Abstract: The production of carboxymethylcellulose (CMC) with a substitution degree of up to 1.72 was achieved through a new approach of lowering crystallinity and activating pretreatment. The experiments sought to examine the effects of water amount, reaction temperature, reaction time and NaOH concentration on the degree of substitution (DS) of CMC, as well as test the performance of the product through deep analysis of the alkali concentration conducted by SEM and XRD. The results showed that the appropriate amount of water used should be 8～10mL, the proper reaction temperature should be 65～75℃, and the recommended reaction time should be 3h. The experiments also demonstrated that the cellulose would swell after the treatment of high concentration of alkali: higher concentration of NaOH would lead to more swollen cellulose, lower degree of crystallinity, more active reaction as well as higher DS. Thus, the optimal concentration of the alkali should be 500～600 g/L. Moreover, CMC with a solid content of 3% had a viscosity of as high as 35000 mPa?s when the viscosimeter was running at 30r/min. The viscosity of such CMC solution varied little when the pH was 6～10, and the solution appeared to have better stability under different pH conditions and in hard water. After this CMC solution was preserved for two weeks, its viscosity remained almost the same, which indicated its stability during storage.

Key words: activation, high degree of substitution, carboxymethylcellulose, viscosity, swelling