WO2005106085A1

WO2005106085A1 - Apparatus , product and process forming micro-fiber cellulosic nonwoven webs

Info

Publication number: WO2005106085A1
Application number: PCT/US2005/013908
Authority: WO
Inventors: Rongguo Zhao
Original assignee: Biax Fiberfilm Corporation
Priority date: 2004-04-26
Filing date: 2005-04-22
Publication date: 2005-11-10

Abstract

A method and apparatus for forming micro-fiber cellulosic nonwoven webs from a cellulosic solution. A cellulose solution is extruded through a first multiplicity of uniformly spaced apart nozzles (5) and upon exiting the nozzles is accelerated and attenuated by high velocity gaseous jets to form fine cellulosic fibers. A coagulating solution (29) is forced through a second multiplicity of nozzles (15) uniformly spaced apart from each other and uniformly spaced apart from and generally parallel to the first multiplicity of nozzles and form high velocity jets so that the coagulating solution impinges upon the fine cellulosic fibers further attenuating them and causing them to coagulate, and entangle to form a product of cellulosic fibers that is collected on a moving collector (27) and further processed for specific properties and specific applications.

Description

APPARATUS, PRODUCT AND PROCESS FORMING MICRO-FIBER CELLULOSIC NONWOVEN WEBS

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefits of Provisional Patent Application, Serial

Number 60/564,890, filed on April 26, 2004.

BACKGROUND OF THE INVENTION This invention relates to an apparatus for performing a process for making fibrous cellulosic products from a cellulose solution and the products made thereby. The apparatus has a plurality of spinning nozzles to form cellulosic filaments and a plurality of hydro jet nozzles to treat the filaments, by means of which different fibrous products can be made.

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 (NMMO), is extruded through a spinnerette to form filaments. These filaments travel a short distance in air (the dry-jet), and then proceed into a coagulation bath for regeneration. An appropriate mechanical pulling force is applied to the regenerated fibers to attenuate the fiber in the "dry-jet" section. Regenerated fibers then go through a series of washing/finishing baths and drying units to form final products in the form of continuous filaments or short fibers. U.S. Patent Nos. 4,142,913; 4,144,080; 4,211,574; 4,246,221, and 4,416,698, and others, describe the details of this process. U.S. Pat. No 5,252,284, to Jurkovic et al., and U.S. Pat. No. 5,417,909, to Michels et al., especially describe the geometry of extrusion nozzles for spinning cellulose dissolved in NMMO. Brandner et al., in U.S. Pat. No. 4,426,228, is exemplary of a considerable number of patents that disclose the use of various compounds to act as stabilizers in order to prevent cellulose and/or solvent degradation.

Zikeli et al., in U.S. Patent Nos. 5,589,125 and 5,607,639, direct a stream of air transversely across strands of extruded lyocell dope as they leave the spinnerettes. This air stream serves only to cool and does not act to stretch the filaments. French laid open application 2,735,794 describes formation of lyocell fibers by a process of melt blowing. These fibers, however, are highly fragmented microfibers useful principally for production of self bonded non- woven webs.

U.S. Patent No. 6,306,334 teaches a process using spinning orifices having much larger cross-sections compared with the above referenced technologies, enabling a higher dope throughput per orifice to minimize any tendency toward orifice plugging problems. Although examples in that patent describe 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 fails to teach more details of a die with multiple orifices, such as, how the orifices are arranged, and how the air is applied to extruded filaments. Due to the unique characteristic of cellulose-NMMO solution and complexity of melt-blown technology, it is uncertain if the results from a single orifice MB die could be obtained from a multiple orifice MB die. This invention relates to improvements over the technology described above, and to solutions to some of the problems raised or not solved thereby.

