U.S. patent application number 11/539742 was filed with the patent office on 2007-04-05 for soluble microfilament-generating multicomponent fibers.
This patent application is currently assigned to Fiber Innovation Technology, Inc.. Invention is credited to Jeffrey S. Dugan.
Application Number | 20070077427 11/539742 |
Document ID | / |
Family ID | 36181119 |
Filed Date | 2007-04-05 |
United States Patent
Application |
20070077427 |
Kind Code |
A1 |
Dugan; Jeffrey S. |
April 5, 2007 |
Soluble Microfilament-Generating Multicomponent Fibers
Abstract
Microfilament-generating multicomponent fibers are provided that
include a first polymer component and a second polymer component
extruded together in separate contiguous polymer segments extending
along the length of the fiber. The first polymer component
comprises a synthetic melt-processable polymer that is
substantially soluble in a first relatively benign solvent selected
from water, aqueous caustic solution, and non-halogenated organic
solvents. The second polymer component is formed from a second
synthetic melt-processable polymer dimensioned to produce one or
more microfilaments upon dissolution of the first polymer, and that
is substantially soluble in an aqueous solvent selected from water
and aqueous caustic solution. The two polymer components are
dissolvable in different solvents.
Inventors: |
Dugan; Jeffrey S.; (Erwin,
TN) |
Correspondence
Address: |
ALSTON & BIRD LLP
BANK OF AMERICA PLAZA
101 SOUTH TRYON STREET, SUITE 4000
CHARLOTTE
NC
28280-4000
US
|
Assignee: |
Fiber Innovation Technology,
Inc.
|
Family ID: |
36181119 |
Appl. No.: |
11/539742 |
Filed: |
October 9, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10967837 |
Oct 18, 2004 |
|
|
|
11539742 |
Oct 9, 2006 |
|
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Current U.S.
Class: |
428/375 ;
264/172.12; 264/172.14 |
Current CPC
Class: |
Y10T 428/2913 20150115;
Y10T 428/2933 20150115; D01F 8/04 20130101 |
Class at
Publication: |
428/375 ;
264/172.14; 264/172.12 |
International
Class: |
D01D 5/32 20060101
D01D005/32 |
Claims
1. A method of forming a microfilament-generating multicomponent
fiber, comprising: i) providing a first molten viscous polymer
composition comprising a first synthetic polymer soluble in a first
solvent such that the polymer breaks apart into particles having an
average particle size of no more than 1 micron after 60 minutes of
exposure to the first solvent, the first solvent being selected
from the group consisting of water at a temperature of 70.degree.
C. or above, water at a temperature of less than 70.degree. C.,
aqueous caustic solution, and a non-halogenated organic solvent;
ii) providing a second molten viscous polymer composition
comprising a second synthetic polymer soluble in a second aqueous
solvent such that the polymer breaks apart into particles having an
average particle size of no more than 1 micron after 60 minutes of
exposure to the second aqueous solvent, the second aqueous solvent
being selected from the group consisting of water at a temperature
of 70.degree. C. or above, water at a temperature of less than
70.degree. C., and aqueous caustic solution, wherein the first
solvent and the second aqueous solvent are different such that the
second synthetic polymer is not dissolvable in the first solvent;
iii) extruding the first molten viscous polymer composition and the
second molten viscous polymer composition together through a
spinneret to form a multicomponent fiber comprising one or more
separate contiguous segments of each of the first polymer
composition and the second polymer composition extending the length
of the fiber, wherein at least a portion of the polymer segments
comprising the second polymer composition are dimensioned to form
microfilaments having a denier of less than 1.5; and iv) collecting
the multicomponent fiber.
2. The method of claim 1, further comprising dissolving the first
polymer composition, thereby forming one or more microfilaments
comprising the second polymer composition.
3. The method of claim 1, further comprising forming a fabric
comprising a plurality of the collected multicomponent fibers.
4. The method of claim 3, further comprising dissolving the first
polymer composition, thereby forming a fabric comprising a
plurality of microfilaments comprising the second polymer
composition.
5. The method of claim 1, wherein the first solvent is water at a
temperature of less than 70.degree. C. and the second aqueous
solvent is water at a temperature of 70.degree. C. or above.
6. The method of claim 1, wherein the first solvent is water at a
temperature of less than 70.degree. C. and the second aqueous
solvent is aqueous caustic solution.
7. The method of claim 1, wherein the first solvent is water at a
temperature of 70.degree. C. or above and the second aqueous
solvent is aqueous caustic solution.
8. The method of claim 1, wherein the first solvent is a
non-halogenated organic solvent and the second aqueous solvent is
water at a temperature of less than 70.degree. C.
9. The method of claim 1, wherein the first solvent is a
non-halogenated organic solvent and the second aqueous solvent is
water at a temperature of 70.degree. C. or above.
10. The method of claim 1, wherein the first solvent is a
non-halogenated organic solvent and the second aqueous solvent is
aqueous caustic solution.
