Filler for paper making process

1. A filler consisting essentially of modified clay and cellulose derivative being an anionic carboxyalkyl cellulose having a degree of substitution of net ionic groups from about 0.15 up to about 0.40, a degree of substitution of carboxyalkyl groups from about 0.10 up to 0.40, and a degree of substitution of cationic quaternary ammonium groups from about 0.05 up to about 0.50, the cationic quaternary ammonium groups being obtained by reacting cellulose or derivatives thereof with a quaternization agent selected from 2, 3 epoxypropyl trimethyl ammonium chloride, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride and mixtures thereof, wherein the clay has been modified by said cellulose derivative, and the filler has a cellulose derivative content of at least 0.01% by weight.

2. The filler according to claim 1 , wherein the cellulose derivative is a cellulose ether.

3. The filler according to claim 1 , wherein the cellulose derivative contains carboxymethyl groups.

4. The filler according to claim 1 , wherein the cellulose derivative is amphoteric.

5. The filler according to claim 1 , wherein the cellulose derivative is at least partly water soluble.

6. The filler according to claim 1 , wherein it has a cellulose derivative content from 0.3 to 10% by weight, based on the weight of the solids of the filler.

7. The filler according to claim 1 , wherein it has a clay content from 60 to about 80% by weight, based on the weight of the solids of the filler.

8. The filler according to claim 1 , wherein the clay is a kaolin clay.

9. The filler according to claim 1 , wherein the clay is calcinated clay.

10. The filler according to claim 1 , wherein the clay is talc.

11. Paper comprising a filler according to claim 1 .

12. The paper according to claim 11 , wherein the total filler content of the paper is from 5 to 40% by weight, based on dry paper.

13. An aqueous filler composition consisting essentially of water, modified clay; and cellulose derivative being an anionic carboxyalkyl cellulose having a degree of substitution of net ionic groups of from about 0.15 up to about 0.40, a degree of substitution of carboxyalkyl groups from about 0.10 up to 0.40, and a degree of substitution of cationic quaternary ammonium groups from about 0.05 up to about 0.50, the cationic quaternary ammonium groups being obtained by reacting cellulose or derivatives thereof with a quaternization agent selected from 2, 3 epoxypropyl trimethyl ammonium chloride, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride and mixtures thereof, wherein the clay has been modified by said cellulose derivative, and the filler has a cellulose derivative content of at least 0.01% by weight.

14. The filler according to claim 13 , wherein the cellulose derivative is amphoteric.

15. The filler according to claim 13 , wherein the cellulose derivative is at least partly water soluble.

16. The filler according to claim 13 , wherein the clay is a kaolin clay.

17. The filler according to claim 13 , wherein the clay is calcinated clay.

18. Paper comprising an aqueous filler according to claim 13 .

19. A filler consisting essentially of modified clay and cellulose derivative being an anionic carboxyalkyl cellulose having a degree of substitution of net ionic groups of around 0.23 and containing cationic quaternary ammonium groups, wherein the clay has been modified by said cellulose derivative, and the filler has a cellulose derivative content of at least 0.01% by weight.

20. An aqueous filler composition consisting essentially of water, modified clay; and cellulose derivative being an anionic carboxyalkyl cellulose having a degree of substitution of net ionic groups of around 0.23 and containing cationic quaternary ammonium groups, wherein the clay has been modified by said cellulose derivative, and the filler has a cellulose derivative content of at least 0.01% by weight.