There are two parts in the emulsifier molecule: hydrophilic and lipophilic. According to the characteristics of their hydrophilic parts, they can be divided into the following categories:
①Anionic emulsifier: It is an emulsifier that is ionized in water to generate anionic hydrophilic groups with alkyl or aryl groups, such as carboxylates, sulfuric acid Salts and sulfonates, etc. This type of emulsifier is the most commonly used, and common products include: soap, sodium stearate, sodium lauryl sulfate, calcium dodecylbenzene sulfonate, etc.
Anionic emulsifiers are required to be used under alkaline or neutral conditions. When using multiple emulsifiers to prepare emulsions, anionic emulsifiers can be mixed with each other or with nonionic emulsifiers. Anionic and cationic emulsifiers cannot be used in the same emulsion at the same time. If they are mixed, the stability of the emulsion will be destroyed.
②Cationic emulsifier:Cationic emulsifierIt is ionized in water to generate positive cationic hydrophilic groups with alkyl or aryl groups. There are fewer varieties of this type of emulsifier, and they are all derivatives of amines, such as N-dodecyldimethylamine, which can be used in polymerization reactions.
③Nonionic emulsifier: Its characteristic is that it does not ionize in water. Its hydrophilic part is a variety of polar groups, the common ones are polyoxyethylene ethers and polyoxypropylene ethers.
Reactive emulsifierAn organic compound that can form a stable emulsion between immiscible liquids. They are all surface-active substances that can reduce the interfacial tension between liquids and make immiscible liquids easy to emulsify. During emulsification, the dispersed phase is evenly distributed in the continuous phase in the form of very small droplets (diameter between 0.1 micron and tens of microns), and the emulsifier forms a thin film or double electric layer on the surface of these droplets. Prevent their mutual aggregation and maintain the stability of the emulsion.
Emulsion is a heterogeneous system. The most common is an oil-in-water emulsion with water as the continuous phase and a water-insoluble organic liquid as the dispersed phase. There are also water-in-oil emulsions with water as the dispersed phase and a water-insoluble organic liquid as the continuous phase. To prepare a stable emulsion, a single component emulsifier can be added, or several emulsifiers can be added at the same time.
The oxygen atoms on the polyether chain of the non-ionic emulsifier can produce hydrogen bonding associations with water, so they can be dissolved in water. It can be used under both acidic and alkaline conditions, and has good emulsification effect. It is widely used in the production of chemicals, textiles, pesticides, petroleum and latex.