11. The method of claim 1, wherein the first solvent is aqueous
caustic solution and the second aqueous solvent is water at a
temperature of 70.degree. C. or above.
12. The method of claim 1, wherein said first polymer is selected
from the group consisting of sulfonated polyesters, sulfonated
polystyrene, ethylene vinyl alcohol, polyvinyl alcohol,
polyethylene oxide, polyglycolic acid, polylactic acid,
polycaprolactone, and polystyrene.
13. The method of claim 1, wherein said second polymer is selected
from the group consisting of sulfonated polyesters, sulfonated
polystyrene, ethylene vinyl alcohol, polyvinyl alcohol,
polyethylene oxide, polyglycolic acid, polylactic acid, and
polycaprolactone.
14. The method of claim 1, wherein said first polymer is polyvinyl
alcohol or a sulfonated polyester and said second polymer is
polylactic acid.
15. The method of claim 1, wherein said first polymer is
polystyrene and said second polymer is selected from the group
consisting of sulfonated polyesters, sulfonated polystyrene,
ethylene vinyl alcohol, polyvinyl alcohol, polyethylene oxide,
polyglycolic acid, polylactic acid, and polycaprolactone.
16. The method of claim 1, wherein said one or more microfilaments
have a fineness of less than about 1.0 denier.
17. The method of claim 16, wherein said one or more microfilaments
have a fineness of less than about 0.5 denier.
18. The method of claim 1, wherein the fiber has a cross-sectional
configuration selected from the group consisting of pie/wedge,
segmented round, segmented oval, segmented ribbon, segmented
multi-lobal, segmented cross, and islands-in-the-sea.
19. The method of claim 1, wherein the fiber has a pie/wedge
cross-sectional configuration.
20. The method of claim 1, wherein the fiber has an
islands-in-the-sea cross-sectional configuration.
21. A fiber bundle comprising a plurality of microfilaments
generated from one or more multicomponent fibers made according to
the process of claim 2.
22. The fiber bundle of claim 21, wherein the microfilaments have a
cross-sectional shape selected from the group consisting of pie
wedge, multi-lobal, hexagonal, rectangular, oval, and circular.
23. A fabric comprising the fiber bundle of claim 21.
24. The fabric of claim 23, wherein the fabric is selected from the
group consisting of woven fabrics, nonwoven fabrics, and knit
fabrics.
25. A fabric comprising a plurality of multicomponent fibers made
according to the process of claim 1.
26. The fabric of claim 25, wherein the fabric is selected from the
group consisting of woven fabrics, nonwoven fabrics, and knit
fabrics.
27. A method of forming a microfilament-generating multicomponent
fiber, comprising: i) providing a first molten viscous polymer
composition comprising a first synthetic polymer soluble in water
such that the polymer breaks apart into particles having an average
particle size of no more than 1 micron after 60 minutes of exposure
to water; ii) providing a second molten viscous polymer composition
comprising a second synthetic polymer soluble in an aqueous caustic
solution such that the polymer breaks apart into particles having
an average particle size of no more than 1 micron after 60 minutes
of exposure to the aqueous caustic solution, wherein the second
synthetic polymer is not dissolvable in water; iii) extruding the
first molten viscous polymer composition and the second molten
viscous polymer composition together through a spinneret to form a
multicomponent fiber comprising one or more separate contiguous
segments of each of the first polymer composition and the second
polymer composition extending the length of the fiber, wherein at
least a portion of the polymer segments comprising the second
polymer composition are dimensioned to form microfilaments having a
denier of less than 1.5; and iv) collecting the multicomponent
fiber.
28. The method of claim 27, further comprising dissolving the first
polymer composition, thereby forming one or more microfilaments
comprising the second polymer composition.
29. The method of claim 27, further comprising forming a fabric
comprising a plurality of the collected multicomponent fibers.
30. The method of claim 29, further comprising dissolving the first
polymer composition, thereby forming a fabric comprising a
plurality of microfilaments comprising the second polymer
composition.
31. The method of claim 27, wherein said first polymer is polyvinyl
alcohol or a sulfonated polyester and said second polymer is
polylactic acid.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 10/967,837, filed Oct. 18, 2004, which is hereby incorporated
herein in its entirety by reference.
FIELD OF THE INVENTION
[0002] The invention is directed to microfilament-generating
multicomponent fibers comprising two or more soluble polymer
components and methods of making such fibers.
BACKGROUND OF THE INVENTION
[0003] The use of nonwoven fabrics has become increasingly
prevalent in a number of industries, and in particular, has found
increasing usefulness as a component of a variety of consumer
products. Exemplary uses for nonwoven fabrics include, without
limitation, absorbent personal care products such as diapers,
incontinence pads, feminine hygiene products and the like; medical
products such as surgical drapes and sterile wipes; filtration
devices; interlinings; disposable wipes; furniture and bedding
construction; insulating products; apparel and the like. A variety
of thermoplastic and thermobondable synthetic fibers have been
found to be particularly useful for nonwoven fabric manufacture due
to their advantageous strength and weight characteristics, as well
as their ease of processing.
