Coextruded biaxially stretched tubular film

• US 5,356,676 A
• Filed: 08/17/1992
• Issued: 10/18/1994
• Est. Priority Date: 08/23/1991
• Status: Expired due to Term

• Current Assignee: Casetech GmbH & Co., KG
• Original Assignee: Wolff Walsrode AG (Dow, Inc.)
• Inventors: von Widdern, Michael H.-C., Weber, Gunter
• Primary Examiner(s): Buffalow, Edith
• Application Number:
  US07/931,175
• Time in Patent Office: 792 Days
• Field of Search: 428/516, 428/47, 428/36.1, 428/34.8, 428/474.4, 428/34.9, 428/35.7, 428/36.7, 428/332, 428/475.8, 428/910, 426/105, 426/127
• US Class Current: 428/34.8
• CPC Class Codes: B32B 1/08 Tubular products
• CPC Class Codes: B32B 2307/518 bi-axially
• CPC Class Codes: B32B 2307/718 Weight, e.g. weight per square meter
• CPC Class Codes: B32B 2309/105 Thickness
• CPC Class Codes: B32B 2439/70 Food packaging
• CPC Class Codes: B32B 27/08 of synthetic resin
• 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 27/36 comprising polyesters
• CPC Class Codes: B32B 7/12 using interposed adhesives or interposed materials with bonding properties
• CPC Class Codes: Y10S 428/91 Product with molecular orientation
• CPC Class Codes: Y10T 428/1324 Flexible food casing [e.g., sausage type, etc.]
• CPC Class Codes: Y10T 428/1328 Shrinkable or shrunk [e.g., due to heat, solvent, volatile agent, restraint removal, etc.]
• CPC Class Codes: Y10T 428/1352 Polymer or resin containing [i.e., natural or synthetic]
• CPC Class Codes: Y10T 428/1383 Vapor or gas barrier, polymer derived from vinyl chloride or vinylidene chloride, or polymer containing a vinyl alcohol unit is sandwiched between layers [continuous layer]
• 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 428/31728 Next to second layer of polyamide
• CPC Class Codes: Y10T 428/31743 Next to addition polymer from unsaturated monomer[s]

Abstract

This invention relates to a coextruded, biaxially stretched tubular film for durable and crease-free wrapping of goods packaged in a liquid or pasty state, in particular foodstuffs such as sausage meat for boiling or cooking and cream cheese, which are heated treated during and/or after the packaging process.

Claims

1. A coextruded, biaxially stretched tubular film for covering goods packaged in the liquid or pasty state which undergo a heat treatment after filling the tubular film consisting of at least three layers, comprising

as the outer layer at least one layer of an aliphatic polyamide,

as the core layer at least one oxygen barrier layer of an ethylene/vinyl alcohol copolymer or a partially aromatic polyamide, and

as the inner layer at least one water vapor barrier layer of an olefinic polymer having the property of adherence to a filling.

2. A tubular film according to claim 1, wherein the outer polyamide layer comprises an aliphatic polyamide selected from the group consisting of polyamide 6, polyamide 66, polyamide 11, polyamide 12, 66, polyamide 6.66, polyamide 6.8, 6.9, polyamide 6.10, polyamide 6.11, 6.12, a copolymer of the monomer units contained therein or a mixture of the said aliphatic polyamides.

3. A tubular film according to claim 1, wherein the outer polyamide layer consists of a polymer mixture containing, in addition to the aliphatic polyamide, a total of 5 to 30% by weight based on the total weight of the polymer mixture, of

a partially aromatic polyamide, or

an acid-modified, olefinic copolymer which is partially compatible with the polyamide matrix, or

a mixture of a partially aromatic polyamide and a partially compatible, acid-modified, polyolefinic copolymer.

4. A tubular film according to claim 1, wherein the outer polyamide layer has a layer thickness of from 10 to 35 μ

m.

5. A tubular film according to claim 1, wherein the inner layer facing the filling consists of polyethylene or polypropylene, a mixture thereof or copolymers of the monomer units contained therein.

6. A tubular film according to claim 1, wherein the inner layer facing the filling consists of an ionomer polymer.

7. A tubular film according to claim 1, wherein the layer containing the olefinic polymer has a layer thickness of from 10 to 30 μ

m.

8. A tubular film according to claim 1, wherein the core layer comprises an ethylene/vinyl alcohol copolymer wherein the vinyl alcohol units constitute 40 to 80 mol-% of the copolymer.

9. A tubular film according to claim 1, wherein the core layer comprises an aromatic polyamide produced by polycondensation of meta-xylylene diamine and adipic acid.

10. A tubular film according to claim 1, including bonding layers inserted between the three layers, the bonding layers differing in composition from the layers they bond.

11. A tubular film according to claim 1, wherein the sum of all the layer thicknesses is from 35 to 80 μ

m.

12. A tubular film according to claim 1, including a scrap layer consisting of a mixture of all extruded individual layers.

13. A tubular film according to claim 1, wherein the inner layer is sealable.

14. An uncooked foodstuff enclosed in and adhering to a tubular film according to claim 1.

15. A cooked foodstuff enclosed in and adhering to a tubular film according to claim 1.

16. A method of making a packaged cooked foodstuff which comprises enclosing the uncooked foodstuff in a film according to claim 1, and thereafter cooking.