Studies on Polymerization of 1, 3-Butadiene in Environment Friendly Solvents using Cobalt Based Catalyst System

Abstract

A study was conducted with the objective of replacement of benzene, which is popularly used as solvent in solution polymerization of 1, 3-butadiene using cobaltbased catalyst system. Benzene is a carcinogenic solvent which leads to Hematoxin that is linked to increased incidence of leukemia in humans. PBR-I plant of RIL-VMD utilizes benzene as the solvent for the polymerization of 1, 3-butadiene. Considering solvent substitution as the objective, an investigation was conducted with the study of properties of various possible solvent candidates. Selected candidates were toluene and toluene-heptane (50/50 wt%) mixture. Choices of these solvents were because of their low commercial cost, their non-toxic nature, their solubility parameter, viscosity and density. Furthermore, toluene-heptane (50/50 wt%) mixture has commercial importance as it is readily used with nickel-based catalyst system. This system is commercialized by Japan Synthetic Rubber Co. and PBR-II plant of RIL-VMD uses this technology. Study was started with toluene, where the effect of various parameters like co-catalyst and catalyst concentration, moisture, chain transfer agent, reaction time and temperature were studied. Effect of these parameters on the rubber quality was checked. Later toluene-heptane (50/50 wt%) mixture was tried. Role of moisture and chain transfer agent was found to be critical and covered in an elaborative way. Study has shown that toluene is not as effective as benzene for the polymerization of 1, 3-butadiene. However, toluene-heptane (50/50 wt%) mixture produced appreciating results. Reaction was faster in this solvent mixture system and the rubber properties were almost within satisfactory range. Hence, this solvent mixture can be considered as potential substituent of benzene.