Sodium cocoyl isethionate: solubilization, applications in synthetic detergent

General Description

Sodium cocoyl isethionate is a safe and effective ingredient widely used in syndet formulations. It exhibits excellent cleansing and skin compatibility properties, making it suitable for delicate and sensitive skin types. Its limited solubility in water has been overcome by incorporating CI ions within micelles, replacing sodium ions with ammonium ions, and emulsifying SCI. Formulators can use these methods to maximize its effectiveness as a primary surfactant in liquid detergent systems. Sodium cocoyl isethionate is biodegradable and environmentally friendly, making it ideal for sustainable and eco-friendly formulations.

Figure 1. Sodium cocoyl isethionate

Solubilization

Sodium cocoyl isethionate is widely used in syndet bar formulations for its cost-effectiveness and good skin compatibility. However, its limited solubility in water has prevented it from being commonly used in liquid detergent systems. A study aims to understand the solubilization process of SCI and its properties when combined with various surfactants. The solubility of SCI in water is not favorable in terms of enthalpy of solvation. To overcome this challenge, three methods have been developed to keep SCI in aqueous solutions without recrystallization. The first method involves incorporating CI ions within micelles formed by secondary surfactants. This helps to enhance the solubility of SCI by creating a stable environment within the micelles. The second method focuses on replacing sodium ions with ammonium ions (and/or triethanolammonium). This ion exchange process further improves the solubility of SCI in water. The third method involves emulsification of SCI, forming micelles that transform into emulsified oil drops. This process effectively prevents the recrystallization of SCI. By combining two or more of these methods, formulators can successfully use SCI as the primary surfactant in liquid detergent systems. Understanding the solubilization equilibrium and utilizing appropriate surfactant systems can help maximize the effectiveness of Sodium cocoyl isethionate in aqueous solutions. ¹

Applications in synthetic detergent

Sodium cocoyl isethionate is a popular surfactant widely used in syndet (synthetic detergent) formulations. Syndets are synthetic cleansing products that offer milder and gentler cleansing compared to traditional soap-based products. Sodium cocoyl isethionate is known for its excellent foaming properties, making it a key ingredient in syndet bars, shampoos, body washes, and facial cleansers. It creates a rich and luxurious foam that effectively removes dirt, oils, and impurities from the skin and hair without causing excessive dryness or irritation. In addition to its cleansing properties, sodium cocoyl isethionate also exhibits excellent skin compatibility. It is known to be mild, non-drying, and non-irritating, making it suitable for sensitive and delicate skin types. It helps maintain the natural moisture balance of the skin, leaving it feeling soft, smooth, and hydrated. Furthermore, sodium cocoyl isethionate has good compatibility with other cosmetic ingredients, allowing for the formulation of stable and aesthetically pleasing syndet products. Its versatility and effectiveness in producing a gentle yet thorough cleansing experience have made Sodium cocoyl isethionate a favored choice for formulators in the personal care industry. ²

Safety

Sodium cocoyl isethionate is considered a safe ingredient in cosmetic and personal care products. Studies have demonstrated that it is well-tolerated by the skin and is less irritative than other anionic detergents, such as sodium laurate and sodium laurylsulphate (SLS).  In a four-day repeated open exposure model, exposure to sodium laurate resulted in burning sensations, erythema, and/or scaling, leading to a lower number of fulfilled exposures compared to SLS and other less irritative agents, such as sodium cocoyl isethionate. The low irritancy of sodium cocoyl isethionate can be attributed to its mildness, non-drying, and non-irritating properties, making it suitable for sensitive and delicate skin types. Furthermore, sodium cocoyl isethionate is considered safe for use in cosmetic products due to its low toxicity and non-carcinogenic nature. It is also biodegradable and environmentally friendly, making it an ideal choice for sustainable and eco-friendly formulations. Overall, studies have demonstrated that sodium cocoyl isethionate is a safe and effective ingredient in cosmetic and personal care products, with excellent cleansing and skin compatibility properties. ³

Reference

1. Sun JZ, Parr JW, Erickson MC. Solubilization of sodium cocoyl isethionate. J Cosmet Sci. 2003 Nov-Dec;54(6):559-568.

2. Korting HC, Lukacs A, Hamm D, Stanzl K, Braun-Falco O. In-use tolerability of two new syndet bars with sodium cocoyl isethionate, disodium lauryl sulfosuccinate and wheat starch as major ingredients in differing relations: results of a cross-over trial. Int J Cosmet Sci. 1992 Dec;14(6):277-282.

3. Tupker RA, Vermeulen K, Fidler V, Coenraads PJ. Irritancy testing of sodium laurate and other anionic detergents using an open exposure model. Skin Res Technol. 1997 May;3(2):133-136.

You may like