Bleached Pulp Research Articles

Analysis of the commercial eucalyptus plantation sector in Uruguay from a macroeconomic perspective

The Uruguayan forest sector has developed based on commercial pine and eucalyptus plantations. This process has been based on the installation of vertically integrated companies, with foreign capital and some local capital, investment funds and medium and small industries. In addition to these groups, there are contractor companies in which several of the activities of the primary sector are outsourced, as well as some of the industry. Investment attraction factors are diverse and related not only to productive conditions, e.g., growth rates, but also to institutional conditions, e.g., macroeconomic stability. With the development of the forest sector, there is currently a preponderance of eucalyptus plantations over pine plantations. This characteristic has implications in terms of the products to be obtained and, therefore, the industries to be developed, and the markets to be accessed. The presentation analyzes the evolution of the participation of the forest sector in Uruguay's macroeconomy, considering its share in the country's exports as well as in international trade, with emphasis on the products obtained from eucalyptus plantations. The scope and limitations of the available data for Uruguay are considered. Finally, the importance of including the value of ecosystem services provided by the forest in the traditional macroeconomic valuation is discussed. Results show that Uruguay has an important participation in non-coniferous wood markets. According to FAO data, in 2022, Uruguay's production ranked 8th among non-coniferous pulpwood producing countries, after Chile, up one place from the previous year. The same year Uruguay ranked 10th in terms of production of bleached wood pulp. Furthermore, it is expected that the wood pulp will increase with the new operations of the third pulp mill. Furthermore, cellulose pulp ranked 3rd among Uruguay's export products in 2022, after beef and soybeans, and 2nd in the previous year. The results of this research are of interest to potential investors in the Uruguayan forest sector as well as to policymakers. Potential investors in the Uruguayan forest sector may find insights into the industry's growth potential. Policymakers can use this information to make informed decisions that support the development and regulation of the sector for the benefit of both the economy and the environment.

Photosensitive cellulosic materials based on a covalently grafted phenosafranin-modified silsesquioxane analog for bactericidal applications

Light-triggered antimicrobial cellulose surfaces were obtained by the immobilization of a photosensitive phenosafranin dye (PSF) in a hybrid organic–inorganic silsesquioxane polymer applied on handsheets prepared from a standard bleached softwood pulp. These coatings were deposited by polycondensation of methyltriethoxysilane and an alkoxysilyl derivative of phenosafranin (TESPSF) obtained by the thiolene addition reaction and coupling of the succinic anhydride derivative with a primary amine group of PSF. TESPSF and coatings were characterized by advanced techniques in terms of chemical structure (1H, 13C, 29Si NMR, MS, ATR-IR), surface properties (SEM, EDX, water contact angles), and optical properties (UV, reflection light intensity, ISO brightness). The light-induced antimicrobial activity of sheets of paper coated with new materials showed the inhibition of the growth of the bacteria Staphylococcus aureus ATCC 6538 and Escherichia coli ATCC 8739. The cytotoxicity studies of modified cellulose surfaces were performed using erythrocyte lysis assays under both dark and light conditions exhibited no toxicity on erythrocytes. Thus, the new material did not reveal harmful effects on erythrocytes, regardless of the presence and absence of light.

Identification of tropical wood species in paper: a new chemotaxonomic method based on extractives

Abstract The European Deforestation Regulation 2023/1115 (EUDR) prohibits trading of wood and wood products obtained from illegal logging on the EU market. While the identification of solid wood via anatomy, chemistry and genetics has already been established, there is a lack of identification methods for pulp and paper that complement anatomy. This publication presents a newly developed chemotaxonomic method for identifying mixed tropical hardwood (MTH) species in pulp and paper products based on their extractives analyzed with thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). The measured data was processed and compared to identify marker substances and was then merged into a fingerprint database for identifying MTH species in paper of unknown composition. As database references, fully bleached kraft pulps were produced from 38 anatomically identified wood samples and then cryo-ball milled and extracted successively with n-hexane and acetone. The results show that the remaining wood extractives generated from bleached pulps are specific enough to find chemical relevant marker substances to detect MTH species. As chemical composition and anatomy are independent characteristics of wood, this paper makes a completely independent method available, which potentially improves the screening for Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) protected species.

