A LID SHEET, A METHOD FOR MANUFACTURE, AND A PACKAGE

Abstract

The present disclosure relates to a transparent lid sheet for being punched to a transparent sheet lid to be attached to a container to produce a package, said lid sheet comprising: a transparent base layer, which comprises a transparent polyethylene terephtalate layer with a barrier layer coated onto the polyethylene terephtalate layer, the base layer having a first major surface, which preferably substantially coincides with an outer major surface of the barrier layer, and a top layer providing a welding layer for welding the sheet lid to the container, the top layer coinciding with the first major surface.

Claims

1-19. (canceled)

20. A transparent lid sheet for being punched to a transparent sheet lid to be attached to a container to produce a package, said transparent lid sheet comprising: a transparent base layer, which comprises a transparent polyethylene terephtalate layer with a transparent barrier layer coated onto the transparent polyethylene terephtalate layer, the transparent base layer having a first major surface, which preferably substantially coincides with an outer major surface of the transparent barrier layer, and a top layer providing a welding layer for welding the transparent sheet lid to the container, the top layer coinciding with the first major surface.

21. The transparent lid sheet of claim 20, wherein said container is specifically a polyethylene terephtalate container.

22. The transparent lid sheet of claim 20, wherein said container is specifically a container comprising a polyethylene terephtalate surface layer.

23. The transparent lid sheet of claim 20, wherein said transparent barrier layer is an oxygen barrier layer.

24. The transparent lid sheet of claim 20, wherein a primer layer is provided between said first major surface and said top layer, the primer layer essentially consisting of a primer, which improves adherence of the top layer to said first major surface.

25. The transparent lid sheet of claim 24, wherein the primer layer essentially consists of a substantially water-insoluble primer.

26. The transparent lid sheet of claim 20, wherein the transparent barrier layer essentially consists of polyvinylidene chloride selected from the group consisting of: aluminium oxide, silicium oxide, magnesium oxide, cerium oxide, hafnium oxide, tantalum oxide, titanium oxide, yttrium oxide, zirconium oxide and mixtures thereof.

27. The transparent lid sheet of claim 20, wherein the transparent barrier layer has a thickness of less than 1.5 μm.

28. The transparent lid sheet of claim 20, wherein the top layer comprises a polyolefin layer and a polyethylene terephtalate welding layer of polyethylene terephtalate coated at the transparent base layer, the polyolefin layer being disposed between the transparent base layer and the welding layer.

29. The transparent lid sheet of claim 20, wherein the top layer comprises a lacquer welding layer of a welding lacquer positioned at or on said first major surface substantially only in a welding area of the transparent lid sheet corresponding to a welding rim of the container.

30. A method for manufacture of a transparent lid sheet for being punched to a sheet lid to be attached to a container to produce a package, comprising the steps of: providing a transparent base layer, which comprises a transparent polyethylene terephtalate layer with a transparent barrier layer provided directly onto the transparent polyethylene terephtalate layer, the transparent base layer having a first major surface, which preferably substantially coincides with an outer major surface of the transparent barrier layer, and coating a top layer at or onto the first major surface to provide a welding layer for welding the sheet lid to the container.

31. The method of claim 30, wherein the container is specifically a polyethylene terephtalate container.

32. The method of claim 30, wherein said transparent barrier layer is an oxygen barrier layer.

33. The method of claim 30, further comprising the step of: applying a primer layer onto said first major surface, the primer layer essentially consisting of a primer, which improves adherence of the top layer to said first major surface, the top layer subsequently being coated onto the primer layer.

34. The method of claim 30, wherein the top layer is coated at said first major surface by coextruding a polyolefin layer and a polyethylene terephtalate welding layer, at or onto said first major surface, the polyolefin layer being disposed between said first major surface and the welding layer.

35. The method of claim 30, wherein the top layer is coated onto the transparent barrier layer by applying a welding layer of a welding lacquer at or onto said first major surface to form a lacquer welding layer disposed substantially only in a welding area of the transparent lid sheet corresponding to a welding rim of the container.

36. The method of claim 30, wherein the resultant lid sheet comprises: the transparent base layer comprising the transparent polyethylene terephtalate layer with the transparent barrier layer coated onto the transparent polyethylene terephtalate layer, the transparent base layer having the first major surface, which preferably substantially coincides with the outer major surface of the transparent barrier layer, and the top layer providing the welding layer for welding the sheet lid to the container, the top layer coinciding with the first major surface.

