Hardwood Kraft Pulp Research Articles

Результаты исследования взаимосвязи вязкости и механической прочности беленой лиственной сульфатной целлюлозы

An assessment has been made of the relationship between viscosity and mechanical strength of industrial samples of bleached hardwood kraft pulp. To produce this type of semi-finished product, birch and aspen wood has been used, which has been harvested in the Northwestern region of the Russian Federation. The viscosity of a solution of high-molecular polymers provides an idea of the average length of the fibers and, accordingly, their degree of destruction. In turn, the mechanical properties of the fibrous semi-finished product and the strength of the products made from it largely depend on the length of the fiber. Since it takes no more than 2 hours to determine the viscosity of a solution of high-molecular polymers, and 8–10 hours to obtain standard mechanical strength characteristics, viscosity analysis can be considered an express method that provides information on the mechanical strength of a semi-finished product. In this work, the ISO 5351:2010 international standard in cupriethylenediamine solution has been used to analyze the viscosity of the semi-finished product. High values of mechanical strength characteristics have been detected for industrial samples of bleached hardwood kraft pulp with a viscosity of more than 800 ml/g. For pulp samples, a correlation has been established only between the number of double folds and viscosity. Further research has been carried out on samples of bleached hardwood kraft pulp with different degrees of fiber destruction, which have been produced with varying the parameters of sodium hypochlorite treatment. The results have made it possible to establish a range of critical viscosity values for bleached hardwood kraft pulp, which has amounted to 600...700 ml/g, and a polynomial relationship between tear resistance, breaking length, a number of double folds and viscosity with a high confidence coefficient of data approximation of no less than 0.89. It has been shown that viscosity can become an analytical tool in the express diagnostics of the mechanical strength of a fibrous semi-finished product at the intermediate stages of production of bleached hardwood kraft pulp and in quality control of the ready-made semi-finished product.

TEMPO/CaBr2/Ca(OCl)2 oxidation of hardwood bleached kraft pulp in water at pH 10 with aqueous Ca(OH)2 solution

The conventional TEMPO/NaBr/NaOCl system for oxidation of cellulose to prepare nanocellulose materials has some shortcomings in terms of controlling side reactions and clogging in washing/filtration process. A new TEMPO/CaBr2/Ca(OCl)2 system was then developed to oxidize a hardwood bleached kraft pulp (HBKP) in water at pH 10 (TEMPO = 2,2,6,6-tetramethylpiperidine-1-oxyl radical). An aqueous Ca(OH)2 solution was used to continuously control the reaction mixture at pH 10. After oxidation, the reaction mixture containing the oxidized products and chemicals was directly filtered on a 40-μm-mesh nylon filter and the water-insoluble oxidized products on the filter were washed with water without any clogging. The carboxy content increased to 1.5 mmol/g and the mass recovery ratio decreased to 87.7% as the amount of Ca(OCl)2 was increased to 10.0 mmol/g-HBKP. The oxidized products contained calcium ions but almost no chloride ions, indicating that they comprised almost pure –(COO)2Ca groups. The ready filtration and washing of the oxidized products was probably owing to the low degree of dissociation of the –(COO)2Ca groups in water. The X-ray powder diffraction (XRD) and solid-state carbon 13 nuclear magnetic resonance (13C-NMR) analyses revealed that the crystallinities and crystal widths of the original cellulose I structure were mostly retained in the oxidized products. However, size-exclusion chromatography and viscosity analyses revealed that substantial depolymerization occurred on the cellulose and oxidized cellulose molecules in the products, as in TEMPO/NaBr/NaOCl-oxidized products.Graphical

Preparation and characterization of handsheet using cellulose based Agri-weed: A sustainable utilization of Urena Lobata fiber

