MAGNESIUM CHLORIDE-SUPPORTED CATALYSTS FOR ZIEGLER-NATTA PROPENE POLYMERIZATION - ETHYL FORMATE AS INTERNAL BASE

MgCl2-supports for Ziegler-Natta polymerization processes were prepare d by an activation method based on the thermal removal of ethyl format e (EF) from adducts between EF and MgCl2. The various steps of activat ion were investigated by X-ray diffraction (XRD) and infrared spectros copy (FT-IR) of MgCl2(EF)x adducts having 0 less-than-or-equal-to x le ss-than-or-equal-to 2. A subsequent titanation process of the above su pports gives rise to a decrease of the EF content in the obtained prod ucts. By XRD on polycrystalline powders, the effects were investigated of the EF concentration in the titanated adducts used in Ziegler-Natt a polymerization processes and having a composition [MgCl2(EF)k(TiCl4) m]. Moreover, the relationships were investigated between yield and st ereospecificity in the propene polymerization tests; a maximum of isos pecificity was observed for the mole ratios Ti/Mg = 0,065, EF/Mg = 0,4 7 and Ti/EF = 0,15. It was also demonstrated that a progressive remova l of EF from the adducts gives rise to supports showing a different st ructural disorder in dependence on the removal time.