Modern industrial production, the bubble everywhere: all kinds of processing fluid tank; all kinds of industrial cleaning pool; all kinds of industrial and agricultural products and preparations; petrochemical production in all aspects of water treatment and so on.
Foam, to bring a variety of problems in industrial production: in order to prevent the bubble overflow, feeding coefficient was forced to reduce 30% to 50%; bubble overflow caused by waste of raw materials; foam space, affecting the reaction rate, the production cycle was extended; Product quality, such as coatings, plastic products; the production of foam, the impact of industrial production stability, resulting in fluctuations in operation, quality and instability. The most straightforward solution to the bubble problem is the use of defoamers.
First, the mechanism of silicone defoamers
Silicone defoaming or suds suppressing the ability is due to its very low surface tension. The organosilicon compound (silicone oil) interferes with the surface tension of the gas and liquid boundary, resulting in defoaming effect.
When the silicone is added to the foam medium, the small particles of silicone oil fall on the surface of the bubble, while effectively reducing the surface tension of the contact point, causing a weak point in the foam skin, causing damage.
The best defoaming activity standard can be described as follows: Free silicone oil particles must be completely, as quickly as possible, and effectively dispersed into the active area. Silicone oil by means of the production process to join the proportion of small, large surface area of the role of SiO2 filler, and quickly dispersed, and in the SiO2 particles outside the point of contact caused by breaking the foam, squeeze together due to the bubble burst near Unstable state, to speed up the effect caused by continuous bubble, to finally reach a stable state. If the emulsion is defoamer, the emulsion is too stable, will reduce the defoaming effect. Poor stability, there is a greater activity. Therefore, there is a need to strike a balance between stability and activity, and to select organosilicon compounds with low solubility in the aqueous and oil phases, but also extremely highly active.
Defoamer function, but also by broken bubble, defoaming, suppression of three mechanisms to define.
Disinfection: relative to the foam, from the air side into the bubble, the bubble will be destroyed.
Foam: from the liquid side into the bubble, the foam will be destroyed.
Defoaming: from the bubble interface into the bubble, so that a bubble out of the liquid surface.
Second, the type of silicone defoamer
1, water emulsion type defoamer
(Dimethyl silicone oil) as the main body, and silica composite, in the surfactant (emulsifier) under the action of O / W type prepared by the different concentrations of water emulsion defoaming (Suitable for water-based media defoaming) or made of high concentration of silicon paste, with the use of smear or temporary dilution after use.
2, oil system defoamer
With the solvent carrying silicone oil and dispersed into the gun solution. Solvent diffusion, silicone oil or droplets to play defoaming (generally high, low viscosity silicone oil blending) or made of silicone oil / mineral oil dispersion. The petroleum industry requires a large amount of silicone surfactants for demulsifiers.
3, solid powder defoamer
Containing 2% ~ 5% silicone decomposition components and mass fraction of 98% to 50% of the powdery solid carrier.
4, defoaming sticks
Silicone oil, sodium sulfonate and wax.
5, self-emulsifying self-dispersing defoamer
The introduction of a hydrophilic group (polyether-modified silicone oil) in the polysiloxane molecular chain with a silicone surfactant copolymerized with polysiloxane and polyether can significantly improve the dispersibility of the silicone in water, Emulsified, as a class of special defoamers, defoaming above the cloud point, suitable for high temperature and high pressure jet dyeing and other defoaming.
Self-emulsifying type "defoamer heat-resistant, mechanical stability, acid, alkali, under the conditions of defoaming, such as polyester fiber high temperature dyeing, diethanolamine aqueous solution desulfurization system, a variety of oil cutting fluid, bubble.