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Measurement and control of extensional viscosity in barrier coating dispersions, TAPPI Journal November 2023
ABSTRACT: This study aimed to understand the effect of various rheological additives on the extensional viscosity of barrier coating dispersions, as well as to understand the role extensional viscosity plays in stabilizing a liquid curtain. The apparent extensional viscosity was measured using two devices that create accelerating flows: a capillary viscometer and an orifice rheometer. Additives tested include several polyvinyl alcohols, a high molecular weight polyethylene oxide, and carboxymethylcellulose. Extensional viscosity plays a significant role in stabilizing a liquid curtain, as it slows down hole expansion and prevents impurities and disturbances from causing holes in the first place. Some of the additives could substantially increase the extensional viscosity of the dispersions without increasing the shear viscosity outside the typical range of processability for a curtain coater. Some of the additives exhibited coil-stretch transition, meaning they start increasing extensional viscosity above a certain extension rate. Polymers with low chain lengths exhibited finite extensibility, which indicates the polymer chain has fully extended and cannot provide further extensional viscosity, even though the extending force is increased. Polymeric additives with stiff or branched chains significantly raised shear viscosity without increasing extensional viscosity. Both methods could reliably measure extensional viscosity in curtain coating barrier dispersions.
Journal articles
Magazine articles
Quantification of hardwood black liquor contamination in pine black liquor, TAPPI Journal February 2024
ABSTRACT: The presence of hardwood black liquor contamination in pine black liquor can negatively impact brownstock washer and evaporator operation, as well as reduce soap separation and yield. It is also believed to negatively impact commercial kraft lignin production. It was desired to develop a method of quantitatively determining the amount of low-level hardwood liquor contamination in pine black liquor. A method employing pyrolysis-gas chromatography mass spectrometry (py-GCMS) was developed to perform the desired measurement. Laboratory cooks with carefully controlled blends of pine and hardwood chips were prepared, and the resulting liquor was measured using this technique. Additionally, samples of pine and hardwood black liquors were blended in known quantities and analyzed. All these samples were submitted as blind samples. The resulting analysis suggests the py-GCMS method was able to accurately determine the level of hardwood contamination between 1% to 10% hardwood liquor using a low-level calibration curve prepared with coniferyl alcohol and sinapyl alcohol as standards.
Journal articles
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Alkyl ketene dimer (AKD) sized paper reversion due to oxidative photodegradation, TAPPI Journal January 2024
ABSTRACT: Alkyl ketene dimer (AKD) is a sizing agent used in papermaking to increase the resistance of paper-board towards water penetration. The acquired hydrophobic property of the paper can be reversed due to the instability of the sizing agent. It is broadly known that AKD size reversion is due to migration, poor orientation, masking, or hydrolysis of the sizing agent. Unfortunately, the environmental parameters that cause this chemical instability are not well understood. Thus, the conditions that initiate or catalyze AKD size reversion and the mechanisms of AKD size reversion under different environmental conditions need to be investigated. In this study, six different experimental setups were used to investigate how temperature, daylight, fluorescent light, oxygen, and ultraviolet (UV) light affect AKD size reversion. Cobb values and pyrolysis gas chromatography-mass spectrometry (py-GCMS) results show that AKD size reversion is due to the degradation of the chemical in the presence of light and oxygen; temperature variations were found to accelerate reversion in the presence of light and oxygen. The oxidative photodegradation mechanism of the sizing agent is explored, and a possible mechanism is proposed.
Journal articles
Magazine articles
Dynamic compression characteristics of fiber-reinforced shoe press belts, TAPPI Journal April 2025
ABSTRACT: Shoe press belts contribute significantly to the overall dewatering performance in the press section of a paper machine. Within the shoe press nip, the press belt faces a dynamic and multidimensional load that mainly leads to a compression of the structure. As this will cause a loss in void volume, knowledge of the dynamic compression characteristics of shoe press belts is crucial for optimized dewatering. A novel method was developed to examine the dynamic compression characteristics of grooved polyurethane press belts. Therefore, an experimental setup allowing realistic boundary conditions to test specimens was placed in a servo-hydraulic testing machine. Press belt specimens with different matrix material formulations and groove patterns were tested under varying load rates equivalent to different paper machine operational speeds. The results showed an evident sensitivity of the dynamic compression stiffness to the operational speed of the paper machine. This behavior was seen to be more sensitive to changes in the matrix material formulation than to adaptions of the groove pattern. As a result, the compression of the press belt within a shoe press nip is not only influenced by the peak pressure within the shoe press nip but also depends on the operational speed of the paper machine.
Journal articles
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Continuous tannin extraction by use of screw reactor, TAPPI Journal February 2021
ABSTRACT: A pilot-size screw reactor (extraction unit) was used for tannin extraction of spruce. Yield of the same magnitude or better was obtained when comparing a screw reactor with batch reactors. A longer presoaking time in water seemed to be better than a short one for obtaining higher yield. A higher yield is obtained with lower dry-water ratio, which suggests that the internal diffusion in bark does not determine mass transfer as much as is the case without presoaking of bark. The higher dry-water ratio decreased the yield. The prior soaking of the bark also minimized the mechanical reactor feeding problems (clogging). The benefits of a screw reactor likely are that run time changes for different process conditions are flexible; it simplifies design and construction of an industrial unit for tannin production; and it saves space because of the need for fewer and smaller intermediate storage tanks.
