Varieties and limitations of current defoamers

There are many types of defoamers in use, and there are three main types of defoamers for water-based coatings:

• Mineral oils, the market share is 80%;
• Polysiloxanes, with a market share of 17%;
• Polyethers have a market share of 3%.
• Among them, mineral oil defoamers have the highest cost performance and are more commonly used. They can be used in most flat and semi-gloss emulsion paints, but their defoaming and defoaming effects are not as good as polysiloxane and polyether defoamers. Agent. Mineral oil defoamers are basically composed of carriers (mostly hydrocarbon oils or water), hydrophobic particles (wax, silicone oil, hydrophobic silica and fatty acids or polyurethanes, etc.), emulsifiers or expanders (fatty acid esters, It is composed of sorbitan (sugar) alcohol esters, etc.], in which the carrier accounts for 75% to 80%, the hydrophobic particles account for 10% to 15%, and the emulsifier or spreading agent accounts for 5% to 10%.

The role of the carrier is to bring the main defoaming substance into the foam system, so that it diffuses on the foam film, and plays the role of bearing and dilution. It has a great influence on the defoaming performance and durability of the defoamer. It is a low surface tension substance, has suitable incompatibility with the foam system, and is easy to rise to the surface of the foam system; the size of the hydrophobic particles is 0.1 Between ~20 μm, it mainly plays an active role in the formulation; emulsifiers or spreaders are used to adjust the compatibility of the active ingredients in the coating system, to balance the compatibility and incompatibility, and to ensure the active ingredients It diffuses quickly and penetrates the surface of the coating film quickly, so that the active ingredients immediately defoam. In addition, mineral oil defoamers also contain a small amount of stabilizers or preservatives.

• Polysiloxane defoamers include polydimethylsiloxane defoamers and modified polydimethylsiloxane defoamers, collectively referred to as silicone defoamers. Among them, the polydimethylsiloxane antifoaming agent is a non-volatile oily liquid, with a degree of polymerization of tens to hundreds, with stable physical and chemical properties and a very low surface tension; modified polydimethylsiloxane Class defoamers have suitable hydrophilic and lipophilic balance values. For example, polydimethylsiloxane defoamer modified with organic fluorine, which is a defoamer with extremely low surface tension and excellent defoaming ability. Although polysiloxane defoamers have low surface tension, strong defoaming and foam suppression capabilities, and do not affect the gloss, improper use will cause film shrinkage and poor recoatability.
• Polyether defoamers are products with suitable incompatibility obtained by selectively modifying some polymers, and are mainly used in some systems that require higher compatibility. For example, there is incompatibility between acrylate and epoxy resin. For this reason, consciously change the polarity, relative molecular weight and distribution of the polymer to make it a proper balance between "miscible" and "immiscible", so that the obtained defoamer product is compatible with silicone defoamer Compared with other agents, it has better miscibility and does not stabilize foam. This is the characteristic of polyether defoamers, but it often has the problem of weak or no defoaming ability, so its market demand share is small.

Amber Zhang Ms.

Foreign trade 

Zhejiang Ruico Advanced Materials Co., Ltd. (Stock No.873233)

Add: No.188, Liangshan Road, Linghu Town, Nanxun District, Huzhou City, Zhejiang Province, China 313018

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