Methyl 2-hydroxyethyl cellulose

Chemical Properties

A white, yellowish-white or grayish-white powder or granules, hygroscopic after drying.

Chemical Properties

soluble in cold water, flocculates at elevated temperatures

Uses

Water retention aid, thickening agent, protective colloid, suspending agent, binder and stabilizer.

Pharmaceutical Applications

Hydroxyethylmethyl cellulose is used as an excipient in a wide range of pharmaceutical products, including oral tablets and suspensions, and topical gel preparations. It has similar properties to methylcellulose, but the hydroxyethyl groups make it more readily soluble in water and solutions are more tolerant of salts and have a higher coagulation temperature.

Safety

Hydroxyethylmethyl cellulose is used as an excipient in various oral and topical pharmaceutical preparations, and is generally regarded as an essentially nontoxic and nonirritant material.

Synthesis

Hydroxyethyl methyl cellulose is prepared from refined cotton using ethylene oxide and chloromethane as etherifying agents. Steps: 1) A mixture of toluene and isopropanol, water, and NaOH are added to the reactor, heated and held. 2) Temperature is lowered, refined cotton is added, solvent is sprayed, vacuum is applied and nitrogen is purged for displacement, then alkalization is performed. 3) Vacuum is applied, ethylene oxide and chloromethane are added. Etherification occurs in two stages with controlled temperature and pressure. 4) The mixture is pressed into a desolvation kettle containing glacial acetic acid for neutralization. Temperature is raised for desolvation, and pH is adjusted. 5) Centrifugal separation, then transfer to a washing kettle for washing. 6) After centrifugation, the material is fed into a dryer, dried, crushed, and packaged.

storage

Hydroxyethylmethyl cellulose is hygroscopic and should therefore be stored under dry conditions away from heat.

Regulatory Status

GRAS listed. Included in nonparenteral medicines licensed in Europe (oral suspensions, tablets, and topical preparations).