Study On The Influence Of Cocatalysts And External Donors On The Propylene/ethylene Copolymerization Of Supported Ziegler-Natta Catalyst

Using spherical Zeagler-Natta catalyst, a polypropylene reactor alloy was prepared by two stage polymerization technics- first propylene homopolymerization, and then propylene / ethylene copolymerization. This polypropylene reactor alloy possess super high impact strength. It is showed that EPR copolymer maily build up of two portions: ethylene-propylene copolymers, block ethylene-propylene copolymers. Abound of PE-b-PP copolymer results in good compatibility between PP and EPR. The thesis presents the study on monomer content and sequence distribution for samples by using DSC and ¹³C-NMR. The influence of H₂, different cocatalysts and external donors on the ethylene-propylene copolymerization were studied.The influences of different comonomer ratios on the ethylene-propylene copolymerization were investigated. It is found that the catalytic efficiency was highest by cocatalyst triethyl aluminium (TEA) when Pp:Pe=1.5:1 but the catalytic efficiency was lowest by cocatalyst tetraethyl aluminoxane(EAO) under the same condition. The octane-insoluble content was highest by cocatalyst TEA when P_p:P_E=1:1.The influences of cocatalyst TEA, EAO and the mixture of them on the ethylene-propylene copolymerization were investigated. It is found that the catalytic efficiency was highest by cocatalyst TEA while the octane-insoluble content was lowest. The octane-insoluble content was highest when TEA/EAO=50/100 but the catalytic efficiency was lowest under the same condition.The influences of cocatalyst TEA, EAO and the mixture of them on the ethylene-propylene copolymerization under high pressure were investigated. It isfound that the octane-soluble copolymer tend to be random while the octane-insoluble copolymer tend to be block ethylene-propylene copolymers. Ethylene will be easy to polymerize by cocatalyst EAO while the molecular weight will be declined.The influences of H2 on the ethylene-propylene copolymerization under high pressure were investigated. It is found that block ethylene-propylene copolymers will be declined but the crystallizable proportion increased. The the molecular weight are declined both the octane-soluble copolymer and the octane-insoluble copolymer.The influences of external donor cyclohexylmethyldimethoxysilane(CMMS), dicyclopentyl-dimethexysilane(DCPMS) and the mixture of them on the ethylene-propylene copolymerization were investigated. It is found that the catalytic efficiency was highest when CMMS/DCPMS=2:3. The octane-insoluble content was highest by external donor DCPMS.The influences of different external donors, different catalysts and H2 on the ethylene-propylene copolymerization were investigated. For catalysts TK or DQ, the catalytic efficiency was higher when using external donor DCPMS but the catalyst B-3 was on the contrary. For catalysts B-3 or DQ, the octane-insoluble content was higher by external donor DCPMS but the catalyst TK was on the contrary. The catalytic efficiency was higher while the molecular weight was declined with H2.The influences of acetyl chloride quenching method for determining the concentration of the active sites in polymerization of 1-hexene by DQ/TEA catalyst system were also investigated in this thesis. We could calculate the concentration of the active sites by 'H-NMR spectra. The present results show that the concentration of the active sites distribution in supported Ziegler-Natta catalyst is quite available.