Process for the production of nano-fibrillar cellulose gels
The present invention relates to a process for the production of nano-fibrillar cellulose gels 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 the at least one filler and/or pigment until a gel is formed, as well as the nano-fibrillar cellulose gel obtained by this process and uses thereof.
1. A nano-fibrillar cellulose gel 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;
(c) combining the cellulose fibres of step (a) and the filler; and
(d) fibrillating the cellulose fibres in an aqueous environment in the presence of the filler from step (c) until a nano-fibrillar cellulose gel is formed;
wherein the formation of the gel is verified by monitoring the viscosity of the mixture in dependence of the shearing rate, wherein the viscosity decrease of the mixture upon step-wise increase of the shearing rate is stronger than the corresponding viscosity increase upon subsequent step-wise reduction of the shearing rate over at least part of the shear rate range as shearing approaches zero;
wherein the filler is natural ground calcium carbonate,
wherein in step (d) the weight ratio of fibres to filler on a dry weight basis is from 1:33 to 10:1, wherein the Brookfield viscosity of the nano-fibrillar cellulose gel formed in step (d) is lower than the Brookfield viscosity of a corresponding nano-fibrillar cellulose suspension having been fibrillated in the absence of the filler.
2. The gel according to claim 1 , wherein the cellulose fibres in step (a) are provided in the form of a suspension.
3. The gel 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.-%.
4. The gel 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.-%.
5. The gel 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 0.5 to 5 wt.-%.
6. The gel 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 4 wt.-%.
7. The gel 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 1.3 to 3 wt.-%.
8. The gel according to claim 1 , wherein the filler in step (b) is natural ground calcium carbonate selected from marble, limestone and/or chalk.
9. The gel according to claim 1 , wherein the filler in step (b) is in the form of particles having a median medium particle size of from 0.01 to 15 μm.
10. The gel according to claim 1 , wherein the filler in step (b) is in the form of particles having a median medium particle size of from 0.1 to 10 μm.
11. The gel according to claim 1 , wherein the filler in step (b) is in the form of particles having a median medium particle size of from 0.3 to 5 μm.
12. The gel according to claim 1 , wherein the filler in step (b) is in the form of particles having a median medium particle size of from 0.5 to 4 μm.
13. The gel according to claim 1 , wherein the filler in step (b) comprises a dispersing agent.
14. The gel according to claim 13 , 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- and tartaric acids, salts or esters thereof; or mixtures thereof.
15. The gel according to claim 1 , wherein in step (d) the weight ratio of fibres to filler on a dry weight basis is from 1:10 to 7:1.
16. The gel according to claim 1 , wherein in step (d) the weight ratio of fibres to filler on a dry weight basis is from 1:5 to 5:1.
17. The gel 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.
18. The gel 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.
19. The gel according to claim 1 , wherein in step (d) the weight ratio of fibres to filler on a dry weight basis is from 1:1.5 to 1.5:1.
20. The gel according to claim 1 , wherein the fibrillating in step (d) is carried out by a homogenizer or an ultra fine friction grinder.
21. A material composite, plastic, paint, rubber, concrete, ceramic, adhesive, food or wound-healing composite comprising the nano-fibrillar cellulose gel according to claim 1 .