Classification and Application of Surfactants

Nov 1, 2021

Surfactant refers to a substance that can significantly change the interface state of the solution system by adding a small amount. It has fixed hydrophilic and lipophilic groups, which can be aligned on the surface of the solution. The molecular structure of surfactants is amphiphilic: one end is a hydrophilic group, the other end is a hydrophobic group; the hydrophilic group is often a polar group, such as carboxylic acid, sulfonic acid, sulfuric acid, amino or amine group and Its salts, hydroxyl groups, amide groups, ether bonds, etc. can also be used as polar hydrophilic groups; while the hydrophobic groups are often non-polar hydrocarbon chains, such as hydrocarbon chains with more than 8 carbon atoms. Surfactants are divided into ionic surfactants (including cationic surfactants and anionic surfactants), nonionic surfactants, amphoteric surfactants, compound surfactants, and other surfactants.

Classification and Application of Surfactants 1 Preface (/    There are many types of surfactants, in order of production: anionic 56%, non-ionic 36%, zwitterionic 5%, and cation 3%.     2 Anionic surface activity    2.1 Anionic surfactant sulfonate    The common types of such active agents are linear sodium alkyl benzene sulfonate and sodium α-alkenyl sulfonate. Linear alkyl benzene sulfonate is also known as LAS or ABS, white or light Yellow powder or flake solid, soluble in water, although the water solubility is poor at lower temperature, the solubility in water at room temperature is less than 3, but it has good solubility in the compound surfactant system. It has good solubility in alkali , Dilute acid and hard water are relatively stable, the decomposition temperature is 240 ℃. 10% solution irritation index 5.0, microbial degradation rate 80% ~ 90%, LD50 is 1300 ~ 2500 mg/kg.     α-alkenyl sulfonate is also known as AOS. Activity When the substance content is 38%-40%, the appearance is a yellow transparent liquid, which is easily soluble in water. It has good stability in a wide range of pH values; 30℃ 3 days, pH2, pH4, pH10, hydrolysis rate All are 0. It has little irritation 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 shampoos, and is rarely used in shower liquids. It is often used in clothing. Liquid detergent and detergent (dishwasher liquid detergent). 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 liquid detergent for clothing is very wide. The water solubility of LAS is mainly reflected under higher temperature (such as 60℃) and under the condition of compounding with certain surfactants. The typical compounding system used in detergent is the ternary system "LAS-AES -FFA". The compound system used in liquid laundry detergents is “LAS-Soap-η·SAA”. It is worth noting that LAS can not be obtained by directly compounding with non-ionic surfactant alkyl alcohol amide. Good results, "LAS-FFA" system is unstable, low viscosity and white and milky in appearance. LAS is the most productive (290 kt/a) and cheapest synthetic surfactant variety. LAS ranks among the top 5 in output The price of synthetic surfactants is the lowest, and it is equivalent to soap (fatty ester soap) among common anionic surfactants. The outstanding advantages of LAS are good stability, good detergency, and low price. The outstanding disadvantage is high irritation. AOS has the best performance among the sulfonate varieties. It has the advantages of general sulfonates or its advantages are more prominent, without the defects of general sulfonates. AOS is the main surface commonly used in shampoos and shower liquids One of the active agents. The application in other liquid detergents will gradually increase with the realization of product localization (price reduction). The outstanding advantages of AOS are good stability, good water solubility, good compatibility, and low irritation. Microbial degradation is also very ideal; the outstanding disadvantage is that the price is more expensive among anionic surfactants .    2.2 Anionic surfactant (sulfate)    The common such activators are fatty alcohol polyoxyethylene ether sodium sulfate and sodium lauryl sulfate. Fatty alcohol polyoxyethylene ether sodium sulfate is alias AES, alcohol ether sodium sulfate. It is easily soluble in water, and the appearance is a light yellow viscous liquid (translucent) when the active content is 70%.

Poor foaming; compared with non-ionic surfactants, some properties of amphoteric surfactants are better, and others are not lagging behind. Amphoteric surfactants have better foaming ability than general nonionic surfactants-poor foaming ability of AE; better bactericidal ability-relatively nonionic and anionic; better conditioning. Therefore, in liquid detergents, amphoteric surfactants are mainly used in shampoos, followed by skin cleansers such as shower liquids. 5 Cation Surfactant    Common cationic surfactant varieties include cetyl dimethyl ammonium chloride (1631), octadecyl trimethyl ammonium chloride (1831), cationic guar gum (C-14S), Cationic panthenol, cationic silicone oil, dodecyl dimethyl amine oxide (OB-2) and so on. Cationic surfactants are different from other surfactants in that they have poor detergency and foaming properties, and tend to have a certain degree of irritating toxicity (low).     Cationic surfactants are used as co-surfactants in liquid detergents—a conditioner component with a small amount of formula; generally used in higher-end products, mainly used in shampoos. Cationic surfactants are not directly compatible with anionic surfactants. The compatibility of cations and anions may produce good results, but the risk of precipitation (crystallization) is greater.     There are many cationic surfactants used in shampoos, and the frequency of use is relatively scattered-instead of using one or two species intensively, they are often formulated into conditioner products. Cationic surfactants have a small production share in surfactants, and their prices are often more expensive than other types of surfactants. Compared with various types of surfactants, cationic surfactants have the most prominent adjustment effect and the strongest bactericidal effect; despite the disadvantages of poor detergency, poor foaming, poor compatibility, high irritation, and high price The conditioning agent component in high-end liquid detergent shampoos cannot be replaced by other types of surfactants. It is worth noting that cationic surfactants can only be used as conditioning agent components or bactericides.