Abstract: Process for the emergency stopping of a polymerization reaction in the gas phase, comprising the injection of a poison of the reaction into a polymerization reactor and the evacuation of the gaseous content of the polymerization reactor via delaying means to a burner at the maximum limited feed rate, characterized in that the delaying means simultaneously serve to obtain a homogeneous distribution of the poison of the reaction inside the polymerization reactor so as to interrupt the polymerization reaction, and to regulate the flow of gasses evacuated to the burner so as not to exceed the maximum feed rate of the burner.

Abstract: A continuous process for obtaining propylene polymers in the presence of a catalytic system of the Ziegler-Natta type containing a catalytic solid comprising chlorine, magnesium and titanium atoms and at least one electron-donor compound, called internal donor, a cocatalyst which is an organoaluminium compound, and optionally an electron-donor compound, called external donor, comprising the following successive stages: (a) polymerization of propylene in liquid propylene to form, per g of titanium in the catalytic solid, from 11000 to 28000 g of a prepolymer chosen from among the homopolymers of propylene, and (b) gas-phase polymerization of propylene in one or more successive fluidized-bed reactors and in the presence of the prepolymer (a), of propylene, optionally in the presence of one or more other monomers chosen from among the &agr;-olefins containing from 2 to 12 carbon atoms to produce a final propylene polymer whose fraction of particles of diameter smaller than 125 &mgr;m (FP) is at most 10 wt %.