| abstract |
(57) [Problem] To produce a polyether polyester excellent in mechanical strength and excellent in molding stability in an industrially stable and economical manner. SOLUTION: The number average molecular weight is 1,000 to 30,000. Polyalkylene oxide and polyanhydride of (1) The water content in the reaction system is reduced to 2000 ppm or less and reacted in a solvent, or (2) after a high molecular weight by a ring opening reaction, followed by a dehydration condensation reaction under reduced pressure by solid-phase polymerization, And / or produce hyperbranched polyether polyesters. |