Summaries of September 2004 peer-reviewed papers.

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SIZING

STATISTICAL MODELING AND SIZING DETERMINATION GUIDES FOR DISPERSED ROSIN SIZES

APPLICATION: Guidelines for the values of pH, temperature, dosages, and water hardness can be used to help control sizing in paper mills.

The performance of four cationic dispersed rosin sizes was studied by varying pH, temperature, dosage, and water hardness. Three of the sizes were based on fortified rosin with different concentrations of fumaric acid, and the fourth size was based on esterified rosin.

The relationships between sizing and pH, temperature, water hardness, and fortification have already been examined, and linear regression models have been proposed to represent the relationships. However, the models are fairly complicated, which makes interpretation difficult.

In this paper, the researchers refine and simplify the models using statistical tools. They also provide proper prediction domains for sizing. The simplified models provide some insight into the difference between esterified sizes and fortified sizes for the relationships between paper sizing and the factors of pH, temperature, water hardness, and fortification. Furthermore, guidelines are proposed for the choices of different factor levels for making paper with the appropriate amount of size. View this paper online at http://www.tappi.org/index.asp?pid=30464

Hongmei Zhang is with the Dept. of Mathematics and Statistics, University of West Florida, 11000 University Parkway, Pensacola, FL 32514; Alan F. Nitzman is with Plasmine Technology, Inc., 3298-35 Summit Blvd., Pensacola, FL 32503; Timothy Royappa is with the Dept. of Chemistry, University of West Florida, 11000 University Parkway, Pensacola, FL 325145. Email Zhang at [e-mail].

ENVIRONMENTAL CONTROL

THE APPLICATION OF PHOTOCATALYSIS ON TI[O.sub.2] FOR DEGRADING COD IN PAPER MILL WASTEWATERS

APPLICATION: Photocatalysis on Ti[O.sub.2] is a feasible treatment method to degrade COD and toxicity in wastewaters when the initial COD is less than 500 mg/L.

Can photocatalysis be used as a wastewater treatment process? The researchers considered this question by using titanium dioxide as a photocatalyst to degrade organic compounds in pulp and paper mill wastewaters.

Wastewaters were taken after primary clarification from a kraft mill, a semi-chemical pulp mill, a TMP mill, a paper mill, and a kraft mill that processes and uses TMP as well as recycled fiber. The chemical oxygen demand (COD) and Microtox analyses of the wastewaters were used to assess the effectiveness of photocatalysis.

Photocatalysis was shown to be feasible as a wastewater treatment under some conditions. The treatment degraded COD by 90% or more when the initial COD concentration was 500 mg/L or less. When the initial concentration was greater than 1000 mg/L, however, photocatalysis degraded COD by less than 50%.

The processes from which the wastewaters were generated also had an impact on the effectiveness of photocatalysis. The treatment degraded COD and toxicity less effectively in wastewater samples from kraft and semi-chemical pulp mills than in the samples from the other mills. View this paper online at http://www.tappi.org/index.asp?pid=30465

At the time of this research, Leah Kanzic Boyd was a senior-ranked undergraduate of Miami University's Paper Science and Engineering Dept. in Oxford, Ohio. She is currently employed at the Cintas Corp. in Cincinnati, Ohio. Catherine Bothe Almquist is with the Dept. of Paper Science and Engineering, Miami University, Oxford, Ohio 45056. Email Almquist at [e-mail]).

SIZING

THE MECHANISM OF PREMIXING ROSIN SIZES FOR NEUTRAL-ALKALINE PAPERMAKING

APPLICATION: This study may help in developing new technologies for rosin sizes to be used in neutral-alkaline papermaking.

This study explores the mechanism of alum-rosin size premixing for neutral-alkaline papermaking systems and technologies for rosin and new anionic resin to be used in neutral-alkaline.

