Antifoaming agent refers to a substance that can reduce the surface tension of water, solution, suspension, etc., prevent the formation of foam, or reduce or eliminate the original foam. In the papermaking process, due to unreasonable sizing, poorly washed pulp, alkaline fillers used in acid systems, and various additives, foams will accumulate in the wet end of the papermaking system, resulting in the formation of foam dots on the paper. Various defoamers can be added in the papermaking production process according to specific conditions. Early defoamers used were kerosene, paraffin oil and other hydrocarbon oils, sulfonated oil, sodium oleate, octanol, etc. The effective components of defoamers that are widely used recently include silicones, polyether surfactants, fatty amide surfactants, and the like. Defoamers can be divided into oil-based and water-based defoamers, and their effective active components are roughly the same. The advantage of water-based defoamers is that it has minimal impact on other additives and does not The accumulation in the circulation avoids the occurrence of resin barriers, and thus becomes the direction of development. The defoamer can weaken the stability of the mineralized foam, thereby eliminating the harmful effect of excessive foam on the sorting effect and foam transportation. Certain inorganic salts and higher fatty alcohols or higher fatty acids, esters, and hydrocarbons have defoaming effects. The defoaming mechanism of defoamers is not clear enough. Therefore, the choice of defoamer is mostly based on the properties of the foam solution and the test effect. The effectiveness of defoamers is often targeted. Foams with different characteristics must use certain types of agents to be effective. Most defoamers are insoluble in water, and most are used in the form of emulsifiers. Commonly used defoamers are: activated carbon, hydrophobic quartz powder, aluminum silicate powder, water glass, sodium tripolyphosphate, sodium hexametaphosphate, organosiloxane, dimethylsiloxane polymer, vegetable oil, animal oil, Castor oil, 2-ethylhexanol, diisobutyl methanol, fatty acid metal soap, fatty acid esters (such as Spans, Span), alkyl lactate, sulfonated tall oil, sulfonated oil, polyamides, Polyethers, polyalkoxylated polymers, polypropylene oxide polyamines, carboxylic acid-N-alkylamides, polybutene defoamers, high molecular weight polyethylene glycols, etc.