稀土-其它过渡金属混合催化剂用于共轭双烯烃的聚合——Ⅱ烷基铝对丁二烯聚合及产物微观结构的影响

POLYMERIZATION OF CONJUGATED DIENES WITH MIXED CATALYST OF RARE EARTH AND OTHER TRANSITION METAL——Ⅱ. EFFECT OF ALKYLALUMINIUM ON BUTADIENE POLYMERIZATION AND MICROSTRUCTURE OF POLYBUTADIENE

某些过渡金属组成的Ziegler-Natta催化剂聚合共轭双烯烃,所得聚合物的微观结构易随聚合条件和主催化剂配体的改变而异.具有d电子的钴、钛催化体系聚合丁二烯,既可得cis-1,4结构聚丁二烯,又可得1,2结构的聚丁二烯;而具有f电子的稀土催化剂聚合共轭双烯烃,无论怎样改变其聚合条件和配体,一般皆得高顺式聚合物.一般认为:这种定向性的特征是由单体向活性中心上配位、插入时的环境及活性中心的本质所决定的.在第一报中作者利用同一种配位体。

It is easy to alter the microstructure of polydienes obtained from some Zicglcr- Natta catalysts which are composed of transition metals and aluminium compounds. For instance, when Co and Ti which contain d-electrons are used as catalyst for butadiene polymerization, products of both high cis-1,4 and 1,2 configuration polybutadicne are obtained. In contrast, when rare earth elements which contain f-electrons are used, only high cis-1,4 configuration polybutadiene is obtained no matter how the polymerization conditions and ligands used are changed. In the first paper, Nd-Fe mixed complex containing f-and d-electrons was prepared with the same ligand phenanthroline, and was used as catalyst for butadiene polymerization. In that work, butadiene polymerization was carried out only in the presence of (NdCl3+FeCl3) nphen-HAl(i-Bu)2 system.In this paper, various type aluminium alkyls have been used as the co-catalyst, and the effect of aluminium alkyls on butadiene polymerization and microstructure of polybutadiene has been studied in the presence of (NdCl3+FeCl3) nphen-A1R3 systems. The results indicate that the catalytic activity of the mixed catalysts is always higher than that of Nd or Fe catalyst alone when a suitable molar ratio of Nd and Fe is used in the mixed catalysts. The catalytic activity and the microstructurc of the resulting polymer change greatly with changing the substituent of co-catalyst alkylaluminium. Upon changing Nd/ Fe ratio from 0 to 100% in the mixed catalyst, the microstructure of polymer obtained changes from one equibinary of cis-1,4 and 1,2 to a high cis-1,4 configuration when HAl(i-Bu)2 is used as the co-catalyst. However, when Al(i-Bu)3 and AlEt3 are used as co-catalyst, the polymers obtained are always equibinary of cis-1, 4 and 1,2 configuration though Nd / Fe ratio is changed in a wide range. The molecular weight distribution (MWD) of the polybutadiene depends on the alkylaluminium used, and decreasing in the order HAl(i-Bu)2>Al(i-Bu)3>AlEt3. The molecular weight of the polymers is affected by solvents used in the polymerization, [η] aromatic hydrocarbons> [η] aliphatic hydrocarbons.