The invention relates to the use of polyesters for increasing the surface tension and improving the hydrophilic behavior of hydrophobic surfaces, wherein said polyesters are obtainable by polymerization of a) one or more unsulfonated aromatic dicarboxylic acids and/or salts thereof and/or anhydrides thereof and/or esters thereof, and b) ethylene glycol, c) 1,2-propylene glycol, and d) one or more polyalkylene glycols, and e) one or more compounds of formula (1) R1O(CHR2CHR3O)nH  (1) where R1 is a linear or branched, saturated or unsaturated alkyl group of 1 to 22 carbon atoms, preferably methyl, R2 and R3 are each independently hydrogen or an alkyl group of 1 to 4 carbon atoms, preferably hydrogen and/or methyl, and n is from 1 to 50, f) in the presence or absence of one or more crosslinking compounds having 3 to 6 functions capable of polycondensation, especially acid, alcohol or ester functions, with the proviso that said components d) are used in weight quantities