Fiber property modification by mechanical pretreatment.

Application: Papermakers can use pretreatment to improve the tear and break length properties of recycled chemical pulp.

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With the increasing challenge of securing wood fibers for making paper products, virgin fiber must be used more effectively and greater reliance will be placed on using recycled fiber. Paper products containing more recycled fibers should have equal or better quality than time ones that now contain less. In this study, of the stock preparation process, we minimized the reduction of fiber length and improved the drainage properties of virgin chemical fibers by applying mechanical pretreatment before refining. Other bonding properties became equivalent or better. For recycled fibers such as OCC (old corrugated containers), pretreatment at the same freeness level produced large improvements in strength properties, including tear strength For recycled pulp from virgin chemical pulp handsheets, we noted positive potential for restoring virgin chemical pulp properties using the pretreatment method.

We used a Hobart mixer and temperature control to repetitively squeeze, twist, and bend the fibers, short of cutting them at room temperature for more than 1 hour at about 25% solid content. This pretreatment increased the fibers ability to hold water and caused severe internal delamination of fiber walls, with little effect on fiber length. Comparing to Valley beater refining, the mechanical pretreatment increased water retention value (WRV) without a significant reduction of fiber length and freeness. The ensuing low consistency refining with a Valley beater enhanced time mechanical pretreatment effect greatly by lowering the curl index.

In this study, mechanical pretreatment before refining enabled us to use virgin chemical pulp and recycled fibers more effectively. Our next challenge is to redesign the equipment for a mill- or industrial-scale trial, with an emphasis on temperature and improved energy consumption.

Y. Seo, Choi, and S. Seo are with the Deptartment of Forest Products, College of Agriculture, Chungnam National University, Daejun, Yousung-Gu, Gung-Dong, 220, South Korea; Lee is with the Seoul National University; and Shin is with the Korean Research Institute of Chemical Technology; email Yung Bum See at [e-mail]