U.S. patent application number 11/799629 was filed with the patent office on 2007-09-06 for treated textile substrate and method for making a textile substrate.
Invention is credited to Randolph S. Kohlman, Daniel T. McBride, Yunzhang Wang.
Application Number | 20070204444 11/799629 |
Document ID | / |
Family ID | 34861583 |
Filed Date | 2007-09-06 |
United States Patent
Application |
20070204444 |
Kind Code |
A1 |
Wang; Yunzhang ; et
al. |
September 6, 2007 |
Treated textile substrate and method for making a textile
substrate
Abstract
Compositions and methods for treating textile substrates to
obtain superior liquid repellent properties are disclosed. Durable
microscopic surface structures imparted to the fibrous substrate
allow liquids to bead up and roll off of its surface. Mechanical
abrasion or sanding techniques may be used to create the
microscopic surface structures on the surface of a fibrous textile
substrate, without substantially breaking fibers, followed by a
chemical treatment using, for example, fluorocarbon-containing
repellent compositions. Particles may be employed in combination
with repellent compositions to achieve superior repellent
properties. A property of the roughened surface fibers, the
Roughness Factor, is used to characterize the microscopic surface
structures on the treated textile surface. Treated textile
substrates are disclosed which achieve superior water and oil
repellency, even after multiple abrasion or laundering cycles.
Inventors: |
Wang; Yunzhang; (Duncan,
SC) ; McBride; Daniel T.; (Chesnee, SC) ;
Kohlman; Randolph S.; (Bolling Springs, SC) |
Correspondence
Address: |
Milliken & Company;Legal Department, M-495
PO Box 1926
920 Milliken Road
Spartanburg
SC
29304
US
|
Family ID: |
34861583 |
Appl. No.: |
11/799629 |
Filed: |
May 2, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10785218 |
Feb 24, 2004 |
7213309 |
|
|
11799629 |
May 2, 2007 |
|
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Current U.S.
Class: |
26/28 ; 442/181;
442/88 |
Current CPC
Class: |
B32B 7/12 20130101; D06M
2200/11 20130101; B32B 2307/754 20130101; D06M 23/08 20130101; D06M
15/277 20130101; D06M 2200/12 20130101; D06M 15/564 20130101; B32B
2307/73 20130101; B32B 5/024 20130101; Y10T 442/2287 20150401; Y10T
156/10 20150115; Y10T 442/2238 20150401; B32B 5/26 20130101; Y10T
442/30 20150401; Y10T 442/2279 20150401; B32B 5/02 20130101; Y10T
442/2221 20150401 |
Class at
Publication: |
026/028 ;
442/181; 442/088 |
International
Class: |
D06C 15/14 20060101
D06C015/14; B32B 5/18 20060101 B32B005/18; D03D 15/00 20060101
D03D015/00 |
Claims
1. A woven fiber-containing substrate with a first surface and a
second surface having integral microscopic surface structures upon
at least a portion of at least one of its surfaces, wherein said
integral microscopic surface structures have projections
substantially normal to the plane of said fiber-containing
substrate, said at least one surface comprised of: (a) portions
having a plurality of substantially unbroken fibers comprising
surface structures along at least part of the length of said
fibers, and wherein said fibers have a Roughness Factor greater
than or equal to about 1.10; and (b) a chemical mixture, said
chemical mixture comprising: (i) a fluorocarbon-containing
repellent component, (ii) a particulate component, and (iii) a
crosslinking component; wherein said woven fiber-containing
substrate exhibits substantially durable water repellency following
washing, said water repellency being at least about 5 when tested
according to the 3M Water Repellency Test II (May 1992).
2. The fiber-containing substrate of claim 1 wherein said integral
microscopic surface structures have a size less than about 100
.mu.m.
3. The woven fiber-containing substrate of claim 1 wherein said
fluorocarbon-containing repellent component is comprised of a
fluoroacrylate material.
4. The woven fiber-containing substrate of claim 1 wherein said
particulate component is comprised of particles having an average
particle size between about 1 nm and about 50 .mu.m.
5. The woven fiber-containing substrate of claim 1 wherein said
particulate component is comprised of at least one material
selected from the group consisting of silicates, doped silicates,
minerals, silicas, polymers, carbon, graphite, metal salts, metal
powders, silica-coated metal powders, inorganic oxides, and
combinations thereof.
6. The woven fiber-containing substrate of claim 5 wherein said
particulate component is comprised of a silica-based material.
7. The woven fiber-containing substrate of claim 6 wherein said
silica-based material is colloidal silica.
8. The woven fiber-containing substrate of claim 1 wherein said
crosslinking component is comprised of a polyurethane-based
material.
9. A method of making a fiber-containing substrate with a first
surface and a second surface having integral microscopic surface
structures upon at least a portion of at least one of its surfaces,
wherein said integral microscopic surface structures have
projections substantially normal to the plane of said
fiber-containing substrate, said at least one surface comprised of:
(i) portions having a plurality of substantially unbroken fibers
comprising surface structures along at least part of the length of
said fibers, and wherein said fibers have a Roughness Factor
greater than or equal to about 1.10; comprising the steps of: (a)
providing a fiber-containing substrate, said substrate having a
first surface and a second surface; (b) face-finishing at least
said first surface of said substrate, thereby forming integral
microscopic surface structures upon said first surface; and (c)
applying a chemical mixture to at least said first surface of said
substrate, said chemical mixture comprising a repellent
component.
10. The method of claim 9 wherein said face-finishing of step (b)
is achieved by mechanical treatment, chemical treatment, or
combinations thereof.
11. The method of claim 1Q wherein said face-finishing of step (b)
is achieved by mechanical treatment.
12. The method of claim 11 wherein said mechanical treatment is
accomplished by exposing at least said first surface to one or more
abrasive surfaces.
13. The method of claim 12 wherein said one or more abrasive
surfaces are coated with diamond grit or sandpaper.
14. The method of claim 13 wherein said abrasive surfaces are
coated with diamond grit having an average grit size of between
about 600 and about 1200.
15. The method of claim 14 wherein said abrasive surfaces are
comprised of one or more abrasive cylindrical rolls.
16. The method of claim 9, wherein said chemical mixture further
includes a particulate component.
17. A method of making a fiber-containing substrate with a first
surface and a second surface having integral microscopic surface
structures upon at least a portion of at least one of its surfaces,
wherein said integral microscopic surface structures have
projections substantially normal to the plane of said
fiber-containing substrate, said at least one surface comprised of:
(i) portions having a plurality of substantially unbroken fibers
comprising surface structures along at least part of the length of
said fibers, and wherein said fibers have a Roughness Factor
greater than or equal to about 1.10; comprising the steps of: (a)
providing a fiber-containing substrate, said substrate having a
first surface and a second surface; (b) face-finishing at least
said first surface of said substrate, thereby forming integral
microscopic surface structures upon said first surface; (c)
applying a first chemical mixture to at least said first surface,
said first chemical mixture comprising a particulate component; and
(d) subsequently applying a second chemical mixture to at least
said first surface, said second chemical mixture comprising a
repellent component.
18. A method of making a fiber-containing substrate with a first
surface and a second surface having integral microscopic surface
structures upon at least a portion of at least one of its surfaces,
wherein said integral microscopic surface structures have
projections substantially normal to the plane of said
fiber-containing substrate, said at least one surface comprised of:
(i) portions having a plurality of substantially unbroken fibers
comprising surface structures along at least part of the length of
said fibers, and wherein said fibers have a Roughness Factor
greater than or equal to about 1.10; comprising the steps of: (a)
providing a fiber-containing substrate, said substrate having a
first surface and a second surface; (b) face-finishing at least
said first surface of said substrate, thereby forming integral
microscopic surface structures upon said first surface; (c)
applying a first chemical mixture to at least said first surface,
said first chemical mixture comprising a repellent component; and
(d) subsequently applying a second chemical mixture to at least
said first surface, said second chemical mixture comprising a
repellent component and a particulate component.
19. A method of making a composite textile substrate comprising the
steps of: (a) providing at least one layer of a fiber-containing
substrate with a first surface and a second surface having integral
microscopic surface structures upon at least a portion of at least
one of its surfaces, wherein said integral microscopic surface
structures have projections substantially normal to the plane of
said fiber-containing substrate, said at least one surface
comprised of: (i) portions having a plurality of substantially
unbroken fibers comprising surface structures along at least part
of the length of said fibers, and wherein said fibers have a
Roughness Factor greater than or equal to about 1.10; (b) providing
at least one additional layer of material selected from the group
consisting of fiber-containing substrates, films, coatings, foams,
reinforcing substrates, and adhesives; and (c) joining the layers
of step (a) and step (b) together.
20. The method of claim 19 wherein said joining step of (c) is
achieved using adhesive, heat lamination, and combinations thereof.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of co-pending application
Ser. No. 10/785,218, filed on Feb. 24, 2004. This co-pending
application is herein entirely incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] There has been great interest recently in the surface
chemistry and textile field about so-called super-hydrophobic
surfaces and their resulting "self-cleaning" properties. This
self-cleaning effect of the super-hydrophobic surface is
principally controlled by how a liquid (typically water) interacts
with the surface of, for instance, a textile substrate. The
interaction between a liquid, air and a flat solid surface is
governed by Young's equation and is often described by a contact
angle between a liquid droplet and a solid surface. The contact
angle is determined by the interfacial tensions between the
solid-liquid, solid-air, and liquid-air interfaces. The solid
surface may be, for example, hydrophilic (having a strong affinity
for or the ability to absorb water) or hydrophobic (lacking
affinity for or the ability to absorb water). Typically, a surface
having a high contact angle is more hydrophobic that a surface
having a lower contact angle. Young's equation and a schematic
illustration of the solid/liquid interface contact angle are shown
in FIG. 1.
[0003] Young's equation is useful to determine the contact angle of
a droplet (such as water) on a uniform flat surface. So far, the
highest water contact angle on a flat solid surface is around 120
degrees for low surface energy fluorinated materials. To further
improve the contact angle, surface structure modifications are
needed. It is known that the contact angle can be substantially
higher on a rough surface than on a flat surface with the same
chemical nature. For highly roughened hydrophobic surfaces with
relatively high aspect ratios, which allows a substantial amount of
air to be trapped underneath a water droplet, the contact angle can
be greater than 150 degrees (i.e., a super-hydrophobic surface). In
both cases having roughened surfaces, Young's equation is modified,
since the surface area in contact with the water droplet has
changed. When a drop of water is put on such a super-hydrophobic
surface, the water droplet beads up like a sphere and may roll off
when the surface is tilted slightly. It is noted, however, to
achieve a low roll off angle, which is defined as the minimum tilt
angle at which a drop starts to roll, high contact angle alone is
not sufficient. It also requires low contact angle hysteresis,
which is defined as the difference between the advancing angle and
receding angle. The advancing angle is the contact angle of a
liquid that is observed while increasing the volume of a drop that
is pinned to a surface by, for instance, a syringe. Decreasing the
volume of the very same drop of liquid results in the receding
angle. If a liquid drop has a high advancing contact angle, but has
a substantially lower receding contact angle (i.e. with a
substantial contact angle hysteresis), the drop may bead up but a
higher roll off angle is required for the drop to roll. It may
furthermore leave a trail of liquid behind it on the surface. On
the other hand, if a liquid drop has both high advancing and
receding contact angles without substantial hysteresis, the drop is
able to bead up and roll off at a small tilt angle without leaving
a significant trail of liquid behind it on the surface (i.e., a
super liquid repellent surface). This beading and rolling action
allows the liquid drop to roll off the surface and carry away loose
dirt or dust with the drop, which leads to the "self-cleaning"
property. On a smooth surface with lower contact angles, on the
other hand, the liquid drop does not pick up the surface dirt. It
typically will only redistribute the dirt. These scenarios are
schematically illustrated in FIG. 2.
[0004] The super water repellent self-cleaning approach is found in
nature in a water loving plant called the Lotus. The Lotus plant is
a wetland species native to Asia, and it is revered as a symbol of
purity because it maintains its cleanliness, although it grows out
of muddy water. The Lotus plant's super water repellent
self-cleaning properties come from a combination of rough physical
surface structures and hydrophobic surface chemistries.
Specifically, the surface of the Lotus leaf exhibits two levels of
surface irregularity, as shown in FIG. 3. Each leaf surface (see
also FIGS. 3A and 3B) is covered in an array of tiny bumps, about
5-10 .mu.m high, and about 10-15 .mu.m apart. A scale showing 20
microns is evident in all three of these Figures, enabling an
estimation of the approximate size of the surface features. This
set of uneven surface structures is also covered with much smaller
waxy, hydrophobic crystals, measuring about 1 nm or less in
diameter. It is believed that this "dual" level of structure on the
Lotus leaf surface increases the overall surface roughness, which
correspondingly boosts its effective hydrophobicity. The two-tier
structure, with hydrophobic "valleys," reduces the likelihood of
surface air spaces being invaded by water, for instance, from
condensation, evaporation, or high impact rainstorms, since it is
not energetically favorable for the water to fill the valley. Thus,
it is believed that the physical surface structure of the Lotus
leaf, coupled with its surface chemistry (hydrophobic wax
crystals), allows the surface to act as a super water repellent,
self-cleaning surface where water beads up and rolls off, carrying
away loose dirt from the surface. This super water repellent
self-cleaning action in the presence of water on surfaces is often
known as the "Lotus-Effect".
[0005] In analogy to the Lotus plant, textile surfaces that repel
fluids and demonstrate super liquid repellency and associated
self-cleaning properties would be able to maintain their
appearances more effectively. Thus, a textile surface having
properties similar to the Lotus plant may be highly desirable. A
textile substrate having Lotus properties might be used to make
highly water repellent and/or fluid stain repellent fabrics for
applications, such as, for example, raingear, boat covers, awnings,
lawn furniture, apparel, etc. In providing fabrics that are water
and/or fluid stain repellent, the fabrics may also be resistant to
bacterial and mold growth, since water and/or other liquids would
not tend to collect or wick into such surfaces to provide a
breeding ground for the bacteria and mold.
[0006] Repellent textile substrates have been available in the
market for some time. For example, fluorocarbon treatments are
known to provide a repellent finish to such substrates. Many
fluorocarbon-containing compositions are known to provide
repellency to both water and oil when applied to a textile
substrate. However, to obtain the high contact angles and low roll
off angles required for a super water repellent surface, a surface
structure similar to that of the Lotus leaf is typically required.
There have been a variety of efforts by others to produce such
Lotus-like surface structures, such as in U.S. Pat. No. 6,068,911
to Shouji et al.; US Patent Application Publication No.
2002/0016433 to Keller et al.; and US Patent Application
Publication Nos. 2002/0150723, 2002/0150724, 2002/0150725,
2002/0150726, 2003/0013795, and 2003/0147932 to Creavis
Gesellschaft Fuer Techn. Und Innovation MBH. These references
disclose means to use particles to build rough structures on
primarily smooth flat surfaces. Textile substrates treated
according to these references generally do not provide durable
repellency because they often lose most or all of their repellency
when laundered or when abraded during normal use. Thus, textile
substrates that retain advantageous superior liquid repellent
properties, after laundering or exposure to abrasion from normal
use, would be very desirable and novel.
[0007] U.S. Pat. No. 5,968,642 to Saito is directed to an article
having a water-repellent fluororesin surface. The article has a
water-repellent fluororesin surface composed of an irregularly
porous material which is formed by irregularly stacking fluororesin
particles, with an average diameter of no more than 40 microns,
over one another. Again, this patent is directed to substrates that
have a flat surface, such as an aluminum sheet. Furthermore, it
fails to demonstrate its applicability to complex structured
textile substrates having irregular surfaces, and it fails to
demonstrate durability of the treatment against laundering and
abrasion for textile applications.
[0008] U.S. Pat. No. 6,649,266 to Gross et al. is directed to
substrates such as glass or metal with a microstructured surface
for easy-to-clean systems and methods to produce such substrates.
The treatment is comprised of a composition that includes
condensates of one or more hydrolysable compounds. At least some of
these compounds contain both hydrolysable and non-hydrolysable
groups with a ratio from 10:1 to 1:2. Inorganic nanoparticles are
used to produce the microstructured surface before the coating
composition is applied to the substrate. The microstructured
surface may also be obtained by embossing the coating composition,
before or during drying and/or curing, with an embossing die. The
contact angle, with respect to water or hexadecane on such
microstructured substrates, is at least 5 degrees higher than the
contact angle of a corresponding smooth surface. While the methods
taught in this patent may work well on flat surfaces, the teachings
therein fail to demonstrate its applicability to complex-structured
textile substrates and further, fail to demonstrate durability of
the treatment against laundering and abrasion for typical textile
applications.
[0009] US Patent Application No. 2003/0096083 to Morgan et al.
relates to surfaces of objects, in particular containers for
receiving liquid, comprising a surface which is extremely
hydrophobic and to a method for producing such surface. According
to the reference, a surface structure is created by fine blasting
the surface with suitable blasting material and/or embossing with
an appropriate embossing step or etching by means of a suitable
etching material. This reference fails to teach how to treat
complex structured textile substrates and fails to demonstrate
durability of the treatment against laundering and abrasion for
typical textile applications.
