Gerhard Fink

Two different, on the same silica supported metallocene catalysts, activated by various trialkylaluminums – a kinetic and morphological study as well as an experimental investigation for building stereoblock polymers

The main focus of this study is the development of new polypropylene macromolecules. The simultaneous supporting of two metallocenes that manufacture polyolefins of different tacticity on the same silica should yield stereoblock polymers of polypropylene, if a chain transfer between the active species takes place. As chain transfer agents two aluminumalkyls (cocatalyst and scavcnger) of distinct steric dcmands were chosen. Two catalyst systems were studied. The first was based on a PQ-silica/MAO on which the two metallocene catalysts rac-Me 2 Si[Ind] 2 ZrCl (isotactic working species) and i-Pr[FluCp]-ZrCl 2 (syndiotactic working species) were fixed. For the second the components rac-Me 2 Si[IndR 2 ] 2 ZrCl and i-Pr[FluCp]-ZrCl 2 were fixed to a Grace Silica/MAO-support. The influence of the type of silica, of MAO-content, of the kind of scavenger and of the supporting procedure on the microstructure, the kinetics and the morphology of the product were investigated.

Kinetics and mechanistic insight into propylene polymerization with different metallocenes and various aluminium alkyls as cocatalysts

Abstract The influence of successive replacement of MAO by different aluminium alkyls in a metallocene catalyzed homogeneous polymerization is discussed. An activating effect was found by the addition of TIBA and TBA, whereas TMA and TEA have a deactivating effect. Propylene polymerizations were carried out with different substituted metallocenes of the general formula Me 2 C[3-RCpFlu]ZrCl 2 , where R is H, methyl, i -propyl or t -butyl. With increasing the size of the substituent, the polymerization activity decreased. Besides, it was found that the deactivating effect of methylaluminoxane (MAO) during the polymerization was compensated with more bulky substituents. Using Me 2 C[3- t -BuCpFlu]ZrCl 2 for the propylene polymerization, a deactivating effect was no longer observed.

Homogeneous and heterogeneous metallocene/MAO-catalyzed polymerization of functionalized olefins

Ethylene was copolymerized with 10-undecene-1-ol, 5-norbornene-2-methanol and 5-(N,N-diisopropylamino)-1-pentene by utilizing Me2Si(Ind)2ZrCl2/MAO, iPr(CpInd)ZrCl2/MAO, iPr(3-Me-CpFlu)-ZrCl2/MAO and the corresponding heterogeneous silica supported catalysts. In the case of the copolymerization with 10-undecene-1-ol and 5-norbornene-2-methanol the rapid catalyst deactivation with the increasing amount of the comonomer in the feed was prevented through a prereaction of the comonomer with triisobutylaluminium (Tiba). Especially with the Tiba-protected 5-norbornene-2-methanol high comonomer contents were achieved. During the copolymerizations with heterogeneous metallocene/MAO/SiO2 catalysts the arising problem of a diffusion retardation exists for the Tiba-protected comonomers. For this reason the ethylene/10-undecene-1-ol copolymerization with the Me2Si(Ind)2ZrCl2/MAO/SiO2 catalyst yields satisfying 10-undecene-1-ol incorporations only at low ethylene concentrations. In comparison to this, the ethylene/5-(N,N-diisopropylamino)-1-pentene copolymerization with the homogeneous or heterogeneous Me2Si(Ind)2-ZrCl2/MAO catalyst yields comparable incorporation rates.

Homogeneous metallocene/MAO‐catalyzed polymerizations of polar norbornene derivatives: copolymerizations using ethene, and terpolymerizations using ethene and norbornene

Terpolymerizations of norbornene derivatives containing different functional substituents were carried out with ethene and norbornene using the homogeneous catalyst system iPr[CpInd]ZrCl2/MAO. The norbornene derivative 5-norbornene-2-methanol and 5-norbornene-2-carboxylic acid were prereacted with triisobutylalmuninium to prevent the deactivation of the catalyst. 13 CNMR studies revealed the composition of the polymer. The incorporation rate was 5-12 mol-% at a content of 50 mol-% of the norbornene derivative in the monomer feed-stock. IR-GPC coupled experiments confirmed the homogeneous composition of the polymer. In addition, we investigated the ethene copolymerization and the ethene/norbornene terpolymerization using the trialkylsilyl protected norbornene derivated such at 5-norbornene-2-methyeleneoxytriethylsilane and 5-norbornene-2-methyeleneoxy-tert-butyldimethylsilane. These norbornene derivatives reveal an incorporation rates of 5-6 mol-% in the polymer at a content of 20 mol-% in the monomer feed-stock.

