U.S. patent application number 15/517075 was filed with the patent office on 2017-10-19 for high melting point resin fibers and nonwoven fabric.
This patent application is currently assigned to Daicel Corporation. The applicant listed for this patent is DAICEL CORPORATION. Invention is credited to Takahiro TEI, Aya YOKOYAMA.
Application Number | 20170298535 15/517075 |
Document ID | / |
Family ID | 55760667 |
Filed Date | 2017-10-19 |
United States Patent
Application |
20170298535 |
Kind Code |
A1 |
TEI; Takahiro ; et
al. |
October 19, 2017 |
HIGH MELTING POINT RESIN FIBERS AND NONWOVEN FABRIC
Abstract
Provided are: a high-melting-point resin fiber having heat
resistance and solvent resistance, offering excellent
workability/formability, and having a diameter of 4 .mu.m or less;
and a nonwoven fabric including the high-melting-point resin fiber.
Also provided is a method for efficiently producing a
high-melting-point resin fiber having a diameter of 4 .mu.m or
less, via laser melt electrospinning. The high-melting-point resin
fiber according to the present invention includes a resin having a
melting point of 250.degree. C. or higher and has a diameter of 4
.mu.m or less. In the high-melting-point resin fiber, the resin
having a melting point of 250.degree. C. or higher is preferably a
PEEK. The fiber preferably has a degree of crystallinity of 30% or
less.
Inventors: |
TEI; Takahiro; (Tokyo,
JP) ; YOKOYAMA; Aya; (Amagasaki-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DAICEL CORPORATION |
Osaka-shi, Osaka |
|
JP |
|
|
Assignee: |
Daicel Corporation
Osaka-shi, Osaka
JP
|
Family ID: |
55760667 |
Appl. No.: |
15/517075 |
Filed: |
August 26, 2015 |
PCT Filed: |
August 26, 2015 |
PCT NO: |
PCT/JP2015/074034 |
371 Date: |
April 5, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D04H 3/016 20130101;
D01D 5/0092 20130101; D01D 5/08 20130101; D01F 6/665 20130101; D01F
6/76 20130101; D01D 5/0023 20130101; D04H 1/728 20130101 |
International
Class: |
D01D 5/00 20060101
D01D005/00; D04H 1/728 20120101 D04H001/728; D01F 6/66 20060101
D01F006/66; D04H 3/016 20120101 D04H003/016; D01D 5/00 20060101
D01D005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 20, 2014 |
JP |
2014-213828 |
Claims
1. A high-melting-point resin fiber comprising a resin having a
melting point of 250.degree. C. or higher, the fiber having a
diameter of 4 .mu.m or less.
2. The high-melting-point resin fiber according to claim 1, wherein
the resin having a melting point of 250.degree. C. or higher
comprises a poly(ether ether ketone) (PEEK).
3. The high-melting-point resin fiber according to claim 1, which
has a degree of crystallinity of 30% or less.
4. A method for producing a high-melting-point resin fiber, the
method comprising: applying planar laser light to a polymer sheet
comprising a noncrystalline high-melting-point resin to heat and
melt an edge of the polymer sheet linearly to thereby form a
band-like molten zone; providing a potential difference between the
band-like molten zone and a fiber collecting plate to form a needle
protrusion in the band-like molten zone of the polymer sheet and to
allow a fiber ejected from the needle protrusion to fly toward the
fiber collecting plate; and collecting the fiber on the fiber
collecting plate or on a collector disposed between the molten zone
and the fiber collecting plate to give the high-melting-point resin
fiber according to claim 1.
5. The method according to claim 4 for producing a
high-melting-point resin fiber, wherein the polymer sheet is fed at
a speed of 2 to 20 mm/min.
6. The method according to claim 4 for producing a
high-melting-point resin fiber, wherein the potential difference is
0.1 to 30 kV/cm.
7. The method according to claim 4 for producing a
high-melting-point resin fiber, wherein the polymer sheet has a
viscosity of 800 Pas or less as measured at a temperature of
400.degree. C. and a shear rate of 121.6 s.sup.-1.
8. A nonwoven fabric comprising the high-melting-point resin fiber
according to claim 1.
9. The high-melting-point resin fiber according to claim 2, which
has a degree of crystallinity of 30% or less.
10. A method for producing a high-melting-point resin fiber, the
method comprising: applying planar laser light to a polymer sheet
comprising a noncrystalline high-melting-point resin to heat and
melt an edge of the polymer sheet linearly to thereby form a
band-like molten zone; providing a potential difference between the
band-like molten zone and a fiber collecting plate to form a needle
protrusion in the band-like molten zone of the polymer sheet and to
allow a fiber ejected from the needle protrusion to fly toward the
fiber collecting plate; and collecting the fiber on the fiber
collecting plate or on a collector disposed between the molten zone
and the fiber collecting plate to give the high-melting-point resin
fiber according to claim 2.
11. A method for producing a high-melting-point resin fiber, the
method comprising: applying planar laser light to a polymer sheet
comprising a noncrystalline high-melting-point resin to heat and
melt an edge of the polymer sheet linearly to thereby form a
band-like molten zone; providing a potential difference between the
band-like molten zone and a fiber collecting plate to form a needle
protrusion in the band-like molten zone of the polymer sheet and to
allow a fiber ejected from the needle protrusion to fly toward the
fiber collecting plate; and collecting the fiber on the fiber
collecting plate or on a collector disposed between the molten zone
and the fiber collecting plate to give the high-melting-point resin
fiber according to claim 3.
12. The method according to claim 5 for producing a
high-melting-point resin fiber, wherein the potential difference is
0.1 to 30 kV/cm.
13. The method according to claim 5 for producing a
high-melting-point resin fiber, wherein the polymer sheet has a
viscosity of 800 Pas or less as measured at a temperature of
400.degree. C. and a shear rate of 121.6 s.sup.-1.
14. The method according to claim 6 for producing a
high-melting-point resin fiber, wherein the polymer sheet has a
viscosity of 800 Pas or less as measured at a temperature of
400.degree. C. and a shear rate of 121.6 s.sup.-1.
15. A nonwoven fabric comprising the high-melting-point resin fiber
according to claim 2.
16. A nonwoven fabric comprising the high-melting-point resin fiber
according to claim 3.
Description
TECHNICAL FIELD
[0001] The present invention relates to high-melting-point resin
fibers and nonwoven fabrics each formed via melt
electrospinning.
