CNF cellular solid material
The present invention relates to cellular solid materials comprising cellulose nanofibers (CNF) and an anionic or non-ionic surfactant, a method for preparation of such materials, as well as their use.
1. A cellular solid material comprising cellulose nanofibers (CNF) and a surfactant, wherein:
a) the surfactant comprises a non-ionic surfactant;
b) the material has a density of less than 500 kg/m 3 ; and
c) at least 50% of the cells of the material have a diameter of at least 10 p.m.
2. The cellular solid material according to claim 1 , wherein the cellulose nanofibers are anionic cellulose nanofibers.
3. The cellular solid material according to claim 1 , wherein the surfactant is non-ionic.
4. The cellular solid material according to claim 3 , wherein the non-ionic surfactant is selected from the group consisting of polysorbate 20, polysorbate 80, triton X-100, sorbitan monolaurate, poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol), and polyvinylalcohol 70 kDa, and a combination thereof.
5. The cellular solid material according to claim 1 , wherein the cellular solid material comprises less than 40 wt % of the surfactant, as calculated on the total weight of the cellular solid material.
6. The cellular solid material according to claim 1 , wherein the CNF has a charge density of from 0 to 2000 μeq/g.
7. The cellular solid material according to claim 1 , wherein the CNF is any one of enzymatic CNF, TEMPO-oxidized CNF or carboxymethylated CNF, or a combination thereof.
8. The cellular solid material according to claim 1 , wherein at least 50% of the cells of the material have a diameter of at least 200 μm.
9. The cellular solid material according to claim 1 , wherein the material has a specific modulus of at least 1 kPa/(kg/m 3 ).
10. The cellular solid material according to claim 1 , wherein the material further comprises essentially no fibrous material in addition to CNF.
11. The cellular solid material according to claim 1 , wherein the material further comprises essentially no crosslinking agents.
12. A sheet comprising the cellular solid material of claim 1 and having a thickness of at least 0.05 mm.
13. A product selected from insulation, packaging material and an absorption material, comprising the cellular solid material of claim 1 .
14. The cellular solid material of claim 1 , wherein the cellular solid material comprises a single type of surfactant.
15. The cellular solid material of claim 1 , wherein the cellular solid material comprises at least 50 wt % CNF.
16. The cellular solid material of claim 1 , wherein the cellular solid material comprises at least 60 wt % CNF.
17. A method for manufacturing a dried cellular solid material with a density of less than 500 kg/m 3 , comprising the steps of:
a) providing a dispersion comprising cellulose nanofibers (CNF) in an aqueous solvent,
b) adding a surfactant comprising a non-ionic surfactant to
the dispersion in (a) to obtain a mixture;
c) preparing a wet foam from the mixture obtained in (b), wherein the wet foam has a density less than 98% of the mixture prepared in (b); and
d) drying the wet foam obtained in (c) to obtain a cellular solid material, wherein at least 50% of the cells of the material have a diameter of at least 10 μm.
18. The method according to claim 17 , wherein the wet foam obtained in step c) comprises no fibrous material in addition to CNF.
19. The method according to claim 17 , wherein the surfactant is non-ionic.
20. The method according to claim 19 , wherein the non-ionic surfactant is selected from the group consisting of polysorbate 20, polysorbate 80, triton X-100, sorbitan monolaurate, poly(ethylene glycol)-block-poly(propylene glycol)-block- poly(ethylene glycol), and polyvinylalcohol 70 kDa, and a combination thereof.
21. The method according to claim 17 , wherein the concentration of CNF in the dispersion obtained in step a) is at least 0.2 wt % of the total weight of said dispersion.
22. The method according to claim 17 , wherein the CNF has a charge density of from 0 to 2000 μeq/g.
23. The method according to claim 17 , wherein the CNF is TEMPO-oxidized any one of enzymatic CNF, TEMPO-oxidized CNF or carboxymethylated CNF, or a combination thereof.
24. The method according to claim 17 , wherein the method further comprises the step of forming the foam to a sheet having thickness of at least 0.1 mm prior to drying.
25. The method according to claim 17 , wherein the solvent has a water content of at least 80%.
26. The method according to claim 17 , wherein the solvent is water.
27. The method according to claim 26 , wherein the foam is formed by mixing the mixture in the presence of a gas, or by blowing a gas into the mixture.
28. The method according to claim 26 , wherein the gas is air.
29. The method according to claim 17 , wherein the preparation of a foam in (c) is made by introducing a gas into the mixture obtained in (b).
30. The method according to claim 17 , wherein the drying is performed at a temperature of 5-95° C.
31. The method according to claim 17 , wherein the drying is performed at a pressure of 5-1000 kPa.
32. The method according to claim 17 , wherein the drying is performed without freeze-drying or supercritical drying.
33. The method according to claim 17 , wherein the obtained dried cellular material is a sheet.