1992 Volume 46 Issue 3 Pages 435-441
The interaction of binder latices with the surface of coating base paper was studied by the technique of osmium tetroxide fixation combined with pH control by buffer solution. The technique, formerly applied to latex-clay systems, was found useful too in visualizing the electrostatic interaction between latex and cellulose fibers. A pulp fiber (bleached softwood kraft pulp) and three types of crystalline cellulose microfibrils (i. e., Valonia cellulose, bacterial cellulose, and cotton-derived microcrystalline powder), all having negative zeta potentials, showed strong interactions with amphoteric latex particles under acidic conditions. The intensity of interaction, as judged from the number of adsorbed latex particles, was consistent well with the order of absolute values of zeta potential. The other combinations of latex type and pH, i. e., amphoteric latex at high and anionic latex at both high and low pHs, resulted in virtually no binding between the components.
These findings, together with the former observations of latex-clay systems, indicate that the use of amphoteric latex provides useful means of controlling the coating processes, i. e., prevention of binder migration or formation of bulky coating layer, through rapid immobilization of latex and/or clay particles at the base paper-coating color interface. Such interactions would also be useful in other areas of paper manufacture including internal sizing or off-machine latex impregnation.
