Fabrizio Piemontesi

• Basell Poliolefine Italia s.r.l.

The nature of Ti(III) species, introduced in working models of industrial Ziegler Natta catalyst precursors, consisting of MgCl2/TiCl4 binary systems, eventually containing different Lewis basis, are studied by a combination of X- and Q-band CW and pulse EPR spectroscopy. In Ziegler Natta catalysts, Ti(III) play the double role of active catalytic...

Adducts of TiCl4 with Lewis bases used as internal or external donors in heterogeneous Ziegler-Natta (ZN) catalysis represents a fundamental interaction contributing to the final composition of MgCl2 supported ZN-catalysts. This study presents the accurate experimental evaluation, from titration calorimetry, of the formation enthalpy of TiCl4 adduc...

A study of the nucleating effects of isotactic poly(trimethylallylsilane) (iPTMAS) and poly(vinylcyclohexane) (iPVCH) for isotactic polypropylene (iPP) and their influence on the mechanical behavior of iPP is reported. The particles of catalyst are covered by poly(trimethylallylsilane) or poly(vinylcyclohexane) by polymerization of the correspondin...

Innovation of the Ziegler-Natta polymerization process for polymerization of propene that allows tailoring of the mechanical properties of isotactic polypropylene (iPP) directly in the polymerization stage is presented. The catalyst is modified by prepolymerization of trimethylallylsilane or vinylcyclohexane so that the catalyst particles are coate...

This work presents novel and, to some extent, surprising information on ethene/4-methyl-1-pentene (E/Y) copolymers prepared with C2 symmetric single center metallocene catalysts: the moderately isopecific rac-ethylenebis(tetrahydroindenyl)zirconium dichloride (EBTHI) and the highly isospecific rac-dimethylsilylbis(2-methyl-4-phenylindenyl)zirconium...

Infrared vibrational spectroscopy has been used to reveal the conformations of the Ziegler−Natta catalysts internal electron donor 9,9-bis(methoxymethyl)-fluorene and its selectively deuterated derivative (9,9-bis(1,1-dideutero-methoxymethyl)-fluorene), in the solid state, complexed with TiCl4 and MgCl2 and in the catalyst precursor. The experiment...

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Ethene/1-olefin blocky copolymers were obtained through nonliving insertion copolymerizations promoted by an isospecific single site catalyst. Propene or 4-methyl-1-pentene were copolymerized with ethene with metallocenes endowed with different stereospecificity in propene polymerization: (i) aspecific “constrained geometry” half-sandwich complex,...

The aim of this work was to study the comonomer distribution and the chemical composition distribution generated by different Ziegler-Natta (ZN) systems (different internal donors, ID, dicyclopentadienyl-dimethoxy silane, D donor, as the external donor) and to define the potentialities of different IDs to produce improved heterophasic copolymers (H...

A calorimetric investigation on the reactions of TiCl4 with phthalates in 1,1,2,2-tetrachloroethane (TCE) is presented in order to better understand the complex interactions present in Ziegler-Natta catalytic systems. The Lewis bases diethyl isophthalate (L1), diethyl terephthalate (L2) and the ortho-isomer diethylphthalate (L3), have been chosen t...

This paper presents a novel microstructure for an ethene/1-olefin copolymer. Ethene/4-methyl-1-pentene copolymers were found to be essentially made of sequences of ethene alternating with sequences of 4-methyl-1-pentene, with a minor amount of isolated ethene units distributed in the 1-olefin sequence. This microstructure is produced by highly isos...

Calorimetric and computational investigation on the interaction of TiCl4 with some Lewis bases (esters and ethers) is presented. The bases were chosen for their relevance in heterogeneous Ziegler-Natta polymerization of propene. Comparison of the theoretical data with the calorimetric data indicates that calculations consistently underestimate the...

We present a theoretical study of the basic interactions occurring at supported hetereogenous Ziegler−Natta catalytic systems. We first investigated the interaction between prototypes of each class of industrially relevant internal donors (1,3-diethers, alkoxysilanes, phthalates, succinates) and the MgCl2 support. Our analysis indicates that donors...

Extensive calorimetric investigations on the interaction of TiCl4 with some Lewis bases are presented. Some of the bases were chosen for their industrial relevance in heterogeneous Ziegler−Natta polymerization of propene (ethyl benzoate, L2, diisobutyl phthalate, L3, (2R,3S)-diethyl 2,3-diisopropylsuccinate, L6, (2S,3S)-diethyl 2,3-diisopropylsucci...

The FT-Raman spectra of a series of mechanically prepared MgCl2–TiCl4 samples with increasing content of TiCl4 have been recorded. Raman scattering lines in the range 600–100cm−1 reveal the formation of TiCl4 molecules complexed on the lateral cuts of activated MgCl2 crystals. This pattern of lines suggests that atleast three types of complexes are...

This work reports on the microstructure of ethene/propene copolymers prepared in solution at high polymerization temperature with single center catalytic systems. Three different organometallic complexes were used as catalysts:  a sterically hindered, highly regio- and stereo(iso)-specific metallocene, rac-[methylenebis(3-tert-butyl-1-indenyl)]zirc...

