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Improving paper wet strength via increased lignin content and hot-pressing temperature, TAPPI JOURNAL October 2020
ABSTRACT: It is known that the strength properties of wood-based paper materials can be enhanced via hot-pressing techniques. Today, there is a desire not only for a change from fossil-based packaging materials to new sustainable bio-based materials, but also for more effective and eco-friendly solutions for improving the dry and wet strength of paper and board. Against this background, hot pressing of paper made from high yield pulp (HYP), rich in lignin, becomes highly interesting. This study investigated the influence of pressing temperature and native lignin content on the properties of paper produced by means of hot pressing. Kraft pulps of varied lignin content (kappa numbers: 25, 50, 80) were produced at pilot scale from the same batch by varying the cooking time. We then studied the effect of lignin content by evaluating the physical properties of Rapid Köthen sheets after hot pressing in the temperature range of 20°C•200°C with a constant nip pressure of 7 MPa. The pilot-scale cooked pulps were compared with reference samples of mill-produced northern bleached soft-wood kraft (NBSK) pulp and mill-produced chemithermomechanical pulp (CTMP).Generally, the results demonstrated that lignin content had a significant effect on both dry and wet tensile index. All of the pilot cooked pulps with increased lignin content had a higher tensile index than the reference NBSK pulp. To obtain high tensile index, both dry and wet, the pressing temperature should be set high, preferably at least 200°C; that is, well above the glass transition temperature (Tg) for lignin. Moreover, the lignin content should prefera-bly also be high. All kraft pulps investigated in this study showed a linear relationship between wet strength and lignin content.
Journal articles
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Comparative analysis and benchmarking of commercial and emerging fast pyrolysis technologies, TAPPI Journal May 2023
ABSTRACT: It is well established that producing sustainable fuels and replacing the fossil-based ones is one of the key solutions to achieving net-zero emissions goals. One of the most advanced commercial-scale pathways to biofuels available today is fast pyrolysis. However, due to the need for a supportive regulatory environment and mitigation strategies for uncertainties related to costs and feedstock quality, fast pyrolysis is not yet being widely implemented. In this case study, three fast pyrolysis technologies with a technology readiness level (TRL) of 6 and above have been compared to distinguish between them and identify the conditions under which they are economically viable. The circulating fluidized bed (CFB), rotating cone (RC), and mechanically assisted fluidized bed (MFB) fast pyrolysis technologies were considered. First, the flow diagram and a mass and energy balance comparison were addressed. It was revealed that the RC configuration has better bio-oil yields because it can handle smaller particles. The MFB configuration has a progressive condensation unit at the end of the process, which produces a nearly dry oil having a higher energy content. Four implementation scenarios were studied. The first was the fast pyrolysis standalone process, where all options had marginal economic attractiveness, and the RC configuration economically outperformed the other two. Integration of a fast pyrolysis plant into a sawmill in the second scenario was found to bring significant improvements in revenues and internal rate of return (IRR). Realization of the full value of bio-oil (the third scenario) brought significantly more revenues for the MFB. Finally, the fourth scenario involved adding a progressive condensation unit, which increased the capital expenditure (CAPEX) by 3%•4% while increasing revenues by 32%•35%. A sensitivity analysis highlighted the importance of financial support towards capital cost and the full valuation of bio-oil for the economic viability of fast pyrolysis processes. Progressive condensation leading to more added-value bio-oil makes the standalone fast pyrolysis process more profitable.
Journal articles
Magazine articles
Enhancing tissue wet pressing performance and dry end material efficiency for cost savings, TAPPI Journal May 2024
ABSTRACT: The steadily growing global tissue paper demand lays a foundation for new technologies targeting tissue production optimization, as well as improved material and time efficiency. Tissue making is an especially energy-intensive field of paper industry, creating unique demands for performance in wet pressing and drying processes to cut energy usage. Intelligent roll solutions offer new tools for tissue making to achieve these goals. These tools aim at improving press nip, moisture, and tension profiles; reeling nip and parent roll hardness profiles; rewinder runnability; and end product web handling characteristics in converting. Intelligent rolls can be utilized in all the main processes and positions on tissue production lines. With these tools, production cost reductions and energy savings can be obtained by optimizing the press nip-to-Yankee cylinder contact, avoiding moisture profile errors requiring overdrying with the Yankee hood and reducing reeling/winding broke under low nip load conditions typical to tissue windups. The intelligent roll system consists of a helically mounted force or temperature sensors, roll covers, measurement electronics, digital radio transmission, and a receiver system connected to a user interface or the mill automation system. What distinguishes these implementations is that no layout changes or added external measurement devices are required, helping to fit into compact tissue machine environments, regardless of the equipment type • traditional, hybrid, or through-air drying (TAD) concept. In tissue processing equipment, the optimal positions for these rolls are press nip rollers, reeling cylinders, rewinder or converting line paper lead rolls, or rewinder winding drums. In addition to these, temperature profile measurements are utilized, with the main application being the sheet temperature profile detection after Yankee drying for moisture profile and drying process optimization.
