【作者】 杭彩云；

【导师】 何瑾馨；

【作者基本信息】 东华大学 ， 纺织化学与染整工程， 2014， 博士

【摘要】 活性染料自问世以来,凭借卓越的染色性能迅速发展成为当今纤维素纤维印染的首选染料。然而,在以水为介质的传统棉织物染色体系中,因活性染料在碱性固色时导致染料水解副反应,失去了与纤维素纤维发生共价结合的能力,大大降低了活性染料的利用率,活性染料的固色率不高,约为40～85%之间。同时,染色结束后,为了获得所要求的染色湿处理牢度,必须通过充分的洗涤去除分布在纤维内部、纤维表面以及纤维间毛细网络孔道中的水解染料。因此,活性染料高固色率染色和高效节水净洗一直是染整工作者长期研究的课题。纯有机溶剂染色虽然提高了染料利用率,但受到染料品种、溶剂安全性和染色工艺可行性限制；小浴比染色受染料溶解性、设备专用性、染色匀染性和织物表面易擦伤的影响未能普及。此外,传统以水为介质的净洗工艺水耗和能耗大,污水排放多。针对这一系列问题,本文尝试以乙醇-水体系作为活性染料染色和净洗介质,分别研究相关的染色和净洗技术。首先根据活性染料的特性及其在溶剂中溶解度参数,研究了RY84、RR120、RB171和RB71四只活性染料在不同溶剂中溶解性能。根据溶剂的物理特性和使用安全性,确定了以乙醇-水体系代替传统水体系,作为活性染料染色和净洗的介质：分析了乙醇-水体系中活性染料溶解度随乙醇体积分数增加的变化规律,以及乙醇-水体系中活性染料对纤维素纤维上染率影响。研究结果表明,染料在乙醇-水体系中随乙醇体积分数的增加,其溶解度逐渐降低,对纤维素纤维的上染率显著提高,这与传统水体系染色中染料随浴比减小上染率提高的规律一致；在乙醇-水体系(乙醇体积分数为90%)中无需添加电解质,RY84、RR120、RB171三只染料的上染率即可达到99%,RB71染料的上染率也大于82%,当加入Na2CO3浓度达到5g/L时,染料的上染率达到最大值。棉织物经Na2C03预处理后,在乙醇-水体系(乙醇体积分数为90%)中活性染料无盐染色的性能明显优于传统水体系中有盐染色的性能,染料浓度为1%,RY84、RR120、RB171和RB71上染率分别提高了13.74%、17.59%、11.87%、39.77%,固色率分别提高了19.67%、23.62%、8.90%、39.26%。由此初步可见,乙醇-水体系作为活性染料染色介质不仅可以实现无盐染色,而且能够提高染料利用率。论文研究了乙醇-水体系(乙醇体积分数为90%)中活性染料染色动力学,包括上染速率曲线、扩散系数、半染时间、染色速率常数、固色速率曲线等。研究结果表明,乙醇-水体系(乙醇体积分数为90%)中染料的扩散系数随着染色时间的延长而减小；升高温度有助于提高扩散系数和比染色速率常数,缩短半染时间；棉织物经过碱预溶胀后纤维直径比水预溶胀后纤维直径大,染料在碱处理棉织物上的扩散系数比在水处理棉织物上的扩散系数大；在乙醇-水体系中,染色初期染料在NaOH预处理棉织物上的固色率高于Na2C03预处理棉织物的固色率,但随着染色时间的延长,由于体系中NaOH浓度偏高,染料与纤维间的共价键发生水解,固色率下降。基于乙醇-水体系(乙醇体积分数为90%)中活性染料染色动力学分析,论文还对乙醇-水体系中活性染料染色工艺进行了深入研究,包括棉织物碱预处理全料恒温染色工艺、两步加料升温染色工艺和三步加料升温染色工艺。研究结果表明,最佳染色工艺为：加入染液和1/4乙醇(染液与乙醇体积比为1：1)40℃运行10min后,再加入3/4乙醇(乙醇体积分数达到80%)并升温至60℃续染30min后,加入碱剂并升温至80℃固色30-60min。优化后的乙醇-水体系活性染料染色工艺,无需加盐促染,染料的上染率和固色率不仅均高于传统水体系染色工艺,染料利用率提高4.87～23.41%,而且染色残液中乙醇通过回收并循环使用,可减少水耗和污水排放；杜绝了盐对生态环境的破坏,简化了生产操作,实现了印染工业污染防治由“末端治理”向“源头预防”的转变,具有很好的推广应用价值。此外,论文还研究了乙醇-水体系作为活性染料染色织物净洗介质时,织物上水解染料的解吸动力学以及乙醇-水体系中乙醇体积分数、温度、时间和pH值等工艺参数对水解染料解吸率的影响。研究结果表明,棉织物上水解染料的解吸率随乙醇-水体系中乙醇体积分数增加先提高后下降,当乙醇体积分数达到40%时,解吸率达到最大值；升高温度和延长时间,可以提高棉织物上水解染料的解吸率；提高净洗浴的pH值有利于水解染料的解吸,且最佳的净洗液pH值应根据活性染料品种而定,一般宜在弱碱性或中性条件下进行。水解染料解吸动力学研究结果表明,乙醇-水体系(乙醇体积分数为40%)中棉织物上水解染料的解吸过程可以分为快反应与慢反应两个阶段,快反应阶段速率常数kd,1是慢反应速率常数kd,2的10倍之多；一级指数衰减方程能很好拟合棉织物上水解染料的解吸过程；当棉织物上水解染料在乙醇-水体系(乙醇体积分数为40%)中和传统净洗溶液中解吸都达到平衡时,水解染料在60℃乙醇-水体系中解吸率可以达到甚至超过95℃传统净洗液中解吸率,说明乙醇-水体系(乙醇体积分数为40%)用于棉织物活性染料染色后的净洗,不仅具有潜在的节能节水效果,而且可以减少废水排放。为了提高乙醇-水体系(乙醇体积分数为40%)中净洗效率,论文还研究了乙醇-水体系中分别添加净洗剂AST、XC-W与乙醇的协同增效作用及其对色牢度的影响。研究结果表明,在乙醇-水体系(乙醇体积分数为40%)体系中加入净洗剂XC-W,可有效地抑制水解染料再吸附并提高染色织物色牢度；提高净洗温度,可抑制水解染料返沾色并提升净洗效果；延长净洗时间,可以提高净洗效率,但对抑制水解染料再吸附不利。因此,净洗时间不宜太长,以防止水解染料二次沾染。在对乙醇-水体系中添加净洗剂对净洗效果影响因素的分析基础之上,通过乙醇-水体系(乙醇体积分数为40%)中多种净洗工艺优化对比研究,确定的最佳净洗工艺为：乙醇-水体系(净洗剂XC-W,乙醇体积分数为40%)80℃洗20min、乙醇-水体系(乙醇体积分数为40%)60℃洗10min和冷水洗10min。与传统净洗工艺相比,不仅净洗效果相同,而且净洗效率高、水耗能耗低、污水排放少。更多还原

【Abstract】 Reactive dyes have become the preferred usage in cellulose fibers dyeing since their introduction in the market, depending on their excellent dyeing properties. However, it is very easy for the reactive dyes to hydrolyze in the conventional dyeing system. So there is considerable loss of reactive dyes and the fixation rate is40～85%. Additionally, in order to achieve the desired level of color fastness, a thorough wash-off treatment is required for reactive cotton dyeings to remove hydrolyzed and/or unfixed dyes distributed inside and outside fibers after dyeing. Hence, many researches have focused on the issue of reactive high fixation dyeing methods and