Development of Ternary Hybrid Ethylene Polymerization Catalysts Composed of Bis(imino)pyridineiron(III) Complex, Zirconocene, and Cr–montmorillonite

A ternary hybrid catalyst, composed of [2,6-{(2,6-(iPr)2C6H3)N = C(CH3)}2C5H3N]Fe(III)L2 (component 1), (n-C4H9C5H4)2ZrCl2 (component 2), and Cr–montmorillonite (component 3) was developed as an ethylene polymerization catalyst. The ethylene polymerization gave a linear polyethylene (Mn = 3.6 × 104) with a broad molecular weight distribution (Mw/Mn = 18.5). In the ethylene copolymerization with 1-hexene, the catalytic activity decreased significantly to one-third of that observed in the ethylene homopolymerization. The resultant copolymer possessed the similar molecular weight and its distribution to the homopolymer (Mn = 2.0 × 104, Mw/Mn = 25.4) with slightly decrease in the melting temperature. The gel permeation chromatography (GPC) profiles obtained in the ethylene homopolymer were analyzed via convolution/deconvolution to determine the ratio of the polyethylene (PE) produced by each catalyst component: PE (component 1) : PE (component 2) : PE (component 3) = 63 : 35 : 2. The ratio of the resultant copolymer was also analyzed and determined to be PE (component 1) : PE (component 2) : PE (component 3) = 85 : 14 : 1. The formation of short-chain branches in the copolymer was evaluated by successive self-nucleation and annealing (SSA), and the microstructure was analyzed by 13C nuclear magnetic resonance (13C-NMR) spectrum. The number of branches in the copolymer, as estimated by the 13C-NMR spectrum, was 0.7 per thousand carbon atoms, suggesting that a small amount of comonomer was incorporated into the main chain of the PE produced by component 2. In conclusion, the developed ternary hybrid catalyst successfully produced PE resin with a broad molecular weight distribution, consisting of PEs derived from each catalyst component.