METHOD FOR CRYSTALLIZING POLYETHYLENE NAPHTHALATE PREPOLYMERS AND SOLID-PHASE POLYCONDENSATION OF THESE CRYSTALLIZED PREPOLYMERS

摘要

A process is disclosed for the crystallization of a PEN prepolymer containing volatile components. The temperature is maintained at a temperature in the range of about 20 DEG C above the Tg and about 10 DEG C below the Tm while the PEN prepolymer is agitated. The PEN prepolymer is present as chips or pellets. The pressure during crystallization is maintained at a level higher than the vapor pressure of the volatile components in the PEN prepolymer chips or pellets, suitably by the presence of a gas and/or a liquid or mixture of liquids.