Preparation and sizing mechanisms of neutral rosin size II: functions of rosin derivatives on sizing efficiency

Four rosin derivatives, including rosin esters and rosinamides, were synthesized and used to prepare neutral rosin sizes. Their effects during sizing are discussed in detail. Compared to natural rosin, the rosin derivatives had nearly no effect on sizing even at high retention levels in paper. However, the rosin derivatives in the rosin sizes improved the stability of the emulsion size particles, and there was good correlation between the sizing effect and the stability of the emulsion sizes under neutral to alkaline conditions. On the other hand, the structure of the rosin derivatives significantly influenced the stability and sizing effect of the neutral rosin sizes. In particular, for glycerin rosin ester-rosin sizes, the emulsion stability and sizing effect increased with an increasing proportion of dirosinate, among the glycerin rosin esters. Consequently, it was suggested that the rosin derivatives hardly contribute to the sizing performance of paper but predominantly function to stabilize the neutral rosin size particles, thereby improving the efficiency of the size under neutral to alkaline sizing conditions. Also it was supposed that glycerol dirosinate in the neutral rosin size would probably enable formation of a more stable particle structure to prevent the destructive action of the OH^– ion.This research was presented in part at the 48th annual meeting of the Japan Wood Research Society, Shizuoka, April 1998