What are the characteristics of the polyether-modified silicone antifoaming agent, the polyether antifoaming agent, and the silicone antifoaming agent respectively

The polyether antifoaming agent belongs to non-ionic surfactants and has excellent defoaming and foam suppression functions. It has characteristics such as no odor, no irritation, and easy dispersion in water. It is one of the important varieties of antifoaming agent products. It is widely used for defoaming treatment in fields such as fermentation for manufacturing antibiotics, vitamins, food processing, papermaking, chemical industry, coatings, building materials, detergents, etc. Maybe everyone has some understanding of the polyether antifoaming agent, or maybe they know nothing about it. It doesn’t matter. Let me introduce the knowledge of the polyether antifoaming agent to you!

The main component of the silicone antifoaming agent (English name: organic silicon defoamer) is the silicone oil, an organic silicon component. Silicone oil is a non-volatile oily liquid at room temperature, which is insoluble or has very low solubility in water, animal and vegetable oils, and mineral oils. It can withstand both high and low temperatures. It has inert chemical properties, stable physical properties, and no biological activity.
The silicone antifoaming agent is a white viscous emulsion. It has been used in various industrial fields since the 1960s, but its large-scale and comprehensive rapid development started from the 1980s. As a silicone antifoaming agent, its application fields are also very extensive and it is increasingly valued by all walks of life. In industrial sectors such as the chemical industry, papermaking, coatings, food, textiles, and pharmaceuticals, the silicone antifoaming agent is an indispensable additive in the production process. It can not only remove the foam on the liquid surface of the process medium in the production process, thereby improving the separation, gasification, liquid discharge, and other effects of processes such as filtration, washing, extraction, distillation, evaporation, dehydration, and drying, and ensuring the capacity of various containers for containing and handling materials. Action Principle: Whenever we stir the liquid or gas is introduced into it, many bubbles will be generated on the surface and inside of the liquid. The bubbles generated in some liquids will quickly break and disappear. In some liquids, the bubbles not only do not disappear but also accumulate more and more, forming foam. Foam is a dispersed system in which a large number of bubbles are dispersed in the liquid, with the dispersed phase being gas and the continuous phase being liquid. The volume fraction of the foaming liquid is very small, and the foam occupies a large volume. The gas is separated by continuous liquid films, forming bubbles of different sizes that accumulate to form foam.
Media that can foam, such as surfactants, have a layer of surfactants adsorbed on the surface of the bubbles in a directional arrangement. When it reaches a certain concentration, a strong film is formed on the bubble wall. The surfactant is adsorbed on the gas-liquid interface, causing the surface tension of the liquid surface to decrease, thereby increasing the gas-liquid contact surface, so that the bubbles are not easy to merge. The relative density of the bubbles is much smaller than that of the liquid itself. When the rising bubbles pass through the liquid surface, a layer of surfactant molecules on the liquid surface is adsorbed again. Therefore, the bubble film with surfactant adsorbed on it exposed to the air is different from the bubble film in the solution. It has two layers of surfactant molecules, forming a bimolecular film, and the adsorbed surfactant has a protective effect on the liquid film. The antifoaming agent is to destroy and inhibit the formation of this film. The antifoaming agent enters the bimolecular directional film of the foam and destroys the mechanical balance of the directional film to achieve the effect of breaking the bubbles.
The antifoaming agent must be a substance insoluble in the foaming medium, and it can be dispersed into the foaming medium in the form of liquid droplets, or liquid droplets encapsulating solid particles, or solid particles. The antifoaming agent has a lower surface tension than the foaming medium and can spontaneously enter the liquid film to make the bubbles burst.
The antifoaming agent spreads easily on the surface of the solution and automatically unfolds on the surface of the foam, which will carry away a layer of the solution on the adjacent surface, making the liquid film locally thinner. When it reaches the critical thickness, the liquid film breaks and the foam is destroyed. The faster the antifoaming agent spreads on the surface of the solution, the thinner the liquid film becomes, the faster the foam is destroyed, and the stronger the defoaming effect. Therefore, on the one hand, the reason for defoaming lies in its easy spreading. The adsorbed antifoaming agent molecules replace the foaming agent molecules, forming a film with poor strength. At the same time, during the spreading process, part of the solution on the adjacent surface layer is carried away, making the foam liquid film thinner and reducing the stability of the foam, making it easier to be destroyed.
An excellent antifoaming agent must simultaneously consider both defoaming and foam suppression functions, that is, it should not only quickly destroy the foam but also prevent the formation of foam for a relatively long time. The reason for this situation may be related to whether the critical micelle concentration of the foaming agent (surfactant) in the solution is exceeded. In a solution where it is exceeded, the antifoaming agent (usually an organic liquid) may be solubilized, resulting in the loss of its spreading function on the surface and a significant reduction in defoaming efficiency. After a period of time, as the antifoaming agent is gradually solubilized, the defoaming effect weakens accordingly.
