Method for catalytic oxidation of cellulose and method for making a cellulose product

Patent metadata

Field	Value
Publication number	US-9410285-B2
Application number	US-201214124520-A
Country	US
Kind code	B2
Filing date	Jun 8, 2012
Priority date	Jun 9, 2011
Publication date	Aug 9, 2016
Grant date	Aug 9, 2016

Abstract

In a method for catalytic oxidation of cellulose a heterocyclic nitroxyl radical is used as catalyst, hypochlorite is used as main oxidant acting as oxygen source, and a tertiary amine or chlorine dioxide as an activator of the heterocyclic nitroxyl radical.

First claim

The invention claimed is:

1. A method for catalytic oxidation of cellulose comprising:
adding a heterocyclic nitroxyl compound as catalyst and main oxidant acting as oxygen source to the cellulose,
activating the heterocyclic nitroxyl compound to an active oxidized form,
oxidizing the cellulose through the active oxidized form of the heterocyclic nitroxyl compound, wherein
the activator is selected from tertiary amines and chlorine dioxide, where the tertiary amines are selected from hexamethylenetetramine, 1,4-diazabicyclo[2,2,2]octane (DABCO) and quinuclidine, and
hypochlorite is used as the main oxidant.

2. The method according to claim 1 , wherein the cellulose is oxidized catalytically in one step where the tertiary amine is used as the activator.

3. The method according to claim 2 , wherein during the oxidation pH is 7 to 10.

4. The method according to claim 1 , wherein the cellulose is oxidized in two steps, where the chlorine dioxide is used as the activator and hypochlorite as the main oxidant in a first catalytic step and chlorite is used as oxidant completing the oxidation in a second step where the pH is lower compared with the first step.

5. The method according to claim 4 , wherein during the first step pH is 6 to 10 and during the second step pH is 1.5 to 4.

6. The method according to claim 4 , wherein during the first step the reaction rate is observed until a predetermined point is reached, whereafter the reaction is stopped by lowering the pH to that of the second step and proceeding with the second step, or washing the pulp and recovering the catalyst before the second step.

7. The method according to claim 4 , wherein protective substance capable of inactivating the hypochlorous acid formed is used in the second step.

8. The method according to claim 7 , wherein the protective substance is dimethyl sulfoxide (DMSO) or dimethyl sulfide (DMS).

9. The method according to claim 1 , wherein chlorine oxide is used as the activator and the catalytic oxidation is performed at pH 7-9 and at temperature of 20-50° C.

10. The method according to claim 9 , wherein the oxidation is performed in said conditions to a level of 0.5-1.0 mmol COOH/g pulp.

11. The method according to claim 9 , wherein consistency of the pulp is above 4%.

12. The method according to claim 9 , wherein the oxidation treatment is stopped after it is performed in said conditions, and the oxidized cellulose is treated further by disintegrating fibrous material containing the oxidized cellulose to nanofibrillated cellulose.

13. The method according to claim 9 , wherein the oxidation treatment is continued in a second step with chlorite as oxidant completing the oxidation at a pH lower than in the first step.

14. The method according to claim 13 , wherein the second step is performed at pH of 1.5 to 4.

15. The method according to claim 1 , wherein the cellulose subjected to catalytic oxidation is cellulose in fibrous starting material.

16. Method for making a cellulose product, comprising
subjecting fibrous starting material to catalytic oxidation by the method according to claim 1 to obtain oxidized fibrous material, and
disintegrating the oxidized fibrous material.

17. The method according to claim 16 , wherein the oxidized fibrous material is disintegrated to nanofibrillated cellulose (NFC).

18. The method according to claim 17 , wherein the fibrils of the nanofibrillated cellulose have mean diameter of 5 to 15 nm and mean length of 0.5 to 2 μm.

19. The method according to claim 17 , wherein the nanofibrillated cellulose has the turbidity below 70NTU (nephelometric turbidity units) as measured at 0.1% concentration in water.

