Preliminary tests have shown that if MnCl2 is used as a support material a polypropylene with a low molecular weight is produced. The activity of these catalysts is low. A low molecular fraction increases, however, the gloss of moulded products. As a molecular fraction with short chain length also acts as a lubricant in the polymer this short chain material would be an advantage if it is produced simultaneously with the normal high molecular weight polypropylene. This ability to influence the molecular weight distribution of the product was the reason why MnCl2 was chosen as a doping salt in the MgCl2 support material. The effect of Mn doping on the MgCl2 support material has been investigated. The following conclusions have been drawn from this investigation: (i) Very good morphology is achieved if the MnCl2 concentration is below 30%. At higher doping concentrations the result is poor morphology. (ii) Large catalyst particles were produced. The particles were of great mechanical strength, leading to the formation of large polymer particles with a very narrow PSD. No fines were produced partly due to agglomerization. This advantage was achieved only if the MnCl2 concentration was below 30%. (iii) Optimum Mn doping concentration was 10 mol%. Using this doping concentration activity increased 25% (100% if kg PP/g Ti units are used). No loss in isotacticity. At higher Mn concentrations activity decreased linearly. The molecular weight distribution was effected. A broader MWD was achieved, The greatest effect was achieved with a Mn concentration of 10 mol%. The polydispercity increased from the standard value of 3 to 7. At higher Mn concentrations the MWD decreased steadily. Low molecular weight polypropene can be produced by using pure MnCl2 as support material. (iv) The pore size distribution is effected by the Mn doping. A large portion of pores between 1 and 3 microns are produced. In standard polypropylene the largest fraction is to be found between 10 and 100 microns.
