Binary metallocene supported catalyst for propylene polymerization

The binary silica supported catalyst system comprising the Cp₂ZrCl₂ and SiMe₂(Ind)₂ZrCl₂ metallocene compounds was prepared with different immobilization methods and evaluated at different propylene polymerization conditions. The performance results of the homogeneous isolated catalysts and also the homogeneous catalyst mixture were also included for comparison. High activities were obtained with the supported systems and the molecular weight of the produced polypropylene was invariably higher than that obtained using the homogeneous precursor.     

Effect of π-donor in unbridged metallocene catalyst for propylene polymerization

A new unbridged metallocene catalyst bis(2,4-dimethyl-7-methoxyindenyl) zirconium dichloride was synthesized and polymerization of propylene was carried out with this catalyst and the results are compared with bis(2,4,7-trimethylindenyl) zirconium dichloride. The presence of π-donor substitutent on the indenyl ring led to a decrease in catalytic activity of the catalyst as well as the resulting molecular weight of the polymer as compared to its tri-alkyl substituted congener. The methoxy group deactivates the catalyst and also suppresses the favorable effect of other methyl substituents present in the indenyl ligand.     

Alkyne-functionalized metallocene complexes: Synthesis, structure, and catalytic ethylene polymerization

Reactions of phenylethynyl lithium with substituted cyclopentenones gave the corresponding pendant phenylethynyl substituted cyclopentadienes. Subsequent deprotonation and transmetallation with TiCl₄·2THF, ZrCl₄, and Cp^∗ZrCl₃ yielded the alkyne-functionalized metallocene complexes [C₅Me₄(CCPh)]₂MCl₂ [M = Ti (1), Zr (2)], Cp^∗[C₅Me₄(CCPh)]ZrCl₂ (3), and Cp^∗[C₅H₂R′₂(CCPh)]ZrCl₂ [R′ = Me (4), Ph (5)]. These complexes were fully characterized by ¹H NMR, ¹³C NMR, MS spectra, and elemental analysis. The molecular structure of 2 was determined by single crystal X-ray diffraction analysis. Ethylene polymerization was studied with these complexes in the presence of methylaluminoxane (MAO).     

Ethylene polymerization by rigid benzene ring centered dinuclear metallocene (Ti, Zr)/MAO systems

Two rigid benzene centered dinuclear metallocene complexes C₆H₂[(CH₂C₅H₄)₂MCl₂]₂, M = Ti (1), Zr (2) have been prepared by treating two equivalents of TiCl₄ and ZrCl₄ with the tetralithium salt of the ligand C₆H₂(CH₂C₅H₅)₄-1,2,4,5 in toluene and characterized by ¹H NMR and elemental analysis. Both complexes are effective catalysts for ethylene polymerization in the presence of methylaluminoxane (MAO). The influence of [MAO]/[Cat] molar ratio, catalyst concentration, polymerization temperature and time has been tested in detail. The catalytic activity of complex 2 is more than two times higher than that of complex 1, which is still more active than that of the tetranuclear titanocene C₆H₂[CH₂C₅H₄Ti(C₅H₅)Cl₂]₄-1,2,4,5 (5). On the other hand, the catalytic activities of 1 and 2 is slightly lower than that of the dinuclear metallocene complexes C₆H₄[CH₂C₅H₄Ti(C₅H₄CH₃)Cl₂]₂-1,3 (3) and C₆H₄[CH₂C₅H₄Zr(C₅H₅)Cl₂]₂-1,3 (4), respectively, which is related to the limited intermolecular rotation of the metallocene units in 1 and 2. The melting points above 130 °C indicate a polyethylene formed by complexes 1 and 2 with highly linear and highly crystalline. GPC spectra show that polyethylene produced by complexes 1 and 2 has a broad and even bimodal molecular weight distribution (MWD).     

The effect of polymerization conditions on crystalline of polybutene-1 catalyzed by metallocene catalyst

Polybutene-1 was synthesized stereoselectively with the precursorη5-(pentamethyl-cyclopentadienyl) tribenzyloxide titanium (Cp*Ti(OBz)3) and methylaluminoxane (MAO). The effects of polymerization conditions, trimethyl alumina (TMA) content in MAO and temperature on the crystalline and molecular weight of the products, and catalytic activity were investigated. The structural properties of the polybutene-1 were characterized with 13C NMR and WAXD.     

