Application of dispersant in waterborne organic pigment

Dispersants play an important role in the pigment industry, especially in the preparation and application of waterborne organic pigments.

1、 Working principle of dispersant

Dispersant is a kind of interfacial active agent with both lipophilic and hydrophilic properties. This unique property enables it to effectively uniformly disperse pigment solid particles that are difficult to dissolve in liquid. Its working principle is mainly based on the following two points:

Electrostatic repulsion: the dispersant can be adsorbed on the surface of pigment particles. By increasing the charge on the particle surface, the particles are separated from each other due to electrostatic repulsion, so as to prevent the settlement and agglomeration of particles and ensure the uniformity and suspension stability of the system.

Steric hindrance effect: in addition to electrostatic repulsion, dispersant can also form a polymer adsorption layer on the surface of pigment particles. This layer has a certain thickness, which can effectively prevent particles from approaching each other and further enhance the stability of the system.

2、 Type of dispersant

According to the structural characteristics, dispersants are mainly divided into the following categories:

Anionic dispersant: this kind of dispersant ionizes in water to form anions, and is adsorbed on the pigment surface by virtue of its surface activity. They are usually suitable for non-polar or low polar oily systems, and improve the dispersion performance of pigments through electrostatic effect. Common anionic dispersants are sodium oleate, carboxylate, sulfate and sulfonate.

Cationic dispersants: these dispersants are positively charged and are mainly suitable for aqueous systems. They can be adsorbed on the pigment surface to form a stable dispersion system. Common cationic dispersants are amine salts, quaternary ammonium salts and pyridinium salts.

Nonionic dispersant: this kind of dispersant is neutral in water, neither ionized nor charged. They mainly prevent pigment aggregation through steric hindrance effect, and have good compatibility and stability. The common nonionic dispersants are glycol type and polyol type.

3、 Application of dispersant in waterborne organic pigment

In aqueous organic pigments, the application of dispersants is mainly reflected in the following aspects:

Improve dispersion efficiency: dispersant can significantly reduce the settling speed of pigment particles in water, improve the dispersion uniformity of pigment, and make pigment particles finer and more evenly distributed.

Enhanced stability: through electrostatic repulsion and steric hindrance effects, dispersants can prevent the re aggregation and sedimentation of pigment particles, thus extending the storage stability and service life of pigments.

Improve application performance: dispersant can improve the application performance of pigment, such as gloss, leveling, coloring power and transparency. In the fields of coatings, inks and so on, the improvement of these properties is crucial to the quality of the final product.

Specifically, in water-based coatings, commonly used dispersants include polyacrylic acid salts, fatty alcohol polyoxyethylene ether sulfate (TES), organic hydrophilic colloids and acid polymers. These dispersants have their own unique advantages and scope of application. Factors such as pigment type, particle size, surface properties and pH value of the coating should be considered when selecting them.

4、 Case analysis

Taking polyacrylate dispersant as an example, this kind of dispersant is widely used in waterborne coatings. They mainly stabilize pigment particles by ionic action and make them suspended in the aqueous phase. Polyacrylate dispersants have good dispersion efficiency and stability, and can significantly improve the transparency and gloss of coatings. At the same time, they also have certain wetting and defoaming effects, which help to improve the application performance and final quality of the coating.

5、 Conclusion

The application of dispersant in waterborne organic pigment is an indispensable part of pigment industry. Through electrostatic repulsion and steric hindrance effect, dispersant can significantly improve the dispersion efficiency and stability of pigment, and improve the application performance of pigment. When selecting dispersant, it is necessary to comprehensively consider the type and nature of pigment and the requirements of coating to ensure the quality of the final product. With the continuous development of the pigment industry, the research and application of dispersants will be more in-depth and extensive, contributing more to the progress of the pigment industry.