The role of dispersants in coatings
The role of dispersants in coatings
As an indispensable material in modern industrial production and daily life, the performance and quality of coatings directly affect the appearance, durability and environmental protection of products. In the preparation process of coatings, dispersants, as a key additive, play a vital role.
1. Basic Concept of Dispersant
Dispersant is a surfactant with two opposite properties, lipophilic and hydrophilic, in the molecule. It can reasonably disperse various powders in the solvent, and through the charge repulsion principle or polymer steric effect, it can stably suspend solid particles in the solvent (or dispersion). The dispersion of the coating slurry is related to the formulation of the coating and the selection of raw materials. Almost all coatings use dispersants.
2. The specific role of dispersants in coatings
Reducing coating viscosity
During the paint making process, dispersants can effectively reduce the viscosity of the coating, making the coating easier to apply and evenly coated. At the same time, dispersants can also reduce the amount of solvents used, adapting to the current environmental protection testing background.
Increasing the content of pigments and fillers
In the water-based paint formula, when the content of pigments and fillers increases, the mutual collision of particles during pulping will also increase accordingly, resulting in an increase in the viscosity of the slurry. After adding dispersants, higher pigment and filler contents can be dispersed, making the particles break more quickly, while preventing the viscosity from increasing during the grinding process. This can not only disperse a higher content of pigments and fillers, but also shorten the dispersion time and reduce energy consumption.
Improving the gloss of coatings
The gloss of the coating is closely related to the particle size of the particles it contains. The smaller the particle size, the higher the gloss. Dispersants can avoid large particles formed due to flocculation, improve the coating film, and thus improve the gloss of the coating.
Improve the hiding power of paint
The amount of light reflected and passed through the paint surface determines the hiding power of the paint. The addition of dispersants can reduce the agglomeration of pigment particles, reduce the particle size to increase the surface area, and further improve the hiding power. For white paint, the addition of polymer dispersants can reduce the agglomeration of pigments and fillers such as titanium dioxide and improve the hiding power.
Improve tinting power
Dispersants can reduce the average particle size of pigments to improve tinting strength. Dispersants increase the collision stability of finer particles and prevent flocculation, thereby giving full play to their inherent tinting strength.
Prevent floating color and floating
During the paint making process, blue and black paints are prone to floating color and floating. This is because if the pigment particles are poorly wetted, the density, particle size, and movement speed of the particles are different, which will cause one pigment to sink and the other to float. Dispersants can improve the wettability of pigment particles and make the irregular movement of particles tend to be uniform, thereby preventing floating color and floating.
Improve the leveling of paint
Leveling is the ability of paint to spread on a specific surface. Dispersants can make pigment particles more stable, thereby improving the leveling of paint.
Prevent flocculation and sedimentation
Dispersants make the pigment particles repel each other by making the charges on their surfaces different; on the other hand, they connect a certain amount of pigment particles by adsorbing on the saturated adsorption layer on the surface of the pigment particles to control flocculation. At the same time, dispersants can also prevent the sedimentation of pigment particles with small specific surface area and large particle size.
3. Types of dispersants
There are many types of paint dyeing dispersants, each of which has its own unique chemical structure and mechanism of action. Common ones include epoxy low molecular weight dispersants, polyamide dispersants, organic amine dispersants, polymer dispersants and adsorption dispersants. These dispersants interact with pigment particles in different ways to enhance their dispersibility and stability in water.
Hydrophilic dispersants: divided into three types: anionic, cationic and non-ionic. Anionic dispersants are mainly used in water-based paints, inks and water-based inks; cationic dispersants are suitable for some special coating systems; non-ionic dispersants are widely used in various water-based and non-aqueous systems.
Polymer dispersants: usually composed of polymer chains, which prevent pigment particles from aggregating again through steric hindrance effects, thereby improving the stability of pigments. Polymer dispersants are particularly important in the preparation of high-performance coatings and special coatings.
4. Application examples of dispersants
Stearamide and higher alcohols: can improve lubricity and thermal stability and are used as slip agents for polyolefins.
Hexenyl bisstearamide: high melting point lubricant used in many plastics.
Monoglyceryl stearate and triglyceryl stearate: used to improve the dispersion and compatibility of coatings.
Hydrocarbon paraffin solids: Although they have poor dispersion, compatibility, and thermal stability, they can exert a synergistic effect when used in combination with stearic acid, calcium stearate, etc.
Low molecular wax: Made from modified polymers such as polyethylene and polypropylene as raw materials through cracking and oxidation, it is used to improve the performance of coatings.
5. Conclusion
Dispersants play a vital role in coatings, not only affecting the preparation process of the coating, but also directly affecting the final performance of the coating. By rationally selecting and using dispersants, the viscosity, gloss, hiding power, tinting power, leveling and other performance indicators of the coating can be significantly improved, while reducing production costs and energy consumption, in line with current environmental protection requirements. Therefore, in the coating industry, dispersants have broad application prospects and are worthy of our in-depth research and exploration.