Kraft pulp viscosity as a predictor of paper strength: Its uses and abuses

For bleached kraft pulps, two factors govern paper strength: the individual fiber strength, and the bond strength that adheres the individual fibers together in the paper matrix. Inherent fiber strength is related to the length of the carbohydrate polymers, also known as the degree of polymerization (DP). Average DP (DP) is inferred by performing pulp viscosity measurements. Under certain circumstances during kraft pulping and bleaching, the average polymer lengths can be shortened, resulting in lower pulp viscosity, and may indicate fiber damage. Fiber damage typically manifests itself as a reduction in tear strength for well-bonded handsheets. This paper will review the literature on how pulp viscosity can predict paper/fiber strength and how it can be used as a diagnostic tool. It can be a means to monitor pulp quality during pulping and bleaching, as well as to alert when such operations approach a critical threshold. However, viscosity losses must be carefully and judiciously analyzed. Like most diagnostic tools, viscosity measurements can be misused and abused, which can lead to incorrect inferences about intrinsic fiber strength. This review will also cover these misuses. The overall goal is to provide the papermaker a better understanding of what pulp viscosity is, how it correlates to potential sheet strength, and what its limitations are. It will be illustrated that when pulp viscosity drops below a critical value, it will indicate an appreciable deterioration in the paper’s tear and tensile strength.

Thermal-degradation characteristics of mechanically nanofibrillated bleached pulps from hardwood and softwood

Nanofibrillated cellulose (NFC) consists of ultrafine cellulose structures in which the fibrils can have widths in the range from about 5 to 100 nm. NFC has been studied and developed in the paper industry, using bleached pulp from wood as the raw material. One of the issues in the application of NFC is their heat resistance to thermal degradation. The production process of NFC results in a decrease in their pyrolysis temperature during the nanofibrillation of bleached pulp; however, the details behind the reason and mechanisms are still unclear. In this study, NFC was prepared from bleached hardwood and softwood pulp by mechanical nanofibrillation using a grinder, and the pyrolysis behavior was investigated. For both bleached pulps, a decrease in the pyrolysis temperature was observed after nanofibrillation. The results suggest that the decrease in the pyrolysis temperature from nanofibrillation is not due to damage of the crystalline cellulose by nano fibrillation, but the damage of the hemicellulose components in the surface of the cellulose microfibrils or the interface between the crystalline cellulose and hemicellulose. If the hemicellulose on the surface of crystalline cellulose could be removed from the NFC, then the decrease in the pyrolysis temperature could be suppressed.

Effects of programmed maintenance shutdowns on effluent quality of a bleached kraft pulp mill

Abstract Routinely, the mills perform programmed maintenance shutdowns (PMS) that can affect the characteristics of the effluents and the performance of the effluent treatment plant (ETP). A careful planning of the PMS, along with the use of industrial process sectorial spill control and the use of the emergency spill lagoon have considerably minimized these effects. The Suzano pulp mill located in Aracruz (Brazil) has three production lines and carry out, on average, PMS of each production line separately, every 15 months of operation. The purpose of the study was to evaluate the effects of the PMS on the effluent characteristics and performance of the ETP compared to the periods of normal operation. The results showed that during the PMS, the physicochemical characteristics of the raw and treated effluents were like those found during normal operation. The lower organic loads found in the effluents during the PMS periods were associated with the decrease of the flow rates and the increase of the hydraulic retention time of the ETP, causing a better performance of COD, BOD, TSS and AOX removal. A proper planning of the PMS improved the performance of the ETP and the treated effluent quality remained similar to those during the normal operating period.

The potential of different hemicelluloses extraction methods in conversion of environmentally friendly ECF and TCF bleached paper-grade bagasse soda pulp to dissolving-grade pulp

The potential of different hemicelluloses extraction methods in conversion of environmentally friendly ECF and TCF bleached paper-grade bagasse soda pulp to dissolving-grade pulp

Spray Drying Enzyme-Treated Cellulose Nanofibrils.