Novel synthetic strategy for developing an isospecific unbridged metallocene system for propylene polymerization

New unbridged zirconocenes functionalized with a Lewis base, [{1-(E-C(6)H(4))-3,4-Me(2)C(5)H(2)}(2)ZrCl(2)] (E = p-NMe(2) (3); p-OMe (4); p-SMe (5)) were prepared and their propylene polymerization behavior was examined. Under methylaluminoxane (MAO) activation at atmospheric monomer pressure, these complexes afford mixtures of polymers exhibiting multimelting transition temperatures and broad molecular weight distribution, whereas they produce completely atactic polypropylenes under [Ph(3)C][B(C(6)F(5))(4)] activation. Stepwise solvent extraction of the polymer mixtures reveals that the polymers consist of amorphous, moderately isotactic, as well as, highly isotactic portions and the weight ratio of each portion is dependent upon reaction temperature. The generation of rigid rac-like cationic active species in situ by the interaction between basic sites of catalysts and acidic sites of the [Me-MAO](-) counter anion is considered to be the origin of the observed isospecificity. Further investigation of bulk polymerization in liquid propylene shows not only a considerable increase of the isotactic portion of the obtained polypropylenes but also apparent isospecificity of 4 and 5/MAO systems even at high temperature. Variation of the Lewis basic center leads to a dramatic change in stereoselectivity of the catalyst in the decreasing order of 3>4>5, in spite of their structural similarity.     

Effect of “topotactic” reduction product of molybdenum disulfide on catalytic activity of metallocene catalyst for olefin polymerization

N,N-Dimethylanilinium salt of molybdenum disulfide (MoS₂) was developed as a novel cocatalyst for metallocene catalysts. The cocatalyst is composed of N,N-dimethylanilinium ion as a cationic part and “topotactic” reduction product of MoS₂, obtained by acquisition of an electron by neutral host lattice of MoS₂ without structural alteration, as an anionic part. In ethylene polymerization, addition of the N,N-dimethylanilinium salt of MoS₂ to the bis(indenyl)zirconium dichloride (Ind₂ZrCl₂)/triethylaluminum (Et₃Al) catalyst improved the catalytic activity per mmol of Ind₂ZrCl₂. The catalytic activity of this system activated by addition of the cocatalyst depended significantly on the amount of the cocatalyst and the N,N-dimethylanilinium ion content in the cocatalyst. Poly(ethylene) and poly(ethylene-co-1-hexene) obtained with the metallocene catalyst activated by addition of the cocatalyst have typical features such as narrow molecular weight distribution and narrow composition distribution like polymers obtained with conventional metallocene catalysts.     

Novel bridged bis-azulenyl and bis-tetrahydroazulenyl hafnocenes: Synthesis, structure, and propylene polymerization behavior

Novel bridged bis-azulenyl hafnocenes: dichlorodimethylsilylenebis(2-methyl-4-phenyl-4H-azulenyl) hafnium (4a) and dichlorodimethylsilylenebis[2-ethyl-4-(4-chlorophenyl)-4H-azulenyl] hafnium (4b) were synthesized from 2-methylazulene and 2-ethylazulene, respectively. Hydrogenation of 4a and 4b gave novel bis-tetrahydroazulenyl hafnocenes: dichlorodimethylsilylenebis(2-methyl-4-phenyl-4H-5,6,7,8-tetrahydroazulenyl) hafnium (5a) and dichlorodimethylsilylenebis[2-ethyl-4-(4-chlorophenyl)-4H-5,6,7,8-tetrahydroazulenyl] hafnium (5b). The structures of 4a and 5b were determined by X-ray crystallographic analysis to fold C₂ symmetry. These hafnocenes were found to be active catalysts for propylene polymerization in the presence of methylaluminoxane (MAO), and the preliminary polymerization behavior of these catalysts was evaluated. The melting point and molecular weight of resultant polypropylene were higher than those of the bis-azulenyl zirconocenes. In particular, a high melting point (160 °C for 5a and 161 °C for 5b) was observed with the bis-tetrahydroazulenyl system, although the activities by these hafnocenes were lower than those by the corresponding zirconocenes.     