The increasing depletion of reserves of natural resources has led to a growing worldwide focus on the exploitation of available waste in new domains. The presence of weedy plants is pervasive on a global scale and has detrimental effects on several aspects of the environment, agriculture, and people's health. Therefore, repurposing these Agri-weed plants for beneficial purposes would be a significant achievement. Furthermore, since raw materials constitute a substantial portion of manufacturing costs, using weeds as a feasible substitute for raw materials might potentially provide considerable advantages for manufacturers. In this study, an endeavor has been made to the utilization of agricultural waste “Urena Lobata”, for the purpose of paper production. In the interim, the utilization of Urena Lobata as an alternative and sustainable raw material for pulp and paper industry could potentially offer a beneficial approach to mitigation of deforestation. The effective production of handsheets with weights of 70 g/m2 and 80 g/m2 was achieved using Urena Lobata fiber, Bleached Urena Lobata Fiber, and hardwood kraft pulp. Mechanical characteristics of handsheet's were comprehensively examined by the bursting index, tensile strength, tear index, brightness percentage and scanning electron microscope for handsheet's morphology. The results show that the handsheets produced by Urena Lobata fiber exhibit a much lower brightness percentage, high tensile strength and bursting index. Alongside, handsheets by bleached Urena Lobata fiber indicate higher brightness percentage, satisfactory values for tensile strength, bursting index, and tear index. The prepared materials are suitable for a broad spectrum of prospective applications, encompassing newsprint, tissue paper, filtration paper as well as high-quality writing and printing paper.

Degrees of hornification in softwood and hardwood kraft pulp during drying from different solvents

Hornification, a complex phenomenon occurring during drying of lignocellulosic materials because of formation of irreversible chemical bonds, remains a subject of scientific interest. This study aims to shed light on the underlying mechanisms of hornification by investigating interactions between the liquid and solid phases through a solvent exchange treatment. The treatment involved replacing water with various solvents in suspensions of never-dried cellulose samples, including alcohols (methanol, ethanol, isopropanol) capable of forming hydrogen bonds, albeit to a lesser extent than water, as well as non-alcohol solvents (acetone, ethyl acetate, toluene, heptane) that do not possess the ability to form chain of hydrogen bond, and no hydrogen bond between each other. The impact of solvents on the hornification process was evaluated using WRV measurements. Our findings reveal that water, as a solvent, plays a dominant role in the hornification process, primarily due to its excellent capability to form bridges of hydrogen bonds. In comparison, hornification with alcohols was considerably lower than with water, likely attributed to the smaller ability of alcohols to engage in such interactions. Furthermore, our results indicate a tendency for reduced hornification also when using non-hydrogen bond solvents with decreased polarity. This strengthens the hypothesis related to chains of hydrogen bonds. Additionally, the interaction between hydrophobic surfaces on cellulose through hydrophobic interactions could provide another plausible explanation.

A comparative study of lignin-containing microfibrillated cellulose fibers produced from softwood and hardwood pulps

The expanding field of lignin-containing nanocellulose offers a sustainable alternative to fossil-based substances in applications such as packaging, coatings, and composites. This has underscored the importance to explore the impact of raw materials due to the complexities of lignin structures and different raw fiber characteristics, which plays a significant role in determining the properties of the resultant lignin-rich cellulose materials. This study presents a detailed investigation and comparison on the production and structure-property relationships of lignin-containing microfibrillated cellulose (LMFC) fibers prepared from unbleached softwood and hardwood kraft pulps. The microfibrillation process was analyzed for both softwood and hardwood pulps, comparing the results across various stages of fibrillation. Distinguishing features of lignin structures in softwood and hardwood pulps were identified through Py-GC/MS analysis. Additionally, Digital Image Correlation was employed to investigate the varying failure patterns in LMFC films derived from different wood species. Softwood-derived LMFC films demonstrate less strain-concentrated regions and strain variation, attributed to the formation of more physical crosslinking joints by the elongated fibers. Consequently, softwood-origin LMFC films displayed superior load-sharing and enhanced tensile strength (287 MPa) compared to those derived from hardwood. Additionally, the denser lignin structures in unbleached softwood pulp further boosted the stiffness of resultant softwood-derived films. Upon recycling, LMFC films exhibited superior recovery of mechanical properties following drying, suggesting their significant potential for widespread commercial use.

Microfibrillated cellulose (MFC) barrier coating for extending banana shelf life

This study evaluated, for the first time, the feasibility of using 100% microfibrillated cellulose (MFC) for a barrier coating to preserve the shelf life of bananas. MFC was produced from a commercial bleached kraft hardwood pulp through mechanical milling. Barrier coating was accomplished by dipping bananas into aqueous MFC suspensions. Performance of the barrier coating on the banana peel surface was evaluated from visual observations, weight loss, firmness, and dissolved soluble sugars content of the bananas. The results indicated that coating the banana peel surface with MFC delayed the browning and softening of the banana and the conversion of banana carbohydrates into soluble sugars. Furthermore, the extent of mechanical fibrillation in producing MFC affected MFC suspension wettability of banana peel surface, as well as the effectiveness of banana preservation. Casting-made MFC films were used to understand various factors of MFC barrier coating performance. The extent of MFC fibrillation was found to be more effective than increasing the amount of coating in reducing water vapor permeation for better fruit protection.

