High activity mixed metal alkyl cocatalysts for α‐olefin polymerization

摘要

AbstractHigh activity α‐olefin polymerization catalysts are generally obtained by mixing MgCl2‐supported TiCl4(MgCl2/TiCl4) with an aluminum trialkyl cocatalyst. Surprisingly, AlEt2Cl, which is the preferred cocatalyst in polymerizations employing nonsupported Ti compounds, is a poor cocatalyst when used with MgCl2/TiCl4. It was found that in propylene and 1‐butene polymerizations, using different MgCl2/TiCl4catalysts, the cocatalyst activity of AlEt2Cl can be greatly improved by the addition of a magnesium or lithium alkyl. The mixed metal alkyl obtained from AlEt2Cl and MgBu2is a particularly effective cocatalyst always yielding more polymer, of about the same stereospecificity, than the conventional aluminum trialkyls. The exact nature of the mixed metal alkyl cocatalysts is not known, but the available evidence argues against in situ aluminum trialkyl formation resulting from the alkylation of AlEt2Cl by the second metal