Research Of Ethylene And 1-octene Coplymer Catalyzed By Metallocene Catalysts

Homogeneous metallocene catalysts which have the characteristics of single-sites,stereoselectivity and high copolymerization activity for a-olefins,have been a hotspot in the field of coordination polymerization after traditional Ziegler-Natta catalysts.DOW Chemical invented the constrained geometry metallocene catalyst(CGC).Combined with its unique InsiteTM high temperature continuous solution polymerization technology,the popular POE products was introduced(represented by ethylene/1-octene copolymer).POE exhibits both high elasticity at room temperature and processability above melting point.It has become an important thermoplastic elastomer for excellent physical properties owing to high comonomer content.However,the core catalyst and high temperature technology are still monopolized by foreign companies.There are some domestic studies in CGC and high temperature solution polymerization,but problems of low yields and unstable quality have always existed in catalysts synthesis.At the same time,it is still difficult to break through the high temperature bottleneck during the specific polymerization operating process.In this project,we utilized cyclopentadiene,indene,and dichlorodimethylsilane(or similar structure)as raw materials to synthesize three ligands with sodium as a protonated reagent.Catalysts possessing novel structure of alkoxy-bridged bi-metallocene were gained when ligands treated with Li-nBu followed by TiCl4 then hydroquinone.These catalysts were used to prepare ethylene/1-octene copolymer after MAO activation.Catalysts and copolymer were characterized by means of 1H/13C NMR,MS,FT-IR and DSC.The problems encountered in the synthesis were analyzed.In the process of demonstrating its high temperature performance,the polymerization method was improved.The reaction process between main catalysts and cocatalyst was isolated from the polymerization container for the purpose of entire activation.Effects such as the temperature,catalyst concentration,Al/Ti molar ratio and 1-octene concentration were studied about ethylene/1-octene polymerization results.When Cat.2 was used at 100?,the polymerization conditions were:activation temperature 60?,catalyst solution 2 mL(concentration 1.5×10-3 mol·L-1),Al/Ti molar ratio 300/1,1-octene concentration 0.3 mol·L-1.In this case,the activity was as high as 6.8×105 g POE·(molTi)-1h-1,with 1-octene insertion of 11.61 mol%.