Process for the production of nano-fibrillar cellulose suspensions
The present invention relates to a process for the production of suspensions of nano-fibrillar cellulose by providing cellulose fibers and at least one filler and/or pigment; combining the cellulose fibers and the at least one filler and/or pigment; and fibrillating the cellulose fibers in the presence of at least one filler and/or pigment, as well as the suspensions of nano-fibrillar cellulose obtained by this process and their uses.
1. A nano-fibrillar cellulose suspension wherein cellulose fibres are at least partially broken down to primary fibrils obtained by the process comprising the steps of:
(a) providing cellulose fibres contained in pulps selected from the group consisting of eucalyptus pulp, spruce pulp, pine pulp, beech pulp, hemp pulp, cotton pulp, or any mixture thereof;
(b) providing a filler, wherein the filler is natural ground calcium carbonate, and further wherein the filler has a median particle size of from 0.03 to 15 μm;
(c) combining the cellulose fibres from step (a) and the filler from step (b); and
(d) fibrillating the cellulose fibres and the filler from step (c) until the cellulose fibres are partially broken down to primary fibrils and the Schopper Riegler degree is increased at least 4° SR; wherein the fibrillating in step (d) is carried out by a device selected from an ultra-fine friction grinder, a refiner, or a homogenizer, and wherein in step (d) the weight ratio of fibres to filler on a dry weight basis is from 1:10 to 10:1.
2. The suspension according to claim 1 , wherein the cellulose fibres in step (a) are contained in kraft pulp.
3. The suspension according to claim 1 , wherein the cellulose fibres in step (a) are contained in bleached longfibre kraft pulp.
4. The suspension according to claim 1 , wherein the cellulose fibres in step (a) are provided in the form of a suspension.
5. The suspension according to claim 1 , wherein the cellulose fibres in step (a) are provided in the form of a suspension at a solids content of from 0.2 to 35 wt-%.
6. The suspension according to claim 1 , wherein the cellulose fibres in step (a) are provided in the form of a suspension at a solids content of from 0.25 to 10 wt.-%.
7. The suspension according to claim 1 , wherein the cellulose fibres in step (a) are provided in the form of a suspension at a solids content of from 1 to 5 wt.-%.
8. The suspension according to claim 1 , wherein the cellulose fibres in step (a) are provided in the form of a suspension at a solids content of from 2 to 4.5 wt.-%.
9. The suspension according to claim 1 , wherein the cellulose fibres in step (a) are provided in the form of a suspension at a solids content of about 1.3 or about 3.5 wt.-%.
10. The suspension according to claim 1 , wherein the filler in step (b) is natural ground calcium carbonate selected from marble, limestone and/or chalk.
11. The suspension according to claim 1 , wherein the filler in step (b) is in the form of particles having a median particle size of from 0.2 to 5 μm.
12. The suspension according to claim 1 , wherein the filler in step (b) is in the form of particles having a median particle size of from 0.2 to 4 μm.
13. The suspension according to claim 1 , wherein the filler particles in step (b) is in the form of particles having a median particle size of about 1.5 or about 3.2 μm.
14. The suspension according to claim 1 , wherein the filler in step (b) comprises a dispersing agent.
15. The suspension according to claim 14 , wherein the dispersing agent is selected from homopolymers or copolymers of polycarboxylic acids and/or their salts or esters, acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, acryl amide or acrylic esters, or mixtures thereof; alkali polyphosphates, phosphonic-, citric- or tartaric acids, salts or esters thereof; or mixtures thereof.
16. The suspension according to claim 1 , wherein before fibrillating in step (d), the pH of the combination of the cellulose fibres and the filler is adjusted to a pH of 10 to 12.
17. The suspension according to claim 1 , wherein after fibrillating in step (d), the pH of the suspension is re-adjusted to a pH of 7.5 to 9.5.
18. The suspension according to claim 1 , wherein after fibrillating in step (d), the pH of the suspension is re-adjusted to a pH of about 8.5.
19. The suspension according to claim 1 , wherein the combination resulting from step (c) is stored for 2 to 12 hours prior to fibrillating in step (d).
20. The suspension according to claim 1 , wherein the combination resulting from step (c) is stored for 3 to 10 hours, prior to fibrillating in step (d).
21. The suspension according to claim 1 , wherein the combination resulting from step (c) is stored for 4 to 8 hours, prior to fibrillating in step (d).
22. The suspension according to claim 1 , wherein a cellulose solvent is added to the combination in step (c) prior to fibrillating in step (d).
23. The suspension according to claim 22 , wherein the cellulose solvent is copper(II)ethylenediamine, iron-sodium-tartrate or lithium-chloride/dimethylacetamide.
24. The suspension according to claim 1 , wherein in step (d) the weight ratio of fibres to filler on a dry weight basis is from 1:6 to 6:1.
25. The suspension according to claim 1 , wherein in step (d) the weight ratio of fibres to filler on a dry weight basis is from 1:4 to 4:1.
26. The suspension according to claim 1 , wherein in step (d) the weight ratio of fibres to filler on a dry weight basis is from 1:3 to 3:1.
27. The suspension according to claim 1 , wherein in step (d) the weight ratio of fibres to filler on a dry weight basis is from 1:2 to 2:1.
28. The suspension according to claim 1 , wherein the combination from step (c) is fibrillated in step (d) until a Schopper Riegler degree is increased by ≥6° SR.
29. The suspension according to claim 1 , wherein the combination from step (c) is fibrillated in step (d) until a Schopper Riegler degree is increased by ≥8° SR.
30. The suspension according to claim 1 , wherein the combination from step (c) is fibrillated in step (d) until a Schopper Riegler degree is increased by ≥10° SR.
31. The suspension according to claim 1 , wherein the combination from step (c) is fibrillated in step (d) until a Schopper Riegler degree is increased by ≥15° SR.
32. The suspension according to claim 1 , wherein the combination of fibres and filler from step (c) is fibrillated in step (d) until a final Schopper-Riegler degree of ≥60° SR is reached.
33. The suspension according to claim 1 , wherein the combination of fibres and filler from step (c) is fibrillated in step (d) until a final Schopper-Riegler degree of ≥70° SR is reached.
34. The suspension according to claim 1 , wherein the combination of fibres and filler from step (c) is fibrillated in step (d) until a final Schopper-Riegler degree of ≥80° SR is reached.
35. The suspension according to claim 1 , wherein the fibrillating in step (d) is carried out by an ultra-fine friction grinder or a homogenizer, and wherein the temperature of the suspension in the ultra-fine friction grinder or the homogenizer is above 60° C.
36. The suspension according to claim 1 , wherein the fibrillating in step (d) is carried out by an ultra-fine friction grinder or a homogenizer, and wherein the temperature of the suspension in the ultra-fine friction grinder or the homogenizer is above 80° C.
37. The suspension according to claim 1 , wherein the fibrillating in step (d) is carried out by an ultra-fine friction grinder or a homogenizer, and wherein the temperature of the suspension in the ultra-fine friction grinder or the homogenizer is above 90° C.
38. Paper comprising the nano-fibrillar cellulose suspension according to claim 1 .
39. A material composite, plastic, paint, rubber, concrete, ceramic, adhesive, food or wound-healing composition comprising the nano-fibrillar cellulose suspension according to claim 1 .