| 摘要 |
<p>Process for polymerizing ethylene, or mixtures thereof with up to 40 wt % of other 1-olefinic monomer comprising contacting the monomer under particle form polymerization conditions at a temperature not greater than 112 DEG C. with a catalyst prepared by heat activating chromium oxide or a compound calcinable thereto, on a refractory oxide support material and a catalyst modifier comprising an aliphatic diene and a trihydrocarbyl boron. The refractory oxide support material can be, for example silica and the heat activation is preferably carried at 400 DEG to 900 DEG C. The aliphatic diene preferably contains 1 to 10 carbon atoms and can be, for example butadiene, isoprene, 1,5-hexadiene, 1,7-octadiene or ethylidene norbornene. The trihydrocarbyl boron, for example trimethyl, triethyl or triisobutyl boron. The quantity of diene is preferably 10 to 5000 moles per gram atom of chromium and the quantity or trihydrocarbyl boron is preferably 0.1 to 20 moles per gram atom of chromium.</p> |
