聚丙烯催化剂预聚合工艺优化研究

考察了釜式淤浆预聚合对Hypol聚合工艺的影响。实验结果表明,对丙烯催化剂进行预聚合可以改善聚丙烯粒子的形态,减少聚丙烯中细粉(粒径小于200μm)的含量,提高聚丙烯粒子的规整性,提高粒子强度。预聚合度的提高会降低催化剂的初始催化活性,但有利于催化活性的平稳释放。当预聚合温度由10℃升高到40℃时,聚合产率降低。预聚合过程中增加助催化剂(三乙基铝)的用量,可以提高催化剂的催化活性(催化活性存在一个最佳值)。预聚合过程中加入外给电子体,可提高聚丙烯粒子的规整性,减少细粉含量,但降低催化剂的催化活性。预聚合后的催化剂在储存时间10~20h内催化活性衰减最快,最大衰减幅度达到40%。

Optimization for Prepolymerization Process of Polypropylene Catalyst

Slurry prepolymerization of propylene was studied in a one-liter reactor at low reaction rate.Ziegler-Natta catalyst was used with tri-ethyl aluminum as promoter and external electron donor.It was found that prepolymerization facilitated surface morphology of polymer,reduced fraction of fine powder in product and increased strength of particles.Higher degree of prepolymerization was favorable to steadily release of catalyst activity although reduced the initial activity.When temperature of prepolymerization was raised from(10℃) to(40℃,)catalyst activity dropped.Appropriate prepolymerization temperature was at 10℃.When dosage of promoter increased,catalyst activity rose to a certain extent.Addition of donor in prepolymerization not only helped enhance the shape of polymer to be better,but also reduced fraction of fine powder in product,although there existed the expense of catalyst activity.Catalyst deactivated most quickly during storage of first 10-20h,and the utmost deactivation extent could reach 40%.