A Monte Carlo Method to Quantify the Effect of Reactor Residence Time Distribution on Polyolefins Made with Heterogeneous Catalysts: Part IIIParticle Composition Distribution Effects

Polymer reactor blends, such as bimodal polyethylene or high-impact polypropylene, are usually produced in multistep processes using two or more reactors in series. Since the polymer particles are subject to reactor residence time distributions (RTD) during the polymerizations, the fractions of the polymer populations made in each reactor will vary from particle to particle. It is shown in the previous publications in this series that reactor RTD has a marked effect on the particle size distribution and on the packing density of polyolefin particles. In this article, the versatile Monte Carlo model is extended to demonstrate how reactor RTD affects particle composition and molecular weight distributions of polyolefin reactor blends made in multistep processes. Increasing the number of reactors in series favors the homogeneity of the product. Moreover, the average fraction of the different polymer populations in the particles depends strongly on the mean reactor residence time and polymerization kinetics.