Sodium carboxymethyl cellulose is widely used in industry, pharmaceuticals and food production. This compound is made on the basis of wood and is a biologically inert material, that is, it does not participate in physiological processes. Due to the special properties of solutions with this component, it is possible to regulate the viscosity of substances and other technical parameters.
Description
Sodium carboxymethylcellulose (CMC) is the sodium s alt of cellulose glycolic acid. The chemical name of the compound according to the IUPAC nomenclature: poly-1, 4-β-O-carboxymethyl-D-pyranosyl-D-glycopyranose sodium.
Empirical formula of sodium carboxymethylcellulose technical: [C6H7 O2 (OH)3-x (OCH2 COONa)x] . In this expression, x is the degree of substitution for CH2-COOH groups, and n is the degree of polymerization.
The structural formula is shown in the figure below.
Properties
In appearance, technical sodium carboxymethyl cellulose is a powdery, fine-grained or odorless fibrous material with a bulk density of 400–800 kg/m3.
Na-CMC has the following characteristics:
-
molecular weight of compound – [236];
- dissolves quickly in both hot and cold water, insoluble in mineral oils and organic liquids;
- forms films resistant to oils, greases and organic solvents;
- increases the viscosity of solutions and makes them thixotropic - with an increase in mechanical action, a decrease in flow resistance occurs;
- absorbs water vapor from the air well, so the substance must be stored in dry rooms (under normal conditions it contains 9-11% moisture);
- compound is non-toxic, non-explosive, but can ignite in a dusty state (self-ignition temperature +212 °C);
- exhibits the properties of an anionic polyelectrolyte in solutions.
When the temperature changes, the laboratory viscosity of sodium carboxymethyl cellulose in solutions varies greatly. This is one of the most important characteristics of this compound, which determines the scope of its application. A high degree of polymerization provides a high viscosity and vice versa. At pH<6 or greater than 9, reduced flow resistancedrops significantly. Therefore, this s alt is advisable to use in neutral and slightly alkaline environments. Viscosity changes under normal conditions are reversible.
Sodium carboxymethylcellulose also has chemical compatibility with many other substances (starch, gelatin, glycerin, water-soluble resins, latexes). When heated to temperatures above 200 °C, s alt decomposes to sodium carbonate.
The main factor influencing the characteristics of this compound is the degree of polymerization. Solubility, stability, mechanical properties and hygroscopicity depend on molecular weight. The substance is produced in seven grades according to the degree of polymerization and two grades according to the content of the main substance.
Receive
Sodium carboxymethyl cellulose has been commercially manufactured since 1946. CMC production now accounts for at least 47% of total cellulose ethers.
The main raw material for the synthesis of this compound is wood cellulose, the most common organic polymer. Its advantages are low price, biodegradability, lack of toxicity and ease of processing technology.
Sodium carboxymethyl cellulose is obtained by reacting alkali cellulose with C₂H₃ClO₂ (monochloroacetic acid) or its sodium s alt. In recent years, work has been underway to find new sources for the extraction of raw materials (flax, straw, cereals, jute, sisal and others), as the demand for this material is constantly growing. Washing is used to improve the quality of the substance.of finished s alt from impurities, cellulose is activated or exposed to microwave radiation.
Sodium carboxymethyl cellulose: industrial applications
Due to its special properties, CMC is used for the following purposes:
- thickening of various formulations, gelatinization;
- binding fine particles in paint films (film formation);
- use as a water-retaining agent;
- stabilization of physical and chemical properties;
- increasing the viscosity of solutions to evenly distribute their ingredients;
- rheological modification;
- prevention of coagulation (adhesion of suspended particles).
One of the largest users of sodium carboxymethyl cellulose is the oil and gas industry, where the compound is used to improve the performance of drilling fluids.
The substance is also used in the manufacture of the following technical products:
- detergents;
-
printing products;
- mortars for construction finishing works;
- adhesives, sizing materials;
- dry building mixes, cement (to prevent cracking);
- paint materials;
- lubricating-coolants;
- medium for hardening rails;
- coating welding electrodes and others.
Sodium carboxymethyl cellulose is used to stabilize foam in fire fighting, the food industry, in the manufacture of perfumes and ceramics. Technicians estimate that this compound is used in more than 200 fields of engineering and medicine.
Protective coatings
One of the promising directions is the introduction of nanoparticles synthesized from CMC suspensions as additives-stabilizers in corrosion-resistant coatings. This allows you to change the structure of polymers, increase adhesion with the base material, improve the physical and mechanical properties of the coating without a significant increase in the cost of the composition. Nanoparticles form microclusters, making it possible to obtain composites with valuable technical properties.
The advantage of this additive is also that it is environmentally friendly and biodegradable. Its production does not require the use of organic solvents, therefore, the risk of pollution of wastewater and the atmosphere is reduced, there is no need to use specialized equipment and a high temperature range.
Dietary supplement
Carboxymethylcellulose sodium is used as a food additive (E-466) at a concentration of not more than 8 g/kg. The substance performs several functions in products:
- thickening;
- stabilizing properties;
- holdmoisture;
- extension of shelf life;
- preservation of dietary fiber after defrosting.
Most often this compound is added to fast food, ice cream, confectionery, marmalade, jelly, processed cheese, margarine, yogurt, canned fish.
Medicine and cosmetology
In the pharmaceutical industry, sodium carboxymethyl cellulose is used in drug groups such as:
- eye drops, solutions for injections - to prolong the therapeutic effect;
- tablet shells - to regulate the release of the active substance;
- emulsions, gels and ointments - to stabilize formative substances;
- antacids - as ion-exchange and complexing components.
In the production of hygiene and cosmetic products, this compound is used as part of toothpastes, shampoos, shaving and shower gels, and creams. The main function is to stabilize the properties and improve the texture.
Effect on humans and animals
Sodium carboxymethylcellulose is hypoallergenic, biologically inactive, does not have a carcinogenic effect and does not impair the reproductive function of living organisms. The use as food additives in a safe concentration does not lead to negative consequences. The dust of the compound may cause irritation if it enters the eyes and upper respiratory tract (MACaerosol is 10 mg/m3).
Films containing sodium s alt release the active ingredient in the alkaline environment of the intestine. The compound is excreted from the human body and animals unchanged. In water bodies for economic purposes, the substance belongs to the third hazard class (moderately hazardous). MPC in this case is 2 mg/l.
