The influences of alkylaluminium as cocatalyst on butene-1 polymerization with MgCl2-supported TiCl4 Ziegler-Natta catalysts

Abstract

The influences of alkylaluminium compounds including triethylaluminium (TEA), triisobutylaluminium (TIBA) and diethylaluminium chloride (DEAC) on the catalyst activity, isotacticity and weight-average molecular weight (Mw) of the products in butene-1 (Bt-1) polymerizations with MgCl2-supported TiCl4 Ziegler-Natta catalysts were investigated. The catalytic activity of polybutene-1 (PB) increased in the order of TEA > TIBA > DEAC, while the Mw of PB synthesized with TEA was the lowest when compared with that with other alkylaluminium compounds. Solvent extracted fractionation combining with differential scanning calorimetry (DSC), gel permeation chromatography (GPC) and carbon-13 nuclear magnetic resonance spectrometry (13C-NMR) were used to conduct composition analysis of PB. Fractions including atactic polybutene-1 (aPB), high isotactic polybutene-1 with high Mw (HiPB) and medium high isotactic polybutene-1 with medium high Mw (MHiPB) were isolated for the first time from the PB. Using TIBA resulted more HiPB fractions with higher Mw. A minor incorporation of TIBA or DEAC in TEA increased the HiPB fractions of PB. The contribution mechanism of alkylaluminium compound in TiCl4/MgCl2 Ziegler-Natta catalyst was proposed to explain the influence of alkylaluminium compound with different structures on the active species and polymer components in PB.