the way to wash off these dyes generated from reactive cotton dyeings.Although dye utilization was improved by pure solvent dyeing, this dyeing method was not popular for the limit of dye species, solvent safety and dyeing process. Little-liquor dyeing method was also rarely used, which was affected by many factors, such as dye solubility, special dyeing machine, dyeing unevenness and the surface of fabric scratched easily. In addition, the conventional wash-off treatment after dyeing consumes a huge amount of water and heating energy as well as sewage discharge. This research aims to investigate application of ethanol-water system acted as medium in reactive cotton dyeing and wash-off.At the beginning of this paper, based on the characteristics of reactive dyes and solubility parameters, the solubility of reactive dyes in different solvents were studied. According to both the physical properties of conventional organic solvents and security of using, ethanol-water system was selected to act as medium in reactive cotton dyeing and wash-off after dyeing. The solubility of reactive dyes and the dye up-take with the increase of the volume fraction of ethanol in ethanol-water system were discussed. It was demonstrated that the solubility of reactive dyes decreased and the dyeing rate increased with the increase of the volume fraction of ethanol in ethanol-water system, which was consistent with the variation of the bath ratio in traditional dyeing system. The exhaustion of the three reactive dyes (RY84, RR120and RB171) in ethanol-water (9:1v/v) system without salt was99%, and that of RB71was more than82%. The maximum exhaustion of the four dyes was achieved when the concentration of sodium carbonate in ethanol-water (9:1v/v) system was optimized to5g/L.The exhaustion and fixation in ethanol-water (9:1v/v) system in the absence of salt with cotton fabrics pretreated in sodium carbonate solution was higher than that of conventional dyeing system in the presence of salt. When the concentration of reactive dyes was1%, the exhaustion of RY84, RR120, RB171and RB71increased by13.74%,17.59%,11.87%and39.77%, respectively. The fixation of RY84, RR120, RB171and RB71increased by19.67%,23.62%,8.90%and39.26%, respectively. So, it can be seen that salt-free dyeing with reactive dyes in ethanol-water system is achievable, and the ethanol-water (9:1v/v) dyeing method improves the utilization of reactive dyes.On the basis of the kinetics of reactive dyeing in ethanol-water (9:1v/v) system, the diffusion coefficient decreased with extension of dyeing times. The diffusion coefficient and dyeing rate constant were increased with the increase of temperature, but half-dyeing time was decreased. The diffusion coefficient on cotton fabrics pretreated in basic solution was larger than that on cotton fabrics pretreated in water solution, because the diameters of cotton fiber pretreated in basic solution were larger than that pretreated in water solution. At the beginning period of reactive dyeing in ethanol-water (9:1v/v) system, the fixation of cotton fabrics pretreated in caustic soda solution was higher than that in sodium carbonate solution. However, the fixation declined gradually with the extension of dyeing times, because of covalent bonds between dyes