Composite body and method of manufacturing it

1. A composite body comprising nanofibrillar cellulose (NFC) together with abrasive particles having a hardness above 7 on Mohs scale, said nanofibrillar cellulose forming a 3-dimensional connecting network for the abrasive particles, wherein the NFC is derivatized NFC.

2. The composite body according to claim 1 , wherein the abrasive particles have a hardness of at least equal to or above 8.

3. The composite body according to claim 1 , wherein the abrasive particles are selected from aluminium oxide, silicon carbide, boron carbide, boron nitride, zirconia alumina, corundum, diamond and ceramic abrasives.

4. The composite body according to claim 1 , wherein the weight average mean particle size of the abrasive particles is 100 nm-1000 μm.

5. The composite body according to claim 1 , wherein the composite body has voids in the structure formed by the connecting network of nanofibrillar cellulose and the abrasive particles.

6. The composite body according to claim 1 , wherein the abrasive particles are at least partly surrounded by the NFC.

7. The composite body according to claim 6 , wherein the abrasive particles are covered by the NFC also on the exterior surface of the composite body.

8. The composite body according to claim 5 , wherein the voids of the composite body form interconnected porosity.

9. The composite body according to claim 1 , wherein the structure formed by the connecting network of nanofibrillar cellulose and the abrasive particles is in the form of coating on a substrate.

10. The composite body according to claim 9 , wherein the substrate is a rigid body.

11. The composite body according to claim 9 , wherein the substrate is a flexible sheet-like body.

12. The composite body according to claim 9 , wherein the substrate has porosity.

13. The composite body according to claim 1 , wherein the structure formed by the connecting network of nanofibrillar cellulose and the abrasive particles is a freestanding structure, a sheet-like product, or a rigid body.

14. The composite body according to claim 1 , wherein the body further comprises binder resin in the structure formed by the connecting network of nanofibrillar cellulose and the abrasive particles.

15. The composite body according to claim 1 , wherein the NFC is an ionically modified cellulose.

16. The composite body according to claim 15 , wherein the derivatized NFC forms an ionic bond or a covalent bond with the abrasive particles and/or with the possible substrate.

17. The composite body according to claim 15 , wherein the abrasive particles form charge complex with the ionically modified cellulose.

18. The composite body according to claim 15 , wherein the NFC is derivatized NFC containing aldehyde groups, which are bound covalently internally to NFC, to the abrasive particles, or to the possible substrate, preferably through acetal or hemiacetal reaction.

19. The composite body according to claim 1 , wherein the ratio of abrasive particles to NFC, as dry matter, is between 1:2 and 1:0.05 (w/w).

20. The composite body according to claim 1 , wherein the nanofibrillar cellulose is of plant origin.

21. A method for manufacturing a composite body comprising nanofibrillar cellulose (NFC), said method comprising

mixing a liquid dispersion, especially an aqueous dispersion of NFC, and abrasive particles having a hardness above 7 on Mohs scale, and

removing the liquid from the mixture of NFC and abrasive particles, wherein the NFC is derivatized NFC.

22. The method of claim 21 , wherein removal of liquid from the mixture of NFC and abrasive particles is carried out at least partly by pressing.

23. The method of claim 22 , wherein removal of liquid from the mixture of NFC and abrasive particles is carried out by pressing, whereafter the rest of liquid is removed by evaporation while the mixture is allowed to shrink freely.

24. The method of claim 21 , wherein removal of water from the mixture of NFC and abrasive particles is enhanced by lowering the pH of the mixture.

25. The method of claim 21 , wherein removal of water from the mixture of NFC and abrasive particles is enhanced by changing the water with water-soluble organic solvent, such as ethanol.

26. The method of claim 21 , wherein over 50% of the liquid is removed by another way than evaporation, and the rest of the liquid is removed by evaporation.

27. The method of claim 21 , wherein the mixture of NFC and abrasive particles is sprayed on a substrate.

28. The method of claim 27 , where the liquid is removed by evaporation.

29. The method of claim 21 , wherein the mixture of NFC and abrasive particles is forced through an orifice, nozzle or extruder die to an elongated object, and the liquid is removed from the elongated object.

30. The method of claim 21 , wherein a circular disc having a total thickness of 0.8-5 mm is made from the mixture alone or mixture and substrate.

31. The method of claim 21 , wherein the nanofibrillar cellulose is of plant origin.

32. A method for treating workpieces comprising using the composit body of claim 1

wherein the treating is grinding, polishing or cutting.

33. The method of claim 32 , wherein the treating is cutting glass or metal.

34. A method for friction surface in braking comprising using the composite body of claim 1 in brakes.

35. The composite body according to claim 1 , wherein the weight average mean particle size of the abrasive particles is 1-500 μm.

36. The composite body according to claim 9 , wherein the substrate comprises a textile substrate.

37. The composite body according to claim 36 , wherein the textile substrate comprises a woven, knitted or non-woven cloth.

38. The composite body according to claim 9 , wherein the textile substrate comprises paper or cardboard.

39. The composite body according to claim 13 , wherein the freestanding structure is in the form of grains, yarns, filaments, or a textile structure made of said yarns or filaments.

40. The composite body according to claim 13 , wherein the rigid body is a disc.

41. The composite body according to claim 14 , wherein the binder resin, comprises formaldehyde resin, urea formaldehyde, or phenol formaldehyde in the structure formed by the connecting network of nanofibrillar cellulose and the abrasive particles.

42. The composite body according to claim 15 , wherein the ionically modified cellulose is anionically or cationically modified cellulose.

43. The method of claim 21 , wherein the abrasive particle have a hardness at least equal to or above 8.

44. The method of claim 21 , wherein the liquid is water.