U.S. patent application number 11/374859 was filed with the patent office on 2006-09-28 for multicomponent fibers having elastomeric components and bonded structures formed therefrom.
Invention is credited to Jackie F. JR. Payne, Andreas Schneekloth, Bennett C. Ward, Jian Xiang.
Application Number | 20060216506 11/374859 |
Document ID | / |
Family ID | 37024488 |
Filed Date | 2006-09-28 |
United States Patent
Application |
20060216506 |
Kind Code |
A1 |
Xiang; Jian ; et
al. |
September 28, 2006 |
Multicomponent fibers having elastomeric components and bonded
structures formed therefrom
Abstract
Elastomeric multicomponent fibers and bonded fiber structures
formed from elastomeric multicomponent fibers are disclosed. The
elastomeric multicomponent fibers may comprise a thermoplastic
polymer core material and an elastomeric polymer sheath material
surrounding the core material. The bonded fiber structure may
comprise a plurality of fibers bonded to each other at spaced apart
points of contact, at least a portion of the fibers being
multicomponent fibers having at least one elastomeric fiber
component.
Inventors: |
Xiang; Jian; (Midlothian,
VA) ; Ward; Bennett C.; (Midlothian, VA) ;
Schneekloth; Andreas; (Hamburg, DE) ; Payne; Jackie
F. JR.; (Chester, VA) |
Correspondence
Address: |
HUNTON & WILLIAMS LLP;Riverfront Plaza
East Tower
951 E. Byrd Street
Richmond
VA
23219-4074
US
|
Family ID: |
37024488 |
Appl. No.: |
11/374859 |
Filed: |
March 14, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60664032 |
Mar 22, 2005 |
|
|
|
60737342 |
Nov 16, 2005 |
|
|
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Current U.S.
Class: |
428/375 |
Current CPC
Class: |
D01F 8/14 20130101; D04H
1/43828 20200501; D04H 1/56 20130101; Y10T 428/2933 20150115; D01F
8/16 20130101; D04H 1/43838 20200501; D01F 8/04 20130101; D01F 8/06
20130101; D04H 3/16 20130101; D04H 1/43832 20200501 |
Class at
Publication: |
428/375 |
International
Class: |
D02G 3/00 20060101
D02G003/00 |
Claims
1. A multicomponent fiber comprising: a thermoplastic polymer core
material; and an elastomeric polymer sheath material surrounding
the core material.
2. The multicomponent fiber of claim 1, wherein the elastomeric
polymer sheath material is a thermoplastic polyurethane.
3. The multicomponent fiber of claim 1, wherein the elastomeric
polymer sheath material is selected from the group consisting of
elastomeric and plastomeric polypropylenes, styrene-butadiene
copolymers, polyisoprene, polyisobutylene, polychloroprene,
butadiene-acrylonitrile, elastomeric block olefinic copolymers,
elastomeric block co-polyether polyamides, elastomeric block
copolyesters, poly(ether-urethane-urea), poly(ester-urethane-urea),
and elastomeric silicones.
4. The multicomponent fiber of claim 1, wherein the thermoplastic
core material comprises a second elastomeric material different
from the elastomeric polymer sheath material.
5. The multicomponent fiber of claim 1, wherein the thermoplastic
polymer core material is selected from the group consisting of
polyethylene, polypropylene, nylon, polyester, polybutylene
terephthalate, and polyethylene terephthalate.
6. The multicomponent fiber of claim 1, wherein the core material
defines a cross-section that is substantially concentric with a
cross-section defined by the sheath material.
7. The multicomponent fiber of claim 1, wherein the core material
defines a cross-section that is substantially non-concentric with a
cross-section defined by the sheath material.
8. The multicomponent fiber of claim 1, wherein the fiber is a
continuous strand.
9. The multicomponent fiber of claim 1, wherein the fiber is a
bicomponent fiber in which the sheath material is bonded to the
core material.
10. The multicomponent fiber of claim 1, wherein the fiber
comprises at least one intermediate component material disposed
intermediate the sheath material and the core material.
11. The multicomponent fiber of claim 1 wherein the sheath material
comprises about 10% to about 90% of the fiber by volume.
12. The multicomponent fiber of claim 1 wherein the sheath material
comprises about 25% to about 40% of the fiber by volume.
13. The multicomponent fiber of claim 1, wherein the fiber has a
diameter in a range from about 1 micron to about 200 microns.
14. The multicomponent fiber of claim 1, wherein the fiber has a
diameter in a range from about 1 micron to about 25 microns.
15. A melt-blown multicomponent fiber, comprising: a first
component comprising a thermoplastic polymer material; and a second
component comprising an elastomeric polymer material.
16. The melt-blown multicomponent fiber of claim 15 wherein the
fiber is formed as a sheath-core fiber in which the first component
is formed as a core and the second component is formed as a sheath
surrounding the core.
17. The melt-blown multicomponent fiber of claim 15 wherein the
fiber is formed as a side-by-side bicomponent fiber in which the
first component and second component are co-extensively bonded to
one another along their lengths.
18. The melt-blown bicomponent fiber of claim 15, wherein the first
component comprises a second elastomeric material having a
different elasticity from the elastomeric polymeric material of the
first component.
19. The multicomponent fiber of claim 15 further comprising a third
component comprising a thermoplastic polymer.
20. A bonded fiber structure comprising: a plurality of fibers
bonded to each other at spaced apart points of contact, at least a
portion of the fibers being multicomponent fibers having at least
one elastomeric fiber component.
21. The bonded fiber structure of claim 20, wherein the
multicomponent fibers are melt-blown side-by-side bicomponent
fibers.
22. The bonded fiber structure of claim 20, wherein the
multicomponent fibers are sheath-core multicomponent fibers having
an elastomeric polymer sheath material.
23. The bonded fiber structure of claim 20, wherein the three
dimensional bonded fiber structure has at least one dimension along
which the structure exhibits can be elongated at least 200% while
retaining its structural integrity.
24. The bonded fiber structure of claim 20, wherein the three
dimensional bonded fiber structure has an overall porosity in a
range from about 20% to about 95%.
25. The bonded fiber structure of claim 20, wherein the bonded
fiber structure is formed as a substantially planar sheet.