[0002] More specifically, the present invention relates to a
high-melting-point resin fiber formed by processing a
high-melting-point resin (film) into an ultrafine fiber via melt
electrospinning using laser light as a heating means (laser melt
electrospinning), where the ultrafine fiber has a diameter of 4
.mu.m or less; and to a nonwoven fabric including the
high-melting-point resin fiber. This application claims priority to
Japanese Patent Application No. 2014-213828, filed Oct. 20, 2014 to
Japan, the entire contents of which are incorporated herein by
reference.
BACKGROUND ART
[0003] Fibers having a fiber diameter on the order of submicrons or
nanometers contribute to development of novel materials using their
large specific surface areas and their fibrous form and have
received attention. Melt electrospinning is proposed as an
exemplary technique for producing such fibers. The melt
electrospinning is an electrospinning technique in which a high
voltage is applied to a polymer melt to form fibers.
[0004] For example, Patent Literature (PTL) 1 proposes a method
using laser melt electrospinning as a melt electrospinning
technique. With this method, fibers are produced via a
heating-melting step and an electrospinning step. In the
heating-melting step, laser light (laser beam) is applied to a
thermoplastic resin to heat and melt the thermoplastic resin. In
the electrospinning step, a voltage is applied to a molten zone of
the thermoplastic resin to elongate a fiber, and the elongated
fiber is collected on a collector. According to this method, the
fibers are produced by preparing or using a linear resin article as
a spinning material and allowing the linear resin article to eject
a fiber from the tip of the linear resin article.
[0005] PTL 2 discloses a method using the laser melt
electrospinning technique. In this method, linear laser light is
applied to a sheet-like article including a thermoplastic resin to
heat and melt an edge of the sheet-like article linearly to form a
molten zone. With this, a potential difference is provided between
the molten zone and a metallic collector to form needle protrusions
in the thermally molten zone of the sheet-like article. Fibers
ejected from the needle protrusions are allowed to fly toward the
metallic collector and are collected on the metallic collector or
on a collector disposed between the molten zone and the metallic
collector.
[0006] High-melting-point resins such as poly(ether ether ketone)s
(PEEKs), poly(phenylene sulfide)s (PPSs), and polyamideimides
(PAIS) have heat resistance, flame retardancy, chemical resistance,
and impact resistance, are also called "super engineering
plastics", and are widely used in applications in the automotive
and electric/electronic fields. Among them, PEEKs have a melting
point of 334.degree. C. and have such super heat resistance as to
be continuously usable at 250.degree. C. The PEEKs are aromatic
plastics which have approximately highest heat resistance among
thermoplastic resins and have chemical resistance typically to
organic solvents.
[0007] These high-melting-point resins have been formed into fibers
typically by meltblowing technique. This technique, however, gives
fibers having diameters of several micrometers to several tens of
micrometers and can hardly give more ultrafine nanofibers. Such
more ultrafine nanofibers have been obtained typically by the
electrospinning technique. This technique, however, is not
applicable to the PEEKs and other super engineering plastics, which
have high melting points. This is because most of these super
engineering plastics are insoluble typically in organic
solvents.
CITATION LIST
Patent Literature
[0008] PTL 1: Japanese Unexamined Patent Application Publication
(JP-A) No. 2007-239114
[0009] PTL 2: JP-A No. 2010-275661
SUMMARY OF INVENTION
Technical Problem
[0010] In contrast, the laser melt electrospinning technique
disclosed in PTL 2 does not control the degree of crystallinity of
the material film and tends to fail to perform the working at a
higher rate when the material film (sheet) has a high degree of
crystallinity. In addition, the technique gives fibers which have
diameters of 5 .mu.m or more and which have high degrees of
crystallinity, and this impedes working/forming of the fibers.
[0011] Accordingly, the present invention has an object to provide
a high-melting-point resin fiber that has heat resistance and
solvent resistance, offers excellent workability/formability, and
has a diameter of 4 .mu.m or less; and to provide a nonwoven fabric
formed from the high-melting-point resin fiber. The present
invention has another object to provide a method for efficiently
producing a high-melting-point resin fiber having a diameter of 4
.mu.m or less, via laser melt electrospinning.
Solution to Problem
[0012] After intensive investigations to achieve the objects, the
inventors of the present invention found that laser melt
electrospinning, when employing a material polymer sheet including
a resin having a melting point of 250.degree. C. or higher, can
give a high-melting-point resin fiber which includes the resin
having a melting point of 250.degree. C. or higher and which has a
diameter of 4 .mu.m or less. The present invention has been made on
the basis of these findings.
[0013] Specifically, the present invention provides a
high-melting-point resin fiber that includes a resin having a
melting point of 250.degree. C. or higher and has a diameter of 4
.mu.m or less.
[0014] In the high-melting-point resin fiber according to the
present invention, the resin having a melting point of 250.degree.
C. or higher is preferably a PEEK.
[0015] The high-melting-point resin fiber according to the present
invention preferably has a degree of crystallinity of 30% or
less.
[0016] The present invention also provides a method for producing a
high-melting-point resin fiber. The method includes applying planar
laser light to a polymer sheet including a noncrystalline
high-melting-point resin to heat and melt an edge of the polymer
sheet linearly to thereby form a band-like molten zone. With this,
a potential difference is provided between the band-like molten
zone of the polymer sheet and a fiber collecting plate to form a
needle protrusion in the band-like molten zone of the polymer sheet
and to allow a fiber ejected from the needle protrusion to fly
toward the fiber collecting plate. The fiber is collected on the
fiber collecting plate or on a collector disposed between the
molten zone and the fiber collecting plate, to give the
high-melting-point resin fiber.
[0017] In the method according to the present invention for
producing a high-melting-point resin fiber, the polymer sheet is
preferably fed at a speed of 2 to 20 ram/min.
[0018] In the method according to the present invention for
producing a high-melting-point resin fiber, the potential
difference is preferably 0.1 to 30 kV/cm.
[0019] In the method according to the present invention for
producing a high-melting-point resin fiber, the polymer sheet
preferably has a viscosity of 800 Pas or less as measured at a
temperature of 400.degree. C. and a shear rate of 121.6
s.sup.-1.
[0020] The present invention also provides a nonwoven fabric
including the high-melting-point resin fiber according to the
present invention.
[0021] Specifically, the present invention relates to the
followings.
[0022] (1) The present invention relates to a high-melting-point
resin fiber which includes a resin having a melting point of
250.degree. C. or higher and which has a diameter of 4 .mu.m or
less.
