易降解乙烯-alpha-烯烃-共轭双烯烃三元共聚物的合成、结构及性能

Agricultural and packaging films made of common linear low density polyethylene (LLDPE) have caused a serious environmental problem for their very slow degradation in natural environment. This problem can be ideally solved by using low cost polyolefin films with enhanced photo-oxidation degradability. This project will study ethylene-alpha-olefin-conjugated diene (butadiene or isoprene) terpolymerizations with supported Z-N catalysts, and prepare novel LLDPE resins containing carbon-carbon double bonds in the main chains. Based on high sensitivity of the double bonds to photo oxidation, this kind of LLDPE may show markedly enhanced degradability in natural environment, and may become the basis for developing novel eco-friendly films. Primitive studies by the applicant show that this kind of copolymerization has rather high catalyst efficiency, and the conjugated diene units were incorporated in the polymer chains mainly via 1,4-addition, which proved feasibility of this project. In this project, the kinetic laws and mechanism of the above mentioned terpolymerizations will be systematically studied in order to understand how the catalytical systems and polymerization conditions determine the incorporation rate and regioselectivity of the conjugated diene. The chain structure of the terpolymers will be fully characterized, and their optical oxidation behaviors and mechanical properties will be evaluated. Structure-properties relationship of the terpolymers will be studied. The catalysts will be modified to further improve the copolymerization activity and broaden the range of diene incorporation rate. The results of reasearch will provide a solid basis for industrial application of the new materials.

普通线型低密度聚乙烯(LLDPE)制造的农膜和包装膜因难降解而造成了严重环境问题。采用低成本的易降解聚烯烃制备塑料膜是解决该问题的最佳途径。本项目拟用负载型Z-N催化剂进行乙烯-alpha-烯烃-共轭双烯烃(丁二烯或异戊二烯)三元共聚，制备一类主链含少量双键的新型LLDPE，利用双键的光氧化敏感性，显著提高LLDPE在自然环境里的降解速率，为开发环境友好农膜和包装膜材料打下基础。申请人的探索研究已发现了这类共聚反应有较高的催化剂效率，共轭双烯烃主要以1,4-加成进入聚合物链，表明研究路线有良好的可行性。拟系统研究上述三元共聚反应的动力学规律及微观机理，掌握催化体系和共聚条件影响反应活性和共轭双烯烃的插入率及其区域选择性的规律和原理；详细表征三元共聚物的链结构，评价其光氧化降解性能和力学性能，初步掌握结构性能关系；改进催化剂以进一步提高共聚活性和共轭双烯烃含量的可调控性，为实现产业化打下基础

分别用不含内给电子体及含有酯类内给电子体的钛/镁负载型Z-N催化剂进行乙烯/1-己烯/共轭双烯烃（丁二烯、异戊二烯）的共聚反应，系统研究了共聚反应条件影响催化活性和共聚物链结构的规律，详细表征了共聚产物的链结构及组成分布，深入研究了这类反应的微观机理，并评价了所得主链含碳碳双键的聚乙烯树脂的氧化降解特性。通过本项目的研究，对负载型Z-N催化剂合成乙烯/α-烯烃/共轭双烯烃三元共聚物的微观机理及共聚物结构调控原理取得了较准确和全面的认识，筛选了适合单烯烃/共轭双烯烃共聚反应的钛/镁负载型催化剂，以接近乙烯/α-烯烃共聚体系的催化剂效率合成得到了共轭双烯烃含量为0.2~2 mol%且共轭双烯烃单元以反式1,4-连接的三元共聚物。初步证明了用负载型Z-N催化剂合成双烯烃含量较低的乙烯/丁二烯二元或三元共聚物具有良好的工业化可行性，其共聚产物具有显著的易氧化降解特性，可望为解决传统聚烯烃材料的环境污染问题提供新的有效途径。