茂金属／后过渡复合催化剂催化乙烯聚合

Ethylene polymerization with metallocene/late transition metal combined catalysts

以二氯二茂钛（Cp2TiCl2）和α-二亚胺溴化镍催化剂（ArN=C（CH3）-C（CH3）=NAr，Ar=2，6-（iPr）2C6H3）（DMN）组成复合催化剂体系，甲基铝氧烷（MAO）为辅助催化剂催化乙烯聚合，考察了温度和催化剂物质的量比对复合催化剂的乙烯聚合性能的影响．示差扫描量热法（DSC）和扫描电镜（SEM）分析结果发现，复合催化剂在聚合温度为0℃时所得聚乙烯能均匀混合，而在聚合温度为50℃时所得聚乙烯混合物存在相分离．研究表明，当聚合温度为0℃时，复合催化剂活性与Cp2TiCl2摩尔分数xTi呈现线性关系；而当聚合温度为50℃时，复合催化剂具有很好的协同作用，聚合活性随xTi增大而增大，并在xTi=0．67时达到最大值．凝胶渗透色谱（GPC）分析结果也表明，单一Cp2TiCl2和DMN催化剂均为单活性中心；复合催化剂具有2种活性中心，分别对应于单一Cp2TiCl2和DMN的活性中心．

Ethylene was polymerized using bis（cyclopentadienyl）titanium dichloride（Cp2TiCl2） and α-nickel-diimine（ArN=C（CH3）-C（CH3）=NAr,Ar=2,6-（iPr）2C6H3）（DMN） binary catalysts,activated with methylaluminoxane（MAO）.The effects of polymerization temperature and Cp2TiCl2 molar fraction on binary catalysts performances were investigated.The activity of binary catalysts increased linearly with Cp2TiCl2 molar fraction at 0 ℃.The binary catalysts system showed a good synergic effect at 50 ℃.The polymerization activity increased with Cp2TiCl2 molar fraction with a maximum at 0.67 of Cp2TiCl2 molar fraction.The gel permeation chromatography（GPC） analysis showed that both Cp2TiCl2 and nickel-diimine have only one type of active site,while the binary catalysts have two types,which are almost the same as that of Cp2TiCl2 and nickel-diimine respectively.Analysis of polyethylene microblends using differential scanning calorimeter（DSC） and scanning electron microscopy（SEM） indicate that phase separation occurres in the obtained polyethylene at 50 ℃,while the linear and branched polyethylene obtained at 0 ℃ are uniformly microblends.