Self-bonded cellulosic nonwoven web and method for making

Abstract

A self-bonded nonwoven web, at least some cellulosic fibers that are self-bonded to each other at points of intersection of the cellulosic fibers with each other; and, an ionic liquid. Methods of making such a web are also disclosed, wherein the method comprises: contacting at least some of the first, cellulosic fibers with an ionic liquid; exposing the ionic liquid and the first, cellulosic fibers to a first temperature; and exposing the ionic liquid and the first, cellulosic fibers to a second temperature that is lower than the first temperature.

What is claimed is: 
     
         1 . A self-bonded nonwoven web, comprising:
 at least first, cellulosic fibers,
 wherein at least some cellulosic fibers of the web are self-bonded to each other at points of intersection of the first, cellulosic fibers with each other; 
 and, 
   from about 1% by weight to about 50% by weight of an ionic liquid.   
     
     
         2 . The nonwoven web of  claim 1  wherein the first, cellulosic fibers include fibers chosen from the group consisting of cellulose fibers, regenerated cellulose fibers, and partially derivatized cellulose fibers, and any combination thereof. 
     
     
         3 . The nonwoven web of  claim 1  wherein the first, cellulosic fibers include natural fibers chosen from the group consisting of fibers derived from cotton, wool, jute, agave, sisal, coconut, soybean, hemp, flax, kenaf, bamboo, abaca, henequen, sunn, ramie, sisal, chitin, chitosan, and any combination of such fibers. 
     
     
         4 . The nonwoven web of  claim 1  wherein the nonwoven web comprises from about 2% by weight to about 40% by weight of an ionic liquid. 
     
     
         5 . The nonwoven web of  claim 1  wherein at least some of the self-bonds between the first, cellulosic fibers are provided by globules of cellulosic bonding material that are distributed throughout at least a portion of the nonwoven web, and wherein at least some of the globules bridge gaps between adjacent portions of first, cellulosic fibers at points of intersection of the first, cellulosic fibers. 
     
     
         6 . The nonwoven web of  claim 1  wherein the ionic liquid is an imidazolium ionic liquid. 
     
     
         7 . The nonwoven web of  claim 1  wherein the web further comprises at least second, non-cellulosic fibers, and wherein the web comprises at least about 40 wt. % first, cellulosic fibers, based on the total weight of the fiber material of the web. 
     
     
         8 . The nonwoven web of  claim 7  wherein the at least second, non-cellulosic fibers include at least some fibers that are melt-bonded to each other at points of contact of the second-non-cellulosic fibers with each other. 
     
     
         9 . The nonwoven web of  claim 1  wherein at least about 20 wt. % of the ionic liquid is in the form of an entrapped ionic liquid that remains in the nonwoven web after the web has been contacted with quiescent 21° C. water for about two hours. 
     
     
         10 . A method for making a self-bonded nonwoven web comprising at least at least first, cellulosic fibers, the method comprising:
 contacting at least some of the first, cellulosic fibers with an ionic liquid;   exposing the ionic liquid and the first, cellulosic fibers to a first temperature, which first temperature is sufficiently high to cause at least some of the cellulosic material of at least some of the fibers to be at least partially dissolved by the ionic liquid;   exposing the ionic liquid and the first, cellulosic fibers to a second temperature that is lower than the first temperature, which second temperature is sufficiently low to cause at least some of the at least partially dissolved cellulosic material to solidify so as to form a cellulosic self-bond at points of intersection of first, cellulosic fibers with each other.   
     
     
         11 . The method of  claim 10  wherein the method does not include contacting the ionic liquid and/or the first, cellulosic fibers with a regenerating liquid. 
     
     
         12 . The method of  claim 10  wherein the method does not include a washing step that would selectively remove ionic liquid from the self-bonded web, and wherein the self-bonded web comprises from about 1% by weight to about 50% by weight of ionic liquid. 
     
     
         13 . The method of  claim 10  wherein the ionic liquid is provided as a mixture with a diluent and wherein the ionic liquid is present in the diluent at from about 10 wt. % to about 70 wt. %. 
     
     
         14 . The method of  claim 13  wherein the ionic liquid is present in the diluent at from about 20 wt. % to about 50 wt. %. 
     
     
         15 . The method of  claim 13  wherein the diluent is water. 
     
     
         16 . The method of  claim 10  wherein the first temperature is least about 100 degrees C. 
     
     
         17 . The method of  claim 10  wherein the second temperature is less than about 40 degrees C. 
     
     
         18 . The method of  claim 10  wherein the at least first, cellulosic fibers are provided as a mat that is a layer of collected, unbonded fibers and wherein the contacting at least some of the first, cellulosic fibers with an ionic liquid is performed by contacting the ionic liquid with at least a first major surface of the mat. 
     
     
         19 . The method of  claim 10  wherein the at least first, cellulosic fibers are provided in the form of a pre-bond web that further comprises at least second, non-cellulosic fibers and wherein at least some of the second, non-cellulosic fibers are melt-bonded to each other at points of contact of the second-non-cellulosic fibers with each other, and wherein the contacting at least some of the first, cellulosic fibers with an ionic liquid is performed by contacting the ionic liquid with at least a first major surface of the pre-bond web. 
     
     
         20 . The method of  claim 19  wherein the web comprises at least about 40 wt. % cellulosic fibers, based on the total weight of the fiber material of the web. 
     
     
         21 . A method of treating a target surface, the method comprising contacting a major surface of the nonwoven web of  claim 1  with the target surface and moving the nonwoven web and/or the target surface relative to each other.