STUDY ON PROPYLENE ISOSPECIFIC POLYMERIZATION USING SUPPORTED METALLOCENE CATALYST rac-Me_2Si(Ind)_2ZrCl_2

A highly active supported metallocene catalyst for propylene isospecific polymerization was prepared by immobilization of SiO\-2 with precontacted compounds of rac Me\-2Si(Ind)\-2ZrCl\-2 and methylaluminoxane (MAO).The influence of \/\ ratio and polymerization temperature on the activity,molecular weight ( M \-W) and polymerization kinetics was investigated.The behavior of this catalyst was also compared with its corresponding homogeneous catalytic system.It was demonstrated that the active site of heterogeneous systems was more stable,and the M W of the obtained polymer improved apparently in parallel.The microstructure of i PP produced by two types of catalysts was determined by 13 C\|NMR spectra.It was found that the isotacticity of i PP obtained by heterogeneous systems was higher,its pentad sequence \ increased to 86 3% from 82 0% for homogeneous systems.Moreover,the regioselectivity of polymers produced by heterogeneous systems was also improved,the 2,1\|insertion and 1,3\|insertion decreased to 3 7‰ and 0 5‰ from the values of 4 4‰ and 1 9‰,respectively for those produced by homogeneous systems.