NMMO/H_2O均相体系制备羧甲基纤维素的研究

A homogeneous technology to prepare carboxymethyl cellulose in NMMO / H_2O

采用N-甲基氧化吗啉（NMMO）/H_2O的纤维素均相溶解体系对羧甲基纤维素（CMC）的制备进行研究。通过~1H-NMR方法测定了羧甲基在脱水葡萄糖单元（AGU）上的取代情况,研究了醚化剂摩尔比、醚化时间及醚化温度对取代度（DS）和取代基分布的影响。结果表明,较优的NMMO/H2O均相羧甲基化工艺条件为：醚化剂摩尔比为10∶1,醚化时间为120 min,醚化温度为90℃,在此条件下取代度为1.26;羧甲基取代顺序表现为C（6）〉C（2）〉C（3）,增加醚化剂用量和延长醚化时间可以促进C（2）和C（6）位的取代,提高反应温度更有利于提高C（6）的取代。与工业淤浆工艺所得的产品进行对比发现,NMMO/H2O均相体系制备的羧甲基纤维素产品具有更高的取代度和均匀的取代基分布。

NMMO / H_2O solution is an ideal solvent for dissolving cellulose to get a homogeneous liquid. It is used as a homogeneous reaction medium to prepare the carboxymethyl cellulose（ CMC） in this study. The degree of substitution（ DS） and the distribution of substituents on anhydroglucose（ AGU） are characterized by ~1H-NMR. The effects of the operation parameters,including dosage of monochloroacetate acid,etherification time and etherification temperature,on the degree substitution（ DS） and distribution of substituents are systematically investigated. The optimum conditions are shown as follows： 10 ∶ 1 molar ratio of monochloroacetate acid and AGU,120 minutes of etherification time and 90℃ of the etherification temperature. Under the optimal operation condition,a DS of 1. 26 is achieved. The results also indicate that the sequence of substitution order is C（ 6） C（ 2） C（ 3）. In addition,increasing the monochloraoacetate acid dosage and etherification time can promote the substitution on C（ 2） and C（ 6）,while increasing the etherification temperature is more conducive to improve the substitution on C（ 6）. The CMC prepared by the homogeneous technology in NMMO / H_2O has a higher DS and an improved substitution uniformity than that of the products obtained by the conventional slurry technology.