Evaluation of structure and compressive properties of eco-friendly cushioning materials based on starch and cellulose types

A reinforced eco-friendly cushioning material (ECM) comprising starch and cellulose material was developed. The ECM was prepared based on the starch type and cellulose material content; it was compared with commercial CMs. Different sizes of refined pulp (RP) and microfibrillated cellulose (MFC) were manufactured from hardwood bleached kraft pulp via beating and grinding, respectively. Thereafter, amylose-containing corn starch (CS) or amylopectin-only-containing glutinous rice starch (GS) was mixed with the manufactured cellulose materials. A slurry comprising starch and cellulose materials was homogenized for 2 min and lyophilized to prepare the ECM, after which the structure and strength characteristics of the prepared ECM were evaluated. The GS-prepared ECM produced a plate-like internal structure because of its amylopectin content, and amylose-containing CS exhibited a net-like shape. The cellulose materials offered support between starches with plate-like or net structure ECMs, and the pore shape was formed by adding MFC. As the cellulose material content increased, the strength of the ECM increased compared with that of the commercial CMs. Thus, ECMs with higher strength than their commercial counterparts could be manufactured with GS and cellulose materials.

EFFECTS OF BALL MILLING AND ENZYME TREATMENT ON CELLULOSE ACETYLATION

A novel process was developed to produce cellulose acetate from bleached hardwood kraft pulp (BHKP) through ball milling and cellulase treatment. The ball milling and/or cellulase treatment of BHKP increased the esterification reaction, but enzyme treatment reduced the viscosity of the produced cellulose acetate (CA). The degree of substitution (DS) values upon acetylation were 2.26 for BHKP, 2.61 for ball-milled BHKP and 2.91 for ball milled followed by cellulase treatment of BHKP. The prepared CA was also characterized by FTIR, XRD, TGA, 1H-NMR and SEM. A strong band for –OH stretching of cellulose disappeared and created a strong band for carbonyl (C=O) group on esterification of BHKP. The crystallinity index of BHKP was 63.3%, which completely disappeared on acetylation, demonstrating the successful esterification of cellulose. The initial weight loss of cellulose acetates was lower than that of the native cellulose, as observed in TGA, indicating the acetylated samples are less hydrophilic. 1H NMR spectroscopy confirmed the complete structure of cellulose acetate.

Ergosterol and Its Metabolites Induce Ligninolytic Activity in the Lignin-Degrading Fungus Phanerochaete sordida YK-624.

White-rot fungi are the most important group of lignin biodegraders. Phanerochaete sordida YK-624 has higher ligninolytic activity than that of model white-rot fungi. However, the underlying mechanism responsible for lignin degradation by white-rot fungi remains unknown, and the induced compounds isolated from white-rot fungi for lignin degradation have never been studied. In the present study, we tried to screen ligninolytic-inducing compounds produced by P. sordida YK-624. After large-scale incubation of P. sordida YK-624, the culture and mycelium were separated by filtration. After the separation and purification, purified compounds were analyzed by high-resolution electrospray ionization mass spectrometry and nuclear magnetic resonance. The sterilized unbleached hardwood kraft pulp was used for the initial evaluation of ligninolytic activity. Ergosterol was isolated and identified and it induced the lignin-degrading activity of this fungus. Moreover, we investigated ergosterol metabolites from P. sordida YK-624, and the ergosterol metabolites ergosta-4,7,22-triene-3,6-dione and ergosta-4,6,8(14),22-tetraen-3-one were identified and then chemically synthesized. These compounds significantly improved the lignin-degrading activity of the fungus. This is the first report on the ligninolytic-inducing compounds produced by white-rot fungi.

Cellulose nanofibrils derived from pulp as a high performance separator for lithium‐ion batteries

AbstractCellulose nanofibrils (CNFs) from hardwood bleached kraft pulp (HwBKP) are produced via enzymatic, chemical, and mechanical treatment. A nanoporous structured CNF‐based separator is produced, and the electrochemical performance, morphology, and thermal stability analyses are performed in comparison to the commercial polyethylene separator. The results obtained show that the electrolyte‐philic CNF separator has capacity retention of 88.6% over 200 cycles and very good ionic conductivity and wettability results due to its high hydrophilic nature. At 140°C, the CNF separator was resilient to heat and remained intact. The CNF separator reflects high thermal resistance and good electrolyte uptake properties that are among the mandatory requirements of a separator hence, a promising contender for use in lithium‐ion batteries.

