U.S. patent application number 10/122927 was filed with the patent office on 2003-10-16 for fibrous webs of bi-component melt-blown fibers of thermoplastic polymers from a bi-component spinnerette assembly of multiple rows of spinning orifices.
Invention is credited to Schwarz, Eckhard C.A..
Application Number | 20030194939 10/122927 |
Document ID | / |
Family ID | 28790651 |
Filed Date | 2003-10-16 |
United States Patent
Application |
20030194939 |
Kind Code |
A1 |
Schwarz, Eckhard C.A. |
October 16, 2003 |
Fibrous webs of bi-component melt-blown fibers of thermoplastic
polymers from a bi-component spinnerette assembly of multiple rows
of spinning orifices
Abstract
Fibrous webs of bi-component fibers are made by extruding a
polymer through one set of nozzles arranged in multiple rows, and
another polymer through a second set of nozzles each of which
surround a nozzle of the first set. In the design of having a
nozzle inside a nozzle, contact between polymer pairs can be
avoided inside a spinnerette, and bic-omponent fibers of unique
properties can be produced. Polymer pairs can be grouped together
which could not be co-extruded in traditional designs where laminar
flow of layered molten masses of different polymers is
rerquired.
Inventors: |
Schwarz, Eckhard C.A.;
(Neenah, WI) |
Correspondence
Address: |
Eckhard C.A. Schwarz
P.O. Box 512
NEENAH
WI
54957-0512
US
|
Family ID: |
28790651 |
Appl. No.: |
10/122927 |
Filed: |
April 16, 2002 |
Current U.S.
Class: |
442/361 ;
442/327 |
Current CPC
Class: |
Y10T 442/68 20150401;
D04H 1/56 20130101; Y10T 442/60 20150401; Y10T 442/652 20150401;
Y10T 442/641 20150401; Y10T 442/637 20150401; Y10T 442/638
20150401 |
Class at
Publication: |
442/361 ;
442/327 |
International
Class: |
D04H 003/00 |
Claims
What is claimed is:
1. A fibrous web comprising a coherent entangled mass of melt-blown
bi-component fibers, said fibers individually comprise a first
polymeric material extending longitudinally along the fiber through
a first circular portion of the cross-sectional area of said fibers
and a second polymeric material adhered to said first polymeric
material and extending logitudinally along said fiber through a
second cylindrical portion of the cross-sectional area of the fiber
surrounding said first circular portion of the cross-sectional area
of the fiber, said fibers being prepared by (a) extruding a mass of
said first polymeric material through a first set of nozzles
arranged in multiple rows and being fed from a first polymer feed
chamber, and a mass of said second polymeric material being fed
through a second set of nozzles arranged in multiple rows and being
fed from a second polymer feed chamber, said second set of nozzles
surrounding each of said first nozzles thus forming nozzle pairs,
and said second nozzles having a larger inside diameter than the
outside diameter of said first nozzles to form a bi-component
extrudate (b) advancing said extrudate into high velocity gas
streams surrounding circumferencially each individual nozzle pair
of said first and second set of nozzles and (c) attenuating said
bi-component extrudate from each of said nozzle pairs to form said
bi-component fibers, (d) said fibers being collected on a moving
screen to form said fibrous web.
2. A fibrous web as of claim 1 wherein said fibers being prepared
by (a) extruding a mass of said first polymeric material through
said first set of nozzles arranged in multiple rows, and a mass of
said second polymeric material through said second set of nozzles
arranged in multiple rows, (b) whereby said first set of nozzles is
recessed into said second set of nozzles by at least 0.030".
3. A fibrous web as of claim 1 wherein said fibers being prepared
by (a) extruding a mass of said first polymeric material through
said first set of nozzles arranged in multiple rows, and a mass of
said second polymeric material through said second set of nozzles
arranged in multiple rows, (b) whereby the ends of said first set
of nozzles are shaped into a semi-circle fitting into said second
set of nozzles thus shaping a fiber having a cross-section in which
each of said first and second polymeric materials occupy
approximately a side-by-side semi-circle.
4. A fibrous web of claim 1 where the points of fiber intersection
are bonded by coalescence of polymeric material.
Description
BACKGROUND OF THE INVENTION.
[0001] This invention relates to an adaptation of bi-component
fiber spinning to a melt-blowing process as described in U.S. Pat.
No. 5,476,616, which is herewith incorporated as reference. More
particularly, it relates to the improvement whereby the number of
rows of spinning orifices can be extended beyond the number
possible before and still maintain fiberforming spinning quality,
using polymer pairs of greatly differing melt viscosities and other
properties.
OBJECTS OF THE INVENTION.
[0002] It is an object of the present invention to provide a
bi-component spinning system whereby a spinning nozzle fed by one
type of polymer from one chamber is located inside another slightly
larger spinning nozzle fed by a second chamber, said nozzle pairs
being arranged in multiple rows of spinning orifices, and directing
streams of gas to each row of spinning orifices.
