Sodium carboxymethyl cellulose (CMC) is an anionic, linear, water-soluble cellulose ether, which is a derivative of natural cellulose and chloroacetic acid by chemical modification. Its aqueous solution has the functions of thickening, film forming, bonding, water retention, colloid protection, emulsification and suspension. It can be used as flocculant, chelating agent, emulsifier, thickener, water retaining agent, sizing agent, film forming material, etc. It is widely used in food, medicine, electronics, pesticide, leather, plastic, printing, ceramics, daily chemical industry and other fields.
Sodium carboxymethyl cellulose is generally a powdery solid, sometimes granular or fibrous, the color is white or light yellow, no special smell, is a macromolecular chemical substance, has a strong hygroscopicity, can be dissolved in water, in water to form a high transparency viscous solution. Insoluble in general organic solutions, such as ethanol, ether, chloroform and benzene, but can be dissolved in water, directly dissolved in water speed 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 hygroscopicity, in a dry environment, can be stored for a long time.
1. production process
1. Water-media method
The water coal method is an early production preparation process in the industrial preparation of sodium carboxymethyl cellulose. In this process, the alkali cellulose and the etherifying agent are reacted in an aqueous solution containing free oxygen ions, and water is used as the reaction medium during the reaction, and no organic solvent is contained.
2. Solvent method
The solvent method is the organic solvent method, which is a production process developed on the basis of the water-borne method to replace water with an organic solvent as a reaction medium. 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 slurping method. The amount of the organic solvent used in the slurries method is much larger than that in the kneading method, the amount of the organic solvent used in the kneading method is the ratio of the amount of the cellulose to the weight of the volume, and the amount of the organic solvent used in the slurries method is the ratio of the amount of the cellulose to the weight of the volume. When preparing sodium carboxymethyl cellulose by the slurping method, the reaction solid is in a slurried or suspended state in the system, so the slurping method is also called suspension method.
3. Slurry method
The slurry process is the latest process for the production of sodium carboxymethyl cellulose. The slurry method can not only produce high purity sodium carboxymethyl cellulose, but also prepare sodium carboxymethyl cellulose with high degree of substitution and uniform substitution. The production process of the slurry method is roughly as follows: the cotton pulp that has been ground into powder is sent to a vertical alkalization machine with isopropanol, and the sodium hydroxide solution added while stirring is alkalized, and the alkalization temperature is about 20 ℃. After alkalization, the material is transported to the vertical etherification machine by pump, and the isopropanol solution of chloroacetic acid is added, and the etherification temperature is about 65 ℃. According to the use and quality requirements of the specific product, the process parameters such as alkalization concentration, alkalization time, amount of etherification agent and etherification time can be adjusted.
2. scope of application
CMC is not only a good emulsifying stabilizer and thickening agent in food applications, but also has excellent freezing and melting stability, and can improve the flavor of the product and extend the storage time.
In detergents, CMC can be used as an anti-soil redeposition agent, especially for hydrophobic synthetic fiber fabrics, which is significantly better than carboxymethyl fiber.
In oil drilling, it can be used to protect oil wells as mud stabilizer and water retaining agent. The dosage of each oil well is 2~3t for shallow wells and 5~6t for deep wells.
In the textile industry as a sizing agent, printing and dyeing pulp thickening agent, textile printing and stiff finishing. Used for sizing agent can improve the solubility and viscosity change, and easy to desizing; As a stiff finishing agent, its dosage is more than 95%; Used for sizing agent, the strength of the size film and the bending performance are obviously improved. The composite membrane composed of regenerated fibroin and carboxymethyl cellulose is used as the substrate for immobilizing glucose oxidase, and the glucose biosensor made of immobilized glucose oxidase and ferrocene carboxylate (or 7,7,8,8-tetracyanodimethylbenzoquinone, TCNQ) has high sensitivity and stability. The results show that when the concentration of CMC solution is about 1.0%(W/V), the chromatographic performance of the thin-layer plate is prepared, and the thin-layer plate coated under the optimized conditions has appropriate layer strength, which is suitable for various sample adding techniques and is convenient to operate. CMC is adhesive to most fibers, which can improve the bonding between fibers, and the stability of its viscosity ensures the uniformity of sizing, thereby improving the efficiency of weaving. It can also be used as a finishing agent for textiles, especially permanent anti-wrinkle finishing, to bring durability changes to the fabric.
Used as an anti-settling agent, emulsifier, dispersant, leveling agent, adhesive, can make the coating solids evenly distributed in the solvent, so that the coating is not layered for a long time, but also a large number of applications in putty.
Used as a flocculant in the removal of calcium ions more effective than sodium gluconate, used as a cation exchange, the exchange capacity of up to 1.6 ml/g.
Used as a paper sizing agent in the paper industry, it can significantly improve the dry strength and wet strength of paper and oil resistance, ink absorption and water resistance.
It is used as a hydrosol in cosmetics and as a thickener in toothpaste, and its dosage is about 5%.