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Mechanistic aspects of nanocellulose–cationic starch–colloidal silica systems for papermaking, TAPPI Journal February 2023
ABSTRACT: Optimization of a chemical additive program for a paper machine can require attention to both colloidal charges and kinetic effects. This work considered an additive program with two negatively charged substances (nanofibrillated cellulose [NFC] and colloidal silica) and two positively charged items (cationic starch and cationic acrylamide copolymer retention aid). Results were shown to depend on charge interactions; however, that clearly was not the whole story. Some findings related to cationic demand, dewatering, fine-particle retention, and flocculation among fibers were best explained in terms of at least partly irreversible complexation interactions between the charged entities. Adjustments in ratios between oppositely charged additives, their sequences of addition, and effects of hydrodynamic shear levels all affected the results. In general, the most promising results were obtained at a cationic starch level of 0.25% to 0.5% based on sheet solids in systems where the cationic starch was used as a pretreatment for NFC.
An analytical method to quantitatively determine the amount of polyamide epichlorohydrin (PAE) in paperboard and white water, TAPPI Journal February 2023
ABSTRACT: Polyamide epichlorohydrin (PAE) is a permanent wet strength resin. When applied to paperboard, some amount of resin is retained in the sheet, and some is lost to the white water. An analytical method for quantify-ing the amount of PAE retained in the sheet and lost into the white water has been developed. This method hydrolyz-es the PAE to adipic acid, which in turn is derivatized to diethyl adipate and quantified by pyrolysis gas chromatogra-phy–mass spectrometry (pyGCMS). In addition, the hydrolysis conditions of the PAE were studied by the Taguchi approach, and PAE material balances around the dry sheet and white water for 3 and 6 lb/ton PAE applications have been performed. The PAE resin recovery was 95.4% with 65.0% in the sheet for the 3 lb/ton PAE-charged paper-board, and the recovery was 96.7% with 36.1% in the sheet for the 6 lb/ton PAE-charged paperboard.
A new method of studying the fundamental mechanisms involved in pigment liberation from recycle papers, TAPPI Journal October 2022
ABSTRACT: Deinking flotation is the most efficient and widely used method of removing ink particles from printed papers to improve the recyclability. A prerequisite for successful deinking flotation is detachment of pigments from paper fibers, a subprocess known as liberation. The degree of liberation is usually determined via hyperwashing tests, which are costly and time consuming. Furthermore, they provide no information on the fundamental mechanisms controlling liberation. In the present work, we developed a new method in which ?-potentials of the particles in a pulp are measured and analyzed. If pigments are not liberated from paper fibers, a frequency distribution plot gives a single peak, while two peaks appear when they are liberated. One can readily determine the degrees of liberation from the peak positions and peak heights. In addition, the ?-potential data can be used to construct disjoining pressure isotherms using the DLVO theory that are useful to better understand the fundamental mechanisms involved and the roles of different reagents used to improve pigment liberation.
Nanocellulose–cationic starch– colloidal silica systems for papermaking: Effects on process and paper properties, TAPPI Journal October 2022
ABSTRACT: Laboratory tests were conducted to better understand effects on the papermaking process and handsheets when recycled copy paper furnish was treated with combinations of nanofibrillated cellulose (NFC), cationic starch, colloidal silica, and cationic retention aid (cPAM; cationic polyacrylamide). Dosage-response experiments helped to define conditions leading to favorable processing outcomes, including dewatering rates and the efficiency of fine-particle retention during papermaking. Effects were found to depend on the addition amounts of cationic starch and colloidal silica added to the system. It was shown that the presence of a polymer additive such as cationic starch was essential in order to achieve large strength gains with simultaneous usage of NFC.
Water chemistry challenges in pulping and papermaking – fundamentals and practical insights: Part 1: Water chemistry fundamentals and pH, TAPPI Journal June 2022
ABSTRACT: Water is an essential component of the papermaking process. Nevertheless, papermakers often overlook its importance compared to fibers and chemical additives. A better understanding of water properties and chemical interactions associated with water at the wet end leads to a sound foundation for high-quality paper production and smooth operation. Not all fresh water and process water is the same. Fresh water varies from mill to mill, primarily due to the location and availability of water sources. Some industrial trends, such as enhancing water conservation and production yield, gradually shift process water quality over time. The current work serves as a primer on water and water chemistry fundamentals to help the papermaker prepare for the future challenges of increased contamination of process water associated with reduced fresh water usage. This paper focuses on basic water chemistry definitions and discusses the impact of pH on wet-end operation. It is clear that pH is a fundamental factor that directly affects the process and impacts other factors relevant to the papermaking process. It is crucial to understand what pH represents, how it is measured, how to select the proper pH and carefully control it, and how to closely maintain the process at target setpoints. Understanding the sensitivity of operation to pH change will lead to an appropriate focus on these issues. In addition to basic theory, we also review onsite experience and practical mill cases. It is imperative to stress that, although critical, pH is not the only chemical parameter impacting papermaking operations. Other factors, such as ionic concentration measured by conductivity, surface, soluble charge, and hardness, are critical and will be discussed in Part II of this series. As pH is a primary and independent factor that impacts various forms of charge and conductivity, the authors decided to start the current series of papers by discussing pH.
