Nonwoven web laminates with improved barrier properties

摘要

There is disclosed a nonwoven web for use as a barrier layer in an SMS fabric laminate. The web is formed at commercially acceptable polymer melt throughputs (greater than 3 PIH) by using a reactor granule polyolefin, preferably polypropylene, that has been modified by the addition of peroxide in amounts ranging from up to 3000 ppm to reduce the molecular weight distribution from an initial molecular weight distribution of from 4.0 to 4.5 Mw/Mn to a range of from 2.2 to 3.5 Mw/Mn. Also the addition of peroxide increases the melt flow rate (lowers viscosity) to a range between 800 up to 5000 gms/10 min at 230 DEG C. The resulting web has an average fiber size of from 1 to 3 microns and pore sizes distributed predominantly in the range from 7 to 12 microns, with a lesser amount of pores from 12 to 25 microns, with virtually no pores greater than 25 microns, and with the peak of the pore size distribution less than 10 microns.