What is CMC?
CMC is a water soluble cellulosic derivative. It has a high commercial value because it
• Reduces fluidity of water,
• Keeps the solids as suspension in aqueous environment,
• Is humectant,
• Forms film,
• Is adhesive and binding.
“Sodium Carboxymethylcellulose”, generally referred to as cellulose glycolate in the literature, is currently known as CMC. It is often used as its ‘’sodium salt’’, rather than ‘’Sodium Carboxymethyl Celluloseve’’, which has a very low commercial value.
CMC is the most commonly used derivative among water soluble cellulose derivatives. Effects of CMC were first discovered in Germany during the end of First World War when found that it enhanced the detergency in detergents. Inefficacy of oil acids during the First World War gave way to increase in and becoming widespread CMC production.
CMC’S Chemical Structure
Cellulose is a high linear polymer and composed of clustered “Cellobiose” unites. Each “Cellobiose” unit is composed of two “anhydroglucose” units. Repeated anhydroglucose units are bond by B-1.4 glycoside bond.
(n) in the structure of cellulose molecule is the number of anhydroglucose units bond to each other by an oxygen bond. This number is equal to polymerization grade of cellulose. Polymerization Degree is the most important factor in viscosity of CMC to be derived.
There are 3 hydroxyl groups in the anhydroglucose units and cellulose achieves its chemical activity with these hydroxyl groups. (However the hydroxyl groups in 2, 3 and 6 have been found to be 2: 1: 2,5 in terms of reactivity.)
Cellulose becomes alkali with Na OH (sodium hydroxide) and is etherilied in a controlled reaction with MCA (Mono Chlorine Acetic Acid) or SMCA (Sodium Mono Chlorine Acetate) to form CMC. Different types of CMC can be achieved by some factors such as reaction grades of hydroxyl groups and length of polymer chain.
R(cell) (OH)3 + CLCH2COONO + NaOH ―――――> R(cell) (OH)2 (OCH2 COONa) + NaCL + H2O
In generation of CMC, some portion of NaOH (sodium hydroxide) produces sodium glycolate, a by product, with MCA depending on the reaction.
2NaOH + CH2CLCOOH ―――――> HOCH2COONa+ H2O
Despite various different techniques used, delay reaction, a principle for CMC production, has not undergone a significant change since the first production of CMC.