Ethylene polymerization over zirconocenes supported on alumina- and titania-based acidic oxides

Ethylene polymerization was performed using bis(n-butylcyclopentadienyl)zirconium dichloride ((n-BuCp)₂ZrCl₂) supported on alumina- and titania-based acidic oxides (Al₂O₃, TiO₂, AlPO₄, TiO₂–Al₂O₃, SiO₂–Al₂O₃, TiO₂–SiO₂ and H–Y zeolite) in the presence of triisobutylaluminum. These oxides were also tested in an isopropylbenzene cracking reaction to determine their acid properties. Among the catalysts, AlPO₄-supported (n-BuCp)₂ZrCl₂ showed the highest polyethylene productivity, but AlPO₄ was inactive in the cracking reaction. FT-IR spectra of pyridine-adsorbed AlPO₄ and Al₂O₃ indicated that the acid sites do not participate in active-site formation. It is possible that the metallocene is activated on sites formed by the reaction of characteristic OH groups of AlPO₄ with triisobutylaluminum.     

Effect of prepolymerization on propylene polymerization

Polymerization of propylene was performed using MgCl₂. EtOH.TiCl₄.ID.TEA.ED catalyst system in hexane, where internal donor (ID) was an organic diester and external donor (ED) was a silane compound and also triethyl aluminum (TEA) as activator. A new method called isothermal/nonisothermal method (INM), a combination of isothermal and nonisothermal methods, was applied to produce the spherical polymer particles. The effects of the INM method and prepolymerization temperature on the final polymer morphology, M_w, and catalyst activity were also investigated. The morphology of the polymers was evaluated through scanning electron microscopy (SEM) images. GPC results were used for molecular weight (M_w) evaluation. It was found that the polymers had a better morphology when they were prepared using INM method. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Ethylene/propylene copolymerization over three conventional C2‐symmetric metallocene catalysts: Correlation between catalyst configuration and copolymer microstructure

This work reports on a correlation between catalyst configuration and copolymer microstructure for ethylene/propylene (E/P) copolymerization using three conventional C₂‐symmetric metallocene catalysts, namely, rac‐Et(Ind)₂ZrCl₂ (EBI), rac‐Me₂Si(2‐Me‐4‐Ph‐Ind)₂ZrCl₂ (SiPh), and rac‐CH₂(3‐tBu‐Ind)₂ZrCl₂ (MBu), with MAO as a common cocatalyst. Copolymerization reactions were conducted in toluene at three different temperatures with varied E/P ratios. Some typically obtained copolymers were characterized in detail using ¹³C‐NMR spectroscopy, by which triad distribution data were elaborated in a statistical method to determine the reactivity ratios (r_E and r_P) of the comonomers, which were also obtained by Fineman‐Rose estimation. The production of alternating‐like copolymers from EBI is attributed to the rapid interconversion between two conformation states of the active site, one of which favors the incorporation of propylene but the other one does not. Both SiPh and MBu are structurally more rigid and of larger dihedral angles than EBI; however, SiPh which owns open active site conformation tend to produce random copolymers at all studied temperatures, and for MBu, sterically hindered catalyst, block‐like copolymers were obtained. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Interrelations between constitution,configuration and conformation in chlorinated polyalkenamers

Summary FTIR-Spectra of poly-1,2-dichloroalkanes are reported as a function of the constitution and of the configuration of the subunits and of the temperature. The intensity of the C-Cl-vibrations of the head-to-head chlorinated polymers with variable tail length seems to be sensitive to changes in configuration and conformation and also to changes in the surrounding of the absorbing group. We conclude from these experiments that an intensity ratio of the different conformers corresponds to every degree of stereoregularity, which is overlapped with the influence of polarity on the absorbance. Assuming that the conformational equilibrium in chlorinated polymers is insensitive against minor disturbances — swelling or blending — the IR-intensity offers information concerning placement and degree of polymer contacts and interactions in polymer blends as well as in plasticized polymers.Prof. Dr. O. Wichterle zum 75. Geburtstag herzlichst gewidmet     

Influence of cocatalyst on the stereoselectivity and productivity of styrene polymerization reactions

Influence of different cocatalysts on the polymerization reaction of styrene using heterogeneous nanoparticle NA-MgO and NA-TiO2 (anatase) supported bis (cyclopentadienyl) zirconium dichloride catalysts is studied. Methyaluminoxane, trityl tetrakis(pentafluorophenyl)borate(1), dimethylanilinium tetrakis (pentafluoro-phenyl)borate (2) and tris(pentafluorophenyl)borane (3) are used as cocatalysts for this study. The productivity and stereoselectivity of the catalysts systems are found to be highest with MAO and lowest with the borane 3 (MAO > 1> 2 > 3). Catalysts derived from the borane 3 yield amorphous atactic polystyrenes but those from cocatalysts MAO, 1, or 2 yield crystalline, syndiotactic polystyrenes under the same reaction conditions. Effects of addition of various scavengers and solvents with different polarities on styrene polymerizations are also reported here. Characterization of the obtained polymers is done by Gel Permeation Chromatography, ¹³C-NMR spectroscopy and Differential Scanning Calorimetry.     

