Process for preparing reactive polyether polyols having an ethylene oxide end block

摘要

Process for preparing polyether polyols having an end block of ethylene oxide by addition of alkylene oxides onto H-functional starter substances, in which A) a polyether polyol precursor is prepared by means of double metal cyanide (DMC) catalysis in a semicontinuous mode of operation in which previously prepared polyether polyol together with the DMC catalyst are placed in a reactor and H-functional starter substance and propylene oxide are added continuously, B) the polyether polyol precursor from stage A) is reacted with propylene oxide or an ethylene oxide/propylene oxide mixture in the presence of the DMC catalyst in a continuously operating reactor to give a polyether polyol intermediate, C) the intermediate from stage B) is mixed with an alkali metal hydroxide as catalyst and D) reacted with ethylene oxide in a continuously operating reactor to give the final product, E) the catalyst is separated off from the final product obtained in stage D).