Synthesis of Isotactic Polybutene-1 with Ziegler-Natta Catalyst

Butene-1 is in excess in the polyolefin plants of Iran. Considering the properties of isotactic polybutene-1, including high creep and environmental stress cracking resistances, excellent elastic reversibility and good chemical abrasion resistance, there is a need to localize it in Iran.

Polybutene-1 was synthesized with an industrial Ziegler-Natta catalyst. To do this, polybutene-1 was synthesized by coordination polymerization of butene-1 with the help of triethylaluminium (TEAL) cocatalyst in n-hexane. By changing the monomer pressure from 1 to 1.7 bar and hydrogen amount from 0.01 to 0.13 L a wide range of polybutene-1s with different properties was obtained.

The highest values of activity and isotacticity for 0.06 L hydrogen and 1.4 bar monomer pressure were 24.76 kgPB-1/gTi.barB-1 and 97%, respectively. An increase in hydrogen led to a decrease in weight average molecular weight. Using cyclohexylmethyl dimthoxysilane as external electron donor, samples with weight average molecular weight from 149500 to 913000 g/mol, polydispersity index from 2.49 to 4.29, MFR from 0.19 to higher than 100 g/10 min, density from 0.876 to 0.911 g/cm3 for crystalline form I, and isotacticity from 81% to 97% were synthesized. The highest polydispersity index was obtained for the sample synthesized under 1.4 bar monomer pressure and 0.01 L hydrogen. The lowest isotacticity index was related to the sample synthesized under 1 bar monomer pressure and 0.13 L hydrogen. This catalyst has the ability to produce polybutene-1 with a narrower molecular weight distribution compared to those reported in other works. Comparison of mechanical properties with those reported by other researchers showed an increase in elongation-at-break for the sample. With the expansion of operational conditions, variety of products and their commercialization will be possible.