Surfactants have a series of physical and chemical effects such as wetting or anti-sticking, emulsification or breaking, foaming or defoaming, solublization, dispersion, washing, corrosion prevention, antistatic and so on, and have become a kind of flexible and versatile fine chemical products with wide uses. Surfactants in addition to daily life as detergents, other applications can cover almost all fine chemical fields.
1. Solubilization requirements: C>CMC (HLB13~18) Critical micelle concentration (CMC) : the lowest concentration of surfactant molecules to form micelles. When the concentration is higher than the CMC value, the surfactants are arranged into spheres, rods, bundles, layers/plates and other structures. The solubilization system is thermodynamic equilibrium system. The lower the CMC and the higher the association number, the higher the solubilization amount (MAC); The influence of temperature on solubilization: Temperature affects the formation of micelles, affects the dissolution of solubilizers, and affects the solubility of surfactants. Krafft point: The solubility of ionic surfactants increases sharply with the increase of temperature. This temperature is called Krafft point, the higher the Krafft point, the smaller the critical micelle concentration. For polyoxyethylene non-ionic surfactants, when the temperature rises to a certain extent, the solubility drops sharply and precipitates, and the solution appears cloudy, this phenomenon is called the haze, and this temperature is called the haze. When the polyoxyethylene chain is the same, the longer the hydrocarbon chain, the lower the turbidity point. When the hydrocarbon chain is the same, the longer the polyoxyethylene chain, the higher the turbidity point.
2. Emulsification Hydrophilic lipophilic balance value (HLB) : the comprehensive affinity of hydrophilic and lipophilic groups in surfactant molecules to oil or water. As a rule of thumb, the HLB value range of surfactants is limited to 0-40, and the HLB value of non-ionic types is limited to 0-20. Mixed addition: HLB=(HLBa Wa+HLBb /Wb)/(Wa+Wb) Theoretical calculation: HLB=∑(hydrophilic group HLB value)+∑(oleophilic group HLB)-7; HLB: 3-8 W /O emulsifier: Span; HLB: 8-16 O/W emulsifier: Tween.
3. Wetting requirements: HLB: 7-9. The degree of wetting between liquid and solid can be controlled by using surfactants. In the pesticide industry, some of the granules and powders used for powder spraying also contain a certain amount of surfactant, the purpose of which is to improve the adhesion and deposition of the agent on the surface of the drug, improve the release speed and expansion area of the active ingredient under water conditions, and improve the effect of disease prevention and treatment. In the cosmetics industry, as an emulsifier is an indispensable ingredient in skin care products such as creams, lotions, cleansers and makeup removers.
4. Suspension aid In the pesticide industry, wettable powders, emulsifiers and concentrated emulsions all require a certain amount of surfactants. For example, the original drugs in wettable powders are mostly organic compounds with hydrophobicity.
5. Foaming and defoaming surfactants are also widely used in the pharmaceutical industry. In the pharmaceutical, some volatile oil soluble cellulose, steroid hormone and many other insoluble drugs can form transparent solution and increase the concentration by using the solubilization of surfactant; In the process of preparation, it is an indispensable emulsifier, wetting agent, suspension aid, foaming agent and defoamer.
6. Disinfection and sterilization can be used as fungicides and disinfectants in the pharmaceutical industry, and their sterilization and disinfection effect is attributed to their strong interaction with bacterial biofilm proteins to denature or lose function, these disinfectants have relatively large solubility in water, according to the concentration of use, It can be used for skin disinfection, wound or mucous membrane disinfection, instrument disinfection and environmental disinfection before operation;
7. Anti-hard water betaine surfactants show very good stability to calcium and magnesium ions, that is, their own tolerance to calcium and magnesium hard ions and the dispersion of calcium soap. In the process of use to prevent the precipitation of calcium soap, improve the use effect.
8. Viscosity and foaming surfactants have the effect of changing the solution system, increasing the viscosity and thickening or increasing the foam of the system, and have a wide range of applications in some special cleaning and mining industries.
9. The removal of grease and dirt is a more complex process, which is related to the wetting and foaming functions mentioned above.
Finally, it should be noted that surfactants work not only because of one aspect, but in many cases because of a combination of factors. For example, in the paper industry can be used as cooking agent, waste paper deinking agent, sizing agent, resin barrier control agent, defoamer, softener, antistatic agent, scale inhibitor, softener, degreasing agent, bactericide and algicide, corrosion inhibitor and so on.
English