Recovering polymer from dilute polymer solutions

Claim 1

A PROCESS FOR CONCENTRATING A RELATIVELY DILUTE POLYMER SOLUTION CONSISTING ESSENTIALLY OF A THERMOPLASTIC POLYMER AND A SOLVENT FOR SAID POLYMER COMPRISING HEATING SAID DILUTE POLYMER SOLUTION AT AN ELEVATED PRESSURE IN A CLOSED SYSTEM FILLED WITH SAID DILUTE POLYMER SOLUTION TO A TEMPERATURE ABOVE THE VAPORIZATION TEMPERATURE OF SAID SOLVENT AT A PRESSURE LOWER THAN THE PRESSURE IN SAID CLOSED SYSTEM; FLASHING SAID HEATED DILUTE SOLUTION TO A LOWER PRESSURE THAN IN SAID CLOSED SYSTEM TO CREATED A TWO-PHASE MIXTURE OF VAPOR AND LIQUID; INTRODUCING SAID MIXTURE TO A MULTI-PASSAGE HEATING ZONE, SAID ZONE BEING MAINTAINED AT A TEMPERATURE ABOVE THE VAPORIZATION TEMPERATURE OF SAID SOLVENT AT THE PRESSURE IN SAID ZONE, ABOVE THE MELTING POINT OF SAID POLYMER AND BELOW THE TEMPERATURE AT WHICH ANY SUBSTANTIAL DECOMPOSITION OF THE POLYMER WILL OCCUR; PASSING SAID MIXTURE THROUGH SAID HEATING ZONE; DISCHARGING SAID MIXTURE FROM SAID ZONE INTO A RECEIVER; WITHDRAWING VAPORIZED SOLVENT FROM SAID RECEIVER; AND WITHDRAWING FROM SAID RECEIVER A POLYMER SOLUTION SIGNIFICANTLY RICHER IN SAID POLYMER THAN SAID DILUTE POLYMER SOLUTION.