Carboxymethyl cellulose CMC is an important cellulose gum, a polyanionic cellulose compound with good water solubility obtained by chemically modifying natural fibers. It is easily soluble in hot and cold water. It has very unusual and valuable physical and chemical properties, such as thickening and emulsifying properties, and is not perishable and physiologically harmless. It is a widely used natural polymer derivative.
The manufacturing process and reaction principle of carboxymethyl cellulose CMC: The main chemical reaction of carboxymethyl cellulose sodium is the alkalization reaction of cellulose and alkali to form alkali cellulose and the etherification reaction of alkali cellulose and monochloroacetic acid. Manufacturing process steps: mixing of raw materials (refined cotton, wood pulp, chloroacetic acid, caustic soda, alcohol, etc.) - alkalization - etherification - washing and neutralization - pressing - washing - raking - drying - Crush - Pack. According to different etherification media, the industrial production of carboxymethyl cellulose CMC can be divided into two categories: water-based method and solvent-based method. The method using water as the reaction medium is called the water medium method, which is used to produce alkaline medium and low grade sodium carboxymethyl cellulose. The method of using organic solvent as the reaction medium is called solvent method, which is suitable for the production of medium and high-grade sodium carboxymethyl cellulose. These two reactions are all carried out in a kneader, which belongs to the kneading process and is currently the main method for producing sodium carboxymethyl cellulose.
Sodium carboxymethyl cellulose is a white to light yellow powder, granular or fibrous substance with strong hygroscopicity and is easily soluble in water. When it is neutral or alkaline, the solution is a high-viscosity liquid. Stable to medicines, light and heat. Sodium carboxymethyl cellulose is the sodium salt of cellulose carboxymethyl ether, which belongs to anionic cellulose ether. White or milky white fibrous powder or granule, density 0.5-0.7g/cm³, almost odorless, tasteless, hygroscopic. Easily dispersed in water to form a transparent colloidal solution, insoluble in alcohol and other organic solvents. The pH value of 1% sodium carboxymethyl cellulose aqueous solution is 6.5-8.5. When the pH value is above 10 or below 5, the viscosity of the solution is significantly reduced, and the performance is best at pH=7.
CMC sodium carboxymethyl cellulose is thermally stable. When the temperature is lower than 20°C, the viscosity will rise sharply, but at 45°C, the change will slow down; heating above 80°C for a long time will modify the colloid, and the viscosity and performance will drop sharply. Sodium carboxymethyl cellulose is easily soluble in water and the solution is transparent. Very stable in alkaline solution, but easily hydrolyzed in case of acid. Precipitation occurs at pH 2-3 or multivalent metal salts (PbSO4, FeCl3, FeSO4, CuSO4, K2Cr2O7, AgNO3, and SnCl2, etc.).