Ethylene/hexene copolymerization with the heterogeneous catalyst system SiO2/MAO/rac‐Me2Si[2‐Me‐4‐Ph‐Ind]2ZrCl2: The filter effect

The main focus of this study is the ethylene/hexene copolymerization with the silica supported metallocene SiO2/MAO/rac-Me2Si[2-Me-4-Ph-Ind]2ZrCl2. Polymerizations were carried out in toluene at a reaction temperature of 40°C–60°C and the cocatalyst used was triisobutylaluminium (TIBA). The kinetics of the copolymerization reactions (reactivity ratios rE/H, monomer consumption during reaction) were investigated and molecular weights Mw, molecular weight distributions MWD and melting points Tm were determined. A schematic model for the blend formation observed was developed that based on a filtration effect of monomers by the copolymer shell around the catalyst pellet.

Ethene-norbornene copolymerizations using two different homogeneous metallocene catalyst systems and investigations of the copolymer microstructure

Abstract Ethene–norbornene copolymerizations were carried out at various ethene pressures by using the homogeneous catalyst systems iPr[(3-iPr-Cp)Ind]ZrCl2/MAO and rac-iPr[Ind]2ZrCl2/MAO. The copolymer microstructures were analyzed by 13 C NMR spectroscopic investigations. On the basis of the obtained results, it could be concluded that copolymers generated with the metallocene iPr[(3-iPr-Cp)Ind]ZrCl2 contain norbornene microblocks with a maximum length of two norbornene units in spite of high norbornene excess in the norbornene and ethene feedstock composition. In the microstructures of copolymers generated with the metallocene rac-iPr[Ind]2ZrCl2 norbornene microblocks with a length of three norbornene units have been detected. Results have shown that the amount of norbornene triblocks in the copolymer chain as well as the stereochemical connection of the norbornene triblocks depends on the monomer concentration and the polymerization temperature.

13C NMR studies of ethene-norbornene copolymers : assignment of sequence distributions using 13C-enriched monomers and determination of the copolymerization parameters

Ethene and norbornene were copolymerized using metallocene catalysts that produce copolymers having isolated norbornene units or microblocks with a maximum of two norbornene units. The resonances of the norbornene C 5/6 and the ethene carbon atoms, which overlap extensively in the 13 C NMR spectrum, were differentiated and assigned by comparing the 13 C NMR spectra of the copolymers obtained from monomers having 13 C at natural abundance with those prepared from feedstocks containing 13 C 1 -enriched ethene or 13 C 5/6 -enriched norbornene. The NMR analysis revealed that the chemical shifts of the norbornene C 5/6 carbon atoms are triad sensitive and those of the ethene carbon atoms are pentad sensitive. 13 C NMR analysis of copolymers containing isolated norbornene units in various proportions allowed the resonances of the norbornene C 5/6 and the ethene carbon atoms to be assigned to the respective triads and pentads. The complete triad distributions of these copolymers determined in this way were used to calculate the copolymerization parameters for a representative metallocene catalyst.

Ethene co- and terpolymerizations with TIBA-protected norbornenemethanol and TIBA-protected norbornenecarboxylic acid using homogeneous metallocene/MAO catalyst systems

Ethene copolymerizations were carried out with triisobutylaluminum (TIBA)-protected norbornenemethanol and norbornenecarboxylic acid, respectively, using homogeneous metallocene/MAO catalyst systems. Moreover, ethene terpolymerizations with both polar norbornene derivatives were investigated for the first time. The metallocenes utilized, such as iPr[CpInd]ZrCl2, iPr[(3-iPr-Cp)Ind]ZrCl2, and iPr[(3-tert-But-Cp)Ind]ZrCl2 contain ligand frameworks of various sterical demands. The incorporation of polar monomers into the polymer chain was determined by NMR spectroscopic investigations. Kinetic and analytical results of the polymerization experiments revealed increasing activities and a decreasing comonomer incorporation into the polymer chain with an increasing sterical demand of the metallocene ligand. Additionally, the TIBA-protected norbornenecarboxylic acid shows a lower incorporation rate into the copolymer chain in comparison with the TIBA-protected norbornenemethanol.

The particle-forming process of SiO2-supported metallocene catalysts

Homogeneous metallocene catalysts for the polyolefin production show compared with conventional Ziegler systems remarkable advantages, like the possibilities to regulate the microstructure leading to optimized polymer properties. However, for industrial application it is necessary to immobilize the metallocenes on a heterogeneous support. The parameters which now influence polymerization kinetics, polymer growth, polymer morphology, the decisive particle fragmentation are demonstrated and summarized in a physical and mathematical model.

Unusual ethylene polymerization results with metallocene catalysts supported on silica

With the development of methods to support metallocenes and methylaluminoxane cocatalysts on suitable carriers, it became possible to combine the specific advantages of homogeneous metallocene catalysis with those of heterogeneous Ziegler catalysts in olefin polymerization. By means of ethylene polymerization it could be shown that the method of supporting methylaluminoxane and metallocene on porous silica has a substantial influence on the progress of polymerization. In particular, fragmentation of catalyst particles during polymerization can be circumvented, maintaining the catalyst activity, if active catalyst sites are being generated on the particle surface only. A method of preparation for such newly designed supported metallocene catalysts is presented, where the active catalyst sites are located exclusively on the particle surface. Furthermore, the kinetics of ethylene polymerization and morphology properties prior to and after polymerization are discussed.