[0023] (2) In the high-melting-point resin fiber according to (1),
the resin having a melting point of 250.degree. C. or higher may be
a PEEK.
[0024] (3) The high-melting-point resin fiber according to one of
(1) and (2) may have a degree of crystallinity of 30% or less.
[0025] (4) The high-melting-point resin fiber according to any one
of (1) to (3) may have an average fiber diameter as an assembly of
4 .mu.m or less.
[0026] (5) The present invention also relates to a method for
producing the high-melting-point resin fiber according to any one
of (1) to (4). The method includes applying planar laser light to a
polymer sheet including a noncrystalline high-melting-point resin
to heat and melt an edge of the polymer sheet linearly to thereby
form a band-like molten zone. With this, a potential difference is
provided between the band-like molten zone and a fiber collecting
plate to form a needle protrusion in the band-like molten zone of
the polymer sheet and to allow a fiber ejected from the needle
protrusion to fly toward the fiber collecting plate. The fiber is
collected on the fiber collecting plate or on a collector disposed
between the molten zone and the fiber collecting plate. Thus, the
high-melting-point resin fiber is obtained.
[0027] (6) In the method according to (5) for producing a
high-melting-point resin fiber, the polymer sheet may be fed at a
speed of 2 to 20 mm/min.
[0028] (7) In the method according to one of (5) and (6) for
producing a high-melting-point resin fiber, the potential
difference may be 0.1 to 30 kV/cm.
[0029] (8) In the method according to any one of (5) to (7) for
producing a high-melting-point resin fiber, the polymer sheet may
have a viscosity of 800 Pas or less as measured at a temperature of
400.degree. C. and a shear rate of 121.6 5.sup.-1.
[0030] (9) In the method according to any one of (5) to (8) for
producing a high-melting-point resin fiber, the planar laser light
may be applied at a power of 5 to 100 W per 13 cm.
[0031] (10) In the method according to any one of (5) to (9) for
producing a high-melting-point resin fiber, the polymer sheet may
have a degree of crystallinity of 25% or less.
[0032] (11) The present invention also relates to a nonwoven fabric
derived from the high-melting-point resin fiber according to any
one of (1) to (4).
Advantageous Effects of Invention
[0033] The high-melting-point resin fiber according to the present
invention has excellent workability because of having a low degree
of crystallinity and also has heat resistance and chemical
resistance at excellent levels because of using a
high-melting-point resin such as a PEEK. The nonwoven fabric
derived from the fiber offers excellent separability when used
typically as a cell (battery) separator or a filter for medical
materials because it includes extremely ultrafine fibers. In
addition, the nonwoven fabric also has durability, heat resistance,
and chemical resistance at excellent levels because of being
derived from (formed from) a material high-melting-point resin such
as a PEEK.
BRIEF DESCRIPTION OF DRAWINGS
[0034] FIG. 1 is a schematic diagram schematically illustrating a
method according to an embodiment of the present invention for
producing a high-melting-point resin fiber;
[0035] FIG. 2 is a schematic view of Taylor cones formed in a
band-like molten zone; and
[0036] FIG. 3 is a schematic cross-sectional view of nonwoven
fabric production equipment using the method according to the
present invention for producing a high-melting-point resin
fiber.
DESCRIPTION OF EMBODIMENTS
[0037] High-Melting-Point Resin Fibers
[0038] The high-melting-point resin fibers according to the present
invention are ultrafine fibers having small fiber diameters and
have diameters of 4 .mu.m or less. The fibers may have diameters of
preferably 3 .mu.m or less (0.1 to 3 .mu.m), and more preferably 2
.mu.m or less. The ultrafine fibers having diameters as above may
include fibers having fiber diameters of typically about 50 to
about 1000 nm. The diameters of the fibers can be adjusted by
adjusting conditions of the after-mentioned method for producing a
high-melting-point resin fiber as appropriate. Examples of the
conditions include the polymer sheet thickness, the polymer sheet
feed speed, and the laser intensity. The diameters of the
high-melting-point resin fibers can be measured typically using an
electron microscope.
[0039] The high-melting-point resin fibers according to the present
invention include a resin having a melting point of 250.degree. C.
or higher. The high-melting-point resin fibers have melting points
of preferably 260.degree. C. or higher, more preferably 270.degree.
C. or higher, and furthermore preferably 280.degree. C. or higher.
Non-limiting examples of such resin having a melting point of
250.degree. C. or higher include poly(ether ether ketone)s (PEEKs)
(melting point: 334.degree. C.), poly(phenylene sulfide)s (PPSs)
(melting point: 290.degree. C.), polyamideimides (PAIS) (melting
point: 300.degree. C.), polytetrafluoroethylenes (PTFEs) (melting
point: 327.degree. C.), silicon resins (melting point: about
300.degree. C.), fluorocarbon resins (melting point: 327.degree.
C.), and liquid-crystal polymers (melting point: 260.degree. C. to
300.degree. C.). Among them, PEEKs are preferred because of having
a high melting point and offering heat resistance and solvent
resistance at excellent levels.
[0040] The high-melting-point resin fibers according to the present
invention have a degree of crystallinity of preferably 30% or less,
more preferably 29% or less, and furthermore preferably 28% or
less. The fibers, when having a degree of crystallinity of 30% or
less, may offer excellent workability and can be easily formed or
shaped typically into nonwoven fabrics, filters, and separators.
The degree of crystallinity may be determined typically by X-ray
diffractometry, differential scanning calorimetry using a
differential scanning calorimeter (DSC), or densimetry. In this
application, the degree of crystallinity is calculated from the
amounts of heat determined by differential scanning calorimetry
according to the method described in experimental examples.
[0041] The high-melting-point resin fibers according to the present
invention are preferably obtained by the after-mentioned method for
producing a high-melting-point resin fiber, using a noncrystalline
high-melting-point resin as a material polymer sheet.
[0042] The noncrystalline high-melting-point resin (sheet), which
is a polymer sheet, has a thickness of typically 0.01 to 10 mm, and
preferably 0.05 to 5.0 mm. The polymer sheet, when having a
thickness within the range, may contribute to easy production of
the high-melting-point resin fibers as mentioned below.
