Monocomponent Monolayer Meltblown Web And Meltblowing Apparatus

• US 20080026659A1
• Filed: 07/31/2006
• Published: 01/31/2008
• Est. Priority Date: 07/31/2006
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Lindquist, Timothy J., Angadjivand, Seyed A., Springett, James E., Kopecky, William J., Brandner, John M.
• Granted Patent: US 7,902,096 B2
• Time in Patent Office: Days
• US Class Current: 442/327
• CPC Class Codes: B01D 2239/064 The fibres being mixed
• CPC Class Codes: B01D 39/1623 of synthetic origin
• CPC Class Codes: D01D 5/082 of mixed yarn
• CPC Class Codes: D01D 5/0985 by means of a flowing gas (e.g. melt-blowing)
• CPC Class Codes: D01F 6/06 from polypropylene
• CPC Class Codes: D04H 1/56 in association with fibre formation, e.g. immediately following extrusion of staple fibres
• CPC Class Codes: D04H 3/02 characterised by the method of forming fleeces or layers, e.g. reorientation of yarns or filaments
• CPC Class Codes: Y10T 442/60 Nonwoven fabric [i.e., nonwoven strand or fiber material]
• CPC Class Codes: Y10T 442/608 Including strand or fiber material which is of specific structural definition
• CPC Class Codes: Y10T 442/614 Strand or fiber material specified as having microdimensions [i.e., microfiber]
• CPC Class Codes: Y10T 442/619 Including other strand or fiber material in the same layer not specified as having microdimensions
• CPC Class Codes: Y10T 442/68 Melt-blown nonwoven fabric
• CPC Class Codes: Y10T 442/681 Spun-bonded nonwoven fabric

Abstract

A porous monocomponent nonwoven web contains a bimodal mass fraction/fiber size mixture of intermingled continuous microfibers and larger size fibers of the same polymeric composition. There are at least five times as many microfibers as larger size fibers, and a histogram of the mass fraction of fibers vs. fiber size exhibits a larger size fiber mode greater than 10 μm. The web may be made by flowing fiber-forming material through a die cavity having larger size orifices and at least five times as many smaller size orifices to form filaments, attenuating the filaments into fibers and collecting the attenuated fibers to form the nonwoven web. The web is especially well suited to the manufacture of self-supporting three dimensional articles such as molded cup-shaped respirators and pleated air filters.

Claims

1. A porous monocomponent nonwoven web containing a meltblown bimodal fiber count/fiber size mixture of intermingled continuous microfibers and larger size fibers of the same polymeric composition, wherein there are at least five times as many microfibers as larger size fibers and wherein a histogram of the mass fraction of fibers vs. fiber size exhibits a larger size fiber mode greater than 10 μ

m.

2. A nonwoven web according to claim 1 wherein there are at least 6 times as many microfibers as larger size fibers.

3. A nonwoven web according to claim 1 wherein there are at least 10 times as many microfibers as larger size fibers.

4. A nonwoven web according to claim 1 wherein the histogram of mass fraction vs. fiber size in μ

m exhibits a larger size fiber mode of about 10 to about 50 μ

m.

5. A nonwoven web according to claim 1 wherein the histogram of mass fraction vs. fiber size in μ

m exhibits a larger size fiber mode of about 10 to about 40 μ

m.

6. A nonwoven web according to claim 1 wherein the histogram of mass fraction vs. fiber size in μ

m exhibits a microfiber mode of about 1 to about 5 μ

m and a larger size fiber mode of about 12 to about 30 μ

m.

7. A nonwoven web according to claim 1 wherein a histogram of fiber count (frequency) vs. fiber size in μ

m exhibits at least two modes whose corresponding fiber sizes differ by at least 50% of the smaller fiber size.

8. A nonwoven web according to claim 1 wherein a histogram of fiber count (frequency) vs. fiber size in μ

m exhibits at least two modes whose corresponding fiber sizes differ by at least 100% of the smaller fiber size.

9. A nonwoven web according to claim 1 wherein the microfibers have a size of about 0.1 to about 10 μ

m and the larger size fibers have a size of about 10 to about 70 μ

m.

10. A nonwoven web according to claim 1 wherein the microfibers provide at least 20% of the fibrous surface area of the web.

11. A nonwoven web according to claim 1 wherein the microfibers provide at least 40% of the fibrous surface area of the web.

12. A nonwoven web according to claim 1 having a basis weight of about 80 to about 250 gsm.

13. A nonwoven web according to claim 1 which exhibits less than 5% maximum penetration when exposed to a 0.075 μ

m sodium chloride aerosol flowing at a 13.8 cm/sec face velocity.

14. A nonwoven web according to claim 1 wherein the polymer is polypropylene.

15. A process for forming a monocomponent nonwoven web comprising flowing fiber-forming material through a die cavity having larger size orifices and at least five times as many smaller size orifices to form filaments, using air or other fluid to attenuate the filaments into fibers and collecting the attenuated fibers as a nonwoven web containing a meltblown bimodal mass fraction/fiber size mixture of intermingled continuous microfibers and larger size fibers of the same polymeric composition, wherein there are at least five times as many microfibers as larger size fibers and wherein a histogram of the mass fraction of fibers vs. fiber size exhibits a larger size fiber mode greater than 10 μ

m.

16. A process according to claim 15 comprising flowing fiber-forming material through a die cavity having at least six times as many smaller size orifices as larger size orifices.

17. A process according to claim 15 comprising flowing fiber-forming material through a die cavity having at least ten times as many smaller size orifices as larger size orifices.

18. A process according to claim 15 comprising flowing fiber-forming material through a die cavity having at least twenty times as many smaller size orifices as larger size orifices.

19. A process according to claim 15 wherein the ratio of larger:

smaller orifice sizes is 2;

1 or more.

20. A process according to claim 15 wherein the ratio of larger:

smaller orifice sizes is 3;

1 or more.

21. A process according to claim 15 wherein the histogram of mass fraction vs. fiber size in μ

m exhibits a larger size fiber mode of about 10 to about 50 μ

m.

22. A process according to claim 15 wherein the histogram of mass fraction vs. fiber size in μ

m exhibits a larger size fiber mode of about 10 to about 40 μ

m.

23. A process according to claim 15 wherein the histogram of mass fraction vs. fiber size in μ

m exhibits a microfiber mode of about 1 to about 5 μ

m and a larger size fiber mode of about 12 to about 30 μ

m.

24. A process according to claim 15 wherein a histogram of fiber count (frequency) vs. fiber size in μ

m exhibits at least two modes whose corresponding fiber sizes differ by at least 50% of the smaller fiber size.

25. A process according to claim 15 comprising collecting a web containing microfibers having a size of about 0.1 to about 10 μ

m and larger size fibers having a size of about 10 to about 70 μ

m.

26. A process according to claim 15 comprising collecting a web containing microfibers having a size of about 0.1 to about 5 μ

m and larger size fibers having a size of about 15 to about 50 μ

m.

27. A process according to claim 15 wherein the microfibers provide at least 20% of the fibrous surface area of the web.

28. A process according to claim 15 wherein the microfibers provide at least 40% of the fibrous surface area of the web.

29. A process according to claim 15 comprising collecting a web having a basis weight of about 80 to about 250 gsm.

30. A process according to claim 15 wherein the fiber-forming material is polypropylene.

31. A process according to claim 15 further comprising charging the web.

32. A process according to claim 31 comprising hydrocharging the web.

33. A process according to claim 31 comprising corona charging and hydrocharging the web.

34. A process according to claim 31 comprising plasma treating and hydrocharging the web.