T. Dall’Occo’s scientific contributions

The most advanced catalysts, based on MgCl2-supported TiCl4 and electron donors, are able to provide polypropylenes with an isotacticity higher than 99%. This, together with the continuous progress made in understanding and exploiting the role of electron donors in controlling polymer MW and MWD, has led to polypropylene products having an unprecedented level of stiffness or stiffness/impact balance. On the other hand, other potential fields of application exist where rigidity is not required and, actually, the key property is softness rather than stiffness. As a matter of fact, it has clearly been established that soft polypropylenes can be more attractive from the business standpoint than their stiff counterparts. Generally, these materials are multiphase copolymers obtained via sequential gas-phase copolymerization of propylene and ethylene-propylene mixtures using the morphology-controlled conventional MgCl2-TiCl4 catalysts based on the couple phthalatesilane as internal and external donors. This communication deals with a new class of donors that can be used either as external donors in combination with phthalates (A) or as internal/external donors (B). When combined with the MgCl2-TiCl4 systems, both donors substantially improve the flexibility and softness of the resulting soft materials while maintaining the operability window of the Catalloy process. This is due to the particular microstructure of the relevant building blocks: the presence of a controlled concentration of stereodefects in the homopolymer fraction, and good comonomer distribution in the copolymer fraction. As compared with the conventional products, the new ones show comparable or better flexibility when the rubber phase is relatively rich in ethylene. This likely opens the door for these products to enter the demanding thermoplastic elastomers (TPE) application field.

A new alumoxane alternative to MAO was synthesised, characterized and used as cocatalyst for metallocene based polymerizations. It is based on Al(2,4,4-trimethylpentyl)3 (TIOA). Alumoxanes were prepared by reacting TIOA and H2O with different molar ratios. 1H NMR spectra of these products are characterized by the presence of broad bands and of resolved multiplets. Their relative amount in the region between 1.9 and 2.5 ppm was identified as the “finger-print” of the polymerization activity.