【作者】 颜婷婷；

【导师】 郁崇文；

【作者基本信息】 东华大学 ， 纺织工程， 2011， 博士

【摘要】 黄麻和红麻纤维是麻纺织工业的主要原料之一。黄麻和红麻纤维的木质素含量高,导致纤维粗硬,因此决定了黄麻和红麻纤维主要应用于生产麻布、麻袋等低档产品。黄麻和红麻纤维中木质素的存在对于纺织染整加工过程也会产生不利影响。实际上,黄、红麻纺织加工中对纤维进行加工的主要目的就是研究如何在保护黄、红麻纤维中纤维素少受损伤的同时,尽可能多地去除黄麻和红麻纤维中的木质素。在纺织行业中,红麻常作为黄麻的代用品用来进行各种加工。木质素是植物体次生代谢合成的一种天然有机高分子物质,在自然界中的含量仅次于纤维素。木质素是苯丙烷结构单元以醚键和碳碳键连接,而在木质素骨架侧链上有各种化学官能团,这些结构单元间的键型组成变化和化学官能团的差异,都会影响纤维的力学性质和化学反应性。因此如何正确制定黄麻和红麻纤维精细化加工工艺、及对黄麻和红麻纤维的研究和应用都有赖于深入研究黄麻和红麻纤维木质素的化学结构特征。本文研究比较了黄麻和红麻纤维木质素的结构特征,并对木质素结构单元之间的连接方式和官能团含量进行了定量分析,从而对黄麻和红麻纤维木质素化学结构进行了更深入的研究,进而为阐明其各种反应机理提供可靠的理论依据。并应用生物酶和化学处理对红麻纤维进行脱胶,评价了纤维中木质素去除的效果并阐述了木质素结构在脱胶过程中的变化。本文的研究结果如下：(1)应用傅里叶变换红外光谱、核磁共振氢谱(1H-NMR)、核磁共振碳谱(13C-NMR)研究了自制的黄麻和红麻纤维磨木木质素的结构特征。结果表明,黄麻纤维和红麻纤维木质素的苯基丙烷结构单元的经验式分别为C9H9.27O3.52(OCH3)1.26和C9H9.66O3.79(OCH3)1.30。黄麻和红麻纤维的木质素中含有羟基、羰基、甲基等复杂的官能团,且含有相当数量的紫丁香基单元,其木质素结构归属于阔叶材木质素化学结构GS型。黄麻和红麻纤维磨木木质素中木质素结构单元愈创木基单元和紫丁香基单元间主要以醚键和碳碳键相互连接,互相连接的方式有如下几种：β-O-4结构、β-1结构、β-β结构、β-5结构。在这几种结构中,β-O-4和β-β结构比例较大,β-1和β-5结构,结构含量相对较少。黄麻和红麻纤维磨木木质素中β-O-4结构、β-β结构是属于非缩合型结构,而β-1结构、β-5结构属于缩合型结构。缩合型木质素结构的存在,增加了黄麻和红麻纤维中木质素结构的复杂性,缩合型木质素结构很难降解,红麻纤维磨木木质素中的缩合型结构较黄麻纤维多。(2)通过化学方法和仪器分析方法对黄麻和红麻纤维木质素结构单元的比例进行了测定。从黄麻和红麻纤维的碱性硝基苯氧化反应产物液相色谱分析可知：黄麻纤维的非缩合型木质素结构中主要含有非缩合型紫丁香基丙烷结构(S)和非缩合型愈创木基结构(G)；红麻纤维的非缩合型未质素结构中含有少量的非缩合型对羟基苯丙烷结构(H),绝大多数结构单元为非缩合型愈创木基结构(G)和非缩合型紫丁香基丙烷结构(S),其总量占非缩合型木质素结构单元的99%。黄麻纤维木质素的非缩合型愈创木基丙烷结构(G)约占7.56%左右,非缩合型紫丁香基丙烷结构(S)约占92.44%左右,其非缩合型S/G值约为12.22；而红麻纤维木质素的非缩合型愈创木基丙烷结构(G)约占10.6%左右,非缩合型紫丁香基丙烷结构(S)约占89.29%左右,其非缩合型S/G值约为8.4。通过裂解气相色谱-质谱联用法对黄麻纤维和红麻纤维磨木木质素的结构进一步分析得出：黄麻纤维木质素中三种结构单元(含缩合型及非缩合型结构单元)的比例H：G：S为0：26.08：73.92,S/G比值为2.835；红麻纤维磨木木质素中三种结构单元(含缩合型及非缩合型结构单元)的比例H：G：S为4.59：34.11：61.30,S/G比值为1.797。(3)应用X-射线光电子能谱确定了黄麻和红麻纤维木质素的碳的结合态C1s各个子峰的电子结合能分别为284.6 eV(C-C或C=C),285.2 eV(C-H),286.5 eV(C-O),289.27 eV (O-C=O);氧的结合态O1s各个子峰的电子结合能分别为532.3eV(O1—碳氧单键中的氧原子),533.3 eV(02—碳氧双键中的氧原子)。相比黄麻纤维木质素,红麻纤维木质素中含有较多的碳碳键连接碳原子,较少的碳氢键连接碳原子,较少的醚键连接碳原子,较多的酯键或羧酸中的羰基碳原子。黄麻纤维木质素的O1/02比值高于红麻纤维木质素,说明黄麻纤维木质素含有更多的单键连接的氧原子。(4)应用漆酶及漆酶/介体体系对红麻纤维进行脱胶处理,对单独使用漆酶、加入介体ABTS以及增加预处理工序的多种脱胶工艺进行了研究,测试了脱胶后红麻纤维的性能指标,并通过X-射线衍射、红外光谱、碱性硝基苯氧化产物的液相色谱分析评价了脱胶效果。结果显示,漆酶单独应用于红麻纤维的脱胶工艺效果不明显,必须加入介体ABTS、增加预处理工序才能发挥其作用效果。漆酶/ABTS处理后红麻纤维的结晶度提高。红外光谱分析可以知漆酶/ABTS方案脱胶后的红麻纤维的光谱图中木质素和半纤维素的主要特征峰强度下降,而大部分纤维素的特征峰强度增加了。由脱胶后纤维的碱性硝基苯氧化实验结果可以推论漆酶/ABTS脱胶方案有助于去除红麻纤维的木质素结构中非缩合型愈创木基丙烷结构单元及非缩合型紫丁香基丙烷结构单元。(5)应用七种化学工艺对红麻纤维进行脱胶处理,并对脱胶后红麻纤维的分裂度及残余木质素含量进行了测试,通过X-射线衍射、红外光谱、扫描电镜、碱性硝基苯氧化产物的液相色谱测试等手段评价了七种化学工艺对红麻纤维脱胶处理的效果。化学脱胶后,纤维的结晶度提高。在氢氧化钠双氧水法或过碳酸钠法处理(CT1和CR1方案)的后道加入强氧化剂过氧单硫酸和过醋酸处理(CT2和CR2方案),再进行硫酸盐法煮练后(CT3和CR3方案),红麻纤维红外光谱图中纤维素特征峰积分面积相对值Ai/As之和逐步增加,木质素和半纤维素特征峰积分面积相对值Ai/As之和逐步减少,且纤维的木质素含量逐步减少,纤维的分裂度逐步增加。说明本试验所采用的七种方案均有明显的脱胶效果,且过氧单硫酸和过醋酸混合液作为一种新型的氧化剂,具有一定的脱除木质素效果。对CT1～CT3脱胶后的纤维进行碱性硝基苯氧化实验,发现CT1～CT3脱胶方案有助于去除红麻纤维的木质素结构中非缩合型对羟基苯丙烷结构单元和非缩合型愈创木基丙烷结构单元,并可能在脱胶过程中导致缩合型紫丁香基丙烷结构苯环C2,C5上的其他连接键被打断,形成更多的非缩合型紫丁香基丙烷结构单元。相比较而言,CTl方案更易于去除非缩合型愈创木基结构单元和非缩合型对羟基苯丙烷结构单元,CT2方案更易于去除非缩合型愈创木基结构单元,CT3方案更易于去除非缩合型对羟基苯丙烷结构单元和非缩合型紫丁香基结构单元。更多还原

