Process for producing polyether carbonate polyols

A process for startup of a reactor for a continuous process of preparation of polyethercarbonate polyols, the process comprising adding alkylene oxide and carbon dioxide in the presence of a DMC catalyst and/or a metal complex catalyst based on the metals cobalt and/or zinc onto H-functional starter substance, wherein

• (α) a portion of H-functional starter substance and/or a suspension medium having no H-functional groups is mixed in a reactor together with DMC catalyst and/or a metal complex catalyst based on the metals zinc and/or cobalt, where the DMC catalyst and/or the metal complex catalyst have a concentration s in the mixture, and
• (γ) after step (α), H-functional starter substance, alkylene oxide and DMC catalyst and/or a metal complex catalyst based on the metals zinc and/or cobalt are metered continuously into the reactor during the addition, and the resulting reaction mixture is removed continuously from the reactor, attaining a steady state,
• wherein, in step (α), the concentration s of the catalyst used, based on the mixture resulting from step (α), is in the range from 10 y≥s≥1.1 y, where y is the catalyst concentration, based on the reaction mixture in step (γ), of the steady state in step (γ), and
• wherein in step (γ), alkylene oxide is metered in at a mass flow rate X1 and X1 is increased continuously until the mass flow rate X2 required for the steady state in the reactor has been attained, where the time until attainment of X2 is at least one hour.