What is a dripping agent and what are its uses?

Dripping agent is a type of surfactant that damages the interfacial tension between water droplets and thin films, preventing the formation of water droplets on the surface.

Drips are generally chemicals with surface activity that are added during polymer processing to distribute condensed small water droplets into a continuous transparent thin layer. Their function is to reduce the contact angle between water and the polymer surface and prevent the formation of water droplets on the surface.

Drips can be divided into additive and coating types according to their usage methods. Additive type drip agents can ensure a certain reserve in the film, continuously replenish the consumption during use, and have long-term anti fog and drip effects, as well as lubrication, anti bonding, and anti-static properties.

Synthesis process

Polyglycerol fatty acid ester

The synthesis of polyglycerol fatty acid esters is carried out in two steps. In the first step, polyglycerol is prepared through glycerol condensation or glycerol ester addition reaction with glycerol. In the second step, the polyglycerol mixture can be directly esterified with fatty acids or transesterification with triglycerides to obtain the corresponding polyglycerol esters.

Preparation of polyglycerol

The preparation method uses alkali as catalyst, and the reaction equation is as follows:

NHOCH2CHOHCH2OH ->HO - (- CH2CHOHCH2O -) - H+(n-1) H2O

Under the protection of inert gases such as nitrogen or carbon dioxide, an O.O1% to 5% (mass ratio) catalyst is added to the raw glycerol, and the reaction is carried out at a temperature of 200-300 ℃ for 2-20 hours. The catalysts used are generally alkaline substances, and their catalytic effects are roughly in the following order: potassium carbonate>lithium carbonate>sodium carbonate>potassium hydroxide>sodium hydroxide>sodium methoxide>calcium hydroxide>lithium hydroxide>magnesium carbonate>magnesium oxide. Food grade polyglycerol must be refined and can be decolorized using activated carbon, acidic clay, or ion exchange resin, followed by further decolorization using ion exchange resin to remove the catalyst.

Synthetic polyglycerol ester

The esterification process conditions are to fully mix polyglycerol and fatty acids under stirring conditions. The reaction endpoint can be determined by approaching zero acid value for 1-2 hours at 200-240 ℃, and can be completed in commonly used esterification reactors. The esterification reaction mechanism is the same as that of conventional esterification

The fatty acids used can be high fatty acids such as stearic acid, palmitic acid, oleic acid, lauric acid, or low fatty acids. The higher the degree of polymerization of polyglycerol esters, the shorter the chain of fatty acids, the lower the degree of esterification, and the stronger the hydrophilicity of polyglycerol esters. By designing different degrees of glycerol polymerization and consciously controlling the ratio of hydrophilic hydroxyl groups to oleophilic fatty acid residues in polyglycerol ester molecules, products with different HLB values can be obtained.

Glycerol monostearate

Add a certain proportion of glycerol, acetone, water entraining agent, and catalyst to a 250 mL three necked flask with a thermometer, water separator, and reflux condenser. Turn on magnetic stirring, heat up to reflux, and the water entraining agent takes out the water generated by the reaction from the reaction system. When the water volume in the water separator remains basically unchanged and the reaction temperature no longer increases, stop the reaction. After cooling, add a certain amount of stearic acid (ST) and catalyst, raise the temperature to boiling, and the water carrier continues to carry out the water generated in the system. After the water volume in the water separator remains basically constant, the esterification process ends. Decompression steam out the water containing agent and reactant acetone, causing the product to condense into a solid.