Patent ID: 6566450
Filing Date: 2003-05-20
Classification: C08F,C08L

Abstract:
A process for the preparation of polyethylene resins having a bimodal molecular weight distribution which comprises:(i) contacting ethylene monomer and a comonomer comprising an alpha-olefin having from 3 to 10 carbon atoms with a first catalyst system in a first reactor under first polymerisation conditions to produce a first polyethylene having a first molecular weight, an HLMI of not more than 0.5 g/10 min and a first density of not more than 0.925 g/ml and the first catalyst system comprising (a) a metallocene catalyst comprising a bis tetrahydroindenyl compound of the general formula (IndH4)2Râ€³MQ2 in which each Ind is the same or different and is indenyl or substituted indenyl, Râ€³ is a bridge which comprises a C1-C20 alkylene radical, a dialkyl germanium or silicon or siloxane, or an alkyl phosphine or amine radical, which bridge is substituted or unsubstituted, M is a Group IVB transition metal or vanadium and each Q is hydrocarbyl having 1 to 20 carbon atoms or halogen; and (b) a cocatalyst which activates the catalyst component; (ii) providing a second polyethylene having a second lower molecular weight and second higher density than the first polyethylene; and (iii) mixing together the first and second polyethylenes to form a polyethylene resin having a bimodal molecular weight distribution, an HLMI of from 3 to 10 g/10 min and a density of from 0.95 to 0.96 g/ml.