A practical criterion for synthesizing ethylen-۱-butene copolymer in powder form in slurry polymerization with a Ziegler-Natta catalyst and predicting its incorporated ۱-butene

The concentration of ethylene and ۱-butene in n-hexane as polymerization media was calculated at five different pressure levels (۴, ۶, ۸, ۱۰, and ۱۲ bar) and four different ۱-butene concentrations (۰.۱۳, ۰.۲۶, ۰.۳۹, and ۰.۵۲ mol/L) in n-hexane at T= ۸۰°C using the Peng-Robinson thermodynamic equation of state. Some combinations of conditions were selected to perform the copolymerization reaction in the presence of an industrial TiCl۴/MgCl۲ Ziegler-Natta catalyst. The forms of the synthesized products were visually and qualitatively classified as either powder or sticky. The percentage of incorporated ۱-butene comonomer into the polyethylene chains was analyzed using calibrated FTIR tests. It was shown that for ethylene/۱-butene concentration ratios (β) in n-hexane above approximately ۱.۸۰, the product forms as a powder. For values below ۱.۳۰ threshold, the product was sticky. Thus, this ratio could be used as a criterion for selecting the proper combination of copolymerization pressure and ۱-butene concentration when aiming to achieve a powdered form of the product. It was shown that β has a strong correlation with the weight percentage of ۱-butene in the final LLDPE polymer. Therefore it can be used as an accurate prediction for wt.% of incorporated ۱-butene into the LLDPE chain within the studied concentration ranges with the specific catalyst system utilized.

Keywords:

Zeigler-Natta catalyst , LLDPE , ethylene-۱-butene copolymerization , ۱-butene incorporation , Peng-Robinson Equation of State