Patent ID: 7291660

Claim:
A method of producing a high concentration polymer solution, comprising the steps of: dissolving a polymer into a solvent to prepare a low concentration polymer solution; and continuously concentrating said low concentration polymer solution to obtain said high concentration polymer solution, said concentrating step comprising the steps of: continuously feeding said low concentration polymer solution to a concentrating tank; evaporating part of said solvent of said low concentration polymer solution as a solvent gas in said concentrating tank; condensing said solvent gas to recover as a condensed solvent; and continuously drawing out from said concentrating tank said high concentration polymer solution obtained during concentrating in said concentrating tank; said method further comprising the steps of: measuring the polymer concentration of said high concentration polymer solution drawn out from said concentrating tank; and controlling at least one of volume of said low concentration polymer solution for feeding into said concentrating tank, temperature of said low concentration polymer solution for concentrating, and recovering volume of said condensed solvent, so as to adjust the polymer concentration of said high concentration polymer solution.