Ethylene Copolymerization with Linear and End-Cyclized Olefins via a Metallocene Catalyst:Polymerization Behavior and Thermal Properties of Copolymers

Olefin solution polymerization can be used to obtain high-performance polyolefin materials that cannot be obtained via other polymerization processes.Polyolefin elastomers(POE)are a typical example.Due to cost,only a few linear a-olefins(e.g.,1-butene,1-hexene,and 1-octene)are used as comonomers in solution polymerization in industry.However,a-olefin comonomers with other structures may have different effects on polymerization in comparison with common linear ones.Moreover,the properties of the corresponding materials may differ significantly.In this work,copolymers of ethylene with linear and endcyclized a-olefins are synthesized using a metallocene catalyst.The copolymerization of ethylene with linear a-olefins results in a higher turn-over frequency(TOF)and lower incorporation than copolymerization with end-cyclized a-olefins,which may indicate that end-cyclized a-olefins have a higher coordination probability and lower insertion rate.In this reaction,the comonomer is distributed randomly in the polymer chain and efficiently destroys crystallization.End-cyclized a-olefins exhibit a much stronger crystallization destructive capacity(CDC)in the copolymer than linear a-olefins,possibly because linear a-olefins act mainly in the radial direction of the main chain of the polymer,while end-cyclized a-olefins act mainly in the axial direction of the main chain.

A New Type of Polymer-Supported Metallocene Catalyst for Ethylene Polymerization

A new polymer-supported metallocene catalyst has been prepared, The polymer-supported metallocene displayed considerably high activity in ethylene polymerization, the highest being 3.62x10(7) gPE/molZr.h, the molecular weight of the polyethylene produced was Mn = 1.29x10(5). about 3-4 times those of corresponding homogeneous zirconocenes. The polymer-supported metallocene keeps the characteristics of homogeneous metallocene catalysts, and offers some features, such as adaptable to gas phase and slurry processes: easy to prepare in low cost: relatively high activity and lower MAO/Zr ratio; lower inorganic residues in the polyolefins as compared to cases of SiO2, Al2O3 or MgCl2; unitary active structure, no complex surface as with SiO2; good control of morphology of the resulting polymer.

The effect of polymerization conditions on crystalline of polybutene-1 catalyzed by metallocene catalyst

Polybutene-1 was synthesized stereoselectively with the precursor η(5)-(pentamethyl-cyclopentadienyl) tribenzyloxide titanium (Cp*Ti(OBz)3) and methylaluminoxane (MAO). The effects of polymerization conditions, trimethyl alumina (TMA) content in MAO and temperature on the crystalline and molecular weight of the products, and catalytic activity were investigated. The structural properties of the polybutene-1 were characterized with (13)C NMR and WAXD.

EFFECTS OF AMINO GROUPS AND MICROSTRUCTURE OF ORGANIC MESOPOROUS SILICA SUPPORTED METALLOCENE CATALYSTS ON ETHYLENE POLYMERIZATION

Mesoporous silica （MS）, 3-aminopropyltriethoxysilane （APTES） modified mesoporous silica （AMS）, bis（3- trimethoxysilylpropyl）amine modified mesoporous silica （BAMS） and APTES modified solid spherical silica （AS） were prepared and used to immobilize metallocene catalysts for ethylene polymerization. Gel permeation chromatography results showed that polyethylenes （PEs） catalyzed by AMS （or BAMS） supported metallocene catalysts at the molar ratios of Al/Zr = 100, 300 and 500 were of bimodal molecular weight distribution （BMWD）; while PEs catalyzed by the above catalysts at the molar ratios of Al/Zr 〉 800 were of monomodal molecular weight distribution （MMWD）. However, MS （or AS） supported metallocene catalysts could only produce PEs with MMWD in spite of the molar ratio of Al/Zr. It was because that AMS （or BAMS） supported catalysts possessed two active sites for ethylene polymerization at low molar ratios of Al/Zr due to the combination effects of mesopore geometrical constraint and amino groups of the supports, which was confirmed by X-ray photoelectron spectroscopy. This brings forward a novel and easy method for the synthesis of polyolefin with BMWD.

