Patent ID: 6451966
Filing Date: 2002-09-17
Classification: C08G

Abstract:
A process for polymerizing low molecular weight polyester prepolymers in the solid state which comprises:(a) contacting the particles with a heat transfer medium to heat the particles to a temperature in the range of from about 205Â° C. to 240Â° C. in less than 10 minutes with the result that the time at which the particles are within the temperature range of 100Â° C. to 205Â° C. is minimized, (b) maintaining the temperature achieved for the particles in step (a) for at least one hour by subjecting the particles to a continuously moving stream of inert gas at elevated temperature and at a mass of gas to mass of solids ratio of at least about 0.05 whereby the progress of polymerization of said particles is preferred over the progress of crystallization, and (c) subjecting the particles to a countercurrently moving stream of heated inert gas at a mass of inert gas to mass of solids ratio which is less than the mass ratio maintained in step (b), but the total mass of inert gas to mass of solids ratio for step (a) and step (b) is equal to or greater than 0.6.