A study of the ziegler‐type combinations TiCl₄‐<i>n</i>‐C₅H₁₁Na and TiCl₄‐(C₂H₅)₂AlBr

Abstract

Abstract The reaction between catalyst components has been studied and polymerization experiments carried out on ethylene using the systems pentyl‐sodium – TiCl 4 (I) and diethylaluminium bromide – TiCl 4 (II). Results of reduction of TiCl 4 can be interpreted on the basis of the following equations: AmNa + TiCl 4 → TiCl 3 + NaCl + Am • , in the case of I, Et 2 AlBr + TiCl 4 → TiX 3 + EtAlX 3 + Et • and EtAlX 2 + TiCl 4 → TiX 3 + + AlX 3 + Et • (X = Cl, Br), in the case of II. The occurrence of the second reaction in II was confirmed by analyses of the precipitates formed in the reaction and by reacting TiCl 4 with EtAlBr 2 . The reducing power of the organometallic compounds examined decreases in the range: AmNa &gt; Et 2 AlBr &gt; EtAlBr 2 . Polymerization results with system I showed that active catalysts are obtained only with AmNa/TiCl 4 mole ratios &gt; unity. The polymer yield appeared to increase with increasing catalyst ratio. This may reasonably be explained by postulating the existence of an AmNa‐TiCl 3 complex as the actual catalytic species. In this range of catalyst ratios, the intrinsic viscosities of the polyethylenes remain approximately constant. In the case of system II, polymerization results could also be interpreted by assuming the existence of one complex or a mixture of a number of complexes as the catalyst. With Et 2 AlBr/TiCl 4 mole ratios &gt; ∼ 2, a complex between Et 2 AlBr and TiCl 3 (Et 2 AlX‐TiX 3 ) is postulated. With catalyst ratios in the vicinity of unity and lower, ambiguous results were obtained due to the occurrence of reactions between the catalyst components during polymerization.