Coal Tar Derived Metallocene Catalyst for Polymerization of 1-Decene into Low-viscosity Poly-α-Olefin Lubricating Base Oil

The production of poly-α-olefins(PAOs)has attracted attention due to their excellent viscosity-temperature dependence,wear characteristics,oxidative properties,and high thermal stability.In this study,indene extracted during coal tar refining was used as a raw material to synthesize a bis(indenyl)zirconium dichloride metallocene catalyst.A PAO with low viscosity and a high viscosity index was produced via the oligomerization of 1-decene in the presence of both the prepared metallocene and a methylaluminoxane(MAO)co-catalyst.Notably,the effects of different synthesis reaction parameters,such as Al:Zr ratio,amount of catalyst,and reaction temperature,on the conversion ratio and product selectivity were investigated in detail.The produced PAO was thoroughly characterized using Fourier-transform infrared,^(13)C,and^(1)H nuclear magnetic resonance spectroscopies;gas chromatography;and viscosity measurements.At 70℃,the metallocene catalyst created more stable active sites.In addition,the alkylation effect of MAO was noticeable.Interestingly,the obtained catalysis results demonstrated that a high conversion ratio of~93%was achieved at a low reaction temperature of 70℃,with a catalyst dosage of 0.0848 mmol and Al:Zr ratio of 8.48mmol:0.0848mmol.Moreover,under these optimal conditions,the kinematic viscosity of PAO was 4.25 mm2/s at 100℃,and the viscosity index was 139,indicating good viscosity-temperature properties.

Synthesis, Characterization and Application of A Novel Carbon Bridged Half-metallocene Chromium Catalyst for Methyl Methacrylate Polymerization

A new carbon bridged cyclopentadienyl chromium complex of the type [（C5H4）C（CH3）2 CH2（C5H4N）]CrCl2 was prepared by treatment of CrCl3·（THF）3 in THF solution with the lithium salt of ligand containing cyclopentadienyl and pyridyl groups. The chromium complex was characterized by 1H NMR and elemental analysis（EA）, and the crystal structure was determined by X-ray diffraction analysis. Activated by Al（i-Bu）3, the chromium complex displayed a very high activity for methyl methacrylate（MMA） polymerization. After 24 hours,more than 95.5% MMA was converted to polymethyl methacrylate（PMMA） with a viscosity average molecular weight（Wη） of 416000 g·mol-1 at 60 ℃ for MMA/ Al（i-Bu）3 /chromium catalyst molar ratio of up to 2000：20：1. Effects of temperature, molar ratios of MMA/catalyst and catalyst/cocatalyst on the polymerization have been studied. The high conversion of MMA and high molecular weight of PMMA with narrow molecular weight distribution is caused by the unique stable active site formed by the new chromium complex and aluminum cocatalyst.

MESOPOROUS ACID SOLID AS A CARRIER FOR METALLOCENE CATALYST IN ETHYLENE POLYMERIZATION AND A CATALYST IN CATALYTIC DEGRADATION OF POLYETHYLENE

The possibility of mesoporous acid solid as a carder for metallocene catalyst in ethylene polymerization and catalyst for polyethylene （PE） catalytic degradation was investigated. Here, HMCM-41 and AIMCM-41, and mesoporous silicoaluminophosphate molecular sieves （SAPO1 and SAPO2） were synthesized and used as acid solid. Much more gases were produced during catalytic degradation in PE/acid solid mixtures via in situ polymerization than those via physical mixing. The particle size distribution results exhibited that the particle size of SAPO1 in the PE/SAPOI mixture via in situ polymerization was about 1/14 times of that of the original SAPO1 or SAPO1-supported metallocene catalyst. This work shows a novel technology for chemical recycling of polyolefin.

Effect of Polymerization Temperature on Propylene Polymerization with C_s-symmetric Metallocene Catalyst

A novel highly active C-s-symmetric metallocene catalyst namely: meso-dimethylsilylbis (2,4,6-trimethyl-1 -indenyl)zirconium dichloride is presented. The effect of polymerization temperature (0-70 degrees C) on the catalyst performance for propylene polymerization has been investigated. This catalyst shows very high activity at 50 degrees C which is higher than the activity of the racemic analogue, and the resulted polypropylene is amorphous in nature with isotactic pentad content [mmmm] of 12 %.

