Seeking advice on the use of defoamers in rubber production

Antifoamers are substances used in food processing to reduce surface tension and eliminate foam. Foam is mostly generated under external forces: surfactants present in the solution form bubbles at the interface between the solution and air, which then rise to the surface; or colloidal substances such as gelatin and proteins form films and bubbles. During food processing, processes such as fermentation, stirring, boiling, and concentration can generate a large number of bubbles, which interfere with normal operations; these bubbles must be eliminated promptly or prevented from forming. Defoamers can be roughly divided into two categories: one type can eliminate bubbles that have already formed, such as ethanol ； Another category can inhibit bubble formation, such as emulsified silicone oils. The antifoam agents permitted for use in our country include six types: emulsified silicone oils, high-carbon alcohol fatty acid ester complexes, polyoxyethylene polyoxypropylene pentaerythritol ethers, polyoxyethylene polyoxypropylene amine ethers, polyoxypropylene glycerol ethers, and polyoxypropylene ethylene oxide glycerol ethers.

Overview: Many harmful foams are generated during industrial production, requiring the addition of defoamers. There are many types of defoamers, including siloxanes, polyethers, silicon and ether grafts, as well as those containing amines, imines, and amides. These defoamers feature faster defoaming speeds, longer foam suppression durations, a wider range of applicable media, and even the ability to function in harsh conditions such as high temperatures, strong acids, and strong bases. It is widely used to remove harmful foam generated during the production processes in various industries such as latex removal, textile sizing, food fermentation, biomedicine, coatings, petrochemicals, papermaking, and industrial cleaning. Preparation methods of defoamers: 1. Diesel fuel and lubricant defoamers and their usage methods; 2. Diesel defoaming compositions; 3. Diesel defoaming composition 2; 4. Composite defoamers based on silicon compounds; 5. Bean-based defoamers; 6. Preparation methods of defoamers for soy product processing; 7. High-efficiency defoamers; 8. High-efficiency defoamer mixtures and their preparation methods; 9. Production methods of industrial silicone defoamers; 10. Solid-dispersed defoamers; 11. Defoaming dispersants for photoresist development solutions; 12. Silica-based antifoaming compositions; 13. Low-foam defoaming compositions containing alkoxylated quaternary ammonium compounds; 14. Defoamers or degassing agents based on oil-in-water dispersions; 15. Polyalkoxy terpenes, their preparation methods, and their use as defoamers. 1. The mechanism of action of defoamers. Bubbles and foams are commonly present in people’s daily lives and industrial processes, and sometimes they are utilized for purposes such as flotation, fire extinguishing, dust removal, washing, and the production of foam ceramics and plastics ； Sometimes it needs to be removed, such as in fermentation, coatings, papermaking, printing and dyeing, to eliminate gas buildup in internal organs, in boiler water, in wastewater treatment, and in the manufacture of prisms (or glass). The so-called “bubbles” refer to the presence of insoluble gases within a liquid or solid, or to separate bubbles enclosed by films of these gases. The state in which many bubbles gather together, separated from one another by thin films, is called foam. A bubble is a dispersion system with gas/liquid, gas/solid, or gas/liquid/solid interfaces, the latter of which are commonly found in bubbles in mineral processing and oil field systems. Generally speaking, pure water and pure surfactants do not form bubbles, as their surfaces and interiors are uniform, making it difficult to form elastic films; and even if such films do form, they are unstable and disappear instantly. However, in the presence of surfactants in the solution, after bubbles are formed, due to intermolecular forces, the hydrophilic and hydrophobic groups in these molecules are attracted to the bubble wall and arrange themselves in an orderly manner, with the hydrophilic groups facing the aqueous phase and the hydrophobic groups facing the inside of the bubble. This results in the formation of an elastic membrane at the bubble interface, which is highly stable and does not easily rupture under normal conditions. The stability of foam is related to factors such as surface viscosity and elasticity, electrostatic repulsion, movement of the surface film, temperature, and evaporation. Furthermore, bubbles are inversely related to the surface tension of the liquid; the lower the tension, the easier it is for bubbles to form. In daily life and production, the appearance of foam sometimes causes many inconveniences for people, so it is necessary to eliminate it. Any factor that can disrupt foam stability can be used for defoaming. Defoaming involves both \"foam suppression\" and \"foam destruction\". Silicone defoamers serve this purpose; they can reduce the surface tension of water, solutions, suspensions, etc., prevent foam formation, or reduce existing foam, and usually exhibit