Patent ID: 7750057
Filing Date: 2010-07-06
Classification: C07C,C08G,C08J,Y02W

Abstract:
1. A method for obtaining an alkali metal salt aqueous solution of an aromatic dihydroxy compound which constitutes a waste aromatic polycarbonate by decomposing the aromatic polycarbonate by an alkali metal hydroxide aqueous solution, the method comprising: (a) a step (dissolution step) of dissolving a waste aromatic polycarbonate in a chlorinated hydrocarbon solvent to prepare an organic solvent solution having the aromatic polycarbonate (PC) dissolved therein in a concentration of 8 to 30 wt%, (b) a step (decomposition step) of reacting the obtained organic solvent solution with an alkali metal hydroxide aqueous solution containing 45 to 55 wt% of alkali metal hydroxide at a temperature of 30 to 50° C. to decompose the aromatic polycarbonate, (c) a step (re-dissolution step) of adding water to the decomposed solution obtained in the step (b) to dissolve an alkali metal salt of an aromatic dihydroxy compound as a solid contained in the decomposed solution in water, (d) a step (two phase formation step) of leaving the treated solution obtained in the step (c) to stand to form an organic solvent solution phase (organic phase) and an aqueous solution phase (aqueous phase), (e) a step (separation/collection step) of separating the aqueous solution phase (aqueous phase) formed in the step (d) from the organic solvent solution phase (organic phase) and collecting the aqueous solution phase (aqueous phase), and (g) a step (re-separation/collection step) of adding a chlorinated hydrocarbon solvent to the aqueous solution phase obtained by the separation/collection step to form an organic solvent phase and an aqueous solution phase, separating the aqueous solution phase from the organic solvent phase and collecting the obtained aqueous solution phase.