活性染料着色棉织物的脱色机制与制浆工艺研究

【作者】 王伟；

【导师】 张传杰；

【作者基本信息】 青岛大学 ， 纺织化学与染整工程， 2023， 硕士

【摘要】 针对目前废旧棉织物蒸煮法制备纤维素浆粕,存在需搭配原生浆粕使用(再生浆聚合度低)、脱色机制不清晰、能耗高、污染重等问题。本课题选用三种典型结构的活性染料着色棉织物,模拟来源复杂、颜色多样的废旧棉织物,提出先温和脱色再漂白降聚的两步法制浆新工艺,制备出高品质纤维素浆粕,并探究了不同染料结构着色棉织物的脱色机制和制浆工艺,以及降聚漂白溶液的循环利用性能,为实现来源广泛的废旧棉织物制备纤维素浆粕奠定理论基础,具体研究内容和结果如下:(1)选用低温型活性红X-3B、中温型活性蓝KN-R和高温型活性红KE-3B三种典型结构的活性染料着色棉织物(4.0%,o.w.f)为研究对象,采用氢氧化钠/保险粉还原体系进行温和脱色,研究染料结构对棉织物脱色工艺和性能的影响,并探究活性染料着色棉织物的脱色机制。结果表明,氢氧化钠/保险粉还原体系可以实现对不同结构活性染料着色棉织物的高效温和脱色,氢氧化钠通过水解破坏染料与纤维间共的价键,将染料转移至脱色液中;保险粉能够破坏染料的发色团,实现脱色。其中,单偶氮-二氯均三嗪结构的活性红X-3B着色棉织物单独使用保险粉即可脱色,蒽醌-乙烯砜结构的活性蓝KN-R着色棉织物仅单独使用氢氧化钠即可脱色,双偶氮-双一氯均三嗪结构的活性红KE-3B着色棉织物需氢氧化钠和保险粉的协效作用才能实现脱色。采用氢氧化钠/保险粉温和脱色体系,棉纤维上活性染料基本除去,脱色棉织物的明度值均可达到70以上;在脱色过程中,棉纤维的化学结构与结晶结构几乎不受影响,脱色棉织物的断裂强力保留率均可达到90%以上。(2)以三种典型结构的活性染料着色棉织物(0.8%,o.w.f)为研究对象,通过库贝尔卡-蒙克函数,以时间为变量,改变脱色剂的浓度,研究了活性染料着色棉织物的脱色动力学反应级数与动力学反应速率,并从动力学的理论基础出发,验证了氢氧化钠与保险粉对活性染料着色棉织物的脱色机理。结果表明,三种结构的活性染料着色棉织物在氢氧化钠/保险粉还原体系中的脱色动力学具有可行性,均符合Langmuir-Hinshelwood(L-H)动力学模型。脱色剂的用量越大,脱色反应速率越快。其中,单偶氮-二氯均三嗪结构的活性红X-3B着色棉织物的脱色速率最快,这是由于保险粉直接作用于纤维上染料的发色团;蒽醌-乙烯砜结构的活性蓝KN-R着色棉织物的脱色反应速率最慢。(3)以三种典型结构的活性染料着色棉织物(4.0%,o.w.f)脱色后棉织物为研究对象,采用氢氧化钠/双氧水体系进行降聚漂白一浴处理,研究脱色棉织物制浆时降聚漂白的工艺调控与机制,并与传统的烧碱法制浆工艺进行对比。结果表明,在降聚漂白过程中,双氧水能够破坏棉纤维上残余染料的发色团,提高白度;另一方面双氧水通过氧化降解作用调控棉纤维素的聚合度。氢氧化钠既能够破坏脱色棉纤维上残余活性染料与纤维间的共价键,提高织物的白度;同时提供双氧水分解色素和氧化降聚纤维素的碱性环境。采用活性染料着色棉织物为原料,通过先温和脱色,再降聚漂白的工艺制备的纤维素浆粕,其聚合度、白度、甲种纤维素含量和灰分含量等均符合行业标准。更多还原

