SILYLATION OF FILLERS FOR IMPROVED RETENTION IN NEWSPRINT

Pretreatment of calcined clay with up to 0.4% of an aminosilane coupling reagent increased first pass retention of the filler in a newsprint sheet when using polyethylene oxide-phenol formaldehyde resin as the retention aid. The treatment makes the filler less negatively charged and more hydrophobic, causing it to settle faster and be more easily redispersed. The interaction of untreated and silylated clay with the polyethylene oxide retention aid was studied by conductometric titration, infra-red, and X-ray photoelectron spectroscopy. Evidence is presented to suggest that the silylated clay is better retained because of the development of hydrogen bridging between the amine protons on the silylated clay and the polyethylene oxide oxygen atoms.