I. Introduction of amphoteric surfactant
Amphoteric surfactants are surfactants that contain both anionic and cationic hydrophilic groups in the same molecule. The biggest feature is that it can both donate protons and accept protons.
II. Classification of Amphoteric Surfactants
The molecules of amphoteric surfactants can be classified according to the anionic structure in its hydrophilic group, and can also be classified according to its cation. According to its anion structure, it can be divided into carboxylate, phosphate, and sulfate type amphoteric surfactants, etc. Classified according to cationic structure is usually divided into the following types:
(1) Amphoteric imidazoline derivatives, the cationic part of which is an imidazoline ring;
(2) Surface-active betaine, the cationic part of which is quaternary ammonium nitrogen;
(3) Chlorine-based acid surfactants, the cationic part of which is primary or secondary amine nitrogen;
(4) Lecithin. The first three types are synthetic surfactants, and lecithin is a natural surfactant. III. Benefits of using amphoteric surfactant
III. Advantages of Amphoteric Surfactants
Amphoteric surfactants carry positive and negative ionic charges at the same time, and the hydrophilic groups of its surface active ions have both anionic and cationic parts. Because of its structure, it has many excellent properties:
(1) Low toxicity and low irritation to skin and eyes;
(2) Excellent resistance to hard water and high electrolyte resistance, even in seawater can be effectively applied;
(3) Good biodegradability;
(4) Softness and antistatic properties;
(5) Certain bactericidal and antifungal properties;
(6) Good emulsification and dispersion;
(7) It can be compatible with almost all other types of surfactants, and generally has a synergistic effect;
(8) It can be adsorbed on the surface of charged substances without forming a thin hydrophobic layer, so it has good wetting and foaming properties.
IV. Applications of amphoteric surfactants
1. Application in personal care products
Since the introduction of amphoteric surfactants into the market, the earliest and most important application area is the personal care products industry. From the 1950s to the 1970s, most amphoteric surfactants were mainly used in children's shampoos and various conditioning shampoos. Later, the application of amphoteric surfactants in personal care products was extended to other products, such as foam baths, body washes, hair dye products, facial cleansers, hand sanitizers and makeup remover products. Amphoteric surfactants have low irritation to human eyes, skin and mucous membranes, stability under extreme pH conditions, and synergy with other formulation components are the main reasons for their wide application in the field of personal care products.
2. Application in daily detergent
The good properties of amphoteric surfactants lead to their wide application in the field of personal care products. The other excellent properties of amphoteric surfactants, such as strong anti-electrolyte performance, easy biodegradation, low toxicity, and high efficiency at low concentrations, have also expanded the application field of amphoteric surfactants to the scope of washing products, such as hand wash fabric detergents, hard surface cleaners, etc. Amphoteric surfactants play a role in these formulations as phosphorus substitutes, enzyme stabilizers, bleach and color protection aids, and as primary surfactants in mild dishwashing detergents. However, general amphoteric surfactants are still difficult to use in detergents due to price issues. It was not until the appearance of the RNnAa series of alkyl oligomeric amino acids that the application of amphoteric surfactants in detergents appeared, achieving acceptable cost performance and unprecedented versatility.
3. Application in industrial detergent
The development trend of metal cleaning agents is from solvent-based to water-based, and amphoteric surfactants are often used in water-based. Amphoteric surfactants can be used in other types of industrial detergents such as high-pressure detergents, traffic film removers, and foam cleaners. At the same time, amphoteric surfactants such as amphoteric sulfonates, betaines and sulfobetaines are also used in acidic cleaning agents containing acetic acid, citric acid, hydrochloric acid, sulfamic acid, phosphoric acid, formic acid, etc. When the acid content is 2% to 5%, the dosage of amphoteric surfactant is 5%.
4. Synergistic decontamination
Any application of amphoteric surfactants has a lot to do with synergistic or compounding effects. When considering the anionic/nonionic compound systems (such as fabric detergents) and anionic/anionic compound systems (such as dish detergents) in almost all common detergents, the synergistic effect or compounding effect brought after adding the amphoteric surfactant is all obvious, especially in the application of fabric detergents and in industrial detergents.
