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Stearic acid is one of several major long-chain fatty acids comprising oils and fats. It is presented in animal fats, oil and some kinds of vegetable oils as wellin the form of glycerides. These oils, after hydrolysis, produce the stearic acid.
Stearic acid is a fatty acid widely existing in nature and has the general chemical properties of carboxylic acids. Almost all kinds of fat and oil contain certain amount of stearic acid with the content in the animal fats being relative high. For example, the content in the butter can reach up to 24% while the content in vegetable oil is relative low with the value in tea oil being 0.8% and the oil in palm being 6%. However, the content in cocoa can reach as high as 34%.
There are two major approaches for industrial production of stearic acid, namely fractionation and compression method. Add decomposition agent to the hydrogenated oil, and then hydrolyze to give the crude fatty acid, further go through washing with water, distillation, bleaching to obtain the finished products with glycerol as the byproduct.
Most domestic manufacturers use animal fat for production. Some kinds of production technology will result in the incompletion of the distillation of fatty acid which produce stimulating odor at the time of the plastic processing and high temperatures. Although these odor is of no toxic but they will have certain effect on the working conditions and the natural environment. Most imported form of stearic acid takes vegetable oil as the raw materials, the production processes are more advanced; the produced stearic acid is of stable performance, good lubrication property and less odor in the application.
Stearic acid is mainly used for the production of stearates such as sodium stearate, magnesium stearate, calcium stearate, lead stearate, aluminum stearate, cadmium stearate, iron stearate, and potassium stearate. The sodium or potassium salt of stearic acid is the component of soap. Although sodium stearate has a less decontamination ability than sodium palmitate, but its presence may increase the hardness of soap.
Take butter as raw material, go through sulfuric acid or pressurized method for decomposition. The free fatty acids was first subject to water pressure method for removing the palmitic acid and oleic acid at 30~40 ℃, and then dissolved in ethanol, followed by addition of barium acetate or magnesium acetate which precipitates stearate. Then further add dilute sulfuric acid to get the free stearate acid, filter and take it, and re-crystallize in ethanol to obtain the pure stearic acid.
The above information is edited by the chemicalbook of Dai Xiongfeng.