The most advanced catalysts, based on MgCl2-supported TiCl4 and electron donors, are able to provide polypropylenes with an isotacticity higher than 99%. This, together with the continuous progress made in understanding and exploiting the role of electron donors in controlling polymer MW and MWD, has led to polypropylene products having an unpreced...

The synthesis of C 1 ‐symmetric zirconocene complexes bearing the 2,5‐dimethyl‐7 H ‐cyclopenta[1,2‐ b :4,3‐ b ′]dithiophene ligand ( S 2 ‐3 ) linked to substituted cyclopentadienes is described. Different syntheses of S 2 ‐3 , the common intermediate for the preparation of these complexes, are discussed. Many of these complexes have been found to b...

The vibrational Infrared and Raman Spectra of a MgCl2-TiCl4 Ziegler-Natta catalyst precursor with a 50/1 MgCl2/TiCl4 ratio have been recorded. The Raman spectrum of this catalyst precursor, in the range 50-500 cm−1, shows clear scattering lines which can be assigned to the complex MgCl2-TiCl4, well separated from those of the initial species. Analo...

Ziegler‐Natta catalysts, discovered in the years 1953–1954, account today for a production volume of ∼65 million tons of polyolefins, including mainly polyethylene and polypropylene products. Since their first discovery, the development of Ziegler‐Natta catalysts has been relentless, and their evolution is the result of the exploitation, starting f...

Melting enthalpies of several ethene-propene samples, obtained by different single-center catalytic systems and having widely different constitutions and compositions in the range of industrial interest, are compared. For the first time, a clear evidence of influence of the regio- and stereoregularity of propene insertion on crystallization behavio...

The solvent effect observed in propene/1-hexene copolymerizations performed with the isospecific catalyst rac-Et(Ind)2ZrCl2/MAO is studied. A range of solvents with increasing donor character and steric hindrance has been tested, and their effect on copolymer yield, composition, and microstructure has been thoroughly analyzed. Our results demonstra...

Details of the preparation and polymerization behavior of two chiral zirconocene catalysts are presented. The results of experimental and molecular-mechanics evaluation of their stereoselectivity with respect to liquid-propene polymerization are compared with those of a related catalyst system. The elastic properties of the obtained amorphous poly(...

Ethene/propene copolymerizations were performed with rac-[ethylenebis(4,5,6,7-tetrahydro-1-indenyl)]zirconium dichloride (r-EBTHIZrCl2) and tetraisooctylaluminoxane (TIOAO). Copolymerizations were carried out at three levels of comonomer concentrations, in a range from about 0.011 M to about 2.6 M. The reactivity ratios of copolymerizations (r11, r...

The catalytic system rac-Me2Si(Ind)2ZrCl2/MAO was used to polymerize ethylene and to copolymerize ethylene with different 1-olefins (copolymers containing 1-olefins up to 1-tetradecene were prepared). In the presence of the 1-olefin, the catalytic activity increases. As expected, the amount of 1-olefin inserted in the polymer chain depends on the m...

The influence of polymerization temperature, propylene concentration and hydrogen on the polymerization performance of the isospecific, highly regiospecific rac-Me2C(3-t-Bu-1-Ind)2ZrCl2 / MAO (1/MAO) catalyst has been investigated. Propagation follows the rate law Rp = (a[M]+b[M]²)/(c+d[M]). 1/MAO is more stereospecific compared to unsubstituted bi...

Metallocene catalysts emerge as a successful catalysts technology and represent the future of polyolefins. In the case of highly crystalline isotactic polypropylene (i-PP), despite a general belief, metallocene catalysts are far less active and efficient than the newest supported Ti/MgCl2 catalysts. Metallocenes are use to make i-PP because i-PP pr...

Propylene/1-hexene copolymers were prepared with the isospecific Et(Ind)2ZrCl2 /MAO catalyst by using a wide range of solvents. In the order of increasing dielectric constant (ε) they are: heptane (1.92), methylcyclohexane (2.02), toluene (2.38), chlorobenzene (CB) (5.68), methylene chloride (8.93) and o-dichlorobenzene (o-DCB) (10.12). The effect...

The influence of molecular hydrogen on propene polymerization promoted by the regio- and isospecific rac-Me2C(3-t-Bu-1-Ind)2ZrCl2/MAO catalytic system has been investigated both by experiment (liquid propene, Tp = 50 °C) and molecular modeling (quantum mechanics/molecular mechanics). A competitive secondary (2,1) propene insertion into the Zr−H bon...

Ethene/propene copolymerizations were performed with catalytic systems composed of a stereorigid racemic isospecific metallocene and polymethylalumoxane. A number of complexes were used as representatives of three different classes of metallocenes. r-Me2C(3-t-Bu-Cp)2ZrCl2, r-Me2C(3-t-Bu-Ind)2ZrCl2, r-EBDMIZrCl2, r-EBDMTHIZrCl2, and r-Me2Si(2-Me-4-P...