26. The bonded fiber structure of claim 20, wherein the bonded
fiber structure is formed as a three dimensional, self-sustaining
structural body.
27. The bonded fiber structure of claim 20, wherein the at least
one elastomeric fiber component comprises a material selected from
the group consisting of thermoplastic polyurethanes, polyester
copolymers, styrene copolymers, olefin copolymers, and polyamide
copolymer.
28. The bonded fiber structure of claim 20, wherein the at least
one elastomeric fiber component comprises a thermoplastic
polyurethane.
29. The multicomponent fiber of claim 20, wherein the elastomeric
polymer sheath material is selected from the group consisting of
elastomeric and plastomeric polypropylenes, styrene-butadiene
copolymers, polyisoprene, polyisobutylene, polychloroprene,
butadiene-acrylonitrile, elastomeric block olefinic copolymers,
elastomeric block co-polyether polyamides, elastomeric block
copolyesters, poly(ether-urethane-urea), poly(ester-urethane-urea),
and elastomeric silicones.
30. A bonded fiber structure comprising: a plurality of polymeric
fibers bonded to each other at spaced apart points of contact to
form a self-sustaining, three dimensional, fluid transmissive body,
the fibers collectively defining tortuous fluid flow paths through
the fluid transmissive body, wherein the self-sustaining, three
dimensional, fluid transmissive body has at least one dimension
along which the structure can be elongated at least 200% while
retaining its structural integrity.
31. A bonded fiber structure according to claim 31 wherein at least
a portion of the thermoplastic fibers are sheath-core
multicomponent fibers having an elastomeric polymer sheath
material.
32. The multicomponent fiber of claim 31 wherein the elastomeric
polymer sheath material is a thermoplastic polyurethane.
33. The multicomponent fiber of claim 31, wherein the elastomeric
polymer sheath material is selected from the group consisting of
elastomeric and plastomeric polypropylenes, styrene-butadiene
copolymers, polyisoprene, polyisobutylene, polychloroprene,
butadiene-acrylonitrile, elastomeric block olefinic copolymers,
elastomeric block co-polyether polyamides, elastomeric block
copolyesters, poly(ether-urethane-urea), poly(ester-urethane-urea),
and elastomeric silicones.
34. The multicomponent fiber of claim 31 wherein the elastomeric
polymer sheath material comprises about 10% to about 90% of the
fiber by volume.
35. The multicomponent fiber of claim 31 wherein the elastomeric
polymer sheath material comprises about 25% to about 40% of the
fiber by volume.
Description
[0001] This application claims priority to U.S. Provisional
Application Ser. No. 60/664,032, titled "Elastomeric Bicomponent
Fibers and Bonded Structures Formed Therefrom," filed on Mar. 22,
2005, and U.S. Provisional Application Ser. No. 60/737,342, titled
"Ink Reservoirs Formed From Elastomeric Bicomponent Fibers," filed
on Nov. 16, 2005, both of which are incorporated herein by
reference in their entirety.
BACKGROUND OF THE INVENTION
[0002] The invention relates generally to the field of
multicomponent fibers and bonded fiber structures. More
particularly, the invention is directed to multicomponent fibers
wherein at least one fiber component is elastomeric and to three
dimensional self-sustaining bonded fiber structures comprised of
such elastomeric fibers.
[0003] There are many forms of and uses for multicomponent fibers,
as well as methods of manufacture. Bicomponent fibers are typically
manufactured by melt spinning techniques (including conventional
melt spinning, melt blowing, spun bond, and other melt spun
methods). Bicomponent fibers may be manufactured in a side-to-side
structure, a centric sheath-core structure, or an acentric (e.g.
self-crimping) sheath-core structure. They can be used in
continuous filament or staple form and/or collected into webs or
tows. They may be produced alone or as part of a mixed fiber
system.
[0004] Multicomponent fibers can be used for a variety of purposes,
including but not limited to woven and non-woven fabrics or
structures and bonded or non-bonded structures. Porous, bonded
structures formed from such fibers have demonstrated distinct
advantages for fluid storage and fluid manipulation applications,
since such bonded fiber structures have been shown to take up
liquids of various formulations and controllably release them. A
typical use for these structures may include use as nibs for
writing instruments, ink reservoirs for writing instruments and/or
ink jet printer cartridges, wicks for a wide variety of devices and
applications, depth filters, and other applications where the
characteristics of such structures are advantageous.
[0005] Additionally, bonded fiber structures may find use in
diverse medical and/or diagnostic applications, for example, to
transport a bodily fluid by capillary action to a test site or
diagnostic device. Other applications of fibrous products are as
absorption reservoirs, products adapted to take up and simply hold
liquid as in a diaper or incontinence pad. Still other applications
of bonded fiber structures may involve their use as filtration
elements. Characteristics beneficial to the application as a
filtration element include the ability to provide a tortuous
interstitial path effective for capturing of fine particulate
matter when a gas or liquid is passed through the fiber filter.
[0006] As described in U.S. Pat. Nos. 5,607,766, 5,620,641,
5,633,082, 6,103,181, 6,330,883, and 6,840,692, each of which is
incorporated herein by reference in its entirety, there are many
forms of and uses for bonded fiber structures, as well as many
methods of manufacture. In general, such bonded fiber structures
are formed from webs of thermoplastic fibrous material comprising
an interconnecting network of highly dispersed fibers bonded to
each other at points of contact. These webs are formed into
substantially self-sustaining, three-dimensional porous components
and structures, which may be produced in a variety of sizes and
shapes.
[0007] Many of the advantageous characteristics of bonded fiber
structures stem from the materials used in the fibers from which
these structures are formed. The above-referenced patents describe
a wide variety of polymer materials that may be used to form fibers
for use in three dimensional bonded structures. These structures,
however, are often unsuitable for certain applications where
resiliency or penetrability is required. There has accordingly been
a need for fibers that can be used to produce resilient bonded
fiber structures.
