Abstract: Disclosed is a process for adding stabilizers and, optionally, additives to polyolefins in particle form obtained in liquid monomer by means of Ziegler-Natta catalysts, where the addition of stabilizers and, optionally, additives is carried out in liquid monomer in a step that follows polymerization, but precedes the flashing of the liquid monomer, after the aluminum alkyl has been deactivated.

Abstract: Disclosed are olefin polymers in nonextruded, aspolymerized particle form having a regular, essentially symmetrical geometrical shape, which are stabilized by depositing on their surface a mixture which is either melted, or in which at least stabilizer (A) is in the liquid state, and which comprises the following stabilizers (percent by weight on the polymer):A) from 0.02% to 0.015% of one or more organic phosphites or phosphonites or mixtures thereof, which are liquid at room temperature or have melting point below 100.degree. C.;B) from 0.025% to 0.2% of one or more phenolic antioxidants with melting point from 45.degree. to 130.degree. C.; and, optionally, one or more of the following additional components:C) from 0.05% to 0.5% of one or more thioethers, or organic polysulfides or mixtures thereof;D) from 0.1% to 1.0% of one or more light stabilizers which are liquid at room temperature or have a melting point below 150.degree. C.