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The advancement of oxygen bleaching by using chemical additives to improve pulp properties.

机译：通过使用化学添加剂改善纸浆性能来促进氧漂白。

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摘要

The purpose of this research was to evaluate the addition of HEDP (1-Hydroxyethylidene-1,1-diphosphonic acid) and magnesium gluconate as additives to improve the selectivity (the ratio of delignification to depolymerization) of the oxygen bleaching process. Through examination of levels of delignification, depolymerization, brightness, strength, radical generation, metal content, and fiber structure it was concluded that both additives are effective at increasing the selectivity of oxygen bleaching, but their mechanisms of action are very different.; HEDP improves selectivity by increasing the rate of delignification, while improving bonding strength. HEDP functions as a chelant, deactivating metal ions that can catalyze the formation of radicals, which attack both lignin and cellulose. Surprisingly, the ability of HEDP to function is slowed by the removal of metal ions, indicating the presence of metals is important to the delignification mechanism. HEDP addition improves fiber flexibility and fiber bonding. Moreover, HEDP addition allows the fibers to be refined more quickly, resulting in an increased amount of external fibrillation, which contributes to fiber bonding. Faster refining might also lead to easier access of bleaching chemicals to cell components, allowing for equivalent delignification levels to be reached in a shorter amount of time. The optimum level of HEDP application for these experiments was determined to be 1%.; Magnesium gluconate also improves reaction selectivity. It functions as a radical scavenger, decreasing the amount of hydroxyl radicals present in the oxygen stage. In the presence of large amounts of manganese, delignification and depolymerization are both severely impaired. When metals are removed, the delignification rate is comparable to the control, while cellulose depolymerization is still slowed, increasing selectivity. Magnesium gluconate appears to function to protect hemicellulose and cellulose components against degradation. While fiber flexibility and bonding are improved over the control, external fibrillation from refining does not appear to be significantly increased. To function optimally, this additive requires a metal removal stage before the oxygen bleaching. The addition of 0.5% magnesium gluconate is the lowest amount necessary to see improvements in reaction selectivity.
机译：这项研究的目的是评估添加HEDP（1-羟基亚乙基-1,1-二膦酸）和葡萄糖酸镁作为添加剂，以提高氧漂白过程的选择性（脱木素与解聚的比率）。通过检查去木质素，解聚，亮度，强度，自由基的产生，金属含量和纤维结构的水平，可以得出结论，两种添加剂均能有效提高氧漂白的选择性，但其作用机理却大不相同。 HEDP通过提高脱木素率来提高选择性，同时提高结合强度。 HEDP起到螯合剂的作用，使金属离子失活，从而可以催化自由基的形成，这些自由基攻击木质素和纤维素。令人惊讶的是，HEDP的功能由于金属离子的去除而减慢，表明金属的存在对脱木素机理很重要。加入HEDP可改善纤维的柔韧性和纤维粘合性。此外，加入HEDP可以使纤维更快地细化，从而增加外部原纤化的数量，从而有助于纤维粘合。提炼速度加快也可能使漂白化学物质更易于进入细胞成分，从而可以在更短的时间内达到等效的脱木素水平。确定用于这些实验的HEDP的最佳水平为1％。葡萄糖酸镁还提高了反应选择性。它起自由基清除剂的作用，减少了氧阶段中存在的羟基自由基的数量。在大量锰的存在下，脱木素和解聚都严重受损。当除去金属时，脱木质素率与对照相当，而纤维素解聚仍然减慢，增加了选择性。葡萄糖酸镁似乎起到保护半纤维素和纤维素组分免于降解的作用。尽管与对照相比改善了纤维的柔韧性和粘合性，但精制引起的外部原纤化似乎并未显着增加。为了实现最佳功能，该添加剂需要在氧漂白之前进行金属去除步骤。添加0.5％葡萄糖酸镁是观察到反应选择性改善所需的最低量。

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  • 作者

    Jewell, Melody Elaine.;

  • 作者单位

    University of Minnesota.;

  • 授予单位 University of Minnesota.;
  • 学科 Chemistry Organic.; Agriculture Wood Technology.
  • 学位 Ph.D.
  • 年度 2002
  • 页码 175 p.
  • 总页数 175
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 有机化学;森林采运与利用;
  • 关键词

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