The influence of pulp furnish components on the property of supercalendered paper

Transcription

1 T11 pulp furnish The influence of pulp furnish components on the property of supercalendered paper By Y. Gao, K. Li and Z. Wang Abstract: The effect of pulp furnish components, including TMP mainline refiner pulp and reject refiner pulp, kraft pulp and fillers, on the SC paper properties were investigated in order to understand the contributions of each component to the SC paper properties. Properties of laboratory SC paper handsheets, such as tensile strength, smoothness, opacity, air permeability, were measured and also compared with a commercial SC paper. Results show that the addition of kraft pulp increases the physical tensile strength of SC paper and refining of the kraft pulp further promotes this effect. Although TMP reject refiner pulp has more long and coarse fibres than the mainline refiner pulp, the negative effect of the reject refiner pulp on paper smoothness and opacity as usually perceived is not significant in this study. Y. GAO, Department of Chemical Engineering and Limerick Pulp and Paper Research Centre University of New Brunswick, Fredericton, NB, CANADA K. LI, Department of Chemical Engineering and Limerick Pulp and Paper Research Centre University of New Brunswick, Fredericton, NB, CANADA Z. WANG, College of Pulp and Paper Engineering, Shaanxi University of Science and Technology, Shaanxi, CHINA S UPERCALENDERED (SC) PAPER is a premium mechanical printing grade used for flyers, inserts, catalogs, and Sunday magazines. Due to the demand for high quality print results, SC paper production has been growing rapidly in recent years. SC paper is produced from a furnish of groundwood pulp (SGW or PGW) or thermomechanical pulp (TMP), kraft pulp, and a high proportion of fillers. The basepaper has to undergo a supercalendering process to achieve the density, smoothness, porosity, and gloss, which are the most important properties of SC paper for a rotogravure printing process [1,2]. The quality of SC paper grade is to a large extent determined by the pulp fibres used. With the advancements in TMP technologies, more and more paper mills use TMP fibre as the major fibre material for SC paper production [3,4,5,6,7,8,9]. As the long and coarse fibres, mainly from TMP reject refiner pulp, negatively affect the paper smoothness and opacity, some mills use only part of the reject refiner pulp in the SC paper and use the rest for lower grade paper. Many efforts have been directed at improving the mechanical pulp fibre quality, in particular, modifying the thickwalled coarse fibres, which not only deteriorates the surface smoothness of paper but also causes surface roughening problems upon rewetting in the printing process [10,11,12,13,14]. In practice, most mills are still using kraft pulp as reinforcement fibres for SC paper production. Some mills use the kraft pulp after deflaking without refining and others refine the kraft pulp first [5]. If a significant amount of kraft pulp is added, surface smoothness may be affected. Moreover, kraft pulp is costly. Refining of kraft pulp can improve not only the interfibre bonding strength but also the surface smoothness and paper porosity. However, refining kraft pulp complicates the process. For some mills, the overall production costs and the existing process configuration are taken into consideration in determining whether the kraft pulp should be refined or not. SC paper is highly filled, mostly with clay. Filler content can reach more than 30%, which gives the paper good smoothness and opacity. However, if too much clay is added, it will lower the physical strength of paper and may also cause picking problems in the printing process. The amount of fillers which can be added in paper depends on the properties of wood fibres used, and also relates to the distribution of fillers in the paper structure. The objective of this study was to investigate how each furnish component, including TMP mainline refiner pulp and reject refiner pulp, reinforcement kraft pulp, and fillers, affect the SC paper properties. SC paper handsheets were made in the laboratory with various furnishes of different proportion of each component to compare the resulting paper properties. Kraft pulp was refined to different freenesses to study the influence of refining on paper properties. It is hoped that the preliminary results obtained from this investigation will provide some useful information for the SC paper mill practice. EXPERIMENTAL Pulp Samples and Fibre Characterization TMP