The role of alkoxysilanes in propylene polymerization catalysis. A study of model Ti(Oi‐C3H7)4‐Al(C2H5)2Cl/Mg(C4H9)2 catalyst system

• Published in: Polymer international Vol. 72; no. 7; pp. 655 - 663
• Main Authors: Kissin, Yury V, Rishina, Laura A, Lalayan, Svetlana S, Krasheninnikov, Vadim G
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01-07-2023; Wiley Subscription Services, Inc
• Subjects: 13C NMR analysis; Alkoxysilanes; Aluminum; Catalysis; Catalysts; DSC analysis; GPC analysis; Isotacticity; Magnesium; Molecular weight; Polymerization; Polypropylene; propylene; propylene polymerization; Titanium; Ziegler–Natta catalysts
• ISSN: 0959-8103; 1097-0126
• DOI: 10.1002/pi.6519

The article describes the modifying effect of methylcyclohexyldimethoxysilane (CH3)(cyclo‐C6H11)Si(OCH3)2 in propylene polymerization reactions with a pseudo‐homogeneous catalyst system: Ti(Oi‐C3H7)4‐Al(C2H5)2Cl/Mg(C4H9)2. This catalyst system is a convenient model for the analysis of modifier effects (effects of ‘external donors’) in supported Ziegler–Natta polymerization catalysts of the fourth generation. A combination of chromatographic, spectroscopic and calorimetric data for crystalline and amorphous fractions of polypropylene prepared in the presence of the silane shows that it has a dual modification effect: (i) the silane is a potent poison of stereo‐aspecific active centers in the catalyst (the centers producing amorphous polypropylene fraction) and (ii) silane molecules coordinate at isospecific centers in the catalyst and changes their nature: the centers produce isotactic polypropylene of higher molecular weight and a higher isotacticity level. © 2023 Society of Industrial Chemistry.
The catalyst system Ti(Oi‐C3H7)4‐Al(C2H5)2Cl/Mg(C4H9)2 is a convenient model for the analysis of modifier effects in supported Ziegler–Natta propylene polymerization catalysts. The dimethoxysilane (CH3)(cyclo‐C6H11)Si(OCH3)2 is a potent poison of stereo‐aspecific active centers in the catalyst and it changes the nature of isospecific centers; they produce isotactic polypropylene of higher molecular weight and higher isotacticity level.