TREATMENT OF CELLULOSE ESTERS

• US 20090203899A1
• Filed: 08/11/2008
• Published: 08/13/2009
• Est. Priority Date: 02/13/2008
• Status: Active Grant

• Current Assignee: Eastman Chemical Company
• Original Assignee: Eastman Chemical Company
• Inventors: Buchanan, Charles Michael, Buchanan, Norma Lindsey
• Granted Patent: US 8,188,267 B2
• Time in Patent Office: Days
• US Class Current: 536/58
• CPC Class Codes: C08B 1/003 Preparation of cellulose solutions, i.e. dopes, with different possible solvents, e.g. ionic liquids solutions used in the manufacture of monocomponent artificial filaments or cellulose or derivatives thereof D01F2/02
• CPC Class Codes: C08B 3/16 Preparation of mixed organic cellulose esters , e.g. cellulose aceto-formate or cellulose aceto-propionate
• CPC Class Codes: C08B 3/18 Aceto-butyrates
• CPC Class Codes: C08B 3/22 Post-esterification treatments, including purification
• CPC Class Codes: C08B 3/24 Hydrolysis or ripening

Abstract

Ionic liquids and cellulose ester compositions and processes for producing ionic liquids and cellulose esters. Cellulose esters can be produced by esterifying cellulose in a reaction medium comprising one or more ionic liquids. Cellulose esters prepared via the methods of the present invention can be contacted with at least one bleaching agent to produce bleached cellulose esters having a ΔE value of less than 30.

Claims

1. A cellulose ester comprising the following characteristics:

(i) a degree of substitution (“

DS”

) in the range of from about 0.1 to about 3.0;

(ii) a degree of polymerization (“

DP”

) in the range of from about 5 to about 1,000; and

(iii) a Δ

E value of less than 30,

wherein said cellulose ester is non-random.

2. The cellulose ester of claim 1, wherein said cellulose ester has a Δ

E value of less than 15.

3. The cellulose ester of claim 1, wherein said cellulose ester has an L* value of at least 90.

4. The cellulose ester of claim 1, wherein said cellulose ester has an L* value of at least 98.

5. The cellulose ester of claim 1, wherein said cellulose ester has a b* value in the range of from about −

12 to about 12.

6. The cellulose ester of claim 1, wherein said cellulose ester has a b* value in the range of from about −

6 to about 6.

7. The cellulose ester of claim 1, wherein said cellulose ester has an a* value in the range of from about −

5 to about 5.

8. The cellulose ester of claim 1, wherein said cellulose ester has an a* value in the range of from about −

2 to about 2.

9. The cellulose ester of claim 1, wherein said cellulose ester has a DS in the range of from about 2.0 to about 2.6.

10. The cellulose ester of claim 1, wherein said cellulose ester has a DP in the range of from about 10 to about 250.

11. The cellulose ester of claim 1, wherein said cellulose ester has a number average molecular weight (Mn) in the range of from about 1,200 to about 200,000, wherein said cellulose ester has a weight average molecular weight (Mw) in the range of from about 2,500 to about 420,000, wherein said cellulose ester has a Z average molecular weight (Mz) in the range of from about 4,000 to about 850,000.

12. The cellulose ester of claim 1, wherein said cellulose ester has a polydispersity (Mw/Mn) in the range of from about 1.3 to about 7.

13. The cellulose ester of claim 1, wherein said cellulose ester is a mixed cellulose ester comprising at least two different pendant acyl groups, wherein said two different pendant acyl groups are each individually selected from the group consisting of an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, a valeryl group, a hexanoyl group, a 2-ethylhexanoyl group, a nonanoyl group, a lauroyl group, a palmitoyl group, a benzoyl group, a substituted benzoyl group, a phthalyl group, an isophthalyl group, and a stearoyl group.

14. A process for making cellulose esters, said process comprising:

(a) subjecting a reaction medium comprising cellulose and an ionic liquid to esterification to thereby produce an initial cellulose ester having a first Δ

E value; and

(b) contacting at least a portion of said initial cellulose ester with at least one bleaching agent to thereby produce a bleached cellulose ester having a second Δ

E value, wherein said second Δ

E value is at least 5 percent less than said first Δ

E value.

15. The process of claim 14, wherein said bleached cellulose ester has a Δ

E value of less than 30.

16. The process of claim 14, wherein said bleached cellulose ester has a Δ

E value of less than 15.

17. The process of claim 14, wherein said bleached cellulose ester has an L* value of at least 90.

18. The process of claim 14, wherein said bleached cellulose ester has a b* value in the range of from about −

12 to about 12.

19. The process of claim 14, wherein said bleached cellulose ester has an a* value in the range of from about −

5 to about 5.

20. The process of claim 14, wherein said bleached cellulose ester is at least partially dissolved in said ionic liquid during said contacting of step (b).

21. The process of claim 14, wherein said bleaching agent is selected from the group consisting of chlorites, hypohalites, peroxides, peracids, permanganates, metals, sodium sulfites, perborates, chlorine dioxide, oxygen, and ozone.

22. The process of claim 14, wherein said bleaching agent is selected from the group consisting of hydrogen peroxide, sodium hypochlorite, sodium chlorite, sodium sulfite, and potassium permanganate.

23. The process of claim 14, further comprising, prior to said contacting of step (b), separating at least a portion of said initial cellulose ester from said ionic liquid and thereafter contacting at least a portion of the resulting separated cellulose ester with at least one bleaching agent to thereby produce said bleached cellulose ester.

24. The process of claim 14, wherein, during said contacting, said bleaching agent is a component in a wash liquid that further comprises at least one non-solvent washing agent.

25. The process of claim 24, wherein said wash liquid comprises said bleaching agent in an amount in the range of from about 0.01 to about 5 weight percent.

