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

Abstract

AbstractIn 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 highlytrans‐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 boilingn‐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]0was 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).