Sodium Carboxymethyl Cellulose (CMC) is a polymer compound widely used in many industries such as food, medicine, cosmetics, textiles, paper, and oil drilling. It is obtained by chemical modification of cellulose. Its structural characteristics are that some hydroxyl groups in the cellulose molecules are replaced by carboxymethyl groups (–CH2COOH) and combined with sodium ions to form water-soluble sodium salts.

1. Chemical structure and properties

The chemical formula of sodium carboxymethyl cellulose is (C6H7O2(OH)2CH2COONa)n, which has certain solubility and water absorption. Its basic structure is a linear structure composed of cellulose monomers-glucose molecules. After chemical modification, some or all of the hydroxyl groups on the cellulose molecules are replaced by carboxymethyl groups to form water-soluble molecules with negative charges. Specifically, the molecular chain of sodium carboxymethyl cellulose contains a large number of carboxymethyl groups (–CH2COOH), which can interact with water molecules, giving it good solubility and viscosity characteristics.

CMC has the following basic properties:

Water solubility: Sodium carboxymethyl cellulose can be quickly dissolved in water to form a uniform colloidal solution.

Viscosity: CMC aqueous solution has a high viscosity, and the viscosity is related to its molecular weight and solution concentration.

Stability: CMC has good stability to acid, alkali and high temperature, but in a strong acid or alkali environment, the stability of CMC will decrease.

Adjustability: By adjusting the molecular weight and degree of substitution of CMC, its physical and chemical properties can be precisely controlled.

2. Preparation method

Sodium carboxymethyl cellulose is usually prepared by reacting cellulose and sodium chloroacetate in an alkaline environment. The specific steps are as follows:

Pretreatment of cellulose: First, cellulose (such as cotton fiber) is washed to remove impurities.

Alkalinization reaction: The pretreated cellulose is reacted with sodium hydroxide solution to separate the hydroxyl part in the cellulose molecule to form an active cellulose sodium salt.

Substitution reaction: Under alkaline conditions, sodium chloroacetate is added, and sodium chloroacetate reacts with sodium cellulose, so that the hydroxyl groups on the cellulose molecules are replaced by carboxymethyl groups.
Washing and drying: After the reaction is completed, the product is washed with water to remove impurities, and finally purified sodium carboxymethyl cellulose is obtained.

3. Application fields

Due to its good water solubility, thickening and stability, sodium carboxymethyl cellulose is widely used in the following fields:

Food industry: as a thickener, stabilizer, emulsifier, gelling agent, etc. It is commonly found in foods such as ice cream, jelly, seasoning, instant soup, etc. Its main function is to improve the taste of food, extend the shelf life and increase the consistency.

Pharmaceutical industry: as a binder, sustained-release agent, suspending agent and thickener for drugs, it is used in tablets, capsules, oral liquids, topical ointments and other preparations. In addition, CMC is also used as a hemostatic material for surgery and dental materials.

Cosmetic industry: used in the production of lotions, creams, shampoos, toothpastes and other products as a thickener and stabilizer. It can adjust the viscosity of the product and enhance the user experience.

Papermaking industry: As a surface treatment agent for paper, CMC can improve the strength, water resistance and printability of paper and reduce dust on the surface of paper.

Oil drilling: During oil drilling, CMC is used in drilling fluid to thicken and stabilize drilling fluid, help remove rock cuttings around the drill bit and stabilize the well wall.

Textile industry: As a dye dispersant and printing paste additive, CMC can improve the dyeing uniformity and quality of textiles.

4. Safety and environmental impact

Sodium carboxymethyl cellulose is generally considered safe, and its use in food and medicine has been approved by the International Food Additives Codex and relevant regulations of many countries. It is non-toxic to the human body and will not have a significant impact on the ecological environment, so it is widely used.

However, although CMC itself is environmentally friendly, its production process may involve the use of some chemical reagents and wastewater treatment issues. Therefore, it is necessary to pay attention to environmental protection measures during the production process to reduce the emission of harmful substances.

Sodium carboxymethyl cellulose is a widely used and multifunctional polymer material. Its thickening, stabilizing and gelling properties make it important for many industries. From food, medicine to industry, CMC plays an important role. With the continuous advancement of technology in the future, the application field of CMC may be further expanded.