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Chemistry Typical Chemical Structures of METHOCEL ProductsMETHOCEL* cellulose ether products are available in two basic types: methylcellulose and hydroxypropyl methylcellulose. Both types of METHOCEL have the polymeric backbone of cellulose, a natural carbohydrate that contains a basic repeating structure of anhydroglucose units (see the figure below). During the manufacture of cellulose ethers, cellulose fibers are heated with caustic solution which in turn is treated with methyl chloride, yielding the methyl ether of cellulose. The fibrous reaction product is purified and ground to a fine, uniform powder. Methylcellulose is made using only methyl chloride. These are METHOCEL A brand products. For hypromellose products (METHOCEL E, F, and K brand products), propylene oxide is used in addition to methyl chloride to obtain hydroxypropyl substitution on the anhydroglucose units. This substituent group, -OCH2CH(OH)-CH3, contains a secondary hydroxyl on the number two carbon and may also be considered to form a propylene glycol ether of cellulose. These products possess varying ratios of hydroxypropyl and methyl substitution, a factor which influences organic solubility and the thermal gelation temperature of aqueous solutions. Methylcellulose - METHOCEL A Products
Hydroxypropyl Methylcellulose - METHOCEL E, F, K, and 40- Series products
There are also special-grade METHOCEL products available that have been formulated to meet the requirements of specific industries. Degree of SubstitutionAll METHOCEL food grade gums meet Food Chemicals Codex IV specifications. METHOCEL A food grade products (methylcellulose) comply as direct food additives under 21 CFR§182.1480 (GRAS). The use of METHOCEL E, F, and K food grade products (hydroxypropyl methylcellulose) is cleared under 21 CFR§172.874 in all foods which do not provide for their use.
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