Method for preparing cellulose acetate fibers

• US 6,184,373 B1
• Filed: 09/03/1999
• Issued: 02/06/2001
• Est. Priority Date: 09/03/1999
• Status: Expired due to Fees

• Current Assignee: Eastman Chemical Company
• Original Assignee: Eastman Chemical Company
• Inventors: Bernard, Bobby Lynn, Davis, Max Ray
• Primary Examiner(s): Peselev, Elli
• Application Number:
  US09/389,732
• Time in Patent Office: 522 Days
• Field of Search: 264/138, 264/289.6, 264/290.5, 264/344, 536/58, 536/63, 536/65
• US Class Current: 536/58
• CPC Class Codes: C08B 3/20 Esterification with maintenance of the fibrous structure of the cellulose surface esterification of textiles D06M13/00
• CPC Class Codes: D01D 5/40 by applying a shearing force to a dispersion or solution of filament formable polymers, e.g. by stirring
• CPC Class Codes: D01F 2/28 from organic cellulose esters or ethers, e.g. cellulose acetate

Abstract

A method for producing an organic cellulose derivative fibrillated fiber includes the steps of mixing a cellulose ester containing stream and a coagulant stream in a first zone of relatively moderate turbulence to produce a slurry containing cellulose ester fibers, passing the slurry containing cellulose ester fibers to a second zone having relatively low turbulence for a sufficient time to increase the hardness of the cellulose ester fiber; and passing the cellulose derivative fibers through a third zone having relatively high shear to produce a fibrillated fiber having a diameter of about 0.5 to about 50 microns and a degree of fibrillation greater than about 6.

Claims

1. A method for producing an organic cellulose derivative fibrillated fiber comprising;

a. mixing a cellulose ester containing stream and a coagulant stream in a first zone of relatively moderate turbulence to produce a slurry containing cellulose ester fibers, wherein said first zone of moderate turbulence is produced by a centrifugal pump;

b. passing said slurry containing cellulose ester fibers to a second zone having relatively low turbulence for a sufficient time to increase the hardness of said cellulose ester fiber; and

c. passing said cellulose derivative fibers through a third zone having relatively high shear to produce a fibrillated fiber having a degree of fibrillation greater than about 6.

2. The method of claim 1 further comprising transferring said fibrillated fibers to a fourth zone having a relatively low turbulence for a period sufficient for the cellulose fiber to harden.

3. The method of claim 2 further comprising recovering said hardened fibrillated fiber.

4. The method of claim 1 wherein said cellulose ester containing stream is an acid dope from a hydrolysis step of a cellulose acetate process.

5. The method of claim 1 wherein said cellulose ester containing stream is a solvent dope.

6. The method of claim 1 wherein said cellulose ester containing stream includes from about 5 weight % to about 45 weight % of said cellulose ester, from about 95 weight % to about 55 weight % of an aliphatic acid and from about 35 to about 10 weight % water.

7. The method of claim 1 wherein the amount of coagulation stream mixed with said cellulose ester containing stream is greater than about 10:

1.

8. The method of claim 1 wherein the amount of coagulation stream mixed with said cellulose ester containing stream is from about 15:

1 to about 20;

1.

9. The method of claim 1 wherein said cellulose ester containing stream includes cellulose acetate.

10. The method of claim 1 wherein said coagulation stream comprises from about 25 to about 35 weight % of an aliphatic acid and about 75 weight % to about 65 weight % water.

11. The method of claim 10 wherein said cellulose ester is selected from the group consisting of cellulose acetate, cellulose butyrate, cellulose propionate, and mixtures thereof.

12. The method of claim 1 wherein said fibrillated fiber has less than about 5 % shives per sample analysis.

13. The method of claim 1 wherein said fibrillated fiber has a mean diameter of from about 0.5 to about 50 microns and a length of from about 0.1 to about 50 mm.

14. The method of claim 13 wherein said fibrillated fiber has a mean diameter of from about 2 to about 10 microns.

15. A method for producing a fibrillated cellulose acetate fiber comprising;

a. mixing a cellulose acetate acid dope stream and a coagulant stream in a first zone of relatively moderate turbulence to produce a slurry containing cellulose acetate fibers, wherein said first zone of moderate turbulence is produced by a centrifugal pump;

b. passing said slurry containing cellulose acetate fibers to a second zone having relatively low turbulence for a sufficient time to increase the hardness of said cellulose acetate fibers;

c. passing said cellulose acetate fibers through a third zone having relatively high shear to produce fibrillated fibers having a mean diameter of about 0.5 to about 20 microns and a degree of fibrillation greater than about 6; and

d. transferring said fibrillated fibers to a forth zone having a relatively low turbulence for a period sufficient for the cellulose acetate fiber to harden.

16. The method of claim 15 wherein said coagulation stream comprises from about 26 to about 36 weight % acetic acid and from about 74 weight % to about 64 weight % water.

17. The method of claim 15 wherein the amount of coagulation stream mixed with said cellulose acetate containing stream is greater than about 10:

1.

18. The method of claim 15 wherein the amount of coagulation stream mixed with said cellulose acetate containing stream is from about 15:

1 to about 20;

1.

19. The method of claim 15 wherein said fibrillated fiber has less than about 3 % shives per sample analysis.

20. A method for producing a fibrillated cellulose acetate fiber comprising;

a. mixing an acid dope stream from a hydrolysis step of a secondary cellulose acetate process and a coagulant stream in a first zone of relatively moderate turbulence to produce a slurry containing cellulose acetate fibers, wherein said first zone of moderate turbulence is produced by a centrifugal pump;

b. passing said slurry containing cellulose acetate fibers to a second zone having relatively low turbulence for a time of about 0.5 minutes to about 5 minutes to increase the hardness of said cellulose acetate fibers;

c. passing said cellulose acetate fibers through a third zone having relatively high shear to produce fibrillated fibers having a mean diameter of about 2 to about 10 microns, a degree of fibrillation greater than about 6 and less than about 5 % shives per sample analysis; and

d. transferring said fibrillated fibers to a forth zone having a relatively low turbulence for a time of about 5 minutes to about 60 minutes for the cellulose acetate fiber to harden.