| 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. |
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