| 摘要 |
<p>PURPOSE:To prepare a homogeneous polyethylene having improved melt flowability and giving molded articles almost free from hard spot and nonuniformity, by carrying out two-stage polymerization with changing the content of hydrogen in the vapor phase, in the presence of a catalyst comprising a transition metal compound carried on a magnesium compound and an organoaluminum compound. CONSTITUTION:A (co)polymer is prepared by the two-stage (co)polymerization of ethylene or ethylene/alpha-olefin in the presence of a catalyst system comprising (A) a solid catalyst component of a transition metal compound, provided by carrying a titanium and/or vanadium compound on a magnesium compound (e.g. the reaction product of a Grignard compound with silicon tetrachloride), and (B) an organoaluminum compound component. At the first stage 30-95wt% of the monomer is polymerized at a hydrogen/ethylene molar ratio in vapor phase of 0.5-15 and at the second stage the residual monomer is polymerized at the molar ratio of <=0.2.</p> |
