【作者】 李兵云；

【导师】 詹怀宇；

【作者基本信息】 华南理工大学 ， 制浆造纸工程， 2010， 博士

【摘要】 机械浆和化学机械浆具有得率高、挺度和松厚度好、光学性能优异等特点,但其可漂性和漂白浆白度稳定性差,因而在生产高等级纸张时无法完全取代化学浆,这在一定程度上阻碍了机械法和化学机械法制浆的发展。为此,本论文研究粉单竹磺化化学机械浆（SCMP）过氧化氢漂白和漂白浆老化过程中木素结构及其抽出物成分的变化,探讨过氧化氢漂白和漂白浆返黄机理,确定抽出物中影响纸浆漂白性能的主要成分,采用脂肪酶、果胶酶和漆酶预处理以改善SCMP的漂白性能,为高得率浆的发展和质量提升提供理论和技术依据。实验使用实验设计软件（MODDE）分析了粉单竹SCMP过氧化氢漂白各工艺参数间相互关系及对漂白浆白度的影响,优化漂白工艺,建立了粉单竹SCMP过氧化氢漂白模型。漂白模型的分析可知,过氧化氢用量、过氧化氢与总的碱用量比、NaOH与Na₂SiO₃用量比、浆浓等参数之间存在相关性;过氧化氢用量、P/A比值和浆浓是影响过氧化氢漂白的主要因素;优化的漂白工艺参数为:H₂O₂用量6%,NaOH用量3%,Na₂SiO₃用量3%,MgSO₄用量0.3%,浆浓20%,温度80℃,反应时间180min。粉单竹SCMP过氧化氢漂白的模型如下:Brightness（%ISO）=51.25+4.62*（PCH）-3.68*（P/A）-0.35*（nA/Si）+1.50*C+0.78*（P/A）²-0.85*（C）²-0.81*（PCH）*（P/A）+0.56*（P/A）*（Na/Si）-0.47*（P/A）*（C）Py-GC/MS分析结果表明,粉单竹SCMP木素是由愈创木基型（G）、紫丁香基型（S）和对-羟基苯基型（H）等木素单元组成,三种木素单元之间的摩尔比为44.0:28.9:27.1（G:S:H）,其漂白浆和老化漂白浆的木素中三种单元的摩尔比分别为40.8:26.2:33.0和34.9:30.2:34.9。31P NMR分析结果表明,粉单竹SCMP及其漂白浆、老化漂白浆木素中的脂肪族羟基含量分别为3.83mmol/g、4.03mmol/g和3.74mmol/g,总酚羟基含量分别为1.27mmol/g、1.71mmol/g和1.18mmol/g,羧基含量分别为0.24mmol/g、0.36mmol/g和0.35mmol/g。说明在粉单竹SCMP过氧化氢漂白过程中,木素结构的醚键会发生部分的断裂,产生更多的脂肪族羟基和酚羟基;而在热老化过程中,木素中的酚羟基会在热的作用下导致部分木素的缩合。利用Py-GC/MS、31P NMR、13C NMR和2D NMR（HSQC）等现代测试技术分析了粉单竹SCMP及其漂白浆、老化漂白浆中木素的组成、连接结构的类型和含量,发现了粉单竹SCMP木素主要连接结构为β-O-4′芳基醚键结构,还有部分的缩合型结构,如树脂酚结构（β-β′/α-O-γ′/α′-O-γ）、苯基香豆满结构（β-5′/α-O-4′）、二苯并-二氧桥-松柏醇结构（5′-5′′/α-O-4′/β-O-4′′）、螺二烯酮结构和β-1′结构;木素结构中H型单元主要以与β-O-4′芳基醚键结构中C-γ上的羟基形成酯键的形式存在。其中粉单竹SCMP木素中β-O-4结构在过氧化氢漂白和老化过程中会发生部分的断裂;α-CO/β-O-4结构在过氧化氢的作用下会发生亲核反应生成α-OH结构,而生成的α-OH结构在老化过程中重新生成α-CO结构;二苯并-二氧桥-松柏醇结构中烷基芳基醚键在过氧化氢漂白和老化过程中会发生断裂;螺二烯酮结构中CO结构、树脂酚结构和苯基香豆满结构中烷基烷基醚键和烷基芳基醚键在过氧化氢漂白和老化过程中相对比较稳定。脂肪酶、果胶酶和漆酶处理粉单竹SCMP均可以提高其过氧化氢的可漂性和漂白浆的白度稳定性,最优工艺条件分别为:脂肪酶处理:脂肪酶用量10IU/g、pH值8,温度35℃,时间为40min、浆浓10%;果胶酶处理:果胶酶用量0.5IU/g、pH值10、温度30℃、时间30min、浆浓10%;漆酶处理:漆酶用量10IU/g、HBT用量0.5%、pH值6、温度50℃、氧压0.2MPa、浆浓10%。在最优工艺条件下,脂肪酶、果胶酶和漆酶处理的漂白浆白度分别从57.1%ISO增加了3.3%ISO、4%ISO和2.9%ISO到60.3%ISO、61.1%ISO和60.0%ISO;其PC值分别从2.97降低了33%、34%和31%到2.03、1.97和2.06;漂白浆打浆度分别从70°SR增加了4°SR、2.5°SR和3.0°SR至74°SR、72.5°SR和73°SR;漂白浆的裂断长分别增加了4.1%、5.9%和3.7%;耐破指数分别提高了8.4%、6.6%和8.8%;撕裂指数分别上升了5%、8.6%和4.7%。XPS和AFM分析结果显示,粉单竹SCMP纤维表面大部分被不规则形状的抽出物和规则形状的木素所覆盖,覆盖在纤维表面的木素量为57.45%,抽出物量为7.57%;经脂肪酶和果胶酶和漆酶处理后, SCMP纤维表面覆盖的木素量分别为66.40%和68.41%,抽出物量分别为3.05%和2.03%,漆酶处理后SCMP纤维表面几乎100%为木素所覆盖,而抽出物的量无法通过计算得到。说明了脂肪酶和果胶酶预处理可以去除部分纤维表面的抽出物,使得纤维表面暴露出更多的木素,而漆酶预处理也可除去部分抽出物和木素,但降解的木素会重新吸附在纤维表面,但这部分木素在过氧化氢漂白过程中容易去除。苯-乙醇抽出物GC-MS分析结果表明,粉单竹SCMP的苯-乙醇抽出物可以分为小分子直链烃类、小分子芳香族类、脂肪族的烯烃和醇类、脂肪酸及其酯类、甾醇等化合物,其中小分子芳香族类、脂肪酸及其酯类和甾醇类化合物对粉单竹SCMP过氧化氢的可漂性和白度稳定性的影响较大。生物酶处理可除去相当部分的抽出物,其中果胶酶去除抽出物的效果最好,脂肪酶次之,漆酶最差。结合脂肪酶、果胶酶和漆酶处理对漂白浆白度和白度稳定性影响的实验结果,说明通过生物酶处理去除纸浆抽出物,可以改善粉单竹SCMP的可漂性和白度稳定性。更多还原