Enzyme-treated cellulose nanofibrils (CNFs) were produced via a lab-scale mass colloider using bleached kraft pulp (BKP) to evaluate their processability and power requirements during refining and spray-drying operations. To evaluate the energy efficiency in the CNF refining process, the net energy consumption, degree of polymerization (DP), and viscosity were determined. Less energy was consumed to attain a given fines level by using the endoglucanase enzymes. The DP and viscosity were also decreased using the enzymes. The morphological properties of the enzyme-pretreated spray-dried CNF powders (SDCNFs) were measured. Subsequently, the enzyme-pretreated SDCNFs were added to a PP matrix with MAPP as a coupling agent. The mixture was then compounded through a co-rotating twin-screw extruder to determine whether the enzyme treatment of the CNFs affects the mechanical properties of the composites. Compared to earlier studies on enhancing PMCs with SDCNF powders, this research investigates the use of enzyme-pretreated SDCNF powders. It was confirmed that the strength properties of PP increased by adding SDCNFs, and the strength properties were maintained after adding enzyme-pretreated SDCNFs.

Influence of temperature and pressure during thermoforming of softwood pulp

In this study, the influence of thermoforming conditions on the resulting material properties was investigated, which aimed at developing advanced wood-fiber-based materials for the replacement of fossil plastics. Two bleached softwood pulps were studied, i.e., northern bleached softwood Kraft pulp (NBSK) and chemi-thermomechanical softwood pulp (CTMP). The thermoforming conditions were varied between 2–100 MPa and 150–200 °C, while pressing sheets of 500 g/m² for 10 min to represent thin-walled packaging more closely. As our results showed, the temperature had a more pronounced effect on the CTMP substrates than on the Kraft pulp. This was explained by the greater abundance of lignin and hemicelluloses, while fibrillar dimensions and the fines content may play a role in addition. Moreover, the CTMP exhibited an optimum in terms of tensile strength at intermediate thermoforming pressure. This effect was attributed to two counteracting effects: 1) Improved fiber adhesion due to enhanced densification, and 2) embrittlement caused by the loss of extensibility. High temperatures likely softened the lignin, enabling fiber collapse and a tighter packing. For the Kraft substrates, the tensile strength increased linearly with density. Both pulps showed reduced wetting at elevated thermoforming temperature and pressure, which was attributed to hornification and densification effects. Here, the effect of temperature was again more pronounced for CTMP than for the Kraft fibers. It was concluded that the thermoforming temperature and pressure strongly affected the properties of the final material. The chemical composition of the pulps will distinctly affect their response to thermoforming, which could be useful for tailoring cellulose-based replacements for packaging products.

Flexibility of active center affects thermostability and activity of Penicillium canescens xylanase E

Xylanases are used in several industrial applications, such as feed additives, the bleaching of pulp and paper, and the production of bread, food, and drinks. Xylanases are required to remain active after heat treatment at 80–90 °C for 30 s to several minutes due to the conditions of feed pelleting. Also, xylanases need to be active at 60–70 °C for several hours while bleaching of pulp and paper or manufacturing of bread, food, and drinks is performed. Xylanases of the glycoside hydrolase family GH10 are good candidates for application in such processes because of their high thermostability and, in particular, as feed additives because of their insensitivity to protein inhibitors in cereal feeds. In the study, the thermostability of GH10 xylanase E from Penicillium canescens was improved to reach a half-inactivation period of 2 min at 80 °C compared to 21 s for the wild-type enzyme (WT). Enzymatic activity was increased by 22–48 % at 40–70 °C, which improved the action of the enzyme as a feed additive in the gastric system of animals and during bleaching of pulp and paper. Molecular dynamics simulations demonstrated lower flexibility of the tertiary structure of the engineered enzyme at elevated temperatures compared to WT. The residues W113, Q116, W313, and W321 in the (−1) and (−2) subsites for the substrate binding were less flexible. In the simulations, the engineered enzyme had a comparable content of α-helixes, 310-helixes, β-sheets, and β-bridges as WT, but a lower content of coils and a higher content of β-turns.

