Defoaming agent for bubble control
In the consumption of architectural coatings, due to the presence of additives such as emulsifiers, dispersants and thickeners in the formula, not only a large number of bubbles will be generated, but also the bubbles can be stabilized, resulting in a large number of bubbles in architectural coatings. In the process of film formation, if the bubbles cannot disappear, it will cause defects such as shrinkage holes and pinholes in the coating. Therefore, adding defoamers to eliminate these bubbles can achieve satisfactory results.
Dynamic defoaming ability:
1) Dynamic defoaming effect in a relatively closed small space, such as in a chamber scraper, Tianjin defoamer involves gas entering the bubble, and the external short-term pressure reduction is more conducive to the generation and stability of bubbles. Wetting agents and emulsifiers have a shrinking effect on the gas in the bubble. One is nothing, but tens of millions are considerable.
2) Open dynamic defoaming effect, I don’t know if you have ever come into contact with the transformation of a single flexographic printing machine into a coating machine. The glue roller and the inking roller are open in a small space and flip at high speed, and the bubble generation speed is quite fast.
Long-term effect: Some defoamers start out very well, but the effect becomes much worse after being left for a while
There are many influencing factors, I think there are at least two reasons
1) Defoamers are expanded by surfactants
2) The main agent of defoamers can be absorbed by the colloidal resin
First, tiny bubbles approach each other, then coalesce into slightly larger bubbles, and then rise to the surface. Large bubbles rise faster than small bubbles. During the drying process, the viscosity increases and the bubble rises slower, so lowering the viscosity of the paint can significantly reduce the generation of bubbles. Therefore, when consuming paint, it is necessary to select some raw materials with low foam content and try to eliminate components that stabilize bubbles; adjust the production process, reduce the occurrence of side reactions, and control the temperature, humidity, and ventilation conditions of paint construction to reduce bubbles. Adding defoamers in proportion can also effectively eliminate bubbles.
