Generally speaking, foam is a coarse dispersion of gas in liquid, which belongs to gas-liquid heterogeneous system. A gas-liquid dispersion with a bulk density close to a gas and not close to a liquid. Gas-liquid dispersions are divided into "bubble dispersions" with more liquid and less gas and "foams" with less liquid and more gas.
What is a bubble? Foam can be defined as a stable gas in a liquid medium. Foam is a dispersion system of gas in liquid. Gas becomes many bubbles separated by continuous phase liquid. Gas is dispersed phase and liquid is dispersion medium.
Foam is a thermodynamically unstable system and cannot be stable. The thermodynamic instability of foams is due to the large decrease in the total surface area of the system's liquid after breaking the bubble, which reduces the system energy (free energy).
The Marangoni effect prevents drainage of the bubble film and restores the bubble film thickness. The bubbles release gas to the air, and the bubbles burst. The factors that affect this process are the apparent viscosity and density of the bubbles affect the permeation and diffusion of the defoamer particles on the surface film of the bubbles.
Long-term defoaming is also called antifoaming. The length of antifoaming time is the main sign of the quality of antifoaming agent. In most cases, we use the defoaming agent instead of the initial defoaming property.
Defoaming and antifoam are relative. Products with good defoaming performance will have relatively poor antifoam performance. In practical applications, it depends on the specific situation.
Defoamers, defoamers, and defoamers are collectively referred to as defoamers.
In contrast to foam (foam polymer), it penetrates into the bubble from the air side and destroys the bubble.
Invasion into the bubble from the liquid side will destroy the bubble together, making it difficult to produce the bubble.
Intrude into the bubble from the interface of the bubble, so that the bubbles are united to the surface.
Defoaming agents are mostly liquid compound products, which are mainly divided into three categories: mineral oils, silicones, and polyethers. Mineral oil defoamers usually consist of a carrier, an active agent, and the like. The carrier is a substance with low surface tension, and its role is to carry and dilute. Common carriers are water, fatty alcohols, etc .; active agents are used to suppress and eliminate foam. Commonly used are waxes, aliphatic amides, fats, etc. Silicone-based defoamers generally include polydimethylsiloxane and the like. Organosilicon defoamers have poor solubility, have fast defoaming speed and good foam suppression at normal temperature, but delamination occurs at high temperature, slow defoaming speed, and poor foam suppression. Polyether-based defoamers include polyoxypropylene oxide glyceryl ether and the like. Polyether defoamers have the characteristics of long foam suppression time, good effect, fast defoaming speed and good thermal stability. For example, defoamers are used in the production of fruit and vegetable beverages, soy products, sucrose, etc.  .
4 physical properties
1. Fast defoaming and good foam suppression performance.
2. Does not affect the basic properties of the foaming system.
3. Good diffusion and permeability.
4. Chemical stability.
5, no physiological activity, no corrosion, no toxicity, no adverse side effects, non-combustible, non-explosive, high safety.
Mainly applicable to PCB process; chemical industry; electroplating; printing and dyeing; paper making; medicine; water-based ink; ceramic cutting; cleaning of steel plates; processing of aluminum industry; Foaming and foam suppression.
1. Foam collapse due to reduced local surface tension of the foam
The origin of this mechanism is that alcohol or vegetable oil is sprinkled on the foam. When it is dissolved in the foam, it will significantly reduce the surface tension there. Because these substances are generally less soluble in water, the surface tension is reduced locally in the foam, while the surface tension around the foam has hardly changed. The part with reduced surface tension is strongly pulled and extended around, and then ruptures.
2. Defoaming agent can destroy the elasticity of the membrane and cause the bubble to burst
When added to the foam system, the defoamer will diffuse to the air-liquid interface, making it difficult for surfactants with a foam-stabilizing effect to recover the elasticity of the membrane.
3． Defoaming agent can promote the drainage of liquid film, which will cause bubbles to burst
The foam drainage rate can reflect the stability of the foam. Adding a substance that accelerates foam drainage can also play a defoaming role.
4． Addition of hydrophobic solid particles can cause bubbles to burst
The hydrophobic solid particles on the surface of the bubble will attract the hydrophobic end of the surfactant, make the hydrophobic particles hydrophilic and enter the water phase, thereby playing a role of defoaming.
5． Solubilizing surfactants can cause bubbles to burst
Certain low-molecular substances that can be thoroughly mixed with the solution can solubilize the surfactant of the bubble and reduce its effective concentration. Low-molecular substances such as alcohols such as octanol, ethanol, and propanol can not only reduce the surfactant concentration in the surface layer, but also dissolve into the surfactant adsorption layer, reducing the tightness between the surfactant molecules. Degree, thereby reducing the stability of the foam.
6. The electrolyte disintegrates the electric double layer of the surfactant and causes the bubble to burst
For the interaction of the electric double layer of the surfactant by means of foam to produce a stable foaming liquid, the ordinary electric electrolyte can be used to disintegrate the electric double layer of the surfactant for defoaming.
