Process for forming micro-fiber cellulosic nonwoven webs from a cellulose solution by melt blown technology and the products made thereby

Abstract

This invention relates to a process of melt blowing a cellulose solution through a concentric melt blown die with multiple rows of spinning nozzles to form cellulosic microfiber webs with different web structures. The process comprises the steps of (a) extruding a cellulose solution (dope) through a melt blown spinneret with multiple rows of spinning nozzles; (b) drawing each individual extrudate filament to fine fiber diameter by its own air jet; (c) coagulating and entangling the fine fibers with a series of pressured hydro needling jets of recycling solution of the mixture of cellulose solvent and non-solvent in the spin-line; (d) collecting the stream of microfibers, air and needling jets on a moving collecting surface to form cellulosic fiber web; (e) hydro-entangling the said pre-bonded web downstream with at least one set of hydro needling jets of recycling solvent/non-solvent solution for forming well bonded nonwoven web; (f) regenerating the fine fibers in at least one bath for at least 5 seconds; (g) further regenerating and washing the fine fibers in another bath for at least 5 seconds; (h) pinching the well bonded melt blown cellulosic nonwoven with pressure rollers to remove major portions of the non-solvent; (i) drying the nonwoven web by heat, or vacuum or both, and (j) winding the nonwoven web into rolls.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] (Not applicable) STATEMENT REGARDING FEDERARALLY SPONSORED RESEARCH OR DEVELOPMENT [0002] (Not Applicable) REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX [0003] (Not applicable) BACKGROUND OF THE INVENTION [0004] 1. Field of the Invention [0005] This invention relates to a process of melt blowing a cellulose solution through a concentric melt blown die with a plurality of spinning nozzles to form cellulosic microfiber webs with different web structures. [0006] 2. Description of the Prior Art [0007] Cellulosic fibers are man-made fibers regenerated from a proper cellulose solution (dope) with different techniques. As an example, Lyocell fiber is one of the regenerated, man-made cellulose fibers. It is traditionally made by a dry-jet-wet-spinning process, where the cellulose solution of a solvent, such as N-methyl morpholine N-oxide, is extruded through a spinneret to form filaments. These fila...

AI Technical Summary

Benefits of technology

[0014] Spinning nozzles have an inside diameter in the range of 0.005-0.050 inch with a length / diameter (L / D) ratio in the range of 40-300. Under proper operation conditions, the resultant melt blown web is free of “shot”, a defect in the form of glob of polymer which is significantly large than the fiber. Fibers produced by the method of this invention possess desirable crimps.

Problems solved by technology

Although Example of this patent described a single orifice melt blown die with air delivered from both sides of the die through parallel slots at an angle of 30 degree, it failed to teach more details of a die with multiple orifices, such as that how the orifices are arranged, and how the air applied to extruded filaments.

Due to the unique characteristic of cellulose-NMMO solution and complexity of MB technology, it is uncertain that if the same results from a single orifice MB die could be obtained from a multiple orifice MB die.

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