Preparation and papermaking properties of dry-cut powder from chemically crosslinked BEKP

Hemicelluloses isolated from eucalyptus wood were adsorbed onto both bleached eucalyptus kraft pulp and pine kraft pulp as part of a general strategy to investigate their role on final sheet mechanics and physical properties. The tensile indices increased upon hemicelluloses addition and respectively reached a maximum at 9 mg/g and 10 mg/g hemicelluloses adsorption for bleached eucalyptus kraft pulp and pine kraft pulp, whereas the tear index increased depending on the pulp type. The air permeability and surface roughness of the bleached eucalyptus kraft pulp slightly decreased, however, brightness and opacity did not changed. SEM analysis shows that hemicelluloses adsorption increases bleached eucalyptus kraft pulp fibers interaction, whereas the effect of hemicelluloses addition on the beaten pine kraft pulp is unclear. The hemicelluloses adsorption also affected printability. It was found that print through for the bleached eucalyptus kraft pulp hand sheet slightly decreased, but for the bleached pine kraft pulp hand sheet it was unaffected. Print densities were not influenced.

The influence of addition of deinked pulps with low and high brightness to bleached eucalyptus and pine kraft pulps on functional tissue paper properties was studied. Deinked pulps with low and high brightness had some different functional properties. Deinked pulp with high brightness has higher bulk, porosity, water absorption after immersion, initial water absorption, bulk softness as well as brightness. On the contrary, the difference in relative bonded area and porosity e between deinked pulps with low and high brightness was moderate. The mixed pulps laboratory pulp sheets from bleached eucalyptus kraft pulp or bleached pine kraft pulp with addition of 20, 40 and 80% of deinked pulp with low brightness or deinked pulp with high brightness were prepared. The addition of the deinked pulp with high or low brightness to bleached kraft pulp leads to increasing of bulk, bulk softness as well as high water absorption after immersion and initial water absorption. The tensile index rapidly decreased by the addition of deinked pulps with high brightness to bleached eucalyptus and pine kraft pulps. Similarly, the addition of deinked pulp with low brightness to bleached pine kraft pulp led to rapid decreasing of tensile index. On contrary, with the addition of deinked pulp with low brightness to eucalyptus kraft pulp, the decreasing of tensile index was less pronounced. Mixed pulp from bleached eucalyptus kraft pulp with a small content of deinked pulp with low brightness with functional properties suitable for production of tissue papers was found as optimal.

Main determinants of export-oriented bleached eucalyptus kraft pulp (BEKP) demand from the north-western regions of Spain

Exploring the action of endoglucanases on bleached eucalyptus kraft pulp as potential catalyst for isolation of cellulose nanocrystals.

Poly-epichlorohydrin-dimethylamine (p-DMA-co-ECH) was synthesized and was used to modify bleached eucalyptus kraft pulp (BEKP). The modified pulp (designated PDMAECH pulp) was characterized by zeta potential, FTIR, NMR, and SEM. Both the PDMAECH pulp and the BEKP were used as adsorbents to remove Acid Scarlet G (ASG) from aqueous solution. The effects of operational parameters on the efficiency of dye removal, including pH, adsorbent dosage, initial dye concentration, and contact time, were investigated. Results showed that modification could change the surface characteristics and effectively enhance the adsorption capacity. The optimum pH for ASG removal with the modified bleached eucalyptus kraft pulp (PDMAECH pulp) was found to be 4.0, and for BEKP it was 2.0. Under the optimized conditions, the maximum capacities for ASG adsorption were also investigated. The adsorption processes of both adsorption reactions were spontaneous and exothermic, and the adsorption capacities decreased with an increase in temperature. Freundlich and Langmuir models were used to analyze the obtained experimental data. The Langmuir model was found to be a better fit for the experimental data for both adsorbents. Kinetic studies showed that the rate of adsorption of ASG on both adsorbents obeyed a pseudo-second-order kinetics model. The desorption process for PDMAECH pulp was also explored.

