Supported Ionic Metallocene Polymerization Catalysts
Supported Ionic Metallocene Polymerization Catalysts
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DOI：
10.1021/ma960889x
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发表时间：
1996
期刊：
影响因子：
5.5
通讯作者：
G. Hlatky;David Jonathan Upton
中科院分区：
文献类型：
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作者：
G. Hlatky;David Jonathan Upton
介绍。茂金属基烯烃聚合催化剂，特别是以甲基铝氧烷为助催化剂的烯烃聚合催化剂是近年来研究的热点。学术研究者通过利用这些系统化学上的简单性和对它们进行合理修改的便利性，对基本的链生长过程有了深入的了解。在工业领域，这些催化剂的高活性和它们所生产的结构均匀的聚合物所赋予的改进的性能引起了聚烯烃生产商的相当大的兴趣。不管单位点催化剂的化学性能有多好，或者它们制造的树脂有多有市场潜力，如果不能在各种聚合过程中有效地发挥作用，这些系统注定只能在边际商业存在。可溶茂金属催化剂体系已成功地用于低压或高压溶液工艺，以生产低结晶度、极低密度的乙烯共聚物和弹性体。另一方面，连续浆料、流化床气相或散装单体工艺用于生产更结晶的线性低密度乙烯共聚物、高密度聚乙烯或立体规则聚丙烯。由于这些聚合物不溶于反应介质，这些过程需要形态均匀的聚合物产物，以避免反应器污染。这反过来又建议将茂金属催化剂固定在合适的载体上。茂金属-铝氧烷催化剂的载体包括淀粉、2种粘土、3种金属和陶瓷、4种金属卤化物、5种聚合物。最常用的支撑材料是多孔的无机氧化物，尤其是二氧化硅。由Cp ' 2MR2与[HNMe2Ph][B (C6F5) 4] 8或[Ph3C][B (C6F5) 4] 9反应生成的离子催化剂对溶液中乙烯和高r烯烃的聚合和共聚具有高活性。然而，这些无铝烷基催化剂的异质化比基于铝氧烷的体系更成问题。路易斯碱表面氧化物与亲电金属中心的配位（图1a）或离子配合物与残留的表面羟基的反应（图1b）可能会降低或熄灭催化剂的活性。我们发现，用清除剂预处理载体，通常是三烷基铝，可以钝化载体并使其与离子茂金属配合物相容。本文概述了我们成功制备的用于烯烃聚合的高活性负载型茂金属离子催化剂。10
Introduction. Metallocene-based olefin polymerization catalysts, especially those using methylalumoxane as a cocatalyst, have been the focus of intense study in recent years. 1 Academic investigators have gained insights into fundamental chain-growth processes by exploiting the chemical simplicity of these systems and the ease with which they can be rationally modified. In the industrial sphere, the high activities of these catalysts and the improved properties imparted by the structurally homogeneous polymers they produce have aroused considerable interest by polyolefins producers. Regardless of the chemical elegance of single-site catalysts or the market potential of the resins they make, these systems would be doomed to a marginal commercial existence if they could not be made to function effectively in various polymerization processes. Soluble metallocene catalyst systems have been used successfully in low-or high-pressure solution processes to produce low-crystallinity, very low-density ethylene copolymers and elastomers. On the other hand, continuous slurry, fluidized-bed gas-phase, or bulk-monomer processes are used to produce more crystalline linear-low-density ethylene copolymers, high-density polyethylene, or stereoregular polypropylene. Since these polymers are insoluble in the reaction media, these processes require a morphologically uniform polymer product in order to avoid reactor fouling. This in turn suggests immobilizing the metallocene catalyst on a suitable support. Carriers for metallocene-alumoxane catalysts have included starches, 2 clays, 3 metals and ceramics, 4 metal halides, 5 and polymers. 6 The most commonly used supports have been porous inorganic oxides, especially silica. 7Ionic catalysts generated by the reaction of Cp′ 2MR2 with [HNMe2Ph][B (C6F5) 4] 8 or [Ph3C][B (C6F5) 4] 9 are highly active for the polymerization and copolymerization of ethylene and higher R-olefins in solution. However, heterogenizing these aluminum-alkyl-free catalysts is more problematic than the alumoxane-based systems. Coordination of Lewis-basic surface oxides to the electrophilic metal center (Figure 1a) or reaction of the ionic complex with residual surface hydroxyl groups (Figure 1b) could be anticipated to diminish or extinguish catalyst activity. We have found that pretreatment of the support with a scavenger, typically a trialkylaluminum, serves to passivate the support and compatibilize it with the ionic metallocene complex. This paper outlines our successful preparation of highly active supported ionic metallocene catalysts for olefin polymerization. 10