2,4,6-TCP migrates and transforms in different cultivated soil in China: Kinetic analysis and mechanistic modeling

Organochlorine pesticides are widely used in agriculture, wood preservation, pulp bleaching and other fields, which increased the pollution risk of cultivated land. In this study, a typical organochlorine pesticides-2,4,6-TCP was conducted as the target pollutants to investigated the migration and transformation characteristics in different cultivated soils in China. The results indicated that the adsorption of 2,4,6-TCP in soil samples was in order: black soil＞laterite＞fluvo-aquic soil, and the maximum adsorption was 71.0870, 27.0575 and 6.1292 mg/kg, respectively. The dispersion coefficient of black soil, laterite and fluvo-aquic soil was 0.0329, 0.0501 and 0.0149, and the hysteretic factor R was 5.381, 1.455 and 2.238, respectively, indicating that the migration ability of 2,4,6-TCP in different cultivated soils samples was in order: black soil＞laterite＞fluvo-aquic soil. The fitting results of one-dimensional migration model indicated that the model well reflected the migration and transformation of 2,4,6-TCP in different cultivated soil samples. Meanwhile, the Two-dimensional migration model fitting results indicated that the maximum concentration of 2,4,6-TCP of different cultivated soil samples were found along the longitudinal flow direction, reaching 40% of the initial pollution concentration at 15 m, corresponding to the center of the pollutant plume.

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.

Nanocellulose Coating on Kraft Paper

Paper is a biodegradable material, but in food packaging, its hygroscopicity and porosity can cause food contamination due to the exchange of gasses and liquids with the environment. Therefore, it is important to use biodegradable materials for paper coatings, such as nanocellulose, which is chemically compatible with paper but less hygroscopic. The objective of this study was to evaluate the effectiveness of nanofibrillated cellulose (NFC) as a paper coating. NFC produced from bleached eucalyptus pulp was used as a coating on kraft paper sheets produced from Pinus pulp. To prepare the coating, two thicknesses of wet nanocellulose (1 mm and 2 mm) were tested, and two nanocellulose films made with the same thicknesses were evaluated. The morphological, physical, mechanical, and thermal properties of the composites were investigated. The presence of NFC improved the surface of the paper by filling the pores; consequently, the density and barrier properties were also improved. All mechanical properties were improved, with the highest increases observed for bursting and tensile strength; however, the films showed low bursting index values and null values for the tearing index. The thermal stability of the paper with NFC coatings met the minimum requirements for food packaging.

Application of Feruloyl Esterase in Wheat Straw Pulp Bleaching

The pulp made from wheat straw fiber contains considerable natural cellulose, but there are more carbohydrate-ferulic acid ester-lignin cross-linking structure in the pulp. this cross-linking structure seriously hinders the recognition and binding of hemicellulase and substrate, thus affecting the efficiency of hemicellulose degradation. Feruloyl esterase, as one of hemicellulose degradation enzymes, can hydrolyze hemicellulose side chain branches. Make the plant grid structure loose, it is more important that it can enhance the accessibility of xylanase to the xylan trunk. Therefore, it is of great significance to apply it to the synergistic xylanase-assisted bleaching of wheat straw pulp.

Influence of different curing regimes and accelerated carbonation on the physical, mechanical, and aging performances of fiber cement

The curing process in fiber cement is essential to improving the characteristics of the fiber-matrix interface, physic-mechanical performance, and durability. This work studied the effect of different curing regimes and accelerated carbonation on fiber cement to optimize these materials' production stages and physic-mechanical performance. The fiber cement flat sheets were produced with 10% bleached eucalyptus pulp by slurry-dewatering method to reproduce the commercial Hatschek process. Carbonated and non-carbonated samples were assessed at different regimes and curing ages to provide a comparative parameter. Thermal curing at 60 °C (7 days) and wet curing (28 days) was carried out after carbonation as supplementary curing. The accelerated carbonation was performed in a climatic chamber at 60 °C, 90% RH, and 20% CO2 concentration. Accelerated aging trials were also conducted for durability evaluation. X-ray diffraction, TGA, and scanning electron microscopy analyses determined the mineralogical composition, chemical components, and fiber cement microstructure. Mechanical results presented an average increase of 33% in resistance of carbonated samples compared to non-carbonated fiber cement. Additional curing increased the materials' hydration potential and demonstrated an 11% increase in calcium carbonate amounts. However, there was no statistically significant difference in fiber cement’ physic-mechanical performance with additional curing. The carbonated samples without supplementary curing presented a fiber-matrix interface like that observed in other curing regimes, even after being subjected to a shorter curing time (3 days) and accelerated aging cycles. The accelerated carbonation process enables the materials’ production at reduced ages, achieving physic-mechanical performance and durability like materials produced at more advanced ages with conventional curing regimes.

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.