By analyzing the mixture solution charge and particle size distribution, we evaluated the effect of the mixture concentration, temperature, and ratio of alum to rosin on the rosin-alum size efficiency. View this paper online at http://www.tappi.org/index.asp?pid=30466

Yong Zou, Jeffery S. Hsieh, and Tim S. Wang are with Pulp and Paper Engineering, School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia; in addition, Wang, Eric Mehnert, and John Kokoszka are with EvCo Research, LLC, Atlanta, Georgia. Email Hsieh at [e-mail].

COATING MEASUREMENT

RAMAN MICROSCOPY IN LATERAL MAPPING OF CHEMICAL AND PHYSICAL COMPOSITION OF PAPER COATING

APPLICATION: Lateral Raman mapping can be used to analyze bulk and surface latex distribution. Moreover, bulk mapping gives information about coating thickness and ink density variations.

This paper shows how confocal Raman microscopy reveals the distribution of paper coating chemicals in the x-y plane. The use of two microscope objectives enabled bulk and surface analysis of styrene butadiene (SB) latex, and calcium carbonate in coated papers. In the bulk coating analysis, spatial mapping of chemical distribution covered a 0.15 m[m.sup.2] area with a 10 [micro]m lateral resolution. We analyzed an area of 1 m[m.sup.2] in shorter measurement time by using a coarser lateral resolution. The bulk compositional maps revealed the distribution of chemicals and provided information on the coating thickness. We were able to obtain these measurements through magenta ink. In the surface analysis, the analyzed layer was only about 2 [micro]m thick. The surface measurements were taken from a larger area, but with fewer measurement points. That shortened the analysis time, while giving even more valid quantitative results on the variation of SB-latex content. Latex content variation in different length scales can be easily studied by averaging measurements.

Raman microscopy provides an easy way to determine relative variations in SB-latex content without calibration. Raman measurements can taken at different probing depths, giving information about bulk coating (including its thickness) or coating surface. The capability to take measurements through certain printing inks may yield new information about printing defects, especially if it is possible to relate printing defects to distribution of coating chemicals or physical structure of paper coating. The capability to characterize coating surfaces also is important because the interaction between a coating and an ink takes place within the first top micrometers of the paper surface. View this paper online at http://www.tappi.org/index.asp?pid=30467

Jouko Vyorykka and Tapani Vuorinen are with the Laboratory of Forest Products Chemistry, Helsinki University of Technology, Finland; Kari Juvonen is with KCL Science and Consulting, Espoo, Finland; and Douglas Bousfield is with the Paper Surface Science Program, Department of Chemical Engineering, University of Maine, Orono, Maine, USA. Email Vyorykka at [e-mail].

NONWOOD FIBERS

RECYCLING POTENTIAL OF BAGASSE AND WHEAT STRAW PULPS

APPLICATION: This study can help mills in evaluating appropriate fibers for recycling. It found that wheat straw pulps can be recycled with much less loss in tensile strength than bagasse or wood pulps.

This study evaluates the recycling potential of pulps made from nonwoods. We prepared five single species soda pulps of varying yields from bagasse and wheat straw in a laboratory. We also included a commercial bagasse chemimechanical pulp in the study. These pulps were subjected to cycles of sheet-making, drying, and reslushing. The results of the study show that wheat straw pulps lose relatively little tensile strength and related properties as they are recycled. Bagasse pulps, however, have a low recycling potential, quite similar to that reported for wood pulps. The alpha, beta, and gamma cellulose contents of chemical pulps of wheat straw and bagasse did not change with the process of recycling. The high gamma celluloses in wheat straw chemical pulps seem to be responsible for their high recycling potential. During recycling, bagasse pulps lost significant amounts of fines (P200), whereas fines were nearly completely retained in the wheat straw pulps. This may be because the wheat straw pulps fines have a high bonding potential. View this paper online at http://www.tappi.org/index.asp?pid=30468

Mayank Garg and Surendra Pal Singh are with the Department of Paper Technology, Saharanpur Campus, Indian Institute of Technology Roorkee, India. Email Garg at [e-mail] or Singh at [e-mail].

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