U.S. patent application number 10/663117 was filed with the patent office on 2005-03-17 for process for forming micro-fiber cellulosic nonwoven webs from a cellulose solution by melt blown technology and the products made thereby.
This patent application is currently assigned to Biax Fiberfilm Corporation. Invention is credited to Schwarz, Eckhard C. A., Zhao, Rongguo.
Application Number | 20050056956 10/663117 |
Document ID | / |
Family ID | 34274283 |
Filed Date | 2005-03-17 |
United States Patent
Application |
20050056956 |
Kind Code |
A1 |
Zhao, Rongguo ; et
al. |
March 17, 2005 |
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.
Inventors: |
Zhao, Rongguo; (Neenah,
WI) ; Schwarz, Eckhard C. A.; (Neenah, WI) |
Correspondence
Address: |
Dr. Rongguo Zhao
Suite B
N992 Quality Dr.
Greenville
WI
54942
US
|
Assignee: |
Biax Fiberfilm Corporation
Greenville
WI
|
Family ID: |
34274283 |
Appl. No.: |
10/663117 |
Filed: |
September 16, 2003 |
Current U.S.
Class: |
264/37.24 ;
156/62.4; 264/103; 264/179; 264/180; 264/187; 264/203; 264/210.8;
264/211.12; 264/211.18; 264/211.2; 264/555; 425/377 |
Current CPC
Class: |
D01F 2/00 20130101; D01D
5/14 20130101; D01D 4/025 20130101; D04H 18/04 20130101 |
Class at
Publication: |
264/037.24 ;
264/555; 264/210.8; 264/187; 264/203; 264/103; 264/211.12;
264/211.18; 264/211.2; 264/179; 264/180; 425/377; 156/062.4 |
International
Class: |
D04H 003/02; D01D
005/06; D01D 005/12; D01D 010/06; D01F 002/02; D04H 003/08 |
Claims
What is claimed is:
1. A process for forming bonded cellulosic microfibers nonwovens
comprises the steps of (a) extruding a cellulose solution (dope)
through a concentric melt blown spinneret with a plurality 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.
2. The process of claim 1 in which the spinning nozzles are
arranged in at least one row with a nozzle-to-nozzle space of
0.050" to 1.000"
3. The process of claim 1 in which the spinning nozzles are 0.005"
to 0.050" in inside diameter and 0.500" to 3.000" in length.
4. The process of claim 1 in which the spinning nozzles are
concentric with their individual gas holes and protruded -0.005" to
0.800" from the top plate of the said gas holes.
5. The process of claim 1 in which the solvent of the cellulose
solution is one or more of the following: NMMO, dilute caustic
soda, phosphoric acid, mixture of liquid ammonia/ammonia thiocynate
and others.
6. The process of claim 1 in which the non-solvent of cellulose is
one or more of the following: water, alcohol (C.sub.nH.sub.2n+1OH,
n.ltoreq.10), and/or water/alcohol/solvent solutions
7. The process of claim 1 in which the recycling
solvent/non-solvent solution is filtered and supplied from the
regenerating bath by a high pressure pump and part of the solution
is continuously removed from the said bath for solvent
recycling.
8. The process of claim 1 in which the recycling NMMO solution is
supplied to the needling jets from and come back to the first
regenerating bath. The second washing bath is continuously filled
with fresh non-solvent, which is sprayed onto the nonwoven web
first. Part of the low concentration solution continuously overflow
from the washing bath to the regenerating bath.
9. The collecting system for manufacturing the said cellulose fiber
nonwoven comprises (a) a paternally perforated drum with a diameter
ranged from 20 inch to 70 inch (b) at least one set of coagulating
hydro needling jets, which contacts with flying fibers 0.5 inch to
30 inch from the collecting surface and at an angle from 5 degree
to 75 degree (relative to the air blowing direction) (c) at least
another set of hydro needling jets downstream for both
hydro-entangling and fiber regenerating. (d) at least one
regenerating bath and one washing bath with conveying belts. (e) at
least one vacuum section across and beneath the drum surface (f) at
least one heating section across and above the drum surface
10. The collecting system of claim 4 in which the regenerating and
washing bathes contain series of rollers to guide the nonwoven
web.
11. The conveying belt of claim 9 submerged in both bathes moves
slower than surface speed of the collecting drum.
12. The cellulosic nonwovens of claim 1 in which the fibers are
essentially continuous with an average size of 1 to 30 micrometer
in diameter and bonded by both self-bonding and hydro-entanglement.
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 filaments travel a short
distance in air (the dry-jet), then get into a coagulation bath for
regeneration. A proper mechanical pulling force is applied onto 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. Pat. Nos. 4,142,913;
4,144,080; 4,211,574; 4,246,221, and 4,416,698 and others described
the details of this process.
[0008] Jurkovic et al., in U.S. Pat. No 5,252,284 and Michels et
al., in U.S. Pat. No. 5,417,909 deal especially with 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.
[0009] Zikeli et al., in U.S. Pat. Nos. 5,589,125 and 5,607,639,
direct a stream of air transversely across strands of extruded
lyocell dope as they leave the spinnerets. 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. However, these are highly fragmented
microfibers useful principally for production of self bonded
non-woven webs.
