About 50% of the plastic waste collected as general waste is recycled today. Recycled plastic waste is used as or for raw materials (4%), chemical resources (3%), solid fuels (1%), waste power generation (35%), and heat sources (7%). However, the remaining half is disposed of at landfill sites or simply burned in incinerators. In Japan, the capacity of landfill sites is continually decreasing. Furthermore, flame-retardant materials such as polyvinyl chloride (PVC) are known to cause corrosion in incinerators during combustion due to their constituent halogen substances; these materials also produce halogen compounds such as dioxins. Moreover, carbon dioxide discharged from the combustion of polymers causes environmental problems such as global warming and acid rain. In addition, suspected endocrine disrupting chemicals, typically bisphenol A, can dissolve out of polycarbonate (PC).

In 2000, with the aim of global environment conservation, the New Energy and Industrial Technology Development Organization (NEDO) initiated a national project for research and development of environmental-load-reducing technologies based on the use of supercritical fluids, in an effort to develop methods of chemical processing that conserve energy and resources and minimize environmental impact. As our company uses molded products made of polymers for medical applications, we have participated in this project to reduce environmental load caused by disposed polymer molded products and have worked to develop technologies for effective utilization of substances in disposed plastics. Further, we are currently engaged in the development of chemical recycling processes for plastic waste.

The plastic waste materials we are presently focusing on include soft polyvinyl chloride, which is a representative addition polymerization material, and polycarbonate, which is a typical condensation polymerization substance.

For chemical recycling of soft polyvinyl chloride, we have established a pretreatment method that separates the plasticizer from pulverized feed material in a subcritical aqueous environment. This has enabled us to develop technology that allows extraction of the plasticizer without damaging the polyvinyl chloride structure of the previously difficult-to-process soft polyvinyl chloride. This method has also enabled conversion (material recycling) of polyvinyl chloride. Further, we have established a two-stage processing method to separate out chlorine after the plasticizer is removed. We are now conducting development aimed at achieving material conversion in supercritical conditions for the production of value-added substances. We have also developed a technology to convert polycarbonate into a raw material, bisphenol A.

Supercritical reactor for plastic waste

conversion technology for plastic