Key Findings
Kirin Holdings (HD), in collaboration with Japan Steel Works, has successfully accelerated the depolymerization of polyethylene terephthalate (PET). By utilizing a twin-screw kneading extruder, the company reduced the time required for depolymerization from the conventional four hours to less than 10 minutes. This breakthrough addresses the cost and energy barriers that have historically hindered the practical application of PET chemical recycling (CR).
Technical Details
The process employs “alkali depolymerization” using a sodium hydroxide aqueous solution as a solvent. Rather than relying solely on high temperature and pressure, the system leverages “mechanochemical reactions.” The twin-screw extruder’s screws apply mechanical force to rub, crush, and mix the PET with the sodium hydroxide solution, triggering the chemical reaction.
- Energy Efficiency: The heat generated by the mechanochemical reaction is utilized for depolymerization, reducing the external thermal energy required.
- Capacity: A single unit, measuring several meters in length, can process 10,000 tons of PET products per year.
- Footprint: The system allows for significant downsizing compared to existing CR facilities.
Background and Context
Chemical recycling breaks plastic down to the molecular level, allowing for the production of recycled resins with quality equivalent to virgin materials. While PET CR has existed since the 2000s, high energy consumption and associated costs have limited its scalability. Kirin HD’s R&D Package Innovation Institute sought a “high-speed, short-time” concept to overcome these economic hurdles.
Significance and Outlook
The current output of the process consists of disodium terephthalate and ethylene glycol. The next research phase focuses on refining these materials by removing sodium and impurities to return them to PET raw materials. Once commercialized, the technology will extend beyond beverage bottles to include fibers and films, creating a large-scale resource loop for all PET products.
Source: https://www.nikkan.co.jp/articles/view/795220
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