Supported stereospecific metallocene binary catalyst for propylene polymerization

In this work, propylene was polymerized with isospecific and syndiospecific catalysts in homogeneous and heterogeneous systems. The binary metallocene system of both isospecific and syndiospecific catalysts in the heterogeneous system was also used. Besides the type of catalyst, parameters such as polymerization temperature and pressure were varied to achieve the better conditions for the polymerization. The objective of this work is to investigate the influence of these parameters on the characteristics of the produced polymer. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2979–2986, 2002     

Ethylene polymerization by 3-oxa-pentamethylene bridged dinuclear metallocene (Ti, Zr)/MAO systems

Two hetero-atom containing bridged dinuclear metallocene complexes, (CpMCl₂)₂(C₅H₄CH₂CH₂OCH₂CH₂C₅H₄) [M = Ti (1), Zr (2)], have been synthesized by treating the disodium salt of the corresponding ligand (C₅H₅CH₂CH₂)₂O with two equivalents of CpTiCl₃ and CpZrCl₃ · DME, respectively, in THF at 0 °C and characterized by ¹H- and ¹³C-NMR, MS and IR spectroscopy. Homogenous ethylene polymerization by those complexes has been conducted systematically in the presence of methylaluminoxane (MAO). The influences of reaction parameters, such as [MAO]/[Cat] molar ratio, catalyst concentration, ethylene pressure, temperature and time, have been studied in detail. The catalytic activities of the dinuclear complexes 1 and 2 were higher than those of (MeCpTiCl₂)₂(C₅H₄CH₂C₆H₄CH₂C₅H₄) (3), (CpZrCl₂)₂(C₅H₄CH₂C₆H₄CH₂C₅H₄) (4) and the mononuclear metallocenes Cp₂TiCl₂ and Cp₂ZrCl₂, respectively. Complex 2 showed high catalytic activity at high temperature (50-100 °C) and high pressure (6 bar). The molecular weight distributions of polyethylene produced by 1 and 2 (MWD = 2.49 and 5.90) were broader than those using the corresponding mononuclear metallocenes (MWD = 2.05 and 2.15). The melting points of the polyethylene produced ranged from 129 to 133 °C, indicating a high linearity and a high crystallinity.     

THE INFLUENCE OF SUBSTITUENTS IN METALLOCENE ON PROPYLENE POLYMERIZATION*

Two new unbridged zirconocenes, bis(2,4,7-trimethyl indenyl)zirconium dichloride (Met-Ⅰ) andbis(2-methyl-4,7-diethyl indenyl)zirconium dichloride (Met-Ⅱ) were prepared in order to investigate thesteric effects of substituents on the nature of the catalysts for the polymerization of propylene. A mixture ofmethyl aluminoxane (MAO) and triisobutylaluminum [Al(iBu)_3] was used as cocatalyst to activate thesecatalysts. The decrease in steric bulkiness of substituents at 4 and 7 positions of the indenyl ring resulted inan increase of both activity and molecular weight as well as the isotacticity.     

Polymerization of propylene by mixed Ziegler–Natta and metallocene catalysts

The polymerization of propylene using a mixture of racemic metallocenes and Ziegler–Natta catalysts was investigated. The polypropylene was obtained as a mixture of a fine powder and beads, with the powder being absorbed partially on the beads. The relative amount of the powder can be controlled by the concentration of the metallocene. The compatibility between the components of the mixed catalytic systems and the effect of the components on the rate of polymerization and on the properties of the new polymers were studied. The metallocene system dramatically affects the melt viscosity, isotacticity and molecular weight of the polymers. The two catalytic systems are able to act jointly, producing different polymers, for which separate melting and crystallization temperatures are obtained. © 1998 John Wiley & Sons, Ltd.     

