Paper grade pulp

Principal Uses. Groundwood pulp contains a considerable proportion (70—80 wt %) of fiber bundles, broken fibers, and fines in addition to the individual fibers. Principal uses of paper-grade pulps are in newsprint, magazine papers including coated pubHcation grades, board for folding and molded cartons, wallpapers, tissue, and other similar products. 

Heteropolysaccharides are, in general, highly desirable components of paper-grade pulps while they are not tolerated in dissolving-grade pulps used for the production of regenerated cellulose products and cellulose derivatives. A vast body of literature exists on the effects of hemicellu-loses on the papermaking process. 

As Rosenau et al. [49] indicated that paper grade pulp, unbleached chemical pulp, cotton and rayon fiber wastes, or even paper wastes can be used as raw materials for Lyocell fiber production, even though problems with spinnability may be encountered in some cases. In preparation for spinning dope, a 50-60% aqueous NMMO is used with the addition of 0.01 0.10% antioxidant to prevent cellulose degradation. A typical antioxidant is PG [50]. In a typical Lyocell industrial process, the slurry is produced from cellulose pulp and an aqueous NMMO solution. Typical compositions are 50-60% NMMO, 20 30% water, and 10-15% pulp [48]. Subsequently excess water is efficiently evaporated at temperatures lower than 150°C and... 

The solubility of untreated and enzyme-treated pine sulphate paper grade pulps with the aid of zinc oxide. 

Nousiainen, P. and Vehvilainen, M., CELSOL - Modification of pine sulphate paper grade pulp with Trichoderma reesei cellulases for fibre spinning, Procds, 2nd Autex Conference, 24-27 June 2000. 

Chemical charge, Hquor composition, time of heatup, and time at temperature of reaction are all functions of the wood species or species mix being digested and the intended use of the pulp. A typical set of conditions for southern pine chips in the production of bleachable-grade pulp for fine papers is active alkaH, 18% sulfidity, 25% and Hquor-to-wood ratio, 4 1. Time of heatup is 90 min to 170°C time at temperature of reaction, 90 min at 170°C. Hardwoods require less vigorous conditions primarily because of the lower initial lignin content. 

Table 21.3 presents an overview of wood pulping types by the method of fiber separation, resultant fiber quality, and percent of 1998 U.S. pulp production.1112 Many mills perform multiple pulping processes at the same site, most frequently nondeink secondary fiber pulping and paper-grade kraft... 

In case that corrugated base papers are not any more produced from recycled paper, as it is typical for testliner and medium in Germany, virgin fibres would have to be used. The corresponding paper grades as kraftliner would be produced from kraft pulp and fluting from semi-chemical pulp. For the simplified calculation of the required wood demand for the fibres, an average process yield of 60% (kraft pulp = 50%, semi-chemical pulp = 70%) is used. The substitution of the... 

Kraftliner as well as fluting are not manufactured in Germany. Corresponding paper grades would have to be imported or at least the necessary raw materials. The required pulp volume for the production of 3.6 Mio t corrugated base papers would exceed the current total chemical pulp import of 3.4 Mio t of the German paper industry. 

Wood logs are pushed under the revolving grindstone and crushed by mechanical pressure to yield low-grade pulps. Lignin is not removed during this process and therefore imparts a dark color to the pulp and paper product. 

Total US production of paper in 2005 was 37.6 million metric tons, and production of paperboard was 45.7 million tons at operating rates of 92% and 97% respectively. Production data and projections are analyzed by RISI,1 and periodic updates on industry issues, grade profiles and production statistics are published in Pulp and Paper, Paper Age, Pulp and Paper International and other trade journals. The US paper industry reuses more than 51% of the product it produces with an ultimate goal of 55%.2... 

The bark of trees contains relatively little fiber and much strongly colored nonfibrous material what fiber there is, is of poor quality. The nonfibrous material usually will appear as dark-colored dirt specks in the finished paper. Therefore, for all but low-grade pulps, bark should be removed as thoroughly as possible, and this removal must be very thorough in the case of groundwood and sulfite pulps if the finished paper is to appear clean. 

The APM mill at Bumie, Tasmania used the soda process to obtain bleachable grade pulps from euealypts for the manufaeture of fine papers, but in 1983 the mill switched to the soda-AQ proeess in order to pulp pine and euealypts together, the deeision being made on the grounds of wood availability. 

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. 

Corrosion rates in mill equipment also depend on the chemical composition within each section of the process. The chemical composition varies from mill to mill depending on the processes involved, the closure of the mill s systems, the desired paper grade, the speed of the process, and the amount of pulp or paper being produced. 

While mechanical pulps are used mostly in low-quality paper grades and assortments, e.g. for newsprint or packing papers, Kraft pulps are the strongest pulps used in all-quality papers and paperboards where high strength properties are required. 

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