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Abstract

A process is described for producing unique and novel sulfonate-containing terpolymers of water soluble monomers with water insoluble monomers which are efficient viscosifiers of aqueous and brine media. The process relies on the complete solubilization of the water insoluble monomer by means of a dilute solution of a suitable water soluble surfactant. The type and concentration of surfactant are chosen to produce a clear, uniform, homogeneous aqueous dispersion of the hydrophobic monomers in the presence of both nonionic and anionic water soluble monomers, and, in addition, the reaction medium remains a clear, uniform, homogeneous mixture with no phase separation as the reaction proceeds to completion. Thus, the terpolymerization is effected without the formation of latexes or fine particulates of water insoluble polymer. The terpolymers, which may be isolated from the reaction mixture, provide efficient viscosification of water or brine solutions. The anionic sulfonate groups improve polymer solubility in water and brine, particularly in the presence of salts containing divalent cations, and impart some chain stiffness due to charge repulsion, particularly in water containing low electrolyte concentration. The hydrophobic N-alkylacrylamide groups associate in solution to create a structure with an apparent increase in molecular weight, resulting in enhanced thickening efficiency.

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