The closed type sulfonic acid catalyst can significantly reduce the coating film temperature or shorten the curing time of the coating film, resulting in high gloss, excellent surface properties, and excellent weathering and outdoor stability. In baking paint, it can greatly reduce the cross-linking reaction temperature of baking paint, and has excellent storage stability compared with uncontained catalysts.
Adding a thickener to the storage latex paint can increase its viscosity. It is required to be greater than 50Pa·s and the yield value greater than 1.0Pa, which will slow down the precipitation of the pigment. Moreover, even if precipitation occurs, the precipitation is loose and easy to stir evenly to prevent uneven color. The thickener and wetting and dispersing agent together ensure the storage stability of the coating.
The precipitation of pigments and filler particles in paint in latex paint is a complicated problem. For the convenience of discussion, only the simplest example can be used for discussion. The settling velocity of a single spherical particle in a Newtonian liquid can be expressed by the following formula:
In the formula-radius of spherical particles;
P particle density;
P-density of liquid;
Settling velocity of particles.
The sedimentation speed of particles in the liquid is proportional to the square of the particle radius, proportional to the density difference between the particles and the liquid, and inversely proportional to the viscosity of the liquid. Using this principle, add thickener to increase the viscosity of the system and stabilize the dispersion system. The adsorption of wetting dispersant and thickener on the surface of wax for pigments, fillers and latex particles reduces the density difference and stabilizes the dispersion system. Of course, reducing the particle size can also achieve the purpose of stability.
For the actual latex paint system, the situation is more complicated and there are more influencing factors. In summary, the main factors that affect the sedimentation of latex paint are the size, shape and density of pigments and fillers, and the viscosity and viscosity of the liquid phase in the latex paint. Density, interaction between pigments, filler particles and liquid phase, charged properties of particles, additives and storage environment, etc. For a given latex paint, emulsions, pigments, and fillers have been determined, and thickeners are the most important influencing factor.
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