26. The process of claim 24, wherein said non-solvent washing agent comprises at least one alcohol and/or water.

27. The process of claim 24, wherein said contacting comprises washing at least a portion of said cellulose ester with said wash liquid.

28. The process of claim 14, wherein said ionic liquid comprises a halide ionic liquid.

29. The process of claim 28, wherein said halide ionic liquid comprises a plurality of cations and a plurality of anions, wherein at least a portion of the cations of said halide ionic liquid comprise imidazolium, pyrazolium, oxazolium, 1,2,4-triazolium, 1,2,3-triazolium, and/or thiazolium cations, wherein at least a portion of the anions of said halide ionic liquid are selected from the group consisting of chloride, bromide, iodide, fluoride, and mixtures of two of more thereof.

30. The process of claim 14, wherein said ionic liquid comprises a carboxylated ionic liquid.

31. The process of claim 30, wherein said carboxylated ionic liquid comprises a plurality of cations selected from the group consisting of imidazolium, pyrazolium, oxazolium, triazolium, thiazolium, and mixtures thereof, wherein said carboxylated ionic liquid comprises a plurality of anions comprising one or more C₁ to C₂₀ carboxylate or substituted carboxylate anions.

32. A process for making cellulose esters, said process comprising:

(a) dissolving a cellulose in at least one ionic liquid to thereby form an initial cellulose solution;

(b) contacting said initial cellulose solution with at least one acylating reagent under conditions sufficient to provide an acylated cellulose solution comprising a cellulose ester;

(c) contacting at least a portion of said acylated cellulose solution with a bleaching agent to thereby produce a bleached cellulose ester solution comprising a bleached cellulose ester; and

(d) separating at least a portion of said bleached cellulose ester from said bleached cellulose ester solution.

33. The process of claim 32, wherein said bleached cellulose ester has a Δ

E value of less than 30.

34. The process of claim 32, wherein said bleached cellulose ester has an L* value of at least 90.

35. The process of claim 32, wherein said bleached cellulose ester has a b* value in the range of from about −

12 to about 12.

36. The process of claim 32, wherein said bleached cellulose ester has an a* value in the range of from about −

5 to about 5.

37. The process of claim 32, wherein said bleaching agent is present in an amount in the range of from about 0.001 to about 2 weight percent based on the weight of said acylated cellulose solution.

38. The process of claim 32, wherein said bleaching agent comprises one or more metals.

39. The process of claim 32, wherein said bleaching agent comprises one or more manganates and/or permanganates.

40. The process of claim 32, wherein prior to said contacting said bleaching agent is dispersed in methanol and/or water in an amount in the range of from about 0.0001 to about 5 weight percent.

41. The process of claim 32, wherein said ionic liquid is a halide ionic liquid, wherein said halide ionic liquid comprises a plurality of cations and a plurality of anions, wherein at least a portion of the cations of said halide ionic liquid comprise imidazolium, pyrazolium, oxazolium, 1,2,4-triazolium, 1,2,3-triazolium, and/or thiazolium cations, wherein at least a portion of the anions of said halide ionic liquid are selected from the group consisting of chloride, bromide, iodide, fluoride, and mixtures of two of more thereof.

42. The process of claim 32, wherein said ionic liquid is selected from the group consisting of 1-butyl-3-methylimidazolium chloride, 1-propyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium chloride, 1-allyl-3-methylimidazolium chloride, or mixtures thereof.

43. The process of claim 32, wherein at least a portion of said acylating reagent is present during said dissolving of step (a).

44. A process for making cellulose esters, said process comprising:

(a) dissolving a cellulose in at least one ionic liquid to thereby form an initial cellulose solution;

(b) contacting said initial cellulose solution with at least one acylating reagent under conditions sufficient to provide an acylated cellulose solution comprising a cellulose ester;

(c) separating at least a portion of said cellulose ester from said acylated cellulose solution; and

(d) washing at least a portion of said cellulose ester with a wash liquid comprising at least one non-solvent washing agent and at least one bleaching agent to thereby produce a bleached cellulose ester.

45. The process of claim 44, wherein said bleached cellulose ester has a Δ

E value of less than 30.

46. The process of claim 44, wherein said bleached cellulose ester has an L* value of at least 90.

47. The process of claim 44, wherein said bleached cellulose ester has a b* value in the range of from about −

12 to about 12.

48. The process of claim 44, wherein said bleached cellulose ester has an a* value in the range of from about −

5 to about 5.

49. The process of claim 44, wherein said wash liquid comprises said bleaching agent in an amount in the range of from about 0.001 to about 50 weight percent.

50. The process of claim 44, wherein said bleaching agent is selected from the group consisting of chlorites, hypohalites, peroxides, peracids, metals, sodium sulfites, perborates, chlorine dioxide, oxygen, and ozone.

51. The process of claim 44, wherein said bleaching agent is selected from the group consisting of hydrogen peroxide, sodium hypochlorite, sodium chlorite and sodium sulfite.

52. The process of claim 44, wherein said non-solvent washing agent comprises at least one alcohol and/or water.

53. The process of claim 44, wherein said washing comprises counter-current washing comprising at least two stages.

54. The process of claim 44, wherein said ionic liquid comprises a carboxylated ionic liquid.

55. The process of claim 54, wherein said carboxylated ionic liquid comprises a plurality of cations selected from the group consisting of imidazolium, pyrazolium, oxazolium, triazolium, thiazolium, and mixtures thereof, wherein said carboxylated ionic liquid comprises a plurality of anions comprising one or more C₁ to C₂₀ carboxylate or substituted carboxylate anions.

56. The process of claim 44, wherein said reaction medium further comprises at least one acylating reagent.