Patent ID: 6740729
Filing Date: 2004-05-25
Classification: C07C,C08G

Abstract:
A process for preparing polycarbonate which comprises the steps of:subjecting a dialkyl oxalate and a phenolic compound to transesterification to give a diaryl oxalate; subjecting the diaryl oxalate to decarbonylation to give a diaryl carbonate; reacting the diaryl carbonate with a polyvalent hydroxyl compound in the presence of a catalyst containing a tertiary amine having C1-C3 alkyl group or a tetra-N-alkyl substituted ammonium hydroxide having C1-C3 alkyl group to give a polycarbonate, removing a mixture containing a phenolic by-product and an amine by-product that has a boiling point lower than that of the phenolic by-product; collecting the mixture; purifying the mixture so that the amount of the amine by-product in the mixture is reduced to give a phenolic by-product mixture not containing the amine by-product in an amount of more than 600 ppm; and utilizing thus purified phenolic by-product mixture as a whole or a part of the phenolic compound in the first step.