Effect of hemicellulose extraction on the solution properties of cellulose carbamate in NaOH/ZnO aqueous system

Abstract

Abstract Hemicellulose removal from bleached bamboo pulp is the key to produce of qualified dissolving pulps. In this work, the alkali/urea aqueous solution was applied to improve the hemicellulose removal efficiency of bleached bamboo pulp. The removal rate of hemicellulose was affected by urea usage, time and temperature. The removal rate of hemicellulose achieved 70.14% in 6 wt% NaOH/1 wt% urea at 40°C for 30 min. After esterification by urea method of the pulp, the dissolution behavior of cellulose carbamate (CC) pulp with different DP, hemicellulose and N contents were studied, and the highest solubility was up to 97.7%. The effect of hemicellulose content on the stability and solubility of CC solution was subsequently analyzed by polarizing microscope and rheology. With a decrease of hemicellulose from 15.9, 8.60 to 5.70%, the gel temperature increased from 59.0, 69.0 to 73.4°C. The apparent gelation time increases from 5640 to 12120 s with the hemicellulose decreased from 15.9 to 8.60%, and HC-5.70 always keeps a liquid-state (G'' > G') until the test time reach 17000 s. The results showed that the removal hemicellulose, reduce DP and increasing esterification endow CC solution with higher solubility and stability.