Journal articles
Adhesion with purpose: The value of primers in sustainable flexible packaging, TAPPI Journal July 2025
ABSTRACT: Primers play a crucial role in flexible packaging by providing adhesion, enhancing performance, and improving the overall quality of packaging structures. As the packaging industry shifts towards more sustainable solutions, it brings new challenges for meeting adhesion requirements. Different types of sustainable materials, with their complicated physical and chemical properties, usually result in poor adhesion in extrusion coating or extrusion lamination, whether this is due to fast crystallization, secondary crystallization, low processing temperature, lack of functional groups, or a combination thereof. Water-based primers ensure that these innovations meet both functional and environmental standards for the packaging of tomorrow. Conventional water-based primers, including polyethyleneimine (PEI) and ethylene acrylic acid (EAA), offer significant advantages in sustainable packaging design by chemically modifying the surface of the substrate to enhance adhesion. In this study, we will discuss adhesion issues in three case studies involving sustainable packaging materials: (1) extrusion coating of polyvinyl alcohol (PVOH) on paper; (2) extrusion lamination of paper and metallized film with starch biopolymer; and (3) extrusion coating of polyhydroxyalkanoates (PHA) on paper. These cases represent three adhesion challenges related to sustainable materials, namely fast crystallization rate, low processing temperature, and secondary crystallization. A three-step adhesion improvement procedure was employed to identify the proper primer in each case study. This procedure included a wetting-out test with primer, an adhesion test, and an extrusion test with priming. In our results, strong fiber tearing or destructive bonds were achieved in each case with the help of water-based primers. These results demonstrate the value of water-based primers in enabling the transition to more sustainable packaging structures without compromising performance.
Journal articles
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Equilibrium moisture content in wet pressing of paper, TAPPI Journal July 2020
ABSTRACT: Equilibrium moisture is a limiting factor in achieving high solids in the later stages of pressing or pressing low basis weight grades. We have developed a model that relates equilibrium moisture directly to the pore size distribution of fibers as measured by the solute exclusion technique. The model shows that chemical pulping and refining increase equilibrium moisture by increasing pore volume at given pore sizes in fibers, which leads to lower pressed solids and greater energy expenditure in the dryer section. Means to increase equilibrium moisture without compromising pulp strength are briefly discussed.
Journal articles
Magazine articles
Novel test method for measuring defects in barrier coatings, TAPPI Journal November 2022
ABSTRACT: In the last several years, activity to develop water-based barrier coatings (WBBCs) that meet challenging packaging performance requirements has increased dramatically. Cellulose-based packaging solutions can provide a more sustainable packaging option for replacing single-use plastic-based options like extrusion-based and laminated materials. An advantage of WBBCs is the opportunity to reduce the coating thickness applied, as long as the barrier requirements can be met. A challenge that must be overcome is the ability to maintain a defect and pin-hole-free coating layer after coating and drying to retain the barrier performance. Many formulation and coating parameters can affect the barrier coating layer quality; however, methods for detecting more subtle differences in these types of studies are not widely available. Work was carried out to develop a quantitative technique for detecting and measuring the quantity and size of defects in the barrier coating layer. A test method has been developed using a combination of dyed oil and image analysis to be able to characterize the imperfections in the coating surface. The use of dyed oil serves two purposes. First, it better simulates the types of materials, in this case, oils and grease, for which the barrier coating is expected to hold out. Second, it also provides contrast between the coating and failure points for testing. An image analysis technique is employed to characterize the number and size of the imperfections. For the former, it reduces the testing time required if a quality control or laboratory technician counts the dots. For the latter, it assists with judgment on the source of the root cause of the imperfection, such as base sheet defects, coating dispersion issues, or perhaps micro-blisters in the coating, as some examples.To show the benefit of this technique, several pilot coating studies were designed to see if the new technique could be utilized to detect differences in WBBC performance. Both process and chemical variables were evaluated. With refinement, it is believed this technique can be utilized in development work, as well as for a potential quality control technique for manufacturing of coated paper and paperboard products.
