Unbleached softwood kraft pulp

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. 

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. 

Degradation of Unbleached Softwood Kraft Pulp by P. cbtnabarinus... 

This experiment was carried out in accord with an established procedure (5). Unbleached softwood kraft pulp (USKP) from Douglas fir was obtained from Pope and Talbot (Halsey, Oregon) and washed with deionized water until the effluent was neutral and colorless. USKP (8.0 g, oven-dried) was autoclaved at 121 °C for 40 min, cooled down at room temperature and then inoculated with 3 mL of P. cinnabarinus spore suspension (ca. 9 x lO spores/mL). The moisture content of the culture was adjusted to 80% and the culture was incubated statically at 30 °C. After a pre-determined incubation time, mycelia were carefully removed fiom pulp. Hie treated pulp was analyzed for kappa number. 

Table V. The Contents of Various Functional Groups (mmol/g Lignin) in the Degradation of Unbleached Softwood Kraft Pulp by P. cimabarbtm "...

The isolation of enzymatic residual LCCs from unbleached softwood Kraft pulps is a well-established procedure producing preparations with high yields (estimated as lignin in isolated preparations per lignin in the original pulp) and relatively low enzyme impurities [46 8]. In contrast, significant problems are encountered when similar procedures are applied to the isolation of enzymatic residual LCCs from hardwood Kraft pulps and semi-bleached pulps [47]. Low yields (25-30%) make these preparations nonrepresentative for the whole pulp LCC. A very large amount of protein impurities... 

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

We have tried to find a suitable level of P-PEG by adding 5 and 10% P-PEG. The results given below in table 1 are for medium size fibers of unbleached softwood kraft pulp. 

Table 1. Partition of medium size fibers, unbleached softwood kraft pulp. Results in percent...

The furnish of a paper machine varies widely, depending on the grade of paper being made. Newsprint usually consists of about 80 percent groundwood and 20 percent chemical fiber (sulfite or semibleached kraft). Bag papers and linerboard are usually 100 percent unbleached softwood kraft. Printing papers are made from bleached pulps and contain both hardwoods and softwoods. By selecting the proper pulps and refining conditions, a wide variety of paper qualities can be achieved. 

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... 

Under alkaline cooking conditions some of the 4-0-MeGlcA residues present in hardwood and softwood xylans are converted into unsaturated hexenuronic acid residues (HexA) by -elimination of methanol. In an early study (4) employing MALDI-MS, we were able to identify a number of different HexA and 4-0-MeGlcA containing xylooligosaccharides in the hydrolysate obtained after endoxylanase treatment of an unbleached hardwood kraft pulp. 

Preparation of Pulp Having Different 7-Cellulose Contents. Unbleached pulp (50 hardwood kraft-50 softwood kraft) was subjected to chloriting treatment to remove lignin. The chemicals and conditions employed were the following 25 g of sodium chlorite, 12.5 mL of glacial acetic acid, a pulp consis-... 

Materials. All test papers were obtained from a single roll or were made from pulp. The following test papers were used (1) Foldur kraft paper, a bleached kraft paper made from 90% southern pine and 10% hardwood pulps, with 0.5% rosin size and 3% titanium filler (2) newsprint paper made from 80% groundwood and 20% unbleached sulfite pulp and (3) handsheets prepared from a 1 1 furnish of Weyerhaeuser New Bern softwood (NBS) and New Bern hardwood (NBH) bleached kraft pulps. 

Wood resin is the water-insoluble material that is soluble in neutral, non-polar organic solvents. Large amounts of it pass through mill systems that utilize softwoods and some of the hardwoods. This resin can cause pitch problems, particularly with sulfite pulping and the manufacture of unbleached sulfite pulps and to a lesser extent with mechanical and chemi-mechanical pulping. Problems are less frequently encountered with kraft pulping and usually they are less severe and of a different type. 

The correction factor Kq depends on the type of pulp. It is considered to be 1.00 for unbleached sulfite softwood, 0.90 for bleached sulfite softwood, 0.90 for unbleached kraft softwood, 0.90 for soda hardwood, 0.90 for reclaimed fiber, 1.0 for presteamed ground-wood-softwood, and 1.42 for stoned groundwood-softwood. (IDP 1995). 

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