【作者】 程正载；

【导师】 孙俊全；

【作者基本信息】 浙江大学 ， 化学工程与技术， 2006， 博士

【摘要】 聚烯烃如聚乙烯（PE）和聚丙烯（PP）等具有密度低、强度高、抗化学腐蚀性强且制造成本低等优点，被广泛应用于制造包装材料和各类容器具，是当今世界应用最广泛的高分子材料。尽管工业上已广泛应用的多活性中心Ziegler-Natta催化剂对乙烯聚合具有很高活性且能高活性催化丙烯聚合得到高等规度聚丙烯，但聚烯烃市场上以茂金属催化剂和限定几何构型催化剂（CGC）为代表的单活性中心催化剂正占据着越来越重要的地位。由于其明确的活性位及对聚合产物分子量，分子量分布、共聚单体组分的含量，以及对聚合物立构规整性的准确控制方面所具有的优势，单活性中心催化剂常被用于合成许多具有高性能的聚烯烃材料，成为研发的前沿课题。研发的关键是设计合适的配体：必需有适当的取代基来修饰配体的空间效应和电子效应。最近开发的单活性中心催化剂中，由三井化学Fujita研究小组首创的含苯氧基亚胺配体烯烃聚合催化剂（被称为FI催化剂）因其远高于茂金属的超高活性和聚合特性而成为又一研究热点。制备该类配合物催化剂的原料来源广泛，合成成本较低。通过配体结构的方便修饰，可任意生产从低分子量到分子量达数百万的超高分子量聚合物。通过乙烯和α—烯烃、甲基丙烯酸甲酯（MMA）和丙烯腈（AN）等单体共聚反应，还能开发出各种新型聚烯烃材料。烯烃聚合用单活性中心催化剂的传统研究重点集中在催化活性中心金属原子上。基于配体导向型催化剂分子设计新理念，本论文着眼于配体结构与配合物催化烯烃聚合性能构效关系，选择桥连茂金属和FI型非茂催化剂两个领域进行有关前过渡金属配合物的合成与催化烯烃聚合研究。采用三种不同大小的螺环（环戊基、环己基、环庚基）碳桥连双环戊二烯基二氯化钛和甲基铝氧烷（MAO）组成的催化体系，研究其在甲苯溶剂中对乙烯聚合的催化性能。结果发现，由于大环桥对茂金属配合物的稳定作用，环己基碳桥连双茂钛化合物A₂和环庚基碳桥连双茂钛化合物A₃均在较高的聚合温度（～60℃）下达到最高活性，而小环碳桥连双茂钛化合物A₁则在相对较低的聚合温度（～50℃）下才具有最佳催化活性。采用环己基桥连双（4，5，6，7-四氢茚基）二氯化锆化合物B₁为主催化剂，以MAO为助催化剂，研究其对乙烯和丙烯的催化性能，并对聚合产物进行了表征。选定实验条件下，锆化合物B₁对丙烯聚合的催化活性最高达6.37x10⁷g-PP（mol-Zr）_-1h^-1。采用¹³C NMR对不同反应温度和助催化剂／主催化剂摩尔比下所得PP的甲基五元组序列结构进行了测定。通过相同条件下的催化聚合结果的比较，可以看出，由于环己基桥连双四氢茚基配体的特殊空间效应和电子效应，使得单碳桥连锆化合物B₁对丙烯聚合的催化活性远高于结构相近的双碳桥连锆化合物，而聚合产物等规度则大大降低。给定实验条件下，桥连锆化合物B₁对乙烯聚合活性为0.46x10⁶到9.87×10⁶g-PE（mol-Zr）^-1h^-1，所得PE粘均分子量在0.97×10⁴到11.16×10⁴g·mol^-1间¹³C NMR的测定表明LPE的合成。本文以两种结构新颖的含吡啶基几何限制型茂铬化合物[（C₅H₄）C(C₅H₁₀)CH₂（C₅H₄N）]CrCl₂（C₁）和[（C₅H₄）C（CH₃）₂CH₂（C₅H₄N）]CrCl₂（C₂）为主催化剂，以MAO为助催化剂，研究了对乙烯和甲基丙烯酸甲酯的催化聚合反应。结果发现，由于茂环上的π电子和吡啶环上给电子N都能给中心金属原子Cr良好的配位，而由桥连碳连接的配体和配位中心Cr构成了稳定的六员环结构，所有电子效应和空间结构的影响都有利于铬化合物与助催化剂MAO形成的阳离子活性中心的稳定，所以，两种茂铬化合物对乙烯聚合都具有极高的催化活性。其中C₁／MAO体系在60℃下催化乙烯聚合活性达7.96×10⁶g-PE／mol-Cr·h，高于文献所报道的普通非桥连茂铬化合物的催化活性。研究还发现，铬配合物C₂在Al（i-Bu）₃的助催化下能高效催化MMA聚合得到PMMA。在较温和的条件（40℃，MMA／Al（i-Bu）₃／Cat．=2000:20:1）下催化反应18小时，77.55％单体MMA聚合得到粘均分子量达26.13万PMMA，高于同条件下Kaminsky型茂金属化合物Cp₂TiCl₂的催化活性。合成了13种单希夫碱配体L₁～L₁₃和8种新型双希夫碱配体L₁₄～L₂₁，并用¹H NMR、¹³C NMR、IR、GC／MS（或LC／MS）和元素分析等手段表征了有关化合物的结构和组成。合成了7种新的FI型单核钛化合物（D₁～D₇）和1种新的FI型双核钛化合物（D₈），并用¹H NMR、¹³C NMR、MS、元素分析和XRD等手段表征了钛化合物的结构和组成。分别采用所合成的三种单核钛配合物：5-硝基水杨醛缩2，6-二异丙基苯胺钛配合物（D₁）、5-氯水杨醛缩2，6-二异丙基苯胺钛配合物（D₂）、5-溴水杨醛缩2，6-二异丙基苯胺钛配合物（D₃）及一种双核钛配合物：2，2-二（4-羟基，3-氨基）苯基丙烷双缩（3，5-二叔丁基水杨醛）双核钛配合物（D₈）为主催化剂，MAO为助催化剂，考察了其对乙烯催化聚合性能。在反应温度为60℃，单体压力为0.2 MPa，MAO与主催化剂摩尔比为1500等条件下，单核钛配合物D₁～D₃催化乙烯聚合活性为（4.55～8.80×10⁷g PE／mol-Ti·h·MPa），比在相同条件下未取代苯氧基亚胺钛配合物D₉的催化活性高得多。可能是配体上硝基、卤素等吸电子取代基的引入增加了金属-碳阳离子活性中心数目所致。所得PE粘均分子量在24.8×10⁴到44.9×10⁴ g·mo^-1，分子量分布M_w／M_n在1.85到2.34间。单核钛配合物D₁～D₃随着反应温度的升高，催化聚合活性增大，在60℃左右达到最高活性，且催化体系活性和聚合产物的分子量随着单体压力增加而增大，表明该体系较适合于现有工业化聚乙烯装置。新型双核钛化合物D₈与结构相近的典型单核FI-Ti催化剂D₁₀（3，5-二叔丁基水杨醛苯亚胺二氯化钛）催化乙烯聚合的对比研究表明：在25～55℃聚合温度范围内，双核钛配合物（D₈）显示中等催化活性，低于类似结构单核钛催化剂。说明该双核FI型催化剂分子内两金属间并不能形成协同效应。更多还原

【Abstract】 Polyolefins, such as polyethylene （PE） and polypropylene （PP）, are the most widely used polymers in our life. Because of their cost effectiveness as well as low density, high strength, and good resistance to chemical attack, these polyolefins can be applied for the manufacture of all kinds of packaging film and containers.Although commercial multi-site Ziegler-Natta catalysts exist very high activity for ethylene and propylene polymerization and high isospecificity in propylene polymerization ,single-site catalysts represented by metallocene catalysts and constrained-geometry catalysts （CGC） are gaining an increasing presence in the worldwide polyolefin market, especially for PE and PP. Duo to the well-defined active sites of these single-site catalysts