Multi-layer heat-shrinkage film with reduced shrink force, process for the manufacture thereof and packages comprising it

• US 6,150,011 A
• Filed: 12/16/1994
• Issued: 11/21/2000
• Est. Priority Date: 12/16/1994
• Status: Expired due to Term

• Current Assignee: Cryovac Incorporated (Sealed Air)
• Original Assignee: Cryovac Incorporated (Sealed Air)
• Inventors: Bax, Serge, Ciocca, Paolo, Mumpower, Edward Lee
• Primary Examiner(s): Resan, Stevan A.
• Application Number:
  US08/357,487
• Time in Patent Office: 2,167 Days
• Field of Search: 428/215, 428/516, 428/518, 428/910
• US Class Current: 428/215
• CPC Class Codes: B32B 2038/0076 Curing, vulcanising, cross-linking
• CPC Class Codes: B32B 2270/00 Resin or rubber layer containing a blend of at least two different polymers
• CPC Class Codes: B32B 2307/736 Shrinkable
• CPC Class Codes: B32B 2323/046 LDPE, i.e. low density polyethylene
• CPC Class Codes: B32B 2329/04 Polyvinylalcohol
• CPC Class Codes: B32B 2331/04 Polymers of vinyl acetate, e.g. PVA
• CPC Class Codes: B32B 2377/00 Polyamides
• CPC Class Codes: B32B 2439/70 Food packaging
• CPC Class Codes: B32B 27/08 of synthetic resin
• CPC Class Codes: B32B 27/30 comprising vinyl (co)polymers; comprising acrylic (co)polymers
• CPC Class Codes: B32B 27/306 comprising vinyl acetate or vinyl alcohol (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 7/12 using interposed adhesives or interposed materials with bonding properties
• CPC Class Codes: B65D 75/002 in shrink films B65D71/08 takes precedence
• CPC Class Codes: Y10S 428/91 Product with molecular orientation
• CPC Class Codes: Y10T 428/24967 Absolute thicknesses specified
• CPC Class Codes: Y10T 428/31913 Monoolefin polymer
• CPC Class Codes: Y10T 428/3192 Next to vinyl or vinylidene chloride polymer

Abstract

A heat-shrinkable film comprising a core layer comprising an ethylene-vinyl alcohol copolymer, two outer layers of blends comprising ethylene-vinyl acetate and ethylene-α-olefin copolymers, and two adhesive layers, characterized in that said film has a free shrink of at least 40%, preferably at least 45% and most preferably at least 50%, in both dimensions at 120° C. and a maximum shrink force in the transversal direction, throughout its range of shrink temperatures, not exceeding 0.5. N/cm. The film is suitable to package deformable articles such as trays to give a tight package without causing deformation.

Claims

1. A heat-shrinkable film comprising:

a) core layer comprising an ethylene-vinyl alcohol copolymer;

b) two outer layers comprising a blend of ethylene-vinyl acetate copolymer and ethylene-α

-olefin copolymer; and

c) two adhesive layers, wherein said film has

i) a free shrink of at least 40% in both directions at 120°

C. and

ii) a maximum shrink force in the transverse direction, throughout its range of shrink temperatures, not exceeding 0.5 N/cm.

2. A heat-shrinkable film according to claim 1 wherein the core layer comprises a blend of ethylene-vinyl alcohol copolymer and polyamide.

3. A heat-shrinkable film according to claim 1 wherein the outer layers comprise a blend of ethylene-vinyl acetate copolymer, and a first and a second ethylene-α

-olefin copolymer.

4. A heat-shrinkable film according to claim 3 wherein

a) the core layer comprises a blend of ethylene-vinyl alcohol copolymer and polyamide;

and

b) the outer layers comprise a blend of an ethylene-vinyl acetate copolymer, an ethylene-α

-olefin copolymer of low density and an ethylene-α

-olefin copolymer of medium density,

wherein said film has a free shrink in both directions at 120°

C. of at least 45%.

5. A heat-shrinkable film according to claim 4 wherein the core layer comprises a blend of an ethylene-vinyl alcohol copolymer and a polyamide, and the film is cross-linked.

6. A heat-shrinkable film according to claim 1 wherein the film has a thickness of from about 15 to about 150 micrometers.

7. A heat-shrinkable film according to claim 6 wherein the film thickness is between 18 and 90 micrometers.

8. A heat-shrinkable film according to claim 1 wherein the film has a free shrink of at least 45% in both directions at 120°

C.

9. A heat-shrinkable film according to claim 1 wherein the film has a free shrink of at least 50% in both directions at 120°

C.