Fiber property modification by mechanical pretreatment

Mechanical pretreatment consisting of compressive impact and shear action (Hobart mixer) on chemical pulp fibers and old corrugated containers (OCC) before refining increased the water retention value (WRV) significantly while keeping fiber length from shortening. Laboratory beating on mechanically pretreated fibers showed significantly higher WRVs for the pretreated ones at equivalent freeness levels compared to the unpretreated ones. Handsheet study also showed that the strength properties (breaking length, tear index, and burst index) of the pretreated fiber furnishes were increased significantly at equivalent freeness levels. The effect of mechanical pretreatment on different fiber furnishes were, however, quite different from one another. The fiber length, the fiber chemical compositions, and the pretreatment temperature could greatly affect the results of the pretreatment. We applied this pretreatment process to recycled fibers such as OCC and obtained large improvements in strength properties without use of synthetic polymers and without causing drainage problems. Our next goal is to design a pilot scale pretreatment device to also evaluate fiber length differences and running temperature adjustments.