A process for preparing a macromonomer M of the general formula H 2 C=C(R 1)-R 2 -O-(-CH 2 -CH 2 -O-) k -(-CH 2 -CH(R 3)-O-) l -(-CH 2 - CH 2 -O-) m -R 4 where the (-CH 2 -CH 2 -O-) k and (-CH 2 -CH(R 3)-O-) l and optionally - (-CH 2 -CH 2 -O-) m units are arranged in block structure in the sequence shown in formula; where the radicals and indices are defined as follows: k:is a number from 10 to 150; l: is a number from 5 to 25; m:is a number from 0 to 15; R 1: is H or methyl; R 2: is independently a single bond or a divalent linking group selected from the group consisting of - (C n H 2n) - and -O-(C n' H 2n') -, where n is a natural number from 1 to 6 and n' is a natural number from 2 to 6; R 3: is independently a hydrocarbyl radical having at least 2 carbon atoms or an ether group of the general formula -CH 2 -O-R 3', where R 3' is a hydrocarbyl radical having at least 2 carbon atoms; R 4: is independently H or a hydrocarbyl radical having 1 to 4 carbon atoms; comprising the steps of a) reacting a monoethylenically unsaturated alcohol A1 of the general formula H 2 C=C(R 1)-R 2 -OH with ethylene oxide, where the R 1 and R 2 radicals are as defined above; with addition of an alkaline catalyst C1 comprising KOMe and/or NaOMe to obtain an alkoxylated alcohol A2; b) reacting the alkoxylated alcohol A2 with at least one alkylene oxide Z of the formula where R 3 is as defined above; with addition of an alkaline catalyst C2; where the concentration of potassium ions in the reaction in step b) is less than or equal to 0.9 mol%, based on the alcohol A2 used; and where the reaction in step b) is performed at a temperature less than or equal to 135°C, to obtain an alkoxylated alcohol A3 of the formula H 2 C=C(R 1)-R 2 -O-(-CH 2 -CH 2 -O-) k -(-CH 2 -CH(R 3)-O-) l -R 4 where R 4 = H, where the R 1, R 2 and R 3 radicals and the indices k and 1 are as defined above; c) optionally reacting at least a portion of the alkoxylated alcohol A3 with ethylene oxide to obtain an alkoxylated alcohol A4 corresponding to the macromonomer M of the formula where R 4 = H and m is greater than 0; d) optionally etherifying the alkoxylated alcohol A3 and/or A4 with a compound R 4 -X where R 4 is a hydrocarbyl radical having 1 to 4 carbon atoms, and X is a leaving group; to obtain a macromonomer M of the formula and/or where R 4 = hydrocarbyl radical having 1 to 4 carbon atoms. k:is a number from 10 to 150; l: is a number from 5 to 25; m:is a number from 0 to 15; R 1: is H or methyl; R 2: is independently a single bond or a divalent linking group selected from the group consisting of - (C n H 2n) - and -O-(C n' H 2n') -, where n is a natural number from 1 to 6 and n' is a natural number from 2 to 6; R 3: is independently a hydrocarbyl radical having at least 2 carbon atoms or an ether group of the general formula -CH 2 -O-R 3', where R 3' is a hydrocarbyl radical having at least 2 carbon atoms; R 4: is independently H or a hydrocarbyl radical having 1 to 4 carbon atoms; a) reacting a monoethylenically unsaturated alcohol A1 of the general formula H 2 C=C(R 1)-R 2 -OH with ethylene oxide, where the R 1 and R 2 radicals are as defined above; with addition of an alkaline catalyst C1 comprising KOMe and/or NaOMe to obtain an alkoxylated alcohol A2; b) reacting the alkoxylated alcohol A2 with at least one alkylene oxide Z of the formula where R 3 is as defined above; with addition of an alkaline catalyst C2; where the concentration of potassium ions in the reaction in step b) is less than or equal to 0.9 mol%, based on the alcohol A2 used; and where the reaction in step b) is performed at a temperature less than or equal to 135°C, to obtain an alkoxylated alcohol A3 of the formula H 2 C=C(R 1)-R 2 -O-(-CH 2 -CH 2 -O-) k -(-CH 2 -CH(R 3)-O-) l -R 4 where R 4 = H, where the R 1, R 2 and R 3 radicals and the indices k and 1 are as defined above; c) optionally reacting at least a portion of the alkoxylated alcohol A3 with ethylene oxide to obtain an alkoxylated alcohol A4 corresponding to the macromonomer M of the formula where R 4 = H and m is greater than 0; d) optionally etherifying the alkoxylated alcohol A3 and/or A4 with a compound R 4 -X where R 4 is a hydrocarbyl radical having 1 to 4 carbon atoms, and X is a leaving group; to obtain a macromonomer M of the formula and/or where R 4 = hydrocarbyl radical having 1 to 4 carbon atoms.