Research On A Emulsion-Based Spherical Self-supported Ziegler-Natta Catalyst For Polymerization Of Propylene And Ethylene

This paper was established in the research on the spherical Ti-based Ziegler-Natta catalysts. The research was aimed to prepare novel spherical Ti-based Ziegler-Natta catalyst for propylene or ethylene polymerization via emulsion technique. The effects of the components and their amounts as well as the conditions during the preparation of the catalyst on catalyst average particle size(APS), particle size distribution(PSD) and morphology were investigated in order to control the APS. PSD and morphology of the catalyst and the polymer.The effects of the amount and injection method of the emulsifier, adding ternpreture and time of the Mg-Complex. mixing speed, and BuCl on catalyst morphology. APS, and PSD were studied. Effects influencing the polymerization performances were also investigated:alkylaluminu/Ti molar ratio, external donors/Ti molar ratio, polymeric temperature and pressure. The ester, elements, APS, PSD, morphology, and structure of the catalysts were characterized by GC, GC/MS, XRD, SEM, BET, Coulter counter analysis, and UV. The polymer was characterized by SEM and DSC.Investigative results indicated that the morphology of catalyst was mainly determined by the amount and injection method of the emulsifier.And then APS and PSD were mainly determined by the adding tempreture and mixing speed. One optimal method produced spherical catalyst with less fines and narrower PSD was after addtion of Mg-Complex to TiCl4at-25℃, then polyester(2.2wt%) and T803B were added, finally the temperature was increased in a controled way. During all the preparation the mixing speed kept200rpm.Results show that the polymerization activity of the catalyst with low surface area was nevertheless high. The polyolefins replicated the shape and PSD of the catalyst. The low surface had few effects on the kinetics of catalyst system; activity for polymerazation firstly increased then decreased when polymeric temperature increased; activity for polymerazation increased when polymeric pressure increased. The effects of alkylaluminu/Ti molar ratio and external donors/Ti molar ratio on the catalyst’s performance accord with the conventional Ziegler-Natta Catalyst. The highest activity obtained with different alkylaluminu/Ti molar ratio based on the characteristic structure of the alkylaluminu in propylene polymerization. And the molar ratio increased with increasing alkyl group size in the cocatalyst. Furthermore the catalyst showed a higher stereospeeificity responsibility in propylene polymerization with CHMDMS rather than DCPDMS.