in contrast to multi-site Ziegler-Natta catalysts and the advantage of control over polymer molecular weight and molecular weight distribution, uniform comonomer incorporation, and precise control of polymer stereoregularity, single-site catalysts have had a significant impact on contemporary polyolefin science and technology and have been in the forefront of these developments.The key step for these researches and developments （R&D） is to design ligands with suitable electronic and steric effects.Among the recently-developed single-site catalysts, phenoxy-based catalysts,which was firstly discovered and named with FI catalysts by the research group of Terunori Fujita of Mitsui Chemicals Inc., constitute an important class of olefin polymerization catalysts. Because of their super-high activities for olefins polymerization and the polymers’ distinctive microstructures and related material properties, R&D for FI catalyst have become another forefront of developments of single-site catalysts. Phenoxy-based ligands can be commercially available in generally good to high yields and low cost, so FI catalysts have the advantageous properties of diversity as well as tunability. The most interesting is that the ligands are readily tailored synthetically from both an electronic and steric point of view and thus a wide range of FI catalyst can be designed for the synthesis of polymers with molecular weight ranging from thousands to several millions. By copolymerization between ethylene anda-olefin, MMA or AN ,various new type polymers can be obtained.Traditional researches for single-site catalysts for olefin polymerization focus on central metals. Basing on the new concept of "ligand-oriented catalyst design" and aiming at the relationship between high performance of single-site catalysts and the structure of their ligands, this dissertation study on the synthesis of early transition metal catalysts including the ansa metallocences and FI type titanium complexes and their catalytic performance in olefins polymerization.Firstly, the properties of ethylene polymerization under the same polymerization conditions with three of cycloalkylidene-bridged cyclopentadienyl titanium catalysts in the presence of MAO are investigated. It is firstly discovered by us that both ofcyclohexenebridged cyclopentadienyl titanocene A₂ and the cycloheptenebridged cyclopentadienyl titanocene A₃, in our polymerization conditions, the activity increase with temperature to a maximum activity at 60℃. This indicates that A₂ and A₃ are very thermally stable and do not deactivate even at higher temperatures. While the cyclopentene-bridged cyclopentadienyl titanocene A₁ has the highest activity at lower temperature （50℃）oSecondly, ansa-Cyclohexyl-bis（4,5,6,7-tertrahydro-l-indenyl） zirconium dichloride （B₁） was used as catalyst for propylene and ethylene polymerization together with methyl aluminoxane （MAO） as the cocatalyst. Isotactic polypropylene （PP） was obtained with the highest activity of 6.37×10⁷g-PP （mol-Zr）^-1h^-1. The meso-meso （mmmm） pentads sequence content of PP was determined by ¹³C NMR spectroscopy. The dependence of the microstructure on the reaction temperature and the Al/Zr molar ratio was examined and the catalytic activity of complex B₁ was compared with that of the similar ansa-zirconocene: trans-1,2-cycloalkylene-bridged bis（tetrahydro-indenyle）ZrCl₂. The high activity of the