Common examples of such active agents are sodium straight-chain alkyl benzene sulfonates and sodium alpha-alkenyl sulfonates. Sodium Linear Alkyl Benzene Sulfonate, also known as LAS, is a white or light yellow powder or flake solid. It is soluble in water. Although the water solubility is poor at lower temperatures, and the solubility in water at room temperature is less than 3, it has good solubility in the compound surfactant system. It is relatively stable to alkali, dilute acid and hard water, and the decomposition temperature is 240°C. The irritation index of 10% solution is 5.0, the microbial degradation rate is 80% to 90%, and the LD50 is 1300 to 2500 mg/kg.
Sodium α-alkenyl sulfonate is also known as AOS. When the active content is 38% to 40%, the appearance is yellow transparent liquid, which is easily soluble in water. It has good stability over a wide PH range. At PH2, PH4 and PH10, its hydrolysis rate is 0. It is less irritating to the skin, the microbial degradation rate is 100%, and the LD50 is 1300-2400 mg/kg. Among them, LAS is generally not used in shampoo, and is rarely used in body wash. It is often used in laundry detergent and dishwashing detergent. The LAS in the detergent can account for about half of the total surfactant, and the actual adjustment range of the proportion of LAS in the laundry liquid is very wide.
The water solubility of LAS is mainly reflected at higher temperature (such as 60°C) and under the conditions of compounding with certain surfactants. The typical compound system used in detergent is the ternary system "LAS-AES-FFA". The compound system used in laundry detergent is "LAS-soap base-η·SAA". It is worth noting that the direct compounding of LAS with the nonionic surfactant alkyl alcohol amide may not achieve good results. The "LAS-FFA" system is unstable with low viscosity and white milky appearance.
LAS is the cheapest synthetic surfactant variety with the largest output (290kt/a). LAS has the lowest price among the top 5 synthetic surfactants in terms of yield, and is comparable to soap base (fatty ester soap) among common anionic surfactants. The outstanding advantages of LAS are good stability, good detergency, and low price, while the outstanding disadvantage is that it is highly irritating.