茂金属催化剂的发展及工业化

讨论了茂金属的发展及其特性，介绍和总结了茂金属聚烯烃的工业化及其最新进展。并从中国茂金属聚烯烃技术发展的实情提出了一些建议。     

茂金属聚烯烃

介绍了国内外金属催化剂和茂金属聚烯烃技术、特点、研究开发和工业化状况，并对我国发展提出了建议。     

我国茂金属催化剂及其聚类烃的开发进展

论述了我国茂金属催化剂及其聚烯烃的开发进展，提出了具体的开发建议。     

茂金属聚烯烃催化剂的设计

回顾了茂金属催化剂聚烯烃工艺、技术和催化剂的发展，根据茂金属催化聚烯烃的机理，探讨了茂金属催化剂结构与催化活性、立构选择性的关系，研究了催化剂设计的原理和方法。     

茂金属催化剂及工业应用

茂金属催化剂是一种具有均匀的活性中心，分子裁剪必和结构可控性的新型催化剂，用它催化制得具有特殊性能的茂金属聚烯烃，本文简要介绍了茂金属催化剂的结构特点及在聚烯烃生产中的应用。     

茂金属加合物技术首次工业试验

采用中国石油化工股份有限公司茂金属加合物技术制备茂金属加合物,并进行负载化研究;完成了茂金属加合物催化剂催化乙烯聚合以及乙烯与α-烯烃共聚合的淤浆、环管淤浆、气相流化床工艺的中试;在中试的基础上,茂金属加合物催化剂于60kt／a气相流化床聚乙烯生产装置上成功进行了工业试验。探索了茂金属催化剂与Ziegler催化剂的切换技术,研究了催化剂组成和聚合工艺参数对聚乙烯树脂性能的影响。用所得茂金属聚乙烯树脂加工成的薄膜具有较好的透明性,并表现出了优异的落镖冲击强度和撕裂强度。     

Synthesis of polyethylene using ultrasonic energy with a metallocene catalyst

Ethylene polymer was synthesized by the treatment of a metallocene catalyst Zr(CP)₂Cl₂ solution with ultrasonic energy. Ultrasonic energy irradiation was used to change the polymer structure of the formed polymer. Different ultrasonic energy irradiation times were applied to the metallocene catalyst solution. The ultrasonic energy had an effect on the average molecular weight, molecular weight distribution, and polymer productivity. A lower average molecular weight and a narrower molecular weight distribution were produced with a longer ultrasonic irradiation time. The polymer productivity was almost constant when the metallocene catalyst was treated with ultrasonic energy. Finer polyethylene particles were produced with longer ultrasonic irradiation times. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 756–759, 2006     

茂金属聚乙烯加工技术评述

综述了几种茂金属聚乙烯加工技术的特点及进展情况,指出在单反应器中用茂－茂复配催化剂生产双峰或宽峰聚乙烯是解决茂金属聚乙烯加工困难的最优技术,开发这一技术应是今后努力的方向。     

In situ fiber composites based on metallocene polyethylene matrices

Binary blends of metallocene polyethylenes with polyethylenes and polypropylene were made in a co‐rotating twin‐screw extruder. A stretching process was carried out afterwards in the melt state at the extruder's exit to study the effect of the induced orientation on their thermal and tensile properties. Capillary rheometry was performed to the neat polymers to determine the viscosity ratios of the blend components as a function of the shear rate. SEM and Micro‐Raman analyses were done to study the morphology of the stretched and nonstretched blends. As expected, an increase in the modulus and tensile stress was obtained through blending. Additionally, the elastomeric behavior of the metallocene polyethylene (mPE) sample is observed in all blends and it was not lost through blending. Nevertheless, all blends without stretching exhibited a negative deviation of the linear additivity rule of blending. The stretching of the blends made with metallocene polyethylenes as matrices and other types of PEs as dispersed phase did not improve the tensile properties, although some differences in the dispersed phases were found by DSC, and microfibrils could be seen in the drawn mPE/HDPE blend. However, blending with PP produced an improvement in the modulus and tensile stress of the drawn samples in comparison to their undrawn counterpart. The tensile stresses of PP blends are more sensitive to the drawing process than the modulus, which can be attributed to the appearance of large fibril fractions during this process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Influence of supported metallocene catalysts on polymer tacticity

Metallocene catalysts in dissolved form are in most cases unsuitable for the production of polyethylene or polypropylene on an industrial scale. In order to use them in existing technical processes, metallocenes have to be supported. C_s-symmetric zirconocenes show a high activity and no leaching additional triisobutyl aluminum is used as scavenger and MAO-covered silica for heterogenization. The aluminum : zirconium ratio can be reduced to values of 500:1 to get optimal activities. The syndiotacticity of the obtained polypropylene is lower compared with polymers of the homogeneous catalyst and decreases strongly with a thinner propene concentration. This revised version was published online in June 2006 with corrections to the Cover Date.     

