Toray, Teijin, Toho and Mitsubishi Rayon team up to develop new carbon fiber

Japan's New Energy Industry Technology Development Agency (NEDO), on January 14, 2016, developed a new process to increase the production efficiency of polyacrylonitrile (PAN) carbon fiber by 10 times compared with the old process. It also reduces the amount of energy and CO2 emissions required for production.

Carbon fiber is mainly used as a reinforcing agent for carbon fiber reinforced resin matrix composite (CFRP), and its representative use is an aircraft. Recently, the adoption of high-priced models and the adoption of automobile bodies are also advancing. CFRP is expensive, so the demand for lowering prices based on the automotive industry is very strong. One of the problems that hinders CFRP from lowering prices is that carbon fiber raw materials are expensive and less productive.

The original PAN-based carbon fiber manufacturing process consists of roughly four processes:

(1) PAN which is melted in a solvent is made into a "filament" of a filamentous PAN fiber;

(2) Before the carbonization of the PAN fiber, heat treatment is performed in advance to oxidize it to improve the "refractory" of heat resistance;

(3) "carbonization" of PAN fibers after high temperature heating and carbonization and refractory;

(4) "Surface treatment". The bottleneck of this manufacturing process is (2) the refractory process. This process is difficult to manage, and it is difficult to process a large amount of PAN fiber at one time.

In the conventional manufacturing process, the PAN fiber after the spinning is heated in the air at 200 to 300 ° C for 30 to 60 minutes for refractory treatment. Thereafter, the treated PAN fibers are heated at 1000 to 2000 ° C to carbonize them, and finally subjected to surface treatment to obtain carbon fibers.

A new manufacturing process that increases production efficiency and removes the refractory process using the newly developed "solvent-soluble refractory polymer". Solvent-soluble refractory polymers are easily spun into filaments and are fire resistant. Since it has been fire-resistant at the spinning stage, it is no longer necessary to perform refractory treatment after the yarn is produced. The solvent-soluble refractory polymer can be produced by using a low-cost PAN for clothing as a raw material, adding a dissolution promoter and an oxidizing agent.

At the same time as the refractory treatment is omitted, a new technology that can be directly heated by microwaves has been developed in the carbonization method. This eliminates the need to keep the carbonization furnace at a high temperature. Moreover, the time required for carbonization can be shortened.

In the surface treatment, a new technology using plasma has also been developed. The process of simplifying the surface treatment can reduce the energy required for the surface treatment process by about 50% compared to the conventional method.

The manufacturing process is based on the University of Tokyo and the Japan Industrial Technology Research Institute, which is based on the University of Tokyo and the research and development of materials and joints and technology development projects. Dongli, Teijin, Toho Texex (Teijin Group), Mitsubishi Liyang jointly developed. The above four companies held a 65% global share in the PAN carbon fiber sector in 2014.

In the future, the industrialization of this manufacturing process will be realized, and an empirical experiment is being carried out at the factory. Technology to achieve high strength and large diameter of carbon fiber will also be developed.