在载体催化体系下二乙基锌对乙烯聚合催化效率的影响及调节分子量的动力学研究

本文对比研究了用(Ⅰ):TiCl_4/MgCl_2/Al(C_2H_5)_3和(Ⅱ):TiCl_4/MgCl_2/Al(C_2H_5)_3/Zn(C_2H_5)_2两种载体催化体系在常压下进行乙烯配位聚合的动力学行为,测定了聚合速率V_p、T_i活性中心比浓度C~*]、聚合活化能△E、聚合速率常数K_p及链增长寿期L值。并分别测定以Al(C_2H_5)_3与Zn(C_2H_5)_2为链转移剂的链转移速度常数乓K_(tr,Al)与K_(tr,Zn)以及链转移活化能△E_(tr,Al)与△E_(tr,Zn)。表明Zn(C_2H_5)_2能有效地进一步提高催化效率和降低聚乙烯的分子量并进行讨论。

THE KINETIC STUDY OF THE SUPPORTED-CATALYTIC ETHYLENE POLYMERIZATION WITH THE EFFECT OF ZINE DIETHYL ON THE CATALYST EFFICIENCY AND REGULATION OF MOLECULAR WEIGHT

In this paper, the kinetics of the coordination polymerization of ethylene have been studied at normal pressure with the highly active catalyst system TiCl4/MgCl2/Al(C2H5)3 (Ⅰ) in comparison with the highly active catalyst system TiCl4/MgCl2/Al(C2H5)3/Zn (C2H5)3 (Ⅱ). The specific number of active centers C] and the propagation rate constants (kp) were determined by kinetics method for the ethylene polymerization. The value of C] for the ethylene polymerization with system (Ⅰ) was found to be 0.02 to 0.06 mole/mole Ti in the range of polymerization temperature 25 to 45℃, and the apparent activation energy to be 2.45 kcal/mole. The kinetics behavious of the system (Ⅱ) was similar to the syste m(Ⅰ), but the value of C] of the system (Ⅱ) was much greater than that of system (Ⅰ), which leads to that the catalytic efficiency increases greatly in comparison with that of the system (Ⅰ). The chain transfer constants were also determined. Zine diethyl is more effective chain transfer agent that causes the great decrease in the molecular weight of polyethylene.