new zirconocene B₁ for propylene isospectic polymerization at high temperature （60 ℃） is the result of its unique bridged-group structure. Complex B₁/MAO displays also high catalytic activity of 0.46×10⁶ to 9.87×10⁶g-PE（mol-Zr）^-1h^-1 in the homopolymerization of ethylene. The visometric molecular weight of PE ranges from 0.97×10⁴ gmol^-1 to 11.16×10⁴ g·mol^-1 under the given conditions. ¹³C NMR spectroscopy analysis proves the PE to be linear polyethylene （LPE）.Thirdly, two carbon bridged cyclopentadienylchromium complexes [（C₅H₄） C (C₅H₁₀) CH₂ （C₅H₄N） ]CrCl₂（C₁）and[ （C₅H₄） C （CH₃） 2CH₂ （C₅H₄N） ]CrCl₂ （C₂） were synthesized and characterized byh mass spectra and elemental analyses. The structure of C₁ and C₂ were determined by X-ray diffraction analysis. Activated by MAO,the complexes C₁ and C₂ were efficient for ethylene polymerization yielding linear polyethylene （LPE） with high molecular weight and narrow molecular weight distribution. For chromium complex C₁, polyethylene was produced with high catalytic activity of 7.96×10⁶g /mol·h and viscometric average molecular weight （M_v） of 2.969×10⁴ and the molecular weight distribution of 3.14 at 60℃ .High melting point and low branching degree of the obtained PE was confirmed by DSC and ¹³C NMR. Activated by Al（i-Bu）₃ ,Complex C₂ displayed a higher activity than Kaminsky catalyst-Cp₂TiCl₂ for methyl methacrylate （MMA） polymerization under the same reaction conditions. After 18 hours, 77.55% MMA was converted to poly（methyl-methacrylate） （PMMA） with a viscosity average molecular （M_v） of 261300 at 40℃ at MMA/ Al（i-Bu）₃ /titanium complex of 2000:20:1 in MMA bulk. High activities of polymerization are related to the unique electronic and steric structure of complexes C₁ and C₂.Finally, in order to study the relationship between ligands structure of FI catalystsand their catalytic performances for ethylene polymerization , thirteen kinds of mono-Schiff bases (ligands: L₁～L₁₃ ) and eight kinds of bis-Schiff bases(ligands: L₁₄～L₂₁)were synthesized and characterized by ¹H NMR , ¹³C NMR, IR ,GC/MS （or LC/MS） and elemental analyses ,then seven kinds of novel FI-catalysts with mono-titanium centre （D₁～D₇） and a novel binuclear titanium complex （D₈） were prepared and characterized by ¹H NMR ,¹³C NMR, MS, XRD and elemental analyses. In the presence of methylaluminoxane （MAO）, the complexes D₁～D₃ in toluene are able to efficiently catalyze ethylene polymerization. Under the conditions of T= 60℃ ,P=0.2 MPa and n（MAO）/n（cat）=1500,the activities of （D₁～D₃） reach （4.55～8.80×10⁷ gPE /mol-Ti·h·MPa） which is much higher than that of bis[N-salicylidene-2,6-diisopropyl anilinato] titanium（IV） dichloride （D₉） .The viscometric average molecular weight of polyethylene rangs from 24.8×10⁴ to 44.9×10⁴ for D₁～D₃ and the molecular weight distribution M_w /M_n is 1.85 to 2.34. The effects of reaction conditions on polymerization were examined in detail. Increase in ethylene pressure and rise in polymerization temperature are favourable for D₁～D₃/MAO to raise catalytic activity and molecule weight of polyethylene. The results of ethylene polymerization under the temperature of 25～55℃ with binuclear titanium complex （D₈） as catalyst displays its moderate catalytic activity which is very lower than that of the similar structural mono-titanium catalyst (D₁₀). So no strong synergism of two metal centre exists within the binuclear FI catalyst.更多还原