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The softness is an important property of tissue papers products and can be a differentiating factor in terms of consumers preference. So, the manufactures have a concern of optimizing this property starting in their industrial base tissue papers. In this work, a dedicated optical system was used for the surface topography reconstruction to characterize the crepe of 13 different industrial base tissue papers, and to study the relationships with their structural properties. In this context, the main objective was the analysis of the 3D reconstruction surface maps of the samples and the corresponding Fourier transformations for the crepe characterization considering the dominant spatial frequencies, depth, and wavelengths of the crepe folds per length unit. A thorough and detailed study was carried out using only the 4 samples that were found to be the extreme cases in terms of handfeel (HF), the worst two and the best two. These calculations, together with the 3D maps obtained with the optical system, the global and magnified images of their surfaces, and the images of their fibrous suspensions, allowed to infer and discriminate the differences that exist between them, which are important for the evaluation and optimization of the global tissue paper quality in line with the conventional methods.

A lot of attention has been paid to cellulose nanocrystals (CNCs) due to their wide availability with a great potential to replace synthetic materials. The formation of CNCs from agricultural waste has numerous positive economic and environmental consequences. Cellulose nanocrystals were synthesized from pineapple leaf by acid hydrolysis and characterized by FT-IR, XRD, SEM, TEM, etc. Different concentrations of cellulose nanocrystals (1%, 3%, and 5% w/w) reinforced gelatin-based bio-nano composite was coated on tissue paper. The optimized fibrogenic solution was infused with three different plant leaf extracts (Banana leaf extract, Mantharai leaf extract, and Lotus leaf extract) used as an antimicrobial agent for hygienic tissue paper. Thickness, grammage, and bulk density analysis show the efficiency of the coating formation. The coated tissue paper shows increased mechanical properties and air permeability but significantly reduced water vapour permeability. Antimicrobial efficacy showed improved activity against Gram-positive bacteria Staphylococcus aureus (ATCC-2913), Gram-negative bacteria Escherichia coli (ATCC-27853), and fungi Candida glabrata (NCYC 388). These results reveal the potential of cellulose materials to serve as accessible platforms for anti-infective or self-sterilizing materials against both bacteria and fungi.

This study focused on the co-fermentation of food waste and tissue paper to produce ethanol, which will eliminate the need for additional nitrogen sources and nutrients, thereby reducing production costs. In response to the inhibitory effect of the high concentrations of glucose present in mixed-substrate hydrolysates on xylose fermentation, a co-fermentation process using Saccharomyces cerevisiae and Candida shehatae was proposed. This approach reduced the fermentation time by 24 h, increased the xylose utilization rate to 88%, and improved the ethanol yield from 41% to 46.5%. The impact of external conditions and corresponding optimization were also analyzed in this process. The optimum conditions were a 1:3 ratio of Saccharomyces cerevisiae to Candida shehatae, a pH of 5, and shaking at 150 r/min, and by employing dynamic temperature control, the ethanol production was increased to 21.98 g/L. Compared to conventional processes that only use Saccharomyces cerevisiae, this method enhanced the ethanol yield from 41% to 49%.

Water absorption is a key property in several tissue paper materials and can be a differentiating factor in terms of consumer choice. The converting modifications applied in the tissue industry can improved absorbency properties. For this purpose, the main goal of the present work is to study the influence of “deco” and “micro” embossing on water absorption capacity, Klemm capillary rise, and liquid spreading kinetics in tissue papers. An industrial never-dried bleached eucalyptus kraft pulp, a creped industrial base tissue paper, and a disintegrated fibrous suspension obtained from the same industrial paper were used to produce structures with and without “deco” and “micro” embossing patterns. The results indicate that the “micro” embossing process promoted bulky and porous structures, enhancing water absorption capacity and Klemm capillary rise properties, while the “dec” embossing pattern decreased water absorption capacity properties. The creping process also increased the water absorption capacity but decreased Klemm capillary rise properties along with the fiber mixtures. Regarding the liquid spreading kinetics, both embossing patterns decreased this property in uncreped isotropic structures, contrary to creped anisotropic structures. The eucalyptus and softwood fibers mixture improved the spreading kinetics compared to the creping process. The performance of structures with and without embossing allowed to quantify the liquid retention properties, combining ISO experimental methods and an optical system that records the liquid interaction with fibrous structures. In conclusion, this laboratory embossing method can be used as an alternative method to optimize converting operations and the final tissue paper characterization, on a laboratory scale.

Softwood bleached chemi-thermomechanical pulp (SW-BCTMP) was added in tissue paper manufacturing, focusing on bulk, absorbency and strength performance. The SW-BCTMP exhibited high fines content (52.4%), elevated polymeric cationic demand (83.0 μeq·L⁻¹), and substantial zeta potential (-93.0 mV), which initially impaired both dynamic drainage performance and first-pass retention of pulp furnishes. The optimal application of polyaluminum chloride (PAC) was found to effectively reduce the cationic demand of pulp furnishes and enhance first-pass retention. The addition of 5.0 to 10.0% SW-BCTMP consistently enhanced the bulk, water absorbency, and air permeability of the handsheets. In the absence of polyamide-epichlorohydrin resin (PAE), dry strength was well maintained or even improved when substituting the bleached hardwood kraft pulp (BHKP), despite a marginal decline upon replacing the bleached softwood kraft pulp (BSKP). However, in PAE-containing systems, a consistent reduction in both dry and wet strength was observed. This detrimental effect was more pronounced when the SW-BCTMP replaced BSKP in the furnishes, which can be attributed to the interference of the SW-BCTMP with the adsorption and effectiveness of the wet-strength resin. The SW-BCTMP showed potential for enhancing bulk and absorbency in tissue products, such as toilet paper, where wet strength agents are not used.