Isobutylaluminum aryloxides as metallocene activators in Homo‐ and copolymerization of olefins

The article describes that sterically hindered isobutylaluminum aryloxides with bulky ^tBu substituents at 2,6‐ positions of aryl fragment, i.e. (2,6‐di‐^tBu,4‐R‐C₆H₂O)AlⁱBu₂ (R = H ( 1‐DTBP ), Me ( 1‐BHT ), ^tBu ( 1‐TTBP )) and (2,6‐di‐^tBu,4‐R‐C₆H₂O)₂AlⁱBu (R=H( 2‐DTBP ), Me( 2‐BHT )) can serve as cocatalysts for metallocene complexes. Isobutylaluminum aryloxides have been applied for activation of rac‐Et(2‐MeInd)₂ZrMe₂ in homopolymerization of ethylene, propylene, copolymerization of ethylene and propylene, and terpolymerization of ethylene, propylene, and 5‐ethylidene‐2‐norbornene at Al/Zr = 300 mol/mol. The type of R substituent at 4‐position has a significant effect on catalyst activity. The catalytic system with 1‐TTBP showed the highest activity in all homo‐ and copolymerization processes. Diisobutylaluminum aryloxides provide much higher activity to the systems in all polymerization processes and stronger ability for propylene incorporation in copolymer than diaryloxides. The activities of the systems with isobutylaluminum aryloxides are similar or exceed that of the system with MAO as activator as have shown for propylene polymerization. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43276.     

Investigation of ethylene and styrene copolymerization initiated with dinuclear constrained geometry catalysts holding polymethylene as a bridging ligand and indenyl as a cyclopentadienyl derivative

A series of polymethylene‐bridged dinuclear constrained geometry catalysts (CGC) [Me₂Si(Ind)(N^tBu) TiCl₂]₂[(CH₂)_n] ( 1 , n = 6; 2 , n = 9; 3 , n = 12) were synthesized to study the copolymerization of ethylene and styrene. The experiments display that the polymerization activity of the dinuclear catalysts increased in the order of 1 < 2 < 3 , which indicated that the dinuclear CGC with the longest methylene units as a bridge showed the greatest activity. According to the activity correlation with the monomer ratio, all the catalysts exhibited maximum polymerization activity at the monomer ratio of ([styrene]/[ethylene]) of 2. The dinuclear CGC 2 and 3 represented excellent characteristics of styrene reactivity while catalyst 1 represented considerably low styrene reactivity. The relation between the molecular weights of the polymers and the catalysts used in the polymerization is not straightforward. The steric interference in catalyst 1 , containing just six methylene bridges, can be applied to explain not only the strikingly decreased activity but also the very low styrene content in the copolymer. In contrast, the electronic effect seems to be more pronounced in manipulating the polymerization properties of catalysts 2 and 3 having nine and 12 methylene bridges, respectively. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2469–2474, 2003     

Synthesis of ethylene and norbornene copolymer with metallocene catalysts and characteristic analysis

To synthesis ethylene (E) and norbornene (NB) copolymer with high glass transition temperature and transparency, three metallocene catalysts with different symmetric structure were evaluated, respectively. The catalyst activity, NB fraction in copolymer and the transparency of copolymers produced under various conditions were investigated. It has been found that C₂ symmetric catalyst such as rac‐[En(Ind)₂]ZrCl₂ was the best choice to produce copolymer with high NB fraction while keeping high catalyst activity. Furthermore, the effects of reaction conditions on activity of rac‐[En(Ind)₂]ZrCl₂ and the resultant copolymer structure have also been thoroughly studied. The results indicate that increasing the NB/E ratio is the effective way to increase NB content of copolymer when NB/E ratio is less than 20. However, when NB/E ratio is over 20, further increase in NB/E ratio will lead to significant lower catalyst activity and very limited increase in NB content of copolymer. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Full‐range kinetic study on bulk syndiotactic polymerization of styrene with homogeneous metallocene catalysis

By choosing a proper agitator and reinforcing its stirring shear, powdery syndiotactic polystyrene (sPS) is prepared in a bulk precipitation process with two homogeneous metallocene catalyst systems [Cp*TiX₃/MAO/TIBA (X = Cl or OPhOMe)]. A full‐range kinetics study of the heterogeneous polymerization is performed in detail to produce this kind of powdery sPS in an industrial process. A typical curve of conversion versus time takes an S shape and an obvious acceleration phenomenon occurs in the middle stage of the polymerization, although the polymer–monomer gel is avoided. The viscous‐average molecular weight of sPS goes through a peculiar increasing–decreasing–increasing change during the bulk polymerization process. These phenomena are viewed in terms of the two‐phase polymerization mechanism and the overheating in particles during polymerization. The influence of the metallocene catalyst type and concentration, MAO/Ti ratio, triisobutyl aluminum (TIBA)/Ti ratio, and polymerization temperature on the polymerization kinetics are investigated. TIBA has dual effects on the polymerization. A small amount of TIBA in the catalyst system promotes polymerization, but more TIBA leads to a low molecular weight sPS. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2635–2643, 2002     

Characterization and evaluation of supported rac‐dimethylsilylenebis(indenyl)zirconium dichloride on ethylene polymerization

rac‐Dimethylsilylenebis(indenyl)zirconium dichloride was grafted onto commercial methyl aluminoxane modified silica (SMAO) at different loadings (0.1–1.5 wt % Zr/SMAO). Supported catalysts were evaluated in ethylene polymerization with isoprenylaluminum as a cocatalyst. The characterization of two supported catalysts bearing 0.3 and 0.8 wt % Zr/SiO₂ by extended X‐ray absorption fine structure indicated that the number and the intensity of the peaks beyond the coordination shell, associated with the next nearest neighbors, depended on the Zr concentration. For the catalyst with a higher Zr content, only one peak (2.8 Å) was observed. The catalyst with 0.3 wt % Zr/SMAO presented two small peaks at 2.8 and 3.8 Å. Polymers produced with the supported catalysts presented lower crystallinity and higher molar mass and polydispersity values in comparison to that produced by the homogeneous one. Gel permeation chromatogram deconvolution suggested the presence of four catalyst sites for the supported systems. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009