Abstract: The invention relates to a process for preparing hydroxyl-containing polymers, in particular for preparing polytetrahydrofuran with terminal hydroxyl groups, from the corresponding acyloxy-containing polymers by transesterification with alcohols in the presence of a sodium-containing catalyst. In this process the polytetrahydrofuiran solution is passed in the presence of a catalytic amount of water directly through at least one ion exchanger following the transesterification in order to remove the sodium cations.The novel process makes it possible to remove the sodium cations from the sodium-containing catalyst in an economic manner and with little complexity. The residual sodium content can be reduced to values of less than 0.5 ppm.

Abstract: A process for preparing hydroxyl-containing polymers and, in particular, a process for preparing polytetrahydrofuran with terminal hydroxyl groups from the corresponding acyloxy-containing polymers by transesterification with alcohols is carried out continuously in at least one stirred vessel, with the foam produced in the transesterification being fed tangentially to a cylindrical container, preferably a cyclone separator, at an adequate velocity to destroy the foam. The liquid phase which separates out is recycled through a line to the at least one stirred vessel.This continuous process is preferably carried out in a cascade of stirred vessels, in which each stirred vessel or a subunit of at least two stirred vessels can in each case be coupled to a cylindrical container, preferably in the form of a cyclone separator.