A PROCESS FOR TRANSITIONING FROM A FIRST POLYMERIZATION REACTION CONDUCTED IN THE PRESENCE OF A CATALYST SYSTEM

摘要

A process for transitioning from a first polymerization reaction conducted in the presence of a first catalyst system of the kind such as herein described to a second polymerization reaction conducted in the presence of a second catalyst system of the kind such as herein described wherein the first and second systems are incompatible, the polymerization reaction being conducted at a temperature of 85 °C and a total pressure of 350 psi 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 through the polymerization zone, characterized in that comprising: a) discontinuing the introduction of the said first catalyst system into the reactor; b) lowering the height of the bed of polymer particles from a first height to a second height in a manner such as herein described; c) introducing the said second catalyst system into the reactor; and d) increasing the height of the bed of polymer particles to a level above the level of the second height in a manner such as herein described; optionally comprises the step of conducting essentially concurrently with the reduction of the height of the bed of polymer particles, at least one modification selected from the group consisting of: reducing the partial pressure of the monomer gases within the polymerization zone from a first partial pressure to a second lower partial pressure; reducing the velocity of the monomer gases passing through the reactor from a first velocity to a second velocity; and optionally introducing an alkoxylated amide or amine into the reactor essentially concurrently with the reduction of the height of the bed of polymer particles.