Characterizing lignin-containing microfibrillated cellulose based on water interactions, fibril properties, and imaging

Morphological characterization of microfibrillated cellulose (MFC) is critically important to process control in production and product specification for trade and product development yet is extremely difficult. This study evaluated several indirect methods for relative comparison of the morphology of lignin-free and lignin-containing ((L)MFCs). The (L)MFCs studied were produced using a commercial grinder through different passes from a dry lap bleached kraft eucalyptus pulp, a virgin mixed (maple and birch) unbleached kraft hardwood pulp, and two virgin-unbleached kraft softwood (loblolly pine) pulps with one bleachable grade (low lignin content) and one liner grade (high lignin content). The (L)MFCs were indirectly characterized using techniques based on water interactions, i.e., water retention value (WRV) and fibril suspension stability, as well as fibril properties, i.e., cellulose crystallinity and fine content. Optical microscopy and scanning electron microscopy were also applied to directly visualize the (L)MFCs to provide some objective measure of the morphology of the (L)MFCs. The results indicate that most measures such as WRV, cellulose crystallinity, fine content cannot be used to compare (L)MFCs from different pulp fibers. Measures based on water interactions such as (L)MFC WRV and suspension stability appeared can provide some degree of indirect assessment. This study provided the utilities and limits of these indirect methods for relative comparison of the morphologies of (L)MFCs.

Development of Drying Energy Saving Technology of Paperboard by Applying Precipitated Calcium Carbonate Made from Oyster-Shell Byproducts

In this study, we aimed to identify the possibility of the internal application of a precipitated calcium carbonate made from oyster shell byproducts (O-shell PCC) for reducing the drying energy in paperboard mills. The micro-fibrillated cellulose (MFC) was also applied to improve the strength of the paperboard containing O-shell PCC. The O-shell PCC was classified through an 80 mesh screen and then its SEM image, particle size, and zeta potential were analyzed. After the MFC was prepared by micro-grinding hardwood bleached kraft pulp (Hw-BKP), its particle size, viscosity, and fiber width were also measured. The O-shell PCC and MFC were added to the Korean old corrugated container (KOCC) stock to prepare handsheets, and their physical properties and drying energy reduction were measured to determine the effect of the O-shell PCC and MFC on the drying energy saving. The O-shell PCC was effective to improve the bulk and drying energy reduction of handsheets, but the strengths decreased. The MFC was effective in improving the strength, but more drying energy was required as the addition of MFC increased due to its hydrophilic property. In addition, the application of the PCC and MFC, which had not been used in paperboard mills, could increase the production cost. However, the reduced cost of drying energy was estimated to be more than the increased cost of PCC and MFC at the optimum dosage (6% O-shell PCC and 0.2% MFC on o.d. fiber). Therefore, it was concluded that the combination of O-shell PCC and MFC could be effective in saving drying energy in paperboard mills.

Preparation and characterization of cellulose nanocrystals from paper mulberry fibers

The applicability of paper mulberry fiber (PM-FB), which is bast fiber, for manufacturing cellulose nanocrystals (CNCs) with high-yield was investigated. The PM-FB and hardwood bleached kraft pulp (Hw-BKP) were hydrolyzed under different sulfuric acid concentrations, reaction times, and reaction temperatures. The dependence of the CNC yield on the hydrolysis conditions and crystallinity of the raw materials was analyzed. The functional groups of the CNCs and their zeta potentials were determined. The fiber length and width of the individual CNCs were determined by transmission electron microscopy image analysis. The PM-FB showed a higher crystallinity of 86.8% compared to that of Hw-BKP and exhibited a high CNC yield of 55% under strong hydrolysis conditions. The sulfate group was introduced into the CNCs, which increased their negative charge. The fiber width of PM-FB-based CNCs (PM-CNCs) was larger than that of Hw-BKP-based CNCs (Hw-CNCs), and the aspect ratio ranged from 29.0 to 12.2 depending on the hydrolysis conditions. The yield of PM-CNCs was higher than that of Hw-CNCs under the same hydrolysis conditions. In addition, both CNCs exhibited similar quality. Therefore, PM-FB is a promising raw material for efficient CNC manufacturing.

Production of Cellulose Pulp and Lignin from High-Density Apple Wood Waste by Preimpregnation-Assisted Soda Cooking.

