Modified silica sols: titania dispersants and co‐binders for silicate paints

Abstract

Purpose The purpose of this paper is to investigate epoxysilane‐modified silica sols as surfactant‐free inorganic pigments dispersants and as co‐binders/reinforcing agents for silicate paints. Design/methodology/approach The performance of epoxysilane‐modified silica sols as dispersants for titania was studied using a polyacrylate‐based dispersant as reference. Furthermore, the effect of the addition of silica sols, with or without silane modification, to potassium silicate on binder properties was investigated. Findings Significant improvements were obtained in stability towards settling in water‐based titania pigments pastes and in light‐scattering efficiency (as much as 50 per cent) for the optimal size of the silica particle of 5 nm. The number of silane molecules per nm 2 silica particle surface must exceed a critical value of at least 1 molecule of epoxysilane per nm 2 particle surface. Additionally, improved stability towards gelling, water resistance and film‐forming properties of sol‐silicate binder mixes were achieved for epoxysilane‐modified silica sols. Research limitations/implications Only epoxysilane‐modified silica sols were studied in this report. Titania pigment was examined but other important pigments (e.g. iron oxides) remain to be studied. In addition, only sol‐silicate mixes were investigated and not fully formulated silicate paints. Practical implications A method that produces stable, high‐performing, surfactant‐free inorganic pigments pastes. Furthermore, stable, high‐ratio, sol‐silicate binders can be obtained with improved water resistance and film properties for use in silicate paints. Originality/value The present method provides an easy route to obtain stable surfactant‐free inorganic pigments pastes, as well as makes stable, high‐ratio, sol‐silicate mixes/paints.