NaOH/硫脲/尿素预处理对棉纤维TEMPO选择性氧化的影响

Effect of NaOH/Thiourea/Urea Pretreatment on TEMPO Selective Oxidation of Cotton Fibers

采用NaOH/硫脲/尿素体系对棉纤维进行预处理,再进行选择性氧化,可以有效提高氧化棉纤维的羧基生成量。对比研究预处理棉纤维与普通棉纤维经2,2,6,6-四甲基哌啶氮氧自由基(TEMPO)选择性氧化后的羧基含量、纤维形态以及黏度。结果表明,经NaOH/硫脲/尿素体系预处理能够加快氧化反应速率,增加羧基生成量,但对纤维有一定的损伤。其中,羧基生成量随着纤维质量分数的增加呈先增加后减少的趋势,当纤维素质量分数为6%时,羧基生成量最大,棉纤维的可及度和反应性提高。纤维形态分析表明,经NaOH/硫脲/尿素体系预处理的棉纤维润胀溶解程度要大于未预处理的氧化棉纤维;在TEMPO的氧化条件下,氧化棉纤维的相对黏度随着纤维素质量分数增加而增加;当纤维素质量分数较高时,氧化过程中氧化棉纤维的羧基生成量和降解程度都近似于原纤维。

In order to improve the carboxyl production quantity of oxidized cotton fibers,the pretreatment of cotton fibers with NaOH/thiourea/urea was performed before selective oxidation in this paper.The carboxyl groups,cellulose morphology and viscosity of 2,2,6,6-Tetramethyl-1-piperidinyloxy（TEMPO） selective oxidized cotton fibers with and without NaOH/thiourea/urea pretreatment are compared.The results showed that NaOH/thiourea/urea pretreatment accelerated the oxidation reaction rate and increased the amount of carboxyl group,but damaged cotton fibers.Among them,the content of carboxyl group increased with the increasing consistency of fiber firstly,reached the maxium at the fiber consistency of 6%,which has improved the accessibility and the reactivity of the cotton fibers.The morphology of cellulose fibers study shows that the extent of the swelling and dissolve for the oxidized cotton fibers after pretreatment exhibits stronger than that before pretreatment.Under the TEMPO oxidation conditions,increasing cellulose concentration enhances the relative viscosity of the oxidized cotton fibers.However,at higher concentration of cellulose,the increment of the carboxyl content and the degradation degree of cotton fibers are similar to the original during the oxidation process.