[0004] Conventional thermoplastic synthetic fibers, however, do not
naturally degrade, thus creating problems associated with the
disposal of products containing such fibers. The recycling of
articles containing nonwoven fabrics is generally not
cost-effective, leading to the creation of non-degradable waste
material. The disposal of diapers provides a good example of the
problems associated with non-degradable waste. Disposable diapers
rely heavily on the use of nonwoven fabrics in their construction.
Millions of diapers are discarded every year, thereby contributing
to landfill capacity problems.
[0005] The use of multicomponent fibers that generate
microfilaments upon dissolution of a soluble polymer component is
known in the art. Fiber bundles comprising the resulting
microfilaments or microfibers exhibit many desirable
characteristics. For example, microfiber fabrics are generally
lightweight, resilient or wrinkle-resistant, have a luxurious drape
and body, retain shape, and resist pilling. Also, such fabrics are
relatively strong and durable in relation to other fabrics of
similar weight. Microfilament fibers are used commercially in a
variety of products such as filtration media, apparel, towels, and
wipes. However, the synthetic polymers conventionally used to form
the microfilaments are neither biodegradable nor soluble in
relatively benign solvents. Thus, the use of such microfilaments
contributes to the waste problems discussed above.
[0006] Thus, there remains a need in the art for a
microfilament-generating multicomponent fiber that does not
exacerbate existing waste problems associated with the use of
conventional synthetic fibers.
SUMMARY OF THE INVENTION
[0007] The present invention provides a microfilament-generating
multicomponent fiber comprising at least two polymer components
that are soluble in different, but relatively benign, solvents.
That is to say, both the polymer component that is dissolved during
fiber or fabric manufacture to form the microfilaments, and the
resulting microfilaments themselves, are soluble in relatively
benign solvents. In a preferred embodiment, the polymer component
that is removed to form the microfilaments is a synthetic
melt-processable polymer that is substantially soluble in water at
a temperature of 70.degree. C. or above, water at a temperature of
less than 70.degree. C., aqueous caustic solution, or a
non-halogenated organic solvent. The microfilament-generating
multicomponent fiber further comprises a second synthetic
melt-processable polymer, at least a portion of which is
dimensioned to produce one or more microfilaments upon dissolution
of the first polymer. The second synthetic melt-processable polymer
is substantially soluble in an aqueous solvent, such as water
(e.g., water at a temperature of 70.degree. C. or above or water at
a temperature of less than 70.degree. C.), or an aqueous caustic
solution. The solvent for the first polymer component and the
solvent for the second polymer component are different such that
the first polymer component can be removed to form the
microfilaments without substantially degrading the
microfilament-forming second polymer component. In this manner,
microfilaments can be generated that are soluble in a relatively
benign aqueous solvent. The present invention provides an
economical means for producing a fiber bundle of microfilaments or
microfibers that can be easily dissolved in a relatively benign
solvent at the end of its useful life, or the useful life of the
article of manufacture incorporating the fiber bundle. In some
cases, the dissolved solution of the microfilament-generating
polymer can be recycled and reused in a fiber-forming process.
[0008] In one embodiment, the solvent for the first polymer
component that is removed to form the microfilaments is water at a
temperature of less than 70.degree. C. and the aqueous solvent in
which the microfilament-forming polymer is soluble is water at a
temperature of 70.degree. C. or above. Thus, in this embodiment,
the entire multicomponent fiber is water-soluble at some
temperature.
[0009] In another embodiment, the solvent for the first polymer
component that is removed to form the microfilaments is water
(e.g., water at a temperature of less than 70.degree. C. or water
at a temperature of 70.degree. C. or above) and the second aqueous
solvent in which the microfilament-forming polymer is soluble is an
aqueous caustic solution.
[0010] In yet another embodiment, the first solvent is a
non-halogenated organic solvent and the second aqueous solvent is
either water at various temperatures or an aqueous caustic
solution.
[0011] In a further embodiment, the solvent used to dissolve the
first polymer in order to form the microfilaments is an aqueous
caustic solution and the microfilament-forming polymer is soluble
in water at a temperature of 70.degree. C. or above.
[0012] Exemplary polymers that can be used as the first polymer
component include sulfonated polyesters, sulfonated polystyrene,
ethylene vinyl alcohol, polyvinyl alcohol, polyethylene oxide,
polyglycolic acid, polylactic acid, polycaprolactone, and
polystyrene. Exemplary polymers for use as the second polymer
component that forms the microfilaments includes sulfonated
polyesters, sulfonated polystyrene, ethylene vinyl alcohol,
polyvinyl alcohol, polyethylene oxide, polyglycolic acid,
polylactic acid, and polycaprolactone.
[0013] The microfilaments generated by the multicomponent fibers of
the present invention have a fineness of less than about 1.5
denier, more preferably a fineness of less than about 1.0 denier,
and most preferably a fineness of less than about 0.5 denier. In
some embodiments, the fineness is less than about 0.2 denier, such
as a fineness in the range of about 0.01 to about 0.2 denier.