SUMMARY OF THE INVENTION
[0008] Aspects of the invention include multicomponent fibers
having one or more elastomeric components and bonded fiber
structures formed from such fibers. A particular aspect of the
invention provides a sheath-core multicomponent fiber comprising a
thermoplastic polymer core material and an elastomeric polymer
sheath material surrounding the core material. Another aspect of
the invention provides a melt-blown multicomponent fiber comprising
a first component comprising a thermoplastic polymer material and a
second component comprising an elastomeric polymer material. Yet
another aspect of the invention provides a bonded fiber structure
comprising a plurality of fibers bonded to each other at spaced
apart points of contact, at least a portion of the fibers being
multicomponent fibers having at least one elastomeric fiber
component.
[0009] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory only, and are not restrictive of the invention as
claimed. The accompanying drawings constitute a part of the
specification, illustrate certain embodiments of the invention and,
together with the detailed description, serve to explain the
principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] In order to assist in the understanding of the invention,
reference will now be made to the appended drawings, in which like
reference characters refer to like elements. The drawings are
exemplary only, and should not be construed as limiting the
invention.
[0011] FIG. 1 is a cross-sectional view of a centric sheath-core
bicomponent fiber in accordance with some embodiments of the
invention.
[0012] FIG. 2 is a cross-sectional view of an acentric sheath-core
bicomponent fiber in accordance with some embodiments of the
invention.
[0013] FIG. 3 is a cross-sectional view of a side-by-side
bicomponent fiber in accordance with some embodiments of the
invention.
[0014] FIG. 4 is a cross-sectional view of a multicomponent fiber
in accordance with some embodiments of the invention.
[0015] FIG. 5 is a cross-sectional view of a multicomponent fiber
in accordance with some embodiments of the invention.
[0016] FIG. 6 is a schematic view of a process line for
manufacturing a bonded fiber structures in accordance with some
embodiments of the invention.
[0017] FIG. 7 a block diagram illustrating a method for
manufacturing a bonded fiber structures in accordance with some
embodiments of the invention.
[0018] FIG. 8 is a photograph of the cross section of sheath-core
fibers having an elastomeric sheath component in accordance with an
embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0019] Reference will now be made in detail to embodiments of the
invention, examples of which are illustrated in the accompanying
drawings.
[0020] Embodiments of the present invention provide multicomponent
fibers having one or more elastomeric components that can be used
to form resilient bonded fiber structures. As used herein, the term
"multicomponent fiber" refers to a fiber having two or more
distinct components formed from polymer materials having different
characteristics and/or different chemical nature. Bicomponent
fibers are a particular type of multicomponent fiber. As used
herein, the term "bicomponent fiber" refers to a fiber having two
or more distinct components integrally formed from polymer
materials having different characteristics and/or different
chemical nature. While other forms of bicomponent fiber are
possible, the most common types are integrally formed with
"side-by-side" or "sheath-core" relationships between the two
polymer components. For example, bicomponent fibers comprising a
core of one polymer and a coating or sheath of a different polymer
are particularly desirable for many applications since the core
material may be relatively inexpensive, providing the fiber with
bulk and strength, while a relatively thin layer of a more
expensive but unique sheath material may provide the fiber with
unique properties, particularly with respect to bonding.
[0021] As used herein, the term "elastomeric component
multicomponent fiber" or "ECM fiber" means a multicomponent fiber
having at least one component comprising an elastomeric material.
The term "elastomeric component bicomponent fiber" or "ECB fiber"
means a bicomponent fiber having at least one component comprising
an elastomeric material. As used herein the term "elastomeric
material" refers to a macromolecular material that returns rapidly
to its initial dimensions and shape after substantial deformation
and release of stress.
[0022] As used herein, the term "fluid" means a substance whose
molecules move freely past one another, including but not limited
to a liquid or gas. The term "fluid" as used herein may also be
multi-phase, and may include particulate matter suspended in a
liquid or gas.
[0023] In seeking to devise structures for certain applications,
the inventors have developed methods for producing ECM fibers whose
resilient characteristics can be used to great advantage in bonded
fiber structures. It has been found, for example, that bonded fiber
structures may be formed from fibers having a first component that
is elastomeric and a second component that is either
non-elastomeric or that is elastomeric but with different physical
and/or thermal characteristics than the first component. These
fibers are of particular value when their elastomeric components
are bondable to one another and to other fiber materials to form a
resilient, porous structure.
[0024] Embodiments of the present invention provide ECM fibers in
various forms. In some embodiments, the elastomeric first component
has an exposed surface and doubles as a bonding material, either as
one component in a side-by-side fiber configuration or as the
sheath component in a sheath/core fiber configuration. As will be
discussed in more detail, ECM fibers according to embodiments of
the invention include (i) sheath-core multicomponent fibers where
the sheath is comprised of an elastomeric material and the core is
comprised of a non-elastic material; (ii) sheath-core
multicomponent fiber where the sheath and the core are both
comprised of elastomeric materials with the core material different
physical and/or thermal characteristics from the sheath material;
(iii) melt blown side-by-side bicomponent fibers, where one
component is comprised of an elastomeric material; and (iv) melt
blown side-by-side bicomponent fibers, where both components are
comprised of elastomeric materials, and one component has different
physical and/or thermal characteristics from the other.
[0025] It will be understood that certain ECM fibers have been
produced in the past. These, however, were limited to (a)
sheath-core bicomponent fibers in which the core material was
elastomeric and the sheath material was substantially inelastic and
(b) conventionally spun side-by-side bicomponent fibers.
Significantly, none of these fibers have been used to produce a
bonded fiber structure.
[0026] In contrast, many of the ECM fibers of the invention are
particularly suited to use in bonded fiber structures. With
reference to FIGS. 1-5, various examples of ECM fiber embodiments
according to the invention will now be discussed in more
detail.
[0027] FIG. 1 illustrates an exemplary elastomeric component
bicomponent fiber (ECB fiber) of the invention. In this embodiment,
the fiber is formed as a sheath/core bicomponent fiber 100 having a
core component 120 surrounded by a sheath component 110 comprising
a thermoplastic elastomer.
[0028] The use of an elastomer as the sheath component is
particularly advantageous in elastomeric materials that bond to one
another and to other fiber materials. When bonded, the core
component of a sheath-core ECB fiber of the invention provides
strength and stability to the fiber, while the elastomeric sheath
component allows the fiber to stretch relative to other fibers to
which it is bonded. This stretchable bond provides a resiliency to
the bonded structure that is not attainable using conventional
sheath-core fibers.
