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Microwaves Depolymerize Polyamide in Energy-efficient Chemical Recycling Process

Asahi Kasei and Microwave Chemical launched a joint demonstration project in April 2023 with the objective of commercializing a chemical recycling process for polyamide (PA) 66 using microwave technology. The process utilizes microwaves to depolymerize PA 66 and directly obtain the monomers hexamethylenediamine (HMD) and adipic acid (ADA), which is expected to be accomplished at high yield with low energy consumption.

The monomers obtained can then be used to manufacture new PA66. In the demonstration, scrap PA 66 from manufacturing and post-use airbag and automobile part waste materials are being depolymerized.

Asahi Kasei currently produces fossil fuel–derived HMD and ADA as intermediates to manufacture Leona PA 66, an engineering plastic featuring outstanding heat resistance and rigidity. PA 66 is used in various applications, including plastic parts for automotive and electronic products, and yarn for airbag fabric, and its demand is increasing globally.

Microwave Chemical employs microwaves that can directly and selectively heat target substances with high energy efficiency for chemical recycling. The company is advancing its proprietary PlaWave technology platform for decomposing plastic using microwaves. Partnering Asahi Kasei, development of a commercialize process for manufacturing PA 66 that can reduce GHG emissions compared to the conventional manufacturing process is targeted.

Image courtesy of Asahi Kasei.

Laboratory-scale studies that began in fiscal 2021 have confirmed high-yield depolymerization of PA 66 using microwaves, as well as the principle of the separation and purification process after depolymerization. Bench-scale equipment will now be assembled at Microwave Chemical’s Osaka Factory by the end of fiscal 2023, and a small-scale demonstration trial using this equipment will be performed in fiscal 2024 to collect basic process data for commercialization.

Microwave Chemical’s PlaWave technology platform for decomposing plastic using microwaves can depolymerize PA 66 with low energy and obtain HMD and ADA monomers in high yield. The manufacturing process for PA 66 using HMD and ADA obtained by depolymerization with this technology is expected to reduce GHG emissions compared to the conventional PA66 manufacturing process, while further reduction of GHG emissions may be achieved by the use of renewable energy for the power required to generate the microwaves.

Moving forward, based on the results of the small-scale demonstration trial, a decision on the possibility of commercialization will be made by fiscal 2025 following detailed analysis. Concurrently with the small-scale demonstration trial, construction of a business model that involves the entire value chain in the chemical recycling of PA 66 will be advanced, aiming to achieve a circular economy together with stakeholders in the PA66 value chain.

Microwave Chemical is working to increase the scale of equipment and to make PlaWave more generally applicable in order to realize chemical recycling of polymethyl methacrylate (PMMA, acrylic resin), automotive shredder residue (ASR), plastic containers and packaging, and flexible polyurethane foam, among other materials.


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