[0010] U.S. Pat. No. 6,306,334 teaches a process using much larger
sectioned spinning orifices compared with the above referenced
technologies enabling a higher dope throughput per orifice to
minimize tendency for orifice plugging problem. 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.
SUMMARY OF THE INVENTION
[0011] The present invention is directed 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 term of
"cellulose" as used here should be understood as either cellulose
from natural resources or a synthetic polymer blend with cellulose.
The term of "die" is often used as the term of "spinneret" in this
invention. The term of "concentric melt blown die" refers to an
apparatus described in U.S. Pat. No 5,476,616 with the hot air
nozzles concentric with the polymer spinning nozzles and the air
flows parallel with the polymer filaments near the exits of the
nozzles.
[0012] The cellulose solution is extruded out through each spinning
nozzle at a proper temperature (ranging from 80 to 140.degree. C.)
and a proper throughput. The extrudates are attenuated quickly by
high velocity hot air jets from a few hundred micrometers in
diameter to a few micrometers in diameter within a few centimeters
from the nozzle exits. These microfibers are collected on the
surface of a moving collecting device, which can be either a drum
collector or a flat screen collector. A set of jets of
solvent/non-solvent mixture shoots from a series of fine
orifices/nozzles on the flying fibers and the collected web. The
term of solvent used in the present invention refers to NMMO,
dilute caustic soda, phosphoric acid, mixture of liquid
ammonia/ammonia thiocynate and others. The term of "non-solvent"
used here refers to water, alcohol (C.sub.nH.sub.2n+1OH,
n.ltoreq.10), and/or water/alcohol/solvent solutions. The term
"water" is often used as the term of "non solvent" in this
invention. Depending on the position and angle of the non-solvent
jet, the amount of non-solvent applied, and other factors, the
resultant cellulose microfiber nonwoven web exhibits different
characteristics. The jets of solvent/non-solvent solution serves
two functions in this process, coagulating (fully or partially) the
filaments and hydro-entangling the filaments to form webs.
[0013] The final cellulose microfibers have an average fiber
diameter ranging from 1 micrometer to 20 micrometer with a
relatively broad fiber diameter distribution
[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.
[0015] There is an object of the present invention to provide a
method of forming cellulose microfiber nonwoven fabrics from a
solution of a cellulose solvent, such as NMMO, by utilizing melt
blown technology with concentric multiple-row spinning nozzles
[0016] It is an additional object to provide a method for making
the said nonwoven web without additional processes, i.e. carding,
web forming, and bonding.
[0017] It is a further object to provide a method for making
cellulose nonwovens with different web structures.
[0018] It is another object to provide a method for forming a
biodegradable nonwoven web.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The foregoing aspects and many of the attendant advantages
of this invention will become more readily appreciated as the same
becomes better understood by reference to the following detailed
description, when taken in conjunction with the accompanying
drawings, wherein:
[0020] FIG. 1 is a schematic view of a melt blowing spinneret with
multiple rows of spinning nozzles and concentric air jets used with
the invention.
[0021] FIG. 2 is a schematic bottom view of part of the melt
blowing spinneret in FIG. 1.
[0022] FIG. 3 is a diagram of the equipment used with the above
melt blowing spinneret.
[0023] FIGS. 4, 5 and 6 are optical micrographs of melt blown
Lyocell nonwoven at 40.times., 100.times. and 400.times.,
respectively.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0024] The process of the present invention is suitable to various
cellulose solutions. The solvent includes NMMO, dilute caustic
soda, phosphoric acid, mixture of liquid ammonia/ammonia thiocynate
and others. The ways making a solution of the 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 B1, 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))
[0025] Reference to FIG. 1, it shows a schematic view of a melt
blowing spinneret. The cellulose solution is supplied by an
extruder and/or metering pump through the cavity 2 of the
distribution plate 1 to the nozzle plate 4. The plate 4 includes a
gas cavity 9, which is supplied with hot compressed air or other
fluids from 3. The baffle plates 8 divert the gas stream and force
the gas through the gas distribution plate 5 and the air holes 13
of the top plate 7. Plates 5 and 7 are separated with a spacer 6.
The hot air jets 11 reach a sonic velocity at the air hole exit,
even at supersonic levels depending on the spinneret geometry and
the processing conditions. The high velocity gas accelerates and
attenuates the exiting cellulose NMMO solution 12 from the nozzles
10 to form fine fibers 12a. The nozzles, made of high quality
stainless steel, have a length ranging from 0.5" to 3", and inside
diameter (I.D.) ranging from 0.005" to 0.050", and preferably, a
length from 1" to 2" and an I.D ranging from 0.009" to 0.020". The
spacing of the nozzles is between 0.045" to 1.0", and preferably,
between 0.050" to 0.2". The length of the nozzle sticking out of
the top plate is between -0.005" to 1", and preferably, between
0.050" to 0.220". FIG. 2 shows a portion of the spinneret bottom
view.
[0026] The present process produces significantly more filaments
per inch spinneret compared to the process disclosed in U.S. Pat.
