Cellulose matrix encapsulation and method

• US 6,808,557 B2
• Filed: 03/21/2003
• Issued: 10/26/2004
• Est. Priority Date: 10/03/2001
• Status: Expired due to Fees

• Current Assignee: University of Alabama (University of Alabama System)
• Original Assignee: PG Research Foundation, University of Alabama (University of Alabama System)
• Inventors: Holbrey, John David, Spear, Scott K., Turner, Megan B., Swatloski, Richard Patrick, Rogers, Robin Don
• Primary Examiner(s): BRUNSMAN, DAVID M
• Application Number:
  US10/394,989
• Publication Number:
  US 20040038031A1
• Time in Patent Office: 585 Days
• Field of Search: 106/163.01, 106/200.2, 106/164.3, 106/501.1, 424/418, 424/493, 424/494, 71/23, 71/641.1, 71/641.3, 435/179, 435/650
• US Class Current: 106/163.01
• CPC Class Codes: A01N 25/10 Macromolecular compounds
• 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 16/00 Regeneration of cellulose
• CPC Class Codes: C08J 2301/02 Cellulose; Modified cellulose
• CPC Class Codes: C08J 3/096 Nitrogen containing compounds
• CPC Class Codes: C08J 3/205 in the presence of a continuous liquid phase
• CPC Class Codes: C08J 3/28 Treatment by wave energy or particle radiation
• CPC Class Codes: C08K 9/10 Encapsulated ingredients
• CPC Class Codes: C08L 1/02 Cellulose; Modified cellulose
• CPC Class Codes: C08L 1/06 Cellulose hydrate
• CPC Class Codes: C09D 101/02 Cellulose; Modified cellulose
• CPC Class Codes: C12N 11/12 Cellulose or derivatives thereof
• CPC Class Codes: Y10T 428/2989 Microcapsule with solid core [includes liposome]

Abstract

A regenerated cellulose-encapsulated active substance and a method for encapsulating an active substance in a regenerated cellulose matrix are disclosed. The distribution of the active substance is preferably substantially homogeneous within the matrix of regenerated cellulose. The regenerated cellulose (i) has about the same molecular weight as the original cellulose from which it is prepared (ii) is substantially free of added substituent groups relative to the starting cellulose and is also substantially free of entrapped ionic liquid degradation products.

Claims

1. A method for forming a regenerated cellulose-encapsulated active substance that comprises the steps of:

(a) providing a composition of cellulose dissolved in a molten hydrophilic ionic liquid solvent along with an active substance dissolved or dispersed substantially homogeneously therein, said solution being substantially free of water, organic solvent or nitrogen-containing base, wherein said ionic liquid is comprised of cations and anions;

(b) admixing said solution with a liquid non-solvent for said cellulose that is miscible with said ionic liquid, said active substance being substantially insoluble in said non-solvent, said admixing forming a regenerated cellulose solid phase and an ionic liquid phase, whereby said active substance is encapsulated and substantially homogeneously dispersed in the formed regenerated cellulose solid phase, and wherein said regenerated cellulose has substantially the same molecular weight as the cellulose of step (a) and is substantially free of ionic liquid degradation products.

2. The method according to claim 1 wherein said ionic liquid is molten at a temperature of less than about 150°

C.

3. The method according to claim 1 wherein the cations of said ionic liquid correspond in structure to a formula selected from the group consisting of

wherein R¹ and R² are independently a C₁-C₆ alkyl group or a C₁-C₆ alkoxyalkyl group, and R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ (R³-R⁹), when present, are independently a hydrido, a C₁-C₆ alkyl, a C₁-C₆ alkoxyalkyl group or a C₁-C₆ alkoxy group, and the anions of the ionic liquid are halogen, pseudohalogen, or C₁-C₆ carboxylate.

4. The method according to claim 1 wherein the anions of said ionic liquid are a halogen ion, perchlorate, a pseudohalogen ion or C₁-C₆ carboxylate.

5. The method according to claim 1 including the further step of collecting the formed cellulose phase.

6. A method for forming a regenerated cellulose-encapsulated active substance that comprises the steps of:

(a) providing a composition of cellulose dissolved in a molten hydrophilic ionic liquid solvent that is molten at a temperature of less than about 150°

C. along with an active substance dissolved or dispersed substantially homogeneously therein, said solution being substantially free of water, organic solvent, or nitrogen-containing base, wherein said ionic liquid is comprised of cations and anions, wherein the cations correspond in structure to a formula selected from the group consisting of

wherein R¹ and R² are independently a C₁-C₆ alkyl group or a C₁-C₆ alkoxyalkyl group, and R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ (R³-R⁹), when present, are independently a hydrido, a C₁-C₆ alkyl, a C₁-C₆ alkoxyalkyl group or a C₁-C₆ alkoxy group, and the anions of the ionic liquid are halogen, pseudohalogen, or C₁-C₆ carboxylate and the anions of said ionic liquid are halogen or pseudohalogen; and