[0029] The sheath-to-core ratio of ECB fibers of the invention may
be tailored depending on the particular materials, the application
of the fibers and the method of manufacture. Typical sheath-to-core
volume ratios may be in a range from 10:90 to 90:10. In particular
embodiments, the sheath-to-core volume ratio may be in a range from
25:75 to 40:60.
[0030] ECB fiber 100 is a concentric sheath-core fiber; that is,
the sheath and core have substantially concentric circular
cross-sections. Other ECB fibers according to the invention may be
formed as acentric sheath core fibers as exemplified by the ECB
fiber 200 shown in FIG. 2. The acentric sheath core ECB fiber 200
has a first component 210 that comprises an elastomeric material
and a second component 220. In this fiber, the first and second
components are substantially circular in cross-section, but their
centers are offset. This geometry may be used to produce a
self-crimping fiber, which may facilitate the production of a
loftier, bulkier, and more elastic web.
[0031] Melt-blown ECB fibers according to the invention may be
formed in a side-by-side configuration as exemplified by the ECB
fiber 300 shown in FIG. 3. Like the sheath core fiber 100, the
side-by-side fiber 300 has a first component 310 that comprises an
elastomer and a second component 320. The side-by-side
configuration assures that at least a portion of the surface of an
elastomeric component is exposed for forming a stretchable bond
with other fibers.
[0032] It will be understood that the ECM fibers of the invention
are not limited to bicomponent fibers. For example, FIG. 4
illustrates an ECM fiber 400 according to the invention that has
three components 410, 420, 430 any one or more of which may
comprise an elastomeric material.
[0033] ECM sheath-core fibers may also be produced with more than
two components. With reference to FIG. 5, an ECM fiber 500 may be
comprised of a sheath component 510 that comprises an elastomeric
material, an intermediate component 520, and a core component 530.
Similar fibers may be produced with acentric components.
[0034] The core components 120, 220, 530 of sheath-core ECM fibers
100, 200, 500, the second component 320 of the side-by-side ECM
fiber 300, and the second and third components 420, 430 of the
side-by-side ECM fiber 400 may be non-elastomeric or may comprise
elastomeric materials having different material and/or thermal
characteristics from the elastomeric materials of the first fiber
components 110, 210, 310, 410, 510. In some embodiments, core
components 120, 220, 530 and side-by-side components 320, 420, 430
may comprise a crystalline or semi-crystalline polymer. Such
polymers may include but are not limited to polypropylene,
polybutylene terephthalate, polyethylene terephthalate, high
density polyethylene and polyamides such as nylon 6 and nylon
66.
[0035] The various elastomeric components of the ECM fibers of the
invention may comprise any suitable elastomeric material. Suitable
thermoplastic elastomers may include but are not limited to
polyurethanes, polyester copolymers, styrene copolymers, olefin
copolymers, or any combination of these materials. More
particularly, thermoplastic polyurethanes, thermoplastic ureas,
elastomeric or plastomeric polypropylene, styrene--butadiene
copolymers, polyisoprene, polyisobutylene, polychloroprene,
butadiene-acrylonitrile, elastomeric block olefinic copolymers
(such as styrene--isoprene--styrene), elastomeric block
co-polyether polyamides, elastomeric block copolyesters, and
elastomeric silicones may be used.
[0036] Thermoplastic polyurethanes have been shown to be
particularly suitable for producing ECM fibers for use in bonded
fiber structures. As used herein, the term "thermoplastic
polyurethane" or "TPU" encompasses a linear segmented block polymer
composed of soft and hard segments, wherein the hard segments are
either aromatic or aliphatic and the soft segments are either
linear polyethers or polyesters. The defining chemicals of TPUs are
diisocyanates, which react with short chain diols to form a linear
hard polymer block. Aromatic hard segment blocks are usually based
in aromatic diisocyanates, most commonly MDI (4,4'-Diphenylmethane
diisocyanate). Aliphatic hard segment blocks are usually based in
aliphatic diisocyanates, most commonly hydrogenated MDI (H12MDI).
Linear polyethers soft segment blocks commonly used include poly
(butylene oxide) diols, poly (ethylene oxide) diols and poly
(propylene oxide) diols or products of reactions of different
glycols. Linear polyester soft segment bocks commonly used include
the polycondensation product of adipic acid and short carbon chain
glycols. Polycaprolactones may also be used. In general,
ether-based TPUs are more resistant to hot, humid, acidic, or basic
environments, while ester-based TPUs are generally more
oil-resistant and typically have a greater mechanical strength.
[0037] Thermoplastic polyurethanes are commercially available from
suppliers such as DuPont.RTM., Bayer.RTM., Dow.RTM., Noveon.RTM.,
and BASF.RTM..
[0038] The particular elastomeric material selected for use in an
ECM fiber may depend on a variety of factors including its spinning
ability, bondability, the degree of resiliency required of the
bonded fiber structure formed from the fiber, and other
characteristics related to the use of the bonded fiber structure. A
particular elastomeric material may be selected, for example, based
on its relative hydrophobicity or hydrophilicity or based on its
compatibility with fluids or other materials expected to interact
with the bonded fiber structure.
[0039] As a general matter, ECM fiber component materials may be
selected at least in part based on their ability to adhere to one
another throughout the manufacturing process and, later, upon
formation into a bonded fiber structure. Illustrative examples of
ECM fiber component combinations that have been produced include
TPU/polypropylene, TPU/nylon, TPU/polyester, TPU/polybutylene
terephthalate, and TPU/polyethylene terephthalate. ECM fiber
component combinations that have also been produced include
ethylene polypropylene copolymer elastomer/polypropylene, ethylene
polypropylene copolymer elastomer/polybutylene terephthalate, and
ethylene polypropylene copolymer elastomer/nylon 6.
[0040] With any of the above-described ECM fiber embodiments, care
must be taken to assure that fiber integrity is maintained
throughout the manufacturing process. As discussed below, the
fibers of the invention may be produced using any of several
methods. Regardless of the method of manufacture, however, the
specific processing parameters must be tailored to the particular
materials used in order to assure that viable fibers are produced.