and fibers hydrolyzed in high concentration of caustic soda.By comparing with dyeing processes of reactive dyes in ethanol-water system, it showed that the optimum dyeing process was that cotton fabrics were immersed in the solution with dyes and one fourth of ethanol and dyed at40℃for10minutes, then the remaining ethanol was added to the solution, which dyed at60℃for30minutes, and finally dyed at80℃for30～60minutes after sodium carbonate was added in ethanol-water (8:2v/v) system. As indicated in this paper for exhaustion and fixation, not only did the ethanol-water (8:2v/v) dyeing method increase the utilization of reactive dyes4.87～23.41%, compared to the conventional water dyeing method, but also reduced the amount of water and sewage discharge by means of distilling the dyeing effluent to recover ethanol. In addition, it is very important that the destruction of environment is prevented because of no salt in the ethanol-water dyeing process. The ethanol-water (8:2v/v) dyeing method is worth promoting widely.Additionally, the factors influencing desorption of hydrolyzed dyes in ethanol-water system acted as wash-off medium after reactive dyeing were investigated, which included volume fraction of ethanol, pH and temperature. The maximum desorption was achieved when the volume fraction of ethanol was optimized to40%. The desorption was increased with the increase of pH and temperature. The kinetic curves of hydrolyzed dyes desorption in ethanol-water (4:6v/v) system at three different temperatures fit the two-step kinetic model, which presents a multi-step desorption process:a rapid desorption step followed by a slow one. When desorption reached equilibrium, the dye desorpability at60℃in ethanol-water system was close to that by using conventional water washing in the presence of detergent at95℃. This study has concluded that the wash-off in ethanol-water system can be considered as an alternative, more effective process for removing hydrolyzed dyes from reactive cotton dyeings.The detergents were added in ethanol-water (4:6v/v) system in order to study the synergy effect between ethnaol and detergents. It showed that when the detergent of XC-W was added in ethanol-water (4:6v/v) system, the inhibition of the adsorption of hydrolyzed reactive dyes to cotton fabrics and fastness of reactive cotton dyeings were increased effectively. The longer wash-off time lasted, the higher the concentration of dye in residue remained, indicating that wash-off time could increase washing efficiency. But wash-off time was unfavorable to inhibit the re-adsorption of hydrolyzed reactive dyes to cotton fabrics. So the wash-off time should not keep too long.After comparing wash-off methods for reactive cotton dyeings, the optimum ethanol-water wash-off method was that cotton fabric were treated successively in the ethanol-water (4:6v/v) system with the detergent of XC-W at80℃for20minutes, in the ethanol-water (4:6v/v) system at60℃for10minutes, then in the water solution at room temperature for10minutes. As indicated in this paper, not only does the optimum ethanol-water (4:6v/v) wash-off method offer potential savings in water and energy consumptions, compared to the conventional water wash-off method, but also reduces dye effluents in wash-off.更多还原