| 摘要 |
<p>Multi-stage polymerization process for the production of a multi-modal linear low density polyethylene in at least two staged reactors connected in series comprising at least
(i) polymerizing in a first slurry phase stage ethylene monomers and optionally one or more alpha-olefine comonomers, in the presence of a Ziegler-Natta polymerization catalyst system to obtain a first polyethylene fraction component (A)
(ii) polymerizing in a second gas or slurry phase stage ethylene monomers and one or more alpha-olefine comonomers, in the presence of a Ziegler-Natta polymerization catalyst system to obtain a second polyethylene fraction component (B),
whereby the Ziegler-Natta polymerisation catalyst system comprises
C) a procatalyst, which procatalyst comprises
a) an Al compound having the formula Al(alkyl) x Cl 3-x (I), where alkyl is an alkyl group with 1 to 12 and 0 ‰¤ x ‰¤ 3,
b) a magnesium hydrocarbyloxy compound of formula Mg(OR 1 ) 2-n (R 2 ) n (II), wherein each R 1 and R 2 is independently a C 1-20 hydrocarbon residue which may optionally be substituted with halogen and 0 ‰¤ n < 2 and
c) a chlorine-containing titanium compound of the formula Cl y Ti(OR 3 ) 4-y (III), wherein R 3 is a C 2-20 hydrocarbon residue and y is 1, 2, 3 or 4 and
compounds a), b) and c) being deposited on a particulate inorganic support and
D) a halogenated aluminium alkyl cocatalyst of the formula (IV) (C 1 -C 4 -alkyl) m -Al-X 3-m , wherein X is chlorine, bromine, iodine or fluorine and m is 1 or 2, and
yielding a multimodal linear low density polyethylene with a narrow molecular weight distribution,
whereby the process shows a higher comonomer conversion compared to multi-stage processes using non-halogenated cocatalysts.</p> |
