| abstract |
The present invention relates to a method for preparing an aqueous polymeric solution of viscosity V3 containing at least one cationic or amphoteric (co) polymer, comprising the following steps: Hofmann degradation reaction on a (co) polymer base of at least one nonionic monomer selected from the group consisting of acrylamide, methacrylamide, N, N-dimethylacrylamide, and acrylonitrile; after-treatment of the resulting aqueous polymeric solution of viscosity V1; characterized in that the post-treatment comprises the following successive steps: a) increasing the viscosity V1 to a value V2 corresponding to at least 1.5 times the value V1 while being less than 100,000 cps, by adjusting the pH of the polymeric solution has a value greater than or equal to 5.5; b) lowering the pH of the polymeric solution to a value of between 2 and 5; c) obtaining a polymeric solution whose viscosity V3 is greater than V1 and less than V2. The invention also relates to the use of this polymeric solution as a flocculation agent, retention and / or drainage, and dry strength in the paper industry. |