Dispersant is a kind of surfactant that has two opposite properties of lipophilicity and hydrophilicity in the molecule. It can increase the compatibility of oily and aqueous components in the same system, and also prevent the sedimentation and agglomeration of particles, forming an amphiphilic reagent required for stable suspensions.

Dispersant, also known as wetting dispersant, has many kinds. According to preliminary estimates, there are more than 1,000 kinds of substances in the world with dispersing effect. According to its structure, there are mainly the following types.

Anionic wetting and dispersing additive

Most of them are composed of non-polar negatively charged lipophilic hydrocarbon chain moieties and polar hydrophilic groups. The two groups are located at both ends of the molecule, forming an asymmetric hydrophilic and lipophilic molecular structure. Its varieties are: sodium oleate c17h33coona, carboxylate, sulfate (r-o-so3na), sulfonate (r-so3na) and so on. Anionic dispersants have good compatibility and are widely used in water-based coatings and inks. Polycarboxylic acid polymers and the like can also be applied to solvent-based coatings, and are widely used as controlled flocculation-type dispersants.


Cationic wetting and dispersing additive

Non-polar bases are positively charged compounds, mainly amine salts, quaternary ammonium salts, pyridinium salts, etc. Cationic surfactants have strong adsorption capacity and have good dispersing effects on carbon black, various iron oxides and organic pigments, but pay attention to their chemical reaction with carboxyl groups in the base material, and pay attention not to use them with anionic dispersants at the same time.


Nonionic wetting and dispersing additive
As the name implies, there are no charged groups in the molecule, and they are not ionized in aqueous solution. The lipophilic groups in the molecule are high-carbon fatty alcohols, alkylphenols, fatty acids, fatty amines, and oils, etc., and their water solubility comes from Polyoxyethylene ether group and terminal hydroxyl group in the molecule. Reduce surface tension and improve wettability. Used together with anionic dispersant as wetting agent or emulsifier, it is widely used in water-based colorants, water-based paints and inks.

The emulsification effect of non-ionic surfactants has nothing to do with the pH value of the solution, it has good acid and alkali resistance, and is less affected by salts and electrolytes. It can be used in combination with other surfactants. It can be used as emulsifier, cleanser and solubilizer in cosmetic formulations. Mainly include polyoxyethylene derivatives, alkyl alcohol amides, polyol mono-fatty acid esters, alkyl amine oxides, N-alkyl pyrrolidones.

Amphoteric wetting and dispersing additive

It is a compound composed of anions and cations. Typical applications are phosphate ester salt type high molecular polymers. These polymers have higher acid numbers, which may affect interlayer adhesion. The size of the anionic and cationic organic groups in the molecule of  neutral wetting and dispersing agent  is basically the same, and the whole molecule is neutral but polar. Such as oil amino oleate c18h35nh3oocc17h33, etc. belong to this type, which is widely used in coatings. Polymer type hyperdispersant The polymer type dispersant is the most commonly used and has the best stability. Polymer type dispersants are also divided into polycaprolactone polyol-polyethyleneimine block copolymer type dispersants, acrylate polymer type dispersants, polyurethane or polyester type polymer dispersants, etc. One end of the anchor group is entangled with the resin, and the other end is attached to the pigment particles, so the storage stability is relatively good.