Production
CMC production has started on industrial scale mid of the 20th century and has risen nowadays to a production of over 450,000 tons per year. The production itself is preferably done in batch processes either in solution of primary alcohols or in semi-dry processes.
Synthesis of CMC
CMC is generally produced in a two-step-process:
- Alkalisation: cellulose is treated with sodium hydroxide (NaOH) in order to receive alkali cellulose, which is reactive and accessible to chemical reactions.
- Etherification: sodium monochloro acetic acid (Cl-CH2-COOH) reacts with alkali cellulose to form the final product sodium carboxymethyl cellulose (NaCMC or in short CMC).
As by-product of the reaction, sodium chloride (NaCl) is obtained. Moreover, the hydrolysis of the etherification agent leads to sodium glycolate (HO-CH2-COONa).
Manufacturing of CMC
The manufacturing of CMC is easy and can be done in a chemical process under atmospheric pressure and reasonable low temperatures up to 80°C.
The process starts with the grinding of cellulose. The choice of the cellulose determines the parameters of the end products in a significant way.
In the first reaction step cellulose is activated with caustic soda. The process is known as mercerisation and requires a careful and homogenous conversion to alkali cellulose in order to guarantee an uniform etherification.
The main reaction step is the etherification itself: alkali cellulose reacts with monochloro acetic acid (MCA) or its sodium salt (NaMCA) in an exothermic reaction to CMC. The extent of etherification defines the degree of substitution (DS).
The direct product received from the etherification process is technical grade CMC containing its reaction salts sodium chloride and sodium glycolate.
Purified CMC is obtained via an alcoholic washing process in order to reduce the salt content.
The further processing involves physical treatment of drying, milling, and sieving, determining the final layout of the product.
Finally, CMC is bagged either in big bags or different bag sizes, including kraft paper as well as water soluble bags.
The finished product needs to be carefully analysed, assessed and classified to guarantee a high and consistent quality.
CMC characteristics
The typical characteristics of technical and purified CMC grades are depicted on the right side.
Please note our products are available in granular or powder formulation.
