Carboxymethyl cellulose
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| Other names
Carboxymethylcellulose; carmellose; E466
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| ECHA InfoCard | 100.120.377 |
| E number | E466 (thickeners, ...) |
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| Properties | |
| variable | |
| Molar mass | variable |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Carboxymethyl cellulose (CMC) or cellulose gum is a cellulose derivative with carboxymethyl groups (-CH2-COOH) bound to some of the hydroxyl groups of the glucopyranose monomers that make up the cellulose backbone. It is often used as its sodium salt, sodium carboxymethyl cellulose.
It is synthesized by the alkali-catalyzed reaction of cellulose with chloroacetic acid. The polar (organic acid) carboxyl groups render the cellulose soluble and chemically reactive.
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 which is used in detergents. A further purification process is used to remove these salts to produce the pure CMC used for food, pharmaceutical, and dentifrice (toothpaste) applications. An intermediate "semipurified" grade is also produced, typically used in paper applications such as restoration of archival documents.
The functional properties of CMC depend on the degree of substitution of the cellulose structure (i.e., how many of the hydroxyl groups have taken part in the substitution reaction), as well as the chain length of the cellulose backbone structure and the degree of clustering of the carboxymethyl substituents.
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