(1) Active ingredients
Role: Break bubbles, defoam, reduce surface tension:
Representatives: silicone oil, polyether, alcohol, mineral oil, vegetable oil, etc. 
Role: Disperse the active ingredients into small particles, which is easy to disperse in water, and has better defoaming and antifoaming effects.
Representatives: Non (octyl) phenol polyoxyethylene ether, soap salts, op series, etc., Tween series, Span series, etc.
Function: It is helpful for the combination of the carrier and the foaming system, and it is easy to disperse into the foaming system. The combination of the two has low surface tension, helps to suppress foaming, and can reduce costs.
Representatives: solvents other than water, such as aliphatic hydrocarbons, aromatic hydrocarbons, oxygen-containing solvents, etc.
(4) Emulsifying additives
Role: Make emulsification better.
Representatives: * dispersant: hydrophobic silica, etc .; * tackifier: CMC, polyvinyl ether, etc.
1) Antifoaming agent; Antifoaming additive; Defoaming agent; Antifoaming agent; Defoaming agent
2) Antifoaming agent; antifoaming agent
3) Defoaming agent; Defoaming agent; Defoamer; Air release agent
4) Antifoaming agent; antifoaming agent; foam breaker; antifoam agent
5) food defoaming agents; deforming agents for food
6) Defoaming agent of pulp
7) food antifoaming agents
8) Silicone defoamer; silicone defoamer
9) Defoamer for drilling fluid;
1. Natural oils (ie soybean oil, corn oil, etc.)
Advantages: easy source, low price, simple to use;
Disadvantages: such as poor storage, easy to deteriorate, increase the acid value.
2. Polyether defoamer
There are many types, including the following:
a. GP type defoamer
It is made from glycerol as the starter, and it is produced by the addition polymerization of propylene oxide or a mixture of ethylene oxide and propylene oxide.
GP type defoamer has poor hydrophilicity and low solubility in foaming medium, so it should be used in thin fermentation broth. Its anti-foaming ability is superior to its anti-foaming ability, and it is suitable to be added to the basic medium to inhibit the foaming of the entire fermentation process.
b.GPE type antifoaming agent
Polyethylene glycol is added to the end of the polypropylene glycol chain link of the GP-type defoamer to form a polyoxyethylene oxypropylene glycerin with a hydrophilic group at the chain end, also called. According to the ethylene oxide addition amount of 10%, 20%, ... 50% are called GPE10, GPE20, ... GPE50.
GPE-type defoamer has good hydrophilicity, easy to spread in foaming medium, strong defoaming ability, but also has large solubility and short duration of defoaming activity, so it has better effect in viscous fermentation broth.
c. GPES-type defoamer: There is a new type of polyether-based defoamer. GPE-type defoamer chain ends are blocked with hydrophobic stearates to form hydrophobic chains at both ends, with hydrophilic spacers in between. Chain block copolymer. Molecules of this structure are prone to gather horizontally at the gas-liquid interface, so they have strong surface activity and high defoaming efficiency.
3.High carbon alcohol
High-carbon alcohol is a linear molecule with strong hydrophobicity and weak hydrophilicity, and is an effective defoamer in water system. In the early 1970s, scholars in the former Soviet Union tested in an aqueous solution of anionic, cationic, and nonionic surfactants, and proposed that the defoaming effect of alcohols is related to its solubility and diffusion degree in the foaming solution. C7 ~ C9 alcohols are effective defoamers.
C12 ~ C22 high-carbon alcohols are formulated into water emulsions with a particle size of 4 ~ 9μm and a content of 20 ~ 50% by means of appropriate emulsifiers, which are defoamers for water systems.
Some esters, such as phenylethanol oleate and lauryl phenylacetate, have defoaming effects in penicillin fermentation, and the latter can also be used as a precursor.
Tributyl phosphate (CAS: 126-73-8), as an ancient defoamer, is still widely used in industry because of its extremely low surface tension (27.79 25 ° C) and extremely low water solubility (0.61 25 ℃, the solvent is soluble in water), the defoaming effect is significant, but because of its irritation and certain toxicity, it is mostly used in other industries that do not come into contact with food / cosmetics.
Commonly used is polydimethylsiloxane, also known as dimethyl silicone oil. It has low surface energy, low surface tension, low solubility and high activity in water and general oils. Its main chain is a silicon-oxygen bond, which is a non-polar molecule. It is incompatible with polar solvents and water, and has low affinity with general oils. It has low volatility and chemical inertness, is relatively stable, and has low toxicity. Pure polydimethylsiloxane is difficult to be used as a defoamer without dispersion treatment. It may be due to its high interfacial tension with water, low spreading coefficient, and difficulty in dispersing on the foaming medium. Therefore, the compound formed by mixing the silicone oil into the SiO2 aerosol, that is, the SiO2 aerosol after the hydrophobic treatment is mixed into the dimethyl silicone oil, and can be prepared after a certain temperature and a certain time treatment.