Journal articles
Magazine articles
Application of fuzzy TOPSIS in the Analyze phase of the DMAIC cycle to aid decision-making, TAPPI Journal April 2020
ABSTRACT: This paper reports the use of multicriteria analysis in the Analyze phase of the DMAIC (Define-Measure-Analyze-Improve-Control) cycle for continuous improvement. The research was carried out in a tissue paper factory located in southern Brazil. A sample of 64 parts of 16 different reels of recycled paper was used. A problem regarding paper quality variability was detected, presenting a scrap index ranging between 9% and 23%, compromising machine productivity and product sales. This motivated the implementation of a structured project supported by the application of the DMAIC cycle. The project team (machine operators, maintenance staff, supervisor, and data analyst) defined the evaluation criteria and determined the control intervals and their equivalence with linguistic variables to support the necessary evaluations for the application of fuzzy TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution). The criteria were C1-Longitudinal Strength (Kgf), C2-Longitudinal Elongation (mm), C3-Cross-strength (kgf), C4-Cross-elongation (mm), C5-Weight (g/m²), and C6-Humidity (%). The results showed that samples with the same ranking had the lowest scrap indexes in the subsequent process. Also, the criterion C5 had a more significant impact on the quality of the product than the other criteria, which was determined from the DMAIC sequence. Improvements related to C5 should be prioritized. The fuzzy TOPSIS method presented is a flexible tool, adapting itself to the solution of the problem and contributing to the decision-making process.
Journal articles
Magazine articles
Improving monochloramine performance with innovative sensor-controlled dosing, TAPPI Journal January 2024
ABSTRACT: Monochloramine (MCA) has become one of the major oxidant chemistries for biological control in the paper industry. Feedback control, such as oxidative-reductive potential (ORP), is often used to provide better control of a dosing scheme. The trademarked Ackumen MCA-i is a chemical-digital solution that uses artificial intelligence with actionable insights to stabilize the wet-end process, providing improved performance and reduction in overall chemical costs. Accurate sensor-controlled dosing can be tied to multiple inputs, such as production rates, grade changes, pH, ORP, chlorine residual, freshwater usage, and more. In this study, a case history will be presented to demonstrate how this technology provided a more consistent MCA molecule throughout the process, resulting in a higher level of efficacy and reduction in chemical costs.
Journal articles
Magazine articles
Spraying starch on the Fourdrinier— An option between wet end starch and the size press, TAPPI Journal January 2021
ABSTRACT: Technology to apply suspensions of starch grains to the wet surface of paper, during the dewatering process, is reviewed. Though the technology is not new, it continues to attract the attention of papermakers as a means to increase bonding strength. Starch grains that are sprayed onto the wet-web of paper can be retained at levels exceeding what can be effectively added to the fiber suspension at the wet end. Unlike adding a starch solution at a size press, no additional drying capacity is required on the paper machine. To be effective, the starch needs to be able to swell and develop bonding during the paper drying process. Paperboard applications with recycled fibers appear to be a good fit. There is potential to increase bonding by processes that favor fuller gelatinization of the starch grains by the time the paper becomes dry.
Journal articles
Magazine articles
A novel approach for determining the reactivity of dissolving pulp based on the COD method
ABSTRACT: A novel approach for determining the reactivity of dissolving pulp according to the chemical oxygen demand (COD) of water has been discussed. First, a sample of dissolving pulp was subjected to mercerization and xanthation in order to obtain dissolved cellulose fractions. Next, the fractions were digested with a testing solution as applied in COD procedures. Finally, the resulting liquid was rapidly tested by ultraviolet-visible spectrophotometry (UV-Vis). By quantifying the absorbance of Cr3+ at a wavelength of 600 nm, the reactivity of dissolving pulp was indirectly calculated. The results measured by this novel COD method correlated well with the most accepted Fock test results with less than 10% relative difference. Meanwhile, this newly developed COD method required less time-consuming procedures as compared to the Fock test.