摘要
本论文采用反应器内合金化技术，用国产DQ-1型高效球形催化剂、采用多段聚合工艺在聚合反应器中直接合成出了外观呈球形、内部有大量孔隙的聚乙烯(PE)和及聚乙烯/聚丙烯(PE/PP)合金颗粒。具体的聚合过程包括三个阶段：第一段为预聚合，采用常压淤浆聚合方法：第二阶段为将第一段预聚所得预聚物转入耐压釜后进行乙烯加压淤浆聚合；第三段为丙烯的加压淤浆聚合。聚合所得产物颗粒形貌良好，颗粒粒径分布较窄，80％以上颗粒粒径分布在1～1.5mm之间。聚合物颗粒孔隙率较高，随聚合条件的不同孔隙率在20～40(mL/100g)％之间可调。对PE/PP合金的力学性能测试表明，这种材料显示出优异的综合力学性能，韧性和刚性均很高，接近常见工程塑料的性能指标。对合金的组成和结构作了较全面的分析表征。用温度梯度萃取分级法(TGEF)对合金按结晶度和组成进行了分级，并对合金及各级分的组成和结构作了充分表征，发现PE/PP合金主要由PE、PP和一定量的乙丙嵌段共聚物组成(＞90％)。根据合金结构、形态和结构性能关系研究的结果，提出了这种聚烯烃合金具有优异力学性能的本质原因。研究了球形多孔的PP、PE均聚物和PE/PP合金粒子上用苯乙烯、马来酸酐等单体进行的固相接枝，发现这些反应均可达到较高的接枝率和接枝效率，接枝反应主要发生在粒子内部，产物粒子无粘连、结块现象。对接枝聚合物进行了深入的结构表征，对接枝苯乙烯、马来酸酐的机理作了分析。接枝产物的力学性能测试结果表明，接枝改性后的聚烯烃合金表现出很好的刚性与韧性平衡，主要力学性能达到常见工程塑料的水平，有良好的应用前景。
论文首先系统研究了反应器内合金化聚合工艺的预聚合阶段的影响因素与基本规律。分别用乙烯、苯乙烯、1-己烯和丙烯为单体进行了淤浆预聚合实验，详细考察了各种预聚条件对聚合物颗粒形貌、聚合活性的影响。由于乙烯聚合活性高，聚乙烯结晶速率快，以乙烯为预聚单体时催化剂颗粒基本被胀裂，聚合物颗粒形貌差，且聚合物颗粒内活性中心被聚合物包裹导致催化效率很低。发现用丙烯预聚可以得到形貌规则、颗粒粒径分布窄、聚合活性高的聚合物颗粒。研究确定了较佳的丙烯预聚条件。
用球形催化剂进行乙烯淤浆聚合时，先经丙烯低温常压预聚3min后再将单体切换成乙烯，经加压淤浆聚合可制得外观为规则球形的PE颗粒。在乙烯加压聚合一定时间后将单体切换成丙烯继续进行淤浆聚合，则制得了外观为规则球形的PE/PP反应器合金颗粒。这种先聚合乙烯、后聚合丙烯的方法合成PE/PP反应器合金的例子在过去已公开的文献中尚未见报道。系统研究了各阶段聚合条件对PE/PP合金组成及各阶段聚合动力学特性的影响，发现可以通过改变乙烯或丙烯聚合的时间及其它反应条件有效地调节合金组成。
用光学显微镜、扫描电镜(SEM)观察了聚合物颗粒的外观及内部形貌，发现所得聚合物粒子呈规整的球形或椭球形，粒径分布窄，孔隙率高，但外表面与球形聚丙烯粒子相
浙江大学博士学位论文
比较为粗糙。聚乙烯及PE含量较高的PE／PP合金粒子的核心存在较明显的中央空洞。聚
合物颗粒孔隙率随颗粒粒径的增大而增大，随聚合物内丙烯含量的增加而降低。用扩散控
制的多粒模型（Multigtan Model）解释了这些现象，提出了乙烯聚合为严重扩散控制过程。
粒子的孔隙率随粒径增大而增大的现象有力地证明了扩散控制的存在。丙烯聚合的扩散阻
力较小，因而聚丙烯倾向于填充进入PE粒子内的孔隙中。发现丙烯在PE中的聚合速率也
受到前段聚合形成的PE层包裹活性中心的影响。
用偏光显微镜（PLM）、DSC、透射电镜（TEM）、WAXD分析等手段研究了PE／PP
合金的结构和物理性能，发现聚合物内PE相与PP相之间存在较强的相互作用。合金材料
的力学性能测试结果表明，这种材料既有极高的抗冲击性能，又有很高的刚性。含有54
mol％聚丙烯的 PENP合金的室温缺口抗冲强度达56．5 kjlm’，弯曲模量则高达2450 MPa。
扫描电镜观察材料冲断面形貌发现，合金的断裂过程属韧性断裂，伴有明显的斯裂现象。
用温度梯度革取分级法（TGEF）对PENP合金进行按结晶度和组成的分级，并对各级分作
了 FTIR、‘’C－NMR、PLM、DSC、WAXD分析，发现 PE／PP合金主要由 PE、PP两种均
聚物组成，同时还有相当量的乙丙嵌段共聚物存在于合金中。由于乙丙嵌段共聚物与PP形
成共晶而无法与PP分离开，用TGEF法尚不能准确测定嵌段共聚物在合金中的含量，但通
过级分的组成分析可以估计进入嵌段物的乙烯的含量。初步分析认为，嵌段共聚物起到PE
与PP间相容剂的作用，这对于实现合金中两种主要组分问性能互补、从而达到优异的刚性
与韧性平衡十分关键。
对PE／PP合金采用固相接枝的方法，进行了苯乙烯和马来酸酥（MAH）的自由基引发
接枝反应，系统考察了各种反应条件对接枝率的影响规律。这些三组分的合金材料均未见
文献报道。研究表明，基体树脂的球形多孔结构为固相接枝提供了大的比表面积，使接枝
聚合物具有较高的接枝率和接枝效率，接枝的聚苯乙烯和 MAH绝大部分进入了聚烯烃粒
子的内部孔隙中，其结果是
Spherical PE and PE/PP in-reactor alloy granules of high porosity were synthesized by two-stage sequential polymerization of ethylene and propylene using a spherical high yield TiCl4/MgCl2 based supported catalyst. The prepolymerization technique was systematically studied by various methods. And it was found that prepolymerization of propylene by slurry at about 0.1 MPa and 40 C, and the prepolymerization time is no more than 5 minutes are necessary to get excellent morphology and high yield PE and PE/PP granules. The second stage is ethylene polymerization at higher pressure and higher temperature by slurry in 1L autoclave and the product is PE granules. As for PE/PP granules, replace ethylene in the autoclave with propylene after ethylene polymerization for a period of time, the final product is PE/PP alloy. The content of C2 and C3 in the PE/PP alloy can be adjusted according to the polymerization time of ethylene and propylene at the second stage.