[0003] Another object of the invention is to provide a uniform
stream of attenuating gas around each spinning nozzle by centering
the nozzle pairs in round holes of gas cover plates to achieve an
even gas flow around the circumference of each nozzle pair.
SUMMARY OF THE INVENTION
[0004] These and other objects of the invention are achieved by
directing a gas flow to the base of the spinning nozzle pair by
means of baffle plates, and extending the length of the spinning
nozzle pairs. The spinning nozzle pairs are guided through a family
of gas cover plates providing for the centering of the round
spinning nozzle pairs through round gas supply holes and supplying
a uniform stream of gas to each nozzle pair and row of nozzle
pairs.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] A better understanding of the present invention as well as
other objects and advantages thereof will become apparent upon
consideration of the detailed disclosure thereof, especially when
taken with the accompanying drawings, wherein like numerals
designate like parts throughout; and wherein
[0006] FIG. 1A is a partially schematic side view of a spinnerette
assembly of the present invention, showing the path of gas and the
two polymer flows;
[0007] FIG. 1B is the same spinnerette where the inner nozzles 4
have been shortened by the distance 22.
[0008] FIG. 2A is a partial bottom view of the concentric spinning
nozzles and gas cover plates, taken along the lines 23-23.
[0009] FIG. 2B is a partial bottom view of the concentric spinning
nozzles and gas cover plates, taken along the lines 24-24.
[0010] FIG. 3 is a partial bottom view of a spinnerette assembly,
wherein the inner nozzle is off-center and shaped in a half-circle
to form side-by-side bi-component fibers.
DETAILED DESCRIPTION OF THE INVENTION
[0011] In previous bi-component spinning assemblies, side-by-side
or sheath-core structures are being formed by having two polymers
flow through capillaries in a laminar flow pattern without mixing
before exiting the capillary and then solidifying. This limits the
polymer pairs to such groups that are capable of laminar flow, i.e.
have similar melt-viscosities and other properties at similar
extrusion temperatures. Bi-component designs have been disclosed in
U.S. Pat. Nos. 2,931,091 and 3,039,174. Most of these designs were
used in traditional textile yarn spinning and are not easily
adaptable to the melt-blowing process.
[0012] In U.S. Pat. No 6,057,256 to Krueger et al. a bi-component
met-blowing process is shown where the polymers are contacted with
each other inside the die-body as previously described, and, by
laminar flow exit the spinning orifice and are drawn down by high
velocity air. This design, however, is limited to a single row of
spinning orifices and consequently relatively low capacity.
[0013] In the present invention, a bi-component melt-blowing system
is shown where bi-component fibers are being spun out of multiple
rows of spinning orifices, and whereby the contact time of two or
more polymers inside the die-body can be controlled from zero to
any finite time chosen, by having one capillary in which a first
polymer flows, being fed from one polymer manifold, is surrounded
by a second, larger than the first capillary, through which a
second polymer fed from a second polymer manifold flows; at the
exit point, each tubular nozzle is surrounded by a concentric flow
of high velocity air as described in previously cited U.S. Pat. No.
5,476,616.
[0014] Referring now to FIG. 1, the spinnerette assembly is mounted
on the die body 1 which supplies polymer melt 2 to first supply
cavity 3 feeding the spinning nozzles 4 which are mounted in the
spinnerette body plate 5 wherein nozzles 4 are mounted. A second
set of nozzles 6, larger than nozzles 4, having an identical
mounting pattern as nozzles 4, is mounted on the die body plate 7
and is being fed with a second polymer 8 from the die body 1 and
through plate 5 to cavity 9 which feeds nozzles 6. Nozzles 4 are
inserted into nozzles 6, and have the same or shorter length than
nozzles 4. The nozzles 4 and 6 lead through the gas cavity 10,
which is fed with gas, air or other suitable fluids from gas inlet
slot 11. The primary gas supply enters the spinnerette assembly
through pipe 12 into the supply cavity 13. The baffle plate 14
diverts the gas stream and forces the gas through the slot 11
toward the base of nozzles 6. The nozzles 4 and 6 protrude through
gas cover plate 15 through tight fitting holes 16 arranged in the
same pattern as the nozzle mounts in spinnerette body plates 5 and
7. The gas cover plate family further consists of spacer plate 18
which forms a second gas cavity 19 between plate 15 and 20. The
complete path of the gas is now from inlet pipe 12 into the gas
supply cavity 13 through inlet slot 11 into gas cavity 19. The gas
then flows through gas holes 17 of plate 15 into the gas cavity 19
and then around the nozzles 6 through holes 21, in which nozzles 6
are centered. The high velocity gas out of holes 21 accelerate and
attenuate the exiting polymer melt to form fine fibers. FIGS. 2A
and B show the bottom view of plates 15 and 20, respectively. FIG.