Graft polymerization of propylene sulfide on crosslinked polystyrene

Sulfur containing graft polymers that may be of interest as polymeric transfer agents were synthesized. Graft polymerization of propylene sulfide on crosslinked polystyrene beads was investigated; both crosslinked polystyrene and its chloromethylated derivative were grafted. Crosslinked polystyrene was metallated by BuLi–TMEDA and was used to initiate anionic graft polymerization of propylene sulfide. Graft polymers of high polypropylene sulfide content corresponding to 10 mmol s/g were obtained. The grafted polypropylene sulfide was evenly distributed across the bead cross section. No change in bead surface characteristics was observed. Grafting on chloromethylated polystyrene beads was achieved by reaction between the chloromethylene groups with sulfide groups of performed polypropylene sulfide, and with terminal sodium thiolate groups of living polypropylene sulfide.     

BCK催化剂丙烯聚合行为的研究

为了提高Innovene等气相工艺用聚丙烯催化剂的性能,开发了性能优良的新型BCK催化剂。为了指导工业应用方向,研究了BCK催化剂在60～85℃时的丙烯聚合的动力学行为,测试了聚合活性和聚丙烯的等规指数、熔点、分子量分布等性能,并与Innovene气相工艺常规应用的催化剂进行了对比分析。结果表明,BCK催化剂的聚合反应速率、聚合活性、立体定向性和聚丙烯的熔点明显高于另外两种催化剂。随着温度的升高,BCK催化剂的聚合反应速率和活性呈现降低趋势,而且聚合速率的衰减越来越快;BCK催化剂的立体定向性随着温度升高而下降;聚丙烯分子量分布随温度升高而变宽。     

混合助催化剂对丙烯本体聚合的影响

分别采用DQ型和BC-MS型Ziegler-Natta催化剂催化丙烯本体聚合,助催化剂为三乙基铝(TEAL)与三异丁基铝(TiBA)的混合物,外给电子体为二苯基二甲氧基硅烷,氢气作相对分子质量调节剂,反应釜内的装料系数为70%。首先在20℃条件下进行预聚合,预聚合结束后迅速升温至70℃聚合。研究了TEAL/TiBA混合助催化剂对聚丙烯(PP)等规指数、熔体流动速率(MFR)和力学性能的影响。结果表明:随着助催化剂中TiBA用量的增加,所制PP的等规指数降低,MFR呈降低趋势。与BC-MS型催化剂相比,用DQ型催化剂制备的PP的弯曲强度和弯曲模量总体上较低,简支梁缺口冲击强度相对较高。     

Catalyst fragmentation during propylene polymerization: Part II. Microparticle diffusion and reaction effects

A mathematical model is used to predict the behavior of the support/catalyst/polymer macroparticle during the gas phase polymerization of propylene. The problem is focused on the micrograin level of the macroparticle, and the emphasis placed on the combined reaction and diffusion processes taking place in the micropartiele. Particular attention is given to the effect of the main geometry parameter, the size of the catalytic nucleus, on polymerization variables. Fragmentation rate, monomer concentration, and temperature are studied in terms of their dependence on the geometry-related dimensionless numbers typical of the process. A strong influence of the micrograin size on the commanding process variables is predicted by the model. Fragmentation proves relevant to the overall process and critical to define the time scale of temperature excursions. Micrograin nucleus size are found to be important when computing both maximum temperatures and minimum yields. The model suggests criteria for predicting “a priori” the combination of reaction parameters that will produce a diffusion-limited reaction regime in the microparticle.     

N催化剂在丙烯聚合反应中的应用Ⅰ.预聚与预络合对N催化剂聚合性能的影响

考察了丙烯预聚、预络合对N催化剂聚合性能的影响，结果表明，预络合有助于提高催化剂的聚合活性以及聚合物的表观密度，提高催化剂的抗杂质干扰能力，预聚除能够提高催化剂的活性外，对提高聚丙烯粉料的表观密度和等规指数，减少聚丙烯颗粒的破碎有显著影响。     

茂金属催化剂催化丙烯聚合研究进展

介绍了茂金属催化剂催化丙烯聚合的发展概况、催化剂结构与聚合物微观结构的关系、丙烯聚合机理及催化体系的结构组成对丙烯聚合的影响     

Gas-phase polymerization of propylene at low reaction rates: a precise look at catalyst fragmentation