[0014] The configuration and type of fiber may vary. The
multicomponent fiber of the invention can be in the form of a
continuous filament, tow, staple fiber, spunbond fiber, or
meltblown fiber, and can have one of various cross-sectional
configurations, such as pie/wedge, segmented round, segmented oval,
segmented ribbon, segmented multi-lobal, segmented cross,
islands-in-the-sea, and the like. The cross-sectional shape of the
microfilaments themselves may also vary. Exemplary cross-sectional
shapes for the microfilaments include wedge, multi-lobal,
hexagonal, rectangular, oval and circular.
[0015] In another aspect of the invention, a fiber bundle
comprising a plurality of microfilaments is provided, the
microfilaments formed of a synthetic melt-processable polymer that
is substantially soluble in an aqueous solvent such as water at a
temperature of 70.degree. C. or above, water at a temperature of
less than 70.degree. C., and aqueous caustic solution.
[0016] In yet another aspect, the invention provides a fabric
comprising the fiber bundle of the invention. The fabric may be in
the form of woven fabric, nonwoven fabric, or knit fabric.
[0017] Further, in another aspect, the invention provides a method
of forming a microfilament-generating multicomponent fiber by
providing a first molten viscous polymer composition comprising a
first synthetic melt-processable polymer substantially soluble in a
first solvent selected from water at a temperature of 70.degree. C.
or above, water at a temperature of less than 70.degree. C.,
aqueous caustic solution, and a non-halogenated organic solvent. A
second molten viscous polymer composition is also provided, the
second polymer composition comprising a second synthetic
melt-processable polymer substantially soluble in a second aqueous
solvent selected from water at a temperature of 70.degree. C. or
above or less than 70.degree. C., or an aqueous caustic solution.
The first solvent and the second solvent are different such that
the second synthetic polymer is not dissolvable in the first
solvent. The two molten viscous polymer compositions are extruded
together through a spinneret to form a multicomponent fiber
comprising one or more separate contiguous segments of each of the
first and second polymer compositions extending the length of the
fiber. At least a portion of the polymer segments comprising the
second polymer composition are dimensioned to form microfilaments
upon dissolution of the first polymer composition. Thereafter, the
resulting multicomponent fibers are collected and, optionally,
formed into a fabric. The first polymer composition can be
dissolved using the first solvent at any point following
manufacture of the multicomponent fiber, including after
manufacture of the resulting fabric, thereby forming one or more
microfilaments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Having thus described the invention in general terms,
reference will now be made to the accompanying drawings, which are
not necessarily drawn to scale, and wherein:
[0019] FIGS. 1A-1F are cross-sectional views of exemplary
embodiments of multicomponent fibers in accordance with the present
invention; and
[0020] FIGS. 2A and 2B are cross-sectional and longitudinal views,
respectively, of an exemplary dissociated fiber in accordance with
one embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0021] The present invention now will be described more fully
hereinafter. However, this invention may be embodied in many
different forms and should not be construed as limited to the
embodiments set forth herein; rather, these embodiments are
provided so that this disclosure will satisfy applicable legal
requirements. Like numbers refer to like elements throughout.
[0022] As used in this specification and the claims, the singular
forms "a," "an," and "the" include plural referents unless the
context clearly dictates otherwise.
[0023] The term "fiber" as used herein means both fibers of finite
length, such as conventional staple fiber, as well as substantially
continuous structures, such as continuous filaments, unless
otherwise indicated. The fibers of the invention can be hollow or
non-hollow fibers, and further can have a substantially round or
circular cross section or non-circular cross sections (for example,
oval, rectangular, multi-lobed, and the like).
[0024] As used herein, a "multicomponent fiber" is a fiber formed
of two or more polymeric materials that have been extruded together
to provide continuous contiguous polymer segments which extend the
length of the fiber. For purposes of illustration only, the present
invention will generally be described in terms of a bicomponent
fiber. However, it should be understood that the scope of the
present invention is meant to include fibers with two or more
components.
[0025] The term "denier" is an expression of fiber diameter and
defined conventionally as grams per 9,000 meters of fiber. A lower
denier indicates a finer fiber and a higher denier indicates a
thicker or heavier fiber, as is known in the art.
[0026] The term "synthetic melt-processable polymer" describes
thermoplastic polymer materials comprising a polymer backbone that
is synthetically derived and having the necessary physical
properties, such as a suitable melting point, for processing by
melt spinning. Typically, the synthetic melt-processable polymers
of the invention will have a melting point in the range of about
50.degree. C. to about 260.degree. C., more typically in the range
of about 65.degree. C. to about 180.degree. C.
[0027] The term "copolymer" as used herein is intended to encompass
polymers formed from any combination of two or more polymers,
including random copolymers, block copolymers, alternating
copolymers, and the like.