Advantages: (1) Wide Application Range: Due to the special chemical structure of silicone oil, it is neither miscible with water or substances containing polar groups, nor with hydrocarbons or organic substances containing hydrocarbon groups. Due to the insolubility of silicone oil in various substances, it has a wide application range and can be used for defoaming in both water-based systems and oil-based systems. (2) Low Surface Tension: The surface tension of silicone oil is generally 20-21 dynes/cm, which is smaller than that of water (72 dynes/cm) and the surface tension of general foaming liquids, and has good defoaming efficiency. (3) Good Thermal Stability: Taking the commonly used dimethyl silicone oil as an example, it can withstand 150°C for a long time and can withstand above 300°C for a short time, and its Si-O bond does not decompose. This ensures that the silicone antifoaming agent can be used in a wide temperature range. (4) Good Chemical Stability: Since the Si-O bond is relatively stable, the chemical stability of silicone oil is very high, and it is difficult to react with other substances. Therefore, as long as it is reasonably formulated, the silicone antifoaming agent can be used in systems containing acids, alkalis, and salts. (5) Physiological Inertness: Silicone oil has been proven to be non-toxic to humans and animals, and its median lethal dose is greater than 34 grams/kg. Therefore, the silicone antifoaming agent (with the appropriate combination of non-toxic emulsifiers, etc.) can be safely used in industries such as food, medical treatment, pharmaceuticals, and cosmetics. (6) Strong Defoaming Ability: The silicone antifoaming agent can not only effectively break the already formed foam but also significantly inhibit the formation of foam. Its dosage is very small. As long as one part per million (1 ppm) of the weight of the foaming medium is added, a defoaming effect can be produced. Its commonly used range is 1 to 100 ppm. It not only has a low cost but also does not contaminate the defoamed substance.
In the molecule of the silicone-ether copolymer, the siloxane segment is a lipophilic group and the polyether segment is a hydrophilic group. The polyoxyethylene chain in the polyether segment can provide hydrophilicity and foaming properties, and the polyoxypropylene chain can provide hydrophobicity and permeability, which has a strong effect on reducing the surface tension. The groups at the end of the polyether also have a great influence on the performance of the silicone-ether copolymer. Common end groups include hydroxyl groups, alkoxy groups, etc. Adjusting the relative molecular mass of the siloxane segment in the copolymer can make the copolymer highlight or weaken the characteristics of silicone. Similarly, modifying the relative molecular mass of the polyether segment will increase or decrease the proportion of silicone in the molecule, which will also affect the performance of the copolymer.
Application: The silicone antifoaming agent has a wide range of uses and application fields. It is used as an antifoaming agent in the fermentation industry of substances such as erythromycin, lincomycin, avermectin, gentamicin, penicillin, oxytetracycline, tetracycline, tylosin, glutamic acid, lysine, citric acid, xanthan gum, etc. It is also used in fields such as textiles, printing and dyeing, coatings, dyes, papermaking, inks, oil fields, and sewage treatment. When used in printing and dyeing, it has good compatibility with the additives in the dye bath and does not affect the color shade and color fastness.
There have been many literature reports on the use of silicone as an antifoaming agent for spray dyeing. In the old dyeing process, generally, dimethyl polysiloxane antifoaming agent can achieve satisfactory defoaming effects and ensure uniform dyeing. However, in the new dyeing process, high-temperature and high-pressure machinery is used. In this machinery, the dyed materials move under the spray of the dyeing liquid and are dyed at the same time. Although the generated foam can be defoamed by ordinary silicone antifoaming agents, under high-temperature and high-pressure conditions, general siloxane antifoaming agents will produce film-like precipitates, causing spots on the dyed materials. The application of block copolymers can overcome the above disadvantages because these antifoaming agent components are soluble in cold water but insoluble in hot water, so they can play a defoaming role. However, the defoaming effect of using only this copolymer antifoaming agent is not satisfactory. If a certain amount of mist-like SiO2 is added to the copolymer, a satisfactory defoaming effect can be achieved and uniformly dyed fabrics can be produced. It is used for defoaming in the high-temperature dyeing process of polyester fabrics and the fermentation process. In addition, it can also be used for defoaming in the diethanolamine desulfurization system and various systems such as oil agents, cutting fluids, antifreeze fluids, and water-based inks. It is also suitable for defoaming after washing off the uncured resin in the photosensitive resin plate-making process in the printing industry. It is a very representative silicone antifoaming agent with excellent performance and wide application.