A light-colored rosin glycerol ester was synthesized from gum rosin and glycerol in the presence of a highly effective decolorizing agent. The effects of the type and dosage of the decolorizing agent and the reaction temperature and time on the yield, softening point, color, and acid number of the rosin glycerol ester were investigated. Experimental results showed that 4,4′-thio-bis(6-tert-butyl-3-methyl phenol) was the best decolorizing agent. It promoted esterification at an optimal dosage of 0.5% (based on the weight percentage of starting material rosin). Suitable conditions for esterification of rosin and glycerol were: reaction temperature, 260–270°C; reaction time, 6–8 h; and rosin/glycerol molar ratio, 2.5:1 (mol mol-1). The characteristics of the rosin glycerol ester obtained under these conditions were as follows: softening point, 90–94°C (ball and ring method); color, 1–2 (Gardner value); acid number, 7–8; and yield, >88% (based on the total weight of rosin and glycerol). The selected additive has a multifunctional effect involving bleaching, disproportionation, and catalysis.
©2007 by Walter de Gruyter Berlin New York