GB2362587A

GB2362587A - Sheet materials for resealable packages

Info

Publication number: GB2362587A
Application number: GB0012984A
Authority: GB
Inventors: Abdul Aziz Okhai
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-05-26
Filing date: 2000-05-26
Publication date: 2001-11-28
Also published as: GB0012984D0

Abstract

A sheet material (10) comprises a substrate layer (16) carrying a laminate of an adhesive layer (14) and a sealable layer (12), the adhesive layer providing a means whereby the substrate layer can be repeatedly detached from and reattached to the sealing layer by way of the adhesive layer. The substrate layer may be polyester, nylon or polypropylene, paper, cellophane. The sealable layer may be a copolyester, acrylic or polycaprolactone lacquer. The lacquer may be sealable onto another article made of PET, PVC or polystyrene. An intermediate layer such as PET, PE, PP or Al foil may be present between the adhesive and sealant layers. The sheet material may be made by applying the sealant layer to one side of substrate layer and the adhesive layer to the other side of the substrate layer and transferring the sealable layer from the side of the substrate to which it is attached to the other side e.g. by rolling up.

Description

2362587 SHEET MATERIALS AND METHODS FOR MANUFACTURING THE SAME The present

invention relates to sheet materials and to methods for their manufacture. In particular, the invention relates to a sheet material comprising a resealable substrate layer.

Resealable packages are currently constructed by incorporating zippers or other mechanical devices, or by using pressure sensitive adhesive as part of the packaging.

In the latter case, a thin polythene film is laminated to a carrier film such as, for example, a polyester film with pressure sensitive adhesive. The polythene layer of this laminate can then be sealed to a structure that is also made of polythene such as a container, tray or bag. In operation, the carrier film can be peeled away from the polythene layer which is attached to the structure, thereby exposing the pressure sensitive adhesive layer. Because the pressure sensitive adhesive layer is exposed, the carrier film can then be returned to its original position by way of the pressure sensitive adhesive and hence, the structure is resealed.

The above laminate uses a thin polythene layer as the layer via which it seals to other structures. However, this polythene layer is only suitable for sealing to polythene and as such, the structure to which it fuses must be made of polythene or laminated with a polythene layer. Although it is economical to incorporate this laminate into a bag made of polythene or to seal two pieces' of the laminate to one another in order to made a bag, this is not the case if it is to he fused to, for example, a container, as containers made of polythene or laminated with polythene are relatively expensive.

In addition, a lot of trays and containers are made of APET or PVC but at present no resealable laminate is available which will fuse to these material. There are PET films available which will fuse to these materials, and these films could be incorporated into the laminate structure described above and then fused to, for example, an APET container. However, such laminates are not resealable because the thinnest PET films currently available are 12 microns thick. Because of their thickness, they do not break at the edge where they seal with the container or tray when peeled. Upon peeling back the carrier film you are, therefore, left with either an intact or badly shredded PET film covering your container or tray.

The current invention seeks to provide an improved sheet material, which overcomes the disadvantages of the resealable larninates already in use by being reclosable and sealable to mono-materials such as APET, CPET, GPET, PVC, PS, ABS, PC etc.

Accordingly, in a first aspect of the invention, there is provided a sheet material comprising a substrate layer carrying a laminate of an adhesive layer and a sealable layer, wherein the sealable layer is preferably a lacquer and the adhesive layer provides a means whereby the substrate layer can be repeatedly detached from and reattached to the sealable layer by way of the adhesive layer. In a preferred embodiment, the sealable layer is less than 15 microns thick and fusible to another article preferably, by heat sealing. The other article is preferably made of APET, PVC or polystyrene. If the article is made of APET or PVC a co- polyester resin based sealable layer can be used. Alternatively, if the article consists of polystyrene an acrylic or polycarprolactone sealable layer is used. In a preferred embodiment, the adhesive layer is a pressure sensitive adhesive which can either have a stronger affinity to the substrate layer than to the sealable layer, a stronger affinity to the sealable layer than to the substrate layer or an equal affinity to the substrate layer and to the sealable layer. In most circumstances, the adhesive layer and sealable layer will overlay at least a part of, if not all of, the substrate layer. In a preferred embodiment, the substrate layer acts as a barrier between one side of the sheet material and the other. For example, the substrate layer could prevent egress of liquids, be impervious to microbes etc or act as a filter by only allowing the passage of certain things. The material for the substrate layer is chosen according to the intended use of the sheet material, for example polyester, nylon, polypropylene, paper, cellophane or other plastic films can be used as well as other suitable materials which will be readily apparent to those skilled in the art.

According to a second aspect of the invention, there is provided a sheet material as described above but further comprising an intermediate layer between the adhesive layer and the sealable layer. This intermediate layer is preferably made of PET (between 2-10 microns thick), PE (between 10-30 microns thick), OPP (between 415 microns thick), aluminium foil (between 4-50 microns thick) or cast or blown polypropylene film (between 10-50 microns thick).

