Multiple layer film with amorphous polyamide layer

• US 6,500,559 B2
• Filed: 05/04/1998
• Issued: 12/31/2002
• Est. Priority Date: 05/04/1998
• Status: Expired due to Fees

• Current Assignee: Cryovac Incorporated (Sealed Air)
• Original Assignee: Cryovac Incorporated (Sealed Air)
• Inventors: Sharps, G. Vince, Hofmeister, Frank M., Kennedy, Thomas D., Satterwhite, Paul J., Musco, Carlo E.
• Primary Examiner(s): Pyon, Harold
• Assistant Examiner(s): Miggins, Michael C.
• Application Number:
  US09/072,075
• Publication Number:
  US 20010010846A1
• Time in Patent Office: 1,702 Days
• Field of Search: 428/34.8, 428/34.9, 428/35.2, 428/35.7, 428/36.91, 428/200, 428/349, 428/474.7, 428/474.9, 428/476.3, 428/475.8, 428/475.5, 428/476.6, 428/500, 428/521, 428/34.1, 428/34.3, 383/109, 383/113, 426/127
• US Class Current: 428/474.4
• CPC Class Codes: B29C 48/10 flexible, e.g. blown foils
• CPC Class Codes: B29C 48/185 comprising six or more components, i.e. each component being counted once for each time it is present, e.g. in a layer
• CPC Class Codes: B32B 27/34 comprising polyamides
• CPC Class Codes: Y10T 428/13 Hollow or container type article [e.g., tube, vase, etc.]
• CPC Class Codes: Y10T 428/1307 Bag or tubular film [e.g., pouch, flexible food casing, envelope, etc.]
• CPC Class Codes: Y10T 428/1324 Flexible food casing [e.g., sausage type, etc.]
• CPC Class Codes: Y10T 428/1334 Nonself-supporting tubular film or bag [e.g., pouch, envelope, packet, etc.]
• CPC Class Codes: Y10T 428/1352 Polymer or resin containing [i.e., natural or synthetic]
• CPC Class Codes: Y10T 428/1393 Multilayer [continuous layer]
• CPC Class Codes: Y10T 428/24843 with heat sealable or heat releasable adhesive layer
• CPC Class Codes: Y10T 428/31725 Of polyamide
• CPC Class Codes: Y10T 428/31728 Next to second layer of polyamide
• CPC Class Codes: Y10T 428/31732 At least one layer is nylon type

Abstract

A film includes a core layer having an amorphous polyamide; two intermediate layers, disposed on opposite surfaces of the core layer, including a semicrystalline polyamide; two adhesive layers, each disposed on a surface of the respective intermediate layer, including a polymeric adhesive; and two outer layers, each disposed on a surface of a respective adhesive layer, including an ethylene/alpha olefin copolymer, propylene homopolymer, or propylene/alpha olefin copolymer; and a second outer layer, disposed on a surface of a respective adhesive layer, including amorphous polyamide, semicrystalline polyamide, ethylene/alpha olefin copolymer, propylene homopolymer, or propylene/alpha olefin copolymer. The film can alternatively have a core layer including a polymeric adhesive, and two intermediate layers each having an amorphous polyamide. A method of packaging a product using these films, and a package, are also disclosed.

Claims

1. A multilayer film comprising:

a) a core layer consisting essentially of an amorphous polyamide;

b) two intermediate layers, disposed on opposite surfaces of the core layer, comprising a semicrystalline polyamide;

c) two adhesive layers, each disposed on a surface of the respective intermediate layer, comprising a polymeric adhesive; and

d) two outer layers, each disposed on a surface of a respective adhesive layer, comprising a material selected from the group consisting of amorphous polyamide, semicrystalline polyamide, ethylene/alpha olefin copolymer, propylene homopolymer, and propylene/alpha olefin copolymer;

wherein the film has a total thickness of between 0.5 and 10 mils; and

wherein the film exhibits a free shrink of less than 5% in the longitudinal direction, and less than 5% in the transverse direction, at 180°

F.

2. The film of claim 1 wherein the amorphous polyamide of the core layer is selected from the group consisting of nylon 6I/6T, nylon 6,6/6,9/6I, and nylon 6,6/610/MXD-6.

3. The film of claim 1 wherein the semicrystalline polyamide is selected from the group consisting of nylon 6, nylon 9, nylon 11, nylon 12, nylon 66, nylon 69, nylon 610, nylon 612, nylon 6/12, nylon 6/69, nylon 66/610, nylon 6/66, nylon 66/6, nylon 12T, nylon 6T, and nylon 666.

4. The film of claim 1 wherein the intermediate layers each comprise a blend of a semicrystalline polyamide and an amorphous polyamide.

5. The film of claim 1 wherein the polymeric adhesive layers each comprise a polymeric adhesive selected from the group consisting of anhydride grafted ethylene/1-butene copolymer, anhydride grafted ethylene/1-hexene copolymer, and anhydride grafted ethylene/1-octene copolymer.

6. The film of claim 1 wherein the first outer layer comprises an ethylene/alpha-olefin copolymer having a density of between 0.916 and 0.945 grams per cubic centimeter.

7. The film of claim 1 wherein the first outer layer comprises a propylene/ethylene copolymer.

8. The film of claim 1 wherein the first outer layer comprises a single site-catalyzed ethylene/alpha-olefin copolymer.

9. The film of claim 1 wherein the film is not oriented.

10. A method of packaging a food product comprising:

a) providing a rollstock film, the film comprising

i) a core layer consisting essentially of an amorphous polyamide;

ii) two intermediate layers, disposed on opposite surfaces of the core layer, comprising a semicrystalline polyamide;

iii) two adhesive layers, each disposed on a surface of the respective intermediate layer, comprising a polymeric adhesive; and

iv) two outer layers, each disposed on a surface of a respective adhesive layer, comprising a material selected from the group consisting of amorphous polyamide, semicrystalline polyamide, ethylene/alpha olefin copolymer, propylene homopolymer, and propylene/alpha olefin copolymer, wherein the film has a total thickness of between 0.5 and 10 mils; and

wherein the film exhibits a free shrink of less than 5% in the longitudinal direction, and less than 5% in the transverse direction, at 180°

F.;

b) forming the film into a tube in a vertical/form/fill/seal process;

c) filling the tube with a food product; and

d) closing the tube to form a sealed pouch containing the food product.

11. A package comprises:

a) a flowable food product; and

b) a pouch containing the food product, the pouch made from a film comprising

i) a core layer consisting essentially of an amorphous polyamide;

ii) two intermediate layers, disposed on opposite surfaces of the core layer, comprising a semicrystalline polyamide;

iii) two adhesive layers, each disposed on a surface of the respective intermediate layer, comprising a polymeric adhesive; and

iv) two outer layers, each disposed on a surface of a respective adhesive layer, comprising a material selected from the group consisting of amorphous polyamide, semicrystalline polyamide, ethylene/alpha olefin copolymer, propylene homopolymer, and propylene/alpha olefin copolymer, wherein the film has a total thickness of between 0.5 and 10 mils; and

wherein the film exhibits a free shrink of less than 5% in the longitudinal direction, and less than 5% in the transverse direction, at 180°

F.