Calcium stearate is carboxylate of calcium that is found in some lubricants and surfactants. It is a white waxy powder.
Production and occurrence
Calcium stearate is produced by heating stearic acid, a fatty acid, and calcium oxide:
2 C17H35COOH + CaO → (C17H35COO)2Ca + H2O
It is also the main component of soap scum, a white solid that forms when soap is mixed with hard water. Unlike soaps containing sodium and potassium, calcium stearate is insoluble in water and does not lather well. Commercially it is sold as a 50% dispersion in water or as a spray dried powder. As a food additive it is known by the generic E number E470.
- Calcium stearate is used as a flow agent in powders including some foods (such as Smarties), a surface conditioner in hard candies such as Sprees, a waterproofing agent for fabrics, a lubricant in pencils and crayons.
- The concrete industry uses calcium stearate for efflorescence control of cementitious products used in the production of concrete masonry units i.e. paver and block, as well as waterproofing.
- In paper production, calcium stearate is used as a lubricant to provide good gloss, preventing dusting and fold cracking in paper and paperboard making.
- In plastics, it can act as an acid scavenger or neutralizer at concentrations up to 1000ppm, a lubricant and a release agent. It may be used in plastic colorant concentrates to improve pigment wetting. In rigid PVC, it can accelerate fusion, improve flow, and reduce die swell.
- Applications in the personal care and pharmaceutical industry include tablet mold release, anti-tack agent, and gelling agent.
- Calcium stearate is a component in some types of defoamers.