Among the components of coatings, there are film-forming substances, solvents (water), pigments and fillers, and additives. Among them, additives account for a small proportion in coatings, but they are very important and cannot be ignored. From the working principle of dispersants, the essence of dispersants is surfactants, which have amphiphilic properties. Therefore, dispersants will inevitably have a certain degree of hydrophilicity, which has a great influence on water resistance in paint films.
Dispersants are interfacial active additives that have two opposite properties of lipophilicity and hydrophilicity in the molecule. They can evenly disperse the solid and liquid particles of inorganic and organic pigments that are difficult to dissolve in liquids.
High-efficiency and environmentally friendly water-based dispersants are non-flammable and non-corrosive, can be infinitely soluble in water, and are insoluble in organic solvents such as ethanol, acetone, and benzene. They have excellent dispersing effects on a variety of pigments such as kaolin, titanium dioxide, calcium carbonate, barium sulfate, talcum powder, zinc oxide, and iron oxide yellow, and are also suitable for the dispersion of mixed pigments.
Most dispersants achieve the purpose of dispersing pigments and fillers through the process of wetting, grinding and dispersing, coupling, and encapsulation stabilization. Among water-based coatings, most of the wetting and dispersing agents used on the market are anionic and non-ionic.
① Anionic surfactants: Most of them are composed of non-polar negatively charged lipophilic hydrocarbon chain parts and polar hydrophilic groups. The two groups are located at the two ends of the molecule, forming an asymmetric hydrophilic and lipophilic molecular structure. Anionic dispersants have good compatibility and are widely used.
② Non-ionic: Cannot be ionized and uncharged. Weakly adsorbed on the surface of pigments, mainly used in water-based coatings. Their function is to reduce surface tension and improve wettability. If some organic siloxanes are added, it can prevent floweriness, floating color and improve leveling.
The functional characteristics of water-based dispersants are as follows:
- Replace ammonia water and other alkaline substances as neutralizers, reduce the smell of ammonia, and improve the production and construction environment.
- Water-based paint dispersants can effectively control the pH value, improve the efficiency of thickeners and viscosity stability.
- Improve the dispersion effect of pigments, improve the bottoming and coarsening of pigment particles, and improve the color development of color pastes and the gloss of paint films.
- Water-based paint dispersants are volatile and will not remain in the paint film for a long time. They can be used in high-gloss paints and have excellent water resistance and scrub resistance.
- Water-based dispersants can be used as post-additives to effectively reduce shear viscosity and improve the fluidity and leveling of paints.