茂金属催化剂及烯烃高分子材料研究新进展

介绍茂金属催化剂的一般组成、主要特性及在烯烃聚合催化技术所具有的显著优势和近年研究取得的一些新进展。详细叙述采用茂金属催化工艺技术合成的一些烯烃聚合物,如聚乙烯(PE)、聚丙烯(PP)、间规聚苯乙烯(sPS)、茂金属环烯烃、茂金属乙丙橡胶、茂金属乙烯-辛烯共聚物等。这些茂金属聚合物与传统催化剂合成的聚合物相比,具有更优良的特性和更广阔的应用范围。许多用传统催化剂难以合成的材料,在采用茂金属催化技术后变得容易进行。在烯烃聚合物合成中茂金属催化剂正在替代传统催化剂。茂金属催化剂在全球增长非常迅速,具有广阔的应用和市场前景。     

茂金属催化剂及新型橡胶

概述了茂金属催化剂的历史发展情况。介绍了茂金属催化剂的性能特点,如单一活性中心、超高活性、工艺性能好、可控制烯烃以特殊方式聚合等。综述了茂金属催化新型弹性体的结构与性能。用茂金属催化剂可以合成具有特定结构和性能的弹性体,这些弹性体正在消除塑料与橡胶在生产工艺方面的明显差别,突破了传统聚合物结构与性能的关系准则。     

单活性中心聚合物的催化技术及工艺进展

综述了近年来主要聚合物生产商采用的单活性中心(包括茂金属催化剂和非茂金属催化剂)催化技术现状及生产装置工艺的最新进展情况。与传统催化剂合成的聚合物相比,单活性中心催化剂生产的聚烯烃具有更优良的特性和更广阔的应用领域,在全球增长非常迅速,具有非常好的市场发展前景。     

茂金属催化剂及其聚烯烃的开发

报导了中国石油化工总公司石油化工科学研究院近两年茂金属催化剂及其催化烯烃聚合技术的研究进展，间规选择性复合型茂金属论剂技术已开发成功；用基催化珙烯聚合，在国内首次得到合格的商业用间规聚丙烯；完成了限制几何构型复合型茂金属的合成探索，获得具有较好活性的系列催化剂。实现了茂金属催化剂的负载化为茂金属催化剂在相烯烃聚合工艺中的应用奠定了基础。     

载体型茂金属催化剂

对载体型茂金属催化剂研究进展进行了评述,讨论了茂金属催化剂载体化方法,载体和茂金属载体化对催化剂性能和聚合物性质的影响以及各种载体型茂金属催化剂对烯烃聚合的催化行为,还简要介绍了生产双峰分子量分布聚合物的双金属催化剂。     

茂金属催化不饱和聚合物加氢研究进展

介绍了茂金属在催化不饱和聚合物加氢的应用、机理、高效催化体系及合成方法的研究进展,重点综述了加氢活性高的茂钛催化体系。指出茂金属是一种很有市场前景的加氢催化剂,多元化降低成本是茂金属催化不饱和聚合物加氢工业突破的关键。     

单环戊二烯基钛类茂金属催化剂的应用

综述了限制几何构型茂金属(单环戊二烯基钛类茂金属)催化剂在烯烃聚合方面的应用,包括乙烯/链烯烃共聚合,长链α-烯烃和降冰片烯的共聚,含乙烯端基大分子单体的共聚,乙烯和苯乙烯的聚合以及高分子量的无规聚丙烯的合成。研究表明,单环戊二烯基允许各种单体的插入,环戊二烯上的取代基团及配体基团的引入,影响催化烯烃聚合活性,控制聚合物的分子量和聚合分散度。     

有机载体负载茂金属催化剂研究进展

综述了近年来天然高分子、聚合物等有机载体用于负载茂金属催化剂的研究现状,评述了有机载体型茂金属催化剂的特点、负载方式、负载化对催化烯烃聚合性能和聚合物性能的影响。分析表明,进一步提高有机载体型茂金属催化剂的活性、改善有机载体的形态和结构仍是值得探索的课题。     

烯烃聚合非茂金属催化剂的研究进展

综述了近年来用于烯烃聚合的非茂金属催化剂的研究进展，分别介绍了非茂前过渡金属类催化剂和非茂后过渡金属类催化剂在烯烃聚合中的应用及催化性能。非茂前过渡金属催化剂具有催化活性高、聚合物结构可控和分散性好的特点，二十世纪九十年代之后已得到了快速的发展。后过渡金属催化剂(特别是Ni和Pd)由于具有独特的性能和较弱的亲氧性，能够合成高支化、具有拓扑结构的聚乙烯并且能催化烯烃与极性单体共聚。简述了α-二亚胺镍和钯催化剂在高支化聚乙烯和催化烯烃与极性单体直接共聚方面的应用，最后对非茂金属催化剂的未来发展进行了展望。     

“焊接”茂金属催化合成的聚烯烃

美国明尼苏达大学和埃克森美孚(ＥｘｘｏｎＭｏｂｉｌ)化学公司的研究人员已经证明 ,茂金属催化聚合的单晶质聚乙烯(ＰＥ)和聚丙烯 (ＰＰ)可以“焊接”形成高强度接头。这是由于茂金属催化合成的聚合物具有结晶结构 ,结晶结构一直延伸到聚合物层的边缘 ,当聚合物熔融时能与相邻层“纤缠”的结果。齐格勒 纳塔催化剂生产的聚烯烃粘合性不良是由于在界面处堆积的是非晶质聚合物。粘合强度有显著差异 ,这可追溯到聚合催化剂。齐格勒 纳塔催化剂生产的ＰＥ和ＰＰ间形成的焊缝极为脆弱 ,而茂金属ＰＰ和ＰＥ的接头强度超过茂金属ＰＥ薄膜的强度。…     

