【作者】 梁辰；

【导师】 詹怀宇；

【作者基本信息】 华南理工大学 ， 制浆造纸工程， 2011， 博士

【摘要】 竹子是我国重要的造纸纤维原料。竹材原料的合理利用是解决我国造纸工业原料匮乏的重要途径之一。但高得率竹浆光学性能较差,漂白浆白度偏低且白度稳定性差,严重制约了高得率竹浆的应用范围。高得率竹浆的抽出物对白度及稳定性有重要影响。因此对竹子抽出物的主要成分、化学结构,及其对漂白影响等的研究可以推动我国高得率竹浆的发展,对合理高效利用竹子资源等具有重大意义。本论文以慈竹、马尾松和尾叶桉磺化化学机械浆(SCMP)为研究对象,以慈竹SCMP为研究重点,通过对慈竹、马尾松、尾叶桉SCMP的纤维形态研究发现慈竹SCMP纤维平均长度与马尾松SCMP相当,接近于尾叶桉SCMP的2倍,宽度则略大于尾叶桉。磺化处理过程中Na2SO3用量为15%,NaOH用量为4%时,纤维平均长度有所增加,纤维平均宽度则出现下降。采用一段H2O2用量为6%的过氧化氢漂白,尾叶桉SCMP漂白浆白度最高,为84.47%ISO,且白度稳定较好;慈竹SCMP不仅初始白度最低,且漂白浆的白度也较低,仅为61.21%ISO,PC值则有4.45,说明慈竹SCMP不仅难漂白而且容易返黄。利用GC-MS、UV-Vis对慈竹SCMP的苯醇抽出物、二氯甲烷抽出物和甲醇抽出物研究发现,慈竹SCMP中有机溶剂抽出物含量较低,主要由小分子酚类、脂肪酸类和甾醇类等物质组成,其中部分物质在紫外330 nm左右有吸收,对纸浆发色及漂白有较大影响。有机溶剂抽提后的纸浆较易漂白,苯醇抽提后的浆料最终漂白浆白度提高了近9%ISO;甲醇和苯醇抽出物中含有较多易发色的物质,其去除后纸浆白度稳定性也得到提高,甲醇抽提的慈竹SCMP的漂白浆PC值下降了65.8%。对比慈竹、马尾松和尾叶桉SCMP的甲醇抽出物可知,马尾松未漂浆中的甲醇抽出物含量最高,为0.57%;过氧化氢漂白后出现不同程度的下降。马尾松SCMP甲醇抽出物中含有较多的小分子酚类和树脂酸类,慈竹SCMP中则是小分子酚类和甾醇类含量较多,漂白后小分子酚类和树脂酸类物质基本被除去,但甾醇类含量仅降低了33.3%。慈竹SCMP甲醇抽出物小分子酚类和甾醇类、马尾松SCMP中的小分子酚类和树脂酸类是它们较难漂白的重要原因。慈竹甲醇抽出物制浆漂白过程中变化较大,磺化处理后的甲醇抽出物含量为原料中的22.3%,磨浆后含量为原料中的11.2%,而过氧化氢漂白浆中的甲醇抽出物含量仅为原料中的7.38%。慈竹甲醇抽出物中的主要由小分子烷烃类、小分子芳香类、糖类、脂肪酸类及甾醇类等物质组成。在制浆漂白过程中,小分子类及糖类在磺化处理中大部分被除去,甾醇类物质的去除率只有约50%。研究发现漂白前的碱抽提处理可以提高慈竹SCMP漂白浆白度和白度稳定性能,在NaOH用量为2.0%,浆浓10%,70 oC,30 min的碱抽提条件下,单段过氧化氢漂白浆的白度可达64.23%ISO,比未处理浆料提高了6.91%ISO,PC值由3.24降至1.07,下降了66.9%。碱抽提后慈竹SCMP的两段过氧化氢漂白(QPP)白度可达77.13%ISO,PC值降至0.86。GC-MS分析表明碱抽出物中的化学成分可以分为短链类小分子、酚类和脂肪酸类,其中酚类是最重要的组成部分。碱抽提过程中酚类物质的溶出量随NaOH的用量增加而增多。慈竹SCMP碱抽出物在UV-Vis光谱中280 nm和330 nm处的吸收,也表明其中含有较多的酚类物质。这些酚类物质是造成慈竹SCMP难以漂白的一个重要原因。模拟碱抽出物在纤维表面的吸附试验表明,溶液中的碱抽出物易于吸附在纤维表面上,吸附在纤维表面的抽出物随溶液pH升高而增多,随着溶液中抽出物的浓度的增大而增加。制浆和漂白过程中溶出酚类抽出物容易吸附而留在纸浆中,尤其是碱性条件下抽出物更易于吸附在纤维表面。通过对过氧化氢与碱抽出物模拟物反应的研究发现,溶液中抽出物浓度较大时,过氧化氢被迅速消耗,即使碱抽出物浓度较低仍有较大量的过氧化氢被消耗。由此可见,慈竹SCMP中的抽出物在碱性条件下容易与过氧化氢发生反应,使得溶液中过氧化氢浓度迅速降低,漂白效率下降。根据SEM-EDS、XPS和AFM分析表明,SCMP纤维表面覆盖有一层木素和抽出物,占纤维表面较大比例,高于纸浆中总木素和抽出物含量,经过氧化氢漂白前后SCMP纤维表面木素含量变化不大。慈竹SCMP未漂浆纤维表面的抽出物占总纤维表面的7.11%,尾叶桉SCMP纤维表面分布的抽出物更多;过氧化氢漂白后慈竹SCMP纤维表面的抽出物的比例出现下降但不明显,大部分酚类物质主要分布于纤维内部。尾叶桉SCMP纤维表面抽出物以脂肪酸类为主,在漂白过程中溶出较多。漂白中过氧化氢主要作用于纤维内部,尾叶桉SCMP纤维内抽出物较少,过氧化氢漂白效率较高;慈竹SCMP纤维内部含量较多酚类物质造成过氧化氢的消耗,影响了漂白效率,使纸浆中残留较大量的发色基团,这是高得率竹浆难漂白、易返黄的主要原因。更多还原

【Abstract】 Bamboo is an important raw material for papermaking in China. The reasonable utilization of bamboo is an effective way to solve the shortage of fibrous materials for China paper industry, but the poor optical properties of bamboo high yield pulp, which are low brightness of bleached pulp and poor brightness stability, influence the application. Extractives in bamboo high yield pulp would impact the pulp brightness and brightness stability. So main component, chemical structure, and its impact on bleaching of extractives in bamboo should be studied, which could serve the development of bamboo high yield pulp in China and be of great significance of efficient use of bamboo.In this thesis, using bamboo (Neosinocalamus affinis.) SCMP, pine (Pinus massoniana) SCMP and Eucalyptus (Eucalyptus urophylla) SCMP as the research objectives and mainly focus on bamboo SCMP, through the study on the fiber morphology of bamboo SCMP, pine SCMP and Eucalyptus SCMP, the results showed the average length of bamboo SCMP fiber was