| abstract |
A process for the preparation of polyethylene resins having anmultimodal molecular weight distribution which comprises:n (i) contacting ethylene monomer and a comonomer comprising annalpha-olefin having from 3 to 10 carbon atoms with a firstncatalyst system in a first reactor under first polymerisationnconditions to produce a product comprising a first polyethylenenhaving a first molecular weight and a first density and the firstncatalyst system comprising (a) a metallocene catalyst selectednfrom one of components A or B, component A comprising a bisntetrahydroindenyl compound of the general formula (IndH 4 ) 2 R''MQ 2 nin which each Ind is the same or different and is indenyl ornsubstituted indenyl, R'' is a bridge which comprises a C 1 -C 20 nalkylene radical, a dialkyl germanium or silicon or siloxane, ornan alkyl phosphine or amine radical, which bridge is substitutednor unsubstituted, M is a Group IVB transition metal or vanadiumnand each Q is hydrocarbyl having 1 to 20 carbon atoms or halogennand component B comprising a metallocene catalyst of generalnformula R''(CpR m )(Cp'R' n )MQ 2 , wherein Cp is a cyclopentadienylnmoiety. Cp' is a substituted or unsubstituted fluorenyl ring;neach R is independently hydrogen or hydrocarbyl having 1 to 20ncarbon atoms in which O ≤ m ≤ 4; each R' is independentlynhydrocarbyl having 1 to 20 carbon atoms in which O ≤ n ≤ 8; R'',nM and Q are each as defined above, the metallocene component Bnhaving a centroid-M-centroid angle in the range 105° to 125°; andn(b) a cocatalyst which activates the catalyst component; (ii) providing a second polyethylene having a second lowernmolecular weight and higher density than the first molecularnweight; and (iii) mixing together the first and second polyethylenes to formna polyethylene resin having a multimodal molecular weightndistribution. |