In sheath-core ECM fibers, for example, processing parameters must
be tailored to assure complete coverage of the core and to assure
that the sheath will remain adhered to the core.
[0041] ECM fibers according to the invention may be produced using
any manufacturing techniques typically used for producing
multicomponent fibers including without limitation conventional
melt spinning, melt blowing and spun bond processes. The particular
methodology used is often dictated by the nature of the polymer
and/or the desired properties and applications for the resultant
fibers.
[0042] While other processes may be used to produce ECM fibers,
melt spinning techniques in general, and melt blowing techniques in
particular, have been found to be highly successful in producing
the ECM fibers of the invention. In a melt spinning process, molten
polymers are pumped under pressure to a spinning head and extruded
from spinneret orifices into a multiplicity of continuous fibers.
Melt spinning techniques are commonly employed to make both
mono-component and side-by-side or sheath-core multicomponent
fibers. Sheath-core multicomponent fibers may be manufactured
through centric or acentric melt spinning processes.
[0043] After extrusion, the fibers may be attenuated to reduce
their diameter. Attenuation can be accomplished by drawing the
fibers from the spinning device at a speed faster than their
extrusion speed. In some processes, this may be done by taking the
fibers up on rolls rotating at a speed faster than the rate of
extrusion. In other processes, the fibers may simply be post drawn
through draw rolls operating at different speeds. Depending on the
nature of the polymer materials, drawing the fibers in this manner
may orient the polymer chains, thus tailoring the physical
properties of the fiber.
[0044] In a particular form of melt-spinning process, attenuation
is accomplished by hitting the fiber with a blast of hot air upon
extrusion. This process is typically referred to as melt blowing
and the fibers produced are referred to as melt blown fibers. In
melt-blowing, a high speed, typically high temperature, gas stream
is applied at the exit of a fiber extrusion die to attenuate or
draw out the fibers while the fibers are in their molten state.
Melt blowing processes are described in detail in U.S. Pat. Nos.
3,595,245, 3,615,995 and 3,972,759, which are incorporated herein
by reference in their entirety.
[0045] Through the use of melt blowing, ECM fibers according to the
invention may be produced with diameters approximately in the range
of about 1 micron to about 50 microns. By comparison, conventional
melt-spinning can be used to produce ECM fibers in a range of about
15 microns to about 200 microns, or even larger. Melt-blowing also
provides the ability to effect process-related characteristics to
the fiber and/or to webs formed therefrom. For example, a chilled
air stream or water spray may be directed transversely to the
direction of extrusion and attenuation of the melt blown
bicomponent fibers. The chilled air or water spray cools the fibers
to enhance entanglement while minimizing bonding of the fibers to
each other at this point in the processing, thereby retaining the
fluffy character of the fibrous mass and increasing productivity.
In some bicomponent fibers, cooling of the fiber immediately after
extrusion may prevent one or more of the component materials from
crystallizing. Depending on the relative characteristics of the
component materials, this may produce a fiber having one or more
crystalline components and one or more amorphous components. In
sheath-core fibers, the cooling of the sheath material may produce
a fiber having a crystalline core and an amorphous sheath as
described, for example, in U.S. Pat. No. 5,607,766. Retaining its
non-crystalline character may enhance the bondability of the sheath
material.
[0046] As noted above, specific processing parameters such as melt
temperature, melt viscosity, melt flow, and melt pressure may be
tailored to the specific materials used in the ECM fibers. These
parameters may be different for different fiber components. As is
described in the Berger '766 patent, however, it may be desirable
when selecting fiber components to choose materials with similar
melt indexes. As also described in the Berger '766 patent, the
viscosity of one or more of the fiber component materials may be
tailored to insure compatibility in the melt extrusion process.
Other parameters may also be tailored to produce fibers with
consistent integrity.
[0047] After extrusion and attenuation, the ECM fibers of the
invention may be gathered or further processed in a variety of
ways. In some processes, continuous fibers may be drawn and taken
up on a bobbin or package in the case of filament yarns, or
combined into a tow and cut into staple fibers. Continuous tows of
ECM fibers may be also subsequently processed into bonded fiber
structures. Staple ECM fibers may be formed into non-woven fabrics
or webs. These too may be subsequently processed into bonded fiber
structures.
[0048] In other processes, the ECM fibers are deposited on one
another, and may or may not be immediately formed into a loosely
bonded fiber web. This is accomplished by depositing the extruded
fibers in a randomly dispersed entangled web on a moving surface
such as a conveyer belt. The web may be collected for later use or
may be drawn directly into an in-line processing system for forming
a bonded fiber structure.
[0049] In some processes, staple fibers may be carded in order to
achieve a web having fibers lying generally in the same
orientation.
[0050] As described in U.S. Pat. No. 6,814,911, which is
incorporated herein by reference in its entirety, fiber webs and
products formed therefrom sometimes require, or are enhanced by,
the incorporation of an additive in the fibrous web during
manufacture. Accordingly, surfactants or other chemical agents in a
particular concentration may be added ECM fiber webs to be used,
for example, in the formation of an ink reservoir for marking or
writing instruments or ink jet printer reservoirs. These additives
may modify the surface characteristics of the fibers to enhance
absorptiveness and/or compatibility with particular ink
formulations. Wicking materials used in various medical
applications may also be treated with solutions of active
ingredients, such as monoclonal antibodies, to interact with
materials passed there-through. Similarly, particulate matter may
be adhered to the fibrous webs, in order to produce certain
characteristics (e.g., increase absorptiveness) in the web.
[0051] Webs comprising ECM fibers according to the invention may be
formed from a single fiber type; that is, all of the fibers
comprise substantially the same component geometry and materials.
Alternatively, bimodal webs comprising ECM fibers may be formed
using the methods described in U.S. Pat. No. 6,103,181. Bimodal
webs are webs formed from a combination of fibers of different
types, materials and/or configurations. For example, a first fiber
type may be a bicomponent fiber in which the sheath material is an
elastomer and the core is a non-elastomer, and a second fiber type
is an elastomeric or non-elastomeric monocomponent fiber. In some
embodiments, a web may comprise a first fiber type that is an
elastomeric sheath core bicomponent fiber in which the core
material is an elastomer and the sheath is a non-elastomer and a
second fiber type that is a monocomponent fiber formed from the
same elastomer as the core of the bicomponent fiber. In other
embodiments, the web may be formed from alternating ECM and
multicomponent fibers with no elastomeric component. In any of
these embodiments, the bimodal fiber collection can be used to form
a bonded web in which fibers of one type serve to bond to each
other and to fibers of the other type.
