Sodium Carboxyl Methyl Cellulose

Brief Overview

Sodium carboxy methyl cellulose is the sodium salt of carboxy methyl cellulose (CMC), and the carboxy methyl cellulose derivative (-CH₂-COOH) is bonded to some of the hydroxy groups of the glucopyranose monomer constituting the cellulose backbone. It is synthesized from the base-catalyzed reaction of cellulose with chloroacetic acid. The polar (organic acid) carboxyl groups make the cellulose soluble and chemically reactive. The functional properties of CMC depend on the degree of substitution of the cellulose structure (i.e., how many hydroxyl groups participate in the substitution reaction), the chain length of the cellulose backbone structure, and the degree of clustering of the Carboxymethyl substituents.

Manufacturing Process

For sodium carboxymethyl cellulose (CMC), the manufacturing process is as follows: raw materials (refined cotton, caustic soda, alcohol) mixed, alkalify, etherification, washing neutralization, squeezing, washing, rake the dry, drying, crushing, and package. The main chemical reactions of sodium carboxymethyl cellulose are the alkalization reaction of cellulose with alkali to generate alkali cellulose and the etherification reaction of alkali cellulose with monochloro acetic acid.

Step 1: Alkalization: [C₆H₇O₂(OH)₃]_n + nNaOH→ [C₆H₇O₂(OH)₂ONa]_n + nH₂O

Step 2: Etherification: [C₆H₇O₂(OH)₂ONa]_n + nClCH₂COONa → [C₆H₇O₂(OH)₂OCH₂COONa]_n + nNaCl

Food Industry 

Sodium carboxy methyl cellulose can be used to improve the texture and consistency of baked goods, such as bread, cakes, and pastries. It helps to retain moisture, prevent staling, and improve the crumb structure.It can be used as a thickener and stabilizer in sauces and dressings, such as ketchup, mayonnaise, and salad dressings. It helps to improve the texture, prevent separation, and increase the shelf life.

Detergent Industry 

Following the initial reaction, the resultant mixture produces about 60% CMC plus 40% salts (sodium chloride and sodium glycolate). This product is the so-called technical CMC used as a surfactant in detergents. Further purification removes these salts to produce pure CMC for food, pharmaceutical, and dentifrice (toothpaste) applications.

Other Applications 

CMC is also used as a thickener for pharmaceuticals and as a component of drilling mud in the oil drilling industry as a viscosity regulator and water retention agent. In the food industry, CMC is used as a filler.