37. The method of claim 36, wherein the top layer comprises a lacquer welding layer of a welding lacquer positioned at or on said first major surface substantially only in a welding area of the resultant lid sheet corresponding to a welding rim of the container.

38. The method of claim 30, further comprising the steps of punching the transparent lid sheet to a final shape of the sheet lid, and subsequently welding the sheet lid to the container, the welding layer facing and adhering to the container in a welding area of the sheet lid along a rim of the container such as to produce a closed package.

39. A package, comprising a polyethylene terephtalate container; a transparent sheet lid; and a transparent lid sheet comprising: a transparent base layer, which comprises a transparent polyethylene terephtalate layer with a barrier layer coated onto the transparent polyethylene terephtalate layer, the transparent base layer having a first major surface, which preferably substantially coincides with an outer major surface of the barrier layer, and a top layer providing a welding layer for welding the transparent sheet lid to the polyethylene terephtalate container, the top layer coinciding with the first major surface, and the transparent sheet lid punched from the transparent lid sheet, the transparent sheet lid being welded to the polyethylene terephtalate container along a welding area, specifically welding seems, at a rim of the polyethylene terephtalate container with the welding layer facing and adhering to the polyethylene terephtalate container, the transparent sheet lid being separable from the polyethylene terephtalate container to open the package by grabbing and pulling at a periphery of the transparent sheet lid causing the welding layer to remain on the polyethylene terephtalate container in the welding area, the welding layer delaminating from the remaining layers of the transparent sheet lid substantially in the welding area only.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Embodiments of the invention will be described in the following detailed description with reference to the drawings.

[0056] FIG. 1 shows a perspective view of an embodiment of a package according to the invention manufactured according to the method according to the invention comprising a container and a sheet lid manufactured from a lid sheet according to an embodiment of the invention, the package being shown prior to welding;

[0057] FIG. 2 shows a detail of the package of FIG. 1 in a sectional view taken along the line II-II in FIG. 1 after the sheet lid has been torn off of the container, i.e. after delamination;

[0058] FIG. 3 shows a schematic sectional view of the lid sheet of FIG. 1 before delamination;

[0059] FIG. 4 shows a schematic sectional view corresponding to that of FIG. 3 of an alternative embodiment of the lid sheet according to the invention before delamination; and

[0060] FIG. 5 shows a schematic sectional view corresponding to that of FIG. 3 of an alternative embodiment of the lid sheet according to the invention before delamination.

DETAILED DESCRIPTION

[0061] In this specification, generally when terms such as “thickness” (unit um) and “distribution” (unit g/m2) are used, unless otherwise indicated it is to be understood that the layer in question has a substantially or essentially uniform thickness across the planar extent of the layer or sheet according to the provided value.

[0062] The package shown in FIGS. 1 and 2 comprises a container 1, which is manufactured of polyethyleneterephtalate, such as amorphous polyester or crystalline polyester (CPET), or polypropylene. The package comprises a sheet lid 2 punched from the lid sheet S shown in FIG. 3, the lid 2 in FIGS. 1 and 2 being shown in a position prior to welding.

[0063] Especially in the case where the container 1 is made of polyethyleneterephtalate the package is specifically suitable for packaging of water, fruit juices, salads or like products. Especially in the case where the container 1 is made of polypropylene the package is specifically suitable for packaging of yoghurt or like milk products. In both cases the container 1 may also be a tray or the like for salad foods or a bottle for milk or soft drinks.

[0064] The container 1 is provided with an upper welding rim 3, which is plane on an upper side, which faces the sheet lid 2, to enable welding of the sheet lid 2 onto the rim 3 to produce the closed package.

[0065] When the container 1 has been filled with its contents, it is closed with the sheet lid 2. The lid 2 has been punched in advance and is thus adapted in shape and size to the opening of the container 1 before welding.

[0066] The lid sheet S and thus the punched lid 2 comprises a transparent base layer 4 with a transparent polyethyleneterephtalate top layer 4a, which has a thickness of between 23 and 50 μm, preferably a thickness of 30-40 μm. This thickness is adapted to the need for strength, barrier properties, size, etc. The polyethyleneterephtalate layer 4a is essentially constituted of polyethyleneterephtalate. The base layer 4 also comprises a barrier coating 4b coated onto the polyethyleneterephtalate layer 4a, see FIG. 3.

