Effect of the structure of external alkoxysilane donors on the polymerization of propene with high activity Ziegler‐Natta catalysts

Abstract

Propene was polymerized in bulk in the presence of high activity heterogeneous Ziegler-Natta catalyst with the purpose of finding correlations between the structure of' an external alkoxysilane donor and the polymer. Nineteen silane compounds (1-8) of the structure R,lSi(OR)4.,l, where n = 1-4, R=C,H,, alkyl or H; R' = C,_,-alkyl, were used as external donors. The effect of Si/AI mole ratio was studied. The effect of the external alkoxysilane donor on the polymerization strongly depends on the number and size of alkoxy groups and the size of hydrocarbon groups attached to the silicon atom. Two major effects were observed: selective deactivation of atactic active centers and the increased production of high-molecular-weight isotactic polypropylene.Evidently, at least one free non-hindered alkoxy group in the complex between alkoxysilane and AIEt, is required for the selective deactivation. Also, the size of the hydrocarbon group of the donor strongly influences the selectivity of the deactivation. 0025.1 16)</89/$03.00Recently, Guyot et al.l0) and Sacchi et

Influences of silane/ether composite external donors on propylene polymerization with MgCl2-supported Ziegler-Natta catalyst in the presence of hydrogen

“…Furthermore, when DCPDMS was used as external donor, the catalytic activity, isotacticity index and molecular weight of PP were obviously higher than the system using DPDMS as external donor. These polymerization results were similar to the previous reports of other research groups [8,9]. The multiplicity of active centers in MgCl 2 -supported Z-N catalysts has been widely recognized.…”

The discovery and progress of MgCl2‐supported TiCl4 catalysts

“…The function of alkoxysilanes in enhancing not only the stereospecificity but also the molecular weight of the resulting PP also was reported. 27,28 Designing suitable structures of dialkyl phthalates and alkoxysilanes gave us about 1000 times higher activity than the TiCl 3 catalysts and extremely high stereoregularity that was more than 98% of I.I. Furthermore, the resulting PP did not have any regio-irregularity except for its chain end.…”

External Donor Induced Direct Contact Effects on Mg(OC2H5)2‐Based Ziegler‐Natta Catalysts for Propylene Polymerization

“…[20,21] In contrast, the external donor is adsorbed in the vicinity of at least some isospecific sites in such a way as to modify their stereochemical behavior or to generate new isospecific centers having different stereoselectivity. [22,23] Recently, aminosilane compounds having dihydrocarbyl amino or cyclic amino groups were noticed because they presented very unique characteristics for the control of molecular weight and its distribution when they were applied to external donors. [24] Aminosilane compounds containing amino groups and alkoxy groups can interact with the catalyst through both nitrogen and oxygen atom.…”