The UV‐visible spectroscopic study of the interaction between rac‐Et(Ind)2ZrCl2 and different aluminoxanes, such as isobutylaluminoxane (BAO) and ethyl(isobutyl)aluminoxane (EBAO), was conducted under normal polymerization conditions. UV‐visible absorption spectra of rac‐Et(Ind)2ZrCl2/aluminoxanes were correlated with the formation of ionic zirconium species. The influence of different aluminoxanes on the tightness of the metallocenium‐aluminoxane ionic pairs was interpreted in terms of the aluminoxane structure. The loose ionic pairs formed in the EBAO system causes a fast decaying kinetic profile, advantageous for copolymerization. 相似文献
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. 相似文献
Supported type cocatalysts using triphenylcarbenium perchlorate (Ph3CClO4) were prepared by impregnation on inorganic carrier, magnesium chloride (MgCl2) and applied to ethylene polymerizations with rac‐Et[Ind]2ZrCl2. Homogeneous polymerizations with Ph3CClO4 were also carried out for comparison. The activity of homogeneous polymerization was much lower than that obtained with methylaluminoxane (MAO). On the other hand, rac‐Et[Ind]2ZrCl2 activated by the supported type Ph3CClO4/MgCl2 system displayed high activity comparable to that obtained with MAO. From the results of fractionation and polymerization of the rac‐Et[Ind]2ZrCl2‐Ph3CClO4/MgCl2 catalyst system, it was found that the increased activity mainly came from the active species in the supernatant part. UV‐vis spectroscopic measurements combined with ICP analysis indicate that the active species in the supernatant fraction are composed of a stoichiometric amount of perchlorate and metallocene catalyst. 相似文献
The incorporation of 5‐vinyl‐2‐norbornene (VNB) into ethylene‐norbornene copolymer was investigated with catalysts [Ph2C(Fluo)(Cp)]ZrCl2 ( 1 ), rac‐[Et(Ind)2]ZrCl2 ( 2 ), and [Me2Si(Me4Cp)tBuN]TiCl2 ( 3 ) in the presence of MAO by terpolymerizing different amounts of 5‐vinyl‐2‐norbornene with constant amounts of ethylene and norbornene at 60°C. The highest cycloolefin incorporations and highest activity in terpolymerizations were achieved with 1 . The distribution of the monomers in the terpolymer chain was determined by NMR spectroscopy. As confirmed by XRD and DSC analysis, catalysts 1 and 3 produced amorphous terpolymer, whereas 2 yielded terpolymer with crystalline fragments of long ethylene sequences. When compared with poly‐(ethylene‐co‐norbornene), VNB increased both the glass transition temperatures and molar masses of terpolymers produced with the constrained geometry catalyst whereas decreased those for the metallocenes. 相似文献
The kinetics of the ethylene‐norbornene copolymerization, catalyzed by rac‐Et(Ind)2ZrCl2/MAO, 90%rac/10%meso‐Et(4,7‐Me2Ind)2ZrCl2/MAO and rac‐H2C(3‐tert‐BuInd)2ZrCl2/MAO was followed by sampling from the reaction mixture at fixed time intervals. Catalyst activity, copolymer composition and molar mass were studied as a function of time. The polymers showed an unusually low polydispersity and a significant increase in their molar mass with time, suggesting a quasi‐living polymerization. 相似文献
Summary: The metallocenes rac‐C2H4(Ind)2ZrCl2 ( 1 ), rac‐Me2Si(Ind)2ZrCl2 ( 2 ), and rac‐Me2Si(2‐Me‐benz[e]Ind)2ZrCl2 ( 3 ) efficiently copolymerize propene and 5‐vinyl‐2‐norbornene (VNB). 1 and 2 give a high VNB content and high productivities, whereas 3 gives moderate incorporation. Surprisingly, precatalysts 1 and 2 , which have very closely related structures, showed very different reactivities toward VNB, with 1 having a greater affinity for VNB than for propene. The copolymers are quantitatively converted into polyolefins with polar functionalities.
