茂金属催化剂淤浆聚合制备高密度聚乙烯

Preparation of high density polyethylene by slurry polymerization with metallocene catalyst

采用自制的负载型茂金属催化剂催化乙烯聚合制备高密度聚乙烯,利用GPC和DSC等方法考察了氢气加入量、氢气加入方式及共聚单体等对聚合活性、聚合物性能及聚合动力学的影响。实验结果表明,负载型茂金属催化剂的聚合活性对氢气敏感性较高。加入少量氢气即能显著提高聚合活性,但加入量较多时聚合活性降低。随氢气用量的增大,聚合物的熔体流动速率、密度和结晶度均显著增大。采用氢气/乙烯混合进料方法得到的聚合物的相对分子质量分布Mw/Mn均小于4.31;采用氢气一次性加入的方法得到的聚合物的相对分子质量分布Mw/Mn均大于5.14。少量1-己烯单体加入能显著提高聚合活性,但随1-己烯加入量的增加,聚合活性降低,所得聚合物的结晶度和密度均下降。

High density polyethylene was prepared with self-made supported metallocene catalyst. The influences of hydrogen,comonomer and hydrogen feeding modes on the polymerization activity,polymer properties and polymerization kinetics were investigated by means of DSC and GPC. It was found that the supported zirconocene catalyst exhibited a high hydrogen response. The polymerization activity was signifi cantly improved with adding a little of hydrogen and then decreased rapidly with increasing the amount of hydrogen. The melt fl ow rate,density and crystallinity of the prepared polymers markedly increased with the increase of hydrogen. The relative molecular mass distribution（Mw/Mn） was lesser than 4.31 when hydrogen and ethylene was fed simultaneously,and it was greater than 5.14 when hydrogen was fed just at the polymerization beginning. A small amount of 1-hexene could increase the polymerization activity evidently,but the polymerization activity,density and crystallinity of the polymers decreased with increasing the amount of 1-hexene.