[0010] One publication, WO 01/75216, discloses a method for
applying a finishing layer to a textile carrier material. According
to the publication, a water repellent layer or an oil repellent
layer is applied to a carrier material of a group of fibers,
tissues and fabrics. The water or oil repellent finishing layer
comprises at least two water or oil repellent components. A first
component comprises at least one dispersing agent and a second
component comprises at least one dispersed phase or a colloid. The
dispersing agent and the dispersed phase are present in a gel
state. The colloids of the dispersed phase are distributed in the
dispersing agent in an anisotropic manner in such a way that the
colloids are present in concentrated form in the region of the
finishing surface, which forms a phase boundary layer between the
finishing layer and the surrounding atmosphere. An essential
feature of this approach is the use of a dispersion system as a
"guest-host" system which allows spatial self organization of the
finishing components. The "guest" component becomes phase separated
from the "host" component and concentrated on top of the finishing
layer with a columnar structured micro rough surface. This approach
relies on the chemical mixtures to be inherently phase instable.
Thus, the process is difficult to control and may cause problems
during large-scale manufacturing.
[0011] Another publication, WO 02/084016, is directed to a flat
textile structure with self-cleaning and water-repellent surfaces
that are composed of (a) at least one synthetic and/or natural
textile base material A and (b) one artificial and, at least
partially, hydrophobic surface with elevations and depressions from
particles that are firmly linked with the base material A without
glues, resins or lacquers. The flat textile structures are obtained
by treating the base material A with at least one solvent that
contains the particles in an undissolved state and then removing
the solvent so that at least a part of the particles are firmly
linked with the surface of the base material A. However, this
publication fails to demonstrate low dynamic rolling angles and
durability of the treatment against laundering and abrasion.
[0012] Yet another publication, WO 02/084013, is directed to a
polymer fiber which has a self-cleaning and water-repellent surface
and which is comprised of: (a) at least one synthetic fiber
material A and (b) a synthetic and, at least partially, hydrophobic
surface with elevations and depressions made of particles that are
joined to the fiber material A in a fixed manner without the use of
adhesives, resins or varnishes. The polymer fiber is obtained by
treating the fiber material A with at least one solvent that
contains the particles in undissolved form and then removing the
solvent so that at least a portion of the particles are joined to
the surface of the synthetic fiber material A in a fixed manner.
Again, this publication fails to demonstrate low dynamic rolling
angles and durability of the treatment against laundering and
abrasion.
[0013] The prior art systems that use hydrophobic particles and
binders in solvent systems on film, metallic, or ceramic surfaces
to achieve super-hydrophobic self-cleaning properties have
significant drawbacks, such as poor durability, when applied to
textile substrates. The coatings applied to the surfaces wear off
easily during normal use. FIGS. 4 and 4A show a fiber from a woven
textile substrate that have been treated with hydrophobic particles
according to procedures described in US Patent Application No.
2002/0016433 A1 to Keller et al. These textile substrates may
achieve some level of repellency, but the repellency is not durable
against laundering of the fibers or the textile substrate. The
hydrophobic particles are easily and undesirably removed from the
surface.
[0014] In summary, most prior art systems that attempt to achieve
the Lotus-Effect, as described herein, are directed to substrates
that have a flat smooth surface, such as glass, ceramic, metal
sheet, plastic film, etc. On such smooth surfaces, the rough
structures required for super-hydrophobic self-cleaning properties
may be achieved by using particles alone. On a typical textile
substrate, such as a woven fabric, a complex surface topology
already exists. For instance, millimeter scale structures are
created by the weaving of yarns; 10 to 100 micrometer scale
structures are created by fibers within the yarn. Furthermore, the
textile substrates are mechanically flexible. On such complex
structured flexible textile substrates, particles alone typically
are not sufficient to build desired rough structures which exhibit
the Lotus-Effect and that are durable against laundering and
abrasion for textile applications.
[0015] Surface structures can be imparted to a textile substrate by
other ways. For instance, mechanical means of treating surfaces of
textiles are known. Desirable hand (or feel) or other properties
may be provided to fabrics using treatments that involve techniques
of abrasion, sanding, or napping the fabric. However, the usual
goal of mechanically treating textile surfaces is to break fibers
and produce broken-fiber "hairs" that make a surface feel softer.
Therefore, the purpose of such conventional mechanical treatment is
typically to modify the hand of a substrate rather than to roughen
the surfaces of fibers without breaking the fibers. For example,
U.S. Pat. Nos. 6,112,381; 5,815,896; 4,512,065; 4,316,928; and
4,468,844 describe various types of mechanical treatments for the
surfaces of textile substrates. However, textile substrates that
are mechanically treated by these types of processes are found to
lack the desired roughness structures that are needed for the
lotus-effect properties.
[0016] Thus, the need exists for a composition and/or a method of
treating or coating textile substrates that results in a textile
substrate having a super liquid repellent self-cleaning surface. A
surface structure and method for treating a textile substrate that
will afford surface properties exhibiting a high degree of
repellency, as measured by low dynamic rolling angle (DRA), is very
desirable. A surface structure and method for treating a textile
substrate that will afford surface properties exhibiting a high
degree of repellency, that is durable after multiple launderings
and/or abrasions, is also desirable.
[0017] Surprisingly, we found that, on such complex structured
textile substrates, superior liquid (e.g. water and oil) repellent
properties can be obtained by mechanically roughening only a
portion, for example 10% or more, of the fibrous textile substrate
surface without substantially breaking fibers. Durability of the
repellent properties may be enhanced by following mechanical
treatment of the substrate with a chemical treatment using, for
example, fluorocarbon-containing repellent compositions. Particles
may be used in combination with the repellent chemical treatment.
The mechanical roughening treatment of the present invention occurs
in a treatment regime very different from that used in the prior
art. The resulting treated textile substrates are believed to be
durable against multiple cycles of laundering and/or abrasion
experienced during normal use because the mechanically roughened
structures on the surfaces of the fibers are part of the fibers
themselves and are attached durably and directly to the fibers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a sketch showing contact angle phenomena and
wetting.
[0019] FIG. 2 is a drawing showing a comparison of droplet behavior
upon a smooth surface when compared to a rough surface.
[0020] FIG. 3 shows a photomicrograph of the super-hydrophobic
"rough" structure of a Lotus leaf, having a microstructure and a
much smaller nanostructure.
[0021] FIG. 3A shows a magnified photomicrographic view of the
two-tiered structure of the Lotus leaf shown in FIG. 3.
[0022] FIG. 3B shows a side profile of the surface irregularity of
the Lotus leaf shown in FIG. 3A.
[0023] FIG. 4 is a magnified photomicrograph view (at 1000.times.
magnification) of a prior art fiber having particles present on the
surface of the fiber to form nanostructures, but which further
exhibits relatively poor durability.
[0024] FIG. 4A is a profile corresponding to the prior art fiber of
FIG. 4.
[0025] FIG. 5 is a magnified photomicrograph view of a plain weave
polyester fabric described in Example 10 showing first regions of
relatively high levels of roughness and second regions of
relatively low levels of roughness.
[0026] FIG. 5A is a magnified photomicrograph view (at 500.times.
magnification) of FIG. 5 showing a first region with surface fibers
that have relatively high levels of roughness.
[0027] FIG. 5B is a magnified photomicrograph view (at 500.times.
magnification) of FIG. 5 showing a second region with surface
fibers that have relatively low levels of roughness.
[0028] FIG. 5C is a magnified photomicrograph view (at 50000
magnification) of FIG. 5 illustrating the individual nanoparticles
present on the surface of a fiber having a relatively high level of
roughness.
[0029] FIG. 5D is a magnified photomicrograph view (at 50000.times.
magnification) of FIG. 5 illustrating an agglomeration of
nanoparticles present on the surface of a fiber having a relatively
high level of roughness.
[0030] FIG. 6 is a magnified photomicrograph view of a plain weave
polyester fabric mechanically treated by conventional coarse grit
abrasive rolls which illustrates the large number of broken fibers
present on the surface of the fabric.
[0031] FIGS. 7A-7C are magnified photomicrograph views of tent
fabric fibers, further described in Example 6, having highly
roughened edges which may be measured to determine the Roughness
Factor of those fibers.
[0032] FIG. 7D shows a calculated silhouette or shadow as estimated
for measuring the Roughness Factor (R.F.) for the fiber shown in
FIG. 7C.
[0033] FIG. 7E shows an edge profile image for the fiber shown in
FIG. 7C.
[0034] FIG. 8A is a magnified photomicrograph view (at 1000.times.
magnification) of a fiber of the tent fabric, as described in
Example 20, taken from an area of relatively high roughness and
which is determined to have a correspondingly high Roughness
Factor.
[0035] FIG. 8B shows an edge profile of the roughened fiber of FIG.
8A, which can be used to estimate the Roughness Factor of the
fiber.
[0036] FIG. 9A is a magnified photomicrograph view (at 50.times.)
of a plain weave polyester fabric, as described in Example 10,
showing first regions of relatively high levels of roughness
(mechanically roughened portions) and second regions of relatively
low levels of roughness.
[0037] FIG. 9B shows the same image as FIG. 9A except that the
highly roughened regions of the textile substrate surface are set
to black (pixel value of 0).
[0038] FIG. 9C shows the same image as FIG. 9B except the pixels
representing the highly roughened regions of the textile substrate
surface are set to 255 (i.e., white) and the pixel values for
everything else are set to 0 (i.e. black) so that the image has
been converted into a binary image where there are only white
pixels and black pixels.
DETAILED DESCRIPTION OF THE INVENTION
[0039] Reference now will be made to various embodiments of the
invention, one or more examples of which are set forth below. Each
example is provided by way of explanation of the invention, not as
a limitation of the invention. In fact, it will be apparent to
those skilled in the art that various modifications and variations
can be made in this invention without departing from the scope or
spirit of the invention. All patents, published patent
applications, and any other publications mentioned in this patent
application are herein incorporated by reference.
[0040] As mentioned previously, to obtain a surface that is super
liquid-repellent, desired surface roughness, preferably with
relatively high aspect ratios, should be built upon that surface.
Air trapped in the valleys of the rough surface causes drops of
liquid to bead up and roll off of that surface. One element of the
present invention is the method of creating the roughened surfaces
on a textile substrate that mimic the Lotus leaf. This invention
provides compositions and methods of treating textiles that afford
superior liquid (e.g. water, oil, etc.) repellency and potentially
easy-clean properties to the textile substrate that are durable to
laundering and abrasion.
[0041] Roughness is generally determined to include any protrusion,
nick, gouge, scuff, indentation, crater or other surface structure
present on the fibrous textile substrate surface, as a result of
mechanical treatment, chemical treatment, or combinations thereof,
that modifies the surface from being characterized as relatively
smooth and regular to a surface that may be characterized as less
smooth and regular. Accordingly, the descriptive term "roughness"
generally refers to these surface structures that are present on
the surface of individual fibers, wherein these surface structures
are located substantially normal to the axis of the fiber. The
descriptive term "surface structures" shall also be used
interchangeably with "roughness" to describe the roughened
features. The term "microscopic surface structures" on a fiber
surface generally refers to those surface structures that are
smaller in size than the diameter of the fiber. The size of these
microscopic surface structures is typically less than about 100
.mu.m.
[0042] The roughness may be imparted to a fibrous surface in an
additive or subtractive manner. Many of the prior art attempts to
build rough structures used the additive approach by adding
particles of various types to a surface, including textile
surfaces. To make a high aspect ratio rough structure on a fiber
surface using particles, either large particles or large
concentrations of small particles should be applied to the surface.
In either case, it is difficult to get a durable high aspect ratio
roughened surface using particles alone on a somewhat smooth,
flexible fibrous textile substrate. The particles tend to be
abrasively or otherwise readily removed from the surface.
[0043] Alternatively, mechanical treatments, chemical treatments or
combinations thereof may be employed in a subtractive approach to
remove or redistribute material from the surface of a textile
substrate to create these microscopic surface structures. The
subtractive roughness approach has the advantage that the roughened
microscopic surface structures of the fiber surface are attached
to, and are part of, the underlying textile substrate. Roughening
the textile substrate surface in this manner may be referred to as
"integral" because the roughness does not result from the addition
of new and different material to the fibers of the textile
substrate. The chemical make-up of the roughened surface and the
unroughened surface has not changed appreciably by the treatment
process (i.e. no new material is appreciably added to the surface
of the fiber or the textile substrate).
[0044] In the present invention, mechanical roughening of a textile
surface, using the subtractive approach, may be preferentially
employed to impart integral microscopic surface structures to the
textile substrate for providing superior liquid repellent
performance. Because the mechanically roughened surface structures
are integral, they are not easily abraded or washed away during
laundering or normal use. Therefore, integral surface roughness, or
integral microscopic surface structures, leads to enhanced
durability of the repellent properties of the textile substrate.
This durability is generally necessary for textile substrates that
are required to withstand abrasion and perhaps repeated laundering
in their normal course of use. For illustrative purposes, FIGS. 5A
and 8A illustrate regions of relatively high integral roughness as
described herein.
[0045] In one embodiment of the present invention, roughness may be
obtained by mechanically roughening the textile surface, according
to techniques described in greater detail later, to generate a
highly liquid repellent textile substrate. In this embodiment, at
least one size range of microscopic surface structures may be
imparted to the fibrous surface of the textile substrate. In
another embodiment, the application of a repellent chemistry may be
used in combination with the mechanical treatment to generate a
highly liquid repellent textile substrate. In yet another
embodiment of the present invention, particles, with diameters of
nanometer to micron size, may be added to the mechanically
roughened textile surface, before, after, or together with the
application of a repellent chemistry to generate a highly liquid
repellent textile surface. In this embodiment, roughened surface
structures having at least two different size ranges are imparted
to the fibrous surface of the textile substrate. The size ranges
may be exclusive of each other such that the sizes do not overlap,
or the ranges may be somewhat overlapping. These embodiments will
be described in more detail below.
[0046] For the present invention, the methods for creating a highly
liquid repellent roughened surface are applicable to a broad range
of textile substrates. The textile substrate may be a
fiber-containing textile substrate, such as a woven, knit, or
nonwoven fabric, or a laid scrim. These fiber-containing textile
substrates may be joined together in any combination to form a
composite structure. The composite structure may include other
materials, such as films, coatings, foams, reinforcing substrates,
adhesives, and the like. The layers of the composite structure may
be joined together using, for example and without limitation,
adhesive, heat lamination, and combinations thereof.
[0047] The fiber-containing textile substrate may be formed from
fibers such as synthetic fibers, natural fibers, man-made fiber
using natural constituents or combinations thereof. Synthetic
fibers include, for example and without limitation, polyester,
acrylic, polyamide, polyolefin, polyaramid, polyurethane,
regenerated cellulose, and blends thereof. More specifically,
polyester includes, for example, polyethylene terephthalate,
polytriphenylene terephthalate, polybutylene terephthalate,
polylacetic acid, and combinations thereof. Polyamide includes, for
example, nylon 6, nylon 6,6, and combinations thereof. Polyolefin
includes, for example, polypropylene, polyethylene, and
combinations thereof. Polyaramid includes, for example,
poly-p-phenyleneteraphthalamid (i.e., Kevlar.RTM.),
poly-m-phenyleneteraphthalamid (i.e., Nomex.RTM.), and combinations
thereof. Natural fibers include, for example and without
limitation, wool, cotton, linen, ramie, jute, flax, silk, hemp, or
blends thereof. Exemplary man-made materials using natural
constituents include regenerated cellulose (i.e., rayon), lyocell,
or blends thereof.
[0048] The textile substrate may be formed from fibers or yarns of
any size, including microdenier fibers and yarns (fibers or yarns
having less than one denier per filament). The fibers or yarns may
be comprised of spun fibers, continuous filament fibers,
bicomponent fibers, bicomponent splittable fibers, or blends
thereof. The fibers may include slit film fibers or tape yarn.
[0049] As mentioned previously, one method for imparting integral
roughness to the textile substrate is via mechanical
face-finishing. For purposes of this invention, the term
"face-finishing" or "face-finished" refers to any one of the
methods or techniques for abrading, sanding, blasting, roughening,
or mechanically altering the surface of a fibrous textile substrate
as, for example, by methods and techniques described in the
referenced patents and publications. For instance, U.S. Pat. Nos.
6,112,381; 5,815,896; 4,512,065; 4,316,928; and 4,468,844 each
describe various types of mechanical face-finishing treatments for
textile substrates. Some examples of these mechanical
face-finishing techniques include, for example, sanding or abrading
with an apparatus (such as a roll) coating with abrasive grits
(such as diamond, SiC, SiO.sub.2, Al.sub.2O.sub.3, TiC, WC, etc.),
particle blasting (such as sand blasting), exposing the substrate
to high temperature fluid, such as water or air, and the like. For
the present invention, all of these face-finishing techniques, and
variations thereof, may be used alone or in combination to roughen
the textile substrate surface and create microscopic surface
structures on the surface of the fibers contained therein.
