助催化剂对Ziegler-Natta催化剂催化丙烯聚合的影响

Influences of Cocatalyst on Propylene Polymerization with MgCl_2 /TiCl_4 Catalysts

研究了纯TEA、纯MAO和TEA/MAO混合助催化剂对二醚类Ziegler-Natta催化剂和二酯类Ziegler-Natta催化剂催化丙烯聚合的影响,并用DSC、GPC和WAXD等表征手段对聚丙烯结构进行分析。结果表明:纯TEA、纯MAO以及任意比例的TEA/MAO混合助催化剂均能催化Ziegler-Natta催化剂,表现出较高的聚合活性;此外,随着TEA/MAO混合助催化剂中MAO含量的增加,聚丙烯的结晶温度、熔点、结晶度和分子量均呈下降趋势,而晶型不发生变化;另外,相同聚合条件下,二醚类Ziegler-Natta催化剂比二酯类Ziegler-Natta催化剂具有更好的聚合活性、更高的聚丙烯分子量以及更宽的分子量分布。

A study of the influence of pure TEA, pure MAO, and TEA/MAO mixture on propylene polymerization catalyzed by both MgCl2/TiCl4/diether catalyst and MgCl2/TiCl4/diester catalyst, and the microstructure of the obtained polypropylene was investigated in detail, by differential scanning calorimetry （DSC） , Gel permeation chromatographic analyses （GPC） and wide-angle X-ray diffraction （WAXD）. It was found that pure TEA, pure MAO, or TEA/MAO mixture could activate Ziegler- Natta catalysts. In addition, the melting temperatures, crystallization temperatures, crystallinity, and average molecular weight of the polypropylene showed a gradual decreased with increasing the content of MAO in TEA/MAO mixture,while the crystal form did not change all the time. Besides, the MgCl2/TiCl4/diether catalyst exhibited considerably higher activity in the polymerization of propylene than that of MgC1E/TiC14/diester catalyst,and the polypropylene prepared by MgCl2/TiCl4diether catalyst had higher molecular weight and relatively wider molecular weight distribution than that by MgCl2/TiCl4diester catalyst under the same polymerization conditions.