The Synthesis of Isotactic Polypropylene with Spherical Morphology via Supported Metallocene Catalyst

Polymerization of propylene was carried out under bulk process at 70 degrees C using the supported metallocene catalyst with four kinds of SiO2 as carrier with triethylaluminum used as cocatalyst. The morphology of the products was studied by SEM. It was found the property of the carriers gave great effect on the fine structure of the products as well as the apperance.

HOMO- AND COPOLYMERIZATION OF ETHYLENE CATALYZED BY ANSA-METALLOCENES WITH DOUBLY HETERO-BRIDGES

Three ansa-metallocenes(Me_2C)(Me_2Si)Cp_2TiCl_2(1),[(CH_2)_5C](Me_2Si)Cp_2TiCl_2 (2)and (Me_2C)(Me_2Si)Cp_2ZrCl_2 (3)with larger dihedral angles and longer distance from metal to the center of Cp planes were synthesized and used as catalysts for ethylene polymerization in the presence of methylaluminoxane (MAO).In the case of ethylene polymerization,compared the feature structures of unbridged metallocenes, singly bridged metallocenes and doubly bridged metallocenes 1,2,3,there exhibit the relationship bet...

Propylene Polymerization Catalyzed by Bis(R_3-indenyl) Zirconium Bichloride/Aluminoxane──Synthesis of Metallocenes and Influence ofSolvent Polarity on Polymerization

Three unbridged metallocenes, bis(2,4,7-Me3-indenyl)zirconium dichloride(1) , bis(2-Me-4, 7-Et2-indenyl)zirconium dichloride (2) and bis (2, 4, 6-Me3-indenyl) zirconium dichloride (3) were synthesized. The effect of solvent polarity on propylene polymerization catalyzed by the metallocenes in the presence of methylaluminoxane(MAO) and triisobutylaluminum(TIBA) was investigated in the toluene/CH2Cl2 mixed solvent. Changing the solvent polarity was found to influence the catalytic activity, polymer molecular weight and stereospecificity of the catalysts. The changes in the position of the substituents on the ligand caused the different responses of the catalyst to the changes in solvent polarity. The isotactic stereosequence of polypropylene was found to increase with the increase in the polarity of the reaction medium.

聚丙烯催化剂研究进展

综述了聚丙烯(PP)催化剂的研究进展,包括Ziegler-Natta(Z-N)、茂金属、后过渡金属及复合催化剂,重点分析了载体、助催化剂、给电子体对Z-N催化剂活性、结构及性能的影响,并对比了各类催化剂的优缺点。指出今后需在反应机理、合成工艺、聚合物形貌控制等方面对催化剂进行深入研究和设计,在保证催化剂成本的同时,产出性能指标更加优异的PP产品。

烯烃聚合用茂金属催化剂及其载体

由于在α-烯烃、二烯烃以及苯乙烯聚合中的单中心催化性能,茂金属催化剂备受学术界和企业界的关注。为了进一步提高催化剂的活性、利用效率以及防止粘釜现象的发生和有效控制催化产物的微形貌,茂金属催化剂通常要负载在载体上进行使用。对茂金属催化剂的基本结构及发展历程进行了介绍,综述了茂金属催化剂载体的种类,包括MgCl 2、分子筛或多孔材料、层状材料、聚合物、碳纳米管和石墨、硅胶载体,总结了其自负载的特点和性能,指出开发高活性催化剂及其高效负载化工艺仍是今后该领域的重要工作。

初生态低缠结超高分子量聚乙烯催化剂研究进展

超高分子量聚乙烯(UHMWPE)具有高耐磨性、高强度和刚度、轻质、耐腐蚀、低摩擦系数、生物相容性等特点,作为一种优异的工程塑料广泛应用于高端新材料等各领域,而调控高分子链的缠结程度对于更好地应用UHMWPE至关重要。从均相催化和非均相催化两方面综述了制备初生态低缠结UHMWPE的催化剂技术的研究进展,其中,单中心催化体系和修饰型Ziegler-Natta催化剂在制备初生态低缠结UHMWPE的工业应用中前景广阔。

