Polymerization of ethene initiated with a mixture of siloxane‐bridged mono‐ and dinuclear zirconocenes

Abstract

In the polymerization of ethene cocatalyzed with modified methylaluminoxane, the catalyst activities of the siloxane-bridged dinuclear zirconocenes, tetramethyldisiloxanediylbis(cyclopentadienylindenylzirconium dichloride) (3) and hexamethyltrisiloxanediylbis(cyclopentadienylindeny1zirconium dichloride) (4) were lower than that obtained with the siloxane-bridged mononuclear zirconocene, tetramethyldisiloxanediyldicyclopenl_adienyldimethylzirconium (1). On the other hand, weight-average molecular weight M, and ratio of weight-to number-average molecular weights Mw/H,, of polyethene (PE) obtained with 3 or 4 were higher than those of PE obtained with 1. For a binary mixture of 1/3 or 1/4, it was found that the obtained PE exhibits a bimodal molecular weight distribution for an appropriate composition of the mixed zirconocenes. mw/@,, of PE could be adjusted by changing the relative concentrations of the two zirconocenes. 0 1996,

From Multisite Polymerization Catalysis to Sustainable Materials and All-Polyolefin Composites

“…Hence, tailored binuclear dual-site catalysts that exploit cooperative effects enabled broadening of polyethylene MWDs and the formation of bimodal MWDs. ,− Although single-site catalyst blends afford better MWD control via the site molar ratio, dinuclear complexes are attractive with respect to their use in tandem catalysis (see section 4) and compartmentalized supported catalysts. Regarding their industrial application in slurry polymerization, heterogeneous multisite catalysts are preferred because they prevent formation of fine particles accompanied by severe reactor fouling, which is typical of most homogeneous catalysts (section 3).…”

A critical examination of polyethylene molecular weight distribution control through the combination of soluble metallocene/methylalumoxane catalysts

“…These include the work of Heiland and Kaminsky,1 Han et al 2 and Lee et al 3 There is also great interest in supporting metallocene catalysts, and many patents and articles have been published which describe the combination of multiple catalyst types on supports.4h7…”

Combination of nickel and titanium complexes containing nitrogen ligands as catalyst for polyethylene reactor blending

“…Considering the latter case, many trials have been performed in order to in situ generate a novel catalytic species via combination of two different types of catalysts objecting to produce polymers with different properties compared to those obtained from separate use of the catalysts [9][10][11][12] . However to the best of our knowledge, no unambiguous evidence related to the formation of these species has been reported in the literature.…”