Ziegler-Natta/茂金属复合催化剂聚合性能的研究

制备了Ziegler-Natta/茂金属复合(Z-M)催化剂,用SEM技术对其形貌进行了表征,在10L丙烯液相本体聚合模试装置上对Z-M催化剂的氢调敏感性进行了评价。通过一段丙烯本体均聚、二段乙烯-丙烯近恒温恒压气相共聚模拟Spheripol-Ⅱ工艺制备了系列聚丙烯(PP)釜内合金;考察了二段共聚时的聚合反应动力学、乙烯与丙烯配比(n(C3)∶n(C2))对PP釜内合金性能的影响。实验结果表明,在一段均聚时Z-M催化剂具有较好的氢调敏感性,得到的均聚PP粒子具有较好的流动性;在二段共聚时,Z-M催化剂能在较长的共聚时间内保持较平稳、较高的共聚活性,改变n(C3)∶n(C2)时PP釜内合金中乙丙橡胶的质量分数可调(7.19%~10.75%),熔体流动速率(10min)可调(14.0~26.5g);n(C3)∶n(C2)对合金弯曲模量的影响不大;当n(C3)∶n(C2)=1.7时制备的PP釜内合金具有最大的冲击强度(92.9J/m)。

Performance of Ziegler-Natta/Metallocene Composite Catalyst in Propylene Polymerization

Zigler-Natta/metallocene(Z-M) composite catalyst was prepared and was characterized by means of SEM.The hydrogen response of the Z-M catalyst was studied through liquid bulk polymerization of propylene in a 10 L model test device.A series of polypropylene(PP) in-reactor alloys were prepared with the Z-M catalyst through the first stage—bulk homopolymerization of propylene and the second stage—gas copolymerization of propylene and ethylene at nearly constant temperature and pressure by simulating Spheripol-Ⅱtechnology.The polymerization kinetics in the second stage and the effect of mole ratio of propylene to ethylene(n(C3) ∶n(C2)) on the properties of the PP in-reactor alloys were investigated.The results showed that in the first stage both the hydrogen response of the Z-M catalyst and the mobility of the produced homo-PP particles were good.In the second stage,the Z-M catalyst could maintain relatively stable copolymerization activity for a long time,and just by changing n(C3) ∶n(C2),the mass fraction of ethylene propylene rubber(soluble in n-hexane) in the PP in-reactor alloys and the melt flowing rate(10 min) of the PP in-reactor alloys could be adjustable between 7.19%-10.75% and between 14.0-26.5 g/min,respectively.The change of n(C3) ∶n(C2) hardly affects flexural modulus of the PP in-reactor alloys.When n(C3) ∶n(C2) was 1.7,the impact strength of the prepared polypropylene in-reactor alloys was maximum 92.9 J/m.