CHEMISTRY OF CMC

Cellulose is a natural polymer universally found in the vegetables materials like wood, cotton. 
The cellulose molecule is made of several hundred anhydrous glucose units linked together by: 1,4-ß-glycosidic bonds.

Cellulose is therefore a partially crystalline and partially amorphous solid insoluble in water and in most of the organic solvents. 

Carboxy methyl cellulose, or CMC, is formed by replacing one or more of three reactive hydroxyl groups present in each glucose unit of cellulose. 

CMC CHEMICAL STRUCTURE

CELLULOSE  R = - H  CMC R = - H        - CH2COONa

The etherification steps can be summarised as following:

The first step is the treatment of the cellulose with caustic to obtain a reaction substrate which is sufficiently swollen and accessible to the reactant.

The second step is represented by the etherification reaction between the alkali-cellulose substrate and mono chloroacetic acid (MCA) with consequent formation of sodium chloride as by-product. The third step is a side reaction that occurs to form sodium glycolate.

After the reaction step the unrequited by-product salts are removed by treatment and an high degree of purity CMC is obtained.

Varying the number of substitutive carboxylic derivative on the free hydroxyl groups of glucose (degree of substitution DS) a wide range of CMC grades are obtained providing numerous levels of viscosity and consistency.

Moreover the chemical treatment described above, converts Cellulose, insoluble in water, into the soluble carboxy methyl cellulose derivative. 
CMC is readily soluble in either hot or cold water, but due to its high water binding capacity CMC should be added very slowly to water under continuous and vigorous mechanical stirring to prevent the possibility of agglomeration.

It is physiologically inert, chemically stable, odourless and tasteless and it acts a thickening, binding, suspending, film-forming, protective colloid, as well as stabilising agent.