Editorial: Reflections on the Page equation, laboratory work, and new concepts, TAPPI Journal May 2022
ABSTRACT: I began teaching paper physics to undergraduates in the late 1980s when the recognized giants in the field were still actively debating their subjects in the literature and scientific conferences.
Development of paper quality parameter measurement in China, TAPPI Journal May 2022
ABSTRACT: Paper quality parameters are important indicators of paper production, such as paper moisture, basis weight, ash content, strength, and so on. This study focuses on the online measurement methods and development of paper basis weight, moisture, and ash measuring. First, the measurable paper parameters and quality control system products in China are analyzed. Then, the basis weight measurement methods, accuracy, and development are given in the range of 10~1000 g/m2. Third, the distinction between infrared and microwave methods for moisture measurement is discussed. Finally, the ash measurement is introduced. Production and consumption of tissue paper in China have continually increased during the past decade. Near-infrared light technology is mature for the measurement of paper parameters in the range of 10~200 g/m2 basis weight. However, the near-infrared online measurement of tissue paper is not widely used, and few tissue paper lines are equipped with this type of quality control system in China. Therefore, technology for near-infrared measurement of basis weight has a great potential market in the field of tissue paper production. This article analyzes the future development trend of near-infrared light in tissue paper basis weight measurement and summarizes the difficulties in near-infrared light measurement of tissue paper basis weight.
Improving refining efficiency with deflocculation, TAPPI Journal May 2022
ABSTRACT: The ability to load a refiner requires the formation of a fiber mat between opposing refiner bars. One of the consequences of this is the formation of flocs that persist through the refiner grooves and exit the refiner. These flocs interfere with sheet strength, requiring additional energy to make up the strength deficit. In addition, flocs can initiate string formation, resulting in machine efficiency issues such as cross-machine profile deterioration and the downtime required to correct it. Novel refiner plate modifications have been shown to improve refining efficiency in otherwise identical refiner plates. Energy savings are typically around 15% of gross refining energy on the basis of the treated stock, although much higher reductions have also been seen. Addressing this previously underappreciated flaw in conventional refining enables greenhouse gas reduction and other benefits related to sheet strength and machine efficiency.
The Effect of Component Removal Upon the Porous Structure of the Cell Wall of Wood. II. Swelling in Water and the Fiber Saturation Point, TAPPI Journal May 2022
ABSTRACT: The word "swelling" applied to an assemblage of fibers such as wood or wood pul p is very vague.
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Numerical investigation of the effect of ultrasound on paper drying, TAPPI Journal March 2022
ABSTRACT: The paper drying process is very energy inefficient. More than two-thirds of the total energy used in a paper machine is for drying paper. Novel drying technologies, such as ultrasound (US) drying, can be assessed numerically for developing next-generation drying technologies for the paper industry. This work numerically illustrates the impact on drying process energy efficiency of US transducers installed on a two-tiered dryer section of a paper machine. Piezoelectric transducers generate ultrasound waves, and liquid water mist can be ejected from the porous media. The drying rate of handsheet paper in the presence of direct-contact US is measured experimentally, and the resultant correlation is included in the theoretical model. The drying section of a paper machine is simulated by a theoretical drying model. In the model, three scenarios are considered. In the first scenario, the US modules are positioned in the dryer pockets, while in the second scenario, they are placed upstream of the drying section right after the press section. The third case is the combination of the first and second scenarios. The average moisture content and temperature during drying, enhancement of total mass flux leaving the paper by the US mechanism, total energy consumption, and thermal effect of heated US transducers are analyzed for all cases. Results show that the application of the US can decrease the total number of dryer drums for drying paper. This numerical study is based on the US correlation obtained with the US transducer direct-contact with the paper sample. Thus, future work should include US correlation based on a non-contact US transducer.