Fines from deinked pulp: Effect of contaminants on their ...

BRIGHTNESSperfectly complement each other [6].— <strong>Fines</strong> <strong>from</strong> UNP:UMG: The fines <strong>from</strong> UNP:UMG (Table III)had the highest brightness due to their origin (30% bleachedmagazine at an ISO brightness <strong>of</strong> 68%, and 70% <strong>of</strong> newsprint atan ISO brightness <strong>of</strong> 60.4%). The ERIC value <strong>of</strong> the UNP:UMGfines was 125 ppm, higher than the 75 ppm for the TMP fines,but lower than the 450-ppm <strong>of</strong> the DIP fines. The 30% DIP contentin the UNP could explain this intermediate ERIC value.Due to their prior bleaching history, high Fe concentration andink carried over <strong>from</strong> recycling, the UNP:UMG fines bleachabilitywas intermediate to those <strong>of</strong> the DIP and TMP; however,their final brightness was only slightly lower than that <strong>of</strong> theTMP fines.The peroxide bleaching response was poor when it was notpreceded by a metal-management stage (only 0.6 <strong>of</strong> a brightnesspoint); however, it was still better than the DIP fines response(–2.3 brightness points), but less than the TMP fines response(10.0 brightness points). A metal-management stage improvedthe ISO brightness gain following peroxide bleaching by nearly10 points, to 67.2%. The ISO brightness increase was betweenthat <strong>of</strong> DIP (2.3 brightness points) and TMP (13.9 brightnesspoints), but the final brightness was similar to that <strong>of</strong> the TMP.The maximum ISO brightness gain was 11.9 points following aQPY-stage, less than the 17.8 brightness points gain for TMP butgreater than the 8.0 brightness points for DIP. The maximumISO brightness attained for the UNP:UMG fines was 68.8%,close to the 70.4% value for the TMP fines, and definitely higherthan that <strong>of</strong> the DIP fines (55.7%).We can conclude that fines that have never been throughprinting respond well to bleaching reagents, provided they aretreated with a metal-management stage. For each furnish, theratio <strong>of</strong> the maximum ISO brightness gains <strong>of</strong> the fines (TableIII) over that <strong>of</strong> the original <strong>pulp</strong>s (Table II) were 0.68 for DIP(8.0/11.8), 1.01 for TMP (17.8/17.6) and 1.05 for UNP:UMG(11.9/11.3), which illustrates again how the high ERIC <strong>of</strong>the DIP fines limited the final brightness gain <strong>of</strong> the unfractionated<strong>pulp</strong>s.It is interesting to note that the long fractions <strong>of</strong> the DIP andUNP:UMG had similar brightness gains and final brightnesses(Table II), while their fines bleachability differed significantly.Therefore, the processing <strong>of</strong> the <strong>pulp</strong> into paper did not significantlyaffect its bleachability, as noted previously by Galland etal. [7]. However, the printing process did affect the bleachabilitydue to the poor deinking <strong>of</strong> the fines.CONCLUSIONInk was extremely difficult to detach and seemed to be permanentlybound to the DIP fines; it was the major factor limitingtheir brightness gain.Iron had a strong affinity for fines. Without a proper metalmanagementstage, their high level <strong>of</strong> iron decreased the performance<strong>of</strong> hydrosulphite bleaching. The peroxide bleachingefficiency on fines <strong>from</strong> UNP:UMG or DIP was practically nilwithout an acid wash or a chelation stage.Therefore, even if fines have a higher percentage <strong>of</strong> ligninthan the long fraction, they can nevertheless be bleached tohigh brightness if they are not contaminated by ink. To bleachDIP to high brightness, either fines have to be removed or a processto detach and remove ink <strong>from</strong> fines is necessary.The fines that had been processed, for example, througha paper machine, had a brightness ceiling similar to the finesthat had not been processed, as long as ink was absent <strong>from</strong>that process.LITERATURE1. SCOTT, G.M., ABUBAKR, S. Fractionation <strong>of</strong> secondary fiber — A review. Prog.Pap. Recycling 3: 50-59 (1994).2. LAPIERRE, L., PITRE, D., BOUCHARD, J. Bleaching <strong>of</strong> <strong>deinked</strong> recycled <strong>pulp</strong>:benefits <strong>of</strong> fibre fractionation. Pulp Paper Can. 102(2): 35-38 (2001).3. EUL, W., SÜSS, H.U., HELMLING, O. Fibre fractionation and post-treatment <strong>of</strong>de-inked <strong>pulp</strong>. Pulp Paper Can. 90(10): T391-397 (1989).4. KARNIS, A. Pulp fractionation by fibre characteristics. Pap. Puu 79(7): 480-488(1997).5. JORDAN, B., O’NEIL, M. The Kubelka-Munk absorption coefficient <strong>of</strong> severalcarbon blacks and water based printing inks. JPPS 20(12): J371-375 (1994).6. AUHORN, W., MELZER, J. Economical integration <strong>of</strong> mechanical <strong>pulp</strong> bleachinginto modern paper technology. Wochenbl. Papierfabr. 110(8): 255-262 (1982).7. GALLAND, G., BERNARD, G., SAURET, G. Désencrage: Intérêt des traitements«haute concentration», Rev. ATIP 37(9): 559-566 (1983).Résumé: Nous avons récemment présenté un rapport indiquantque la blancheur et l’aptitude au blanchiment des fines de pâte désencrée(PDE) étaient en général substantiellement inférieures à celles dela fraction de fibres longues. Nous ne savions pas à ce moment ce quiavait entraîné la pauvre réponse des fines de PDE aux agents deblanchiment. Nous avons conclu que deux facteurs liés à la contaminationexterne étaient la cause principale de la pauvre réponse aublanchiment et au faible degré de blancheur maximale des fines dePDE : un taux effectif élevé d’encre résiduelle et une forte quantité demétaux de transition, principalement le fer.Reference: LAPIERRE, L., PITRE, D., BOUCHARD, J. <strong>Fines</strong> <strong>from</strong><strong>deinked</strong> <strong>pulp</strong>: <strong>Effect</strong> <strong>of</strong> <strong>contaminants</strong> on their bleachability and on the<strong>pulp</strong> final brightness. Pulp & Paper Canada 104(8): T208-211 (August2003). Paper presented at the 6th Research Forum on Recycling inMagog, QC, on October 1 to 4, 2001. Not to be reproduced without permission<strong>of</strong> PAPTAC. Manuscript received on August 10, 2001. Revisedmanuscript approved for publication by the Review Panel on December5, 2002.Keywords: FINES, DEINKED STOCK, BRIGHTNESS, BLEACH-ABILITY, CONTRARIES, TRANSITION METALS.Pulp & Paper Canada T 211 104:8 (2003) ❘❘❘ 39