申请人:Hoang Peter Phung Minh
公开号:US20100190936A1
公开(公告)日:2010-07-29
Polyethylene is made by (co)polymerizing ethylene in a gas-phase reactor using a mixed catalyst system comprising a chromium catalyst supported on silica and a Group 4 transition metal catalyst, separately supported on silica. The Group 4 transition metal catalyst is defined by the formula shown, wherein M is a Group 4 metal, PI is a phosphinimide or ketimide ligand (shown), L is a monoanionic ligand which is a cyclopentadienyl or a bulky heteroatom type ligand, m is 1 or 2, n is 0 or 1, and p is an integer. The mixed catalyst system gives access to polyethylene having a broad or bimodal molecular weight distribution. In the copolymerization of ethylene, reversed or partially reversed comonomer distribution is achieved: the supported Group 4 component provides polymer segments having higher molecular weight and also higher comonomer incorporation than polymer segments produced at the supported chromium sites.
聚乙烯是通过在气相反应器中使用混合催化剂体系的乙烯(共)聚合制得的,该体系包括支持在二氧化硅上的铬催化剂和支持在二氧化硅上的第四族过渡金属催化剂。第四族过渡金属催化剂由所示的公式定义,其中M是第四族金属,PI是膦亚胺或酮亚胺配体(如图所示),L是单负离子配体,是环戊二烯基或臃肿的杂原子型配体,m为1或2,n为0或1,p是一个整数。混合催化剂体系可获得具有宽分子量分布或双峰分子量分布的聚乙烯。在乙烯的共聚合中,实现了反向或部分反向的共聚单体分布:支持的第四族组分提供具有更高分子量和更高共聚单体掺入量的聚合物片段,而支持的铬位点产生的聚合物片段则较低。