[0028] The term "relatively benign solvent" is intended to
encompass aqueous solvents and non-halogenated organic solvents
that typically create fewer handling and environmental problems as
compared to generally disfavored halogenated solvents, such as
methylene chloride, perchloroethylene, and trichloroethylene, which
are listed as hazardous air pollutants in the Clean Air Act (CAA),
toxic chemicals in the Superfund Amendments and Reauthorization Act
(SARA), and hazardous substances in the Comprehensive Environmental
Response, Compensation, and Liability Act (CERCLA). Examples
include water at various temperatures, aqueous caustic solutions,
xylene, hexane, acetone, pyrrolidones (e.g.,
N-methyl-2-pyrrolidone), turpentine, kerosene, isopropanol,
methanol, tetrahydrofuran, toluene, cresols, and the like.
[0029] The term "aqueous caustic solution" refers to an aqueous
salt solution that provides an alkaline pH, such as a solution of
an alkali metal or alkaline earth metal hydroxide (e.g., sodium
hydroxide or potassium hydroxide). Typically, the aqueous caustic
solution comprises about 2 to about 10 percent by weight of the
salt (e.g., about 3 weight percent), such as sodium hydroxide.
Typically, treatment of the fiber with the aqueous caustic solution
occurs at a solution temperature of about 80-100.degree. C. (e.g.,
90.degree. C.) and over a treatment period of about 3-20 minutes,
although other treatment temperatures or times could be used. For
example, a caustic solution temperature below about 70.degree. C.
could be used to avoid degradation of hot water soluble fiber
components.
[0030] As used herein, the terms "substantially soluble" or
"dissolvable" are intended to refer to polymers that dissolve,
decompose (e.g., by hydrolysis), or otherwise disperse in solution
to the point where no visually discernible solid portions of the
polymer remain after 60 minutes of exposure to the solvent.
Typically, the polymer breaks apart into discrete particles having
an average particle size of no more than about 1 micron following
dissolution, and preferably the polymer breaks down on a molecular
level.
[0031] The present invention provides a microfilament-generating
multicomponent fiber that includes at least two polymer components
that are soluble in relatively benign solvents. Thus, the
multicomponent fiber of the invention includes a first polymer
component and a second polymer component that are extruded together
in separate contiguous polymer segments extending along the length
of the fiber. The first polymer component is adapted for removal by
dissolution in order to form microfilaments. This polymer component
is sometimes referred to in the art as the "fugitive" polymer
component. In the present invention, the fugitive polymer component
is a synthetic melt-processable polymer that is substantially
soluble in a first benign solvent, such as water (e.g., water at a
temperature of 70.degree. C. or above or water at a temperature of
less than 70.degree. C.), an aqueous caustic solution, or a
non-halogenated organic solvent.
[0032] The second polymer component, at least a portion of which is
dimensioned to produce one or more microfilaments upon dissolution
of the first polymer, also comprises a synthetic melt-processable
polymer. In one embodiment, the entire second polymer component is
dimensioned to produce microfilaments, meaning each discrete
portion of the second polymer component is dimensioned to produce a
microfilament upon dissolution of the fugitive polymer.
Alternatively, as shown in the example, a portion of the second
polymer can be dimensioned to produce a fiber cross sectional
segment of larger size. For example, the second polymer component
may comprise a plurality of microfilament-sized sections
surrounding a larger core section. The synthetic melt-processable
polymer used for the second polymer component is also substantially
soluble in a relatively benign solvent. In the case of the second
polymer component, the relatively benign solvent is an aqueous
solvent, such as water (e.g., water at a temperature of 70.degree.
C. or above or water at a temperature of less than 70.degree. C.)
or an aqueous caustic solution. In order to successfully form
microfilaments by dissolution of the first polymer, the solvent for
the fugitive polymer component and the solvent for the second
polymer component must be different such that the solvent for the
fugitive polymer does not substantially degrade or dissolve the
second polymer component.
[0033] Unlike prior art microfilament-generating multicomponent
fibers, the present invention provides a multicomponent fiber
wherein both the fugitive polymer component and the
microfilament-generating polymer component are soluble in
relatively benign solvents, such as water, aqueous caustic
solutions, or non-halogenated organic solvents. In a preferred
embodiment, both polymer components are soluble in an aqueous
solvent. In this manner, an economical method for forming
microfibers is provided that does not require the use of highly
toxic and environmentally-unfriendly solvents. Further, unlike
prior art microfilaments, the microfilaments of the invention are
soluble in an aqueous solvent, such as water or an aqueous caustic
solution. Thus, the microfilaments of the invention can be readily
dissolved as a means of disposal at the end of the useful life of
the microfilaments or the fabric or other article of manufacture
made using the microfilaments. Depending on the polymer, the
dissolved microfilaments may be recycled for reuse in fiber
formation. By providing microfilaments that can be dissolved in
benign solvents at the end of their useful life, both environmental
concerns and waste disposal concerns associated with fiber
production and use can be favorably addressed.
