Polymer-coated heat-sealable packaging material, method for manufacturing the same and a closed package made thereof

• US 20040258893A1
• Filed: 03/12/2004
• Published: 12/23/2004
• Est. Priority Date: 07/13/2001
• Status: Active Grant

• Current Assignee: Stora Enso Oyj
• Original Assignee: Stora Enso Oyj
• Inventors: Jarvinen, Jalliina, Penttinen, Tapani, Nevalainen, Kimmo
• Granted Patent: US 7,335,409 B2
• Time in Patent Office: Days
• US Class Current: 428/212
• CPC Class Codes: B32B 2250/242 All polymers belonging to those covered by group B32B27/32
• CPC Class Codes: B32B 2250/40 Symmetrical or sandwich layers, e.g. ABA, ABCBA, ABCCBA
• CPC Class Codes: B32B 2307/31 Heat sealable
• CPC Class Codes: B32B 2307/7244 Oxygen barrier
• CPC Class Codes: B32B 2307/7246 Water vapor barrier
• CPC Class Codes: B32B 2323/043 HDPE, i.e. high density polyethylene
• CPC Class Codes: B32B 2323/046 LDPE, i.e. low density polyethylene
• CPC Class Codes: B32B 2439/46 Bags
• CPC Class Codes: B32B 2439/62 Boxes, cartons, cases
• CPC Class Codes: B32B 2439/70 Food packaging
• CPC Class Codes: B32B 27/12 next to a fibrous or filamentary layer
• CPC Class Codes: B32B 27/32 comprising polyolefins comprising vinyl (co)polymers or acrylic (co)polymers B32B27/30
• CPC Class Codes: B32B 37/153 at least one layer is extruded and immediately laminated while in semi-molten state
• CPC Class Codes: B32B 7/12 using interposed adhesives or interposed materials with bonding properties
• CPC Class Codes: Y10T 428/1303 Paper containing [e.g., paperboard, cardboard, fiberboard, etc.]
• CPC Class Codes: Y10T 428/1307 Bag or tubular film [e.g., pouch, flexible food casing, envelope, etc.]
• CPC Class Codes: Y10T 428/24942 including components having same physical characteristic in differing degree
• CPC Class Codes: Y10T 428/31971 Of carbohydrate
• CPC Class Codes: Y10T 428/31982 Wood or paper
• CPC Class Codes: Y10T 428/31986 Regenerated or modified
• CPC Class Codes: Y10T 428/31993 : Of paper

Abstract

The invention relates to a manufacturing method of a heat-sealable packaging material, a polymer-coated packaging material manufactured using the method, and a sealed package to be manufactured of the material. The packaging material comprises a fibre base, such as a packaging board (5), and an inner, extruded water vapour barrier layer (2, 9) on both sides, containing high-density polyethylene (HDPE), and an outer heat sealing layer (1, 10), the material of which is, for example, low-density polyethylene (LDPE). Further, polymeric oxygen barrier layers (7) can be incorporated in the packaging material, the material of the oxygen barrier layers being, for example, ethyl vinyl alcohol copolymer (EVOH) or polyamide (PA). With the HDPE layer, the permeation of water vapour is prevented to both directions, and the location of the extruded layers on both sides of the fibre base reduces the curling of the material. The packages according to the invention comprise carton, box and bag packages for dry and liquid foods.

Claims

1. Method for manufacturing a heat sealable packaging material, in which method both sides of a fibre base are provided with a polymeric heat sealing layer, characterized in that a polymeric water vapour barrier layer (2, 9) containing high-density polyethylene (HDPE) is extruded on both sides of the fibre base (5) so that the water vapour barrier layer remains between the fibre base and the outer heat sealing layer (1, 10) in the packaging material.

2. Method according to claim 1, characterized in that the inner water vapour barrier layer (2, 9) containing HDPE and the outer heat sealing layer (1, 10) are brought onto the fibre base (5) in one step by coextrusion.

3. Method according to claim 2, characterized in that superimposed water vapour barrier and heat sealing layers (2, 1;

9, 10) are coextruded on both sides of the fibre base (5) so that the layer structure of the packaging material thus achieved is symmetrical.