Organosilicon defoamers are made by mechanically emulsifying silicone grease, emulsifier, waterproofing agent, thickening agent, etc. with an appropriate amount of water. It is characterized by low surface tension, high surface activity, strong defoaming power, low dosage and low cost. It is immiscible with water and most organic substances, and can defoam to most bubble media. It has good thermal stability and can be used in a wide temperature range of 5 ℃ -150 ℃; its chemical stability is good and it is difficult to react with other substances. As long as it is properly configured, it can be used in acid, alkali and salt solutions It does not damage the quality of the product; it also has a physiologically inert LD250g / Kg rat, which is usually used in the food and pharmaceutical industries. It has antifoam and bubble breaking functions for all bubble systems, and belongs to the broad-spectrum defoamer category. It is widely used for defoaming in the production process of detergents, papermaking, pulp, sugar making, electroplating, fertilizers, additives, wastewater treatment and other production processes. In the petroleum industry, it is widely used in the desulfurization of natural gas to accelerate the separation of oil and gas; it is also used to control or suppress air bubbles in devices such as drying of ethylene glycol, extraction of aromatic hydrocarbons, processing of asphalt, dewaxing of lubricants . In the textile industry, it is used for defoaming in processes such as dyeing, scouring, sizing; in the chemical industry, it is used for defoaming in processes such as synthetic resins, latexes, coatings, and inks; in the food industry it is used For defoaming in various concentration, fermentation and distillation processes. Silicone grease can be applied to the wall of the pot, at the exit or on a wire mesh to defoam. The silicone grease is formulated into a solution and can be used for defoaming in oil phase systems. Silicone grease and low viscosity silicone oil are formulated into an aqueous emulsion, which can be used for defoaming in various aqueous systems. In medicine, it is usually used to remove flatulence of organs or stomach organs before surgery, X-ray and gastroscopy.
Defoaming agents can be roughly divided into two categories: one can eliminate the bubbles that have been generated, such as ethanol, and the other can inhibit the formation of bubbles, such as emulsified silicone oil. The defoamers approved for use in China are emulsified silicone oil, high-carbon alcohol fatty acid ester complex, polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxyethylene polyoxypropylene alcohol amine ether, polyoxypropylene glyceryl ether, and polyoxypropylene.
5.Polyether modified silicon
Combining the advantages of both polyether and silicone defoamer, it is non-toxic and harmless, harmless to bacteria, and added in very small amounts. It is a cost-effective product.
Polyether-modified silicone is a polyether-siloxane copolymer (abbreviated as a silicone ether copolymer) made from polyether segments in siloxane molecules. Polysiloxane defoamer has the characteristics of rapid defoaming, long foam suppression time and safety and non-toxicity, but it is difficult to dissolve in water, high temperature resistance, poor alkali resistance, and polyether defoamer has good water solubility. High temperature resistance, strong alkali resistance, but its defoaming speed and foam suppression time are not ideal. The polyether chain is introduced into the polysiloxane chain by condensation technology to make it have the advantages of second-class defoamer. , Become a kind of defoamer with excellent performance and wide application prospects. In the molecule of the silicone ether copolymer, the siloxane segment is a lipophilic group, and the polyether segment is a hydrophilic group. The polyethylene oxide chain in the polyether segment provides energy saving and hydrophilicity, while the polypropylene oxide chain provides hydrophobicity and permeability, and has a strong effect on reducing surface tension. The group of polyether end group also has a strong influence on the properties of the silicone ether copolymer. Common end groups are hydroxyl, alkoxy and so on. Adjusting the relative molecular mass of the siloxane segment in the copolymer can make the copolymer highlight or weaken the properties of the silicone. Similarly, changing the relative molecular mass of the polyether segment will increase or decrease the proportion of silicone in the molecule, which will also affect the performance of the copolymer. Polyether modified silicone defoamer is easy to emulsify in water, also known as "self-emulsifying defoamer". When its cloud point temperature is above, it will lose its solubility in water and mechanical stability, and it is resistant to acid and alkali. And inorganic salts, which can be used for defoaming under severe conditions, and are widely used for defoaming in high temperature dyeing and fermentation processes of polyester fabrics. In addition, it can also be used for defoaming of diethanolamine desulfurization system and defoaming of various oil agents, cutting fluids, antifreezes, water-based inks, etc. It is also suitable for the printing industry to wash off uncured resin Defoaming is a very representative, excellent performance and versatile silicone defoamer. Polysiloxane defoamer is usually composed of two main components: polydimethylsiloxane and silicon dioxide. The defoamer based on polydimethylsiloxane is one of the defoaming systems. An ideal type of defoamer is that it is insoluble in water and difficult to emulsify. Polydimethylsiloxane has lower surface properties than carbon chain hydrocarbons, and therefore has lower surface tension than surfactants commonly used in the textile industry. Pure polydimethylsiloxane has poor foam suppression and is slow. The defoaming effect needs to be strengthened by silica particles. The silica particles are carried by the silicone oil to the air-water interface of the foam and enter the bubble film due to its hydrophobicity. The contact angle with the foamed droplets of the surfactant is greater than 90 °, thereby forcing the foamed liquid to drain away from the surface of the solid hydrophobic particles, causing the foam to drain quickly and cause rupture. In this way, due to the synergistic effect, the two compositions produce a good defoaming effect.