selective activity. Traditional physical defoaming methods are difficult to eliminate foam instantly, whereas chemical and interfacial defoaming methods are very fast, convenient, and efficient. In summary, defoamers are agents that possess chemical and interfacial chemical defoaming properties. As defoamers, there are low-carbon alcohols, mineral oils, organic polar compounds, and silicone resins, etc. Its forms include oil-type, solution-type, emulsion-type, and foam-type. As defoamers, they all possess strong defoaming capacity, chemical stability, physiological inertness, heat resistance, oxygen resistance, corrosion resistance, gas dissolution capability, air permeability, easy diffusion and penetration, low solubility in the defoaming system without any physical or chemical effects, as well as the advantage of requiring small amounts for effective performance. There are a wide variety of defoamers, with diverse applications. The process of defoamers in suppressing and breaking bubbles is as follows: when a defoamer is added to the system, its molecules spread randomly across the liquid surface, preventing the formation of elastic membranes and thus stopping bubble formation. When the system produces a large amount of foam, an antifoaming agent is added; its molecules immediately spread across the surface of the foam, spreading rapidly to form a very thin double-layer membrane. They then continue to diffuse and penetrate, invading in layers, thereby replacing the thin walls of the original foam membrane. Due to its low surface tension, it flows toward liquids with higher surface tension that produce foam. As a result, the molecules of this low-surface-tension defoamer continuously diffuse and penetrate across the gas-liquid interface, causing the membrane walls to thin out rapidly. At the same time, the foam is subjected to strong pulling forces from the surrounding membranes with high surface tension, which leads to an imbalance in the stresses around the foam and thus its collapse. The defoaming agent molecules that are not soluble in the system re-enter the surface of another foam membrane, and this process repeats itself, resulting in the destruction of all the foams. 2 Properties and Applications of Silicone Defoamers Silicone defoamers are produced by mechanically emulsifying silicone oils, emulsifiers, waterproofing agents, thickeners, etc., along with an appropriate amount of water. It is characterized by low surface tension, high surface activity, strong defoaming ability, low usage amount, and low cost. It is immiscible with water and most organic substances, and it can defoam most bubble-forming media. It possesses good thermal stability and can be used within a wide temperature range of 5°C to 150°C ； It has good chemical stability and does not react easily with other substances; when properly formulated, it can be used in acidic, alkaline, and saline solutions without compromising product quality ； It also exhibits physiological inertness with an LD250 of 250 g/Kg in rats, and is commonly used in the food and pharmaceutical industries. It has both antifoaming and defoaming functions for all bubble systems, and belongs to the category of broad-spectrum defoamers. It is widely used for defoaming in various production processes such as detergents, papermaking, pulp production, sugar manufacturing, electroplating, fertilizer production, additives, and wastewater treatment. In the oil industry, it is widely used for the desulfurization of natural gas and to accelerate the separation of oil and gas ； It is also used in devices for drying ethylene glycol, extracting aromatic hydrocarbons, processing asphalt, and dewaxing lubricating oils to control or suppress bubbles. In the textile industry, it is used to eliminate foam in processes such as dyeing, scouring, and sizing ； In the chemical industry, it is used to eliminate foam in processes such as the synthesis of resins, latex, coatings, and inks ； In the food industry, it is used to eliminate foam in various concentration, fermentation, and distillation processes. Silicone grease can be applied to the walls of the pot, at the outlet, or onto the metal mesh to eliminate bubbles. Silicone grease can be prepared as a solution for defoaming in oil-phase systems. A water-emulsion prepared by mixing silicone grease with low-viscosity silicone oil can be used for defoaming in various aqueous systems. In medicine, it is commonly used to remove gas from the organs or stomach contents before surgery, X-rays, and gastroscopy. :victory:

This is an overview of defoamers; more specific industry-specific technical information would be better. Still, thank you: handshake

We produce synthetic rubber, as well as antifoaming agents for Emulsifiable Liquid Antifoam (XPJ-2).

Bubbles that appear during rubber processing are related to the formulation and processing methods; specific issues need to be analyzed on a case-by-case basis. It is possible to read more materials on rubber processing

I’m not sure whether you’re referring to the foaming issue during the rubber synthesis process or during the rubber processing process; the situations are different in both cases

We don’t even use antifoam agents for the rubber here!!:lol