Residual metal content in Ethylene-Propylene-Diene Monomers synthesized using vanadium- and zirconocene-based catalysts

Abstract

Ethylene-propylene-diene monomer (EPDM) terpolymers were prepared using either vanadium (VOCl3/Al2Et3Cl3) or zirconocene (Et(Ind)2ZrCl2/MAO) catalyst systems. Residual metal contents in EPDM films were determined by Rutherford backscattering spectrometry. Metallocene catalyst systems exhibited a higher activity, producing EPDM with lower molecular weight and narrower molecular weight distribution. The highest activity guaranteed lower residual metal content (Zr/C = 10−5) than in the case of EPDM produced by VOCl3/Al2Et3Cl3 (V/C = 10−4). Subsequent steps of dissolution of the polymer and its reprecipitation were seen to reduce the metal contents in both metal systems. Concerning the cocatalyst retention, despite initial use of a very high amount of methylaluminoxane/metallocene (Al/Zr = 3000) in the reactor, only about 4% of this initial concentration remained in the polymer. On the other hand, in the case of vanadium-based catalyst, almost all Al present in the initial conditions (≃8.3) remained in the polymer. In both cases, the residual Al/M ratio was close to the value generally proposed for the generation/stabilization of the active species. In the case of vanadium systems, a test in the synthesis of ethylene propylene rubbers indicated that the absence of diene in the polymer structure leads to a reduction in the residual vanadium content, indicating that the diene double bond might be responsible for partially vanadium coordination. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1997–2003, 1999