[0052] It can be seen from the above that that ECM fibers according
to the invention may be gathered in the form of bundled individual
filaments, continuous filaments, tows, roving or lightly bonded
non-woven webs or sheets. Fibers collected in any of these forms
may be further processed into bonded fiber articles such as sheets
or porous three dimensional structures. The process used to form
these bonded fiber articles may depend on the form in which the ECM
fibers were collected, the desired geometry and/or physical
characteristics of the bonded structure, and the constituent
materials in the fibers.
[0053] A bondable web of collected ECM fibers according to the
invention may be used to form an essentially two dimensional
non-woven fabric having recoverable elasticity properties. As will
be discussed in more detail below, these webs may be used to
produce bonded two dimensional three dimensional structures.
Alternatively, the fibers may be subjected to needle-punching,
where multiple needles push through the fibers, causing the fibers
to be tangled in such a manner as to cause a sustainable web. The
fibers may also be hydro-entangled. The sustainable webs may then
be rolled up or otherwise gathered and prepared for further
processing.
[0054] In some processing embodiments, ECM fibers in the form of a
web, bundled fibers or tows may be fed to a continuous processing
line for producing bonded fiber articles. There, the fibers are
heated to establish bonds between the fibers and formed into a
desired cross-section. If desired and depending on the form in
which they are provided, the fibers may be mechanically crimped or
self-crimping may be induced (e.g., by stretching and then relaxing
the fibers) during the continuous forming process. Additionally, in
some embodiments, self-sustaining webs formed from ECM fibers may
be post-drawn to create more elastic crimps along the machine
direction. The additional crimps may help to generate a loftier,
bulkier and more elastic substrate.
[0055] FIG. 6 is a schematic illustration of an overall processing
line 600 in accordance with a particular embodiment of the
invention. In this embodiment, the ECM fibers themselves are
produced in-line with equipment utilized to process the fibers into
three dimensional, self sustaining bonded fiber structures. While
the in-line process depicted has some advantages, it is to be
understood that the present invention is not to be construed as so
limited, and, as previously noted, the ECM fibers and webs of the
invention may be separately made, gathered and processed.
[0056] The processing line 600 of FIG. 6 includes a fiber spinning
and web-forming portion 610 and a bonding/forming portion 650. The
web-forming portion 610 includes a fiber spinning machine 620
configured to produce ECM fibers 630 in accordance with embodiments
of the invention. The fiber spinning machine 620 may use multiple
extruders for producing a plurality of fibers. Each fiber may have
multiple extruders depending on the number of fiber components. The
fiber spinning machine 620 may be configured for production of
fibers via the melt-blowing techniques discussed above. The fiber
spinning machine 620 deposits the ECM fibers 630 on a conveyer belt
640 or other moving surface where the fibers 630 form a randomly
dispersed entangled web 632. This web 632 may be in a form suitable
for immediate processing without subsequent attenuation or
crimp-inducing processing. In some embodiments, however, the web
632 may be drawn at a predetermined ratio selected to change the
bulk or loft of the web.
[0057] The bonding/forming portion 650 of the processing line 600
may comprise nip rolls 620 or other mechanism for drawing the web
632 from the belt 640. The bonding/forming portion 650 may include
a heating zone 660 through which the fiber material 632 is passed.
The heating zone 660 may include any of various mechanisms for
heating the fiber material to a desired temperature, typically a
temperature in excess of the melt or softening temperature of at
least one fiber component to facilitate bonding of the fibers in
the web at their points of contact with one another. In particular
embodiments, the heating zone 660 is configured to heat the fibers
to a temperature in excess of the melt or softening temperature of
an elastomeric fiber component such as, for example, an elastomeric
sheath material in a sheath-core ECB fiber. The heating mechanism
of the heating zone 660 may include but is not limited to sources
of radiant heat, hot air or steam. The heating mechanism may
include an oven or, in some embodiments, a heated die that not only
serves as a heating mechanism, but also forces the web to adopt a
predetermined cross-section.
[0058] Once the fiber material has been heated to a temperature
sufficient to melt or soften one or more of the fiber components,
it may be passed through a cooling zone 670 configured for cooling
the fiber material and set the bonds established in the heating
zone, thereby producing a self-sustaining bonded fiber structure
634. The cooling zone 670 may comprise any of various mechanisms
for cooling the now-bonded fiber material including the application
of relatively cool air or water. In some embodiments, the cooling
zone may simply be configured to allow passage of the bonded fiber
material through ambient air. In some embodiments, the cooling zone
670 may also comprise a chilled die through which the fiber
material is forced, thereby causing the bonded material to
permanently adopt a particular cross-section. In some embodiments,
the bonding/forming portion 650 may be configured to pass the fiber
material through multiple dies, one or more of which may be in the
heating zone 660 and one or more of which may be in the cooling
zone 670.
[0059] The processing line may also include a cutting station (not
shown) where the bonded fiber structure 634 may be cut to desired
lengths.
[0060] FIG. 7 illustrates a particular method M100 for
manufacturing a bonded fiber structure comprising ECM fiber
materials using the processing line 600 of FIG. 6. The method
begins at S110, and at S120, fiber component materials including at
least one elastomeric material are separately melted in the
spinning machine 620. It will be understood by those of ordinary
skill in the art that particular materials may require processing
before introduction into the extruder. For example, many materials,
including TPUs, polyesters and nylons, may require pre-drying to
remove residual moisture. This is because the process of melting
and extruding these polymers with water present may result in
decomposition and/or depolymerization, resulting in a loss of
properties and/or an inability to spin the fiber. As a result,
typical TPU materials may require for 2-4 hours of drying at
60-90.degree. C. This may be accomplished using a conventional
polymer dryer, which would be well know to one skilled in the
art.
