Patent ID: 9458292
Filing Date: 2016-10-04
CPC Classification: C08G

Claim Text:
1. A method for purifying a polyethylene glycol compound having one amino group and having a total average molar number of ethylene oxide units added in a molecule thereof of 20 to 2300, the method comprising the following steps (A), (B) and (C): (A) a step of preparing an aqueous solution of the polyethylene glycol compound having one amino group, the solution having a pH of 1 to 5, (B) an extraction step of mixing the aqueous solution obtained in the step (A) with a mixed organic solvent at a temperature of 10° C. or higher and 55° C. or lower and causing layer separation into an organic layer and an aqueous layer, wherein a ratio of an organic solvent I is 25 to 65% by mass and a ratio of an organic solvent II is 75 to 35% by mass in the mixed organic solvent, the organic solvent I is selected from an aromatic hydrocarbon-based solvent having a total carbon number of 8 or less and an ester compound solvent containing no hetero atom and having a total carbon number of 5 or less, the organic solvent II is a halogenated hydrocarbon-based solvent, and a mixing ratio Y of the organic solvent I to the organic solvent II (organic solvent I/organic solvent II), temperature T (° C.) at the mixing, and molecular weight M of the polyethylene glycol compound satisfy the following relationship: and (C) a step of recovering the polyethylene glycol compound from the aqueous layer.