新型高活性催化剂乙烯气相聚合的研究(Ⅵ)——锌化合物对催化剂及产物性能的影响

Studies on Gaseous Phase Polymerization of Ethylene with Highly Active Catalyst (Ⅵ) The Effects of Zinc Compound on the Properties of Catalysts and Products

研究了新型高活性乙烯气相聚合催化剂ＴｉＣｌ４、Ｔｉ（ＯＢｕ）４／ＭｇＣｌ２、ＳｉＯ２和ＺｎＣｌ２／醇／ＡｌＲ３体系中ＺｎＣｌ２－ＡｌＥｔ３／ＳｉＯ２重量比和锌化合物含量对气相均聚合的影响，比较了２种不同催化剂Ｃａｔ＃Ａ和Ｃａｔ＃Ｂ的聚合反应动力学及性能差异．催化剂中锌化合物作为复合载体的重要组分，可显著改善产物分子量调节效果．通过比表面积、ＳＥＭ、ＤＳＣ以及ＦＴＩＲ对催化剂和聚合物的形态、结构及性能进行了分析和表征．结果表明，均聚产物与采用ＭｇＣｌ２作载体的催化剂制备的产物相比，支化度较高，结晶度较低，熔融峰较宽．发现Ｃａｔ＃Ｂ制得的均聚产物具有新颖的熔融双峰．

The gaseous phase homopolymerization of ethylene has been studied in the presence of TiCl 4, Ti(OBu) 4/MgCl 2, SiO 2, ZnCl 2/SiCl 4/alcohol/AlR 3 highly active catalysts (named Cat#A and Cat#B) which were prepared by different precipitating reaction procedures. It was found that the catalytic efficiency increased and there was an optimum value respectively in bulk density and mass distribution of polymer with the increase of the amount of ZnCl 2 AlEt 3 used to treat SiO 2. The kinetics curves of gaseous phase etheylene polymerization with two catalysts showed a decline and the decay rate with Cat#A was larger than that with Cat#B. The analysis of the components of the catalysts showed that zinc compound is one of the important compositions of supports, which can notably control the molecular weight of the products. This should be ascribed to the fact that diethyl zinc compound formed in site of the ethylene polymerization system due to the interaction between ZnCl 2 and trialkyl aluminnium is liable to induce transfer reaction of PE propagation chains. The particle structures and the properties of the catalysts and the obtained products of PE were characterized by the determination of surface area and SEM, FTIR and DSC. The morphology of the catalysts and products of polymerization by SEM showed that all the particle shapes were nearly spherical. Compared with the matrix PE prepared by MgCl 2 supported titanium catalyst, the products prepared with Cat#A and Cat#B have a higher branching degree, lower crystallinity and wider melting peak. The products prepared with Cat#B with melting dual peak(peak temperature 133 0 ℃ and 140 0 ℃) have newly been found.