mainline refiner pulp and reject refiner pulp, kraft pulp and delaminated clay were obtained from a SC paper mill. Basepaper and SC paper samples were also obtained from the mill for comparison with the laboratory-made supercalendered handsheets. The kraft pulp was refined in a PFI mill at 2,000 and 4,000 revolutions. Fibre fractions of TMP mainline refiner and reject refiner pulps and kraft pulp were analyzed by using a Bauer-McNett Fibre Classifier. Fibre length and coarseness were measured with a Fibre Quality Analyzer. Handsheet Making and Supercalendering Handsheets of a basis weight of 56±2 g/m 2 were prepared according to Tappi standard method. The proportion of TMP mainline refiner pulp (TMP-M), TMP reject refiner pulp (TMP-R), kraft pulp, and clay fillers were altered to have different furnishes for handsheet making. A retention aid, Percol-182, was used to help retain clay and fines in the handsheets. Handsheets were calendered in a laboratory supercalender (DT Paper Science, Finland), at :1 (2007) PULP & PAPER CANADA

2 pulp furnish T12 TABLE I. Bauer-Mcnett and FQA Analysis of TMP-M and TABLE II. Bauer-Mcnett and FQA Analysis of Kraft Pulp. TMP-R. PFI Revolutions Pulp TMP-M TMP-R R14 (%) P14/R48 (%) P14/R48 (%) P48/R100 (%) P48/R100 (%) P100/R200 (%) P100/R200 (%) P200 (%) P200 (%) CSF (ml) CSF (ml) Coarseness (mg/m) Coarseness (mg/m) Length Weighted Length (mm) Length Weighted Length (mm) Note: TMP-M: TMP mainline refiner pulp; TMP-R: TMP reject refiner pulp. nip pressure of 175 kn/m and steel roll temperature of 120 C. All the handsheets underwent one nip pass with the topside of the handsheets facing the steel roll of the supercalender. Paper Property Measurement The strength properties of handsheets were tested with a Tensile Strength Tester by L&W. Sheet opacity was measured with a TechniBrite Micro TB-1C Tester. Smoothness was measured with both a Bekk Smoothness Tester and a Parker Print Surf Tester. Air permeablity was measured by Gurley-Hill method. Gloss was measured with a GlossMeter (HunterLab) at 75. All the measurements were conducted according to the relevant Tappi standard methods. Images of paper cross-section views of the handsheet were imaged with a JSM-6400 SEM. RESULTS AND DISCUSSION Fibre Classification and Fibre Quality Analyisis Mechanical pulps have a complex spectrum of fibre fractions, i.e., long fibre fraction, middle fibre fraction, short fibre fraction and fines. Within the long fibre fraction, there are thick-walled coarse fibres and thin-walled slender fibres, and some fibres are well developed with larger extent of both internal and external fibrillation and some have a higher degree of splitting along the fibre s longitudinal direction. It is quite well understood that long fibres will result in higher strength, while coarse fibres will lead to poor surface smoothness and surface roughening upon rewetting in printing process. Fines contribute to high opacity and high smoothness. Therefore, to understand the contributions of each furnish component to SC paper properties, TMP- M, TMP-R and kraft pulp were characterized with a Bauer- McNett Fibre Classifier and a Fibre Quality Analyzer. It can be seen from Table I that the mainline refiner TMP used in this study has two major fractions, i.e. the long fibre fraction (P14/R48) of 36.2% and the fines fraction (P200) of 43.2%. The middle fraction (P48/R100) is only about 10%. The reject refiner pulp (TMP-R) has a similar fibre length distribtuion to that of TMP-M. However, TMP-R has a larger proportion of long fibres and a smaller proportion of fines. Fibre coarseness of TMP- R is also slightly greater than that of TMP-M, i.e mg/m versus mg/m. Compared with the mechanical pulps, the length distribution of the kraft pulp fibres is markedly different, as shown in Table II. The major component of the pulp is the long fibre fraction (R14 plus R48), which accounts for 85% of the pulp. The fines fraction is less than 5%. The average fibre length is about 2mm, greater than the lengths of both TMP-M and TMP-R, but the coarseness of the kraft pulp, mg/m, is much smaller than that of TMP-M and TMP-R. Therefore, in contrast with the mechanical pulp fibres, the kraft fibres are long, thin-walled, and slender. After refining to PFI 2,000 revs. and 4,000 revs., some long fibres were cut short and more fines were generated, but these changes are not significant, as shown in Table II. Influence of Kraft Pulp and Kraft Pulp Refining Although the quality of TMP has been increasingly improved over the past few decades, particularly in