Spunbond filters with low pressure drop and high efficiency

Abstract

Disclosed are methods of partially or fully fibrillating bicomponent filaments of the island-in-the-sea configuration by hydroentangling. The hydroentangling energy can both fibrillate the sea component as well as entangling the sea and island components for bonding. Fabrics that are made from these at least partially fibrillated and bonded fibers are also disclosed. These fabrics have low pressure drop and high efficiency and can be used for filters and masks.

What is claimed is: 
     
         1 . A method for producing a nonwoven fabric, comprising:
 providing a bicomponent filament having an external fiber component and an internal fiber component; wherein the external fiber component at least partially enwraps the internal fiber component; and wherein the external fiber component is 5% to 25 wt. % of the filament; and   partially fibrillating the filament by hydroentangling with at least three manifolds, each manifold having a plurality of water jets, and wherein at least two of the manifolds have water jets at least 1200 microns apart.   
     
     
         2 . The method of  claim 1 , wherein there are at least three manifolds with water jets at least 1200 microns apart. 
     
     
         3 . The method of  claim 1 , wherein there are at least four manifolds with water jets at least 1200 microns apart. 
     
     
         4 . The method of  claim 1 , wherein there are at least five manifolds with water jets at least 1200 microns apart. 
     
     
         5 . The method of  claim 1 , wherein there are at least six manifolds. 
     
     
         6 . The method of  claim 1 , wherein at least two manifolds have waters jets at least 2400 microns apart, and at least two manifolds with water jets at least 1200 microns apart. 
     
     
         7 . The method of  claim 1 , wherein hydroentangling exposes the nonwoven fabric to water pressure from one or more hydroentangling manifolds at a water pressure from 10 bars to 300 bars. 
     
     
         8 . The method of  claim 1 , wherein the fabric comprises a first surface and a second surface, and wherein the first surface is hydroentangled. 
     
     
         9 . The method of  claim 8 , wherein the second surface is hydroentangled. 
     
     
         10 . The method of  claim 1 , further comprising pressing the web in an unheated set of rollers. 
     
     
         11 . The method of  claim 1 , wherein the internal fiber component comprises a thermoplastic polymer. 
     
     
         12 . The method of  claim 11 , wherein the thermoplastic polymer is a copolyetherester elastomer with long chain ether ester units and short chain ester units joined head to tail through ester linkages. 
     
     
         13 . The method of  claim 11 , wherein the thermoplastic polymer is selected from nylon 6, nylon 6/6, nylon 6,6/6, nylon 6/10, nylon 6/11, nylon 6/12, nylon 11, nylon 12, polypropylene or polyethylene. 
     
     
         14 . The method of  claim 11 , wherein the thermoplastic polymer is selected from polyesters, polyamides, thermoplastic copolyetherester elastomers, polyolefins, polyacrylates, PHA, PHB, PBS, PLA, and thermoplastic liquid crystalline polymers. 
     
     
         15 . The method of  claim 1 , wherein the external fiber component comprises a thermoplastic polymer. 
     
     
         16 . The method of  claim 15 , wherein the thermoplastic polymer is a copolyetherester elastomer with long chain ether ester units and short chain ester units joined head to tail through ester linkages. 
     
     
         17 . The method of  claim 15 , wherein the thermoplastic polymer is selected from nylon 6, nylon 6/6, nylon 6,6/6, nylon 6/10, nylon 6/11, nylon 6/12, nylon 11, nylon 12, polypropylene or polyethylene. 
     
     
         18 . The method of  claim 15 , wherein the thermoplastic polymer is selected from polyesters, polyamides, thermoplastic copolyetherester elastomers, polyolefins, polyacrylates, PHA, PHB, PBS, PLA, and thermoplastic liquid crystalline polymers. 
     
     
         19 . The method of  claim 1 , wherein the filament further comprises a polyolefin additive. 
     
     
         20 . The method of  claim 1 , wherein the filament is an islands-in-the-sea fiber with 2 to 1000 islands. 
     
     
         21 . The method of  claim 1 , wherein the filament is an islands-in-the-sea fiber with 30 to 40 islands. 
     
     
         22 . The method of  claim 1 , wherein the internal fiber component comprises fibers having round cross-sections. 
     
     
         23 . The method of  claim 1 , wherein the internal fiber component comprises fibers having non-round or multi-lobal cross-sections. 
     
     
         24 . The method of  claim 1 , wherein the internal fiber component is polylactide and the external polymer component is polypropylene. 
     
     
         25 . The method of  claim 1 , wherein the internal fiber component is polypropylene and the external polymer component is polylactide. 
     
     
         26 . An article comprising: a nonwoven fabric made the process of  claim 1 . 
     
     
         27 . The article of  claim 26 , wherein the article is a surgical mask, fitted mask, pleated mask, mask filter insert, respirator, or multi-layer mask. 
     
     
         28 . The article of  claim 26 , wherein the article has an efficiency of at least 95% at capturing particles of 0.3 microns at a flow rate of 32 L/min. 
     
     
         29 . The article of  claim 26 , wherein the article has a pressure drop of from 5 to 90 pascals at a flow rate of 85 L/min.