【作者】 楼均勤；

【导师】 范志强；

【作者基本信息】 浙江大学 ， 高分子化学与物理， 2009， 博士

【摘要】 负载型钛/镁催化剂在聚丙烯的工业生产中占有主导地位。这类催化剂一般均通过在聚合体系中加入给电子化合物(外给电子体)来提高立体定向能力,合成高立构规整度的聚丙烯(PP)。在利用序贯聚合工艺合成PP/EPR(EPR：乙烯-丙烯共聚物)反应器合金时,外给电子体在影响PP链结构的同时还会影响.EPR的组成和结构。因此,深入研究外给电子体在丙烯聚合及乙丙共聚体系中的作用机理具有重要的意义,探索新型的外给电子体以更好地调控和优化PP及PP/EPR合金的结构与性能则是具有重要应用价值的问题。本文较系统地研究结构为ROCH3的醚类化合物及其与R2’Si(OCH3)2类硅氧烷化合物的混合物作为外给电子体对TiCl4/DIBP/MgCl2 (DQcat)-Al(C2H5)3(TEA)催化丙烯聚合或乙烯-丙烯共聚合反应的影响,考察聚合活性、分子量、聚合物链结构及活性中心分布的变化规律,在此基础上提出外给电子体作用的机理模型。首先合成了4种醚类化合物：n-BuOCH3 (ED-1)、PhCH2OCH3 (ED-2)、i-BuOCH3 (ED-3)、CH3(CH2)3CH(C2H5)CH2OCH3 (ED-4)。分别将四种醚作为外给龟子体加入到DQcat-TEA催化丙烯聚合体系后,发现所得聚丙烯的等规度并未提高,只是提高了沸腾庚烷可溶物的立构规整度。将四种醚与Ph2Si(OMe)2(DDS)分别组成复合外给电子体添加到DQcat-TEA催化体系时,随醚的结构不同,聚合活性可高于仅添加DDS的体系或略有降低。在H2存在下,添加立体位阻相对较大的ED-3和ED-4与DDS的复合给电子体时,所得PP的等规度高于只加DDS的体系,也高于单纯提高DDS用量(由DDS/Ti=5提高到10)的体系,且PP分子量对氢气的敏感性强于单一DDS为外给电子体的体系。使用复合外给电子体合成的PP中具有极高等规度的链段含量增多,结晶度提高。研究了(cyclo-C5H9)2Si(OCH3)2 (DCPDMS)为外给电子体的作用,发现其产物PP的极高等规度的链段含量大幅度提高,分子量也显著提高。通过对DCPDMS影响活性中心分布的分析,提出了其特殊调节作用的微观机理。单醚与DCPDMS组成复合给电子体后引起的聚合活性和聚合物结构的改变与醚/DDS体系相似,只是变化的幅度较小。这些结果说明,以单醚/R2’Si(OCH3)2混合物为外给电子体与单纯的R2’Si(OCH3)2相比具有一些优点,主要是聚合活性和PP的等规度较高,氢调敏感性较好,且聚合物的链结构也有新的特点。研究了ED-1、ED-2、ED-4三种醚分别与DDS或DCPDMS组成复合外给电子体时DQcat-TEA催化乙烯-丙烯共聚反应的影响规律。与使用单一的DDS或DCPDMS为外给电子体的体系相比,复合外给电子体对聚合活性、共聚物组成分布和共聚物链结构等有显著的影响,表现在：共聚物中结晶性多嵌段性共聚物级分的含量增大(ED-2/DDS体系)或减小(ED-1/DDS、ED-1/DCPDMS体系),共聚物分子量提高(ED-2/DDS、ED-2/DCPDMS、ED-4/DCPDMS等体系)、嵌段共聚物级分的丙烯序列长度增大而无规共聚物级分的无规程度提高等。预计这些变化有利于改善EP共聚物与PP的相容性,并提高乙丙共聚物对PP的增韧效率。因此,将醚/硅氧烷类复合外给电子体应用于合成PP/EPR反应器合金将对聚合物结构产生有效的调节作用。基于负载型钛/镁催化剂的多活性中心特性及外给电子体在活性中心的镁上配位络合的机理模型,对复合外给电子体的作用机理提出了初步解释。本文的主要创新点有：1、首次研究了四种醚类化合物与R2’Si(OCH3)2组成的复合外给电子体对TiCl4/DIBP/MgCl2-TEA催化丙烯聚合的影响规律,发现其提高聚合活性、提高PP的等规度和改变其等规序列长度、改善催化体系的氢调敏感性等有应用价值的特点,并研究了其作用机理；2、首次研究了三种醚与R2’Si(OCH3)2组成的复合外给电子体对TiCl4/DIBP/MgCl2-TEA催化乙烯-丙烯聚合的影响规律,发现其能提高聚合活性、改变共聚物中嵌段共聚物级分的含量、改变共聚物的组成和序列分布,并研究了其作用机理；3、首次研究了TiCl4/DIBP/MgCl2-TEA/DCPDMS催化丙烯聚合体系的产物分子量及分子量分布、链结构和活性中心分布,并与DDS作为外给电子体及不含外给电子体的体系进行对比,对DCPDMS的显著提高催化体系立体定向性和产物分子量的特殊作用提出了机理解释。更多还原

