共查询到20条相似文献,搜索用时 31 毫秒
1.
Esa Kokko Anneli Malmberg Petri Lehmus Barbro Lfgren Jukka V. Seppl 《Journal of polymer science. Part A, Polymer chemistry》2000,38(2):376-388
A study was made on the effects of polymerization conditions on the long‐chain branching, molecular weight, and end‐group types of polyethene produced with the metallocene‐catalyst systems Et[Ind]2ZrCl2/MAO, Et[IndH4]2ZrCl2/MAO, and (n‐BuCp)2ZrCl2/MAO. Long‐chain branching in the polyethenes, as measured by dynamic rheometry, depended heavily on the catalyst and polymerization conditions. In a semibatch flow reactor, the level of branching in the polyethenes produced with Et[Ind]2ZrCl2/MAO increased as the ethene concentration decreased or the polymerization time increased. The introduction of hydrogen or comonomer suppressed branching. Under similar polymerization conditions, the two other catalyst systems, (n‐BuCp)2ZrCl2/MAO and Et[IndH4]2ZrCl2/MAO, produced linear or only slightly branched polyethene. On the basis of an end‐group analysis by FTIR and molecular weight analysis by GPC, we concluded that a chain transfer to ethene was the prevailing termination mechanism with Et[Ind]2ZrCl2/MAO at 80 °C in toluene. For the other catalyst systems, β‐H elimination dominated at low ethene concentrations. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 376–388, 2000 相似文献
2.
Tsuneji Sano Hitoshi Hagimoto Jizhu Jin Yasunori Oumi Toshiya Uozumi Kazuo Soga 《Macromolecular rapid communications》2000,21(17):1191-1195
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
3.
James C. W. Chien 《Macromolecular Symposia》1992,63(1):209-217
Racemic ethylenebis(η5-indenyl)zirconium dichloride (Et[Ind]2ZrCl2) activated with methylaluminoxane (MAO) catalyzed propylene polymerization with varying degree of stereochemical control which decreases greatly with the increase of Tp (temperature of polymerization). The PP&s are characterized by low melting temperature (Tm), high solubility, and prefers to crystallize in the γ-modification. The catalytic activity of Et[Ind]2ZrCl2/MAO becomes very small with the lowering of Tp. Very active and highly stereoselective cationic metallocene alkyl, Et[Ind]2Zr+(CH3), was produced by the reaction of Et[Ind]2Zr(CH3)2 with Ph3C+B(C6F5)4−. Comparison of this system with the Et[Ind]2ZrCl2/MAO catalyst showed that in the latter case a quarter of the Et[Ind]2ZrCl2 was converted by MAO to Et[Ind]2Zr+CH3 at room temperature but less than 0.14% of the Zr was so activated at −20°C. The Et[IndH4]ZrCl2/MAO catalyst was shown to have two kinds of catalytic species one with high propagation rate constant (kp) and stereoselectivity and another with low kp and poor stereoselectivity. The very narrow molecular weight distribution of the PP produced may be attributed to the fact that the different types of active species have comparable kp/ktrA, the latter is the rate constant of transfer. Non-symmetric, rac-[anti-ethylidene(1-η5-indenyl)(1-η5-tetramethylcyclopentadienyl)-Ti-Cl2 and -(CH3)2 have been synthesized and structures determined. The complexes provide dissimilar steric environment to propagating chains to produce crystalline-amorphous multiblock thermoplastic elastomeric PP. The polymerization process here involves a two-state propagation mechanism. 相似文献
4.
Naoya Kishi Cheol‐Hee Ahn Jizhu Jin Toshiya Uozumi Tsuneji Sano Kazuo Soga 《Macromolecular rapid communications》2000,21(11):775-778
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
5.
