PROCESS FOR PREPARING A POLYETHER POLYOL WITH A HIGH ETHYLENE OXIDE CONTENT

The invention relates to a process for preparing a polyether polyol comprising: continuously feeding into a reactor which contains a composite metal cyanide complex catalyst and (i) a poly(oxyalkylene) polyol or (ii) a polyether polyol obtainable by the process according to the invention: (a) ethylene oxide, (b) a substituted alkylene oxide corresponding to Formula (I)in which R1, R2, R3 and R4 independently of each other represent hydrogen, a C1-C12-alkyl group and/or a phenyl group, provided that: (I) at least one of the radicals R1 to R4 does not represent hydrogen and (II) one or more methylene groups in any C1-C12-alkyl radical may be replaced by an oxygen atom or a sulfur atom, (c) optionally a starter compound having a hydroxyl functionality of from 1 to 8, wherein the weight ratio of the total amount of ethylene oxide fed to the total amount of the substituted alkylene oxide fed is of from 50:50 to 95:5, and wherein the ethylene oxide concentration is below 13,000 parts per million by weight (ppmw) per minute during continuously feeding ethylene oxide, wherein the ethylene oxide concentration is defined as the weight of ethylene oxide in the reactor based on the total weight of the reactor contents. Further, the invention relates to a process for preparing a polyurethane foam comprising reacting a polyether polyol and a polyisocyanate in the presence of a blowing agent, wherein the polyether polyol is a polyether polyol obtained by the above-mentioned process.