CONTAINER OF PAPER OR PAPERBOARD WITH A PARTIAL BARRIER LAYER

Abstract: A container of paper or paperboard which primarily consists of paper or paperboard and which has a water-resistant, and preferably to some extent water vapor permeable, barrier layer which is degradable in a compost is disclosed. The container has a barrier layer only on those parts of the container surface which are intended for exposure to wet material. Also, a method of disposing of such a container with or without compostable contents by placing it in a compost, is described, as well as use of such a container for storage and transport of compostable waste.

Description: Container of paper or paperboard with a partial barrier layer. The present invention relates to a container of paper or paperboard with a partial barrier layer. More precisely, the invention relates to a container which primarily consists of paper or paperboard and which has a water-resistant, and preferably to some extent water vapor permeable, barrier layer, which is degradable in a compost, only on those parts of the container surface which are intended for exposure to wet material. Further, the invention relates to a method of disposing of such a container and the use of such a container for storage and transport of compostable waste. Background Ecological thinking has made it important to look at how different used materials are disposed of. Waste management is dependent on the type of waste in question. Composting is one favourable way of disposing of biologically degradable material, such as garden and food waste. Up to now, an average household has not pre-sorted household waste. However, at least in some European countries like Germany and Sweden many households pre-sort glass and waste paper from the rest of the domestic waste. Serious attempts are now made to get households to also pre-sort compostable waste, such as fruit and potato peels, left-over food, coffee filters with contents, etc. One of the main problems encountered in field trials a-iming at pre-sorting of compostable waste in ordinary households are that untreated paper bags, which are themselves compostable, cannot be used for storage of wet contents for a few days without bursting or littering the surroundings, and plastics bags are normally not compostable. Another problem has been that compostable waste which is gathered and stored for a few days starts to smell since odor-forming anaerobic degradation starts. Therefore, the containers in which the comostable waste is stored are kept closed to trap such smell. It is desirable that the container which is used for transport and storage of compostable waste is in itself compostable, since it is convenient for i.a. restaurants, shops and households to assemble compostable waste in a container which, after it has been filled up, can be thrown into the compost together with its contents. One solution to the container problem has been presented in US patent No. 5 178 469. This patent discloses a collapsible biodegradable container bag for liquid-containing waste solid materials, which container is formed of a single sheet of a two-ply construction of an outer paper layer and an inner cellulose film layer having a controlled porosity and a specified vapor transfer rate through said layer. Preferably said container bag comprises a liquid absorbing wick liner located on the inner surface of the bottom wall. The container has a controlled porosity of the cellulose film layer for the slow passage of water vapor and gases therethrough for enhanced biodegradability of the bag and its contents in a composting environment. Further, according to said patent, the bag-like container construction should be such that odors are substantially trapped within the container during standby periods. In the development of containers for compostable waste, it has now been found that the containers should be kept open for maximum admission of air during storage of compostable waste in order to minimize odour-forming anaerobic degradation of the waste. Also, the container should be kept with free admission of air to the side walls and optionally to the bottom thereof, possibly in a wire basket. Further, the compostable container should be constructed so that it contributes to the aerating of the container contents by allowing some penetration of air and water vapor through the container walls. Description of the invention The object of the present invention is to provide a container which can be disposed of by composting and which primarily consists of paper or paperboard and which may hold dry, se i- dry and/or wet solid and/or semi-solid material for at least a few days without littering the surroundings. Furthermore, it should counteract odour-forming anaerobic degradation of such material, i.e. the material should not start to putrefy. The paper or paperboard contributes to good composting results by providing a carbon source. Further, in a container which primarily consists of paper or paperboard, the paper or paperboard will provide the physical form of the container and the mechanical strength thereof. For the purpose of the invention, the paper or paper board may in principle be of any type of paper or paperboard, such as coated or uncoated paper or paperboard which has been manufactured from bleached, partially bleached or unbleached paper pulp or recycled fibre. It is well known in the art that paper and paperboard "breathe", i.e. some air and water vapor will penetrate the paper or paperboard. However, to be able to use a container of paper or paperboard for transport and/or storage of wet or semi-dry material the container needs a water-resistant barrier layer on the surface of the paper or paperboard. To be able to compost a container of paper or paperboard which has a water-resistant barrier layer, said layer must be biodegradable or at least degradable in a functioning compost to such a degree that there are no obviously distinguishable residues of said layer in the composted material . The same applies for other parts of the container, such as optional handles or adhesive used for the construction of the container. By the expression "degradable" is intended that the material is degraded, i.e. that it can undergo an irreversible process which leads to a significant change of the chemical and/or physical structure of the material, which is typically characterized by loss of properties (e.g. integrity, molecular weight or structure, mechanic strength) and/or fragmentation. There are a number of suitable barrier materials which satisfy the above requirements and some of them are available on the market, such as Biopol from Zeneca, Germany, and DC 1708 and DC 1718 from Dusseka Campbel Great Britain. Biodegradable adhesives are also available, such as starch and polyvinyl acetate adhesives. In order to improve the air and water vapor permeability of the container intended for disposal in a compost, and since only those parts of the container which are exposed to wet contents for an extended period of time need a water-resistant barrier layer, the container of the invention has a barrier layer only on those parts of the container surface which are intended for exposure to wet material. An additional advantage will be lower costs for the barrier material, since it is only needed for a part of the surface of the container. Thus, the present invention provides a container which can be disposed of in a compost and which primarily consists of paper or paperboard having a water-resistant, preferably to some extent water vapor permeable, barrier layer which is degradable in a compost, the characteristic feature being that the container has a barrier layer only on those parts of the container surface which are intended for exposure to wet material . In a preferred embodiment of the invention the container has a barrier layer only on the surface of the lower part of the container. In a further embodiment of the invention said barrier layer is on the bottom and a few centimetres up on the side walls of the container. In an other embodiment of the invention said barrier layer is on the inside of the container. In yet another embodiment of the invention, the dry weight of the barrier layer is between 1 and 12 grams, especially approximately 5 to 6 grams, per square meter paper or paperboard. In another preferred embodiment of the invention the container is a bag or a sack. The container according to the invention may be manufactured by the use of any suitable technique in the packaging industry. Also, the barrier layer may be applied onto the paper or paperboard in any suitable known manner, such as by the use of blade or roller coating, size press, film press or printing technique, such as flexographic technique. Another aspect of the invention is directed to a method of disposing of a container according to the invention, with or without compostable contents, by placing it in a compost. Yet another aspect of the invention is directed to the use of a container according to the invention for storage and transport of compostable waste. The container of the invention may have any primary use, such as a container for food or detergents, carry bag or bag for compostable waste. If the container of the invention is to be used for storage and transport of wet or semi-dry compostable household waste, the container is preferably a paper bag or sack which has a barrier layer only on the inside of the bag and only on the lower part thereof, such as on the bottom and a few centimetres up on the side walls of the container. If on the other hand the container of the invention is " to be used as a carry bag, then the barrier layer is preferably on the outside of the bag and covers the bottom and optionally a few centimetres on the side walls of the bag, so that the bag may be put down on a wet pavement without the risk of soaking the paperbottom of the bag. Then such a carry bag may be turned inside out for the purpose of being used as a container for compostable waste.

