Containing Pulps

The rapid, light-induced yellowing of lignin is one of the most serious and recalcitrant problems preventing the wider use of high-yield pulps in value-added paper grades. Much research effort has been devoted to this problem over the last 40 years. 

FIGURE 3.12 Action spectra for irradiation of peroxide-bleached softwood CMP. The y axis is the inverse of the incident energy required to produce a unit change in PC number at either 457 nm or 557 nm. (Reproduced from Forsskahl, I. and Tylli, H., Photochemistry of Lignocellulosic Materials, Washington, DC American Chemical Society, 45-59, 1993. With permission.) 

Unlike newsprint, neither CMP nor CTMP were photobleached by any wavelength. However, pulp previously yellowed by broadband exposure was photobleached by almost all wavelengths of light, except for a narrow band around 350 nm. 

FIGURE 3.13 Absorption difference spectra for ultraviolet irradiation of peroxide-bleached softwood TMP and CTMP, calculated from diffuse reflectance measurements. (Reproduced from Schmidt, J.A. and Heitner, C., J. Wood Chem. TechnoL, 15, 223-245, 1995. With permission.) 

Davidson et al. [122] reported the difference spectra of spruce wood sections and groundwood pulp that had been irradiated and then stained with phlo-roglucinol. The irradiated and stained samples showed an absorption increase at = 550 nm, which the authors attributed to photochemical formation of coniferaldehyde, based on the well-known Wiesner reaction. However, in a subsequent pnblication [123], they found that phloroglucinol gives a similar color reaction with methoxy-p-quinone, which would be a more reasonable explanation of the earlier resnlts. 

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Eds. "Pollution Abatement by More Effective Lignin Utilization. Grafting to Lignin and Lignin-Containing Pulps" North Carolina State University, Raleigh, New York, 1970. 

Extraction of stevia sweeteners from dried leaves can be accomplished with acetonitrile in the presence of calcium carbonate solution (116) or with boiling water adjusted to pH 9.0 (107). Ahmed and Dobberstein (117) extracted stevioside and rebaudioside A and C from dried leaves of S. rebaudiana in a micro-Soxhlet apparatus. They observed that chloroform/methanol provided the best results, compared to chloroform or to chloroform/methanol/water. Extraction of stevioside, rebaudioside A and C, and dulcoside A can also be performed by subcritical fluid extraction using C02 and methanol as a modifier. Such an extraction technique has been gaining popularity as an analytical tool because it is rapid, simple, and less expensive in terms of solvent cost (110). Beverages, tabletop sweeteners, beverages containing pulp, and candies are prepared as indicated in Sec. I.C (110,115,118). 

Cole B.J.W., Sarkanen, K.V. and Hooper, J.E., "Sulfur-Containing Pulp Brightness Stabilizers", Proceedings of the Fourth International Symposium on Wood and Pulping Chemistry Paris, 1987 Vol. 1, pp 321-325. 

Francis, R.C., Dence, C.W. and Alexander, T.C., "Method For Reducing the Brightness Reversion in Lignin-Containing Pulps and Article of Manufacture Thereof, United States Patent 5,080,754, Jan. 14, 1992. 

Comparison of Absorption Spectra of Quinones in Solution and Adsorbed on Lignin-Containing Pulp... 

FIGURE 3.15 Two pathways proposed to account for yellowing of lignin-containing pulps and the formation of aromatic carbonyls from (3-0-4 guaiacylglycerol ketyl radieals. 

JH Zhu, JA Ohnstead, and DG Gray. Fluorescent Detection of o—Quinones Formed in Lignin-Containing Pulps during Irradiation. J. Wood Chem. Technol. 15 43-64, 1995. 

Raman spectroscopy was also used to analyze lignin-containing pulps that were chemically modified (sulfonated, acetylated, hydrogenated, methylated, and acid hydrolyzed) [5,9], In each case, the nature of the change and the extent to which pulp lignin was modified were discerned from the changes in the spectra. 

Lignin-containing pulp and paper samples have been frequently analyzed by FT-IR (for a review see [103]). For instance, bleached [91,104,105], yellowed (both thermal and photo) [91,104-107]and biomechanical pnlps [101] have been analyzed. Of the various methods of sampling, DRIFT has been nsed most often photoaconstic, ATR, and micro methods have been used sparingly. 

The coniferyl alcohol end group in lignin survives alkaline hydrogen peroxide bleaching [13,38] and is therefore a potential photoactive group in both bleached and unbleached lignin-containing pulps and in wood. The initial research on the... 

C Fabbri, M Bietti, and O Lanzalunga. Generation and Reactivity of Ketyl Radicals with Lignin Related Structures. On the Importance of the Ketyl Pathway in the PhotoyeUowing of Lignin Containing Pulps and Papers. J Org Chem 70 2720-2728, 2005. 

The juice is first mixed with tetrahydrofuran. The nonpolar pigments are transferred in petroleum ether. The water phase is discarded and the organic phase is washed with water. This is repeated until the water phase becomes colorless. The ether extracts are pooled and dried on anhydrous sodium sulfate. When the juice contains pulp, it is advisable to remove it... 

The books say that ricin is an albumin. Egg vrhite is also an albumin. I reasoned I should take out the SSVo of oil from the castor beans as the books say it isn t in the oil. After the oil is removed the albumin containing pulp remains. The next step was to extract the albumin from the pulp and the whole process is childishly simple. 

U. Schroder, Effects of calcium hydroxide-containing pulp-capping agents on pulp cell migration, prohferation, and differentiation, J. Dent Res. 64 (1985) 541-548. 

Semiindustrial tests were carried out on zirconium and hafnium extraction by TVEX-65% TBP from nitric silica-containing pulps with the following composition Zr 17.0-44.0 g/L, Hf 0.2-0.5 g/L, A10.2-0.37 g/L, Fe 1.7-4.0 g/L, Si 0.8-8.2 g/L, HNO3 260.0-420.0 g/L. The pulp was received as a result of HNO3 leaching of cake of zircon with soda. 

Paper grades that contain pulp produced by mechanical or chemimechanical processes are referred to as wood-containing papers. Mechanical pulps are mainly used in short-Hfe printing papers, hygienic papers and board. 

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