Abstract: A process for feeding a slurry of thermoplastic synthetic polymer particles such as polyethylene terephthalate homopolymers and copolymers in combination with a liquid such as water at a liquid temperature greater than the normal boiling point of the liquid, under a pressure greater than the vapor pressure of the liquid at the liquid temperature, into a separation zone such as a centrifugal dryer, and within the separation zone: a. separating the liquid from the particles, and b. drying the particles; while under a high pressure equal to or greater than the vapor pressure of the liquid. There is also provided a process for decoupling the dried particles from the separation zone to an atmosphere having a pressure less than the vapor pressure of the liquid while maintaining the vapor pressure of the particles prior to decoupling equal to or above the vapor pressure of the liquid at the liquid temperature.

Abstract: A process for thermally crystallizing a polyester polymer by introducing pellets into a liquid medium having a temperature of at least 140° C. within a liquid medium zone and crystallizing the submerged pellets at or above the vapor pressure of the liquid medium without increasing the molecular weight of the pellets, and while the pressure on at least a portion of the pellets is equal to or greater than the vapor pressure of the liquid medium, separating at least a portion of said pellets and at least a portion of the liquid medium from each other. The crystallization is desirably conducted in the liquid medium zone without mechanically induced agitation. Optionally, the pellets are formed by an underfluid pelletizer.