Liquid and Supercritical Carbon Dioxide Assisted Blending of Poly(vinyl acetate) and Citric Acid

The use of liquid and supercritical carbon dioxide was explored for the blending of poly(vinyl acetate) and citric acid as a basis for developing a new process for making chewing gum which would allow for flavorings to be released slower during chewing. Mixtures of 75% of polymer and 25% citric acid by mass were blended with carbon dioxide from 5 to 60 min over a temperature range of 25 to 55 (degree)C and a pressure range of 83 to 241 bar in a batch process. Samples were then artificially chewed and citric acid dissolution monitored. Comparisons were made with samples prepared without carbon dioxide. In all cases, carbon dioxide blending produced polymers which retained the critic acid longer and hence produced more desirable products. With carbon dioxide, temperature had the largest effect on citric acid retention while pressure (or density) had only a modest effect. To make the flavoring be retained the longest in the polymer, the highest temperature and pressure (density) should be used with the longest blending time in carbon dioxide.