Kirin Holdings’ Packaging Innovation Institute and The Japan Steel Works (JSW) have achieved more than 95 per cent depolymerisation of PET in a demonstration of an alkaline chemical recycling process.
The test used production-scale equipment and established operating conditions for stable PET depolymerisation at a throughput of at least 250kg per hour.
Kirin developed the alkaline depolymerisation technology, which was tested using JSW’s TEX αⅢ series twin screw extruder.
The co-rotating processing system is designed for polymer compounding, reactive extrusion, and recycling.
Addressing conventional challenges
The companies said the technology addresses challenges associated with conventional chemical recycling processes, including high temperatures and long reaction times.
The test provided what the companies described as ‘valuable knowledge’ about equipment specifications and operating conditions that could be used when designing commercial scale processes.
Kirin said the growing use of PET bottles worldwide has increased the need for greater resource circularity.
Mechanical recycling remains the main method for recycling PET bottles, and Kirin noted it can be limited in the range of PET materials that can be processed.
Purified and used again
Chemical recycling, on the other hand, breaks PET down into its constituent materials, which can then be purified and used to produce PET again.
The companies said conventional chemical recycling processes can require high temperatures and long reaction times, affecting energy use and costs.
Rather than relying solely on heating, the process developed by Kirin also uses mechanical forces generated by the equipment, including mixing and friction, to accelerate the chemical reaction.
The companies said this allows the reaction to take place in a shorter time and with less energy.
Integrated recycling process
Kirin and JSW plan to continue developing the technology by working towards an integrated recycling process covering PET collection, depolymerisation and resource recovery.
They also intend to assess whether the process can handle a wider range of PET packaging feedstocks, including non-food-contact material grades.
The companies will present further results from the demonstration at the 57th Autumn Meeting of the Society of Chemical Engineers in Japan later this month.
Kirin and JSW also plan to work with companies, local governments, research institutions and other partners on further development and potential commercialisation of the technology.
The development follows research at the University of Surrey into a polymer that depolymerises into a gas at 90°C and reforms when cooled. The researchers said the work could provide a basis for new approaches to circular materials.
