In industrial production, foam is everywhere: the trough of various processing fluids; Various industrial cleaning pools; In various industrial and agricultural products and preparations; In all production links of petrochemical industry, water treatment and so on.


Foam, to bring various problems to industrial production: in order to prevent foam overflow, the feeding coefficient is forced to reduce 30%~ 50%; Foam overflow leads to waste of raw materials; Foam occupies space, affects the reaction speed, and the production cycle is forced to extend; Foam will affect the quality of products, such as paint, plastic products; The production of foam has an impact on the stability of industrial production, resulting in fluctuations in operation and unstable quality.


For the foam problem, the most direct solution is to use defoamer.


The defoamer shall have the following properties:


1, strong defoaming power, small dosage;


2. The basic nature of the system will not be affected after joining;


3, small surface tension;


4, good balance with the surface;


5. Good diffusivity and permeability;


6. Good heat resistance, acid resistance and alkali resistance;


7, chemical stability, strong oxidation resistance;


8, gas solubility, good permeability;


9, small solubility in foaming solution;


10, high physiological safety.




The development of defoamer is mainly divided into four stages
The first stage of defoamer: mainly composed of various organic compounds, such as: fatty acids, mineral oils, fatty amides, low alcohols and so on. Most of these defoamants are natural substances, which have little pollution to the environment and low price. Due to the weak defoaming performance, it can not meet the production requirements for a large number of foams.


The second stage defoamer: polyether defoamer CnH(2n+1)O(EO)a(PO)bH, polyoxyethylene segment (EO) is a hydrophilic group; The polyoxyepropenyl segment (PO) is an oleophilic group. This defoamer has good anti-foam performance, non-toxic, non-irritating, and has good dispersion. In actual production, the relative molecular weight of polyether and the proportion of EO and PO in polyether chain segments are adjusted to meet the needs of various production fields. At present, polyether defoamer in the market mainly includes linear polyether, ether amine, fatty alcohol polyether, fatty acid polyether and other polyether derivatives.


The third stage defoamer: silicone defoamer, which has better defoamer performance than the first two. Usually, the silicone oil with a larger molecular weight is insoluble in the surfactant solution, and for small molecules, the silicone oil is easily soluble by the surfactant molecule, which changes the composition of the defoamer and weakens the defoamer performance. For the defoamer mixed with silicone oil, it is insoluble in water and mineral oil, so it has strong anti-foam ability and greatly enhances its defoaming effect. Because Si-O and Si-C bonds are relatively stable, they are allowed to be used in systems containing small amounts of acids, bases, and salts. Most of the silicone defoamer commonly used in industrial production is a class of silicone oil secondary processing products made by adding dispersion additives to silicone oil, which belong to liquid mixtures. In terms of appearance and fluidity, the mixture is mainly divided into five categories: silicone paste type, silicone oil type, emulsion type, solution type and solid type.


The fourth stage defoamer: polyether modified silicone oil defoamer, on the basis of the previous generations of defoamer, and strive to integrate the advantages of polyether and silicone, the polyether chain segment is introduced into the silicone oil chain segment, with stronger defoamer and foam suppression performance. Polyether modified silicone oil is a new type of special silicone surfactant, which is formed by addition reaction of polyether containing double bond and low hydrogen silicone oil. It is a kind of silicone non-ionic surfactant with unique properties, which not only retains the properties of silicone oil such as high and low temperature resistance, weather resistance, release property, hydrophobicity and physiological inertia. Polyether has the characteristics of non-irritant, high surface activity and easy dispersion. Polyether modified silicone oil is widely used because of its good heat resistance, shear resistance, acid and alkaline resistance, non-toxic, tasteless and stable storage.


Mechanism of organosilicon defoamer
The ability of silicone to defoamer or suppress bubbles is due to its very low surface tension. Silicone compounds (silicone oil) interfere with the surface tension of the gas-liquid boundary, resulting in a defoaming effect.


The function of defoamer is also defined by three mechanisms: breaking, defoaming and suppressing bubbles.


Bubble breaking: Relative to the foam, from the air side into the bubble, the bubble will be destroyed.


Bubble suppression: from the liquid side into the bubble, the bubble will be destroyed.


Defoaming: invading the bubble from the interface of the bubble, so that the bubble emerges from the liquid surface.


Silicone defoamer type
1, water and milk dosage type defoamer


With polydimethylsiloxane (dimethylsilicone oil) as the main body, and white carbon black complex, under the action of surfactant (emulsifier) to prepare O/W type of various concentrations of water emulsion defoamer (suitable for water-based media defoamer) or into high concentration silicon paste, when the use of smears or temporary dilution after use.






Dimethyl silicone oil structural formula


2, oil system defoamer


Silicone oil is carried by solvent and dispersed into the firing fluid. Solvent diffusion, silicone oil or droplets play a defoaming role (generally high, low viscosity silicone oil blend) or make silicone oil/mineral oil dispersion. The petroleum industry needs a large number of organosilicon surfactants as demulsifiers.


3, solid powder defoamer


The powder solid carrier containing 2%~5% organic silicon defoamer component and 98%~50% mass fraction.


4. Antifoam stick


Preparation of silicone oil, sodium sulfonate and wax.


5, self-emulsifying self-dispersing defoamer


With polysiloxane and polyether copolymerized silicone surfactant, the introduction of hydrophilic group (polyether modified silicone oil) on the polysiloxane molecular chain can significantly improve the dispersion of silicone in water, or self-emulsifying, becoming a special defoamer, defoaming above the cloud point, suitable for high temperature and high pressure jet dyeing and other defoaming.





Polyether modified silicone oil structural formula


"Self-emulsifying type" defoamer heat resistance, mechanical stability, acid and alkali resistance, defoamer under harsh conditions, such as polyester fiber high temperature dyeing, diethanolamine aqueous desulfurization system, various oil cutting fluid, non-freezing fluid and other systems defoamer.