Toray develops chemical recycling technology for nylon 66

Tokyo-based Toray Industries Inc. has announced what it calls a “breakthrough” in the recycling of nylon 66.

The company recently deployed a proprietary depolymerization technology using subcritical water to depolymerize nylon 66 resin uniformly and efficiently in minutes and recover it as a raw monomer material. The company says subcritical water is in a high-temperature, high-pressure state, just below the critical point of water (705 degrees Fahrenheit), and differs from water at normal temperatures and pressures in several ways, such as by dissolving and hydrolyzing organic compounds.

According to Toray, demand for nylon 66 is estimated at 100,000 metric tons annually in Japan and 1.3 million tons worldwide, with the material’s high heat resistance and strength making it ideal for automotive and industrial applications. The material can be found in automotive textiles such as airbags and tire cords and in plastic components such as radiator tanks, cylinder head covers and oil pans. The company notes that tighter recycling regulations for automotive and other plastics in Japan have made it mandatory to collect used nylon 66-based airbags, making it a “promising material” for chemical recycling.

Toray says chemical recycling demonstrations for nylon 6 are already underway and entail recovering a monomer called caprolactam. Contrastingly, the company says the process for chemically recycled nylon 66 requires recovering hexamethylenediamine and adipic acid monomers. Toray says it drew on its expertise in nylon 6 chemical recycling technology to assess the depolymerization reaction of nylon 66 in subcritical water and developed its proprietary technology to suppress side reactions, making it possible to efficiently recover high yields of those two monomers and regenerate nylon 66 through repolymerization.

Toray says it initially plans to target automotive materials, establishing technologies to separate other materials in used equipment such as airbags, and technologies to depolymerize nylon 66 and separate and refine monomers. This year, the company says it plans to set up a framework to verify quality and evaluate customers through sample work. It will prepare for mass production around 2030, when stricter plastic recycling regulations are enacted.

The company says it will develop comprehensive nylon recycling technologies for both nylon 6 and nylon 66 and plans to broaden its chemical recycling technologies beyond apparel and automotive materials to other industrial applications to help create a circular economy and contribute to carbon neutrality.