Continental, along with its supplier and fibre specialist Otiz, Oriental Industries has developed technology for recycling polyethylene terephthalate (PET) bottles for tyre construction.
The technology enables the use of reprocessed polyester obtained from recycled plastic bottles in its tyre production from next year.
The new sustainable polyester yarn will be obtained from PET bottles by a mechanical process and will be used in the construction of the tyre carcass. This can completely replace conventional polyester. The new technology does without previously necessary intermediate chemical steps and helps make the polyester yarn functional for the high mechanical requirements of the tyre. In the course of so-called upcycling, a PET bottle becomes a high-performance PET material.
"As early as 2022, we will be able to use material obtained from recycled PET bottles in tyre production. In our innovative recycling process, the fibers are spun from recycled PET without having to break the material down into its components beforehand," says Dr. Andreas Topp, responsible for materials, process development and industrialization in Continental’s Tires business area. He adds: "Already at this year's IAA MOBILITY in Munich, we will present a highly innovative concept tire with polyester yarn made from recycled PET bottles. 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, caps removed and finally mechanically cleaned. After mechanical shredding, they are melted down and granulated; this is followed by solid state polymerisation and a modified spinning process. "Our modified manufacturing process enables us to obtain polyester yarn for tyre construction from PET bottles without any polymerisation process from monomers," explains Dr. Derren Huang, Chief of Research and Development at OTIZ.
Laboratory and tyire tests conducted by Continental have shown that secondary raw material fibres perform equally well as the fibres used up to now. They have the same quality as virgin PET, are just as stable, and are particularly suitable for tyres due to their breaking strength, toughness and thermal stability.
Conventional PET has long been used as a material in car tyre construction because it retains its shape even under high loads and temperatures and thus ensures safety at all driving speeds. The use of recycled PET conserves valuable resources in tyre construction: today, a conventional passenger car tire consists of around 400 grams of polyester yarn. This, according to Continental, means that more than 60 recycled PET bottles can be used for a complete set of vehicle tyres in the future.