Method and device for increasing the intrinsic viscosity of polyester material by means of solid phase polymerisation

Abstract

The invention relates to a process and a device for increasing the intrinsic viscosity of a polyester material by solid-state polymerization, wherein the polyester material is heat-treated in a heat treatment container (), the polyester material being introduced into a preheating container () prior to being conveyed into the heat treatment container (), in which preheating container it is heated to a heat treatment temperature of the heat treatment container () or to a temperature above that and is delivered to the heat treatment container () after having reached said temperature. The preheating container () is small in comparison with the heat treatment container () so that the relatively small amount of polyester material contained therein can quickly be heated to the intended temperature, thereby leading to a short residence time in the preheating container. After reaching the intended temperature, the entire content of the preheating container can be delivered all at once to the heat treatment container, whereupon the preheating container can be charged with fresh polyester material. Due to the short residence time, the preheating container is operable well in a discontinuous operation.