Carboxymethyl cellulose

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 used to be marketed under the name Tylose, a registered trademark of SE Tylose. 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 used to be marketed under the name Tylose, a registered trademark of SE Tylose. 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. CMC is used in food under the E number E466 or E469 (when it is enzymatically hydrolyzed) as a viscosity modifier or thickener, and to stabilize emulsions in various products including ice cream. It is also a constituent of many non-food products, such as toothpaste, laxatives, diet pills, water-based paints, detergents, textile sizing, reusable heat packs, and various paper products. It is used primarily because it has high viscosity, is nontoxic, and is generally considered to be hypoallergenic as the major source fiber is either softwood pulp or cotton linter. CMC is used extensively in gluten free and reduced fat food products. In laundry detergents, it is used as a soil suspension polymer designed to deposit onto cotton and other cellulosic fabrics, creating a negatively charged barrier to soils in the wash solution. CMC is used as a lubricant in artificial tears. CMC is also used as a thickening agent, for example, in the oil-drilling industry as an ingredient of drilling mud, where it acts as a viscosity modifier and water retention agent. Sodium CMC(Na CMC) for example, is used as a negative control agent for alopecia in rabbits. Knitted fabric made of cellulose (e.g. cotton or viscose rayon) may be converted into CMC and used in various medical applications. Insoluble microgranular CMC is used as a cation-exchange resin in ion-exchange chromatography for purification of proteins. Presumably, the level of derivatization is much lower, so the solubility properties of microgranular cellulose are retained, while adding sufficient negatively charged carboxylate groups to bind to positively charged proteins. CMC is also used in ice packs to form a eutectic mixture resulting in a lower freezing point, and therefore more cooling capacity than ice.