Variations or modifications to these techniques may include process
alterations which allow for effective roughening of the surface of
the textile substrate without breaking a substantial number of the
fibers contained therein.
[0050] A potentially preferred, non-limiting, mechanical means of
face-finishing a textile substrate includes exposing the textile
substrate to an abrasive surface that may be stationary,
oscillating or rotating in relation to the textile substrate. The
abrasive surface may be coated with sandpaper, diamond, or other
abrasive particles. If a rotating, cylindrical roll is used, it may
be presented to the textile substrate, either normal to the length
of the textile (i.e. perpendicularly across its width) or at an
angle to the length of the textile, to control which areas or
portions of the textile surface receive more or less treatment. For
example, in a woven fabric for a specific application, it may be
most desirable that the warp yarns, rather than the fill yarns,
receive the bulk of the roughening treatment. In order to control
such treatments, various parameters of the process may be adjusted
to achieve the desired results. Such parameters include, for
example, (a) the tension of the textile substrate as the abrasive
roll is presented, (b) the engagement pressure of the abrasive
roll, (c) the relative speed of the roll's rotation compared to the
textile's translation, (d) the residence time of contact between
the abrasive roll(s) and the textile, and (d) the abrasive grit
size on the treatment roll.
[0051] Frequently, conventional face-finishing techniques are used
to impart certain characteristics to a fabric such as, for example,
to impart a more desirable hand (which includes softness of the
surface), to improve drapeability of the fabric, to improve
wickability of the fabric, etc. In order to impart these
characteristics to a textile substrate, conventional techniques,
(using rotating abrasive rolls with 400 grit or coarser) are often
used to purposefully break fibers and make dense areas of short,
broken fibers or loose fibers, which in turn, increases the
"hairiness" of the textile substrate surface. For the purpose of
the present invention, these broken fibers and the increased
hairiness of the substrate are considered undesirable features of
the textile substrate due to the fact that a broken fiber, which
may be considered as a fiber that substantially projects out from
the surface of the textile substrate, may serve as an obstacle to
liquid rolling off of that surface. As a result, a substrate having
many broken fibers on its surface will tend to reduce the liquid
repellency of the substrate. In practice, broken fibers can be
identified in a surface image because they are generally fibers
that show a definite end or tip which projects out from the surface
of the textile. They may also be identified as fibers that have
been moved substantially away from their initial location so that a
substantial portion of the fiber projects out from the surface of
the textile. This latter case can occur when, for instance, a fiber
can be seen in an image of a woven fabric that has moved away from
its initial yarn bundle and has crossed over or into a different
yarn bundle. The short fiber tips or ends that regularly present at
the surface of staple or spun yarns prior to the face-finishing
treatment generally are not considered to be broken fibers for the
purpose of the present invention.
[0052] The surface of a textile substrate, treated in the manner
conventionally practiced in the prior art of mechanical
face-finishing, is illustrated in FIG. 6. A substantial amount of
broken fibers and/or filaments can be seen on the surface of
substrate 40. In fact, the broken fibers are the dominant feature
on that surface. A scale showing 1 mm is evident near the lower
portion of FIG. 6, enabling an estimation of the approximate size
of the surface features. The number of broken fibers per square
millimeter can be counted on typical textile substrates treated in
this manner, and it has been found to be in the range of about 9 to
about 30 when treated with the coarse abrasive treatments in the
prior art. As mentioned previously, these long, broken fibers that
project out from the textile substrate surface have been found to
be detrimental to creating a super liquid repellent self-cleaning
textile substrate. Therefore, mechanical face-finishing treatments,
as practiced conventionally in the prior art, generally do not
impart microscopic surface structures to textile substrates that
are useful for super liquid repellency.
[0053] To create a textile substrate having super liquid repellent
properties, it has been found that mechanical face-finishing
treatments may be used in an unconventional manner to impart
surface roughness to the substrate. As illustrated in FIG. 5, the
face-finishing processes utilized in the present invention may
provide a level of roughening that is much lighter or finer than is
customarily practiced in the industry, to lightly roughen, but not
break, the fibers or filaments on the surface of the textile
substrate. The textile substrate surface that has been mechanically
face-finished according to methods of the present invention, as
shown in FIG. 5, is far different from the one that has been
face-finished in the manner of the prior art, as shown in FIG. 6.
Accordingly, the ability to use mechanical face-finishing
techniques to create a super-hydrophobic textile substrate, when
compared with the purposes of conventional face-finishing
techniques, is considered to be a novel and unobvious method for
imparting the lotus-effect to a textile substrate.
[0054] To obtain the inventive treatments described herein using
mechanical face-finishing via abrasive sanding, very fine grit
abrasive or sanding rolls, wherein the rolls are coated with
abrasive grit in the range of between about 600 and about 1200
grit, or finer, have been utilized. These abrasive rolls are able
to roughen large areas of the surface of fibers without breaking a
significant number of fibers. Thus, they are able to create
desirable integral microscopic surface structures on the surface of
the fibers, which results in a textile substrate having durable
super liquid repellency. The number of broken fibers which have
been found to be detrimental to creating a super liquid repellent,
self-cleaning textile substrate according to the present invention
is substantially less than the number of broken fibers observed on
a textile substrate treated by traditional face-finishing
techniques. The number of broken fibers observed on the inventive
treated substrate is typically less than about 5 fibers per square
millimeter, and preferably less than about 3 fibers per square
millimeter. In some cases, it has been observed that a broken fiber
may lie substantially in the plane of the textile substrate, rather
than protruding out from the surface of the substrate.
[0055] For purposes of this invention, "in the plane of the
fiber-containing substrate" or "in the plane of the textile
substrate" may be interpreted by the following discussion. A
textile substrate is generally manufactured or provided in a sheet
form. In application, the textile substrate has a sheet character,
at least piecewise. The plane of the fiber-containing substrate may
be determined, at least locally, by the sheet of the textile
substrate. Operationally, the substrate may be placed, smoothed out
and unwrinkled, on a flat horizontal supporting surface, and the
supporting surface may be used to determine the plane of the
substrate.
[0056] The specific distribution of roughened surface structures
imparted to the surface of a textile substrate by the mechanical
roughening taught in the present invention is very characteristic
and different from those imparted to by other means. If, for
example, the yarns or fibers that make up the textile substrate
were roughened before incorporation into the textile structure, a
uniform distribution of roughened surface structures on the yarn or
fibers would be expected. In contrast, the inventive method of
treating a textile substrate with an abrasive roll results in a
more non-uniform distribution of roughened surface structures.
[0057] In particular, for some textile substrates, the fibers may
be grouped into yarn bundles. Mechanically treating a textile
surface with an abrasive roll tends to treat the elevated portions
of the textile substrate. Depending on the normal force that keeps
the textile in contact with the abrasive treatment roll, a
different amount of the elevated portions on the surface may be
treated. Also, mechanically face-finishing a textile substrate does
not tend to roughen the inner fibers of a yarn bundle, since the
inner fibers tend to be protected by the outer fibers of the yarn
bundle. Furthermore, fiber-containing textile substrates, such as
woven fabrics, may possess roughened surface structures on either
one or both of the elevated and depressed regions characteristic of
a woven fabric (i.e. warp yarn bundles and fill yarn bundles)
without exhibiting any substantial increased bulk to the
fabric.
[0058] Additionally, depending on the angle or orientation of the
abrasive roll, fibers with different orientations within the
textile substrate may be treated differently. For instance, many
prior art abrasive roll treatment systems preferentially treat the
fill yarns of a woven structure. Accordingly, when an abrasive roll
is used to mechanically roughen a textile surface, while the entire
top or bottom surface of a fibrous textile substrate may be
treated, the entire top or bottom surface of a textile substrate
may not be roughened uniformly. The percentage of the textile
substrate surface that has been treated according to the current
invention has been determined, on average, to be approximately 20%,
as will be disclosed in more detail in the Examples section below.
It may seem surprising that treating only relatively small portions
of a textile substrate surface may give such a dramatic improvement
in liquid repellency, but the only surface areas that contribute
significantly to liquid repellency are the those most likely to be
contacted by an impinging liquid, which are primarily the elevated
portions of the surface that have been mechanically roughened. This
non-uniform distribution of surface roughness is contemplated to be
exhibited by mechanically roughened woven, knit, nonwoven and laid
scrim substrates. It is anticipated that increasing the percentage
of the roughened portions of the textile substrate may improve the
liquid repellency performance even further.
[0059] Another aspect of mechanically roughening a textile
substrate, rather than the yarns or fibers before incorporation
into a substrate, is that a fiber that is on the top surface of a
yarn at one point in the fabric may not be at the top surface at a
different point in the fabric. Therefore, that fiber may be
roughened in one part of the fabric and not in another part of the
fabric. Accordingly, when an abrasive roll is used to mechanically
roughen a textile surface, while the entire top or bottom surface
of a fibrous textile substrate may be treated, the entire surface
of the fibers or yarns comprising the surface of the substrate are
generally not roughened. Accordingly, a roughened fiber may only be
roughened over a part of its circumference and only along a portion
of its length. To be of value in providing high liquid repellency,
that roughened portion should be of a suitable length (at least to
substantially cover the elevated regions of a fabric that a liquid
drop will contact) and the roughened portion of the circumference
of the fiber should be located substantially normal to the surface
of the textile substrate. The fact that only a portion of the total
surface area of the fibers that make up the textile substrate needs
to be treated to provide high liquid repellent properties may be
surprising. However, liquids that contact the surface of the
textile substrate will not tend to wick into or penetrate the yarn
bundle of a highly repellent textile substrate and further contact
the inner fibers. This understanding allows for a much simpler and
more economical treatment method, such as abrasive roll treatment
of the whole textile, which can be easily implemented, rather than
having to treat the entire surface of each fiber or yarn, though
this type of treatment may effective as well.
[0060] The degree of roughening imparted to a fiber has been
quantified for a number of textile substrates, as described in
detail below. In general though, if a roughened fiber is examined
microscopically along a roughened portion of the edge substantially
away from any broken fiber ends or tips, the length of the profile
(basically, a shadow) of the roughened fiber can be measured. The
ratio of that roughened profile length to the rectilinear length
along the fiber serves as a Roughness Factor (R. F.). In general,
fibers removed from textile substrates treated according to the
current invention have Roughness Factors equal to or larger than
1.10, as will be discussed in detail later.
[0061] Based on the preceding detailed discussion, the invention
can be described in one embodiment as a fiber-containing substrate
with a first surface and a second surface having integral
microscopic surface structures upon at least a portion of at least
one of its surfaces, wherein said microscopic surface structures
have projections substantially normal to the plane of said
fiber-containing substrate, said at least one surface comprised of
portions having a plurality of substantially unbroken fibers
comprising surface structures along at least part of the length of
said fibers, and wherein said fibers have a Roughness Factor
greater than or equal to about 1.10. It may be more preferable that
the Roughness Factor is greater than or equal to 1.20, and even
more preferable, greater than or equal to 1.30. A liquid repellent
chemical treatment may be applied to the fiber-containing substrate
if the substrate material itself is not liquid repellent already.
Typically, the fiber-containing substrate may have integral
microscopic surface structures upon at least 10% of at least one of
its surfaces in order to achieve superior liquid repellent
properties. However, it may be more preferable to have integral
microscopic surface structures upon at least 15% of at least one of
its surfaces, and even more preferable, upon at least 20% of at
least one of its surfaces.
[0062] In the above description, "substantially normal to the plane
of the fiber-containing substrate" shall mean that the object,
specifically the surface structure, has a sizeable component that
projects away from, or into, or is substantially perpendicular to
the plane of the fiber-containing substrate, as defined previously.
For the projections normal to the plane of the textile substrate to
enhance liquid repellent performance, they should be on a top
surface, or a contact surface, of the textile substrate.
[0063] In other embodiments, an additional particulate component
may be added to at least one of the surfaces of the
fiber-containing textile substrate before, after or together with
the application of a repellent component to form another size scale
of roughness. It should be mentioned that the additional surface
area provided on the fiber-containing textile substrate by the
mechanical roughening treatment also results in more anchor points
for attaching particles and/or chemicals to the textile substrate
surface, thereby allowing the particles and chemicals to become
more durably adhered to the surface of the textile substrate. Other
mechanical means of roughening the textile substrate surface could
also be practiced within the scope of the invention. In general,
any face-finishing treatment may be employed that achieves the
desired fiber Roughness Factor, an effective percentage of
treatment surface area, and/or the desired Dynamic Rolling
Angle.
[0064] In addition to using mechanical face-finishing techniques to
roughen the surface fibers of a textile substrate, a chemical
treatment using, for example, fluorocarbon-containing compositions
or other liquid repellent compositions, may be applied to the
textile substrate to convert non-liquid repellent elements of the
substrate into liquid repellent elements. If the substrate is
already liquid repellent, the additional repellent chemical
treatment may not be necessary. Furthermore, another size scale or
size range of roughness, in addition to the integral microscopic
surface structures formed by face-finishing, may be obtained
through the addition of nanometer-sized particles to the textile
substrate surface. It is believed that these small particles, when
properly made hydrophobic, will mimic the nano structures of the
waxy crystals previously mentioned on the Lotus leaf. Surprisingly,
it has been found that textile substrates which receive mechanical
face-finishing treatment and then subsequently receive a treatment
of a fluorocarbon-containing component and a particulate component
(preferably having a particle size of less than 1000 nanometers)
exhibit superior performance properties, including an elevated
Roughness Factor (R.F.), as herein defined, and a lowered Dynamic
Rolling Angle (DRA).
[0065] In some applications of the invention, it is useful to apply
crosslinking agents as well as repellent compounds. Repellent
compounds may include fluorocarbon-containing repellent compounds.
In one embodiment, aqueous compositions comprising a fluorochemical
dispersion and a crosslinking agent may be used to treat the
face-finished textile substrates. In another embodiment, aqueous
compositions comprising hydrophilic particles, a crosslinking
agent, and a fluorochemical dispersion may be used to treat the
face-finished textile substrates. Application of the chemistry to
the textile substrate may be accomplished by a variety of
application methods which include, but are not limited to, coating,
padding, spraying, foam coating, printing, exhaustion techniques or
by any other technique whereby one can apply a controlled amount of
a liquid suspension to a textile substrate. Employing one or more
of these application techniques may allow the chemical to be
applied to the textile substrate in a uniform manner.
[0066] The chemical agents may be applied simultaneously or
sequentially to the textile substrate. For example, in one
embodiment, a mixture comprising a repellency agent, a particulate
agent, and a crosslinking agent, which are mixed together in one
bath, is applied simultaneously to the textile substrate by, for
example, padding. After application of the chemical agents to the
textile substrate, the treated substrate is exposed to a drying
step to evaporate excess liquid, leaving the solid active
components on the surface of the treated substrate. Drying can be
accomplished by any techniques typically used in manufacturing
operations, such as dry heat from a tenter frame, microwave energy,
infrared heating, steam, superheated steam, autoclaving, or the
like, or any combinations thereof. In another embodiment, a mixture
comprising a particulate component (with or without a crosslinking
agent) is applied to the textile substrate, the substrate may be
dried or left wet, and then a mixture comprising a repellency agent
and a hydrophobic crosslinking agent is applied on top of the
particulate component, creating a sequential chemical treatment on
the surface of the textile substrate. The substrate is then dried.
In yet another embodiment, a mixture comprising a repellent agent
(with or without a crosslinking agent) is applied to the textile
substrate, the substrate may be dried or left wet, and then a
mixture comprising a repellency agent, a particulate agent, and a
hydrophobic crosslinking agent is applied on top of the repellent
agent previously applied, creating a sequential chemical treatment
on the surface of the textile substrate. The substrate is
subsequently dried.
[0067] It may be desirable to expose the treated textile substrate
to an additional heating step to further enhance the performance or
durability of the chemical agents. This step may be referred to as
a curing step. By way of example, additional heating may (a) enable
some of the active components of the chemical agents to melt-flow
together, resulting in uniform, cohesive film coverage on the
surface; (b) induce preferred alignment of certain segments of the
chemical agents; (c) induce crosslinking reactions between the
chemical agents or between the chemical agents and the substrate;
or (d) combinations thereof.
[0068] In many instances, for a textile substrate to perform
satisfactorily, regardless of its end-use application, other
attributes, in addition to durable liquid repellent self-cleaning
properties, may be desirable. Examples of such attributes include,
but are not limited to, static protection, wrinkle resistance,
desirable hand (or feel) requirements, dyefastness requirements,
odor control, flammability requirements, resistance to dry soiling,
and the like. In such cases, the textile substrate may be treated
with various other chemical finishes, in addition to those
described previously. For example, it may be desirable to treat the
textile substrate with finishes containing chemicals such as
antimicrobial agents, antibacterial agents, antifungal agents,
flame retardants, UV inhibitors, antioxidants, coloring agents,
lubricants, antistatic agents, fragrances, and the like, or
combinations thereof. Many such chemical treatments can be
incorporated simultaneously with the chemical composition of the
current invention, or such treatments may be carried out prior to
treatment with the chemical composition of the current invention.
