Characteristics of diether‐ and phthalate‐based Ziegler‐Natta catalysts for copolymerization of propylene and ethylene and terpolymerization of propylene, ethylene, and 1‐butene

Abstract

Copolymerization of propylene and ethylene and terpolymerization of propylene, ethylene, and 1-butene were carried out to compare the characteristics of diether-and phthalate-based Ziegler-Natta catalysts in a reaction system of pilot scale. The ethylene incorporation with the diether-based catalyst was higher but the 1-butene incorporation was lower compared with those of the phthalate-based catalyst. In the case of copolymers from the diether-based catalyst, melting behavior, determined through differential scanning calorimetry (DSC), showed a distinct shoulder peak and lots of nuclei were formed during crystallization. The diether-based catalyst led to polymers having blockier ethylene sequences compared with those of the phthalate-based catalyst; the highly crystallizable fraction (HIS) containing blockier ethylene sequences was produced with the diether-based catalyst. These results seem to be the result of regio-irregular characteristics of the diether-based catalyst.

Propylene Polymerization over MgCl2‐Supported Ziegler–Natta Catalysts Containing Tri‐Ether as the Internal Donor

“…9 In 1989, the polypropylene catalyst with 1,3-diether as the internal donor was developed by the Himont company. 26 This new internal donor provided a polypropylene catalyst with extremely high activity, isotacticity, hydrogen response, 19 and also narrower MWD without the need for any external donor, 25,26 which breaks the restrictions of the last two generations of catalyst that the polypropylene catalyst, must contain both internal and external donors. It could be considered as the fifth generation of Ziegler-Natta catalyst.…”

“…26 Concerning the high activity and high hydrogen response of the diether-based catalysts, it was reported that dietherbased catalysts had a high content of active sites with low regioselectivity, 19 that this effect can be ascribed to chain transfer after the occasional secondary (2,1-) rather than the usual primary (1,2-) insertion. 27 Additionally, the 1,3-diether strongly coordinates to the support and cannot be easily extracted 2 from the catalyst surface on contact with a cocatalyst such as alkylaluminum 19 because the 1,3-diether show higher affinity toward magnesium chloride than to a cocatalyst, and consequently diether-based catalysts make polypropylene having comparatively high isotacticity without an external donor. 16,19 The development of new electron donors (Lewis bases, usually containing oxygen atoms) is one of the chief areas of research in Ziegler-Natta olefin polymerization systems.…”

“…3 The internal donors prevent the coagulation of MgCl 2 particles during the milling process 14 and stabilize small primary crystallites of MgCl 2 , [15][16][17] resulting in an enhancement of the effective surface area, 14 and also control the amount and the distribution of TiCl 4 on the support surface. 4,16,[18][19][20] Additionally, the internal donor could prevent the formation of aspecific sites or transforms aspecific sites into highly stereoselective sites. 17,21 It is believed that the internal donor blocks particular sites on the MgCl 2 surface which otherwise, upon coordination with TiCl 4 , would generate precursors of nonstereospecific active sites.…”

“…27 Additionally, the 1,3-diether strongly coordinates to the support and cannot be easily extracted 2 from the catalyst surface on contact with a cocatalyst such as alkylaluminum 19 because the 1,3-diether show higher affinity toward magnesium chloride than to a cocatalyst, and consequently diether-based catalysts make polypropylene having comparatively high isotacticity without an external donor. 16,19 The development of new electron donors (Lewis bases, usually containing oxygen atoms) is one of the chief areas of research in Ziegler-Natta olefin polymerization systems. The addition of such donors has led to improvement in the activity and selectivity of Ziegler-Natta systems.…”

“…6,21,22 The role of the internal donor in the Ziegler-Natta catalyst system is very crucial in terms of activity, isotacticity, 23 hydrogen response, and molecular weight distribution (MWD). 19 External donors play a major role in controlling polypropylene catalyst activity, stereospecificity, MWD, and hydrogen response. 9 External donors markedly increase the stereospecificity of polypropylene and usually decrease the activity of Ziegler-Natta catalysts.…”