Despite the fact that strategy for PET bottle recycling is well defined, there is little data about the recycling of food containers as they are generally considered not recyclable. That is due to the fact that food containers are made of a combination of different plastic films and, therefore, a recycling strategy similar to that for PET bottles is not possible for food containers as PET is not the only plastic material of the container and it is not possible to separate easily the other different plastics. Moreover, the sorting procedure is very difficult because of the large variety of different multi- material sheets used for packaging.
The best solution for the environment would be to produce PET containers for primary packaging by using mainly food grade RPET that is approved by EFSA. However, apart from a small amount of virgin material in contact with food, the rest of the container should be in RPET with high functional properties (oxygen barrier, durability) and aesthetics (full transparency, above all) and these containers should be recyclable as well.
At present, this solution has never been adopted and the state of the art is quite far from producing a 100% recyclable plastic container for food. Current research and development is focused on ‘monolayer barriers’ which can be incorporated uniformly within the container material itself. Unfortunately, the brittleness of the inorganic coating leads to poor performances of the coated PET.
In order to improve the PET container’s recyclability without affecting their handling, recent developments mainly deal with active barriers by means of oxygen scavenger. Several patents deal with the definition of PET active barriers: for instance, the US patent 6455620 describes a barrier layer where oxygen is scavenged by means of a UV activated process. In the multi-layer structure, 5 different layers are present. The active barrier is made of a mixture of PET, a polyester-polyether copolymer, a photo-initiator and a catalyser consisting of a cobalt organic compound. The use of cobalt as well as the need of a photo-initiation makes this solution non optimal for food preservation or for low environmental impact applications. Still, other patents (WO 2005/023530, WO 2009/0302560) deal with mono-layer oriented sheets (typically used for bottles) and are not applicable to multi-layered solutions. Multi-layer structures are probably essential in the case of calendered sheets because of the low final orientation and the resulting low intrinsic barrier properties of the sheets.