Defoamer is a substance with low surface tension and high surface activity, which can inhibit and eliminate foam in liquid, that is to say, defoamer can reduce the surface tension of water, solution, suspension, etc., prevent foam generation or make original Some bubbles are eliminated. Long-term defoaming is also called antifoaming. The length of antifoaming time is the main indicator of the quality of defoamers. In most cases, the use of defoamers is to use his antifoaming properties rather than the initial defoaming properties. Defoaming and antifoaming are relative, and the antifoaming performance of products with good defoaming performance will be worse. In practical applications, depending on the specific situation. Therefore, the defoamer from the defoaming effect, including a foam breaker, a suds suppressor, a degassing agent, is generally referred to as defoamer.
Some components of water-based adhesives are easy to produce bubbles and have a tendency to be stable and durable. In addition, rapid mixing in production and high-speed painting during use can also cause foam generation, which prevents production from proceeding properly and affects product quality. The formation of the foam is very difficult to produce and coat the tape, and the pores of the rubber layer appear, affecting the outside of the product and the adhesive properties, so it is necessary to try to destroy the foam or prevent the generation of foam. The most effective method is to use defoamer.
There are a wide variety of defoamers used in the water-based adhesives industry, but there are two main categories: polysiloxane defoamers and non-siloxane defoamers.
Polysiloxane defoamers have strong defoaming and anti-foaming properties and are widely used in the coatings industry. In the water-based adhesive industry, especially emulsion-type low-viscosity systems, such as laminating adhesives and pressure-sensitive adhesives, it is very easy to cause shrinkage and fisheye problems. In addition, after the emulsion is formed into a film, the surface migration of the silane causes a decrease in the bonding strength at a later stage and affects the bonding effect, so it is rarely used.
Mineral oil-based defoamers are commonly used in the water-based pressure-sensitive adhesive and laminating adhesive industries. It is mainly composed of mineral oil, hydrophobic particles, lower alcohols, emulsifiers and the like. The quality of these products is susceptible to the grade and batch variation of mineral oil. Since the whole system is a thermodynamically unstable system, it is easy to stratify, mainly relying on its dispersion in the emulsion to provide defoaming effect, and the small molecule additive in the emulsion. The influence of surfactants, mineral oil defoamers are easy to slick in these systems, which will cause the defoaming effect to drop seriously, and the uneven distribution of mineral oil will also affect the coating effect, which gives us production. And the application brings a lot of trouble.
Post time: Oct-30-2019