WO2020008167A1

WO2020008167A1 - Multilayer film

Info

Publication number: WO2020008167A1
Application number: PCT/GB2019/051756
Authority: WO
Inventors: Gary BUCHALTER
Original assignee: British Polythene Limited
Priority date: 2018-07-02
Filing date: 2019-06-21
Publication date: 2020-01-09

Abstract

A multilayer film or sheet is provided and comprises a first layer of polyethylene having a first density and a second layer of polyethylene having a second density, the first and second densities being different, and at least one core or inner layer which is a polyethylene based layer having oxygen barrier properties.

Description

MULTILAYER FILM

The present invention relates generally to films (a thin continuous polymeric material) and sheets prepared from polyethylene resins. More specifically, the invention relates to multi-layer films and sheets made from particular polyethylene compositions and polyethylene based organic mixtures.

Polyethylene is a polymer of ethylene; especially: any of various partially crystalline lightweight thermoplastics (CH₂CH₂)_X that are resistant to chemicals and moisture, have good insulating properties, and are used, for example, in packaging and insulation. Polyethylene is a family of materials with densities ranging typically from 0.86g/cm³ to 0.965g/cm³.

According to an aspect of the present invention there is provided a multilayer film or sheet comprising a first layer of polyethylene having a first density and a second layer of polyethylene having a second density, the first and second densities being different, and at least one core or inner layer of a polyethylene based layer having oxygen barrier properties. According to a further aspect of the present invention there is provided a multilayer film or sheet comprising a first surface layer of polyethylene having a first density and a second, opposite surface layer of polyethylene having a second density, the first and second densities being different, and at least one core or inner layer of a polyethylene based layer having oxygen barrier properties. i In some embodiments the barrier layer/s comprise a mixture of organic raw material based on PE.

According to an aspect of the present invention there is provided a multilayer film or sheet comprising a first layer of polyethylene having a first density and a second layer of polyethylene having a second density, the first and second densities being different, and an inner layer of a polyethylene based organic mixture having oxygen barrier properties. According to an aspect of the present invention there is provided a multilayer film comprising a first layer of polyethylene having a first density and a second layer of polyethylene having a second density, the first and second densities being different, and an inner layer of a polyethylene based organic mixture having oxygen barrier properties.

According to an aspect of the present invention there is provided a multilayer sheet comprising a first layer of polyethylene having a first density and a second layer of polyethylene having a second density, the first and second densities being different, and an inner layer of a polyethylene based organic mixture having oxygen barrier properties.

In some embodiments the film or sheet is a three-layer structure. Other embodiments have more than three layers, for example five layers. The inner layer may have a thickness in the range 4 m to I 20pm, for example approximately 8pm or 12pm for a film and approximately 50pm or 60pm for a sheet structure. In some embodiments the first layer is an outside layer and the second layer is an inside layer i.e. the first and second layers are the “skin” at the top and bottom (in section) of the film.

In some embodiments the first density is higher than the second density. This allows, for example, a temperature differential to be formed in a film if two sections of film are heat sealed together, for example with two respective inside layers facing each other.

The first density may be in the range 0.9 1 0g/cm³ to 0.965g/cm³. For example the first density may be approximately 0.93 l g/cm³ for a film and approximately 0.920g/cm³ for a sheet structure.

For a film structure the second density may be in the range 0.80g/cm³to 0.90g/cm³. For example the second density may be approximately 0.88g/cm³. For a sheet structure the second density may be in the range 0.90g/cm³to 0.965g/cm³ For example the second density may be approximately 0.92g/cm³

The density of the core or inner layer may be in the range 0.95g/cm³ to 1 .5g/cm³. For example the density of the core layer may be approximately I . l g/cm³. The first layer of a thin film may have a thickness in the range 4 m to 25pm. For example the first layer may be a thickness of approximately I 5pm.

The second layer may have a thickness in the range 4pm to 30pm. For example the second layer may have a thickness of approximately 1 5.0pm.

The overall thickness of the film may be in the range 30pm to 200pm. For example the thickness of the film may be approximately I 20pm. The thickness of a sheet may be in the range 200pm to I OOOpm. The first layer may have a thickness in the range 20pm to 200pm. The second layer may have a thickness in the range 20pm to 200pm.

A barrier layer may have a thickness in the range 5pm to l OOpm, for example approximately I Opm for a film and approximately 30pm for a sheet structure

In some embodiments the film is formed by a co-extrusion process (the extrusion of multiple layers of material simultaneously), for example a blown film co-extrusion process (involving the extrusion a tube of molten polymer through an annular die and inflating to a size greater than its initial diameter to form a thin film bubble). Sheets may be formed, for example, using a sheet die.