6.New self-emulsifying defoamer
Contains specially modified polysiloxane. With excellent heat resistance, acid and alkali resistance and chemical stability, it can be widely used for foam elimination and suppression in various harsh systems over a wide temperature range.
7, polysiloxane defoamer
Polysiloxane defoamer is usually composed of two main components: polydimethylsiloxane and silicon dioxide. The defoamer based on polydimethylsiloxane is one of the defoaming systems. An ideal type of defoamer is that it is insoluble in water and difficult to emulsify. Polydimethylsiloxane has lower surface properties than carbon chain hydrocarbons, and therefore has lower surface tension than surfactants commonly used in the textile industry. Pure polydimethylsiloxane has poor foam suppression and is slow. The defoaming effect needs to be strengthened by silica particles. The silica particles are carried by the silicone oil to the air-water interface of the foam and enter the bubble film due to its hydrophobicity. The contact angle with the foaming droplets of the surfactant is greater than 90 °, thereby forcing the foaming liquid to be discharged from the surface of the solid hydrophobic particles, causing the local foam to drain rapidly and causing rupture. In this way, due to the synergy, the two components The substance produces a good defoaming effect. Polysiloxane defoamers have been widely used in many fields due to their excellent defoaming performance and other advantages, especially in the textile dyeing and finishing process. Development has been particularly rapid. Research has found that polydimethylsiloxane Copolymer with polyethylene as the substrate is a silicone glycol defoamer. Due to its special solubility, it has an ideal defoaming effect in jet dyeing and other textile processing.
1. Alkali-resistant defoamer
Under the conditions of high temperature and strong alkali, it can quickly defoam and suppress foam lastingly. Good stability, low dosage, high efficiency, no oil bleaching; widely used in papermaking and cooking black liquor treatment, strong alkali-type refining agent in the textile printing and dyeing industry, cleaning agents under strong alkali conditions, and other high-temperature strong alkali aqueous phase systems Defoaming.
2.Acid resistant defoamer
It is composed of fatty acid esters and fatty amides, and is widely used in wet-process phosphoric acid, titanium dioxide production, boric acid production, and other strong acid systems.
3.High viscosity foam defoamer
This product is a composite defoamer developed for the characteristics of papermaking pulping black liquor, chemical beneficiation, and special chemical reaction foams. It has the characteristics of high viscosity, fine foam, and difficult elimination.
4. Coating defoamer
Contains a variety of defoaming ingredients, so it has a wide range of applications. It is particularly suitable for eliminating foam in styrene-acrylic latex, ethylene-propylene latex, pure acrylic latex, vinyl acetate latex and other systems.
5. Papermaking defoamer
Can effectively control pulp, foam overflow and improve papermaking quality. It is widely used in defoaming of papermaking and papermaking systems, and can also be used in defoaming of papermaking wastewater treatment, antifreeze and distillation systems.
6. Cement mortar defoamer
It can effectively control the generation of foam in the cement mortar system, making the concrete components more dense and bright.
7. Oilfield industrial defoamer
It can effectively control the generation of internal foam in the oilfield industrial process and improve the efficiency of oil production.
8.Defoaming agent for cleaning
Can effectively control the foaming of cleaning agents.
9, cationic system defoamer
It can effectively control the production of foam containing cationic systems, and is widely used in papermaking cationic rosin gum, cationic cleaning agents, and can also be used in papermaking wastewater treatment, antifreeze, and defoaming of distillation systems.
It overcomes the shortcomings of ordinary silicone defoamers, such as poor temperature resistance and short foam suppression time; the foam accumulated in the fermenter can be eliminated as quickly as polyether, and the product has time incomparable with polyether. The advantages.
11. Water treatment defoamer
Silicone defoamer has a strong defoaming and antifoaming function for aqueous foaming systems. It has a small amount of addition and low cost. It is an ideal defoamer for aqueous systems.
12.High temperature defoamer
High temperature and acid and alkali resistance, high shear and a wide range of PH value (2-14), high temperature (300 ° C) stability, can be used for defoaming in water-based and oily systems, higher temperature use The higher the efficiency, the better the effect. It can be used for defoaming and foam suppression in high temperature and strong acid-base media under extreme conditions such as bottle washing additives and oil field drilling.
13. Bottle washing additive defoamer
High temperature resistance and strong alkali resistance, can adapt to the high temperature and strong alkali use conditions of bottle washing additives.
9 common sense
Foam is a universal natural phenomenon that may not be unfamiliar to all of us. If you cook rice, make dumplings, and cook noodles in your daily life, you can overflow the pot due to bubbles; if you play as a child, you will blow bubbles and blow out colorful bubbles, floating in the sky; The foam overflowing from beer; the spectacular foam formed by hitting the shores and hitting the reefs on the coast; and the common soap and detergent powder water foam when people wash clothes; the shower gel and shampoo The bubble is even more familiar.
