Processes for preparing a polyethylene in at least one continuously stirred tank reactor are described herein. The process may comprise the step of: polymerizing ethylene in the presence of at least one supported metallocene catalyst, a diluent, optionally one or more co-monomers, and optionally hydrogen, thereby obtaining the polyethylene, wherein the supported metallocene catalyst comprises a solid support, a co-catalyst and at least one metallocene, wherein the solid support has a surface area within the range of from 100 to 500 m2/g, and has a D50 value within the range of from 4 μm to 18 μm, with D50 being defined as the particle size for which fifty percent by weight of the particles has a size lower than the D50; and D50 being measured by laser diffraction analysis on a Malvern type analyzer. Polyethylene obtained by the disclosed process and articles comprising the polyethylene are also described.