[0034] Examples of polymers that are substantially soluble in water
at a temperature of 70.degree. C. or above include, without
limitation, sulfonated polyesters (e.g., sulfonated polyethylene
terephthalate), sulfonated polystyrene, and copolymers or polymer
blends containing such polymers. A commercially available example
of a sulfonated polyester is the Eastman AQ line of copolyesters,
such as Eastman AQ 55S.
[0035] Examples of polymers that are substantially soluble in water
at a temperature of less than 70.degree. C. include, without
limitation, ethylene vinyl alcohol (EVOH), polyvinyl alcohol
(PVOH), polyethylene oxide, and copolymers or polymer blends
containing such polymers.
[0036] Examples of polymers that are substantially soluble in
aqueous caustic solution include, without limitation, polyglycolic
acid (PGA), polylactic acid (PLA), polycaprolactone (PCL), and
copolymers or blends thereof. The term "polylactic acid" is
intended to encompass polymers that are prepared by the
polymerization of either lactic acid or lactide. Reference is made
to U.S. Pat. Nos. 5,698,322; 5,142,023; 5,760,144; 5,593,778;
5,807,973; and 5,010,145, the entire disclosure of each of which is
hereby incorporated by reference.
[0037] An example of a polymer that is substantially soluble in one
or more non-halogenated organic solvents, such as hexane or xylene,
is polystyrene.
[0038] Referring now to FIG. 1, cross-sectional views of exemplary
multicomponent fibers of the present invention are provided. The
multicomponent fibers of the invention, designated generally as 4,
include at least two structured polymeric components, a first
polymer component 6, comprising a synthetic melt-processable
polymer dimensioned to form microfilaments or microfibers, and a
second fugitive polymer component 8, comprising a synthetic
melt-processable polymer that can be dissolved to provide one or
more microfilaments of the first component 6. As noted above, the
first and second components, 6 and 8, are both soluble in
relatively benign solvents, with the microfilament-generating
polymer component 6 being dissolvable in an aqueous solvent and the
fugitive polymer component 8 being dissolvable in either an aqueous
solvent different from the solvent for the microfilament-generating
polymer component or a non-halogenated organic solvent.
[0039] Exemplary embodiments include the following combinations of
microfilament-generating polymer components 6/fugitive polymer
component 8: sulfonated polyester or sulfonated polystyrene/PVOH;
PVOH/polystyrene; sulfonated polyester or sulfonated
polystyrene/polystyrene; PLA/polystyrene; PLA/sulfonated polyester
or sulfonated polystyrene; PLA/polystyrene; and PLA/PVOH.
[0040] As illustrated in FIGS. 1A-1E, a wide variety of fiber
configurations that allow the polymer components to be free to
dissociate are acceptable. Typically, the fiber components are
arranged so as to form distinct unocclusive cross-sectional
segments along the length of the fiber so that none of the
components is physically impeded from being separated. One
advantageous embodiment of such a configuration is the pie/wedge
arrangement, shown in FIG. 1A. The pie/wedge fibers can be hollow
or non-hollow fibers. In particular, FIG. 1A provides a bicomponent
filament having eight alternating segments of triangular shaped
wedges of microfilament-generating components 6 and fugitive
components 8. It should be recognized that more than eight or less
than eight segments can be produced in fibers made in accordance
with the invention. Other fiber configurations known in the art may
be used, such as but not limited to, the segmented round
configuration shown in FIG. 1B. Reference is made to U.S. Pat. No.
5,108,820 to Kaneko et al., U.S. Pat. No. 5,336,552 to Strack et
al., and U.S. Pat. No. 5,382,400 to Pike et al. for a further
discussion of multicomponent fiber constructions.
[0041] The multicomponent fibers need not be conventional round
fibers. For example, the fibers can be in the form of a segmented
oval. Other useful shapes include the segmented rectangular or
ribbon configuration shown in FIG. 1C, the segmented cross
configuration in FIG. 1D, and the multi-lobal configuration of FIG.
1E. Such unconventional shapes are further described in U.S. Pat.
No. 5,277,976 to Hogle et al., and U.S. Pat. Nos. 5,057,368 and
5,069,970 to Largman et al. As shown in FIG. 1F, the multicomponent
fiber of the invention can also be configured as an
islands-in-the-sea fiber, with the microfilament-generating
segments or islands 6 of the fiber imbedded in a sea of the
fugitive polymer component 8.
[0042] Both the shape of the fiber and the configuration of the
components therein will depend upon the equipment used to prepare
the fiber, the process conditions, and the melt viscosities of the
two components. As described above, a wide variety of fiber
configurations are possible.
[0043] To provide dissociable properties to the multicomponent
fiber, the polymer components are chosen so as to be mutually
incompatible. In particular, the polymer components do not
substantially mix together or enter into chemical reactions with
each other. Specifically, when spun together to form a
multicomponent fiber, the polymer components exhibit a distinct
phase boundary between them so that substantially no blend polymers
are formed therebetween, preventing dissociation. In addition, a
balance of adhesion/incompatibility between the components of the
multicomponent fiber is considered highly beneficial. The
components advantageously adhere sufficiently to each other to
allow the unsplit multicomponent fiber to be subjected to
conventional textile processing such as winding, twisting, weaving,
or knitting without any appreciable separation of the components
until desired. Conversely, the polymers should be sufficiently
incompatible so that adhesion between the components is
sufficiently weak, so as to provide ready dissolution upon
extraction of the fugitive polymer component.
