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 fibres and at least one filler and/or pigment; combining the cellulose fibres and the at least one filler and/or pigment; and fibrillating the cellulose fibres 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 process for the production of a nano-fibrillar cellulose suspension comprising the steps of:
(a) providing cellulose fibres, wherein all or part of the cellulose fibres may be obtained from a recycled pulp;
(b) providing a filler; wherein the filler is selected from the group consisting of precipitated calcium carbonate (PCC); natural ground calcium carbonate (GCC); dolomite; talc; bentonite; clay; magnesite; satin white; sepiolite, huntite, diatomite; silicates; and mixtures thereof;
(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) to obtain a nano-fibrillar cellulose suspension,
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 process according to claim 1 , wherein the cellulose fibres in step (a) are provided in the form of a suspension.
3. The process according to claim 2 , 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-%.
4. The process according to claim 2 , 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-%.
5. The process according to claim 2 , 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-%.
6. The process according to claim 2 , 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-%.
7. The process according to claim 2 , 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-%.
8. The process according to claim 1 , wherein the filler in step (b) is precipitated calcium carbonate.
9. The process according to claim 1 , wherein the filler in step (b) is precipitated calcium carbonate having a vateritic, a calcitic or an aragonitic crystal structure.
10. The process according to claim 1 , wherein the filler in step (b) is natural ground calcium carbonate.
11. The process according to claim 1 , wherein the filler in step (b) is natural ground calcium carbonate selected from marble, limestone and/or chalk.
12. The process according to claim 1 , wherein the precipitated calcium carbonate in step (b) is ultrafine discrete prismatic, scalenohedral or rhombohedral precipitated calcium carbonate.
13. The process according to claim 1 , wherein the filler in step (b) is in the form of particles having a median particle size of from 0.03 to 15 um.
14. The process 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.
15. The process 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.
16. The process 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 um.
17. The process according to claim 1 , wherein the filler in step (b) comprises a dispersing agent.
18. The process according to claim 17 , 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.
19. The process 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.
20. The process 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.
21. The process 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.
22. The process according to claim 1 , wherein the combination resulting from step (c) is stored for 2 to 12 hours prior to fibrillating in step (d).
23. The process according to claim 1 , wherein the combination resulting from step (c) is stored for 3 to 10 hours, prior to fibrillating in step (d).
24. The process according to claim 1 , wherein the combination resulting from step (c) is stored for 4 to 8 hours, prior to fibrillating in step (d).
25. The process according to claim 1 , wherein a cellulose solvent is added to the combination in step (c) prior to fibrillating in step (d).
26. The process according to claim 1 , wherein the cellulose solvent is copper(II)ethylenediamine, iron-sodium-tartrate or lithium-chloride/dimethylacetamine.
27. The process 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.
28. The process 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.
29. The process 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.
30. The process 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.