[0067] On this base layer 4 a top layer comprising a polyolefin layer, specifically a polyethylene layer, which is designated 5a, and either a polyethyleneterephtalate welding layer or a welding layer comprising a polypropylene polymer, which is designated 5b, is provided by coextrusion of the two layers 5a and 5b directly onto a first major surface 4c of the polyethyleneterephtalate base layer 4. The welding layer 5b is intended to be welded together with the rim portion 3 of the container 1.

[0068] The polyolefin layer 5a is a homopolymer or a copolymer of polyethylene—a suitable polyethylene copolymer is an acrylic copolymer of polyethylene or an ethyl vinyl acetate containing polyethylene—and will be denoted the polyethylene layer in the following. Use of any of these copolymers ensures that delamination between the welding layer 5b and the polyethylene layer 5a only occurs in the welding area.

[0069] In the case where the welding layer 5b is a polyethyleneterephtalate welding layer, the welding layer may be or comprise a homopolymer or a copolymer of polyethyleneterephtalate. It may comprise other polymers, additives etc., but preferably mainly comprises polyethyleneterephtalate. A highly suitable material for the welding layer is polyethyleneterephtalate glycol-modified, a pure polyester which does not crystallize, i.e. it remains amorphous. This results in a welding layer with improved welding properties in contrast to normal polyester, which loses its welding properties when it crystallizes at temperatures well below 220 to 230° C., which is the maximum temperature level for sealing, due to the softening point of the base layer 4.

[0070] In the case where the welding layer 5b is a polypropylene welding layer, the welding layer may be or comprise a homopolymer or a copolymer of polypropylene. It may comprise other polymers, additives etc., but preferably mainly comprises polypropylene. A suitable copolymer of the polypropylene welding layer may contain polyethylene.

[0071] The two layers 5a and 5b are preferably distributed in an accumulated amount of about 12 to 22 g/m2, preferably 15 to 17 g/m2. The polyethylene layer 5a preferably has a thickness of 5 to 15 g/m2, corresponding to about 5.5 to 17 μm. In the case were a polyethyleneterephtalate welding layer is used, the welding layer 5b preferably has a thickness of 2 to 10 g/m2, corresponding to about 2.8 to 7.5 μm. In the case where a polypropylene welding layer 5b is used, the polypropylene welding layer 5b is preferably distributed in an amount of about 4 to 6 g/m2 corresponding to about 4.3 to 6.5 μm.

[0072] The base layer 4 has applied thereto a primer layer 6, which ensures enhanced adhesion between the first major surface 4c of the base layer 4 and the polyethylene layer 5a.

[0073] An alternative method of manufacture of a lid sheet according to the invention comprises extrusion of the base layer 4 and, by coextrusion, the creation of the layer 5 by a first layer 5a and a welding layer 5b, said layers 4, 5 being put together to form the lid sheet S.

[0074] It is preferred that the lid sheet S is calendered immediately after the application of the coextruded layer to the base layer.

[0075] The resultant lid sheet S is transparent and weldable in its full planar extent. Thereby, any lid shape and dimension may be punched from a roll of lid sheet, as the resultant lid 2 may be adapted to the size and shape of the container 1. The lid 2 is supplied from a roll of the lid sheet S and is punched into its final shape prior to being applied to the containers 1.

[0076] In connection with the filling of containers, e.g. cups, in a filling machine, the lid 2, preferably pre-punched into its final shape, is applied subsequently and welded to the rim portion 3.

[0077] When the container 1 has thus been filled and closed with the sheet lid 2, the user will be able to pull off the lid 2 by pulling in a periphery of the sheet lid 2, specifically in a lid flap or lid tap visible in FIG. 1.

[0078] Hereby, the polyethylene layer 5a and the welding layer 5b will be sepa-rated or delaminated from each other in such a manner that the pulling-off or opening of the package along the rim portion 3 is controlled and precise. The welding layer 5b will essentially remain on the container 1 in the welding area, i.e. on the rim portion 3 thereof, and remain on the lid 2 in the non-welded area.

[0079] Since the two layers 5a and 5b are relatively stiff, the dimensions of the base layer 4 may be reduced, thus saving weight as well as consumption of material. Moreover, as a result of the enhanced rigidity of the lid sheet, the punched lid 2 does not curl after the punching.