Apple wood waste (AWW), mainly tree trucks, is collectible lignocellulosic biomass from orchard rotation. The biorefinery of AWW is challenging because of the hard and dense structure. In the present work, chemical composition determination and microstructure observation was performed for the first time on AWW. Alkali-preimpregnation-assisted soda cooking (APSC) was developed to separate cellulose a pulp and lignin from AWW. APSC attained pulp yield of 34.2% at 23% NaOH, showing a 13.2% improvement compared to conventional soda cooking (SC). Fiber length analysis showed APSC-AWW pulp consisted mainly of medium and short fibers, which means blending with long-fibered pulp to enhance the physical strength of pulp sheets. A blend of APSC-AWW pulp and long-fibered pulp in the proportion of 80:20 attained comparable physical strength to hardwood kraft pulp. ASPC-AWW lignin was separated from spent liquor by acidification and then purified by dialysis desalination. The purified ASPC-AWW lignin showed a weight-average molecular weight of 4462 g/mol, similar to softwood kraft lignin but more uniform. Structural analysis revealed that ASPC-AWW lignin was composed of a syringyl unit (S), guaiacyl unit(G), and p-hydroxyphenyl unit (H), and an S unit was dominant with an S/G/H ratio of 74.5:18.2:7.3. It is believed the utilization of fruit tree wood waste as the feedstock of biorefinery is attractive to countries without sufficient forestry resources. Furthermore, the developed APSC is based on conventional SC, which ensures the feasibility of an industrial application.

Recycling performance of softwood and hardwood unbleached kraft pulps for packaging papers

The scope of this work is to evaluate the recyclability potential of hardwood and softwood unbleached kraft pulps, leading to a sound basis for comparison and even to support a decision about fibers according to the performance achieved. The influence of successive recycling cycles (up to 10 cycles) on the fiber morphology, pulp suspension drainability, water retention capacity, and handsheet mechanical properties were studied for Eucalyptus globulus and Pinus sylvestris unbleached kraft pulps. The performance of these pulps as linerboard and corrugating medium for packaging was also evaluated. The requirements for brown kraftliner and for high performance recycled fluting grades is preserved for E. globulus pulp during all 10 recycling cycles, evidenced by the moderate decrease of burst index and crush resistance index and by the short-span compression index, whereas the P. sylvestris pulp loses this rating after the second cycle. These results strongly support the higher performance of E. globulus pulp for recycling as compared with softwood kraft pulp from the perspective of packaging papers.

Sustainability of cellulose micro-/nanofibers: A comparative life cycle assessment of pathway technologies

Cellulose micro- and nanofibers (CNFs) are commonly regarded as “greener” than petro-based materials. The high energy input that their production still demands, along with the use of chemicals or heat in some pretreatments, asks for a critical view. This paper attempts a life cycle assessment of CNFs produced from bleached hardwood kraft pulp via three different pre-treatments before mechanical homogenization. First, a fully mechanical route, based on a Valley beating pre-treatment. Second, an enzymatic route, based on endoglucanases and requiring certain temperature (~50 °C). Third, a TEMPO-mediated oxidation route, considering not only the impact of the chemical treatment itself but also the production of TEMPO from ammonia and acetone. The main output of the study is that both, mechanical and TEMPO-mediated oxidation routes, present lower impacts than the enzymatic pre-treatment. Although the mechanical route presents slightly milder contributions to climate change, acidification, eutrophication, and other indicators, saying that TEMPO-mediated oxidation is environmentally unfeasible should be put under question. After all, and despite being disregarded in most assessment publications up to date, it is the only well-known way to selectively oxidize primary hydroxyl groups and thus producing kinds of CNFs that are unthinkable by other ways.

Sustainable high-yield lignocellulosic fibers and modification technologies educing softness and strength for tissues and hygiene products for global health

Unbleached hardwood kraft pulp was treated with a non-ionic surfactant to decrease the concentration of a hydration shell by dislodging hard-to-remove water through a targeted reduction in surface tension. Energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry techniques were used to investigate and evaluate these fiber-surfactant interactions. Scanning electron microscopeimages were taken to observe the change in the morphology from the surfactant treatment. The surface tension was measured by using pendant drop tests, which reduced from 71.46 mN/m to ∼ 49–51 mN/m for different pretreatment techniques and hence, reduced the pulling force exerted by the liquid bridge water on the fibers by 28–31%. This consequently led to reduced fiber collapse, and the surfactant-treated fibers showed higher bulk and softness without a concomitant sacrifice of mechanical properties. The scanning electron microscopeimages confirmed a more cylindrical fiber structure and showed an unaffected fiber–fiber interaction because of which the tensile strength was not compromised with the increase of bulk. The surfactant-treated fibers showed better recovery or spring back, i.e. a return to their original form after compression relative to the untreated fibers. Therefore, it was possible to make tissue papers with higher bulk, softer hand-feel, and a higher absorbing capacity, without reducing the tensile strength by simple and green processes involving chemical and mechanical modifications.

