Carboxymethyl cellulose is a product of carboxymethyl group substitution of cellulose. According to its molecular weight or degree of substitution, it can be a completely soluble or insoluble polymer. The latter can be used as a weak acid cation exchanger to separate neutral or basic proteins. Carboxymethyl cellulose (CMC) can form colloid, solution, adhesive, thickening, flow, emulsifying dispersion, excipient, water retention, protective colloid, film forming, acid resistance, salt resistance, suspension and other characteristics of high viscosity, and is physiologically harmless, so it is obtained in food, medicine, daily chemical, petroleum, paper making, textile, construction and other fields. Widely used.