Deflocculating effect of sodium polymethacrylates on aqueous clay suspensions

The ability of sodium polymethacrylates salts with various molecular weights (1200 to 30000) to deflocculate concentrated aqueous suspensions (56 wt%) of two Indian ball clays was investigated. The ball clays were one from Bikaner, Rajasthan and the other from Bhimandole, Andhra Pradesh, which are widely used in Indian sanitaryware and tile industry. The clays were characterized for their chemical analysis, cation exchange capacity (methylene blue index test) and for particle size distribution. The clay slips were prepared with distilled water and water containing calcium ions (0 to 60 ppm) using sodium polymethacrylates as deflocculant. All the slurries showed non-Newtonian behaviour. Polymethacrylates with low molecular weights (1200 to 2500) were found to be the most efficient deflocculants for these clay suspensions. The salts acted by an essentially electrosteric stabilization mechanism in combination with a high sequestering ability towards flocculating cations (calcium ion binding power values of 760 to 790 mgCaCO3.g−1). For their efficient deflocculating capabilities towards concentrated clay suspensions, sodium polymethacrylates may be considered for practical industrial application, in particular, for the preparation of liquid deflocculants. © 2006 Taylor and Francis Group, LLC.