预络合对TiCl_4/SiO_2-MgCl_2催化剂活性及聚丙烯颗粒形态的影响

采用MgCl2-SiO2复合载体,制备了TiCl4/SiO2-MgCl2催化剂,并将该催化剂用于丙烯聚合,研究了预络合对TiCl4/SiO2-MgCl2催化剂的活性及聚丙烯颗粒形态的影响。实验结果表明,预络合有助于提高TiCl4/SiO2-MgCl2催化剂的活性,可有效控制聚丙烯颗粒形态,防止聚丙烯颗粒破碎。预络合后,TiCl4/SiO2-MgCl2催化剂的活性从29kg/(g.h)提高至41kg/(g.h),聚丙烯的表观密度从0.38g/mL提高到0.45g/mL。在乙烯-丙烯共聚物的制备中,预络合有助于提高乙烯-丙烯共聚物的抗冲性能,常温冲击强度(25℃)由4.9kJ/m2增至12.8kJ/m2,低温冲击强度(-20℃)由2.2kJ/m2增至9.6kJ/m2。

Effects of Precomplexation on Activity of TiCl4/SiO2-MgCl2Catalyst in Propylene Polymerization and Polymer Particle Morphology

A novel TiCl4/MgCl2-SiO2 catalyst for propylene polymerization was prepared by using MgCl2-SiO2 as composite support. Effects of precomplexation on activity of TiCl4/SiO2-MgCl2 catalyst in propylene polymerization and on particle morphology of obtained polymer were studied. Precomplexation can lift activity of TiCl4/SiO2-MgCl2 catalyst from 29 kg/(g·h) to 41 kg/(g·h) and bulk density of prepared polypropylene from 0.38 g/mL to 0.45 g/mL. Particle morphology of the obtained polypropylene can be controlled by using the prepared catalyst and breakage of polypropylene powder can be diminished. In preparation of ethylene-propylene copolymer, the precomplexation can improve impact strength of the copolymer from 4.9 kJ/m2 to 12.8 kJ/m2 (25 ℃). Impact strength of the copolymer at -20 ℃ increases from 2.2 kJ/m2 to 9.6 kJ/m2.