Wentian Lin Hui Niu T. C. Mike Chung Jin‐Yong Dong 《Journal of polymer science. Part A, Polymer chemistry》2010,48(16):3534-3541
This article discusses a new borane chain transfer reaction in olefin polymerization that uses trialkylboranes as a chain transfer agent and thus can be realized in conventional single site polymerization processes under mild conditions. Commercially available triethylborane (TEB) and synthesized methyl‐B‐9‐borabicyclononane (Me‐B‐9‐BBN) were engaged in metallocene/MAO [depleted of trimethylaluminum (TMA)]‐catalyzed ethylene (Cp2ZrCl2 and rac‐Me2Si(2‐Me‐4‐Ph)2ZrCl2 as a catalyst) and styrene (Cp*Ti(OMe)3 as catalyst) polymerizations. The two trialkylboranes were found—in most cases—able to initiate an effective chain transfer reaction, which resulted in hydroxyl (OH)‐terminated PE and s‐PS polymers after an oxidative workup process, suggesting the formation of the B‐polymer bond at the polymer chain end. However, chain transfer efficiencies were influenced substantially by the steric hindrances of both the substituent on the trialkylborane and that on the catalyst ligand. TEB was more effective than TMA in ethylene polymerization with Cp2ZrCl2/MAO, whereas it became less effective when the catalyst changed to rac‐Me2Si(2‐Me‐4‐Ph)2ZrCl2. Both TEB and Me‐B‐9‐BBN caused an efficient chain transfer in the Cp2ZrCl2/MAO‐catalyzed ethylene polymerization; nevertheless, Me‐B‐9‐BBN failed in vain with rac‐Me2Si(2‐Me‐4‐Ph)2ZrCl2/MAO. In the case of styrene polymerization with Cp*Ti(OMe)3/MAO, thanks to the large steric openness of the catalyst, TEB exhibited a high efficiency of chain transfer. Overall, trialkylboranes as chain transfer agents perform as well as B? H‐bearing borane derivatives, and are additionally advantaged by a much milder reaction condition, which further boosts their applicability in the preparation of borane‐terminated polyolefins. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3534–3541, 2010 相似文献
6.
Esa Kokko Pirjo Pietikinen Jari Koivunen Jukka V. Seppl 《Journal of polymer science. Part A, Polymer chemistry》2001,39(21):3805-3817
Ethene was copolymerized (1) with 1,5‐hexadiene with rac‐ethylenebis(indenyl)zirconium dichloride/methylaluminoxane (MAO) used as a catalyst and (2) with 1,7‐octadiene with bis(n‐butylcyclopentadienyl)zirconium dichloride/MAO and rac‐ethylenebis(indenyl)hafnium dichloride (Et[Ind]2HfCl2)/MAO used as catalysts at 80 °C in toluene. The copolymer microstructure and the influence of diene incorporation on the rheological properties were examined. Ethene and 1,5‐hexadiene formed a copolymer in which a major fraction of the 1,5‐hexadiene was incorporated into rings and a small fraction formed 1‐butenyl branches. The copolymerization of ethene with 1,7‐octadiene resulted in a higher selectivity toward branch formation. Some of the branches formed long‐chain‐branching (LCB) structures. The ring formation selectivity increased with decreasing ethene concentration in the polymerization reactor. Melt rheological properties of the diene copolymers resembled those of metallocene‐catalyzed LCB homopolyethenes and depended on the vinyl content, the catalyst, and the polymerization conditions. At high diene contents, all three catalysts produced crosslinked polyethene. This was especially pronounced with Et[Ind]2HfCl2, where only 0.2 mol % 1,7‐octadiene in the copolymer was required to achieve significantly modified rheological properties. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3805–3817, 2001 相似文献
7.
Kyung‐Jun Chu Joao B. P. Soares Alexander Penlidis 《Journal of polymer science. Part A, Polymer chemistry》2000,38(3):462-468
The polymerization of ethylene was carried out with a novel in situ supported metallocene catalyst that eliminated the need for a supporting step before polymerization. In the absence of trimethyl aluminum (TMA), in situ supported Et[Ind]2ZrCl2 was not active, but the addition of TMA during polymerization activated the catalyst. Et[Ind]2Zr(CH3)2 was active even in the absence of TMA, whereas the addition of TMA during polymerization enhanced the catalytic activity. The polymerization‐rate profiles of the in situ supported metallocene catalysts did not show rate decay as a function of time. A polymerization mechanism for the in situ supported metallocene catalysts is proposed for this behavior. During polymerization, the in situ supported metallocene catalysts may deactivate, but homogeneous metallocene species present in the reactor may form new active sites and compensate for deactivated sites. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 462–468, 2000 相似文献
8.