[0043] The high-melting-point resin fibers according to the present
invention may have an average fiber diameter as an assembly not
limited, but preferably 4 .mu.m or less (0.1 to 4 .mu.m), more
preferably 3 .mu.m or less, and furthermore preferably 2 .mu.m or
less. The average fiber diameter may be determined typically by
taking two or more (e.g., ten) images of fibers using a scanning
electron microscope, measuring diameters of about ten optional
fibers per image in the images typically using an image processing
software, and averaging the measured diameters.
[0044] Method for Producing High-Melting-Point Resin Fibers
[0045] The high-melting-point resin fibers according to the present
invention are preferably produced using the laser melt
electrospinning below. Specifically, the laser melt electrospinning
is performed in the following manner.
[0046] The method according to the present invention for producing
a high-melting-point resin fiber (via laser melt electrospinning)
will be illustrated with reference to the attached drawings. FIG. 1
is a schematic diagram schematically illustrating a method
according to an embodiment for producing a high-melting-point resin
fiber. According to the method for producing a high-melting-point
resin fiber, the fibers are produced in the following manner.
Band-like laser light (laser beam) is applied to a polymer sheet
including a high-melting-point resin (sheet) to heat and melt an
edge of the polymer sheet linearly to thereby form a band-like
molten zone. With this, a potential difference is provided between
the band-like molten zone and a fiber collecting plate to form
needle protrusions in the band-like molten zone of the polymer
sheet and to allow fibers ejected from the needle protrusions to
fly toward the fiber collecting plate. The fibers are collected on
the fiber collecting plate or on a collector disposed between the
molten zone and the fiber collecting plate.
[0047] In the method for producing a high-melting-point resin fiber
illustrated in FIG. 1, laser light having a spot cross section
emitted from a laser source 1 is converted into planar laser light
5 having a linear cross section by the working of a light-path
controller. The light-path controller includes a
beam-expander-homogenizer 2, a collimation lens 3, and a
cylindrical lens group 4. The planar laser light 5 is applied to a
band-like melt zone 6a of a polymer sheet 6, where the polymer
sheet 6 is held by a holder 7. With this, a voltage is applied from
a high voltage generator 10 to form a potential difference between
the band-like melt zone 6a and a fiber collecting plate 8 disposed
under the polymer sheet 6. A thermography 9 observes the
temperature of the band-like melt zone 6a so as to optimize
conditions such as the voltage and the laser light to be
applied.
[0048] In the embodiment illustrated in FIG. 1, the holder 7 that
holds the polymer sheet 6 functions also as an electrode and, when
receives the voltage from the high voltage generator 10, imparts an
electric charge to the band-like melt zone 6a of the polymer sheet
6. The fiber collecting plate 8 has a surface electric resistance
approximately equal to those of metals. The fiber collecting plate
8 may be in the form selected typically from plate, roller, belt,
net, sawlike, wave, needle, and linear shapes. The light-path
controller is an assembly of optical components and typically
includes the beam-expander-homogenizer 2, the collimation lens 3,
and the cylindrical lens group 4. The light-path controller can
convert the spot laser light into the planar laser light 5.
[0049] In the embodiment illustrated in FIG. 1, the planar laser
light 5 is applied to heat and melt the band-like melt zone 6a of
the polymer sheet 6 to thereby form a heated, molten zone, and an
electric charge is imparted to the molten zone. As illustrated in
FIG. 2, electrical charge accumulates and repels on the surface of
the band-like melt zone 6a to which the electric charge is
imparted, and this causes needle protrusions (Taylor cones) 6b to
gradually form on the surface. When the repulsive force of the
electric charge exceeds the surface tension, the molten
thermoplastic resin is ejected as fibers from the tips of the
Taylor cones toward the fiber collecting plate 8 by the action of
electrostatic attraction. Namely, fibers are formed from the needle
protrusions 6b and fly toward the fiber collecting plate 8. As a
result, the fibers elongate and are collected by the fiber
collecting plate 8. In an embodiment, a collector is disposed on or
over the fiber collecting plate 8. In this embodiment, the fibers
are collected on the collector. Specifically, in the method
according to the present invention for producing a
high-melting-point resin fiber, a member for collecting fibers may
be the fiber collecting plate itself, or not the fiber collecting
plate, but a collector (collecting member) disposed on the fiber
collecting plate. FIG. 2 is a schematic view of Taylor cones formed
in the band-like melt zone 6a.
[0050] The number (intervals) of the Taylor cones as illustrated in
FIG. 2 can be controlled by changing the thickness of the polymer
sheet 6 as appropriate. The "growth" of a Taylor cone refers to
increase of the height (h in FIG. 2) of the Taylor cone.
[0051] The number of the Taylor cones is not limited, but is
preferably 1 or more per 2 cm of the heated, molten zone of the
polymer sheet and is more preferably 1 to 100 per 2 cm. This is
because as follows. Fiber production, if using Taylor cones present
in a number of 1 per 2 cm or less, is not preferred from the
viewpoints of uniformity ratio and production amount of the
nonwoven fabric. In consideration of this, the Taylor cones are
preferably present in a larger number. However, fiber production
using Taylor cones present in a number of 100 per 2 cm or more, may
cause lower uniformity ratio because of electric repulsion between
Taylor cones. The number of Taylor cones is more preferably 1 to 50
per 2 cm, and particularly preferably 2 to 10 per 2 cm.
[0052] Non-limiting examples of the laser source include YAG laser,
carbon dioxide gas (CO.sub.2) laser, argon laser, excimer laser,
and helium-cadmium laser. Among them, carbon dioxide gas laser is
preferred because of having high power source efficiency and being
capable of highly melting PEEK resins. The laser light may have a
wavelength of typically about 200 nm to about 20 .mu.m, preferably
about 500 nm to about 18 .mu.m, and furthermore preferably about 5
to about 15 .mu.m.
[0053] The laser light, when to be applied as planar laser light
(laser sheet) in the method for producing a high-melting-point
resin fiber, preferably has a thickness (sheet thickness) of about
0.5 to about 10 mm. The laser light, if having a thickness of less
than 0.5 mm, may fail to contribute to the formation of Taylor
cones. The laser light, if having a thickness of greater than 10
mm, may cause deterioration of the material because of longer
residence time in melting.
