Patent ID: 7084232

Claim:
A process for preparing high molecular weight polycarbonate resin comprising the steps of: a) melting dialkyl(aryl)carbonate and aromatic hydroxy compound and conducting transesterification thereof to prepare low molecular weight amorphous polycarbonate prepolymer with weight average molecular weight of 1,500˜15,000 glmol; b) conducting condensation polymerization of the a) low molecular weight amorphous polycarbonate prepolymer under pressure of 0˜50 mmHg or nitrogen gas in an amount of at least 0.1 Nm 2 /kg·h for 2˜120 minutes, to prepare middle molecular weight amorphous polycarbonate with weight average molecular weight of 20,000˜30,000 g/mol and remove unreacted dialkyl(aryl)carbonate and by-products of low polymerization degree less than 3 in step a); c) conducting solvent-induced crystallization of the b) middle molecular weight amorphous polycarbonate to prepare semi-crystalline polycarbonate; and d) conducting solid state polymerization of the c) semi-crystalline polycarbonate to prepare high molecular weight polycarbonate with weight average molecular weight of 35,000˜200,000 g/mol.