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Some Knowledge about Silicone defoamer

Apr 16, 2019

In industrial production, foam is everywhere: machine tanks of various types of processing fluids; various industrial cleaning tanks; various industrial and agricultural products and preparations; various production links of petrochemicals, water treatment, etc.


Foam, brings various problems to industrial production: in order to prevent foam overflow, the feed coefficient is forced to reduce by 30% to 50%; foam overflow leads to waste of raw materials; foam takes up space, affects reaction speed, production cycle is forced to prolong; foam will affect Product quality, such as coatings, plastic products; the generation of foam, has an impact on the stability of industrial production, resulting in operational fluctuations, unstable quality.


The most straightforward solution to the bubble problem is to use an antifoaming agent.


Defoamers should have the following properties:


1, strong defoaming power, less dosage;


2. After joining, it does not affect the basic nature of the system;


3. The surface tension is small;


4, good balance with the surface;


5. Good diffusion and permeability;


6, heat, acid and alkali resistance;


7. Chemically stable and resistant to oxidation;


8, gas solubility, good permeability;


9. The solubility in the foaming solution is small;


10. High physiological safety.

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In the development of defoamers, it is mainly divided into four stages.


The first stage defoamer: mainly composed of various organic substances, such as: fatty acids, mineral oils, fatty amides, lower alcohols, and the like. Most of these defoamers are natural substances, which are less polluting to the environment and are inexpensive. Due to the weak defoaming performance, the production requirements cannot be met for a large number of foams.


Second stage defoamer: polyether defoamer CnH(2n+1)O(EO)a(PO)bH, polyoxyethylene segment (EO) is hydrophilic; polyoxypropylene based segment ( PO) is a lipophilic group. The antifoaming agent has good antifoaming performance, is non-toxic, non-irritating, and has good dispersibility. In the actual production, the relative molecular weight of the polyether and the ratio of EO and PO in the polyether segment are adjusted to meet the needs of various production fields. Polyether defoamers currently on the market mainly include linear polyethers, ether amines, fatty alcohol polyethers, fatty acid polyoxyethylene ethers, and the like.


The third stage defoamer: silicone defoamer, this type of defoamer is better than the former two defoaming performance. Generally, a silicone oil having a relatively large molecular weight is insoluble in a surfactant solution, and a small molecular silicone oil is easily solubilized by a surfactant molecule, thereby changing the composition of the antifoaming agent and deteriorating the defoaming performance. For the defoamer compounded with silicone oil, it is insoluble in water and insoluble in mineral oil, so it has strong antifoaming ability and greatly enhances its foam breaking effect. Since the Si-O bond and the Si-C bond are relatively stable, they are allowed to be used in a system containing a small amount of an acid, a base or a salt. Most of the silicone defoamers commonly used in industrial production are a class of silicone oil secondary processed products obtained by adding dispersing aids to silicone oil, and those are liquid mixtures. The mixture is mainly classified into five types: silicone paste type, silicone oil type, emulsion type, solution type and solid type from the appearance and fluidity.


The fourth stage defoamer: polyether modified silicone oil defoamer, based on the previous generations of defoamer, strive to integrate the advantages of polyether and silicone, and introduce the polyether segment into the silicone oil segment. Stronger defoaming and antifoaming properties. Polyether modified silicone oil is a new type of special silicone surfactant. It is a unique silicone nonionic surfactant which is formed by the addition reaction of polyether containing double bond and low hydrogen silicone oil. The properties of the silicone oil which are resistant to high and low temperature, weather resistance, mold release, water repellency and physiological inertness are retained, and the polyether is non-irritating, high in surface activity and easy to disperse. Polyether modified silicone oil is widely used because of its good heat resistance, shear resistance, acid and alkali resistance, non-toxicity, tastelessness and storage stability.


Mechanism of action of silicone defoamer


The ability of silicone to defoam or inhibit foam is due to its low surface tension. The organosilicon compound (silicone oil) interferes with the surface tension of the gas-liquid boundary, resulting in a defoaming effect.


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


Breaking: Relative to the foam, entering the bubble from the air side, destroying the bubble.


Anti-foaming: entering the bubble from the liquid side, destroying the bubble.


Defoaming: Invade the bubble from the interface of the bubble, and let the bubble come together to float out of the liquid surface.


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Silicone defoamer type


1. Water emulsion type defoamer


Polydimethylsiloxane (dimethicone) as the main component, and white carbon black composite, prepared by O surfactant under the action of surfactant (emulsifier), various concentrations of water emulsion defoaming (suitable for defoaming of aqueous media) or high-concentration silicone paste, used in smearing or temporary dilution.


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2. Oil system defoamer


The silicone oil is carried by means of a solvent and dispersed in the gun fluid. The solvent diffuses, the silicone oil or droplets act as a defoaming (generally high and low viscosity silicone oil blending) or as a silicone oil/mineral oil dispersion. The petroleum industry requires a large amount of silicone surfactant as a demulsifier.


3, solid powder defoamer


A powdery solid carrier containing 2% to 5% of a silicone defoaming component and a mass fraction of 98% to 50%.


4, defoaming rod


A preparation of silicone oil, sodium sulfonate and wax.


5, self-emulsifying self-dispersing defoamer


The silicone surfactant copolymerized with polysiloxane and polyether introduces a hydrophilic group (polyether modified silicone oil) on the molecular chain of the polysiloxane, which can significantly improve the dispersibility of the silicone in water, or Emulsifying, it becomes a special type of defoaming agent, defoaming above the cloud point, suitable for defoaming such as high temperature and high pressure jet dyeing.


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Polyether modified silicone oil structure


"Self-emulsified" defoamer heat resistance, mechanical stability, acid and alkali resistance, defoaming under severe conditions, such as polyester fiber high temperature dyeing, diethanolamine aqueous solution desulfurization system, various oil cutting fluids, antifreeze system, etc. Defoaming.


RH-9300-Professional-Antifoam-Agriculture-Adjuvant-Silicone


Contact:Sharon Song(Sales manager)

Zhejiang Runhe Organosilicone New Material Co.,Ltd(Factory)

Zhejiang Runhe Chemical New Material Co.,Ltd(Exporter)

Tel:+86-571-85092338
Mob:+86-13805735673
Fax:+86-571-87246635
E-mail:sharon@chinarunhe.com

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