Abstract:

Vacuum drying was applied to dry bleached shellac instead of normal temperature drying which has an outstanding disadvantage of low production efficiency dry. Response surface methodology (RSM) based on a three-level, two-variable central composite rotatable design (CCRD) was employed to evaluate the interactive effects of vacuum drying temperature and pressure on color index of bleached shellac and required drying time and two mathematical models were established for them as a function of vacuum drying temperature and pressure. The observed responses were in close agreement with the predicted values. This demonstrated the reliability of the two models in describing the vacuum drying of bleached shellac. The 8.48 h drying at 30 ℃ and 30 kPa resulted in a color index of bleached shellac of 1.0, and the bleached shellac product reached the first grade of the Chinese national standard; after drying at 50 ℃ and 30 kPa for 7.20 h, a product with a color index of 1.4 was obtained, which reached the second grade.

Key words: bleached shellac, vacuum drying, verification of optimized conditions, response surface methodology (RSM)