茂金属聚合物的加工与应用现状

综述了茂金属聚合物加工对工艺和设备的要求，同时对茂金属聚合物的应用现状和发展趋势做了探讨。     

茂金属聚合物进展

综述了茂金属聚合物的新进展 ,重点介绍了五种茂金属聚合物的性能、应用现状和发展趋势。     

茂金属催化剂及烯烃齐聚物研究进展

21世纪是全新的科学技术时代,茂金属聚合物是化学工业中新型树脂产品,其产品开发进展很快。本文综述了近些年茂金属催化剂的发展状况,系统的介绍了茂金属催化剂的主要特征和优势,并对茂金属烯烃聚合物的加工和应用情况进行了阐述。     

用于选择性氢化共轭二烯聚合物的茂金属催化体系研究进展

简要介绍了茂金属催化剂的结构及催化机理,综述了近年来国内外茂金属催化体系用于选择性氢化共轭二烯聚合物方面的研究进展,对比了不同类型茂金属催化剂在氢化SBS、SIS时的活性,对国内相关产业的发展提出了建议。     

Thermal and rheological studies on the molecular composition and structure of metallocene‐ and Ziegler–Natta‐catalyzed ethylene–α‐olefin copolymers

The relationship between the molecular structure and the thermal and rheological behaviors of metallocene‐ and Ziegler–Natta (ZN)‐catalyzed ethylene copolymers and high‐density polyethylenes was studied. Of special interest in this work were the differences and similarities of the metallocene‐catalyzed (homogeneous) polymers with conventional coordination‐catalyzed (heterogeneous) polyethylenes and low‐density polyethylenes. The short‐chain branching distribution was analyzed with stepwise crystallization by differential scanning calorimetry and by dynamic mechanical analysis. The metallocene copolymers exhibited much more effective comonomer incorporation in the chain than the ZN copolymers; they also exhibited narrower lamellar thickness distributions. Homogeneous, vanadium‐catalyzed ZN copolymers displayed a very similar comonomer incorporation to metallocene copolymers at the same density level. The small amplitude rheological measurements revealed the expected trend of increasing viscosity with weight‐average molecular weight and shear‐thinning tendency with polydispersity for the heterogeneous linear low‐density polyethylene and very‐low‐density polyethylene resins. The high activation energy values (34–53 kJ/mol) and elevated elasticity found for some of our experimental metallocene polymers suggest the presence of long‐chain branching in these polymers. This was also supported by the comparison of the relationship between low shear rate viscosity and molecular weight. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1140–1156, 2002     

Metallocene‐based functionalized polyolefins as compatibilizers in polyolefin nanocomposites

This article reports a study of some functionalized polyolefins evaluated as compatibilizers in polyethylene nanocomposites. The functionalized polymers were prepared by direct metallocene‐mediated copolymerizations of ethylene and a functional comonomer. The prepared nanocomposites were evaluated for mechanical and barrier property enhancement. A good combination of mechanical and barrier properties was obtained with the metallocene‐based functionalized polyethylene. The toughness–stiffness balance was better than or comparable to that achieved with conventional functionalized polymers such as maleic anhydride grafted polyethylene. The results also indicated that these metallocene‐based functionalized polyolefins, when used as compatibilizers, could have relatively higher molar masses and lower functionality than those of conventional post‐reactor‐modified compatibilizers, and so the drawbacks associated with the latter could be avoided. Their inherent properties could also further improve the final nanocomposite properties. This was attributed to the more homogeneous nature of metallocene‐catalyzed polymers in comparison with post‐reactor‐modified products. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1094–1100, 2004     

Rotational moulding of metallocene polyethylenes

Abstract

This paper compares the rotomouldability and mechanical properties of conventional polyethylenes with metallocene polymers having a similar melt flowrate or the same density. The rotomouldability has been evaluated in terms of bubble removal, cycle times, and heat stability during the moulding process. The mechanical properties, such as tensile strength and peak impact energy, were measured on parts produced using a variety of moulding conditions. It was found that the metallocene polymers display greater toughness if subjected to the same moulding conditions as the conventional polymers. Conversely, the same toughness can be obtained in both materials if shorter cycle times are used for the metallocenes. This behaviour has been linked to the relaxation behaviour of the molecules in the solid state. Other material parameters, such as the nature of the comonomer, the long chain branching density, and the crystalline morphology were studied by NMR, DSC, and polarising light microscopy. The differences between the molecular structures of the two types of polyethylene can be used to explain why the metallocene materials possess many rheological and other characteristics that are desirable in rotational moulding.     

Melt fracture of HDPEs: Metallocene versus Ziegler–Natta and broad MWD effects

The melt fracture of high-density polyethylenes (HDPEs) is studied primarily as a function of molecular weight and its distribution for broad molecular weight distribution metallocene and Ziegler–Natta catalyst resins. It is found that sharkskin and other melt fracture phenomena are very different for these two classes of polymers, although their rheological behaviors are nearly the same for many of these. Moreover, the metallocene HDPE shows significant slip at the die wall without exhibiting stick-slip transition. Important correlations are derived between the critical conditions for the onset of melt fracture and molecular characteristics.