Process for treating cellulose and cellulose treated according to the process

Patent metadata

Field	Value
Publication number	US-9447541-B2
Application number	US-201214116590-A
Country	US
Kind code	B2
Filing date	May 11, 2012
Priority date	May 13, 2011
Publication date	Sep 20, 2016
Grant date	Sep 20, 2016

Abstract

The present invention relates to a process for purifying a slurry comprising cellulose, such as microfibrillated cellulose, wherein the process comprises the following steps: —providing a slurry comprising cellulose and liquid, —subjecting the slurry to an electric field inducing the liquid of the slurry to flow, —separating the liquid from the cellulose thus obtaining a liquid depleted slurry, —adding a washing liquid, such as an organic solvent, to the liquid depleted slurry—subjecting the liquid depleted slurry to an electric field inducing the washing liquid of the slurry to flow and—separating the washing liquid from the cellulose, thus obtaining a purified cellulose. The invention also relates to cellulose such as microfibrillated cellulose obtainable from said process.

First claim

The invention claimed is:

1. A process for purifying by salt/ion depletion or free sugar depletion a slurry comprising microfibrillated cellulose, wherein the process comprises the following steps:
a) providing a slurry comprising at least 20% microfibrillated cellulose by solids weight and a liquid,
b) subjecting the slurry to a first application of an electric field inducing the liquid of the slurry to flow,
c) separating the liquid from the microfibrillated cellulose thus obtaining a liquid depleted slurry,
d) adding a washing liquid to the liquid depleted slurry,
e) subjecting the liquid depleted slurry to a second application of an electric field inducing the washing liquid of the slurry to flow and
f) separating the washing liquid from the microfibrillated cellulose, thus obtaining a purified microfibrillated cellulose.

2. The process according to claim 1 wherein the liquid separation is done by electro-osmosis.

3. The process according to claim 1 wherein the electric field has a voltage between 10-100 V.

4. The process according to claim 1 wherein pressure also is applied in order to separate the liquid from the microfibrillated cellulose.

5. The process according to claim 4 wherein the pressure is applied after the electric field has been applied and the dewatering has started.

6. The process according to claim 4 wherein the pressure is a mechanical pressure.

7. The process according to claim 1 wherein the dry content of the slurry before dewatering, salt/ion depletion or free sugar depletion, is 1-50% by weight.

8. The process according to claim 1 wherein the dry content of the dewatered slurry is 5-50% by weight.

9. The process according to claim 1 wherein the temperature of the slurry during dewatering is above 30° C. and below 100° C.

10. The process according to claim 1 wherein the slurry comprises one or more of the constituents selected from the group consisting of nanoparticles, absorbents, salt, free sugars and surfactants which are stimulated by the electric field.

11. The process according to claim 1 wherein the washing liquid is water, an organic solvent or a combination thereof.

12. The process according to claim 1 followed by a counter-ion change step.

13. The process according to claim 1 wherein the washing liquid is an organic solvent.

14. The process according to claim 1 further comprising at least one additional washing step.

15. A process for purifying a slurry comprising microfibrillated cellulose by salt/ion depletion or free sugar depletion, wherein the process comprises the following steps:
providing a slurry comprising at least 20% microfibrillated cellulose by solids weight and a liquid,
subjecting the slurry to a first application of an electric field inducing the liquid of the slurry to flow,
applying pressure in combination with the electric field to the slurry after the first application of the electric field, the flow of the liquid has started and the solids of the slurry is at least about 4% by weight,
separating the liquid from the microfibrillated cellulose thus obtaining a liquid depleted slurry,
adding a washing liquid to the liquid depleted slurry,
subjecting the liquid depleted slurry to another application of an electric field inducing the washing liquid of the slurry to flow, and
separating the washing liquid from the microfibrillated cellulose, thus obtaining a purified microfibrillated cellulose.

Assignees

• Heiskanen Isto
• Backfolk Kaj
• Kotilainen Ari
• Gaidelis Valentas
• Sidaravicius Jonas
• Stora Enso Oyj

Inventors

• Heiskanen Isto
• Backfolk Kaj
• Kotilainen Ari
• Gaidelis Valentas
• Sidaravicius Jonas

Classifications

• D21H11/18

  Highly hydrated, swollen or fibrillatable fibres · CPC title

• B01D61/56 Primary

  Electro-osmotic dewatering · CPC title

• D21C9/007

  by mechanical or physical means · CPC title

• C02F1/4698

  electro-osmosis · CPC title

• C02F11/006

  Electrochemical treatment, e.g. electro-oxidation or electro-osmosis · CPC title