High-concentration TiO2 suspension (>70 wt%) with low viscosity suitable for waterborne coatings

Abstract

High-concentration TiO2 suspension is favored by industry since it would effectively simplify the processing of coatings, benefiting energy and cost savings. However, achieving a dense TiO2 suspension with low viscosity and good dispersion remains a challenge due to the large particle size and high density of pigment-grade TiO2 particles (200–400 nm). In this work, we proposed high-concentration TiO2 suspensions with low viscosity and excellent storage stability by grafting copolymer nanospheres to TiO2. The TiO2 particles are isolated through the steric hindrance and electrostatic repulsion of PMS (P(MMA-MPS)) nanospheres which are synthesized by emulsion polymerization of methyl methacrylate (MMA) and γ-methacryloxypropyltrimethoxysilane (MPS). The TiO2 suspension modified by PMS of 90 nm exhibits the highest concentration in water (74 wt%) while maintaining the lowest viscosity (95 mPa·s at the shear rate of 200 r/s). Through thermal storage at 50 °C in 28 d, the concentrated TiO2-PMS suspensions demonstrated excellent stability without any noticeable decline in coating properties compared to pure TiO2. The coating film of TiO2-PMS-90 suspension exhibited the optimal contrast ratio (92.4 %) and gloss value (78.5 GU) after thermal storage. The 50 L macro production results of TiO2-PMS-90 coincided with the lab results which will favor larger scale-up production. This work presents a strategy to enhance the dispersion stability of TiO2 particles to obtain a high-concentration slurry with low viscosity and superior flowability, particularly suitable for waterborne coatings.