Research On Copolymerization Of Ethylene And Propylene With Novel MgCl₂-Supported Vanadium-Based Catalysts

This paper was established in the research on the novel MgCl₂-supported vanadium-based Ziegler-Natta catalysts. We are aimed to prepare novel MgCl₂-supported vanadium-based Ziegler-Natta catalysts and to apply them in copolymerization of ethylene and propylene with AlEt3 as cocatalyst. This is the first time that the internal donors, such as diisobutyl phthalate (DIBP), 9,9-bis(methoxymethyl)fluorine (BMMF) were added to traditional vanadium-based Ziegler-Natta catalyst. It is expected that the catalytic activity can be improved by the novel vanadium catalysts and the properties of products will not be influenced obviously. Especially, ethylene/propylene elastomer with excellent properties will be synthesized.The performances of supported catalyst systems for copolymerization of ethylene and propylene, including effects of internal donors, polymerization temperature, the molar ratio of alkylaluminum to vanadium and the concentration of comonomer, have been studied systematically. The products have been characterized by gel permeation chromatography (GPC), differential scanning calorimeter (DSC) and ¹³C-NMR analysis to learn the performances of copolymers containing the molecular weight and the molecular weight distribution, the composition and microstructure, the crystalline and melting behaviors.Three catalyst systems (VCl₄/MgCl₂/BMMF, VCl4/MgCl₂/DIBP and VCl₄/MgCl₂) were compared, which contain free donor and different internal donors such as diisobutyl phthalate, 9,9-bis(methoxymethyl)fluorine by investigating the performance on copolymerization of ethylene and propylene. The copolymerization results indicated that the novel catalyst with internal donor behaved higher catalytic activity in copolymerization of ethylene and propylene. The low-crystalline and high molecular weight copolymers were obtained with these novel MgCl₂-supported vanadium catalysts. The reactivity ratio data indicated the catalytic systems had a tendency to produce elastomeric ethylene-propylene copolymers with random sequence structures.