POLYMERIC STRANDS WITH ENHANCED TENSILE STRENGTH, NONWOVEN WEBS INCLUDING SUCH STRANDS, AND METHODS FOR MAKING SAME

摘要

A melt-extrudable polymeric strand with enhanced tensile strength formed by extruding a melt-extrudable polymer while subjecting the a portion of the polymer to ultrasonic energy. The melt-extrudable polymeric strand has a tenacity which is from about 1.5 to about 3 times the tenacity of an otherwise identical strand not made by applying ultrasonic energy to a portion of the melt-extrudable polymer while the melt-extrudable polymer is extruded. Desirably, the strand has a tenacity within a range from about 0.3 to about 0.9 g/denier. In a method for making such a strand, a molten melt-extrudable polymer is extruded through a die assembly, ultrasonic energy is applied to a portion of the melt-extrudable polymer within the chamber and without applying ultrasonic energy to the die tip, while an extrusion exit orifice receives melt-extrudable polymer from an extrusion chamber, and the extruded polymer is attenuated to form a strand. The extrusion of the melt-extrudable polymer and the excitation of the means for applying ultrasonic energy are controlled such that the strand has the above-described tenacity. A nonwoven web comprises the strands with enhanced tensile strength.