Humans began using cleaning substances that resemble modern soaps nearly five millennia ago. Early crude soaps were made from natural fats and oils and alkalis such as wood ashes or lye (sodium or potassium hydroxide). Sodium stearate is an important component of many industrial products, used as an emulsifier, dispersant, gelling agent, stabilizer, binder, viscosity modifier and more. It is a salt of stearic acid, most commonly obtained from vegetable triglycerides such as coconut and palm oil or animal triglycerides such as tallow.
The USP/NF monograph specifies a maximum water content of 6 %, which allows for the formation of multiple hydrated forms depending on the ratio of stearic to palmitic acid, pH and conditions of drying. The present invention enables the preparation of magnesium stearate/palmitate with high purity, low water content and free of other hydrated forms by alternately basification-acidifying the reaction mixture during production.
To this slurry, a solution of magnesium sulfate is added without agitation to precipitate the excess sodium soap as magnesium stearate/palmitate. The resulting product is washed to remove the magnesium sulfate byproduct, and then dried in a flash dryer. A final adjustment of the pH to a range of 9.0 to 9.5 is performed, and then the product is fed to a tableting line where it is converted into the solid form of magnesium stearate/palmitate.
Acme-Hardesty offers two different types of sodium stearate: the conventional tallow-based, and the vegetable-derived version which is GMO-free. Both are very versatile materials with many applications and a two-year shelf life.