Metallocene catalysts classification

For the synthesis of stereospecific metallocene catalysts for propylene polymerization, C2 symmetric precursors are necessary to obtain a catalyst for isospecific polymerization, and C5 symmetric precursors to produce a catalyst for syndiospecific polymerization. Asymmetric precursors can be used to synthesize metallocene catalysts that produce hemiisotactic and isotactic-stereoblock PP. Farina et al. [7] have proposed an useful classification of metallocene catalysts based on their symmetry (Figure 3). 

Norbornene-ethene copolymer, 16 113 Norbornene-ethylene copolymers, 20 433 physical properties of, 20 420-422 Norbornenodiazetine derivatives, 13 306 Nordel IP (metallocene), 7 637 Nordihydroguaiaretic acid, antioxidant useful in cosmetics, 7 830t Nordstrandite, 2 421, 425 activation, 2 394 classification, 2 422 decomposition sequence, 2 392 from gelatinous boehmite, 2 427 structural properties of, 2 423t NO-reduction reactions, TWC catalyst, 10 49... 

Table 1.2 provides a summary of commonly used classifications in the polyethylene industry. A brief note is warranted here to conclude the survey of polyethylene classifications and nomenclature. In the early 1990s, several types of polyethylene manufactured with metallcxiene catalysts (a type of single site catalyst, see Chapter 6) were introduced to the market. To differentiate polyethylene produced with metallocenes from polyethylene manufactured using older conventional catalysts, metallocene grades are sometimes abbreviated mVLDPE, mLLDPE, etc. 

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