太陽電池パネル並びに合わせガラスの解体とリサイクルを中心とした「半導体の熱活性」(TASC: Thermal Activation of Semiconductors)技術の最近の進歩

Abstract

Thermal activation of semiconductors (TASC) is our novel technology characterized by radical propagation in giant molecules, allowing us to decompose any polymers, in an instant, into H2O and CO2. The present phenomenon has successfully been applied to complete decomposition of VOC (volatile organic compound), or to elimination of polymer matrix in composites to recover valuables, for example, decomposition and recovery of FRPs (fiber reinforced plastic), repair of partially damaged FRPs, reclaim of rare-earth powder from resin-bonded magnets, disassembly and recycling of solar panels and laminated glass. The TASC technology dates back to our accidental finding that significant oxidative properties appear in semiconductors when heated at about 350-500 ℃ while quite inactive at room temperature. The oxidative effect (i.e. removal of bonded electrons) has been interpreted as arising from thermally generated defect electrons (“hole”) formed in the valence band of semiconductors. This triggers the decomposition of polymers by creating unstable radicals. Then, the radicals propagate, just like a domino effect or chain reaction, throughout the polymer to make the whole polymer unstable, resulting in the fragmentation of the giant molecule into small pieces such as ethylene and propane. Finally, the fragmented molecules react with oxygen in air to give H2O and CO2 (i.e. complete combustion). This process caused by radical propagation is compared to the reverse reaction of “radical polymerization”. The present overview describes the recent advances in TASC technology with major focus on the disassembly and recycling of solar panels and laminated glass.