Causes of surfactant foam formation
When surfactants are mixed with water, the hydrophilic end will dissolve in the water, and the hydrophobic end will break away from the water and gather on the water surface. In surfactants on the water surface, the hydrophobic group will leave the water surface and enter the air, while the hydrophilic group will dissolve in the water and line up on the water surface. When water is stirred, air will enter the water. At this time, the hydrophobic group will surround the air and become bubbles. Generally speaking, anionic and cationic surfactants have the highest foam, while non-ionic surfactants have relatively lower foam. In most processes, foam brings negative effects, which means we are pursuing low-foaming and non-foaming surfactants. But in some fields, it is just the opposite, such as daily chemicals, shower gel and facial cleanser, etc., what is pursued is more foam and fine foam; another example is flotation deinking in the field of papermaking and deinking, which also requires surfactants with good foaming performance.
Low-foaming surfactants refer to surfactants that produce less foam during reuse. There are four main types of surfactants with low foaming properties: EO/PO block polyether, isooctyl phosphate derivatives, ethoxylated fatty acid methyl ester derivatives, polyether modified Silicone surfactant.
EO/PO block polyether
This type of surfactant mostly uses fatty alcohols , fatty acids, and low-carbon chain polyols as starting agents, and is combined with EO ethylene oxide (C2H4O), PO propylene oxide (C3H6O) It is produced by condensation according to a certain molar ratio. Among them, polyoxypropylene group-O(CH2CH2O)nH is a hydrophilic group, and polyoxypropylene group-O(CHCH3CH2O)nH is a lipophilic group. On the one hand, this lipophilic and hydrophilic mixed structure is easier to form micelles in aqueous solutions. , thus htm The surface tension of l3 is larger than that of . In addition, the hydrophilic and lipophilic groups are staggered and arranged in a staggered and mixed manner. The space hinders each other and forms a large number of gaps between the liquid films, which weakens the strength of the liquid film. The resulting foam film wall is more likely to burst. , thus having low foaming properties. The introduction of hydrophilic EO groups will achieve excellent wetting, emulsifying, cleaning and high foaming properties. PO propylene oxide is a hydrophobic group. The introduction of propylene oxide can effectively reduce the surface tension of the foam surface, causing the foam to burst and disappear. However, the introduction of PO will inevitably reduce the content of EO, thereby reducing the emulsification, dispersion and other decontamination properties of the surfactant. Therefore, for EOPO block polyether, its cleaning functions such as emulsification and dispersion and low foaming must be contradictory to each other. The lower the foam, the worse other properties will be. EO/PO block polyether is widely used. As a water reducing agent, EO/PO block polyether has good dispersion and dispersion retention. It can be used as a water emulsion in water-based pesticides, which can well adjust the hydrophilic-lipophilic balance of pesticides. EO/PO block polyether can also be used as a low-foam cleaning agent in industrial cleaning.
Isooctanol and its derivatives phosphate ester salts
Among various alcohols, isooctyl alcohol has the best defoaming effect, and surfactants derived from isooctyl alcohol also have low foaming effects. Introducing the structure of phosphate ester into the isooctyl alcohol molecular formula will increase the surface tension of the product and further reduce the foam of the product. Common surfactants of this type include isooctyl alcohol phosphate, isooctyl alcohol polyoxyethylene ether phosphate, etc. Phosphate ester derivatives of isooctyl alcohol are a type of low-foaming anionic surfactant, which generally have good penetration and wetting properties. They are mostly used in textile printing and dyeing, tanning, ceramic bleeding, papermaking and pulp filtration, etc. In particular, isooctyl polyoxyethylene ether phosphate has certain emulsifying properties and is often used in alkaline cleaning processes such as wine bottles and curtain walls.
block polyether modified silicone surfactant
silicone surfactant is a type of organic-inorganic hybrid synthetic material with inorganic siloxane as the backbone (Si-O-Si) and containing organic group side chains. , has good spreading effect on the surface of objects and has high wetting performance. The silicone structure alone does not have low-foaming and defoaming effects. Commonly used silicone defoaming agents only use silicone surfactants to quickly spread on the foam surface, and can only be supplemented with hydrophobic silica black. It can achieve the effect of breaking and defoaming.Replacing the methyl groups in the silicone structure with polyether and further increasing the surface tension can effectively reduce the foaming of silicone surfactants. Low-foaming EO/PO block polyether-modified silicone can be used in the textile and papermaking fields to improve the softness of textiles or paper and reduce foaming problems in intermittent production processes; in the agricultural field, EO/PO block polyether modified silicone is used as an emulsifier and wetting agent for pesticides. During the spraying process, it can effectively prevent excessive foam from flying in the wind; in the field of cleaning, especially for hydrophobic solid surfaces, EO/PO block polyether modified silicone surfactant can significantly speed up the cleaning of objects. The surface wetting speed enhances the oil removal effect and reduces the cleaning time.
Ethoxylated fatty acid methyl esters and their derivatives
esters all have low foam properties. Some esters can even be used as defoaming agents in some specific fields. For example, natural oils can be used as defoaming agents in soy milk production processes. , high carbon chain fatty acid methyl ester can be used as a strong alkali-resistant defoaming agent in the papermaking field. Ethoxylated fatty acid methyl ester (FMEE) also has low foam characteristics and has surface activities such as emulsification and dispersion. Fatty acid methyl ester ethoxylates are polyether ester compounds. They inherit the advantages of polyether ester surfactants such as easy dispersion, high surface activity, strong foam suppression and defoaming capabilities, and are hydrophilic after ethoxylation. Further improvement weakens the hydrogen bonds between the original polyoxyethylene chains and water molecules, reduces the strength of the foam film layer, and makes the foam easier to burst. Fatty acid methyl ester ethoxylates and their sulfonates are acid and alkali resistant and are widely used in the secondary oil flooding process of oilfield production. This type of compound also has emulsification and dispersion effects and is used as a cleaning agent in industrial cleaning, printing and dyeing and other fields, and as a deinking agent in the paper industry.
soap
When discussing low-foaming surfactants, we must first explain the conditions, processes, etc. of use. In addition to its own structure, the foam of surfactants is also related to water hardness, operating temperature, acid-base pH value, pressure, etc. Many connections. Soap can be called a low-foaming surfactant under the conditions of use in hard water . Sometimes you can use soap to test and distinguish soft water and hard water. Water with more foam is soft water, and water with less foam is hard water. The main reason is that in hard water, soap will combine with calcium and magnesium ions to form water-insoluble calcium soap or magnesium soap, which can easily form gaps on the surface of the foam, causing the foam to burst.
fatty acid methyl ester ethoxylate and its derivatives
fatty acid methyl ester, especially 18-carbon methyl stearate, itself is also a defoaming agent, so 18-carbon methyl stearate is the raw material surfactant Correspondingly, it will have low foaming performance, and this low foaming performance is not at the expense of its cleaning performance unlike EOPO block polyether, so it is a low foaming detergent with great practical application value.
Domestic low-foaming surfactant supply
Zhejiang Real Madrid Group and Liaoning Aoke Polyether are professional domestic manufacturers of EOPO block alcohol ethers. For isooctyl polyoxyethylene ether and its derivatives, there are many manufacturers, such as Xingtai Auxiliary Factory, Xi'an Chulongda Chemical, Baoji Tianze Chemical, etc. Fatty acid methyl ester ethoxylate products are currently not produced domestically and are mostly imported products