Vacuum-assisted water removal from highly refined furnishes

A vacuum-assisted sheet former was used for analyzing water removal from refined bleached hardwood kraft pulp furnishes. The Schopper Riegler (SR) values of the studied furnishes ranged from 43 to 97. Water removal time increased significantly with increasing SR value; the water removal time for SR97 furnish was two orders of magnitude longer than for SR43. Retention behaved differently with different SR levels. Retention was approximately constant for SR43 and SR72, for SR85 retention was initially slightly lower, and for SR97 retention was initially very low. The clogging of the wire due to the fines was very strong for SR97. A simple model of flow resistance of the filtered sheet worked very well for SR43 and SR72, and the model worked reasonably well for SR85. However, for higher SR levels, a retention model is needed to predict accurately the water removal in real-life applications.

Production of Biomodified Bleached Kraft Pulp by Catalytic Conversion Using Penicillium verruculosum Enzymes: Composition, Properties, Structure, and Application

The global development of the bioeconomy is impossible without technologies for comprehensive processing of plant renewable resources. The use of proven pretreatment technologies raises the possibility of the industrial implementation of the enzymatic conversion of polysaccharides from lignocellulose considering the process’s complexity. For instance, a well-tuned kraft pulping produces a substrate easily degraded by cellulases and hemicelulases. Enzymatic hydrolysis of bleached hardwood kraft pulp was carried out using an enzyme complex of endoglucanases, cellobiohydrolases, β-glucosidases, and xylanases produced by recombinant strains of Penicillium verruculosum at a 10 FPU/g mixture rate and a 10% substrate concentration. As a result of biocatalysis, the following products were obtained: sugar solution, mainly glucose, xylobiose, xylose, as well as other minor reducing sugars; a modified complex based on cellulose and xylan. The composition of the biomodified kraft pulp was determined by HPLC. The method for determining the crystallinity on an X-ray diffractometer was used to characterize the properties. The article shows the possibility of producing biomodified cellulose cryogels by amorphization with concentrated 85% H3PO4 followed by precipitation with water and supercritical drying. The analysis of the enzymatic hydrolysate composition revealed the predominance of glucose (55–67%) among the reducing sugars with a maximum content in the solution up to 6% after 72 h. The properties and structure of the modified kraft pulp were shown to change during biocatalysis; in particular, the crystallinity increased by 5% after 3 h of enzymatic hydrolysis. We obtained cryogels based on the initial and biomodified kraft pulp with conversion rates of 35, 50, and 70%. The properties of these cryogels are not inferior to those of cryogels based on industrial microcrystalline cellulose, as confirmed by the specific surface area, degree of swelling, porosity, and SEM images. Thus, kraft pulp enzymatic hydrolysis offers prospects not only for producing sugar-rich hydrolysates for microbiological synthesis, but also cellulose powders and cryogels with specified properties.

Study of Refining Effect of Mixed Pulps Using Refiner Plates with Different Bar Patterns

A new lightweight vertical bar plate was developed by inserting individual bars into the plate base rather than the typical sand casting method. The lightweight vertical bar plate has a very sharp bar edge because vertical bars are inserted instead of trapezoidal bars. The refining effects of the mixed stock with softwood bleached kraft pulp (Sw-BKP) and hardwood bleached kraft pulp (Hw-BKP) were compared using two types of lightweight vertical bar plates with cutting edge lengths of 55 km/s (PA55) and 97 km/s (PB97). The fine bar plate (PB97) with large CEL (PB97) was very effective in reducing the refining energy required to reach the final freeness regardless of the mixing ratios of Sw-BKP and Hw-BKP compared to the plate with a small CEL (PA55). PB97 also consumed less refining energy than PA55 until proper sheet strength was achieved. In particular, irrespective of the mixing ratios of Sw-BKP and Hw-BKP, the tensile strength of sheets at the final freeness was greater in PB97 than in PA55. For stock throughput during refining, PA55 with the wide groove was almost similar to PB97 with the narrow groove.