Supramolecular structure and sizing performance of rosin-based emulsion size microparticles

Compared with conventional acidic rosin emulsion size, neutral rosin size has good sizing efficiency under neutral–alkaline conditions of paper manufacture because its emulsion particles are stable to the action of hydroxide ions. Therefore, the sizing efficiency of emulsion-type rosin sizes, i.e. their ability to increase resistance to fluid penetration, was considered to be related with their particulate structure. The supramolecular structure of the neutral glycerin rosin ester–rosin size microparticles and acidic rosin size microparticles were investigated by using differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR) absorption spectroscopy, and electron spectroscopy for chemical analysis (ESCA) techniques in this study. The results indicated that the neutral glycerin rosin ester–rosin size is quite distinct from the acidic rosin sizes in their particulate supramolecular structure. A glycerol dirosinate bilayer existed in the particle structure is hypothesized for the neutral glycerin rosin ester–rosin size microparticles. The results also suggest that the glycerol dirosinate bilayer distributes on the outermost layer of the neutral rosin size microparticles, covering the rosin acid molecules, so as to prevent the dissociation of rosin by hydroxide ions under neutral–alkaline conditions. Consequently, the difference in the supramolecular structure of the rosin sizes particles resulted in their different stabilities and retention characteristics.