[0080] Optionally, an additional print or colour layer may be applied in a generally known manner on for example a top surface or a bottom surface of the sheet lid 2 either before or after the punching of the lid 2, and/or an additional barrier coating may optionally be applied to the lid sheet before or after the coating and/or punching.

[0081] FIG. 4 is a view similar to that of FIG. 3 showing an alternative embodiment of the lid sheet S according to the invention. This lid sheet S is generally similar to the embodiment of the lid sheet S shown in FIGS. 1 to 3 except for the differences mentioned in the following.

[0082] Thus, in the embodiment of FIG. 4 the top layer 5 is a non-transparent lacquer welding layer 5c coated onto the major surface 4c substantially only in a welding area of the lid sheet S corresponding to the welding rim 3 of the container 1. On the remaining parts of the major surface 4c no lacquer or any other layer is present, i.e. the surface of the sheet lid 2 facing the contents of the container 1 is the major surface 4c of the base layer 4.

[0083] A fully covering transparent lacquer (not shown) may optionally be applied on the first major surface 4c before the welding lacquer layer 5c is applied.

[0084] The lid sheet S shown in FIG. 4 may be applied to a similar container 1 as shown in FIGS. 1 and 2. If the container 1 is a polyethyleneterephtalate container, a polyethyleneterephtalate welding lacquer is applied. If the container 1 is a polypropylene or polystyrene container a combi welding lacquer is applied.

[0085] During manufacture the top layer 5 is coated onto the barrier coating 4b by means of rotogravure and dried at 220° C. to 230° C. The top layer 5 is distributed with an amount of 6 g/m2.

[0086] FIG. 5 shows an embodiment of the lid sheet according to the invention, which is similar to that of FIG. 3 with the only difference being that the barrier coating 4b is positioned on the opposite side of the lid sheet S so that the barrier coating 4b faces away from the lid sheet S. As is shown, the top layer 5 is coated on the surface 4c of the polyethyleneterephtalate layer 4a of the base layer 4 via a primer layer 6. The primer layer 6 can be composed of a primer similar to the primer applied in the embodiment of FIG. 3.

[0087] Generally, in the lid sheets S and the sheet lids 2 described above the layers are preferably provided extending substantially along the entire area of the adjacent layer so that the area sizes of major surfaces of all layers are similar to each other. However, specifically in the embodiment where the top layer 5 is a lacquer welding layer 5c the top layer 5 substantially only extends in or at a welding area.

Example 1: Lid Sheets According to the Prior Art

[0088] A lid sheet was prepared according to WO 2013/075713 A1 with a polyethyleneterephtalate base layer with a thickness of 36 μm coated with an additional layer or top layer with a thickness of 16 g/m2 on top of the base layer in the form of a polyolefin layer and a polyethyleneterephtalate welding layer of amorphous polyester, coextruded onto the base layer, the polyolefin layer being disposed between the base layer and the welding layer.

[0089] A further lid sheet was prepared according to WO 2011/160627 A1 with a polyethyleneterephtalate base layer with a thickness of 36 μm coated with an additional layer or top layer with a thickness of 16 g/m2 on top of the base layer in the form of a polyolefin layer and a polypropylene welding layer, coextruded onto the base layer, the polyolefin layer being disposed between the base layer and the welding layer.

[0090] In both cases the oxygen transmission rate (ASTM D3985, 23° C., 0% RH) was measured to approximately 45 cm3/m2/24 h/bar. The water vapour transmission rate (ASTM F1249, 38° C., 90% RH) was approximately 15 g/m2/24 h.

[0091] A further lid sheet was prepared by coating a non-transparent 6 g/m2 top layer welding lacquer onto a 50 μm transparent polyethylene terephtalate sheet only at a welding area at a rim of the lid.

[0092] In this case the oxygen transmission rate (ASTM D3985, 23° C., 0% RH) was measured to approximately 35 cm3/m2/24 h/bar. The water vapour transmission rate (ASTM F1249, 38° C., 90% RH) was approximately 12 g/m2/24 h.

[0093] The difference in the transmission rates is believed to mainly be due to the different thicknesses of the base layers.

