Patent ID: 7541427

Claim:
A method of desolvating a polymer solution, comprising: (a) steam stripping solvent from a polymer solution in an upstream desolvation tank; (b) steam stripping solvent from the polymer solution in a downstream desolvation tank wherein the upstream desolvation tank has a liquid phase portion and a gas phase portion, downstream desolvation tank has a liquid phase portion and a gas phase portion, the liquid phase portion of the upstream desolvation tank and the gas phase portion of the downstream desolvation tank are connected by a pipe, and at least one opening-degree adjusting mean is fixed to the pipe; and (c) controlling pressures such that a pressure difference (ΔP=P2−P1) between pressure (P2) of the gas phase portion of the downstream desolvation tank and pressure (P1) of the gas phase portion of the upstream desolvation tank is larger by from 0.005 to 0.6 MPa than a pressure difference (ΔP0=P20−P10) between pressure (P 20 ) of the gas phase portion of the downstream desolvation tank and a pressure (P10) of the gas phase portion of the upstream desolvation tank when the opening-degree adjusting mean is fully opened.