No. 6,306,334 B1 and U.S. Pat. No. 6,358,461 B1, where a melt
blowing die of single row of spinning holes employed.
[0027] FIG. 3 shows an example of detailed melt blowing process of
this invention. The multiple row filaments of the cellulose
solution are attenuated from a few hundred micrometers in diameter
to a few micrometers in diameter within a short distance from the
spinneret. With the high velocity air jets 11, these molten
microfibers 12a are blown onto a paternally perforated moving
surface 14, which is located 3 inch to 50 inch from the spinneret.
At a point in the spinline, two sets of jet heads 15 shoot high
pressure/speed hydro jets 16 onto the fiber/air stream with an
angle 17 to coagulate/regenerate and entangle the cellulose
microfibers. At least another set of jet heads 19 shooting hydro
jets 20 is used down stream to enhance the integrity and properties
of nonwoven web. The term of "hydro jet" in the present invention
refers to jets of pressured liquid or mixture of liquid/air.
Through a set of cartridge filters 43 and transfer lines 18, these
hydro-jets 16 and 20 are supplied with circulating
solvent/non-solvent solution 26 from the first regenerating bath 27
by a high-pressure pump 44. The solvent/non-solvent solution
applied to the nonwoven web will return to the first generating
bath with the help of the gutter 42. The hydro-entangled web 22
guided by a roller 21 enters into the nip of pressure roller 23 and
driving roller 24 travels in the first bath 27 for major
regeneration. The web 22 folds in layers on slow-moving conveyer
screen 28 submerged in bath 27. The conveyer screens 28 and 28a are
supported by rollers 29 and 29a. The layered web 25 is submerged in
solution 26 for at least 30 seconds, then enters into the nip of
pressure roller 31 and driving roller 32 for liquid removing. The
squeezed web folds to form web layers 33 onto the conveyer screen
28a in the bath 34 for further regeneration in fresh water. After
at least 25 seconds, the web comes out of the bath 34, gets washed
with fresh water sprays 35, and goes through the nip of 21a and
pressure roller 36. The washed and squeezed web travels with the
collector surface 14 through a zone heated with heater 37 and
vacuumed with a vacuum duct 38 and vacuum head 39. The dried
Lyocell fiber nonwoven web is winded up as roll 41 on the surface
of the collector. At least one gutter 40 is attached to the vacuum
duct to guide the penetrated solution back to the nonwoven web. The
solution in bath 27 and bath 34 is stirred constantly by helical
stirrers 43.
[0028] The optical micrographs shown in FIGS. 4-6 are of Lyocell
fibers made by the process of the present invention. The average
fiber diameter is about 5.about.15 micrometers.
EXAMPLE 1
[0029] A 3/4 inch extruder is fed with a NMMO solution comprising
10.5% by weight cellulose, 77.5% by weight of NMMO and the rest is
mainly water. The solid solution are in the form of pellet of
0.05".about.0.08" in size. The feeding hoper is filled with Argon
gas to prevent moisture takeup. The cellulose has an average degree
of polymerization from 330.about.360.
[0030] The extruder has three heating zones and the temperatures
were set as 165.degree. F. (Zone 1, near the feeding hoper),
210.degree. F., 230.degree. F., respectively. The molten solution
was forced into the body of a 5-inch-2-row spinneret, with 126
spinning nozzles (I.D.=0.009") and protruding length of 0.1915".
The solution temperature and pressure at the spinneret were kept in
230.degree. F. and 600 PSI, respectively. The air temperature and
pressure in the spinneret were held at 250.degree. F. and 15 PSI
respectively. The solution throughput was about 0.16
gram/nozzle/min.
[0031] The attenuated microfibers are deposited on a perforated
rotating drum right after contacted with the hydro needling jets.
These strong needling jets serve as a pre-coagulation means and a
fiber entangling means. The web goes through another set of hydro
needling jets for better mechanical bonding and regenerating. The
well bonded web is regenerated, washed, post-treated, and air
dried.
EXAMPLE 2
[0032] A 1 inch extruder is fed with a NMMO solution comprising 14%
by weight cellulose, 76% by weight of NMMO and the rest is mainly
water. The solid solution are in the form of pellet of
0.05".about.0.08" in size. The feeding hoper is filled with Argon
gas to prevent moisture takeup. The cellulose has an average degree
of polymerization of 670.
[0033] The extruder has three heating zones and the temperatures
were set as 185.degree. F. (Zone 1, near the feeding hoper),
230.degree. F., 250.degree. F., respectively. The molten solution
was forced into the body of a 5-inch-2-row spinneret, with 63
spinning nozzles (I.D.=0.020") and protruding length of 0.180". The
solution temperature and pressure at the spinneret were kept in
250.degree. F. and 860 PSI, respectively. The air temperature and
pressure in the spinneret were held at 270.degree. F. and 10 PSI
respectively. The solution throughput was about 0.8
gram/nozzle/min.
[0034] The inventors have herein described the best present mode of
practicing their invention. It will be evident to others skilled in
the art that many variations that have not been exemplified should
be included within the broad
* * * * *