CNF cellular solid material with anionic surfactants
The present invention relates to cellular solid materials comprising cellulose nanofibers (CNF) and an anionic surfactant, a method for preparation of such materials, as well as their use.
1. A cellular solid material comprising at least 50 wt% cellulose nanofibers (CNF), based on the total weight of the cellular solid material, and a surfactant, wherein:
a) the surfactant is anionic;
b) the material has a density of less than 100 kg/m 3 ; and
c) at least 50% of the cells of the material have a diameter of at least 10 μm.
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 anionic surfactant is selected from sodium dodecyl sulfate, sodium lauryl ether sulfate, sodium oleate, and potassium oleate, or a combination thereof.
4. The cellular solid material according to claim 1 , wherein the cellular solid material comprises less than 5 wt% of anionic surfactant, as calculated on the total weight of the cellular solid material.
5. The cellular solid material according to claim 1 , wherein the CNF has a charge density of from 0 to 2000 μeq/g.
6. 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.
7. 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.
8. The cellular solid material according claim 1 , wherein the material has a specific modulus of at least 1 kPa/(kg/m 3 ).
9. The cellular solid material according to claim 1 , wherein fibrous material in the cellular solid material consists essentially of CNF.
10. The cellular solid material according to claim 1 , wherein the material further comprises essentially no crosslinking agents.
11. A sheet comprising the cellular solid material of claim 1 and having a thickness of at least 0.05 mm.
12. A method for manufacturing a dried cellular solid material with a density of less than 100 kg/m 3 , comprising the steps of:
a) providing a dispersion comprising cellulose nanofibers (CNF) in an aqueous solvent,
b) adding an anionic 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 the cellular solid material comprises at least 50 wt% cellulose nanofibers (CNF), based on the total weight of the cellular solid material, and at least 50% of the cells of the material have a diameter of at least 10 μm.
13. The method according to claim 12 , wherein the anionic surfactant is selected from sodium dodecyl sulfate, sodium lauryl ether sulfate, sodium oleate, and potassium oleate, or a combination thereof.
14. The method according to claim 12 , 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.
15. The method according to claim 12 , wherein the CNF has a charge density of from 0 to 2000 μeq/g.
16. The method according to claim 12 , wherein the CNF is any one of enzymatic CNF, TEMPO-oxidized CNF or carboxymethylated CNF, or a combination thereof.
17. The method according to claim 12 , 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.
18. The method according to claim 12 , wherein the solvent has a water content of at least 80%.
19. The method according to claim 12 , wherein the solvent is water.
20. The method according to claim 12 , wherein the preparation of a foam in (c) is made by introducing a gas into the mixture obtained in (b).
21. The method according to claim 20 , wherein the introduction of a gas is made by mixing the mixture in the presence of a gas, or by blowing a gas into the mixture.
22. The method according to claim 20 , wherein the gas is air.
23. The method according to claim 12 , wherein the drying is performed at a temperature of 5-120° C.
24. The method according to claim 12 , wherein the drying is performed at a pressure of 5-1000 kPa.
25. The method according to claim 12 , wherein the drying is performed without freeze-drying or supercritical drying.
26. The method according to claim 12 , wherein the wet foam obtained in step c) comprises no fibrous material in addition to CNF.
27. The method according to claim 12 , wherein the resultant dried cellular solid material is a sheet.
28. A product selected from the group consisting of insulation materials, packaging materials, absorption materials, and construction materials, comprising the cellular solid material of claim 1 .