ⅣB族金属催化丙烯与烯烃极性单体共聚研究进展

对聚烯烃进行功能化可弥补传统聚烯烃非极性和表面能低的不足。目前常见的是乙烯与极性单体共聚,而聚丙烯功能化修饰报道较少。综述了ⅣB族金属催化丙烯与烯烃极性单体共聚对聚丙烯材料功能化的发展,主要以锆金属和铪金属为催化剂进行介绍,重点按引入氧原子、氮原子、硼原子和硅原子种类讨论了聚丙烯功能化的研究进展,指出了茂金属催化剂在聚丙烯功能化研究中的挑战,并对茂金属催化丙烯与烯烃极性单体共聚的发展进行了展望。

茂金属催化剂催化丙烯与乙烯共聚合研究

以桥联茂金属催化剂催化丙烯与乙烯共聚合,探究了助催化剂、反应温度、共聚单体用量、n(Al)∶n(Zr)和n(B)∶n(Zr)等对丙烯与乙烯共聚合及聚合物结构与性能的影响,优化了间歇溶液聚合的工艺参数,制备了丙烯-乙烯无规共聚物。在合适条件下,该催化体系的活性最高达2.05×10^(7)g/(mol·h)。溶液聚合小试最佳工艺条件:反应温度为70℃,n(Al)∶n(Zr)=150,n(B)∶n(Zr)=1.5。

我国高端聚烯烃产业发展现状分析

随着我国消费结构不断升级,战略新兴产业不断发展,对高端聚烯烃产品的需求也不断增加。对我国茂金属聚乙烯、茂金属聚丙烯、乙烯-醋酸乙烯树脂、超高分子量聚乙烯树脂、聚烯烃弹性体、乙烯-乙烯醇共聚树脂、环烯烃聚合物、交联聚乙烯等高端聚烯烃的产业现状、存在问题及制约因素进行了分析,对高端聚烯烃产业存在的问题进行了探讨并对未来发展提出了建议。

乙烯聚合催化剂发展综述报告

聚乙烯具有质轻、无味、无毒、优异的耐湿性和耐热性等性能,广泛应用于注塑、管材、板材、薄膜类等制品。聚乙烯材料高性能新产品的开发高度依赖于乙烯聚合新型催化剂的研发,故乙烯聚合催化剂的设计一直是国内外研究的热点。本文综述了不同时期聚乙烯催化剂的研究进展,主要从铬基、Ziegler-Natta、茂金属、非茂金属和复合金属催化剂五个方面展开论述。

固体甲基铝氧烷用于负载茂金属催化剂的研究

在烯烃聚合领域,甲基铝氧烷(MAO)是茂金属催化剂体系中最常用的助催化剂。本研究以苯甲酸催化三甲基铝(TMA)受控水解生成甲基铝氧烷(MAO),经热解过程后合成了一种不溶形式的固体聚甲基铝氧烷(sMAO)。系统考察了制备过程条件如前驱体三甲基铝浓度、热解温度、己烷用量等对产品sMAO形貌的影响规律。利用扫描电镜、电感耦合等离子体质谱仪、激光粒度分布仪等手段对sMAO进行了分析表征。sMAO可以作为载体负载茂金属化合物,用于乙烯淤浆聚合反应。以rac-乙烯双(1-茚基)二氯化锆为茂金属活性组分,将其固定化于sMAO载体上,可在己烷溶剂中获得极高的催化聚合活性,与传统硅胶负载茂金属催化剂相比提高了4~5倍。

无规共聚聚丙烯研究进展

综述了用于生产无规共聚聚丙烯的Ziegler-Natta催化剂和茂金属催化剂的性能及由两种催化剂制备的无规共聚聚丙烯的特点,并总结了近年来关于乙烯-丙烯无规共聚物、丙烯-1-丁烯无规共聚物和其他几种典型的无规共聚聚丙烯产品的聚合机理、聚合工艺及共聚物物理性能的研究进展。