Two-step synthesis and characterization of carboxymethylcellulose from rayon grade wood pulp and cotton linter

Carboxymethylcellulose (CMC) was prepared from bleached cellulose pulps obtained from the wood of Eucalyptus globulus (Eup), Picea smithiana (Picp) and cotton linter pulp (CLP), which are used for viscose rayon fiber. The chemical composition of cellulose pulps (alpha-cellulose, hemicellulose, moisture, ash, intrinsic viscosity and color brightness) was also determined. The dried cellulose was alkalized using 40% NaOH at 25 degrees C for 1.5 hour. Sodium monochloroacetic acid (MCA) from 5-7 g per 5 g cellulose was added to the slurry and the temperature was adjusted to 55 degrees C for 3.5 h. The pulps carboxymethylated by one successive reaction step, were again etherified, using monochloroacetic acid as an etherifying agent and isopropyl alcohol as a solvent. The best result of etherification was obtained in the case of cotton linter pulp. The degree of substitution (DS) of CIVIC was found to be dependent upon the source of cellulose, but generally it was high in the case of cotton linter pulp. The second etherification reaction step increased the DS up to 1.9, by increasing the concentration of MCA, which in turn improved the CIVIC solubility in water. Qualitative and quantitave analysis of CMC were carried out to determine the moisture, ash, sodium chloride, degree of substitution, purity and viscosity of carboxymethylcellulose. This investigation helped to find the proper conditions for the etherification of rayon grade pulps and showed that high quality CMC can be prepared from cotton linter pulp by two consecutive etherification reactions.