The present invention also provides a three-layer coextruded polyethylene film comprising an inside layer of polyethylene having a first density and an outside layer of polyethylene having a second density, the first and second densities being different, and a core or inner layer of a polyethylene based organic mixture between the inside and outside layers, the core or inner layer having oxygen barrier properties.

In some embodiments the barrier material is only used in the core layer.

In some embodiments the material used to provide the barrier in the barrier/core layer is a PE-compatible organic, food approved mixture.

The present invention also provides a product, such as a pouch, flow wrap, tray or lid, formed from a film or sheet as described herein. In some embodiments all of the layers of the product are polyethylene or polyethylene based organic mixture, enabling it to be easily recycled through standard polyethylene recycling channels.

The present invention also provides for the use of commercially available adhesion enhancers in layers adjacent to a barrier layer to ensure cohesion of the overall structure. Layer concentration of this additive may be between 1 0% and 1 00% and typically 20% when not in a discrete layer of its own.

The present invention also provides for the preparation of a polyethylene film for use in the manufacture of a disposable pouch and pouches formed therefrom.

The present invention also provides a stand-up pouch which is easily recyclable in the polyethylene recycling stream, the pouch being formed from film as described herein, and formed by sealing opposing panels of film together, with respective inside layers sealed together. In some aspects and embodiments a film is designed to seal inside layer to inside layer with a temperature differential to the outside layer. In other aspects and embodiments a tray structure provides an upper surface to seal to a suitable lid. In other aspects and embodiments a lid structure provides with a lower surface to seal to a suitable tray.

Different aspects and embodiments of the invention may be used separately or together.

Further particular and preferred aspects of the present invention are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with the features of the independent claims as appropriate, and in combinations other than those explicitly set out in the claims.

The present invention will now be more particularly described, by way of example, with reference to the accompanying drawings.

The example embodiments are described in sufficient detail to enable those of ordinary skill in the art to embody and implement the systems and processes herein described. It is important to understand that embodiments can be provided in many alternative forms and should not be construed as limited to the examples set forth herein. Accordingly, while embodiments can be modified in various ways and take on various alternative forms, specific embodiments thereof are shown in the drawings and described in detail below as examples. There is no intent to limit to the particular forms disclosed. On the contrary, all modifications, equivalents, and alternatives falling within the scope of the appended claims should be included. Elements of the example embodiments are consistently denoted by the same reference numerals throughout the drawings and detailed description where appropriate.

Unless otherwise defined, all terms (including technical and scientific terms) used herein are to be interpreted as is customary in the art. It will be further understood that terms in common usage should also be interpreted as is customary in the relevant art and not in an idealised or overly formal sense unless expressly so defined herein.

In the following description, all orientational terms, such as upper, lower, vertical, horizontal, radially and axially, are used in relation to the drawings and should not be interpreted as limiting on the invention.

In Figure I a co-extruded multilayer film is generally indicated 10. The film 10 comprises a first, “outside” layer of polyethylene 15, a second, “inside” layer of polyethylene 20 and a core, barrier layer of polyethylene 25.

The layer 15 is formed from polyethylene having a higher density than the layer 20. The layer 25 is formed from a PE-compatible organic, food approved oxygen barrier compound resin. As represented in Figure 2, when two portions of the film are sealed together the two layers 1 5a, 1 5b become outside layers and the two layers 20a, 20b are sealed to each other and become inside layers. The film can be heat sealed together using existing commercially available equipment because of the density gradient between the layers 15a, 1 5b and the layers 20a, 20b.

In some embodiments the layers are formed based on heat resistance (which may correspond with density but not necessarily) with a PE layer with a higher heat resistance being formed as an outside layer and a layer with a lower resistance formed as an inside layer, providing a temperature resistance differential across the thickness of the film.

Figure 3 shows a film 1 30 formed according to a further embodiment.

The film 1 30 comprises, from“outside” to“inside”, an outside layer of medium density PE 1 35, a layer of high density PE 140, a further layer of high density PE 145, a barrier layer of PE 1 50, and an inside layer of low density PE 1 55. For sealing purposes then inside layer 1 55 would seal against another such layer, with the layer 1 30 forming both external faces.

