METHOD FOR INCREASING THE MOLECULAR WEIGHT USING THE RESIDUAL HEAT OF POLYESTER GRANULATE

摘要

The present invention relates to the increase of molecular weight during the thermal treatment of polyester in combination with a granulation of latent heat. The newly developed method allows combining a solid state postcondensation (SSP) directly with underwater granulation. The method differs from a conventional solid state postcondensation in that the increase of molecular weight can be achieved without additional input of heat and thus only by using the residual heat and the crystallization heat obtained in the process. The characterizing element is an improved water deposition and dehumidification during granulation. This is the only way to ensure that an increase in viscosity can be achieved in the presence of a small granulate having a mean grain weight of no more than 20 mg.