Carboxymethyl cellulose (CMC) and sodium carboxymethyl cellulose (CMC-Na) are common compounds in the chemical industry and the food industry. They have certain differences and connections in structure, performance and use. This article will analyze in detail the properties, preparation methods, applications and importance of the two in different fields.
(1) Carboxymethyl cellulose (CMC)
1. Basic properties
Carboxymethyl cellulose (CMC) is a carboxymethylated derivative of cellulose and is an anionic linear polysaccharide. Its basic structure is that some hydroxyl groups (-OH) in the cellulose molecule are replaced by carboxymethyl groups (-CH₂-COOH), thereby changing the solubility and functional properties of cellulose. CMC is generally white to slightly yellow powder, odorless and tasteless, insoluble in organic solvents, but can absorb water to form a gel.
2. Preparation method
The preparation of CMC usually includes the following steps:
Alkalinization reaction: Mix cellulose with sodium hydroxide (NaOH) to convert the hydroxyl groups in cellulose into alkaline salts.
Etherification reaction: Alkalized cellulose reacts with chloroacetic acid (ClCH₂COOH) to generate carboxymethyl cellulose and sodium chloride (NaCl).
This process is usually carried out in water or ethanol solution, and the reaction temperature is controlled between 60℃-80℃. After the reaction is completed, the final CMC product is obtained through washing, filtering, drying and other steps.
3. Application fields
CMC is mainly used in the food industry, medicine, textile, papermaking and other fields. It has multiple functions such as thickening, stabilization, water retention and film formation. For example, in the food industry, CMC can be used as a thickener, stabilizer and emulsifier for ice cream, jam, yogurt and other products; in the pharmaceutical field, CMC is used as a binder, thickener and stabilizer for drugs; in the textile and papermaking industries, CMC is used as a slurry additive and surface sizing agent to improve the quality and stability of the product.
(2) Sodium carboxymethyl cellulose (CMC-Na)
1. Basic properties
Sodium carboxymethyl cellulose (CMC-Na) is the sodium salt form of carboxymethyl cellulose. Compared with CMC, CMC-Na has better water solubility. Its basic structure is that the carboxylmethyl groups in CMC are partially or completely converted into their sodium salts, that is, the hydrogen atoms on the carboxylmethyl groups are replaced by sodium ions (Na⁺). CMC-Na is usually white or slightly yellow powder or granules, easily soluble in water, and forms a viscous transparent solution.
2. Preparation method
The preparation method of CMC-Na is similar to that of CMC, and the main steps include:
Alkalinization reaction: cellulose is alkalized using sodium hydroxide (NaOH).
Etherification reaction: Alkalized cellulose is reacted with chloroacetic acid (ClCH₂COOH) to produce CMC.
Sodiumization reaction: CMC is converted into its sodium salt form by neutralization reaction in aqueous solution.
In this process, it is necessary to pay attention to controlling the reaction conditions, such as pH and temperature, to obtain CMC-Na products with optimal performance.
3. Application fields
The application fields of CMC-Na are very wide, covering many industries such as food, medicine, daily chemicals, and petroleum. In the food industry, CMC-Na is an important thickener, stabilizer and emulsifier, and is widely used in dairy products, juices, condiments, etc. In the pharmaceutical field, CMC-Na is used as an adhesive, gel and lubricant for tablets. In the daily chemical industry, CMC-Na is used in products such as toothpaste, shampoo, and conditioner, and has good thickening and stabilizing effects. In addition, in oil drilling, CMC-Na is used as a thickener and rheology regulator for drilling mud, which can improve the fluidity and stability of the mud.
(3) The difference and connection between CMC and CMC-Na
1. Structure and properties
The main difference between CMC and CMC-Na in molecular structure is that the carboxylmethyl group of CMC-Na exists partially or completely in the form of sodium salt. This structural difference makes CMC-Na show higher solubility and better stability in water. CMC is usually partially or completely carboxymethylated cellulose, while CMC-Na is the sodium salt form of this carboxymethyl cellulose.
2. Solubility and Uses
CMC has a certain solubility in water, but CMC-Na has better solubility and can form a stable viscous solution in water. Due to its better water solubility and ionization characteristics, CMC-Na exhibits better performance than CMC in many applications. For example, in the food industry, CMC-Na is widely used as a thickener and stabilizer due to its good water solubility and high viscosity, while CMC is more often used in applications that do not require high water solubility.
3. Preparation process
Although the preparation processes of the two are roughly similar, the final product of CMC production is carboxymethyl cellulose, while CMC-Na further converts carboxymethyl cellulose into its sodium salt form through a neutralization reaction during the production process. This conversion gives CMC-Na better performance in some special applications, such as better performance in applications requiring water solubility and electrolyte stability.
Carboxymethyl cellulose (CMC) and sodium carboxymethyl cellulose (CMC-Na) are two cellulose derivatives with important industrial value. Although they are similar in structure, CMC-Na shows higher water solubility and stability due to the conversion of some or all of the carboxyl groups in CMC-Na into sodium salt. This difference makes CMC and CMC-Na have their own unique advantages and functions in different industrial applications. Understanding and correctly applying these two substances can help optimize product performance and improve production efficiency in many fields such as food, medicine, and chemical industry.