A reaction product containing urethane groups, comprising one or more species of the general formula (I) (R1—X)p—Z1—(XH)y  (I) where p+y=w and w is an integer from 2 to 10, p is an integer from 2 to 10, y is an integer from 0 to 8, and X is independently O, NH and/or NZ2 and XH is independently a hydroxyl group OH, a primary amino group NH2 and/or a secondary amino group NHZ2 where Z2 is independently a branched or unbranched, saturated or unsaturated organic radical G(U)a where U is independently a hydroxyl group, a primary amino group or a secondary amino group and a is an integer from 0 to 8, where w+a≤10, G is a branched or unbranched, saturated or unsaturated organic radical, the p R1 radicals are independently a radical of the general formula (II) Y—O—CO—NH—R2—NH—CO  (II) in which the p Y radicals are independently a branched or unbranched, saturated or unsaturated organic radical which has 1 to 1000 carbon atoms and does not contain any hydroxyl groups, any primary amino groups or any secondary amino groups, the p R2 radicals are independently a branched or unbranched, saturated or unsaturated organic radical having 6 to 20 carbon atoms, and Z1 is a branched or unbranched, saturated or unsaturated organic radical which contains at least one tertiary nitrogen group and is free of XH groups.