Influencing factors of defoamer in coating formulation


Eliminant,






Factor 1: Surface tension


The surface tension of the coating has a greater impact on the defoamer, the surface tension of the defoamer must be lower than the surface tension of the coating, otherwise it can not have the effect of defoamer and defoamer. The surface tension of the coating is a variable factor, so the surface tension should be constant when selecting the defoamer, and then the surface tension change factor is taken into account.


Factor 2: The influence of other auxiliaries


Most of the surfactants used in coatings are functionally incompatible with defoamer. In particular, emulsifiers, wetting dispersants, leveling agents, thickening agents and so on have an impact on the effect of defoamer. Therefore, when cooperating with various auxiliaries, we must pay attention to the relationship between different auxiliaries and choose the best balance point.


Factor three: Baking temperature


When the coating is baked at room temperature at high temperature, the viscosity starts to drop back immediately, and the bubbles can move to the surface. However, due to the volatilization of the solvent, the solidification of the coating and the increase of the surface viscosity, the foam will become more stable and be trapped on the surface, resulting in shrinkage and pinholes. Therefore, the baking temperature, fixed-line speed and solvent volatilization rate also have an impact on the effect of the defoaming agent.


Factor 4: Solid content, viscosity and elasticity of the coating


High solid film, high viscosity and high elasticity coatings are very difficult to defoamer. In these coatings, defoamer diffusion is difficult, the speed of microbubble enlargement is slow, the foam migration ability to the surface is reduced, and the foam viscoelasticity is high. The foam in these coatings is quite difficult to eliminate, and it is best to choose a combination of defoamer and defoamer.


Factor five: coating method and construction temperature


Paint construction methods are many, brush coating, roll coating, spray coating, scraping coating, spraying, screen printing coating and so on. The foaming degree of different coating methods is also different. The foam of brush coating and roll coating is more than that of spray coating and scraping coating. The foam of high temperature is more than that of low temperature, but the foam can be easily eliminated at high temperature.




The selection of defoamer There are many types of defoamer and their characteristics are different, so the defoamer selected in different formulas is also different.
Flat coating


Formula features: low viscosity, low defoaming pressure


Recommendation: Mineral oil or mineral oil modified polyethers


Elastic coatings


Formula features: high viscosity, high defoaming pressure


Formula suggestion: polyether modified silicone


Surface coating and laminating adhesive


Formula suggestion: Polyether, can effectively prevent surface defects, and have less impact on gloss


Water in water colorful


Formula features: more surfactants, stable foam


Formulation suggestion: Use polyether or mineral oil modified polyether






Precautions for the use of defoamer








1. Before use, it must be fully stirred and mixed evenly;


2. Add in the case of mixing paint;


3. Before use, generally dilute without adding water;


4. The dosage should be appropriate, too much dosage will cause shrinkage, shrinkage, poor brushing and other problems; Too little dosage, poor defoaming effect;


5. It is best to add it in two times, that is, in the grinding stage and the paint mixing stage respectively, generally half of the total amount each time, with a good antifoam effect in the grinding stage, and a good foam breaking effect in the paint mixing stage.