In a third aspect of the present invention, there is provided a method of forming a sheet material, comprising:

(a) applying the sealable layer to one side of the substrate layer and the adhesive layer to the other side of the substrate layer; (b) transferring the sealable layer from one side of the substrate layer to which it is attached in (a) to the other side, so that it is now attached to the adhesive layer.

In a specific embodiment, the sealable layer is applied to the substrate layer with additives that facilitate the transfer of the sealable layer from the substrate layer to the adhesive layer. The sealable layer can be transferred to the adhesive layer by bringing the sealable layer and the adhesive layer into direct contact with each other so that the sealable layer detaches from the substrate layer and attaches instead to the adhesive layer. In a preferred embodiment the sealable layer is transferred to the adhesive layer by rolling up the substrate layer with the adhesive layer on one side and the sealable layer on the other side. This rolling up can be done under tension and into a reel.

According to a fourth aspect of the present invention, there is provided a method of forming a sheet material, comprising applying an adhesive layer to a substrate layer and then a sealable layer to the adhesive layer wherein the adhesive layer is preferably applied to the substrate layer by extrusion, gravure roll coating, Mayer bar coating, or hot melt coating and the sealable layer is preferably applied to the adhesive layer by extrusion, hot meh coating or by conventional coating by solution.

In a fifth aspect of the present invention, there is provided a method of forming a sheet material comprising applying an adhesive layer to a substrate layer, an intermediate layer to the adhesive layer and then a sealable layer to the second layer. In this case, the adhesive layer is preferably applied to the substrate layer by extrusion or hot melt coating, the intermediate layer is preferably laminated to the layer and the sealable layer is preferably applied to the intermediate layer as an extrusion, hot melt or as a conventional coating.

According to a sixth aspect of the present invention, there is provided the sheet material used as a packaging material or as part of a packing, preferably wherein the packaging is a bag, and the sheet material is fused to itself, or a lid for a container or a tray, wherein the sheet material is not fused to itself, but is preferably fused to the container or tray. The packaging material or package can be used for packaging food, pharmaceuticals or other consumables.

In a seventh aspect of the present invention, there is provided a package article comprising a sheet material.

In order that the invention may be better understood, an embodiment thereof will now be described by way of illustration only and with reference to the accompanying drawings, wherein:

Figure 1 shows a piece of conventional resealable material; Figure 2 shows a piece of sheet material in accordance with the invention in its first aspect; Figure 3 shows a sheet material in accordance with a second aspect of the invention; Figure 4 illustrates the steps involved in the method, in accordance with a third aspect of the present invention, used to produce the sheet material in accordance with the invention in its first aspect.

Figure 5 shows a bag in accordance with a sixth aspect of the present invention, made of the sheet material in accordance with the invention in its first aspect.

Figure 6 shows a tray with a resealable lid in accordance with a sixth aspect of the present invention, made from sheet material in accordance with the invention in its first aspect; and Figure 7 shows a tray with a sealing film in accordance with a sixth aspect of the 5 invention, being peeled away.

Figure 1 shows a piece of conventional resealable film 2 comprising a thin polythene film 8 laminated to a substrate layer 4 by way of a pressure sensitive adhesive layer 6. When the film 2 is fused to, for example, a polythene tray by way of the thin Polythene film 8, the substrate layer 4 can be peeled off the container thereby exposing the pressure sensitive adhesive layer 6. The substrate layer 4 can then be placed back over the container, and is held in place by the pressure sensitive adhesive layer 6, so that the container is resealed.

The sheet material 10, shown in Figure 2, is in accordance with the first aspect of the present invention. The adhesive layer 12 is composed of a lacquer which is chosen depending upon the type of container to which the material 10 is to be fused. For example, if the container is made of a PET or PVC a co-polyster resin based lacquer can be used. However, if the container is made of polystyrene an acrylic or polycarolactone lacquer can be used. On top of the adhesive layer 12 is a pressure sensitive adhesive layer 14 and on top of that is a substrate layer 16 that is capable of acting as a barrier between one side of the material 10 and the other. The substrate layer 16, which can be made from, for example, polyester, nylon, polypropylene, paper, cellophane or other plastic film, can be detached from the container to which the material 10 is fused by way of the lacquer 12 thereby exposing the pressure sensitive adhesive 14. Exposing the pressure sensitive adhesive 14 in this way means that the substrate layer 16 can now be replaced and held in place by the pressure sensitive adhesive 14.

Figure 3 shows another piece of sheet material 18, which is in accordance with the second aspect of the present invention. In this particular case, the material further comprises a intermediate layer 20 between the adhesive layer 14 and the sealable layer 12. This intermediate layer can be made from, for example, PET, PE, OPP, aluminium foil or cast or blown polypropylene. The sheet material 18 is reseable in the same way as the sheet material 10 shown in Figure 2.