For example, firefighters cleverly used foam to extinguish some fires. The dim sum chef used the foam phenomenon to make delicious breads, cakes, and muffins. How hot a thirst is to drink a bottle of soda or beer on a hot summer day. It is the role of foam. Also such as foam flotation, foam metallurgy, foam printing and dyeing, foam printing, foam plastic ...
1. The production capacity is greatly restricted: such as various fermentation tanks, reaction tanks, cooking tanks and other equipment in various biological fermentation (beer production, alcohol production, production of major antibiotics in medicine, etc.), in order to prevent the occurrence of foam and prevent For overflow losses, the input coefficient must be greatly reduced, and sometimes it cannot reach 30%.
2. Cause waste of raw materials and products: Due to the foam, it can cause useful or valuable raw materials to be lost due to overflow, and the resulting waste is self-evident. For example, the filling process of paper mills, sugar mills, and weaving processes of textile mills often cause overflow due to foam.
3. Extending the reaction cycle: Because gas and liquid are included in the chemical reaction products, foam will cause gas retention, prolong the reaction cycle, and consume more power than necessary. And if the wine is fermented due to the presence of foam, the reaction will become over-flavored ...
4. Affecting product quality: During the dyeing, printing and water-based coating process in the textile industry, the retention of air bubbles causes spots and defects on the finished fabric; in addition to the foam of the pulp slurry causing harm to environmental hygiene and worker health, the finished paper is also Many holes will appear, resulting in a serious degradation of product quality.
5. It is not conducive to accurate measurement: In the industrial process, due to the presence of foam, it interferes with the accurate measurement of the level meter, causing measurement errors. Due to the presence of foam in the liquid, the density of the liquid fluctuates greatly, which can often cause the reaction kettle to absorb The liquid level of the distillation tower is too high, which results in unbalanced operation and even accidents.
6. Pollution of the environment and one of the causes of accidents: due to the overflow of bubbles, it will inevitably pollute the production environment and its surroundings, and some even cause major accidents. For example, an oil refinery in the United States caused a major fire and suffered heavy losses due to the overflow of residue foam, which not only caused waste, but also caused serious loss of human life and property.
In addition, there are applications of new technologies such as high-temperature spray dyeing and overflow dyeing, which cannot be achieved without solving the problem of foam. Another example is the washing machine that is very popular now. If it does not solve the problem of non-foaming and low foaming of washing powder and detergent, then the washing machine will not be so popular. The above is far from the full damage of the bubble, but it is enough to see its severity.
In short, the existence of a bubble affects all sectors and aspects of the national economy. If it cannot be resolved well, it can be said without exaggeration that the "bubble" will become our obstacle and a "bottleneck" for certain processes. It is gratifying that we have a good strategy for eliminating bubbles.
Test method A (jet test): This method is a qualitative evaluation of the defoaming and antifoaming effects
Air bubbles are produced by spraying a special foaming solution with air. The "defoaming efficiency" of a material is evaluated by testing the foam height after a specific spray time and the foam elimination time.
Test method B: Foam suppression performance test (wrist shaking method) This method is a relative method for testing defoaming performance
A quantified sample is added to the surfactant solution. Shake the mixture and record the time (in seconds) required for foam elimination.
Test method C (circulating pump test): This method is used to test the quantitative evaluation of foam suppression performance under the dynamic state of agitation, emulsification and shear. When the solution is circulated in a closed loop, it is necessary to determine the foam height Time to evaluate defoaming efficiency.
Test method D: Use a densitometer to measure the density of the bubble mixture. The difference between the density value and the density of the bubble solution before stirring represents the amount of foam. The larger the density difference, the higher the gas content in the bubble mixture. The larger the foaming power, the foaming rate is represented by the percentage of the density difference in the density of the foaming liquid before stirring; the foaming amount of the pulp after adding the defoaming agent is tested and the difference between the foaming amount of the blank pulp and the foaming amount of the blank is the foam suppression amount. The foaming amount of the blank pulp is compared to obtain the foam suppression rate of the defoaming agent.
Some practical tests for defoamers 
The effectiveness of a defoamer must first be determined in the laboratory. It is not advisable to transfer laboratory test results to production scale applications without further testing. The test methods we developed in our work, combining the conditions of the coating manufacturing and construction process, make it possible to evaluate the performance of the defoamer.
According to different construction conditions (such as brushing, spraying, dipping, printing, etc.), different testing methods can be selected.
1. Stirring test For our users, the simple test method is stirring test. Under certain conditions, a turbine blade is used to infiltrate the air into the coating system to be tested with a defoamer.
After stirring, immediately pour the material into a measuring bottle with a graticule scale, and then weigh it. Based on the comparison of the weight difference, determine the amount of air infiltration in the system, and infer the effect of the defoamer. This test also shows how much air is contained in the system in the form of spherical bubbles. Another test method is to detect the number of macrobubbles. Under certain conditions, air is infiltrated into the system, and the height of the same weight material is measured by a graduated cylinder to evaluate the effect of the defoamer. This method can guide us to choose the capacity ratio of the mixing container in actual work. Many defoamers also cause surface defects of the paint film, such as shrinkage, etc. It is the same as the foam problem, which is unwilling to be seen by all our ink producers. Experiment and test.
