Preparation and characterization of styrene acrylate emulsion surface sizing agent modified with rosin

A series of core‐shell type cationic soap‐free latex were prepared by using styrene(St), butyl acrylate(BA), and methyl methacrylate(MMA) as main materials and introducing rosin as the functional monomer. Cationic starch (CS‐8), which has low relative viscosity, was used as the emulsifier and dispersant. The influencing factors of the reaction were studied and the optimal conditions were achieved. Then the products were characterized by scanning electron microscope (SEM), FT‐IR, laser particle sizer, and particle charge detector (PCD). The results showed that the excellent performance and good sizing effects of SAE were achieved when the reaction conditions were as follows: the starch amount was 8 wt %, the charge of the initiator (APS) was 0.5%, and the amount of rosin was 2 wt %. Under these conditions, the particle size of the latex was around 100 nm and had a narrow distribution, and the charge density of latex was 0.61 mmol L^?1. The water‐resistant performance of paper was improved significantly when SAE was modified with rosin, and the Cobb value decreased by 46.8% compared to that of the paper sized by SAE without rosin. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011