Early Publications of Kaminsky

In order to circumvent the results of Breslow and Reichert that had both reported the increase in ethylene polymerization rate by addition of water to titanium-based metallocene compoimds with other aluminum alkyls, Kaminsky and coworkers continued their research with mostly zirconium-based metallocenes activated by TMA/water mixtures [1-3]. 

The 1980 paper by Sinn, Kaminsky, Vollmer and Woldt [3] is probably the classic paper that initiated enormous interest in the metallocene/alumox-ane catalyst system in both industrial and academic laboratories worldwide. In this paper it became clear that the addition of a metallocene compound 

In a later paper, Herwig and Kaminsky [22] were able to isolate by fractional precipitation one methylalumoxane compoimd that was shown 

Chien and Wang [23] determined the initial active site concentration of this homogeneous catalyst system using a radiolabeling technique based on CHjOT and found that 80% of all the Zr atoms are catalytically active at 70°C and an Al/Zr molar ratio of 1,000, and that 100% of the Zr atoms are active at an Al/Zr ratio of 10,000. Lowering the polymerization temperature to 50°C and the Al/Zr ratio to 550 reduces the Zr active site content to 20%. The ethylene propagation rate constant at 70 C and an Al/Zr ratio of 11,000 was calculated to be 1.6 x 10 M/sec with the maximum ethylene polymerization rate obtained in about one minute at 1.06 x 10 M/sec and the rate decayed to about one-half the maximum rate of polymerization in about 40 minutes. 

As pointed out by Kaminsky and Arndt [24], this Cp ZrCl /MAO catalyst is about 10-100 times more active in ethylene polymerization than the conventional Ziegler systems, as an activity of 4 x lO g polyethylene/g Zr/hour are obtained, which translates to about 46,000 polymer molecules/ hour or one ethylene insertion in 3 x 10 seconds. 

---