丙烯聚合用TiCl_4/MgCl_2催化剂的研究——内给电子体的作用

STUDY ON TiCl_4/MgCl_2 CATALYSTS FOR PROPYLENE POLYMERIZATION ——THE FUNCTIONS OF THE INTERNAL DONORS IN CATALYST SYSTEMS

采用相同制备工艺 ,制备分别以邻苯二甲酸二异丁酯 (DIBP)和 9,9 双 (甲氧基甲基 )芴 (BMMF)为内给电子体和不加入内给电子体 3种催化剂 .研究了它们在无外给电子体时聚合性能 ,以及合成的聚丙烯的等规度 ,分子量及其分布 .并采用CRYSTAF和1 3C NMR对聚丙烯沸腾庚烷不溶部分结晶性能和序列结构进行分析 ,结果表明内给电子体对聚丙烯分子链序列结构有很大影响 ;BMMF催化剂、DIBP催化剂和无内给电子体催化剂合成的聚丙烯规整性依次下降 .对BMMF催化剂 ,当烷基铝为Et3Al时 ,铝钛比增加 ,等规度和活性明显下降 .当烷基铝i Bu3Al时 ,铝钛比增加 ,等规度略微下降而活性增加 ;但是1 3C NMR研究发现其 (铝钛比为 3 0 0时 )庚烷不溶物的规整性与DIBP催化剂的庚烷不溶物的规整性一致 .这表明内给电子体在聚合中的作用不在于是酯还是醚 ,在于它与氯化镁的络合强度 .络合越强 。

Three N catalyst systems were prepared,which contain free donor or different internal donors such as diisobutyl phthalate(DIBP) and 9,9 bis(methoxymethyl)fluorine(BMMF).The performances of propylene polymerization without external donors in catalyst systems were studied.Poly(propylene)s have been characterized by using gel permeation chromatography (GPC),crystallization fractionation analysis(CRASTAF) and 13 C NMR analysis.It was found that the catalyst with BMMF as the internal donor resulted in polypropylene of best tacticity.It suggests that the internal donors have important influence on polymer tacticity.The polymerization was performed in the presence of different cocatalysts—Et 3Al and i Bu 3Al.It was found that the microstructure of polymers obtained with catalyst BMMF ( i Bu 3Al/ T i=300) was as same as that obtained with catalyst DIBP (Et 3Al/ T i=50).It indicated that the stereoselectivity of the active site depended on the strength of donor coordination.