Optimization of process parameters for masterbatch sulfur dispersion in chemical plant

Abstract

One of the main factors limiting the production of a stable sulfur dispersion in masterbatch or in mass scale is finding the optimized parameters set for each of the processes employed, subject to its particle size, viscosity, pH and TSC. Instable sulfur could affect the final product’s quality, for example, “sulfur bloom” on the produced rubber film. In this study, the experimental design follows Taguchi’s L9 orthogonal array to determine the optimum parameters for sulfur dispersion prepared via masterbatch mixing in 4 MT mixing tank; to determine the optimum parameters for sulfur dispersion grinded in 60-Litre grinding mill; and finally, to analyze the morphology of sulfur dispersed in rubber film from selected sulfur dispersion sets. The study involved mixing of sulfur with water and surfactant of a fixed dosage in 4 MT mixing tank with various mixing speed and mixing time. The sulfur dispersion with optimized mixing parameter set was chosen for the grinding mill optimization which involved various grinding mill’s motor speed and pump rate. The plot of means and tabulated ANOVA based on respective S/N ratio show that particle size and viscosity were mostly affected with both processes’ parameter changes. At higher mixing speed of 800 rpm and longer mixing time of 30 minutes, an optimized sulfur dispersion was able to be obtained according to the viscosity and particles size responses. It was also found that higher motor speed and lower pump rate of the grinding mill at 800 rpm and 350 L/min respectively produces smaller particle size of sulfur dispersion which also hinders severe formation of sulfur crystals observed on the casted rubber film. Severe sulfur crystals were observed on the rubber film’s casted with larger sulfur particle size or ‘less stable’ sulfur dispersion. Overall, higher mixing speed and longer mixing time, followed by higher grinding mill’s motor speed and lower pump rate favors the production of smaller particle size of sulfur dispersion that is optimized and is more stable especially when applied in rubber products.