3 shows a bottom view of plate 20, wherein the inner nozzles 4 are
shaped in a half circle to produce a side-by-side bi-component
fiber.
[0015] The following examples are included for the purpose of
illustrating the invention and it is understood that the scope of
the invention is not to be limited thereby.
EXAMPLE 1
[0016] A 5" long spinnerette was used of the type shown in FIG. 1.
The spinnerette had 12 rows of nozzles, spaced 0.060" apart, within
each rows, the nozzles were also spaced 0.060" apart, resulting in
a total number of nozzles of 1000. The inner nozzles 4 mounted in
plate 5 had an outside diameter of 0.020" and an inside diameter of
0.010". The outside nozzles 6 mounted in plate 7 had an outside
diameter of 0.035" and an inside diameter of 0.023". Air cavity 10
had a height of 0.500", air cover plate 15 a thickness of 0.063".
Air holes 17 shown in FIGS. 1 and 2A had a diameter of 0.020". Air
cavity 19 had a height of 0.100" and air cover plate 20 a thickness
of 0.063". The air holes 21 in plate 20 had a diameter of 0.048".
The resin inlets 2 and 8 were each connected to a 1" (24/1
length/diameter ratio) extruder, subsequently referred to as
extruder A and B, respectively each capable of extruding
approximately 10 lb/hr of polymer resin.
[0017] Extruder B (sheath polymer) was charged with high density
polyethylene of Melt Index 105 (Dow Chemical Co's "ASPUN" 6808A)
and the resin was extruded into the spinnerette at a rate of 30
gram per minute; Extruder A (core polymer ) was charges with
polypropylene of MFR 70 (Melt Flow Rate, as determined by
ASTM-Method D-1238-65T)(HIMONT "HIH442") and extruded at a rate of
45 gram per minute, 3% of blue polypropylene color concentrate was
added to the polypropylene resin to give the core fiber a blue
appearance. The spinnerette temperature and the air temperature
were 480 degree Fahrenheit, and the air pressure was 20 psi. 12"
below the spinnerette there was a moving screen that collected a
web of highly entangled blue fibers of 3 to 6 micrometer diameter.
The web had a typical slick, silklike polyethylene feel, indicating
that the polyethylene from extruder B was on the outside. Parallel
strands of fibers were imbedded and cured into an epoxy resin, and
cross sections were cut therefrom. Microscopic examination showed a
concentric sheat/core fiber structure, with the blue color visible
in the core section. When the fibrous web was heated to a
temperature of 250 degree F, most of the point of intersection
bonded by coalescence and the web formed a stiff, shape-retaining
structure.
EXAMPLE II
[0018] Additional experiments were conducted using polymer pairs as
shown in Table 1:
1TABLE 1 Experiment No.: 1 2 3 4 Polymer from PET Polyester* 6/6
Nylon** PBT Polyester*** Polypropylene Extruder A 0.59 IV**** 35
RV***** 0.59 IV 70 MFR Extrusion rate 30 g/min 35 g/min 45 g/min 40
g/min Polymer from 6,6 Nylon PET Polyester Nylon 6****** Nylon 6
Extruder B 35RV 0.59W 4ORV 4ORV Extrusion rate 45 g/min 50 g/min 30
g/min 25 g/min Spinnerette Temp. (F.) 520 520 480 470 Air Temp.(F.)
510 520 480 470 Air pressure (psi) 25 25 23 24 *Poly-(ethylene)
terephthalate **Poly-(hexamethylene adipamide) ***Poly-(butylene)
terephthalate ****Intrinsic Viscosity *****Relative Viscosity
******Poly (caproamide)
[0019] Microscopic examination of the fiber cross sections, which
ranged from 3 to 7 micrometer in diameter, revealed that the
sheat/core structure was concentric or near concentric.
EXAMPLE III
[0020] Example I was repeated using identical polymers and process
conditions, but with a spinnerette described in FIG. 1B where the
inner nozzles 4 where recessed by the length 22 of 0.150". Under a
microscope, the fiber cross sections showed the same concentric
sheath/core structure as in Example I, with the blue polypropylene
inside.
EXAMPLE IV
[0021] EXAMPLE I was repeated using a nozzle arrangement as shown
in FIG. 3. Upon microscopic examination, the fiber cross-section
showed that the two polymers had each formed a semi-circle in a
side-by-side configuration.
[0022] While the invention has been described in connection with
several examplary embodiments thereof, it will be under stood that
many modifications will be apparent to those of ordinary skill in
the art, and that this application is intended to cover any
adaptations and variations thereof. Therefore, it is manifestly
intended that this invention be only limited by the claims and the
equivalents thereof.
* * * * *