BASF has developed a chemical recycling process that sets new standards in the recycling of technical plastics and demonstrated the capabilities in a pilot project. This process makes it possible to recycle even heavily used and contaminated plastic parts – in this case also ZF Group used oil pans from end-of-life vehicles – efficiently and sustainably at the end of their life cycle. At the core of the process is depolymerization, where the long polyamide chains are broken down at their inherent cleavage points into their original building blocks – the monomers. In the subsequent step, the monomer caprolactam obtained from the depolymerization of PA6 is purified.
This allows potentially disruptive impurities from the material’s history of use to be completely removed. These impurities would have remained in the material during mechanical recycling and would have potentially impaired the quality and safety of the recycled material. The material is then re-polymerized into high-quality polyamide, which is further processed into a polyamide compound in accordance with the requirements of the application. This meets the highest quality standards and is suitable for demanding components in the automotive industry – closing the loop automotive-to-automotive.
The successful processing of the recycled material by the project partner ZF Group into a complex, technically sophisticated chassis component – the so-called Stabilizer Link – for Mercedes-Benz is a notable proof of its suitability for practical use. Tests carried out on test specimens and the manufactured components themselves show that depolymerization enables polyamide compounds that can be used without compromising on performance or other chemical and physical properties.
The second pilot project is dedicated to the recycling of automotive shredder residue (ASR) – a complex mix of different materials that remain after the removal of mainly metals and glass. Thanks to close cooperation with a recycling company, it has now been possible to extract the polyamides from this mixture in a largely pure form using newly available sorting and processing technology.
The polyamide fraction obtained in this way was used as the starting material for a new solvent-based recycling process as part of the pilot project. In this process, the polymer chain is not split but selectively dissolved with the aid of a suitable solvent, then purified and finally reprocessed into PA6 compounds.
This technology was validated using a chain guide rail in series production at Mercedes-Benz. The components were manufactured and successfully tested under near-series conditions by the project partner Pöppelmann as part of the pilot project.
Accompanying the pilot projects, life cycle analyses (LCA) were carried out by an external partner. The results clearly illustrate the advantages of the new recycling processes: Both the solvent-based technology and recycling via depolymerization demonstrate substantial CO₂ emission savings – compared not only to the production of conventional polyamide compounds based on fossil raw materials, but also to traditional plastic recycling methods such as thermal recovery. Each process can therefore make an important contribution to the circular economy and the sustainable transformation of the plastics industry in the future.
