Process for producing a polyurethane molded part, comprising the steps of: a) providing a reaction mixture capable of reacting to polyurethane, b) providing a mold for shaping the polyurethane molded part, wherein the mold in the area of the surface intended for the molding exhibits a surface energy of ≤ 24.8 mN/m and/or a polar share of the surface energy of ≤ 2.0 mN/m, each measured according to DIN55660-2 of December 2011. c) providing an additive of the general formula,, or with wherein each R 1 independently of the others denotes an alkyl residue having 1 to 18 carbon atoms or an aryl residue, R 2 represents one of the residues or each R 3 independently of the others denotes hydrogen or an alkyl residue, each R 4 and each R 5 independently of each other and of the others denotes a hydrocarbon residue, respectively, preferably having 1 to 18 C - atoms or a hetrerocyclic ring system having at least one nitrogen atom and preferably 3 to 17 C - atoms, x represents a number of 5 to 90, y represents a number of 1 to 5, and z represents a number of 1 to 25, or wherein wherein R 1 and R 3 have the meaning described above, and x represents a number of 10 to 65, or wherein R 1 and y have the meaning described above, each R 6 independently of the others represents a residue -(CH 2) 3 NHR 7, each R 7 independently of the others represents H or a residue -(CH 2) 2 NH 2, and x represents a number of 5 to 90, preferably 10 to 65, or HO(CH 2 CH 2 O) n CH 2 CF 2 O(CF 2 PF 2 O) p (CF 2 O) q CF 2 CH 2 (OCH 2 CH 2) n OH wherein n represents a number of 1 to 20, and p and q independently of each other represent a numbers of 1 to 20, d) mixing the additive with the reaction mixture, and e) curing the mixture produced in step d) in the mold. a) providing a reaction mixture capable of reacting to polyurethane, b) providing a mold for shaping the polyurethane molded part, wherein the mold in the area of the surface intended for the molding exhibits a surface energy of ≤ 24.8 mN/m and/or a polar share of the surface energy of ≤ 2.0 mN/m, each measured according to DIN55660-2 of December 2011. c) providing an additive of the general formula,, or with wherein each R 1 independently of the others denotes an alkyl residue having 1 to 18 carbon atoms or an aryl residue, R 2 represents one of the residues or each R 3 independently of the others denotes hydrogen or an alkyl residue, each R 4 and each R 5 independently of each other and of the others denotes a hydrocarbon residue, respectively, preferably having 1 to 18 C - atoms or a hetrerocyclic ring system having at least one nitrogen atom and preferably 3 to 17 C - atoms, x represents a number of 5 to 90, y represents a number of 1 to 5, and z represents a number of 1 to 25, or wherein wherein R 1 and R 3 have the meaning described above, and x represents a number of 10 to 65, or wherein R 1 and y have the meaning described above, each R 6 independently of the others represents a residue -(CH 2) 3 NHR 7, each R 7 independently of the others represents H or a residue -(CH 2) 2 NH 2, and x represents a number of 5 to 90, preferably 10 to 65, or HO(CH 2 CH 2 O) n CH 2 CF 2 O(CF 2 PF 2 O) p (CF 2 O) q CF 2 CH 2 (OCH 2 CH 2) n OH wherein n represents a number of 1 to 20, and p and q independently of each other represent a numbers of 1 to 20, each R 1 independently of the others denotes an alkyl residue having 1 to 18 carbon atoms or an aryl residue, R 2 represents one of the residues or each R 3 independently of the others denotes hydrogen or an alkyl residue, each R 4 and each R 5 independently of each other and of the others denotes a hydrocarbon residue, respectively, preferably having 1 to 18 C - atoms or a hetrerocyclic ring system having at least one nitrogen atom and preferably 3 to 17 C - atoms, x represents a number of 5 to 90, y represents a number of 1 to 5, and z represents a number of 1 to 25, wherein R 1 and R 3 have the meaning described above, and x represents a number of 10 to 65, wherein R 1 and y have the meaning described above, each R 6 independently of the others represents a residue x represents a number of 5 to 90, preferably 10 to 65, n represents a number of 1 to 20, and p and q independently of each other represent a numbers of 1 to 20, d) mixing the additive with the reaction mixture, and e) curing the mixture produced in step d) in the mold.