羧甲基壳聚糖制备中的溶剂影响及精制方法研究

Effect of solvents on preparation of carboxymethyl Chitosan and its purification

研究了有机溶剂中两步法制取羧甲基壳聚糖的反应过程。采用有机溶剂溶胀、氢氧化钠碱化、氯乙酸改性、乙醇溶析等步骤制备了高取代度羧甲基壳聚糖。考察了碱用量、氯乙酸用量和有机溶剂类型三个因素对羧甲基壳聚糖取代度的影响。通过比较二甲基亚砜、异丙醇、丙酮和乙醇四种有机溶剂中壳聚糖羧甲基化取代度变化规律,分析了羧甲基化的机理。实验结果表明,以极性非质子型二甲基亚砜为溶剂,壳聚糖5g,氢氧化钠22.5g,氯乙酸25g,溶胀时间1h,碱化温度30℃,碱化时间2h,醚化温度60℃,醚化时间4h,合成的羧甲基壳聚糖取代度高达1.87。实验还发现,采用等电点结合溶析结晶精制方法可制得水溶性好且易于干燥的颗粒状羧甲基壳聚糖。

Carboxymethylation reaction of chitosan using two-step process in an organic solvent was studied.A carboxymethyl chitosan of high substitution degree was prepared by the swelling of chitosan with organic solvent,alkalization with sodium hydroxide solution,modification with chloroacetic acid,and dilution crystallization with ethanol.Effects of alkali and chloroacetic acid amounts,different organic solvents on the substitution degree of carboxymethyl chitosan were investigated,focusing on the effect of four organic solvents,DMSO,isopropyl alcohol,acetone and ethanol.Carboxmethylation reaction mechanism was analyzed.Experimental results indicated that under the conditions of solvent DMSO,chitosan 5g,sodium hydroxide 22.5g,chloroacetic acid 25g,swelling time 1h,alkalization temperature of 30 ℃,alkalization time 2h,etherification temperature 60℃ and etherification time of 4h,substitution degree of carboxymethyl chitosan was up to 1.87.An easily soluble,drying and granular carboxymethyl chitosan was obtained by the combination of dilution crystallization and isoelectric point purification.