改性Ziegler-Natta体系催化乙烯/1-辛烯共聚合反应

Copolymerization of ethylene and 1-octene catalyzed by a modified Ziegler-Natta catalyst

采用改性Ziegler-Natta(Z-N)催化体系(n-BuO)TiCl3/MgCl2/AlEt3催化乙烯/1-辛烯共聚合。考察了聚合温度、Al/Ti物质的量比、单体投料比及乙烯压力对聚合行为的影响,并与传统Z-N催化体系TiCl4/MgCl2/AlEt3催化乙烯/1-辛烯共聚合行为进行了对比研究。采用GPC,DSC1,3C-NMR,SEM对共聚物的结构、形态及性能进行了表征。结果表明,改性Z-N催化体系催化乙烯/1-辛烯共聚合时1,-辛烯的共聚能力明显高于传统Z-N催化体系,在共聚物中1-辛烯的插入量达2.26%(摩尔分数),而传统Z-N催化剂1-辛烯的插入量仅为0.34%(摩尔分数);Al/Ti物质的量比及单体投料比对催化剂的活性1、-辛烯的插入量、共聚物的分子量与分子量分布及共聚物的微观结构有明显的影响;根据13C-NMR结果计算了单体的竞聚率:rE=55.00r,O=0.023,其乘积rE.rO=1.27,表明该聚合物为无规共聚物。

A novel modified supported Ziegler-Natta catalyst, （n-BuO）TiCl3/MgCl2 has been prepared and employed for ethylene/1-octene copolymerization, with AlEt3 as cocatalyst. The influence of varying the polymerization temperature, the Al/Ti molar ratio, the feed molar ratio of ethylene to 1-octene and the ethylene pressure on the copolymerization reaction were investigated. The structure, properties and morphology of the copolymer were charac- terized by 13C-NMR, GPC, DSC and SEM. It was found that the catalytic activity in ethylene/1-octene copolymerization of the modified Ziegler-Natta catalyst was higher than that of the traditional Ziegler-Natta catalyst. The Al/Ti molar ratio and the feed molar ratio of ethylene to 1-octene have obvious effects on the catalytic activity, the com- onomer content within the copolymer chain, the molecular weight and molecular weight distribution, and the micro- structure of the resulting copolymer. Compared with the traditional Ziegler-Natta catalyst for ethylene/1-octene co- polymerization which gives a comonomer content of 0.34% , the modified Ziegler-Natta catalyst showed higher ac- tivity for ethylene/1-octene copolymerization, and the comonomer content within the copolymer chain reached as high as 2.26 mol%. The microstructure of the copolymer was determined and the reactivity ratios of the monomers were confirmed by 13C-NMR. Values of rE =55.00 for ethylene and ro =0. 023 for 1-octene with rE-ro = 1.27 were obtained, suggesting the tendency for random distribution of the comonomers within the copolymer chain.