NEUTRAL TO ALKALINE ROSIN SOAP SIZING WITH METAL-IONS AND POLYETHYLENIMINE AS MORDANTS

With the understanding of coordination chemistry, metal ions Mg2+, Mn2 +, Fe3+, Cu2+ and Zn2+ are used with polyethylenimine (PEI) as mordant s of rosin soap size. While Mg2+/PEI and Mn2+/PEI show no effect and F e3+/PEI is very effective in acidic pH range, Zn2+/PEI can induce mode rate sizing and Fe2+/PEI and Cu2+/PEI can induce very high levels of s izing under neutral to alkaline conditions (up to pH 10) in various pu lps. The tensile and bursting strength of the handsheets can also be i mproved by 20-30% with the new mordants. It is observed that the pH of maximum sizing efficacy of these metal ions is in the vicinity of the ir pK(1) values. In addition, their performances as mordants or rosin soap sizing coincide with the Irving-Williams Effect which describes t he general trends in the stability of metal complexes. Discussions on the mechanism of the HST sizing test with formic acid ink are also giv en based on some unusual observations.