A graft polymer comprising: (A) a copolymer backbone as a graft base, wherein said copolymer backbone (A) is obtainable by polymerization of at least two monomers selected from the group of ethylene oxide, 1,2-propylene oxide, 1,2-butylene oxide, 2,3-butylene oxide, 1,2-pentene oxide or 2,3-pentene oxide, a. wherein the distribution of the alkylene oxide moieties within the copolymer backbone is in random order, and b. wherein the molecular weight of the copolymer backbone Mn in g/mol is within 500 to 7000, preferably not more than 6000, more preferably not more than 5000, even more preferably not more than 4500, even more preferably not more than 4000, even more preferably not more than 3500, even more preferably not more than 3000, and most preferably not more than 2500, and preferably at least 1000, more preferably at least 1200, and (B) polymeric sidechains grafted onto the copolymer backbone, wherein said polymeric sidechains (B) are obtainable by polymerization of at least one vinyl ester monomer (B1), and optionally at least one other monomer (B2), wherein - if present - the weight ratio of monomer (B2) to monomer (B1) is less than 0.5, preferably less than 0.4, more preferably less than 0.3, even more preferably less than 0.2, and most preferably less than 0.1, comprising in percent by weight in relation to the total weight of the graft polymer 25 to 85%, preferably 30 to 80%, more preferably 35 to 80%, even more preferably 40 to 75%, and most preferably 55 to 75%, of the copolymer backbone (A), And 15 to 75%, preferably 20 to 70%, more preferably 20 to 65 %, even more preferably 25 to 60%, most preferably 25 to 45%, of the polymeric sidechains (B). (A) a copolymer backbone as a graft base, wherein said copolymer backbone (A) is obtainable by polymerization of at least two monomers selected from the group of ethylene oxide, 1,2-propylene oxide, 1,2-butylene oxide, 2,3-butylene oxide, 1,2-pentene oxide or 2,3-pentene oxide, a. wherein the distribution of the alkylene oxide moieties within the copolymer backbone is in random order, and b. wherein the molecular weight of the copolymer backbone Mn in g/mol is within 500 to 7000, preferably not more than 6000, more preferably not more than 5000, even more preferably not more than 4500, even more preferably not more than 4000, even more preferably not more than 3500, even more preferably not more than 3000, and most preferably not more than 2500, and preferably at least 1000, more preferably at least 1200, and a. wherein the distribution of the alkylene oxide moieties within the copolymer backbone is in random order, and b. wherein the molecular weight of the copolymer backbone Mn in g/mol is within 500 to 7000, preferably not more than 6000, more preferably not more than 5000, even more preferably not more than 4500, even more preferably not more than 4000, even more preferably not more than 3500, even more preferably not more than 3000, and most preferably not more than 2500, and preferably at least 1000, more preferably at least 1200, (B) polymeric sidechains grafted onto the copolymer backbone, wherein said polymeric sidechains (B) are obtainable by polymerization of at least one vinyl ester monomer (B1), and optionally at least one other monomer (B2), wherein - if present - the weight ratio of monomer (B2) to monomer (B1) is less than 0.5, preferably less than 0.4, more preferably less than 0.3, even more preferably less than 0.2, and most preferably less than 0.1, 25 to 85%, preferably 30 to 80%, more preferably 35 to 80%, even more preferably 40 to 75%, and most preferably 55 to 75%, of the copolymer backbone (A), And 15 to 75%, preferably 20 to 70%, more preferably 20 to 65 %, even more preferably 25 to 60%, most preferably 25 to 45%, of the polymeric sidechains (B). <EOS>