Flame-retardant non-woven fibrous webs

Abstract

A nonwoven fibrous web and a method of making thereof. The nonwoven fibrous web includes greater than 0% but no greater than 30 wt % of a plurality of melt-blown fibers comprised of a crystalline (co)polymer; and at least 70 wt % of a plurality of randomly-oriented staple fibers, the plurality of randomly-oriented staple fibers including: at least 60 wt % of oxidized polyacrylonitrile fibers; and from 0 to 40 wt % of reinforcing fibers having an outer surface comprised of a (co)polymer with a melting temperature of from 100° C. to 350° C.; wherein the plurality of melt-blown fibers and the plurality of randomly-oriented staple fibers are bonded together to form a cohesive non-woven fibrous web.

1 . A nonwoven fibrous web comprising
 greater than 0% but no greater than 30 wt % of a plurality of melt-blown fibers comprised of a crystalline (co)polymer; and   at least 70 wt % of a plurality of randomly-oriented staple fibers, the plurality of randomly-oriented staple fibers comprising:
 at least 60 wt % of oxidized polyacrylonitrile fibers; and 
 from 0 to 40 wt % of reinforcing fibers having an outer surface comprised of a (co)polymer with a melting temperature of from 100° C. to 350° C.; 
   wherein the plurality of melt-blown fibers and the plurality of randomly-oriented staple fibers are bonded together to form a cohesive non-woven fibrous web, optionally wherein the crystalline (co)polymer exhibits a melting temperature from 100° C. to 250° C.   
     
     
         2 . The nonwoven fibrous web of  claim 1 , wherein at least one of the plurality of reinforcing comprise polyolefin fibers. 
     
     
         3 . The nonwoven fibrous web of  claim 2 , wherein the polyolefin fibers are selected from the group consisting of polyethylene fibers, polypropylene fibers, polybutylene fibers, polyisobutylene fibers, poly(4-methyl-1-pentene), and combinations thereof. 
     
     
         4 . The nonwoven fibrous web of  claim 1 , wherein the crystalline (co)polymer is selected from the group consisting of polyethylene, polypropylene, polybutylene, polyisobutylene, poly(4-methyl-1-pentene), and combinations thereof. 
     
     
         5 . The nonwoven fibrous web of  claim 1 , wherein the non-woven fibrous web passes the UL-94V0 flame test. 
     
     
         6 . The nonwoven fibrous web of  claim 1 , wherein the oxidized polyacrylonitrile fibers have a median Effective Fiber Diameter of from 5 micrometers to 100 micrometers. 
     
     
         7 . The nonwoven fibrous web of  claim 1 , wherein the melt-blown fibers have a median Effective Fiber Diameter of from 0.1 to 20 micrometers. 
     
     
         8 . The nonwoven fibrous web of  claim 1 , wherein the non-woven fibrous web has a thermal conductivity coefficient of less than 0.04 W/K-m at 25° C. in its relaxed configuration. 
     
     
         9 . The nonwoven fibrous web of  claim 1 , wherein the non-woven fibrous web has a sound absorption coefficient of greater than 0.08 at 1000 Hz at normal sound incidence. 
     
     
         10 . The nonwoven fibrous web of  claim 1 , wherein the non-woven fibrous web has a base weight of from 100 gsm to 500 gsm. 
     
     
         11 . An article comprising the nonwoven fibrous web of  claim 1 , wherein the article is an acoustic insulation article, a thermal insulation article, or combinations thereof. 
     
     
         12 . A non-woven fibrous web comprising
 a cohesive nonwoven fibrous matrix comprising of a plurality of randomly-oriented staple fibers, the plurality of randomly-oriented staple fibers comprising:
 at least 60 wt % of oxidized polyacrylonitrile fibers; and 
 from 0 to 40 wt % of reinforcing fibers having an outer surface comprised of a (co) polymer with a melting temperature of from 100° C. to 350° C.; wherein the plurality of randomly-oriented staple fibers are bonded together to form the cohesive non-woven fibrous matrix; and 
   a plurality of discrete domains of at least partially melted melt-blown fibers distributed within the cohesive nonwoven fibrous matrix, wherein the at least partially melted melt-blown fibers comprise a crystalline (co)polymer, optionally wherein the crystalline (co)polymer exhibits a melting temperature from 100° C. to 250° C.   
     
     
         13 . A method of making a cohesive nonwoven fibrous web comprising:
 mixing a plurality of oxidized polyacrylonitrile fibers with a plurality of reinforcing fibers to form a mixture of randomly-oriented fibers, wherein the plurality of reinforcing fibers have outer fiber surfaces comprised of a (co)polymer with a melting temperature between 100° C. and 350° C.;   combining the mixture of randomly-oriented fibers with a plurality of melt-blown fibers comprised of a crystalline (co)polymer to form nonwoven fibrous web; and   heating the mixture of randomly-oriented fibers combined with the plurality of melt-blown fibers to a temperature sufficient to melt the outer surfaces of the plurality of reinforcing fibers; optionally wherein the crystalline (co)polymer exhibits a melting temperature from 100° C. to 250° C.   
     
     
         14 . The method of  claim 13 , wherein the crystalline (co)polymer is selected from the group consisting of polyethylene, polypropylene, polybutylene, polyisobutylene, poly(4-methyl-1-pentene), and combinations thereof. 
     
     
         15 . The method of  claim 13 , further comprising heating the nonwoven fibrous web above the melting temperature of the (co)polymer.