Types and functions of dispersants commonly used in coatings

Dispersants are also called wetting and dispersing agents. On the one hand, they have a wetting effect. On the other hand, one end of their active groups can be adsorbed on the surface of pigments crushed into fine particles. , the other end is solvated into the base material to form an adsorption layer (the more adsorption groups, the longer the links, and the thicker the adsorption layer), generating charge repulsion (water-based paint) or entropy repulsion (solvent-based paint), so that the pigment particles can be dispersed for a long time Suspended in the paint to avoid re-flocculation, thus ensuring the storage stability of the finished paint system.

Commonly used dispersant types:

1. Anionic wetting and dispersing agent

Most of them are composed of non-polar negatively charged lipophilic hydrocarbon chain parts 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 include: sodium oleate C17H33COONa, carboxylate, sulfate ester salt (R—O—SO3Na), sulfonate (R—SO3Na), etc. Anionic dispersants have good compatibility, and polycarboxylic acid polymers can also be used in solvent-based coatings and are widely used as controlled flocculation dispersants.

2. Cationic wetting and dispersing agent

It is a non-polar compound with a positive charge, mainly including amine salts, quaternary ammonium salts, pyridinium salts, etc. Cationic surfactants have strong adsorption power and have good dispersion effects on carbon black, various iron oxides, and organic pigments. However, attention should be paid to its chemical reaction with the carboxyl groups in the base material, and care should be taken not to use it at the same time with anionic dispersants.

3. Controlled free radical hyperdispersant

2. The role of dispersant

1. Improve gloss and increase leveling effect.

2. Prevent floating colors and blooming.

3. Improve coloring power.

4. Reduce the viscosity and increase the pigment loading.

5. Reduce flocculation and increase construction and usability.

6. Prevent thickening and increase storage stability.

7. Increase color rendering and color saturation.

8. Increase transparency or hiding power.

9. Improve grinding efficiency and reduce production costs.

10. Prevent settlement.