Carboxymethyl cellulose (CMC) is a carboxymethylated derivative of cellulose, also known as cellulose gum, and is the most important ionic cellulose gum. CMC was first synthesized by Germans in 1918 and patented in 1921, after which it was commercialized in Europe. Initially, it was a crude product used as a colloid and binder. During World War II, Germany used CMC in synthetic detergents. In 1947, the U.S. FDA, based on toxicological studies, confirmed that CMC is non-toxic and allowed its use as an additive in the food industry for thickening purposes. Industrially, CMC is mainly produced through two methods: aqueous medium method and solvent method, with the latter, also known as organic solvent method, being more commonly used.

CMC is often referred to as the 'industrial MSG' and has wide applications across various industries. In papermaking, it is primarily used as a surface sizing agent, coating water retention agent, and paper strength enhancer. Carboxymethyl cellulose is a water-soluble anionic surfactant with certain dispersion capabilities, optimizing fiber distribution within the network and promoting uniform fiber entanglement. Upon dissolving in water, it forms a transparent viscous solution that envelops the fibers when added to pulp. During the paper formation, drying, and dewatering process, due to the presence of hydroxyl and carboxymethyl groups, the molecules bond firmly through hydrogen bonds. This bridging effect between fibers creates numerous hydrogen bonds, enhancing the bonding force and thus increasing paper strength. 

Electrostatic adsorption is the primary force for the retention of wet-end chemicals, and the presence of carboxyl groups on the fiber surfaces gives them a slight negative charge, providing crucial attachment points for the adsorption of wet-end chemicals onto the fibers. Carboxymethyl cellulose exhibits strong affinity and, when used in combination with suitable cationic additives, demonstrates synergistic effects, improving the retention rate on the paper machine and the effectiveness of the additives.