Ethylene-Butadiene Copolymerization and Ethylene-1-Hexene-Butadiene Terpolymerization with a MgCl2-Supported Ziegler-Natta Catalyst: Polymer Structure and Active Centers

In this work, systematic studies on ethylene/butadiene copolymerization and ethylene/1-hexene/butadiene terpolymerization with a TiCl4/ID/MgCl2 (ID=diester) type Z-N catalyst were conducted in slurry process under 1 atm ethylene pressure, and the effects of initial butadiene concentration ([Bd](0)) on polymerization activity, copolymer structure, active center number ([C*]/[Ti]) and active center distribution were studied. Activity of the co- and terpolymerization was evidently lowered by raising [Bd](0). The butadiene incorporations were highly trans-1,4 regio /stereoselective. Addition of 1-hexene caused increase in polymerization activity, and 1-hexene incorporation rate was reduced by raising [Bd](0). Both the copolymer and terpolymer were composed of two fractions with high and low butadiene content, respectively. The fraction with low butadiene content (insoluble in boiling n-heptane) accounted for more than 85 % of the copolymer and more than 70 % of the terpolymer. [C*]/[Ti] was determined by quench-labeling the propagation chains by thiophene-2-carbonyl chloride. [C*]/[Ti] first increase to about 80 % and then decreased with increase of [Bd](0). A part of active centers was deactivated by butadiene when [Bd](0) was higher than 0.2 mol/L. Addition of 1-hexene slightly increased [C*]/[Ti] ratio. By using supported Z-N catalysts, it is feasible to synthesize ethylene-butadiene copolymer and ethylene-1-hexene-butadiene terpolymer with relatively low butadiene content (<= 1 mol %) at acceptable catalyst efficiency (about 50 % of the polymerization systems without butadiene).

Automated summary

In this study, ethylene/butadiene copolymerization and ethylene/1-hexene/butadiene terpolymerization were systematically investigated using a TiCl4/ID/MgCl2 type Z-N catalyst under 1 atm ethylene pressure. The study revealed that the initial butadiene concentration significantly impacted polymerization activity, active center number, and butadiene structure.