GB2436323A

GB2436323A - A biodegradable container

Info

Publication number: GB2436323A
Application number: GB0605444A
Authority: GB
Inventors: Ian Henry Balchin; Carl John Sofield
Original assignee: Stanelco RF Technologies Ltd
Current assignee: Stanelco RF Technologies Ltd
Priority date: 2006-03-20
Filing date: 2006-03-20
Publication date: 2007-09-26
Also published as: GB0605444D0

Abstract

A container for a product such as potato crisps consists of two or more packets inside each other 12,16, each container or packet 12,16 being of a biodegradable polymeric material, and at least two of the containers or packets 12,16 have different permeability properties. For example a packet 12 formed from a thermoplastic starch film may be enclosed within a packet 16 formed from a poly lactic acid film. The container 12 preferably provides a barrier to oxygen while the container 16 preferably provides a barrier to moisture.

Description

Container This invention relates to containers, particularly but not

exclusively those for packaging foodstuffs such as potato crisps or chips.

Potato crisps, and crisps made from other vegetables, are usually packaged in packets either for individual use or in slightly larger quantity for family use. The packets are made of a variety of different materials, for example incorporating a layer of paper or of metallic material, and usually also a polymeric film.

Indeed the use of packets made only of a polymeric film is widely known. For example packets may be made of two layers of polypropylene laminated together, with a printed layer (and a metallised layer, if required) sandwiched between the two layers of polypropylene.

However such materials are typically not biodegradable, and so cause a waste problem. To make a satisfactory packet the materials must provide an adequate barrier to both moisture and oxygen, and in some cases also to light, to ensure that the contents do not suffer degradation during storage.

According to the present invention there is provided a container for a product, the container comprising a first container of a first biodegradable polymeric material to contain the product, and an outer container of a second biodegradable polymeric material which encloses the first container, wherein the first container and the outer container have different permeabilities.

Preferably each container is a flexible packet formed of a flexible film of a respective biodegradable polymeric material. Preferably the outer container provides a moisture barrier, while the first container provides a barrier to oxygen. The first and outer containers may be laminated together, but are preferably separate items. Each of the containers may itself be formed of laminated materials.

Where printing is required, this may be performed on the inside of the outer container. This may provide a sufficient light barrier, but alternatively a light-tight coating, such as a metallised surface coating, might be provided preferably being incorporated in the first container. Additional coatings, preferably of biodegradable materials, may also be provided such as a coating of wax. Printing might instead be performed on the outside of the first container.

Preferably the outer container comprises a polymer such as polylactic acid (PLA), is this can provide transparent films which are substantially impermeable to moisture, and which is biodegradable when composted. The first container may comprise a polymer such as thermoplastic starch which provides a satisfactory oxygen barrier and which is both water-soluble and biodegradable. If the product is substantially dry, then the first container may be of thermoplastic starch.

Indeed if the first container is of thermoplastic starch (TPS) it may be edible, and may be provided with flavourings, perfumes or colourings. If the product is moist, then the first container preferably comprises an inner container of a biodegradable polymeric material providing a moisture barrier, and this inner container is enclosed within a second container of a biodegradable polymeric material. Thus in this case the product might be contained within an inner container of PLA, enclosed within a second container of TPS, and then an outer container of PLA.

The invention will now be further and more particularly described, by way of example only, and with reference to the accompanying drawings in which on Figure 1. shows a cross-sectional view of a packet of the invention for containing potato crisps; and Figure 2 shows a cross-sectional view of a packet of the invention for containing a moist foodstuff.

It is widely recognised that it would be desirable if materials used in packaging were biodegradable and compostable. In this regard, standards have been proposed for classifying polymeric films as compostable and biodegradable, one such standard requiring that no more than 10% of the film's original weight should remain on a 3/8 inch (9.5 mm) screen following 12 weeks of exposure to a compost medium. Polymers based on lactic acid comply with such standards, but do not necessarily provide an adequate barrier to gases or vapours. The use of starch-based material in polymers has also been proposed, and such material is also biodegradable and may indeed be water-soluble. But again, such starch-based films do not necessarily provide adequate barrier properties.

Transparent films made of starch, typically combined with a plasticiser, are now available commercially, for example those developed by Biotec Biologische Naturverpackungen GmbH. As explained in US 6 235 8l5B (Loercks et al), suitable thermoplastic starch can be made from essentially anhydrous starch that is homogenised in an extrusion process with the addition of a plasticiser such as glycerol or sorbitol, and is melted within a temperature range between 120 and 220 C. (Such thermoplastic starch should be distinguished from destructured starches which have been known for several years and which are made by treating starch in the presence of more than about 5% water.) As described in Loercks et al, instead of adding the plasticiser (such as glycerol or sorbitol), biodegradable polymers which may be hydrophobic may be provided instead, for example aliphatic polyesters, copolyesters, polyester amides, polyethylene oxide polymers, or poly glycols.

Referring to figure 1, a packet 10 for containing potato crisps 11 consists of an inner packet 12 made of a TPS film 14. This film 14 provides a satisfactory barrier to prevent oxygen diffusing in, and to prevent carbon dioxide or nitrogen diffusing out, and it is white. It is made by firstly welding opposite edges 13 of a long sheet together to form a tube, and then forming welds 15 across the tube to define the packets 12, the top weld 15 being formed after the packet has been filled with the appropriate quantity of crisps 11. This welding may be performed by dielectric welding between opposed electrodes, preferably using electrodes coated with a barrier material, between which a radio-frequency signal is applied.

The packet 10 also includes an outer packet 16 made of a PLA film 18, which is transparent. The inner surface of this film 18 is printed with trade marks, descriptive information and decoration. Preferably this printing uses biodegradable inks. The outer packet 16 completely encloses the inner packet 12. The outer packet 16 may be made in substantially the same way as the inner packet, the welds again being formed by dielectric welding between opposed electrodes. The combination of the inner packet 12 and the outer packet 16 very effectively prevents moisture and oxygen from reaching the contents of the inner packet 12.

Referring to figure 2, a packet 30 for containing a moist food product (such as a cucumber sandwich 31) consists of an inner packet 32 made of a PLA film 18.

This packet 32 is enclosed within a middle packet 34 formed of a TPS film 14. And this middle packet 34 is enclosed within an outer packet 36 formed of a PLA film 18. The inner packet 32 and the outer packet 36 prevent moisture either leaving the food product 31 or getting into it. The middle packet 34 prevents oxygen transfer similarly.

Claims

Claims 1. A container for a product, the container comprising a first

container of a first biodegradable polymeric material to contain the product, and an outer container of a second biodegradable polymeric material which encloses the first container, wherein the first container and the outer container have different permeabilities.

2. A container as claimed in claim 1 wherein each container is a flexible packet formed of a flexible film of a respective biodegradable polymeric material.

3. A container as claimed in claim 1 or claim 2 wherein the outer container provides a moisture barrier, while the first container provides a barrier to oxygen.

4. A container as claimed in any one of the preceding claims wherein printing is performed on the inside of the outer container.

5. A container as claimed in any one of the preceding claims wherein the outer container comprises a transparent biodegradable polymer which is substantially impermeable to moisture.

6. A container as claimed in any one of the preceding claims wherein the first container comprises a polymer which provides a satisfactory oxygen barrier and which is both water-soluble and biodegradable.

7. A container as claimed in any one of the preceding claims wherein each container is formed by dielectric welding of a sheet of polymeric material.

8. A container for a product substantially as hereinbefore described with reference to, and as shown in, figure 1 or figure 2 of the accompanying drawings.