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Now showing 1 - 10 of 510
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The Effects of Retention Aid Dosage and Mechanical Energy Dissipation on Fiber Flocculation in a Flow Channel

2004-12-23 , Weseman, Brian D.

Formation plays an important role in the end-use properties of paper products, but before formation can be optimized to achieve superior properties, an understanding about the causes of formation must be developed. Formation is caused by variations in the basis weight of paper that are results of fiber floc formation before and during the forming of the sheet. This project is a first step in a larger research program aimed at studying formation. By observing the effects that mechanical energy dissipation (in the form of turbulence) and retention chemical dosage have on floc formation, we may develop a better understanding of how to control formation. In this study, a rectangular cross-section flow channel was constructed to aid in the acquisition of digital images of a flowing fiber suspension. The furnish consisted of a 55:45 spruce:pine bleached market pulp mix from a Western Canadian mill. Turbulence was varied by changing the flow rate; Reynolds numbers achieved range from 20,000 to 40,000. The retention aid used was a cationic polyacrylamide with a medium charge density. Dosage of the retention aid was varied from 0 to 2 pounds per ton OD fiber. Digital images of the flowing fiber suspension were acquired with a professional digital SLR camera with a forensics-quality lens. Three separate image analysis techniques were used to measure the flocculation state of the fiber suspension: morphological image operations, formation number analysis, and fast Fourier transform analysis. Morphological image analysis was capable of measuring floc size increases seen in the acquired floc images. It was shown how floc diameter could increase simultaneously with decreasing total floc area and total floc number. A regression model relating retention aid dosage and energy dissipation was constructed in an effort to predict flocculation. The regression model was used to predict F2 (formation number squared) results from the study. The interaction effect RE was shown to have a differing effect across the retention aid dosage levels. As a result, this model and technique may prove to be a beneficial tool in optimizing retention aid applications.

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Elucidating the nature of bonding in mechanical pulps

2004-11 , Lehtonen, Lauri Kalevi

Bond strength is classically characterized into two separate factors; area of the bond and specific bond strength. This separation is especially important in pulps that lack strength properties, and are specifically used for their optical properties, such as mechanical pulps. In this research the applicability of the Ingmansson and Thode method for distinguishing between specific bonded area and specific bond strength in mechanical pulps is studied. It is shown that the rigid, non-collapsable, nature of the mechanical pulp can be overcome by press drying the sheets until they approach their 50% relative humidity moisture content. Mechanical pulps have been assumed to operate in a domain where fiber failure can be considered insignificant, and the bonded area to tensile strength relationship is linear. In this study it was shown that most commercial pulps operate in a significant fiber failure domain. However, it is shown that pure fines and fines rich mechanical pulp better follow a linear bonded area to tensile strength relationship rather than a non-linear (significant fiber failure) model, suggesting that only the fiber fraction undergoes fiber failure and the finer fractions predominantly bond failure. The Ingmansson and Thode method relies on the use of scattering coefficient as a measure of specific surface area. It is shown that scattering coefficient is an accurate estimate of mechanical pulp specific surface area at a constant wavelength of light, provided that the wavelength used to measure scattering coefficient is above the significant absorption limit.

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Epi-halohydrin modified polyamines as mordant agents for alkaline rosin sizing.

2004-01-13 , Hartong, Bradley H.