20. The method according to claim 16 , wherein the nanofibrillated cellulose has the zero shear viscosity of 5000 to 50000 Pa·s and yield stress of 8-40 Pa as measured at 0.5% concentration in water.

21. The method according to claim 16 , wherein the carboxylate content of the oxidized cellulose is 0.9-1.4 mmol COOH/g pulp.

22. The method according to claim 3 , wherein the pH is 8 to 9.5.

23. The method according to claim 3 , wherein the pH is 8.5 to 9.0.

24. The method according to claim 5 , wherein during the first step the pH is 7.5 to 8.5 and during the second step the pH is 2 to 3.

25. The method according to claim 10 , wherein the oxidation is performed to a level of 0.6-0.95 mmol COOH/g pulp.

26. The method according to claim 10 , wherein the oxidation is performed to a level of 0.7-0.9 mmol COOH/g pulp.

27. The method according to claim 11 , wherein the consistency of the pulp is above 6%.

28. The method according to claim 11 , wherein the consistency of the pulp is in the range of 8-12%.

29. The method according to claim 10 , wherein the oxidation treatment is stopped after it is performed in said conditions, and the oxidized cellulose is treated further by disintegrating fibrous material containing the oxidized cellulose to nanofibrillated cellulose.

30. The method according to claim 11 , wherein the oxidation treatment is stopped after it is performed in said conditions, and the oxidized cellulose is treated further by disintegrating fibrous material containing the oxidized cellulose to nanofibrillated cellulose.

31. The method according to claim 25 , wherein the oxidation treatment is stopped after it is performed in said conditions, and the oxidized cellulose is treated further by disintegrating fibrous material containing the oxidized cellulose to nanofibrillated cellulose.

32. The method according to claim 26 , wherein the oxidation treatment is stopped after it is performed in said conditions, and the oxidized cellulose is treated further by disintegrating fibrous material containing the oxidized cellulose to nanofibrillated cellulose.

33. The method according to claim 27 , wherein the oxidation treatment is stopped after it is performed in said conditions, and the oxidized cellulose is treated further by disintegrating fibrous material containing the oxidized cellulose to nanofibrillated cellulose.

34. The method according to claim 28 , wherein the oxidation treatment is stopped after it is performed in said conditions, and the oxidized cellulose is treated further by disintegrating fibrous material containing the oxidized cellulose to nanofibrillated cellulose.

35. The method according to claim 13 , wherein the second step is performed at pH of 2 to 3.

36. The method according to claim 13 , wherein protective substance capable of inactivating the hypochlorous acid formed is used in the second step.

37. The method according to claim 36 , wherein the protective substance is dimethyl sulfoxide (DMSO) or dimethyl sulfide (DMS).

38. The method according to claim 1 , wherein
the cellulose subjected to catalytic oxidation is cellulose in fibrous starting material, whereby oxidized fibrous material is obtained through the catalytic oxidation of cellulose, and
the oxidized fibrous material is disintegrated to nanofibrillated cellulose.

39. The method according to claim 2 , wherein
the cellulose subjected to catalytic oxidation is cellulose in fibrous starting material, whereby oxidized fibrous material is obtained through

Assignees

• Vuorinen Tapani
• Pääkkönen Timo
• Nuopponen Markus
• Upm Kymmene Corp

Inventors

• Vuorinen Tapani
• Pääkkönen Timo
• Nuopponen Markus

Classifications

• D21C9/002

  by chemical means; preparation of dewatered pulp, e.g. in sheet or bulk form, containing special additives · CPC title

• D21C9/007

  by mechanical or physical means · CPC title

• C08B15/04 Primary

  Carboxycellulose, e.g. prepared by oxidation with nitrogen dioxide · CPC title

• D21C3/003 Primary

  with organic compounds (D21C3/20 and D21C3/222 take precedence) · CPC title

• D21H11/20

  Chemically or biochemically modified fibres · CPC title