Asahi Kasei has developed the basic technology for recycling continuous carbon fiber under the project “Circular Economy Program for the Automotive Carbon Fiber” (the Project), together with the National Institute of Technology, Kitakyushu College, and Tokyo University of Science, which was supported by the Feasibility Study Program on Energy and New Environmental Technology, of the New Energy and Industrial Technology Development Organization (NEDO) from fiscal 2021 to 2022.
The project was adopted in May 2021 by the NEDO Feasibility Study Program on Energy and New Environmental Technology, which aims to discover technology seeds needed for medium- to long-term solutions in the field of energy and the environment, including energy conservation, new energy, and CO2 reduction, that is unlike existing technologies and can be applied in future national projects contributing to dramatically increased energy efficiency and achievement of a low-carbon society.
The project aims for the practical application of a recycling system where carbon fiber derived from carbon fiber reinforced plastic (CFRP) or carbon fiber reinforced thermoplastic (CFRTP) discarded from automobiles is reused as CFRP or CFRTP for automobiles. By recycling carbon fiber discarded from automobiles as continuous carbon fiber, high-quality and inexpensive CFRTP can be provided, resulting in vehicle weight reduction and energy saving. This is also expected to economically benefit and strengthen the competitiveness of Japan’s leading carbon fiber and automobile industries.
Conventional recycling technology recycles carbon fiber as chopped carbon fiber1. However, as chopped carbon fiber differs greatly from the original continuous carbon fiber, it was necessary to develop individual composite technology. In contrast, the Project enables continuous carbon fiber recycling, allowing existing composite technology to be used, making it possible to achieve closed-loop recycling2 of the circular economy.
An “electrolyzed sulfuric acid method” was developed for the Project. The “electrolyzed sulfuric acid method” is a technology that uses oxidative active species3 generated by electrolyzing sulfuric acid to decompose the resin components of CFRP/CFRTP and extract and recycle carbon fibers. This technology has three features: (1) it can decompose any kind of resin, (2) the strength of the recycled carbon fiber does not decrease, and (3) carbon fiber can be recycled as continuous fiber.
The basic technology was developed for recycling continuous carbon fiber from small commercially available CFRP tanks for scuba diving. The recycled continuous carbon fiber has no “twisting” or “fluffing” and can be handled in the same way as new carbon fiber. This enables a tank-to-tank circular economy through the repeated use of filament winding4. Asahi Kasei is also developing CFRTP-UD tape (unidirectional tape, a unidirectional continuous fiber reinforced material) using recycled continuous carbon fiber and Leona™ polyamide resin. Having higher strength than metal, CFRTP-UD tape is expected to be applied to automobile frames and bodies, further enabling the recycling of automobile parts into other automobile parts.