SUMMARY OF THE INVENTION This invention provides a method and apparatus for forming micro-fiber cellulosic nonwoven webs from a cellulosic solution. According to the invention, the apparatus includes a first nozzle plate with a first set of nozzles arranged in at least one row passing through and projecting from the first nozzle plate. Together with the first nozzle plate, a polymer plate defines a solution chamber therebetween. A polymer solution is fed from the solution chamber through the first set of nozzles. A second nozzle plate has a second set of nozzles passing therethrough and projecting therefrom, arranged in at least one row and adjacent to a set of holes defined by the second nozzle plate that allows the first set of nozzles to pass through the second plate. The first nozzle plate and the second nozzle plate define a fluid chamber from which a fluid is fed to the second set of nozzles. A third plate defines three sets of holes, the first set of holes for the first set of nozzles to pass through, the second set of holes for the second set of nozzles to pass through, and the third set of holes for a gaseous fluid to pass through. A second fluid chamber is defined by the second nozzle plate and the third plate. From this second fluid chamber, a second fluid is fed to the third set of holes of the third plate. A fourth plate defines a first set of holes and a second set of holes, wherein the first set of holes receives the first set of nozzles and permits a gaseous fluid to pass therethrough. The second set of holes receives the second set of nozzles and permits the gaseous fluid to pass therethrough. A gaseous fluid chamber is defined between the third and fourth plates from which the gaseous fluid is fed to the first and second sets of holes of the fourth plate. The invention also provides a structure for keeping the plates aligned and sealed together as one assembly,

Other objects and advantages of the invention will become apparent hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of an apparatus constructed according to a preferred embodiment of this invention with multiple rows of spinning nozzles, with concentric air jets, and multiple rows of hydro jet nozzles. FIG. 2 is a schematic plan view of part of a first plate, of spinning nozzle openings, for use as a part of the apparatus shown in FIG. 1. ,

FIG. 3 is a schematic plan view of part of a second plate, of hydro-jet nozzles, for use as a part of the apparatus shown in FIG. 1.

FIG. 4 is a schematic plan view of a third plate, for distributing gaseous fluid, for use as a part of the apparatus shown in FIG. 1.

FIG. 5 is a schematic plan view of a part of a fourth plate, having the spinnerette nozzles and gaseous fluid holes for use as a part of the apparatus shown in FIG. 1. FIG. 6a is a schematic plan view of a part of the fourth plate according to an alternative embodiment, having the spinnerette nozzles and gaseous fluid holes, showing another pattern of the nozzles and gaseous fluid holes.

FIG. 6b is a schematic plan view of a part of the fourth plate according to another alternative embodiment, having the spinnerette nozzles and gaseous fluid holes, showing yet another pattern of the nozzles and gaseous fluid holes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention relates to an apparatus and a process for making fibrous cellulosic products from a cellulose solution. The apparatus has a plurality of spinning nozzles to form cellulosic filaments and a plurality of hydro jet nozzles to treat the filaments.

The term "cellulose," or any form of that term, as used herein, should be understood to include either cellulose from natural resources or a synthetic polymer blend with cellulose. The term "solvent" as used herein refers to NMMO, dilute caustic soda, phosphoric acid, mixture of liquid ammonia/ammonia thiocynate and others.

The term "non-solvent" as used herein refers to water, alcohol (C_nH_2n+ιOH, n<10), and/or a water/alcohol mixture.

The term "hydro jets" as used herein should be understood as jets of solvent(s) of cellulose, non-solvents of cellulose, or mixtures of those two types of compounds.

The hydro-jet nozzles are positioned alongside the spinning nozzles and generally parallel to the filament streams. The hydro-jets serve at least three functions, drawing the filaments, coagulating (fully or partially) the filaments, and hydro-entangling the filaments to form fibrous products.

The cellulose solution is extruded out through each spinning nozzle at a suitable temperature (ranging from 80 to 140°C) and an appropriate throughput. The extruded filaments are attenuated quickly by high velocity hot air jets from a few hundred micrometers in diameter to a few micrometers in diameter within a short distance from the nozzle exits, to become microfibers. These microfibers are further drawn, coagulated (or partially coagulated), and entangled by the hydro jets, and collected on the surface of a collector. The final cellulose microfibers have an average fiber diameter ranging from 1 micrometer to 20 micrometers with a relatively broad fiber diameter distribution.

