Preparation of regenerated cellulose fiber via carbonation. I. Carbonation and dissolution in an aqueous NaOH solution
Cellulose carbonate was prepared by the reaction of cellulose pulp and CO2 with treatment reagents, such as aqueous ZnCl2 (20–40 wt%) solution, acetone or ethyl acetate, at −5–0°C and 30–40 bar (CO2) for 2 hr. Among the treatment reagents, ethyl acetate was the most effective. Cellulose carbonate was dissolved in 10% sodium hydroxide solution containing zinc oxide up to 3 wt% at −5–0°C. Intrinsic viscosities of raw cellulose and cellulose carbonate were measured with an Ubbelohde viscometer using 0.5 M cupriethylenediamine hydroxide (cuen) as a solvent at 20°C according to ASTM D1795 method. The molecular weight of cellulose was rarely changed by carbonation. Solubility of cellulose carbonate was tested by optical microscopic observation, UV absorbance and viscosity measurement. Phase diagram of cellulose carbonate was obtained by combining the results of solubility evaluation. Maximum concentration of cellulose carbonate for soluble zone was increased with increasing zinc oxide content. Cellulose carbonate solution in good soluble zone was transparent and showed the lowest absorbance and the highest viscosity. The cellulose carbonate and its solution were stable in refrigerator (−5°C and atmospheric pressure).
KeywordsCellulose carbonate CO2 Sodium hydroxide solution Solubility Phase diagram
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