1. Causes of surfactant foam formation
When a surfactant is mixed with water, the hydrophilic end dissolves in the water, and the hydrophobic end detaches from the water and gathers at the surface. In surface surfactants, hydrophobic groups will leave the water surface and enter the air, and hydrophilic groups will dissolve in water and sit side by side on the water surface. When the water is stirred, it pushes air into the water, where hydrophobic groups envelop the air as bubbles. In general, anionic and cationic surfactant foams are the highest, while non-ionic surfactant foams are relatively lower.
In most processes, foam has a negative effect, that is, we are pursuing low-bubble and non-bubble surfactants. But in some areas, it is just the opposite, such as daily chemicals, shower gel and facial cleanser, the pursuit is more foam, foam delicate; For example, flotation deinking in the field of paper deinking also requires surfactants to have good foaming properties.
Second, a low-foam surfactant with cleaning function
When discussing low-foam surfactants, we must first explain the conditions and processes of use. In addition to its own structure, the foam of surfactant is also related to the hardness of water, the use temperature, pH value, pressure and so on.
Soaps used in hard water can be called low-foam surfactants. Sometimes soap can be used to test and distinguish between soft and hard water, with more foam for soft water and less foam for hard water. Mainly because in hard water, soap will combine calcium and magnesium ions to form insoluble calcium soap or magnesium soap, which is easy to form a gap on the surface of the foam, resulting in the foam bursting.
2, polyoxyethylene ether of EO/PO block of fatty alcohol
As we all know, fatty alcohols and EO (ethylene oxide) condensation addition, that is, the AEO series, the introduction of hydrophilic EO groups, will obtain excellent wetting, emulsification, cleaning and high foam properties. While PO propylene oxide is a hydrophobic group, the introduction of propylene oxide can effectively reduce the surface tension of the formed foam surface, resulting in the foam bursting and disappearing. However, the introduction of PO inevitably reduces the content of EO, thus reducing the decontamination properties of surfactants such as emulsification and dispersion. Therefore, for EOPO block polyether, its cleaning functions such as emulsification and dispersion must be contradictory with low foaming. The lower the foam, the worse the other properties will be.
3. Fatty acid methyl ethoxide and its derivatives
Fatty acid methyl ester, especially the 18-carbon methyl stearate, is also a defoamer itself, so the 18-carbon methyl stearate as the raw material of the surfactant will also have the corresponding low foam performance, and this low foam performance is not like EOPO block polyether at the cost of losing its cleaning performance, so it is quite practical application value of low foam cleaning agent.
4. Low carbon chain fatty alcohol ethers and their derivatives
Low carbon chain fatty alcohols have a certain defoamating function, so the surfactants with low carbon chain fatty alcohols as raw materials also have low foam characteristics, the most common isoctyl alcohol polyoxyethylene ether, isoctyl alcohol phosphate ester and isoctyl alcohol ether phosphate ester have low foam characteristics. However, the low carbon chain fatty alcohol derivatives often only have permeability, and other properties are poor, thus limiting their application range.