Tire maker Continental is to start using reprocessed polyester obtained from recycled plastic bottles in its tire production as of 2022.
The sustainable polyester yarn will be obtained from polyethylene terephthalate (PET) bottles via a mechanical process and will be used in the construction of the tire carcass. This material, says Continental, should be able to completely replace conventional polyester.
Together with partner and supplier Otiz, a fiber specialist and textile manufacturer, Continental says it has developed the technology to recycle PET bottles without the previously necessary intermediate chemical steps, while making polyester yarn that meets the high mechanical requirements of tires.
“As early as 2022, we will be able to use material obtained from recycled PET bottles in tire production. In our innovative recycling process, the fibers are spun from recycled PET without having to break the material down into its components beforehand,” said Andreas Topp, responsible for materials, process development and industrialization in Continental’s Tires business area. “With the use of recycled polyester yarn, we are taking another important step in the direction of cross-product circular economy.”
As part of the recycling process, the bottles are first sorted, the caps removed and finally mechanically cleaned. After mechanical shredding, they are melted down and granulated; this is followed by solid state polymerization and a modified spinning process.
“Our modified manufacturing process enables us to obtain polyester yarn for tire construction from PET bottles without any polymerization process from monomers,” explained Derren Huang, chief of research and development at Otiz.
Laboratory and tire tests conducted by Continental have shown that the secondary raw material fibers perform equally as well the fibers used up to now. They have the same quality as virgin PET, are just as stable, and are particularly suitable for tires due to their high breaking strength, toughness and thermal stability.
Conventional PET has long been used as a material in car tire construction because it retains its shape even under high loads and temperatures. The use of recycled PET conserves valuable resources in tire construction: today, a conventional passenger car tire consists of around 400g of polyester yarn. When using the recycled material, 60 recycled PET bottles can be recycled for a complete set of vehicle tires.
