Coating dispersants refer to additives that can improve and improve the dispersion performance of solid or liquid materials. When the solid coating is ground, a dispersant is added to help the particles pulverize and prevent the crushed particles from agglomerating to keep the dispersion stable. The water-insoluble oily liquid can be dispersed into very small droplets under high-shear stirring. After the stirring is stopped, it will be separated quickly under the action of interfacial tension, and a stable liquid can be formed after adding a dispersant and stirring. Emulsion. Its main function is to reduce the interfacial tension between liquid-liquid and solid-liquid.
In the components of water-based coatings, there are film-forming substances, solvents (water), pigments and fillers, and additives. Among them, the additive is the smallest part of the coating, but it is also a very important part and cannot be ignored.
Most of the pigments used in water-based paints are mixed in the form of aggregates and aggregates. If these particles cannot be dispersed into smaller particles or primary particles, and form a stable dispersion, defects such as coarsening, flocculation, precipitation, floating color, and reduction in coloring power will occur.
Water-based coating additive-dispersant, the main function is to reduce the time and energy required to complete the dispersion process, stabilize the dispersed pigment dispersion, and modify pigment particles Surface properties, adjust the movement of pigment particles.
The dispersants used in water-based coatings must be water-soluble, and they are selectively adsorbed on the interface between powder and water. There is a big difference between water-based industrial coatings and ordinary architectural coatings. The viscosity is generally low. The viscosity measured by Tu-4 cup is generally 60-120s. Therefore, the requirements for water-based industrial coatings on dispersants are not only good Viscous, also need to have good anti-settling performance.
The dispersion of coating slurry is not only related to the formulation of the material formula and the selection of raw materials, but also related to the dispersant. Therefore, in the paint production process, pigment dispersion is a very important production link, which is directly related to the storage, construction, appearance and performance of the paint film.
So choosing a dispersant reasonably is a very important production link. The types of dispersants are anionic, cationic, nonionic, amphoteric and polymer.
Most dispersants achieve the purpose of dispersing pigments and fillers through the process of wetting, grinding and dispersing, coupling and wrapping stability.
In water-based coatings, due to cost control reasons, more expensive dispersants cannot be used. Most of the wetting and dispersing agents used in the market are anionic and nonionic. Their principle is low surface tension, quickly wetting the pigment particles, and then through high shear force, such as disperser, grinding machine, etc., to make the pigment particles form a semi-flocculation, or a dispersion called controllable flocculation. If the viscosity of the paint is relatively high at this time, there will be no pigment anti-coarseness and severe flocculation, but if the viscosity is not well controlled, problems will occur over time; some use coupling agents as dispersants, through Their hydrophilic groups and thiohydric groups couple two different substances together. The advantages of this method are: good comprehensive performance, dispersible, less dosage, and can increase the adhesion of the paint. But the disadvantage is that it is not a deflocculation group, so it is not suitable for the paint with high requirements and strong color development. Through research and practice, it is recommended to use dispersants that can deflocculate in waterborne coatings. The advantages of this are: good color development for pigments and fillers, high vividness, and good gloss.
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