Method for making a nonwoven web

Abstract

Melt blown or spun bond nonwoven webs are formed by flowing fiber-forming material through a die cavity having a substantially uniform residence time and then through a plurality of orifices to form filaments, using air or other fluid to attenuate the filaments into fibers and collecting the attenuated fibers as a nonwoven web. Each die orifice receives a fiber-forming material stream having a similar thermal history. The physical or chemical properties of the nonwoven web fibers such as their average molecular weight and polydispersity can be made more uniform. Wide nonwoven webs can be formed by arranging a plurality of such die cavities in a side-by-side relationship. Thicker or multilayered nonwoven webs can be formed by arranging a plurality of such die cavities atop one another.

Description

This invention relates to devices and methods for preparing nonwoven webs, and to melt blown or spun bonded fibrous nonwoven webs. BACKGROUND Nonwoven webs typically are formed using a meltblowing process in which filaments are extruded from a series of small orifices while being attenuated into fibers using hot air or other attenuating fluid. The attenuated fibers are formed into a web on a remotely-located collector or other suitable surface. A spun bond process can also be used to form nonwoven webs. Spun bond nonwoven webs typically are formed by extruding molten filaments from a series of small orifices, exposing the filaments to a quench air treatment that solidifies at least the surface of the filaments, attenuating the at least partially solidified filaments into fibers using air or other fluid and collecting and optionally calendaring the fibers into a web. Spun bond nonwoven webs typically have less loft and greater stiffness than melt blown nonwoven webs, and the filamen...

AI Technical Summary

Benefits of technology

This approach results in more uniform nonwoven webs with consistent fiber properties, improved web quality, and reduced sampling errors, enabling the production of wide, thick, and ultrafine fibers with enhanced uniformity and accuracy.

Problems solved by technology

Although useful, macroscopic nonwoven web properties such as basis weight, average fiber diameter, web thickness or porosity may not always provide a sufficient basis for evaluating nonwoven web quality or uniformity.

These approaches can be susceptible to sampling and measurement errors that may skew the results, especially if used to evaluate low basis weight or highly porous webs.

In addition, although a nonwoven web may exhibit uniform measured basis weight, fiber diameter, web thickness or porosity, the web may nonetheless exhibit nonuniform performance characteristics due to differences in the intrinsic properties of the individual web fibers.

Meltblowing and spun bonding processes subject the fiber-forming material to appreciable viscosity reduction (and sometimes to considerable thermal degradation), especially during passage of the fiber-forming material through the die and during the subsequent attenuation step.

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