【Abstract】 In China, the production of machenical and chemimechanical pulp has made great progress, due to its high yield, high bulk and stiffness, superior optical properties and good printability. However, the machenical and chemimechanical pulps could not be used to produce high grade paper product because of its poor bleachability and inferior brightness stability. The changes of lignin substructure and the component content of benzene-ethanol extractives of Bambusa chungii SCMP were investigated during the process of its hydrogen peroxide bleahing and yellowing. The changes of the fiber surface properties and the component content of benzene-ethanol extractives of Bambusa chungii SCMP were discussed during pretreatment with lipase, pectinase and laccase. The mechanism of hydrogen peroxide bleaching and yellowing and the effect of the extractives on the bleachability and brightness stability were also studied.The model of hydrogen peroxide bleaching of Bambusa chungii SCMP was set up by MODDE software. It could be found from the model that there exits the correlation among hydrogen peroxide dosage, ratio of hydrogen peroxide dosage to alkali usage, the ratio of NaOH to Na₂SiO₃ usage and pulp consistency. And hydrogen peroxide dosage, the ratio of hydrogen peroxide dosage to alkali usage and consistency are the main factors that influence the the brightness of bleached SCMP. The optimal conditions of hydrogen peroxide bleaching of Bambusa chungii SCMP were H2O2 6%,NaOH 3%,Na₂SiO₃ 3%,MgSO₄ 0.3%,pulp consistency 20%,temperature 80℃,time 180min. The bleaching model was: Brightness（%ISO）=51.25+4.62*（PCH）-3.68*（P/A）-0.35*（nA/Si）+1.50*C+0.78*（P/A）²-0.85*（C）²-0.81*（PCH）*（P/A）+0.56*（P/A）*（Na/Si）-0.47*（P/A）*（C）From the analysis of Py-GC/MS spectra, lignin isolated from Bambusa chungii SCMP constitutes of gluaiacyl （G）, syringyl （S） and p-hydrophenyl （H） units, with a G:S:H molar ratio of 44:29:27. And the molar ratios of G, S and H in lignin isolated from bleached SCMP and yellowed bleached SCMP are 40.8:26.2:33 and 34.9:30.2:34.9, respectively. The data of 31P NMR spectra shows that the contents of alphatic hydrogen group in lignin isolated from SCMP, bleached SCMP and yellowed bleached SCMP are 3.83mmol/g, 4.03mmol/g and 3.74mmol/g, the contents of phenolic hydroxyl group 1.27mmol/g, 1.71mmol/g and 1.18mmol/g, the contents of carboxylic hydrogen group 0.24mmol/g, 0.36mmol/g and 0.35mmol/g, respectively. During hydrogen peroxide bleaching, the ether bond between the lignin units could be broken down, and more alphatic and phenolic hydroxyl groups were formed, but during the process of yellowing, the condensation of lignin would occur.From the analysis of 31P NMR, 13C NMR and 2D NMR （HSQC）, it could be concluded that the linkage among lignin units was mainly ?-O-4′aryl ether substructure linkage, there was also some condensed substructure linkage, such as dibenzodioxocins substructures（5′-5′′/α-O-4′/β-O-4′′）, phenylcoumaran structures（β-5′/α-O-4′）, resinol substructures（β-β′/α-O-γ′/α′-O-γ）, spirodienone andβ-1′substructure, . And most of H lignin unit was acetated at ?