Suitable fermentation substrates and fermentation modes can effectively improve the fermentation ethanol yield. In this study, we optimised the hydrothermal pretreatment conditions by orthogonal optimisation using waste tissue paper as substrate. These conditions consisted of 50 min duration in a high-pressure reactor with pure water as solvent at a temperature of 160 °C. The biomass to water ratio was maintained at a constant level. The cellulose content of the pretreated TP was 81.19 ± 4.06%, which was an increase of 21.59% compared to the blank control. The 72 h reducing sugar yield of pretreated TP was 0.61 g sugar/g paper, which was 38.64% higher than that of untreated TP. Subsequently, the pretreated TP was fermented under optimal conditions. The mixed group of Saccharomyces cerevisiae and Candida shehatae (SC) showed a distributed saccharification fermentation pattern, with an ethanol yield of 28.11 g/L in 72 h. On the other hand, the single Saccharomyces cerevisiae (S) exhibited a homobloc saccharification fermentation pattern, with an ethanol yield of 35.15 g/L in 72 h.

Tissue furnish optimization plays a key role in enhancing tissue properties, making the process cost-effective. Typically, this furnish is composed of a mixture of hardwood eucalyptus fibers (HW) and softwood (SW) fibers, which ensure strength and tissue machine runnability. However, the tissue paper production with the maximization of eucalyptus fibers achieves softer papers at less cost, since SW fibers are often more expensive than HW fibers. From this perspective, this study aims to investigate the effect of micro/nano-fibrillated cellulose (MFC/NFC) as an additive, on structural, softness, strength, and water absorption properties of tissue papers, promoting partial or total removal of SW fibers to produce 100% eucalyptus materials. MFC/NFC was characterized in terms of morphological, chemical, and water interaction properties. The results showed that MFC/NFC presents a high bonding surface area, high carboxyl group content and, when incorporated into tissue furnishes, it promotes strong inter-fiber bonds. This evidence was also supported by SEM image analysis methods and FTIR. Additionally, laboratory tissue handsheets with low basis weight were produced and used in the characterization assays. Overall, the results indicated that MFC/NFC improved strength, at the expense of bulk, porosity, softness, and absorption properties. Compared to typical industrial furnish mixtures (75%HW + 25%SW), MFC/NFC enhanced the production of bulkier, porous, and softer structures, but with reduced strength and absorption. It was possible to optimize the furnish composition by using fiber modeling to obtain 3D structure computation simulations with predictive capability. The MFC/NFC proved to be a high-quality additive to improve softness and strength properties.Graphic abstract

Impinging air jets can be used to dewater, heat, and dry the web of tissue paper. High velocities of the air jets degrade the paper, and appropriate adjustments to the jet velocity and the distance of the nozzle from the surface of the wet web are crucial to obtain the highest quality product. This work investigated the correlation between the velocity of the air jet and the strength of paper subjected to the impingement method. Papers with an initial moisture content of 20% and various pulp mixes were tested, and the physical properties of papers were explored. After impinging an air jet, different tensile strength limits were obtained in the machine and cross directions. The paper had lower apparent density and higher roughness compared to classical pressing. The dependence of tensile strength and roughness on the fibers composition also was determined. Increasing the amount of eucalyptus fibers in impingement dewatered paper resulted in a decrease in its tensile strength and roughness. The value of elongation before breaking was the highest for softwood papers after the impingement method. The maximum velocity of an air jet that can be used to dewater or dry paper without the risk of damage to the papers was determined.

The influence of the temperature of the paper pulp and drying of towel papers containing polyamidoamine-epichlorohydrin (PAE – 3.5 mg/g ADM) on their wet tensile strength was investigated. The paper was produced from pulp containing 40% pine fibers and 60% eucalyptus bleached kraft fibers, heated to 25 °C, 40 °C, and 50 °C, after which the paper was dried with hot air in the temperature range of 190 to 330 °C. The aim of the research was to determine the influence of the temperature of the paper pulp and drying of the paper formed from it on the degree of PAE bonding with fibers and its self-crosslinking ability. The sheets obtained were tested for wet strength in both the machine direction (MD) and cross direction (CD). The results indicated that the paper drying temperature had a key influence on the increase in its wet strength, while heating the pulp before forming the sheets had a relatively minor effect. The increase in drying temperature to 330 °C allowed the wet tensile index (WTI) to be improved over 100% compared to drying at ambient temperature, with the highest strength demonstrated by samples formed from pulp heated to 50 °C and dried at 330 °C. Paper samples with PAE, tested wet for CD, showed strength at a level of 36 to 44% of the values obtained for MD. The obtained results contribute to the deepening of knowledge on the mechanism of increase in wet strength of PAE-modified towel papers, depending on the temperature conditions used during their production.