Synthesis Of Ethylene-Propylene Rubber By Indenyl-based Metallocene Catalyst Systems

Metallocene catalysts have developed rapidly in the field of polyolefins in recent years, There are some advantages of metallocene catalysts compared to Zigler-Natta catalysts in ethylene-propylene rubber production. Indenyl-based metallocene catalysts have potential to applied in the synthesis of ethylene-propylene rubber.In this thesis, copolymerization of ethylene/propylene and terpolymerizations of ethylene/propylene/5-ethylidene-2-norbornene (ENB) were carried out with Bis(2,4,6-tri-Me-Ind)ZrCl2, rac-Et(Ind)2ZrCl2 and rac-Me2Si(Ind)2ZrCl2. Isobutyl modified methylaluminoxane (MMAO) was used as cocatalyst, n-heptane was used as solvent. Continuous gas feeding method was employed for keeping gas composition in the reactor constant during the polymerization. The effects of polymerization conditions were systematically investigated. The composition, chain structure and thermal property of the polymers were characterized by GPC, DSC, FTIR and NMR et al. Then the relationship between the characteristic of polymerization conditions and the above properties were established. This thesis achieved some results as follows:1) Copolymerization of ethylene and propylene were carried out with Bis(2,4,6-tri-Me-Ind)ZrCl2/MMAO. The effects of ethylene/propylene gas feed ratio on the copolymerizations were studied. The Crystallized segment of copolymers’ chain were determined by Successive Self-nucleation and Annealing (SSA). The chain structure and sequence distribution were characterized by 13C-NMR, the reactivity ratio and average sequence length of ethylene and propylene were calculated from 13C-NMR spectra. It was shown that, the ethylene content and crystallinity of copolymers were relatively high; Copolymers had the structure of various long sequences of ethylene chain segments; The tensile stress-strain properties of copolymers were similar to the polyolefin thermoplastic elastomer.2) Terpolymerizations of ethylene/propylene/ENB were carried out with rac-Et(Ind)2ZrCl2/MMAO. The effects of concentration of rac-Et(Ind)2ZrCl2, initial concentration of ENB, polymerization pressure, polymerization time and ethylene/propylene gas feed ratio on the terpolymerizations were investigated. The chain structure and sequence distribution were characterized by 13C-NMR. It was shown that, the terpolymerization activity of rac-Et(Ind)2ZrCl2/MMAO was as high as 42000 kgpolym·molZr-1·h-1; Terpolymer containing 13.5 wt% of ENB units was produced; The chemical composition of terpolymers were about the same as the ethylene/propylene gas feed composition; The product of reactivity ratios were in close to value 1, the terpolymers had random structure; The triads distribution of some terpolymers made in this work was similar to that of commercialized EPDM; However, the molecular weight of terpolymrs were low.3) Copolymerizations of ethylene/propylene and terpolymerizations of ethylene/propylene/ENB were carried out with rac-Me2Si(Ind)2ZrCl2/MMAO. The effects of polymerization temperature, [Al]/[Zr], ethylene/propylene gas feed ratio and initial concentration of ENB on the polymerizations were investigated. The chain structure and sequence distribution were characterized by 13C-NMR. It was shown that, The rac-Me2Si(Ind)2ZrCl2/MMAO catalyst system exhibited high polymerization activity (21900 kgpoiym·molzr-1·h-1); Lower polymerization temperature and lower [Al]/[Zr] were beneficial to producing higher molecular weight copolymers; This catalyst had relatively high tendency to copolymerize propylene, high content of [PPP] triads sequence distribution were observed; The product of reactivity ratios were less than value 0.5, The polymer chains were random and tended to be alternate; This catalyst showed high ENB insertion ability at low initial concentration of ENB; the molecular weight of terpolymrs were relatively high.4) Ethylene-propylene rubber samples were vulcanized and tested for tensile stress-strain property. It was shown that, the tensile stress-strain properties of vulcanized ethylene-propylene rubbers produced by rac-Et(Ind)2ZrCl2 were poor, due to the low molecular weight; The vulcanized ethylene-propylene rubbers produced by rac-Me2Si(Ind)2ZrCl2 had tensile strength of 13.0 MPa, elongation at Break of 340%.