【Abstract】 Jute and kenaf are renewable, cheap, and easily grown annual plant. The lignin content of jute and kenaf fiber is high which resulted in the coarse and rigidity handle of the fiber, therefore, jute and kenaf fiber are mainly used to make the low grade products such as package fabric and bag. At the same time, the existence of lignin in jute and kenaf fiber have more disadvantages to the performances of fiber obtained after fiber preparation and to the fiber post-processing. Actually, the predominant task aiming at getting finer and soft fiber in degumming process is to remove lignin with as less as possible damage to the fiber cellulose. In the textile industry, jute and kenaf fiber are processed as the same fiber.Lignin is a three-dimensional polymer that basically consists of numerous, various substituted phenylpropane units linked by carbon-carbon and ether bonds. This skeleton bears a wide variety of functional groups affording reactive centers for chemical and biochemical modification. There are many kinds of function groups in the side chain of lignin. The changes of linkages among units and the differences of function groups in lignin structure will affect the mechanical character and chemical reactivity of fiber. Therefore, an understanding of the chemical composition of jute and kenaf fiber lignin gives insight into the preparation to get finer fibers and application of kenaf fiber as material for clothing and other high grade products.In this paper, milled wood lignin (MWL) were isolated and purified from jute and kenaf fiber, the lignin obtained was characterized and compared. Linkage style among lignin structure units and content of functional group were quantitatively analyzed for further research on the chemical structure of lignin between jute and kenaf fiber, which provided reliable theoretical basis for illuminating the various reaction mechanisms, and furthermore, kenaf fiber was degummed by the biological enzyme and chemical treatment, the effect of lignin removal was evaluated and the changes of lignin structure during the degumming process was explained. Results were illustrated as follows: (1) Milled wood lignin (MWL) of jute and kenaf fiber were characterized by elemental analysis, FTIR, 1H-NMR and 13C-NMR spectroscopy. The C9 formula were calculated for MWL from jute and kenaf fiber as C9H9.27O3.52(OCH3)1.26 and C9H9.32O3.69(OCH3)1.30. The spectra of FTIR,1H-NMR and 13C-NMR indicated the jute and kenaf fiber lignin to be of the G/S type with high proportion of syringyl (S) unit. It is evident that theβ-O-4 structures mainly linkaged in the MWL of jute and kenaf fiber which contain more erythro stereochemistry type than thero stereochemistry type. In general, the characteristics of lignin of jute and kenaf fiber were similar to that of hardwood. Comparing with lignin of jute fiber, lignin of kenaf fiber contained more condensedβ-5 structures.(2) The chemical method and instrument analysis method were adopted in the determination of three types basic lignin unit ratio. The HPLC results of the products of alkalinous nitrobenzene oxidation about the jute and kenaf fiber showed a predominance of syringyl(S) units over guaiacyl(G), the uncondensed lignin of jute contained 7.56% uncondensed guaiacyl units and 92.44% uncondensed syringyl units, the uncondensed S/G value was 12.22; the uncondensed lignin of kenaf contained 10.6% uncondensed guaiacyl units and 89.29% uncondensed syringyl units, and few 4-hydroxyphenyl units were found in lignin of kenaf fiber, the uncondesnde S/G value was 8.4; Furthermore, the MWL of jute and kenaf fiber were analyzed by Py-GC-MS, the molar ratio of H:G:S in jute lignin was 0:26.08:73.92, the S/G value was 2.835, the molar ratio of H:G:S in kenaf lignin was 4.59:34.11: 61.30, the S/G value was 1.797. It was concluded that the lignin structure in kenaf fiber was more difficult for delignification in degumming process than jute fiber.