【Abstract】 Aimed at the current issue of using waste cotton fabric cooking method to prepare cellulose dissolved pulp,there are issues such as the need to use it with pimary pulp（low polymerization degree of recycled pulp）,unclear decolorization mechanism,high energy consumption,and heavy pollution.This subject selected dyed cotton fabric with three typical structures of reactive dyes,as waste cotton fabrics with complex sources and diverse colors,proposed a two-step pulping process of mild decolorization followed by bleaching and depolymerization to prepare high-quality cellulose dissolved pulp.To lay a theoretical foundation for the preparation of cellulose dissolving pulp from waste cotton fabrics with a wide range of sources,the decolorization mechanism and pulping process of colored cotton fabrics with different dye structures were explored,as well as the recycling performance of depolymerization and bleaching solutions.The specific research content and results are as follows:（1）The cotton fabrics dyed with three typical structures of reactive dyes（4.0%,o.w.f）,named low-temperature Reactive Red X-3B,middle temperature Reactive Blue KN-R,and high-temperature Reactive Red KE-3B,were selected as the research objects.A sodium hydroxide/sodium hydroxide reduction system was used for mild decolorization to study the effect of dye structure on the decolorization process and performance of cotton fabrics,and to explore the decolorization mechanism of dyed cotton fabrics.The results indicated that the sodium hydroxide/sodium hydrosulfite reduction system can achieve efficient and mild decolorization of cotton fabrics dyed with different structural reactive dyes.Sodium hydroxide hydrolyzed the covalent bonds between dyes and fibers,transferring the dyes to the decolorization solution;sodium hydrosulfite can destroy the chromophore of dyes to achieve decolorization.Among them,the cotton fabric dyed with Reactive Red X-3B with a structure of dichlorotriazine only need sodium hydrosulfite to achieve decolorization,the cotton fabric dyed with Reactive Blue KN-R with a structure of anthraquinone vinyl sulfone only need sodium hydroxide to achieve decolorization,and the cotton fabric dyed with Reactive Red KE-3B with a structure of double azo bis monochlorotriazine need the synergistic effect of sodium hydroxide and sodium hydrosulfite to achieve decolorization.The dyes on the cotton fiber were basically removed,and the lightness values of the decolorized cotton fabric could reach over 70.During the decolorization process,the chemical and crystalline structures of cotton fibers were almost unaffected,and the retention rate of the breaking strength of the decolorized cotton fabric could reach over90%.（2）The cotton fabrics dyed with three typical structures of reactive dyes（0.8%,o.w.f）were used as the research object to investigate the decolorization kinetics reaction order and kinetics reaction rate of reactive dye cotton fabric by using Kubelka Munk function and changing the concentration of decolorizing agent with time as a variable.Based on the theory of kinetics,the decolorization mechanism of Na OH and Na₂S₂O₄ on reactive dyed cotton fabric were verified.The results indicated that the decolorization kinetics of cotton fabrics dyed by three reactive dyes in the sodium hydroxide/sodium hydrosulfite reduction system were feasible and all complied with the Langmuir Hinshelwood（L-H）kinetic model.In addition,the higher the amount of decolorizing agent used,the faster the decolorization reaction rate.Among them,the decolorization rate of cotton fabric dyed with Reactive Red X-3B with a structure of the dichlorotriazine was the fastest,due to the direct action of sodium hydrosulfite on the chromophore of the dye on the fiber.The decolorization reaction rate of cotton fabric dyed with Reactive Blue KN-R with anthraquinone vinyl sulfone structure was the slowest.（3）Using cotton fabrics dyed with three typical structures of reactive dye（4.0%,o.w.f）as the research object,a Na OH/H₂O₂ system was used for one bath treatment of depolymerization and bleaching.The control process and mechanism of depolymerization and bleaching of decolorized cotton pulp were studied and compared with traditional caustic soda pulping process.The results indicated that on the one hand,H₂O₂ could destroy the chromophores of a small amount of residual dyes on cotton fibers to improving the whiteness during the process of depolymerization and bleaching;on the other hand,the degradation effect of H₂O₂ reduced the degree of polymerization of cotton cellulose.Na OH could destroy the covalent bonds between a small amount of residual reactive dyes on the decolorized cotton fiber and the fiber to improve the whiteness and provide an alkaline environment for H₂O₂ to decompose pigments and oxidize cellulose.The cellulose dissolving pulp prepared from cotton fabric dyed with reactive dyes through a process of mild decolorization followed by depolymerization and bleaching compliated industry standards in terms of polymerization degree,whiteness,alpha cellulose content,and ash content.更多还原