Synthesis, molecular structure, and polymerization reactivity of ethylenebis(1,3-dimethylcyclopentadienyl)zirconium dichloride

An ethylene-bridged zirconocene complex bearing methyl substituents only on the cyclopentadienyl carbons adjacent to bridge point, ethylenebis(1,3-dimethylcyclopentadienyl)zirconium dichloride (5) was synthesized. Crystal structure of 5 was determined. The complex, 5, when activated with MAO, shows better comonomer incorporation ability than [Ph₂C(Fluo)(Cp)]ZrCl₂ in the ethylene–norbornene copolymerization but it is not better than rac-Et(Ind)₂ZrCl₂ for the ethylene-1-hexene copolymerization in terms of activity and comonomer incorporation.     

镍系催化丁二烯聚合条件的新探索

通过改变环烷酸镍─三异丁基铝─三氟化棚乙醚络合物［（Ni（naph）2－Al（i－Bu）3－BF3OEt2）］体系中催化剂的配比，丁二烯浓度，聚合温度等聚合条件，考察了它们对适宜Al／B比活性范围的影响，结果表明：采用固定Ni变Al或者固定Al变Ni两种方式改变Al／Ni摩尔比，都能有效地调节适宜Al／B比范围，并认为目前工业生产顺丁橡胶的配方中Al／Ni＝4是太低的，有必要适当加以提高；丁二烯浓度太低时，适宜Al／B比范围很窄，从提高聚合活性和聚合速率来看，适当地提高丁二烯浓度是有益的；在一定范围内改变聚合温度，对适宜Al／B比范围没有明显影响。     

The Synthesis of Isotactic Polypropylene with Spherical Morphology via Supported Metallocene Catalyst

Tile morphology control of polypropylene products is one of the technological obstaclesto the industrial polymerization of propylene via metallocene catalyst. One efficient wayto solve this problem had been proposed that the metallocene catalyst should besupported on suitable carrier. Although lots of work has been reported'-', up to date, nobreakthrough has been got yet. The stUdies on morphology control of supportedmetallocene catalysts will be of great value in either scientific or practice…     

A study of the synthesis and characterization of ethylene/dicyclopentadiene copolymers using a metallocene catalyst

Copolymers of ethylene/dicyclopentadiene were produced using a Me₂Si(Ind)₂ZrCl₂/methylaluminoxane catalyst system. The melting and crystallization points of the freshly prepared copolymers steadily decreased with increasing comonomer concentration. This was attributed to increased comonomer concentration in the polymer. When the comonomer incorporation, as measured by ¹³C NMR, is plotted against the comonomer concentration in the reactor, a plateau appears at concentrations higher than 0.12 mol/L. At concentrations greater than 0.12 mol/L time dependant crosslinking begins to be observed in the copolymers after exposure to air for several months. This crosslinking is also apparent in the thermosetting behavior of the copolymers when they are allowed sufficient time to crosslink. Copolymers with lower comonomer concentrations possess melting enthalpies even after several weeks, suggesting that there is a threshold concentration of 0.12 mol/L for the crosslinking process. Tensile tests of thermoplastic samples showed that incorporation of ca. 5 mol% of comonomer into the polyethylene main chain results in a semi-elastomeric material which possesses high strain recovery and whose strain hardening is similar to that observed for the homopolymer.     

新型二茂锆化合物(1,2-Ph2-4-PrCp)2ZrCl2的合成及催化烯烃聚合反应研究

3,4-二苯基环戊-2-烯-1-酮与丙基锂反应,经酸化脱水得新环戊二烯衍生物1,2-二苯基-4-丙基-1,3-环戊二烯(1).用丁基锂处理1得到相应的环戊二烯基锂,再与ZrCl₄在甲苯中反应,生成大立体阻碍二氯二茂锆化合物(1,2-Ph₂-4-PrCp)₂ZrCl₂(2).化合物1和2均经元素分析和核磁共振谱学表征.经甲基铝氧烷(MAO)活化,化合物2在较低Al/Zr比条件下既可有效地催化乙烯聚合,生成高分子量、高熔化温度聚乙烯.2/MAO体系对丙烯聚合表现出高活性,生成低分子量齐聚物,其分子量随聚合温度的降低而升高.     

