Copolymerization of ethylene/1-olefin with spherical silica-supported metallocene catalyst

Abstract

At present, the first consideration and largest volume of polymers in the plastics industry (Polyolefins) are mostly consisting of polyethylenes and polypropylenes, which are often used in any application because of their excellent cost/performance value. LLDPEs (Linear low-density polyethylenes), synthesized by the copolymerization of ethylene with α-olefin, is the great commercial significance in polyethylene series. Which the metallocene / methylaluminoxane catalyst system participate in production of LLDPEs provide the great among of advantage. But there are only a few major problems, such as difficulty in controlling polymer morphology, inability to be used homogeneous metallocene in slurry or gas-phase, and need very large amount of methylaluminoxane to achieve maximum of catalytic activity. So,the way to wipe out the few constraints is attaching the metallocene to the support without losing the performances of the homogeneous complex and activation step of metallocene. This research proposed the development of metallocene catalyst by spherical silica supports with different particle diameter such as submicron, 3, 5, and 10 µm. This study was divided into two parts, which difference in the impregnation method. In the first part, the polymerization reaction was performed using a supported zirconocene/MAO catalyst, which was prepared by in situ impregnation method. The higher outer surface area of supports apparently resulted in increased polymerization activity for SiO2 3 µm. The polymerization activity was also dramatically increased when comonomer was added. The second part was similar to the first, but catalyst precursors were prepared by ex situ impregnation method. The optimum particle size gave the better activity, but too strong interaction between MAO and support affected the negative result to the catalytic system. All copolymer were characterized by means of 13C NMR and DSC.