[0054] The power (output) of the laser light may be controlled
within such a range that the band-like molten zone has a
temperature equal to or higher than the melting point of the
thermoplastic resin and equal to or lower than the ignition point
of the polymer sheet. The power is preferably high from the
viewpoint of allowing the ejected fibers to have small fiber
diameters. The specific power of the laser light can be selected as
appropriate according typically to properties (such as melting
point and limiting oxygen index (LOI)) and shape of the
thermoplastic resin to be used, and to the feed speed of the
polymer sheet. The power is generally about 5 to about 100 W per 13
cm, preferably 20 to 60 W per 13 cm, and furthermore preferably 30
to 50 W per 13 cm. The intensity of the laser light is the output
(power) of the spot beam emitted from the laser source.
[0055] The temperature of the band-like molten zone is not limited,
as long as being equal to or higher than the melting point of the
high-melting-point resin and equal to or lower than the ignition
point of the resin, but is generally about 300.degree. C. to about
600.degree. C., and preferably 350.degree. C. to 500.degree. C.
[0056] In the method for producing a high-melting-point resin fiber
according to the embodiment of the present invention as illustrated
in FIG. 1, the laser light is applied from only one direction to
the band-like molten zone (edge) of the polymer sheet. In another
embodiment, the laser light may be applied typically from two
directions through a reflector to the band-like molten zone (edge)
of the polymer sheet. This configuration contributes to more
uniform melting of the edge of the sheet-like article (sheet) even
when the sheet has a large thickness.
[0057] The potential difference to be generated between the edge of
the polymer sheet and the collector in the method for producing a
high-melting-point resin fiber is preferably of a high voltage
within a range not causing discharge. The potential difference can
be selected as appropriate according typically to the required
fiber diameter, the distance between the electrode and the
collector, and the irradiance of the laser light, and is generally
about 0.1 to about 30 kV/cm, preferably 0.5 to 20 kV/cm, and more
preferably 1 to 10 kV/cm.
[0058] The voltage may be applied to the molten zone of the polymer
sheet by a direct application method, in which the portion to be
irradiated with the laser light (band-like molten zone of the
polymer sheet) is coincident with an electrode unit for imparting
the electric charge. However, the voltage is preferably applied by
an indirect application method, in which the portion to be
irradiated with the laser light is disposed at a position different
from the position of the electrode unit for imparting the electric
charge. The indirect application method is preferred because the
equipment can be prepared easily and simply, the laser light can be
effectively converted into thermal energy, and the reflection
direction of the laser light can be easily controlled to offer high
safety. Among such indirect application methods, preferred is a
method in which the portion to be irradiated with the laser light
is disposed downstream in the feeding direction of the polymer
sheet. In particular, in a preferred embodiment of the production
method, the planar laser light is applied to the polymer sheet
downstream from the electrode unit, and the distance between the
electrode unit and the portion to be irradiated with the laser
light (e.g., the distance between the lower end of the electrode
unit and the upper outer periphery of the planar laser light) is
controlled within a specific range (e.g., about 10 mm or less).
This distance can be selected according typically to the electric
conductivity, thermal conductivity, and glass transition point of a
PEEK resin, and the irradiance of the laser light. The distance is
typically about 0.5 to about 10 mm, preferably about 1 to about 8
mm, more preferably about 1.5 to about 7 mm, and particularly
preferably about 2 to about 5 mm. When the two portions are
disposed at a distance within this range, the resin adjacent to the
portion to be irradiated with the laser light offers higher
molecular mobility and can receive sufficient electric charge in a
molten state. This contributes to better productivity.
[0059] The distance between the edge of the polymer sheet (tip of a
Taylor cone) and the collector is not limited and may be generally
5 mm or more. For efficient production of ultrafine fibers, the
distance is preferably about 10 to about 300 mm, more preferably
about 15 to about 200 mm, furthermore preferably about 50 to about
150 mm, and particularly preferably about 80 to about 120 mm.
[0060] The polymer sheet, when fed continuously, may be fed at a
feed speed not limited, but generally about 2 to about 20 mm/min,
preferably 3 to 15 ram/min, and more preferably 4 to 10 mm/min. The
feeding of the polymer sheet at a higher speed contributes to
higher productivity. However, the feeding, if performed at an
excessively high speed, may impede sufficient melting of the resin
adjacent to the portion to be irradiated with the laser light and
may impede fiber production. In contrast, the feeding, if performed
at an excessively low speed, may cause decomposition of the
high-melting-point resin and lower productivity.
[0061] The space between the edge of the polymer sheet and the
collector may be in an inert gas atmosphere in the production
method. The presence of the inert gas atmosphere in the space
restrains the ignition of the fibers and allows the laser light to
be applied at a higher power. Non-limiting examples of the inert
gas include nitrogen gas, helium gas, argon gas, and carbon dioxide
gas. Among them, nitrogen gas is generally used. In addition, the
use of the inert gas can restrain oxidation reactions in the
band-like molten zone.
[0062] The space may be heated. This allows the resulting fibers to
have smaller fiber diameters. Specifically, heating of the air or
inert gas in the space can restrain abrupt temperature fall of
fibers under growing, and this promotes growth or extension of the
fibers to give more ultrafine fibers. The heating may be performed
typically by using a heater (such as a halogen heater) or by
applying laser light. The heating temperature may be selected
typically within the range of from 50.degree. C. to lower than the
ignition point of the resin. In consideration of spinnability, the
heating temperature is preferably lower than the melting point of
the resin.
[0063] Polymer Sheet
[0064] The noncrystalline polymer sheet has a degree of
crystallinity of typically preferably 25% or less, more preferably
20% or less, and furthermore preferably 15% or less. The polymer
sheet, when having a degree of crystallinity of 25% or less, may
give high-melting-point resin fibers having a low degree of
crystallinity. The degree of crystallinity of the polymer sheet may
be determined by the same method as the degree of crystallinity of
the high-melting-point resin fibers.
[0065] As used herein, the term "noncrystallinity" refers to such a
property of a resin that the resin has a bulky molecular chain
(molecular chain with large steric hindrance) in its molecular
frame, thereby cannot take a regular molecular arrangement during
process of cooling and solidifying from a molten state, but takes a
random molecular arrangement even in a solidified state.
[0066] The noncrystalline (amorphous) polymer sheet preferably has
a low viscosity for the formation of ultrafine fibers such as
nanofibers and may have a viscosity of typically preferably 800 Pas
or less (50 to 800 PaS), more preferably 600 Pas or less, and
furthermore preferably 400 Pas or less, as measured at a
temperature of 400.degree. C. and a shear rate of 121.6 5s.sup.1.
