Study on a Separation Technique for Plastic-Metal Wastes by the Molten Salt (I)

Observation of Separation Process

Abstract

Compound materials consisting of plastic and metal have been com-ing into wide use in industrial products, and wastes of compound material are also in-creasing. For establishing the material recycle system, it is desired to develop an useful technology of plastic separation from metal. In this study, we developed a new separa-tion technique of plastics from compound wastes. In this technique, a high temperature molten salt (KNO₃-NaNO₃-NaNO₂) was used as a separation medium. The compound wastes were immersed directory into the molten salt bath. Plastics was heated and flui-dized in the molten salt bath. Fluidized plastics were separated from the metal by the buoyancy effect. Five major plastics; policarbonate, polypropyrene, polystyrene, polyacetal and polyvinylchloride were tested by this technique, and the following results were obtained.(1) The separation of plastics from metal was observed when plastics were heated up to their fluidized temperatures.(2) The time of separation becomesshorter and the ratio of separation becomes larger with the molten salt temperature rise.(3) The “melting separation technique” developed here was usefulfor the separation of plastics from the compound wastes such as a F-cable.