Propylene copolymers with different polar groups were synthesised using rac‐Et[1‐Ind]2ZrCl2/MAO as the catalyst system. 10‐Undecen‐1‐ol, 10‐undecenoyl chloride, 10‐undecenoic acid, 2‐(9‐decen‐1‐yl)‐1,3‐oxazoline, 2‐(9‐decen‐1‐yl)‐4,4‐dimethyl‐1,3‐oxazoline, and 2‐[4‐(10‐undecene‐1‐oxy)phenyl]‐1,3‐oxazoline were used as comonomers. The addition of water to the 10‐undecenoyl chloride copolymer solution led to an acid‐functionalised copolymer. In the case of 2‐(9‐decen‐1‐yl)‐1,3‐oxazoline and its homopolymers, polymerisation temperature was varied. Up to 0.61 mol‐% comonomer were incorporated into the poly(propylene)s. The catalyst activities for 10‐undecen‐1‐ol, 10‐undecenoyl chloride and 10‐undecenoic acid were much higher than for the oxazoline comonomers. 相似文献
Ethylene was copolymerized with allylbenzene using rac-ethylenebis(indenyl)zirconium dichloride (Et(Ind)2ZrCl2)/methylaluminoxane (MAO) as a catalyst. Analysis of the copolymers obtained revealed that chain transfer to aluminium was a preferred chain transfer reaction during the copolymerization. It seems that chain termination through aluminium transfer is induced by the allylbenzene unit incorporated in the propagating chain end. Hydroxy-terminated ethylene copolymers were obtained when the copolymer solution was exposed to air before precipitation of the polymer in acidic methanol. 相似文献
Inorganic siliceous porous materials such as MFI type zeolite, mesoporous silica MCM‐41 and silica gel with different average pore diameters were applied to the adsorptive separation of methylaluminoxane (MAO) used as a cocatalyst in α‐olefin polymerizations. The separated MAOs combined with rac‐ethylene‐(bisindenyl)zirconium dichloride (rac‐Et(Ind)2ZrCl2) were introduced to propylene polymerization, and their influences on the polymerization activity and stereoregularity of the resulting polymers were investigated. The polymerization activity and isotactic [mmmm] pentad of the produced propylene were markedly dependent upon the pore size of the porous material used for adsorptive separation. From the results obtained from solvent extraction of the produced polymers, it was suggested that there are at least two kinds of active species with different stereospecificity in the rac‐Et(Ind)2ZrCl2/MAO catalyst system. 相似文献
The catalyst dichlorobis(acetylacetone)zirconium was intercalated into montmorillonite (MT) together with AlEt2Cl as a cocatalyst. Reacting ethylene in the presence of this catalyst yields α‐olefin oligomers with over 80% selectivity. [rac‐Et(Ind)2ZrCl2]/MAO was then added to form a dual functional catalyst system. An MT particle‐dispersed polyethylene composite was prepared by copolymerization of the in‐situ produced oligomers with ethylene using this dual system. 相似文献
The oligomerization and polymerization of 1‐pentene using Cp2ZrCl2, Cp2HfCl2, [(CH3)5C5]2ZrCl2, rac‐[C2H4(Ind)2]ZrCl2, [(CH3)2Si(Ind)2]ZrCl2, (CH3)2Si(2‐methylbenz[e]indenyl)2ZrCl2, Cp2ZrCl{O(Me)CW(CO)5}, Cp2ZrCl(OMe) and methylaluminoxane (MAO) has been studied. The degree of polymerization was highly dependent on the metallocene catalyst. Oligomers ranging from the dimer of 1‐pentene to polymers of poly‐1‐pentene with a molar mass Mw = 149000 g/mol were formed. Cp2ZrCl{O(Me)CW(CO)5} is a new highly active catalyst for the oligomerization of 1‐pentene to low molecular weight products. The activity decreases in the order Cp2ZrCl{O(Me)CW(CO)5} > Cp2ZrCl2 > Cp2ZrCl(OMe). Furthermore, poly‐1‐olefins ranging from poly‐1‐pentene to poly‐1‐octadecene were synthesized with (CH3)2Si(2‐methyl‐benz[e]indenyl)2ZrCl2 and methylaluminoxane (MAO) at different temperatures. The temperature dependence of the molar mass can be described by a common exponential decay function irrespective of the investigated monomer. 相似文献
Synthesis and characterization of a novel carbazole‐based monomer, 9‐(bicyclo[2.2.1]hept‐5‐en‐2‐ylmethyl)‐9H‐carbazole (BHMCZ) and its copolymerization with ethylene by using two metallocene/MAO catalyst systems are presented. The monomer was characterized by means of NMR spectroscopy, MS and elementary analysis. Copolymerization studies were conducted using [Ph2C(Ind)(Cp)ZrCl2] and [Ph2C(Flu)(Cp)ZrCl2] catalysts. The [Ph2C(Ind)(Cp)ZrCl2] catalyst gave a copolymer containing as much as 4.6 mol‐% of BHMCZ. Polymers were characterized using NMR spectroscopy, gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). 相似文献