2. Flow coating test The flow coating test can be used to evaluate the compatibility and defoaming effect of the defoamer with the coating system being tested. The stirred test sample was immediately poured onto a piece of polyester film.
The polyester film is placed on a frame which is inclined at an angle of 25 degrees in advance. Carefully observe the flow-coating test piece to see if there are air bubbles on it. This method can also evaluate the defoaming effect of the antifoaming agent by observing the dry film. In some cases, the amount of defoamer screened by the stirring test and flow coating test is extremely large, and those substrates that are not very smooth and that contain air are not enough to explain the problem and give evaluation. When deciding on the best amount of defoamer, take full account of the end use of the product.
3. Roller coating test The roller coating test method is very close to the actual application conditions of the coating, so that the role of different defoamers can be distinguished. You can even test the amount of addition.
When doing the roller coating test, use a porous sponge as a pad roller and apply 40 grams of paint to the non-adhesive substrate. It can be a special test card or other standardized test cardboard. The total coating area is 500 cm2. Before each test, the rollers should be wet with an equal amount of water to ensure the reproducibility of each test. The wet film coverage is about 300 g / m2. After the coating film was dried, the experimental cardboard was compared to evaluate the surface defects of the test plate. If in a standard light source, the test panel is backlit checked and the bubbles appearing as light spots are carefully observed, it is easier to distinguish the advantages and disadvantages of the defoamer. The above-mentioned agitation test, flow coating test and roll coating test all help to test the effect and performance of the defoaming agent, so as to determine the best type and amount of defoaming agent suitable for the product in order to meet Requirements for defoamers due to comprehensive factors such as printing or construction conditions.
12 organic silicon
Thoroughly mix the emulsion before use or sampling.
The oil-in-water emulsion can be diluted arbitrarily, but at the same time the stability of the emulsion will also decrease sharply, such as delamination.
When diluting, add water to the defoamer and stir slowly.
Because the emulsion is stable at the original concentration, the diluted emulsion must be used up in a short time.
The emulsion is sensitive to frost and temperatures above 40 ° C and is susceptible to damage.
Prevent frost! Frozen lotions can be defrosted carefully, but must be tested before further use.
Prolonged strong shaking or shearing (such as using a mechanical pump, homogenizer, etc.) or stirring will damage the stability of the emulsion.
Increasing the viscosity of the emulsion or adding a thickener can improve the stability of the emulsion.
Characteristics and uses
Silicone defoaming agent is made of silicone grease, emulsifier, waterproofing agent, thickening agent, etc. with appropriate amount of water and mechanically emulsified. It is characterized by low surface tension, high surface activity, strong defoaming power, low dosage and low cost. It is immiscible with water and most organic substances, and can defoam to most bubble media. It has good thermal stability and can be used in a wide temperature range of -5 ° C to -150 ° C. It has good chemical stability and is difficult to react with other substances. As long as it is properly configured, it can be used in acid, alkali and salt solutions It is used in non-destructive products; it is also physiologically inert and is commonly used in the food and pharmaceutical industries. It has antifoam and bubble breaking functions for all bubble systems, and belongs to the broad-spectrum defoamer category. It is widely used for defoaming in the production process of detergents, papermaking, pulp, sugar making, electroplating, fertilizers, additives, wastewater treatment and other production processes.
The selection of defoamers should meet the following points:
1.Insoluble or hardly soluble in foaming liquid
To break the foam, the defoamer should be concentrated and concentrated on the foam film. In the case of a defoamer, it should be concentrated and concentrated in an instant, and in the case of antifoam, it should always be kept in this state. Therefore, the defoaming agent is in a supersaturated state in the foaming liquid, and it is easy to reach the supersaturated state only if it is insoluble or hardly soluble. Insoluble or hardly soluble, it is easy to aggregate at the gas-liquid interface, it is easy to concentrate on the bubble film, and it can work at a lower concentration. For defoamers used in water systems, the molecules of active ingredients must be strongly hydrophobic, weakly hydrophilic, and have an HLB value in the range of 1.5-3.
2. The surface tension is lower than the foaming liquid.
Only when the intermolecular force of the defoamer is small and the surface tension is lower than that of the foaming liquid, can the antifoam particles be immersed and expanded on the bubble film. It is worth noting that the surface tension of the foaming solution is not the surface tension of the solution, but the surface tension of the foaming aid solution.
3. Have a certain degree of affinity with the foaming liquid.
Because the defoaming process is actually a competition between the speed of foam collapse and the rate of foam formation, the defoamer must be able to disperse quickly in the foaming liquid in order to quickly function in a wider range of the foaming liquid. To make the defoamer diffuse faster, the active ingredients of the defoamer must have a certain degree of affinity with the foaming liquid. The defoamer's active ingredient is too close to the foaming liquid and will dissolve; it is too sparse and difficult to disperse. Effectiveness is good only if it's appropriate.
