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首页> 外文期刊>Journal of Applied Polymer Science >Ethylene homo- and copolymerization over MgCl2-TiCl4 catalysts: Polymerization kinetics and polymer particle morphology
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Ethylene homo- and copolymerization over MgCl2-TiCl4 catalysts: Polymerization kinetics and polymer particle morphology

机译：MgCl2-TiCl4催化剂上的乙烯均聚和共聚：聚合动力学和聚合物颗粒形态

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摘要

Three procatalysts of the MgCl2/TiCl4 type, differing mainly in their morphological characteristics, were investigated in ethylene polymerization and ethylene-l-butene copolymerization. Apparently, hydrogen has an intrinsic and general deactivating effect but it can also play an activating effect in homopolymerization. This peculiarity was found to be related to a catastrophic breakage of the polymer/catalyst particles during growth and thus to the exposure of new active centers. In this case the kinetic profiles are irregular and characterized by one or more secondary peaks which reflect the moment when this morphology-driven rate-enhancement effect takes place. In general, the prepolymerization of the procatalysts with propylene tends to slightly enhance homopolymerization rate, to slow down copolymerization rate and to stabilize the morphology of the growing polymer particles, thus preventing the occurrence of the irregular kinetic profiles observed during homopolymerization in the presence of hydrogen. The behavior of the procatalysts investigated was found to depend on the distribution of their pore size rather than the absolute values of their porosity. Likely this is due to an easier diffusion of the monomer and a more regular and homogeneous growth of the polymer within larger as opposed to smaller pores. (C) 2008 Wiley Periodicals, Inc.
机译：在乙烯聚合反应和乙烯-1-丁烯共聚反应中，研究了三种MgCl2 / TiCl4型主催化剂，它们的主要形态不同。显然，氢具有固有的和一般的失活作用，但它在均聚中也可以起到活化作用。发现该特性与生长期间聚合物/催化剂颗粒的灾难性破裂有关，并因此与新的活性中心的暴露有关。在这种情况下，动力学曲线是不规则的，并具有一个或多个次级峰的特征，这些峰反映了这种由形态学驱动的速率增强效应发生的时刻。通常，前催化剂与丙烯的预聚合趋于稍微提高均聚速率，减慢共聚速率并稳定生长的聚合物颗粒的形态，从而防止在氢气存在下均聚过程中观察到不规则的动力学曲线的发生。 。发现所研究的前催化剂的行为取决于其孔径的分布而不是其孔隙率的绝对值。这可能是由于单体在较大孔（而不是较小孔）中更容易扩散，以及聚合物更规则和均匀地生长。 （C）2008 Wiley期刊公司

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