[0044] The weight ratio of the microfilament-generating polymer
component and the fugitive polymer component can vary. Preferably
the weight ratio is in the range of about 10:90 to 90:10, more
preferably from about 20:80 to about 80:20, and most preferably
from about 50:50 to about 80:20.
[0045] The fugitive polymer component and the
microfilament-generating polymer component of the multicomponent
fibers of the invention may optionally include other additives or
components that do not adversely affect the desired properties of
the polymer composition. Exemplary conventional additives include,
without limitation, pigments, antioxidants, stabilizers,
surfactants, waxes, flow promoters, solid solvents, particulates,
and other materials added to enhance processability. These
additives can be used in conventional amounts, which typically do
not exceed about 10% by weight based on the total weight of the
polymer composition.
[0046] Dissociation of the multicomponent fibers provides a
plurality of fine denier filaments or microfilaments, each formed
of the microfilament-generating polymer component of the
multicomponent fiber. As used herein, the terms "microfilament" or
"microfiber" refer to filaments and fibers having a fineness of
less than about 1.5 denier, more preferably a fineness of less than
about 1.0 denier, and most preferably a fineness of less than about
0.5 denier. In some embodiments, the fineness is less than about
0.2 denier, such as a fineness in the range of about 0.01 to about
0.2 denier. The cross-sectional shape of the microfilaments may
vary. Exemplary cross-sectional shapes for the microfilaments
include wedge, multi-lobal, hexagonal, rectangular, oval and
circular.
[0047] FIG. 2 illustrates an exemplary multicomponent fiber of the
present invention which has been separated into a coherent fiber
bundle 10 of microfilaments 6 as described above. In the
illustrated example, the fiber bundle 10 comprises 4 microfilaments
6. Typically, the fiber bundle 10 produced upon dissolution of the
fugitive polymer component will comprise 1 to about 64
microfilaments, preferably about 4 to about 37 microfilaments.
[0048] The extrusion process for making multicomponent continuous
filament fibers is well known and need not be described here in
detail. Generally, to form a multicomponent fiber, at least two
polymers are extruded separately and fed into a polymer
distribution system wherein the polymers are introduced into a
spinneret plate. The polymers follow separate paths to the fiber
spinneret and are combined in a spinneret hole. The spinneret is
configured so that the extrudant has the desired overall fiber
cross section (e.g., round, trilobal, etc.). Such a process is
described, for example, in U.S. Pat. No. 5,162,074 to Hills, the
contents of which are incorporated herein by reference in their
entirety.
[0049] In the present invention, a microfilament-generating polymer
stream and a fugitive polymer stream are fed into the polymer
distribution system. The polymers typically are selected to have
melting temperatures such that the polymers can be spun through a
common capillary at substantially the same temperature without
degrading one of the components. The two polymer components are
extruded together into a continuous filament comprising separate
contiguous segments of each polymer component extending along the
length of the filament.
[0050] Following extrusion through the die, the resulting thin
fluid strands or filaments remain in the molten state for some
distance before they are solidified by cooling in a surrounding
fluid medium, which may be chilled air blown through the strands.
Once solidified, the filaments are taken up on a godet or other
take-up surface. In a continuous filament process, the strands are
taken up on a godet which draws down the thin fluid streams in
proportion to the speed of the take-up godet.
[0051] Continuous filament fiber may further be processed into
staple fiber. In processing staple fibers, large numbers, e.g.,
10,000 to 1,000,000 strands, of continuous filament are gathered
together following extrusion to form a tow, which is then cut into
predetermined lengths to form the staple fiber. The length of the
staple fibers generally ranges from about 25 to about 50
millimeters, although the fibers can be longer or shorter as
desired. See, for example, U.S. Pat. No. 4,789,592 to Taniguchi et
al. and U.S. Pat. No. 5,336,552 to Strack et al. Optionally, the
tow may be subjected to a crimping process prior to the formation
of staple fibers, as is known in the art. Crimped multicomponent
fibers are useful for producing lofty woven and nonwoven fabrics
since the microfilaments formed from the multicomponent fibers
largely retain the crimps of the composite fibers and the crimps
increase the bulk or loft of the fabric. Such lofty fine fiber
fabric of the present invention exhibits cloth-like textural
properties, e.g., softness, drapability and hand, as well as the
desirable strength properties of a fabric containing highly
oriented fibers.