The viscosity at a temperature of 400.degree. C. may be determined
by the method described in the experimental examples using a
capillary rheometer (trade name Capillograph 1D, supplied by Toyo
Seiki Seisaku-Sho Ltd.). The shear rate may also be determined
using such a capillary rheometer.
[0067] The noncrystalline polymer sheet may be produced typically
by heating, melting, and molding a noncrystalline resin in the form
of chips into a sheet typically using a T-die extruder. The
noncrystalline resin in the form of chips may be selected from
commercial products, a preferred, but non-limiting example of which
is one available under the trade name of VESTAKEEP 1000G (supplied
by Daicel-Evonik Ltd.). The heating temperature in the T-die
extruder has only to be equal to or higher than the melting point
of the resin and is typically 350.degree. C. to 400.degree. C.
[0068] The noncrystalline polymer sheet may contain any of various
additives for use in fibers. Non-limiting examples of the additives
include stabilizers (such as antioxidants, ultraviolet absorbers,
and thermal stabilizers), flame retardants, antistatic agents,
colorants, fillers, lubricants, antimicrobial agents, insect/tick
repellents, antifungal agents, flatting agents, heat storage media,
flavors, fluorescent brighteners, wetting agents, plasticizers,
thickeners, dispersants, blowing agents, and surfactants. The
polymer sheet may contain each of different additives alone or in
combination.
[0069] Among these additives, for example, one or more surfactants
are preferably used. Assume that a high voltage is applied to the
polymer sheet to inject electric charge into the polymer sheet. In
this case, since including the high-melting-point resin, the
polymer sheet offers high electric insulation and resists injection
of the electric charge into a thermally molten zone having a lower
electric resistance. However, the use of a surfactant allows the
fiber having high electric insulation to have a lower electric
resistance in its surface, and this allows the electric charge to
be injected sufficiently into the thermally molten zone. Assume
that the polymer sheet includes multiple components. In this case,
the impartment of an additive such as a surfactant is effective for
phase separation upon application of a high voltage to the polymer
sheet to inject electric charge into the sheet.
[0070] Each of these additives may be used in a proportion of 50
parts by mass or less, typically about 0.01 to about 30 parts by
mass, and preferably about 0.1 to about 5 parts by mass, per 100
parts by mass of the resin in the polymer sheet.
[0071] Nonwoven Fabric
[0072] The nonwoven fabric according to the present invention may
be one produced by the after-mentioned production method, or one
which is derived from the high-melting-point resin fibers according
to the present invention, but which is produced by another
method.
[0073] The thickness of the nonwoven fabric according to the
present invention may be selected as appropriate according to the
intended use within the range of about 0.0001 to about 100 mm, and
is generally about 0.001 to about 50 mm, preferably about 0.01 to
about 15 mm, and more preferably about 0.05 to about 1 mm. The mass
per unit area (METSUKE) of the nonwoven fabric may also be selected
according to the intended use and is generally about 0.001 to about
100 g/m.sup.2, preferably about 0.05 to about 50 g/m.sup.2, and
more preferably about 0.1 to about 10 g/m.sup.2. The fiber
diameter, thickness, mass per unit area, and other geometries of
the nonwoven fabric according to the present invention to be
produced can be controlled by regulating conditions such as the
sheet feed speed, laser intensity, and collector traveling speed in
the after-mentioned nonwoven fabric production method.
[0074] The nonwoven fabric according to the present invention may
be subjected to an after-processing according to the purpose.
Non-limiting examples of the after-processing include
electrification treatment via electretizing, plasma discharge
treatment, corona discharge treatment, sulfonation treatment, and
hydrophilization treatment typically via graft polymerization. The
nonwoven fabric may be further subjected to secondary processing
(fabricating) and/or may be laminated and integrated with another
material. Non-limiting examples of the other material include other
nonwoven fabrics (such as spunbond nonwoven fabrics), woven knitted
fabrics, films, plates, and substrates.
[0075] Nonwoven Fabric Production Method
[0076] Next, an exemplary method for producing a nonwoven fabric
will be illustrated. The nonwoven fabric production method as
mentioned below can continuously produce high-melting-point resin
fibers while moving the collection position of fibers with time,
where the fibers are allowed to fly toward the fiber collecting
plate.
[0077] Exemplary techniques for moving the collecting position of
the fibers with time, where the fibers are allowed to fly toward
the fiber collecting plate, include (1) the technique of moving the
collector (or the fiber collecting plate when the fiber collecting
plate itself functions as a collector), (2) the technique of moving
the position at which the polymer sheet is held, (3) the technique
of allowing mechanical, magnetic, or electric force to act upon
fibers flying from the Taylor cones toward the collector, such as
the technique of blowing air to the fibers during flying, and (4) a
technique as any selective combination of the techniques (1) to
(3).
[0078] Among them, the technique (1), namely, the technique of
moving the collector is desirable. This is because the technique
(1) contributes to easy simplification of the configuration of the
equipment and to easy control of the geometries (such as thickness
and mass per unit area) of the nonwoven fabric to be produced. The
nonwoven fabric production method according to an embodiment using
the technique (1) will be illustrated in detail below.
[0079] The nonwoven fabric production method using the technique
(1) is based on the production method illustrated in FIG. 1, in
which a collector is placed on the fiber collecting plate 8. While
moving the collector in a direction (right hand or left hand in the
figure) perpendicular to the width direction of the polymer sheet
6, the high-melting-point resin fibers according to the present
invention are produced continuously. The collector may travel at a
constant speed, or at speed varying with time, or may be moved and
stopped repeatedly. To continuously produce the high-melting-point
resin fibers according to the present invention, the polymer sheet
6 may be continuously fed toward the fiber collecting plate 8
(toward the collector) with the progress of the fiber production
process, as has been described above. The speed (feed speed) of the
continuous feeding of the polymer sheet is as described in the
method for producing a high-melting-point resin fiber.
[0080] The traveling speed of the collector on or over the fiber
collecting plate 8 is not limited, may be selected as appropriate
in consideration typically of the mass per unit area of the fiber
sheet to be produced, and is generally about 10 to about 2000
ram/min. For example, assume that a polymer sheet having a mass per
unit area of 1000 g/m.sup.2 is fed at a feed speed of 0.5 ram/min.
In this case, a nonwoven fabric having a mass per unit area of
about 0.5 g/m.sup.2 can be continuously produced by setting the
traveling speed of the collector at about 1000 mm/min.
