Polymerization of Ethylene with Catalyst Mixture in the Presence of Chain Shuttling Agent

Abstract

Mixture of two catalysts in one reactor for ethylene/α-olefin copolymerization in the solution process can result in the combination of microstructures related to both catalysts in the polymer framework. Thus, novel polymer configuration is synthesized, which is characterized by containing sequences of monomers produced with each catalyst in the same polymer chain. Adding a reversible transfer agent (CSA) to the binary system enables the production of new block copolymers with enhanced properties. Late transition metal catalysts, such as α-diimine nickel catalyst when activated with methylaluminoxane (MAO) show high activity towards olefin polymerization and produces highly branched homopolymers. On the other hand, C 2 symmetry metallocene catalysts produce linear polyethylenes. This paper describes the synthesis of ethylene homopolymer with amorphous and crystalline blocks using a binary mixture containing a nickel catalyst with α-diimine ligand, which produces ф highly branched polyethylene (soft PE) and a metallocene (rac-ethylene bis(H 4-indenyl)ZrCl 2) that converts ethylene into polyethylene with high activities and melting temperatures (hard PE). The influence of polymerization temperature and CSA concentration were investigated. The polymeric materials were characterized by density, thermal properties, X-ray diffractometry and dynamic-mechanical properties.

Zn‐assisted cooperative effect for copolymers made by heterodinuclear Fe−Ni catalyst

“…It also has been claimed that there is a possible complexation of active center and DEZ leading to an inactive site. [5,18,21] For M 2 , catalyst activity increased in the presence of DEZ. It has been reported that CSA cannot act as an activator or a cocatalyst, individually, so it may imply that DEZ acts as CTA and polymerization can last for longer time (Figure 1-b).…”

“…Similar catalytic systems based on an α-diimine Ni structure and a zirconocene catalyst in the presence of DEZ also have been reported, however, they were much more suitable for a control production of bimodal PE. [21,23] With respect to bimodality, bimodal PE represents an important class of polyolefin material with many unique properties and wide applications such as bimodal film resins, pipes and large part blow-molding articles. [33] The molecular weight distribution (MWD) as well as the branching type, density and distribution significantly affect the polymer properties (thermal, rheology, mechanical and etc.).…”

“…[5] In addition to catalyst structure, polymerization parameters such as CSA type and concentration, ratio of the catalysts, polymerization time, temperature and monomer pressure have striking effects on the chain transfer efficiency (CTE), length of the olefinic blocks and polymer properties. [2,15,17,21,[37][38][39][40] On the other side, multinuclear catalysts have shown remarkable behaviour such as cooperative effects. [41,42] This metal•••metal interactions may change the polymerization mechanism and cause an increasing of catalytic features and polymer properties such as catalyst activity, selectivity of chain branching, Mw, tacticity and so on.…”

Synthesis of polyolefin‐block‐polystyrene through sequential coordination and anionic polymerizations

“…The traditional heterogeneous Ziegler‐Natta catalyst has been replaced by homogeneous catalysts . The “coordinative chain transfer polymerization” (CCTP) technique employing a homogeneous catalyst and a chain transfer agent (e.g., dialkylzinc) is a useful tool for achieving precise architecture of the polymer chains; reversible alkyl exchange between the catalyst and Zn centers results in chain growth from the fed dialkylzinc (the first step in Scheme ) . The CCTP technique was judiciously utilized for commercial production of olefin block copolymers composed of semicrystalline and amorphous PO segments …”

Molecular Architecture of Multi‐Block Polymer Synthesized in a Dual‐Catalyst Single CSTR

“…The authors also concluded that for the system under investigation, chain shuttling was kinetically competitive with chain transfer. Martins et al described the synthesis of ethylene homopolymer with amorphous and crystalline blocks using a nickel catalyst with α‐diimine ligand, which produced highly branched polyethylene and a metallocene catalyst that converted ethylene into polyethylene with high activities and melting temperatures. They investigated the effect of CSA concentration on the system.…”