Reinforced natural rubber (NR) nanocomposites were prepared by solution mixing. casting. and evaporation of pre-vulcanized natural rubber latex and an aqueous suspension of cellulose nanofibrils (CNFs) extracted from bleached eucalyptus kraft pulp. Scanning electron microscopy (SEM) images showed that there were no micro-scaled aggregates observed in the nanocomposites. The addition of CNFs changed the mechanical behavior of the nanocomposites as observed in tensile tests. The tensile strength was significantly enhanced with CNFs, but the material became brittle at higher CNFs loading levels. Dynamic mechanical analysis (DMA) proved the strong reinforcing tendency of CNFs in the NR matrix as the storage modulus of the nanocomposites increased with CNFs content across the entire temperature range. Thermal gravimetric analysis (TGA) showed that CNFs had a slightly negative impact on the thermal stability of NR nanocomposites. There was no change in the glass transition temperature of the rubber matrix with the addition of cellulose nanofibrils, which was characterized by differential scanning calorimetry (DSC) measurements.

We used a new cellulosic material, cellulosic solid residue (CSR), to produce cellulose nanofibrils (CNF) for potential high value applications. Cellulose nanofibrils (CNF) were produced from CSR recovered from the hydrolysates (waste stream) of acid hydrolysis of a bleached Eucalyptus kraft pulp (BEP) to produce nanocrystals (CNC). Acid hydrolysis greatly facilitated homogenization to fibrillate CSR to CNF with only 15 passes in a microfluidizer compared with at least 47 passes to fibrillate BEP to nanofibrils. CNF from CSR were nanowhiskers with a length between 50 and 400 nm and a diameter 3-10 nm with limited aggregation while CNF from BEP were entangled networks of nanofibrils with a length of 500-1000 nm and a diameter of 10-50 nm. CNFs from CSR had good spectral transparency from UV to infrared, i.e, transmittance of CNF-CSR suspensions at 0.1% solids consistency is greater than 90% at wavelengths greater than 340 nm, compared with less than 30% for CNF suspension produced from BEP. Specific tensile strength and modulus of CNF films from CSRs reached 75 kN·m/kg and 12 MN·m/kg, respectively, approximately 175% of the respective values for conventional paper made of refined BEP.

Nanofibrillated cellulose (NFC) extracted from biomass has potential applications in material science and biomedical engineering. In this study, NFC was obtained from bleached eucalyptus Kraft pulp (BEKP) using two commercial enzyme cocktails with cellulolytic and hemicellulolytic activities and non-catalytic protein (swollenin), followed by ultrasonication. This work represents an initial study of the implementation of non-catalytic proteins along with enzymes to extract NFC from biomass. Enzymatic pretreatment was performed to partially remove hemicellulose while enhancing cellulose accessibility for NFC extraction. Cellulase pretreatment with xylanase and swollenin supplementation increased cellulose accessibility and fiber swelling due to extensive hemicellulose removal (> 80%) and fiber morphology changes. Subsequent ultrasonication was performed for cellulose nanofibrillation resulting in high NFC yields (61–97%), while keeping NFC properties almost unchanged. Through this process, cellulose nanofibers with diameters ranging from 3 nm to 10 nm were effectively isolated from BEKP, which allows to produce high quality NFC for further applications.

Evaluating the reinforcing potential of enzymatic cellulose nanocrystals in polypropylene nanocomposite

Cellulose nanocrystals (CNCs) have become valued bionanomaterials with enormous potential to bring fundamental changes and benefits to society. We evaluated the techno‐economic viability of using sulfuric acid and enzymatic hydrolysis technologies to produce CNCs from bleached eucalyptus Kraft pulp (BEKP) in stand‐alone facilities. Experiments were performed on the enzymatic and acid hydrolysis of BEKP and the separation and isolation of the generated CNCs. The results obtained were used to determine reaction yields and compositions through the process stages and to build mass balances for the production of CNCs via acid and enzymatic hydrolysis. We used the process data that were generated to simulate and scale up process models of the production of CNCs using Aspen Plus. Techno‐economic analyses of the simulated processes were performed using Aspen Process Economic Analyzer to generate capital and operating cost estimates. At an estimated minimum selling price (MSP) of $10 031/dry tonne of CNCs, the production of CNCs via acid hydrolysis can be technically and economically competitive. Further research and process optimization efforts should focus on low‐cost technologies that minimize water use and on sulfuric acid recovery technologies that lead to lower production costs. The production of CNCs via enzymatic hydrolysis requires a low capital investment. However, due to its low reaction yield, a reflection of the still early stage of process development, the production cost of the enzymatic CNCs, with an MSP of $65 740 dry tonne of CNCs t–1, is too high to be commercially attractive. Nonetheless, the low capital cost of producing CNCs by using enzymatic hydrolysis indicates that the process may be profitable if the enzymatic hydrolysis yield is drastically improved. Research efforts towards developing an enzyme cocktail designed and optimized specifically for CNCs production and the introduction of an efficient and low‐cost pretreatment stage prior to enzymatic hydrolysis to increase the accessibility of enzymes to cellulose may improve the hydrolysis yield. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