Figure 4 illustrates the steps involved in one of the methods used to produce the material 10 shown in Figure 2. Initially, the sealable layer 12 is attached to one side, and the adhesive layer 14 to the other side, of the substrate layer 16 in order to produce the sheet material 22. The sheet material 22 is then wound up to produce the reel 24. In the reel 24 the sealable layer 12 and the adhesive layer 14 are brought into contact. The bond between the sealable layer 12 and the substrate layer 16 is weaker than the bond which is now able to form between the sealable layer 12 and adhesive layer 14. Finally therefore, when the reel 24 is unwound the sheet material 10 results. Thus, the sheet material 10 produced by this method comprises the adhesive layer 14 sandwiched between the substrate layer 16 and the sealable layer 12.

The sheet material 10, in Figure 2 and the sheet material 18, in Figure 3 can both be used to produce the resealable bag 26 shown in Figure 5. In Figure 5, the bag shown is composed of sheet material 10 whereby the adhesive layer 14 and the sealable layer 12 overlay completely the substrate layer 16. However, the adhesive layer 14 and the sealable layer 12 can only overlay the part of the substrate layer 16 which fuses to the other sheet. In either case fusing the sealable layers 12 of two pieces of sheet material 10 produces the bag 26. In addition, a bag could also be produced from one piece of sheet material 10 ( or 18) by folding the material and then fusing the sealable layers 12 along the edges which come together. The bag 26 can be used to house something in the space 28.

The resealable container 32 shown in Figure 6 comprises of sheet material 10 (but could equally comprise the sheet material 18, shown in Figure 3). The sealable layer 12 of the sheet material 10 fuses with the container 3 0 at the point 3 1. Again, the adhesive layer 14 and the sealable layer 12 are shown completely overlaying the substrate layer 16. However, the adhesive layer 14 and the sealable layer 12 may only overlay part of the substrate layer 16, preferably just the part of the substrate layer which is aligned with the bp 31 of the container 30 when the container is closed.

Figure 7, shows the resealable container 32, in Figure 6, being opened. In this particular case the sealable layer 12 breaks at position 34 due to its stronger affinity for the container 30 than for the adhesive layer 14. Equally however, the adhesive layer 14 could also break at a similar position to the sealable layer 12 and hence also remain behind on the container 30. Both of the above could also occur when the bag 26 in Figure 5 was opened.

Claims

1. A sheet material comprising a substrate layer carrying a laminate of an adhesive layer and a sealable layer, wherein the sealable layer is a coating and the adhesive layer provides a means whereby the substrate layer can be repeatedly detached from and reattached to the sealable layer by way of the adhesive layer.

2.

A sheet material as claimed in claim 1, wherein the sealable layer coating is a lacquer.

3. A sheet material as claimed in claim 1 or claim 2, wherein the sealable layer is less than 15 microns thick.

4.A sheet material as claimed in any of claims 1-3, wherein the sealable layer is fusable to another article.

5. A sheet material as claimed in claim 4, wherein the sealable layer is heat sealable to another article.

6.

A sheet material as claimed in claim 5, wherein the other article consists of APET or PVC.

7.

A sheet material as claimed in claim 5, wherein the other article consists of polystyrene.

8.

A sheet material as claimed in claim 6, wherein the sealable layer is a copolyester resin based lacquer.

9.

A sheet material as claimed in claim 7, wherein the sealable layer is an acrylic or polycarprolactone lacquer.

10. A sheet material as claimed in any of the preceding claims, wherein the adhesive layer is a pressure sensitive adhesive.

11. A sheet material as claimed in any of the preceding claims, wherein the adhesive layer has a stronger affinity to the substrate layer than to the sealable layer.

12.

A sheet material as claimed in claims 1-10, wherein the adhesive layer has a stronger affinity to the sealable layer than to the substrate layer.

13. A sheet material as claimed in claims 1-10, wherein the adhesive layer has an equal affinity to the substrate layer and to the sealable layer.

14. A sheet material as claimed in any of the preceding claims, wherein the adhesive layer and sealable layer overlay at least a portion of the substrate layer.

15. A sheet material as claimed in claims 1-13, wherein the adhesive layer and sealable layer overlay substantially all of the substrate layer.

16. A sheet material as claimed in any of the preceding claims, wherein the substrate layer, acts as a barrier between one side of the sheet material and the other.

17. A sheet material as claimed in claim 16, wherein the barrier prevents egress of liquids from one side to the other.

18. A sheet material as claimed in claim 16, wherein the barrier is impervious to microbes.

19. A sheet material as claimed in claims 16-18, wherein the substrate layer is made from polyester, nylon or polypropylene, paper, cellophane or other plastic film.

