Defoamers principle describes how the foam is eliminated?-Iota

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News > Dynamic industry > Defoamers principle describes how the foam is eliminated?

Defoamers principle describes how the foam is eliminated?

Defoamers refers to drugs having chemical and interfacial chemistry defoaming effect. As a defoaming agent, there are lower alcohols, mineral oils, organic polar compounds and silicone resins. Defoamers have a strong anti-foaming, oxidation stability, physical inertia, heat resistance, oxygen, corrosion, dissolved air, breathable, easy to spread, easy to penetrate, insoluble defoaming system and unreasonable shadow of the ring, defoamers with less efficient characteristics. Defoamers variety, versatility, often used in our lives, but we know the principles and methods of use defoamers it?

First, the principle of defoamer
In the industrial production process, if the presence of large amounts of foam, the production process will bring a lot of trouble, such as production capacity will be greatly restricted; wastage of raw materials and products; the impact of product quality; environmental pollution, So if not properly addressed, it is no exaggeration to say that the "bubble" will be our stumbling block, some processes become a "bottleneck." Thus, in the production process of how to effectively control bubble, it has become the focus of attention of researchers!
In fact, many of the foam can be eliminated by defoamers. Defoamers to eliminate the foam is usually in the following two ways.
1. defoamer in the foam diffusion, diffusion bilayer membrane formed on the walls of the foam, a stabilizing role in this diffusion process will spread out the surfactant, and reduce the surface tension of the foam partial destruction of self-healing foam effect, the bubble burst.
2. defoamers may enter the bubble wall, but only spread to a very limited extent, with the blowing agent blended together to form a single, cohesive poor if such a monolayer, the bubble will burst.

Defoamers used in industry is generally divided into organic defoamers, silicone defoamers and polyether defoamers categories. Wherein the silicone defoamers defoaming ability due to a low concentration and stoves for people and the environment substantially non-toxic characteristics, so more and more people are welcome.

Silicone defoamer dimethyl silicone oil and SiO2 composite made by a certain percentage. Defoamers thus produced having insoluble in water, very difficult emulsification, surface low viscosity, surface tension than some surfactant to lower the surface and can interfere with the elastic foam film characteristics, particularly for defoaming effect than the oil-soluble solution good; better diffusion modified composite silicone antifoam emulsions, anti-foaming capacity and role performance. Defoamers and abroad are currently widely used mostly in this category.

Second, the amount and use of defoamers
Antifoam active substance content of 100% silicone defoamers less directly used in the production process, which is not only due to the high cost and difficult to work when used in small amounts, the amount will cause more pollution. So common are mostly already formulated into a silicone mass fraction of 1% to 2% of anti-foaming emulsion. An amount based on changes in process conditions appropriately.

From the use of speaking, it is simple to operate, of course, is the best anti-foaming agent was added to the solution, the foam can be controlled throughout the process. But sometimes this effect is not good. Because defoamers must be a liquid at the interface of the second air foam stabilizer arranged, only play the role of anti-foaming. In this process, there are many factors that can be removed from the surface defoamers, namely the growth over time will slowly dissolved or emulsified into the liquid, the loss of anti-foaming ability (speed with the following factors defoamers emulsified dissolution rate related); shear, type and concentration of the surfactant, temperature, pH value, solvent type and content, and there may be some special material, etc.).

Therefore Defoamers safest and most effective way is to add in the production process in a continuous or semi-continuous manner low concentrations dilute emulsion. This can prevent the generation of silicone foam also prevent oil pollution problem, if you must start adding sufficient operational silicone defoamers it should avoid excessive.

Third, the choice of defoamer
Select defoamers to comply with the following:
1, insoluble or poorly soluble in the bubble solution
To burst the bubble, bubble film defoamers should concentrate, concentrate. To break foaming agent, shall have at the moment is concentrated, focused, in the case of suds should always remain in this state. So defoamers in the bubble solution is supersaturated, only insoluble or poorly soluble only easy reached saturation. Insoluble or poorly soluble, it is easy to gather in the gas-liquid interface, it is easy to concentrate in the bubble membrane, it can play a role in lower concentrations. Defoamer molecular water system, the active ingredient, the weak shall be strong hydrophobic hydrophilic, HLB value in the range of 1.5-3, only the best effect.

2, the surface tension of the liquid below the bubble.
Only defoamers intermolecular forces between small, surface tension is lower than bubble solution, defoamers particles to be able to film immersed in the bubble and expansion. It is worth noting that the surface tension of the bubble generation liquid surface tension of the solution is not, but a co-bubble surface tension of the solution.

3, with the bubble generation liquid has a certain degree of affinity.
Since the anti-foaming process is actually competition collapse of the bubble and the bubble generation rate of speed, it must be able to quickly disperse defoamers in the bubble solution, in order to quickly play a role within the broader context of the bubbling liquid. For faster diffusion defoamers, defoamer and bubble generation liquid active ingredient to be a certain degree of affinity. Defoamers active ingredient and the bubble-liquid pro, will dissolve; too sparse and difficult to disperse. Only affinities suitable effect will be good.

4, and the bubble was not a chemical reaction.
Antifoaming agent reacts with the bubble generation liquid, on the one hand defoamer lose effect, on the other harmful substances may affect the growth of microorganisms.

5, volatile small, long duration of action.
You must first determine the system requires the use of defoamers, aqueous systems or oil system. Such as fermentation industry, it is necessary to use oil-based defoamers, such as polyether modified silicone or polyether. Water-based paint industry should aqueous defoamers, silicone defoamers. Selected defoamers, compare the amount of, the reference price can be drawn from the most suitable and most economical defoamers products.

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