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 10-300. Under appropriate operating conditions, the resultant cellulose fibers are free of "shot", a defect in the form of a glob of polymer which is significantly large than the fiber. Fibers produced by the method of this invention sometimes possess desirable crimps.

The apparatus and process of the present invention are suitable to various cellulose solutions and other polymer solutions. For cellulose, the solvent includes NMMO, dilute caustic soda, phosphoric acid, mixture of liquid ammonia/ammonia thiocynate and other compounds known to persons of ordinary skill in the art. Methods of making a solution of cellulose are known to the art, as reported by Petrovan, Collier, and Negulescu in "Rheology of Cellulosic N-Methymorpholine Oxide Monohydrate Solutions of Different Degrees of Polymerization" (Journal of Applied Polymer Science, Vol 79, 396-405 (2001)); by Albrecht in "Lyocell Fibers" (Chemical Fiber International, Vol 47, 298-304 (1997)); by Luo in U.S. Pat. No 6,306,334 Bl; and by Liu, Cuculo, Smith in "Diffusion competition between solvent and nonsolvent during the coagulation process of cellulose / ammonia / ammonium thiocynate fiber spinning system" (Journal of Polymer Science Part B: Polymer Physics Vol 28, Issue 4, Pages 449 - 465 (1990)).

Referring now to FIG. 1, four chambers are defined by five plates in the embodiment shown. A polymer plate 2 and a first nozzle plate 8 are formed so that, when they are assembled together, a polymer chamber 3 is defined therebetween, that is, first nozzle plate 8 and polymer plate 2 are in sealed engagement together around their perimeter to form polymer chamber 3. Although in the preferred embodiment shown in FIG. 1 the polymer chamber 3 is formed mostly by means of a recess in polymer plate 2, the chamber could also be formed by a suitable recess in first nozzle plate 8, or by a combination of recesses in both plates.

First nozzle plate 8 and a second nozzle plate 13 are formed so that, when they are assembled together, a fluid chamber 6 is defined therebetween, that is, first nozzle plate 8 and second nozzle plate 13 are in sealed engagement together around their perimeters. Although in the embodiment shown in FIG. 1 the fluid chamber 6 is formed mostly by means of a recess in first nozzle plate 8, the chamber could also be formed by a suitable recess in second nozzle plate 13, or by a combination of an amount of recessed space in both plates. Second nozzle plate 13 and a third plate 16 are formed so that, when they are assembled together, a gaseous fluid chamber 14 is defined therebetween, that is, second nozzle plate 13 and a third plate 16 are in sealed engagement together around their perimeters. Again, although in the embodiment shown in FIG. 1 the fluid chamber 14 is formed mostly by means of a recess in second nozzle plate 13, the chamber could also be formed by a suitable recess in third plate 16, or by a combination of recesses in both plates.

The third plate 16 and fourth plate 18 are formed so that, when they are assembled together, a gaseous fluid distribution chamber 21 is defined therebetween, that is, third plate 16 and fourth plate 18 is in sealed engagement together around their perimeters. Here again, although in the embodiment shown in FIG. 1 the fluid distribution chamber 21 is formed mostly by means of a recess in third plate 16, the chamber could also be formed by a suitable recess in fourth plate 18, or by a combination of recesses in both plates. The invention includes a device or devices 40 for maintaining all of these the plates in assembly and alignment. In this embodiment, that device is shown schematically as conventional threaded fasteners which pass all the way through all the plates 2, 8, 13, 16 and 18, but other suitable devices could also be used, such as dowel pins, or separate threaded fasteners that pass through each plate and are threaded into each respective next adjacent plate. Any such device that accomplishes the function of ensuring that each nozzle has sufficient clearance all the way around so as to function properly is contemplated by devices 40. FIGS. 2 through 5 show the upstream surfaces of first nozzle plate 8, second nozzle plate 13, third plate 16, and fourth plate 18 respectively. In the embodiment shown, first nozzle plate 8 (FIGS. 1 and 2) has passing therethrough and sealed therein a multiplicity of first nozzles 5 arranged in a substantially uniform distribution on the plate 8. A polymer solution stream 1 enters polymer chamber 3 under pressure and passes into nozzles 5 through nozzle entrances 28 and exits nozzles 5 as extrudate 23.

