Ziegler-Natta catalysts, very high pressure

Conventionally, HAS are blended with PO during processing. 2-(Diethy-lamino)-4,6-bis[butyl(l,2,2,6,6-pentamethyl-4-piperidyl) amino]-l,3,5-triazine may be fed with an olefin directly into the low pressure polymerization process catalyzed with a modified MgCl2 supported Ziegler-Natta catalyst [142]. The catalytic activity was not impaired [143], Tetramethylpiperidine was reported to be a useful component in MgC -supported Ziegler-Natta catalysts as well. Very high stereospecificity of the synthesised PO was achieved. A complex of HAS with the alkyl aluminium activator was envisaged without interaction with the catalytically active alkyl titanium compound [144],... 

It was discovered by Ziegler in Germany and Natta in Italy in the 1950s that metal alkyls were very efficient catalysts to promote ethylene polymerization at low pressures and low temperatures, where free-radical polymerization is very slow. They further found that the polymer they produced had fewer side chairrs because there were fewer growth mistakes caused by chain transfer and radical recombination. Therefore, this polymer was more crystalline and had a higher density than polymer prepared by free-radical processes. Thus were discovered linear and high-density polymers. 

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