[0052] Rather than being taken up on a godet, continuous
multicomponent fiber may also be melt spun as a direct laid
nonwoven web. In a spunbond process, for example, the strands are
collected in a jet, such as an air jet or air attenuator, following
extrusion through the die and then blown onto a take-up surface
such as a roller or a moving belt to form a spunbond web. As an
alternative, direct laid multicomponent fiber webs may be prepared
by a meltblown process, in which air is ejected at the surface of a
spinneret to simultaneously draw down and cool the thin fluid
polymer streams which are subsequently deposited on a take-up
surface in the path of cooling air to form a fiber web. The
techniques of spunbonding and meltblowing are known in the art and
are discussed in various patents, e.g., U.S. Pat. No. 3,987,185 to
Buntin et al.; U.S. Pat. No. 3,972,759 to Buntin; and U.S. Pat. No.
4,622,259 to McAmish et al.
[0053] Regardless of the type of melt spinning process that is
used, typically the thin fluid streams are melt drawn in a molten
state, i.e., before solidification occurs, to orient the polymer
molecules for good tenacity. Typical melt draw down ratios known in
the art may be utilized. The skilled artisan will appreciate that
specific melt draw down is not required for meltblowing
processes.
[0054] In another aspect, the present invention provides a fabric
formed from the multicomponent fibers of the invention. In a
preferred embodiment, the fabric is a nonwoven product, wherein the
multicomponent fibers can be either melt-spun into fibers, which
are then formed into a fibrous web using methods known in the art
(e.g., carding, airlaying, or wetlaying), or as noted above,
melt-spun directly into the form of a fibrous web by a spunbonding
or meltblowing process. The fibrous web can then be bonded to form
a nonwoven fabric. Webs of the fibers of the invention can be made
according to any of the known commercial processes for making
nonwoven fabrics, including processes that use mechanical,
electrical, pneumatic, or hydrodynamic means for assembling fibers
into a web, for example carding, wetlaying,
carding/hydroentangling, wetlaying/hydroentangling, and
spunbonding.
[0055] The webs can be bonded using techniques as known in the art,
such as but not limited to mechanical bonding, such as
hydroentanglement and needle punching, adhesive bonding, thermal
bonding, and the like, to form a coherent fabric structure. An
example of thermal bonding is air bonding, although other thermal
bonding techniques, such as calendering, microwave or other RF
treatments, can be used.
[0056] The fibers of the invention can also be used to make other
textile structures such as, but not limited to, woven and knit
fabrics. Yarns prepared for use in forming such woven and knit
fabrics are similarly included within the scope of the present
invention. Such yarns may be prepared from the continuous filament
or staple fibers of the present invention by methods known in the
art, such as twisting or air entanglement.
[0057] The present invention will be further illustrated by the
following non-limiting example.
EXAMPLE
[0058] In a bicomponent fiber melt-spinning process, one extruder
was fed with dried pellets of NATUREWORKS.TM. 6201D polylactic acid
(PLA) from Cargill Dow LLC, and the second extruder was fed with
dried pellets of EXCEVAL.TM. polyvinyl alcohol (PVOH) from Kuraray.
The PLA was melted and extruded at 245.degree. C. and pumped by a
gear pump into a spinneret assembly. The PVOH was melted and
extruded at 255.degree. C. and pumped into the same spinneret
assembly. Polymer distribution plates in the spinneret assembly
delivered the polymers independently through multiple flow paths to
positions in each spinneret backhole such that in each, the PLA
formed islands in the contiguous "sea" of PVOH, forming a
polymer-to-polymer cross sectional arrangement that was maintained
in the fiber through extrusion through the round capillaries of the
spinneret and subsequent solidification in a cross-current air
stream, and takeup across rolls and onto a winder at a speed of 815
meters/minute. In each fiber cross section, the PLA was delivered
to form a single, relatively large core "island" surrounded in the
PVOH "sea" by twelve smaller satellite "islands."
[0059] This process formed bicomponent 8 denier bicomponent
filaments with about 80% of the cross sectional area comprising the
PLA islands and about 20% of the cross sectional area comprising
the PVOH sea.
[0060] The PVOH sea was removed from the fibers by dissolution in
water at 35.degree. C., accompanied by agitation. The resulting
fibers were a blend of the relatively large core islands of PLA,
each with a denier of approximately 4 and the smaller satellite
islands of PLA, each with a denier of approximately 0.2. The PLA
fibers, including the 0.2 denier microfibers, maintained their
integrity and strength during and after the dissolution of the PVOH
component.
[0061] At a later time, the PLA fibers, including the 0.2 denier
microfibers, were immersed in a caustic aqueous solution of 3% NaOH
at 90.degree. C. for ten minutes, with agitation. The PLA fibers
lost their integrity and disappeared into the solution.
[0062] Many modifications and other embodiments of the inventions
set forth herein will come to mind to one skilled in the art to
which these inventions pertain having the benefit of the teachings
presented in the foregoing description. Therefore, it is to be
understood that the inventions are not to be limited to the
specific embodiments disclosed and that modifications and other
embodiments are intended to be included within the scope of the
appended claims. Although specific terms are employed herein, they
are used in a generic and descriptive sense only and not for
purposes of limitation.
* * * * *