Organochlorine Formation in Tertiary Amine Catalyzed Pulp Bleaching

An oxygen delignified eucalyptus kraft pulp was bleached by applying a catalytic amount of a tertiary amine, 1,4-diazabicyclo[2,2,2]octane, and hypochlorous acid at varying pH, temperature, and time. The bleaching filtrate was analyzed for chloroform and AOX and the pulp for residual lignin, hexenuronic acid, and OX. In comparison with chlorine dioxide bleaching, the novel catalytic bleaching (pH < 6) generated only traces of chloroform and low contents of AOX and OX. Separate catalytic oxidations of authentic hexenuronic acid showed that it was a major precursor of chloroform. The results demonstrate a practical way to reduce organochlorine formation in pulp bleaching and provide new understanding on the reaction pathways that yield chloroform.     

废胶粉和锯末对废纸浆性能的影响

试验研究废胶粉和锯末对废纸浆性能的影响.结果表明:废胶粉/废纸浆、锯末/废纸浆和废胶粉/锯末/废纸浆复合材料的物理性能提高,且废胶粉/废纸浆复合材料的物理性能优于废胶粉/锯末/废纸浆复合材料,因此以废胶粉改性废纸浆效果较好.废胶粉/废纸浆复合材料的最佳配方为:废纸浆100(干基计),废胶粉8,防老剂D 0.2,硫黄0.2,促进剂M 0.2;最佳固化条件为150℃/10 MPa×30 min.此时材料表面比较光滑,结构紧密,排列比较均匀,废胶粉与废纸浆的相容性较好.     

Combination of bifunctional aldehydes and poly(vinyl alcohol) as the crosslinking systems to improve paper wet strength

Two bifunctional aldehydes (i.e., glyoxal and glutaraldehyde) are used as the crosslinking agents to improve paper wet strength in the presence of fully hydrolyzed poly(vinyl alcohol) (PVA) as a co‐reactant. These bifunctional aldehydes alone improve paper wet strength but diminish its folding endurance. The use of PVA as a co‐reactant not only improves paper wet strength but also increases its dry strength and folding endurance. Glutaraldehyde is able to impart much higher levels of wet strength to the treated paper than glyoxal when a catalyst is present. The wet strength of the treated paper increases as the amount of PVA added is increased, and it also increases as the molecular weight (M_w) of the PVA increases. The data suggest that the reaction between glutaraldehyde and PVA promotes the formation of interfiber crosslinking, thus improving the wet strength without diminishing the flexibility of the treated paper. The use of a catalyst is critical to achieve high levels of durable wet strength of the treated paper. We studied the effects of different Lewis acids as the catalysts for crosslinking of pulp cellulose by glutaraldehyde and found that Zn(NO₃)₂ is the most effective one. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1673–1680, 2004     

紫穗槐碱法纸浆的漂白性能研究

紫穗槐烧碱—蒽醌浆的实验室漂白的研究表明,其白度可达到生产一般书写纸和有光纸的要求。采用常规次氯酸盐单段或次氯酸盐两段漂白,白度能达到66—70°。研究中发现,碱法紫穗槐浆的硬度对漂白的影响最大,当硬度为高锰酸钾值14～16时,其漂率相当于麦草浆的漂率。研究中还发现,选用HA—P(次氯酸盐/酸处理—过氧化氢)法漂白时,也能获得较好的白度。     

纤维用浆粕中重金属含量的测定

介绍了一种检测浆粕中重金属含量的方法,即通过烧灰法将浆粕灰化,再加入盐酸和醋酸溶解,用等离子体原子发射光谱(ICP-OES)仪检测浆粕中重金属元素的含量。该方法能够准确测定铜、镉、铁、锰、钼、镍等6种重金属元素的含量,具有重复性能好、检出限低、操作简便的优点。     

