Carboxymethylcellulose Sodium Powder for Pharmaceutical Excipients Industry

Sodium carboxymethyl cellulose crosslinked

Cross-linked carboxymethyl cellulose sodium (Croscamellose sodium) is a kind of sodium carboxymethyl cellulose in certain conditions for cross-linking reaction and become an insoluble in water and swelling to the original volume of 4~8 times the cross-linked polymer, commonly used as tablets, capsules disintegration agent.

Some scholars have developed a thickening agent suitable for the characteristics of tomato paste by cross-linking carboxymethyl cellulose technology, and established a cross-linking reaction test of carboxymethyl cellulose with propylene oxide as the cross-linking agent. The results showed that the cmc-na was suitable for the thickening of tomato paste.

Preparation of sodium carboxymethyl cellulose

Cmc-na was prepared from cellulose by a two-step method. First is the process of cellulose alkalization. Cellulose reacts with sodium hydroxide to produce alkali cellulose, and then alkali cellulose reacts with chloroacetic acid to produce cmc-na, which is called etherification.

The reaction system must be basic. The process belongs to Williamson ether synthesis. The reaction mechanism is nucleophilic substitution. The reaction system is alkaline, which is accompanied by some side reactions in the presence of water, such as the generation of by-products such as sodium hydroxylacetate and hydroxylacetic acid. Due to the existence of side reactions, the consumption of alkali and etherifying agent will be increased, thus reducing the etherifying efficiency. At the same time, sodium oxyacetic acid, oxyacetic acid and more salt impurities will be generated in the side reaction, resulting in reduced purity and performance of the product. In order to suppress side reactions, rational use of alkali, control of water system dosage, concentration of alkali and stirring mode should be taken into account for the purpose of full alkalinization. At the same time, requirements for viscosity and substitution degree of products should also be taken into account. Factors such as stirring speed and temperature control should be taken into comprehensive consideration to increase etherification rate and inhibit side reactions.

According to the different etherified media, the industrial production of cmi-na can be divided into two categories: water-medium method and solvent method. The method using water as the reaction medium is called the water-medium method and is used to produce cmc-na at medium and low alkaline levels. The method using organic solvent as reaction medium, called solvent method, is suitable for the production of medium and high grade cmc-na. These two reactions are carried out in kneading machines, which belong to kneading process and are the main methods of cmc-na production at present.

Water medium method

Water-based process is an early industrial process in which alkali cellulose and etherifying agent react under the conditions of free alkali and water. In the process of alkalization and etherification, there is no organic medium in the system. The equipment of water - borne method is simple, low investment and low cost. The disadvantage is the lack of a large number of liquid medium, the heat generated by the reaction makes the temperature rise, speeding up the speed of side reactions, resulting in low etherification efficiency, poor product quality and so on. This method is used to prepare medium and low grade cmc-na products, such as detergent and textile sizing agent.