Defoaming agent for water-based industrial additives
Defoaming agent foam is a stable dispersion formed by air in a liquid medium. Stable foam will be formed after surface-active substances are mixed into the liquid. Paints are not single components, and many components in the formula will inevitably bring some surface activity. Substances produce stable foam in paints, so defoaming agents are one of the necessary additives for water-based paints.
The foaming and defoaming process includes three aspects: the generation of bubbles inside the liquid; the rise of the bubbles in the liquid phase and migration to the liquid surface; and the collapse of the bubbles on the liquid surface. It can be seen from the bubble formation and stabilization process that preventing air from being mixed into the liquid, accelerating the merger of the mixed bubbles and rising to the liquid surface, thereby promoting the rapid collapse of the bubbles, is the entire process of defoaming.
The process of reducing and preventing the generation of bubbles is called foam suppression. The process of bubbles merging in the liquid and rising to the surface of the liquid is called defoaming. The bursting of bubbles on the liquid surface is called defoaming or defoaming. Therefore, there are also foam suppressors and defoaming agents. and defoaming agents, collectively called defoaming agents.
According to the defoaming mechanism and application requirements of defoaming agents, it can be seen that defoaming agents should have the following characteristics:
1. The surface tension of the defoaming agent should be smaller than the surface tension of the system to be defoamed.
2. The solubility in the system to be defoamed should be as small as possible
3． Must have good penetration ability
4. It is stable for the system and will not produce other side effects, such as small odor and low toxicity. It has no impact on the production, storage and construction properties of the paint.
Defoaming agents are generally divided into:
① Mineral oil – excellent defoaming ability and durability of defoaming effect, good compatibility, and not prone to shrinkage cavities
② Organosilicon – strong defoaming ability, does not affect the gloss of the system, is used in low concentration and is basically non-toxic to people and the environment
③Polymer – long foam suppression time, good effect, fast defoaming speed, good thermal stability and other characteristics.
Due to the complexity and variability of coating formulas, choosing a suitable defoaming agent is very important for the performance of the coating, such as storage stability and workability. It should also be noted that the selection of defoaming agents should also consider the corresponding emulsification system and resin system. Compatibility
