POLYOXYETHYLENE DI-PHOSPHONATES AS EFFICIENT DISPERSING POLYMERS FOR AQUEOUS SUSPENSIONS

Polyoxyethylenes having a di-phosphonate functional group at one of th eir chain ends strongly adsorb on calcium carbonate particles in aqueo us colloidal suspensions. An enhanced colloidal stability of such susp ensions results with a concomitant drastic reduction of the viscosity of concentrated aqueous suspensions. The viscosity of a 20 wt % CaCO3 colloidal suspension in water could be lowered to 2 mPa.s with low con centrations of polymer. The adsorption and viscosity reduction were st udied as a function of the chemical nature of the end chain group and the polymer molecular weight. The di-phosphonate group was found the m ost efficient anionic group when associated with a polyoxyethylene of polymerization degree larger than 20. The main features of this di-blo ck architecture of the polymer are discussed. (C) 1997 John Wiley & So ns, Inc.