One of the most exciting developments in the areas of catalysis, organometallic chemistry, and polymer science in recent years has been the intense exploration and commercialization of new polymerization technologies based on single-site and metallocene coordination olefin polymerization catalysts.1 The vast number of specifically designed/synthesized transition metal complexes (catalyst precursors) and main-group organometallic compounds (cocatalysts) allows unprecedented control over polymer microstructure, the generation of new polymer architectures, and the development of new polymerization reactions. Commercialization of new generations of single-site and metallocene catalyst-based technologies has provided the multibillion pound per year polyolefins industry with the ability to deliver a wide range of new and innovative olefin-based polymers having improved properties.2-4 The intense industrial activity in the field and the challenges to our basic understanding that have come to light have in turn 1391 Chem. Rev. 2000, 100, 1391−1434

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Cocatalysts for Metal-Catalyzed Olefin Polymerization: Activators, Activation Processes, and Structure−Activity Relationships

Elastic substantially linear olefin polymers are disclosed which have processability similar to highly branched low density polyethylene (LDPE), but the strength and toughness of linear low density polyethylene (LLDPE). The polymers have processing indices (PI's) less than or equal to 70 percent of those of a comparative linear olefin polymer and a critical shear rate at onset of surface melt fracture of at least 50 percent greater than the critical shear rate at the onset of surface melt fracture of a traditional linear olefin polymer at about the same I2 and Mw?Mn. The novel polymers can also have from 0.01 to 3 long chain branches/1000 carbons along the polymer backbone and have higher low/zero shear viscosity and lower high shear viscosity than comparative linear olefin polymers. The novel polymers can also be characterized as having a melt flow ratio, I10/I2, » 5.63, a molecular weight distribution, Mw/Mn, defined by the equation: Mw/Mn « (I10/I2) - 4.63, and a critical shear stress at onset of gross melt fracture greater than 4 x 10?6? dyne/cm2.

Elastic substantially linear olefin polymers

Selectivity in propene polymerization with metallocene catalysts.

Components of bimetallic catalysts for the polymerization of olefins comprising a compound of a transition metal M selected from Ti, V, Zr and Hf containing at least one M-π bond, a compound of Ti or V not containing metal-π bonds and a support comprising a magnesium halide. The catalysts obtained from the components of the invention are particularly suitable for gas-phase polymerization processes.

Components and catalysts for the polymerization of olefins

Cationic alkyl complexes of Group 4 metallocenes of the type [MCp2R]+(M = Ti, Zr or Hf, Cp = C5H5) have been recognised as the catalytically active species in metallocene-based olefin polymerisation catalysts. These highly electrophilic 14-electron species possess a very complex chemistry in which the formation of temporarily dormant stabilised adducts plays a dominant role. Cationic metal alkyls of this kind are found to be extremely active polymerisation catalysts, with high stereoselectivities and the potential to produce numerous previously inaccessible polymeric materials. A detailed understanding of the chemistry of these species promises to lead to a new generation of well defined polymerisation catalysts. Metallocene-based catalysts already play an increasing role in major industrial polymerisation processes.

Cationic Group 4 metallocene complexes and their role in polymerisation catalysis: the chemistry of well defined Ziegler catalysts

There is disclosed a process for the stereoregular polymerization of alpha olefins or mixtures thereof with ethylene conducted in the presence of highly active and stereospecific new catalysts. The catalysts are obtained from the reaction of a particular Al-alkyl compound which is at least in part in the form of a complex and/or a substitution reaction product with an electron-donor compound free from ester groups of oxygenated organic and inorganic acids, with a supported component characterized by having surface area exceeding certain values or by showing a particular X-rays spectrum and which is obtained by contacting a halogenated Ti compound, preferably in the form of a complex with an electron-donor compound, with a support comprising a Mg or Mn dihalide in an active state. In the catalysts the ratio between the Ti compound expressed in Ti g-atoms and the g-moles of the electron donor compounds is lower than 0.3.

Process for the stereoregular polymerization of alpha-olefins

Etude comparative par 13 C RMN de la structure stereochimique d'echantillons prepares dans differentes conditions de reaction

Microstructure of isotactic polypropylene prepared with homogeneous catalysis: stereoregularity, regioregularity, and 1,3 insertion

Homogeneous Ziegler-Natta systems for the ethylene polymerization, deriving from R2R2′M complexes (R = cyclopentadienyl; R′ = alkyl, aryl; M = Ti, Zr, Hf) and oligomeric oxoalane compounds, were studied Further results concerning the methyl aluminoxane synthesis and the related chemistry are reported On the basis of spectroscopic data a delocalized electronic structure could be inferred for these compounds Results from polymerization experiments showed that the highest productivities are obtained only by oxoalane cocatalysts having a high degree of oligomerization The catalytic activity of the systems under investigation was strongly affected also by changing both the σ-alkyl and the π-cyclo-pentadienyl ligands Furthermore, it was found that in the presence of methyl aluminoxane, the homoleptic σ-alkyl derivatives of IVB transition metals, such as Zr(CH2C6H5)4, are also able to polymerize ethylene with a fairly high productivity Active species containing ZrOAl bonds have been postulated

Homogeneous Ziegler–Natta catalysis. II. Ethylene polymerization by IVB transition metal complexes/methyl aluminoxane catalyst systems

Copolymerization of ethylene with propene in the presence of homogeneous catalytic systems based on group 4 metallocenes and methylalumoxane : implications of the reactivity ratios on the reaction mechanism

Alpha-olefins C3 -C6 are polymerized stereospecifically with the aid of catalysts obtained by mixing (a) a catalyst-forming component which is an addition and/or substitution product of an electron-donor compound (or a Lewis base) with an aluminum trialkyl, or an addition product of an electron-donor compound with an alkyl aluminum compound containing two or more Al - atoms bound to each other through an oxygen or nitrogen atom with (b) a supported catalyst-forming component which is the product obtained by contacting a titanium compound, preferably in the form of an addition product with an electron donor, with a carrier which is a mixture of an active anhydrous Mg or Mn dihalide and a solid organic material which is inert to all other components of the catalyst including the Mg or Mn dihalide carrier.

Romano Mazzocchi

Papers

Process for the stereoregular polymerization of alpha-olefins

Microstructure of isotactic polypropylene prepared with homogeneous catalysis: stereoregularity, regioregularity, and 1,3 insertion

Homogeneous Ziegler–Natta catalysis. II. Ethylene polymerization by IVB transition metal complexes/methyl aluminoxane catalyst systems

Copolymerization of ethylene with propene in the presence of homogeneous catalytic systems based on group 4 metallocenes and methylalumoxane : implications of the reactivity ratios on the reaction mechanism

Process for the stereospecific polymerization of alpha-olefins