It is also possible, using appropriate techniques, to apply many
such chemical treatments after treatment with the chemical
composition of the current invention.
[0069] Additionally, the textile substrate may also be treated by
typical mechanical finishing techniques to achieve desired
appearance, strength, porosity, and/or hand of the fabric. For
example, it may be desirable to expose the textile substrate to
mechanical treatment such as calendaring, embossing, etching,
rainbow or hologram embossing, film or metal foil hologram
embossing, fabric metallization, heat setting, sanforizing,
glazing, schreinering, sueding, sanding, emorizing, napping,
shearing, tigering, decating, fabric patterning through the use of
water, air, or patterned rolls, and the like, or combinations
thereof. Depending on which mechanical treatment is utilized,
advantages may be obtained by treatment either before or after the
mechanical and/or chemical treatment of the current invention is
applied. By way of example, in addition to creating roughness on a
first surface of a textile substrate, benefits from subsequently
calendaring a second surface of the textile substrate, without
significantly affecting the roughness structures already created on
the first surface, prior to chemical treatment may be envisioned.
In such instances, the hydrostatic properties of the substrate may
be improved significantly without affecting the highly liquid
repellent, self-cleaning properties created on the first surface of
the textile substrate.
[0070] Within the scope of the current invention, it is also
contemplated that asymmetric textile substrates may be created with
surfaces having dual functional attributes. For example, a textile
substrate, having a first and a second surface, may be produced
that possesses a first hydrophobic surface and a second hydrophilic
surface. Such a dual functional textile substrate may be made, for
example, by face-finishing the first surface to create integral
microscopic surface structures, coating both surfaces of the
textile substrate with a hydrophilic chemical agent, and then
coating the first surface of the substrate with the chemical
treatment of the present invention. Alternatively, the first
surface may be face-finished to create integral microscopic surface
structures, and the hydrophilic chemistry may be applied only to
the second surface. Chemical application methods include any of
those previously discussed, such as spray coating, foam coating,
and the like. As a result, textile substrate made in this manner
may provide increased protection from environmental or chemical
assault by repelling liquids on the first surface of the substrate
and, at the same time, provide increased user comfort by absorbing
moisture, such as perspiration, on the second surface of the
substrate. Clearly, these are desirable features if, for example,
the textile substrate is used in apparel applications.
[0071] It is noted that attempts made by others to create the
Lotus-Effect surfaces using only hydrophobic particles (and without
using fluorochemicals) do not exhibit any repellency against
wetting components, such as oil, although they may exhibit some
level of repellency against water. The textile substrate treated
according to the present invention, however, exhibit both super
water repellency and superior oil repellency. More specifically,
drops of oil, such as corn oil, may bead up and roll off the
surface of the treated textile when the textile is tilted at an
angle, without leaving behind a substantial trace of the oil.
[0072] Turning to FIG. 5, a fiber-containing textile substrate 20
is shown having a first side with a fibrous surface. A scale
showing 100 .mu.m is evident near the lower portion of FIG. 5,
enabling an estimation of the approximate size of the microscopic
surface structures. FIG. 5 corresponds to the flat woven polyester
fabric of Example 10 described in greater detail below. The fibrous
surface comprises fibers 23-25 and fibers 30-32 extending upon the
surface, as shown in FIGS. 5A and 5B. A scale showing 10 .mu.m is
evident near the lower portion of FIGS. 5A and 5B, enabling an
estimation of the approximate size of the microscopic surface
structures. First elevated regions 21a-c and second depressed
regions 22a-c, which are characteristic of a woven textile
substrate, are shown.
[0073] In this particular example, the substrate 20 is woven, and
the roughened surface is caused by abrading the textile substrate
with a fine diamond grit coated roll. The weave pattern causes the
first elevated regions 21a-c to be higher than the second depressed
regions 22a-c. Thus, the first elevated regions 21a-c receive much
more roughening during the abrading treatment, while the second
depressed regions receive much less roughening, and in fact may
receive no roughening at all from such face-finishing treatment.
This selective mechanical treatment of the textile substrate
surface, wherein some regions are more likely to be roughened than
other regions, is generally a function of the construction of the
textile substrate. For instance, whether the substrate is a woven,
knitted, nonwoven, or laid scrim structure affects the fiber
orientation of and the placement within the textile substrate,
thereby altering which regions or fibers (for example, the fill
yarns versus the warp yarns in a woven substrate) may be roughened
by the face-finishing treatment.
[0074] The inset box 21b of FIG. 5 is expanded in FIG. 5A, so that
the detail can be seen of the first elevated regions 21b.
Furthermore, the individual fibers 23-25 can be seen, with
substantial surface roughness, resulting in features that mimic the
Lotus leaf surface; that is, features that are desirable in
creating and maintaining repellency and/or superior liquid
repellency upon the textile substrate. This repellency is not
easily lost during laundering, abrasion, or normal use of the
textile substrate because the roughened surface is an integral part
of the textile substrate surface. In addition, nanometer-sized
particles, if utilized, are attached more durably to these
roughened regions of the fibers because of the high surface
area.
[0075] The inset box of 22b of FIG. 5 is expanded in FIG. 5B, and
it shows an expanded view of second depressed region 22b. As can be
seen, there is much less roughness and surface irregularity on the
fibers 30-32 in this latter region. Thus, this region, due to its
geometrical location, receives almost no surface roughening from
the face-finishing treatment, as practiced in the invention. The
relative percentage of the areas with substantial fiber roughness
and the areas with significantly less fiber roughness may vary
depending on the face-finishing treatment employed and the
construction of the textile substrate. In fact, it may be the case
that only those portions of yarns or fibers that are hidden from
treatment, because they are at crossover points where, for example,
the fill yarns physically cover the warps yarns in a woven
construction, may show significantly less surface roughness.
[0076] FIGS. 5C and 5D illustrate the nanoparticles present on the
surface of textile substrate 20 shown in FIG. 5. FIG. 5C shows the
individual nanoparticles 41a-41c that are present on the surface of
a roughened fiber. FIG. 5D shows that some of these individual
nanoparticles may come together to form agglomeration 41d on the
surface of a roughened fiber.
[0077] FIG. 7A shows a scanning electron micrograph image (SEM) (at
500.times. magnification) of roughened fiber 41 that has been
pulled out from the tent fabric described in Example 6. Roughened
fiber 41 is created by application of at least two different sized
features--(a) microscopic surface structures on the fiber as a
result of mechanical face-finishing treatment and (b) the addition
of nanometer-sized particles which are applied to the fiber. FIG.
7B shows a close-up view of roughened fiber 41, and further views
7C, 7D, and 7E show the series of steps taken to measure the
Roughness Factor (R.F.) of the fiber(s), which is further discussed
below. The total length of the upper margin of the silhouette is
measured relative to the linear length of the image box to
determine the approximate or average amount of roughness imparted
to the fiber surface within the first elevated regions, as
indicated in the procedure outlined below.
[0078] FIG. 8A shows a SEM image (at 1000.times. magnification) of
fiber 50 pulled out from the tent fabric described in Example 20
below and illustrates the microscopic surface structures formed on
the fiber due to mechanical face-finishing. A corresponding
silhouette, or profile, of this image is shown in FIG. 8B. A scale
showing 10 .mu.m is evident near the lower portion of FIG. 8A,
enabling an estimation of the approximate size of the surface
features. The roughness features generated on this fiber closely
resemble those present on a Lotus leaf.
Repellent Components
[0079] There are numerous compositions that may be adapted to serve
as the repellent component in the present invention. "Repellency"
is generally defined as the ability of a substrate to block fluids,
such as water and/or oil, from penetrating into a substrate. For
example, the substrate may be a textile substrate which is capable
of blocking water and oil from penetrating into the fibers of the
textile substrate.
[0080] One composition that is particularly useful is a
fluorochemical composition. The terms "fluorocarbons,"
"fluoropolymers," and "fluorochemicals" may be used interchangeably
herein and each represents a polymeric material containing at least
one fluorinated segment. Numerous fluorochemical compositions are
known to be capable of achieving repellency on a textile
substrate.
[0081] Generally, repellent fluorochemicals useful in the present
invention include any of the fluorochemical compounds and polymers
known in the art to impart dry soil resistance and water- and
oil-repellency to fibrous substrates. These repellent
fluorochemical compounds and polymers typically comprise one or
more fluorochemical radicals that contain a perfluorinated carbon
chain having from 3 to about 20 carbon atoms, more preferably from
about 6 to about 14 carbon atoms. These fluorochemical radicals can
contain straight chain, branched chain, or cyclic fluorinated
allylene groups or any combination thereof. The fluorochemical
radicals are preferably free of polymerizable olefinic unsaturation
but can optionally contain catenary heteroatoms such as oxygen,
divalent or hexavalent sulfur, or nitrogen. Fully fluorinated
radicals are preferred, but hydrogen or chlorine atoms may also be
present as substituents, although, preferably, no more than one
atom of either is present for every two carbon atoms. It is
additionally preferred that any fluorochemical radical contain from
about 40% to about 80% fluorine by weight, and more preferably,
from about 50% to about 78% fluorine by weight. The terminal
portion of the radical is preferably fully fluorinated, preferably
containing at least 7 fluorine atoms, e.g., CF.sub.3CF.sub.2
CF.sub.2--, (CF.sub.3).sub.2CF--, SF.sub.5CF.sub.2--.
Perfluorinated aliphatic groups (i.e., those of the formula
C.sub.nF.sub.2n+1--) are the most preferred fluorochemical radical
embodiments.
[0082] Representative repellent fluorochemical compounds useful in
treatments of the present invention include fluorochemical
urethanes, ureas, esters, ethers, alcohols, epoxides, allophanates,
amides, amines (and salts thereof, acids (and salts thereof,
carbodiimides, guanidines, oxazolidinones, isocyanurates, and
biurets. Blends of these compounds are also considered useful.
Representative fluorochemical polymers useful in treatments in the
present invention include fluorochemical acrylate and substituted
acrylate homopolymers or copolymers containing fluorochemical
acrylate monomers interpolymerized with monomers free of
non-vinylic fluorine such as methyl methacrylate, butyl acrylate,
acrylate and methacrylate esters of oxyalkylene and polyoxyalkylene
polyol oligomers (e.g., oxyethylene glycol dimethacrylate,
polyoxyethylene glycol dimethacrylate, methoxy acrylate, and
polyoxyethylene acrylate), glycidyl methacrylate, ethylene,
butadiene, styrene, isoprene, chloroprene, vinyl acetate, vinyl
chloride, vinylidene chloride, vinylidene fluoride, acrylonitrile,
vinyl chloroacetate, vinylpyridine, vinyl alkyl ethers, vinyl alkyl
ketones, acrylic acid, methacrylic acid, 2-hydroxyethylacrylate,
N-methylolacrylamide, 2-(N,N,N-trimethylammonium)ethyl
methacrylate, and 2-acrylamido-2-methylpropanesulfonic acid (AMPS).
The relative amounts of various non-vinylic fluorine-free
comonomers used are generally selected empirically depending on the
textile substrate to be treated, the properties desired, and the
mode of application onto the textile substrate. Useful
fluorochemical treatments also include blends of the various
repellent fluorochemical polymers described above as well as blends
of the aforementioned fluorochemical compounds with these repellent
fluorochemical polymers.
[0083] Commercially available examples of repellent fluorochemicals
that can be used in conjunction with the current invention include,
but are not limited to, the Scotchgard.TM. family of repellent
fluorochemicals by 3M, the Zonyl.TM. family of repellent
fluorochemicals by Dupont, the Repearl.TM. family of repellent
fluorochemicals by Mitsubishi International Corporation.
Repearl.RTM.) F-8025 or Repearl F-7000 by Mitsubishi are
particularly useful in the practice of the current invention. Other
fluorochemicals, such as the Unidyne.TM. products distributed by
Daikin America, Inc. or products distributed by OMNOVA Solutions
may also be employed.
[0084] In addition to fluorochemicals, other repellent chemistry,
such as repellent silicones, waxes, and the like, may also be
employed in the practice of the present invention to achieve
repellent properties. Repellent silicones are commercially
available from GE Chemical, Dow Corning, Kelmar Industries, and
others. Examples of the repellent silicones are Dow Corning 346
Emulsion available from Dow Corning, Midland, Mich.; SE-40A
available from Kelmar Industries, Duncan, S.C. Waxes can be
obtained commercially from PetroLite, Allied Chemical, Cabot,
Consos, and others. One example of the repellent wax is Consopel
ZW, a zirconium wax based emulsion available from Consos, Inc.,
Charlotte, N.C.
Particulate Components
[0085] Various particulate materials, inorganic or organic, may be
used in conjunction with the present invention. Preferably, the
particles are comprised of at least one material selected from the
group consisting of silicates, doped silicates, minerals, silicas,
polymers, carbon, graphite, metal salts, metal powders,
silica-coated metal powders, inorganic oxides (such as metal
oxides), and the like, and combinations thereof.
[0086] More specifically, examples of particles that may be
employed include, but are not limited to, silica, colloidal silica,
alumina, zirconia, titania, zinc oxide, precipitated calcium
carbonate, polytetrafluoroethylene (PTFE), perfluorinated
copolymers, copolymers with tetrafluoroethylene,
polyvinylpyrrolidone (PVP), and the like. Such particles can also
be surface modified, for instance by grafting.
[0087] The size of the selected particles should be taken into
consideration for several reasons. Particles that are too small may
not provide appropriate surface roughness to trap air on the
substrate surface or may require high loading with subsequent
agglomeration to achieve the desired roughness features of the
current invention. Particles that are too large may give a frosty,
white appearance to dyed textiles or may be removed easily during
use or routine maintenance of the textile substrate. In general,
particle sizes of between about 1 nm and about 50 .mu.m are
believed to be capable of providing good results in various
applications of the invention. Particle sizes in the range of
between about 5 nm and about 1 .mu.m are particularly useful, and
particle sizes in the range of between about 10 nm and about 50 nm
have been found to work well in some applications. These sized
particles can be employed to build a nanometer scale roughness,
similar to that of the wax crystals on the Lotus leaf, to augment
the fiber roughness imposed by mechanical roughening or
face-finishing, which results in microscopic surface structures
that are generally less than 100 .mu.m in size.
[0088] As used herein, the terms "inorganic oxide" or "metal oxide"
refer to a general class of materials comprising at least one
species of metal cation combined with oxygen anions or hydroxyl
anions, or mixtures of oxygen and hydroxyl ions. This material can
additionally contain water in bound or adsorbed form and can
further comprise small amounts, for example less than 5% by weight,
stabilized counter ions such as sodium ion, carboxylate ion,
chloride ion, nitrate ion, or the like. For the purposes of the
present invention, it is usually desirable that the metal oxides or
inorganic oxides be in a very finely divided state. Colloidal
dispersions provide a particularly useful form for use in the
present invention.
[0089] The following may be utilized in the practice of the present
invention, depending upon the specific application to be
employed:
[0090] Nalco 1042.TM. Colloidal Silica--a 34% solids (by weight)
aqueous colloidal acidic silica sol cation available commercially
from Nalco Chemical Co. ("Nalco"), Naperville, Ill.
[0091] Nalco 1050.TM. Colloidal Silica--a 50% by weight solids
aqueous colloidal silica sol available commercially from Nalco. The
sol has a pH of 9, an average particle size of 20 nm in
diameter;
[0092] Nalco 2326.TM. Colloidal Silica--a 15% by weight solids
aqueous colloidal silica sol available commercially from Nalco. The
sol has a pH of 9, an average particle size of 5 nm in
diameter;
[0093] Nalco 2327.TM. Colloidal Silica--a 40% by weight solids
aqueous colloidal silica sol available commercially from Nalco. The
sol has a pH of 9, an average particle size of 20 nm in
diameter.
[0094] Nalco 2329.TM. Colloidal Silica--a 40% by weight solids
aqueous colloidal silica sol available commercially from Nalco. The
sol has a pH of 9, an average particle size of 75 nm in
diameter;
[0095] Nalco 1056.TM. Aluminized Silica--a 30% by weight solids
aqueous colloidal suspension of aluminized silica particles (26%
silica and 4% alumina) available commercially from Nalco;
[0096] Nalco 88SN-126.TM. Colloidal Titanium Dioxide--a 10% by
weight solids aqueous dispersion of titanium dioxide available
commercially from Nalco;
[0097] Nalco 88SN-123.TM. Colloidal Tin Oxide--a 22% by weight
solids aqueous dispersion of tin oxide available commercially from
Nalco;
[0098] Cab-O-Sperse S3295.TM. Fumed Silica--a 15% by weight solids
aqueous dispersion of fumed silica available commercially from
Cabot Corporation of Boyertown, Pa. The dispersion has a pH of 9.5,
and an average agglomerated primary particle size of about 100 nm
in diameter;
[0099] Cab-O-Sperse A205.TM. Silica available from Cabot
Corporation;
[0100] Ludox AS40.TM. Colloidal Silica--a 40% by weight solids
aqueous colloidal silica sol available commercially from Grace
Davison, Columbia, Md. The sol has a pH of 9, an average particle
size of 22 nm in diameter;
[0101] Ludox AM.TM. Colloidal Silica--a 30% by weight solids
aqueous sol, available from Grace Davison. The sol has a pH of 9,
an average particle size of 12 nm in diameter;
[0102] Ludox CL-P.TM. Colloidal Alumina Coated Silica--a 40% by
weight solids aqueous sol, available from Grace Davison. The sol
has a pH of 4, an average particle size of 22 nm in diameter;
[0103] Ludox TMA.TM. Colloidal Silica--a 34% by weight solids
aqueous colloidal silica sol, available from Grace Davison. The sol
has a pH of 4.7 and an average particle size of 22 nm in
diameter;
[0104] Sipernat 22LS.TM. Hydrophilic Precipitated Silica--dry
powder available from Degussa Corporation of Germany. The average
particle size is 4.5 nm in diameter; and
[0105] Viviprint 540.TM. poly(vinylpolypyrrolidone) particles with
10% by weight solids from ISP Technologies.
