Patent ID: 6545122
Filing Date: 2003-04-08
Classification: B01D,C08G

Abstract:
A multi-stage, continuous process for evaporating a feed polymer solution by indirect heat exchange by passing the feed polymer solution through a series of heat exchangers each having a downstream separator, said process comprising:a) concentrating, at a temperature of from 100 to 250Â° C., in at least a single stage, the feed polymer solution having a polymer content of from 5 to 20 wt. %, to form an intermediate polymer solution having a polymer content of from 60 to 75 wt. %, in one of (i) a combination of a tubular heat exchanger with one of a thin-film evaporator and a coiled tube evaporator, and (ii) a tubular heat exchanger, each evaporator having a downstream separator, the pressure of each separator being from 0.1 to 0.4 MPa; b) concentrating and degassing in a further stage, the intermediate polymer solution of step (a) to form a product polymer having a polymer content of at least 95 wt. %, in a tubular heat exchanger having a downstream separator, at a temperature of from 130 to 350Â° C., the tubular heat exchanger having vertical, heated, straight tubes, optionally with built-in static mixers, having an inside diameter of from 5 to 30 mm, and a length of from 0.5 to 4 m, the throughput per heat exchanger tube being from 5 to 30 kg/h, based on the polymer, the pressure in the separator being from 3 kPa to 0.1 MPa, an entrainer being introduced into a delivery device located downstream of the separator, at the intake side; and c) isolating and optionally granulating said product polymer of step (b).