Patent ID: 7157603

Claim:
A method of separating thermally precipitabie oligomeric N-substituted (meth)acrylamides and conjugates thereof from aqueous solutions in the absence of organic solvents, said oligomeric N-substituted (meth)acrylamides having an average molecular weight between 500 g/mol and 5000 g/mol; wherein said method comprises the steps of: a) thermally precipitating the oligomeric N-substituted (meth)acrylamides and the conjugates thereof from an aqueous solution containing at least one salt and cellulose fiber as a filter aid at a temperature of 1° C. to 20° C. above a lower critical solution temperature to fan an aqueous mixture; b) filtering the aqueous mixture containing the cellulose fiber and the at least one salt in addition to the oligomeric N-substituted (meth)acrylamides and the conjugates with a filter medium at said temperature, so that a separation degree of the at least one filter aid and the oligomeric N-substituted (meth)arylamides and the conjugates thereof from the aqueous solution is more than 90 percent; wherein, prior to the thermally precipitating of step a), the aqueous solution contains no organic solvents and contains from 0.1 percent by weight to 10 percent by weight of a total amount of said oligomeric N-substituted (meth)acrylamides with said molecular weight between 500 g/mol and 5000 g/mol and said conjugates thereof and from 0.01 M to 3 M of said at least one salt; and wherein said at least one salt is selected from the group consisting of potassium chloride, sodium chloride, ammonium chloride, calcium chloride, magnesium chloride, potassium acetate, sodium acetate, ammonium acetate, calcium acetate, magnesium acetate, potassium sulfate, sodium sulfate, ammonium sulfate, calcium sulfate, magnesium sulfate, and mixtures thereof.