Guoqiang Fan Jin‐Yong Dong Zhigang Wang T. C. Chung 《Journal of polymer science. Part A, Polymer chemistry》2006,44(1):539-548
This paper discusses a new process of preparing borane‐terminated isotactic polypropylenes (i‐PPs) via in situ chain transfer reaction, which avoids the use of B‐H‐containing chain transfer agent and thus can be carried out with Al‐activated metallocene catalyst under mild reaction conditions. The chemistry centers on a consecutive chain transfer reaction, first to a trialkylborane‐containing styrene derivative, 4‐[B‐(n‐butylene)‐9‐BBN]styrene (B‐styrene), then to hydrogen in the isoselective polymerization of propylene catalyzed by rac‐Me2Si(2‐Me‐4‐Ph‐Ind)2ZrCl2/MAO. The borane‐terminated i‐PP thus obtained keeps the desired properties of a polymeric alkyl‐9‐BBN reagent and was used to initiate radical polymerization of methyl methacrylate (MMA) to prepare i‐PP‐b‐PMMA diblock copolymer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 539–548, 2006 相似文献
9.
Jung Dae Kim Joo B. P. Soares Garry L. Rempel 《Journal of polymer science. Part A, Polymer chemistry》1999,37(3):331-339
Tailoring of the molecular weight distribution (MWD) in ethylene polymerization was attempted by selectively combining different types of metallocene catalysts onto a single support. The catalyst produced by supporting Et[Ind]2ZrCl2 and Cp2HfCl2 onto a single MAO pretreated silica support was able to produce polymers with unimodal or bimodal MWD's. This approach permits the synthesis of polyethylene with different MWD's using the same catalyst as a function of the polymerization conditions. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 331–339, 1999 相似文献
10.
Daryoosh Beigzadeh Joo B. P. Soares Thomas A. Duever 《Macromolecular rapid communications》1999,20(10):541-545
The solution polymerization of ethylene in Isopar E in a semi-batch reactor using combined CGC-Ti and Et[Ind]2ZrCl2 catalysts was studied. Methylaluminoxane (MAO) and tris(pentafluorophenyl)borane were used as co-catalysts. Samples were analyzed by 13C NMR and gel permeation chromatography (GPC) for their branching content and molecular weight distribution. It was shown that there was an optimum ratio of CGC-Ti/Et[Ind]2ZrCl2 that maximizes the number of long-chain branches of the formed polyethylene. 相似文献
11.
Marco Antnio da Silva Griselda Barrera Galland 《Journal of polymer science. Part A, Polymer chemistry》2008,46(3):947-957
Ethylene (E), propylene (P), and 1‐pentene (A) terpolymers differing in monomer composition ratio were produced, using the metallocenes rac‐ethylene bis(indenyl) zirconium dichloride/methylaluminoxane (rac‐Et(Ind)2ZrCl2/MAO), isopropyl bis(cyclopentadienyl)fluorenyl zirconium dichloride/methylaluminoxane (Me2C(Cp)(Flu)ZrCl2/MAO, and bis(cyclopentadienyl)zirconium dichloride, supported on silica impregnated with MAO (Cp2ZrCl2/MAO/SiO2/MAO) as catalytic systems. The catalytic activities at 25 °C and normal pressure were compared. The best result was obtained with the first catalyst. A detailed study of 13C NMR chemical shifts, triad sequences distributions, monomer‐average sequence lengths, and reactivity ratios for the terpolymers is presented. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 947–957, 2008 相似文献
12.
