Chemical conversion of poly(carbonate) to 1,3-dimethyl-2-imidazolidinone (DMI) and bisphenol A: a practical approach to the chemical recycling of plastic wastes

A method for the chemical recycling of poly(carbonate) (PC) plastic wastes in the forms of bisphenol A (BPA) and 1,3-dimethyl-2-imidazolidinone (DMI) was investigated. Treatment with N,N′-dimethyl-1,2-diaminoethane (DMDAE) of PC pellets or PC wastes, derived from compact discs, in dioxane with/without a catalytic amount of base (e.g. Na2CO3 0.5 mol%) for a short period at 100 °C produced DMI and BPA, both in nearly quantitative yields. The aminolysis reaction can be carried out also in DMI, thus saving the use of conventional solvents. A sequential profile of this reaction was verified by examining two model reactions of diphenyl carbonate with N-methylbutylamine and DMDAE, respectively, both proceeded through low-activation energy processes.