the strength properties, kraft pulp is still needed as reinforcement fibres in most cases of SC paper production. However, the amount of kraft pulp added and the level of refining treatment for the kraft pulp varies from mill to mill. Therefore, the influence of the kraft pulp on the SC paper properties would differ for different production lines. In this study, the amount of kraft pulp varied from 10-25% in the furnishes. The TMP-M varied from 70-55% correspondingly, while the clay remained at a constant proportion of 20%. It can been seen from Fig. 1 that the tensile strength of paper increases with the increase of the amount of kraft pulp added. This is expected since kraft pulp has not only higher intrinsic fibre strength, but also greater fibre length and better interfibre bonding ability than TMP. It can also be seen that with refining of the kraft pulp, paper strength can be further improved for all the addition levels of the kraft pulp. In fact, with refining as shown in Fig. 1, the increase in tensile strength is greater than the increase due to the increased addition level of kraft pulp. For example, when the addition level of the un-refined kraft pulp was increased from 10% to 25%, the tensile strength was increased from 33.5 N.m/g to 35.0 N.m/g. However, at the same kraft pulp addition level of 10%, the tensile strength was increased to 37.6 N.m/g when the pulp was refined to CSF 483ml, which is higher than that of un-refined kraft pulp at 25% addition level. From the slopes of the curves, it can be seen that at higher kraft pulp addition levels, the effect of refining on the tensile strength is greater. It is well understood that through refining, the cell wall structure of a fibre can be modified by splitting, delaminating and unravelling actions of refining. When appropriately controlled, refining can further develop the bonding potential of fibres. Therefore, to achieve improved machine runnablity in SC paper production, one can choose between adding more kraft pulp or adding less but refining the pulp, depending on the existing process settings and overall production costs. It can been seen from Fig. 2 that refining does not overly change the paper smoothness. This can be explained by the effect of refining on the fibre properties. As shown in Table 2, although refining shortened fibres and generated more fines, this change is not significant, particularly when compared with the fibre length and fines content of the TMP. Compared with the percentage of clay (20%) and TMP (55-70%) in the furnish, the fines content of the kraft pulp is minimal. Therefore, its contribution to paper smoothness is not significant. However, if the kraft pulp is not refined and the addition level is too high, it can negatively affect the paper smoothness. For example, at 25% addition level of un-refined kraft pulp, the smoothness is 554 sec. in comparison with 613 sec. at the kraft pulp addition level of 10%. The effect of the kraft pulp refining on sheet air permeabilty is apparent as seen in Fig. 3. When the kraft pulp addition level is 20-25%, refining of the pulp to a PFI 4,000 revs. decreased the air permeability by almost 40%; and when the kraft pulp addition level is 10-15%, the air permeability is decreased by more than 20% by refining. It is understandable that by refining, fibres become more flexible and collapsible, which will lead to more PULP & PAPER CANADA 108:1 (2007) 45

3 T13 pulp furnish FIG. 1. Tensile strength development of kraft pulp with PFI refining. FIG. 2. Paper smoothness versus kraft pulp refining. FIG. 3. Paper air permeability versus kraft pulp refining. FIG. 4. Paper opacity versus kraft pulp refining. bonded area between fibres and thus denser sheet structure. Due to the decreased porosity of the paper structure, the show-through property of a sheet can be improved. If the kraft pulp is not refined, it will affect the air permeability when the addition level is high. It is in agreement with the observation for paper smoothness. When the kraft pulp is refined to PFI 4,000 revs. as in this study, the air permeability approaches the same level for all the kraft pulp addition levels, ranging from 10% to 25%. Figure 4 shows the opacity change with refining of kraft pulp. Since the opacity is mostly attributed to the fines and fillers in the paper sheet, which scatter more light than long fibres due to their higher specific surface area, the contribution of kraft pulp refining to opacity improvement is negligible as evidenced from the experiemtal results. Influence of the Ratio of