[0106] In some cases, particles having other functional properties
may be used. Such particles may provide additional attributes
beyond the structural building feature described herein. For
example, AlphaSan.RTM. particles, available from Milliken Chemical
of Spartanburg, S.C., may provide antimicrobial features to the
textile substrate. Zinc oxide particles may offer odor-absorbing
properties. Zelec.TM. particles, also available from Milliken
Chemical, may provide antistatic properties. Zinc borate particles
or antimony pentoxide may provide flame retardant and fungicide
properties. Iron-based microparticles may provide magnetic and
microwave-absorbing properties.
Crosslinking Component
[0107] Cross-linking components may optionally be employed in the
invention, including cross-linking components that are essentially
insoluble in water (i.e. hydrophobic). In other formulations,
hydrophilic cross-linkers could be useful.
[0108] In other embodiments, hydrophobic cross-linking components
may include protected derivatives of isocyanates and the like, or
combinations thereof. Protected diisocyanates may be a suitable
cross-linking component. Monomers or polymers containing two or
more blocked isocyanate compounds may be the most preferred
cross-linking components. One useful cross-linking component is
REPEARL.RTM. MF.TM., available from Mitsubishi Corp. Others include
ARKOPHOB.RTM. DAN (a polyurethane), available from Clariant, and
HYDROPHOBOL.RTM. XAN.TM., available from DuPont.
[0109] Another useful cross-linking agent is Milligard MRX.TM., a
polyurethane-based cross-linking agent available from Milliken
Chemical of Spartanburg, S.C.
Description of Testing Methods
a) Water Repellency Test
[0110] Water repellency was tested according to the 3M Water
Repellency Test II (May, 1992). The rating scale is 0-10, with "0"
indicating the poorest degree of repellency (substrates having
higher surface energy) and "10" indicating the best degree of
repellency (substrates having lower surface energy). The 3M Water
Repellency Test scale is: [0111] 0 is 0% Isopropanol (IPA), 100%
water (by weight) [0112] 1 is 10% IPA, 90% water [0113] 2 is 20%
IPA, 80% water [0114] 3 is 30% IPA, 70% water [0115] 4 is 40% IPA,
60% water [0116] 5 is 50% IPA, 50% water [0117] 6 is 60% IPA, 40%
water [0118] 7 is 70% IPA, 30% water [0119] 8 is 80% IPA, 20% water
[0120] 9 is 90% IPA, 10% water [0121] 10 is 100% IPA
[0122] A test sample was placed on a flat, horizontal surface. 3
small drops of the test liquid, approximately 5 mm in diameter, was
placed gently in three different areas on the test sample using a
dropper or pipette. The drops were allowed to stand undisturbed for
10 seconds. If after 10 seconds, two of the three drops are still
visible as spherical to hemispherical, the sample passes the test.
The numerical rating given to the sample is the highest numbered
test liquid which remains visible.
b) Oil Repellency Test
[0123] Oil Repellency was tested according to the AATCC Test Method
118-2000. The rating scale is 0-8, with "0" indicating the poorest
degree of repellency (substrates having higher surface energy) and
"8" indicating the best degree of repellency (substrates having
lower surface energy). The oil repellency scale is:
[0124] 0 is Nujol.TM. Mineral Oil (the substrates wets with the
oil) [0125] 1 is Nujol.TM. Mineral Oil [0126] 2 is 65/35
Nujol/n-hexadecane (by volume) [0127] 3 is n-hexadecane [0128] 4 is
n-tetradecane [0129] 5 is n-dodecane [0130] 6 is n-decane [0131] 7
is n-octane [0132] 8 is n-heptane
[0133] A test sample was placed on a flat, horizontal surface.
Beginning with the lowest numbered test liquid, a small drop of the
test liquid, approximately 5 mm in diameter, was placed gently in
several different areas on the test sample using a dropper or
pipette. The drops were allowed to stand undisturbed for 30 seconds
and observe the drop at a 45.degree. angle. If after 30 seconds, no
penetration or wetting of the sample substrate at the
liquid-substrate interface and no wicking around the drop occurs,
the sample passes the test. The numerical Oil Repellency Rating
given to the sample is the highest numbered test liquid which will
not wet the substrate within a period of 30 seconds.
c) Spray Rating Test
[0134] The Spray Rating Test was conducted in accordance with AATCC
(American Association of Textile Chemists and Colorists) Test
Method 22-2000. The rating scale is as follows:
[0135] 100--No sticking or wetting of upper surface
[0136] 90--Slight random sticking or wetting of upper surface
[0137] 80--Wetting of upper surface at spray points
[0138] 70--Partial wetting of whole of upper surface
[0139] 50--Complete wetting of whole of upper surface
[0140] 0--Complete wetting of whole upper and lower surfaces.
d) Dynamic Rolling Angle (DRA) Test
[0141] It is difficult to compare the repellent properties of a
highly hydrophobic surface, such as that of the present invention,
using conventional contact angle measurement methods because it is
very difficult to measure a high contact angle (>150.degree.)
reliably. On a textile substrate, it is even more difficult because
of the not-well-defined base line caused by the textile
construction. A water droplet dynamic rolling angle test was used
instead. Here, the dynamic rolling angle is defined as the minimum
angle of a surface at which a water droplet will roll pass a
predetermined distance when the water droplet was dropped onto the
pre-inclined surface. Smaller dynamic rolling angle values indicate
higher repellency.
[0142] The dynamic rolling angle is determined by the following
procedure.
[0143] A sample is mounted on a measurement bench that is 6 inches
by 4 inches in size and whose inclination can be adjusted from 0 to
90 degrees relative to horizontal. The sample is under moderate
tension to smooth out any wrinkles. The sample is then blown with a
bench top air ionizer to dissipate any static charges that might be
present on the surface. Deionized water droplets, with a
predetermined mass (typically 11-12 mg), are dropped onto the
pre-inclined sample across the width of the sample from a distance
of 1 cm above the sample surface using a syringe needle. By
adjusting the angle of inclination in increments, the minimum angle
of inclination at which at least 5 water droplets will roll past a
predetermined distance is recorded. The predetermined distance is
typically 3 cm.
e) Home Wash Procedure
[0144] The Home Wash Procedure undertaken to test for wash
durability was conducted in accordance with AATCC Test Method
130-2000, using wash procedure 1 (105.degree. F. wash) and
Tide.RTM. Quick Dissolving Powder detergent.
[0145] "Wash durability" is generally defined as the ability of a
substrate to retain an acceptable level of a desired function
through a reasonable number of standard laundering cycles. The
substrate may be a textile substrate, such as a fabric.
f) Martindale Abrasion Test
[0146] The Martindale Abrasion Test was performed according to ASTM
D4966-98 modified using a Mark III Abrasion Tester BS5690 (Shirley
Developments Ltd.). A 7 inch.times.7 inch sample was mounted onto
the test station. A woven wool fabric, which was placed on the
abrasion cylinder (without extra weight), was used as the abrasive
material. The fabric was a plain weave crossbred worsted wool
fabric with a mass of 5.8 oz/yd.sup.2 available from TexFabric
Inc., West Pittston, Pa. The fabric was comprised of R63 Tex/2 warp
yarns and R74 Tex/2 fill yarns woven together in a plain weave
construction with 43 ends/inch and 30 picks/inch. The warp yarns
were made from 27.5 .mu.m diameter wool fibers in a single 540 TPM
z twist and the fill yarns were made from 29 .mu.m diameter wool
fibers in a single 500 TPM z twist. The sample was then exposed to
a pre-determined number of abrasion cycles.
FURTHER DETAILED DESCRIPTION
A) Mechanical Roughening Treatment
[0147] The textile substrate (such as for example a woven, knitted,
or nonwoven fabric, laid scrim) was roughened with a face-finishing
process. This involved gently roughening the surface of the
substrate using a series of diamond-coated rolls (or sandpaper in
some cases) with a specific grit size or combination of grit sizes.
It is envisioned that any machines known in the art for sanding
abrasion could be used with appropriate grit sizes for treatment.
Additionally, it is contemplated that chemical swelling agents may
be used before or during the face-finishing treatment to enhance
the treatment effectiveness. The face-finishing process was
performed at an unconventionally low level such that at least a
portion of the surface was roughened without generating a
significant amount of broken fibers on the fibrous textile
substrates. Other means of roughening the textile substrate surface
may also be employed, such as, for example, fine particle blasting,
laser ablation, plasma treatment, and chemical etching (such as
with acid). Thus, chemical means, mechanical means, or any other
means, or combination thereof of roughening the surface of the
textile substrate surface may be employed.
[0148] In the Examples presented herein, the substrate
pre-treatment was performed according to the following
procedure:
[0149] A piece of fabric was cut to a size of approximately 13
inches.times.60 inches. The two ends of the fabric were sewn
together to form a loop. The fabric was then mounted on a
proprietary homemade abrasion machine so that the loop of the
fabric is presented to the abrasive roll. The tension of the fabric
was controlled by an air-filled cylinder. The fabric was running at
a speed of approximately 8 yards per minute. For a balanced
treatment, the fabric was typically treated in both directions with
the same number of cycles. The level of treatment depends on the
grit of the treatment roll (g), tension of the fabric, which is
determined by the pressure of the cylinder (p), and the number of
cycles the fabric was exposed to (n). The level of treatment is
denoted by g-p-n. For example, 1200-30-12 means the fabric was
treated with a 1200 grit roll at 30 psi cylinder pressure for 12
cycles in each direction. In general, a grit of between about 600
and about 1200 has been found to be quite useful in the practice of
the invention. Typically, only a portion of the fabric surface is
roughened by the face-finishing process. The percentage of the
roughened areas over the total surface area depends on the fabric
construction and may be estimated from representative scanning
electron microscope pictures. The procedures to estimate the
percentage of the roughened areas are described in details below.
Because of the fine grit rolls are used in the present invention,
the number of broken fibers per unit area that are caused by the
face-finishing process of the present invention is substantially
less than that caused by the traditional face-finishing process
which uses coarse grit rolls.
B) Procedure Employed to Determine the Percentage of Surface Area
Roughened
[0150] All images were captured as described in detail in the
section below on SEM imaging and Sample Preparation for Measuring
Surface Roughness and Determining Roughness Factor. The treated
fabrics are positioned in the SEM so that a clear image of the
surface, positioned so that surface roughness caused by
protrusions, scuffing, particles, etc. can be clearly seen, can be
produced. The digital images were 800 pixels long by 600 pixels
high. The images were captured at 50.times. magnification of the
fabric surface. The image files were saved as 8 bit RGB files in a
jpeg format. For example, FIG. 5 shows the initial image of Fabric
Q, Example 10, as obtained from the SEM. To focus on the percentage
of the fabric surface that is roughened (i.e. shown as regions
21b), a portion of the image can be extracted that focuses only on
the treated surface of the textile, as shown in FIG. 9A. The
treated surface of the textile substrate in this case corresponds
to those first elevated regions 21b that received a face-finishing
treatment and results in these regions having significant surface
roughness. These regions 21b, as will be described in more detail
below, typically have a Roughness Factor of greater than or equal
to 1.10. The actual dimensions of the sample shown in FIG. 9A are
2.4 mm wide by 1.48 mm high. A minimum surface area in this range
is required for this analysis.
[0151] For analysis, two software packages were employed: Adobe
Photoshop 6.0.1, as offered by Adobe Systems Incorporated of San
Jose, Calif., and Image Pro Plus 4.5, as offered by Media
Cybernetics, Inc of Silver Spring, Md. The extracted images were
converted to an 8-bit grayscale (each pixel takes on a gray value
from 0, or black, to 255, or white) image in Image Pro Plus. The
extracted file was then transferred to Adobe Photoshop. To separate
the pixels of the image that represent roughened surface of the
textile (regions similar to 21b) from un-roughened textile surface
(regions similar to 22b), a 3-pixel diameter eraser tool was used
to tag those pixels in the image where surface fibers were
roughened. To do this, the eraser tool was set to convert all
pixels that it crossed over while activated to black, a pixel value
of 0. Using a mouse with the magnified image (200% or greater on
the screen in Adobe Photoshop), those portions of the 50.times.SEM
image where process-imposed surface roughening (fibers that were
roughened and remained substantially in a plane parallel to the
surface of the textile) was evident were traced accurately by hand
to set those image pixels to 0. FIG. 9B shows the same image as
FIG. 9A, but with the roughened portions of the textile surface
(all of the regions similar to 21b) set to black (pixel value of 0)
by the procedure described above. This image is saved as a TIFF
file for later analysis in Image Pro Plus.
[0152] Using Image Pro Plus, the image file (e.g. as in FIG. 9B)
where the pixels representing roughened surface are set to black
(pixel value of 0) is opened. This image will be used to calculate
the percentage of the surface area that is roughened. In principal,
the percentage of surface area treated (PS) will be calculated as
the percentage of the black pixels that represent roughened areas
of the surface compared to the total number of pixels in the
surface image. To determine PS, Image Pro Plus allows the user to
select portions of an image based on the portion's pixel value and
size. Because the pixels representing roughened surface have been
set to black (a pixel value of zero), the background can be
selected from the image by segmenting out (selecting) the pixels
that have a value near 0. There are some complications. Because
there can be shadows in an image, there are some pixel objects that
have numerical pixel values near zero but do not represent the
roughened portion of the surface. These pixel objects invariably
include much fewer pixels than the roughened portions of the
surface. Therefore, the analyst can exclude shadows from the
profile by requiring that the pixel objects that are tagged as the
background have a pixel size larger than the sizes of the shadows
in the image (this will vary depending on the image). For
completeness, it will be indicated that the roughened surface
object pixels are counted so that any pixel "holes" in a big
background of selected pixels are automatically selected, and
pixels should be neighboring each other in a 4-connected sense to
be tagged as part of the background. This means that objects in an
image should be connected to the main body of the image by having a
neighbor directly above, below or on either side of the specified
pixel; pixels that are connected through a diagonal only will not
be included in the selected background object. An example of the
tagged surface roughness image for FIG. 9B is shown in FIG. 9C. In
this case, the pixels representing the portion of the surface that
is roughened (all regions similar to 21b) are set to 255 (i.e.,
white) and the pixel values for everything else are set to 0 (i.e.
black). The image has been converted into a binary image where
there are only white pixels and black pixels.
[0153] With the image as in FIG. 9C in hand, the task is to measure
the number of pixels that are white (roughened) and the total
number of pixels in the image. Using the segmentation tools in
Image Pro Plus, the number of pixels that represent roughened
portions (X.sub.R) can be counted in this example as all pixels
that have a value of 255 (white). The total number of pixels in the
image (X.sub.T) can be obtained from the bitmap in Image Pro Plus
or again counted with the segmentation tools where no segmentation
level is set. The percentage of the surface area roughened PS can
now be calculated as: PS=X.sub.R/X.sub.T. C) Chemical Application
Procedures:
[0154] All Examples utilizing textile substrates provided below
were treated according to one of the following procedures and are
noted accordingly. I) One-step application procedure: [0155] 1. A
piece of fabric approximately 13 inches.times.17 inches was
immersed into a bath containing the chemical composition comprised
of the desired chemical agents. [0156] 2. Unless otherwise stated,
all chemical percents (%) were % by weight based on the total
weight of the bath prepared, and the balance remaining, when
chemical percents or grams of chemical are given, is comprised of
water. In addition, the % chemical was based on the chemical as
received from the manufacturer, such that if the composition
contained 30% active component, then X % of this 30% composition
was used. [0157] 3. After the fabric was completely wet, the fabric
was removed from the treatment bath and run between squeeze rolls
at a pressure of about 40 psi to obtain a uniform pickup generally
between about 30 and about 100%. [0158] 4. The fabric was pulled
taut and pinned to a frame to retain the desired dimensions. [0159]
5. The pin frame was placed into a Despatch oven at a temperature
of between about 350 and about 380 degrees F. for between about 5
and about 10 minutes to dry and to cure the finish. [0160] 6. Once
removed from the oven, the fabric was removed from the pin frame
and allowed to equilibrate at room temperature prior to testing.
