Acrylamide-derived cationic copolymers, and uses thereof

1. A cationic or amphoteric (co)polymer obtained by Hofmann degradation reaction, in aqueous solution, in the presence of an alkaline-earth or alkali metal hydroxide or combination thereof and of an alkaline-earth or alkali metal hypohalide or combination thereof, on a base (co)polymer comprising at least one nonionic monomer chosen from the group consisting of acrylamide, methacrylamide and N,N-dimethylacrylamide, wherein said base (co)polymer is modified beforehand with at least one polyfunctional compound containing at least 3 heteroatoms chosen from N, S, O and P and each having at least one mobile hydrogen.

2. The (co)polymer as claimed in claim 1 , wherein said polyfunctional compound is chosen from the group consisting of polyethyleneimines, polyamines (primary or secondary), polyallylamines, polythiols, polyalcohols, polyamide-epichlorohydrin resins and polyamine amides.

3. The (co)polymer as claimed in claim 1 , wherein said polyfunctional compound is polyethyleneimine.

4. The (co)polymer as claimed in claim 1 , wherein said polyfunctional compound is polyamine amide.

5. The (co)polymer as claimed in claim 1 , wherein said base (co)polymer is modified by incorporation of the polyfunctional compound before or during the polymerization of the monomers.

6. The (co)polymer as claimed in claim 1 , wherein said base (co)polymer contains at least 5 mol % of nonionic monomer and at least 1000 ppm of polyfunctional compound.

7. The (co)polymer as claimed in claim 1 , wherein said base (co)polymer additionally contains at least:

one unsaturated cationic ethylenic monomer, chosen from the group consisting of monomers of dialkylaminoalkyl, acrylamide, methacrylamide, diallylamine and methyldiallylamine type and the quaternary ammonium or acid salts thereof,

or one nonionic monomer,

or one anionic monomer of acid or anhydride type chosen from the group consisting of acrylic acid, methacrylic acid acrylamidomethylpropyl-sulfonic acid, itaconic acid, maleic anhydride, maleic acid, methallylsulfonic acid, vinylsulfonic acid and salts thereof,

or mixtures thereof.

8. The (co)polymer as claimed in claim 7 , wherein said unsaturated cationic ethylenic monomer is chosen from the group consisting of dimethyldiallylammonium chloride (DADMAC), acrylamidopropyltrimethylammonium chloride (APTAC) and methacrylamidopropyltrimethylammonium chloride (MAPTAC).

9. The (co)polymer as claimed in claim 7 , wherein said nonionic monomer is chosen from the group consisting of N-vinyl acetamide, N-vinyl formamide, N-vinylpyrrolidone and vinyl acetate.

10. The (co)polymer as claimed in claim 1 , wherein said base (co)polymer consists of:

acrylamide,

polyethyleneimine,

and at least one unsaturated cationic ethylenic comonomer, chosen from the group consisting of monomers of, dialkylaminoalkylacrylamide, dialkylaminoalkylmethacrylamide, diallylamine and methyldiallylamine type and the quaternary ammonium or acid salts thereof.

11. The (co)polymer as claimed in claim 10 , wherein said unsaturated cationic ethylenic monomer is dimethyldiallylammonium chloride.

12. The (co)polymer as claimed in claim 1 , wherein said base (co)polymer is branched.

13. The (co)polymer as claimed in claim 1 , wherein said Hofmann degradation product is produced at a concentration of greater than 4% by weight.

14. The (co)polymer as claimed in claim 1 , wherein said base (co)polymer is modified by grafting of the polyfunctional compound after the final base (co)polymer has been obtained.

15. The (co)polymer as claimed in claim 1 , wherein said Hofmann degradation product is produced at a concentration of greater than 7% by weight.

16. The (co)polymer as claimed in claim 1 , wherein said Hofmann degradation product is produced at a concentration of greater than 8% by weight.

17. A method of making paper, comprising: employing a (co)polymer according to claim 1 as a flocculation, retention drainage or dry strength aid.