Patent ID: 8802002

Claim:
A method for making a bonded nonwoven fibrous web comprising the sequential steps: a) extruding melt blown fibers comprising a polymeric material; b) collecting the melt blown fibers as an initial unbonded nonwoven fibrous web, wherein the fibers are substantially free of strain induced crystallization; c) annealing the initial unbonded nonwoven fibrous web with a controlled heating and cooling operation comprising: i) heating through the initial unbonded nonwoven fibrous web by forcefully passing through the initial unbonded nonwoven fibrous web a first fluid having a temperature above a cold crystallization temperature (T cc ) of the polymeric material of step a) to decrease the orientation of amorphous regions of the melt blown fibers, thereby providing a bonded nonwoven fibrous web; and ii) cooling through the bonded nonwoven fibrous web by drawing a second fluid having a temperature below a glass transition temperature (T g ) of the polymeric material of step a) over and through the bonded nonwoven fibrous web to retain the amorphous regions of the melt blown fibers providing a cooled bonded nonwoven fibrous web; and d) collecting the cooled bonded nonwoven fibrous web providing a dimensionally stable bonded nonwoven fibrous web; wherein the melt blown fibers of the cooled bonded nonwoven fibrous web retain a substantial cold crystallization exotherm.