TMP-M/TMP-R in Furnishes In a TMP process, about 30-50% pulp is seperated as rejects and is then sent to the reject refiner for further refining. As shown in Table 1, reject pulp contains more long fibres fraction and less fines fraction, and the coarseness of the reject refiner fibres is greater. This difference in fibre quality would lead to different SC paper quality. Reject refiner pulp may improve the tensile strength of a paper but it may deteriorate the smoothness of the paper. In this study, the ratio of TMP mainline refiner pulp, designated as TMP-M, to TMP reject refiner pulp, designated as TMP-R, was altered from 100/0 to 60/40 and the response of the paper properties to the TMP-M/TMP-R change was investigated. At all the TMP-M/TMP-R ratios, the proportion of kraft pulp at PFI 4,000 revs. refining level in the furnish was 10% and the proportion of fillers was 25%, i.e., the total amount of TMP-M and TMP-R was 65%. It can be seen from Fig. 5 that the tensile strength increases with the increase of TMP-R portion. This is apparently due to the larger amount of long fibres (P14/R48) and the greater average fibre length of the reject refiner pulp. However, the smoothness decreases but not quite significantly with the increase of the TMP-R proportion in the furnish as shown in Fig. 6. When the TMP- M/TMP-R ratio was altered from 100/0 to 60/40, the paper smoothness decreased from 537 sec. to 472 sec., by 12%. The opacity virtually does not change with change of the TMP-M/TMP-R ratio, as shown in Fig. 7. Since the TMP-R has a larger proportion of long and coarse fibres, and a smaller proportion of fines, it is expected to deteriorate the paper smoothness and opacity. However, from the above results, it can be seen that this effect is not as significant. This indicates that the effect of the TMP-R on the paper property will depend on how the reject pulp is refined. In mill practice, some SC paper manufacturers blend all the TMP-R with TMP-M to furnish the SC paper machine, and others use only part of their TMP-R with the TMP-M for SC paper production and send the remaining part of TMP-R to a lower grade production line. As TMP-R also increases the tensile strength of the paper, it has the potential to save some more costly reinforcement kraft pulp and also has the potential to allow for more fillers to be added in the furnish. This will likely compensate the loss in smoothness and opacity caused by the TMP-R. Therefore, it is very important to optimize the operation of the reject refiner in order to use the pulp to its full advantage in the SC paper production. Influence of Filler Addition Fillers content in paper sheet improves the opacity and smoothness of paper and reduces the production costs. However, :1 (2007) PULP & PAPER CANADA

4 pulp furnish T14 FIG. 5. Ratio of TMP-M to TMP-R on tensile strength, KP of PFI-4,000 at 10% and clay at 25%. FIG. 6. Ratio of TMP-M to TMP-R on smoothness, KP of PFI- 4,000 at 10% and clay at 25%. FIG. 7. Ratio of TMP to TMP-R on opacity, KP of PFI-4000 at 10% and clay at 25%. FIG. 8. Filler addition versus smoothness, KP of PFI-4,000 at 10%. adding too many fillers will lead to lowered paper strength and result in picking problems in the printing process. Too high content of fillers in paper will also increase paper porosity, and thus, may result in print-through in the printing process. In mill practice, filler addition ranges from 20-30% or even higher, depending on furnish pulp properties and the SC grades to be produced. In this study, the proportion of kraft pulp was kept constant at 10%. The clay proportion was altered from 15% to 30%, and the TMP-M proportion was changed correspondingly, from 75% to 60%. It can be seen from Fig. 8 that increasing the amount of fillers added increases paper smoothness. However, this is significant only at lower addition levels of fillers. When the amount of fillers is more than 20%, the paper smoothness does not increase with increasing addition of fillers. This probably relates to the distribution of fillers across the paper thickness. If the increased fillers are mostly distributed in the paper bulk rather than on the paper surface, it may not contribute much to the surface smoothness. Increasing of clay addition increases the porosity of paper markedly, as shown in Fig. 9. As the amount of clay increases from 15% to 30%, air permeabilty increases from µm/pa s to µm/pa s. In contrast to the smoothness change, porosity increases almost continuously with the increase in clay addition. This is understandable since the more clay