[0061] At S130, ECM fibers are spun by the fiber spinning machine
620 and deposited onto the moving surface 610 where they form a
loosely bonded web. This action may include attenuation of the
extruded fibers. The action may be carried out using the melt
blowing technique discussed above if the fiber spinning machine 620
is so configured. The action may include quenching the fiber upon
extrusion. As previously discussed, additional fibers may be
simultaneously extruded if a bimodal fiber distribution is
desired.
[0062] At S140, the fibers are lifted or removed from the moving
surface 610. At this stage, the fiber surface may optionally be
chemically modified through the application of finishes or
surfactants at S141. Fibrous products often require, or are
enhanced by, the incorporation of an additive (or "finish") in the
fibrous web during or after fiber manufacture. Melt additives may
be added to the polymer in the spinning machine 620 before fiber
spinning. Topical additives may be added immediately following
fiber extrusion, before the fibers are deposited on the conveyor
belt 640 or other moving surface. The addition of selected
surfactants or other chemical agents in a particular concentration
to a fibrous media may modify and enhance certain characteristics
of the fibers. For example, in a fibrous structure used as an ink
reservoir, additives may enhance absorptiveness and/or
compatibility with a particular ink formulation. Similarly, wicking
materials used in various medical applications may be treated with
solutions of active ingredients, such as monoclonal antibodies, to
interact with materials passed there-through. If desired, a
reactive finish may be incorporated into the water spray to make
fiber surface more hydrophilic or hydrophobic.
[0063] At S142, particulate matter may optionally be adhered to the
fibers. Such particulate matter may improve particular
characteristics of the fibers and any resultant fiber structure,
making for example, the fibers more absorptive of liquids or
odors.
[0064] At S150 the collected web, which may or may not be loosely
bonded, may be drawn through the heating zone 660, where the fibers
are heated to the melt or softening temperature of one of the
exterior components (e.g., the sheath component of a sheath-core
ECM fiber). The temperature may be selected so that it will melt or
soften the sheath component, but will not melt or soften the core
component. This causes the ECM fibers to bond to one another at
their points of contact. As discussed above, this action may
include drawing the web through a heated die, thereby causing the
bonded fibers to adopt the cross-section of the die.
[0065] At S160, the bonded fiber material may be passed through a
cooling zone wherein the melted or softened fiber material may
harden to produce a self sustaining bonded fiber structure. In
certain instances, cooling of the fiber structure may be
accomplished merely by introduction into the ambient
environment.
[0066] At S170, the self sustaining bonded fiber structure may be
cut to its desired size. The size of the final product may be
determined based upon the bonded fiber structure's application. The
method ends at S180.
[0067] It will be understood that integrally formed three bonded
fiber structures comprising ECM fibers may be made by other
manufacturing processes. For example, a pneumatic forming process
such as that disclosed in U.S. Pat. Nos. 3,533,416, 3,599,646
3,637,447 and 3,703,429, each of which is incorporated herein by
reference in its entirety may be used. These processes utilize tows
of fibers that may be impinged in a forming die with air pressure
and then treated with steam to form a porous, three dimensional,
self sustaining, bonded fiber structure.
[0068] The fibers used to form bonded ECM fiber structures may be
in the form of bundled individual filaments, continuous filaments,
filament tows, lightly bonded (or mechanically entangled) webs or
sheets of filament fibers, staple fibers, staple fiber tows,
rovings of staple fibers or lightly bonded (or mechanically
entangled) webs or sheets of non-woven staple fibers The fibers may
be mechanically crimped or may be structured so that self-crimping
may be induced (e.g., by stretching and then relaxing the fibers)
during the continuous forming process. Additionally, in some
embodiments substantially self-sustaining webs formed from ECB
fibers may be post-drawn to create more elastic crimps along the
machine direction. The additional crimps help to generate a
loftier, bulkier and more elastic substrate.
[0069] The structures produced by the methods described above are
each a self-sustaining network of bonded ECM fibers. This network
defines a tortuous flow path for passage of fluids through the
structure. Depending on the characteristics of the fibers (e.g.,
surface energy) and such over all structure characteristics as
density and porosity, bonded fiber structures of this type may be
used for wicking applications, diagnostic devices or filtration
devices. The bonded fiber structures of the invention may be formed
as substantially planar sheets or as three dimensional structures.
In either case, the bonded fiber structures may typically have
porosities in a range of about 20% to 95%.
[0070] The properties of the bonded ECM fiber structures provide
advantages in a wide range of applications. They provide a unique
set of properties as a result of the combination of stretchability
and resiliency provided by their more elastic constituents and the
strength and stability provided by their less elastic (or
non-elastic) constituents. A high degree of structural resiliency
may be achieved based on the bonding of the elastomeric components
of the fibers. Particularly valuable applications include
filtration applications where elasticity or partial elasticity is
required or use as a reservoir in an ink jet cartridge. As will be
discussed, one particular advantage is the ability of these
structures to return to their original state after having been
deformed, such as by penetration by a needle or other device.
Bonded ECM fiber structures may also provide for a high coefficient
of friction, abrasion resistance, biocompatibility, insulation and
sound absorption. In addition, the stretchable bonds of these
structures allow them to be elongated by 200% to 700% while
retaining their structural integrity.
[0071] These characteristics make bonded ECM fiber structures ideal
for widely disparate applications, including without limitation use
in a white board eraser, a sponge contraceptive, a wound care
dressing, ear plugs, disposable wipes/cleaners, nibs for writing
instruments, face masks, automobile fluid filters, squeegees,
cosmetic pads, sound deadening materials, non-skid pads, and stamp
pads.
[0072] It is also contemplated that bonded ECM fiber structures may
be used in such widely varying products as penetrable wine corks,
diaper liners, scouring pads, blood separation devices, lateral
flow wicks, saliva wicks, drug delivery devices, chamois, seals,
pump gaskets, aircraft condensation pads, pipette filters, mattress
pads/table cloths, and non-slip gloves.
