Studies on the low pressure polymerization of ethylene by use of catalysts containing potassium alkyls

Abstract

AbstractThe low pressure polymerization of ethylene by use of catalysts prepared from either butyl or amyl potassium, or the reaction product of potassium with chlorobenzene and titanium tetrachloride was studied. The efficiency of the catalysts depended on the molar ratio of the potassium alkyl to titanium tetrachloride but was in every case considerably lower than that of the corresponding lithium or sodium alkyl containing catalysts. Optimum molar ratios of the butyl potassium–titanium tetrachloride catalysts were between 2.8 to 6.1 with sharp drops on both sides of the optimum; for the amyl potassium between 1.1 to 3.7. The reaction product of potassium with chlorobenzene yielded much weaker catalysts with titanium tetrachloride, and the properties of the polymers obtained were different. The physical properties of the polyethylenes obtained, as determined from x‐ray diffraction diagrams, infrared spectra, and from melting points, showed similarity to those obtained with the lower alkali metal catalysts. The lower activity of the potassium catalysts may be related to the large ionic radius of the potassium, which influences the properties of the catalyst complex formed with titanium tetrachloride. Propylene did not undergo polymerization with the potassium alkyl containing catalysts at low pressure.