Calcium stearate
Calcium stearate is a stearic acid metal soap that is formed by replacing calcium ions with hydrogen acid ions and its appearance is white powder. Calcium stearate was first used in 1924 to improve the texture of bread dough and reduce the level of roundness in flour, and its unique properties have led to its use in many non-food industries.
Calcium stearate, also known as calcium octadecanoic acid, is a clear white crystalline powder with the chemical formula (C17H35COO)2Ca. Calcium stearate is a calcium carboxylate that is classified as a calcium soap. Calcium stearate is commercially available in 50% water or as a spray powder. Unlike soaps that contain sodium and potassium, calcium stearate is insoluble in water and does not foam well. Figure (1) shows the molecular structure of calcium stearate.
Figure (1): Molecular structure of calcium stearate
It has been used as an additive by Hoochst since 1955 and by Montel since the late 1960s. Manufacturers of calcium stearate use the reaction of calcium oxide with stearic acid in the presence of heat during the following reaction to produce this substance:
2C17H35COOH + CaO (C17H35COO)2Ca + H2O
Figure (2): Calcium stearate production reaction
Calcium neutral soap is made from high quality stearic acid under controlled conditions and the final product is very uniform. This product does not dissolve in most solvents and, if heated, dissolves in very small amounts in aromatic compounds, chlorinated hydrocarbons or mineral and vegetable oils and waxes. Calcium stearate is the most important type of calcium salt, but due to the insolubility of this substance, it is not commonly used as a soap at the present time and has been replaced by a synthetic substance that is soluble in water.
Applications of calcium stearate
Food industry
This salt is used as an emollient, stabilizer, and surfactant, and is a substance that the US Food and Drug Administration (FDA) has generally recognized as a safe food additive. According to FAO / WHO regulations, calcium stearate can be used to cover glucose powder, sucrose powder and food cubes, etc., and the maximum allowable amount is 15 grams per kilogram.
Calcium stearate is an anti-baking agent used in a wide variety of foods, including salts, spices, sweets, snacks and dry mixes. Calcium stearate is also used in the production of some foods (such as smarties), to soften the surface of hard sweets.
Hygiene industry
This substance is used intermittently in cosmetics, especially hair spray products. It is also used in cosmetic powders, ointments and beauty packages. Despite the very low risk of skin irritation, topical contact may cause redness, itching, and burning of the eyes. It can also be used in gels or in bulk in cosmetic powders.
Chemical industry
Calcium stearate is calcium carboxylate, which is found in some lubricants and active substances on the surface and is a white powder. This chemical is commonly used for non-toxic soft products such as food packaging films, medical instruments, etc. This combination with lead base salts and lead soaps used for hard products speeds up gelling. This product is also widely used as a lubricant and release agent for thermal plastics such as polyolefin, polyester-reinforced plastics, phenolic resins, amino resins, etc.
It is commonly used in various antifoam formulations. In general, anti-foaming compounds are composed of insoluble agents in the foam environment. It is important that these countertops have a low viscosity and are easily spread in the environment. The dose of stearate is usually 0.5% to 1% higher than the solids in the dispersion.
Calcium stearate is added to various fabrics, shoes and even rock wool, which is used as insulation, for impermeability. Another advantage of this additive is its effectiveness as waterproof and its low cost.
With a concentration of about 2%, calcium stearate and zinc stearate are used in the production of fire extinguishers. It is also present in soundproofing compounds and other construction products such as suspended ceilings and panels.
This chemical compound is used for polyethylene and polypropylene and can eliminate the adverse effects of the remaining catalyst on the dye and the resin stabilizer.
Due to properties such as high resistance to heat and light has been considered. It is mainly used as a stabilizer for PVC resins and lubricants for powder or plastic molding tablets. Due to the high content of stearic acid, calcium stearate in PVC can be used as an external lubricant in PVC processing and cause fusion.
Paper industry
The paper industry uses calcium stearate because it is a low-cost additive that extends the life of the paper and gives it a semi-opaque appearance.
Cement and concrete industries
This compound is also used to control the corrosion of cementitious materials in concrete products such as paving stones and blocks and to increase their water resistance.
Plastic industry
In plastics, it can act as an acid sequestrant or neutralizer at concentrations above 1000 ppm and a lubricant or release agent.
Calcium stearate is also used in colored plastic concentrates to improve pigment drying.
In general, the use of calcium stearate can be summarized as follows:
- Fluidity agent in powder form
- Waterproof fabrics
- Pencil and wax pencil softener
- In the concrete industry
- Paper and cardboard making
- Rubber and plastic industry as an effective emollient in the process and releasing agent
- In colored plastic concentrates as pigment kneaders