Control of molecular weight distribution for polypropylene obtained by commercial ziegler-natta catalyst: Effect of electron donor

Abstract

Polymerization of propylene was carried out using a MgCl 2 -supported TiCl 4 catalyst in conjunction with triethylaluminium (TEA) as the cocatalyst and various types of alkoxy silane compounds as an external donor. The effect of the external donor on the performance of the catalyst with different internal donors was investigated. The polydispersity index (PDI) of polypropylene (PP) obtained with the diether and succinate based catalyst were decreased with the introduction of an external donor and the PDI increased for the phthalate based catalyst. The molecular weight and PDI increased with the introduction of an external donor. The highest PDI of PP was obtained by polymerization with di-n-propyldimethoxysilane (DnPDMS) as an external donor. In addition, a mixture of external donors was used to control the PDI of PP and the composition of the catalyst was examined after treated with TEA/external donor. Furthermore, the theoretical PDI value was calculated for a mixture of external donor systems. The PDI of PP could be controlled and predicted while retaining high activity, high isospecificity and high molecular weight by changing the structure of the external donor and/or their mixture.

Mechanism of Propylene Polymerization with MgCl2-Supported Ziegler–Natta Catalysts Based on Counting of Active Centers: The Role of External Electron Donor

“…The industrial production of more than 50 million tons of isotactic polypropylene (PP) each year is based on catalyzed propylene polymerization with MgCl 2 -supported Ziegler–Natta catalysts. , Organic electron donors like esters, ethers, and alkoxysilanes are widely used in the catalyst preparation and polymerization processes, which play key roles in enhancing isotacticity and regulating molecular weight distribution of the PP products. − The electron donor added in the process of catalyst preparation is called the internal electron donor (Di), and the electron donor added in the polymerization process is called the external electron donor (De). In recent decades, the most commonly used catalyst in PP production contains phthalate as Di and alkoxysilane as De.…”

Investigating Effects of Using Mixtures of Two External Electron Donors on Microstructure and Properties of Polypropylene/Poly(ethylene‐co‐propylene) in‐Reactor Blends Based on Ziegler–Natta Catalyst

“…Also, it is believed that an increase in the bulkiness of the alkyl group increases the I.I., while the I.I. decreases with increase in the bulkiness of alkoxy groups . So, the lower activity of polymerization in the presence of donor A can be related to its higher electron density.…”

Internal donors on supported Ziegler Natta catalysts for isotactic polypropylene: a brief tutorial review

“…For this type of IDs, owing to ester bonds, leaching is quite significant in the presence of cocatalyst. The EDs would normally add to this catalyst to maintain stereo specificity of the polymer formed and the appropriate selection of EDs is required for fine tuning to improve the isotacticity of the PP [83]. PP grades from this catalyst have good processability with applications like injection molding and pipes.…”