Many grades of paper have shifted from acid to alkaline production conditions. This change excludes the usage of traditional alum-rosin sizing chemistry. In some cases however, rosin sizing could prove beneficial if it could be used under neutral to alkaline paper making conditions. One effort toward this goal has been the use of epi-halohydrin modified polyamine/polyaminoamide in place of alum. The optimum sizing conditions, as well as the mechanism that modified polyamines/polyaminoamides use to size rosin, is investigated. Polyethyleneimine modified with epi-chlorohydrin was used in these studies. Rosin dosage was found to be the main variable that controlled the degree of sizing achieved. As the only hydrophobic material added, this was expected. In addition to rosin dosage, the polymer and pH had significant impacts on this sizing chemistry. Laboratory data shows that the synthesis procedure for and structure of polyethyleneimine-epi-cholohydrin (PEI-epi) impacts the degree of sizing achieved. Use of different modification techniques and degrees of modification illustrated several key factory regarding the polymer as a rosin sizing mordant. Prevention or removal of by-products from epi-chlorohydrin imporves the sizing efficiency of PEI-epi with rosin. A critical molecular weight of the PEI-epi was found to be important to sizing. Higher charge density on PEI-epi provides better the sizing efficiency. In addition to the polymer, other important factors where examined. The pH of the stock impacted the degree of sizing and permanency of the sizing achieved. Varying stock pH showed changes in sizing that are consistent with effects seen for rosin retention and of PAE as a wet strength agent. Low and high pH levels also caused reversion of the sizing effect. A pilot trial of the PEI-epi-rosin sizing chemistry was conducted at the Herty Foundation. The pilot trial shows that PEI-epi-rosin can reach the required level of sizing for linerboard. Trial results showed that calcium carbonate filled sheets could be sized by this chemistry. No significant impact on strength is seen from the sizing chemistry at the required dosage levels. As would be expected, addition of filler diminishes sheet strength. No sizing reversion was seen from any samples of this trial. Size reversion at low stock pH indicated that acid catalytic cleavage of an ester bond could have been occurring. Addition of acid or base to permanently sized sheets showed significant levels of reversion, similar to that seen for low stock pH sheets. This provides further supporting eviden ce for the formation and importance of an ester bond between rosin and PEI-epi. FTIR spectra were collected for model compounds to further examine the presence and importance of ester bonds. An ester bond was found to form at room temperature with aging or immediately with drying. Further, the ester bonds were found to decrease when the sample was subjected to acidic or basic environments. Solid state NMR was run to demonstrate the presence and importance of ester bonds to sizing in handsheets. Use of a [superscript 13]C labeled fatty acid showed that the ester bond peak dominated when sizing was present. After treatment with sodium hydroxide, the sizing disappeared and much of the ester bond signal shifted to a carboxylic acid or salt. Further solid state NMR of a non-reactive cationic polymer or a fully pre-reacted PEI-epi polymer shows retention of the fatty acid, but no ester bond and no sizing. The sizing mechanism of PEI-epi-rosin sizing appears to be connected to an ester bond formed during drying or with aging. While the amount of rosin retained controls the degree of sizing, retention alone is not enough to give sizing. The most effective pH for this sizing chemistry is near neutral, pH 6-8. FTIR and solid state NMR shows that an epichlorohydrin modified polyamine can form ester bonds with fatty acids in handsheets under conditions comparable to papermaking. The presence of residual acid or base in handsheets destroys the sizing effect achieved. Destruction of the sizing by addition of sodium hydroxide parallels the cleavage of many of the ester bonds present. PEI-epi appears to function as a mordant for rosin by creating an ester bond to anchor and help orient the hydrophobic portion of rosin.

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Chemo-enzymatic modification of high-kappa kraft pulps with laccase

2003-07 , Chandra, Richard P.

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A Statistical Treatment of Non-Normal SEM Data and the Application to Designed Fiber/Filler/Polymer Structures

2004-12-13 , Peterson, Fern Sterling

One of the primary objectives of this thesis was to design fiber/filler/polymer structures for newsprint and in the process develop a greater understanding of fiber/filler/ polymer structures. Five different designed structures were created for study. The designed structures were composed of virgin, hydrosulfite bleached, TMP southern pine, Georgian kaolin clay and various polymers. Five filler levels from 0% to 20% were employed with each of these different structures. Numerous physical tests were used to gather data which would help to develop an understanding for the macroscopic properties of the structures. Paper structures were created and data from bulk physical tests and particle based SEM image analyses were compared. Comparisons were made using a statistical method called Principal Component Analysis (PCA) where the data is grouped and reduced to find data correlations not readily apparent in the raw data.

