From old plastic to new adhesive – a chemical recycling project

This is underlined by the planned investment of EUR 9.8 billion in chemical recycling technologies by large industry by 2030. Together with the Fraunhofer IFAM, the German Plastics Center SKZ is working on a process that is affordable for small and medium-sized companies because it uses existing machine technology.

A recently launched research project by the Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM in Bremen (Germany) and the German Plastics Center SKZ in Würzburg aims to add thermally damaged plastics to the recycling economy through chemical recycling. The material of choice is PET, which is already well established in mechanical recycling. Thanks to the well-known bottles and the deposit system in Germany, the material is mostly sorted by type and most of it is already efficiently recycled. The RezyBond project is dedicated to PET fractions that have been recycled several times and are too old, or that do not end up in this (bottle) cycle at all, such as other PET packaging.

The process is unique in that the chemical recycling is performed on a standard twin-screw extruder. "Our goal is to develop a continuous, reactive recycling process for PET recyclates into polyester polyols. These can then be used as chemical feedstock", explains Hatice Malatyali, Group Manager Extrusion and Compounding at SKZ. The polyols obtained can be used as raw materials for a wide range of technological applications, such as adhesives and coatings. In the project, they will be used as starting materials for adhesive formulations and thus transferred directly to an application. A demonstration plant is also planned at the SKZ to make the process accessible to interested medium-sized companies.

Mechanical recycling has become an established technology. Unfortunately, the plastics to be recycled are usually not of the same type. As a result, recyclates are made up of a mixture of different plastics, resulting in a loss of material properties. The result is often downcycling, i.e. the use of these recyclates in other (inferior) applications. In addition, there is a certain amount of material damage in each recycling cycle, which also negatively affects the properties of the plastics. To integrate these two cases into the circular economy, chemical recycling is considered a possible solution. In this process, the polymers are broken down into their basic materials, which can then be recycled without any loss of quality and with the minimum use of new raw materials. The disadvantage, especially for medium-sized companies, is the high investment in the technology. AT

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