Preparation Of Novel Ziegler-Natta Catalyst For High Molecular Weight Polyethylene Produced And Characterization Of Metallocene Polyethylene

The synthesis of high molecular weight polyethylene with novel Z-N catalyst was carried out and the polymerization process was optimized. The properties of metallocene polyethylene (mPEs) sample offered by DaQin Petrochem and EXXON Co. were well characterized respectively.Siloxane compounds was combined with traditional ethers or esters compounds and used as electron donor to prepare novel Z-N catalysts for high molecular weight polyethylene. The catalytic activitie of novel Z-N catalyst reach 1.55×104gPE/gTi with higher molecular weight 2.9×106 g/mol. Optimization of preparation process of novel catalyst by orthogonal design was carried out and the effect of electron donors 1 (ED1) and electron donor 2 (ED2), the mole ratios of ED1, ED2 and isobutyl alcohol (iBuOH) with magnesium chloride (MgCl2), and the mole ratio of the added ED2 before and after titanium adding on catalyst activity and polymer molecular weight were also fulfilled. The result discovered the relationship between the catalyst preparation process and catalytic activity and properties of polymer and the optimized process was determined.It is found that the addition order of ED2 and titanium complex had the greatest impact to the catalytic activity and polyethylene molecular weight. The optimum conditions were obtained:solvent is n-hexene, isobutyl alcohol is used as modify agent and the mole ratio of i-BuOH/MgCl2 is 2.25; hexy1 trimethoxy-Silane (HTMS) and diethyl succinate (DIES) are used as ED1 and ED2 respectively; the mole ratio of HTMS and DIES with MgC12 both are 0.05; the ratio of HITS before and after the titanium addition is 6; DIES is added before titanium addition.In recent years, mPEs which has attracted wide interest and became a research focus. The PE sample (HPR18H10AX and HPR18H20DX) come from Daqing Daqing Petrochemical Company and from Exxon Company (1018CA and 1018FA) were investigated for determination the relationship of structure and properties. Some structural parameters, such as the content of comonomer, molecular weight, molecular weight distribution, sequence distribution, lamellar thickness, crystallite size, crystallinity and thermal stability were charactered by GPC,13C-NMR, FTIR, DSC thermal classification, XRD and TG Moreover, the rheological properties, tensile properties and tear strength of film of mPEs were also tested.The result indicates that the mechanical properties of mPEs are greatly influenced by microstructure of intramolecular and intermolecular, and among them, the branching degree plays important roles. It is observed that methylene sequence length, the crystallinity and the thickness all decrease as the branching degree augment. Actually, the mechanical properties such as melt index, tensile strength, yield strength and tensile strength are increased with the degree of branching increases, while the tear strength film was deceased. It suggested that rheological properties of HPR18H10AX and HPR18H20DX were better than that of 1018CA and 1018FA, which lead to more advantageous processing molding. The tensile properties of plastics of HPR18H10AX and HPR18H20DX are superior to 1018CA and 1018FA, but the film tear strength poor compared 1018CA and 1018FA.