Carboxymethylation of wood residues : Effect of etherification process variables

Abstract

A study of carboxymethylation of wood residues from <i>Terminalia superba</i> (ash content 0.01.8; organic extractives, 2.14;holocellulose, 76.45; α-cellulose, 55.87 % ; DP331.86) was carried out using various alkali/cellulose ratios in various organic solvent mediums (benzene, methylene chloride) and organic solvent mixtures (benzene/isopropanol, and acetonitrile/ acetone). The extent of etherification was found to be dependent on the strength of the aqueous alkali solution and was the highest (DS, 0.431) for cellulosic materials impregnated with CuSO₄prior to alkali treatment. It was found that an increase in the time of alkali-treatment from 0.5-24 h was accompanied by marked changes, of up to 44%, in the degree of substitution. The lowest DS (0.315) was obtained for carboxymethylation in methylene chloride and in acetonitrile/acetone (1:1) mixture and the highest (0.438) in benzene<span style="font-size:12.0pt;font-family:Arial; mso-bidi-font-family:" times="" new="" roman""="">/isopropanol (1:1) mixture. The viscosity of dilute aqueous solutions of carboxymethyl cellulose prepared, was measured at low shear rate (200 s^-l) at various temperatures, in the presence of mono-, di-, and trivalent cations; in order to determine the reduction in viscosity with time.

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