Aqueous dispersions of reactive gluing agents, method for the production and the use thereof

1. An aqueous dispersion of a reactive size which comprises:

a reactive phase comprising one or more diketenes and an anionic dispersant; and

a protective colloid comprising a cationic polymer comprising vinylamine units;

wherein the protective colloid comprises less than 0.0001% by weight, based on the protective colloid, of the diketenes; and

wherein the anionic dispersant is at least one selected from the group consisting of a condensate of a naphthalenesulfonic acid and formaldehyde; a condensate of a phenol, phenolsulfonic acid and formaldehyde; a condensate of a naphthalenesulfonic acid, formaldehyde and urea; a condensate of a phenol, phenolsulfonic acid, formaldehyde and urea; a ligninsulfonate; a cationic acrylate polymer; and a cationic acrylamide polymer,

wherein the aqueous dispersion contains less than 0.1% by weight of cationic starch.

2. The aqueous dispersion according to claim 1 , wherein the protective colloid is substantially free of diketenes.

3. The aqueous dispersion according to claim 1 , wherein the cationic polymer comprising vinylamine units comprises from 1 to 100 mol % of hydrolyzed homo- or copolymers of N-vinylformamide.

4. The aqueous dispersion according to claim 1 , wherein the cationic polymer comprising vinylamine units has an average molecular weight Mw of from 1000 to 2 million.

5. The aqueous dispersion according to claim 1 , wherein the content of protective colloid is from 10 to 100% by weight, based on the reactive size.

6. The aqueous dispersion according to claim 1 , wherein the diketenes comprise one or more selected from the group consisting of a C12- to C22 alkylketene dimer, a C5- to C22-alkyl-succinic anhydride, a C5- to C22-alkenylsuccinic anhydride and a C12- to C36-alkyl isocyanate.

7. The aqueous dispersion according to claim 6 , wherein the diketenes are present in an amount of from 1 to 50% by weight, based on the total weight of the dispersion.

8. A process for the preparation of an aqueous dispersion according to claim 1 , comprising homogenizing the diketenes and the cationic polymer comprising vinylamine units in an aqueous mixture in the presence of the anionic dispersant at from 20 to 100° C. under the action of shear forces.

9. A process for engine sizing paper, board and cardboard comprising adding an aqueous dispersion of claim 1 to an aqueous slurry of cellulose fibers and draining the paper stock.

10. The aqueous dispersion according to claim 1 , wherein the cationic polymer is a hydrolyzed poly-N-vinylformamide polymer having a K value of 75-110 and a degree of hydrolysis of 65-95 mol % of vinylamine units.

11. The aqueous dispersion of claim 10 , wherein the ketenes comprise stearyldiketene.

12. The aqueous dispersion of claim 11 , having a pH of 3.4-3.7.

13. The aqueous dispersion according to claim 11 , wherein the stearyldiketene is present in an amount of from 1 to 50% by weight.

14. The aqueous dispersion according to claim 1 , wherein the anionic dispersant is at least one selected from the group consisting of a condensate of a naphthalenesulfonic acid and formaldehyde; a condensate of a phenol, phenolsulfonic acid and formaldehyde; a condensate of a naphthalenesulfonic acid, formaldehyde and urea; and a condensate of a phenol, phenolsulfonic acid, formaldehyde and urea.

15. The aqueous dispersion according to claim 1 , which is completely free of a cationic starch.

16. A non-cellulose aqueous dispersion of a reactive size which comprises:

a reactive phase comprising one or more diketenes and an anionic dispersant; and

a protective colloid comprising a cationic polymer comprising vinylamine units;

wherein the protective colloid comprises less than 0.0001% by weight, based on the protective colloid, of the diketenes,

wherein the aqueous dispersion contains less than 0.1% by weight of cationic starch.

17. The non-cellulose aqueous dispersion of claim 16 , wherein the anionic dispersant is at least one selected from the group consisting of a condensate of a naphthalenesulfonic acid and formaldehyde; a condensate of a phenol, phenolsulfonic acid and formaldehyde; a condensate of a naphthalenesulfonic acid, formaldehyde and urea; a condensate of a phenol, phenolsulfonic acid, formaldehyde and urea; a ligninsulfonate; a cationic acrylate polymer; and a cationic acrylamide polymer.

18. The aqueous dispersion according to claim 16 , wherein the protective colloid is free of diketenes.

19. The aqueous dispersion according to claim 16 , wherein the cationic polymer comprising vinylamine units comprises from 1 to 100 mol % of hydrolyzed homo- or copolymers of N-vinylformamide.

20. The aqueous dispersion according to claim 16 , wherein the cationic polymer comprising vinylamine units has an average molecular weight Mw of from 1000 to 2 million.

21. The aqueous dispersion according to claim 16 , wherein the content of protective colloid is from 10 to 100% by weight, based on the reactive size.

22. The aqueous dispersion according to claim 16 , wherein the ketenes comprise one or more selected from the group consisting of a C 12 - to C 22 -alkylketene dimer, a C 5 - to C 22 -alkyl-succinic anhydride, a C 5 - to C 22 -alkenylsuccinic anhydride and a C 12 - to C 36 -alkyl isocyanate.

23. The aqueous dispersion according to claim 16 , wherein the ketenes are present in an amount of from 1 to 50% by weight, based on the total weight of the dispersion.

24. The aqueous dispersion of claim 16 , wherein the ketenes comprise stearyldiketene.

25. The non-cellulose aqueous dispersion of claim 16 , wherein the anionic dispersant is at least one selected from the group consisting of a condensate of a naphthalenesulfonic acid and formaldehyde; a condensate of a phenol, phenolsulfonic acid and formaldehyde; a condensate of a naphthalenesulfonic acid, formaldehyde and urea; and a condensate of a phenol, phenolsulfonic acid, formaldehyde and urea.

26. The aqueous dispersion according to claim 16 , which is completely free of a cationic starch.