ABSTRACT http://dx.doi.org/10.7584/ktappi.2016.48.2.056Journal of Korea TAPPIVol. 48. No. 2, 2016, 56-60pISSN (Print): 0253-3200Printed in Korea • 서울대학교 농업생명과학대학 산림과학부(Department of Forest Sciences, CALS, Seoul National University, Seoul 08826 , Korea) † 교신저자(Corresponding Author): 서울대학교 농업생명과학대학 산림과학부(Department of Forest Sciences, CALS, Seoul National University, Seoul 08826 , Korea) Neutral or alkaline papermaking provides many advantages in paper strength and pro-cessing conditions. It also provides the opportunity of using calcium carbonate fillers in papermaking. These diverse advantages have made almost all paper machines of printing and writing papers run under neutral and alkaline conditions. On the other hand, lin-erboard machines, which use recycled papers as a raw material, are running under acid conditions using a rosin sizing system. Because the recycled raw materials used by the li-nerboard industry contain significant amounts of alkaline papers, the linerboard industry has an interest in the possibility of using the neutral or alkaline papermaking opportu-nity. In this study, the compatibility of the recycled linerboards under neutral or alkaline papermaking conditions was examined by recycling them under various pH conditions. The sizing degree of the papers recycled under neutral or alkaline was significantly lower than that of acid formed papers indicating that during the neutral or alkaline recycling process the rosin sized papers lost their sizing efficiency. Recycling of acid formed liner-boards under neutral or alkaline conditions increased the amount of foam, and the foam contained substantial amount of solid materials derived from the acid sizing systems. Use of cationic polyelectrolytes including PEI and poly-DADMAC improved the sizing degree of the recycled papers under neutral and alkaline conditions. PEI decreased the foam gen-eration as well while poly-DADMAC did not show any reducing effect of the foam. These results suggest that PEI forms coordinate bonds with rosin acid and precipitate them onto