Abstract: The present invention relates to a process of preparing a polyethylene in a loop reactor in the presence of antifouling agent comprising the steps of: a) feeding into said loop reactor diluent, monomers, optionally hydrogen, and optionally one or more co-monomers to produce a liquid phase; b) introducing antifouling agent into said loop reactor, c) introducing a catalyst into the liquid phase to produce a slurry; and d) polymerizing the monomers and optional co-monomers to form the polyethylene, characterized in that the time difference between introduction of the antifouling agent and introduction of the catalyst is at most 3 hours.