The syndiotactic polypropylene ( s PP) with high bulk density and sphere like was prepared in bulk process by syndiospecific metallocene catalyst,which was synthesized and supported on silica by ourself.To avoid the a...The syndiotactic polypropylene ( s PP) with high bulk density and sphere like was prepared in bulk process by syndiospecific metallocene catalyst,which was synthesized and supported on silica by ourself.To avoid the active center of the metallocene catalyst leaching from silica surface that would foul reactor in polymerization,the blend of methylaluminoxane (MAO) and metallocene catalyst was deposited on silica treated by MAO first,then washing three times at least by hexane.The polymerization was carried out in 5 L reactor.The results verified that the high polymerization activity and syndiospecification of the metallocene catalyst were preserved after being supported.The polymerization activity and the pentad concentration of s PP are more than 10 6 g s PP/molZr\5h and 75%,respectively.The morphology and distribution of s PP particles were modified remarkably.Through studying the polymerization process,the effects of the polymerization temperature and the catalyst concentration on the polymerization results were inspected including polymerization activity,polymer morphology and the bulk density of polymer.When polymerization activity is in the range of 3～4×10 6g s PP/molZr\5h,the sphere like s PP with weight average molecular weight ( M w) between 15～45×10 4 and the bulk density between 0 35～0 45?g/cm 3 was obtained.展开更多
文摘The syndiotactic polypropylene ( s PP) with high bulk density and sphere like was prepared in bulk process by syndiospecific metallocene catalyst,which was synthesized and supported on silica by ourself.To avoid the active center of the metallocene catalyst leaching from silica surface that would foul reactor in polymerization,the blend of methylaluminoxane (MAO) and metallocene catalyst was deposited on silica treated by MAO first,then washing three times at least by hexane.The polymerization was carried out in 5 L reactor.The results verified that the high polymerization activity and syndiospecification of the metallocene catalyst were preserved after being supported.The polymerization activity and the pentad concentration of s PP are more than 10 6 g s PP/molZr\5h and 75%,respectively.The morphology and distribution of s PP particles were modified remarkably.Through studying the polymerization process,the effects of the polymerization temperature and the catalyst concentration on the polymerization results were inspected including polymerization activity,polymer morphology and the bulk density of polymer.When polymerization activity is in the range of 3～4×10 6g s PP/molZr\5h,the sphere like s PP with weight average molecular weight ( M w) between 15～45×10 4 and the bulk density between 0 35～0 45?g/cm 3 was obtained.