Second nozzle plate 13 (FIGS. 1 and 3) has passing therethrough and sealed therein a multiplicity of second nozzles 15, also arranged in a substantially uniform distribution. First nozzles 5 also pass through and are sealed into second nozzle plate

13. The arrangement of nozzles 5 and nozzles 15 with respect to each other is such that they are located and spaced substantially equidistant from each other. A solution A enters fluid chamber 6 through an inlet 10 under pressure and enters nozzles 15 through nozzle openings 29. Solution A exits nozzles 15 as hydro jet 25. Nozzles 5 and nozzles 15 also pass through, and are sealed in, third plate 16.

(FIGS. 1 and 4). Third plate 16 further includes a first set of holes 28b and a second set of holes 29a (FIG. 4). A gaseous fluid B enters gaseous fluid chamber 14 through inlet 12 under pressure and passes through distribution holes 17 formed for that purpose in third plate 16, and into distribution chamber 21. The nature and composition of solution A and gaseous fluid B will become apparent in the Examples given below. Fourth plate 18 has jet ports 20 and 20a passing therethrough. Jet ports 20a and 20 have diameters greater than the outside diameter of nozzles 5 and 15, respectively, and nozzles 5 and 15 pass through jet ports 20a and 20 and can project beyond plate 18, as shown at FIG. 1. Nozzles 5 and 15 can also be flush with plate 18, or be slightly recessed therein. Nozzles 5 and 15 must at least extend into the jet ports 20 and 20a. Gaseous fluid B enters distribution chamber 21 from gaseous fluid chamber 14, as described above, and exits distribution chamber 21 through jet ports 20 and 20a to form gaseous jets 22, which surround nozzles 5 and 15.

The above described apparatus is well suited to forming fibers wherein the process requires the extruding of a polymeric liquid through a set of nozzles, in association with the extruding of a second liquid through a second set of nozzles and introducing the extrudate from one or both of the nozzles into a gaseous jet.

In FIGS. 5, 6a, and 6b, alternative configurations of fourth plate 18 are shown. In a typical application of the apparatus of this invention, the extrudates are collected on a moving collector 27 (FIG. 1). In FIGS. 5, 6a, and 6b, the direction of travel of the moving collector is shown by arrow 41. In the configuration of fourth plate 18 illustrated in FIG. 5, the nozzles 5 and nozzles 15 are arranged alternatively in each column, that is, the first with solution and other with the non-solvent, respectively. For example, the nozzles in one column in the direction 41 of the collector 27 are in the pattern of 5, 15, 5, 15, 5 and the nozzles in the adjacent column are in the pattern of 15, 5, 15, 5, 15. In the configuration of fourth plate 18 illustrated in FIG. 6a, one column contains only nozzles 5 and each adjacent column contains only nozzles 15.

That is, each column contains the same type of nozzles, and the columns alternate the types of nozzles. In the configuration of plate 18 illustrated in FIG. 6b, the nozzles 5 and nozzles 15 are arranged alternatively in each column. In the configuration shown in FIGS. 5 and 6a, the extrudates from all of the nozzles 5 and 15 have jet ports 20a, and are therefore provided with gaseous jets 22 (FIG. 1). In the configuration shown in FIG. 6b, only the extrudates of nozzle 5 have jet ports 20a, and will therefore be attenuated by gaseous jets 22 (FIG. 1).

Any clearance between the nozzles 5 and the holes 28a (FIG. 3) is properly sealed to prevent fluid leakage from chamber 6 into chamber 14.

