硫酸钠在低带液轧-焙-蒸活性染料染色中的作用

为探究加入硫酸钠后低带液轧-焙-蒸活性染料染色效果更好的原因,通过分子动力学模拟的方法,建立纤维表面染液层模型,研究在有无硫酸钠的条件下焙-蒸过程中体系水分蒸发、染料和离子分布情况,计算了数密度和径向分布函数。结果表明:硫酸钠在低带液轧-焙-蒸染色过程中存在保水作用,且在碱处理后,即纤维素糖环上的羟基变成氧负离子之后,保水作用更明显;硫酸钠的加入产生了纤维素氧负离子-钠离子-硫酸根离子-钠离子的稳定、定向排列的多电位层,能够有效锁住纤维表面的水分,为染料和纤维提供更好的反应环境,而且能够防止染料随着水分子在高温下发生解吸附、泳移以及水解反应。

Role of sodium sulfate in low add-on pad-cure-steam reactive dyeing process

Aiming to explain the reasons that the dyeing performance became better after adding sodium sulfate in the low add-on pad-cure-steam reactive dyeing process, a model of dyeing solution layers on the surface of cellulose fibers were created. The water evaporation, dye and ion distribution in the systems during curing process with or without sodium sulfate were studied by means of molecular dynamics simulations. By calculating the number densities and radial distribution functions, the results show that sodium sulfate has a water retention effect in the process of low add-on pad-cure-steam reactive dyeing. After the alkali treatment, the hydroxyl groups on the cellulose sugar rings become oxygen negative ions, which make the effect of water retention becomes more obvious. The main reason for the water retention effect is that the addition of sodium sulfate produces stable and directional multi-potential layers: cellulose oxygen anion-sodium ion-sulfate ion-sodium ion. Such multi-potential layers can effectively lock moisture on the surface of the fiber, provide a better reaction environment for the dye and the fiber, and prevent desorption, migration and hydrolyzation of the dye with the water molecules at high temperature.