Claims: CLAIMS 1. A container of paper or paperboard which primarily consists of paper or paperboard and which has a water-resistant, and preferably to some extent water vapor permeable, barrier layer which is degradable in a compost, c h a r a c t e r i z e d in that said container has a barrier layer only on those parts of the container surface which are intended for exposure to wet material 2. The container according to claim 1, wherein said barrier layer is only on the surface of the lower part of the container. 3. The container according to claim 2, wherein said barrier layer is on the bottom and a few centimetres up on the side walls of the container. 4. The container according to claim 3, wherein said barrier layer is on the inside of the container. 5. The container according to any one of claims 1-4, wherein the dry weight of the barrier layer is between 1 and 12 grams per square meter paper or paperboard. 6. The container according to any one of claims 1-5, wherein the dry weight of the barrier layer is approximately 5 to 6 grams per square meter paper or paperboard. 7. The container according to claim 1, wherein said container is a bag or a sack. 8. The container according to any one of claims 1-7, wherein the barrier layer has been applied onto the paper or paperboard by the use of printing technique. 9. A method of disposing of a container according to any one of claims 1-8, c h a r a c t e r i z e d in that said container, with or without compostable contents, is placed in a compost. 10. Use of a container according to any one of claims 1-8 for storage and transport of compostable waste.

Inventors: HANSSON PER ULF, JOEVES HAAKAN, LOEFROTH JOHANNA, RODELL LUNDGREN KERSTIN, SOEDERBERG BO, HANSSON, PER, ULF, JOEVES, HAAKAN, LOEFROTH, JOHANNA, RODELL, LUNDGREN, KERSTIN, SOEDERBERG, BO
Applicants: HANSSON PER ULF, JOEVES HAAKAN, KORSNAES AB, LOEFROTH JOHANNA, RODELL LUNDGREN KERSTIN, SOEDERBERG BO, HANSSON, PER, ULF, JOEVES, HAAKAN, LOEFROTH, JOHANNA, RODELL, LUNDGREN, KERSTIN, SOEDERBERG, BO
Application year: 1995
Main classification: B65D65
IPC codes: B65D30, B65D65, C05F17