Process for making thermoplastic granules from polymer solutions

摘要

A process is claimed for the prodn. of polymer granules (I) from solns. of thermoplastics (II) by pre-concn. followed by further concn. and drying, extrusion and granulation. The process comprises: (a) heating a 3-30 (pref. 15-25) wt.% soln. of (II) in organic solvent at 1-15 bar and 50-300 degrees C in one or more heat exchangers with a total heat exchange surface of 0.02-2 m<2>/100 kg/hr. solvent, or with superheated steam at a solvent:steam ratio of at least 10:1 in a heated or unheated holding tube with a length:dia. (L/D) ratio of 100-10,000, or wit steam at 100-300 degrees C and 1-100 bar in a heat exchanger with a heat exchange surface in the above range, then removing vapour from th heated mixt. in a separator to give a polymer soln. or paste with a concn. of 25-80 wt.% and opt. removing condensed water vapour; and (b) heating and further concentrating or degassing the conc. soln. at 1 mbar to 5 bar in a dried fitted with rotating baffles to scrape th drier walls and move the material, by heating te baffles and opt. also the drier mantle to 150-400 degrees C, opt. under inert gas or water vapour, with a residence time of 5-90 mins. and an integral energy input (specific kneading energy w.r.t. prod. throughput) of 0.01-1 kWh/kg dried polymer melt.