【作者】 王文钦；

【导师】 王立；

【作者基本信息】 浙江大学 ， 高分子化学与物理， 2005， 博士

【摘要】 近年来,负载型茂金属催化体系特别是聚合物负载型茂金属体系,正越来越多地受到人们重视。然而到目前,许多问题依然有待解决,例如茂金属负载化过程中如何控制活性中心在载体上的分布、载体对活性中心的影响、茂金属的负载机理以及负载型茂金属的催化机理等问题还不是十分清楚,进一步弄清这些问题具有深远的理论意义和重大的应用价值。 本论文利用悬浮聚合的方法制备了线型聚苯乙烯,对线型聚苯乙烯进行氯甲基化后引入环戊二烯基,将环戊二烯基锂盐化后通过其和CpZrCl₃的反应将茂锆负载到聚苯乙烯上,制备了具有不同锆含量的两个系列的聚苯乙烯负载型茂锆催化剂,并通过NMR等测试手段进行了表征。以所得聚苯乙烯负载型茂锆为主催化剂,以MAO为助催化剂催化烯烃聚合,考察了不同聚合条件下,如聚合温度、[Al]/[zr]比、共聚单体比对催化活性、聚合动力学及所得聚合物性能的影响。研究结果表明载体的结构对催化活性具有重要的影响,具有低交联度载体的催化剂的催化活性高于具有高交联度载体的催化剂。催化乙烯/α-烯烃共聚过程中发现明显的“共单体效应”。 采用DSC、GPC、¹³C NMR对聚苯乙烯负载型茂锆催化剂催化所得聚烯烃产物进行较为详细的表征。结果表明:在所得乙烯/α-烯烃共聚物中随着共聚单体含量的增大,共聚物的熔点和结晶度明显降低;对所得乙烯/己烯共聚物的¹³C NMR的研究显示,在聚合过程随加入己烯浓度的增大,共聚物中己烯含量增加;不同载体负载的催化剂制得的乙烯/1-己烯共聚物的组成基本相同,己烯单元在共聚物链上是均匀分布的。 用Schulz-Flory“最可几分布”函数对苯乙烯负载型茂锆催化所得聚乙烯的分子量分布进行了拟合,发现体系中可能存在三种活性中心。结合拟合分析的结果我们建立了乙烯聚合动力学模型,用此模型来拟合实际的动力学曲线,得到了令人满意的结果。在共聚原理和一些相应的假设基础上建立了乙烯/1-己烯共聚动力学模型,该模型与实验数据吻合得很好,说明该模型具有一定的合理性。 本文通过在氯甲基化线型聚苯乙烯上引入环戊二烯基,在Cp₂ZrCl₂存在下利用环戊二烯基间的Diels-Alder反应形成聚苯乙烯网络,同时将Cp₂ZrCl₂茂金属包裹到网络内,制备了聚苯乙烯负载的固态均相茂锆催化剂。以2,2,6,6-四甲基哌啶酮氮氧自由基作为探针,用ESR技术对聚苯乙烯网络的结构进行了研究,结果表明在交联聚苯乙烯网络中能形成类似均相反应的微环境。 研究了以聚苯乙烯负载的固态均相茂金属为主催化剂,以MAO为助催化剂催化烯烃聚合的规律,结果显示该类催化剂的载体在聚合过程中是否能有效地破碎是决定催化剂性能的重要因素之一。该类催化剂催化乙烯聚合动力学结果显示:具有低交联密度的载体负载的茂金属催化剂催化乙烯聚合速率较为平稳,而具有高交联密度的载体负载的茂金属催化剂催化乙烯聚合速率衰减得较快。此外我们还发现具有低交联密度的聚苯乙烯负载的茂锆催化剂在催化乙烯聚合时,聚苯乙烯载体逐步解离并分散到聚乙烯产品中去,可以得到聚乙烯/聚苯更多还原

