Patent ID: 7803899

Claim:
A method of preparing dry water-soluble polymer comprising: a) combining a water-soluble polymer in water with at least one dry polar solvent to form a mixture that separates into a first layer comprising a majority of said dry polar solvent and water and a second layer comprising a majority of said water-soluble polymer, wherein said water-soluble polymer is an ionene polymer, a polyaminoamide polymer, or a polyacrylamide/diallyldimethyl-ammonium halide copolymer; b) separating said first layer from said second layer; and c) drying said second layer to obtain a solid comprising said water-soluble polymer, wherein said water-soluble polymer having at least one polar solvent content or impurity level selected from: a polar solvent content of from about 5 ppm to about 1,000 ppm, a low molecular weight organic impurity level of from about 50 ppm to about 5,000 ppm, wherein the low molecular weight organic impurity has an average molecular weight of 50,000 or less, an epichlorohydrin or daughter thereof impurity level of from about 50 ppm to about 5,000 ppm, and an impurity level of from 5 ppm to about 1,500 ppm with respect to impurities soluble in an organic solvent.