METHOD OF CRYSTALLIZING LOW-MOLECULAR POLYCARBONATE AND PROCESS FOR PRODUCING POLYCARBONATE RESIN FROM THE SAME

摘要

A method for crystallizing a low molecular weight aromatic polycarbonate effectively and a method for preparing a polycarbonate resin having a desired intrinsic viscosity by using the polycarbonate crystallized with the above method of crystallization. A low molecular weight aromatic polycarbonate (preferably, the one produced by melt polycondensation) is crystallized by bringing it into contact with an aromatic monohydroxy compound or a mixture of said compound and water. Or, a low molecular weight aromatic polycarbonate is melt mixed with at least one or more kinds of compounds selected from the group consisting of aromatic monohydroxy compounds, carbonic acid diester compounds and aromatic dihydroxy compounds to crystallize the low molecular weight aromatic polycarbonate. The crystallized product is heated at a temperature lower than its melting point under reduced pressure or in an inert gas flow to convert it into a high polymerized state. Thus, a polycarbonate resin having a desired intrinsic viscosity is prepared.