Use of a potassium salt of a fatty acid in a process for extruding polypropylene comprising, in order, the steps of (a) forming a first extrudate by extruding a first composition comprising a first polypropylene, a first acid scavenger, and ≥ 50 ppm of a nucleating agent; and (b) forming a second extrudate by extruding a second composition in the same extrusion system as the first composition, the second composition comprising a second polypropylene and the potassium salt of a fatty acid, wherein the second extrudate contains < 10 ppm of the nucleating agent and the content of all nucleating agents in the second extrudate is < 10 ppm; as a second acid scavenger for deactivating residual amounts of nucleating agent in the second extrudate, wherein the nucleating agent is selected from phosphate ester salts, sodium benzoate, lithium benzoate, bis(4-tert-butyl-benzoate) aluminum hydroxide, talc, compounds of formula (I) wherein M 1 is an organic or inorganic cation, x is 1 or 2, y is 1 or 2, R 1 -R 10 each independently are H, OH, C 1-9 -alkyl, C 1-9 -alkoxy, C 1-9 -alkyleneoxy, amine, C 1-9 -alkylamine, halogen or phenyl, wherein any two vicinal or geminal alkyl groups may be combined to form a carbocyclic ring of up to six carbon atoms and wherein the carboxyl moieties of Formula (I) are present in cis configuration; and formula (II) wherein M 11 and M 12 are each independently selected from metal or organic cations, or are combined to form a single moiety, and R 20 -R 29 each independently are H, OH, C 1-9 -alkyl, C 1-9 -alkoxy, C 1-9 -alkyleneoxy, amine, C 1-9 -alkylamine, halogen, phenyl, alkylphenyl, or geminal or vicinal C 1-9 -carbocyclic. (a) forming a first extrudate by extruding a first composition comprising a first polypropylene, a first acid scavenger, and ≥ 50 ppm of a nucleating agent; and (b) forming a second extrudate by extruding a second composition in the same extrusion system as the first composition, the second composition comprising a second polypropylene and the potassium salt of a fatty acid, wherein the second extrudate contains < 10 ppm of the nucleating agent and the content of all nucleating agents in the second extrudate is < 10 ppm; as a second acid scavenger for deactivating residual amounts of nucleating agent in the second extrudate, wherein the nucleating agent is selected from phosphate ester salts, sodium benzoate, lithium benzoate, bis(4-tert-butyl-benzoate) aluminum hydroxide, talc, compounds of formula (I) wherein M 1 is an organic or inorganic cation, x is 1 or 2, y is 1 or 2, M 1 is an organic or inorganic cation, x is 1 or 2, y is 1 or 2, R 1 -R 10 each independently are H, OH, C 1-9 -alkyl, C 1-9 -alkoxy, C 1-9 -alkyleneoxy, amine, C 1-9 -alkylamine, halogen or phenyl, wherein any two vicinal or geminal alkyl groups may be combined to form a carbocyclic ring of up to six carbon atoms and wherein the carboxyl moieties of Formula (I) are present in cis configuration; and formula (II) wherein M 11 and M 12 are each independently selected from metal or organic cations, or are combined to form a single moiety, and R 20 -R 29 each independently are H, OH, C 1-9 -alkyl, C 1-9 -alkoxy, C 1-9 -alkyleneoxy, amine, C 1-9 -alkylamine, halogen, phenyl, alkylphenyl, or geminal or vicinal C 1-9 -carbocyclic. <EOS>