High stretch recovery non-woven fabric and process for preparing

Abstract

The present invention is concerned with a novel non-woven fabric characterized by high stretch recovery and a process for preparing said fabric by employing fibers of latent crimp.

What is claimed is:  
     
         1 . A non-woven fabric comprising a plurality of entangled helically crimped asymmetric bicomponent fibers comprising a first crystallizable polyester component and a second crystallizable polyester component, said first crystallizable polyester component exhibiting a lower rate of crystallization than said second crystallizable polyester component, said fibers being characterized by a denier range of 0.5 to 6 denier, said fibers exhibiting at least 50 crimps per inch with a crimp radius of curvature of 0.2 mm or less, and wherein said fibers are preponderantly entangled with one another, and wherein further said fibers are preponderantly oriented in a well-defined plane said non-woven fabric being characterized by a bulk density of 0.2-0.4 g/cm 3 .  
     
     
         2 . The non-woven fabric of  claim 1  wherein the bicomponent fibers are side-by-side bicomponent fibers.  
     
     
         3 . The non-woven fabric of  claim 1  wherein said first crystallizable polyester component is poly(ethylene terephthalate) and said second crystallizable polyester component is poly (propylene terephthalate).  
     
     
         4 . The non-woven fabric of  claim 1  wherein said first crystallizable polyester component is poly(propylene terephthalate) and said second crystallizable polyester component is poly (butylene terephthalate).  
     
     
         5 . The non-woven fabric of  claim 1  wherein said first crystallizable polyester component is poly(ethylene terephthalate) and said second crystallizable polyester component is poly (butylene terephthalate).  
     
     
         6 . The non-woven fabric of  claim 1  wherein said bicomponent fibers are predominantly staple fibers.  
     
     
         7 . The non-woven fabric of  claim 6  wherein said first crystallizable polyester is poly (ethylene terephthalate) and said second crystallizable polyester is poly (propylene terephthalate) at a concentration ratio in the range of 70:30 to 30:70 respectively.  
     
     
         8 . The non-woven fabric of  claim 7  wherein the concentration ratio is in the range of 60:40 to 40:60 respectively.  
     
     
         9 . The non-woven fabric of  claim 1  wherein said bicomponent fibers are continuous.  
     
     
         10 . The non-woven fabric of  claim 1  further characterized by an initial Young's modulus of 1.2 to 12 MPa and ultimate stretch of up to 150%.  
     
     
         11 . A non-woven fabric comprising a plurality of entangled helically crimped side-by side staple bicomponent fibers in the range of 0.5 to 6 denier and an uncrimped length in the range of 20 to 25 millimeters comprising polyethylene terephthalate and polypropylene terephthalate at a concentration ratio in the range 60:40 to 40:60, said fibers exhibiting at least 50 crimps per inch with a crimp radius of curvature of 0.2 mm or less, and wherein said fibers are preponderantly entangled with one another, and wherein further said fibers are preponderantly oriented in a well-defined plane said non-woven fabric being characterized by a bulk density of 0.2-0.4 g/cm 3 , an initial Young's modulus of 1.2 to 12 MPa, and ultimate stretch of up to 150%.  
     
     
         12 . A process for forming a non-woven fabric, the process comprising disposing a plurality of asymmetric bicomponent fibers having latent crimp in a planar array of overlapping fibers, said fibers being preponderantly oriented in the plane thereof, disposing said planar array between two constraining surfaces; heating said planar array to develop at least a portion of said latent crimp with the proviso that during at least a portion of said heating, said non-woven structure is in constraining contact with said constraining surfaces.  
     
     
         13 . The process of  claim 12  wherein said planar array is in the form of a fibrous mat preform.  
     
     
         14 . The process of  claim 12  wherein the bicomponent fibers are side-by-side bicomponent fibers.  
     
     
         15 . The process of  claim 12  wherein the bicomponent fibers consist essentially of polyesters.  
     
     
         16 . The process of  claim 12  wherein said first crystallizable polyester component is poly(ethylene terephthalate) and said second crystallizable polyester component is poly (propylene terephthalate).  
     
     
         17 . The process of  claim 12  wherein said first crystallizable polyester component is poly(propylene terephthalate) and said second crystallizable polyester component is poly (butylene terephthalate).  
     
     
         18 . The process of  claim 12  wherein said first crystallizable polyester component is poly(ethylene terephthalate) and said second crystallizable polyester component is poly (butylene terephthalate).  
     
     
         19 . The process of  claim 12  further comprising the step of forming the fibrous mat preform from an aqueous slurry of floc having an average length of 3 to 25 millimeters.  
     
     
         20 . A process for forming a non-woven fabric, the process comprising forming a fibrous mat preform from an aqueous slurry of side by side uncrimped staple bicomponent fibers having a latent crimp contraction of at 70-80%, 20-25 millimeters in length, disposing said fibrous mat preform between two constraining surfaces; heating said planar array to develop at least a portion of said latent crimp with the proviso that during at least a portion of said heating, said fibrous mat preform is in constraining contact with said constraining surfaces; said bicomponent fibers comprising polyethylene terephthalate and polypropylene terephthalate in a respective concentration ratio in the range of 60:40 to 40:60.