P. Galli’s scientific contributions

The dynamic commercial development of the polyolefin (PO) materials was discussed. The revolutionary and evolutionary technology advances contribute to the significant expansion of the polymer property through synergetic combination of the new catalysts and potential processes. The metallocene catalysts show achievements of significantly improved polymer properties due to the excellent capability of distributing the comonomers in the polymer chain in an ideal way. It is stated that the continuous improvements in the Zn-based RGT catalysts are driving a dynamic expansion of the property envelope of PP-based materials.

A historical survey about the development of Ziegler-Natta catalysts for polymerization of propylene is given. After having employed catalysts based on titaniumtrichloride for several years, in the 70's catalysts of the so-called second generation were introduced, which are more effective and yield products of higher crystallinity. Catalysts of the so-called third generation and their morphological properties are extensively dealt with. These catalysts give high yields and highly stereoregular polymers and enable simplification of polypropylene technology and energy saving. In the future polypropylene manufacturing will probably consist only of the polymerization steps with no need for centrifuging, extruding or another post-treatment.Es wird ein historischer Überblick der Entwicklung von Ziegler-Natta-Katalysatoren für die Propylenpolymerisation gegeben. Nach dem jahrelangen Einsatz von Titantrichlorid wurden in den 70er Jahren neue Katalysatoren der sogenannten zweiten Generation eingeführt, die schneller wirken und zu kristallineren Produkten führen. Ausführlich wird auf die neuere Entwicklung zu Katalysatoren der „dritten Generation”, speziell auf ihre morphologischen Eigenschaften eingegangen. Diese Katalysatoren ergeben sehr hohe Ausbeuten, sterisch sehr regelmßige Polymeren und eröffnen Möglichkeiten zur Vereinfachung der Polypropylentechnologie und Energieeinsparung. In Zukunft wird die Polypropylenherstellung nur aus der eigentlichen Polymerisationsstufe bestehen, und es wird keinerlei Nachbehandlung wie Zentrifugieren oder Extrudieren erforderlich sein.

The scientific and industrial significance of Ziegler–Natta catalysis for the development of polyolefin polymerisation processes and the improvement of product properties has been proven by the explosive growth of their worldwide consumption.The key of this huge evolution, still in progress, has been the revolutionary developments of the catalytic system, which can be considered as the true ‘engine’ for the technological innovation.A long and systematic research effort resulted in the truly scientific understanding of the complex catalysis mechanisms.This has allowed a great process simplification, which has culminated in the polymer particles themselves working as microreactors. This catalysis and process breakthrough, the reactor granule technology (RGT) has made multimonomer polymerisations possible, enhancing enormously the degree of freedom in achieving new materials.In order to continue the guaranteeing of the achievement of novel properties, a continuous development in the catalyst performance is needed.In recent years, a lot of attention has been focused on metallocene catalysts and polymeric materials they have generated.In spite of the huge expenditure from companies for research and development, metallocene polymers have acquired only niche positions in the marketplace due to their poor processability and catalyst costs.The possibility to combine Ziegler–Natta and metallocene (singe site, more in general) catalysts has been explored.Polymerisations synergistically coupling with the advantages of the two catalytic systems will allow the improvement and enlarging of the property envelope of today's polyolefins.The full exploitation of this potentiality will make the future for the revitalised Ziegler–Natta catalysis brighter still.

In the long history of materials, the development of the polyolefins represents a real unique adventure. The discovery of the new Ziegler-Natta catalyst families in the fifties activated a process that entered in a dynamic revolutionary development, still very much in progress in the present days, after having been kept quiet and at a very low profile for two decades. Their early development, in spite of the bright promises, was more difficult than expected and their commercial growth was very disappointing, at least during the first 20 years of their life. In the last 20 years we have assisted in the tremendous technology development and in an ever increasing explosive, commercial success, which is incomparable in the history of materials. Considering the past and looking at the future, strange and interesting similarities appear, being that in both cases there were, and there are, bright promises and heavy drawbacks for the polyolefin material family. We have to recognise that in both cases the commercial success has been, and will only be, the result of a continuous process technology innovation and consequent polymer property envelope expansion generated by an intensive commitment in basic research on catalysts, polymerisation processes and material technology. The situation at the beginning of the new millennium is totally different, but there are analogies at present that could perhaps be faced and solved by adopting the approach that has been the key to the solution of the problems of the sixties: the understanding, optimisation and management of the catalyst towards the new polymer properties.

Polypropylene is one of the most versatile and successful materials in the market because of the ever-increasing spectrum of polymer composition and properties which have originated from continuing breakthroughs in catalyst and process technology. Industrial polypropylene production is based on Ziegler-Natta supported catalysts. The success of MgCl2-supported catalysts is also due to the development of spherical catalysts with controlled particle size and porosity, used in bulk liquid monomer and gas-phase processes for production of a broad range of homo- and copolymers and multiphase polymer alloys via “Reactor Granule” technology. The most recent development is the discovery of MgCl2/TiCl4/diether catalysts which can give PP yields twice as high as those obtained with previous catalysts. The achievement of a better control of the polymer structure has resulted in an increased capability to tailor the products according to the performance requirements, both in the conversion technologies and in the application life cycle, as well as to extend their application to new market areas.