Antifoaming agents refer to agents that have chemical and interface chemical defoaming effects. As defoamers, there are lower alcohols, mineral oils, organic polar compounds and silicone resins. All defoamers have strong defoaming power, stable chemical properties, physiological inertness, heat resistance, oxygen resistance, corrosion resistance, dissolved air, air permeability, easy diffusion, easy penetration, insoluble in the defoaming system, and no physical and chemical effects. Feature of low consumption of defoamer and high efficiency. There are many varieties of defoamers and they are widely used. They are often used in our lives. But do you know the principle and use of defoamers?

In the process of industrial production, if there is a large amount of foam, it will cause a lot of troubles in the production process, such as production capacity will be greatly restricted; cause waste of raw materials and products; affect product quality; pollute the environment, etc. Therefore, if it cannot be resolved properly, it is no exaggeration to say that the "bubble" will become our obstacle and the "bottleneck" of certain processes. Therefore, how to effectively control foam in the production process has become the focus of attention of researchers! In fact, many foams can be eliminated by defoaming agents.

1. The defoamer diffuses in the foam and forms a double-layer film on the foam wall during diffusion. During this diffusion process, the stabilizing surfactant is discharged to reduce the local surface tension of the foam and destroy the self-healing of the foam. The effect caused the bubble to burst.

2. The defoamer may enter the foam wall, but only spread to a very limited extent, forming a mixed monolayer together with the foaming agent. If the cohesion of this monolayer is not good, the foam will burst.

The defoamers commonly used in industry can generally be divided into three categories: organic defoamers, silicone defoamers and polyether defoamers. Among them, organosilicon defoamers are more and more popular because of their strong defoaming ability, low concentration and basically non-toxic to human stoves and the environment.

Organosilicon defoamer is compounded by dimethyl silicone oil and SiO2 in a certain proportion. The defoamer made in this way has the characteristics of insoluble in water, very difficult to emulsify, low surface viscosity, lower surface tension than some surfactants, and can interfere with the surface elasticity of the foam film, especially for oil-soluble solutions. Good; the diffusibility, defoaming ability and performance of the modified composite silicone defoaming emulsion are better. Most of the defoamers currently widely used at home and abroad fall into this category.

Silicone defoamers with a defoaming active content of 100% are less directly used in the production process. This is not only due to high cost, but also difficult to work when used in small amounts, and large amounts will cause pollution problems. Therefore, most commonly used antifoam emulsions are formulated into silicone with a mass fraction of 1% to 2%. The amount is appropriately changed according to the process conditions.

In terms of use, it is easy to operate. Of course, it is best to add the defoamer to the solution at once to control the foam during the entire process. But sometimes this does not work well. This is because the defoamer must expel the foam stabilizer at the interface between liquid and air to defoam. In this process, there are many factors that can remove the defoamer from the surface, that is, it will slowly dissolve or emulsify into the liquid over time, and lose the defoaming ability (the speed of the defoamer dissolving emulsification speed and the following factors Relevant); shear force, type and concentration of surfactant, temperature, pH value, type and content of solvent, and some special substances that may exist).

Therefore, the safest and most effective way to use defoamers is to add low-concentration dilute emulsions in a continuous or semi-continuous manner during the production process. In this way, it can prevent both foaming and oil contamination of silicone. If you must add enough silicone defoamer at the beginning of the operation, you must avoid excess.

In order to burst the foam, the defoamer should be concentrated and concentrated on the foam film. In the case of foam breaking agents, it should be concentrated and concentrated in an instant, and in the case of foam suppression, it should be kept in this state frequently. Therefore, the defoamer is supersaturated in the foaming liquid, and only insoluble or insoluble can it easily reach the supersaturated state. Insoluble or poorly soluble, it is easy to gather at the gas-liquid interface, it is easy to concentrate on the bubble film, and it can play a role at a lower concentration. For defoamers used in water systems, the molecules of the active ingredients must be strong hydrophobic and weakly hydrophilic, with an HLB value in the range of 1.5-3 for the best effect.

Only when the defoaming agent has a small intermolecular force and the surface tension is lower than that of the foaming liquid, the defoaming agent particles can immerse and expand on the foam film. It is worth noting that the surface tension of the foaming liquid is not the surface tension of the solution, but the surface tension of the foaming solution.

Since the defoaming process is actually a competition between the foam collapse speed and the foam generation speed, the defoamer must be able to quickly disperse in the foaming liquid in order to quickly play a role in a wider range of the foaming liquid. To make the defoamer diffuse faster, the active ingredient of the defoamer must have a certain degree of affinity with the foaming liquid. The active ingredient of the defoamer is too close to the foaming liquid and will dissolve; too thin and difficult to disperse. The effectiveness will be good only if the close relationship is appropriate.

The defoamer reacts with the foaming liquid. On the one hand, the defoamer will lose its effect, and on the other hand, it may produce harmful substances that affect the growth of microorganisms.

First of all, determine whether the system that needs to use the defoamer is an aqueous system or an oily system. Such as the fermentation industry, it is necessary to use oily defoamers, such as polyether modified silicon or polyether. The water-based paint industry needs water-based defoamers and silicone defoamers. Choose a defoamer, compare the addition amount, and get the most suitable and economical defoamer product at the reference price.



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