A METHOD OF MAKING A PACK FOR FOOD AND THE ASSOCIATED PACK

Abstract

A method of making a pack for food comprising the following steps. Forming a tray by providing a tray laminate comprising a fibrous web (21) bonded to a web of a gas barrier film (20) comprising a multi-layer laminate comprising a heat sealable layer and a gas barrier layer. Vacuum and/or thermoforming the laminate to create a tray with an upstanding rim. Filling the tray with a food product (F). Providing a web of lid film (13), the lid film (13) being a gas barrier film comprising a multi-layer laminate comprising a heat sealable layer and a gas barrier layer. Heat sealing the lid film (13) to the gas barrier film of the tray around the periphery of the tray to create a hermetic seal between the two barrier films. Severing the pack from the webs of material.

Description

The present invention relates to a method of making a pack for food. In particular, the invention is directed at an improvement of a pack for food of the type which comprises a shallow tray hermetically sealed by a film lid. Such packs are widely used for the packaging of flat foods such as sliced meat and cheese. They can, however, be used for any type of food which can be fitted into a relatively shallow container.

Traditionally, the tray is made from a thermoformed plastic and a film lid is heat sealed to the tray to create a hermetically sealed closure for the food. A separate sticker is then adhered to the completed pack to provide information concerning the contents of the pack and promotional information.

For environmental reasons, there is a need to reduce the amount of plastic used in packaging.

A recent development of a pack of this type is a tray which is formed of a fibrous material such as paper which is provided with an extrusion coating of a polymer. However, such a coating is not suitable for uses where a modified atmosphere (i.e. where a pack is filled with a gas other than air) is required where gas transmission needs to be prevented. The present invention aims to provide a pack which reduces the amount of plastic involved, but which can also provide a good gas barrier such that it is suitable for modified atmosphere applications.

According to the present invention there is provided a method according to claim 1

By providing a tray which is a laminate of the fibrous web and a gas barrier film, the tray is able to reduce significantly the amount of plastic required as compared to a conventional plastic tray. Further, as the tray has a laminated gas barrier film, the film is much more readily able to form a reliable gas barrier seal than the extrusion coating of the prior art. This is because a multi-layer film can be used, with enhanced barrier properties to provide a hermetic seal with the barrier film of the lid. The extrusion coating process used in the prior art is limited to a simple, single layer material such that it is not suitable for providing complex film properties.

The lid may comprise just the barrier film layer. However, preferably, the lid film is part of a lid laminate further comprising a second fibrous web adhered to the lid film to create a lid laminate before the step of heat sealing the lid film to the tray.

This provides a fibrous layer on both the base and the lid of the container which has a pleasant “natural” feel for a consumer. It also allows printing to be applied directly to the fibrous web on the tray and/or the lid thereby removing the need to apply a sticker to the pack in order to provide the necessary information on the pack contents. This provides a much simpler manufacturing process and also creates a much nicer looking pack.

The method preferably also further comprises cutting a window in the second fibrous web before adhering it to the lid film. By cutting the window before adhering the second fibrous web to the lid film, a well-defined window can be created without the possibility of cutting into the film and spoiling the integrity of the pack. Again, this step provides a pack with good aesthetic appeal in which the user can see the contents of the pack.

The fibrous web of the tray is preferably able to provide most of the structural integrity of the tray with the amount of plastic in the gas barrier film being minimised whilst ensuring that it is sufficient to prevent any moisture passing into the fibrous web and also to provide the hermetic seal with the lid film. Preferably, therefore, the fibrous web in the tray is at least three times, preferably at least four times and most preferably at least five times thicker than the gas barrier film of the tray.

The present invention also extends to a pack according to claim 7.

The pack has the advantages described above in relation to the first aspect of the invention. It also preferably has the second fibrous web creating the lid laminate and the window in the lid as well as the optional printing described above.

