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Ethylene Polymerization with “Constrained‐Geometry” Titanium Catalysts over Borate‐Modified Silica Supports
Author(s) -
Musikabhumma Kittichote,
Spaniol Thomas P.,
Okuda Jun
Publication year - 2002
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/1521-3935(20020101)203:1<115::aid-macp115>3.0.co;2-w
Subject(s) - polyethylene , boron , polymerization , catalysis , materials science , polymer chemistry , mesoporous material , ethylene , titanium , chemistry , chemical engineering , polymer , organic chemistry , composite material , engineering
Two different mesoporous silica materials, Sylopol® 948 and MPS5, were used as substrates for the preparation of silica‐bound trityl tris(pentafluorophenyl)borate activators. The borate‐modified silica supports, B‐Sylopol and B‐MPS5, were characterized by solid‐state NMR spectroscopy and ICP mass spectrometry, and applied as activators for slurry polymerization of ethylene using “constrained‐geometry” titanium complexes of the formula Ti(η 5 : η 1 ‐C 5 Me 4 SiMe 2 NR)X 2 (R = Me, i Pr, t Bu; X = Me, Bz, Cl) in the presence of triisobutylaluminium (TIBA). The activity of the B‐Sylopol system was higher than that of the corresponding homogeneous catalysts Ti(η 5 : η 1 ‐C 5 Me 4 SiMe 2 NR)X 2 /Ph 3 C + [B(C 6 F 5 ) 4 ] – , whereas that of the B‐MPS5 system was lower. These supported catalysts produced polyethylenes with higher molecular weights ( M̄ w in the range of 10 6 ), narrower molecular weight distributions ( M̄ w / M̄ n = 1.5–2.3) and higher bulk densities (up to 0.4 g/cm 3 ) compared to those of polyethylenes obtained with the homogeneous system. The resulting polyethylenes were found to replicate the shapes of the supported borate activators. Fine polyethylene particles due to the cracking of the support were observed with the B‐Sylopol system, while well‐shaped polyethylene spheres were formed with the B‐MPS5 system.