Highly active and stereospecific $MgCl_2$-supported catalyst, MPDT ($MgCl_2/EH/PA/TiCl_4/DIBP$) was prepared from $MgCl_2$ solution containing $MgCl_2$, EH(2-ethyl hexanol), PA(phthalic anhydride) which reacted to from the corresponding phthalic ester. This catalyst contains aromatic diester, DIBP(diisobutyl phthalate), as internal electron donor.
Propylene polymerizations were carried out in a slurry reactor under atmospheric pressure using MPDT catalyst cocatalyzed TEA(triethylaluminum) in the absence of PTES(phenyl triethoxy silane) and in the presence of PTES as external electron donor to study the effects of TEA and PTES concentration on the activity and stereospecificity. Also, polymerization temperature and hydrogen effects were observed. Maximum average polymerization rate($Rp_{max}$) was at 20-30 molar ratio of TEA/Ti and isotacticity decreased as the increase of TEA/Ti molar ratio in the absence of PTES. In the presence of PTES, however, $Rp_{max}$ was shifted to 50 molar ratio of TEA/Ti and isotacticity hold up higher than 96%. Isospecific sites were more sensitive to temperature than non-stereospecific sties. Addition of hydrogen enhanced the activity and decreased slightly the isotactic index(I.I.) of polypropylene.
To investigate the role of PA in catalyst, polymerizations were performed with $MDT(MgCl_2/EH/TiCl_4/DIBP$) catalyst synthesized from $MgCl_2$ solution without PA. Also the catalyst without DIBP, $MPT(MgCl_2/EH/PA/TiCl_4$) was prepared. The importance of diester in stability and stereospecificity of catalyst were discussed in the polymerization.