II) Two-Step Application Procedure: [0161] 1. The one-step
application procedure was repeated, except that rather than adding
all the chemical agents to one chemical bath, one or more chemical
agents comprising the chemical composition were separately applied
to the fabric in a specified order as described below. [0162] 2.
The fabric was immersed into a bath containing one or more of the
chemical agents comprising the chemical composition. [0163] 3.
After the fabric was completely wet, the fabric was removed from
the bath and run between squeeze rollers as described in the one
step application procedure. [0164] 4. The fabric was dried at a
temperature of between about 300 and about 350 degrees F. for about
5 minutes in a Despatch oven. (This drying step is optional. The
fabric may remain wet, while proceeding to the next step.) [0165]
5. The fabric was then immersed into a fresh second bath containing
the desired chemical agents comprising a second chemical
composition. [0166] 6. The fabric was then dried and cured as
described in the one step application procedure. III) Spraying
Application Procedure: [0167] 1. A piece of fabric approximately 13
inches.times.17 inches was pulled taut and pinned to a frame.
[0168] 2. The fabric was then sprayed with the chemical composition
comprised of the desired chemical agents using an airbrush Model
150 (Badger Air-Brush Co.) operated under 20 psi pressure. The
spray operation was performed until the fabric surface was
completely wet without dripping. [0169] 3. The pin frame was placed
into a Despatch oven at a temperature of between about 200 and
about 350 degrees F. for between about 5 and about 10 minutes to
dry and to cure the finish. [0170] 4. Once removed from the oven,
the fabric was removed from the pin frame and allowed to
equilibrate at room temperature prior to testing.
[0171] Various embodiments of the invention are shown by way of the
Examples below, but the scope of the invention is not limited by
the specific Examples provided herein.
EXAMPLE 1
Microdenier Twill Fabric
Face-Finished
One Step Treatment
[0172] A 200 grams bath containing the following chemicals was
prepared: [0173] 1. 2 grams (or 1%) of Sipernat 22LS.TM.,
hydrophilic silica particles available from Degussa Corporation of
Germany. [0174] 2. 8 grams (or 4%) Repearl F-7000, a fluorinated
stain repellent agent available from Mitsubishi Corp.; and [0175]
3. 2 grams (or 1%) Milligard MRX.TM., a cross-linking agent
available from Milliken Chemical.
[0176] A 100% microdenier polyester fabric was treated with this
chemical composition according to the one step application
procedure described previously. The wet pickup of the chemical
composition on the fabric was about 50%.
[0177] The microdenier polyester fabric was obtained from Milliken
& Company of Spartanburg, S.C. The fabric was comprised of
textured filament polyester 1/140/200 denier warp yarns and
textured filament polyester 1/150/100 denier fill yarns woven
together in a 2 by 2 right hand twill pattern having 175 warp yarns
and 80 fill yarns per inch of fabric (hereinafter referred to as a
"microdenier twill fabric" specifically for this invention). The
fabric was roughened with a face-finishing process using a diamond
coated roll at a level of 1200-30-32. Approximately 19% of the
surface areas were roughened by the face-finishing process.
[0178] The treated fabric was tested for water and oil repellency,
spray rating, dynamic rolling angle by the methods described
previously for the as received ("AR") samples. The results are
shown in Table 1A. The spray rating and dynamic rolling angle of
the treated fabric were tested after 1 home wash, 5 home washes, 10
home washes, and 20 home washes. The test results are shown in
Table 1B. The spray rating and dynamic rolling angle were also
tested after 1000 cycles, 2000 cycles, 5000 cycles, 10000 cycles
and 20000 cycles of Martindale abrasion. Test results are shown in
Table 1C.
EXAMPLE 2
Microdenier Twill Fabric
Face-Finished
Two Step Treatment
[0179] The face-finished polyester microdenier twill fabric as
described in Example 1 with the same level of face-finishing was
treated in accordance with the two-step application procedure
described previously. In the first step of the procedure, 2% of
Ludox AM, colloidal silica particles with an average particle
diameter of 12 nm available from Grace Davison, was applied to the
fabric, and the fabric was subsequently dried. In the second step
of the procedure, a mixture of 4.0% Repearl F-7000 and 1% Milligard
MRX.TM. was subsequently applied to the fabric.
[0180] The treated fabric was tested for water and oil repellency,
spray rating, dynamic rolling angle by the methods described
previously for the as received ("AR") samples. The results are
shown in Table 1A. The spray rating and dynamic rolling angle were
tested after 1 home wash, 5 home washes, 10 home washes, and 20
home washes. The test results are shown in Table 1B. The spray
rating and dynamic rolling angle were also tested after 1000
cycles, 2000 cycles, 5000 cycles, 10000 cycles and 20000 cycles of
Martindale abrasion. Test results are shown in Table 1C.
COMPARATIVE EXAMPLE 3
Microdenier Twill Fabric
No Particles and No Face-Finishing
[0181] Example 1 was repeated, except that the Sipernat 22LS.TM.
component was eliminated from the bath and the microdenier twill
fabric was not roughened with a face-finishing process.
[0182] The treated fabric was tested for water and oil repellency,
spray rating, dynamic rolling angle by the methods described
previously for as received ("AR") samples. The results are shown in
Table 1A.
EXAMPLE 4
Automotive Twill Fabric
Face-Finished
One Step Treatment
[0183] Example 1 was repeated except that the microdenier twill
fabric was replaced by an automotive upholstery polyester fabric.
The wet pickup of the chemical composition on the fabric was about
98%.
[0184] The automotive upholstery polyester fabric was obtained from
Milliken & Company of Spartanburg, S.C. The fabric was
comprised of textured filament polyester 2/150/34 denier warp and
fill yarns woven together in a 2 by 2 right hand twill pattern
(hereinafter referred to as a "automotive twill fabric"
specifically for this invention). The fabric was dyed with a light
brown color. The fabric was roughened with a face-finishing process
using a diamond coated roll at a level of 1200-30-24. Approximately
20% of the surface areas were roughened by the face-finishing
process.
[0185] The treated fabric was tested for water and oil repellency,
spray rating, dynamic rolling angle by the methods described
previously for as received ("AR") samples. The results are shown in
Table 1A. The spray rating and dynamic rolling angle were tested
after 1 home wash, 5 home washes, 10 home washes, and 20 home
washes. The test results are shown in Table 1B. The spray rating
also tested after 1000 cycles, 2000 cycles, 5000 cycles, 10000
cycles and 20000 cycles of Martindale abrasion. Test results are
shown in Table 1C.
COMPARATIVE EXAMPLE 5
Automotive Twill Fabric
No Particles and No Face-Finishing
[0186] Example 4 was repeated, except that the Sipernat 22LS.TM.
component was eliminated from the bath. The fabric was not
roughened with a face-finishing process.
[0187] The treated fabric was tested for water and oil repellency,
spray rating, dynamic rolling angle by the methods described
previously for as received ("AR") samples. The results are shown in
Table 1A.
EXAMPLE 6
Polyester Tent Fabric
Face-Finished
One Step Treatment
[0188] Example 1 was repeated except that the microdenier twill
fabric was replaced by a polyester tent fabric. The wet pickup of
the chemical composition on the fabric was about 88%.
[0189] The polyester tent fabric was obtained from Milliken &
Company of Spartanburg, S.C. The fabric was a plain weave, with 70
denier 36 filament textured PET yarns in the warp and fill
direction. The fabric was comprised of approximately 90 warp yarns
and 80 fill yarns per inch of fabric. (hereinafter referred to as a
"tent fabric" specifically for this invention). The fabric was
roughened with a face-finishing process using a diamond coated roll
at a level of 600-30-12. Approximately 17% of the surface areas of
were roughened by the face-finishing process.
[0190] The treated fabric was tested for water and oil repellency,
spray rating, dynamic rolling angle by the methods described
previously for as received ("AR") samples. The results are shown in
Table 1A. The treated fabric was also tested for spray rating after
1000 cycles, 2000 cycles, 5000 cycles, 10000 cycles, and 20000
cycles of Martindale abrasion. Test results are shown in Table
1C.
COMPARATIVE EXAMPLE 7
Tent Fabric
No Particles and No Face-Finishing
[0191] Example 6 was repeated, except that the Sipernat 22LS.TM.
component was eliminated from the bath. The fabric was not
roughened with a face-finishing process.
[0192] The treated fabric was tested for water and oil repellency,
spray rating, dynamic rolling angle by the methods described
previously for as received ("AR") samples. The results are shown in
Table 1A.
EXAMPLE 8
Polyester Boat Cover Fabric
Face-Finished
One Step Treatment
[0193] A 200 gram bath containing the following chemicals was
prepared:
[0194] 1. 2 grams (or 1%) of Sipernat 22LS.TM., hydrophilic silica
particles available from Degussa.
[0195] 2. 10 grams (or 5%) Repearl F-7000, a fluorinated stain
repellent agent available from Mitsubishi Corp.; and
[0196] 3. 2.4 grams (or 1.2%) Milligard MRX.TM., a cross-linking
agent available from Milliken Chemical.
[0197] A 100% polyester boat cover fabric was treated with this
chemical composition according to the one step application
procedure described previously. The wet pickup of the chemical
composition on the fabric was about 66%.
[0198] The polyester boat cover fabric was obtained from Milliken
& Company of Spartanburg, S.C. The fabric was comprised of
textured filament polyester 4/150/36 denier warp yarns and textured
filament polyester 4/150/36 denier fill yarns woven together in a
plain weave construction with 54 ends/inch and 36 picks/inch
(hereinafter referred to as a "boat cover fabric" specifically for
this invention). The fabric was roughened with a face-finishing
process using a combination of 600 grit and 1200 grit diamond
coated rolls at levels of 600-30-12 followed by 1200-30-24.
Approximately 25% of the surface areas were roughened by the
face-finishing process.
[0199] The treated fabric was tested for water and oil repellency,
spray rating, dynamic rolling angle by the methods described
previously for as received ("AR") samples. The results are shown in
Table 1A. The spray rating and dynamic rolling angle were tested
after 1 home wash, 5 home washes, 10 home washes, and 20 home
washes. The test results are shown in Table 1B. The spray rating
also tested after 1000 cycles, 2000 cycles, 5000 cycles, 10000
cycles and 20000 cycles of Martindale abrasion. Test results are
shown in Table 1C.
COMPARATIVE EXAMPLE 9
Boat Cover Fabric
No Particles and No Face-Finishing
[0200] Example 8 was repeated except that the Sipernat 22LS.TM.
component was eliminated from the bath. The fabric was not
roughened with a face-finishing process.
[0201] The treated fabric was tested for water and oil repellency,
spray rating, dynamic rolling angle by the methods described
previously for as received ("AR") samples. The results are shown in
Table 1A.
EXAMPLE 10
Flat Woven Polyester Fabric (Fabric Q)
Face-Finished
One Step Treatment
[0202] Example 8 was repeated except that the boat cover fabric was
replaced by a flat woven polyester fabric. The wet pickup of the
chemical composition on the fabric was about 32%.
[0203] The flat woven polyester fabric was obtained from Milliken
& Company of Spartanburg, S.C. The fabric was a 1.times.1 plain
weave with 34 filament, 4.45 denier per filament polyester yarns in
the warp direction and 34 filament, 4.19 denier per filament
polyester yarns in the fill direction (hereinafter referred to as
"Fabric Q" specifically for this invention). The fabric was
roughened with a face-finishing process using a combination of 600
grit and 1200 grit diamond coated rolls at levels of 600-30-6
followed by 1200-30-16. Approximately 18% of the surface areas were
roughened by the face-finishing process.
[0204] The treated fabric was tested for water and oil repellency,
spray rating, dynamic rolling angle by the methods described
previously for as received ("AR") samples. The results are shown in
Table 1A. The spray rating and dynamic rolling angle were tested
after 1 home wash, 5 home washes, 10 home washes, and 20 home
washes. The test results are shown in Table 1B. The spray rating
also tested after 1000 cycles, 2000 cycles, 5000 cycles, 10000
cycles and 20000 cycles of Martindale abrasion. Test results are
shown in Table 1C.
COMPARATIVE EXAMPLE 11
Flat Woven Polyester Fabric (Fabric Q)
No Face-Finishing and No Particles
[0205] Example 9 was repeated except that the boat cover fabric was
replaced by the Fabric Q. The fabric was not roughened with a
face-finishing process, and the Sipernat 22LS.TM. component was
eliminated from the bath.
[0206] The treated fabric was tested for water and oil repellency,
spray rating, dynamic rolling angle by the methods described
previously for as received ("AR") samples. The results are shown in
Table 1A.
COMPARATIVE EXAMPLE 12
Microdenier Twill Fabric
No Face-Finishing
Prepared According to US Patent Application No. 2002/0016433 A1 to
Keller et al.
[0207] A chemical composition according to Example 9 in US Patent
Application No. 2002/0016433 A1 to Harald Keller et al. was
prepared.
[0208] The polyester microdenier twill fabric was treated with this
chemical composition according to the spraying application
procedure described previously. The fabric was not roughened with a
face-finishing process.
[0209] The treated fabric was tested for water and oil repellency,
spray rating, dynamic rolling angle by the methods described
previously for as received ("AR") samples. The results are shown in
Table 1A. The treated fabric was also tested for wash and abrasion
durability. The test results are shown in Table 1B and Table 1C,
respectively.
COMPARATIVE EXAMPLE 13
Automotive Twill Fabric
No Face-Finishing
Prepared According to US Patent Application No. 2002/0016433 A1 to
Keller et al.
[0210] Example 12 was repeated except that the microdenier twill
fabric was replaced by the automotive twill fabric. The fabric was
not roughened with a face-finishing process.
[0211] The treated fabric was tested for water and oil repellency,
spray rating, dynamic rolling angle by the methods described
previously for as received ("AR") samples. The results are shown in
Table 1A. The treated fabric was also tested for wash and abrasion
durability. The test results are shown in Table 1B and Table 1C,
respectively.
COMPARATIVE EXAMPLE 14
Tent Fabric
No Face-Finishing
Prepared According to US Patent Application No. 2002/0016433 A1 to
Keller et al.
[0212] Example 12 was repeated except that the microdenier twill
fabric was replaced by the tent fabric. The fabric was not
roughened with a face-finishing process.
[0213] The treated fabric was tested for water and oil repellency,
spray rating, dynamic rolling angle by the methods described
previously for as received ("AR") samples. The results are shown in
Table 1A. The treated fabric was also tested for wash and abrasion
durability. The test results are shown in Table 1B and Table 1C,
respectively.
COMPARATIVE EXAMPLE 15
Boat Cover Fabric
No Face-Finishing
Prepared According to US Patent Application No. 2002/0016433 A1 to
Keller et al.
[0214] Example 12 was repeated except that the microdenier twill
fabric was replaced by the boat cover fabric. The fabric was not
roughened with a face-finishing process.
[0215] The treated fabric was tested for water and oil repellency,
spray rating, dynamic rolling angle by the methods described
previously for as received ("AR") samples. The results are shown in
Table 1A. The treated fabric was also tested for wash and abrasion
durability. The test results are shown in Table 1B and Table 1C,
respectively.
COMPARATIVE EXAMPLE 16
Flat Woven Polyester Fabric (Fabric Q)
No Face-Finishing
Prepared According to US Patent Application No. 2002/0016433 A1 to
Keller et al.
[0216] Example 12 was repeated except that the microdenier twill
fabric was replaced by Fabric Q. The fabric was not roughened with
a face-finishing process.
[0217] The treated fabric was tested for water and oil repellency,
spray rating, dynamic rolling angle by the methods described
previously for as received ("AR") samples. The results are shown in
Table 1A. The treated fabric was also tested for wash and abrasion
durability. The test results are shown in Table 1B and Table 1C,
respectively.
EXAMPLE 17
Boat Cover Fabric
Face-Finished
One Step Treatment
[0218] A 200 gram bath containing the following chemicals was
prepared: [0219] 1. 10 grams (or 5%) Repearl F-7000, a fluorinated
stain repellent agent available from Mitsubishi Corp. [0220] 2. 5
grams (or 2.5%) of LUDOX CL-P, colloidal alumina coated silica
particles available from Grace Davison. [0221] 3. 8 grams (or 4%)
Milligard MRX.TM., a cross-linking agent available from Milliken
Chemical.
[0222] The polyester boat cover fabric described in Example 8
(roughened with a face-finishing process at levels of 600-30-12
followed by 1200-30-24) was treated with this chemical composition
according to the one step application procedure described
previously. The wet pickup of the chemical composition on the
fabric was about 65%.
[0223] The treated fabric was tested for water and oil repellency,
spray rating, dynamic rolling angle by the methods described
previously for as received ("AR") samples. The results are shown in
Table 1A. The treated fabric was also tested for wash and abrasion
durability. The test results are shown in Table 1B and Table 1C,
respectively.