(3) The structure of MWL from jute and kenaf fiber were studied by using XPS. The binding energy of C1s was assigned to 284.6 eV(C-C or C=C),285.2 eV (C-H), 286.5 eV (C-O) and 289.27 eV (O-C=O). The binding energy of O1s was assigned to 532.3 eV(O1) and 533.3 eV (O2). Comparing with lignin of jute fiber, the lignin of kenaf fiber contained more carbon atom in C-C or C=C bonds, less carbon atom in C-H bonds and ether bonds, more carbon atom in carboxyl group. The ratio O1/O2 of jute fiber lignin was higher than kenaf fiber lignin indicating more single O bond in lignin of jute fiber.(4) Laccase and laccase/mediator system were employed in kenaf fiber degumming process. The effects of single laccase and combined with ABTS were studied. The effects on the properties of the degummed fiber such as fiber fineness, residual lignin content and tensile property were tested by the designed experiments. Meanwhile the degumming effects were analyzed by XRD, IR and HPLC of the products of alkalinous nitrobenzene oxidation about the degummed kenaf fiber. The results showed that the effect of laccase used in degumming of kenaf fiber was not obvious, and its effect could be strengthened with the existence ABTS as mediator and the process with pre-treatment. IR indicated that the intensity of characteristic peak of lignin and hemicellulose decreased, while the intensity of characteristic peak of cellulose increased. The HPLC results showed that it helped to remove the uncondensed G and S units of lignin by using laccase/ABTS degumming process.(5) Seven chemical treatments were employed in kenaf degumming process. The properties of degummed fiber such as fiber fineness, residual lignin content were tested, and the degumming effects were analyzed by XRD, IR and HPLC of the products of alkalinous nitrobenzene oxidation about the degummed kenaf fiber. The crystallinity of kenaf fiber increased after being treated. Adding the strong oxidizing agents including potassium peroxymonosulfate and peracetic acid (plan CT2 and CR2) in the later process of caustic soda and sodium percarbonate methods (plan CT1 and CR1), then after scouring using the sulfate method (plan CT3 and CR3), the relative integral area value Aj/As of the characteristic peek of the cellulose in IR gradually increased, while the sum of those of the lignin and hemicellulose gradually decreased, and the content of lignin gradually decreased, while the finess gradually increased. The results indicated that the seven chemical treatments adopted in degumming had obvious effects. As a new oxidant, the mixed liquid of potassium peroxymonosulfate and peracetic acid was effective on delignification. The HPLC results showed that it helped to remove the uncondensed G and H units of lignin by using plan CT1, it helped to remove the uncondensed G unit of lignin by using plan CT2, and it helped to remove the uncondensed H and S unit of lignin by using plan CT3.更多还原