Organic/inorganic support for immobilizing (n‐BuCp)₂ZrCl₂/TiCl₃ hybrid catalyst for use in the preparation of polymer blends

Abstract

Reactor blends of ultrahigh‐molecular‐weight polyethylene (UHMWPE) and low‐molecular‐weight polyethylene (LMWPE) were synthesized by two‐step polymerization using a hybrid catalyst. To prepare the hybrid catalyst, styrene acrylic copolymer (PSA) was first coated onto SiO2/MgCl2‐supported TiCl3; then, (n‐BuCp)2ZrCl2 was immobilized onto the exterior PSA. UHMWPE was produced in the first polymerization stage with the presence of 1‐hexene and modified methylaluminoxane (MMAO), and the LMWPE was prepared with the presence of hydrogen and triethylaluminium in the second polymerization stage. The activity of the hybrid catalyst was considerable (6.5 × 106 g PE (mol Zr)−1 h−1), and was maintained for longer than 8 h during the two‐step polymerization. The barrier property of PSA to the co‐catalyst was verified using ethylene polymerization experiments. The appearance of a lag phase in the kinetic curve during the first‐stage polymerization implied that the exterior catalyst ((n‐BuCp)2ZrCl2) could be activated prior to the interior catalyst (M‐1). Furthermore, the melting temperature, crystallinity, degree of branching, molecular weight and molecular‐weight distribution of polyethylene obtained at various polymerization times showed that the M‐1 catalyst began to be activated by MMAO after 40 min of the reaction. The activation of M‐1 catalyst led to a decrease in the molecular weight of UHMWPE. Finally, the thermal behaviors of polyethylene blends were investigated using differential scanning calorimetry. Copyright © 2011 Society of Chemical Industry

Long‐term efficiency for reducing entanglements of nascent polyethylene by a polystyrene‐modified Ziegler‐Natta catalyst

“…In addition, the catalytic activity is still promoted, although the pore size and specific surface area are decreased. 31 To recall, the same chemical environment of Ti (See XPS result) and similar TiCl 4 loading in the PS-modified and PS-free catalyst demonstrate the less interaction between PS chains and active species. Thus, this enhanced activity may be attributed to the isolated effect of the inert PS blocks, since the PS phase is thermally immiscible with the polyethylene and serves as the inert isolator for separate the propagated chains.…”

TiCl4 immobilized on a composite support SiO2/MgCl2·x(1,4‐butanediol)/poly[styrene‐co‐(acrylic acid)] for ethylene polymerization: The barrier effect of poly[styrene‐co‐(acrylic acid)]

“…We have developed an improved phase inversion method to prepare polymer‐coated SiO 2 microspheres 27. These microspheres have been successfully used to support Ziegler–Natta or hybrid Ziegler–Natta/metallocene catalysts for production of polyethylene with broad or bimodal MWD 28, 29. Besides the role as the hybrid support, our results implied that the polymer affected the mass transfer of different reactants.…”

Blending ultrahigh‐molecular‐weight polyethylene and poly(ethylene/10‐undecen‐1‐ol) in one nascent particle

“…It was evidenced in our previous work that the PSA layers were compact with a nonporous structure . The immobilization of vanadium active sites depended on the swelling behaviors of PSA in n ‐hexane (in Cat‐2); this made the distribution of vanadium along the radial direction of PSA layer continuous . Thus, the synthesized polymer showed the numbers of thread structure with closest packing (see Figure S3, Supporting Information, for the particle morphology); this suggested that the PSA layer endowed a strong transfer resistance to the monomer during polymerization .…”

“…The activity of Cat‐2 only reached 2.3 × 10 5 g of PE/(mol [Fe] ·h) with the addition of MAO (run 3 in Table ). This low activity was attributed to the strong transfer resistance endowed by the outside PSA layer . Cat‐2 showed no catalytic activity with the presence of DEAC because the strong Lewis acid of DEAC could not activate the Fe active centers .…”

“…However, it is more challenging when PE and polar polyolefin are blended through this method because the strong polarity of the polar monomer will deactivate the active sites and decrease the molecular weight of the synthesized polymer . Our group developed a core–shell support for immobilizing hybrid catalysts . Two kinds of catalyst can be immobilized on the core and shell part, respectively.…”