4. No chemical reaction with the foaming liquid.
The antifoaming agent reacts with the foaming liquid. On the one hand, the antifoaming agent will lose its effect, and on the other hand, it may produce harmful substances and affect the growth of microorganisms.
5. Low volatility and long action time.
The first thing to determine is the system that requires the use of a defoamer, whether it is an aqueous system or an oily system. Such as the fermentation industry, it is necessary to use oily defoamers, such as polyether modified silicon or polyether. Waterborne coatings industry must use water-based defoamer, silicone defoamer. Choose a defoamer, compare the added amount, and at the reference price, you can get a suitable and economical defoamer product.
A) Defoaming agent formula-1
1.Emulsion type defoamer
[Recipe] Mass parts
C4-8 alcohol amine 15.5 hydrocarbonized oil 45 C10-18 fatty acid 27.5 co-defoaming agent 7 dispersant 4.7 water amount
(1) Mix hydrocarbonated oil and C4-8 alcohol amine with defoamer and dispersant. Esterification at 70-150 ° C for 30-150min;
(2) The esterified product (1) is mixed with a defoaming aid and a dispersant, and water is added at 20-80 ° C for emulsification for 1-4 hours to obtain a finished product.
[Use] This product can eliminate foam, can be used in places where silicone is not suitable, widely used in papermaking, cleaning, printing and dyeing, fermentation and other industries, especially in the rubber and plastic industry in the polymerization, condensation, deaeration process of defoaming, Suppressive foam.
[Characteristics] This product has simple preparation method, mild reaction conditions, and easy operation; fast defoaming speed and strong antifoaming ability, corresponding to various foaming agents used in rubber and plastic systems, such as expanded powder, dodecylbenzenesulfonate Sodium, rosin soap, naphthalenesulfonic acid formaldehyde condensate, etc. all have good defoaming effects; it has no adverse effects on the rubber-plastic polymerization system and does not affect the performance of the final rubber and resin products; no by-products and three wastes are generated during the reaction Does not pollute the environment.
2. Silicone defoamer
[Recipe] Mass parts
Methylsiloxane oil 10 Sodium tripolyphosphate 10 Common salt 70 Mannitol 5 Silicon dioxide 2
(1) Mix methyl siloxane oil and silica at room temperature;
(2) Mix the pulverized sodium tripolyphosphate, mannitol, common salt, etc. and mix well with the mixture (1) to obtain a white powdery finished product.
[Use] This product is used to eliminate foam, and is widely used in the production of antibiotics, monosodium glutamate fermentation, soy products, molasses cooking, printing and dyeing, pulp and paper, petrochemicals, paints and detergents.
[Characteristics] This product has a wide range of applications and good defoaming effect; the finished product is a solid powder with good stability, which is convenient for transportation and storage; non-toxic, no side effects, safe and convenient to use.
3. Compound defoamer
[Recipe] Mass parts
Glyceryl monostearate 60 rice bran oil 4 polyether compounds 6 light calcium carbonate 30
(1) Put glyceryl monostearate into a special reaction kettle and heat it to melt;
(2) After melting, raise the temperature while stirring, and add rice bran oil and polyether compounds at 100-150 ° C for compounding;
(3) In the case of high-speed stirring, add light calcium carbonate, and after uniform dispersion, stop stirring, maintain a certain temperature in the kettle, discharge and make tablets;
(4) Put the flakes into a granulator and granulate according to the specified mesh to obtain the finished product.
[Use] This product can be used in the processing of soybean products, dairy products and beverage industries.
[Characteristics] This product has stable and reliable performance, good comprehensive defoaming effect, pure whiteness and no moisture absorption and agglomeration; good water holding capacity, when the consumption of defoamer is 0.3% of dry soybeans, it can increase the yield of soybean products More than 7%; clean and hygienic, easy to use, can improve the quality of soybean products after use.
4. Defoaming agent
[Recipe] Mass parts
Polyoxypropyl polyoxyethyl glyceryl ether 57.1 C10-18 fatty acids 12.5 Co-defoamer 29.4 Dispersant 0.7
(1) Put polyoxypropyl glyceryl ether or polyoxypropyl polyoxyethyl glyceryl ether and C10-18 fatty acid into the reactor, and stir under normal pressure. The temperature is controlled at 90-150 ° C and the time is controlled at 20-90min, complete the esterification reaction;
(2) Reduce the temperature of the esterification reaction product (1) to about 50 ° C, add co-defoaming agent and dispersant, and stir at 40-50 ° C for 30-60min to obtain pH value 5-7 and density 0.8 -1 colorless to yellow liquid product.
[Use] This product is a defoamer used in aqueous media.
[Characteristics] The product has excellent performance, fast defoaming speed, strong antifoaming ability, and little. The method is simple, the product yield is high, no by-products and three wastes are generated, which is beneficial to environmental protection.
