Sodium carboxymethyl cellulose (CMC) is an anionic, straight chain, water-soluble cellulose ether, a derivative of natural cellulose and chloroacetic acid by chemical modification. Its aqueous solution has the functions of thickening, film forming, bonding, water retention, colloidal protection, emulsification and suspension, and can be used as flocculant, chelating agent, emulsifier, thickener, water retaining agent, sizing agent, film forming material, etc., which is widely used in food, medicine, electronics, pesticides, leather, plastics, printing, ceramics, daily chemical industry and other fields.
Sodium carboxymethyl cellulose is generally a powdered solid, sometimes granular or fibrous, white or light yellow in color, no special odor, is a macromolecular chemical substance, has a strong wettability, can dissolve in water, in water to form a viscous solution with high transparency. Insoluble in general organic solutions, such as ethanol, ether, chloroform and benzene, but can be dissolved in water, directly dissolved in water is relatively slow, but the solubility is still very large, and the aqueous solution has a certain viscosity. Solid in the general environment is more stable, because it has a certain water absorption and humidity, in a dry environment, can be preserved for a long time.
① Production process
1. Water medium method
The water-coal process is a relatively early production process in the industrial preparation of sodium carboxymethyl cellulose. In this process, the alkali cellulose and etherifying agent react in an aqueous solution containing free oxygen oxide ions, and water is used as the reaction medium in the reaction process, without organic solvents.
2. Solvent method
Solvent method is organic solvent method, which is a production process developed on the basis of water medium method to replace water with organic solvent as a reaction medium. A process of alkalization and etherification of alkali cellulose and monochloroacetic acid in an organic solvent. According to the amount of reaction medium, it can be divided into kneading method and swimming slurry method. The amount of organic solvent used in the pulping method is much larger than that of the kneading method, and the amount of organic solvent used in the kneading method is the ratio of the volume weight of the cellulose amount, while the amount of organic solvent used in the pulping method is the ratio of the volume weight of the cellulose amount. When sodium carboxymethyl cellulose is prepared by swimming slurry method, the reaction solid is in a slurry or suspension state in the system, so the swimming slurry method is also called the suspension method.