Paper-Based Packaging – Challenges and Solutions
Materials expert Paula Goderbauer has found that paper packaging is up and coming – whether as composite or mono-materials. However, besides advantages such as recyclability and mechanical stability, paper also brings certain challenges. One major obstacle, for example, is that it does not have barrier properties. Through coatings, however, the material can be equipped with properties that even qualify it for use in food packaging. As Goderbauer explains, chemical coating, extrusion coating and skin moulding are available for this purpose.
The crucial point for the barrier quality is above all the surface quality of the paper. “If a paper fibre sticks out, the coating is thinner at this point and air or water vapour can pass through,” says Goderbauer. Different formulations and types of coating can counteract this. For example, the paper used should be as smooth as possible, e.g. white coated or already coated with a polymer layer.
Fabian Kayatz, Group Manager Processes and Machine Integration, pointed out further challenges in the process flow. For example, what can manufacturers do to prevent damage to the barrier during mechanical processing? One solution is to clean the surfaces of the machines at regular intervals. The longer a paper roll is processed on a machine, the greater the negative effects on the further course of the process. Higher temperatures in the machines can also have a positive influence on the reliability of the production process. According to Kayatz, poor thermal conductivity or the tendency to wrinkle can be brought under control by appropriate sealing and forming processes. Paper has special properties, but the researchers expressed confidence that its material properties will be further optimised and that the fields of application can thus be expanded.
A Circular Future for Flexible Plastic Packaging
The second part of the presentations focussed on plastics. Dipl.-Ing. Jochen Neubauer is convinced: “Plastic packaging is great because you can do a lot with it even with low material input.” Problems arise when different composite materials are used that are difficult or impossible to recycle.
For this reason, the EU Commission launched the Multi Cycle Project. The solvent-based Creasolv process, which was developed at the Fraunhofer Institute in Freising together with Creacycle, was used. It is suitable for recycling post consumer packaging. For this purpose, the packaging waste is shredded and passes through various treatment stages together with a solvent. At the end of the closed process, a granulate is produced that is free of unwanted polymers, contaminants and other substances. A plant in northern Bavaria proves that the process works and that granulate can be produced at competitive prices.
Food Packaging Has Special Requirements
For non-food packaging, nothing stands in the way of using the recyclate. In the case of food packaging, there are still some legal and technological hurdles to be overcome, says Nelly Freitag, a materials development scientist: “As long as we cannot separate food packaging from other packaging waste, it is difficult to reuse recyclate from it in food packaging”. One way to do this, she says, is with functional barriers that separate the recyclate from the food.
In another project called Circular FoodPack, the researchers want to tackle this challenge and recycle food packaging again in the same quality. For example, they want to optimise sorting with the help of chemical trackers that can be integrated into the packaging, Freitag reveals. In the meantime, the process has been tried and tested. Marked and unmarked packaging could be separated with an accuracy of 97 percent and thus reused as high-quality recyclate.
Jens-Peter Majschak concluded by emphasising that these developments show that composite materials would not be a dead end for recycling either. “What matters is that the business community embraces these recycling concepts and tries them out,” Majschak said. He said that prohibitions on thinking are out of place in order to realise the circular economy of the future.