【Abstract】 Recently, the supported-metallocene catalysts, especial polymer-supported metallocene catalysts have attracted more attentions. However, some problem such as how to controlling the distribution of active sites on the carriers, the effect of carriers on the active sites, the mechanism of immobilization of metallocene catalyst and the mechanism of polymerization over supported metallocene still are unclear completely. It is of great theoretical significance and practical value to clear the above-mentioned problem.In this work, the linear polystyrene is prepared by suspension polymerization. Subsequently, the polystyrene is chloromethylated and cyclopentadienes are attached on the polystyrene. The cyclopentadienes attached on polystyrene react with BuLi for supporting CpZrCl₃ to form polystyrene-supported zirconocene catalyst. The two kinds of polystyrene-supported zirconocene catalysts with different Zr contents are synthesized and characterized by NMR. The polystyrene-supported zirconocene are employed as catalyst in a study of olefin polymerization in the presence of MAO cocatalyst. The influence of polymerization temperature, [Al]/[Zr] molar ratio, different comonomer on catalytic activities, （co）polymerization kinetics, the properties of resultant polyolefin have been investigated. The results show that the carriers have important effect on activities of those catalysts. The activities of the catalyst with lower cross-linked degree carriers are higher than those of catalysts with higher cross-linked degree carriers. The obvious "comonomer effect" is observed in the ethylene/α-olefin copolymerization catalyzed by the polystyrene-supported zirconocene catalysts.The polyoiefins obtained by the polystyrene-supported zirconocene catalysts are characterized with the techniques of DSC, GPC and ¹³C NMR. The results show that the melting temperature and crystallinity decrease markedly with the increase of comonomer in the ethylene/a-olefin copolymer. The microstructure of ethylene/1-hexene copolymer is investigated using ¹³C NMR. The results reveal that the content of comonomer in copolymer increases with increasing the concentration of comonomer in the feed. The composition of the ethylene/1-hexene copolymer obtained by the different catalysts is nearly same and the 1 -hexene units are distributed evenly in copolymer chains.The molecular-weight distribution（MWD） graphs of polyethylene obtained by polystyrene-supported zirconocene catalyst are fitted with Schulz-Flory "the most probable" distributions. The results show that it is possible there lie three kinds of active species in the catalytic system. According to the above-mentioned results, a novel kinetic model is presented. Simulating results using the model are consistent with experimental results. According to the theory of copolymerization and some assumption, a kinetic model of ethylene/1-hexene copolymerization isdeveloped. The model could fit the experimental results well, which suggests the model is reasonable.In this work, in the presence of Cp2ZrCl2, utilizing the Diels-Alder reaction of cyclopentadienes attached on the linear polystyrene to form the cross-linked polystyrene network, the Cp2ZrCl2 are encapsulated inside the cross-linked polystyrene network. The polystyrene-supported solid-homogeneous zirconocene catalyst is prepared. Using 4-oxo-2,2,6,6-tetramethyl -1-piperidinyloxy radicals as probe, the structure of cross-linked polystyrene network is investigated. The results show that the homogeneous microenvironment could form in the cross-linked polystyrene network.The olefin polymerization catalyzed by the polystyrene-supported solid-homogeneous zirconocene catalyst is studied in the presence of MAO cocataiyst. The results show that the fragmentation of carrier is the one of important reasons, which influence on the property of catalyst. The kinetic curves of ethylene polymerization catalyzed by the catalyst with low cross-linked degree carrier is stable and the polymerization rate of the catalyst with high cross-linked degree carrier decrease quickly. In addition, we find that polystyrene carrier could fragment and is distributed into polyethylene during ethylene polymerization. By the method, the polyethylene/polystyrene molecular composite membrane is prepared.The polyolefin obtained by the polystyrene-supported solid-homogeneous zirconocene catalyst are characterized by the techniques of DSC and GPC. The results show that the carrier has important effect on the molecular weight and molecular-weight distribution of polyethylene. The molecular-weight of polyethylene obtained by the catalyst with higher cross-linked density carrier is lower. The molecular-weight distribution（MWD） graphs of polyethylene obtained by polystyrene-supported solid-homogeneous zirconocene catalyst are fitted with Schulz-Flory "the most probable" distributions. The results show that it is possible there lie four kinds of active species in the catalytic system.更多还原