Definition
Sodium lauryl ether sulfate(SLES) is an anionic surfactant which is widely used in rinse off products as a primary surfactant. In addition to excellent detergency (also referred as cleansing), it also has excellent emulsification and foamability. It is major component of rinse-off products. It is compatible with all surfactants except cationic.
Production Methods
Sulfation. Initially, lauryl ethoxylate is sulfated in batches by cholorosulfonic acid. Both reagents are fed to a glass-lined, stirred, jacketed reactor, with the acid being gradually added to the reaction. The sulfation is carried out at 25 - 30°C under a vacuum for about 2.5 hours. The gaseous HCl by-product is led off the sulfation product and directed to a scrubber downstream. The sulfation product is fed to the neutralization.
Neutralization. The sulfation product is fed to a neutralization vessel, where it is contacted with a 50 wt% caustic soda solution along with process water to adjust its active component. The neutralization reaction is carried out below 45 °C, generating a 70 wt% sodium lauryl ether sulfate further routed to packaging.
Scrubbing. The HCl evolved during the sulfation is fed to a scrubber, which is absorbed in process water, generating a 33 wt% hydrochloric acid solution by-product.
benefits
The product has good solvency, favorable hard-water resistance and high-biodegradation. It also facilitates ease of formulation and production. In addition, it also creates a degree of thickening to the final product formulation.
Hazard
sodium laureth sulfate may be contaminated with measurable amounts of ethylene oxide and 1,4-dioxane. The International Agency for Research on Cancer ethylene oxide as a known human carcinogen and 1,4-dioxane as a possible human carcinogen. Ethylene oxide can also harm the nervous system and the California Environmental Protection Agency has classified it as a possible developmental toxicant based on evidence that it may interfere with human development. 1,4-dioxane is also persistent. In other words, it doesn’t easily degrade and can remain in the environment long after it is rinsed down the shower drain. 1,4-dioxane can be removed from cosmetics during the manufacturing process by vacuum stripping, but there is no easy way for consumers to know whether products containing sodium laureth sulfate have undergone this process. The industry panel that reviews the safety of cosmetics ingredients notes that sodium laureth sulfate can irritate the skin and eyes (though approving of its use in cosmetics).
Side effects
Sodium lauryl ether sulfate(SLES) can irritate eyes, skin, and lungs, especially with long-term use. It may also be contaminated with a substance called 1,4-dioxane, which is known to cause cancer in laboratory animals. This contamination occurs during the manufacturing process.
