Process for preparation polyeter-polyol of low alkali metal ion content

The invention relates to a process for obtaining a poly ether polyol with a low content of alkali metal ions, comprising the following steps: (a) a polyaddition reaction of at least one alkylene oxide to a starter containing at least two active hydrogen atoms in the presence of a catalyst being an alkali metal hydroxide or alkoxide thereof; (b) neutralisation of the crude polyether polyol obtained in step (a) by the addition of sodium acid pyrophosphate (Na2H2P2O7) and water to the reaction mixture; (c) reducing the water content of the mixture obtained in step (b) to less than 0.1% by weight through distillation under reduced pressure; (d) removal of alkali metal salt crystals from the mixture obtained in step (c) by filtration to obtain a polyether polyol with a content of alkali metal ions of not more than 5 ppm. The inventive process allows for obtaining polyether polyols with a low content of alkali metal ions, which allows for significantly reducing side reactions in polyurethane plastics production processes.