Polycondensation product comprising as monomer components: A) at least one aryl polyoxyalkylene ether of the formula where Ar is an aryl group, R 1 and R 2 each independently of one another are selected from H, methyl and ethyl, with preferably at least one of the groups R 1 and R 2 being H, m is an integer from 1 to 300 and R 3 is selected from the group consisting of H, alkyl, aryl, aralkyl, alkaryl, phosphate, and also mixtures thereof; B) at least one aromatic compound of the formula, where R 4 and R 5 each independently of one another are selected from H, R 8, OH, OR 8, C R 8, COOH, COOR 8, SO 3 H, SO 3 R 8 and NO 2 and also alkali metal salts, alkaline earth metal salts and ammonium salts thereof, or together are a further fused-on ring, where R 8 each independently is selected from the group consisting of alkyl, aryl, aralkyl, alkaryl, and R 6 and R 7 each independently of one another are selected from OH, OR 9, C R 9, COOH and COOR 9 and also alkali metal salts and alkaline earth metal salts and ammonium salts thereof, where R 9 each independently is selected from the group consisting of alkyl, aryl, aralkyl, alkaryl; C) at least one aldehyde; and also D) at least one further aromatic compound, selected from the group consisting of phenol, 2-phenoxyethanol, 2-phenoxyethyl phosphate and phosphonate, 2-phenoxyacetic acid, 2-(2-phenoxyethoxy)ethanol, 2-(2-phenoxyethoxy)ethyl phosphate and phosphonate, 2-[4-(2-hydroxyethoxy)phenoxy]ethyl phosphate and phosphonate, 2-[4-(2-phosphonatooxyethoxy)phenoxy]ethyl phosphate and phosphonate, methoxyphenol, phenolsulphonic acid, furfuryl alcohol, and also mixtures thereof. A) at least one aryl polyoxyalkylene ether of the formula where Ar is an aryl group, R 1 and R 2 each independently of one another are selected from H, methyl and ethyl, with preferably at least one of the groups R 1 and R 2 being H, m is an integer from 1 to 300 and R 3 is selected from the group consisting of H, alkyl, aryl, aralkyl, alkaryl, phosphate, and also mixtures thereof; Ar is an aryl group, R 1 and R 2 each independently of one another are selected from H, methyl and ethyl, with preferably at least one of the groups R 1 and R 2 being H, m is an integer from 1 to 300 and R 3 is selected from the group consisting of H, alkyl, aryl, aralkyl, alkaryl, phosphate, and also mixtures thereof; B) at least one aromatic compound of the formula, where R 4 and R 5 each independently of one another are selected from H, R 8, OH, OR 8, C R 8, COOH, COOR 8, SO 3 H, SO 3 R 8 and NO 2 and also alkali metal salts, alkaline earth metal salts and ammonium salts thereof, or together are a further fused-on ring, where R 8 each independently is selected from the group consisting of alkyl, aryl, aralkyl, alkaryl, and R 6 and R 7 each independently of one another are selected from OH, OR 9, C R 9, COOH and COOR 9 and also alkali metal salts and alkaline earth metal salts and ammonium salts thereof, where R 9 each independently is selected from the group consisting of alkyl, aryl, aralkyl, alkaryl; C) at least one aldehyde; and also D) at least one further aromatic compound, selected from the group consisting of phenol, 2-phenoxyethanol, 2-phenoxyethyl phosphate and phosphonate, 2-phenoxyacetic acid, 2-(2-phenoxyethoxy)ethanol, 2-(2-phenoxyethoxy)ethyl phosphate and phosphonate, 2-[4-(2-hydroxyethoxy)phenoxy]ethyl phosphate and phosphonate, 2-[4-(2-phosphonatooxyethoxy)phenoxy]ethyl phosphate and phosphonate, methoxyphenol, phenolsulphonic acid, furfuryl alcohol, and also mixtures thereof.