Method and apparatus for increasing an intrinsic viscosity of polyester

Apparatus for increasing the intrinsic viscosity of polyester by solid state polymerization comprising

• a supply of heated polyester material including an extruder for producing strands of the material,
• a polyester granulator having a chamber housing a cutter for cutting the polyester material strands received from the extruder into granules while subjecting the strands to a coolant to only surface-cool the strands to a strand temperature slightly below the melting temperature of the polyester,
• a screening device directly bordering the chamber for separating the granules from the coolant so as to maintain the granules at a temperature only slightly below the melting temperature of the polyester by receiving polyester granules and coolant directly from the chamber,
• a solid state polymerization-thermal treatment unit including a polymerization-thermal treatment container, and
• a screw conveyor receiving granules at a temperature only slightly below the melting temperature of the polyester directly from the screening device for transporting the granules from the screening device directly into an interior of the container to thereby utilize residual heat in the granules received from the conveyor during a polymerization process of the granules conducted in the interior of the container.