EXAMPLE 18
Boat Cover Fabric
No Face-Finishing
One Step Treatment
[0224] Example 17 was repeated except that the face-finished boat
cover fabric was replaced with a boat cover fabric that was not
roughened with a face-finishing process.
[0225] The treated fabric was tested for water and oil repellency,
spray rating, dynamic rolling angle by the methods described
previously for as received ("AR") samples. The results are shown in
Table 1A. The treated fabric was also tested for wash and abrasion
durability. The test results are shown in Table 1B and Table 1C,
respectively.
EXAMPLE 19
Boat Cover Fabric
Face-Finished
One Step Treatment
[0226] A 200 gram bath containing the following chemicals was
prepared: [0227] 1. 10 grams (or 5%) Repearl F-7000, a fluorinated
stain repellent agent available from Mitsubishi Corp. [0228] 2. 2
grams (or 1%) Viviprint 540, poly(vinylpolypyrrolidone) particles
available from ISP Technologies. [0229] 3. 1.6 grams (or 0.8%) of
LUDOX CL-P, colloidal alumina coated silica particles available
from Grace Davison. [0230] 4. 2.4 grams (or 1.2%) Milligard
MRX.TM., a cross-linking agent available from Milliken
Chemical.
[0231] The polyester boat cover fabric described in Example 8
(roughened with a face-finishing process at levels of 600-30-12
followed by 1200-30-24) was treated with this chemical composition
according to the one step application procedure described
previously. The wet pickup of the chemical composition on the
fabric was about 68%.
[0232] The treated fabric was tested for water and oil repellency,
spray rating, dynamic rolling angle by the methods described
previously for as received ("AR") samples. The results are shown in
Table 1A. The treated fabric was tested for wash and abrasion
durability. The test results are shown in Table 1B and Table 1C,
respectively.
EXAMPLE 20
Polyester Tent Fabric
Face-Finished
No Particles
One Step Application
[0233] The polyester tent fabric described in Example 6 (with a
face-finishing process at a level of 600-30-12) was treated in
accordance with the one step application procedure described
previously, in which a mixture of 1.0% Repearl F-7000 and 2%
Milligard MRX.TM. was applied to the fabric.
[0234] The treated fabric was tested for water and oil repellency,
spray rating, dynamic rolling angle by the methods described
previously for as received ("AR") samples. The results are shown in
Table 1A. The treated fabric was also tested for wash and abrasion
durability. The test results are shown in Table 1B and Table 1C,
respectively.
COMPARATIVE EXAMPLE 21
Tent Fabric
No Face-Finishing and No Particles
[0235] The polyester tent fabric described in Example 6 (without a
face-finishing process) was treated in accordance with the one step
application procedure described previously, in which a mixture of
1.0% Repearl F-7000 and 0.25% Milligard MRX.TM. was applied to the
fabric.
[0236] The treated fabric was tested for water and oil repellency,
spray rating, dynamic rolling angle by the methods described
previously for as received ("AR") samples. The results are shown in
Table 1A.
EXAMPLE 22
Nylon/Cotton Blend Fabric
Face-Finished
Two Step Application
[0237] A 50% nylon/50% cotton blend fabric was treated in
accordance with the two step application procedure described
previously. In the first step of the procedure, 2% of Ludox AM
colloidal silica particles with an average particle diameter of 12
nm, available from Grace Davison, was applied to the fabric. In the
second step of the procedure, a mixture of 5.0% Repearl F-7000 and
1.2% Milligard MRX.TM. was subsequently applied to the fabric.
[0238] The nylon/cotton blend fabric was obtained from Milliken
& Company of Spartanburg, S.C. The fabric was comprised of 20/1
ring-spun nylon/cotton (52/48) warp yarns and 17/1 ring-spun
nylon/cotton-combed (52/48) filling yarns in a 2.times.1 left-hand
twill construction. (hereinafter referred to as a "nylon/cotton
blend fabric" specifically for this invention). The fabric was
roughened with a proprietary face-finishing process using 1000 grit
sand paper disks. The fabric was subsequently singed to remove long
loosened fibers.
[0239] The treated fabric was tested for water and oil repellency,
spray rating, dynamic rolling angle by the methods described
previously for as received ("AR") samples. The results are shown in
Table 1A. The treated fabric was tested after 1 home wash and 5
home washes. The test results are shown in Table 1B.
COMPARATIVE EXAMPLE 23
Nylon/Cotton Blend Fabric
No Face-Finishing and No Particles
[0240] The nylon/cotton blend fabric as described in Example 22
(without a face-finishing process) was treated in accordance with
the one step application procedure described previously, in which a
mixture of 5.0% Repearl F-7000 and 1.2% Milligard MRX.TM. was
applied to the fabric.
[0241] The treated fabric was tested for water and oil repellency,
spray rating, dynamic rolling angle by the methods described
previously for as received ("AR") samples. The results are shown in
Table 1A. The treated fabric was tested after 1 home wash and 5
home washes. The test results are shown in Table 1B.
EXAMPLE 24
Automotive Twill Fabric
Face-Finished
Two Step Application
[0242] The automotive twill fabric (roughened with a face-finishing
process at a level of 1200-30-24), as described in Example 4, was
treated in accordance with the two step application procedure
described previously. In the first step of the procedure, a mixture
of 4% Repearl F-7000, 1.2% Milligard MRX, and 0.1% Wetaid NRW (a
non-rewetting wetting agent available from Noveon, Inc., Cleveland,
Ohio) was applied to the fabric. In the second step of the
procedure, a mixture of 2.5% Ludox CL-P.TM.1, 2.5% Milligard MRX,
and 5% Repearl F-7000 was subsequently applied to the fabric while
the fabric was still wet. The fabric was then dried and cured.
[0243] The treated fabric was tested for water and oil repellency,
spray rating, and dynamic rolling angle by the methods described
previously for as received ("AR") samples. The results are shown in
Table 1A. The treated fabric was also tested for wash and abrasion
durability. The test results are shown in Table 1B and Table 1C,
respectively.
EXAMPLE 25
Polyester Tent Fabric
Face-Finished
One Step Application
[0244] The face-finished polyester tent fabric (roughened with a
face-finishing process at a level of 600-30-12), as described in
Example 6, was treated with 5% SE-40A (a polydimethysiloxane based
emulsion available from Kelmar Industries of Duncan, S.C.)
according to the one step application procedure described
previously.
[0245] The fabric was pre-washed with water (without detergent) to
remove the residual repellent and dried before further testing. The
dynamic rolling angle of the fabric was tested and determined to be
25 degrees by the method described previously.
COMPARATIVE EXAMPLE 26
Polyester Tent Fabric
No Face-Finishing
One Step Application
[0246] Example 25 was repeated except that the face-finished
polyester tent fabric was replaced with a polyester tent fabric
that was not face-finished. The dynamic rolling angle of the fabric
was tested and determined to be greater than 50 degrees (which is
the limit of the test instrument) by the method described
previously.
EXAMPLE 27
Polyester Tent Fabric
Face-Finished
One Step Application
[0247] The face-finished polyester tent fabric (roughened with a
face-finishing process at a level of 600-30-12), as described in
Example 6, was treated with 5% Consopel ZW (a zirconium wax based
emulsion for water repellent available from Consos of Charlotte,
N.C.) according to the one step application procedure described
previously.
[0248] The dynamic rolling angle of the fabric was tested and
determined to be 18 degrees by the method described previously.
COMPARATIVE EXAMPLE 28
Polyester Tent Fabric
No Face-Finishing
One Step Application
[0249] Example 27 was repeated except that the face-finished
polyester tent fabric was replaced with a polyester tent fabric
that was not face-finished. The dynamic rolling angle of the fabric
was tested and determined to be 23 degrees by the method described
previously.
EXAMPLE 29
Nonwoven Fabric
Face-Finished
One Step Application
[0250] Example 8 was repeated except that the polyester boat cover
fabric was replaced by a nonwoven fabric. The wet pickup of the
chemical composition on the fabric was about 78%.
[0251] The nonwoven fabric was a polyester spunbond fabric with a
weight density of 25 g/m.sup.2 available from BBA Nonwovens,
Simpsonville, S.C. The fabric was mechanically roughened with a
face-finishing process using a diamond coated roll at a level of
1200-15-6.
[0252] The treated nonwoven fabric was tested for water and oil
repellency, spray rating, and dynamic rolling angle by the methods
described previously for as received ("AR") samples. The results
are shown in Table 1A.
COMPARATIVE EXAMPLE 30
Nonwoven Fabric
No Particles and No Face-Finishing
[0253] Example 29 was repeated, except that the Sipernat 22LS.TM.
component was eliminated from the bath. The nonwoven fabric was not
treated with a face-finishing process.
[0254] The nonwoven fabric was tested for water and oil repellency,
spray rating, and dynamic rolling angle by the methods described
previously for as received ("AR") samples. The results are shown in
Table 1A. TABLE-US-00001 TABLE 1A Repellency Test Results Spray
DRA* Sample Water Repellency Oil Repellency Rating (degree) Ex. 1 5
5 100 3.0 Ex. 2 5 5 100 3.5 Comp. Ex. 3 5 5 100 7.0 Ex. 4 7 7 100
3.5 Comp. Ex. 5 7 6 100 7.0 Ex. 6 6 6 100 2.0 Comp. Ex. 7 6 6 100
7.2 Ex. 8 6 6 100 4.0 Comp. Ex. 9 6 6 100 10.0 Ex. 10 5 5 100 10.0
Comp. Ex. 11 3 4 100 27.0 Comp. Ex. 12 1 0 90 4.5 Comp. Ex. 13 1 0
70 5.0 Comp. Ex. 14 1 0 70 4.5 Comp. Ex. 15 1 0 90 5.4 Comp. Ex. 16
1 0 70 22.5 Ex. 17 7 6 100 4.5 Ex. 18 7 6 100 7.0 Ex. 19 6 6 100
6.5 Ex. 20 6 6 100 5.0 Comp. Ex. 21 6 6 100 9.5 Ex. 22 5 5 100 4.7
Comp. Ex. 23 5 5 100 7.0 Ex. 24 7 6 100 4.9 Ex. 25 N/A N/A N/A 25
Ex. 26 N/A N/A N/A >50 Ex. 27 N/A N/A N/A 18 Ex. 28 N/A N/A N/A
23 Ex. 29 8 6 100 20.0 Comp. Ex. 30 8 6 100 38.0 *Dynamic rolling
angle for rolling of 3 cm.
[0255] TABLE-US-00002 TABLE 1B Wash Durability Test Results Spray
DRA* Spray DRA* Spray DRA* Spray DRA* Spray DRA* Rating (degree)
Rating (degree) Rating (degree) Rating (degree) Rating (degree)
Sample (AR) (AR) (1 Wash) (1 Wash) (5 Wash) (5 Wash) (10 Wash) (10
Wash) (20 Wash) (20 Wash) Ex. 1 100 3.0 90 4.5 75 14 70 18.5 60
26.5 Ex. 2 100 3.5 100 3.5 100 7.5 100 8.0 100 10.0 Ex. 4 100 3.5
100 7.0 100 13.0 100 18.0 75 23.0 Ex. 8 100 4.0 100 6.5 90 15.5 85
23.0 85 34.5 Ex. 10 100 10.0 70 13.0 10 28.0 10 35.0 N/A N/A Comp.
90 4.5 0 Wetting N/A N/A N/A N/A N/A N/A Ex. 12 Comp. 70 5.0 0
Wetting N/A N/A N/A N/A N/A N/A Ex. 13 Comp. 70 4.5 0 Wetting N/A
N/A N/A N/A N/A N/A Ex. 14 Comp. 75 5.4 0 Wetting N/A N/A N/A N/A
N/A N/A Ex. 15 Comp. 85 22.5 0 Wetting N/A N/A N/A N/A N/A N/A Ex.
16 Ex. 17 100 4.5 N/A N/A 100 18.5 85 20.5 80** 22.5** Ex. 18 100
7.0 N/A N/A 100 19.5 90 24.0 85** 26.5** Ex. 19 100 6.5 100 9.0 100
N/A N/A N/A N/A N/A Ex. 20 100 5.0 N/A N/A 100 10.5 100 13.0 100**
15.0** Ex. 22 100 4.5 100 8.0 90 18.0 N/A N/A N/A N/A Comp. 100 7.0
90 16.0 70 37.5 N/A N/A N/A N/A Ex. 23 Ex. 24 100 4.9 100 8.5 100
13.0 100 17.0 100 20.0 *Dynamic Rolling Angle for rolling of 3 cm.
**Data for 15 washes. "N/A" indicates that test data was not
available.
[0256] TABLE-US-00003 TABLE 1C Abrasion Durability Test Results
Spray DRA* Spray DRA* Spray DRA* Spray DRA* Spray DRA* Rating
(degree) Rating (degree) Rating (degree) Rating (degree) Rating
(degree) (2000 (2000 (5000 (5000 (10000 (10000 (20000 (20000 Sample
(AR) (AR) cycles) cycles) cycles) cycles) cycles) cycles) cycles)
cycles) Ex. 1 100 3.0 75 11.0 75 17.0 70 21.5 60 N/A Ex. 2 100 3.5
100 12.0 100 16.5 100 20.5 90 N/A Ex. 4 100 3.5 70 N/A 70 N/A 60
N/A 50 N/A Ex. 6 100 2.0 70 N/A 70 N/A 70 N/A 50 N/A Ex. 8 100 4.0
75 N/A 75 N/A 70 N/A 70 N/A Ex. 10 100 10.0 100 N/A 95 N/A 90 N/A
85 N/A Comp. 90 4.5 50 N/A 50 N/A N/A N/A N/A N/A Ex. 12 Comp. 70
5.0 60 N/A 60 N/A N/A N/A N/A N/A Ex. 13 Comp. 70 18.0 45 N/A 45
N/A N/A N/A N/A N/A Ex. 14 Comp. 90 5.4 70 N/A 50 N/A N/A N/A N/A
N/A Ex. 15 Comp. 85 22.5 60 N/A 60 N/A N/A N/A N/A N/A Ex. 16 Ex.
17 100 4.5 100 28.0 100 33.5 95 N/A N/A N/A Ex. 18 100 7.0 100 30.0
100 35.5 85 N/A N/A N/A Ex. 19 100 6.5 100 27.5 100 35.0 N/A N/A
N/A N/A Ex. 20 100 4.5 100 14.0 100 18.0 100 16.5 N/A N/A Ex. 24
100 4.9 100 16.5 100 20.5 90 25.0 70 30.0 *Dynamic Rolling Angle
for rolling of 3 cm. "N/A" indicates that test data was not
available.
[0257] The results in Table 1A show that the fabrics treated
according to the present invention all exhibited good water and oil
repellency and excellent spray rating. When compared to Comparative
Examples 11-16, the fabrics treated according to the present
invention performed exceptionally well with regard to water and oil
repellency and spray rating. Furthermore, the fabrics treated
according to the present invention generally exhibited much lower
dynamic rolling angles than any of the Comparative Examples.
Additionally, Examples 25-28 illustrate the use of a
non-fluorochemical repellent. Examples 25 and 26 use silicone as a
repellent, and Examples 27 and 28 use zirconium wax as a repellent.
The face-finished fabrics of Examples 25 and 27 (treated with
silicone and wax, respectively) exhibit a lower dynamic rolling
angle than the control fabrics of Examples 26 and 28 (treated with
silicone and wax, respectively) indicating that the face-finishing
treatment provides a much more hydrophobic substrate than that
treated with a repellent alone. Example 29 illustrates that the
inventive process may be used to achieve a hydrophobic nonwoven
fabric with a dynamic rolling angle that is much lower than the
same nonwoven fabric, as shown in Example 30, without
face-finishing and particle treatment.
[0258] Thus, the results for these Examples illustrate the benefit
of the face-finishing treatment and the optional addition of
nanoparticles to the surface of a textile substrate, thereby
creating a surface roughness similar to that on the surface of
Lotus leaf, to create superior liquid repellent textile substrate.
The treatment further imparts a "self-cleaning" feature to the
fabric such that, for example, undesirable liquids that contact a
textile substrate will easily bead up and roll off the surface of
the substrate.
[0259] The results in Table 1B show that the fabrics treated
according to the present invention generally exhibited good
durability to washing when tested for spray rating through 20
washes. When compared to Comparative Examples 11-16, the fabrics
treated according to the present invention performed exceptionally
well with regard to spray rating. Furthermore, the fabrics treated
according to the present invention generally exhibited much lower
dynamic rolling angles than any of the Comparative Examples. More
specifically, Comparative Examples 12-16 failed to exhibit any
hydrophobic characteristics after 1 wash, while most of the other
Examples remained at least moderately hydrophobic through 20
washes. Thus, the results for these Examples illustrate the benefit
of the face-finishing treatment and the optional addition of
nanoparticles to the surface of a textile substrate, thereby
creating a surface roughness similar to that on the surface of
Lotus leaf, to create a super-hydrophobic, self-cleaning textile
substrate that is durable to laundering.