Gaseous fluid B is heated, and passes through the gaseous jets 22 at a high velocity, up to supersonic levels depending on the spinnerette geometry and the processing conditions. The gaseous jets 22 escaping the openings 20a at high velocity attenuate the extrudate cellulose solution 23 from the nozzles 5 to form fine fibers 24. The nozzles 5 and nozzles 15, made of high quality stainless steel, have a length ranging from 0.5" to 3", and inside diameter (ID.) ranging from 0.005" to 0.050". Preferably, nozzles 5 and nozzles 15 have a length from 1" to 2" and an I.D ranging from 0.009" to 0.020". The spacing of the nozzles is between 0.025" to 1.0", and preferably between 0.030" to 0.2". The length of the nozzle projecting beyond the fourth plate 18 is between -0.005" to 1", and preferably, between -0.005" to 0.300".

The present process produces significantly more filaments per inch of spinnerette compared to the process disclosed in U.S. Patent No. 6,306,334 Bl and

U.S. Patent No. 6,358,461 Bl, where a melt blowing die of a single row of spinning nozzles is employed. The multiple rows of extrudate filaments 23 of the cellulose solution are attenuated from a few hundred micrometers in diameter to the fine fibers 24 a few micrometers in diameter within a short distance from the end of the nozzle 5. The hydro jets 25 formed from nozzles 15 cause the filaments to attenuate within a certain distance without contacting the hydro jets 25. After a distance from the tips of nozzles 5, the fine fibers 24 begin to flap, due to turbulence caused by the gas jets 22. That distance, in an example where the tips of the nozzles 5 are substantially flush with the lower edge of plate 18, would likely be in the range of .050" to .300."

The fine fibers 24 interact with gas jets 22 and hydro-jets 25, and become further attenuated, entangled and coagulated. Fine fibers 24 are then deposited onto a perforated moving collector 27 to form a fibrous product 26, which require further treatments, such as regenerating, washing, finishing, drying, and/or other treatments. The surface of the collector 27 is located a distance from the end of nozzles 5 ranging from 3 inches to 100 inches. Depending on this die-to-collector distance (DCD), the pattern of the surface of collector 27, the collector type, and other factors, the cellulosic fibrous products can be in the forms of filament, yarn, fabric, web, tube, cartridge, and other 3-dimensional products.

The above disclosures of the apparatus of this invention teach an apparatus that is configured to extrude an extrudate from multiple rows of nozzles to form a fiber product. The configuration disclosed in FIGS. 1 through 5 is particularly useful in a process of forming cellulosic fibers wherein nozzles 15 extend beyond plate 18 further than nozzles 5. Extrudate from nozzles 5 is accelerated and attenuated by gaseous jets 22 to form fine cellulosic fibers 24. Non-solvent from nozzles 15 may be accelerated by gaseous jets 22 and contacts fibers 24 where it further attenuates fibers 24 and coagulates and entangles the fibers to form a fibrous product 26 as it is collected on collector 27.

In the above described process a cellulose solution is extruded through a first multiplicity of uniformly spaced apart nozzles and upon exiting the nozzles is accelerated and attenuated by high velocity gaseous jets to form fine cellulosic fibers. A coagulating solution is forced through a second multiplicity of nozzles uniformly spaced apart from each other and uniformly spaced apart from and generally parallel to the first multiplicity of nozzles and form high velocity jets so that the coagulating solution impinges upon the fine cellulosic fibers further attenuating them and causing them to coagulate, and entangle to form a product of cellulosic fibers that is collected on a moving collector and further processed for specific properties and specific applications.

The above disclosures are enabling and would permit one skilled in the art to make and use the invention without undue experimentation. However, the above disclosures can not include all variants of the apparatus and process that would become apparent to one skilled in the art, without greatly multiplying the drawings and causing the specifications to become prolix. Therefore the scope of the invention should not be limited to the embodiments disclosed. The scope of the invention should only be limited by the appended claims and all equivalents thereto that would be made apparent thereby to one skilled in the art.