EXAMPLE 1
Bicomponent Sheath-Core Fiber Using Thermoplastic Polyurethane
(TPU)/Polypropylene (PP)
[0073] Sheath-core ECB fibers were formed by the previously
described melt blown process using Noveon.RTM. Estane.RTM. X4280
polyester-based TPU and Atofina.RTM. PP3960 polypropylene as sheath
and core materials, respectively. The ratio of dried TPU sheath
material to the polypropylene core material was approximately 35:65
by volume. The TPU sheath material, which has a melt temperature of
151.degree. C. was heated to and extruded at temperatures in a
range of 218.degree. C. to 241.degree. C. The PP core resin, which
has a melt temperature of 165.degree. C., was heated to and
extruded at temperatures in a range of 177.degree. C. to
200.degree. C. The fiber forming die tip was at 168.degree. C.
Fibers were produced with an average diameter of about 10 microns
and demonstrated complete coverage of the core by the sheath and
good integrity.
[0074] Fibers having the same material components but formed by
free-fall without quench were also produced. A photograph of these
fibers, which have diameters ranging from 40 to 50 microns, is
shown in FIG. 8. This photograph clearly illustrates the consistent
complete coverage of the core material by the TPU sheath.
EXAMPLE 2
Bicomponent Sheath-Core Fiber Using Thermoplastic Polyurethane
(TPU)/Polypropylene (PP)
[0075] Sheath-core ECB fibers were formed by the
previously-described melt blown process using Noveon.RTM.
Estane.RTM. 58245 polyether-based TPU and Atofinae PP3960
polypropylene as sheath and core materials, respectively. The ratio
of dried TPU sheath material to the polypropylene core material was
approximately 35:65 by volume. The TPU sheath material, which has a
melt temperature of 150.degree. C. was heated to and extruded at
temperatures in a range of 193.degree. C. to 210.degree. C. The PP
core resin, which has a melt temperature of 165.degree. C., was
heated to and extruded at temperatures in a range of 177.degree. C.
to 199.degree. C. The fiber forming die tip was at 168.degree. C.
Fibers were produced with an average diameter of about 11 microns
and demonstrated complete coverage of the core by the sheath and
good integrity.
EXAMPLE 3
Bonded Fiber Structures Using Melt Blown Thermoplastic Polyurethane
(TPU)/Polypropylene (PP) Sheath-Core Fibers
[0076] Self-sustaining, bonded fiber structures were formed from
melt blown sheath-core ECB fibers. In an illustrative example, the
ECB fibers were formed using a Noveon.RTM. Estanee X4280 TPU and an
Atofina.RTM. PP3960 PP as sheath and core materials, respectively.
The TPU was initially dried for 4 hours at 60.degree. C. The ratio
of dried TPU sheath material to PP core material was about 30:70 by
volume. The TPU sheath material was extruded in a temperature range
of 218.degree. C. to 240.degree. C., and the core resins were
extruded in a temperature range of 177.degree. C. to 199.degree.
C., with the fiber forming die tip at 168.degree. C. The resulting
web displayed good bulk and softness. Steam bonding was used to
form a self-sustaining rod, which was cut to length. Bonded fiber
structures were produced with a diameter of 7.5 mm and a length of
3 mm and densities in a range of 0.2 to 0.7 g/cc using fiber sizes
in a range of 5 to 15 microns. These structures exhibited effective
porosities in a range of 42% to 87% and exhibited the capability of
returning to these porosity levels after penetration by and
withdrawal of a 0.9 mm diameter needle.
[0077] The mechanical properties of the bonded ECB units with
various densities were measured by an Instron 3365 with a 1 kN load
cell using Instron Series IX/S Automated Materials Test, Version
8.27.00 software. Samples were placed in the hydraulic clamps, with
an initial 50.0 mm gap between upper and lower clamps. Testing
began by stretching the sample at speed of 10 mm/min until break.
Stress, strain, modulus and energy to break were collected and
recorded at the end of each specimen. These values are illustrated
in table 1. TABLE-US-00001 TABLE 1 Stress, Strain, Modulus, and
Energy for Example 3 Stress at Rod Density Peak Strain@ peak
Modulus Energy to Break g/cc MPa % MPa J 0.442 9.5 771 182 124
0.498 10.7 406 223 155 0.622 13.4 658 265 172
EXAMPLE 4
Bonded Fiber Structures Using Melt Blown Ethylene Polypropylene
Copolymer Elastomer/Polypropylene(PP) Sheath-Core Fibers
[0078] Self-sustaining bonded fiber structures were formed from
melt blown sheath-core ECB fibers. In an another illustrative
example, the ECB fibers were formed using a ExxonMobil.RTM.
Vistamaxx 2330 ethylene polypropylene copolymer elastomer and an
Atofina.RTM. 3860 PP as sheath and core materials, respectively.
The ratio of Vistamaxx sheath material and PP core material was
about 30:70 by volume. The Vistamaxx sheath material was extruded
in a temperature range of 204.degree. C. and 238.degree. C., with
the fiber forming die tip at 277.degree. C. The resulting web
displayed good loftiness and bulk. Steam bonding was used to form a
self-sustaining rectangular rod with width of 3 mm and length of 13
mm, resulting a cross-section area of 39 mm.sup.2. The bonded fiber
unit was produced in a density range of 0.15-0.75 g/cc using fiber
sizes in a range of 6-20 microns.
[0079] The mechanical properties of the bonded ECB units using
Vistamaxx/PP sheath-core materials with various densities were
measured by an Instron 3365 with a 1 kN load cell using Instron
Series IX/S Automated Materials Test, Version 8.27.00 software.
Samples were placed in the hydraulic clamps, with an initial 50.0
mm gap between upper and lower clamps. Testing began by stretching
the sample at speed of 10 mm/min until break. Stress, strain,
modulus and energy to break were collected and recorded at the end
of each specimen. These values are illustrated in Table 2.
TABLE-US-00002 TABLE 2 Stress, Strain, Modulus, and Energy for
Example 4 Stress at Rod Density Peak Strain@ peak Modulus Energy to
Break g/cc MPa % MPa J 0.212 2.6 323 60 18 0.301 4.1 336 96 30
0.313 4.4 414 102 36
[0080] It will be apparent to those skilled in the art that various
modifications and variations can be made in the method,
manufacture, configuration, and/or use of the present invention
without departing from the scope or spirit of the invention.
* * * * *