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Elucidating the formation and chemistry of chromophores during kraft pulping

2004-08 , Dyer, Thomas J.

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Part 1: Employing conventional defoamer emulsions to enhance the flotation removal of flexographic news inks. Part 2: Single fiber modification via the addition of exogenous expansin

2003-12 , DeLozier, Greg

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Enzymatic Biobleaching of Recalcitrant Paper Dyes

2004-12-07 , Knutson, Kristina Parks

Modern manufacturing processes assume efficient utilization and recycling of natural resources whenever possible. Over the past decade paper recycling has progressed from 33.5% in 1990 to just above 48% in 2002.1 Indeed, for certain select grades, (newspaper and old corrugated containers) greater than 70% is currently being recycled. In contrast, mixed office waste and colored directory papers are often underutilized. A major difficulty in recycling these grades of paper is the problems associated with decolorizing the dyes present in the paper.2 Of the commonly used paper dyes, the stilbene dye Direct Yellow 113 and methine dye Basazol 46L are notorious4 for poor bleachability with the commonly used chemical bleaching agents including chlorine dioxide, oxygen, hydrogen peroxide and sodium dithionite. The ability of white-rot fungi to decolorize colored effluents containing textile dyes is currently the subject of intensive research efforts. The secreted enzymes involved in dye decolorization include manganese peroxidase, lignin peroxidase and laccase. Laccase, a lignolytic enzyme, has also been studied for many years for the biobleaching of wood pulps. The ability of laccase to delignify pulp is greatly enhanced by the addition of small molecule mediators such as 2-2´ azinobis (3-ethylbenzthiazoline-6-sulfonate) (ABTS) and 1-hydroxybenzotriazole (HBT). This research project focused on applying laccase combined with a mediator to decolorize C.I. Direct Yellow 11 and Basazol 46L. Three mediators were tested: ABTS, HBT and violuric acid. Laccase/ABTS was most effective with 60% of the color being removed. The level of color removal was maintained at 60% even when ABTS concentration was lowered from 5 mM to 0.01 mM. When laccase/1 mM ABTS was applied to Direct Yellow 11 in solution, the majority of color loss occurred within 60 minutes. The ability of soybean (SBP) and horseradish (HRP) peroxidases and laccase to decolorize Direct Yellow 11 and Basazol 46L in solution was also examined. The results demonstrated that these two recalcitrant dyes could be effectively decolorized by enzymatic treatments by horseradish peroxidase, soybean peroxidase, and laccase with ABTS as mediator. SBP is effective from pH 4.5 to 8.5. The stilbene dye Direct Yellow 11 responded to both SBP and laccase/ABTS. For the methine dye Basazol 46L, SBP was a more effective treatment than HRP or laccase/ABTS. Basazol 46L responded quickly to SBP treatment with 74% reduction in signal intensity within 5 minutes. To evaluate the effectiveness of laccase/ABTS treatment, pulp dyed with Direct Yellow 11 and three commercial colored pulps were subjected to seven different bleaching treatments. These treatments consisted of 1)laccase/ABTS; 2)laccase/ABTS followed by alkaline extraction; 3)laccase/ABTS followed by bleaching with sodium dithionite; 4)oxygen bleaching; 5)oxygen bleaching followed by dithionite treatment; 6)alkaline hydrogen peroxide bleaching; and 7)alkaline peroxide bleaching followed by dithionite treatment. The best results were obtained by including reductive bleaching with sodium dithionite. For Direct Yellow 11 dyed pulp, laccase/ABTS followed by dithionite yield comparable reduction in color to oxygen or peroxide followed by dithionite.

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Dielectric barrier discharge-initiated fiber modification

2004-06-14 , Vander Wielen, Lorraine C.

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Hydrogen peroxide delignification in a biomimetic system based on manganese peroxidase

2003-12 , Djerdjouri, Nour-Eddine

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