木浆纤维素/NMMO·H_2O溶液的流变性能研究

以含水率13.7%的N-甲基吗啉-N-氧化物(NMMO)为溶剂溶解木浆纤维素形成溶液,采用红外光谱分析仪对木浆纤维素的溶解过程进行表征,并采用黏度计研究了木浆纤维素/NMMO·H2O溶液的流变性能。结果表明:木浆纤维素在NMMO中先溶胀后溶解,且可完全溶解;木浆纤维素/NMMO·H2O溶液的流动呈现切力变稀的假塑性流体特征;木浆纤维素质量分数为6%时,溶液的非牛顿流动特征明显,溶液的表观黏度(ηa)随木浆纤维素浓度的增加明显增加,随剪切速率(γ)及温度的上升而下降,当γ高于一定值即logγ大于1.3时,溶液的ηa不受温度的影响,只随γ的上升而下降,且剪切应力不随γ变化而变化,为恒定值。     

Stereo-Preference in the degradation of the erythro and threo isomers of β-O-4-type lignin model compounds in oxidation processes. part 2: In the reaction with hydroxyl and oxyl anion radicals under hydrogen peroxide bleaching conditions

We examined which isomer, the erythro or threo, of non-phenolic β-O-4-type lignin model compounds is stereo-preferentially attacked by hydroxyl radical and its conjugate base, oxyl anion radical, generated by the decomposition of hydrogen peroxide in the presence of ferric ion and its precipitates under hydrogen peroxide bleaching conditions. The intrinsic stereo-preference of oxyl anion radical was slightly toward the erythro isomer, while hydroxyl radical had a further smaller stereo-preference. These stereo-preferences can be explained by our prior knowledge that oxyl anion radical preferentially attacks the side-chain of the lignin model compounds rather than the aromatic nucleus. The amount of the degraded lignin model compounds became less great with decreasing pH, but reversely and intensively greater in the pH range below 10. This phenomenon can be attributed to the change in the decomposition mechanism of hydrogen peroxide accompanying the pH variation.     

Effect of two drying methods on antioxidant activity and hypoglycemic action of polysaccharides in three cultivars of lychee pulp

Effect of air drying and freeze drying on polysaccharides of lychee with three cultivars was determined in terms of polysaccharides yield, antioxidant capacity and hypoglycemic action. The results show that Guiwei lychee pulp had the highest crude polysaccharide yield among three lychees. However, Feizixiao lychee had the lowest EC₅₀ concentration and the highest FRAP (Ferric reducing antioxidant power) value. Moreover, Guiwei lychees dried by air drying had the best effect for improving glucose tolerance of normal mice and diabetic mice. Three freeze dried lychees had no significant effect. The effect of air dried Guiwei samples on decreasing TG was the best and it was even better than dapagliflozin group. Only freeze-dried Guiwei lychee could significant decrease the TC content in blood among all lychee samples. In a word, Feizixiao lychees had the best antioxidant capacity and Guiwei lychees had the best hypoglycemic effect. Air drying was better drying method for lychee polysaccharides than freeze drying in this study.     

间硝基苯磺酸钠助催化硫酸水解制备芦苇浆纳米纤维素

以间硝基苯磺酸钠(SMS)为助催化剂,质量分数 55% 硫酸水解芦苇浆制备纳米纤维素(NCC)。研究反应温度、反应时间以及SMS添加量对NCC的产率及粒径的影响。结果表明NCC最佳制备工艺条件为:反应温度 50℃,反应时间 3.0 h,间硝基苯磺酸钠添加量10%(以芦苇浆质量计)。傅里叶变换红外(FT-IR)光谱分析表明最佳工艺条件制备的NCC为纤维素类物质;透射电子显微镜和扫描电子显微镜图分析表明以SMS为助催化剂制备的的NCC形貌更规整,呈棒状。相同NCC制备工艺条件下,与十二烷基苯磺酸钠(SDBS)和硫酸铜(CuSO₄)两种助催化剂相比,助催化剂SMS制备的NCC产率最高。     

对位芳纶浆粕在密封制品中的应用

介绍了对位芳纶浆粕的发展现状及其无石棉垫片的基本特性,通过应用实例表明泰普龙浆粕能满足无石棉垫片技术和市场的需求。指出随着石棉的禁用和限制以及国产对位芳纶生产质量与规模的快速发展,国产芳纶浆粕将有实质性突破,从而促进国产无石棉垫片的研究与生产。