20.

A sheet material as claimed in any of the preceding claims, further comprising an intermediate layer between the intermediate layer and the adhesive layer.

21.

A sheet material as claimed in claim 20, wherein the intermediate layer is PET.

22.

A sheet material as claimed in claim 21, wherein the PET is between 2-10 microns thick.

23.

A sheet material as claimed in claim 20, wherein the intermediate layer is PE.

24.

A sheet material as claimed in claim 23, wherein the PE is between 10-30 microns thick.

25.

A sheet material as claimed in claim 20, wherein the intermediate layer is OPP.

26. A sheet material as claimed in claim 25, wherein the OPP is between 4 to 15 microns thick.

A sheet material as claimed in claim 20, wherein the intermediate layer is aluminium foil.

28. A sheet material as claimed in claim 27, wherein the aluminium foil is between 4 to 50 microns thick.

29. A sheet material as claimed in claim 20, wherein the intermediate layer is cast at blown polypropylene film.

30. A sheet material as claimed in claim 29, wherein the intermediate layer is between 10 to 50 microns thick.

31. A method of forming a sheet material, comprising:

(a) applying the sealable layer to one side of the substrate layer and the adhesive layer to the other side of the substrate layer; and (b) transferring the sealable layer from the side of the substrate layer to which it is attached in (a) to the other side so that it is now attached to the adhesive layer.

32. A method of forming a sheet material as claimed in claim 3 1, wherein the sealable layer is originally applied to the substrate layer with additives that facilitate the transfer of the sealable layer from the substrate layer to the adhesive layer.

33. A method of forming a sheet as claimed in claim 31 and 32, wherein the sealable layer is transferred to the adhesive layer by bringing the sealable layer and adhesive layer into direct contact with each other so that the sealable layer detaches from the substrate layer and attaches instead to the adhesive layer.

34. A method of forming a sheet material as claimed in claims 31-33, wherein the sealable layer is transferred to the adhesive layer by rolling up the substrate layer with the adhesive layer on one side and the sealable layer on the other side so that as the sealable layer and adhesive layer come into contact with each other and the sealable layer then detaches from the substrate layer and attaches instead to the adhesive layer.

A method of forming a sheet material as claimed in claim 34, wherein the rolling up is done under tension and into a reel.

36. The reel produced by the method of claim 35, whereby the substrate layer with the sealable layer on one side and the adhesive layer on the other side has been rolled up so that the sealable layer is now in direct contact with the adhesive layer.

37.

38.

A method as claimed in claims 32-35, wherein the bond between the substrate layer and the sealable layer is less than 50g per 15 MM2.

A method as claimed in claims 32-35 and 37, wherein the adhesive layer is applied to the substrate layer by any conventional method.

39. A method as claimed in claim 38, wherein the adhesive layer is applied by extrusion, gravure roll coating or Mayer bar coating.

40. A method of forming a sheet material, comprising applying an adhesive layer to a substrate layer and then a sealable layer to the intermediate layer.

41.

A method as claimed in claim 40, wherein the adhesive layer is applied to the substrate layer by extrusion or hot melt coating.

42. A method as claimed in claim 40 or claim 41, wherein the sealable layer is applied to the adhesive layer by extrusion, hot melt coating or by conventional coating by solution.

43. A method of forming a sheet material, comprising applying an adhesive layer to a substrate layer, an intermediate layer to the intermediate layer and then a sealable layer to the second intermediate layer.

44. A method as claimed in claim 43, wherein the adhesive layer is applied to the substrate layer by extrusion or hot mek coating.

45. A method as claimed in claim 43 and claim 44, wherein the intermediate layer is laminated to the adhesive layer.

46.

47.

48.

49.

50.

51.

A method as claimed in claims 43-45, wherein the sealable layer is applied to the intermediate layer as an extrusion, hot melt or as a conventional coating.

Use of a sheet material as claimed in claims 1-30 as a packaging material or as part of a packaging.

A use as claimed in claim 47, wherein the packaging is a bag.

A use as claimed in claim 47, wherein the sheet material is a lid for a container.

A use as claimed in claim 49, wherein the container is a tray.

A use as claimed in claim 47 and claim 48, wherein the sheet material is fused to itself

52. A use as claimed in claim 47, claim 49 and claim 50 wherein the sheet material is not fused to itself.

53. A use as claimed in claim 52, wherein the sheet material is fused to a container or tray.

54. A use as claimed in claims 47-53, wherein the packaging material or package is used for packaging food, pharmaceuticals or other consumables.

55. A sheet material formed by a method as claimed in claims 31-35 and 3746.

56. A packaged article comprising a sheet material as claimed in claims 130.

57. A composite sheet material as shown in the accompanying drawings.

58. A method for making a composite sheet material as shown in the accompanying drawings.