Figure 4 shows a sheet 260 formed according to a further embodiment. The film 260 comprises, from“outside” to“inside”, an outside layer of medium density PE 265, a barrier layer of PE 270, a layer of high density PE 275, a further barrier layer of PE 280, and an inside layer of low density PE 285. Films and sheets formed in accordance with the present invention can be used to produce, for example, recyclable stand-up pouches, tray, lids and flow wrap packs with oxygen barrier properties.

Figure 5 shows the results of tests performed in relation to a variety of different films (all of which are five layer films with two barrier layers) formed in accordance with the present invention.

Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiments shown and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.

Claims

1. A multilayer film or sheet comprising a first layer of polyethylene having a first density and a second layer of polyethylene having a second density, the first and second densities being different, and at least one core or inner layer which is a polyethylene based layer having oxygen barrier properties.

2. A film or sheet as claimed in claim I , in which the core or inner layer has a thickness in the range 5pm to 20pm.

3. A film or sheet as claimed in claim 2, in which the core or inner layer has a thickness of approximately I 0pm or I 5pm.

4. A film or sheet as claimed in any preceding claim, in which the first layer is an outside layer and the second layer is an inside layer.

5. A film or sheet as claimed in any preceding claim, in which the first density is higher than the second density.

6. A film or sheet as claimed in any preceding claim, in which the first density is in the range 0.929g/cm³ to 0.965g/cm³.

7. A film or sheet as claimed in claim 6, in which the first density is approximately

0.93 l g/cm³.

8. A film or sheet as claimed in any preceding claim, in which the second density is in the range 0.80g/cm³to 0.90g/cm³.

9. A film or sheet as claimed in claim 8, in which the second density is approximately 0.88g/cm³.

10. A film or sheet as claimed in any preceding claim, in which the density of the core or an inner layer is in the range 1 .0g/cm³ to 1 .5g/cm³.

1 1 . A film or sheet as claimed in claim 1 0, in which the density of the core or an inner layer is approximately l . l g/cm³.

12. A film or sheet as claimed in any preceding claim, in which the first layer has a thickness in the range 5pm to 25pm.

1 3. A film or sheet as claimed in claim 12, in which the first layer has a thickness of approximately I 6pm.

14. A film or sheet as claimed in claim 1 3, in which the second layer has a thickness in the range 5pm to 30pm.

15. A film or sheet as claimed in claim 14, in which the second layer has a thickness of approximately I 3pm.

16. A film as claimed in any preceding claim, in which the thickness of the film is in the range 30pm to 200pm.

17. A film or sheet as claimed in any preceding claim, in which the thickness of the sheet is in the range 200pm to I 000pm.

18. A film or sheet as claimed in any preceding claim, in which the first layer has a thickness in the range 20pm to 200pm.

19. A film or sheet as claimed in any preceding claim, in which the second layer has a thickness in the range 20pm to 200pm.

20. A film or sheet as claimed in any preceding claim, in which the first density is in the range 0.900g/cm³ to 0.965g/cm³.

21. A film or sheet as claimed in any preceding claim, in which the or at least one of the barrier layers has a thickness in the range 5 pm to 50 pm.

22. A three-layer coextruded polyethylene film or sheet comprising an inside layer of polyethylene having a first density and an outside layer of polyethylene having a second density, the first and second densities being different, and a core layer of polyethylene formed between the inside and outside layers, the core layer having oxygen barrier properties.

23. A film or sheet as claimed in claim 22, in which the barrier material is only used in the core or an inner layer.

24. A five-layer film or sheet comprising: an inside layer of polyethylene having a first density; a polyethylene-based barrier layer; a central layer of polyethylene; a polyethylene-based oxygen barrier layer; and an outside layer of polyethylene having a second density, the first and second densities being different.

25. A multilayer film or sheet comprising a first layer of polyethylene having a higher heat resistance and a second layer of polyethylene having a lower heat resistance, and a core or inner layer of polyethylene layer having oxygen barrier properties arranged between the first and second layers.

26. A film as claimed in claim 25, in which the first layer is arranged as an outside layer and the second layer is arranged as an inside layer so that, when sealed together, two opposing second layers seal against each other.

27. A pouch, flow wrap pack, tray or lid formed from a film or sheet as claimed in any preceding claim.

28. A stand-up pouch, flow wrap pack or lid which is easily recyclable in the polyethylene recycling stream, the pack being formed from film as claimed in any of claims I to 26, and formed by sealing opposing panels of film together, with respective inside layers sealed together.

29. A tray formed from a sheet containing an inner layer comprised, in part or entirely, of a polyethylene based organic oxygen barrier mixture which is easily recyclable in the polyethylene recycling stream where the first layer is heat sealable to a suitable lidding film.