Effect of internal electron donor on copolymerization of ethylene and 1-hexene catalyzed by supported Ziegler- Natta catalysts

Abstract

Abstract:The four kinds of TiCl 4 /MgCl 2 type supported Ziegler-Natta catalysts, Cat-1, Cat-2, Cat-3 and Cat-4, were prepared by reaction of MgCl 2 -ethanol adduct with TiCl 4 . Cat-1 contains no internal electron donor (ID), Cat-2 contains diethyl phthalate (DEP) as ID, Cat-3 contains anisole as ID, and Cat-4 contains both DEP and anisole as ID. Ethylene copolymerizations with 1-hexene by these catalysts were compared. Influences of the internal electron donor on catalyst activity, copolymer composition, composition distribution, molecular weight and molecular weight distribution were investigated. Cat-3 showed the largest ability of incorporating 1-hexene into copolymer chains among the four catalysts. Each copolymer sample was fractionated into two fractions: fraction soluble in boiling nheptane (HS) and fraction insoluble in boiling n-heptane (HI). 1-Hexene content of the HS fraction is 6~10 times of that in the HI fractions. Amount of the HS fraction of copolymer by Cat-2 and Cat-4 was much lower than that of Cat-1 and Cat-3. Introduction of internal donor to the catalysts, especially diethyl phthalate (DEP), increased the blockiness of HI fractions. The molecular weight of both fractions increased when there is ID in the catalyst. Addition of anisole reduced the difference in molecular weight between HS fraction and HI fraction, but addition of PA enlarged the difference. The results are discussed based on a mechanistic model of MgCl 2 -supported Ziegler-Natta catalysts.

A Novel Ziegler–Natta-Type Catalytic System—TiCl4/2,2′-Dimethoxy-1,1′-Binaphthalene/Et3Al2Cl3/Bu2Mg for Production of Ultrahigh Molecular Weight Polyethylene Nascent Reactor Powders, Suitable for Solvent-Free Processing

“…Research aimed at developing of new internal donors among aliphatic ethers is in progress [20,21,22], but the use of alkoxyarenes in this role has been studied to a lesser extent. It is noted that the use of anisole instead of the “classical” diethyl phthalate leads to an increase in the activity of ZN catalysts in the copolymerization of ethylene and hexene-1 [23] and, also, the polymerization of hexene-1 [24]. Since the internal donors with two oxygen atoms have been found to be more effective than single oxygen-containing donors [25], in the present work, we used 2,2′-dimethoxy-1,1′-binaphthalene as a neutral bidentate chelating ligand, capable of forming an octahedral titanium complex.…”