4. Method according to any one of the preceding claims, characterized in that the heat sealing layers (1, 10) contain low-density polyethylene (LDPE).

5. Method according to claim 1, characterized in that at least one extruded polymer layer (4, 6, 7) forming an oxygen barrier is incorporated in the packaging material.

6. Polymer-coated heat sealable packaging material, characterized in that it is manufactured using a method according to claim 1 and that it comprises a fibre base (5) and an inner extruded polymer layer (2, 9) containing high-density polyethylene (HDPE) and acting as a water vapour barrier layer and an outer heat sealing layer (1, 10) on both sides of the fibre base.

7. Packaging material according to claim 6, characerized in that the heat sealing layers (1, 10) contain low-density polyethylene (LDPE).

8. Packaging material according to claim 7, characterized in that the material consists of layers, the order of which is:

LDPE heat sealing layer (1);

HDPE water vapour barrier layer (2);

fibre base (5);

HDPE water vapour barrier layer (9); and

LDPE heat sealing layer (10).

9. Packaging material according to any one of the claims 6-8, characterized in that the weight of the water vapour barrier layers (2, 9) on both sides of the fibre base (5) is the same, and that also the weight of the heat sealing layers (1, 10) on both sides of the fibre base is the same so that the layer structure of the packaging material is symmetrical.

10. Packaging material according to claim 6 or 7, characterized in that the material further comprises at least one polymer layer (4, 6, 7), which forms an oxygen barrier.

11. Packaging material according to claim 10, characterized in that the oxygen barrier layer (4, 6, 7) contains ethyl vinyl alcohol copolymer (EVOH), polyamide (PA), or a mixture of these.

12. Packaging material according to claim 11, characterized in that the material consists of layers, the order of which is:

LDPE heat sealing layer (1);

HDPE water vapour barrier layer (2);

fibre base (5);

one or a plurality of EVOH and/or PA oxygen barrier layers (6, 7);

polymeric binding agent layer (8);

HDPE water vapour barrier layer (9); and

LDPE heat sealing layer (10).

13. Packaging material according to claim 6, characterized in that the water vapour barrier layers (2, 9) are formed of Borstar-HDPE, the density of which is approx. 0.963 g/cm³.

14. Packaging material according to claim 6, characterized in that heat sealing layer (1, 10) is formed of LDPE, to which polypropylene (PP) has been blended.

15. Packaging material according to claim 6, characterized in that the fibre base (5) is a board, the weight of which is 130-500 g/m², preferably 170-300 g/m².

16. Packaging material according to claim 6, characterized in that the fibre base (5) is a paper, the weight of which is 20-120 g/m², preferably 40-100 g/m².

17. Packaging material according to claim 6, characterized in that the weight of the water vapour barrier layer (2, 9) is 5-50 g/m², preferably 7-30 g/m², and most preferably 10-20 g/m².

18. Packaging material according to claim 6, characterized in that the weight of the heat sealing layer (1, 10) is 5-50 g/m², preferably 5-30 g/m², and most preferably 7-20 g/m².

19. Packaging material according to claim 10, characterized in that the weight of the oxygen barrier layer (4, 6, 7) is 3-15 g/m², preferably 5-10 g/m².

20. Sealed package, which has been manufactured by folding and heat sealing from a packaging material manufactured using a method according to claim 1, characterized in that, in the material, on both sides of a fibre base (5) under an outer heat sealing layer (1, 10) there is an extruded polymer layer (2, 9) containing high-density polyethylene (HDPE) and acting as a water vapour barrier.

21. Package according to claim 20, characterized in that, inside the fibre base (5), between it and the water vapour barrier layer (9) there is further at least one polymer layer (7), forming an oxygen barrier.

22. Package according to claim 20 or 21, characterized in that it is a carton package for liquid food, formed of polymer-coated board.

23. Package according to claim 20 or 21, characterized in that it is a box package for dry food, formed of polymer-coated board.

24. Package according to claim 20 or 21, characterized in that it is a bag package formed of polymer-coated paper.