(b) admixing said solution with a liquid non-solvent for said cellulose that is miscible with said ionic liquid, said active substance being substantially insoluble in said non-solvent, said admixing forming a regenerated cellulose solid phase and an ionic liquid phase, whereby said active substance is encapsulated and substantially homogeneously dispersed in the formed regenerated cellulose solid phase, and wherein said regenerated cellulose has substantially the same molecular weight as the cellulose of step (a) and is substantially free of ionic liquid degradation products; and

(c) collecting the formed regenerated cellulose solid phase.

7. The method according to claim 6 wherein said ionic liquid is molten at a temperature of about −

44°

to about 120°

C.

8. The method according to claim 6 wherein said liquid non-solvent for said cellulose that is miscible with said ionic liquid is also miscible with water.

9. The method according to claim 8 wherein said liquid non-solvent for said cellulose that is miscible with said ionic liquid and is also miscible with water is water, an alcohol, or a ketone.

10. The method according to claim 9 wherein said liquid non-solvent is water.

11. The method according to claim 6 wherein the cations correspond in structure to a formula selected from the group consisting of

wherein R¹ and R² are independently a C₁-C₆ alkyl group or a C₁-C₆ alkoxyalkyl group, and R³, R⁴, R⁵ (R³-R⁵) are independently a hydrido, a C₁-C₆ alkyl group, a C₁-C₆ alkoxyalkyl group or a C₁-C₆ alkoxy group and the anions of the ionic liquid are a halogen or pseudohalogen.

12. The method according to claim 11 wherein said cation is a N,N-1,3-di-C₁-C₆ alkyl imidazolium ion that corresponds in structure to Formula A

13. The method according to claim 12 wherein one of said N,N-1,3-di-C₁-C₆ alkyl groups is methyl.

14. The method according to claim 13 wherein R¹ is C₁-C₄-alkyl.

15. The method according to claim 14 wherein said R³-R⁵ groups are each hydrido.

16. The method according to claim 15 wherein said cations correspond in structure to Formula B.

17. The method according to claim 11 wherein said anions are chloride ions.

18. The method according to claim 6 wherein said cellulose is initially present in said solution in an amount of about 10 to about 25 weight percent.

19. The method according to claim 6 wherein said admixing step is carried out by extruding said cellulose solution through a die and into said non-solvent.

20. The method according to claim 6 wherein said active substance is selected from the group consisting of a microbial cell, herbicide, insecticide, fungicide, bactericide, repellent for an animal or insect, a plant growth regulator, fertilizer, a flavor or odor composition, catalyst, enzyme, photoactive agent, indicator, dye, and a UV adsorbent.

21. The method according to claim 6 wherein said active substance is coated with a hydrophobic ionic liquid prior to being dissolved or dispersed in said hydrophilic ionic liquid, and wherein said hydrophobic ionic liquid is not miscible with said liquid non-solvent diluent.

22. The method according to claim 21 wherein said hydrophobic ionic liquid is not soluble in said liquid non-solvent diluent.

23. A regenerated cellulose-encapsulated active substance that comprises an active substance substantially homogeneously distributed within a matrix of regenerated cellulose, wherein said regenerated cellulose (i) has about the same molecular weight as the original cellulose from which it is prepared, (ii) is substantially free of an increased amount of substituent groups relative to the starting cellulose, and is (iii) substantially free of entrapped ionic liquid degradation products.

24. The regenerated cellulose-encapsulated active substance according to claim 23 wherein the weight ratio of cellulose to active substance is about 1000:

1 to about 1;

2.

25. The regenerated cellulose-encapsulated active substance according to claim 23 wherein said active substance is selected from the group consisting of a microbial cell, herbicide, insecticide, fungicide, bactericide, repellent for an animal or insect, a plant growth regulator, fertilizer, a flavor or odor composition, catalyst, enzyme, photoactive agent, indicator, dye, and a UV absorbent.

26. The regenerated cellulose-encapsulated active substance according to claim 23 wherein said active substance is coated with a hydrophobic ionic liquid within said matrix of regenerated cellulose.

27. A regenerated cellulose-encapsulated active substance that comprises a hydrophobic ionic liquid-coated active substance substantially homogeneously distributed within a matrix of regenerated cellulose, wherein said regenerated cellulose (i) has about the same molecular weight as the original cellulose from which it is prepared, (ii) is substantially free of an increased amount of substituent groups relative to the starting cellulose, and is (iii) substantially free of entrapped ionic liquid degradation products.