Polymeric strands with enhanced tensile strength, nonwoven webs including such strands, and methods for making same

• Main Author: LEE KIRBY JAMESON
• Format: Patent
• Language: English
• Published: 05.12.1997
• Edition: 6
• Subjects: AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING; APPLYING LIQUIDS OR OTHER FLUENT MATERIALS TO SURFACES, IN GENERAL; ATOMISING APPARATUS; BLASTING; BRAIDING; BURNERS; COMBUSTION APPARATUS; COMBUSTION ENGINES; COMBUSTION PROCESSES; COTTON-WOOL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS,NON-WOVEN FABRICS; HEATING; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS; KNITTING; LACE-MAKING; LIGHTING; MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARYMATERIAL; MECHANICAL ENGINEERING; MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OFARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES ORRIBBONS; MIXING, e.g. DISSOLVING, EMULSIFYING, DISPERSING; NATURAL OR ARTIFICIAL THREADS OR FIBRES; NON-WOVEN FABRICS; NOZZLES; PERFORMING OPERATIONS; PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDEDFOR; SHAPING OR JOINING OF PLASTICS; SPINNING; SPRAYING APPARATUS; SPRAYING OR ATOMISING IN GENERAL; SUPPLYING COMBUSTION ENGINES IN GENERAL, WITH COMBUSTIBLEMIXTURES OR CONSTITUENTS THEREOF; TEXTILES; TRANSPORTING; TRIMMINGS; WADDING; WEAPONS; WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL

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.