Mathematical Models for Metallocene-Polyolefins Containing Long Chain Branches: An Overview of Different Techniques

摘要

Two mathematical models were developed to describe the populations of polymer chains containing different number of long chain branches (LCB) made with a combination of two single-site catalysts. One of the catalysts produces only linear chains (linear-catalyst) and the other produces linear and long-branched chains (LCB-catalyst). Simulations show that when the selectivity for macromer formation of the linear-catalyst is the same as that of the LCB-catalyst, it is not possible to maximize the number of LCB per chain, even though the number of LCB per 1000 carbon atoms can be maximized. On the other hand, if the selectivity for macromer formation of the linear-catalyst is higher than that of the LCB-catalyst, both LCB/1000 carbon atoms and LCB/chain pass through maximum values when varying the fraction of linear-catalyst in the reactor. More importantly, polymer populations with different number of LCB per chain will reach their maximum values at different ratios of linear-catalyst to LCB-catalyst, thus permitting the maximization of individual polymer populations in the mixture.