【作者】 王苇；

【导师】 王立；

【作者基本信息】 浙江大学 ， 化学工艺， 2006， 硕士

【摘要】 低等规聚丙烯（LIPP）是一种新型的聚丙烯材料,在工业上该种聚丙烯主要由低载钛MgCl₂负载型的Ziegler-Natta催化剂来催化合成,但是目前该种催化剂的催化活性较低,因此如何提高低载钛的Ziegler-Natta催化剂的催化活性正日益受到学术界和产业界的重视。 本文采用一釜球磨法（工艺Ⅰ）制备了一种新型的复合载体MgCl₂/AlCl₃负载的Z-N催化剂,该制备工艺简单,操作方便,且钛含量可控,稳定性好,便于工程放大。研究了不同的AlCl₃/MgCl₂摩尔比对催化剂催化丙烯聚合的影响,发现AlCl₃/MgCl₂摩尔比为0.12、催化剂的载钛量为1.2wt%时,催化剂的催化丙烯聚合活性达到极大值,相对于MgCl₂单载体负载型Z-N催化剂,活性提高了近一倍;且采用该种工艺制备的催化剂催化丙烯聚合时,聚合动力学较平稳,适宜于工业化生产。发现较好的聚合条件是[Ti]=6.4*10^-6gTi/ml,Al/Ti（mol/mol）=40.T=40℃,t=30min,在这个条件下能得到低等规聚丙烯。在工艺Ⅰ的基础上,我们发展了一种一釜球磨法简化工艺（工艺Ⅱ）。与工艺Ⅰ制备的催化剂相比,在相同的载钛量的情况下,用工艺Ⅱ制备的复合载体AlCl₃/MgCl₂负载型Z-N催化剂催化丙烯聚合的活性较高,且聚合产物的等规度基本不变;工艺Ⅱ方法更简单,便于工程放大,所得催化剂催化丙烯聚合动力学较平稳,适宜于工业化生产。发现较好的聚合条件是[Ti]=6.4*10^-6gTi/ml,Al/Ti（mol/mol）=40,T=40℃,t=30min,在这个条件下能得到低等规聚丙烯。我们也用化学反应法制备了MgCl₂负载型Ziegler-Natta催化剂,所得催化剂的催化活性较高,且催化丙烯聚合动力学曲线较平稳,适宜于工业化生产。发现较好的聚合条件是[Ti]=1.1*10^-5gTi/ml,Al/Ti（mol/mol）=80.T=20℃,t=30min,在这个条件下能得到低等规聚丙烯。 由于聚丙烯是非极性聚合物,分子链上不含有极性基团,因而其相容性、粘结性、染色性和抗静电性不佳,极大限制了聚丙烯的应用,因此聚丙烯的改性研究显得非常必要,其中接枝改性和氯化改性是较为常用且有效的改性手段。 本文发展了一种溶胀法氯化新工艺,采用该工艺,粒径不大于0.18mm的等规聚丙烯粒子可以经水相悬浮氯化获得氯化较均匀的氯化聚丙烯:为了能使粒径大于0.18mm的等规聚丙烯粒子在水相悬浮氯化中获得较好的氯化效果,我们又发展了一种多段溶胀氯化新工艺,采用该工艺,能将粒径为0.35mm的等规聚丙烯粒子经氯化获得氯化较均匀的产物。所得氯化产物能全部溶于四氯化碳;在80℃下能全部溶于二甲苯,冷却后能成均一透明溶液。本文采用两步法接枝反应工艺对聚丙烯纤维进行接枝改性,有效地减少了均聚物的形成,反应具有很好的可控性,接枝率高。实验结果表明,较好的接枝反应条件为引发剂分解温度353K、引发剂浓度1.25%wt/v、接枝反应时间1h、接枝反应温度353K、接枝单体浓度1.09mol/l。同时我们用高压液相色谱研究了接枝反应机理,进而对聚丙烯上的接枝点数目以及每个接枝点上的平均接枝聚丙烯酸的链长进行了计算。结果表明在上述接枝反应条件下,平均914个丙烯单元有一个接枝点,每个接枝点上聚丙烯酸的平均接枝链长为136个丙烯酸单体。更多还原

【Abstract】 Low isotactic polypropylene （LIPP）, as a unique kind of polypropylene, is usually synthesized by low-Ti loading Ziegler-Natta catalyst system. However, the polymerization activity per-gram Ti of the traditional MgCl₂-supported catalyst is rather low and therefore how to improve the catalyst’s polymerization activity is being paid more and more attention.A one-pot ball-milling method （Process I） is used to prepare the MgCl₂/AlCl₃ supported Ziegler-Natta catalyst. The process is available in industry due to its simplicity, easily being controllable and good stability. The effects of different AlCl₃/MgCl₂ molar ratio of the catalyst on the propylene polymerization are investigated and the polymerization activity reaches its maximum 8478gPP/（gTi*h）, which is larger than that of MgCl₂-supported Ziegler-Natta catalyst （5500gPP/（gTi*h））, when the AlCl₃/MgCl₂ molar ratio is 0.12 and Ti-loading of the catalyst is 1.2wt%. LIPP can be synthesized under the optimum conditions: [Ti]=6.4*10^-6gTi/ml, Al/Ti （mol/mol） =40, T=40℃, t=30min. Based on Process I, a simplified method （Process II） is proposed. The polymerization activity of the catalyst prepared by Process II is higher than that of the catalyst prepared by Process I while both kinds of catalysts are of the same Ti-loading. LIPP is also synthesized under the optimum conditions: [Ti]=6.4*10^-6gTi/ml, Al/Ti （mol/mol） =40, T=40℃, t=30min. MgCl₂-supported Ziegler-Natta catalyst is also prepared using the chemical method. The polymerization activity of this kind of catalyst is much higher than that of the above two catalysts. LIPP can be synthesized using this kind of catalyst under the optimum conditions: [Ti]=1.1*10（-5）gTi/ml,Al/Ti （mol/mol） =80, T=20℃, t=30min.Although polypropylene has many advantages, its non-polar properties result in its low compatibility with other polar polymers and inorganic filling, and in turn confine its many uses as engineering plastics. Therefore the modification of polypropylene seems very significant. So far grafting modification and chlorination modification of polypropylene are the two common and effective modification methods.As to the chlorination modification of polypropylene, a novel aqueous chlorination method is put forward in the paper. The polypropylene particle of which the particle diameter is no more than 0.18mm can be chlorinated uniformly using this method. A several-step chlorination method is proposed in order to make polypropylene particle of larger particle diameter be chlorinated uniformly in the aqueous medium. Using three-step chlorination method, polypropylene particle of particle diameter 0.35mm can be chlorinated uniformly and the chlorinated products can be dissolved in CC1₄ at room temperature. The chlorinated products can be dissolved in xylene at 80℃ and no deposits are formed after the solution is cooled. The two-step grafting method is used in the surface modification of polypropylene in the paper. Compared with traditional graftingmethods, the two-step grafting method is more effective and easily being controllable. It was found that the most appropriate preparation conditions are: the concentration of BPO=1.25% （wt/v）;the decomposition temperature of BPO=353K;the grafting temperature=353K;the monomer concentration^ .09mol/l;the time for grafting reaction=lh. Also the mechanism of the grafting reaction and the microstructure of grafted products are investigated by HPLC. The results indicate that at the above grafting conditions one active site is formed for every 914 propylene units and the average grafting length is 136 acrylic acid monomer units.更多还原