Patent attributes
The present invention relates to a process for the preparation of polyether carbonate polyols from one or more H-functional starter compounds, one or more alkylene oxides and carbon dioxide in the presence of a double metal cyanide catalyst, wherein (α) the H-functional starter substance or a mixture of at least two H-functional starter substances is initially introduced into the reaction vessel, (β) for the activation, a part amount (based on the total amount of the amount of alkylene oxides employed in steps (β) and (γ)) of one or more alkylene oxides is added to the mixture resulting from step (α), it also being possible for step (β) to be carried out several times for the activation, (γ) one or more alkylene oxides and carbon dioxide are metered continuously into the mixture resulting from step (β) (“copolymerization”), the alkylene oxides employed for the copolymerization being identical to or different from the alkylene oxides employed in step (β), characterized in that in step (γ) the carbon dioxide is passed into the mixture by (i) gassing the reaction mixture in the reactor from the bottom, (ii) using a hollow shaft stirrer, (iii) a combination of the metering operations according to (i) and (ii), and/or (iv) gassing over the surface of the liquid by using stirrer units configured in several stages.