Claims

What is claimed is:

1. An apparatus for forming cellulosic fibers, comprising: a first nozzle plate having openings formed therethrough in at least one row, a first set of nozzles passing through the first nozzle plate and projecting therefrom, a polymer plate which, together with the first nozzle plate, defines a polymer chamber therebetween, from which polymer chamber a polymer solution is fed into the first set of nozzles, a second nozzle plate having a first set of openings formed in at least one row, which set of openings allow the first set of nozzles to pass through the second nozzle plate, the second nozzle plate together with the first nozzle plate defining a fluid chamber therebetween, a second set of nozzles, arranged in at least one row and passing through the second nozzle plate through a second set of openings formed in the second nozzle plate; the first nozzle plate and the second nozzle plate together defining a fluid chamber from which a first fluid is fed to the second set of nozzles; a third plate having three sets of openings formed therein, a first set of openings for the first set of nozzles to pass through, a second set of openings for the second set of nozzles to pass through, and a third set of holes, the second nozzle plate and the third plate together defining a fluid chamber, from which a gaseous fluid is fed to the third set of holes; a fourth plate having formed therein a first set of holes and a second set of holes, the first set of holes receiving the first set of nozzles and permitting the gaseous fluid to pass therethrough, and the second set of holes receiving the second set of nozzles and permitting the gaseous fluid to pass therethrough, the third and fourth plates together defining a gaseous fluid chamber from which the gaseous fluid is fed to the first and second sets of holes of the fourth plate, and a device for maintaining the plates aligned and sealed together as one assembly.

2. The apparatus of claim 1 wherein the first set of nozzles have a length- to-inside-diameter ratio of at least 10 and a nozzle-center-to-nozzle-center space of 0.025" to 1.000".

3. The apparatus of claim 1 wherein the second set of nozzles have a length to inside-diameter ratio of at least 10 and a nozzle-center-to-nozzle-center space of 0.025" to 1.000".

4. The apparatus of claim 1 wherein the polymer solution is a cellulose solution of NMMO, or dilute caustic soda, or phosphoric acid, or a mixture of liquid ammonia/ammonia thiocynate.

5. The apparatus of claim 1 wherein the first fluid is a non-solvent of cellulose.

6. The apparatus of claim 5 in which the non-solvent of cellulose is water or an alcohol (C_nH_2n+ιOH, n<10), or water/alcohol mixture.

7. The apparatus of claim 1 wherein the first fluid is a mixture of solvent(s) and non-solvent(s) of cellulose.

8. The apparatus of claim 1 wherein the gaseous fluid is a heated, compressed, and gaseous fluid.

9. A process wherein the apparatus of claim 1 is employed in the manufacture of fibrous cellulosic products, comprising the steps of; a) extruding a mass of the polymeric solution through the first set of nozzles to form a plurality of extrudates, b) expressing a mass of the first fluid through the second set of nozzles to form a plurality of high velocity fluid jets, c) advancing the extrudates of the first set of nozzles into a multiplicity of high velocity gaseous jets formed around the first set of nozzles by the fourth plate d) attenuating the extrudates by means of the high velocity gaseous jets to form a multiplicity of fine fibers, e) coagulating and further attenuating the fine fibers by the high velocity fluid jets from the second set of nozzles, f) entangling the fine fibers by the high velocity liquid jets before and/or on a surface of a collector to form a fibered product.

10. The process of claim 9 wherein each of the first set of nozzles has a length-to-inside-diameter ratio of at least 10 and a nozzle-center-to-nozzle-center space of 0.025" to 1.000".

11. The process of claim 9 wherein each of the second set of nozzles has a length-to-inside- diameter ratio of at least 10 and a nozzle-center-to-nozzle-center space of 0.025" to 1.000".

12. The process of claim 9 wherein the polymer solution is a cellulose solution of NMMO, or dilute caustic soda, or phosphoric acid, or a mixture of liquid ammonia/ammonia thiocynate.

13. The process of claim 9 wherein the first fluid is a non-solvent of cellulose.

14. The process of claim 9 wherein the first fluid is a mixture of solvent(s) and non-solvent(s) of cellulose.

15. The process of claim 9 in which the non-solvent of cellulose is water, or an alcohol (C_nH_2n+ιOH, n<10), or a water/alcohol mixture.

16. The process of claim 9 wherein the gaseous fluid is a heated, compressed, and gaseous fluid.

17. A fibered product produced by the process of claim 5 wherein the product comprises an entangled accumulation of coagulated cellulose fibers.