Paper 360
The papers summarized here are from the TAPPI Journal August issue. TAPPI Journal is an online publication of relevant and timely peer-reviewed research delivered via email and free to all TAPPI members. To receive TAPPI Journal, join TAPPI at www.tappi.org.
RECYCLING
Effect of pulper consistency on stickies size distribution
Mahendra Doshi, Salman Aziz, Robert de Jong, and Carl Houtman
Pulper consistency affects production capacity, defibering efficiency, and particle size distribution of contaminants and, in particular, stickies and inks. The effect of pulper consistency on stickies size distribution, though important, has not been studied in detail.
Handsheets after pulping at high, medium, and low consistencies.
In this project, pressure-sensitive adhesive (PSA)-containing furnish was pulped in a laboratory at 5 percent, 10 percent, and 15 percent consistency. Results show that 15 percent consistency pulp produced many more small-sized stickies compared to pulps produced at 5 percent and 10 percent consistency. This is contrary to the generally accepted hypothesis and needs further investigation.
Calcium carbonate, usually present in varying proportions in many recovered paper grades, is known to have some pacifying effect on stickies. A new pacifying agent prepared from silicone release liner, called desiliconized pulp (DSP), behaves like bleached virgin hardwood kraft pulp. DSP seems to have a pacifying effect similar to that of calcium carbonate. Thus, DSP may potentially replace a small amount of bleached virgin hardwood kraft pulp, with a bonus stickies-pacifying effect.
Stickies size distribution is important for paper recycling mills. The goal is to keep stickies particles large enough for easy removal by screens, cleaners, and flotation. Small-sized stickies or microstickies may be pacified by the new DSP additive.
PAPERMAKING
Impact of fiber structure on edge-wicking of highly-sized paperboard
Lebo Xu, Jeremy Meyers, and Peter W. Hart
Coffee edge-wicking testing was conducted on two groups of highly-sized paperboard manufactured at two mills with similar manufacturing processes, but with vastly different local fiber sources. Although the Hercules size test (HST) indicated similar internal size levels between the two types of board, the edge-wicking behavior was noticeably different.
Cross-section SEM images, where white areas are fibers and black areas are voids between fibers, show the raw edge of sample S would have a larger exposed hydrophilic fiber wall and lumen with no sizing protection when cut, contributing to more edge-wicking.
Analysis of fiber structure revealed that the board with more edge-wicking had fibers with thicker fiber walls, which kept the fiber lumen more open after pressing and drying on a paper machine. Tests demonstrated that liquid penetration through voids between fibers in highly-sized paperboard was limited, because the fiber surface was well protected by the presence of sufficient sizing agent. Nevertheless, freshly exposed fiber walls and lumens at the cut edge of the sheet were not protected by sizing material, which facilitated edge-wicking.
This study shows the contribution of fiber structure to the edge-wicking process for highly-sized paperboard after all the surfaces are protected with size. The correlation between fiber structure and edge-wicking behavior was highlighted to inspire development of novel sizing strategies that protect the freshly cut edge of the sheet from edge-wicking.
FIBER PROPERTIES
Enzymatic treated viscose fibers functionalized by chitosan
Urška Vrabič Brodnjak, Diana Gregor-Svetec, and Maja Klančnik
This research focused on the sorption properties of enzymatically treated viscose/chitosan and viscose fibers treated with enzymes and chitosan. To improve sorption properties of viscose fibers and to obtain the characteristics similar to viscose/chitosan fibers, the researchers performed two different treatments. First, they treated both fibers with enzyme cellulase for 60 minutes and afterwards treated viscose fibers with the chitosan in an ultrasonic bath. In their research, they investigated structural characteristics and the accessibility of free adsorption places.
SEM images show that the surface area of enzymatic treated fibers was less even than that of untreated fibers, and that chitosan bound on viscose fiber surfaces is clearly seen.
The researchers noted a noticeable change in the structure (degree of polymerization, crystallinity, and molecular orientation) of treated viscose and viscose/chitosan fibers. Changes that occurred in the morphology and in the structural properties of both types of tested fibers were also reflected in their physical and chemical properties. The research showed that sorption properties of enzymatic treated fibers were improved.
This study provides structure and sorption properties of viscose/chitosan fibers and viscose fibers treated with chitosan and analyzes the improvement of sorption properties of fibers, based on enzymatic treatment. Such treated fibers could be used in paper, packaging, hygiene towels, pads, and other applications.
OTHER RESEARCH IN TAPPI JOURNAL’S AUGUST 2018 ISSUE:
PAPER PHYSICS
Prediction of box failure from paper data for asymmetric corrugated board
Heinz Joachim Schaffrath, Felix Reichenbach, and Samuel Schabel