Journal articles
Magazine articles
New opportunities in the paper and nonwovens industries with foam-assisted web forming and chemical application, TAPPI Journal January 2023
ABSTRACT: Foam-assisted web forming and chemical application technologies have great potential to improve manufacturing efficiency and product quality in the paper and nonwovens industries. In this study, the benefits of foam forming and foam-assisted application of chemicals were demonstrated in a pilot machine trial. Uniform high-bulk webs of unrefined bleached softwood kraft pulp (BSKP) and viscose fibers were manufactured by foam forming. It was shown that foam formed low-grammage and high-bulk viscose fiber webs can be strengthened by foam-assisted application of latex onto the wet web. Correspondingly, foam-assisted application of carboxymethyl cellulose (CMC) and anionic polyacrylamide (A-PAM) improved the strength of the foam formed low-grammage and high-bulk BSKP web. Overall, the pilot machine results indicated that material cost savings could be achieved and a high-performance product could be manufactured with foam-based technologies.
Journal articles
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Case study: Paper mill power plant optimization—balancing steam venting with mill demand, TAPPI Journal June 2020
ABSTRACT: Most Power departments are tasked with generating steam to support mill wide operations, generate electricity, and reduce operating costs. To accomplish these tasks, power boilers generate high pressure steam that is reduced to intermediate and low pressures for process utilization in the mill by means of steam turbine generator extraction or pressure reducing valves. The most economical method to reduce steam pressure is the use of steam turbine generators, as electricity is generated from the steam when it is reduced in pressure. Electricity that is produced by these generators provides a substantial financial benefit and helps offset overall operational costs. To achieve tangible financial gains, the mill must evaluate the overall cost of steam production and the price of electricity.The current work provides a case study of power plant optimization that evaluated electricity production and steam production costs balanced with mill steam demand. Process and cost optimization led to a significant reduc-tion in low pressure steam venting, resulting in reduced fuel consumption and reduced operating cost.
Journal articles
Magazine articles
Incorporation of post-consumer pizza boxes in the recovered fiber stream: Impacts of grease on finished product quality, TAPPI Journal March 2021
ABSTRACT: Grease and cheese contamination of used pizza boxes has led to misunderstanding and controversy about the recyclability of pizza boxes. Some collection facilities accept pizza boxes while others do not. The purpose of this study is to determine whether typical grease or cheese contamination levels associated with pizza boxes impact finished product quality. Grease (from vegetable oil) and cheese are essentially hydrophobic and in sufficiently high concentration could interfere with interfiber bonding, resulting in paper strength loss.Findings from this study will be used to determine the viability of recycling pizza boxes at current and future con-centrations in old corrugated containers (OCC) recovered fiber streams. These findings will also be used to inform the acceptability of pizza boxes in the recycle stream and educate consumers about acceptable levels of grease or cheese residue found on these recycled boxes.
Journal articles
Magazine articles
Evaluation of rice straw for purification of lovastatin, TAPPI Journal November 2021
ABSTRACT: Cholesterol synthesis in the human body can be catalyzed by the coenzyme HMG-CoA reductase, and lovastatin, a key enzyme inhibitor, can reduce hypercholesterolemia. Lovastatin can be obtained as a secondary metabolite of Aspergillus terreus ATCC 20542. In this study, rice straw of lignocellulose was used in aeration and agitation bath fermentation in a 1-L flask, and a maximal crude extraction rate of 473 mg/L lovastatin was obtained. The crude extract was treated with silica gel (230•400 mesh) column chromatography. Ethyl acetate/ethanol (95%) was used as the mobile phase, and isolation was performed through elution with various ethyl acetate/ethanol ratios. The highest production rate of 153 mg/L was achieved with ethyl acetate/ethanol in a ratio of 8:2. The lovastatin gained from the crude extract was added to 12 fractions treated with 0.001 N alkali, and acetone was then added. After 24 h of recrystallization at 4°C, the extract underwent high-performance liquid chromatography. The purity had increased from 25% to 84.6%, and the recovery rate was 65.2%.
Journal articles
Magazine articles
Probing the molecular weights of sweetgum and pine kraft lignin fractions, TAPPI Journal June 2021
ABSTRACT: The present investigation undertook a systematic investigation of the molecular weight (MW) of kraft lignins throughout the pulping process to establish a correlation between MW and lignin recovery at different extents of the kraft pulping process. The evaluation of MW is crucial for lignin characterization and utilization, since it is known to influence the kinetics of lignin reactivity and its resultant physico-chemical properties. Sweetgum and pine lignins precipitated from black liquor at different pHs (9.5 and 2.5) and different extents of kraft pulping (30•150 min) were the subject of this effort. Gel permeation chromatography (GPC) was used to determine the number average molecular weight (Mn), mass average molecular weight (Mw), and polydispersity of the lignin samples. It was shown that the MW of lignins from both feedstocks follow gel degradation theory; that is, at the onset of the kraft pulping process low molecular weight-lignins were obtained, and as pulping progressed, the molecular weight peaked and subsequently decreased. An important finding was that acetobromination was shown to be a more effective derivatization technique for carbohydrates containing lignins than acetylation, the technique typically used for derivatization of lignin.