Silicone defoamers
There are four stages in the development of defoamers.
The first stage defoamers are mainly composed of various organic substances, such as fatty acids, mineral oils, aliphatic amides, low alcohols, etc. Most of these defoamers are natural substances, which have little environmental pollution and low price. Because the defoaming property is relatively weak, a large amount of foam can not meet the requirements of production.
The second stage defoamer: polyether defoamer CnH (2n + 1) O (EO) a (PO) bH, polyoxyvinyl chain (EO) is hydrophilic, and polyoxypropylene chain (PO) is lipophilic. The defoamer has good antifoaming property, non-toxicity, no stimulation and good dispersibility. In actual production, the relative molecular weight of polyether and the proportion of EO and PO in polyether chain are adjusted to meet the needs of various production fields. At present, the main polyether Defoamers in the market are straight chain polyether, ether amine, aliphatic alcohol polyether, fatty acid polyoxyethylene ether, and other polyether derivatives.
The third stage defoamer: organosilicon defoamer, which has better defoaming performance than the former two. Generally, the higher molecular weight silicone oil is insoluble in surfactant solution, while the smaller molecular weight silicone oil is easily solubilized by surfactant molecules, which changes the composition of defoamer and weakens the defoaming performance. For the defoamer of silicone oil, it is insoluble in water and mineral oil, so it has strong foam suppression ability and greatly enhances its foam breaking effect. Because Si-O bond and Si-C bond are relatively stable, they are allowed to be used in systems containing small amounts of acid, alkali and salt. Silicone defoamers commonly used in industrial production are mostly secondary processed products of silicone oil prepared by adding dispersing additives in silicone oil, which belong to liquid mixtures. The mixture is mainly divided into five types: silicon paste type, silicone oil type, emulsion type, solution type and solid type from appearance and fluidity.
The fourth stage defoamer: polyether modified silicone oil defoamer, on the basis of previous generations of defoamers, strives to integrate the advantages of polyether and organosilicon, and introduces polyether segments into silicone oil segments, which has stronger defoaming and anti-foaming properties. Polyether modified silicone oil is a new type of special silicone surfactant. It is a kind of non-ionic silicone surfactant with unique properties, which is formed by addition reaction of polyether containing double bond and silicone oil containing low hydrogen. It not only retains the properties of silicone oil such as high and low temperature resistance, weatherability, demoulding, hydrophobicity and physiological inertia, but also has non-irritating and high surface activity of polyether. It is easy to disperse. Polyether modified silicone oil is widely used because of its good heat resistance, shear resistance, acid resistance and alkaline properties, non-toxic, odorless and stable storage.
Conversion from organosilicon