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Cationic surfactant synthesis method

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The main reaction for the synthesis of cationic surfactants is N-alkylation, in which tertiary amines react with alkylating agents to form quaternary ammonium salts. This reaction is also called quaternization.
Alkyl quaternary ammonium salt
The alkyl quaternary ammonium salt is one of the important varieties of quaternary ammonium salt type cationic surfactants, and has been widely used as a bactericide, fiber softener, mineral flotation agent, emulsifier, etc. Its structural feature is that there are four alkyl groups connected to the nitrogen atom, that is, the four hydrogen atoms of the ammonium ion are all replaced by alkyl groups, usually only one or two of this alkyl group are long-chain hydrocarbon alkyl groups, and the remaining alkyl groups The number of carbon atoms is one or two. According to its structural characteristics, there are three main methods for synthesizing alkyl quaternary ammonium salts, that is, it is prepared by the reaction of a higher alkyl halide and a lower tertiary amine, by the reaction of a higher alkyl amine and a lower alkyl halide and by the formaldehyde-formic acid method.

Quaternary ammonium salts containing heteroatoms
The so-called heteroatom-containing quaternary ammonium salt generally refers to a quaternary ammonium salt containing O, N, S and other heteroatoms in the hydrophobic hydrocarbon chain, which means that the lipophilic group contains an amide bond, ether bond, ester bond or Surfactant with sulfide bond. Because the quaternary ammonium cation of the hydrophilic group and the hydrophobic group of the alkyl group are connected by groups such as amide, ester, ether, or thioether, rather than directly connected together, some people also call this type of quaternary ammonium salt as an indirect connection type Surfactant.
Quaternary ammonium salt containing benzene ring
Such surfactants are mainly used as bactericides, foaming agents, wetting agents and dye fixing agents. In the synthesis process, the main method of introducing aromatic rings is to use benzyl chloride as an alkylating agent to react with tertiary amines. Benzyl chloride is produced by the side chain chlorination reaction of toluene. In order to avoid chlorination on the benzene ring, the reaction is required to be carried out in an enamel kettle or glass-lined tower reactor.

Quaternary ammonium salt containing heterocycle
The heterocyclic ring contained in the quaternary ammonium salt molecule is mainly morpholine ring, piperazine ring, pyridine ring, quinoline ring and imidazole ring.
Amine salt type
Amine salt type cationic surfactants mainly include three major categories of long-chain alkyl primary amine salts, secondary amine salts and tertiary amine salts.

Cationic surfactants have good sterilization, softness, antistatic, anti-corrosion and other emulsification and wetting properties, and are often used as phase transfer catalysts. However, such surfactants are rarely used alone as detergents, because the surface of many substrates is usually negatively charged in aqueous solutions, especially in alkaline aqueous solutions. During the application process, positively charged surfactants will The surface of the substrate forms an arrangement of hydrophilic groups inwards and hydrophobic groups outwards, making the surface of the substrate hydrophobic and not conducive to washing, or even negative effects. In addition, the main application areas of these surfactants are not like other surfactants, used to reduce surface tension, but to use its structural characteristics for other special aspects

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