Continuous solution copolymerization of ethylene and octene‐1 with constrained geometry metallocene catalyst

Abstract

The solution copolymerization of ethylene (1) with octene-1 (2) in Isopar E using constrained geometry catalyst system, [C5Me4(SiMe2NtBu)]TiMe2 (CGC-Ti)/tris(pentafluorophenyl)boron (TPFPB)/modified methylaluminoxane (MMAO), has been carried out in a high-temperature, high-pressure continuous stirred-tank reactor (CSTR) at 140°C, 500 psig and with a mean residence time of 4 min. A series of copolymer samples with octene-1 content up to 0.337 mole fraction were synthesized and characterized. The estimated reactivity ratios were r1 = 7.90 and r2 = 0.099. The CGC-Ti showed a higher ability to incorporate high α-olefins than other metallocene catalysts investigated in the literature due to its open structure. The presence of octene-1 lowered the catalyst activity, particularly at octene-1 levels higher than 0.45 mole fraction. Octene-1 was also found to reduce the molecular weight of polymer and broaden the molecular weight distributions. The triad distributions were measured by 13C-NMR. A minor penultimate effect was observed. The penultimate octene-1 unit appeared to slow down monomer insertion rates. A comparison of the propagation rate of octene-1 with the incorporation rate of macromonomer in the homopolymerization of ethylene suggests that the addition of macromonomer is effectively instantaneous after it is generated with diffusion to or from the active center reaction volume playing a minor role. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2949–2957, 1999