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用δ-Ticl_8-Et_2AlCl作催化剂,合成了含长乙烯序列的无规乙丙共聚物。影响乙烯丙烯共聚合产率的主要聚合参数是[Ti]、[Al]/[Ti]比和聚合温度,在55℃左右聚合产率呈现极大值;影响共聚物组成的主要参数是乙丙混合气中单体C_2的含量,当其在60克分子％以上,有利于生成长乙烯序列无规乙丙共聚物;[Ti]、单体C_2含量和聚合温度对共聚物的分子量有显著影响。用沉淀分级方法证明了共聚物组成的不均一性;用DSC,扭摆和TEM等方法对共聚物和与其组成相同的共混物进行对比,发现共聚物的T_m,T_c和X_c％均小于共混物;共聚物的T_g随C_2含量的增加向低温方向迁移,而共混物的T_g则随C_2含量增加移向高温;共聚物与共混物的形态结构均呈两相体系,前者PE片晶堆砌疏松,后者堆砌紧密;共聚物的常温断裂强度高达140公斤/厘米~2,与钒催化剂制备的序列型AP447的强度(135公斤/厘米~2)相近。
Using δ-Ticl_8-Et_2AlCl as a catalyst, a random ethylene-propylene copolymer containing long ethylene sequences was synthesized. The main polymerization parameters influencing the copolymerization yield of ethylene-propylene are [Ti], [Al] / [Ti] and the polymerization temperature. The maximum yield of polymer at 55 ℃ is the maximum. The content of monomer C_2 in the mixed gas is more than 60 mol%, which is favorable for the formation of long ethylene sequence random ethylene-propylene copolymer [Ti]. The content of C_2 and the polymerization temperature have a significant influence on the molecular weight of the copolymer . The heterogeneity of copolymer composition was confirmed by precipitation classification method. The copolymers and the same blends were compared by DSC, torsion and TEM. The results showed that T_m, T_c and X_c% T_g of the copolymer migrated toward lower temperature with the increase of C_2 content, while the T_g of the blend shifted to higher temperature with the increase of C_2 content. The morphology of the copolymers and blends showed a two-phase system. The latter is densely packed; the breaking strength of the copolymer at room temperature is as high as 140 kg / cm 2, which is similar to the strength of the sequence type AP447 prepared by the vanadium catalyst (135 kg / cm -2).