Olefin polymerization and copolymerization
Evgeny E Faingol'd; Stanislav L. Saratovskikh; Andrei N. Panin; Olga N. Babkina; Igor V. Zharkov; Artur T. Kapasharov; Nikita N. Lashmanov; Gennadii V. Shilov; Natalia M. Bravaya
Abstract
Ethylene-propylene copolymerization reactions were carried out using rac-Et(2-MeInd)2ZrMe2 catalyst and (2,6-tBu2PhO-)AliBu2 as activator under varying reaction conditions. We demonstrate that reaction conditions such as monomer concentration, Al/Zr molar ratio and solvent type (toluene and heptane) ...
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Ethylene-propylene copolymerization reactions were carried out using rac-Et(2-MeInd)2ZrMe2 catalyst and (2,6-tBu2PhO-)AliBu2 as activator under varying reaction conditions. We demonstrate that reaction conditions such as monomer concentration, Al/Zr molar ratio and solvent type (toluene and heptane) all have significant effect on activity of the system and copolymers composition. The decrease in reaction pressure from 11 to 3 atm leads to: a) 1.6-fold increase in specific activity (from 3030 to 4840 kg copolymer/(mol Zr•h•atm)), b) increase of Mn value from 38 to 89 kg/mol, and c) increase of ethylene content in copolymer from 87 to 92 mol %. The increase of ethylene/propylene molar ratio from 0.7 to 2 does not significantly affect activity but leads to the rise in the ethylene content in copolymer from 92 to 97 mol % and, correspondingly, to the increase of copolymer crystallinity from 43 to 48%. As a result, thermal and mechanical properties of the obtained polymers also change, according to the shifts in copolymers composition. The change in Al/Zr molar ratio is confirmed to have great effect on the catalytic activity of our systems. In a row of Al/Zr= 100, 150, 200, 300 mol/mol, the lowest activity of 80 and the highest one of 8550 kg copolymer/(mol Zr•h•atm) are observed at 100 and 150 molar ratios correspondingly. We have also demonstrated the ability of catalytic systems with isobutylaluminum aryloxide activators to operate in aliphatic medium (heptane). On another note, during the reaction quenching, aryloxide activator hydrolyzes the polymer infused with 2,6-di-tert-butylphenol antioxidant. This results in the increased resistance of copolymers to the thermal-oxidative degradation. The presence of 4 wt.% phenol in the copolymer leads to an increase in the 5% mass loss temperature by 67°C. Moreover, increasing the residual phenol content from 2 to 4 wt.% affects the mechanical properties of the copolymers: the elongation-at-break increases from 500 to 600%, and the tensile strength decreases from 10 to 8 MPa.
Wei Wang; Shuzhang Qu; Xinwei Li; Jian Chen; Xiaolei Wang; Cui Zheng; Min Guo; Ying Wang
Abstract
Cyclic olefin copolymer is a type of high-performance polyolefin material, which is prepared by using a single-site catalyst in solution polymerization. The common activator of this system is alkyl aluminoxane or organic boron/aluminum system. Among them, organic boron is mostly triphenylcarbenium ...
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Cyclic olefin copolymer is a type of high-performance polyolefin material, which is prepared by using a single-site catalyst in solution polymerization. The common activator of this system is alkyl aluminoxane or organic boron/aluminum system. Among them, organic boron is mostly triphenylcarbenium tetrakis(pentafluorophenyl)borate or dimethylanilinium tetrakis(pentafluorophenyl)borate. In this study, ethylene and norbornene were copolymerized with metallocene catalyst activated with the combination of tris(pentafluorophenyl)boron and triisobutylaluminium. Compared with homopolymerization of ethylene, copolymerization shows high activity. The molecular weight of the polymer increased significantly with the increase of the insertion rate of norbornene. Fineman-Ross method was used to calculate the reactivity ratio, which showed that the reactivity ratio of norbornene was much lower than that of ethylene. The high copolymerization activity may indicate that, although norbornene has a lower coordination probability, its insertion rate is higher than ethylene. The copolymer with higher norbornene incorporation has a higher glass transition temperature, and the relationship between them is linear.
Olefin oligomerization
Ahad Hanifpour; Mahdi Hashemzadeh Gargari; Mohammad Reza Rostami Darounkola; Zahra Kalantari; Naeimeh Bahri-Laleh
Abstract
Herein a quenched-flow kinetic technique was applied to calculate the rate constants of 1-hexene and 1-octene oligomerization catalyzed by the Cp2ZrCl2 and Cp2HfCl2/MAO catalyst systems, and subsequently a mechanism for the higher α-olefin oligomerization reaction was proposed. The oligomerization ...
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Herein a quenched-flow kinetic technique was applied to calculate the rate constants of 1-hexene and 1-octene oligomerization catalyzed by the Cp2ZrCl2 and Cp2HfCl2/MAO catalyst systems, and subsequently a mechanism for the higher α-olefin oligomerization reaction was proposed. The oligomerization results showed that Zr-based catalyst in the oligomerization of 1-octene had the highest activity of 17 in comparison to Hfbased one with an activity value of 15 g oligomer/(mmolCat.h)). According to the obtained results, increasing monomer length led to a shift in molecular weight and polydispersity index value (Mw/Mn) to lower values. Furthermore, the microstructure-viscosity relationship was followed by the calculation of branching ratio and short-chain branching percentage. The obtained results revealed that, the oligomers synthesized by the Cp2HfCl2 catalyst had lower short chain branching ratio value and short-chain branching percentages. According to the kinetic results, the initiation rate constant (ki) of Zr-based catalyst was higher than that of Hf-based catalyst, and the order of calculated propagation rate constants was Zr>Hf for both the 1-hexene and 1-octene-based oligomerizations.
Catalysis
Gholam-Reza Nejabat; Mehdi Nekoomanesh; Hassan Arabi; Hamid Salehi-Mobarakeh; Gholam-Hossein Zohuri; Mohammad-Mahdi Mortazavi; Saeid Ahmadjo; Stephen A. Miller
Abstract
Several types of hybrid catalysts are made through mixing of 4th generation Ziegler-Natta (ZN) and (2-PhInd)2ZrCl2 metallocene catalysts using triethylaluminum (TEA) as coupling agent. Response surface methodology (RSM) is used to evaluate the interactive effects of different parameters including ...
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Several types of hybrid catalysts are made through mixing of 4th generation Ziegler-Natta (ZN) and (2-PhInd)2ZrCl2 metallocene catalysts using triethylaluminum (TEA) as coupling agent. Response surface methodology (RSM) is used to evaluate the interactive effects of different parameters including amounts of metallocene and TEA and temperature on metallocene loading. Analyzing the amounts of Al and Zr elements in the hybrid catalysts through ICP-OES and EDXA reveals that temperature plays a crucial role on anchoring of the metallocene catalyst on ZN while TEA has the least determining effect. The ICP analysis shows that as the concentration of Al goes up in the hybrid catalyst the concentration of Zr passes a maximum, while EDXA shows a direct relationship between the Al and Zr contents. Using triisobutylaluminum (TIBA) and methylaluminoxane (MAO) as the coupling agents, almost similar metallocene loadings are observed. Finally, the performance of hybrid catalysts is investigated in propylene polymerization and the obtained polymers are characterized using DSC and DMTA through which the presence of two types of polymers in the final product are confirmed.
