Thickeners are mainly used to increase the viscosity or consistency of products. They have the characteristics of small dosage, obvious thickening, and easy use. They are widely used in pharmaceuticals, printing and dyeing. , cosmetics, food additives, oil extraction, papermaking, leather processing and other industries. There are many types of thickeners. Generally, thickeners are classified according to relative molecular weight, including low molecular thickeners and high molecular thickeners; according to functional groups, they mainly include inorganic thickeners, cellulose, polyacrylate and Type 4 associative polyurethane thickeners.
Low molecular thickeners can be divided into the following types:
1. Fatty alcohol and fatty acid thickeners:Fatty alcohols, fatty acids (such as lauryl alcohol, myristyl alcohol, decanol, hexanol, octanol, cetyl alcohol, stearyl alcohol, Behenyl alcohol, lauric acid, linoleic acid, linolenic acid, myristic acid, stearic acid, etc.) are polar organic compounds. They can be regarded as nonionic surfactants. They have both lipophilic groups and Has hydrophilic groups. The presence of a small amount of this type of organic matter has a significant impact on the surface tension, critical micelle concentration and other properties of the surfactant. The size of its effect increases with the lengthening of the carbon chain. Generally speaking, it shows a linear relationship. The principle of action is that fatty alcohols and fatty acids can insert (join) surfactant micelles and promote the formation of micelles. At the same time, there may be strong interactions between the molecules of the polar organic matter and the surfactant (between hydrocarbon chains). The hydrophobic interaction plus the hydrogen bonding between the polar heads) causes the two molecules to be oriented and arranged very closely on the surface, which greatly changes the properties of the surfactant micelles and achieves a thickening effect.
2. Inorganic salt thickener: Use inorganic salts (such as sodium chloride, chlorine Potassium chloride, ammonium chloride, monoethanolamine chloride, diethanolamine chloride, sodium sulfate, sodium phosphate, disodium phosphate and pentasodium triphosphate, etc.) are used as thickeners, and inorganic salts are used as thickeners. Generally, it is a surfactant aqueous solution system. The surfactant forms micelles in the aqueous solution. The presence of electrolytes increases the association number of the micelles, leading to the transformation of spherical micelles into rod-shaped micelles, which increases the movement resistance and thus increases the system’s resistance to movement. Increased viscosity. The most commonly used inorganic salt thickener is sodium chloride, which has obvious thickening effect.
3. Alkanolamide thickeners:Alkanolamides can thicken Thickens and achieves best results. Various alkanolamides vary greatly in performance, with the most commonly used being cocodiethanolamide. The effect is different when used alone and when used in combination. The disadvantage of this type of thickener is that alkanolamides contain free amines as impurities, which are potential sources of nitrosamines.
4. Ether thickeners:This type of thickener is a non-ionic thickener , generally based on fatty alcohol polyoxyethylene ether sulfate (AES). Under normal circumstances, only inorganic salts can be used to adjust the appropriate viscosity. In addition, its thickening effect is closely related to the distribution width of unreacted alcohol and homologues contained in the product. The narrower the distribution of homologues, the greater the thickening effect.
5. Ester thickeners:This type of thickener is also a non-ionic thickener agent, mainly used in surfactant aqueous solution systems. Its advantages are that it is not easily hydrolyzed and has stable viscosity over a wide pH and temperature range. Currently the most commonly used is PEG-150 distearate.
6. Amine oxide thickener:Amine oxide is a polar nonionic surfactant , has a thickening effect. Its characteristics are as follows: under neutral or alkaline conditions, amine oxide exists as an unionized hydrate in aqueous solution, showing non-ionic properties; in acidic solutions, it shows weak cationic properties. The cationic nature of amine oxide is particularly obvious when the pH value of the solution is <3. Therefore, it can be well compatible with cationic, anionic, nonionic and zwitterionic surfactants under different conditions and show synergistic effects. Amine oxides are commonly used in cosmetics for thickening.
7. Other thickeners: A few betaines and soaps can also be used as thickeners. Soaps can be used for thickening in stick cosmetics, and betaine is mainly used for thickening. surfactant in water system.
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