![]() ![]() Typical waxes are ethylene bis stearamide (EBS), paraffin waxes, ester waxes and fatty alcohol waxes. An oil-based defoamer also contains a wax and/or hydrophobic silica to boost the performance. The oil might be mineral oil, vegetable oil, white oil or any other oil that is insoluble in the foaming medium, except silicone oil. These caused better washing, reduced biological oxygen demand (BOD) in effluent and reduced deposits.Ĭlassification Oil-based defoamers In the early 1990s, silicone emulsion defoamers that caused less surface disturbances were used in the wood pulping industry with great success. The development of silicone-based defoamers has continued, using different emulsifiers and modified silicone oils. So water extended (water in oil emulsion) and water-based (oil in water emulsion) defoamers appeared. These types of defoamers were very efficient, but the oil crisis of 1973 made these too expensive and resulted in a push for reduction of the oil content. In the early 1970s, hydrophobic waxes like ethylene bis stearamide dispersed in oils developed. In 1963 the first antifoams with hydrophobic particles ( hydrophobic silica) in light oil were patented. Silicone oils worked well, but caused surface disturbances in many applications like paints and papermaking. These were based on polydimethylsiloxane (silicone oil) dispersed in water or light oil. ĭuring the 1950s, experiments with silicone-based defoamers started. Milk and cream were forebears for modern day emulsion type defoamers. They were added to oil products to boost the efficiency. Fatty alcohols (C7 – C22) were effective but expensive antifoams. Kerosene, fuel oil and other light oil products were used to break down foam. The first defoamers were aimed at breaking down visible foam at the surface. Entrained air bubbles are agglomerated, and the larger bubbles rise to the surface of the bulk liquid more quickly. This causes rupture of the air bubbles and breakdown of surface foam. It has affinity to the air-liquid surface where it destabilizes the foam lamellas. An essential feature of a defoamer product is a low viscosity and a facility to spread rapidly on foamy surfaces. Generally a defoamer is insoluble in the foaming medium and has surface active properties. A variety of chemical formulae are available to prevent formation of foams. They cause defects on surface coatings and prevent the efficient filling of containers. In industrial processes, foams pose serious problems. ![]() The additive is used to prevent formation of foam or is added to break a foam already formed. Commonly used agents are insoluble oils, polydimethylsiloxanes and other silicones, certain alcohols, stearates and glycols. Strictly speaking, defoamers eliminate existing foam and anti-foamers prevent the formation of further foam. The terms anti-foam agent and defoamer are often used interchangeably. A defoamer or an anti-foaming agent is a chemical additive that reduces and hinders the formation of foam in industrial process liquids. ![]()
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