The reference to a gas barrier film in this context is a film which will provide a significant barrier to the flow of gas through the matrix of film itself (as opposed to any faults, tears or pinholes created at edges of the film). In particular, we are concerned with a film which will prevent the flow of oxygen. Food packages are frequently provided with a modified atmosphere, for example by being flushed with a gas (e.g. nitrogen) or by being evacuated thereby reducing as much as possible the level of oxygen within the food pack. The purpose of a gas barrier film is to provide a sufficient barrier to the gases normally found in air (particularly oxygen), that the atmosphere within the container will remain within an acceptable oxygen level for the desired shelf life of the product.

According to one definition, the gas barrier film should be sufficient to ensure that, in a hermetically sealed container, the film is able to prevent an oxygen level within the pack from rising from 1% (following the introduction of the modified atmosphere) to above 10% and preferably above 5% in 15 days (assuming normal storage and display at a temperature of less than or equal to 20° C.).

Put another way, the film should have barrier properties for oxygen which ensure that the film has an oxygen transmission rate of less than 15 g/m²/24 hours. More preferably this is below 6 g/m²/24 hours (as determined by standard test ASTM D3985).

An example of a method and pack in accordance with the present invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 is a schematic drawing showing the manufacturing process and FIG. 2 is a cross-section through an edge of the pack showing the layer structure.

With reference to FIG. 1, the materials required to create the lidding for the final pack are supplied from two reels, 1, 2 in a lid manufacturing stage L. The reel 1 supplies a web of fibrous lid material 5. This may be, for example, a paper of 70 gsm. Having a thickness of 80 microns. The fibrous lid material 5 may have been pre-printed on its upper surface 6. Alternatively, the fibrous lid material 5 may be printed in-line as part of the lidding production process by a printer 7. The film then passes a cutter 8 which will cut apertures into the web which will become windows in the finished pack P.

The reel 2 supplies the gas barrier film for the lid. The film is a multi-layer high barrier film, where one side is a polyolefin, such as 12-40 microns of Poly-Ethylene, which will form a heat seal layer. The other surface of the film may be the same, or a different polymer, such as 12-40 microns of PET. In addition, the film will contain typically 1-5 microns of a barrier substance, such as EVOH or SiOx. Additional layers and tie layers may also be present to complete the gas barrier film. The gas barrier lid film 9 may have antimist properties on the internal, heatseal surface or a food grade antimist coating may be applied separately before it passes below an adhesive applicator 11 which applies a film of adhesive to the other side of film 9 before the two webs or material are brought together in a lamination region 12 to create a lid laminate 13. Alternatively, adhesive may be applied to the fibrous lid material 5.

The materials required to make the tray of the final pack are supplied from two reels, 3, 4 in a tray manufacturing stage T. A gas barrier film 20 is fed from the reel 3 past an adhesive station 21 which applies a film of adhesive to the gas barrier film 20. This film is preferably a PE/EVOH/PE High Barrier film with or without additional layers and a total thickness of typically 35-50 micron but could be any other formable HB film. A web of fibrous tray material 21 is fed from the reel 4. The fibrous tray material is a material of typically 200-400 micron thickness at (150-300 gsm) and may either be pre-printed or printed in line with this process, as described for the lidding material. The adhesive may alternatively be applied to this material. The two materials 20, 21 are laminated at rollers 22 to produce a tray laminate 23.

The final, sealed, packaging product, is produced on lines at a pack manufacturing stage P. Typically, this is done on a site where the packs are to be assembled and filled which is generally different to the site where the lid laminate 13 and tray laminate 23 are formed. The tray laminate 23 is fed to a thermoforming tool 24 with a male die 25 and female die 26 in the shape of the tray. These apply heat and pressure to the tray laminate 23 in a manner well known in the art to create a recessed tray shape having a depth of typically 15 mm. Alternatively there may only be one die and a combination of air pressure and vacuum may be used to shape the web to the die, with or without the application of heat. Although the schematic drawing shows only one such tray being formed, in practice, there will be an array of male and female dies such that multiple tray shapes will be formed in the web across and along the base laminate 23 simultaneously.

The tray laminate 23 then passes to a filling station 28 and a conveyor 29 where the recessed tray shapes are filled with a stack of food items F or an individual item. The tray laminate 23 then passes on the conveyor 29 beneath a roller 30 which receives the lid laminate 13. The lid laminate 13 is pressed onto the tray laminate and heat is applied around the rim of each tray using a heat sealing platen to create a continuous heat seal between the two laminates to hermetically seal the lid to the container.

