Brief Introduction of Defoamer for Coatings


With the development of modern science and technology, the coatings industry is required to have high quality and high efficiency. That is, water-borne coatings and solvent-based coatings should be formulated with various additives, including additives to help the wetting and dispersing of pigments; additives to improve the storage stability of finished coatings; additives to adjust the appearance of paint film; and some additives to achieve special functions. Most of these auxiliaries belong to surfactants, which can change the surface tension of coatings, resulting in the existence of internal factors such as foaming or stabilizing foam. Various high-speed mixers, such as three-roll mill, grinder and ball mill, are needed in the manufacture of coatings. Various methods used in coating, such as air spraying, airless spraying, roll coating, flow coating and spraying, etc. In these processes, the free energy of the coating system will be increased differently, and the foam will be created, which is the external factor of foams.


The foam problem of waterborne latex paint in coatings industry is the most prominent problem, which is caused by its special formula and special production process.


(1) latex paint is water thinner. In emulsion polymerization, it is necessary to use a certain amount of emulsifier to produce stable aqueous dispersions. The use of emulsifier causes the surface tension of emulsion system to drop greatly, which is the main reason for foaming.


(2) wetting agents and dispersants of disperse pigments in latex paint are also substances that reduce the surface tension of the system and contribute to the generation and stability of foams.


(3) the low viscosity of latex paint is not easy to construct. After thickening agent, the film thickness of the foam increases and its elasticity increases, so that the foam is stable and not easy to eliminate.


(4) the extraction of free monomer in the production of emulsion; adjustment, dispersion and mixing when making latex paint; operation of spray, brush and roller in the process of construction. All of these can change the free energy of the system to some extent, and create bubbles.


The foam problem of latex paint makes the production operation difficult. The air in the foam will not only impede the dispersion of pigments or fillers, but also make the utilization rate of the equipment inadequate and affect the output. The bubbles left in the paint film during construction cause surface defects, which not only damage the appearance, but also affect the anti-corrosion and weather resistance of the paint film.