Insertion vs. site epimerization with singly-bridged and doubly-bridged metallocene polymerization catalysts

A statistical model has been employed to determine the unidirectional site epimerization probability, ε, during propylene polymerization with the following C₁-symmetric metallocene precatalysts activated with MAO (MAO = methylaluminoxane): doubly-bridged rac-(1,2-SiMe₂)₂{η⁵-C₅H₂-4-(CHMe(CMe₃))}{η⁵-C₅H-3,5-(CHMe₂)₂}ZrCl₂ (1) and (1,2-SiMe₂)₂{η⁵-C₅H₂-4-(1R,2S,5R-menthyl)}{η⁵-C₅H-3,5-(CHMe₂)₂}ZrCl₂ (2); and singly-bridged Me₂C(3-(2-adamantyl)-C₅H₃)(C₁₃H₈)ZrCl₂ (3) and Me₂Si(3-(2-adamantyl)-C₅H₃)(C₁₃H₈)ZrCl₂ (4). For 1/MAO a steep tacticity dependence on monomer concentration was found, as ε increased from 0.114 to 0.909 as [C₃H₆] decreased from 12.5 M to 0.5 M; similarly, ε increased for 2/MAO from 0.177 to 0.709. For 3/MAO, ε was moderately responsive to an increase in polymerization temperature, as ε increased from 0.000 to 0.485 from T_p = 0-90 °C ([C₃H₆] = 1.1 M). Similarly, ε increased for 4/MAO from 0.709 to 0.913 from T_p = 0-40 °C; at higher temperatures, bidirectional site epimerization was implicated.     

Exploring Si/Mg composite supported Ziegler-Natta Ti-based catalysts for propylene polymerization

A series of(Si_O2/MgO/ID/MgCl_2)·TiClx Ziegler-Natta catalysts for propylene polymerization has been prepared with a new method. These catalysts were synthesized using soluble Mg-compounds as the Mg-source and the preparation progress was relatively simple. The catalyst could copy the spherical shape of the carrier very well. The propylene polymerization results showed that the catalyst revealed the best activity with 9,9-di(methoxymethyl)fluorene(BMMF) as internal donor at 50 °C with the optimal molar ratio Al/Ti = 5, which was much lower than what the industrial polypropylene catalyst used(at least molar ratio Al/Ti = 100), resulting in great cost saving. Additionally, the polymerization kinetics of the catalyst exhibited very stable property after achieving a relatively high value. These catalysts possessed rather high activity and good hydrogen response. The isotactic index(Ⅱ.) value of the PP products could be higher than 98% in the presence of both internal and external electron donors. Moreover, temperature rising elution fractionation method was used to understand the influence of donors and H2 on the properties of the PP products.     

Ethylene polymerization and ethylene/1-hexene copolymerization using homogeneous and heterogeneous unbridged bisindenyl zirconocene catalysts

Unbridged bis-substituted-indenyl zirconocene complexes, [(2,4-Me₂Ind)₂ZrCl₂, Met-1; (2,4,6-Me₃Ind)₂ZrCl₂, Met-2], were supported on silica and montmorillonite carriers (resulting in silica-supported catalysts MS-1 and MS-2, and montmorillonite-supported catalyst MT-1). Ethylene polymerization by homogeneous and heterogeneous catalysts showed high activity, affording polyethylenes with high molecular weight. The catalytic activity and the molecular weight of the polymer were improved using the heterogeneous systems. The activities for the ethylene/1-hexene copolymerization by heterogeneous systems were lower than those using homogeneous systems, however, the comonomer was incorporated efficiently into polymer in both the homo- and the heterogeneous systems, and moreover, the microstructure of the copolymer derived from the heterogeneous catalysts showed different characteristics from those resulting from the homogeneous systems. The r_Er_H values of the heterogeneous catalysts (1.82 for MS-1 and 0.70 for MS-2), are quite different from those of their homogeneous analogues (1.25 for Met-1 and 1.26 for Met-2).