Glazed Nonwoven Fabric and Methods of Manufacture

Abstract

A glazing method for improving abrasion resistance using a heated smooth roll to melt the lower-melting-point portion of bicomponent fibers as the spunbond web passes over the heated smooth roll. Because there is no external pressure exerted in a nip by an opposing second roller, as in calendering, the outer surface of the web which does not contact the heated smooth roll remains essentially unchanged and the nonwoven fabric exhibits no compression as a result of the glazing process. The roll temperature and dwell time (roll diameter, wrap angle and line speed) are controlled for the purpose of surface treating only one side of the nonwoven fabric to improve abrasion resistance while allowing the air permeability and web thickness to remain essentially unchanged.

1 . A method of enhancing the abrasion resistance of a surface of a nonwoven fabric, comprising applying heat and pressure on one surface of a portion of a nonwoven fabric, while not applying any heat or pressure on the other surface of said portion of the nonwoven fabric. 
     
     
         2 . The method as recited in  claim 1 , wherein the heat and pressure are applied by a circumferential surface of a heated smooth roll, said portion of the nonwoven fabric being wrapped around and in contact with a portion of said circumferential surface which subtends a wrap angle. 
     
     
         3 . The method as recited in  claim 2 , wherein the wrap angle is in a range of 25 to 85 degrees inclusive. 
     
     
         4 . The method as recited in  claim 2 , wherein the surface temperature of the heated smooth roll is in a range of 290 to 330° F. 
     
     
         5 . The method as recited in  claim 4 , wherein the surface temperature of the heated smooth roll is in a range of 300 to 330° F. 
     
     
         6 . A method of enhancing the abrasion resistance of a surface of a nonwoven fabric, comprising:
 (a) supporting a nonwoven fabric in a position whereat a portion thereof is wrapped around and in contact with a portion of a circumferential surface of a heated smooth roll which subtends a wrap angle; and   (b) advancing the nonwoven fabric in a tensioned state to maintain some portion thereof in wrapped contact with some portion of the circumferential surface of the heated smooth roll which subtends the wrap angle,   wherein the length of the surface of the wrapped portion of the nonwoven fabric is a function of a diameter of the circumferential surface of the heated smooth roll and the wrap angle.   
     
     
         7 . The method as recited in  claim 6 , wherein the surface temperature of the heated smooth roll is in a range of 290 to 330° F. 
     
     
         8 . The method as recited in  claim 7 , wherein the surface temperature of the heated smooth roll is in a range of 300 to 330° F. 
     
     
         9 . The method as recited in  claim 6 , wherein the wrap angle is in a range of 25 to 85 degrees. 
     
     
         10 . The method as recited in  claim 6 , wherein the heated smooth roll forms a nip with a patterned roll, a terminal portion of the wrapped portion of the nonwoven fabric being disposed in said nip. 
     
     
         11 . The method as recited in  claim 6 , wherein while one portion of the nonwoven fabric is in wrapped contact with the heated smooth roll, another portion of the nonwoven fabric is wrapped around and in contact with a portion of a circumferential surface of a movable guide roll, the wrap angle of the one portion being adjustable by changing the position of the movable guide roll relative to the position of the heated smooth roll. 
     
     
         12 . A method for fabricating a pattern bonded nonwoven web having a surface with enhanced abrasion resistance, comprising:
 (a) randomly depositing extruded filaments onto a moving carrier belt or screen to form a nonwoven web;   (b) forming discrete thermally bonded areas in the nonwoven web by passing the nonwoven web through a nip formed by a patterned roll and a heated smooth roll, said nip continuously forming discrete thermally bonded areas in the nonwoven web in a pattern as the nonwoven web passes therethrough; and   (c) glazing a surface of the pattern bonded nonwoven web by wrapping the nonwoven web around a portion of a circumferential surface of the heated smooth roll.   
     
     
         13 . The method as recited in  claim 12 , wherein the surface temperature of the heated smooth roll is in a range of 290 to 330° F. 
     
     
         14 . The method as recited in  claim 13 , wherein the surface temperature of the heated smooth roll is in a range of 300 to 330° F. 
     
     
         15 . The method as recited in  claim 12 , wherein the wrap angle is in a range of 25 to 85 degrees. 
     
     
         16 . The method as recited in  claim 12 , wherein a terminal portion of the wrapped portion of the nonwoven web is disposed in said nip. 
     
     
         17 . The method as recited in  claim 12 , wherein while an upstream portion of the nonwoven web is in wrapped contact with the heated smooth roll, a downstream portion of the nonwoven web is wrapped around and in contact with a portion of a circumferential surface of a movable guide roll, the wrap angle of the one portion being adjustable by changing the position of the movable guide roll relative to the position of the heated smooth roll. 
     
     
         18 . A nonwoven fabric comprising thermoplastic filaments and having a thickness to basis weight ratio of at least 5 μm/gsm, wherein at least one side of said nonwoven fabric comprises thermoplastic filaments which are at least partially flattened, said one side having an average weight loss not greater than 0.62% when subjected to Taber shaving. 
     
     
         19 . The nonwoven fabric as recited in  claim 18 , wherein said thermoplastic filaments are bicomponent sheath/core filaments. 
     
     
         20 . The nonwoven fabric as recited in  claim 19 , wherein said bicomponent sheath/core filaments comprise a polyethylene sheath and a polyethylene terephthalate core. 
     
     
         21 . The nonwoven fabric as recited in  claim 18 , wherein said thermoplastic filaments are fused in a multiplicity of discrete areas, the total area of said multiplicity of discrete areas being less than 22% of the total area of the fabric. 
     
     
         22 . The nonwoven fabric as recited in  claim 18 , wherein said basis weight is less than 40 gsm. 
     
     
         23 . The nonwoven fabric as recited in  claim 18 , wherein said one side does not fail a Taber abrasion resistance roping test method before 13 cycles. 
     
     
         24 . The nonwoven fabric as recited in  claim 18 , wherein another side of said nonwoven fabric has no thermoplastic filaments which are at least partially flattened. 
     
     
         25 . A spunbond web comprising bicomponent thermoplastic filaments and having a thickness to basis weight ratio of at least 5 μm/gsm, wherein at least one side of said spunbond web comprises bicomponent thermoplastic filaments which are at least partially flattened, said one side having an average weight loss not greater than 0.62% when subjected to Taber shaving.