Toray Industries and Honda Motor Co., Ltd. are cooperating on the joint development of a chemical recycling technology for glass-fiber reinforced PA6 parts recovered from end-of-life vehicles, the companies have announced.
Deploying a depolymerisation technology that uses subcritical water, the companies have successfully regenerated the materials as caprolactam, the monomer used for synthesising PA 6. Subcritical water is in a high-temperature, high-pressure state, just below the critical point of water (374°C, 22 megapascals). Taking advantage of subcritical water characteristics such as high permeability, dissolving power and hydrolysis effect in resins, the partners found it was possible to depolymerise PA 6 in minutes, with as result high yields of raw monomer. Subcritical water is free of catalysts and unaffected by additives. Separating, refining, and repolymerising the monomer produced a virgin-quality PA 6.
The technology was developed and adopted within the scope of a fiscal 2023 project established by the Japanese ministry of the environment and aimed both at establishing a decarbonised circular economy system and at validating recycling systems for plastics and other resources.
Toray and Honda are now seeking to take the technology forward, with plans to set up a 500 t/a pilot facility for validation testing.
The initial goal is to develop successful closed loop recycling of automotive plastic parts. The two companies will start with intake manifolds - developing depolymerisation, monomer separation and refining technologies to recycle these into raw materials for engine intake system parts. If all goes according to plan, the technologies should be available for recycling chemicals in automotive resin parts by around 2027.
Down the track, the partners will also work to broaden the scope of this technology to include the recycling of apparel, films, and other non-automotive applications. As well, they are considering the feasibility of expanding the effort to include other companies, which could make it possible to a create a chemical recycling scheme for PA 6 in Japan.