Kaminsky catalyst

EinaHy, in 1976, Kaminsky and Sinn in Germany discovered a new family of catalysts for ethylene polymerization. These catalysts (ie, Kaminsky catalysts) contain two components a metallocene complex, usually a zkconocene, and an organoaluminum compound, methylaluminoxane (8,9). These catalysts and thek various later modifications enable the synthesis of ethylene copolymers with a high degree of branching uniformity. Formally classified as MDPE, LLDPE, or VLDPE, the resins thus produced have a number of properties that set them apart from common PE resins in terms of performance... 

Most Kaminsky catalysts contain only one type of active center. They produce ethylene—a-olefin copolymers with uniform compositional distributions and quite narrow MWDs which, at their limit, can be characterized by M.Jratios of about 2.0 and MFR of about 15. These features of the catalysts determine their first appHcations in the specialty resin area, to be used in the synthesis of either uniformly branched VLDPE resins or completely amorphous PE plastomers. Kaminsky catalysts have been gradually replacing Ziegler catalysts in the manufacture of certain commodity LLDPE products. They also faciUtate the copolymerization of ethylene with cycHc dienes such as cyclopentene and norhornene (33,34). These copolymers are compositionaHy uniform and can be used as LLDPE resins with special properties. Ethylene—norhornene copolymers are resistant to chemicals and heat, have high glass transitions, and very high transparency which makes them suitable for polymer optical fibers (34). 

Fig. 3. Metallocene catalyst systems for LLDPE synthesis (a) Kaminsky catalyst (b) cationic catalyst and (c) Dow catalyst.

Metallocene Catalysts. Polymerization of cycloolefins with Kaminsky catalysts (combinations of metallocenes and methylaluminoxane) produces polymers with a completely different stmcture. The reactions proceeds via the double-bond opening in cycloolefins and the formation of C—C bonds between adjacent rings (31,32). If the metallocene complexes contain bridged and substituted cyclopentadienyl rings, such as ethylene(hisindenyl)zirconium dichloride, the polymers are stereoregular and have the i j -diisotactic stmcture. 

Kaminsky-Brintzinger systems, 16 82 Kaminsky catalysts, 17 702 20 426 Kaminsky metallocene catalysts,... 

Kaminsky catalysts - [OLEFINPOLYMERS - POLYETHYLENE - HIGH DENSITY POLYETHYLENE] (Vol 17) - [OLEFINPOLYMERS - POLYETHYLENE - INTRODUCTION] (Vol 17) -higher a-olefms [OLEFIN POLYMERS - POLYMERS OF HIGHER OLEFINS] (Vol 17) -for LLDPE production [OLEFIN POLYMERS - POLYETHYLENE - LINEAR LOW DENSITY POLYETHYLENE] (Vol 17)... 

Metallocene Catalysts. Higher a-olefins can be polymerized with catalyst systems containing metallocene complexes. The first catalysts of this type (Kaminsky catalysts) include metallocene complexes of zirconium such as biscyclopentadienylzirconium dichloride, activated by methylaluminoxane. These catalysts polymerize a-olefins with the formation of amorphous atactic polymers. Polymers with high molecular weights are produced at decreased temperatures and have rubber-like properties. 

The chiral complex EBTHI—Ti is an excellent chiral catalyst [40]. This complex is a derivative of titanocene and used as the Kaminsky catalyst, which has brought epoch-making progress in polypropylene production. The chiral bridged titanocene complex is used for the production of optically active polypropylene arising from the helical structure of the polymer chain. The chiral complex also behaves as an excellent... 

The Catalyst System Eleven years ago, Kaminsky invented a novel olefin polymerization catalyst derived from Cp2ZrCl2 (Cp = 7 -5-C5H5) and methylaluminoxane (1), a result that has stimulated intense interest in synthesis and reactions of metallocenium ions. Important questions still remain, however, regarding the nature of the Kaminsky catalyst. These include (1) what is methylaluminoxane and how does it interact with Cp2ZrMe2 to initiate polymerization and (2.) what are the mechanisms of chain initiation, propagation, transfer and termination A collateral question is how these steps may be controlled. 

Hexene Polymerization Polymerization of 1-hexene (and also propylene) by the Kaminsky catalyst [(Cp2ZrCl2/(MeAlO) /toluene] differs fundamentally from that of ethylene in that beta hydrogen elimination is the only detectable chain transfer mechanism. Insertion of 1-hexene into the Zr-C bond in Cp2ZrCH3+ produces Cp2ZrCH2CH(CH3)C4H9+. The electron donating... 

Kinetics of Hexene Polymerization We have measured the kinetics of 1-hexene polymerization by the Kaminsky catalyst by following monomer consumption with time. 

Figure 1. Scheme showing steps in ethylene polymerization by Kaminsky catalyst... 

Table 1 Effect of Variation in Organometallic Component of Kaminsky Catalyst on Relative Rate of Polymerization, Molecular Weight and Ratio of [1,2] to [2,1]...

In homogeneous polymerization catalysis (see Kaminsky Catalysts), constrained-geometry (CG) catalysts differ from bis Cp metallocenes in their ability to readily incorporate a-olefins in copolymerization with ethylene. This ability is due to the open nature of the catalyst active site. 

Scheme 6.20J Formation of the single site Kaminsky-catalyst from ZrCp2Me2 and a large excess of MAO. Adapted from Whiteley (2012).

In the 1970 s Kaminsky, Sinn, and others discovered that bis(cyclo-pentadienyl)dimethyltitanium when mixed with trimethyl aluminum and water provided a catalyst system capable of polymerizing ethylene [5]. The titanium structure bears some resemblance to that of ferrocene. Ferrocene was reported in 1951 [6,7] and the following year, the correct structure reported [8]. A brief, interesting account of the early days of the research on the structure proof of ferrocene has been written [9]. Because the Kaminsky catalysts have the same sandwich structure of ferrocene, they are referred to as metallocene catalysts. Just as the ferrocene ushered in a new era of organometallic chemistry, the Kaminsky metallocene spurred a tremendous amount of research in olefin polymerization catalysts. 

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