The morphology, particle size distribution, porosity and composition of the alloy granules were studied by optical microscope, scanning electron microscope (SEM), infrared (FTIR), polarized microscope (PLM), transmission electron microscope (TEM) and other means. The granules showed excellent spherical morphology, high porosity and narrow size distribution. Much of the tiny cavities present in the PE granules were filled up by PP in the alloy, resulting in lower porosity of the alloy than the PE granules. As disclosed by the DSC thermal behavior and revealed by PLM and TEM crystalline morphology of the alloy, the PE and PP phases are partially compatible with each other. The PE/PP alloy showed excellent impact strength and flexural modulus. A sample containing 64% PP showed a Notched Charpy impact strength of 56.5 kJ/m2 and a flexural modulus of 2450 MPa. The morphology of the impact fracture surface is characteristic of ductile materials, also implying the presence of strong interaction between the PE and PP components.
The PE/PP alloy was fractionated into five fractions (20 C, 100 C, 113 C, 120 C and >120 C) through temperature-gradient extraction fractionation, and the fractionations were analyzed through infrared (RTIR), 13C-NMR and other means. The PE/PP alloy was found to contain mainly four portions: PP, PE, a series of segmented copolymer with PE and PP segment of different length, and an ethylene-propylene random copolymer. As disclosed by the RTIR, 13C-NMR and DSC, the insoluble fraction (>120 C) is mainly PP (about 80%) and small amount of PE (about 20%), the 120 C fraction is completely PE (more than 99%), the 100 C and 113 C fractions are segmented copolymer with PE and PP segment of different length, and the 20 C fraction is ethylene-propylene random copolymer. The total amount of insoluble fraction and 120 C fraction is more than 90%, and the weight percentage of the other three fractionations is no more than 10%.
Spherical PP and PE/PP of high porosity graft polymerization of styrene in solid phase after styrene (St)/benzoyl peroxide (BPQ) mixture adsorbed into the granules under different conditions. Effects of various reaction parameters, such as St/PP weight ratio, BPO/St weight ratio, reaction temperature, reaction time on the amount of the grafted PS in the PP, graft efficiency, and the
molecular weight of the product were investigated. The structure and phase morphology of the produced PP/PP-g-PS alloy were characterized by infrared (FTIR), different scanning calorimetry (DSC), GPC, viscometry and polarized microscope (PLM). The results showed that solid phase graft polymerization of St in PP granule produced PP/PP-g-PS alloy with high amount of grafted PS (maximum 24.3 wt% of PS based on PP/PP-g-PS) and high graft efficiency (maximum 56.7%). The size of PP crystals was greatly reduced after grafting PS on PP. The final product is still in the form of regular spherical granules, which is beneficial to the industrial process. Under the studied conditions, there was slight degradation of the PP chains in the graft reaction.
The gr
引文
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