【Abstract】 Supported Ti/Mg based Ziegler-Natta catalysts have played a major role in in-dustrial production of polypropylene for years. Electron donating complexes (External Donor) are generally introduced into this kind of polymerization system to increase its stereospecificity. In the synthesis of PP/EPR (EPR:ethylene propylene rubber) in-situ reactor alloy via sequential polymerization process, external donors not only affect chain structure of PP, but also the composition and chain structure of EPR. Therefore, it is of great significance to thoroughly study the effects and mechanism of external donor in Ti/Mg catalyst systems, and of course, novel external donors that can regu-late and optimize the structure and performance of PP and PP/EPR in situ reactor al-loy will find important applications in the industrial production of polyolefins.In this paper, effects of methyl ethers (ROCH3) and its mixture with siloxane (R2’Si(OCH3)2) as external donors in TiCl4/DIBP/MgCl2 (DQcat)-Al(C2H5)3 (TEA) catalyzed Propylene Polymerization and Its Copolymerization with Ethylene propyl-ene were systematically investigated, a mechanism model of external donor effects was proposed.Four ethers were synthesized:n-BuOCH3 (ED-1), PhCH2OCH3 (ED-2), i-BuOCH3 (ED-3), CH3(CH2)3CH(C2H5)CH2OCH3 (ED-4), which were then intro-duced into DQcat-TEA catalyzed propylene polymerization system as external donor respectively. The ethers exerted slight influences on the isotacticity of PP, but in-creased the tacticity of boiling n-heptane soluble fractions. Combination of those four ethers with Ph2Si (OMe)2(DDS) as composite external donors resulted in an increase or slightly reduction of catalytic activity, comparing to systems with only DDS as ex-ternal donor. In the presence of H2, more sterically hindered ED-3 and ED-4 in com-bination with DDS improved the isotacticity of PP and hydrogen response of the catalyst as compared to merely increased the DDS/Ti molar ratio from 5 to 10. PP synthesized with the composite external donors indicated an increase of the content of PP chains with extremely high isotacticity. Using of (cyclo-C5H9)2Si(OCH3)2 (DCPDMS) as external donor were also studied. It greatly improved the content of PP chains with extremely high isotacticity, and the molecular weight of PP was markedly increased.Based on the analysis of the distribution of the active centers, we proposed a mechanism model for the special effects of DCPDMS. Mixtures of methyl ethers and DCPDMS showed similar results, but the ether played exterted samller influences on the regulation effects of DCPDMS as the ether/DDS system in words of polymeriza-tion activity and polymer chain structure. These results indicated that the composite external donors showed some advantages over the single componet external do-nor(R2’Si(OCH3)2) system, such as higher activity and isotacticity, better hydrogen response, and new features in the PP chain structure.Effects of different composite external donors formed by ED-1, ED-2 and ED-4 mixed respectively with DDS or DCPDMS on DQcat-TEA catalyzed ethyl-ene-propylene copolymerization system were also studied. Comparing with the sys-tems with only DDS or DCPDMS, composite external donors performed apparent differences in catalytic activity, copolymer composition and chain structure. Crystal-line blocky copolymers in the product were increased by using ED-2/DDS system composite donors, while the molecular weight of copolymer were raised by using ED-2/DDS, ED-2/DCPDMS, ED-4/DCPDMS. With the use of composite external donors, the average sequence length of PP segments in the blocky copolymer fraction was increased, and randomness of the random copolymer fraction was improved. These changes in copolymer structure were expected to improve the compatibility between EPR and PP, and improve the toughening efficiency of EPR in PP/EPR in-reactor alloy. Based on the active center multiplicity of the supported Ti/Mg cata-lyst and mechanism model of external donor coordination with Mg in the vicinity of active center, a mechanissmic model of the effects of composite external donor in the catalytic system was proposed.Main novelties of the sissertaion:1. For the first time, effects of composite external donors formed by four ethers and R2’Si(OCH3)2 in TiCl4/DIBP/MgCl2-TEA catalyzed propylene polymerization were investigated. The composite external donors showed beneficial features like increas-ing activity, improving polymer isotacticity and improving hydrogen response of the catalyst, etc., and the mechanism of the effects were also studied.2. For the first time, effect of composite external donors formed by three ethers and R2’Si(OCH3)2 on TiCl4/DIBP/MgCl2-TEA catalyzed ethylene-propylene copolymeri-zation were investigated. The composite external donors showed beneficial features like increasing activity, changing the content of block copolymer fraction, copolymer composition and sequential distribution, etc., and the mechanism of the effects were also studied.3. For the first time, molecular weight and molecular weight distribution, chain struc-ture and active center distribution of PP catalyzed by TiCl4/DIBP/MgCl2-TEA/DCPDMS system were studied, which was compared to those of systems using DDS as external donor or no external donor. Mechanism for DCPDMS’s strong influences on catalyst sterospecificity and molecular weight in-creasing during polymerization was proposed as well.更多还原