The development history of defoaming agents
The German physicist Quincke first proposed chemical defoaming methods in the 19th century. For example, ether vapor can eliminate soap bubbles. So far, the defoaming agent has been updated four times.
The first-generation defoaming agents are mainly represented by mineral oils, alcohols, amides, fatty acids and their derivatives. Currently, high-carbon alcohol defoaming agents are widely used in the pulp and paper industry.
The second generation defoamer is polyether, and its main component polyether is a linear copolymer composed of ethylene oxide and propylene oxide. Polyether defoaming agents mainly utilize the relationship between solubility and temperature for defoaming. When the temperature rises to the cloud point, the polyether molecular chain links change from zigzag to zigzag shape. The hydrophilicity of the polyether molecules decreases and becomes insoluble. It can be adsorbed on the bubble surface and reduce its surface tension, causing the bubble to burst.
The third generation defoamer is silicone-based. It has the characteristics of stable structure and strong hydrophobicity; its large relative molecular mass and multi-branched structural characteristics enable it to have good low-temperature performance, compatibility performance and environmental compatibility; and its hydrophobic silicone chain has high Surface activity can significantly reduce the surface tension of water and give it excellent defoaming properties.
In recent years, based on the first three generations of defoaming agents, a fourth generation of defoaming agents—polyether-modified silicones—has been developed. This type of defoaming agent is prepared by introducing polyether segments into the polysiloxane chain through chemical graft modification technology. It has the characteristics of both silicone defoaming agents and polyether defoaming agents. After the polyether-modified silicone defoaming agent enters the foaming system, the polyether-modified silicone will show a certain degree of self-emulsification due to the different repellencies and affinity of the siloxane chain segment and the polyether chain segment to the foaming liquid. , in the structure, the polyether segments stretch outside and the polysiloxane segments curl inside. Under the action of self-emulsification, the defoaming agent can be quickly and evenly dispersed in the foaming liquid, giving full play to its anti-foaming and anti-foaming capabilities.
