Polymerization at temperatures lower than the temperature of catalyst formation induces no changes in the solid phase of the catalyst formed by Al(C2H5)3 + TiCl4. In polymerizations with catalysts of this class, maximum activity is observed when the titanium component of the catalyst is trivalent. Any different behavior indicates the presence of aluminum alkyl chlorides in the liquid phase of the catalyst.
The polymerization activity of the Ziegler‐Natta catalysts is significantly affected by the aluminium alkyls in the liquid phase. These may be studied provided the solid phase of the catalyst remains unchanged. Part of these aluminum alkyls is adsorbed on the surface of the solid phase. It is possible to displace one type of alkyls by another one or to elute it from the adsorbed layer. This last affects the polymerization rate.
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