Ethene/propene copolymerizations were performed in solution with a single centre catalyst system composed of a “constrained geometry” half-sandwich organometallic complex {η1: η5-[(tert-butylamido)dimethylsilyl](2,3,4,5-tetramethyl-1-cyclopentadienyl)}titanium dichloride, and methylaluminoxane. The statistical treatment of polymerization data allow...

Ethene/propene copolymerizations were performed with a catalytic system composed of a metallocene and an alumoxane. The role played by the alumoxane was investigated by comparing the effects of three different compounds:  poly(methylalumoxane) (MAO), tetraisobutylalumoxane (TIBAO), and tetraisooctylalumoxane (TIOAO). A thorough comparison was perfo...

This paper will discuss the role of organometals in the production of elastomeric copolymers of ethylene, propylene and a diene (EPDM). Catalyst technologies based on vanadium and titanium will be compared, and the properties of resulting products are illustrated.

Ethene and propene were copolymerized using a metallocene-based catalytic system, composed of rac-isopropylidenebis(3-tert-butylcyclopentadienyl) zirconium dichloride, and poly(methylalumoxane) (MAO). Ethene/propene copolymers were prepared in a broad range of chemical composition, from 17% to 92% as ethene molar content. The use of an isospecific...

A new class of isospecific and highly regiospecific C2-symmetric ansa-zirconocenes, characterized by a bisindenyl ansa ligand with bulky substituents in the 3 position of indene and a single carbon bridge is disclosed:  variation of the size of the substituent in C(3) has a strong effect on the extent of chain transfer and isospecificity in propene...

Metallocene catalysts leave a well-characterized fingerprint in the polypropene structures. Attempts to expand this catalyst-polymer correlation to ethylene-propene copolymers are presented. The 13C nuclear magnetic resonance (NMR) are run on 10% solutions of the copolymers in o-dichlorobenzene (50%d2) at 130 °C, with a 12 second pulse delay and 90...

The known rac-[ethylenebis(4,7-dimethyl-η5-1-indenyl)]ZrCl2 (2r) and its meso isomer (2m) have been compared with the prototypal chiral isospecific rac-[ethylenebis(η5-1-indenyl)]ZrCl2 (1r) and its aspecific meso isomer 1m in terms of molecular structures, solution dynamics, and ligand substitution effect on polymerization performance. In liquid pr...

The structural details of isotactic polypropene (iPP) produced with the moderately isospecific racemic-ethylenebis(l-indenyl)zirconium dichloride/methylaluminoxane (rac-(EBI)ZrCl2/MAO) catalyst are strongly dependent on monomer concentration. Polymerizing propene at 50 degrees C in toluene, at propene concentrations in the experimentally measurable...

The crystal and molecular structures of the C-2 symmetric rac-(EBI)ZrCl2 (1r) [monoclinic, space group I2/c, No. 15, a = 11.957(1) Angstrom, b = 10.627(1) Angstrom, c = 13.775(2) Angstrom, beta = 106.06(1)degrees] and of its meso isomer (1m) [monoclinic, space group P2(1)/n, No. 14, a = 11.119(3) Angstrom, b = 10.467(1) Angstrom, c = 14.949(2) Angs...

In this paper, new polyolefin elastomers, obtained from metallocene based catalytic systems, are presented. The potentialities of metallocenes for the preparation of polyolefin elastomers are discussed with reference to the traditional vanadium and titanium based catalysts. The role played by a Ziegler - Natta catalyst, either stereospecific or asp...

Zirconium tetrabenzyl was used as the cocatalyst in olefin polymerization together with MgClâ-supported titanium catalysts. Its behavior was compared with those of aluminum and titanium organometallic compounds. In propylene polymerization performed with a MgClâ/TiClâ catalyst containing ethyl benzoate as the internal donor and with tetrabenzylzirc...

Zirconium tetrabenzyl was used as the cocatalyst in olefin polymerization together with MgCl2-supported titanium catalysts. Its behavior was compared with those of aluminum and titanium organometallic compounds. In propylene polymerization performed with a MgCl2/TiCl4 catalyst containing ethyl benzoate as the internal donor and with tetrabenzylzirc...

Chain transfer via {beta}-CH{sub 3} elimination by a homogeneous bimetallic Ziegler-Natta propylene polymerization catalyst is reported. Propylene is converted by Cp{sup {double_dagger}}{sub 2}MCl{sub 2}/MAO catalysts (Cp{sup {double_dagger}} = pentamethylcyclopentadienyl; M=Zr, Hf; MAO = methylalumoxane) to atactic propylene oligomers and low poly...

In this paper we report on some preliminary results on ethylene polymerization with Cp*2ZrX2 (Cp*=pentamethylcyclopentadienyl, X=Cl, OH, Me) - AlR3 (R=Me, Et, i-Bu). Furthermore, we carried out a study on propylene polymerization with Cp*2MCL2 (M=Zr, Hf) - MAO in comparison with Cp2MCL2-MAO: some data concerning the different chain-transfer mechani...