added, the less the extent of interfibre bonding forms, thus generating more voids in the paper sheet. The effect of clay on interfibre bonding can also be accounted for by the decrease in tensile strength with increasing clay proportion as shown in Fig. 10. However, when kraft pulp is refined, the adverse effect of clay on the tensile strength is reduced. At all the clay addition levels, the tensile strength of the paper containing refined kraft pulp is always higher than that of the paper containing un-refined pulp. This is expected since refining leads to more fibre fibrillation and loosens the fibre structure. This will help increase fibre-fibre bonding in the paper, which compensates for the strength loss due to the fillers. It can also be seen that by refining kraft pulp, paper strength and porosity are improved. This makes it possible to add less kraft pulp for reinforcement purposes, or to add more fillers. Comparison of Lab SC Paper and A Commercial SC Paper Making SC handsheets in the laboratory is not an easy undertaking. In particular, the supercalendering condition is very difficult to be simulated, as it is in the mill operation. In order to get to know how close the laboratory-made SC sheets are to the real SC paper, three lab-made SC handsheets of different furnishes were compared with a commercial SC paper grade, as shown in Table 3. The properties of the SC paper and SC handsheets were measured in the laboratory under the same conditions. It can be seen that the lab-made SC handsheets are quite similar to the SC paper in terms of the properties measured. Lab SC-1 has basically the same furnish composition, so the tensile strength is very close to that of the SC paper. As the proportion of the kraft pulp is reduced in the furnishes as in Lab SC-2 and Lab SC-3, tensile strength decreases. All the three lab-made SC handsheets have lower surface roughness, lower porosity, higher gloss, and lower opacity. This probably results from the different supercalendering conditions between the laboratory supercalender and the mill PULP & PAPER CANADA 108:1 (2007) 47

5 T15 pulp furnish FIG. 9. Filler addition versus air permeability, KP of PFI- 4,000 at 10%. FIG. 10. Filler addition versus tensile strength, KP of PFI- 4,000 at 10%. FIG. 11. SEM image of laboratory SC handsheet. (pulp furnish: 65%TMP-M + 10%KP + 25%Clay) FIG. 12. SEM image of a commercial SC paper. TABLE III. Physical Properties of Lab SC Handsheets and A Commercial SC Paper. Sample Basis Weight Density Tensile Index Roughness Porosity Opacity Gloss (g/m 2 ) (g/cm 3 ) (N.m/g) (PPS, µm) (PPS, ml/min) (ISO, %) (75 ) SC Lab SC Lab.SC Lab SC Note: SC furnish: 56%TMP + 22%KP+ 22%Clay Lab SC-1 furnish: 55%TMP-M + 25%KP + 20%Clay Lab SC-2 furnish: 60%TMP-M + 20%KP + 20%Clay Lab SC-3 furnish: 70%TMP-M + 10%KP + 20%Clay supercalender. Apparently, the lab supercalendering condition was set a little heavier than the mill supercalendering condition. This can also be seen from the cross-section images of the two sample sheets as in Figs. 11,12. As shown in Figs. 11,12, the two sheets basically have a similar structure. Most fibres are collapsed and fillers are distributed between fibre layers. The sheets are quite compact. However, the lab-made sheet has smaller thickness although its basis weight is higher, and it also has less cracks or pore structures inside the sheet. CONCLUSIONS TMP reject refiner pulp contains longer and coarser fibres, and less fines fraction than mainline refiner pulp. Long fibres benefit the paper strength but coarse fibres are in general not good for paper smoothness and porosity. However, from the present study, the negative effect of the reject refiner pulp on paper is not significant within the addition range of 10% up to 40%. Since the pulp is sampled from a commercial TMP line with a reject ratio of 30-35%, use of 40% reject refiner pulp in the furnish means that more than all the reject refiner pulp from the same TMP line is used in the pulp furnish. This indicates that if appropriately refined, TMP reject refiner pulp can be completely used in the furnish for SC paper production, as it is already in practice in some SC paper mills. Addition of kraft pulp can increase the tensile strength of SC paper. Refining of the kraft pulp added in the furnish will further promote this advantage. When pulp is refined to CSF 483ml, adding 10% of the refined kraft pulp increases tensile strength from 33.5 N m/g to 37.6 N m/g :1 (2007) PULP & PAPER CANADA

