SYNTHESIS OF STARCH ACETATE - STATISTICAL DESIGNED EXPERIMENTS TO OPTIMIZE THE REACTION CONDITIONS

The synthesis conditions for Durabond A corn starch acetate (SA) were varied by using statistical designed experiments with the aim to optim ize the yield and solubility, and to minimize the color. The thirty ex periments in the design vary the: (1) Percentage water in the starch ( 0, 3, 6); (2) catalyst concentration (0.25, 0.60, 0.95 wt%); (3) total amount of acetic anhydride (1.0, 1.25, 1.5 mol times the number of hy droxyl groups on the starch); (4) starch concentration (15, 25, 35 wt% ); (5) reaction time (1, 2.5, or 4 h); and (6) reaction temperature (6 0, 80 or 100 degrees C). The major factors controlling the acetyl valu e (AV), yield and the solubility are the reaction temperature (T) and the T squared. Some two factor interactions that effect the process ar e: (1) water percentage with T, (2) the reaction time with T, and (3) the catalyst concentration with starch concentration. The optimal cond itions are: (1) a T range from 84 degrees C to 92 degrees C; (2) a sul furic acid catalyst concentration of 0.25 wt% with respect to the star ch concentration, (3) an acetic anhydride ratio of 1.0; (4) a 35 wt% s tarch concentration; (5) a 4 h reaction time, and (6) a percentage wat er in the starch of(0-6%). There is a strong correlation between the 1 0% and 20% SA solution solubility in acetone:water (96:4) with the AV. if the AV is > 55 then > 90% of the SA at a concentration of 10% is s oluble in acetone:water (96:4).