Atila Kaya Lothar Jakisch Hartmut Komber Gisela Pompe Jürgen Pionteck Brigitte Voit Ulrich Schulze 《Macromolecular rapid communications》2000,21(17):1267-1271
Using two different zirconocene/MAO catalyst systems, propene was copolymerized with the comonomers 2‐(9‐decene‐1‐yl)‐1,3‐oxazoline and 2‐(4‐(10‐undecene‐1‐oxo)phenyl)‐1,3‐oxazoline, respectively. The catalysts used were rac‐Et[Ind]2ZrCl2 and rac‐Me2Si[2‐Me‐4, 5‐BenzInd]2ZrCl2. Up to 0.53 mol‐% oxazoline could be incorporated into polypropene. Oxazoline content, molecular weight, degree of isotacticity and melting behavior were dependent on the catalyst system, comonomer structure and comonomer concentration in the feed. 相似文献
13.
Johannes Carolus Jansen Raniero Mendichi Paolo Locatelli Incoronata Tritto 《Macromolecular rapid communications》2001,22(17):1394-1398
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
14.
Alireza Talaei Faramarz Afshar Taromi Ahmad Arefazar Saeid Ahmadjo Omid Moini Jazani 《高分子科学》2014,32(2):137-142
Ethylene polymerization was carried out by immobilization of rac-ethylenebis(1-indenyl)zirconium dichloride(Et(Ind)2 ZrCl2) and rac-dimethylsilylbis(1-indenyl)zirconium dichloride(Me2 Si(Ind)2 ZrCl2) preactivated with methylaluminoxane(MAO) on calcinated silica at different temperatures. Polymerizations of ethylene were conducted at different temperatures to find the optimized polymerization temperature for maximum activity of the catalyst. The Me2 Si bridge catalyst showed higher activity at the lower polymerization temperature compared to the Et bridge catalyst. The highest catalytic activities were obtained at temperatures about 50 °C and 70 °C for Me2 Si(Ind)2 ZrCl2 /MAO and Et(Ind)2 ZrCl2 /MAO catalysts systems, respectively. Inductively coupled plasma-atomic emission spectroscopy results and polymerization activity results confirmed that the best temperature for calcinating silica was about 450 °C for both catalysts systems. The melting points of the produced polyethylene were about 130 °C, which could be attributed to the linear structure of HDPE. 相似文献
15.
Xiao‐Yan Wang Ying‐Yun Long Yong‐Xia Wang Yue‐Sheng Li 《Journal of polymer science. Part A, Polymer chemistry》2014,52(23):3421-3428
This article discussed the root causes of the interesting differences between rac‐Et(Ind)2ZrCl2 and dimethyl (pyridyl‐amido)hafnium in catalyzing the propylene/ω‐halo‐α‐alkene copolymerization. Confirmed by density functional theory (DFT) calculations, the larger spacial opening around the active center of rac‐Et(Ind)2ZrCl2 contributes to the coordination and insertion of the monomers, resulting in the higher catalytic activity, while the narrow spacial opening around the Hf center retards the chain transfer reaction, leading to the much higher molecular weights (Mws) of the copolymers. The superior tolerability of Zr catalyst toward halogen groups might be attributed to that the dormant species generated from halogen coordination could be promptly reactivated. DFT calculations indicated the higher probability for the ω‐halo‐α‐alkene vinyl to coordinate with the Hf catalyst leading to the better ability to incorporate halogenated monomers. The high Mws and the outstanding isotacticity achieved by the Hf catalyst determined the higher melting temperature values of the copolymers with a certain amount of halogen groups. In addition, the chain transfer schemes were employed to analyze why the presence of halogenated monomers greatly decreased the Mws of the copolymers when rac‐Et(Ind)2ZrCl2 was used, while had no or little effect upon the Mws in the copolymerization by the Hf catalyst. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3421–3428 相似文献
16.
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
17.
