Significance of recycling waste paper dicharged out of offices, especially so-called waste Office Automation (OA) papers such as Xerographic copied or computer printed paper, is getting more importance from the view points of saving forest resources and fossil fuel as well as managing municipal garbage.
However, considerable portion of these papers are cut into thin stripes by shredders at offices to keep confidenciality. And it is widely refered that the paper-making properties of such shredded waste paper are deteriorated mainly because of pulp fiber cutting.
The authors have investigated the effect of shredding on fiber length and mechanical strengths of recycled handsheets from Xerographic copied papers and obtained the following results.
(1) The weight average fiber length was decreased by shredding as much as several percentage in case of 3-6 mm shredding width, and 18% in case of 1 mm width.
(2) Tensile strength of handsheets from shredded papers in 3-6 mm width showed litte difference compared with unshredded. However, a significant drop was found in case of shredding of 1 mm width. Similar tendecies were conceived in tear resistance and folding endurance.
(3) The decrease in fiber length of shredded paper was smaller than that calculated from a simulated cutting of a random sheet of model fibers. It was implied that shredding of paper was partly carried out by pulling fiber out, not breaking it. This was confirmed from observation on the edge of cut paper by electron micrographs.