Gas phase etylene polymerization without any solvent: A new reactor study

Polyethylene, the most important materials of plastic industry, is classified according to molecular weight, density and crystallinity. UHMWPE attracts attention in the industry with excellent material properties and usability in wide range areas of industry. However, when the open literature is investigated, it is understood that nearly all studies are focused on catalysts. Although many types of polyethylene can be produced by using slurry or gas phase, only slurry process is being used for UHMWPE production because of the heat transfer phenomena. Therefore, mass transfer from gas to liquid and from liquid to solid phase can be limiting factor for UHMWPE. The aim of this study is to see the realizability of gas phase process for UHMWPE, determine important parameters and optimum working conditions, gather information to design a continuous reactor to obtain UHMWPE in gas phase. Taguchi method was used to analyze optimization of gas phase ethylene polymerization performed by using a semi-batch minireactor system. Temperature, pressure, TEA/Ti and time were chosen as parameters. Effect of each parameter on results was determined according to "bigger is better" approach. It was shown that UHMWPE formation in gas phase process is possible. Moreover, all parameters were effective for UHMWPE. While increasing temperature and TEA/Ti increased the molecular weight until optimum value, increasing the polymerization time had an adverse effect. In this study, semi-batch minireactor system was developed as a pre-study of important outputs to perform gas phase process in continuous phase. Polyethylene with molecular weight of 6.89 million grams/moles was obtained.