Jing‐Yu Lee Jing‐Cherng Tsai 《Journal of polymer science. Part A, Polymer chemistry》2011,49(17):3739-3750
Structurally well‐defined end functionalized isotactic polypropylene (iPP) is prepared by conducting a selective chain transfer reaction during the isospecific polymerization of propylene in the presence of norbornadiene (NBD) and hydrogen using rac‐Me2Si(2‐Me‐4‐Ph‐Ind)2 ZrCl2/MAO as the catalyst. The production of NBD‐capped iPP involves a unique consecutive chain transfer reaction, first to NBD and then to hydrogen, for situating the incorporated NBD at the iPP chain end. The NBD end group of NBD‐capped iPP can be converted into other reactive functional group through functional group transformation reactions. The resulting functional group end‐capped iPP can be used for the construction of stereoregular block copolymers (e.g., iPP‐b‐PMMA and iPP‐b‐PS) through postpolymeriztion reactions. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
18.
Chengbin Liu Tao Tang Zhongfu Zhao Baotong Huang 《Journal of polymer science. Part A, Polymer chemistry》2002,40(11):1892-1898
Ethylene polymerization was carried out with zirconocene catalysts supported on montmorillonite (or functionalized montmorillonite). The functionalized montmorillonite was from simple ion exchange of [CH3O2CCH2NH3]+ (MeGlyH+) ions with interlamellar cations of layered montmorillonites. The functionalized montmorillonites [high‐purity montmorillonite (MMT)‐MeGlyH+] had larger interlayer spacing (12.69 Å) than montmorillonites without treatment (9.65 Å). The zirconocene catalyst system [Cp2ZrCl2/methylaluminoxane (MAO)/MMT‐MeGlyH+] had much higher Zr loading and higher activities than those of other zirconocene catalyst systems (Cp2ZrCl2/MMT, Cp2ZrCl2/MMT‐MeGlyH+, Cp2ZrCl2/MAO/MMT, [Cp2ZrCl]+[BF4]/MMT, [Cp2ZrCl]+[BF4]?/MMT‐MeGlyH+, [Cp2ZrCl]+[BF4]?/MAO/MMT‐MeGlyH+, and [Cp2ZrCl]+[BF4]?/MAO/MMT). The polyethylenes with good bulk density were obtained from the catalyst systems, particularly (Cp2ZrCl2/MAO/MMT‐MeGlyH+). MeGlyH+ and MAO seemed to play important roles for preparation of the supported zirconocenes and polymerization of ethylene. The difference in Zr loading and catalytic activity among the supported zirconocene catalysts is discussed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1892–1898, 2002 相似文献
19.
Based on coordination polymerization mechanism only, novel stereoregular graft copolymers with syndiotactic polystyrene main chain and isotactic polypropylene side chain (sPS‐g‐iPP) were synthesized via two steps of catalytic reactions. First, a chain transfer reaction was initiated by a chain transfer complex composed of a styrene derivative, 1,2‐bis(4‐vinylphenyl)ethane, and hydrogen in propylene polymerization mediated by rac‐Me2Si[2‐Me‐4‐Ph(Ind)]2ZrCl2 and MAO, which gave iPP macromonomer bearing a terminal styryl group (iPP‐t‐St). Then the iPP‐t‐St macromonomers of varied molecular mass were engaged in syndiospecific styrene polymerization over a typical mono‐titanocene catalyst (CpTiCl3/MAO) under different conditions to produce sPS‐g‐iPP graft copolymers of varied structure. With an effective purification process, well‐defined sPS‐g‐iPP copolymers were obtained, which were then subjected to differential scanning calorimetry (DSC) and polarized optical micrograph (POM) studies. The graft copolymers were generally found with dual melting and crystallization temperatures, which were ascribable respectively to the sPS backbone and iPP graft. However, it was revealed that the two segments displayed largely different melting and crystallization behaviors than sPS homopolymer and the precursory iPP‐t‐St macromonomer. Consequently, the graft copolymer exhibited much distinctive crystalline morphologies when compared with their individual components. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011. 相似文献
20.
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