[0081] FIG. 3 is a schematic cross-sectional view of nonwoven
fabric production equipment using the method for producing a
high-melting-point resin fiber as illustrated in FIG. 1. The
equipment illustrated in FIG. 3 includes a laser source 11; a
light-path controller 12; a polymer sheet feeder 13 capable of
continuously feeding the polymer sheet 6; and a cabinet 23. The
cabinet 23 houses a holder 16 that holds the polymer sheet 6; an
electrode 17 that imparts electric charge to the polymer sheet 6; a
collector 22 that collects fibers; a fiber collecting plate 14 that
is arranged so as to face the electrode 17 through a band-like melt
zone (edge) 6a of the polymer sheet 6 and the collector 22; and a
heater 15. The equipment also includes high voltage generators 20a
and 20b that apply voltages independently to the electrode 17 and
the fiber collecting plate 14; and a pulley 21 for moving the
collector 22. The light-path controller 12 is an assembly of
optical components as described above and includes, for example,
the beam-expander-homogenizer 2, the collimation lens 3, and the
cylindrical lens group 4 as illustrated in FIG. 1.
[0082] With reference to FIG. 3, the planar laser light 5 exits
from the laser source 11, travels via the light-path controller 12,
is introduced into the cabinet 23, and is applied to the band-like
melt zone (edge) 6a of the polymer sheet 6. The polymer sheet
feeder 13 is mounted on the cabinet 23 and includes a motor, and a
mechanism that converts the rotation of the motor into a
rectilinear motion. The polymer sheet feeder 13 accepts the polymer
sheet 6 and continuously feeds the same into the cabinet 23. In
contrast, the lower part of the polymer sheet 6 is held by the
holder 16 to which the electrode 17 is mounted. The polymer sheet 6
and the electrode 17 are always in contact with each other, and
this allows electric charge to be imparted to the polymer sheet 6
when a voltage is applied to the electrode 17.
[0083] The fiber collecting plate 14 pairs up with the electrode 17
and functions as a counter electrode to the electrode 17. The fiber
collecting plate 14 is disposed at such a position as to face the
electrode 17 through the band-like melt zone (edge) 6a of the
polymer sheet 6 and the collector 23. This configuration gives a
potential difference between the band-like melt zone (edge) 6a of
the polymer sheet 6 and the collector 22 when voltages are applied
to the electrode 17 and the fiber collecting plate 14. The high
voltage generators 20a and 20b are coupled respectively to the
electrode 17 and to the fiber collecting plate 14 and apply
voltages to the electrode 17 and the fiber collecting plate 14. In
the nonwoven fabric production equipment, the electrode 17 is a
positive electrode, and the fiber collecting plate 14 is a negative
electrode. The reverse configuration will also do. The collector 22
is a conveyor belt including the pulley 21 and a conveyor belt, and
the conveyor belt itself corresponds to the collector 22.
Accordingly, the collector 22 (conveyor belt) travels to a
predetermined direction (e.g., right hand in the figure) with the
driving of the pulley 21.
[0084] The nonwoven fabric production equipment illustrated in FIG.
3 includes the heater 15 and can heat fibers ejected and elongated
from the band-like melt zone (edge) 6a of the polymer sheet 6
toward the collector 23. The equipment also includes a laser light
absorber 19 and a heat absorber 18 in the cabinet 23.
[0085] In the nonwoven fabric production equipment illustrated in
FIG. 3, while voltages are applied to both the electrode 17 and the
fiber collecting plate 14 and while the polymer sheet 6 is fed by
the working of the polymer sheet feeder 13 and the holder 16, the
planar laser light 5 is applied to the band-like melt zone (edge)
6a of the polymer sheet 6. This allows Taylor cones to form in the
band-like melt zone (edge) 6a of the polymer sheet 6, allows the
Taylor cones to eject fibers, and allows the fibers to fly (to be
jetted) toward the fiber collecting plate 14. As a result,
elongated fibers are collected by the collector 22, as has been
described above. Then, while the polymer sheet 6 is continuously
fed (while fibers are continuously ejected), the collector 22 is
moved, to yield a nonwoven fabric on the collector 22.
[0086] In the nonwoven fabric production equipment illustrated in
FIG. 3, the collector 22 is a sheet-like member. In this equipment,
the collector 22 is not limited, as long as being in the form of a
sheet, but may be made of a material selected typically from paper,
films, various woven fabrics, nonwoven fabrics, and meshes. The
collector may also be made of a metal, or may be a sheet or belt
having a surface electric resistance equivalent to such metals.
[0087] In the nonwoven fabric production equipment illustrated in
FIG. 3, materials to constitute the electrode 17 and the fiber
collecting plate 14 may be selected from conductive materials
(generally, metal components). Non-limiting examples of such
materials include elementary metals including Group 6A elements
such as chromium; Group 8 metal elements such as platinum; Group 1B
elements such as copper and silver; Group 2B elements such as zinc;
and Group 3B elements such as aluminum. The examples also include
alloys of these metals (such as aluminum alloys and stainless
alloys (stainless steels)), and compounds including these metals
(exemplified by metal oxides such as silver oxide and aluminum
oxide). Each of different metal components as above may be used
alone or in combination. Among these metal components, particularly
preferred examples are copper, silver, aluminum, and stainless
steels. The shape of the fiber collecting plate 14 is exemplified
by, but not limited to, plate, roller, belt, net, sawlike, wave,
needle, and linear shapes. Among these shapes, plate and roller
shapes are particularly preferred. Non-limiting examples of the
laser light absorber 19 include metals and porous ceramics each
coated with a black body. Non-limiting examples of the heat
absorber 18 include black ceramics. With the equipment as mentioned
above, the high-melting-point resin fibers and the nonwoven fabric
according to the present invention can be efficiently produced.
EXAMPLES
[0088] The present invention will be illustrated in further detail
with reference to several examples below. It should be noted,
however, that the examples are by no means intended to limit the
scope of the present invention.
[0089] Polymer Sheet Preparation
[0090] Polymer sheets A to D were prepared in the following
manner.
[0091] Sample PEEK resins in the form of chips as mentioned below,
which are high-melting-point resins, were each extruded into sheets
using the LABO PLASTOMILL T-Die Extruder (supplied by Toyo Seiki
Seisaku-Sho Ltd.) with a T-die having a die width of 150 mm and a
lip width of 0.4 mm, at an extrusion temperature of 345.degree. C.
to 360.degree. C. The extruded sheets were coiled at a haul-off
roller temperature of 140.degree. C. and a coiling speed of 1.0 to
2.0 m/min, and yielded the polymer sheets A to D each having a
thickness of 0.1 mm. The polymer sheets B, C, and D were subjected
to a heat treatment at 230.degree. C. for 20 min after the molding
using the extruder.