Example 2: Lid Sheets According to the Invention Applying a Coextruded Top Layer

[0094] A transparent lid sheet was prepared according to the embodiment described above with reference to FIGS. 1 to 3 using a base layer with a thickness of 36 μm coated with a top layer with a thickness of 16 g/m2 on top of the base layer in the form of a polyolefin layer and a polyethylene terephtalate welding layer, coextruded onto the base layer, the polyolefin layer being disposed between the base layer and the welding layer. The base layer comprised a transparent polyethylene terephtalate layer with a transparent<1 μm aluminium oxide barrier coating and a 1 μm protective layer applied directly onto the polyethylene terephtalate layer. A 1 μm water-insoluble primer was applied between the top and base layers.

[0095] A further transparent lid sheet was prepared according to the embodiment described above with reference to FIGS. 1 to 3 using a base layer with a thickness of 36 μm coated with a top layer with a thickness of 16 g/m2 on top of the base layer in the form of a polyolefin layer and a polypropylene welding layer, coextruded onto the base layer, the polyolefin layer being disposed between the base layer and the welding layer. The base layer comprised a transparent polyethylene terephtalate layer with a transparent<1 μm aluminium oxide barrier coating and a 1 μm protective layer applied directly onto the polyethylene terephtalate layer. A 1 μm water-insoluble primer was applied between the top and base layers.

[0096] In both cases the oxygen transmission rate (ASTM D3985, 23° C., 0% RH) was measured to approximately 1-3 cm3/m2/24 h/bar. The water vapour transmission rate (ASTM F1249, 38° C., 90% RH) was approximately 1-3 g/m2/24 h.

[0097] A further transparent lid sheet was prepared according to the embodiment described above with reference to FIGS. 1 to 3 using a base layer with a thickness of 36 μm coated with a top layer with a thickness of 16 g/m2 on top of the base layer in the form of a polyolefin layer and a polypropylene welding layer, coextruded onto the base layer, the polyolefin layer being disposed between the base layer and the welding layer. The base layer comprised a transparent polyethylene terephtalate layer with a transparent 1 μm polyvinylidene chloride barrier coating and a 1 μm protective layer applied directly onto the polyethylene terephtalate layer. A 1 μm water-insoluble primer was applied between the top and base layers.

[0098] In this latter case the oxygen transmission rate (ASTM D3985, 23° C., 0% RH) was measured to approximately about 8 cm3/m2/24 h/bar. The water vapour transmission rate (ASTM F1249, 38° C., 90% RH) was approximately 8 g/m2/24 h.

Example 3: Lid Sheets According to the Invention Applying a Welding Lacquer Top Layer

[0099] A transparent lid sheet was prepared according to the embodiment described above with reference to FIG. 4 using a base layer with a thickness of 50 μm coated with a top layer with a thickness of 6 g/m2 on top of the base layer in the form of a polyethylene terephtalate lacquer welding layer. The base layer comprised a transparent polyethylene terephtalate layer with a transparent<1 μm aluminium oxide barrier coating and a <1 μm protective layer applied directly onto the polyethylene terephtalate layer.

[0100] A further transparent lid sheet was prepared according to the embodiment described above with reference to FIG. 4 using a base layer with a thickness of 50 μm coated with a top layer with a thickness of 6 g/m2 on top of the base layer in the form of a combi lacquer welding layer. The base layer comprised a transparent polyethylene terephtalate layer with a transparent <1 μm aluminium oxide barrier coating and a 1 μm protective layer applied directly onto the polyethylene terephtalate layer.

[0101] In both cases the oxygen transmission rate (ASTM D3985, 23° C., 0% RH) was measured to approximately 1-3 cm3/m2/24 h/bar. The water vapour transmission rate (ASTM F1249, 38° C., 90% RH) was approximately 1-3 g/m2/24 h.

[0102] A further transparent lid sheet was prepared according to the embodiment described above with reference to FIG. 4 using a base layer with a thickness of 50 μm coated with a top layer with a thickness of 6 g/m2 on top of the base layer in the form of a combi lacquer welding layer. The base layer comprised a transparent polyethylene terephtalate layer with a transparent<1 μm polyvinylidene chloride barrier coating and a 1 μm protective layer applied directly onto the polyethylene terephtalate layer.

[0103] In this latter case the oxygen transmission rate (ASTM D3985, 23° C., 0% RH) was measured to approximately 8 cm3/m2/24 h/bar. The water vapour transmission rate (ASTM F1249, 38° C., 90% RH) was approximately 8 g/m2/24 h.

[0104] It appears from the examples that when using a barrier coating the thickness of the polyethylene terephtalate layer of the base layer is not decisive for the barrier properties.