Investigation of Alkoxysilanes in the Presence of Hydrogen with Ziegler-Natta Catalysts in Ethylene Polymerization

Effect of hydrogen and alkoxysilanes as external donor were investigated using two commercial Ziegler-Natta catalysts (TiCl4/MgCl2•nEtOH and TiCl4/phthalate type/MgCl2) in ethylene polymerization. These catalysts were analyzed by EDX, FTIR and XRD measurements. Furthermore, catalytic activity was tested. According to the results, when alkoxysilane was introduced into the system, catalytic activity reduced. Compared these two alkoxysilanes, cyclohexylmethyldimethoxysilane (CHMDMS) can decrease activity more than dimethoxydimethylsilane (DMDMS) did. This was because CHMDMS has more bulky hydrocarbon groups than DMDMS. This led to restrict the direction of monomer insertion to active sites. In addition, when hydrogen was added into the system, CHMDMS is more sensitive to hydrogen than DMDMS. However, CHMDMS showed lower hydrogen response than DMDMS with increased hydrogen concentration. This was owing to its hydrogen sensitivity. Among the two catalysts, catalyst having internal donor can decrease sensitivity of catalyst activity in the system with hydrogen. The obtained polymers were further characterized by DSC and GPC.