[0092] The prepared polymer sheet had degrees of crystallinity and
viscosities as measured at a temperature of 400.degree. C. and a
shear rate of 121.6 s.sup.-1 as follows. The viscosities were
measured by the after-mentioned polymer sheet viscosity measuring
method, and the degrees of crystallinity were determined by the
same method as in the degree of crystallinity of high-melting-point
resin fibers as mentioned below.
[0093] Polymer sheet A: VESTAKEEP 1000G (noncrystalline sample
original sheet: having a degree of crystallinity of 12.7% and a
viscosity of 151 Pas)
[0094] Polymer sheet B: VESTAKEEP 1000G (crystalline sample
original sheet: having a degree of crystallinity of 35.5% and a
viscosity of 151 Pas)
[0095] Polymer sheet C: VESTAKEEP 3300G (crystalline sample
original sheet: having a degree of crystallinity of 36.7% and a
viscosity of 761 Pas)
[0096] Polymer sheet D: VESTAKEEP 4000G (crystalline sample
original sheet: having a degree of crystallinity of 37.7% and a
viscosity of 1012 Pas)
[0097] Polymer Sheet Viscosity Measuring Method
[0098] The viscosity as measured at a temperature of 400.degree. C.
and a shear rate of 121.6 s.sup.-1 was measured using the capillary
rheometer (trade name Capillograph 1D, supplied by Toyo Seiki
Seisaku-Sho Ltd.) with a jig having a capillary diameter of 1 mm
and a length of 10 mm.
[0099] Next, high-melting-point resin fibers were produced
according to Examples 1 to 3 and Comparative Examples 1 to 5 by the
following method using the polymer sheets A to D prepared by the
above-mentioned method. In Examples 1 to 3 and Comparative Examples
1 to 5, the polymer sheets used, the polymer sheet feed speeds, the
laser light powers, and degrees of crystallinity and fiber sizes
(diameters) of the resulting high-melting-point resin fibers are as
given in Table 1. No fiber was obtained according to Comparative
Examples 2 and 5.
[0100] High-Melting-Point Resin Fiber Production
[0101] The high-melting-point resin fibers according to Examples 1
to 3 and Comparative Examples 1 to 5 were produced using the
equipment schematically illustrated in FIG. 1.
[0102] The laser source 1 of the equipment illustrated in FIG. 1
used herein was a CO.sub.2 laser system (supplied by Universal
Laser Systems, Inc., having a wavelength of 10.6 .mu.m and a power
of 45 W, with air cooling, and having a beam diameter of 4 mm). In
the equipment, there were arranged a beam expander with 2.5-fold
magnification and a homogenizer (having an incident beam diameter
of 12 mm (designed value) and an outgoing beam diameter of 12 mm
(designed value)) both as the beam-expander-homogenizer 2; a
collimation lens (having an incident beam diameter of 12 mm
(designed value) and an outgoing beam diameter of 12 mm (designed
value)) as the collimation lens 3; and a cylindrical lens group
(plano-concave lenses, f-30 mm) and a cylindrical lens group
(plano-convex lenses, f-300 mm) both as the cylindrical lens group
4 in the specified sequence at predetermined positions. By passing
through these light-path controllers, the spot-like laser light was
converted into planar laser light having a width of about 150 mm
and a thickness of about 1.4 mm and was irradiated to the band-like
melt zone (edge) 6a of the polymer sheet 6. This gave the
high-melting-point resin fibers.
[0103] Method for Measuring Degree of Crystallinity of
High-Melting-Point Resin Fiber
[0104] The degree of crystallinity of each high-melting-point resin
fiber was calculated from the amounts of heat determined by
differential scanning calorimetry.
[0105] The differential scanning calorimetry was performed using a
differential scanning calorimeter (DSC Q2000, supplied by TA) with
alumina as a reference material in a nitrogen atmosphere at
temperatures in the range of 0.degree. C. to 420.degree. C., and at
a rate of temperature rise of 20.degree. C/min.
[0106] On the basis of the amounts of heat determined by the
differential scanning calorimetry, the degree of crystallinity was
determined according to the expression:
Degree of crystallinity (%)=[(Heat of fusion of sample)-(Heat of
recrystallization of sample)]/(Heat of fusion of perfect crystal
(130 J/g)).times.100
TABLE-US-00001 TABLE 1 Voltage Feed Laser Degree of Fiber size
difference speed power crystal- (diameter) Resin (kV/cm) (mm/min)
(W) linity (.mu.m) Example 1 Polymer sheet A 6 6 61 24% 0.7 Example
2 Polymer sheet A 5 4 61 24% 1 Example 3 Polymer sheet A 4 4 61 24%
2 Comparative Example 1 Polymer sheet A 4 1 61 33% 5 Comparative
Example 2 Polymer sheet B 4 4 61 -- not fiberized Comparative
Example 3 Polymer sheet B 4 1 61 36% 7 Comparative Example 4
Polymer sheet C 4 1 61 36% 8 Comparative Example 5 Polymer sheet D
4 1 61 -- not fiberized
REFERENCE SIGNS LIST
[0107] 1 laser source [0108] 2 beam-expander-homogenizer [0109] 3
collimation lens [0110] 4 cylindrical lens group [0111] 5 planar
laser light [0112] 6 polymer sheet [0113] 6a band-like melt zone
[0114] 6b needle protrusion [0115] 7 holder [0116] 8 fiber
collecting plate [0117] 9 thermography [0118] 10 high voltage
generator [0119] 11 laser source [0120] 12 light-path controller
[0121] 13 polymer sheet feeder [0122] 14 fiber collecting plate
[0123] 15 heater [0124] 16 holder [0125] 17 electrode [0126] 18
heat absorber [0127] 19 laser light absorber [0128] 20a high
voltage generator [0129] 20b high voltage generator [0130] 21
pulley [0131] 22 collector [0132] 23 cabinet
INDUSTRIAL APPLICABILITY
[0133] The high-melting-point resin fibers according to the present
invention are extremely fine, have heat resistance and chemical
resistance at excellent levels, and give nonwoven fabrics which are
useful typically as fuel cell separators, filters for medical
materials, and space materials.
* * * * *