Process for manufacturing alkoxylated polyethyleneimines

A process for manufacturing ethoxylated polyethyleneimines by reacting at least one polyethyleneimine (PEI) with at least one ethylene oxide EO, wherein, in a first step (1), the polyethyleneimine (PEI) is reacted with ethylene oxide EO in a quantity of less than one molar equivalent per PEI, and subsequently, in a second step (2), the product of step (1) is reacted with a further quantity of ethylene oxide EO, in the presence of a basic catalyst C, and wherein the ethylene oxide EO is added in step (1) in an amount of 0.01 to 0.85 ethylene oxide units per NH-group of the polyethyleneimine (PEI), and wherein the polyethyleneimine (PEI) has a weight average molecular weight Mw prior to ethoxylation in the range of 1000 to 5000.