similar to pine SCMP fiber, about 2 times of eucalyptus SCMP fiber, while the width of bamboo SCMP fiber was a little larger than that of eucalyptus. The average length of bamboo SCMP fiber, which Sulfonated with 15% Na2SO3 and 4% NaOH, was longer than that with the same dosage of Na2SO3 and soda dosage of 2%, meanwhile the average width was decreased. Results of three SCMP that bleached by one stage peroxide bleaching with hydrogen peroxide dosage of 6% showed that, the brightness of bleached Eucalyptus SCMP pulp was the highest, 84.47%ISO, so as the brightness stability; bamboo SCMP was not only with lowest initial brightness, but also lower brightness of bleached pulp, only 61.21%ISO. PC number of bleached bamboo SCMP was 4.45, meaning that bamboo SCMP was hard to bleach and is easily yellowed.Using GC-MS and UV-Vis, extractives with benzene-alcohol, dichlorometane and methanol from Bamboo SCMP were studied; results showed that, contents of extractives in bamboo SCMP were low. And the extractives were mainly composed of phenols, fatty acids, sterols and so on. Some substances in the extractives, whose UV spectrum had absorbance around 330 nm, had great impact on the bleachability of SCMP pulp. After organic solvent extraction, the SCMP was easy to bleach. The brightness gain of the bleached pulp of benzene-alcohol extracted bamboo SCMP was nearly 9 %ISO. Removal of substances by methanol and benzene-alcohol extraction could improve the pulp brightness stability. PC number of the bleached pulp of methanol extracted bamboo SCMP decreased by 65.8%. Comparison on methanol extractives of bamboo, pine and Eucalyptus SCMP showed, methanol extractives content of unbleached pine pulp was the highest, about 0.57%; after hydrogen peroxide bleaching, methanol extractives content was decreased differently. Methanol extractives of pine SCMP contained more phenols and resin acids, while methanol extractives of bamboo SCMP contains more phenols and sterols. Phenols and resin acids were removed mostly after bleaching, but sterols were only decreased by 33.3%. Phenols and sterols in methanol extractives of bamboo SCMP, as well as phenols and resin acids in pine SCMP, were the most important reasons for their difficulties of bleaching. Methanol extractives changed greatly during pulping and bleaching process. Content of methanol extractives in the sulfonated bamboo chips was about 22.3% of that in bamboo chips, and bamboo SCMP of 11.2%, hydrogen peroxide bleached pulp of only 7.38%. Methanol extractives of bamboo were mainly consisted by small molecule alkanes, phenols, saccharides, fatty acid and sterols. During sulfonation process, small molecules substances and saccharides were removed mostly; in the other hand, the removal rate of steroid alcohols was about 50%.It was found that alkaline extraction before bleaching could improve the brightness and brightness stability of bleached bamboo SCMP. Under alkaline extraction condition of soda dosage 2.0%, pulp consistency of 10%, 70 oC, 30 min, the brightness of one-stage peroxide bleached bamboo SCMP could reach 64.23 %ISO, 6.91%ISO higher