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Solubilization of sodium cocoyl isethionate
James Ziming Sun1, James W Parr, Michael C E Erickson
1Advanced Research Laboratories, 151 Kalmus Dr Suite H-3, Costa Mesa, CA 92626, USA.
Journal of Cosmetic Science
|January 20, 2004
Summary
Sodium cocoyl isethionate (SCI) is difficult to dissolve in water, limiting its use in liquid detergents. This study presents three methods to improve SCI solubility, enabling its use in liquid formulations.
Area of Science:
- Physical Chemistry
- Surfactant Science
- Formulation Chemistry
Background:
- Sodium cocoyl isethionate (SCI) is a widely used surfactant in syndet bars for over 30 years.
- Its excellent skin compatibility and cost-effectiveness are well-established.
- Limited water solubility hinders SCI's application in liquid detergent systems.
Purpose of the Study:
- To investigate the thermodynamic principles governing SCI solubilization.
- To understand the equilibrium of solubilization for SCI in aqueous systems.
- To develop strategies for incorporating SCI into liquid detergent formulations.
Main Methods:
- Analysis of enthalpy and equilibrium of solubilization for SCI.
- Characterization of SCI and various co-surfactants.
- Development of three distinct methods to prevent SCI recrystallization in aqueous solutions.
Main Results:
- The enthalpy of solvation for SCI in water is unfavorable.
- Three methods were developed: (1) micellar entrapment of SCI using secondary surfactants, (2) ion exchange of sodium with ammonium or triethanolammonium, and (3) emulsification of SCI.
- These methods effectively prevent SCI recrystallization in aqueous solutions.
Conclusions:
- SCI can be effectively utilized as a primary surfactant in liquid detersive systems.
- Combining two or more of the developed methods enhances SCI's stability in aqueous formulations.
- This research provides formulators with viable strategies to overcome SCI's solubility limitations.