[0260] The results in Table 1C show that most of the fabrics
treated according to the present invention exhibited good spray
rating after the treated fabrics have been exposed to 20000 cycles
of abrasion testing. When compared to Comparative Examples 12-16,
the fabrics treated according to the present invention performed
exceptionally well. More specifically, the Comparative Examples
12-16 only exhibited spray ratings in the range of 45 to 60 through
5000 cycles, while many of the Examples treated according to the
present invention exhibited spray ratings in the range of 50 to 90
though 20000 cycles--a four fold improvement. Furthermore, Examples
1 and 2 exhibited fairly low dynamic rolling angles through 10000
cycles of abrasion and Example 24 exhibited a fairly low dynamic
rolling angle through 20000 cycles, thus illustrating that the
fabric treated according to the present invention is capable of
maintaining hydrophobic properties when exposed to abrasion, such
as that which may be encountered by a fabric during normal use.
Thus, the results for these Examples illustrate the benefits of the
face-finishing treatment and optionally, the addition of
nanoparticles to the surface of a textile substrate, thereby
creating a surface roughness similar to that on the surface of
Lotus leaf, to create a super-hydrophobic self-cleaning textile
substrate that is durable to abrasion.
Sample Preparation for Measuring Fiber Surface Roughness
[0261] Representative fibers or yarns from the fabric samples
previously described in the Examples section were carefully placed
on specimen supports prior to examination in the microscope. These
representative roughened fibers that provide the lotus-effect were
found to be substantially in the plane of the fiber-containing
substrate. A Roughness Factor (R.F.) was determined by actual
physical measurement of fibers, as further explained below. In
general, the Roughness Factor may be somewhat higher when higher
magnification is used, since the units employed in the analysis
procedure are more numerous when higher magnifications are used.
Therefore, a given magnification of 500.times. was chosen to
standardize the measurement of textile fiber Roughness Factors.
Calculations based on other magnifications are shown only for
samples where obtained from literature or to make a specific
point.
[0262] These representative fibers or yarns were then gold-coated
in a Denton Desk II model sputter coater (Denton Vacuum, Inc.,
Morristown, N.J.) such that a uniform coating of approximately
150-200 Angstroms of gold was deposited prior to examination in a
scanning electron microscope (SEM).
[0263] Imaging was done using an Amray Model 1845FE scanning
electron microscope (KLA-Tencor, Inc. 160 Rio Robles, San Jose,
Calif. 95134) operating at 5 kV accelerating voltage.
[0264] Fiber samples were examined at various magnifications,
although 500.times. was utilized most frequently due to the optimum
level of detail observed at this magnification; images were made
using a WIN TV-GO (Happauge Computer Works, Inc., Happauge, N.Y.)
video card and saved as .jpg image files at 800.times.600 pixels
resolution on an IBM-compatible personal computer.
Procedure Employed to Determine the Roughness Factor (R.F.)
[0265] The Roughness Factor ("R.F.") of representative fibers may
be objectively measured as indicated below. Images were captured as
described previously. Roughened regions within the treated fibers
of the textile substrate (see FIG. 7A) were positioned within the
SEM so that a clear image of the side silhouette of a treated fiber
may be seen. Surface roughness of the fibers due to indentations,
protrusions, scuffing, particles, and the like, as a result of the
finishing of the textiles, may be clearly seen. It is pointed out
that the fibers are not uniformly roughened. That is, the side of
the fiber away from the top surface of the textile substrate may
not be roughened at all even though the top surface may be
roughened substantially. The fiber R.F. is measured on the top
surface of the fiber on a continuous side of a fiber. It is not
measured near or in the region of a broken fiber tip or end.
[0266] Generated digital images were 800 pixels long by 600 pixels
high. The images were captured at 500.times. magnification of the
individual fibers. The images files were saved as 8 bit RGB files
in a JPEG format.
[0267] FIG. 7A shows initial images of fiber from the tent fabric
described in Example 6, as obtained from the SEM. To focus on the
edge and its corresponding roughness, a section of the image can be
extracted that only shows the roughened edge of the treated fibers
in profile. In the extracted image, fiber orientation is directed
along one of the sides of the image. That direction is referred to
herein as the image length. The length of the image for analysis is
100 microns or longer. For example, FIG. 7B shows an extracted
portion from the initial image of the tent fabric as obtained from
the SEM.
[0268] For analysis, two software packages were employed: Adobe
Photoshop 6.0.1, as offered by Adobe Systems Incorporated of San
Jose, Calif., and Image Pro Plus 4.5, as offered by Media
Cybernetics, Inc of Silver Spring, Md. The extracted images were
converted to an 8-bit grayscale (each pixel takes on a gray value
from 0, or black, to 255, or white) image in Image Pro Plus. The
extracted file was then transferred to Adobe Photoshop. To separate
the pixels of the image that represent the edge of the fiber from
the background and increase the resolution for analysis, a three
pixel diameter eraser tool was used to trace the boundary between
the fiber edge and the background. The eraser tool was set to
convert all pixels that it crossed over while activated to black, a
pixel value of 0. Using a mouse with the magnified image (200% or
greater on the screen in Adobe Photoshop), the boundary between the
fiber edge and the background was traced accurately by hand to set
the background pixels to 0. After the pixels at the edge of the
background were set to zero, the rest of the background was also
set to 0 (black).
[0269] FIG. 7C shows the same image as from FIG. 7B, with the
background set to black by the procedure described above. This
image is saved as a TIFF file for later analysis in Image Pro
Plus.
[0270] Using Image Pro Plus, the dark background image files were
opened. This image was used to calculate the roughness of the fiber
edge. In principal, the roughness parameter was defined to be the
length of the actual fiber edge including all protrusions from the
surface (the "profile") divided by the length of the image
(assuming that the fiber in question extends the whole length of
the image).
[0271] To determine the profile, the background pixels may be
tagged to create a black and white image of the background which
shows the shape (i.e. shadow) of the surface roughness of the
fiber. To determine the profile, Image Pro Plus allows the user to
select portions of an image based on the portion's pixel value and
size. Because the background pixels have been set to black (a pixel
value of zero), the background can be selected from the image by
segmenting out the pixels that have a value near 0.
[0272] Because there can be shadows in an image, there are some
pixel objects that have numerical pixel values near zero but do not
represent the background and thus, the profile. These objects
invariably include fewer pixels than the background. Therefore, the
analyst can exclude shadows from the profile by requiring that the
pixel objects that are tagged as the background have a pixel size
larger than the sizes of the shadows in the image (this will vary
depending on the image).
[0273] For completeness, objects are selected so that pixel "holes"
in a big background of selected pixels are automatically selected.
Pixels neighboring each other in a four-connected sense are tagged
as part of the background. This means that objects in an image
should be connected to the main body of the image by having a
"neighbor" directly above and/or below or on either side of the
specified pixel. Pixels that are connected through a diagonal only
will not be included in the selected background object. An example
of the tagged background image for FIG. 7C is shown in FIG. 7D.
With this image in hand, the task is to measure the length of the
background interface with the fiber, or the length of the
profile.
[0274] To measure the length of a profile, the black and white
shadow images are used. The procedure used estimates the length of
the interface by defining a one pixel wide line that traces the
edge of the background/fiber boundary. To generate this one pixel
wide line, the following procedure is used.
[0275] The shadow image is duplicated first. The first copy of the
shadow image is treated with a morphological filter called an
erosion filter. The erosion filter takes a black and white image
and causes the boundary of the white portion of the image to move
so that the white portion of the image has decreased (fewer pixels)
and the dark portion has increased (more pixels) but the boundary
line shape is intact.
[0276] The shape of the erosion filter is a 3.times.3 cross. This
filter is applied one time to the image. The second copy of the
original shadow image is then treated with a dilation filter. This
is the opposite of the erosion filter. For a dilated image, the
white portion of the image grows and the dark portion decreases,
thereby preserving the shape of the boundary. The dilation filter
again uses a 3.times.3 cross-shaped filter with one pass. Using
image arithmetic, the absolute difference of the eroded and dilated
image gives an image where only a line (wider than one pixel) at
the original background/fiber interface remains. This results
because the erosion and dilation filters have left all portions of
the image the same except in the interface region. To obtain the
one-pixel wide line, the absolute difference image is treated with
one pass of a so-called "pruning" filter. This procedure takes
multi-pixel wide lines and shrinks them to one pixel. Any branches
off of the boundary line are removed. This final image called the
profile image gives us a one-pixel wide white (pixel value 255)
line that represents the roughness profile of the treated fiber. An
example of the profile image for FIG. 7B is shown in FIG. 7E.
[0277] The Roughness Factor ("R.F.") corresponds to the length of
the roughened edge, and is, in general, directly proportional to
the degree of surface roughness exhibited by a textile fiber. It is
calculated as defined herein. The counting tools of Image Pro Plus
are used on the profile image. The counting tool is set up to count
all white (pixel value 255) objects of size one pixel or larger.
Multiple pixels are counted as a single object only if they are
four-connected as described above.
[0278] The counting tool gives at least two pieces of information.
The counting tool provides the number of pixels in the boundary and
the number of objects in the boundary. The significance of the
objects relates back to whether the pixels are four-connected or
not. This is important for calculating the length of the border
because a connection along a diagonal (called an eight-connection)
has a length by geometry of 2.sup.1/2 pixels while a 4-connection
has a length of only 1 pixel. If there are N objects and M pixels
in the boundary, there are N-1 diagonal connections (length
2.sup.1/2) and M-N straight connections (length 1). Therefore, the
length of the profile (L.sub.P) is (in pixel units):
L.sub.P=(N-1)2.sup.1/2+(M-N).
[0279] The image length (L.sub.I) is simply the pixel length of the
image, which is equivalent to the length being sampled along the
fiber. This can be found in Image Pro Plus, for instance, by
looking at the bitmap and counting the column length of the image.
The roughness factor (R.F.) parameter for the fiber in question can
now be obtained by calculating the ratio R.F. as:
R.F.=L.sub.P/L.sub.I.
[0280] Data generated for the selected examples are reported in
Tables 1D and 1E below. The Example number, which corresponds to
the data generated in Tables 1A-1C, is also utilized in Tables 1D
and 1E. For instance, "Ex. 2" refers to a textile substrate
prepared as indicated previously in Example 2. Also, for
comparison, a fiber extracted from the substrate in a region having
a highly roughened surface as a result of the face-finishing
treatment and having particles present on its surface (notated as
"FF+particles" in the Tables) was compared with a fiber extracted
from the substrate in a region having little to no surface
roughness from the face-finishing treatment but having particles on
its surface (notated as "particles" in the Tables). TABLE-US-00004
TABLE 1D Roughness Factor (R.F.) Data from Examples Number of
Number of Length of Length of Pixels Objects Profile Image Sample
Treatment Magnification (N) (M) (L.sub.P) (L.sub.I) R.F. Lotus leaf
Natural 2000 653 325 480 786.21 1.64 Automotive FF + 500 584 231
474 678.27 1.43 Twill Fabric particles Ex. 4 Boat Cover FF + 500
858 304 771 982.51 1.27 Fabric particles Ex. 8 Boat Cover FF + 500
798 209 771 883.16 1.15 Fabric particles Ex. 8 Boat Cover particles
500 771 75 771 800.65 1.04 Fabric Ex. 8 Boat Cover particles 500
772 85 771 805.79 1.05 Fabric Ex. 8 Microdenier FF + 500 365 121
300 413.71 1.38 Twill Fabric particles Ex. 1 Microdenier particles
500 300 32 300 311.84 1.04 Twill Fabric Ex. 1 Microdenier particles
500 300 44 300 316.81 1.06 Twill Fabric Ex. 1 Fabric Q FF + 500 967
331 699 1102.69 1.58 Ex. 10 particles Fabric Q particles 500 699 74
699 728.24 1.04 Ex. 10 Tent Fabric FF + 500 680 248 594 781.31 1.32
Ex. 6 particles Tent Fabric particles 500 594 38 594 608.33 1.02
Ex. 6 Tent Fabric FF + 1000 919 335 717 1056.35 1.47 Ex. 6
particles Tent Fabric particles 1000 717 56 717 738.78 1.03 Ex. 6
Tent Fabric FF 1000 894 424 717 1068.21 1.49 Ex. 20
[0281] TABLE-US-00005 TABLE 1E Roughness Factor (R.F.) Data from
Comparative Examples Number of Number of Length of Length of Pixels
Objects Profile Image Sample Treatment Magnification (N) (M)
(L.sub.P) (L.sub.I) R.F. Automotive Treated as in US 500 789 150
785 849.72 1.08 Twill Fabric Patent App. No. Comp. Ex. 13
2002/0016433 A1 Automotive Treated as in US 500 828 214 785 915.23
1.17* Twill Fabric Patent App. No. Comp. Ex. 13 2002/0016433 A1
Automotive Treated as in US 500 790 129 785 842.02 1.07 Twill
Fabric Patent App. No. Comp. Ex. 13 2002/0016433 A1 Automotive
Treated as in US 500 806 143 785 863.82 1.10 Twill Fabric Patent
App. No. Comp. Ex. 13 2002/0016433 A1 Automotive Treated as in US
500 860 240 785 958.00 1.22* Twill Fabric Patent App. No. Comp. Ex.
13 2002/0016433 A1 Boat Cover Treated as in US 500 786 142 785
843.40 1.07 Fabric Patent App. No. Comp. Ex. 15 2002/0016433 A1
Boat Cover Treated as in US 500 824 254 785 927.80 1.18* Fabric
Patent App. No. Comp. Ex. 15 2002/0016433 A1 Boat Cover Treated as
in US 500 785 156 785 848.20 1.08 Fabric Patent App. No. Comp. Ex.
15 2002/0016433 A1 Boat Cover Treated as in US 500 794 186 785
869.63 1.11 Fabric Patent App. No. Comp. Ex. 15 2002/0016433 A1
Microdenier Treated as in US 500 785 110 785 829.15 1.06 Twill
Fabric Patent App. No. Comp. Ex. 12 2002/0016433 A1 Microdenier
Treated as in US 500 795 117 785 842.05 1.07 Twill Fabric Patent
App. No. Comp. Ex. 12 2002/0016433 A1 Microdenier Treated as in US
500 620 64 620 645.10 1.04 Twill Fabric Patent App. No. Comp. Ex.
12 2002/0016433 A1 Microdenier Treated as in US 500 620 69 620
647.17 1.04 Twill Fabric Patent App. No. Comp. Ex. 12 2002/0016433
A1 Tent Fabric Treated as in US 500 619 96 618 657.35 1.06 Comp.
Ex. 14 Patent App. No. 2002/0016433 A1 Tent Fabric Treated as in US
500 618 118 618 665.46 1.08 Comp. Ex. 14 Patent App. No.
2002/0016433 A1 *These unusually high Roughness Factors are
believed to be caused by one or a few large isolated agglomerates
of particles on the fiber surface.
[0282] The results shown in Tables 1D and 1E illustrate that the
fabrics treated according to the present invention have a surface
composed of fibers that exhibited a higher Roughness Factor than
other super-hydrophobic textile fiber surfaces in the prior art,
such as those described herein for the Comparative Examples. The
Roughness Factor data also shows that attempting to use particles
alone to create a roughened surface results in fibers on the
treated surface of the fabric having a low Roughness Factor
(typically RF<1.10). However, in some unusual cases, high
Roughness Factor values may be generated by large isolated particle
agglomerations, which are not durably bound to the substrate. The
last three Examples shown in Table 1D are provided to illustrate
that even at higher magnification (1000.times.), particles added to
the fiber surface do not contribute significantly to the Roughness
Factor as described in the present invention. Thus, the combination
of face-finishing the textile surface and treating it with
particles, as described by the present invention, creates a surface
with features imposed on the fibers with length scales most like
those on the surface of the Lotus leaf, wherein the surface
exhibits a Roughness Factor of greater than or equal to 1.10, and
wherein the treated substrate exhibits superior liquid repellent
properties.
[0283] The results shown in Tables 1A-1E indicate that surface
roughness indeed affects the liquid repellent properties imparted
to a textile substrate, as evidenced by low dynamic rolling angles,
high spray ratings, and high repellency to water and oil. As
illustrated and described herein, a surface of the present
invention exhibits greater and more durable liquid repellency and
self-cleaning characteristics than others in the prior art. In
comparing the data in the Tables, the present invention clearly
illustrates that those fabrics having the best repellency, spray
rating, and wash durability also exhibit the highest Roughness
Factor.
[0284] Accordingly, this invention is capable of filling the need
for creating textile substrates that have superior liquid repellent
and self-cleaning properties which may be useful in many end-use
applications where such attributes are desirable. Some of these
end-uses include, without limitation, outerwear (such as raingear),
outdoor fabric (such as tents, awnings, and boat covers),
automotive fabrics (such as for automotive convertible tops), and
apparel.
[0285] These and other modifications and variations to the present
invention may be practiced by those of ordinary skill in the art,
without departing from the spirit and scope of the present
invention. Furthermore, those of ordinary skill in the art will
appreciate that the foregoing description is by way of example
only, and is not intended to limit the scope of the invention
described in the appended claims.
* * * * *