Role of intrinsic and extrinsic xylan in softwood kraft pulp fiber networks

Xylan is primarily found in the secondary cell wall of plants providing strength and integrity. To take advantage of the reinforcing effect of xylan in papermaking, it is crucial to understand its role in pulp fibers, as it undergoes substantial changes during pulping. However, the contributions of xylan that is added afterwards (extrinsic) and xylan present after pulping (intrinsic) remain largely unexplored. Here, we partially degraded xylan from refined bleached softwood kraft pulp (BSKP) and adsorbed xylan onto BSKP. Enzymatic degradation of 1 % xylan resulted in an open hand sheet structure, while adsorption of 3 % xylan created a denser fiber network. The mechanical properties improved with adsorbed xylan, but decreased more significantly after enzymatic treatment. We propose that the enhancement in mechanical properties by adsorbed extrinsic xylan is due to increased fiber-fiber bonds and sheet density, while the deterioration in mechanical properties of the enzyme treated pulp is caused by the opposite effect. These findings suggest that xylan is decisive for fiber network strength. However, intrinsic xylan is more critical, and the same properties cannot be achieved by readsorbing xylan onto the fibers. Therefore, pulping parameters should be selected to preserve intrinsic xylan within the fibers to maintain paper strength.

Energy saving potential of interstage screen fractionation for production of board grade BCTMP

Over the last few decades, the continuing decline in mechanical pulp-based grades has led pulp producers to modify operations and implement measures to reduce production costs in order to stay competitive. In spite of a considerable effort to reduce energy consumption, the latter is still a major portion of production costs in the process of making bleached chemithermomechanical pulp (BCTMP). In this study, we evaluated the impact of interstage screening fractionation (ISSF) and secondary refining strategy for producing BCTMP with the objective of reducing refining energy consumption while maintaining or improving bulk and strength properties. In the first step and to establish a baseline for a mill’s existing configuration, the collected primary refined pulp and reject streams from the ISSF were refined in a high consistency (HC) refiner to target freeness levels. The accepts and refined rejects streams were recombined, and their properties were compared to those of the refined primary pulp. The results showed that, at a given freeness of 400 mL and compared to the control case (without fractionation), the ISSF using an 0.070 in. basket followed by rejects refining could lead to about 25% energy saving in the second stage HC refining. Handsheet properties showed that utilization of ISSF could produce BCTMP with higher bulk and similar average fiber length and tear index. However, a slight reduction in tensile strength was observed. In the second set of trials, the primary refined pulp and the rejects from the ISSF using the 0.070 in. basket were refined by a low-consistency (LC) refiner. The results showed that, at the same freeness of 400 mL and compared to refined primary pulp, the ISSF saved about 26% in net LC refining energy. At a specific edge load (SEL) of 0.4 J/m, the produced pulp had similar bulk and strength properties compared to those of the control sample. A higher SEL of 0.6 J/m in LC refining could further decrease net refining energy consumption; however, it also led to reduction in fiber length, bulk, and strength properties.

Isolation of Nanocellulose by Enzymatic Hydrolysis of Bleached Musa textilis (Abaca) Pulp

Nanocellulose is commonly isolated from cellulosic materials by chemical methods using strong acids. In this study, the enzymatic method was explored to isolate nanocellulose from commercial bleached S 2 grade abaca pulp. It was first disintegrated for 10 min and was subjected to enzyme hydrolysis while incubated with Bacillus sp. cellulase for 72 h at 50 °C and 120 revolutions/min. A clear liquid material was obtained after enzymatic hydrolysis after a series of centrifugation and ultrasonication. Results showed that the isolated nanocellulose had an average particle size of 375.9 nm ± 2.9 with a polydisperse index of 0.404 ± 0.059. Transmission electron and atomic force images showed that nanocellulose was longitudinal in size and highly aggregated and agglomerated. Through FTIR analysis, crystallinity indexes (i.e. lateral order index, total crystallinity index, and hydrogen bond intensity) of bleached abaca pulp and the isolated nanocellulose were compared. Results showed that the enzymatic hydrolysis of bleached abaca pulp resulted in higher cellulose crystallinity. Overall, nanocellulose can be isolated using biological methods using Bacillus sp. cellulase. These results could be used as a baseline to isolate smaller particle sizes, highly monodisperse, and stable nanocellulose that could be further applied in packaging, papermaking, cosmetics, medicine, and numerous other applications.