than that of untreated pulp, and PC number decreased by 66.9%. Multistage bleaching would improve the brightness. After alkaline extraction under conditions of 2.0% NaOH dosage, 70°C, 30 min, brightness of two-stage (QPP) peroxide bleahed bamboo SCMP could reach 77.13 %ISO and PC number reduced to 0.86. Results of GC-MS analysis showed that the alkaline extractives were composed of short-chain alkanes, phenols and fatty acids, and phenols were the most important compositions. The amount of phenols dissolving out the pulp during alkaline extraction increased with the increase of NaOH dosage. Absorbance around 280 nm and 330 nm of UV-Vis spectrum of bamboo SCMP alkaline extractives showed there were a lot of phenols, which was the important reasons that caused the difficulty of bamboo SCMP bleaching.Study on the model alkaline extractives adsorption on the fiber, using tannin as a model compound, showed that alkaline extractives in the solution could be easily adsorbed on the fiber surface. Adsorption of the extractives on fiber surface increased with higher concentration of extractives in solution, as well as the increased pH of solution. Phenols dissolved out during pulping and bleaching process would be easily adsorbed on the fiber and remain in the pulp, especially under alkaline conditions. Research on hydrogen peroxide reaction with model alkaline extractives found that hydrogen peroxide was rapidly consumed when the concentration of extractives in solution was high. Even concentrations of alkaline extractives was lower, there was a lot of hydrogen peroxide was consumed. So, extractives in bamboo SCMP were intended to react with hydrogen peroxide under alkaline condition caused the rapid decrease of the concentration of hydrogen peroxide in the solution decreased rapidly. this was also the reason of poor bleachability of bamboo SCMP.Results of SEM-EDS, XPS and AFM analysis showed that, SCMP fiber surface covered with a layer of lignin and extractives, accounting for a large proportion of the fiber surface, which were higher than the total contents of lignin and extractives in pulp. Coverage of lignin on SCMP fiber surface after hydrogen peroxide bleaching remained almost the same as unbleached SCMP fiber surface. Content of extractives on unbleached bamboo SCMP fiber surface was 7.11%, whereas content of extractives on unbleached eucalyptus SCMP fiber surface was more. Coverage of extractives on SCMP fiber surface was deceased slightly after hydrogen peroxide bleaching, most of the phenols inside of fiber reacted with peroxide. Extractives covered the eucalyptus SCMP fiber surface were mainly fatty acids, which would dissolved out during bleaching. Hydrogen peroxide attacked inside of fiber in bleaching, so bleaching of eucalyptus SCMP was more efficient due to less extractives in the; while phenols in the Bamboo SCMP fiber would caused consumption of the hydrogen peroxide, and affected bleaching efficiency, led to a lot chromophore structure remained in pulp, which was the main reasons caused difficulties to bamboo SCMP bleaching, and yellowing of bleached pulp.更多还原