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UV/Vis Spectrometry-Based Analysis of Alkyl Ketene Dimer (AKD) Retention to Solve the Waxy Spot Problem in the Papermaking Process Kyong Ho Lee, Hye Jung Youn, and Hak Lae Lee *
Cite This: ACS Omega 2020, 5, 11227 − 11234
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ABSTRACT: A sudden surge in the number of translucent and oval-shaped waxy spots caused a serious production loss of the papermaking process. The investigation of the spots revealed that the alkyl ketene dimer (AKD) sizing agent caused the waxy spot problem. A ultraviolet/visible (UV/vis) spectrometry method for the quantitative analysis of AKD was developed and used to reduce the waxy spot problem in paper products. The results showed that the method could be used to quantify AKD in both papermaking stock and white water. The major factors in the papermaking wet end that were associated with the waxy spot problem were evaluated, and practical approaches to solving the AKD retention problem and the waxy spot problem were proposed and implemented. The dosage of a retention aid was found to be the principal factor controlling AKD retention. However, varying the retention aid dosage resulted in the deterioration of
the paper formation; therefore, this was not a suitable solution to the waxy spot problem. The type of fi xing agent and AKD used was found to be the secondary factor a ff ecting the AKD retention and papermaking system cleanliness. Mill trials were conducted on a paper machine to examine the e ff ects of di ff erent fi xing agents and AKD types on AKD retention and the waxy spot count at the reel. This approach identi fi ed a combination of fi xing agent and AKD type that substantially improved AKD retention and reduced the formation of translucent waxy spots in the resulting paper products.
1. INTRODUCTION The hydrophilicity of the cellulose fi ber that forms the basic structure of paper means that paper tends to be highly water absorbing. This limits the use of paper in many types of packaging, printing, and writing. To control the water absorption property of paper, various internal sizing agents have been developed. Alkyl ketene dimer (AKD), which was developed by Downey 1 and introduced by Davis et al., 2 is one of the most widely used internal sizing agents for printing and writing grades of paper. AKD can be anchored to paper without the use of papermaking alum (aluminum sulfate) because it reacts with the hydroxyl group of cellulose to form ester bonds. 3,4 However, the slow rate of this esteri fi cation reaction 5 − 7 often causes problems that do not occur when conventional rosin- based sizing agents are used. Problems such as slippery paper 8,9 and size reversion 10,11 are attributable to AKD sizing. In addition to the slow reactivity of AKD with hydroxyl groups, AKD has been shown to react with water, 12 resulting in a dialkylketone that has no or low internal sizing ability. 6,13 In addition to having the above-described negative e ff ects on paper properties, AKD also causes problems in the paper production stage. For instance, hydrolyzed AKD has been
reported to be the main cause of deposit formation in the papermaking process. 14,15 Similarly, we have also observed a periodic pipe plugging problem at the fi nal reject line of the screen system of a paper machine producing printing and writing grades of paper. A chemical analysis of the plugged material retrieved from the screen discharge line con fi rmed that AKD was the main cause of the plugging problem. Moreover, we also observed white granular deposits on the fabric of polydisk fi lters, which substantially decreased the fi ltration e ffi ciency, and the chemical analysis showed that the white deposits were hydrolyzed AKD. These experiences showed us that it was crucial to manage AKD retention in our papermaking machine to ensure a clean production process. Speci fi cally, when the retention level of AKD is low, it circulates through the short or long circulation lines, where it is exposed to high temperatures for a prolonged
Received: March 26, 2020 Accepted: April 22, 2020 Published: May 6, 2020
https://dx.doi.org/10.1021/acsomega.0c01374 ACS Omega 2020, 5, 11227 − 11234
© 2020 American Chemical Society
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