilayer heat shrinkable film of claim 11 wherein at least one of said additional layers is a tie layer.

15. A multilayer heat shrinkable film of claim 1 in the form of a tube.

16. A multilayer beat shrinkable film of claim 1 wherein said structural layer is adjacent to and in contact with said gas barrier layer.

17. A multilayer heat shrinkable film of claim 1 wherein said heat seal layer is adjacent to and in contact with said gas barrier layer.

26. An article formed from the multilayer film of claim 1.

18. A shrinkbag comprising an oriented multilayer film, said oriented film comprising:

A) a structural layer comprising a polymer selected from the group consisting of copolymers of ethylene and a C₃ to C₈ α

,β

-ethylenically unsaturated carboxylic acid, ionomers of said copolymers, polyesters, and blends thereof;

B) a heat sealing layer comprising a polymer selected from the group consisting of ethylene vinyl acetate copolymers, ethylene alkyl acrylate copolymers, ethylene alkyl methacrylate copolymers, polyethylene, and blends thereof; and

C) a gas barrier layer comprising at least one ethylene vinyl alcohol copolymer, said gas barrier layer being positioned between said structural layer and said heat sealing layer;

characterized in that said film is capable of shrinking to a size that is at least 25% less than its original size on initial exposure of said film to a temperature of 85°

C. for at least one minute.

19. A shrinkbag of claim 18 wherein said structural layer comprises a copolymer of ethylene and a C₃ to C₈ α

,β

-ethylenically unsaturated carboxylic acid wherein said acid is acrylic acid or methacrylic acid.

20. A shrinkbag of claim 18 wherein said structural layer comprises an ionomer of a copolymer of ethylene and a C₃ to C₈ α

,β

-ethylenically unsaturated carboxylic acid.

22. A shrinkbag of claim 18 additionally comprising an adhesive layer, wherein said adhesive layer comprises:

1) at least one functionalized polymer component selected from the group consisting of a) anhydride-modified polymers, b) copolymers comprising copolymerized units of ethylene and a comonomer selected from the group consisting of C₄-C₈ unsaturated anhydrides, monoesters of C₄-C₈ unsaturated acids having at least two carboxylic acid groups, diesters of C₄-C₈ unsaturated acids having at least two carboxylic acid groups and c) mixtures thereof,

2) an ethylene copolymer, chemically distinct from said functionalized polymer component, comprising copolymerized units of ethylene and a comonomer selected from the group consisting of vinyl acetate, alkyl acrylates, alkyl methacrylates and mixtures thereof, said alkyl groups having flour 1 to 10 carbon atoms; and

optionally

3) a tackifier resin

23. A shrinkbag of claim 18 wherein said ethylene vinyl alcohol polymer has from about 2 to about 8 mol % 1,2 glycol structural units present in the polymer chain.

24. A shrinkbag of claim 18 wherein said multilayer film comprises additional layers.

25. A shrinkbag of claim 18 wherein said multilayer film is a biaxially oriented film.

21. (canceled)