化学法镁钛系高效载体催化剂多活性中心的DSC证据

DSC EVIDENCE ON THE EXISTENCE OF MULTIPLE ACTIVE CENTERS IN SUPPORTED Ti-Mg ZIEGLER- NATTA CATALYST

用高效载体钛催化剂进行乙丙共聚物的合成,已有大量报道,但从聚合产物热分析出发对其催化活性中心的性质进行探讨,报道尚少。我们用化学反应法制备的高效载体钛催化剂进行乙丙共聚反应,所得产物进行热分析结果表明,共聚产物具有很宽的链段序列分布,呈现出吸热双峰模式,与催化体系及其聚合过程ESR分析,共聚物溶剂萃取及其^(13)C-NMR分析结果一起,有力地支持催化体系多活性中心的结论。

The DSC melting curves of lthylene/propylene copolymers double melting peaks, and he crystallite melting process was a wide temperature range. The ether and hexane fractionation gave randomly distributed low crystallinie ethylene/propylene copolymers, whereas the heptane fractionation gave copolymer containing long ethylene sequences with high ethylene content and high crystallinity. The latter has showed longest ethylene sequence length (<E>) (5.156) and largest r1,r2 value for 13C-NMR results. These results can be attributed to the inter-molecular non-homogeneity and can be explained by the existence of multi active-centers in the catalytic system.