Patent ID: 6841630
Filing Date: 2005-01-11
Classification: C08F,Y10S

Abstract:
1. A process for transitioning from a first polymerization reaction conducted in the presence of a first catalyst system to a second polymerization reaction conducted in the presence of a second catalyst system, the polymerization reaction being conducted in a polymerization zone of a gas phase fluidized bed reactor which contains a fluidized bed of polymer particles by the essentially continuous passage of monomer gases comprising ethylene through the polymerization zone, comprising: a) discontinuing the introduction of the first catalyst system into the reactor wherein the first catalyst system comprises a chrome-based catalyst system and allowing the reactor temperature to drop to or below 80° C.; b) maintaining polymerization conditions in the reactor and permitting polymerization to continue for a period of time to allow the components of the first catalyst system present in the reactor to produce additional polymer particles; c) establishing appropriate conditions within the reactor for the second catalyst system, wherein the second catalyst system comprises a mixed catalyst system comprising a metallocene component; f) introducing the second catalyst system into the reactor; and g) increasing reactor temperature to 105° C. essentially simultaneously with the commencement of the second polymerization reaction.