Patent ID: 6576719
Filing Date: 2003-06-10
Classification: C08F,G01N

Abstract:
Process for maintaining a property P of a polyisobutene at a constant desired value in the course of an isobutene polymerization conducted continuously in a reactor comprising a boiling liquid reaction phase which contains the monomer and the polymer being formed and is in equilibrium with a gas phase on top of the said liquid phase, the process comprising:conducting the polymerization by continuous introduction into the reactor of a catalyst and of a C4 hydrocarbon feed mixture comprising the monomer; continuously withdrawing from the reactor the liquid reaction phase; and subsequently subjecting the liquid reaction phase continuously to at least one purification step which is intended to isolate the polyisobutene produced; wherein the property P is selected from the group consisting of viscosity and the average molecular mass of the polyisobutene produced; and wherein, by virtue of an empirical relationship established beforehand between the property P of the polyisobutene produced and the partial pressure piC4 of the isobutene in the gas phase of the reactor, a target value V is determined for piC4, corresponding to the desired value of the property P; and wherein, during the polymerization, the partial pressure piC4 in the gas phase of the reactor is measured and the said partial pressure piC4 is held constant at around the said target value V by acting on the flow rate Qc of the catalyst introduced into the reactor and/or on the flow rate Qh of the C4 hydrocarbon feed mixture.