Calcium stearate (also known as calcium oxide or stearic salt) is a common calcium salt found in food, cosmetics and plastics. The use of calcium stearate is not without its pros and cons.
Synthesis and use of calcium stearate
1. Synthesis of Calcium Stearate. The sodium stearate and calcium chloride solutions are mixed together at 65degC. The calcium stearate product is separated by precipitation. The finished product is obtained after it has been filtered, washed in water, and then dried at around 90degC.
2. In 300mL hot water at 55degC, dissolve 5.60g of calcium oxide (0.1mol). Pour 51.3g stearic acetic acid, which is chemically pure, in 350mL water heated to 70degC. Add 0.75g Diethanolamine and stir it until it emulsifies. The prepared stearic-acid emulsion, after being fully stirred for 2 hours, was slowly added to the suspension of calcium oxide.
3. Direct method: Add a certain quantity of stearic acids and CaO in a pot equipped with a stirring device and thermometer. Heat it to melting, then add the catalyst slowly while constantly stirring. Apply a vacuum for controlling the reaction temperature to 140-150degC. The reaction lasts 1.52.0h. The reaction is complete when the material has been discharged, cooled down, and crushed.
4. Metathesis method – Dissolve the stearic solution in 20 times as much hot water. Add caustic soda saturated solution. Perform saponification at approximately 75degC. This will generate a dilute sodium stearate. The sodium stearate is then mixed with the calcium chloride, which has a 1074kg/m3 content. A metathesis reaction takes place at 65 degrees Celsius, and precipitates the calcium stearate. Then, it is filtered and washed in water before being dried at around 90degC.
Calcium stearate applications
Calcium stearate has many uses, including as a heat stabilizer for polyvinylchloride, as a lubricant to release molds, and for plastic processing. When mixing lead soap with basic salt, it can accelerate the gelation process.
The non-toxic film and appliance, such as medical equipment and food packaging, also uses calcium stearate. Calcium stearate may also be used in polyethylene or polypropylene as a halogen-absorbing agent to reduce the harmful effects of residual catalyst on color stability and durability.
In rubber processing, calcium is used to soften rubber. It can be used on both natural rubber and synthetic, but it does not affect vulcanization. It is used in lubricants for polyolefins fibers and mold compounds, as well as a grease thickener, waterproofing agents for textiles, paints flatteners, and plasticizers for plastic records. As a halogen absorbent for polyethylene and polypropylene, as well as a release agent and lubricant in thermosetting plastics like phenolic and amino; as lubricant or thickener for grease; as waterproofing fabric for waterproof fabrics; as an agent of flattening paint; and as lubricant to remove pencil lead. Anticaking agents are made from food-grade Calcium Stearate.
Calcium stearate can also be used to make pencil lead and in medicine.
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