The role of surfactants and their various applications in coatings
The application of surfactants in coatings is an additive, which is an indispensable component in the production of coatings. It can improve the coating production process, construction conditions and product quality, which in turn can reduce costs and improve economic efficiency. Coating is a colloidal dispersion system, which consists of continuous phase and dispersed phase. The continuous phase is solvent, polymer or polymer solution, polymer is either solution type, particle type, such as emulsion, or solid; the dispersed phase is color, filler. From the classification of colloids, coatings are dispersed colloids with colloidal kinetics, electrical properties, etc. Therefore, it has extensive and close connection with surface colloid chemistry. The emulsification principle, dispersion principle, foaming and defoaming principle and rheology principle of surface chemistry also play a very important guiding role for coatings and provide the theoretical basis for the application of surfactants in the coatings industry. The application functions of surfactants in coatings are the following respectively.
I. Wetting and dispersing agent.
The process of grinding and dispersing pigments is the main process of manufacturing coatings, and about 80% of the electrical energy and man-hours are consumed in this process. The process of pigment dispersion in the base material can be divided into three stages, namely, wetting, dispersing and stabilizing. These three stages are not separate, but overlap each other. The wetting agent can promote the wetting of the pigment aggregates by the base material, and the dispersant can improve the stability of the pigment dispersion. Therefore, the function of wetting and dispersing agent is irreplaceable. The role of pigment wetting and dispersing agent is shown in.
1、Improve production efficiency, reduce manufacturing costs, improve the storage stability of coatings and reduce waste.
2、Improve the state of coating film.
3, the best pigment dispersion can improve the absorption and reflection ability of ultraviolet light, increase the weather resistance and chemical resistance of pigments.
Defoamer both inhibit the role of foam generation, and the role of eliminating foam. Suitable defoamer itself usually has a low surface tension, while the defoamer should also have limited compatibility, so that it does not dissolve in the foaming medium, and can be well dispersed. In aqueous system, defoamer can not affect the stability of the emulsion. In the coating industry, the amount of defoamer is not large, and the speciality is strong.
Commonly used defoamer in water-based coatings are mineral oil, fatty acid lower alcohol ester, senior alcohol, senior fatty acid, senior fatty acid metal soap, senior fatty acid glycerol, senior fatty acid amide, senior fatty acid and polyethylene polyamine derivatives, propylene glycol and ethylene oxide adducts, organic phosphate ester, silicone resin, etc. Shanghai Cang Hong’s propylene glycol surfactants are a class of multifunctional surfactants used in water-based coatings, which have the functions of defoaming, wetting and leveling.
Solvent-based coatings commonly used defoamer are low-grade alcohol, senior fatty metal soap, low-grade alkyl phosphate, organosilicon resin, modified silicone resin, etc.
Third, leveling agent.
After the construction of the coating there is a flow and drying process of film formation, this process is called leveling process. A good leveling paint will soon level out to form a smooth and flat coating after construction; a bad leveling paint will leave obvious brush marks, orange peel and other defects after film formation, affecting the appearance. The factors to consider to improve the leveling of paint are
1、The use of surfactants that can appropriately reduce the surface tension of the coating to improve the leveling of the coating.
2, choose the solvent with proper evaporation speed and can reduce the viscosity of paint construction, improve the flow of paint, extend the leveling time and achieve the final leveling. Common leveling agents are high boiling point solvents, silicone leveling agents, polyacrylate leveling agents, vinegar butyl cellulose class (CAB ), etc.
Emulsion paint with water as the dispersion medium of emulsion coatings, is based on polymeric emulsion, face, filler, additives dispersed in which the composition of the water-based dispersion system. As emulsion coatings with water dilution, easy construction, fast drying, non-flammable, low toxicity, energy saving, excellent film performance, etc., is widely used in a variety of applications such as interior and exterior coatings, industrial paints, fiber treatment, paper, etc., is one of the important direction of the current development of the coatings industry.
V. Antistatic agent.
Antistatic coating is a coating with the ability to exclude the accumulated static charge. Adding antistatic agent to the coating can prepare antistatic coating. Antistatic agent is a surfactant, which can leak static charge or reduce the friction factor through different channels to inhibit the generation of static charge. It is generally required to have the following characteristics: good effect of preventing static electricity; long-lasting effect of preventing static electricity; good miscibility with film-forming substances; and does not affect other properties of the coating. Anti-static coating decorative coating does not absorb dust, pollution resistance; can ensure that instruments and meters are not electrostatic interference, to ensure its accuracy and sensitivity; can eliminate static electricity on high-altitude facilities, to prevent damage from lightning, conducive to the leakage of static electricity, to prevent the occurrence of fire.