-position ofβ-O-4′aryl ether linkages. Fraction ofβ-O-4′aryl ether linkages in lignin of Bambusa chungii SCMP was broken down during the process of bleaching and yellowing. Part ofα-CO inβ-O-4′aryl ether linkages was changed intoα-OH during hydrogen peroxide bleaching, and then some of -OH would be changed intoβ-CO during the process of yellowing. Some of Alk-O-Alk ether linkage in dibenzodioxocins substructures was also broken down during bleaching and yellowing. But carbonyl group（CO） in spirodienone substructure and Alk-O-Alk and Alk-O-Aryl linkages in penylcoumaran and resinol substructure would be relative stable during bleaching and yellowing.The bleachability and brightness stability of Bambusa chungii SCMP could be improved after pretreatment with lipase, pectinase and laccase. The opitmal pretreatment conditions were as follows: lipase pretreatment: lipase dosage 10IU/g, pH 8,temperature 35℃, time 40min, pulp consistency 10%; pectinase pretreatment: pectinase dosage 0.5IU/g, pH 10, temperature 30℃, time 30min, pulp consistency 10%; laccase pretreatment: laccase dosage 10IU/g、HBT 0.5%, pH 6, temperature 50℃, oxygen pressure 0.2MPa, pulp consistency 10%. Under the optimal conditions, the brightness of bleached SCMP pretreated by lipase, pectinase and laccase increased from 57.1%ISO to 60.3%ISO、61.1%ISO and 60.0%ISO, respectively. The PC number decreased from 2.97 to 2.03、1.97 and 2.06;the beating degree rose up from 70°SR to 74°SR、72.5°S and 73°SR;the breaking length inceased by 4.1%、5.9% and 3.7%;the bursting index also increaded by 8.4%、6.6%和8.8%;the tearing index rose up by 5%、8.6% and 4.7%. From the analysis of AFM and XPS, it could be found that 57.45% and 7.57% of fiber surface of Bambusa chungii SCMP were covered with lignin and extractives. After pretreatment with lipase and pectinase, the percentages of lignin covered on the fiber surface were 66.40% and 68.41%, percentages of extractives 3.05% and 2.03%, respectively. After pretreatment with laccse, almost all of the surface of fiber were covered with lignin, and pecentage of extractives on the fiber surfacet could not be calculated.The analysis results of GC-MS indicate that the benzene-ethanol extractives of Bambusa chungii SCMP consist of low molecular linear hydrocarbon, low molecular aromatic substances, fatty alkene and alcohol, fatty acid and sterol. And the main extractives that affect the bleachability and brightness stability are low molecular aromatic substances, fatty acid and sterol. The extractives covered on the fiber surface could be partially removed by enzyme pretreatment, which could evidently improve the bleachability and brightness stability of Bambusa chuangii SCMP.更多还原