Action process of dispersant


First, the dispersion process of solid particles in media is generally divided into three stages.


1. The wetting and wetting of solid particles is the most basic condition for the dispersion of solid particles. If the solid particles are to be evenly dispersed in the medium, first of all, each solid particle or particle group must be able to be fully wetted.


2. In the process of dispersion or fragmentation of ion clusters, the separation of particle clusters and solid-solid interface is involved. Different types of surfactants play different roles in the dispersion or fragmentation of particle clusters.


A. generally, when water is used as the medium, the solid surface tends to be negatively charged. Although the anionic surfactant also has negative charge, under the condition that the solid surface potential is not very strong, the anionic surfactant can overcome the electrostatic repulsion force by van der Waals force or be adsorbed on the surface of the gap by inlaying way, so that the repulsion force of the surface increases because of the same charge, and the osmotic pressure produced by the permeated water reduces the adhesion between the particles and reduces The mechanical work required for the fragmentation of solid particles or particle clusters is obtained, so that the particle clusters are broken up or broken into smaller crystals, and gradually dispersed in the liquid medium.


B. the non-ionic surfactant is also adsorbed on the crack wall through van der Waals force. The existence of the non-ionic surfactant can not make it generate point repulsion force, but can generate entropy repulsion force and osmotic hydration force, which can reduce the bond strength between the micro cracks in the particle cluster and facilitate the particle cluster fragmentation. C. the cationic surfactant can be adsorbed on the crack wall through electrostatic attraction, but in the adsorption state Different from anionic surfactant and non-ionic surfactant.


3. Once the solid particles are dispersed in the liquid, a uniform dispersion system will be obtained. However, the stability depends on whether the dispersed solid particles can regroup to form agglomerates.


2. Dispersion and stability of surfactants in water


1. Dispersion of non-polar solid particles after adding the surfactant into the suspension, because the surfactant can reduce the surface tension of water, and the water release bond of the surfactant can be adsorbed on the surface of non-polar solid particles through van der Waals force, and the hydrophilic base can be extended into the water to improve the surface hydrophilicity, so that the wettability of non-polar solid particles can be improved.


2. Dispersion and stability of charged particles


A. the surface of ionic surfactant fish particle has the same charge. When the charge of ionic surfactant is the same as that of particle surface, the ionic surfactant is not easy to be adsorbed on the particle surface because of electrostatic repulsion force. However, if the van der Waals force between ionic surfactant and particle is strong, the ionic surfactant can be adsorbed by characteristics when the electrostatic repulsion force can be overcome When adsorbed on the surface of particle, the absolute value of zeta potential on the surface of particle will increase, and the particle with point will be more stable in water.


B. the ionic surfactant and the particle surface have opposite charges. If the ionic surfactant used has opposite charges with the particle, if the surfactant concentration is low, the particle surface charge will be neutralized, so that the electrostatic repulsion will be eliminated, and flocculation may occur. But if the surfactant concentration is high, the second layer of surface activity will be adsorbed on the particles with electric neutralization After the agent ion, the solid particles are charged again, and the solid particles are redistributed due to the repulsive force of static electricity.


III. dispersion and stability of surfactants in organic media


The dispersion of particles in organic media is mainly realized by the entropy repulsion generated by the steric hindrance. For nonpolar particles, the van der Waals force between particles can be overcome and the particles can be stably dispersed in organic medium. The surface treatment of organic pigments can be realized in several ways.


1. Surface treatment of organic pigments with organic amines


2. Surface treatment of organic pigments with pigment derivatives.


From surfactant platform