[Recipe] Mass parts
Stearic acid 0.5 Polyoxypropyl polyoxyethyl glyceryl ether 99 Dimethicone 0.5
[Manufacturing method] Stearic acid, polyoxypropyl polyoxyethyl glyceryl ether and / or polyoxypropyl glyceryl ether are placed in a container, and the temperature of the liquid phase when heated under stirring conditions exceeds 70 ° C to stearin The acid is melted. After all the stearic acid is melted, add dimethyl silicone oil and stir for 20-30 minutes to obtain a semi-transparent liquid finished product.
[Use] This product is a foam inhibitor for oil-water media, and is widely used in food, medicine, and other industries.
[Characteristics] This product has excellent performance, large surface activity, small surface tension, large contact angle with water, strong defoaming ability, and long foam suppression time; high chemical stability, temperature resistance, oxidation resistance, non-volatile, and easy Chemical reaction occurs in the foaming medium; it has no toxic and side effects and is not harmful to human health; it is safe and convenient to use and has a small amount.
6.Defoaming agent for soy products
[Recipe] Mass parts
Rice bran oil 82 Soy phospholipid 5 Sorbitan fatty acid ester 6 Solid powder 5 Silicone oil 1.8
[Manufacturing method] The above materials can be heated and stirred to obtain a finished product.
[Use] This product can be used to eliminate or suppress the foam produced in the processing of soybean products, and can also be used in other (P199) product processing industry, pharmaceutical manufacturing, printing and dyeing, papermaking, chemical industry and other aspects.
[Characteristics] The product has high defoaming efficiency and good effect. It has excellent defoaming effect on raw pulp and cooked pulp in the processing of soybean products. It is easy to use and has good stability.
（二） Defoaming agent formula-2
Virkler Corporation of the United States has introduced a new silicone defoamer Virco HCS-194, which is stable to high concentrations of salt and caustic. According to the company's recommendation, it can be used for reactive and direct dyeing, bleaching and causticizing without the risk of silicon flakes. It is a white emulsion, easy to handle, non-ionic, and has great compatibility with various chemical systems. Zhou Hongxiang excerpted from ADR, 1994/3; 65, Original: Dyeing and Finishing Technology 1995/12; 62
2. Soymilk defoaming agent made from soybean lecithin
92 parts of glycerin-hardened palm oil fatty acid ester, 4.2 parts of soy lecithin, 0.8 parts of silicone resin, and 3 parts of calcium phosphate powder were mixed and stirred to obtain a finished product.
This product has excellent defoaming properties. Adding this product to soybean milk is equivalent to 6% of soybeans. When the milk is boiled, it can be defoamed within 10 seconds.
3.Defoaming agent for fabric jet dyeing
This defoamer contains poly (meth) acrylate, emulsifier and non-polar solvent, has alkali resistance, and is used for defoaming of fabric jet dyeing bath.
Butyl acrylate 900
Isooctyl maleate 900
Isohexadecyl alcohol 1493
Ethoxylated dimethylsiloxane 268
Oleic acid 134
Styrene oxide / isotridecyl alcohol polyoxyethylene ether (9) 134
Preparation method: firstly, a copolymer is prepared by using butyl acrylate and isooctyl maleate, and then mixed with isohexadecanol, adding ethoxylated dimethylsiloxane and oleic acid, and then adding styrene oxide / iso An adduct of tridecyl alcohol polyoxyethylene ether (9) to prepare an antifoaming agent for fabric jet dyeing bath.
Build a bath: Add TP-18 defoamer 150 ~ 250 ml per 100L of solution
Equipment: 316 stainless steel tank, PP tank or PE tank.
Adding: When the working tank generates bubbles continuously, take a defoaming agent of 30 ml / 100L tank solution, add a little water to dilute and pour into the working tank
(The above are reference suggestions, please adjust according to the actual situation)
1. This product is packed in 50kg plastic drum.
2. Store in a cool and dry place to avoid direct sunlight. The storage period is half a year.
Recent research on defoamers has focused on compound defoamers such as the compounding of organosilicon compounds and surfactants, the compounding of polyethers and silicones, and the compounding of water-soluble or oil-soluble polyethers and silicon-containing polyethers. On the agent, compounding is one of the development trends of defoamers. As far as the current defoamers are concerned, the performance of polyether and silicone defoamers is excellent, and the modification and development of new varieties of these defoamers are also active.
In order to eliminate the inevitable disadvantages of traditional defoamers, molecular-level defoamers have emerged. These defoamers are composed of special mineral oils and special molecular-level defoamers. The branch structure has multiple anchor points and has a certain self-emulsifying effect. No additional emulsifier is needed, and no shrinkage caused by emulsifier detachment will occur.
- 孙宝国． 1. Sun Baoguo. Inevitable Food Additives: Chemical Industry Press, 2012
- 泡剂的分类． 2. Classification of foaming agents. Plastic Forum [reference date 2012-11-21]
- 针对消泡剂的一些实用性测试． 3. Some practical tests for defoamers. Plastic Forum [reference date 2012-11-21]