Abstract:

To solve the problems brought by organic or basic solvents in the modification process of shellac, this study used supersaturation method to prepare a weakly acidic, well-dispersed aqueous dispersion of bleached shellac. A three-variable, three-level Box-Behnken experimental design combining with response surface modeling (RSM) was employed for minimizing average particle size of bleached shellac dispersion. A regression model was proposed for the average particle size as a function of three crucial process parameters. A minimum average particle size of 20.34μm was obtained under the optimized conditions: rotational speed of dispersion machine 11054 r/min, dropping speed of shellac, and alcohol concentration 6.42%. Granularity analysis using a laser granularity analyzer indicated that the size of 99.99% particles was distributed uniformly, less than or equal to 0.6 μm. Optical microscope and scanning electron microscope (SEM) observations revealed that bleached shellac existed in globular particles in the dispersion and could form smooth resin membrane.

Key words: supersaturation method, aqueous bleached shellac dispersion, submicron, film-forming capacity, soapfree emulsion