NONWOVEN WEB WITH BIMODAL FIBER DISTRIBUTION
A nonwoven web comprising a layer of polymeric fibers, wherein, based on the total number of polymeric fibers, at least 10% the polymeric fibers in said layer are coarse fibers having a fiber diameter of 4 μm or more, and at least 10% of the polymeric fibers in said layer are fine fibers having a fiber diameter of 2 μm or less. Also described herein is a method for making the nonwoven web, comprising melt-blowing a polymer mixture comprising two immiscible or partially miscible polymers.
1 . A nonwoven web comprising a layer of polymeric fibers, wherein, based on a total number of polymeric fibers, at least 25% of the polymeric fibers in said layer are coarse fibers having a fiber diameter of 4 μm or more, and at least 25% of the polymeric fibers in said layer are fine fibers having a fiber diameter of 2 μm or less, and wherein the polymeric fibers in said layer have a bimodal distribution of their fiber diameters, comprising a first peak at a first fiber diameter of 2μm or less, a second peak at a second fiber diameter of 4 μm or more, and a trough at a third fiber diameter between the first fiber diameter and the second fiber diameter, wherein 10% or less of the polymeric fibers have a fiber diameter within ±0.5 μm of the third fiber diameter, based on the total number of polymeric fibers.
2 . (canceled)
3 . The nonwoven web of claim 1 , wherein at least 25% polymeric fibers in said layer are coarse fibers having a fiber diameter of 5 μm or more, based on the total number of polymeric fibers.
4 . (canceled)
5 . The nonwoven web of claim 1 , wherein at least 25% polymeric fibers in said layer are fine fibers having a fiber diameter of 1 μm or less, based on the total number of polymeric fibers.
6 . The nonwoven web of claim 1 , wherein the polymeric fibers in said layer have a bimodal distribution of their fiber diameters, based on the total number of polymeric fibers.
7 . The nonwoven web of claim 1 , wherein the polymeric fibers in said layer have a bimodal distribution of their fiber diameters, comprising a first peak at a first fiber diameter of 2 μm or less and a second peak at a second fiber diameter of 4 μm or more.
8 . (canceled)
9 . The nonwoven web of claim 1 , wherein the polymeric fibers in said layer have a bimodal distribution of their fiber mean, comprising a first peak at a first fiber diameter of 2 μm or less, a second peak at a second fiber diameter of 4 μm or more, and a trough at a third fiber diameter between the first fiber diameter and the second fiber diameter, wherein 5% or less of the polymeric fibers have a fiber diameter within ±0.5 μm of the third fiber diameter, based on the total number of polymeric fibers.
10 . The nonwoven web of claim 1 , wherein the polymeric fibers in said layer are melt-blown fibers.
11 . The nonwoven web of claim 1 , wherein the polymeric fibers in said layer comprises 0.5-10 wt. % liquid crystalline polymer.
12 . The nonwoven web of claim 1 , wherein the polymeric fibers in said layer comprises polybutylene terephthalate.
13 . The nonwoven web of claim 1 , wherein the nonwoven web has an air permeability of 20 cfm or more.
14 . The nonwoven web of claim 1 , wherein the nonwoven web has an air permeability of 40 cfm or more.
15 . The nonwoven web of claim 1 , wherein the nonwoven web has a filtration ratio of 40% or more at particle size of 10 μm.
16 . The nonwoven web of claim 1 , wherein the nonwoven web has a filtration ratio of 60% or more at particle size of 10 μm.
17 . The nonwoven web of claim 1 , wherein the nonwoven web has a filtration capacity of 50 mg/in 2 or more.
18 . The nonwoven web of claim 1 , wherein the nonwoven web has a filtration capacity of 130 mg/in 2 or more.
19 . A method for making the nonwoven web of claim 1 , comprising melt-blowing a polymer mixture comprising at least two immiscible or partially miscible polymers.
20 . The method of claim 19 , wherein the polymer mixture is obtained by compounding the two immiscible or partially miscible polymers.
21 . The method of claim 19 , wherein the polymer mixture is obtained by physically blending the two immiscible or partially miscible polymers.
22 . The method of claim 19 , wherein the polymer mixture comprises (a) 0.5-30 wt. % liquid crystalline polymer and (b) polybutylene terephthalate.
23 . A nonwoven web comprising a layer of polymeric fibers, wherein, based on a total number of polymeric fibers, at least 25% of the polymeric fibers in said layer are coarse fibers having a fiber diameter of 3 μm or more, and at least 25% of the polymeric fibers in said layer are fine fibers having a fiber diameter of 1 μm or less, and wherein the polymeric fibers in said layer have a bimodal distribution of their fiber diameters, comprising a first peak at a first fiber diameter of 1 82 m or less, a second peak at a second fiber diameter of 3 or more, and a trough at a third fiber diameter between the first fiber diameter and the second fiber diameter, wherein 10% or less of the polymeric fibers have a fiber diameter within ±0.5 μm of the third fiber diameter, based on the total number of polymeric fibers.
24 . (canceled)
25 . (canceled)
26 . A nonwoven web comprising a layer of polymeric fibers, wherein, based on the total number of polymeric fibers, at least 25% of the polymeric fibers in said layer are coarse fibers having a fiber diameter of 5 μm or more, and at least 25% of the polymeric fibers in said layer are fine fibers having a fiber diameter of 3 μm or less, and wherein the polymeric fibers in said layer have a bimodal distribution of their fiber diameters, comprising a first peak at a first fiber diameter of 3 μm or less, a second peak at a second fiber diameter of 5 μm or more, and a trough at a third fiber diameter between the first fiber diameter and the second fiber diameter, wherein 10% or less of the polymeric fibers have a fiber diameter within ±0.5 μm of the third fiber diameter, based on the total number of polymeric fibers.
27 . (canceled)
28 . (canceled)
29 . The nonwoven web of claim 1 , wherein said layer of polymeric fibers is obtained by a method comprising melt-blowing a polymer mixture comprising (a) 0.5-30 wt. % liquid crystalline polymer and (b) polybutylene terephthalate.