Process of forming a non-woven cellulose web and a web produced by said process

• US 20090258562A1
• Filed: 04/11/2008
• Published: 10/15/2009
• Est. Priority Date: 04/11/2008
• Status: Active Grant

• Current Assignee: Reifenhauser GmbH & Co
• Original Assignee: Biax Fiberfilm
• Inventors: Granato, Carmen A. SR., Stark, Jeffrey D., Zacharias, Duane K., Brown, Douglas B.
• Granted Patent: US 8,303,888 B2
• Time in Patent Office: Days
• US Class Current: 442/411
• CPC Class Codes: B29C 48/05 Filamentary, e.g. strands
• CPC Class Codes: B29C 48/345 Extrusion nozzles comprising two or more adjacently arranged ports, for simultaneously extruding multiple strands, e.g. for pelletising
• CPC Class Codes: B29C 48/693 Substantially flat filters mounted at the end of an extruder screw perpendicular to the feed axis
• CPC Class Codes: B29K 2001/00 Use of cellulose, modified cellulose or cellulose derivatives, e.g. viscose, as moulding material
• CPC Class Codes: B29K 2105/08 of continuous length, e.g. cords, rovings, mats, fabrics, strands or yarns
• CPC Class Codes: D01D 4/025 Melt-blowing or solution-blowing dies
• CPC Class Codes: D01D 5/02 Starting the formation
• CPC Class Codes: D01D 5/14 with flowing liquid or gaseous stretching media , e.g. solution-blowing
• CPC Class Codes: D01F 2/00 Monocomponent artificial filaments or the like of cellulose or cellulose derivatives; Manufacture thereof
• CPC Class Codes: D04H 1/56 in association with fibre formation, e.g. immediately following extrusion of staple fibres
• CPC Class Codes: Y10T 442/69 Autogenously bonded nonwoven fabric
• CPC Class Codes: Y10T 442/692 Containing at least two chemically different strand or fiber materials

Abstract

A process is disclosed of forming cellulose fibers. The process includes extruding an aqueous solution of cellulose and a solvent through a first member to form molten filaments. The first member has multiple rows of first and second openings with a nozzle positioned in each of the first openings. At least one of the nozzles in one row is staggered from at least one of the nozzles in an adjacent row. At least a portion of each of the molten filaments is shrouded in a pressurized gas emitted through each of the first openings. Each of the molten filaments is contacted with a liquid to remove some of the solvent and transform each of the molten filaments into a continuous solid fiber. The continuous solid fibers are then collected on a moving surface to form a non-woven cellulose web.

Claims

1. A process of forming a non-woven cellulose web, comprising the steps of:

a) forming an aqueous solution of cellulose and a solvent;

b) directing said aqueous solution through a first member having multiple rows of first and second openings, each of said first openings having a nozzle positioned therein, and at least one of said nozzles in a row being staggered from at least one of said nozzles in an adjacent row;

c) extruding said aqueous solution through each of said nozzles to form multiple molten filaments;

d) shrouding at least a portion of each of said molten filaments in a pressurized gas emitted through each of said adjacently aligned first and second openings;

e) attenuating said molten filaments into a circular cross-sectional configuration having a diameter of less than about 15 microns;

f) contacting said molten filaments with a liquid, said liquid mixing with said solvent to remove some of said solvent whereby each of said molten filaments is transformed into a continuous solid fiber; and

g) collecting said continuous solid fibers on a moving surface to form a non-woven cellulose web.

2. The process of claim 1 further comprising heating said aqueous solution to a temperature of from between about 80°

C. to about 140°

C. and heating said pressurized gas to a temperature of at least about 120°

C.

3. The process of claim 1 further comprising extruding said aqueous solution through each of said nozzles at a throughput of greater than 0.1 grams/hole/minute.

4. The process of claim 1 further comprising extruding said aqueous solution through each of said nozzles at a throughput of greater than 0.5 grams/hole/minute.

5. The process of claim 1 further comprising emitting said pressurized gas through each of said first openings at a velocity of at least 45 meters per second and each of said first openings includes at least two crescent shaped slots.

6. The process of claim 1 further comprising emitting said pressurized gas through each of said second openings at a velocity of at least 45 meters per second.

7. The process of claim 1 wherein said pressurized gas is pressurized air which is emitted from each of said first openings essentially parallel to said molten filament extruded through each of said nozzles, and said pressurized air accelerates and attenuates each of said molten filaments.

8. The process of claim 7 further comprising contacting each of said molten filaments with a liquid which causes said molten filaments to coagulate into a continuous solid fiber.

9. The process of claim 8 wherein said liquid is water, and each of said molten filaments is contacted with said water at a distance of at least about 3 centimeters from each of said nozzle.

16. A non-woven cellulose web produced by the process of claim 1 wherein said web is an entangled accumulation of coagulated cellulose fibers.

17. The non-woven cellulose web of claim 16 wherein said web contains essentially no solvent.

18. The non-woven cellulose web of claim 16 wherein said web is formed of cellulose and polymer fibers.

19. The process of claim 1 further comprising starting up said process by:

a) heating said aqueous solution to a predetermined temperature above 80°

C.;

b) directing said heated aqueous solution to said first member and extruding said heated aqueous solution through each of said nozzles at a back pressure of at least 10 bar;

c) routing said pressurized gas through each of said first and second openings at a velocity of from between about 1 meter per second to about 10 meters per second;

d) heating said pressurized gas to a temperature of about 100°

C.; and

e) gradually increasing said velocity of said heated pressurized gas until said pressurized gas reaches a velocity of at least about 45 meters per second.

20. The process of claim 1 further comprising shutting down said process by:

a) turning off said heat used to heat said pressurized gas;

b) gradually reducing said velocity of said pressurized gas to 0 meters per second;

c) stopping said aqueous solution from flowing through each of said nozzles; and

d) allowing said aqueous solution to cool to room temperature.

10. A process of forming a non-woven cellulose web, comprising the steps of:

a) forming an aqueous solution of cellulose and a solvent, said aqueous solution having a temperature of at least about 100°

C.;

b) directing said aqueous solution through a first member having multiple rows of first and second openings, each of said first openings having a nozzle positioned therein, and at least one of said nozzles in a row being staggered from at least one of said nozzles in an adjacent row;

c) extruding said aqueous solution through each of said nozzles at a back pressure of at least 10 bar to form multiple molten filaments;

d) shrouding at least a portion of each of said molten filaments in a pressurized gas emitted through each of said adjacently aligned first and second openings;

e) attenuating said molten filaments into a circular cross-sectional configuration having a diameter of less than about 5 microns;

f) contacting said molten filaments with a liquid, said liquid mixes with said solvent to remove some of said solvent whereby each of said molten filaments is transformed into a continuous solid fiber; and

g) collecting said continuous solid fibers on a moving surface to form a non-woven cellulose web.

11. The process of claim 10 wherein said pressurized gas emitted from each of said second openings prevents each of said molten filaments from physically contacting one another.

12. The process of claim 10 further comprising extruding said aqueous solution downward from each of said nozzles parallel to a longitudinal central axis and contacting each of said molten filaments with water introduced at an angle of from between about 5 degrees to about 175 degrees, said water causing each of said molten filaments to coagulate into a continuous solid fiber.

13. The process of claim 10 further comprising heating said pressurized gas to a temperature from between about 120°

C. to about 160°

C.

14. The process of claim 10 wherein said moving surface is a rotatable drum having a porous surface.

15. The process of claim 10 wherein said moving surface is a conveyor belt having a porous surface.