The combined laminates which have now been filled are then fed by the conveyor 29 to a cutter 32 where the individual packs P are cut from the web.

The detail of the pack is shown in FIG. 2. This shows the four layer structure comprising the fibrous lid material 5 and the lid film 9 which are joined together by an adhesive 40 as described above to create the lid laminate 13. The fibrous lid material 5 terminates at an edge 41 providing exposed film 42 which provides the window formed by cutters into an inner cavity 43 in which the food is positioned.

The tray film 20 is adhered to the fibrous tray material 21 by an adhesive 44 as described above to create the tray laminate 23. The recessed shape which is apparent from FIG. 2 is the shape which is formed in the thermoforming process by the thermoforming tool 24.

At the lip of the tray, there is a region 45 where the films 9, 20 are heat sealed to one another around the full periphery of the tray thereby ensuring that the enclosure 43 is hermetically sealed. This region 45 may extend in certain regions almost to the outer periphery of the rim. However, in at least one region, ideally a corner portion, there is preferably a release region 46 where the films are left unconnected allowing the user to peel apart the film 9, 20 starting from this region.

The finished product is one which can be made on a continuous basis on a web-based system. Two webs are brought together in a manner which can create a hermetically sealed container with gas barrier properties which requires significantly less plastic than in the prior art. The fibrous layers can be printed with full colour printing directly onto the pack removing the need for a sticker. Also, different and distinctive shapes of windows can readily be created simply by changing the cutter 8. The finished pack can therefore be made to have a striking overall appearance as well as having a pleasant and more natural feel of a fibrous container as opposed to the conventional plastic.

Claims

1. A method of making a pack for food, the method comprising the steps of:

forming a tray by providing a tray laminate comprising a first fibrous web bonded to a web of a gas barrier film comprising a multi-layer laminate comprising a heat sealable layer and a gas barrier layer;

vacuum and/or thermoforming the laminate to create a tray with an upstanding rim;

filling the tray with a food product;

providing a web of lid film, the lid film being a gas barrier film comprising a multi-layer laminate comprising a heat sealable layer and a gas barrier layer;

adhering a second fibrous web having a window to the lid film to form a lid laminate;

heat sealing the lid film to the gas barrier film of the tray around the periphery of the tray to create a hermetic seal between the two barrier films; and

severing the pack from the webs of material.

2. (canceled)

3. (canceled)

4. A method according to claim 1, wherein the first fibrous web of the tray is at least three times the thickness, preferably at least four times the thickness and more preferably at least five times the thickness of the gas barrier film of the tray.

5. A method according to claim 1, further comprising the step of printing on the first fibrous web of the tray prior to creating the tray laminate.

6. A method according to claim 1, further comprising the step of printing on the second fibrous web prior to creating the lid laminate.

7. A pack for food, the pack comprising a tray thermoformed from a laminate of a fibrous web and a web of a gas barrier film into a tray with an upstanding rim, and a gas barrier film lid heat sealed to the sheet of gas barrier film in the tray around the periphery of the tray to create a hermetically sealed enclosure between the two barrier films.

8. A pack according to claim 7, wherein the lid is a laminate of a second fibrous web and the gas barrier film.

9. A pack according to claim 8, further comprising a window in the second fibrous web.

10. A pack according to claim 7, wherein the fibrous web is printed.

11. A pack according to claim 8, wherein the second fibrous web is printed.

12. A pack according to claim 7, wherein the heat sealable layer is a polyolefin.

13. A pack according to claim 7, wherein the gas barrier film is ethylene vinyl alcohol copolymer (EVOH) or silicon oxide (SiOx).

14. A pack according to claim 7, wherein the heat sealable layer has an anti-mist coating.

15. A method according to claim 1, wherein the heat sealable layer is a polyolefin.

16. A method according to claim 1, wherein the gas barrier film is ethylene vinyl alcohol copolymer (EVOH) or silicon oxide (SiOx).

17. A method according to claim 1, wherein the heat sealable layer has an anti-mist coating.