In this work, we reported the development of a mini-reactor experimental setup for synthesizing of polypropylene with heterogeneous Ziegler–Natta catalysts in gas-phase. Use of pro-activated 4th generation of Ziegler–Natta catalyst and preheated monomer feed enabled the polymerization reaction to be carried out at constant temperature. Evaluation of monomer consumption with high precision (0.01 bar pressure drop) allowed the detection of polymerization yield at low reaction rates. In this regard, polymerization yield, particle morphology and catalyst fragmentation were studied, as well. The results of melt microscopy showed that catalyst fragmentation was developed during the reaction, and was not restricted to the initial rupture of catalyst particles. The rate determination showed a peak during the polymerization (not necessarily at the initial stage). The results showed that depending on the reaction condition, this peak could be either a consequence of a major catalyst fragmentation or overheating. Low reaction yield, large fragments of catalyst and agglomeration of particles were considered as evidence of particle overheating and polymer local melting. As we imposed the results of melt microscopy for the polymerization conditions, a layer-by-layer fragmentation of the catalyst was found to be the main fragmentation process, at least at the beginning of the polymerization reaction.     

锌/钴双金属氰化络合物催化环氧丙烷聚合机理

用以二乙二醇二乙醚为有机配体的锌／钴双金属氰化络合物进行了环氧丙烷的聚合,并用扩展X射线精细结构分析方法研究了催化剂激活和环氧丙烷聚合过程中锌离子和钴离子的区域结构变化。结果表明,锌／钴双金属氰化络合物催化环氧丙烷的聚合是一个活性聚合体系。在环氧丙烷聚合过程中锌离子由与3．0个氧原子配位转变为与5．7个氧原子配位,表明聚合活性中心为5．0个氧原子配位的螯合锌离子。     

用调节剂改善聚丙烯高效催化剂性能的研究

在原聚丙烯合成催化剂的基础上,通过在制备过程中加入调节剂,制备了一种新型催化剂.试验结果表明新型催化剂与原催化剂相比,表面形态也得到明显改善,具有更高的活性、优良的动力学性能.     

同轴异速桨在丙烯淤浆反应釜中的流场研究

针对丙烯聚合反应过程,设计了一种同轴异速桨,基于CFD对反应过程进行了数值模拟。建立12 m~3反应釜模型,采用多重参考系方法MRF、Mixture多相流模型、标准k-ε湍流模型模拟搅拌过程,获得了反应3个阶段釜内流体的速度场及浓度场。结果表明:同轴异速桨可以使釜内流体轴向和径向都有着很好的交换;其在反应的各个阶段都能使流体得到很好的混合;桨的转速对混合效果有着较大的影响,随着反应的进行,应逐渐增加折叶桨转速。     

Studies on the effects of external electron donor in propylene polymerization

In order to investigate effects of an electron donor in propylene polymerization (in gas and slurry phase reactions each) by using a 3rd generation Ziegler-Natta catalyst, the catalytic activities were measured before and after the addition of an electron donor. And physical properties of produced polymer were estimated. Polymerization rate was decreased with increasing EB/A1 mole ratio because atactic sites on catalyst were selectively poisoned by the addition of the electron donor, and consequently total number of active sites were diminished. It was found that the overall reaction order was the 2nd order, and a reaction rate form was suggested by using a CO inhibition technique. Catalyst deactivation was due to the formation of dense isotactic polypropylene on the catalyst at the beginning of polymerization so that monomers had the difficulties in diffusion into catalyst surface through the dense polymer. From the measurements of polymer physical properties, probability of active site transitions from atactic→low isotactic→high isotactic sites could be considered, which may be due to the formation of a complex between co-catalyst and electron donor.     

丙烯聚合用HR催化剂的性能

在5 L高压反应釜中利用本体聚合法研究了丙烯聚合用HR催化剂的活性、立构定向性和氢调敏感性。考察了不同聚合条件(如助催化剂用量、外给电子体用量、氢气用量等)对HR催化剂活性、所制聚丙烯等规指数和熔体流动速率的影响,并与商业化DQC催化剂进行了对比。结果表明:与DQC催化剂相比,HR催化剂具有高的立构定向性及氢调敏感性,且活性更高。基于其性能特点,HR催化剂适用于制备高流动性高刚性聚丙烯。     

丙烯聚合用BCZ型催化剂的开发

在MgCl2溶解过程中加入内给电子体,开发了一种新型丙烯聚合用BCZ型催化剂,并在5 L聚合釜中进行了本体聚合考核评价,在12 m3小本体工艺装置上进行工业应用试验,在25 kg/h的连续法Innovene气相工艺装置进行中试试验。研究表明:用BCZ型催化剂制备聚丙烯(PP)时,催化剂活性高出国产同类催化剂近50%,氢调敏感性好,同样氢气用量下,PP的熔体流动速率可提高25%左右;所制PP的相对分子质量分布大于7.5,等规指数高;BCZ型催化剂可用于小本体法工艺、连续法气相工艺装置制备均聚和共聚PP。