As a category of paper auxiliaries, defoamer plays an important role in the paper industry although the amount is not large. During the coating process, foam will affect the normal production and paper quality. As a category of paper auxiliaries, defoamer plays an important role in the paper industry although the amount is not large. During the coating process, foam will affect the normal production and paper quality. So people take many methods to eliminate the foam in the coating process, such as chemical method, physical method, mechanical method and so on. Chemical method is the most widely used. The working principle of this method is that a special additive is added in the production process, and the foam is controlled by the defoamer. This type of substance has a strong surface activity, can displace or destroy the foaming agent in the production system, reduce the surface tension, so that it is unable to form a strong bubble film, resulting in foam rupture. So people take many methods to eliminate the foam in the coating process, such as chemical method, physical method, mechanical method and so on. Chemical method is the most widely used. The working principle of this method is that a special additive is added in the production process, and the foam is controlled by the defoamer. This type of substance has a strong surface activity, can displace or destroy the foaming agent in the production system, reduce the surface tension, so that it is unable to form a strong bubble film, resulting in foam rupture.

The mechanism of foam suppression is to destroy the conditions of foam formation. There are two mechanisms of bubble inhibition: First, the foam inhibitor is first adsorbed by the bubble membrane ‚ and then squeezes or eliminates the adsorbed layer of the foaming agent. Because the spreading property of the foam suppressor is strong and the cohesion is small, the formation of foam is inhibited. The second is that the foam suppressor replaces the foaming agent in the bubble film, forming the inelastic bubble film, which is easy to destroy under gas pressure, resulting in the foam can not be formed.

Defoamer can also be divided into three categories: silicone defoamer, non-silicon defoamer and polyether defoamer. Silicone defoamer has good defoamer effect, but incomplete emulsification seriously affects its effect, such as methyl silicone oil and ethyl silicone oil, which are satisfied with the defoamer effect of oil solution, while modified silicone oil has good defoamer effect of water-based system. Non-silicon defoamer refers to fatty amide and phosphoric ester organic compounds. This kind of defoamer has poor ability to eliminate dense foam and has some limitations in application. Polyether type defoamer refers to block copolymer of propylene oxide and ethylene oxide.

Defoamer products generally contain three substances: active ingredient, dispersant and carrier. The active ingredient is the substance that has the effect of defoaming. Defoamer is generally an oily substance with poor hydrophilicity, which is difficult to penetrate into the foam and expand in the surface film of the foam ‚, so some defoamer is added to the dispersant, and low-carbon alcohols can be used directly without adding dispersant. The function of the carrier is to dilute and disperse the defoamer and dispersant. Water and organic solvent are commonly used as the carrier, and water as the carrier can be made into water-based emulsified defoamer.

At present, the active ingredients of coating defoamer are mainly polyether and modified silicone. Polyether and modified silicone not only have a strong anti-foam, anti-foam effect, but also have a variety of functions such as glazing, lubrication, and emulsification, dispersion, permeability, thermal stability, chemical stability are very good, non-toxic, very suitable for use as a coating defoamer. In the actual application of coating defoamer, polyether is generally combined with other defoamer such as fatty acid derivatives, silicone and so on to form a composite defoamer.

Qingdao Jieruixin Machinery&Technology Co.,Ltd,has various defoamers to use in paper coating processing.If you have any question,pls feel free to contact us!