Nonwoven Fabrics Made From Polymer Blends And Methods For Making Same

Abstract

The present invention is directed to polymer blends for use in nonwoven fabric applications, and to fabrics formed from the polymer blends. In one or more embodiments, the polymer blends comprise from about 70 to about 99.9 wt %, based on the total weight of the composition, of a first propylene-based polymer and from about 0.1 to about 30 wt % of a second propylene-based polymer. The first polymer has a melt flow rate of from about 100 to about 5,000 g/10 min, and the second polymer has a melt flow rate of from about 1 to about 500 g/min, and the second polymer has either a lower melt flow rate or a higher triad tacticity than the first polymer.

1 . A nonwoven fabric made from a polymer composition comprising:
 a. from about 70 to about 99.9 wt %, based on the total weight of the composition, of a first propylene-based polymer having a melt flow rate of from about 100 to about 5,000 g/10 min; and   b. from about 0.1 to about 30 wt % of a second propylene-based polymer having a melt flow rate of from about 1 to about 500 g/10 min, wherein the second propylene-based polymer has at least one of: (i) a lower melt flow rate than the first propylene-based polymer; or (ii) a higher crystallinity than the first propylene-based polymer;   wherein the first propylene-based polymer is prepared using a catalyst system comprising a metallocene catalyst.   
     
     
         2 . The fabric of  claim 1 , wherein the polymer composition comprises from about 5 to about 15% by weight of the second propylene-based polymer. 
     
     
         3 . The fabric of  claim 1 , wherein the second propylene-based polymer is prepared using a catalyst system comprising a Ziegler-Natta catalyst. 
     
     
         4 . The fabric of  claim 1 , wherein the nonwoven fabric is meltblown. 
     
     
         5 . The fabric of  claim 1 , wherein the first propylene-based polymer is a propylene homopolymer. 
     
     
         6 . (canceled) 
     
     
         7 . The fabric of  claim 1 , wherein the second propylene-based polymer is a propylene homopolymer. 
     
     
         8 . The fabric of  claim 1 , wherein the second propylene-based polymer further comprises from 0.01 to 25% by weight of the second propylene-based polymer of one or more comonomers selected from C 2  and/or C 4 -C 10  alpha-olefins. 
     
     
         9 . The fabric of  claim 1 , wherein the first propylene-based polymer has a melt flow rate of from about 500 to about 3000 g/10 min. 
     
     
         10 . The fabric of  claim 1 , wherein the second propylene-based polymer has a melt flow rate of from about 1 to about 250 g/10 min. 
     
     
         11 . (canceled) 
     
     
         12 . The fabric of  claim 1 , wherein the first propylene-based polymer has a triad tacticity of greater than about 0.94. 
     
     
         13 . The fabric of  claim 1 , wherein the second propylene-based polymer has a higher triad tacticity than the first propylene-based polymer. 
     
     
         14 . The fabric of  claim 1 , wherein the first propylene-based polymer has a meso run length, as determined by  13 C NMR, greater than about 75. 
     
     
         15 . (canceled) 
     
     
         16 . (canceled) 
     
     
         17 . A process for producing nonwoven fabrics comprising:
 a. forming a polymer composition comprising: (i) from about 70 to about 99.9 wt %, based on the total weight of the composition, of a first propylene-based polymer prepared using a catalyst system comprising a metallocene catalyst and having a melt flow rate of from about 100 to about 5,000 g/10 min; and (ii) from about 0.1 to about 30 wt % of a second propylene-based polymer having a melt flow rate of from about 1 to about 500 g/10 min wherein the second propylene-based polymer has at least one of: (i) a lower melt flow rate than the first propylene-based polymer; or (ii) a higher crystallinity than the first propylene-based polymer;   b. forming fibers comprising the polymer composition using a meltblown process; and   c. forming a fabric from the fibers.   
     
     
         18 . The process of  claim 17 , wherein the second propylene-based polymer has a higher triad tacticity than the first propylene-based polymer. 
     
     
         19 . The process of  claim 17 , wherein the second propylene-based polymer is prepared using a catalyst system comprising a Ziegler-Natta catalyst. 
     
     
         20 . The process of  claim 17 , wherein the first propylene-based polymer is a propylene homopolymer. 
     
     
         21 . (canceled) 
     
     
         22 . The process of  claim 17 , wherein the second propylene-based polymer is a propylene homopolymer. 
     
     
         23 . (canceled) 
     
     
         24 . (canceled) 
     
     
         25 . The process of  claim 17 , wherein the first propylene-based polymer has an MWD of from about 1.0 to about 4.0. 
     
     
         26 . The process of  claim 17 , wherein the first propylene-based polymer has a meso run length, as determined by  13 C NMR, greater than about 75. 
     
     
         27 . The process of  claim 17 , wherein the fibers are formed using an extruder having a throughput rate of from about 0.1 to about 3 ghm. 
     
     
         28 . The process of  claim 27 , wherein the throughput rate is from about 0.3 to about 1.0 ghm. 
     
     
         29 . The process of  claim 27 , wherein the melt temperature of the extruder is from about 175° C. to about 290° C. 
     
     
         30 . The process of  claim 17 , wherein the air temperature of the meltblown process is from about 175° C. to about 290° C. 
     
     
         31 . The process of  claim 17 , wherein the air pressure at the die of the meltblown process is about 10 kPa to about 215 kPa. 
     
     
         32 . The process of  claim 17 , wherein the fabric has a basis weight of from about 0.1 to about 500 g/m 2 .