Chemical recycling is considered an important step on the way to a circular economy. Planned investments by large-scale industry amounting to 9.8 billion euros by 2030 in chemical recycling technologies underline this. Together with Fraunhofer IFAM, the German Plastics Center SKZ is working on a method which is affordable for small and medium-sized enterprises because it uses existing machine technology.
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A recently started research project of the Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM in Bremen and the German Plastics Center SKZ in Würzburg aims to recycle thermally damaged plastics by chemical recycling. The material of choice is PET, which is already very 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 aged too much as a result of several recycling passes or do not end up in this (bottle) cycle at all, such as other PET packaging. The special feature of the process is that in this case the chemical recycling is carried out on a standard twin-screw extruder.
"Our goal is to develop a continuous, reactive recycling process of PET recyclates into polyester polyols. These then serve as chemical base material again," explains Hatice Malatyali, group manager extrusion and compounding at SKZ. The polyols obtained serve as a base material for a wide variety of technological areas, such as adhesives or even coatings. In the project, these are to be used as starting materials for adhesive formulations and thus transferred directly into an application. A demonstrator plant is also planned at the SKZ in order to make the process accessible to interested medium-sized companies.
Unfortunately, the plastics to be recycled are usually not sorted by type. The consequence is recyclates consisting of a mixture of different plastics and the associated 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 damage to the material with each recycling cycle, which also negatively affects the properties of the plastics.
In order to integrate these two cases into the circular economy, chemical recycling is considered a possible solution. Here, the polymers are degraded down to their basic materials, in order to be subsequently recycled with a low input of new raw materials without any loss of quality. The disadvantage, especially for medium-sized companies, is the high investment in the technology.