Circular action treatment (CAT): a new strategy for mechanical treatment of old corrugated container I – effects of control parameters on paper strength

Abstract Circular action treatment (CAT) was developed for improving the strength of paper made from old corrugated containers (OCCs). The effects of the revolution speed of the circular blade, number of passes, and consistency of the stock were studied for application to paper recycling. The slowness, water retention value (WRV), and strength of the paper increased with increasing revolution speed of the circular blades and the passing time without changing the fiber characteristics (length, width, and kink angle) due to the improvement in flexibility and hydration degree of hornified fibers. However, the effect of CAT declined when the stock was passed more than 20 times. The thickening of the stock up to 25 % consistency enhanced WRV and strength of the resulting paper. Below 20 % consistency, the stock adhered to the wall of the CAT apparatus, whereas at higher consistency, the stock could not be treated effectively due to uneven impact. Consequently, when the OCC stock was thickened to 25 % and allowed to free fall from 20 times at the maximum revolution speed (875 rpm) of the circular blades, the strength of OCC paper could be effectively enhanced by CAT.