6 pulp furnish T16 In comparison, if the kraft pulp is not refined, even at 25% addition level, the tensile strength increases to only 35.0 N m/g. Therefore, by refining kraft pulp, the amount of kraft pulp can be reduced while achieving the same paper strength. In addition, refining of kraft pulp will also improve the porosity and surface smoothness of SC paper. The addition of fillers can increase paper smoothness. However, at higher filler addition level, the increase in paper smoothness is not proportional to the increase of filler addition. Furthermore, the tensile strength and the porosity of paper are directly affected by the addition of fillers. ACKNOLEDGEMENTS The authors would like to acknowledge the financial support from NSERC, Mat- Net and NBIF for this research. We would also like to thank Dr. Z. Li of the Irving Paper for discussions. REFERENCES 1. J.A. KNOCEL, Supercalendered Paper Bucks Downturn in Pringting Papers, Solutions, (4): (2004). 2. D. MACKAY, M. TUOMISTO and P. SCHOMIN, Supercalender Conversion to Optiload for SC-A+ Grades at St. Marys Paper PAPTAC 90st Annual Meeting, C143-C146, Montreal, Canada, January (2004). 3. H. HOGLUND and O. BODIN, Modified Thermo-Mechanical Pulp Svensk Papperstidning, 79 (11): , 353 (1976). 4. D. MCDONALD, K. MILES and R. AMIRI, The Nature of The Mechanical Pulping Process Pulp and Paper Canada, 105 (8): (2004). 5. H-E. HOYDAHL and G. DAHQVIST, The Dual Demand on Fibres in SC Papers, Proccedings of International Mechanical Pulping Conference, p , Stockholm, Sweden, June 9-13 (1997). 6. W.J. BATCHELOR, K-A. KURE and D. OUELLET, Refining and The Development of Fibre Properties, Nordic Pulp and Paper Research Journal, 14 (4): (1999). 7. A. KARNIS, The Mechanism of Fibre Development in Mechanical Pulping, JPPS, 20 (10): J280-J288 (1994). 8. M. SYKES, J. KLUNGNESS, F. TAN and S. ABUBAKR, Value-Added Mechanical Pulps for Light Weight, High Opacity Paper, Proccedings of Tappi Pulping Conference, p , Montreal, QC October (1998). 9. K. LUUKKO and H. PAULAPURO, Mechanical Pulp Fines: Effect of Particle Size and Shape Tappi Journal, 82 (2): (1999). 10. P.A. REME, T. HELLE and P.O. JOHNSEN, Fibre Characteristics of Some Mechanical Pulp Grades, Nordic Pulp and Paper Research Journal, 13 (4): (1998). 11. R. DANBY, SC Print Quality Inluenced by Fiber Length, Fabric Structures, and Machine Drainage Characteristics, Tappi Journal, 1(9): 3-9 (2002). 12. T. NESBAKK and T. HELLE, The Influence of the Pulp Fibre Properties on Supercalendered Mechanical Pulp Handsheets, J. Pulp Paper Sci. 28 (12): (2002). 13. O. SHAGAEV and B. BERGSTROM, Advanced Process for Production of High Quality Machanical Pulps for Value-Added Paper Grades, Proccedings of International Mechanical Pulping Conference, p , Oslo, Norway, June 7-9 (2005). 14. K-A. KURE, G. DAHLQVIST, J. EKSTROM and T. HELLE, Hydrocyclone Separation, and Reject Refining, of Thick-Walled Mechanical Pulp Fibres Nordic Pulp and Paper Research Journal, 14 (2): (1999). Résumé: Nous avons analysé les effets des éléments de la composition de fabrication, notamment de la pâte du circuit principal de raffinage de la PTM et de la pâte du circuit de raffinage des refus, de la pâte kraft et des charges, sur les propriétés du papier SC, afin de mieux comprendre la contribution de chaque élément aux propriétés du papier SC. Nous avons mesuré les propriétés de formettes de pâte SC de laboratoire, comme la résistance à la traction, le lissé, l opacité, et la perméabilité à l air, et nous les avons aussi comparées à celles d un papier SC commercial. Les résultats indiquent que l ajout de pâte kraft impartit une plus grande résistance physique à la traction au papier SC et que le raffinage de la pâte kraft accroît encore davantage cet effet. Bien que la pâte du circuit de raffinage des refus présente des fibres plus longues et plus grossières que la pâte du circuit principal de raffinage de la PTM, l effet négatif sur le lissé et l opacité du papier habituellement perçu pour la pâte du circuit de raffinage des refus n a pas un effet significatif dans le contexte de la présente étude. Reference: Y. GAO, K. LI, Z. WANG. The influence of pulp furnish components on the property of supercalendered paper. Pulp & Paper Canada. 108(1) T11-16 (January, 2007). Paper presented at the 92nd Annual Meeting in Montreal, QC, February 6-10, Not to be reproduced without permission of PAPTAC. Manuscript received December 02, Revised manuscript approved for publication by the Review Panel June 23, Keywords: SC PAPER, PULP REFINING, PULP FURNISH COMPONENTS, TMP, REJECT PULP, TENSILE, SMOOTHNESS, OPACITY. PULP & PAPER CANADA 108:1 (2007) 49