Catalyst for polyethylene giving an improved short chain branching distribution

摘要

A catalyst composition for polymerising ethylene with a superior activity, productivity, and giving, in particular, copolymers with an improved narrower short chain branching distribution, and especially an improved cling development in PIB formulated films. The catalyst composition for the (co-)polymerisation of ethylene, optionally with an alpha olefin of 3 to 10 carbon atoms, has a catalyst precursor and an organoaluminium cocatalyst, wherein the catalyst precursor has i) a catalyst carrier material, having from 0.3 to 1.2 mmoles of OH groups per gram of catalyst carrier; ii) a dialkylmagnesium compound of the formula RMgR¹, where R and R¹ are the same or different C2-C12 alkyl groups, in an amount between 1.1 and 2.4 mmoles of diakylmagnesium per gram of catalyst carrier; iii) a tetraalkyl orthosilicate, in which the alkyl group contains from 2 to 6 carbon atoms, in an amount between 0.4 and 1.6 mmoles of tetraalkyl orthosilicate per gram of catalyst carrier; and iv) a titanium compound in an amount between 1.3 to 2.4 mmoles per gram of catalysts carrier.