How To Choose A Suitable Defoamer for Low Viscosity Water-based Acrylic Adhesives

Defoaming agent is a substance with low surface tension and high surface activity that can inhibit and eliminate foam in liquid. In other words, defoaming agent can reduce the surface tension of water, solution, suspension, etc., prevent the generation of foam or eliminate the original foam. Long-term defoaming is also called anti-foaming, and the length of anti-foaming time is the main indicator of the quality of defoaming agent. In most cases, defoaming agent is used for its anti-foaming performance rather than the initial defoaming property. Defoaming and anti-foaming are relative. Products with good defoaming performance will have relatively poor anti-foaming performance. In practical applications, it depends on the specific situation. Therefore, from the perspective of defoaming effect, defoaming agents include defoaming agents, anti-foaming agents, and deaerators, which are collectively called defoaming agents.

Some ingredients in water-based adhesives are prone to produce bubbles and tend to be stable and long-lasting. In addition, rapid stirring during production and high-speed brushing during use will also promote the generation of bubbles, which will prevent normal production and affect product quality. The formation of foam brings great difficulties to production and gluing, and causes pores in the adhesive layer, affecting the appearance and adhesive properties of the product. Therefore, it is necessary to try to destroy the foam or prevent the generation of foam. The most effective method is to use a defoamer.

There are many types of defoamers used in the water-based adhesive industry, but they are mainly divided into two categories: polysiloxane defoamers and non-silicone defoamers.

Polysiloxane defoamers have strong defoaming and anti-foaming capabilities and are widely used in the coating industry. In the water-based adhesive industry, especially emulsion-type low-viscosity systems, such as laminating adhesives, pressure-sensitive adhesives, etc., it is very easy to cause problems such as shrinkage and fish eyes. In addition, after the emulsion is formed into a film, due to the surface migration of silane, the later bonding strength will decrease, affecting the bonding effect, so it is generally rarely used.

In the water-based pressure-sensitive adhesive and laminating adhesive industries, mineral oil defoamers are generally used. It is mainly composed of mineral oil, hydrophobic particles, low-carbon alcohols, emulsifiers, etc. The quality of this type of product is easily affected by the brand and batch differences of mineral oil. Since the entire system is a thermodynamically unstable system, it is easy to stratify. It mainly relies on its dispersion in the emulsion to provide defoaming effect. Affected by small molecule additives and surfactants in the emulsion, mineral oil defoamers are easy to float in these systems, which will cause a serious decline in the defoaming effect. The uneven distribution of mineral oil will also affect the coating effect, which brings great trouble to our production and application.