Method for preparing high molecular weight polycarbonate

A method of preparing polycarbonate by the melt process comprising the steps of: (a) melting a dihydric phenol and a diester of carbonic acid for a time and at a temperature sufficient to form a melt; and thereafter introducing a catalyst composition comprising a tetraorganophosphonium salt or a derivative thereof and (1) an alkali and/or alkali earth metal compound or derivative thereof or (2) a less active alkali and/or alkali earth metal derivative thereof into the melt; and (b) oligomerizing the product from step (a) to a number average molecular weight of from about 3000 to about 7500; and (c) polymerizing the product from step (b) to a number average molecular weight of from about 16,000 to about 35,000.