Synthesis and application of cationic spherical polyelectrolyte brushes as retention and drainage aid in bleached eucalyptus kraft pulp

The present study concerns the preparation of cellulosic powders with two-stage dry milling of chemically crosslinked birch kraft pulp sheets. Chemical crosslinking of kraft pulp sheets using glyoxal with and without a catalyst (aluminium sulphate) made the pliable, tenacious kraft pulp sheets brittle. Due to the brittleness, the crosslinked pulp sheets could be disintegrated easily and rapidly using a Wiley mill. The length-weighted average fibre length of the crosslinked pulp powders (0.31–0.33 mm) was shorter than the Wiley-milled reference powder (0.44 mm). The notably higher density and less fluffy character of the crosslinked pulp powders enabled their effortless further processing with an air-flow-type ultra-fine microniser. The medium size value (D50) of the micronised crosslinked powders was around 40 μm. The study finds that chemical crosslinking pre-treatment enhances the dry milling of kraft pulps to a fine powder. Chemical crosslinking may offer a new tool for industrial cellulosic powder manufacturing.

Life cycle assessment of Brazilian bleached eucalyptus kraft pulp: Integrating bleaching processes and biogenic carbon impacts

The present work is focused on alkaline extraction of xylans from bleached Kraft pulp of Eucalyptus globulus, and its isolation from the alkaline extract, aiming high purity product and yields. Alkaline extraction was optimized, through the stirring speed and extraction time. A higher stirring speed increased extraction yields which varied between 65 and 85%. However, extraction time did not have influence on extraction yields. Xylans isolation was performed by precipitation with diluted acids and with various alcohol concentrations. Washing of the precipitates, to remove impurities, was performed either with water and/or with methanol. Water washing yielded xylans with purity values up to 99%, while with methanol those values were lower, in the range of 36–84%. Xylans characterization indicated average molecular weights of 16.8–22.7 kDa. The isolated xylan yields varied between 43 and 97%. Nitric acid showed to be the most adequate solvent to get pure xylan. On the other hand, in alcohol experiments lower yields were obtained due to the losses in the subsequent water washing process.

Chemical crosslinking is an established method for improving the wet performance of paper. In the chemical crosslinking process, covalent bonds are formed between cellulosic surfaces. The formed intra- and inter-fiber bonds increase the paper’s wet strength and reduce its water absorptivity. The majority of published studies concern crosslinking treatments with glyoxal, citric acid (CA), or with 1,2,3,4-butanetetra-carboxylic acid (BTCA). The most severe disadvantage of the crosslinking treatments with glyoxal, CA, and BTCA is that the formed crosslinks make the fibers and the paper more brittle. This downside effect has largely impeded the utilization of crosslinking in paper and paperboard making. In the present study, handsheets made from Nordic bleached softwood kraft pulp (NBSK) were crosslinked with methylated 1,3-dimethylol-4,5-dihydroxyethylene urea (mDMDHEU), which is commonly used in cotton fabric finishing. Similar to using glyoxal and citric acid, crosslinking with mDMDHEU notably increased the handsheet wet strength and decreased the water absorption. Compared to the use of glyoxal or CA, the crosslinking with mDMDHEU did not make the handsheets that brittle. These results suggest that mDMDHEU could be a more viable crosslinking agent for improving the wet performance of paper products.