Patent ID: 6479589
Filing Date: 2002-11-12
Classification: C08F,C08L

Abstract:
A process for the preparation of a linear low density polyethylene resin 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 catalyst system in a first reactor under first polymerisation conditions to produce a first polyethylene and the 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) transferring the catalyst system and the first polyethylene to a second reactor serially connected to the first reactor and in the second reactor contacting ethylene monomer and a comonomer comprising an alpha-olefin having from 3 to 10 carbon atoms with the catalyst system under second polymerisation conditions to produce a product comprising a second polyethylene having a different molecular weight distribution than that of the first polyethylene; and (iii) blending together the first and second polyethylenes in the second reactor to form a linear low density polyethylene resin having a bimodal molecular weight distribution and a density of around 0.925 g/ml.