Softwood kraft pulping

A cross-sectional view of kenaf is shown in Figure 3d. The ultimate cells are nearly cylindrical with thick cell walls. Kenaf fibers are shorter and coarser than those of jute. Both chemical (kraft) and mechanical pulps have been produced from kenaf, and successful demonstration mns of newsprint have been made for the Dallas Morning Nem, the St. Petersburg Times, and the Bakersfield Californian with a furnish of 82% kenaf chemithermomechanical pulp and 18% softwood kraft pulp. Kenaf fiber is also considered a substitute for jute and used in sacking, rope, twine, bags, and as papermaking pulp in India, Thailand, and the former Yugoslavia. RoseUe bleached pulp is marketed in Thailand. 

Fig. 31. AOX formation in chlorination (C) and extraction (E) stages for 30 kappa softwood kraft pulp chlorinated at 4% consistency in mixer, using...

Axegard, P. Bergnor, E. Elk, M. Ekholm, U. Bleaching of softwood Kraft pulps with H2O2, O2 and CIO2. TappiJ. 1996, 79, 113-119. 

Reid, I.D. Paice, M.G. Ho, C. Jurasek, L. Biological bleaching of softwood Kraft pulp with the fungus, Trametes (Coriolus) versicolor. Tappi J. 1990, 73, 149-153. 

Ramos, L. P., Zandon, A., Filho, A., Deschamps, F. C., and Saddler, J. N., The effect of Trichoderma cellulases on the fine structure of a bleached softwood kraft pulp. Enzyme Microbial Technol 1999, 24 (7), 371-380. 

In a related approach, Ni et al (1990) have developed a procedure for determining lignin in softwood kraft pulp based on the conversion of methoxyl groups in the lignin to methanol when the pulp is chlorinated under a specified... 

Jiang J-E, Chang H-m, Bhattacharjee SS, Kwoh DLW (1987) Characterization of residual lignins isolated from unbleached and semi-bleached softwood kraft pulps. J Wood Chem Techno 1 7 81-96... 

A peroxide stage, P stage, is occasionally used as a polishing bleach for chemical pulps, using the conditions discussed. Peroxide has also been tested for initial bleaching of softwood kraft pulps after an acid pretreatment. A significant reduction in waste loads is obtained but at high cost [28]. 

An example of such a series of transient experiments for a sample of paper without conductive additives (softwood Kraft pulp, 450 CSF, 80 g/m2 basis weight, Sample 1), is shown in Fig. 16. This series of transient currents represents the electric field dependence of charge transport associated with mobile ions within the water associated with the fibrous network of the papor. The initial transient current, labeled (a), corresponds to the first application of an electric field (E = 2.5 x 103 Volts/cm) to the new sample. After reversing the polarity of the power supply an electric field of the same magnitude is applied to the sample which leads to the transient current shown by label (b) in Fig. 16. (N.B. the scale of the ordinate is different for... 

M Tenkanen, G Gellerstedt, T Vuorinen, A Teleman, M Perttula, J Li, J Buchert. Determination of Hexenuronic Acid in Softwood Kraft Pulps by Three Different Methods. J Pulp Pap Sci 25 306-311, 1999. 

FIGURE 11.22 Remaining amount of specific phenolic end-groups in lignin when a softwood kraft pulp is bleached according to the sequence OD(EO)DD. 

FIGURE 11.24 Comparison of remaining amount of methoxyl groups and presence of organically bound chlorine in the dissolved lignin after prebleaching (CE —> DE) of softwood kraft pulp using different ratios of chlorine to chlorine dioxide. 

FIGURE 11.25 Successive dissolution of lignin from a softwood kraft pulp after repeated treatment with chlorine followed by alkaline extraction (CE). (Reprinted with permission of de Gruyter from Berry, R.M., and Fleming, B.L., Holzforschung, 41, 177-183, 1987.)... 

FIGURE 11.29 Formation of tetrachloroguaiacol (a), 3,4,5-trichloroguaiacol (b), and dichloroguaiacol (c) as a function of the amount of chlorine dioxide charged in the prebleaching of softwood kraft pulp. 

J Wang, Z-H Jiang, DS Argyropoulos. Isolation and characterization of lignin extracted from softwood kraft pulp after xylanase treatment. J Pulp Pap Sci 23 J47-J51, 1997. 

M Lawoko, G Henriksson, G Gellerstedt. New method for quantitative preparation of lignin-carbohydrate complex from unbleached softwood kraft pulp Lignin polysaccharide networks I. Holrforschung 57 69-74, 2003. 

A-S Jaaskelainen and K Poppins-Levhn. Chemical changes in residual lignin structure during peroxyacetic acid delignification of softwood kraft pulp. Nord. Pulp Paper Res. J. 14 116-122, 1999. 

Various fungi, including P. chrysosporium, and T. versicolor were shown capable of degrading lignin and bleaching kraft pulp. These abilities were mostly correlated with the MnP activity found in the culture fluids. Reid [100] demonstrated that in a 14-day culture of T. versicolor on unbleached softwood kraft pulp followed by a DED bleaching sequence increased brightness from 33 to 61% and lowered kappa number from 24 to 8.5. 

In another study, when MnP from the fungus IZU-154 was incubated with softwood or hardwood kraft pulp in the presence of Mn +, glucose oxidase and glncose, the amount of effective chlorine needed to increase brightness was substantially lowered. After the enzyme treatment, chlorine consumption required to increase the brightness to 85% ISO decreased 51, 66, and 69% for normal-lignin-content softwood kraft pnlp, low-lignin-content softwood kraft pulp and hardwood kraft pulp respectively [109]. 

K Ehara, Y Tsutsumi, T Nishida. Biohleaching of softwood kraft pulp with manganese peroxidase./SWPC 26 1, 1997. 

ID Reid, MG Paice. Effects of manganese peroxidase on residual lignin of softwood kraft pulp. Appl Environ Microbiol 64(6) 2273-2274, 1998. 

B Marcoccia, DAI Goring, and DW Reeve. Photo-enhanced Oxygen Delignification of Softwood Kraft Pulp Effect of Some Process Variables. J Pulp Paper Sci 17 134—138, 1991. 

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